Patent Publication Number: US-2010111653-A1

Title: Vertical lift with synchronizer

Description:
BACKGROUND 
     The present invention relates to vertical lifts and/or conveyors. 
     Vertical lifts are employed in warehouses, factories and the like to convey material or cargo between different vertical levels. The typical vertical lift includes a supporting structure and a carriage, which is adapted to support cargo and is guided for vertical movement on the supporting structure. 
     In one type of vertical lift, as shown in U.S. Pat. No. 5,205,379, the carriage is straddled between two vertical columns of the support structure and is guided for vertical movement on the columns. The lifting of the carriage is accomplished through the use of two hydraulic cylinder units, each of which is mounted on one of the vertical columns. A piston rod of each cylinder unit is, in turn, connected to a wire rope or roller chain, having one end connected to the carriage and the other end dead headed. The piston rod of each unit carries either a sheave adapted for wire rope or a sprocket adapted for roller chain. As the cylinder rod retracts, it pulls on either the roller chain or wire rope causing the carriage to elevate from the lower to the upper level. 
     In another example, as shown in U.S. Pat. No. 5,908,088, a lift uses a pair of hydraulic cylinder units to elevate the carriage between levels. The cylinders are attached to each other and disposed so that one piston rod pushes downward and one piston rod pushes upward against the carriage structure. 
     SUMMARY 
     Existing lifts that utilize hydraulic cylinder units to raise and lower the carriage are often routed in a single hydraulic circuit such that when the valves are open the hydraulic pressure in all the hydraulic cylinder units is equal. If the payload is shifted off center toward one of the cylinders, the carriage will lag on the light side until the carriage guide rollers contact the vertical guide surfaces (there is running clearance between the rollers and the guide surfaces). The moment caused by the offset load is taken up by the rollers so that each cylinder carries the same load. 
     The present invention provides a synchronizer system that may be used with ram-drive hydraulic cylinders that push directly on the carriage, or another drive system. The use of ram-drive hydraulic cylinders eliminates the need for broken chain safeties (e.g., safety cams) and the synchronizer system allows for one single cylinder to maintain the carriage in a substantially level position should the other cylinder fail. In previous lifts, such a cylinder failure would allow the side of the carriage with the failed cylinder to drop significantly and cause damage to the lift guide structure and carriage structure. 
     In one aspect, the invention provides a vertical lift that includes a support, a carriage that is mounted for vertical movement relative to the support, a drive system that includes an actuator (e.g., a hydraulic actuator) that is coupled directly to the carriage, and a synchronizer (e.g., separate from the drive system) that is coupled between the carriage and the support. In one embodiment, the synchronizer is a cross shaft that reduces the carriage tilting and reduces the load on the guide rollers. This system maintains the carriage in a substantially level condition under all loading conditions, or under failure of one cylinder. 
     Preferably, the synchronizer includes a first engagement member (e.g., a tensioned chain) that is attached to the support and a second engagement member (e.g., a sprocket) that is attached to the carriage and is meshed with the first engagement member. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a vertical lift embodying the present invention. 
         FIG. 2  is a partial perspective view of the vertical lift of  FIG. 1 . 
         FIG. 3  is a perspective view showing a portion of the vertical lift of  FIG. 1 . 
         FIG. 4  is a perspective view showing a portion of the vertical lift of  FIG. 1 . 
         FIG. 5  is a perspective view showing a portion of another vertical lift that is another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
       FIG. 1  shows a vertical lift  10  that includes two vertical supports  14 , a carriage  18 , a drive system  22 , and a synchronizer assembly  26 . The two vertical supports  14  extend at least between a first level  30  and a second level  34  and support the carriage  18  for movement between the first level  30  and the second level  34 . The illustrated vertical supports  14  are constructed of steel and include guides  38  that engage the carriage  18  and provide added support such that the carriage  18  maintains a desired alignment with the vertical supports  14 . A cross beam  42  connects the vertical supports  14  to add rigidity to the vertical supports  14 . The vertical supports  14  also include a lower stop  46  and an upper stop  50 . The lower and upper stops  46 ,  50  inhibit the carriage  18  from traveling beyond the first and second levels  30 ,  34 , respectively. In other embodiments, the support structure may be different and may include additional truss work, cross supports, more or less than two vertical supports  14 , or other support structures, as desired. In addition, the vertical supports  14  may be built into walls or another structure such as a building, a warehouse, or a quarry. Furthermore, although two vertical supports  14  are shown, more or less than two vertical supports  14  may be utilized, as desired. 
