US3534754A

US3534754A - Transducer

Info

Publication number: US3534754A
Application number: US707202A
Authority: US
Inventors: Basil B Beeken
Original assignee: Pitney Bowes Inc
Current assignee: Pitney Bowes Inc
Priority date: 1968-02-21
Filing date: 1968-02-21
Publication date: 1970-10-20
Anticipated expiration: 1987-10-20
Also published as: DE1908250A1; GB1205735A; FR2002307A1; FR2002307B1

Description

United States Patent [72] Inventor Basil B. Beeken New Haven, Connecticut [21] Appl, No. 707,202 [22] Filed Feb. 21, 1968 [45] Patented Oct. 20, 1970 [73] Assignee Pitney-Bowes, Inc.

Stamford, Connecticut a corporation of Delaware [54] TRANSDUCER 5 Claims, 5 Drawing Figs.

[52] US. Cl 137/81.5 [51] Int. Cl Fl5c H18, H50 3/00 [50] Field ofSearch 137/8 1 .5

[5 6] References Cited UNITED STATES PATENTS 1,628,723 5/1927 Hall 137/8 1 .5 3,122,039 2/1964 Sowers 137/81.5X 3,144,037 8/1964 Cargilletal. 137/315 I Primary Examiner-Samuel Scott Att0rneysWilliam D. Soltow, J r., Albert W. Scribner, Martin D. Wittstein and Donald F. Daley ABSTRACT: An improved electrical to fluidic transducer including an electrical circuit for driving a piezoelectric crystal that generates ultrasonic sound waves that are adapted to control the operation of a two stage fluid amplifier circuit. The electrical circuit includes a voltage divider and a multivibrator for adjustably controlling the excitation frequency of said crystal, while the fluid amplifier circuit includes two turbulence type fluid amplifiers. A convergent passage is provided for conducting the sound waves from said crystal to a point adjacent the downstream end of the emitter of one of said turbulence type amplifiers.

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Sheet 1 of 2 Fly, i 02 4 ml 27 4 f/ .4 Ml r o lnllh H I" will I.\'\ 'ENTOR.

Eds/ll B. Beaker;

ATTORNEY TRANSDUCER This invention relates to an improved transducer for converting electrical signals to corresponding fluid pressure signals. More particularly, this invention relates to a novel arrangement for operatively coupling electrical and fluidic circuits.

There are many instances in the practical application of fiuidics where a fluidic circuit must be controlled by the output of an electrical device. This situation gives rise to the need for transducing means in order that the fluidic and electrical circuits may be properly coupled. Several arrangements have been previously proposed for such transducing functions however these arrangements have not always proved to be entirely satisfactory.

(Zine object of the instant invention is to provide a more efficient and reliable electric to fluid pressure transducer.

Another object of the invention is to provide a novel arrangement for electromechanically controlling a turbulence type amplifier.

Other objects of the invention will become apparent as the disclosure progresses.

In the drawings:

FIG. 1 is a plan view in partial section and shows the various components of the instant apparatus as mounted in a box-like housing.

FlG. 2 is a partial sectional view taken along section line 2-2 of FIG. 1.

FIG. 3 is a plan view of a fluidic element circuit board which is incorporated in the instant apparatus.

FIG. 4 is a partial sectional view taken along a section line corresponding to line tl of FIG. 3 and illustrates the fluidic element circuit board and associated cover plate assembly.

FIG. 5 is a circuit diagram illustrating an electrical control for the instant transducer.

A general description of the instant apparatus will be made first in connection with FIGS. 1 and 2. A box-like housing is provided which comprises a base H. with integral ends 12 and i3 and

sides

14 and 15, and a cover 16 that is removably secured to said sides l4, l5 by any suitable means such as screws 17, FIG. I. Mounted in substantially parallel-spaced relation in the housing 10 is a fluidic assembly I8 and an electrical control board 19. The fluidic assembly 18 is held in place by a ridge formed on the upper surface of base it as is best seen in FIG. 2, while the circuit board 19 is slidably inserted into and retained by the slots formed by the opposed projections 20a on the inner surface of the said housing ends 12 and 13 as is best seen in FIG. 1.

The structural and functional characteristics of the fluidic assembly 18 will now be considered in detail with particular reference to FIGS. 3 and 4. The assembly 18 essentially comprises a two-stage fluidic circuit that includes two

fluid amplifiers

22 and 23. These two fluid amplifiers are formed by the appropriate grooving of the upper surface 24 of a main fluidic element circuit board 25, this grooved surface then being covered and sealed by a suitable cover plate 26, FIG. 4, as is well understood in the art. The specific fluidic circuit defined by said grooved surface is illustrated in FIG. 3 and comprises a fluid supply inlet groove 30 that is formed in the board 25; said inlet groove communicating through a suitable groove 31 with the emitter groove or channel 33 of said fluid amplifier 22, and also communicating directly with the emitter groove or channel 34 of amplifier 23. Amplifier 22 includes a slightly diverging (as viewed in FIG. 3) groove 35 that defines an interaction chamber the upstream end of which communicates with said emitter channel 33 while the downstream end thereof communicates with an angularly extending venting channel 36 that ultimately extends longitudinally out through the end 37 of said circuit board 25. The downstream end of the interaction chamber also communicates with a collector groove or channel 40 that is coaxially aligned with said emitter groove 33. The amplifier 23 includes a widened groove 42 that defines an interaction chamber, the upstream end of which communicates with the emitter groove 34 while the downstream end thereof communicates with venting channels 43 and 44), the latter extending out through the said end 37 of the circuit board 25.'The downstream end of this interaction chamber also communicates with a collector groove or channel 4'75 that is coaxially aligned with said emitter groove 34. A control groove or channel 16 communicates at one end thereof with one side of the upstream end of said interaction chamber groove 42 while the other end thereof communicates with said collector groove 4-0 through a suitable groove or channel &7.

