Patent Publication Number: US-9422142-B2

Title: Scissor-type lift assembly

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to lift assemblies. 
     2. Description of Related Art 
     Transportation systems such as lift systems are well known for moving items or people between two vertically differing locations. Transportation systems such as conveyor assemblies are well known for moving items or people between two horizontally differing locations. It is also known to move the platform or carriage of these systems through a belt-driven apparatus. 
     One well-known and useful type of lift system is the scissor-type lift assembly, which includes a pair of scissor arms coupled to a platform with the pair of scissor arms pivoting as the platform is moved between an elevated state and a lowered state. Such lift systems are commonly driven through hydraulic cylinders connected to a single hydraulic pump. 
     Some lift systems, including the pair of scissor arms, can be susceptible to wear due to flexing and undesired movement of the pair of scissors during operation. Each of the pair of scissor arms pivot about a shaft as a platform moves between elevated and lowered states. The shaft can flex or move as the pair scissor arms pivot, which can lead to wear to the shaft and the pair of scissor arms. 
     SUMMARY OF THE INVENTION AND ADVANTAGES 
     The subject invention includes a lift system including a first scissor-type lift assembly and a second scissor-type lift assembly. The first scissor-type lift assembly includes a first base and a first platform coupled to the first base for movement between elevated and lowered states in which the first platform and the first base are distant and proximate, respectively. The first scissor-type lift assembly includes a first and second pair of scissor arms each having upper and lower ends respectively coupled to each of the first platform and the first base. The first and second pair of scissor arms are connected to each other intermediate their respective upper and lower ends about a first pivot axis for pivoting relative to each other during the movement of the first platform between the elevated and lowered states. The first scissor-type lift assembly includes a first guide arrangement mounted to the first and second pair of scissor arms to define a first path with the first guide arrangement being movable with the first and second pair of scissor arms during the movement of the first platform. The first scissor-type lift assembly includes a first spool coupled to the first base and defining a first spool axis. The first scissor-type lift assembly includes a first belt routed through the first path of the first guide arrangement with the first belt having a primary end engaged with the first spool onto which the first belt is wound and from which the first belt is unwound. The first scissor-type lift assembly includes a first motor mounted to the first base and operatively coupled to the first spool to wind and unwind the first belt through the first path to move the first and second pair of scissor arms and move the first platform between the elevated and lowered states. 
     The second scissor-type lift assembly includes a second base and a second platform coupled to the second base for movement between elevated and lowered states in which the second platform and the second base are distant and proximate, respectively. The second scissor-type lift assembly includes a third and fourth pair of scissor arms each having upper and lower ends respectively coupled to each of the second platform and the second base. The third and fourth pair of scissor arms connected to each other intermediate their respective upper and lower ends about a second pivot axis for pivoting relative to each other during the movement of the second platform between the elevated and lowered states. The second scissor-type lift assembly includes a second guide arrangement mounted to the third and fourth pair of scissor arms independent from the first guide arrangement to define a second path with the second guide arrangement being movable with the third and fourth pair of scissor arms during the movement of the second platform. The second scissor-type lift assembly includes a second spool coupled to the second base and defining a second spool axis. The second scissor-type lift assembly includes a second belt routed through the second path defined by the second guide arrangement with the second belt spaced from the first belt and having a primary end engaged with the second spool onto which the second belt is wound and from which the second belt is unwound. The second scissor-type lift assembly includes a second motor mounted to the second base and operatively coupled to the second spool to wind and unwind the second belt independently from the first motor through the second path to move the third and fourth pair of scissor arms and move the second platform between the elevated and lowered states. 
     The lift system includes a controller in communication with the first and second motors to synchronize operation of the first and second motors for moving the first and second platforms between the associated elevated and lowered states in synchronization. 
     The first scissor-type lift assembly includes a first shaft disposed along the first pivot axis and the second scissor-type lift assembly includes a first shaft disposed along the second pivot axis. The first shaft having a first end and a second end spaced from the first end along the first pivot axis with the first and third pair of scissor arms pivotably disposed about the first shaft. The first and second ends extending from the first and third pair of scissor arms with the second end terminating at a first shaft face. Both of the first and second scissor-type lift assemblies of the lift system include a first retention device coupled to the first end of the first shaft with the first retention device engaging one scissor arm of the first and third pair of scissor arms. 
     The first scissor-type lift assembly includes a second shaft disposed along the first pivot axis and the second scissor-type lift assembly includes a second shaft disposed along the second pivot axis. The second shaft having a third end and a fourth end spaced from the third end along the second pivot axis with the second and fourth pair of scissor arms pivotably disposed about the second shaft. The third and fourth ends extending from the second and fourth pair of scissor arms with the fourth end terminating at a second shaft face. 
     The first and second scissor-type lift assemblies of the lift system include a second retention device coupled to the third end of the second shaft with the second retention device engaging one of the scissor arms of the second and fourth pair of scissor arms. Both of the first and second scissor-type lift assemblies of the lift system include a first brace fixed to another one of the first and third pair of scissor arms with the first brace abutting the first shaft face of the first shaft to maintain alignment of the first shaft along the first and second pivot axes for reducing wear between the first and third pivot axes and the first and third pair of scissor arms. Both of the first and second scissor-type lift assemblies of the lift system include a second brace fixed to another one of the second and fourth pair of scissor arms with the second brace abutting the second shaft face of the second shaft to maintain alignment of the second shaft along the first and second pivot axes for reducing wear between the first and second pivot axes and the second and fourth pair of scissor arms. 
     Advantageously, since the first motor of the first scissor-type lift assembly and the second motor of the second scissor-type lift assembly are in communication with and controlled by the controller, the lift system may be precisely controlled. Further, the force is divided between the first and second motors to allow a reduction in motor size. Additionally, since the first and second braces abut the first and second shafts to maintain alignment of the first and second shafts along the first and second pivot axes, wear to the shafts and the pairs of scissor arms is reduced as the pair of scissor arms pivot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. 
