Filter belt edge structure

Abstract: The edge 17 of a filter cloth 18 is received in a slot 14 formed in an edge 13 of a planar part 12 of an edge strip 10, extending parallel to and preferably lying in the axis of the plane of said planar part 12. The edge strip also comprises a track portion 11 defining its outer edge and formed integrally with the planar part 12. The slot 14 may be formed by use of a hot air knife or by a metal blade and defines upper and lower flaps 15,16 which are adhered to the edge 17 of the cloth.

Description: This invention relates to edge structures of filter belts. It is known for example to provide a drum filter belt with a rubber edge track which runs in guides to keep the filter cloth running perfectly straight. The rubber edge track is attached to a fabric reinforcement strip by means of several rows of stitching and the fabric reinforcement strip is in turn secured to the edge of the filter cloth. In US 3327839, a conveyor apparatus is described wherein a reinforcement fabric is secured on top of each edge of a belt and a triangular sectioned rod is then secured to the top side of the reinforcement by bonding. In US 5391427 a filter belt edge structure is proposed wherein the edge of a filter belt cloth is received between upper and lower rods of a two-ply fabric reinforcement strip and an elongate track is also received between the rods of a two-ply fabric strip along the opposite edge thereof. The reinforcement strip is welded to the track and welded or stitched to the filter cloth. The various known edge structures are relatively complex and involve multiple stitching or bonding operations, and the presence of a reinforcing strip makes the edge region somewhat inflexible and an abrasion susceptible fabric region is present at the belt edges. It is an object of the invention to provide a simplified filter belt edge structure with improved flexibility and abrasion resistance properties. The invention therefore provides a filter belt edge comprising at least one length of fabric and an edge strip welded to at least one length edge of said fabric, the edge strip being bifurcated to provide a slot extending in the said plane to receive the said one edge of said fabric. The edge strip is preferably formed with an edge track portion of a standard cross section which is compatible with the machine on which the fabric, e.g. a filter cloth is to be used. The edge strip and edge track portion are preferably integrally formed. The bifurcation may define upper and lower flaps which are, after insertion of the said one edge of the fabric, in turn welded to respective upper and lower surfaces ofthe region of the fabric adjacent said one edge. The bifurcation may be a slot formed in the free edge of said strip by means of a hot air knife, or preferably heated metal blade. The slot extends along the free edge, penetrating some way into the strip and preferably along the centre line and in the plane of the strip. Alternatively, the bifurcation may be formed by moulding it into the strip as the strip is produced by extrusion through a die. The upper flap may be the first secured to the fabric, followed by the lower flap. The flaps may be secured to the fabric with the use of an adhesive or by thermal (eg hot air) or ultrasonic welding. From another aspect, the invention provides an edge strip for a filter belt comprising a planar part for extending in the plane of the filter belt cloth, the planar part being bifurcated to provide a slot extending in said plane to receive an edge of a filter belt cloth. A preferred embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:- Fig.1 is a cross-sectional view of an edge strip according to the further aspect of the invention, for a filter belt; Fig.2 shows a first stage in forming the edge strip of fig. 1 in the construction of a filter belt edge structure according to the invention; and Fig.3 is a cross sectional view of a completed edge structure of a filter belt in accordance with the invention. Referring first to fig. 1, an edge strip 10 for a filter belt comprises a rod like track portion 11 and a planar part 12 which is formed integrally with the track portion 11. The free edge 13 of part 12 opposite the track portion 11 is provided with a deep slot 14, which extends substantially along the centre line ofweb 12, along the length of the part and penetrating more than 50% of the distance from the edge 13 to the track portion 11. Slot 14 defines an upper flap 15 and a lower flap 16 and the slot 14 may be formed by use of a hot air knife or a metal blade. As shown in fig.2, the edge strip 10 is mounted on an edge 17 of a filter cloth 18 of a belt filter by receiving the edge 17 of the cloth into slot 14 and then adhering the upper flap 15 to the upper surface of filter cloth 18 by means of an adhesive, thermal (eg hot air) or ultrasonic welding. The lower flap 16 may be bent down out of the way (as shown) during this operation. To complete the edge structure, the lower flap 16 is then adhered in turn to the lower surface of the filter cloth 18 by the same method as used for the upper flap. The resulting edge structure is shown in fig.3 wherein the edge 17 of filter cloth 18 is received in the slot 14 of the edge strip 10, which provides as a simple integral structure an edging strip composed by planar part 12 and a track rod 11. This structure avoids the need to provide a separate edge track rod and an edge strip of eg fabric, and avoids the need for stitching or a multiple stage assembly operation. The structure also encapsulates the edge 17 of the belt cloth so that the edge is not exposed to abrasion or fraying, resulting in extended useful life for the filter cloth. The edge strip 10 may be of natural or synthetic rubber or of any suitable flexible and hard wearing plastics material. Thermoplastics with rubber like properties and a significant polyolefine content (eg Polypropylene) are preferred, such as for example SANTROPENE (trade mark). The fabric 18 may be a woven or nonwoven structure, typically a woven polypropylene monofilament fabric, between 1 and 20 metres long and made endless by steel seaming clips inserted into the belt ends, which clips are interdigitated and held together by a hinge wire. The material of the edge strip 10 is preferably vulcanised to confer temperature stability to the strip and the material may also have an olefin content which suffers under heat so as to impart the degree of adhesion sufficient to enable the fabric edge to be permanently bonded to the edge strip material. The slot 14 may extend, e.g. 30-80 mm into the strip, which may be 4-12 mm thick in the region of the slot.

Claims: An edge structure for a filter belt comprising at least one length of fabric and an edge strip lying in the plane of the fabric, the edge strip being bifurcated to provide a slot extending in said plane to receive said one edge of the fabric. An edge structure according to claim 1, wherein the edge strip comprises an edge track portion and planar part extending in the plane of the fabric, the edge track portion and the planar part being integrally formed. An edge structure according to claim 1 or claim 2, wherein the bifurcation defines upper and lower flaps on the planar part which are, after insertion of the said one edge of the fabric, in turn welded to respective upper and lower surfaces of the region of the fabric adjacent said one edge. An edge structure according to any preceding claim, wherein the bifurcation is a slot formed in the free edge of said strip by means of cutting means; said slot extending along the free edge and penetrating some way into the strip along or parallel to the centre line and in the plane of the strip. An edge structure according to claim 1, 2 or 3, wherein the bifurcation is formed by moulding as the strip is extruded through a die. An edge structure according to any preceding claim wherein the upper flap of the bifurcated edge strip has been first secured to the edge region of the fabric, followed by securement of the lower flap to said edge region. An edge strip for a filter belt comprising a planar part for extending in the plane of the filter belt cloth, the planar part being bifurcated to provide a slot extending in said plane to receive an edge of a filter belt cloth. An edge structure for a filter belt, including an edge strip according to claim 7. A filter belt having an edge structure according to any one of claims 1 to 6 or claim 8.

Inventors: MACQUET ANTHONY JOSEPH, MACQUET, ANTHONY JOSEPH
Applicants: MADISON FILTER 981 LTD, MADISON FILTER 981 LIMITED
Application year: 1998
Main classification: B01D33
IPC codes: B01D33, B01D29