Bearings – Linear bearing – Recirculating
Reexamination Certificate
2001-03-05
2002-11-19
Butler, Douglas C. (Department: 3683)
Bearings
Linear bearing
Recirculating
C384S043000
Reexamination Certificate
active
06481893
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a linear rolling bearing comprising a guide carriage that is slidably supported through balls on a guide rail, the balls being retained in guide members that are detachably secured to the guide carriage while being arranged on longitudinal sides of the guide rail that comprise raceways, said guide members comprising for each endless circuit of balls, one raceway for load-bearing balls, one return channel for returning balls and two deflecting channels that connect the regions of the load-bearing and returning balls to each other, and the return channel of each guide member comprising an opening that extends over an entire length of the return channel and has a width that is smaller than the diameter of the inserted balls.
BACKGROUND OF THE INVENTION
In linear rolling bearings with an unlimited travel, the task of leading the rolling elements out of the load-bearing zone, their deflection and return and re-leading into the load-bearing zone together with the reliable retention of the balls in the unassembled state of the carriage poses a problem that is difficult to resolve. Usually, inner deflector elements, outer deflector elements and retaining crossbars are used that can lead to disturbances at their junction points and at the transition to the carrier body because, due to the great number of individual parts, the formation of an edgeless circuit is rendered more difficult. Besides this, the great number of parts results in higher tool, storage and assembly costs. The exact positioning of the deflector elements relative to the rolling element-supporting parts of the guide carriage is often an unsatisfactory compromise with economy.
Besides profiled rail guides with a plurality of separate parts, profiled rail guides with integrally formed inner deflectors and plastic-lined returning members are also known. This results in the formation of an almost edgeless circuit. Drawbacks of such configurations are the very high tool costs that result from the sealing required relative to load-bearing raceways and environment, the problem of inserting and removing of the finished part out of the hot mold and the costs caused by sealing and positioning surfaces on the part comprising the load-bearing raceways.
The publication DE 33 04 895 C2 discloses a linear rolling bearing in which the ball recirculating shoe or bearing body has attached sheet metal parts, viz., a W-shaped ball retainer for the load-bearing balls and a cover with a U-shaped cross-section that closes ball guide tracks for the non-loaded returning balls on the outside. Due to these additional sheet metal parts, the construction and assembly of the ball recirculating shoe are expensive and complex.
From the publication DE 30 19 131 A1, a linear rolling bearing of the initially cited type is known in which the guide members made as retaining plates comprise in the ball-returning regions, longitudinally extending continuous openings that form the return channels. Therefore, each guide member not only has a narrowed, outwardly oriented opening but is also open towards the machine element that acts as a guide carriage. The balls extend through these openings and are guided on longitudinal raceways that have to be made as grooves in the machine element so that additional machining and tool costs are incurred.
SUMMARY OF THE INVENTION
The object of the invention is to provide a linear rolling bearing with the smallest possible number of attached parts that is very similar to a bearing with integrally formed or sprayed-on plastic regions but does not have the drawbacks of high tool costs and costs of making sealing surfaces on the carrier body and of spraying.
This object is achieved according to the invention by the fact that the opening also extends over the entire length of the respective deflecting channel, and the deflecting channels and the return channel comprise on their longitudinal sides opposite to the opening, a closed bottom that cooperates in the guidance of the balls. Thus, the circuit raceways comprise a closed bottom on one side and the channels are narrowed down on the side opposite to the bottom so that the balls are wholly guided in a channel and cannot be displaced sideways nor in vertical direction.
During circulation, the rolling elements are in contact with at least three points of a guide member. Thus, the precision obtained in connection with the centerings is comparable to that obtained by spraying in a mold with an exactly fixed carrier body. Especially at the inlet into the load-bearing zone, the ball enters the circular cross-section of the load-bearing zone formed by the guide carriage and the rail without lateral or vertical offset. The roof-shaped inclination directly on the load-bearing raceways of the guide carriage therefore also assures an exact positional correspondence. This centering, preferably ground together with the load-bearing raceways, assures that at the most vital point, i.e. at the transition from the deflecting into the load-bearing zone, a measurable offset hardly ever occurs. Even directly at the transition to the carrier body, the central raised edge on the inner side of the deflector prevents an upward displacement of the balls.
The invention has the further advantage that only one single plastic or metal part has to be attached to the carrier body or guide carriage for each longitudinal side of the guide rail, which part comprises complete deflecting raceways and the ball retainer, or complete deflecting raceways, return channels and the ball retainer and is closed by two identical covers, and which, by an exact positional correspondence to the load-bearing raceways through a support on three points by over-dimensioning leads to the formation of an almost edgeless circuit exactly positioned with regard to the load-bearing raceways.
The invention provides a bearing having circuit regions that through appropriate undercuts enable the rolling elements to be deflected, guided back and prevented from falling out before or during assembly by one single component. This component can be made of a plastic or a metal.
The linear rolling bearing can be configured as a four-row ball bearing for guide carriages having two load-bearing regions, or as a two-row ball bearing for carriages supported only on one side of a rail. In the case of guides having raceways situated very close to each other, a convex lug can be formed between or next to two adjacent load-bearing raceways on the crossbars containing these raceways, or directly on the carriage if this is supported only on one side. If the raceways are situated further apart from each other, the fixing contour may also be concave or have a rectangular cross-section. If the spacing on the carrier body is larger than on the guide member, an exact fixing can be achieved by chamfers or countersinks on the return bores in the case of bored return channels, or by fixing contours in the case of return channels not made by boring. Besides this, due to their positive engagement, the parts are safe against displacement when subjected to impacts, so that a change in the channel cross-section cannot occur for this reason. The deflecting and guide member may also be made up of two parts that may be joined to each other, for example, by ultrasonic welding. Four-, six- or eight-row guides can be made in this way.
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Bierman, Muserlian and Lucas
Butler Douglas C.
INA Walzlager Schaeffler oHG
Kramer Devon
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