FR2505442A1 - DOSER VALVE - Google Patents

Abstract

DOSING VALVE FOR PROVIDING A DETERMINED VOLUME OF GAS WITH DETERMINED INTERVALS, CHARACTERIZED BY THE FACT THAT IT INCLUDES A BODY 12 WITH INPUT OPENINGS 14 AND OUTLET 18; A PASS 84, 86 BETWEEN THESE OPENINGS, A SHUTTER 82 FOR CONTROLLING THE FLOW OF GAS THROUGH THIS PASS, MEANS 88 FOR MOVING THIS SHUTTER A DETERMINED DISTANCE, DURING A DETERMINED DURATION AND THEN OPENING THE PASS AND MEANS MEASUREMENT 90 TO DETERMINE THE POSITION OF THIS SHUTTER AND, THEREFORE, THE GAS FLOW THROUGH THE VALVE.

Description

Many types of gas supply and use devices

gases require relatively metering

  precise gas flow rate When the device

  tif uses or supplies a mixture of two or more gases, the volumetric flow rate of each gas must be precisely measured. An example of such a device is a medical respirator used to facilitate or regulate the breathing of a patient. respirators, it is common to mix varying amounts of oxygen and ambient air and to infuse a predetermined volume of

  mixing of these gases with the patient, at determined intervals.

  This process is known as volume ventilation -

  has largely replaced the previous technique of ventilating the patient known as pressure ventilation. Because the same ventilator is frequently used for many different patients including

  breathing requirements are different, one must

  see adjust the mixture of oxygen and air supplied by these respirators within a range from 100% oxygen to 100% ambient air Similarly, we must be able to adjust the waveform of signals to build a model

of breathing.

  A third technique for ventilating the patient, known as high frequency positive pressure ventilation (V P P H F) is becoming more and more prejudiced

  favorable for the ventilation of patients in districts

  various tances In this technique, the patient's lungs

  are arrested and the patient is breathed in in rapid succession

  air jets, of small volume, simulating a model of breathless breathing We can thus realize in a minute up to 60 breaths and many people of the medical profession estimate that the technique VPPHF can be tolerated

  more easily by the patient than ventilation is tolerated

  volumetric A VPPHF fan must also

  have means to regulate the gas mixture internally

  range from 100% ambient air to 100% oxygen, and you also need to be able to adjust the waveform of the breathing pattern signals to achieve

  a variety of different breathing patterns.

  A device for implementing any of the aforementioned patient ventilation techniques requires valves performing three basic functions. First, a mixing of the gases must be carried out in predetermined proportions, usually by using a mixing valve. Second a timer is required to provide a signal to control the pattern of induced respiration and the frequency of breaths, and thirdly, a throttle valve is required to adjust the volume of gas passing through each breath.

  three functions are generally performed by devices

  separate reils, which leads to a relatively large device with many working parts and many potential sources of breakdowns.

  makes different specifications of volumes and caden-

  these to implement the ventilation technique volu-

  metric compared to the specifications for implementing the VPPEF technique, and due to the limitations of the devices & valve currently used for this purpose, separate fans are necessary for the implementation of each technique Therefore, the investments required by these different types of fans in

  medical facilities are relatively expensive.

  Another disadvantage of current fans is that there is no precise feedback on the actual flow of the fan to regulate its operation. Normal fans generally have controls to select various ratios of gas mixtures and various rates of blowing, as well as for choose a model

  of flow among several models However, no indication

  a precise return of the actual flow rate is not provided and the

  fan flow model is limited to a few mo-

  specific models available in this fan However, most fans only allow very low

  variants of models and flow rates.

  It is therefore a main object of the present invention to provide a metering valve which allows both regulation of the ratio of gases inside the mixture, adjustment of the volumetric flow rate of the mixed gas and determination of the model of fan flow in one compact device, which can produce a rate

  flow corresponding to any waveform of signals.

  Another object of the present invention is to provide

  a particularly interesting mixing and dosing valve

  for use in medical ventilation devices for the sick, and which can be used for both

  volumetric ventilation and for pressurized ventilation

positive frequency at high frequency.

  Another object of the present invention is to provide a mixing and metering valve making it possible to measure and determine its actual flow rate in order to reassess and adjust the flow rate during the next flow phase if necessary, and which

  eliminates any unwanted movement of the provo-

  due to fluctuations in inlet pressures

and / or exit.

