GB1603360A - Valve assembly - Google Patents

Abstract

The safety device (4) serves for closing a shut-off element (1) arranged in a pipe carrying a fluid, by means of the fluid pressure upstream of this shut-off element (1). The safety device (1) is used to protect heat-generating or consuming systems from impermissibly high temperatures. The safety device (1) is provided with a control valve (11) which allows the fluid pressure to take effect. On one side, the said valve has, branching off from the pipe, a branch line (3 and 3a respectively) for the closing fluid. On its other side, chamber (5c), a branch line leads to the shut-off element (1, 2, 17). The control valve (11) opens under the action of a control fluid (7a, 5a) counter to the force of a spring (15) of the control valve (11). <IMAGE>

Description

(54) A VALVE ASSEMBLY (71) We, INDUSTRIE-WERKE KARLSRUHE AUGSBURG A. G., a Joint Stock Company organised under the laws of Germany (Fed. Rep.) of Postfach 3409,7500 Karlsruhe 1, Germany (Fed. Rep.) do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement :- The invention relates to a valve assembly for the protection of heat producing or using installations.

Known devices for protecting heat producing or using installations operate with a stored springs force. Usually this force is released to actuate a valve upon attainment of a predetermined temperature so as to protect the installation.

Using stored spring force of this type the springs are retained in their pre-tensioned position by means of detents, pawls, locks, bell cranks or the like, or the hydraulic pressure of a sensor liquid. In this case the release of the spring force is usually effected by dis-engagement of the detents, which in turn is initiated, for example, by the thermostat sensor. In many instances however the springs must be able to exert a large force in order to close the valves.

When the spring force diminishes in the course of time, or if the spring breaks, there is no longer protection for the installation to be supervised since the valve is not closed when the predetermined temperature has been reached.

Additionally the temperature at which the valve actually closes frequently rises far above the predetermined temperature before the dis-engagement of the stored spring force. This is due to the occurrence of relatively high friction forces at the detent used for retaining the stored spring force. Obviously in such a case the protection for the installation is ineffective. All these arrangements have in common unsatisfactory spring release characteristics which are caused by the friction associated with the mechanical locking of the spring force.

In view of the defects and disadvantages which attach to the known devices for protecting heat producing or using installations it is an object of the invention to provide a valve assembly for protecting such installations which is simple and at the same time extremely reliable in operation.

According to the present invention there is provided a valve assembly, comprising a main valve through which fluid passes and which is closable to control such passage of fluid, a fluid pressure operated actuator mechanism for the main valve, a fluid containing temperature sensor, and a control arrangement having a first fluid filled expansible chamber associated with said temperature sensor, the control arrangement further including a first control valve normally held in a closed position and operable on expansion of the first chamber to provide communication between the main valve and the fluid pressure operated actuator mechanism whereby above a predetermined temperature expansion of the fluid in the temperature sensor causes the expansible chamber to expand and open the first control valve to allow fluid from the main valve to cause the actuator mechanism to close the main valve.

The invention is illustrated by way of example only with reference to the accompanying drawing which shows a vertical section through one embodiment of valve assembly in accordance with the invention.

The illustrated valve assembly includes a main valve I which may be a regulator and/or shut-off valve, associated with a diaphragm housing 2. The valve I includes a valve rod la, a head lb and a valve seat lc.

Valve rod la is connected with a diaphragm 17 in the housing 2 so as to form a fluid pressure operated actuator for the valve I as will be appreciated from the following description. In use of the assemblv fluid (not shown) flows through the valve 1.

The valve I and diaphragm housing 2 are in operative connection with a control member 4 by means of control pipes 3,3a.

Control member 4 in conjunction with a temperature sensor 7 serves, as described more fully later, to effect closure of the valve I should the temperature rise above a predetermined value.

The control member 4 comprises a pressure-resistant casing S which is closed on all sides. The interior of the casing 5 is divided into several chambers 5a, 5b, 5c.

The chamber 5a is an expansible chamber and is closed off in a pressure and liquid tight manner by means of diaphragms 6, 6a, 6b. Chamber 5a is filled with an expansion liquid. This liquid in turn is in operative connection with a temperature sensor 7 through a capillary tube 7a.

Chamber 5b is associated with means for presetting the temperature at which the valve I will be closed. In the illustrated embodiment, these means include an open topped, hollow cylindrical body 8 concen trically arranged and guided in a correspondingly constructed part of the diaph, ragm 6b. A helical spring 9 is arranged coaxially above the body 8 and is supported in compression between the top of body 8 and the interior of the casing 5. A screw threaded spindle 10 is centrally arranged in the helical spring 9 and may be adjusted to alter the distance"a"between the top surface 8b of the base of body 8 and the lowersurface 10bofthespindle 10.

Two control valves 11, 14 biased by springs 15 and 16 respectively are arranged in the chamber 5c and provide connections in parallel relationship between the valve I and housing 2. Valves I 1, 14 are each associated with a respective control surface which engage against the associated diaphragms 6,6a respectively. The control surface 12 of the valve 11 is substantially smaller than the control surface 13 of the valve 14 in order to render available sufficient closing force for this valve.

Chamber 5c contains a fluid which is the same as th't passing in use of the assemblv. through the valve (and as will be appreciated one side of valve 11 communicates with the diaphragm housing 2 via the pipe 3 whereas the other side of valve 11 communicates with the valve 1 lwia the pipe 3a.

