Wheel assembly

Abstract

A castor roller 10 for supporting a sliding door panel or a window pane on a track 12, the wheels can move vertically relative to others to remain in contact with uneven surface. The roller running su

Description

The invention relates to a roller assembly and to a track and wheel system suitable, for example, for supporting a slidable panel, such a door, a window or a room separator. Background of the invention It is known to support sliding panels on wheels that run along a track that both bears the weight of the panel and constrains the movement of the wheels to follow the path defined by the track. In order for the wheels to be guided by the track, the track may be a concave channel within which there rolls a wheel having a convex running surface, or the running surface of the wheel may be concave to straddle a ridge-like convex track. The track can be mounted beneath the panel to support its weight directly, or it may be mounted above the panel, whereupon the wheels may be secured to a frame or brackets, by means of which the panel is suspended. The weight of the panel needs to be supported by bearings, if the panel is to be able to slide smoothly and freely. In some cases, each wheel is fast in rotation will an axle that is itself supported in pillow blocks secured to the panel journal or rolling bearings being provided between the axle and the pillow blocks. In other cases, the wheel axle is fixed relative to the panel, and a rolling bearing is built into the wheel. In the latter configuration, rolling elements, which may be balls, rollers or needles, engage inner and outer races that are fast in rotation, respectively, with the axle and the running surface of the wheel. In order to support heavier panels, it is known to use roller assemblies that have multiple wheels. In such roller assemblies, it is desirable to ensure that all wheels engage the track, even when the track is not level. To this end, the individual wheels may be mounted for vertical movement relative to one another, such as shown for example in Figure 4 of the Applicant’s GB2573876. Alternatively, it is known for wheels to be mounted on a pivot arm, or a system of pivot arms if there are more than two wheels, to allow individual wheels, or pairs of wheels, to see-saw and thereby remain in contact with the track at all times, even if the track is uneven. Obiect of the invention The present invention seeks in its different aspects to provide a wheel, a wheel and track system and a roller assembly which can offer the advantages of being able to withstand high loads while at the same time reducing wear and noise during operation. Summary of the invention According to a first aspect of the invention, there is provided a roller assembly for supporting a slidable panel on a surface, comprising a plurality of wheels that are vertically movable relative to one another, when in use, to enable all the wheels to remain in contact with an uneven support surface, wherein at least one of the wheels has a running surface that comprises an axially central region made of a first material, and side regions made of a second, softer, material, flanking the opposite axial sides of the central region. The wheel assembly of the present invention is able to withstand high loads on account of the fact that the central region of its running surface is made of a relatively hard material that can also withstand wear. One the other hand, the side regions of the running surface, that serve to maintain the wheel aligned with the track guide, are made of a softer material, so that they generate less noise when rubbing against the track and can furthermore suppress noise produced by the harder central region of the running surface. In some embodiments, the at least one wheel may comprise a bearing having rolling elements engaging with an inner race and an outer race, an axle constituting, or fast in rotation with, the inner race, and a concave or convex running surface fast in rotation with the outer race. The outer surface of the outer race of the bearing may itself constitute the axially central region of the running surface and a softer material is laminated or bonded onto the outer race on opposite sides of the central region. Alternatively, a harder first material may be bonded to the axially central region of the outer race of the bearing and a softer second material is laminated or bonded onto the outer race on opposite sides of the first material in the central region. In accordance with a second aspect of the invention, there is provided a track and wheel system comprising a wheel having a convex or concave running surface, and a track of complementary shape to the wheel running surface for supporting and guiding the wheel, wherein the running surface of the wheel comprises an axially central region for contacting the track made of a first material, and side regions, made of a second, softer, material, flanking the opposite axial sides of the central region and ensuring alignment of the wheel with the track. Brief description of the drawings The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure lisa side view of a wheel and track assembly of a first embodiment of the invention, Figure 2 is a section in the plane designated A-A in Figure 1, Figure 3 and 4 are sections similar to that of Figure 2 through the wheel of alternative embodiments of the invention, and Figure 5 is an exploded view of a prior art roller system that may employ the wheels shown in Figures 2 to 4. Detailed description of the drawings Figure 5 shows an example of a roller system for enabling a support panel to ride over an uneven track while ensuring that all wheels always remain load bearing. This figure is the same as Figure 4 of the Applicant’s GB 2573876, to which reference is made for a fuller description of the way in which unevenness in a track may be accommodated. This roller system is given only as an example of a roller system to which the invention may be applied, the improvement offered by the invention being now further described by reference to Figures 1 to 4 which detail how the wheels of such an assembly may be designed to reduce noise at the same time as improving wear resistance. Figures 1 and 2 show, respectively, a side view and a section through a wheel and track assembly comprising a wheel 10, which may be one of the wheels in Figure 5, and a track 12 along which the wheel is designed to roll. The wheel 10 comprises a rolling bearing having an inner race 14, an outer race 16 and rolling elements 18, in this case balls, in rolling contact with the inner and outer race 14 and 16. As the bearing is lubricated, typically using grease, elastomeric seals 20 are provided to prevent egress of the lubricant. The illustrated bearing is a full complement bearing but it is alternatively possible for the bearing to include a cage separating the individual rolling elements 18 from one another. The inner race 14 in the drawings is intended to receive a separate shaft to serve as the wheel axle which is connected to the panel to be supported. However, it is alternatively possible for the inner race to be constitute by a tubular, or solid, shaft that itself serves as the axle. The outer race 18 of the bearing has bonded onto its two sides a tyre or rim 22 made of a material that is softer than the material of the outer race 16, which is usually a metal such as steel. The softer material may be a plastics material, such as a nylon, polyurethane, or polypropylene or an elastomeric material. The concave running surface of the wheel has a central region 24 formed by an exposed part of the outer race 16 of the bearing and two side regions 26, 28 straddling the central region 24 made of the softer material of the tyre 22. The embodiment of Figure 3 differs from that of Figure 2 in that instead of the outer surface of the outer race itself serving as part of the running surface of the wheel, the tyre or rim is itself axially layered, its central region 22a being made of a harder material than the two side regions 22b. The embodiment of Figure 4 is structurally the same as that of Figure 3, the only difference being the shape of the rim, which in this case is outwardly convex instead of outwardly concave. In all the illustrated embodiments of the invention, the hard central region of the running surface of the wheel supports the majority of the load from the supported structure. The softer material laminated on either side of the central hard region forms the outer planes of the wheel which assists in guiding the wheel, supporting additional load, reducing noise, and minimising wear. In the embodiment of Figure 2, the outer race of the bearing is directly utilised as the central load-bearing surface. This simplifies the wheel assembly by integrating the bearing component into the wheel's contact surface. This construction allows for the maximisation of the bearing size, as there is no need to accommodate additional tyre material thickness in the central region of the running surface. By using the outer race as the contact surface, the design eliminates the space typically required for tyre material between the bearing and the wheel's rolling surface. In the embodiments of Figures 3 and 4, a hard material (e.g., metal or hard plastics material) is added over the bearing's outer race to form the central region of the running surface of the wheel. In this case, the bearing is better protected as it remains enclosed within the wheel and the central region of the running surface can be customised independently of the material of the outer race of the bearing. The invention is particularly suited for use in sliding door roller assemblies, as shown in Figure 5, offering the following advantages: • Enhanced Load Support: o The hard central region of the running surface effectively bears the weight of the sliding door, ensuring smooth and stable movement along the track. • Improved Guidance and Alignment: o The softer outer planes provide lateral support, keeping the door aligned and preventing derailment or jamming. • Noise Reduction: o The softer side materials absorb vibrations and reduce noise generated during the door's movement, contributing to a quieter environment. • Wear Minimisation: o The combination of hard and soft materials reduces wear on both the rollers and the track, extending the lifespan of the sliding mechanism. • Adaptability to Track Profiles: o The design can accommodate different track shapes, whether the roller is concave or convex, matching the corresponding track profile for optimal performance.

