US2762305A - Variable delivery pump system, including a standby unit - Google Patents

Description

Sept 11, 1956 H. E. HUBER ETAL 2,762,305

VARIABLE DELIVERY PUMP SYSTEM, INCLUDING A STANDBY UNIT Filed Dec. 4, 1952 Nwm ill.'

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rNvENToRs How ard E.Huber and JohnToper ATTORNEYS United States Patent O VARIABLE DELIVERY PUR/IP SYSTEM, INCLUDING A STANDBY UNTI' Howard E. Huber and John Toper, Watertown, N. Y.,

assignors to The New York Air Brake Company, a co1'- poration of New Jersey Application December 4, 1952, Serial No. 323,998 4 Claims. (Cl. 10S- 11) This invention relates to pump systems and will be described as embodied for furnishing parasite power on helicopters, airplanes, and the like.

In installation of the above type a common practice is to use a variable delivery pump driven by a propelling engine and controlled by the pressure which the pump itself develops. Obviously failure of such a pump cre# ates a very dangerous condition. The invention permits the use of a standby pump, which operates at zero delivery unless and until the main pump fails to maintain the desired pressure.

The invention contemplates the use of two variable delivery pumps, which may be identical and which are each continuously driven. The two pumps are connected in parallel with the same delivery line, each through a check valve so that back-flows and cross-flows are inhibited.

Each pump has stroke-varying regulating means, responsive to pressure in its own discharge connection, the responsive element of each pump being elastically loaded so that it can move and start to reduce pump delivery in response to discharge pressures above a first chosen value. This first chosen value can be, and commonly is quite close to the pressure which it is desired to maintain.

The primary pump is always so loaded, but the secondary pump includes neutralizing means for its loading means, responsive to the delivery-pressure of the primary pump. As long as this pressure is above a second chosen value, lower than said first chosen value, the neutralizing means overpowers the elastic loading means of the secondary pump, so that the stroke-regulating means of the secondary pump moves to zero-delivery position and remains there. Thus the secondary pump normally operates at zero delivery. By proper dimensioning it is possible to choose a third and still lower delivery pressure value which will permit the secondary pump to deliver full stroke.

In effect, the control range for the two-pump system is divided into a higher pressure part (above the second chosen pressure) in which the control mechanism of the primary pump exercises sole control, and a lower pressure part (below the second chosen pressure), in which the control mechanism of the secondary pump takes over to whatever extent the disablement of the primary pump requires.

One advantage offered by the invention is that the neutralizing means is an expansible chamber motor capable of ready association with the control mechanism of a standard pump. The preferred installation comprises two basically identical variable delivery'pumps, one with a manual adjusting means for the loading spring, and the other having substituted for such manual adjusting means a neutralizing motor capable of suspending the function of the pump-loading spring. Means affording ICC `advantage of this is obvious.

The invention will now be described by reference to the accompanying drawing in which Fig. 1 is a view part in section and part in elevation showing the disabling motor applied to a variable delivery pump.

Fig. 2 is a diagram of the system.

All statements of direction refer to the pump as positioned in Fig. 1.

The pump shown in partial section in Fig. l is constructed according to the M. W. Huber Patent 2,433,222, December 23, 1947, which is selected as typical of variable displacement pumps having a displacement-controller shiftable to vary displacement between zero and full capacity.

The pump has nine plungers parallel with the axis of the drive shaft, and these plungers are reciprocated by a swash plate fixed to the shaft and reacting against the plungers, each of which may be spring-returned. This driving mechanism is not illustrated.

The housing v6 encloses the swash plate. The outer end of the rotary drive shaft, on which the swash plate is fixed, appears at 7. One of the plungers 8 is on the plane of section in Fig. 1 and other plungers are visible. All the plungers have a uniform actual reciprocating .stroke, but their effective strokes are varied in unison 'by spill-back valves 9 which are sleeves through which the plungers reciprocate. These sleeves control spillback ports 11 each of which leads from the working space at the end of a plunger to lateral outlets 12 controlled by the sleeve 9. The lateral ports 13 are auxiliary inlet and lubricating ports.

