JPH0756256B2 - Double-acting liquefied gas pump - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a liquefied gas pump, and in particular, to liquefied oxygen, liquefied nitrogen, liquefied argon, liquefied hydrogen, and liquefied natural gas, which are in a highly vaporizable state. The present invention relates to a liquefied gas pump used to do so.

(Prior Art) A liquefied gas pump is used to store liquid from a storage tank or a gas generator.
It is widely used in the fields of inhaling liquefied gas, transferring or discharging it to an evaporator, consuming it, or filling it in a container. The types of liquefied gas include oxygen, nitrogen, argon, hydrogen, and natural gas. is there.

Cavitation, strength, and sealing are important items to consider when designing a liquefied gas pump. A high-pressure pump has a heavy structure due to its strength, the amount of residual liquid discharged increases, the residual liquid also becomes hot, and the heat generated by the surface pressure required for sealing makes it difficult to prevent cavitation.

U.S. Pat. No. 3,181,1 as a known reference for a liquefied gas pump.
No. 473, No. 4396362, JP-B-51-44165 and JP-B-59-32668.

U.S. Pat. No. 3,181,473 shows a structure for reducing the residual liquid discharged, U.S. Pat. No. 4,393,362 shows a structure for not sucking the residual liquid discharged, and Japanese Utility Model Publication No. 51-44165 discloses a piston piston bottom dead center A structure in which a suction port is provided in the part is shown, and JP-B-59-32668 discloses a structure for reducing the amount of residual liquid discharged and a structure for opening and closing the suction valve by the operation of a piston.

(Problems to be solved by the invention) As a measure for preventing cavitation in a liquefied gas pump, 1) reduction of pressure loss of suction passage and suction valve 2) prevention of gasification of fluid by heat 3) reduction of leakage of valve 4) residual discharge Reduction of amount 5) Removal of gas contained in intake fluid 6) Treatment of leak fluid from piston ring.

Regarding the preventive measure 1), there is a method of shortening the suction passage by suctioning from the cylinder head side (US Pat. No. 3,181.473). In that case, the weight of the suction valve body and the suction valve spring cause pressure loss. Becomes If the suction flow path is provided in the piston, the flow path becomes long and the gas in the flow path cannot be separated. Japanese Examiner Sho 59-
Although the valve operating pressure loss of 32668 is close to zero, the pressure loss in the suction passage remains, and it is considered that the surface pressure of the valve seat becomes excessive and wear is large.

With regard to the preventive measures 2), it is a known fact that the pump section is thermally insulated (vacuum, simple, dipping) in order to prevent the heat effect on the pump from the outside, and it is adopted according to the application. The generation of frictional heat and compression heat of the piston ring cannot be prevented as much as when high pressure is required, and there is only a general method of cooling using a leaking fluid from the piston ring.

Preventive measures 3) There is a method of increasing the seat surface pressure with a spring to prevent the intake valve from leaking, but the spring force acts as an inflow resistance. There is a method to reduce the intake valve lift to prevent intake valve leakage, but the inflow resistance increases as the inflow speed increases.

Preventive measures 4) In JP-B-59-32668, the clearance between the piston and the cylinder head can be zero, but the residual liquid between the intake valve seat and the discharge valve seat cannot be zero.

Regarding preventive measures 5) Generally, a gas return line is provided. However, in the gas-liquid mixed state, the gas exists in the form of fine bubbles, so there is a limit to the separation based on the principle of specific gravity difference.

About preventive measures 6) Generally, the leak fluid from the piston ring is sent to the gas return line after cooling the cylinder.

It is an object of the present invention to provide a double-acting liquefied gas pump that solves the above-mentioned problems in the conventional technique, particularly the problem that cavitation is likely to occur and the volumetric efficiency is reduced.

