WO2000046531A1

WO2000046531A1 - Improvements in air motors

Info

Publication number: WO2000046531A1
Application number: PCT/AU2000/000059
Authority: WO
Inventors: Alan Patrick Casey
Original assignee: Split-Cycle Technology Limited
Priority date: 1999-02-03
Filing date: 2000-02-02
Publication date: 2000-08-10

Abstract

An air motor wherein a 'split-cycle rotary machine' acts as a linear to rotary motion converter under the supply of compressed gas. The motor has a spool valve associated with each cylinder to controlling feed compressed air into and exhaust air out of that cylinder. The spool valve includes a plenum chamber surrounding an inlet for pressurized gas to the valve.

Description

IMPROVEMENTS IN AIR MOTORS

Introduction

The present invention relates to air motors as may be driven by pressurized air or other gases. This invention is particularly but not exclusively adaptable to the environment of bicycles. It will be readily understood that air motors can be used in numerous environments and can be employed in other land, water and possibly flying vehicles. We envisage that air motors with which the present invention is concerned would be suitable for use in water borne vehicles where pollution of waterways by hydrocarbon fuelled power boats is to be avoided.

Background to the Invention

Relatively small powered vehicles such as mopeds are an important mode of transport throughout the developed and developing worlds. The motor assist system that is currently in wide use is powered by two- or four-stroke internal combustion engines. With the advent of ever more stringent engine emission requirements, there is expected to be a phasing out of small internal combustion engines as are used for such vehicles.

Adaptation of a "split-cycle rotary machine", as defined in Australian Patent 694858, the contents of which are included herein by reference, to be driven by pressurized gas such as air entails the development of a control system and componentary for the efficient operation of an air motor in the form of a "split-cycle rotary machine".

Summary of the Invention It is the aim of the present invention to provide a mechanically powered system for use in, say, land or water borne vehicles, such as mopeds, dinghies and the like which avoids the use of internal combustion engines. In a first aspect of the present invention there is provided a spool valve for controlling the admission and exhaust of gas to and from each cylinder of a split-cycle rotary machine, said spool valve comprising a spool valve piston movable within a spool valve cylinder for admitting pressurized gas in one direction to a cylinder of the split-cycle rotary machine and for opening a fluid connection to the cylinder of the split-cycle rotary machine for exhausting gas at a lower pressure from the cylinder of the split cycle rotary machine to atmosphere downstream of the spool valve, said spool valve incorporating a plenum chamber surrounding a pressurized gas inlet to the spool valve for receiving pressurized gas from a pressurized gas source.

In a second aspect, the present invention provides a spool valve having a spool valve piston within a spool valve cylinder characterized in that motion of the piston is adapted to be controlled by an extension thereof contacting a cammed surface to facilitate timed movement of the piston for enabling movement of pressurized gas through the valve as the working fluid for a split-cycle rotary machine, wherein the extension of the spool valve piston which contacts the cammed surface is formed from a plastics material impregnated with wax. In a preferred embodiment the wax impregnated plastics material is polyethylene wax nylon 6 GPE which has a 50% lower co-efficient to friction than standard nylon 6.

The self damping properties of the extension of the shaft of the spool valve piston of the second aspect of the invention have been found to be highly beneficial in regulating the performance of an air motor of the type with which the various aspects of this invention are concerned.

In a third aspect of the present invention there is provided a spool valve adapted for the purpose of the first aspect of the present invention wherein gas inlet and/or exhaust ports in the cylinder wall containing the spool valve piston are formed as circumferentially extending slots having chamfered or filleted edges sloping inwardly toward the cylindrical surface containing the spool valve piston. It has been found that formation of the pressurized gas inlet ports in accord with the third aspect of the present invention significantly improves the performance of an air motor in accord with the form of a split- cycle rotary machine. That performance is even more markedly improved when the first and third aspects of the present invention are combined in a single embodiment.

A fourth aspect of the present invention provides an hydraulic or pneumatic or combined hydraulic/pneumatic power train for a bicycle wherein a split-cycle rotary machine, as herein defined, is adapted to have the output shaft mounted to drive a wheel of a bicycle or similar and wherein pedals of the bicycle are adapted to drive a fluid medium as the working fluid in a plurality of cylinders of the split-cycle rotary machine to thereby power the wheel of the bicycle via the output shaft of the split-cycle rotary machine.

In an embodiment of the fourth aspect of the invention, the working fluid is an hydraulic fluid.

