US2537742A - Stressed pumping cylinder assembly for liquid oxygen - Google Patents

Description

Jan. 9, 1951 s. c. COLLINS 2,537,742

STRESSED PUMPING CYLINDER ASSEMBLY FOR LIQUID OXYGEN Filed May 24, 1949 b k g u mm M 1 Q will/1111111111111; w

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Patented he. 9, 1951]] UNITED srA'rEs PATENT OFFlCE STRESSED PUMPING CYLINDER ASSEMBLY FOR LIQUID OXYGEN same] 0. Collins, Water-town, a 1 the United States or America the Secretary of the Air Force Mass., assignor to as represented by Application May 24, 1949, Serial No. 95,060

' 3 Claims. (Cl. 103-153) This invention relates to a stressed-case pumping cylinder assembly adapted, to handle liquifled at pressures lap- Q gen or other liq'uifled bases proximating 3,000 pounds per square inch.

One object of the invention is to provide a pumping cylinder assembly, the casing of which is under substantial tension for the purpose of tight-assembly which has a-minimum of leakage.

Another object is to provide a pumping cylinder assembly of the above character in which the tension on the casing and the compression of the'intemal the turning of a screw.

Another object is toprovide a pumping cylinder assembly capable of handling liquid oxygen in whichthe valves have an parts under pressure in a parts are easily regulatable by with oxygen] liquifled gas (not shown) and the outlet pipe I 3 is connected to an empty oxygen cylinder .(likewise not shown) which is intended to be filled The liquid oxygen (or other liquifled gases) is evaporated and its temperature is subsequently raised to substantially room. temperature before it is stored in a cylinder under pressure. The

' heating occurs in apparatus capable-of withstanding internal pressure of the order of 3000 p. s. i. and provided with heat transfer surface over which the heating fluid (usually a blast of air from a fan) flows. The oxygen passes through the pump while it is still in the liquid phase and then it enters the evaporator. When the pres sure in the storage cylinder reaches the desired especially simple and eflicient arrangement so that a minimum of leakage will take place and aminimum of space will Briefly stated, the salient feature of themthe pumping cylinder, this casing being provided with internally beveled edges in their flanges. ,A combined system for putting tension on the easing and compression on most of the parts which the casing contains is provided and arranged to be regulatable by the turning of a single screw. In the drawings, Fig. 1 'is'an exterior elevation of the pumping cylinder and valve cages, the inlet and outlet pipes being shown in the section.

Fig. 2 isa vertical cross section taken along line 2--2 of Fig. 1. It shows the constructional" details of the valve'cages, the pumping piston and the novel casing of the tension of the compre sion adjusting screw.

Fig. 3 is a cross section of the casing and inlet valve cages taken along line3-3 of Fig. 2. The inlet valves and valve seats are shown in end and sectional views.

vention is that a casing which isprovided .to f enclose the valve cages and part of the bore of level, the pump is stopped.

His 9. piston of an oxygen pump (not shown) which pump is able to reciprocate the piston I 1 within a close fitting and highly polished bore l8 ofa pumping cylinder IS. The. latter is inclosed by a Jacket or sleeve 20 which is provided with a re-entrantbeveled flange 2|. The beveled angle approximates 45. Fitting the sleeve -III. The casing 20 is a flange 22 which is a part of the casing flanges, the. lower one being 23. The latter engages a circular tightening nut 24 which carries a matching bevel 25 adapted to fit an internal bevel 26 closely, this bevel being on the inner surface of flange 23 which likewise approximates 45 degrees in angle. The nut 24 is provided with an internally threaded bore 21 through which i an externally threaded screw or bolt 28' is en-' gaged. The screw 28 is preferably provided with a hexagonal head 29 for the attachment of a wrench.

