Push-type scooters are extremely popular and a large quantity have been sold world- wide. Arising from the success of the push-type scooters motorised mini-scooters have been developed. Motorised scooters have also met with widespread acceptance. The cost of a motorised scooter is however considerably more than the cost of a push-type scooter. A need therefore exists for a relatively inexpensive and easy to use apparatus which can be used to drive a push-type scooter.

SUMMARY OF THE INVENTION The invention provides an electric drive apparatus for a scooter which includes a support structure, a drive pinion which is peripheral engageable with a wheel of the scooter, an electrical arrangement for rotatably driving the pinion, a mounting device on the support structure which is engageable with a complementary formation on the scooter, and a mechanism on the support structure which is engageable with a formation on the scooter and which is adjustable to vary the degree of force which is exerted by the drive pinion on the scooter wheel.

Preferably the mechanism imparts force to the drive pinion, which bears on the scooter wheel, through the medium of a biasing device.

The biasing device may be a coil spring or any equivalent component.

The mechanism may be arranged so that the force exerted by the biasing device increases as the pinion bears with a greater degree of force on the scooter wheel,

The biasing device may be hooked onto, or otherwise engaged with, a component of , the scooter. In a preferred form of the invention the biasing device includes two formations which respectively are engageable with structure on respective opposing sides of the scooter front wheel e. g. on suitable formations on a fork which supports the front wheel.

Preferably the mounting device is such that the support structure is suspended from the complementary formation on the scooter. This may be achieved by engaging the mounting device with a hook-type action with the complementary formation.

The complementary formation is preferably located on a steering column of the scooter.

The complementary formation may be in the nature of a projection and the mounting device may include an aperture or recessed formation with which the projection is releasably engageable.

Preferably the mounting device is partly insertable into a recess and is then pivotable downwardly so that the projection is engageable with the mounting device. This action also preferably brings the pinion into abutting relationship with a peripheral surface of the wheel.

The mechanism may be of any appropriate kind and may be engageable with any suitable formation or location of the scooter. Preferably though the mechanism is engageable with the scooter at or near a fork which supports a front wheel of the scooter. Thus the pinion is preferably peripherally engageable with a front wheel of the scooter.

The mechanism may be such that it can be actuated to draw the pinion into tighter ' ? engagement with a peripheral surface of the front wheel of the scooter. Preferably the arrangement is such that as the pinion is drawn towards the front wheel this movement takes place against a biasing force which is exerted by the mounting device which tends to move the pinion away from the front wheel.

The electrical arrangement preferably includes a power source, a motor which, in use, is driven by the power source, and which drives the pinion and a switching system which connects the power source to the motor only when the scooter has at least a predetermined minimum forward speed.

The predetermined minimum forward speed may be detected by measuring rotational speed of a wheel.

The switching system may include a sensor for detecting rotational speed of a wheel.

This may be done in any suitable way. For example use may be made of a signal generator which is driven by the wheel and which generates a signal which is dependent on the rotational speed of the wheel. When the signal reaches a certain level, indicative of the predetermined minimum forward speed, a switch is closed to connect the motor to the power source.

In a preferred embodiment of the invention the motor is engaged with a wheel of the scooter via the pinion and, initially, acts as a generator when the scooter is manually propelled forward. The voltage which is generated by the motor is proportional to the rotational speed of the wheel with which the motor is engaged. The switch is closed when the voltage reaches a predetermined level which corresponds to a predetermined

minimum forward speed of the scooter and the motor then functions as a motor and not as a generator for it is driven by the power source and drive is transferred to the wheel.

Although the pinion may be connected to a rear wheel of the scooter it is preferred for the pinion to be engaged with a front wheel of the scooter.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is further described by way of example with reference to the accompanying drawings in which : Figure 1 is a side view of a scooter which includes an electric drive apparatus according to the invention attached to the scooter, Figure 2 shows a mounting device which is used to support the electric drive apparatus, Figure 3 is a front view of the device of Figure 3, Figure 4 is an enlarged view showing the way in which the electric drive apparatus is attached to the mounting device, Figure 5 shows a mechanism detached from the electric drive apparatus, Figure 6 illustrates a mechanism according to one form of the invention, Figure 7 shows a mechanism according to a variation of the invention, and Figure 8 is a circuit diagram of electric drive apparatus according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 of the accompanying drawings illustrates a steering column 10 of a scooter, which is not shown in detail, and which extends downwardly through a steering bush 12 to a fork 14 to which a front wheel 16 of a scooter is mounted.

