Flow Control Valve

This invention relates to a discharge flow rate control valve in a multiple cylinder type reciprocating pump used for instance for supplying the boiler feed water or in conjunction with hydraulic machines wherein the working fluid is subjected to a rather elevated pressure.

The discharge flow rate control valve of the present invention makes it possible to simultaneously adjust the flow and pressure in plural cylinders of the pump without regard to the operation of the discharge valves for modifying the overall discharge flow rate of the pump.

Heretofore, when the multiple cylinder reciprocating pump of this kind is employed for supplying the feed water to a boiler, both the cold water and warm water may be obtained by suitably adjusting the water temperature. However, when desired to produce steam besides cold and warm water, it is necessary to use a special device for that purpose. In addition, some safety measures must be resorted to when steam is to be produced by high pressure injection with resulting complex overall structure and necessity for special maintenance and services.

In consideration of the conventional practice as defined above, the present invention envisages to provide a flow rate control valve for a multiple cylinder type reciprocating pump wherein the valve is mounted on the discharge side of the pump and operable to simultaneously control the flow rate and pressure of the fluid in two cylinders of the pump to present valves for controlling the overall pump discharge as desired. It is also possible for only one pump to yield cold water, warm water and steam through suitable control of the water temperature.

FIG. 1 is a longitudinal section showing a fluid control valve of the present invention as applied to a multiple cylinder type reciprocating pump;

FIG. 2 is a plan view of the same with parts thereof shown in transverse section; and

FIGS. 3 and 4 are the views similar to FIG. 2, and showing the fluid control valve in different operational states than those shown in FIG. 2.

Reference is now made to the accompanying drawings for illustration of a preferred embodiment of the present invention.

FIG. 1 shows the flow rate control valve of the invention as applied to a triple cylinder type reciprocating pump 3 having a driving portion 1 and a pump portion 2. A crankshaft 4 connected to a drive source, not shown, is rotatably mounted in the driving portion 1. To this crankshaft 4 are connected three juxtaposed pistons 6 by way of respective crank arms 5 operatively associated with the crankshaft 4, these pistons 6 extending into the pump portion 2 and slidably disposed within three juxtaposed cylinders 7 in the pump portion 2. Although each one of the crank arms 5, pistons 6 and cylinders 7 is shown in the sectional side elevation of FIG. 1, it should be understood that the respective three members 5, 6, 7 are juxtaposed parallel to each other in the pump section and are operatively connected to the sole crankshaft 4.

The cylinder bore of each cylinder 7 communicates with a suction port 8 and a discharge port 9 and has inlet and outlet ducts 10, 11 in which suction and discharge valves 12, 13 are mounted respectively as shown in FIG. 1. The fluid is introduced through suction port 8 with reciprocating motion of the pistons 6 and discharged through discharge ports 9 by way of suction valve 12 and discharge valve 13 to a boiler or similar device, not shown.

The reciprocating pump is shown in plan view in FIG. 2 wherein the first and second cylinders are denoted by reference numerals 7.sub.1 and 7.sub.2, respectively. To the discharge sides of these two cylinder 7.sub.1, 7.sub.2, there is mounted a flow rate control valve 14 of the present invention for enabling the flow rate of the fluid in the first and second cylinders 7.sub.1, 7.sub.2 to be adjusted in a manner to be described below. Thus, as shown in FIG. 2, on the discharge sides of the first and second cylinders 7.sub.1, 7.sub.2 are formed two passages 16.sub.1, 16.sub.2, in addition to the outlet ports as described with reference to FIG. 1, these passages having orifice ports 15.sub.1, 15.sub.2. A body member 18 of the flow control valve 14 is secured with screws 17 to the reciprocating pump 3 and has a first duct 19.sub.1 communicating with the passage 16.sub.1, a second duct 19.sub.2 communicating with the passage 16.sub.2, a double stepped cylinder chamber 20 communicating with these ducts 19.sub.1, 19.sub.2, and a bypass duct or passage 21 for communication between the stepped cylinder chamber 20 at back of a first step 24 and the suction port 8 of the reciprocating pump 3. The stepped cylinder chamber 20, arranged coaxially with the first duct 19.sub.1, has a female threaded passage 22 opening to the outside of the flow control valve. A valve needle 23 has a male threaded portion engaging with the female threaded passage 22 and is reciprocably introduced into the stepped cylinder chamber 20. The numeral 25.sub.1 denotes a first control zone where the valve needle 23 may be seated on a valve seat provided by the first step 24 of the cylinder chamber which is disposed between the first duct 19.sub.1 and the bypass passage 21. The numeral 25.sub.2 denotes a second control zone where a partly conical and partly cylindrical valving member 26 slidably fitted on a valve stem 23a of a needle valve 23 is seated on an inclined surface 27 ahead of a second step of the cylinder chamber 20 which is disposed between said second duct 19.sub.2 and the bypass passage 21. It is to be noted that the valving member 26 is always urged towards and into engagement with the valve seat 27 under the resilient force of a coil spring 28 placed under compression between the larger diameter end face of the valving member 26 and a flange 23b provided to the valve stem 23a. It is also to be noted that the lesser diameter end face of the valving member 26 may be engaged by a ring-like engaging projection 29, said projection being stationarily fitted into a peripheral groove 23c on the stem 23a slightly ahead of the inclined surface 27 and having its peripheral portion slightly projecting beyond the outer surface of the valve stem 23a, and that, when the needle valve 23 has been shifted out of contact with valve seat 24 by operation of a handle 23d secured to a root portion of the needle valve 23, the valving member 26 may be abutted by the projection 19 and thus shifted out of contact with the valve seat 27 with a certain time delay relative to the freeing of the first control zone.