In normal operation of the valve assembly the surface 8b of the hollow body 8 does not rest against the end lOb of the screwthreaded spindle 10. Because of the compression of the spring 9 a hydraulic minimum pressure is maintained in the chamber Sa which pressure maintains the valve 14 always closed by means of the diaphragm 6a acting against the control surface 13. However the pressure is insuffi cient or opening the valve 11 against the force of spring) 5 by means of the control surface 12.

However, if the surface 8b which forms a control surface, of the body 8 rests against the front face 10b of the screw-threaded spindle 10 and the temperature at the sensor 7 rises by a small amount, for example by 1 C, a steep pressure rise occurs within the chamber 5a owing to the increase in volume of the expansion liquid. Thereby the valve f I opens so that fluid passes from the valve 1 via pipe 3a into chamber 5c and thence via pipe 3 to diaphragm housing 2. As a result valse stem la is moved upwardly to close valve 1. The diaphragm l7 wiil close the valve I with a force of the area of dia phragm 17 times control pressure (= bias pressure). The valve I is maintained closed because the control pressure cannot escape from the diaphragm housing 2. In this way the valve I is hydraulically locked.

Unlocking is possible only when, with the sensor temperature lowered, the control pressure is manually released by means of a relief valve 18. This corresponds to a requirement in accordance with DIN 3440.

It will be manifest that the temperature at which the pressure increase will occur in chamber 5a to effect closing of the valve I is dependent on the distance"a".

Consequentlv the spindle 10 mas be adjusted to vary distance"a"and hence alter the temperature at which the valve I will close. During the abovedescribed operation the valve 14 is maintained securely closed. If however the hydraulic pressure in the chamber 5a drops, owing for example to leakage or fracture of control pipes or capillary tubes, the spring 16 will open the valve 14 providing of course that the force of spring 16 exceeds the pressure exerted by diaphragm 6. The spring 16 may thus be selected to open the valve 14 belo a particular pressure exerted by diaphragm 6. Upon opening of valve 14 (in which condition valve 11 will be closed) fluid again passes from . aUe I via line 3 into chamber 5c and thence into diaphragm housing 2 so as to close the valve 1. Consequentlv the valve I is again hvdraulicallv locked.

In the event of spring) 5 fracturing the valve 11 opens at once, so that the valve I closes at once, in the abovedescribed manner. If, however, the spring 9 in the adjuster breaks, the pressure of the expansion liquid in the chamber 5a collapses and the valve t4 is opensd so that the valve I is again closed.

If, in another possible case of trouble, the control val-, es 11, 14 do not close tightlv, closure of the valve I ensues liliexzise. Ths any failure of the valve assembly results in shutting of the valve 1.

It will be appreciated from the foregoing description that the va ! ve assembly of the invention is simple and effective in respect of construction as xell as manner of operation. The simplicity of its construc- tion is evidenced by the relatively small number of component parts which are necessary for the operation and which are subjected to practically no wear. The effectiveness of the valve assembly is clear from its simple construction and by the use of the expansion of liquids under thermal influence for controlling the valve.

Claims (9)

1. WHAT WE CLAIM IS :- 1. A valve assembly, comprising a main valve through which fluid passes and which is closable to control such passage of fluid, a fluid pressure operated actuator mechanism for the main valve. a fluid containing temperature sensor, and a control arrangement having a first fluid filled expansible chamber associated with said temperature sensor, the control arrangement further including a first control valve normally held in a closed position and operable on expansion of the first chamber to provide communication between the main valve and the fluid pressure operated actuator mechanism whereby above a predetermined temperature expansion of the fluid in the temperature sensor causes the expansible chamber to expand and open the first control valve to allow fluid from the main valve to cause the actuator mechanism to close the main valve.
2. 2. A valve assembly as claimed in claim 1, wherein the control arrangement includes a second control valve adapted to open when the pressure exerted by the expansible chamber falls below a predetermined value to provide communication between the main valve and the fluid pressure actuator to effect closing of the valve.
3. 3. A valve assembly as claimed in claim 5, wherein the first and second control valves are connected in parallel between the main valve and the fluid pressure actuator and are operabte in opposite directions.
4. 4. 4 vafve assembly as claimed in claim 2 or 3, wherein each control has a control surface associated with the expansible chamber and the control surface of the second control valve is SLibstantiall), larger than that of the first. alve.
5. 5. A valve assembl as claimed in any one of claims I to 4 wherein the control arrangement has a second fluid filled chamber in communication with the main valve and a third fluid filled chamber in communication with the actuator mechanism. said second and third chambers being communicable with each other by means of said first control valve and also by means of said second control valve where provided.
6. 6. A valve assembly as claimed in any one of claims I to 5, wherein the first chamber is defined by a diaphragm arrangement.
7. 7. A valve assembly as claimed in any one of claims I to 6, wherein the control arrangement inclues an adjuster for setting the temperature at which the first control valve will open.
8. 8. A valve assembly as claimed in claim 7, wherein the adjuster comprises a hollow body acting against the expansible chamber. a position ajustable spindle extending axiallv into the hollow body and adapted to limit movement of the body on expansion of the expansible chamber, and a helical spring tending to urge the body against the expansible chamber.
9. 9. A valve assembly substantially as hereinbefore described with reference to the accompanying drawing.