Electric drive apparatus 18 is attached to the scooter. The apparatus 18 includes a housing or support structure 20 which contains a battery 18A, a control circuit 18B, and an electric motor 18C (shown in outline only). A pinion 22 which is driven by the motor is positioned so that it can be peripheral engaged with the front wheel 16 of the scooter.

A mounting device 24 is attached to the steering column 10. As is shown in Figures 2 and 3 the mounting device includes a two-part clamp 26A, 26B which can be clamped onto the column by means of bolts 28. On its forward side the mounting device has a depression 30 which at its upper end is covered by a bridging piece 32 to define a cavity 34. A pin 36, fixed to the mounting device, projects forwardly at a lower end of the depression 30.

The support structure 20 has a flat spring steel rod 38 fixed to it, extending upwardly.

The rod is shaped so that it can be inserted into the recess 34. The rod is formed with a hole 40 into which the projection 36 can be inserted.

A mechanism 44, shown in Figure 5, is engaged with the support structure 18. The mechanism includes a hook-shaped member 46, a threaded shank 48 and a nut 50 which is engaged with the shank and which is rotatable by means of a knob or handle 52. The mechanism passes through an aperture in the support structure which allows the hook-shaped member 46 to be engaged with the fork 14, as is shown in Figure 1, and which positions the handle 52 so that it projects from a front face 54 of the support structure, again as shown in Figure 1.

The mounting device 24 is normally left permanently engaged with the steering column 10. The electric drive apparatus 18 can readily be engaged with, or disengaged from,

the mounting device. To engage the electric drive apparatus with the mounting device the rod 38 is inserted at an angle into the recess 34 (see Figure 4) and the electric drive apparatus 18 is then pivoted downwardly as is indicated by means of an arrow 56 in Figure 4 so that the hole 40 is threaded over the projection 36. At the same time the flat bar is brought into the depression 30. The electric drive apparatus is thus suspended from the mounting device.

The hook-shaped member 46 is then engaged with the fork 14 and the handle 52 is rotated to bring the pinion 22 into firm engagement with the peripheral surface of the front wheel 16. When this takes place the rod 38 is pivoted about the projection 36 so that an upper end of the rod, designated 60, is brought into engagement with an opposing surface 62 of the bridging piece 32. The rod 38, which is made from spring steel, thus acts as a biasing member which tends to urge the pinion 22 away from the wheel 16. The biasing force is however overcome by rotating the handle 52 which threads the nut 50 further onto the shank 48. Clearly, by rotating the handle 52 the degree of force which is exerted by the pinion on the front wheel can be varied according to requirement.

On the other hand when the nut is released the biasing force exerted by the rod 38 urges the pinion 22 away from the wheel 16. This is an important feature for if the battery in the electric drive apparatus should become discharged the user is able to disengage the pinion from the wheel in a simple yet effective manner. The wheel is then for all practical purposes freed from the pinion and the scooter can then be driven manually, i. e. with a push-type action, and the pinion does not exert drag on the wheel.

In addition to or in place of the biasing force which is exerted by the flat bar 38, the '* ; biasing force can be exerted by any appropriate spring or biasing device, schematically shown and designated by the reference numeral 60 in Figures 1 and 5, which acts between the scooter and the support structure 20. The spring is preferably attached to the tensioning device but can be located at any other appropriate position.

It is advantageous for the tensioning device to exert force on the pinion via a biasing member and Figure 6 illustrates a mechanism 110 which enables this objective to be achieved.

The mechanism includes a hook-shaped member 112, a threaded shank 114, and a nut 116 which is engaged with the shank and which is rotatable by means of a handle 118.

A coil spring 120 connects the member 112 to the shank 114.

