EP0238580A1

EP0238580A1 - Flow controller

Info

Publication number: EP0238580A1
Application number: EP19860905823
Authority: EP
Inventors: Väinö Ilmari KALPIO
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-10-02
Filing date: 1986-10-01
Publication date: 1987-09-30
Also published as: FI853804A0; WO1987002114A1; FI853804L

Abstract

Un régulateur du débit de substances fluides, telles que des liquides ou gaz, comprend un dispositif régulateur (7) composé d'un réservoir (7a) résistant à la pression qui contient un matériau (3) dont le volume subit des variations considérables avec des changements de température et une partie de soupape (2) montée sur ce dispositif régulateur de façon à créer une isolation thermique et commandée par un dispositif de fermeture (4) en un matériau élastique. Le volume du matériau contenu dans le dispositif régulateur est modifié en chauffant le matériau avec des résistances électriques (8) et l'augmentation de la pression provoquée par l'expansion est transférée à travers de fins orifices dans l'isolant thermique (5) afin d'exercer une influence directe sur la surface du dispositif de fermeture (4). Le dispositif de fermeture (4) est ainsi forcé vers la paroi du corps (2) de la soupape en réduisant l'écoulement entre la paroi et le dipositif de fermeture. Dans un deuxième mode de réalisation de l'invention, ledit dispositif régulateur est divisé en deux chambres séparées l'une de l'autre par un diaphragme élastique en caoutchouc. La chambre plus petite, située derrière ce diaphragme en caoutchouc, est reliée par un tuyau à la partie de soupape et remplie d'un fluide approprié de transmission de pression dont le volume ne dépend guère de la température. Une pression de régulation créée dans le dispositif régulateur est transmise par le diaphragme élastique et par le fluide hydraulique à la surface du dispositif de fermeture.A regulator for the flow of fluid substances, such as liquids or gases, comprises a regulating device (7) composed of a pressure-resistant reservoir (7a) which contains a material (3) whose volume undergoes considerable variations with temperature changes and a valve part (2) mounted on this regulating device so as to create thermal insulation and controlled by a closing device (4) made of an elastic material. The volume of the material contained in the regulating device is modified by heating the material with electrical resistances (8) and the increase in pressure caused by the expansion is transferred through fine orifices in the thermal insulator (5) so to exert a direct influence on the surface of the closing device (4). The closing device (4) is thus forced towards the wall of the body (2) of the valve by reducing the flow between the wall and the closing device. In a second embodiment of the invention, said regulating device is divided into two chambers separated from each other by an elastic rubber diaphragm. The smaller chamber, located behind this rubber diaphragm, is connected by a hose to the valve part and filled with a suitable pressure transmission fluid whose volume hardly depends on the temperature. A regulating pressure created in the regulating device is transmitted by the elastic diaphragm and by the hydraulic fluid to the surface of the closing device.

Description

Flow controller

The present invention relates to a means for control- ing the flow of a substance, such as a liquid or gas flowing in a tube.

The presently available flow controllers are mostly those having a metal clappet or disc as a shut-off means. The clappet or disc is fitted with a rod or shaf running through the wall of a valve bod . The through-hole or lead-in must be sealed to prevent leaks. The position of a clappet or disc is adjust¬ ed mechanically by means of a rod or shaft either manually or with a motor.

Also available are valves in which a metal clappet or disc is replaced with a shut-off means made of a resilient material, e.g. rubber. This type of valve is disclosed e.g. in US Patent 3 753 626. The shut- off membrane is actuated mechanically by means of a bellows, the variations of its length being caused by the volume changes of a substance inside the bellows. The bellows are connected by means of a pipe to a sensor which is placed at the point of control. The sensor contains a substance whose vol¬ ume changes as a result of temperature changes. This volume change is transmitted to the bellows by way of a pipe joint.

A similar valve control system is also known from US Patent 3 661 324 in which a cylindrical piece of metal serves as a shut-off means. The volume changes of a substance in a sensor actuate a resilient mem¬ brane which carries a shut-off means. Also the Publication print DK 112 136 discloses the use of a substance that changes its. volume as a result of a temperature change for controlling the position of a valve shut-off means.

In the three above cases, the question is about a so- called self-powered control system, wherein the tem¬ perature changes of a sensor placed at a point of control regulate the position of a shut-off means with¬ out having to supply the controller with additional energy.

US Patent publication 3 778 021 discloses a thermally powered shut-off valve in which the shut-off means is a conical plug whose rod is run through the wall of a valve body into a membrane chamber, wherein the rod end is fastened to a membrane, the chamber on the op¬ posite side thereof being connected by means of a pipe to a reservoir containing a highly heat-expansible substance and an electric resistance for heating it.

