TYRE CHAIN LINK WITH ANTI-SLIP FORMATIONS

Abstract: A link for a tyre chain (10) including a tread portion and flanking side-wall portions with at least the tread portion comprising vertically extending links (12), three or four of which are interconnected by horizontal connectors (14) to form a mesh of a desired shape. The link comprises a base portion (16), a medial portion (18) and a head portion (22), with at least one traction member (15, 30, 32, 36) of a material that is relatively harder than the material of the link partially embedded in the head portion and partially exposed on the surface of the head portion. The traction member may be in the form of tungsten carbide buttons (15, 30) or plates (32) secured in holes in the head portion of the link or may be in the form of a plurality of particles consolidated in a cemented compact or steel matrix (36) that is secured to the head portion of the link, either by being cast or formed on the head portion or by being provided on a body (38) that is weldable to the head portion.

Description: TYRE CHAIN LINK WITH ANTI-SLIP FORMATIONS TECHNICAL FIELD: This invention relates to steel chain links, having application primarily, though not exclusively, in tyre chains for heavy duty vehicles, such as for mining, quarrying, earth-moving and forestry applications, to protect the rubber tyres on one or more axles of such vehicles and/or provide additional traction. BACKGROUND ART: Tyre chains of the type with which this invention is concerned have a tread portion spanning the tread of a tyre and two flanking side-wall portions that respectively span a portion of the inner and outer side-walls of the tyre. The chain is composed of links that extend substantially normal to the surface of the tyre and connecting rings or connectors interconnecting the links to form a net of a desired pattern. This type of tyre chain is referred to as "a tyre chain of the type set forth" below. Tread links each comprise a base portion to provide a smooth, suitably large contact area with a tyre in use; a medial portion formed with at least one opening through which a connector can be threaded, with the lateral thickness being reduced relatively to the base portion to permit increased lateral movement with respect to the connectors; and a head portion of a shape suited to the intended application of the chain. A broad head portion that may have a diamond shape decreases the mesh opening and thereby increases protection, whilst a relatively thinner head portion decreases protection and increases traction. Protrusions in the form of ribs or buttons of the material of the link of various configurations, shapes and sizes may be provided to increase traction, but these have limited long term value as they wear away fairly rapidly in use, particularly if they are operated in highly abrasive conditions such as chrome mines, smelting works and on silica. Whilst increasing the hardness of the link to inhibit wear is possible, the benefits obtained are usually more than counteracted by the increased tendency of the link to fracture or break in use. This invention seeks to provide a link for a tyre chain that has a reduced tendency to slip in use and/or has increased resistance to wear. Optionally the invention seeks to provide a method of modifying a tyre chain to increase the traction and/or wear resistance properties thereof; to provide a method of restoring tyre chains that have worn in use; and/or to provide parts or components for use in the aforesaid methods or in a tyre chain. DISCLOSURE OF THE INVENTION: The invention provides a link for a tyre chain of the type set forth comprising a base portion, a medial portion and a head portion, characterised in that the link has at least one traction member of a material that is relatively harder than the material of the link partially embedded in the head portion and partially exposed on the surface of the head portion. The link may have the following features, alone or in combination: - the traction member may be in the form of a solid body, such as a cylinder that is preferably substantially round in cross-section or a thick plate locked in an opening formed in the head portion of the link; -- a plurality of such solid body traction members may be arranged at desired positions on the head, either adjacent to or spaced apart from one another; ~ the traction member may be in the form of a particle in which event a plurality of such particles are preferably consolidated in a cemented compact or steel matrix; - the traction member is of a suitable hard, abrasion resistant carbide, nitride and the like compounds in particle, cemented or sintered form; - the traction member or members are secured to a body that is weldable to the head portion of the link. The latter form is particularly suited to restoring links that have worn in use, but may also be used for new chain links. The invention also includes a tyre chain of the type set forth characterised by having at least one link of the invention. Further features, variants, and/or advantages, of the invention will become apparent from the following, non-limiting description made with reference to the accompanying schematic drawings of presently preferred examples of the invention and from the claims, which are to be regarded as an integral part of this description. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a portion of a tread portion of a tyre chain including links of the invention; Figure 2 shows a side view of a link of the invention; Figure 3 shows an end view of the link of Figure 2; Figure 4 shows a plan view of the link of Figure 2; Figure 5 shows a side view and a cross-section of an embodiment of traction member for a link of the invention; Figure 6 shows a side view and a cross-section of another embodiment of traction member for a link of the invention; Figure 7 shows a side view and an end view of another embodiment of traction member for a link of the invention; Figure 8 shows a side view and an end view of yet another embodiment of traction member for a link of the invention; Figure 9 shows plan and sectioned side and end views of an embodiment of tread member of the invention; and Figure 10 shows plan and sectioned side and end views of yet another embodiment of tread member of the invention. BEST KNOWN MODE FOR CARRYING OUT THE INVENTION and DESCRIPTION OF PREFERRED EMBODIMENTS: In the drawings the same or similar parts have the same reference numbers, certain parts having sub-numbers to identify them for this description. Figure 1 shows a portion of a tyre chain 1 0 comprising links 1 2 threaded onto and interconnected by welded ring connectors 14. Four links are threaded onto each connector to form a mesh with a square pattern. As shown each link has a diamond shaped head portion that maximises the surface area covered by the chain for optimum protection. Each link has three traction members 1 5 in the form of stepped-nose, cylindrical, tungsten-carbide button bits. The bits 1 5 are shown in detail in Figure 5. Figures 2 to 4 show a link 1 2.1 comprising a base portion 1 6, a medial portion 18 formed with two oval eyes or openings 20, and a diamond shaped head portion 22. Stepped layers 24 and 26, each of a diamond shape are formed on the top of the head portion. The stepped layers provide traction formations to inhibit slipping, ie. increase traction, of the chain. Vertically extending grooves 28 are formed in the edges of the head portion 22, the grooves extending in depth to the shoulder of the first layer 24. The grooves provides additional grip, which persists in use even when the stepped layers 24 and 26 have been worn away. Two traction members 30 in the form of round-nose, cylindrical, tungsten-carbide button bits are brazed into holes in the head portion of the link. The bits 30 are shown in greater detail in Figure 6. Figure 7 shows a substantially rectangular, thick plate traction member 32 formed as a sintered tungsten carbide body. This traction member is dimensioned substantially to span the length of the head of a link and has one of its longitudinal edges bevelled as shown. In use, the traction member is secured to a link by brazing it into a slot extending along the length of the head, with the bevelled edge being exposed. The upper edge of the bevelled portion need not be flat as shown and may slope downwards from the centre towards, or vice versa, for increasing its gripping or traction properties in use. Figure 8 shows an elongate, rectangular tread member 34 comprising a wear resistant portion 36 and a body portion 38. The wear resistant portion 36 forms a traction member and is a compact or matrix of tungsten carbide particles embedded in a suitable steel alloy. The body portion 38 is of a weldable steel or cast iron or steel alloy, which may be the same steel alloy as used to embed the tungsten carbide, and has a lower edge 40 that is bevelled on both sides to facilitate welding it to a link. The lower edge 40 need not be bevelled and can be a flat edge. The tread member is dimensioned substantially to span the width and length of the head of a link. In use, the tread member may be welded to a worn link, ie. one in which the head has been worn away through use, to restore the link or may be welded to a new link for a new tyre chain. Figure 9 shows a tread member 42 comprising a substantially rectangular body 44 having a bevelled lower edge and three button bits 30 press fitted into holes in the body. The button bits are shorter than the holes into which they are pressed and secured in the holes by peening the mouth portions of the holes. This securing method is suited for use with tyre chains that will be used in silica sands, because in use sand particles enter the hole and wedge between the button bits and the walls of the holes to secure the button bits. It is not suited for tyre chains that will be used on, for example, hot slag as the thermal expansion of the steel is greater than that of the button bits, so that the holes widen and the bits fall out. Figure 10 shows a tread member 46 comprising a weldable steel body 48 that is diamond shaped in plan view and two button bits 1 5 secured in holes in the body by a cross-pin 50. The steel of the body can have a low hardness for manufacture, eg. about 30 HRC (hardness Rockwell "C" scale) which can then be heat treated to about 55 to 60 HRC after fitting the button bits and cross-pin. Apart from increasing traction the tread members also increase the wearing properties of the link because of their hardness. Typically the tungsten carbide bits or particles have a hardness of 86 to 92 HRA (Rockwell hardness "A" scale) that resists wear and the steel of the link has a hardness of 50 to 60 HRC that is sufficiently hard in combination with the harder buttons not to wear away unacceptably rapidly and at the same time soft enough not to be too brittle to break under bending forces in use. The invention is not limited to the precise details described above and shown in the drawings. Modifications may be made and other embodiments developed without departing from the scope of the invention as defined in the claims.

