US3742140A

US3742140A - Arrangement for damping torsional oscillations induced in a helical spring, particularly in artificial reverberation devices

Info

Publication number: US3742140A
Application number: US00138208A
Authority: US
Inventors: B Weingartner; W Fidi
Original assignee: AKG Akustische und Kino Geraete GmbH
Current assignee: AKG Acoustics GmbH
Priority date: 1970-05-19
Filing date: 1971-04-28
Publication date: 1973-06-26
Anticipated expiration: 1990-06-26
Also published as: DE2124164A1; AT298826B; GB1306194A; JPS5412781B1

Abstract

A spring system, particularly for an artificial reverberation device, includes a helical spring in which torsional oscillations are induced, and a moving coil system connected to the helical spring for damping the oscillations electromechanically. The moving coil system includes two electrically and magnetically decoupled windings disposed in a permanent magnetic field with one winding being electrically connected to the input of an amplifier and the other winding being electrically connected to the amplifier output. The two windings are mechanically interconnected and arranged in tandem along the turn axis of the helical spring, with the axes of the two windings being mutually perpendicular to each other. The two windings may be mechanically interconnected in directly contiguous arrangement to form a rigid unit, or may be spaced apart and resiliently interconnected by a resilient coupling, such as a metal strip. The moving coil system may serve either as a driving system, for inducing torsional oscillations in the helical spring, or as a pick-up system, for detecting such oscillations. Preferably, the two windings are rectangular, but other configurations may be used with some decrease in the quality.

Description

United States Patent [191 Weingartner et al.

Werner Fidi, Baden Bei Vienna, both of Austria AKG Akustische u. Kino-Gerate G.m.b.II., Vienna, Austria Filed: Apr. 28, 1971 Appl. No.: 138,208

Assignee:

Foreign Application Priority data May 19, 1970 Austria ..'...A 4486/70 US. Cl 179/1 J, 333/30 R, 324/125 Int. Cl. H02k 33/18 Field of Search 179/1 J, 110 B; 84/1.13, 1.14, 1.15, 1.16, 1.24, 1.26; 333/30 R, 71, 30 M; 324/125; 310/36 References Cited UNITED STATES PATENTS 7/1951 Sias 324/125 l/l972 Pasqualli. 9/ l 970 Fidi 5/1930 l-Iotopp 12/1958 Robillard 324/125 FOREIGN PATENTS OR APPLICATIONS Germany 179/1 J 11] 3,742,140 [451 June 26, 1973 886,491 10/1943 France 324/125 Primary Examiner-Kathleen H. Claffy Assistant Examiner.lon Bradford Leaheey Attorney-John J. McGlew and Alfred E. Page [57] ABSTRACT A spring system, particularly for an artificial reverberation device, includes a helical spring in which torsional oscillations are induced, and a moving coil system connected to the helical spring for damping the oscillations electromechanically. The moving coilsystem includes two electrically and magnetically decoupled windings disposed in a permanent magnetic field with one winding being electrically connected to the input of an amplifier and the other winding being electrically connected to the amplifier outpunThe two windings are mechanically interconnected and arranged in tandem along the turn axis of the helical spring, with the axes of the two windings being mutually perpendicular to each other. The two windings may be mechanically interconnected in directly contiguous arrangement to form a rigid unit, or may be spaced apart and resiliently interconnected by a resilient coupling, such as a metal strip. The moving coil system may serve either as a driving system, for inducing torsional oscillations in the helical spring, or as a pick-up system, for detecting such oscillations. Preferably, the two windings are rectangular, but other configurations may be used with some decrease in the quality.

Claims, 4 Drawing Figures PATENTED JUN 26 I975 SHEEI 1 0F 2 PIC-7.2

ARRANGEMENT FOR DAMPING TORSION AL OSCILLATIONS INDUCED IN A HELICAL SPRING, PARTICULARLY IN ARTIFICIAL REVERBERATION DEVICES BACKGROUND OF THE INVENTION An arrangement of this kind is described, for example, in East German Pat. specification No. 56829, in which driving and pick-up systems for a helical spring are mechanically combined with the picked-up signal being fed back to the driving system through an amplifier. The difficulties arising in this known system are due to the fact that adequate separation must be provided between the driving and pick-up systems, with such separation corresponding to an attenuation of 70-90 dB.

