US3125365A

US3125365A - eigelbach

Info

Publication number: US3125365A
Authority: US
Publication date: 1964-03-17
Anticipated expiration: 1981-03-17

Description

March 17, 1964 R. c. YEIGELBACH DODR LATCH MECHANISM Filed Sept. 5, 1961 3 Sheets-Sheet 1 INVENTOR. RAY C. E l GELBACH H \S ATTORNEY March 17, 1964 R. c. EIGELBACH noon LATCH MECHANISM 3 Sheets-Sheet 2 Filed Sept. 5, 1961 INVENTOR. RAY C. ElGELBAC-H BY g PIC-5.5

H l5 ATTORNEY March 1954 R. c. EIGELBACH 3,125,365

DOOR LATCH MECHANISM Filed Sept. 5, 1961 3 Sheets-Sheet 3 INVENTOR. RAY C. El GELBAC H orm HIS ATTORNEY United States Patent 3,125,365 DGOR LATCH MECHANISM Ray C. Eigelbach, Louisville, Ky., assignor to General Electric Company, a corporation of New York Filed Sept. 5, 1961, Ser. No. 135,876 5 Claims. (Cl. 292-7) The present invention relates to a door latch mechanism for holding a hinged door in a tightly locked position. Such doors are sometimes referred to as the selfsealing type, i.e., doors which are so designed that during the final stages of their closing movement they engage with a yieldable sealing means or gasket.

This invention was conceived during the development of a new concept in baking ovens for domestic use wherein the interior oven walls may be cleaned automatically by a high temperature cleaning cycle. Such a high temperature oven is described in an earlier co-pending application of Bohdan Hurko, Serial No. 27,926, filed May 9, 1960, and now abandoned in favor of a continuation-inpart application Serial No. 244,493 filed on December 13, 1962 which application is also assigned to the General Electric Company, the assigneeof the present invention. The food soil and grease spatter that accumulates on the oven walls may be completely removed automatically by raising the temperature of the oven to a heat cleaning temperature within the range of about 750 F. to 950 F. so as to burn off all foreign matter from the oven walls. In such a high temperature oven it is of primary importance to latch the door before the cleaning cycle is set in motion so that the door cannot be opened during the heat cleaning cycle. 'It is also important to seal the door so that there is only a small amount of smoke, odors, and heat escaping from the oven while the food soil is being burned from the oven liner. The oven cont-r01 circutis are so designed that the heat cleaning cycle cannot be initiated until the door latch mechanism has clamped the door in its sealed position.

The primary object of the present invention is to provide a simplified latch mechanism that is of compact size for mounting in a recessed position in a door frame, where the latching means has a swinging motion which operates in a single plane for pulling the door tightly closed.

A further object of the present invention is to provide a novel door latch mechanism which is easy to operate and made of few parts, and which cannot be fully locked unless the door is in a closed position to be engaged by the mechanism.

The present invention, in accordance with one form thereof, embodies a novel latch mechanism for a hinged door. The mechanism is adapted to be mounted in the door frame adjacent the distal edge of the door. While I have elected to illustrate the invention as it would be used on a front-opening dropdoor of a domestic oven, it will readily be apparent to those skilled in this art that such a mechanism has general utility in the latch art and. it may be so used wherever it is found advantageous. The latch mechanism includes a mounting bracket and a pair of crank arms pivotally connected to the mounting bracket. A hook member in turn is pivotally connected to each crank arm, and link means join the two hook members so that the hook members are capable of a swinging action in a common plane. The hooks are retracted into the door frame when the door is unlocked, and they swing out of the door frame and into engagement with the door when a locking action is desired. A handle member cooperates with the link means and extends outwardly of the door frame to be available for manual operation. Biasi'ng means is used for urging the crank arms to remain in position until the hook members engage the door. After the engagement takes place, the crank arms tend to swing away from the door so that the hook members tightly clamp the door shut. Another feature which may be of importance in some applications is a stop means engageable with the link means in the event the door is not closed when the latch mechanism is being operated to a locked position. In this event the latch mechanism is prevented from being fully closed for reasons which will be fully explained hereinafter.

My invention will be better understood from the following description taken in conjunction with the accompanying drawings and its scope will be pointed out in the appending claims.