The handle 23d is substantially U-shaped in cross-section and mounted so as to overlie a portion of the body member 18. The handle 23d has a pin 30 projecting inwardly from its recessed portion and engaging in a peripheral groove 31 on the body member, 18 to prevent incidental removal of the needle valve 23. A packing 32 is interposed between the needle valve 23 and the stepped cylinder chamber 20 to prevent fluid leakage to the outside. Similarly, a packing 33 is mounted in a sliding contact portion between the valve stem 23a of the needle valve 23 and the valving member 26 for assuring fluid tightness.

In operation of the inventive flow rate control valve of the present invention, when the handle 23d is manipulated for rotating the needle valve 23 for slightly separating the needle valve 23 away from the first step 24, the fluid contained in the first cylinder 7.sub.1 flows through passage 16.sub.1, orifice port 15.sub.1, first duct 19.sub.1 and the first control zone 25.sub.1 of the stepped cylinder chamber 20 its the bypass passage 21 to be returned to the suction port 8 of the pump. Thus, the flow and pressure of the fluid being delivered through the first cylinder 7.sub.1 may be adjusted as desired, thus resulting in a modified overall discharge flow rate from the pump. When desired to further modify the pump discharge flow rate, the handle 23d is further turned so that the needle valve 23 is moved further away from valve seat 24 and the engaging projection 29 abuts on the valving member 26 for disengaging the valving member from the inclined surface 27 against the force of coil spring 28. The fluid in the second cylinder 7.sub.2 may then flow through passage 16.sub.2, orifice port 15.sub.2, second duct 19.sub.2 and second control section 25.sub.2 of the stepped cylinder chamber 20 into the bypass passage 21 to be returned to the suction port 8 similarly to the fluid in the first cylinder 7.sub.1. Thus the fluid flow rate and pressure in the second cylinder 7.sub.2 may also be adjusted as desired, resulting in a further modified discharge flow rate from the pump. Thus, with the first and second control zones 25.sub.1, 25.sub.2 being opened for adjusting the discharge flow rate of the first and second cylinders 7.sub.1, 7.sub.2, the sum of the fluid flow rate through the third cylinder, not shown, and the fluid flow through the first and second cylinders less the fluid flow returned to the suction port 8 through the first and second control sections 25.sub.1, 25.sub.2, represents the total discharge flow rate from the pump.

From the forgoing it is seen that discharge flow rate from the multiple cylinder type reciprocating pump may be controlled by having the fluid in the two cylinders thereof fed back to the suction side so as to bypass the respective discharge valves. Since the fluid feedback operation for these two cylinders may be made simply by manipulating the handle of one and the same needle valve, the operation may be facilitated and the overall device may be made more compact in size. When the pump is used for feeding to a boiler, supply of cold water, warm water and steam may be realized by means of a single pump. Moreover, safety in steam production may be assured by pressure decrease caused by modified discharge flow rate. The present pump has great practical utility because of these and other advantages.