Rolling element chain

Details Rolling element chain Rolling element chain

2002-01-30

2003-06-10

Footland, Lenard A. (Department: 3682)

Bearings

Linear bearing

Recirculating

C384S044000, C384S045000

Reexamination Certificate

active

06575630

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rolling element chain of the type including a plurality of rolling elements arranged in close succession, a longitudinal supporting band having a plurality of recesses for the accommodation of the rolling elements, a plurality of retaining elements for retaining the rolling elements accommodated in the recesses, each rolling element being assigned at least one retaining element, and at least one longitudinal flexible element for interconnecting the retaining elements.
BACKGROUND OF THE INVENTION
A rolling element chain of this kind is disclosed in, for example, DE 198 24 250 A1.
Japanese Letters of Disclosure 5-52217 (1993) for Japanese Patent Application 3-235563 (1991) disclose a rolling element chain, which comprises a plurality of balls that are arranged in recesses of a supporting band. A retaining element having, at each of its leading and following sides in the longitudinal direction of the supporting band, a retaining surface for sliding engagement with the leading or following ball is arranged between two successive balls in each instance. The retaining elements are interconnected by means of two flexible strip elements and together therewith form the supporting band.
This known ball-bearing chain has the advantage that the balls may be arranged in close succession, i.e., at a short distance apart. In such case, the ratio of the ball diameter to the distance between the midpoints of two adjacent balls is approximately 1:1. Because of the resultant high ball density, the known ball-bearing chain has a high loading or carrying capacity. However, stiffening of the supporting band, which goes hand in hand with fastening of the two strip elements to the retaining elements in the region between two successive balls, is disadvantageous. The strip elements of the supporting band are able to react to bending of the supporting band about an axis running parallel to the transverse direction of the band, for example in the turn-around sections of the raceway of a linear bearing, only in the region of the lateral contact of the band with the balls, but not in the region of its lateral fastening to the retaining elements.
The consequent relatively high bending of the supporting band in the region of its lateral contact with the balls results in a corresponding restoring force of the band in its straight-line position, resulting from the elasticity of the material of the supporting band. Because of the retaining engagement of the supporting band with the balls, this restoring force influences the motion of the balls in the turn-around sections of the raceway. In a linear bearing provided with the known rolling element chain, high bending of the supporting band may result in the pronounced development of noise, in increased friction of the strip elements in the guide grooves, and in deterioration in fatigue strength because of high bending stress.
Other ball-bearing chains with balls in close succession are disclosed, for example, in U.S. Pat. No. 2,897,021 and U.S. Pat. No. 3,292,981. In these chains, too, a retaining element that has a retaining surface for sliding engagement with the preceding ball as well as a retaining surface for sliding engagement with the following ball bearing is arranged between two successive balls in each instance.
Another non-generic rolling element chain is disclosed in Japanese Letters of Disclosure 62-242126 (1987) for Japanese Patent Application 60-253865 (1985). In the rolling element chain disclosed in
FIGS. 5 and 6
thereof, each rolling element is retained by two retaining elements assigned to it and to it only. Thus, two physically separate retaining elements, which are arranged in a central section of the supporting band at a specific distance apart, are provided between two successive rolling elements.
The supporting band of this known rolling element chain has the advantage that it can be bent about an axis running parallel to the transverse direction not only in the regions of its lateral contact with the rolling elements, but in the regions between two successive rolling elements as well. Owing to twice the number of bending points as compared with JP-A-5-52217 (1993), at a like curvature of a turn-around section of the raceway the supporting band is bent less at each individual bending point and influences travel of the rolling elements to a correspondingly lesser extent, which results in quieter operation of a linear bearing provided with this rolling element chain. However, the rolling element chain disclosed in JP-A-62-242126 (1987) has the disadvantage that the rolling elements are arranged in loose succession, i.e., at a relatively greater distance apart, in order to be able to provide the required space for the separate retaining elements. In that chain, the ratio of the ball diameter to the distance between the midpoints of two adjacent balls is about 1:1.5. The resulting lower density of rolling elements is attended by a corresponding decrease in loading capacity of the rolling element chain.
German Patent 835 718 discloses a rolling element chain in which the distance between successive rolling elements is about twice the diameter of the rolling elements. The rolling elements are retained by tongues, which are arranged between them, of a spring steel band carrying them. A rolling element chain with a similar distance between rolling elements, i.e., a similar loose succession of rolling elements, is disclosed in U.S. Pat. No. 2,557,476.
DE 36 35 261 A1 describes a ball-bearing chain of moderate spacing apart of the balls, i.e., the ratio of the ball diameter to the distance between the midpoints of successive balls is about 1:1.25. Each of the balls is assigned retaining elements, separated from one another, which are arranged between the balls. The retaining elements therefore are very small and can hardly provide the balls with any retention.
The ball chain disclosed in DE 29 06 128 A1 is made of a number of chain units designed independent of one another, each of which serves for the guidance of only one of the balls. This arrangement results in a loose succession of balls in which the apertures accommodating the balls provide no retention for the balls. The chain units, therefore, additionally have guide blocks, separated from the accommodation apertures, which center the chain units in the ball-bearing raceway and especially the turn-around sections with regard to travel of the balls.
In addition, reference is made to DE 37 09 039 C2, DE 89 14 085 U and U.S. Pat. No. 2,566,421.
DE 198 24 250 A1, mentioned above, improved the quietness of operation of the known chains of rolling elements discussed above by increasing the number of possible bending points of the supporting band.
In contrast, the object of the present invention is to allow the rolling element chains to become even more flexible without losing loading or carrying capacity.
SUMMARY OF THE INVENTION
According to the invention, the foregoing object is attained by a rolling element chain that comprises a plurality of rolling elements arranged in close succession and a longitudinal supporting band having a plurality of recesses for accommodation of the rolling elements. The supporting band has a plurality of retaining elements for retention of the rolling elements accommodated in the recesses, with each rolling element being assigned at least one retaining element. The supporting band further comprises at least one longitudinal flexible element for interconnection of the retaining elements, while in addition each rolling element is retained, by the at least one retaining element assigned to it, in the longitudinal direction of the supporting band either at its leading side only or at its following side only. In other words, when at least some of the rolling elements are assigned a plurality of retaining elements, the retaining elements assigned to one and the same rolling element are arranged, viewed in the longitudinal direction of the supporting band, either all before this rolling element or all a

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