Height adjustable table

1 . A spring assembly for use in a counterbalance system, the assembly comprising:

a datum member;

a compression spring having proximal and distal ends, the proximal end of the spring supported by the datum member;

an elongated guide having proximal and distal ends and including at least a first substantially straight edge that extend between the proximal and distal ends of the guide, the proximal end of the guide supported by the datum member, the first edge extending along the length of the spring from the proximal end of the spring to the distal end of the spring wherein a space between the first edge and an adjacent portion of the spring is less than one quarter of an inch; and

a strand including first and second ends, the first end of the strand linked to the distal end of the spring and the second end of the strand extending toward and past the proximal end of the spring.

2 . The assembly of claim 1 wherein the spring includes an internal surface that forms a spring passageway between the proximal and distal ends of the spring and wherein the guide is positioned within the spring passageway.

3 . The assembly of claim 2 wherein the guide includes at least a second substantially straight edge and wherein a space between the second edge and an adjacent portion of the spring is less than one quarter of an inch.

4 . The assembly of claim 3 wherein the spaces between the first and second edges and adjacent portions of the spring are less than one sixteenth of an inch.

5 . The assembly of claim 3 wherein the first and second edges extend in substantially opposite directions.

6 . The assembly of claim 3 wherein the guide includes at least a third substantially straight edge and wherein a space between the third edge and an adjacent portion of the spring is less than one quarter of an inch.

7 . The assembly of claim 6 wherein the guide forms a fourth substantially straight edge and wherein a space between the fourth edge and an adjacent portion of the spring is less than one quarter of an inch.

8 . The assembly of claim 7 wherein the first, second, third and fourth edges face in directions that are separated by at least 60 degrees.

9 . The assembly of claim 8 wherein the guide forms a central channel along the guide length and the datum member forms an opening aligned at least in part with the spring passageway and wherein the assembly further includes a plunger, the plunger positioned within the guide for sliding motion there along, the plunger including first and second ends, the first end mechanically linked to the distal end of the spring with the second end located within the spring passageway, the plunger linked to the first end of the strand with the second end of the strand extending through the spring passageway and the datum member opening.

10 . The assembly of claim 9 wherein the guide includes at least a first guide member and a plurality of separator members, the at least a first guide member forming first through fourth extension members, a separate separator member secured to each of the extension members and having external surfaces that form the first through fourth edges.

11 . The assembly of claim 10 wherein the guide member is formed of a first material and the separator members are formed of a second material and wherein the second material is a lower friction material than the first material.

12 . The assembly of claim 11 wherein the guide member forms at least first and second rails along at least a portion of a guide member length and the plunger is mounted to the rails for sliding movement there along.

13 . The assembly of claim 12 further including separator members secured to the rails, the separator members secured to the rails isolating the plunger from the rails.

14 . The assembly of claim 13 wherein the separator members that are secured to the rails are formed of a material that is a lower friction material than the first material.

15 . The assembly of claim 14 wherein the guide member also forms third and fourth rails along at least a portion of the guide member length and wherein the plunger is also supported by the third and fourth rails.

16 . The assembly of claim 11 wherein the first material is metal and the second material is plastic.

17 . The assembly of claim 9 wherein the plunger includes first and second oppositely facing arm members that contact the distal end of the spring.

18 . The assembly of claim 9 for use in a telescoping assembly including first and second telescoping members, the datum member supported by the first telescoping member and the second end of the strand linked to the second member.

19 . The assembly of claim 18 wherein the first and second telescoping members are first and second columns.

20 . The assembly of claim 3 wherein the guide includes first and second guide members that are separated by a space and that extend substantially parallel to each other to form a guide channel therebetween.

21 . The assembly of claim 20 wherein the guide further includes separator members, the first guide member forms a first extension and the second guide member forms a second extension and wherein a separate separator member is provided over each of the extensions, the external surface of the separator members forming the first and second edges.

22 . The assembly of claim 21 wherein the first and second guide members are formed of a first material and the separator members are formed of lower friction material than the first material.

