MEANS FOR DMEIPENG VIBRATORY STRUCTURES OF VIBRATION AiPARATUS Mimi 0%. 22. 192% TEIIEICH HJECH'I, HUGO LICHTE, AND JBERNHARD; NIELSEN, F KIEL, GE! ll ASSIGNORS TO SIGN l GE 1 w a .GESELLSCHQAFT i w mar nnsonnllrmrnn narrower, or KIEL,
s roe, a PING- naronr srauc'ru'nns or vrnrmrron ranarcs;
Application filled October 22,1923. Serial Ito. 670,017.
To all whom itrrmg concern."
Be it known that we, HEINRICH I-IEoHT, IIUoo LICHTE, and BERNHARD NIELSEN, citizens of the German Republic, and residing t at Kiel, Germany, Province of Schleswig- Holstein, State of Prussia, have invented certain new and useful Improvements in Means for Damping Vibratory Structures of Vibration Apparatus, of which the folno lowing is a specification.
It has been proposed to damp the motions of vibratory structures of acoustic apparatus by causin the size "of chambers filledwith fluid an adjacent to said structures to be altered by the vibratory motions of these structures and allowing the fluid in the chambers to flow through narrow open ings in their walls. The consumption of energ required for the damping effect is 0 cause by the passage of the fluid medium through the sald openings.
It has also been proposed to make these chambers very low or flat in order to increase the damping effect.
In practical apparatus it has been found that to obtain a good damping eflect these chambers have to be so very flat or shallow that their construction is very diflicult.
In accordance with the invention these 30, chambers, instead of being made so extremelp shallow, are tuned to the frequency of vibratory structures to be damped. The degree and nature of the eflect thus accomcplished is the same; The tuning results in the medium flowing throu h the narrow openings as violently as i very shallow chambers were employed.
The invention is' illustrated in the drawinfiq in which 4o ig. .1 is a cross section of a sound receiver fitted with a microphone and a tuned damping-chamber,
i Fig. 2iis a mction of an electromagnetic sound apparatus (telephone receiver) with a tuned damping chamber which may be d both for sending and'receiving, and
Fig. 3 is a graph s owing the frequencies of resonance of an apparatus according to the invention. l I
The apparatus of Hi 1 is provided with a diaphragm sound ra iator to which is attached a microphone comprising a casing 2, an electrode 3 connected thereto, a; freely vibrating electrode 5 connected through the elastic member'or diaphragm4 to the casing 2. Disposed between the electrodes in a known manner is a filling of carbon 6 which isprevented from falling out by a soft packing ring 7. The damping chamber is \formed by the space in the casing 2 closed by the diaphragm 4. There are small openings 8 in the diaphragm 4. These openings 'andthe damping chamber itself are of such size as to result in the damping chamber being tuned to the frequency of the vibratory structure '(microphone) so that the chamber acts as a resonator and when the structure is excited at the frequency of resonance a correspondingly strong damping efl'ect is roduced by the volume of air that passes t rough the small openings 8.
In Fig. 2,.the vibratory structure itself composed 'of a diaphragm sound radiator) 9 with an armature 10. armature is a permanent magnet 11 fixed to the back-12 of the casing which envelops pposite the I the apparatus. The coils 13 receive or deliver alternating current. The subject of this invention consists more particularly in the narrow space 14 located at one side by the inner surface of the diaphragm, bounded at the other side by the rigid. wall 15, and
containing air. The fluid passage in which thedamping action takes place is the circular air gap lfi'between the armature 10 and the inner edge of the wall or plate 15 which has the shape of a'disk with a central hole. The dampin chamber 14 is tuned to the frequency 0 the diaphragm 9 'with its armature 10.
In telephones intended for the reproduction of articulate speech the two different vibratory structures or units consisting of the diaphragm and the damping chamber respectively are preferably both tuned to a frequency of 1500 cycles and coupled together in such a manner that the resulting frequencies of resonance after coupling lie between 1000 and 1500 cycles on the one hand and between 1500 and 2000 cycles on the other hand. This is represented by the graph in Fig. 3. In this graph the abscissae denote frequencies and the ordinates the amplitudes or loudness of the apparatus shown in Fig; 2. .The dotted curve whose crest lies at 1500 represents the resonance curve of each vibratory structure or unit but instead is a chamber that any. case in constructing the apparatus.
by itself, while the solid curve is the resonance curve of the apparatus with its vibratOIX structures cou led together. characteristic eature of the apparatus of Fig. 1 is' the arrangement of the damping chamber itself. The chamber employed as such is not a separate additional space provided especially for dampingi purposes, evelops in This type in itself is of technical importance because it leads to a simple and cheap instrument. Of course, the chamber has to be tuned to accord with the invention.