  Another object of the present invention is to provide a metering valve which can be used individually to regulate the volume and frequency of the flow of a gas, and which can be used in combination with another metering valve to regulate frequency and volume of flow and

  mixing two or more gases in the device.

  These objects are achieved according to the present invention by a proportional control valve connected to means for determining the actual position of its shutter, by

  example a linear variable differential transformer.

  In the preferred embodiment the proportional valve

  has an infinite number of indoor work positions

  of its operating range and can be connected

  to a microprocessor to control the frequency and the am-

  full opening, thereby adjusting the volume of gas passing through it and the frequency and pattern of gas flow The proportional control valve has a shutter to which a rod is connected; a solenoid

  receives electrical pulses creating an electro-

  magnetic which moves the rod and opens the valve

  gas flow rate and volume are controlled by

  dant the arrival of electric current to the solenoid and the electromagnetic field thus created The rod is connected to the core of the linear variable differential transformer and it moves this core according to the displacement of

  the shutter The displacement of the nucleus in the transforma-

  tor causes variations in its output voltage,

  which can be analyzed by standard microprocessors

  to determine the actual flow rate of the valve.

  phrasing inside the valve balances the pressures

  sions on either side of the shutter so that fluctuations in inlet and / or outlet pressures do not displace this element Two or more metering valves can be connected together to provide variable mixes of any volume and any frequency searched at

  inside the operating ranges of the valves.

  The invention will be better understood on reading the

  detailed description given below as an example

  only, of a preferred embodiment, with reference to the accompanying drawing in which FIG. 1 is a perspective view of a set of

  mixing and dosing valve used in a fan.

  FIG. 2 is a perspective view of the mixing and metering valve assembly, the cover being removed,

  showing the two mixing valves inside.

  Fig 3 is a top view of the assembly shown

  felt in fig 1, some of the hidden parts being

shown in dashes.

  Fig 4 is a side elevation view of the

  appears in Fig 1, some hidden parts being shown again in dashes; and Fig 5 is a large-scale sectional view along

line 5-5 of fig 3.

  We now refer to the drawing, and in particular to the

  fig 1 We see a set of mixing valve and do-

  threshold 10 used in a patient ventilator Cet

  assembly includes a valve body 12 with oxygen inlet

  gene 14, air inlet 16 and gas mixture outlet 18.

  Anodized aluminum alloys can be used as the suitable material for the body 12, although other materials can also be used. An oxygen metering valve 20 regulates the oxygen flow between the oxygen supply 14 and the outlet of the gas mixture 18, and an air metering valve 22 regulates the air flow between the air inlet 16 and the outlet of the gas mixture 18 An oxygen pressure tap 24 and a pressure tap 26 are arranged in the body 12 and a pressure tap

  outlet 28 is also provided The dtoxy- metering valve

  gene 20 and the air metering valve 22 are produced in a similar manner and perform similar functions to regulate the flow of gases between their arrival and the outlet of the gas mixture It is understood that one can use a metering valve individually to

  provide a predetermined flow of gas in any form of

  des selected Similarly, in a device with more than

  two gas inlets, three metering valves can be used

  ses or more to provide a calculated volumetric flow rate of each gas at a predetermined frequency and depending on all

  waveform model for obtaining mixtures varying

  various gases The achievement shown on the

  drawing, comprising two metering valves, is only an example

  full of an advantageous use of the present invention.

  The metering valves 20 and 22 are connected by wire bundles 30 and 32 respectively to electrical terminals 34, 36, 38 and 40 disposed on a support 42 Ce

  support can be stainless steel, aluminum or ana-

  log, and is fixed to the body 12 by screws 44, 46, 48 and 50 A cover 52 encloses the metering valves and the support and has holes 54, 56, 58 and 60 through which the terminals 34, 36 pass, 38 and 4 o when the cover is placed on the body 12 The cover can be an acrylic thermoplastic, such as

  methyl methacrylate, or any other suitable material

  required, and it is held on the body 12 by screws 62, 64, 66 and 68 It is understood that the shapes of the body 12 and of the cover 52 and that the position and orientation of the various inlets and outlets, as well as terminals

  may vary and the arrangement of parts

  these shown in the drawing is only given as

example.

