1 The present invention relates to a power conver¬ sion machine comprising a piston which is in drive connection with a rotary shaft via an eccentric disc which is obliquely disposed on the center axis of the rotary shaft, where a first axis, that is to say the center axis of the rotary shaft and a second axis, that is to say the center axis of the eccenter disc cross each other in the center of a double-curved space, where the double-curved space is defined within a ball shell and is divided into two opposing, substan¬ tially semi-spherical spaces by means of a stationarily secured, circular partition plate, and where the piston, which operates simultaneously in the two semi-spherical spaces, comprises two oppositely directed roller por- tions which are received in their respective semi- spherical spaces and adapted to roll against their respective sides-- of the partition plate, a main portion, which connects the roller portions with each other and passes through the partition plate via an aperture in the latter, being adapted to move with a combined turning and rocking movement in the aperture of the partition plate.

In German Patent Specification there is shown a power conversion machine of the above kind. The aper- ture of the partition plate is extending over approxi¬ mately the half of the diametrical extension. Corre¬ spondingly the main portion of thepiston is extending between the roller portions only at the one side, that is to say that it is extending outwards from the center axis of the roller portions only at one side of the latter. The combined turning and rocking movement to which the piston is exposed by operation and control from the two eccenter discs, and the control which is secured via the main portion of the piston in the aperture of the partition plate, cause that the piston is working simultaneously in both semi-spherical spaces with a corresponding working effect. The two

roller portions which are rolling against their respec¬ tive sides of the partition plate divide together with the main portion of the piston the respective two semi-spherical spaces into two working chambers. When the one working chamber in the one semi-spherical space goes towards a minimum, the other working chamber in the same semi-spherical space goes towards a maximum. The operating cycle in the other semi- spherical space is displaced 180 in relation to the operating cycle in the first-mentioned semi-spherical space. Each working chamber has an operation cycle of 720°, that is to say a volume expansion phase of 360° and a volume compression phase of corresponding 360°. With the present invention the aim is to achieve a larger effect of the work of the piston per rotation.

More particularly the aim is to reduce the operating cycle of each working chamber from 729 to 540 , or said in another way the aim is that each working chamber will have a volume expansion phase of 270 and a volume compression phase of corresponding 270 . Further the aim is to increase the number of working chambers in each semi—spherical spase from two to three. The power conversion machine according to the invention is characterized in that the aperture of the partition plate is extending continuously between the diametrically opposing ends of the partition plate, and that the main portion of the piston is extending symmetrically outwards in opposite directions from the center axis of the roller portions, the main portion together with an appurtenant roller portion dividing each semi-spherical space into two main chambers, that is to say a first continuous main chamber at one side of the piston and a second main chamber which, by means of the abutment of the roller portion against the partition plate, are divided into two separate part chambers at the opposite side of the piston, so

that each semi-spherical space, with exception of those two positions in the moving path of the piston where the roller portion is rolling over the aperture of the partition plate, is divided into three mutually conse- cutive, separate working chambers.

By the solution according to the invention it is achieved a particularly high volume capacity, as relative to the known solution it has both been attained a shorter operating cycle and besides it has been attained more working chambers in each semi- spherical space. The piston according to. the present solution is acting simultaneously against three diffe¬ rent working chambers in each semi-spherical space, that is to say simultaneously against six working chambers in the two separate semi-spherical spaces. By turn of the rotation shaft a turning angle of 360 it is attained to empty from each semi-spherical space two optimum working chamber volumes per rotation, that is to say altogether four such optimum working chamber volumes per rotation for the two semi-spherical spaces. In addition to the favourable, high volume capa¬ city which has been achieved according to the inven¬ tion it is achieved according to the invention a favour¬ able balancing of the moveable parts relative to each other. By the solution according to the invention it has been attained almost a vibration-free movement of the machine. An essential reason for attaining such a favourable balancing is presumed to be that the main por¬ tion of the piston is formed symmetrically around the center axis of the roller portions. By this it is achieved a particularly favourable distribution of the working chambers in each semi-spherical space and with diametrically corresponding pressure conditions in the two semi-spherical spaces. It has also been ascertained that there is achieved a machine with a low noise level. It is used a small number, and the parts can be pro¬ duced by simple moulding and with low weight.

