US2855859A - Liquid-oxygen pumps - Google Patents

Description

Oct. 14, 1958 B. PETzoLD LIQUID-OXYGEN PUMPS Filed NGV. 3, 1955 ATTORNEY United States atent LIQUID-OXYGEN PUMPS Bruno Petzold, rlrostberg, Upper Bavaria, Germany, assignor to Adolf Messer G. m. b. H., Frankfurt-am- Main, Germany, a German company Application November 3, 1955, Serial No. 544,788

Claims priority, application Germany September 20, 1955 8 Claims. (Cl. 10B- 178) This invention relates to pumps, and, more specifically, to pumps for increasing the compression of liquid oxygen.

Reciprocating-piston liquid-oxygen pumps l build up pressures of 3000 lbs.and higher, and it is of the greatest importance that tendencies for oxygen to escape be minimized or eliminated. The importance of this is increased because of the combustible nature of oxygen, and its tendency to ilash when there is any signiiicant pressuredrop. The difliculty in effectively compressing liquid oxygen and in minimizing leakage is, moreover, increased because ordinary lubrication is impossible in the presence of liquid oxygen. These difculties are also increased because liquid-oxygen pumps are operated at temperatures below minus 200 F. and ordinarily at temperatures below minus 300 F.

The conditions of operation also increase the importance of simplicity and compactness of construction and of precise centering of all portions of the moving parts at all stages of the operation.

With the foregoing and other considerations in view, the present invention, in various of its aspects, contemplates the provision of sealing means which is tough and yet ilexible at low temperatures, the provision of effective and positive self-sealing means operated by the liquid oxygen or other uid being pumped, and the provision of a combined piston-rod-and-interior-piston arrangement having a non-canting driving action on a hollow exterior piston.

In accordance with the invention in one of its aspects, there is provided sealing means formed of a solidied plastic which does not become brittle at temperatures between minus 200 F. and minus 430 F. but which remains tough and flexible at such temperatures. Among such materials are polymerized fluorinated ethylenes (e. g., Teflon) and triuorochloroethylene polymers (e. g., Kel-F).

In accordance with the invention in another of its aspects, there is provided a positive seal which is selfsealing in the sense that the liquid oxygen or other fluid seeking to escape is trapped in a chamber containing a sealing ring one annular portion of which has a surface in contact with one of the relatively-moving parts and an opposite surface exposed to the pressure of fluid within said chamber and another annular portion of which is tightly lclamped against the other of the relativelymoving parts.

In accordance with the invention in still other of its aspects, a two-part piston is provided by extending the piston rod into the interior of a hollow piston, forwarddriving surfaces are provided interiorly of the hollow piston at a point forward of the rear end of the hollow piston and preferably generally centrally thereof, and/ or return-drive surfaces are provided at a forward point.

Further in accordance with the invention, various combinations of the features above indicated are provided.

The invention accordingly comprises the features of construction, `combinations of elements, and arrangement ice of parts, which will be exemplified in the constructions hereinafter set forth and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

Figure l is a transverse sectional view of the pump with thepiston members in their forward position:

Fig. 2 is a similar view thereof with the piston members in their rearward position;

Fig. 3 is `an enlarged View ofthe central portion of Fig. 2; and

Fig. 4 is an enlarged fragmentary sectional view showing a modification.

There is exemplified in Figs. 1-3 a form of oxygen pump embodying the invention. A hollow piston 10 is mounted for reciprocation within a cylinder 12, and is driven thru a lost-motion drive arrangement as hereinafter described by a combined interior piston member and piston rod 14, which is hereinafter referred to merely as a piston rod. During the rear stroke of the piston members, liquid oxygen, for example, at a pressure of one atmosphere, or other fluid is drawn into a pumpchamber 15 thru a passageway 16-17-18-19 from a liquid-oxygen chamber 20 and compressed, as to a pressure of 3000 lbs. When, during the forward stroke of the piston members, a desired pressure is built up, a valve 22'is forced open `to a chamber 23 against the pressure of a spring 24, and the compresed liquid oxygen forced into the chamber 23.

At the beginning of the forward movement of the piston rod 14, an annular shoulder 26 thereon contacts an annular shoulder 28 on the inner surface of the hollow piston 10, closing the passageway 16-17-18-19 and driving the piston 10 forwardly with the piston rod 14 to force the liquid oxygen ahead of a shoulder 29 on the piston rod and ahead of the forward ends of the piston 10 and the piston rod 14.

At their forward ends, the piston rod and piston are formed with cooperating shoulders 30 and 31. It will be noted, as shown in Fig. 1, that these shoulders are separated when the shoulders 26 and 28 are in engagement during the forward movement of the piston rod and piston. When, however, the piston rod begins its rearward movement, the shoulder 26 moves away from the shoulder 28 until the shoulder 30 meets the shoulder 31, whereupon the piston 10 moves rearwardly with the priston rod 14 to the position of Fig.'2. As the shoulder 26 moves away from the shoulder 28, the passageway 16-17181 9 is. opened, permitting liquid oxygen from the chamber 20 to be drawn into the chamber 15.

