Abstract: A tension control device is provided, for example, for locking and unlocking a movable support arm for a keyboard or the like, by engaging or disengaging rotational joints having axially displaceable rotationally lockable couplings traversed by a tension line. A control, preferably a caliper, has levers pivoted on a pin, normally biased by a spring to close. The spring pulls the caliper closed; however, the caliper is arranged by linkages to clamp tension onto the line rather than to couple spring tension to the line. A front linkage isolates the spring bias from the line when closed, by folding inwardly such that tension is transmitted substantially exclusively via compression of two pivoted members of the from linkage that align nearly parallel to the line. The biasing spring is coupled between a rear linkage that operates oppositely, and a fixed point such as the caliper pivot pin.

Abstract: A movable support arm positions a surface platform for a keyboard, display monitor, pointing device, wrist support or the like relative to a base structure such as the underside of a desk top. Articulated members between a base member and the platform are coupled by joints having rotational couplings on two mutually perpendicular axes, forming universal joints. The joints have axially facing rotational engagement surfaces that can be splined or otherwise made engageable, and are displaceable toward and away from one another, the latter preferably by a spring coupling that is axially limited in extension. The rotational engagement surfaces resist rotation when engaged. A line such as a cable traverses the joints and normally applies tension via a spring, causing all the joints to lock and to hold the supporting platform at a given position and orientation.

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.

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.