WO2003068638A1

WO2003068638A1 - Conveyor belt training idler roller and installations including same

Info

Publication number: WO2003068638A1
Application number: PCT/IB2003/000443
Authority: WO
Inventors: Douglas John Cumberlege
Original assignee: Douglas John Cumberlege
Priority date: 2002-02-11
Filing date: 2003-02-11
Publication date: 2003-08-21
Also published as: WO2003068639A1; AU2003205967A1; AU2003245717A1

Abstract

A training idler roller of the type in which the entire outer surface of the roller rotates as a single unit along its length and wherein the idler roller is rotatably supported by a support assembly (7, 8, 9, 11) that enables the roller to slew about an axis (5) that is operatively transverse to a conveyor belt supported by the idler roller. The idler roller has, in its outer surface (12) a central circumferentially extending band (13) that ehibits a lower coefficient of friction with a cooperating conveyor belt than the coefficient of friction between the belt and the balance of the outer surface of the idler roller. The central band may be a recessed band (13) so that there is no contact between the belt and band in that area in use thereby creating a zero friction situation, or it may be defined by a material different from the material defining the balance of the outer surface of the roller. The low friction exhibited on the central band of a conveyor belt enables the friction of the roller surface to each side of the band to effect a steering action on the roller. An installation including such a training idler roller is also described.

Description

CONVEYOR BELT TRAINING IDLER ROLLER AND INSTALLATIONS

INCLUDING SAME

FIELD OF THE INVENTION

This invention relates to a conveyor belt training idler roller of the type that is adapted to slew about a pivot axis generally transverse to the plane of the conveyor belt in order to steer the belt back towards a central position on the idler roller when the belt tends to drift laterally to one or other side of the intended conveyor path. The invention also relates to conveyor belt installations including such a training idler roller.

Still more particularly, but not exclusively, the invention is concerned with a conveyor belt training idler roller that can be used effectively in conveyor belt installations in which the belt moves rather slowly such as are typical in the food industry.

BACKGROUND TO THE INVENTION

It is well known in the art that conveyor belts in general require some form of steering facility for returning a conveyor belt to a central position on its support rollers whenever it tends to drift laterally to one or other side of the desired path of movement during operation. Various solutions have been proposed and implemented.

Some of these employ arrangements that engage the edges of the conveyor belt in order to urge the conveyor belt inwards to a central position whenever it drifts away from such a central position. These are considered by applicant to be undesirable, particularly in the food industry, as a result of the fact that the edges of the conveyor belt become frayed or damaged relatively rapidly. Because the damaged areas can allow bacteria to set in, the conveyor belt must be replaced.

Other devices generally tend to fall into one of two categories. The first is that of complex devices in which the position of the edge of a conveyor belt is continuously monitored, optically for example using optical fibres or infrared radiation, or electronically. In this case sophisticated pneumatic, hydraulic, or electrical steering mechanisms are activated to impart movement to a training roller to counteract the lateral drift of the conveyor belt. These complicated devices are, in the first place, generally costly and, secondly, often require significant maintenance in view of their complexity.

The other general category of training rollers is that of freely rotatable training idler rollers wherein the lateral movement of the belt itself is arranged to achieve the steering effect and it is to this category that the present invention belongs.

One general arrangement in this category is described in United States patent No 2,330,923 to Samuel D Robins. In this case a training idler roller is pivotally mounted centrally of the length of the roller (in other words centrally across the width of the conveyor) and internally on a support shaft so as to be capable of slewing within the limits around an axis transverse, and in particular at right angles to, the conveyor belt that is being supported. The outer surface of the roller is crowned so that its outer diameter decreases from the centre of the roller towards each end and drag created by engagement of the belt with the roller surface tends to slew the idler roller about the pivot axis when the belt drifts laterally towards one or other end of the roller. This results from the increased drag on that side of the pivot.

Subsequent United States patent number 5,911 ,304 describes this type of arrangement with a somewhat improved bearing construction and wherein the crowned effect is achieved by tapering the two ends of the outer surface of the roller.

