GB2163494A

GB2163494A - Cross-linear bearing unit

Info

Publication number: GB2163494A
Application number: GB08421277A
Authority: GB
Inventors: Hiroshi Teramachi
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-07-04
Filing date: 1984-08-22
Publication date: 1986-02-26
Also published as: GB8421277D0; GB2163494B

Abstract

A cross-linear bearing unit for use at an intersection of, for example, a column and a cross rail in a machine tool includes a bearing body (1) having a pair of oppositely facing recesses (10,11) extending orthogonally to one another. The bearing body (1) further has loaded ball guide grooves (16,17,18,19) respectively formed in the inner walls (12,13,14,15) of ridges (24,25,26,27) and non-loaded ball guide bores (20,21,22,23) formed through the ridges. Track rails (40,41) slidably fit in the recesses (10,11) of the bearing body (1). Each track rail is provided in the lateral outer walls thereof with loaded ball raceway grooves (42,43) which are parallel to the corresponding loaded ball guide grooves (16,17,18,19) and provide loaded ball passages therewith. The track rails are guided in the recesses by endless trains of balls circulating through the loaded ball passages and corresponding non-loaded ball guide bores, with which they communicate via end plates providing U-grooves. <IMAGE>

Description

SPECIFICATION Cross-linear bearing unit The present invention relates to a cross-linear bearing unit which may be used at an intersection of a column and a cross rail in a machine tool such as boring or planing machine or at an intersection of vertical and horizontal shafts in a general conveyor such as to support and slide a heavy object.

It is a primary object of the present invention to provide a cross-linear bearing unit in which a bearing body may be reduced in wall thickness so that it is possible to reduce the weight of the bearing unit as a whole, to minimize inertia force produced when the parts of the bearing unit move and thus allow the bearing unit to satisfy the need for quick changes in motion.

To this end, according to the invention, there is provided a cross-linear bearing unit comprising a bearing body having a pair of recesses formed in orthogonal relation to each other with a solid portion interposed therebetween, loaded ball guide grooves repsectively formed in the inner walls of ridges which face the corresponding recesses, and non-loaded ball guide bores formed through the ridges in parallel to the corresponding loaded ball guide grooves and with a necessary distance therebetween; end plates respectively mounted to end portions of the bearing body, each end plate being provided in the inner surface thereof with a ball guiding U-groove for providing communication between the non-loaded ball guide bores and the corresponding loaded ball guide grooves; and track rails slidably fitted in the recesses, respectively, of the bearing body through balls, each track rail being provided in the lateral outer walls thereof with loaded ball raceway grooves which are parallel to the corresponding loaded ball guide grooves.

This arrangement enables the use of lightweight parts, and consequentially low inertia forces.

Further, since the track rails of the bearing unit may be reduced in wall thickness but increased in width as compared to a conventional unit it is favorably possible to prevent any horizontal or vertical distortion of the track rails, that is, axial distortion or other machining errors produced when the track rails are ground. Thus, a desired degree of accuracy can be attained satisfactorily.

Furthermore, since the bearing body may have a relatively wide width, similar to the track rails, it is conveniently possible to grind simultaneously the right and left loaded ball guide grooves by employing a large-sized grinding wheel. Therefore, operating efficiency is greatly increased, and the production cost is favorably reduced. It is, moreover, possible to easily obtain a required degree of accuracy.

Additionally, it becomes possible to further reduce the weight of the bearing unit by forming cut out portions, such as through holes and slits, in the bearing body and the track rails. In such case, it is conveniently possible to observe the movement of a table mounted on the bearing body by making use of the through hole and slits.

Two examples of bearing units constructed in accordance with the invention are illustrated in the accompanying drawings, in which: Fig. 1 is a partly-sectional plan view of the first example.

Fig. 2 is a section taken on the line Ni in Fig. 1; Fig. 3 is a front elevational view of an essential part of the bearing unit shown in Fig. 1 as viewed in the direction of the arrow A ; Fig. 4 is a section taken on the line IV-IV in Fig. 2; Fig. 5 is an exploded perspective view of a bearing body and track rails employed in the bearing unit shown in Fig. 1; Fig. 6 is a perspective view of an end plate employed in the bearing unit shown in Fig. 1; Fig. 7 is an exploded perspective view of most parts of the second example; and, Fig. 8 is a section taken on the line VIII-VIII in Fig. 7.

