US2306237A - Electronic timing device - Google Patents

Electronic timing device Download PDF

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US2306237A
US2306237A US36468140A US2306237A US 2306237 A US2306237 A US 2306237A US 36468140 A US36468140 A US 36468140A US 2306237 A US2306237 A US 2306237A
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potential
means
switch
circuit
grid
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William F Wolfner
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PHOTOSWITCH Inc
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PHOTOSWITCH Inc
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    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03KPULSE TECHNIQUE
    • H03K17/00Electronic switching or gating, i.e. not by contact-making or -braking
    • H03K17/28Modifications for introducing a time delay before switching
    • H03K17/288Modifications for introducing a time delay before switching in tube switches

Description

Dec.,22, 1942. w. WQLFNER, 213 2,305,237

ELECTRONIC TIMING DEVICE Filed Nov. 7, 1940 Mew-(5607': Willchvz .Z: lVoZj 73H rat-5 dag ,5.

Patented Dec. 22, 1942 ELECTRONIC TIMING DEVICE William F. Wolfner, II, Methuen, Mass., assignor to Photoswitch,

Incorporated, Cambridge,

Mass, a corporation of Massachusetts Application November '7, 1940, Serial No. 364,681

8 Claims.

The present invention relates to improvements in electronic timing apparatus for effecting a time delay in the actuation of a relay element by means of the controlled dissipation of electric energy stored for that purpose.

It is the main object of the invention to provide a device for theabove purpose which is organized especially with a view to simplicity of construction, exactness, reliability of and constant readiness for operation, and adaptability to varied industrial and scientific purposes.

- In oneaspect, the invention has the object of providing a circuit which is continuously ready for initiating a timed control function by a single operation, as closing a switch or varying an electric constant therein. In another aspect, the invention has the object of providing a circuit which permits, if desired, continuous indication of readiness foroperation as for example intactness for an emergency function, and also, if desired, indication of its timing function proper. object of controlling the operation of external circuits or other apparatus for predetermined effectiveness during single or repeated periods of time whose duration may also be controlled as function of a determining value.

Still further objects are to provide a time delay relay circuit adapted for visual indication of readiness for operation as well asoperation of the relay; to provide a new and improved time delay relay employing a light sensitive device for controlling the period of the time delay effected in the energization and deenergization of an external circuit or other apparatus; to provide a time delay relay circuit which can be in the simplest possible manner modified for various ways of operation as for example for simple time delay operation, or time delay operation with controlled instantaneous cycle interruption, or continuous cycle operation through a certain period of time.

One of the features or the arrangement according to the invention which makes the above advantages possible, is the introduction of an element in its circuit which supplies, so long as the circuit is conditioned to be ready for operation, a potential which is, or can be rendered, more positive than the simultaneously prevailing potential of a control element; for exampla'the positive potential of a point connected to one terminal of the supply sourcemay be permanently applied to one plate of'an energy storing condenser whose other plate is connected to the control grid of an electron tube connected to the In still another aspect the invention has the.

source and which condenser can discharge in controlled manner. The condenser can be normally kept charged by the grid current through the conducting tube, but if the potential of the above point is changed as for example byconnecting it with an element carrying a lower potential, as the other source terminal which supplies the cathode of the tube, or by modifying an existing connection thereof with such an element, the control grid will be rendered more negative than the cathode due to the condenser charge algebraically added to the newly introduced potential. In

this manner it is possible to interrupt or modify the conductivity of the tube, dependent upon the discharge of the condenser or other energy storing means, for example through an impedance which may be permanently set to a predetermined energy dissipating value or which may itself be a functionnf a controlling value.

Among other advantages, the above feature offers that of continuous readiness for immediate response to a single circuit modification as closing of a switch, of adaptability to various ways of operation and for correlation with further similar circuits with a minimum of interrelating elements, and of the possibility of variably conditioning the tube conductivity as controlled by the grid.

These and other objects, aspects and features of the invention will be apparent from the following description of several embodiments thereof by way of illustrating its genus and referring to a drawing in which:

Fig. l is a diagram of a circuit according to the invention;

Figs. 2 to 4 are similar diagrams of several modifications of the invention according to Fig.

1; and

Fig. 5 is a further modification employing two electron tubes.

In Fig.1, two terminals A and B of an alternating or direct current source supply a conventional electron discharge tube T with anode a, control electrode 9 and cathode is, the latter being for example heated in conventional manner by means of heater element 71..

