WO1997019240A1

WO1997019240A1 - A lock mechanism

Info

Publication number: WO1997019240A1
Application number: PCT/GB1996/002829
Authority: WO
Inventors: Bernard John Viney
Original assignee: Surelock Mcgill Limited
Priority date: 1995-11-17
Filing date: 1996-11-18
Publication date: 1997-05-29
Also published as: AU7583096A; GB2307270B; GB2307270A; ZA969632B; GB9523627D0

Abstract

There is described a lock mechanism for fixing to a moveable member or frame for locking the moveable member in a closed position in the frame. The lock mechanism comprises a bolt member (10) moveable between a disengaged position and an engaged position for engagement with the frame or moveable member. A restraining mechanism is provided to engage and restrain the bolt member (10) when the bolt member (10) is in the disengaged position. Status detecting means is also provided for detecting when the moveable member is in a closed position in the frame, the status detecting means being coupled to the restraining mechanism to cause the restraining mechanism to release the restraint on the bolt member (10) when the closed position is detected. Electrical drive means (134) moveable between a closed position and an open position is provided to drive the bolt member (10) into the disengaged position and to hold the bolt member (10) in that disengaged position. Finally, bolt (10) biasing means is provided to urge the bolt member (10) into the engaged position and to hold the bolt member (10) in the engaged position when the electrical drive (134) means moves to the closed position and the restraining mechanism releases the restraint on the bolt member (10).

Description

A LOCK MECHANISM

The present invention generally relates to a lock mechanism for fixing to a movable member or to a frame for locking the movable member in a closed position in the frame, and in particular, but not exclusively, the present invention relates to a lock mechanism which can be both electrically and manually driven.

There is a need for lock mechanisms for medium or high security applications which can be locked both electrically and manually. Such locks have particular applications in prisons and the like. A particular requirement for such applications is that the lock mechanism is able to be operated electrically to remotely unlock and lock a door whilst still allowing for the manual unlocking of the door in an emergency, for example, when there has been a power failure to the electrical drive mechanism.

One such lock mechanism which is currently available are the 120M Series locks supplied by Folder Adam Company of 163000W 103rd Street, Lemont, Illinois 60439, United States of America. The 120M Series locks have a latch-bolt member which extends from a latch mechanism which can be mounted on the door or the door frame to contact the other of the door frame or the door. There is also provided a ball catch to detect whether the door is in the closed position. Once the door has been unlocked by the energisation of a motor, the latch-bolt is held mechanically in a retracted position. If the motor is energised to extend the latch-bolt, the latch-bolt is still held mechanically in the retracted position until the door is opened whereupon the ball catch detects the opening of the door and the latch-bolt is released.

The lock mechanism is also provided with a cylinder key for the manual operation of the latch- bolt. Under key operation, when the door is closed the latch-bolt can be retracted and held mechanically in the retracted position. However, if the key is rotated in the opposite direction to extend the latch- bolt, the latch-bolt is held mechanically retracted until the door is opened. When the door is open, the latch-bolt will automatically extend.

When the door is open, the electric motor and the key mechanism can be used to retract and extend the latch-bolt .

Thus this prior art lock mechanism suffers from the serious disadvantage that when the door is closed and the latch-bolt is retracted, either using the electric motor or manually using the key, it cannot be extended again until the door has been opened. The lock mechanism requires the latch-bolt to be in its extended position as the door is closed. The latch- bolt cannot be extended once the door is closed. Thus, if, for instance, in a prison environment, the motor was accidentally energised, or, in a situation where the latch-bolt was retracted to open the door and it was necessary to quickly re-lock the door, the door must first be opened before it can be relocked. Where the lock mechanism is normally operated remotely, this requires an individual to go to the door and carry out the opening and closing operation which is undesirable. In a high security environment m which a potentially dangerous situation might arise, for example, with a prisoner as the door is being unlocked, it would be highly advantageous to be able to immediately re-lock the door without having to open it first. The prior art lock mechanism also suffers from the disadvantage that a latch-bolt is used. Such a bolt requires an angled face to enable the latch-bolt to latch into its locked position as the door is closed. This angled face provides an inherent weakness n a lock mechanism and severely reduces the mechanical strength of the bolting mechanism. It is therefore an object of the present invention to provide a lock mechanism which can be operated both electrically and manually when affixed to a movable member, such as a door, or to a frame to allow the extension and retraction of a bolt member when the movable member is in a closed position. According to a first aspect of the present invention there is provided a lock mechanism for fixing to a movable member or frame for locking said movable member in a closed position in said frame, the lock mechanism comprising a bolt member movable between a disengaged position and an engaged position for engagement with said frame or moveable member; a restraining mechanism to engage and restrain said bolt member when said bolt member is in said disengaged position; status detecting means for detecting when said moveable member is in a closed position in said frame, said status detecting means being coupled to sa d restraining mechanism to cause said restraining mechanism to release the restraint on said bolt member when said closed position is detected; electrical drive means moveable between a closed position and an open position to drive said bolt member into said disengaged position and to hold said bolt member m said disengaged position; and bolt biasing means to urge said bolt member into said engaged position and to hold said bolt member in said engaged position when said electrical drive means moves to said closed position and said restraining mechanism releases the restraint on said bolt member.

A number of embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: -

Figure 1 is a side elevational view of a lock mechanism in accordance with a first embodiment of the present invention from which a cover plate has been removed;

Figure 2 is a left-hand side view of the lock mechanism of Figure 1 from which details of the bolt member have been omitted for the sake of clarity;

Figure 3 is a cross-sectional view taken along line III-III of Figure 1 from which details of the restraint mechanism and electrical drive means have been omitted for the sake of clarity;

Figure 4 is a cross-sectional view taken along line IV-IV of Figure 1 from which details of the restraint mechanism and electrical drive means have again been omitted for the sake of claζity;

Figure 5 is a cross-sectional view taken along line V-V of Figure 1;

Figure 6 is a cross-sectional view taken along line VI-VI of Figure 1;

Figure 7A is a plan view of a restraint member of the lock mechanism of Figure 1 and its engagement with a cylindrical headpiece of the electrical drive means; Figure 7B is an elevational view of the restraint member and cylindrical headpiece of the Figure 7A; Figure ΘA is a plan view of a bistable of the lock mechanism of Figure 1;

Figure 8B is an elevational view of the bistable of Figure 8A; Figure 9 is an elevational view of the electrical drive means of the lock mechanism of Figure 1;

Figure 10 is an elevational view of a cover plate of the lock mechanism of Figure 1;

Figure 11 shows the position of the lock mechanism when the door is closed, the bolt member is in the engaged position, the electrical drive means is in a closed position, the restraint mechanism is off and the sprung flap is disengaged;

Figure 12 shows the position of the lock mechanism when the door is closed, the bolt member is in the disengaged position, the electrical drive means is in an open position, the restraint mechanism is off and the sprung flap is disengaged;

