US2982218A - Rotary swash-plate type pump - Google Patents

Description

y 1961 R. LUCIEN 2,982,218

ROTARY SWASH-PLATE TYPE PUMP Filed March a, 1957 4 Sheets-Sheet 1 W W I v 56 May 2, 1961 R. LUCIEN ROTARY SWASH-PLATE TYPE PUMP 4 Sheets-Sheet 2 Filed March 6, 1957 May 2, 1961 R. LUCIEN ROTARY SWASH-PLATE TYPE PUMP 4 Sheets-Sheet 5 Filed March 6, 1957 y 1961 R. LUClEN 2,982,218

ROTARY SWASH-PLATE TYPE PUMP Filed March 6, 1957 4 Sheets-Sheet 4 Fry 6a United States Patent ROTARY SWASH-PLATE TYPE PUMP Ren Lucien, Neuilly-sur-Seine, France, assignor to Socit a responsabilit limite: Recherchcs Etudes Production R.E.P., Paris, France, a French company Filed Mar. 6, 1957, Ser. No. 644,245 Claims priority, application France Mar. 15, 1956 9 Claims. (Cl. 103-42) This invention relates to a rotary swash-plate type pump and is herein described in its application to a pump of this type in which a multi-cylinder block contains cylinders. extending parallel with the axis of a driving shaft on which the swash-plate is mounted.

The pump in accordance with the invention is pro vided with an automatic regulating device, which is characterised by comprising, in combination with ports arranged in each cylinder head, a part driven by the shaft and the rotation of which is timed to co-act with the delivery strokes of the successive pistons in such a way that this part causes a series of orifices to pass in front of 'the said'ports, which orifices form the commencement of passages terminating, at the opposite end, in an axial bore, a second series of by-pass orifices being arranged spirally in such a manner that, when the delivery pressure exceeds a predetermined value, they are successively uncovered by the displacement of a member dependent on this pressure, and when so uncovered place the cylinders successively in communication with the inlet chamber of the pump during a fraction of the delivery stroke. This fraction may be able even to attain unity when all the orifices are uncovered.

In accordance with a further feature of the invention, the said ports arranged in the head of each cylinder function not only for automatic regulation but also as inlet orifices.

On the other hand, the pump has, compared with pumps of this type already known, the advantages of a greater energy efficiency and of less wear on the parts in frictional contact. One of the arrangements ensuring a higher efficiency is that the chamber in which the swash-plate rotates does not function as a reservoir for i the working fluid, so that if this fluid is a liquid, and

These dilferent features of the invention will appear from the description below, by way of example, of one embodiment, which is shown in the attached drawings, in which:

Figure l is a longitudinal section of a pump;

Figure 2 is a partial transverse section along AA of Figure 1;

Figure 3 is a section along CC of Figure 1;

Figure 4 shows a modification of the construction from a similar view-point to Figure 3;

Figure 5 is a partial section on the line B-B of Figure 1; a

Figures 6 and 7 are two sections on the line D-D, of Figures 3 and 4 respectively;

Figure 8 is of an alternative embodiment, in longitudinal section;

Figure 8a illustrates the structure of Figure 8 in a different operational position;

Figure 9 is a section on the line E-E of Figure 8; and

Figure 10' is a section on the line F-F of Figure 8.

Referring first to Figure l, the pump comprises a pump body formed by a central section 1 in which there are distributed parallel to the axis, at equal distance from the same, and equally spaced, cylinders 2 of the individual pumps. This central part has an axial bore'3 and is trued at its ends in accordance with two planes 4 and 5 perpendicularly to the axis x--x of the pump. Against these two planes there abut tightly two end covers 6, 7, which enclose, on each side of the faces 4 and 5, two chambers 8 and 2, the chamber 9 being in communication through the orifice 10 with a suction conduit.

Pistons 11 are movable in the cylinders. Firm in the bore 3 is a bushing 12 in which are roller bearings to support a revolving stem 13, which has a head 32 having a fiat surface perpendicular to the shaft, trued so as to be in perfect contact with the face 14 of the central section. The .stem '13 is rotatably driven by a motor shaft the end of which enters a splined bore in a swash-plate 16 screwed into the stem 13 at 15. The swash plate 16 having a flat surface 17 inclined to the axis x--x is secured to the stem 13 by a key 18. Between the parts 13 and 16 there is interposed an annular wedge 19, which turns with the parts 13 and 16. It has a flat surface perpendicular to the axis xx in contact with a corresponding surface of the bushing 12, and its opposite oblique face is parallel to the face 17 of the swash-plate 16. The swash-plate 16 has a cylindrical spigot 20 on which there is mounted, on roller bearings 21, a disc 22. In spite of the presence of these bearings, the disc 22 tends to be carried round by friction in the same direction as the swash-plate 16. To prevent this there has been provided the following device which can be seen in Figure 2: The pump being supposed to turn in the direction of the arrow, the housing 6 has an external tangential boss 23 extending in the direction of the arrow. This projection is hollow and is closed by a screw 24 comprising a-semi-spherical recess opposed to another semi-spherical recess on the periphery of the disc 22. Between these two there is arranged a strut 25 having ball-shaped ends which fit in the two recesses. The result of this arrangement is that the disc 22 cannot turn about the axis xx, but can nevertheless wobble with the swash-plate owing to the ball and socket joints.