Connected to grid 0 is a condenser C which is in parallel with dissipatingimpedance D; condenser C and impedance D are dimensioned to provide for discharge of the condenser through the impedance to a predetermined potential during a given time; for example if d and 0 stand for impedance and capacitance respectively, of elements D and C, and a dissipation time of the 55 approximate magnitude of 1 minute is desired,

D- The cathode is connected to one source termi- I nal, for example B, and the anode to the other terminal, for example A. Devices responsive to conductivity changes of tube'T may be connected in the cathode-anode circuit; for example a solenoid I actuating armatures 2 and 3, may be inserted between anode a and terminal A, a sustaining condenser 5 being connected across magnet I. Armature 2 may normally, that is when solenoid I is energized, connect conductor ID of a controlled circuit 0 with contact II, and when I is deenergized with contactIZ of that circuit. Armature 3 forms with contact I3 a normally open holding circuit bridging switch SI.

The operation of the circuit illustrated in'Fig. 1, is as follows: a

Assuming for purposes of illustration that the circuit is supplied with alternating current and that switch SI is open whereas switch S2 is closed, if terminal A is at a given instant positive, tube T will pass current sufficient to effect energization of solenoid I causing its armatures 2 and 3 to retain closed external contact II and to retain open external circuit contact I2 and holding circuit contact I3. This results from the circumstance that, with switch SI open, only the very low grid current is flowing in impedances RI and R2, hence tap X will be at substantially the same voltage as terminal A and condenser ID will be charged, due to the grid current, to approximately the maximum peak voltage between terminals A and B. Under these conditions the potential of point Y between the grid and the energy storing-dissipating device is relatively negative with respect to the potential at tap X, to an amount substantially equal to that peak voltage. The energy corresponding to this poof terminal B. By properly selecting the electric constants of the circuit in accordance with standard practice, the bias of grid 9 can be caused to drop below the blocking potential of the tube and hence to interfere with the current flow through the tube during each half cycle when terminal A is positive and terminal B is negative. gized, whereupon armature 2 opens the controlled circuit contact II and closes contact I2, and armature 3 closes the holding circuit at I3.

As mentioned above, the holding circuit with switch 3, I3 is connected in parallel with switch SI of the relay circuit; hence, if starting switch SI (which may be a push button switch) is momentarily closed causing grid g to interrupt current fiow through the tube T and to deenergize solenoid I, the armature 3 will lock the holding circuit into the relay circuit, so that the initial operating potentials of the latter are maintained even though the starting button SI is immediately released. It will now be understood that the deenergization of solenoid I will continue for an appreciable length of time dependent upon the duration of interruption of the current flow through tube T which, in turn, is dependent upon the relation of condenser C and impedance D controlling the discharge of the former. This discharge will continue until the grid potential becomes higher than the blocking value, whereupon the tube again becomes conducting, armatures 2 and 3 are attracted, the holding circuit opened and the external circuit restored from I2 to II.

In order to reenergize solenoid I at any moment during the time delay measured by the rate of discharge of capacitor C, the normally closed stop switch S2 may be used. Opening of this switch immediately destroys the grid bias, the tube becomes conducting, and solenoid i reenergized. Push buttons SI and S2 may be 10- tential diiference between tap X and connection Y normally tends to discharge through dissipating impedance D, but since, in an arrangement of this type, the time constant of the discharge is very high as compared with the alternating current frequency of the potential difference between points X and Y, very little discharge takes place during one alternating current cycle, so that the charge on C can be considered to be substantially constant.

On the reversal of polarity when terminal A is negative, the tube will not pass current but, due to the eflfect of sustaining condenser 5, solenoid I will remain energized and the positions of the armatures 2 and 3 unchanged during this half cycle.

If now switch SI still closed), changes proaches is closed (switch S2 being then the, potential at point X relative to its original potential and apthe potential at terminal B. Accordingly, due to the voltage across condenser C, the potential at connection Y is changed a corresponding amount, and grid g now becomes negative relative to cathode is; the change made in the potential of grid g with respect to cathode it corresponds and is equal to the change made in the potential of tap X relative to the potential cated at, or operated by remote control from starting and stopping stations at different points.

If it is desired to prevent premature interruption of a timing interval, switch S2 can be shunted by means of a jumper. Still another mode of operation can be provided by opening the holding circuit, for example at 20, and permanently short circuiting switch S2. The remaining switch SI will then operate as a sustaining switch; closing of switch SI starts a timing cycle which will be completed if the switch is kept closed during its entire duration. The timing cycle will be interrupted and magnet I re-energized as soon as switch SI is released.

