Self-locking lifting mechanism
United States Patent 11 1 Turner 1 1 Apr. 22, 1975 SELF-LOCKING LlFTlNG MECHANISM 22 Filed: May 14.1974  
  211 Appl. No.: 469,899  
 [58] Field of Search 294/78 R. 82 R, 83 R, 85, 294/92. 101. 103. 104, 106: 24/2305 AC,  
 230.5 T. 238. 243 AB. 243 G, 248 A, 248  
 [56] References Cited UNlTED STATES PATENTS 2.422.865 6/1947 Tucker 248/228 2.765.139 10/1956 White 248/228 12/1960 Edwards 294/83 R X 1/1972 Rcnfroe 294/85 Primary E.\&#39;umim&#39;r-Evon C. Blunk Assistant E.\uminer.l0hnny D. Cherry [57] ABSTRACT A self-locking lifting mechanism comprises an at least part-circular disc which in use is connected by an eye or shackle to a lifting device for lifting the mechanism. The disc has guide means such as a curved slot. while a pair of links is pivotally carried by the disc, the pivot also being slidable along the guide slot. A block with a slot for gripping stock to be lifted is carried pivotally by the links at their end remote from the guide slot. while a second such block is pivoted on the disc at a spacing from the guide slot. Movement of the links along the guide slot moves the first block towards or away from the second block. and lifting of the disc by means of the eye or shackle causes the disc to pivot. thereby to cause the links to move along the guide slot to grip the stock.  
 10 Claims, 1 Drawing Figure SELF-LOCKING LIFTING MECHANISM BACKGROUND OF THE INVENTION It is often necessary to be able to handle articles or stock such as steel joists and similar sections. which are to be transferred for example overhead by a moving crane. rapidly and in a safe manner. This can be done by securing the hook of the crane to the article or stock. for example by means of chains and hooks or shackles. This however is often a highly cumbersome manner of proceeding. since the chains must be passed around the article or stock to be lifted. and this may be difficult if the article or stock is resting flush on the surface from which it is to be lifted. since there is then below the article or stock no space through which the lifting chains can be passed.  
 SUMMARY OF THE INVENTION It is an object of the present invention to provide a lifting mechanism for lifting article or stock. which has a self-locking action.  
  It is a further object of the present invention to provide a self-locking lifting mechanism whose locking action tends to increase with the weight of the article or stock applied thereto.  
  Yet another object of the present invention is to provide a self-locking lifting mechanism which has the minimum of components and whose components moreover can be of sturdy and simple construction.  
  A still further object of the present invention is to provide a lifting mechanism which can be adapted to widely varying stock dimensions.  
 According to the present invention. the self-locking lifting mechanism comprises a disc which is preferably completely circular. The disc has a guide means which may be in the form ofa curved slot extending in the periphral direction of the disc. Connected to the disc at the position adjacent a first end of the guide slot is a connecting means in the form for example of a lifting eye or shackle. for connecting the lifting mechanism to a lifting device such as a crane. The disc also carries pivotal links, the pivot being slidable along the guide slot. At the end of the links remote from the guide slot is pivotally carried a first gripping means which can comprise an elongate block with a slot for gripping the stock. while a second gripping means which may be in the form also of an elongate block with a stock-gripping slot, is pivotally carried by the disc adjacent the second end of the guide slot. Movement of the links along the guide slot causes the first gripping means to be moved towards or away from the second gripping means. When the lifting mechanism is fitted to an article to be lifted, the guide slot will extend in a direction which is inclined relative to the direction oflifting. so that as the disc is lifted by the lifting device connected to the lifting eye or shackle, the disc will pivot about the pivot connection of the second gripping means. thereby causing the first gripping means to slide along the guide slot and also pivot therein. to cause the stock to be automatically gripped between and by the two gripping means.  
