Rotatable Refrigerated Valve

By way of an example of the problems with which the invention is concerned, a standard diffusion pumping system has a gate valve between the main chamber to be evacuated and a cold trap and a water cooled cold trap between the cold trap and the diffusion pump which is backed by a mechanical vacuum pump.

A gate valve has large areas to be exhausted and typically includes castings which are costly to machine and if not machined present rough surfaces interfering with pumping efficiency.

The general objective of the present invention is to provide a valve that, while useful in other systems, is particularly well adapted for use in vacuum pumping systems and that not only are free of the previously noted deficiencies but also include means meeting other requirements, particularly that of providing a cold trap.

In accordance with the invention, this general objective is attained with a rotatable valve, herein disclosed as a ball valve, the valve element of which has a passage of substantial axial extent effecting communication between the inlet and outlet ports of the valve casing when the valve member is in its first or open position, the valve member blocking flow through the valve when turned into its second or closed position. Such a valve member has a neck exposed externally of the casing by which it may be turned from one position to another. The passage is provided with refrigerating means establishing a cold trap ensuring the thermal contact therewith of gas flowing through the passage. The terms "refrigerant" or "refrigerating means" as used throughout the specification and in the claims mean cryogenic as well as conventional refrigeration means facilitating servicing of the cold trap, an objective attained by providing the valve casing with sealed clean-out ports which open into the passage when the valve is closed thus permitting any required cold trap service without losing vacuum in the main chamber or elsewhere in the pumping system.

Another objective is to provide a ball valve element that is effectively sealed without materially effecting the ease with which it may be turned from one position to another, an objective attained with the valve element held centered by the neck and an aligned ball bearing unit and with the valve element provided with ribs engageable with seals encircling the ports with the ribs arranged to effect sealing in either valve position.

Other objectives of the invention will be apparent from the specification and appended claims.

In the accompanying drawings, refrigerated valves for use in diffusion pumping systems are illustrated and

FIG. 1 is a schematic view of a conventional diffusion pumping system;

FIG. 2 is a like view of such a system incorporating a refrigerated valve in accordance with the invention;

FIG. 3 is a section taken approximately along the indicated line 3--3 of FIG. 4;

FIG. 4 is a section taken approximately along the indicated line 4--4 of FIG. 3;

FIG. 5 is a fragmentary section, on an increase in scale, through a seal between the casing and the valve element; and

FIG. 6 is a like section through the seal between the neck of the valve element and the casing.

Before detailing a refrigerated valve in accordance with the invention, reference is first made to high vacuum pumping systems and particularly to a conventional diffusion pumping system such as that schematically shown in FIG. 1 wherein a gate type of valve 10 is disposed between the main chamber 11 and a cold trap 12 between which and the diffusion pump 13, backed by a mechanical vacuum pump 14, is a water cooled trap 15.

In accordance with the invention and as is illustrated by FIG. 2, the gate valve 10 and the cold trap 12 in any system where a valve and a cold trap or traps are used are replaced by a refrigerated valve shown as of the ball type and generally indicated at 16.

The casing of the valve 16 includes a cylindrical section 17 having end walls 18, each secured to the section 17 by screws 19 outside an O-ring seal 20 thus providing a chamber 21. Each end wall includes a cylindrical part 22 having a port 23 opening into the chamber 21 where it is provided with a socket 24 that is arcuate with respect to the center of the chamber 21. The ports 23 are in alignment with one port 23, when the valve 16 is incorporated in the system, an inlet and the other outlet. The casing section 17 has a cylindrical port 25 having a shoulder 26 in its inner end and its axis includes the center of the chamber 21 and the centering pin 27 of a ball bearing unit 28 held in a socket 29 directly opposite the port 25 and having a service port 30 sealed by a plug 31 threaded therein.

A ball type valve element, generally indicated at 32, fits freely within the chamber 21 with diametrically opposed portions within the sockets 24. The valve element 32 includes a neck 33 fitting the port 25 and provided with a shoulder 34 that is a free fit within the shoulder 26. The port 25 carries an O-ring seal 35 in sealing engagement with the neck 33. The axis of the neck 33 passes through the center of the valve element and includes an opposite socket 36 which receives the pin 27 holding the valve element in position.

The valve element 32 has a diametrically disposed passage 37 intersecting its axis of rotation and dimensioned to enable communication to be effected between the inlet and outlet ports 23 with its end shoulders 38 defining openings of the size of the ports 23.

Each socket 24 is provided with an O-ring seal 39 and the valve element has a rib 40 surrounding and adjacent each end of the passage 37 and in engagement with the appropriate one of the seals 39 and a rib 41 interconnecting the ribs 40 and extending along the sides of the valve element in a manner such that the seals 39 are engaged by the ribs 41 as the valve member is turned 90.degree. from the open position of the valve 16, that illustrated by FIG. 3, into its closed position and the ribs 40 are in engagement therewith in either of said positions.

In practice at least the valve element 32 is nickel coated as by a process developed by General American Transportation Corporation and identified by the trademark "Kanigen", the coating being extremely smooth and non-porous and the neck 33 is made as a separate part. The neck 33 is attached to the valve member by screws 42 threaded through the valve member into the base of the neck 33 which carries a sealing ring 43 inside of which the screws 42 are located and which are vented as by an axial bore, not shown. A sprocket 44 fixed on the exposed end of the neck enables the valve element 32 to be turned as by a rack, a fragment of which is indicated at 45 in FIG. 3.

While, as previously stated, the refrigerating means may be of a cryogenic type, such are shown as of a conventional type and includes metal plates or baffles 46 within the passage 37 the main portions of which are parallel to the flow of gas but with bent ends 47 rendering the baffles optically dense, the arrangement being such that gas flowing through the passage 37 and between the baffles 46 is in thermal contact with at least part of each of them.

The neck 33 has a recess 48 in its outer end having bores 49 each in registry, respectively with the appropriate one of the bores 50 in the valve member 32 and opening into the passage 37. A conduit 51 extends through a metal seal 52 anchored in the appropriate bore 49 and through the subjacent bore 50 and into the passage 37 where it includes a U-shaped portion with which all the plates 46 are in thermal contact and by which the plates are supported and then extends outwardly through the other port 50 and its seal 52 with the two ends of the condiut 51 connectable to corresponding flexible conduits leading to and from a refrigerant source.

In practice radial bores 53 enable any gas entrapped in the casing outside the valve element 32 to be quickly exhausted when the system is operating.

It will be noted that the casing section 17 has diametrically disposed ports 54 each closed by a plate 55 secured to the section 17 by screws 56 outside the seals 57, the ports 53 for use in purging or otherwise servicing the interior of the valve, monitoring the valve and for rough pumping the valve.

While the rib-to-seal construction described is advantageous the seal arrangement shown in FIG. 6 may be used to reduce machining costs, the seal receiving channel 58 desirably having outwardly and inwardly inclined walls to permit expansion of the seal 59.