23 . The assembly of claim 20 wherein the first guide member forms the first edge and the second guide member forms the second edge and wherein the first guide member forms a third substantially straight edge and the second guide member forms a fourth substantially straight edge where the first and second edges face is substantially opposite directions and the third and fourth edge face in substantially opposite directions and wherein at least portions of the third and fourth edges forms spaces with adjacent portions of the internal surface of the spring that are less than one quarter of an inch.

24 . The assembly of claim 23 wherein the spaces between the first, second, third and fourth edges and adjacent portions of the internal surface of the spring are less than one sixteenth of an inch.

25 . A spring assembly for use in a counterbalance system, the assembly comprising:

a datum member that forms an opening;

a compression spring having proximal and distal ends and including an internal surface that forms a spring passageway along the length of the spring, the proximal end of the spring supported by the datum member with the opening in the datum member at least partially aligned with the spring passageway;

a guide including at least a first elongated guide member and a first separator member, the elongated guide member supported at a proximal end by the datum member and extending from the proximal end to the distal end within the spring passageway, the first separator member covering a portion of the guide member and separating the portion of the guide member from the spring; and

a strand including first and second strand ends, the first end linked to the distal end of the spring, the second end extending through the spring passageway and the opening in the datum member;

wherein the guide member and the separator member are formed of first and second materials and the second material is a lower friction material than the first material.

26 . The assembly of claim 25 wherein the guide member forms at least a first rail along at least a portion of the length of the guide member, the assembly further including a plunger supported by the rail for movement there along and at least a second separator positioned between the plunger and the rail for isolating the plunger from the rail, the plunger having a first and second ends, the first end linked to the distal end of the spring and the second end positioned within the spring passageway, the plunger linked to the first end of the strand.

27 . The assembly of claim 25 wherein the guide includes first and second guide members and wherein separator members cover portions of each of the first and second guide members and form surfaces adjacent the internal surface of the spring, the first and second guide members extending substantially parallel to each other and forming a channel therebetween, each guide member forming a rail and the plunger supported by the rails formed by each of the first and second guide members.

28 . A spring assembly for use in a counterbalance system, the assembly comprising:

a datum member that forms an opening;

a compression spring having proximal and distal ends and including an internal surface that forms a spring passageway along the length of the spring, the proximal end of the spring supported by the datum member with the opening in the datum member at least partially aligned with the spring passageway;

a guide supported at a proximal end by the datum member and extending from the proximal end to the distal end within the spring passageway, the guide including first and second guide members that are substantially parallel to each other and that are separated by a space to form a channel therebetween, the first guide member forming first and third extension members that extend generally away from the second guide member and first and second rails that extend generally toward the second guide member, the second guide member forming second and fourth extension members that extend generally away from the first guide member and third and fourth rails that extend generally toward the first guide member;

a plunger supported by the rails for movement there along, the plunger having first and second ends, the first end linked to the distal end of the spring;

separator members secured to at least portions of the first, second, third and fourth extension members and that form external surfaces, at least portions of the external surfaces proximate the internal surface of the spring, the separator members also including members positioned between the plunger and the rails to separate the plunger from the rails; and

a strand including first and second ends, the first end linked to the plunger and the second end extending through the spring passageway and the opening formed by the datum member.

29 . An extendable leg apparatus comprising:

a first column having a length dimension parallel to a substantially vertical extension axis;

a second column supported by the first column for sliding motion along the extension axis between at least an extended position and a retracted position;

at least one of the first and second columns forming an internal cavity; and

a counterbalance assembly including:

a spring guide supported substantially within the cavity;

a compression spring having first and second ends and forming a spring passageway, the spring positioned such that the spring guide resides at least in part in the spring passageway and with a first end supported within the cavity; and

an equalizer assembly including a first end linked to the second end of the spring and a second end linked to the first column, the force equalizer assembly and spring applying a force between the first and second columns tending to drive the columns into the extended position wherein the applied force is substantially constant irrespective of the position of the second column with respect to the first column.

