Background of the Invention It is known to form a pulley by any one of a number of processes such as sand casting, die casting or metal stamping.

Sand casting, for example, involves the formation of a pulley cast from a mould.

The mould is firstly positioned in a sand bed, in which a channel is also provided, to allow molten metal to be poured into the mould. After a curing and cooling period, the cast is removed by breaking the mould, such as by hammering, and transferred to a machining stage, to machine the pulley to appropriate standards and to cut grooves into the cast. The cast is preferably formed of iron ore. Impurities in the ore may cause small holes to be formed in the resulting cast, which subsequently need to be filled with putty and painted to provide a suitable finish and to prevent rusting.

The formation and machining of individual pulleys and the destruction of the mould each time a pulley is made, renders sand casting somewhat time consuming, labour intensive and expensive.

Object of the Invention The present invention seeks to provide an alternative form of pulley and a method forming the pulley.

Summary of the Invention In accordance with the invention, there is provide a method of forming a pulley, including: extrusion moulding a body of the pulley; and

producing at least one peripheral groove in the body so as to form the pulley.

Preferably, the method includes cutting the body from an extrusion prior to producing the at least one peripheral groove.

Preferably, the method includes formation of the body as a hollow section and, more preferably, the hollow section defines a central bore in the body.

Preferably, the central bore is formed with a keyway to secure the pulley against rotation relative to an axle passing through the central bore.

Preferably, the method includes machining a threaded hole through the body, toward the central bore, for receipt of a lock-screw, for securing the pulley on an axle passing through the central bore.

Preferably, the pulley is subsequently treated so as to be provided with a coloured and/or protective anodised coating.

Preferably, the method includes forming the pulley of aluminium alloy, composite plastic or other suitable materials.

In another aspect, there is provided a pulley formed in accordance with the above described method.

Brief Description of the Drawings The invention is described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a flow chart illustrating a manufacturing method for producing a pulley; Figure 2 is a perspective view of a pulley body ; Figure 3 is a perspective view of another pulley body ; Figure 4a to 4e illustrate pulleys of different length, with different numbers of grooves.

Detailed Description Referring firstly to Figure 1 a flow chart illustrating a manufacturing method for producing a pulley is shown as including a first step 1, where an extrusion is received from an extruder and is subsequently cut by, for example, a circular saw, at step 2, to form a respective pulley body of a desired length. At step 3, one or more peripheral grooves are formed in the body and additional machining, such as the drilling of holes and the formation of thread, is performed. The machined pulley is then ready to be sold at step 4.

An example of a body 5, which has been cut from an extrusion, is illustrated in Figure 2. As can be seen, the body 5 is formed as a hollow section which includes an outer sleeve 6 and an inner core 7 connected to the sleeve by interconnecting webs 8. The core 7 is provided with a central bore 9, which has a keyway 10 adapted to fit over a complimentary structure on an axle which passes through the bore 9, in order to secure the body 5 against rotation relative to the axle.

Another example of a pulley body 5 is illustrated in Figure 3, wherein like reference numerals denote like parts. As can be seen, the body 5 is of essentially the same construction as that shown in Figure 2, except that the keyway 10 in the central bore 9 is absent. As an alternative to the keyway 10, a threaded hole (not shown) may be provided in the core 7, extending toward the bore 9, for receipt of a locking screw, or the like, to secure the body 5 relative to an axle passing through the bore 9. The bore 9 may also be machined so as to include a thread, if required.

The body may be cut from the extrusion so as to have any desired length"L"and then transferred to the machining step 3 where an appropriate number of peripheral V- shaped grooves 12, for receipt of a respective transmission belt, or the like, may be formed in an external surface 11 of the sleeve 6 so as to produce the final form of the pulley 20.

Various examples of pulleys 20 with different length dimensions and numbers of grooves are illustrated in Figs. 4a to 4e.

The pulley 20 is preferably formed of aluminium alloy which may be subsequently treated to have a coloured anodised coating, if required. Alternatively, the pulley 20 may

be formed of composite plastics or any other material suitable for extrusion moulding.

As may be appreciated, the extrusion process allows the dimensions of the pulley to be fairly readily modified. For example, the diameter of the central bore 9, the size of the keyway 10, the thickness of the core 7, the thickness and number of the webs 8, the thickness of the sleeve 6 and the depth and dimensions of the grooves 12 may all be varied, as required. Further, the overall size of the pulley 20 is only limited by the minimum and maximum dimensions obtainable in the extrusion moulding industry. In addition, a large number of pulleys may be manufactured using a single die for the extrusion process, with uniformity of design and sizes, which avoids secondary machining, as compared to a sand casting technique.

Accordingly, the invention may provide for cheaper start-up and operating costs, as compared to a conventional pulley formed by sand casting and pulleys can be made relatively quickly in large quantities, which allows for faster production time and mass manufacturing economies to be realised. The manufacturing method may also be computerised in which case a saving may also be made by reducing manual labour, which is also required with the sand casting technique.

Since the pulleys 20 may be manufactured from a reduced number of dies and in mass production, a reduction in required factory floor space may also result, as compared to a cast iron pulley manufacturing technique where the smelting and casting stages require a relatively large floor space. Using an extrusion process also avoids the production of any toxic fumes which may otherwise be generated using a conventional smelting technique.

Further, an extrusion moulding process will generally require less parts, which will also be manufactured to a relatively good component tolerance, and that will in turn require less inventory and allow for easier factory management.

Since the extrusion manufacturing process provides for mass production with minimal manpower, a relatively high turnover as per overhead costs may result. The extrusion manufacturing process can also provide a product without any small holes and no painting is required, which may lead to further cost savings.

The pulleys 20 may also be made of lighter material, as compared to the cast iron pulleys formed by sand casting. Lastly, cost advantages may be realised as a result of less inventory required to manufacture pulleys in accordance with invention and transport costs lessened due to the reduced weight of the product. In addition, the pulleys, which are preferably formed of aluminium alloy, may be manufactured of a material which is 100% recyclable.