Rolling bearing for linear movements

#The invention concerns a rolling bearing for linear movements comprising a carrier which is displaceable along a guide rail and supported on two longitudinal sides of the guide rail on several pairs of rolling element circuits, a one-piece cage being associated with each longitudinal side and each rolling element circuit being comprised of a rectilinear row of load-transmitting rolling elements guided by the cage, a row of returning rolling elements arranged in a return passage in the carrier and two rolling element deflector arches connecting the two said rows at ends thereof, a part of each deflector arch being arranged in the one-piece cage as a continuation of the rectilinear row of rolling elements while another part of the deflector arch is arranged in a head piece disposed on an adjacent end face of the carrier.

#Such a rolling bearing is known from the document EP-A-0 427 238 and comprises two pairs of rolling element circuits for supporting the carrier on the guide rail so that four ball circuits with the balls which constitute the rolling elements are obtained. The load which can be transmitted by the carrier to the guide rail is limited by the four load-transmitting rolling element rows of the rolling element circuits. Therefore, with these four rolling element circuits, only a certain maximum static and dynamic load rating of the rolling bearing can be obtained. An increase of the load ratings by increasing the number of rolling element circuits with otherwise unchanged structural features of the rolling bearing, is, however, opposed by the difficulty encountered in designing the two cages each of which has to be made in one piece and accommodate several load-transmitting rows of rolling elements. If such a cage is to be made as an injection moulded part of a polymeric material, it would require complicated moulding tools. It is desirable to be able to injection mould and remove the workpiece from the mould in a simple manner using the simplest possible tool and without the need of additional mould slides. The cage for the known rolling bearing for two rows of load-transmitting rolling elements is made so as to be removable from the mould in the vertical direction.

#The document EP-A-0 211 243 discloses a rolling bearing for linear movements with four rolling element circuits in which each of the cages is formed by two mutually aligned parallel retaining webs which abut together at their ends. The two load-transmitting rolling element rows of each pair of rolling element circuits are made at their other ends in one piece with the head piece. Such a component can be made in an injection moulding tool without slides and be removed therefrom in the longitudinal direction of the cage. In the most favourable case therefore, the tool path must be slightly larger than half the length of the cage and this leads to the disadvantage of large removal paths thus resulting in longer manufacturing cycle times in series production. This rolling bearing has the further disadvantage that in the installed state of the cages, the mould seam along the length of the cage leads to a reduction of stability which has to be compensated by additional fixing measures such as grooves extending in the longitudinal direction of the two cage halves or bores in which fixing pins are inserted.

#Examples of embodiment of the invention are represented in the drawings and described more closely below.

#FIG. 1 is a cross-sectional view taken along line I--I of FIG. 2 at right angles to the direction of displacement and shows a rolling bearing assembly with a carrier which is displaceable along a guide rail which, however, is not hatch-lined in the drawing;

#FIG. 2 is a top view of the carrier;

#The rolling bearing assembly of FIGS. 1 to 3 comprises a carrier 1 which is mounted for displacement along a horizontal guide rail 2 on three pairs of rolling element circuits wherein the rolling element are balls 3 supported on tracks formed on the carrier 1 and on the guide rail 2, one rolling element circuit of each pair of rolling element circuits is arranged on one longitudinal side of the guide rail and the other rolling element circuit of the pair is arranged on the other longitudinal side of the guide rail 2. The three rolling element circuits of each side are arranged vertically above one another.

#Each rolling element circuit comprises a load-transmitting row 4 of rolling elements, a returning row 5 of rolling elements parallel thereto, and two rolling element deflector arches 6 which are adjacent to the ends of the rolling element rows 4 and 5 and connect these rows with each other. During movement, the returning rows 5 of rolling elements pass through return passages 7 arranged in the carrier 1. The load-transmitting rows 4 of all three rolling element circuits of each side of the guide rail 2 are guided by a common cage 8. One such cage 8 is arranged on each side of the guide rail 2 in the carrier 1 and projects out of the carrier 1 in the direction of movement thereof at both ends where the rolling element row 4 transfers into the rolling element deflector arch 6.

#The ends of the cages 8 projecting out of the carrier 1 at each front end thereof are surrounded by a head piece 9 in which the other part of the rolling element deflector arch is located. In this example of embodiment, the part of the deflector arch pertaining to the cage and the part pertaining to the head piece each extends through 90.degree. so that a mould seam 10 extending parallel to the direction of movement of the carrier 1 is formed between the cage and the head piece 9. The head pieces 9 are fixed on the carrier 1 with the help of screws 11 while further screws 12 serve to secure scraper plates 13 and a lubricating nipple 14 on the carrier 1.