 BRIEF DESCRIPTION OF THE DRAWING The accompanying single FIGURE shows an embodiment of the self-locking lifting mechanism according to the present invention by way of example.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT The lifting mechanism comprises a main chamber in the form of a circular disc 11 which is made for example of solid steel. The disc 11 has connection means in the form of a series of apertures 12 which are spaced in the peripheral direction of the disc 11 and which are each disposed at a uniform radial distance from the centre of the disc. A lifting shackle (not referenced) can be connected selectively to one of the apertures 12, for raising the lifting mechanism. The width of the stock to be lifted will determine which of the apertures 12 receives the lifting shackle. as described hereinafter.  
  The disc 11 also carries a guide means in the form of an arcuately curved slot 13, which is produced for example by milling. The slot 13 is concentric relative to the disc 11 and as shown extends for example over an angular distance of substantially in the peripheral direction of the disc 11. The slot 13 may vary in length and width.  
  The lifting mechanism further has link means pivotally carried by the disc 11 and formed by a pair of links 14, one link 14 being disposed on each side of the disc 11. The links 14 are connected to the disc 11 by a pivot member 15 which is slidably displaceable within the slot 13 in the disc 11, so that the links 14 are both bodily displaceable and also pivotal about the pivot member 15 relative to the disc 11.  
  Pivotally connected to the end of the links 14 which is remote from the disc 11. is a gripping means in the form of an elongate gripping block 16 with means for engaging a respective edge portion of stock to be lifted. The pivotal connection between the links 14 and the block 16 is by means of a pivot member 17, while the stock engaging means in the block 16 is in the form of a slot which extends over the entire length of the block 16 and which is produced for example by milling. The size of the slot will depend on the dimensions of the stock. and the block 16 may be removable for replacement by a gripping block with a different size of slot.  
  Disposed at a position which is substantially diametrically opposite the centre point along the series of apertures 12 is a further aperture 21. As shown. the aperture 21 is adjacent to the lower end of the slot 13. The radial distances of the apertures 12, the slot 13 and the aperture 21, from the centre of the disc 11, are all substantially identical. One end of a pair of links 22 is pivotally connected to the disc 11 by means of a pivot member 15A extending through the links and the aperture 21. Pivotally connected to the other end of the links 22 by a pivot member 17A is a gripping means in the form of a gripping block 16A with means for engaging a respective edge portion of the stock to be lifted. again in the form of a slot extending over the entire length of the block 16A.  
  Each block 16 and 16A carries a respective locating handle 18 which the operator of the lifting mechanism can use in order to locate the blocks 16 and 16A on the edge portions of the stock to be lifted.  
  Operation of the above-described mechanism is as follows:  
  In the position of the mechanism in which it is ready to grip stock. such as steel joist. to be lifted. the disc 11 is substantially vertical. while the two blocks 16 and 16A hang downwardly from their respective pivot members 17 and 17A, with the slots in the blocks 16 and 16A open towards each other horizontally. as illustrated. The blocks 16 and 16A have their direction of elongation substantially horizontal. when the disc 11 is substantially vertical. With the blocks 16 and 16A in this position. the slots in the blocks 16 and [6A are engaged onto flange edge portions of the joist. while the slot 13 in the disc 11 permits the links 14 to slide in the slot 13. thereby to adapt the operable gripping distance between the gripping blocks 16 and 16A to the distance across the flange edges.  
  When a vertically directed lifting force is applied to the lifting shackle carried in one of the apertures 12. this force will in effect cause the disc ll to pivot about the pivot member 15A. and the co-operation between the radially outward side face of the slot 13 and the pivot member 15 therein will cause a sliding movement of the links 14 relative to the disc 11., in the generally downward direction of the slot 13. At the same time the links will at least to a certain extent pivot about the pivot member 15. This combined movement will cause the blocks 16 and 16A to move towards each other. thereby to lock the stock between them as the stock is lifted.  
