US3263622A

US3263622A - Pump

Info

Publication number: US3263622A
Application number: US371666A
Authority: US
Inventors: Jr Lewis Tyree
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-06-01
Filing date: 1964-06-01
Publication date: 1966-08-02
Anticipated expiration: 1983-08-02

Description

L. TYREE, JR

Aug. z, 1966 PUMP 2 Sheets-Sheet 1 Filed June l, 1964 Dlsc.

L. TYREE, JR

Aug. 2, 1966 PUMP 2 Sheets-Sheet 2` Filed June l, 1964 United States Patent O PUMP u Lewis Tyree, Jr., 9955 S. Hamilton Ave., Chicago, lll. Filed June 1, 1964, Ser. No. 371,666 16 Claims. (Cl. 103--153) This invention relates to positive displacement, reciprooating pumps. More particularly, the invention is directed to pumps such as these which are designed for pumping cryogenic liquids, and especially for pumping cryogenic liquids near their boiling points.

One important criterion for a pump of this type, as for any pump, is that it should have good volumetric efficiency. By volumetric efficiency is meant the percentage of the potential volume of liquid in the pumping chamber that is actually pumped. In pumping cryogenic liquids, especially :cryogenic liquids which are at or near their boiling point, the problem of achieving good volumetric eiciency becomes more diicult. To achieve good volumetric efficiency, the pumping chamber Vof the pump must be nearly completely filled with liquid. Cryogenie liquids are generally in the liquid state only at temperatures below ambient or room temperature, and they tend to flash to vapor .at every opportunity,.either as a result of heat gained or of a drop in pressure.

If a portion of the pumping chamber is occupied by vapor on the intake stroke, this of course means that the entire pumping chamber is not filled with liquid. Less liquid will accordingly be discharged, resulting in lower volumetric efficiency. Even if the cryogenic liquid to be pumped is a few degrees below its boiling point, it has a substantial tendency to vaporize because every pumping processis accompanied by some heat lbuild-up in the pumping chamber. The temperature of the fluid in the pumping Ichamber rises as its pressure is raised during the discharge stroke. This rise in temperature results in a transfer of some heat to the walls of the pumping chamber. This heat is referred to as the residual heat of the pumping chamber and is subsequently returned to the incoming cryogenic fluid on the next intake stroke, raising its temperature. If the residual `heat of the pumping chamber is allowed to gradually increase, the amount of vapor created will also increase. Eventually it is possible that the entire pumping chamber might be lled with Vapor instead of liquid. In such a case, the pump would act only as a compressor. Thus, an increase in residual heat is clearly harmful to eflicient cryogenic pumping and should be held within practical limits in order to achieve good volumetric elficiency.

Furthermore, not al1 of the fluid is exhausted from the pumping chamber on the discharge stroke.4 The volume of fluid remaining in the chamber at the end of a discharge stroke is referred to as the clearance volume of the pumping chamber. At the beginning of the intake stroke, some flashing of the liquid remaining in the clearance volume may occur and thus partially lill the pumping chamber with vapor. Such a reaction is, of course, undesirable. To minimize this elfect it is desirable to design the pumping chamber to have a very low clearance volume and to minimize ilashing of the residual liquid therein. y

Another factor which impairs volumetric efficiency is incomplete filling of the pumping chamber with iluid at each stroke. In reciprocating, positive displacement pumps having relatively high delivery capacity, reciprocating motion is rapid, and the pumping chamber has only lan instant of time in which to be fllled. Accordingly, a pumping chamber designed to assure as complete filling as possible on every intake stroke is desired.

Another problem com-mon to pumps of this general design, when used to pump cryogenic lluids, is vapor- Patented August 2, 1'966 locking. Especiallyiwhen liquids at or near their boiling point are beingipumped, the `possibility of vapor-'build-up within the pumping chamber becomes likely. If a cryogenic pump employs a check-type valve as its intake valve, vapor-lockingbecomes a distinct possibility. Such a valve requires some pressure on behalf of the incoming uid to open it; if vapor pressure is built up within the pumping chamber, the incoming fluid pressure may not be su'cient to `open the valve and vapor-lock will occur. Vapor-locking `can quickly result in over-heating of the pumping chamber and consequent injurytothe4 pump. Therefore, pumps for handling cryogenic liquids are desired which have positive Vprotections against vaporlocking.

In pumps which are designed to operate at high discharge pressure, the sealing of the pumping chamber `is an important consideration. Because in a positive displacement, reciprocating pump there is generally a sliding lit between mating surfaces of the pump members that dene a variable volume pumping chamber, the highpressure seal is most efciently and practically located between these sliding surfaces. l i

Any effective high pressure seal4 will produce some frictional heat. Moveover, the use of pressure-responsive seals in `pumps of 'this type has |become fairly common. Such seals, when subjected to higher pressures in the pumping chamber, rub harder .against the surfaces being sealed and provide a more `eifective seal. However, the higher the pressure to rwhich the seal is subjected, the more -frictional heat which is generated.

