GB2145494A

GB2145494A - A drive transfer device

Info

Publication number: GB2145494A
Application number: GB08419418A
Authority: GB
Inventors: Richard Douglas Pearson
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-08-20
Filing date: 1984-07-30
Publication date: 1985-03-27
Also published as: GB8322463D0; GB8419418D0; GB2145494B

Abstract

A drive transfer device, for example for a child's pedal car, all-terrain vehicle or tracked vehicle comprises a drive shaft (1) having at each end an intermediate member (2) and an output member (3). The output member (3) is rotatable relatively to the drive shaft (1) but the intermediate member (2) is splined to the drive shaft (1) so that it can be displaced into driving engagement with the output member 3 to provide selective drive to a wheel 4 connected to the output member (3). Steering, or steering assistance, can then be effected by transmitting drive to one or other of the wheels (4) while allowing the other to freewheel or braking it by braking surface 18a. <IMAGE>

Description

SPECIFICATION A drive transfer device This invention relates to a drive transfer device.

When a vehicle having two driven wheels on the same axle negotiates a bend, one or both of the wheels will be forced to slip and there will be considerable resistance to steering. In most three- or four-wheeled motor vehicles, this problem is avoided by splitting the drive to the wheels in a differential. However, the cost of a differential cannot be justified in less expensive vehicles, such as children's pedal cars. Consequently, in children's pedal cars it is usual for only one of the rear wheels to be driven, the other rotating freely on the axle. Unfortunately, this ieads to loss of traction, and a turning circle that is limited by the scrubbing of excessively pivoted wheels.

In so-called All Terrain Cycles (ATC's) there are two rear wheels which are mounted on a common drive shaft, and a front wheel which can be steered by handlebars. Because the rear wheels must rotate together, steering is very difficult except on loose surfaces such as sand.

According to the present invention there is provided a drive transfer device comprising a drive shaft, an output member mounted rotatably on the drive shaft at each end of the drive shaft, and coupling means for selectively coupling each output member to the drive shaft for rotation with the drive shaft, whereby drive can be transmitted to either or both of the output members.

Embodiments of drive transfer devices in accordance with the present invention may be used, for example, in a child's pedal car on an All Terrain Cycle (ATC) to transmit drive to two wheels mounted on a common drive shaft when travelling in a straight line, but to disconnect one of the wheels (preferably the inside one) when negotiating a bend.

In a preferred embodiment, there is an intermediate member at each end of the drive shaft. The intermediate member is fixed against rotation relative to the drive shaft, and the coupling means acts to couple each intermediate member to the respective output member. The coupling means may, for example, comprise mating formations or friction surfaces on each intermediate member and output member.

In one embodiment, each intermediate member is axially displaceable on the drive shaft into and out of driving engagement with the output member. Alternatively, each output member may carry a displaceable element which is rotationally fixed to the output member but is axially displaceable into and out of driving engagement with the respective intermediate member.

Each displaceable element may also be movable into engagement with a stationary member thereby to brake the output member.

Alternatively, each output member may be -provided with a separate braking element which is movable into engagement with the stationary member.

Steering assistance can be achieved, particularly for track-laying vehicles, if the output members can be driven in opposite directions to each other. To this end the intermediate member at one end of the drive shaft may be movable into a position in which it is released for rotation relatively to the drive shaft and engages drive means to rotate the intermediate member in a direction opposite to the direction in which the drive shaft is driven by the drive means.

For a better understanding of the present invention and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a partly sectioned plan view of one embodiment of a drive transfer device; Figure 2 is a sectional view of another embodiment of a drive transfer device; Figure 3 is a sectional view of a third embodiment of a drive transfer device; Figure 4 is a sectional view of a fourth embodiment of a drive transfer device; and Figure 5 is a sectional view of a fifth embodiment of a drive transfer device.

The drive transfer device of Fig. 1 is suitable for use in, for example. a child's pedal car. The device comprises a drive shaft 1 on which is mounted, at each end, an intermediate member 2 and an output member 3. A driven wheel 4 of the pedal car is secured by screws to each output member 3. Alternatively, the wheels 4 may constitute the output members.