  As previously mentioned, the oxygen metering valve

  gene 20 and the air metering valve 22 are made of

  similar way, and the description of the metering valve

  of oxygen 20 which follows also applies to the air metering valve 22 The oxygen metering valve will be described in more detail with particular reference to FIG. 5 and the parts of the air metering valve 22 which correspond to the parts described for the metering valve

  20 are designated by reference marks with indi-

  these premium similar to the benchmarks used for the valve

oxygen doser.

  The metering valve 20 comprises a valve 80, actuated by a proportional solenoid, with a shutter 82

  acting between passages 84 and 86 to regulate the flow

  oxygen between the oxygen inlet 14 and the outlet

  tie of the gas mixture 18 and a proportional solenoid 88 to move the shutter 82 in order to open or close the passage The valve 80 is connected to a linear variable differential transformer 90 which provides a signal

  voltage output can be interpreted by a micro-

  processor to analyze the position of element 82 and

  accordingly the volume and frequency of the transmission-

  oxygen supply between the oxygen inlet 14 and the outlet

of the gas mixture 18.

  The element 82 comprises a sealing element or seal 92 which cooperates with a seat 94 in the passage 84 to prevent oxygen from passing from the passage 84 to the passage 86 The element 92 is disposed on a shutter body 96 connected to a rod 98 which extends through the assembly

  of solenoid 88 and is connected to the different transformer

  rentiel 90 as described in more detail below A set of

  ble 100 extends from the element 82 in the direction opposite to the rod 98 and comprises a rod 102 in an open space 104 between the passage 84 and the passage 86 The space 104 in the body 12 extends through the outer face of the body and a cap 106, for closing the opening, made of a material similar to that of the body, is fixed on the latter

  by screws 108 A membrane 110 is mounted at the end

  stem tee 102 and is held there by a washer 112

  and a screw 114 We can use for the membrane of the ma-

  synthetic materials such as silicones or dacron.

  The diaphragm is arranged between the cap 106 and a shoulder

  116 in the body 12 and seals the volume between the cap and the body and also the end of the rod 102 The membrane is a rolling watertight seal without

  friction, which allows a balancing of the pressures

  on the shutter so that variations in the

  output pressure does not affect operation.

  The proportional solenoid 88 comprises a housing 130 screwed onto the body 12 by threads 132 and fixed in the body by a locking screw 134 Inside the housing 130 are housed a front annular assembly 136 and

  a rear annular assembly 138 between which is provided

  a magnet 140 A set 142 is arranged axially

  in assembly 88, and assembly 144 is arranged axially-

  ment in the assembly 142 The rod 98 extends through the assembly 144 and carries a membrane 146, applied by

  a nut 148 against the element 96 The membrane 146 is simi-

  membrane 110 and is kept applied against a shoulder 150 in the housing 130 by a retaining ring 152 The membrane 146 functions like the membrane

  to balance the pressure forces on arrival.

  Thus, the membranes 146 and 110 balance the pressure forces on either side of the element 82, so that the application of the element 92 on its seat 94 or its lifting are not affected by the differences in the strengths of

  pressure on either side of the element.

  The front annular assembly 136 comprises a ring 154 and a spring 156 disposed between the nut 148 and a shoulder 157 of the ring 154 The rear annular assembly 138 comprises a ring 158 and a spring 160 disposed against a shoulder 161 of the ring 158 The springs are

  strips of hardened spring steel which bend when

  that the element 92 is distant from the seat 94 and which move the rod axially to return the element to its seat when the excitation current of the proportional solenoid

  is cut The assembly 142 comprises a coil 162 with a coil

  swims with magnetic wire in area 164 Wires 166 and

  168, which are part of a bundle 30, start from the set

  ble 142 and can be connected to a power source

  electric through the pre-

  cited The assembly 144 comprises a frame 170, a plate

  that of armature 172 disposed on the armature and separated from the spring 156 by a shim 174 The armature is screwed onto the rod 98 and moves this rod axially in response to the field created by the assembly 142 and the magnet when a current is applied to assembly 142 by the

  sons 166 and 168 Therefore, by controlling the electric field

  element created, element 92 can be moved from any distance

  tance of its seat 94 within the operating range of the valve, and it can be maintained in

  open or closed position for the desired time.

  The valve can be opened quickly, slowly, or in stages, and can be held in

  any position partially open or completely open or

  green for any desired time Therefore, any form of gas flow waves can be created through the valve. The assembly 90 comprises a support 190 connected to the

  linear variable valve and transformer

  area 192 held in the support by a locking screw 194.