Figure 13 shows the position of the lock mechanism when the door is closed, the bolt member is in the disengaged position, the electrical drive means is in a closed position, the restraint mechanism is on, the sprung flap is engaged and the key is in; Figure 14 shows the position of the lock mechanism when the door is closed, the bolt member is in the engaged position, the electrical drive means is in the closed position, the restraint mechanism is off, the sprung flap is engaged and the key is in; Figure 15 shows the position of the lock mechanism when the door is open, the bolt member is in the disengaged position, the electrical drive means is in the open position, the restraint mechanism is on and the sprung flap is disengaged;

Figure 16 shows the position of the lock mechanism when the door is open, the bolt member is in the disengaged position, the electrical drive means is in the closed position, the restraint mechanism is on, the sprung flap is engaged and the key is out; Figure 17 shows the position of the lock mechanism when the door is open, the bolt member is in the engaged position, the electrical drive means is in the closed position, the restraint mechanism is off, the sprung flap is engaged and the key is out;

Figure 18 shows the position of the lock mechanism when the door is open, the bolt member is in the disengaged position, the electrical drive means is in the closed position, the restraint mechanism is on and the sprung flap is disengaged;

Figure 19 shows a table of the possible methods of operating the lock mechanism of Figure 1 in conjunction with the door of a prison cell; and

Figure 20_^ is a table showing the possible methods of operating the lock mechanism of Figure 1 in conjunction with an access control door. Referring to the drawings, a lock mechanism in accordance with one embodiment of the present invention comprises a bolt member 10 retained by a guide 12 within a housing 16 and movable translationally between an engaged position in which the bolt member extends from the housing, and a disengaged position in which an end surface 18 of the bolt member lies substantially flush with a face 20 of the housing. At an end of the bolt member 10 which extends from the housing 16 there is provided a roller 22 which is free to rotate about an axis 24 parallel to the longitudinal axis of the housing and perpendicular to the translational direction of movement of the bolt member. The roller 22, although free to rotate, is held captive with respect to the bolt member 10 by means of an axial pin 26 received within an upper surface 28 of the bolt member. Within the bolt member 10 there is also provided a second pin 30 of hardened steel as a security measure to prevent the bolt member from being sawn. This second pin 30 extends in the translational direction of movement of the bolt member 10 and is located rearwardly of the roller 22.

A compression spring 32 anchored to a pm 34 is provided to urge the bolt member 10 outwardly of the housing 16 and towards its engaged position. In order to constrain this movement the pm 34 is arranged to slide withm a guide slot 36 provided with the bolt member 10 to the rear of the hardened steel p 30. Two spacers 35 and 37 on either side of the bolt member 10 ensure that throughout its movement the bolt member is held in spaced relationship to the front and back cover places 179 and 180.

Beneath the compression spring 36 the bolt member 10 is provided with a downwardly extending contoured flange 38 which will be described in more detail later.

In a position to one side of the housing 16 and adjacent the bolt member 10, there is provided a restraint drive member 40 which is again movable translationally between a disengaged and an engaged position which the restraint drive ember extends from withm the housmg 16 through the same housing face 20 to a greater or lesser extent As with the bolt member 10, the restraint drive member 40 is provided at its protruding end with a roller 42 which is free to rotate about an axis 44 parallel to the longitudinal axis of the housing 16 and perpendicular to the translational direction of movement of the restraint drive member Although free to rotate, the roller 42 is held captive with respect to the restraint drive member 40 by means of an axial pm 46

The restraint drive member 40 is biased outwardly of the housing 16 by means of a second compression spring 48 which is anchored to the housing at one end by a p 50. The p 50 is constrained to move withm a guide slot 52 which serves to limit the movement of the restraint drive member 40. Nevertheless, when the door is open, the restraint drive member 40 is urged by the compression spring 48 to extend outwardly from the face 20 of the housing 16 and into its disengaged position. By contrast, when the door is closed, the roller 42 engages with a ramp 41 provided on a socket plate 43. The socket plate 43 may be mounted on either the door frame or the door depending on whether the lock mechanism is mounted in the door or the door frame respectively, and the engagement of the roller 42 and the ramp 41 serves to move the restraint drive member 40 rearwardly against the action of the compression spring 48 and into its engaged position. The socket plate 43 also provides a recess 45 in which to receive the protruding portion of the bolt member 10 when the bolt member is in its engaged position. The recess 45 is in part defined by vertical side walls 47 and 49 and these provide a surface along which the roller 22 may roll in order to reduce the friction associated with the movement of the bolt member 10. This is particularly useful in a prison environment during a siege when an aggrieved prisoner might try to hold a door closed by pushing against it. Attached to an under surface 54 of the restraint drive member 40, two substantially triangular arms 56 extend downwardly on either side of the bolt member 10 to engage with a restraint mechanism 57.

The restraint mechanism 57 comprises a substantially U-shaped restraint member 58 and a bistable 60.

Looking firstly at the restraint member 58, the member comprises two parallel plate-like limbs 59 and 61 which are held in spaced relationship and extend on either side of the bolt member 10. Each limb 59, 61 is of substantially identical construction and may be considered to comprise a first part 62 which extends generally longitudinally of the housing 16 and a second part 64 which extends perpendicular to the first and generally parallel to the translational direction of movement of the bolt member 10. As a result the limbs 59 and 61 are substantially L-shaped although each limb also spans much of the angle subtended by the two parts 62 and 64 to leave the resulting limb neither truly L-shaped nor truly triangular.

The restraint member 58 is pivotally mounted with respect to the housing 16 about a pivot point 66 located on the first part 62 close to its intersection with the second 64. Consequently, the restraint member 58 is able to pivot between two positions, a restraining position and a releasing position.

Although substantially planar, one of the limbs 59 is provided with an upstanding side wall 68 along one side of the first part 62. An opening 70 is provided in the side wall 68 at an end of the first part 62 remote from the second part 64 and receives one end of a spring 72. The other end of the spring 72 is anchored to the housing 16 by means of a pin 74 and enables the spring to bias the restraint member 58 into the restraining position.

Other features of the limbs of the restraint member 58 includes a restraint release pin 76 located at an end of the first part 62 remote from the second 64 which interconnects the two limbs 59 and 61 and holds them in spaced relationship; a respective inwardly projecting boss 78 located at an end of the second part 64 remote from the first 62; and, on one of the limbs 59, a rearwardly projecting finger 70 located adjacent the relevant inwardly projecting boss 78. At the same time, at the intersection of the two parts 62 and 64, but on the same side of the pivot point 66 as the second part, there is provided a generally downwardly extending guide slot 80. The bistable 60 also comprises two parallel plate-like elements 81 and 83 which are held in spaced relationship by spacers 90 and 92 which additionally serve as first and second coupling pins in a manner to be described. The two elements 81 and 83 are both of substantially triangular shape and extend on either side of the restraint member 58 sandwiching not only the restraint member but also the bolt member 10. Both elements 81 and 83 are pivotally mounted with respect to the adjacent limb of the restraint member 58 about a respective pivot point 82 located close to a first of the three apices 84. As a result the bistable 60 is pivotable between two positions, an electrically driven position and a manually driven position. However, as with the restraint member 58, the bistable 60 is biased to one of these two positions, the electrically driven position, by means of a spring 86 connected between the apex of one of the elements 81 to the pivot point 82 and an attachment point 88 on the adjacent limb of the restraint member at an end of the second part 64 close to the boss 78.

