GB2104462A - Transmission arrangement for pedal driven vehicles - Google Patents

Abstract

A triangular frame 2 with pedal 1, is fitted to either, or both, sides of a bicycle, and is pivoted at one apex to a bracket 3. One end of a transmission chain 4, is connected to the rearward side, (and may be movable along that side to vary the Gear ratio), and drives the rear wheel via a free-wheel 5. The other end may be connected, by a cable and pulley 6, to a similar arrangement on the other side of the bicycle, for two pedal operation, or by a spring to the bicycle frame, for single pedal operation. The pedal moves up and down in an arc and is returned to the raised position by the mechanisms described. Alternatively, an arm with pedal, pivoted on bracket 3, drives the triangular frame on the opposite side via a transverse member. <IMAGE>

Description

SPECIFICATION Transmission arrangement for pedal driven vehicles This invention relates to a transmission arrangement for pedal driven vehicles.

According to the present invention a transmission for a pedal driven vehicle comprises reciprocable pedal means, unidirectional drive means so connected between the pedal means and an output member that generally downward strokes of the pedal means are transmitted to the output member through the unidirectional drive means, and wherein the transmission is so contructed that a correct working relationship is maintained between the various parts of the mechanism. The reciprocable pedal means may comprise a pair of pedals reciprocable in antiphase, the unidirectional drive means may comprise two unidirectional drives and a synchronising coupling may be provided for the pedals.

The synchronising coupling may be provided by means of an extension of the connection between the pedals and the unidirectional drive means, passing via an idler means. The pedals may, however, be independent of each other, and raised by springs. The unidirectional drives may be connected directly to a drive wheel, and are conveniently constituted by a pair of appropriately handed freewheel devices on opposite sides of the rear wheel of a bicycle.

In one range of embodiments of the invention, the reciprocable pedal means comprises a single driving pedal, means being provided to effect the upstroke of the driving pedal. These latter means may take the form of resilient means associated with the connection between the pedal and the unidirectional drive means. A separate pedal arm and transverse member may transmit the driving force from one side of the vehicle to the mechanism on the other side thereof. It has been found convenient to carry the, or each, pedal on a pivoted triangulated frame, and also to vary the ratio of the transmission by suitable gear means. When both these expedients are utilised, the point on the, or each, triangulated frame from which connection is made to the unidirectional drive means may be arranged to be movable along the side of the frame thereby to vary the transmission ratio.The said side of the, or each, frame may be curved. The movement of the, or each, point of connection may conveniently be effected by cable means running in flexible sleeving and drivable by a twist-grip selector adapted to be mounted as a handle-bar twist-grip. Where this form of gear is used in a transmission provided with two pedals, it should be arranged that the two corresponding points of connection are movable in unison.

The invention will now be explained in greater detail with reference to the accompanying diagram matic drawings, of which: Figure I is a side view of a bicycle provided with a transmission arrangement according to the invention; Figure2 is a rear view, partly broken away, of Figure 1.

Figure 3 is a side view of the handle-bar twist-grip Gear selector.

Figure 4 is a rear view of Figure 3.

Figure 5 is a side view of a triangulated frame with attachments.

Figure 6 is a pian view of Figure 5.

Figure 7 is a side view of a bicycle provided with a transmission arrangement according to the second embodiment of the invention.

Figure 8 is a rear view, partly broken away, of Figure 7.

Figure 9 is a side view of a bicycle provided with a simplified transmission according to the second embodiment of the invention, which is driven from the opposite side.

Figure 10 is a rear view, partly broken away, of Figure 9.

Figure 1 7 is a side view of a lever arrangement applied to the second embodiment of the invention.

Figure 12 is a plan view of Figure 11.

In the drawings, later Figures are assumed to incorporate reference numerals from earlier Figures where common parts are present, and will be described accordingly.

As will be readily appreciated, Figures 1 and 2 show a standard bicycle to which the present invention has been applied, and no detailed description of the standard parts will be given.

The drive to the bicycle rear wheel is effected by a pair of pedals 1 Land 1 R carried on the forward ends of a respective pair of triangulated frames 2L and 2R, which are pivotally mounted on a bracket 3 attached to the bicycle frame beneath and to the rear of the bottom bracket. Downward forces applied to the pedals are transmitted to a loop member 4. The loop member is coupled at its ends 4L and 4R to frames 2L and 2R in a manner which will be described below.

The line of the loop member is defined by a pair of free-wheel sprockets 5L and 5R secured to the rear wheel of the bicycle on opposite sides thereof, and a central idler 6 mounted beneath the bottom bracket of the bicycle with its axis normal to the plane formed by the loop. It will be seen that if a downward force is applied to the pedal 1 R when it is in the position shown in Figure 1, the end 4R of the loop member 4 is pulled forwardly, thus moving the loop member along its path and pulling the curved side of the triangulated frame 2L rearwardly, thus raising pedal 1 L.

