US3434428A - Intake control for multiple piston pump - Google Patents

Description

March 25, 1969 c, |1 3,434,428

INTAKE CONTROL FOR MULTIPLE PISTON PUMP Filed June 5, 1967 Sheet of 4 m rewrae. 4J (bra/ray b/ef March 25, 1969 c. E. LILES 3,434,428

INTAKE CONTROL FOR MULTIPLE PISTON PUMP Filed June 5, 1967 Sheet 2 of4 m nswraz 4 flare/me 61 Z//e.r

% yfkp ds Ta/a/ Lfdl C. E. LILES INTAKE CONTROL FOR MULTIPLE PISTON PUMP 4. w x I w w m wmn mm/ DZ 7 w w r e m wdfi/ w fimr an fl 3m W #6 ,7 a? w March 25, 1969 Filed June 5, 1967 March 25, 1969 c. E. LILES 3,434,428

INTAKE CONTROL FOR MULTIPLE PISTON PUMP Filed June 5, 1967 Sheet io4 Anne/veg:

nited States Fatent U US. Cl. 10340 7 Claims ABSTRACT OF THE DISCLOSURE An automatic control for a multiple cylinder pump maintains substantially constant output pressure by regulating the intake flow in response to changes in the output pressure. A small intake port for each cylinder is used for stable operation of the pump at extremely low rates and an adjacent larger intake port for each cylinder is used additionally for larger output rates. An intake valve has an opening movement which uncovers the small ports and the large ports progressively in overlapping sequence with a resultant combined rate of flow which varies with the opening movement of the valve in accord with a curve having a desirable gradually rising toe with the rest of the curve inclined at a desirably moderate slope.

Background of the invention The invention relates to multiple cylinder pumps including both radial cylinder pumps and axial cylinder pumps wherein an automatic control maintains substantially constant output pressure by varying the rate of output of the pump in response to variations in the output pressure. More specifically, the invention relates to such a multiple cylinder pump in which the output pressure is regulated by controlling the rate of intake flow to the multiple cylinders. For this purpose a single intake valve simultaneously controls the inflow to the multiple cylinders respectively.

The problem to which the invention is directed is the instability in the operation of the automatic control that occurs at extremely low levels of the volumetric output of the pump when the pump is operating at below ten percent of its capacity. A time lag occurs in the rise in pump output in response to changes in the low level demand, which time lag causes instability of the operation of the control mechanism, the control mechanism overshooting and becoming out of phase with the delivery of the pump pistons.

By careful investigation it has been discovered that the time lag occurs because the intake port is so much larger than necessary to accommodate extremely low rates of intake flow and is in addittion to the inherent piston fill lag time. The nature of the cause of the volume time lag may be understood when it is considered that the intake port to each cylinder is periodically uncovered by the corresponding piston only when the piston is retracted during one-third of its cycle, the retraction of the piston creating a vacuum with the pressure in the cylinder dropping as low as a fraction of a p.s.i.a. When the intake valve is adjusted for a moderately high rate of intake flow, the intake fluid flows freely through the cavity into the evacuated cylinder with no troublesome time lag. When the intake valve is adjusted for a very low rate of intake flow, however, the restricted intake stream expands in the intake port cavity because the abrupt pressure drop and the expansion releases the approximately 10% of dissolved air content of the hydraulic fluid to cause the hydraulic fluid to froth and behave more like a gas than a liquid. The time required for expansion of the restricted stream of fluid in the relatively large intake port cavity results in a time lag of 200 to 300 milliseconds which is suificient to cause the undesirable instability of the control loop.

Snmmaiy of the invention The invention meets the foregoing problem by providing a plurality of intake ports for each cylinder with a single valve member controlling all of the ports and preferably by also placing the intake valve close to the cylinders to minimize the axial dimensions of the intake ports. In the presently preferred embodiment of the invention there is a pair of intake ports for each cylinder comprising a small intake port of low intake capacity and a larger intake port.

With progressively increasing demand starting from an extremely low level, the intake valve progressively uncovers the small port and the large port for each cylinder in overlapping sequence. Thus when the pump is operat ing at an extremely low rate in the range of below ten percent of its volumetric capacity, flow into each cylinder is solely through the corresponding small intake port and the size of the small intake port matches the rate of intake flow closely enough to avoid a troublesome degree of fluid expansion. As demand increases with progressive unmasking of the small port, progressive unmasking of the larger port is initiated before the smaller port is completely uncovered. Thus the progressive uncovering of the small port overlaps the progressive uncovering of the larger port.