In the known arrangement, a bridge circuit is used for this purpose, but such a bridge circuit can not provide satisfactory results over the entire frequency range extending to at least kHz, as at least one branch of the bridge contains both the driving system and the pick-up system, the electrical impedance of this arm depending greatly on the position of the coil or winding in the magnetic field. Aside from this, bridge circuits require a relatively high degree of electrical and technical sophistication, and this affects production costs.

SUMMARY OF THE INVENTION This invention relates to spring systems, particularly for artificial reverberation devices, and more particularly, to a novel and improved spring system providing adequate separation between driving and pick-up systems over the entire frequency range.

In accordance with the invention, a spring system particularly for an artificial reverberation device, includes a helical spring in which torsional vibrations are to be induced, and also includes a moving coil system connected to the helical spring for electromechanically damping the oscillations of the spring. The moving coil system includes two mechanically interconnected coils or windings which are electrically and magnetically decoupled and disposed in a permanent magnetic field. One of the coils is electrically connected to the input of an amplifier and the other to the output of the amplifier. The two coils are arranged in tandem in the spring system along the winding or turn axis of the spring, and with their axes orthogonal, or mutually perpendicular, to each other.

An advantage of a system embodying the invention is that the physical position of the two coils means that the common magnetic flux necessarily is small, while the orthogonal or mutually perpendicular relation between the planes of the two coils or windings, namely the winding planes perpendicular to the coil axes, reduces this flux completely so that only a small magnetic coupling remains. Experimentally, a system embodying the invention produced a crosstalk attenuation of more than 80 dB. in a frequency range of up to 10 kHz.

Advantageously, the coils or windings have the shape of a rectangular frame, but it is also possible that the framelike shape of each coil or winding may be elliptical, circular or other configuration, provided that a certain loss of quality is acceptable, for example, for reasons associated with easier coil winding techniques.

In one embodiment of the invention, the windings are connected together in a directly contiguous arrangement to form a rigid unit.

In another embodiment of the invention, the windings are spaced apart longitudinally of the spring system and are resiliently interconnected by a resilient coupling, for example, a metal strip, so that a frequency-dependent attenuation is obtained, more particularly high attenuation of the low frequencies, the degree of coupling being variable as required by appropriate choice of the strip material, length and shape.

The advantage of a resilient coupling of the two windings is that all the mechanical systems in an artificial reverberation device, from the spring system to the reverberation chamber, have better quality at the lower frequencies. Therefore, it is frequently advantageous to attenuate mainly the lower frequencies without appreciably affecting the higher frequencies. In addition, the mechanical systems tend toward uncontrolled oscillations above a limiting freque cy for example, the frequency above which torsional oscillations are no longer possible, so that although there is a high crosstalk attenuation between the two windings of a spring system embodying the invention, undesirable oscillations may occur as a result of mechanical types of oscillation in the entire amplifier system. All these difficulties can be reduced, or practically eliminated, by resiliently'mechanically coupling the two windings.

For production reasons, it is advantageous to make the windings substantially identical both mechanically and electrically.

Variations in reverberation time can be obtained, in a reverberation device embodying the invention, by making the amplification variable.

An object of the invention is to provide an improved spring system, particularly for artificial reverberation devices. I r

Another object of the invention is to provide such a system including a helical spring in which torsional oscillations are to be induced and a moving coil system connected to the helical spring for electromechanically damping the oscillations of the spring.

A further object of the invention is to provide such asystem in which the moving coil system comprises two mechanically interconnected windings which are electrically and magnetically decoupled and disposed in a permanent magnetic field. i Another object of the invention is to provide such a system in which the two windings are disposed in tandem along' the axis of the helical spring with their axes mutually perpendicular to each other.

A further object of the invention is to provide such a system in which adequate separation between driving and pickup systems can be attained.

Another object of the invention is to provide such a system providing satisfactory results over the entire frequency range.

