DE2116197A1 - Pneumatic displacement pilot valve - Google Patents

Description

* Patent attorneys DIpK-In π. R. BEETZ sen. Dlpl-Inj ;. K. LAMPi-JECHT

Dr.-Ing. Π. D ί ETZ Jr.
Munich 22, Stefnsdorfetr. 10

81-16.857P (16.858H) 2, 4th 1971

HITACHI / LTD., Tokyo (Japan)

Pneumatic displacement pilot valve

The invention relates to a pneumatic displacement pilot valve which is used as a pneumatic amplifier in a pneumatic measuring and control device.

State of the art

Two types of pneumatic pilot valves are known so far, namely, displacement pilot valves and force balancing pilot valves. In the following, let us begin with the The difference between the two types is described.

Fig. 1 shows a basic design of the previously known pneumatic displacement pilot valves, and

81- (Pos 2U8i3) Bgn-r (7)

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Fig. 2 shows a block diagram illustrating the operation of the represents the pilot valve shown in Fig. 1.

In Fig. 1, the reference number 1 denotes the housing of the pilot valve and the number 2 denotes a pressure sensor - here a membrane - which, under the action of an input pressure Pjj, moves a valve spindle 9 and an outlet valve closure piece 3, which is firmly connected to the valve spindle 9 and an air duct limited on the outlet side »The character h means an air supply valve closure piece, which is arranged between the valve spindle 9 and a compression spring 11 and delimits an air duct on the air supply side. Closure piece 3 delimits an outlet channel, and the supply valve seat is designated by 6, which delimits a supply channel with the supply valve closure piece h . Furthermore, the symbol 7 denotes an inlet pressure chamber, the symbol 8 an air supply chamber, the symbol 12 an output chamber for outputting an output _{pressure P 0} and the symbol 10 an outlet chamber which leads to the ambient air pressure P.

In the design described, an input pressure PP "is exerted on the pressure sensor 2 and converted into a force Fi, and this force Fi in turn acts against the spring force (this is made up of the spring force of the compression spring 11 and the elastic force of the diaphragm 2). and moves the outlet valve 3 and the supply valve h. By the movement of the supply valve and the outlet valve closure body change .the distances between the valve closure pieces 3 and h on the one hand and the

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Valve seats 5 and 6 on the other hand, and thereby change the amount flowing from the supply chamber 8 to the outlet chamber 12 and that from the outlet chamber 12 to the outlet chamber 10 pouring crowd. As a result of this change in the flow rate, the output pressure P_ changes. That so The built-in pilot valve that acts in this way is called a displacement pilot valve.

As can be seen, the displacement pilot _{valve determines the output pressure P Q} by the difference between the air supply amount, which is supplied from the gap formed by the supply valve closure body k and the supply valve seat 6, and the air outlet amount, which is through the the gap formed by the outlet valve closure body 3 and the outlet valve seat 5 goes.

Fig. 2 shows a block diagram of the operation of the pilot valve shown in Fig. 1 · In this formula P _n acting on the pressure sensor Z inlet pressure, the effective area of the pressure sensor 2, S ₁ a spring constant (kg / cm), KQ _{1 is} a coefficient, which is represented by the relationship between the outlet pressure and the movement of the plug of the outlet pressure valve. As can be seen from the drawing, one of the features of the positive displacement pilot valve is that there is no return means.

FIG. 3 shows a basic design of the previously known force compensation pilot valves, and FIG. 4 shows FIG. 3 is a block diagram showing the performance of the one depicted in FIG Represents pilot valve.

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When an input pressure P _n acting on the pressure sensor 202 of the pilot valve shown in Fig. 3, this so'wird in the force F. converted, and this force is gen ge the composite spring force (composed of the elastic force of the inlet pressure sensing diaphragm 202 , also from the elastic force of the output pressure from feeling diaphragm 2 Oh and the force of the compression spring 206) and moves the closure piece 203 of the outlet valve and the closure piece 205 of the supply valve.

