ZA200108853B

ZA200108853B - Conveyor idler.

Info

Publication number: ZA200108853B
Application number: ZA200108853A
Authority: ZA
Inventors: Tertius Francois Dreyer
Original assignee: Trackstar Trading 91 Pty Ltd
Priority date: 1999-11-02
Filing date: 2001-10-26
Publication date: 2002-02-07

Description

-1- SEES CL

CONVEYOR IDLER

FIELD OF THE INVENTION

THIS invention relates to a brake mechanism for a conveyor idler, and to a kit of parts for a brake mechanism for a conveyor idler.

BACKGROUND TO THE INVENTION

Typically a conveyor belt arrangement inciudes a conveyor belt supported on a series of conveyor idlers located along the length of the conveyor belt.

Conveyor idlers are also referred to as conveyor rollers and, in this specification, a reference to a conveyor idler includes a reference to a conveyor roller. In the art it is known to drive the conveyor belt via a motor so that the conveyor belt runs on the conveyor idlers which are rotatably connected to a support frame.

CONFIRMATION COPY

The conveyor idlers typically do not include braking means and run freely in both a forward or reverse direction. This can create problems, especially with inclined conveyor belt arrangements. If the conveyor belt snaps, or the motor trips, then the conveyor belt may move in the reverse direction under "the load on the conveyor belt. This will result in the load being deposited at the back of the conveyor belt arrangement which creates a safety hazard for employees, can cause damage to surrounding structures and results in production downtime.

Brake mechanisms for conveyor belts are known, but these are usually separate mechanisms which act on the conveyor belt itself and are located adjacent the conveyor belt where they are easily damaged. In addition, because these brake mechanisms are exposed they require regular maintenance.

It is desirable to have a conveyor idler which incorporates a braking mechanism which is not exposed to the elements, permits rotation of the conveyor idler in a forward direction, and retards rotation of the conveyor idler in a reverse direction thereby providing a braking effect on the conveyor belt.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a brake mechanism for a substantially hollow conveyor idler which is rotatable about an idler shaft, the brake mechanism comprising: - a brake guide secured to the idler shaft and defining an outer surface adapted to fit rotatably within the hollow conveyor idler, the E outer surface including at least one recess thereon; and N - a brake element located in the recess, between an inner surface of the conveyor idler and the brake guide, and movable in the recess, between a first position and a second position;

wherein the recess is shaped such that in the first position the brake element is received substantially within the recess and in the second position the brake element protrudes from the recess and engages the inner surface of the conveyor idler.

Preferably the at least one recess defines a brake surface along which the brake element is moveable between the first and sécond positions.

Typically the brake guide is cylindrical and the outer surface of the brake guide is substantially complemental to the inner surface of the conveyor "idler. Conveniently the brake guide defines a cylindrical surface and at least one end surface and at least one recess is located on the cylindrical - surface. Optionally at least one recess is located on the end surface.

The brake element may be spherical. Alternatively the brake element may be cylindrical.

Ideally the brake guide includes a plurality of recesses located at regular intervals on the outer surface.

According to a second aspect of the invention there is provided a kit of parts for a brake mechanism for a hollow conveyor idler which is rotatable about an idler shaft, the kit comprising: . - a brake guide securable to the idler shaft and defining an outer surface adapted to fit rotatably within the hollow conveyor idler, the outer surface including at least one recess thereon; and - a brake element locatable in the recess, between an inner surface of the conveyor idler and the brake guide, and movable in the recess, between a first position and a second position; wherein the recess is shaped such that in the first position the brake element is received substantially within the recess and in the second position the brake element protrudes from the recess to engage the inner surface of the conveyor idler.

The brake element may be a ball bearing. Alternatively the brake element may be an elongate roller bearing.

BRIEF DESCRIPTION OF THE DRAWINGS oo The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which;

Figure 1 shows an exploded perspective view of a conveyor idler with a braking mechanism according to a first embodiment of the invention; }

Figure 2 shows a cross sectional end view of the brake mechanism taken along line II-11 in Figure 1, with the idler rotating in a forward direction;

Figure 3 shows a cross sectional end view of the brake mechanism taken along line II-II in Figure 1, with the idler stopped from rotating in a reverse direction;

Figure 4 shows a close-up cross sectional end view of a portion of a brake guide of the brake mechanism shown in Figure 2;

Figure 5 shows a cross sectional side view of a brake mechanism according a second embodiment, with the idler rotating in a forward direction;

Figure 6 shows a cross sectional side view of the brake mechanism according to the embodiment in Figure 5, with the idler stopped from rotating in a reverse direction; and

YF 5.