Pursuantto the invention, the shoulder 28 is disposed well forward of the rear end of the pisotn 10, and preferably in a position generally centrally of its length, and the shoulders 30 and 31 are disposed near the forward ends of the piston members, so that tendencies for the piston to cant, with consequent binding, cocking, buckling, and/or uneven wearing, are minimized.

The piston rod is mounted within bushing 33 and stuffing box 34. The bushing 33 is carried in a wall portion 35 which serves as part of the closure for the chamber 20. Another portion of this closure is shown at 36. A bracket 36a serves to additionally support the cylinder. The stuffing box 34 is mounted on a wall portion 36o, which provides part of the closure for a chamber 36d, as

does also the wall portion 35.

The piston rod 14is reciprocated by a suitable drive mechanism, not shown, and is centered within the piston 10 by struts 37.

The cylinder 12 is provided with cold-resistant bushinns .3 8 an d3 9 which seal thespace .betweenitandthe piston as effectively as tpossible, and act as bearings for radial loading of the piston. In order, however, to yproyidea Tpositive s ealiwhich :will preMent, f to` a maximum rextetlt, leakage Aof the liquid :oxygen or .other iuid, lthere 1s provided, in the iinterior wall :of the cylinder 12, a :chamber 4 0 .which :open to :the :outer surface -of ithe misten 1.0, and, -Wthin the chamherand alying :againstzt'he outer surface :.of thei piston 21.0 and tightly lclampedagainst the rearward portion of the tehamher 4.0., :an :annular :Seal 42 Which is formed ,of ;a ,cold-,resistant #plastic which is of the nature indicated above and :may rb e `one of ithe .types indicated above In the present instance thecylindertis out away as indieated1atr44 and -.the-.c hamb er 40 is provided within 'metal annuli 45, 46, and 47. The space forward iof the an- -ullhle =,45 Vandthe space A between the :annulus 45 .and the annulus 46 are both closed by cold-resistaui-sealing ma- :terial E48. The rear `end .zof the sealing rannulus 42 is clamped .firmly betweenthe annuli 146 and 41, the latter of which has 4a forward extension 49 :at its inward edge over -which the sealing ,annulus l2 4is ycurved. lu the present `-instance the forward :port-ion of the sealing an- ,nulusAZ is urged against the outer surface ofthe piston lllfnotionly by the .pressure of the liquid oxygen or other :fluid which leaks into the chamber 40 between the forward portions -of the cylinder and rpiston vand past the bushing 3 8 and the annulus .45, :but also by a metal ring 50.; but in many instances vthis ring Imay be .omitted as :indicated lin Fig. `4, the :pressure :of the liquid oxygen within the chamber 4 0 being in itself s utlicient to press :the forward end of the 'sealing ring V42. against the outer Isurface of 4the piston 10 with such firmness as to prevent substantial leakage of oxygen past (the fpoint of Contact of the sealing ring 42 with the piston.

The spaceibetween the self-sealing annulus 42 and the .wall 36 is vented as at v52' to leak into .a .chamber 5 3 any roxygen or other -uid which vmay by-.pass the self-sealing .annulus 42.

:Since certain changes may be made in fthe above con- 'struction and different embodiments of the invention could be made without departing from `the scope thereof, -it Lis intended that all -matter contained inthe .above description or shown in the accompanying drawings shall he .interpreted as illustrative and I not in a limiting oense.

The .invention claimed is:

fl. A pump comprising :a piston cylinder, a vhollow :pis- -tonireciprocable therein, a piston :rod reciprocable lwithin said piston, a rearwardly-facing yshoulder .on the inner surface of said piston at a point 4forwardly ofthe rear vportion thereof, a shoulder `on lsaid piston rod adapted to :engage the first-mentioned shoulder, 4said piston being recessed rearwardly of the first-mentioned shoulder to .permit rearward movement tof the piston rod therewithin, a forward shoulder at a forward portion of said ipiston, a 'rearward shoulder ata forward portion .of said ,piston rod adapted to engage said forward shoulder after rearward movement of said piston rod within said piston, a 4u'id passageway having ra rearward portion :between said' lpiston and said piston rod and a forward portion extending forwardly of the forward tends of said piston ,and said lpiston lrod, said rearward Aportion being adapted to be closed by engagement of the second-mentioned .shoulder lwith the `first-mentioned shoulder, and `rearwardlylspring-pressed valve means in said forward portion for closing said forward portion except when ,opened by the forward movement of fluid within said forward portion upon for-ward movement of said piston and piston rod 4after engagement of said shoulders.

