D E S C R I P T I O N

GATE VALVE FOR A VACUUM CHAMBER AND VACUUM CHAMBER

Field of -the invention

The invention concerns a gate valve for closing openings in a wall of a vacuum chamber where diverse processing steps like physical vapour deposition, plasma etching etc. can be carried out as well as a vacuum chamber comprising at least one such gate valve.

Prior art

From US 5 693 238 A a gate valve of the generic type is known where the carrier is a slide reciprocatable in the longitudinal, i.e., vertical, direction as well as in a direction perpendicular to a front containing a roe of openings, with the latter motion opening and closing the openings whereas the vertical motion of the slide shifts the sealing plates to positions where they do not overlap with the openings, allowing direct access through them in a horizontal direction. The gate valve in question is relatively bulky and requires a complex drive.

US 6 427 973 Bl shows another gate valve according to the generic type where a slide moveable in the longitudinal, i.e., vertical, direction carries sealing plates which are movable with respect to the carrier by pneumatic means in a direction perpendicular to a front containing a row of openings. The gate is again rather complex and requires much space, particularly in the direction perpendicular to the front .

Summary of the invention

It is an object of the present invention to provide a gate valve of the generic type as circumscribed in the generic part of claim 1 which is simple in structure and which can be actuated by a simple drive mechanism.

This object is achieved by the features in the characterising clause of claim 1. The invention provides a gate valve which is simple, space-saving and reliable and can be actuated by a simple linear drive, e.g., a piston. It also offers facile maintenance, being easy to assemble and disassemble. The invention also provides a vacuum chamber which is easy to use and reliable and has a relatively small footprint .

Brief description of the drawings

In the following the invention is described in more detail with reference to drawings referring to an embodiment of the invention where

_ Fig. 1 shows a gate valve according to the invention and adjoining parts of a vacuum chamber, in part in exploded view,

Fig. 2 shows a partial sectional view of the gate valve and adjoining parts of the vacuum chamber as shown in Fig. 1, with the gate valve in a first state, and

Fig. 3 shows a partial sectional view essentially like Fig. 2, with the gate valve in a second state.

Description of the preferred embodiments

The vacuum chamber which may be part of an assembly of vacuum chambers with a transport unit as shown in US 5 693 238 A comprises (Fig. 1) a frame structure consisting of an outer frame 1 which surrounds a relatively large essentially oblong frame opening. The latter is filled by several also essentially oblong wall plates 2 which follow upon each other in a longitudinal direction which coincides with the vertical. Each of the wall plates 2 is provided with two slot-like openings 3 which are arranged one above the other and extend essentially over the wall plate 2 in a lateral direction which is perpendicular to the longitudinal direction and consequently horizontal. Through each of the openings 3 a compartment of the vacuum chamber is accessible. Each opening 3 is surrounded by an O-ring 4 as an elastic sealing means.

The frame structure, i.e., the outer frame 1 and the wall plates 2, define a substantially plane front facing away from the compartments which contains the openings 3. At a distance from this front a gate valve for sealing the openings 3 is arranged which comprises two rod-shaped carriers 5a, b which are each connected to the outer frame 1 by two links 6 at their upper ends and lower ends, respectively, i.e., at positions spaced from each other in the longitudinal direction. The links 6 are connected to the outer frame 1 on the one hand and the carrier 5a;b on the other hand pivotably about axes 7; 8 parallel to the lateral direction. As for each one of the links 6 the distance between the two axes 7, 8 is the same the outer frame 1, the carrier 5a;b and the links 6 connecting each carrier 5a;b to the outer frame 1 form a parallelogram suspension for the carrier 5a;b, i.e., a mechanical guide means which causes

its distance from the frame structure to vary while it remains parallel to the longitudinal direction whenever it is shifted longitudinally forward and backward over a switching interval.

The carriers 5a, b carry a longitudinal row of bar-shaped sealing plates 9, one sealing plate 9 for each one of the openings 3. The sealing plates 9 extend in the lateral direction from the carrier 5a to the carrier 5b. Their opposite end portions are fixed to the first and to the latter, respectively. The surface of each sealing plate 9 facing the front of the frame structure is essentially plane but slightly convex along the lateral direction. Each sealing plate 9 is connected to each carrier 5a;b by a pair of compression springs 10 (s. Figs. 2, 3) such that the sealing plate 9 is displaceable in a direction away from the front against their elastic force. The displacement is limited by an adjustable stop, a spacer bolt 11 mounted on the carrier 5a;b.

Two actuating members in the shape of actuating rods 12a, b extend in the longitudinal direction, each guided by a succession of plain bearing bushes 13 mounted to the outer frame 1. Each actuating rod 12a;b is close to one of the carriers 5a;b and connected to it at its lower and at its upper end and in the middle, respectively, by three levers 14 which are appropriately spaced in the longitudinal direction. Each lever 14 is pivotable with respect to the carrier 5a;b about an axis 15 and with respect to the actuating rod 12a;b about an axis 16 with both axes parallel to the lateral direction. The carrier 5a;b, the levers 14 and the actuating rod 12a;b again form a paralleogram connection allowing the distance between the actuating rod 12a;b and the carrier 5a;b to vary in a direction

perpendicular to the front while keeping them parallel. Each actuating rod 12a;b is mounted on a piston 17 of a pneumatic drive 18, which acts as a linear drive for the actuating rod 12a;b.

In Fig. 2 the sealing plates 9 are in an active position. Each of them presses against a plane front of one of the wall plates 2 which surrounds one of the openings 3 and in particular against the 0-ring 4, compressing the same and thereby keeping the opening 3 sealed. As the surfaces of the sealing plates 9 are slightly convex the latter are deformed somewhat when pressed against the front whereby the pressure is equalised and the sealing effect at the central parts of the sealing plate 9 which are removed from the carriers 5a, b is improved. The compartments closed by the sealing plates 9 can then be evacuated and a vacuum processing step like PVD or plasma etching carried out therein. Depending on the construction details a relatively large pressure difference between the compartments and the outside is feasible.

To open the compartments the pistons 17 are retracted, drawing the actuating rods 12a, b downward. Via the levers 14 the carriers 5a, b are also forced downward and pulled away from the front. Due to the guidance by the links 6 the motion of the carriers 5a, b follows a defined circular path, the carriers 5a, b first moving the sealing plates 9 in parallel away from their active positions essentially perpendicularly and then more and more in a downward direction. When the carriers 5a, b reach the opposite end of the switching interval, the sealing plates 9 are at inactive positions (Fig. 3) where the orthogonal projection of each sealing plate 9 onto the front does not overlap with the opening 3 it covers in its active position. The sealing plate 9 is completely out of the way and the compartment is

easily accessible through the opening 3 in a direction perpendicular to the said plane. Insertion or retrieval of a substrate to be treated or having been treated, respectively, by a transport device can be carried out largely unencumbered by the gate valve.

For bringing the sealing plates 9 back to their active positions where they seal the openings 3 the piston 17 is extended and the actuating rods 12a, b, the levers 14, and the carriers 5a, b are each subjected to a reverse motion along the same trajectory. The final parallel motions of the sealing plates 9 into their active positions are essentially perpendicular to the frame whereby friction is avoided.

List of reference symbols

1 outer frame 2 wall plate

3 opening

4 O-ring

5a, b carriers

6 link 7, 8 axes

9 sealing plate

10 compression spring

11 spacer bolt

12a, b actuating rods 13 plain bearing bush

14 lever

15, 16 axes

17 piston

18 pneumatic device