GB2122274A - Linear bearing runners - Google Patents

Abstract

This invention relates to linear bearing runner assemblies as used, for example, to support "sliding" drawers in cabinets. The runner consists of an outer channel (10), an intermediary telescopic channel member (11), and an inner telescopic channel (12). A ball bearing set (13) is disposed between members (10 and 11), whilst a ball set (15) is located between members (11) and (12). The cage supporting ball set (13) is formed as two sub-cages (21) and (22), which are independently movable (within limits). The ball bearings are located loosely in the cages and are held between curled fingers (32, 33). <IMAGE>

Description

SPECIFICATION Linear bearing runners This invention relates to linear bearing runner assemblies as used, for example, to.support "sliding" drawers in cabinets. However, the invention may equally be applied to linear bearing runners for other purposes.

The invention is of particuiar utility where the bearing runner is required to project horizontally a considerable distance in its extended position and may have to support a considerable weight. Thus the invention is particularly though not exclusively applicable to drawer runners for supporting heavy drawers when extended from a cabinet. Such drawer runners are commonly ofthe double telescoping type that is to say having three relatively movable elongate runner members with two intervening sets of bearing elements.

One of the problems which occurs with a double telescoping runner assembly is that one of the runner pairs may be extended to its maximum without its bearing elements necessarily having moved into the correct position. It will be appreciated that the bearing elements, usually balls, will normally roll between the two members and normally move bodily by exactly one half the relative horizontal displacement of the two members. The balls are normally located in apertures in a moving cage. Provided that the balls perform true rolling movement the cage will always be positioned at exactly half the projected distance of the runners, but in practice this cannot be relied upon, and the balls and the cage may in time adopt a position such that with the runners fully projected the balls are not properly located between their overlapping ends.

This can cause overload and distortion or even destruction of the assembly. Accordingly it is one object of the invention to provide a runner assembly which will avoid or mitigate such problems.

The invention is concerned essentially with bearing runners of the type comprising an outer elongate channel and an inner elongate member with intervening bearing elements located by a longitudinally movable cage.

Broadly stated from one aspect the invention consists in a linear bearing asssemblyofthetype referred to in which two separate cages are provided independently movable in relation to each other and to the inner and outer members.

Conveniently one of the cages is limited in movement to a range of travel adjacent one end of the members. For example, the said cage may be arranged to engage a stop fixed in relation to the said member and is so formed that the balls located by the cage will lie close to the extreme end of the said member when the other member is moved to the appropriate limit of its travel.

According to another preferred feature of the invention the two cages are so formed that when in closest proximity the balls located by the cages form a substantially continuous spaced chain.

The invention also consists in an extending bearing arrangement, including a bearing runner of the type referred to and a third relatively movable member separated from the outer channel or the inner elongated member by a secondary movable cage, the arrangement being such that one member is restrained against movement until the other member has extended to a predetermined position.

The invention is also concerned to provide an improved bearing cage for use with such bearing runners and from another aspect the invention consists in a bearing runner of the type referred to in which the bearings the balls and are located in slots between spaced fingers on the cage, each finger being curled to provide location for the ball loosely in three dimension.

Preferably the curled edges of the fingers on the cage are formed with small projections to make point contact with each ball. It is also preferred to design the fingers of the cage such that the balls have greater freedom of movement in one direction than in a perpendicular direction.

The invention may be performed in various ways and one specific embodiment with a number of possible modifications will now be described by way of example with reference to the accompanying drawings, in which: Figure l is a general side elevation illustrating a three-piece extending cabinet drawer runner of conventional design, Figure 2 is a diagrammatic side elevation of an outer cabinet runner with separate twin ball cages according to the invention, Figure 3 is an end view of the cabinet runner of Figure 2 with the inner runner and drawer runners assembled, Figure 4 is a detailed partial sectional view on an enlarged scale illustrating the arrangement of the bearings and cages in Figure 3, Figure 5 is a partial perspective view of the inner bearing cage, Figure 6 is an elevation of the same cage, Figure 7 is a detailed end view of the ball retaining curled fingers according to the invention formed on one of the bearing cages, Figure 8 is a view of the two adjacent fingers as seen in the direction of arrow VIII in Figure 7, and Figure 9 is a developed view of the metal blank from which the curled fingers are formed.

Referring first to the conventional prior art threepiece double extending drawer support of Figure 1, this is seen to comprise an outer channel 10 designed to be fixed to a side wall of the cabinet and commonly known as a cabinet runner, an intermediate telescoping channel member 11 commonly referred to as the intermediate runner, and an inner telescoping channel 12 designed to be fixed to the moving drawer (not illustrated) and commonly known as the drawer runner. Between the first pair of members 10 and 11 is a ball bearing set 13, including a ball cage 14, and between the second set of members 11 and 12 is a further ball bearing set 15, including a ball cage 16. Thus the arrangement provides a double telescoping support system which provides freely extending substantially frictionless movement and can support appreciable loads at the drawer.

