US2719280A - Echo sounders - Google Patents

Description

Sept. 27, 1955 ROLFE 2,719,280

ECHO SOUNDERS Filed March 15 195] United States Patent 2,719,280 ECHO soUNnERs Denis Hugh Rolfe, Gidea Park, England, assiguor to Marconi Sounding Device Company Limited, London, England, a company of GreatBritain Application March 13, 1951, Serial 'No. 215,200 Claims priority, application Great Britain March 27, .1950

1 Claim. (Cl. 340-3) This invention relates to echo sounders and has for its object-t0 provide improved means -for producing from a comparatively low voltage source a high voltage pulse for operating an echo sounding transmitter.

It is common-echo sounding practice to obtain a pulse for transmission by discharging a condenser through the winding of a magneto-strictive projector. For any given projector there -is usually an optimum value of condenser capacity and, of course, output 'power depends on the initial charge on the condenser. 'For sounding in great depths or for such purposes as detecting shoals of fish, a very high peak power is required and, for such purposes, it is common to use a condenser charged to 1000 volts or more. The obtaining of a direct :current voltage as high as this involves, with I known arrangements, the use of a costly and large rectifier or low utilization factor.

Where the transmitting projector is also used for reception it is of advantage to restrict the condenser discharge to the first half cycle in order to maintain the residual magnetism of the magneto-strictive projector and leave it suitably polarized for reception. One known way of doing this is to control the discharge of the condenser by a cold cathode gas filled tube arranged to be non-conducting until a suitable trigger pulse is applied to it and applying such a pulse when it is desired to transmit. With such an arrangement the main discharge continues until the current falls to zero, whereupon the tube ceases to conduct. The result is therefore, that only the first half cycle of discharge takes place as is desired. However, with known arrangements of this nature tubes capable of passing peak currents of the order of from 50 to 150 amperes are necessary. So long as the operating voltage is fairly low e. g. up to about 400 volts, neon filled tubes can be satisfactorily used for currents of this order. For higher voltages,

speaking, the only types at present available which are suitable for such high currents but a mercury vapor filled tube for operating at 1500 volts and capable of passing a peak current of 150 amperes has the serious practical defects of being large, heavy, costly and requiring careful handling.

The present invention seeks to overcome these difiiculties and defects and to provide improved and relatively simple arrangements employing relatively inexpensive discharge devices and capable of producing a high voltage, high peak current discharge from a relatively low voltage source, preferably the source already normally provided as the anode voltage source for the echo sounder receiver circuit.

According to this invention an echo sounder wherein a high voltage high peak current discharge is required for transmission comprises a plurality of condensers, means for charging said condensers in parallel from a voltage source, and a plurality of discharge devices the first of which is a triggered device and each of which 7 however, tubes filled with mercury vapor are, practically (except the last) is soconnected that, when it becomes conductive, it adds the charge voltage or voltages on the condenser :or-condensers'on the voltage supply source side thereof to the voltage charge on the condenser next on -the other side thereof, means being provided for triggering the first device and each ofthe other devices being such'as to be unable to withstand the sumof the charge voltage of the condensers on the voltage source side thereof, the final discharge device being connected in series with the echo sounding :transmitter.

'In :the preferred and simplest embodiments of the invention there are .only'two condensers and two discharge devices, which are so connected that, when the discharge devices are non-conducting, the condensers are charged in parallel through resistance inseries, but upon the application of a triggering voltage to one of the discharge devices to break it down, the voltage in the first condenser is added in series to that in the second to produce a sum voltage which is suflicient to breakdown the second discharge device and discharge both condensers in 'a :series circuit through the transmitter.

The invention is illustrated inthe accompanying drawings in which Figs. .1 :and 2 show diagrammatically two embodiments thereof.

