A WHEEL FOR A TRACK-LAYING VEHICLE

Abstract: A method of manufacturing a metal article by squeeze forming comprises locating a set of hard metal wear-resistant studs 14 in the mould 12 so that during forming of the article, the metal flows on to and around the studs whereby they become embedded in the formed article. Typically the article comprises an aluminium or aluminium alloy wheel 20 for use in a back-to-back support wheel assembly in a tracklaying vehicle. The studs 14 are located at the wheel rim edges subject to wear by the horns 34 of the track 36.

Description: 79.065/BT Method of producing metal articles with wearresistant areas and articles produced thereby This invention relates to the manufacture of articles by the technique known variously as squeeze forming, squeeze casting or extrusion casting which, for the sake of convenience, throughout this specification and Claims will be referred to as "squeeze forming. Basically the technique of squeeze forming comprises introducing liquid metal into a first part of a mould, closing the mould under pressure so that the liquid metal is displaced by the mould closure to fill a cavity within the mould without entrapping air, maintaining the metal under pressure whilst solidification takes place so as to ensure that any shrinkage cavities which may form are closed and filled, and then opening the mould and removing the formed article. Metals most conveniently employed to produce squeeze formed articles are aluminium and aluminium alloys and although such squeeze formed aluminium or aluminium alloy articles are of sound metallurgical structure and strength. they can sometimes be subject to unacceptably severe wear conditions. For example, a support wheel for a track-laying vehicle of the type described in European Patent Application 79,300,842.6 (published as No. 0,005.937) is produceable by squeeze forming in aluminium or aluminium alloy but that part of the wheel which is engaged by the steel horns of the track is subject to extreme wear conditions. It will be understood that many differing squeeze formed articles can be subject to severe wear conditions. and it IS an object of the present invention to provide a squeeze formed article, and method of producing such article. when wear-resistant means are incorporated. In accordance with one aspect of the invention there is provided a method of manufacturing a metal article by squeeze forming characterised by the steps of locating a set of hard metal wear-resistant elements in a mould at a position corresponding to the position at which it is desired to produce a wear-resistant area in the formed article. the hardness of the metal elements being greater than the hardness of the metal being formed; introducing molten metal into the mould; closing the mould under pressure so that the molten metal is displaced by the mould closure to fill a cavity in the mould within which the hard metal elements are located; maintaining the metal under pressure whilst solidification thereof takes place and the hard metal elements become embedded therein, and opening the mould and extracting the formed article. Conveniently the hard metal elements are initially located in a first part of the mould which provides at least part of the die cavity whereby. when the molten metal is introduced to said first part of the mould and the mould is closed under pressure, the metal is displaced to fill the cavity and to flow on to and around the hard metal elements. Alternatively the hard metal elements may be initially located in that part of the die cavity wherein the molten metal is introduced so that the liquid metal flows at least partially on to and around the hard metal elements before the mould is closed under pressure and the metal is displaced to fill the cavity. As a further alternative the hard metal elements may be releasably carried by a second part of the mould providing part of the die cavity which is brought towards said first part of the mould when the mould is closed under pressure. the molten metal then being displaced to fill the cavity and to flow on to and around the hard metal elements. In accordance with a further aspect of the invention there is provided a squeeze formed metal article having a plurality of hard metal wear-resistant elements embedded therein during the forming operation, the hardness of said elements being greater than the hardness of the metal of the article. The metal to be formed is a light metal such as magnesium or aluminium or an alloy thereof and the hard metal elements are conveniently formed of hardened steel; the metal being formed having a hardness within the range 60 - 200 VPN and the hard metal elements having a hardness within the range 350 - 1000 VPN. Conveniently the hard metal elements comprise a set of spaced apart metal studs carried on a support member which may be a flexible member for enabling it and the studs carried thereon to be located