Frictional heat is a particular problem for pumps handling cryogenic liquids because, if it isallowed to reach the pumping chamber, the intake liquid is undesirably heated and partially vaporized. In such an instance, the volumetric eiiciency of the pump is impaired, for the reasons previously discussed. These problems are further complicated when `the lpump is to be adapted to pump fluids of extremely low viscosity which `are quite `diflicult to contain. Moreover, whatever type of sealing material which is chosen, the operating temperature of the seal mustV be maintained within a fairly constant temperature rangebecause operation at temperatures considerably above the planned temperature causes excessive seal wear and premature seal failure. A pump design which alleviates these problems is desired.

A principal object of the present invention is to provide a reciprocating, positive displacement` pump which is simple in mechanical design and which will pump fluids with increased volumetric efficiency. Another object is to provide a pump of this type which will pump fluid at high discharge pressures and relatively high capacities. A further object is to provide a pump of this type which is inherently incapable of vapor-locking. A still further object is to provide a pump which has a very low clearance volume so that the pumping cham-ber retains a minimum amount of residual liquid at the end of the discharge stroke. These and other objects of the invention are more particularly `set forth in the following detailed description and in the accompanying drawings wherein:

FIGURE 1 is a vertical sectional view of a pump embodying various features of the invention; I

FIGURE 2 is an enlarged fragmentary sectional view taken along line 2 2 of FIGURE 1;

FIGURE 3 is a schematicview of a system using two of the pumps shown in FIGURE l; p

FIGURE 4 is a diagrammatic view` of the pumping chamber of the pump illustrated in FIGURE 1 at `the beginningof `the discharge stroke; 1 i i FIGURE` 5 is a View similar to FIGURE 4 at a later point during the discharge stroke;

:endof the discharge stroke; and

'adjacent the high pressure seal.

trated in FIGURE 1.

*which can be used to pump cryogenic fluids under boil- 'ing point conditions with increased volumetric efficiency.

The pump has an intake valve designed so that vaporlocking is inherently avoided and so that the 'action of the pump durinug the intake stroke dynamically induces the filling of the pumping chamber; The pump construction is such that the two 'surfaces of the respective ends o'f the cylindrical pumping chamber are in face-to- 'face relationship and closely adjacent at the end of the discharge stroke, thus minimizing the pump clearance volume and the amount of residual liquid.

Moreover, the pump discharge passageway is located This arrangement utilizes the effluent, high pressure liquid to absorb the frictional heat generated at the high pressure seal and veffectively keeps the high pressure seal within a fairly narrow and low operating temperature range. Moreover,

' this arrangement prevents the frictional heat from reaching, and undesirably affecting, the intake fluid in the pumping chamber.

Now referring more particularly to the drawings, a pump 11 designed for pumping cryogenic fluids is illus- The pump 11 includes a pump casing 13 having a central sump 15 and upper and lower co-axial, vertical,

cylindrical passageways

17, 19 which open into the sump 15. A horizontal inlet 21 and outlet l23 are also provided in the casing 13 which are in communication with the sump 15. The pump casing 13 is suitably mounted, as by bolts 25, on a pump base 27, and sealed thereto by an appropriate 'gasket 29. A vacuum jacket 31 is disposed adjacent the outer surface of the 'pump casing 13 and insulates the pump 11 from the higher temperature of the surrounding atmosphere. Ap-

propriate expansion joints 33 are provided to allow for differential `thermal contraction.

A pair of pump members, a pump plunger 33 and a ,'hollow pump cylinder or sleeve 35, define a pumping chamber 37 and are disposed in the lower vertical passageway 19 of the pump casing. The plunger 33 is stationary and is mounted concentrically within the lower passageway19. A central bore 39 in the hollow cylinder f 35 allows the cylinder to fit downward over the top of the plunger 33 and occupy the annular space between the plunger and the inner wall of passageway 19 of the pump casing 13.

The stationary plunger 33 contains a central drilled hole 41 which serves as the beginning of a discharge passageway 43 `from the pumping chamber 37 to the outlet (not shown) of the pump 11. A discharge valve 45 is located at the upper end of this drilled hole 41, at the junction between the discharge passageway 43 and the pumping chamber 37. The valve 45 is a poppet valve and comprises a cylindrical valve port 47 and an elongated cylindrical valve stem 49 having a tip of reduced diameter. As best seen in FIGURES 4-7, an annular surface 50 provided by the reduction in diameter seats against the bottom of surface in which the valve port 47 is formed when the valve 45 is closed. Because of the relatively small diameter of the plunger 33', the valve l stem 49 is elongated so that a spring mechanism 51 that biases the valve 45 to the closed position can conveniently be accommodated at the bottom of the plunger 33' in an enlarged portion thereof.

