US2831509A - Pumps - Google Patents

Description

April 22, 1958 Filed Aug. 3, 1954 R. l. N. WEINGART ET AL PUMPS 4 Sheets-Sheet l //v l/E/YTORS M4 liMldm wf- ATTbR/vEY April 1958 R. l. N. WEINGART ET AL 2,831,509

PUMPS 4 Sheets-Sheet 2 Filed Aug. 3, 1954 NVEN To/s mull-411m fly, 4 AM ATTORNE Y April 1953 R. l. N. WEINGART ET AL 2,831,509

PUMPS Filed Aug. 3. 1954 4 Sheets-Sheet 3 A TTORNEY April 22, 1953 R. l. N. WEINGART ET AL 2,831,509

PUMPS 4 Sheets-Sheet 4 Filed Aug. 3, 1954 lN VEN TORS WW1 (A L ATTORNEY I United States Patent O PUMPS Richard Isaac Newton Weingart, New York, N. Y., and James Comber Sanderson, London, England, assignors to McCorquodale Colour Display Limited, London, England Application August 3, 1954, Serial No. 447,518

Claims priority, application Great Britain August 12, 1953 11 Claims. (Cl. 141-53) The present invention relates to a pump suitable for use in filling a closed space and more particularly a a closed space of small dimensions, with a liquid, the pump being adapted for intermittent operation and to deliver a similar quantity of liquid in successive operations. Such pumps are sometimes referred to as metering pumps.

The pump according to the invention is of particular utility in the production of deposits in thin layers, of

' pigments, inks and like liquid materials in accurately defined areas on surfaces, by the known method which makes use of a matrix having a shallow cavity or a number of shallow cavities formed in its operative face, which cavities are closed by the application of the surface intended to receive the deposit, against the said operative face of the matrix, and the liquid to be deposited being introduced into the thus closed cavities by Way of conduits leading through the matrix to the cavities and thereby deposited on the applied surface in patches of areas definedby the boundaries of the cavities in the matrix.

It is desirable and sometimes essential that the thickness and volume of the deposited patches of liquid material shall correspond accurately with the volume of the cavities in the matrix and where the sheet or body on which deposit is to be effected is of a material which is impervious or only reluctantly pervious to air, difficulty is encountered in efiecting a complete filling of the closed cavities due to the inability of the air entrapped in the closed cavities to escape as the liquid to be deposited enters the closed cavities.

Making use of the pump according to the invention the liquid to be deposited may be fed to a closed cavity in a quantity corresponding to that required to completely fill the closed cavity, or slightly in excess of that quantity, and an outlet or vent is provided for emergence of air from the cavity by displacement by the entering liquid 4 and also for emergence of any liquid in excess of that required to completely fill the cavity.

In accordance with the present invention a pump for the delivery of a succession of similar amounts of liquid material is provided comprising a barrel having a receiving chamber at one end adapted for connection with a supply source of the liquid material and a delivery chamber at the other end provided with an outlet, a vent tube extending from the exterior of the pump near said outlet and axially through the barrel, and a non-return valve member mounted within the barrel and on said vent tube for movement axially relative to the vent tube to control the transfer of a charge of liquid material from the said receiving chamber to the said delivery chamber and the ejection of liquid material through the outlet from the said delivery chamber.

The liquid material is delivered from the supply container either by gravity or under pressure through a feed tube, usually a flexible tube, connected between the container and the receiving chamber of the barrel of thepump, and the outlet end of the vent tube may extend into the feed tube so that vented air-may pass away iii) through the feed tube into the supply container. The vent tube is provided With a non-return valve at its inlet end.

In some cases e. g. when the liquid material is of low viscosity, the outlet end of the vent tube may be connected with a separate tube leading through the feed tube to the supply container preferably to a point above the liquid level therein so that accumulation of air bubbles in the feed tube is avoided.

Again, the outlet end of the vent tube may be led out from the barrel of the pump and connected with a separate external tube leading to the supply container or alternatively to a separate receiver.

The invention is illustrated in the accompanying drawings as applied to the deposition of patches of liquid material making use of a recessed matrix in the manner referred to above.

In the drawings Fig. 1 illustrates diagrammatically an apparatus utilising a matrix having a number of cavities in one of its surfaces for depositing patches of pigment on the surface of a sheet material 'held in contact with the operative surface of the matrix containing the cavities.

