US3043323A - Bakable ultra-high vacuum valve - Google Patents

Description

July 10, 1962 J. T. MARK ET AL BAKABLE ULTRA-HIGH VACUUM VALVE 3 Sheets-Sheet 1 Filed Dec. 8, 1959 INVENTORS JOHN T. MARK 8. IRA H. GANTZ ATTORNEY July 10, 1962 .1. T. MARK ET AL ,3

BAKABLE ULTRA-HIGH VACUUM VALVE Filed Dec. 8, 1959 3 Sheets-Sheet 2 j as 42- EEG/ON TO as I V4CU4TEO I .60 a0 32 92 i 1 as as 200 I y 66 64 4, ea v I I INVENTORS 54 TO PUMPS JOHN T. MARK 8. IRA Hv GANT'Z.

1 BY jaw ATTORNEY July 10, 1962 J. T. MARK ET AL BAKABLE ULTRA-HIGH VACUUM VALVE 3 Sheets-Sheet 3 Filed Dec. 8, 1959 4 n 6 5 H x. 2 m 6M4.- 6 7 VRT B M mm T 6 h 0 H i 4 H N 41 M mnu 5 a 2/ 1 m 2 8 n n w. H. u 6 (I (I a 45 8 7 J a u 1 H 2 4 d all 5 1. J M 9 N I M 4 6 z 5 m M 6 M 1 z 2 a a u 0 m5 ATTOR N EY nite Sates This invention relates to valves useful in applications involving successively closing and opening communication between a chamber evacuated to an ultra high vacuum condition and another chamber or the ambient. By the term ultra high vacuum is meant a gas pressure of the order of to 10' millimeters of mercury or lower. At such relatively low pressure, the gases occluded in the material of the valve constitute a source of gas evolution which adversely affects the attainment and preservation of a desired ultra high vacuum in the evacuated chamber. It has been found that such occluded gases are driven out effectively in response to a baking temperature of about 450 (3., applied for an appreciable period determined by the type of metal to be outgassed. For stainless steel and copper, this period is about twenty-five hours.

Accordingly, it is an object of the invention t provide an improved valve that is adapted to function advantageously under conditions involving ultra-high vacuum and a baking temperature of the order of 450 C.

Another purpose is to provide a valve adapted to be opened and closed repeatedly under the conditions of reduced gas pressure and temperature, aforementioned, and without any measurable loss of efficiency as a closing means.

A feature of the invention resides in the use of valve members made of materials adapted to be heated to a temperature of the order of 450 C. without any measurable softening thereof or other deleterious effect on their opening and closure functions.

According to another feature of the invention, the valve members aforementioned are made of such materials and are so constructed that in response to an appreciable force, they actually become joined in a Weld without the deliberate application of heat. Thus, the nature of the material selected for the valve members is such that a mechanical joinder thereof under conditions of relatively high pressure, produces an interdiffusion of the material of one of the members into the material of the other of the members, char acterstic of a weld.

In one example, one of the valve members comprises a relatively short cylinder or ring made of stainless steel and having an upper edge defined by a lip provided with a curvature of predetermined radius. The other of the valve members comprises a cylindrical block of copper having a diameter slightly larger than the inner diameter of the ring aforementioned. In attempts to forcefully telescope the block into the ring, with a force, say of twelve tons, the lip aforementioned is caused to penetrate an annular portion of the copper block adjacent to the periphery thereof with a pressure sufficient to produce the mutual interdiffusion of material referred to in the foregoing.

While in the example discussed, the lip of the ring-like valve member is provided with a curvature having a radius of three mils, it has been found that a good valve is obtainable when that radius is from two to siX mils in value.

Observance of this range of radius value is desirable for at least two reasons. First, it provides a desirably small area of contact between the two members for increasing the pressure per unit area, when the members are urged together forcefully in effecting a closure of the valve. And secondly, it facilitates a rupture of the weld protilt duced by the pressure referred to, when the valve is subsequently opened.

Further objects and features of the invention will become apparent, as the present description continues.