The rate at which the grid potential rises relatively to the cathode potential is governed by the dissipating impedance D and the capacity of condenser C and the time delay can be adjusted by changing resistance D, as indicated at 2| of Fig. 1; in many instances it is however preferable to regulate the timing period by varying the relation of the potential between cathode and grid on the one hand and the potential between points X and Y due to the charge on condenser C on the other hand, by adjusting the position of tap X Y relatively to impedance R2. As mentioned above,

larger step by step changes can be made by means of exchanging impedance RI.

For practical purposes of the invention it is a quite important feature that readiness for op" eration is. continuously indicated by the glow of tube T if a tube suitable for that purpose is u. d or by an indicator (as 36 or 31 of Fig.

2, sea: W

Consequently solenoid I is deenerfor shunting portions of the resistance.

low); the timing period will be accordingly indicated by the non-conductivity of the tube.

Any means for lowering the potential of point X with respect to the cathode will be satisfactory for operation of the circuit, but it should be noted that for proper functioning, tap X must previously have been at a higher potential than the cathode It is feasible to charge condenser previously, in some manner, with voltage in the proper direction, as, for example, to drive it positive by an auxiliary voltage source. This is for example indicated in Fig. 1 where a battery 22 may be introducedand R2 disassociated from the supply source by opening connector 23.

A circuit of this type may be used 'for control may be utilized for controlling the time delay by means of external controlling factors. For example, as shown in Fig. 2, resistor D may be replaced by a variable impedance element or elements, for example, light-sensitive cells as phototubes 30, 3|. With tap X at a fixed point on resistor R2 the time of deenergization of solenoid l is thus made a function of the quantity or intensity of light falling on the light-sensitive circuit element. If several phototubes are placed in series, as indicated in Fig. 2, the time delay interval will depend on the least quantity or intensity of light on any of the phototubes, that -is to say, the time delay will be governed by the darkest cell. By means of a change over switch 35, or by permanently reconnecting the tubes,

the latter can bearranged in parallel; the time delay will then depend upon the average quantity or intensity of light on all the cells. It will be understood that any suitable electronic device can be used as a variable dissipating impedance controlling the time delay period.

Instead of employing the circuit according tothe invention for the delayed closing or opening a controlled circuit, it can be used for selectively delayed initiation of differentiated controlled effects; an arrangement of this type is also shown in Fig. 2. In this figure, R is a resistance with a number, for example two, switches S3 and S4 R has a value, and tap X is so arranged that, with switches S3 and S4 open, the grid current will charge condenser C as above described, whereas closing of switch S3 or S4 will bring the potential at X more or less below the value at which current flow through tube T is blocked and magnet IA deenergized. The time delay periods following the closing of one of the switches will differ accordingly.

Instead of selecting the electrical constants involved in such a manner that lowering of the potential at X (for example by closing switch S3 or S4) will render the tube substantially unconductive, they can be so selected that, upon closing switch S3 or S4, the respective potentials at Y will be above the blocking potential, but reduce the conductivity of the tube to corresponding de grees. In this instance the varying conductivity of the tube may be utilized for'efiecting'varying functional stages of a controlled device; for example a gaseous discharge lamp 36 may be operated with light intensities varying to a predeterdescribed with reference to switches Sl, S2 and 20 of Fig. 1.

Instead of using "a switch or a stepped ohmic resistance for lowering the potential at X for initiating a time delay period, acontinuously variable impedance, for example the inductance coil Ll of Fig. 3 can be employed. Such a coil may be in parallel with a resistance 4| and have an iron core 42, for example movable by means of a feeler- 43 running on a controlling pattern 44,. for examplea sheet to be supervised as to thickness. The potential at X is set to be, under normal conditions,-not more positive than the cathode potential. Upon movement of the core 42, the impedance of LI changes, the potential at X increases accordingly and draws a corresponding grid current which again applies a proportionate charge to condenser C. Upon return of the core to original position, the timing begins andthe period during which the tube is non-conductive will be proportionate to the maximum travel of core 42 which may be proportional to either the minimum or the maximum dimension of the article to be supervised. The duration of the time delay period, proportionate to the measured extreme value, can be measured by suitable means as for example a counter 45 started and stopped upon deenergization and reenergization respectively of magnet lb. I

It is further understood that the various above-mentioned impedance elements may predominantly represent ohmic resistances, capacitances or reactances, as the particular purpose may require. The use of a reactance for varying the potential at X has already been explained; Fig. 4 shows as a further example in this regard an alternative connection of the dissipating impedance Da; it will be understood that any energy consuming element efiective to increase the grid potential during the time delay period by diminishing the potential difference between points X and Y will serve the purpose.

