US2247261A - Unloading valve for reciprocating ram pumps - Google Patents

Description

June 24, 1941;

J. M. TOWLER ETAL UNLOADING VALVE FQR RECIPROCATING RAM PUMPS Filed May 25, 1940 I Fig. I.

Patented June 24, 1941 UNITED STATES PATENT OFFICE UNLOADING "ALVE FOR RECIPROCATING RAM PUMPS John Maurice Towler and Frank Hathorn Towler, Yorkshire, England Application May 23, 1940, ScrialNo 336,874 In Great Britain March 6, I939 9 Claims.

the above type is to effect the unloading by lifting the suction valve, this being done through the medium of a hydraulic piston the operating cylinder 'for which is connected to the delivery main, a weight or spring being employed to eli'ect the return stroke.

The disadvantage. of unloading the bore of a pump by lifting the suction valve, or employing an auxiliary mitre type valve for this purpose, is that, when the pressure is only just lifting the valve ofi, its seat, or when the pressure is falling so thatthe valve is just aboutto re-seat, there is a tendency for the valve to chatter.

The object of the present invention is to provide a reciprocating ram pump having improved means for effecting the unloading which will obviate the aforesaid disadvantage,

Broadly the present invention consists in the combination with a reciprocating, ram pump for delivering liquid of an automatically operating piston valve which is moved longitudinally and relative to a discharge outlet in the wall of each pump bore against a predetermined load in consequence of the pressure of the discharged liquid to open one or more of said outlets thereby to by-pass some or all of the liquid in one or more of the pump bores during the delivery stroke so that the delivery of liquid by the pump to the delivery main is either progressively reduced as the pressure of the liquid in said main increases or immediately reduced when the liquid in the delivery main attains a predetermined pressure.

According to a practical application of the invention, each pump bore of the reciprocating ram pump has at least two discharge outlets, one of said outlets being the normal discharge outlet through which pumped liquid is ,discharged into the delivery main, and the other outlet constituting a by-pass passage through which some or all of the Dumped liquid may,

under the automatic control of the unloading valve, pass as an alternative to being discharged into the delivery main. The unloading valve, which is preferably of the packingless type, is moved, against a predetermined load such as a spr ngor s. equiva ent, to, open. e ch l y-pass passage, by the pressure of the liquid in the delivery main.

In one arrangement this is effected by causiing the piston valve to be subjected to the full pressure in the delivery main by directly connecting the interior of a pressure cylinder for the valve to the interior of the delivery main. In this arrangement thevalve will be operated progressively to reduce the delivery of liquid by the pump to the delivery main as the pressure.

of, liquid in, said main increases.

In a further arrangement the piston valve is subjected to a pressure which is less than that which exists in the delivery mainby connecting the interior of the valve operating cylinder to the exhaust passage of a relief valve connected to the delivery main. This exhaust passage is choked at a point beyond the connection with the valve operating cylinder; soas to provide sufiicient back -pressure to operate the valve so as thereby immediately to reduce the delivery of liquid, by the pump. to the delivery main w en h iq id in he delivery main attains the predetermined pressure required toopen v the relief valve.

In a pump according to the present invention the pressure liquid. serving to operate the piston valve may either be applied to a ram associated with the valve or the same may be applied directly to one end of the valve.

In order that the invention may be clearly understood and carried into efiect pumps according toboth of the described embodiments will now be described by way of example by aid of the accompanyingvdrawing in which:

Fig. 1 is a horizontal or transverse section taken through. the main dischargev and by-pass outlets of a three ram, pump according to the first described embodiment in which the bypass control valve is subjected to the full pressure existing in the delivery main.

Fig. 2 is a diagrammatic view illustrating the second embodiment in which the by-pass control valve is subjected to badk-pressure on the exhaust side of a relief valve in the delivery main In the drawing, having particular reference to Fig. 1, the pump illustrated comprises a pump body I which is bored to provide three pump bores 2, 3 and 4.

. On opposite sides of each pump bore and at the inner end thereof are situated two transverse outlet passages, the passages 5, 6 and 1 being the normal discharge outlets for the pumped liquid to pass to a common. delivery main 8 and the opposing passages 9, I and H being the by-pass passages which form one of the features of the present invention.

The by-pass passages 9, I0, ll open into a transverse bore [2 in the'pump body which is machined to receive a piston valve [3 with a fit which While permitting the piston valve to move freely therein will yet prevent the leakage of the pressure liquid without packing.

The spindle which constitutes the piston valve i3 has a passage I 4 extending longitudinally through its centre, which passage is open at one or both ends to exhaust.