The plunger 33 terminates in a flange 53 which extends outwardly from the enlarged portion of the plunger.

The plunger 33 is seatedatop an O-ring 55 in a threaded cavity provided in the pump ybase 27 and secured therein by a bushing 57 which screws into the cavity and bears against the flange 53. The valve spring mechanism 51 comprises a hollow plug 59 and a compression spring 61. The spring 61 is yheld within a small Valve chamber 63, counterbored at the bottom of the plunger hole 41, by the plug 59 which screws into threads at the bottom of the valve chamber 63. The compression spring 61 bears upward against a flat bottom plate 65 carried at the end of the valve stem 49, seating the reduced tip of the stem 49 in the valve port 47.

To define the upper limit of the pumping chamber 37, the internal bore 39 in the slidable cylinder 35 is necked inward to an opening 66 of lesser diameter. Immediately above this neck, the bore 37 in the slidable cylinder flares outward to provide a funnel-like upper portion 67 having ra conical inner surface 69. This funnel-shaped upper portion 67 serves to dynamically induce the filling of the pumping chamber 37 on the intake stroke, as will be described more fully hereinafter.

The pumping chamber 37 is closed at the top by an intake valve 71. The opening 66 is the intake valve port, and lower part of the conical surface 69 serves as the seat for the intake valve 71. A stem 73 for the intake Valve 71 is fashioned from the bottom portion of a piston rod 75 that is disposed in the upper vertical passageway 17 of the pump casing 13. Through a drive connection (not shown) to the upper end of the piston rod 75, the pis-ton rod is driven in reciprocating motion. Bushings 77 are provided within the lower section of the upper vertical passageway 17 to maintain correct alignment between the piston rod 75 and the inner wall of the passageway 17 and, more importantly, to maintain alignmen-t between the intake valve stem 73 and the intake valve seat.

Attachment of the piston rod 75 to the slidable cylinder 35 is made thro'ugh a lost-motion connection. A

'horizontal connecting pin 79 diametrically spans the sides of the funnel-like end portion 67 of the sli-dable cylinder 35. The ends Iof the pin 79 are mounted in suitable holes drilled in the wall of the cylinder 35. As best seen in FIGURE 2, a key-hole shaped opening 81 i-s provided in the piston rod 75, a short distance above its lower end.

lIt is in this opening 81 that the central portion of the connecting pin 79 resides establishing a lost-motion connection between the piston rod 75 and the slidable cylinder 35. When the piston rod 75 begins its downward discharge stroke, the intake valve 71 closes, transmitting `power through the mating -conical surfaces to force the slidab-le cylinder 35 downward. Location of the key-hole opening 81 is such that the top of the pin 79 never touches the upper interior surface of the opening 81.

A low pressure stuffing box 83, provided in a cylindrical recess near the -top of the upper vertical passageway 17, seals the upper end of the sump 15 against loss of fluid therethrough. Likewise, low pressure packing 85 is provided between a pair of bushings 87 that guide the slidable cylinder 35 within the lower vertical passageway 19 in which it resides. The bushings 87 assure proper alignment of the intake valve port 66, whereas the low-pressure packing 85 sea-ls the bottom of the sump 15 against fluid loss.

The seal which is of the most interest from the standpoint of the frictional heat generated thereat is the high pressure seal. This seal is provided by high pressure packing 89 which is disposed between-a pair of bushings 91 in a cylindrical recess provided in the lower portion of the central bore 39 in the slidable cylinder. This high-pressure packing 89 seals the pumping chamber 37 against Huid loss,

The pump 11 is designed to efficiently pump cryogenic fluids at pressures up to about 12,000 p.s.i. To efficiently operate at pressures in this high pressure range, especially with fluids having fairly low viscosities, such as liquid nitrogen, it is necessary to have a good high pressure seal. Good high pressure seals for `a sliding fit mean creation of frictional heat. Any suitable high pressure packing may be used, as for example, commercially available chevron-type packing. This type of packing is what is termed heavily loaded packing because the higher the pressure which is applied to it, the greater is the frictional force with which it bears against the surfaces being sealed.

Regardles-s of the type of high-pressure packing chosen, it is important to maintain the temperature of the packing Within 'a fairly narrow openating range. Because of differential thermal expansion of the materials of which the pump members being sealed are made .and the material of which the packing is marde, it is important that the high-pressure seal 4operates iat a fairly constant, relatively cool temperature. If the temperature of the high-pressure packing 89 is Iallowed to rise :above the desired temperature range, 'as may easily happen because of the frictional heat to which it is subjected, greater than normal wear on the packing 89 occurs, the high-pressure seal loses its effectiveness, and more fluid is lost therethrough.