Figure 7 shows a partially exploded perspective view of the brake guide of the brake mechanism according to the embodiment in Figure 5.

Embodiments of the invention are described in detail in the following passages of the specification which refer to the accompanying drawings. The drawings, however, are merely illustrative of how the invention might be put into effect, so that the specific form and arrangement of the features shown is not to be understood as limiting on the invention.

DESCRIPTION OF THE EMBODIMENTS :

Figure 1 shows a brake mechanism 10 for a hollow conveyor idler 12.

Conveyor idlers of this nature are known in the art. The conveyor idler is cylindrical and is typically formed from metal, but could be formed from any suitable material including a thermoplastics material. In the embodiment shown in Figure 1, the conveyor idler has an outer diameter of approximately 65 mm and an inner diameter of approximately 60 mm. It should be understood that the diameter of the conveyor idler varies depending on the specific application.

The conveyor idler is rotatably connected to an idler shaft 14 which is co- axial with the conveyor idler. The idler shaft is formed from steel and in the embodiment shown in Figure 1 has a diameter of 25mm. The diameter of the idler shaft can be varied depending on the specific application. The ends of the idler shaft are fixed to a frame of a conveyor belt arrangement (not shown). The conveyor idler is rotatably connected to the idler shaft by means of bearing assemblies 16 which engage an inner surface of the conveyor idler and run on the idler shaft. The bearing assemblies are retained in position by end caps 18 which fit over the idler shaft and into either end of the conveyor idler in a press fit configuration. The end caps are made from a thermoplastics material and include a seal arrangement (not shown) which prevents the ingress of dirt into the conveyor idler and the bearing arrangements. A conveyor belt (not shown) runs on the outside surface of the conveyor idler.

As can be seen more clearly in Figure 2, the brake mechanism 10 comprises a brake guide in the form of a plate 20. The plate is metal and is substantially circular in cross section with a bore 22 located centrally therein. The bore has the same diameter as the idler shaft, approximately mm, which allows the plate to be located on the idler shaft. The plate is connected to the idier shaft by means of a keyway 24 in the idler shaft. The keyway is approximately 8 mm long and 4 mm deep and a complemental key is located in the keyway in order to secure the plate to the idler shaft. It should be understood that the plate could be connected to the idler shaft by ~ other means, including welding, a retaining screw, bolts or rivets. The plate could also be formed from another material such as Vascanite™.

Depending on the application, there could be multiple plates located along the length of the idler shaft. However, typically one plate is sufficient to provide sufficient braking action for general use. In a preferred embodiment, the plate is located between bearing assemblies within the ) conveyor idler. Brushes 25 are located against the end surfaces of the plate and the bearing assemblies to reduce wear and friction.

The plate has an effective outer diameter of approximately 59 mm so that it can be inserted into the conveyor idler without restricting the rotation of the conveyor idler. In this arrangement, the plate is secured to the idler shaft and the conveyor idler rotates around the idler shaft and plate. The plate is approximately 5 mm thick. As will be described in more detail below, the thickness of the plate can be varied depending on the amount of braking force desired. The plate defines a cylindrical outer surface 26, a first end surface 28 and a second end surface 30.

Eight recesses 32 are located on the cylindrical outer surface and are spaced evenly around the circumference of the plate. It should be understood that the plate could include more or less recesses, depending on the amount of braking action desired. However, it has been found that

4 -7- eight recesses provides sufficient braking action for general use. Each recess extends across the width of the plate, between the first and second end surfaces. lt should be understood that each recess could extend along only a portion of the width of the plate, i.e. not from the first end surface to the second end surface. Each recess is shaped, in cross section, to define a step with a front end 34 and a back end 36. The depth of each step, with respect to the cylindrical outer surface, is tapered so that it increases from the front end to the back end. The front end of the step is substantially flush with the outer diameter of the plate whereas the back end of the step is approximately 5 mm below the outer diameter of the plate.