In the example illustrated the valve spindle is provided with two circumferential reduced portions I5 and I6 whilst the closed end of the valve is tapered off as indicated at IT. The reduced portions I5 and it are connected by radial passages l8 with the hollow centre passage M of the valve spindle whilst a similar connection between said hollow centre passage and the tapered end i! is afforded by the opening H3 at said end of thevalve.

The piston valve .is'shown in the drawing in its closed position in which position it is held byv a spring 20 which acts against the open or exhaust end of the valve. through a thrust washer 2|, the load on the spring being adjusted by a screw 22 which acts against a corresponding thrust washer 23 on the outer end of the spring. In this position of the valve its opposite end is heldforcibly against the opposing face of a side plate 24 forming part of the casing which contains. the liquid to be pumped and in which the pump 'body is immersed.

-With the construction above described endwise movement of the piston valve against the spring ZObrings the reduced portions I5 and [6 in turn into registration with the open ends of the by-pass passages 9 and H] respectiv l 4.

thus placing the corresponding pump bores in communication with the passage [3 in the valve and so, through the open end of said passage, to exhaust into the interior of the aforesaid liquid containing casing. The remaining pump bore is opened to exhaust when the tapered end I! of the valve commences to pass across the icy-pass passage ll.

The reduced portions i5 and IB of the valve spindle are so arranged that, as the valve is made to traverse thelby-passj passages by the actuating ram, the passage! is first uncovered to such an extent thatthe pressure in the associated pump bore is not suflicient to lift the delivery valve, eachof which is indicated, by the reference numeral 25, and therefore that pump ram stops pumping, although it is. not fully unloaded. As the pressure rises infthe delivery main, the spindle is moved furtherover so as completely to unload the pump bore 2 and the second reduced. portion 16 of the spindlebegins to uncover the intermediate by-pass passage It! connected to the intermediate pump bore 3 so that ,the pressure in that pump bore is released to such an extent that the intermediate ram ceases to pump. Finally, as the pressure in the delivery main increases still further, the tapered end I! of the valve spindle partially uncovers the third-by-pass passage H, thereby reducing the delivery of the third up to such a point that it ceases pumping. As the pressure drops, the sequence is reversed until the three rams are pumping again.

I The endwise movement of the piston. Valve to unload each pump ram is imparted, in the example illustrated, through means comprising a small hydraulic ram 26 which projects from one end of the valve spindle and extends into a cylinder 21, an enlargement 28, on the outer end of the ram, being provided to limit the said endwise movement of the valve spindle. The interior of the cylinder 21 is in permanent connection with the interior of the delivery main by means of a connecting pipe 29.:

In consequence of the above arrangement the ram 26 is always subjected to the full pressure of the liquid existing in the delivery main and when this pressure increases to the point at which the resistance of the spring 2!] is overcome the ram 26 will be forced inwards thus moving the piston valve to cause each pump ram in turn progressively to be unloaded.

In an alternative arrangement, not illustated, the ram 26 may be dispensed with by a construction in which the valve spindle is extended into the operating cylinder 21. In this arrangement a third circumferential reduced portion will be provided in the body of the valve spindle to effect unloading of the ram in the pump bore 4.

The pump rams, in the case of a multi-ram pump to which the present invention is particularly applicable, may be unloaded in any desired order by a suitable relative disposition of the aforesaid circumferential reduced portions and either altogether or one or more at a time. Further, although it is preferred to bevel off the leading edge of each reduced portion as indicated at 3|] so as to ensure a more gradual reduction in load on each ram, such a refinement is not an essential.

In connection with the relative dis-position of the reduced portions in the valve spindle it must be understood that, unless there is another pump also delivering into the delivering main the pump bore which is finally unloaded can only be partially unloaded for the reason that, as the pump unloads itself progressively, in the final position of the valve the pump must be delivering some liquid into the delivery main in order to provide sufficient pressure to overcome the spring 20 and hold the valve in the extreme endwise position.

In the embodiment illustrated in Fig. 2 the cylinder 21 receives pressure liquid from the exhaust pipe 3| of an automatically operating relief valve 32 which is connected to the delivery main 8, suflicient pressure to'operate the by-pass valve, of the pump being obtained by throttling the outlet of the exhaust pipe 3| as'at 33. By this means a back-pressure is created in the exhaust pipe sufficient to overcome the spring 20, which in this embodiment is of course considerably lighter than the spring required in the first embodiment.

With the arrangement just described a pressure having but a comparatively small variation may be maintained in the delivery main. It is also possible to employ a plurality of pumpsall delivering into the same. delivery main, with buta single relief valve, the pumps being loaded and unloaded progressively in accordance with the demand.

In both embodiments the valve spindle may be balanced when under pressure by chambering the bore !2, in which the valve spindle reciprocates, to provide recesses 34, see Fig.1, Where the openings 9, II), II break into the bore I2.

We claim:

1. In a reciprocating ram pump, in combination with a pump bore, a ram reciprocable in said pump bore, inlet and outlet ports respectively leading to and from said pump bore, and a delivery main for pumped liquid discharged through the outlet port, a further outlet in the pump bore for by-pa'ssing pumped liquid, a by-pass valve for opening and closing said by-pass outlet,loading means acting on said by-pass valve to hold said valve closed, means actuated by fluid pressure and cooperating with said by-pass valve to open said valve against the pressure of said loading means and means connecting said by-pass valve operating means to the pump delivery main to cause said means to open said valve and to unload said ram pump when the pumped liquid in said main reaches a predetermined pressure in excess of that exerted by the loading means, thereby to stabilize the pressure in said delivery main.

2. In a reciprocating ram pump, in combination with a pump bore, a ram reciprocable in said pump bore,inl'et and outlet ports respectively leading to and from said pump bore, and a delivery main for pumped liquid discharged through the outlet port, a further outlet in the pump bore for by-passing pumped liquid, a bypass valve for opening and closing said by-pass outlet, loading means acting on said by-pass valve to hold said valve closed, a hydraulic cylinder, a ram working insaid cylinder and operatively connected to said by-pass valve and means connecting said hydraulic cylinder to the pump delivery main whereby 'the pressure of the pumped liquid in the delivery main is exerted on the ram in the cylinder to cause the ram to open the by-pass valveand to unload the pump when the liquid in said main reaches a predetermined pressure in excess of that exerted by the loading means, thereby to stabilize the pressure in said delivery main.

3. In a reciprocating ram pump, in combination with a pump bore, a ram reciprocable in said pump bore, inlet and outlet ports respectively leading to and from said pump bore, and a delivery main for pumped liquid discharged through the outlet port, a further outlet in the pump bore for Icy-passing pumped liquid, a bypass valve for opening and closing said by-pass outlet, loading means acting on said by-pass valve to hold said valve closed, a hydraulic cylinder, a ram working in said cylinder and operatively connected to said by-pass valve and means connecting said hydraulic cylinder directly to the pump delivery main whereby the ram in the cylinder is subjected to the full pressure in the delivery main, so that when the pressure acting on the cylinder ram is sufficient to overcome the pressure exerted by the loading means, the by-pass valve will be moved to open the by-pass passage progressively to reduce the delivery of liquid to the main as the pressure in said delivery main increases.

4. In a reciprocating ram pump, in combination with a pump bore, a ram reciprocable in said pump bore, inlet and outlet ports respectively leading to and from said pump bore, and a delivery main for pumped liquid discharged through the outlet port, a further outlet in the pump bore for by-passing pumped liquid, a bypass valve for opening and closing said by-pass outlet, loading means acting on said by-pass valve to hold said valve closed, a hydraulic cylinder, a ram working in said cylinder and operatively connected to said by-pass valve, and means serving to operatively connect said hydraulic cylinder to the pump delivery main, said means comprising a relief valve connected to said main, an exhaust passage from said relief valve, a choke in said passage and a conduit serving to connect said exhaust passage between the relief valve the choke and the by-pass valve operating cylinder, so that the ram in the cylinder is subjected to a pressure equivalent to the back pressure produced in said exhaust passage by the choke, whereby when the liquid in said delivery main attains the predetermined pressure required to open the relief valve, the ram in the cylinder is subjected to a pressure in excess of that exerted by the loading means on said bypass valve, thereby opening the by-pass valve and immediately reducing the delivery of the pump to the delivery main.

5 In a reciprocating multiram pump, in combination with a plurality of pump bores, a series of rams reciprocable one in each pump bore, inlet and outlet ports leading to and from each pump bore, and a common delivery main for pumped liquid discharged through the respective outlet ports, a further outlet in each pump barrel for lay-passing pumped liquid, a piston valve common to said by-pass outlets and movable longitudi nally relative to said outlets for opening and closing the same, loading means acting against said valve yieldably to resist movement of the valve to open said outlets, a hydraulic cylinder, a ram working in said cylinder and operatively connected to said valve and means connecting said hydraulic cylinder to the pump delivery main whereby the pressure of the pumped liquid in the delivery main is enabled to act on said ram in the cylinder to overcome the load on saidpiston valve and cause the same to bemov-ed to open the by-pass outlets when the pressure in said main reaches a pressure in excess of that exerted by the loading means against said piston.