In a fifth aspect, the present invention provides a split-cycle rotary machine adapted to have the output shaft mounted to drive a wheel of a bicycle or similar, wherein a first pressurized fluid supply tank is connectable via power transfer means, to a plurality of cylinders of the split-cycle machine to thereby supply a second pressurized fluid to power the wheel of the bicycle via the output shaft of the split-cycle rotary machine.

In a first embodiment of the fifth aspect, the first pressurized fluid supply tank contains pressurized gas.

In a second embodiment of the fifth aspect of the present invention, the pressurized gas of the first embodiment is air which is replenished by a regenerative compressor driven by rotary motion of a wheel or pedals of the bicycle. In a third embodiment of the fifth aspect of the present invention, the pressurized gas of the first embodiment is nitrogen.

A particularly preferred bicycle embodiment incorporating the present invention includes the fourth and fifth aspects wherein a half of the cylinders of the split-cycle rotary machine are supplied by the pedal powered working fluid and other half of the cylinders are adapted to be supplied by the second pressurized fluid driven optionally or together by compressed air from a first regeneratively pressurized tank or nitrogen from a second pressurized tank.

In yet another embodiment, instead of pressurized gas driven assist power, or auxiliary or booster hydraulic drive, there could be employed sequentially driven electrical solenoids on to the lobes of the Geneva wheels. Such an embodiment would require that a rechargeable electrical power source be carried on the bicycle in place of the pressurized gas tank(s).

In a bicycle in accord with the present invention, there is optionally a chain drive between the pedals and a wheel of the bicycle.

Brief Description of the Drawings

The present invention will now be described by way of example with reference to the accompanying drawings, in which: -

Figure 1 is a perspective view of a rear wheel of a bicycle fitted with an air motor embodiment incorporating embodiments of first to third aspects of the present invention; Figure 2 is a perspective view of a prototype arrangement in accord with Figure 1 ; Figure 3 is a close-up perspective of portion of Figure 2;

Figure 4 is a perspective of the separated components of a spool valve prototype embodiment in accord with the first to third aspects of the present invention; Figure 5 is a perspective view of the assembled spool valve of Figure 4; Figure 6 is a perspective view of a piston and seal of the form employed in the prototype of Figure 2;

Figure 7 is a front elevation view of an embodiment of a spool valve formed in accord with the first to third aspects of the present invention; Figure 8 is a perspective view of an embodiment of the third aspect of the present invention;

Figure 9 is a graphical representation displaying horse power versus rpm measured on a test for the embodiment shown in Figure 2 with inlet air at a pressure of 50 psi;

Figure 10 is a graphical representation displaying torque versus rpm for the same test as displayed in Figure 9; Figure 11 is a schematic circuit diagram showing an embodiment of all of the aspects of the invention; and

Figure 12 is a side elevation view of a bicycle embodiment incorporating the embodiment of Figure 1.

Best Modes

In Figure 1 an air motor in accord with the present invention and of the general form contemplated by Figure 11 is shown fitted to the hub region of a bicycle wheel 11 fitted with an off-road tyre 12.

Air motor 10 is of the form of a split-cycle rotary machine and the depicted embodiment has twelve working cylinders 13 with pressurized air being delivered to those cylinders via respective spool valves 14 which control the ingress and egress of pressurized air to each cylinder from an external source of pressurized air (not shown).

A prototype air motor 20 shown in Figures 2 and 3 is marked with corresponding reference numerals for like parts to those shown in Figure 1. In the depicted prototype a brake disc 21 has been added to spin with air motor 20 and wheel 11 by a coupling to the air motor via a spider coupling 22 which is bolted to motor 20 via its respective arms and to which disc 21 is in turn bolted. Pressurized air is supplied to the spool valves via inlet line 23 which feeds pressurized air into the interior of axle 24 to be radially distributed from the interior of axle 24 to each of spool valves 14.

The prototype spool valve 30 is shown in Figure 4 and comprises piston 31, formed from a wax impregnated plastics material, fitted within spool valve cylinder 32 having pressurized gas inlet slots 33 and exhaust ports 34. Plenum chamber 35, adapted to fit over inlet ports 33, is held in place by threaded nut 36 as can be readily seen in the assembled arrangement of Figure 5. Extremity 37 of piston 31 slidingly contacts a cammed surface (not shown) which is fixed relative to the frame of a bicycle. The cammed surface, contacting extremity 37, limits motion of piston 31 during rotation of motor 10 and wheel 11. The interaction between the rotary cammed surface and each extremity 37 of each spool valve piston controls the opening and closing of inlet and exhaust ports 33 and 34, respectively of each spool valve 30 to provide timed opening to allow pressurized air to flow to and from each motor cylinder 13 to impart rotary motion to wheel 11.

