US3151569A

US3151569A - Axial piston pump having a control device for varying the delivery

Info

Publication number: US3151569A
Application number: US145145A
Authority: US
Inventors: Muller Theodor
Original assignee: Schweizerische Lokomotiv und Maschinenfabrik AG (SLM)
Current assignee: Schweizerische Lokomotiv und Maschinenfabrik AG (SLM)
Priority date: 1960-10-19
Filing date: 1961-10-16
Publication date: 1964-10-06
Anticipated expiration: 1981-10-06
Also published as: GB958059A; CH385632A

Description

Oct. 6, 1964 T. MULLER 3,151,569

AXIM.y PIsIoNIEuuE HAVING A CONTROL nEvIcE Foa vVEREINE THE DELIVERY Filed Oct. 16, 1961 2 Sheets-Sheet 1 Fig. 1

y Y Z Oct. 6, 1964 T. MULLER 3,151,5694

AXIAI. PIsIoN PUMP HAVING A CONTROL DEVICE Foa VARYING THE DELIVERY Filed OCT.. 16, 1961 2 Sheets-Sheet 2 l t 97 9083 50 53 I 84 a7 88 51 s2 55 y l V i i l i l l, r n

United States Patent Ofice 3,151,569 AXIAL PISTGN PUMP HAVING A CONTROL DEVCE EGR VARYING THE DELIVERY Theodor Mller, Winterthur, Switzerland, assigner to Schweizerische Lokomotivund Maschinenfabrik, Winterthur, Switzerland Filed Get. 16, 1961, Ser. No. 145,145 Claims priority, application Switzerland, Get. 19, 1960, 11,723/60 12 Claims. (Cl. 193-173) This invention relates to axial piston pumps of the type having a control device for varying the delivery by restricting the ducts leading to the cylinder chambers.

In a known axial reciprocating pump of the swash plate type, a reduction of the rate of delivery is obtained by axial movements of the entire system consisting of the swash plate and the operating piston set in the direction of the delivery stroke, for example by means of a mechanical device.

It is an object of the invention to simplify the control system and to facilitate the automatic control or" such pumps, as well as to obtain a shorter overall length of the pump unit. According to the invention, an axial piston pump of the specified type comprises a control slide valve provided in the pump housing and having ports which are associated with at least some of the cylinder chambers and communicate with the suction space of the pump, the position of said ports being adjustable relatively to admission ducts leading to the cylinder chambers, so that the sectional area of ow provided for the admission of the liquid to the cylinder chambers will be variable.

The present invention will now be described in more detail with reference to the accompanying drawings illustrating, by way or example, two preferred embodiments of the invention, and in which:

FIGURE l is an axial section through a piston pump of a rst embodiment of the invention.

FIGURE 2 is a cross-section through the control slide along the line Il-Il of FIGURE l,

FIGURE 3 represents a developed view of the inlets of the control ducts in dillerent relative control positions,

FIGURE 4 is a fragmentary axial section through a piston pump of the second embodiment,

FIGURE 5 is a transverse section along the line V-V of FIGURE 4,

FIGURE 6 shows a detail pertaining to the second embodiment, drawn to a larger scale, and

FIGURE 7 is a modification of the rst embodiment of the invention.

FIGURES l to 3 of the drawing illustrate an application of the invention to that type or" pump in which a plurality of plungers are circularly spaced around the axis of rotation of the pump driving shaft and are operated by a swash plate of constant inclination. Said plungers, moreover, are subdivided into two groups of plungers having dilerent diameter. With this subdivision of the plungers and cylinders it is known that by cutting out the large diameter cylinders at higher delivery pressure, it is possible to obtain a considerable increase of the delivery ratio at minimum and at maximum delivery pressure, while the load applied on the axial thrust bearings of the swash plate at e.g` 400 lig/cm.2 operating pressure is approximately equal to that at low operating pressure of e.g. 40 lig/cm?. g

Within the pump housing 1 the drive shaft 2 is mounted in ball bearings 3 and 4. The swash plate 5 is rigidly ixed to the shaft 2 for rotation with the shaft. A plurality, eg. ten bores 6 and 7 extend parallel to the drive shaft in circularly spaced arrangement in the actual cylinder block part of the housing 1. The bores serve aS g 3,151,569 Patented Oct. V, 1964 cylinders for the pump plungers. There are ve bores 6 of larger diameter d1 and iive bores 7 of smaller diameter d2. The pump plungers 8 and 9 are provided with conical heads 11 which are urged against a disk 12 by means of springs 10. The disk 12 forms part of the swash plate and is rotatably supported on the swash plate body 5 by

ball bearings

13 and 14.

