US2803814A

US2803814A - bloser

Info

Publication number: US2803814A
Authority: US
Priority date: 1945-07-30
Filing date: 1945-07-30
Publication date: 1957-08-20
Anticipated expiration: 1974-08-20
Also published as: FR74002E; GB655437A; US2444210A; FR939211A; GB636113A; BE482082A

Description

D. w. BLOSER I ELECTRONIC TIMERl Aug. 20, 1957 4 Shee'ts-Shaet l Filed .my so, 1945 Aug. 20, 1957 D. w/BLosr-:R

ELEcTRomc TIMER 4 sheets-sheet 2 Filed July 550,- 1945 gmc/wwf,

@wig/U Wler Nswm D.v W. BLOSER ELECTRONIC TIMER Aug. 20, 1957 4 sheets-sheet s Filed July 50, 1945 Aug. 20, 1957 D. w. BLosx-:R

ELECTRONIC TIMER Filed July 30, 1945 United States Patent Otitice 2,803,814 Patented Aug. 20, 1957 ELECTRONIC TIMER Dwight Wilson Bloser, West Englewood, N. J., assignor to Bendix Aviation Corporation, Teterboro, N. J., a corporation of Delaware Application July 30, 1945, Serial No. 607,736

36 Claims. (Cl. 340-234) This invention relates to electrical timing apparatus, and particularly to that type of timing apparatus wherein a series of load devices are sequentially operated for a predetermined time and there is automatically provided a predetermined interval of time between cycles of operation.

An object of the invention is to provide improved electrical timing apparatus `controlled by the charged condition of a capacitor or condenser.

Another object of the invention is to provide a novel circuit for effecting a charging operation of the timing condenser through a diode so as to eliminate all unnecessary switch contacts and wearing parts.

Another object of the invention is to provide a novel circuit in which the charging operation of a timing condenser may be eiected through a diode and the electronic valve controlled thereby.

Another object of the invention is to provide a resistor connecting the timing condenser to the source of electrical energy during the charging operation and applying a positive bias to the cathode of the controlled tube so as to ldeionize the tube during the latter charging operation.

Another object of the invention is to provide a resistor connected across the plate and cathode of an electronic Valve so as to control the inductive voltage rise across a coil in the plate circuit so as to effect a greater time delay than would normally be obtained with the time constant and voltage of the main electronic supply source.

Another object of the invention is to provide novel manually operable means for selecting the interval of time between cycles of operation of the same.

Another object of the present invention is to provide novel electrical means for timing the periods of operation of an electric motor.

Another object of the invention is to provide improved timing apparatus for controlling the periods of inflation of a series of solenoid controlled inflatable elements or boots for preventing the accumulation of ice on or the removal of ice from aerofoil surfaces of an aircraft. The latter 1system of inflatable elements may be of the type -described and claimed in the copending applications Serial Numbers 498,248 of Donald M. Lawrence, David Gregg and Myron L. Taylor, filed August 11, 1943, now U. S. Patent No. 2,515,519, and application Serial Number 498,250 of Myron L. Taylor, William B. Pond and Herbert A. Eayrs, filed August 11, 1943, now U. S. Patent No. 2,444,208, and all of which patents have been assigned to Bendix Aviation Corporation.

These and other objects and features of the invention are pointed out in the following description in terms of the embodiment thereof which is shown in the accompanying drawings. It is to be under-stood, however, that the drawings are for the purpose of illustration only, and are not designed as a definition of the limits of the invention, reference being had to the appended claims for this purpose.

. In the drawings:

Figure 1 shows a plan view of the control panel and indicator lights of the present invention;

Figure 2 represents an electrical timing circuit embodying certain features of my invention;

Figure 3 is a view of the circuit of Figure 2 with certain -non-pertinent elements omitted and showing the electron ilow during the charging operation of the tim` ing condenser by solid arrows, while the electron ow' during the discharging operation is indicated by dotted arrows;

Figure 4 is a view of a modified circuit from Figure 3 with the non-pertinent elements omitted and showing the electron ow during the charging operation by solid arrows and the electron flow during the discharging operation by dotted arrows;

Figure 5 represents an electrical timing circuit embodying a third form of the invention, including an electric motor.

Referring now to Figure 2, there i-s shown a system for timing the operation of a stepper relay 10 which controls the energization of a series of loads 11, indicated as a plurality of electromagnets. The electronic timer is particularly adapted for use in conjunction with the manifold type of inflatable ice eliminating systems described in t-he aforenoted copending applications. The electromagnets 11 may serve upon energization to open the boot-inflating valves automatically in the proper sequence and for proper time intervals.