(Means for Solving the Problems) According to the present invention, a mechanism that double-acts in one reciprocation of the piston by a cylinder provided with a main and preload pump chamber and a piston provided with a main and preload piston section, Provided is a double-acting liquefied gas pump including a preload adjusting valve provided on a piston and arranged between a main pressure chamber and a preload pump chamber, and a spring-loaded automatic valve that opens and closes a preload suction valve and a preload discharge valve by piston operation. It

(Operation) By providing a main piston part and a preload piston part and operating the main piston part under the preload of the preload piston part, cavitation can be reliably prevented.

By providing the preload adjusting valve between the main and preload piston parts, it is possible to prevent the preload applied by the preload piston parts from becoming excessive.

Since the preload suction valve and the preload discharge valve are automatic valves that open and close by the operation of the piston, it is possible to prevent the preload pump chamber from becoming excessively low pressure.

(Embodiment) In the figure, reference numeral 1 is a housing, which is provided with an intake port 2, a discharge port 3, and a gas return port 4. A cylinder 5 is fitted in the housing 1, and a stepped hole including a small diameter hole 5A and a large diameter hole 5B is formed in the cylinder 5. A piston 6 is slidably fitted in a small diameter hole 5A of a cylinder 5, and a piston rod 7 connected to the piston 6 extends in the large diameter hole 5B. The piston 6 is provided with a piston ring 8. Piston 6
A main pump chamber 9 is defined between the front end of the main pump chamber 9 and the small diameter hole 5A of the cylinder 5, and a suction valve 10 and a discharge valve 11 are provided in association with the main pump chamber 9.

An annular preload pump chamber 12 is defined between the large diameter hole 5B of the cylinder 5 and the piston rod 7. A preload cylinder head 13 is provided at the rear end (right end in FIG. 1) of the preload pump chamber 12.
A preload suction valve 14 is arranged in the preload cylinder head 13.
The preload suction valve 14 communicates with a gas-liquid separation chamber 15 formed in the housing 1 between the suction port 2 and the gas return port 4 through an annular flow path 16, and when the piston 6 moves to the left. Preload suction valve
14 moves to the left with respect to the cylinder head 13 to open the flow passage 16, and when the piston 6 moves to the right, the preload suction valve 14 moves to the right to close the flow passage 16.

The preload suction valve 14 is of a split ring type having stepped notches 14B as shown in FIGS. 2 and 3, and is in sliding contact with the piston rod 7 by the inner peripheral surface, and is formed in the circumferential groove provided on the outer peripheral surface. It is pressed inward in the radial direction by a stretched spring 14A. When the preload suction valve 14 moves rightward in FIGS. 1 and 3, it comes into contact with the valve seat provided on the cylinder head 13, and the leftward movement is restricted by the retainer 17.

A front end of the preload pump chamber 12 is limited by an annular preload piston 18 fixed to the piston rod 7, and a preload discharge valve 19 which also functions as a piston ring is provided in an outer peripheral annular groove of the preload piston 18. Preload discharge valve 19 is a preload suction valve
A large split hole 5B of the cylinder 5 is provided with a split ring type having a stepped notch similar to that of 14, and is given a tension outward in the radial direction by a spring 19A stretched in an inner peripheral annular groove.
Make sliding contact with. That is, while the preload suction valve 14 has an inner spring, the outer spring 19
Have an A The preload discharge valve 19 opens when it moves to the left in FIG. 1 with respect to the preload piston 18, and closes when it moves to the right in FIG.

The piston rod 7 has a central hole 20 extending rearward from its front end.
And the hole 20 communicates with the outlet of the preload discharge valve 19 through a radial hole provided in the preload piston 18 and a radial hole 21 provided in the piston rod 7. The intake valve (10) comes into contact with and separates from a valve seat provided at the front end of the hole (20). The discharge valve 11 is arranged in the stepped holes 5C and 5D at the front end of the cylinder 5 so as to face the suction valve 10. Reference numerals 30 and 31 are springs and spring guides that press the discharge valve 11 toward its valve seat.
Is a stopper that limits the movement of the suction valve.