This simple expedient operates effectively in many different applications in which belt speeds are relatively high and the conveyor belts themselves are of a robust, generally heavy duty, construction.

However, applicant's attempts to apply the simple principles set out in the patents referred to above has not met with adequate success in the case of the slow-moving, relatively thin and insubstantial conveyor belts typical of such industries as the food industry.

These slow-moving conveyor belts, typically moving at speeds of from 1 mm to 500 mm (about 0.04 to about 20 inches) per second, are often composed of mono film belting, extruded plastic sheet or even textile or webbing materials that may be as thin as 1 mm (about 0.04 inches) or even less in some instances, have not been successfully tracked, as far as applicant is aware, utilizing training idler rollers of this general type.

OBJECT OF THE INVENTION

It is an object of this invention to provide a training idler roller of the latter general type that exhibits a satisfactory steering effect and, more particularly, enhanced sensitivity to the lateral drift of a conveyor belt supported thereon. It is another object of the invention to provide an installation including such training idler roller.

SUMMARY OF THE INVENTION

In accordance with one aspect of this invention there is provided a training idler roller comprising an idler roller having an outer surface for contacting and supporting a conveyor belt in use and wherein said outer surface rotates as a single unit along the entire length of the roller, the idler roller being rotatably supported by a support assembly that enables the roller to slew about an axis that is operatively transverse to a conveyor belt supported by the idler roller, the idler roller being characterized in that its outer surface has a central circumferentially extending band that exhibits a lower coefficient of friction with a cooperating conveyor belt than the coefficient of friction between the belt and the balance of the outer surface of the idler roller.

Further features of this aspect of the invention provide for the central band to be either a recessed band so that there is no contact between the belt and band in that area in use thereby creating a zero friction situation, or alternatively, for at least the surface of the band to be defined by a material different from the material defining the balance of the outer surface of the roller, typically a low friction material such as polytetrafluoroethylene (PTFE), high-density polyethylene, a silicon based low friction material or other low friction material; for the support assembly to comprise a pivot arrangement positioned generally centrally of the length of the roller and internally thereof such that the pivot axis may be operatively transverse to a conveyor belt in contact with the outer surface of the roller; for the support assembly to include, on the outside of each end of the roller, a resistance element, generally, but not necessarily, a non-rotatable element, conveniently a disc, providing a skid surface adjacent and in line with the operative support surface of the roller so that a conveyor belt drifting off the roller will contact the skid surface and friction between the belt and skid surface will slew the roller about said axis upon contact between the conveyor belts surface and skid surface; and for the diameter of the outer surface of the idler roller to be constant along the entire length of the roller (other than in the region of said band when said band is defined by a groove) or, alternatively, for the end regions of the outer surface of the idler roller to be tapered, preferably with an angle of taper of about one to about three degrees. The width of the low friction, or no friction band is highly significant and will depend entirely on circumstances. In particular, in instances in which the band is formed by a groove, the width thereof will be limited by the characteristics of the conveyor belt that it supports and, in some cases, a groove will be inappropriate such as in applications to extremely thin conveyor belts used for example as cooler belts in the chocolate industry. This results from the general tendency of the central region of the belt to collapse at least partially into the groove in the event that the belt is insufficiently rigid to bridge the groove effectively. In instances in which the band is defined by a low friction material compared to the balance of the outer surface of the roller, the width of the low friction band can be greater as the belt is adequately supported throughout the width of the roller.

As a general rule, the wider the band the more sensitive or faster the reaction to a lateral drift of the conveyor belt. Nevertheless, as a general indication, in the case of a groove, the width thereof will generally range from about 2% to about 20% of the length of the roller, preferably from about 4% to about 10% of the length thereof. In the case of the band being formed by the outer surface of a low friction material substantially coplanar with the balance of the outer surface of the belt, the width of the band could be as much as about 50% of the width of the belt.

In accordance with a second aspect of the invention there is provided a conveyor belt installation comprising a series of support rollers supporting a conveyor belt in conventional endless manner and wherein the installation includes a training idler roller as defined above installed in the return pass of the conveyor belt between two non-training idler rollers, the arrangement being such that the angle of contact (wrap) between the conveyor belt and training idler roller is from 15 to 180 degrees, preferably from about 40 to about 150 degrees. In order that the above and other features of the invention may be more fully understood different embodiments of the invention will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:-

Figure 1 is a schematic plan view illustrating the general mode of operation of a training idler roller according to the invention;

Figure 2 is a schematic side elevation of a portion of the length of a conveyor belt installation including a training idler roller according to the invention and illustrating the angle of wrap;

Figure 3 is a sectional elevation of one embodiment of idler roller according to the invention;

Figure 4 illustrates, in a view similar to Figure 3, a variation in the formation of the central band in the outer surface of the roller as well as an alternative pivot assembly;

Figure 5 illustrates in exploded detail of the basic compliments of the pivot assembly illustrated in Figure 4;

Figure 6 illustrates an embodiment of the invention in which resistance elements having skid surfaces have been added to the construction illustrated in Figure 3 and still further illustrates another alternative pivot assembly;

Figure 7 illustrates an embodiment similar to Figure 6 wherein the outer surface of the roller is provided with tapered zones and wherein an alternative support assembly is employed; and,

Figure 8 is a schematic end view of the embodiment of the invention illustrated in Figure 7.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

Referring firstly to Figures 1 and 2, the training idler roller according to the invention, generally indicated by numeral (1), is most effectively introduced into a conveyor belt installation in the return pass (2) of a conveyor belt (3).

In this embodiment of the invention the idler roller is installed between two freely rotatable conventional idler rollers (4) supporting the return pass of the conveyor belt, but, unlike the conventional installation, it is installed below the level of the two coplanar horizontal rollers (4) so that an increased angle of wrap around the training idler roller is achieved. The exact angle of wrap required will vary from one application to the next and according to the nature of the belt and the nature of the surface of the rollers themselves and will generally have to be established empirically at the present state of development of the invention for each particular application. The angle of wrap is indicated by the letter "A" in Figure 2. Clearly, this angle can easily be changed simply by adjusting the spacing between the two conventional rollers (4) or adjusting the vertical position of the training idler roller (1).

As will be more fully described below the training idler roller is mounted so that it is freely rotatable, within restricted limits, about an axis indicated by numeral (5) that is generally vertical so that it can rotate about this axis when subjected to unequal forces (drag) on each side of the centre of the conveyor in order to direct the conveyor belt back to a central position. The exact direction in which the axis (5) extends relative to the conveyor belt will usually be at right angles to the belt, but certain steering effect can be achieved by inclining the axis somewhat forwards or rearwards relative to the direction of travel of the belt. The general functioning of such a training idler roller is set out in the earlier patents referred to above as well as earlier US patent No 1 ,833,180 and the disclosure of those patents is incorporated herein by reference.

Referring now particularly to Figure 3, the training idler roller has a tubular base (6) mounted so as to be freely rotatable about its own axis. This is achieved by means of a pair of laterally spaced bearings (7) carried on an inner sleeve (8) through which a support shaft (9) passes with appreciable clearance that is indicated by numeral (10). The inner sleeve is carried by a pivot and journal arrangement indicated by numeral (11) so that the roller and sleeve can slew about the axis (5) in order to achieve the steering effect referred to above. As indicated above, the axis of the pivot will be generally transverse and, in particular, generally at right angles to the belt where it passes over the roller. It should be pointed out that this axis could be at an incline to the belt but in that case the belt itself is restricted to movement in only one direction, that is, the direction towards which the pivot is inclined.

In this embodiment of the invention the outer surface of the roller is defined by that of an elastomeric layer (12) bonded onto the tubular base and the surface of which is of constant outer diameter for the entire length of the roller. As provided by this invention the outer surface of the roller has a central band of relatively low coefficient of friction, and in this embodiment of the invention the band assumes the form of the a groove (13) that simply remains out of contact with the belt and therefore exhibits no friction with the belt.

