US2640926A - Automatic release and reset system - Google Patents

Description

June 1953 WILLIAM IEU-LIANG wu 2,640,926

AUTOMATIC RELEASE AND RESET SYSTEM Filed July 4, 1944 WILL/AM /E U 'L/A/VG WU MffiZ/K Patented June 2, 1953 AUTOMATIC RELEASE AND RESET SYSTEM William Ieu-Liang Wu, New York, N. Y., assignor to the United. States. of Americaasrepresented by; the Secretary of. the Navy Application July 4, 1944, Serial No. 543,494

6 Claims...

This inventionrelatesto automatimrelcase systerns, and more particularly to systems; inxwhich. automatic. means are provided for operating: a

release device in response to input signals haw ing; particular characteristi'cs.v

In: general, automatic: release;- systems; or: trip pers are used to actuate switching circuits. 0.1? to control the operation of various, mechanisms in: response to. input: signals. derived from. some de vice with: which they are, associated. Suchv trippersystems ordinarily include discriminating means such that they will operate only in response to. signals having certain chosen charaeteristics. Signal characteristics usually chosen for. discrimination are peak. amplitude and. predominant. frequency component; Thus, in some trippers, the release deviceis; actuated whenever the; input signal reaches a peak. value greater than. a predetermined threshold. In such devices, tripping occurswhenever the threshold is exceeded irrespective of the frequency of the. in put signal. Unsatisfactor operation may thereforeresult: due to tripping; in response tcspurious signals or noise such as high.- or low-frequency pulses deriwedv from sources other, than the control device and having amplitudes in excess of thechosen threshold. Furthermore, when signals of. widely varying amplitudes are received, the threshold value will be exceeded. at varying intervals,- before the occurrence of the peak. signal, thus introducing further inaccuracies.

It is an object oi this invention, therefore, to provide an automatic release system which will, not trip on signals having characteristics other than those chosen to actuate the device even though the amplitude of such undesired. signals exceeds the. chosen amplitude by appreciable amounts.

In. view of the above,,the present invention pro.- vides in one aspect in an automatic releasec ircult arranged to. operate in response to. iI-naut.v sig nals of a chosen type, a release device, and means for actuating this device only when. aninput sis-- nal of the chosen type. is received, these circuits including at least two differentiating circuits having time. constants. differing by an amount such that. the. difiercnce in. amplitudes ot the: differem tiated output potentials in response to. the same input signal is appreciable only when the input signal. is of. the chosen type, and mean for adding these diiierentiated potentials algebraically and applying the. resultant potential to! the release device.

one embodiment of the invention, the automatic release system is used to govern the operation of a release device comprising a relay cone. trolled by an arc-discharge tube. It will he understood; however, that. the. release system may be. used for the control of any-other suitable release. device.

The above and otherfeatures of the invention. will be described in detail in the following specifi cation and pointed, out in the claims.

In the drawings:

1 isa circuit. diagram of an automatic release systemaccording to the invention; and.

Figs. 2. 3 and 4 are reproductions of Oscillograms: showing potentials existingat various points. oi the circuit of\ Fig. 1.

The system illustrated in; Fig. 1 of the drawings is' arranged for operation. in response totwo sided; input. sicnals such as, for example, those appear ing at. thev eutput o1- apush-pullamplifier. Thus, input terminals It, and 12. are provided from which a two-sidedsignal may he applied through coupling capacitors; Ht, series resistors. [6, tentiometers l8 and protective resistors 2!! to. the grids of a push-pull classA amplifier stage com;- prising; vacuum. tubes 2-2. and 24. As indicated in Fig. 1,, potentiometers it. are linked together me chanically and control. the, signal potentials, respect to" ground, applied to the grids. of amplilie-r tubes, 22 and 24. The setting of these potentiometers determines the threshold or minimum amplitude of input signal for which trip.- ping-- will occur. Preterably, the input circuits. to vacuum tubes. 22 and. 24 are designed so that they have a relatively high. time constant irrespective. of the setting of potentiometers. l8, thuspreventing undesirable distortion of the input signal.