The disc 22 is pierced with holes 26 equidistant from its centre and the centres of which are equally spaced over the same circumference.

holes is equal to that of the individual pumps. In these holes there are located shoes 27 (Figure 1); these shoes have fiat surfaces 28 in contact with the inclined surface of the swash-plate 16. The shoes 27 and the corresponding pistons '11 are connected by, connecting-rods 29, with ball and socket joints at each of their ends, which connecting rods impress on the pistons, each in its cylinder 2, the reciprocating movements resulting from the rotation of the swash-plate.

In the known manner, each shoe 27 has, on its face 28, a cavity 30 which communicates, through the rod 29 and the piston 11, with the compression chamber of the cylinder 2. This cavity forms, with the surface 17 of the plate 16, a chamber in which, at the time of compression, there is present a fluid pressure which partially balances the thrust of the shoe 27 on the part 16 and thus reduces the forces of friction and in consequence the wear on these parts.

Patented May 2, 1961,

The number of these pump. The stem 13 and swash-plate 16 are keyed with respect to one another in such a way that during the semi-rotation of the swash-plate 16 in which it draws out each piston 11 from one end to the other of its suction stroke, the port 33 registers with the port 31. Thus each piston 11, during its suction stroke, draws fluid from the chamber 9 through the semi-annular port 33 and the port 31.

Referring now to Figure 5, it is seen that the heads of the cylinders are each in communication through a lateral passage 34 with a delivery chamber 35 closed externally by a plug 36 and which is provided with a non-return delivery valve 37 controlled by a spring 38. In its delivery stroke, each piston 11 compresses the fluid in the chamber 35 and the valve 37 prevents it from returning to the cylinder during the suction stroke of the piston.

As can be seen in Figure 1, each chamber 35 is in communication through an oblique passage 39 with an annular manifold chamber 40 formed between the bushing 12 and the part 1. This chamber communicates through a passage 41 with the delivery orifice 42 of the pump.

There will now be described the system of regulation of the pump. Over that half of the surface 14 of the head 32 which is opposite to the semi-annular port 33,

that is to say that half which, in its rotation, registers with the pistons which are effecting their delivery stroke, and at a radius equal to the average radius of the port 33, there are arranged equidistant regulating ports 43, of an arbitrary number, for example, for the pump shown, six regulating ports in the case of Figure 3 and nine in the case of Figure 4. Each of the ports 43 leads to a radial passage having the generic reference 44. The radial passage 44 has been shown, as likewise the orifice 31 of the corresponding head of the cylinder 1, at the moment when suction has just stopped and when compression is about to start. The passages 44 open into ports 45 in an axial bore 46. In this bore there is movable a piston valve comprising two pistons 47, 48 and a portion 47a of reduced diameter coupling pistons 47 and 48 together, forming an annular chamber 49 between pistons 47 and 48 and surrounding portion 47a. Chamber 49 communicates by passages 50 through piston 48 with the suction chamber 9. The piston valve 4748 is urged towards the right by a spring 51. The piston 48 abuts against one end of a differential piston 52, movable in an axial cylinder 53 formed in the end cover 7. The other end of piston 52 abuts against the head of a hood 54. A spring 55 enclosed by a screwed cap 56 exerts thrust on the flange of the hood 54, in a direction opposite to that of the spring 51. One at least of the delivery chambers 35 is in communication through a conduit 57, an annular space 58, and radial bore-holes, with an annular space 58a, arranged around the part of the differential piston 52 having the smallest diameter. The springs are calibrated in such a way that, as long as the delivery pressure acting thus on the differential piston 52, to which there is added the force of the spring 51, does not exceed a given value, the spring 55 has a preponderating action and maintains the hood 54 applied against the surface of end cover 7. In this position the orifices 45 are all closed by the piston 48, and the delivery of the pump is at a maximum.

