US3318256A - Means for pressurising liquids - Google Patents

Description

May 9, 1967 D. GREEN MEANS FOR PRESSURISING LIQUIDS V I??? 'IV Filed Jan. 29, 1965 United States Patent 3,318,256 MEANS FOR PRESSURISING LIQUIDS Derek Green, St. Annes, England, assignor to United Kingdom Atomic Energy Authority, London, England Filed Jan. 29, 1965, Ser. No. 429,104

Claims priority, application Great Britain, Feb. 20, 1964,

7,238/ 64 1 Claim. (Cl. 103178) This invention relates to means for pressurising liquids.

Means for pressurising liquids has one application in hydrostatic extrusion apparatus, in which a work piece is forced through a die mounted at the end of a pressure container by liquid pressure acting directly on the workpiece. The pressure is normally generated by a plunger and barrel assembly but because the plunger has no physical contact with the workpiece and because the workpiece is side supported by the liquid in passage through the die, bending forces are substantially avoided thus enabling long and slender workpieces such as wire to be extruded. Furthermore, as a coating of the liquid is passed through the die with the workpiece thus providing lubricant and as there is no physical contact of the workpiece with the wall of the pressure container, frictional resistance to extrusion is also considerably reduced. The production of long and slender articles by the apparatus is facilitated if the pressure container is horizontally disposed so that the extrusion takes place horizontally through a die in the end of the container. The plunger and barrel assembly are preferably vertically mounted being interconnected with the pressure container by a duct, the plunger acting downwardly to pressurise the liquid in the container. However, because of the high pressure involved making it preferable to avoid weakening the wall of the barrel or container by penetrations, it becomes necessary to remove the plunger to replenish liquid lost as lubricant to the workpiece and not only is this an expensive time consuming operation but it is made more complex by the vertical disposition of the plunger. The lack of penetrations in the wall of the barrel also makes diflicult the bleeding of air entrapped during assembly from the underside of the plunger. In conventional apparatus the gland sealing means for the plunger can include an embracing mitre sealing ring, that is to say, an annular member having a right angle triangular shaped cross section; the base of the triangle defines the width of the member and is the side which contacts the wall of the barrel, the side normal to the base defines the depth of the face of the ring which face is presented to the pressurised fluid, and the hypotenuse defines an oblique face which in use abuts a a cooperating oblique annular face formed on the plunger so that when the plunger is moved on a liquid pressurising stroke the annular ring is urged against the oblique annular face formed on the plunger causing the ring to expand radially outwardly to engage the wall of the barrel in sealing manner. Hereinafter the term mitre sealing ring is intended to mean a sealing ring of this kind. Initial sealing is effected by a rubber O ring which is in front of the mitre sealing ring on a pressurising stroke and which serves to prevent liquid pressure escaping past the mitre sealing ring at the commencement of the pressurising stroke before the mitre sealing ring has expanded radially sufficiently to provide a satisfactory seal and also to prevent the ingress of air on the return stroke. However, the rubber O ring is subject to damage and/or displacement from its location on the plunger as a result of the return motion of the plunger on the non-pressurising stroke because the thrust required to overcome the frictional resistance between the mitre "ice gland sealing ring and the barrel wall is applied through the rubber O ring.

According to the invention, means for pressurising liquids comprises a barrel having a cylindrical bore, a loose fitting plunger entered into the bore of the barrel, a cylindrical body member movable in the bore of the barrel, means sealing circumferentially between the cylindrical body member and the bore of the barrel, coupling means retaining the body member in front of the plunger when the plunger is moved in the barrel, said coupling means having a lost motion characteristic, such that the plunger is movable longitudinally in the barrel between limits relative to the body member, a duct extending from end to end of the body member, sealing means operable to close said duct when the plunger is in end to end abutment with the body member on a liquid pressurising stroke of the plunger, said sealing means being inoperable such that the duct is open when the plunger parts from the cylindrical body member on the return nonpressurising stroke of the plunger by an amount governed by the lost motion characteristic of the coupling means between the cylindrical body member and the plunger.

The invention provides that on the return non-pressurising stroke, when the body member and plunger part sufiiciently to open the duct, entrapped air is expelled from the underside of the plunger via said duct.

A reservoir for liquid is provided outside the barrel for feeding liquid to the annular space defined between the loose fitting plunger and the bore of the barrel so on the return or non-pressurising stroke of the plunger and body member, liquid can flow through the annular space and through the duct in the body member to replenish the liquid in the barrel. The means sealing circumferentially between the body member and the bore of the barrel comprises a mitre sealing ring held between an external oblique face on the body member and a thrust ring fixed on the body member, a rubber sealing ring being disposed around the thrust ring in sealing contact with the bore of the barrel.

A liquid pressurising plunger and barrel assembly embodying the invention, for application for example to hydrostatic extrusion apparatus, will now be described, by way of example with reference to the accompanying drawings wherein:

FIGURES 1, 2 and 3 are fragmentary views in section showing the plunger and barrel assembly in three operative positions, FIGURE 1 showing a part of the assembly in section whilst FIGURES 2 and 3 show that part in elevation.

