US3724476A

US3724476A - Pneumatic amplifier

Info

Publication number: US3724476A
Application number: US00141691A
Authority: US
Inventors: H Bader
Original assignee: JC Eckardt AG
Current assignee: JC Eckardt AG
Priority date: 1971-05-10
Filing date: 1971-05-10
Publication date: 1973-04-03
Anticipated expiration: 1990-04-03

Abstract

A fluid medium amplifier which includes an operating nozzle, a suction channel and a mixing chamber adjoining the suction channel and operating nozzle as well as a control nozzle downstream of the operating nozzle which as input signal disturbs the mixing progress in the mixing chamber so that an amplified output signal is produced in the suction channel.

Description

Umted States Patent 1191 1111 3,724,476

Bad'er 1451 Apr. 3, 1973 54 PNEUMATIC AMPLIFIER 3,490,477 1/1970 Ezekiel ct a1. ..137/s1.5

3,417,770 12/1968 Denison ..137/81.5 [75] Bad", stungm'Fasanmmf 3,507,294 4/1970 Fix B181 ..147 s1.s Germany 3,507,296 4/1970 Fix etal ..l37/8l,5 3,592,213 7/1971 Smith ..137/8l.5 X [73] Ass'gnee' Eckm Stuttgart 3,636,964 1/1972 Colamussietal ..137/s1.sx

'[22] Filed: May 10, 1971 Primary Examiner-Samuel Scott [21] App! I 691 Attorney-Craig, Antonelli & Hill 1 [57] ABSTRACT [if] A fluid medium amplifier which includes an operating [58] Eu .1! 135/81 5 nozzle, a Suction charm? and a mixing chamber 1e 0 care joining the suction channel and operating nozzle as well as a control nozzle downstream of the operating [56] References Cited nozzle which as input signal disturbs the mixing UNITED STATES PATENTS prcgreseln the mixing chamber :sothat an amplified 3 565 091 2/197 A [37/81 5 output s1gnal 1s produced 1n the suct1on channel.

ugei' 3,614,962 10/1971 Atkinson et al. ..l37/8l.5 14 Claims, 14 Drawing Figures PATENTEDAPR3 ms 3.724.476

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ATTORNEYS PATENTEUAPRB ma 3.724.476

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INVENTOR Hows-r 5Q DER BY 0154 AM M am. ATTORNEYS PNEUMATIC AMPLIFIER This invention relates to a fluid medium amplifier, especially for measuring and control devices, consisting of a so-called jet apparatus with an operating or working nozzle of a suction channel from which a fluid medium is entrained by suction by the operating or working jet leaving the operating or working nozzle and of a mixing channel adjoining the suction channel.

It has been proposed already to employ jet apparatus or ejector devices as transmission members for pressure-medium-operated measuring and control devices, whereby the pressure signals to be mutually correlated can be applied to the jet apparatus as operating or working jet pressure, as back pressure, or as pressure in the suction channel. In contrast thereto, fluid medium amplifiers, if they are to be employed for larger amplification outputs, include mass-exhibiting mechanical parts actuated by diaphragms, which parts control an energy flow in the manner of throttle members in valves. Apart from the disadvantages inherent in mechanical parts, the dimensions and properties of the diaphragms essentially determine the size and the static and dynamic properties of such pneumatic amplifiers. Therefore, the manufacture of such types of amplifiers is very expensive, and the dimensions cannot fall below a certain size.

The present invention is concerned with the task of avoiding these disadvantages and to provide an amplifier having no movable mechanical parts, and making it possible to obtain relatively high amplification outputs even with small space requirements.

In that connection, the invention starts with the fluid medium arrangement mentioned hereinabove which has already been proposed as the transmission member for measuring and control devices and has become known under various designations, such as ejector, injector, jet blower, jet pump, or also jet apparatus. In the technical literature of fluid dynamics and thermodynamics, the designation jet apparatus has come into more frequent use recently. Accordingly, in the following description the term jet apparatus will be used exclusively to designate any such devices which consists in a known manner, of an operating or output nozzle, of a suction channel, and of a mixing chamber which is generally adjoined by a diffuser. For a better understanding, it is to be noted that the venturi-type jet, with which the present invention is concerned, evolved from the venturi nozzle, in which the pressure difference of the flow in the narrowest cross section and of the flow downstream of the diffuser is utilized for drawing in a liquid or gas and for carrying the same away. The pressure difference results from the basic physical aspects described by the Bernoulli s law.