Reference now to the drawing for a detailed description of an embodiment of the invention selected only by Way of example, Will reveal that FIG. 1 is an elevational perspective view of a valve construction embodying the invention;

FIG. 2 is a transverse view taken along the line 22 of FIG. 1; I

FIG. 3 is an enlarged view in sectional elevation taken in the direction of the arrow A of FIG. 1;

FIG. 4 is a fragmentary sectional view of valve members in accordance with the invention and prior to an ini tial closure thereof;

FIG. 5 is a fragmentary sectional View of the Valve members in FIG. 4, after a closure thereof has been effected;

FIG. 6 is a schematic illustration, partly in section, of a system in which the valve of the invention is useful;

FIG. 7 shows in cross section a type of pressure regulating valve that may be used in practicing the invention; and

FIG. 8 shows in section a type of vent valve suitable for a practice of the invention.

The embodiment of the invention selected for illustration comprises a valve structure, as shown in FIG. 1, for selectively closing and opening communication between a duct it) leading to a region or chamber 12 under evacuation and a duct 14 extending to one or more pumps 16, 18 utilized for evacuating the chamber 12. The chamber 12 may comprise the envelope of a relatively large vacuum tube or other region wherein an ultra high vacuum is desired. The pump 16 may be a mercury diffusion pump of a type known commercially by the designation MHG900. The pump 18 may be a conventional mechanical pump known as a Kinney KC46. Also associated with the pumping system may be one or more cold traps (not shown), refrigerated by liquid nitrogen, for example, for aiding the out-gassing of chamber 12 to a state of ultra high vacuum.

The valve in the present embodiment includes a casing 20, within which are housed two valve members to be described. A piston rod 22 extends from a cylinder 24 and is fixed to one of the valve members. The piston rod 22 is connected to a piston to be described and positioned within cylinder 24 for axial movements therein. The cylinder and piston referred to constitute a portion of a pneumatic system which is adapted to be energized by a selective communication of ducts 26, 28 with a region of air under pressure. The pneumatic system referred to serves to apply a thrust to piston rod 22 of a magnitude to effect desired sequential closing and opening of the valve members aforementioned.

In view of the relatively high magnitude of thrust required to close and open the valve in the embodiment discussed, the structure associated with the valve members is relatively rugged. Accordingly, the structure includes a two-part flange 30 including flange members 32 and 34, which are sufiiciently rugged, as will be made clear in the following, for effectively absorbing the thrust of piston rod 22 during actuation of the valve. The flange assembly 30 is ruggedly tied to an additional flange 38, and loosely through flange 36, spaced axially of the valve structure, by means of elongated rods or bolts 40', 42, 44, spaced equidistantly around the structure. and fixed to certain of the flanges aforementioned by suitable means, such as nuts 46, 48 engaging opposite faces of flange 38, and by nuts 50 engaging the lower face of flange assembly 30.

The valve casing 20 is positioned between flange assembly 30 and flange 36. The space between flanges 36, A

38 provides a region for accommodating an indicating system including an adjustable switch 52 and a switch actuating member 54. Also accommodated in this region is a structure, shown more clearly in FIG. 3, for restraining relative axial rotation of the piston 22 with respect to the valve structure. \Aswill be explained, on later reference to FIG. 3, this restraining structure comprises a key and keyway combination. On the outer face of flange 38 is mounted the cylinder 24 of the pneumatic system aforementioned. The cylinder 24 is inggedly fixed to the flange 38 by a plurality of bolts and nuts, not shown, to preserve the cylinder against separation from the flange 38 during actuation of the valve.

Further particulars of the valve embodiment being described will become evident from a consideration of FIGS. 2 and 3. As shown in FIG. 3, the piston rod 22 extends into the chamber defined by cylindrical wall 29 and passes through an opening in a back-up block 56, which may be made of stainless steel. The back-up block may be fixed to the piston rod 22 in a suitable manner as by welding. To enable the piston rod to transmit a thrust to the back-up block of twelve tons, the piston rod is provided with an annular shoulder 58 which engages a ledge on the back-up block. In this way the appreciable thrust by the piston rod on the block aforementioned is allowed to take place without causing relative axial movement of the piston rod and block. It should be noted that the weld alone, between the piston rod and block might not be strong enough to restrain such movement.

