GB2114260A

GB2114260A - Toothed belt drive

Info

Publication number: GB2114260A
Application number: GB08202704A
Authority: GB
Inventors: Vernon Preston; John William Monks
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1982-12-30
Filing date: 1982-12-30
Publication date: 1983-08-17
Also published as: GB2114260B

Abstract

A toothed belt drive transmission includes a toothed belt (7a) extending partly around a rotatable toothed wheel (1a) to establish a drive via intermeshing teeth. A belt stop plate (9) is disposed at a side of the toothed wheel (1a) to provide an abutment to prevent the belt (7a) from sliding off the wheel (1a). The plate (9) has a water drainage channel (12) at a location in line with the teeth (10) on the wheel (1a) to permit liquid to drain away from the teeth (10). <IMAGE>

Description

SPECIFICATION Toothed belt drive This invention relates to belt drives. To facilitate an understanding ofthe invention, an example of a belt drive (which does not constitute an embodiment of the invention) will now be described with reference to Fig. 1 ofthe accompanying drawings, which is a side view of a reciprocating piston internal combustion engine suitableforuse in acommercialvehicle,for example a truck.

The engine shown in Fig 1 includes a pulleywheel 1 which is mounted fast on the front end of the engine crankshaft 2. Ashaft 3 extends above the engine and parallel to the crankshaft 2, this shaft 3 being rotatably mounted bysupports4and 5.Asecond pulleywheel 6 is mounted fast on the shaft3directlyabovethe pulley wheel 1, and a V-section drive belt 7 extends overthe pulleys 1 and 6 so that the crankshaft2 drives the shaft3 by way of the pulley 1, belt 7, and pulley 6.

The pulleys 1 and 6 are provided with respective v-section grooves to receive the v-section belt 7.

A disadvantage ofthe belt drive just described is that, being a friction drive, it is unsuitable for transmitting a high torque. Itmightwell be necessary to transmit a high torque in the case of the engine described above, because the shaft 3 could be a power take-off shaft used to drive equipment such as a rotary cement mixing drum, a hydraulic pump, a firetender water pump, a generator, or an air pump. In orderto establish connection to the power take-off shaft 3, the shaft 3 could extend (either directly, or via reduction or reversing gearing) rearwardly beyond the position shown in Fig 1 to terminate at a space behind a driver's cab.

If it is desired to use a belt drive to transmit high torque, then this can be achieved by providing teeth on the belt which mesh with corresponding teeth provided on the wheels on which the belt runs.

However, there are problems which would occur if one were to replacethefriction drive shown in Figure 1 by a conventional toothed belt drive. Conventional toothed belt drives do not use v-section belts and pulley grooves, but instead the belts are basically flat in cross-section and the toothed surfaces of the pulley wheels are basically cylindrical. Now, if engine shown in Fig 1 were to be mounted in a vehicle in such a position thatthe front end of the crankshaftwas higherthanthe rearend,then a conventional toothed belt would tend to slide sideways off its pulleys in the direction ofthe arrow A in Fig 1. One could, of course, use v-section toothed belts and pulley wheels to avoid this problem, but these are relatively expensive to manufacture.Furthermore, in the exposed environment of a vehicle engine compartment, water may splash onto the belt drive from the road or from the coolant system and when the engine is stopped the water could become trapped in a pulleywheel groove.

If the water subsequently freezes so that the pulley wheel teeth are filled with ice, then this may damage the belt and/or cause itto slip.

It is an object of the invention to provide a toothed belt drive which is suitable for use in circumstances in which the rotational axis of a toothed wheel on which the belt runs slopes relative to the horizontal, and which can be used in a exposed environment in which water may splash onto the drive and subsequently freeze.

According to the invention there is provided a toothed belt drive transmission in which a toothed belt extends partly around a rotable toothed wheel to establish a drive via intermeshing teeth, a belt stop plate being disposed at a side of the toothed wheel to provide an abutmentto preventthe beltfrom sliding offthewheel, the belt stop plate having at least one aperture or recess at a location in line with the teeth on the wheel to permit liquid to drain away from the teeth on the wheel.

An embodiment of a belt drive according to the invention will now be described by way of example and with reference to Figures 2 and 3 of the accompanying drawings, in which: Figure 2 isafrontviewofthe lower end of a belt extending around a toothed wheel, and Figure3 is a corresponding sideview.