         FIG. 1  is a perspective view of a lift system having a first scissor-type lift assembly and a second scissor-type lift assembly with the lift system shown in an elevated state. 
         FIG. 2  is a fragmented side view of the first scissor-type lift assembly of the lift system shown in the elevated state. 
         FIG. 3  is a perspective view of an alternative lift system having an interconnected platform with the lift system shown in the elevated state. 
         FIG. 4  is a fragmented perspective view of a first brace coupled to a first pair of scissor arms at a first pivot axis. 
         FIG. 5  is an exploded perspective view of the first brace, the first pair of scissor arms, a first shaft, and a first retention device. 
         FIG. 6  is a fragmented cross-sectional perspective view of the first brace, the first pair of scissor arms, the first shaft, and the first retention device. 
         FIG. 7  is a fragmented cross-sectional perspective view of a second brace, a second pair of scissor arms, a second shaft, and a second retention device. 
         FIG. 8  is an exploded perspective view of the second brace, the second pair of scissor arms, the second shaft, and the second retention device. 
         FIG. 9  is a fragmented cross-sectional perspective view of an alternative arrangement of the first brace, the first pair of scissor arms, and the first shaft. 
         FIG. 10  is a fragmented perspective view of a first lubrication feature coupled to a first engagement shaft. 
         FIG. 11  another fragmented perspective view of the first lubrication feature coupled to the first engagement shaft. 
         FIG. 12  is a fragmented perspective view of a first spool coupled to a first base and having a plurality of first belts and a plurality of first rollers. 
         FIG. 13  is an exploded perspective view of the first spool coupled to the first base with the plurality of first belts and the plurality of first rollers. 
         FIG. 14  is another perspective view of the first spool coupled to the first base with the plurality of first belts and the plurality of first rollers. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the Figures wherein like numerals indicate like or corresponding parts throughout the several views, a lift system  20  including a first scissor-type lift assembly  22  and a second scissor-type lift assembly  24  spaced from the first scissor-type lift assembly  22  is generally shown in  FIG. 1 . 
     The first scissor-type lift assembly  22  includes a first base  26  and a first platform  28  coupled to the first base  26  for movement between elevated and lowered states in which the first platform  28  and the first base  26  are distant and proximate, respectively. The first scissor-type lift assembly  22  includes a first motor  30  mounted to the first base  26  to move the first platform  28  between the elevated and lowered states. The first scissor-type lift assembly  22  is shown in the elevated stated in  FIGS. 1 and 2 . 
     The second scissor-type lift assembly  24  includes a second base  32  and a second platform  34  coupled to the second base  32  for movement between elevated and lowered states in which the second platform  34  and the second base  32  are distant and proximate, respectively. The second scissor-type lift assembly  24  includes a second motor  36  mounted to the second base  32  to move the second platform  34  between the elevated and lowered states. 
     As shown schematically in  FIG. 1 , the lift system  20  includes a controller  38  in communication with the first and second motors  30 ,  36  to synchronize operation of the first and second motors  30 ,  36  for moving the first and second platforms  28 ,  34  between the associated elevated and lowered states in synchronization. The controller  38  has encoders (not shown) which sense and maintain the synchronization of the first and second motors  30 ,  36 . It is to be appreciated that the controller may have a wired connection to the first and second motors  30 ,  36  or may have a wireless connection to the first and second motors  30 ,  36 . It is to be appreciated that the lift system  20  may use the controller  38  with any suitable number of platforms or motors. It is to be appreciated that the encoders may be any suitable type of electronic control component such as a sensor. 
     As shown in  FIGS. 1 and 3 , the first and second bases  26 ,  32  are interconnected for synchronized movement of the first and second bases  26 ,  32 . Specifically, the first and second bases  26 ,  32  are integral with each other. It should be appreciated that the first and second base  26 ,  32  may be separate components of the lift system  20  coupled to each other or separate components spaced from each other. Referring to  FIG. 3 , the first and second platforms  28 ,  34  can be interconnected for synchronized movement of the first and second platforms  28 ,  34 . It should be appreciated that the first and second platforms  28 ,  34  may be separate components of the lift system  20  coupled to each other. 
     The following disclosure describes components and features of the first scissor-type lift assembly  22  of the lift system  20 . It should be appreciated that the second scissor-type lift assembly  24  includes corresponding components and features as the first scissor-type lift assembly  22  and operates in substantially the same fashion as the first scissor-type lift assembly  22 . The same numbers assigned to the components or features of the first scissor-type lift assembly  22  are used to identify equivalent components and features of the second scissor-type lift assembly  24  in the figures with the exception of components and features of the second scissor-type lift assembly  24  previously numbered. 
     The first base  26  and the first platform  28 , each of which may be metal, are distant as the first platform  28  is in the elevated state. The first base  26  and the first platform  28  are proximate as the first platform  28  is in the lowered state. It is to be appreciated that the first platform  28  can be moved to states between the elevated and lowered states. It is to be appreciated that the first base  26  and the first platform  28  may be any suitable alternative material such as wood or plastic. 
     The first scissor-type lift assembly  22  includes a first and second pair of scissor arms  40 ,  42 , each of which may be made of steel. The first pair of scissor arms  40  are spaced from the second pair of scissor arms  42  and are transverse to the first base  26  and the first platform  28 . The first and second pair of scissor arms  40 ,  42  each include a first arm  44  and a second arm  46  spaced from the first arm  44  along the first pivot axis A 1 . It is to be appreciated that the first and second pair of scissor arms  40 ,  42  may be any suitable alternative metal such as iron or any suitable alternative material such as wood or plastic. 
     The first and second pair of scissor arms  40 ,  42  each have upper and lower ends  48 ,  50  respectively coupled to each of the first platform  28  and the first base  26 . The upper ends  48  of the first and second pair of scissor arms  40 ,  42  are coupled to the first platform  28 . The lower ends  50  of the first and second pair of scissor arms  40 ,  42  are coupled to the first base  26 . 