Referring to Fig. 1 a voltage source (not shown) preferably the normally provided anode voltage supply source for the echo sounding receiver=has its negative terminal :1 grounded and its positive terminal 2 connected through a series circuit including a first resistance 3, the anode-to-cathode space of a1first-cold cathode gas :filledrelay tube-4 and .the coil 'of thefecho sounding transmitter (represented only by said coil) back to ground. The relay tube 4 has its anode 6 towards the positive terminal 2 and is of a known type having, in addition to the anode, a cathode 7 and two grids 8 and 9. The grid 8 nearer the cathode is connected thereto through a resistance 10. A potentiometer consisting of two further resistances 11, 12 in series is connected across the source, a condenser 13 being shunted across that of resistance 12 which is on the negative side. The remaining grid 9 of the relay tube 4 is connected to the junction point of the two resistances 11, 12 through a resistance 14. The anode 6 of the said relay tube 4 is connected through two parallel branch circuits to ground, the first branch circuit consisting of a first main condenser 15 in series with a resistance 16 and the other consisting of a resistance 17 in series with a second main condenser 18, these elements being in the order stated, in each case. The anode 19 of a second similar gas filled relay tube 20 is connected to the junction point of the elements 17, 18 and the cathode 21 thereof is connected to the junction point of the elements 15, 16. The grid 22 of the second relay tube which is nearer the anode thereof is connected through a resistance 23 to the junction point of the resistances 11, 12 and the remaining grid 24 is connected to ground through a resistance 25. The said grid 24 is also connected to ground through a condenser 26 and a transmitting key 27 (or through a pair of transmitting contacts), the junction point of said condenser 26 with said key or contacts being connected to the junction point of the resistances 11, 12 through yet another resistance 28.

With this arrangement, so long as the gas filled relay tubes are not conductive, the two main condensers 15, 18 are charged in parallel to the voltage of the supply source. On closing the transmitting key or contacts, however, a triggering pulse is applied to the control grid 24 of the relay tube 20. This pulse causes the relay tube to ionize so that the voltage across it falls almost to zero. The voltage across the relay tubes 4 accordingly rises towards a value equal to twice the supply voltage value.

The said relay tube 4 is, however, unable to withstand this voltage-in practice, the relay tube may conveniently be chosen to break down when the voltage across it exceeds that of the supply source by about 30 voltsand accordingly itbreaks down and a voltage approaching twicethe supply'voltage appears across the transmitter coil .T, and the main condensers 15, .18 discharge therethrough in series. When the discharge current falls to zero the gas filled relay tubes extinguish and the main condensers recharge.

The arrangement shown in Fig. 1 may be regarded as a two stage embodiment but, as already stated, the invention may. be carried into practice with as many stages .assare desired or are necessary to obtain the required highdischarge voltage from the relatively low voltage supply source. .Thus, as shown in Fig. 2, there may be four main condensers here designated C1, C2, C3, C4 andfour .gas filledrelaytubes here designated R1, R2, R3,.R4, the condenserscharging in parallel so long as the .gas filled relay tubes are non-conductive. The relay.tubes and condensers are connected as shown so that when the first relay tube R1 is triggered, the chargein .thefirst condenser C1 is added to the voltage across the second relay tubeRZ causing it to break down and add the sum of the voltages in the first two condensers C1, C2 to that across the third relay tube R3, which in turn breaks down and adds the sum of the voltages in the first three condensers C1, C2, C3 to that across the fourth relay tube R4 which in turn breaks down and discharges the sum voltage clue to all four condensers C1, C2, C3, C4 in series through the transmitter coil T.

What I claim is:

An echo sounder transmitter arrangement comprising a voltage source, an echo sounding transmitter, a plurality of condensers, circuits including said condensers for charging said condensers in parallel from said source, a plurality of discharge devices each constituted by a cold cathode gas filled relay having a cathode, an anode and at least one triggering grid between said anode and cathode, means for applying a triggering potential to the triggering electrode of the first of said devices, circuits connecting each of said devices except the last between two of said condensers to add, when conductive, the charge voltage or voltages on the condenser or condensers on the voltage supply source side thereof, each of said devices except the first having a breakdown voltage below the sum of the charge voltage of the condensers on the voltage source side thereof, the final discharge device being connected in series with the echo sounding transmitter, wherein an input circuit is arranged between said voltage source and said first mentioned discharge device, said input circuit including a pair of resistances connected in series and connected across said voltage source and a connection including a further condenser and a further resistance in series between the junction point of said pair of resistances and the triggering grid of said first mentioned discharge device, another resistance connected between said triggering and earth and a switch connected across the further condenser and the last mentioned resistance in series.

References Cited in the file of this patent UNITED STATES PATENTS

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