Fig. 4 shows further a modification of the circuit according to Fig. 1 which permits continuous operation for initiating series of periodical impulses.

In Fig. 4, C and Da are the energy storing and dissipating elements, respectively, connected to supply source A, B, tube T and conductivity responsive element lb as described with reference to Fig, 1.

A switch S5 is connected between one source terminal and point X and this switch is bridged by a holding circuit with normally open contacts 3b, l3b in a manner similar to the arrangement of switch SI and contacts 3, l3 of Fig. 1. The contact l2b of the controlled circuit is in this instance connected to the source terminal B, and contact I lb to the other source terminal over a switch S6 and a magnet 5| which latter tends to close switch S5 upon energization. Care is taken by conventional means that, upon enerbefore holding contact 3b opens, and that, upon deenergization of l contact llb will not open before contact 3b closes.

Assuming that switches S6 and S are open, tube T will be conductive, magnet lb energized, contacts 3b and l2b open and contact lib closed and L2 will carry current. If now switch S6 is closed, magnet 5| will close switch S5, the grid potential will be lowered below the blocking value, lb will be deenergized, the holding circuit established, the circuit of magnet 5| interrupted at lib, and the controlled external circuit closed at I2b. Condenser C now discharges through Da and the tube will resume conductivity after a time interval determined by the values of C, R and Da and the settings of X and Y. lb is again energized, the holding circuit opened and 5| energized to start another cycle; this will continue until switch S6 is opened.

More elaborate timing functions can be performed by combining, according to another aspect of my invention, several timing circuits; an example of such arrangements will now be described with refeernce to Fig. 5.

In Fig. 5, A and B are the supply terminals, I and II are two time delay units connected thereto, and O is an external controlled circuit..

Each unit has a tube (Tl, T2), an impedance (R3, R l) in series with a timer switch (63, 64), an energy storing and dissipating element (SDI, SD2), and a magnet (66, 62). Elements SDI and SD2 are connected at points XI and X2 respectively to impedances R3 and R4 and at the points YI and Y2 to the grids of tubes Tl, T2 respectively. Magnet 6| closes switch. 64 if energized and magnet 62 similarly keeps switch 63 closed so long as it is energized. Magnet is of the control circuit is in series with switch 63 and will close contact ii if switch 63 is closed, but change over to iii if 63 is open.

Assuming for example that switch 64 of unit II is closed, during a period when the potential at Y2 is below its blocking value but gradually increases due to energy dissipation at SD2, tube T2 will be non-conducting and switch 63 open. Hence, tube Ti of unit I will be conducting and keep switch 64 closed, as assumed. As soon as the potential at Y2 rises above the blocking value, tube T2 becomes conducting, switch 63 closes, connecting the exterior circuit at H and starting a time delay interval during which tube TI is non-conducting and causes opening of switch 64. Energy is now stored at SD2 until the potential at Yl rises above the blocking potential, switch 64 closes and starts another energy dissipating and time delay interval at unit II during which switch 63 is open and contact I 2 closed. In other words, the following sequence of operations will prevail. Contact ll stays closed during an interval controlled by unit I; ll opens and I2 closes; l2 stays closed during an interval controlled by unit II; l2 opens and II closes; ll stays closed, etc. It will be evident that the above time intervals can be independently controlled by suitably setting units I and II for respective timing periods,-or varying them according to an independent function for example in the manner explained with reference to Figs. 2 and 3.

The operation of .a circuit according to Fig. 5

can be initiated for example by closing switch 65 in the circuit of one of the timer switches.

It should be understood that the present disclosure is for the'purpose of illustration only and 2,306,237 gization of magnet lb, contact llb will not close that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. A time delay device comprising a source of I more positive than the simultaneously prevailing potential of said cathode, means adapted for storing electric energy and for dissipating it at a predetermined rate substantially permanently connectedbetween said gridand said potential supply means, and means for applying the energy of said storing means to said grid for lowering its potential relatively to said cathode and raising it again as the energy is dissipated at said predetermined rate, said conductivity being controlled through said application of said energy to said grid and the nature of said dissipating rate.

