WO2010046090A1

WO2010046090A1 - Variable flow rate valve system

Info

Publication number: WO2010046090A1
Application number: PCT/EP2009/007513
Authority: WO
Inventors: Thomas Kirst; Stefan Müller; Kersten Grosse; Egon HÜFNER
Original assignee: Bürkert Werke GmbH
Priority date: 2008-10-20
Filing date: 2009-10-20
Publication date: 2010-04-29
Also published as: EP2340381B1; DE202008013969U1; JP2012506010A; US20110192471A1; EP2340381A1; US8783645B2; JP5737810B2

Abstract

A variable flow rate valve system is disclosed in which the flow rate is adjusted using the flow medium itself by creating differential pressures that determine the position of a valve member in relation to its valve seat. The valve system includes a valve chamber with an inlet (6) and an outlet (7). A diaphragm (9) divides the valve chamber into a control chamber (20) and a flow chamber (22) connected with the inlet (6). A valve seat (8a) is arranged in the flow chamber (22) on the side of the outlet (7). A valve body (8) is connected with the diaphragm (9) and cooperates with the valve seat (8a) to modulate a flow from the inlet to the outlet and through the flow chamber. A first pilot valve (24) is located in a first bypass (28) that extends between the outlet (7) and the control chamber (20), and a second pilot valve (26) is located in a second bypass (27) that extends between the inlet (6) and the control chamber (20). The first and second pilot valves are controlled to selectively open or close the first and second bypasses thereby varying the flow through the flow chamber between a fully open and a fully closed condition continuously or in discrete steps in response to a control signal. The valve member is actuated solely by the medium itself, e.g. water, by creating appropriate differential pressures on both sides of the diaphragm (9).

Description

Variable Flow Rate Valve System

The present invention relates to a variable flow rate valve system, preferably for liquid media. Variable flow rate valves have a valve member that cooperates with a valve seat to modulate a fluid flow, usually between a minimum value which may be zero and a maximum value. An actuator moves the valve member relative to the valve seat to vary the effective cross-sectional area of the flow. The actuator may be pneumatic, electro-magnetic, piezo-electric, mechanical etc. depending on a particular application and may be controlled to achieve a continuous or discontinuous characteristic of the valve responsive to a control signal. When the response is a linear function of the control signal, the valve is often referred to as a proportional valve.

The present invention provides a variable flow rate valve system in which the flow rate is adjusted using the flow medium itself by creating differential pressures that determine the position of a valve member in relation to its valve seat. Specifically, the valve system includes a valve chamber with an inlet and an outlet. A diaphragm divides the valve chamber into a control chamber and a flow chamber connected with the inlet. A valve seat is arranged in the flow chamber on the side of the outlet. A valve body is connected with the diaphragm and cooperates with the valve seat to modulate a flow from the inlet to the outlet and through the flow chamber. A first pilot valve is located in a first bypass that extends between the outlet and the control chamber, and a second pilot valve is located in a second bypass that extends between the inlet and the control chamber. The first and second pilot valves are controlled to selectively open or close the first and second bypasses thereby varying the flow through the flow chamber between a fully open and a fully closed condition continuously or in discrete steps in response to a control signal. The valve member is actuated solely by the medium itself, e.g. water, by creating appropriate differential pressures on both sides of the diaphragm. The first and second pilot valves are preferably pulse controlled by a control unit that receives a control signal on an input. The valve system may have a proportional characteristic. Preferably, the first pilot valve is a normally closed valve and the second pilot valve is a normally open valve. This ensures that the valve is safely closed in case of a current supply failure.

An advantageous application of the inventive valve system is an armature for a shower-bath where two such valve systems would be used feeding into a common mixing chamber under control of a temperature regulator.

In a further aspect of the invention a valve member is provided which is advantageously, but not necessarily, used in the variable flow rate valve system. The valve member has a generally cylindrical valve body with two opposed end faces and a peripheral wall extending between the end faces. At least one recess is formed in the peripheral wall extending inwardly, and a bore extends from one of the end faces and opens into the recess. The recess is generally wedge- shaped and extends transversely to the axis of the valve body. The recess can be defined by surfaces composed of surface sections having different angles of inclination in relation to the axis of the valve body.

