US3016429A

US3016429A - Magnetostructure recording device

Info

Publication number: US3016429A
Application number: US808739A
Authority: US
Inventors: George N Johnson; Charles L Vice
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1959-04-24
Filing date: 1959-04-24
Publication date: 1962-01-09
Anticipated expiration: 1979-01-09

Description

Jan. 9, 1962 G. N. JOHNSON ETAL 3,016,429

MAGNETOSTRUCTURE RECORDING DEVICE 2 Sheets-Sheet 1 Filed April 24, 1959 2 1 M i f H. 06% 9 LT r a 4 d MJL r z Judd/Haw wMr a r w .k w w WM a a a a. a: Z a ma 6 W 6 w M a 2% w 5 a a 4 4 g f M A Z Z v a w 1 a w w F 2 Jan. 9, 1962 2 Sheets-Sheet 2 Filed April 24, 1959 United States Patent of Delaware Filed Apr. 24, 1959, Ser. No. 808,739

11 Claims. (Cl. 179-1001) This invention relates to a transducer head for use with magnetic tape in a transverse recording system and, more particularly, refersto a transducer in the form of a tube of magnetostrictive material having a longitudinal nonmagnetic gap. A transverse recording system employing such a transducer tube is disclosed in the co-pending Wayne R. Johnson patent application, Serial No. 733,165, filed May 5, 1958.

In accord with the teaching of the co-pending Johnson application, the material of the transducer tu-be may be of either positive or negative magnetostrictive character. The transducer tube is placed under longitudinal stress and a signal generator creates in the tube longitudinal lelastic .waves of pulse form that are of opposite sign to the stress applied to the tube. Thus, if the transducer tube is stressed in tension, the acoustic signal generator applies compressive waves to the transducer tube. The tube functions in effect as an acoustic transmission line down'which the compressive pulses are propagated while a second signal generator develops circumferential magnetic fields in thetube wall. The longitudinal tensioning 'creates high reluctance in the tube as a whole but the elastic pulses from the acoustic signal generator create narrow traveling zones where the longitudinal tension of the tube is relaxed for local lowering of the tube reluctance, and where the second signal generator. creates local circumferential magnetic fields for recording on the traveling tape. The components of such a transducer head must be accurately related to each other. The longitudinal stressing of the transducer tube must be adjustable for close control and the structure employed must be capable of maintaining any selected stress adjustment. The acoustic signal generator must also be internally stressed with close adjustment and, in addition, must be maintained in effective pressure communication with the longitudinally stressed transducer tube. In the preferred practice of the invention, a tapered tubular driver section isinterposed between the acoustic signal generator and the end of the transducer tube for impedance matching and the required pressure communication must be provided and maintained through this driver section.

' One requirement to which the invention is directed is to provide a transducer head assembly incorporating convenient and efficient means for making and maintaining these various adjustment-s. Another requirement is to provide a transducer assembly of this character in the form of a self-contained unit in which all of the necessary adjustment may be made in advance of installation of the unit. A further requirement is shielding of the two signal generators and the electrical connections. A still further requirement is provision of means for mounting the transducer tube under purely longitudinal stress without introducing bending stress or stress in torsion.

To meet these requirements, the invention provides a ,;support structure in the form of a bracket or yoke having means at its opposite ends to engage the opposite ends of ice the transducer tube with suitable provision for adjustably tensioning the tube. The use of universal joints for connecting the transducer tube with the bracket prevents the application of bending forces and torsional forces to the transducer tube and thus insures that the transducer tube is subjected solely to longitudinal stress. Mounted on one end of the bracket is a shield for the magnetic signal generator. Mounted on the other end of the bracket is a tubular structure which houses'and shields the acoustic signal generator and the driver section. This tubular structure serves as a conductor for one side'of the exciting circuit and shields an axial conductor for the other side of the circuit. 1 5' The tubular structure incorporates means to stress the acoustic signal generator itself and to create pressure communication' between the acoustic signal generator and the tube. .In the preferred practice of the invention which includes a driver section interposed between the acoustic signal generator and the transducer tube, the tubular shielding structure also incorporates means to clamp the intermediate driver section against the transducer tube. Thus the-structural arrangement provides three independ- "ent adjustments, one for the stressing of the transducer tube, one for pre-loading the acoustic signal generator, and one to hold the driver section in position for transmitting the acoustic signals to the transducer tube.

