WO1989011435A1

WO1989011435A1 - A crane

Info

Publication number: WO1989011435A1
Application number: PCT/SE1989/000274
Authority: WO
Inventors: Lars Bohman
Original assignee: Lars Bohman
Priority date: 1988-05-24
Filing date: 1989-05-18
Publication date: 1989-11-30
Also published as: SE8801916D0; SE463453B; SE8801916L

Abstract

A crane comprises a first arm (8) pivotably arranged on a frame (2) about a substantially horizontal axis (9), a second arm (12) pivotably arranged on the first one about a substantially horizontal axis (11), a load (27), for example a tool, being intended to be carried by the second arm, and an arrangement for maintaining the arms (8, 12) in desired relative positions with respect to the frame (2) and each other. The arrangement comprises connecting members (14, 19) connecting each arm to a bearing arrangement (17, 18) arranged to bear upon and be displaceable along a support surface (7') on the frame (2), so that in every position assumed by the arms the torques generated by the forces emanating from the weights of the load and the arms with respect to the two pivot axes (9, 11) mentioned above are balancing each other.

Description

A crane

FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a crane according to t preamble of the appended claim 1.

The conception crane is here intended to comprise all kinds devices for moving loads between two points, and these poin may be located in the same or in different horizontal planes.

Cranes of this kind may be utilized within a great number different fields, of which moving tools and other objects ov a working place, such as an engineering work shop, will described here so as to illustrated but in no way delimit th invention.

The most common cranes for moving loads over and within working place do not not completely correspond to the preambl of claim 1, but they must nevertheless be considered to consti tute the prior art in this field. One type of such cranes has frame and an arm usually rigidly fastened thereon and extendin substantially horizontal, along which arm a carriage means ma be driven by influence of power. A load carrying means, such a a steel wire with for instance a hooking member, hangs in th carriage means. The frame may be turnably arranged on a stan about a substantially vertical axis, so that at all points i the room within the circle, the radius of which is formed b the arm, may be reached. The greatest disadvantage of thi crane consists in that it through its arm continuously project far in the room, even if the load to be moved is located ver close to the frame of the crane, and it is therefore perhap in the way for other works or transports of other objects utilized in carrying out a certain work. Additionally, th torques on the frame may be high and the latter must b properly reinforced.

Another type of cranes with this field of use has a frame rotatably arranged about a substantially vertical axis, o which frame a first arm extending substantially horizontally is secured. This first arm is terminated by a bearing with substantially vertical center axis, in which one end of a second arm extending also substantially horizontally is ar ranged. Through the turnability of the frame and by that of the first arm about a first substantially vertical axis and a second arm in the bearing of the first arm about a secon substantially vertical axis, it is possible to reach all points located within a distance equal to the combined length of the two arms from the frame. A load carrying member is arranged on the extremity of the second arm. This crane has considerable disadvantages. Firstly, said bearing has to have small tole¬ rances, so that no play and by that difficulties in pivoting the two arms with respect to each other shall be established, whereby the manufacturing costs may increase considerably. Secondly, it can after a certain period of use not be avoided that torques caused by loads carried on the extremity of the second arm upon said bearing lead to plays in the same. This results in bitings and irregular operating of the crane. It should be noticed that irrespectively how close to the frame the load is carried, the moment arm exerted by the load on s bearing is always equal to the length of the second a However, an advantage of this crane with respect to the previously described is the possibility to fold it together a substantially shorter extension in the horizontal direct than in its maximally extended position, when it is not used transports load close to its frame.

It would in fact be possible to use a crane designed accordi to the preamble of the appended claim 1 in order to rem these drawbacks, since such a crane never has to extend mo distant from the frame than the load carried is located fr the same and no problems with plays in any vertical bearing present, but utilizing a crane designed in that way for the purposes has been stopped because of several difficulties get the two arms to assume stable relative positions, since load carried by the second arm in such cranes tends to swi the load carrying end of the second arm and also the end of t first arm applied to the second arm inwardly towards the fra of the crane. It has been necessary to arrange different typ of power means acting either between the frame and the fir arm and between the first and the second arm or between t frame and the second arm, in order to avoid such swinging. Su power means complicate the function of the crane substantial and make the manufacturing costs of the crane considerab higher. Another disadvantage consists in that the breaki forces on the arms and the frame of the crane are getti important.

