US1747265A - Transmitter element - Google Patents

Description

Feb. 18, 1930. L. H. RICHMOND 1,747,265

TRANSMI TTER ELEMENT Filed March 29, 1928 I /4 E i; Z7

aka/$4M,

Patented Feb. 18, 1930 UNITED STATES TRANSMITTER ELEMENT Application filed March 29, 1928. Serial No. 265,670.

bratory diaphragm of a transmitter that will result in the maximum amplification of the effect of the movement of the diaphragm or any part of the electromagnetic device.

Another object is to avoid distortion in the electrical circuit by so constructing the electromagnetic element that none of the parts will have natural periods of vibration.

With the foregoing and other objects in view, the invention consists in the combination of parts and in the details of construction hereinafter described, certain embodiments thereof being illustrated in the accompanying drawings, in which:

Fig. 1 is a side elevation of the device (re moved from the housing) shown attached to a diaphragm.

Fig. 2 is a detail view in elevation of the thrust lever.

Fig. 3 is a detail view in perspective of the pivot post.

Fig. 4 is a view in elevation of the pivot post with a coil of wire wound around same, and with the rocker arm pivoted thereon.

Referring more particularly to the drawings, there is shown in Fig. 1 a substantially U-shaped magnetic frame 1 with an upper arm 2 and a lower arm 3. Fig. 3 shows a pivot post i which is wound with many turns of wire 13 which is adapted to carry an electric current thus making it a source of electromagnetic lines of force. The pivot post is made of magnetic material such as iron or preferably a good grade of high silicon transformer steel.

The pivot post 4 is attached to the frame 1 by means of the screw bolt 22 with the two legs 4 straddling the frame. The interior screw threads in the post to receive the bolt 22 are shown in dotted lines at 11. For purposes of clarity the windings 13 are omitted in the showing in Fig. 1. On the upper end of the post a is pivotally supported between the two legs I a rocker arm 5 which is attached to the post 4: by bolts 12 engaging the rocker arm and passing through the apertures 10 in the legs 4 of the post. The rocker arm 5 is accurately balanced and is essentially an armature in its operation, as it is made of the magnetic material as the pivot post.

The rocker arm has rigidly fastened thereto a thrust lever 14 by means of screw bolts 8 and loclrnuts 9. A thrust arm 17 is also provided for transmitting motions of the diaphragm 20 to the thrust lever 14:. This is accomplished by passing the screw threads 17 through the upright 16 of the thrust lever, and the screw threads 17* at the other extremity of the thrust arm into the barrel 19 of the diaphragm 20. This connection between the thrust lever and the thrust arm is made adjustable, by means of nuts 18 on either side of the upright 16, in order that the effective length of the arm 17 may be varied at will. The thrust arm is made of non-magnetic material.

A relative adjustment of the thrust lever and thrust arm varies the clearances 21 between the contact end 7 of the rocker arm 5 and the arm 3 of the frame 1, and that between end 6 of the rocker arm and the arm 2 of the frame 1. This clearance is preferably .004 inch. A coating of varnish or shellac is applied to the adjoining parts of the frame and the rocker arm in order to prevent them from coming into actual metallic contact at any time. It is sometimes desirable to fill this space with spongy rubber which holds the parts in correct relation to each other with out preventing their vibration.

In the operation of the device, a small energizing direct current is caused to flow in the winding on the pivot post a by the use of a suitable source of electromagnetic force. This current in the winding causes an electromagnetic field to be set up, this field having a single path in the pivot post, from which it divides into two paths of approximately equal length, one part passing through one side of the rocker arm, through the air gap 21 betweenthe rocker arm 5 and the frame,

and thence through that side of the frame back to the pivot post 4. The other path is symmetrically the same. The strength of this magnetic circuit is determined by the number of turns of wire in the winding, by the strength of the current flowing therein, and by the reluctance in the magnetic field. The greatest part of the reluctance in the magnetic field is caused by the air gaps 21 between the ends 6 and 7 of the rocker arm 5 and the ends 2 and 3 respectively of the frame 1. Any variation in the length of these air gaps greatly changes the reluctance of the circuit and hence causes a correspondingly large change in the magnetic flux through the windings. Changes in the magnetic flux causes induced electromagnetic forces in the windings. The variations in the air gaps are in exact response to the sound which causes the diaphragm to move, which movement is communicated by means of the thrust arm and lever. Thus the varying electromagnetic force in the windings are caused by and are exactly similar to the varying pressures of the sound waves, which result is the object of the apparatus.

IVhile there has been shown and described a specific type of apparatus, it is not the purpose to so limit the invention, as variations of the particular apparatus are possible within the scope of the proposed invention, such as a Variation in the shape and size of any or all parts of the device; the placing of the Winding 13 on other parts of the magnetic circuit; the splitting of the winding into two or more parts, which may be put at various places in the magnetic circuit; the use of a permanent magnet to establish the magnetic field. This could be the rocker arm or any part of the frame. A permanent magnet may also'be used in any part of the circuit in addition to the use of the windings to establish a magnetic field, each contributing its part.

I claim:

1. In a telephonic transmitter, a vibratory diaphragm, an electromagnet comprising an angular frame with vertically staggered extremities and a wire wound pivot post supported by said frame, an armature comprising a rocker arm which is pivotally mounted on said pivot post and in overlapping and spaced relation to the opposite sides of the staggered ends of said frame, a lever arm se cured to said rocker arm, a screw threaded rod connecting said lever and rocker arm to said diaphragm for imparting movements of said diaphragm to said rocker arm, and adjustment nuts on said rod for maintaining the adjustment thereof and the consequent clearance between the rocker arm and the extremities of the frame.

2. In a telephonic transmitter, a diaphragm, an electromagnet comprising a frame and a wire wound post secured thereto, an armature pivoted on said post with a clearance between said armature and said frame, a screw threaded rod connecting said lever and armature to said diaphragm for imparting movements of said diaphragm to said armature, and adjustment nuts on said rod for maintaining the adjustment thereof and of the air gap between said armature and said frame.

3. In a telephonic transmitter, a diaphragm, an electromagnet comprising a frame and a wire wound post secured thereto, an armature pivoted on said post, an adj ust able lever and arm connecting said diaphragm with said armature for adjusting the relative spaced relation between said armature and said frame.

4. In a telephonic transmitter, a diaphragm, an electromagnet comprising a frame and a wire wound post secured thereto, an armature pivoted on said post, adjustable means connecting said diaphragm, and adapt- LEON I-I. RICHMOND.

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