Jet apparatus of various types of constructions are known because the connection of the suction channel can be constructed and realized in a variety of ways. In the venturi nozzle, this suction channel is formed, in the simplest manner, by a radial bore terminating at the narrowest cross section; however, the suction effect is enhanced by shaping the suction channel as a type of annular chamber disposed coaxially with respect to the operating or working nozzle and terminating in the mixing chamber, whereby this termination is constructed in the shape of a nozzle.

A mixing process is taking place in the jet apparatus. This is so because a flow of high kinetic energy leaves the operating or output nozzle, and the molecules of this flow or stream impinge on the molecules which arrive from the suction channel at a substantially lower velocity. By the exchange of momentum, the differing velocities of the two streams or flows are equalized in the mixing chamber, and it was found that an influencing of the flow processes and especially of the mixing process downstream of the operating or working nozzle exerts a decisive effect on the pressure conditions in the suction channel.

The present invention is based on the concept of quite purposely influencing the flow processes in the jet apparatus and particularly the mixing process thereof, by means of a control jet, with the objective to effect a specific pressure change in the suction channel.

The present invention essentially consists in that a control nozzle for the feed of a fluid medium is provided downstream of the orifice of the operating nozzle, the pressure of which corresponds to the input signal of the amplifier, and in that the output signal of the amplifier is established at the suction channel. It is attained by means of this arrangement that the degree of efficiency of the jetapparatus decreases with an increasing control flow and the flow resistance of the flow in the mixing channel and/or in the diffuser is increased. As a result thereof, the mixing process is interfered with, and less pressure medium is sucked out of the suction channel. The pressure in the suction channel consequently rises with an onlyslight increase in pressure at the control nozzle to a substantially greater extent so that the desired amplification effect is attained if the input signal and the output signal of the amplifier are connected according; to the invention to the jet. 7

It is possible to arrange the controlnozzle at various places in the jet apparatus. The amplification effect becomes particularly advantageous if the control nozzle terminates in the mixing chamber of the jet apparatus. For the lowest pressure prevails thereat by reason of the flow conditions, and the novel amplifier operates in that case in the manner of a pneumatic transistor. The turbulences through the control nozzle, generated by means of small amounts of energy, con: siderably increase the flow resistance in the mixing chamber, which manifests itself in a marked pressure increase in the suction channel. If the control nozzle is disposed in such a manner that it terminates in the mixing chamber oppositely to the operating or working nozzle, then a rapid and effective influencing of the pressure conditions in the jet apparatus can be achieved. In order to prevent that the dynamic back pressure from the operating nozzle becomes effective on the control nozzle, which maybe undesirable in particular in case of very low input pressures, the provision can also be made advantageously that the control nozzle terminates at an angle to the axis of the mixing chamber, which is constructed a tubular element. In that connection, the'control nozzle may also terminate tangentially in the tubular mixing chamber whereby this type of construction exhibits advantages from a manufacturing viewpoint.

A particularly advantageous embodiment is realized if the output signal is taken off from a pressure divider,

which is in communication, on the one hand, with the pressure prevailing in the suction chamber and, on the other hand, with a supply pressure, because in that case the change caused in the suction channel by the input signal has an effect on the output signal at a higher pressure level. By the input connection of the pressure divider, it is possible, by matching the two resistances of the pressure divider, to determine the level as well as the range of the pressure for the output signal, and thus to adjust the operating point.

The novel amplifier exhibits the decisive advantage that it has no movable parts and that no leakage problems need be feared, so that a particularly operationally reliable fluid medium amplifier, operated by a pressure medium, is provided which can also be manufactured in extremely small dimensions. Moreover, the manufacture of the novel amplifier is extremely simple, because essentially only rotationally symmetrical parts are being employed.

