EP0749519A1

EP0749519A1 - Reciprocating machine

Info

Publication number: EP0749519A1
Application number: EP95915925A
Authority: EP
Inventors: Frank Moeller
Original assignee: DECORULE Ltd
Current assignee: DECORULE Ltd
Priority date: 1994-04-21
Filing date: 1995-04-19
Publication date: 1996-12-27
Also published as: AU2261895A; CA2188126A1; WO1995029323A1

Abstract

A reciprocating machine comprising a working piston (10) and cylinder (12) assembly, a counter rotating crank drive having an inner crankshaft (22) carrying an eccentric in driving connection with the piston (10), the eccentric being rotatable within a big end bearing housing and the piston (10) being connected to said bearing housing, wherein the inner crank shaft (22) is eccentrically journalled about an intermediate axis in a single outer crankshaft (26) which is rotatably mounted relative to a crank case (28) of the machine for rotation about a main axis, the inner crank shaft (22) having an inner gear (56) in engagement with an outer ring gear stationary (54) with respect to the crank case (28).

Description

Title: "Reciprocating Machine"

This invention relates to reciprocating machines, hereinafter referred to as being of the kind specified, comprising a working piston and cylinder assembly, a counter rotating crank drive having an inner crankshaft carrying an eccentric in driving connection with the piston, the eccentric being rotatable within a big end bearing housing and the piston being connected to said bearing housing.

The machine may be, for example, an internal or external combustion engine or a compressor.

GB-B-2080483 discloses a reciprocating machine of the kind specified in which the eccentric is connected by spaced webs to opposed journals disposed on opposite sides of the eccentric whereby the inner crank is eccentrically journalled in two outer crankshafts which are axially aligned and are rotatably mounted relative to a crankcase. The inner crankshaft has a gear associated with each journal and engaged with a respective stationary gear.

Such a machine suffers from the disadvantages that it is necessary accurately to align not only the axes of rotation of the two separate outer crankshafts but, in addition, the engagement between the gears associated with the journals of the single crankshaft must be accurately circumferentially mutually aligned. The alignment of such relatively widely separated components to the required degree of accuracy is difficult to achieve in practice. Moreover, it is relatively expensive to manufacture such an engine, not only because of the need to attempt to achieve such alignment, but because of the number of parts required. Furthermore, the overall size of the machine in the direction of the axis of rotation of the pair of outer crankshafts is relatively great.

In addition, such a machine when having a single or a small number of pistons is prone to vibration due to out-of-balance forces and cyclic irregularities.

An object of the invention is to provide a machine of the kind specified whereby the above mentioned disadvantages are overcome or reduced.

A subsidiary object of the invention is to provide a machine of the kind specified wherein the above mentioned additional disadvantages are overcome or are reduced.

According to the present invention, we provide a reciprocating machine of the kind specified wherein the inner crank shaft is eccentrically journalled about an intermediate axis in a single outer crankshaft which is rotatably mounted relative to a crank case of the machine for rotation about a main axis, the inner crank shaft having an inner gear in engagement with an outer ring gear stationary with respect to the crank case.

The inner and outer gears may be provided respectively with external and internal spur or helical or bevel gear teeth.

The outer crankshaft may be journalled in the crank case by two bearings disposed at positions spaced longitudinally of the crankshaft and preferably disposed on opposite sides of said externally toothed gear.

The outer crankshaft may be provided with bearing means at positions spaced apart longitudinally thereof in which spaced apart journals of the inner crankshaft are rotatably mounted.

Said spaced apart journals of the inner crankshaft may be disposed on opposite sides of said externally toothed gear.

The outer crankshaft may be provided with a cut-out to accommodate the inner gear.

The eccentric may be mounted in cantilever by the inner crankshaft.

The inner crankshaft may be provided with a further journal, on the opposite side of the eccentric to the bearings whereby the inner crankshaft is rotatably mounted on the outer crankshaft, said further journal being eccentrically relative to a sub-shaft and the sub-shaft being mounted for rotation relative to the crank case about the axis of rotation of the outer crankshaft.

The machine may have a further working piston and cylinder assembly, the further piston being connected to a further big end bearing housing within which said eccentric is rotatable.

