The invention relates to a diaphragm-controlled valve having a valve housing, which between an inlet and an outlet has a flow path and a valve opening formed between a valve seat and a valve closure member, and having a spring-loaded diaphragm adjusting the valve opening and clamped at its outer edge, which diaphragm separates from one another a self-pressure chamber which is in connection with the interior of the valve and a counter-pressure chamber which is arranged to be supplied with a counter-pressure to be introduced from the outside.

Such a valve is known, for example, from EP 0 354 427 A2. The diaphragm, including the self- pressure chamber and the counter-pressure chamber, are located in a diaphragm capsule, which has to be mounted on the valve housing, for example, by screw fixing. On the diaphragm capsule there is mounted a further component which contains the spring for loading the diaphragm and a closure device for closure of the valve as desired. This construction has a comparatively large overall height. Manufacture and installation are additionally comparatively expensive.

The invention is based on the problem of providing a diaphragm-controlled valve of the kind described in the introduction which can be manufactured more compactly and more inexpensively.

This problem is solved according to the invention in that the diaphragm is arranged in the valve housing and

has passing through it a central pipe forming part of the flow path, the valve seat is provided at one end of the central pipe and the other end of the central pipe is sealed with respect to the valve housing.

In this construction no diaphragm capsule is required, because all the parts of the diaphragm-controlled valve are arranged in the valve housing. In the simplest case, the central pipe itself forms the valve seat. The seal at the other end enables the counter-pressure chamber, which surrounds the central pipe, to be securely separated from the flow path. In addition, the total number of parts required is reduced and the subsequent step of establishing the connection between the diaphragm capsule and the valve housing is avoided. This enables manufacturing costs to be considerably reduced. A further advantage consists in that the diaphragm is effective in the immediate vicinity of the valve opening and relatively long force transmission paths, which are prone to jamming, are avoided.

It is especially advantages for the valve housing to consist of two parts fixedly clamping between them the outer edge of the diaphragm, of which one part has the inlet and the other part the outlet. Before the two parts are assembled together, the individual components can be installed very easily. As the two parts are joined together, the diaphragm is clamped at its edge at the same time.

Inlet, outlet and central pipe are advantageously arranged with their axes are aligned, and their axis runs perpendicularly to the diaphragm. This produces the lowest losses resulting from indirect paths and additionally a very compact structure.

A preferred embodiment provides for the central pipe to be built into the housing and to have guided on its outside a control bush which it connected to the diaphragm and to the closure member. This construction is especially suitable for the application in which the valve is arranged in the feed pipe of a hot water heating circuit. The self-pressure chamber is located at the outlet side of the valve.

The control bush advantageously has a flange for forming a diaphragm plate. No separate component is therefore required for this diaphragm plate, which is a customary reinforcement.

It is also advantageous for a closure member carrier having through-openings beyond the closure member to be secured to the control bush. The medium leaving the valve opening is able to flow onwards by way of the through-openings. The closure member can nevertheless be securely connected to the control bush.

It is also recommended that the spring surrounds the central pipe and is clamped between the control bush and an abutment built into the housing. This produces an arrangement of short axial length having great operational reliability.

In another preferred embodiment, provision is made for the central pipe to be movably arranged in the valve housing and to be connected to the diaphragm, and for the closure member to be fixedly held. This construction is especially suitable for a valve arranged in the return pipe of a heating system, because the self-pressure chamber is located on the inlet side of the valve.

A closure member carrier is advantageously axially guided in the valve housing, is held by the spring surrounding the central pipe against a fixed stop and is provided beyond the closure member with through- openings. The medium flowing to the valve opening is here able to be conveyed through the through-openings. The fact that the closure member is held in position only by applied force facilitates assembly.

A further simplification is achieved by the fact that the central pipe has an external flange against which the spring bears and to which the diaphragm is fastened.

It is also advisable for the closure member carrier to have an internal flange against which the spring bears and the inner circumference of which guides the central pipe. The valve carrier thus assumes further functions here.

In further development of the invention, in the valve housing close to the closure member there is arranged an adjusting peg rotatable from the outside, which has a profiled surface such that on rotation it displaces the closure member. The adjusting peg in particular allows the valve to be closed as desired. Hardly any additional space is required for this.