It .should also be understood that, no matter howeffective the high-pressure packing 89 is in sealing this sliding joint, it will not be perfect, and some fluid will escape therethrough. The fluid lost is commonly referred to as blow-by, and it is the purpose of the seal to keep the blow-by at as low :a level as practical. The blow-by which escapes through the high pressure packing 89 and reaches the bottom of the lower vertical passageway 19 is removed through an exit 93 in the side wall of the pump casing 13. The exit 93 leads to a helical pas-sageway 95 formed in the outer surface of the pump casing 13. Thus, an upwardly leading passageway, between the vacuum jacket 31 and the pump casing 13 is provided which conducts blow-by, via an upper passageway system 97, to an exit port 99 where it enters a conduit (not shown). This conduit carries the blow-by back to the source of fluid supply, keeping fluid losses in the pump at a low level. r

Because the pump 11 is designed to operate with a feed of cryogenic uid lat a temperature near its boiling point, which are the prevailing conditions in a large, unrefrigerated supply tank 101 (see FIG. 3), both the inlet 21 and the vapor return outlet 23 are provided. Through the inlet 21, the .sump 15 is flooded with cryogenic fluid. If the pump 11 is .operated in close proximity to the lstorage tank 101 of the cryogenic fluid, the vapor fraction, which invariably accompanies liquid near its boiling point, may be allowed to return to the storage tank 101 directly through the supply line or to pass with the liquid through the pump. In such instances, the vapor return outlet 23 may be eliminated.

One way of operating the pump 11 at a remote location from the supply vessel is depicted in FIGURE 3. In this embodiment, a pair of pumps 11 in parallel are used in a location `substantially distant from the storage vessel 101. In this case, an auxiliary vapor return line 103 is provided for connection to the pump outlets 23. Moreover, it is preferred to use an auxiliary, W pressure, high capacity pump 105 positioned close to the storage tank 101. Such a pump 105 is commonly referred to as a fore pump. The function of the fore pump 105 is to circulate cryogenic uid from the storage tank 101 through a continuous exterior circuit. Included in this circuit, as illustrated in FIGURE 3, there may be the sumps of `a plurality of high pressure pumps 11. Disposition of the inlet 21 at a lower vertical level than the vapor outlet 23 enhances the complete filling of the pumping chamber 37 and the return of the vapor fraction to the storage tank 101. The fore pump 105 is operated to circulate a greater amount of uid than the pumps 11 in the circuit are pumping.

In operation of the pump 11, circulation of cryogenic fluid through the inlet 21 and into the sump 15 is first established. The pump drive is then actuated so that the piston rod 75 begins to reciprocate. In the position illustrated in FIGURE l, the piston rod 75 has just completed the intake stroke and is about to reverse direction.

FIGURE 4 shows the pumping chamber 37 just after the piston rod has reversed direction and begun its downward discharge stroke. In this View, it can be seen that the intake valve stern 73 has been seated too close to the intake valve 71 at the top of the pumping chamber 37. Inasmuch as all the force that moves the slidable cylinder 35 downward is transmitted to it through the mating conical surfaces of the intake valve 71, a good seal at the intake valve is assured.

In FIGURE 5, the pumping chamber 37 is shown after the piston rod 75 has driven the slidable cylinder 35 some distance downward. As can be seen, the volume of the pumping chamber 37 decreases during this discharge stroke. The pressure on the fluid contained in the chamber 37 accordingly increases so any vapor which was present at the beginning of the stroke is compressed to liquid. As soon as the pressure pumping chamber over-comes the pressure in the discharge line 43 (e.g., pumping may be into a closed cylinder), the poppet valve 45 opens. Discharge of Huid immediately begins through the central hole 43 in the stationary plunger 33', through the bottom hollow plug 59 and out through the pump base 27.

FIGURE 6 shows the pump 11 at the end of the discharge stroke where the piston rod '75 has reached the bottom of its stroke and the discharge valve 45 has closed. The bottom horizontal surface of the piston rod 75 is face-to-face with the upper horizontal surface of the stationary plunger 33', `in which the discharge valve port 47 is located. Proportioning of these elements is `su-ch that the vertical clearance between these two faces is about 0.020 inch. Accordingly, the clearance volume of the pumping chamber 37 is only about l percent of the total volume of the chamber 37 at the beginning of the discharge stroke.

As the piston rod 75 begins to move upward at the beginning of the intake stroke, the intake valve 71 immediately opens, as illustrated in FIGURE 7. The cylinder 35 does not move until the intake valve 71 is completely open and the piston rod 75 has traveled a sufficient distance upward so that the connecting pin 79 is engaged by the bottom of the key-hole opening 81, as shown in FIGURE 2. Because the sump 15 is always kept substantially full of cryogenic uid, as a result of the circulation of an excess of Huid therethrough by the fore pump 105, the funnel-like portion 67 of the slidable cylinder moves upward through a body of cryogenic fluid. During this upward movement, the conical surface 69 of the cylinder acts as an inducer to produce dynamic induction of cryogenic Huid into the continually enlarging pumping chamber 37. This effect is similar to that which a funnel exhibits when it is dragged through a water bath, i.e, the liquid velocity at the funnel exit is higher than the velocity of the funnel. In the pump 11, the neck of the slidable cylinder 35 is akin to the funnel exit. The surface area of the conical surface 69 is preferably at least as large as the cross sectional area of the pumping chamber 37 to assure effective filling.