™ If the inlet pressure P "is greater than that through

the movement of the outlet valve plug 203 and the supply valve plug 205 equalized pressure, then there is a gap between the supply valve plug 205 and the supply valve seat 207, but there is no gap between the supply valve plug 205 and the outlet valve seat 208 be. Venn, however, the inlet pressure is less than the equalized pressure, then there is a gap between the supply valve closure piece 205 and the outlet valve seat 208 edge no gap between the supply valve closure piece 205 and the supply valve seat 207 present. If the inlet _{pressure Ρ ΛΤ is} greater than

When the pressure is equalized, the supply valve plug 205 is pressed downwards (in the drawing) and the supply pressure P _e increases the air flow from the supply pressure chamber 211 to the output pressure chamber 210, and the output pressure P_ increases . The output _{pressure P Q} acts on the output pressure sensor 20 ^, and this is _{pressed in the opposite direction to the effect of the supply pressure P n} , and thereby the supply valve closure piece 205 is pressed onto the supply valve seat 207. If then the force F ., which the input pressure P _n on the input

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pressure sensor 204 exerts, equal to the force F _Q , which the output pressure P_ exerts on the output pressure sensor 20 * 1 ·, then the supply valve closure piece 205 sits tightly on the supply valve seat 20? and exhaust valve seat 208. So the pilot valve comes into its balanced position.

Further, when the inlet pressure is less than the balanced pressure, a gap is formed between the supply valve closure piece 205 and the outlet valve seat 208, as described above, and the air contained in the outlet pressure chamber 2to is through the outlet pressure chamber 209 let out into the outside air. If the force F exerted by the input pressure P on the input sdruek sensor 202 then becomes _{equal to the force F Q exerted by the output pressure P Q} on the output pressure sensor 204, then the supply valve closure piece 205 is seated on the supply valve -Seat 207 and the exhaust valve seat 208 on. So the pilot valve comes into its balanced position.

In short: the output pressure P_ is determined by the Difference between the amount of air coming from the supply valve plug piece 205 and the gap formed by the supply valve seat is supplied, and the amount of air that through that of the outlet valve seat 208 and the supply valve plug 205 formed gap flows out. With this type of pilot valve, that of the inlet pressure sensor Force exerted by the elastic force of the inlet pressure sensor diaphragm, by the force of the supply valve spring and counterbalanced by the elastic force of the outlet pressure sensing diaphragm. Another characteristic of the force

1Ö9842 / 1319

Balancing pilot valve consists in that when the pilot valve is balanced, the supply valve closure piece 205 sits sealingly on the supply valve seat 207 and on the outlet valve seat 208. The equilibrium state mentioned herein means that F, = F., where F, equals the product of the inlet pressure P "and the effective area A_ of the Einarigsdnick sensor 202 and F _Q equals the product of the outlet _{pressure P 0} and the effective Area A _{0 of} the outlet pressure sensor 204 is «

FIG. Jf shows a block diagram of the mode of operation of the pilot valve shown in FIG. 3. The reference _{symbol S 2} therein denotes a spring coefficient of the overall system * the pilot valves of FIG. 2 and the reference symbol KQ ₂ denotes a coefficient of the stroke movement of the valve at the output pressure P, which is determined by the ratio between the external pressure and the valve lift for the output pressure. The reference symbol A_ indicates the effective area of the outlet pressure sensor. One of the features of the force balancing pilot valve is that there is a return action.

P As described above, the displacement pilot valve has no feedback device and therefore permanent air loss, but the force compensation pilot valve is a feedback device and therefor no air losses

As a result of that difference in the feedback system, the air consumption is different for the two types of pilot control valve. That means ι the air consumption of the displacement pilot valve is about 0.2 to 1.5 Nm / h, but with the force compensation pilot valve about 0.2 to 0 _t k Nm / ho

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With regard to air consumption, therefore, there is the force balancing pilot valve cheaper.

However, the type of force compensation pilot valve is less favorable than the displacement pilot valves 5 because the force equalization pilot valve is a complicated one Construction necessary, e.g. B. between the output pressure camera 210 and the outlet pressure chamber 209 arranged outlet pressure sensor 20 ^ and the slot in the outlet valve closure set be present and extend from its lower end face to the outlet pressure chamber 209 got to.

