GB1602578A

GB1602578A - Cycle

Info

Publication number: GB1602578A
Application number: GB24583/78A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1981-11-11
Also published as: DE2921534A1; JPS5522590A; ZA792498B; FR2427244A2; FR2427244B2; BE876574R

Description

(54) CYCLE (71) We, LUCAS INDUSTRIES LIMITED, a British Company of Great King Street, Birmingham B19 2XF do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- In our co-pending British patent application No. 26449/75 (Serial No. 1,546,069) there is described and claimed in claim 1, an electrically assisted pedal cycle, particularly but not exclusively a bicycle including a frame, a ground engaging wheel rotatably mounted on the frame, a rotatable drive member rotatably mounted on the frame, and arranged to be rotated by the rider of the cycle, an endless, non-extensible, flexible member for transmitting motion of said drive member to said wheel whereby rotation of said drive member propels the bicycle, an electric drive assembly and an associated power source carried by the frame, the output of the drive assembly being coupled to said wheel whereby said electric drive assembly can drive the wheel, at least that part of the drive assembly carrying the drive output being mounted on the frame for limited movement relative thereto against the action of a resilient bias, electrical switch means operable in response to movement of said part of the drive assembly relative to the frame, and the arrangement being such that said part of the drive assembly is moved relative to the frame, against said resilient bias to operate said switch, by the application to said drive member, by the rider, of driving force to propel the cycle, said switch means in use, being so associated with the electric drive assembly that the electric drive assembly cannot be energised unless said switch means is operated.

Our co-pending British patent application number 26449/75 (Serial No. 1,546,069) describes and claims in claims dependent upon claim 1, a cycle wherein the mounting of the drive assembly, or said part of the drive assembly, on the frame involves the use of resilient coupling members, the resilient coupling members affording the possibility of movement of the drive arrangement, or said part thereof relative to the frame, and also providing said resilient bias.

The present invention relates to a cycle claimed in any one of claims 1, 2 and 4 of our co-pending British Patent application No.

26449/75 (Serial No. 1,546,069) wherein at least that part of the drive assembly carrying the drive output is mounted on the frame for limited movement relative thereto against the action of a compression spring interposed between said part of the drive assembly and a part fixed relative to the frame, said compression spring urging said part of the drive assembly towards a position wherein said switch means is not operated.

Preferably said compression spring is a helical compression spring.

Desirably the rest position of said part of the drive assembly, to which it is urged by said compression spring, is adjustable.

Conveniently at least that part of the drive assembly carrying the drive output is mounted on the frame for limited movement relative thereto by means including a link member pivotally connected at one end to said part of the drive assembly and pivotally connected at its other end to a part fixed relative to the remainder of the frame.

Desirably, the axis about which the link member can pivot relative to the frame is parallel to the axis about which the link member can pivot relative to said part of the drive assembly.

Conveniently the means mounting at least said part of the drive assembly on the frame includes a sliding coupling, said sliding coupling permitting movement of at least said part of the drive assembly in a direction to operate said switch.

Preferably said sliding coupling incorporates a ball and socket connection, the ball being engaged in the socket in a rest position to which at least said part of the drive assembly is urged by said compression spring.

Desirably the electric drive assembly includes an electric motor and a gear mechanism, the gear mechanism transmitting rotation of the motor shaft to the output of the drive assembly and the electric motor and the gear mechanism being combined to form a single unit which is mounted on the frame for said limited movement relative to the frame.

One example of the present invention is illustrated in the accompanying drawings, wherein: Figure 1 is a diagrammatic side elevational view of part of a bicycle; and Figure 2 is a view similar to Figure 1 of a modification thereof.

Referring firstly to Figure 1 of the drawings, the bicycle includes a relatively conventional frame 11 formed from metal tube, and supporting a ground engaging wheel 1 la towards the rear thereof. Adjacent the front of the frame is a movable handle bar assembly carrying at its lower end a second ground engaging wheel whereby the bicycle is steered in use.

The rear ground engaging wheel 1 la of the bicycle carries a sprocket 25 around which extends a non-extensible endless drive chain 26.

The drive chain 26 extending forwardly of the frame of the cycle and extends around a large diameter chain wheel 12 mounted for rotation on the frame 11. The plane of rotation of the wheel 12 is parallel to the plane of the frame 11 and connected to the chain wheel 12 are a pair of pedals 12a. Thus the rider can, in the normal manner, apply driving force to the chain wheel 12 by way of the pedals 12a to rotate the chain wheel and by virtue of the drive chain 26 rotate the sprocket 25 and the wheel 1 la to propel the cycle. The sprocket 25 can if desired incorporate a free wheel mechanism so that reverse rotation of the chain wheel 12 does not drive the cycle, and the cycle can overrun the chain wheel, for example, when travelling downhill.