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawing.

, BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a diagrammatic illustration of a first embodiment of a spring system in accordance with the invention;

V FIG/2 is a diagrammatic illustration of a second embodiment;

FIG. 3 is a diagrammatic illustration of a spring system, embodying the invention, incorporated in an artificial reverberation device having separate driving and pick-up systems; and

FIG. 4 is a diagrammatic illustration of a spring system embodying the invention, incorporated in an artificial reverberation device and serving as either a driving system, a pick-up system, or both.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, the spring system illustrated therein includes a helical spring 1 to which is connected a moving coil system for electromechanically damping torsional oscillations of spring 1. The moving coil system includes two frame-like coils or

windings

3 and 4, which preferably have a rectangular form, as illustrated, although they may have other less advantageous shapes with a corresponding loss of quality. Coils or

windings

3 and 4 are disposed in succession, or in tandem, along the winding or turn axis 6 of spring 1, and are rigidly mechanically interconnected, for example by adhesive, to form a contiguous rigid unit in which the planes of the coils are mutually perpendicular to each other. The coils or windings are disposed for rotation about axis 6 in a permanent magnetic field between a north pole N and a south pole S of a permanent magnet system 2.

It is frequently advantageous not to connect the winding 3 and 4 to form a rigid unit, but rather to mechanically interconnect them with a varying degree of resilience. A construction of this type is shown in FIG. 2, wherein a resilient mechanical coupling 12 is provided between

windings

3 and 4, and constitutes a thin resilient strip, for example a steel strip, mechanically interconnecting the two windings. One of the two windings, illustrated as winding 3 in FIG. 2, is rigidly connected to the terminal turn of spring 1, particularly at points 10 and 11. A synthetic resin adhesive is most suitable for this purpose.

FIG. 3 illustrates a spring system embodying the invention serving simply as an attenuating element in an artificial reverberation device. Torsional .oscillations are induced in coil spring 1, at one end thereof, by a driving system E. The oscillations are propagated along spring I and are picked up at the other end of spring 1 by a pick-up system A. An attenuating system D, embodying the invention, is incorporated, for example, at substantially the middle of coil spring 1. 'Attenuating system D includes permanent magnet system 2 in the air gap of which there are situated windings 3- and 4 with their planes at, right angles to each-other. The windings are rigidly interconnected, and therefore form a unit which moves about the winding or turn axis 6 of coil spring I.

In FIG. 3, the moving coil system isconnected as rigidly as possible at the points 5, to a turn of coil spring 1, so that the oscillations of the spring are also transmitted to the moving coil unit formed by

windings

3 and 4. The EMF induced in winding 3 by movement in the permanent magnetic field of permanent magnet system 2, is fed to the input of a variable gain amplifier 7. The resulting amplifier output is fed to the winding 4, arranged so that the current flowingtherein interacts with the magnetic field of system 2 to transmit, to the unit formed by

windings

3 and 4, a torque directed in opposition to the torque of winding 3. The magnitude of the torque depends upon the amplification factor of amplifier 7. Since amplifier 7 has a variable amplification, the attenuation required for coil spring 1, and hence different reverberation times, can be finely adjusted.

From transmission line theory, it is known that high attenuation can be obtained most satisfactorily by disposing an attenuation system at the end of the transmission line. Using this principle, it is possible to provide a reverberation device in which a two-coil moving coil system, embodying the invention is used both as a driving or input system and as a pick-up or output system. An arrangement of this kind is shown in FIG. 4.

Referring to FIG. 4, the simple driving system E shown in FIG. 3, is replaced by a moving coil system embodying the moving coils or

windings

3 and 4 in accordance with the invention. The signal for reverberation is also fed to amplifier 7, whose output 9 is connected to winding 3. Angular or torsional oscillations about axis 6 of coil spring 1 thus are induced in winding 3 positioned in the magnetic field of permanent magnet system 2, and are transmitted to winding 4 through the rigid connection between

windings

3 and 4, and to coil spring 1 by virtue of connection of coil spring 1 to winding 4 at the points 5. The EMF induced in winding 4 by its movement in the permanent magnetic field is supplied to input 8 of amplifier 7.

