The machine operates as an engine for delivery of mechanical work for an extended duration in comparison to the duration of energy input into the engine, Background Art With a typical engine, input energy is delivered to the engine in a substantially constant manner for conversion into output energy (in the form of mechanical work). By way of example, in the operation of an electric motor, input electrical energy is delivered continuously to the motor for conversion into output energy in the form of mechanical work.

There are circumstances where it is desirable to have an engine which can provide a sustained energy output with only intermittent energy input. One such circumstance is where an engine is required to drive an electrodynamic machine for producing electrical power at a location where a reticulated power supply is unavailable. Some of the electrical power so produced can be utilised to operate the source providing the intermittent input energy.

One such engine is disclosed in international application PCT/AU00/00778, the contents of which are incorporated herein by way of reference. While such an engine performs satisfactorily in operation, it is somewhat unwieldy, owing to the use of drive mechanisms comprising rack and pinion mechanisms which involve racks undergo linear movement. The unwieldy construction may have an adverse affect on the range of possible applications of the engine.

It would be advantageous to provide a machine which is of more compact construction.

Disclosure of the Invention The present invention provides a machine comprising : a drive shaft ; a first gear train and a second gear train both driving connected to the drive shaft; the first gear train having a first input shaft ; the second gear train having a second input shaft; a first drive mechanism driving connected to the first input shaft ; a second drive mechanism driving connected to the second input shaft; the first and second drive means each comprising a gear and pinion mechanism ; and a power means for operating the first and second drive mechanisms to sequentially move through power and return strokes whereby upon each power stroke the drive mechanisms respectively apply torque to the first and second input shafts.

Preferably, the sequence in which torque is applied to the first and second input shafts is such that torque is initially delivered to both the first and second input shafts and subsequently to only one of the input shafts. This is achieved by one drive mechanism completing its power stroke after completion of the power stroke by the other drive mechanism. Conveniently, said one drive mechanism has completed about one-half of its power stroke at the stage where the other completes its power stroke.

The first and second gear trains may share some common gears.

The power means may comprise a spring structure associated with each gear and a loading means for loading the spring structure to generate a spring force therein.

The spring structure may comprise at least one, and preferably two or more, axial springs (such as extension springs or compression springs) each having one end attached to the respective gear and the other end fixed, whereby rotation of the gear in one direction corresponds to extension of the spring and rotation of the gear in the other direction corresponds to contraction of the spring.

Conveniently, each spring is an extension spring in which case rotation of the gear in one direction causes extension of the spring to effect loading thereof such that the spring force so generated subsequently effects reverse rotation of the gear upon contraction of the spring.

With such an arrangement, the drive mechanism performs a loading (return) stroke upon rotation of the gear in the direction corresponding to loading of the spring and a power stroke when moving in the reverse direction under the influence of the spring.

The loading means may be common to both the first and second drive mechanisms.

The loading means may comprise a movable element operably connected to the gears of the two gear and pinion mechanisms, whereby linear movement of the movable element in one direction causes rotation of the gears and thus loading of the respective springs connected thereto.

The movable element may provide a cam having an arcuate cam profile, and each gear may have a crank element engagable with the cam profile for movement therealong upon linear movement of the movable element in said one direction.

The movable element may comprise an arcuate rail which in effect provides the cam for driving the cranks of the two gears. The arcuate rail may be of channel cross-section and each crank may incorporate a roller received in the channel for rolling movement therealong.

The loading means may further comprise a power mechanism for effecting linear movement of the movable element in said one direction. The power mechanism may comprise a ram operable by a working fluid.

Conveniently, the movable element can undergo reverse movement under the influence of at least one of the gears as the latter rotates to perform its power stroke.

The pinion of each gear and pinion mechanism is adapted to freewheel as its respective gear undergoes a loading (return) stroke.

The transmission ratio between the first drive mechanism and the drive shaft, and the transmission ratio between the second drive mechanism and the drive shaft, can each be selected according to the particular application of the engine.

However, the arrangement is such that the two drive mechanisms perform their loading (return) strokes in unison under the influence of the common power means, and perform their respective power strokes at different rates, with one drive mechanism completing its power stroke after completion of the power stroke of the other drive mechanism.

The machine may further comprise ., a third gear train and a fourth gear train both driving connected to the drive shaft; the third gear train having a third input shaft; the fourth gear train having a fourth input shaft; a third drive mechanism driving connected to the third input shaft;

a fourth drive mechanism drivingly connected to the fourth input shaft, wherein the power means drives the third and fourth drive mechanisms to sequentially move the third and fourth through power and return strokes whereby upon each power stroke the third and fourth drive mechanisms apply torque to the third and fourth input shafts, and wherein each drive mechanism comprises a gear and pinion mechanism.

The various drive mechanisms are preferably arranged to operate in a pre- determined sequence.

Preferably, the pre-determined sequence is such that torque is initially delivered to both the first and second input shafts and subsequently to only first input shaft during which stage torque is initially delivered to both the third and fourth input shafts and subsequently to only the third input shaft during which stage torque is initially delivered to both the first and second input shafts and subsequently to only the first input shaft.

The third and fourth gear trains may share some common gears with each other and may also share some common gears with the first and second gear trains.