The mechanism is used essentially in the manner which has been described and which, for this reason, is not elaborated on herein. The use of the coil spring 120 does however result in two advantages namely: (a) the force which is exerted on the pinion, when the nut 116 is tightened, is exerted through the medium of the spring 120 which therefore"cushions"the force. A more effective transfer of drive from the pinion to the wheel results ; and (b) the member 112 is, to a limited extent at least, pivotally movable relatively to the shank 114 about an engagement point 122. This assists in manipulating the member 112 so that it can more readily be engaged with the front wheel fork, or any other component of the scooter.

Figure 7 illustrates a mechanism 130 which in many respects is similar to the device 110 shown in Figure 6. Where applicable therefore like reference numerals are used to designate like components. It is to be noted though that the mechanism 130 includes two hook-shaped members designated 112A and 112B respectively which are connected via springs 120A and 120B respectively to a threaded shank 114.

The mechanism 130 is used in the same way as the device 110 but the hook-shaped members 112A and 112B are respectively engaged with formations, preferably on the front wheel fork, on opposing sides of the front wheel. This provides a more balanced attachment of the scooter drive apparatus to the scooter.

It has been found when the scooter is started, from rest, that the drive force available from the drive pinion may not be sufficient to propel the scooter from standstill. A forward manual push is required and thereafter the drive pinion acts effectively. Figure 8 shows a control circuit 18B (refer to Figure 1) of an electric drive apparatus which enables the pinion to be rotated by the motor only when the scooter's forward speed is at least a predetermined minimum speed.

The circuit is connected to the motor 18C from which extends the pinion 22 which is engaged with the front wheel, and to the battery 18A. The circuit includes a fuse 216 or any similar overload protective device, a relay 218 which controls contacts 220, a transistor switch 222, and a rectifier and bridge network 224 connected to the base of the transistor switch 222.

The pinion 22 is, as has been explained, engaged directly with a peripheral surface of the front wheel of the scooter. As the motor is a DC motor which, normally, is driven by the battery 18A, it is apparent if the motor were to be rotated by the front wheel acting

on the pinion, without the battery driving the motor, that the motor would act as a generator and generate a voltage across its input terminals 226 and 228. This voltage is stabilised by a capacitor 230 and rectified by a diode 232 in the network 224.

A switch 234 is provided for a user to control on/off operation of the motor. If the switch is closed and the motor is stationary i. e. it is not driven by the front wheel, then there is no voltage at the base of the transistor switch 222, for the switch 220 is open and the battery is isolated from the transistor base, and consequently the transistor does not turn on. When the scooter is manually pushed forward by a user then, as explained, the motor is driven and a voltage is generated at the terminals 226 and 228. A portion of the rectified voltage is tapped by the network 224 and applied to the base of the transistor. If this voltage is sufficiently high, i. e. the forward speed of the scooter is above a predetermined minimum speed and, at the same time, the switch 234 is closed, then the transistor is turned on. The relay 218 is energised and the contacts 220 are closed. The voltage of the battery 214 is then applied to the terminals 226 and 228 and the motor is driven by the battery. At the same time a latching arrangement results in that the battery voltage is also tapped and applied to the base of the transistor which is thereby held on.

The aforementioned arrangement ensures that it is not possible to drive the motor, from the battery, when the scooter is at standstill. It is necessary to ensure that the scooter is moving forward at least with a predetermined minimum speed and this is obtained with a manual push. Once the minimum speed is achieved the battery is quite capable of driving the motor to ensure ongoing forward movement with minimum strain.

If the switch 234 is open and the scooter is pushed forward it is not possible for the relay coil to be energized.

The use of the motor as a generator to detect forward speed is preferred although it is evident that other techniques may be employed. For example it may be possible to use an auxiliary signal generator which produces a voltage signal the strength of which is determined by the rotational speed of the wheel which is being monitored. In other respects however the switching arrangement is similar to what has been described.

A further benefit has been observed. When the switch 220 is closed and the motor is driven by the battery the motor is pulled towards the front wheel of the scooter. The degree of frictional engagement of the pinion with the front wheel is such that the pinion drives the front wheel with a minimum of power loss. The engagement force of the pinion with the front wheel is, on the other hand, not so great that the pinion deforms, or removes material from, the front wheel.