US2500497A - Reciprocating pump - Google Patents

Description

March 14, 1950 T. B. PHILIP RECIPROCATING PUMP 3 Sheets-Sheet 1 Filed Dec. 17, 1947 2 NN\\\ /4/////r// /r/ l m 8.9@ 96.8.96 A j 1 4\7/. H

9 Thomas BM VHN? lnuenlor B y 83+. mmm

Allorney March 14, 1950 T. B. PHILIP 2,500,497

RECIPROCATING PUHP Filed Dc. 17. 1947 s sheets-sheet 2 O 50 /OO 20(2) 250 300 350 De//vr ressa/'e s a" I y P Thomas rae Phill p Inventor By eaq'* WM,

Allorney March 14, 1950 1'. B. PHILIP RECIPROCATING PUMP I5 Sheets-Sheet 5 Filed D60. 17, 1947 Thomas .Emme Plum? nvenlor By @AMM Attorney rammed Mu. 14, 195o nnclrnocamo PUMP Thomas Bruce Philip,y Emngham, England, as-

signor to The Company Limited.

Edinburgh, Scotland, a British company Application December 17, 1947, Serial No. 792,240

In Great Britain June 6, 1944 Section Llublic Law 690, August 8, 1948 Patent expires June 6, 1964 5 Claims. (CL 10S-37) This invention is for improvements in or relating to reciprocating pumps and hasfor an object to provide means for ing reciprocating pump to control the output thereof so that the volume of iiuid delivered'is substantially constant irrespective of the delivery. pressure and to enable the delivery of the pump to be adjusted to any fraction of its maximum output capacity at any given speed without adjustment of any of the moving parts of the Onpe method by which the capacity of a pump can be varied consists in varying the stroke of the plunger or piston in a simple piston or plunger pump cylinder but this has the disadvantage that when a pump has been run for some time at a given output wear may have taken place over a part only of the various surfaces of the pump with the results that great diiilculty may be experienced in obtaining an adequate seal at the pump glands and/or the piston-cylinder surface when the pump is readjusted to give a different output whilst, particularly where the power absorbed by the pump is large, expensive and elaborate mechanism is necessary to eifect the alteration of the stroke ofthe piston or plunger.

Another method which has been widely adopted in piston or plunger pumps is to form by-pass passages in the pump body, controlled by pistonvalves driven by cams or the like from the driving mechanism of the pump, to provide a cut-oi! at different parts of the'stroke of the pump plunger or piston, as required, to provide a variable rate of delivery or to achieve delivery at constant pressure. Such arrangements are commonly used in fuel pumps for metering fuel to the cylinders of Diesel-type internal combustion engines.

. According to the present invention there is provided, for connection in the pump delivery line of a reciprocating pump for the control of the delivery of fluid therefrom, control means comprising a pipe for connection'in said delivery line between the pump outlet port and the delivery valve, an outlet in said pipe between said outlet port and said delivery valve, a relief valve assoelated with said outlet to release fluid from said pump delivery line, adjustable means for controlling the period of time that said relief valve is open during the delivery stroke of the pump and driving means, arranged for connection with the pump driving mechanism, for driving said adjustable means. Where the fluid being pumped is air, water or other non-valuable iiuid, the fluid released by said relief valve may be merely reattachment to an existor to the atmosphere. Where the fluid being pumped is a noxious, toxic or valuable iluid, the control means according to a feature of the present invention comprises a pipe for connection to a point at a position between the outlet port on the cylinder and delivery valve and tothe pump inlet, a relief valve in said pipe to permit fluid from the pump cylinder to be shortcircuited to the lmet pipe to the pumpl adjustable means for controlling the period of time that said relief valve is open during the delivery stroke ofthe pump and driving means, arranged for connection with thepump driving mechanism, for driving said adjustable means.

Where the delivery pressure is low, it may be necessary to introduce a resistance in the pump delivery line in order that the frictional resistance of ow through the relief valve and its interconnecting pipes or passages is low in relation to the pump delivery pressure and accordingly a further 'feature ofthe invention comprises means 'in the pump outlet pipe for producing a resistance in the short-circuit system. A suitable means of achieving this result is a spring-loaded valve to increase the delivery pressure in the pump outlet pipe above the value at which, for a given pressure, the resistance to fluid flow in the shortcircuit system is greater than the resistance to iluid ow in the pump delivery line.