Summary of the invention

A primary object of the invention is to provide a positive displacement pilot valve to create that is built just as simply as the well-known valve of this type and with less air consumed"

dThe well-known, displacement pilot valve has except the above-mentioned disadvantage of high air consumption Disadvantages that it responds only slowly and that it is different when the output pressure increases than when the output pressure decreases β responds. Therefore, a second object of the invention is to provide a positive displacement pilot valve which responds quickly.

The third object of the invention is to provide a positive displacement prop To create a control valve that responds equally quickly in any case, whether the output pressure increases or decreases.

1 Ö 9 8 4 2/1 3 1 p

2116-97

A fourth invention would be a positive displacement pilot valve to create that is insensitive to fluctuations in the supply pressure "

The invention thus relates to a displacement pilot valve.

The invention consists in that it contains in a common housing:

w 'an inlet chamber into which an inlet pressure is introduced,

an air supply pressure chamber into which air is pressurized is introduced,

an outlet pressure chamber which air from the air supply pressure chamber receives and emits an output pressure proportional to the input pressure,

an outlet pressure chamber leading from the inlet chamber separated by a membrane and with the output βpressure-Kamfc connected to the outside air,

a valve rod, at one or the other end are attached '

an outlet valve closure piece which is fastened at one end to the membrane and delimits an outlet channel, which leads from the outlet chamber to the outlet chamber, and

an air supply valve closure piece that provides an air

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supply channel limited »the -from the air supply pressure chamber leads to the exit chamber, as well

a compression spring, which is in the air supply chamber located valve rod "pushes towards the membrane, with the outlet valve plug and the air supply valve plug are freely movable in and out of the exit chamber »

Brief description of the drawing It show *

Fig. 1 shows the known, constantly air-consuming displacement pilot valve in vertical section;

FIG. 2 is a block diagram showing the operation of the pilot valve shown in FIG shows}

Fig. 3 the known, not constantly consuming air Force compensation pilot valve in vertical section?

Fig. H is a block diagram showing the operation of the dargd in Fig * 3 tellten Before st pilot valve s;

Fig. 5 shows an embodiment of the invention Pilot valve in vertical section;

Fig. 6 shows the closure body and the seats of the in Fig.

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pilot valve shown in the same section on a larger scale;

7A to 7C show the pilot valve shown in FIG. 5 in operation in different phases of operation;

8A to 8D show several other modified ones Embodiments of the pilot valve according to the invention;

9 shows yet another embodiment of one according to the invention Pilot valve in vertical. Cut;

10 shows the characteristic of a displacement pilot valve according to the invention. with only low internal air consumption compared to the characteristic curve the usual displacement pilot valve with constant air consumption;

11 is a diagrammatic representation of a return device with a pilot valve in a pneumatic measuring or control device; °

12 shows a device in which there is a Pilot valve is used in its main parts together with the pilot valve according to the invention in schematic section;

13 A to 13 C are diagrams of the characteristics of the invention Pilot valve, which

10904 2/1 3 1 β '

flow of the baffle plate and the nozzle to the outlet pressure the pilot valve depending on the fluctuation in the supply pressure;

Fig. Ik is a graph showing a characteristic curve showing the relationship between the supply air pressure and the output air pressure in the pilot valve, and

FIG. T5 is a diagram of the combination of the inventive Pilot valve that is not influenced by fluctuations in the supply pressure.

Description of the Preferred Embodiment

Fig. 5 shows an embodiment of the pilot valve according to the invention in section. The reference numeral 501 denotes a housing of the valve, 502 a pressure-sensing component such as, for example, a valve body. B.eine membrane, which moves a valve closure member 503 according to the input pressure PN, 504 an exhaust valve-closure member, which forms an air passage on the outlet side chlußstück 505 a Zufuhrventil- Vers, which forms an air duct on the air supply side, 506 an exhaust valve Seat which, together with the exhaust valve seat $ 0k, forms an exhaust port, 50? a supply valve seat which, together with the air supply valve closing piece 505, forms an air supply channel, 508 an inlet pressure chamber, 509 an air supply pressure chamber, an outlet pressure chamber, 511 an outlet pressure chamber, 512 a compression spring which presses the valve closing piece 503 against the diaphragm , P _{g is} a supply pressure, PN is an input pressure, P _{Q is} an output _{pressure and P A is} the outside air pressure.

