AU689076B2 - Axial piston machine, in particular an axial piston pump or an axial piston motor - Google Patents

Abstract

An axial piston machine of the axial piston pump or motor type, having a first subassembly (1), including a plurality of circumferentially spaced cylinder-piston units (2) around a central axis (3), a second subassembly (29) rotatable in relation to the first subassembly in a force-transmitting manner with the cylinder-piston units in a coupling plane (30) at a predetermined angle to the central axis, wherein one of these subassemblies is rotatably arranged within a housing (10) and coupled with rotational drive means, with the driving subassembly including two spaced first bearings (33, 34) that act at least substantially in a radial direction and a swivel-joint type second bearing (35) having a pivot center (36) located at about the mid point of the center-to-center distance between the two first bearings, with this type of construction being applicable to swash-plate, skew-plate and skew-drum type machines.

Description

OP1 DATE 03/03/94 AOJP DATE 26/05/94 APPLN. ID 47083/93 III I I I I PCT NUMBER PCT/EP93/02106111 1 AU9347083 INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 5 (11) International Publication Number: WO 94/03708 F01B 3/02, 3/00, F02B 75/26 Al (43) International Publication Date: 17 February 1994 (17.02.94) (21) International Application Number: PCT/EP93/02106 (81) Designated States: AU, BB, BG, BR, BY, CA, CZ, FI, HU, JP, KP, KR, KZ, LK, MG, MN, MW, NO, NZ, PL, RO, (22) International Filing Date: 6 August 1993 (06.08.93) RU, SD, SK, UA, US, VN, European patent (AT, BE, CH, DE, DK, ES, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE).

Priority data: 2566/92-4 6 August 1992 (06.08.92) CH Published With international search report.

(71) Applicant (for all designated States except US): HYDRO- WATT SYSTEMS LTD. [GB/GB]; 90 Great Russel Street, London WCIB 3RJ (GB).

(72) Inventor; and Inventor/Applicant (for US only) FREY, Bernhard [CH/ CH]; FreistraBe 2, CH-8200 Schaffhausen (CH).

(74)Agent: FIEDLER, Otto, Karl; Freistrae 2, CH-8200 F Schaffhausen (CH).

(54) Title: AXIAL PISTON MACHINE, IN PARTICULAR AN AXIAL PISTON PUMP OR AN AXIAL PISTON MOTOR (57) Abstract An axial piston machine of the axial piston pump or 8 47 1 motor type, having a first subassembly including a plurali- 45 8 40 29 31 3 ty of circumferentially spaced cylinder-piston units around 4 4 l a central axis a second subassembly (29) rotatable in relation to the first subassembly in a force-transmitting manner with the cylinder-piston units in a coupling plane (30) at a predetermined angle to the central axis, wherein one of these 49 subassemblies is rotatably arranged within a housing (10) and coupled with rotational drive means, with the driving subassembly including two spaced first bearings (33, 34) that act at least substantially in a radial direction and a swivel-joint type 7 second bearing (35) having a pivot center (36) located at about the mid point of the center-to-center distance between the two 3 first bearings, with this type of construction being applicable to swash-plate, skew-plate and skew-drum type machines.

-1- AXIAL PISTON MACHINE, IN PARTICULAR AN AXIAL PISTON PUMP OR AN AXIAL PISTON MOTOR Cross-reference to Related Applications This application claims the priority of Swiss Application No. 02566/94-4 filed 6 August 1992, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention pertains to an axial piston machine, in particular an axial piston pump or motor of the type having a first subassembly, including a plurality of circumferentially-spaced cylinder-piston units around a central axis; a second subassembly rotatably connected with the first assembly in a force-transmitting manner with the cylinder piston units in a coupling plane arranged at a predetermined angle to the central axis, wherein one of these subassemblies is rotatably arranged within a housing and coupled with rotational drive means.

2. Discussion of the Background of the Invention and Material Information Different types of such axial piston machines, namely "swash-plate machines", "skew-plate machines" and "skew-drum machines" are known in the art, e.g. from printed lecture notes entitled "Grundlagen der Oelhydraulik" (Fundamentals of Oil Hydraulics), by Prof W. Backe, Institut fir hydraulische und pneumatische Antriebe a.

und Steuerungen der Rhenisch-Westfalischen Technischen Hochschule Aachen, 2nd edition 1974, p. 116, together with illustrations 4-22 to 4-25, which are incorporated herein by reference.

