GB2183740A - Ball cages - Google Patents

Abstract

A drawer slide includes a moulded plastics ball cage (22) which includes a rectilinear row of apertures, each of which contacts an associated ball (21) at two diametrically opposite positions (25,26) only. The surfaces (25,26) which are part-spherical have a radius substantially equal to the radius of the ball. The boundary of each aperture is also partly defined by opposed party cylindrical surfaces (27,28). A clearance exists between each ball and each respective surface (27,28). <IMAGE>

Description

SPECIFICATION Ball slide, method of assembling same and cage for use in the slide Description of Invention From one aspect, the present invention relates to a ball cage for use in a slide, for example a draw slide.

According to a first aspect of the invention, there is provided a ball cage defining a plurality of apertures for receiving respective balls, wherein the boundary of each said aperture is defined partly by a plurality of contact surfaces having a common centre of curvature and the same radius of curvature and partly by further surfaces spaced from said centre of curvature by more than said radius, wherein one of said contact surfaces lies diametrically opposite to another of said contact surfaces and wherein said contact surfaces are capable collectively of restraining against movement relative to the cage in any direction a ball, when that ball is fitted between the contact surfaces of one aperture with the centre of the ball at said centre of curvature.

A cage in accordance with the first aspect of the invention is capable of holding in the required positions a number of balls, once those balls have been fitted into the cage.

Thus, the assembly of balls and cage can be moved as a unit without the use of additional control elements specifically for the purpose of maintaining the balls in the required positions relative to the cage. Furthermore, a ball of appropriate diameter, occupying one of said apertures, can rotate relatively freely about an axis which passes through opposed contact surfaces of the cage, as compared with the ease of rotation of the ball about an axis such that the contact surfaces engage the ball at an equator where the surface speed of the ball is relatively high.

A further advantage of a cage in accordance with the invention is that the position of the cage can be properly controlled by the bails, when the cage is in use with several balls spaced apart along its length.

The contact surfaces of a cage in accordance with the invention are confined to first and second diametrically opposite regions, each of which preferably extends no more than 30 from an axis passing through both regions and through the centre of curvature.

The contact surfaces preferably extend at least 15" from this axis.

The invention also provides a structure comprising a cage in accordance with the first aspect of the invention, a plurality of balls disposed in respect of apertures of the cage and first and second bearing members disposed at opposite sides of the cage, wherein the bearing members define respective tracks along which the balls can roll, each ball is contacted by the corresponding contact surfaces of the cage in regions spaced apart in a direction transverse to the lengths of said tracks and wherein there is no contact between the cage and each ball along an equator of the ball which touches respective centres of the tracks.

According to a further aspect of the invention, there is provided a method of manufacturing a drawer slide wherein a plurality of balls are fitted at a first station into respective apertures of a cage according to a first aspect of the invention, the cage carrying the balls, is moved to a second station, the cage and balls are assembled at the second station with a bearing member and wherein the cage and balls are assembled with a second bearing member either at the second station or after being moved to a third station.

In a method in accordance with the invention, whilst a first cage is being assembled with a bearing member at the second station, a second cage can occupy the first station and receive its compliment of balls.

An example of an assembly incorporating a cage which embodies the first aspect of the invention will now be described, with reference to the accompanying drawings, wherein: Figure 1 shows certain parts of a drawer slide in cross-section in a plane which is perpendicular to the length of the slide; and Figure 2 shows a fragmentary cross-section on the line ll-ll of Fig. 1; The drawer slide illustrated in the accompanying drawings comprises an outer channelshaped bearing member 10 having a web 11 extending between a pair of flanges 12 which project from the web in the same direction.

Only a part of the web and one of the flanges is shown in Fig. 1. The flange 12 defines a part-cylindrical track 13 for a ball. Between the flanges 12 of the outer bearing member there is disposed an intermediate bearing member 14 which also is channel shaped and an inner bearing member 15 is disposed inside the intermediate member. The inner bearing member has a web 16 which is spaced from and opposite to the web 11 and a pair of flanges 17 which extend from the web 16 towards the web 11. One only of the flanges 17 and a part of the web 16 are shown in Fig. 1. The flanges 17 define respective partcylindrical tracks for further balls. The intermediate bearing member 14 has a web 18 which lies between the webs 11 and 16 and has a pair of limbs 19 (one only of which is shown) lying between corresponding flanges 12 and 17.Each limb 19 is formed with two partcylindrical tracks, a first 20 of which is arranged to receive a ball 21 which runs in the track 13 and the second of which is arranged to receive a further ball which runs in the track of the adjacent flange 17.