FIGURE 1 is a right side elevational view of a freestanding range having a door latch mechanism embodying the present invent-ion;

FIGURE 2 is a fragmentary plan view partly in crosssection taken along the line -22 of FIGURE 1 and showing the latch mechanism in its open position disengaged from the oven door which would be its position during normal cooking operations;

FIGURE 3 is a plan view similar to that of FIGURE 2 with the latch mechanism in its fully locked position;

FIGURE 4 is a fragmentary cross-sectional elevational view of the latch mechanism in the unlocked position taken on the line 44 of FIGURE 2;

FIGURE 5 is a fragmentary elevational view taken on the line 5- 5 of FIGURE 2 of the solenoid operated interlock mechanism that is associated with the latch mechanism;

FIGURE 6 is a fragmentary plan view of a portion of the latch mechanism showing its position in the middle of the closing operation when the oven door is closed;

FIGURE 7 is a plan view similar to that of FIGURE 6 showing a different effect in the event the oven door is not in a closed position when the latch is being moved to a locked position;

FIGURE 8 is a partial diagram of the power control circuit for the heating elements of an oven with which this novel latch mechanism may be used.

Turning now to a consideration of the drawings and in particular to FIGURE 1, there is shown for illustrative purposes a free-standing electric range 16 having a top cooking surface 11 with a plurality of surface heating elements 12, an oven cavity '13, a front-opening drop-door 14, and a backsplasher -15 arranged along the back edge of the cooking surface 11 and containing a control panel (not shown) which governs the energization of the various heating elements of the range. Speaking of the heating elements, the oven cavity 13 includes the two standard electric heating elements; namely, the lower bake unit 16 arranged in the bottom of the oven cavity and the upper broil unit 17 which is arranged under the top wall of the oven cavity. As mentioned previously, this invention of a novel latch mechanism has been found of primary importance when used with a heat cleaning oven of the type disclosed in the aforementioned application of Bohdan Hurko. In such a heat cleaning oven there is a third heating element or mullion heater 18 that is located near the front opening of the oven cavity for compensating for the loss of heat through and around the door opening. This mullion heater 18 may best be seen in FIGURE 4. It is a type of heating element that has a helical resistance element encased in a high temperature insulating material such as magnesium oxide, and which in turn is covered with a metal sheath or jacket.

The oven cavity 13 is formed by an oven liner 19 of box-like construction with an open front that is adapted to be closed by the oven door 14. Since this oven is designed for high temperature usage in the vicinity of 750 F. and 950 F., the door 14 is of special construction with good thermal insulating properties to reduce the amount of heat conduction therethrough. Also, resilient gaskets and 21 are positioned between the door and body of the oven to control the amount of smoke, odors and heat which may pass through the door gap and cool the oven while overheating the kitchen. A suitable heat insulating material 22 such as fiberglass or the like is packed around the outside of the oven liner 19 to prevent the outer surfaces of the range from becoming overheated and avoid the possibility of painful burns for the housewife. The maximum allowable temperature for the outer surfaces of a range, that is currently permitted by the Underwriters Laboratory Inc., as a safe external temperature is 194 F. Of course, if during tests the surface temperature rises above this amount the range is rejected and Underwriters approval is withheld and the outcome is that such a range cannot be sold in many states of the country in the absence of U.L. approval.

There is an important advantage in designing a door latch mechanism which is adapted to be mounted in the range body or door frame rather than in the door structure. When the latch mechanism is in the range body it can be mounted above the insulation 22 so that it is protected from the high temperature of the oven liner. The door is relatively thin and would provide little heat protection for the latch as compared with the available space under the cooktop 11 so that the latch mechanism as shown may occupy a large area but be of extremely simple design.

Looking at the top plan view of FIGURE 2, the latch mechanism is identified as element 25 and it will be recognized that it has an overall configuration of a letter T turned on its left side. The head of the T is represented by an elongated mounting bracket 26, while the base or shank of the T is formed by an elongated mounting plate 27 which extends from the front edge of the range body to the back edge where it is supported on a back panel 32 of the oven as is best seen in the dotted line showing in FIGURE 1. The mounting bracket 26 is of generally C-shape or channel shape in side view as best seen in FIGURE 4, and it has a bottom flange 23, a vertical wall 29, and a top flange 30. A fastening screw 31 is threaded down through a surface of the range body and into the top flange 30. At the other end of the latch mechanism the mounting plate 27 extends through and is supported in a small opening in a back panel 32 of the range as is best seen in FIGURE 1.

