GB1580315A

GB1580315A - Nozzle flapper arrangement for use in a fluidic measurement and/or control system

Info

Publication number: GB1580315A
Application number: GB15549/78A
Authority: GB
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1977-04-27
Filing date: 1978-04-19
Publication date: 1980-12-03
Also published as: DE2718764B2; IT7822524A0; IT1094722B; DE2718764C3; DE2718764A1

Description

(54) NOZZLE FLAPPER ARRANGEMENT FOR USE IN A FLUIDIC MEASUREMENT AND/OR CONTROL SYSTEM (71) We, SEMENS AKTIENGESELLS- CHAFT, a German company, of Berlin and Munich, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly desciibed in and by the following statement: This invention relates to nozzle-flapper arrangements for use in fluidic measurement and/or control systems.

Figure 1 of the accompanying drawings shows, schematically, a conventional nozzleflapper arrangement as used in pneumatic control and regulating techiques, for example, as used in mechanical-pneumatic measurement transducers and for controlling amplifiers.

A control nozzle 1, customary in pneumatic measuring techniques, has a discharged orifice 3 or circular cross-section with a diameter D in the order of 1 mm and is acted on a supply air pressure Pz via an air density control throttle 8. A flapper plate 2 can be moved by a force K in an axial direction relative to the nozzle 1 , to control the rate of air flow through the nozzle and thus pressure p in the nozzle in the manner of an adjustable pressure regulating throttle, having a control cross-section which has the appearance of the surface of a cylinder defined by the circumference of the orifice 3 and the clearance h between the orifice 3 and the flapper 2.

The jet pressure p prevailing in the nozzle 1 produces a counter-force K' acting on the flapper 2 and counter-acting force K, the counter-force K' being proportional to the pressure p and to the cross-sectional surface and thus not constant. In the case of an average nozzle pressure p of 0.6 bar, the pressure p can fluctuate by, for example + 0.1 bar because of variations in the supply air pressure pz. Thus, variations in the counter-force K' in the order of 10-2 N may arise for viable jet cross-sections of about 1 mm2, which is unacceptable for many applications.

Therefore, it is desirable to construct a nozzle-flapper arrangement in such a way that the counter-force K is reduced as far as possible without disturbing the other measuring technique characteristics of the arrangement.

However, we have found that an obvious reduction of the diameter of the circular crosssection of a nozzle 1 can only go as far as a diameter of about 0.5 mm, because below this a satisfactory control effect is not possible with the control throttles 8 which can still be produced.

According to the present invention, there is provided a nozzle-flapper arrangement for use in a fluidic measurement and/or control system, wherein the nozzle has a discharge orifice of non-circular cross-section.

Thus, the cross-sectional area of the discharged orifice is reduced as compared with circular orifices.

The discharged orifice can be constructed, for example, in the shape of an ellipse, a rectangle or another geometrical figure.

Different examples of embodiments of the invention are shown schematically in Figures 2, 3 and 4 of the accompanying drawing.

In all the Figures, circles 4 drawn with dashed lines signify the edge contours of conventional nozzles 1 according to Figure 1 with circular orifices 3, whereas the orifice contours in accordance with the invention are drawn with solid lines, to modify the orifice 3 of Figure 1.

In Figure 2, the discharged orifice 3 has a cross-section which is an ellipse 5, in Figure 3 a rectangle 6 and in Figure 4 a geometrical form 7 constructed from parallel straight lines and semi-circular arc pieces, to form a generally oval shape.

We have found that, in use of the embodiments of Figures 2 to 4 in an arrangement as shown in Figure 1, there is no significant effect on the fluid flow through the clearance between the nozzle 1 and flapper 2 as long as the smallest diametral dimension of the orifice 3 cross-section (measured over the centre axis of the nozzle 1) is greater than the maximum possible clearance hrnax between the orifice 3 and the flapper 2.

In order not to reduce the control crosssection, that is the product of the orifice 3 circumference and the clearance h, compared with the customary circular orifice 3 contour, and to thus be able to use the nozzles of Figures 2 to 4 directly in place of a nozzle with circular cross-section, it is advantageous to make the circumferences of the non-circular orifice cross-sections equal to the circumferences of the customary circular cross-section.

That is, the nozzle-flapper arrangement would be so dimensioned and arranged as to be capable of operation if the nozzle (of the invention) was exchanged for another conventional nozzle of which the discharged orifice has the same circumference but is of circular crosssection. We have found that the counter-force K', dependent on the nozzle cross-sectional surface, can thus be reduced by about 70% for equal control cross-sections.

WHAT WE CLAIM IS: 1. A nozzle-flapper arrangement for use in a fluidic measurement and/or control system, wherein the nozzle has a discharged orifice of non-circular cross-section.

2. An arrangement according to claim 1, wherein the minimum diametral dimension of the orifice is greater than the maximum spacing between the orifice and the flapper.

3. An arrangement according to claim 1 or 2, wherein said cross-section is elliptical.

4. An arrangement according to claim 1 or 2, wherein said cross-section is rectangular.

5. An arrangement according to claim 1 or 2, wherein said cross-section is oval.

6. An arrangement according to any preceding claim, so dimensioned and arranged as to be capable of operation if the nozzle was exchanged for another nozzle of which the discharge orifice has the same circumference but is of circular cross-section.

7. A nozzle-flapper arrangement substantially as hereinbefore described with refence to Figures 1 and 2, Figures 1 and 3, or Figures 1 and 4 of the accompanying drawing.

8. Fluidic measurement and/or control apparatus including a nozzle-flapper arrangement according to any preceding claim.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

3 and the flapper 2.

In order not to reduce the control crosssection, that is the product of the orifice 3 circumference and the clearance h, compared with the customary circular orifice 3 contour, and to thus be able to use the nozzles of Figures 2 to 4 directly in place of a nozzle with circular cross-section, it is advantageous to make the circumferences of the non-circular orifice cross-sections equal to the circumferences of the customary circular cross-section.

That is, the nozzle-flapper arrangement would be so dimensioned and arranged as to be capable of operation if the nozzle (of the invention) was exchanged for another conventional nozzle of which the discharged orifice has the same circumference but is of circular crosssection. We have found that the counter-force K', dependent on the nozzle cross-sectional surface, can thus be reduced by about 70% for equal control cross-sections.

WHAT WE CLAIM IS: 1. A nozzle-flapper arrangement for use in a fluidic measurement and/or control system, wherein the nozzle has a discharged orifice of non-circular cross-section.
2. An arrangement according to claim 1, wherein the minimum diametral dimension of the orifice is greater than the maximum spacing between the orifice and the flapper.
3. An arrangement according to claim 1 or 2, wherein said cross-section is elliptical.
4. An arrangement according to claim 1 or 2, wherein said cross-section is rectangular.
5. An arrangement according to claim 1 or 2, wherein said cross-section is oval.
6. An arrangement according to any preceding claim, so dimensioned and arranged as to be capable of operation if the nozzle was exchanged for another nozzle of which the discharge orifice has the same circumference but is of circular cross-section.
7. A nozzle-flapper arrangement substantially as hereinbefore described with refence to Figures 1 and 2, Figures 1 and 3, or Figures 1 and 4 of the accompanying drawing.
8. Fluidic measurement and/or control apparatus including a nozzle-flapper arrangement according to any preceding claim.