Discharge Controlled Reciprocating Pumps

Abstract

The discharge controlled pump means comprises a piston, a cylinder and an electromagnetic valve provided in a fluid inlet passage communicating with a compression chamber formed between the piston and a cylinder. The electromagnetic valve is normally open to provide for supply of fluid into the compression chamber but is closed when the volume of the compression chamber has been decreased in the upward stroke of the piston to a value corresponding to a desired discharge quantity of fluid, whereby the fluid is confined and metered in the compression chamber.

Description

The present invention relates to a pump means comprising a piston, a cylinder and an electromagnetic valve, by which the fluid is electrically metered for the purpose of controlling the rate of discharge of the pump.

In conventional reciprocating pumps, the discharge of the pump is controlled by supporting the lower end of a connecting rod, connected with a piston, by means of a lever mechanism consisting of a stopper or the like and changing the position of the stopper, utilizing the principle of the lever, to limit the return stroke of the piston. However, such construction had the disadvantage that the mechanical construction becomes very complicated because of the use of lever mechanism.

In order to eliminate such disadvantage, the present invention proposes to meter the fluid electrically. Namely, the object of the invention is to easily control the discharge of the fluid from the pump, merely by opening or closing an electromagnetic valve in accordance with the desired rate of discharge.

The present invention will be described in detail hereinafter with reference to the accompanying drawing which is a diagramic view of the pump controlling system, showing an embodiment of the discharge controlled pump means according to the present invention.

Referring to the drawing, reference numeral 1 designates a pump driving cam shaft and 2 designates a cam fixedly mounted on said cam shaft 1. The cam 2 is in engagement with a pushing rod 3 which is biased by a return spring 3'. Reference numeral 4 designates a piston having a fluid passage 5 formed therein which establishes the end of the fluid discharge operation of the piston. The piston 4 is reciprocably disposed within a cylinder 6, with its lower end connected with the pushing rod 3 integrally therewith. Reference numeral 7 designates a compression chamber in which metering and compression of fluid are effected. Reference numeral 8 designates a throttle. Reference numeral 10 designates an electromagnetic valve, 11 a return spring which causes a return movement of a valve rod 13, 12 a valve seat on which the valve rod 13 will be seated, in the energized state of the electromagnetic valve, to stop the flow of fluid, and 14 a fluid passage formed in the valve rod 13. Reference numeral 15 designates a discharge valve which is set to discharge fluid at an optional discharge pressure. Reference numeral 16 designates a fluid tank which is communicated with the throttle 8 through a conduit and with the electromagnetic valve 10 via a feed pump 17 through another conduit. Reference numeral 18 designates a controller controlling the electromagnetic valve 11 by a signal from a timing pick up 19 which generates the signal in synchronism with the rotation of the driving cam shaft 1.

The device of the present invention constructed as described above operates in the following manner: Namely, when the cam shaft 1 is rotated in the direction of arrow a, the pushing rod 3 in engagement with the cam 2 is caused to move in the direction of arrow b, whereby the piston is moved upwardly to compress the fluid. The electromagnetic valve 10, during this period, is held in the deenergized state and the valve rod 13 is held away from the valve seat 12 by the action of the return spring 11, so that the fluid is constantly supplied by the feed pump 17 from the fluid tank 16 as indicated by the arrow c. The fluid passing through the fluid passage 14 of the electromagnetic valve 10 enters the compression chamber 7 through an inlet passage 9 to fill the same and excessive fluid flows through the throttle 8 to a tank 16 as indicated by the arrow d. As the piston 4 further rises, the throttle 8 is completely closed by the side wall of the piston 4 and, thereafter, the fluid pressure in the compression chamber 7 is built up by the rising piston 4. While the fluid pressure in the compression chamber 7 is lower than the valve opening pressure of the discharge valve 15, the fluid in said chamber flows out through the electromagnetic valve 10 as indicated by arrow e and returns to the tank 16 by-passing the feed pump 17 through a pressure regulating valve arranged in the pump and set to open at a pressure less than that of the discharge valve 15. When the volume of the compression chamber 7 is reduced to a value corresponding to a required quantity of fluid to be discharged upon further upward movement of the piston 4, the electromagnetic valve 10 is energized, by the controller 18 which receives a signal from the timing pick-up 19 with the result that the valve rod 13 snugly seats on the valve seat 12, stopping the flow of fluid, whereby the fluid is positively confined within the compression chamber 7 and metered thereby. As the piston 4 further rises, the fluid pressure overcome the valve opening pressure of the discharge valve 15 and the fluid thus metered is discharged through said discharge valve in the direction of arrow g. As the discharge proceeds and the piston 4 further rises, the fluid passage 5 in the piston 4 is communicated with the throttle 8, so that the fluid confined within the compression chamber 7 is released to the outside in the direction of arrow d. Thus, the fluid pressure in the compression chamber is reduced and the fluid discharge is positively ended. Namely, the end of the fluid discharge operation can be maintained constant. From the foregoing description, it will be understood that by electrically determining the time when the electromagnetic valve 10 is closed, with the valve rod 13 in intimate engagement with the valve seat 12, it is possible to accurately control the discharge quantity of fluid.

