A casting mould for casting of vehicle wheels and method for manufacturing them

Abstract: Cast vehicle wheels formed with a re-entrant portion (7) or lightening pocket beneath the tyre bead retaining seat (6a), and a casting mold and method of manufacture thereof. The mold (A1,A2,A3,A4,B,C) is manufactured with movable side portions enabling the formation of the said re-entrant portion in the wheel. The re-entrant portion reduces the weight of the wheel without adversely affecting the wheel characteristics.

Description: This invention relates to a casting mould for casting of a vehicle wheel and to a method for manufacturing them. BACKGROUND OF THE INVENTION The unsprung weight of a vehicle, in particular a high performance motor car, is extremely significant in determining the handling and speed characteristics of the vehicle. It is for this reason, among others, that cast alloy road wheels are fitted, as compared with pressed steel road wheels. However, the final, detailed design of a cast alloy wheel is a compromise between, on the one hand, the optimum strength/weight ratio needed from a merely engineering/operational point of view and, on the other hand, the shape/volume of metal and mold construction required for the efficient casting of the metal during production. International Patent Application WO81/03465 discloses a cast vehicle wheel which is of imperforate annular disc form and which has a bead seating wall spaced radially outward from a surface of the rim member in order to define a space between the rim and the bead seating wall. Corresponding to the preambles of independent claims 1 and 4, there is disclosed in European Patent Application 0 070 812 a casting mould for casting a cast vehicle wheel which includes a tyre rim profile block comprising a plurality of segments, a styling face block, an inside profile block, means for locating the blocks in relation to one another to form a mould cavity defining the wheel to be cast, the tyre rim profile block having a substantially annular portion shaped to define the substantially annular recess in the moulded wheel, a base member, means connecting the tyre rim to profile block segments to the base member to enable the tyre rim profile block segments to be moved between an open inoperative position and a closed operative position where the segments together with the other blocks define the casting cavity. The present invention is concerned with reducing the weight of cast metal wheel, at the same time keeping the manufacturing process and apparatus relatively simple. According to the present invention a casting mould for casting a vehicle wheel is as defined in claim 1. According to the present invention a method of manufacturing a cast wheel is as defined in claim 4. An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an alloy wheel; Figure 2 is a sectional side view of a casting mould in accordance with the present invention; and Figure 3 is a plan view of the casting mould of Figure 2. Figure 1 A one-piece cast alloy wheel 1 includes a hub member 2, a disc section 3 surrounding and formed integrally with the hub member 2, a generally cylindrical rim member 4 formed integrally with the disc section 3 and located radially outwardly of the hub member 2, a tyre retaining wall 5a,5b at each end of the cylindrical rim member 4, and a substantially cylindrical tyre bead seating surface 6a,6b formed integrally with each one of the tyre retaining walls 5a,5b. An annular recess 7 is formed radially inwardly of the bead seating surface 6a and substantially beneath it, in order to reduce the weight of the cast wheel. The annular recess 7 has a number of struts 8 formed therein. The purpose of the struts 8 is to assist in tyre fitment, as well as acting as a reinforcement. The portion of the wheel between the disc section 3 and the rim member 4 is shaped to form a plurality of spoke sections 9, each pair of spoke sections 9 being separated by a perforation 10, there being eight spoke sections 9 and perforations 10. All the elements or members 1 to 9 are cast integrally with one another to form a one-piece wheel. The material of the wheel is a metal alloy, preferably of aluminium or magnesium. A mould for manufacturing the cast wheel shown in Figure 1 will now be described with reference to Figures 2 and 3. Figures 2 and 3 A casting mould consists of tyre rim profile block comprising a plurality of segments A1, A2, A3, A4 a styling face block B and an inside profile block C. In the assembled condition of the mold the single-piece styling face B and the single-piece inside profile C are located together by a plurality of dowels 11 to ensure concentricity. The styling face B is mounted on a support member or plate (not shown) and the whole assembly is then fitted onto the casting machine. Each of the four tyre rim profile block segments A1, A2, A3 and A4 is each in the form of a 90° segment so that together they define the outer profile of the rim of the wheel to be cast. Two of these four segments are shown at A1 and A2 in Figure 3. Each tyre rim profile block segment A1, A2, A3 and A4 is hinged at 13 to the support structure 12 so that it can be pivoted between a closed position, shown on the left in Figure 2, and an open position, shown on the right in Figure 2. In their closed positions the block segments A1, A2, A3 and A4 define the tyre rim profile and in their open positions enable the cast wheel to be removed from the mold. The annular recess 7 is formed by an arcuate projection 14 which itself is formed as part of each of the four tyre rim profile block segments A1, A2, A3, A4 so that together the four arcuate projections (90° each) form a continuous annular projection when the mould blocks are in their closed positions. Each block segment A1, A2, A3, A4 has an arcuate recess 15 so that together in their closed position the recesses 15 define a tyre bead retaining rim 16 which is located axially inwardly of the cylindrical tyre bead seating surface 6a in relation to the front styling face of the wheel. When in use, the casting mold, including the side portions 17, are bolted together so as to form the mould area for the required wheel and molten metal to be poured, pumped or injected into the mold and allowed to set in the normal manner. Thereafter the side portions 17 are hingeably moved so as to remove the undercutting member 14 from the newly formed wheel 1 without damaging the tyre bead retaining seat 3. The remainder of the casting mold may also be removed without damaging the remainder of the wheel in the normal manner. The top portions 18 of the mould are then hinged about hinges 19 in the direction of the arrows in Figure 2. The style and dimensions of the wheel may vary depending on commercial requirements and the method and apparatus are not limited to any particular style or dimension. The mold when closed may be filled using any appropriate known process such as those known as 'low-pressure' 'counter pressure' 'gravity fill' 'centrifugal' 'semi-solid' or 'squeeze casting'. The sequence of operations can vary, but the rim profile block A always creates the lightening recess 7 by undercutting the bead retaining seat 6a, 6b. When the mold is in the closed position an alloy of magnesium or aluminium can be injected into the mold either under pressure or the mold may be evacuated by a vacuum pump (not shown) and the alloy drawn into the mold under suction or counterpressure. The mould may also be filled merely by pouring the alloy into the mold under gravity. After the alloy has solidified, the mold is opened. The cast wheel is then removed in the normal manner. The mold is closed again and the cycle repeated. By employing the present invention a weight saving of around 0.5 kg per wheel can be achieved.

