GB2371280A

GB2371280A - Drive assembly

Info

Publication number: GB2371280A
Application number: GB0101509A
Authority: GB
Inventors: Roger Smith Hall
Original assignee: R S HALL ENGINEERING Ltd
Current assignee: R S HALL ENGINEERING Ltd
Priority date: 2001-01-20
Filing date: 2001-01-20
Publication date: 2002-07-24
Also published as: GB0101509D0

Abstract

A drive assembly for a separation web 14 comprises a drive portion having an elongate planar drive face for driving engagement with an engagement zone on the web. Typically, the assembly comprises a continuous belt or chain 1 passing around at least one driven cylinder 3 and at least one non-driving guide cylinder 11. The driven cylinder preferably comprises a sprocket having teeth 12 which engage with an inner surface of the belt or chain. A portion of the belt or chain which abuts the web preferably constitutes the drive face and complimentary projections 4, 16 and recesses may be provided on the drive face and the web. A support frame (5, Fig. 2) may be further incorporated so as to move the assembly into and out of contact with the web. Typically, the separation web is of the conventional ladder type and is particularly useful in harvesting root crops.

Description

DRIVE FOR SEPARATION WEB AND SEPARATION WEB ASSEMBLY INCORPORATING SUCH DRIVE The invention relates to a drive for driving a separation web, separation conveyor, screening conveyor, sizing or grading conveyor of the sort which is used in the food industry to separate products according to size and/or to separate desired product from unwanted debris. In particular, the invention relates to a separation web or screen conveyor for use in association with root crop harvesters to facilitate the separation of stones, mud, crop tops and other debris from the crop. The invention also relates to a separation web assembly incorporating such drive means.

Separation webs, screens and graders which take the form of an endless conveyor belt onto which the product to be separated is transferred, the conveyor belt surface being provided with a grid, screen or the like suitably sized to effect the desired separation, have widespread application in a number of areas of the food industry. Such devices, known variously as separation webs, separation conveyors, screen conveyors, grading conveyors, and the like have a range of applications in the food industry, both in separating and sizing products and in separating products from debris. In each case, the conveyor is driven by suitable drive means and the desired separation effect is produced by the appropriately sized grid, screen or the like.

A particular form of conveyor, to which the invention is particularly though not exclusively applicable, is a screening conveyor for use with a root crop harvester to enable separation of stones, mud, extraneous vegetation and other debris from the root crop. In such devices, the conveyor is typically an endless conveyor comprising an endless grid screen, the grid screen typically

taking the form of at least two parallel endless conveyor belts linked transversely by a plurality of generally parallel and generally evenly spaced transverse members, such as solid rods. The evenly spaced solid rods make up the screen with the pitch of the rods giving the effective screening. As the endless conveyor is driven, with product on top of the conveyor screen, the desired crop is generally retained above the screen, whilst mud, stones and other debris generally falls through the gaps defined by adjacent cross members to be discarded.

In the prior art devices, drive means are provided which typically take the form of drive cylinders located internally with the endless conveyor belt or belts wound therearound. Since the belts are heavy, and used in dirty, out of door environments where fouling can be a problem, difficulties may be encountered in ensuring that the driving force is properly imparted from the drive cylinder to the belt without slipping etc.

Two basic approaches can be found in the prior art. In the first approach, a drive cylinder is provided with sprockets to engage the belt directly. Although this gives a very effective keying between drive cylinder and belt in optimum conditions, it is prone to problems. The sprockets are prone to wear and high stresses, and are particularly prone to fouling.

This had led to the use of an alternative approach, in which the belt is friction driven, and in which the drive rollers, whilst they may be provided with surfaces to increase the friction between roller and belt, do not specifically key into the belt. Such an approach tends to involve the use of several rollers to get the necessary consistency of drive and minimise slipping, with the conveyor being wound around these several drives in a complex configuration.