The central hole 20 of the piston rod 7 is
A preload adjusting valve 24 communicates with an annular intermediate chamber 23 defined between the piston rod 7 and the holes 5A, 5B of the cylinder 5 behind the piston 6 and in front of the preload piston 18. The preload adjusting valve 24 is a sleeve-shaped member having a stepped inner diameter hole, and the end of the large diameter hole comes in contact with and separates from the valve seat formed on the side surface of the piston 6, and the small diameter hole portion slides airtightly with the outer circumference of the piston rod 7. To do. A spring 25 is arranged between the preload adjusting valve 24 and the preload piston 18. The intermediate chamber 23 is a radial hole provided in the cylinder 5.
It communicates with the annular gas seal chamber 27 formed between the outer periphery of the cylinder 5 and the inner surface of the housing 1 via 26, and the radial hole 26 constitutes a gas escape passage. The gas seal chamber 27 communicates with the gas return port 4 through the gas return passage 28. 29 is a seal ring provided between the preload adjusting valve 24 and the piston rod 7.

The operation of the illustrated apparatus is as follows. In the state shown in FIG. 1, the piston 6 and the preload piston 18 are at the frontmost part values, the main pump chamber 9 is at the end of the discharge stroke, and the preload pump chamber 12
Indicates the end of the inhalation process. With the completion of the discharge stroke of the main pump chamber 9, the discharge valve 11 is closed by the force of the spring 30 and the reverse flow from the discharge port 3 to the main pump chamber 9 is prevented.

When the piston rod 7 moves backward, that is, moves to the right from the position shown in Fig. 1, the preload suction valve 14 moves the lining spring 14A.
The valve is closed because it is lightly pressed against the piston rod 7 and moves backward together with the piston rod. The preload discharge valve 19 has a cylinder hole 5
Since it is pressed against B, the valve will open automatically. If piston rod 7 continues to move backward, preload piston 18
Moves backward together with the piston rod 7, and the fluid in the preload pump chamber 12 flows into the center hole 20 of the piston rod 7. The preload discharge valve 19 acts as a piston ring of the preload piston 18 and prevents the fluid in the preload pump chamber 12 from flowing into the intermediate chamber 23. The preload suction valve 14 is kept closed. That is, the preload pump chamber 12 is in the discharge stroke when the piston rod 7 moves backward.

At this time, the main pump chamber 9 is in the suction stroke, and the fluid in the center hole 20 of the piston rod 7 pushes the suction valve 10 open and flows into the main pump chamber 9. That is, the main pump chamber 9 is in the suction stroke.

Since the fluid flowing into the main pump chamber 9 is precompressed by the preload pump chamber 12, (a) the residual liquid discharged from the main pump chamber 9 is gasified, and (b) the fluid resistance when passing through the suction valve 10. Gasification occurs, (c) gasification occurs due to heat due to sliding resistance of the piston ring 8,
(D) Problems such as gasification of the leak fluid from the discharge valve 11 are prevented.

If the preload pressure rises more than necessary, the preload adjustment valve 24 opens against the spring 25, and a part of the fluid flows into the intermediate chamber 23.

When the piston rod 7 reaches the rearmost position, the suction stroke of the main pump chamber 9 and the discharge stroke of the preload pump chamber 12 are completed.

When the piston rod 7 starts the forward movement, the preload suction valve 14
Automatically opens because it is pressed against the piston rod 7 by the spring 14A, the preload piston 18 moves forward together with the piston rod 7, and the preload discharge valve 19 springs 19.
Since it is pressed against the cylinder, that is, the large-diameter hole 5B by A, it automatically closes, and the fluid has a small resistance and the preload pump chamber 12
Flows in. This is effective in lowering NPSH,
The suction valve 10 is closed, and the fluid in the main pump chamber is pushed open by the forward movement of the piston 6 to be discharged from the discharge port 3. At this time, the fluid in the center hole 20 is the piston rod 7
It moves forward together with the suction valve 10, preload discharge valve 19, preload adjustment valve
No flow occurs because all 24 are closed. From the above, it can be seen that during the forward movement of the piston rod 7, the main pump chamber 9 is in the discharge stroke and the preload pump chamber 12 is in the suction stroke.