The damping openings ma be arranged at an parts of the walls'o the'dampmg cham n They form in their entirety the opening of the resonator which the dam ing chamber constitutes. By altering their number and size this resonator can be tuned. Obviously they are best arranged at ornear the-parts of the vibratory structure (Fig.
1 there are three vibratory units or' b0 i es to deal with, the one being formed by damping chamber itself,-'the second by the masses and elastic members of the microphone or elec'tro-ma net, and the third by the diaphragm. If t e three units or bodies are all coupled together extremely closely the dampin' action of the damping-chamber is distri uted approximately un formly amnn the three units or bodies, particular- -ly 1ft ey are all tuned to the samenatural rate of vibration. The scope of the invention is not limited to sound'apparatus as used for example in telephony, wire or wireless telegraphy, and sound transmission throu h air and under water etc, but includes al kinds of vibra-' tors for all manner of technical uses. It
, can therefore also produce excellent results I in. vibratory apparatus for balancing phases in alternatin current supply systems, apparatus in w ich vibratory structures are used for testing materials and in similar machines.
We claim:- 1.-In acoustic apparatus,- a vibratory structure, and a chamber containing fluid.- which' latter is adapted to be acted upon by saidvibratory structure and having an ope in its wall through which'the fluid. may pass vrhen the vibratory structure is excited, said chamber being tuned to the frequency of the vibratory structure and being of suchsize and shape as to effect the desired damping of said vibratory structure.
2. In acoustic apparatus, a vibratory structure, and a chamber containing fluid abutting thereon and having an o ening in its wall through which the flui may pass when the vibratory structure is excited, said chamber being tuned to the frequency of'the vibratory structure and being of such size and sha e as to efiect the desired damping of sai vibratory structure.
3. In acoustic apparatus, a vibratory diaphragm, and a chamber containing fluid abutting thereon and having an opening in its wall through which the fluid may ass when the vibratory diaphragm is excited, said chamber bein tuned to the frequency of the vibratory iaphragm and bein of such size and shape as to eifect the desired damping of said vibratory diaphragm.
4. In acoustic apparatus a casing having an aperture, a vibratory diaphragm closing said aperture, and a chamber containing fluid abutting on said vibratory diaphragm and having an opening in its wall through which the fluid may pass when the vibratory diaphragm is excited, said chamber being tuned tothe frequency of the vibratory diaphragm and being of such size and shape as to effect the desired damping of said'vibratory diaphragm.
5. In acoustic apparatus, a casing having an aperture, a vibrator diaphragm closin said aperture, a rigid p ate mounted in sai casing in such relation to said vibratory diaphra as to form a chamber therebetween a apted to contain fluid said ri 'd plate having an aperture throu hwhich t e fluid may pass when the vi ratory diaphra m is excited, and said chamber being tune to the frequency of the vibratory diaphragm and being of such size and shape as to eflect the desired damping of said vibratory diaphragm.
6. In acoustic apparatus, a vibratory structure having points executing diflerent amplitudes of movement, and a chamber containing fluid abutting thereon and havingan opening in its wall through which the fluid may pass when the vibratory structure is excited, said opening being located adjacent a point of the vibratory structure having relatively reat amplitude of movement, and said cham r being t ed to the frequency of the vibratory struc ure and being of such size and shape as to effect the desired damping of said vibratory structure.
7. In a vibration apparatus; an electromagnet; a primary vibratory unit consisting of a diaphragm with an armature attached thereto located in the held of the I magnet; a rigidplatewith'an opening in it 5 ed in aspace between the rigid plate and emoea Vibratory unit consistin of fluid located in a space between the rig1 plate and the die.-
' phra-gm and in a gap between the armature and. the edge of the said opening, the two vibratory units being each tuned to a frequency 1500.
8. In a vibration apparatus; an eleetro-' magnet; a primary vibratory unit consist ing of, a diaphragm with .an armature attached thereto located in the field of the magnet; a rigid plate with an opening in it adjacentthesaid armature; and a secondary vibratory unit consisting of fluid .locattit the diaphragm and in a ap between the armature and the edge of t e said opening, the two vibratory units being each tuned to a frequency 1500 and coupled so that two frequencies of resonance are obtained the one lying between 1000 and 1500, and the other between'1500 and2000. h
In testimony whereof we afiix our signatures in presence of two witnesses.
' HEINRICH HECHT.
HUGO LICHTE. v BERNRD NIELSEN. Witnesses:
1E Lifi'rr, Omo Donn.