It is additionally possible for the profiled surface to form the fixed stop for the closure member carrier. The adjusting peg has a dual function in this respect.

Furthermore, a pin pressed into the valve housing and which co-operates with a stop face on the adjusting peg for the purpose of limiting the angle of rotation is advisable. This limits the angular rotation range of

the adjusting peg, so that different basic settings of the closure member can be achieved.

The invention is explained in further detail hereinafter with reference to preferred embodiments illustrated in the drawing, in which:

Fig. 1 is a longitudinal section through a first embodiment of a valve according to the invention and

Fig. 2 is a longitudinal section through a second embodiment.

Fig. 1 shows a diaphragm-controlled differential- pressure valve which is intended for installation in the feed pipe of a heating system. A valve housing 1 consists of two parts 2 and 3 which are held together, with the edge 5 of a diaphragm 6 between them, by a clamping ring 4. The axes of an inlet 7 in part 2 and an outlet 8 in part 3 and the axis of a central pipe 9 are aligned with one another, the axis running perpendicularly to the diaphragm 6.

The central pipe 9 forms part of the flow path between the inlet 7 and outlet 8. At one end it is mounted fixedly in the housing 1 with a seal 10 between it and the housing. The other end forms a valve seat 11 which together with a closure member 12 forms an adjustable valve opening 13.

A control bush 14 is axially displaceable on the central pipe 9. It has a flange 15 which acts as a diaphragm plate reinforcing the diaphragm. A spring 16 bears at one end against the control bush 14 and at the other end against a stop 17 of the central pipe 9. A

closure member carrier 18 is secured to the control bush 14 and fixedly clamps the inner edge of the diaphragm at the same time. The closure member carrier also holds fixed a sealing ring 19 for forming a seal with respect to the central pipe 9. Beyond the closure member 12 it has through-openings 20 for the passage of the flowing medium.

Inside the valve housing 1 there is a self-pressure chamber 21, the pressure of which acts on the right hand side of the diaphragm 6 in Fig. 1, and a counter- pressure chamber 22 in which a spring 16 is arranged. This counter-pressure chamber can be supplied by way of a line connection 23 with a control pressure, for example, the return pressure of the heating system. The valve opening 13 therefore assumes a size at which the pressure difference is held at a value preset by the spring 16.

An adjusting peg 24 is inserted in the valve housing 1 so that its axis runs parallel to the diaphragm 6. Its two ends 25 and 26 are of cylindrical construction. The end 25 is provided with a seal 27 and a hexagon socket 28 so that the adjusting peg 24 can be rotated until it engages a stop face 29 on a pin 30 pressed into the valve housing 1. Between the two cylindrical ends 25 and 26 there is a profiled surface 31 which comes into contact with the closure member carrier 18 by rotation of the adjusting peg 24. In this manner the closure member 12 can be displaced as desired as far as its closed position.

Fig. 2 illustrates a valve which can be inserted in the return pipe of a heating system. Reference numbers increased by 100 have been used for corresponding parts. The essential difference is that the self- pressure chamber 121 is connected to the inlet 107 and

is therefore located on the left-hand side of the diaphragm 106, whilst the counter-pressure chamber 122 connected to the line connection 123, which is supplied, for example, with the input pressure, is located on the right-hand side. To achieve this, the central pipe 109 is movably held in the valve housing 101 and connected to the diaphragm 106. The central pipe 109 has an outer flange which serves to support the spring 116, together with a diaphragm plate 132 fixedly clamps the inner edge of the diaphragm 106, and co-operates with a stop 133 built into the housing, in order to define the end position of the valve seat.

The closure member carrier 118 has an inner flange 134 against which the spring 116 bears and which guides the central pipe 109 with its inner circumference. By virtue of the spring force, the closure member carrier 118 is pressed against the profiled surface 127 of an adjusting peg 124, producing a fixed stop 135. The closure member carrier 118 itself is guided with its cylindrical outer surface in an insert 136 which has been pressed into the valve housing 1.

In this construction, the valve opening 113 adjusts itself to a value at which the pressure difference acting on the diaphragm 106 is the same as a value preset by the spring 116. The spring force itself can be changed by rotating the adjusting peg 124. Here too, the valve can be closed completely using the adjusting peg.