30 . The apparatus of claim 29 further including a table top mounted to the second column for movement therewith.

31 . The apparatus of claim 30 wherein the table top and second column have a combined weight of more than 25 pounds.

32 . The apparatus of claim 29 wherein the equalizer includes a spiral cam pulley and at least one strand, the pulley supported substantially within the cavity for rotation about a pulley axis, the pulley including a lateral surface spaced from the pulley axis, the lateral surface forming a helical cable channel that wraps around the pulley axis and that includes first and second channel ends so that at least a portion of the channel and the pulley axis forms channel radii perpendicular to the pulley axis, the radii increasing along at least a portion of the channel in the direction from the first channel end toward the second channel end, the at least one strand having a central portion and first and second strand ends, the central portion received within at least a portion of the pulley channel with the first and second strand ends extending from a first radii portion and a second radii portion of the channel where the first portion has a radii that is smaller than the second portion, the first and second strand ends linked to the first column and the second end of the spring, respectively.

33 . The assembly of claim 32 wherein the first radii portion is at least 0.5 inches irrespective of the relative positions of the first and second columns.

34 . The assembly of claim 33 wherein the first radii portion is approximately 0.5 inches when the second column is in the retracted position and is approximately 2.0 inches when the second column is in the extended position.

35 . The apparatus of claim 29 wherein the spring passageway is cylindrical and wherein the spring guide is also substantially cylindrical.

36 . The apparatus of claim 35 wherein the counterbalance assembly further includes a plunger mounted for sliding movement to the spring guide, the plunger linked to the second end of the spring and the second end of the strand linked to the plunger.

37 . The apparatus of claim 32 wherein the pulley is mounted to a pulley shaft via bearings for rotation there about.

38 . The apparatus of claim 32 wherein a table top is mounted to the second column, the table top includes an undersurface and wherein the spring is supported within the cavity between the undersurface and the pulley.

39 . The apparatus of claim 38 wherein each of the first and second strand ends extend from the pulley generally toward the undersurface.

40 . The apparatus of claim 29 wherein the cavity is a second column passageway, the first column forms a first column passageway and wherein the second column is supported for telescopic sliding motion within the first column passageway.

41 . The apparatus of claim 32 wherein the pulley, spring and strand apply an upward force on the second column that is substantially constant irrespective of the relative positions of the first and second columns.

42 . The apparatus of claim 32 wherein the channel portion from which the first strand end extends is of substantially constant radius independent of the relative positions of the first and second columns.

43 . The apparatus of claim 29 wherein the spring includes an internal surface that forms the spring passageway and wherein the guide includes at least first and second substantially straight edges that are separated from the internal surface of the spring by less than one quarter of an inch.

44 . The assembly of claim 43 wherein the guide includes at least a first guide member and a separator member, the guide member forming an extension member and the separator member secured to the extension member and forming the straight edges adjacent portions of the internal surface of the spring.

45 . The assembly of claim 29 further including at least one separator member that isolates the guide from the spring where the guide and the separator member are formed of first and second materials and wherein the second material is a lower friction material than the first material.

46 . A telescoping assembly, the assembly comprising:

a first elongated member including an internal surface that forms a first passageway extending along an extension axis;

a second elongated member including an external surface, the second member received within the first passageway for sliding movement along the extension axis;

a first of the internal and external surfaces forming a first mounting surface pair including first and second co-planar and substantially flat mounting surfaces;

a second of the internal and external surfaces forming a first raceway along at least a portion of the first surface length, the first raceway having first and second facing raceway surfaces adjacent the mounting surface pair; and

at least a first roller pair including first and second rollers mounted to the first and second mounting surfaces for rotation about first and second substantially parallel roller axis, respectively, the first and second roller axis spaced apart along the extension axis, the first roller axis closer to the first raceway surface than to the second raceway surface and the second roller axis closer to the second raceway surface than to the first raceway surface wherein the first and second rollers interact with the first and second raceway surfaces to facilitate sliding of the first elongated member with respect to the second elongated member along the extension axis.