As shown in Figs. 1 to 6 a bearing body 1 is constituted by a block of a substantially rectangular parallelepiped shape. The bearing body 1 is provided in the upper and lower surfaces thereof with recesses 10,11 which are in orthogonal relation to each other with a solid portion 2 interposed therebetween. The bearing body 1 is formed from a steel material or a composite material which has a strength equal to that of a steel material, or a heattreated thermoplastic material, for example, polyacetal resin. Further, loaded ball guide grooves 16,17,18,19, each having a curvature slightly larger than that of each of the balls, are respectively formed one in each of the opposing inner walls 12,13,14,15 of the recesses 10,11.

Non-loaded ball guide bores 20,21,22,23 are respectively formed through ridges 24,25, 26,27 which face their respective recesses 10, 11. The non-loaded ball guide bores 20, 21,22,23 are formed in parallel to the corresponding loaded ball guide grooves 16,17, 18,19 and with a necessary distance therebetween.

End plates 28,29,30,31 are formed from a metallic or nonmetallic material, e. g., a synthetic resin material such as polyacetal resin and nylon resin. Each of the end plates 28, 29,30,31 is provided in the inner surface thereof with a ball guiding U-groove 32 for providing communication between the nonloaded ball guide bores 20,21,22,23 and the corresponding loaded ball guide grooves 16,17,18,19. Each of the end plates 28, 29,30,31 is further provided on the side thereof which faces the associated loaded ball guide groove with a tongue 33 for smoothly guiding the balls.

Each of the end plates 28,29,30,31 is formed with through holes 34,35 for receiving mounting bolts. Each of the through holes 34,35 is subjected to spot facing so as to properly receive the head portion of a mounting bolt.

Female threads 36,37 are formed in each of the portions of the bearing body 1 which are respectively closer to the ridges 24,25, 26,27. The female threads 36,37 are positioned so as to correspond to the through holes 34,35 of each of the end plates 28, 29,30,31, thereby allowing the female threads 36,37 and the through holes 34,35 to align with each other when the bearing unit is assembled. The reference numeral 38 denotes each of the mounting bolts for mounting the end plates 28,29,30,31 to the ridges 24,25,26,27 of the bearing body 1.

Flat and wide-width track rails 40,41 are formed, similar to the bearing body 1, from a steel material or a composite material which has a strength equal to that of a steel material, or a heat-treated thermoplastic material.

The track rails 40,41 are slidably fitted in the recesses 10,11, respectively, of the bearing body 1 through balls. The widths of the track rails 40,41 are substantially equal to that of the recesses 10,11. On the other hand, the thicknesses of the track rails 40,41 are selected so that they outwardly project slightly beyond the associated ridges 24,25,26,27 of the bearing body 1.

Each of the track rails 40,41 is provided in the lateral outer walls thereof with loaded ball raceway grooves 42,43 which are parallel to the corresponding loaded ball guide grooves 16,17,18,19 of the bearing body 1.

In the drawings, the reference numeral 44 denotes a loaded ball train constituted by a multiplicity of balls interposed between the loaded ball guide grooves 16,17,18,19 of the bearing body 1 and the corresponding loaded ball raceway grooves 42,43 of the track rails 40,41. The reference numeral 45 denotes a non-loaded ball train constituted by a multiplicity of balls within the non-loaded ball guide bores 20,21,22,23 in the bearing body 1. The reference numeral 46 denotes each of the through holes for receiving set bolts when the lower track rail 40 is secured to the bed of a machine tool, for example.

Further, the reference numeral 47 denotes each of the through holes for receiving set bolts when a table, for example, is secured to the upper track rail 41.

The following is a description of the operation of the cross-linear slide bearing unit having the above-described construction.

The lower track rail 40 mounted on the bearing body 1 through the balls is secured to the bed of a machine tool, for example, through the set bolts, and a table, for example, is secured to the upper track rail 41 through set bolts.

As the bearing body 1 is moved in the direction of the arrow A in Fig. 1 by means of a drive mechanism (not shown) such as a ball screw, the balls between the loaded ball guide grooves 18,19 and the loaded ball raceway grooves 42,43 and those within the nonloaded ball guide bores 22,23 smoothly recirculate through the end plates 30,31 while changing over their rolling states from one to the other, that is, from the state wherein they roll as the loaded ball train 44 to the state wherein they roll as the non-loaded ball train 45, and vice versa, as shown by the arrow in Fig. 4.