This funnel-like configuration ofthe upper cylinder portion 67 not only `dynamically induces the filling of the pumping chamber 37, but also it increases the velocity head of the fluid entering the pumping chamber 37, which is then converted to static head. This effect accordingly promotes the filling of the pumping chamber 37 with cryogenic fluid in the liquid form. As a result, at the end of the intake stroke, the pumping chamber 37 is filled with cryogenic fluid, substantially entirely in liquid form, in time for the discharge stroke to begin.

Thus, the advantageous features of the design of the slidable cylinder 35 reduces the need for sub-cooling of the cryogenic liquid before pumping, a device employed by other cryogenic pumping systems. Sub-cooling is generally effected by vaporizing some of the liquid from the bottom of the storage tank to raise the pressure therein and sub-cool the remaining liquid. Such sub-cooling by partial vaporization is undesirable in terms of overall economy and is only a temporary measure, effective until equilibrium conditions are re-established.

If the pump 11 is intended to be used to handle cryogenic uids, it is preferred to construct the structural ele- -ments of the pump out of stainless steel, although other suitable materials may also be used. Relative to Teflon, stainless steel also has good thermal conductivity. A stainless steel plunger 33 is suitable to conduct the frictional heat from the high pressure packing S9 radially yinward to the discharge passageway 43. In any respect,

it is preferred that the plunger 33 be constructed of a metal, or of a material having a thermal conductivity the approximate equal of a metal.

Location of the discharge passageway 43 adjacent the high pressure seal, allows the high pressure, low temperature discharge stream of cryogenic fluid to be used as a heat sink for the purpose of cooling the packing 89. A relatively high quantity of cryogenic fluid is discharged through this passageway when the pump 11 operates near its rated capacity, i.e., about two gallons per minute for a pumping chamber 37 with a 1%-inch diameter and a length or stroke of 3% inch. Thus, the discharge stream provides a heat sink of ample capacity to easily absorb the frictional heat generated by the high pressure packing S9 and maintain the packing 89 within the desired temperature range. When liquid nitrogen is being pumped at rated capacity, the packing 89 is maintained at about 250 F. Thus, a heavily loaded packing may easily be used.

Although the single cylinder pump 11 is designed to produce a discharge of about two gallons of liquid per minute at pressures up to about 12,000 p.s.i.g., when the piston rod 75 is connected to a crank shaft rotating at about 100 r.p.m., it is also suitable for operation at speeds of up to about 700 r.p.m. Pumping cryogenic liquids at 2 gallons lper minute and at pressures up to about 12,000 p.s.i., can be accomplished with high volumetric efficiency. Although the volumetric efficiency of the pump 11 is not as good at the higher speeds possible, it is considered an improvementover the volumetric eiciency of comparable pumps operating in this pressure range.

With these conditions of operation in mind, the importance of completely filling the pumping chamber 37 on each intake stroke is apparent. Furthermore, the limited entrance area there is through the intake valve and the fraction of a second in which the pumping chamber 37 must be filled on the intake stroke, the dynamic induction which is provided by the design of the pump 11 is of considerable advantage. The combination of features in this design that provides both a low clearance volume and excellent filling of the pumping chamber results in very good volumetric efficiency and makes the use of the pump 11 especially advantageous in handling cryogenic liquids at temperatures near their boiling point.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. A positive displacement reciprocating pump for handling cryogenic liquids, which pump comprises first and second cooperating pump members which are movable relative to each other and which define a pumping chamber, means disposed between said members effective to seal said pumping chamber, said first pump member having a discharge passageway formed therein in iiuid cornmunication with said pumping chamber, and discharge valve means closing said discharge passageway, a portion of said discharge passageway being located in close thermally conducting relation to said sealing means so that heat frictionally generated by said sealing means is absorbed by the discharge stream of cryogenic liquid and carried away from said pumping chamber.

2. A positive displacement reciprocating pump for handling cryogenic liquids which pump comprises first and second cooperating pump members which are slidable relative to each other and which define a pumping cham- 8 ber of variable volume, means disposed between said members effective to seal said pumping chamber, said first pump member having a discharge passageway formed therein in fluid communication with said pumping chamber and discharge valve means closing said discharge passageway, a portion of said discharge passageway being located in close thermally conducting relation to said sealing means so that heat frictionally generated by said sealing means is absorbed by the discharge stream of cryogenic liquid and carried away from said pumping chamber.

