Abstract:
A lift with a multiple locking position safety leg includes a lift bed for engaging in objects to be lifted together with a fluid cylinder to be connected to the lift bed and extendable and retractable to move the lift bed between two extreme positions including a fully lowered position and a fully raised position. A latching mechanism is provided for holding the lift bed in any of a plurality of positions between the extreme positions and includes a plurality of vertically spaced latches operated by gravity to move to latching positions, one for each of the plurality of positions, and a single actuator for simultaneously moving and holding each of the latches against gravity from the latching positions to allow the lift bed to be moved to the fully lowered position. Also disclosed is a kit for retrofitting existing lifts with the safety leg.

Description:
FIELD OF THE INVENTION 
   This invention relates to lifts for elevating heavy objects as, for example, vehicular lifts, and more particularly, to a safety leg for use in such lifts to prevent the lifts from inadvertently descending. 
   BACKGROUND OF THE INVENTION 
   Lifts have long been utilized for elevating heavy objects for any of a large variety of purposes. One potential hazard associated with any type of lift is that the same will inadvertently descend as a result of malfunction or human error. If a person or an object is under the lift at such a time, injury to the person or damage to the object are likely to occur, particularly when the lift is bearing a load. 
   One common form of a lift is that utilized for vehicle repair. Such lifts are commonly found in service stations, the service departments of vehicle dealers, and the places of business of vehicle mechanics. In recognition of the potential dangers posed by inadvertent descent of vehicular lifts, The Automotive Lift Institute of Indialantic Fla., at least as early as 1998, promulgated the following standard which in turn has been approved by The American National Standards Institute of New York, N.Y. The standard is as follows: 
   8.2.11 Load Holding Device
         All automotive lifts except screw drive systems shall incorporate a mechanical device to prevent downward movement of more than 6″ (6 inches) after stopping motion. Function shall begin within twenty-four (24) inches of rise, and shall continue to the full rise position. If latches do not automatically reset after disengagement to prevent lowering the load, then the lifts shall incorporate a warning label at the point of latch operation and at the point of lift operation, that states that the latches do not automatically reset after lowering. The printed materials furnished with the lift shall incorporate the same warning.       

   In practice, The Occupational Safety and Health Agency (OSHA) inspects places of vehicular lift use such as those identified above for compliance with the foregoing industry developed standard. 
   A particularly vexing difficulty occurs when lifts not meeting the foregoing standard are found. The owner/operator of the lift is then required to bring the lift into compliance, frequently at considerable expense. 
   For example, a common type of lift used for vehicular purposes is the well-known in-ground lift. Such lifts typically include a lift bed having a pair of spaced parallel rails engageable with the frame of a vehicle and connected by a cross brace typically referred to as the superstructure. 
   A hydraulic cylinder is located wholly within an excavation within the facility housing the lift and arranged so that its piston end is connected to the superstructure and moves the superstructure, and thus the lift bed, between a fully lowered position, resting on the underlying terrain and an elevated position, typically sufficiently high that an adult may walk, substantially unimpeded, beneath the lift. 
   Such lifts have also been typically provided with so called antirotation tubes which are cylindrical tubes connected to the superstructure in depending relation and located parallel to the lift cylinder. A tube is located in the excavation housing the lift cylinder and the antirotation tube is set to telescope into and out of such tube. 
   Of course, when excavation is required to remedy the deficiency, considerable expense is involved both in breaking the typical concrete floor and excavating below it, and then filling the excavation and replacing the floor once the upgrade is complete. 
   In one prior art structures, a single latch, and actuator therefor has been located on the antirotation tube so as to latch the lift and prevent descent more than a few inches below its uppermost position 
   Though the prior art design utilizing a single latch does allow replacement of a conventional antirotation tube with one provided with a single latch without the need for excavation or the like, the same structure does not provide for a limiting of inadvertent downward moment of more than 6″ for all lift position above 24 inches of rise. 
   The present invention is directed to overcoming the foregoing problems. 