The toothed belt drive shown in Figures 2 and 9 intended to be used on the engine shown in Figure 1 in place of the friction belt drive shown. The drive includes a toothed pulley wheel 1 afast on the front end of a crankshaft 2a, the wheel 1 a serving to drive a toothed belt 7a. The upper end of the belt 7a (not shown) will extend around a similartoothedwheel corresponding to wheel 4 of Fig 1 mounted on a power take-off shaft as shown at 3 in Fig 1.Assuming thatthe crankshaft 2 slopes downwardly from the front end shown towards the rearend,then in operation oftl1e belt drive (i.e. with the engine running) the belt 7a will tend to slip o < f the pulley wheel 1 a in the direction of the arrow A. To prevent this, a belt stop plate 9 is disposed at one side ofthe wheel 1 ato provide an abutmentforthe belt.

The stop plate 9 comprises a disc rotable with the wheel 1 a aboutthe crankshaft axis, the disc extending radially outwardly beyond the profile of the teeth 10 on the wheel 1 a. In the illustrated arrangement the stop plate 9 is mounted directly on the crankshaft2 and abuts the wheel 1 a, but instead the stop plate 9 could be integral with toothed wheel 1 a so that it would be attached to the wheel 1 a rather than to the crankshaft 2. A similar stop plate may be provided on the second pulleywheel 6.

In useofthe drive, the belt 7a will abutthestop plate 9which has a lower centre of rotation than the wheel 1 a. As mentioned above, it is likely that the drive may become splashed with water from the road or from a vehicle coolant system. If this happens, then when the engine is stopped water may run down the belt, and if the belt stop plate 9 were a plain disc, then water could be trapped in the spaces 11 between adjacent gear teeth 10 atthe top of the wheel 1 a. This water could freeze, sothatwhen the enginewas re-started, the spaces 11 would be filled with ice causing the belt7ato The drawing(s) originally filed were informal and the print here reproduced is taken from a laterfiled formal copy. bestretched ordamaged, and possiblycausingthe belt to slip.To avoid this, the belt stop plate 9 is formed with an annular drainage channel 12 open towards the teeth 10 and ir line with the teeth around .he wheel 1 a.

Anywaterthatwould otherwise be trapped in the spaces 11 will thus flow into the top of the annular chunnel 12 and drain down to the bottom ofthe channel to the region 13 from where it will run off.

In place of the single channel 12, the plate 9 could have several through apertures (not shown) spaced around the plate 9so thatthe water could run through the plate9fromfrontto backtothencedrain away. It would also be possible forthe plate 9 to have both the channel 12 and the through apertures.

The toothed wheel 1 a can be made by extruding aluminium through a suitable die and cutting the extruded length into pieces of the required thickness.

Claims

1. A toothed belt drive transmission in which a toothed belt extends partly around a rotatable toothed wheel to establish a drive via intermeshing teeth, a belt stop plate being disposed art a side of the toothed wheel to provide an abutment to preventthe belt from sliding offthe wheel, the belt stop plate having at least one aperture or recess at a location in line with the teeth on the wheel to permit liquid to drain away from the teeth on the wheel.

2. A drive according to claim 1, in which the belt stop comprises a disc rotatable with the toothed wheel aboutthe same axis as the toothed wheel, the disc extending radially outwardly beyond the profile of the teeth on the toothed wheel.

3. A drive according to claim 2, in which the disc and the toothed wheel are mounted abutting one another on a common shaft.

4. A drive according to claim 2, in which the disc is integral with the toothed wheel.

5. A drive according to any of claims 2 to 4, in which the disc has an annular drainage channel open towards and in line with the teeth on the toothed wheel.

6. A drive according to any ofclaims 2 to 5, in which the axis of rotation ofthe disc and the toothed wheel slants so thatthe centre of rotation of the disc is lower than the centre of rotation of the toothed wheel.

7. Adrive according to claim 6, in which, in use of the drive, the belt abutsthe disc.

8. A drive according to any preceding claim, in which the belt extends upwardly from the toothed wheel.

9. A drive substantially as described herein with reference to Figs 2 and 3 of the accompanying drawings.

10. A drive according to any preceding claim, in which the toothed wheel is mounted to rotate with the crankshaftofavehicle engine.