Positioned on the free end of the piston rod 22 is a valve member 60, made of copper, for example. The positioning of the valve member is effected by means of a bushing 62, made of stainless steel for example, and brazed to the valve member 60. The inner wall of the bushing is provided with screw threads which engage complementary threads on the free end portion of the piston rod. Since the threaded relation alone, between the rod 22 and the bushing 62, may not be adequate to assure an ultra high vacuum tight joint therebetween, the free end of the bushing is closed by a plate 64, made of stainless steel, for example, which is fixed to the bushing by means of an annular weld 66. The accomplishment of this weld is facilitated by an annular groove 68 in the bushing which defines an annular lip for low heat drain from the region of the weld.

To allow the piston rod 22 to move axially within chamber 20, without adversely affecting an ultra high vacuum condition therein, a bellows structure 7t] is provided having a rigid cylindrical end portion 72 welded to the upper surface of the back-up block 56, and to the lower end of the corrugated resilient portion 74. The bellows structure includes a second rigid cylindrical end portion 76 Welded to the upper end of the resilient bellows portion 74 and to the inner wall of a flange 89. A plurality of air holes 82 extend through the flanges 80 and into the region defined by the bellows structure aforementioned, for the purpose of equalizing the pressure therein with the ambient during axial movements of the piston rod 22. An axially extending keyway 84 in the piston 22 is engaged by a key 86 supported by the flange 80, for restraining rotation of the piston rod with respect to the housing 20 and a second valve member to be described.

The second valve member 88 comprises a ring made of stainless steel for example, and having a lip 90. The valve member 88 is -welded to flange member .34 in an annular weld 92 (FIG. 3).

As shown in FIG. 4, the inner diameter of the ring valve member 88 is slightly less than the outer diameter of the valve member 60; Therefore, when the valve member 60 is urged into telescoped relation with respect to member 88, a peripheral portion of the material of member 60 is displaced as shown in FIG. 5 to form an annularlip 94. The force involved in such displacement, in combination with the shape of the lip 96 on member 88, serves to produce a molecular interdiifusion of the material of one of the valve members into the material of the other valve member, for producing an effective welded joint between the two members, capable of advantageously isolating a region under ultra high 'vacuum, from another region. A relatively small axial portion of valve member so is involved in the aforementioned material displacement, so that a relatively large number of valve openings and closures are feasible during the effective lifetime of valve member 663. It will, of course, be appreciated, that the useful life of valve'member 69 is dependent upon the magnitude of its axial dimension. However, such dimension is subject to limitations imposed by the length of thrust of piston 22, the tolerance of the bellows 74, and the overall required strength of the valve. In the example under consideration, a valve member oil having an axial dimension of three inches, has permitted 200 cycles of valve opening and closure.

However, the complete consumption of the valve member 65 in a plurality of valve openings and closures, does not destroy further utility of the valve. This is because the valve member 60 is so constructed and mounted on the piston rod 22, as to be readily replaceable with a new valve member. As indicated before herein, the valve member 60 is part of an assembly including the member referred to, the bushing 62, and the closure plate 64. This assembly'is readily screw mounted on or removed from the piston rod 22 by means of a wrench adapted to engage holes 98, ltlfl in the valve member 60. Access to the assembly aforementioned is provided by removal of flange 89 and piston rod 22 from the valve region defined by the casing 2t). Such removal is effected by loosening bolts 162 between flanges and 36 and nuts 46 from flange 33.

The embodiment described, not only constitutes a valve adapted to accomplish a closure by a weld produced without the deliberate application of heat, but one which may be successively opened and closed a number oftimes and which forms a new weld at each closure. While heat involved in the aforementioned bake-out temperature is present, it is not a requisite for the weld.

To form a weld involving interdiffusion of the material of one body into the material of another body, without the deliberate application of heat, requires the application of tremendous pressure between the two bodies. For the formation of a Weld, the bodies must be so shaped as to avoid dissipation of the pressure in relative movement of the bodies. For example, if the shape of one of bodies to be involved in a weld is in the nature of a lmife edge, a pressure application of the other body to the knife edge will merely cause the knife edge to penetrate the aforementioned other body without producing a weld. On the other hand, if the facing surfaces of the two bodies to be welded have a relatively large area, a prohibitively large pressure force would be required to form a weld therebetween.