The genus of axial piston machines is subdivided into the following types: 25 I. swash-plate machines; to II. skew-plate machines; and III. skew-drum machines All three types are deemed to be encompassed by this invention, wherein in a type I. machine the first subassembly is represented by a cylinder-piston 30 arrangement fixed in a housing, and the second subassembly is represented by a 23 January 1998 PRS:AM:426947.RES -2rotating swash-plate, with the second subassembly, therefore, being a drive subassembly.

In a type II. machine the first subassembly is represented by a rotating drum containing a cylinder-piston arrangement, with this first subassembly thus being a drive subassembly, while the second subassembly is represented by a fixed skewplate.

In a type III. machine the first subassembly again is represented by a rotating drum, containing a cylinder-piston arrangement, while the second subassembly is represented by a rotating drive plate arranged perpendicular to its axis of rotation.

The rotational axes of both subassemblies are arranged at an angle relative to each other. In this embodiment the second subassembly is the drive subassembly.

Substantially no drive torque is transferred to the first subassembly.

Disclosures of the general type of machine to which this invention relates are to be found in the following patent specifications, FRA,2588617 and (2) US,A,2424660.

discloses a type I. pump with a swash-plate overhung-mounted in a housing and rotatingly driven through a circumferentially toothed ring meshing with a drive pinion mounted eccentrically mounted in relation to the geometrical central axis of the machine, which, accordingly, has no rotating central shaft at all. The 20 rotating swash-plate has only one housing-fixed tapered roller bearing transferring :axial and radial reaction forces to the housing, while a second tapered roller bearing :00: is arranged so as to transfer axial and radial forces from a non-rotating wobble-plate V.e to the rotating swash-plate. Said wobble-plate represents a coupling member transferring the wobble-induced axial oscillations to a cylinder-piston subassembly 25 through double ball-jointed rods, and it is mounted for its wobbling movement on o a big sliding ball-bearing. The latter is part of a non-rotating, housing-fixed central •beam device extending axially through the machine. With such a structure it seems highly difficult, to secure the roller bearings against undue edge-pressurising. Said 00" coupling wobble-plate is fixed against continuous rotation around the geometrical S 30 central axis by means of a usual double-jointed arm arranged substantially tangential PRS:AM:#26947.RES 23 Januaty 1998 -3to the central axis and connected by one joint to the housing and by the other joint to said wobble-plate. Such anti-rotational fixing contrivance cannot avoid certain undesired rotational oscillations around the central axis.

also discloses a type I. pump with a rotatingly driven swash-plate, however, with a usual central drive shaft extending half-way through the machine.

The axial reaction forces from the swash-contrivance are transferred to the housing merely by a ball-bearing, which admittedly is immune against edge-pressurising, however, generally is inappropriate for high-pressure performances. Anti-rotational fixation of the coupling wobble-device is realised by means of a double-cardanic arrangement housed in and with regard to its radial dimensions limited to the central region of the machine. In the field of high-duty performance this entails extreme load concentrations in the cardan bearings, as expressively stated in the text of this reference.

SUMMARY OF THE INVENTION With reference to the previous definition of the axial piston machines encompassed by this invention an object of the invention is to provide an improvement in the lubrication system of such machines specifically in relation to lubrication of the cylinder-piston units so as to provide a substantially steady and vibration free lubricant supply to the pistons.

20 Accordingly one form of the invention provides a hydraulic axial high pressure discharge pump, comprising: a) a first subassembly including a plurality of cylinder-piston units, said cylinder-piston units being spaced from a central axis and either parallel to or at an acute angle to said central axis and being circumferentially offset, relative to each other, around said central axis by a predetermined angle; b) a second subassembly being coaxial with and arranged rotationally :around said central axis on a drive shaft, said second subassembly further having a force-transmitting connection with said cylinder-piston units so as to receive the oscillating drive forces of said cylinder-piston units; c) said drive shaft extending coaxially to said central axis from its drive PRS:AM:#26947.RES 23 January 1998 -4input end through at least one of a central opening of said first subassembly and of a pump housing, respectively; d) said first subassembly including a lubricant system being situated in proximity of said central axis and at least in part within a space between said cylinder-piston units and extending over an axial length which is covered at least in part by the axial length of said cylinder-piston units; and e) said lubricant system including a lubricant pump which is in a drive connection with said drive shaft and has a lubricant output connected through output means comprising at least one substantially radially extending lubricant channel to at least one of said cylinder-piston units so as to provide a lubricant supply to the piston of said unit or units.