Alternatively, when the inner crankshaft is provided with said further journal rotatable relative to said sub-shaft, the machine may have a second working piston and cylinder assembly, the second piston being connected to a second big end housing within which a second eccentric is rotatable, the second eccentric being carried by a second journal which is eccentrically journalled in a second sub-shaft, which is rotatably mounted relative to the crankcase and by a second further journal and wherein the further journals are each in eccentric rotatable relationship with said sub-shaft with the respective further journals being disposed in a predetermined angular relationship such as diametrically oppositely disposed.

Such a further journal or journals may be provided if, for example, a power take-off shaft is required at the end of the machine provided with the further journal; or a second in-line piston and cylinder assembly is required; or two pistons or groups of pistons, each having a cantilevered eccentric, are mounted in axial relationship, for example to provide double the power input; or to couple two machine with different functions, for example an engine and a compressor.

In all such cases where a further journal is provided it is not necessary to provide a second pair of gears in association with the further journal.

Particularly when the machine has a single or small number of pistons it is prone to vibration due to outer balance forces and cyclic irregularities, accordingly, to overcome this additional problem an inner balance weight means may be provided to at least partly dynamically balance the masses which are rotatable about the intermediate axis and an outer balance weight means may be provided to at least partly dynamically balance the masses which are rotatable about the main axis.

Preferably the inner and outer balance weight means are provided so that their respective resultant centre of gravity is co-axial with the intermediate axis and the main axis respectively.

Accordingly, the inner crankshaft has an inner balance weight means and the outer crankshaft has an outer balance weight means having its centre of gravity radially opposite the resultant centre of gravity of the inner crankshaft and the inner balance weight means. The inner balance weight means may comprise first and second inner balance weight means disposed on either side of the piston centre line so as to avoid or reduce any couple around the piston centre line.

The inner balance weight means may comprise a single inner balance weight means or a plurality of longitudinally spaced inner balance weight means.

Said plurality of inner balance weight means may comprise first and second balance weight means longitudinally spaced on opposite sides of the piston or pistons.

The single, or at least one of the, inner balance weight means may comprise a plurality of radially spaced balance weights.

The outer balance weight means may comprise a single outer balance weight means or a plurality of longitudinally spaced outer balance weight means.

Said plurality of outer balance weight means may comprise first and second outer balance weight means disposed at positions spaced apart longitudinally of the outer crankshaft.

The single, or at least one of the, outer balance weight means may comprise a plurality of radially spaced balance weights.

The outer balance weight means may comprise a first and a second outer balance weight means each having a centre of gravity disposed at positions spaced apart longitudinally of the outer crankshaft and disposed on radially opposite sides thereof.

The balance weight or weights which comprise the single or said plurality of outer balance weight means may be disposed at any desired position or positions longitudinally of the axis of rotation of the outer crankshaft and/or may be provided on an auxiliary element separate from the outer crankshaft and arranged to rotate therewith, such as an auxiliary drive shaft.

The auxiliary element may be mounted by bearing means and provided with a drive means so as to be driven by the outer crankshaft at the same speed as the speed of rotation of the outer crankshaft.

Where the machine has a sub-shaft at least part of the outer balance weight means may be provided thereon. The outer balance weight means may comprise first and second longitudinally spaced outer balance weight means, the first longitudinally spaced outer balance weight means may be provided on said outer crankshaft and the second longitudinally spaced outer balance weight means may be provided on said sub-shaft.

A reciprocating machine embodying the invention will now be described by way of example with reference to the accompanying drawings, wherein:

FIGURE 1 is a diagrammatic cross-section through an internal combustion engine embodying the present invention;

FIGURE la. is a fragmentary cross-section showing the engine of Figure 1 in more detail;

FIGURE 2 is a fragmentary diagrammatic end view of the engine of Figure 1;

FIGURE 3 is a fragmentary cross-section through a second embodiment of the invention;

FIGURE 4 is a fragmentary cross-section through a third embodiment of the invention;

FIGURE 5 is a diagrammatic cross-section through a fourth embodiment showing an internal combustion engine of narrow V-2 configuration;

FIGURE 6 is a fragmentary diagrammatic end view of the engine of Figure 5;

FIGURE 7 is a diagrammatic cross-sectional view through a fifth embodiment of the invention showing an engine of twin opposed cylinder configuration;

FIGURE 8 is a diagrammatic cross-section showing an engine as described with reference to Figure 7 in more detail;

FIGURE 9 is a diagrammatic cross-section through another embodiment of the invention;

FIGURE 10 is a diagrammatic cross-section showing a further internal combuston engine embodying the invention;

FIGURE 10a shows the engine of Figure 10 in more detail; FIGURE 11 is a diagrammatic cross-section through a further embodiment of the invention;

FIGURE 12 is a diagrammatic cross-section through a still further embodiment of the invention;

FIGURE 12a shows the engine of Figure 12 in more detail;

FIGURE 13 is a diagrammatic cross-section of a yet further embodiment of the invention; and

FIGURE 14 is a diagrammatic transverse cross-section of the engine of Figure 13.

The same reference numerals have been used throughout the drawings to refer to corresponding parts.

Referring to Figure 1, la. and 2, there is shown an engine which comprises a working piston and cylinder assembly comprising a piston 10 reciprocatable within a cylinder 12 provided with a cylinder liner 14. A combustion chamber 16 is provided in conventional manner.

The piston 10 is rigidly connected to a rod 17 and is rigidly connected by the rod to a big end bearing housing 18 and is drivingly connected to an eccentric 20 carried on an inner crankshaft 22 rotatable about an intermediate axis Y-Y. If desired the piston 10 can be connected by a "little end" to the rod 17 but this is not necessary.

The inner crankshaft 22 carries first and second longitudinally spaced inner balance weight means which each comprise an inner balance weight 24 which are disposed directly longitudinally adjacent and on opposite sides of the eccentric 20 and are arranged to balance the weight of the eccentric, piston bearing and housing assembly 20, 10, 17 and 18 so that the masses rotating about the axis Y-Y have a resultant centre of gravity which is coincident with the axis Y-Y.

The inner crankshaft 22 is eccentrically journalled in an outer crankshaft 26 for rotation about the axis Y-Y. The outer crankshaft 26 is itself rotatably mounted in a crankcase 28 by main bearings 30, 32 for rotation about a main axis X-X. The outer crankshaft 26 is relatively elongated and has first and second journals 34, 36 which are disposed at positions which are spaced longitudinally of the outer crankshaft and are engaged by the inner races of roller element bearings which provide the main bearings 30, 32. The outer races being received in seats 38, 40 respectively in the crank case 28.

The outer crankshaft 26 is provided with plain bearings 41, 42 disposed in seats 44, 46 disposed at positions which are spaced longitudinally of the outer crankshaft 26 and are rotatably engaged with journals 48, 50 of the inner crankshaft 22 which are spaced longitudinally apart thereof so that the eccentric 20 is mounted in cantilever by the remainder of the inner crankshaft 22.

The outer crankshaft 26 is provided with a cut-out 52 to accommodate an externally toothed spur or helical gear 54 fixed relative to the inner crankshaft 22 which meshes with a corresponding internal ring gear 56 provided fixed relative to the crank case 28. If desired bevel gear teeth may be provided.

In operation, the inner crankshaft 22 rotates about its axis Y-Y in the opposite direction to the direction of rotation of the outer crankshaft 26 about its axis X-X. The gear ratio of the externally toothed gear 54 to the ring gear 56 is 2 : 1 so that the inner crankshaft 22 rotates, relative to the outer crankshaft 26, in the opposite direction and at twice the speed to that at which the outer crankshaft 26 rotates relative to the crankcase. The geometric centre of the eccentric 20, shown at Y-Y, reciprocates along a straight line indicated at A and the piston 10 thus accurately reciprocates along its respective axis.

As the arrangement and operation of a counter rotating crank drive is well known, it will not be further described herein. Such a drive can be completely dynamically balanced by inner counter weight means 24 and outer balance weight means now to be described.

Referring now to Figure 1, the outer crankshaft 26 is provided with a flywheel 57 which carries an outer balance weight means which comprises a first outer balance weight means 58.

However, because of the cantilever design the balance weight means 58 is off-set axially relative to the masses to be balanced and to avoid an out-of-balance couple being created the weight 58 is made larger than needed for dynamic balancing in a radial direction and a second outer balance weight means 60 is provided situated longitudinally outside the bearing 30 and radially opposite the first outer balance weight means 58. The magnitudes of the first and second balance weight means 58, 60 are arranged so that the couple created by the off- centre position of the weight 58 is compensated for by the weight 60 and the weights 58, 60 together ensure that the centre of gravity of the masses rotating about the axis X-X is coincident with the axis.

If desired, the weight 60 and/or the weight 58 may be provided in any suitable position along the outer crankshaft 26. Furthermore, either or both of the outer balance weight means 58 and 60 may be provided by a single weight or by a plurality of weights at different angular and/or longitudinal positions relative to the axis X-X so that the composite effect of the respective weight parts sums to the desired mass and position.

For example, an alternative or additive position for weight 58 is indicated at 58' in Figure la.

In another example, shown in Figure 3, which is a section through an air cooled single cylinder diesel engine having a relatively long flywheel 57, i.e. a flywheel which is relatively long in the direction of the axis X-X, the first balance weight means 58 can be mounted on the inner face of the flywheel as shown at 58" instead of, or in addition to, a weight provided at a location which corresponds to the position of the first balance weight means 58' shown in Figure la. Of course, if a weight is provided both at the location indicated at 58' in Figure la. and the location indicated at 58" the masses of the two weights is such as to sum to the desired mass.

In another example, shown in Figure 4, where the flywheel 57 is formed by the rotor of a brushless generator, the first counter weight means can be fixed directly to a rotating canister C holding the permanent magnets of the brushless generator (different magnet configurations being shown in the top and bottom halves of Figure 4), as shown at 58'" in Figure 4. Again the weight shown at 58'" can be additive to or instead of the weight shown at 58 in Figure 4. In another example, where the engine has a drive to a camshaft and/or an oil pump or another auxiliary taken from the opposite end of the engine to the normal power take-off as is also illustrated in Figures 3 and 4 at 70, an auxiliary element or shaft 70 is arranged to carry a weight 58a_ which, as in the previously described examples, can provide the whole, or part of the weight required in combination with weights at least at one of the other locations described hereinbefore to achieve dynamic balance of the masses rotating about the axis X- X.

The mass of the balance weight 60 is determined so as to balance the longitudinal couple and is disposed radially opposite the balance weight 58, the mass of which is increased over that necessary to radially balance the machine by an amount equal to the mass of the weight 60.

Correct balancing is achieved by counteracting the masses (M^) of the piston 10, connecting rod 17 and the crank pin journal 20 with the weight 24 of mass M_b, whereby the active radius of the parts to be balanced is the crank pin radius "R" (eccentricity of 22 and 26). The active radius of the weight 24 does not need to be "R", but can be any length "L", as long as:

M^ * R = M_b * L

The axial position of the inner balance weight means 24 is preferably the same as M^. For that reason the weight 24 is split and is disposed on either side of the connecting rod. The inner crankshaft balance weight means 24 and the oscillating masses can then be added up and concentrated on axis Y-Y which is rotating and can therefore be balanced by the outer balance weight means as described.

In this specification when referring to masses of the balance weight, the effective mass at the radius of rotation of the respective centre of gravity is referred to.

Although the present example has only a single piston, if desired, the engine may be provided with more than one piston. Any crank pin positioned on the pitch diameter of the gear 54 will describe a straight line oscillating movement in a respective direction. Any piston mounted on such a crank or pins can be balanced by an appropriate inner counter weight means 24 of a mass and position to counteract the resultant oscillating masses. Alternatively, the connecting rod

17 may be extended in the diametrically opposite direction to the rod 17 illustrated and connected with another piston assembly. Of course, appropriate cylinders would also be provided in all cases.

Figures 5 and 6 illustrate another embodiment of the invention of narrow V-2 cylinder configuration.

This engine differs from that shown in Figure 1 by virtue of being provided with a compound eccentric assembly having eccentrics 20 which are angularly displaced, as shown in Figure 6, and there being a second big end bearing housing

18 associated with the second piston and cylinder assembly.

Figure 7 illustrates a further example having two opposed cylinders and in which a single big end housing 18 has the piston rods 17 of two pistons 10 rigidly connected thereto. Again, of course, the piston may be pivotally connected to the rod 17 by a "little end" bearing.

It is to be noted that in this embodiment the first outer counter weight means 58 is carried at the inner end of the outer crankshaft 26 whilst the second outer counter weight means 60 is carried by the flywheel 57.

Figure 8 illustrates the engine shown in Figure 7 in more detail.

In this example all the rotary bearings of the engine can be rolling element type bearings. In particular, in this example, the bearings between the inner and outer crankshafts are roller bearings 41', 42' which correspond to plain bearings 41, 42 shown in Figure la. and 2 so that the eccentric 20 is mounted in cantilever by the remainder of the inner crankshaft 22.

An additional support for the inner crankshaft 22 may be provided on the opposite side of the or each piston if desired, for example, if a power take-off is required at that end of the engine, or if a second in-line piston assembly is required, or if an engine having a counter-rotating crank drive is provided in axial alignment to provide twice the power output, or, for example, to couple two machines with different functions, for example an engine and a compressor. Figures 9, 10 and 10a. illustrate two examples of machines having such an additional support for the inner crankshaft.

In any of these cases it is not necessary to provide a second pair of inner and outer gears, thereby avoiding the difficulty of achieving angular alignment referred to hereinbefore.

It is necessary only to provide the shaft of the said opposite end with an orbiting support by means of a sub-shaft rotatable about the axis of the outer crankshaft and eccentrically carrying a further journal at said opposite end of the engine.

Figure 9 shows a four stroke in-line two cylinder engine in which the eccentric 20 is elongated axially and rotatably received within a second big end bearing housing of the second piston 10. At this end the eccentric 20 is provided with a further journal 51 which is rotatably eccentrically mounted in a sub-shaft 53 rotatable about the axis X-X whilst the journal 51 is rotatable about the axis Y-Y.

Figures 10 and 10a illustrate another example of the invention showing a modification of the invention having two side by side piston and cylinder assemblies.

One of the pistons 10 is drivingly connected to an eccentric 20 associated with an inner crankshaft 22 shown on the right-hand side of Figures 10 and 10a and is as described in connection with previous embodiments, except for the provision of a further journal 109 eccentrically rotatable relative to a sub-shaft 105. It may, however, be noted that the outer crankshaft 26 is provided with a gear 120 which meshes with a further gear 120a. to provide a power take-off drive, for example to a cam shaft charger or generator.

The other piston 10 at the left-hand side of Figures 10 and 10a has its big end bearing housing 18 rotatably received on a second eccentric 20 which is carried by a second journal 112 rotatably eccentrically mounted by bearings 113, 114 in a second sub-shaft 115 which is rotatably mounted in the crankcase 28 by bearings 116, 117. The second journal 112 is unprovided with a gear corresponding to the gear 54. A dividing wall 100 between the adjacent cylinders 12 has seats 101, 102 for taper roller bearings 103, 104 which rotatably mount the sub-shaft 105 in the wall 100. The sub-shaft 105 has a pair of generally cylindrical passages 106, 107 the centres of which are disposed on a diametral plane of the shaft 105 and on opposite sides of the centre 108 thereof. The passage 106 receives the further journal 109 projecting from the inner crankshaft 22 associated with one of the cylinders 12 whilst the other passage 107 receives a second further journal 110 projecting from the inner second eccentric 20 of the other piston 10. The further journals 109, 110 are thus each in eccentric rotatable relationship with said sub- shaft 105 with respective journals being disposed in a predetermined angular relationship such as diametrically opposite.

Accordingly, firing and inertia loads from the respective inner cranks are supported by the relatively large bearings 103, 104 which support the common further sub-shaft 105 with which the further journals 109, 110 are engaged. Because of torque loads the inner crankshaft is provided with a small support bearing at the drive end as shown at 41.

Figure 11 illustrates another example of the invention where it is desired to provide a generator and charger facility. In this case, if a sub-shaft is provided on the opposite side of the piston or pistons, the flywheel 57 is preferably mounted on the side of the engine provided with the inter-engaging gears 54, 56 to avoid high loads on the intermediate bearings 41, 42 due to torque fluctuations.

To make the best use of the available space the flywheel 57 should preferably be of generally can shape, as illustrated in Figure 11 and in other Figures. Accordingly the generally cylindrical wall 57a of the flywheel may contain a permanent ring magnet 130 with any desired number of poles. A stationary armature 131 may be mounted inside the ring to create an integrated brushless generator which may match the full power output of the engine. As the electrical energy generated is a proportion to the peripheral speed of the magnet ring and to avoid oversizing the flywheel flux ring, an epicyclic gearbox may be provided between the engine output shaft and the flux ring to increase the speed of rotation of the latter. Such an embodiment is illustrated in Figure 12 and 12a. An epicyclic gear box 80 comprising a sun gear 81, planet gears 82 and an annulus 83 is provided to increase the output speed from the engine and the space around a tubular bearing extension 84 is used to house a brushless generator 85 provided on a drum 86 keyed to the shaft of the sun gear 81.

The flywheel illustrated in Figures 12 and 12a may carry a further gear drive to drive a high speed coupled charger as is required for two stroke operation.

Referring now to Figures 13 and 14 there is illustrated a two stroke opposed cylinder arrangement with a charging piston.

The opposed pistons 10 are drivingly connected to an eccentric 20 carried by an inner crankshaft 22 as described hereinbefore. The inner crankshaft 22 has a further eccentric 140 at the same radius as the axis of rotation Y-Y as the eccentric 20 but angularly offset therefrom and drivingly connected by a further bearing housing 141 to a piston rod 143 of a charging piston 144 slidable in a cylinder 145. The cylinder 145 is provided at one end with an inlet valve 146 and an outlet valve 147 whilst at its other end it has an inlet valve 148 and an outlet valve 149. The outlet valve 147 is connected, via a first plenum chamber 150 to the interior of the cylinder 12 associated with one of the pistons 10 via an inlset valve 151 whilst the outlet valve 149 is connected via a second plenum chamber 152 to the interior of the cylinder 12 of the other piston 10 via a second inlet valve 153. Accordingly, as the pistons 10 reciprocate so does the charging piston to alternately charge the working cylinders 12. The engine is also provided with an oil sump 154 and with exhaust valves 155 for the cylinders 12 in conventional manner.

The plenum chambers 150, 152 are provided to take care of the 90° phase angle between the charging and working pistons but at high engine speeds these may not be required.

Although in some of the previously described embodiments plain bearings have been described as being provided between the inner and outer crankshafts, if desired rolling element bearings may be provided therebetween. Although all the illustrated examples are internal combustion engines the invention and the structural features described and illustrated herein can be applied to other reciprocatory machines such as an external combustion engine or a compressor or pump.

In all embodiments, although only a single pair of inter-engaged inner and outer gears 54, 56 are illustrated, if desired a plurality of axially spaced pairs of inter-engaged inner and outer gears may be provided rotatable with the single inner crankshaft 22 on one axial side only of the piston or pistons. Such single pair or said plurality of pairs of gears provide a single pair of inter-engaged inner and outer gear means.

If desired, a machine may comprise a plurality of reciprocating machines embodying the invention.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in the terms or means for performing the desired function, or a method or process for attaining the disclosed result, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS:

1. A reciprocating machine comprising a working piston and cylinder assembly, a counter rotating crank drive having an inner crankshaft carrying an eccentric in driving connection with the piston, the eccentric being rotatable within a big end bearing housing and the piston being connected to said bearing housing, wherein the inner crank shaft is eccentrically journalled about an intermediate axis in a single outer crankshaft which is rotatably mounted relative to a crank case of the machine for rotation about a main axis, the inner crank shaft having an inner gear in engagement with an outer ring gear stationary with respect to the crank case.

2. A machine according to claim 1 wherein the inner and outer gears are provided respectively with external and internal spur or helical or bevel teeth.

3. A machine according to claim 1 or claim 2 wherein the outer crankshaft is journalled in the crank case by two bearings disposed at positions spaced longitudinally of the crankshaft.

4. A machine according to claim 3 wherein said bearings are disposed on opposite sides of said externally toothed gear.

5. A machine according to any one of the preceding claims wherein the outer crankshaft is provided with bearing means at positions spaced apart longitudinally thereof in which spaced apart journals of the inner crankshaft are rotatably mounted.

6. A machine according to claim 5 wherein said spaced apart journals of the inner crankshaft are disposed on opposite sides of said externally toothed gear.

7. A machine according to any one of the preceding claims wherein the outer crankshaft is provided with a cut-out to accommodate the inner gear.

8. A machine according to any one of the preceding claims wherein the eccentric is mounted in cantilever by the inner crankshaft.