47 . The assembly of claim 46 wherein the external surface of the second elongated member forms the substantially flat first and second mounting surfaces and the internal surface of the first elongated member forms the first raceway.

48 . The assembly of claim 47 wherein the internal surface forms a second raceway along at least a portion of the first passageway, the second raceway including third and fourth facing raceway surfaces and, wherein, the external surface forms a second mounting surface pair including third and fourth co-planar and substantially flat mounting surfaces adjacent the second raceway, the assembly further including at least a second roller pair including third and fourth rollers mounted to the third and fourth mounting surfaces for rotation about third and fourth substantially parallel roller axis, respectively, the third and fourth roller axis spaced apart along the extension axis, the third roller axis closer to the third raceway surface than to the fourth raceway surface and the fourth roller axis closer to the fourth raceway surface than to the third raceway surface.

49 . The assembly of claim 46 wherein the first and third roller axis are at substantially the same location along the extension axis and wherein the second and fourth roller axis are at substantially the same location along the extension axis.

50 . The assembly of claim 48 wherein the internal surface of the first elongated member forms third and fourth raceways along at least a portion of the first passageway, the third raceway including fifth and sixth facing raceway surfaces and the fourth raceway including seventh and eighth raceway surfaces and, wherein, the external surface of the second elongated member forms third and fourth mounting surface pairs including fifth and sixth co-planar and substantially flat mounting surfaces adjacent the third raceway and seventh and eighth co-planar and substantially flat mounting surfaces adjacent the fourth raceway, respectively, the assembly further including third and fourth roller pairs including fifth and sixth rollers mounted to the fifth and sixth mounting surfaces for rotation about fifth and sixth substantially parallel roller axis and seventh and eighth rollers mounted to the seventh and eighth mounting surfaces for rotation about seventh and eighth substantially parallel roller axis, respectively, the fifth and sixth roller axis spaced apart along the extension axis, the fifth roller axis closer to the fifth raceway surface than to the sixth raceway surface, the sixth roller axis closer to the sixth raceway surface than to the fifth raceway surface, the seventh and eighth roller axis spaced apart along the extension axis, the seventh roller axis closer to the seventh raceway surface than to the eighth raceway surface and the eighth roller axis closer to the eighth raceway surface than to the seventh raceway surface.

51 . The assembly of claim 50 wherein the first and third mounting surface pairs are substantially parallel and generally face in opposite directions, the second and fourth mounting surface pairs are substantially parallel and generally face in opposite directions and the first and second mounting pairs form an angle between 60 and 120 degrees.

52 . The assembly of claim 51 wherein the angle between the first and second mounting surface pairs is substantially 90 degrees.

53 . The assembly of claim 52 wherein the first elongated member has a substantially rectilinear cross section and wherein the first, second, third and fourth raceways are formed at the corners of the rectilinear cross section.

54 . The assembly of claim 53 wherein the second elongated member has a substantially rectilinear cross section and wherein the first, second, third and fourth mounting surface pairs are formed at the corners of the rectilinear cross section of the second elongated member.

55 . The assembly of claim 53 wherein the first elongated member includes first and second substantially flat wall members that form a substantially 90 degree angle, a third wall member substantially parallel to and facing the first wall member and a fourth wall member substantially parallel to and facing the second wall member, the first, second, third and fourth raceways separate the first and second, second and third, third and fourth, and fourth and first wall members and wherein the first raceway surface is adjacent the first wall member, the third raceway surface is adjacent the second wall member, the fifth raceway surface is adjacent the third wall member and the seventh raceway surface is adjacent the fourth wall member.

56 . The assembly of claim 55 wherein the first raceway surface forms a substantially 45 degree angle with the first wall member, the third raceway surface forms a substantially 45 degree angle with the second wall member, the fifth raceway surface forms a substantially 45 degree angle with respect to the third wall member and the seventh raceway surface forms a substantially 45 degree angle with respect to the fourth wall member.