Another form of the invention provides a hydraulic axial discharge pump, in particular a high-pressure water discharge pump, comprising: Sa) a first subassembly including a plurality of cylinder-piston units, said cylinder-piston units being spa ,ed from a central axis and either parallel to or at an acute angle to said central axis and being circumferentially offset, relative to each other, around said central axis by a predetermined angle; b) a second subassembly being coaxially positioned and arranged for rotation around said central axis on a drive shaft, said second subassembly further 20 having a force-transmitting connection with said cylinder-piston units so as to C 44 receive oscillating drive forces of said cylinder-piston units; c) said drive shaft, including at least two rotationally coupled longitudinal sections, coaxially extending along said central axis from a drive input end and t through a corresponding central opening of at least one of said first subassembly and 25 of a pump housing, respectively, and to a head-subassembly; 4.• d) said first subassembly including a lubricant system being positioned in proximity of said central axis and at least partially within the space between said cylinder-piston units, and to extend over an axial length which is covered at least partially by an axial length of said cylinder-piston units; 30 e) said lubricant system including a lubricant pump being arranged on one PRS:AM:#26947.RES 23 January 1998 of said at least two rotationally coupled longitudinal sections of said drive shaft and in a rotational drive connection therewith, the lubricant output from said pump being connected via output means comprising radially extending lubricant channels to said cylinder-piston units, respectively, so as to provide lubricant supply to the pistons of said units; and f) said head-subassembly including a filler pump coupled with said drive shaft, a flow path of said filler pump being connected in series with a main flow path of the hydraulic axial discharge pump to deliver substantially an entire admission flow at an enhanced hydraulic input pressure to said cylinder-piston units sufficient for avoiding cavitation.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein throughout the various figures of the drawings, there have generally been used he same reference characters to denote the same or analogous components and wherein: Figure 1 is an axial section of a portion of a type I. axial piston pump; and Figure 2 is an axial section of a further portion of the type I. axial piston 20 pump of Figure 1, with Figures 1 and 2 showing two axially adjacent parts of this pump. The common radial plane of the two adjacent pump portions is identified by lines 0-0.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will now be described in detail with reference to the example of a type I. swash-plate axial piston pump illustrated in the drawings. It should also be understood that all the features of the invention can be constructed with reference to the illustrated embodiment, with particular reference to the previously-noted type II. and III. machines.

~drawings, there have generally been used the same reference characters to denote the same or analogous components and wherein: 23 January 1998 PRS:AM:#26947RES -6- Figure 1 is an axial section of a portion of a type I. axial piston pump; and Figure 2 is an axial section of a further portion of the type I. axial piston pump of Figure 1, with Figs. 1 and 2 showing two axially adjacent parts of this pump. The common radial plane of the two adjacent pump portions is identified by lines 0-0.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will now be described in detail with reference to the example of a type I. swash-plate axial piston pump illustrated in the drawings. It should be understood that all the features of the invention can be constructed with reference to the illustrated embodiment, with particular reference to the previously-noted type II. and III. machines.

Specifically, in Figure 2, a first subassembly 1 is comprised of a plurality of, for example five, cylinder-piston units 2, which units are arranged at a radial distance from and parallel to a central longitudinal axis 3 as well as being circumferentially offset, relative to each other around the central axis by an appropriate angle, for example 720. Each cylinder-piston unit is comprised of a piston 4 slidably arranged in a cylinder 5 with piston 4 and cylinder 5 being shown in axial sections only over a part of their axial length. Specific design details of cylinder 5 and piston 4 are only of minimal interest in the present context, since i. 20 cylinder-piston units 2 may be of any type well known in the art.

