Linear bushing

Details Linear bushing Linear bushing

2000-05-24

2002-09-10

Footland, Lenard A. (Department: 3682)

Bearings

Linear bearing

Tensioned or resilient race or roller member

C384S037000, C384S038000

Reexamination Certificate

active

06447166

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is in the field of linear bushings which are mounted to a panel or other structural element, where each such linear bushing has a central bore in which a rod or bolt is situated and may be axially slidable.
2. Description of the Prior Art
A linear bushing is used to provide a slidable connection between two structural members, where, typically, the first member is a panel and the second member is a rod or bolt. For the discussion that follows the term “rod” will be used to include a rod, bolt or other element that is positionable within the bore of the bushing. The bushing is to maintain such rod in proper relative position and orientation while it moves axially and/or while it is axially stationary. To insure such freedom of movement merely requires a sliding or clearance fit; however, for mass-produced bushings and rods inserted therein, it is quite possible for the fit to be too loose due to manufacturing tolerance stack-ups, namely the combined dimensional variations in the rod diameter, in the bore diameter of the bushing, and in the panel hole diameter in which the bushing is secured. Typically, a tolerance stack-up results in a fit so loose that the rod will rattle within the bushing, which might occur while the rod is moving axially or while it is axially still. Such rattling is worsened when the rod is subjected to lateral, tilting and/or vibration forces and when the dimensional stack-up increases due to wear.
Some prior art bushings or grommets include a set of flexible arms which extend from a wall of the bushing to engage and press radially inward on the rod situated within such arms. These arms sometimes are initially compressed radially inward when the bushing is inserted into the aperture of a panel, and subsequently they expand to define a diameter less than the outside diameter of the rod. Thus, these arms will bear inwardly against the rod at a specific axial location at one end or the other of the bushing; however, the portion of the loose-fitting rod not engaged by the flexible arms will still be able to tilt or rattle. A variety of prior art bushings and grommets may be seen in U.S. Pat. Nos. 2,424,757, 2,664,458, 5,733,046, 5,664,888, 5,476,350 and 4,874,276, none of which provides a structure as disclosed herein.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention is a new linear bushing structure that greatly reduces or eliminates any excess looseness of the rod within the bushing bore by applying inward radial force via two sets of flexible arms located respectively both above and below the panel. These arms are in constant contact with the rod whether it is stationary or moving axially and whether it is aligned coaxially with the bushing or tilted, and even when the rod is urged and moved laterally. At all times at least one flexible arm above and one flexible arm below the panel is resiliently bearing against the rod and thus preventing it from rattling. In actual use of the new linear bushing the rod is usually engaged at all times by two or more of these flexible arms above the panel and by two or more of these arms below the panel.
Accordingly, even if there is a tolerance stack-up due to excess bore diameter of the bushing and/or excess bore diameter of the panel aperture and/or reduced outside diameter of the rod, the flexible arms will always contact and apply appropriate force above and below the panel to stabilize the rod within the bushing.
It is thus an object of this invention to provide a linear bushing that compensates for tolerance stack-up and assures a good sliding fit with a rod in all conditions normally encountered.
It is a further object to provide a linear bushing that is simple and economical to manufacture, and simple and reliable to use.
By utilizing this new structure to compensate for variations in critical dimensions of the respective components, it is now possible to have mass production of these bushings without highly expensive manufacturing equipment otherwise required to maintain very close tolerances. Thus, the new invention permits great economy of manufacture while still producing a simple and reliable product that is also better in use than known prior art linear bushings.
The new linear bearing has a tubular body having a lead end for insertion into an aperture in a panel or other structural element and an opposite tail end. This tubular body is formed by a cylindrical wall having an inner surface which defines a bore about a central axis and an outer surface. There is a first set of flexible arms extending from the lead end axially in the lead-end direction and radially inwardly, with the terminal ends of these arms defining a bore diameter that is smaller than the diameter of the rod to be inserted into the bushing. These arms are spaced apart circumferentially, but are otherwise similar in dimensions and shape. Non-uniform arms might be used in specific situations.
The new bearing further includes a second set of flexible arms extending from the bore surface of the bushing axially in the lead-end direction and radially inwardly. The terminal ends of these arms also define a bore diameter that is smaller than the outer diameter of the rod to be inserted therein. These upper and lower sets of arms are flexible, but strong and resilient so as to constantly apply a stabilizing force on the rod regardless of whether it is moving, stationery, tilted or urged laterally.
Finally, there are panel mounting elements for attaching the bushing to a panel or other structural member, these elements typically comprising one fixed element extending transversely outward from the tubular body, and axially spaced therefrom one or more movable resilient elements also extending transversely outward. In the first embodiment shown herein the fixed element is a radially outwardly extending disc or other form of lateral projection from the outer surface of the cylindrical body and situated axially between said upper and lower sets of flexible arms. Cooperating with such fixed element are projections or tabs which are either flexible and resilient or are attached to a flexile and resilient portion of the tubular body. The fixed element and flexible elements are axially spaced apart a distance generally corresponding to the thickness of the panel on which the bushing is to be mounted.
In use, this bushing is inserted lead-end first through the aperture in the panel. The tabs deflect inward to allow the lead part to pass through the aperture until the panel mounting element bars further axial motion of the bushing. The bushing then becomes locked onto the panel, barred by the tabs and the fixed element from further axial movement. The sets of flexible arms are situated above and below the panel, and a rod, when inserted or otherwise positioned within the bore of the bushing, is “captured” by the sets of flexible arms, which assure a snug sliding fit and significant reduction of tolerance stack-up, resultant rattling or other defective operation.
Numerous variations in the structure of the new linear bushing are possible as shown in the drawings appended hereto and as described in the detailed description of same as follows.


REFERENCES:
patent: 2424757 (1947-07-01), Klumpp, Jr.
patent: 2664458 (1953-12-01), Rapata
patent: 4874276 (1989-10-01), Iguchi
patent: 5476350 (1995-12-01), Kurtz et al.
patent: 5664888 (1997-09-01), Sabin
patent: 5733046 (1998-03-01), Bellmore et al.

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