57 . The assembly of claim 46 wherein each roller includes an annular inner bearing race, an annular outer bearing race and ball bearings between the inner and outer races wherein the inner race is mounted to an associated mounting surface.

58 . The assembly of claim 46 wherein the first and second mounting surfaces are formed by a single substantially flat mount surface.

59 . The assembly of claim 47 further including a table top supported by the second elongated member and wherein the elongated members are supported in a position wherein the extension axis is substantially vertical.

60 . The assembly of claim 46 wherein the internal surface of the first elongated member forms the mounting surfaces and the external surface of the second elongated member forms the raceway.

61 . A telescoping assembly, the assembly comprising:

a first elongated member including an internal surface that forms a first passageway extending along an extension axis;

a second elongated member including an external surface, the second member received within the first passageway for sliding movement along the extension axis;

a first of the internal and external surfaces forming first, second, third and fourth mount surfaces wherein the first and third mount surfaces form less than a 30 degree angle and are non-co-planar, the second and fourth mount surfaces form less than a 30 degree angle and are non-co-planar and the first and second mount surfaces form an angle between 60 and 120 degrees;

a second of the internal and external surfaces forming first, second, third and fourth raceways along at least a portion of the second surface length, the first, second, third and fourth raceways adjacent the first, second, third and fourth mount surfaces and including first and second spaced apart, third and fourth spaced apart, fifth and sixth spaced apart and seventh and eighth spaced apart raceway surfaces, respectively;

first, second, third and fourth bearing pairs mounted to the first, second, third and fourth mount surfaces and including first and second, third and fourth, fifth and sixth, and seventh and eighth bearings, respectively, where the bearings of each pair are spaced apart along the extension axis, the first, third, fifth and seventh bearings supported relatively closer to the first, third, fifth and seventh raceway surfaces than to the second, fourth, sixth and eighth raceway surfaces and the second, fourth, sixth and eighth bearings supported relatively closer to the second, fourth, sixth and eighth raceway surfaces than to the first, third, fifth and seventh raceway surfaces and, wherein, the first, second, third, fourth, fifth, sixth, seventh and eighth bearings interact with the first, second, third, fourth, fifth, sixth, seventh and eighth raceway surfaces, respectively, to facilitate sliding motion of the second elongated member with respect to the first elongated member.

62 . The assembly of claim 61 wherein the first elongated member includes the internal surface and the second elongated member includes the external surface.

63 . The assembly of claim 62 wherein the cross sections of each of the first and second elongated members are substantially rectilinear.

64 . The assembly of claim 63 wherein the second elongated member includes first, second, third and fourth substantially flat wall members, the first, second, third and fourth mount surfaces are formed between the first and second, second and third, third and fourth and fourth and first wall members and form substantially 45 degree angles with respect to the first, second, third and fourth wall members, respectively.

65 . The assembly of claim 64 wherein the first raceway surface faces the second raceway surface, the third raceways surface faces the fourth raceway surface, the fifth raceway surface faces the sixth raceway surface and the seventh raceway surface faces the eighth raceway surface.

66 . The assembly of claim 64 wherein the first elongated member includes first and second substantially flat wall members that form a substantially 90 degree angle, a third wall member substantially parallel to and facing the first wall member and a fourth wall member substantially parallel to and facing the second wall member, the first, second, third and fourth raceways separate the first and second, second and third, third and fourth, and fourth and first wall members and wherein the first raceway surface is adjacent the first wall member, the third raceway surface is adjacent the second wall member, the fifth raceway surface is adjacent the third wall member and the seventh raceway surface is adjacent the fourth wall member.

67 . The assembly of claim 61 wherein the bearings are one of rollers, ball bearings and needle bearings.

68 . The assembly of claim 61 wherein the first and second mount surfaces form a substantially 90 degree angle and wherein the third and fourth mount surfaces are substantially parallel to the first and second mount surfaces, respectively.