Other features of the elements of the bistable 60 include the first coupling pin 90 which is mounted at a second apex and passes through the guide slots 80 of the restraint member 58; the second coupling pin 92 which is mounted at the third apex at a position which no longer overlies the restraint member 58 but which is sufficiently close to engage an edge thereof; and, on one of the elements 81, an outwardly projecting stud 94 which extends in a direction away from the restraint member 58 from a location close to the third apex.

Beneath the restraint mechanism 57 two coaxial cams 96 are mounted for rotation about an axis 98 perpendicular both to the longitudinal axis of the housing 16 and the translational direction of movement of the bolt member 10. The two cams 96 are arranged m mutual alignment and occupy planes which enable the cams to pass between the limbs 59 and 61 of the restraint member 58. Each cam 96 is of identical construction but of opposite hand and comprises a substantially radially projecting finger 100 which is shaped at its distal end to form a hook 102 On either side of the hook 102, the finger 100 is provided with first and second cam surfaces 104 and 106, the first being of generally concave shape and the second being generally convex. Both cams 96 are provided with a respective axial slot 108 which is adapted to receive a tang of an associated key cylinder Each cam 96 may therefore be rotated by inserting the appropriate key withm a keyway of the key cylinder concerned.

As previously mentioned, the bolt member 10 is provided with a downwardly extending, contoured flange 38 For the most part this flange 38 occupies a plane parallel to, and overlain by, the limbs 59 and 61 of the restraint member 58. However, at a rearward edge, the flange 38 is provided with an upstanding side wall 114 By contrast, no such side wall is provided at a forward edge 116 or at a lower edge 117 although at an upper corner there is provided a pivot point 118 by which a pivoting member 120 is mounted for pivotal movement with respect to the flange 38 The pivoting member 120 comprises a forward and downward extending leg 122 on one side of the pivot point 118 and a rearward and similarly downwardly extending leg 124 on the other. The rearward leg 124 terminates in a downwardly projecting point 126 and is so arranged that ordinarily the mass of the rearward leg causes the member as a whole to pivot n a clockwise fashion about the pivot point 118. However, this rotational movement is limited by the engagement of the rearward leg 124 with an upstanding pin 128 provided on the underlying flange 38. In order to inhibit unwanted pivotal movement the opposite sense the pivoting member 120 is preferably biased mto engagement with the upstanding pin 128 by means of a spring 129 which extends between the upstanding p 128 and an attachment point 131 located at an upper edge of the rearward leg 124. In any event, pivotal movement m this opposite sense, unwanted or otherwise, is limited by the engagement of the rearward leg 124 with an upstanding shoulder 130 formed at the intersection between the bolt member 10 and the downwardly extending flange 38.

To the rear of the two cams 96 there is provided an electrical drive means 132 to drive the bolt member 10 between the engaged and disengaged positions. The electrical drive means 132 comprises an electric motor 134, a coaxially mounted gear box 136 and, protruding from the gear box 136, an output shaft 138. The electric motor 134 and the gear box 136 are so adapted that if the door is open (i.e. if the restraint drive member 40 is in its disengaged position) the output shaft 138 is caused to rotate in one direction and if the door is closed (i.e. the restraint drive member s m its engaged position) the output shaft rotates in the opposite direction. A cylindrical headpiece 140 is mounted on the output shaft 138 to rotate therewith, the headpiece terminating m a radial flange 142 of increased diameter. At one point about its circumference, the radial flange 142 s provided with a flat 144 to which there is mounted a flap 146. The flap 146 is provided with a smoothly curved leading edge 148 and a steeply curved trailing edge 150 such that, in profile, the upper surface of the flap resembles that of an aeroplane wing reverse. The flap 146 is pivotally mounted to the flat 144 close to its trailing edge 150 about an axis perpendicular to that of the headpiece 140 and the output shaft 138. Furthermore, this mounting is resiliently biased so that a downward pressure on the leading edge 148 will cause the flap 146 to collapse downwardly until the downward pressure is removed. Elsewhere, and spaced by 180° from the trailing edge 150 of the flap 146, the radial flange 142 is provided with an upwardly projecting spur 152 on which there is mounted a roller 154 and a stationary washer 155. Overlying the roller 154, and indeed the whole of the downwardly extending flange 38 and much of the restraint mechanism 57, lies a sprung flap 156 which is secured at one edge to the housing 16 by means of a pm 158. A spring 157 extends between the p 158 and an attachment point 159 located on the sprung flap 156 and serves to bias the flap into engagement with the restraint mechanism 57. Generally speaking the sprung flap 156 is substantially L-shaped and comprises an elongate portion 160 which extends in the translational direction of movement of the bolt member

10 and is provided close to its distal end with a notch 162.

The lock mechanism is controlled by a programmable logic controller (not shown) mounted externally of the housing 16 and this requires the necessary electrical leads to pass in and out of the housmg through an appropriately located feed-through 164. The status of various elements with the lock mechanism is determined by a number of contact switches. For example, a first switch 166 is located rearwardly of the restraint drive member 40 and co¬ operates with a rearwardly extending actuator 168 to sense whether the restraint drive member is in the disengaged or engaged position. A second switch 170 is located adjacent the first 166 and arranged to sense whether the bolt member 10 is in the engaged or disengaged position while two further switches 172 and 174 are located adjacent the cylindrical headpiece 140 and co-operate with radially extending lugs 176 and 178 to sense the relative rotational position of the electrical drive means 132.

Finally, in order to enclose the lock mechanism, cover plates 179 and 180 are fitted to either side of the housing 16 and secured thereto by means of suitable security screws which pass through screw holes 182, 183, 184 and 185. A cylinder plate 186 is mounted on the cover plate 180, again by suitable security screws, this time passing through screw holes 188, 190, 192 and 194 The cylinder plate 186 is provided with an aperture 196 through which may pass the tang of the key cylinder to engage the axial slot 108 of one of the two cams 96. The key cylinder is itself attached to the cylinder plate 186 by means of suitable screws passing through screw holes 198 and 200. In this way, if it is desired to exert a large torque on the cams 96 durmg, for example, a siege situation, the cylinder plate 186 may be temporarily removed to allow the passage of a specially adapted tool. If the cylinder is not required to be removed for siege purposes, it may be directly attached to either of plates 179 or 180 or both.

