Patent GB-190521823-A (GB)
Title: Improvements in Automobile Horns and like Instruments.
Inventor: HUTCHISON MILLER REESE
Filed: 1905-10-26
Granted: 1906-10-25
Abstract: 21,823. Hutchison, M. R. Oct. 26. Electrically-vibrated sounding plates and diaphragms.-An automobile horn or like instrument of the kind containing a flexible diaphragm which is vibrated by the varying magnetization of an electro-magnet core to sound the instrument is operated by a low voltage, and has the following features; namely (1) an exciting-circuit of small self-induction and low resistance, (2) a period of demagnetization small compared with the period of the interrupter, (3) means for adjusting the period of the interrupter to correspond with the natural note of the horn, or other selected frequency, and (4) a diaphragm in which the free vibratory period is small compared with the frequency of the interrupter. When applied to an automobile, the horn may be controlled from any of the seats. The mechanism is shown in Fig. 3, enclosed in an aluminium or non-magnetic casing for attachment to a horn. The diaphragm 22 is mounted between paper washers and is pressed away from the core by a buckling spring 23 which touches it at three or more points. Between the diaphragm and magnet is placed an adjustable partition or resonator 24, having a central hole for a magnet core. The magnet 31 is mounted on a screwed bridge-piece 34, by rotation of which its distance from the diaphragm may be adjusted. This bridgepiece 34 also carries an interrupter consisting of a leaf-spring carrying a contact-spring which has a contact-piece of platinum or platinum-iridium. A fixed contact is carried by a split arm and a locking-screw on the bridge-piece, and is itself capable of fine adjustment by a screw and flexible shaft after a coarse adjustment has been made by a screw on the spring. By this means, the frequency of the diaphragm can be changed to suit the period of the air column in the horn, the magnet being placed near the diaphragm while this is being effected. The resounding partition 24 is then moved away from the diaphragm until the best result is obtained. The apparatus is placed in circuit with a battery, which may be that used for the motor ignition of an automobile, and with one or more switches, which may be placed at different parts of the car. The apparatus may be constructed to produce a musical note by using a thin elastic diaphragm and a winding of high inductance. As shown in Fig. 6, each switch 64, 65, 66, 67 may operate a separate interrupter of different frequency, and tuning inductances 68, 69, 70, 71, 72 may also be added. Preferably, the tuning inductance is formed by the magnet winding. A series of notes may be obtained by moving the adjusting handle, or four diaphragms may be connected by branch tubes 74 with one born, as shown in Fig. 7. When the sound is intended to be unpleasant, for use at high speeds, a thicker diaphragm is used, with a low-resistance winding and a core of fine wire, rusted for magnetic insulation. The diaphragm is also caused to vibrate in many divisions by using a buckling spring touching it at more than three points. The core may also be rounded off or provided with a striking- piece which taps the diaphragm at each vibration.