GB2172414A - Modulating operator device for pressure regulators for gas burners - Google Patents

Abstract

In a pressure regulator (1) for supplying a gas burner, a main valve located in the path of the gas is servo-assisted by a pilot valve (2, 3, 4) in which the position of the shutter (3) relative to the corresponding valve seat (2) is adjusted by means of a hot-wire operator (29-30) supplied with an electrical current dependent on the temperature of the element to be controlled. Wire (29-30) operates via an adjustable extendible rod (15) on a lever 8. <IMAGE>

Description

SPECIFICATION Modulating operator device for pressure regulators for gas burners The present invention relates to a modulating operator device for pressure regulators for gas burners, particularly but not exclusively for gas burners of mixed systems for heating and producing sanitary hot water.

The requirement that small-volume boilers or heating appliances for sanitary water be used in systems of the aforesaid type has imposed the need to devise and use valve systems for regulating the gas flow to the burner which allow appropriate control of the temperature within as narrow a range of values as possible, both for safety reasons and for energy saving.

It is known that a valve system which satisfies these requirements is that in which a main valve located in the path of the gas is piloted by an operating member of the so-called "modulated" type, that is a "modulating valve", which allows the instantaneous gas flow rate to be adapted to the actual requirements of the appliance, the traditional regulating system of the so-called on-off type not being sufficient to ensure good regulation.

It is also known that, in the field of modulating valves, the ones which are particularly successful are those in which the movements of the shutter relative to the respective valve seat are controlled by operators or actuators including a member which has a noticeable expansion through the effect of temperature and is connected to the shutter through a more or less complex series of levers subject to the action of one or more calibratable springs. In particular, the advantages of modulating operators based on the use of bimetallic strips, ampoules or cartridges containing an expansible liquid, which are immersed in the environment whose temperature it is wished to control, are recognised.

Nevertheless these prior art devices also have technical disadvantages which have not been overcome until now. In particular, the so-called mechanical systems which do not require electrical supplies (particularly those based on the expansion of liquids) have the disadvantages of allowing measurement of the temperature (and hence the relative control of the gas flow) at only one point; of not accepting complex signals which do not have a simple linear temperature-expansion relationship; of being very inflexible and not allowing ready modification of the modulation characteristics of the apparatus (proportional band). The known electrically supplied systems, on the other hand, generally have the disadvantage of having either high hysteresis (solenoid control) or very long response times (bimetallic systems) and in any case require a lot of piloting energy.

Another disadvantage is that of being very sensitive to the ambient temperature, with a consequent drift of characteristics.

The problem behind this invention is that of devising a modulating device for the pressure regulators of gas burners, which has structural and functional characteristics such as to overcome the disadvantages explained above with reference to the prior art.

This problem is solved according to the invention by a modulating device comprising a pressure regulator body, a valve seat formed in a gas path defined in the regulator body, a shutter cooperating with the valve seat and carried by a disc diaphragm retained peripherally in the body downstream of the valve seat, and a lever pivoted in the body and having one end acting on the diaphragm with the interposition of at least one spring member, characterised in that it includes a wire fixed at one end to a point on the regulator body and associated at its opposite end with the other end of the lever, the wire being electrically connected to a pair of terminals supported by the regulator body so as to conduct a temperature-dependent electrical current.

In accordance with one preferred embodiment, the wire is associated with the lever with the interposition of at least one adjustably extensible rod, means operable from outside the body being provided for varying the length of the rod.

The advantages and the characteristics of the invention will become more apparent from the detailed description of one embodiment of a modulating operator device according to the invention, which follows with reference to the appended drawing provided purely by way of non-limiting example and in which the device is shown in schematic sectional elevation.

The drawing shows only the upper part of a pressure regulator for gas burners, of the so-called servo-controlled type, this being of importance for an understanding of the invention.

In particular, that part of a pressure regulator incorporating the modulating operator device of the invention is shown.

With reference to the drawing, a modulating operator device according to the invention comprises, in a pressure regulator body 1, a valve seat 2 formed in a gas path defined in the regulator body and cooperating with a shutter 3 supported by a disc diaphragm 4 which is retained peripherally in the body downstream of the valve seat 2, with reference to the gas flow direction indicated by the arrow F. The diaphragm 4 defines a chamber 5 within the valve body 1 above the valve seat 2, which is in communication with the outlet side of the regulator body 1 through an aperture or duct 6.

The valve seat 2, the shutter 3 and its disc diaphragm 4 constitute a pilot valve of a main valve (not shown) of the pressure regulator under consideration, as will be better understood from the following description.

Above the disc diaphragm 4 and within a chamber 7 formed in the regulator body 1 is a cranked lever 8 pivoted on a pin 9 fixed in the chamber 7.

One arm 10 of the lever 8 extends into a position overlying the disc diaphragm 4. To the free end of this arm 10 of the lever 8 is fixed a blade 11 bent substantially into an inverted C shape and acting on the aforesaid diaphragm 4.

To advantage, a screw 11a allows the lower arm of the blade 11 to be stiffened when the pressure regulating function is to be excluded while that of regulating the flow in dependence on temperature is maintained.