Havmg described the construction of the lock mechanism its method of operation will now also be discussed. Fig. 11 shows the lock mechanism in a state which the door with which the mechanism is associated is closed, the bolt member 10 is n the engaged position, the electrical drive means 132 is what may be termed a closed position, the restraint mechanism 57 is n an off position and the sprung flap 156 is disengaged. Looking at the Figure more detail, the bolt member 10 extends from the housmg 16 having been urged into this position by the compression spring 32. Further translational movement of the bolt member 10 however, is prevented by the engagement of the side wall 114 with the roller 154. Should access somehow be gained to the end surface 18 of the bolt member 10, forced rearward movement of the bolt member against the action of the compression spring 32 is prevented by the engagement of the downwardly projecting point 126 of the pivoting member 120 agamst the washer 155. The end force protection provided by the pivoting member 120 is particularly advantageous where the lock mechanism finds use n high security installations such as prisons

Because the door is closed, the restraint drive member 40 is urged rearwardly agamst the action of the second compression spring 48 by virtue of the engagement of the roller 42 with the ramp 41 of the socket plate 43. Because the restraint drive member 40 s urged rearwardly, so too are the downwardly extending arms 56 which are attached to its under surface 5 . At an end remote from the restraint drive member 40, each of the arms 56 engage the first coupling pin 90 of the bistable 60 This not only causes the bistable 60 to rotate about the pivot point 82 but, because the first coupling pin is positioned above a horizontal line passing through the pivot point, also thrusts the first coupling pin 90 upwards and into engagement with a lower edge of the bolt member 10. When this happens further upward movement of the first coupling pin 90 is no longer possible and therefore further force results in a turning moment on the restraint member 58 about pivot point 66 against the action of spring 72. With the restraint member 58 in this position the bosses 78 provided at the end of the second part 64 are in engagement with the lower edge 117 of the downwardly extending flange 38.

From this position the lock mechanism may be operated to withdraw the bolt (i.e. to move the bolt member 10 translationally from its engaged position to its disengaged position) by either electrical or mechanical means. Describing the electrical operation first, upon actuation of the appropriate command signal, the electric motor 134 causes the cylindrical headpiece 140 to rotate through 180° thereby causing the roller 154 to move from the forward position shown in Fig. 11 to the rearward position shown in Fig. 12. In so doing, the roller 154 bears against the side wall 114 of the downwardly extending flange 38 causing the bolt member 10 to move rearwardly against the action of the compression spring 32. As before, the pivoting member 120 provides a limit to this rearward movement by engaging the washer 155 should an additional rearward force be applied to the projecting end 18 of the bolt member 10.

Since the door has not yet been opened the restraint drive member 40 has not moved with respect to the housing 16, neither has the restraint member 58 or the bistable 60. All that has happened is that the bolt member 10 has moved rearwardly during which process the bosses 78 have moved along the lower edge 117 of the downwardly projecting flange 38 to a position in which they lie forward of the forward edge 116 of the flange 38. This then is the situation shown in Fig. 12 in which the door is closed, the bolt member 10 is in its disengaged position, the electrical drive means 132 is in what may be termed an open position, the restraint mechanism 57 is off and the sprung flap 156 is disengaged.

To return the lock mechanism to the locked position (i.e._^the position shown in Fig. 11) all that is needed is for the appropriate command signal to be sent to the electric motor 134 to cause the headpiece 140 to rotate through another 180°. This brings the roller 154 back to its forward position and allows the bolt member 10 to extend outwardly of the housing 16 under the action of the compression spring 32. Once again, because the door has not been opened, the positions of the restraint drive member 40, the restraint member 58 and the bistable 6Q remain unchanged.

In order to perform the same operation of moving the bolt member 10 from its engaged to its disengaged position mechanically, the appropriate key is first inserted into the keyway of the key cylinder and turned so as to cause the tang to rotate within the axial slot 108 of the cams 96. As the tang is rotated so too are the fingers 100, each of which is brought into engagement with the second coupling pin 92 of the bistable 60. As the fingers 100 continue to be rotated, the second coupling pin 92 moves up the second convex cam surface 106 towards the hook 102. At the same time, the bistable 60 is caused to rotate about the pivot point 82 which in turn moves the first - 1 !

coupling pin 90 downwardly within its guide slot 80 and the outwardly projecting stud 94 laterally with respect to the sprung flap 156. In addition to this movement, the tip of the hook 102 also engages the forward leg 122 of the pivoting member 120. As a result, the pivoting member 120 pivots about its pivot point 118 raising the downwardly projecting point 126 clear of the washer 155 against the action of the spring 129. Since the pivotal movement of the pivoting member 120 is limited by its engagement with the shoulder 130, continued rotation of the cams 96 causes the tip of the hook 102 to force the pivoting member 120 rearwardly together with the downwardly extending flange 38 to which it is attached. As the downwardly extending flange 38 moves rearwardly, the bosses 78 on the second part 64 of the limbs of the restraint member 58 once again move along the lower edge of the flange 117 until they reach a position forward of the forward edge 116. As a result of the pivotal movement of the bistable 60, the first coupling pin 90 _^is no longer in engagement with the arms 56 of the restraint drive member 40. Consequently, the restraint member 58 is free to pivot about pivot point 66 under the action of spring 72. This is not possible until the bosses 78 are free of the lower edge 117 of the downwardly extending flange 38 but as soon as they are the bosses rotate with the restraint member 58 to a position in which they engage the forward edge of the flange 116. Another consequence of the movement of the bistable 60 is that the outwardly projecting stud 94 which normally bears against a distal end of the elongate portion 160 of the sprung flap 156 is moved so that it is received within the notch 162. This then is the position illustrated in Fig.13 in which the door is still closed, the bolt member 10 is in its disengaged position, the electrical drive means 132 is in a closed position, the restraint mechanism 57 is on, the sprung flap 156 is engaged and the key is still in. If the key is now withdrawn from the keyway of the key cylinder, the bolt member 10 would still be retained in its disengaged position by virtue of the engagement of the bosses 78 with the forward edge 116 of the downwardly extending flange 38. Furthermore, the bistable 60 is held in position against the restoring action of the spring 86 by means of the engagement of the outwardly projecting stud 94 and the notch 162.

To return the bolt member 10 to its engaged position, all that is required is for the key to be again inserted into the keyway of the key cylinder and rotated in the opposite sense as before. In this way the tang received within the axial slot 108 will cause the cams 96 to rotate in such a way that the fingers 100 and hooks 102 disengage from the pivoting member 120 and second coupling pin 92. Further rotational movement of the cams 96 eventually brings its first concave cam surface 104 into engagement with the restraint release pin 76. This engagement causes the restraint member 58 to pivot about pivot point 66 thereby moving the bosses 78 out of engagement with the forward edge 116 of the downwardly extending flange 38. Consequently, the bolt member 10 is free to move towards its engaged position under the action of the compression spring 32. As it does so, the downwardly projecting point 126 of the pivoting member 120 rides over the washer 155 which in turn prevents further translational movement of the bolt member 10 by its engagement with the side wall 114. Because the outwardly projecting stud 94 is held by the notch 162 of the sprung flap 156, the orientation of the bistable 60 is not affected by the pivotal movement of the restraint member 58. Thus, although the bolt member 10 has been returned to its engaged position, the lock mechanism is not exactly the same position as that shown m Fig.11. Instead, the lock mechanism assumes the position shown m Fig. 14 in which the door is still closed, the bolt member 10 is in its engaged position, the electrical drive means 132 is in the closed position, the restraint mechanism 57 is off, the sprung flap 156 is still engaged and the key is in.