In the embodiment under consideration, a novel structure of valve members is provided, resulting in a weld therebetween on each closure of the valve, and in a rupture of the previously formed weld, during each opening of the valve. Several factors are significant in'the structure of a valve functioning as indicated. These factors, so far as they affect the valve member 88, concern the ring type construction of member 88 and its composition of a material having relatively high tensile strength, such as stainless steel, the radius of curvature of the free end of lip 90, and the angle described by the sloping surface 106 with respect to a plane transverse of the member 88. So far as the valve member 60 is concerned, the aforementioned factors relate to the diameter of the member 60, its axial length and its composition of a material such as copper, respondingto pressure in plastic llOlW.

Considering these factors in more detail, the diameter of the valve member 60 should be larger than the inner diameter of the valve member 88. This diiference in diameter should be large enough to provide a desired reserve of material of the member 60 required for a pressure condition demanded by a weld of the type discussed. It should be small enough to limit the mass of the lip- 94 to a size which will offer the least resistance to a pressure engagement between members 60 and 88 for a good weld. The free end of annular lip 90 on valve member 88, should have a radius of curvature large enough to avoid entrance of the lip into the material of member '60, at a pressure below that required for a weld. It should be small enough to produce a desired concentration of the applied pressure to a region of relatively small area for securing a desired pressure per unit area. An additional demand on the radius of curvature of the lip 90 is that it contribute to the application of a force to the member 60' in a direction describing a relatively small angle with respect to a transverse axis of the member referred to, thereby resulting in amplification of the force with which the members 60 and 88 are urged together axially. A still further requirement with respect to the radius of curvature of the lip 90, is that it be sufliciently small to limit the area of high pressure contactbetween the two valve members at which the weld is formed, to a small enough value to render rupture of the weld feasible during a subsequent separation of the valve members when the valve is opened. Furthermore, it is desirable that the leading end portion of valve member 60 have a taper 104 (FIGS. 4 and 5) to produce a precision axial alignment automatically between the valve members 60 and 88.

Considering the aforementioned factors in relation to actual values determined in a constructed embodiment,

it has been found by applicants that the following dimensions contributed to good results. In a constructed example, the valve member 60 was made of copper and had an outer diameter of inches. Its axial length along its periphery was 3 inches. The periphery referred to defined a cylindrical contour with one end portion tapered. The valve member 88 was made of stainless. steel and had an inner diameter of 9.760 inches. Its outer diameter was 11.5 inches. The lip 90 had a radius of curvature of three mils, although a radius within the range of from about two to about six mils was satisfactory for the purpose of the invention. The slope 106 described an angle of about 10 from a plane normal to the axis of the member 88. This value was dictated by two factors. If the slope were at a smaller angle than indicated, it would result in a greater upward bend of the lip 9'4 thereby reducing the area of contact between the valve members. If the slope 106 were characterized by a larger angle, the lip 90' of member 88 would be weakened. It should be observed in this connection that an appreciable radial thrust is absorbed by the lip 90 during formation of the weld. Such thrust in the direction of arrow 110 (FIG. 5) for example, is at an angle appreciably less than 45 with respect to a plane normal to the axis of member 60. Consequently the force applied in the direction referred to, when the member is urged downwardly, is appreciably greater than the downwardly urging force. If the lip 90 were relatively thin, as in a case when the slope of surface 106 describes a. larger angle than about 10 with respect to a plane normal to the axis of the member 88, the lip would be too weak to absorb the appreciably greater force referred to. Consequently, the slope of surface 106 must be small enough to provide a mass of material in the lip 90 sufficient to enable it to absorb the aforementioned greater force, without any measurable deformation.

While the angle of slope of surface 106 and the radius of curvature of the free end portion of lip- 90 should be within the limits defined by the foregoing considerations, no particular critioality is associated with other dimensions of the valve members 60 and 88, other than that opening the valve.

valve member 60' should have anaxial dimension of sufiicient magnitude to permit several openings and closings of the valve to take place before replacement of valve member 60 is necessary, and that the valve member 88 have sufiicient mass to confer upon it the tensile strength required to absorb the relatively large force incidental to the formation of a weld.

It will be noted from the foregoing that virgin material of the valve member 60 is presented to the valve member 88 on each closure of the valve. This feature contributes to the formation of a weld between the members without the deliberate application of heat. It is believed that the molecular interdiifusion of the materials of the valve members occurs more readily where the material of the one of the members presents a newly formed surface to the other of the members. The resultant provision of a new seat on each closure of the valve, in the instant example, is also of appreciable advantage in that it avoids reliance on a previously formed seat which may involve irregularities resulting from the rupture of the prior weld, such rupture being required for opening the valve.

