GB2037690A - Chain conveyors - Google Patents

Abstract

A conveyor comprising a track preferably defined by two spaced parallel rails, an endless conveyor band transversing said track and comprising link elements pivotally connected together and each presenting a load supporting surface, and means, conveniently permanent magnets for generating a magnetic field to maintain the link elements and the track in desired relationship. <IMAGE>

Description

SPECIFICATION Improvements in or relating to chain conveyors This invention relates to conveyors and more particularly to such conveyors as comprise a plurality of link elements, each presenting a load bearing surface, successively linked together by pivotal connections to form an endless band intended to traverse a track, including bends in a plane parallel to the load bearing surfaces of the link elements, defined by two generally parallel rails. Such a conveyor is, hereinafter, referred to as a "chain" conveyor and a special problem with such conveyors is that, due to forces in the chain elements at bends in the track, the elements tend to lift from the outer rail so that the load supporting surfaces of the links at said bends become inclined to the desired plane for conveying.

A chain conveyor of the type defined above and designed for the transportation of bottles, tins and like containers is disclosed in U.S. patent specification No. 3,262,550 and in this disclosure the problem of preventing links from lifting from the track on the outside of a bend is overcome by providing guide surfaces on the chain links below their load supporting surfaces, and which guide surfaces diverge away from the carrying surface, and providing at the bends guide surfaces in the vicinity of the track co-operable with the guide surfaces of the links.

Such mechanical means for keeping a conveyor chain flat on its track at a bend have a number of drawbacks in that, in addition to the inevitable guide means at the bend sections of the track, they require the formation of laterally projecting or inclined guide surfaces on all the links. In particular in the case of metallic links the provision of guide surfaces on the links will require an additional operation in link manufacture which makes the links relatively expensive and, in addition, can considerably weaken the links.

Tracks for chain conveyors of the type defined above have been standardized to a great extent that is to say, in practice, the shortest distance between the two rails constituting the track has a fixed value, namely, approximately 44 mm.

The hinge connection between adjacent links of the chain generally comprises a hinge pin, embraced by two spaced bearings connected to one link and a bearing of an adjacent link situated centrally between said two spaced bearings. Naturally, in order that the chain may traverse around a bend, the hinge connection must permit relative movement between the links in the plane of trasportation.

In the chain links described in U.S. patent specification No. 3,262,550, the lateral end faces of the outer bearings of each hinge are formed as guide surfaces diverging downwardly away from the road carrying surface, so that the bottom part of the hinge, i.e. the part of the hinge remote from the carrying surface is the broadest.

Accordingly, for the hinge to pass between the rails of the track in the straight portions of the latter, the broadest part of the hinge must not be broader than approximately 42 mm. This means, however, that at the point of connection, that is to say at the point of the force transmitting connection of the hinge to the carrying surface of the adjacent link, the hinge is less than 42 mm wide. In practice, compared with chains designed exclusively for straight paths, which therefore do not require anay guide surfaces for keeping the chain flat in any bends, this involves a weakening of approximately 20% with regard to the maximum permissible tensile force in the chain.

Another drawback of mechanical chain guides of the subject type in which in the bends, in one way or another, a guide surface of each chain link engages under a corresponding guide surface of the track, is that foreign body contaminations, such as grit from broken bottles, can deposit on the rails or enter between the guide surfaces to cause damage thereto, especially if one or other of the guide surfaces is made of soft synthetic plastics materials, frequently selected for their lower-friction characteristics.

The present invention seeks to provide a conveyor arrangement which does not require guide surfaces beneath the rails to maintain the coneyor band on the track.

According to the present invention there is provided a conveyor comprising a track, an endless conveyor band traversing said track and comprising link elements pivotally connected together and each presenting a load supporting surface, and means for generating a magnetic field to maintan the link elements and the track in desired relationship.

Preferably the track includes one or more bends in a plane parallel to the conveying run of the conveyor band and said magnetic field is limited to the, or each, bend.

Preferably, at least the load carrying part of each link element is made from a ferro-magnetic material.

Preferably the means for generating said magnetic field comprise permanent magnets.

Preferably said track comprises two spaced parallel rails.

In one embodiment in accordance with the invention said permanent magnets are located to generate a magnetic field adjacent the outer rail at the, or each, bend but preferably both said rails include permanent magnets and a field strip connects said magnets remote from the link elements.

In a preferred embodiment said track is defined by a field strip extending across the track width, spaced apart permanent magnets on one side of the field strip defining rails for one run of the conveyor band, and spaced apart permanent magnets on the other side of the field strip defining rails for another run of the conveyor band.

Preferably the track and/orthe links present low friction sliding surfaces.

In a preferred embodiment the track comprises two spaced apart rails and each link element presents a substantially rectangular load supporting surface, wider than the track, and guide surfaces intended to locate between said rails.

Preferably each link element presents at or adjacent one transverse edge region, two spaced apart bearings below the level of the under-surface of the load carring part of the link and, at or adjacent its other transverse edge, a bearing enterable between the two spaced bearings of an adjacent link and whereby adjacent links are pivotally connected together by a pivot pin through the two bearings of one link and the single bearing of the adjacent link.

Preferably the said bearings of said links lie between said rails and the outer faces of the two spaced apart bearings define the guide surfaces between said rails serving to guide the conveyor band along the track.

Preferably the whole of each link elemnt comprises a ferrous material.

Although electromagnets may be used, it has been found in practice that a good anti-tilt effect can be achieved with permanent magnets and chain links of ferro-magnetic material.