With a conventional cone-shaped valve member and in the case of a small actuating travel for realizing low rates of flow of media, high flow velocities may appear when the medium flows past on the entire periphery of the cone. This produces a suction which acts in a direction opposite to the actuation direction, which makes a sensitive closed-loop control more difficult or even impossible. The proposed valve member can reliably and precisely control desired flow rates even in the case of a small actuating travel.

A further advantage resides in the reduction of the tendency to oscillate, which is an undesirable phenomenon frequently observed in similar systems. In an advantageous configuration of the valve system, the end face on the drive side of the valve member is connected to the diaphragm which seals the valve seat in the closed valve position. The diameter of the bore in the valve body advantageously corresponds to the nominal width of the valve.

This geometry of the valve member allows the full medium flow to be able to flow off downwards and laterally even in the case of small flow rates. In addition, with the surface area of the valve member acted upon by the flow having the same slope and with a small actuating travel, a considerably smaller flow area is exposed to the medium than in conventional valves with a cone- shaped valve member. The control characteristic is adjustable by the number and the geometric configuration of the wedge-shaped incisions, the angles defining the surfaces of the at least one wedge in relation to each other and to the end faces of the valve member taking a determinative role for the characteristic.

Drawings - Figure 1 shows a three-dimensional illustration of a valve member for the valve according to the invention;

- Figure 2 shows a schematic sectional view of a section taken through part of a diaphragm valve having a conventional control cone;

- Figure 3 shows a schematic sectional view of a first embodiment of the valve member with a valve seat;

- Figure 4 shows a schematic sectional view of a second embodiment of the valve member with a valve seat;

- Figure 5 shows a schematic view of a variable flow rate valve system; and

- Figure 6 perspective view of a diaphragm valve with two pilot valves.

Detailed Description

Fig. 1 shows a valve member 1 which in the valve system according to the invention may replace the conventional cone-shaped valve body that is otherwise normally used. The valve member 1 has a generally cylindrical valve body with an attachment hole 2 in one of the two oppositely located, parallel end faces and a bore 4 through the other end face with a sufficiently large diameter w (Fig. 3, 4) to correspond to the nominal width of the valve system. At this end the cylindrical geometry of the valve member is maintained over the full periphery at least in a partial area 3 for guidance purposes. In this way, any tilting or jamming of the valve member 1 during the sequence of movement in operation is ruled out. The valve member 1 includes at least one wedge-shaped recess which extends transversely to the central axis of the valve member 1 and is defined by side surfaces 5.

The side surface 5 adjacent to the end face in which the bore 4 is located is at least partly also part of the bore 4, as a result of which an open connection is produced between this end face and the side surface adjacent to it.

When the valve is in the open condition, there is a flow of medium through this connection, the connection determining the path between the inlet and the outlet.

The valve member 1 may be manufactured either from a metallic material or from a suitable plastic material.

Fig. 2 illustrates a typical diaphragm valve having a conventional cone- shaped valve body δ.

Inlet 6 and outlet 7 are arranged in a valve housing 11 of the valve. In the closed condition of the valve the inlet 6 and the outlet 7 are separated by virtue of the valve body 8 sitting on a valve seat 8a in a sealing manner. A diaphragm 9 to which the valve body 8 is attached is held in the valve housing 11 by clamping means 10.

Preferably, the cone-shaped valve body 8 is replaced by the valve member 1 described above, as illustrated in Fig. 3. In this case, the valve member 1 has only one wedge-shaped recess, and is connected to an actuating rod 9a.

In the embodiment shown in Fig. 4, the valve body has two identical wedge- shaped recesses located radially opposite each other. Otherwise the embodiments of Figs. 3 and 4 are similar.