These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein:

FIGS. 1 and la are cross-sectional views of two embodiments of prior art jet apparatus as known in fluid dynamics;

FIG. lb is a diagram illustrating the suction characteristics of the prior art jet apparatus;

FIGS. 2, 2a, and 2b are cross-sectional views through various embodiments of an amplifier according to this invention;

FIG. 2c is a diagram illustrating the schematic curve of the amplifier of FIGS. 2, 2a, and 2b;

FIGS. 3 and 3a are, respectively, a cross-sectional view through a further embodiment of an amplifier according to this invention completed by a throttling resistor and a symbolic representation thereof in the form of a circuit diagram;

FIG. 3b is a diagram illustrating the amplifier characteristics of the amplifier of FIGS. 3a and 3b;

FIGS. 4 and 4a are respectively a cross-sectional view through a still further embodiment of the amplifier of this invention, completed by a pressure divider, and the corresponding symbolic representation thereof; and

FIGS. 5 and 5a are respectively a cross-section through still another embodiment of an amplifier with two control nozzles, whereby one nozzle is fed by the output pressure of the amplifier, and the corresponding circuit diagram thereof.

Referring now to the drawing, wherein like reference numerals are used throughout the various views to designate like parts and, more particularly, to FIGS. 1 and 1a, these two figures illustrate two conventional prior art jet apparatus, from which the present invention departs. In the housing 1, an operating or work nozzle 2 is arranged, which is adjoined by the channel 3 and the diffuser 4. The suction channel 5 terminates radially in the channel 3, the latter representing the narrowest flow cross-section of the jet apparatus.

The operating or working nozzle 2 is in communication with the supply pressure P and produces a flow having a high velocity and a low static pressure in accordance with the Bernoulli s law. The suction channel 5 terminates in this zone of low pressure, within which prevails the pressure P,. Due to the pressure difierence, pressure medium flows from the suction channel 5 into the channel flow or stream within the channel 3. Both streams mix with each other and are converted to the pressure P, in the diffuser 4. The pressure P, is, in many cases, the atmospheric P,,, but it can also be higher than atmospheric pressure.

FIG. 1a shows a customary embodiment of a jet apparatus, consisting of the operating or working nozzle 2, the mixing channel 3, and the diffuser 4. The suction channel 5 terminates nozzle-shaped in the mixing channel 3. The embodiments of FIGS. 1 and 1a differ by the type of the connection of the suction channel 5 with the mixing channel 3. In the construction according to FIG. la, the suction channel 5 enters the mixing channel 3 as a radial bore. In contrast thereto, in the embodiment according to FIG. 1, the suction channel 5 terminates coaxially in the mixing channel 3. The discharge orifice itself is shaped like a nozzle. This embodiment of FIG. 1 attains a higher degree of efficiency and the suction efiect is better than in the embodiment of FIG. 1a. FIG. 1b illustrates the suction characteristics of the prior art jet apparatus, and it can be seen that, with increasing pressure P,, in the operating nozzle 2, the pressure P, in the suction chamber is decreased. This effect is known and is described by Bemoullis equation.

One embodiment of the amplifier according to this invention is shown in FIG. 2. The jet apparatus accord- 'ing to FIG. 2 is provided with a control nozzle 6 to which is connected the input pressure P of the amplifier. The discharge aperture of the control nozzle 6 terminates in the mixing channel 3. An amount of pressure medium (air) correlated to the input pressure P enters through the control nozzle 6 into the channel flow. As a result thereof, the mixing process of the particles leaving the operating nozzle 2 with a high velocity with the particles of a lower velocity which enter the mixing channel 3 through the suction channel 5, is disturbed. A control flow is introduced by way of the control nozzle 6 which changes the flow resistance of the channel flow in the mixing channel 3. Since this channel flow reacts strongly to disturbances, a larger effect can be attained with a small cause (control flow), i.e., a small change in the control flow has as result a large change in the flow resistance. Consequently, less pressure medium (air) can be sucked out and supplied out of the suction chamber 5. The degree of efficiency of the jet apparatus has been reduced. The pressure P, in the suction chamber increases. With an increase in the input pressure P the pressure P, in the suction chamber is likewise increased. This correlation is utilized as a pressure amplification effect.