The present invention also provides a machine comprising : a drive shaft; a first gear train and a second gear train both driving connected to the drive shaft ; the first gear train having a first input shaft ; the second gear train having a second input shaft ; a first drive mechanism driving connected to the first input shaft;

a second drive mechanism driving connected to the second input shaft; each drive mechanism comprising a gear and pinion mechanism; a power means for operating the first and second drive mechanisms to sequentially move through power and return strokes whereby upon each power stroke the drive mechanisms respectively apply torque to the first and second input shafts ; and the power means comprising a spring structure associated with the gear of each gear and pinion mechanism, and a loading means common to both drive mechanisms for loading the spring structures to generate spring forces therein.

The present invention also provides a machine comprising a drive shaft, and first, second, third and fourth drive mechanisms driving connected to the drive shaft for applying rotational torque thereto during power strokes of the drive mechanisms, the drive mechanisms being operable to perform their respective power strokes in a cycle whereby the first and second drive mechanisms operate together during part of their power strokes and thereafter the second drive mechanism completes its power stroke while the first drive mechanism continues its power stroke during which stage the third and fourth drive mechanisms operate together during part of their power strokes and thereafter the fourth drive mechanism completes its power stroke while the third drive mechanism continues its power stroke during which stage the first and second drive mechanisms operate together during part of their power strokes to repeat the cycle.

The invention also provides a method of operating a machine having a drive shaft, and first and second drive mechanisms operatively connected to the drive shaft for applying rotational torque thereto during power strokes of the drive mechanism, the method comprising the steps of operating the machine in an operating cycle in which both drive mechanisms operate together during part of their power strokes and thereafter one drive mechanism completes its power stroke while the other drive mechanism continues its power stroke, and following

completion of the power stroke of said other drive mechanism both drive mechanisms operate together during part of their power strokes to repeat the cycle.

The invention also provides a method of operating a machine having a drive shaft, and first, second, third and fourth drive mechanisms operatiVely connected to the drive shaft for applying rotational torque thereto during power strokes of the drive mechanisms, the method comprising the steps of operating the machine in an operating cycle in which the first and second drive mechanisms operate together during part of their power strokes and thereafter the second drive mechanism completes its power stroke while the first drive mechanism continues its power stroke during which stage the third and fourth drive mechanisms operate together during part of their power strokes and thereafter the fourth drive mechanism completes its power stroke while the third drive mechanism continues its power stroke during which stage the first and second drive mechanisms operate together during part of their power strokes to repeat the cycle.

Brief Description of the Drawings The invention will be better understood by reference to the following description of several specific embodiments thereof, as shown in the accompanying drawings in which: Figure 1 is a schematic elevational view of an engine according a first embodiment viewed from one side thereof ; Figure 2 is a view similar to Figure 1 with the exception that the engine is viewed from the other side thereof ; Figure 3 is a schematic plan view of the engine according to the first embodiment; Figure 4 is an elevational view of part of a drive system for the engine according to the first embodiment ;

Figure 5 is a view similar to Figure 4 with the exception that a further part of the drive system is illustrated; Figure 6 is a fragmentary side elevational view of the engine, showing in particular two drive mechanisms and an associated power means therefor comprising a spring structure and loading means; Figures 7 and B are views similar to Figure 6 showing the spring structure and loading means at various operational positions ; Figure 9 is a schematic view of a power means for an engine according to a second embodiment; Figure 10 is a schematic view of a control system used in the power means shown in Figure 9; Figure 11 is a schematic view of a power means for an engine according to a third embodiment.

Figure 12 is a schematic view of a power means for an engine according to a fourth embodiment ; Figure 13 is a schematic view of a power means according to a fifth embodiment ; Figure 14 is a schematic elevational view of an engine according to a still further embodiment ; Figure 15 is a schematic plan view of the engine of Figure 14; Figure 16 is a schematic elevational view of part of a drive system for the engine shown in Figure 14; and Figure 17 is a schematic view of a part of the drive mechanism.

Best Mode (s) for Carrying out the Invention The first embodiment, which is shown in Figures 1 to 8 of the drawings, is directed to an engine 200 which can deliver mechanical work for an extended duration in comparison to the duration of energy input into the engine.

The engine 200 includes a drive shaft 201 through which it delivers mechanical work. in this embodiment, the drive shaft 201 may be driving connected to an electrodynamic machine for generating electrical energy, some of which is used to operate the engine 200. The electrodynamic machine may be of the type disclosed in international application PCT/AUOO/00778, the contents of which are incorporated herein by way of reference.

The drive shaft 201 is driven by a drive system 203 which incorporates various drive mechanisms 205, power means 207 for operating the drive mechanisms 205, and gearing 209 for driving connecting the drive mechanisms 205 to the drive shaft 201.

The engine 200 further comprises a hydraulic circuit 211 which incorporates a reservoir (not shown) to contain a supply of hydraulic fluid and electrically operable hydraulic pumps 213 for pumping the hydraulic fluid through the hydraulic circuit. The hydraulic pumps 213 receive electrical energy for their operation from an electrical supply which in this embodiment comprises an electrical storage means in the form of batteries which are continuously charged, using electricity generated by the electrodynamic machine. Surplus electricity generated by the electro-dynamic machine can be used for other purposes such as lighting or powering electrical equipment.

The various drive mechanisms 205 comprise a first drive mechanism 221, a second drive mechanism 222, a third drive mechanism 223, a fourth drive mechanism 224, a fifth drive mechanism 225, a sixth drive mechanism 226, a seventh drive mechanism 227, and an eighth drive mechanism 228.