Where several rollers are used, tolerances can be especially critical, and the relative speeds of the rollers must be very accurate to avoid strain. A number of problems are encountered in such prior art drives. In particular, quite severe strains can build up in the conveyor web as it is wound around the drive cylinders. This is particularly the case where a friction drive using multiple cylinders is employed.

In typical web constructions, the belt comprises a pair of parallel webbing strips with transverse metal rods which make up the separation web itself. Webbing strips are manufactured typically from rubber encased polymeric fabric, for example 3 ply terylene-nylon. The design is a compromise on stiffness, which cannot be too high to accommodate the areas where the webbing is passed around the cylinder drives and is bent quite markedly, but needs to be adequate if the conveyor is to retain reasonable rigidity. Avoiding excessive stiffness also places a practical limitation on strength. Increasing beyond 3 ply is likely to take the stiffness of the material beyond that which is suitable for winding round a tight drive roller. However, making the roller bigger to accommodate this will increase the machine size and the drive torque required and is unlikely to be practical.

As a result of the above design compromises, significant stresses can build up in the webbing strips as the conveyor passes around the cylinder drives. In particular, the simultaneous effect of pulling stresses as the web is moved by the drive and bending stresses as it passes around the drive seems to be a problem. While this can be offset to some extent by dividing the conveyor into sections with articulated joints between the webbing strips in adjacent sections, failure of the webbing, particularly in the vicinity of these joints, is a problem.

Further problems arise in the conventional design in that the drive cylinder (s) are located within the conveyor, and hence in use typically below the active upper part of the endless conveyor belt, where separation occurs. This renders them particularly prone to fouling. Fouling is especially problematic in any case, not only given the frequently dirty and muddy environments in which the equipment is to be used, but also since cleaning can prove profoundly difficult, as it generally necessitates removal of the separation web from the drive means, which is no easy operation, particularly in the case of the complex windings found with friction driven webs.

However, an external cylinder drive is not practical, since it would produce only point contact with the belt, increasing sprocket wear and/or slippage. To get adequate contact between drive cylinder and belt it is necessary in conventional designs for the belt to be wound around an internally located cylinder drive.

It is an object of the present invention to mitigate some or all of the above disadvantages.

It is a particular object of the present invention to provide a drive means for a separation web which reduces the bending stresses experienced by the web.

It is a particular object of the invention to provide a drive means for a separation web which facilitates ready engagement and disengagement of the drive means for the web for cleaning and the like.

Thus according to a first aspect of the present invention, a drive means for a separation web comprises a drive portion adapted to drivingly engage a drive

engagement zone on a web to be driven, wherein the drive portion presents an elongate generally planar drive face for engagement with the said drive engagement zone. The generally elongate drive face ensures that in use the web is engaged in a similar generally planar manner along a portion of its length. In consequence, the web is pulled in a generally straight line through the drive zone.

As a result of this, the bending stresses on the webbing, and in particular on the side belts of a conventional, ladder-type separation web, are reduced. By ensuring that the drive means engages the web in a generally linear manner, the pulling strain experienced by the web in association with its being driven is separated from the bending strain experienced by the web as the endless conveyor passes around cylinders, which in this case will be merely guide cylinders. Since the cylinders are not driven, a number of the problems associated with driven cylinders are obviated.

Preferably, the invention comprises a web drive means for a separation web which comprises a plurality of web engaging portions disposed consecutively at substantially the same pitch as complementary drive engagement portions on the web to be driven, such that in use several consecutive web engaging portions simultaneously engage the complementary drive engaging portions of the web. The complementary engaging portions thus make up the generally planar elongate drive face and the drive engagement zone of the conveyor which engages therewith in use.

The engaging portions are conveniently complementary projections and recesses, for example projections on the drive face complementary to recesses on the web, or vice versa, or some combination thereof. In a particularly preferred embodiment, the web to be engaged is of the ladder type comprising

at least one pair of endless driven belts with generally evenly pitched transverse members and especially rigid members such as rods or web bars extending therebetween, and the engaging portions on the drive face comprise projections of substantially the same pitch as the gaps between the transverse members of a separation web to be engaged, the projections being configured to engage with the gaps between such transverse members.