Figs. 2, 3 and 4 are views in sectional elevation of one form of pump according to the invention suitable for use with an apparatus. as shown in Fig. l for effecting controlled delivery of the liquid material to be deposited, the moving parts of the pump being shown in different relative positions in the several figures.

Figs. 5 to 9 show an alternative form of pump according to the invention, Figs. 5 and 6 being sectional side elevations showing the moving parts of the pump in different relative positions. Figs. 7 and 8 are views in end section of the non-return valve member taken on the lines VII-VII and VIII-VIII respectively of Fig. 5 and Fig. 9 is a view of the outlet end of the pump of Figs. 5 and 6.

Fig. 10 shows a modification of the pump of Fig. 5.

Referring to the drawings, Fig. 1 represents diagrammatically a form of apparatus for depositing patches of pigment on sheets of paper or cardboard, the apparatus consisting of a fixedly mounted matrix 1 having cavities 2 in its lower face, and a rising and falling platen 3 for holding a sheet of paper or cardboard 4 in firm engagement with the lower face of the matrix 1 so that the cavities 2 are closed and sealed by the sheet 4.

Control members 5 mounted on a bar 6 communicate on the one hand with passages '7 leading through the body of the matrix 1 to the respective cavities 2, and on the other hand with flexible feed pipes 8 leading from supply containers 9 for the liquid pigments.

The bar 6 is capable of being lowered parallel to itself and relative to the matrix 1 to actuate the control members 5 to cause delivery of pigment to the cavities 2 e. g. by the engagement of inclined surfaces 10 on horizontally reciprocated bars 11 with rollers 12 on the bar 6. The bar 6 is guided by posts 13 and is returned to the raised position by springs 14 on the guide posts 13. In one position of the bar 6 the control members 5 serve to prevent flow of pigment to the cavities in the matrix 1 so that the table 3 may be lowered and the sheet 4 with the deposited patches thereon removed and another sheet 4 substituted on the platen 3 in preparation for. the next depositing operation.

The present invention is directed to providing an improved form of pump for use with such apparatus for the control of the flow of pigment to the cavities of the matrix, and which willv effect the delivery of the liquid pigment in pro-determined similar quantity in successive operations of the pump and which enables air entrapped within the cavities of the matrix when the sheet of paper or cardboard is applied to the operative face thereof, to

escape in its entirety as liquid is introduced so that the cavities may be entirely filled with the liquid deposit material.

The form of pump illustrated in Figs. 2 to 4 comprises a barrel formed by a tube 16 and two internally bored end plugs, the plug 17 at the upper end being formed for connection with a supply pipe 8, leading from a convenient source of liquid such as a container 9 of Fig. 1, and the plug 18 at the lower end being a sliding fit on a delivery tube 19, extending axially part-way through the barrel 15.

The upper plug 17 is intended for connection with the rising and falling plate 6 Fig. 1 whereby the barrel 15 may be raised and lowered between pre-determined limiting positions and relative to the delivery tube 19.

The lower end of the delivery tube 19 is screw threaded for engagement in an internally threaded hole 7 extending through the matrix 1, and the extremity of the tube 19 is closed by a plug 20 having one or more restricted or capillary outlet apertures 21, substantially flush with the bottom wall of the cavity 2 in the matrix 1.

A small diameter vent pipe 22 is fixed inside the delivery tube 19 with its lower or inlet end opening through the plug 20 and with its upper end extending above the delivery tube 19 and through a cap 23 closing the upper end of the delivery tube 19, and axially through the barrel 15 and into the bore of the plug 17 at the upper end of the barrel, the upper end of the vent pipe 22 being held centrally within the bore of the plug 17 by means of a spider 24.

The lower end of the vent pipe 22 is provided with a non-return valve 25.

On the part of the vent pipe 22 within the barrel 15 and immediately below the spider 24 is slidably mounted a conical non-return valve member 26 adapted for co-operation with a conical seating 27 formed at the lower end of the bore of the upper plug 17 of the barrel 15.

The cone valve member 26 is urged yieldingly into an upper position (Fig. 2) by a compression spring 28 sur- 5 rounding the vent pipe 22 between the cap 23 closing the upper end of the delivery pipe 19 and the cone valve member 26.

