US2403371A

US2403371A - Variable output pump

Info

Publication number: US2403371A
Application number: US467408A
Authority: US
Inventors: Richard Joseph Ifield; Walter Edward Wilfrid Nicolls
Original assignee: Joseph Lucas Ltd
Current assignee: ZF International UK Ltd
Priority date: 1941-09-16
Filing date: 1942-11-30
Publication date: 1946-07-02
Anticipated expiration: 1963-07-02
Also published as: SE155476C1

Description

July 2, 1946. R. J. IFIELD ET AL VARIABLE OUTPUT PUMP 3 Sheets-Sheet 1 Filed Nov. 30, 1942 inve zvz'a a RJZiLehZ July 2, 1946.

R. J. lFlELD ETAL VARIABLE OUTPUT PUMP Filed Nov. 30, 1942 3 Sheets-Sheet 2 1712. hzflllco L a y 1946- R. J. IFIELD ETAL 2,403,371

VARIABLE OUTPUT PUMP Filed Nov. 30, 1942 3 Sheets-Sheet .5

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I Patented July 2, 1946 VARIABLE OUTPUT PUMP Richard Joseph Ifield, Solihull, Birmingham, and Wilfrid Edward Walter Nicolls, Ealing, London W. 5, England, assignors to Joseph Lucas Limited, Birmingham, England Application November 30, 1942, Serial No. 467,408 In Great Britain September 16, 1941 6 Claims.

This invention relates to variable-output pumps of the swash-plate type, and has for its object to enable such a pump to be controlled in a simple and convenient manner.

The invention comprises a variable-output pump of the above mentioned type having in combination with it a cylinder which at one end is adapted to communicate with the delivery side of the pump, a fluid vent at the other end of the cylinder, a spring-loaded piston slidable in the cylinder under fluid pressure and adapted to vary the position of the swash plate of the pump, means for eflecting a restricted communication between the two ends of the cylinder, a movable closure member for controlling the vent, and means responsive tofiuid pressure for actuating the closure member,

In the accompanying sheets of explanatory drawings:

Figure 1 is a sectional side elevation of a variable-output pump embodying the invention and adapted to supply liquid fuel to a prime mover.

Figure 2 is a section on the line 3-3 of Figure 1.

Figure 3 is a similar view to Figure 1 illustrating a modification.

Figures 4 to 6 are sectional views illustrating.

modified details of the pump shown in Figure 1 or Figure 3.

The pump shown in Figures 1 and 2 comprises a rotary body arranged in a casing p and having formed around its axis a plurality of bores as q in each of which is arranged a reciprocatory plunger as 1'. When the body 0 is rotated the plungers r are moved in one direction by an angularly adjustable swash plate s and in the other direction by springs as t, the latter being situated within the body bores q, and serving to hold an end face of the body in contact with an end face u of the casing 10. The end face u of the casing is formed with an arcuate inlet port (not shown) communicating with a liquid inlet 27 in the casing, and is also formed with an arcu-' ate outlet port w communicating with a liquid outlet (not shown) in the casing.

The purpose of the invention as applied to the pump shown in Figures 1 and 2 is to control the output of the pump in response to fluid pressure determined by the speed of rotation of the pump body 0. For developing this fluid pressure a centrifugal pump may be formed in or combined with the rotary body 0. Thus, the body 0 may be formed as shown with an axial bore a: which at one end communicates with the inlet 1), and at the other end communicates with a plurality of radial passages as y in the body. Liquid from the inlet 1) flows through the bore .1: and is expelled by centrifugal action through the radial passages y into the interior of the pump casing p around the pump body 0.

In carrying the invention into effect as shown in Figures 1 and 2, we provide on one end of the pump casing p a cylinder 2 having closed ends. Arranged in the cylinder 2 is a controlling piston 3 loaded by a spring 4, and extending from one side of this piston and through a bore in the inner end of the cylinder is a md 5 connected to the swash plate .9. The inner portion of the cylinder 2, that is the portion at the piston-rod side of the piston 3, is in free communication with the outlet port to through a passage 6 in the casing 1), and this portion of the cylinder is in communication with the other or outer portion of the cylinder (which contains the spring 4) through a restricted passage 1, the restriction being efiected by a fixed or adjustable plug 8 (Figure 2). The outer end of the cylinder 2 is provided with a small vent 9 which at its outer end forms a seating for a closure member I0 provided on a lever II, the latter being pivoted on the outer end of the cylinder 2. This lever I I is acted on by a spring I2 which tends to hold the closure member I 0 on its seating. The cylinder 2 is contained in a chamber I3 formed or secured on the adjacent end of the pump casing 10, and this chamber communicates with the pump inlet 1) or with a sump. The outer side of the chamber I3 is bounded by a diaphragm I4 having at its centre an abutment I5 which is adapted to bear on the end of the lever I I remote from the closure member I0. At the outer side of the diaphragm I4 is another chamber I6 which is bounded in part by the diaphragm and in part by an end cover I1, the latter chamber being in communication with the above-mentioned centrifugal pump through a passage I8 and the interior of the pump casing p. Also a rod I9 is attached to the diaphragm I4 by a spring 20, the latter being situated in a tubular housing 2| on the centre of the end cover I1, and the rod being arranged to extend through a gland in the outer end of the spring housing. The rod I9 is operable by the attendant through a lever 22 carried by a bracket 23 on the spring housing 2|.