As is illustrated in FIGS. 3 and 4 the depth FIG. 4. of the groove 3i, said venting groove 36 and the interaction chamber groove 35 of amplifier 22 is considerably greater than that for the emitter groove 33 and collector groove 4t associated with this amplifier. In similar fashion the corresponding depth of groove 3'0, the interaction chamber groove 42 and

venting channels

43, 44 of amplifier 23 is considerably greater than that for the emitter groove 34, control groove 46 and collector groove 45 associated with said amplifier 23. The groove and channel configuration illustrated in FIG. 3 is approximately to scale, the typical lengths for the interaction chamber grooves 35 and d2 each being in the order of five-sixteenths of an inch. One circuit board model has been con structed wherein the cross-sectional size of the emitter groove 33 was made approximately .007 inches wide and .007 inches deep while the cross-sectional size of the emitter groove 34- was made approximately .015 inches wide and .015 inches deep. The cross-sectional sizes of collector grooves 4! and 45 were made substantially the same as those for said

emitter grooves

33 and 34 respectively. The above-noted dimensions represent only exemplary values and are not to be construed as being limiting values. When the cover plate as is sealingly secured to the circuit board 25, as by rivets 4b and gasket 45 or by other suitable means well-l nown in the art, the various above-described grooves and channels will have substantially rectangular cross-sectional profiles.

Amplifier 22 is provided with a bell-shaped control passage 50 which is formed through the circuit board 25 and which terminates at a port Sll disposed along one side of the upstream end of said interaction chamber groove 35. The side walls 52 defining the control passage Stl arcuately diverge so as to form an externally facing exponentially contoured (as seen in FIG. 4) horn or sound wave receiving opening.

The side M of the box-like housing lift is formed with two appropriate apertures 60, fill, FIG. 1, through which extend flexible input and output fluid conduit lines s2 and 63 which are coupled respectively to fittings 65 and 66 that are integrally formed on the outer side of said cover plate 26. These fittings are provided with

passages

67 and 68 which communicate with said supply groove Sid and said collector groove 45 respectively; the passage 6'7 communicating with the supply groove Eltl as is diagrammatically illustrated by the phantom line 7% of FIG. 3, which the passage 68 communicates with said groove 45 through a recess 71 formed in said upper surface 34 of circuit board 25.

Each of the

amplifiers

22 and 23 is monostable in operation. The normal mode of operation of each amplifier is such that a laminar jet of fluid flows from the emitter and into the collector thereof whereby the pressure in said collector will be relatively high. When a suitable signal is applied to the amplifier the fluid flow in said laminar jet will become turbulent and this turbulent flow will interact with the side walls of the associated interaction chamber and will, for the most part, exhaust through the associated amplifier vent grooves leaving the pressure in the collector relatively low. This turbulent mode of operation will continue until the said signal is removed whereupon the amplifier will immediately resume operating in its said normal laminar mode.

Operatively mounted in a cylindrical recess 74, FIG. 4, formed in the board 25 and substantially coaxially disposed with respect to said passage 5d is a piezoelectric crystal 75, said crystal being secured in said recess by any suitable means such as the flanged button 76 that is cemented to the lower surface (as seen in FIG. 4) of board 25. A disc like pad 77 of sponge rubber or similar resilient material is mounted between the upper surface 760 of button 76 and the crystal 75 so as to assure proper seating, in the recess 74. of said crystal but without mechanically loading the latter. Two diametrically opposed slots 79 and 78 are formed in the board 25 so as to allow the electric leads 80. 81 access for connection with opposite sides of the mounted crystal, these leads also being respectively connected to the

adjacent terminal posts

82 and 83 that are fixed to the said board 25. As will be apparent when the crystal 75 is electrically excited or energized at the proper frequencies the sound waves generated will pass through the exponential horn or passage 50 and into the interaction chamber of the amplifier 22 so as to effect the fluid flow therein as will be described more fully below.

