US3725856A

US3725856A - Push-pull transducer

Info

Publication number: US3725856A
Application number: US00611798A
Authority: US
Inventors: J Chervenak
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1956-09-24
Filing date: 1956-09-24
Publication date: 1973-04-03
Anticipated expiration: 1990-04-03

Abstract

An electro-acoustic transducer is disclosed comprising an enclosing hollow piston element of relatively light rigid nonmagnetic material; a central vibratory mass element is situated within said piston element having opposite portions of magnetic material. The use of the piston-action vibrator unit eliminates complex modes of vibration, resulting in higher efficiency than ordinary diaphragm action.

Description

Unite States 1191 Chervenals Apr. 3, 1973 .mw nm 3 HC [54] PUSH-PULL TRANSDUCER 2,413,012 12/1946 2,713,127 7/1955 [75] Inventor. JohnChervenak,Wash1ngton,D.C. 2,723,386 "955 The United States of America as [73] Assignee:

represented b th secretary f th Primary ExaminerR0dney D. Bennett, Jr. N Assistant Examiner-D, M. Potenza Attorney-R. S. Sciascia, A. L. Branning and M. 1. Crane [22] Filed: Sept. 24, 1956 [57] ABSTRACT An electro-acoustic transducer is disclosed comprising 21 Appl. No.: 611,798

an enclosing hollow piston element of relatively light rigid nonmagnetic material; a central vibratory mass element is situated within said piston element having opposite portions of magnetic material. The use of the piston -action vibrator unit eliminates complex modes ation, resulting in higher efficiency than ordinary diaphragm action.

References Cited UNITED STATES PATENTS of vibr 12 Claims, 7 Drawing Figures 1,640,538 DuBois-Reymond ....................340/8 2,025,041 Colton............ ....340/8 PATENTEUAPR3 I975 SHEET 1 UP 3' VENTOR ENAK JO H N. CH ERV Pmimmm m5 3,725,856

sumaors INVE. JOHN CHERVEN BY Z L,

W ATTORNEY) PUSH-PULL TRANSDUCER The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates in general to underwater electro-acoustic transducers and has particular reference to such a transducer for projection and reception of underwater low-frequency compressional waves.

An object of the invention is the provision of a piston-action vibrator unit in which complex modes of vibration, as in the case of a diaphragm, are avoided and a substantially true piston action is attained resulting in higher efficiency than realizable from ordinary diaphragm action of an energy radiating face. The term piston action indicates such action as the movement of a substantially flat surface element such that all parts on the surface element oscillate in synchronism, normal to the surface and with the same amplitude.

Another object of the invention is the attainment of a high radiating power at low frequencies in the neighborhood of l kilocycle with simple and sturdy apparatus in the form of independently operable units capable of being used in various multi-unit arrays.

A further object is the provision of a vibrator unit having a piston action and operable to vibrate bodily as a unit and only along the axis of the piston surface, and readily adaptable to combination with any number of light units in various compact arrays for operation in synchronism as a single large piston or in any desired phase relation.

Various other objects and advantages of the invention will become apparent upon a perusal of the following specification and the drawings accompanying the same.

In the Drawings:

FIG. 1 is a partially expanded view in autographic projection of a preferred embodiment of the invention.

FIG. 2 is a section on the line 22 of FIG. 3

FIG. 3 is a staggered section on the line3-3 of FIG. 2.

FIG. 4 is a side view of a complete unit with the waterproof covering and sponge rubber backing in section.

FIG. 5 is a front view of an array of four of the units.

FIG. 6 is a schematic circuit diagram of a unit.

FIG. 7 is a fragmentary sectional view of a modification.

Referring to the drawings in detail, the partially expanded view of FIG. 1 shows the various parts in their proper cooperative relation except that the rear wall 10, here shown on top, together with the magnetic inwardly facing element 11 carried thereby is moved away from the remainder of the assemblage to show lower adjacent parts otherwise obscured. With all parts in their proper relative position as shown in FIGS. 2 and 3, the

magnetic elements

11 and 12 are positioned in close proximity through a suitable narrow working air gap 13.