Tests were conducted on a pair of identical training idler rollers constructed as indicated above. Each roller had an outer diameter of 80 mm and a length of 500 mm and outer layer was made of white food grade rubber having a Shore hardness of 45. The only difference between the two training idler rollers was that one had a central groove, as described above, with a width of 20 mm. The belt was a 400 mm monofilm single ply food grade belt made of polyurethane surface coated with polyvinylchloride (PVC).

In the case of the roller not having the groove, when the belt was purposely steered to the outer edge of the roller, the belt remained at the outer edge for about one minute and then drifted on both sides of the centre to an extent of about 50 mm.

In the case of the roller having the groove, however, the belt was immediately steered back to the centre of the roller and there was an overrun of only 5 to 8 mm. The results were generally the same when lesser drifts were purposely imposed on the belts steered by the two rollers.

The use of a groove to define a friction free band encircling the roller will only be appropriate in the event that the conveyor belt is adequately self- supporting and does not tend to deform into the groove. The latter would be undesirable and impose unnecessary wear on the belt.

In instances in which the conveyor belt would thus deform or, in fact, in any event, the outer surface of the central band could be that of a band (14) of material set into a groove or space between zones of material defining the balance of the outer surface (15) of the usual rubber material (16) as illustrated in Figure 4. This material is chosen to exhibit a low coefficient of friction when compared to that of the balance of the outer surface with the same result as indicated above. The material could be a PTFE or high- density polyethylene material as already indicated. In general, it is envisaged that the band of low coefficient of friction could have a Shore hardness of from 95 to 120 on the D scale whilst the Shore hardness the surface and in the higher the ignition friction could be from 45 to 50 Shore hardness. The steering effect achieved using a band of low friction in the centre of the length of the training idler roller can be enhanced in different ways, as may be required.

Referring now to Figure 6 of the drawings, one method of enhancing the steering effect is to provide a resistance element, in this case in the form of a skid disc (17), at each end of the roller. In the event that the belt drifts off the edge (18) of the roller, it will contact a skid surface (19) that does not move relative to the sleeve (20) carried by the support shaft (21) or, alternatively, is associated with a rotatable disc that has resistance applied to its freedom of rotation. The frictional force applied by the belt to the skid element immediately steers the roller to move the belt back to the centre thereof.

Figures 7 and 8 illustrate an alternative form of support assembly for the roller on a support shaft and, in this case, the pivot is replaced by a self aligning ball bearing (22) carried on a centre bush (23). The centre bush has a pair of oppositely directed extensions that are each provided with two oppositely directed flat faces (24) that each cooperate with flat faces (25) in a slotted bush (26). Cooperation between these flat faces restricts slewing movement of the roller relative to the support shaft to a plane that is generally parallel to the plane of the conveyor belt. The cooperation between the flat faces (24) and (25) is best the illustrated in Figure 8. Smooth and stable support of the roller base (27) is achieved by means of a pair of laterally spaced roller bearings (28) one of which is supported on each slotted bush within the base.

Figure 7 also illustrates an alternative or additional expedient for enhancing the steering effect provided by the low friction band in the outer surface of the training idler roller. In this case, the outer surface of the roller is provided with a gently tapered portion (29) on each side of a central portion (30) in which the low friction band is located. In this embodiment of the invention each of the portions (29) and (30) extends for about one-third of the total length of the roller.

A further alternative pivot assembly is illustrated in Figure 4 in which the inner sleeve has a pair of oppositely located caps (31) each of which has a part spherical recess (32) (see clearly in Figure 5), and the shaft (33) has corresponding part spherical recesses (34) so that a pair of steel bulls (35) can be seated in the oppositely located part spherical recesses that a diametrically opposite each other to form the pivot. One of the caps, or alternatively both, (31a) and could be made adjustable in order to ensure that correct seating of the balls is achieved.