BRIEF DESCRIPTION OF THE INVENTION

The object of the present invention is to provide a crane n having the drawbacks of the cranes described above.

This object is obtained according to the invention by providi a crane of the kind described in the introduction with t features defined in the characterizing part of the appende claim 1.

Thus, the advantages associated with the crane type lastl disclosed has been utilized through the invention while solvin the problems caused by the torques about the substantiall horizontal axis of the crane, without utilizing any form o power means. To the extent that the weight of the load carrie and the dimensions of the crane according to the inventio permit this, the relative position between the two arms of th crane and between these and the frame, i.e. the position of th load, could in practice be changed by hand by pushing o pulling the load or the second arm in the desired direction Owing to the fact that different types of power means fo maintaining the arms in desired relative positions with respec to the frame and to each other in accordance with the inventio have been replaced by connecting members connecting each ar with a bearing arrangement, which is arranged to bear upon an be displaceable along a support surface of the frame, self-braking crane could be achieved, which is stably main tained in each working position thanks to the fact that th torques about on one hand the pivot center of the first arm o the frame and on the other hand the pivot center of the firs arm on the second arm are continuously balanced.

Further advantages and preferred features of the invention wil appear from the detailed description of a preferred embodimen of the invention following below as well as the appende claims.

A particularly advantageous embodiment of the invention i defined in claim 7. When the connecting members together wit the two arms of the crane form a parallel linkage and th distances between the different substantially horizontal pivo axes of the crane are dimensioned in the particular way define in claim 6 and 7, it is possible to move a load between point located at the same height, without raising or lowering t load by means of any lifting means arranged on the second ar and thanks to the self-braking function of the crane, stab resting positions may immediately be assumed in these arbitra points. As a result of this tools, such as welding machine may in a simple way be brought between different stations places of a working place under continuous maintaining of certain altitude.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows specific description of a preferred embodiment according to t invention cited as an example.

In the drawings:

Fig 1 is a perspective front view obliquely from above of first preferred embodiment of the crane according to t invention,

Fig 2 is an enlarged perspective rear view of a portion of t crane in Fig 1 with some parts broken away for clarity,

Fig 3 is an enlarged side view of a portion of the cran according to Fig 1 with some parts broken away and some const ructional parts indicated by dashing, and

Fig 4 is a perspective view of a second preferred embodimen according to the invention in another position than the cran according to Fig 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

A first embodiment of the crane 1 according to the invention i shown i Fig 1, which crane has a frame 2 adapted to b pivotably arranged by a pivot 3 on a stand not shown about preferably substantially vertical axis.

With reference also to Fig 2 the construction of the frame wil now be described. The frame 2 has a lower support plate 4, o which two square beams 5 extending upwardly substantiall perpendicular from this are arranged at mutual distance. lying square beam 6 interconnecting beams 5 is arranged on th plate 4. The pivot 3 is secured in the former square beam 6. U-beam 7 is arranged behind each square beam 5 extending in th vertical direction, which U-beam is open towards the opposit U-beam. The legs of the U-beams 7 have substantially the sam length as the sides of the square beams 5 against which one le of each U-beam bears and is secured to. A first arm 8 i pivotably arranged on the frame 2 about an axle 9 extendin between the two U-beams 7 and intended to be substantiall horizontally directed.

The first arm 8 consists of a hollow square beam extendin through the space between the square beams 5 and the U-beams of the frame on both sides of said axle 9. Walls have bee removed from the first arm 8 at one 10 of its ends, so that i may receive a second arm 12 pivotably arranged on an axle 1 substantially parallel to the axle 9. The second arm 12 als consists of a hollow square beam which extends on both sides o the axle 11.

The second arm 12 is adapted to carry a load through the firs end 13 located most distant from the frame 2, while a firs link 14 in the form of a hollow square beam is pivotabl connected to the second end 16 of the second arm about an axl 15 substantially parallel to the axles 9 and 11. The end of th first link located opposite to the second arm 12 is secured t an axle 17 substantially parallel to the axle 9, on each end o which axle 17 rollers or ball bearings 18 are rotatably ar ranged. The rollers 18 are arranged to bear upon a suppor surface 7' of their own in the form of that leg of each U-be which bears against the square beam 5 in question. The diamet of the rollers 18 is slightly smaller than the distance betwe the two legs of the U-beam in question.

