GB2077387A - Toothed wheels - Google Patents

Abstract

A toothed wheel, for use with a timing belt, comprises two interfitted parts 72, 78 of injection moulded plastic. One part carries the teeth 74 and each part has a belt retention flange 82, 78. This arrangement enables the parts to be withdrawn axially from the mould. <IMAGE>

Description

SPECIFICATION Improvements relating to tooth wheels for timing belts This invention relates to toothed wheels for driving or being driven by, timing belts.

Timing belts as is known are belts which have ridges or teeth which are for engagement with teeth on the periphery of a wheel or gear.

This invention is concerned with the manufacture of toothed wheels (gears) for use with timing belts.

Traditionally, because toothed wheels used with timing belts do not normally carry large torques, they have been produced as one piece injection mouldings. Because they are produced in one piece, if the wheel is provided with retaining flanges at the ends of the teeth to keep the belt on the wheel when the wheel is in use, the moulds for producing such wheels have been complicated and expensive.

The present invention seeks to produce toothed wheels for use with timing belts whereby the said disadvantage will be obviated or mitigated.

According to the invention there is provided a toothed wheel for use with a timing beit, said wheel comprising at least two parts, one of which at least is injection moulded plastic, the parts being fitted together to provide the wheel.

The wheel is preferably made up of the two parts only, and has belt retaining flanges at the ends of the teeth, said flanges being formations of said parts respectively. The teeth of the wheel may be carried entirely by one of said parts.

The parts may be friction fitted, welded, glued or otherwise connected.

An embodiment of the invention as applied to the use of toothed wheels in a glass plate washing machine will now be described, by way of example, with reference to the accompanying drawings, wherein Fig. 1 is a perspective view of the glass plate washing machine; Fig. 2 is a pian view of part of a support rail apparatus embodying the present invention; Fig. 3 is a perspective view of the apparatus shown in Fig. 2; Fig. 4 is a diagrammatic sectional elevation of the apparatus shown in Figs. 2 and 3; Fig. 5 is a diagrammatic sectional elevation of the plug bearing shown in Fig. 4; Fig. 6 is a diagrammatic sectional elevation of the drive roller shown in Fig. 4; Fig. 7 is a diagrammatic sectional elevation of one of the idler rollers shown in Figs. 2 and 3; Fig. 8 is an exploded perspective view of one of the belt drive wheels shown in Figs, 2 and 3; and Fig. 9 is a sectional elevation of the wheel shown in Fig. 8, when assembled.

Referring to the drawings, in Fig. 1 there is shown a washing machine for washing glass plates. The machine comprises a housing 10 through which the glass plates are transported by transporting mechanism 12. The said mechanism 12 includes a bottom rail 14 supporting rollers 1 6 by which the glass plates are transported in upright disposition, the rollers being driven by means of a drive mechanism 1 8. The mechanism 1 2 has a support framework 14 having rods carrying idler rollers 20 against which the glass rests as it is transported through the machine casing 10.

The machine described is a known machine, and the present invention is concerned with improvements relating to the guide rail structure 14.

Referring now to Figs. 2 and 3, a section of the guide rail structure 14 embodying the present invention is shown, and it will be seen that the guide rail structure comprises a rail bar 22 along which are spaced spindle assemblies 24, the spindle assemblies 24 being interspaced with idler roller assemblies 26.

Of each spindle assembly 24, a through spindle 28 is driven by means of timing belts 30, the timing belts 30 being driven from an input drive shaft (not shown) at one end of the rail assembly 14.

To one side of the rail 22, as regards a single spindle assembly 24, there is a drive support roller 32 having a wear resistant tyre 34 on which the edge of the glass engages, the roller 32 being fast with the end of the spindle 28.

To the other side of rail 22 each spindle 24 carries a pair of timing belt rollers 36 and 38, these rollers also being rigid with the spindle 28.

The idler roller assemblies 26 comprise idler rollers 40 having wear resistant tyres 42. The rollers 40 are supported on spindles 44, but in fact the rollers 40 embody a roller bearing, and the outer race, carrying tyre 42, is rotatable relative to the spindle 44.