2. A pump as set forth in .claim :l wherein an interior surface of a portion of said piston cylinder surrounding .said piston Eis formed with an annular chamber open to the outer surface of said piston and wherein there is provided therein an -auuulus tightly Seeured .te 011e :side of said chamber and adapted to lie against said surface 4 .and to be .pressed thereagainst `by .the pressure .of fluid leaking into the other side .of said chamber.

3. A liquid oxygen pump or the like comprising a piston cylinder, a hollow piston movable within said cylinder, a piston rod movable forwardly Within said piston for a given distance and thereupon engaging the piston to move the sameforwardly for a further distance, an outlet passageway extending forwardly from said pistori `and said piston rod, rearwardly-seating and rearwardly-spring-pressed valve means in said passageway, a second passageway betweensaid piston and said piston rod and communicating with the aforesaid passageway, cooperating portions on said piston and piston rod to close said ysecond lpassageway ywhen said piston "rod engages said piston ,prior .to moving `said piston forwardly to 4force iiuid forwardly to open said valve means, said cylinder being formed with an annular chamber open to the surface yof -said piston, 'and an .annular lseal Iin said chamber .and .formed `essentially of -a halo-ethylene :polymer and having an :annular portionsecuredtto a Itrans- .verse side of said chamber and an annular portion .lying against the surface .tof said .piston .and to be pressed there- Vagainst by fluid .escaping along lthe adjoining surfaces of ,said pistonrand'cylinder.

V4. .A pump .comprising :a hollow v4reciprocable .piston Ahaving :an entrance portion and an exterior icylindrical surface, a piston vcylinder havingfan .exit portion land .an :interior cylindrical surface, said `exterior .cylindrical sur- .face being in sliding lengagement with said rinterior cylindrical .-surface, Ymeans Ifor v controlling .the lflow Lof fluid from said entrance portion to said exit portion in respense to the operation of said piston, an annular recess -in one of :said cylindrical surfaces open to Athe other of saidtcylindrical surfaces, .and 5a sealing lannulus having an ,annular .portion with :a surface lying against :the other of said surfaces and with :an opposite surface exposed to fluid witihn said recess s o as to be presed against said other :of :said rsur-faces `by fluid tending to escape from said texit portion between said .cylindrical surfaces into said recess, 4means including another lannular portion of said :annulus and forming a .fluid-tight seal Ybetween the wall of said recess and the aforesaid .annular portion of vsaid lannulus, 4said sealing -annulus being composed of a :plastic which lis tough, :exible, and vnon-brittle at ytemperatures below minus 200 F.

5. A :pump comprising ka piston cylinder, ea hollow piston Ihaving a rearward aportion and having a forward -portion with .an imperforate .continuous wall and reciproeable within said cylinder, a .piston rod reciprocable l.within said hollow .piston ,and having 'atforward end portion ywith awall .spaced from ftheiaforesaid wallto provide a channel for the free flow lof rliquid within the forward portion of said hollow piston and having a rear end portion providing a channel for the free ow o-f liquid within the rearward portion of said hollow piston .and vhaving a forwardly-:facing driving portion between .said forward .end :portion and said .rear end portion, a rearwardly-facing seat on said hollow 4piston between `said .channels and .adapted to'be engaged by said driving portion duri-ng the forward stroke of said piston rod to close communication between said `channels and to drive said hollow :piston forwardly, said :driving portion being withdrawn from said rearwardly-facing seat at :the beginning Aof .the :rearward stroke of ysaid piston to open communication between said channels, rearwardly-facing shoulder means Ion said piston rod, a forwardly-facing seat on said hollow .piston adapted to be :engaged by said shoulder means during 4the rearward stroke of said piston member to draw said hollow piston rearwardly without closing communication between said channels, ymeans extending vfrom a forward portion of said cylinder and providing an Outlet conduit, .and valve means disposed in said outlet conduit and adapted to be `open when-said hollow piston is driven forwardly and .to close when said hollow piston is drawn rearwardly.

6. A pump as set forth in claim 5 wherein there is provided means to impart to said piston rod reciprocating movement such that a major portion of said hollow piston is always within said cylinder.

7. A pump as set forth in claim 5 wherein there is provided fluid-containing chamber means surrounding the greater part of said cylinder, a portion of `said chamber means communicating with the second-mentioned channel.

8. A pump as set forth in claim 5 wherein said valve means is in the form of a spring-pressed element blocking flow from the forward end of the cylinder but opening in response to the pressure of liquid within said hollow 6 piston when said piston rod and said hollow piston are moved forwardly.

References Cited in the file of this patent UNITED STATES PATENTS 56,414 Hoagland July 17, 1866 2,447,741 De Baufre Aug. 24, 1948 2,467,312 Jack Apr. 12, 1949 FOREIGN PATENTS 58,543 Netherlands Nov. 15, 1946

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