A pretensioned return coil or compression spring 6 surrounds cylinder 5 and 9*O* acts through a sleeve 7 against a radially projecting bottom flange 8 of piston 4, thus tending to push piston 4 in its restoring or cylinder-filling direction (in the Figures 0:09 :i from the left to the right). The inner (in Figure 2 the left) end of spring 6 abuts on the right end face of a support sleeve 9 fixedly retained in an axial bore of a machine housing 10. Support sleeve 9, on its right side, is fixedly secured to the left end portion of cylinder It should also be understood that, instead of an arrangement of cylinders 5 in parallel to axis 3, a design may be adopted with the c-linder axes being arranged at 30 an acute angle, e.g. between 5' and 100, relative to axis 3. This may be 23 January 1998 PRS:AM;#26947.RES -7advantageous in view of the space available between the cylinders for auxiliary elements or units.

The left end face of housing 10 is tightly connected, e.g. by means of highly pretensioned axial screws 11, with a head-subassembly 12, which among other parts houses a valve assembly 13 and a filler or feed pump 14 attached to a section 15 of a drive shaft 16 (Figure Drive shaft section 15 is coupled, by means of a toothed-clutch 17, to a central drive shaft section 18. Filler pump 14 serves to enhance the input hydraulic pressure for the cylinder-piston units 2 to a value sufficient for avoiding cavitation. Drive shaft section 18 also drives a lubricant pump 19, which in turn feeds a lubricant channel system 20 via a lubricant filter 21 so as to provide a steady and vibration free lubricant supply to the piston of the cylinder-piston units 2.

Coaxially attached to each cylinder-piston unit 2 is a combined inlet-outlet valve 22 having an inlet side 23 connected, via an inlet channel system 24, to the output 25 of filler pump 14. Pump 14 e.g. is of the well-known "side-channel" type and will not be described in detail here since it is not material for the essence or function of the invention. Filler pump 14 is connected, via an input 26, to a nonillustrated external low-pressure hydraulic feed system. Inlet/outlet valve 22 further has an output side 27, connected through an output channel system 28, to a non- 20 illustrated external high-pressure hydraulic system. Valve 22 has substantially coaxial internal flow channel systems and spring-loaded check valve members for both flow directions, i.e. to and from the corresponding cylinder-piston unit 2. The internal structure of valve 22 is of no specific interest for the invention and thus will not be described in further detail. In principle, instead of the noted example of the combined inlet/outlet valve 22 described here, other conventional and well-known valve types may be used.

6 In Figure 1, a second subassembly 29 is rotatably arranged relative to first subassembly 1. Subassembly 29 is in force-transmitting connection with cylinderpiston units 2 within the range of a coupling plane 30, arranged at least 30 approximately right-angled or perpendicular to the central longitudinal axis 3, so as PRS:AM:#26947.RES 23 January 1998 -8to absorb the oscillating drive forces produced by cylinder-piston units 2.

Subassembly 29 is constructed as a driving subassembly that is rotatably arranged in housing 10 and coupled with a main section 31 of drive shaft 16. Drive shaft sections 18 and 31 are cbupled by means of any type of a conventional clutch.

It should also be mentioned that different design modes or types of subassembly 29 may be utilised. Thus, cylinder-piston subassembly 2 may be designed as a rotating drum, i.e. in the sense of previously-noted machine types II.

and III. In the latter case, this subassembly would be a substantially torqueless rotating unit.

Driving subassembly 29 includes a bearing assembly comprising two first bearings 33, 34, which act at least substantially in the radial direction and are arranged at a predetermined axial distance or spacing from each other, and a swiveljoint or pivot-type second bearing 35 acting both axially and radially. In the noted example, bearings 33 and 34 may take the form of axially movably cylindrical roller bearings, while bearing 35 may be a mainly axially acting spherical roller bearing.

The swivel or pivot centre 36 of second bearing 35 is located at about the axial mid-point (centre-to-centre distance) 37 between the mid-points 38, of the bearing axial width 39, of axially spaced first bearings 33, 34.

Subassemblies 1 and 29 are arranged so as to be rotatable, in relation to each 20 other; around their common central axis 3. Only one of these subassemblies, here subassembly 29, is arranged to be rotatable in housing 10 and functions as a driving subassembly, coup.ed with the drive shaft 16. However, as already noted earlier, a design according to machine type III. may also be utilised.