Each of the ve large and the ve small cylinders 6 and 7 is connected by means of a

control duct

18 and 19, respectively, to an interior space 17. When a plunger is at top dead centre position, the

ducts

18 and 19 are opened by the bottom edge of the plunger through an amount equal to h. In the interior 17 of the housing the control slide 29 common to all cylinders is guided for axial movement, but maintained against rotation by a bolt 21 engaging an axial groove 22 of the slide 20. The control slide has

radial ports

23 and 24 which register with the control ducts 1S, 19 in the position of the slide shown in FIGURE l.

FIGURE 3 shows in the section a the

control ducts

18, 19 in the development of the inner surface of the interior space 17, and also the development of the outer surface of the slide 20 together with the

ports

23, 24 in the lowermost position of the slide, in which the bores 18 and

ports

23, or 19 and 24, respectively, are in register. The sections b and c correspondingly illustrate the

ports

23, 24 of the slide in different vertical positions, and also the

control ducts

18, 19 as circles, drawn in dash and dot lines. The operating liquid is supplied to the interior space 17 by means of the radial bores 25 in the housing 1 which pass between the cylinders 6, 7.

The slide Ztl is urged by a spring 27 against a control cylinder 28 which is retained in the pump housing 1 by a snap ring 29. A step piston 3) is movable within the control cylinder 28. The distance f between its

control edges

32 and 33 corresponds to the distance g provided between

control edges

34 and 35 of transverse bores 36 and 37 of the control cylinder 28.

The control of the delivery of the pump is as follows:

At low operating pressure the control piston and the control slide 20 assume the lowermost position, as indicated in FIGURE 1. As shown in section a of FIGURE 3 and as pointed out above, in this position the

ducts

18, 19 communicating with the cylinders are in register with the

ports

23, 24 oi the slide 20, and the plungers deliver through the pressure valves 38 the maximum output into the pressure chamber 39. When the operating pressure of the pump in the pressure chamber 39 reaches a predetermined valve, the control piston 30 is forced upwardly by the uid pressure and moves the control slide 2l) upwards against the action of the spring 27. The

ports

23, 24 then arrive for instance in a position with respect to the

control ducts

18, 19 as shown in the developed view in section b of FIGURE 3. As will be readily understood, the admission of liquid to the control ducts 18 only is now restricted owing to the upwardly displaced control edges 23a of the ports 23; accordingly the delivery of the live large diameter plungers S is reduced. The admissionof liquid to the small diameter cylinders, however, approximately remains the same as in the lowermost position of the slide 20, so that the delivery of liquid by the live small plungers substantially remains unchanged.

When the operating pressure of the pump in the pressure chamber 39 rises still higher and the control piston 30 moves upwardly through the distance k, so that the edge 32 of the piston 30 meets the edge 34 of the duct 36, then the annular space 40 in the control cylinder 28 is cut ot trom its communication with the pressure chamber 39 of the pump, and pressure in this space is relieved through

ducts

37, 37a and 37b. The control piston 30 now moves suddenly through the distance i to its upper- "ports 24, and still are in full operation.

In a modification, thercontrol slide may be constructed so that the large plungers 8 only operate when 'the slide is in its uppermost position. Instead of making the diameter of the one group of plungers 9 smaller than the diameter of the plungers 8 of the other group, the diameter of 'both groups of plungers could also be the same.

When at still increasing operating pressure the output ofthe small diameter plunger also shall be reduced, this may |be obtained for example, as shown in FIGURE 7, by providing a bore through the control piston 30 and Y inserting a piston 44 in this bore, the lower end of the piston being subjected to `the pressure prevailing in the chamber 39. When the control piston 30 is in its uppermost position, the small piston 44 may continue to move upwards owing to the pressure in -the chamber 39, and the piston 44, in turn, causes the slide 20 to move further upwardly. The admission conditions to ythe small diameter 'cylinders will then change either-by a restriction of the inlet ducts bythe upper edge 42 of the control slide 20, or by a restriction'of the admission to the ducts 19 by the edges 43 at the lower endV of the grooves 22 of the control slide. It 'is possible in ,this matter, by providing some of the edges 43`at a lower level than the others, to still operate certain of the small diameter plungers at full delivery rate.` The piston 44 may also be constructed as ,step piston, of which the .thicker portion moves Within thethicker section of thepiston 30.