2. A time delay device comprising a source of electric potential, an electron discharge device having cathode, anode and control grid, substantially permanent supply connections from said cathode and said anode to said source, means responsive to the conductivity of said discharge device, substantially permanently effective means for supplying a potential which is more positive than the simultaneously prevailing potential of said cathode, means adapted for storing electric energy substantially permanently connected between said grid' and said potential supply means, means for dissipating said energy at a predetermined rate connected to said storing means, and adjustable means for applying the energy of said storing means to said grid for lowering to a predetermined degree its potential relatively to said cathode and raising it again as the energy is dissipated at said predetermined rate, said conductivity being controlled through said application of said energy to said grid and the nature of said dissipating rate.

3. A time delay device comprising a source of electric potential, an electron discharge device having cathode, anode and control grid, substantially permanent supply connections from said cathode and said anode to said source, means responsive to the conductivity of said discharge device, substantially permanently effective means for deriving from said source a potential which can be rendered more positive than the simultaneously prevailing potential of said cathode, means adapted for storing electric energy substantially permanently connected between said grid and said potential deriving means, means for dissipating said energy at a predetermined rate connected to said storing means, and means for applying the energy of said storing means to said grid for lowering to a predetermined degree its potential relatively to said cathode and raising it again as the energy is dissipated-at said predetermined rate, said conductivity being controlled through said application of said energy to said gridand the nature of said dissipating rate.

' 4. A time delay device comprising a source of electric potential, an electron discharge device having cathode, anode and control grid, supply connections from said cathode and said anode to respective terminals of said source, means renected to said anode terminal, means adapted for storing electric energy and for dissipating it at a predetermined rate connected between said impedance and said grid, and circuit making and breaking switch means connected, in parallel to said cathode supply connection, at a point between said impedance and said storing means on the one side and said cathode terminal on the other side, said conductivity being controlled through the energy stored when said switch means is open, and applied to said grid upon closing of said switch means.

5. A time delay device comprising a source of controlled by the potential supplied to said condenser through the grid current when said switch 'is open, applied by the condenser to the grid upon closing said switch, and diminishing by its discharge through said control resistance.

6. A time delay device comprising a source of electric potential, an electron discharge device having cathode, anode and control grid, supply connections from said cathode and said anode to respective terminals of said source, means responsive to the conductivity of said discharge device in one of said connections, an impedance connected to said anode terminal, means adapted for storing electric energy and for dissipating it at a predetermined rate connected between said impedance and said grid, and a step by step adjustable impedance means connected, in parallel to said cathode supply connection, at a point between said impedance and said storing means on "the one side and said cathode terminal on the other side, said conductivity being varied "through the stored energy applied to said grid at a bias level determined by the impedance means.

7. A time delay device comprising a source of electric potential, an electron discharge device having cathode, anode and control grid, supply connections from said cathode and said anode to respective terminals of said source, means responsive to the conductivity of said discharge device in one of said connections, an impedance connected to said anode terminal, means adapted for storing electric energy and for dissipating it at a predetermined rate connected between said impedance and said grid, continuously adjustabl impedance means connected, in parallel to said cathode supply connection, at a point between said impedance and said storing means on the one side and said cathode terminal on the other side, and means for adjusting said impedance in conformity with a controlling value, said conductivity being varied through the stored energy applied to said grid at a bias level determined by said impedance means.

8. A time delay device comprising a source of electric potential; two electron discharge tubes each having cathode, anode and control grid, supply connections from said cathodes and said anodes to respective terminals of said source, current responsive actuating means in one of the connections of each tube, circuit making and breaking means controlled by said actuating means to be in circuit-closing position during conductivity of the tube of the respective actuating means, means for supplying a potential which can be rendered more positive than the simultaneously prevailing potential of the re spective cathode, and means adapted for storing electric energy and for dissipating it at a predetermined rate permanently connected between the grids and the potential supply means of the respective tubes; said circuit making and breaking means of each respective tube being connected between the cathode supply terminal and said potential supply means of the other tube; and impulse transmitting means controlled by one of said actuating means.

WILLIAM F. WOLFNER, II.