   SUMMARY OF THE INVENTION 
   It is the principal object of the invention to provide a hew and improved safety leg for a lift. More specifically, it is an object of the invention to provide a multiple locking position safety leg. It is also an object of the invention to provide a kit for retrofitting lifts with a multi-locking position safety leg as well as to provide a lift with a multiple locking position safety leg. 
   According to one facet of the invention, the above objects are accomplished in the kit for retrofitting an in-ground lift having an antirotation tube with a load holding device. The kit includes an elongated, cylindrical tube having the same outer diameter as an antirotation tube for the lift. A nut is connected to the tube at one end thereof and a plurality of first slots are spaced at predetermined locations in one side of the tube. A plurality of second slots are located generally in alignment with corresponding ones of the first slots and located in the side of the tube opposite the one side. An additional slot is provided in the opposite side between the nut on the one hand and the second slots on the other. A plurality of elongated dogs each having a length greater than the outside diameter of the antirotation tube, are provided, one for each aligned pair of the first and second slots. A plurality of pivot pins, one for each dog are provided within the interior of the tube and each journals an associated dog for rotation about an axis mutually transverse to the tube and a corresponding one of the aligned pairs of slots between a first position actuator within the tube and a second position wherein opposite ends of the dog extend out of both the first and second slots of the associated pair. The rotational axis and/or the dogs are further such that each dog has more mass between the rotational axis at one end of the dog than the other end. A manual actuator is pivoted within the tube and is moveably between a first position within the tube and a second position extending exterior of the tube. A linkage connects the actuator on each of the dogs and is moveable in response to movement of the actuator to the actuator second position to allow movement of the dogs from the second position of the dogs toward the first position of the dogs and is further responsive to movement of the actuator towards the actuator first position to allow the dogs to move toward the second position thereof. 
   In a preferred embodiment, the linkage includes an elongated, generally rigid link mounted for reciprocal movement within the tube and a plurality of cams are spaced along the length of the link at positions where at they may be brought into engagement with a corresponding one of the dogs to one side of the corresponding axis. 
   One embodiment of the invention contemplates that the link and the cams be located so as to engage each dog between its axis and its other end so as to positively move each dog toward the dog first position while allowing each dog to be biased towards the dog second position by gravity. 
   In a highly preferred embodiment, the link and the cams are defined by a ladder-like structure. 
   Preferably, the actuator is connected to the link by lost motion connection. 
   According to another facet of the invention there is provided a lift that includes a lift bed for engaging an object to be lifted. A fluid cylinder is connected to the lift bed and is extendable and retractable to move the lift bed between two extreme positions including a fully lowered position and a fully raised position. The invention further contemplates the inclusion of a latching mechanism for holding the lift bed in any of a plurality of positions between the extreme positions including a plurality of vertically spaced latches operated by gravity to move to latching positions, one for each of the plurality of positions. Also provided is a single actuator for simultaneously moving and holding each of the latches against gravity from the latching position to allow the lift bed to be moved to the fully lowered position. 
   In a preferred embodiment, each of the latches is a dog pivoted about a substantially horizontal axis and the single actuator includes a lever having a lost motion connection to each of the dogs. 
   In a preferred embodiment, the lift is an in-ground lift and the cylinder is generally below ground when the lift bed is in the fully lowered position. An elongated, antirotation tube is connected to the lift bed for movement therewith and is parallel to the cylinder. A below ground tube is provided to telescopically receive the antirotation tube and is located parallel to the cylinder and has an open end at about ground level. The lever includes a manually operable end. The dogs and the lever are pivoted to the antirotation tube and moveable between positions only within the antirotation tube and positions projecting outwardly of the antirotation tube and are constructed to be cammed into the antirotation tube when the actuator has been operated to move the dogs out of the latching positions by engaging with the ground and ground level or with the open end of the below ground tube. 