     The first base  26  has a pair of first tracks  52  with the lower ends  50  of the first arms  44  movably disposed in the pair of first tracks  52 . The pair of first tracks  52  guide the lower ends  50  of the first arms  44  to move along the first base  26  as the first platform  28  moves between the elevated and lowered states. The first platform  28  has a pair of second tracks (not shown) with the upper ends  48  of the second arms  46  movably disposed in the pair of second tracks. The pair of second tracks guide the upper ends  48  of the second arms  46  to move along the first platform  28  as the first platform  28  moves between the elevated and lowered states. 
     The first and second pair of scissor arms  40 ,  42  are connected to each other intermediate their respective upper and lower ends  48 ,  50  about a first pivot axis A 1  for pivoting relative to each other during the movement of the first platform  28  between the elevated and lowered states. The first pivot axis A 1  is transverse to the first pair of scissor arms  40  and moves as the first platform  28  moves between the elevated and lowered states. As shown  FIGS. 4-6 , the first pair of scissor arms  40  define a first pair of holes  54  aligned with each other along the first pivot axis A 1 . As shown  FIGS. 7 and 8 , the second pair of scissor arms  42  define a second pair of holes  56  aligned with each other along the first pivot axis A 1 . 
     As shown in  FIGS. 5 and 6 , the first scissor-type lift assembly  22  includes a first shaft  58  disposed along the first pivot axis A 1 . The first shaft  58  has a cylindrical configuration and a first shaft diameter D 1 . The first shaft  58  is disposed in the first pair of holes  54  of the first pair of scissor arms  40  aligned with and along the first pivot axis A 1 . The first pair of scissor arms  40  are pivotably disposed about the first shaft  58 . It is to be appreciated that the first shaft  58  may be any alternative configuration such as a tubular configuration. 
     The first shaft  58  has a first end  60  and a second end  62  spaced from the first end  60  along the first pivot axis A 1 . The first and second ends  60 ,  62  extend from the first pair of scissor arms  40  with the second end  62  terminating at a first shaft face  64 . The first end  60  extends from the first arm  44  of the first pair of scissor arms  40  toward the second pair of scissor arms  42 . The second end  62  extends from the second arm  46  of the first pair of scissor arms  40  away from the second pair of scissor arms  42 . The first shaft face  64  is transverse to the first pivot axis A 1 . 
     The first scissor-type lift assembly  22  includes a first spacer  66  disposed about the first shaft  58  between the first pair of scissor arms  40  to space the first pair of scissor arms  40  from each other along the first pivot axis A 1 . The first spacer  66  has a tubular configuration and may be made of plastic. The first spacer  66  prevents the first arms  44  and the second arms  46  from interfering with each other as the first pair of scissor arms  40  pivot about the first pivot axis A 1 . It is to be appreciated that the first spacer  66  may be fixed to the first shaft  58  or rotatably disposed about the first shaft  58 . It is to be appreciated that the first shaft  58  may be any suitable alternative configuration such as a rectangular cuboid configuration with a void defined along the first pivot axis A 1 . It is to be appreciated that the first spacer  66  may be any suitable alternative material with friction reducing properties such as a lubricated metal. 
     As shown in  FIGS. 4-6 , the scissor-type lift assembly includes a first brace  68  fixed to another one of the first pair of scissor arms  40 . In the illustrated embodiment, the first brace  68  has a rectangular cuboid configuration and is fixed to the second arm  46  of the first pair of scissor arms  40  transverse to the first pivot axis A 1 . The first brace  68  has a first brace face  70  facing the second arm  46 . Referring to  FIG. 5 , the first brace  68  has a first length L 1  greater than the first shaft diameter D 1  of the first shaft  58 . It is to be appreciated that the first brace  68  may have any suitable alternative configuration such as a cylindrical configuration with a diameter greater than the first shaft diameter D 1  of the first shaft  58 . 
     The first brace  68  abuts the first shaft face  64  of the first shaft  58  to maintain alignment of the first shaft  58  along the first pivot axis A 1  for reducing wear between the first pivot axis A 1  and the first pair of scissor arms  40 . Specifically, the first shaft face  64  is parallel to and abuts the first brace face  70 . The first brace face  70  abuts the first shaft face  64  and applies a compressive force to the first shaft  58  to prevent pivoting of the first shaft  58  away from alignment with the first pivot axis A 1 . 
     As shown in  FIGS. 5 and 6 , the first brace  68  has a first central portion  72  and a first support portion  74  extending from the first central portion  72  toward the another one of the first pair of scissor arms  40  to define a first gap  76  between said first central portion  72  and the another of the first pair of scissor arms  40 . The first brace face  70  is defined by the first central portion  72  of the first brace  68  with the first gap  76  partially defined by the first brace face  70 . The first shaft face  64  is disposed in the first gap  76 . Specifically, the second end  62  of the first shaft  58  extends from the second arm  46  of the first pair of scissor arms  40  and is disposed in the first gap  76 . 
     As shown in  FIGS. 4 and 5 , the first support portion  74  is further defined as a pair of first support portions  74 . In the illustrated embodiment, the pair of first support portions  74  have a rectangular cuboid configuration and are disposed between the first brace  68  and the second arm  46  of the first pair of scissor arms  40 . The first brace  68  has opposing distal ends  78 . The opposing distal ends  78  are spaced from each other and are defined relative to the pair of first support portions  74  of the first brace  68 . The pair of first support portions  74  partially define the first gap  76  with the second end  62  of the first shaft  58  disposed between the pair of first support portions  74 . It is to be appreciated that the pair of first support portions  74  may be any alternative suitable configuration such as a cylindrical configuration. It is to be appreciated that the pair of first support portions  74  may be integral with the first central portion  72 . 
     One of the pair of first support portions  74  extends from each of the opposing distal ends  78  of the first brace  68 . It is appreciated that the pair of first support portions  74  may be mounted to the first brace  68  in any suitable method such as being fixed to the first brace  68 , being disposed between the first brace  68  and the second arm  46  of the first pair of scissor arms  40 , or being integral with the first brace  68 . 