The drive shaft 1 is provided with drive means (not shown) for rotating it. As is conventional in pedal cars, the drive means may comprise a pedal-operated linkage acting on cranked portions of the drive shaft 1 or a pedal-operated chain drive to the drive shaft 1. Each intermediate member 2 is axially slidable along the drive shaft 1, but is fixed against rotation by a key 5. A spring 6 acts between a flange 2a of each intermediate member 2 and an abutment plate 9 welded to the drive shaft 1. The oppositely facing surfaces of each intermediate member 2 and the respective output member 3 have cooperating formations so that these two members function as a dog clutch.

Each output member 3 is journalled in a plain bearing 7 which is fixed to a frame 1 5 of the pedal car. Each bearing 7 has axial end flanges 10 which abut against, respectively, a shoulder on the output member 3 and a face of the wheel 4 in order to prevent axial movement of the output member 3. Each output member 3 is freely rotatable on the drive shaft 1 at a bearing interface 8. In order to provide good bearing characteristics, the output member 3 may be made from a suitable plastics material, such as nylon.

Support members 11 having channel sections 11 a are fixed to the frame 1 5 and each carry a yoke 1 3 which is pivotally connected to the respective support member 11 by pivot pin 1 2. The yokes 1 3 are connected to a steering drop arm 40 by respective links 42.

The drop arm 40 may be, for example, part of a steering mechanism for front wheels of the pedal car. Alternatively, however, the drop arm 40 may be used solely to control the yokes 13, the non-driven wheels of the pedal car comprising swivelling castors. The links 42 are connected to the yokes 1 3 by pin and slot connections 44 in order to provide a lost motion connection between the links 42 and the yokes 1 3. Each yoke 1 3 has a bearing face 14 for engagement with a flange 2a of the respective intermediate member 2.

Operation of the transfer device is as follows. During straight-ahead travel, the device is in the condition shown in Fig. 1. The intermediate members 2 are pressed by the springs 6 into driving engagement with the respective output members 3. Drive is then transmitted from the drive shaft 1, through the intermediate members 2, to the output members 3 and the wheels 4. Both wheels are driven. To make a turn, for example a turn to the right, the drop arm 40 is turned clockwise. This causes the yoke 1 3 on the right-hand side to pivot to the left about its pivot pin 13, which brings its bearing face 14 into engagement with the flange 2a of the respective intermediate member 2. Further movement carries the intermediate member 2 to the left against the action of the spring 6.

This takes the intermediate member 2 out of engagement with the output member 3, which then freewheels, with the wheel 4, on the drive shaft 1. During this manoeuvre, the lost motion connection 44 between the yoke 1 3 on the left hand side and its link 42 allows the yoke 1 3 to remain stationary as the drop arm 14 is turned. Drive to the left hand wheel 4 is thus maintained, all the available torque being transferred to that wheel only, and the pedal car can turn sharply to the right without tyre scrub. The friction in the bearing 7 of the free-wheeling wheel 4 retards this wheel to some extent, thus providing steering assistance. A turn to theleft can be made in an analogous manner.

The construction of Fig. 1 could be modified by omitting the springs 6 and using the yokes 1 3 to cause positive engagement of the intermediate members 2 with the output members 3.

Fig. 2 shows an alternative construction.

Only the mechanism on the right-hand end of the drive shaft 1 is shown in Fig. 2, the mechanism on the left-hand end being similar.

Parts shown in Fig. 2 and the subsequent Figs. which have the same function as those in Fig. 1 are given the same reference numbers.

In Fig. 2, the intermediate member 2 is formed as one part of a cone friction clutch, the other part of the clutch being constituted by the output member 3. The cooperating faces of the clutch may have an appropriate facing of friction material. The intermediate member 2 is axially movable, but rotationally fixed, on a sleeve la by means of a key 5.

The sleeve 1 a is fixed to the drive shaft 1.

The intermediate member 2 is biassed outwardly by the spring 6, which reacts against an abutment in the form of a locknut 9 which engages a threaded portion of the sleeve 1 a.

The output member 3 is rotatably mounted on the drive shaft 1 by means of plain bearings 8, and is supported in a bearing housing 7a by a plain bearing 7, for example of oil impregnated nylon. Alternatively a deep groove ball bearing may be used. The bearing housing 7a is fixed to the frame 1 5 of the pedal car. As in Fig. 1, a wheel 4 is secured to the driven member 3. A nylon thrust washer 10 is provided to take up end float in the assembly.

Operation of the construction shown in Fig.