The power conversion machine according to the invention can find application in various areas. For example the machine can be used as a passive power conversion machine with external rotation shaft coup- ling on the rotation shaft of the machine, by being designed as a compressor or pump (hydraulic, pneumatic) . The machine can however also be used as an active power conversion machine, for example as an hydraulic or pneumatic motor or another piston power machine for converting static pressure in steam, gases arid fluid to mechanical work (rotation) . The machine can also be employed as a compound machine, by being used as a combination of active and passive operation.

In the embodiment which is to be described in the following description the machine in a simple design is intended to be used as an air compressor. With cer¬ tain modifications the machine can however be adapted for another application, as a passive power conversion machine as well as an active power conversion machine. In the following description, which shows a pre¬ ferred embodiment, reference is made to the accom¬ panying drawings, in which:

Fig. 1 shows a vertical section through a machine according to the invention. Fig. 2 shows a vertical section through the machine according to Fig. 1 in a plane at right angles to the section plane of Fig. 1.

Fig. 3 shows an end view of the machine with certain parts broken away for the sake of simplicty. Fig. 4 shows a corresponding end view to Fig. 3 with certain parts broken away for the same of simpli- ^' city.

Fig. 5a-8a show schematically different phases of the movement of the piston in the machine according to the invention.

Fig. 5b, 6b, 7b, 8b show schematically the same phases of the movement of the piston seen in the

direction of the arrow 66 of Fig. 5a, 6a, 7a, 8a.

Fig. 9a and 9b show schematically produced three volume curves for three different working ^• chambers of the machine illustrated respectively in a first and a second semi-spherical space.

Fig. 10a to lOe illustrate some theoretical con¬ siderations, shown in schematic views, so as to clarify certain part movements of the piston in the machine according to the invention. Fig. 11 shows schematically the movement pattern for certain points of the piston relative to the inner wall of the one semi-spherical space.

Fig. 12 shows schematically the movement pattern of the roller portion of t e ^, piston relative to the inner wall of the semi-spherical space.

In the embodiment which is shown in the drawing the power conversion machine according to the invention is illustrated in the form of a compressor. With certain modifications (not shown further herein) ^' the machine according to the invention can however also be used for example as a hydraulic pump, hydraulic motor, combustion engine with continuous combustion etc.

The compressor as shown in Fig. 1 and 2 has a compressor housing 10 which is composed of two housing portions 11 and 12 together with an intermediate, cir¬ cular partition plate 13. The partition plate 13, which physically defines the two housing portions 11 and 12 relative to each other, is rigidly connected with flange portions 11a, 12a into the two housing portions by means of common fastening screws 14 which pass through the par¬ tition plate via fastening holes 14a.

The housing 10 is provided with a sperical hollow space which has its center centrally of the partition plate 13. This hollow space is divided by means of the partition plate 13 into two similar, substantially semi-spherically shaped hollow spaces 15, 16. In the partition plate 13 there is however cut out an aperture

17 which extends diametrically in the partition plate and which forms a through passage between the hollow spaces 15, 16.

The compressor is provided with a piston 18 which is adapted to work simultaneously in the two semi- spherically shaped hollow spaces. In this connection the piston is provided with a disc-shaped main portion

19 which is adapted to move itself backwards and for¬ wards and at the same time outwards.arid.inwards in the two hollow spaces 15, 16 with a movement about two axes 20, 21 crossing mutually at right angles. The one

20 of these axes extends at right angles to the main portion 19, through the center point of the piston 18, while the other axis extends coaxially with the longi- tudinal center axis through the aperture 17 in the partition plate 13 and thereby also through the mid¬ point of the piston. The piston is adapted to be sub¬ jected to a combined turning and rocking movement about the said two axes 20 and 21. There is fastened to the disc-shaped main portion