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Fig. 6 shows the closure body in detail and the seats of the pilot valve shown in Fig. 5, and Figs. 7A to 70 show the operation of these valve parts in operation, namely Fig. 7A in that Phase in which the inlet pressure is not yet balanced * Fig. 7b in the phase in which the valve is balanced and Fig. 7C in the phase in which the excessive thing pressure acts on the valve.

In Fig. 6 and 7A-7C, the reference numeral 513 denotes an air supply channel formed by the air supply valve closure piece 505 and the air supply valve Sitζ 507, furthermore the symbol 51 ^ a leakage outlet gap formed by the valve closure piece and the valve seat 519, which determines the amount of leakage at the time of the force equalization, the character 515 (Fig. 7A) an air supply leakage gap formed by the valve closure piece 503 and the valve seat 519, which determines the amount of leakage before the force equalization, and the character 5-1-6 one of the air supply valve closure piece and the air supply valve Seat 507 formed air supply gap, which determines the amount of air supply when an excessive inlet pressure acts on the valve.

Furthermore, one of the essential features of the valve according to the invention is to be dimensioned in such a way that the relationship dg> d ₁ and h ..> hg is satisfied, of which d_ is the diameter and hud the height of the outlet pressure chamber 510 of the housing 501 and d .. the diameter and h ₁ the total height of the valve closure piece 503, as shown in FIG. is shown mean.

If the inlet pressure P «is now in the inlet pressure

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Chamber 508 enters and the valve closing piece is brought into its balanced position, then the diaphragm 502 depresses the valve closing piece 503 by virtue of this pressure. Then the valve closing piece 503 comes to a standstill in that position in which the elastic force of the diaphragm 502 is equal to the force of the spring 512. Such a balanced state is shown in FIG. 7B. As a result, the air supply _{amount Q 0} and the leakage output amount Q. result from the size of the air supply channel 513 and the size of the leak outlet channel 513, which in turn are determined by the position of the valve closure piece 503. So the output _{pressure P Q} is controlled by the input pressure P ".

As long as the inlet pressure P "is not yet balanced with the air supply, the air supply _{pressure P g} acts on the cross-sectional area of the valve closure piece 503 and, in cooperation with the spring 512, presses the valve closure piece 503 upwards, and the air supply channel 513 takes the form of an air leakage gap 515 and the air outlet channel the side 518 as shown in Figure 7A. In this position, the air supply amount is extremely small and the air discharge amount is increased; this improves the response of the valve during exhaust.

If an excessively large inlet pressure comes into the inlet pressure chamber, then the air supply channel 513 t widens as shown in FIG. 7C at 516; the leakage outlet gap 51 ^ increases its resistance, and consequently the leakage outlet amount decreases by an effect similar to that described above in the explanation of the unbalanced condition.

1 Ö 8 8 4 2/1 3 1 9

As a result of the process described above, ie thanks to the design that the outlet channel is normally narrowed by the valve closure piece, the air consumption is extremely small. With the pilot valve according to the invention, the air consumption can be reduced to less than i / OK of the consumption of a conventional displacement pilot valve of the same sensitivity. The main object of the invention is thus achieved. Since the outlet valve closure piece and the air supply valve closure piece si ^ h can move freely in the outlet pressure chamber, the valve closure piece can move proportionally to the level of the inlet pressure s P _n . Furthermore, the valve lift can be made very large. Thanks to the design of the valve closing piece described, the response time is shorter than with the usual pilot valve. In this way, the second inventive task is also fulfilled.

Furthermore, the pilot valve according to the invention has the Advantage that if the valve plug is made of light metal, the valve lift is made very large kanne Since the air outlet quantity remains constant regardless of whether the input pressure PN rises or falls, there is there is no difference in the speed of operation or Response speed of the valve closure, regardless of whether the closure rises or falls. So is also fulfilled the third task of the invention.