The drive means is preferably a continuous drive means. For example, the drive means comprises at least one continuous flexible drive belt or chain or the like. A portion of the belt or chain facing a web to be driven at a given time constitutes the drive face.

This continuous flexible drive belt or chain or the like conveniently passes about and is driven by at least one driven cylinder, and further passes about at least one laterally spaced further cylinder, which may be driven or non-driven.

Other driving or non driving (i. e. guide) cylinders may be provided. The space between the endmost cylinders provides the elongate length for the drive face, and the cylinders are selectively sized and positioned to ensure that the drive face remains essentially planar in use. Guide cylinders preferably comprise pressure cylinders, in that means are provided to apply force to the guide cylinders so that they serve to engage the drive surface in position on the driven region of the web in use.

The drive means may incorporate means for adjusting the length of the drive face, for example in the form of means to adjust the distance between one or more of the cylinders, and in particular between the two endmost cylinders.

In one embodiment, the drive means comprises a flexible endless belt with web engaging means on an outer surface thereof, for example web engaging

teeth configured to engage the web, and in particular configured to engage the gaps between transverse web bars of a ladder type web consisting of at least a pair of endless web strips with laterally extending generally parallel bars of generally even pitch. The teeth are therefore the same pitch as the pitch of the web bars.

The drive belt or chain is driven by at least one driven cylinder. Preferably, at least the driven cylinder has sprocket engagement means to engage with an inner surface of the drive belt or chain, and/or the inner surface of the drive belt or chain has means to receive the teeth of the said sprocket.

For example, in a preferred embodiment, the drive belt comprises a webbing core, teeth moulded from rubber or like material disposed on an outer surface to engage the web to be driven as above described, and projections and/or recesses on a rubber or like material moulded inner surface to engage with the cylinder drive for example to receive sprocket teeth thereof.

A sprocket drive is to be preferred in many instances at least for the driven cylinder (s). In some instances, in particular for guide cylinders, frictional engagement will be sufficient.

Since the driven cylinder drives only the endless drive belt, chain or the like and does not drive the much more heavyweight endless belt of the separation web itself, driving mechanisms can be much simpler. The driven cylinder may employ a smaller shaft, allowing higher speeds without torque problems and simpler gearing. Preferably the drive incorporates an epicyclic gearing system.

It is a key feature of the present invention that the drive pulls the web in a straight line, and engages a generally planar driven region on the web. Thus, the drive means engages an adequate length of the belt to be driven to ensure adequate imparting of drive force and reduce slippage regardless of whether it is located in contact with an inside or outside surface of the endless conveyor web. This contrasts with a drive cylinder, which needs to be located internally in practice to ensure adequate length of contact.

To exploit this advantage, the drive is preferably adapted to engage the outside rather than the inside of the conveyor loop of the endless conveyor of a separation web. This avoids many of the fouling problems associated with prior art drives, and provides a design which is inherently easier to engage and disengage from the web to be driven for any purpose.

Preferably, a support frame is provided to support the drive means, the support frame being adapted for mounting the drive means for use with a conventional web separator conveyor, preferably in a position external to the endless conveyor loop and in particular above the upper surface thereof. Preferably, the support frame incorporates means to move the drive into and out of contact with the separation web. For example, the support frame is pivotable relative to the web. Mechanical actuation means, such as a hydraulic ram, spring or combination thereof, may be provided to effect this.

Preferably, the system incorporates means to measure the pull imparted on the conveyor web by the drive, and hence give an indication of the stresses and/or strains involved. Conveniently, this takes the form of a load cell, provided with suitable data communication and/or data display means, associated with or integral with or attached to the drive means.

In a further aspect of the invention, a separation web and drive arrangement comprises a separation web or the like of conventional design as above described in combination with and adapted to be driven by a drive means according to the first aspect of the present invention.