19 of the piston two conic stump-shaped portions 22, 23 b means of fastening screws 24. Angle cavities 19a and 19b are made in the main portion 19 of the piston for the reception of the conic stump-shaped portions 22, 23, and at the same time there are cut out rolling off grooves 22a, 22b and 23a, 23b in the portions 22, 23 for rolling off against a crosshead pin 26. The conical angle is shown with a size of 120 , but this angle can alternatively be somewhat larger or somewhat smaller. In the illustrated embodiment the piston consists of a coherently rigid construction of the main portion 19 and the conic stump-shaped portions 22, 23 which form roller portions in thepiston. The two roller portions 22, 23 are adapted to effect with their respective conic stump surface 22d, 23d a rolling move¬ ment at the same time against each respective roller plane-forming side of the partition plate 12, that is

to say with a roller portion 22 and 23 respectively received in its respective hollow space 15 and 16. The conic stump surfaces of the roller portions 22, 23 thus effect an equivalent rolling movement in their respective hollow spaces 15, 16 with completely balanced, synchronised movement of the two roller portions 22, 23 in their respective diametrically opposing portion of the inner hollow space 15, 16 of the compressor housing 10. Simultaneously with the conic stump surfaces 21d, 23d of the roller portions 22, 23 effecting a rolling off against the partition plate 13 the disc-shaped main portion 19 makes a turning movement forwards and- backwards about the axis 20 over an angle of 120 (corresponding to the conic angle of the conic stump-sbaped roller .portions 22, 23) on movement through the aperture 17 of the partition plate 13. At the same time the main portion 19 of the piston is subjected to a rocking movement of 120° about the said other axis 21 in the aperture 17 in the partition plate 13.

In the illustrated practical embodiment the main portion 19 of the piston is led through the aperture 17 in the partition plate 13 via a control-forming through groove 25 in a mainly cylindrical crosshead pin 26. The groove 25 is designed with a slide fit for the main portion of the piston. The crosshead pin 26 is received turnably mounted about its main axis (the axis 21) with a slide fit in bearing-forming, part-cylindrical surfaces in the aperture 17 in the partition plate 13. By means of the slide fits be¬ tween the groove 25 of the crosshead pin 26 and the main portion 19 of the piston 10 and the slide fit between the aperture 17 of the partition plate 13 and the cylindrical outer surface of the crosshead pin 26 there is obtained a simple and advantageous sealing between the parts. In the central region of the crosshead pin 26 (see Fig. 3) there is formed

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on the opposing outer side of the crosshead pin ball shell-forming projections 27, 28 which are received in corresponding ball shell-shaped cavities 29, 30 in the central region of the aperture 17, provision being made for equivalent slide fit ^* and thereby sealing between the ball shell-forming projections 27, 28 and the cavities 29, 30 in the partition plate 13. Provision has been made for corresponding concavely spherical cavities 31, 32 in the pointed end on the conic stump-shaped, roller portion-forming portions 22, 23 and equivalent slide fit. and thereby sealing between cavities 31, 32 of the portions 22, 23 and the ball shell-formed projections 27, 28. By means of the rolling off grooves 22a, 22b and 23a, 23b of the roller portions 22, 23 there is obtained a corresponding slide fit between the roller plates 22, 23 of the piston 18 and the crosshead pin 26 in the rocking region of the piston. Provision is made for a slide fit with corresponding slide seal between the peripheral surface of the main portion 19 and the inner surface of the hollow spaces 15, 16 also. In the illustrated embodiment additional sealing means have been avoided and by means of slide fits provision has been made for sealing between the various parts which are moveable relative to each other. In prac¬ tice there can be employed in addition if desired (but not necessarily) rubber seals at the surfaces where ^' slide fit is used. If desired the crosshead pin can also be left out and for example rubber seals can be used directly between the the disc-shaped main portion 19 of the piston 10 and the aperture 17 of the partition plate 12 by fastening the rubber seals to opposite surfaces of the aperture. In the last- mentioned instance provision can be made for the rubber seal to form an abutment directly against the pointed ends of the conic stump-formed, roller portion-forming portions 22, 23.