The first drive mechanism 221 is in the form of a first gear and pinion mechanism 231 comprising a first gear 233 and a first pinion 235 in meshing engagement with the first gear 233. The first pinion 235 is connected to a first input shaft 237 through a clutch mechanism 239. The clutch mechanism 239 allows torque transmission from the first pinion 235 to the first input shaft 237 upon rotation of the pinion 235 in one direction while allowing the pinion 235 to freewheel with respect to the input shaft 237 upon rotation of the pinion 235 in the reverse direction so as not to transmit torque.

The second drive mechanism 222 is in the form of a second gear and pinion mechanism 241, comprising a second gear 243 and a second pinion 245 in meshing engagement with the second gear 243. The second pinion 245 is connected to a second input shaft 247 through a clutch mechanism 249. The clutch mechanism 249 allows torque transmission from the second pinion 245 to the input shaft 247 upon rotation of the second pinion 245 in one direction while allowing the second pinion 245 to freewheel with respect to the input shaft 247 upon rotation of the second pinion 245 in the reverse direction so as not to transmit torque.

The third drive mechanism 223 is in the form of a third gear and pinion mechanism 251 comprising a third gear 253 and a third pinion 255 in meshing engagement with the third gear 253. The third pinion 255 connected to a third input shaft 257 through a clutch mechanism 259. The clutch mechanism 259 allows torque transmission from the third pinion 255 to the input shaft 257 upon rotation of the third pinion 255 in one direction while allowing the third pinion 255 to freewheel with respect to the input shaft 257 upon rotation of the third pinion 255 in the reverse direction so as not to transmit torque.

The fourth drive mechanism 224 is in the form of a fourth gear and pinion mechanism 261 comprising a fourth gear 263 and a fourth pinion 265 in meshing engagement with the fourth gear 263. The fourth pinion 265 is connected to a fourth input shaft 267 through a clutch mechanism 269 The clutch mechanism 269 allows torque transmission from the fourth pinion 265 to the fourth input shaft 267 upon rotation of the fourth pinion 265 in one direction while allowing the fourth

pinion 265 to freewheel on the fourth input shaft 267 upon rotation of the fourth pinion 265 in the reverse direction so as not to transmit torque.

The fifth drive mechanism 225 is in the form of a fifth gear and pinion mechanism 271 comprising a fifth gear 273 and a fifth pinion 275 in engagement with the fifth gear 273. The fifth pinion 275 is connected to the fourth input shaft 267 mounted through a clutch mechanism 279. The clutch mechanism 279 allows torque transmission from the fifth pinion 275 to the fourth input shaft 267 upon rotation of the pinion in one direction while allowing the pinion to freewheel on the fourth input shaft upon rotation of the pinion in the reverse direction so as not to transmit torque.

The sixth drive mechanism 226 is in the form of a sixth gear and pinion mechanism 281 comprising a sixth gear 286 and a sixth pinion 285 in engagement with the sixth gear 286. The sixth pinion 285 is connected to the third input shaft 257 through a clutch mechanism 289. The clutch mechanism 289 allows torque transmission from the sixth pinion 285 to the third input shaft 257 upon rotation of the pinion in one direction while allowing the pinion to freewheel on the third input shaft upon rotation of the pinion in the reverse direction so as not to transmit torque.

The seventh drive mechanism 227 is in the form of a seventh gear and pinion mechanism 291 comprising a seventh gear 293 and a seventh pinion 295 in engagement with the seventh gear 293. The seventh opinion 295 is connected to the second input shaft 247 through a clutch mechanism 299. The clutch mechanism 299 allows torque transmission from the seventh pinion 295 to the second input shaft 247 upon rotation of the pinion in one direction while allowing the pinion to freewheel on the second input shaft upon rotation of the pinion in the reverse direction so as not to transmit torque thereto.

The eighth drive mechanism 22B is in the form of an eighth gear and pinion mechanism 301 comprising an eighth gear 303 and an eighth pinion 305 in engagement with the eighth gear 303. The eighth pinion 305 is connected to the first input shaft 237 through a clutch mechanism 309. The clutch mechanism 309

allows torque transmission from the eighth pinion 305 to the first input shaft 237 upon rotation of the pinion in one direction while allowing the pinion to freewheel on the first input shaft upon rotation of the pinion in the reverse direction so as not to transmit torque.

In this embodiment, the gear of each of the gear and pinion mechanisms forming the various drive mechanisms 205 has 120 teeth and the pinion has 12 teeth.

A first drive gear 311 is mounted on the first input shaft 237 for rotation therewith.

The first drive gear 311 is in meshing engagement with an idler gear 3t3 which in tum is in meshing engagement with a first driven gear 315 rigidly mounted on a layshaft 317.

A second drive gear 321 is rigidly mounted on the second input shaft 247 for rotation therewith. The second drive gear 321 is in meshing engagement with a second driven gear 323 which is rigidly mounted on the layshaft 317 for rotation therewith.

A first output gear 325 is rigidly mounted on the layshaft 317 for rotation therewith.

The first output gear 325 is in meshing engagement with a first output pinion 327 rigidly mounted on the drive shaft 201.

