GB2170458A

GB2170458A - Disengageable drive and electric power pack for bicycle

Info

Publication number: GB2170458A
Application number: GB08602930A
Authority: GB
Inventors: Brian Colin Danks; John Wiles
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-02-06
Filing date: 1986-02-06
Publication date: 1986-08-06
Also published as: GB8503006D0; GB8602930D0

Abstract

A bracket 10 is secured to bicycle seat stays 12 next to the seat tube 14. A drive assembly 20, comprising an electric motor 26 and drive roller 28, depends from a pin 22 on the bracket to enable the drive roller to be swung rearwardly into drive-transmitting engagement with the rear wheel 24 of the bicycle. The geometry of the arrangement is such that the torque on the drive roller tends to maintain the roller 28 in engagement with the wheel 24, but as the road speed increases so does the tendency for the roller to be thrown forwardly and the drive disengaged. Drive can be engaged initially by means of a cable control 40 to a rocking lever 36 which acts on a stud 44 of the drive assembly 20. <IMAGE>

Description

SPECIFICATION Disengageable drive This invention relates to a disengageable drive, from a motor to an output wheel, which has been developed in the first instance for use in providing electric power assistance for a bicycle or other cycle but which could find wider application.

The invention provides, in one of its aspects, a disengageable drive comprising a motor which is arranged to drive a rotatable drive roller for rotation of an output wheel with which the drive roller is arranged to be drivingly engaged, the motor and drive roller being pivotally mounted in common whereby the drive roller can swing into and out of drive-transmitting engagement with the periphery of the output wheel, the arrangement being such that the drive roller in swinging into engagement with the output wheel moves in a general direction contrary to that in which the periphery of the output wheel at the point of engagement travels when driven and engages the output wheel without passing between the swing axis of the drive roller and the rotational axis of the output wheel.

In another of its aspects the invention provides a power-assisted cycle comprising a disengageable drive as set out in the last preceding paragraph, the output wheel being a roadwheel of the cycle, the motor being an electric motor, and the motor and drive roller being pivotally mounted in common on supporting means secured to the cycle frame.

Whilst the terms "roller" and "wheel" are used throughout herein, as most appropriate in the context of power assistance for a cycle, it is to be understood that the terms could have broad meanings in application of the invention to other kinds of machine.

In a further one of its aspects the invention provides power pack equipment suitable for fitment to a cycle in providing a cycle as set out in the last preceding paragraph but one, the pack comprising supporting means which is adapted to be secured to the cycle frame, and a motor and drive roller assembly which is pivotally mounted on the supporting means for engagement of the drive roller with a roadwheel of the cycle when the supporting means is secured to the frame.

There now follows a detailed description, to be read with reference to the accompanying drawings, of power pack equipment fitted to a bicycle. The equipment, and the cycle fitted with the equipment, illustrates the invention by way of example.

In the accompanying drawings: Figure 1 is a schematic view from one side showing power pack equipment fitted to a bicycle; and Figure2 shows the equipment from the other side of the bicycle.

Power pack equipment fitted to a bicycle comprises supporting means in the form of a mounting bracket 10 which is secured to the seat stays 12 adjacentto the seat tube 14. The bracket 10 is provided with fitting means 16 (not shown in detail) which is adapted to permit the bracket to be secured to seat stays of various forms, in order that the equipment is suitable for sale for addition to any of a variety of manufactured bicycles. The bracket 10 projects rearwardly and upwardly from the stays 12, and a carrier 18 of a drive assembly 20 is pivotally secured to depend from a pin 22 between two leaves of an upper end portion of the bracket 10. The drive assembly is so arranged to swing about an axis parallel to that of the rear wheel 24 of the bicycle.

The carrier 18 comprises two spaced-apart side plates (one omitted, for clarity, from each Figure) between which an electric motor 26 is arranged to drive a rotatable drive roller 28 by means of pulleys 30 and 32 and a drive belt 34 extending between the pulleys. The motor 26 and the drive roller 28 are mounted one above the other (drive roller lowermost) on the carrier with their axes in parallel with the rear wheel axis.

The motor 26 and drive roller 28 are so pivotally mounted in common on the pin 22. The arrangement of the drive assembly 20 on the bracket 10 is such that the drive roller 28 can be swung, about the axis of the pin 22, into and out of engagement with the periphery of a pneumatic tyre of the rear wheel 24.

The assembly is mounted forwardly of the wheel axis, with the drive roller 28 at a level below the ievel of the top of the wheel. Accordingly, the drive roller is suspended to engage the tyre in a rearwards swinging movement, away from the bracket 10.

A push-on drive-engaging rocking lever 36 is pivotally mounted (as indicated at 38) on the bracket 10. An actuating cable 40, extending from a control lever ortwistgrip mounted on the cycle frame in a convenient place for a rider, is secured to one end of the lever. An opposite end portion 42 of the lever is positioned to bear against a fixed stud 44 of the carrier 18 when the one end of the lever is pulled by the cable; by this means the drive assembly can be urged to swing away from the bracket 10, owing to the lever pushing the stud 42 when the actuating cable 40 is pulled, and the drive roller 28 so brought into engagement with the wheel 24.

A spindle 46 extends rearwardly from a pivotal mounting 48 on the bracket 10. The spindle extends through a fixed eye 50 of the carrier 18, and a compression coil spring 52 on the spindle acts between the eye 50 and a nut 54 positioned rearwardly of the eye on a threaded end portion of the spindle. The nut 54 provides an adjustable stop which can be set to determine the limit of possible swinging movement of the drive roller 28 away from the bracket 10, into engagement with the compressible tyre of the bicycle wheel 24.

