US1821823A - Sound transmitting apparatus - Google Patents

Description

Sept. 1, 1931. E. WILCKENS SOUND TRANSNIITING APPARATUS Filed June 18, 1928 Patented Sept. 1, 1931 UNITEDISTATES PATENT oFnca mmsr WILCKENS, or BERLIN, GERMANY SOUND TRANSMITTING APPARATUS Application filed Inne'18, 1928, SerialNo. 286,315, and in Germany June 23, 1927. v

v This invention'relates to sound-transmitting apparatus of the dia hragm type, and

more particularly to such Eindof apparatus operated by means of a gaseous pressure agent. a p

In the case of the hitherto known senders of this kind the operating agent is introduced from a feedpipe to that particular side of the diaphragm which transmits the 10 sound to the medium either indirect fashion or by means of tuned amplifyingchambers. Between the air outlet opening and the air containerthe pi e dimensions are such that the diameter 0 the piping is relatively large as compared with the crosssection at the air exit point.

Now in the operation of such senders it has been discovered that the large piping cross-section is an important feature as re- 2 gards losses in the pipes, while on the other hand the disadvantage exists that the consumption of air is extremely high, making the operation of such apparatus very uneconomical as compared, for example, with electrical transmitters.

It has hitherto been considered desirable in apparatus of the kind in question to allow the operating agent to flo'w directly into the field of sound. This, however, is

not correct, since both by reason of the currents as also the diiierent nature and condi-' tion of the active medium and that acted upon disturbances are caused which exer-' cise detrimental action on a proper acoustical effect. Y

- It is the object of the invention to overcome the disadvantages referred to, and this is accomplished by employed a sender. or transmitter, in which not the radiating face ofthe diaphragm, but the side opposite thereto, is acted upon by the inflowing agent. By the provision of a throttling wall in the piping it is also attained that the 1 losses in the pipes remain very small. while on the other hand the sender is not fed with a greater amount'of air than is essential for economical operation thereof. The disadvantages arising in conjunction with existing apparatus will be readily apparent to anyone skilled'in the art in observing tus according to the invention.

'plished in the case of senders of the present a sound transmitter of this kind when operated by steam. In this case hot air greatly saturated with particles of water is whirled into still, cool and relatively dry air.

Experiments have hitherto been conducted with many different types of apparatus with a viewto generating sound with asmall amount of energy. Thus, for example,-it has already been proposed to provide chambers in the piping tuned to the sound frequency. In 'thesame manner tuned chambers may also be provided directly against the diaphragm. These measurcs, however, do not lead to a direct improvement in the efli'ciency, as the watt-consuming energy remains the same, and merely the so-called. idle oscillation energy is 'reduced; no efficiency, however, is associated with the latter. On the other hand the position is diflerent in the case of the arrangement accordingto the invention. This arrangement is principally concerned with reduclng the, watt consuming, or in other words, the output consuming energy. With the above remarks the invention, which will now be described more fully with reference to the accompanying drawing, willbe read- I ily understood. 7

Fig. 1 shows the principle of the appara- Figs. 2 and3 being modifications".

Referringto Fig. 1, a is thediaphragm, whichis totransmit sound. For this purpose-it is necessary for the same to cause pressure variations in the surrounding medium during; vibration. of the 'diaphragm.

, For attaining= the desired vibrations a cer-' tail-1' force'isi required, which is accomkind by, with a given operating pressure, a 0

certain pipe diameter atthe exit point I). In order to utilize this pipe diameter on the one hand. independently of the size of'membrane or diaphragm and on the other hand. the greatest possible movement of the diaphragm for the air outlet point, a plate d is mounted at the centre point e of the diaphragm. This plate may be furnished with an edge portion or otherwise, as desired.

The plate d is situated directly opposite the air outlet 6. If, for exam le, the air feed is very' strong vibration 0 the diaphragm will not occur despite the fact that that the plate is lifted, since by reason of the strong feed a drop of pressure in front of the plate d does not occur. The movement ofthe diaphragm accordingly remains a constant one, and despite large amounts of air consumed the diaphragm does not emit any sound. If the feed of air is reduced, pressure variations will occur under the plate when a certain amount of air is being introduced, and the diaphragm will accordingly vibrate and emit sound. In this case, however, merely a small proportion of the air flowing through the (pipe I) assists to cause vibration of the i aphragm, and the remainder leaves the sender or transmitter in the manner of direct current, and is to be regarded as a loss. By the fact that a throttle wall having a. throttling hole 6 is provided, and furthermore by reason of the fact that the hole 0 is only of such size that all or practically all of the air allowed to pass into the tra-nsmit'er participates in causing vibration of the diaphragm, it will be readily obvious that. a transmitter of the kind described operates with extremely good efliciency, a fact which has also been proved] by the experiments conducted. It will also be apparent that due to the provision of the throttling wall entire independency of the size of the feed pipe is achieved, and by proper selection of the size of hole the amount of air introduced into the apparatus may be correctly set.

It has as a matter of fact proved to be most desirable in practice to arrange the throttling wall within the transmitter itself, as independency as regards the piping is then attained to a large degree when the ap aratus is being mounted in position.

l ig. 2 shows a modified construction, in which in the case of large diameter of the piping h'the outlet point 0 possesses a smaller diameter. By reason of the nozzle form any desired arrangement may be selected;

thus, for example, a pipe of small diameter.

may have a larger diameter at the'outlet point.

Fig. 3 shows a modification, in which the air is introduced laterally. The throttling wall is formed by g, with the throttle hole a. While the me In emerges at b, the same is fed to the diaphragm through a movable piping f.

,It will'be readily apparent that also in the case of this embodiment the diaphragm may be furnished with a plate having an edge portion, or also a plate without edge portion.

It will be quite understood that no restriction is made to the actual forms of embodiment shown, but that various other modifrom the discharge end of the pipe by vary ing pressure of the fluid, said plate being of the same diameter as the pipe and of a diameter less than the diaphragm.

2. A sound transmitting device as claimed in claim 1, in which the fluid conducting ipe has mounted therein a wall having a throttling opening therein and of a diametcr less than the plate. a

In testimony whereof I have aflixed my signature.

ERNST WILCKENS.

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