FIG. 2a shows an embodiment in which the control stream enters tangentially. The control nozzle 6 may be disposed thereby at an angle with respect to the axis of the jet apparatus (FIG. 3), but it may also extendat right angles to the axis of the jet apparatus (FIG. 2).

FIG. 2b illustrates a modified embodiment in which the suction channel 5 and the control nozzle 6 terminate in the mixing chamber 3 substantially at right angle to the axis thereof, the latter downstream of the former. However, the suction channel 5 and/or the control nozzle 6 may also terminate tangentially, as shown in FIG. 2a.

In FIG. is illustrated the curve of the amplifier characteristics. It produces a range which is suitable for the pressure amplification between P and P P Another embodiment of the invention is shown in FIG. 3. The suction chamber 5 of the jet apparatus is connected with the energy source P, by way of a throttle resistor 7. The same amount of pressure medium enters the suction chamber 5 by way of the throttling resistor 7 as is withdrawn by suction by the jet apparatus by way of the suction channel 5 if the output pressure P,, P is received by a pressure measuring device, the input pressure chamber of which is delimited by an elastic wall, which is the case in most applications. The control nozzle 6 is disposed at an angle to the flow direction (to the axis of the mixing channel 3). The control jet from this nozzle 6 impinges on the stream in the immediate vicinity of the entrance of the suction stream from the suction channel 5, which has the shape of a circular ring gap.

The mode of operation of this embodiment of the amplifier can be readily explained with reference to the symbolic representation according to FIG. 3a. The amplifier arrangement can be assumed to be a pressure divider fed by the energy source P Pressure medium flows by way of the throttling resistor 7 into the suction space 5, from which the suction space pressure P is picked up as the output pressure. The jet apparatus 1 provided with a control nozzle 6 serves as a controllable flow resistance 8.

The amplifier curve of the embodiment of FIG. 3 is shown in FIG. 3b. The measure of connecting the suction chamber of the jet apparatus with the energy source P by way of throttling resistor 7 has the efiect that the output pressure P,., is higher than in the embodiment of FIG. 2, as can be seen from a comparison of the two amplifier characteristics of FIG. 20 and FIG. 3b.

In the embodiment according to FIG. 4, the control nozzle 6 is disposed in the center of the mixing channel 3 and of the diffuser 4. The control jet discharged from the control nozzle 6 terminates in the mixing channel 3 in opposition to the flow direction. Furthermore, this embodiment is provided with two throttling

resistors

7, 9, which are arranged as a pressure divider. The suction space 5 is connected to the energy source P by way of the throttling

resistors

7, 9. The output pressure P, of the amplifier is taken off between these two resistors.

Provision is made that at least one of these two resistors 7 is adjustable. This resistor can be constructed, for example, as a needle valve.

In accordance with FIG. 4a, this amplifier arrange ment can be considered a pressure divider arrangement consisting of the two

resistors

7, 9, as well as of a resistor 8 controllable by the input pressure. The controllable resistor 8 is realized by means of the conventional jet apparatus 1 and the control nozzle 6.

Another embodiment is shown in FIG. 5. In this figure, an additional control nozzle 10 is provided which is in communication with the output pressure P of the amplifier by way of the throttling resistor 1 I. The output pressure P is taken off between the

resistors

7 and 9, as in the embodiment according to FIG. 4.

This measure represents a positive feedback arrangement:

With increasing input pressure P in the control nozzle 6, the output pressure P as explained above, in-

creases initially. An increase in the control stream, which enters the mixing channel 3 from the control nozzle ll), is connected with this pressure increase. This second control stream, like the control stream discharged from the control nozzle 6, produces a further pressure increase P, which in turn, increases the control stream, and so forthQuntil an equilibrium condition is attained, which is determined by the magnitudes of the pressures P P and i and the dimensions of the arrangement. By this positive feedback effect, the slope of the amplifier curve becomes greater, which is synonymous with a larger amplification factor. A larger change in output pressure P is associated with a smaller change in the pressure of the input pressure P Furthermore, a throttling resistor 12 is provided, through which the stream of the jet apparatus, which leaves the diffuser 4, flows off against the atmospheric pressure P,,. Therefore the back pressure P downstream of the diffuser is larger than the atmospheric pressure P,,. Consequently, this arrangement can be utilized for raising the pressure level of the amplifier.