The first driven gear 315 is larger than the second driven gear 323. More particularly, in this embodiment the first driven gear 315 has 30 teeth and the second driven gear 323 has 20 teeth. The first and second drive gears 311, 321 each have 120 teeth. The reason for the first driven gear 315 being larger than the second driven gear 323 is to provide different transmission ratios between the first and second drive mechanisms 221, 222 respectively and the drive shaft 201, and similarly different transmission ratios between the seventh and eighth drive mechanisms 227, 228 respectively and the drive shaft.

It will be noted that the transmission ratio between the first drive mechanism 221 and the drive shaft 201, and the transmission ratio between the eighth drive mechanism 226 and the drive shaft 201, are the same. Similarly, the transmission

ratio between the second drive mechanism 222 and the drive shaft 201 and the seventh drive mechanism 227 and the drive shaft 201 are the same.

A third drive gear 331 is mounted on the third input shaft 257 for rotation therewith. The third drive gear 331 is in meshing engagement with an idler gear 333 which is in turn in meshing engagement with a third driven gear 335. The third driven gear 335 is rigidly mounted on a layshaft 337 for rotation therewith, A fourth drive gear 341 is rigidly mounted on the fourth input shaft 267 for rotation therewith. The fourth drive gear 341 is in meshing engagement with a fourth driven gear 343 which is rigidly mounted on the layshaft 337 for rotation therewith.

A second output gear 345 is rigidly mounted on the layshaft 337 for rotation therewith and is in meshing engagement with a second output pinion 347 rigidly mounted on the output shaft 201 for rotation therewith.

The third driven gear 335 is larger than the fourth driven gear 343. More particularly, in this embodiment the third driven gear 335 has 30 teeth and the fourth driven gear 343 has 20 teeth. The third and fourth drive gears 331,341 each have 120 teeth. The reason for the third driven gear 335 being larger than the fourth driven gear 343 is to provide different transmission ratios between the fourth and fifth drive mechanisms 224,225 respectively and the drive shaft 201, and similarly diFferent transmission ratios between the third and sixth drive mechanisms 223, 226 respectively and the drive shaft.

It will be noted that the transmission ratio between the fourth drive mechanism 224 and the drive shaft 201, and the transmission ratio between the fifth drive mechanism 225 and the drive shaft 201, are the same. Similarly the transmission ratio between the third drive mechanism 223 and the drive shaft 201 and the sixth drive mechanism 226 and the drive shaft 201 are the same.

The various drive mechanisms 205 operate in pairs. Specifically, the first and second drive mechanisms 221,222 operate as a pair, as does the third and fourth

drive mechanisms 223, 224, the fifth and sixth drive mechanisms 225, 226, and the seventh and eighth drive mechanisms 227, 228.

The two drive mechanisms of each pair are disposed on the same side of the engine 200 with one above the other.

The two drive mechanisms constituting each, pair are driving connected to the drive shaft 201 through different gear transmission ratios This is evident from Figure 4 in relation to the pair constituted by the first and second drive mechanisms 221, 222, from which it can be seen that the first drive mechanism 221 is connected to the drive shaft 201 through a train of gears involving the first driven gear 315, and the second drive mechanism 222 is connected to the drive shaft 201 through a train of gears involving the second driven gear 323. The different transmission ratios arise because of the different sizes of the first and second driven gears 315,323. Similar arrangements apply to the other pairs of drive mechanisms, as is evident from Figures 4 and 5.

The power means 207 operates the various drive mechanisms 205.

The power means 207 comprises a loading means 351 common to the two drive mechanisms constituting each pair, and a spring structure 353 associated with the gear of the gear and pinion mechanism of each respective drive mechanism within the pair. This will now be described in relation to the drive mechanism pair constituted by the first and second drive mechanisms 221,222, with specific reference to Figures 6,7 and 8 of the drawings.

As shown in Figures 6 7 and 8, the spring structure 353 associated with the first drive mechanism 221 comprises two extension springs 355,357 each fixed at one end 359 to a frame structure 361 of the engine 200 and connected at the other end 363 to the gear 233 of the first gear and pinion mechanism 231. The ends 363 of the extension springs 355,357 are connected to lugs 367, 369 on the gear 233 at locations offset from the rotational axis of the gear 233, whereby rotation of the gear 233 in one direction causes extension of the springs 355,357 and the spring forces so generated urge the gear 233 to rotate in the other direction.

Similarly, the spring structure 353 associated with the second drive mechanism 222 comprises two extension springs 371, 373, each fixed at one end 375 to the frame structure 361 of the engine 200 and connected at the other end 377 to the gear 243 of the second gear and pinion mechanism 241. The ends 379 of the extension springs 371,373 are connected to lugs 381, 383 on the gear 243 at locations offset from the rotational axis of the gear 243, whereby rotation of the gear 243 in one direction causes extension of the springs 371,373 and the spring forces so generated urge the gear 243 to rotate in the other direction.

As previously mentioned, the loading means 351 is common to the first and second drive mechanisms 221,222. The loading means 351 is operable to cause rotation of the gears 233,243 in their respective directions to load the spring structures 353 connected thereto.

The loading means 351 comprises a movable element 391 and a ram structure 393 operable by a working fluid to move the movable element 391 and thereby cause loading of the spring structures 353, as will be explained. In this embodiment, the working fluid is a hydraulic fluid and the ram structure 393 comprises a hydraulic ram incorporated in the hydraulic circuit.