In particular, the separation web is of the conventional ladder type, comprising at least one pair of endless conveyor strips, with a plurality of rigid transverse members such as rods extending therebetween, the transverse members being generally parallel and generally evenly pitched to define the pitch of the web. The endless conveyor strips pass around undriven guide rollers, consisting of at least a pair of such rollers laterally spaced to give the required length to the separation web.

The drive means then comprises a drive portion comprising a plurality of web engaging projections disposed consecutively at substantially the same pitch as the transverse members of the separation web such that in use several consecutive web engagement projections simultaneously engage the gaps between the said transverse elements to drive the web in a substantially linear manner.

Preferably, the separation web and drive means are co-operably mounted on a frame which allows for relative movement therebetween to bring the drive means into and out of engagement with the separation web.

The invention will now be described by way of example only with reference to Figures 1 and 2 of the accompanying drawings in which: Figure 1 illustrates the drive means in accordance with the invention in engagement with an endless belt separation web;

Figure 2 illustrates a mounting frame for the drive means of Figure 1 to move the drive into and out of contact with the separation web.

Referring to the Figures, a drive means in accordance with an embodiment of the invention is shown, together with, in Figure 1, a part of a conventional sieve web such as is used on agricultural or other machinery.

The sieve web consists of two flexible side tension strips (14), the ends of each strip being joined together to form a continuous conveyor loop, with the strips (14) being joined ladder fashion by means of bars (4). The length, width and bar spacing are altered to suit the particular application. The bars are evenly spaced and parallel, and the space between the bars defines the sieving dimension. The endless conveyor loops formed by the strips (14) pass around at least two separated guide rollers (not shown) so that the whole arrangement constitutes an endless conveyor web, with the separation of the two main guide rollers defining the length of the separation web. Only a portion of the upper surface is shown in Figure 1, being the portion driven by the drive means.

The strips (14) consist of a three-ply webbing core of nylon/terylene encased in rubber. The combination gives a reasonable degree of flexibility as the strips pass around the guide rollers to form the endless conveyor loop, and the rubber enhances grip and allows for profiling to enhance grip further. The transverse bars (4) are of a suitable rigid material, such as steel, and may be given a suitable coating to enhance weather resistance.

The drive means is shown in greater detail in Figure 1. The drive means consists of an endless conveyor (1) which in this instance is an endless conveyor belt of similar construction to the conveyor strips (14), although it

would be understood that other belt constructions, chains or the like could be used. The belt (1) has teeth in the form of projections in the rubber material on both the inside (15) and the outside (16). The teeth (15) are suitably configured to engage with corresponding teeth (12) on drive sprockets (3) of a main cylindrical drive. The teeth (16) are configured with a pitch to correspond with the pitch of the web bars (4) so as to engage with the web to be driven in the gaps between the web bars (4).

The drive belt (1) passes around the sprocket drives (3), and also passes around a guide cylinder (11) transversely spaced therefrom to form the endless conveyor loop. The distance between the guide cylinder (11) and main drive sprockets (3) determines the drive length, and is set so that the number of bars engaged relates to the expected load.

The particular advantages of the invention arise because the web moves substantially in a straight line through the drive. This is facilitated by the use of subsidiary guide pressure rollers (2a, 2b) acting to keep the drive belt (1) and the webbing conveyor (4,14) in close and effectively linear contact throughout the driven region.

In the embodiment, only the main drive sprocket (3) is provided with teeth which key directly into the drive belt (1), the guide drives and guide rollers (2a, 2b, 11) relying upon frictional engagement with their respective belts.

These guide rollers could of course be similarly sprocketed.

The drive and guide rollers are mounted on a frame (5) so as to bring the drive into engagement with an upper surface of the sieve web. Figure 2 shows a convenient arrangement for bringing the drive belt into and out of contact with the web.

In Figure 2 drives (2a), (3) and (11) are mounted upon the frame (5). The frame (5) has a lateral extension (5a) which pivots about a bearing (6) whereat it is mounted in association with the main web conveyor (for example on a main supporting frame thereof). This allows the frame (5) to be lifted into and out of engagement with the main web (not shown in Figure 2). In the embodiment, this is effected by lifting the frame out of contact using the cylinder (7) and returning to the operational position by means of the spring (8) operating against an adjustable stop (9).

