GB2272748A

GB2272748A - Hydraulic transmission for bicycle etc.

Info

Publication number: GB2272748A
Application number: GB9322296A
Authority: GB
Inventors: Herbert Thompson Storr
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-11-18
Filing date: 1993-10-29
Publication date: 1994-05-25
Also published as: GB9322296D0

Abstract

An hydraulic transmission, particularly for use with a cycle, fig. 1, or with a stationary drive means fig. 10 comprises at least one input piston 18, drive means 21 connected to said piston 18 to effect reciprocating linear movement of said piston, an output piston 20, means 26 - 30 for transmitting pressure from the input piston 18 to the output piston 20 such that the reciprocating linear movement of the input piston causes pressure to be applied alternately to opposed sides of the output piston 20 to cause the output piston to move in a reciprocating manner. The pressure transmitting means 26 - 30 comprise a diaphragm 27 or a piston1cylinder etc. arrangement which, in combination with the input and output pistons, transmits the input force applied by the drive means to enable the output piston to apply a force to output means connected thereto. The transmission may be applied to a tandem (fig. 5), here enclosed pressure transmitting means (figs. 4 - 6), or the transmission may include three distinct hydraulic units (fig. 9) linked only by connecting rods. <IMAGE>

Description

HYDRAULIC XMPLIFIER The invention relates to an hydraulic amplifier, particularly for use with a cycle or other device, where work input is amplified and transmitted to power or drive an object.

Bicycles and other forms of cycle are regarded as being a useful and enjoyable form of transport which is economical and ecologically sound. The drawbacks are that a reasonable amount of strength and stamina are required by the rider to power the bicycle over any distance or up any inclines. The same applies to any other apparatus which requires work input at one end to power or drive an object.

It is an object of the present invention to provide a hydraulically amplifier, which can be used in particular to assist in driving a cycle, which does not necessarily require any fuel to drive it, and which reduces the amount of work required to be input.

According to the invention there is therefore provided an hydraulic amplifier comprising input piston, drive means connected to said at least one input piston to effect reciprocating linear movement of said at least one input piston, an output piston, means for transmitting pressure from the input piston to the output piston such that the reciprocating linear movement of the input piston causes pressure to be applied to alternative sides of the output piston to cause the output piston to move in a reciprocating manner, in which the pressure transmitting means comprise a valve which, in combination with the input and output pistons, transmits and increases an input force applied by the drive means to enable the output piston to apply an increased force to output means connected thereto.

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic representation of a hydraulically assisted bicycle showing the amplifier of the present invention in an external form with the pedals in one position; Figure 2 is a schematic representation of the bicycle of Figure 1 with the pedals in an alternative position; Figures 3 and 4 are schematic representations of a hydraulically assisted tandem with the amplifier of the present invention in an internal form; and Figures 5 and 6 are schematic representations of alternative embodiments of a bicycle with the amplifier in an internal form; Figures 7 and 8 are schematic representations of an alternative embodiment of the invention with dual input, Figure 7 being shown for use in a pedal driven tandem and Figure 8 for use with stationary drive means; and Figures 9, 10, 11 and 12 are schematic representations of further alternative embodiments of the invention with single input, Figure 9 being shown for use in a bicycle and Figure 10 for use with stationary drive means.

Referring first to Figure 1, there is shown an hydraulic amplifier 10 supported on a bicycle frame 11 (parts of which are shown in dotted lines) which is connected to a front and a rear bicycle wheel 12.

The bicycle includes a pair of pedals 13 mounted to the frame 11 by means of a rotating crank wheel 14.

The hydraulic amplifier 10 comprises first, second and third hydraulic cylinders 15, 16 and 17 located within which are first, second and third hydraulic pistons 18, 19, 20 respectively.

The first piston 18 is connected by means of a connecting rod 21 to the crank wheel 14. The third piston 20 is attached by means of a second connecting rod 22 to the hub 23 of the rear wheel 12.

A network of hydraulic pipes 26 connects the three cylinders 15, 16 and 17 so that each end of each cylinder has two pipes 26 leading therefrom.

Positioned in the pipes 26a, b, e, f between cylinders 15 and 16 is a diaphragm valve comprising a chamber 28 located within which is a flexible diaphragm 27.

A network of mechanical valves 30 is included in the hydraulic amplifier 10 operable to open and close various parts of the pipes 26 and to direct the flow of hydraulic fluid therein. This network of valves 30 essentially includes a valve for each of the four pipes 26 connected to the first and second cylinders 15 and 16 located in such a way as to be capable of closing off the pipes 26 on all sides of the cylinders 15, 16. The valves 30 are interlinked to operate in the way described below and are activated to open and close by means of a lever 29 on the pedal connecting rod 21 when it reaches one of the certain positions. The valves 30 may conveniently be quarter-turn valves.