The cathodes oi amplifier tubes 22. and 2,4, are connected through, a common. resistor to ground, while the plates are connected through load. resistors 2.8 to. a source of positive potential indicated: by B+. In addition, eachv plate isxb passed. to ground by av capacitor 313., these capacitors acting in conjunction with the dynamic. plate resistances of the vacuum tubes to produce filtering action which tends to discriminate. against any very high-frequency components present. in the input signal.

The; plates. of vacuum tubes 22 and 24 are coupled through, capacitors 32 to the grids of vacuum tubes 3d and 36. which are operated as a cathode-follower stage. Thus, the plates of these vacuum tubes are connected together and to. the source. ofpositive potential indicated by B and the grids are co nected through resistors 38 to ground. The cathodes of these tubes are con-. nee-ted to the fixed contacts of a two-pole, three.- positionswitch 49;, in such; a manner that either cathode or both, cathodes may be connected through resistor 42 to the junction of resistors 44 and 46,. which are connected in series as. avoltage divider between the source of positive potential at B+ and ground.

The positive potential applied to the cathodes of vacuum tubes 34 and 36 is such that each of the tubes is biased beyond cutoff and operates as a rectifier, conducting only when a positive signal appears at its grid. In addition, since these tubes operate as cathode followers, their output has a low internal impedance. Thus the voltage applied to the circuits following this stage will be substantially independent of the loading due to such circuits.

Since the signals applied to the grids of vacuum tubes 34 and 36 have opposite polarities at all times, it will be understood that, by means of switch 40, control-signal peaks of either polarity may be transmitted to the remaining circuits of the release system. Depending upon the setting of this switch, the system may be made to trip on the positive peak, on the negative peak, or on the first peak received whether it be positive or negative. In the following description it is assumed that the common cathode connection corresponding to the last-mentioned condition is used. Thus a positive pulse, having the same form as the first pulse received, whether it be positive or negative, is applied to the remaining portions of the release system.

The positive pulse just referred to is applied simultaneously to two differentiating networks which together operate as a frequency-discriminatory circuit. These networks comprise respectively capacitor 43 and resistor 45, and capacitor 48 and resistor 50. Preferably, capacitor 43 has a capacitance difiering from that of capacitor 48 by an amount determined by the type of signal chosen to operate the release system, while resistors 45 and 50 have the same resistance. Resistors 45 and 50 are connected together and to the junction of voltage- divider resistors 52 and 54 connected between the source of positive potential at B+, and ground.

Capacitors 43 and 48 are so chosen that for input-signal components or noise of very high frequency, each offers negligible reactance. The potentials appearing across resistors 45 and 50 are, therefore, substantially equal and their difference is very small. On the other hand, when the input signal has components of very low frequency, the reactance of either of the capacitors is so high that negligible potentials appear across resistors 45 and 50. When, however, the input signal possesses the desired frequency characteristics, each of the capacitors taken in conjunction with its series resistor tends to differentiate the signal. The two derivative outputs now have different amplitudes due to the fact that the two differentiating circuits have different time constants.

The outputs of the two differentiating circuits are applied through series resistors 56 to the grids of a two-sided cathode-follower stage comprising vacuum tubes 58 and 68. The cathodes of vacuum tubes 58 and 60 are connected through cathode resistors 62 to ground, while the plates of these tubes are connected together and to the source of positive potential at 13+. Thus it will be understood that the positive potential appearing at the junction of resistors 52 and 54 is applied to the grids of vacuum tubes 58 and 60. Preferably this potential is relatively high and serves to raise the static plate current of these vacuum tubes to such a value that they will operate on a linear portion of their plate currentgrid voltage transfer characteristic. This reduces the possibility that the two tubes will introduce faulty operation due to mismatching and, in addition, gives them the high mutual conductance necessary to cause them to operate as cathode followers. I

Due to their differentiating action, the fre quency-discriminatory circuits above described have outputs including both posiitve and negative pulses. The negative portions of these outputs are clipped by means of diodes 63 and 64, the cathodes of which are connected to the grids of tubes 58 and 60, respectively, while the diode plates are connected together and to the junction of resistors and 56. Whenever the signal output of the differentiating circuits becomes negative, the diodes become conducting and act to by-pass the negative portions of the signals. Positive pulses are not afiected by the diodes and are, therefore, applied to the grids of the succeeding stage.