In addition, a disk-like coupling member 40 is rotatably connected to second subassembly 29 around a swash axis 41, which is arranged at an angle relative to the central axis 3. Coupling member 40 is further connected to first subassembly 1 in a manner so as to be blocked against continuous rotation around central axis 3, and is connected in a force-transmitting manner with the cylinder-piston units 2 within the range of coupling plane 30. Coupling plane 30 is arranged at least approximately right-angled or perpendicularly to swash axis 41. Thus, coupling 0

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#4p oo! 7, PRS:AM:#26947.RES 23 January 1991 -9member 40 takes over or absorbs the substantially axial, oscillating drive forces produced by cylinder-piston units 2 and transmits such forces to second subassembly 29. It should be understood that coupling member 40 can also be regarded as a part of second subassembly 29.

The noted rotation-blocking connection between coupling member 40 and first subassembly 1 is accomplished by means of a positively-acting holding device 42.

In the illustrated embodiment, holding device 42 is a cardan type of device comprising a cardan ring 43, which extends along the external perimeter of coupling member 40 and which is connected with each of coupling members 40 and subassembly 1 by means of a pair of diametrical pivots 44. In view of first subassembly 1 being fixedly arranged in machine housing 10, cardan ring 43 is fixed to housing 10 by means of a further pair of non-illustrated diametrical pivots. In the illustrated embodiment, double-jointed rods 45, preferably double ball-jointed rods, are provided for the force transmission between cylinder-piston units 2 and coupling member 40. Each of double-jointed rods 45 is connected by means of a first joint 46 to a corresponding piston 2 and by means of a second joint 47 to a corresponding junction assembly 48 of.coupling member As already previously noted, in the illustrated embodiment, drive shaft 16 is comprised of three rotationally coupled sections 31, 18 and 15. Drive shaft 16 20 extends coaxially with central axis 3 from its drive input end 49 through a

S

corresponding central opening of first subassembly 1 and of housing 10 to headsubassembly 12 with feed pump 14 and valve assembly 13.

Obviously, the mode of design according to the invention, as specifically depicted in the illustrated embodiment, can also be utilised for axial piston motors.

25 Of course, the valve assembly then must be positively coupled to and synchronised o with the rotation of the drive shaft, which then functions as a power output shaft.

The filler pump can be omitted or replaced by other useful auxiliary units.

While there are shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope of the PRS:AMN;926947.ES 23 January 1998 following claims and the reasonably equivalent structure thereto.

In particular it is to be understood that the angle between the swash axis and the central axis may be predetermined so as to be of a fixed acute angle value or so as to be variably adjustable in operation between 00 and a maximum acute angle value, and this with angle variation to both sides of the zero angle value if desired for purposes of hydraulic flow direction reversal. Such variation obviously entails a corresponding variation of the angle between the coupling plane and the central axis, which is the complementary angle to the one between the swash axis and the central axis and determinative for the magnitude of the piston stroke. This type of swash plate axial piston machines with variable swash-angle is well known in the art per se. Thus the realisation of the subject of the present invention for such variable-swash-angle machines can be established by usual structures near at hand and needs no further explanation.

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Claims (3)

11- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A hydraulic axial high pressure discharge pump, comprising: a) a first subassembly including a plurality of cylinder-piston units, said cylinder-piston units being spaced from a central axis and either parallel to or at an acute angle to said central axis and being circumferentially offset, relative to each other, around said central axis by a predetermined angle; b) a second subassembly being coaxial with and arranged rotationally around said central axis on a drive shaft, said second subassembly further having a force-transmitting connection with said cylinder-piston units so as to receive the oscillaing drive forces of said cylinder-piston units; c) caid drive shaft extending coaxially to said central axis from its drive input end through at least one of a central opening of said first subassembly and of a pump housing, respectively; d) said first subassembly including a lubricant system being situated in 15 proximity of said central axis and at least in part within a space between said cylinder-piston units and. extending over an axial length which is covered at least in part by the axial length of said cylinder-piston units; and e) said lubricant system including a lubricant pump which is in a drive connection with said drive shaft and has a lubricant output connected through output 20 means comprising at least one substantially radially extending lubricant channel to at least one of said cylinder-piston units so as to provide a lubricant supply to the piston of said unit or units. 9o 2. A hydraulic axial discharge pump, in particular a high-pressure water discharge pump, comprising: a) a first subassembly including a plurality of cylinder-piston units, said cylinder-piston units being spaced from a central axis and either parallel to or at an acute angle to said central axis and being circumferentially offset, relative to each other, around said central axis by a predetermined angle; b) a second subassembly being coaxially positioned and arranged for PRS:AhM:#26947.R2 28 January 1998