' -The various features and advantages of the invention may be understood by reference to the following detailed description considered with the accompanying drawings.

'lustrative:

In the drawings, which are to be regarded as merely il- FIG. 1 is a longitudinal sectional view of a selected embodimcnt of the invention; 7 FIG. 2 isa side elevation of the same embodiment of the invention on a reduced scale;

FIG. 3 is a fragmentary view partly in side elevation and partly in section showing how the transducer tube is connected to the upper arm of the bracket;

FIG. 4 is a similar view showing how the transducer tube is connected to the lower arm of the bracket;

FIG. 4a is an enlarged transverse section of the transducer tube taken as indicated by the line 4a-4a of FIG.

4; and

FIG. 5 is a view partly in side elevation and partly in section showing a modification of the invention in which the driver section is omitted.

The principal parts of the first embodiment of the-invention shown in FIGS. 1 to 4 include; a transducer tube 10; a toroidal signal coil 12 mounted on the lower end of the tube; a tapered tubular driver section 14; an acoustic signal generator in the form of a piezoelectric crystal 15 of annular configuration; a metal disk 16 for electrically connecting the piezoelectric crystal to an axial conductor 18; and a second annular'shaped crystal 20 that is insullated by a pair of non-conductive rings 22 and serves as means to absorb acoustic signals that are directed upward from the piezoelectric crystal 15. As indicated in FIG. 4a, the transducer tube 10 is formed with a longitudinal non-magnetic gap 21. Thetransducer cooperates with a traveling magentic tape 23 that moves across the longitudinal gap 21 transversely thereof.

As best shown in FIG. 2, a support structure in the form 'of a yoke or bracket 24 serves to hold the transducer tube "10in tension and carries an upwardly extending tubular structure. This tubular structure includes a tubular body and an adjustment sleeve 26 which engages an external screw thread 28 of the tubular body. A plug 30 having an axial bore 32 to clear the axial conductor 18 is mounted above the adjustment sleeve 26 for connection to a coaxial cable 34. In the construction shown, a coaxial fitting 35 is mounted on the plug 30 by screws 36 for releasable connection with a complementary coaxial fitting 38 in a well-known manner, the complementary fitting being carried by the coaxial cable.

The bracket'24 may be formed with an integral mounting lug 40 having an aperture 42 to receive a screw or bolt. The bracket has an upper arm 44 which, as best shown in FIG. 3, has an aperture 45 to receive the upper end of the transducer tube 10. In like manner, the bracket 24 has a lower arm 46 which, as best shown in FIG. 4, has an aperture 48 to receive the lower end of the transducer tube.

What may be termed a first engagement means engages the upper end of the transducer tube '10 to connect the upper end of the tube to the bracket arm 44 and what may be termed a second engagemcnt'rneans engages the lower end of the transducer tube to connect the lower end to the lower arm 46 of the bracket.

The first engagement means includes a spehrically curved seat 50 formed in the aperture 45 in the upper arm 44 of the bracket 24 and further includes a spherically curved lower portion 52 of the previously mentioned tubular body 25. As shown in section in FIG. 1, this first engagement means also includes an adjustment bushing 54 with a shoulder 55 for engaging a radial flange 56 that is formed on the upper end of the transducer tube 10. The adjustment bushing 54 is threaded into. the interior of the tubular body 25 and has a pair of diametrically opposite recesses 57 whereby the adjustm n bu ng nay be con i nt y man pulated y means of a spanner.

