FR2589260A1 - Temperature-compensated flow rate regulator - Google Patents

Abstract

Flow rate regulator for fluid, with a membrane comprising a primary element integral with the membrane whose flow rate drift due to the variation in viscosity with temperature is eliminated by a compensator.

Description

The invention relates to 'fluid flow regulators which operate by controlling the opening of a valve actuated by a membrane subjected to the pressure difference which appears at the ends of a pressure-reducing element, otherwise called primary element and such that capillary, diaphragm etc, and generally by any element whose pressure difference between the inlet and the outlet is in relation to the fluid flow which crosses it, the invention relates in particular, to membrane regulators for micro flows.

The object of the invention is to simplify the production of the regulator by the use of a primary element linked to the membrane and to provide a thermal compensation device which reduces the flow variations inherent in the modification of the viscosity of the fluid as a function of the temperature. FIG. 1 illustrates the mechanism of a conventional flow regulator with the fixed pressure-reducing element constituted in the example by a capillary. It comprises a body (1) whose volume forms two cavities (2) and (3) separated by a flexible membrane (4) subjected to the pressure resulting from the flow of the fluid from the inlet (5) to the outlet ( 6) through the capillary (7) inserted in a pipe integral with the body. The pressure in relation to the flow of the fluid in the capillary causes the closure of a valve (8) on a seat (9).

The nominal flow rate is obtained when the displacement force of the valve plus the force of the spring (10) positioned between the body and the membrane, balances the force due to the pressure on the membrane.

FIG. 2 illustrates the particular embodiment of the invention with a primary element integral with the membrane.

According to the invention, the primary element (it) is installed on the support (12) of valve (8) fixed by the flanges (13) on the membrane (14) thus eliminating the complex bypass circuit that is necessary made in known flow regulators; The primary element is located in the axis of the membrane.

The nominal flow rate is adjusted by modifying the position of the valve seat (15) in the body (16) which has the effect of changing the compression of the spring at the operating point (17). The seal between the valve seat and the body being, in the example, nonlimiting of the invention provided by the seal (18).

In the invention, the flow drift caused by variations in the viscosity of the fluid, at different operating temperatures, is eliminated by a compensation device which acts by the automatic modification of the compression of the spring under the effect of the displacement of the free surface. an elastomer molded or fitted in a cavity. An elastomer behaving like a liquid, that is to say being incompressible, the displacement takes place as a result of the variation in expansion between its volume and that of the cavity which contains it.

The invention uses to obtain a nonlinear law of the calibration of the spring which will lead to a constant flow whatever the temperature; a cavity of appropriate shape and size determined by the expansion coefficients of the elastomer and the material of the cavity which receives it.

In FIG. 2, the compensator produced according to the invention consists of the cavity (19) produced in the body (16) in which an elastomer (2 O) is molded, silicone rubber for example, and a plate (21) on which the spring (17) is supported.

The compensator allows the realization of regulators for micro flows with a capillary linked to the membrane as provided for the use of a primary element with high pressure drop to obtain sufficient force for the proper functioning of the valve.

In practice, only a capillary is used and this because of its possibilities of high pressure drop; a diaphragm does not make it possible alone, obtaining the high pressure drop because the dimension of a precise orifice of very small diameter is not feasible in the current state of the art, the pressure drop with diaphragm does not could therefore be obtained by combining several diaphragms in a bulky and heavy assembly which could not be supported by the membrane whose flexibility must be very great. The flow rate of a capillary being strongly dependent on the temperature, the compensator, object of the invention, ensures the constancy of the flow rate by automatically adjusting the calibration of the spring at each temperature.

The invention relates to the field of instrumentation, regulation and control of fluids.

Claims (5)

1 - Flow regulator for fluid, with membrane, comprising an element  primary (11) integral with the membrane (14) whose flow drift  dbe the variation in viscosity with temperature is eliminated by a  compensator. 2 - Regulator according to claim 1, characterized in that the element  primary (11) is located in the axis of the membrane (14). 3 - Regulator according to claim 1 characterized in that the element  primary (11) is located on the valve support (12) (8). 4 - Regulator according to claim 1, characterized in that the compen  sator which eliminates the flow drift consists of a plate (21)  on which the calibration spring (17) is supported, pushed by an elas  tomera (20) molded in a cavity (1 9). 5 - Regulator according to claim 4, characterized in that the cavity  (19) has an appropriate size and shape so that the differences  expansion between the elastomer and the material of the cavity lead  to the non-linear spring calibration law (17) to compensate for drift  of the primary element.