  Voltage input and output conductors, identified as a whole in 196, which are also part of the

  harness 30, extend from the transformer to the electrical terminals

  and can be connected to a microprocessor to compare the voltage output with the voltage input for the interpretation of the valve flow.

  feels a flange 198 which starts from the main body cy-

  lindrique of the support to the housing 130 The flange is disposed against the end of the ring 158, and a

  wavy washer 200 is arranged on top of the collar

  lerette 198, while a spacer 202 is disposed on top of the washer The transformer is held by a retaining ring 204 disposed in a groove of the

  interior surface of the housing 130.

  The linear variable differential transformer is a classic structure in which the position of a

  axially movable core 206 is detected by comparing the

  voltage input at the voltage output of the device A suitable type is an electromechanical transformer, having a ferromagnetic core and a primary winding and two secondary windings on a coil The core can move axially and causes a change in

  the voltage induced in the secondary windings during

  that current is applied to the primary winding The voltage from the output terminals is proportional

  displacement of the nucleus When using such an arrangement

  In the present metering valve, the axially movable core of the linear variable differential transformer is connected by a pin 210 to the rod 98 Therefore, the axial displacement of the rod when the valve opens and closes displaces the transformer core , changing

  thus the output voltage of the transformer.

  The output voltage can be interpreted by a microprocessor which controls the operation of the solenoid-controlled valve assembly, and we obtain

  thus an indication in return of the actual flow rate of the valve.

  The microprocessor knows the characteristics of pres-

  gas flow rate, as well as the position of the valve element 82 by interpreting the valve flow rate A nut 212 is placed on the rod 98 on the opposite side

  of the spring 160 with respect to the spindle 210 This comprises

  carries a shoulder 214 on which is arranged a round

  delle 216 A spring retaining element 218 is disposed on the pin 210 and is connected to an inwardly extending portion 220 of the support 190 A spring 222 is

  disposed between the retaining element 218 and the washer 216.

  The spindle slides axially in the retaining element 218 when the rod 98 moves axially; therefore, when the valve opens, the element 92 moving away from

  its seat 94, the spindle 210 is moved towards the transformer

  differential dies, thus moving its axial nucleus

  and modifying the output voltage of this transformer.

  The air metering valve 22 is similar to the oxygen metering valve; therefore, it will not be given

  detailed description For clarity, several

  parts of the air metering valve 22 have been shown in FIG. 5 and are designated by the same references as the corresponding parts of the oxygen metering valve

  , but assigned prime indices A passage 230 from

  from the air metering valve intersects the passage 86 at the outlet of the gas mixture 18 Therefore, the oxygen passing through the valve 20 meets and mixes with the air having passed through the valve 22 at this outlet of the gas mixture 18 Feet 232, 234, 236 and 238 can be arranged under the body 12 and, if these feet are connected by thread to the body, they can be adjusted to put

the level valve assembly.

  When using a mixing and dosing valve

  according to the present invention, the arrival of oxygen 14 and

  the air inlet 16 are connected to sources of these gases.

  Appropriate connections are made between the terminals

  nes 34, 36, 38 and 40 a microprocessor and an electric current source to provide an electrical input to the solenoid assembly 88 and a voltage input and

  output connections to the differential transformer 192.

  In the stop or rest position, when no current arrives at the solenoid assembly 88, the springs 156, and 222 maintain the rod 98 in a position such that the element 92 is applied to its seat 94, and that the oxygen arriving by the arrival of oxygen 14 cannot cross the space 104 and the passage 86 until the exit 18 When an electric current arrives at the set of

  solenoid, causing the creation of an electromagnetic field

  tick, the rod 98 is moved axially due to the displacement

  axial cementing of the armature 170 to which the rod is connected

  roped Element 92 is lifted from its seat 94, allowing

  both oxygen to pass from passage 84 to passage 86 through space 104 The strength of the field required to move the rod is determined by the force of the springs

