Abstract:
The present invention relates to an ergonomic platform lift of the type that can be vertically adjusted while supporting a person thereon. More specifically, this lift combines rack and pinion units with at least one screw jack so that a person can be solidly supported without any tilting in the lift and so that the height of the lift can be adjusted with great precision.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an ergonomic platform lift of the type that can be vertically adjusted while supporting a person thereon. More specifically, this lift combines rack and pinion units with at least one screw jack with self-locking thread so that a person can be solidly supported without any tilting in the lift and so that the height of the lift can be adjusted with great precision. 
     BACKGROUND OF THE INVENTION 
     In certain occupations, it is often necessary to use an apparatus to raise or lower a person to a desired height while having that person be solidly supported thereon. 
     Accordingly, platform lifts provide solid support and allow the placement of people, such as workers, at optimal heights to properly perform specified tasks. With a focus towards the workplace, proper height placement of workers on lifts providing solid support allows workers to safely perform tasks using proper body mechanics. As such, platform lifts can reduce worker injuries and increase work productivity. 
     The present platform lift differentiates from other types of lifting platforms in that this lift combines rack and pinion units with at least one screw jack to afford a person a solid support and give them the ability to adjust the height of the lift with great precision. This invention is most suitably adapted for use in connection with assembly lines used in food processing, material handling, manufacturing plants, such as automotive plants, and the like. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an ergonomic platform lift adapted to move vertically such that the height of a worker situated thereon can be adjusted to an optimum working height. The present invention further provides a worker with a solid support and the ability to adjust the height of the lift with great precision. The invention is best suited for use along an assembly line. 
     The platform lift includes a floor plate having a bottom surface and opposing longitudinal and lateral side edges. An upper movable frame supports the floor plate and is secured to the bottom surface of the floor plate. 
     The platform lift further comprises at least one jack screw supported by a lower stationary frame and operably connected with the floor plate to provide vertical movement or displacement of the floor plate thereof. A driving mechanism, preferably a motor, drives at least one screw jack to vertically move the floor plate. If more than one screw jack is used, the screw jacks are operably connected to each other by a drive shaft such that the driving mechanism drives at least one screwjack causing simultaneous movement of each due to the drive shaft connection therebetween. In a preferred embodiment, first and second screw jacks are operably connected therebetween by a drive shaft, are driven by a motor, and operably connected to the floor plate for vertical movement thereof. 
     The platform lift further includes first and second rack and pinion assemblies positioned apart and located below the floor plate for stabilization of the floor plate and to prevent tilting thereof. Each rack is fixedly mounted to the lower frame with the pinions carried and supported by an extension of the upper movable frame. The first and second rack and pinion assemblies are comprised of first and second rack and pinion units which also are positioned apart. In a preferred embodiment the first and second rack and pinion assemblies are positioned apart proximate opposing lateral side edges of the floor plate, and each of the first and second rack and pinion units of the first and second rack and pinion assemblies are positioned apart proximate opposing longitudinal side edges of the floor plate. 
     Each of the first and second rack and pinion units comprise a stationary rack securely supported vertically by the lower frame and a pinion supported by the upper frame for vertical movement with the floor plate. The pinion further is operably associated with the stationary rack for rotational movement therealong during vertical movement of the floor plate. Each pinion of the first rack and pinion assembly and each pinion of the second rack and pinion assembly further is operably connected therebetween by a cross shaft to allow simultaneous rotation of each pinion during vertical movement of the floor plate. 
     Additionally, multiple rollers are supported by the upper frame for vertical movement with the floor plate wherein one of each roller is located adjacent each stationary rack such that the rack is sandwiched between the roller and a pinion to increase the stability of the floor plate. During vertical movement of the floor plate, the roller moves along the rack in unison with the pinion. 
     To operate the lift, a worker activates the motor which, in turn, activates the screw jack system for vertical movement of the floor plate to a desired position. As the floor plate is raised or lowered by the screw jack(s), the pinions and associated rollers move in unison along their respective racks to provide stability to the floor plate. Notably, the use of a screw jack(s) allows precise adjustment of the floor plate when placing a worker at their optimum working height. 