Figure 6 shows a form of piston 40 as is fitted within each cylinder 13 where rubberized insert 41 contacts the lobed shafts or Geneva wheels of the split-cycle rotary machine to control the motion of each piston 40 under the action of pressurized air within each cylinder 13 that impinges upon top 42 of piston 40.

Surrounding top 42 of each piston 40 there is a sealing member 43 which acts as a suction cup to hold each piston 40 as its top dead centre position when not being acted upon by pressurized air. Inserts 41 are preferably of natural rubber while cup sealing member 43 can be of any suitably resilient material compatible with the lubricant employed between piston 40 and its complementary cylinder wall.

Figure 7 shows a spool valve 14 as employed in the prototype of Figures 2 and 3 where each spool valve piston 31 is fitted within a sleeved cylinder 52 mounted within spool valve retainer body 53 to be mounted in radial fashion around motor 20 as shown in Figures 2 and 3. Circumferential slots 54 through the wall of sleeve 52 are surrounded by plenum 55. As piston 31 moves outwardly of sleeve 52 from the position shown in Figure 7, slots 54 open to allow fluid connection between those slots and passage 56 which is coupled to an inlet of a respective cylinder 13.

Figure 8 shows a sleeve 52 with chamfered or filleted edge slots 54 formed in accord with an embodiment of the third aspect of the present invention.

The graphical representation of Figure 9 shows a plot of horsepower versus rpm for the prototype air motor and wheel combination of Figures 2 and 3 when operated under an inlet air pressure of 50 psi. Increasing volumetric flow rates of pressurized air increases the rpm of the motor/wheel combination.

Figure 10 is a graphical plot for the same air motor and wheel unit which provided the results of Figure 9. It can be seen from a reading of the graphs of Figures 9 and 10 that at very low rpm the air motor torque is at its highest thereby providing good standing start performance for that prototype air motor.

In Figure 11, pedals 60 of a bicycle crank are adapted to drive gear train 61 to which is mounted crank 62.

Crank 62 cyclically drives pistons in separate hydraulic cylinders 63 which pump hydraulic fluid each to an alternative three cylinder set of split-cycle Geneva wheel crank 64. Hydraulic fluid reservoir 65 is coupled to supply lines 66, 67 via relief valve 68.

Rotation of pedals 60 provides cyclical pumping of hydraulic fluid in lines 66 and 67 to respective three cylinder sets of crank 64 to drive the rotary output shaft of the crank and a wheel of a bicycle or similar coupled directly or indirectly to the output shaft. Two alternative auxiliary power supplies are provided via regenerative pressurized air supply tank 69 and highly pressurized air or nitrogen bottle 70. Either or both of those pressurized gas supplies can be employed by opening valve 71 (and valve 72) which power air or gas cylinders 73 in alternate fashion by switching of flip-flop valves 74 which time the air/nitrogen into the air cylinders 73. Air cylinders 73 drive alternate hydraulic cylinders which are set up in similar manner to hydraulic cylinders 63 as discussed above.

The hydraulic lines 75, 76 supply pressurized hydraulic fluid under alternating pumping action of cylinders 73 to separate three cylinder sets of crank 64 to drive the output shaft of crank 64. This drive from tanks 69, 70 can be used to boost the pedal power on uphill sections either from the pressurized air of tank 69 and/or by the expansion of nitrogen or air from tank 70.

Other variations in operation could be that full pressure is applied to each air cylinder 73 when its piston is at top dead centre and then cutting off of the pressurized gas supply to allow gas to fully expand in driving the piston in its cylinder 73. Alternatively, gas at full pressure could be maintained throughout the power strokes of each piston in its respective cylinder 73, upon opening of valve 72 as well as valve 71.

The crank of pedals 60 supports a gear wheel having a ratchet arrangement. The pedal gear wheel inputs to gearbox 61 which speeds up the operation of double crank pistons in hydraulic master cylinders 63. The gearing up of gearbox 61 could be as high as 24: 1 while the throw of crank 62 could be such as to give a master cylinder stroke of, say 9mm. the crank 64 acts a reduction box of 6:1 in relation to the speed of master cylinder 63.