The brake mechanism includes further a brake element in the form of a ball - bearing 40. A ball bearing is located in each recess, between the conveyor : idler 12 and the plate 20. It should be understood that instead of a ball bearing, the brake element could be in the form of a cylindrical roller bearing extending across the width of the recess. When compared with the ball bearings, the roller bearings provide a larger surface area in contact with the inner surface of the conveyor idler and thus create a greater braking action. However, it has been found that the ball bearings provide sufficient braking action for general use. Each ball bearing is movable along the recess, between a first position at the back end 36 of the recess, as shown in Figure 2, and a second position at the front end 34 ofthe recess, as shown in Figure 3. The ball bearings are retained in place in the recesses by the brushes 25 which are located against both end surfaces of the plate in order to reduce wear and friction with the bearing assemblies, as described above. The diameter of the ball bearing is selected so that when the ball bearing is in the first position, the ball bearing is received substantially within the recess, i.e. the diameter of the ball bearing is substantially equal to the depth of the step at the back end. As the ball bearing moves from the first position towards the second position, it begins to protrude from the recess and engage the inner surface of the conveyor idler.

-8- 8

Figure 2 shows the conveyor idler rotating in a forward direction, indicated by arrow F. With the conveyor idler rotating in the forward direction, the inner surface of the conveyor idler draws the ball bearings 40, under the influence of friction, towards the back end 36 of the recess 32 and thus the ball bearings are received substantially within the recesses. As a result, there is no braking force applied to the conveyor idler. Figure 3 shows the conveyor idler which has been prevented from rotating in a reverse direction, indicated by the arrow R, by the brake mechanism. With the conveyor idler rotating in the reverse direction, the inner surface of the conveyor idler draws the ball bearings 40, under the influence of friction, ‘towards the front end 34 of the recess 32. As the ball bearings move towards the front end of the recesses they begin to protrude from the recesses and create a braking action on the inner surface of the conveyor idler.

Figure 4 shows a close-up view of a portion of the plate 20 with an optional feature. As can be seen, at the back end 36 of each recess there is located a shaft 42 which houses a spring mechanism 44. The spring mechanism includes a spring 46 located in the shaft and biased towards the recess. As indicated above, when the conveyor idler is rotating in a forward direction, the ball bearing 40 is drawn under the influence of friction towards the back end 36 of the recess 32. This has the effect of compressing the spring 46 as shown in Figure 4. When the conveyor idler rotates in the reverse direction (not shown), the ball bearing is drawn under the influence of friction towards the front end 34 of the recess. With the compression force removed, compressed spring 46 pushes the ball bearing towards the front end thus ensuring that the ball bearing does not get stuck in the back end of the recess.

Figures 5 to 7 show another embodiment of the braking mechanism according to the invention. The braking mechanism 10.1 is once again adapted for use with a hollow conveyor idier 12. The conveyor idler is rotatably connected to an idler shaft 14 which is co-axial with the conveyor idler. As with the embodiments shown in Figures 1 to 4, the conveyor idler

> .9- is rotatably connected to the idler shaft by means of bearing assemblies (not shown) which again engage an inner surface of the conveyor idler and run on the idler shaft. The bearing assemblies are retained in position by end caps (not shown) which fit over the idler shaft and into either end of the conveyor idler in a press fit configuration. A conveyor belt (not shown) runs on the outside surface of the conveyor idler.

As can be seen more clearly in Figure 5, the brake mechanism 10 comprises a brake guide in the form of a plate 20.1. The plate is metal and is substantially circular in cross section with a bore 22.1 located centrally therein. The bore has the same diameter as the idler shaft which allows the plate to be located on the idler shaft. The plate is again connected to the idler shaft by means of a keyway (not shown) in the idler shaft. The keyway is approximately 8 mm long and 4 mm deep and a complemental key is located in the keyway in order to secure the plate to the idler shaft. It should be understood that the plate could be connected to the idler shaft by other means, including welding, a retaining screw, bolts or rivets. The plate 20.1 could also be formed from another material such as Vascanite™. The plate is located between bearing assemblies within the conveyor idler.

Brushes 25 are located against the end surfaces of the plate and the bearing assemblies to reduce wear and friction.

The plate has an effective outer diameter such that it can be inserted into the conveyor idler without restricting the rotation of the conveyor idler. In this arrangement, the plate is secured to the idler shaft and the conveyor idler rotates around the idler shaft and plate. The plate is approximately 15 mm thick. As will be described in more detail below, the thickness of the plate can be varied depending on the amount of braking force desired. The plate defines a cylindrical outer surface 26.1, a first end surface 28.1 and a second end surface 30.1.

