Anti-fail device for locking a drawing-board pillar against motion
First Claim
1. A drawing board construction comprising a frame structure including a base, a vertical pillar guided by said frame structure for movement vertically relative to said frame structure, a drawing board proper pivotally mounted on said pillar, means for counterbalancing the weight of said pillar and drawing board proper, said counterbalancing means comprising a pulley rotatably supported by said frame structure, a cable passing over said pulley and attached to said pillar and spring means for tensioning said cable, spring actuated locking means for frictionally gripping said pillar to hold it in selected position, user actuated means for releasing said locking means to permit movement of said pillar relative to said frame structure, said releasing means comprising a foot pedal pivotally mounted on said base and tension members connecting said foot pedal with said locking means, and safety means responsive to slackening or breaking of said cable for disconnecting said foot pedal from said tension members in the event of slackening or breaking of said cable, whereby said locking means cannot be released by operation of said foot pedal.
1 Assignment
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Accused Products
Abstract
Permanent locking mechanism can be released temporarily by depressing a pedal when adjusting the height and orientation of the drawing board. The movable assembly comprising the table supporting pillar is connected to the balancing system by a cable attached at one end to a spring passing around a return pulley having its axle supported by a strap of which the corresponding notch is directed towards the base of the frame structure, then around another return pulley formed with a helical groove and secured to the top of the frame structure, the other end of the cable being attached to the pillar. A locking member interconnects the axle and the pedal, this connection being discontinued in case of undesired slackening or breakage of the cable.
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Citations
5 Claims
- 1. A drawing board construction comprising a frame structure including a base, a vertical pillar guided by said frame structure for movement vertically relative to said frame structure, a drawing board proper pivotally mounted on said pillar, means for counterbalancing the weight of said pillar and drawing board proper, said counterbalancing means comprising a pulley rotatably supported by said frame structure, a cable passing over said pulley and attached to said pillar and spring means for tensioning said cable, spring actuated locking means for frictionally gripping said pillar to hold it in selected position, user actuated means for releasing said locking means to permit movement of said pillar relative to said frame structure, said releasing means comprising a foot pedal pivotally mounted on said base and tension members connecting said foot pedal with said locking means, and safety means responsive to slackening or breaking of said cable for disconnecting said foot pedal from said tension members in the event of slackening or breaking of said cable, whereby said locking means cannot be released by operation of said foot pedal.
Specification