Toothed belt having a woven fabric layer and method for making the same

Abstract

A toothed belt includes a toothed profile made of a base material and defining a toothed profile drive side and a far side facing away from the drive side. A woven ply has a thickness and is applied to the far side of the toothed profile. The woven ply has a first side in contact with the far side causing the base material to penetrate the woven ply at least partly at the first side thereof. The woven ply has a second side facing away from the first side. A coating of plastic on the second side causes the plastic to penetrate the woven ply at least partly at the second side. The base material and the plastic each penetrate the woven ply to an extent to cause the woven ply to be free of the base material and the plastic in an inner lying thickness region thereof.

Claims

1. A method for making a toothed belt from thermoplastic polyurethane, the toothed belt comprising: a toothed profile defining a toothed profile drive side and a far side facing away from said drive side; said toothed profile including a base material; a woven ply having a predetermined thickness and being applied to said far side of said toothed profile; said woven ply having a first side in contact with said far side causing said base material of said toothed profile to penetrate said woven ply at least partly at said first side thereof; said woven ply having a second side facing away from said first side; a coating of polymer on said second side of said woven ply causing said polymer to penetrate said woven ply at least partly at said second side; and, said base material and said polymer each penetrating said woven ply to an extent to cause said woven ply to be free of said base material and said polymer in an inner lying thickness region thereof with reference to said predetermined thickness; the method comprising the steps of: a) first extruding the base material of the toothed belt; b) during the extrusion of the corresponding exit die of the extruder, incorporating strengthening elements or tensile elements into the extruded material; c) forming the resultant precursor together with tensile elements between a forming wheel provided with the negative of the tooth pattern on its outer circumference and a belt that runs around the forming wheel with removal of heat to yield the finished toothed belt, where the belt wraps around the forming wheel over a wrap angle of about 200 under pressure; d) shortly before the precursor enters the wrapping arc of the forming wheel, running a woven ply onto the forming wheel and then indenting together with the precursor into the shapingly toothed outline of the forming wheel; wherein: i) the woven ply, on its side facing the forming wheel, before running into the forming wheel, has been provided with a coating of polymer, preferably polyethylene, such that the woven ply has been penetrated up to a penetration depth of 5 to 50% of the ply thickness (weave thickness) by the polymer coating; ii) the coated woven ply has then been preformed such that it already has essentially the geometry of the toothed form of the forming wheel even before it runs into the forming wheel; e) intermeshing then the woven ply preformed with the toothed form on the forming wheel and indenting into the shapingly toothed outline of the forming wheel together with the precursor; and, adjusting the viscosity of the base material of the toothed belt that includes thermoplastic polyurethane such that the polymer-coated woven ply preformed with the toothed form is indented into the precursor such that the woven ply is not penetrated by polyurethane in the inner lying thickness region.

2. The method of claim 1, wherein the coated woven ply is preformed such that a defined texture or crimping of the warp threads of the weave that forms the woven ply is conserved.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described with reference to the drawings wherein:

(2) FIG. 1 shows part of a toothed belt of the invention,

(3) FIG. 2 shows a schematic diagram of the construction of the toothed belt of the invention with the tooth pattern in an enlargement of detail A from FIG. 1, and

(4) FIG. 3 shows an enlargement of detail A from FIG. 1 under shear force stress.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

(5) FIG. 1 shows part of a toothed PU belt 1, the tooth profile 2 of which has been provided with a woven ply 3 on the outside. The woven ply 3 has, on its outside facing away from the tooth profile, a coating 4 of polyethylene, as becomes clear more particularly when viewed together with the enlargement of detail A from FIG. 1 in FIG. 2. The woven ply 3, in relation to its thickness 5, has firstly been at least partly penetrated on its side facing the tooth profile by base material of the toothed belt, while it has been at least partly penetrated on its outside by the polyethylene coating 4.

(6) FIGS. 1 and 2 thus show, as schematic diagrams of the construction of the toothed belt of the invention, the configurations of the features of the present toothed belt, i.e. the manner in which the woven ply lies on the actual raw material of the toothed belt (PU) and has been provided in turn with an outer coating (PE).

(7) The penetration depth of the polyethylene coating 4 into the woven ply 3 here is 37% of the ply thickness, i.e. of the weave thickness 5. The woven ply is free of penetration material in an internal thickness region 6, i.e. both free of polyethylene material and free of polyurethane base material of the toothed belt.

(8) In the toothed belt of the invention, the woven ply is thus preformed at the early stage of production such that it already has the tooth profile and does not have to be stretched out and pressed into the tooth pattern again. In combination with this, seepage or penetration of the PU material in the shaping is avoided, and 100% formation of the teeth is achieved. By virtue of the specific construction of the woven ply, in operation/in the toothed belt drive under stress, the surface tensions at the tooth flanks are reduced on meshing into the toothed disks. This reduces tooth wear and correspondingly increases the lifetime.

(9) FIG. 3 shows this very clearly once again by the detail A from FIG. 1, namely that, under shear force stress, the outer coating, i.e. the PE film 4 here, can move in a virtually force-free manner in relation to the inner structure of the belt tooth. The particular advantage of such a form of the toothed belt 1 is that this specific construction of the weave with an unpenetrated thickness region 6 can reduce the surface tensions at the tooth flanks on interdigitation into the toothed disks. This reduces tooth wear and correspondingly increases the lifetime.

(10) It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

REFERENCE NUMERALS

Part of the Description

(11) 1 Toothed belt 2 Tooth profile 3 Woven ply 4 Coating of the woven ply/polyethylene (PE) coating 5 Thickness of the woven ply 6 Inner unpenetrated thickness region