US Patent 2 662 550 discloses also a thermally powered control valve, wherein a solid shut-off means, made of some resilient material, has been embedded in a flowing liquid. The shut-off means contains some highly heat-expansible substance and it is provided with an electric resistance for heating the substance. When shutting off the valve, the substance in said shut-off means is heated and the shut-off means cuts off the flow as a result of its expansion.

All the above types of valves have drawbacks owing to their complicated design.

The most important drawback in a mechanical clappet or disc valve is .caused by the leaks owing to the wear of a rod or shaft packing, leading gradually to the formation of crust or scale and to valve sei¬ zure. Another drawback is caused by debris remaining in closed position between the clappet or disc and the seat of a valve, said debris preventing tight closure of the valve. This leads readily to trouble in adjustment. A third drawback, caused by a mechan¬ ical actuating system, is the inaccuracy of adjust¬ ment. The question is always about a stepwise pro¬ ceeding discontinuous adjustment and, as a result of wear, there is always back-lash in the mechanical actuating components.

The above description includes also valves in which, instead of mechanical drive, the actuator is provided by using the volume changes of a medium contained in a sensor.

However, the prior art valve types are structurally complicated and, being self-powered, are not suitable for highly sophisticated control duties which require high accuracy and great closing forces.

A thermally powered valve as set out in US Patent 2 662 550, wherein some expansible medium is heated with an electric resistance, is co plicatod in its construction.

When thermally expansible medium is in direct heat transfer relationship with the valve body and the shut-off means is placed in a liquid flow to be controlled, it is difficult to prevent the effect of temperature changes in liquid flow on the accuracy of control. The shut-off means of a valve according to the invent¬ ion is made of a resilient material and fitted in the valve in a manner that a flowing medium will remain on just one side of the shut-off means. Control of the flow is effected by squeezing a membraneous shut- off means with pressure towards a medium flowing in the valve house for reducing the gap between shut-off membrane and valve house to constrict the flow. In a valve of the invention, -the control pressure acts directly on the surface of a shut-off means and the pressure required for such control, e.g. hydraulic pressure, is produced by heating a medium contained in a closed non-resilient space, said medium expand¬ ing dramatically as temperature rises, and by pass¬ ing this pressure by some suitable arrangement behind the shut-off means. As a thermally expansible mater¬ ial it is possible to use oil, wax, semi-solid or liquid plastics.

This type of valve is prior known from the published British Application GB 2 125 938 in which fig. 10 shows a working example of a valve operating as de¬ scribed above. In the design shown in fig. 10, a heat insulator carried by the shut-off means has been used in an effort to eliminate a heat flow between the liquid flowing out of the valve house and the ex¬ pansible med m in closed space. The tr.ir.sfer of heat e.g. from heat liquid flowing in the valve to variable-volume medium and to the walls of a reser¬ voir containing said medium has not, however, been prevented in prolonged operation. In view of the control stability of a thermally powered valve such transfer of heat is detrimental. Another drawback is the fact that the structure and operation of the shut-off means provides a small cross-sectional flow area with respect to the surface area of a shut-off means and requires, substantial changes in the direct¬ ion of a flow channel in the valve body.

An object of the invention is to eliminate these draw¬ backs and thus to provide a stable-control and simple- design valve.

In a valve of the invention, this problem is resolved in a manner that the surface of a shut-off means fac¬ ing the flow duct, which in a closed position of the controller rests against a solid seat surface, is made deformable in response to the deformation of a resil¬ ient shut-off means whereby, in a closed controller position, the shut-off means and its above-mentioned surface conform through the action of said control pressure to the configuration of said solid seat surf¬ ace, and that said variable-volume medium is thermal¬ ly insulated from the valve body.

The design of a shut-off means and its co-operation with the solid seat surface ensures high accuracy at small flow-through rates, tight sealing and long service life (no components subjected to abrasive wear) . In addition, the control means and the valve body portion are separated from each other so as to produce no heat flow which would be detrimental to operation (impaired control accuracy) . Insulation can be effected by means of a sufficiently thick insulat¬ ing member, the control pressure being passed there¬ through to the surface of a shut-off means along one or a plurality of thin holes, or by separating the control means and the valve body from each other and connecting them together with a pipe. In a second embodiment, a valve of the invention is further char- acterized in that the bottom of said control means is provided with a smaller reservoir, separated from the upper reservoir of said control means by a flex- ible membrane. The smaller reservoir contains hyd¬ raulic fluid whose volume only slightly depends on temperature. Thus, the temperature changes of a li¬ quid in said pipe do not affect the. stability of control»

Fig. 1 is a cross-sectional view of one embodiment of a control valve of the invention.

Fig. 2 is a cross-sectional view of a second embodi¬ ment of the control means in a control valve of the invention, the control means being se¬ parated from the valve member and connected to it by means of a pipe.