Assuming the swash plate 5 to be in the position of maximum output as shown in Figure 1, it will remain in this position so long as the pressure in the chamber I6, and thus acting on the diaphragm I4, is below some predetermined amount. In this condition the vent closure member I is in its closed position and the liquid pressures at the two sides of the controlling piston 3 are equal. But when the pressure acting on the diaphragm I4 exceeds the predetermined amount the diaphragm (in response to the pressure acting on it) will move the closure member I0 off its seating. The liquid pressure in the outer portion of the cylinder 2 will new fall and the piston 3 will be moved by the fluid pressure in the inner portion of the cylinder against the action of the spring 4, so moving the swash plate s in the direction for reducing the pump output until a new condition of equilibrium is reached. When it is required to vary the speed at which the pressure acting on the diaphragm I4 becomes effective, the lever 22 can be appropriately actuated by the attendant. In Figure 1 the lever 22 is shown in full lines in one extreme position, and in broken lines in the other extreme position.

Any convenient means may be provided for enabling the closure member I0 to be moved by the attendant away from its seating on the vent 9, and an example of such means is shown in Figure 3. In this example we employ a lever 94 for varying the speed at which pressure acting on the diaphragm I4 becomes effective, this lever being situated on a shaft 95 at the outer side of the diaphragm, and being operable under the control of the attendant through another lever 96 on the shaft at a position outside the chamber I6. The lever 94 is connected to the diaphragm I4 by a spring 91, and the arrangement is such that the effect of the spring on the diaphragm can be varied by angular movement of the lever. Also we form on or otherwise combine with the lever 94 an abutment 98 adapted by acting on the diaphragm I4 to move the lever II carrying the closure member I0 into a position in which the closure member is separated from its seating. This condition, which is useful when it is required to allow the prime mover to operate idly, releases the liquid in the outer portion of the cylinder 2. The controlling piston 3 in thecylinder 2 is then capable of being moved against the action of its loading spring 4 by pressure of the liquid in the inner portion of the cylinder until it reaches a position of equilibrium in which the opposing fluid and spring pressures are balanced. This action of the controlling piston 3 is such that it moves the swash plate s to a position in which the pump gives a suitably reduced output. The piston 3 will then remain in this position and the pump will give a constant output sufficient to keep the prime mover in action.

When it is required to restore the normal action of the pump the attendant releases the lever 96 and the lever II then responds to the action of the liquid pressure acting on the diaphragm I4.

When the lever 94 is moved out of the position in which the spring 91 has its maximum eiifect, any tendency for the diaphragm is opposed by a spring strip 95, one end of the latter being connected to the diaphragm l4 at a position near its centre, and the other end being connected to the end cover I1.

In other respects the pump shown in Figure 3 is essentially similar to that shown in Figures 1 and 2 and is indicated by the same reference characters.

Figure 4 illustrates means for enabling the pump shown in Figures 1 and 2 or Figure 3 to operate automatically as a constant-delivery pump in the event or the fluid pressure acting the spring to distorton the controlling piston 3 falling below a preby a helical compression spring IOI of appropri-' ate strength. This valve I00 is slidable in a bore I02 in the pump casing p, and is subject at one end to the pressure of liquid discharged by the pump, which pressure tends to move the valve against the action of its loading spring IOI.

When the pump is in action and the pressure of the liquid delivered by the pump exceeds a predetermined amount, the pressure overcomes the spring IOI acting on the valve I00 and moves the latter to its open postion. In this position the valve I00 is clear of the adjacent end of a passage I03 leading to the inner end of the cylinder 2, and thus establishes free communication between this end of the cylinder and the delivery side of the pump. Should a condition occur in which the pressure of the fluid delivered by the pump falls below the predetermined limit, the valve I00 is returned by its spring IN to the position shown in which it interrupts the supply of liquid from the pump to the cylinder 2. In this position of the valve I00 the piston 3 is caused by its loading spring 4 to movethe pump adjusting rod 5 into a position in which the pump gives its maximum output and operates as a constant delivery pump.

