Conveyor

Abstract: An endless conveyor having a belt which follows a helical conveying path over part of its length and comprises a plurality of self-supporting tiers, wherein the lowermost tier of the stack is supported by a plurality of trolleys (36) running around a support rail (30), the trolleys being individually driven around the support rail by an internal drum (13) which is driven in rotation also to drive the belt.

Description: This invention relates generally to conveyors and in particular to a conveyor of the kind which comprises an endless belt arranged to convey a product in a helical path consisting of a number of superimposed helically extending tiers. Conveyors of the above-described kind are known in which, at least at the inside or the outside of the helically conveying path, or possibly both, the tiers of the conveyor belt are self-supporting, i.e. by means of spacers or the like any one helically extending tier is supported by the one below it. In this case, means are necessarily provided for supporting the lowermost tier, and this means in effect determines the pitch of the helical conveying path. A known means for this purpose is a supplementary conveyor, which optionally may also be employed to drive the lowermost tier of the stack thereof. It is an object of this invention to provide an improved means of supporting the lowest tier of a helically extending conveyor belt. According to the invention, there is provided an endless conveyor belt a portion of the length of which is caused to follow a helical conveying path consisting of a plurality of tiers stacked one on top of the other in a self-supporting manner : at least on the inside of said path, the belt being drivable by a capstan located inside the helical conveying path and itself drivable in rotation about a generally vertical central axis, wherein the lowermost tier of the stack is supported by a plurality of spaced trolleys mounted on a fixed helically extending rail, the trolleys being individually driven directly by the internal capstan with a vertical component of movement while travelling around the helically extending rail, which extends in a helical path around the major part of a single turn of 360 degrees, and over the remaining minor part has a transition section via which in use the trolleys descend from a raised end of said major part to a lower starting point of said major part. Above the transition section, the conveyor belt may be supported by a fixed transition plate, beyond the end of which begins the next tier of the stack above the lowermost tier. For enabling the vertical component of movement whilst also being driven around the helically extending rail, the trolleys may be slidably attached to vertical guides carried by or forming part of the internal capstan. A preferred helically extending rail is a rail of generally round cross-section, the trolleys each having at least one wheel with a concavely curved rim for running on said rail. Additionally each trolley preferably has a pair of opposed rollers which engage opposite sides of the vertical guides of the capstan in order to maintain the trolley in a generally constant or upright orientation whilst being driven around the helically extending rail. The wheel or wheels on each trolley is or are preferably spring mounted to allow limited movements thereof generally along the radius of the helix defined by the helically extending rail. Additionally, said wheel or wheels is or are preferably carried by a supporting element which forms part of the trolley and is pivotally mounted about a vertical axis to allow limited turning movement of the wheels These measures ensure that the trolleys are free running in use, notwithstanding manufacturing deviations or tolerances from the helical path nominally defined by the support rail. The conveyor of the invention is more especially intended for conveying a product, such as a food product, within a confined space within which the product is to be treated, for example by freezing. At least the major components of the trolleys, and especially the at least one wheel and the opposed rollers thereof, are preferably made of ultra-high molecular weight (UHMW) plastics material, which has a low coefficient of friction, thus avoiding any requirement to lubricate the trolleys, is very resistant to abrasion, thus ensuring long life, and is non-absorbent to water, which is especially important in the context of industrial freezers. A conveyor in accordance with the invention is exemplified in the following description, making reference to the accompanying drawings, in which:- Figure 1 is a pictorial view of a spiral conveyor; Figure 2 shows a means in accordance with the invention for supporting the lowermost tier of the conveyor belt; Figure 3 is a side elevational view of one of the trolleys visible in Figure 2; and Figure 4 is a plan view of the trolley. Referring to Figure 1, reference numeral 10 denotes an Ashworth-type flexible conveyor belt. This belt, as known in the art, comprises transverse rods extending between articulated links which form the longitudinal edges of the belt, said rods supporting a flexible mesh of stainless steel wire or plastics material, which forms the surface of the belt on which in use a product is conveyed. By virtue of the articulated links, the belt is able to flex in such a manner that the transverse rods are displaced closer together at either one longitudinal edge of the belt than at the other, and also to flex in a direction transverse to the plane of the belt. This Ashworth-type belt is thereby able to follow a relatively tortuous conveying path. Figure 1 shows an endless Ashworth-type conveyor belt 10 whereat the belt is arranged, over a major part of its length, to follow a helical conveying path consisting of a stack of helically extending tiers 11. The Ashworth-type belt is intended to be used under a tension kept below a predetermined threshold, and in the case of a helical conveying path it is known to impart the drive from an internal capstan in the form of a drum or cage on the inside of the helix. In the present conveyor, the conveyor belt 10 is self-supporting on the inside of the helix, by means of spacer plates 20, and on the outside of the helix the conveyor belt is supported by a fixed helically extending guide (not shown, but carried on the inside of the vertical posts 17). Because this outer guide is required only to take part of the weight of the belt and the product, and is not required to extend across the product space, the helically extending tiers 11 of the conveyor belt 10 do not have to be spaced by a distance substantially exceeding that necessary for accommodation of the product. The guide on the outside of the helix is conveniently a lipped rail provided with a plastics capping on which the outer longitudinal edge of the conveyor belt 10 is supported and over which it can freely slide. The plastics capped rail supports the belt just inside the articulated links forming the outside longitudinal edge of the belt. Figure 1 shows the internal drum or cage 13 employed to drive the Ashworth-type belt 10. The return path of the conveyor belt, from the top back to the bottom of the helical conveying path, is generally indicated by reference 15. The spacer plates 20, for example provided on alternate conveyor links on the inside longitudinal edge of the conveyor belt 10, may be incorporated into the belt during manufacture thereof, but alternatively added to the belt as a separate production step. The plates 20 connect between a pair of transverse rods of the conveyor belt by means of a slot, in the case of at least one rod, so as not to detract from the flexibility of the belt. For further details of the above-described conveyor illustrated in Figure 1, reference may be made to our European Patent Application EP-A-0293095. The present invention is concerned with a means for supporting the lowermost tier of the conveyor belt. As the conveyor belt is supported by a fixed guide at its outside edge and is self-supporting at its inside edge, the supporting means for the lowermost tier effectively determines the pitch of the helical conveying path, to which the fixed helical guide for the outside edge of the belt must also conform. The supporting means in question is shown in Figures 2 to 4. Figure 2 shows that the capstan 13 comprises a cage-type drum with vertical bars 22 upstanding from a circular base 24, to which a drive is imparted by suitable power means (not shown) in use to drive the drum in rotation about a vertical centre shaft 26. The Ashworth-type conveyor belt, omitted from Figure 2 for reasons of clarity, is driven at its inside edge by a projecting rib 28 (see Figure 4) formed on a facing on each of the cage bars 22, which rib suitably cooperates with the inside edge of the belt. For simplicity, in Figure 2, only a few bars 22 of the drum are illustrated. For supporting the lowermost tier of the belt, there is provided a fixed support ring 30 in the form of a round cross-sectioned rail which over the major part 32 of its length extends in a helical path of pitch corresponding to the pitch of the helical conveying path. The remaining minor part of the ring comprises a transition section 34 returning from the upper end of the major part 32 to the lower starting point of the major part. Trolleys, generally referenced 36, are mounted on the support ring 30, and have upper surfaces 38 with which the inner edge of the belt directly cooperates for support. One trolley 36 is provided for each bar 22 of the internal drum 13, and each said trolley is directly driven around the support ring 30, individually and positively, by the bar with which it is associated. Thus, in use, the conveyor belt returning to the bottom of the stack via the return path 15 (Figure 1) is picked up by the trolleys 36 at the starting point 40 of the major part of the support ring 30 and moves with the trolleys 36 around the support ring until the start 42 of the transition section 34 is reached. The belt then slides over a transition plate 44, fixedly mounted with the support ring above the transition section 34 thereof, and at the end of this transition plate the belt engages over the start of the lowermost tier of the belt which is moving around the support ring with the trolleys. At the transition section 34, the trolleys 36 drop away from the belt and pass beneath the transition plate 44 to the lower level at which the belt is first picked up. The illustrated conveyor is especially although not exclusively intended for use in industrial freezing equipment, wherein a product is intended to be conveyed through a cold enclosure in order to freeze said product. Accordingly, the trolleys 36, shown in detail in Figures 3 and 4, are designed for use in the environment of an industrial freezer. Each trolley 36 comprises a rectangular block 50 of UHMW plastics material, below which is an inverted-U bracket 52 pivotally mounted to the block by vertical pivot bolt 54, with an anti-friction plastics washer 56 interposed between the lower surface of the block and the upper surface of the bracket. To one side of the bracket 52, the block 50 divides into two parallel arms 58 between which are spindle mounted two rollers 60 of UHMW plastics material. The rollers 60 are spaced apart for engaging and rolling on two opposite faces, the inner and outer faces, of a vertical bar 22 of the internal drum 13 (Figure 2). The bar 22 thus serves to drive the trolley around the support ring 30, whilst permitting its vertical component of movement in travel around the support ring and also maintaining the orientation of the trolley. Reverting to the pivotally mounted inverted-U bracket 52, this supports a wheel 62 of UHMW plastics material, said wheel having a concave peripheral edge face 64 for cooperation with the surface of the round cross-sectioned support ring 30. The wheel 62 is spindle mounted between the limbs of the bracket 52 with the interposition of two coil springs 66, which allow the wheel a freedom for limited movement along the spindle on which it is mounted, i.e. generally in the direction of the radius of the support ring. This freedom for limited movement, taken in conjunction with the pivotal mounting of the bracket 52 which carries the wheel, ensures free running of the trolley around the support ring 30 notwithstanding any small manufacturing deviations and tolerances which may cause said ring to depart from its nominally helical path. The trolley 36 is completed by a cover 70 of UHMW plastics material, which provides the upper surface 38 on which the inner edge of the conveyor belt rests when the trolley is being driven around the support ring 30 to define the lowermost tier of the helical conveyor. The use of UHMW plastics material for the major components of the trolleys 36 renders lubrication unnecessary, due to the low coefficient of friction of such material, whilst its hardness (and thus resistance to abrasion and durability) also assists in ensuring free movement of the trolleys up and down the vertical bars of the internal cage. The non-water-absorbent characteristic of the material is also important in the context of industrial freezers.

Claims: An endless conveyor having a belt (10) a portion of the length of which is caused to follow a helical conveying path consisting of a plurality of tiers (11) stacked one on top of the other, in self-supporting manner at least on the inside of the path, the belt (10) being drivable by a capstan (13) located inside the helical conveying path and itself drivable in rotation about a generally vertical central axis, characterised in that the lowermost tier of the stack is supported by a plurality of spaced trolleys (36) mounted on a fixed helically extending rail (30), the trolleys (36) being individually driven directly by the internal capstan (13), with a vertical component of movement while travelling around the helically extending rail (30), which extends in a helical path around the major part of a single turn of 360 degrees, and over the remaining minor part has a transition section (34) via which in use the trolleys (36) descend from a raised end of said major part to a lower starting point of said major part. A conveyor according to claim 1, characterised in that, above the transition section (34), the conveyor belt is supported by a fixed transition plate (44), beyond the end of which begins the next tier of the stack above the lower-most tier. A conveyor according to claim 1 or claim 2, characterised in that, for enabling the vertical component of movement whilst also being driven around the helically extending rail, the trolleys (36) are slidably attached to vertical guides (22) carried by or forming part of the internal capstan (13). A conveyor according to claim 3, characterised in that the helically extending rail (30) is a rail of generally round cross-section, the trolleys (36) each having at least one wheel (62) with a concavely curved rim for running on said rail. A conveyor according to claim 4, characterised in that each trolley (36) has a pair of opposed rollers (60) which engage opposite sides of the vertical guides (22) of the capstan in order to maintain the trolley in a generally constant or upright orientation whilst being driven around the helically extending rail (30). A conveyor according to claim 4 or claim 5, characterised in that the wheel or wheels (62) on each trolley (36) is or are spring mounted to allow limited movements thereof generally along the radius of the helix defined by the helically extending rail. A conveyor according to claim 6, characterised in that said wheel or wheels (62) is or are carried by a supporting element (52) which forms part of the trolley (36) and is pivotally mounted about a vertical axis to allow limited turning movement of the wheels. A conveyor according to any of claims 4 to 7, characterised in that at least the major components of the trolleys (36), and especially the at least one wheel (62) and the opposed rollers (60) thereof, are made of an ultra-high molecular weight (UHMW) plastics material which has a low coefficient of friction. A conveyor according to any of claims 1 to 8, characterised in that the conveyor is self-stacking by means of spacer plates (20) on the inside of the helical path and is supported by a fixed helical guide on the outside of said path.

Inventors: CAWLEY KEITH, CAWLEY, KEITH
Applicants: FRIGOSCANDIA FOOD PROCESS SYST, FRIGOSCANDIA FOOD PROCESS SYSTEMS AKTIEBOLAG
Application year: 1990
Main classification: B65G21
IPC codes: B65G17, B65G21, B65G15