BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to a table assembly in which the table top is movable to varying elevations above a supporting surface such as a floor.

It is known to construct a table in such a manner that the table top is movable to varying eleva¬ tions above a supporting surface such as floor. Tables of this type conventionally include a table top and a base assembly having a lower stationary portion engage- able with the floor and an upper portion, to which the table top is secured, movably mounted to the stationary lower portion. An adjustment mechanism is provided for fixing the position of the upper portion of the base relative to the lower portion, for adjusting the height of the table relative to the floor. Many types of ad¬ justment mechanisms are known for adjusting the vertical position of the upper base portion relative to the lower base portion. It is an object of the present invention to provide an improved adjustable height table assembly in which the upper base portion is movably secured to the lower base portion so as to provide an extremely stable support for the table top, even when the table top is in its uppermost position above the floor. It is a further object of the invention to provide a compact and easily assembled arrangement for movably mounting the base upper portion to the lower portion, while maintaining a smooth and stable arrangement. Yet another object of the inven- tion is to provide an operating mechanism for turning a rotatable threaded member forming a part of the height adjustment mechanism, in which the operating mechanism can be placed in most any location on the table top.

In accordance with one aspect of the invention, a table assembly includes a table top and a pair of spaced base assemblies, each of which includes a foot engageable with a supporting surface such as the floor,

extending in a front-rear direction. Each base further includes a pair of vertical guide members spaced from each other in the front-rear direction, and a bearing or slide assembly is slidably mounted to the guide members. A table top support forms the movable upper portion of the base to which the table top is mounted, and includes a vertical leg member fixedly mounted to the bearing assembly. The base assembly includes a housing mounted to the foot member and extending upwardly therefrom. The housing encloses the vertical guide members and the bearing assembly, and the vertical member of the table top support extends outwardly from an upper end defined by the housing.

A vertical adjustment mechanism is intercon- nected between the base and the table top support, for adjusting the vertical position of the table top relative to the floor. The vertical adjustment mechanism includes a rotatable threaded member, such as a lead screw, ex¬ tending through a passage defined by the vertical leg member of the table top support. A tubular member is mounted within the housing between the vertical guide members, and receives the lower portion of the lead screw. A fixed threaded member, such as a lead nut, is mounted toward the upper end of the tubular member and is threadedly engaged with the threads of the lead screw.

The table top support further includes an arm to which the table top is secured. The arm defines an axial passage, which is in communication with the passage formed in the vertical leg member through which the lead screw extends. A driven sprocket is mounted to the lead screw toward its upper end, and a drive sprocket is rotatably mounted to the arm below the table top. A chain is engaged with the drive sprocket and with the driven sprocket, and a manually operable crank provides rotation of the drive sprocket, which is transferred through the chain and the driven sprocket to impart

rotation to the lead screw and to thereby adjust the height of the table top.

The base housing is preferably formed so as to include an upper wall and a lower wall, with upper and lower ends of the vertical guide members being secured to the upper and lower walls, respectively. The tubular member, which receives the lower end of the lead screw, is also mounted to the lower wall of the housing. The housing lower wall is secured to an upwardly facing surface defined by the foot, for rigidly mounting the housing, and thereby the vertical guide members, to the foot.

The bearing assembly includes a pair of bearing members, each of which defines an axial passage within which one of the vertical guide members is received, and shell structure secured to the bearing members and to the lower end of the vertical support member.

The invention thus contemplates an improved and advantageous structure for mounting the adjustable por- tion of a table base to the stationary portion, as well as an improved chain-driven actuator mechanism for im¬ parting rotation to a lead screw forming a part of a table top height adjustment mechanism. These aspects of the invention can be satisfactorily used independently of each other. However, in a particularly preferred embodi¬ ment both aspects are incorporated into a single adjust¬ able height table assembly for providing highly advanta¬ geous construction and operation.

The invention further contemplates a method of making an adjustable base for a table assembly, substan¬ tially in accordance with the foregoing summary.

Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the best mode presently contemplated of carrying out the invention.

