US 3636820 A
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United States Patent Lambeth 1 HYDRAULIC APPARATUS [451 Jan. 25, 1972v FOREIGN PATENTS OR APPLICATIONS Primary Examiner-William L. Freeh Attorney-Young & Thompson 5 7] ABSTRACT A hydraulic pump or motor intended to fit on an engine or the like for connection to a drive shaft carried in bearings in the engine or the like. The pump comprises a rotarycylinder block having a plurality of cylinders either parallel to or inclined to the rotation axis. Pistons in the cylinders are reciprocable during block rotation by means of a swashplate at one end of the block. The cylinder block is mounted for rotation in a bearing which directly absorbs the side thrust exerted on the block through the pistons. Liquid is introduced to and taken from the pump through a valve having a flat valve surface located at the end of the block remote from the swashplate. An opening is defined by an aperture in the valve and a 1 Claims, 2 Drawing Figures  Inventor: Dennis Ernest Lambeth, Benhall, Cheltenham, England  Assignee: Dowty Technical Developments Limited,
Brockhampton, Cheltenham, England  Filed: July 2,1969
 App]. No.: 838,607
 Foreign Application Priority Data July 5, 1968 Great Britain ..32,l09/68  U.S.C| ..91/499  lnt.C| ..F04b l/20  Field ofSearch ..103/l62;91/507, 198,199, 91/484-489; 230/178  References Cited UNITED STATES PATENTS 3,225,701 12/1965 Griffith ..91/488 2,956,508 10/1960 Wahlmark. ..103/162 3,089,426 5/1963 Budzich 103/162 3,124,079 3/1964 Boyer 103/162 2,845,941 8/1958 Wagner 103/162 3,241,495 3/1966 Diedrich et a1. ..103/162 1 v x "1 2 E/ Q) sic-336.820
PATENTEU JANZS I972 f/V JV FIG. 2.
INVEN TOR .Dawws Z-Zwzsr lmwa lw r (7% fr? ATTORNEYS HYDRAULIC APPARATUS This invention relates to a hydraulic pump or motor comprising a rotary cylinder block having a plurality of cylinders either parallel to or inclined to the rotation axis. Pistons in the cylinders are reciprocable during block rotation by engagement either directly, or indirectly, with a swashplate located at one end of the block. The cylinder block is mounted for rotation by a bearing which is so located as to absorb directly the total side thrust exerted on the block through the pistons by the swashplate. Liquid is introduced into and taken from the pump through a valve having a flat valve surface located at the end of the block remote from the swashplate to engage a flat surface at that end of the block. The flat block surface has ports opening from the cylinders which cooperate with supply and return ports in the valve surface and the block is capable of slight axial and tilting movement with respect to the bearing in order to seat accurately on the valve surface.
For convenience this kind of pump or motor will be called a pump or motor of the kind referred to.
It is often necessary for such a pump or motor to be connected to a shaft which forms part of another device. Such connection gives rise to difficulties in practice.
It is an object of the present invention to provide an improved pump or motor of the kind referred to which can readily be connected to the shaft of another device.
According to the invention a pump or motor of the kind referred to has, at the end of the pump or motor remote from the swashplate, an opening defined by an aperture in the valve and a blind hole in the block, whereby a shaft may pass through the valve and be mechanically connected to the cylinder block, an annular sealing device mounted between the valve member and the block concentric with the opening and located, radially inwards of the ports, said sealing device being capable of accommodating said slight axial and tilting movement.
The seal may include a ring of sealing material such as carbon loaded axially against the block surface.
The blind hole in the block may be splined and so arranged, having regard to the shaft, that slight tilting and/or axial movement of the block may take place without causing corresponding movement of the shaft.
The ring of sealing material may be bonded to a flexible rubber mounting adapted to make sealing engagement in a recess surrounding the aperture in the valve.
Alternatively, the ring of sealing material may itself be engaged by a soft rubber or like sealing ring which in turn makes sealing engagement in such a recess.
Two embodiments of the invention will now be particularly described with reference to the accompanying drawings, in which,
F l6. 1 is a cross section through the first embodiment and FIG. 2 is a cross section through the second embodiment.