A recess 50 is located on each of the end surfaces 28.1 and 30.1. In

Figure 7 the recess on the second end surface 30.1 is shown in broken lines. These recesses extend to the circumference of the plate thereby

-10- 4 also forming recesses in the cylindrical outer surface of the plate. It should be understood that the plate could include more or less recesses, depending on the amount of braking action desired. Each recess is shaped, in cross section, to define a step with a front end 34.1 located on the circumference of the plate, and a back end 36.1. The depth of each step, with respect to the end surface on which it is located, is tapered so that it increases from the front end to the back end.

The brake mechanism includes further a brake element in the form of a ball bearing 40.1. A ball bearing is located in each recess, between the conveyor idler 12, the plate 20.1 and the associated brush. Each ball bearing is movable along the recess, between a first position at the back end 36.1 of the recess, as shown in Figure 5, and a second position at the front end 34.1 of the recess, as shown in Figure 6. The diameter of the ball bearing is selected so that when the ball bearing is in the first position, the ball bearing is received substantially within the recess, i.e. the diameter of the ball bearing is substantially equal to the depth of the step at the back end. As the ball bearing moves from the first position towards the second position, it begins to protrude from the recess and engage the inner surface of the conveyor idler and the brush 25.

Figures 5 and 7 show the conveyor idler rotating in a forward direction, indicated by arrow F. With the conveyor idler rotating in the forward direction, the movement of the brush draws the ball bearings 40.1, under the influence of friction, towards the back end 36.1 of the recess 32.1 and thus the ball bearings are received substantially within the recesses. As a result, there is no braking force applied to the conveyor idler. Figure 6 shows the conveyor idler which has been prevented from rotating in a reverse direction, by the brake mechanism. With the conveyor idler rotating in the reverse direction, the brush draws the ball bearings 40.1, under the influence of friction, towards the front end 34.1 of the recess 32.1. As the ball bearings move towards the front end of the recesses they begin to protrude from the recesses and create a braking action on the inner surface of the conveyor idler and on the brush.

AG -11-

According to a second aspect of the invention there is provided a kit of parts for a brake mechanism for a conveyor idler which is rotatable about an idler shaft, the kit comprising a plate connectable to the idler shaft and including eight recess on a surface of the brake guide. The kit includes eight ball bearings locatable in the recess, between the idler and the brake guide, and movable along the recess, between a first position and a second position, wherein the recess is shaped such that in the first position the brake element is received substantially within the recess and in the second position the brake element protrudes from the recess.

Claims

1. A conveyor idler having an outer surface and an inner surface, a shaft about which the conveyor idler can rotate in a forward direction, the ends of the shaft being fixed to a frame of a conveyor belt arrangement having a conveyor belt which is supported on and which runs on the outer surface of the conveyor idler, a braking mechanism for preventing the conveyor idler from rotating in a reverse direction, but which braking mechanism permits rotation of the conveyor idler in the forward direction, the braking mechanism being located within the conveyor idler and includes at least one brake element which can move between a first position in which the conveyor idler can rotate in the forward direction, and a second position in which the brake element prevents the conveyor idler from rotating in the reverse direction.

2. The conveyor idler of claim 1 wherein the braking mechanism includes a brake guide for the at least one brake element.

3. The conveyor idler of claim 2 wherein the brake guide is secured to the shaft.

4. The conveyor idler of claim 2 or claim 3 wherein the brake guide has an outer surface with a plurality of recesses each having a brake surface and wherein the at least one brake element is located on one of the brake surfaces and wherein the at least one brake element is moveable on its brake surface between the first position and the second position.

5. The conveyor idler of claim 4 wherein a plurality of brake elements are provided, with each brake element being located on its respective brake surface. AMENDED SHEET - DATED 31 MAY 2006

6. The conveyor idler of any one of the above claims wherein the at least one brake element is a ball bearing or a roller bearing.

7. The conveyor idler of claim 2 wherein the at least one brake element is interposed between the brake guide and the conveyor idler.

8. The conveyor idler of claim 3 wherein the brake guide is secured to the shaft by a key and keyway.

9. The conveyor idler of claim 4 wherein in its second position the at least one brake element protrudes from its recess and engages the inner surface of the conveyor idler.

10. A conveyor idler substantially as herein described and illustrated with reference to the accompanying drawings. AMENDED SHEET - DATED 31 MAY 2006