The crosshead pin 26 is turnably mounted in the illustrated embodiment with a slide fit in the par¬ tition plate and in the housing portion at firmly clamped side portions of the partition plate 13, radially just outside the hollow spaces 15 and 16, that is to say at the inner portion of the wall por¬ tion of the housing portion. In the outer portion of the wall portion of the housing portion there is fastened in a sealing plug 33, 34, 35, 36. The sealing plug comprises a nut 33 which is fastened to an externally threaded pin 34 which is supported on a stop disc 35. Between the stop disc 35 and the nut 33 there is fixed a rubber sealing ring 36 which is pressed against the inner wall in a corresponding cavity in the housing portions 11 and 12. In addition the sealing plug can serve as a grease cup for lubri¬ cating bearings of the crosshead pin.

By broken lines 37 and 38 (especially in Figs. 1 and 3) there are indicated four pairs of valve ports which extend through walls of the housing portions 11, 12 to the hollow spaces 15, 16 at a certain distance from the respective sealing plugs 33-36. With the broken line 39 there is indicated a ball valve in each valve port. The pairs of valve ports 37, 38 are dis- posed relatively tightly up to the crosshead pin 26 and their respective plug 33-36, that is to say with two pairs of valve ports opening out into each hollow space" 15 and 16 and with a valve port on each side of the respective sealing plug. The significance of this positioning will be returned to later below.

The piston 18 is drivably connected in the illu¬ strated embodiment to a separate rotation shaft (drive shaft) 40, 41 at opposite ends of the piston 18, that is to say via the respective conic stump-shaped roller portion 22, 23. The drive connection between the roller portion 22 and 23 and the associated rotation shaft 40 and 41 is identical at opposite ends of the compressor.

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The operation occurs via an eccentric disc 42 the main plane of which extends obliquely on the axis 40a, 41a of the rotation shaft. The center axis of the eccentric disc 42 is shown by chain line 43. The eccentric disc 42 is provided with a ball shell-shaped, outwardly directed surface 42a and a level, inwardly directed surface 42b. The eccentric disc 42 is con¬ nected to the associated piston- oller portion 22 (23) via a thrust bearing 44a which is screwed fast to the eccentric disc 41 via head portion 45 of the screw 44 and projects with the outer end of a stem portion 46 inwardly into a corresponding cavity 47 in the piston- roller portion 22 (23) . The roller portion 22 (23) is subsequently adapted to be moved freely about its center axis in the eccentric disc 42, that is to say about the center axis 43 of the eccentric disc. Between the head 45 of the screw 44 and a shoulder portion 48 internally in the eccentric disc 42 there is inserted a slide seal 49. Ball bearings 50, 51, 52 are arranged in oppositely facing cavities between the eccentric disc and the associated piston-roller portion, the central portion of the eccentric disc projecting end¬ wise inwards into the cavity in the piston-roller por¬ tion by means of a sleeve-shaped projection to support the inner portion 52 of the ball bearings.

In the transition between the rotation shaft 40 (41) and the eccentric disc 42 and between the hollow space 15 (16) of the housing portion 11 and the bearing-forming portion of the housing portion there is located a slide seal 55. At 56 there is shown a distance ring and at 57 there is shown a first ball bearing (inner support bearing) for the rotation shaft. The support bearing is held firmly in place on inter¬ nal screw threads in the housing portion by means of an adjusting nut 59 and a locking nut 60. At 61 there is shown a distance ring, and at 62 there is shown a second ball bearing (outer support bearing) which is

held firmly in position by an adjusting nut 64 and a locking nut 65 on the outer, external threaded end 40b (41b) of the rotation shaft. The most outermost, free portion of the rotation shaft can be employed for ^' 5 fastening on a suitable drive .means (not shown further) for the rotation shaft.

On operation of the compressor provision is made for synchronous operation of the rotation shafts 40, 41. Alternatively the operation can only occur .via the on 0 rotation shaft, the other rotation shaft being in that case free-running and mainly providing for the control of one roller portion of thepiston, so that it is moved synchronously with the other roller portion of the piston which is connected to the driving rotation 5 shaft.