in the mould or may be a rigid member configured to be positively located in the mould. The article may comprise a one piece support wheel for a track laying vehicle comprising a disc and a rim. the adjacent parts of the disc and rim being of T-shape, and the disc being of dished configuration with the centre part of the disc extending axially of the wheel beyond one of the edges of the rim, and the set of hard metal elements being embedded in said rim edge for resisting wear imparted thereto by the horns of a track supported by said wheel. It will be appreciated that, in a track laying vehicle, a pair of such wheels would be arranged to be secured together in back-toback configuration so that a continuous circumferential groove is provided between each pair of wheels into which the track horns project to guide the movement of the track beneath the wheels. Other features of the invention will become apparent from the following description given herein solely by way of example with reference to the accompanying drawings wherein Figures 1 to 3 show sectional diagrammatic views of three steps in the sequence of squeeze forming a metal wheel wherein a set of hard metal studs are incorporated around the rim of the wheel Figure 4 is a top plan view of a set of hard metal studs in a roller chain arranged at the wheel rim edge Figure 5 is a side view of the roller chain studs of Figure 4 Figure 6 is a top plan view of an alternative hard metal stud set Figure 7 is a side view of the stud set shown in Figure 6 Figure 8 is a top plan view of a further alternative hard metal stud set Figure 9 is a side view of the stud set shown in Figure 8 Figure 10 is a top plan view of a still further alternative arrangement of stud set Figure 11 is a side view of the stud set of Figure 10 Figure 12 is a top plan view of a yet further arrangement of stud set Figure 13 is a side view of the stud set of Figure 12 Figure 14 is a side cross sectional view of a pair of T shaped support wheels for use in a track laying vehicle bolted together and to a hub wherein a set of hard metal studs is incorporated at the inner rim edges Figure 15 is an end view of one of the wheel elements of Figure 14 and Figure 16 is a side view of a track assembly in a tracklaying vehicle incorporating support wheels of the type shown in Figures 14 and 15. Referring to Figure 1 of the drawings there is illustrated a mould having an upper mould part 10 and a lower mould part 12 configured to provide, when closed together, a die cavity in the shape of a wheel. The wheel is produced by the squeeze forming technique out of an aluminium or aluminium alloy material which is introduced in molten liquid form (by means of a suitable inlet nozzle) to that part. of the die cavity provided in the lower mould portion. To provide a wear-resistant surface to the rim of the wheel, a set of hard metal wear resistant elements 14 is located in the die cavity in the lower mould part 12 at a position corresponding to that which will provide, in the formed article, the rim thereof. Thus, referring to Figure 1, a ring of cylindrical steel studs on a support member is located around the periphery of the die cavity in the lower mould part 12 before the liquid aluminium or aluminium alloy is introduced to the mould. After a predetermined quantity of liquid metal has been introduced to the die cavity the mould is closed by downward movement of the upper mould part 10. Such closure of the mould under pressure forces the liquid metal within the die cavity to flow radially outwardly and upwardly of the cavity defined between the upper and lower mould parts 10 and 12 whereby the liquid metal also flows on to and around the stud set 14 as is clearly shown in Figure ? The mould is held closed under pressure whilst solidification of the metal takes place so as to ensure that any shrinkage cavities which may form are closed and filled and during which time the stud set 14 becomes embedded in the metal. After a predetermined time the upper mould part 10 is withdrawn upwardly away from the lower mould -portion. as shown in Figure 3. and the formed wheel 16 is ejected from the die cavity by means of suitable ejector rods 18. Referring to Figure 3. it will be seen that the squeeze formed wheel 16 is thus provided with the wear-resistant stud set 14 around the lower edge of its rim and such a wheel is conveniently used as part of a back-to-back support wheel arrangement for the track of a track-laying vehicle substantially of the type described and illustrated in European Patent Application 79 300 ¯842.6 (published as No. 0005937). Referring now to Figures 4 to 13 there will be described various alternative forms of stud sets 14 suitable for location in the mould as hereinbefore described for providing a wear resistant surface to the edge of a wheel rim. In all of these embodiments the actual wear resistance is afforded by a set of cylindrical hardened steel