The lateral extension (5a) of the frame (5) further incorporates a load cell (10) to continually or otherwise measure the straight line pull exerted on the web bars by the drive belt.

Claims

1. A drive for a separation web comprises a drive portion adapted to drivingly engage a drive engagement zone on a web to be driven, wherein the drive portion presents an elongate generally planar drive face for engagement with the said drive engagement zone such that in use the web is engaged in a similar generally planar manner along a portion of its length.

2. A drive for a separation web in accordance with claim 1 which comprises a plurality of web engaging portions disposed consecutively at substantially the same pitch as complementary drive engagement portions on the web to be driven, such that in use several consecutive web engaging portions simultaneously engage the complementary drive engaging portions of the web.

3. A drive in accordance with claim 2 wherein the engaging portions are complementary projections and recesses, comprising projections on the drive face complementary to recesses on the web, or vice versa, or some combination thereof.

4. A drive in accordance with claim 3 wherein the web to be engaged is of the ladder type comprising at least one pair of endless driven belts with generally evenly pitched transverse members and especially rigid members such as rods or web bars extending therebetween, and the engaging portions on the drive face comprise projections of substantially the same pitch as the gaps between the transverse members of a separation web to be engaged, the projections being configured to engage with the gaps between such transverse members.

5. A drive in accordance with any preceding claim comprising a continuous drive means.

6. A drive in accordance with claim 5 wherein the drive means comprises at least one continuous flexible drive belt or chain or the like, such that a portion of the belt or chain facing a web to be driven at a given time constitutes the drive face.

7. A drive in accordance with claim 6 wherein the continuous flexible drive belt or chain or the like passes about and is driven by at least one driven cylinder, and further passes about at least one laterally spaced further cylinder.

8. A drive in accordance with claim 7 comprising at least one non driving guide cylinder.

9. A drive in accordance with claim 6 or claim 7 wherein at least the driven cylinder has sprocket engagement means to engage with an inner surface of the drive belt or chain, and/or the inner surface of the drive belt or chain has means to receive the teeth of the said sprocket.

10. A drive in accordance with claim 8 wherein the drive belt comprises a webbing core, teeth moulded from rubber or like material disposed on an outer surface to engage the web to be driven as above described, and projections and/or recesses on a rubber or like material moulded inner surface to engage with the cylinder drive for example to receive sprocket teeth thereof.

11. A drive in accordance with any preceding claim wherein the drive means comprises a flexible endless belt with web engaging means on an outer surface thereof, for example web engaging teeth configured to engage the web, and in particular configured to engage the gaps between transverse web bars of a ladder type web consisting of at least a pair of endless web strips with laterally extending generally parallel bars of generally even pitch.

12. A drive in accordance with any preceding claim incorporating an epicyclic gearing system.

13. A drive in accordance with any preceding claim wherein the drive is adapted to engage the outside rather than the inside of the conveyor loop of the endless conveyor of a separation web.

14. A drive in accordance with any preceding claim wherein a support frame is provided to support the drive means, the support frame being adapted for mounting the drive means for use with a conventional web separator conveyor, preferably in a position external to the endless conveyor loop and in particular above the upper surface thereof.

15. A separation web and drive arrangement in accordance with claim 14 wherein the separation web is of the conventional ladder type, comprising at least one pair of endless conveyor strips, with a plurality of rigid transverse members such as rods extending therebetween, the transverse members being generally parallel and generally evenly pitched to define the pitch of the web, and wherein the drive means comprises a drive portion comprising a plurality of web engaging projections disposed consecutively at substantially the same pitch as the transverse members of the separation web such that in use several consecutive web engagement projections simultaneously engage the gaps between the said transverse elements to drive the web in a substantially linear manner.

15. A drive in accordance with claim 14 wherein the support frame incorporates means to move the drive into and out of contact with the separation web.