Claims: CLAIMS: 1 . A link for a tyre chain of the type set forth comprising a base portion, a medial portion and a head portion, characterised in that the link has at least one traction member (1 5, 30, 32, 36) of a material that is relatively harder than the material of the link partially embedded in the head portion and partially exposed on the surface of the head portion. 2. The link of claim 1 , characterised in that the traction member is in the form of a solid body, such as a cylinder (1 5, 30) or a thick plate (32), locked in an opening formed in the head portion of the link. 3. The link of claim 1 , characterised in that a plurality of such solid body traction members is arranged at desired positions on the head. 4. The link of claim 1 , characterised in that the traction member is in the form of a plurality of particles consolidated in a cemented compact or steel matrix (36). 5. The link of claim 1 , characterised in that the traction member is of a suitable hard, abrasion resistant carbide, nitride and the like compounds in particle, cemented or sintered form; 6. The link of claim 1 , characterised in that the traction member is secured to a body (38) of a weldable material, the body being secured by welding to the head portion of the link. 8. A tyre chain of the type set forth characterised by having at least one link of the invention.

Inventors: DOHMEIER HANS-OTTO, DOHMEIER, HANS-OTTO
Applicants: DOHMEIER HANS OTTO, DOHMEIER, HANS-OTTO
Application year: 1999
Main classification: B60C27
IPC codes: B60C27