In use, a force is applied by the rider to the pedals 13 which causes them to move in the direction of arrow A. This causes connecting rod 21 and therefore piston 18 to move downwards. With the valves 30 open or closed in the positions shown in Figure 1, the hydraulic fluid in the cylinder 15 beneath piston 18 is pushed along the pipe 26a into the chamber 28 beneath the diaphragm 27 thus forcing the diaphragm 27 upwards. The hydraulic fluid in the chamber 28 above the diaphragm 27 is forced out of the chamber along pipe 26b thereby forcing piston 19 downwards in chamber 16. The fluid in chamber 16 beneath piston 19 is pushed out along pipe 26c and pushes piston 20 to the left of the cylinder 17.

This has the result that the second connecting rod 22 also moves to the left thereby causing rotation of the hub 23 of the rear wheel 12 in the direction of arrow B.

Figure 2 shows the bicycle of Figure 1 but with the pedals turned through 1800 from the position shown in Figure 1. In this position, the piston 18 has reached the lowest point of travel and the movement of the connecting rod 21 has caused the position of the valves 30 to reverse simultaneously.

In this position, as piston 18 begins to rise, the fluid in chamber 15 moves through pipe 26f into chamber 28 forcing the diaphragm 27 downwards. The fluid below the diaphragm 27 is expelled along pipe 26c into the lower end of chamber 16. As piston 19 rises, the fluid above the piston 19 is expelled along pipe 26d into the cylinder 17. This causes piston 20 to move to the right, thus effecting further rotation of the rear wheel 12. The fluid from the right hand side of chamber 17 travels around pipe 26g to assist the upward movement of piston 18 and thus the pedalling.

As the piston 18 reaches the top of its stroke and the valve positions have again changed to those shown in Figure 1, the excess fluid in the left hand end of cylinder 17 will be forced through pipe 26h back into the top of cylinder 15 to assist movement of the piston and thus ease the work required in pedalling.

The assistance provided by the hydraulic amplifier thus alleviates the hard work required in pedalling the bicycle.

The diameters of the pistons 18, 19, 20, diaphragm 27, length of stroke and forces can be calculated to be within an acceptable range for the application of the amplifier 10. The following is one numerical example of such an acceptable range.

If a load of 178 N is applied to the first piston 18 which has a diameter of 3 cm, the pressure created in the first cylinder 15 would be as follows:

This pressure of 0.25 Mum 2 acts, with the valve set as shown in Figure 1, on the underside of the diaphragm 27 which has a diameter of 15 cm. This means that the force which is transmitted by the diaphragm is as follows: F = P x A = 0.25 x it (0.075)2 = 0.005 my With the force of 0.005MN acting on the surface of the second piston 19 the pressure transmitted by the second piston 19, which has a diameter of 3 cm is calculated as follows:

This pressure of 7.07MNm-2 is transmitted to the third (wheel driving) piston 20, which has a diameter of 4 cm.This results in a total of force applied to the hub of the rear wheel as follows: F = P x A = 7 x it (0.02)2 = 0.009 MN There has therefore been an increase of the force from the 178N initially applied by the rider to the pedals, to the resulting output force of 9000 N on the wheel which is an amplification of over fifty times.

The length of the stroke can be calculated to ensure that the cubic capacity of each of the cylinders in the chamber is the same.

Suitable gears could be fitted to the bicycle if required and the speed of the circulating medium could be controlled by a stop valve to regulate the flow.

All the tubes of the hydraulic amplifier 10 can be flexible for convenience and the component parts could be moulded into a compact unit i.e. the diaphragm 27 could be vertical, instead of horizontal, to enable it to be fitted fore and aft between two sections of the cross bar instead of the usual single cross bar of a bicycle. Obviously, the wider the tubes, the easier it is to pedal and these should be taken into consideration when choosing the diameters of the cylinders.

The amplifier 10 may also have other uses i.e.

it could be installed in a tandem cycle as shown in figure 3. In this embodiment of the invention an enclosed amplifier is shown utilising throttle valves, which are enclosed within the hydraulic ducts. The changeover linkage can also be enclosed within the cylinder and ducts and operated directly by the piston 18 at either end of each stroke. The outside linkage between the top and bottom ducts can be enclosed as shown in figure 3 to contain any possible seepage. This arrangement can be used either in the tandem as shown, in an ordinary bicycle or any other suitable application.