The relative flow capacity of the two intake ports and their relative positions for the overlapping sequence are such that the rise in total flow with increasing demand is represented by a curve having a desirably prolonged and graduated toe with the main portion of the curve rising at a desirably moderate slope. During transient conditions when additional flow through the larger port is required to meet the demand, the small port provides sulficient intake flow to sustain the output of the pump and to sustain the pressure signal from the output manifold while the larger port is being brought up to operating pressure.

In a radial piston pump the intake valve that is common to all of the cylinders is preferably in the form of a rotary valve disk mounted in the intake manifold of the pump. In an axial piston pump the intake valve is preferably an axially movable sleeve cooperating with an inner circumferential wall from which the pairs of intake ports radiate to the several cylinders.

The features and advantages of the invention may be understood from the following detailed description and the accompanying drawings.

Brief description of the drawings In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is an axial cross section of a radial piston pump embodying the invention;

FIG. 2 is an elevational view of the intake valve and the pairs of intake ports that are controlled by the valve;

FIG. 3 is a fragmentary sectional view perpendicular to the axis of one of the cylinders as seen along the line 33 of FIG. 5 and showing the two intake ports in longitudinal section;

FIG. 4 is a section along the line 4-4 of FIG. 1 and the line 44 of FIG. 3, the section being perpendicular to the two intake ports;

FIG. 5 is a fragmentary view like FIG. 2 showing the valve member at a diiferent position;

FIG. 6 is a diagram that illustrates the cycle of operation of a piston in a cylinder with reference to the opening of the associated pair of inlet ports;

FIG. 7 shows curves representing the pressure and rate of flow through the two intake ports respectively throughout the range of adjustment of the intake valve;

FIG. 8 is a view similar to FIG. showing different configurations for the intake valve and a large intake port;

FIG. 9 is a transverse section of an axial piston pump embodying the invention with a section broken away to disclose the porting arrangement;

FIG. 10 is a fragmentary view showing the relation of a sleeve-type intake valve in FIG. 9 to a pair of the intake ports; and

FIG. 11 is a view similar to FIG. 4 showing the relation of a pair of intake ports to the piston in a cylinder.

Description of the preferred embodiments The first embodiment of the invention shown in FIGS. 1-5 is a six-cylinder radial piston pump wherein the discharge end of each of the cylinders is normally closed by a discharge valve 22 under the pressure of a coil spring 24. The discharge valve controls communication with a corresponding discharge passage 25 that leads to a common annular high pressure manifold 26. The pistons in the various cylinders 20 are actuated by an eccentric 32 on a drive shaft 34 that is journalled in suitable bearings 35, the axis of the shaft being the operating axis of the pump. In a well known manner the eccentric 32 is embraced by a roller bearing comprising a circumferential series of rollers 36 and an outer race in the form of a sleeve 38. In the construction shown the sleeve 38 is equipped with a pair of flanged rings 40 which engage circumferential grooves 42 in the inner ends of the pistons to retract the pistons after they are driven radially outward by the action of the eccentric.

An annular low pressure intake manifold 44 has a planar annular face 45 from which pairs of intake ports extend to the respective cylinders 20 under the control of a rotary intake valve 46 that presses against the annular face. In a well known manner, a control system for maintaining substantially constant pressure in the high pressure manifold 26 includes a pressure-sensing means represented diagrammatically by a block 48 which responds to the pressure in the high pressure manifold and which controls a hydraulic actuator 50. The hydraulic actuator 50 regulates the position of the intake valve 46 by engagement with a control pin 52 that extends laterally from the intake valve.

FIGS. 3 and 4 show how each of the cylinders 20 is provided with a small intake port 54 and an adjacent large intake port 55, the two intake ports being in the form of bores that open to the annular face 45 of the intake manifold 44. It is to be noted that when a piston 30 retracts from the corresponding discharge valve 22 the piston initiates uncovering of the two intake ports 54 and 55 simultaneously as may be seen in FIG. 4. The diagram in FIG. 6 shows the piston cycle and shows how the two inlet ports communicate with a cylinder during one-third of the piston cycle when the piston is retracted from the corresponding discharge valve.