2 is generally the same as that of Fig. 1. To disconnect the drive from the illustrated right hand wheel 4, the yoke 1 3 is moved to the left to bring its bearing face 14, constituted by a nylon thrust washer, into contact with a flange on the intermediate member 2, and then to displace the intermediate member 2 against the action of the spring 6 to take it out of contact with the conical surface on the output member 3. The wheel 4 can then freewheel on the drive shaft 1. The force applied by the spring 6 to engage the cone clutch constituted by the intermediate member 2 an the output member 3 can be adjusted by means of the lock nut 9. Furthermore, by unscrewing the lock nut 9 from the sleeve 1 a, access can be gained to the conical surfaces of the intermediate member 2 and the driven member 3 for routine cleaning. It will be appreciated that, as in the embodiment of Fig. 1, the force applied by the yoke 1 3 on one end of the shaft 1 is reacted by the cone clutch at the other end, so increasing the grip of that other clutch.

Fig. 3 shows an embodiment for selectively driving industrial machinery disposed at opposite ends of the drive shaft 1. Like Fig. 2, Fig.

3 shows only the right-end of the drive shaft 1, the drive mechanism at the left hand side being the same. In Fig. 3, the output element 4 is shown as a pulley instead of a drive wheel of a pedal car. The pulley 4 could be used, for example, to drive a conveyor or a tool such as a circular saw or grinding wheel.

Alternatively, the output element 4 could itself be a saw or grinding wheel instead of a pulley.

As in the embodiment of Fig. 2, the intermediate member 2 constitutes one part of a cone clutch and is mounted on a sleeve la which is fixed to the drive shaft 1. In Fig. 3, however, the intermediate member 2 is axially fixed on the shaft 1 by the lock nut 9. The output member 3 is in two parts, namely a splined inner sleeve 3a on which an axially displaceable element 3b is mounted. The element 3b constitutes the other part of the cone clutch. The spring 6 acts between a flange on the displaceable element 3b and the inner race of a ball bearing 7 which supports the inner sleeve 3a in the housing 7a. The inner sleeve 3a is supported on the drive shaft 1 by plain bearings 8. The flange of the displaceable element 3b has a conical outer surface for cooperation with a corresponding stationary conical surface formed on the housing 7a.

In operation, actuation of the yoke 3 causes the yoke to engage a thrust washer 14 on the displaceable element 3b to move this element to the right against the force of the spring 6.

The first part of this movement takes the conical surface of the displaceable element 3b out of contact with the corresponding surface of the intermediate member 2, so disengaging the output member 3 from the drive shaft 1.

The pulley 4 can then freewheel and all the drive is transferred to the pulley on the other end of the drive shaft. Further displacement of the displaceable element 3b brings the conical surface on the flange into contact with the corresponding surface on the housing 7a, which brakes the output member 3 and consequently also brakes the pulley 4. This provides a useful safety feature, in that the pulley 4 which is not receiving drive, and any machinery associated with it, is positively arrested. The embodiment of Fig. 3 thus provides a rapid stop/start capability for equipment driven from opposite ends of the drive shaft 1.

The embodiment of Fig. 4 is a more sophisticated version of the construction of Fig. 3, and is suitable for use in, for example, an All Terrain Cycle (ATC). The drive shaft 1 is provided with a chain sprocket 1 6 which itself carries the intermediate members 2. As with the embodiment of Fig. 3, the output member 3 comprises an inner sleeve 3a and an outer displaceable element 3b which is slidable on the inner sleeve 3a by means of splines 5.

The displaceable elements 3b have internal conical surfaces which cooperate with conical surfaces of the intermediate members 2 to form a cone clutch. The displaceable elements 3b also have outer conical surfaces which correspond to conical surfaces 1 8a formed in an outer bearing support 1 8 of the transfer device. Each displaceable element 3b is acted upon by a spring 6 which reacts against an inner bearing support 1 7 for a tapered roller bearing 7 which supports the inner sleeve 3a in the housing 18. The inner sleeve 3a is supported on the drive shaft 1 by plain bearings 8. The yokes 1 3 act on the displaceable element 3b of the drive member 3 through bearing faces 14.The outer bearing supports 1 8 are secured to flanges on a casing, which is part of the frame 15, by bolts 1 9. Shims 20 are provided between the flanges of the frame 1 5 and of the outer bearing support 18. Low friction thrust washers 10 take axial loads applied to the drive members 3.