The embodiment of the invention shown in figures 4, 5 and 6 show an amplifier with an enclosed arrangement of valves, incorporating sleeve valves shown in different positions. An advantage of the enclosed embodiments of the invention is that all the moving parts can be immersed in oil, so that friction and wear can be minimised. Figure 4 illustrates the use of sleeve valves in an arrangement for use in driving a tandem bicycle. This arrangement differs from that shown in Figure 3 in that it has a dual input. The second crank wheel 14a is connected to the second piston 19 by means of a second connecting rod 21a. This spreads the load which needs to be applied by the first crank wheel 14.The use of this dual input is not confined to a tandem bicycle application of the amplifier 10, but can be used in any embodiment of the invention to ensure and maintain synchronisation of the second piston 19 with the first piston 18.

In all the embodiments of the invention, the diaphragm 27 could be replaced by pistons and cylinders or another appropriate valve, but the diaphragm is considered to be the preferred option.

In any embodiment of the invention the crank wheel may be weighted to form a fly-wheel, and the cycle rear wheel may be fixed or free rotating.

The amplifier 10 could also be used in other forms of transport, such as a rickshaw, or in a stationary unit for any other use e.g. a pump for raising water in third world countries, manned by one or more persons. The amplifier 10 could also be driven by means other than foot pedals, for example, by electric, diesel or petrol motors or other driven appliances to amplify the output from that source.

Figures 7 and 8 illustrate a further alternative embodiment of the invention, but in these the third cylinder and piston arrangement 17, 20 is shown in a horizontal position, whilst retaining the valves and change mechanism enclosed. Figure 7 shows the first and second pistons 18, 19 at the start of their downward stroke and the hydraulic amplifier 10 attached to a bicycle (parts of which are not shown for clarity). Figure 8 shows the first and second pistons 18, 19 at the start of their upward stroke, and the amplifier is adapted to be activated by any other driving means, such as a small electric motor, with an appropriate arrangement of connecting rods 30 connecting the driving means to the input connecting rods 21, 21a.

Figures 7 and 8 also show the use of a slotted tube 31, 31a to afford protection to the connecting rods 21, 21a against possible damage whilst in use, although the connecting rods may be unprotected as illustrated in Figures 1 to 6. It should also be noted from Figure 8 that a link 32 is included which acts across the connecting rods 21, 21a and this helps to ensure that the pistson 18, 19 act in tandem. Again this can be applied to any of the previous examples of the invention.

In the preceding examples of the invention described, extensive use is made of valves to direct the circulation of pressurised fluid to assist the diaphragm and pistons during their working strokes.

Figures 9 and 10 show an alternative embodiment of the invention, wherein the use of these valves is obviated.

Referring to Figure 9, the hydraulic amplifier 10 is illustrated for use in a bicycle application, connected to a rear bicycle wheel 12 and driven by pedals 13 mounted to the bicycle frame by means of a rotating crank wheel 14. As before, the hydraulic amplifier 10 comprises first, second and third hydraulic cylinders 15, 16, 17 located within which a first, second and third hydraulic pistons 18, 19, 20 respectively. Again the first piston 18 is connected by means of a connecting rod 21 to the crank wheel 14. The third piston 20 is attached by means of a second connecting rod 22 to the hub 23 of the rear wheel 12.

Instead of having a network of interconnecting hydraulic pipes and valves, as described in the previous examples, this embodiment of the invention has three distinct hydraulic units 35, 36, 37 which are not hydraulically linked. To enable the pressures generated by the pistons to be transmitted across the amplifier 10, the units are mechanically linked. This is achieved by duplication of the diaphragm 27 in unit 35 with a similar diaphragm 27a in unit 36 and piston 19 in unit 36 with piston 19a in unit 37 which are linked by means of suitable connecting rods.

In use, a force applied to the pedals 13 causes connecting rod 21 and piston 18 to move downwards.

The hydraulic fluid in unit 35 circulates in an anti-clockwise direction into the right-hand side of the chamber 28 forcing the diaphragm 27 to move to the left. The fluid in the left-hand side of the chamber continues to circulate in an anti-clockwise direction thereby assisting the movement of the piston 18 in a downwardly direction. As the diaphragm moves to the left, this movement is mirrored, by means of the mechanical connection, by diaphragm 27a thereby causing the hydraulic fluid in unit 36 to be forced out of the left-hand side of chamber 28a in an anti-clockwise direction within the unit 36. The fluid forces the piston 19 upwards in chamber 16 and the fluid above the piston 19 is forced into the right-hand side of the chamber 28a thereby assisting the movement of the diaphragm 27a.

The movement of piston 19 causes identical movement of piston 19a within cylinder 16a, thereby causing the fluid in unit 37 to circulate also in an anti-clockwise direction. This fluid bears on the left-hand side of piston 20 forcing it to the right thereby causing rotation of the hub 23 of the rear wheel 12 in the direction of arrow B.

