INTRODUCTION

The invention relates to a valve, and a method of making the valve. In particular, the invention relates to a valve comprising a closing means movably arranged in a housing and interacting with a valve seat to open or close a fluid passage through the valve. The flow through the passage depends on the position of the closing means relative to the seat. The valve comprises connecting means, e.g. in the form of a bush or sleeve for connecting a handle or a bar to the valve or in the form of a handle or bar which is accessible from outside the housing for moving the closing means inside the housing. The handle or bar could be moved manually or by power driven means e.g. pneumatically and thus enables control of the flow from outside the housing. In the valve, a bellow is fastened to the closing means to isolate the connecting means from the passage.

BACKGROUND OF THE INVENTION

Valves of the above-mentioned kind are used e.g. for controlling a flow rate of a process gas in vacuum systems. In such a valve, the bellow serves to separate the passage and the vacuum system in general from the surrounding atmosphere while allowing actuation of the valve

EP 0244 185 discloses a bellow valve wherein a valve stem has a first end adapted for selective sealing engagement with a valve seat, and a second end of the stem is operatively connected to an actuator assembly. An expansible bellow has a first end connected to the valve housing surrounding the valve stem, and a second end sealingly connected to a closing member so that a portion of the valve stem is surrounded by the

bellows. In a valve of this type, a leak between the bellow and the valve stem would lead to atmospheric air in the vacuum system. In particular in a vacuum system, such a leaking valve would be unsuitable.

US 6,305,665 discloses a lifting valve designed for reliable and hygienic static sealing of a connecting flange of a closing-member unit in a valve box. In this document, a closing-member comprises a bellow and a connecting flange with a fastening component to absorb the forces resulting from the valve-lift induced deformation of the bellow. In DE 32 15 799, an antiseptic valve is provided with a replaceable spare-part unit comprising a closing-member and a bellow. The disclosed unit is made as a single unit from a flexible synthetic material. Also in EP 0 508 658, a valve is disclosed with an actuator sleeve adapted to be secured to a valve body, and a shaft mounted in the sleeve to permit axial movement of the shaft in the sleeve to move a diaphragm between open and closed positions.

In the disclosed valves, the closing-member forms part of the bellow. This design, although it may facilitate an impervious valve, limits the available methods of manufacturing, the possible shapes of the closing-member, and the freedom to select materials for the valve. In particular, the disclosed synthetic materials are not suitable in connection with a valve for a vacuum system.

DESCRIPTION OF THE INVENTION

It is an object to provide a valve which can be operated via an impermeable bellow and which has improved characteristics in particular in combination with vacuum systems. Accordingly, the invention in a first aspect provides a valve of the kind described in the introduction, wherein the bellow comprises a corrugated tubular sidewall forming a longitudinally

extending conduit, and in an axial end of the bellow, the conduit is sealed by a bottom part, wherein the bottom part and the sidewall are formed from one piece of a sheet material. In a valve comprising such a bellow, the permeability of the bellow is determined merely by the permeability of the material itself and it is not influenced by the permeability of a joint between the bellow and a closing means. The bellow is preferably made from a steel plate, e.g. made from stainless steel, or from a sheet of a similarly plastically deforrnable material which is deformed, e.g. by deep drawing, to form a cup shaped member with a sidewall and a bottom part, and subsequently by forming corrugations into the sidewall.

To facilitate welding of the closing means and attachment of connecting means to the bellow, the bottom part could be at least substantially plane ^" e.g. extending transverse to the longitudinal direction. In order to improve attachment by welding, the material thickness of the bottom part could be larger than the material thickness of the sidewall.

To facilitate attachment of the closing means to the bottom part, it is an advantage to establish a well defined, sharp line of close contact between the bottom part and the closing means. For that purpose, an upper surface of the closing means wh ich faces towards a surface of the bottom part may have a projection, e.g. forming a circular, elevated mark on the closing means to abut the bottom part when the two parts are joined. To further facilitate a close contact along a periphery of the circular mark, trie elevation may preferably form a relatively sharp, ring-shaped edge, e.g. with an elevation height of 0,5-5 mm above the planar bottom part, and with a width below 5 mrn. In a cross section, the mark could form a triangular shape with one sharp corner facing towards the bottom part. The ring-shape facilitates the welding process but has the drawback that a space is formed within the ring-shaped mark, between the bottom part and the closing means. In particular in combination with a vacuum system,

such a space, e.g. with confined air, is undesirable since it may prevent complete evacuation of the system. In order to facilitate evacuation, the ring-shaped mark may therefore comprise at least one ventilating groove which forms passage across the ring-shaped mark when the bottom part and the closing means are joined.