In Fig. 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b the piston 18 is shown in four consecutive phases on turning the rotation shaft 40, 41 in the direction of the arrow 66. The piston 18 -is moved stepwise 90° from the position 0 shown in Fig. 5a and 5b to the position shown in Fig. 6a and 6b, from the position shown in Fig. 6a and 6b to the position shown in Fig. 7a and 7b and from the position shown in Fig. 7a and 7b to the position shown in Fig. 8a and 8b. The sketches as shown in Fig. 5a, 6a, 7a and 8a are seen from the same direction, while the sketches as shown in Fig. 5b, 6b, 7b and 8b are seen in the direction of the arrow 67 in Fig. 5a, 6a, 7a and 8a.

In the starting position as shown in Fig. -5a and 5b the piston 18 occupies a position in which it divides up the hollow space 15 into two equally large parts which are shown by the part hollow spaces 15b and 15c in Fig. 5b.

On turning of the rotation shaft 42 in the direc- tion of the arrow 66 90 from the position shown in

Fig. 5a and 5b to the position shown in Fig. 6a and 6b the one part hollow space 15b will reduce, while the

other part hollow space 15c will increase. However one must be observant here of the roller movement which is effected by the roller portion 22 of the ^" piston 18. Gradually as the conical surface of the roller portion 22 is rolled off against the adjacent roller track of the partition plate 13 and thereby forms a continuous sealing abutment between the roller portion of the piston and the roller track of the partition plate at an inreasing distance from the main plane of the piston - there is obtained a further re¬ duction of the part hollow space 15b, at the same time as there occurs a new part hollow space 15d on the same side of the main surface of the piston, but on the opposite side of the abutment of the roller portion 22 against the partition plate 13. In this position the part hollow space 15c has its maximum volume.

On further turning of the rotation shaft 42 in t *he direqtion of the arrow 66 90o from the position shown in Fig. 6a and 6b to the position shown in Fig. 7a and 7b the part hollow space 15b is reduced still further towards a minimum volume, at the same time as the said new part hollow space 15d has increased to a volume size corresponding to the part hollow space 15c which now has decreased relative to the position shown in Fig. 6a and 6b and the corresponding volume size as shown in Fig. 5a, 5b.

On further turning of the rotation shaft 42 an angle of 90 from the position shown in Fig. 7a and 7b to the position shown in Fig. 8a and 8b there is ob- tained a part hollow space 15d going towards its maxi¬ mum (after 270 turning) , while the part hollow space 15c is further reduced. At the same time as the part hollow space 15c is reduced, there is built up on the same side of the main portion 19 of the piston, but on the opposite side (the rear side) of the abutment of the roller portion 22 against the partition plate 13, a new part hollow space 15e (Fig. 8a).

On turning the rotation shaft further an angle of 90° back to the starting position, as shown in Fig. 5a, 5b, the part hollow space 15c is reduced to its minimum volume. Parallel to the volume development in the illustrated part hollow spaces 15b-15e in the upper semi-spherical space 15 there are obtained corresponding part hollow spaces 16b-16e in the lower semi-spherical space 16.

In Fig. 9 the volume curve is shown for the part hollow spaces 15b, 15c, 15d and 15e. It is evident from this that each part hollow space requires a turning cycle of the rotation shaft 42 of 270° (3/4 of a revo¬ lution) in order to go from a minimum to a maximum and correspondingly 270 in order to go from a maximum back to a minimum, that is to say a combined turning of the rotation shaft 22 of 540° (1,5 revolutions) in order to effect a complete suction and exhaust cycle in each part hollow space.

From Fig. 9a it will also be evident that there are present three active part hollow spaces wherein volume increases and volume reductions occur respec¬ tively at any time in the illustrated cycle of 540 (except in the positions as illustrated in Fig. 5a, 5b and 7a, 7b) . In any phase of the illustrated cycle the volume on opposite sides of the piston is used to the maximum by means of the said three active part hollow spaces.