10 shows a diagram of the characteristics of a conventional displacement pilot control valve that constantly consumes air and of a displacement pilot control valve according to the invention with only low internal air consumption (the The amount of leok in this valve is remarkably small compared to

100842/1 3 1 NC

over the conventional pilot valves) · It means ■ "'l ^x

reference numeral Q _Q by air flowing amount of the off ** '' 'input side, Q. the Ausiaß air quantity (which is the Le okmenge), A is a characteristic of the relationship between P _n and Q ₀ in the conventional pilot valve, B is a characteristic curve of the · ■ '■■ Relationship between P _n and Q ₀ in the pilot control valve according to the invention, (a) a (P "-Q.) Curve, of the conventional ^? ^ ^! Pilot control valve and (b) a (P _{w -Q.)} .) - Curve of the invention ^

JW ** ~ -i

appropriate pre control valves. Vie can be seen from A in Fig. 10, 'J'" ¹ *

takes Q _Q even if P _{n is} greater than a certain - ¹ M- ']'

Veite does not increase and increases Q. when P _n increases «IV

down to zero. £ Ί

The reason for the described behavior of the pilot valve according to the invention is that, while in the conventional pilot valve as a result of the stabilization of the inlet pressure PN, the outlet valve * closure piece 3 shown in FIG. 1 sits sealingly on the outlet valve seat 5 and the air outlet amount is zero, in the case of the J 'according to the control valve, the outlet valve closure piece - * ¹ * 50h and the air supply valve closure piece 505 depending on' the fluctuation of the input base P _n freely in the output pressure chamber 510 and can enter. Therefore, in the pilot valve according to the invention, there is no shut-off of the outlet air at any position, as is the case with the conventional valve. It will therefore be easily understood that the valve _{according to the invention responds more quickly to the input pressure P n} than the conventional valve under otherwise identical conditions.Furthermore, since V is the amount of leakage air in the pilot valve according to the invention, as described above, it will be easily understood that the discharge amount is represented by curve b. - *

OWfQINAL INSPECTED

106842/1319

Pig, Figures 8A to 8D show several different embodiments of the valve closure piece used in the pilot valve according to the invention. In the different Embodiments, the reference numeral 803 denotes a closure piece, 8O4 an exhaust valve plug, 805 an air supply valve plug and 801 the housing of the pilot valve. The valve and the outlet pressure chamber can Any of those shown in Figures 8A-8D Have shapes. Of course, many others can too Shapes of the valve and the outlet pressure chamber in the invention Pilot valve are used} they fall within the scope of the invention.

Fig. 9 shows yet another embodiment of the pilot valve according to the invention, in which the valve seat consists of elastic material.

In FIG. 9, those components which are equivalent to the components of the valve shown in FIG. 5 are given the same reference numerals as in FIG. 5. A chamber formed by two elastic diaphragms 905 and 906 is an outlet pressure chamber. Except for this chamber, all other parts are the same as those in FIG used within the scope of the invention.

Now let the design of the displacement force compensation pilot valve, which achieves the fourth object of the invention.

It works in general with pneumatic measuring and control devices Fluctuation in air supply pressure (usually

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ORIGINAL INSPECTED

1.2 to 1.6 atu) in fluctuations in the outlet pressure at the baffle plate, the nozzle and the pilot valve. 11, the reference symbol Z denotes an input signal, the symbol 111 denotes a transducer, 112 a baffle plate * · nozzle, 113 a pilot valve, 114 a return device, P _g the air supply pressure, P "a nozzle back pressure, P _Q the output pressure and G ₁ the gain.

Normally, as the air supply _{pressure P g} decreases, the nozzle back pressure P _n and the outlet pressure Pq also decrease. If the gain G i of the return loop is made large enough, the output pressure fluctuation becomes smaller as i / (i + G ₁ ). If, however, the degree of gain G _{1 is made} large, the system becomes unstable and can excite itself. Therefore the value G _{1 is} limited. This also applies in the event that the air supply pressure increases »

According to the invention can be in a system that a flapper nozzle and a pilot valve are used, a pilot valve of simple design that is insensitive to fluctuations in the air supply pressure By appropriately shaping the cross-section of the air supply valve of the displacement pilot valve, that when the air supply pressure falls, the outlet pressure increases and this increase compensates for the decrease caused by the baffle plate nozzle. Even if as the air supply pressure increases, the same effect can be obtained.