The hydraulic ram 393 has a cylinder body 395 fixed to the engine frame structure 361 and a piston 397 on which the movable element 391 is carried.

The moveable element 391 comprises a rail 401 providing a cam 403 having an arcuate cam profile.

Each gear 233, 243 has a cam follower 405 in rolling engagement with the cam 403. The cam follower 405 on gear 233 comprises a roller (not shown) supported on lug 367 on the gear. Similarly, the cam follower 405 on gear 243 comprises a roller (also not shown) supported on lug 381 on the gear.

As can be seen in the drawings, the cam profile is disposed symmetrically with respect to the line of movement of the cam 403, and the two cam followers 405 are disposed one to each side of that line of movement.

With this arrangement, extension of the hydraulic ram 393 causes linear movement of the cam 403 which in turn causes the gears 233,243 to rotate in their respective directions corresponding to extension of the spring structures 353 connected thereto. As the cam 403 undergoes the linear movement, the cam followers 405 travel along the arcuate cam profile and in so doing cause the gears 233, 243 to rotate as described. In this embodiment, a stroke length of about 240mm for the hydraulic ram 393 causes each cam follower 405 to travel about 450mm along the cam profile.

Rotation of the gears 233, 243 under the influence of the loading means 351 causes the springs to load (i. e. undergo extension) as previously described. This is evident from Figures 6 and 7 of the drawings, in which Figure 6 illustrates the y arrangement before extension of the ram 393 and rotation of the gears 233, 243, and Figure 7 illustrates the arrangement after full extension of the ram 393. As can be seen in Figure 7, the gears 233, 243 have rotated an equal extent and the spring structures 353 are fully loaded.

As each gear 233,243 is rotated under the influence of the common loading means 351 to load the respective spring structures 353, torque is not transmitted to the first and second input shafts 237,247 as the pinions 235, 245 freewheel with respect thereto because of the clutch mechanisms 239, 249.

The hydraulic pressure, which is supplied to the hydraulic ram 393 to cause it to move from the retracted condition of Figure 6 to the extended condition of Figure 7, is interrupted once the hydraulic ram 393 arrives at the extended condition thereby to remove, or at least significantly reduce, the force exerted by the ram.

The gears 233,243 are then caused to rotate in the reverse direction under the influence of the loaded spring structures 353. Each gear 233, 243 thus performs a power stroke and applies torque through its respective pinion 235,245. The torque applied to the first pinion 235 is transmitted through the clutch mechanism 239 to the first input shaft 237, from where it is transmitted through the gear train involving the first driven gear 315 to the drive shaft 201. Similarly, the torque applied to the second pinion 245 is transmitted through the clutch mechanism 249

to the second input shaft 237, from where it is transmitted through the gear train involving the second driven gear 323 to the drive shaft.

Because of the different transmission ratios involved through their driving connection to the drive shaft 201, the first gear 231 travels at a faster rate than the second gear 241 during their power strokes. This is evident in Figure 22 which illustrates the gears 231, 241 undergoing their power strokes and from which it can be seen that the first gear 231 has travelled further than the second gear 241.

Because the first gear 231 travels at the faster rate, it acts on the movable element 391 and thereby causes the hydraulic ram 393 to retract. As can be seen from Figure 22, the second gear 241 does not remain in contact with the moveable element 391 throughout its power stroke owing to the slower rate at which it travels.

The first and second drive mechanisms 221, 222 commence their respective power strokes at the same time. Both drive mechanisms 221, 222 initially apply torque to the drive shaft 201. Because the second drive mechanism 222 operates at a slower rate than the first drive mechanism 222, it continues to apply torque to the output shaft 201 for a limited time after completion of the power stroke of the first drive mechanism 221.

Once the second drive mechanism 222 has also completed its power stroke, the loading means 351 again operates to rotate the gears 233,243 in unison and thereby again load the spring structures 353 so that the cycle can be repeated.

The hydraulic ram 393 is controlled in its movement by a control system incorporating limit switches (not shown) which detect the presence of the ram 393 at its fully retracted and fully extended conditions.

The other drive mechanism pairs operate in a similar fashion to apply torque to t the drive shaft 201. The various drive mechanism pairs operate in a timed sequence. In this embodiment, the drive mechanism pair constituted by the first and second drive mechanisms 221, 222 operate in unison with the drive mechanism pair constituted by the fifth and sixth drive mechanisms 225,226.

Similarly, the drive mechanism pair constituted by the third, and fourth drive mechanisms 223, 224 operate in unison with the drive mechanism pair constituted by the seventh and eighth drive mechanisms 227, 228.

The timed sequence of operation of the various drive mechanism pairs ensures that rotational torque is applied to the drive shaft 201 substantially constantly throughout operation of the engine 200.

With the engine according to this embodiment, each spring structure has a loading time of about 2 to 3 seconds and this provides an output at the drive shaft for a duration of about 150 seconds at a speed of about 40ûrpm.

The particular configuration of the loading means 351 for each drive mechanism pair, together with the use of a gear and pinion mechanism as the drive mechanism, provides an arrangement which is conducive to compact construction while enabling the spring structures 353 to be loaded rapidly.

In the engine 200 according to the first embodiment, the power means 207 for operating the various drive mechanisms 205 comprises loading means 351 each comprising moveable element 391 and hydraulic ram 392 incorporated in hydraulic circuit 211. It will be appreciated that other arrangements are, of course, possible.