The cathodes of tubes 58 and 69 are connected through coupling capacitors 66 and 68 to a peaktripping stage comprising diodes It and J2 and associated circuits. The plate of diode I0 is thus connected to capacitor 66 and through resistor 14 and bias battery 16 to ground, while the plate of diode 12 is connected to capacitor 68 and through resistor I8 to ground. The cathode of diode Hl is connected through battery "it to ground, While that of diode 12 is connected directly to ground. The plates of diodes 1!] and 72 are also connected through series resistors 88 to the grid and cathode, respectively, of a grid-controlled arc-discharge tube 82 such as, for example, a thyratron. Capacitor 84 is connected between the cathode and grid of discharge tube 82, and serves to filter out high-frequency disturbances associated with the signal applied between these points.

Considering now the action of the peak-tripping circuits comprising diodes 70 and I2, together with their input circuits including respectively capacitor 66 and resistor 14 and capacitor 68 and resistor 18, it will be seen that, so long as the potentials at the cathodes of vacuum tubes 58 and 68 are increasing, the plates of diodes l0 and 12 will be driven positive, thereby rendering them conductive and hence allowing coupling capacitors 66 and 68 to charge through the diodes. When the peak of the signal is reached, however, and the potentials at the cathodes of vacuum tubes 58 and 60 begin to fall, conduction 1 through diodes l0 and 72 stops, and capacitors 66 and 68 discharge through resistors 74 and 18, respectively. The negative potentials thus applied at the plates of diodes I0 and 12 are in turn applied to the grid and cathode, respectively, of arc discharge tube 82.

The plate of discharge tube 82 is connected through series resistor 85 and contacts 86 of relay 8'! to the source of positive potential at 13+, and its shield grid is connected to its cathode. In addition, the cathode of this tube is connected to the plate of diode 88, the cathode of which is connected through series resistor 90 to the junction of voltage-divider resistors 92 and 94 connected in series between the source of positive potential at B and ground. Thus, so long as and prevents the flow of residual current therethrough.

It will be recognized that due to the action of bias battery I6, which normally maintains the grid of the discharge tube at a negative potential with respect to its cathode, the discharge tube will not fire until its grid is made somewhat less negative in respect to the cathode. However, due to the difierence in amplitudes of the differentiated signals at the plates of diodes l and 12, the negative potential applied to the cathode of the discharge tube is somewhat greater than that applied to the grid thereof whenever the input signal to the release system is of the chosen type. The net result is then to reduce the grid bias by the algebraic sum of these two potentials. If the difference in amplitudes of the differentiated signals resulting from the input signal from the tripper system as limited by threshold potentiometers I8 is sufficient to overcome the normal negative bias on discharge tube 82, therefore, this tube fires.

The cathode of diode 88 is also connected through rheostat 06 and delay capacitor 98 to ground. A voltage-regulator tube I00 is connected in series with protective resistor 102, delaying resistor I04 and bias battery I00 across delay capacitor 98. The cathode of voltage-regulator tube I00 is also connected through resistor I08 to the grid of control tube N0, the cathode of which is connected through cathode resistor II2 to ground. Thus it will be seen that battery I08 supplies bias voltage to this tube. The plate of control tube H0 is connected through coil II3 of relay 81 to the source of positive potential at B+, so that the flow of current through this tube causes operation of the relay which is provided with control-circuit contacts H4, to which may be connected a device to be controlled by the release system. Preferably, the bias voltage supplied by battery I08 to control tube H0 is sumcient to cut off the tube thereby to prevent the flow of residual current therethrough. Such residual current would otherwise flow through the coil of relay 81 and render the release action of the relay more sluggish.