Reference is made initially to FIG. 1 of the drawings. The casing l is of substantially cylindrical shape and encloses a rotary cylinder block 2. The cylinder block 2 is located for rotation in the casing l by means of a bearing in the form of a skirtlike extension 3 from one end of the cylinder block which engages in a cylindrical surface 4 formed within the casing. Within the cylinder block a plurality of cylinders 5 are formed being spaced equidistantly around the rotation axis and each directed parallel to the rotation axis. It is equally within the scope of the present invention for the cylinders to be inclined to the rotation axis. Within each cylinder a piston 6 is located which during reciprocation is capable of movement from the open end of the cylinder 5 within the zone of the cylinder block surrounded by bearing 3. The outer end of each piston includes a spherical socket 7 which engages on a ball joint 8. The ball is integrally formed with a slipper 9 which engages against a swashplate 11. The swashplate is integrally fonned with a part cylindrical trunnion member 12 which engages within a part cylindrical bearing surface 13 formed interiorly of a cover member 14 secured to the casing 1. Adjusting means (not shown) are provided for the adjustment of the swash plate 11 angularly within the bearing surface l3.
The end of the cylinder block opposite to the bearing 3 is formed with a flat surface 14 set at right angles to the rotation axis of the block. Into the surface 14a part 15 opens from each cylinder 5. The casing 2 is formed as part of a valve 16 having a flat valve surface 17 which cooperates with the block surface 14. In the valve surface a pair of main ports 18 and 19 are formed having a supply and return functions. The ports 18 and 19 are connected internally of the valve to hydraulic screw-threaded connections 21 and 22. A flange 23 around the valve 16 forms the means by which the pump may be secured in its operative position. Centrally of the valve an aperture 24 is formed extending completely therethrough and opening centrally of the valve surface 17. A blind hole or recess 25 centrally formed in the cylinder block opens only into the surface 14 towards the aperture 24 and the interior surface of the recess 25 is provided with splines 26.
Within the aperture 24 adjacent to the surface 17,.a seal assembly 26 is located which comprises an annular sheet metal casing 27 having secured thereto a first seal comprising an annular ring 28 of hard material such as carbon arranged to engage the interior portion of the surface 17, a second seal comprising a rubber O-ring 30 engaging between the ring 28 and the casing and a helical compression spring 40 acting on the ring 28. A rotating seal is thus provided between the valve and the cylinder block at the position of the aperture 24. An annular groove 29 extends into the cylinder block from the surface 14 to collect any leakage liquid passing radially inwards from the ports l5, l8 and 19 and a passage 31 within the block connects the recess 29 to the interior of the casing.
A retaining plate 32 engages all slippers 9 under the action of a central spring-loaded ball 33 to ensure that the slippers remain in contact with the swashplate. The spring 34 which loads the ball 33 also reacts on the cylinder block to provide initial loading to help hold the block surface 14 against the valve surface 17.
For use, the illustrated pump is secured to an engine or other power source which carries an output drive shaft in suitable bearings. The pump is adapted to be secured to the engine by means of a flange 23 so that the drive shaft 35 passes through the aperture 34 and enters into the splined recess 25 in the cylinder block. The end surface 36 in the drive shaft is suitably splined to engage within the splined recess so that driving torque may be transmitted to the cylinder block. However, the engagement of the spline is arranged to permit a slight degree of tipping and axial movement of the cylinder block relative to the drive shaft. The shaft includes a quill portion 37 arranged in the conventional way to break if the pump should become jammed.
In operation rotary driving power is supplied by the shaft 35 to cause rotation of the cylinder block 2. Such rotation will cause reciprocation of the pistons in synchronism with the connection of the cylinder ports 15 to the supply and return ports 18 and 19 such that liquid enters the cylinders from one of these ports 18 or 19 and is delivered at pressure at the other of these ports. The drawing, for convenience, shows the the cross section through the valve out of the plane of the remainder of the cross section in order to illustrate the ports 18 and 19. The interior of the casing 1 may be connected either directly to a low-pressure reservoir or alternatively it may be connected to the port 18 or 19 at the lower pressure. During operation liquid will leak in between the valve and block surfaces from the ports l5, l8 and 19 and liquid which moves radially outwards will clearly be retained by the casing and ultimately be directed either to the low-pressure reservoir or to the low-pressure port 18 or 19. Liquid which leaks inwardly will enter the annular recess 29 and from there will pass through passage 31 to the interior of the casing from which it will either flow to the low-pressure reservoir or to the low-pressure port 18 or 19. The seal assembly acting on the surface 17 radially inwards of the recess 29 will prevent any liquid within recess 29 from entering the aperture 24. The seal assembly 26 will also operate at the same time to prevent any fluid within the aperture 24 from obtaining access into the recess 29 and thus into the pump. This feature is of particular importance where air has access to the aperture 24 since the entry of air into the illustrated pump can cause noisy operation of the pump and could cause damage to the pump. The arrangement of the annular ring 28 to engage the flat surface 17 will accommodate any slight radial movement of the block in seating itself on the valve surface. The resilient-backing ring 27 will also be capable of accommodating slight axial movement of the ring 28 following axial movement of the cylinder block.
