GB2092085A

GB2092085A - Improvements in or relating to conveyor belts

Info

Publication number: GB2092085A
Application number: GB8103031A
Authority: GB
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1981-01-31
Filing date: 1981-01-31
Publication date: 1982-08-11
Also published as: AU7997582A

Abstract

A drive system for a conveyor belt 3 comprises a single-sided induction motor having a stationary primary 1 position adjacent to one surface of the belt 3 and a secondary incorporated in and extending the length of the belt comprising a ferrous component 5 and an electrical conductor 6. As a result the other surface of the belt 3 which in use provides the load carrying surface is not restricted by the drive system. The ferrous component 5 comprises one or more layers of elongate parallel elements such as steel strands, cords, or cables and the electrical conductor 6 comprises a sheet of aluminium. The elements of the ferrous components may extend transversely or longitudinally of the belt or at a bias angle therebetween. In an alternative construction the ferrous component comprises one or more layers of steel strip. <IMAGE>

Description

SPECIFICATION Improvements in or relating to conveyor belts This invention concerns improvements in or relating to conveyor belts.

Conventional direct drive for conveyor belts is provided by one or more of the conveyor support rollers. The operating speeds attainable by such an arrangement are restricted by the frictional force that exists between the belt material and that of the rollers while direct contact between the belt and rollers contributes to wear in the belt.

To overcome these problems it has been proposed to use linear induction motors for the direct drive of conveyor belts, such a system avoiding direct contact with the belt and hence mechanical damage and wear thereto.

Heretofore such proposals have been confined to the use of double-sided induction motors with the belt construction being modified to include a non-ferrous secondary having the required electrical conductance. To minimise stresses in the belt it is preferred to apply the drive to the load carrying section as opposed to the return section of the belt with the result that it has been necessary in the known arrangements to locate the motor primaries at the lateral edges of the belt, one adjacent to each surface of the belt so as to avoid obstructing the load carrying surface of the belt. Such an arrangement is not entirely satisfactory since it is necessary to accept either a reduction in the overall width of the belt available for conveying material etc or to increase the width of the belt to accommodate the motors, the latter being undesirable on a cost basis.Furthermore the application of such an arrangement is restricted in that care must be taken to ensure any material conveyed cannot be displaced into the air gap between the belt and motor, this spacing being critical to the electrical efficiency of the motor and hence operation of the drive system.

In accordance with one aspect of the present invention there is provided a drive system for a conveyor belt in which the primary of a singlesided induction motor is positioned adjacent to one surface of the belt and the belt incorporates as the secondary a ferrous component and an electrical conductor both extending longitudinally therethrough.

The use of single-sided induction motor the primary of which may be located adjacent to that surface remote from the load carrying surface of the conveyor belt enables the drive to be applied to the load carrying section whilst avoiding the above-mentioned problems encountered with the use of double-sided induction motors.

Furthermore the location of the primary is not restricted to the lateral edge regions of the belt.

Conveniently the ferrous component is provided by one or more layers of elongate parallel elements consisting of strands, cords or cables or steel wire. Each layer may be disposed with the elements extending longitudinally or transversely of the belt or at any bias angle therebetween.

Where the ferrous component comprises several layers the elements of each layer may extend in the same direction or the elements of successive layers may be angled relative to one another e.g.

to either side of the longitudinal axis of the belt depending on the required flexibility of the belt.

Such layer or layers may constitute all or part of the belt reinforcement. Where additional reinforcement is incorporated in the belt to provide the required load carrying capability this may be of metal or textile having any suitable construction known to those skilled in the art.

Alternatively the ferrous component may comprise one or more layers of steel strip. The strip may be in the form of a closed loop extending across part or all of the belt width. More than one loop may be provided tranversely of the belt width.

Preferably such ferrous component is of laminate construction comprising several layers of steel strip separated by polymeric material, as opposed to a single strip of the required overall thickness.

The electrical conductor may be continuous along the length of the belt or may be of the ladder or squirrel cage construction formed with a plurality of central cut-outs spaced relative to one another in the longitudinal direction of the belt.

The cut-outs may be filled with an insert of ferrous material. Preferably the spacing between successive rungs or bars of the latter construction is less than the pole pitch of the induction motor and more preferably less than half pole pitch thereof. A suitable material for the electrical conductor is aluminium which may be in the form of a single sheet of the required thickness or a laminate of several thinner sheets or a plurality of overlapping plates.

Preferably the belt construction is such that in use the electrical conductor is positioned between the ferrous component and the motor primary, for example where the electrical conductor comprises a continuous sheet of aluminium extending the length of the belt. However where the electrical conductor is formed with a series of cut-outs or the like the ferrous component and conductor may be interlinked, for example the cut-outs may contain ferrous inserts or where the ferrous component comprises longitudinal steel cords these may pass through the cut-outs so as to extend above and below the conductor.

Alternatively the conductor may incorporate transverse ferrous elements for example steel rods mechanically interlinked with the conductor.

According to another aspect of the present invention there is provided a conveyor belt incorporating a ferrous component and an electrical conductor both extending therethrough and adapted to form the secondary of a singlesided induction motor.