One such other arrangement, which is illustrated in Figures 9 and 10, comprises a power means 410 for an engine according to a second embodiment. The engine according to the second embodiment is essentially the same as the engine 200 according to the first embodiment, apart from the power means 410.

The power means 410 comprises a loading means 411 common to a pair of drive mechanisms (not shown), and a spring structure (also not shown) associated with the gear of the gear and pinion mechanism of the drive mechanisms. The loading means 411 comprises a moveable element 413 operating in a similar fashion to the moveable element 391 of the first embodiment, and a ram structure 415 operable by a working fluid in a similar fashion to the ram structure 393 of the first

embodiment. In this embodiment, however, the ram structure 415 is operated by a working fluid operating in a two-phase cycle, involving a liquid phase and a gaseous phase. In this embodiment, the working fluid comprises Freon.

The working fluid operates in a circuit 417 which incorporates two of the rams 415 operating in a controlled sequence, a first heat exchanger 420 for transferring heat to the working fluid, a reservoir 421 for the gaseous working fluid. a second heat exchanger 423 functioning as a condenser for condensing the working fluid, and a fluid pump 425 for conveying condensed working fluid from the condenser 423 to the first heat exchanger 420. The circuit 417 also includes a non-return valve 426 between the pump 425 and the condenser.

The first heat exchanger 420 is incorporated in a boiler 427 which also includes a burner 429 at which a fuel is burnt. In this embodiment, the fuel is a gaseous fuel such as LPG contained within a storage tank 431. Fuel from the storage tank 431 is delivered to the burner 429 by way of a delivery line 433 incorporating a shut-off valve 435. An ignition circuit 437 is provided for igniting fuel at the burner 429.

Heat generated by the burner 429 in the boiler 427 is transferred to the working fluid through the heat exchanger 419.

A regulating system 439 is responsive to fluid pressure in the reservoir 421 and regulates operation of the burner 429 accordingly, thereby maintaining an appropriate pressure of working fluid in the gaseous phase within the circuit.

For communication with the ram structures 415, the circuit 417 divides into an intake line 418 and a discharge line 419.

Each ram structure 415 incorporates a valve system 441 for controlling flow of working fluid with respect thereto. The valve system 441 includes an intake valve 443 communicating with the intake line 418 for controlling intake of gaseous working fluid into the ram, and an exhaust valve 445 communicating with the discharge line 419 for controlling discharge of working fluid from the ram. The valves 443,445 are controlled by way of a control system 450, as illustrated in

Figure 10 of the drawings. The control system 450 utilises a control relay 351 for selectively opening and closing the valves 443,445. The relay 351 is electrically powered from a battery 353. Each ram structure 415 is fitted with limit switches 355,357 which operate in association with the relay In operation, working fluid within the circuit 417 enters the gaseous phase at the boiler 427 and accumulates in the reservoir 421. The gaseous working fluid enters each. ram structure 415 in timed sequence determined by the control system 450. Working fluid under pressure enters each ram upon opening of the respective inlet valve 4437 so causing the ram to undergo a power stroke, The inlet valve 443 is sequentially closed and the exhaust valve 445 opened, thereby allowing discharge of spent working fluid on the return stroke of the-ram 415 under the influence of the spring structure.

Referring now to Figure 11 of the drawings, there is shown a power means 460 for an engine according to a third embodiment.

The power means 460 comprises a loading means 461 common to a pair of drive mechanisms (not shown), and a spring structure (also not shown) associated with the gear of the gear and pinion mechanism of the drive mechanisms. The loading means 461 comprises a moveable element (not shown) operating in a similar fashion to the moveable element 391 of the first embodiment, and a ram structure 463 operable by a working fluid.

The ram structure 463 comprises a piston and cylinder assembly 465 defining a combustion chamber 467 into which a combustible mixture is introduced as the working fluid. Ignition of the combustible mixture causes displacement of the piston 469, thereby driving the moveable element The combustible mixture comprises an air/fuel mixture, in which the fluid is of any appropriate form such as petrol (gasoline).

Each piston and cylinder assembly 465 operates on a two-stroke cycle, undergoing sequential power and exhaust strokes.

In this embodiment, there are two ram structures 463 operating in timed sequence. An inlet rail 471 is provided for delivery of fuel to each piston and cylinder assembly 465, and an exhaust manifold 473 is provided for receiving spent products of combustion from the piston and cylinder assemblies, A control system (not shown) is provided for operating the piston and cylinder assemblies 465 in timed sequence.

Referring now to Figure 12 of the drawings, there is shown a power means 480 for an engine according to a fourth embodiment. The power means 480 comprises a loading means 481 common to a pair of drive mechanisms (not shown), and a spring structure (also not shown) associated with the gear of the gear and pinion mechanism of the drive mechanisms. The loading means 461 comprises a moveable element 483 operating in a similar fashion to the moveable element 391 of the first embodiment, and a ram structure 485 operable by a working fluid. The ram structure 485 comprises a piston and cylinder assembly 487 defining a combustion chamber 4B9 into which a combustible mixture is introduced as the working fluid. In this way, the arrangement is similar to that in the previous embodiment. In this embodiment, however, the piston and cylinder assembly 487 is designed to operate with a diesel fuel. Accordingly, the piston and cylinder assembly is provided with a fuel injector 491 to which fuel is delivered by way of delivery line 493 from a delivery pump 495 driven by the engine.