Thus, as has been described, the bolt member 10 may be moved from its engaged to its disengaged position and back again either electrically or mechanically. What is not possible however, is for the bolt member 10 to be moved from its engaged to its disengaged position electrically and moved back again mechanically. This is because if one looks at Fig. 12 which shows the position of the lock mechanism once the bolt member 10 has been moved to its disengaged position using the electrical drive means 132, one can see that the restraint mechanism 57 is already m the off position and that further pivotal movement of the restraint member 58 by virtue of the engagement of the restraint release pm 76 is of no avail. Furthermore, there is no mechanical means by which the roller 154 can be disengaged from the side wall 114 and it is this engagement which is currently holding the bolt member 10 in its disengaged position.

By contrast, what is possible is to move the bolt member 10 from its engaged to its disengaged position by mechanical means and then return it to its engaged position using the electrical drive means 132. Thus, starting with the lock mechanism in the position shown in Fig. 13, once the appropriate command signal has been sent the electric motor 134 causes the cylindrical headpiece 140 to rotate through 360°. As it does so the roller 154 bears against the elongate portion 160 of the sprung flap 156 lifting the notch 162 out of engagement with the outwardly projecting stud 94. The bistable 60 is then free to pivot about its pivot point 82 under the action of the spring 86. In this way, when the roller 154 returns to its initial position the outwardly projecting stud 94 is no longer in a position to be engaged by the notch 162.

As the bistable 60 pivots about pivot points 82, the first coupling pin 90 is moved upward within the guide slot 80 in which it is received. However, the action of the spring 86 is not in itself sufficient to cause pivotal movement of the restraint member 58. Instead, as the cylindrical headpiece 140 rotates, the leading edge 148 of the flap 146 is brought into engagement with a downwardly sloping surface 77 of the rearwardly projecting finger 79 provided on one of the limbs of the restraint member 58. Because the leading edge 148 is at a height slightly above that of the downwardly sloping surface 77, this engagement forces the rearwardly projecting finger downward causing the restraint member 58 to pivot about pivot point 66. As the restraint member 58 pivots about pivot point 66 the bosses 78 are moved out of engagement w th the forward edge 116 of the downwardly extending flange 38 enabling the bolt member 10 to move forward to its engaged position under the action of the compression spring 32. As it does so, the pivoting member 120 rides over the washer 155 and the forward movement of the bolt member 10 is eventually halted by the engagement of the roller with the side wall 114 to leave the lock mechanism in the position shown in Figure 11.

So far in the description the operation of the lock mechanism the door has not yet been opened. If, after the bolt member 10 has been moved from its engaged to its disengaged position by virtue of the electrical drive means 132 (in other words, starting with the situation shown in Fig. 12) the door is then opened, the restraint drive member 40 is no longer held in its engaged position and is free to move translationally to its disengaged position under the action of the second compression spring 48. As a consequence of this movement, the two arms 56 also move translationally and out of engagement with the first coupling pin 90. This then frees not only the bistable 60 but more importantly the restraint member 58 to pivot about its pivot point 66 under the action of spring 72. As they do so, the bosses 78 are brought into engagement with the forward edge 116 of the downwardly extending flange 38. Once opened, the door may be opened and closed continually without the fear that the door will lock in a closed position since the bolt member 10 is held in the disengaged position by the engagement of the roller 154 and the side wall 114. This then is the situation shown in

Fig. 15 in which the door is open, the bolt member 10 is in its disengaged position, the electrical drive means 132 is in the open position, the restraint mechanism 57 is on and the sprung flap 156 is disengaged.

Once the bolt member 10 has been moved from its engaged to its disengaged position using the electrical drive means 132 and the door has been opened, it is important to note that the bolt member 10 cannot be returned to its engaged position while the door remains open either mechanically or electrically. The mechanical reason for this is, as has already been seen with reference to Fig 12, there is no mechanical means of disengaging the roller 154 from its engagement with the side wall 114. As for the electrical reason, the programmable logic controller is programmed to prevent the electrical drive means 132 acting to move the bolt member 10 to its engaged position when the first switch 166 indicates that the restraint drive member 40 is no longer m its engaged position and that the door is consequently open. For added security, the programmable logic controller may determine that the door is open even if the restraint drive member 40 is temporarily held in its engaged position agamst the action of the second compression spring 48 as might be the case with a prisoner attempting to overcome the lock on his cell door. The length of time that the restraint drive member 40 must be held in its engaged position before the programmable logic controller determines that the door is in fact clqsed may be varied from one application to the next. Alternatively, one or more additional sensors may be provided to determine the status of the door with respect to the frame

The same situation in which the door may be opened and closed continually may be arrived at by first mechanically moving the bolt member 10 from its engaged position to its disengaged position Thus, starting with the door mechanism the situation shown m Fig. 13, the door may be opened causing the restraint drive member 40 to move from its disengaged position to its engaged position under the action of the second compression spring 48. The two arms 56 move with the restraint drive member 40 but are already disengaged from the first coupling pin 90. As a result, the opening of the door has no effect on either the restraint member 58 or the bistable 60. The bosses 78 therefore remain in engagement with the forward edge 116 of the downwardly extending flange 38 to hold the bolt member 10 in the disengaged position. As a result the door may be opened and closed continually without the fear that the door will lock unexpectedly. This then is the position shown in Fig. 16 in which the door is open, the bolt member 10 is in the disengaged position, the electrical drive means 132 is in the closed position, the restraint mechanism 57 is on, the sprung flap 156 is engaged and the key has been removed from the keyway of the key cylinder. As with the situation in which the bolt member 10 is first moved from the engaged to the disengaged position using the electrical drive means 132, it is to be noted that it is undesirable for the bolt member 10 to be capable of being returned to the engaged position from that shown in Fig. 16 using the electrical drive means while the door is open. As before, this may be prevented by appropriately programming the programmable logic controller and using the signals derived from the first switch 166 to determine the status of the door with respect to the frame.