     The carriage  18  includes a frame  54  and a platform  58 . The frame  54  includes guide beams  62  that engage the guides  38  of the vertical supports  14  to maintain the carriage  18  in the desired alignment with respect to the vertical supports  14 . The illustrated guide beams  62  have rollers  66  (see  FIG. 4 ) that engage the guides  38  and reduce the friction between the carriage  18  and the vertical supports  14  while the carriage  18  is moving between the first level  30  and the second level  34  relative to the vertical supports  14 . The platform  58  supports goods that may be moved between the first level  30  and the second level  34 . In other embodiments, the carriage  18  may include guard rails, truss work, or other supports, as desired. In addition, while the illustrated carriage  18  is straddled by the two vertical supports  14 , the carriage  18  could be a cantilevered carriage  18  or have another arrangement, as desired. 
     The drive system  22  includes two actuators in the form of hydraulic actuators  70  that are directly connected to the frame  54  of the carriage  18  and push the carriage  18  from the first level  30  to the second level  34 . The illustrated hydraulic actuators  70  are telescoping actuators. If the vertical lift  10  looses power, the carriage  18  is inhibited from moving by the hydraulic fluid trapped in the hydraulic actuators  70 . In other embodiments, the hydraulic actuators  70  may be sized differently to move the carriage  18  between more than two levels. In addition, any desired number of hydraulic actuators  70  may be used. 
     With reference to  FIG. 2 , the illustrated synchronizer assembly  26  is separate from the drive system  22  (i.e., the synchronizer assembly  26  does not move the carriage  18 ) and includes a rotary shaft  74  coupled to the frame  54  of the carriage  18  by bearings (not shown) held within a bearing housing  78  such that the rotary shaft  74  is coupled to the carriage  18  and movable therewith. The synchronizer assembly  26  is substantially the same on the right and the left. Therefore, only the right side (as viewed in  FIG. 2 ) will be described in detail. 
     With reference to  FIG. 4 , a sprocket  82  is connected to the end of the rotary shaft  74  and held in rotational alignment with the rotary shaft  74  by a keyway (not shown) and a set-screw  86 . The sprocket  82  is one embodiment of a toothed rotary engagement member. Other toothed rotary engagement members may be utilized, such as a gear  90  (see  FIG. 5 ). In addition, other engagement members exist and may be used, as desired. Furthermore, the keyway (not shown) may be another form of alignment arrangement (e.g., a spine, a pin) or the engagement member may be fixed to the rotary shaft  74  with welds or in another way, as desired. 
     The sprocket  82  engages a chain  94  that is mounted to the vertical support  14 . The chain  94  includes multiple links, a tensioner bolt  98 , and a hard mount  102  welded to the vertical support  14  adjacent the upper stop  50  (see  FIG. 3 ). The illustrated tensioner bolt  98  is threaded and threads into a tensioner mount  106  that is welded to the vertical support  14 . Rotating the tensioner bolt  98  relative to the tensioner mount  106  adjusts the tension of the chain  94 . The chain  94  is one embodiment of a toothed longitudinal member. Other toothed longitudinal members may be utilized, such as a toothed rack  110  (see  FIG. 5 ). The toothed rack  110  may be used with the gear  90  to achieve a substantially similar result as that shown in  FIG. 4 . In other embodiments, different engagement members may be used (e.g., indexed belts and pulleys), as desired. 
     The two sprockets  82  are secured to the rotary shaft  74  in spaced relation to one another and each engage the respective chain  94 . In this way the right and left sides of the carriage  18  are synchronized such that the carriage  18  moves between the first and second levels  30 ,  34  smoothly while maintaining the platform  58  substantially level. In other words, the synchronizer assembly  26  causes the two hydraulic actuators  70  to move the carriage  18  at substantially the same rate and maintain the carriage  18  in substantially the same position relative to the vertical supports  14  at any given time. 
     In operation, the carriage  18  is positioned at the first level  30  with the guide beams  62  contacting the lower stops  46  and the hydraulic actuators  70  fully lowered. Then, a load is positioned on the platform  58  and the carriage  18  is raised to the second level  34  by the hydraulic actuators  70 . While moving from the first level  30  to the second level  34 , the sprockets  82  rotate synchronously up the chains  94 , thereby maintaining the two hydraulic actuators  70  in substantially the same position and moving at substantially the same speed. 
     When the carriage  18  reaches the second level  34 , the load is removed from the platform  58 . Then, the hydraulic actuators  70  move the carriage  18  from the second level  34  back to the first level  30  where a new load may be positioned on the platform  58 . Alternatively, the load may be moved from the second level  34  to the first level  30 . While the carriage  18  is moving from the second level  34  to the first level  30 , the sprockets  82  rotate down the chain  94 , thereby maintaining the two hydraulic actuators  70  in substantially the same position and moving at substantially the same speed. In other embodiments, the vertical lift  10  may travel between more than two levels. 
     Various features and advantages of the invention are set forth in the following claims.