It will be appreciated that, for deliveries at the maximum capacity of the pump the relief valve will remain closed throughout the whole of the delivery stroke or cycle of the pump. In the simplest case of a single-acting plunger pump, the essential parts of the pump are the cylinder, plunger, inlet valve, outlet valve and the driving mechanism for the plunger. Such a pump, with constant length of stroke and running at a constant speed, will deliver uid at a substantially constant rate. By fitting a relief valve between the compartment below the delivery valve and the compartment below the suction valve of the pump and by operating the opening and closing of this valve from the pump drive mechanism, a part of the fluid which would normally be displaced by the plunger to the pump outlet can be short-circuited back to the pump suction chamber or to the pump suction pipe line, or to any convenient position at which the pressure is less than the pressure in the pump de livery chamber. The relative time cycle of the vopening and closing of the valve in relation to the pump cycle can be adjusted to give the best volumetric efllciency over the range of capacileased from the pump outlet. e. g. ventedtoasump Il ties at which the pump is normally required to capacity is made by altering the time period that the valve is open during the pump cycle, means being provided so that this adjustment can be made while the pump is in operation. With a double-acting piston or plunger pump, the said valve gear may be duplicated. The said valve mechanism can conveniently be operated by motion transmitted from an eccentric or from a cam coupled with the main drive of the pump and by simple adjustment of the contour of the cam, quick opening and closing of the valvecan be arranged, this being found advantageous in maintaining a constant `delivery ilow in dependent of delivery pressure.

The following is a description of one embodiment of the invention, as applied to a singleacting pump, with reference to the accompanying drawings, in which:

Figure 1 shows the control means and the pump in part section,

Figure 2 shows the performance of the pump of Figure 1 at varioussettings of the control means, and

Figure 3 is a view showing the control means and the pump with parts in cross-section.

sleeve or slide valves provided a suitable connection to the relief valve can be made on the pressure side of the sleeve or slide valve.

The pump cylinder I, shown in Figure 1 arl ranged with a reciprocating plunger 2 is completed by a crank or eccentric driving gear and a suction valve 3 and delivery valve 4. The valve 5 which forms the subject of this invention is l shown tted between the delivery valve 4 and the pipe-line 9 from which the uld is delivered to the pump. In the example shown, the relief valvel 5 is operated from the driving shaft of the pump through the eccentric or cam 6 which provides the means of opening the relief valve 5 during a part of the delivery stroke of the pump. The valve is shown closed by the spring II. The period in the pump cycle during whichtlie relief valve remains open is controlled'by the position of the adjusting spindle 'I. When the spindle is in its lowest position the valve does not open and the pump operates as an ordinary positive plunger pump. When the adjusting spindle is raised suitably the eccentric or cam 6 operates the lever I2 and this in turn, opens the relief valve 5 and allows a part of the iiuid which would otherwise be delivered through valve I vto. the pump delivery line I0 to pass, through the pipe 8, to the suction side of the pump and pipe-work assembly.

'The mechanism indicated'is a typical example of the mechanism which can be employed and serves only to indicate the essential feature of the invention, which is the provision of a relief valve which can be controlled to open in cycle with the pump for a greater or longer period of the cycle and which, by an adjustment of the relative timing of thev operating gear, can be caused to operate in any desired cycle in relation to the pump plunger cycle.

In practise, it has been found that it is an advantage for the relief valve to be partially open at the end of the pump suction stroke and to close during the pump delivery stroke. Exactly similar principles apply in adaptingV the invenf tion to piston pumps, single 0r double acting or multi-cylinder pumps.

'I'he regulating delivery mechanism is tted to operate with each delivery valve or if it is not required to have an adjustment down to zero delivery the mechanism maybe tted between two or more of the delivery valves in pumps where there is more than one delivery valve.

' 'I'he method can also be adapted to pumps with l system.

In Figure 2, typical results with a simple singleacting plunger pump flttedwith the type of control mechanism described above areA reproduced. The horizontal lines indicate the effectiveness of this method of volume control in a range controlled by movement of the adjusting spindle and extending from full delivery (line A) down to a delivery of about 1A; of the full capacity (line H).

There now follows a vdescription of a second embodiment of this invention as applied to a double-acting piston pump and having reference to Figure 3 of the accompanying drawings which shows the control means and the pump in part section: 1

I'he pumpv cylinder shown at I is divided into two pump chambers by the piston 2, each of which is provided with a suction valve 3 connected to the inlet pipe 9', and a delivery valve 'c'onnected to the outlet pipe I0. The piston 2 is reciprocated by the crank or eccentric driving gear 6. The relief valve 5 which forms the subject of this invention connects the two pump chambers by way of the pipes 8. In this embodiment the relief valve is operated from the driving shaft of the pump through the eccentric or cam 6 which provides the means for opening the relief valve during a part of each stroke of the pump. The valve is shown closed by the spring II. The length of the periods in the pump cycle during which the relief valve remains open, is controlled by the position of the adjusting spindle 1. When the spindle is in its lowest position the valve does not open and the pump operates as an ordinary positive piston pump. When the spindle is raised suitably, the eccentric or cam 6 operates the lever I2 and this in turn opens the relief valve and allows a part of the uid which would otherwise be delivered'through one of thevalves 4, to pass through the pipe 8 from the pump chamber which is 1n the delivery phase via the relief valve to the other chamber, which is in the suction phase.