On the other hand, when the table secured to the upper track rail 41 is moved in the direction perpendicular to the direction of the arrow A in Fig. 1, the balls between the loaded ball guide grooves 16,17 and the loaded ball raceway grooves 42,43 and those within the non-loaded ball guide bores 20,21 smoothly recirculate through the end plates 28,29 while changing over their rolling states from one to the other, that is, from the state wherein they roll as the loaded ball train 44 to the state wherein they roll as the non-loaded ball train 45, and vice versa.

As described above, in the cross-linear slide bearing unit in accordance with the invention, the wall thickness T, of the solid portion 2 is substantially equal to the wall thickness T2 of the recesses 10,11 as well as the wall thickness T3 of the track rails 40,41, as clearly shown in Fig. 3, for example. It is, consequently, possible to reduce the wall thickness of the bearing unit as a whole, which advantageously makes it possible to minimize inertia force produced when the bearing unit moves.

Further, since the upper and lower track rails have a relatively wide width, a multiplicity of through holes for receiving set bolts can be bored in two rows in both side edges of each track rail. Accordingly, it is possible to secure the lower track rail reliably to the bed of a machine tool to the like and also a table or the like to the upper track rail.

It is to be noted that although the abovedescribed cross-linear bearing unit employs no retainer for preventing the balls from falling out, the bearing unit may, of course, employ retainers.

Figs. 7 and 8 show a second example of the cross-linear bearing unit, in which the same portions of those found in the first example are denoted by the same reference numerals.

Referring now to Fig. 7, a through hole 50 of any desired shape, but preferably square or circular, is formed in an approximately central portion of a solid portion 2a of a bearing body 1a. The width of the through hole 50 is substantially equal to the width of track rails 40a, 41 a which are incorporated in the bearing body 1a.

Further, windows or slits 51,52 are respectively formed in the central portions of the track rails 40a, 41a. Although the shape of the windows or slits is not specifically limite, it is preferable that a rectangular or elliptical window or slit should be formed with its longer dimension in parallel to the longitudinal axis of each of the track rails 40a, 41a.

Since the bearing body 1a is provided with the through hole and each track rail is provided with the window or slit as described above, it is possible to reduce the weight of the bearing unit as a whole. In addition, the provision of the through hole and the windows or slits permits a mutual communication bore to be constantly formed through the track rails crossing each other at right angles and the bearing body which retains and guides these track rails. Accordingly, it is possible easily to confirm the position of, for example, a table moving in the X-Y directions by, for example, utilizing a ray of light emitted from a light source placed above or below the bearing unit. Thus, the bearing unit is suitable for use in the feed device of a precision apparatus requiring fine or precise feed.

Claims

1. A cross-linear bearing unit comprising a bearing body having a pair of oppositely facing, mutually orthogonally extending recesses, each defined between a pair of ridges; loaded ball guide grooves respectively formed in the inwardly facing side walls of the ridges; non-loaded ball guide bores formed through the ridges in parallel to the corresponding loaded ball guide grooves ; a pair of track rails slidably mounted in respective ones of the recesses by means of ball trains, each track rail being provided in its outwardly facing side walls with loaded ball raceway grooves which are parallel to the corresponding loaded ball guide grooves and form therewith loaded ball passages; and end plates mounted on respective end portions of the bearing body, each end plate being provided in the inner surface thereof with a ball guiding U-groove for providing communication for the balls of a train between a respective one of the non-loaded ball guide bores and the corresponding loaded ball passage.

2. A bearing unit according to claim 1, wherein one of the loaded ball guide grooves of the bearing body is provided in each of the inwardly facing side walls of the ridges.

3. A bearing unit according to claim 1 or claim 2, wherein the bearing body has, substantially centrally, a through hole and the track rails are formed with windows which communicate with the through hole.

4. A bearing unit according to claim 3, wherein the through hole is substantially square or circular.

5. A bearing unit according to claim 3 or claim 4, wherein the windows of the track rails are rectangular or elliptical with their longer dimensions parallel to the longitudinal axes of the respective track rails.

6. A cross-linear bearing unit substantially as described with reference to Figures 1 to 6, or to Figures 1 to 6 as modified in accordance with Figures 7 and 8, of the accompanying drawings.