GB2275977A

GB2275977A - Braked rotatable elements

Info

Publication number: GB2275977A
Application number: GB9305203A
Authority: GB
Inventors: Richard Joseph Taberner; Christopher Clive Gort Gregory
Original assignee: R T BEARINGS Ltd
Current assignee: R T BEARINGS Ltd
Priority date: 1993-03-13
Filing date: 1993-03-13
Publication date: 1994-09-14
Also published as: AU6286094A; ZA941712B; GB9305203D0; WO1994021543A1

Abstract

A braked rotatable element, such as a conveyor roller, comprises a sleeve 1 carried on two spaced bearings 3 coaxial with the sleeve, and fluid-pressure responsive braking means 10, 11 connected to one part of one of the bearings and arranged to make frictional contact with the complementary part of the bearing and/or with a member connected to it when fluid under pressure is admitted to the interior of the sleeve so as to apply a braking force thereto. <IMAGE>

Description

BRAKED ROTATABLE ELEMENTS.

Braked rotatable elements have many applications in mechanisms. For example, in roller conveyors used to assist the movement of goods, which comprise a succession of parallel rollers mounted in a framework so that goods placed on the rollers can readily be moved along the framework, it may be desirable to have one or more braked rollers to regulate the speed at which the goods travel. A roller may itself be such a braked rotatable element or it may frictionally engage or be connected to such an element so as to be braked by it.

Braked rotatable elements are known which comprise a drum or flange which is frictionally engaged when desired by a mechanically-operated stationary brake shoe. Others include a brake shoe to engage a stationary element adjacent to the rotatable element. Such a rotatable element requires an operator or automatic apparatus to operate the brake shoe when desired.

For example weighted brake shoes may be arranged to move under centrifugal force to make frictional contact with a stationary part at a predetermined rotational speed of the rotatable element. The brake shoes operate only at or above the predetermined speed and if that is a low speed they may include gearing so as to rotate them at a sufficient speed to apply an effective braking force. Braked rotational elements as described above are limited in application, mechanically relatively complicated and somewhat expensive. They may also be operative only in one direction of rotation.

According to this invention a braked rotatable element comprises a hollow member rotatable with respect to a stationary member, sealing means rendering the interior of the hollow member substantially fluid-tight, a fluid-conveying passage from the exterior to the interior of the hollow member for admitting fluid under pressure to the interior of the hollow member and fluid pressure-responsive braking means connected non-rotatably to one of the said members and arranged to make frictional contact with the other member or a part connected therewith when fluid under pressure is admitted to the interior of the hollow member.

Further according to the invention a braked rotatable element comprises a sleeve carried on two spaced bearings coaxial with the sleeve, each bearing comprising an inner part and an outer part rotatable relative to the inner part about the common axis and connected to the sleeve, sealing means for rendering the interior of the sleeve between the bearings substantially fluidtight, a fluid-conveying passage from the exterior to the interior of the sleeve for admitting fluid under pressure to the interior of the sleeve and fluid-pressure responsive braking means connected non-rotatably to one of the said parts of one of the said bearings and arranged to make frictional contact with the complementary part of the said one bearing andSor with a member connected to the complementry part when fluid under pressure is admitted to the interior of the sleeve.

With this arrangement the sleeve is normally rotatable freely about its axis but the rotation can be controlled or prevented by admitting fluid under pressure through the fluid-conveying passage to its interior. The braking force will be proportional to the pressure of the fluid and may thus readily be controlled and released when desired by releasing the fluid pressure.

Conveniently the fluid is air.

The fluid-conveying passage may be connected externally of the sleeve to a vessel containing fluid in which the pressure of the fluid is controlled as desired. It may include valve means for regulating the flow -of fluid.

There may be a second passage for allowing fluid to escape from the interior of the sleeve. If the fluid is air the second passage may be vented to the atmosphere, with a control valve to allow the air to escape when desired.