   More preferably, the lost motion connection includes a link within the antirotation tube which is vertically moveable by the lever and has a plurality of engagement projections, one for each dog, for engaging the associated dog in response to actuation of the lever so as to move and hold the latches against gravity from the latching positions. 
   In a preferred embodiment, the engagement projections are free of connections to the dogs. 
   Other objects and advantages will become apparent from the following specification taken in connection with the accompanying drawings. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a somewhat schematic, elevational view of an in-ground lift incorporating a multiple position locking system made according to the invention; 
       FIG. 2  is an enlarged, fragmentary, broken vertical section of the locking mechanism as contained in an antirotation tube; 
       FIG. 3  is a view of an antirotation tube from one side thereof; 
       FIG. 4  is a view of the antirotation tube from the opposite side thereof; 
       FIG. 5  is a view taken at 90° to either of the views of  FIG. 3  or  FIG. 4 ; 
       FIG. 6  is an elevation of a link utilized in the locking mechanism. 
   

   DESCRIPTION OF PREFERRED EMBODIMENT 
   An exemplary embodiment of the invention will be described in the context of use in an in-ground lift having an antirotation tube. However, it is to be understood that the invention is not so limited. That is to say, the invention will find applicability in above ground lifts and in structures other than antirotation tubes. Hence, no limitations to in-ground lifts and/or antirotation tubes is intended except insofar as expressly stated in the appended claims. 
   Referring now to  FIG. 1 , an in-ground lift embodying the invention is illustrated and is seen to include a lifting bed, generally designated  10 , having two parallel rails  12  and  14  which may engage the underside of the frame of a vehicle to be elevated. The rails  12 ,  14  are connected to one another by a superstructure  16  of conventional construction. The superstructure  16  is connected to the upper end  18  of a piston  20  of a hydraulic cylinder, generally designated  22 . The cylinder  22  is located below ground level shown at  24  in  FIG. 1 . A conventional pumping system, generally designated  26 , is employed to pressurize the lower end of the piston  20  and drive the same upwardly to any of several elevated positions, including the position shown in  FIG. 1  which is an uppermost position. The piston  20  may also be lowered into the cylinder  22  to a lowermost position, not shown, whereat the superstructure  16  will be essentially resting on the ground at ground level  24 . 
   A guide tube  28  is located below ground level and is located parallel to the cylinder  22 . The guide tube  28  receives an antirotation tube  30  in a telescoping fashion. The upper end of the antirotation tube  30  is connected by a bolt  32  to the superstructure  16  in a conventional fashion. 
   According to the invention, the antirotation tube  30  includes a single manual actuator  34  and a plurality of latches  36  in the form of dogs in vertically spaced relation. As illustrated in  FIG. 1 , the dogs  36  are in a latching position so that should the piston  20  begin to descend, one of the latches  36  will engage the ground at ground level  24  or the upper end of the guide tube  28  to block further descent. This construction is shown in greater detail in  FIG. 2  wherein the upper end of the guide tube  28  is given the reference numeral  38 . It will be seen that the bolt  32  is threaded into a nut  40  contained within the upper end  42  of the antirotation tube  30 . 
   The antirotation tube, at a location closely proximate to the nut  40  contains an elongated slot  44  as seen in both  FIG. 2  and  FIG. 3 . The actuator  34 , which is in the form of a lever, is moveable between the solid and dotted line positions illustrated in  FIG. 2  by pivoting around a pivot pin  46  impaled in the tube  30 . It is to be noted that the upper side of the lever actuator  34  includes a gripping end  48  which may be manually grasped by an operator and which flows into a cam surface  50  for purposes to be described. 
   Below the slot  44  there are pairs of slots  52  and  54  formed in opposite sides of the wall of the antirotation tube  30 . The slots  52  are also visible in  FIG. 3  while the slots  54  are visible in  FIG. 4 . 
   As noted, the slots are paired and are aligned across from one another within the wall of the tube  30  and are located on six inch or less centers along the length of the antirotation tube  30 . 
