Bearings – Linear bearing – Recirculating
Utility Patent
1999-02-10
2001-01-02
Ta, Khoi Q. (Department: 3681)
Bearings
Linear bearing
Recirculating
C384S045000
Utility Patent
active
06168313
ABSTRACT:
This application corresponds to and claims priority under 35 U.S.C. §119 with respect to German Application No. P 19806139.0 filed on Feb. 14, 1998, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention generally relates to bearings. More particularly, the present invention pertains to a linear bearing integrated into a cylindrical bore provided in a housing.
BACKGROUND OF THE INVENTION
Linear bearings are typically constructed to possess a cage in which are arranged several infinite or endless ball rows consisting of circumferentially distributed and longitudinally extending ball tracks for load-bearing balls, and longitudinally extending return tracks for non-load-bearing balls. Deflection tracks connect the longitudinally extending tracks in pairs at the ends and track plates are arranged in longitudinal slits of the cage which radially outwardly cover the ball tracks for the load-bearing balls.
In known linear bearings of this type, the track plates arranged in the longitudinal slits of the cage rest over their entire length with the outer surface fully on the cylindrical bore of the housing as described in DE-PS 12 68 442. In the case of momentary load and/or shaft bending or form errors in the guide system, this solution is so rigid that in some cases the balls running into the tracks of the track plates may jam. The consequences of this are jerky or non-smooth movements and sawing noises.
DE-PS 15 75 608 discloses another linear bearing design in which the track plates have a support in the center of their length, and are angled from this support point towards the ends. The track plates are thus able to swivel about the support point in relation to the cylindrical bore of the housing, and thus are able to compensate for shaft bending to a certain extent. In this bearing construction, the support points may work themselves into the housing, resulting in an increase in operating play. As a result, reduced rigidity can arise, and a loss in bearing capacity and thus useful life can occur.
In an attempt to avoid this, hardened support rigs are sometimes pushed over the track plates as described in EP-0 636 803 A1. However, this necessarily requires additional components.
Other proposed alternatives involving the use of funnel-shaped intakes into the track plates as disclosed in DE-PS 26 31 808 have not proved to be an acceptable solution to the above-described problems because load peaks still continue to occur at the ball intake. This does not even take into account that the intakes require additional working steps.
In light of the foregoing, a need exists for a linear bearing unit that is not as susceptible to the same disadvantages and drawbacks as other know linear bearing units.
It would thus be desirable to provide a bearing unit having a housing in which is integrated a linear bearing, where in the presence of a relatively high rigidity in the system, a uniform intake of the load-bearing balls is ensured, thus significantly improving the running properties and running noises during momentary load and shaft bending as well as in the presence of form errors in the guide system.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a bearing unit includes a housing provided with a cylindrical bore and a linear bearing positioned within the cylindrical bore. The linear bearing includes a cage in which are arranged a plurality of endless ball rows each defined by a longitudinally extending ball track for load-bearing balls, a longitudinally extending return track for non-load-bearing balls, and deflection tracks connecting ends of the longitudinally extending ball track and the longitudinally extending return track, with each longitudinally extending ball track being open radially outwardly. A track plate is arranged to cover the longitudinally extending ball track for the load-bearing balls. The cylindrical bore of the housing is provided with a plurality of recesses each located in the area of the cylindrical bore facing one axial end of one of the track plates to permit radial deflection of the one axial end of the track plate.
The recesses provided in the cylindrical bore of the housing make it possible for the end of the track plate to move into the recesses during momentary loads acting on the linear bearing unit and/or during shaft bending, thus enabling a relatively smooth intake of the balls into the tracks of the track plates without significant noise. Thus, the ball running into the track does not come into an abrupt contact with the track plate, but rather experiences a gradual contact with the track plate and is loaded under rolling friction conditions. There are also no longer any load peaks which substantially increases the useful life of the linear bearing.
According to another aspect of the present invention, a bearing unit includes a housing provided with a cylindrical bore and a linear bearing positioned within the cylindrical bore. The linear bearing includes a cage in which is arranged at least one endless ball row defined by a radially outwardly open longitudinally extending ball track for load-bearing balls, a longitudinally extending return track for non-load-bearing balls, and deflection tracks connecting ends of the longitudinally extending ball track and the longitudinally extending return track. The linear bearing also includes a track plate covering the longitudinally extending ball track for the load-bearing balls. A space is provided between the outer surface of the track plate at one axial end and the inner surface of the cylindrical bore of the housing for permitting radial deflection of the axial end of the track plate. The space between the outer surface of the track plate at the one axial end and the inner surface of the cylindrical bore of the housing is greater than the spacing between the outer surface of the track plate at the intermediate portion of the track plate and the inner surface of the cylindrical bore.
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patent: 4989996 (1991-02-01), Binder et al.
patent: 1 268 442 (1968-05-01), None
patent: 15 75 608 (1981-02-01), None
patent: 26 31 808 (1983-10-01), None
patent: 0 636 803 (1995-02-01), None
Edelmann Ludwig
Geyer Andreas
Glockner Hermann
Hierl Georg
Kristandt Holger
Burns Doane Swecker & Mathis L.L.P.
SKF Linearsysteme GmbH
Ta Khoi Q.
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