Load compensator for spring counter-weighting mechanism
First Claim
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;
means for effectively reconfiguring the cam surface of said snail cam during a portion of the rotation of said snail cam; 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.
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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. The spiral surface can be effectively reconfigured with respect to a portion of the cable fitting therearound.
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Citations
24 Claims
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1. A load compensator for a spring counter-weighting mechanism, said counter-weighting mechanism comprising:
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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; means for effectively reconfiguring the cam surface of said snail cam during a portion of the rotation of said snail cam; 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. Counter-weighting mechanism for counter-weighting a load movable vertically with respect to a fixed member, comprising:
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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; means for effectively reconfiguring the cam surface of said snail cam during a portion of the wrapping of said flexible tension means over said cam surface; 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. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification