GB2135400A

GB2135400A - A linear rolling bearing

Info

Publication number: GB2135400A
Application number: GB08404686A
Authority: GB
Inventors: Rudiger Neumann; Lothar Walter; Walter Reith
Original assignee: SKF Kugellagerfabriken GmbH
Current assignee: SKF GmbH
Priority date: 1983-02-23
Filing date: 1984-02-22
Publication date: 1984-08-30
Also published as: GB8404686D0; FR2541394B1; DE3306280A1; GB2135400B; FR2541394A1

Abstract

A rolling bearing (2) for linear movement on a shaft (3) comprises a cage (4) surrounding the shaft (3). The cage (4) has at least one radially continuous, longitudinally extending guide slot and also a support element which externally covers the guide slot (5) and which is retained longitudinally/axially between two end rings (12) on the cage (4) and which is supported in the bore of a housing (1). Load-transmitting rolling bodies (6) run between the support element and the shaft (3) and are installed successively in a row in the guide slot (5). To enable the load-bearing capacity of the rolling bearing (2) to be varied in an economical manner, while retaining the same diameter, the support element optionally comprises one or more uniformly designed individual sections (9) which are arranged immediately juxtaposed in longitudinal direction and which, with uniform design of the associated rolling bodies (6) and end rings (12), are fitted on a cage (4) of corresponding length. <IMAGE>

Description

SPECIFICATION A linear rolling bearing The present invention relates to a linear rolling bearing comprising a cage surrounding a shaft with at least one longitudinally extending guide slot for rolling bodies installed successively in a row, a support element which externally covers the guide slot or slots and which is supported in the bore of a housing, and load-transmitting rolling bodies running between longitudinally directed tracks of the support element and shaft.

A linear rolling bearing is known, which can be produced economically in certain standard sizes in large quantities (patent specification DE 25 57 351). If a rolling bearing with higher load-bearing capacity than normal is to be installed in a housing with a predetermined bore then in a separate production operation the bearing has to be provided with different support elements and cages so that it has a greater loadbearing length. However, rolling bearings of this type produced in a separate manufacturing operation are relatively complicated and expensive. Conventionally, therefore, two or more rolling bearings with normal dimensions are seated end to end on the shaft and in the housing, if relatively high loads are to be taken up (patent specification U.S. 40 05 913).Of course, each of the rolling bearings arranged end to end then has a relatively short support element for the loadtransmitting rolling bodies, in which case two end rings have to be accommodated in the housing bore between the two support elements. Such an arrangement of rolling bearings of normal dimensions thus requires a relatively large amount of space in axial direction.

The object of the invention is to devise a linear rolling bearing of the type described, which can be produced largely with standard structural elements, although with constant diameter it may be varied in its load-bearing capacity or its load-bearing length and can thus be adapted to the requirements of the respective application.

According to the invention, for varying the loadbearing capacity of the rolling bearing of the same diameter, the support element optionally comprises one or more uniformly designed individual sections which are arranged immediately juxtaposed in longitudinal direction and which, with uniform design of the associated rolling bodies, are fitted on a cage of corresponding length.

With the arrangement according to the invention it is achieved that the linear rolling bearing consists of standard structural elements which can be produced economically in mass production. To obtain a variable load-bearing capacity of the rolling bearing in relation to a rolling bearing of normal length, it is only necessary for one cage to be produced in different lengths.

The cage may be composed of two cage. halves which are divided along a transverse plane and which are connected with one another at the mutual butt joint of this transverse plane by welding or the like.

The cage halves can be produced economically from plastics material in a simple injection mould with radial and/or axial sliders.

The transverse plane of the butt joint of the two cage halves may pass through the centre of an individual section installed at one of the two ends of the cage.

For all rolling bearings of a specific outer diameter it is possible to utilise the same cage half which is securely connected by welding or adhesion to the associated second cage half of the same or a correspondingly greater length.

The or each individual section may be of annular design and securely fixed on a circumferential surface of the cage.

The individual sections can be hardened and finish-ground in economical mass production, as tubular sections of steel or the like.

The or each individual section may be designed as a longitudinally extending plate and installed in the guide slot or slots of the cage.

Each individual row of load-transmitting rolling bodies is supported radially outwards on one or more plates installed end to end in longitudinal direction in the cage. If these plates have bevelled ends in longitudinal direction and are thus supported tiltably in longitudinal direction in the housing bore, the load-transmitting balls of each row will also be uniformly loaded if the shaft, as a result of shaft deflection or the like, is positioned slightly skewed relative to the housing bore.

Embodiments of the invention will now be described by way of example, reference being made to the accompanying drawings, in which: Figure 1 shows a longitudinal section along the line I-I through the linear recirculating rolling bearing illustrated in Figure 2, which is installed in a housing and with augmented (doubled) load bearing capacity; Figure 2 shows a sectional view along the line Il-Il through the rolling bearing illustrated in Figure 1, which is installed in a housing; Figure 3 shows a partial plan view of the rolling bearing (without housing) illustrated in Figures 1 and 2; Figure 4 shows a plan view of the cage of the rolling bearing illustrated in Figures 1, 2 and 3;; Figure 5 shows a plan view of a cage for a rolling bearing corresponding to the rolling bearing indicated in Figures 1 to 3 with the same diameter but with normal (single) load-bearing capacity; Figure 6 shows a longitudinal section through a modified linear recirculating rolling bearing with augmented (doubled) load-bearing capacity; Figure 7 shows a partial plan view of the rolling bearing illustrated in Figure 6; and Figure 8 shows a sectional view along the line VIll-VIll through the rolling bearing illustrated in Figure 7.

In Figures 1 and 2; a linear recirculating rolling bearing 2 is secured in the cylindrical bore of a housing 1 and with'augmented (doubled) load -bearing capacity. The rolling bearing 2 surrounds a longitudinally movable cylindrical shaft 3 which is indicated in chain lines in Figures 1 and 2. The rolling bearing 2 has a sleeve-shaped plastics cage 4 which incorporates a plurality of radially continuous, longitudinally extending guide slots 5 arranged on the periphery (Figure 4). For receiving an endlessly closed row of balls 6, each guide slot 5 is provided at its two longitudinal ends with a respective semicircular reversal track 7 and a track 8 connecting these two reversal tracks 7 with one another.

The guide slots 5 of the cage 4 are covered externally by a support element in the housing 1.

The support element comprises two uniformly designed annular individual sections 9 which are disposed immediately juxtaposed in longitudinal direction and which are fixed on the cylindrical circumferential surface 10 of the cage 4.

The load-transmitting balls 6 are guided in longitudinal direction in the guide slots 5 of the cage 4 and run between the cylindrical track 11 in the bore of the relevant individual section 9 and the cylindrical circumferential surface of the shaft 3. An end ring 12 is fitted respectively at the two ends of the cage 4 on the circumferential surface 10 of the cage 4 and is secured to the cage by adhesion. With their axially inward facing end surfaces 13, these two end rings 12 contact the opposite end face of the relevant individual section 9 and retain it longitudinally/axially on the cage (Figure 3).

It is evident from the illustration of Figure 4 that the cage comprises two cage halves 14, 1 5 divided along a transverse plane IV--IV. These two cage halves 14, 15 are securely joined together at their butt joint lying on the transverse plane IV--IV by ultrasonic welding. In the present case, the transverse plane lV-IV passes through the centre of the individual section 9 which is installed at the left-hand longitudinal end of the cage 4 in Figure 1 of the drawing.

The cage 4 comprises a short cage half 14 and a longer cage half 15, so that it has a relatively great axial length. The juxtaposed individual sections 9 of the rolling bearing 2 have a large combined load-bearing length so that, compared with a rolling bearing with only one individual section 9, the rolling bearing 2 has double the load-bearing capacity.

To produce a rolling bearing (not shown) having the same diameter as the rolling bearing 2, but with normal (single) load-bearing capacity, only a single individual section 9 is pushed axially on to a relatively short cage 1 6 (Figure 5) and is secured co-axially between the end rings 12. The length of the left-hand cage half 1 4 shown in Figure 5 is exactly the same as the length of the right-hand cage half 1 7. Both cage halves 14, 1 7 are welded together at the mutual butt joint lying on the transverse plane V-V and passing centrally through the rolling bearing with normal loadbearing capacity.Furthermore, rolling bodies 6 and end rings 1 2 of the same dimensions as for the rolling bearing 2 (shown in Figures 1,2 and 3) with augmented load-bearing capacity are installed in this rolling bearing.

Figures 6, 7 and 8 illustrate a modified rolling bearing 1 8 with augmented load-bearing capacity, which is of similar construction to the rolling bearing 2 shown in Figures 1, 2 and 3 but which has a one-piece (non-welded) sleeve-type cage 19.

The cage 1 9 is secured in the bore of a housing (not shown) and surrounds a shaft 3 (see chainline representation in Figures 6 and 8). It has longitudinally extending guide slots 5 which are disposed on its periphery and which at each of their two ends is provided respectively with a semicircular reversal track 7 and a return track 8 of circular cross-section and connecting these two reversal tracks 7 with one another. In each guide slot 5 there are guided in longitudinal direction the load-transmitting balls 6 of an endlessly closed row of rolling bodies 6 arranged immediately one behind the other.

Each guide slot 5 is covered externally by two uniformly designed individual sections which are arranged immediately juxtaposed in longitudinal direction end to end and which, in the present case, are designed as longitudinally extending plates 20. By axial insertion into the cage 1 9 in similar manner to a tongue and groove connection, these plates 20 are installed side by side in the stepped recessed guide slot 5 of the cage 1 9 and are secured radially therein (see cross-section 21 of the plates 20 in Figures 7 and 8).

The above-described examples of embodiments of the present invention can be modified in construction. For example, the sleeve-like cage may have, instead of a plurality of guide slots, only one radially continuous guide slot for the loadtransmitting rolling bodies, which is covered externally by one or more individual sections supported in the housing bore and arranged immediately juxtaposed or end to end longitudinally.

Furthermore, the guide slot of the cage does not need to be provided at both its ends with a respective semicircular reversal track and a return track connecting the two reversal tracks with one another. Moreoever, this slot may be limited if, in operation, only slight axial to-and-fro movement occurs between shaft and housing, so that the load-transmitting rolling bodies can only run up to the longitudinal end of each guide slot. The loadtransmitting rolling bodies must then be installed with a sufficient amount of axial play at the ends of the guide slots, corresponding to the extent of the to-and-fro movement. Optionally, it is possible to install in the cage a spring, which is under compressive load and which yields in longitudinal direction, between each end of the guide slot and the load-transmitting rolling bodies.

Claims

1. A linear rolling bearing, comprising a cage surrounding a shaft with at least one longitudinally extending guide slot for the rolling bodies installed successively in a row, a support element which externally covers the guide slot or slots and which is supported in the bore of a housing, and loadtransmitting rolling bodies running between longitudinally directed tracks of the support element and shaft, wherein for varying the loadbearing capacity of the rolling bearing of the same diameter, the support element optionally comprises one or more uniformly designed individual sections which are arranged immediately justaposed in longitudinal direction and which, with uniform design of the associated rolling bodies, are fitted on a cage of corresponding length.

2. A rolling bearing according to Claim 1, wherein the cage is composed of two cage halves which are divided along a transverse plane and which are connected with one another at the mutual butt joint of this transverse plane by welding or the like.

3. A rolling bearing according to Claim 2, wherein the transverse plane of the butt joint of the two cage halves passes through the centre of an individual section installed at one of the two ends of the cage.

4. A rolling bearing according to one of the preceding claims, wherein the or each individual section is of annular design and is securely fixed on a circumferential surface of the cage.

5. A rolling bearing according to one of Claims 1 to 3, wherein the or each individual section is designed as a longitudinally extending plate and is installed in the guide slot or slots of the cage.

6. A linear rolling bearing comprising an annular cage having a longitudinally extending guide slot which slot extends radially through the cage, a plurality of rolling elements arranged to travel along the guide slot and two or more support elements disposed end to end longitudinally, each support element providing a longitudinally extending radially inner surface along which in use of the bearing travel the rolling elements in the guide slot, load being transmitted, in use of the bearing, radially of the bearing between the rolling elements and the support elements.

7. A linear rolling bearing as dlaimed in Claim 6, wherein the cage comprises two parts joined together at a common plane extending cross-wise of the length of the bearing.

8. A linear rolling bearing comprising an annular cage having a longitudinally extending guide slot, which slot extends radially through the cage, a plurality of rolling elements arranged to travel along the guide slot and one support element or two or more support elements disposed end to end longitudinally, the or each support element providing a longitudinally extending radially inner surface along which, in use of the bearing, travel the rolling elements in the guide slot, load being transmitted, in use of the bearing, radially of the bearing between the rolling elements and the or each support element, wherein the cage comprises two parts joined together at a common plane extending cross-wise of the length of the bearing.

9. A linear rolling bearing as claimed in Claim 7 or 8, wherein the plane bisects the or one of the support elements.

10. A linear rolling bearing as claimed in any one of Claims 6 to 9, wherein the or each support element is annular and extends around the cage.

11. A linear rolling bearing as claimed in any one of Claims 6 to 9, wherein the or each support element is a rail secured in the guide slot.

1 2. A linear rolling bearing substantially as herein described with reference to and as shown in the accompanying drawings.

13. A process of manufacturing linear rolling bearings, each bearing comprising an annular cage having a longitudinally extending guide slot, which slot extends radially through the cage, a plurality of rolling elements arranged to travel along the guide slot, and a support element providing a longitudinally extending radially inner surface along which, in use of the bearing, travel the rolling elements in the guide slot, load being transmitted, in use of the bearing, radially of the bearing between the rolling elements and the support element, the process comprising making for one size of the bearing, that is the same external diameter and the same internal diameter, a plurality of support elements of one and the same length, and at least two different lengths of cage parts, any two cage parts being adapted to be joined together at a common plane extending cross-wise of the length of the bearing, the length of the support elements and the lengths of the cage parts being such that at least three different lengths of bearing can be assembled: a first length of bearing comprising two shorter cage parts of one and the same length and one support element; a second length of bearing comprising one shorter cage part and one longer cage part and two support elements disposed longitudinally and end to end; and a third length of bearing comprising two longer cage parts of one and the same length and three support elements disposed longitudinally and end to end, the process including assembling the cage parts, one or more support elements and rolling elements.

14. A process of manufacturing linear rolling bearings substantially as herein described with reference to and as shown in the accompanying drawings.