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Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2419276A (en) * 1944-05-27 1947-04-22 Dallas A Miller Remote control means for electrical circuits
US2431284A (en) * 1943-11-20 1947-11-18 Westinghouse Electric Corp Pulsation timing system
US2436872A (en) * 1944-05-19 1948-03-02 Taylor Winfield Corp Timing circuits
US2443660A (en) * 1945-05-19 1948-06-22 Westinghouse Electric Corp Electronic timer
US2450460A (en) * 1944-08-23 1948-10-05 Photoswitch Inc Electronic timing apparatus
US2461266A (en) * 1946-05-31 1949-02-08 Godwin R F Gay Timing device
US2468791A (en) * 1945-06-30 1949-05-03 Photoswitch Inc Conductivity control
US2519247A (en) * 1947-12-31 1950-08-15 Bell Telephone Labor Inc Timing circuit
US2519265A (en) * 1948-02-28 1950-08-15 Westinghouse Electric Corp Sector scanning unit
US2534323A (en) * 1943-08-20 1950-12-19 Photoswitch Inc Electronic control apparatus
US2573360A (en) * 1948-11-06 1951-10-30 Robotron Corp Electric valve sequenced multifunction timer
US2574383A (en) * 1947-11-17 1951-11-06 Honeywell Regulator Co Temperature control apparatus
US2574618A (en) * 1947-02-14 1951-11-13 Photoswitch Inc Electronic timing device
US2583792A (en) * 1948-05-22 1952-01-29 Lloyd E Nelson Timer circuit
US2597082A (en) * 1948-11-02 1952-05-20 Westinghouse Electric Corp Reverse plating timer
US2624784A (en) * 1949-05-31 1953-01-06 Charles W Davis Electronically controlled relay
US2631524A (en) * 1947-02-21 1953-03-17 Arvin Ind Inc Toaster and electronic timer
US2639361A (en) * 1948-04-02 1953-05-19 Westinghouse Electric Corp Timer for welding systems
US2727189A (en) * 1951-03-15 1955-12-13 Raytheon Mfg Co Split relay locks
US2914789A (en) * 1957-03-11 1959-12-01 Precise Vac U Tronic Inc Vacuum cleaner system
US2942160A (en) * 1955-03-04 1960-06-21 Burroughs Corp Triggered thyratron circuit

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2534323A (en) * 1943-08-20 1950-12-19 Photoswitch Inc Electronic control apparatus
US2431284A (en) * 1943-11-20 1947-11-18 Westinghouse Electric Corp Pulsation timing system
US2436872A (en) * 1944-05-19 1948-03-02 Taylor Winfield Corp Timing circuits
US2419276A (en) * 1944-05-27 1947-04-22 Dallas A Miller Remote control means for electrical circuits
US2450460A (en) * 1944-08-23 1948-10-05 Photoswitch Inc Electronic timing apparatus
US2443660A (en) * 1945-05-19 1948-06-22 Westinghouse Electric Corp Electronic timer
US2468791A (en) * 1945-06-30 1949-05-03 Photoswitch Inc Conductivity control
US2461266A (en) * 1946-05-31 1949-02-08 Godwin R F Gay Timing device
US2574618A (en) * 1947-02-14 1951-11-13 Photoswitch Inc Electronic timing device
US2631524A (en) * 1947-02-21 1953-03-17 Arvin Ind Inc Toaster and electronic timer
US2574383A (en) * 1947-11-17 1951-11-06 Honeywell Regulator Co Temperature control apparatus
US2519247A (en) * 1947-12-31 1950-08-15 Bell Telephone Labor Inc Timing circuit
US2519265A (en) * 1948-02-28 1950-08-15 Westinghouse Electric Corp Sector scanning unit
US2639361A (en) * 1948-04-02 1953-05-19 Westinghouse Electric Corp Timer for welding systems
US2583792A (en) * 1948-05-22 1952-01-29 Lloyd E Nelson Timer circuit
US2597082A (en) * 1948-11-02 1952-05-20 Westinghouse Electric Corp Reverse plating timer
US2573360A (en) * 1948-11-06 1951-10-30 Robotron Corp Electric valve sequenced multifunction timer
US2624784A (en) * 1949-05-31 1953-01-06 Charles W Davis Electronically controlled relay
US2727189A (en) * 1951-03-15 1955-12-13 Raytheon Mfg Co Split relay locks
US2942160A (en) * 1955-03-04 1960-06-21 Burroughs Corp Triggered thyratron circuit
US2914789A (en) * 1957-03-11 1959-12-01 Precise Vac U Tronic Inc Vacuum cleaner system

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