In the drawings:

Fig. 1 is an isometric view showing an adjust¬ able height table assembly constructed according to the invention; Fig. 2 is a partial top plan view of the oper¬ ating mechanism for the adjustable height table assembly of Fig. 1;

Fig. 3 is a partial longitudinal section view, taken generally along line 3-3 of Fig. 2; Fig. 4 is an enlarged partial section view of the portion of Fig. 3 encircled at 4-4;

Fig. 5 is a partial section view taken along line 5-5 of Fig. 3; and

Fig. 6 is a partial section view taken along line 6-6 of Fig. 3.

DETAILED DESCRIPTION OF THE INVENTION Referring to Fig. 1, an adjustable height table assembly 10 generally consists of a table top 12 and a pair of base assemblies 14. Each base assembly 14 in- eludes a foot 16 extending in a front-rear direction, a housing 18 mounted to and extending upwardly from foot 16, and a vertical leg 20 secured to table top 12 and movably mounted to housing 18, in a manner to be ex¬ plained. Referring to Fig. 2, a pair of open-ended hubs

22, 24 are mounted to the upper ends of legs 20. An H- shaped frame assembly 22 is mounted to the underside of table top 12. A channel member 26 extends between hubs 22, 24, and includes flanges 28 through which threaded screws extend for securing channel member 26 to the underside of table top 12. A pair of channel-shaped arms 30, 32 extend in opposite directions from hub 22, and channel-shaped arms 34, 36 extend in opposite directions from hub 24. End caps 38 are engaged with the ends of arms 30-36, and end caps 40 are engaged with the outer ends of hubs 22, 24.

Arms 30, 32 and 34, 36 are welded at their inner ends to the side walls of hubs 22, 24, respective¬ ly. Each of arms 30-36 defines an internal passageway over which table top 12 lies. The internal passageway of arm 32, shown at 40, is in communication with the inter¬ nal channel defined by hub 22, shown at 42, via an open¬ ing 44 formed in the side wall of hub 22.

As shown in Fig. 3, a leg 20 is mounted to the lower wall of each of hubs 22, 24. Leg 20 may assume any satisfactory shape or form, such as rectangular or ellip¬ tical tubing or the like. Leg 20 defines an internal passage 46 extending between its open upper and lower ends.

Referring to Fig. 3, the housing 18 of each base assembly 14 includes an inner housing subassembly consisting of an upper bracket 48 and a lower bracket 50, with vertical guide shafts 52, 54 extending between brackets 48 and 50. Brackets 48 and 50 define aligned openings which received reduced-diameter end portions of guide shafts 52, 54. A peripheral wall assembly 56

(Figs. 3, 6) forms the inner housing in combination with upper bracket 48 and lower bracket 50, and is secured at its upper end to downturned end portions 57 of upper bracket 48 via screws 58, and is secured at its lower end to upturned end portions 59 of lower bracket 50 via screws 60. In this manner, wall structure 56 in combina¬ tion with upper bracket 48 and lower bracket 50 defines an enclosure or inner housing having an internal cavity

66 through which guide shafts 52, 54 extend. As shown in Fig. 3, the housing subassembly defined by upper bracket 48, lower bracket 50, shaft 52, 54 and wall structure 56 is secured to foot 16 by thread¬ ed fasteners extending upwardly through vertical passages

67 formed in foot 16, with threaded nuts being engaged with lower bracket 50 and with the threaded fasteners.

A tube 68 is mounted at its lower end to lower bracket 50 between guide shafts 52, 54, and a lead nut 70 is mounted to the upper end of tube 68.

As shown in Fig. 3, a top cap or grommet is positioned over upper bracket 48, and a depending periph¬ eral oval wall structure 72 encloses wall structure 56 between top cap 71 and leg 16. Top cap 71 and wall 72 are primarily ornamental, serving to enclose the func¬ tional internal components of housing 18. As shown in Figs. 3 and 6, a slide or bearing assembly 73 is received within internal cavity 66. Bearing assembly 73 includes a pair of bearing tubes 74 into which low-friction bearing members 76 are press-fit. Bearing members 76 are constructed of any satisfactory low-friction material, such as Duralon, and are arranged relative to tubes 74 such that one bearing member 76 is located toward the upper end of tube 74 and another bearing member 76 is located toward the lower end of tube 74. Bearing members 76 define axial passages within which guide shafts 52, 54 are received, for slidably mounting bearing tubes 74 to guide shafts 52, 54.