16. A drive in accordance with any preceding claim incorporating a load cell, provided with suitable data communication and/or data display means, associated with or integral with or attached to the drive means to measure the pull imparted on the conveyor web by the drive, and hence give an indication of the stresses and/or strains involved.

17. A separation web and drive arrangement comprising a separation web or the like of conventional design in combination with and adapted to be driven by a drive means according to any preceding claim.

18. A separation web and drive arrangement in accordance with claim 17 wherein the separation web is of the conventional ladder type, comprising at least one pair of endless conveyor strips, with a plurality of rigid transverse members such as rods extending therebetween, the transverse members being generally parallel and generally evenly pitched to define the pitch of the web, and wherein the drive means comprises a drive portion comprising a plurality of web engaging projections disposed consecutively at substantially the same pitch as the transverse members of the separation web such that in use several consecutive web engagement projections simultaneously engage the gaps between the said transverse elements to drive the web in a substantially linear manner.

Amendments to the claims have been filed as follows

CLAIMS 1. A drive for a separation web comprises a drive portion adapted to drivingly engage a drive engagement zone on a web to be driven, wherein the web to be engaged is of the ladder type comprising at least one pair of endless driven belts with generally evenly pitched transverse members and especially rigid members such as rods or web bars extending therebetween, and wherein the drive comprises a plurality of web engaging projections disposed consecutively at substantially the same pitch as the gaps between the transverse members of a separation web to be engaged, the projections being configured to engage with the gaps between such transverse members such that in use the drive presents an elongate generally planar drive face comprising several consecutive projections for simultaneous engagement with several consecutive such gaps comprising the drive engagement zone to drive the web.

2. A drive in accordance with claim 1 comprising a continuous drive means.

3. A drive in accordance with claim 2 wherein the drive means comprises at least one continuous flexible drive belt or chain or the like, such that a portion of the belt or chain facing a web to be driven at a given time constitutes the drive face.

4. A drive in accordance with claim 3 wherein the continuous flexible drive belt or chain or the like passes about and is driven by at least one driven cylinder, and further passes about at least one laterally spaced further cylinder.

5. A drive in accordance with claim 4 comprising at least one non driving guide cylinder.

6. A drive in accordance with claim 3 or claim 4 wherein at least the driven cylinder has sprocket engagement means to engage with an inner surface of the drive belt or chain, and/or the inner surface of the drive belt or chain has means to receive the teeth of the said sprocket.

7. A drive in accordance with claim 5 wherein the drive belt comprises a webbing core, teeth moulded from rubber or like material disposed on an outer surface to engage the web to be driven as above described, and projections and/or recesses on a rubber or like material moulded inner surface to engage with the cylinder drive for example to receive sprocket teeth thereof.

8. A drive in accordance with any preceding claim wherein the drive means comprises a flexible endless belt with web engaging means on an outer surface thereof, for example web engaging teeth configured to engage the web, and in particular configured to engage the gaps between transverse web bars of a ladder type web consisting of at least a pair of endless web strips with laterally extending generally parallel bars of generally even pitch.

9. A drive in accordance with any preceding claim incorporating an epicyclic gearing system.

10. A drive in accordance with any preceding claim wherein the drive is adapted to engage the outside rather than the inside of the conveyor loop of the endless conveyor of a separation web.

11. A drive in accordance with any preceding claim wherein a support frame is provided to support the drive means, the support frame being adapted for mounting the drive means for use with a conventional web separator conveyor, preferably in a position external to the endless conveyor loop and in particular above the upper surface thereof.

12. A drive in accordance with claim 11 wherein the support frame incorporates means to move the drive into and out of contact with the separation web.

13. A drive in accordance with any preceding claim incorporating a load cell, provided with suitable data communication and/or data display means, associated with or integral with or attached to the drive means to measure the pull imparted on the conveyor web by the drive, and hence give an indication of the stresses and/or strains involved.

14. A separation web and drive arrangement comprising a separation web or the like of conventional design in combination with and adapted to be driven by a drive means according to any preceding claim.