The pick-up system A is provided at the other end of coil spring 1, and its construction is identical with that of the drive system E. The only difference in the circuit arises from the fact that the arrangement functions as a pick-up system rather than as a driving system. The torsional oscillations arriving at pick-up system A, after travelling along coil spring 1, induce similar angular oscillations in the unit consisting of the rigidly interconnected windings 3', 4' in the magnetic field of permanent magnet system 2'. The EMF induced in winding 4' is supplied to the input 8 of amplifier 7, and the reverberated signal is picked up from a second output. From the first output 9', the signal is supplied to winding 3, the polarity of which, in the permanent magnetic field, is such that it tends to counteract the angular movement of winding 4. The required attenuation of .coil spring 1 can be adjusted in accordance with the magnitude of the output voltage.

It is, of course, possible to use a moving coil system, comprising the two

interconnected windings

3 and 4, only as a driving system or only as a pick-up system, and to use a moving coil system having only one coil for the other of the two systems. An arrangement of this kind is adequate in many cases, particularly when quality requirements are not strict.

As mentioned, the windings used in the spring system embodying the invention preferably have the shape of a rectangular frame, but circular, elliptical or other frame shapes for the windings also can be employed.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that theinvention may be embodied otherwise without departing from such principles.

What is claimed is:

l. A spring system, particularly for an artificial reverberation device, including a helical spring, in which torsional oscillations are to be induced, and a moving coil system connected to the helical spring for damping the oscillations electromechanically and including two electrically and magnetically decoupled windings disposed in a permanent magnetic field, with one winding being electrically connected to the input of an amplifier and the other winding being electrically connected to the amplifier output, said two windings being mechanically interconnected with each other and being arranged in tandem along the turn axis of said helical spring, with the axes of said windings being mutually perpendicular to each other.

2. A spring system, particularly for an artificial reverberation device, as claimed in claim 1, in which said two windings are fixedly connected together in directly contiguous relation, to form a rigid unit.

3. A spring system, particularly for an artificial reverberation device, as claimed in claim 1, in which said two windings are spaced apart along the turn axis of said spring; and a resilient coupling resiliently interconnecting said two windings.

4. A spring system, particularly for an artificial reverberation device, as claimed in claim 3, in which said resilient coupling is a metal strip.

5. A spring system, particularly for an artificial rever beration device, as claimed in claim 1, in which said windings have substantially identical shapes.

6. A spring system, particularly for an artificial reverberation device, as claimed in claim 1, in which said windings have substantially identical electrical properties.

7. A spring system, particularly for an artificial reverberation device, as claimed in claim 1, in which said windings have the shape of a rectangular frame.

8. A spring system, particularly for an artificial rever beration device, as claimed in claim 1, wherein said two windings serve additionally as a driving system for inducing torsional oscillations in said helical spring.

9. A spring system, particularly for an artificial reverberation device, as claimed in claim 1, wherein said two windings serve additionally as a pick-up system detecting the torsional oscillations in said helical spring.

10. A spring system, particularly for an artificial reverberation device, as claimed in claim 1, in which said two windings are disposed at substantially the middle of said helical spring; a moving coil drive system connected to one end of said helical spring; and a moving coil pick-up system connected to the opposite end of said helical spring.

Claims

1. A spring system, particularly for an artificial reverberation device, including a helical spring, in which torsional oscillations are to be induced, and a moving coil system connected to the helical spring for damping the oscillations electromechanically and including two electrically and magnetically decoupled windings disposed in a permanent magnetic field, with one winding being electrically connected to the input of an amplifier and the other winding being electrically connected to the amplifier output, said two windings being mechanically interconnected with each other and being arranged in tandem along the turn axis of said helical spring, with the axes of said windings being mutually perpendicular to each other.

5. A spring system, particularly for an artificial reverberation device, as claimed in claim 1, in which said windings have substantially identical shapes.

8. A spring system, particularly for an artificial reverberation device, as claimed in claim 1, wherein said two windings serve additionally as a driving system for inducing torsional oscillations in said helical spring.