Corresponding volume changes for corresponding part hollow spaces are shown in the volume curves as shown in Fig. 9b.

From the curves in Fig, 9a and 9b it is evident that for each 360 turning of the rotation shaft 22 two equally large volumes will be ejected from each semi-spherical space 15 and 16 respectively, that is to say together four equally large volumes in the compressor. Each such volume is as shown in Fig. 9a

3 and 9b in the illustrated embodiment of 56 cm , so that

combined there is obtained a volume yield of 224 cm per 360 turning. The net inner volume of each part hollow space (see Fig. 5b and 7b) constitutes in the illustrated instance 32 cm , and the combined net inner volume of the part hollow spaces (see especi¬ ally Fig. 5b and 7b) constitutes in consequence 128 cm . The total internal volume of the compressor is

3 ^• estimated as 288,6 cm , and compared with the volume yield of 224 cm per 360 turning there is obtained a capacity of 77.5%.

As mentioned above, the valve ports 37, 38 in to the semi-sperical space 15 are positioned just by the crosshead pin 26, the ejection of the compressed volume from a first part hollow space occuring prior to the rolling of the roller portion 22 across the crosshead pin, while the sucking in to a part hollow space which is built up on the opposite side of the piston and*on opposite side of the crosshead pin occurs just after the roller portion 22 has passed the crosshead pin. The different suction valves 37 and exhaust valves 38 can if desired be adjustable by means of regulatable pressure springs or other suitable pressure regulating means. Alternatively the valves can be opened and closed by cam control from the chamber (not shown) on the crosshead pin, so that the valves open and close in fixed phases of the movement of the piston 10 in the compressor.

It must also be added that when the roller portion 22 of the piston rolls against the roller track of the partition plate 13, the roller portion makes a combined roll movement and push movement. In the illustrated embodiment, where the roller portion 22 has a conic angle of about 120°, end portions of the roller portion 22 which have the largestdiameter nevertheless have a substantially smaller diameter than the diameter of the semi-sherical space 15. When the rotation shaft 42 is turned 180°, the roller portion 22 is rolled off

correspondingly 130 , while it is displaced 50 at the same time, that is to say for every 360 turning of the rotation shaft ^' 42 the roller portion rolls about 260 , while it is displaced about 100 . For the understanding of the solution according to the invention certain theoretical assumptions of the construction according to the invention shall be examined.

As the starting point for forming the working chambers of the machine one begins with a speriσally shaped hollow space 70 which is surrounded by a permanent wall 71 (ball shell) which forms the outer boundary surface of the different working chambers and which at the same time forms a guide for moveable parts 42, 18 in the spherically shaped hollow space 70. The different moveable parts are consequently adapted to move themselves in a turning and a sliding movement along the inner surface of the ball shell. The diffe¬ rent moveable parts are moveable about different axes which all cross the center of the ball, so that the moveable parts can be separately considered as a part of an imaginary spere which effects a controlled move¬ ment along the inner surface of the ball shell. Such an imaginary sphere, which is mounted in its associ- ated ball shell, will thus be able to carry out any turn- or swing-movement about an arbitrarily chosen axis through the center of the ball, since this axis can always be a symmetrical axis for diametrically opposing parts of such an imaginary sphere. In Fig. 10a there are shown four such current symmetrical axes 40a, 43, 20 and 21 through the center point of the ball.

A first axis 40a (see Fig. 10b) constitutes a common main axis for a pair of rotation shafts 40, 41, that is to say the turn axis for an associated eccentric disc-forming connecting part 42, which is fixed to its respective rotation shaft 40 and 41. The

eccentric disc-forming connecting, parts 42 are shown defined as ball skullcap parts by means of their re¬ spective-mutually parallel cutting planes 80, 81, which are disposed an equal distance from the center point of the ball.

Between the said cutting planes 80, 81 a center- symmetrical, ball belt-shaped hollow space 82 is de¬ fined which constitutes the theoretically optimum working chamber. The theoretically optimum working chamber is thus to a significant degree limited by the said ball skullcap parts which form eccentric disc¬ forming connecting parts 42 on associated rotation shafts 40, 41.