As shown in Fig. 6, a pair of mirror-image shell members 78, 80 are mounted to bearing tubes 74, such as by welding, to form a one-piece bearing assembly 73 defining a vertical passageway through bearing assem¬ bly 73. Bearing members 76 function to slidably mount bearing assembly 73 to guide shafts 52, 54 for vertical movement upwardly and downwardly on shafts 72, 74.

Bearing assembly 73 is mounted to the lower end of leg 20 via bolts or the like extending through aligned openings, such as shown at 84 (Fig. 3) formed in shell members 78, 80 and in the side walls of leg 20. In this manner, table top 12 is mounted for upward and downward vertical movement to housing 18 by upward and downward movement of bearing assembly 73 on guide shafts 52, 54.

Referring to Figs. 3, 4 and 5, a height adjust¬ ment mechanism includes a lead screw 86 extending through

passage 46 in leg 20 and threadedly engaged with lead nut 70 mounted to the upper end of tube 68. Lead screw 86 is rotatably mounted at its upper end to the lower wall of hub 24 via a bearing assembly 88. An idler sprocket 90 and a driven sprocket 92 are fixed to an upper extension 94 of lead screw 86. Extension 94 and sprockets 90, 92 have mating irregular cross-sections, so as to non-rotat- ably mount sprockets 90 and 92 to lead screw 86. The upper end of extension 94 is rotatably mounted by a suitable bushing or the like to the upper wall of hub 24.

Referring to Fig. 4, a drive sprocket 96 is mounted to end cap 38, which in turn is secured to the end of arm 32. A drive shaft 98 extends upwardly through a passage 100 formed in table top 12, terminating flush with or slightly below the upper surface of table top 12. A grommet 102 is received within the upper portion of opening 100, and defines a recess 104 into which the upper end of drive shaft 98 extends. A manually operable crank 106 (Fig. 1) is removably engageable with drive shaft 98 from above table top 12.

As shown in Figs. 2 and 6, a drive chain 108 extends between drive sprocket 96 and driven sprocket 92. A idler chain 110 (Fig. 2) extends between idler sprocket 90 and an idler sprocket 112 mounted to the upper end of a lead screw 86' identical to lead screw 86 associated with base assembly 14 at the opposite end of table assem¬ bly 10.

In operation, the height of table top 12 is adjusted by the operator first manually engaging crank 106 with the upper end of drive shaft 98. The operator then turns crank 106 to rotate drive sprocket 96, which in turn imparts rotation to driven sprockets 92 and 112 through chains 108 and 110, respectively. Lead screws 86, 86' are then rotated relative to lead nuts 70, to raise or lower table top 12. Engagement of bearing members 76 with spaced guide shafts 52, 54 throughout the range of motion of bearing assembly 73 provides stability

in the adjustable height mounting of table top 12 rela¬ tive to base assemblies 14. In addition, the use of a drive chain 108 to impart rotation to lead screw 86 enables a manufacturer to position the drive shaft 98 in any satisfactory location. In the preferred embodiment, drive shaft 98 is located adjacent the end of one of arms 30-36, but it is understood that drive shaft 98 could be in any other satisfactory location by simply providing a suitable housing for chain 108 and forming any openings as necessary in hub members 22, 24 and/or arms 30-36 to allov drive chain 108 to pass therethrough between drive sprocket 96 and driven sprocket 92.

To construct table assembly 10, arms 30, 32 and leg 20 are first welded to hub 24 in a subassembly, which is then in turn movably assembled to housing 18 by mount¬ ing bearing assembly 73 to the lower end of leg 20 and movably mounting bearing assembly 73 to guide shafts 52, 54 and then assembling housing 18 together and mounting housing 18 to leg 16. These assembled components are then secured to the underside of table top 12 adjacent one of its ends, and a similar assembly is secured to the opposite end of table top 12. Chain 110 is then trained between sprockets 90 and 112, and chain channel 26 is cut to length and secured to the underside of table top 12 so as to enclose the portion of chain 110 extending between hubs 22, 24. In this manner, the distance between the leg and base assembles can be varied and the associated lead screws interconnected simply by altering the length of chain 110 and chain channel 26. Various alternatives and embodiments are con¬ templated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.