In its turn, a spring 12 acts on the arm 10 with a resilient force which can be calibrated by means of a screw 13 accessible from outside the regulator body 1. A further chamber 14, the side parts of which are indicated 14a and 14b, is formed above the chamber 7 in the regulator body 1. A rod provided with a length -preselection device, generally indicated 15, is movably supported in the chamber 14. More particularly, and in accordance with a preferred embodiment, the rod 15 comprises a pin 16 having an end portion 17 slidably engaged in a through-hole 18 formed in the wall 14a of the chamber. The free end 17a of the portion 17 normally abuts the arm 10a of the lever 8. The pin 16 has an intermediate portion 19 of enlarged external diameter, which has peripheral axial teeth so as to constitute a straight-toothed gear.A screw 20 accessible from outside the regulator body 1 is constantly engaged with this gear. The other end 22 of the pin 16 is threaded and screwed into an arm 23 of a cranked member 24. The arm 23 is slidably engaged in an aperture 25 formed in the wall 14b of the chamber 14 opposite the wall 14a considered above.

A pair of wires 29, 30 of the same metal alloy are in mutual head-to-head association through a rocker arm 31 rotatably mounted on a pin 32 supported by the regulator body 1. The wire 29 has one end fixed to a support 33 of the regulator body 1.

Externally of this support 33, the wire 29 is electrically connected to a terminal 34.

The wire 30 has one end fixed to the arm 26 of the member 24. Beyond this arm 26, the wire 30 forms a loop 30a which is electrically connected to a respective terminal 35 and has the purpose of allowing free movement of the arm 26 relative to the contact 35.

It should be noted that for the purposes of the following description of the operation of the modulating device of the invention, the wires 29 and 30 may be considered as a single wire while the connecting rocker arm between them has been devised basically to satisfy particular and everpresent requirements of reduced bulk.

The wire 29-30 is supplied with an electrical current dependent on (in particular, inversely proportional to) the temperature of the element (water) to be controlled. The resultant heating of the wire 2930 causes an expansion thereof which may be considered proportional to the current itself. The lengthening of the wire 29-30 causes, through the cranked member 24 which is acted on by a spring 24a, a movement of the rod 15 with a consequent correlated angular movement of the lever 8. For each angular movement of the lever 8 there is a corresponding movement of the shutter 3 towards or away from its valve seat 2, causing an increase or decrease in the gas pressure in the chamber 1 beneath the valve seat.

When no current flows through the wire 29-30, the wire is cold and at its minimum length. In this case, the rod 15 controlled by the wire acts on the lever 8 which, overcoming the spring 12, causes the maximum raising of the shutter 3 from its valve seat 2 by means of the blade 11. Consequently, the pressure in the chamber 1 is at a minimum in that the pressure is exhausted through the seat 2.

When the electrical current in the wire 29-30 is at its maximum, the wire is at its maximum temperature and hence at its maximum length. The rod 15 is consequently moved away from the cranked lever 8 which, through the spring 12 and the blade 11, causes the minimum raising of the shutter 3 from its valve seat 2. Consequently, the pressure of the gas in the chamber 1 is at a maximum.

Electrical current values between those considered above determine intermediate positions of the shutter 3 relative to the valve seat 2, with respective intermediate rates of flow through the valve (modulating operation).

A suitable choice of the material of the support, of the member 33 and the pin 32, and of the material of the rod 16, allows the system to be rendered independent of the ambient temperaure, whereby the position of the end 17a of the rod 16 and hence of the shutter 3 is a univocal function solely of the electrical power supplied to the wire 29-30 through the terminals 34 and 35.

It should be noted that the maximum pressure of the gas flowing from the valve may be regulated by the screw 13 which acts on the spring 12, while the minimum pressure may be regulated by means of a screw 21. Moreover, it is possible to stiffen the leaf spring 11 by means of the screw 11 a, whereby the position of the shutter 3 relative to the seat 2 becomes independent of the value of the pressure in the chamber 5 acting on the diaphragm 4.

Claims (5)

1. Modulating operator device for pressure regulators for gas burners, particularly for mixed systems for heating and producing sanitaiy hot water, comprising a pressure regulator body a valve seat formed in a gas path defined in the regulator body a shutter cooperating with the valve seat and carried by a disc diaphragm retained peripherally in the body downstream of the valve seat and a lever pivoted in the body and having one end acting on the diaphragm with the interposition of at least one spring member characterised in that it includes a wire fixed at one end to a point on the regulator body and associated at its opposite end with the other end of the lever the wire being electrically connected to a pair of terminals supported by the regulator body so as to conduct a temperature-dependent electrical current.

2. Device according to Claim 1, characterised in that the wire is associated with the lever with the interposition of at least one adjustably extensible rod means operable from outside the body being provided for varying the length of the rod.

3. Device according to Claim 1, characterised in that the wire is constituted by two pieces of wire in mutual head-to-head association through a rocker member rotatably mounted on a pin supported by the regulator body.

4. Device according to Claim 1, characterised in that the lever is a cranked lever having one arm acting on the disc diaphragm and the other arm associated with the end of the rod the arm being subject to the action of a spring which can be cali brated by means of a screw accessible from out side the regulator body and constituting a maximum pressure screw.

5. A modulating operator device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.