     Accordingly, it is an object of the invention to provide a vertically adjustable platform lift that will provide a solid support for a worker so that the lift does not tilt. 
     It is another object of the invention to provide a vertically adjustable platform lift which can accommodate people having a wide range of heights. 
     Lastly, it is another object of the invention to provide a vertically adjustable platform lift that allows a worker the ability to adjust the height of the lift with great precision. 
     The invention will be further described in conjunction with the appended drawings and following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cut-away elevated longitudinal side view of the platform lift of the present invention wherein a portion of the frame has been cut-away to reveal the association between the crossbeam and first and second screw jacks; 
     FIG. 2 is a top plan view of the platform lift of the present invention wherein shown in phantom are first and second screw jacks connected by a drive shaft; 
     FIG. 3 is a top plan view of the platform lift of the present invention wherein the floor plate has been partially removed and the crossbeam has been partially cut-away; 
     FIG. 4 is an elevated lateral side view of the platform lift of the present invention wherein a portion of the frame has been cut-away to reveal the association between the crossbeam and a screw jack and to reveal stationary racks; and 
     FIG. 5 is a cut-away perspective view of a rack and pinion unit of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1-5 show the present invention which concerns an ergonomic platform lift  10  of the type that can be vertically adjusted to control the height of an individual supported thereon while providing a firm and solid support therefore. 
     In a preferred embodiment, as shown in FIG. 1, the platform lift  10  includes a floor plate  12  preferably made of a metal, such as steel, having a bottom surface  14  and opposing longitudinal and lateral side edges  16 ,  18  (FIG.  2 ). An upper, movable frame  20 , also preferably made of a metal, such as steel, supports the floor plate  12  and is secured thereto preferably by welding. As best shown in FIGS. 3 and 4, the upper frame  20  further includes a crossbeam  21  having a bottom surface  27  and extending substantially centrally substantially adjacent the bottom surface  14  and parallel with the longitudinal side edges  16  of the floor plate  12  for additional support thereof. 
     As shown in FIG. 2, the floor plate  12  additionally may comprise at least one access panel  22  for access therebelow. The access panel(s)  22  may be set-off from the floor plate  12  by being painted a different color than the floor plate  12  and either may be hinged to the floor plate  12  for easy opening or adapted such that the access panel(s)  22  can be completely removed. 
     FIG. 1 further shows the platform lift  10  comprising a first and second screw jack  24 ,  26  vertically supported by a lower stationary frame  20   a  and operably connected with the bottom surface  14  of the floor plate  12  to provide vertical displacement of the floor plate  12 . More particularly, each screw jack  24 ,  26  comprises a jack portion  28  that is vertically adjustable and which comprises a top portion having a lifting surface  32  that preferably is secured to the bottom surface  27  of the crossbeam  21  so that the floor plate  12  can be raised or lowered as the jack portion  28  vertically moves. The artisan will appreciate that the lifting surfaces  32  also could be secured directly to the bottom surface  14  of the floor plate  12 . 
     Each screw jack  24 ,  26  preferably has a 10-ton lifting capacity and about 12 inches of vertical movement. Although the preferred embodiment comprises first and second screw jacks  24 ,  26 , the artisan will appreciate that the floor plate  12  could be vertically moved with just a single screw jack or with a plurality thereof. 
     The first and second screw jacks  24 ,  26 , shown in FIG. 1, further are operably connected by a common drive shaft  34 . A driving mechanism, such as a motor  38 , is operably connected to at least one of the screwjacks  24 ,  26 . The jacks may be driven for reciprocal upward and downward motion in the vertical direction by employment of suitable gear connection drives such as the worm and wheel gear arrangements as shown in U.S. Pat. No. 6,158,720—hereby incorporated by reference herein. In FIG. 1, the motor  38  is shown operably connected to the first screw jack  24 . Accordingly, the motor  38  drives the first screw jack  24 , causing the second screw jack  26  to move simultaneously due to the connection therebetween by the common drive shaft  34 . Consequently, the screw jacks  24 ,  26  are able to simultaneously vertically move the upper frame  20 , thereby carrying the floor plate  12 . 