Turning back to FIGURE 2, the latch mechanism must be provided with means for engaging the door 14 so that the door may be pulled against its

gaskets

20 and 21 to seal the door against the door frame or range body. This engaging means is represented by a pair of

hook members

35 and 36 which lie within a common horizontal plane and are positioned behind small openings or windows 37 in both the front wall of the door frame and the vertical wall 29 of the mounting bracket 26 so the hook members may swing through the windows and engage slots 38 or keepers formed on the inner surface of the door 14. The

hook members

35 and 36 are not mounted on fixed pivots, but instead are each mounted on a

separate crank arm

39 and 40 respectively which is of generally Z-shape. As seen in FIGURE 4 at 40 the lower arm of the Z is pivotally fastened to the bottom flange 28 of the mounting bracket while the upper arm of the Z is offset sidewise from the first arm and extends vertically upward for pivotally receiving the hook member 36. Each

hook member

35 and 36 is stamped from thin metal stock and it gains stability on the crank arm by having a foldedover bearing portion 41 which establishes a pair of vertically spaced bearing surfaces that are rotatably supported about the upper arm of the crank. It is necessary to join the two hook members together so that they act in unison. This is accomplished by providing each hook with an angular extension 45 which is on the side of the pivot point of the hook member that is opposite the door engaging portion. A link member 46 is pivoted to the drawings.

extension 45 of the hook member 35, while a link member 47 is likewise pivoted to the hook member 36. These two

link members

46 and 47 are in turn pivotally joined together adjacent the center of the mechanism by a common pin 43.

Next it is imperative to have an external manual control for actuating the latch mechanism. This need is met by a sliding handle 50 which extends through a suitable elongated slot in the front face of the range body and directly beneath the cooktop 11. The handle is attached at its innermost end to a handle extension 51 that is pivotally supported from the mounting bracket 26 as by the pivot pin 52. The handle extension 51 is a channel-shaped member which is fastened at its top flange to the handle 50 and is pivotally attached at its bottom flange to the mounting bracket 26. This transition is necessary because the handle is located above the mounting bracket and of course above the hook members and links conmeeting the hook members. Moreover, the bottom flange of the handle extension 51 is pivotally connected to the pin 4-8 that joins the two

links

46 and 47. This completes the linkage between the handle 50 and the

hook members

35 and 36 by means of the handle extension 51 and the

link members

46 and 47.

Limit means in the form of a pair of lanced tabs 53 are struck up from the top flange 30 of the mounting bracket to restrict the angular movement of the handle 50 and definitely establish the two extreme positions of the handle. Another pair of lanced tabs 54 are struck upwardly from the lower flange 28 of the mounting bracket to serve as a limit means for both crank

arms

39 and 40 when they are in the position shown in FIGURE 2. It should be noted in the unlatched position of this figure that each crank arm is normally held against a tab 54 by a tension spring 55. The spring means 55 tend to retain the crank arms against the limit means 54 as the handle is first moved toward the closed position, and the crank arms remain in this position until the hook members engage in the slots 38 of the door at which time the crank arms tend to pivot clockwise in FIGURE 2 about their lower arms that extend through the mounting bracket. Then the crank arms shift away from the door thereby tending to withdraw the hook members back into the door frame and serving to pull the door tightly against the door gaskets 2t) and 21 to seal the door in place. In other words, the movement of the hook members has two phases; namely, a first phase where each hook member pivots about the upper arm of its supporting crank arm, and a second phase whereby the crank arm shifts to bodily retract the hook member once the hook engages the door. An overcenter spring 56 is also fastened to the handle extension 51 and attached at its opposite end to the mounting bracket as at 57 in FIGURE 4 so that a positive force is necessary to shift the handle from one extreme position to the other.

Looking at FIGURE 3 where the latch mechanism is shown in its fully locked position it is well to note that the crank

arms

39 and 40 have swung clockwise so that they are overcenter. Hence any pulling force on the door handle would merely tend to increase the latching force and thereby insure that the door could not be opened when the latch is locked.