3. A positive displacement reciprocating pump for handling cryogenic liquids which pump comprises a hollow pump cylinder, a pump plunger partially disposed in the hollow bore of said pump cylinder, said plunger being proportioned so that said plunger and said cylinder are slidable relative to each other and define a pumping chamber of variable volume, means disposed between said plunger and said cylinder effective to seal said pumping chamber, said plunger having a discharge passageway formed therein in liuid communication with said pumping chamber and discharge valve means closing said discharge passageway, a portion of said discharge passageway being located in close thermally conducting relation to said sealing means so that heat frictionally generated by said sealing means is absorbed by the discharge stream of cryogenic liquid and carried away from said pumping chamber.

4. A positive displacement reciprocating pump for handling cryogenic liquids which pump comprises a hollow pump cylinder lwhich has a cylindrical bore, a cylindrical pump plunger of good thermal conductivity being partially disposed in the bore of said pump cylinder, said plunger being proportioned so that said plunger and said cylinder are slidable relative to each other and define a pumping chamber of variable volume, heavily loaded high pressure packing disposed between said plunger and said cylinder effective to seal said pumping chamber, said plunger having a central discharge passageway formed therein in fiuid communication with said pumping chamber and discharge valve means located in said discharge passageway, said central discharge passageway being in good thermally conducting relation to said packing so that heat frictionally generated by said high pressure packing is absorbed by the discharge stream of cryogenic liquid and carried away from said pumping chamber.

5. In a positive displacement reciprocating pump for handling cryogenic liquids which pump includes a hollow pump cylinder having a bore therein, a pump plunger partially disposed in the bore of said pump cylinder, said plunger being proportioned so that said plunger and said cylinder are slidable relative to each other and define a pumping chamber of variable volume, means disposed between said plunger and said cylinder effective to seal said pumping chamber, the improvement which comprises said plunger having a discharge passageway formed therein in iiuid communication with said pumping chamber and discharge valve means closing said discharge passageway, a portion of said discharge passageway being located in close thermally conducting relation to said sealing means so that heat frictionally generated by said sealing means is absorbed by the discharge stream of cryogenic liquid and carried away from said pumping chamber.

6. A positive displacement reciprocating pump which comprises a stationary pump plunger, a hollow pump cylinder having an opening therein for slidably receiving said stationary plunger and defining therewith a pumping chamber of variable volume, said plunger having a dis1 charge passageway formed therein in fluid -communication with said pumping chamber, discharge valve means closing said discharge passageway, intake valve means for selectively controlling the flow of fluid into said pumping chamber, and means connected to said hollow cylinder for effecting reciprocating movement thereof relative to said stationary plunger and for opening and closing said intake valve incident to said reciprocating movement.

7. A positive displacement reciprocating pump which comprises a stationary pump plunger, a hollow pump cylinder having an opening therein for slidably receiving said stationary plunger and defining therewith a pumping chamber of variable volume, intake valve means for selectively controlling the fiow of fluid to be pumped into said pumping chamber, ysaid intake valve means including a valve port in said hollow cylinder and a separable valve stem, means connected to said valve stem for moving said stem in reciprocating motion, and means connecting said valve stem to said hollow `cylinder for moving said cylinder in reciprocating motion relative to said stationary plunger incident to the reciprocating motion of said stem.

8. A positive displacement reciprocating pump which comprises a stationary pump plunger, a hollow pump cylinder having fan opening therein for slidably receiving stationary plunger in sliding contact therewithin and defining a pumping chamber of variable volume, means disposed `between said plunger and said hollow cylinder effective to seal said pumping chamber, said plunger having a discharge passageway formed therein in fluid communication with said pumping chamber, discharge valve means closing said discharge passageway, intake valve means in said hollow cylinder, said intake valve means including a valve port in said hollow cylinder in fluid communication with said pumping chamber and a separable valve stem, means connected to said valve stem for moving said stem in reciprocating motion and a lost-motion connection between said valve stem and said hollow cylinder for moving said cylinder in reciprocating motion relative to said stationary plunger.

9. A positive displacement reciprocating pump that operates on a two-stroke intake and discharge cycle, which pump comprises a stationary pump plunger, a hollow pump cylinder having an opening therein for slidably receiving said stationary plunger and defining therewith a pumping chamber of variable volume, said hollow pump cylinder also having an intake valve port formed therein which 'opens into said pumping chamber, an intake valve stem for closing said port adapted for movement along an axis co-axial with the axis of said plunger, means connected to said intake valve stem for moving said stem in reciprocating motion to open and close said intake valve on the intake and discharge strokes of the pump, and means connecting said valve stem to said -hollow cylinder for moving said cy-linder in reciprocating motion relative to said stationary plunger and thereby create pumping action.