In the drawing there is shown a gland sealing assembly I mounted on the plunger 2 in the barrel 3. The gland seal assembly comprises a substantially cylindrical body member 4 slidable in the barrel and retained on the plunger by a screw bolt 5. Circumferential sealing of the body member 4 with the wall of the barrel is effected by a rubber O ring 6 and a nylon mitre backing ring 7. The ring 7 is located between an oblique face on the body member 4 and a stepped thrust ring 8 which is retained on the body member by a nut 9 and is sealed to the body member by a second rubber O ring 10 and a mitre backing ring 11. A central bore through which the bolt extends to engage the plunger together with the shank of the bolt defines an annular duct 12 and at the mouth of the duct 12 adjacent the plunger, a mitre backing ring 13 serves to seal the duct when the bodymember 4 is in abutment with the plunger. The bolt 5 has a head 14 with a groove 15 and is disposed so that the plunger 2 is capable of moving axially into or out of abutment with the body member. When the plunger 2 is out of abutment with the body member and in abutment with the head of the bolt as shown in FIGURES 2 and 3 the groove 15 and body member 4 define a duct which coincides with the annular duct 12. The plunger 2 and bore of the barrel 3 are of diameters suitable to define an annular duct 16 which extends to a reservoir 17.

In the construction of hydrostatic extrusion apparatus of which the described plunger and barrel assembly forms a part, the barrel is mounted with its longitudinal axis vertically disposed and in FIGURE 1 the plunger is shown on a downward liquid pressurising stroke as indicated by the arrow designated A so that the plunger 2 is urged into abutment with the body member 4 to seal the head of the plunger against leakage of pressure.

In FIGURE 2 the plunger is shown to have commenced the upward return stroke as indicated by the arrow A so that, because of the frictional resistance to movement of the gland seals, the plunger is drawn out of abutment with the body member 4. The ducts 15, 12 interconnect the ends of the seal assembly so that any air entrapped in the liquid is ejected to the reservoir 17 via the annular duct 16 as indicated by the arrows designated B.

In FIGURE 3 the plunger 2 is shown continuing its upward return stroke as indicated by the arrow A and liquid is able to flow from the reservoir 17 as indicated by the arrows designated C to replenish the interior of the barrel on the pressurising side of the seal assembly via the ducts 12, 15 thereby compensating for liquid lost as lubricant for the workpiece in passage through the die and also filling the voidage resulting from the expulsion of air from the liquid. During the upward return stroke the frictional resistance to movement of the mitre backing ring in contact with the wall of the barrel is overcome when the head 14 of the bolt abuts the body member. The thrust is taken via the thrust ring 8 instead of the O ring 6 as in the previously known equipment thus avoiding consequential damage to the O ring.

I claim:

Means for pressurising liquids comprising a barrel having a cylindrical bore, a loose fitting plunger entered into the bore of the barrel, a cylindrical body member movable in the bore of the barrel, sealing mean-s sealing circumferentially between the cylindrical body member and the bore of the barrel, said sealing means comprising a mitre sealing ring held between an oblique face on the body member and a thrust ring fixed on the body member, a rubber sealing ring being disposed around the thrust ring in sealing contact with the bore of the barrel, coupling means retaining the body member in front of the plunger when the plunger is moved in the barrel, said coupling means having a lost motion characteristic such that the plunger is movable longitudinally in the barrel between limits relative to the cylindrical body member, a duct extending from end to end of the body member, duct sealing means operable to close said duct when the plunger is in end to end abutment with the body member on a liquid pressurising stroke of the plunger, said duct having a conical mouth opening to face the adjacent end face of the plunger, said duct sealing means comprising a mitre sealing ring having a conical face engaging with the conical mouth of the duct and a flat annular end face engaging to seal with the end face of the plunger when the plunger is in end to end abutment with the body member on a liquid pressurising stroke of the plunger, the fiat annular end face of the mitre sealing ring being disengaged from sealing with the end face of the plunger, such that the duct is open when the plunger parts from the cylindrical body member on a return non-pressurising stroke of the plunger by an amount governed by the lost motion characteristic of the coupling means between the cylindrical body member and the plunger, a reservoir for liquid being provided in connection with the barrel for feeding of liquid into the bore of the barrel so that on the return non-pressurising stroke of the plunger liquid can flow between the plunger and the bore of the barrel and then through the duct in the body member to replenish liquid in the bore of the barrel below the cylindrical body member.

References Cited by the Examiner UNITED STATES PATENTS 2,462,586 2/1949 Whittingham 277188 2,739,855 3/1956 Bruning 277l88 2,894,665 7/1959 Zerlin 103-178 2,931,313 5/1960 Hughes 103-203 FOREIGN PATENTS 740,114 1/1931 France. 622,824 7/1961 Italy.

DONLEY I. STOCKING, Primary Examiner.

W. L. FREEH, Assistant Examiner.

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