     As shown in FIG. 3, the first and second screw jacks  24 ,  26  preferably are positioned centrally between the opposing longitudinal side edges  16  and proximate the opposing lateral side edges  18  to help balance the floor plate  12 . The access panel(s)  22  (FIG. 2) in the floor plate  12  can be positioned proximate the first and second screw jacks  24 ,  26  for access thereto. As best shown in FIG. 1, each screw jack  24 ,  26  further comprises a base  40  adapted to house the jack portion  28 , especially when the jack portion  28  is completely retracted. Notably, the base  40  of each screw jack  24 ,  26  extends below the base frame  20  thereby creating a need for the platform lift  10  to be supported such that each base  40  can be accommodated. Consequently, the longer the jack portion  28 , the longer the base  40 . Accordingly, the platform lift  10  should be installed onto a platform  42  (FIG. 4) having a covered central pit or opening  43  to accommodate the jack extension, or it may be placed on supports  44  (FIG. 1) that are elevated relative to the support floor to accommodate for the jack extensions. 
     FIG. 3 shows the platform lift  10  having first and second rack and pinion assemblies  48 ,  50  positioned apart proximate opposing lateral side edges  18  of the floor plate  12  and, as best represented in FIG. 4, supported by the upper frame  20  for stabilization and to prevent tilting thereof. As further shown in FIG. 3, the first and second rack and pinion assemblies  48 ,  50  have first and second rack and pinion units  52 ,  54  which preferably are positioned apart proximate opposing longitudinal side edges  16  of the floor plate  12 . 
     FIGS. 4 and 5 best show that each of the first and second rack and pinion units  52 ,  54  are comprised of a stationary rack  56  and a pinion  58 . Each rack  56  being securely supported vertically by the lower frame  20   a  and comprises opposing first and second mating surfaces  60 ,  62  with the first mating surface  60  having a row of teeth  64  vertically aligned. Each pinion  58  is supported by the vertical extension  100  of upper frame  20  for vertical movement with the floor plate  12  and contains a row of teeth  68  aligned therearound to mate with the row of teeth  64  on the first mating surface  60  of a stationary rack  56 . Each pinion  58  further is operably associated with a stationary rack  56  for rotational movement along the first mating surface  60  during vertical movement of the upper frame  20  carrying the floor plate  12 . Each pinion  58  of the first rack and pinion assembly  48  and each pinion  58  of the second rack and pinion assembly  50  is operably connected therebetween by a cross shaft  70  to allow simultaneous rotation of each pinion  58  during vertical movement of the upper frame  20 . 
     FIGS. 1,  3  and  5  further show multiple rollers  72  supported by the vertical extension  100  of upper frame  20  for vertical movement with the floor plate  12  wherein one of each rollers  72  is positioned adjacent the second mating surface  62  of a rack  56  so that each rack  56  is sandwiched between a roller  72  and a pinion  58 . Each roller  72  further is operably associated with the stationary rack  56  and operably connected with a pinion  58  for simultaneous movement along the rack  56  during vertical movement of the floor plate  12 . The rollers  72  are adapted to rotate or slide along the second mating surface  62 . 
     To operate the lift  10 , a worker activates the motor  38  which, in turn, drives the first and second screw jacks  24 ,  26  simultaneously due to the connection by the drive shaft  34 . The jack portions  28  of the screw jacks  24 ,  26  move up or down to raise or lower the upper frame thereby carrying floor plate  12  to a desired position. As the floor plate  12  is raised or lowered by the screw jacks  24 ,  26 , the pinions  58  and rollers  72  move up or down in unison along their respective rack  56  to keep the floor plate  12  stable. As noted earlier, the use of screw jacks  24 ,  26  allows precise adjustment of the floor plate  12  when placing a worker at his/her optimum working height. When a new height is desired, the platform lift  10  easily may be readjusted. 
     While the form of apparatus herein described constitutes a preferred embodiment of this invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.