Although in the embodiment described and illustrated herein the end of the fluid discharge operation of the piston 4 is defined before said piston reaches its top dead center, by the fluid passage 5 and the throttle 8 provided in the piston 4 and on the cylinder 6 respectively, it may be possible to define the end of the fluid discharge operation by the arrival of the piston 4 at its top dead center.

As described above, according to the present invention the quantity of fluid to be discharged from a reciprocating pump, is metered by providing the electromagnetic valve 10 in the fluid inlet passage 9 communicating with the compression chamber 7 formed between the piston 4 and the cylinder 6, said electromagnetic valve 10 being normally held in the open state to provide for constant supply of fluid into the compression chamber 7 but being closed when the volume of said compression chamber has been decreased, in the upward stroke of the piston 4, to a value corresponding to the desired discharge quantity of fluid, to confine and meter the fluid in said compression chamber. Therefore, with the device of the present invention, it is only necessary to maintain the electromagnetic valve in the open state or in the closed state according to the desired rate of discharge, as contrasted to the conventional discharge control devices wherein the end of the return stroke of the piston is defined mechanically. Consequently, the present invention has the excellent advantage that an electrical discharge controlled pump means of an extremely simple construction can be obtained.

Claims

What is claimed is:

1. A discharge-controlled pump means comprising:

a cylinder having a piston reciprocally received therein, and defining a compression chamber within said cylinder on one side of said piston;

means for intermittently reciprocating the piston to decrease the volume of the compression chamber and means for alternately restoring the piston to a position wherein the volume of the compression chamber is increased;

a fluid supply;

reversible flow conduit means for forwarding fluid from the fluid supply to the compression chamber and for returning fluid from the compression chamber to the fluid supply;

a discharge valve in communication with said compression chamber, and arranged for discharging fluid from the compression chamber when the piston has reached the vicinity wherein the volume of the compression chamber is at least nearly its smallest;

pressure responsive means on said discharge valve for maintaining said discharge valve in a closed condition until the fluid pressure in said compression chamber increases to a predetermined threshold value;

a normally open electromagnetic valve interposed in said conduit means;

a controller interconnecting the normally open electromagnetic valve and the means for intermittently reciprocating the piston for controlling the electromagnetic valve in response to reciprotation of the piston, said controller being set to close the normally open electromagnetic valve only for a period of time beginning after the piston has begun to decrease the volume of the compression chamber but before the piston has reached the vicinity wherein the volume of the compression chamber is its smallest;

and normally closed back pressure relief valve means interposed in said conduit means between said electromagnetic valve and said fluid supply, said back pressure relief valve means having a threshold pressure for opening which is lower than the threshold pressure for opening said discharge valve;

said compression chamber being so arranged that, upon reciprocation of said piston to decrease the volume of the compression chamber, the threshold pressure for opening the normally closed back pressure relief valve is reached before said normally open electromagnetic valve is closed by said controller; whereby a controlled amount of fluid is present in the compression chamber when the normally open electromagnetic valve is closed by said controller, so that a controlled amount of fluid may be expelled from the compression chamber through said discharge valve, upon further reciprocation of the piston in a sense to decrease the volume of the compression chamber.

2. The discharge controlled pump means of claim 1 wherein the back pressure relief valve is incorporated in a feed pump, said feed pump being configured for pumping fluid from the fluid supply to the compression chamber.

3. The discharge controlled pump means of claim 1 further including further conduit means communicating between the compression chamber and the fluid supply for returning excess fluid from the compression chamber to the fluid supply during an initial portion of each reciprocation of the piston in a sense to decrease the volume of the compression chamber, the further conduit means being adapted for this task by being communicated to the compression chamber at a location disposed to be shut-off by the piston at the conclusion of said initial portion of each reciprocation of the piston.

4. The discharge controlled pump means of claim 3 wherein the communication of the further conduit means to the compression chamber is so located that said communication is shut-off by said piston before the threshold pressure for opening the back pressure relief valve has been reached.

5. The discharge controlled pump means of claim 3 wherein flow restricting throttle means are interposed in said further conduit means.

6. The discharge controlled pump means of claim 3 further including fluid passage means in said piston disposed for communicating between the compression chamber and the further conduit means only during a terminal portion of each reciprocation of the piston, after the discharge valve has opened during each respective reciprocation.