   The dogs  36  are placed on pivot pins  56  carried by the antirotation tube  30  and located between the slots  52  and  54  of each pair so that the dogs  36  may pivot to the dotted line position illustrated in  FIG. 2  or may be pivoted counter clockwise as viewed in  FIG. 2  to wholly enter the interior of the antirotation tube  30 .  FIG. 5  illustrates the relative position of the pivot location  56  in relation to the slots  52  on the one hand and slots  54  on the other. 
   It will be observed that the pivot pins  56  are located between the ends  58  and opposite ends  60  of the dogs  36  and define pivot axes that are mutually transverse to the elongated axis of the tube  30  and the alignment of the slots  53  and  54  of each pair. It will also be noted that the pivot point for each dog is closer to the ends  60  than to the ends  58  and that the ends  58  are enlarged so that there is more mass in each dog  36  from the pivot pin  56  to the end  58  than from the pivot pin  56  to the end  60 . It will also be observed that the pivot pins  56  are mounted closely adjacent an upper edge of each of the dogs  58 . As a consequence of this, gravity will cause the dogs to pivot toward the dotted line position shown in  FIG. 2 . Webs  62  (see also  FIG. 4 ) between the slots  54  act as stops to prevent the dogs  36  from moving substantially beyond the dotted line positions illustrated in  FIG. 2 . 
   When the dogs  36  are in the dotted line positions, both ends  58  and  60  will extend outwardly of the tube  30 , that is, project to opposite sides thereof. As a consequence, should there be an inadvertent descent of the piston  20 , the ends  58  and  60  will jam against the upper end  38  of the guide tube  28  or the ground level (as for example, a concrete or metal base) and provide support for the superstructure  16 , thereby preventing further descent. And, of course, this will occur at any position of the piston  20  above the ground level  24  if at least one of the dogs  36  is in the dotted line position shown in  FIG. 2  and above the upper end  38  of the guide tube  28 . 
   By placing the pivots on centers that are no more than 6″ apart, the previously quoted industry standard requiring prevention of more than 6″ of movement is met. Of course, other spacing could be used if desired. And by placing the uppermost dog  36  such that it will move to the dotted line position before twenty-four inches of rise of the lift has occurred, that requirement of the standard is likewise met. 
   To allow for controlled lowering of the lift, the actuator  34  is employed. As will be seen, when the actuator  34  is in its dotted line position as shown in  FIG. 2 , the dogs  36  rotate under the influence of gravity to the dotted line positions illustrated in  FIG. 2  to provide for position locking after no more than 6″ of movement. However, when it is desired to intentionally lower the lift, the actuator is moved counter-clockwise as shown in  FIG. 2  about the pivot  46  to the solid line position. 
   Within the antirotation tube is an actuator link, generally designated  70 . 
   The link  70  is a ladder like structure as can be seen from  FIG. 6  and includes a pair of spaced, parallel side pieces  72  interconnected by camming pins  74 , one for each of the dogs  36 . Above the uppermost camming pins  74  are a pair of pins  76  and  78  which loosely sandwich the cam surface  50  of the actuator lever  34  to provide a lost motion connection therewith. This is best seen in  FIG. 2 . The link  70  is quite narrow and is disposed within the antirotation tube  30  in close proximity to the side thereof containing the slot  52  and the slot  44 . Guide blocks  80  are placed in the positions illustrated in  FIG. 2  to confine the link  70  while guiding it for reciprocal movement in close proximity to that part of the wall of antirotation tube  30  having the slots  44  and  52 . 
   Turning to the dogs  36 , the same, between the pivots  56  and the ends  60 , include a slightly concave cam surface  82  which may be engaged by a corresponding one of the camming pins  74 . When so engaged, and when the link  70  is moved downwardly, assuming that the dogs  36  are not jammed against the upper end  38  of the guide tube  28  or the ground  24 , the dogs  36  can be moved to the solid line position illustrated in  FIG. 2  whereat at least one of the ends  58  and  60  is totally within the antirotation tube  30 . Thus, the dogs  36  are no longer in latching positions and the lift may be lowered. During such lowering, the dogs  36  will be progressively cammed into the interior or the antirrotation tube  30  by the upper end  38  of the guide tube  28  or the ground  24 . 