The stepper relay 10 may be of a conventional type comprising an electromagnetic winding 12 which controls the movement of an armature 13 pivotally supported at 14. A ratchet arm 15 is pivotally mounted on the armature 13 and is biased into engaging relation with a ratchet wheel 16 by a spring 17. A second spring 18 biases the armature 13 in a counterclockwise direction into contacting relation with a stop 19. A pawl 20 is biased into engaging relation with the teeth of the ratchet wheel 16 by a spring 21 so as to prevent rotation of the ratchet wheel 16 in a counterclockwise direction.

It will be readily seen from the foregoing that upon energization of the electromagnet 12 the armature 13 will be pivoted in a clockwise direction in opposition to the force of the spring 18 causing the ratchet arm 15 to engage the next succeeding tooth of the ratchet wheel 16. At the extreme limit of movement of the armature 13 an actuating member 22 carried thereby engages the free end of a leaf spring 23 so as to open the contacts of a switch 24.

The opening of the switch 24 breaks the circuit of the electromagnet 12, as will be explained hereinafter. causing de-energization of the electromagnet 12, whereupon the spring 18 actuates the armature 13 in a counterclockwise direction causing the pawl 15 to impart an increment of movement to the ratchet wheel 16 in a clockwise direction.

The ratchet wheel 16 is connected through a suitable shaft 25 indicated herein by dotted lines to switch

arms

26, 27, 28 and 29.

The

switch arms

26, 27 and 28 are each arranged to contact in succession a series of contacts 26A-L, 27A-L and 28A-L. The

switch arms

26, 27 and 2S move from one contact to the next succeeding contact for each increment of movement imparted to the ratchet wheel 16 by the stepper relay 10 and upon one end of the switch arm moving out of contacting relation with the contact K the opposite end closes the contact L.

The switch contacts 26A-K are connected through suitable electrical conductors 30A-K, respectively to one terminal of corresponding load devices or electromagnets 11. The opposite terminal of the electromagnets 11 are .conductor 34 which leads to a switch contact 35 controlledby a switch 36. The switch 36 is connected by a conductor 37 through an electric light or indicator 38 to the negative terminal of the source of electrical energy 32.

There may also be connected in parallel to the electromagnets 11 suitable indicator lights 39A-K for each load device or boot operating solenoid. The latter lights may be mounted on the panel of the timer or may be preferably provided in a separate unit as indicated in Figure 1. There is also provided a light 39L connected to the contact 26L by conductor 30L. Another light 39M is connected to the main energizing circuit by conductor 30M as will appear. The lights 39A-M are connected by conductor 31A to the conductor 31 through a switch 31B.

As will be explained, the light 38 is arranged so as to indicate the timer is in operation, while the lights 39A-L will indicate the particular load device or ice eliminating boot in operation. The light'39M indicates whether the system is energized.

l The switch arm 36 is arranged so that it may alternatep be provided as desired.

The contact 26L is not connected to the load devices 11, soA that upon the switch arm 26 contacting the same, the circuit to all of the load devices 11 are open for a purpose which will appear hereinafter.

The switch arm 27 is arranged to successively close contacts 27A-L. The latter contacts are interconnected by an electrical conductor 42 to a conductor 43. The

conductor 43 is connected to the positive terminal of the source of electrical energy 32 through a conductor 43A so as to complete the circuit for the light 38, lights 39 and Vthe load devices 11.

The switch arms 27 by opening the contacts 27A-K in unison with the opening of contacts 26A-K by the switch arm 26 is arranged to reduce the arcing at contacts 26A-K by providing a series break. Similarly the switch arm 27 in opening the contacts 27A-L causes flickering of the light 38 which will indicate to the operator that the system is in operation.

There also leads from the conductor 43 a conductor 45 which leads to manually

operable switches

46, 47, 48, 49 Land 50 connected in series and arranged to close respectively contacts I-K, H-G, E4F, D*C and A-B connected through suitable conductors to the circuits controlling the load devices or solenoids 11. The

switches

46, 47, 48, 49 and 50 thus provide manually operable means for controlling energization of the load devices or ice eliminating boot operating solenoids 1l. It will be noted, moreover, that since the latter switches are connected in series only one of the set of load devices may be energized at a time, through operation of the manual switch means. The latter arrangement thus prevents an overload from being inadvertently applied to the ice eliminating system.

The switch arm 28 is arranged to sequentially close contacts 28A-L connected to suitable resistor elements 51 for a purpose which will be explained hereinafter.