One of the objectives of this invention is to provide a safety feature whereby the latch mechanism cannot be fully locked if the door is not in its closed position to be engaged by the hook members. This feature can be best understood by referring to FIGURES 6 and 7 of the FIGURE 6 shows the latch mechanism where the handle is in a midway position and the hook member 36 has engaged in the keeper 38 of the door 14. Now looking at FIGURE 7 it is clear that the door is not shown because it is in its open position away from the door frame. Again the handle is in a mid-position between fully open and fully closed but the hook member 36 is unable to engage the door so that it continues to pivot about the crank arm 41) and the crank arm does not shift clockwise as heretofore. Further movement of the handle is prevented by the interengagement of a fixed stop means 60 in the form of a lanced tab which cooperates with an extension 61 of the link 47-. This link extension 61 has a bifurcated end 62 which slips over the tab 60 as seen in FIGURE 7 if the door is open when the latch mechanism is operated to latch the door. It should be apparent that this jamming feature does not come into action if the door is present because the crank arms tend to shift away from the door when the

hook members

35 and 36 engage the keepers of the door. When this shifting action takes place the link member 47 likewise moves away from the door and the link extension 61 easily slides past the stop tab 60 as is best seen in FIG- URE 3.

The avowed purpose of the door latch mechanism is to insure that the heat cleaning cycle cannot be set in motion unless the door is first latched shut. Hence, the latch mechanism must be connected into the control circuit in such a way that the latch mechanism must be in its locked position before the three oven heating elements may be energized. This prerequisite is supplied by a solenoid-operated interlock mechanism (see FIGURES 3 and 5) that includes a pair of

switches

65 and 66 which are located on the back end of the mounting plate 27 to lie Within the air channel and wiring cavity behind the back plate 32 of the oven as seen in FIGURE 1. The latch mechanism 25 includes an elongated switch arm 67 tht is pivoted 'at one end to the handle extension 51 and is guided in its movement at its opposite end by a pin and slot connection 68 between the switch arm 67 and the mounting plate 27. Accordingly, it will be understood that as the handle 50 moves from one extreme position to the other the switch arm 67 will reciprocate from the retracted position of FIGURE 2 to the extended position of FIGURE 3. As best seen in FIGURE 5, the door latch switch 65 consists of a pair of

switch contact blades

69 and 70 which are disposed one above the other in two horizontal planes. The

contact blades

69 and 70 are supported from a stack of insulating washers 71. The uppermost contact blade 70 is the movable contact and its movement is governed by an integral upwardly extending cam 72 which extends through the mounting plate 27 and into the path of movement of the switch arm 67. As is seen in FIGURE 3, the switch arm 67 has ridden over the cam 72 of the switch 65 thereby closing the circuit between

blades

69 and 70.

Cooperating with the latch lock switch 66 is a solenoid 73 which is located over the switch and fastened to the mounting plate 27. The solenoid includes an armature 74 that cooperates with a trip lever 75 that is pivoted adiacent its top to a stationary frame 76 that forms part of the solenoid structure. The connection between the armature and the trip lever 75 is by way of a pin and slot connection 77. The action of the solenoid is to pull in the armature when the solenoid is energized thereby swinging the trip lever 75 inwardly toward the edge of the switch arm 67. Notice in FIGURE 2 that the edge of the switch arm 67 includes a notch 78. The function of the trip lever 75 is to serve as a switch actuator to close the contacts of switch 66, but this cannot be done until the notch 78 of the switch arm 67 is aligned with the trip lever 75 and this occurs only when the latch mechanism is fully locked. Looking again at FIGURE 5, the switch 66 comprises two

switch contact blades

79 and 80 which are supported from a stack of insulating washers (not shown) similar to those of switch 65. These

contact blades

79 and 80 are arranged parallel to each other and are shown as lying in planes that are perpendicular to to the sheet of the drwing which includes FIGURE 5. Cooperating with contact blade 79 is cam member 81 which underlies the mounting plate 27 and is in the path of movement of the trip lever 75. It should be understood that the trip lever 75 extends through a slot in the 6 mounting plate for engagement with the cam 81 of the switch 66. Once the switch 66 is closed the oven heating elements 16-, 17 and 18 are energized and the heat cleaning cycle is commenced.