Preferably the inner parts of the two bearings are mounted nonrotatably on a common shaft and the fluid-conveying passage and the second passage, if provided, isVare a bore or bores in the shaft. The shaft may be made non-circular in section with the inner parts having complementary noncircular bores which are a close fit on the shaft.

The sleeve may be secured permanently to the outer parts of the bearings, for example by shaping, welding or adhesive, or it may be a frictional fit on the outer parts. If necessary, a sealing ring may be included to ensure a fluid-tight joint between the sleeve and each outer part.

The fluid-pressure responsive braking means is preferably a diaphragm of rubber or like flexible resilient material which is bonded or otherwise secured to the said one inner part and extends outwardly therefrom so as to overlie at least a portion of the complementary outer part. Instead of being secured to the inner part it may be secured to or integral with a washer, sealing ring or the like designed to fit non-rotatably on the shaft in fluidtight relation thereto and to lie close to the inner part of a bearing.

Instead of the washer or the like being fluid-tight a separate sealing arrangement may be provided. The portion of the diaphragm which overlies the outer part has a surface of frictional material confronting the surface of the outer part or of a liner fixed thereto and normally either lies clear of that surface or makes light contact therewith so as not to cause any significant resistance to rotation of the sleeve. Hovever, when fluid under pressure is admitted to the interior of the sleeve the portion of the diaphragm which overlies the outer part is forced against the confronting surface of the outer part or liner so that its frictional material resists rotation of the outer part.

Instead of or in addition to being arranged to make contact with the outer part of a bearing or of a liner fixed thereto, the diaphragm may extend outwardly sufficiently to make light contact with the interior surface of the sleeve or a liner fixed in the sleeve so that when fluid pressure is applied that contact is increased so as to apply a braking force directly to the sleeve.

Preferably there is similar fluid-pressure responsive braking means connected to or adjacent to the inner part of each bearing.

Instead of the diaphrgagm being connected to the inner part of a bearing to engage frictionally the outer part in response to pressure in the interior of the sleeve, it could be connected to the outer part and be arranged to engage frictionally the inner part. Instead of a diaphragm or like flexible element the fluid pressure-responsive braking means may comprise a piston or like rigid element which is slidable in response to an increase in pressure to apply a braking force to the sleeve.

Braked rotatable elements as described above may be manufactured cheaply compared with the known elements described earlier. The only control necessary is a fluid pressure control, which may be a simple compressor and control valves if the fluid used is air. The fluid-conveying passage may be closed, for example with a non-return valve, so as to maintain a substantially constant fluid pressure and thus a sustantially constant frictional resistance to rotation. The elements can be operable equally in both directions of rotation.

An embodiment of the invention is illustrated by way of example by the accompanying drawing, which is an axial cross-section of a braked conveyor roller.

The roller comprises a sleeve 1 mounted on a shaft 2 by two spaced bearings 3. Each bearing comprises an inner part 4 and an outer part 5 rotatable relative to the inner part 4 about the axis of the shaft 2, antifriction balls 6 being mounted between the inner and outer parts of each bearing and being held in position by a cage assembly 7 in conventional manner. The ends of the sleeve 1 are a close fit on the outer parts 5 and are swaged on to them, O-ring seals 8 being fitted between the sleeve 1 and each outer part to ensure fluid-tight joints. Each outer part 5 has a cylindrical flange 9 extending inwardly from its outer edge, for a purpose which will be described.

The shaft 2 is of hexagonal cross-section and the inner parts 4 of the bearings 3 have complementary hexagonal bores so as to fit closely on the shaft 2 and be non-rotatable in relation to it. A diaphragm 10 of rubber or like resilient and flexible material is bonded to the inner surface of each inner part 4 and has a hexagonal central aperture designed to fit the shaft 2 in sealing relation. Each diaphragm 10 extends radially outwardly so as to lie close to the inner surface of the respective outer part 5 and the radially inner surface of the flange 9. Its surface which confronts those surfaces has a coating 11 of wear-resistant frictional material which normally makes light rubbing contact with those surfaces when the sleeve 1 is rotated relative to the shaft 2. Thus the interior of the sleeve 1 is substantially fluid-tight, though fluid could pass between the confronting faces of the coating 11 and the outer part 5 and its flange 9 under pressures insufficient to cause sealing contact between the confronting surfaces.