In order to provide a measure of assistance to the rider of the cycle when propelling the cycle there is provided an electric drive arrangement 13 carried by the frame and an electric storage battery (not shown) also carried by the frame 11. The drive arrangement 13 includes an electric motor 14 and a gear mechanism 15 in the housing of the gear mechanism 15 being securely fixed to the housing of the motor 14 so that the motor 14 and the gear mechanism 15 define a single unit for the purpose of mounting the drive arrangement on the frame 11. The gear mechanism 15 transmits rotation of the output shaft of the motor 14 to an output sprocket 16 on the exterior of the housing of the mechanism 15. The sprocket 16 is rotatable in the same plane as the plane of rotation of the chain wheel 12 and the drive chain 26 which extends around the sprocket 25 and the chain wheel 12 also extends around the sprocket 16 so that when the motor 14 is energised the sprocket 16 is caused to rotate and will drive the rear wheel by way of the chain and the rear wheel sprocket However, in order that the electric drive arrangement can only be used to assist the rider in propelling the cycle, and cannot be used to propel the cycle without effort from the rider, there is provided an electrical switch 17 which controls energisation of the motor 14 and which must be closed in order for the motor 14 to be energised. In practice the switch 17 will be a microswitch of relatively low current capacity and will not directly control the current to the motor 14.

In preference to switch 17 will control energisation of a relay having heavy current contacts which carry the motor current. In order that the switch 17 is only closed while the rider of the cycle is applying driving force by way of the pedals the drive arrangement 13 is mounted for limited movement relative to the frame 11 and the switch 17 is arranged to be sensitive to the movement of the drive arrangement relative to the frame. Thus the drive arrangement 13 is connected to the frame by way of a link member 31 pivotally connected at one end to the housing of the gear mechanism 15 and pivotally connected at its other end to a bracket 22 rigidly secured to the frame. The axis about which the link member 31 can pivot relative to the bracket 22 is parallel to the axis about which the link member 31 can pivot relative to the housing of the gear mechanism 15. In practice, a pair of parallel and identical link members 31 are provided, the two link members 31 being pivotable about common axes relative to the mechanism 15 and the bracket 22, and being spaced apart in the direction of these axes so as to lie on opposite sides respectively of the housing of the gear mechanism 15.

The mounting of the drive arrangement 13 on the frame 11 further includes a sliding coupling 32 at the end of the drive arrangement 13 remote from the sprocket 16. The housing of the motor 14 carries a post 33 having a spherical portion 34 intermediate its ends. The post 33 extends through an aperture in a part spherical recess 35 in a bracket 36 secured to the frame. A helical compression spring 37 is interposed between the housing of the gear mechanism 15 and the bracket 22 and urges the drive arrangement 13 to move relative to the frame 11 in a direction away from the switch 17, and to seat the spherical portion 34 of the post 33 in the recess 35 of the bracket 36. Thus in the rest position, which is defined by the engagement of the spherical portion 34 in the recess 35 the portion 34 and recess 35 define a ball and socket joint between the drive arrangement 13 and the frame 11.

A spring retaining pin (not shown) extends from the bracket 22 into the spring 37 and thus locates the spring 37 in position. A clearance is left between the free end of the spring retaining pin and the housing of the gear mechanism 15 of sufficient magnitude to permit the drive arrangement 13 to be moved sufficiently far against the action of the spring 37 to operate the switch 17. The pin is adjustably mounted on the bracket 22 so that it can be utilised as a positive abutment preventing movement of the drive arrangement 13 against the action of the spring 37 beyond the position in which the switch 17 is operated. Similarly, the post 33 is adjustably mounted on the housing of the motor 14 so as to provide adjustment of the rest position of the drive arrangement 13 relative to the switch 17.

The provision of a ball and socket connection between the drive arrangement 13 and the frame permits a degree of latitude in the alignment of the drive arrangement relative to the frame thus accommodating any slight misalignment of the other connection between the drive arrangement 13 and the frame, by way of the links 31. During movement of the drive arrangement 13 relative to the frame to operate the switch 17 the post 33 of course slides relative to the bracket 36 as permitted by the extension of the post 33 beyond the spherical portion 34.

It will be recognised therefore that when the rider applies a driving force by way of the pedals 12a the drive chain 26 passing over the sprocket 16 will be subject to tension and the effect of tension in the drive chain 26 will be to move the drive arrangement 13 against the action of the spring 37 so as to operate the switch 17. Upon release of driving force by the rider, although there will still be tension in the run of the drive chain 26 between the sprocket 16 and the rear wheel sprocket 25, this tension will not be sufficient to retain the drive arrangement 13 in its operative position against the action of the spring 37 and the drive arrangement 13 will thus be moved by the spring 37 back to its rest position so permitting the switch 17 to open and deenergise the motor 14.