A further adjustable stop comprises the head of a screw 56 which is threaded engaged in a nut 58 mounted on the bracket 10. This stop is provided adjacent to that end of the push-on lever 36 to which the actuating cable 40 is connected, so to limit the movement of the drive assembly 20 towards the bracket 10, and so the possible swinging movement of the drive roller 28 from the wheel 24.

The power pack equipment comprises also at least one battery pack 60, suitable battery-supporting means 62 secured to the bicycle frame, and leads extending between the battery, the motor and a motor control device 64. The control device 64 is mounted on the bracket 10 and is arranged to be operated by means of the same actuating cable 40 as operates the push-on lever36.

Accordingly in use of the device, to obtain power assistance for the bicycle, the motor 26 is actuated and the drive roller 28 swung rearwards, into engagement with the rear wheel, by a common movement of the cable 40. As viewed in Figure 1, the roiler 28 is rotated anti-clockwise in order to drive the wheel 24 clockwise, and the bicycle forwards.

The torque on the drive roller, which is in frictional drive-transmitting engagement with the tyre, acts to swing the drive assembly 20 clockwise about its mounting pin 22, so to maintain the drive roller in engagement with the tyre with the stop provided by the nut 54 engaged. At all times the drive roller axis remains forwardly of an imaginary line connecting the axis of the pin 22 (the swing axis of the drive roller) and the rotational axis of the wheel 24, the drive roller in swinging into engagement with the tyre moving in a general direction (rearwards) contrary to that (forwards) in which the periphery of the tyre at the point of engagement travels when driven.

As the speed of the bicycle increases, so does the tendencyforthe drive roller 28to be thrown from the tyre. By suitable selection of the geometry of the arrangement, and the motor drive gear ratio, effective disengagement of the drive is so arranged to occur automatically at a predetermined road speed, the drive becoming automatically re-engaged should the road speed drop below that predetermined speed.A stop (not shown) associated with the control lever (or twistgrip) for moving the actuating cable 40, is so adjusted that the push-on lever 36 can itself serve to bring the drive roller 28 nearly but not quite into engagement with the wheel 24, the drive roller then remaining free to swing between that position and the position of maximum engagement determined by the setting of the nut 54, and so remaining free for the drive to become automatically disengaged. With well-charged batteries, the torque reaction from starting the motor 26 can itself be enough to engage the drive initially, but the provision of the push-on lever 36 enables the drive assembly 20 to be nudged to ensure engagement in the event of insufficient kick from the motor start.

An electronic variable speed control for the motor 26 may be provided. In addition to affording a greater degree of control, such an arrangement can permit the cycle to be drlven from stationary by the motor, rather than having to pedal the cycle up to a certain minimum speed before relying on the motor drive.

Claims

1. A disengageable drive comprising a motor which is arranged to drive a rotatable drive roller for rotation of an output wheel with which the drive roller is arranged to be drivingly engaged, the motor and drive roller beng pivotally mounted in common whereby the drive roller can swing into and out of drive-transmitting engagement with the periphery of the output wheel, the arrangement being such that the drive roller in swinging into engagement with the output wheel moves in a general direction contrary to that in which the periphery of the output wheel at the point of engagement travels when driven and engages the output wheel without passing between the swing axis of the drive roller and the rotational axis of the output wheel.

2. A power-assisted cycle comprising a disengageable drive according to claim 1, the output wheel being a roadwheel of the cycle, the motor being an electric motor, and the motor and drive roller being pivotally mounted in common on supporting means secured to the cycle frame.

3. A cycle according to claim 2 comprising a cable operated drive-engaging lever which is pivotally mounted on the supporting means and so arranged as to cause the drive roller to swing towards engagement with the output wheel upon the cable being pulled.

4. A cycle according to claim 3 in which an adjustable stop associated with the lever can be set to limit the possible swinging movement of the drive roller away from the output wheel.

5. A cycle according to any one of claims 2,3 and 4 in which he periphery of the output wheel is compressible and an adjustable stop is provided which can be set to limit the possible swinging movement of the drive roller into engagement with the output wheel.

6. Power pack equipment suitable for fitment to a cycle in providing a cycle according to any one of claims 2 to 5, the pack comprising supporting means which is adapted to be secured to the cycle frame, and a motor and drive roller assembly which is pivotally mounted on the supporting means for engagement of the drive roller with a roadwheel of the cycle when the supporting means is secured to the frame.

7. A power-assisted cycle substantially as hereinbefore described with refernce to the accompanying drawings.

8. Power pack equipment according to claim 6 substantially as hereinbefore described with reference to the accompanying drawings.

9. A power-assisted cycle having a disengageable drive comprising a motor which is arranged to drive a rotatable drive rollerfor rotation of a roadwheel with which the drive roller is arranged to be drivingly engaged, the motor and drive roller being pivotally mounted in common on supporting means secured to the cycle frame whereby the drive roller can swing freely into and out of drivetransmitting engagement with the periphery of the wheel, and the arrangement being such that the drive roller wi swing out of drive-transmitting engagement with the wheel upon a predetermined road speed being attained.

10. Power pack equipment suitable for fitment to a cycle in providing a cycle according to claim 9, the pack comprising supporting means which is adapted to be secured to the cycle frame, and a motor and drive roller assembly which is pivotally mounted on the supporting means for engagement of the drive roller with a roadwheel of the cycle when the supporting means is secured to the frame.