US3707440A

US3707440A - Temperature compensating fluidic circuit

Info

Publication number: US3707440A
Application number: US54980A
Authority: US
Inventors: Gary L Frederick
Original assignee: Garrett Corp
Current assignee: Garrett Corp
Priority date: 1970-07-15
Filing date: 1970-07-15
Publication date: 1972-12-26
Anticipated expiration: 1989-12-26

Abstract

This temperature compensating fluidic circuit has a conventional proportional amplifier which includes an interaction chamber with a beam-forming inlet at one side, spaced outlet passages on the opposite side, opposed control jet nozzles at the sides of the inlet, and passages leading from a common control pressure source to the control jet nozzle. One of these passages contains a restriction of the orifice type and the other contains one or more vortextype resistors. Since the resistance of the vortex-type resistor is due mainly to angular momentum rather than viscosity effects, to which the orrifice-type restriction is particularly responsive, the vortex-type resistor is less affected by temperature change and consequently control signals bearing a predetermined relation to temperature will be applied by the control jets to the fluid beam. A differential pressure output, dependent on temperature will thus be delivered by the amplifier.

Description

Dec# 26, 1972 G. l.. FREDERxcK 3.707,440

TEMPERATURE COMPENSATING FLUIDIC CIRCUIT Filed July 15, 1970 Hrm/elven United States Patent O U.S. Cl. IS7-81.5 8 Claims ABSTRACT OF THE DISCLOSURE This temperature compensating fluidic circuit has a conventional proportional amplifier which includes an interaction chamber with a beam-forming inlet at one side, spaced outlet passages on the opposite side, opposed control jet nozzles at the sides of the inlet, and passages leading from a common control pressure source to the control jet nozzles. One of these passages contains a restriction of the orifice type and the other contains one or more vortextype resistors. Since the resistance of the vortex-type resistor is due mainly to angular momentum rather than viscosity effects, to which the orifice-type restriction is particularly responsive, the vortex-type resistor is less affected by temperature change and consequently control signals bearing a predetermined relation to temperature will be applied by the control jets to the fluid beam. A differential pressure output, dependent on temperature, will thus be delivered by the amplifier.

SUMMARY This invention relates generally to the control system art and more particularly to that branch of such art more recently becoming popularly known as Flnidics Still more particularly, the invention is directed to the provsion of a temperature compensating fluidic amplifier which may be arranged in a control system to make it less affected by temperature change, either in ambient conditions or in the fluid employed in the system.

Apparatus of this general type has previously been proposed, as exemplified in U.S. Pats. No. 3,314,294 to J. R. Colston and No. 3,442,278 to R. S. Peterson; however, such apparatus has been objectionable since certain parts thereof required extremely small cross-sectional flow areas and/or long passage lengths. The reduced flow areas make the components susceptible to failure due to contamination of the working fluid, while the use of long passage lengths presents packaging problems and prevents the use of the components in small or compact quarters.

An object of the invention is to provide a fluidic amplifier having the usual fluid beam for delivering fluid under pressure to a plurality of receivers in proportion to the forces of control jet streams applied to opposed sides of the fluid beam, the forces of the control jet streams being varied in accordance with temperature change to cause the amplifier to produce a differential pressure output which is temperature dependent, the fluidic amplifier avoiding the objections to prior structure noted above.

An object also is toprovide a fluidic amplifier having control jet applying means with components for creating differential pressure control flows, one component being a restrictor which is affected by changes in viscosity of the system fluid and the other being a restrictor which is relatively unaffected by such changes, the differential control flows thus varying in accordance with temperature changes producing variations in fluid viscosity.

Another object also is to provide a fluidic amplifier having control jet applying means with a restrictor of the orifice type in communication with one control jet and a restrictor of the vortex type communicating with the other control jet, since the resistance of the vortex-type restric- Mice tor is due primarily to angular momentum of the fluid rather than viscosity effects, it varies less with absolute temperature change than the resistance of the orifice-type restrictor and a control pressure differential which varies as a function of temperature is produced, the result is an amplified temperature-dependent differential output.

A further object of the invention is to 'vary the sensitivity to temperature change by placing an orifice-type resistor in parallel with the control jet port which is in communication with the vortex-type resistor.

Another object is to vary the sensitivity of the device to temperature change by placing a shunt resistance across the output passages of the amplifier, or by placing degaining orifices in the output passages.

A further object is to change the Vortex dimensions to vary the sensitivity of the device to temperature change.

The foregoing and other objects may be secured with various forms of structure schematically illustrated in the accompanying drawing and described hereinafter.

THE DRAWINGS FIG. 1 is a schematic View of a temperature compensating fluidic circuit embodying the present invention;

FIGS. 2, 3 and 4 are schematic views of the structure or parts thereof modified to increase the sensitivity of the circuit shown in FIG. l; and

FIG. 5 is a graph showing the results of tests of various forms of the invention.

Referring more particularly to the drawing, and especially FIG. 1, the circuit shown therein includes a conventional proportional amplifier 10. While a proportional amplifier has been illustrated, it should be understood at this point that the principles of the invention are equally applicable to a digital amplifier. The amplifier 10 includes an interaction chamber 11, having a beam-forming inlet nozzle 12 at one side and a pair of

output passages

13 and 14 at the opposite side. The chamber is also provided with a pair of

control jet nozzles

15 and 16, these being arranged between the nozzle 12 and the output passages at opposite sides of the nozzle 12. The latter is adapted to receive fluid under pressure from a source 17 and direct a fluid beam 18 generally toward the

output passages

13, 14. The beam 18 is controlled by the application of fluid pressures to either side thereof through the

nozzles

15 and 16, the quantity of fluid received by the

output passages

13 and 14 being in proportion to the difference in forces of the control streams issuing from the

jets

15 and 16. These jets are connected by passages 20 and 21 with a source of control pressure which may be either the source 17 or other suitable source.