Reference is now made to FIG. 2 of the drawings. The pump is similar in structure to the FIG. 1 embodiment and similar reference numerals will refer to similar parts. For convenience only the parts of FIG. 2 which differ substantially from FIG. 1 will be discussed in detail. The pump illustrated in FIG. 2 is similar in structure to the pump illustrated in K. R. Boydells application Ser. No. 694,717. In FIG. 2 liquid enters the pump by a port in the casing 1 (not shown) such that liquid flows over the swashplate 11 and through dynamic pumping passages 41 extending through the cylinder block to an annular channel 42 defined between the casing 1, the cylinder block 2 and the bearing surfaces 3 and 4. The dynamic pumping effect of the passages 41 delivers liquid at a slightly increased pressure in the annular channel 42 from which it enters the inlet port in the valve surface 14. The delivery port in the valve surface 14 connects to a screw-threaded connection (not shown) in the valve block 16.
In FIG. 2 a first seal comprising a sealing ring 28 of carbon engages the interior portion of the valve surface 17. The ring 28 is supported by means of a second seal comprising a flexi ble rubber mounting 43 sealingly seated Within the aperture 24 in the valve. The rubber mounting 43 encloses a compression spring 44 which reacts from the aperture 24 on to the ring 28 to urge it against the block surface 17. The annular groove 29 in the surface I7 around the position of engagement of seal 28 is rather smaller in cross section than in FIG. 1. Again the recess 29 is vented by means of a passage 31 to the interior of the casing l.
The operation of the FIG. 2 embodiment is as described with reference to FIG. 1 and in particular the action of the seal assembly 26 will prevent any liquid from recess 29 from entering the aperture 24 and also will prevent any fluid particularly air within aperture 24 from entering into the recess 29. Also the annular ring 28 will encase the flat surface 17 to accommodate any slight radial movement of the block in seating itself on the valve surface and will also accommodate any axial movement of the block.
While the illustrated embodiments each propose the use of a sealing ring engaging against the flat block surface, it is equally within the scope of the present invention to arrange the seal in any conventional manner so as to accommodate the possible movements of the cylinder block. For example the seal may be carried by the cylinder block to engage the flat surface of the valve or again alternatively either the valve surface or the block surface might include a cylindrical projection having a flat surface engaged by a seal carried in the other member.
1. A hydraulic pump or motor of the axial piston kind comprising a rotary cylinder block having a plurality of cylinders substantially parallel to the rotation axis, pistons in the cylinders, a swashplate located at one end of the block for engagement directly or indirectly by the pistons during rotation of the cylinder block to cause piston reciprocation, a bearing locating the cylinder block for rotation so as to absorb directly the total side thrust exerted on the block through the pistons by the swashplate, a flat block surface located at the end of the block remote from the swashplate, a valve having a flat valve surface for engagement by the block surface, the valve surface having supply and return ports which cooperate with cylinder ports in the block surface, the cylinder block being capable of slight axial and tilting movement relative to its bearing in order to seat accurately on the valve surface, an opening defined by an aperture in the valve and a blind hole in the block whereby a shaft may pass through the valve and be mechanically connected to the cylinder block, an annular sealing device mounted between the valve and the block concentric with the opening and radially inwards of the ports to surround the position of the said shaft, said sealing device being held against rotation within the valve about the block axis but at the same time being capable of slight axial and tilting movement to engage against the cylinder block surface to prevent leakage of liquid from between the valve and block surfaces into said opening, said sealing device comprising a first seal spaced from said valve and continuously in engagement with said block and a second resilient seal between and continuously in engagement with said valve and said first seal to accommodate movements of said first seal relative to said valve.