As shown in FIG. 4, the second engagement means for the lower end of the transducer tube 10 includes a Collar 58 which is secured on the lower end of the trans: ducer tube by a cross pin 60 and which has a spherically curved upper surface 62. A sleeve 64 which surrounds the transducer tube has a spherically curved concave surface 65 to cooperate with the spherically curved surface 62. An adjustment bushing 66 which threads into a counterbore 68 has an inner circumferential shoulder 70 in engagement with .an outer circumferential shoulder 72 of the sleeve. The adjustment bushing 66 is of hexagonal configuration, as shown in FIG. 2, and is exposed for convenient manual adjustment.

The tubular body 25 is formed with an inner circumferential shoulder 73 which engages a radial flange 74 of the driver section and which also supports a cylindrical member 75 of suitable material, such as Teflon. This cylindrical member 75 serves both to center the two piezoelectric crystals 15 and 20 and to insulate the two crystals from the surrounding structure.

Downward pressure against the two piezoelectric crystals 15 and 20 is exerted by a thrust body 76 having an axial bore 78 to clear the axial conductor 18, This thrust body has a counterbore 80 which is threaded to receive a reduced axial portion of the plug 30, as shown. The previously mentioned adjustment sleeve 26 overhangs the thrust body 76 for abutment against the upper end thereof to create the required pressure against the two annular crystals.

Any suitable structure may be employed to shield the toroidal signal coil 12. In the construction shown in FIGS. 2 and 4, a ferrous metal block is anchored to the bracket 24 by screws 92. This metal block has a central bore 94 to clear the transducer tube 10 and a counterbore 95 to clear the toroidal coil 12. A cover plate 96 with an aperture 98 to clear the transducer tube is secured by the same screws 92. The insulated wires 100 for the toroidal signal coil enter through a transverse bore 102 in the metal block 90.

The manner in which the invention serves its purpose may be readily understood from the foregoing description. It is apparent that tightening of the lower hexagonal adjustment bushing 66 pulls the sleeve 64 downward against the collar 58 to exert downward pull on the lower end of the transducer tube 10. The seating of the spherically curved surface 62 of the collar 58 against the spherically curved surface 65 of the sleeve 64 and the seating of the spherically curved surface of the lower portion 52 of the tubular body 25 against the spherically curved surface of the seat 50 prevents transmission to the transducer tube of any forces that would tend to flex the tube or to place the tube under torsional stress.

With the adjustment sleeve 26 abutting the thrust body 76 and with the inner circumferential shoulder 73 of the tubular body 25 engaging the radial flange 74 of the driver section 14, it is apparent that the two crystals 15 and 20 may be clamped against the'end of the driver section with a desired pressure. It is further apparent that the adjustment bushing 54 in engagement with the radial flange 55 at the upper end of the transducer tube 10 may be manipulated to clamp the driver section 14 against the end of the tube. All of these adjustments may be made in advance of the actual installation of the unit.

If the driver section 14 is omitted, the tubular structure shown in FIG. 5 may be substituted for the tubular structure shown in FIGS, 1 and 2. The tubular structure shown in FIG. 5 comprises a relatively short tubular body 82 which has a spherically curved lower portion 84 that fits into the previously described spherically curved seat 50 in the upper arm 44 of the bracket 34.- The tubular body 82 has an inner circumferential shoul der 85 which engages the previously mentioned radial flange 74 at the upper end'of the transducer tube 10 This inner shoulder 85 also supports a previously a scribed cylindrical plastic member 75 that een'ters and insulates the two pieioelectr'ic crystals 15 20. The previously mentioned adjustment sleeve 26 is threaded onto the tubular body 82 and presses the previously described inner thrust body 76 toward the two piez'o electric crystals. Thus the adjustment sleeve 26 and the inner thrust body 76 cooperate with the tubular body' 82 to clamp the two crystals against the end of the transducer tube 10 as required for effective transmission of the elastic wave pulses to the transducer tube.