A system in which the valve embodiment described may be incorporated is shown in FIG. 6. This system is of a pneumatic type and includes means for transmitting a relatively large force tothe piston rod 22, say ofthe order of twelve tons. The system may include the duct 26 made of'relatively strong material to withstand the force aforementioned and which communicates with a top region 112 in cylinder 24. A second duct 28 also made of relatively strong material for the purpose indicated, communicates with a bottom region 114 of the cylinder referred to. The piston 116 is caused to move upwardly or downwardly, depending on whether air under pressure is directed through duct 26 or duct 28. Upward movement of the piston is transmitted through piston rod 22 to the valve member 60 (FIG. 3) for Downward movement of the piston is similarly transmitted to the valve member 60 for closing the valve.

Means for selectively directing air under pressure to ducts 26 and 28 is provided. This means includes a tank 118 having a pressure, say of 2500 pounds per square inch, and provided with a'valve 120. Connected in series between the tank 118 and the duct 26 are a pressure regulator 122, a first duct'124, a second pressure regulator 126, and a second duct 128. A solenoid actuated vent valve 130 is disposed in parallel relation to ducts 128 and 26.

The pressure regulators 122 and 126 may be of the type shown in FIG. 7. Thus, each regulator may include a casing 132 defining a first chamber 134 and a second chamber 136. Assuming the regulator shown in FIG. 7 is placed in the environment of the regulator 126 of FIG. 6, it will be found that chamber 134 connects to duct 124 and chamber 136 is connected to duct 128. Chamber 136 is partly defined by a diaphragm wall 138 fixed to the side walls 140, 142 of the chamber 136. The central portion of the diaphragm is provided with an opening closed by a flange 144 fixed to the lower end of a pin 146 as viewed in FIG. 7. The flange has a central opening through which a reduced diameter end portion of a pressure regulating screw 148 is adapted to extend, and into a cavity 150 in the pin 146. The'diaphragm 138 together'with the fiange 144 and pin 146, constitutes a hermetically tight wall. The diaphragm may be placed relatively close to a wall of casing 142 (FIG. 7) extending parallel to the diaphragm, with only sufficient space therebetween to allow the diaphragm to undergo a flexing movement of a magnitude to move pin 146 to closed position. This permits the diaphragm to absorb thebackward thrust of 'the operating pressure transmitted through valve 174 to ducts 26 and-128 when the piston is lowered to closedvalve position.

In the example shown, and involving pressure regulator 126, the screw 148 is adjusted to provide a pressure of 125 pounds per square inch on spring 152. Pressure regulator 122 is similar to regulator 126 except that it is adjusted to provide an operating pressure of 500 pounds per square inch.

The solenoid actuated vent valve 130 (FIG. 8) includes valve members 154, 156, which, when the normally closed switch 52 and the manual switch 158 (FIG. 6) are closed, are urged into seated relation by the spring 161} and the solenoid 162. Valve 13% includes a casing 164 defining a chamber 166 housing the valve members referred to. The housing is provided with a vent 168 to the ambient. Valve member 156 constitutes a free end of duct 170, which is connected to ducts 26 and 128. The solenoid 162 is supported on a support 161, and is fixed to casing 164 by rods 167.

\Vhen the solenoid 162 is de-energized on completion of a downward valve seating thrust of the piston 116, the spring 160 pushes solenoid core 163 inwardly and against wall 165, and urges the valve member 154 downwardly by engaging shoulder 169 thereon. While this movement of the core 163 slightly distends the spring 160, the spring continues to exert a thrust on valve member 154 which in the instant example involves a pressure of 130 pounds per square inch. Consequently, air pressure above this value will be dissipated through vent 168. This maximum pressure tolerated by vent valve 136 when the solenoid 162 is de-energized, is above the pressure of 125 pounds per square inch to which pressure regulator 126 has been set, as aforementioned. Therefore, when communication of duct 26. with the pressure regulator 122, through bypass duct 172 is stopped, the region 112 will be maintained at a pressure determined by the pressure regulator 126. The setting of the valve 130 to vent at a pressure of 130 pounds per square inch is advantageous, in that this is a slightly higher pressure than that to which pressure regulator 126 has been set. Accordingly, when the valve members 60', 88 (FIG. 3) are held in closed position by their welded relation and by the pressure of 125 pounds per square inch determined by regulator 126, for any appreciable length of time, the slightly greater vent pressure of valve 136 prevents loss of air from thepneumatic system and contributes to economy.