In a preferred embodiment of the invention, removable magnet units are mounted in the track, each of said units consisting of a field strip extending across the track width and permanent magnets on both the inner bend side and outside bend side and both above and below the strip, the magnets disposed below the field strip extending in a track for guiding the return run of the conveyor chain. The location and intensity of the magnetic field can thus be selected to suit requirements. As the magnets on the bottom side of the field strip guide the return run ofthe chain, hold-down rollers, commonly employed to prevent sagging and/or tilting of the return run, can be omitted.

The invention will now be described further by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a bend section of a conveyor according to the present invention; Figure 2 is a cross-sectional view on the line ll-ll of Figure 1, on an enlarged scale; and Figure 3 is a cross-sectional view similar to Figure 2, and showing an alternative embodiment of the invention.

Referring to the drawings, a conveyor frame comprising upstanding side walls 1 and 2, supports a track defined by rails 3 and 4. Resting on the rails 3 and 4 is a link chain, composed of chain links of ferrous material 5, each provided at one end with spaced apart hinge bearings 6 and on the other end with a centrally situated hinge bearing 7. The hinge bearing 7 of each link 5 locates between the bearings 6 of the adjacent link 5 and a hinge pin 8 passes through the bearings 6 and 7.

In the embodiment shown in Figures 1 and 2, rails 3 and 4 are provided, at least in the bend sections, with permanent magnets 9 and 10, which may be formed as elongated permanent magnets each extending throughout the bend section of its respective rail 3 or 4 or, alternatively, an array of short magnets may be provided around the inner bend and outside bends defined by rails 3 and 4. Magnets 9 and 10 are accommodated within rails 3 and 4, which are hollow, and connected at their underside by a field strip 11, that is to say, a strip of a material having a high magnetic permeability, such as soft iron, so that, together with the chain of magnetizable material, resting on rails 3 and 4, a closed force field is formed as indicated by dash-dot lines.

The horizontal guidance of the chain is effected by hinge bearings 6,7 being confined between rails 3 and 4, and the vertical "guidance" is effected by magnets 9 and 10.

In order to reduce the resistance which the chain has to overcome in its movement over the rails, a plastics moulding 12 may be provided on each rail.

Good results are obtained with a high molecular weight polyethylene, a soft and wear resistant material.

In the preferred embodiment of the invention, illustrated in Figure 3, the magnet chain guide for each bend section is composed of one or more lengths of a unit consisting of a field strip 11' with magnets at both the upper and the underside, namely, magnets 9 and 9' at the inner bend side and magnets 10 and 10' at the outside bend. Here again, a closed force field can be provided by a proper selection of the polarity of the magnets, but not in this instance through field strip 11' but at the underside by a return run R of links 5 and at the top by the links 5 in the conveying run T of the chain.

As the drive for the chain forms no part of the present invention, said drive will not be described herein and it will be understood that the chain drive may comprise any conventional drive and may for example employ sprockets engaging with the chain links.

Although the present invention has been described by way of example many modifications and variations will be apparent to persons skilled in the art within the scope of the appended claims.

Claims (14)

1. A conveyor comprising a track, an endless conveyor band traversing said track and comprising link elements pivotally connected together and each presenting a load supporting surface, and means for generating a magnetic field to maintain the link elements and the track in desired relationship.

2. A conveyor as claimed in claim 1 in which the track includes one or more bends in a plane parallel to the conveying run of the conveyor band and said magnet field is limited to the, or each, bend.

3. A conveyor as claimed in claim 1 or 2 in which at least the load supporting part of each said link element is made from a ferro-magnetic material.

4. A conveyor as claimed in claim 1 or 2 or 3 in which the means for generating said magnetic field comprise permanent magnets.

5. A conveyor as claimed in any preceding claim in which said track comprises two spaced parallel rails.

6. A conveyor as claimed in claims 4 and 5 in which said permanent magnets are located to generate a magnetic field adjacent the outer rail at the or each bend.

7. A conveyor as claimed in claims 4 and 5 or 6 in which both said rails include permanent magnet and a field strip connects said magnets remote from the link elements.

8. A conveyor as claimed in any preceding claim in which said track is defined by a field strip extending across the track width, spaced apart permanent magnets on one side of the field strip defining rails for one run of the conveyor band, and spaced apart permanent magnets on the other side of the field strip defining rails for another run of the conveyor band.

9. A conveyor as claimed in any preceding claim in which the track and/or the links present low friction sliding surfaces.

10. A conveyor as claimed in any preceding claim in which the track comprises two spaced apart rails and each link element presents a substantially rectangular load supporting surface, wider than the track and guide surfaces intended to locate between said rails.

11. A conveyor as claimed in any preceding claim in which each link element presents at or adjacent one transverse edge region, two spaced apart bearings below the level of the undersurface of the load carrying part of the link and at or adjacent its other transverse edge a bearing enterable between the two spaced bearings of an adjacent link and whereby adjacent links are pivotally connected together by a pivot pin through the two bearings of one link and the single bearing of the adjacent link.

12. A conveyor as claimedin claim 10 and 11 in which the said bearings of said links lie between said rails and the outer faces of the two spaced apart bearings define the guide surfaces between said rails and serving to guide the conveyor band along the track.

13. A conveyor as claimed in anypreceeding claim in which at last the load carrying part of each link element is made from a ferrous material.

14. A conveyor substantially as hereinbefore described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.