The free-wheel mechanisms are so phased that the sprocket 5R is engaged to drive the rear wheel of the bicycle in an anti-clockwise direction, as shown in Figure 1, thereby propelling the bicycle forwardly, while the sprocket 5L idles. When the downward stroke of pedal 1 R is complete, or partially complete, the rider can then depress pedal 1 L, the loop member will move in the opposite direction, and the free-wheel sprocket 5Lwill drive the wheel while sprocket 5R idles. In this way substantially continuous drive can be imparted to the bicycle by a reciprocating movement of the pedals.The driving torque applied to the rear wheel, produced by a downwardly directed force on the pedal, throughout each full stroke, is substantially more constant than that due to a similar force applied to a conventional crank pedal over half a revolution. By keeping the inertia of the reciprocating parts as low as possible, the overall efficiency of the transmission may be kept above that of a conventional bicycle in which the efficiency at the top of each pedal stroke is very low.

Complete coupling of the triangulated frames may be effected as shown dotted in Figure 1 only, for clarity. Each end of a cable loop 25 wraps around the surface of, and is anchored to, a sector of drum 26L and 26R forming part of triangulated frame 2L and 2R respectively. The loop 25 is directed over idler 27, which is attached to the bicycle frame beneath the bottom bracket, with its axis of rotation perpendicularto the plane formed by the loop. The movement of the pedals is fully synchronized and engagement of the loop member 4 with the free-wheel sprockets 5L and 5R is ensured. A further advantage of the invention is that variation of the Gear ratio may be easily made whilst the bicycle is stationary or in motion.The provision of a handle-bar twist Gear selector assembly 7 shown in Figure 1, and in greater detail in Figure 3 and 4, and the way in which this operates, will now be described: The ends 4L and 4R are coupled to the respective triangulated frames in the manner indicated in Figure 5 and 6 which show the frame 2L and pedal 1 L. A pin gear wheel 8L, with cheeks to provide lateral location, engages in the curved rack 9L, forming a side of the triangulated frame 2L. A hook member 10L is connected to the loop member 4 end 4L and to the axle on which the pin gear wheel rotates. The position of the pin gear wheel on the curved rack is controlled by a cable 11 L which extends in a loop along the length of the curved rack side of the triangulated frame between a guide at the top of the rack and a guide at or adjacent to the pivot axis of bracket 3.The forward run of the cable is secured to a point on the axle of the pin gear wheel 8L.Theends11LAand 11LBofcable 11Lpass through respective sleeves 14LA and 14LB, which are anchored to the bicycle frame and bracket 3 at either end, and are secured to the ends 1 3L and 13R, passing through respective sleeves 1 6L and 16R, also anchored to the bicycle frame, of cable loop 13 towards the Gear selector. It will be understood that the right hand triangulated frame is similarly equipped and the control cable ends 12RA and 12RB emerging from respective sleeves 15RA and 15RB, also anchored to the bicycle frame, are similarly secured to cable ends 13L and 13R as shown in Figure 6.Referring now to Figure 3 and 4, the handle-bar twist grip Gear selector 7, comprises a cable winding drum 17 being coaxial and part of a hand grip 18, that is free to rotate about the handle-bar axis. A main control cable 13 passes around the periphery of the drum, being secured to the latter at 19. A bracket 20 attached to the handle-bar, provides an anchorage for a pair of cable sleeves 16L and 1 6R as well as locating the twist grip along the axis of the handle-bar. Consequently, rotation of the twist grip will cause the pin gear wheels to be simultaneously traversed along the curved racks of the triangulated frames 2L and 2R thereby altering the Gear ratio of the transmission in the discrete steps provided by the spacing of the teeth in the curved racks.The proportions of the pin gear wheel and the curved rack are chosen such that tension forces in the loop member 4 hold the pin gear wheel in the selected position along the curved rack throughout each pedal stroke. The radius of the winding drum 17 may be kept to a minimum by wrapping the cable 13 around it more than one turn and allowing the drum to rotate through more than 360 degrees. An indicator 21 on the twist grip Gear selector provides the rider with a visual indication of the ratio selected and will now be described in detail: A tubular co-axial extension of the winding drum 17, acting as a pulley, imparts drive to a flexible belt 22, which is run over an idler 23 pivoted to bracket 20. The outside face of the belt is marked to indicate the Gear ratios available and a pointer 24 fixed to bracket 20 indicates the ratio selected.

The second embodiment of the invention is illustrated in Figure 7 and 8 and is specifically for disabled riders who can apply a reciprocating vertical motion to one pedal only, either right or left, and is described in relation to the original invention as follows: One triangulated frame, complete with pedal and Gear change feature, is pivoted to the bracket 3 and one free-wheel sprocket is fitted to the appropriate side of the driven rear wheel. An extension spring 28, attached to the end 4L or 4R of the transmission chain loop 4 at a point beneath the chain stay and forward of the free-wheel sprocket 5L or 5R and anchored at a point beneath the bottom bracket of the bicycle, maintains the transmission chain loop 4 in engagement with the free-wheel sprocket 5L or 5R.