     The first scissor-type lift assembly  22  includes a first plurality of fasteners  80  extending through the pair of first support portions  74  to secure the first brace  68  to another one of the first pair of scissor arms  40 . Specifically, the first plurality of fasteners  80  are disposed in the pair of first support portions  74  and are secured to the second arm  46  of the first pair of scissor arms  40 . The first plurality of fasteners  80  are further defined as bolts. It is to be appreciated that the first plurality of fasteners  80  may be any alternative fastener such as a screw. 
     As shown in  FIGS. 4-6 , the first scissor-type lift assembly  22  includes a first flange  84  coupled to the first shaft  58  to further define the first shaft face  64  and further maintain alignment of the first shaft  58  along the first pivot axis A 1  for reducing wear between the first pivot axis A 1  and the first pair of scissor arms  40 . As illustrated, the first flange  84  is fixed to the second end  62  of the first shaft  58  and is disposed in the first gap  76  between the pair of first support portions  74 . The first flange  84  may be separately mounted to the first scissor-type lift assembly  22  (as shown) or the first flange  84  may be integral with the first shaft  58 . 
     Referring to  FIGS. 5 and 6 , the first flange  84  has a substantially flat washer like configuration defining a first cavity  86  about the first pivot axis A 1 . It is to be appreciated that the first flange  84  may be any suitable alternative configuration such as a solid cylindrical configuration. 
     The first shaft  58  has a first shaft periphery  88  with a circular configuration. The first flange  84  has a first flange periphery  90 . Specifically referring to  FIG. 5 , the first flange  84  has a first flange diameter D 2  and the first flange periphery  90  has a circular configuration. The first flange periphery  90  is disposed radially further from the first pivot axis A 1  than the first shaft periphery  88  to further maintain alignment of the first shaft  58  along the first pivot axis A 1  for reducing wear between the first pivot axis A 1  and the first pair of scissor arms  40 . Specifically, the first flange diameter D 2  is greater than the first shaft diameter D 1  of the first shaft  58  with the first flange  84  extending further from the first pivot axis A 1  than the first shaft  58  to engage the second arm  46  of the first pair of scissor arms  40  and the first brace  68  to prevent the first shaft  58  from moving along the first pivot axis A 1  toward the second pair of scissor arms  42 . The first flange  84  prevents tilting or rocking of the first shaft  58  out of alignment with the first pivot axis A 1 . Said differently, the first flange  84  prevents the first shaft  58  from wobbling in the first pair of holes  54  of the first pair of scissor arms  40 . It is to be appreciated that the first flange  84  may directly abut the another one of the first pair of scissor arms  40 . 
     As shown in  FIGS. 5-6 , the first scissor-type lift assembly  22  includes a first bushing  92 . The first bushing  92  has an annular configuration and may be made of as plastic. The first bushing  92  is disposed between the first flange  84  and the another one of the first pair of scissor arms  40  to reduce friction between the first flange  84  and the another one of the first pair of scissor arms  40  as the first pair of scissor arms  40  pivots about the first pivot axis A 1 . The first flange  84  and the first bushing  92  engage the second arm  46  of the first pair of scissor arms  40  and first brace  68  to prevent the first shaft  58  from pivoting away from alignment with the first pivot axis A 1 . The first bushing  92  also reduces friction between the first flange  84  and the second arm  46  of the first pair of scissor arms  40  as the first pair of scissor arms  40  pivot about the first pivot axis A 1 . Specifically, the first bushing  92  is disposed about the first shaft  58  between the first flange  84  and the second arm  46  of the first pair of scissor arms  40 . As the first pair of scissor arms  40  pivot, the first flange  84  and first bushing  92  abuts the second arm  46  and prevents pivoting of the first shaft  58 . It is to be appreciated that the first bushing  92  may be of any suitable alternative materials with friction reducing properties such as a lubricated metal. It is to be appreciated that the first bushing  92  may be of any suitable alternative configuration such as a rectangular cuboid. 
     The first scissor-type lift assembly  22  can also include a first plate or shim  82  coupled to the first shaft  58  to further define the first shaft face  64  and to further maintain alignment of the first shaft  58  along the first pivot axis A 1  for reducing wear between the first pivot axis A 1  and the first pair of scissor arms  40 . Specifically, the first plate  82  is disposed in the first gap  76  between the first flange  84  and the first brace  68 . The first plate  82  is also disposed in the first gap  76  between the first shaft  58  or the first flange  84  and the first brace  68  to ensure contact between the first shaft  58  or first flange  84  and the first brace  68 . It is to be appreciated that the first scissor-type lift assembly  22  may include the first plate  82  and the first flange  84  with the first plate  82  defining the first shaft face  64  and the first flange  84  disposed between the second end  62  of the first shaft  58  and the first plate  82 . 
     The first shaft  58  defines a first groove  94  about the first end  60 . The first groove  94  is defined in the first shaft  58  about the first pivot axis A 1 . The first scissor-type lift assembly  22  includes a first retention device  96  coupled to the first end  60  of the first shaft  58 . The first retention device  96  has tubular configuration and is disposed about the first end  60 . Specifically, the first retention device  96  disposed about the first shaft  58  and aligned with the first groove  94 . It is to be appreciated that the first retention device  96  may be any suitable alternative configuration such as a cylindrical configuration. 
     The first scissor-type lift assembly  22  includes a first retention fastener  98  extending through the first retention device  96  and disposed in the first groove  94  of the first shaft  58  to secure the first retention device  96  to the first shaft  58 . Specifically, the first retention fastener  98  is further defined as a bolt. The first retention fastener  98  prevents the first retention device  96  from moving along the first shaft  58  away from the first arm  44  of the first pair of scissor arms  40 . The first retention device  96  prevents the first shaft  58  from moving along the first pivot axis A 1  away from the second pair of scissor arms  42 . It is to be appreciated that the first retention fastener  98  may be any suitable alternative fastener such as a screw. 