A number of balls are spaced apart along the track 13 and these balls are maintained in required positions relative to each other by an outer cage 22 whilst an inner cage 23 controls the positions of a plurality of balls which run in the tracks defined by the flanges 17 of the inner bearing member. The cages 22 and 23 both are generally channel-shaped, the balls being disposed in respective apertures formed in flanges of the cages. Each cage has two such flanges, one only of which is shown in Fig. 1.

The structure illustrated in Fig. 1 is typically used as a drawer slide, in which case the inner bearing member 15 is secured to one side of a drawer with the web 16 vertical and the outer member bearing 10 is secured to the carcass of a cabinet or the like in which the drawer is to be contained. The cages 22 and 23 are adapted to co-operate with the bearing members in a known manner to limit travel of the various components so that the drawer can be withdrawn completely from the cabinet but movement in positively limited so that the drawer cannot be separated completely from the cabinet.

One flange 24 of the outer cage 22 defines a rectilinear row of apertures, one of which contains the ball 21. The boundary of this aperture is defined partly by opposed, partspherical surfaces 25 and 26 and partly by opposed part-cylindrical surfaces 27 and 28.

The surfaces 25 to 28 and the ball 21 all have a common centre of curvature. The surfaces 25 and 26 have a radius substantially equal to the radius of the ball, so that these surfaces contact the ball at least around the perimeter of each of the surfaces 25 and 26.

The shape and radius of curvature of the surfaces 25 and 26 may be modified slightly so that there is a small clearance between the centre of each of these surfaces and the ball.

The radius of curvature of the surfaces 27 and 28 is substantially greater than the radius of the ball 21, so that there are substantial clearances between the ball and the surfaces 27 and 28. These surfaces are diametrically opposite to each other and are spaced apart in a direction along the track 13.

The surfaces 25 and 26 also are diametrically opposite each other. These surfaces are spaced apart in a direction transverse to the length of the track 13. An axis 29 which passes through the centre of the surface 25, through the centre of-the ball 21 and through the centre of the surface 26 is perpendicular to the length of the track 13 and lies in a plane mid-way between the track 13 and the track 20.

In the particular example illustrated, the track 20 lies above the ball 21 and the track 13 lies directly below the ball. Load is transmitted from the inrier bearing member 15 to the intermediate bearing member by one set of balls and is transmitted from the intermediate bearing member to the outer bearing member by further balls, including the ball 21.

If the bearing members are moved longitudinally relative to each other, the ball 21 rolls along the track 13 about the axis 29. Such rolling is not significantly impeded by friction between the ball and the surfaces 25 and 26.

It will be understood that, at the axis 29, there is no displacement of the surface of the ball relative to the surface 25. At the periphery of the surface 25, there is moderate rubbing contact between the surface and the ball but those parts of the surface of the ball which have the highest speed during rolling about the axis 29 do not contact the cage 22.

We have found that the friction between the ball and the surfaces 25 and 26 when the ball rotates about the axis 29 is only slight, as compared with the friction between the ball and the surfaces 25 and 26 if the ball is rotated about an axis perpendicular to the axis 29.

The contact surfaces 25 and 26 extend sufficiently far from the axis 29 to ensure that the surfaces 25 and 26 restrain movement of the ball 21 relative to the carrier 22 in all directions. Preferably, the surfaces 25 and 26 extend at least 15 from the axis 29. However, the surfaces 25 and 26 do not extend so far from the axis 29 that there is considerable friction between these surfaces and the ball when the ball turns about the axis 29.

Preferably, the surfaces 25 and 26 do not extend more than 30 from the axis 29.

The drawer slide is preferably symmetrical about a plane 30 lying midway between the flanges 12 of the outer bearing member 10.