10. A positive displacement reciprocating pump that operates on a two-stroke intake and discharge cycle, which pump comprises a stationary pump plunger, a hollow pump cylinder having longitudinal bore therein for slidably receiving said stationary plunger in one end thereof and defining therewith a pumping chamber of variable volume, said hollow pump cylinder having an intake valve port formed therein which opens into the other end of said longitudinal bore and also having an intake valve seat formed around said port, an intake valve stem for closing said port adapted for movement along .an axis co-axial with the axis of said plunger, means connected to said valve stem for moving said stem in reciprocating motion to open and close said intake valve on the intake and the discharge stroke of the pump, and means connecting said valve stem to said hollow cylinder for moving said cylinder in reciprocating motion relative to said stationary plunger.

11- A positive displacement reciprocating pump that operates on a two-stroke intake and discharge cycle which comprises a pump casing having a sump formed therein and a passageway opening into said sump, a stationary pump plunger mounted in said passageway, a hollow pump cylinder proportioned to intert within said passageway and having lan opening formed therein for slidably receiving said stationary plunger thereby defining therewith a pumping chamber of variable volume, said hollow pump cylinder having an intake valve port formed therein in fiuid communication with said pumping charnber and a funnel-like portion surrounding said port, means for closing said intake valve port, means connected to said hollow cylinder for effecting reciprocating movement thereof relative to said stationary plunger and for opening and closing said intake valve incident to said reciprocating movement, said axis of said funnel-like portion being parallel to the axis along which said reciprocating movement occurs so that movement of funnel-like portion of said cylinder through said sump and away from said plunger causes said pumping chamber to be filled by dynamic induction.

12. A positive displacement reciprocating pump that operates on a two-stroke intake and discharge cycle which pump comprises a pump casing having a sump formed therein and a passageway opening into said sump,

a stationary pump plunger mounted in said passageway,`

a hollow pump cylinder proportioned to in-tert within said passageway and having an opening formed therein for slidably receiving said stationary plunger thereby defining therewith a pumping chamber of variable volume, said hollow pump cylinder having formed therein an inintake valve port in fluid communication with said pumping chamber and a frustoconical surface surrounding said port and opening outward in a direction away from said pumping chamber, the area of said surface being at least equal t0 the cross sectional area of said pumping chamber, means for closing said lintake valve port, means connected to said hollow cylinder for effecting reciprocating movement thereof relative to said stationary plunger and for opening and closing said intake valve incident Ato said reciprocating movement, said axis of said frustoconical surface be-ing parallel to the axis along which said reciprocating movement occurs so that movement of said cylinder through said sump away from said plunger causes said pumping lchamber to be filled by dynamic induction.

13. lIn a positive displacement reciprocating pump that operates on a two-stroke intake and discharge cycle which pump inclu-des a pump casing having a sump formed therein Vand a passageway opening into said sump, the improvement which comprises a stationary cylindrical pump plunger mounted in said passageway, a hollow pump cylinder proportioned to intert wi-thin said passageway and having a bore formed therein for slidably receiving said stationary plunger thereby defining therewith a pumping chamber of variable volume, said hollow pump cylinder having an intake valve port formed therein in fluid `communication with said pumping chamber and a `funnel-like portion surrounding said por-t and flaring outward in a direction away from said pumping chamber, means for closing; said intake valve port, and means connected t-o said hollow cylinder for effecting reciprocating movement thereof relative to said stationary plunger and for opening Iand closing said intake valve inci-dent to said reciprocatingmovement, the axis of said funnel-like portion being parallel to the axis along which said reciprocating movement occurs so that movement of funnel-like portion of said cylinder through said sump and away from said plunger causes said pumping chamber to be filled hy dynamic induction.

l14. A positive displacement reciprocating pump that operates on a two-stroke intake and discharge cycle which pump comprises la pump casing having a sump formed therein and a passageway opening into said sump, a stationary pump plunger mounted in said passageway, a hollow pump cylinder proportioned to interfit within said passageway and having an opening formed therein for slidably receiving said stationary plunger thereby detining therewith a pumping chamber of variable volume, said hollow pump cylinder having an intake valve port formed therein in fluid communication with said pumping chamber and a `funnel-like portion surrounding sai-d port, a valve stem for closing said valve port adapted for movement along an axis co-axial with the axis of said plunger, means connected to said valve stem for moving to be filled by dynamic induction.