It is also possi-ble to adjust the position of the control slide, e.g. by manual actuation, when extending the piston 44 downwardly through a central bore in the cover 45 of the pressure chamber, as indicated by dot and dash lines in FIGURE 7. It thus may beactuated from its portion -projecting outwardly of the coverv 45.V The slide Z0, however, mayfalso be Voperated exclusively at will, when piston is omitted and only the piston rod 44 leading to the slide will be provided..

' The ,pump shown in FIGURE 1 operates automatically y so that its delivery decreases with increasing pressure. The manner 'of decrease in Ydelivery asV l'function of the pressure depends on the selection of the spring 27; ina modilication, foi-example, a plurality of springs could be provided which can be subjected to pressure at the usame time or one after another. s l s The'modication according to FIGURES 4 4tof@ also relates to an axial piston pump havingrcircularly arranged,

Y parallel plungers'which are driven from a Vswash'plate of Y Kconstantrinclination similar to FIGURE n l. 'For` this reasonthe lower section of the pump only is shown in VYFIGUIUE .4, In this case, however, Vlhe jcontrols'lide'is not arranged in thefinteriorY of Ithe housing YVso as to be 'axially' movable, but is positioned outside thereof and' Yformed asan annular slide'sSG which is angularly movable about the axisro'f the pump. Y The liquid tobe delivered Venters through'the intake sleeves 51 and passes through the admission valves 52 and the ducts 53 tothe cylinder spaces 54. The intake sleeves 51 are urged againstrthe annular vwall of the slide valve j50 `by theA springs 55 (see .Y

V.FIGURE '6),' whereby a reliable seal'is secured between the slideY and the Vintake sleeves, since the o uterrsurface of Vthese sleeveshas the ksame radius as the vinner'surfaceV of Vthe slideA 5,0.VV VSpring loaded discharge valves 57 are prol vided for the deliveryofthe liquidato the pressure'chamber 56, The pressure liquid leaves the pumpthroughthe 'two dschargeopenings 58. f

For the control of the annular slide 56 the latter is connected for example to yan automatic adjusting device, as shown in'FIGURE. 5. This device comprises an arm 6i) which is connected to a control piston 61. The pis- Iton is urged outwardly in a xed cylinder 62 by a spring 63 bearing against 'the top of the cylinder 62. The pressure chamber of this cylinder is connected by means of a conduit 64 with the pressure chamber 56 of the pump. The annular slide 5t) is provided with

admission ports

71, 75 and 79 which are larger in circumferential direction than the

ports

72, 73, 74, 76, 77, 7S, S0, 81 and 82. Due to vthe different size of the ports in circumferential direction not all inlet sleeves 51 are out out at the same time when the control valve is angularly moved in the direction of the arrow 65. In the position of the control valve 50 shown in FIGURE 5, the smaller admission ports 72- 74, 76-78 and Sil-82 have already been closed and the associated nine pistons v66 are relieved. Then the ad-V mission through the control port 71 is just being closed, while the

control ports

75 and 79 are still open. When the slide 50 owing to an increasing pressure is rotated still further in clockwise direction, the lport 75 will close and finally also the port 79. -By means Vof the described arrangement of staggered admission control edges it is possible to allow the pump to operate atreduced delivery Y against very high delivery pressure without requiring an lincrease in driving power.

Yof the pump housing as a further improvement in theV koperatlon of the pump. This device comprises a cylinder 83, a control piston 84 which is axially movable within said cylinder but not rotatable, and a piston rod 85 cooperating with a resetting spring 86. Each cylinder, which communicates with one of the smaller admission ports in the slide 50, is connected with the vinterior of the cylinder 83 by awduct 87and 88. The duct 88 opens into the bottom end -of the pump cylinder. For eachV duct 87, 88, the controlpiston 84.is provided with a small transverse bore 89 and longitudinalbore 90. All bores 90 at' their top end open in the inner spaceV of the pump and are coveredwith a rubber membrane 91 which Vpermits the discharge of liquid from the'rbores 90 in upward direction but prevents liquid lfrom entering into these bores.

