Scissor lift

• US 5,722,513 A
• Filed: 06/20/1995
• Issued: 03/03/1998
• Est. Priority Date: 06/20/1995
• Status: Expired due to Term

• Current Assignee: Pentalift Equipment Corp.
• Original Assignee: Pentalift Equipment Corp.
• Inventors: Cooke, Gary, Sutherland, Leonard G., Pedersen, Paul A., Rowan, Richard T.
• Primary Examiner(s): NOLAND, KENNETH W
• Application Number:
  US08/492,602
• Time in Patent Office: 987 Days
• Field of Search: 182/269, 182/211, 182/210, 312/71, 108/136, 254/89 R, 254/90
• US Class Current: 187/269
• CPC Class Codes: B65G 1/07 the upper article of a pile being always presented at the same predetermined level
• CPC Class Codes: B66F 7/065 Scissor linkages, i.e. X-configuration

Abstract

A scissor lift has a pair of leg assemblies pivotally connected to a base. Relative movement between the legs and the base is opposed by spring assemblies that may be selectively connected to a carriage to vary the bias on the legs. A cam member secured to the leg acts on the carriage to modify the motion between the leg and the carriage to maintain a uniform vertical spring rate.

Claims

1. A scissor lift to maintain a load at an elevated location comprising a base, a support to support said load, at least one leg assembly having a pair of legs pivoted to one another intermediate their ends, said leg assembly extending between said base and said support and being connected thereto to permit relative movement between said support and said base while maintaining a predetermined orientation of said support to said base, and biasing means acting on said leg assembly to oppose relative movement between said support and said base, said biasing means including a plurality of biasing units selectively engageable with said leg assembly to vary the bias acting thereon.

2. A scissor lift according to claim 1 wherein a carriage is operably connected to said leg assembly for movement therewith and said units are selectively engageable with said carriage.

3. A scissor lift according to claim 2 wherein said carriage is supported upon said base and is moveable relative thereto.

4. A scissor lift according to claim 3 wherein said biasing units are mounted on said base.

5. A scissor lift according to claim 4 wherein said biasing units include mechanical spring elements.

6. A scissor lift according to claim 5 wherein said mechanical spring elements are selectively connected to said carriage by removable pins.

7. A scissor lift according to claim 4 wherein said carriage is supported on rollers for movement relative to said base and said biasing units act between said carriage and an abutment on said base.

8. A scissor lift according to claim 7 wherein said leg is pivotally connected to said base and a cam member is provided on said leg to engage a follower on said carriage and cause relative movement thereof upon pivotal movement between said leg and said base.

9. A scissor lift according to claim 8 wherein said follower is rotatably mounted on said carriage adjacent said roller.

10. A scissor lift according to claim 7 wherein said biasing units include coil springs.

11. A scissor lift according to claim 10 wherein said coil springs are supported on rods secured to said abutment and passing through said carriage.

12. A scissor lift according to claim 10 wherein said coil springs may pass between spaced components on said carriage and removable pins act between said components and respective ones of said springs to interconnect said spring and carriage.

13. A scissor lift according to claim 12 wherein said coil springs are supported on rods secured to said abutment and passing through said carriage and said pins pass to either side of said rods to engage said coil springs.

14. A scissor lift to maintain a load at an elevated location comprising a base, a support to support said load, at least one leg assembly having a pair of legs pivoted to one another intermediate their ends, said leg assembly extending between said base and said support and being connected thereto to permit relative movement between said support and said base while maintaining a predetermined orientation of said support to said base, biasing means acting on said leg assembly to oppose relative movement between said support and said base and load transfer means acting between one end of one of said legs and said biasing means to transmit displacement of one of said legs to said biasing means.

15. A scissor lift according to claim 14 wherein said load transfer means acts upon a carriage moveable relative to said base and said biasing means act between an abutment on said base and said carriage.

16. A scissor lift according to claim 15 wherein said biasing means includes longitudinally compressible elements to oppose relative movement between said carriage and said base.

17. A scissor lift according to claim 16 wherein said elements are coil springs.

18. A scissor lift according to claim 17 wherein said coil springs are supported on rods extending from said abutment surface.

19. A scissor lift according to claim 18 wherein said coil springs are selectively engageable with said carriage.

20. A scissor lift according to claim 15 wherein said biasing means are selectively engageable with said carriage.

21. A scissor lift to maintain a load at an elevated location comprising a base, a support to support said load, at least one leg assembly having a pair of legs pivoted to one another intermediate their ends, said leg assembly extending between said base and said support and being connected thereto to permit relative movement between said support and said base while maintaining a predetermined orientation of said support to said base, and biasing means acting on said leg assembly to oppose relative movement between said support and said base, said biasing means being connected to said leg assembly by a load transfer means to transmit displacement of one of said legs to said biasing means, said load transfer means including a motion modifying mechanism to modify the effect of such displacement on said biasing means.

22. A scissor lift according to claim 21 wherein said motion modifying means includes a cam member and a follower.

23. A scissor lift according to claim 22 wherein said biasing means acts upon said leg by a carriage displaceable relative to said base and said follower is mounted on said carriage and said cam is secured to said leg.

24. A scissor lift according to claim 23 wherein said biasing means includes coil springs acting between an abutment on said base and said carriage.

25. A scissor lift according to claim 24 wherein said coil springs are disposed normal to the direction of relative movement between said support and said base.

26. A scissor lift according to claim 23 wherein opposite ends of said carriage are interconnected by a linkage secured to said base to maintain alignment of said carriage during relative movement between said base and carriage.

27. A scissor lift according to claim 26 wherein said linkage includes a bar rotatably secured to said base for movement about an axis normal to displacement of said carriage and a pair of links spaced apart along said bar and extending between said carriage and arms connected to said bar whereby relative movement between opposite ends of said carriage induces a torsional load in said bar to maintain alignment of said carriage.

28. A scissor lift according to claim 23 wherein said cam member is permanently secured to said leg.

29. A scissor lift according to claim 23 wherein said cam member is selectively removable from said leg.