69 . A telescoping assembly, the assembly comprising:

a first elongated member including an internal surface that forms a first passageway extending along an extension axis;

a second elongated member including an external surface, the second member received within the first passageway;

one of the internal and external surfaces forming first and third non-coplanar mount surfaces that form less than a 30 degree angle and second and fourth non-coplanar mount surfaces that form less than a 30 degree angle where the second mount surface forms an angle between substantially 60 and 120 degrees with respect to the first mount surface;

the other of the internal and external surfaces forming first, second, third and fourth raceways adjacent the first, second, third and fourth mount surfaces; and

first, second, third and fourth roller assemblies mounted to the first, second, third and fourth mount surfaces, respectively, each roller assembly including at least one roller mounted for rotation about an axis that is substantially perpendicular to the mounting surface to which the roller is mounted and that is substantially perpendicular to the extension axis, the first, second, third and fourth roller assemblies interacting with the first, second, third and fourth raceways to facilitate sliding motion of the first elongated member along the extension axis with respect to the second elongated member.

70 . The assembly of claim 69 wherein the first and third mount surfaces are substantially parallel, the second and fourth mount surfaces are substantially parallel and the first and second mount surfaces form a substantially 90 degree angle.

71 . The assembly of claim 70 wherein the first, second, third and fourth roller assemblies include first and second, third and fourth, fifth and sixth, and seventh and eighth rollers, respectively.

72 . The assembly of claim 71 wherein the first roller is spaced apart from the second roller along the extension axis, the third roller is spaced apart from the fourth roller along the extension axis, the fifth roller is spaced apart from the sixth roller along the extension axis and the seventh roller is spaced apart from the eighth roller along the extension axis, the first, second, third and fourth raceways include first and second facing, third and fourth facing, fifth and sixth facing and seventh and eighth facing surfaces, respectively, the first, third, fifth and seventh rollers are supported relatively closer to the first, third, fifth and seventh raceway surfaces than to the second, fourth, sixth and eighth raceway surfaces and the second, fourth, sixth and eighth rollers are supported relatively closer to the second, fourth, sixth and eighth raceway surfaces than to the first, third, fifth and seventh raceway surfaces, respectively.

73 . The assembly of claim 72 wherein the other of the internal and external surfaces includes first and second substantially parallel wall members and third and fourth substantially parallel wall members wherein the first and second wall members form a substantially 90 degree angle, the first, second, third and fourth raceways between the first and second, second and third, third and fourth and fourth and first wall members, respectively, the first, third, fifth and seventh raceway surfaces adjacent the first, second, third and fourth wall members, respectively.

74 . An extendable leg apparatus comprising:

a first column having a length dimension parallel to a substantially vertical extension axis;

a second column supported by the first column for sliding motion along the extension axis;

at least one of the first and second columns forming an internal cavity;

a table top supported by one of the first and second columns; and

a counterbalance assembly including:

a spring having first and second ends;

a spiral cam pulley supported for rotation about a pulley axis, the pulley including a lateral surface spaced from the pulley axis, the lateral surface forming a helical cable channel that wraps around the pulley axis and that includes first and second channel ends so that at least a portion of the channel and the pulley axis forms channel radii perpendicular to the pulley axis, the radii increasing along at least a portion of the channel in the direction from the first channel end toward the second channel end; and

at least one strand having a central portion and first and second strand ends, the central portion received within at least a portion of the pulley channel with the first and second strand ends extending from a first radii portion and a second radii portion of the channel where the first portion has a radii that is smaller than the second portion, the first and second strand ends linked to the first column and the second end of the spring, respectively;

wherein the strand has a cross sectional diameter and the minimum radii of the channel from which the first strand end extends is at least five times the strand diameter.

75 . The apparatus of claim 74 wherein the minimum radii of the channel from which the strand extends is at least 0.5 inches.

76 . The apparatus of claim 75 wherein the maximum radii of the channel from which the first strand end extends is approximately 2.0 inches.