In a similar manner, the connecting means may form a bottom surface facing towards a surface of the bottom part, which bottom surface comprises a projection, e.g. a ring-shaped projection, which abuts the bottom part to facilitate joining of the bottom part and the connecting means by welding. In particular, the projection of the connecting means and the projection of the closing means may be located adjacently on opposite sides of the same portion of the bottom part. The assembly may be carried out by pressing the connecting means and the closing means against each other from opposite sides of the bottom part. The closing means and the connecting means are thereby used against each other to provide sufficient backpressure to achieve the desired lines of close contact to the bottom part. When the parts are pressed into such a close contact, the joining may be carried by welding, e.g. by resistance welding or electron beam welding. The welding is preferably carried out at adjacent welding spots on opposite sides of the bottom part simultaneously, or in case of resistance welding, along the entire ring-shape of the closing means and the connecting means simultaneously.

In an opposite end of the bellow, i.e. at the open end of the bellow, the bellow could be attached in the valve housing, e.g. via a bellow ring which is welded onto the bellow and which comprises a sealing O-ring which can be held against a surface of the housing to seal tightly.

To bias the closing means against a valve seat of the housing, e.g. to form a valve which is normally closed, the bellow may comprise spring means ,

e.g. a helical spring, which is biased to exert an axial force to press the closing means towards the valve seat.

In a second aspect, the invention provides a method of making a bellow comprising the steps of forming from a single piece of a sheet material a cup-shaped body comprising a tubular sidewall and a bottom part, the sidewall and bottom part forming together a cavity. The method further comprises the step of forming corrugations into the sidewall.

In a third aspect, the invention provides a bellow of the above described kind, e.g. for use in a valve.

In a fourth aspect, the invention provides a method of making a valve of the above mentioned kind, wherein the welding operations for attaching the closing means and the connecting means to the bottom part are performed simultaneously and without penetrating the bottom part.

All features disclosed in relation to the first aspect of the invention may apply to any of the other aspects of the invention.

DETAILED DESCRIPTION

In the following, a preferred embodiment of the invention will be described in further details with reference to the drawing in which:

Fig. 1 shows a side view of a bellow according to the invention,

Fig. 2 shows an enlarged view of a part of the bellow,

Fig. 3 shows a closing means, and

Fig. 4 shows a valve with a bellow.

The bellow in Figs. 1-2 has a corrugated tubular sidewall 1 forming a conduit extending longitudinally around the axis 2. In an axial end 3 of the bellow, the conduit is sealed by a bottom part 4, c.f. Fig. 2. The bottom part and the sidewall are formed from one single piece of a sheet material which is deep drawn to form a cup shape with a smoothly rounded corner 5 in the transition between the sidewall and the bottom. The bellow is fitted with a closing means 6 , and connecting means 7. The closing means is movably arranged in a valve housing and interacts with a valve seat thereof to open or close a fluid passage through the valve depending on the position of the closing means relative to the seat. To seal tightly against the valve seat, the closing means comprises a resilient rubber gasket 8 which, in one position of the closing means relative to the housing, abuts the valve seat. The connecting means is located in the cavity of the bellow and enables actuation of the closing means through the bellow from outside the housing. The connecting means is thereby isolated from the passage by the bellow. The closing means and the connecting means are welded to the bottom part via projections 9, 10 forming ring-shaped contact faces on which contact with the bottom part is established along a line of close contact. In Fig. 2, it is shown that the ring shaped contact faces are triangular in a cross-sectional view. As shown, the projection 9 of the closing means is located adjacent the projection 10 of the connecting means to enable welding of the two components to opposite side surfaces of the same portion of the bottom part. In the assembled state, the closing means and the bellow form a space Λ 1. In its opposite end, the bellow is fastened to a bellow ring 12 which is attached to the housing of the valve. An inner surface 13 of the bellow ring comprises an O-ring which is located in a groove of the surface. The inner surface is pressed against the housing of the valve whereby the O-ring seals tightly. The connecting means could extend out of the cavity and form part of a handle or the connecting means could be connected to power driven means. As indicated, the closing means and the con necting

means are welded to the bottom part without penetrating the bottom part, thereby maintaining an impervious structure of the bellow.

Fig. 3 shows the closing means 6 with a circumferentially extending groove 14 for holding a resilient rubber gasket in the shape of an O-ring. The closing means further comprises a ventilating groove 15 provided in the circumferentially extending projection 16 for ventilating the space 11 (c.f. Fig. 2) confined between the bottom part of the bellow and the closing means. The ventilating groove is an important feature in applications wherein complete evacuation of the valve is desired.

Fig. 4 shows a valve with an inlet 17 and an outlet 18. In the passage between the inlet and outlet, a closing means 6 can be moved between an open and a closed position for controlling flow through the valve. The closing means is attached to a bellow 19 which seals between the passage and a control area 20 which is located above the passage. Connecting means 21 for moving the closing means from outside the passage is fastened in the bottom part of the bellow. In an opposite end of the bellow, a bellow ring 22 with an O-ring 23 made of rubber. The connecting means extends upwardly into the control area where it joins with a control handle 24. The valve further comprises a spring 25 which is incorporated into the bellow to bias the closing means against a valve seat of the housing 26.