By contrast, once the bolt member 10 has been moved mechanically from the engaged position to the disengaged position and the door opened, the bolt member 10 may be manually returned to the engaged position even though the door is still open. This might be desirable in a prison context, for example, if a cleaner wished to clean an unoccupied cell and wanted to make sure that having unlocked the door mechanically the door could not close behind him. Starting then with the lock mechanism in the position shown in Fig. 16, the appropriate key is first inserted into the keyway of the key cylinder and rotated so as to cause the tang to rotate in the axial slot 108. As it does so, the cams 96 are rotated so as to bring the first concave cam surfaces 104 into engagement with the restraint release pin 76. This engagement causes the restraint member 58 to pivot about pivot point 66 and move the bosses 78 out of engagement with the forward edge 116 of the downwardly extending flange 38. With the electric drive means 132 in the closed position, the bolt member 10 is then free to move towards its engaged position under the action of the compression spring 32. As it does so the pivoting member 120 once again rides over the washer 155. This then is the position shown in Fig. 17 in which the door is open, the bolt member 10 is in its engaged position, the electrical drive means 132 is in the closed position, the restraint mechanism 57 is off, the sprung flap 156 is engaged and the key has been removed from the keyway of the key_^ cylinder.

Because in Fig. 17 the outwardly projecting stud 94 is engaged by the notch 162 of the sprung flap 156, the bistable 60 does not move relative to the casing 16. All that is necessary therefore in order to return the lock mechanism to the situation shown in Fig. 16 is to insert the key in the keyway of the key cylinder and rotate it so as to cause the tang to rotate within the axial slot 108 of the cams 96. This causes the tip of the hook 102 to move into engagement with the forward leg 122 of the pivoting member 120, lifting the downwardly projecting point 126 clear of the washer 155 against the action of the spring 157. Once the pivoting member 120 has engaged the shoulder 130 further rotational movement of the cams 96 results in the rearward movement of the pivoting member and the downwardly extending flange 38 to which it is attached.

As well as enablmg the door to be opened and closed continually, the lock mechanism can also be placed in a state such that, once opened, the door will lock the next time it is closed. This slam lock condition can be instigated irrespective of whether the bolt member 10 has been initially moved from its engaged to its disengaged position by mechanical or electrical means. For example, if the bolt member 10 has initially been moved to its disengaged position using the electrical drive means 132 (in other words, starting with the situation shown in Fig. 15) , the slam lock condition can be achieved by actuating the electric motor 134 to rotate the cylindrical headpiece 140 through 180°. This brings the roller 154 out of engagement with the side wall 114 and into a forward position. At this stage the bolt member 10 does not move because it is still held against the action of the compression spring 32 by the engagement of the bosses 78 with the forward edge 116 of the downwardly extending flange 38. However, when the door next closes, the ramp 41 of the socket plate 43 will come mto engagement with the restraint drive member 40 forcing it rearwardly aga st the action of the second compression spring 48. At the same time the arms 56 will also move rearwardly and into engagement with the first coupling pin 90. As a result, the bistable 60 on which the first coupling p 90 is mounted pivots about its pivot point 82 bringing the first coupling pm mto engagement w th a lower edge of the bolt member 10. This transfers the rearward pressure to the pivot point 82 which in turn causes the restraint member 58 to pivot about pivot point 66. However, as the restraint member 58 pivots about pivot point 66, the bosses 78 are moved out of engagement with the forward edge 116 of the downwardly extending flange 38 enabling the bolt member 10 to move forward to its engaged position under the action of the compression spring 32. As it does so, the pivoting member 120 once again rides over the washer 155 and the forward movement of the bolt member 10 is eventually halted by the engagement of the roller 154 with the side wall 114.

This then is the position shown in Figure 18 in which the door is open, the bolt member 10 is in its disengaged position, the electrical drive means 132 is in the closed position, the restraint mechanism 57 is on and the sprung flap 156 is disengaged.

As previously stated, the slam lock condition can also be achieved if the bolt member 10 is initially mechanically moved from its engaged to its disengaged position. Thus, starting with the lock mechanism in the position shown in Fig. 16, the electric motor 134 is actuated so as to cause the cylindrical headpiece 140 to rotate through 360° but in the opposite sense from that previously described. As a result, rather than the leading edge 148 of the flap 146 being brought into engagement with the rearwardly projecting finger 79 and forcing it downward, the rearwardly projecting finger is first engaged by the steeply curved trailing edge 150. The trailing edge 150 is at a height slightly lower than that of the rearwardly projecting finger 79 and under these conditions and by virtue of the resilient mounting of the flap 146, the flap collapses and rides under the rearwardly projecting finger thereby enabling the cylindrical headpiece 140 to return to its starting position without causing the restraint member 58 to pivot about pivot point 66 . However, the same is not true of the bistable 60. As the cylindrical headpiece 140 rotates the roller 154 bears against the elongate portion 160 of the sprung flap 156 lifting the notch 162 out of engagement with the outwardly projecting stud 94. The bistable 60 is then free to pivot about its pivot point 82 under the action of the spring 86. In this way, when the roller 154 returns to its initial position the outwardly projecting stud 94 is no longer in a position to be engaged by the notch 162.

Durmg the movement of the cylindrical headpiece 140 the bolt member 10 is held in its disengaged position by the engagement of the bosses 78 with the forward edge 116 of the downwardly extending flange 38. However, when the door is next closed, the socket plate 43 on either the door or the frame, depending where the lock mechanism is mounted, will come into engagement with the restraint drive member 40 forcing it rearwardly against the action of the second compression spring 48. At the same time the arms 56 will also move rearwardly and into engagement with the first coupling pin 90. As a result, the bistable 60 on which the first coupling pin 90 is mounted pivot about its pivot point 82 bringing the first coupling pin into engagement with a lower edge of the bolt member 10. This transfers the rearward force to the pivot point 82 which in turn causes the restraint member 58 to pivot about pivot point 66. However, as the restraint member 58 pivots about pivot point 66 the bosses 78 are moved out of engagement with the forward edge 116 of the downwardly extending flange 38 enablmg the bolt member 10 to move forward to its engaged position under the action of the compression spring 32. As it does so, the pivoting member 120 once again rides over the washer 155 and the forward movement of the bolt member 10 is eventually halted by the engagement of the roller 154 with the side wall 114.

Once again, this is the position shown m Figure 11 in which the door is closed, the bolt member 10 is in its engaged position, the electrical drive means 132 is m the closed position, the restraint mechanism 57 is off and the sprung flap 156 is disengaged.

Irrespective of how the slam lock condition has been achieved, the programmable logic controller may once again be adapted to discriminate between the genuine closing of the door and a temporary depression of the restraint drive member 40 by, for example, a disaffected inmate of an open prison cell. Indeed, the programmable logic controller may be so adapted that when it is determined that a slam lock has been executed and yet the restraint drive member 40 is in its disengaged position because the inmate has now released his rearward pressure on the roller 42, the electric motor 134 can be actuated to rotate the cylindrical headpiece 140 through 360° moving the lock mechanism firstly to the position shown in Fig. 16 and then to the position shown in Fig. 19 to again arrive at the slam lock condition. Although the present lock mechanism has been described with reference to its use in high security establishments such as prisons, its use is not limited to such establishments. Indeed, the lock mechanism may also find use m any opening havmg a lockable closure. For example, the lock mechanism may find use m conjunction with an access control door which may be operated both mechanically by means of a key or handle and electrically via a push-button, swipe card, keypad or some other suitable means. In this situation, not all of the methods of operating the prison lock would be appropriate but, for example, the lock mechanism may be adapted so as to move from the situation shown in Fig. 11 to that shown in Fig. 12 when actuated electrically by a push- button, swipe card, keypad or other similar means. The lock mechanism may then automatically return to the situation shown in Fig. 11 if the door is not opened within a predetermined time limit of, for example, five seconds. At the same time, the lock mechanism may also be adapted to move from the position shown in Fig. 11 to that shown in Fig. 13 when acted upon by the appropriate mechanical means such as a key or handle. As before, once unlocked mechanically, the door may be mechanically relocked thereby moving the lock mechanism from the situation shown m Fig. 13 to that shown in Fig. 14. As before, having been unlocked mechanically, the door may be relocked electrically and this facility might be adapted to relock the door if the door has not been opened after a predetermined time limit again of, for example, five seconds.