As may be seen in FIG. 2, the rotary intake valve 46 has a circumferential series of peripheral masking portions 56 separted by gaps 58 for cooperation with the various pairs of intake ports 54 and 55. FIG. 2 shows the position of the intake valve 46 relative to the pairs of intake ports 54 and 55. In FIG. 2 the intake valve 46 is adjusted for a moderately high rate of intake flow with all of the small intake ports 54 at the gaps 58 and with each of the large intake ports 55 partially covered by a masking portion 58 of the valve.

FIG. 5 shows the position of the intake valve 46 for an exceedingly low rate of intake flow, each of the small intake ports 54 being partially covered by a masking portion 56 of the valve member and each of the larger intake ports 55 being completely covered by a masking portion. It is apparent from FIGS. 2 and 5 that when the intake valve 46 progressively rotates counterclockwise from a completely closed position it first initiates uncovering of the small intake ports 54 and then before the small intake ports are completely uncovered the intake valve initiates uncovering of the larger intake ports 55.

Referring now to FIG. 7 the curve 60 shows the delayed rise of pressure in a large intake port 55 that accounts for the troublesome time delay that would occur if solely the large intake port was relied upon for intake flow at an extremely low flow level. The curve 62 shows the abrupt rise of pressure in a small intake port 54 that eliminates the time lag that is inherent in the functioning of the larger intake port.

The curve 64 shows the delayed rise in rate of fiow through a large intake port 55 as the intake valve is moved progressively from completely closed position towards fully open position, the curve showing how initiation of flow through the large intake port is delayed by the delayed uncovering of the large port. Curve 65 in FIG. 7 shows how the flow through a small intake port 54 is initiated as soon as the valve moves out of its completely closed position and shows how the flow initially rises at a desirably graduated rate. Curve 66 shows the result or combined flow through the two intake ports, the curve being ideal for the purpose of the invention since the curve has a prolonged graduated toe 68 with the rest of the curve at a moderate slope.

FIG. 8 shows different configurations that may be employed for the intake valve and the larger intake port of each pair of intake ports. In FIG. 8 the small intake port 54a is of the usual circular cross-sectional configuration at the planar face of the intake manifold but the larger intake port 55a is tapered in cross section as shown with the tapered portion in overlapping relation to the smaller intake port. The rotary intake valve 46a in FIG. 8 is shaped and dimensioned to initiate uncovering of the small intake port 54a and then before the small intake port is completely uncovered the intake valve initiates uncovering of the tapered portion of the larger intake port 55a. Thus the arrangement shown in FIG. 8 functions in the same general manner as the arrangement shown in FIGS. 2 and 5.

FIGS. 911 show how the basic concept of the invention may be embodied in an axial piston pump, generally designated 70, that has a circumferential series of cylinders 72 that are parallel to and equally spaced from an operating axis represented by the dot 74. The pump has a concentric low pressure intake manifold 75 that has a cylindrical inner circumferential surface 76 with pairs of intake ports comprising small intake ports 54]) and large intake ports 55b extending from the cylindrical surface to the various cylinders 72. Each of the larger intake ports 55b includes a crescent shaped recess 78 in the Wall of the corresponding cylinder. FIG. 11 shows the positions of the two intake ports 54!) and 55b relative to the corresponding piston 80 in each of the cylinders 72.

All of the pairs of intake ports 54b and 55b are controlled simultaneously by an intake valve 84 in the form of an axially slidable sleeve that fits snugly against the inner circumferential wall 76 of the intake manifold. FIG. 10 shows the relation of a pair of the intake ports 54b and 55b to the intake valve 84 and shows how the rim of the intake valve may be formed with a semi-circular recess 85 to cooperate with each of the small intake ports 54b. It is apparent in FIG. 10 that retraction of the intake valve 84 towards its fully open position first initiates uncovering of a small intake port 5412 by the corresponding recess 85 of the valve and then before the small intake port is completely uncovered the valve initiates uncovering of the larger intake port 55b. Thus the intake valve 84 regulates the intake flow in the same general manner as in the first described embodiment of the invention.