If reference is now being made to Fig. 4, it will be seen that rail 22, for each spindle 28, is provided with a through aperture 46, in which is received a plug-in roller bearing 48, comprising inner and outer races 50 and 52, between which are arranged two rows of balls 54. The plug-in bearing 48 is a friction fit in the hole 46, and therefore assembly of the spindle assemblies 24 on the rail 22 is extremely simple. The outer race 50 is provided at one end with a radial flange 56, to ensure automatically the correct positioning of plug-in bearing 48 in the rail 22. The races 50 and 52 are preferably of plastics material, and the outer surface of outer race 50 is preferably cylindrical.

Fig. 5 shows a sectional view of the plug-in roller 48 in greater detail.

Fig. 6 shows in detail, and in sectional elevation, one of the rollers 32, and it will be seen to comprise a solid plastic body 58, which is recessed in order to receive the wear resistant tyre 34.

Fig. 7 shows in sectional elevation one of the rollers 40, and it will be seen to comprise an outer race 60 which is recessed in the outer periphery to receive a rubber tyre 42, and inner race 62 between which are arranged two rows of steel balls 64 to define the rolling elements, whereby the races 60 and 62 can rotate frictionlessly one relative to the other. Plastic snap-in cages 66 serve to retain the balls 64 equally angularly spaced.

Figs. 8 and 9 show respectively in exploded perspective and in sectional elevation, one of the timing belt wheels 36 or 38 of each spindle assembly 24. Timing belt wheels 36 and 38 are identical, but are arranged to face one another in symmetrical fashion on the spindle 28.

The timing belt wheel shown in Figs. 8 and 9 represents a novel construction in that it comprises two injection moulded parts 70 and 72, with part 70 having a drum portion 74, provided with timing belt teeth 76. At one end of the teeth 76 is a retention flange 78. Located inside the drum portion 74 is a sleeve portion 80, on which the part 72 engages. Part 72 is provided with a flange 82, of the same size as flange 78, so that the flanges 78 and 82 form retaining flanges of the timing belt, as shown in Fig. 9, which is a sectional elevation showing the parts 70 and 72 coupled together securely. This securing may be achieved by friction, glueing, pins, screws, or any other means.By the construction of the timing belt wheel described, injection moulding of same is much simplified, in that simpler moulds can be used and the mould parts 70 and 72 can be ejected from mould cavities by pusher means, rather than by having the mould parts move apart, as would be necessary if the component were moulded in one piece in conventional fashion.

Fig. 3 shows clearly how the timing belts 30 couple alternative pulleys 38 and 36 in order to ensure that all of the rollers 32 will be driven in the same direction, and the driving of the rollers will therefore be clearly understood. In use, the glass plates will ride on tyres 34 and 42 in an edgewise fashion, while supported substantially in a vertical plane, with the faces of the glass plates resting against rollers such as rollers 20 shown in Fig. 1. The particular points of novelty in the arrangement described are that the bearings 48 can be plugged int othe rail 22, thereby simplifying can be plugged into the rail 22, thereby simplifying construction, and the timing belt wheels are injection moulded in two parts, and each of these particular novelties can of course be used in other applications.

The principle advantage of constructing the timing belt pulley as illustrated in Fig. 9, is that the moulds for producing the respective parts 70 and 72 can be made much simpler than in the case where the timing belt pulley is made in a single piece. Part 72 is of relatively standard construction, but part 70 especially designed so that it can be withdrawn from the mould by moving the component in a direction parallel to the axis of the tube 80. This means that the teeth 76 can be formed to a very accurate contour. This will not be the case if the item were moulded in one piece and the mould halves were, as would be necessary, moved apart in a direction transverse to the axis of the tube 80. An extremely efficient design has therefore been created enabling the production of injection moulded timing belt pulleys with retention flanges.

Claims (5)

1. A tooth wheel for use with a timing belt, said wheel comprising at least two parts, one of which at least is injection moulded plastic, the parts being fitted together to provide the wheel.

2. A wheel according to claim 1, which is made up of two parts only, and with belt retaining flanges at the ends of the feet, said flanges being formations of said parts respectively.

3. A wheel according to claim 2, wherein one of said parts comprises the retention flange and a drum portion extending from the retention flange, said drum portion having teeth on the outer periphery thereof extending axially of the drum, the part being injection moulded in a mould from which the part is removed in a direction axially of the drum.

4. A wheel according to claim 3, wherein the parts are connected by tongue and socket arrangement, and if desired are welded or otherwise fixed together.

5. A toothed wheel for use with a timing belt substantially as hereinbefore described, with reference to Fig. 9 of the accompanying drawings.