The shaft also drives a switch arm 29 arranged to actuate an oi normal switch 52 to an open position upon the

switch arms

26, 27 and 28 being positioned so as to close the

respective contacts

26L, 27L and 28L respectively. Upon the

switch arms

26, 27 and 28 being adjusted into contacting relation with one of the other contacts, the member 29 is adjusted out of contacting relation with the otnormal switch 52 soy as to permit the switch 52 to close for purposes which will be explained.

The winding 12 of the stepper relay 10 has one terminal connected by an electrical conductor 53 to conductor 43A and thus to the positive terminal of the source of electrical energy 32. The opposite terminal of the winding 12 is connected by an electrical conductor 54 to an anode or plate 55 of an electronic valve 56.

The electronic valve 56 has a cathode 57, a control grid 58, a cathode shield grid 59, a heater or iilament 60 and the plate 55.

The cathode 57 is connected by a conductor 61 to one contact of the olf normal switch 52 while the opposite contact of the off normal switch 52 is connected by a conductor 62 to one contact of the switch 24. The opposite contact of the switch 24 is connected by a conductor 63 to the negative terminal of the source of electrical energy 32.

The conductor 62 also leads to one contact of a push pull switch 64. The opposite contact of the switch 64 is connected by a conductor 65 to the conductor 61 through a contact 66 and adjustable switch arm 67. Thus it will be seen that the cathode 57 may be connected to the negative terminal of the source of electrical energy 32 by closing the push pull switch 64 upon the switch arm 67 being adjusted to a position closing contact 66.

.The switch arm 67 is mechanically connected to switch

arms

68, 69, 70 and manually adjustable knob 71 through a shaft 72 for a purpose which will be explained hereinafter.

Other contacts controlled by the switch arm 67 include contact 72 which is an open contact and three contacts 73 which are electrically connected by a conductor 74 to the conductor 62. Thus the negative terminal of the source of electrical energy 32 may be connected to the cathode 57 upon the switch arm 67 closing one of the contacts 73.

The electron flow from the cathode 57 to the plate 55 is controlled by a grid 58 connected by a conductor 75 to one end of a resistor 76. The opposite end of the resistor 76 is connected by a conductor 77 to a plate 78 of a condenser 79. The opposite plate 80 of the condenser 79 is connected by a conductor 81 to the conductor 61.

The plate 78 is connected through a conductor 82 to the switch arm 28 previously described and which is arranged to close sequentially the contacts 28A through L.

Leading from the contacts28A through L, respectively are resistors 51A-L each of a value suicient to elect a predeterminedtime interval for energizing the load device 11 .corresponding thereto. The resistors 51A-L may be of different value so as to effect different time intervals of operation for each load device.

Leading from Vthe opposite terminals of the resistors 51A-L is a conductor 83 which leads to the conductor 43. Connected to the conductor 43 are four contacts 84 and there is provided a switch arm 70 for closing the same. The conductor 43A connects the switch arm 7 0 to the positive terminal of -the source of electrical energy 32. Cooperating with the switch arm 70 is a fth and open contact 86. Leading from the contacts 84 is a conductor 87 which connects the same to the switch arm 69. The conductor 87 also connects the light 39M to the positive terminal of the source of electrical energy 32 through arm 70.

The switch arm 69 is arranged to selectively contact one of ve contacts including two open contacts 88 and three contacts 89 connected by an electrical conductor 90 to the resistor 51L at a point intermediate the opposite ends of the latter resistor.

It will be seen then that when the switch arm 69 closes one of the contacts 89 a portion of the resistor S1 leading from the contact 28L will be shunted out of the circuit leading from the positive terminal of the source of electrical energy 32 and the plate 78 of the condenser 70. However, upon the switch arm 69 contacting one of the open contacts 88 and the switch arm 70 closing one of the contacts 84 the full resistance of the resistor S1 leading from the contact 28L will be inserted in the latter circuit.

The switch arm 68 is arranged to selectively contact one of the' five contacts including four open contacts 91 and one contact 92 from which a conductor 93 leads to the conductor 82. A conductor 94 leads from the switch arm 63 to the plate of a second condenser 9S. The op'- posite plate of the condenser 95 is connected to the conductor 81. Thus upon switch arm 68 closing contact 92 Ithe condenser 95 is connected in parallel to condenser 79 so as to increase thel total condenser capacity.

Upon the switch arm 68 being adjusted so as to open the contact 92, it will be seen that condenser 79 only will apply the controlling bias on fthe grid 58.

The condenser 79 or

condensers

79 and 95 are charged through operation of a diode 100 having an anode 101, cathode 102 and heater or filament 103. The anode 101 is connected by a conductor 104 to the conductor 82 leading to the plate 78 of condenser 79. The cathode 102 is connected by a conductor 105 leading to the negative terminal of the source of electrical energy 32.