However, as before, one of the methods of operation which is not possible is to disengage the bolt member 10 electrically and attempt to re-engage it mechanically. Once again, this is simply because there is no mechanical means of disengaging the roller 154 from its engagement with the side wall 114.

Irrespective of how the door is unlocked, once it has been opened the lock mechanism may be adapted to move to a condition m which it will automatically relock the next time the door is closed. This is the equivalent of the slam lock condition of the prison lock so, for example, if a door has been unlocked electrically, the lock mechanism starts in the position shown m Fig. 12, moves to the position shown in Fig. 15 once the door has been opened and then to the position shown in Fig. 18 to automatically lock the door the next time it is closed. Alternatively, if the door is initially unlocked mechanically, the lock mechanism moves from the position shown in Fig.

13, to the position shown in Fig. 16 once the door has been opened and then to the position shown in Fig. 18 so that the door is locked automatically the next time it is closed. As with the prison lock, it is not possible to mechanically move the bolt member 10 from its disengaged to its engaged position if the door is open and it was initially unlocked electrically. Again, this is because there is no mechanical means for disengaging the roller 154 from the side wall 114 and prevents the door from being accidentally placed in a condition in which it will not close because the bolt member 10 has been extended.

When the door is open and the lock mechanism is in a position so that it will lock the next time the door is closed, tampering with the door is safeguarded by the ability of the lock mechanism to automatically reset to the equivalent of the slam lock condition if it is determined that a slam lock has been executed and yet the door is still open. Likewise, if an attempt is made to mechanically move the bolt member 10 from its disengaged position to its engaged position using either a key or a handle while a slam lock condition exists, the programmable logic controller may be adapted to detect the status of the open door by means of a combination of the restraint drive member 40 and the switch 166. The electric motor 134 may then be actuated to rotate through 360° to move the lock mechanism back into the slam lock condition shown in Fig. 18. The use of the present lock mechanism in conjunction with an access control door provides a number of additional advantages. For example, by providing separately identifiable electronic keys, whether they be in the form of swipe cards, pin numbers or some other suitable means, it is possible to identify the user gaining access to the control door. If the control door is the front door of an office it then becomes possible to use the lock mechanism in order to time people's arrival at work.

By providing separate monitoring systems to either cam 96 in the form, for example, of one or more micro switches, it is also possible to monitor from which side the access door is being operated. This provides one method of determining whether the access door is being used to enable people or goods to pass in or to pass out .

Although the present lock mechanism has been described as having two cams 96, it will be apparent that if the lock mechanism is to be operated mechanically from only one side then the mechanism only requires the presence of a single cam. Under such circumstances the void left by the second cam may be filled with a suitable spacer in order to maintain the balance of the lock mechanism. Likewise, if the mechanical operation of the lock is not required then both cams 96 may be omitted from the lock mechanism. Since the actuation of the lock mechanism from one side is independent of the actuation means on the other, there are a large number of possible ways of operating the lock. For example, as has already been stated, the lock mechanism may be adapted so as to provide key release on one side only, on neither side or on both sides. A turn knob release may also be provided on one of the sides. Alternatively, break dome protection may be provided. This inhibits the casual use of the turn knob and provides a clear visual indication of unauthorised use.

Likewise, although the present lock mechanism has been described as incorporating a restraint drive member 40, any suitable status detecting means may be provided for detecting when the door is m a closed position m the frame. Such status detecting means may include electrical or optical sensors. Under such circumstances the status detecting means may be coupled to the restraining mechanism electrically rather than mechanically. Similarly, although the present lock mechanism has been described as comprising a single status detecting means, there are obvious advantages in providing further means for determining when the door is in a closed position the frame This makes it far more difficult for an aggrieved person to generate a false determination that the door is closed by tampering with the various status detecting means. Once the status of the door can be accurately determined it is then possible for two or more such doors to be programmed to operate as an interlock or airlock making it impossible for two or more specified doors to be open simultaneously In order that the lock mechanism may be operated m the event of an electrical power failure, a localised battery backup may be provided If the lock mechanism is provided with mechanical means for moving the bolt member 10 between its engaged and disengaged positions, then the battery backup is only required if, at the time of the power failure, the door is open and had been opened electrically Under these circumstances, the battery backup need only rotate the roller 154 to the forward position and thereafter the lock mechanism may be operated entirely mechanically Because of this, the battery backup need not be very large and indeed may be located within the housing 16. This provides an additional advantage of preventing the cutting of the connection between the battery backup and the lock mechanism by someone in an attempt to prevent the lock mechanism from being reset .

The described lock mechanism thus provides a means whereby a bolt member can be moved between its engaged and disengaged positions either electrically or mechanically while the moveable member, such as a door, is in a closed position. Furthermore, the lock mechanism may be either surface mounted or forend mounted.

Claims

1. A lock mechanism for fixing to a movable member or frame for locking said movable member in a closed position in said frame, the lock mechanism comprising a bolt member movable between a disengaged position and an engaged position for engagement with said frame or moveable member; a restraining mechanism to engage and restrain said bolt member when said bolt member is in said disengaged position; status detecting means for detecting when said moveable member is in a closed position in said frame, said status detecting means being coupled to said restraining mechanism to cause said restraining mechanism to release the restraint on said bolt member when said closed position is detected; electrical drive means moveable between a closed position and an open position to drive said bolt member into said disengaged position and to hold said bolt member in said disengaged position; and bolt biasing means to urge said bolt member into said engaged position and to hold said bolt member in said engaged position when said electrical drive means moves to said closed position and said restraining mechanism releases the restraint on said bolt member.

2. A lock mechanism as claimed in Claim 1, wherein said status detecting means is coupled to said restraining mechanism electrically and is adapted to generate a signal indicative of the status of said moveable member when said moveable member is in a closed position in said frame.

3. A lock mechanism as claimed in Claim 1, wherein said status detecting means is coupled to said restraining mechanism by a mechanical linkage.

4. A lock mechanism as claimed in Claim 1 or Claim 3 , wherein said status detecting means comprises a restraint drive means coupled to said restraining mechanism and adapted to engage with said frame or said moveable member when said moveable member is in a closed position in said frame to drive said restraining mechanism to release the restraint on said bolt member.