     The first scissor-type lift assembly  22  includes a first retention bushing  100 . The first retention bushing  100  has a tubular configuration and may be made of as plastic. The first retention bushing  100  is disposed between the first retention device  96  and the first arm  44  of the first pair of scissor arms  40  with the first shaft  58  reducing friction between the first retention device  96  and the first arm  44  of the first pair of scissor arms  40  as the first pair of scissor arms  40  pivot about the first pivot axis A 1 . It is to be appreciated that the first retention bushing  100  may be of any suitable alternative materials with friction reducing properties such as a lubricated metal. It is to be appreciated that the first retention bushing  100  may be of any suitable alternative configuration such as a rectangular cuboid. 
     The first shaft  58  has a first removal feature  102  defined in the second end  62  for removing the first shaft  58  from the first pair of scissor arms  40 . Specifically, the first shaft  58  defines the first removal feature  102  as a threaded void extending through the first shaft face  64 . The first removal feature  102  is defined in the first cavity  86  of the first flange  84 . An operator may insert a threaded rod (not shown) into the first removal feature  102  and use a removal tool (not shown) to pull the first shaft  58  along the first pivot axis A 1  and remove the first shaft  58  from the first pair of scissor arms  40 . 
     As shown in  FIGS. 7 and 8 , the second scissor-type lift assembly  24  includes a second shaft  104  disposed along the first pivot axis A 1 . The second shaft  104  has a second shaft diameter D 3 . The second shaft  104  is disposed in the second pair of holes  56  of the second pair of scissor arms  42  aligned with and along the first pivot axis A 1 . The second pair of scissor arms  42  are pivotably disposed about the second shaft  104 . 
     The second shaft  104  has a third end  106  and a fourth end  108  spaced from the third end  106  along the first pivot axis A 1 . The third and fourth ends  106 ,  108  extend from the second pair of scissor arms  42  with the fourth end  108  terminating at a second shaft face  110 . The third end  106  extends from the first arm  44  of the second pair of scissor arms  42  toward the first pair of scissor arms  40 . The fourth end  108  extends from second arm  46  of the second pair of scissor arms  42  away from the first pair of scissor arms  40 . 
     The second scissor-type lift assembly  24  includes a second spacer  112  disposed about the second shaft  104  between the second pair of scissor arms  42  to space the second pair of scissor arms  42  from each other along the first pivot axis A 1 . The second spacer  112  prevents the first arms  44  and the second arms  46  from interfering with each other as the second pair of scissor arms  42  pivot about the first pivot axis A 1 . It is to be appreciated that the second spacer  112  may be fixed to the second shaft  104  or rotatably disposed about the second shaft  104 . 
     The scissor-type lift assembly includes a second brace  114  fixed to another one of the second pair of scissor arms  42 . In the illustrated embodiment, the second brace  114  has a second brace face  116  with a second length L 2  greater than the second shaft diameter D 3  of the second shaft  104 . The second brace  114  abuts the second shaft face  110  of the second shaft  104  to maintain alignment of the second shaft  104  along the first pivot axis A 1  for reducing wear between the first pivot axis A 1  and the second pair of scissor arms  42 . The second brace face  114  abuts the second shaft face  110  and applies a compressive force to the second shaft  104  to prevent pivoting of the second shaft  104  away from alignment with the first pivot axis A 1 . 
     The second brace  114  has a second central portion  118  and a second support portion  120  extending from the second central portion  118  toward the another one of the second pair of scissor arms  42  to define a second gap  122  between said second central portion  118  and the another of the second pair of scissor arms  42 . The second brace face  116  is defined by the second central portion  118  of the second brace  114  and the second gap  122  is partially defined by the second brace face  116 . The second shaft face  110  is disposed in the second gap  122 . Specifically, the fourth end  108  of the second shaft  104  extends from the second arm  46  of the second pair of scissor arms  42  and is disposed in the second gap  122 . 
     The second support portion  120  is further defined as a pair of second support portions  120 . The second brace  114  has opposing distal ends  124 . The opposing distal ends  124  are spaced from each other and are defined in the pair of second support portions  120  of the second brace  114 . The pair of second support portions  120  are disposed between the second brace  114  and another one of the second pair of scissor arms  42 . The second brace  114  has a opposing distal ends  124 . 
     One of the pair of second support portions  120  extends from each opposing distal ends  124  of the second brace  114 . The second scissor-type lift assembly  24  includes a second plurality of fasteners  126  extending through the pair of second support portions  120  to secure the second brace  114  to another one of the second pair of scissor arms  42 . Specifically, the second plurality of fasteners  126  are disposed in the pair of second support portions  120  and are secured to the second arm  46  of the second pair of scissor arms  42 . 
     The second scissor-type lift assembly  24  includes a second flange  130  coupled to the second shaft  104  to further define the second shaft face  110  and further maintain alignment of the second shaft  104  along the first pivot axis A 1  for reducing wear between the first pivot axis A 1  and the second pair of scissor arms  42 . As illustrated, the second flange  130  is fixed to the second end  109  of the second shaft  104  and is disposed in the second gap  122  between the pair of second support portions  120 . The second flange  130  may be separately mounted to the second scissor-type lift assembly  24  (as shown) or the second flange  130  may be integral with the second shaft  104 . The second flange  130  defines a second cavity  132  about the first pivot axis A 1 . 
     The second shaft  104  has a second shaft periphery  136 . The second flange  130  has a second flange periphery  136 . The second flange  130  has a second flange diameter D 3  and the second flange periphery  136  has a circular configuration. The second flange periphery  136  is disposed radially further from the first pivot axis A 1  than the second shaft periphery  136  to further maintain alignment of the second shaft  104  along the first pivot axis A 1  for reducing wear between the first pivot axis A 1  and the second pair of scissor arms  42 . Specifically, the second flange diameter D 3  is greater than the second shaft diameter D 2  of the second flange  130  with the second flange  130  extending further from the first pivot axis A 1  than the second shaft  104  to engage both the second arm  46  of the second pair of scissor arms  42  and the second brace  114  to prevent the second shaft  104  from moving along the first pivot axis A 1  toward the first pair of scissor arms  40 . The second flange  130  prevents tilting or rocking of the second shaft  104  out of alignment with the first pivot axis A 1 . Said differently, the second flange  130  prevents the second shaft  130  from wobbling in the second pair of holes  56  of the second pair of scissor arms  42 . It is to be appreciated that the second flange  130  may directly abut the another one of the second pair of scissor arms  42 . 