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In Fig. 12, reference numeral 501 denotes a housing, 531 a pressurized air supply pipe, 520 an air pressure supply port, 523 an output pressure port, 524 an exhaust port, 525 a nozzle back pressure (input pressure) introducing port, 526 and 52 ? two lines introducing the nozzle back pressure, 509 an air supply pressure chamber, 512 a compression spring, 505 an Luftaufuhrventil-Versohlußstück, 503 a valve rod, 507 ednen air supply valve seat, 506 an exhaust valve seat, 50 ^ an exhaust valve integrally connected to the valve rod 503 -Closure, 5 ' ¹ O an outlet pressure chamber, 508 an inlet pressure chamber-

™ mer "which leads to the nozzle back pressure, 502 a membrane, 528 a throttle, 529 a nozzle, 530 a baffle plate, P _g an air supply _{pressure, P Q} an outlet pressure, P. the outside air pressure and P" a nozzle back pressure (inlet pressure). When the nozzle back pressure P _n in the Dttsenriickdruck chamber (inlet pressure chamber) 508 occurs, then by virtue of this pressure forces the diaphragm 502, the exhaust valve Verschlußstüok 50k _t the valve rod 503 and the air supply valve-closure member 505 upwardly (in Fig. 12 ) and comes to a standstill in a position in which the compressive force is balanced by the spring force of the compression spring 512. Depending on the distance between the air supply valve closure

& piece 505 and the air supply valve slot 5Ο7 and the distance between the exhaust valve closure piece 504 and the exhaust valve seat 506 "in this standstill position, the air supply amount, the amount of Aassan and the amount of discharge are determined · So the output pressure P _Q controlled by the nozzle back pressure P "If the loaded side of the outlet pressure P _Q is not opened to the outside air, the following equation is fulfilled in the balanced state!

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P _0. «G (X) .XP _S (1)

where g (x) is a function representing the valve characteristic, X is a displacement of the valve end piece and P- a Air supply pressure is. X is represented by the following formula

X = (P "A" - P _S A _V ) / S

where S is a spring constant, A- is an effective area of Diaphragm 502 and Ay one through the diameter of the valve seat certain area is "

Further, if the output _{pressure P Q} changes by A ^ ₀ when the air supply _{pressure P g} changes by APg, the relationship between Δρ_ and ΔP _{Q is} represented by the formula

^K P · ¹ D

where AP ' _{o is} a fluctuation in the output associated with the increase in the air supply, which is caused by the fluctuation in the air supply _{pressure Ap g} , and ÄP "a fluctuation in the OUsen back pressure associated with the fluctuation in the air supply pressure ΔΡ _{Ο and K p} a gain in the pilot valve is·

Although the second term of the formula (2) and the second and third terms of the numerator of the formula (3) have so far been neglected one can be the second link of the

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ORIGINAL INSPECTED

-. 20 -

Make formula (2) equal to the first term of formula (2) by taking the area A-. appropriately sized. For example, when the air supply _{pressure P g} is changed by Δ Pg, the nozzle return pressure P "changes by Δ P _n , as shown in FIG. 13A. By changing Δ P _{n of} the back pressure of the nozzle, the output pressure P _Q is changed by ΔP _Q , as in FIG. 13B. Accordingly, as shown in FIG. 13C, the change Δρ ″ in the air supply pressure P ″ changes the output _{pressure P_ of the pilot valve by ΔP Q1} as a result of the influence of the nozzle back pressure. On the other hand, the air supply pressure variation Δ Ρ "results in a variation - Pq A as shown in Fig tk shown ~..

The size of the valve seats 507 and 506 and the diameter of the throttle 528 and nozzle orifice 529 are other factors in the output fluctuations caused by the air pressure fluctuations. As drawn in Fig. 15, fluctuation in the air supply _{pressure causes a fluctuation Δ P n in} the nozzle back pressure. _{If the relationship between the fluctuation ΔP 01 of} the outlet pressure caused by the above-mentioned fluctuation in the inlet pressure and the air supply pressure fluctuation Δ-Pg is represented by the curve 10.1 in the diagram of FIG. 15, then the relationship between the air supply pressure P_ and the outlet pressure becomes P ₀ like the curve 100 drawn in FIG. 15, if the pilot valve is to have the characteristic curve shown by the curve 102 in FIG. dimensioned appropriately, so that the first term of formula (2) is omitted. So you can get a pilot _{valve in which the output pressure P Q} regardless of fluctuations in the air supply _{pressure Ρ α} within the practically occurring

fflenden thickness area remains constant, as with the thickness Line L shown in FIG.