Referring now to Figure 13, there is shown a power means 500 in which the loading means 501 comprises a moveable element 503 and a ram structure 505, with the ram structure 505 being operable by a working fluid in the form of steam.

The steam is generated by a boiler system 507 incorporating a heat exchanger 509 and a burner 511. The burner 511 operates with a gaseous fuel, The boiler system 507 incorporates a reservoir 513 in which steam accumulates and from which steam is admitted into the working chamber of the ram in timed sequence to cause extension thereof. A control system is provided for controlling admission of steam into, and discharge of spent steam from, the ram 505. The control

system operates in association with limit switches which are responsive to the fully extended and fully retracted conditions of the ram.

Referring now to Figures 14 to 17, there, is shown an engine according to a further embodiment. The engine 600 according to the further embodiment is similar in many respects to the engine 200 according to the first embodiment and so similar reference numerals are used to identify corresponding parts, as appropriate. As with the first embodiment, the engine 600 according to the second embodiment comprises a drive shaft 201 driven by a drive system 203 which incorporates various drive mechanisms 205, power means (not shown) for operating the drive mechanisrns 205, and gearing 209 for driving connecting the drive mechanisms to the drive shaft 201. The power means in this embodiment are of similar construction to the power means 207 of the first embodiment and so will not be described further.

As with the first embodiment, the various drive mechanisms 205 comprise a first drive mechanism 221, a second drive mechanism 222, a third drive mechanism 223 and a fourth drive mechanism 224, a fifth drive mechanism (not shown), a sixth drive mechanism 226, a seventh drive mechanism 227 and an eighth drive mechanism 228.

The first drive mechanism 221 is in the form of a first gear and pinion mechanism 601 comprising a first gear 603 and a first pinion 605 in meshing engagement with the first gear 603. The first pinion 605 is driving connected to a first clutch gear 607 through a drive shaft 609 and a clutch mechanism 611. The first clutch gear 607 incorporates a hub 613 in which the clutch mechanism 611 is accommodated.

The clutch mechanism 611 allows torque transmission from the pinion 605 via the shaft 609 to the drive clutch 607 upon rotation of the pinion 605 in one direction, while allowing the pinion 605 to free-wheel (and not transfer torque to the clutch gear 607) upon rotation of the pinion in the reverse direction.

The second drive mechanism 222 is in the form of a second gear and pinion mechanism 621 comprising a second gear 623 and a second pinion 625 in meshing engagement with the second gear 623. The second pinion 625 is

driving connected to a second clutch gear 627 through a drive shaft and a clutch mechanism. The second clutch gear 627 incorporates a hub in which the clutch mechanism is accommodated. The clutch mechanism allows torque transmission from the pinion via the shaft to the clutch gear 627 upon rotation of the pinion in one direction, while allowing the pinion to free-wheel (and not transfer torque to the clutch gear) upon rotation of the pinion in the reverse direction.

The third drive mechanism 223 is in the form of a third gear and pinion mechanism 631 comprising a third gear 633 and a third pinion 635 in meshing engagement with the third gear. The third pinion is driving connected to a third clutch gear through a drive shaft and a clutch mechanism. The third clutch gear incorporates a hub in which the clutch mechanism is accommodated. The clutch mechanism allows torque transmission from the pinion via the shaft to the third clutch gear upon rotation of the pinion in one direction, while allowing the pinion to free-wheel (and not transfer torque to the third drive gear) upon rotation of the pinion in the reverse direction.

The fourth drive mechanism 224 is in the form of a fourth gear and pinion mechanism 641 comprising a fourth gear 643 and a fourth pinion 645 in meshing engagement with the fourth gear. The fourth pinion 645 is driving connected to a fourth clutch gear through a drive shaft and a clutch mechanism. The fourth clutch gear incorporates a hub in which the clutch mechanism is accommodated.

The clutch mechanism allows torque transmission from the pinion via the shaft to the fourth clutch gear upon rotation of the pinion in one direction, while allowing the pinion to free-wheel (and not transfer torque to the fourth clutch gear) upon rotation of the pinion in the reverse direction.

The fifth drive mechanism 225 is in the form of a fifth gear and pinion mechanism comprising a fifth gear and a fifth pinion in meshing engagement with the fifth gear. The fifth pinion is driving connected to the fourth clutch gear through a drive shaft and a clutch mechanism. The fourth clutch gear incorporates a hub in which the clutch mechanism is accommodated. The clutch mechanism allows torque transmission from the pinion via the shaft to the fourth clutch gear upon rotation of the pinion in one direction, while allowing the pinion to free-wheel (and

not transfer torque to the fourth clutch gear) upon rotation of the pinion in the reverse direction.

It will be noted that both the fourth and fifth drive mechanisms are driving connected to the fourth clutch gear.

The sixth drive mechanism 226 is in the form of a sixth gear and pinion mechanism comprising a sixth gear and a sixth pinion in meshing engagement with the sixth gear. The sixth pinion is driving connected to the third dutch gear through a drive shaft and a clutch mechanism. The third clutch gear incorporates a hub in which the clutch mechanism is accommodated. The clutch mechanism allows torque transmission from the pinion via the shaft to the third clutch gear upon rotation of the pinion in one direction, while allowing the pinion to free-wheel (and not transfer torque to the third clutch gear) upon rotation of the pinion in the reverse direction.