Claims

1. A roller assembly for supporting a slidable panel on a surface, comprising a plurality of wheels that are vertically movable relative to one another, when in use, to enable all the wheels to remain in contact with an uneven support surface, wherein at least 5 one of the wheels has a running surface that comprises an axially central region made of a first material, and side regions made of a second, softer, material, flanking the opposite axial sides of the central region, wherein the at least one wheel comprises a bearing having rolling elements engaging with an inner race and an outer race, an axle constituting, or fast in rotation with, the inner race, and a concave or convex running surface fast in rotation io with the outer race, characterised in that the outer surface of the outer race of the bearing itself constitutes the axially central region of the running surface and a softer material is laminated or bonded onto the outer race on opposite sides of the central region.

2. A track and wheel system for supporting a slidable panel, comprising a wheel having a convex or concave running surface, and a track of complementary shape to the 15 wheel running surface for supporting and guiding the wheel, wherein the running surface of the wheel comprises an axially central region for contacting the track made of a first material, and side regions, made of a second, softer, material, flanking the opposite axial sides of the central region and ensuring alignment of the wheel with the track, wherein the wheel comprises a bearing having rolling elements engaging with an inner race and an 2 o outer race, an axle constituting, or fast in rotation with, the inner race, and a concave orconvex running surface fast in rotation with the outer race, characterised in that the outer surface of the outer race of the bearing itself constitutes the axially central region of the running surface and a softer material is laminated or bonded onto the outer race on opposite sides of the central region.2 5 3. A wheel for use in a track and wheel system of Claim 2, the wheel comprising anaxle, a roller bearing having rolling elements and an outer race surrounding the axle, and a concave or convex wheel running surface surrounding and fast in rotation with the outer race of the bearing, wherein the outer surface of the outer race of the bearing constitutes the axially central region of the running surface for contacting the track and a softer3 0 second material is laminated or bonded onto the outer race on opposite sides of the centralregion.s

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