Means to raise the pedal from a partial or extreme downward position may comprise a spring to exert a clockwise torque about the pivot of the triangulated frame at bracket 3, in addition to spring 28.

A simplified version of this second embodiment of the invention, in which the Gear change feature is deleted entirely, substitutes a simple triangular frame for triangulated frame 2L or 2R. The end 4L or 4R of loop 4 is pivoted directly to the upper apex of the triangular frame. This version may be used with conventional variable gear transmissions to improve the overall efficiency.

Figure 9 and 10 show a pedal arm and transverse member for driving the simplified transmission, (or that shown in Figure 7 and 8) from the opposite side.

A pedal arm 29L or 29R is pivotally mounted to the bracket 3, on the same axis as the triangular frame, and carries a pedal 1 L or 1 Rat its forward end. A transverse member 30 connects the forward end to the forward apex of the triangular frame. The transverse member 30 may be hinged near its middle for structural reasons, the axis of the hinge being parallel to the pedal arm.

Figure 11 and 12 show a variation of the simplified version, in which the triangular frame is replaced by a lever 31 L or 31 R connected to a shaft 33, pivotally mounted to the bracket 3, driven by a lever arm 32R or 32L with pedal 1 R or 1 L attached. The end 4R or 4L of the loop 4 is pivoted directly to the upper end of lever 31R or 31 L.

In both embodiments of the invention, the loop member 4 can be constructed of transmission chain and/or cable to suit the overall design. It is also possible to include elastic links in the loop member 4 to act as a shock-absorber. Obviously, stops to limit pedal travel, and guards to maintain engagement of the loop member 4 will be applied where necessary.

Moving parts will normally be provided with guards to avoid the risk of damage or injury to the rider or clothing, although such guards have been omitted from the drawings for the sake of clarity. A stationary pedal for resting a foot not used for propulsion may also be applied. Although the invention has, for simplicity, been described in relation to conventional bicycle frames, the distribution of forces in the transmission of the invention is not the same as that which the conventional bicycle frame has been designed to accommodate, and it is envisaged that the optimum design for a bicycle embodying the invention may be considerably different from the frames in the accompanying drawings.

Claims (15)

1. A transmission for a pedal driven vehicle comprising reciprocable pedal means, unidirectional drive means so connected between the pedal means and an output member that generally downward strokes of the pedal means are transmitted to the output member through the unidirectional drive means, and wherein the transmission is so constructed that a correct working relationship is maintained between the various parts of the mechanism.

2. A transmission as claimed in Claim 1 wherein the reciprocable means comprises a pair of pedals reciprocable in antiphase, the unidirectional drive means comprises two unidirectional drives and a synchronising coupling is provided for the pedals.

3. A transmission as claimed in Claim 2 wherein the synchronising coupling is provided means of an extension of the connection between the pedals and the unidirectional drives, passing via an idler means.

4. Atransmission as claimed in Claim 2 wherein the pedals are independent of each other and raised by springs.

5. A transmission as claimed in any of Claims 2 to 4 wherein the unidirectional drives are connected directly to a drive wheel.

6. A transmission as claimed in Claim 5 wherein the unidirectional drives are constituted by a pair of appropriately handed free-wheel devices on opposite sides of the rear wheel of a bicycle.

7. A transmission as claimed in Claim 1 wherein the reciprocable pedal means comprises a single driving pedal, and means are provided to effect the up-stroke of the driving pedal.

8. A transmission as claimed in Claim 7 wherein the upstroke of the pedal is effected by resilient means associated with the connection between the pedal and the unidirectional drive means.

9. Atransmission mechanism as claimed in Claim 7 or Claim 8 wherein a separate pedal arm and transverse member transmit the driving force from one side of the vehicle to the mechanism on the other side thereof.

10. Atransmission as claimed in any one of Claims 2 to 9 wherein the, or each, pedal is carried on a pivoted triangulated frame.

11. A transmission as claimed in any one of Claims 1 to 10 wherein the transmission ratio may be varied by suitable gear means.

12. Atransmission as claimed in Claim 11 when appendentto Claim 10 wherein the point on the or each triangulated frame from which connection is made to the unidirectional drive means is movable along the side of the frame thereby to vary the transmission ratio.

13. Atransmission as claimed in Claim 12 wherein the said side of the or each triangulated frame is curved.

14. Atransmission as claimed in Claim 12 or Claim 13 wherein the movement of the or each point of connection is effected by cable means running in flexible sleeving and drivable by a twist-grip selector adapted to be mounted as a handle-bar twist-grip.

15. Atransmission as claimed in any one of Claims 12 to 13 wherein the transmission is provided with two pedals, and the points of connection are movable in unison.