A passage from the exterior to the interior of the sleeve 1 is provided by an axial bore 12 extending from one end of the shaft 2 to a position within the sleeve 1 where it joins a radial bore 13. Air or other fluid under pressure may be admitted to the interior of the sleeve 1 through this passage. It will be appreciated that any increase of pressure in the interior of the sleeve will force the diaphragms 10 axially outwardly so as to increase the contact between the confronting faces of the wear-resistant frictional coatings 11 and the outer parts 5 af the bearings 3 and their flanges 9. This will cause frictional resistance to rotation of the sleeve 1 relative to the shaft, braking the sleeve 1 if it is rotating. Further increase of the pressure will increase the frictional resistance or braking force.

If the outer end of the axial bore 12 is connected to a source of compressed air through a control valve then air under pressure can be admitted to the interior of the sleeve when desired to effect braking. If the control valve also includes a vent passage which can be opened selectively, the air may be released when desired to reduce the pressure and so reduce the braking effect. Alternatively a separate vent passage may be provided, with an independent control valve. If a non-return valve, for example a tyre valve, is fitted to the outer end of the bore 12 then the pressure inside the sleeve 1 may be increased to a certain value so as to provide a constant braking effect whether the sleeve is rotating or not.

Claims

1. A braked rotatable element comprising a hollow member rotatable with respect to a stationary member, sealing means rendering the interior of the hollow member substantially fluid-tight, a fluid-conveying passage from the exterior to the interior of the hollow member for admitting fluid under pressure to the interior of the hollow member and braking means connected non-rotatably to one of the said members and arranged to make frictional contact with the other member or a part connected therewith when fluid under pressure is admitted to the interior of the hollow member.

2. A braked rotatable element comprising a sleeve carried on two spaced bearings coaxial with the sleeve, each bearing comprising an inner part and an outer part rotatable relative to the inner part about the common axis and connected to the sleeve, sealing means for rendering the interior of the sleeve between the bearings substantially fluid-tight, a fluid-conveying passage from the exterior to the interior of the sleeve for admitting fluid under pressure to the interior of the sleeve and fluid-pressure responsive braking means connected non-rotatably to one of the said parts of one of the said bearings and arranged to make frictional contact with the complementary part of the said one bearing and/or with a member connected to the complementry part when fluid under pressure is admitted to the interior of the sleeve.

3. A braked rotatable element as claimed in Claim 2 wherein the inner parts of the two bearings are mounted on a common shaft.

4. A braked rotatable element as claimed in Claim 3 wherein the fluid conveying passage and the second passage, if provided. are bores in the shaft.

5. A braked rotatable element as claimed in any of Claims 2 to 5 wherein the fluid-pressure responsive braking means is a diaphragm of rubber or like flexible resilient material connected to the said one part of one bearing and extends therefrom so as to lie close to at least a portion of the said complementary part.

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6. A braked rotatable element as claimed in Claim 5 wherein the diaphragm is secured directly to the said one part.

7. A braked rotatable element as claimed in Claim 5 wherein the diaphragm is secured to or integral with an element which is non-rotatably connected to the said one part.

8. A braked rotatable element as claimed in Claim 7 wherein the said one part is the inner part of one of the said bearings and is mounted non rotatably on a shaft and the said element is mounted non-rotatably on the same shaft adjacent to the inner part.

9. A braked rotatable element substantially as hereinbefore described with reference to and as illustrated by the accompanying drawing.

10. A braked rotatable element as claimed in any preceding claim including valve means for maintaining a substantially constant fluid pressure in the interior of the hollow member or the sleeve.

10. A conveyor roller comprising a braked rotatable element as claimed in any preceding claim.

11. A conveyor comprising a conveyor roller as claimed in Claim 10.