Load compensator for spring counter-weighting mechanism

• US 5,311,827 A
• Filed: 06/18/1992
• Issued: 05/17/1994
• Est. Priority Date: 06/18/1992
• Status: Expired due to Term

• Current Assignee: Greene H. Peter
• Original Assignee: Greene H. Peter
• Inventors: Greene, H. Peter
• Primary Examiner(s): Cuomo, Peter M.
• Assistant Examiner(s): Milano, Michael J.
• Application Number:
  US07/900,489
• Time in Patent Office: 698 Days
• Field of Search: 108/144, 108/147, 74/89.22, 74/506, 248/297.1
• US Class Current: 108/147
• CPC Class Codes: A47B 9/02 with balancing device, e.g. by springs, by weight
• CPC Class Codes: E05D 13/1207 with tension springs
• CPC Class Codes: E05Y 2201/67 in tackles
• CPC Class Codes: E05Y 2900/20 for furnitures, e.g. cabinets
• CPC Class Codes: F16H 19/0659 combined with means for creating non-linear characteristics, e.g. cams; Means for creating different velocity on forward and reverse stroke
• CPC Class Codes: F16M 11/18 with mechanism for moving the apparatus relatively to the stand
• CPC Class Codes: F16M 11/24 changeable in height or length of legs, also for transport only, e.g. by means of tubes screwed into each otherF16M11/42 takes precedence
• CPC Class Codes: F16M 2200/047 for balancing translational movement of the head
• CPC Class Codes: Y10T 74/18848 with pulley

Abstract

An improved load compensator for a spring counter-weighting mechanism including a snail cam to provide a constant counter-weight force is described. The cam provides a constant torque to a drum on which are wound cables for exerting a constant counter-weighting force. A manually operable device for altering the relative radial positions of the cam and drum varies the amount of the constant counter-weighting force. The cam is rotated with respect to the drum by a spur gear fitting within a ring gear fixed to the drum and rotated by a knob connected to an axle carrying a pinion gear engaging the spur gear.

Claims

1. A load compensator for a spring counter-weighting mechanism, said counter-weighting mechanism comprising:

a spring arranged to exert tension on a tension member, said tension varying linearly with extension of said spring;

a snail cam journaled for rotation about an axis and comprising a cam surface for receiving said tension member, said cam surface effectively spacing the point at which said tension member contacts said cam surface from said axis by a radial distance varying continuously radially about said snail cam, such that a net torque applied to said snail cam due to tension applied to said tension member by said spring varies with respect to the point at which said tension member contacts said cam surface; and

fixed-radius lever arm means pivotable about an axis and adapted to receive torque exerted on said snail cam by said tension member and to transfer said torque from said snail cam to means for exerting a constant counter-weighting force on a load to be counter-weighted;

said load compensator comprising means for controllably varying the relative radial positions of said snail cam with respect to said lever arm means.

2. The load compensator of claim 1, wherein said lever arm means and said snail cam are coaxially mounted for free rotation on a single first axle, said first axle being journaled for rotation with respect to a fixed frame member, and said means for controllably varying the relative positions of said snail cam and said lever arm means comprising a pinion gear fixed to said axle effectively engaging gear teeth fixed to said lever arm means, and a manually operable means for turning said axle with respect to said snail cam and lever arm means, whereby said snail cam may be controllably rotated with respect to said lever arm means.

3. The load compensator of claim 2, wherein said pinion gear engages a spur gear engaging gear teeth fixed to said lever arm means.

4. The load compensator of claim 3, wherein said spur gear is engaged by said pinion gear and by an internally-toothed ring gear, said ring gear comprising said gear teeth fixed to said lever arm means.

5. The load compensator of claim 4, wherein said spur gear is journaled to rotate freely about a stub axle, said stub axle being fixed to said snail cam at a point radially spaced from said first axle, whereby rotation of said pinion gear drives said spur gear around said internally toothed ring gear, rotating said snail cam with respect to said lever arm means.