77 . The apparatus of claim 74 wherein minimum radii of the channel from which the first strand end extends is at least eight times the strand diameter.

78 . The apparatus of claim 74 wherein the strand is metallic.

79 . The apparatus of claim 78 wherein the strand is at least 1/16 th of an inch in diameter.

80 . The apparatus of claim 78 wherein the strand is at least ⅛ th of an inch in diameter.

81 . A support assembly, the assembly comprising:

a first elongated member having a length dimension parallel to a substantially vertical extension axis and forming an internal surface;

a second elongated member supported by the first member for motion along the extension axis between at least an extended position and a retracted position, the second elongated member forming an external surface;

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;

an equalizer assembly including a first end linked to the second end of the spring and a second end linked to the first member, the force equalizer assembly and spring applying a force between the first and second members tending to drive the elongated members into the extended position wherein the applied force is substantially constant irrespective of the position of the second elongated member with respect to the first elongated member; and

rollers positioned between the internal and external surfaces to facilitate movement of the second column along the vertical extension axis with respect to the first column wherein each roller includes an annular inner bearing race, an annular outer bearing race and bearings between the inner and outer races.

82 . The assembly of claim 81 wherein a first of the internal and external surfaces forming a first mounting surface pair including first and second co-planar and substantially flat mounting surfaces, a second of the internal and external surfaces forming a first raceway along at least a portion of the first surface length, the first raceway having first and second facing raceway surfaces adjacent the mounting surface pair, the rollers including at least a first roller pair including first and second rollers mounted to the first and second mounting surfaces for rotation about first and second substantially parallel roller axis, respectively, the first and second roller axis spaced apart along the extension axis, the first roller axis closer to the first raceway surface than to the second raceway surface and the second roller axis closer to the second raceway surface than to the first raceway surface wherein the first and second rollers interact with the first and second raceway surfaces to facilitate sliding of the first elongated member with respect to the second elongated member along the extension axis.

83 . The assembly of claim 82 wherein the external surface of the second elongated member forms the substantially flat first and second mounting surfaces and the internal surface of the first elongated member forms the first raceway.

84 . The assembly of claim 83 wherein the internal surface forms a second raceway, the second raceway including third and fourth facing raceway surfaces and, wherein, the external surface forms a second mounting surface pair including third and fourth co-planar and substantially flat mounting surfaces adjacent the second raceway, the assembly further including at least a second roller pair including third and fourth rollers mounted to the third and fourth mounting surfaces for rotation about third and fourth substantially parallel roller axis, respectively, the third and fourth roller axis spaced apart along the extension axis, the third roller axis closer to the third raceway surface than to the fourth raceway surface and the fourth roller axis closer to the fourth raceway surface than to the third raceway surface.

85 . The assembly of claim 84 wherein the first and third roller axis are at substantially the same location along the extension axis and wherein the second and fourth roller axis are at substantially the same location along the extension axis.

86 . The assembly of claim 84 wherein the internal surface of the first elongated member forms third and fourth raceways, the third raceway including fifth and sixth facing raceway surfaces and the fourth raceway including seventh and eighth raceway surfaces and, wherein, the external surface of the second elongated member forms third and fourth mounting surface pairs including fifth and sixth co-planar and substantially flat mounting surfaces adjacent the third raceway and seventh and eighth co-planar and substantially flat mounting surfaces adjacent the fourth raceway, respectively, the assembly further including third and fourth roller pairs including fifth and sixth rollers mounted to the fifth and sixth mounting surfaces for rotation about fifth and sixth substantially parallel roller axis and seventh and eighth rollers mounted to the seventh and eighth mounting surfaces for rotation about seventh and eighth substantially parallel roller axis, respectively, the fifth and sixth roller axis spaced apart along the extension axis, the fifth roller axis closer to the fifth raceway surface than to the sixth raceway surface, the sixth roller axis closer to the sixth raceway surface than to the fifth raceway surface, the seventh and eighth roller axis spaced apart along the extension axis, the seventh roller axis closer to the seventh raceway surface than to the eighth raceway surface and the eighth roller axis closer to the eighth raceway surface than to the seventh raceway surface.