This additional control device operates in therfollow- .ing manner: When the delivery pressure has increased to a predeternnned amount situated close to the maximum value and at the same time the'annular slide 5G has been automatically Vturned Vthrough such an angle that the smaller control ports 72-74, 76-78, 80-82 are already Y n the ducts 87. 'Incase that'the lsuction valves 52, the in- 'takesle'eves 51 vor the pressure'valves '57 should not keep quite tight and for this reason small amounts of delivered Y liquid should have penetrated to'theV cylinder spaces 54 during the suctionstroke of the pump, then these small amounts of liquid will be discharged without. any pressure through the ducts and bores S7-9i). Y InY the cut-out cylindersV no pressure action due to liquid entered therein canV be` formed and the pump Willhe protectedagainst impacts of liquid against the pistons ofthese cylinders.

The described device Vmay also'be applied to the typepoii` `fpump construction shown in FIGURE 1. Y A As further modification ofY a pistonpumpaccording' to` the invention, the` control slide may be used for variT A ably supplyingronly a portion of the pump cylinders While Ythe remainingcylinders operatecontinuously un-1 i changed adjustment, or are controlled in any other manner for varying the delivery.

I claim:

l. A pump comprising a pump housing, a plurality of parallel pump cylinders circularly arranged in said housing and divided into two groups of cylinders, pump plungers reciprocable in said cylinders, a rotatably mounted swash plate coacting with said pump plungers for reciprocating said plungers, said housing having uid admission ducts leading to each cylinder, a movable annular control sleeve having ports in the annular Wall thereof for controlling the supply of tluid through said admission ducts, pressure responsive piston means to move said annular control sleeve, each of said ports in said sleeve coacting with one of said fluid admission ducts whereby a movement of said control sleeve causes the sectional area of ow between said ports and said lluid admission ducts to vary, the ports of said control sleeve having closing edges which cooperate With the admission ducts leading to the cylinders of one of said groups being displaced with respect to the closing edges of the ports leading to the cylinders of the other of said groups, so that upon a movement of said control sleeve the admission ducts of one of said groups of cylinders are closed and those of the other group are open.

2. A pump comprising a pump housing, a plurality of parallel pump cylinders circularly arranged in said housing and divided into two groups of cylinders, pump plungers reciprocable in said cylinders, a rotatably mounted swash plate coacting with said pump plungers for reciprocating said plungers, said housing having fluid admission ducts leading to each cylinder, a movable annular control sleeve having ports in the annular wall thereof for controlling the supply of duid through said admission ducts, pressure responsive piston means to move said annular control sleeve, each of said ports in said sleeve coacting with one of said uid admission ducts whereby movement of said control sleeve causes the sectional area of flow between said ports and said fluid admission ducts to vary, the ports of said control sleeve having closing edges which cooperate with the admission ducts leading to the cylinders oi the first of said groups being displaced with respect to the closing edges of the ports leading to the cylinders of the second of said groups, the closing edges cooperating with the admission ducts leading to the cylinders of the second group moreover being displaced with respect to one another, so that upon a predetermined movement of said control sleeve the admission ducts of the rst of said groups of cylinders are closed and those of the second group are open, while on further movement of said control sleeve the admission ducts of the cylinders of the second group will successively and gradually be closed.

3. A pump in accordance with claim 2, in which said control sleeve is mounted for axial displacement in said housing.

4. A pump in accordance with claim 2, in which said plungers and cylinders of one of said groups have a diameter differing from the diameter of the plungers and cylinders of the other of said cylinder groups.

5. A pump in accordance with claim 2, in which means are provided for the pressure responsive piston means to respond to an increase of delivery pressure to move said annular control sleeve.

6. A pump in accordance with claim 2, in which said control sleeve is angularly movable and iixed against axial displacement, and in which the ports in said sleeve coacting with the uid admission ducts leading to the second group of cylinders are larger in circumferential direction, than the ports in said sleeve coacting with the iiuid admission ducts leading to the tirst group of cylinders.