A still further alternative pivot is achieved by forming a part spherical ball and knuckle (36), as shown in Figure 6, with the restriction the two diametrically opposite coaxial pins restricts the ball and knuckle to movement about a single axis (38) that is generally at right angles to the belt, in the manner indicated above. The part spherical ball could be in made integral with a journal (39) fitting on the shaft (21) and the knuckle fixed to the inner sleeve (40).

It is also to be noted that the expedient employed for enhancing the steering effect described with reference to Figure 5, that is to say the skid surfaces, could be used in combination with the tapered surfaces described with reference to Figure 7 so that all three expedients can be used together.

It will be understood that numerous other embodiments of the invention possible without departing from the scope of the invention. In particular, as indicated above, the width of the low friction band could be substantially greater than that illustrated in Figure 4 and, in the case that the band is a solid surface, it could be as wide as the centre of the length of the roller as indicated by numeral (41) in Figure 6.

Claims

CLAIMS:

1. A training idler roller comprising an idler roller (1) having an outer surface for contacting and supporting a conveyor belt (2) in use and wherein said outer surface rotates as a single unit along the entire length of the roller, the idler roller being rotatably supported by a support assembly (7, 8, 9, 11) that enables the roller to slew about an axis (5) that is operatively transverse to a conveyor belt supported by the idler roller, the idler roller being characterized in that its outer surface (12) has a central circumferentially extending band (13,14, 41) that exhibits a lower coefficient of friction with a cooperating conveyor belt than the coefficient of friction between the belt and the balance of the outer surface of the idler roller.

2. A training idler roller as claimed in claim 1 in which the central band is a recessed band (13) so that there is no contact between the belt and band in that area in use thereby creating a zero friction situation.

3. A training idler roller as claimed in claim 1 in which at least the surface of the band (14) is defined by a material different from the material defining the balance of the outer surface (16) of the roller.

4. A training idler roller as claimed in claim 3 in which the material defining the surface of the band is a low friction material selected from polytetrafluoroethylene (PTFE), high-density polyethylene, and a silicon based low friction material.

5. A training idler roller as claimed in any one of the preceding claims in which the support assembly comprises a pivot arrangement positioned generally centrally along the length of the roller and internally thereof such that the pivot axis may be operatively transverse to a conveyor belt in contact with the outer surface of the roller.

6. A training idler roller as claimed in any one of the preceding claims in which the support assembly includes, on the outside of each end of the roller, a resistance element (17).

7. A training idler roller as claimed in any one of the preceding claims in which the resistance element is a non-rotatable element providing a skid surface (19) adjacent and in line with the operative support surface (18) of the roller so that a conveyor belt drifting off the roller will contact the skid surface and friction between the belt and skid surface will tend to slew the roller about said axis (5, 38) upon contact between the conveyor belt surface and skid surface.

8. A training idler roller as claimed in any one of the preceding claims in which the diameter of the outer surface of the idler roller is constant along the entire length of the roller (other than in the region of said band when said band is defined by a groove).

9. A training idler roller as claimed in any one of claims 1 to 7 in which the end regions (29) of the outer surface of the idler roller are tapered.

10. A training idler roller as claimed in claim 9 in which the angle of taper is about one to about three degrees.

11. A training idler roller as claimed in any one of the preceding claims in which the low friction band is a groove whereof the width ranges from about 2% to about 20% of the length of the roller.

12. A training idler roller as claimed in claim 11 in which the width of the groove ranges from about 4% to about 10% of the length of the roller.

13. A training idler roller as claimed in any one of the preceding claims 1 in which the low friction band is formed by the outer surface of a low friction material substantially coplanar with the balance of the outer surface of the belt and the width of the band ranges up to about 50% of the length of the roller.

14. A conveyor belt installation comprising a series of support rollers (4) supporting a conveyor belt in endless manner and wherein the installation includes a training idler roller as claimed in any one of claims 1 to 13 installed in a return pass of the conveyor belt between two non- training idler rollers, the arrangement being such that the angle of contact (wrap) between the conveyor belt and training idler roller is from 15 to 180 degrees.

15. A conveyor belt installation as claimed in claim 14 in which the angle of contact is from about 40 to about 150 degrees.