The hollow piston element designated as a whole by the reference numeral 14 is formed of the six walls l0, l5, l6, 17, 18 and 19, of relatively light, rigid, nonmagnetic material such as aluminum, the walls and forming ,the rear and front end walls of the bodily vibrating piston-action unit. In the present embodiment the walls are secured in assembled relation by screws as indicated at 20 (FIG. 1) threaded into threaded bores such as 21 in an abutting wall element and bonded together for rigidity and watertightness by a suitable cement suchas Epox and epoxy cement, not shown.

A central vibrating mass element consisting of a center slab 22 preferably of aluminum or other nonmagnetic material with opposite side portions 12, 23 (FIG. 2) of low reluctance magnetic material secured to the plate 22 through

intermediate mass elements

24, 25, is supported within the hollow piston element free of the side walls l6, l7, l8 and 19, by a spring coupling to the

opposite end walls

10, 15, which form the endsof the hollow piston, through spring elements 26. The side walls and piston ends thus have freedom of movement as a unit independently of the central vibratory mass. This coupling to the

end walls

10 and 15 of the piston is effected through spring assemblies each consisting of a row of three ring-shaped springs 26 secured between a pair of mounting bars such as the

bars

27 and 28. As shown in FIGS. 1 and 2, the spring elements 26 connect the central element to opposite end walls of the piston element in the direction of relative movement between the central'element and the piston .element and independently of the side walls. The bars 27 are rigidly bonded to one side of the center plate 22 along a marginal edge in any known or other suitable manner as by brazing, welding or bonding with a suitable cement such as an epoxy cement, the latter being used in the present instance. To insure proper alignment and facilitate the bonding, use is made of bolts 29. (FIG. 1 passing through the center plate to similarly secure the barv 27 of another spring assembly on the opposite side of the plate. The bars 28 of the spring assemblies are also rigidly .bonded to the inner side of an

adjacent end wall

10 or 15 near the outer marginal edges of the end walls. In the present instance the spring rings 26 are secured to the bars by brazing, the rings being fitted into complementary curved notches 31 (FIG. 1) in the bars to provide substantial brazing surface between the ring and bar.

The low reluctance

magnetic elements

12 and 23 carried by the center plate 22 are laminated as indicated for element 12 in FIGS. 1 and 3, and rigidly secured to adjacent

intermediate slabs

24, 25 by a suitable cement such as an epoxy cement, while the

slabs

24, 25 are similarly rigidly secured to the center plate 22. The

intermediate slabs

24, 25 are of metal which may be nonmagnetic or magnetic inasmuch as their main function is to add mass and desired thickness to the central vibratory mass element comprised of the

elements

22, 24, 25, 12 and 23. Where expedient, the low reluctance

magnetic elements

12 and 23 may be made of sufficient depth to take on the function of the

elements

24 and 25, of supplying mass and spacing.

Laminated electro-

magnet elements

11 and 32 are rigidly secured to the inner sides of the rear and

front end walls

10 and 15 respectively to form in effect substantially rigid end walls having a portion formed of low reluctance material for cooperation with the'magnet

elements

12 and 23. Energization of these low reluctance portions or

elements

11 and 32 is effected by suitable

energizing coil elements

33 and 34 potted in plastic and formed to fit into E-slots in the outer laminated

magnet elements

11, 32, there being three such potted coils for each of the electro-magnetic elements ll, 32. Thus when the coils are energized there will be induced a magnetic flux confined substantially to pairs of adjacent magnetic elements such as 11, 12 and the air gap 13 between them as indicated by the flux path arrows 35 in FIG. 2, with consequent variation in attractive force between the complementary magnetic elements in proportion to variations in current flow through the coils. Current leads 36 (FIGS. 1 and 3) for the coils are continued out from the piston element through the back end wall via a suitable water-tight stuffing box 37 and cable 38 (FIG. 1).

To complete the unit for use under water in an array of a plurality of such units, it is provided as indicated in FIG. 4 with a protective water-tight coating 39 of noncorrosive material such as neoprene or other suitable material and backed at the rear end wall with a sound absorbing pad 40 of any known or other suitable material such as air-cell rubber to prevent substantial back radiation or reception by the vibratory piston unit. For use in an array, any number of units may be placed in a suitable frame as in FIG. 5 where an arrangement for a four unit array is shown. Here the frame 41 comprises four cells with open fronts into which the units 14 are nested and held in place by retaining cleats 42 backed with a sheet rubber pad 43 and bolted on at the corners of the cells. These rubber pads function to allow the maximum displacement of the piston units required for the particular use. For example, in one particular use for underwater sound transmission and reception the displacement may be of the order of two-thousandths of an inch.

In use each piston unit is connected in a circuit as shown in the schematic diagram of FIG. 6. Here the two multiple groups, one consisting of the three rear coils 33 connected in multiple, and the other the three front coils 34 connected in multiple, are connected in series across a direct current source B of polarizing current such as a battery, over a circuit which may be traced from the battery B through coils 33 in parallel, coils 34 in parallel and back to battery B. For signal current each group of coils is connected in parallel through a

blocking condenser

44 and 45 with a source 46 of alternating signal current. To obtain good linearity and maximum power the circuit is arranged to so direct the biasing and signal currents through the coils as to operate the unit in push-pull and in a manner which requires no chokes in the direct current polarizing circuit. This is accomplished by directing the polarizing current flow from the battery through the coils in a given direction in series through the two groups and the signal current through the two groups in parallel thus aiding the polarizing current in one group and reducing it in the other according to the direction of the signal current. The polarization being of sufficient strength as not to be reduced to zero by opposing cycles in the signal current, opposite variations in the attraction between opposite sides of the central element and the adjacent ends of the enclosing piston element will take place in a push-pull effect to produce corresponding vibration of the piston element as a unit. While the above operation has been described as applied to a single unit it will be understood that all or any number of the units in an array may be so operated inphase or in any phase relation desired, and that both projection and reception of compressional waves is substantially unidirectional due to the absorption pads on the rear end walls of the unit.

It will be noted that with the central vibratory element mounted within the hollow piston element free of the side walls and connected only to the peripheral margins of the substantially rigid end walls, the end walls are caused to vibrate bodily in true piston action without breaking up into out-of-phase vibrations or vibrations of different amplitude, as in the case of a vibrating diaphragm. Thus due to the mounting of the central vibratory element free of the side walls, there is no lateral movement of the side walls and substantially all parts of the piston element vibrate only along the axis X-X, FIG. 1.

In the modification of FIG. 7, the nonmagnetic elastic means connecting the movable elements takes the form of a sheet 47 of elastic, nonmagnetic, nonconducting material such as rubber, filling the gap between the complementary

magnetic elements

11 and 12.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An electro-acoustic transducer comprising an enclosing hollow piston element of relatively light rigid nonmagnetic material having substantially rigid side walls and a pair of parallel opposite substantially flat rigid end walls, a central vibratory mass element situated within said piston element having opposite portions of magnetic material, said end walls of the piston element having portions of magnetic material spaced from adjacent said portions of the central mass element by an air gap, spring means of heavy duty spring material, as compared with said portions of magnetic material, directly connecting said central mass element and end walls independently of the side walls for transmitting motion directly between the vibrating mass and the end walls, and means for inducing a magnetic flux in said portions of magnetic material, whereby flux paths through magnetic material in shunt of the air gap are avoided.

2. An electro-acoustic transducer comprising a vibratory central mass element having opposite outwardly facing side portions of magnetic material, an enclosing substantially rigid freely movable hollow piston element having substantially rigid end walls with inwardly facing portions of magnetic material separated from adjacent outwardlyfacing sides of the central element by air gaps and side walls of substantially rigid nonmagnetic material, spring means directly connecting said central mass element with the said end walls, and means for inducing a magnetic flux in the said outwardly facing side portions of the central element and said inwardly facing portions of the end walls whereby the induced flux is confined substantially to the said gages independently of the side walls.

