Supports – Stand – Standard type
Reexamination Certificate
1999-03-02
2001-03-13
King, Anita M. (Department: 3632)
Supports
Stand
Standard type
C248S404000, C248S631000
Reexamination Certificate
active
06199806
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a longitudinally displaceable column of the type in which a longitudinal adjusting unit is supported on a base plate of a vertical support tube and, in particular, in which a rod of the adjusting unit receives an axial bearing that is interposed between the rod and the base plate to enable the rod to rotate relative to the base plate.
2. The Prior Art
DE 41 29 089 A1 discloses a longitudinally displaceable column for height adjustment of chairs, tables or the like, having a vertical tube with a longitudinal pneumatic or hydropneumatic adjusting unit arranged therein concentric to a common central longitudinal axis. A housing of the adjusting unit is supported radially in the tube and is guided for displacement in the direction of the axis. A piston rod is affixed on a base plate of the tube against movement in the direction of the axis and is supported for rotation with respect to the base plate by means of an axial rolling bearing preassembled into a unit. U.S. Pat. No. 5,120,011 also describes and shows a longitudinally displaceable column.
The purpose of a preassembled bearing unit can be seen in that assembly of the longitudinal adjusting unit is substantially facilitated. Rolling members cannot fall out of the bearing. Despite this, the bearing unit has the disadvantage of relatively high costs, which it is the object of the invention to minimize.
SUMMARY OF THE INVENTION
According to the present invention, the above-mentioned object is accomplished in that the axial bearing is a sliding bearing having a sliding member. The sliding member of a sliding bearing does not involve the high production cost of a rolling bearing. The disadvantage that a rolling bearing may disassemble into its component parts on assembly is avoided. The materials available for sliding members, synthetic materials in particular, have a very favorable coefficient of friction, so that no functional disadvantages need be feared. The sliding member is annular so as to have a pass-through opening for receiving the rod of the longitudinal adjusting unit.
In addition, it is provided, preferably, that the sliding bearing have a supporting disk, the rod of the longitudinal adjusting unit being supported on the supporting disk. A pneumatic unit whose piston rod has a comparatively small diameter, where the supporting surface of the piston rod is formed by a shoulder on the rod, is very often used as the longitudinal adjusting unit. Consequently, great surface pressures may occur, which are exerted on the supporting disk, which is preferably of a metallic or ceramic material, and transmitted to the sliding member. The outside diameter of the supporting disk is significantly greater than the diameter of the piston rod, so that the surface pressure on the sliding member is reduced.
So that the sliding member will under no circumstances detach from the rod after assembly, the rod has an annular groove in which locking projections of the slide member are engaged and form a locking connection. A locking connection is subject to less friction than a frictionally engaged connection.
For easier assembly the sliding member has free spaces that provide for radial expansion of the locking projections. The locking projections are arranged in the region of the pass-through opening and do not project over the end surfaces of the sliding member, so that both end surfaces are available as supporting surfaces.
With regard to increased reliability of assembly, the locking projections have bevels tapering outwardly in the direction of assembly of the sliding member onto the rod, which convert axial motion of the sliding member in the direction of assembly into radially outward motions of the locking projections. In the event of assembly of the sliding member in the wrong direction, faces of the locking projections encounter the piston rod and make further assembly at least difficult due to a large resistance force at the faces.
It is advantageously provided that the depth of the free spaces in the axial direction is greater than the height of the locking projections. The free spaces thus allow the sliding member to be deformed within limits, in order to compensate for any possible skewed position of the rod with respect to the end surface of the sliding member.
With regard to a fixed installation position that ensures against incorrect assembly of the sliding bearing on the rod, the sliding member has a peripheral flange portion, an end part of which is offset axially in the direction of a shoulder of the rod. Thus, in the event of an incorrect installation position, an installation height increased by the shoulder is produced for the rod, so that a securing arrangement on the rod for fastening the longitudinal adjusting unit within the tube cannot be installed.
For securing the supporting disk in the radial direction, the peripheral flange portion of the sliding member forms a recess and centers the supporting disk within the recess. In addition, the supporting disk is fixed axially to the sliding member by retaining overhangs on the end part of the flange portion of the sliding member.
In order not to overload the peripheral flange portion of the sliding member when the supporting disc is installed in the recess within the flange portion, the retaining overhangs are in the form of segments around the periphery. Lastly, the flange portion has spaced-apart recesses which increase its elasticity.
REFERENCES:
patent: 5120011 (1992-06-01), Mintgen et al.
patent: 5269398 (1993-12-01), Wolf et al.
patent: 5702083 (1997-12-01), Lai
patent: 5740997 (1998-04-01), Van Wieran
patent: 5979845 (1999-11-01), Battey et al.
patent: 5988605 (1999-11-01), Weisser et al.
patent: 5992815 (1999-11-01), Metzdorf et al.
patent: 6007044 (1999-12-01), Harrer
patent: 6056251 (2000-05-01), Knopp et al.
patent: 76 23 283 (1977-01-01), None
patent: 33 37 598 (1984-05-01), None
patent: 41 29 089 (1993-03-01), None
patent: 296 08 147 (1996-09-01), None
patent: 512 434 A1 (1992-11-01), None
patent: WO 96/03065 (1996-02-01), None
Knopp Axel
Sauer Rainer
Baker & Botts L.L.P.
King Anita M.
Le Tan
Stabilus GmbH
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