Load compensator for height adjustable table

Abstract

A table assembly, the assembly comprising a first member having a length dimension parallel to a substantially vertical extension axis, a second member supported by the first member for sliding motion along the extension axis between at least an extended position and a retracted position, the second member forming an internal passageway, a table top mounted to one end of one of the first and second members, a spring that generates a variable spring force that depends at least in part on the degree of spring loading, the spring having first and second ends, aligned substantially parallel to the vertical extension axis, located at least partially within the internal passage formed by the second member and linked to each of the first and second members and a rotatable cam member engaged with the spring, the cam member and spring applying a force between the first and second members tending to drive the second member into the extended position, the cam member rotating around an axis as the second member moves between the extended and retracted positions, the rate of cam member rotation changing in a non-linear fashion as the second member moves toward the extended position.

1 . A table assembly, the assembly comprising:
 a first member having a length dimension parallel to a substantially vertical extension axis;   a second member supported by the first member for sliding motion along the extension axis between at least an extended position and a retracted position, the second member forming an internal passageway;   a table top mounted to one end of one of the first and second members;   a spring that generates a variable spring force that depends at least in part on the degree of spring loading, the spring having first and second ends, aligned substantially parallel to the vertical extension axis, located at least partially within the internal passage formed by the second member and linked to each of the first and second members; and   a rotatable cam member engaged with the spring, the cam member and spring applying a force between the first and second members tending to drive the second member into the extended position, the cam member rotating around an axis as the second member moves between the extended and retracted positions, the rate of cam member rotation changing in a non-linear fashion as the second member moves toward the extended position.   
     
     
         2 . The assembly of  claim 1  wherein the cam member rotates around a substantially horizontal axis as the second member moves between the extended and retracted positions. 
     
     
         3 . The assembly of  claim 1  wherein the cam member moves in the same direction as the second member as the second member moves between the extended and retracted positions. 
     
     
         4 . The assembly of  claim 1  wherein the cam member includes a cylindrical outer surface and wherein the outer surface forms a groove that wraps at least partially around a rotation axis of the cam member. 
     
     
         5 . The assembly of  claim 1  further including a base member that extends from a lower end of the first member to support the first member in an upright position, the first member forming a first member internal passageway, the second member received at least in part in the first member internal passageway, the cam member located at least in part within the passageway formed by the second member, the table top supported at the end of the second member that extends from the passageway formed by the first member. 
     
     
         6 . The assembly of  claim 5  wherein the cam member moves upward with respect to the first member as the second member moves toward the extended position. 
     
     
         7 . The assembly of  claim 1  further including rollers positioned between the first and second members. 
     
     
         8 . The assembly of  claim 7  wherein at least a subset of the rollers are mounted to an outer surface of the second member. 
     
     
         9 . The assembly of  claim 1  wherein the spring compresses as the second member moves toward the retracted position. 
     
     
         10 . The assembly of  claim 1  wherein the table top is mounted to an end of the second member that extends from the first member. 
     
     
         11 . The assembly of  claim 1  wherein the force applied by the spring and cam member to the second member is substantially constant irrespective of the position of the second member with respect to the first member. 
     
     
         12 . The assembly of  claim 1  wherein the cam member includes a snail cam pulley. 
     
     
         13 . The assembly of  claim 12  further including a strand having first and second ends and an intermediate portion between the first and second ends, the spring supported by the second member, the first end of the strand linked to the first member, the second end of the strand linked to one end of the spring and the intermediate portion of the strand wrapped around the snail cam pulley. 
     
     
         14 . The assembly of  claim 1  wherein the first and second members are column members. 
     
     
         15 . The assembly of  claim 1  wherein the table top is supported by a single leg assembly that includes the first and second members and wherein the table top is only connected to the single leg assembly via a top end of the second member. 
     
     
         16 . The assembly of  claim 1  further including a pre-loader for adjusting a preload force applied by the spring between the first and second members. 
     
     
         17 . The assembly of  claim 16  wherein the pre-loader includes first and second guide members, the second guide member forming a channel, the first guide member positioned within the channel for sliding movement along an adjustment axis, a threaded shaft mounted at least partially within the channel for rotation about the adjustment axis, a nut threadably receiving the shaft and supported by the first guide member and a lever member supported by the first guide member and including at least a first nut engaging member, wherein the lever member restricts rotation of the nut with respect to the first guide member during at least a portion of travel of the first guide member within the channel and allows nut rotation in at least a first direction with respect to the first guide member when the first guide member is in at least a first position. 
     
     
         18 . The assembly of  claim 17  wherein the first guide member is capable of assuming positions within the channel between and including a maximum preload force position and a minimum preload force position, the lever member restricting rotation of the nut with respect to the first guide member when the first guide member position is between the maximum and minimum preload force positions and allowing the nut to rotate in at least one direction when the first guide member is in one of the maximum and minimum preload force positions, the maximum preload force position being the first position of the first guide member. 
     
     
         19 . The assembly of  claim 17  further including an indicator linked to the first guide member for indicating the position of the first guide member with respect to the second guide member. 
     