The conductor 105 also leads to a resistor 106 through which the conductor 105 is connected to one terminal of the heater or lament 60 of the electronic valve S6. The opposite terminal of the filament 60 is -connected by a conductor 107 to one terminal of the heater or filament 103 of the diode 100. A conductor 108 connects the opposite terminal of the filament 103 to the conductor 43. Through the conductor 43, .switch contacts 84, and switch arm 70, the conductor 108 is connected to the positive terminal of the source of electrical energy 32.

The shield grid 59 is connected to the negative terminal of the source of electrical energy 32 by a conductor 110 leading to the conductor 105. There is connected between the anode 55 and the conductor 110 a resistor 111 to limit the rise of induced voltage that occurs across the stepper relay coil 12 as its field decays. By proper choice of the resistor 111 the same may be so arranged as to allow a controlled voltage rise to occur which will be reflected in a higher charge voltage on the condenser 79 with a corresponding increase in the time of discharge for the same resistor 51, capacitor 79 and line voltage combination.

Operation The foregoing electronic timer is particularly designed for use in conjunction with the manifold type of ice eliminating system for airfoil surfaces of aircraft and is arranged to open the boot inflating valves automatically in the proper sequence for the proper time intervals. Since ice does not form at the same rate or to the same degree on all occasions, a certain flexibility of control has been incorporated to permit the operator to vary certain components of the system to suit the prevailing conditions.

As shown in Figure l, the control system may be mounted o-n a control panel A which is preferably mounted in the Engineers Compartment of :the aircraft, while the indicator lights 39A-M and switch 31B are carried by a separate unit B. The unit B is electrically connected with the control panel A through a conduit C as indicated in Figure 2 and the unit B is mounted apart from the control panel A. The unit B is preferably mounted in the pilots compartment of the aircraft.

It will be seen, moreover, that the panel A has mounted thereon the single control knob 71, indicator light 38 and I the emergency flip switches A-K for manually controlling the operation of the inflatable ice eliminating elements or boots.

Starting with the knob 71 in single cycle position as shown in Figure 2 with switch arm 67 on contact 66, switch arm 68 on contact 91, switch arm 69 on contact 89 and switch arm 70 on contact 84, operation of the system is initiatedA by closing single cycle button or switch 64,

whereupon the electronic valve 56`fires energizing thel stepper relay coil 12 and drawing up the ratchet arm 12 until it engages the next tooth on ratchet wheel 16 and simultaneously opens interrupter switch 24. The opening of the interrupter switch 24 breaks the circuit between the negative terminal of the source of electrical energy 32 andthe cathode 57 of the electronic valve 56.

Electronic flow continues through the valve 56 for part of the open time of interrupter switch 24 so as to charge the condenser 79. The charging circuit is shown in Figure 3 in which certain of the non-pertinent parts of the system have been omitted for clarity of illustration.

The electronic flow during the charging action as indicated by solid arrows in Figure 3 is from the plate 80 of the condenser 79 though the electronic valve 56, from the cathode 57 to the plate 55, and through relay coil 12 to the positive terminal of the source of electrical energy 32. The opposite plate 78 of the condenser 79 is negatively charged by an electronic flow from the negative terminal of the source of electrical energy 32 through the diode 100.

Plate 78 of condenser 79 is also connected by means of conductor 82 and resistance 51 to the positive side of the source of electrical energy 32, but since the resistance of diode 100 to electron flow in the charging direction is negligible compared to resistance 51, essentially the full line voltage is impressed across the condenser 79. The diode 100 therefore, acts in the nature of a switch contact on charging to connect plate 78 of condenser 79 to the negative side of the source of electrical energy 32.

lt will be noted that the resistor 111 serves to limit the rise of induced voltage that occurs across the stepper relay coil 12 as its field decays. By a proper choice of this resistor 111 there may be allowed a controlled voltage rise to occur that will be reflected in a higher charge voltage on the condenser 79 with a corresponding increase in the time of discharge for the same resistor 51, capacitor 79 and line voltage combination.

The condenser 79 is charged for a time interval determined by the impedance of the coil 12 in the charging circuit until the control grid 58 becomes biased sufficiently negative with respect to the cathode 57, because of the charge on the condenser 79, that electronic flow through the electronic valve 56 ceases and the stepper relay coil 12 becomes sufficiently deenergized as to release the switch 24. After the charging of the condenser 79, the remainder of the open time of the interrupter switch 24 allows the electronic valve 56 to deionize. Upon de-energization of the relay coil 12 following the opening of the switch 24 and charging of the condenser 79, the spring 18 draws the ratchet arm 15 downward driving through the ratchet wheel 16, contact

arms

26, 27 and 28 so as to close

contacts

26A, 27A and 28A, while off normal switch arm 29 is moved to a position out of contacting relation with switch 52 so as to permit the same to close the circuit between the cathode and interrupter switch 24. The downward movement of the ratchet arm 15 has also closed interrupter switch 24 so that the negative terminal of the source of electrical energy 32 is now connected through

switches

24 and 52 to the cathode 57.