Fig. 4 is a cross section taken on the line 4-4 The inner end of screw 28 and the inner end of nut 24 do not bear against an imperforate washer 30, but leave about A" clearance for assembly purposes. The washer 30 is preferably made of brass and fits casing l0 internally with a reasonably close fit to constitute an obturating means within the casing I0. Adjoining the washer 30 there is an exhaust valve body 31. Valve body 3| incorporates an opening 32 which is intended to serve as a combined exhaust valve chamber and exhaust port. The exhaust 16 projects through the opening 14 in the casing to to the exhaust port 32 in which it isheld by silver Q solder between the main body of the valve 3| i5, respectively. In practice, the inlet pipe isconnected to a reservoir of liquid oxygen or other and an upper annular portion 33 thereof. A soft metal gasket 34 separates the annular portion 33 of exhaust valve body 3| from an adjoining valve body which is the inlet valve body 35.

I0 bears two such re-entrant The latter incloses combined inlet port and inlet valve chamber 36 and from the port 33 projects the inlet pipe l which is silver soldered to the mainbody of the inlet valve body 35. A metal washer or diaphragm 38 surmounts an annular portion 31 of the inlet valve body 35 and is provided with a single opening 38 which is directly in front of the center of the piston H, the travel of which preserves a degree of clearance between the piston face and the washer 39. Contact between the inlet valve body 35 and the pumping cylinder I9 is stepped. Washer 40 surrounds the stepped portion 4| andserves with washer 34 to seal the valve chambers against leakage to the atmosphere. The stepped portion 4i serves to contain an inlet valve 42 and a valve spring 43, the latter being retained by the washer 38 and arranged to keep the valve 42 under compression in the seat 44.

An exhaust valve 45 is contained within the inlet passage 32 and faces in a direction opposite to that occupied by the inlet valve 42. It seats within the inlet valve body 35 and is retained in contact therewith by a valve spring 46.

In operation, an upward stroke of the piston II unseats the inlet valve 42 from its seat 44 against pressure of its spring 43 thereby admitting liquid oxygen through the inlet pipe I5 into the inlet passage 36 and through the opening 39 into the bore l8 of the pump.

As will be seen from Fig. 5, the valve 42 shown, which may be the inlet valve, comprises a cupshaped portion 41, therim of which bears a slot 48. Depending from the bottom 49 of the cupshaped portion 41 there is a three-lobed stem 50, the shape of which is intended to provide vertical support for the cup-shaped portion without interfering with the flow of liquid through the bore in which the valve 42 is positioned and which it is intended to open and close. In the present construction there are two bores of this nature; the inlet bore 5! which is machined from the seat 44, and the exhaust bore 52 which is machined from the inlet valve body 35.

Therefore, when liquid oxygen enters from the pipe l5 it can flow around the stem 50 of the valve 42 within the bore 5| and lift the cupshaped portion 41' from its seat against the pressure of the spring 43. On the return stroke of the piston, the cup-shaped portion again returns to the seat 44 thereby sealing the inlet pipe from the space 36. Piston pressure forces the liquid oxygen through the space 36 into channel 52 thereby pressing upon the cup-shaped portion 41 of exhaust valve 45, and lifting the latter off its seat thus allowing liquid oxygen to flow through the channel 53 around the valve stem 50 to the exhaust port space 32 and out the exhaust pipe i6.

Liquid oxygen pumps of this nature customarily operate in a bath of liquid oxygen. The