For enabling the required movement of the piston 3 to take place, the valve I00 is provided with bores I04 through which the two ends of the cylinder 2 communicate freely when the valve is closed. Also the diameters of the valve I00 and the bore I02 are such that there is provided around the valve a restricted or leakage path through which fluid can flow between the ends of the cylinder 2 when the valve is open.

Instead of the valve I00 shown in Figure 4, we may employ the piston valve I00 shown in Figure 5. The valve I00 is movable against the action of a loading spring I0I by the pressure fluid from the pump to establish free communication between the adjacent end of the cylinder 2 and the delivery side of the pump through an inlet port I05 and a passage I03 in the pump casing. But the required restricted or leakage path through which fluid can flow between the ends of the cylinder 2 is provided around a fixed or adjustable plug I06 in the bore I02 containing the valve I00. Further the valve I00 when closed puts the adjacent end of the cylinder 2 into communication with the suction side of the pump or any other convenient part of the pump system in which the pressure is relatively low, this communication being effected through a port I01 in the pump casing.

If desired the pump shown in Figures 1 and 2, with or without any of the modifications shown in Figures 3 to 6, may be provided with means whereby the output of the pump is subject to a temperature control such that in the event of an excessive temperature being attained in any part of the system supplied by the pump the output of the latter is reduced. An example of such means isshown in Figure 6. In this example we provide in the same end of the controlling cylinder 2 as the vent above described, another vent I08 which is normally closed by a spring-loaded closure member I00. It is desired that the latter shall be opened against the action of its loading spring IIO when an excessive temperature condition exists in the prime mover supplied by the pump, and so cause the controlling means to move the swash plate of the pump in the direction for reducing the pump output to any desired extent. We therefore employ for actuating the valve I09 an electromagnet having a winding HI arranged in an electric circuit containing a pair of normally open contacts H2 responsive to a thermostatic device (such as a bi-metal strip H3) situated in the position in which the excessive temperature is liable to occur. The electromagnet is also provided with a movable core I which is connected to and adapted tovactuate the closure member I09. When a predetermined temperature above the normal is reached the contacts I 12 are closed by the strip H3 and the closure member I09 is opened, causing the desired reduction of the pump output. Alternatively we may control the circuit of the electromagnet by a relay energised by a thermo-couple located in the said position.

In a modification of the means shown in Figure 6 we may make use of the first mentioned vent, by combining with the lever which is responsive to the action of the diaphragm, an overriding device such as an electromagnet as above described, this electromagnet being normally inactive and being adapted to open the vent when the circuit of the electromagnet is closed by the temperature-responsive means.

The invention is not limited to the examples described as subordinate details of construction or arrangement may be varied to suit different requirements.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

l. A variable-output pump of the swash plate type having in combination with it a cylinder which at one end is adapted to communicate with the delivery side of the pump, a fluid vent at the other end of the cylinder, a spring-loaded piston slidable in the cylinder under fluid pressure and adapted to vary the position of the swash plate of the pump, means for eflecting a restricted communication between the two ends of the cylinder, a movable closure member for controlling the vent, and means responsive to fluid pressure for actuating the closure member.

2. A variable-output pump as claimed in claim 1, in which the means for actuating the closure member comprises a diaphragm having associated with it a spring whereby a variable loading can be exerted on the diaphragm, and a lever operable by an attendant and adapted by acting on the diaphragm to move the closure member away from the vent, the lever serving also to control the spring loading of the diaphragm.

3. A variable-output pump as claimed in claim 1 and having controlling means for enabling the pump to operate automatically as a constantdelivery pump in the event of the fluid pressure acting on the piston falling below a predetermined amount.

4. A variable-output pump as claimed in claim 1 and having controlling means for enabling the pump to operate automatically as a constantdelivery pump in the event of the fluid pressure acting on the piston falling below a predetermined amount, the said controlling means comprising a. fluid-operable and spring-loaded valve adapted to interrupt communication between the delivery side of the pump and the cylinder.

5. A variable-output pump as claimed in claim 1 and having in association with the cylinder, a relief valve which when opened enables the piston to move the swash plate in the direction for reducing the pump output.

6. A variable-output pump as claimed in claim 1 and having in association with the cylinder, a relief valve which when opened enables the piston to move the swash plate in the direction for reducing the pump output, the relief valve having in combination with it an actuating electromagnet, and a thermostatic device controlling the electromagnet.

RICHARD JOSEPH IFIELD. WIIFRID EDWARD WALTER NICOLLS.