Finally, attention will be given to the circuit diagram of FIGURE 8 for a brief description of some of the electrical components of the system. First, there is a three wire 240 volt AC. power supply for the range 10 which includes power lines L1 and L2 and a neutral line N. An oven switch 85 is connected to the neutral line N and lines L1 and L2 by means of

terminals

86, 87 and 88 respectively. The oven switch 85 is likewise connected to the

oven heating elements

16, 17 and 18 by lead 89 connected to the bake unit 16, and lead 90 connected to the series connection of the broil unit 17 and the mullion heater 18. The heating elements are connected back to neutral by lead 91 by means of three sets of

relay contacts

92, 93 and 94 which are operated in unison by relay 95. Thus during the heat cleaning cycle the

relay contacts

92, 93 and 94 are closed and the bake and broil units are connected in a parallel circuit while the mullion heater is operated in a series circuit with both the bake and broil units. In this particular circuit diagram the length of the heat cleaning cycle is governed by a conventional oven timer mechanism (not shown) that has timer contacts 96 which are connected across line L1 and neutral through the oven switch 85 and lead 97 to a transformer 98 and then back to the lead 91 that is connected to neutral. Accordingly, the timer is one of the controls that must be set in order to initiate the heat cleaning cycle. The transformer 98 supplies power to a low voltage temperature controlling circuit (not shown) which includes a tem perature actuating responder for governing the degree of oven temperature to insure that it does not rise above a maximum limit of about 950 F. Such a responder is part of a combination that includes an oven thermostat (not shown) which is used both during normal cooking operations as well as during the heat cleaning cycle.

The solenoid 73 which had been previously mentioned as part of a solenoid operated interlock mechanism cooperating with the switch arm 67 of the door latch mechanism is illustrated in the wiring diagram of FIGURE 8 as connected to the oven switch 85 through lead 89, and through door latch switch 65 and lead 99 that is joined with terminal 100 of the oven switch. This creates a circuit between the neutral and line L1 when both the timer contacts 96 and the door latch switch 65 are closed. The relay is connected by lead 101 through the contacts of latch lock switch 66 and lead 102 to line L2, and by lead 103 to lead 91 that is connected to neutral.

The operation of this circuit during the setting of the controls to initiate the heat cleaning cycle is as follows:

(1) Oven switch 85 is first set to the heat cleaning position.

(2) Thermostat (not shown) is likewise set to the heat cleaning position.

('3) Oven timer is set to the proper length of the clean ing cycle; for example, one hour.

(4) Door latch mechanism 25 is locked and door is sealed thereby closing the contacts of the door latch switch 65. This energizes the transformer 98 and the solenoid 73 causing the trip lever 75 to close the contacts of the latch lock switch 66, which in turn energizes the relay 95 and closes the

relay contacts

92, 93 and 94 thereby energizing the

oven heating elements

16, 17 and 18. Thus the heat cleaning cycle is started and will continue until the timer contacts 96 are opened either by the completion of the timed cycle or by manual manipulation of the timer. A suitable thermal interlock could be provided to insure that once the heat cleaning cycle were terminated the door latch mechanism could not be unlocked until the oven temperature dropped to a safe degree to provide freedom from burns. Such a thermal 7 interlock forms no part of the present invention therefore it is not being disclosed in detail.

Modifications of this invention will occur to those skilled in this art and it is to be understood, therefore, that this invention is not limited to the particular embodiments disclosed but that it is intended to cover all modifications which are within the true spirit and scope of this invention as claimed.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A latch mechanism adapted for looking a door, a door and a door frame where the door is hinged ly mounted to the door frame along one edge thereof, said mechanism comprising a mounting bracket which is supported from the door frame adjacent the distal edge of the door, a pair of crank arms pivotally connected to the mounting bracket, a hook member pivotally supported from each crank arm, link means joining the two hook members, and a handle member cooperating with the link means and adapted for pivoting the hook members into and out of engagement with the door, the hook members being in a plane that lies parallel to the distal edge of the door, said latch mechanism being recessed within the door frame so as to be hidden when the handle member is in the unlatched position, and spring means for biasing the crank arms to remain in position until the hook members engage the door, after which the crank arms tend to shift away from the door so that the hook members tightly clamp the door shut.