In the condition shown, the drive transfer device transmits drive to both of the wheels 4. Drive is transmitted from the sprocket 1 6 to the intermediate members 2, and thence to the displaceable elements 3b, the inner sleeves 3a and the wheels 4. To make a turn to the right, the right hand yoke 1 3 is operated to displace the respective displaceable element 3b to the right, thus disengaging the output member 3 from the intermediate member 2. The right hand wheel 4 can then freewheel, while drive is transmitted through the left hand wheel 4, and the vehicle can turn without tyre scrub. Further movement of the right hand displaceable element 3b brings it into contact with the stationary conical surface 18, and the right hand wheel is braked.This provides additional steering assistance, and the vehicle can turn about the point of contact of the right hand wheel and the ground. Upon release of the yoke 13, the respective spring 6 breaks the frictional contact between the displaceable element 3b and the stationary surface 18a. A turn to the left is made in an analagous manner.

The position of each conical surface 1 8 with respect to the frame 1 5 and the stress in each spring 6 can be adjusted by removing the respective bolts 1 9 and inserting shims 20 of the appropriate thickness. In order to avoid dismantling the bearing 7 during this operation, screws or bolts 1 9b are inserted to hold the inner and outer bearing supports 1 7 and 1 8 together.

The yokes 1 3 are preferably connected to the steering mechanism of the ATC by a lost motion connection so that the front wheel can be turned through small angles without affecting the drive to the rear wheels. This avoids frequent slipping of the clutches, since the transfer device would become operative only when making relatively tight turns.

Fig. 5 shows a drive transfer device suitable for use in all terrain short wheel base vehicle or a track-laying vehicle. In this embodiment, drive is transmitted to the drive shaft 1 from a drive pinion 35 which meshes with a crown wheel 21. Correct meshing between the pinion 35 and the crown wheel 21 is achieved by means of shims 22 disposed between the crown wheel 21 and a flange 1b provided on the drive shaft 1. On the left-hand side of the crown wheel 21, a driving cone 52 of a cone clutch 50 is fixed to the crown wheel 21. A pressure cone 54 is rotationally connected to the driving cone 52 by means of pins 56. The driving cone 52 and the pressure cone 54 are pressed towards each other by springs 6. The output member 3 in this embodiment includes an inner sleeve 3a on which a displaceable element 3b, constituting the driven cone of the clutch 50, is splined.A braking element 27 is also splined to the inner sleeve 3a and has a conical surface for cooperation with a corresponding stationary surface 1 8a on an outer bearing support 1 8. A spring 28 acting between the inner race of the bearing 7 and the braking element 27 biasses the braking element 27 out of contact with the conical surface 18a. As in the embodiment of Fig. 4, the bearing 7 is a tapered roller bearing, and is mounted between the outer bearing support 1 8 and an inner bearing support 1 7 which is mounted on the inner sleeve 3a.

The yoke 1 3 is positioned to act through bearing faces 14 on the pressure cone 54. A further bearing face 1 4 is also provided on the braking element 27 to permit rotating contact between the braking member 27 and the pressure cone 54.

The drive mechanism on the right hand side of the crown wheel 21 is generally the same as that on the left hand side, except that the driving cone 52 is fixed to a crown wheel 29 which is axially displaceable along the drive shaft 1. The crown wheel 29 has a splined portion 23, and axial displacement of the crown wheel 29 to the left from the position shown in Fig. 5 moves these splines out of engagement with corresponding splines on the drive shaft 1. A spring 30 acting against shims 33 abutting the flange 1 b biasses the crown wheel 29 to the right. Thrust bearings 32 are provided on the left hand face of the crown wheel 29, and a plain bearing 31 supports the unsplined portion of the crown wheel 29 on the drive shaft 1.

As well as the yoke 13, a yoke 24 is provided for engagement with the crown wheel 29 through further friction facings 14.

The output element of the transfer device shown in Fig. 5 comprises, instead of a wheel, a fork 4 of a universal joint for connecting the driven member 3 to, for example, a track wheel of the vehicle. The inner sleeve 3a of the driven member 3 also carries a secondary chain sprocket 26 for transmitting drive to other track wheels on the same side of the vehicle.