3. An electro-acoustic transducer comprising a central vibratory mass element, an enclosing piston element of nonmagnetic material having substantially rigid side walls and parallel opposite end walls, two opposite sides of said central element facing the end walls having portions of magnetic material, said end walls of the piston element being adjacent to said opposite sides of said central element and having portions of magnetic material separated by an air gap from the said portions of the central element, means for inducing a magnetic flux through said portions of magnetic material and air gap, and spring means directly connecting said magnetic portions of said central element and the piston element through nonmagnetic material independently of said side walls, all portions of said piston element except said magnetic portions of the end walls being of nonmagnetic material, whereby the paths of lowest reluctance of said induced flux is limited to said air gap and said portions of magnetic material.

4. An electro-acoustic transducer comprising a central vibratory mass element having a portion of magnetic material, a hollow piston element of nonmagnetic material enclosing said central element and having a portion of one end wall formed of magnetic material spaced from the central element by an air gap, means for inducing a magnetic flux through said portions of magnetic material and air gap, and means resiliently connecting said portions around the air gap through nonmagnetic material, whereby the path of lowest reluctance for said induced flux is confined mainly to said portions of magnetic material and said air gap, independently of said connecting means and piston element.

5. An electro-acoustic transducer comprising a pair of separate relatively movable vibratory mass elements one within the other, the outer mass element being in the form of a hollow piston having rigid side walls of nonmagnetic material and a pair of rigid end walls of nonmagnetic material, a pair of complementary magnetic elements carried one on each of a pair of adjacent portions of said mass elements and spaced by an air gap, and compression spring means connecting said inner mass element directly with the end walls independently of the side walls.

6. An electro-acoustic transducer comprising a rigid hollow piston element of nonmagnetic material having substantially rigid side walls and a pair of opposite parallel end walls, an inner platform element of nonmagnetic material situated centrally within the hollow piston spaced from the side walls thereof and parallel to said end walls, pairs of complementary magnetic elements fixed respectively to the inside of each of said pair of end walls and adjacent side wall of said platform with an air gap between said magnetic elements, means for inducing a magnetic flux through said magnetic elements and said air gap, and spring means directly connecting said platform with the peripheral margin of the inner side of the end walls independently of the side walls, said pairs of complementary elements being magnetically separated from each other by the nonmagnetic material of the inner platform and piston, whereby the induced magnetic flux is confined to a passage through the magnetic elements and the intervening air gap.

7. An electro-acoustic transducer comprising a substantially rigid cubicle hollow piston element having side walls and a pair of end walls of nonmagnetic material, a relatively movable inner vibratory mass element of nonmagnetic material wholly disconnected from the inner sides of the piston element, spring means directly connecting the peripheral margin of said inner element and the peripheral margins of said two opposite end walls of said piston element for transmission of pressure variations from said inner element to said opposite end walls independently of the side walls, mass elements of magnetic material carried on opposite sides of said inner elements, other mass elements of magnetic material one carried by each of said opposite end walls and spaced from the adjacent inner mass element by an air gap, and means for inducing a magnetic flux through a pair of adjacent said mass elements and the intervening air gap.

8. An electro-acoustic transducer comprising a pair of separate relatively movable vibratory mass elements one within the other, a pair of complementary magnetic elements carried one on each of a pair of adjacent sides of said mass elements and spaced by a gap to permit relative movement between them, and spring means connecting said relatively movable elements through nonmagnetic material interposed between said complementary magnetic elements, whereby a shunting of magnetic flux through the connection between the relatively movable elements is prevented.