6. In a reciprocating multi-ram pump, in combination with a plurality of pump bores, a series of rams reciprocableone in each pump bore, inlet and outlet ports leading to and from each pump bore, and a common delivery main for pumped liquid discharged through the respective outlet ports, a further outlet in each pump barrel for by-passing pumped liquid, a piston valve common to said by-pass outlets and movable longitudinally relative to said by-pass outlets for opening and closing the same, loading means acting against said valve yieldably to resist movement of the valve to open said by-pass outlets,

a hydraulic cylinder, a ram working in said cyl- I inder and operatively connected to said valve and means serving to connect said hydraulic cylinder directly to the pump delivery main whereby the ram in the cylinder is subjected to the full pressure in the delivery main to overcome the load on said piston .valve and cause the piston valve to be moved to open the by-pass outlets when the pressure in said main reaches a pressure in excess of that exerted by the loading means against said piston valve.

7. In a reciprocating multi-ram pump, in combination with a plurality of pump bores, a series of rams reciprocable one in each pump bore, inlet and outlet ports leading to and from each pump bore, and a common delivery main for pumped liquid discharged through the respective outlet ports, a further outlet in each pump barrel for Icy-passing pumped liquid, a piston valve common to said by-pass outlets and movable longitudinally relative to said outlets for opening and closing the same, loading means acting against said valve yieldably to resist movement of the valve to open said by-pass outlets, a hydraulic cylinder, a ram working in said cylinder and operatively connected to said piston valve and means serving to connect said hydraulic cylinder to the pump delivery main, said means comprising a relief valve connected to said main, an exhaust passage from said relief valve, a choke in said passage and a conduit serving to connect said exhaust passage, between the relief valve and the choke and the valve operating cylinder, whereby the ram in the cylinder is subjected to a pressure equivalent to the back pressure produced in said exhaust passage by the choke, said pressure being sufficient to overcome the load on said piston valve to cause the piston valve to be moved to open the by-pass outlets when the liquid in the delivery main attains the predetermined pressure required to open the relief valve.

8. In a reciprocable multi-ram pump, in combination with a plurality of pump bores, a series of rams reciprocable one in each pump bore, inlet and outlet ports leading to and from each pump bore, and a common delivery main for pumped liquid discharged through the respective outlet ports, a further outlet in each pump barrel for by-passing pumped liquid, a piston valve common tosaid by-pass outlets and movable longitudinally relative to said outlets for opening and closing the same, loading means acting against said'valve yieldably to resist movement of the valve to open said outlets, a hydraulic cylinder, a ram working in said cylinder and operatively connected to said piston valve and means connecting said hydraulic cylinder to the pump delivery main whereby the pressure of the pumped liquid in the delivery main is enabled to act on said ram in the cylinder to overcome the load on said piston valve and cause the piston valve to be moved to open the by-pass outlets when the liquid in said main attains a pressure in excess of that exerted by the loading means against the piston valve, said piston Valve having a hollow interior and having a series of conduits spaced by unequal distances, each of said conduits being adapted to be set in alignment with the by-pass outlets in succession as the said piston valve is moved to open position,whereby'the respective pump bores may be unloaded insuccession as the pressure rises inithe delivery main. 1

'9. In a reciprocating multi-ram pump, in combination with a plurality of pump bores, a series oframs reciprocable one in each pump bore, inlet and outlet ports leading to and from each pump bore, and a common delivery main for pumped liquid discharged through the respective outlet ports, a further outlet in each pump barrel for by-passing pumped liquid; a piston valve common to said by-passoutlets and movable longitudinally relative to said outlets for opening and closing the same, loading means acting against said valve yieldably to resist movement of the valve to open said outlets, a hydraulic cylinder, a ram working in said cylinder and operatively connected tosaid piston valve and means serving to connect said hydraulic cylinder to the pump delivery main, said means comprising a relief valve connectedto said main, an exhaust passage from said relief valve, a choke in said passage and a conduit serving to connect said exhaust passage, between the relief valve and the choke and the piston valve operating cylinder, whereby the ram in the cylinder is subjected to a pressure equivalent to the back pressure produced in said exhaust passage by the choke and suflicient to overcome the load on said piston valve to cause the piston valve to be moved to open the by-pass outlets when the liquid in the delivery main attains the predetermined pressure required to open the relief valve, said piston valve having a hollow interior and having a series of conduits spaced by unequal distances, each of said conduits being adapted to be set in alignment with the by-pass outlets in succession as said piston valve is moved toopen' position, whereby the respective pump bores may be unloaded in succession as the pressure rises in the delivery main.

JOHNMAURICE TOWLER. FRANK HATHORN TOWLER.

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