Constant Pressure Liquid Supply System

Abstract

A constant pressure liquid supply system including a tank having an inlet; pump which has an inlet for receiving fluid and an outlet which is connected to the tank inlet; switch means connected to the pump for turning the pump on and off; and means responsive to fluid pressure within the tank and cooperable with the switch means for turning the pump on when the tank fluid pressure falls below a predetermined level and turning the pump off when the tank fluid pressure attains said predetermined level. A bladder for containing liquid may be mounted in the tank and may have an outlet which extends therefrom for discharging the liquid when squeezed down by fluid pressure within the tank.

Description

STATEMENT OF GOVERNMENT INTEREST

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION

In U. S. Pat. No. 3,434,443 entitled "Underwater Buoyancy Transport Vehicle" to Estabrook there is disclosed a diver operated underwater vehicle which includes a hollow sphere for changing the buoyancy thereof. It has been found that the decomposition products of liquid hydrazine are an excellent medium for deballasting this sphere. This hydrazine or similar medium, is under pressure in a supply tank, and must be available for the beckoning call of the diver. It is desirable that the supply tank remain at a constant pressure until all of the hydrazine is expelled therefrom, and that the tank enable safe loading of the hydrazine and use thereof. Prior art methods of pressurizing underwater fuel tanks involved bottled gas pressurization systems, or the use of elastomers or springs to squeeze the fuel container. Bottled compressed gas loses its efficiency with depth and requires another refueling step before operation of the vehicle. Springs and elastomers result in a pressure drop in the tank as the fuel is expelled therefrom. In some instances a large fraction of the fuel remains in the tank when the tank pressure has dropped to the lowest acceptable level. In regard to the supply tank itself, it is necessary that the hydrazine fuel be separated from the pressurizing medium and that the tank be safe during loading, use, and storage. Prior tank systems for hydrazine stored the hydrazine fuel under pressure. These systems require the transfer of fuel under hazardous field conditions and subjected personnel to possible exposure to hydrazine contamination should the fuel tank rupture. Accordingly, there is a need for a safe system which will efficiently provide hydrazine upon demand for deballasting purposes in an underwater vehicle.

SUMMARY OF THE INVENTION

The present invention overcomes the aforementioned problems associated with the prior art by providing a unique constant pressurization system and tank which is especially adapted for handling hazardous liquids, such as hydrazine, in an underwater environment. This system may include a tank which has an inlet; a pump which has an inlet for receiving fluid, such as seawater, and an outlet which is connected to the tank inlet; a switch means connected to the pump for turning the pump on and off; and means responsive to fluid pressure within the tank and cooperable with the switch means for turning the pump on when the tank fluid pressure falls below a predetermined level and for turning the pump off when the tank fluid pressure attains said predetermined level. A bladder may be mounted in the tank and may be capable of containing the liquid. The bladder may have an outlet extending from the tank for discharging the liquid when squeezed down by the fluid pressure within the tank. It should be understood that the liquid supply system is not confined for use to hazardous liquids such as hydrazine, but can be utilized for supplying practically any liquid or even a gas.

STATEMENT OF THE OBJECTS OF INVENTION

An object of the present invention is to overcome the aforementioned problems associated with prior art pressure liquid supply systems.

Another object is to provide a constant pressure liquid supply system which can be utilized safely for loading hazardous fuel, using such fuel, or storing such fuel.

A further object is to provide a constant pressure liquid supply system which is capable of expelling substantially all of the fuel from the system under a constant pressure.

Other objects and many of the attendant advantages of this invention will be readily appreciated as it becomes better understood by reference to the description and accompanying drawings which follow.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic block diagram illustration of the constant pressure liquid supply system; and

FIG. 2 is a detailed cross-sectional view of the supply tank for the constant pressure liquid supply system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawing wherein like reference numerals designate like or similar parts throughout the several views there is shown in FIG. 1 an exemplary constant pressure liquid supply system 10 which is capable of supplying under a constant pressure a hazardous liquid, such as hydrazine, for use in underwater operations. The system 10 includes a tank 12 which has an inlet 14. A pump 16 is provided which has an inlet 18 for receiving fluid, such as ambient seawater, and an outlet 20 which is connected to the tank inlet 14. A switch means, such as push button switch 22, is connected by electrical leads 24 to the pump 16 for turning the pump on and off. Means, such as an accumulator 26, responsive to fluid pressure within the tank 12 and cooperable with the switch 22, is provided for turning the pump 16 on when the tank fluid pressure falls below a predetermined level and turning the pump off when the tank fluid pressure attains the predetermined level. This level will depend upon the needs of the follow on system which demands the fluid supply. When the system 10 is utilized in a seawater environment it is desirable to provide a filter 28 at the inlet 18 of the pump so as to prevent the intake of foreign material which may damage the system.

The accumulator 26 may include a piston 30 and rod 32 which are disposed within a piston cylinder 34. One end of the piston cylinder 34 may have an inlet 36 which is connected to the outlet 20 of the pump, and at the other end of the cylinder 34 the piston rod 32 may extend therefrom opposite the pushbutton of the switch 22 for turning the pump on and off. A spring 38 may be disposed between the bottom of the piston 30 and the end of the cylinder for biasing the piston toward the cylinder inlet 36. In the arrangement shown the switch 22 is a normally on switch so that when pressure within the volume 40 of the accumulator attains a predetermined level the piston rod 32 engages the push button of the switch 22 and causes the switch to turn the pump 16 off. It should be noted that when this condition occurs the accumulator 26 has stored a supply of fluid within the chamber 40 which will supply fluid to the tank 12 under spring pressure 38 until such time that the piston rod 32 backs off sufficiently from the push button of switch 22 to turn on the pump 16. Accordingly, the accumulator 26 serves a double function as an accumulator as well as a means for actuating the system on and off to maintain a constant pressure. The level of actuation is determined by the strength of the spring 38 and the range of fluid pressure between off and on conditions of the pump 16 is determined by the amount of movement of the piston rod 32 before the push button reactivates the switch 22. In order to prevent loss of fluid pressure from the tank 12 during the period when the pump 16 is in an off condition, a check valve 42 may be located between the outlet 20 of the pump and the inlet 14 of the tank as well as between the outlet 20 of the pump and the inlet 36 of the accumulator.