In FIG. 5a, the mode of operation of this embodiment is represented on the basis of a circuit made of resistors.

Pressure medium from the energy source P flows off against atmospheric pressure I, by way the

resistors

9, 7, 8 and 12. The output pressure P establishes itself between the throttling

resistors

9 and 7. This pressure, like the input pressure P,;, has a positive effect on the controllable resistor 8, which means:

The value of the resistor 8 increases together with P and P The back pressure ll, establishes itself between the controllable resistor 8 and the resistor 12.

While I have shown and described several embodiments of the present invention, it is understood that the same is not limited thereto, but is susceptible of numerous changes and modifications as known to those skilled in the art, and I therefore do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

I. A fluid medium amplifier, especially for measuring and control devices, which includes a jet apparatus with an operating nozzle means, a suction channel means from which fluid medium is entrained by suction by the operating jet leaving the exit orifice of the operating nozzle means, and a mixing chamber means adjoining the suction channel means, the mixing chamber means receiving the entrained fluid medium from the suction channel means, characterized in that a control nozzle means for the supply ofa fluid medium is provided downstream of the exit orifice of the operating nozzle means, the pressure of said last-mentioned fluid medium corresponding; to the input signal of the amplifier, and the output signal of the amplifier being established at the suction channel means.

2. A fluid medium amplifier according to claim 1, characterized in that the suction channel means is in communication with a supply pressure by way of a resistance means.

3. A fluid medium amplifier according to claim 1, characterized in that the control nozzle means terminates in the mixing chamber means substantially opposite to the operating nozzle means.

4. A fluid medium amplifier according to claim 1,

characterized in that the control nozzle means terminates at an angle to the axis of the mixing chamber means constructed as tubular member tube.

5. A fluid medium amplifier according to claim 1, characterized in that the output signal of the amplifier also acts on the mixing chamber means by way of a further resistance means.

6. A fluid medium amplifier according to claim 1, characterized in that the control nozzle means terminates in the mixing chamber means of the jet apparatus.

7. A fluid medium amplifier according to claim 6, characterized in that the control nozzle means terminates in the mixing chamber means substantially opposite to the operating nozzle means.

8. A fluid medium amplifier according to claim 6, characterized in that the control nozzle means terminates tangentially in the mixing chamber means.

9. A fluid medium amplifier according to claim 6, characterized in that the control nozzle means terminates at an angle to the axis of the mixing chamber means constructed as tubular member tube.

10. A fluid medium amplifier according to claim 9, characterized in that the control nozzle means terminates tangentially in the tubular mixing chamber means.

11. A fluid medium amplifier according to claim 1, characterized in that the output signal of the amplifier is taken off from a pressure distributor means which is in communication, on the one hand, with the pressure prevailing in the suction channel means and, on the other hand, with a supply pressure.

12. A fluid medium amplifier according to claim 11,

' characterized in that the output signal of the amplifier also acts on the mixing chamber means by way of a further resistance means.

13. A fluid medium amplifier according to claim 1, characterized in that a throttling resistance means is arranged in the discharge of the jet apparatus.

14. A fluid amplifier according to claim 13, characterized in that the throttling resistance means is arranged at the end of a diffusor.

Claims

1. A fluid medium amplifier, especially for measuring and control devices, which includes a jet apparatus with an operating nozzle means, a suction channel means from which fluid medium is entrained by suction by the operating jet leaving the exit orifice of the operating nozzle means, and a mixing chamber means adjoining the suction channel means, the mixing chamber means receiving the entrained fluid medium from the suction channel means, characterized in that a control nozzle means for the supply of a fluid medium is provided downstream of the exit orifice of the operating nozzle means, the pressure of said lastmentioned fluid medium corresponding to the input signal of the amplifier, and the output signal of the amplifier being established at the suction channel means.

4. A fluid medium amplifier according to claim 1, characterized in that the control nozzle means terminates at an angle to the axis of the mixing chamber means constructed as tubular member tube.

12. A fluid medium amplifier according to claim 11, characterized in that the output signal of the amplifier also acts on the mixing chamber means by way of a further resistance means.