It can be seen from Figures 6 and 7, that the ports 45 are arranged spirally in. the bore 46. If the delivery pressure, on increasing, comes to exceed a predetermined value, the differential piston 52 is moved towards the right, compressing the spring 55 so that the hood 54 leaves its seat. The piston valve 47-4-8 follows it in this movement, urged by the spring 51, so that the port 45 which is nearest to the left-hand edge of the piston 48 and is the first to be freed places the head of the corresponding cylinder 2 in communication with the inlet chamber 9, through the annular space 49 and the passages or conduits 50. The result of this is that, during the time of rotation of the head 32 which leaves the orifice 45 in communication with the orifice 31, the piston 11 delivers fiuid to the inlet chamber 9, and not to the delivery chamber 35 through valve 37. Therefore, the piston 1, at the commencement of its delivery stroke will be inactive, and the same will be true for each of the pistons each time that the port 43 of the plate 32 passes in front of a port 31 in the cylinder-block. The delivery is therefore reduced, but if, notwithstanding this the delivery pressure continues to increase, the piston valve 4748 will move further towards the right, uncovering the second port 45 In these conditions, on each rotation of the pump, the cylinders will be successively placed in communication with the inlet, not only through the first passage 44 and its port 45 but through the following passage and its port 45 that is to say during a greater part of the delivery stroke of each of the pistons. As long as the pressure continues to increase the piston valve moves further to the right, uncovering further ports 45 and reducing the delivery still more. At the limit, if it is reached, all the cylinders will be placed in communication through each of the ports 45 45 45 with the inlet, during the whole of the respective delivery strokes of their pistons, so that the pump will no longer supply the delivery conduit, and the pressure can no longer increase, but will tend on the contrary to diminish. The piston valve 4748, owing to the decrease of pressure on the differential piston 52, will then come back again; thus, the pressure will always be adjusted between two predetermined limits. The limits are variable at will, according to the variations of initial stress which it is possible to give to the spring 55 by screwing the hood 56 in or out.

It has been stated above that the number of the ports 4-3 is arbitrary. In practice it will depend on the crosssection given to the ports 31. In Figure 3 these ports have been given an elongated arcuate shape, while in Figure 4 the ports 31 are circular and have a diameter less than the length of those of Figure 3. As the ports 43 must succeed one another in front of the ports 31 in such a way that these latter are never blocked, the number of ports 43 of Figure 4 must be greater than that of Figure 3.

it will be noticed that, during the time that the pistons deliver the fluid under pressure, the head 32 is subjected through the orifices 31, to the delivery pressure. This tends to lift the head 32 from the cylinder-block 1 while the reaction of the shoes 27 tends to move it nearer. By arranging a suitable ratio between those surfaces 17 and 14 which are subjected to the same pressure of the fluid, that is to say, that prevailing in the chambers 30 and in the orifices 31, the pressure loads on the two opposed surfaces can be substantially balanced and the wear of the rubbing surfaces, on both sides of the cylinder head 1, can thus be reduced.

Apart from the small leakages which may occur between the pistons and their cylinders, the chamber 8 is practically devoid of liquid, any leakages which may arise being moreover evacuated through an orifice 59. In the case of an oil pump this feature of the pump is of great advantage. In known oil pumps of the same type the swash-plate rotates in the oil and the agitation of the oil resulting from this is the cause of an appreciable loss of energy.

The alternative construction shown in Figures 3 to 10 differs from that which has just been described only as far as concerns the regulating device. In these drawings, for convenient description, the driving shaft and the parts which it drives are assumed to have been turned by with respect to the position which they occupied in Figure 1, so that the section through the swash-plate does not appear inclined.

As in the case of Figures 1 to 7, the suction chamber is at 9, in communication with the tank through the orifice 10 and the cylinders such as 2 communicate with it through ports 31. Ahead 32, integral with stem or shaft 13, is applied with its face 14 against the face 5 of the cylinder-block 1. This plate has a semi-annular port 33 which, during a semi-rotation of the shaft 13, spans the orifices 3 1 of the cylinders which are in the suction phase.

The head 32 has a rear surface 60 which is flat and parallel with surface 14 and on the surface 60 there rests a regulating valve 61 comprising a hub 61a, an arm 61b and a semi-circular sector 61a. The hub 61a is driven by stem 13 through a spring blade or torsion bar 62 of which one end 63 can slide to a certain extent in the direction of the axis, but not turn with respect to the shaft 13. The flexibility of the spring formed by the leaf or. tension bar 62 renders possible a relative angular displacement of the arm 61b, with respect to the shaft 13, facilitated by mounting the hub 61a in anti-friction bearings 64, 65. This displacement is limited by two cheeks 66, 67 fixed to the head 32. The sector 610 of the regulating valve 61 is pressed against the surface 60 by the delivery pressure of the pump in the following manner: Pressure is conducted from one of the chambers 35, through the conduit 57, the circular throat 58 and the conduit 59, into a cylinder 68 where it acts on a piston 69 which presses on the hub 61a.