So long as discharge tube 82 is not conducting, its cathode is isolated by diode 88 as explained above. Once the discharge tube fires, however, its cathode and therefore the plate of diode 88 become positive, thereby causing diode 88 to conduct. This allows capacitor 98 to charge through rheostat 96, the rate of charge being determined by the amount of resistance offered by the rheostat, After a time determined by the time constant of the RC circuit formed by rheostat 98 and capacitor 90, the potential across capacitor 98 reaches the break-down "potential of voltageregulator tube I00, and this tube breaks down, thereby transferring the charge from capacitor 98 to delay capacitor I09 connected between the cathode of voltage-regulator tube I00 and ground. The potential across the latter capacitor is applied to the grid of control tube H0 and causes it to conduct thereby tripping relay 81, opening contacts 86, and closing contacts I. The opening of contacts 86 extinguishes discharge tube 82 by removing the plate potential therefrom, while the closing of contacts 1 I4 establishes the circuit of the device to be controlled. The charge of capacitor 109 leaks off slowly through delaying resistor I04 to ground, and eventually lowers the grid potential of tube H0 to such a value that the relay returns to its normal position, opening the controlled circuit and reestablishing the circuit to the plate of the discharge tube. The time constant of the circuit comprising capacitor I09 and resistor I04 is so chosen that the difference in potential betweenthe grid and the cathode of discharge tube 82 will have returned to such a value before the plate voltage is reapplied to that tube that the tube does not again become conducting. At the end of the cycle of operations just described, the tripper circuit is thus reset for another cycle.

For a better understanding of the operation of the above-described circuits, reference is made to Figs. 2, 3 and 4 of the drawings. These figures are oscillograms, taken on a common time base, showing the variations in potentials at various points in the circuits.

In Fig. 2, the solid trace indicates the form of a typical input signal of a particular type in response to which the device of the invention may be arranged to operate. This signal is' amplified in vacuum tubes 22 and 24 and is applied to the grids of the rectifier stage comprising cathodefollower tubes 34 and 36. Assuming that switch 40 is set for the common cathode connection mentioned above, both positive and negative peaks will appear as positive pulses at the common connection to the differentiating circuits. The shape of the signal at this point is indicated by the dashed trace in Fig. 2.

The differentiating circuits operate simultaneously on this signal and the negative portions of the differentiated output signals from these circuits are clipped by diodes 63 and 64. The two signals applied to the grids of vacuum tubes 58 and 60 are shown in Fig. 3, the solid trace indicating the signal at the grid of tube 58 and the dashed trace indicating that at the grid of tube 60. It will be noted that, due to the difiering time constants of the differentiating circuits, the signals applied to the grids of vacuum tubes 58 and B0 differ appreciably in amplitude.

These signals are introduced to the peak-tripping stage which operates upon them in the manner already described. The signals applied to the discharge tube are then as indicated in Fig. 4, in which the solid trace represents the signal at the grid of the discharge tube and the dashed trace the signal at the cathode of the sametube, each with respect to ground.

If the difierence between the potentials at grid and cathode of the discharge tube is such that the bias on that tube due to battery 16 is overcome, this tube fires and the remaining circuits operate as already described ultimately to close relay 81.

' While the vacuum tubes used in the tripper system of the invention may be of various types and the magnitudes of the circuit components used depend to a large extent upon the type of signal chosen to operate the system and may, in general, vary between wide limits, the following were used in one successful embodiment of the invention: Vacuum tubes 22 and 24 each formed one half of a type 12SL'7 tube. Likewise, each of vacuum tubes 34 and 36 formed one half of a type 1281.7 tube. Each of diodes 63v and 54 formed one half of a type 6116 tube as did each of diodes I0 and I2. Each of vacuum tubes 58 and '60 formed one half ofa type 12SL'7 tube, and discharge tube 82 was a type 2050 tube. The voltage regulator tube I00 was a type VR-IS tube, while diode 88 formed one half of a type 12SL7 tube having its grid and plate joined together, and vacuum tube III] formed the other half of the same type 125117 tube.

7 Other circuit componentshad the following values:

Resistors 38, I04 megohms 5.1 Resistors i6 do 1.8 Resistors 45, 46, 50, 56, 14, 18, 94, I08

do 1.0 Resistors 20 do 0.5 Resistors 28, 62 do 0.25 Resistors 80 do 0.2 Resistor 90 do 0.1 Resistor 54 ohms 50,000 Resistor 44 do 40,000 Resistor 52 do 25,000 Resistor 92 and rheostat 96 do 10,000 Resistor 85 do 7500 Resistor I02 do 3000 Resistor H2 do 2000 Resistor 26 do 1500 Potentiometers l8 megohms 1.25 Capacitors I 4, 32, 98 microfarads 2.0 Capacitors 30 do 0.1 Capacitor 43 do 0.25 Capacitors 48, 66, 68, I09 do 0.5 Capacitor 84 do 0.001

Batteries 16 and W6 each had a rating of 6 volts and the source of positive potential at B was 300 volts.