2/1319

As described above * !, thanks to the invention, one can use a This type of pilot valve, in which the outlet pressure remains independent of fluctuations in the air supply pressure, by simply dimensioning the cross-section of the air supply valve «

Furthermore, with a pilot valve according to the invention, the space requirement of the entire valve can be reduced to a fifth reduce the space required by conventional valves, since the valve, because it is designed as a slide, has a compact design Has. In addition, since the stroke of the valve can be made large can increase the efficiency of air transport.

As described above, the invention significantly reduces air consumption, makes the valve more economical, improves sensitivity and makes the response time constant even when the inlet pressure increases or decreases. Thus, this improved pre-displacement pilot valve with its low internal air consumption results in greater applicability for controls and better stability of the process control. Furthermore, a better pilot valve of this type can be achieved by the invention in control units with a flapper nozzle and with a pilot valve, in which the output pressure is independent of fluctuations in the air supply pressure _{in the area in which the value ΔP n} / ΔΡ _{ς is approximately constant} is achieved by such a design of the air supply valve closure piece 505 and the effective cross section A ^. of the gap at the valve seat 507t that the condition A ^ = P _N .A _D / P_ is fulfilled, where P _{n is} the nozzle back pressure, A _{D is} the effective area of the membrane 502 and P _{a is} a predetermined air supply pressure

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Claims (6)

Claims 1. Displacement pilot valve characterized in that it is in the common housing (501, 801) contains an input chamber (508) into which an input pressure (P _n ) is introduced _s ^w © ine air supply pressure chamber (509) »in which air is introduced with pressure (P _g ), an outlet pressure chamber (51O) ₉ which receives air from the air supply pressure chamber (509) and emits an outlet pressure (Pq) proportional to the inlet pressure (Pjj), an outlet pressure chamber (511) separated from the inlet chamber (508) by a membrane (502) and connected to the Outlet pressure chamber (510) and the outside air is connected, a valve rod (503), on one or the other of which & End are attached an exhaust valve plug (50 * 0, which comes with a End is attached to the membrane (502) and delimits an outlet channel which leads from the outlet chamber (510) to the outlet chamber (511), and an air supply valve closure piece (505) defining an air supply channel leading from the air supply pressure chamber (509) to the exit chamber (510), and 109842/1319 a compression spring (512), which in the air supply chamber (509) located valve rod (503) to the membrane (502) pushes towards, wherein the outlet valve closure piece (504) and the air supply valve closure piece (505) in the exit chamber (510) are freely movable in and out 2. Pilot valve according to claim 1, characterized in that the outlet valve closure piece (504) and / or the air supply valve closure piece (505) in the normal state in a pressure corresponding to the inlet pressure (P ») Dimensions is open. 3. pilot valve according to claim 1, characterized in that the outlet valve closure piece (5O4) and the exit chambers (51i) are shaped so that the gap between the outlet valve closure piece (504) and the channel leading from the outlet chamber (510) to the outlet pressure chamber (511) is narrowed in the normal state 4. Pilot valve according to claim 1, characterized in that the valve rod (503) together with the valve closure pieces (504, 505) attached to it consists of light metal 5. pilot valve according to claim 1, characterized in that the formula A-. = P ". A-VPg is fulfilled, in which A-. the effective area of the air supply valve closure piece (505) and the gap between this (505) and its valve seat (50?), P _{n is} the inlet pressure, Α- is the effective area of the membrane (502) and PS is the air supply pressure. 109042/1319 , ORIGINAL MSPEGTED 6. Pre-poppet valve after. Claim 1, characterized in that the outlet valve seat (50d) and the air supply clock valve-Sitζ (507) consist of elastic material. 108842/1319