5. A lock mechanism as claimed in Claim 1 or either of Claims 3 or 4, wherein said restraint drive means comprises a driving member moveable translationally between an engaged position when said driving member is engaged with said frame or said moveable member and a disengaged position, said driving member having roller means at an end thereof which engages with said frame or said moveable member and which is arranged to have an axis of rotation perpendicular to the direction of movement of said driving member and parallel to a direction of insertion of said moveable member into said frame as said moveable member is moved to said closed position.

6. A lock mechanism as claimed in any preceding claim and comprising manual override means moveable in a first direction to drive said bolt member into said disengaged position from said engaged position and to decouple said status detecting means from said restraining mechanism, and moveable in a second direction to drive said restraining mechanism to release the restraint on said bolt member and to re- couple said status detecting means to said restraining mechanism, said manual override means being adapted to be operative only when said electrical drive means is in said closed position.

7 A lock mechanism as claimed m Claim 6, wherein said manual override means comprises a cam rotatable about an axis by manual force m said first and second directions .

8. A lock mechanism as claimed in Claim 7, wherein said cam has a slot on said axis, the lock mechanism including a key assembly having a tang extending therefrom mto said slot, said tang being rotatable by manual operation of an appropriate key when inserted into said key assembly

9. A lock mechanism as claimed m Claim 7 or Claim 8, wherein said cam has a recess for receiving a lever for manual rotation of said cam m said first and second directions.

10 A lock mechanism as claimed n any of Claims 6 to 9, wherem said restraint mechanism comprises a restraint member connected to a bistable, said bistable having an electrically driven position in which sa d bistable provides coupling between said restraint member and said status detecting means, and a manually driven position in which said restraint member is decoupled from said status detecting means.

11 A lock mechanism as claimed m Claim 10, wherein said bolt member has a shoulder for engagement with said restraint member and said restraint mechanism including a pivot, said restraint member bemg pivotably mounted on said pivot and pivotable between a restraining position in which said restraint member engages said shoulder and a releasing position

12. A lock mechanism as claimed in Claim 11, wherein said restraint mechanism includes biasing means to urge said restraint member into said restraining position, said restraint member having a first arm member for engaging with said shoulder of said bolt member and positioned on one side of said pivot, and a second arm member comprising a release member on the other side of said pivot to said first arm member.

13. A lock mechanism as claimed in Claim 10, wherein said restraint mechanism includes biasing means to bias said restraint member towards engagement with said bolt member for restraint of said bolt member when said bolt member is in said disengaged position, and a release member for engagement by said manual override means when driven in said second direction to release the restraint on said bolt member.

14. A lock mechanism as claimed in any of Claims 10 to 13, wherein said bistable is moveable by said manual override means from said electrically driven position to said manually driven position.

15. A lock mechanism as claimed in any of Claims 10 to 14 , wherein said restraint member has a second pivot point mounted thereon, said bistable being pivotably mounted on said second pivot point and pivotable between said electrically driven position and said manually driven position.

16. A lock mechanism as claimed in any of Claims 10 to 15, wherein said bistable includes a first pin for engagement with said status detecting means to couple said status detecting means and said restraining mechanism when said bistable is m said electrically driven position and a second coupling pin for engagement with said manual override means to move said bistable to said manually driven position as said manual override means is moved in said first direction.

17. A lock mechanism as claimed in any of Claims 10 to 16, wherein said bistable is biased towards said electrically driven position and includes a member for engagement by a latch mechanism to hold said bistable in said manually driven position.

18. A lock mechanism as claimed in Claim 17, wherein said latch mechanism is adapted to release said bistable as said electrical drive means moves between said open and closed positions.

19. A lock mechanism as claimed in any preceding claim, wherein said bolt member is moved translationally between said engaged and disengaged positions.

20. A lock mechanism as claimed in Claim 19, wherein an end of said bolt member which engages with said frame or said moveable member is provided with roller means having an axis of rotation perpendicular to the direction of movement of said bolt member and parallel to a direction of insertion of said moveable member into said frame as said moveable member is moved to said closed position.

21. A lock mechanism as claimed in any preceding claim and including an end force latch connected to said bolt member to engage said electrical drive means when said bolt member is in said engaged position to prevent said bolt member being moved from said engaged position to said disengaged position by the application of force to an end of the bolt member protruding from the lock mechanism.

22. A lock mechanism as claimed in any preceding claim, wherein said bolt member has a drive face facing the direction of engagement of said bolt member and said electrical drive means comprises an electric motor coupled to a shaft, said shaft carrying a drive arm arranged to engage said drive face of said bolt member to drive said bolt member from said engaged position to said disengaged position as said shaft rotates.

23. A lock mechanism as claimed in Claim 22, wherein said drive arm includes roller means arranged to rotate about an axis parallel to the axis of rotation of said shaft .

24. A lock mechanism as claimed in Claim 22 or Claim 23 wherein said drive arm is arranged to rotate through a half turn to drive said bolt member between said engaged position and said disengaged position.

25. A lock mechanism as claimed in any of Claims 22 to 24, wherein said electrical drive means includes a gear box arranged between said shaft and said electric motor to reduce the rotation rate of said shaft relative to said electric motor.

26. A lock mechanism as claimed in any of claims 22 to 25, wherein said electrical drive means is coupled to said status detecting means and is adapted to rotate said shaft in a first direction when said moveable member is in a closed position in said frame and in a second direction when it is not .

27. A lock mechanism as claimed in any of Claims 22 to 26, wherein said drive arm includes engagement means for rotation into engagement with said restraining mechanism to release the restraint on said bolt member.

28. A lock mechanism as claimed in Claim 27, wherein said engagement means is adapted to engage said restraining mechanism to release the restraint on said bolt member when said shaft is rotated in one direction and to collapse under said restraining mechanism and not cause the restraining mechanism to release the restraint on said bolt member when said shaft is rotated in the other direction.

29. A lock mechanism as claimed in any preceding claim and including an electric switch arrangement to monitor the position of said bolt member and provide a bolt member position signal.

30. A lock mechanism as claimed in any preceding claim and including a second electric switch arrangement to monitor the state of said electrical drive means and provide an electric drive status signal.

31. A lock mechanism as claimed in Claim 4 and including a third electric switch arrangement to monitor the position of said restraint drive means and to provide a restraint drive position signal.

32. A lock mechanism in accordance with any preceding claim in combination with a socket plate, the socket plate including a ramp for engagement with said status detecting means.

33. A lock mechanism in accordance with any of Claims 1 to 31 in combination with a socket plate, the socket plate including a recess for the receipt of an end of said bolt member when said bolt member is in said engaged position, said recess being in part defined by one or more side walls extending perpendicular to the direction of movement of said bolt member and parallel to a direction of insertion of said moveable member into said frame as said moveable member is moved to said closed position.