The means for applying electrical signals to the crystal 75 will now be generally described in connection with FIGS. 1. 2 and 5. The said circuit board 19, which includes the various electrical components and interconnections as are indicated in the circuit diagram of FIG. 5, is electrically coupled to said

terminal posts

82 and 83 by means of

leads

84 and 85. In FIG. 5 the circuit input terminals 100 101, are connected across a stepped voltage source as might be afforded by the output of an external electrical control system. The

terminals

100 and 101 are coupled to a conventional type adjustable voltage divider I05 the output of which controls the transistorized multivibrator 106 in a well-known manner. The multivibrator 106 is coupled to a driver stage 107 in a conventional manner, and the output of this driver stage is connected to said crystal leads 84, 85. As will be apparent when a stepped control voltage is applied to

terminals

100, 101, the predetermined voltage applied by the set voltage divider 105 to the multivibrator 106 will cause the latter. through driver stage 107. to energize or excite the crystal 75 at a desired frequency. The said units 106 and 107 are commercially available and may each for example. be a Model #RTUL99I4 integrated circuit as presently marketed by the Fairchild Company of Mountain View. California. in the instant arrangement the voltage divider 105 is set so as to apply to the crystal 75 an ultrasonic signal frequency in the order of 50.000 c.p.s.

I The operation of the above described transducer will now be described. Assuming the fluid supply line 62, FIG. 1. is operatively coupled to a suitable pressure source, fluid (such as air) flows through both

emitter channels

33 and 34 so that the downstream end of each of said emitters thereby issues a laminar jet of fluid that is normally directed into the associated

collector groove

40 or 45. The resultant higher fluid pressure in the collector groove 40 of amplifier 22 however, produces a control signal or fluid flow which passes through the control groove 46 of amplifier 23 to thereby cause the latter to assume a turbulent mode of operation. With no excitation of the crystal 75 the normal state of operation of the instant fluidic circuit is such that amplifier 22 remains in its laminar mode while amplifier 23 remains in its turbulent mode operation. Under these normal conditions the fluid pressure in the collector 45 of amplifier 23 will be relatively low and, with the collector 45 operatively connected through passages 70 and 68 said low pressure condition will also exist in said output line 63. When the crystal 75 is energized by the application of the stepped control voltage to the terminals 100, FIGS. 1 and 5, an effective portion of the resultant sound waves generated by the vibrating crystal 75 will pass through the exponential horn 50 and impinge on said laminar jet issuing from emitter groove 33 so that the small amplifier 22 is thereby switched from its laminar mode to its turbulent mode wherein the flow in said laminar jet becomes turbulent and exhausts through said venting channel 36. The resulting pressure drop in collector 40 and the control groove 46 will cause amplifier 23 to switch to its laminar mode whereby the pressure in collector 45 and said output line 63 will become relatively high. An interruption of said control voltage will terminate the excitation of crystal so that the

amplifiers

22 and 23 will immediately revert to their previously described normal laminar and turbulent modes respectively whereb the fluid ressure in output line 63 will again be relatively ow. As W1 be apparent then any stepped voltage control signals applied to the terminals 100, 101 (which terminals as shown in FIG. I may effectively comprise a two-pronged plug 108). will be functionally converted to corresponding pneumatic signals as represented by the above-described fluid pressure differentials in the output line 63 of the instant transducer.

The instant compact unit has been found to perform reliably and efficiently during extended periods of use.

Since many changes could be made in the embodiment of the invention as particularly described and shown herein without departing from the scope of the invention, it is intended that this embodiment be considered as exemplary and that the invention not be limited except as warranted by the following claims.

l claim:

1. An electric to pneumatic signal converter comprising:

a two-staged fluidic circuit including two turbulence-type fluid amplifiers. the output of a first one of said amplifiers being connected so as to control the operation of the second one of said amplifiers, said first one of said amplifiers including an emitter adapted to issue a laminar jet of fluid and a collector that is adapted to receive at least a portion of the fluid issuing from said emitter;

a piezoelectric crystal mounted so as to control the operation ofsaid first fluid amplifier:

conduit means for conducting sound waves from said crystal to said first fluid amplifier, said conduit means terminating at a control port located adjacent the downstream end of said emitter; and

electrical means for exciting said crystal.

2. Apparatus as defined by claim 1 wherein said conduit means defines a passage that converges in shape towards said control port.

3. Apparatus as defined by claim I wherein said electrical means comprises a voltage divider and a multivibrator.

4. A transducer comprising:

a box-like housing;

a fluidic assembly mounted in said housing;

an electrical circuit board mounted in said housing adjacent said fluidic assembly;

said fluidic assembly including a two-stage fluidic circuit including two turbulence-type amplifiers, a first one of said amplifiers comprising an emitter adapted to issue .a laminar jet of fluid;

a collector adapted to receive at least a portion of the fluid issuing from said emitter;

enclosure means defining an interaction chamber in the region between said emitter and collector;

means defining a sound wave conducting passage, the inner end of said passage terminating at a small aperture disposed at the inner surface of the walls defining said interaction chamber and located at a point adjacent the downstream end of said emitter;

said collector being coupled so as to control the operation of said second turbulence-type amplifier;

a piezoelectric crystal adapted when excited to generate sound wave in said passage; and

electrical means on said electrical circuit board for exciting said crystal which in turn will thereby generate sound waves that are adapted to pass through said passage and small aperture so as to impinge on said laminar jet of fluid issuing from said emitter.

5. Apparatus as defined by claim 4 wherein said crystal is resiliently mounted at the outer end of said passage; said passage being generally bell-shaped and converging towards said aperture.