     The second scissor-type lift assembly  24  includes a second bushing  138 . The second bushing  138  is disposed between the second flange  130  and the another one of the second pair of scissor arms  42  to reduce friction between the second flange  130  and the another one of the second pair of scissor arms  42  as the second pair of scissor arms  42  pivots about the first pivot axis A 1 . The second bushing  138  disposed about the fourth end  108  of the second shaft  104 . The second bushing  138  abuts the second arm  46  of the second pair of scissor arms  42  and the second flange  130 . Specifically, the second bushing  138  is disposed about the second shaft  104  between the second flange  130  and the second arm  46  of the second pair of scissor arms  42 . As the second pair of scissor arms  42  pivot, the second flange  130  and the second bushing  138  abut the second arm  46  and prevent pivoting of the second shaft  104 . 
     The second scissor-type lift assembly  24  includes a second plate or shim  128  coupled to the second shaft  104  to further define the second shaft face  110  and to further maintain alignment of the second shaft  104  along the first pivot axis A 1  for reducing wear between the first pivot axis A 1  and the second pair of scissor arms  42 . Specifically, the second plate  128  is disposed in the second gap  122  between the second flange  130  and the second brace  114 . The second plate  128  is disposed in the second gap  122  between the second shaft  104  or the second flange  130  and the second brace  114  to ensure contact between the second shaft  104  or the second flange  130  and the second brace  114 . It is to be appreciated that the second scissor-type lift assembly  24  may include the second plate  128  and the second flange  130  with the second plate  128  defining the second shaft face  110  and the second flange  130  disposed between the fourth end  108  of the second shaft  104  and the second plate  128 . 
     The second shaft  104  defines a second groove  140  about the third end  106 . The second scissor-type lift assembly  24  includes a second retention device  142  coupled to the third end  106  of the second shaft  104 . Specifically, the second retention device  142  disposed about the second shaft  104  and aligned with the second groove  140 . 
     The second scissor-type lift assembly  24  includes a second retention fastener  144  extending through the second retention device  142  and disposed in the second groove  140  of the second shaft  104  to secure the second retention device  142  to the second shaft  104 . The second retention device  142  prevents the second shaft  104  from moving along the first pivot axis A 1  away from the first pair of scissor arms  40 . The second shaft  104  has a second removal feature  148  defined in the fourth end  108  for removing the second shaft  104  from the second pair of scissor arms  42 . 
     As shown in  FIGS. 1 and 3 , the first scissor-type lift assembly  22  includes a first guide arrangement  150  mounted to the first and second pair of scissor arms  40 ,  42 . Specifically, the first guide arrangement  150  is further defined as a first engagement shaft  152  and a first pulley shaft  154 . The first engagement shaft  152  is movably disposed between the second arms  46  of the first and second pair of scissor arms  40 ,  42 . The first pulley shaft  154  is disposed between the lower ends  50  of the first arms  44  of the first and second pair of scissor arms  40 ,  42 . The first pulley shaft  154  defines a first pulley axis A 2  and has a first pulley  156  rotatably disposed about the first pulley shaft  154 . 
     The first and second pair of scissor arms  40 ,  42  have a first pair of rods  158  with one of the first pair of rods  158  coupled to one of the first arms  44  and another one of the first pair of rods  158  coupled to another one of the first arms  44 . The first pair of rods  158  have a cylindrical configuration and extend along the first arms  44  between the upper ends  48  of the first arms  44  and the first pivot axis A 1 . As shown in  FIG. 11 , the first pair of rods  158  have a lowered rod end (not shown) relative to the upper ends  48  of the first arms  44  and an elevated rod end  160  relative the first pivot axis A 1 . It is to be appreciated that the first pair of rods  158  may be any suitable alternative configuration such as a rectangular cuboid configuration. 
     As shown in  FIGS. 1 and 3 , the first and second pair of scissor arms  40 ,  42  have a first pair of cams  162  with one of the first pair of cams  162  extending from one of the second arms  46  and another one of the first pair of cams  162  extending from another one of the second arms  46 . The first pair of cams  162  have an arcuate configuration and extend along the second arms  46  between the lower ends  50  and the first pivot axis A 1 . The first pair of cams  162  have a lowered cam end  164  relative to the lower ends  50  of the second arms  46  and an elevated rod end  160  (not shown) relative the first pivot axis A 1 . It is to be appreciated that the first pair of cams  162  may be any suitable alternative configuration such as a flat configuration. 
     As shown in  FIGS. 1, 3, and 10 , the first engagement shaft  152  has a first pair of cam followers  166  with one of the first pair of cam followers  166  rotatably abutting one of the first pair of cams  162  and another one of the first pair of cam followers  166  rotatably abutting the another one of the first pair of cams  162 . The first pair of cam followers  166  are disposed along the first pair of cams  162  at the lowered cam ends  164  as the first platform  28  is in the lowered state and the first pair of cam followers  166  are disposed along the first pair of cams  162  at the elevated cam ends as the first platform  28  is in the elevated state. As the first and second pair of scissor arms  40 ,  42  pivot about the first pivot axis A 1 , the first pair of cam followers  166  move along the first pair of cams  162  to lower and raise the first platform  28 . 
     As shown in  FIGS. 1, 3, and 10-11 , the first engagement shaft  152  has a first pair of rod followers  168  with one of the first pair of rod followers  168  rotatably abutting one of the first pair of rods  158  and another one of the first pair of rod followers  168  rotatably abutting another one of the first pair of rods  158 . The first pair of rod followers  168  are disposed along the first pair of rods  158  at the lowered rod ends as the first platform  28  is in the lowered state and the first pair of rod followers  168  are disposed along the first pair of rods  158  at the elevated rod ends  160  as the first platform  28  is in the elevated state. As the first and second pair of scissor arms  40 ,  42  pivot about the first pivot axis A 1 , the first pair of rod followers  168  move along the first pair of rods  158  to lower and raise the first platform  28 . 