In order to ensure that the operation of the motor 14 without the addition of force provided by the rider by way of the pedals 12a cannot maintain the drive arrangement 13 in its operative position it is desirable that the circumferential length of the sprocket 16 which is engaged by the chain 26 is kept to a minimum, so that the run of the chain 26 between the sprocket 16 and the sprocket 25 extends as closely as is possible at right angles to the direction of movement of the drive arrangement 13. Clearly if this run of the chain were to extend in the direction of movement of the drive arrangement 13 then there would be a tendency for the drive arrangement 13 while the motor 14 is operating, to drive itself down this particular run of the chain and so maintain the switch 17 operated. However it will also be appreciated that there is a minimum circumferential length of the sprocket 16 which must be in engagement with the chain if the sprocket is to satisfactorily transmit driving force to the chain. Clearly if only a single tooth of the sprocket 16 is in driving co-operation with a link of the chain then there will be severe loading on this tooth and in addition there will be a tendency for the chain to ride over the tooth rather than to be driven thereby. Thus in order to provide the necessary circumferential engagement between the chain 26 and the sprocket 16 and also to maintain adequate tension in the chain 26 there is provided an idler wheel 38 carried by the frame, and engaging the run of the chain 26 between the sprocket 16 and the sprocket 25. It will be recognised that the tension in the chain can be adjusted simply by moving the idler wheel 38 towards the chain wheel 12 and so in use as the chain becomes slack and as a result of stretching its tension can be adjusted by a simple adjustment of the position of the idler wheel 38 rather than the more normal, and complex adjustment of the position of the wheel 1 la relative to the frame. It is to be recognised that it is undesirable to move the idler wheel 38 to close to the chain wheel 12 since this will increase the likelihood of the drive arrangement 13 driving itself along the run of the chain 26 between the sprocket 16 and the idler wheel 38, and thus operating the switch 17 without the application of rider power.

In a modification shown in Figure 2 the idler wheel 38 is dispensed with and chain tension to accommodate wear and slackness in the chain is adjusted in the conventional manner by moving the rear wheel 11 relative to the frame. The engagement of the chain with the sprocket 16 is maintained by a metal, or more preferably synthetic resin shoe 39 carried by the housing of the gear mechanism 15 and pressing the chain 26 firmly into engagement with the teeth of the sprocket 16.

As described in our co-pending application 26449/75 (Serial No. 1,546,069) the switch 17 need not be the only switch controlling energisation of the motor 14 since it is desirable to have a manually operable control switch on the handle bars of the cycle. Other features of the cycle which are disclosed in co-pending application 26449/75 (Serial No. 1,546,069) can of course be applied to the cycle arrangement disclosed herein.

WHAT WE CLAIM IS: 1. A cycle as claimed in any one of claims 1, 2 and 4 of our co-pending British Patent Application No. 26449/75 (Serial No.

1,546,069) wherein at least that part of the drive assembly carrying the drive output is mounted on the frame for limited movement relative thereto against the action of a compression spring interposed between said part of the drive assembly and a part fixed relative to the frame, said compression spring urging said part of the drive assembly towards a posi