9. An electro-acoustic transducer comprising a pair of separate relatively movable vibratory mass elements one within the other, a pair of complementary magnetic elements carried one on each of a pair of adjacent sides of said mass elements and spaced by a gap to permit relative movement between them, and nonmagnetic elastic means interposed directly between and connecting said complimentary magnetic elements.

10. The improvement of an electro-acoustic transducer comprising a sealed housing formed of a tubular body having an end plate at each end thereof, a center plate having a pair of axially opposed faces, resilient means suspending said center plate for axial movement between said end plates, a first electromagnetic assembly having a portion mounted on one end plate and a portion mounted on one face of said center plate, a second electromagnetic assembly having a portion mounted on the other end plate and a portion mounted on the other face of said center plate, magnetizing coil means associated with each one of said electromagnetic assemblies, sealed electrical terminal means in said housing connected to each magnetizing coil means for enabling electrical connection to be established through said housing to said magnetizing coil means.

11. In an electro-acoustic transducer the combination comprising a base plate having a pair of opposite parallel plane surfaces, a first set of magnetic armature assemblies securely bonded to each of said plane surfaces, each of said armature assemblies having its unbonded surface positioned in a plane parallel to the surface of said base plate, a sealed housing structure totally enclosing said base and armature assemblies, said housing structure having a pair of opposite end plates, a second set of magnetic armature assemblies bonded to the inner surfaces of said opposite end plates, the unbonded surfaces of said second set of magnetic armature assemblies lying in parallel planes and positioned closely adjacent to the plane surfaces of said first set of magnetic armature assemblies, spring spacer means attached between the opposite plane surfaces of said base plate and the inner surfaces of said opposite end plates of said housing structure, magnetizing coil means associated with each set of magnetic areach of said magnetic means, connection means for supplying electrical current to said current coil, and spring elements attached between said first and second magnetic means to hold said magnetic means in operable relationship to each other whereby translatory vibration of the housing structure will result in opposite phase to the translatory vibration of said first magnetic means whenever alternating current is supplied to the current coils.

Claims

2. An electro-acoustic transducer comprising a vibratory central mass element having opposite outwardly facing side portions of magnetic material, an enclosing substantially rigid freely movable hollow piston element having substantially rigid end walls with inwardly facing portions of magnetic material separated from adjacent outwardly facing sides of the central element by air gaps and side walls of substantially rigid nonmagnetic material, spring means directly connecting said central mass element with the said end walls, and means for inducing a magnetic flux in the said outwardly facing side portions of the central element and said inwardly facing portions of the end walls whereby the induced flux is confined substantially to the said gages independently of the side walls.

11. In an electro-acoustic transducer the combination comprising a base plate having a pair of opposite parallel plane surfaces, a first set of magnetic armature assemblies securely bonded to each of said plane surfaces, each of said armature assemblies having its unbonded surface positioned in a plane parallel to the surface of said base plate, a sealed housing structure totally enclosing said base and armature assemblies, said housing structure having a pair of opposite end plates, a second set of magnetic armature assemblies bonded to the inner surfaces of said opposite end plates, the unbonded surfaces of said second set of magnetic armature assemblies lying in parallel planes and positioned closely adjacent to the plane surfaces of said first set of magnetic armature assemblies, spring spacer means attached between the opposite plane surfaces of said base plate and the inner surfaces of said opposite end plates of said housing structure, magnetizing coil means associated with each set of magnetic armature assemblies, sealed electrical terminal means connected to said magnetizing coil means and adapted to permit electrical connection to be established through the housing structure to the magnetizing coil means.

12. An electromagnetic transducer comprising a sealed housing structure having positioned therewithin first magnetic means mounted for translatory vibration, second magnetic means attached to said housing structure and located in operable relationship to said first magnetic means, current coil means associated with each of said magnetic means, connection means for supplying electrical current to said current coil, and spring elements attached between said first and second magnetic means to hold said magnetic means in operable relationship to each other whereby translatory vibration of the housing structure will result in opposite phase to the translatory vibration of said first magnetic means whenever alternating current is supplied to the current coils.