The design and operation of a valve of the invention will now be described with reference to what is shown in fig. 1.

In the embodiment of fig. 1 , the flow to be controlled runs in a flow duct 1. The controller valve member is designated by reference numeral 2 and the variable- volume material by reference numeral 3. Reference numeral 4 indicates a resilient shut-off means, which yields to the volume changes of material 3 and con¬ trols the flow in flow duct 1. Between material 3 and shut-off means 4 as well as valve body 2 there is fit¬ ted a heat insulator 5. Flow duct 1 is fitted with a heat insulator 6. Most of the variable-volume mater¬ ial 3 is inside the reservoir 7a of a control means 7. Temperature control of material 3 is effected by means of electric resistances 8. An NTC-resistance 9 is provided for measuring the temperature of material 3. Control means 7 is fastened with bolts 10 to valve body 2. Bolts 10 press control means 7 and valve body 2 against the opposite sides of heat insulator member 5 and the edges of shut-off means 4 , formed by a re¬ silient membrane, are pressed between valve body 2 and insulator member 5. The lead-in of resistances 8 and resistance 9 into reservoir 7 is packed or seal¬ ed with a casting 11.

A second embodiment of the invention is illustrated in fig. 2. In this embodiment, the bottom of the reservoir 7a of a control means 7 is provided by a resilient membrane 16, on the other side of which is formed a smaller reservoir member 12, comprising a bottom section 14 fastened to the larger reservoir member 7a by means of a screw-thread 13. The smaller reservoir member 12 is filled with a fluid 12a, suit¬ able for pressure transmission and characterized by only slight dependence on temperature. Pressure from said lower reservoir 12 is delivered along a pipe 15 to one or a plurality of control valves, e.g. to a control valve as shown in fig. 1.

The embodiment shown in fig. 2 can be used in such operating conditions, in which major temperature dif¬ ferences and tern--,e at hr-nre--. w .il l 1 p-n i t iT.— accuracy in control if a control means were directly connected to the valve member, Furthermore, there is a possibility of using just one control means 7 to control a plurality of valves by employing a plurality of parallel pipes 15.

Claims

1. A flow controller for regulating the flow of a liquid, gas or. some other flowing medium, said con¬ troller comprising a valve body (2) defining a flow duct (1), provided on the inside with a seat surface (2a) and facing this, on the other side of said flow duct, there is a shut-off means (4) made of a resil¬ ient material and adapted to be pressed towards seat surface (2a) with a pressure created in a control means (7) by means of a variable-volume medium (3) by regulating the temperature of this medium by means of an electric resistance (8) placed inside said medium, the pressure created upon heating said ex¬ pansible material being delivered by means of at least one fluid column (3a, 15) from control means (7) to the surface of shut-off means (4) , c h a r a c ^■ t e r i z e d in that the surface (4a) of a shut-off means, which faces said flow duct (1) and in a closed controller position rests against said solid seat surface (2a) , is made deformable in response to the deformation of a resilient shut-off means (4) whereby, in a closed controller position, said shut-off means (4) and its above-mentioned surface (4a) conform through the action of said control pressure to the configuration of said solid seat surface (2a) , and that said variable— olume material (3) is thermally insulated (5; 12, 15) ^"from valve body (2).

2. A flow controller as set forth in claim 1, c h a r a c t e r i z e d in that said control means (7) is fastened to valve body (2) with a heat insulat¬ or member (5) in between and said fluid column (3a) is passed through insulator member (5) .

3. A flow controller as. set forth in claim 1, c h a r a c t e r i z e d in that the other end of control means (7) is provided with a smaller reser¬ voir (12), separated by a resilient membrane (16) from a larger reservoir of said control means, the latter reservoir containing said variable-volume material, said smaller reservoir being connected with a pipe (15) to valve body portion (2) and filled with a hydraulic fluid (12) having a low coefficient of heat expansion.

4. A flow controller as set forth in claim 1, c h a r a c t e r i z e d in that the wall of flow duct (1) is provided with a ridge (2a), rising to¬ wards shut-off means (4) and building a seat surface integrally with valve body (2) .

5. A flow controller as set forth in claim 2, c h a r a c t e r i z e d in that said control means (7) is fastened to valve body (2) with bolts (10) forcing said control means (7) and valve body (2) against the opposite sides of heat insulator member (5) , the edges of shut-off means (4) , formed by a resilient membrane, being squeezed between valve body (2) and insulator member (5) .

^' - A flow controller as^* set forth in claim 5. c h a r a c t e r i z e d in that said shut-off means (4) and insulant member (5) confine therebetween a pressure chamber (3b) , in which prevails a control pressure for actuating said shut-off means (4).