.15. A positive displacement reciprocating pump the opcrates on a two-stroke intake and discharge cycle which pump comprises a pump casing having a sump formed therein and a passageway opening into said sump, a stationary pump plunger mounte-d in said pump passageway, a hollow pump cylinder proportioned to intert within said passageway and having an opening formed therein for slidably receiving said stationary plunger thereby detining therewith a pumping chamber of variable volume,

Vsaid hollow pump cylinder having formed therein an inintake valve port in fluid communication with said pumping chamber and a frustoconical surface surrounding said port and opening -outward in a direction away from said pumping chamber, the area of said surface being a-t least equal to the cross sectional area of said pumping chamber, means disposed between said pump plunger and said hollow cylinder effective to seal said pumping chamber, said pump plunger having a discharge passageway formed therein in fluid communication with said pump- -ing chamber, discharge valve means closing said discharge passageway, a portion -of said discharge passageway being located in close thermally conducting relation to said sealing means so that heat frictionally generated by said sealing means is absorbed by the discharge stream and carried away from said pumping chamber, a valve stem for closing said intake valve port adapted for movement along an axis co-axial with the axis of said plunger, means connected to said valve stem for moving said stem in reciprocating motion to open said intake valve port on the intake stroke of the pump and to close said valve port on the discharge stroke of the pump, and lost-motion connection means between said valve stem and said hollow cylinder for moving said cylinder in reciprocating motion relative to said stationary plunger, said axis of said frustoconical surface being parallel to the axis along which said reciprocating movement occurs so that movement of said cylinder through said sump away from said plunger causes said pumping chamber to be filled by dynamic induction.

16. A positive displacement reciprocating pump for handling cryogenic liquids that operates on a two-stroke intake and discharge cycle, which pump comprises a pump casing having a sump formed therein and a vertical passageway opening upward into said sump, a stationary cylindrical pump plunger mounted in said pump passageway, a hollow pump cylinder proportioned to interdit within said vertical passageway and having a central bore dormed therein for slidably receiving said stationary plunger thereby deiining therewith a pumping chamber of variable volume, said hollow pump cylinder having formed therein an intake valve port which opens into the top lof said pumping chamber and a frusto-conical surface which surrounds said port and opens outward in a direction away from said pumping chamber, the axis of the surface being co-axial with said cylindrical plunger and the area of said surface being at least equal to the cross sectional area of said pumping chamber, a highpressure seal disposed between said cylindrical pump plunger and the bore of said hollow cylinder effective to seal said pumping chamber, said cylindrical pump plunger having a discharge passageway formed therein in liuid communication with said pumping chamber, discharge valve means closing the junction between said discharge passageway and said pumping chamber, a portion of said discharge passageway being located in close thermally conducting relation to said high-pressure seal so that heat frictionally generated by said seal is absorbed by the discharge stream of cryogenic liquid and carried away from said pumping chamber, a frustum-shaped valve stem for closing said intake valve port and seating against said frusto-c-onical surface, said stem being adapted for movement along an axis co-axial with the axis of said pump plunger, means connected to said valve stem for moving said stem in reciprocating motion to open said intake valve port on the intake stroke of the pump and to close said intake valve port on the discharge stroke of the pump, and lost-motion -connection means between said valve stem and said hollow cylinder for moving said cylinder in reciprocaing motion relative to said stationary plunger so that said motion of said hollow cylinder lags said motion of said valve stem, whereby movement of said cylinder on the intake stroke through said sump away from said plunger causes said pumping chamber to be filled by dynamic induction.

References Cited by the Examiner UNITED STATES PATENTS 1,683,617 9/ 1928 Hennessy 10.3--153 2,598,528 5/1952 French 10S-41.1 2,765,625 10/1956 Hart 103-227 y2,779,295 1/1957 Manning 10-3-158 2,855,859 10/1958 Petzold 62-55 3,023,710 3/ 1962 Tyree 103-1153 3,101,057 8/1963 Heiser 103-154 3,137,143 6/1964 Jacobs et al. 62-55 SAMUEL LEVINE, Primary Examiner.

H. F. RADUAZO, Assistant Examiner.

Claims

1. A POSITIVE DISPLACEMENT RECIPROCATING PUMP FOR HANDLING CRYOGENIC LIQUIDS, WHICH PUMP COMPRISES FIRST AND SECOND COOPERATING PUMP MEMBERS WHICH ARE MOVABLE RELATIVE TO EACH OTHER AND WHICH DEFINE A PUMPING CHAMBER, MEANS DISPOSED BETWEEN SAID MEMBERS EFFECTIVE TO SEAL SAID PUMPING CHAMBER, SAID FIRST PUMP MEMBER HAVING A DISCHARGE PASSAGEWAY FORMED THEREIN IN FLUID COMMUNICATION WITH SAID PUMPING CHAMBER, AND DISCHARGE VALVE MEANS CLOSING SAID DISCHARGE PASSAGEWAY, A PORTION OF SAID DISCHARGE PASSAGEWAY BEING LOCATED IN CLOSEE THERMALLY CONDUCTING RELATION TO SAID SEALING MEANS SO THAT HEAT FRICTIONALLY GENERATED BY SAID SEALING MEANS IS ABSORBED BY THE DISCHARGE STREAM OF CRYOGENIC LIQUID AND CARRIED AWAY FROM SAID PUMPING CHAMBER.