In Fig. 5, a variable flow rate valve system is shown. The system has a diaphragm valve similar to that shown in Fig. 2, with a cone-shaped valve body 8 which, however, may be replaced by valve member 1 described above. The valve housing 11 contains a valve chamber which is divided by diaphragm 9 into a control chamber 20 and a fluid flow chamber 22 connected with inlet 6. Pilot valves 24 and 26 are associated with the diaphragm valve. The first pilot valve 24 is inserted in a first bypass 25 that extends between control chamber 20 and outlet 7. The second pilot valve 26 is inserted in a second bypass 27 that extends between control chamber 20 and inlet 6.

The pilot valves 24 and 26 are pulsed by electric control signals received from a common control unit 30, an input of which receives a control signal Ucont- The first pilot valve 24 is a normally closed valve, and the second pilot valve 26 is a normally open valve. Accordingly, as long as no control pulses are applied to the pilot valves, bypass 27 is open and control chamber 20 is exposed to pressure from the inlet 6, which pressure acts on diaphragm 9 to urge valve body 8 against valve seat 8a, thereby completely blocking any flow from inlet 6 to outlet 7. In case of a current supply failure, the valve system ensures blocking between inlet 6 and outlet 7. This is an important safety feature.

In operation, the control unit 30 applies control pulses to both pilot valves 24, 26 to obtain a desired flow rate in response to control signal IW In particular, the flow rate may be proportional to the value of the control signal U_cont- In fact, the position of the valve body 8 relative to the valve seat 8a depends on the differential pressure acting on diaphragm 9 which, in turn, depends on the opening/closing conditions of bypasses 25 and 27. Otherwise expressed, it is the volume of fluid in control chamber 20 that determines the position of valve body 8 relative to valve seat 8a. When bypass 27 is open, input pressure is applied to control chamber 20, tending to move valve body 8 closer to valve seat 8a. When bypass 25 is open, pressure in control chamber 20 is allowed to be released by draining fluid to outlet 7, thereby tending to move valve body 8 away from valve seat 8a. Accordingly, any response of the resulting rate of fluid flow to the applied control signal Ucom, be it proportional, continuous or in discrete steps, can be easily tailored by programming control unit 30 to issue pulse patterns to both pilot valves 24, 26 so as to achieve a target value of flow.

In Fig. 6, one out of many possible physical implementations of the valve system is illustrated. Valve housing 11 is generally cylindrical, with a cover 11a. Pilot valves 24 and 26 are connected to housing 1 1 at integrally formed housing flanges 24a and 26a, respectively. This is an important aspect of the invention since conventional and commercially available miniature valves can be used as pilot valves.

Claims

1. A valve system comprising a valve chamber with an inlet and an outlet; a diaphragm dividing the valve chamber into a control chamber and a flow chamber connected with the inlet; a valve seat arranged in the flow chamber on the side of the outlet; a valve body connected with the diaphragm and cooperating with the valve seat to modulate a flow from the inlet to the outlet and through the flow chamber; a first pilot valve located in a first bypass that extends between the outlet and the control chamber; a second pilot valve located in a second bypass that extends between the inlet and the control chamber; and a control unit for controlling the first and second pilot valves to selectively open or close said first and second bypasses thereby varying the flow through the flow chamber between a fully open and a fully closed condition.

2. The valve system according to claim 1 , wherein the first and second pilot valves are pulse controlled by the control unit.

3. The valve system according to claim 1 or claim 2, wherein the first pilot valve is a normally closed valve and the second pilot valve is a normally open valve.

4. The valve system according to any of claims 1 to 3, wherein the control unit controls the first and second pilot valves to adjust the amount of flow in response to an input signal.

5. A valve member for use in a variable flow rate valve, in particular a valve system in accordance with any of claims 1 to 4, and having a generally cylindrical valve body with two opposed end faces and a peripheral wall extending between the end faces, at least one recess being formed in the peripheral wall extending inwardly, and a bore extending from one of said end faces and opening into the recess.

6. The valve member according to claim 5, wherein the recess is generally wedge-shaped and extends transversely to the axis of the valve body.

7. The valve member according to claim 5 or 6, wherein the recess is defined by surfaces composed of surface sections having different angles of inclination in relation to the axis of the valve body.

8. The valve member according to any of claims 5 to 7, wherein the bore has a width that corresponds to a nominal width of the a valve in which the valve member is used.