Our description in specific detail of the selected embodiments of the invention will suggest various changes, substitutions and other departures from our disclosure within the spirit and scope of the appended claims.

We claim:

I. In a transducer assembly of the character described wherein a longitudinally stressed transducer tube of magnetostrictive material formed with a longitudinal non magnetic gap is subjected by a first signal generator to longitudinal elastic pulse waves of opposite sign to its longitudinal stress and is provided with a second signal generator in the form of a signal winding to develop a circumferential magnetic field therein, the combination therewith of means to hold the parts of the assembly together to form a self-contained transducer unit, said holding means comprising: a support structure .to support the assembly and place said tube under longitudinal stress; first engagement means engaging one end of said tube and connecting said one end with said support structure for transmission of stress between the tube and the support structure; second engagement means engaging the second end of said tube and connecting said second end with said support structure for transmission of stress between the tube and the support structure; adjustment means to vary the efiective distance between said first and second means to vary the longitudinal stressing of the tube; and adjustable means supported by said support structure to stress said first signal generator longitudinally for transmission of said elastic pulse waves to the tube.

2. A combination as set forth in claim 1 which includes a pair of conductor-s for connecting said first signal generator with an energizing circuit; and in which said first engagement means together with said stressing means forms a tubular metal structure constituting one of said two conductors, said tubular structure enclosing and shielding both said first signal generator and the other of sald two conductors.

3. In a transducer assembly of the character described wherein a longitudinally stressed transducer tube of magnetostrictive material formed with a longitudinal nonmagnetic gap is subjected by a first signal generator to longitudinal elastic pulse waves of opposite sign to its longitudinal stress and is provided with a second signal generator in the form of a signal winding to develop a circumferential magnetic field therein, the combination therewith of means to hold the parts of the assembly together to form a self-contained transducer unit, said holding means comprising: a support structure to support the assembly and place said tube under longitudinal stress; first engagement means engaging one end of said tube and connecting said one end with said support structure for transmission of stress between the tube and the support structure; second engagement means engaging the second end of said tube and connecting said second end with said support structure for transmission of stress between the tube and the support structure, each of said engagement means including a convex spherically curved element seating in a cooperating concave spherically curved element to form a universal joint to avoid subjecting the tube to bending stress; adjustment means to vary the effective distance between said first and second means to vary the longitudinal stressing of the t be; and adjustable means supported by said support structure to stress said first signal generator longitudinally for transmission of said elastic pulse waves to the tube.

4. In a transducer assembly of the character described wherein a longitudinally stressed transducer tube of magnetostrictive material formed with a longitudinal nonmagnetic gap is subjected by a first signal generator to longitudinal elastic pulse waves of opposite sign to its longitudinal stress and is provided with a second signal generator in the form of a signal winding to develop a circumferential'magnetic field therein, the combination therewith of means to hold the parts of the assembly together to form a selfcontained transducer unit, said holding means comprising: a support structure to support the assembly and place said tube under longitudinal stress; first engagement means engaging one'end of said tube and connecting said one end with said support structure for transmission of stress between the tube and the support structure; second engagement means engaging the second end of said tube and connecting said second end with said support structure for transmission of stress between the tube and the support structure, each of said engagement means including a convex spherically curved element seating in a cooperating concave spherically curved element to form a universal joint to avoid subjecting the tube to bending stress, at least one of said engagement means being adjustable to vary the longitudinal stressing of the tube; and means to stress said first signal generator longitudinally for transmission of said elastic pulse waves to the tube, said stressing means being supported by said first engagement means and being adjustably connected therewith for adjustment of the stressing of said first signal generator.

5. In a transducer assembly of the character described wherein a longitudinally stressed transducer tube of magnetostrictive material formed with a longitudinal nonmagnetic gap is subjected to longitudinal elastic pulse waves of opposite signs to its longitudinal stress by a first signal generator cooperating with a tapered tubular driver section and is provided with a second signal generator in the form of a signal winding to develop a circumferential magnetic field therein, the combination therewith of means to hold the parts of the assembly together to form a self-contained transducer unit, said holding means comprising: a support structure to support the assembly and place said tube under longitudinal stress; first engagement means engaging oneend of said tube and connecting said one end with said support structure for transmission of stress between the tube and the support structure; second engagement means engaging the second end of said tube and connecting said second end with said support structure for transmissionof stress between the tube and the support structure; and means to retain said first signal generator against said driver section and to retain said driver section against the end of the transducer tube, said retaining means being supported by said support structure and being adjustable relative to said first engagement means for cooperating therewith to urge said first signal generator toward the tube and to clamp said driver section between the first signal generator and the tube.

6. A combination as set forth in claim 5 which includes an axial conductor for connecting said first signal generator to one side of an energizing circuit; and in which said retaining means is a tubular structure to serve as a conductor to connect the first signal generator to the other side of the circuit, said tubular structure surrounding and shielding said axial conductor, said first signal generator and said driver section.

7. In a transducer assembly of the character described wherein a longitudinally stressed transducer tube of magnetostrictive material formed with a longitudinal non-magnetic gap is subjected to longitudinal elastic pulse waves of opposite sign to its longitudinal stress by a first signal generator cooperating with a tapered tubular driver section and is provided with a second signal generator in the form of a signal winding to develop a circumferential magnetic field therein, the combination therewith of means to hold the parts of the assembly together to form a self-contained transducer unit, said holding means comprising: a support structure to support the assembly and place said tube under longitudinal stress; first engagement means engaging one end of said tube and connecting said one end with said support Structure for transmission of stress between the tube and the support structure; second engagement means engaging the second end of said tube and connecting said second end with said support structure for transmission of stress between the tube and the support structure; and means clamping said first signal generator and said driver section together, said clamping means being supported by said support structure in position to hold said first signal generator and said driver section in axial alignment with the tube.

8. A combination as set forth in claim 7 in which said first engagement means is adjustable relative to said clamping means for adjustably pressing said tube and driver section together.

9. A combination as set forth in claim 7 in which said clamping means is a tubular structure to serve as a conductor to connect the first signal generator to one side of an energizing circuit; and in which said tubular structure surrounds and shields said first signal generator and said driver section.

10. A combination as set forth in claim 7 in which said first and second engagement means incorporate universal joints for transmitting stress to the opposite ends of said transducer tube without subjecting the transducer tube to bending stress or stress in torsion.

11. In a transducer assembly of the character described wherein a longitudinally stressed transducer tube of magnetostrictive material formed with a longitudinal non-magnetic gap is subjected by a first signal generator to longitudinal elastic pulse waves of opposite sign to its longitudinal stress and is provided with a second signal generator in the form of a signal winding to develop a circumferential magnetic field therein, the combination 7 therewith of means to hold the parts of the assembly together to form a self-contained transducer unit, said holding means comprising: a support structure to support the assembly and place said tube under longitudinal stress; first engagement means engaging one end of said tube and connecting said one end With said support structure for transmission of stress between the tube and the support structure; second engagement means engaging the second end of said tube and connecting said second end with said support structure for transmission of stress between the tube and the support structure, each of said engagement means including a universal joint to prevent the creation of bending stresses or torque stresses in the tube; and clamping means holding said first signal generator in direct pressure contact with the end of said transducer tube, said clamping means connected with said first engagement means.

References Cited in the file of this patent UNITED STATES PATENTS 2,001,132 Hansell July 18, 1930 2,101,272 Scott Dec. 7, 1937 2,683,856 Ko'rnei July 13, 1954 2,780,774 Epstein Feb. 5, 1957 2,921,989 Serrell Jan. 16, 1960