7. A pump comprising a pump housing, a plurality of parallel pump cylinders circularly arranged in said housing and divided into two groups of cylinders, purnp plungers reciprocable in said cylinders, a rotatably mounted swash plate coacting with said pump plungers for reciprocating said plungers, said housing having fluid admission ducts leading to each of said cylinders, an axially movable annular control sleeve having ports in the annular wall thereof for controlling the supply of iluid through said admission ducts, an axially movable step piston to move said control sleeve, said step piston having one end of relatively greater diameter and one end of relatively smaller diameter, an annular groove upon said piston separating said ends, said piston end of greater diameter being directly exposed to the delivery pressure of the pump and the smaller piston end abutting against said control sleeve, a supplementary duct connecting said annular groove under normal operating conditions with the delivery pressure, said piston end of greater diameter, upon a predetermined axial stroke caused by increased delivery pressure, raising said control sleeve and closing said supplementary duct whereby the piston is subjected to full delivery pressure acting solely on said end of greater diameter to further raise said control sleeve.

8. A pump in accordance with claim 7, in which said step piston has a cylinder provided with au abutment which limits an additional iinal stroke of the step piston after this latter has closed said supplementary duct, said piston in the final stroke position completely closing the control ducts of the large diameter plungers.

9. A pump in accordance with claim 2, in which said control sleeve is operatively connected with a separate regulating device subjected to the delivery pressure of the pump.

10. A pump in accordance with claim 2, in which said control sleeve has an annular Wall provided with a plurality of admission ports, certain ot said admission ports being larger in circumferential direction than the other ports, so that the closing edges of the larger ports become effective in staggered relation with respect to those of the smaller ports.

11. A pump in accordance with claim 2, having its cylinders at least partly provided with suction valves and said control sleeve is arranged outside of the cylinder and plunger assembly of the pump.

12. A pump in accordance with claim 11, in which said annular control sleeve surrounds said suction valves for the admission or" liquid, and intake sleeves are provided between said control sleeve and said suction valves radially supported in said suction valves and resiliently bear against the inner surface of said control sleeve.

References Cited in the file of this patent UNITED STATES PATENTS 1,913,003 Shai June 6, 1933 2,093,477 Parsons Sept. 21, 1937 2,268,000 Treer Dec. 30, 1941 2,357,563 Truxell Sept. 5, 1944 2,448,347 Beeh Aug. 31, 1948 2,518,619 Huber Aug. l5, 1950 2,684,630 Widmer et al. July 27, 1954 2,940,396 Misulis June 14, 1960 FOREIGN PATENTS 585,128 Canada Oct. 13, 1959 808,811 France Feb. 16, 1937 516,721 Great Britain Jan. 10, 1940 516,764 Great Britain Ian. 10, 1940 346,434 Switzerland June 30, 1960

Claims

1. A PUMP COMPRISING A PUMP HOUSING, A PLURALITY OF PARALLEL PUMP CYLINDERS CIRCULARLY ARRANGED IN SAID HOUSING AND DIVIDED INTO TWO GROUPS OF CYLINDERS, PUMP PLUNGERS RECIPROCABLE IN SAID CYLINDERS, A ROTATABLY MOUNTED SWASH PLATE COACTING WITH SAID PUMP PLUNGERS FOR RECIPROCATING SAID PLUNGERS, SAID HOUSING HAVING FLUID ADMISSION DUCTS LEADING TO EACH CYLINDER, A MOVABLE ANNULAR CONTROL SLEEVE HAVING PORTS IN THE ANNULAR WALL THEREOF FOR CONTROLLING THE SUPPLY OF FLUID THROUGH SAID ADMISSION DUCTS, PRESSURE RESPONSIVE PISTON MEANS TO MOVE SAID ANNULAR CONTROL SLEEVE, EACH OF SAID PORTS IN SAID SLEEVE COACTING WITH ONE OF SAID FLUID ADMISSION DUCTS WHEREBY A MOVEMENT OF SAID CONTROL SLEEVE CAUSES THE SECTIONAL AREA OF FLOW BETWEEN SAID PORTS AND SAID FLUID ADMISSION DUCTS TO VARY, THE PORTS OF SAID CONTROL SLEEVE HAVING CLOSING EDGES WHICH COOPERATE WITH THE ADMISSION DUCTS LEADING TO THE CYLINDERS OF ONE OF SAID GROUPS BEING DISPLACED WITH RESPECT TO THE CLOSING EDGES OF THE PORTS LEADING TO THE CYLINDERS OF THE OTHER OF SAID GROUPS, SO THAT UPON A MOVEMENT OF SAID CONTROL SLEEVE THE ADMISSION DUCTS OF ONE OF SAID GROUPS OF CYLINDERS ARE CLOSED AND THOSE OF THE OTHER GROUP ARE OPEN.