In practice, however, it has been found that this known system suffers from a number of disadvantages and problems in manufacture and operation. It will be appreciated from Figure 1 that when the system is fully extended the full weight W of the loaded drawer acting downwards at a displaced point on the drawer runner 12 will apply a very considerable cantilever effect or force couple to the whole system. This must be resisted and supported by the bearing set 13 and the maximum loads to resist the applied couple will appear at positions M and N. In addition there will be a vertical component of the applied load Wto be supported by the bearing system and the net result is that the maximum load occurs at point M. in practice in extreme cases it has been found that this can cause distortion or failure of the bearings or runners at this point.

The problem is further increased by the fact that the bearing set 13 and the bearing cage 14 after a period of use tend to "drift" away from the extreme left-hand end 18 of the cabinet runner. Since the bearing elements 13 normally behave as simple rollers the cage 14 normally moves exactly one half the distance of the intermediate runner 11. However, in practice the balls do not always move in a true rolling manner and as a result the cage 14 tends to drift out of position. It cannot drift to the left owing to the stops 19, but it can drift to the right away from this limiting position. This rightward drift means that the bearing at point M on the cage becomes shifted somewhat to the right. The force couple is increased and the load on the bearing is increased thus further increasing the tendency for failure.

Now in accordance with the present invention this problem is obviated or reduced by providing a split bearing cage system, as illustrated in Figure 2. Here the cage 14 of Figure 1 is formed as two sub-cages 21 and 22 both independently movable (within limits). The lefthand sub-cage 22 may be only half the length of the normal full cage and its movement is limited to a small range towards the lefthand end of the cabinet runner 10 by two pairs of stops 19 and 23. This sub-cage has a cut out 24 to permit its extreme lefthand end 25 to project beyond the end of the cabinet runner so that the ball bearings shown at M can move close to the extreme lefthand end of the cabinet runner, in which position the force couple is reduced and the risk of failure likewise.

The righthand sub-cage 21 is also shorter in length than the normal ball cage 14 and it is constrained to move between the fixed stops 23 and a further pair of fixed stops 27. This sub-cage also has cut outs 28, 29 to allow the sub-cages to move into close abutting relationship when in their lefthand positions, and when the greatest applied loads are experienced.

The multiple three-piece sliding assembly according to the invention is preferably formed from three pressed sheet metal parts, as illustrated in Figures 3 and 4. It will be noted that each of these parts provides a pair of shallow elongated grooves to locate the respective ball bearings. The intermediate runner 11 has double bent limbs providing bearing .channelS both for the outer bearings 13 and the inner bearings 15. Both of these bearing sets are located between cages 21, 22 and 31, the ball bearings being located loosely in the cages as illustrated for example in Figures 5 and 6. In Figure 5 the cage 31 is formed with curled beads 32, 33 at opposite edges, the beads being interrupted at positions 34 to accomodate the balls 15.These curled "fingers" provide a very effective substantiallyfrictlonaless location of the balls and also greatly facilitate manufacture. The metal blank from which the cage 31 is formed has slots formed initially in its opposite edges and in manufacture these marginal parts are pressed over and curled simultaneously in a press too, with the balls roughly located in position in the slots before pressing takes place. This avoids the requirement to insert the balls in the locating slots by hand as a final assembly operation, which occurs in existing ball cage assemblies.

According to another preferred feature of the invention the location of the balls between the curled beads is so designed that the balls have only limited point contact with the lip of the beads, as illustrated in Figures 7, 8 and 9. As shown in Figure 9, the blank 36 from which the cage is formed is initially provided with slots 37 which have pairs of small projections 38, 39 spaced along their opposite edges. When the beads are curled over, as shown in Figure 7, these projections adopt the positions shown at 38 and 39 in Figures 7 and 8 and by appropriate design of the projections it can be arranged so that the balls have minimal freedom of movement in the direction of arrow X in Figure 7 and greater movement in the direction of arrow Y. When these directions of movement are compared with the complete runner system illustrated in Figure 4, it will be seen that this is of advantage in allowing optimum frictionless running while maintaining accurate location.

Claims (8)

1. A linear bearing assembly, comprising an outer elongate channel and an inner elongate member, and a plurality of intervening bearing elements located by a longitudinally movable cage, in which the bearing elements are balls and are located in slots between spaced fingers on the cage, each finger being curled to locate the ball loosely in three dimensions.

2. A bearing assembly according to Claim 1, in which the curled edges of the fingers on the cage are formed with small projections to make point contact with each ball.

3. A bearing assembly according to Claim 1, or Claim 2, in which the fingers of the cage are so formed that the balls have greater freedom of movement in one direction than in a perpendicular direction.

4. A linear bearing assembly comprising an outer elongate channel and an inner elongate member, and a plurality of intervening bearing elements located by a longitudinally movable cage, in which two separate cages are provided independently movable longitudinally in relation to each other and to the inner and outer members.

5. A bearing assembly according to Claim 4, in which one of the cages is limited in movement to a range of travel adjacent one end of one member.

6. A bearing assembly according to Claim 5, in which the said cage is arranged to engage a stop fixed in relation to the said member and is so formed that the balls located by the cage will lie close to the extreme end of the said member when the other member is moved to the appropriate limit of its travel.

7. A bearing assembly according to any of the preceding claims 4 to 6, in which the two cages are so formed that when in closest proximity the balls located by the cages form a substantially continuous spaced chain.

8. A linear bearing assembly substantially as described with reference to the accompanying drawings.