It will be noted that both the third and sixth drive mechanisms are driving connected to the third clutch gear.

The seventh drive mechanism 227 is in the form of a seventh gear and pinion mechanism comprising a seventh gear and a second pinion in meshing engagement with the seventh gear. The seventh pinion is driving connected to the second clutch gear 627 through a drive shaft and a clutch mechanism. The second clutch gear 627 incorporates a hub in which the clutch mechanism is accommodated. The clutch mechanism allows torque transmission from the pinion via the shaft to the second clutch gear 627 upon rotation of the pinion in one direction, while allowing the pinion to free-wheel (and not transfer torque to the second clutch gear 627) upon rotation of the pinion in the reverse direction.

It will be noted that both the second and seventh drive mechanisms are driving connected to the second dutch gear.

The eighth drive mechanism 228 is in the form of an eighth gear and pinion mechanism 651 comprising an eighth gear 653 and an eighth pinion 655 in

meshing engagement with the eighth clutch gear 6531 The eighth pinion 655 is driving connected to a first clutch gear 607 through a drive shaft and a clutch mechanism 663. The clutch mechanism 663 is accommodated in the hub 613 of the first clutch gear 607. The clutch mechanism 663 allows torque transmission from the pinion 655 via the shaft 661 to the first clutch gear 607 upon rotation of the pinion in one direction, while allowing the pinion to free-wheel (and not transfer torque to the first clutch gear) upon rotation of the pinion in the reverse direction.

The first and eighth drive mechanisms are counterparts in the sense that they are both driving connected to first dutch gear. Similarly, the second and seventh drive mechanisms are counterparts in the sense that they both are driving connected to second clutch gear. While not shown in the drawings, the third and sixth drive mechanisms are also counterparts in the sense that they are driving connected to a third drive gear (not shown), and the fourth and fifth drive mechanisms are also counterparts in the sense that they are driving connected to a fourth drive gear (not shown) The first clutch gear 607 is driving connected to the drive shaft 201 through a gear train 670. The gear train 670 comprises a lay gear 671 in meshing engagement with the clutch gear 607 and also in meshing engagement with a pinion 673 directly connected to a transmission gear 675 which in turn is in meshing engagement with a pinion 679 mounted on the drive shaft 201. In the gear train 670, the lay gear 671 is larger than the pinion 673. Specifically, in this embodiment the lay gear 671 has 30 teeth and the pinion 673 has 20 teeth.

The second clutch gears 627 is driving connected to the drive shaft 201 through a gear train 680. The gear train 680 comprises a lay gear 681 in meshing engagement with the clutch gear and also in meshing engagement with a pinion 683 directly connected to a transmission gear 685 which is in turn in meshing engagement with a pinion 669 mounted on the drive shaft 201. In the gear train 680, the lay gear 681 is smaller than the pinion 683. Specifically, in this embodiment the lay gear has 20 teeth and the pinion has 30 teeth,

While not shown in the drawings, the third and fourth clutch gears are similarly driving connected to the output shaft through gear trains.

As was the case with the first embodiment, the various drive mechanisms operate in pairs. SpeciTically, the first and second drive means 221, 222 operate as a pair, as does the third and fourth drive mechanisms 223, 224, the fifth and sixth drive mechanisms 225, 226, and the seventh and eighth drive mechanisms 227, 226.

As also was the case with the first embodiment, there is a loading means (not shown) common to the two drive mechanisms constituting each pair, and a spring structure associated with the gear of the gear and pinion mechanism of each respective drive mechanisms within the pair.

In this embodiment, the transmission ratio within the gear and pinion mechanisms of each pair is different, thus ensuring that one gear travels at a faster rate than the other gear, as was the case with the first embodiment. In this embodiment, the difference in transmission ratios is achieved by having different numbers of teeth on the pinions. Specifically, in this embodiment, the pinions in the gear and pinion mechanisms of the first, fourth, sixth and seventh gear and pinion mechanisms have several more teeth than the pinions in the second, third, fifth and eighth gear and pinion mechanisms. Typically, the smaller pinions have about 12 teeth and the larger pinions have about 14 teeth.

In this embodiment, there are eight drive mechanisms and four loading means.

The loading means operate in a timed sequence such that each is about 90° out of phase with another during operation of the engine.

It is a feature of the present embodiment that the engine can continue to operate for some time after cessation of operation of the power means, owing to the presence of a flywheel 690 on the drive shaft. This provides an additional benefit in that operation of the power means can be intermittent in light load conditions, with the engine being allowed to run without operation of the power means until such time as further input from the power means is required in order to keep the engine operating.

From the forgoing, it is evident that the present embodiment provides an engine capable of sustained delivery of mechanical energy with intermittent energy input.

The engine operates to deliver mechanical energy for an extended duration in comparison to the duration of energy input into the engine. Further, the engine according to the embodiment is of more compact construction than the engine disclosed in international application PCT/AUOO/00778, the contents of which are incorporated herein by way of reference.

Improvements and modifications may be incorporated without departing from the scope of the invention, It should be appreciated that the invention is not limited to an engine for driving an electro-dynamic machine. The engine may be used to drive any appropriate load, Throughout the specification, unless the context requires otherwise, the word "comprise"or variations such as"comprises"or"comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.