v coldness of the oxygen bath has a very considerable contracting force on the metal parts which make up a liquid oxygen pumping cylinder and necessitates selection of metals of coeflicients of expansion which do not differ greatly. Since the internal pressure in such cylinders is 3,000 or more pounds per square inch it will be understood that very heavy pressure is necessary to hold the metal parts together against leakage. Therefore, it will be seen that the valve bodies asshown in Fig. 2 must be in exceedingly close contact before pumping occurs so that flow will take place through the intended channels and not elsewhere. Likewise the pump bore l8 must be sealed by the gasket or washer 43 so that all of the pump charge is directed through that body into the exhaust valve body. It will readily be understood that the tightening of the screw 2| by a wrench applied to its head 23 will cause heavy pressure to be applied to the washer 33 thereby squeezing all the parts which lie between that washer and the flanges 2i and 22. The same force that pushes the parts toward the flanges Just mentioned will at the same time stress cooperating flanges 23 and 25. This adjustment is made before the pumping cylinder is immersed in the oxygen bath. After the adJustment has been made and immersion has taken place, the intense cold of the liquifled oxygen shortens or tends to shorten all of the dimensions or the metal parts and increases the grip with which the screw 28 and the casing) cooperate in holding the assembly together. The result is that the casing I0 is put under tension which is also proportional to the difl'erence of coefllcients of expansion of the metals used in constructing the-cylinden The fact that the casing I0 is longitudinally split gives rise to no substantial leakage in this construction because access to the space between the casing Ill and the valve bodies 3| and 35 is efl'ectively prevented by the washers or gaskets 34, 40 and 38. The size of the pumping cylinder has been held to a minimum by reason of this unique construction and therefore the size of the oxygen bath, with its consequent loss from evaporation can also be held to a minimum.

What I claim is:

1. A pumping assembly comprising a cylinder having a pumping bore, a reciprocable piston in said bore, the necessary inlet and exhaust valve operatively attached in an assembly to the end of said bore in the order named, an inlet and an exhaust pipe attached to enter said cylinder at the appropriate valves thereof, a nut positioned to abut the valve assembly, a screw threadedly engaging said nut, an externally projecting flange disposed around said pumping bore, an externally projecting flange disposed about the outer surface of said nut, a longitudinally split casing enclosing the entire pumping cylinder but clearing the inlet and exhaust pipes, said casing having internally projecting flanges adapted to cooperate with said outwardly projecting flanges and obturating means slidable in said casing under the urging of said screw, said obturating means being. in contact with the exhaust-valve assembly whereby tightening said screw against the obturating means will put the casing under tension and the valve assembly in tight contact with the pumping bore and with itself to minimize leakage.

2. A pumping assembly comprising a cylinder having a'pump bore, inlet and exhaust valves mounted in the order named at the working end of said pump bore, inlet and exhaust pipes operatively connected with said inlet and exhaust valvesand means comprising outwardly extending sharply beveled flanges external to the working and of said pump bore, a nut having similar shoulders, said nut positioned to abut thevalve assembly, a longitudinally split casing substantially SlllTGi. iding the working parts of said cylinder, said casing having an inwardly extending sharply beveled flange at each and adapted to cooperate with the respective flange on the cylinder and on the nut, a screw threadedly engaging said nut and a washer abutting the exhaust valve and forming an obturating means in sais pump bore, an inlet valve operatively positioned in said body, an inlet pipe operatively connected with said inlet valve body, an exhaust valve body, an exhaust valve operatively positioned therein, an exhaust pipe operatively connected to said exhaust valve body, a nut substantially adjoining said exhaust valve body, a screw adapted to compress the valve bodies and to hold them against the pump bore, a longitudinally split casing substantially surrounding the working end of said pump bore and pump bore jacket, and a solid washer filling the internal diameter of said oasing and abutting the lower side of the exhaust valve with its upper end and the inner end of 25 the screw with its lower end, said valve bodies,

said valves and a substantial portion of said nut, the nut and the working end of the pump bore having flanges which project outwardly at an acute angle, said casing having flanges at each end thereof adapted to fit and cooperate with he flanges on the nut and on' the pump bore jacket whereby when the screw is tightened in the nut against the washer, the-valve bodies will be tightened against the pump bore, the latter will be tightened against the pump bore jacket and the jacket will be tightened against one casing flange and the nut will be tightened against the other casing flange substantially to seal thepumping cylinder except at its inlet and outlet pipes.

' SAMUEL C. COLLINS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,572,045 Scott Feb. 9, 1926 2,312,857 Wcelfcr, Jr. Mar'. 2, 1943

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