Leak fluid passing through the piston ring 8 enters the intermediate chamber 23 during the discharge stroke of the main pump chamber 9. The fluid in the intermediate chamber 23 enters the gas seal chamber 27 through the escape passage (radial hole) 26. The gas vaporized by cooling the cylinder 5 flows to the gas return port 4 through the gas return passage 28. By doing so, there is no problem that cavitation occurs due to re-inhalation of the leaked fluid.

When the piston rod 7 reaches the most advanced position, the discharge stroke of the main pump chamber 9 and the suction stroke of the preload pump chamber 12 are completed.

In the figure, reference numeral 15 is a gas-liquid separation chamber, and liquefied gas from the storage tank or the liquid reservoir of the gas generator flows into the gas-liquid separation chamber 15 in the housing 1 through the suction port 2. The bubbles mixed in the fluid are separated from the liquid, flow out from the gas return port 4, and the liquid is sucked into the preload pump chamber as described above.

(Effect of the Invention) Cavitation can be reliably prevented by providing the main piston portion and the preload piston portion and operating the main piston portion under the preload of the preload piston portion.

By providing the preload adjusting valve between the main and preload piston parts, it is possible to prevent the preload applied by the preload piston parts from becoming excessive.

Since the preload suction valve and the preload discharge valve are automatic valves that open and close by the operation of the piston, it is possible to prevent the preload pump chamber from becoming excessively low pressure.

Therefore, the occurrence of cavitation can be minimized and the volumetric efficiency can be maximized.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a liquefied gas pump according to the present invention, FIG. 2 is a plan view of a preload suction valve, and FIG. 3 is a partial sectional view taken along line III-III of FIG. It is schematically shown by a chain line in the figure. 1: Housing, 2: Suction port, 3: Discharge port 4: Gas return port, 5: Cylinder, 5A: Small diameter hole 5B: Large diameter hole, 5C, 5D: Discharge valve flow path 6: Piston, 7: Piston rod 8 : Piston ring, 9: Main pump chamber 10: Suction valve, 11: Discharge valve, 12: Preload pump chamber 13: Preload cylinder head 14: Preload suction valve, 14A: Spring, 15: Gas-liquid separation chamber 16: Preload suction valve Flow path, 17: Retainer 18: Preload piston, 19: Preload discharge valve 19A: Spring, 20: Center hole 21: Radial hole, 22: Radial hole 23: Intermediate chamber, 24: Preload adjusting valve, 25: Spring 26 : Radial hole, 27: Gas seal chamber 28: Gas return flow path, 29: Seal ring 30: Spring, 31 Spring guide 32: Stopper

Claims (1)

[Claims] 1. A double-acting liquefied gas pump, a cylinder, a piston rod reciprocally provided in the cylinder, and a main pump chamber fixed to the piston rod at a downstream end in the cylinder. A piston defining a preload piston fixed to the piston rod, defining a preload pump chamber at an upstream end in the cylinder, and an intermediate chamber intermediate between the preload pump chamber and the main piston chamber, respectively. A center hole that is defined in the piston rod and connects the preload pump chamber and the main pump chamber, and is slidably attached to the outer circumference of the piston rod, and the fluid is preloaded according to the movement of the piston rod. An annular preload suction valve for flowing into the pump chamber, and an annular preload discharge valve provided in the preload piston for letting out a preloaded fluid in the preload pump chamber. A suction valve which is provided in the main pump chamber and allows a fluid sent from the preload pump chamber through the center hole to flow into the main pump chamber; A discharge valve for discharging and a slidable attachment to the piston rod, and when the preload of the fluid in the preload pump chamber rises above a predetermined value, a part of the flow is released to the intermediate chamber to preload the fluid. A double-acting type liquefied gas pump comprising: