GB2219261A - Reciprocating human drive mechanism - Google Patents

Abstract

A bicycle drive unit consists of a pair of angularly reciprocable pedal levers 2, 3 connected to drive a hollow cylindrical casing 4 through respective pawl-and-ratchet one-way clutches 10, 11, the cycle rear wheel being chain-driven from a main sprocket wheel 5 carried by the casing 4. A motion reversing mechanism interconnects the pedals 2, 3, consisting of bevel gears 8, 9 and reversing pinions 7. The drive unit is arranged on a common cross-shaft 1 fixed to the cycle frame. The arrangement permits the drive wheel of the bicycle to be given more useful pedal effort per unit of time than a conventional crank arrangement. <IMAGE>

Description

MANUAL OR PEDAL POWERED DRIVE This invention relates to a drive unit for manualand pedal-powered machines.

Cranks have long been used to convert reciprocating forces into torque. For example, pedal cycles since their invention by Kirkpatrick Macmillan have been driven by cranks.

The torque produced by a crank varies considerably during its rotation, being at a maximum when the applied force is acting at right angles to the lever arm and decreasing to zero when the force is in line with the lever arm.

An object of the present invention is to provide an improved drive unit avoiding the mentioned limitations of the crank arrangement.

According to the present invention, there is provided a drive unit for a manually-powered or a pedal-powered machine, comprising two input members mounted for to-and-fro angular movement on a frame, a rotary output member mounted on the frame, and one-way drive transmitting means operative in use to rotate the output member uni-directionally in response to the to-and-fro movement of the input members.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig 1 shows a bicycle incorporating a drive unit in accordance with the present invention; Fig 2 is a plan view of part of the bicycle of Fig 1, to a larger scale, and showing the drive unit; Fig 3 is a plan view corresponding with part of Fig 2, to a larger scale, and showing the drive unit in cross section; Fig 4 is a diagram illustrating circular or arcuate movement of pedal levers; Fig 5 is a graphical representation of torque/pedal displacement with reference to crank operation of pedals; and Fig 6 is a graphical representation of torque/pedal displacement with reference to a drive unit in accordance with the present invention.

In Figs 1 to 3 of the drawings, a cross shaft 1 is fixed to the frame of the bicycle shown in Fig 1. A pair of mutually facing bevel gears 8 and 9 are mounted for rotation on.the cross shaft 1, and the outer ends of these gears 8,9 are in driving connection with respective pedal levers 2 and 3.

The bevel gears 8,9 mesh with reversing pinions 7 which are mounted on secondary shafts 6 which extend radially with respect to cross shaft 1. Thus, the bevel gears 8,9 and the reversing pinions 7 constitute motion reversing means operative to raise one pedal when the other pedal is depressed and vice versa. The pedals 2,3 constitute input members.

A rotary output member in the form of a hollow cylindrical casing 4 is mounted for rotation on the axis of cross shaft 1 by virtue of location on intermediate shoulders of the bevel gears 8,9 by means of bearings 8A,9A. The casing is secured to a main sprocket wheel 5 for delivering drive to the rear wheel of the bicycle in conventional manner.

Angular movement of either pedal 2,3 is transmitted to the sprocket wheel 5 or casing 4 by one-way drive transmitting means in the form of pawl-and-ratchet devices of rotary configuration - 10,11.

The lower limit of travel of either pedal lever 2,3 is determined by a stop bar 12. Generally, each pedal is angularly reciprocable through an arc of approximately 900.

In order to propel the bicycle, the pedal levers 2,3 are depressed alternately. For example, if the pedal lever 2 is depressed then drive is transmitted to the main sprocket wheel 5 by way. of the clutch 10 and the casing 4.

Simultaneously, the forward motion of the bevel gear 8 is reversed by the pinions 7 causing bevel gear 9 to raise the pedal lever 3. Similarly, depression of the pedal lever 3 drives the bicycle with simultaneous raising of pedal lever 2.

In Fig 4, the circular diagram shows the upper and lower positions of the pedal levers 2,3. Also, the Fig 4 diagram, in broken line, shows the "other" pedal levers in a conventional crank arrangement. It is well-known that in propelling a bicycle useful effort can be input through the pedals to drive the bicycle for only about one quarter of the full rotation of either pedal. Thus, in Fig 4, the "useful" input portion of the circular diagram is identified by crosshatching.

In Fig 5, there is shown a graphical representation of torque/pedal displacement, assuming a substantially constant pedalling effort (in terms of angular speed and force applied). It can be seen that for the "useful" input from a crank arrangement the work done is represented by mutually separate areas under the upper parts of the graphs for left and right hand pedals.

In Fig 6, the graphical representation is for torque/ pedal displacement for the drive unit described with reference to Figs 1 to 3. Because the pedal levers of the drive unit move only within the "useful" area shown in Fig 4, a new pedal effort can begin immediately on completion of a previous pedal effort. Thus, as can be seen in Fig 6, a greater propelling effort is delivered to the bicycle drive wheel in the same amount of time.

A drive unit in accordance with the present invention may be used to drive any machine suitable for manual or pedal operation.

In a modification of the drive unit, within the scope of the present invention, the pawl-and-ratchet clutches may be replaced by any one-way clutch device such, for example, as a sprag clutch; and the motion reversing gears could have different gear configurations or be substituted by reversing lever arrangements.

Claims (11)

1. A drive unit for a manually-powered or a pedalpowered machine, comprising two input members mounted for to-and-fro angular movement on a frame, a rotary output member mounted on the frame, and one-way drive transmitting means operative in use to rotate the output member unidirectionally in response to the to-and-fro movement of the input member.

2. A drive unit as claimed in Claim 1, wherein the input members are levers.

3. A drive- unit as claimed in any one of the preceding claims, wherein the one-way drive transmitting means comprises one-way clutch means.

4. A drive unit as claimed in Claim 3, wherein the oneway clutch means comprises pawl-and-ratchet devices of rotary configuration.

5. A drive unit as claimed in any preceding claim, wherein the input members and the output members are arranged on a common rotary axis.

6. A drive unit as claimed in any one of the preceding claims, including motion reversing means interconnecting the input members.

7. A drive unit as claimed in Claim 6 in which the motion reversing means comprises a pair of bevel gears arranged mutually facing and connected to respective input members, and reversing pinions engaging the bevel gears and carried by the frame.

8. A drive unit as claimed in Claim 6 or 7, wherein the output member comprises a hollow cylindrical casing, and the motion reversing means is disposed within the casing.

9. A drive unit as claimed in Claim 8 wherein the oneway clutch means is disposed respectively in mutually opposite end-wall portions of the hollow cylindrical casing.

10. A drive unit for a manually-powered or a pedal-powered machine, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

11. A bicycle incorporating a drive unit according to any one of the preceding claims.