A second axis 43, which constitutes the center axis for the eccentric discs or the ball skullcap parts 42, will, as is illustrated by broken lines 79 in Fig. 10c, form a rotation surface in the form of a double conic ^' surface. This second axis 43 also con¬ stitutes a control axis for controlling the symmetri- cal axis of a centrally moveable part 18 in a corre¬ sponding double conic surface-shaped path of movement (see Fig. 10c) . The said centrally moveable part forms a piston 18 in the said ball belt-shaped hollow space 82. On turning of the moveable parts 42 about the axis 75 the internediate ball belt-shaped hollow space 82 will be subjected to a rock movement within the spherically shaped hollow space 70 relative to the center pin of the ball, the rock movement having a turning movement component corresponding to the turn movement of the part 42.

A third axis 20, which extends at right angles to the plane of the drawing (see Fig. lOd) , consti¬ tutes a permanent turning axis for the central moveable portion, that is to say the piston 18. The piston 18 is consequently forced to be turned about the axis 20 at the same time as the piston is prevented

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from taking part in the turning movement about the shaft 40a. That movement which is transferred from the eccentric disc-forming moveable parts 42 to the piston- forming, central moveable part 18 via the shaft 43 constitutes in consequence a corresponding rock move¬ ment to the rock movement of the ball belt-shaped hollow space 82. The symmetrical axis of the piston 18, which can be coinciding with the shaft 43, is conse¬ quently subjected to a controlled movement in the path of movement of the shaft 43, which has said double conic form, without the piston thereby being turned about its symmetrical axis.

A fourth axis 21 (see Fig. lOe) , which extends in the plane of the drawing at right angles to the axes 40a and 20, constitutes the central axis in a partition plate 13 which divides the sperically shaped hollow space 70 into two equally large, substantially semi- spheriσally shaped spaces 15 and 16. At the same time the -partition plate divides up the ball belt-shaped hollow space 82 into two equally large, wedge-like half parts. The axis 21 constitutes at the same time the central axis for a diametrically extending, through aperture in the partition plate 13. This aperture per¬ mits parts of the piston 18 to move forwards and back- wards a definite swing arc through the aperture, the piston being swung a correspondingly definite swing arc forwards and backwards about the axis 43. At the same time the shaft 21, which is running parallel with the main plane of the piston through the aperture, per- mits that the piston can be swung about the axis 21 at the same time as it is swung about the axis 43. The piston which is controlled by the path of movement of the axis 43 is subjected thereby to a compound turning and rocking about the center of the ball, that is to say about the axes 20 and 21, without the piston taking part in the turning movement about the axis 40a. Stated in another way the movements of the piston are forcibly

controlled depending upon the opposing control forces in the aperture of the partition surface 13 and depen¬ dent upon the control pins 44 which connect the con¬ necting parts 42 and the rotation shafts 40, 41 with the piston 18.

If a level piston had been employed, only a limited compression and limited expansion would have been attained in the two chamber formations which occur on opposite sides of the piston in each of the two semi-spherical spaces 15, 16. In order to achieve an optimum compression and a corresponding optimum expansion in the chamber formations the piston has been designed with a centrally level main portion 19 and two mutually opposing, conic stump-shaped roller forming parts 22 and 23. The roller-forming parts 22, 23 take part in the compound or combined turning and rocking movement of the piston 18 and execute as a result a rolling movement about the axes 20 and 21 in each of their semi-sherical spaces 15, 16 against the intermediate roller-surface forming partition plate 13. By means of the volume-expelling roller portions

22 and 23 there occurs quite definitely a certain further narrowing of the theoretical optimum work chamber 82 in the sperical hollow space 70 - together with the narrowing from the main portion 19 of the pis¬ ton 18 together with the narrowing from the partition plate13-but an essential effect of the roller parts 22,