studs conveniently having a hardness within the range 350 - 1000 VPN as compared with the hardness of the aluminium forming the wheel itself which has a hardness within the range 60 - 200 VPN. Thus referring to Figures 4 and 5, the studs 14a are provided in a roller chain assembly, each stud having a spigot 14b projecting from either side of the stud and the spigots being connected to adjacent studs by means of plate-like support links 14c to provide a completely flexible assembly. Thus a single length of such a roller chain. or a plurality of lengths thereof, can be arranged in the mould prior to the introduction of molten aluminium for the squeeze forming operation. Figure 6 and 7 show an alternative form of flexible stud set assembly 14 wherein a set of cylindrical studs 14d are each provided with a spigot 14e at the rear face only and are interconnected by means of plate-like support links 14° having a force fit on the spigots and links 14ff having a free fit on the spigots. Again a single length of such an assembly, or plurality of individual lengths. can be located in the mould prior to the introduction of the molten aluminium. Figures 8 and 9 show a very similar stud set arrangement 14 to that shown in Figures 6 and 7 with the exception that the rear ends of the spigots 14e of the studs 14d are upset whereby the studs are rivetted to the support links to provide a flexible assembly for location in the mould. Figures 10 and 11 show a yet further variation wherein the studs 14d are retained on the support links 14f by means of a star washer 14g engaging over each spigot 14e with a friction fit. Figures 12 and 13 show an arrangment wherein a plurality of studs 14d are each spot welded at their rear face to a single steel wire 14h which, as will be clearly seen from Figure 13, is of convoluted shape. This convoluted shape of the support wire enables the stud set 14 to be located more positively in the mould whereby there is less likelihood of its position being disturbed during the squeeze forming operation prior to solidification of the molten aluminium. It will be appreciated that, in all of the arrangements shown in Figures 4 to 13, the actual stud length may be varied as betweeen adjacent studs to provide for the possibility of differential wear life at the wheel rim edge. Thus, after the wheel has been formed, some of the studs may be visible at the rim edge surface whilst other studs may be totally embedded within the aluminium and be located beneath the rim edge surface. However in all of the variations in design of the stud assembly it will be appreciated that. after the wheel has been formed, the studs will be effectively mechanically locked into the wheel rim edge due to the penetration of the molten aluminium around the studs and support members during the forming operation. Furthermore an intermetallic bond will be established between the steel studs and the aluminium. Referring now to Figures 14 to 16, there is shown squeeze formed aluminium wheels 20 with wear-resistant steel studs 14 at the rim edges produced in accordance with the invention as used in a support wheel assembly of a track laying vehicle. Referring particularly to Figures 14 and 15. each wheel 20 comprises a dished disc portion 22 and a rim portion 24 wherein the disc merges into the rim substantially in the axially central zone 26 of the - rim so that the adjacent portion of the disc and rim together are of T-shape. The centre portion 28 of the disc 22 extends axially beyond the edge 30 of the rim 24 so that, when a pair of similar wheels 20 are secured to the hub 32, the wheels are in back-to-back configuration and a continuous circumferentially extending groove is defined between the two wheels into which the horns 34 of the track 36 are arranged to extend and to guide the track beneath the wheels. Appropriate bolt holes 38 are formed in the centre portion 28 for securing the two wheels 20 together and also for securing the wheels to a vehicle hub 32. It will be seen that the hardened steel stud set 14 extends circumferentially around the wheel rim edges 30 between which the track horns 34 project so as. to afford the required wear resistance. In the particular arrangement shown in Figures 14 and 15 the cylindrical steel studs are spot welded at their rear faces to a single length of steel wire It will also be seen that the outer peripheral surfaces 40 of the wheel element rims 24 are cylindrical for locating a solid rubber tyre 42 on each rim; the tyre being conveniently moulded in situ on the rim. Although the foregoing specific description has been with reference to a support wheel for use in a track-laying vehicle, it will be appreciated that the invention. in its broadest terms. envisages the production of squeeze formed articles for any suitable purpose wherein it is desirable to provide a wear resistant area by the incorporation of a set of hard metal wear resistant elements.

Claims: CLAIMS 1. A method of manufacturing an article by squeeze forming wherein molten metal is introduced into a mould, the mould is closed under pressure so that the molten metal is displaced by the mould closure to fill a cavity in the mould, the metal is maintained under pressure whilst soldification thereof takes place and the mould is then opened and the formed article extracted therefrom characterised in that a set of hard metal wear-resistant elements (14) are located in the mould (10), (12), prior to the introduction of the molten metal thereto, at a position corresponding to the position at which it is desired to produce a wear-resistant area in the formed article and that the hardness of the hard metal elements (14) is greater than the hardness of the metal being formed; the hard metal elements becoming embedded in the metal being formed during solidification thereof in the mould cavity. 2. A method according to Claim 1 further characterised in that the hard metal elements (14) are initially located in a first part (12) of the mould which provides at least part of the die cavity whereby, when the molten metal is introduced to said first part of the mould and the mould is closed under pressure, the metal is displaced to fill the cavity and to flow on to and around the hard metal elements. 3. A method according to Claim 2 further characterised in that the hard metal elements (14) are releasably carried by a second part (10) of the mould providing part of the die cavity which is brought towards said first part (12) of the mould when the mould is closed under pressure so that the molten metal is displaced to fill the cavity and to flow on to and around the hard metal elements. 4. A method according to Claim 1 further characterised in that the hard metal elements (14) are initially located in that part (12) of the die cavity wherein the molten metal is introduced so that the molten metal flows at least partially on to and around the hard metal elements before the mould is closed under pressure and before the metal is displaced to fill the cavity. 5. A method according to any one of Claims 1 to 4 further characterised in that the metal to be formed is a light metal such as magnesium or aluminium or an alloy thereof and the hard metal elements (14) are hardened steel. 6. A method according to any one of claims 1 to 5 further characterised in that the metal to be formed has a hardness within the range 60 -200 VPN and the hard metal elements (14) have a hardness within the range 350 - 1000 VPN. 7. A method according to any one of the preceding claims further characterised in that the hard metal elements (14) comprise a set of spaced apart metal studs carried on a support member. 8. A method according to claim 7 further characterised in that the support member is a flexible member for enabling it and the studs carried thereon to be located in the mould. 9. A method according to claim 7 further characterised in that the support member is a rigid member configured to be positively located in the mould. 10. A method according to any one of the preceding claims further characterised in that the article comprises a wheel (16) and the hard metal elements (14) are located in the mould to produce a wear resistant surface to a rim edge of the wheel. 11. A squeeze formed metal article characterised in that a plurality of hard metal wear resistant elements (14) are embedded therein during the forming operation, the hardness of said elements being greater than the hardness of the metal of the article. 12. An article as claimed in claim 11 further characterised in that it comprises a one piece support wheel (20) for a track-laying vehicle comprising a disc (22) and a rim (24), the adjacent parts of the disc and rim being of T-shape, and the disc being of dished configuration with the centre part (28) of the disc extending axially of the wheel beyond one of the edges (30) of the rim, and the set of hard metal elements (14) being embedded in said rim edge (30) for resisting wear imparted thereto by the horns of a track supported by said wheel. 13. An article as claimed in either one of claims 11 or 12 further characterised in that the hard metal elements (14) are formed of hardened steel and the metal of the article is a light metal such as magnesium or aluminium or an alloy thereof. 14. An article as claimed in any one of claims 11 to 13 further characterised in that the metal to be formed has a hardness within the range 60 - 200 VPN and the hard metal elements (14) have a hardness within the range 350 - 1000 VPN 15. An article as claimed in any one of claims 11 to 14 further characterised in that the hard metal elements (14) comprise a set of spaced apart metal studs carried on a support member.

Inventors: BARLOW, JOHN, EDWARDS, MICHAEL FREDERICK, FOREMAN, FREDERICK ARTHUR, WILLIAMS, GWYNNE
Applicants: GKN TECHNOLOGY LIMITED
Application year: 1981
Main classification: B22D13
IPC codes: B22D19, B62D55, B60B1, B22D17, B60B21, B22D18, B21C25