Using the above circuit components, the two differentiating circuits had time constants of 0.25 and 0.5 second, respectively. With these time constants signals having predominant frequencies lying between 0.1 cycle per second and 10 cycles per second were effective to operate the tripper,

while signals having other predominant frequencies and much greater amplitudes were discriminated against and did not operate the tripping circuits.

Having thus described my invention, what I claim is:

1. In a discriminating circuit arranged to operate in response to input signals of a chosen minimum peak amplitude and a chosen frequency range, means for actuating a load only when an input signal of the chosen characteristics is received, said means including at least two differentiating circuits having time constants differing by an amount such that the difference in amplitudes of the differentiated output potentials in response to the same input signal is appreciable only when the input signal is of the chosen characteristics, and means for adding said differentiated potentials algebraically and applying the resultant potential to the load.

2. In a discriminating circuit arranged to operate in response to input signals of a chosen minimum peak amplitude and a chosen frequency range, a grid-controlled arc-discharge tube for controlling a load, circuits for controlling the potential at the grid of said tube to render it conductive only when an input signal of the chosen characteristics is received, said circuits including at least two differentiating circuits havin time constants differing by an amount such that the difference in amplitudes of the differentiated output potentials in response to the same input signal is appreciable only when the input signal is of the chosen characteristics, and means for adding said differentiated potentials algebraically and applying the resultant potential to the grid of said discharge tube.

3. In a discriminating circuit arranged to operate in response to input signals of a chosen minimum peak amplitude and a chosen frequency range, means for actuating a load only when an input signal of the chosen characteristics is received, said means including amplifying and rectifying stages and at least two differentiating circuits having time constants differing by an amount such that the difference in amplitudes of the differentiated output potentials in response to the same input signal is appreciable only when the input signal is of the chosen characteristics, and means for applying the difference potential to the load.

4. In a discriminating circuit arranged to operate in response to input signals of a chosen minimum peak amplitude and a chosen frequency range, means for actuating a load only when an input signal of the chosen characteristics is received, said means including a polarity-selecting rectifying stage and at least two differentiating circuits having time constants differing by an amount such that the difference in amplitudes of the differentiated output potentials in response to the same input signal is appreciable only when the input signal is of the chosen characteristics, and means for adding said differentiated potentials algebraically and applying the resultant potential to the load.

5. In a discriminating circuit arranged tooperate in response to input signals of a chosen minimum peak amplitude and a chosen frequency range, a grid-controlled arc-discharge tube for controlling a load, circuits for controlling the potential at the grid of said tube to render it conductive only when an input signal of the chosen characteristics is received, said circuits including amplifying and rectifying stages and at least two differentiating circuits having time constants differing by an amount such that the difference in amplitudes of the differentiated output potentials in response to the same input signal is appreciable only when the input signal is of the chosen characteristics, and means for adding said differentiated potentials algebraically and applying the resultant potential to the grid of said discharge tube.

6. In a discriminating circuit arranged to operate in response to input signals of a chosen minimum peak amplitude and a chosen frequency range, a grid-controlled arc-discharge tube for controlling a load, circuits for controlling the potential at the grid of said tube to render it conductive only when an input signal of the chosen characteristics is received, said circuits including a polarity-selecting rectifying stage and at least two differentiating circuits having time constants differing by an amount such that the difference in amplitudes of the differentiated output potentials in response to the same input signal is appreciable only when the input signal is of the chosen characteristics, and means applying the difference potential to the grid of said discharge tube.

WILLIAM IEU-LIANG WU.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,555,893 Thompson Oct. 6, 1925 1,733,045 Baker Oct. 22, 1929 1,959,161 Grondahl May 15, 1934 1,968,068 Blanchard July 31, 1934 2,166,991 Guanella 1- July 25, 1939 2,194,559 Koch Mar. 26, 1940 2,231,174 Trogner Feb. 11, 1941 2,275,930 Torcheux Mar. 10, 1942 2,340,275 Shook Jan. 25, 1944

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