  If the stock to be lifted is of narrow width. the pivot member 15 will be moved towards the lower end of the slot 13 so that the two blocks 16 and 16A are relatively close together. The lifting shackle connected to the disc II will then be moved to an aperture 12 which is at such a position on the disc 11 that the application of the lifting force will cause the disc I] to pivot about the pivot member 15A. Thus. generally. if a diametral line which passes through the centre of the disc 11 and between the two pivot members l and l5A at an equal distance from each is set in a vertical position. the lifting shackle must be connected to an aperture 12 which lies at the same side of the said diametral line as the pivot member 15. Desirably however, the aperture 12 to which the lifting shackle is connected for a given width of stock lifting will not be excessively spaced from the diametral line. as otherwise this could cause the disc 11 to be turned about the pivot member A to an excessive degree. namely until the line of the vertical lifting force was passing through the centre of gravity of the lifted stock. and excessive turning of the disc 11 would cause the stock gripped between the blocks 16 and 16A to be lifted in a canted position.  
  lt is apparent that the above-described mechanism will provide a self-locking action. which means that it can be used for the safe handling of stock. besides being simple to operate by virtue of its self-locking action.  
  In the embodiment described above. the guide means is in the form of an arcuately curved slot 13. but other suitable forms of guide means are obviously possible. The guide means may also be substantially rectilinear. provided that it is so arranged relative to the member 11 that. when the lifting mechanism is fitted to stock to be lifted and when a lifting device for lifting the lifting mechanism is connected to one of the apertures 12, the guide means extends in a direction which is inclined relau. o the direction of lifting. thereby to cause the above-described sliding movement of the links 14, to cause the stock to be engaged and locked by the blocks 16 and 16A.  
  Although the disc shown is circular, it would be possible to use a disc which is only part-circular; for example, the disc 11 will have a circular peripheral contour only in its regions in which are disposed the apertures 12 and the guide slot.  
 I claim:  
  1. A self-locking lifting mechanism comprising a main member in the form of a disc. a guide means on the disc extending generally peripherally of the disc. connection means on the disc at a position adjacent a first end of the guide means for connecting the mecha nism to a lifting device for lifting the mechanism. link means pivotally carried by the disc. the link means pivot being slidable along the guide means. a first gripping means pivotally carried at or adjacent the end of the link means which is remote from the guide means. and a second gripping means pivotally carried by the disc at a position adjacent the second end of the guide means. movement of the link means along the guide means moving the first gripping means towards or away from the second gripping means. the arrangement being such that when the lifting mechanism is fitted to an article to be lifted. the guide means extends in a direction which is inclined relative to the direction of lift- 2. A self-locking lifting mechanism according to claim 1 wherein said guide means is arcuately curved and extends substantially in the peripheral direction of the disc.  
  3. A lifting mechanism according to claim 1 wherein the connection means comprises a lifting eye.  
  4. A lifting mechanism according to claim 1 wherein said guide means comprises an arcuately curved slot extending in the peripheral direction of the disc over an angular distance of substantially and the connec tion means comprises aperture means.  
  5. A lifting mechanism according to claim 4 wherein the aperture means comprises a series of apertures for selective connection to said lifting device for lifting the mechanism. the series of apertures extending in the peripheral direction of the disc away from the first end of the arcuately curved slot.  
  6. A lifting mechanism according to claim 4 wherein the radial distances from the disc centre to the aperture means. the arcuately curved slot. and the pivot connection of the second gripping means are substantially equal.  
  7. A lifting mechanism according to claim 1 wherein the second gripping means is pivotally connected to the disc by way of a further link means.  
  8. A lifting mechanism according to claim 1 wherein the first and second gripping means comprise respective elongate gripping blocks so arranged that when the main member is in a substantially vertical position for a lifting operation. the direction of elongation of the gripping blocks is substantially horizontal.  
  9. A lifting mechanism according to claim 1 wherein said link means comprises two links. one link being disposed on each side of the main member.  
  10. A self-locking lifting mechanism comprising a main member in the form of a circular disc. a curved guide slot in the disc extending in the peripheral direction of the disc over substantially a 90 sector thereof. connection means on the disc at a position adjacent a first end of the guide means for connecting the mechanism to a lifting device for lifting the mechanism. link means pivotally carried by the disc. the links means pivot also being slidable along the guide slot. a first gripping means pivotally carried at or adjacent the end of the link means which is remote from the guide means. and a second gripping means pivotally carried by the disc at a position adjacent the second end of the guide means. movement of the link means along the guide means moving the first gripping means towards or away from the second gripping means.