It will be appreciated that the foregoing description of this embodiment is not to be. read in any way` as limiting the arrangement or position of the relief valve in relation to the other parts of the pump as Figure 3 shows only one of the possible arrangements of said valve in a pump 1. Control means connected to the pump delivery line of a reciprocating pumpcontrolling the delivery of iiuid therefrom, comprising a pipe for connection in said delivery line between the pump outlet port andthe delivery valve, an outlet in said pipe between said outlet port and said delivery valve, a relief valve associated with said outlet to release fluid from said pump deliveryy relief valve actuating means for actuating" line, said relief valve, said actuating means being driven by the pump driving mechanism, means being provided to vary the eiectivedistance of the connection between` the relief valve and its actuating drive to control the period of time in which said relief valve is open during the delivery stroke of the pump, the pump delivery stroke being timedy exactly in phase with the actuating drive of the relief valve in order that the pump delivery is directly proportional to the effective length of said connection.

2. Control means connected to the pump delivery line of a reciprocating pump controlling 76 the delivery oi' uid therefrom, comprising a pipe for connection at one end in said delivery line between the pump outlet port and the delivery valve and at the other end to the pump inlet line, a relief valve in said pipe to permit fluid from the pump cylinder to be returned to said pump inlet line, relief valve actuating means for actuating said relief valve, said actuating means comprising a cam driven by driving means operable by the pump driving mechanism, and a member co-operating with said cam, means to vary the effective length of said member between the relief valve and its actuating drive to control the period of time that the relief valve is open during the delivery stroke of the pump, the pump delivery stroke being timed exactly in phase with the actuating drive of the relief valve in order that the pump delivery is directly proportional to the effective length of said member.

3. A reciprocating pump comprising a pump cylinder, a piston in said cylinder, pump driving mechanism adapted to reciprocate said piston in said cylinder, an inlet line to said cylinder, an outlet port in said cylinder, a delivery line associated with said outlet port, a delivery valve in said delivery line, a pipe connected in-said delivery line between said outlet port and said delivery valve, a relief valve associated with said pipe to release fluid from said delivery line, relief valve actuating means driven by the pump driving mechanism, the period of time in which said relief valve is open during the delivery stroke of the pump being controlled by the manual adjustment of the effective length of the connection between the relief valve and its actu- -ating drive, the pump delivery stroke being timed exactly in phase with the actuating drive of the relief valve in order that the pump delivery is directly proportional to the effective length of said connection.

4. A reciprocating pump comprising a pump cylinder, a piston in said cylinder, pump driving mechanism adapted to reciprocate said piston in said cylinder, an inlet line to said cylinder, an outlet port in said cylinder, a delivery line associated with said outlet port, a delivery valve in said delivery line, a pipe connected at one end in said delivery line between said outlet port and said delivery valve and at the other end in said inlet line, a relief valve in said pipe to permit fluid from said delivery line to be returned to said inlet line, resistance means in said delivery line adapted to produce therein a resistance to fluid-flow at least equal to the fluid-flow resistance in said pipe and the associated relief valve,

relief valve actuating means for actuating said relief valve, said actuating means comprising a cam driven by driving means operable by the pump driving mechanism and a member cooperating with said cam, means to vary the effective length of said member between the relief valve and its actuating drive to control the period of time that said relief valve is open during the delivery stroke of the pump, the pump delivery stroke being timed exactly in phase with the actuating drive of the relief valve in order that the pump delivery is directly proportional to the effective length of said member.

5. A double-acting reciprocating pump comprising a pump, cylinder, a piston in said cylinder dividing said cylinder into two pump chambers, pump driving mechanism adapted to reciprocate said piston in said cyilnder whereby said pump chambers are alternately put under suction and pressure, an inlet port and an outlet port in each of said pump chambers, inlet and outlet valves associated with said inlet and outlet ports, a pipe connecting both said pump chambers independently of said ports associated with said inlet and outlet valves, a relief valve in said pipe, relief valve actuating means for actuating said relief valve, said actuating means comprising a cam driven by driving means operable by the pump driving mechanism and a member cooperating with said cam, means to vary the effective length of said member between the relief valve and its actuating drive to control the period of time that said relief valve is open during each delivery stroke of the pump, the pump delivery stroke being timed exactly in phase with the actuating drive of the relief valve in order that the pump delivery .is directly proportional to the eective length of said member.

THOMAS BRUCE PHILIP.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Sprado Feb. 5, 1935

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