Patent Application
20100111653
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.
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.
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.
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
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
With reference to
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
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.