The invention will now be described in more detail, by way of example only, with reference to the accompanying schematic drawings in which: Figure 1 shows in transverse cross-section a first embodiment of a drive system in accordance with the present invention utilising a transverse flux motor; Figure 2a shows in plan view a longitudinal flux motor forming part of a second embodiment of a drive system in accordance with the present invention, and Figure 2b shows in perspective view, partly in section, a conveyor belt for use with the longitudinal flux motor of Figure 2a.

Both the drive systems for conveyor belts illustrated in the accompanying drawings utilise a singie-sided induction motor the primary of which is stationary and positioned adjacent to one surface of the belt and the secondary of which is incorporated in the belt.

Referring to Figure 1 the motor primary 1 has the coils 2 disposed to provide a flux pattern extending transversely of the belt 3. The motor secondary comprises a ferrous component 5 and an electrical conductor 6 extending longitudinally through the belt 3. The ferrous component 5 is constituted by a plurality of layers of parallel steel cords embedded in an elastomeric matrix in which the steel cords of each layer extends transversely of the belt. The electrical conductor 6 consists of an aluminium sheet bonded to one facing surface of the ferrous component 5. The conductor 6 is continuous in the direction of the length of and across the width of the belt. An elastomeric cover 7 is bonded to the other facing surface of the ferrous component and provides the load carrying surface in use of the belt.

Referring to Figure 2a the motor primary 11 has the coils 12 disposed to provide a flux pattern extending longitudinally of the belt 1 3. The motor secondary comprises a ferrous component 1 5 and an electrical conductor 1 6 extending longitudinally through the belt 13. The ferrous component 1 5 is constituted by two layers of parallel steel cords embedded in an elastomeric matrix in which the steel cords of each layer extend longitudinally of the belt. The electrical conductor 1 6 consists of an aluminium sheet bonded to one facing surface of the ferrous component 15.The conductor 16 is of ladder construction formed with a plurality of similar central cut-outs spaced relative to one another in the longitudinal direction of the belt with the spacing between the successive transverse rungs of the ladder being less than half the pole pitch of the primary. Each cut-out contains a ferrous insert 1 8. An elastomeric cover 1 7 is bonded to the other facing surface of the ferrous component 1 5 and provides the load carrying surface in use of the belt.

In each of the above-described embodiments the flux pattern of the motor primary extends parallel to the reinforcing cords of the ferrous member 5, 15, such an arrangement being understood to provide high electrical efficiency.

It wili be apparent that the above-described drive systems utilising a single motor primary positioned adjacent to that surface of the belt remote from the load carrying surface are particularly suited to drive the load carrying section of the belt since no part of the motor obstructs the load carrying surface and therefore the aforementioned problems associated with known linear motor drive systems are avoided.

However, it is to be understood the drive system may be applied to the return section of the belt where such location is permissible.

Although both the motor secondary and the flux pattern of the motor primary extend across substantially the entire width of the belt in the above-described drive systems it is to be understood that both the motor secondary and the flux pattern of the motor primary may extend across part only of the belt width, for example the drive system may be applied to the centre section only or to one or both lateral edge sections of the belt, thus the system is applicable both to belts which adopt a troughed cross-section in service and to belts which remain substantially flat in surface. Additionally where the drive system is applied to the load carrying section of the belt support rollers may be provided engageable with the belt to restrict deflection of the belt under increased load and thereby retain a minimum air gap between the motor primary and secondary.

Claims

1. A drive system for a conveyor belt in which the primary of a single-sided induction motor is positioned adjacent to one surface of the belt and the belt incorporates as the secondary a ferrous component and an electrical conductor both extending longitudinally therethrough.

2. A drive system according to Claim 1 wherein the ferrous component comprises at least one layer of elongate parallel ferrous elements.

3. A drive system according to Claim 2 wherein said elements comprise strands, cords or cables or steel wire.

4. A drive system according to Claim 2 or Claim 3 wherein said elements extend longitudinally of the belt.

5. A drive system according to Claim 2 or Claim 3 wherein said elements extend transversely to the belt.

6. A drive system according to any of Claims 2 to 5 wherein the ferrous component comprises a plurality of layers.

7. A drive system according to Claim 6 wherein the elements of successive layers are inclined relative to one another.

8. A drive system according to any one Claim 2 to 7 wherein the or each layer constitutes part or all of the belt reinforcement.

9. A drive system according to Claim 1 wherein the ferrous component comprises one or more layers of steel strip.

10. A drive system according to any one of the preceding Claims wherein the conductor is formed with a series of uniformly spaced cut-outs in the longitudinal direction of the belt.

1 A drive system according to Claim 10 wherein the cut-outs contain a ferrous insert.

12. A drive system according to Claim 10 wherein the ferrous component passes through the cut-outs and extends above and below the conductor.

13. A drive system according to Claim 10 wherein the ferrous component is disposed adjacent that surface of the conductor which in use is remote from the motor primary.

14. A drive system according to any one of Claims 2 to 6 wherein the flux pattern of the primary extends parallel to the direction of said elements.

1 5. A drive system for conveyor belts substantially as herein described with reference to the accompanying drawings.

1 6. A conveyor belt incorporating a ferrous component and an electrical conductor both extending therethrough and adapted to form the secondary of a single-sided induction motor.