US 3344746 A
Description (OCR text may contain errors)
Oct. 3, 1967 P. E. SCOVELL 3,344,746
PISTON OPERATED PUMPS FOR LIQUID CARBON DIOXIDE Original Filed Aug. 7, 1964 INVENTOR avi /M %M ATTORNEYS United States Patent 3,344,746 PISTON OPERATED PUMPS FOR LIQUID CARBON DIOXIDE Peter Eric Scovell, South Croydon, England, assignor to The Distillers Company Limited, Edinburgh, Scotland, a British company Continuation of application Ser. No. 388,205, Aug. 7, 1964. This application Dec. 22, 1966, Ser. No. 604,068 Claims priority, application Great Britain, Aug. 21, 1963, 33,004/ 63 7 Claims. (Cl. 103-153) This is a continuation of application Ser. No. 388,205 filed Aug. 7, 1964, now abandoned.
This invention is concerned with improvements in or relating to piston operated pumps adapted to pump liquid carbon dioxide.
Piston operated pumps adapted to pump liquid carbon dioxide have been known for a number of years. These pumps are not entirely satisfactory in that liquid carbon dioxide tends to leak from the pumping chamber between the piston and cylinder wall where, due to the sudden reduction in pressure, it changes to gas and solid. The presence of the solid carbon dioxide between the piston and cylinder wall causes wear and unsatisfactory pumping action. The term cylinder wall used throughout this specification includes any surfaces encircling the piston, such as for example sealing surfaces.
An object of the present invention is to provide an improved piston operated pump in which the disadvantage hereinbefore described is either reduced or eliminated.
Accordingly the present invention is a piston operated pump adapted to pump liquid carbon dioxide wherein a device is provided which is capable of applying a gas under pressure to any liquid carbon dioxide which leaks from the pumping chamber between the piston and cylinder wall, said pressure being sufiicient to prevent liquid carbon dioxide from solidifying between the piston and cylinder wall. 7
The device is preferably an annular recess in the wall of the cylinder below the piston head which forms a cavity in combination with the piston and a passageway in the wall through which fluid under pressure can be supplied to the cavity. A sealing gland or glands are preferably provided in this cavity which reduce the tendency for liquid carbon dioxide to leak past the piston. The passageway which connects this cavity and the outside of the cylinder can be formed by a hole bored through the cylinder wall. Gas can be supplied through this passageway to the cavity to give a pressure sufiicient to prevent any liquid carbon dioxide which leaks between the piston and the cylinder wall from solidifying.
Any pressure greater than the pressure at the triple point pressure of any carbon dioxide which has leaked between the piston and cylinder wall is suitable. When the pump is operated at ambient temperatures a suitable pressure is between 200 and 800 pounds per square inch. This is the pressure range under which liquid carbon dioxide is normally stored. Thus in a preferred embodiment the device is supplied with carbon dioxide by connecting it to a container of liquid carbon dioxide, for example the liquid carbon dioxide which it is desired to pump.
The preferred gas is carbon dioxide. When the device is an annular recess in the cylinder wall as hereinbefore described the carbon dioxide can be supplied to the cavity as a liquid where it forms the gas under pressure under the influence of the heat generated by the pump as soon as it is operated.
An embodiment of the present invention is illustrated in the accompanying drawing which shows a longitudi- Patented Oct. 3, 1967 nal section of a piston operated pump. The pump consists of a body 1 formed internally into a cylinder with a cylinder wall 3 and a piston 2 attached to a crank 4 within the cylinder. One end of the cylinder is formed into a pumping chamber 5 which is provided with an inlet valve 6 and exit valve 7 to allow liquid carbon dioxide to enter and leave the pumping chamber. The cylinder wall is provided with an annular recess 8 which forms a cavity 9 in combination with the piston. A gland 10 is provided in this cavity at the end nearest to the pumping chamber. This gland forms a seal which reduces the amount of liquid carbon dioxide entering the cavity from the pumping chamber. A gland 11 is provided at the other end of the cavity to prevent or retard the escape of carbon dioxide gas from the cavity. A passageway 12 is formed between the cavity and the outside of the cylinder by a hole bored through the cylinder wall. This passageway allows gas under pressure to pass into the cavity.
In operation when piston 2 is lowered liquid carbon dioxide is drawn into the pumping chamber 5 through an inlet valve 6 from a container in which it is stored under a gas pressure of approximately 300 pounds per square inch. It is then forced out of the pumping chamber through outlet valve 7 when piston 2 is raised. During this reciprocating movement of the piston cavity 9 is pressurised to a pressure of 300 pounds per square inch by carbon dioxide gas from the container. Any liquid carbon dioxide which leaks from the pumping chamber 5 between the piston and cylinder wall past gland 10 is prevented from expanding to form solid carbon dioxide by the pressure of carbon dioxide gas in cavity 9.
1. A piston pump apparatus adapted to pump liquid carbon dioxide, comprising a cylinder member having a pumping chamber therein, a piston member reciprocally slidable within the cylinder member to pump fluid from the pumping chamber, the members having sizes such that liquid carbon dioxide leaks from the chamber between the members, at least one of said members having a cavity therein opening laterally against the other member, a source of gas under a pressure greater than the triple point pressure of the carbon dioxide being pumped, and conduit means coupling said source of gas and said cavity for applying the gas under said greater pressure to the space between the piston member and the cylinder member wall, whereby when said gas is supplied to the cavity and applied to the liquid carbon dioxide which leaks from the pumping chamber between the piston member and the cylinder member Wall, it will prevent liquid carbon dioxide from solidifying between the piston member and cylinder member wall.
2. A pump apparatus as claimed in claim 1 in which the cavity is an annular recess in the cylinder member wall below the piston member head, and said conduit means includes a passageway in the wall through which the gas under pressure can be supplied to the cavity.
3. A pump apparatus as claimed in claim 2 in which the cavity has a sealing gland at the end thereof toward the piston member head which reduces the tendency of liquid carbon dioxide to leak past the piston member.
4. A pump apparatus as claimed in claim 1 in which the source of gas under pressure is a source of carbon dioxide.
5. A process for pumping liquid carbon dioxide which comprises supplying liquid carbon dioxide to the pumping 6. A process as claimed in claim 5 wherein the ap-' plied gas is carbon dioxide.
7. A process as claimed in claim 5 wherein the gas is carbon dioxide formed from liquid carbon dioxide under the influence of heat generated by the pump when it is 5 operated.
References Cited UNITED STATES PATENTS Slate 6210 Seligmann 62-10 White 103153 Prosser 103204 Tyree 103153 Yaindl 62-55 Loliger 103204 DONLEY I. STOCKING, Primary Examiner.
7/1921 Schlacks 230-203 10 HENRY F. RADUAZO, Examiner.