Furthermore, two other links 19, for instance in the form iron plates, are pivotably arranged on each side of the fir arm 8 about an axle 20 extending substantially parallel to a right through the first arm. The second links 5 are at the opposite ends pivotably arranged about the axle 17.

In order to complete the description of the frame 2 it mentioned that a rear sheet 21 is arranged between the U-bea 7 in order to protect the inner parts of the frame but all the first arm to pivot to a position in parallel with the pla 4, and the two square beams 5 are at their tops closed by ca 22, preferably made of plastic.

The distance between the axle 17 and the axle 20 is substa tially just as long as the distance between the axle 11 and t axle 15, and the distance between the axle 20 and the axle is substantially just as long as the distance between the ax 17 and the axle 15, whereby the links 14 and 19 together wi the two arms 8 and 12 form a parallel linkage. Furthermore, t axle 17 provided with rollers is located substantially in t same vertical plane as the axle 9 of the first arm on t frame, and as a result of this the distance between the axles and 20 has to be substantially equal to the distance betwee the axles 11 and 15. Owing to the latter fact the first 8 an the second 12 arm will in every assumed position make substan tially the same angle with the vertical line, provided that th pivot 9 of the frame is substantially vertically directed Furthermore, if the distances between the two pivot axes 9 an 11 of the first arm on the frame 2 and on the second arm 12 respectively, is chosen to be equal to the distance between th pivot axis 11 and that point 23 of the first end 13 of th second arm in which a load is intended to be suspended, possib ly by any type of grasping means, the point 23 will continuous ly move in the horizontal plane in which this point and th axle 9 are located, when the two arms 8, 12 are pivoted wit respect to each other. Thanks to this the load may be moved i one and the same horizontal plane by changing the inclinatio of the two arms 8, 12 with respect to each other and possibl pivoting the frame about the axis of the pivot 3, but withou the necessity of further regulation of the position of the loa in the vertical direction.

The great advantage of the crane according to the invention consists in that it is self-braking, i.e. it assures by itself that every relative position between the two arms 8, 12 and the frame is stable. This is achieved by the arrangement accordin to the invention of the linkage with the bearing of the rollers 18 against the support surfaces 7 ' formed by the legs of the U-beams 7.

Already the dead weight of the two arms 8 and 12 generates a torque about the axles 9 and 11, which in every position of these arms tends to pivot the arms clockwise about these two axles as seen in Fig 1. The torque about the axle 11, generated by the forces acting in the direction of the arrow A and emanating from the dead weight of the second arm and the weight of the load, will give rise to a force acting in the direction of the arrow B in the first link 14. This force will press the rollers 18 against the front legs of the U-beams 7 and through the second links 19 tend to pivot the firs arm 8 counter-clock¬ wise as seen in Fig 1 in rolling the rollers 18 upwardly on the support surfaces 1 ' of the U-beams. However, this movement of the rollers is counter-acted by the torque about the axle 9 in the opposite direction, i.e. clockwise as seen in Fig 1, generated by the forces emanating from the weight of the load, the weight of the second arm and the weight of the first arm. The heavier the load carried the greater the forces acting in the links 14, 19 for preventing pivoting of the first about the axle 9. The torques acting about the axle 9 will this way cancel out each other and a stable position will achieved for the first arm 8 in every relative position of first arm 8 relative to the frame 2. By means of the sta position of the first arm and its linkage together with second arm 12, the latter will continuously be in a sta position.

Should displacement of the load be desired it would be suf cient to for example by hand grasp the latter and bring it t desired position in rolling the rollers 18 along the suppo surfaces 1 ' of the U-beams.

The end of the first arm located on the opposite side of t frame 2 with respect to the second arm 12 is provided with rod 24, on which a suitable number of weights 25 acting balances may be laid, in order to reduce breaking forces a torques generated by the weight of the two arms, the links a the load mainly on the axles 11, 15, 17 and 20 and the pivot The magnitude of the balance is adjusted according to the lo intended to be carried by the second arm. Thanks to the loc tion of the rear leffe of the U-beams 7 in a short distan behind the rollers 18 (see Fig 3), violent pivoting of t first arm counter-clockwise as seen in Fig 1 is prevented, too high a number of weights 25 accidentally are laid on, sin these rear legs of the U-beams 7 will receive the rollers a thus function as a safety catch against falling of the rolle off the frame.

A second embodiment of the crane according to the invention shown in Fig 4 in a position arranged on a stand 26. The cra in this Figure is by the load receiving end of the second a extending at a great distance from the frame 2 with respect the crane shown in Fig 1, so that the rollers running insi the U-beams are located on a lower level than in Fig 1. Th crane is adapted to carry loads 27, as the one indicated b dashed lines, which are excentrically located with respect to vertical line through the point 23 of the second arm 12. further parallel linkage has been arranged in order to maintai the load in a certain position relative to a vertical line, preferably in parallel with this. This has been obtained by prolonging the first arm 8 beyond the second arm and th arrangement of a third link pivoted about an axle 28 substan¬ tially parallel to the axle 9 on the extremity of the first arm. The other end of the third link 29 is pivotably arranged on a fourth link 39 about an axle 30 substantially parallel to the axle 9. The fourth link is in its turn pivotably arranged on the second arm 12 at the point 23. A load carrying means 32 is rigidly secured to the fourth link 31. It is easily under¬ stood that this linkage achieves a continuous alignment of the load carrying means 32 with respect to a vertical line.

The means 32 may be a telescope device for lifting a load 27, which for instance is grasped by means of a fork 33. Possible hydraulic conduits or the like for operating the telescope means 32 has not been shown in the Figure.

Although the preferred embodiments of the invention described above are very advantageous, the invention is of course not at all restricted thereto, but a man with ordinary skill in the art to which the invention pertains should without any particular problems find a number of possibilities to modify these without departing from the basic idea of the invention.

The distance between the axle 11 and the point 23 could for instance be made longer or shorter than the distance between the axles 9 and 11, through which a movement of the point 23 along a line inclined with respect to a horizontal line will be achieved. The distance between the axle 9 and the axle 20 could be ma different from the distance between the axle 11 and the ax 15, through which the arms 8 and 12 would not have the sa inclination with respect to a vertical line any more and a lo would not be moved in a horizontal plane any longer.

Furthermore, the frame could naturally be arranged on a sta with the pivot 3 inclined with respect to a vertical line, b this would seldom be desired. In addition thereto the sta could be made vertically adjustable.

The frame could be designed in different other ways, in whi it is only necessary to provide a support surface for a beari arrangement. The bearing arrangement may be constituted by o single roller or for instance a carriage sliding on a suppo surface in the form of a rail. The axle 17 could be rotatab arranged in the link 14 and the rollers 18 rigidly secured the axle.

The different squarebeams could of course be replaced by oth types of longitudinal elements, by which it is only requir that the first 14 and the second 19 link are transmittin tractive forces but not transmitting coΛ^ressive forces, an they could therefore be replaced by for example steel wires.

The balance could if desired be removed or designed in anothe way.

An arbitrary motor device could be arranged in order to achiev motorized operation of the crane. Such an operation could b obtained for example by making the rollers 18 motordriven an design them as gear wheels engaging stationary teeth path forming the support surfaces. The crane could if desired b provided with holding or locking means arranged to hold or loc the arm 8 in the desired positions relative to the frame 2.

Claims

1. A crane comprising a first arm (8) pivotably arranged on frame (2) about a substantially horizontal axis (9), a secon arm (12) pivotably arranged on the first one about a substan tially horizontal axis (11), a load (27), for example a tool being intended to be carried by the second arm, and an arrange ment for maintaining the arms (8, 12) in desired relativ positions with respect to the frame (2) and each other, c h a r a c t e r i z e d in that the arrangement comprise connecting members (14, 19) connecting each arm to a bearin arrangement (17, 18) arranged to bear upon and be displaceabl along a support surface (7') on the frame (2) , so that in ever position assumed by the arms the torques generated by th forces emanating from the weights of the load and the arms wit respect to the two pivot axis (9, 11) mentioned above ar balancing each other.

2. A crane according to claim 1, c h a r a c t e r i z e d i that the point (11) for the pivotable interconnection of th two arms is so located that the second arm (1.2) forms a two armed lever with respect to this point, that the crane i arranged to carry the load through the first end (13) of th second arm (12) most far from the frame (2), that a firs connecting member (14) is at one of its ends pivotably con nected to the opposite second end (16) of the second arm abou substantially horizontal axes (15) and at its other end con nected to the bearing arrangement (17, 18) displaceable on th support surface on the frame, that a second connecting membe (19) is at one of its ends pivotably connected to the first ar (8) about substantially horizontal axes (20), at a poin located between the point (9) for the pivotable connection o the first arm with the frame (2) and the point (11) for pivot able connection of the first arm with the second arm (12), an at its other end connected to the bearing arrangement (17, 18 about the same pivot axis (17) a-s the first connecting membe (14), and that the bearing arrangement is arranged to bear u the support surface (7') on the frame at a higher level t the location of the pivotable connection of the first arm w the frame.

3. A crane according to claim 2, c h a r a c t e r i z e d that the connecting members (14, 19) consist of rigid links.

4. A crane according to any of the claims 1-3, c h a r a c ¬ t e r i z e d in that the support surface of the frame directed away from the second arm, and that the bearing rangement comprises at least one roller (18) arranged to pressed against the supporting surface (7 ') through the co necting members (14, 19) and upon change of the positions the two arms (8, 12) roll along said surface.

5. A crane according to claim 4, c h a r a c t e r i z e d that the support surface (7') extends substantially verticall and that the pivot center (9) of the first arm on the frame ( is intended to be located at a lower level than the piv center (11) thereof on the second arm (12) and the latter piv center is intended to be located at a higher level than the e (13) of the second arm (12) adapted to carry a load.

6. A crane according to claim 2 and 5 and possibly claim 3, c h a r a c t e r i z e d in that said substantially hor zontal pivot axes (9, 11) are substantially parallel to ea other and to the support surface, and that the connecti members (14, 19), the first (8) and the second (12) arm t gether form a parallel linkage, in which the distance betwe the pivot center (9) of the first arm on the frame (2) and t pivot center (20) of this arm in common with the seco connecting member (19) is substantially as long as the distan between the pivot center (11) of the first arm on the seco arm (12) and the pivot center (15) of the other in common wi the first connecting member (14), so that the first and seco arm in every position assumed make substantially the same angl with the vertical line.

7. A crane according to claim 6, c h a r a c t e r i z e d i that the distance between the pivot center (9) of the first ar (8) on the frame (2) and its pivot center (11) on the secon arm (12) is substantially as long as the distance between th pivot center (11) of the second arm on the first arm (8) an the load suspension point (23) of the second arm, so that load hanging in the second arm (12) is displaced along substantially horizontal line when the arms (8, 12) are pivote with respect to each other and to the frame (2) .

8. A crane according to claim 7, c h a r a c t e r i z e d i that the frame (2) is pivotably arranged on the frame (26 about a substantially vertical axis (3), so that a load carrie by the second arm (12) is displaceable in a horizontal plan around the frame.,

9. A crane according to any of the proceeding claims, c h a r a c t e r i z e d in that the bearing arrangemen comprises a substantially horizontal axle (17), on which th connecting members (14, 19) are pivotably arranged, and that o each extremity of the axle a roller (18), such as a bal bearing, rotatable about the axle is concentrically arrange and adapted to bear upon and running along the support surfac (7^Λ) on the frame in displacing said axle (17) parallelly t this surface.

10. A crane according to claim 5 and possibly any of the othe proceeding claims, c h a r a c t e r i z e d in that the firs arm (8) extends beyond the pivot center (9) on the frame (2 and is terminated by an end located on the opposite side t the second arm (12) with respect to the frame, close to whic end a first arm is provided with means (24) for receiving counter weight (25) for reducing breaking forces and torque generated by the weight of the two arms (8, 12), the connecting mem (14, 19) and the load at hinge points (9, 11, 15, 17, 20) the arms, the connecting members and the frame, that the fr (2) comprises at least one U-beam (7), that the inner surf of one leg of the U-beam forms the support surface (7') of frame, and that the inner surface of the other leg of U-beam oppositely directed is arranged to receive and suppor bearing arrangement (18) when the counter weight (25) is high and by that function as a safety catch against disapp ring of the bearing arrangement from the frame.