As illustrated in FIG. 2, a bladder 44 is mounted in the tank 12, and is capable of containing liquid, such as hydrazine. The bladder 44 has an outlet 46 which extends from the tank 12 for discharging the liquid when squeezed down by fluid pressure within the tank. The tank 12, which may be generally cylindrical, may have an annular retainer plate 48 which seals the end of the tank by an O-ring 50, and is removable therefrom when a retainer ring 52 is removed. The retainer ring 52 may be locked in place by a block and bolt combination 54 which is disposed between a space in the ring and is threaded into retainer plate 48.

As illustrated in FIG. 2, the bladder 44 may be generally elongated and may have a rigid end plate 56 and 58 mounted at each end thereof. The end plate 56 may be utilized for connecting the bladder 44 to the retainer plate 48 by bolts 60. In this manner, the bladder 44 is easily removed from the tank 12 upon removal of the retainer plate 48.

A quick disconnect fitting 62, which provides the bladder outlet 46, may be connected to the end plate 56 and may extend through the tank's retainer plate 48 for connection to the liquid consuming system (not shown). The end plate 58 may include bolts 64 which are capable of resting on the bottom of the tank 12 when the tank is uprighted so as to relieve the weight of the bladder and its end plates from the bladder walls when in such position.

In order to facilitate loading of the bladder 44 with liquid fuel, the tank 12 is provided with a vent hole 66 and a removable plug 68 disposed therein. When the bladder 44 is to be filled with liquid, the plug 68 is removed and the pump 16 is turned on to pump fluid, such as water, into the tank 12. When all air has been vented from the tank the pump 16 is turned off and the plug 68 is inserted. The pump 16 is then turned on again and fluid pressure is applied within the tank 12 until the bladder 44 is squeezed down to a minimum volume. The bladder is now readied for receiving a hazardous liquid fuel, such as hydrazine. A hydrazine supply hose may be connected to the quick disconnect 62, after which the vent plug 68 may be removed to relieve fluid pressure within the tank 12. Pressure at the quick disconnect opening 46 can then easily completely fill the bladder 44 with the hazardous hydrazine. After the bladder 44 is completely filled the vent plug 68 is inserted so as to ready the system for operation.

In the operation of the system the pump 16, when on, pumps fluid, such as seawater, into the tank 12 and applies a pressure to the bladder 44 which contains liquid fuel, such as hydrazine. The accumulator 26 sees the pressure of the pump and when this pressure has reached a predetermined level the piston rod 32 of the accumulator engages the push button of switch 22 to turn the pump 16 off. The accumulator 26 accumulates a certain amount of seawater to supply operating pressure to the tank 12. When this pressure is lowered sufficiently the piston rod 32 backs off of the push button of the switch 22 to again turn on the pump 16. The pump 16 then operates until the desired fluid pressure is again obtained within the tank 12. In this manner, a substantially constant fluid or seawater pressure is applied to the bladder 44 so that the liquid fuel within the bladder 44 is likewise supplied under a constant pressure through the opening 46.

It is now readily apparent that the present invention provides a unique combination of constant pressurization means as well as a tank for supplying hazardous liquid, such as hydrazine. The present invention has been especially useful in supplying hydrazine fuel for deballasting a buoyancy sphere within the underwater buoyancy transport vehicle described hereinabove.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

Claims

I claim:

1. A constant pressure liquid supply system comprising:

a tank having an inlet;

a pump having an inlet for receiving fluid and an outlet which is connected to the tank inlet;

switch means connected to the pump for turning the pump on and off;

means responsive to fluid pressure within the tank and cooperable with the switch means for turning the pump on when the tank fluid pressure falls below a predetermined level and turning the pump off when the tank fluid pressure attains said predetermined level;

a bladder mounted in the tank and capable of containing liquid;

said bladder having an outlet extending from the tank for discharging the liquid when squeezed down by fluid pressure within the tank;

said tank having a retainer plate which seals the tank and is removable therefrom;

said bladder being elongated and having a rigid end plate mounted at each end thereof; and each of

the bladder end plate being mounted to the retainer plate.

2. A system as claimed in claim 1 including:

said tank having a fluid vent hole and a removable plug disposed therein.

3. A system as claimed in claim 2 including:

a quick disconnect fitting mounted to said one of the bladder end plates serving as the bladder outlet, and extending through the tank's retainer plate.

4. A system as claimed in claim 3 including:

means mounted to the other bladder end plate for engaging an inside wall of the tank and relieving the weight of the bladder and other end plate when such weights are directed toward said wall.

5. A system as claimed in claim 4 including:

the fluid pressure responsive means being an accumulator which includes a spring biased piston and rod within a cylinder;

the outlet of the pump also being connected to the accumulator for applying pressure against said piston;

said switch means being a push button switch; and

said rod extending from the cylinder and being engageable with the push button of the switch for turning the pump on and off.

6. A system as claimed in claim 5 including:

a check valve connected between the pump and the tank, and the pump and the accumulator.