9. A machine according to any one of the preceding claims wherein the inner crankshaft is provided with a further journal, on the opposite side of the eccentric to bearings whereby the inner crankshaft is rotatably mounted on the outer crankshaft, said further journal being eccentrically rotatable relative to a sub-shaft and the sub-shaft being mounted for rotation relative to the crank case about the axis of rotation of the outer crankshaft.

10. A machine according to any one of the preceding claims wherein the machine has a further working piston and cylinder assembly, the further piston being connected to a further big end bearing housing within which said eccentric is rotatable.

11. A machine according to claim 9 wherein the machine has a second working piston and cylinder assembly, the second piston being connected to a second big end housing within which a second eccentric is rotatable, the second eccentric being carried by a second journal which is eccentrically journalled in a second sub-shaft, which is rotatably mounted relative to the crankcase and by a second further journal and wherein the further journals are each in eccentric rotatable relationship with said sub-shaft with the respective further journals being disposed in a predetermined angular relationship.

12. A machine according to any one of the preceding claims wherein an inner balance weight means is provided to at least partly dynamically balance the masses which are rotatable about the intermediate axis and an outer balance weight means is provided to at least partly dynamically balance the masses which are rotatable about the main axis.

13. A machine according to claim 12 wherein the inner and outer balance weight means are provided so that their respective resultant centre of gravity is co-axial with the intermediate axis and the main axis respectively.

14. A machine according to claim 13 wherein the inner crankshaft has an inner balance weight means and the outer crankshaft has an outer balance weight means having its centre of gravity radially opposite the resultant centre of gravity of the inner crankshaft and the balance weight means.

15. A machine according to any one of claims 12 to 14 wherein the inner balance weight means comprises first and second inner balance weight means disposed on either side of the piston centre line.

16. A machine according to any one of claims 12 to 15 wherein the inner balance weight means comprises a single inner balance weight means.

17. A machine according to any one of claims 12 to 15 wherein the inner balance weight means comprises a plurality of longitudinally spaced inner balance weight means.

18. A machine according to claim 17 wherein said plurality of inner balance weight means comprises first and second balance weight means longitudinally spaced on opposite sides of the piston or pistons.

19. A machine according to any one of claims 16 to 18 wherein the single, or at least one of the, inner balance weight means comprises a plurality of radially spaced balance weights.

20. A machine according to any one of claims 12 to 19 wherein the outer balance weight means comprises a single outer balance weight means.

21. A machine according to any one of claims 12 to 19 wherein the outer balance weight means comprises a plurality of longitudinally spaced outer balance weight means.

22. A machine according to claim 21 wherein said plurality of outer balance weight means comprises first and second outer balance weight means disposed at positions spaced apart longitudinally of the outer crankshaft.

23. A machine according to any one of claims 20 to 22 wherein the single, or at least one of the, outer balance weight means comprises a plurality of radially spaced balance weights.

24. A machine according to claim 21 wherein the outer balance weight means comprises a first and a second outer balance weight means each having a centre of gravity disposed at positions spaced apart longitudinally of the outer crankshaft and disposed on radially opposite sides thereof.

25. A machine according to any one of claims 12 to 24 wherein the balance weight or weights which comprise the single or said plurality of outer balance weight means are disposed at any desired position or positions longitudinally of the axis of rotation of the outer crankshaft and/or are provided on an auxiliary element separate from the outer crankshaft and arranged to rotate therewith.

26. A machine according to claim 25 wherein the auxiliary element is mounted by bearing means and provided with a drive means so as to be driven by the outer crankshaft at the same speed as the speed of rotation of the outer crankshaft.

27. A machine according to any one of claims 12 to 25 when dependent on any one of claims 9 to 11 wherein at least part of the outer balance weight means is provided on said sub-shaft.

28. A machine according to claim 27 wherein the outer balance weight means comprises first and second longitudinally spaced outer balance weight means, the first longitudinally spaced outer balance weight means being provided on said outer crankshaft and the second longitudinally spaced outer balance weight means being provided on said sub-shaft.

29. A reciprocating machine substantially as hereinbefore described with reference to Figs. 1 to 2; Fig.3; Fig.4; Figs. 5 & 6; Figs. 7 & 8; Fig.9; Figs. 10 & 10a; Fig.ll; Figs. 12 & 12a; or Figs. 13 & 14 of the accompanying drawings.

30. Any novel feature of novel combination of features described herein and/or in the accompanying drawings.