Claims: A casting mould for casting vehicle wheel (1) having a central disc (3), said casting mould comprising: a tyre rim profile block comprising a plurality of segments (A1, A2, A3, A4), a styling face block (B) located at a base of the mould, an inside profile block (C), means for locating said blocks in relation to one another to form a mould cavity defining the wheel to be cast, the tyre rim profile block (A1-A4) having a substantially annular portion (14) shaped to define a substantially annular recess (7) in the cast vehicle wheel (1), a support member constituting the base of the mould, means for connecting the tyre rim profile block segments (A1-A4) to said support member to enable said tyre rim profile block segments to be moved between an open inoperative position and a closed operative position where said segments (A1-A4) together with said other blocks (B,C) define said mould cavity, characterised in that: the annular recess (7) is an undercut and is located on the underside of a tyre bead seating (6a) surface of the cast vehicle wheel (1) and is substantially coplanar with respect to the mould cavity defining the central disc of the wheel, the means for connecting the tyre profile block segments (A1-A4) to the support member comprising hinges (13) to enable the tyre rim profile block segments (A1-A4) to be hinged between an open inoperative position and a closed operative position, the hinges (13) being located immediately below the styling face block (B) so as to enable said substantially annular portion to be extracted from the under-cut annular recess (7) formed thereby without fouling the material of the cast vehicle wheel adjacent said recess. A casting mould as claimed in claim 1 or 2 in which each hinged segment comprises a first element (17), means (13) for hingedly connecting the first element (17) to the support member, a second element (18) and means (19) for hingedly connecting the second element (18) to the first element (17), the second element (18) being shaped to define the axially innermost surface of the rim of the cast wheel. A casting mould as claimed in any previous claim in which there are four tyre rim profile block segments (A1-A4) each defining substantially one-quarter of the circumference of the tyre rim. A method of manufacturing a cast metal wheel (1) having an outer rim surface and a central disc (3), which comprises the following steps to be carried out in ascending alphabetic/numeric order: a1) forming a casting mould including a tyre rim profile block comprising a plurality of segments (A1-A4), a styling face block (B) located at a base of the mould, an inside profile block (C), means for locating said blocks in relation to one another to form a mould cavity defining the wheel (1) to be cast, the tyre rim profile block (A1-A4) having a substantially annular portion (14) shaped to define a substantially annular recess (7) in the cast vehicle wheel (1), a support member constituting the base of the mould, means for connecting the tyre rim profile block segments to said support member to enable said tyre rim profile block segments to be moved between an open inoperative position and a closed operative position where said segments together with said other blocks define said mould cavity; b) introducing molten metal into the said mould cavity; c1) allowing the molten metal to cool and set; and d) extracting the cast vehicle wheel from the remaining mould block, characterised by the steps of a2) forming the substantially annular recess (7) of undercut shape on the underside of a tyre bead seating surface in the cast vehicle wheel (1) and located substantially coplanar with respect to the mould cavity defining the central disc of the wheel, hinging the tyre profile block segments (A1-A4) to said support member to enable said tyre rim profile block segments (A1-A4) to be hinged between an open inoperative position and a closed operative position, locating hinges (13) immediately below the styling face block (B) so as to enable said substantially annular portion to be extracted from the under-cut annular recess (7) formed thereby without fouling the material of the cast vehicle wheel adjacent said recess, c2) hingedly moving the said segments (A1-A4) forming the tyre rim profile block substantially radially away from the cast vehicle wheel (1) to expose the outer rim surface of the cast vehicle wheel, c3) removing in a substantially axial direction the styling face block (B) or the inside profile block (C). A method as claimed in claim 5 in which step b) comprises injecting the molten metal into the mould cavity. A method as claimed in claim 5 in which step b) comprises introducing the molten metal into the mould cavity by means of gravity. A method as claimed in claim 5 in which the step b) comprises evacuating the mould cavity to a pressure below ambient pressure and then allowing the molten metal to be drawn into the mould cavity by a pressure differential.

Inventors: SCOTT ROY, SCOTT, ROY
Applicants: ALLOY WHEELS INT LTD, ALLOY WHEELS INTERNATIONAL LTD
Application year: 1992
Main classification: B60B3
IPC codes: B22C9, B60B3, B60B21