     
         20 . The assembly of  claim 19  wherein the indicator includes an elongated indicator member that includes first and second ends and that is supported at the first end at a pivot point by the second guide member, wherein an intermediate portion of the indicator member is in communication with the first guide member which forces the second end of the indicator member to move as the first guide member moves along the channel. 
     
     
         21 . The assembly of  claim 16  wherein the pre-loader is located within the passageway formed by the second member. 
     
     
         22 . The assembly of  claim 21  wherein the pre-loader includes a threaded shaft mounted for rotation about an adjustment axis. 
     
     
         23 . The assembly of  claim 22  wherein the adjustment axis is aligned substantially parallel to a length of the spring. 
     
     
         24 . The assembly of  claim 22  wherein a top end of the threaded shaft is located near a top end of the second member. 
     
     
         25 . The assembly of  claim 22  wherein the pre-loader further includes a nut received on the threaded shaft where rotation of the nut is restricted so that the nut moves along the threaded shaft when the threaded shaft rotates about the adjustment axis. 
     
     
         26 . The assembly of  claim 25  wherein rotation of the nut adjusts compression of the spring and the force of the spring between the first and second members. 
     
     
         27 . The assembly of  claim 26  further including a strand having a first end linked to the spring, a second end linked to the first member and an intermediate portion supported by the cam member, the pre-loader further including a pulley linked to the nut to move along with the nut, the intermediate portion of the strand also supported by the pulley. 
     
     
         28 . The assembly of  claim 22  wherein the threaded shaft is supported by the second member such that the threaded shaft moves along with the second member as the second member moves between the extended and retracted positions. 
     
     
         29 . The assembly of  claim 16  wherein the pre-loader is supported by the second member such that the pre-loader moves along with the second member as the second member moves between the extended and retracted positions. 
     
     
         30 . The assembly of  claim 1  further including a locking mechanism including at least a first locking member moveable between a locked position wherein the locking member substantially minimizes movement of the second member with respect to the first member and an unlocked position wherein the first locking member allows movement of the second member with respect to the first member. 
     
     
         31 . The assembly of  claim 30  wherein the first locking mechanism is located within the passageway formed by the second member. 
     
     
         32 . The assembly of  claim 30  wherein the locking mechanism further includes a coupler that rotates as the second member moves between the extended and retracted positions and wherein the locking member contacts the coupler in the locked position to prohibit rotation of the coupler and is separated from the coupler in the unlocked position thereby allowing rotation of the coupler and movement of the second member. 
     
     
         33 . The assembly of  claim 32  wherein the coupler includes a nut mounted on a threaded shaft. 
     
     
         34 . The assembly of  claim 32  wherein the locking mechanism includes at least one spring that biases the locking member toward the locked position. 
     
     
         35 . The assembly of  claim 34  wherein the locking mechanism further includes a cable and a handle, the handle mounted to an undersurface of the table top and the cable linking the handle to the locking member. 
     
     
         36 . The assembly of  claim 1  wherein one end of the spring is mounted to the second member such that the mounted end of the spring remains stationary with respect to the second member as the second member moves between the extended and retracted positions. 
     
     
         37 . The assembly of  claim 1  wherein the cam member is mounted below the spring and wherein the spring is a coil spring. 
     
     
         38 . The assembly of  claim 1  further including a strand having first and second ends and an intermediate portion between the first and second ends, the spring supported by the second member, the first end of the strand linked to the first member and the second end of the strand linked to one end of the spring. 
     
     
         39 . A table assembly, the assembly comprising:
 a first member having a length dimension parallel to a substantially vertical extension axis;   a second member supported by the first member for sliding motion along the extension axis between at least an extended position and a retracted position, the second member forming an internal passageway;   a table top mounted to one end of one of the first and second members;   a spring that generates a variable spring force that depends at least in part on the degree of spring loading, the spring having first and second ends, aligned substantially parallel to the vertical extension axis, located at least partially within the second member and linked to each of the first and second members; and   a rotatable cam member linked between the spring and the second member, the cam member and spring applying a force between the first and second members tending to drive the second member into the extended position, the cam member rotating around an axis as the second member moves between the extended and retracted positions; and   a pre-loader for adjusting a preload force applied by the spring between the first and second members.   
     
     
         40 . The assembly of  claim 39  wherein the pre-loader is located within the passageway formed by the second member. 
     
     
         41 . The assembly of  claim 39  wherein the pre-loader includes a threaded shaft mounted for rotation about an adjustment axis. 
     
     
         42 . The assembly of  claim 41  wherein the pre-loader further includes a nut received on the threaded shaft where rotation of the nut is restricted so that the nut moves along the threaded shaft when the threaded shaft rotates about the adjustment axis. 
     
     
         43 . The assembly of  claim 42  wherein rotation of the nut adjusts compression of the spring and the force of the spring between the first and second members. 
     
     
         44 . The assembly of  claim 43  further including a strand having a first end linked to the spring, a second end linked to the first member, the pre-loader further including a pulley linked to the nut to move along with the nut, an intermediate portion of the strand supported by the pulley. 
     