     The first guide arrangement  150  is movable with the first and second pair of scissor arms  40 ,  42  during movement of the first platform  28 . The first engagement shaft  152  moves along the first pair of rods  158  and the first pair of cams  162  as the first and second pair of scissor arms  40 ,  42  pivot and the first platform  28  moves between the elevated and lowered states. The first pulley shaft  154  moves along the first base  26  as the first and second pair of scissor arms  40 ,  42  pivot and the first platform  28  moves between the elevated and lowered states. 
     As shown in  FIGS. 10 and 11 , the first scissor-type lift assembly  22  includes a first pair of interfaces  170  at which the first engagement shaft  152  engages the first and second pair of scissor arms  40 ,  42 . Specifically, the first pair of interfaces  170  are defined as the first pair of rod followers  168  rotatably abut the first pair of rods  158  of the first arms  44 . The first scissor-type lift assembly  22  includes a first pair of lubrication features  172  coupled to the first engagement shaft  152  with the first pair of lubrication features  172  lubricating the first pair of interfaces  170  as the first platform  28  moves between the elevated and lowered states. Specifically, the first pair of lubrication features  172  lubricate the first pair of rod followers  168  as the first pair of rod followers  168  move along the first pair of rods  158 . 
     As shown in  FIGS. 1, 3 and 12-14 , the first scissor-type lift assembly  22  includes a first spool  174  coupled to the first base  26  and defining a first spool axis A 3 . The first scissor-type lift assembly  22  has a first spool shaft  176  rotatably mounted to the first base  26  and extending along the first spool axis A 3 . The first spool shaft  176  is rotatably coupled to the first motor  30 . The first spool  174  has a first spool base  178  disposed about the first spool shaft  176  along the first spool axis A 3 . The first spool  174  and the first spool base  178  rotate about the first spool axis A 3  as a unit. The first spool  174  has a first pair of spool flanges  180  spaced from each along the first spool axis A 3  and abutting the first spool base  178 . 
     As shown in  FIGS. 1 and 3 , the first guide arrangement  150  defines a first path. The first path is defined from the first spool  174  along the first base  26  to the first pulley  156  of the first engagement shaft  152 . The first path is defined about the first pulley  156  of the first engagement shaft  152  and between the first arms  44  to the first pulley shaft  154 . It is to be appreciated that the first path may have any suitable alternative route or configuration depending on the number of pulleys or shafts. 
     The first scissor-type lift assembly  22  includes a first belt  182  routed through the first path of the first guide arrangement  150 . The first belt  182  has a primary end  184  engaged with the first spool  174  onto which the first belt  182  is wound and from which the first belt  182  is unwound. Specifically, the primary end  184  of the first belt  182  is fastened to the first spool base  178 . The first belt  182  is coupled to and wound about the first spool base  178  between the first pair of spool flanges  180 . The first belt  182  has a secondary end (not shown) engaged with the first engagement shaft  152 . It should be appreciated the first belt  182  may be fastened to the first spool  174  in any suitable manner such as being bolted to the first spool  174 . It should be appreciated the first belt  182  may be any suitable alternatives such as a rope or a cable. 
     The first belt  182  is routed through the first path about the first pulley shaft  154  and coupled to the first engagement shaft  152  for reducing the force required to move the first platform  28  between the elevated and lowered states. Specifically, the primary end  184  of the first belt  182  is coupled to the first spool  174  relative to the lower ends  50  of the second arms  46 . The first belt  182  extends along the first base  26  towards the lower ends  50  of the first arms  44  and to the first pulley shaft  154 . The first belt  182  is disposed about the first pulley  156  of the first engagement shaft  152  and extends between the first arms  44  towards the first pivot axis A 1  and is coupled to the first engagement shaft  152 . 
     The first belt  182  is further defined as a plurality of first belts  182  routed through the first path defined by the first guide arrangement  150 . The plurality of first belts  182  each have a pair of edges  186 . Specifically, the plurality of first belts  182  are defined as three first belts  182  routed through the first path defined by the first guide arrangement  150 . 
     The first scissor-type lift assembly  22  includes a plurality of first rollers  188  movably disposed about the first spool  174 . The plurality of first rollers  188  each have a pair of outer surfaces  190 . Specifically, the plurality of first rollers  188  are defined as two first rollers  188  disposed about the first spool base  178  between the first pair of spool flanges  180 . One of the plurality of first rollers  188  is disposed between two of the plurality of the first belts  182  to align the plurality first belts  182  as the first spool  174  winds and unwinds the plurality first belts  182 . The plurality of first rollers  188  are movable along and about the first spool base  178 . The plurality of rollers  188  move with the plurality of first belts  182  as the first belts  182  wind and unwind about the first spool base  178 . The first pair of outer surfaces  190  of the plurality of rollers abut the pair of edges  186  of the plurality of first belts  182  as the plurality of first belts  182  are wound and unwound to align the plurality of first belts  182  on the first spool base  178 . The alignment of the plurality of first belts  182  on the first spool base  178  prevents fraying and deterioration of the plurality of first belts  182 . 
     The first motor  30  is mounted to the first base  26  and is operatively coupled to the first spool  174  to wind and unwind the first belt  182  through the first path to move the first and second pair of scissor arms  40 ,  42  and move the first platform  28  between the elevated and lowered states. The first motor  30  is coupled to the first spool shaft  176  to rotate the first spool  174  about the first spool axis A 3  in a first direction R1 to wind the plurality of first belts  182  onto and about the first spool base  178  to raise the first platform  28 . The first motor  30  also rotates the first spool  174  about the first spool axis A 3  in a second direction R2 to unwind the plurality of first belts  182  from the first spool base  178  to lower the first platform  28 . 
