GB2038450A - Conveyor roller assemblies - Google Patents

Abstract

A conveyor roller assembly has an external cylindrical shell 2 made of a plastics material, and comprises a bush 5, also made of a plastics material, provided with a seating 5a into which an inner race 3a of a bearing 3 fits, while an outer race 3b thereof is wedged into an end-plate member 6, again made of a plastics material, the external cylindrical part 6a of which is fixed to the cylindrical shell 2 of the roller; the sealing of the end-plate being assured by an annular gasket 7 that acts on the bush 5 and is contained in an annular chamber 10 sealed with a lid 9 which can be snap fitted on to the end of the member 6 and is removable. The bush 5 is free to slide axially upon the shaft 1, in order to accommodate any axial expansion of the shell 2, in use. <IMAGE>

Description

SPECIFICATION Improvement to the lateral heads of conveyor rollers This invention relates to an improvement to the lateral heads of conveyor rollers, and particularly to rollers that have a rotatable cylindrical surface made of a plastics material.

Conveyor rollers comprise, as is known, a fixed metal shaft on which is rotatably mounted, with the interposition of suitable bearings placed in the region of the lateral heads, a cylindrical surface that can be made either of metal or of a plastics material.

In particular, when the cylindrical surface is made of a plastics material, it is necessary to take account of the fact that the linear expansion coefficient of this type of surface is much greater (some six to seven times greater) than that of the metal shaft and thus it is necessary to compensate for variations in length, which can also be very large in the case of rollers of a considerable length, in the region of the lateral heads.

In the rollers currently in use, compensation of this nature is achieved in the region of the labyrinth seals normally provided at points corresponding to the outer sides of the bearings, by making provision for the labyrinth seals to be of an elongated conformation in an axial direction, in such a way that the respective parts integral with the rotatable cylindrical surface can slide quite some way with respect to the parts integral with the fixed shaft.

With a known method of this type, the preparation of the labyrinth seals is rather complicated and, moreover, since the seals are subjected to a noticeable variation in their overall axial dimensions, it can happen that under certain conditions sealing defects can occur which jeopardize the life span and the efficiency of the bearings.

The main object of the present invention is to overcome the aforementioned difficulties with the conveyor rollers in use at the present time by making avaiiable a device for compensating the variations in length of the outer surface with respect to the fixed shaft, which is constructionally simple, operationally reliable and does not give rise to sealing defects even in rollers of a considerable length that have a cylindrical surface made of a plastics material.

Another important object of the invention is to make available a device that is easy to fit to conveyor rollers of any size and type and allows the lateral heads for rollers to be made of a plastics material.

According to the invention, a device for compensating dimensional variations in an axial direction for conveyor rollers, and particularly for rollers that have a rotatable cylindrical surface made of a plastics material, comprising a fixed metal shaft and a bearing in the region of each of the lateral roller heads, comprises in the region of at least one of the lateral heads, a bush, preferably made of a plastics material, which coaxially enshrouds the shaft at the relevant extremity thereof and has, on its lateral surface, a housing into which the inner part of the bearing concerned fits, in such a way as to axially lock the latter to the bush, whilst the rotatable outer part of the bearing is integral with the cylindrical surface, the bush being able to slide axially with respect to the shaft in order to allow a variation in length, due to axial expansion, of the cylindrical surface with respect to the shaft and, furthermore, an annular oil seal for the bearing being provided around the bush, on the outer side of the bearing.

In this way, should the cylindrical surface expand axially with respect to the shaft, this brings about a sliding movement of the said bush, and with it the whole lateral head, with respect to the shaft, whilst the part of the sealing means applicable to the bearing remains unvaried.

The sealing action is, therefore, always assured, even in the event of considerable axial deviation in the region of the lateral heads due to the effect of the different thermal expansion of the cylindrical surface and the fixed shaft.

The invention will now be described by way of example with reference to the accompanying drawing, which shows one end of a conveyor roller with a metal shaft and a plastics material surface, partly in plan view and partly in axial section.

The accompanying figure shows a fixed metal shaft 1 of a roller, a rotatable, cylindrical, roller surface 2 made of a plastics material, and a ball bearing 3, the latter being provided in the region of each lateral head 4 of the roller.

A bush 5, made of a plastics material, coaxially enshrouds the shaft 1 in the region of each extremity of the shaft and is able to slide axially with respect thereto. The bush 5 has on itslateral surface a housing 5a into which the inner part 3a of the bearing 3 fits, in such a way that the latter is ocked axially to the bush.

In order to allow the inner part 3a of the bearing 3 to penetrate into the housing 5a, the part of the bush 5 which is turned towards the inside of the roller is provided with a number of longitudinal slits 5b which, at the time the lateral head is being fitted to the roller, allow the body of the bush to collapse momentarily and sufficiently for the body to be inserted without difficulty into the inner part 3a of the bearing 3 until the bearing reaches a stable position in the housing 5a. The subsequent fitting of the bush 5 to the shaft 1 then stabilizes the position of the inner part 3a of the bearing 3 in the housing 5a.

The outer part 3b of the bearing is rendered integral with the cylindrical surface 2 through a plug member 6, made of a plastics material, which has an external cylindrical part 6a, designed to be forced into the terminal part of the cylindrical surface 2 (and secured to the surface if necessary by a suitable adhesive), and an internal cylindrical part 6b into which the outer part 3b of the bearing 3 is forced.