The housing made up of the body closes a cylinder block 15 formed with cylinder bores 6 and cap 14 enguideways 16 and 17 separated by inlet chambers 18. The

- inlet connection 19 communicates by axial bore 21 and branches 22 with the inlet chamber 18. Discharge valves 23, urged closed by springs 24, seat across the entire end area of the corresponding cylinder bore 17 and are mounted in an annular discharge passage 25 which is connected with discharge connection 26.

The spill-back valve sleeves 9, one of which encircles each plunger are actuated in unison by a spider 27 which engages a groove in each sleeve and which is mounted on the end of an axially shiftable stern 28. This stem is shiftable in a cylinder unit 29 and is coaxial with bore 21 and shaft 7. The right hand portion of stem 28 is slightly larger in diameter than the left hand portion and affords a shoulder at 31 which serves as an annular piston on which discharge pressure acts to urge the stem 28 to the right. Pressure liquid from the discharge passage 25 enters via choke 32 and ports 33, 34.

A spring-seat 35 is mounted on the end of stem 2.8 and receives the thrust of two springs 36 connected in tandem by guide 37.

In the upper one of the two pumps shown in Fig. 2 the right hand end of the spring assembly 36-37-36 is sustained by an adjustable spring seat 38, screwed into the threaded opening 39, and functionally identical with the parts numbered 58, 59, 61, 62 and 63 of the identiiied Huber patent.

ln short the pump so far described; i. e. the upper pump in Fig. 2 is essentially the pump yof the identified Huber patent without material change.

In the lower one of the two pumps shown in Fig. 2, which is the pump shown in greater detail in Fig. l the seat 3S is replaced by the housing 41 which contains both an adjustable spring seat and the spring neutralizing motor. Except for Ithis it is essentially the pump of the identified Huber patent.

Thus, in each pump of Fig. 2, the range of motion of stem 28 and spider 21 is such as to carry the sleeves 9 from the position in which the plungers deliver full stroke (sce Fig. l) to the position in which vthe delivery is zero.

The housing 41 is screwed into the threaded lopening 39 and has a bore, coaxial with the bore 21, and made up of two end portions 42, 43 conveniently equal in diameter and a smaller diameter threaded portion 44. into this threaded portion is screwed a combined end closure and adjusting member 45. This carries two spaced toric gaskets 46 of rubber-like material mounted in grooves and sealing member 45 to the walls of bore 43.

The left hand or inner end of member 4S engages the outer end of member 47 formed with a shoulder 48 on which seats the outer end of the spring assembly 36-37-36- Turning of member 45 shifts member 47 axially and sp adjusts the stress developed by the loading springs 36. Member 47 has a two-diameter axial bore to receive the differential piston having a smaller diameter at 49 with a slightly larger head 51-see Fig. l.

Because of the high pressures contemplated the eiective area of the piston shoulder at 52 must be very small.

Actuating pressure is delivered by line `53 to chamber E4 in member 45, thence through the interval between gaskets via ports 55 and 56 to side passage-57. The member 47 is sealed in bore 42 by two spaced toric gaskets 58, 59 and passage 57 communicates with the cylinder space around piston shoulder 52 through the interval between these gaskets via ports 61, 62. Consequently pressure in connection 53 urges pistonhead 51 to the right.

Stem 49 is connected with spring seat 35 by tension rod 63 which is threaded into the end of stem 49 and locked by nut 60. The differential piston 49, 51has an axial bore for venting purposes. Other vents are provided as needed and are shown on the drawing.

The basic component of a typical installation are illustrated in Fig. 2. The sump from which hydraulic liquid is drawn by the pumps and to which it is discharged is not illustrated. Instead the sump connections are indicated by legends. standby pump B draw hydraulic liquid (oil) from the sump and respectively deliver it through line 65 and check valve 66 and through line 67 and check Valve 463 to line 69 leading to the multiway valve 71. Line 65 is connected to branch 53 to motor 41.