     As the first and second platforms  28 ,  34  are in the lowered state, an operator engages the controller  38  to operate the first and second motors  30 ,  36  in synchronization to raise the first and second platforms  28 ,  34  to the elevated state. The lift system  20  may be precisely controlled with the first motor  30  of the first scissor-type lift assembly  22  and the second motor  36  of the second scissor-type lift assembly  24  both in communication with and controlled by the controller  38 . 
     As the operator utilizes the controller  38  and initiates the first scissor-lift assembly  22 , the first motor  30  rotates the first spool shaft  176  and the first spool  174  about the first spool axis A 3  in the first direction R1. As the first spool  174  rotates in the first direction R1, the plurality of first belts  182  are wound about the first spool base  178 . The plurality of first rollers  188  guide and align the plurality of first belts  182  onto the first spool base  178 . As the plurality of first belts  182  are wound about the first spool base  178 , the plurality of first belts  182  exert a force along the first path to engage the first engagement shaft  152 . The force moves the first pair of cam followers  166  along the first pair of cams  162  from the lowered cam ends  164  toward the elevated cam ends and moves the first pair of rod followers  168  along the first pair of rods  158  from the lowered rod ends toward the elevated rod ends  160 . 
     As the first pair of cam followers  166  move along the first pair of cams  162  and the first pair of rod followers  168  move along the first pair of rods  158 , the first and second pair of scissor arms  40 ,  42  pivot about the first pivot axis A 1  with the lower ends  50  of the first arms  44  moving along the pair of first tracks  52  and the upper arms of the second arms  46  moving along the pair of second tracks. As the first and second pair of scissor arms  40 ,  42  pivot about the first pivot axis A 1 , the first platform  28  moves from the lowered state to the elevated state until the operator disengages the controller  38  to cease operation of the first motor  30  or until the first pair of cam followers  166  move along the first pair of cams  162  to the elevated cam ends and the first pair of rod followers  168  move along the first pair of rods  158  to the elevated rod ends  160 . 
     As the first and second platforms  28 ,  34  are in the elevated state, an operator can utilize the controller  38  to operate the first and second motors  30 ,  36  to lower the first and second platforms  28 ,  34  to the lowered state. The operator engages the controller  38  to initiate synchronized operation of the first and second motors  30 ,  36 . 
     As the operator utilizes the controller  38  and initiates the first scissor-lift assembly  22 , the first motor  30  rotates the first spool shaft  176  and the first spool  174  about the first spool axis A 3  in the second direction R2. As the first spool  174  rotates in the first direction D 2 , the plurality of first belts  182  are unwound from the first spool base  178 . The plurality of first rollers  188  guide and align the plurality of first belts  182  away the first spool base  178 . As the plurality of first belts  182  are unwound about the first spool base  178 , the plurality of first belts  182  release the force exerted along the first path to holding the first engagement shaft  152  along the second arms  46 . The releasing of the force moves the first pair of cam followers  166  along the first pair of cams  162  from the elevated cam ends toward the lowered cam ends  164  and moves the first pair of rod followers  168  along the first pair of rods  158  from the elevated rod ends  160  toward the lowered rod ends. 
     As the first pair of cam followers  166  move along the first pair of cams  162  and the first pair of rod followers  168  move along the first pair of rods  158 , the first and second pair of scissor arms  40 ,  42  pivot about the first pivot axis A 1  with the lower ends  50  of the first arms  44  moving along the pair of first tracks  52  and the upper arms of the second arms  46  moving along the pair of second tracks. As the first and second pair of scissor arms  40 ,  42  pivot about the first pivot axis A 1 , the first platform  28  moves from the elevated state to the lowered state until the operator disengages the controller  38  to cease operation of the first motor  30  or until the first pair of cam followers  166  move along the first pair of cams  162  to the lowered cam ends  164  and the first pair of rod followers  168  move along the first pair of rods  158  to the lowered rod ends. 
     As the first pair of scissor arms  40  pivot about the first pivot axis A 1 , the first retention device  96  and the first retention bushing  100  are secured to the first end  60  of the first shaft  58  and engage the first arm  44  of the first pair of scissor arms  40 . The first retention device  96  prevents movement of the first shaft  58  along the first pivot axis A 1  away from the second pair of scissor arms  42 . The first flange  84  and the first bushing  92  engage the second arm  46  of the first pair of scissor arms  40  with the first flange  84  preventing movement of the first shaft  58  along the first pivot axis A 1  towards the second pair of scissor arms  42 . 
     The first brace  68  is secured to the second arms  46  of the first pair of scissor arms  40  of the first flange  84  and the first bushing  92  with the second arm  46  of the first pair of scissor arms  40 . The engagement of the first flange  84  and the second arm  46  prevents the first shaft  58  from tilting or rocking and retains the first shaft  58  in alignment along the first pivot axis A 1  to reduce wear to the first shaft  58  and the first pair of scissor arms  40  as the first pair of scissor arms  40  pivot about the first pivot axis A 1 . 
     As the second pair of scissor arms  42  pivot about the first pivot axis A 1 , the second retention device  142  and the second retention bushing  146  are secured to the third end  106  of the second shaft  104  and engage the first arm  44  of the second pair of scissor arms  42 . The second retention device  142  prevents movement of the second shaft  104  along the first pivot axis A 1  away from the first pair of scissor arms  40 . The second flange  130  and the second bushing  138  engage the second arm  46  of the second pair of scissor arms  42  with the second flange  130  preventing movement of the second shaft  104  along the first pivot axis A 1  towards the first pair of scissor arms  40 . 
     The second brace  114  is secured to the second arm  46  of the second pair of scissor arms  42  with the second brace face  116  abutting the second shaft face  110 . The second brace  114  applies the compressive force to the second plate  128  to retain the engagement of the second flange  130  and the second bushing  138  with the second arm  46  of the second pair of scissor arms  42 . The engagement of the second flange  130  and the second arm  46  prevents the second shaft  104  from tilting or rocking and retains the second shaft  104  in alignment along the first pivot axis A 1  to reduce wear to the second shaft  104  and the second pair of scissor arms  42  as the second pair of scissor arms  40  pivot about the first pivot axis A 1 . 
     The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. As is now apparent to those skilled in the art, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described.