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. retaining pin and the housing of the gear mechanism 15 of sufficient magnitude to permit the drive arrangement 13 to be moved sufficiently far against the action of the spring 37 to operate the switch 17. The pin is adjustably mounted on the bracket 22 so that it can be utilised as a positive abutment preventing movement of the drive arrangement 13 against the action of the spring 37 beyond the position in which the switch 17 is operated. Similarly, the post 33 is adjustably mounted on the housing of the motor 14 so as to provide adjustment of the rest position of the drive arrangement 13 relative to the switch 17. The provision of a ball and socket connection between the drive arrangement 13 and the frame permits a degree of latitude in the alignment of the drive arrangement relative to the frame thus accommodating any slight misalignment of the other connection between the drive arrangement 13 and the frame, by way of the links 31. During movement of the drive arrangement 13 relative to the frame to operate the switch 17 the post 33 of course slides relative to the bracket 36 as permitted by the extension of the post 33 beyond the spherical portion 34. It will be recognised therefore that when the rider applies a driving force by way of the pedals 12a the drive chain 26 passing over the sprocket 16 will be subject to tension and the effect of tension in the drive chain 26 will be to move the drive arrangement 13 against the action of the spring 37 so as to operate the switch 17. Upon release of driving force by the rider, although there will still be tension in the run of the drive chain 26 between the sprocket 16 and the rear wheel sprocket 25, this tension will not be sufficient to retain the drive arrangement 13 in its operative position against the action of the spring 37 and the drive arrangement 13 will thus be moved by the spring 37 back to its rest position so permitting the switch 17 to open and deenergise the motor 14. In order to ensure that the operation of the motor 14 without the addition of force provided by the rider by way of the pedals 12a cannot maintain the drive arrangement 13 in its operative position it is desirable that the circumferential length of the sprocket 16 which is engaged by the chain 26 is kept to a minimum, so that the run of the chain 26 between the sprocket 16 and the sprocket 25 extends as closely as is possible at right angles to the direction of movement of the drive arrangement 13. Clearly if this run of the chain were to extend in the direction of movement of the drive arrangement 13 then there would be a tendency for the drive arrangement 13 while the motor 14 is operating, to drive itself down this particular run of the chain and so maintain the switch 17 operated. However it will also be appreciated that there is a minimum circumferential length of the sprocket 16 which must be in engagement with the chain if the sprocket is to satisfactorily transmit driving force to the chain. Clearly if only a single tooth of the sprocket 16 is in driving co-operation with a link of the chain then there will be severe loading on this tooth and in addition there will be a tendency for the chain to ride over the tooth rather than to be driven thereby. Thus in order to provide the necessary circumferential engagement between the chain 26 and the sprocket 16 and also to maintain adequate tension in the chain 26 there is provided an idler wheel 38 carried by the frame, and engaging the run of the chain 26 between the sprocket 16 and the sprocket 25. It will be recognised that the tension in the chain can be adjusted simply by moving the idler wheel 38 towards the chain wheel 12 and so in use as the chain becomes slack and as a result of stretching its tension can be adjusted by a simple adjustment of the position of the idler wheel 38 rather than the more normal, and complex adjustment of the position of the wheel 1 la relative to the frame. It is to be recognised that it is undesirable to move the idler wheel 38 to close to the chain wheel 12 since this will increase the likelihood of the drive arrangement 13 driving itself along the run of the chain 26 between the sprocket 16 and the idler wheel 38, and thus operating the switch 17 without the application of rider power. In a modification shown in Figure 2 the idler wheel 38 is dispensed with and chain tension to accommodate wear and slackness in the chain is adjusted in the conventional manner by moving the rear wheel 11 relative to the frame. The engagement of the chain with the sprocket 16 is maintained by a metal, or more preferably synthetic resin shoe 39 carried by the housing of the gear mechanism 15 and pressing the chain 26 firmly into engagement with the teeth of the sprocket 16. As described in our co-pending application 26449/75 (Serial No. 1,546,069) the switch 17 need not be the only switch controlling energisation of the motor 14 since it is desirable to have a manually operable control switch on the handle bars of the cycle. Other features of the cycle which are disclosed in co-pending application 26449/75 (Serial No. 1,546,069) can of course be applied to the cycle arrangement disclosed herein. WHAT WE CLAIM IS: 1. A cycle as claimed in any one of claims 1, 2 and 4 of our co-pending British Patent Application No. 26449/75 (Serial No.

tion wherein said switch means is not operated.

2. A cycle as claimed in claim 1 wherein the rest position of said part of the drive assembly, to which it is urged by said compression spring, is adjustable.

3. A cycle as claimed in claim 1 or claim 2 wherein said compression spring is a helical compression spring.

4. A cycle as claimed in any one of claims 1 to 3 wherein at least that part of the drive assembly carrying the drive output is mounted on the frame for limited movement relative thereto by means including a link member pivotally connected at one end to said part of the drive assembly and pivotally connected at its other end to a part fixed relative to the remainder of the frame.

5. A cycle as claimed in claim 4 wherein the axis about which the link member can pivot relative to the frame is parallel to the axis about which the link member can pivot relative to said part of the drive assembly.

6. A cycle as claimed in any one of claims 1 to 5 wherein the means mounting at least said part of the drive assembly on the frame includes a sliding coupling, said sliding coupling permitting movement of at least said part of the drive assembly in a direction to operate said switch.

7. A cycle as claimed in claim 6 wherein said sliding coupling incorporates a ball and socket connection, the ball being engaged in the socket in the rest position to which at least said part of the drive assembly is urged by said compression spring.

8. A cycle as claimed in any one of the preceding claims wherein the electric drive assembly includes an electric motor and a gear meachanism, the gear mechanism transmitting rotation of the motor shaft to the output of the drive assembly and the electric motor and the gear mechanism being combined to form a single unit which is mounted on the frame for said limited movement relative to the frame.

9. A cycle substantially as hereinbefore described with reference to the accompanying drawings.