The piston 69 has an axial conduit, extended by a conduit 70 in the hub 61a, and a conduit 71 in the arm 61b, to the head of a tangential cylinder 72 in the arm 61b. in cylinder 72 there is a piston 73 which abuts against a part 74 integral with the stem 13 of head 32.

As can be seen from Figure 10, the ports 31 of cylinders 2 are elongated. The head 32 (Figure 9) has, on a radius equal to the average radius of the slit 33, equidistant by- pass ports 77, 78, 79 82, here 6 in number; the elongation of the ports 31 is such that, opposite each of the ports 31 of the cylinders in the compression stage, there is always found one of the ports 77 t082 as shown; for example, in Fig. 8a.

The sector 610 of the regulating valve 61 has likewise ports or by-pass channels 77a 82a, but arranged at a slightly greater pitch in such a way that, in a position of rest, such as that of Figure 9, corresponding to that of delivery pressures less than the critical pressure, all

the by-pass ports 77 to 82 are closed by the solid parts of the regulating valve. If the critical pressure is exceeded, however, the arm 61b, is displaced in the direction of the arrow with respect to the plate 32, exerting a torsional effect on the spring 62. By this movement, the by-pass channel or port 82a partially opens the bypass port 82, thus placing successively all the cylinders 2 in communication with the suction chamber 9 during a small part of their compression phase. If, however, the delivery pressure continues to increase, the spring blade or torsion bar 62 twisting further, the port 81a comes in its turn to communicate with port 81, without the by-pass ports 82 and 82a ceasing to do so. Each cylinder is thus placed during a longer time, in the course of its compression phase, in communication with the suction, which further decreases the delivery. If the pressure persists however in increasing, the ports 81a and 81 come into communication, without the preceding ones ceasing to do so however, and so on. At the limit, if it is reached, the arm 61b then coming into contact with its stops, all the ports are in communication in pairs and all the cylinders communicate with the inlet during the whole of their compression strokes, so that delivery ceases.

If the delivery pressure of the pump, after having passed the critical value, commences to fall the torsion bar or spring leaf 62 gradually resumes its initial condition, bringing back the regulating valve 61 with sector 61c into the position in which it closes all the orifices 77 to 82 and delivery is resumed.

The number of parts in the head 32 and the sector 61c depends evidently on the relative dimensions of these orifices with respect to those of the ports 31 of the cylinders.

I claim:

1. A rotary pump for a fluid, said pump comprising a plurality of piston and cylinder arrangements aligned on circularly disposed and parallel axes, each cylinder having a first opening for the selective receipt and by-pass of the fluid and a further opening for the discharge of the fluid, a head engaged with the cylinders and having circularly disposed inlet and by-pass ports registerable with the first openings of the cylinders, means including a sector member displaceably engaged with the head and having a plurality of by-pass channels registerable with the by-pass ports of the head, and control means on the sector member responsive to fluid pressure determinable at said further opening to register the by-pass channel with said first opening of the cylinder to exhaust th fluid therefrom.

2. A pump as claimed in claim 1 comprising a rotatable hollow shaft concentric with said circularly disposed axes and rigidly supporting said head, and a torsion bar coupled to the shaft within the same and to the sector member to permit a displacement of the same relative to the head.

3. A pump as claimed is claim 1 comprising a housing common to all of the cylinders, pump exhaust means in the housing and coupled to the cylinders, an abutment on said head, an auxiliary piston and cylinder included in said control means and supported on said sector member with the auxiliary piston engaging said abutment, and means defining a conduit coupling the pump exhaust means with the auxiliary cylinder.

4. A pump as claimed in claim 1 comprising pump ex haust means coupled to said cylinders, a further piston and cylinder arrangement whereof the piston engages the head for urging the same against the first openings of the first said cylinders, and means defining conduits coupling the pump exhaust means to the further cylinder to control said urging of the head.

5. A pump as claimed in claim 1 wherein said head defines an arcuately elongated inlet port for registration simultaneously with a plurality of first openings of the cylinders. V

6. A pump as claimed in claim 1 wherein said first openings are oblong.

7. A pump as claimed in claim 1 wherein the by-pass ports are arranged on an arc.

8. A pump as claimed in claim 1 wherein the sector member comprises an arm adapted for pivoting about an axis relative to which the first said axes are circularly disposed, and an arc-shaped membercoupled'to said arm.

9. A pump as claimed in claim 1 wherein the driving means comprises an inclined swash plate operatively associated with the pistons.

References Cited in the file of this patent UNITED STATES PATENTS 818,382 Lemp Apr. 17, 1906 1,025,222 Wallace May 7, 1912 1,842,569 Richer Ian. 26, 1932 1,971,601 Dilg Aug. 28, 1934 2,429,806 Deschamps Oct. 28, 1947 2,674,197 Dudley Apr. 6, 1954 2,784,671 Wilcox Mar. 12, 1957

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