The cone valve member 26 in its uppermost position abuts a stop 29 below the spider 24 and in this position and with the barrel 15 fully raised relative to the delivery tube 19 (see Fig. 2), the cone valve member 26 is spaced from the conical seating 27 so that the receiving space 30 of the barrel 15 is represented by the space within the upper plug 17 connected with the feed tube 8 is in communication with the delivery space 31 within the tube part 16 of the barrel 15.

In the wall of the delivery pipe 19 near the closed upper end thereof inside the tube 16 of the barrel 15 are formed one or a number of circumferentially distributed ports 32, the said ports in the fully raised position of the barrel 15 being surrounded and closed by a cupped ring washer 33 fitted to slide between the tube part 16 of the barrel and the upper end of the delivery tube 19 and abutting upon a shoulder 34 formed by cupping the inner end of the plug 18 forming the lower end of the barrel 15. The ring washer 33 is made a tighter fit on the upper end of the delivery tube 19 than in the tube part 16 of the barrel 15.

A stop 35 is provided on the exterior of the delivery tube 19 within the barrel 15 to limit the extent of movement of the ring washer 33 downwards on the delivery tube 19.

A small air vent 36a may be formed through the bottom plug 18 of the barrel 19 leading from the interior of the inner cupped end of the plug 18 to the exterior.

The upper plug 17 of the barrel 15 is shown as externally threaded for the reception of a pair of nuts 36 to na e the ar 1.5 t9 sstmss s wit t e ri in d falling bar 6 (Fig. 1).

The operation of the pump is as follows:

With the bar 6, and therefore the barrel 15, fully raised as shown in Fig. 2, the cone valve member 26 is engaged with the stop 29 near the upper end of the vent pipe 22 and held spaced from the seating 27 on the upper end plug 17 of the barrel 15 and liquid is free to transfer from the receiving space 30 to the delivery space 31 of the barrel 15 to fill the space 31. In this position of the barrel 15 the cupped ring washer 33 is held up by tr e shoulder 34 on the bottom plug 15 in the position in which it covers the ports 32 in the wall of the delivery tube 19.

By operation on the rising and falling bar 6, the barrel 15 is moved downwards and then upwards relative to the delivery tube 19. During the early part of the downward movement of the barrel 15 the conical seating 27 at the lower end of the upper plug 17 approaches and finally engages the conical valve member 26 to isolate the delivery space 31 of the barrel from the receiving space 30 and the supply conduit 8, and the shoulder 34 on the rim of the inner cupped part of the lower end plug 18 of the barrel 15 recedes downwards from the under side of the cupped ring washer 32 (Fig. 3).

Continued downward movement of the barrel 15 with the cone valve member 26 in the closed position as shown in Fig. 3, causes the cupped ring washer 33 to move downwards under the pressure of the column of liquid in the delivery space 31 of the barrel 15, to uncover the ports 32 in the wall of the delivery pipe 19, the cupped ring washerv 33 being arrested in a position immediately below the ports 32 by the stop 35 on the delivery pipe 19 (Fig. 4).

Thereafter the liquid is fed under pressure from the delivery space 31 of the barrel 15 through the ports 32 and the delivery pipe 19 and the outlet 21 thereof to the cavity 2 in the face of the matrix 1 in a quantity related to the length of stroke of the barrel 15. Air in the closed cavity 2 is displaced past the non-return valve 25 at the lower end of the vent pipe 22, through the vent pipe and away to the receiving space 30 of the barrel and to the supply conduit 8, and in the event of any excess quantity. of liquid being delivered by the pump to the cavity, the excess is also permitted to emerge by way of the vent pipe 22.

On the rising or return stroke of the barrel 15 the spring loaded conical valve 26 can yield so that the delivery space 31 of the barrel 15 is placed in communication with the receiving space 30 and the supply conduit 8 and little or no suction takes place at the ports 32 in the delivery pipe 19 prior to the return or raising of the cupped ring washer 33, by the engagement therewith of the shoulder 34 of the cupped inner end of the bottom plug 18 of the barrel 15, to the position in which it closes the said ports in preparation for the next succeeding operation.

As the barrel 15 moves into its raised position the delivery space 31 therein is replenished with liquid passing from the receiving space 30 and the supply conduit 8 and past the conical valve member 26 the latter being open in the fully raised position of the barrel 15 as shown in Fig. 2, and during this transfer the delivery pipe 19 and its outlet 21 are isolated from the delivery space 31 by the ring washer 33.