87 . The assembly of claim 86 wherein the first and third mounting surface pairs are substantially parallel and generally face in opposite directions, the second and fourth mounting surface pairs are substantially parallel and generally face in opposite directions and the first and second mounting pairs form an angle between 60 and 120 degrees.

88 . The assembly of claim 87 wherein the angle between the first and second mounting surface pairs is substantially 90 degrees.

89 . The assembly of claim 88 wherein the first elongated member has a substantially rectilinear cross section and wherein the first, second, third and fourth raceways are formed at the corners of the rectilinear cross section.

90 . The assembly of claim 89 wherein the second elongated member has a substantially rectilinear cross section and wherein the first, second, third and fourth mounting surface pairs are formed at the corners of the rectilinear cross section of the second elongated member.

91 . The assembly of claim 89 wherein the first elongated member includes first and second substantially flat wall members that form a substantially 90 degree angle, a third wall member substantially parallel to and facing the first wall member and a fourth wall member substantially parallel to and facing the second wall member, the first, second, third and fourth raceways separate the first and second, second and third, third and fourth, and fourth and first wall members and wherein the first raceway surface is adjacent the first wall member, the third raceway surface is adjacent the second wall member, the fifth raceway surface is adjacent the third wall member and the seventh raceway surface is adjacent the fourth wall member.

92 . The assembly of claim 91 wherein the first raceway surface forms a substantially 45 degree angle with the first wall member, the third raceway surface forms a substantially 45 degree angle with the second wall member, the fifth raceway surface forms a substantially 45 degree angle with respect to the third wall member and the seventh raceway surface forms a substantially 45 degree angle with respect to the fourth wall member.

93 . The assembly of claim 82 wherein the inner races are mounted to associated mounting surface.

94 . The assembly of claim 82 wherein the first and second mounting surfaces are formed by a single substantially flat mount surface.

95 . The assembly of claim 81 further including a table top supported by the second elongated member and wherein the elongated members are supported in a position wherein the extension axis is substantially vertical.

96 . The assembly of claim 82 wherein the internal surface of the first elongated member forms the mounting surfaces and the external surface of the second elongated member forms the raceway.

97 . The assembly of claim 95 wherein the spring and equalizer assembly together tend to drive the second elongated member and table top upward.

98 . The assembly of claim 81 wherein the spring is a coil compression spring.

99 . The assembly of claim 98 wherein the equalizer includes a strand and a cam pulley, the cam pulley mounted to the second member for rotation about a pulley axis substantially perpendicular to the vertical extension axis, a first end of the strand linked to the second end of the spring, a second end of the strand linked to the first member and a central section of the strand wrapped around the cam pulley.

100 . The assembly of claim 99 wherein the pulley includes a lateral surface spaced from the pulley axis, the lateral surface forming a helical cable channel that wraps around the pulley axis and that includes first and second channel ends so that at least a portion of the channel and the pulley axis forms channel radii perpendicular to the pulley axis, the radii increasing along at least a portion of the channel in the direction from the first channel end toward the second channel end, the central section of the strand received within at least a portion of the pulley channel with the first and second strand ends extending from a first radii portion and a second radii portion of the channel where the first portion has a radii that is smaller than the second portion.

101 . The assembly of claim 101 wherein the first radii portion is at least 0.5 inches irrespective of the relative positions of the first and second columns.

102 . The assembly of claim 102 wherein the first radii portion is approximately 0.5 inches when the second column is in the retracted position and is approximately 2.0 inches when the second column is in the extended position.

103 . The assembly of claim 81 wherein the spring is a linear spring.

104 . The apparatus of claim 74 wherein the first end of the spring is supported substantially within the cavity and wherein the spiral cam pulley is supported substantially within the cavity.

105 . The assembly of claim 81 wherein the first end of the spring is supported by and stationary with respect to the second elongated member