23 is however that they produce an optimum compression in the subsequent part chamber formations, the roller parts being able theoretically to reduce the part chamber formation in certain phases to zero volume size by means of the rolling off movement against the roller surface-forming partition plate 13. Another significant additional effect is obtained on the rear side surface of the roller portion 22, 23, that is to sa at the conic surface side which has just effected a rolling off towards the roller surface-forming par-

tition plate 13, the roller portion producing a subsequently expanding part chamber formation on the same side of the piston in the associated semi- spherical space 15, 16 at the same time as it com- presses a forwardly disposed part chamber formation in an associated semi-spherical space 15, 16. The stamp 18 operates thereby at the same time as the three different part chambers in each semi-spherical space. In Fig lOd there is elucidated a conic angle of 120 which is reckoned from a conic angle point which is placed on the shaft 43 at a distance from the center of the ball corresponding to somewhat over half the thickness of the partition plate. The roller por- tion will as a result be able to effect a theoretical rolling off towards the partition plate along a line corresponding to the radius of the partition plate 13 within the sperical space 70.

In the drawings there is shown a cylindrical crosshead pin 26 in the aperture 17 of the partition plate 13. The crosshead pin 26 has a greater thickness (diameter) than the thickness of the partition plate, ^' so that it projects a distance outwards on the oppo¬ site side of the partition plate 13 in its aperture 17. The conic surface of the roller portion 22 (23) is adapted to effect a rolling off movement along the respective roller surface of the partition plate 13, and in this connection the crosshead pin constitutes an obstacle to such a rolling off movement. Therefore provision is made for the roller portions 22, 23 of the piston 18 to effect a rolling off towards the crosshead pin also. In this connection there are cut out corresponding concavely rounded off grooves 22a, 22b and 23a, 23b in the roller portions 22, 23. In the design of the grooves 22a, 22b and 23a, 23b in the roller portions 22, 23 the pointed ends of the roller portions are correspondingly cut off and pro-

vided with concave (half moon-shaped) cavities 31, 32 which are adapted to corresponding ball shell-shaped projections 27, 28 on corresponding outer sides of the crosshead pin 26. Correspondingly concave cavi- ties 29, 30 are also formed in the partition plate 13 in order to permit turning of the ball shell-shaped projections 27, 28 of the crosshead pin in groove 17 of the partition plate 13. The ball shell-shaped pro¬ jections 27, 28 forms a permanent slide abutment against the cavities 29, 30 in the aperture 17 of the partition plate 13, while the grooves 22a, 23a and 22b, 23b form a sliding abutment against the main part of the crosshead pin 26 only in particular, de¬ fined regions of the swing movement of the piston 18 in opposing rock positions of the piston, that is to say in a 0 fastening point and in a 180 faste- .-. _ ning point respectively, every time there is effected a rolling off of the roller portion 22 (23) towards the crosshead pin 26. In these instances the one part of the roller portion within at the main portion 19 of the piston is in its.lowest position, while the opposite part of the roller portion within at the main portion 19 of the piston is in its highest position relative to the partiion plate 13. In Fig. 11 there is shown schematically the pattern of movement for a Q . ^■ fastening point and a 180 fastening point on the piston 18 compared with the roller plane on the par¬ tition plate 13. Fig. 12 shows schematically the pattern of movement of roller portion 22 (23) relative to inner walls of the semi-spherical space 15, 16. From the drawings Fig. lOb-lOe it is evident that the largest diameter of the roller portions 22, 23 is substantially less than the diameter of the roller surface, that is to say the outer roller sur- face diameter of the partition plate. This involves that the rolling off movement which the roller portion 22 (23) is subjected to does not constitute a pure rolling

off movement, but on the other hand comprises a com¬ bined rolling off movement and displacement movement. With a suitable clearance between the roller portion (22 (23) and the adjacent roller surfac on the par- tition plate 13 the roller portion slides forwards with a combined rolling off movement and a somewhat forwardly pushing slide movement. For example the roller portion can effect a rolling off movement along the roller surface of the partition plate 13 of 260 and a pushing movement of 100 , while the rotation shafts 40, 41 make an angle turn of 360°.