Direct flow of liquid from the receiving space of the barrel 15 or the supply conduits, to the interior of the cavity 2 by way of the vent pipe 22 is prevented by the non-return valve 25 at the bottom or inlet end of the vent pipe 22.

The sheet 4 with the deposit thereon may now be disengaged from the face of the matrix. The risk of drip of further liquid from the delivery pipe during such disengagement is avoided by the use of the restricted or capillary outlet apertures 21 from the delivery pipe and the possibility of drip from any excess liquid which may have entered the vent tube 22 is avoided by the non-return valve 25.

The upper end of the vent tube 22 may in some cases be connected with a further tube 37 of small diameter extending through the receiving space of the barrel 15 and through the supply conduit 8 and away to the supply container 9 in the manner represented in dotted lines at 37 in Fig. 1.

Again, the upper end of the vent tube 22 may be connected with a branch pipe 64a leading through the wall of the upper plug 17 of the barrel as shown in Fig. 4 and the branch pipe 64a connected with a separate return pipe 65 leading back to the supply container 9 or to a separate receiver (not shown).

In the alternative construction illustrated in Figs. 5 to 9, the barrel 15 comprises a main cylinder 38 having an external flange 39 intermediate its ends and a secondary cylinder 40 fitted over the lower end of the main cylinder 38, and screwed as shown at 41, in abutting engagement with the flange 39, and a hollow end plug formed by a gland ring 42 screwed into the counterbored and screw-threaded upper end of the main cylinder 38 with the interposition of a packing ring 43.

The lower end of the main cylinder 38 is open and formed with a peripheral chamfer as shown at 44, and at a location spaced from the chamfered end of the main cylinder 33 there is formed in its interior a shallow elongated annular recess 45.

The lower end of the secondary cylinder 40 is formed with an end closure 46, the inner surface of which is spaced from the chamfered end 44 of the main cylinder 38 and the end closure 46 is traversed by a plurality of small circumferentially distributed outlet apertures 47 and a central screw threaded bore 48.

A vent tube 49 is mounted co-axially within the barrel 15, being fixed at its lower end within a hollow bored plug 50 screwed into the threaded bore 48 in the end closure 46 of the secondary cylinder 40. The lower end of the plug 50 is substantially flush with the outer surface of the end closure 46 and is provided with a small aperture 51, and in the hollow plug 50 between the small aperture 51 and the lower end of the vent tube 49 itself is mounted a ball 52 to form a non-return valve at the lower end of the vent tube.

In the space between the lower chamfered end 44 of the main cylinder 38 of the barrel 15 and the inner surface of the end closure 46 is mounted a cupped diaphragm 53 of spring metal, said diaphragm being held in position by engagement beneath a flange 54 on the plug 50 and normally engaging, by its inherent spring, with its peripheral portion against the chamfered end 44 of the main cylinder 38.

Within the main cylinder 38 of the barrel 15 is contained an axially bored non-return valve member 55.

The valve member 55, which also functions as a pump plunger, is an elongated body axially bored to be a sliding fit on the vent tube 49, and it comprises a body portion 56 at its lower end of a size to be a sliding fit in the cylinder 38 of the barrel 15 and a stem portion 57 at its upper end, the stem portion being of smaller diameter than the body portion 56 so that a circumferential shoulder 64 is presented at the junction of the parts 56 and 57.

The stem portion 57 of the valve member 55 is of a diameter to have sliding fit with the inner wall of tube 58 and is provided with a number of external longitudinal grooves 59 Figs. 5, 6 and 8 terminating at their lower ends in outwardly directed slots 59a in the wall of the body portion 56 of the valve member 55 immediately below the shoulder 64.

The stem portion 57 of the valve member is inserted into the lower end of a tube 58 until the tube abuts the shoulder 64 and the stem and tube are fixed to one another e. g. by welding.

The tube 58 is a sliding fit in the cylinder 38 and its upper end extends through the upper end of the barrel 15 and is connected in a manner not shown, with a flexible feed tube such as 8 of Fig. l, and also with the rising and falling bar of that figure.

The grooves 59 in the stem portion 57 of the valve member 55 constitute in conjunction with the tube 58 passages for liquid, these passages terminating in the outwardly directed slots 59a in the body portion 56 of the valve member below the shoulder 64 and the lower ends of all the outwardly directed slots 59a are on a common circumferential line indicated at 60 in Fig. 5 in the body portion 56 of the valve member 55.