The forces of the control jets in the present instance are varied by incorporating restrictions in the passages 20 and 21. Passage 20 is provided with a restriction 22 of the orifice type and passage 21 is provided with one or

more restrictions

23, 23a, the resistance of which is due to angular momentum of the fluid flowing through the passage 21. Since resistance, which is due to angular momentum, is less affected by variations in the Viscosity of the fluid flowing through the restrictions, the resistance offered by restrictors 22 and Z3 will differ at different temperatures. By reason of this difference, control pressure signals due to temperature change will be applied to the beam 18 and will cause a differential pressure output in

passages

13 and 14 dependent on temperature. The forces of the pressure output signals will be increased due to the natural action of the amplifier 10.

One form of resistor of the angular momentum type is a vortex resistor, schematically illustrated at 23. Such a resistor comprises a circular chamber 24 into which fluid is introduced tangentially, as at 25, through passage branch 21a. An outlet port 26 leads from the center portion of the chamber 24 via passage branch 2lb to passage 21.

Fluid flowing through branch 21a swirls around in chamber 24 and exits through outlet port and branch 2lb to passage 21. The resistance to liow offered by the vortextype resistor will be substantially the same regardless of any change in viscosity due to temperature change. The resistance offered by the restrictor 22, however, will vary with changes in viscosity of the fluid and, as previously mentioned, the forces applied to beam 18 by

jets

15 and 16 will differ as temperature changes. A single vortextype resistor could be employed. It is desirable, however, to utilize a plurality of

such resistors

23, 23a to permit the use of an orifice-type resistor in line 20 of a size which will be relatively immune to contamination of the fluid. The vortex-

type resistors

23, 23a are arranged in parallel as shown in FIG. 1. Sensitivity of the control to variations in temperature may be increased by connecting an orifice-type restriction 27 to passage 21 on the downstream side of the vortex resistors, restrictor 27 venting to the ambient atmosphere.

Use of resistor at 27 discharging to ambient increases the flow through the vortex resistors and thus increases the swirl strength therein. The sensitivity of the amplifier may be varied in a number of different ways. For example, FIG. 2 schematically illustrates a change in dimensions of the vortex resistors 30 and 31. In FIG. 2, resistor 30 is represented as having a smaller diameter chamber than resistor 31. Other dimensions, such as the depth of the chamber, may be varied with similar results.

In FIG. 3, a shunt resistance is applied across the

output passages

13, 14. In FIG. 4, each passage 13a, 14a is provided with a de-gaining orifice 32.

In the graph of FIG. 5, there are shown the results of tests of amplifiers with different sensitivity adjusting means. The traces A, B, C, D1, D2, and D3 show that the variation in differential output of the amplifier due to temperature change is linear. In this graph the curves show differential pressure changes in the output of the amplifier with different size restrictions at 27. Curve A indicates the output pressure differential with an orifice 27 of a selected size. Curve B shows the results of the use of an orifice 27 twice as large, and Curve C results from an orifice three times -as large. Curves D1, D2 and D3 result from the use of orice 27 of the selected size in combination with various size de-gaining orices in the output passages.

It should be obvious that, as indicated, the restrictions of the orifice type could also be made adjustable, if desired or found advisable.

I claim:

1. Temperature compensating fluidic circuit means comprising:

(a) an amplifier having means forming an interaction chamber with a beam-forming inlet nozzle at one side, spaced output passages at the opposite side, and a control jet nozzle at either side of said inlet nozzle, said inlet nozzle being adapted to receive fiuid under pressure from a supply source;

(b) a first passage with viscosity sensitive resistance means leading from a control pressure source to one of said control jet nozzles; and

-(c) a second passage with resistance means of a vortex type leading from said control pressure source to the other of said control jet nozzles.

2. Temperature compensating fiuidic circuit means oi claim 1 in which a shunt resistance across the output passages is provided to vary the sensitivity of the amplifier means.

3. Temperature compensating uidic circuit means of claim 1 in which predetermined dimensions of the vortex type resistance means is varied to adjust the sensitivity of the amplifier means.

4. Temperature compensating liuidic circuit means of claim 1 in which the output passages are provided with adjustable de-gaining orifices to vary the sensitivity of the amplifier.

5. Temperature compensating fluidic circuit means of claim 1 in which the second passage is provided with a plurality of resistance means of the vortex type.

6. Temperature compensating fluidic circuit means of claim 5 in which the resistance means in said second passage are arranged in parallel.

7. Temperature compensating fluidic circuit means of claim 1 in which the second passage has an oriiice discharging to ambient in parallel with said other control jet.

8. Temperature compensating uidic circuit means of claim 7 in which the orifice discharging to ambient is adjustable.

References Cited UNITED STATES PATENTS 3,587,602 6/1971 Urbanosky 137-815 3,587,606 6/1971 Howland 137-815 3,587,616 6/1971 Boothe 137-815 3,598,137 8/1971 Glaze 137-815 3,603,334 9/1971 Davies et al IS7-81.5 3,442,278 5/1969 Petersen 137-815 3,529,614 9/1970 Nelson 137-815 3,557,810 1/1971 Lomas 137-815 3,250,469 5/1966 Colston 132-815 3,536,085 10/1970 Taplin 137-815 3,570,511 3/1971 Bermel 137-81.5

SAMUEL SCOTT, Primary Examiner