Valve 71 has connections 72 and 73 to the'opposite ends of a double-acting cylinder motor 74 and a connection 75 to sump. The valve has a lap position in which all corrections are closed, and two relativelyreverse operating positions in which a selected one of the two cylinder working spaces is connected to-supply line 69 and the other to sump.

Both pumps are driven continuously. So long as pump A maintains the desired pressure, this pressure is effective to move .pistonhead 51 to the right collapsing springs 36 and maintaining pump B unloaded. Spring seat 47 can be adjusted to cause pump B to start delivering when pressure in line 65 falls to some chosen value. Use of selected springs 36 in pump B may be availed of to cause pump B to deliver full stroke at any desired still lower chosen value.

The spring seat is not fixed to the stem Z8, but when seat 35 is drawn to the right stem 28 will follow it and maintain engagement. There must be pressure to move piston 51 to the right, from which it follows that The main pump A and the at such time shoulder 31 is also under pressure and so maintains engagement of stem and seat. "This circumstance avoids the need of connecting seat and stem, with the result that the spring assemblies may readily be withdrawn. The adjusting means 38 on pump A is interchangeable with the motor unit 41 on pump B, each in conjunction with its own spring assembly.

Pump failures are infrequent but in aeronautical installations they would be fraught `with great danger. The loaded pump A would be the one most likely to fail. Depending onwhat happens to pump A, line 65 may gradually lose pressure, or it may be `suddenly vented. In the iirst case pump B would gradually pick up the load commencing after pressure in line 65 fell below a chosen value. Should pressure in the line far enough, pump B would control on substantially the same pressure pattern as pump A had done. In the second case pump B would take over the entire load immediately' and would control on a pressure pattern substantially identical with that of pump A.

It is this substantial identity of control pattern that justifies the use-of a second pressure motor. It would be mechanically simpler to use two .identical pumps A vand B, pump A set to control at say 3000 p, sfi. and pump B at say 2000 p. s. i. Pump B would run idly as long as pump A kept pressure above 2000 p. s. i. However, when and if pump B took over it could only be on a 2000 p. s. i. basis.'

The arrangement according to the invention is not s limited.

The pumps illustrated are chosen as a basis for dis-' closing the invention because 'they have good control characteristics over the full range yof delivery, and are available commercially. Any variable delivery pump with similar control characteristics may be used according to the invention.

What is claimed is:

l. The combination of two continuously driven positive displacement pumps, namely a main pump vand a standby pump, ,eachl pump including a discharge connection, a controller included on each pump, and movable to vary the displacement of the corresponding pump `per cycle between zero and full displacement, pressure motor means in communication with, and subject to pressure 1n the corresponding discharge connection and connected with the controller of the corresponding pump to urge said controller in the direction to reduce displacement, and a loading spring mechanism opposing and normally overpowering the corresponding motor when pressure in the discharge connection is below a chosen value; fa delivery line; one way ilow connections, one between the discharge connection of each pump and said delivery line; and a-n expansible chamber motor, having an eifective area larger than the effective area of said pressure motor means, in Viluid communication with and subject to pressure in the discharge connection of the main pump and including a part moved -by the motor and adapted to react upon and neutralize the loading spring mechanism of the standby pump when the last named pressure is above a chosen subnormal value.

2. The combination defined in claim l in which the expansible chamber' motor comprises a cylinder and a piston located at one end of the loading spring mechanism of the standby pump, the piston having a oneway connect-ion with the other end of said loading spring mechanism such that motion of the piston under pressure overpowers said spring mechanism and suspends its loading action.

3. The `combination defined in claim l in which the expansible chamber motor comprises a cylinder and a piston, the cylinder having a seat for the loading spring mechanism of the standby pump and an adjustable support whereby said seat for the loading spring mechanism is rendered adjustable, and the piston having a one-way connection withthe remote end of the loading spring References Cited in the file of this patent UNITED STATES PATENTS Vickers Sept. 13, 1932 Huber Dec. 23, 1947 Kellogg Nov. 8, 1949 Orr Mar. 20, 1951 Carey May 19, 1953

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