The lower end of the body portion of the non-return valve member 55 is provided with a number of circumferentially distributed notches 61 (Figs. 5, 6 and 7) in its peripheral edge all terminating at their upper ends on a common circumferential line shown at 62 in Fig. 5 on the body portion 56.

The axial distance between the two circumferential lines 66 and 62 is slightly less than the axial length of the internal annular recess 45 formed in the wall of the main cylinder 38 of the barrel 15.

The pump may be mounted by screwing the secondary cylinder 40 into a threaded aperture in the matrix 1, the flange 39 on the main cylinder 38 being located so that the lower side of the end closure 46 of the secondary cylinder 40 of the barrel is substantially flush with the surface of the bottom wall of the cavity 2 in the matrix.

The operation in this case is as follows:

With a sheet of paper 4 applied against the operative face of the matrix 1 as previously described the deposition of a charge of liquid may be in this case effected by first raising the bar 6 from a lowered and rest position and thereafter returning the bar 6 to the lowered position.

In the lowermost or rest position the non-return valve member 55 occupies the lowered position shown in Fig. 5 in which the receiving space of the barrel 15 as represented by the annular recess 45 in the wall of the cylinder 38 and the grooves 59 in the stem 57 of the member 55 is open to the feed tube 8 by way of the sliding tube 58, and is filled with liquid.

As the bar 6 is raised the tube 58 and the non-return valve member 55 move upwards relative to the barrel 15 into the position shown in Fig. 6 in which both the circumferential lines 60 and 62 representing the terminations of the grooves 59 in the stem 57, and the notches 61 in the body portion of the non-return valve member, lie between and slightly spaced from the axial ends of the annular recess 45. Liquid is now free to flow into and fill the delivery space 15a of the barrel 1-5 below the lower end of the body part 56 of the non-return valve member 55, suction through the outlet apertures 47 as the member 55 is raised, and which might tend to interfere with such flow, being prevented by the diaphragm 53 which by its inherent spring engages the chamfered lower end 44 of the barrel 38 to isolate the outlets 47 from the delivery space 15a. I

Return or downward movement of the bar 6 now takes place to move the tube 58 and the non-return valve mem ber 55 downwards. The notches 61 move from register with the annular recess 45, so that member 55 now functions as a non-return valve preventing return of liquid from the delivery space to the receiving space of the pump and thereafter pressure is exerted by the member 55 on the column of liquid in the delivery space of the barrel 15 to eject the liquid through the outlet apertures 47 and into the cavity 2 closed by the sheet of paper 4, the diaphragm 53 being deflected by the pressure of the liquid to permit the liquid to pass the lower chamfered end 44 of the main cylinder 38.

Air within the cavity 2 is swept by the liquid past the ball valve 52 into the vent tube 49 and away into the sliding tube 58, feed tube 8 and the receptacle 9.

The quantity of liquid ejected by the pump may be determined by setting the down stroke of the bar 6 and of the non-return valve member 55 and is preferably slightly 'in excess of that required to fill the cavity 2, the excess being permitted to emerge from the cavity 2 by way of the vent tube 49.

Drip of liquid from the pump when the sheet 4 bearing the liquid deposit is disengaged from the matrix 1 is avoided by the use of the small capillary outlet aperture 4-7 and the diaphragm 53 which re-engages with the chamfered end of the main cylinder 38 on termination of the down stroke of the non-return valve member 55, and drip of excess liquid from the vent tube 43 is prevented by the non-return ball valve 52.

The outlet apertures 47 are preferably directed at an outward inclination from the axis of the pump as shown in Figs. 5 and 6 and they may also with advantage be directed in tangential planes as indicated in Fig. 9 so that a whirl is imparted to the ejected liquid to sweep air from the corners and edges of the cavity in the matrix into the vent tube 49.

In Fig. 10 there is illustrated a modification in which the lower end of the pump barrel is of a form to itself constitute a matrix for direct engagement with the sheet 4 intended to receive the deposit. In this case the lower end of the secondary cylinder 49 is turned to provide a recess or cavity 2 surrounded by an edge boundary 63 intended to be contacted by the paper sheet, and the outlet apertures 37 and the plug 50 at the entry end of the vent tube 4& terminate at the bottom wall of the recess or cavity 2.