     
         45 . The assembly of  claim 39  wherein the force applied by the spring and the cam member is substantially constant irrespective of the position of the second member with respect to the first member. 
     
     
         46 . A table assembly, the assembly comprising:
 a first member having a length dimension parallel to a substantially vertical extension axis;   a second member supported by the first member for sliding motion along the extension axis between at least an extended position and a retracted position, the second member forming an internal passageway;   a table top mounted to one end of one of the first and second members;   a spring that generates a variable spring force that depends at least in part on the degree of spring loading, the spring having first and second ends, aligned substantially parallel to the vertical extension axis, located at least partially within the second member and linked to each of the first and second members;   a rotatable cam member linked between the spring and the second member, the cam member and spring applying a force between the first and second members tending to drive the second member into the extended position, the cam member rotating around an axis as the second member moves between the extended and retracted positions; and   a locking mechanism including at least a first locking member moveable between a locked position wherein the locking member substantially minimizes movement of the second member with respect to the first member and an unlocked position wherein the first locking member allows movement of the second member with respect to the first member.   
     
     
         47 . The assembly of  claim 46  wherein the applied force is substantially constant irrespective of the position of the second member with respect to the first member. 
     
     
         48 . The assembly of  claim 46  wherein the first locking mechanism is located within the passageway formed by the second member. 
     
     
         49 . The assembly of  claim 46  wherein the locking mechanism further includes a coupler that rotates as the second member moves between the extended and retracted positions and wherein the locking member contacts the coupler in the locked position to prohibit rotation of the coupler and is separated from the coupler in the unlocked position thereby allowing rotation of the coupler and movement of the second member. 
     
     
         50 . The assembly of  claim 49  wherein the coupler includes a nut mounted on a threaded shaft. 
     
     
         51 . The assembly of  claim 46  wherein the locking mechanism includes at least one spring that biases the locking member toward the locked position. 
     
     
         52 . A table assembly comprising:
 a base member;   a first column member having first and second ends and forming an internal passageway, the first end of the first column member secured to the base member;   a second column member having first and second ends and forming an internal passageway, the second column member at least partially received in the internal passageway formed by the first column member for telescoping motion between a retracted position and an extended position where the second end of the second column member extends from the second end of the first column member along an extension axis when the second column member is in the extended position;   a table top mounted to the second end of the second column member;   a coil spring that generates a variable spring force that depends at least in part on the degree of spring loading, the spring having first and second ends, aligned substantially parallel to the vertical extension axis, located at least partially within the second member and linked to each of the first and second members; and   a rotatable cam member linked between the spring and the second member, the cam member and spring applying a force between the first and second members tending to drive the second member into the extended position, the cam member rotating around an axis as the second member moves between the extended and retracted positions;   a pre-loader for adjusting a preload force applied by the spring between the first and second members; and   a locking mechanism including at least a first locking member moveable between a locked position wherein the locking member substantially minimizes movement of the second member with respect to the first member and an unlocked position wherein the first locking member allows movement of the second member with respect to the first member.   
     
     
         53 . A height adjustable table assembly comprising:
 a first elongated member having a length dimension parallel to a substantially vertical extension axis;   a second elongated member supported by the first member for sliding motion along the extension axis between at least an extended position and a retracted position;   a velocity governor supported by at least one of the first and second elongated members for, while the second elongated member is moving, restricting the speed with which the second elongated member moves with respect to the first elongated member along the extension axis; and   a table top member mounted to at least one of the first and second elongated members in a substantially horizontal orientation.   
     
     
         54 . The assembly of  claim 53  wherein the first elongated member includes a length dimension along the extension axis and wherein the velocity governor further includes a threaded shaft linked to and stationary with respect to the first elongated member and aligned substantially along the extension axis, a brake member forming a braking surface proximate the threaded shaft, a nut supported by the threaded shaft for movement there along and coupled to the second member, at least one brake shoe supported by the nut proximate the braking surface for sliding motion away from the threaded shaft and toward the braking surface and a biaser for biasing the brake shoe toward the threaded shaft and away from the braking surface, wherein, when the nut rotates about the shaft, centrifugal force on the brake shoe causes the brake shoe to move toward the braking surface and, when the centrifugal force exceeds a threshold level, the shoe contacts the braking surface. 
     
     
         55 . A table assembly comprising:
 a first member having a length dimension along an extension axis;   a second member supported by the first member for movement along the extension axis;   a threaded shaft linked to and stationary with respect to the first member and aligned substantially along the extension axis;   a brake member forming a braking surface proximate the threaded shaft;   a nut supported by the threaded shaft for movement there along and coupled to the second member;   at least one brake shoe supported by the nut proximate the braking surface for sliding motion away from the threaded shaft and toward the braking surface;   a biaser for biasing the brake shoe toward the threaded shaft and away from the braking surface;   wherein, when the nut rotates about the shaft, centrifugal force on the brake shoe causes the brake shoe to move toward the braking surface and, when the centrifugal force exceeds a threshold level, the shoe contacts the braking surface; and   a table top member mounted to at least one of the first and second elongated members in a substantially horizontal orientation.