GB2233741A - A servo-mechanism for gas pressure regulators - Google Patents

Abstract

In an electromagnetic actuator (2) servo-mechanism for gas pressure regulators, control members for a membrane valve (16), intended for calibration to adjust the maximum and minimum outlet pressures, are implemented in the form of an individually handled unit comprising a replaceable cartridge (20) which can be bench calibrated. The cartridge comprises a tubular guide (21) which houses an armature (29), a valve actuating rod (25) and a spring (42), together with means for adjusting the spring. <IMAGE>

Description

A SERVO'MECHANISM FOR GAS PRESSURE REGULATORS.

This invention relates to a servo-mechanism for gas pressure regulators, comprising: an electromagnetic actuator having a stationary core and an armature which is movable axially within a tubular guide toward and away from said core to urge a shutter of the servo-mechanism to shut off a corresponding seat; a shutter-driving rod extending from said movable armature; a first elastic means intervening between said shutter and said rod; a second elastic means intervening between said movable armature and a stationary part relatively to said tubular guide, and a travel-limiting means adapted to adjustably bound the travel distance of said rod toward and away from said shutter.

Servo-mechanisms of this kind, also referred to as "modulators" or "modulating valves", are employed for controlling gas pressure regulators which, in turn, control the feed pressure to a burner according to a physical parameter, such as the temperature of a heated fluid.

The temperature at which the servo-mechanism cuts in is converted, in a manner known per se, into an electric parameter, such as a current, which is then supplied to a solenoid of the servo-mechanism.

Since different types of the gas fed to a burner will generate different diagrams indicative of the link between the current flowing through the solenoid and a corresponding change in the gas pressure, the servo-mechanism is to be calibrated specifically for the type of gas to be used.

This calibration is accompLished both through the elastic means which appLies a closure pre-load to the shutter of the servo-mechanism and through the travel-limiting means for the shutter driving rod.

This operation is comparatively complex and critical, and shouLd be bench performed by skilled personnel using special equipment.

It follows that, when an existing system requires to be converted for use with another gas type, the servo-mechanism of the pressure regulator must be removed and replaced with another which has been pre-calibrated for the type of gas to be used.

This operation, additional to being a relatively laborious one, involves repLacement of all the servo-mechanism components, including those which bear no influence on the calibration made necessary on account of the different characteristics of the gas being used, because of their integrated construction.

The problem that underlies this invention is to provide a servo-mechanism for pressure regulators which has such structural and functional features as to areliorate the problems mentioned in connection with the prior art, in particular a servo-mechanism which can be tield-adapted.for.different gas types.

The solutive idea underlying this invention consists of providing the control members for the membrane shutter, intended for calibration to regulate the maximum and minimum gas outlet pressures, in the form of a unit for individual handling as a replaceable cartridge apt for bench calibration.

In this way, the personnel engaged in converting a gas system are only required to replace the cartridge of the servo-mechanism with a new pre-calibrated cartridge of a suitable type, leaving the other parts unaltered.

This solutive idea is embodied by a servo-mechanism of the kind mentioned at the outset being characterized in that said tubular guide forms, in combination with said movable armature, said rod, said elastic means, and said travel-limiting means, an individually handled unit detachably affixed to said actuator.

Advantageously, said tubular guide is connected to the actuator by threadway engagement so as to be readily removable and make for easy replacement of said unit.

The features and advantages of this invention will be more clearly understood from the following detailed description of a preferred embodiment thereof, to be taken by way of illustration and not of limitation in conjunction with the accompanying drawings, where: Figure 1 is an axial section view of a servo-mechanism for gas pressure regulators embodying this invention; and Figure 2 is exploded perspective, part-sectional view of the detail indentified by the arrow II in Figure 1.

Generally indicated at 1 in Figure 1 is a servo-mechanism for gas pressure regulators embodying this invention.

The servo-mechanism 1 comprises an electromagnetic actuator 2 having a coil 3 which is powered through connection terminals 4, and a stationary tubular core 5 made of a material which has enhanced ferromagnetic properties and extending a distance into a center cavity 6 of the coil, being secured on a mounting bracket 7 for the servo-mechanism 1.

The bracket 7 is attached by means of screws 8 removably to a body 10 defining a chamber 11 into which there open two conduits ia and 13, respectively.

The chamber 11 is closed off by a membrane 14 is trapped between the body 10 and the bracket 7.

Secured at the center of the membrane 14 is a cap 15 carrying a shutter 16 which functions to controllably shut off a valve seat provided on the end of the conduit 12.

The combination of the above-mentioned members constitutes a stationary part of the servo-mechanism, and requires neither adjustment nor replacement where the type of the gas to be pressure regulated is changed.

The servo-mechanism 1 further comprises a cartridge element, generally denoted by 20, which contains all the members requiring adjustment for the purpose of adapting the servo-mechanism for different gas types.

The cartridge element 20 comprises a tubular guide 21 made of a non-magnetic material, such as brass, which has first, second, and third coaxial cylindrical sections denoted by Zla, b, c, respectively.

The first section 21a has on its exterio; an engagement formation for a tightening tool, and -has internally a threaded cylindrical seat 22; the second section 21b is formed internally with a cylindrical cavity having a smaller cross-sectional area than the seat 22; and the third section 21c has a further reduced cross-sectional area and is provided externally with a threadway 23 whereby the guide 21 is threaded onto the core 5 in continuation of the latter. A rod 25 extends axially through the guide 21 and is guided slidably within the section 21c.

The rod 25 is terminated at one end with a ball joint on which a socket 26 is held oscillably and carries a spring 27 intervening, in use, between the socket 26 and the shutter 16.