12- rotation around said central axis on a drive shaft, said second subassembly further having a force-transmitting connection with said cylinder-piston units so as to receive oscillating drive forces of said cylinder-piston units; c) said drive shaft, including at least two rotationally coupled longitudinal sections, coaxially extending along said central axis from a drive input end and through a corresponding central opening of at least one of said first subassembly and of a pump housing, respectively and to a head-subassembly; d) said first subassembly including a lubricant system being positioned in proximity of said central axis and at least partially within a space between said cylinder-piston units, and to extend over an axial length which is covered at least partially by an axial length of said cylinder-piston units; e) said lubricant system including a lubricant pump being arranged on one of said at least two rotationally coupled longitudinal sections of said drive shaft and in a rotational drive connection therewith, the lubricant output from said pump being 0* 15 connected via output means comprising radially extending lubricant channels to said oo0o &0 cylinder-piston units, respectively, so as to provide lubricant supply to the pistons 0000 .:of said units; and Sf) said head-subassembly including a filler pump coupled with saia drive shaft, a flow path of said filler pump being connected in series with a main flow 20 path of the hydraulic axial discharge pump to deliver substantially an entire admission f ow at an enhanced hydraulic input pressure to said cylinder-piston units sufficient for avoiding cavitation. toe C 3. The hydraulic axial discharge pump of claim 2, wherein said head- subassembly further includes an input valve assembly coupled to the hydraulic axial discharge pump and wherein said filler pump is arranged with at least one output port adjacent to said input valve assembly. 4. The hydraulic axial discharge pump of claim 2, wherein said head- Ssubassembly further includes an input valve assembly coupled to the hydraulic axial PRS:AM:#26947J.2 28 JanUary 1998 13 discharge pump, said filler pump being a side channel type and arranged with a side channel and at least one output port adjacent to said input valve assembly. The hydraulic axial discharge pump of claim 2, wherein said lubricant pump and said filler pump are arranged on separate ones of said at least two rotationally coupled longitudinal sections of said drive shaft, each with a rotational drive connection, said separate drive shaft sections being coaxially arranged and coupled in drive connection with each other, said head-subassembly including an input valve assembly to the hydraulic axial discharge pump and wherein said filler pump is axially positioned in front of said input valve assembly. 6. A hydraulic axial discharge pump substantially as hereinbefore described with reference to the accompanying drawings. DATED: 28 January 1998 Patent Attorneys for the Applicant: *HYDRWATT SYSTEMS LTD. ALI a S SDATED: 28 January 19981998 PRSAM:#26947.R2 28 Januaay 1998

14- ABSTRACT An axial piston machine of the axial piston pump or motor type, having a first subassembly including a plurality of circumferentially spaced cylinder-piston units around a central axis a second subassembly (29) rotatable in relation to the first subassembly in a force-transmitting manner with the cylinder-piston units in a coupling plane (30) at a predetermined angle to the central axis, wherein one of these subassemblies is rotatably arranged within a housing (10) and coupled with rotational drive means, with the driving subassembly including two spaced first bearings (33,34) that act at least substantially in a radial direction and a swivel-joint type second bearing (35) having a pivot centre (36) located at about the mid point of the centre-to-centre distance between the two first bearings, with this type of construction being applicable to swash-plate, skew-plate and skew-drum type machines. A lubricant pump (19) is driven by drive shaft (18) and feeds a lubricant channel system (20) so as to provide a steady and vibration free lubricant supply to the piston of the cylinder-piston units 0 0* o IS:AM:#2694R ES 23 Jauary 1999 S S l A/ S :AM:#26947.RES 23 Jauary 1998