I claim:

1. In a multiple cylinder pump wherein the intake ports of the respective cylinders are controlled by an intake valve for control of the output pressure and a control system regulates the intake valve in response to changes in the output pressure, the improvement to minimize instability in the operation of the control system at low flow adjustments of the intake valve, comprising:

each of the cylinders having a pair of intake ports comprising a relatively small intake port and a separate larger intake port, said small intake port being positioned relative to the intake valve to be progressively opened thereby as intake flow is increased from substantially zero,

said large intake port being positioned relative to the intake valve to be progressively opened and to be initially opened subsequent to the initial opening of the small intake port as the intake flow is increased, the progressive opening of the two ports overlapping to result in smoothly increasing total flow through the two ports with no substantial time lag between a drop in the output pressure of the pump and the consequent opening movement of the intake valve when the pump output is at a low level.

2. An improvement as set forth in claim 1 in which the axes of the multiple cylinders are arranged radially of an operating axis and the corresponding multiple pairs of intake ports open onto a planar surface that is parallel to the cylinders with the pairs of intake ports arranged in a circle on said surface,

and in which said intake valve is rotatable about the operating axis in abutment with said surface and has circumferentially spaced masking portions to control flow into the pairs of intake ports,

each of said masking portions having an edge positioned to unmask a substantial portion of the corresponding small intake port before unmasking the corresponding large intake port.

3. An improvement as set forth in claim 1 in which the axes of the multiple cylinders are parallel and equally spaced from an operating axis,

in which the corresponding multiple pairs of intake ports open onto a cylindrical surface concentric to the operating axis,

and in which said valve means is a sleeve axially movable along the cylindrical surface with an edge portion of the sleeve positioned to cooperate with each of the pairs of intake ports,

each of said edge portions being shaped and positioned to unmask a substantial portion of the corresponding small intake port before unmasking the corresponding large intake port.

4. An improvement as set forth in claim 1 in which said ports of each of said pairs of ports are dimensioned and located relative to the corresponding masking portion of the intake valve for a total flow which varies with the opening movement of the intake valve in accord with a curve having a toe portion of low inclination and a main portion of greater but moderate inclination.

5. An improvement as set forth in claim 4 in which the flow through each of the large intake ports varies with the opening movement of the intake valve in accord with a curve having a main portion of approximately the inclination of said main portion of the first mentioned curve and the flow through each of the small intake ports varies with opening movement of the intake valve in accord with a curve that has a relatively long toe and rises to a relatively low plateau.

6. In a pump having a radial array of cylinders with pistons therein, said pump having an arcuate intake manifold and a control system which regulates the rate of output of the pump by varying the rate of the pump intake in response to changes in the output pressure, the improvement to promote stability in the operation of the control system at low output rates, comprising:

said intake manifold having a planar face on the side thereof adjacent the cylinders,

pairs of intake ports extending from said face to said cylinders respectively,

one intake port of each pair being of relatively small cross section to provide intake flow at the lower end of the range of pump output, the other port of each pair being of relatively large cross section to provide additional intake flow at higher rates of pump output; and

a rotary valve member regulated by said control systern, said valve member being in abutment with said planar surface and having masking portions corresponding to the respective cylinders,

each of said masking portions being shaped and dimensioned to uncover the corresponding small intake port and large intake port progressively in overlapping sequence.

7. In a pump having multiple cylinders, the axis of which are parallel and equally spaced from a central axis, said pump having an intake manifold and a control system which regulates the rate of output of the pump by varying the rate of pump intake in response to changes in the output pressure, the improvement to promote stability in the operation of the control system at low output rates, comprising:

said intake manifold having an inner circumferential cylindrical surface concentric to said central axis, pairs of intake ports extending from said cylindrical surface to said cylinders respectively, one intake port of each pair being of relatively small cross section to provide intake flow at the lower end of the range of pump output, the other port of each pair being of relatively large cross section to provide additional intake flow at higher rates of pump output, and a cylindrical valve member movable axially along said cylindrical surface and regulated by said control system with portions of the valve member positioned to mask and unmask the pairs of ports respectively,

each of said masking portions being shaped and dimensioned to uncover the corresponding small intake port and large intake port progressively in overlapping sequence.

References Cited UNITED STATES PATENTS 2,433,220 12/ 1947 Huber. 2,677,326 5/ 1954 Schindele. 3,050,004 8/ 1962 Heintzmann. 3,151,569 10/1964 Muller.

FOREIGN PATENTS 475,311 6/ 1946 Canada. 808,811 10/1935 France.

WILLIAM L. FREEH, Primary Examiner.

US Cl. X.R. 103-174

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