  156, 160 and 222, and the distance which element 92 is under

  lifted from its seat 94 is determined by the strength of the field created in the solenoid assembly Thus, the volume of gas passing through the valve is regulated in part by the degree of opening of the valve which is controlled by the force of the electromagnetic field, and in part by the valve opening time This remains open until the current applied to the winding is interrupted and the electromagnetic field ceases In this case, the springs 156, 160 and 222 move the rod 98 axially Until the element 92 comes to apply on its seat 94, thus preventing any gas flow through the valve It is clear that it is possible to create in the present valve any form of gas flow waves by simply controlling the characteristics of the electromagnetic field created in the solenoid For example, an abrupt arrival of high voltage at the winding will move quickly

  the valve element to a fully open position

  tale As a variant, the current arriving at the winding can first of all be moderate and increase regularly, whence results a slow opening of the valve; or else the electromagnetic field can be first of all moderate and maintained at this level, with a subsequent increase, from which results a low gaseous volumetric flow followed by a higher volumetric flow One can similarly create other variations in the gas flow characteristics and volume Therefore, when used in a ventilator, the metering valve can provide gas for both positive and high frequency positive pressure ventilation, and only one can be used fan for both techniques,

  thus creating virtually any wave of inspira-

tion desired.

  The axial movement of the rod 98 is directly

  transmitted to the axial movement of the core 206 in the transformer

  differential die 192, by the fact that the pin 210 is connected to the rod and to the core Thus, when the valve element 92 is lifted from the seat 94, the core 206 is moved axially in the differential transformer 192 and the voltage output of this transformer changes the

  changes in the voltage leaving the transformer

  respond to changes in the position of the valve element 82 Thus, the exact characteristics of the valve flow and the exact waveform of this flow are reflected by changes in the voltage exiting the transformer The microprocessor controlling the current

  arriving at solenoid assembly 88 can also receive

  see and interpret the voltage signals going and coming

  from the differential transformer to interpret the valve flow and make the necessary adjustments

  in the current arriving at the solenoid assembly.

  The air metering valve 22 functions like the oxygen metering valve 20, and the air which passes through it enters the passage 230 and meets the oxygen coming from the passage 86 at the gas mixture outlet 18 Thus, by regulating the flow of the gases through each valve, we can obtain precise proportions of each gas in the mixtures at the outlet 18 We can obtain 100% oxygen

  or air simply by not sending electric current

  than to the valve solenoid assembly for the unwanted gas, so that the valve does not open and that only the gas from the other valve reaches the outlet 18 Normally in a respirator, the two valves open during the same time when mixed gas is required To vary the proportions of oxygen and

  air in the gas mixture, the distances

  valve elements are lifted from their seat are ordered

  so that a larger volume of the desired gas in a larger percentage will pass through the corresponding valve

until exit 18.

  One can use a metering valve according to the present invention to regulate the flow of a gas in a device and one can obtain with it any wave form of a

  flow model for gas, in addition to an indication signal

  In return which can be used to analyze the exact flow rate of the valve In devices through which more than two gases pass, three metering valves or

  more, namely a metering valve for each of the gases.

Claims (17)