2. A latch mechanism adapted for looking a door, a door and a door frame where the door is hingedly mounted to the door frame along one edge thereof, said latch mechanism having a mounting bracket which is supported from the door frame adjacent the distal edge of the door, a pair of crank arms pivotally connected to the mounting bracket, a hook member pivotally connected to each crank arm, link means joining the two hook members, a handle member connected to the link means for shifting the hook members into and out of engagement with the door, the hook members lying in a plane that is parallel to the distal edge of the door, said latch mechanism being recessed within the door frame so as to be hidden when the handle member is in the unlatched position, and spring means for biasing the crank arms to remain in position until the hook members engage the door, after which the crank arms shift in a direction away from the door so that the hook members pull the door into a tightly clamped position, resilient gasket means sandwiched between the door and door frame when the door is in its closed position, said crank arms shifting overcenter in the fully locked posi tion and applying a compressive force to the gasket means, said overcenter relationship being related to the pivotal support axis of each crank arm and the outward force applied by the gasket means against the door, said gasket means tending to retain the crank arms in an overcenter locked position so that only the movement of the handle member will unlock the door.

3. A latch mechanism as recited in claim 2 with the addition of fixed stop means to obstruct the complete movement of the -latch handle if the door is not in a closed position when the hook members swing outwardly of the door frame to engage the door.

4. A latch mechanism as recited in claim 1 wherein the link means comprises a link member pivotally connected to each hook member and hinged together adjacent the center of the mechanism between the two hook members, the handle being located above the latch mechanism and joined indirectly to the hinged connection means of the two link members through a handle extension that is itself pivotally fastened to the mounting bracket at a point offset inwardly from the door and link members.

5. A latch mechanism adapted for locking a door, a door and a door frame where the door is hingedly mounted to the door frame along one edge thereof, said latch mechanism having a mounting bracket which is supported from the door frame adjacent the distal edge of the door, a pair of crank arms pivotally connected to the mounting bracket, a hook member pivotally' supported from each crank arm, link means joining the two hook members, a handle member connected to the link means for shifting the hook members into and out of engagement with the door, the hook members lying in a plane that is parallel to the distal edge of the door, said latch mechanism being recessed within the door frame so as to be hidden when the handle member is in the unlatched position, and spring means for biasing the crank arms to remain in one position until the hook members are caused to swing outwardly and engage the door, once the hook members reach the door the crank arms shift about their pivotal support axis thereby retracting the hook members back into the door frame, a fixed stop means provided on the mounting bracket, said link means connecting the hook members including an extension portion which will become engaged with the fixed stop means if the handle member is moved toward the latched position without the door being closed, said extension being shifted to avoid the fixed stop means when the hook members engage the door and the crank arms are caused to shift against the bias of the spring means and move in a direction away from the door.

References Cited in the file of this patent UNITED STATES PATENTS 2,274,711 Krause Mar. 3, 1942 2,378,654 Pekny June 19, 1945 2,954,252 Carpenter Sept. 27, 1960 2,955,861 Claud-Mantle Oct. 11, 1960

Claims

1. A LATCH MECHANISM ADAPTED FOR LOCKING A DOOR, A DOOR AND A DOOR FRAME WHERE THE DOOR IS HINGEDLY MOUNTED TO THE DOOR FRAME ALONG ONE EDGE THEREOF, SAID MECHANISM COMPRISING A MOUNTING BRACKET WHICH IS SUPPORTED FROM THE DOOR FRAME ADJACENT THE DISTAL EDGE OF THE DOOR, A PAIR OF CRANK ARMS PIVOTALLY CONNECTED TO THE MOUNTING BRACKET, A HOOK MEMBER PIVOTALLY SUPPORTED FROM EACH CRANK ARM, LINK MEANS JOINING THE TWO HOOK MEMBERS, AND A HANDLE MEMBER COOPERATING WITH THE LINK MEANS AND ADAPTED FOR PIVOTING THE HOOK MEMBERS INTO AND OUT OF ENGAGEMENT WITH THE DOOR, THE HOOK MEMBERS BEING IN A PLANE THAT LIES PARALLEL TO THE DISTAL EDGE OF THE DOOR, SAID LATCH MECHANISM BEING RECESSED WITHIN THE DOOR FRAME SO AS TO BE HIDDEN WHEN THE HANDLE MEMBER IS IN THE UNLATCHED POSITION, AND SPRING MEANS FOR BIASING THE CRANK ARMS TO REMAIN IN POSITION UNTIL THE HOOK MEMBERS ENGAGE THE DOOR, AFTER WHICH THE CRANK ARMS TEND TO SHIFT AWAY FROM THE DOOR SO THAT THE HOOK MEMBERS TIGHTLY CLAMP THE DOOR SHUT.