The switch 52 should be raised slightly in arm 173 between successive closures of the valve shown in FIG. 3 to allow a new valve seat to be defined on each closure of the valve, as pointed out above. A raising of switch 52 in the arm 173 permits the piston rod 22 to travel downwardly a greater distance than before. This increment in distance in the example being described is .005 inch. Adjustments in the position of switch 52 may be made by unloosening lock screw 177, and tightening the same after adjustment.

Stoppage of communication between duct 26 and the pressure regulator 122 is effected by means of a valve 174 (FIG. 6) which may be manually operable. This valve includes a casing 175 having a port 176 communicating with ducts 172 and 26, a port, 178 communicating with duct 124, a port 181 connected to duct 28, and a port 182 vented to the ambient. Within the casing 175 is posi-. tioned a valve member 184, manually rotatable by a handle 186. In the position shown in FIG. 6, passagea way 188 extending through the valve member 184, communicates with ducts 172 and 124, and passageway 190 extending through the valve member interconnects duct 28 with the ambient. In this situation, and until the normally closed switch 52 isopened, the operating pressure of 500 pounds per square inch is applied to the upper region 112 of cylinder 24 for closing valve members 60, 88 (FIG. 3).

Rotation of the valve member 184 through an arc of 90 degrees in a clockwise direction as viewed in FIG. 6, will produce communication between the upper region 112 of cylinder 24, .and the ambient, and between the lower region 114 and duct 124. This raises the piston 8 116 and opens the valve defined by valve members 60, 88 (FIG. 3). Since duct 26, communicating with the aforementioned upper region, also communicates with the ambient through valve 174, and results in loss of air at 'the pressure determined by pressure regulator 126, this position of the valve member 184 is maintained only long enough to operate the valve members 60, 88 to openvalve position.

When it is desired to maintain the piston 116 in any given position, the valve member 184 should be rotated to a holding position spaced 45 degrees in a clockwise direction from the position thereof shown in FIG. 6. When in this holding position, the passageways 188', 190 in the valve member 184, are closed by the casing 175.

If a closing of valve members 60, 88 (FIG. 3) without forming a welded seated relation is desired, the manual switch 158 (FIG. 6) may be opened prior to the opening of switch 52, thereby venting the operating pressure from pressure regulator 126 through the vent valve 130. Thereafter the valve 174 should be promptly moved to holding position to reduce air loss from the pneumatic system. I

It should be noted that on completion of any downward movement of piston 116 resulting in the opening of switch 52, the valve 174 should be closed promptly to avoid loss of air under pressurethrough vent valve 130.

If desired, the valve 174 may be solenoid operated in synchronism with vent valve 130, so that the valve174 opens communication between region 112 and duct 124, at the same time that solenoid 162 is energized, and closes such communication when the solenoid referred to is deenergized.

It is apparent from the foregoing that an improved ultra high vacuum valve is provided which utilizes the principle of welding by pressure alone and without the deliberate application of heat, for securing a maximum isolation of a region under ultra high vacuum, from another region of higher or lower gas pressure.v

The valve described is of particular value in association with an evacuation system wherein it may serve to provide an efliective' seal between a pumping system-and an envelope being evacuated. Such seal is desired when a leak develops in either the envelope being evacuated or in the pumping system.

What is claimed is:

1. A bakable ultra high vacuum valve comprising a first valve member having two adjacent coaxial portions, one of said portions having a cylindrical periphery and the other of said portions having a frusto-conical periphery extending inwardly of said cylindrical periphery, said valve member being made of copper and said one of said portions having a predetermined outer diameter, a ring shaped second valve member made of a harder material than copper and having an inner diameter smaller than said predetermined outer diameter, said cylindrical periphery of said first valve member extending parallel to the longitudinal axis of said first member and to the inner surface of said second valve member, said ring shaped valve member having an aunularlip defined in part by a continuation of the outer surface of said ring shaped valve member, said lip having a radius of curvature of from about two to about six mils, means mounting said members in coaxial relation, and means. connected to one of said members for moving the same toward and into telescoped relation with respect to the other of said members, said lip opposing said moving means with sufiicient force to produce a weld between said members while refraining from a deliberate application of welding heat to said members, during a closure of said valve, and to facilitate rupture of said weld on a subsequent opening thereof.

2. In a valve adapted to be successively closed and opened repeatedly, two valve members adapted to as.

sume seated relation, one of said members being made. of arelatively soft metal and having two adjacent coaxial portions, one of said portions having a cylindrical pen'phery and the other of said portions having a frustoconical periphery extending inwardly of said cylindrical periphery, the other of said members being made of a relatively hard metal and having an inner surface defining a cylindrical space, said cylindrical space having a smaller diameter than said cylindrical periphery, means movably supporting said members in coaxial relation, with an end portion of said other of said members in register with said frusto-conical periphery, and means urging said members into seated relation, said other of said members defining an annular lip extending from the leading end of said other of said members and having an inner side defined by said inner surface, said lip having a free end engaging said frusto-conical periphery only, and characterized by a sufliciently large area to oppose said urging means with a force to produce a weld between said members without the deliberate application of heat and a sufiiciently small area to cause said lip to penetrate appreciably the material of said other of said portions, to provide a new seat on each closure of said valve.

3. A valve comprising first and second valve members, said first member having a structure including adjacent coaxial cylindrical and inwardly extending frustoconical portions, and having an annular peripheral portion extending throughout the length of said cylindrical portion and made of a metal responding in plastic flow to the application of a predetermined pressure thereto, said second member being made of a relatively hard material substantially free from plastic flow at said pressure, and defining an annular lip having a smaller diameter than the outer diameter of said annular portion, means movably supporting said first member in coaxial relation and with said lip adjacent to an end portion of said first member, means urging said members together with a force to produce said predetermined pressure, said lip having a free end surface area for opposing said urging means with a force at least equal to the force of said pressure, for welding said lip to said first member for closing said valve, and means adapted to urge said members apart with said force for opening said valve, said free end surface area being sufficiently small to produce rupture in said weld in response to said force.

4. A valve adapted to tolerate a temperature of the order of 450 C. and to successively provide communication with and closure of a region under ultra high vacuum, said valve comprising a housing, a port in said housing, a ring shaped first valve member surrounding said port, a second valve member in said housing, said second valve member including a cylindrical portion and an inwardly extending frusto-conical portion, a support for said second valve member extending through a wall of said housing opposite to said port and supporting said second member to axial relation with said ring member, said second valve member throughout the length of its cylindrical portion having a larger diameter than the inner diameter of said ring member, the periphery of said second member to a radial depth at least equal to the difference between the diameter of said cylindrical portion and said inner diameter being made of a metal responsive in plastic flow to a predetermined pressure, said ring member being made of a material resistant to such flow at said pressure, said ring member having an annular lip facing said second member, the inner side surface of said lip being cylindrical and having the same diameter as the inner diameter of said ring, the outer side surface of said lip being tapered about from a plane normal to the axis of said ring member and away from the axis of said ring member and from said second member, the free end surface of said lip having a curvature characterized by a radius of from two to six mils, means for producing said pressure, and actuating means connected to said pres sure producing means for selectively urging said members together and pulling them apart, said lip at said pressure producing a Weld with said peripheral portion for closing said valve, said weld being adapted to rupture in response 10 to said pulling force, said tapered portion of said ring displacing the material of said peripheral portion subjected to plastic flow, for facilitating the accomplishment of a succeeding closure of said valve.

5. A valve comprising a first valve member of relatively hard material, a second valve member of relatively soft material adapted to form a welded relation to said first member solely in response to a predetermined pressure per unit area, said first member having a lip provided with an end surface having a curvature characterized by a radius of from two to six mils said second valve member including a cylindrical portion and an inwardly extending frusto-conical portion coaxial therewith, said lip being annular and having a smaller inner diameter than the outer diameter of said cylindrical portion, means movably supporting said members in coaxial relation, with said lip adjacent to said frusto-conical portion, means for urging said lip against said frusto-conical portion of said second valve member with said predetermined pressure, whereby said end surface at least partly enters the material of said second valve member for forming a new seat therein and for welding said end surface to said second valve member.

6. A valve adapted for operation at a temperature of about 450 for selectively closing and opening communication between a region having a relatively low pressure and another region having a difierent pressure, said valve comprising a first valve member having a cylindrical peripheral portion and an inwardly extending frustoconical peripheral portion and made of a metal having a relatively high plastic flow response to a predetermined pressure, a ring-like second valve member made of a material having a relatively high tensile strength and low plastic flow response to said pressure, said ring-like valve member having a smaller inner diameter than the outer diameter of said cylindrical portion of said first valve member, said frusto-conical peripheral portion having a taper for entrance into said ring-like member for disposing said members in coaxial relation, said cylindrical peripheral portion having a thickness greater than the difference between the outer diameter of said cylindrical portion and the inner diameter of said ring-like memher, said ring-like member having an annular lip coaxial therewith and terminating in a free end having a radius of curvature of from about two to about six mils, said lip engaging said frusto-conical peripheral portion when said members are in said coaxial relation and in engaging position, and means engaging said members for urging said members against each other in said coaxial relation with sutficient force to cause said lip to enter said cylindrical peripheral portion and produce a weld therebetween.

7. A valve operable in a relatively high temperature ambient comprising two valve members, one of said members comprising coaxial cylindrical and frusto-conical portions made of a metal having a relatively high plastic flow response to pressure, the other of said members comprising a ring-like structure made of a material having a relatively low plastic flow response to pressure, said other of said members having a smaller inner diameter than the outer diameter of said cylindrical portion of said one of said members and including a lip extending from one end thereof and formed by a continuation of the inner surface of said other of said members, said lip having a rounded end of smaller radial extent than that of the difference between the said diameters of said members, means supporting said members in coaxial relation, and means for urging said members together when in said relation for causing said lip to sheaningly penetrate said frusto-conical portion of said one of said members, said lip having a radius of curvature of such magnitude as to cause said lip to oppose said urging means with a force suificient to produce plastic flow in said one of said members for accomplishment of a welded relation between said members, said lip having a tapered outer periphery describing an angle of said lip, for ruggedizing said lip and for outwardly displacing a peripheral portion of the material of said one of said members, to contribute to said welded relation.

*8. A valve adapted for operation at relatively high temperatures comprising a first valve member made of a metal free from plastic flow solely in response to said temperatures and having a relatively high plastic flow in response to a predetermined pressure, a second valve member characterized by substantial freedom from plastic flow at said temperatures and at said predetermined pressure, said first member comprising a relatively thick disc including a cylindrical portion and a frusto-conical portion, said second member comprising a ring-like structure having an annular lip extending axially therefrom, said lip having a smaller inner diameter than the outer diameter of said disc, said lip having a predetermined radius of curvature at its free end, means movably supporting said members in coaxial relation and with said lip in register with said frusto-conical portion, and means engaging said supporting means and urging said members into engagementwhile in said register and With said predetermined pressure, said radius of curvature of said lip having a magnitude to cause said lip to shearingly penetrate the material of said first member with a force to produce a rupturable Weld between said members in the absence of a deliberate application of heat.

9. A valve adapted for operation at relatively high temperatures comprising a first valve member having a thickened disc-like structure made of copper, the periphery adjacent one end of said structure being tapered, the

remainder of the periphery of said structure being par allel to the longitudinal axis of said structure and having a predetermined diameter, a second valve member havconstituting a continuation of the inner surface of said ing a ring-like structure made of stainless steel and having 1 an axialdimension, an annular lip extending axially from said second valve member, said lip having a first surface second member, the entire of said inner surface being parallel to the axis of said second member, and a second surface constituting an end of said axial dimension, said second surface defining a tapered contour extending away from the free end of said lip and radially outwardly from said inner surface at an angle of about 10 with respect to the transverse axis of said second member, said lip having an annular region where said first and second surfaces merge, said region having a radius of curvature of from about two to about six mils, said region having an outer diameter smaller than said predetermined diameter of said first member, means supporting said members coaxially with said lip facing said first member and said tapered end of said first member facing said second member and for relative movement along their common axis in a predetermined path, and means urging together adjacent ends of said members in said path with a pres-.

sure of about 500 pounds per square inch, whereby said lip shearingly penetrates the material of said first member and displaces a peripheral portion thereof along said tapered contour for producing a weld between said memers.

References Cited in the file of this patent Ireland r July 22, 1930-

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