6. The load compensator of claim 4, comprising a grippable handle fixed to said first axle to facilitate rotation of said pinion gear and consequent rotation of said snail cam with respect to said lever arm means.

7. The load compensator of claim 4, wherein said lever arm means is a drum supported for free rotation on said first axle, and said internally-toothed ring gear is mounted to said drum.

8. The load compensator of claim 7, wherein said means for exerting a constant counter-weighting force comprises at least one flexible tension member extending at least partially around said drum.

9. The load compensator of claim 1, wherein said tension member is a flexible cable wrapped around said snail cam along said cam surface, one end of said cable being fixed to said spring.

10. The load compensator of claim 9, wherein the other end of said cable is anchored to said lever arm means to transfer torque from said snail cam to said lever arm means.

11. Counter-weighting mechanism for counter-weighting a load movable vertically with respect to a fixed member, comprising:

a spring secured at one end with respect to said fixed member;

a snail cam freely pivoting about a first pivot axis fixed to said fixed member, said snail cam comprising a spiral cam surface disposed at a smoothly varying radial distance from said axle;

a drum freely pivoting about a second pivot axis fixed to said fixed member;

means for transmitting torque from said snail cam to said drum;

means for transmitting a constant counter-weighting force from said drum to said load;

flexible tension means fixed at one end with respect to a second end of said spring, and adapted to be wrapped about said snail cam so as to rest on said spiral cam surface to exert torque on said snail cam; and

manually operable means for altering the relative radial positions of said snail cam with respect to said drum, whereby said constant counter-weighting force may be altered without the use of tools.

12. The mechanism of claim 11, wherein said drum and said snail cam are coaxially supported for free rotation about a single axle, whereby said first and second pivot axes coincide.

13. The mechanism of claim 12, wherein a pinion gear is fixed to said axle, said pinion gear effectively engaging gear teeth fixed to at least one of said drum and said snail cam, whereby rotation of said axle alters the relative radial positions of said snail cam and said drum.

14. The mechanism of claim 13, wherein said manually operable means comprises a manually grippable handle fixed to said axle for rotating said axle with respect to said fixed member.

15. The mechanism of claim 13 wherein said pinion gear engages a spur gear, and said spur gear engages internal teeth fixed to said drum, whereby rotation of said pinion gear is effective to cause said spur gear to pivot about said axle and to alter the relative radial positions of said drum and said snail cam.

16. The mechanism of claim 15, wherein said spur gear is received in a recess formed in one end of said drum, said internal teeth of said ring gear forming the circumferential inner surface of said recess.

17. The mechanism of claim 15, wherein a stub axle is fixed to the center of said spur gear, said stub axle extending through a bore in said snail cam spaced radially from said first axle.

18. The mechanism of claim 11, wherein said load comprises a table top and supporting structure, and said fixed member comprises a stationary transverse frame member of said table extending horizontally between laterally spaced legs of said table.

19. The mechanism of claim 18, wherein said drum and said snail cam rotate freely about an axle extending horizontally from and rotating with respect to said transverse frame member.

20. The mechanism of claim 19, wherein said means for transmitting a constant counter-weighting force from said drum to said load comprises at least one flexible cable wrapped around and secured to said drum and fixed at one end to said table top and at the other to a vertically extending table top support member, said cable passing over pulleys fixed to said frame of said table, such that torque exerted on said drum responsive to force exerted on said snail cam by said spring and transmitted from said snail cam to said drum tends to urge said table top upwardly.

21. The mechanism of claim 20, wherein two such flexible cables are provided, one end of each being fixed to said table top at opposite lateral sides thereof and the other end of each being fixed to vertically extending structure supporting said table top at opposite lateral ends thereof, said cables being wrapped upon said drum so as to move cooperatively upon rotation of said drum to raise said table top equally at both lateral ends.

22. The mechanism of claim 11, wherein said spring is a tension spring.