Figure 10, although shown to be driven by other drive means, such as a small electric motor, shows the upward stroke of piston 18.

As before, the diameters of the pistons, diaphragm, the length of stroke and forces can be calculated to be within an acceptable range for the application of the amplifier 10. The calculations given previously apply equally to this arrangement of the invention as the previous arrangements. However, this version of the hydraulic amplifier 10 is much simplier in design, includes fewer components and is therefore more lightweight and less liable to failure.

Turning now to Figures 11 and 12 there is shown another embodiment of the amplifier 10 which eliminates the use of the intermediate piston or pistons 19, 19a. The functioning of this embodiment of the amplifier 10 is essentially the same as before, except that the movement of the second diaphragm 27a causes the fluid to act directly on either side of the output piston 20. This means that the third stage in the increase of pressure/force is omitted and the output of this embodiment of the invention is therefore more modest than that of the previous examples.

The following is one numerical example where a load of 178N is applied to the first piston 18 which has a diameter of 3 cm. The pressure created in the first cylinder 15 will be as follows:

This pressure of 0.25 MNm ~ acts on the left-hand side of the diaphragm 27 which has a diameter of 15 cm. This means that the force which is transmitted by the linked diaphragms 27, 27a is as follows: F = P x A = 0.25 x it (0.075)2 = 0.005 NN With a force 0.005 MN acting on the surface of the output piston 20, which has a diameter of 4 cm is calculated as follows:

This represents an increase of approximately 16 times the pressure created in the first cylinder.

Claims

CLAIMS:

1. An hydraulic amplifier comprising an input piston, drive means connected to said at least one input piston to effect reciprocating linear movement of said at least one input piston, an output piston, means for transmitting pressure from the input piston to the output piston such that the reciprocating linear movement of the input piston causes pressure to be applied to alternative sides of the output piston to cause the output piston to move in a reciprocating manner, in which the pressure transmitting means comprise a valve which, in combination with the input and output pistons, transmits and increases an input force applied by the drive means to enable the output piston to apply an increased force to output means connected thereto.

2. An hydraulic amplifier as claimed in claim 1 in which the pressure transmitting means further comprise an intermediate piston connected hydraulically between the input and output pistons.

3. An hydraulic amplifier as claimed in any one of the preceding claims in which the valve is hydraulically connected to opposite ends of a cylinder in which the input piston is located.

4. An hydraulic amplifier as claimed in claim 2 or claim 3 in which the valve is hydraulically connected to opposite ends of a cylinder in which the intermediate piston is located.

5. An hydraulic amplifier as claimed in any one of the preceding claims in which the valve comprises a diaphragm located in a chamber filled with hydraulic fluid.

6. An hydraulic amplifier as claimed in any one of the preceding claims in which the valve comprises two diaphragms, mechanically linked, located in separate chambers.

7. An hydraulic amplifier as claimed in any one of claims 2 to 6 in which the intermediate piston is located in a cylinder which is connected at each end thereof to opposite ends of a cylinder in which the output piston is located.

8. An hydraulic amplifier as claimed in any one of claims 2 to 7 in which there are two intermediate pistons, mechanically linked, located in separate cylinders.

9. An hydraulic amplifier as claimed in any one of claims 2 to 9 in which a cylinder in which the input piston is located is connected at each end thereof to opposite ends of a cylinder in which the output piston is located.

10. An hydraulic amplifier as claimed in any one of the preceding claims further comprising secondary valve means operable to change the direction of flow of hydraulic fluid.

11. An hydraulic amplifier as claimed in claim 10 in which the secondary valve means comprise a plurality of secondary valves which are operable simultaneously to reverse their position.

12. An hydraulic amplifier as claimed in claim 11 in which the secondary valve means are operated when the input piston is at one or more predetermined positions.

13. An hydraulic amplifier as claimed in any one of claims 10 to 12 in which pairs of secondary valves of the secondary valve means are operable to close off one output at each end of the input and intermediate piston cylinders whilst leaving another output at each end of the cylinders open.

14. An hydraulic amplifier as claimed in any one of the preceding claims in which the input and output pistons and the hydraulic means amplify and transmit the load applied by the drive means to the output means.

15. An hydraulic amplifier as claimed in any one of the preceding claims in which the intermediate piston is connected to the drive means.

16. An hydraulic amplifier as claimed in any one of the preceding claims, in which the input and intermediate pistons are mechanically linked so as to act in synchronisation.

17. An hydraulic amplifier as claimed in any one of the preceding claims in which the intermediate piston is mechanically linked to the output piston.

18. An hydraulic amplifier as hereinbefore described with reference to and as shown in the accompanying drawings.