At the opposed end, the rod 25 has a threaded section 28 terminated with a cutout grip formation.

Thread-engaged onto the threaded section 28 in an adjustably displaceable manner is an armature 29 made of a ferromagnetic material, which armature can be pulled in by the core 5 on the coil 3 being energized.

Also threaded onto the threaded section 28, above the armature 29, is a sleeve 30 which has at one end an enlarged head 31 provided with a grip formation for a wrench and being terminated with a collar 32.

Threaded into the seat 22 in an adjustable manner is a cylindrical cup-shaped element 35 having threaded inner and outer surfaces and being provided exteriorly with a knurled nut 36.

A second cup-shaped element 37 is threaded in an adjustable manner into the element 35. The element 37 is also threaded, both inside and out, and terminated at one end with a lip 38 extending radially inwards, and at the other end with a polygonal head.

The cup-shaped element 37 is partially formed with four equidistant axial cutouts which make it partially resilient and shrinkable inwardly such that it can be threaded into the element 35 at a slight interference.

Threaded into the inside threadway of the second cup-shaped element 37 is an end plug 40 defining a shoulder 41.

The head 31 of the sleeve 30, with the cartridge element 20 in the assembled condition, will lie between the lip 38 of the second cup-shaped element 37 and the shoulder 41 on the plug 40, which act, therefore, as travel-limiting means for the sleeve 30, rod 25, and the members associated with the latter.

A spring 42 is interposed between the head 31 and the bottom of the first cup-shaped element 35 to bias the sleeve 30 in the direction toward the shoulder 41.

To calibrate the spring 27 of the cartridge element 20, the latter is assembled without items 30, 40 and 42. By rotating the first cup-shaped element 35, the movable armature 29 is caused to abut against the shoulder defined in the tubular guide 21 between the sections 21b and Z1c. Then, by rotating the rod 25 relatively to the armature 29, the distance of the socket 26 from the shutter 16 is changed along with the preload on the spring 27, and after adjusting the latter, the armature 29 is locked relatively to the rod 25.

Thereafter, the sleeve 30 is assembled, with the spring 42 and intervening washer, by threading it onto the rod 25 to rest close against the movable armature 29, and then locking it by caulking the collar 32.

After completing these steps, the coil 3 is energized with a preset current, and by rotating the first cup-shaped element 35, the preload on the auxiliary spring 42 is calibrated to suit desired operating conditions for the servo-mechanism 1.

This step completes the preload adjusting procedure for the springs 27 and 42, and the first cup-shaped element 35 can therefore be locked in the threaded seat 22 by caulking.

The travel limiters for the rod 25 are next adjusted by rotating the second cup-shaped element 37, with the electromagnetic actuator energized with the maximum working current, until a minimal gap is established between the armature 29 and the core 5. Then, the plug 40 is threaded in until the target adjustment is achieved for the maximal gap between the armature 29 and the core 5, with the electromagnetic actuator de-energized.

The calibration of the travel limiters 37, 40 may be further changed, where required, on installing or servicing the gas user incorporating the servo-mechanism 1 to suit actual specific operating conditions.

After having completed the installing and adjusting phases, a cap 50 is placed onto the free end of the cartridge element 20 in order to protect it from further manipulations.

As may oe appreciated, the cartridge element 20 can be easily and quickly replaced (e.g. in the event that the type of fuel gas is changed whose pressure is regulated through the servo-mechanism 1) by just unscrewing the element 20 and replacing it with a suitable element which has been bench set to meet the specifications for the new fuel gas used.

Claims (9)

1. A servo-mechanism for gas pressure regulators, comprising: an electromagnetic actuator having a stationary core and an armature which is movable axially within a tubular guide toward and away from said core to urge a valve head of the servo-mechanism to shut off a corresponding seat; a valve head driving rod extending from said movable armature; a first elastic means intervening between said valve head and said rod; a second elastic means intervening between said movable armature and a stationary part relative to said tubular guide; and a travel-limiting means adapted to adjustably bound the travel distance of said rod toward and away from said valve head; characterised in that said tubular guide forms, in combination with said movable armature, said rod, said elastic means, and said travel-limiting means, an individually handled unit detachably affixed to said actuator.

2. A servo-mechanism according to Claim 1, characterised in that said tubular guide is connected to said actuator by threaded engagement.

3. A servo-mechanism according to Claim 2, characterised in that said actuator comprises an internally threaded tubular core, and said guide comprises a threaded section adapted to be threaded into said core.

4. A servo-mechanism according to Claim 1, characterised in that said second elastic means is interposed between a sleeve tied to said movable armature and a first cup-shaped element adjustably displaceable on said tubular guide to calibrate the elastic pre-load applied by said second elastic means to said armature.

5. A servo-mechanism according to Claim 4, characterised in that said travel-limiting means is mounted on said first cup-shaped element in an adjustably displaceable manner.

6. A servo-mechanism according to Claim 5, characterised in that said first cup-shaped element is threaded internally and accommodates in an adjustable manner a second cup-shaped element adapted to define one member of said travel-limiting means and, in turn, accommodating adjustably therein a plug defining the other member of said travel-limiting means.

7. A servo-mechanism for gas pressure regulators, the servo-mechanism comprising an electromagnetic actuator having a stationary core and an armature which is movable relative to said core to control the position of a gas valve member, the servo-mechanism further comprising one or more parts adjustable to calibrate the servo-mechanism for different gas types, wherein the armature and the or each part requiring adjustment for calibrating the servo-mechanism for different gas types comprise a removable unit apt for adjustment when removed.

8. A cartridge as defined in Claim 7.

9. A servo-mechanism substantially as hereinbefore described with reference to the accompanying drawings.