Patent GB-256584-A (GB)
Title: Indicating apparatus applicable to use in depth-sounding by the acoustic method and other purposes
IPC: G01S1/72
Filed: 1926-06-28
Abstract: 256,584. Behm, A. Aug. 6, 1925, [Convention date]. Indicating, optical devices for.-Apparatus for measuring the time interval of a physical disturbance of short duration more particularly for use in depth sounding by the echo method comprises a short-time oscillatory projector adapted to project a spot of light on to a screen, and a deflector adapted to deflect the light from its path, the projector and deflector being started and actuated respectively at the beginning and end of the interval to be measured. The apparatus may indicate the strength of the disturbance and in depth sounding may indicate to some extent the nature of the ground. In the form shown as applied to depth sounding in Figs 1 to 3, a small electric lamp 1 throws a beam of light through a spherical lens 2 and a microscope objective 6 on to a mirror 10 and projects it on to a screen 7 protected from stray light by a hood 9. The mirror 10 is mounted on the spindle of a known device for measuring short time intervals comprising a disc 15 normally held against the action of a spring 12 by a projection 14 on the disc forming part of the armature 19 of an electromagnet 11. When a sound is emitted a microphone 1<a>, Fig. 3, is excited, or a contact is opened, to de-energize the electromagnet 11 whereupon the disc is rotated to cause the point of light 13 to travel along the scale 31 of the screen 7. If during this travel the lens 2 is deflected the point of light 13 will also be deflected; this is arranged to take place under the control of the receiver 26 of the echo the lens 2 being carried by the spring armature 3 of an electromagnet 5 in the receiver circuit. The spring 3 may be associated with a thinner spring 32 and the lens 2 mounted in a light opaque screen to exclude stray light. The receiver circuit may be self-interrupting or the magnet may have two windings, one excited by a local battery and the other by the microphone and a transformer. The disc 15 after rotation through an angle strikes by means of an abutment 14<a> a contact 16 thereby breaking the circuit of a relay 17 and energizing a relay 18 causes the light to be extinguished during the return of the disc. Alternatively the light may be dimmed by introducing a resistance or be obscured by interposing a screen. During the return of the disc 15 the relay 18 causes the current in the coil 11<b> of the electromagnet 11 to be increased so that the armature 19 will be attracted, thereupon another abutment 14<b> closes contacts 14d, 14<c>, 14f, 14h, to de-energize the relay 18 and energize the relay 17 causing the lamp to be lighted and the current in the electromagnet 11 to be reduced. A resistance 30 is provided in the lamp circuit and is adapted to be short circuited through contacts 14e, 14f when the disc is released. The velocity of the disc may be varied by regulating the spring 12 as by means of a set-screw or pointer as shown in Fig. 3. A modified form of projector, for use where vibration occurs as on an aircraft, is shown in Fig. 4, the mirror 10 is supported on a spindle close to the poles of an electromagnet its movement being controlled by two springs. In another modification, Fig. 11, a complete revolution of the mirror spindle is utilized, the deflector 2 being mounted on the spindle of the time measuring device. In still another modification, Figs. 12, 13, the mirror spindle carries a glass scale 40 of the kind described in Specification 238,639, the scale being projected on to a screen in a circular window 51 and utilized for great depths, i.e. when the beam has passed the highest division of the scale 52. When this occurs a brake device 90 operating in known manner comes into action and a contact 60 is closed to light the lamp, a relay, after a delay of about one second for reading purposes, operating to release the brake. The projector may be actuated by a spring or electric motor controlled by a relay device responding to the emitted sound and automatically disengaged after one revolution. The deflector may be actuated acoustically as by tuning forks with mirrors and sound boxes or membranes with mirrors. The interval between soundings can be varied by adjusting the position of the contact 16. Means may be provided for automatically releasing the projector after completing its return movement so that the operation is recurrent as by maintaining the circuit of the coil 11<a>, Fig. 3, open and utilizing the contacts 14<c>, 14<d> to control a sound emitter or detonator. If a sound receiver is used in which excitation is proportional to the strength of the echo, a scale may be provided at right angles to the height or time scale to indicate the strength and thus afford a means of determining the nature of the ground, a series of curves being provided, as shown in Fig. 13, of normal echo strength for known grounds.