Typically, the stroke of each Geneva wheel in crank 64 is 3 mm so that there is a relatively high cycle rate of relatively small strokes. The additional air and nitrogen pressure from tanks 69, 70 to the opposite side of crank 64 when needed acts to accelerate 64 without applying additional pedal power. The pressurized air in tank 69 can be replenished during downhill running by regenerative air compressor 77, driven by the front or preferably rear wheel of the bicycle. Once tank

69 has been repressurized by downhill running of the bicycle after being drained on an uphill leg, it is again readied for further assistance.

An added power assist provided by nitrogen bottle 70, cannot be regenerated but the bottle

70 could be replaced by a fully charged replacement bottle 70, made available at service stations or similar locations along a travel route.

The depicted embodiment does not show a backup conventional chain drive between pedals 60 and the wheel driven by crank 64, but such could be readily provided to enable the bicycle to be driven in a conventional manner should a drive system of the present invention fail.

The bicycle of 80 of Figure 12 is fitted with the drive system shown in Figure 11 and like components in Figure 12 are identically numbered with those in Figure 11.

As will be appreciated from the foregoing, the present invention offers an alternative power system for a bicycle with a possibility of a significant mechanical advantage without use of polluting internal combustion engines.

Even though the embodiments discussed above are in relation to an air motor employed in the hub of a bicycle wheel it will be readily understood that an air motor of this invention is equally well suited to environments other than the hub of a wheeled vehicle. Such air motors are envisaged as being well adaptable for use as motors for water borne vehicles for driving a propeller instead of a wheel.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the various aspects of the present invention as shown in these specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1 A spool valve for controlling the admission and exhaust of gas to and from each cylinder of a split-cycle rotary machine, as hereinbefore defined, said spool valve comprising a spool valve piston movable within a spool valve cylinder for admitting pressurized gas in one direction to a cylinder of the split-cycle rotary machine and for opening a fluid connection to the cylinder of the split-cycle rotary machine for exhausting gas at a lower pressure from the cylinder of the split cycle rotary machine to atmosphere downstream of the spool valve, said spool valve incorporating a plenum chamber surrounding a pressurized gas inlet to the spool valve for receiving pressurized gas from a pressurized gas source.

2 A spool valve piston within a spool valve cylinder characterized in that motion of the piston is adapted to be controlled by an extension thereof contacting a cammed surface to facilitate timed movement of the piston for enabling movement of pressurized gas through the valve as the working fluid for a split-cycle rotary machine, as hereinbefore defined, wherein the extension of the spool valve piston which contacts the cammed surface is formed from a plastics material impregnated with wax.

3 A spool valve as claimed in claim 2, wherein the plastics material impregnated with wax is polyethylene wax nylon 6 GPE.

4 A spool valve as claimed in claim 1 , wherein gas inlet and/or exhaust ports in the cylinder wall containing the spool valve piston are formed as circumferentially extending slots having chamfered or filleted edges sloping inwardly toward the cylindrical surface containing the spool valve piston. An hydraulic or pneumatic or combined hydraulic/pneumatic power train for a bicycle wherein a split-cycle rotary machine, as hereinbefore defined, is adapted to have the output shaft mounted to drive a wheel of a bicycle or similar and wherein pedals of the bicycle are adapted to drive a fluid medium as the working fluid in a plurality of cylinders of the split-cycle rotary machine to thereby power the wheel of the bicycle via the output shaft of the split-cycle rotary machine.

A power train as claimed in claim 5 wherein the working fluid is an hydraulic fluid.

A split-cycle rotary machine, as hereinbefore defined, adapted to have the output shaft mounted to drive a wheel of a bicycle or similar, wherein a first pressurized fluid supply tank is connectable via power transfer means, to a plurality of cylinders of the split-cycle machine to thereby supply a second pressurized fluid to power the wheel of the bicycle via the output shaft of the split-cycle rotary machine.

A split-cycle rotary machine as claimed in claim 7 wherein the first pressurized fluid supply tank contains pressurized gas.

A split-cycle rotary machine as claimed in claim 7 or 8 wherein the pressurized gas is air which is replenished by a regenerative compressor driven by rotary motion of a wheel or pedals of the bicycle.

A machine as claimed in claim 8 wherein the pressurized gas is nitrogen.

A split-cycle rotary machine, as hereinbefore defined, adapted to have the output shaft mounted to drive the wheel of a bicycle or similar wherein there are sequentially driven electrical solenoids which contact the lobes of the Geneva wheels, said solenoids being powered by a portable electrical power source carried by the bicycle.