  1 metering valve for supplying a determined volume of gas at determined intervals, characterized in that it comprises a body (12) with inlet (14) and outlet (18) openings; a passage (84, 86) between these openings, a shutter (82) for controlling the flow of a gas through this passage, means (88) for moving this shutter by a determined distance, for a determined duration and thus open the passage and measuring means (90) to determine the position of this shutter   and, therefore, the gas flow through the valve.   2 Metering valve according to claim 1, in la-   which rod is connected to this shutter and the   means for moving this shutter comprise a solenol   of to create a magnetic field causing a displacement axial of the rod.   3 Metering valve according to claim 2, in la-   which the measuring means comprise a linear variable differential transformer with an axially movable core, the axial displacement of which causes variations in the   transformer output signal, and the rod is connected dedicated to this nucleus.   4 Metering valve according to claim 1, in la-   which the measurement means comprise a linear variable differential transformer with an axially movable core, the axial displacement of which causes variations in the output signal of this transformer, the shutter being connected to the core.   Metering valve according to claim 1, in which the body has a second inlet, a passage from this second inlet intersects the passage from the first inlet, a second shutter controls the flow of a gas through the second passage, means   are provided to move the second shutter of a device   tance chosen for a chosen duration and open the two   x pass, and a second measurement means is provided to calculate the position of the second shutter and in   Consequently, the gas flow through this valve.   6 Metering valve according to claim 5, in la-   which the means for moving the shutters to open the passages comprise rods connected to these shutters and to the solenoids creating electric fields   magnetic causing the axial displacement of these rods.   7 Metering valve according to claim 6, in la-   which measurement means include transformers   linear variable differentials with axially movable cores   Lement, these rods being each connected to each of transformer cores.   8 Metering valve according to claim 5, in la-   which measurement means include transformers   linear variable differentials with axially movable cores-   ment, each shutter being connected to each of the cores transformers.   9 Metering valve, characterized in that it comprises a body with inlet and outlet openings and a passage between these openings, a shutter to control the flow of a fluid through this passage, a solenoid to create an electromagnetic field, a rod connected to this shutter and passing through the solenoid assembly, the electromagnetic field causing the axial displacement of the rod to move the shutter and open this passage, a linear variable differential transformer connected to this solenoid assembly and having a core connected to said   rod, the axial displacement of the rod causing the displacement   axial cementing of the core to vary the voltage leaving the transformer and obtain a return signal indicating   the actual flow rate of the metering valve.   Metering valve according to claim 9, in the-   which solenoid assembly has a housing, front and rear rings disposed in the housing, a   magnet placed in the housing between the rings, a   bearing arranged axially in this magnet and in these   rings and an axially movable frame in the winding- and connected to the rod.   Il Metering valve according to claim 9, in the-   which a spring is connected to this rod for the   place axially and apply the shutter to its seat in the passage when the electromagnetic field is interrupted.   12 Metering valve according to claim 9, in the-   which one pin is connected to the core of the transformer and extends outwards, the rod being connected to this pin.   13 Metering valve according to claim 10, in la-   which a support is fixed on the housing, transforms it   being placed in this support.   14 Mixing and dosing valve, characterized in that it comprises a body with two gas inlets, a gas mixture outlet and passages from one   from the arrivals to the exit, the shutters in the   ges to control the flow of gases through these passages, solenoid to move these elements independently of each other by preselected distances during   preselected durations, and measurement means   strung to each of these shutters to determine their   position and actual flow rate of the valve.   Mixing and metering valve according to claim   14, wherein each of the solenoids has a coil   and an axially movable armature, the winding creating an electromagnetic field causing displacement   axial of the armature, a rod being connected to this arma-   one of the shutters, the measuring means being connected to this rod.   16 Mixing and dosing valve according to the claim   tion 15, in which each of the measuring means comprises   carries a linear variable differential transformer with an axially movable core, the axial displacement of which causes changes in the voltage exiting the transformer to determine the actual flow rate of the valve, each of these   cores being connected to a rod.   17 Mixing and metering valve according to claim 16, in which membranes are arranged on either side of each of these plugs to balance   the pressure forces at the arrival and at the exit.   18 Mixing and dosing valve according to the claim   tion 16, in which housings are connected to the body, the solenoids being arranged in these housings,   supports being connected to these housings and trans-   trainers being arranged in these supports.   19 Mixing and dosing valve according to the claim   tion 16, in which springs are connected to these rods to move them axially and close the passages   when the electromagnetic fields are interrupted.   Metering valve to deliver a selected volume of gas at selected intervals, volume and intervals   being set in response to the actual through flow prior to   the valve, characterized in that it comprises   a body with inlet and outlet openings, a passage between the openings, a shutter for controlling the flow of a gas through this passage between the openings, means for moving this shutter by a chosen distance for a period of time chosen to open this passage, measuring means to determine the gas flow through this valve and to provide a commanding signal   the means of movement of this shutter.   21 Metering valve according to claim 20, in which a rod is connected to the shutter, the means for moving this shutter comprising a solenoid for axially moving the rod in response to a signal supplied to the solenoid, the signal of the measuring means influencing   the signal supplied to the solenoid and the movement of this obtuse   rator. 22 A metering valve according to claim 20, in which the body has a second inlet, a passage going from this second inlet intersects the passage coming from the first inlet, a shutter is arranged in the second passage to control the flow of a gas the through, means are connected to the second shutter to move it by a chosen distance for a selected time and open the second passage, and second measuring means being provided for determining the flow of gas through the second passage and providing a signal controlling the means of movement of the second shutter. 23 Mixing and metering valve, characterized in that it has a body with two gas inlets, a gas mixture outlet and passages from the inlets   at the outlet, shutters in these passages for control   der the gas flow passing through them, solenoids to move these shutters independently of each other   over preselected distances for pre-   selected, and measuring means to determine   the gas flow through each of these passages and provides   set signals to tune solenoids in response to actual valve flow.   24 Mixing and dosing valve according to the claim   tion 23, in which each solenoid has a winding   and an axially movable armature, the winding creating an electromagnetic field for axially displacing the armature, a rod being connected to this armature and to one of the shutters.