The pump barrel 15 is fixedly mounted upon a suitable fixed support (not shown) and the axial tube 58 operated as previously described to effect deposit on a sheet of paper supported in direct and firm engagement with the end of the pump.

We claim:

1. A pump for the delivery of a succession of similar amounts of liquid material, comprising a barrel having a receiving chamber at one end adapted for connection with a supply source of the liquid material and a delivery chamber at the other end communicating with an outlet, a vent tube extending from the exterior of the pump near said outlet and axially through the barrel, and a nonreturn valve member separating the said receiving chamber and the said delivery chamber and mounted within the barrel and on said vent tube for movement axially relative to the vent tube to control the transfer of a charge of liquid material from the said receiving chamber to the said delivery chamber and the ejection of liquid material through the outlet from the said delivery chamber, and

means isolating the delivery chamber from the said outlet during transfer of liquid material from the receiving chamber to the delivery chamber.

2. A pump as claimed in claim 1 wherein the barrel is a tubular body having a closure at one end traversed by at least one outlet aperture and a venting aperture in communication with the inlet end of said axially disposed vent tube the said axially disposed vent tube being fixed relative to the pump barrel, and the receiving chamber of the pump includes a recess. of limited length in the internal wall of the pump barrel and the non-return valve member is formed by a body arranged for axial sliding. movement within the barrel of the pump and on the said vent tube between twoextreme positions in one of which the peripheral surface of said body is between the ends of said recess so that said recess provides through com mnnication between the supply source for the liquid and the delivery space of the pump and in the other of which communication between said recess and the delivery space of the pump is interrupted.

3. A pump as claimed in claim 2 wherein an annular shoulder is provided in the pump barrel near to but spaced from the end closure and a spring washer is mounted on said end closure with its periphery extending between said shoulder and the outlet aperture through the end closure, the arrangement being such that in an unstressed condition said washer makes contact under its inherent spring with said shoulder, to interrupt communication between the delivery space of the pump and the outlet apertures through the end closure.

4. A pump as claimed in claim 2 wherein the nonreturn valve member sliding on the said axially disposed vent tube includes a head portion of a diameter to be a sliding fit in the barrel and a stem portion of smaller diameter fixed Within the end of a tube extending through the end of the pump barrel remote from the end closure and slidable axially therein, said tube being adapted for connection with the liquid supply source, and passages being provided between the Wall of the tube and the stem of the non-return valve member and terminating in circumferential outlets at the end of the head of the nonreturn valve member adjacent the stem thereof and communicating with the recess in the interior of the Wall of the barrel.

5. A pump as claimed in claim 1 and having a nonreturn valve at the end of the vent tube adjacent the outlet end of the pump for preventing flow of fluid out of the intake end of said vent tube.

6. A pump as claimed in claim 1 and including a delivery tube extending axially from within the barrel and having the outlet from the pump at its free end, said barrel and said delivery tube being capable of relative movement in the axial direction, the vent tube being fixed relative to the delivery tube and extending from the outlet of the pump axially through the delivery tube at least to the receiving chamber of the pump barrel.

7. A pump as claimed in claim 6 wherein the nonreturn valve separating the receiving chamber and the delivery chamber is formed by a conical body mounted to slide on the vent tube, a valve seating for said conical body carried by the valve between said chambers, and a return spring urging said conical body towards said seating.

8. A pump as claimed in claim 6 wherein the end of the delivery tube Within the pump barrel is closed and at least one port provided in its wall for communication between the delivery chamber of the pump barrel and the interior of the delivery tube and an annular washer is provided between the pump barrel and the delivery tube for opening and closing said port, said annular washer being capable of axial sliding movement relative to both the pump barrel and the delivery tube and being located in a position in which it closes the port by engagement of a part of the pump barrel with said washer in one extreme position of the pump barrel relative to the delivery tube.

9. A pump asclaimed in claim 8 wherein a stop is provided on the delivery tube to limit the sliding movement of the annular washer in the direction for opening the ports in the delivery tube.

10. A pump as claimed in claim 2 having a plurality of circumferentially distributed outlet apertures through the end closure of the pump barrel, said apertures being directed outwards at an inclination to the axis of the pump barrel.

11. A pump as claimed in claim 10 wherein the outlet apertures through the end closure extend in directions tangential to a circle concentric with the pump barrel.

References Cited in the file of this patent UNITED STATES PATENTS

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