An elastic annular sealing gasket 7 is fitted to the bush 5 at the outer side of the bearing 3. The gasket is preferably toroidal and is closely attached to a truncated cone section of the bush 5 and to an annular member 8 integral with the body 6, though it can be of a known type.

A labyrinth seal can be provided between the annular member 8 and the bearing 3.

The aforementioned internal cylindrical part 6b of the plug member 6 extends coaxiallyto the shaft 1 in such a way as to project towards the outside for a certain distance beyond the bearing 3. A plastics material lid 9 which is drilled in the centre to allow the terminal part of the bush 5 to pass through, can be snap fitted to the aforementioned protruding section. Once fitted, the lid defines, together with the member 8, an annular chamber 10 in which it is possible to insert a certain amount of grease or a sponge or similar material impregnated in lubricant.

An internal annular projection 9a on the lid 9 seals the annular chamber 10 against the shaft, whilst the lubricant is able to pass towards the gasket 7 through a plurality of small radial holes with which the internal annular projection 9a is provided.

The lid 9 can be easily removed and reattached to permit topping up of the lubricant in the chamber 10.

It is advantageous for the bush 5 to extend axially towards the outside and then to terminate in a tail piece Sc so as to completely cover the corresponding extremity of the shaft 1, with the possibility always existing of it being able to slide axially with respect to the latter.

The end of the bush 5 rests on fixed means of support (not illustrated).

With the device shown, it is possible for the cylindrical surface 2, the lateral heads 4 and the members 5, 6 and 9 to be made entirely of plastics material. Only the bearing 3, the member 8 plus the labyrinth seal if provided, and the shaft 1 are made out of metal.

Owing to a considerable difference in the linear expansion coefficients of the metal shaft 1 and of the plastics material cylindrical surface 2, the extremities of the latter undergo, following thermal variations, considerable axial displacements, in one direction or the other, with respect to the extremities of the former.

During the time these are taking place, the device allows both the lateral heads 4 to be displaced freely in an axial direction because of creep of the bush 5 with which each lateral head on the shaft 1 is provided.

The plug member 6 renders the outer part 3b of the bearing 3 integral with the corresponding extremity of the cylindrical surface 2, whilst the inner part 3a of the bearing remains locked in an axial direction to the bush 5 which, therefore, is displaced axially on the shaft 1 in relation to the variation in length of the cylindrical surface 2 with respect to the shaft 1.

Thus full compensation is achieved in respect of dimensional variations in an axial direction due to thermal variations, whereby the roller is always able to operate satisfactorily under any temperature condition, and to keep the means for sealing the bearings always in the same condition.

The particular structure makes it possible, furthermore, to prepare the lateral heads 4 fully assembled with their bearings and bushes, 3 and 5, respectively, and to then fit the lateral heads into the extremities of the cylindrical surfaces 2 and onto the shafts 1, in a very easy and quick assembly operation.

In one embodiment, it is possible to provide just one lateral head of a roller, leaving the other lateral head thereof to be of conventional type.

When this is done, compensation for dimensional variations due to thermal effects will take place in the region of the first of the lateral heads.

Claims (7)

1. A device for compensating dimensional variations in an axial direction for a conveyor roller, comprising a fixed metal shaft and a bearing in the region of each of the lateral heads of the roller, which device comprises, in the region of at least one of the lateral heads of the roller, a bush which coaxially enshrouds the shaft at the relevant extremity thereof and has, on its lateral surface, a housing into which the inner part of the bearing concerned fits, in such a way as to axially lock the bearing to the bush, whilst the rotatable outer part of the bearing is fast with the cylindrical surface of the roller, the bush being able to slide axially with respect to the shaft in order to allow a variation in length, due to axial expansion, of the cylindrical surface with respect to the shaft, and an annular oil seal for the bearing being provided around the bush, on the outer side of the bearing.

2. A device as claimed in claim 1 in which the bush is made of plastics material.

3. A device according to Claim 1 or 2, wherein the lateral head comprises a plug member made of a plastics material, which is provided, externally, with a cylindrical part designed to be forced into the corresponding terminal part of the cylinder surface, of the roller and, internally, with a further cylindrical part into which the outer part of the bearing can be fixed, the further cylindrical part extending coaxially to the shaft, towards the outside, projecting for a certain distance with respect to the bearing and it being possible to snap fit on the protruding section a lid designed to define an annular chamber to house grease or similar material for the lubricant of an annular gasket with which the bush is provided in the region of the annular chamber.

4. A device according to Claim 3, wherein the lid is provided with an internal annular projection that defines the annular chamber towards the shaft and has in it a plurality of smali radial holes for the lubricant to pass through towards the annular gasket.

5. A device according to any of the preceding claims, wherein the bush extends axially towards the outside and terminates in a tail piece so as to cover the corresponding extremity of the shaft.

6. A device according to any of the preceding claims, wherein the laterial head is pre-assembled with the bush, the bearing, the plug, the gasket and the lid, and the assembly being fitted on to the extremity of the shaft and to the end of the cylindrical surface.

7. A compensating device substantially as herein described with reference to the accompanying drawing.