   If the link  70  is lifted to its dotted line position as shown in  FIG. 2 , it will be appreciated that the camming pin  74  will move upwardly to the dotted line position illustrated in  FIG. 2  and essentially out of engagement with the cam surface  82  of each one of the dogs  36 . Under the influence of gravity, the dogs  36  then pivot to the dotted line position illustrated in  FIG. 2 . Such movement of the link  70  is accomplished through manual actuation of the single actuator  34 . The gripping end  48  is grasp by the operator who will pivot the lever  34  in a clockwise direction as viewed in  FIG. 2 . The cam surface  50  will engage the cam pin  78  and move it to the dotted line position illustrated in  FIG. 2 , thereby elevating the link  70  to cause the action mentioned previously. 
   On the other hand, when it is desired to set the device for latching, the operator takes the opposite action by pivoting the lever  34  in a counter-clockwise direction whereupon it will eventually engage the cam pin  76  to allow the link to drop or to drive the link downwardly, causing the camming pin  74  to engage the cam surfaces  82  and move the dogs to a non latching position and hold the same in that location. 
   In operation, the cylinder  22  is pressurized to elevate the lift to the desired height. At this time, the actuator lever  34  will be in its dotted line position wholly within the antirotation tube  30  by reason of being cammed into such position upon the previous lowering of the lift when the upper end  38  of the guide tube  28  strikes the underside. As a consequence, as each dog  36  rises above the end  38  of the guide tube  28  during the elevating process, it will move to its dotted line position as illustrated in  FIG. 2 , that is, the locking position, to prevent more than 6″ of downward movement in accordance with the standard. Thus, there is automatic resetting of the dogs  36  to their latching position, obviating any need for the warning labels specified by the standard which could be ignored by a careless lift operator. 
   When it is desired to lower the lift, the operator need only move the actuating lever  34  from the dotted line position illustrated in  FIG. 2  to the solid line position. This will urge the link  70  downwardly to pivot the dogs  36  to the solid line position. Lowering of the link will cause the dogs  76  to enter the interior of the antirotation tube  30  as they sequentially engage the upper end  38  of the guide tube  28  or the ground  24 . 
   Installation of the apparatus in an in-ground lift having an antirotation tube is readily accomplished to the point where the assembled antirotation tube may be sold as a kit to retrofit existing lifts. It is only necessary to elevate the lift bed  10  a few feet above the ground. The bolt  32  may then be removed to loosen the existing antirotation tube from the superstructure  16 . Suitable care is taken to prevent the existing antirotation tube from dropping into the guide tube  28 . 
   The lift bed  10  is then rotated about the vertical axis of the cylinder  20  sufficiently so that the upper end of the existing antirotation tube is clear of the superstructure  16  where upon the existing antirotation tube may be fully removed from the guide tube  28 . At this time, the new antirotation tube  30  provided with a multiple locking position means of the invention, is inserted into the guide tube  28  and partially lowered therein. The superstructure  16  is then pivoted to overlie the tube  30  of the invention whereupon the bolt  32  is reinstalled and the system is ready to operate. In the usual case, the retrofit can be accomplished in 10 minutes or less. 
   From the foregoing, it will be appreciated that a multiple locking position safety leg made according to the invention is ideally suited for its intended purpose. The same provides full compliance with the applicable standard in that the multiple dogs  36  are provided to allow no more than 6″ of downward movement before lockup occurs. At the same time, the apparatus is automatically resetting insofar as when the lift is intentionally lowered, ultimately, the single actuating lever  34  is cammed into a position that releases the dogs  36  to move to locking positions as they emerge from the guide tube  28 . 
   The structure is relatively inexpensive, easily installed and in full compliance with applicable standards.