The second flange of the outer cage 22 and both flanges of the inner cage 23 preferably each define a row of apertures having the same form and dimensions as does the aperture in which the ball 21 is contained.

The cages 22 and 23 are formed by moulding a plastics material. Nylon 6,6 is a suitable plastics material. Typically, in a case where each ball has a diameter of 6.2mm, the flange 24 has a general thickness of 2mm. In the immediate vicinity of the contact surfaces 25 and 26, the thickness may be slightly greater.

The structure illustrated in the accompanying drawings may be modified by substitution of pressed metal cages for the moulded plastics cages 22 and 23. The metal cage corresponding to the cage 22 may have, for contacting the ball 21, four part-spherical surfaces arranged with a first of these surfaces extending towards one side of the flange of the cage, an adjacent contact surface extending towards the opposite side of the flange and with the other two contact surfaces each in a position diametrically opposite to one of the aforementioned contact surfaces. With this arrangement, each of the contact surface extend upto, but not beyond, the axis 29. The contact surfaces of the metal cage are confined to diametrically opposed regions, each of which extends no more than 40 from the axis 29.

The drawer slide shown in Fig. 1 is assembled by fitting the appropriate numbers of balls into the outer cage 22 at a first station, moving the first cage, carrying the balls, to a second station, assembling the outer cage with the outer bearing member 10 at the second station, assembling the appropriate number of balls with the inner cage 23 at a third station, moving that cage to a fourth station, assembling the inner bearing member 15 with the inner cage at the fourth station, moving to a fifth station the sub-assembly of inner cage and inner bearing member and a sub-assembly of outer cage and outer bearing member and there assembling the two sub-assemblies with the intermediate bearing member to complete the assembly. Whilst first inner and outer bearing members are being assembled together at the fifth station, a second outer bearing member can be assembled with the corresponding cage at the second station and balls can be fitted into a further cage at the first station.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (12)

1. A ball cage defining a plurality of apertures for receiving respective balls, wherein the boundary of each said aperture is defined partly by a plurality of contact surfaces having a common centre of curvature and the same radius of curvature and partly by further surfaces spaced from said centre of curvature by more than said radius, wherein one of said contact surfaces is diametrically opposite to another of said contact surfaces and wherein said contact surfaces are arranged collectively to restrain against movement relative to the cage in any direction a ball of appropriate size, when that ball is disposed between the contact surfaces with the centre of the ball at said centre of curvature.

2. A cage according to Claim 1 wherein said contact surfaces are confined to first and second diametrically opposite regions, each of which extends no more than 30 from an axis passing through both regions and through the centre of curvature.

3. A cage according to Claim 2 wherein the contact surfaces extend at least 15 from said axis.

4. A cage according to any preceding Claim comprising an elongated web in which said apertures are formed and wherein the opposed contact surfaces of each aperture are spaced from each other in a direction transverse to the length of the web.

5. A cage according to any preceding Claim formed as a moulding of a plastics material.

6. A structure comprising a cage according to any preceding Claim, a plurality of balls disposed in respective apertures of the cage and first and second bearing members disposed at opposite sides of the cage, wherein said bearing members define respective tracks along which the balls can roll, each ball is contacted by the corresponding contact surfaces of the cage in regions spaced apart in a direction transverse to the lengths of said tracks and wherein there is no contact between the cage and each ball along an equator of the ball which touches respective centres of the tracks.

7. A structure according to Claim 6 wherein each track, as viewed along its length, subtends at the centre of an associated ball an angle which exceeds the largest angle subtended at the centre of that ball by any one of said contact surfaces.

8. A structure according to Claim 6 or Claim 7 further comprising a third bearing member and a further cage interposed between the second and third bearing members.

9. A structure according to Claim 8 wherein each bearing member is formed as a channel and has a pair of flanges which define respective ball tracks and wherein each cage is formed as a channel and has a pair a flanges defining apertures in which respective balls are disposed.

10. A cage according to any one of Claims 1 to 4 or a structure according to any one of Claims 6 to 9, comprising a cage according to Claim 1, wherein the cage is formed of metal.

11. A slide substantially as herein described with reference to and as shown in the accompanying drawings.

12. Any novel feature or novel combination of features disclosed herein or in the accompanying drawings.