In operation of the transfer device of Fig. 5, drive is transmitted to the drive shaft 1 through the pinion 35 and the crown wheel 21. For forward drive, the device is in the condition shown in Fig. 5, and drive is transmitted through the cone clutch 50 on the left-hand side of the crown wheel 21 to the inner sleeve 3a and thence to the universal joint fork 4 and the secondary sprocket 26.

Also, drive is transmitted from the crown wheel 21, through the splines 23 to the crown wheel 29 and thence to the right-hand clutch 50 and the right-hand fork 4 and secondary wheel 26. If a turn to the right is to be made, the right hand yoke 1 3 is operated to move the right hand pressure cone 54 away from the driving cone 52 against the pressure of the spring 6, thus releasing the driven cone 3b. The right hand output member 3 can then freewheel, while drive continues to be transmitted to the left hand output member 3 to cause the vehicle to turn to some extent.Further displacement of the yoke 1 3 will bring the pressure cone 54 into contact with the braking element 27 to displace the braking element 27 into contact with the stationary surface 18a, thus braking the output member 3 and increasing the sharpness of turning of the vehicle. The control linkage may be arranged so that both braking elements 27 may be moved simultaneously into contact with the stationary surfaces 1 8a to brake the vehicle. Upon release of the yokes 1 3, the springs 28 move the braking elements 27 out of contact with the surfaces 18a.

An even sharper turn can be achieved by operating the yoke 24 to displace the crown wheel 29 to the left. This brings the crown wheel 29 into engagement with the pinion 35, the depth of meshing being controlled by the shim 33 which is engaged by the thrust bearing 32. This movement of the crown wheel 29 causes the splines 23 to disengage from the corresponding splines on the drive shaft 1, enabling the crown wheel 29 to rotate freely on the drive shaft 1. In its axial movement, the crown wheel 29 takes with it the cone clutch 50, the driven cone 3b moving along the inner sleeve 3a. The driven member 3 is thus driven from the pinion 35 in a direction opposite to the direction of rotation of the drive shaft 1, enabling the vehicle to turn about an axis situated between its tracks.

Adjustment of the clearance between the braking element 27 and the conical surfaces 1 8 can be effected using the shims 20 in the same manner as described with reference to Fig. 4. It will be appreciated that, instead of splines 23, other forms of coupling, such as dogged coupling, could be used to connect the crown wheel 29 releasably to the drive shaft 1.

Claims

1. A drive transfer device comprising a drive shaft, an output member mounted rotatably on the drive shaft at each end of the drive shaft, and coupling means for selectively coupling each output member to the drive shaft for rotation with the drive shaft, whereby drive can be transmitted to either or both of the output members.

2. A drive transfer device as claimed in claim 1, in which an intermediate member is provided at each end of the drive shaft, each intermediate member being fixed against rotation relative to the drive shaft.

3. A drive transfer device as claimed in claim 2, in which each intermediate member is axially displaceable relatively to the drive shaft into and out of driving engagement with the respective output member.

4. A drive transfer device as claimed in claim 2, in which each output member is provided with a displaceable element which is rotationally fixed but axially displaceable relatively to the output member for movement into and out of driving engagement with the respective intermediate member.

5. A drive transfer device as claimed in claim 4, in which each displaceable element is displaceable into engagement with a stationary member, thereby to brake the output member.

6. A drive transfer device as claimed in claim 4, in which each output member is provided with a further displaceable element which is displaceable into engagement with a stationary member thereby to brake the output member.

7. A drive transfer device as claimed in any one of claims 2 to 6, in which each intermediate member and the respective output member or displaceable element are formed as cooperating parts of a dog clutch.

8. A drive transfer device as claimed in any one of claims 2 to 6, in which each intermediate member and the respective output member or displaceable element comprise parts of a cone clutch.

9. A drive transfer device as claimed in any one of the preceding claims, in which means is provided for causing rotation of the output members in opposite directions to each other.

10. A drive transfer device substantially as described herein with reference to, and as shown in, any one of lTigs. 1 to 5 of the accompanying drawings.

11. A vehicle having driven wheels and a drive transfer device in accordance with any one of the preceding claims, the driven wheels being secured to, or constituted by, the output members.

12. A vehicle as claimed in claim 11, in which the coupling means is operatively connected to a steering mechanism of the vehicle.

1 3. A vehicle as claimed in claim 11 or 12, which is a pedal-powered vehicle.