The invention concerns a linear rolling bearing comprising a guide carriage with a U-shaped cross-section having a U-crossbar and two U-legs so that the guide carriage forms a carriage cavity and partially surrounds a guide rail while being slidably supported through balls on two longitudinal sides of the guide rail, each U-leg of the guide carriage having on an inner surface opposing the guide rail a ground raceway with an approximately quarter circle cross-section for the balls, the raceway being made by a grinding wheel whose diameter is larger than a diagonal dimension of the carriage cavity and whose axis of rotation is situated outside of the guide carriage and forms an acute angle with an axis of symmetry of the guide carriage.
Raceways of carriages for profiled rail guides are made either using small vertical grinding wheels or several inclined grinding wheels arranged behind one another. Small grinding wheels result in unfavorable grinding values, short tool lives and poor surface quality. If several inclined wheels are used, the inner space of the guide carriage i.e., the carriage cavity likewise limits the size of the wheels. The advantage, however, is the inclined position of the grinding wheel. Therefore a limited but somewhat larger wheel is used.
At the same speed of rotation, a higher peripheral speed is obtained with a grinding wheel having a large diameter than with a wheel having a small diameter. With a large diameter, a higher grinding performance and a prolongation of the service life of the wheel are obtained. The rotational speed of the grinding spindle cannot be infinitely increased because this would lead to a destruction of its bearings.
The publication EP 0 318 980 B1 discloses a linear ball bearing having a guide carriage, designated as a bearing body, that has a leg section with an upper groove with an approximately semi-circular cross-section for load-bearing balls and a lower groove with an approximately quarter circle cross-section for load-bearing balls. A drawback of this lies in the continuation of the radius of the upper groove up to the vertical inner wall of the leg section. This necessarily means that for making the upper groove by grinding, a small grinding wheel must be used.
The publication DE 33 31 287 C2 discloses a method of grinding the bearing body of a linear ball bearing. In this method, two raceways for load-bearing balls are ground on the inner surface of a U-crossbar of a guide carriage using a grinding wheel with a large diameter which is placed inclined to the guide carriage. The return canals for the balls that are arranged in circuits are configured as bores in the guide carriage and have to be made in special work steps in addition to the raceways for the load-bearing balls.
The publication DE 33 04 895 C2 shows a linear ball bearing with bearing bodies in which each ball recirculating shoe or bearing body comprises attached sheet metal parts viz., a W-shaped ball retainer for the load-bearing balls and a cover with a U-shaped cross-section which outwardly closes ball-guiding grooves for the non-loaded returning balls. Due to these additional sheet metal parts, the structure and assembly of the ball recirculating shoe is complicated and expensive.
The publication DE 30 19 131 A1 discloses a linear ball bearing in which continuous longitudinal openings are provided in the load-bearing regions and the return regions for the balls in the guide elements that are made as retaining plates. Therefore each guide element not only has in its ball region a narrow 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.
It is an object of the invention to provide a linear rolling bearing which can be made with low machining costs and a short machining time under good grinding conditions so that raceways with a very high surface quality can be realized.
This and other objects and advantages of the invention will become obvious from the following detailed description.
The invention achieves the above objects by the fact that a stop surface having a retaining contour for a guide member containing the balls is configured on a guide rail-distal outer surface of each U-leg of the guide carriage, and the raceway on one of the two U-legs and the stop surface having the retaining contour on the other of the two U-legs are made in common in one work step by the grinding wheel. Due to the simultaneous grinding of a raceway and a stop surface, the machining time of the guide carriage of the linear bearing is considerably shortened.
Further advantageous features of the invention and a detailed description of one example of embodiment of the invention shown in the drawings will be given hereinafter.