The condenser 79 has now been charged and provides a negative bias on the control grid 58 to prevent further firing of the electronic valve 56 until the condenser 79 has been discharged.

As shown in Figure 3, the condenser 79 discharges as indicated by dotted arrows. The electron charge applied to the plate 78 of condenser 79 flows through switch arm 28 and resistor 51 to the positive terminal of the source of electrical energy 32, while there is electronic flow from the negative terminal through the closed switch 24 to the plate 80 of the condenser 79. The duration of the discharge period will, of course, be dependent upon the value of the resistor 51 in the discharge circuit.

There is no electron flow through diode during discharge, since the plate of the diode 100 is connected Vto. the `negatively charged plate 78 of the condenser 79 4ridftliecathhde is connected to positively charged plate The diode 100 therefore, acts in the nature' of a switch on discharging to disconnect plate 78 of condenser 79 from the negative side of the source of electrical energy -32. Thus it will be seen that the diode 100 acts to replace a pair of contacts that would otherwise be necessary for connecting and disconnecting plate 78 of the condenser 79 for charging and discharging, respectively.

While I have shown a diode as applied to the foregoing, it will be readily seen that any unidirectional current device such as a dry plate rectifier or liquid electrolytic rectifier may be used. However, a diode is preferable since the same has infinite resistance to reverse How.

` After the elapse of a predetermined interval of time Aduring which Ythe condenser 79 discharges, as indicated,

ing the

switch contacts

26L, 27L and 28L the circuit to the load devices 11 is open and the ofi normal switch arm 29 once again opens the switch 52 in the cathode circuit.

Under the single cycle operation the timer causes each boot to be inflated in turn once, after the starting button 64 is depressed and then waits until the starting button 64 is again depressed before proceeding with another intlation cycle. This operation is useful under low rate icing conditions.

Continuous operation may be effected by adjusting the knob 71 so as to position switch arm 67 so as to close one of the contacts 73. The switch arm 67 will then shunt the single cycle switch 64 so that continuous operav tion may be effected,

will be seen that since contact 88 is an open Contact the conductor 90 will be cut out of operation.

However, since switch arm 70 closes contact 84 to which conductor 83 is connected through conductor 43, it will be seen that the full resistance of resistor 51L will be connected into the discharge circuit of the condenser 79 so that the electronic valve 56 will be held from firing until the condenser 79 has discharged sufiiciently. The latter interval is shown as a sixty second dwell, but the period may be for a greater or less period as` determined by the value of the resistor 51L.

After the condenser 79 has discharged the electronic Avalve 56 tires and the operation of the system repeats.

Under the latter adjustment of the knob 71 the timer Vcauses the sequential intiation of each of the ice eli-minating boots in turn, waits sixty seconds or such other predetermined period and then repeats until the timer is turned off. This operation is preferable under mediumrate icing conditions. If the knob 71 be adjusted so as to cause switch arm 67 to close `one of the contacts 73 and the switch arm 69 to close one of the contacts 89, it will be seen that only a portion of the resistor 51L will be connected into the discharge conduit of the condenser 79 through conductor 90 so that the delay period between cycles of operation may be imperceptible or approaching zero second dwell.

In the latter operation, the timer keeps repeating the inflating cycles just as in the previous operation, but docs not delay between successive inflation cycles. The

latter operation is adapted for high rate icing conditions.

Should it be desired to increase the intiation period for l each boot, this may be accomplished by adjusting the V79. The'latter adjustment will also cause adjustment ofswitch arm 67 to'close contact 73, switch arm 69 to close contact 89 and switch arm 70 to close contact`84.

By thus connecting the condenser in parallel to the condenser 79"the period of inflation for each boot may be increased for example by fty percent or any other predetermined amount.

In this operation, the cycling is repetitive without delay between cycles, but the ination period for each boot is increased for example by fifty percent,

This operation is particularly effective under high alti tude conditions and sub-normal air flows from the engine arr pump.

As a safety fall-back there are provided a row of auxiliary hand operated switches 46, 47, 48, 49 and 50 connected so as to directly control the inflation andderlation of the several boots.

The timer may be cut off by adjusting the knob 71 so as to cause

switch arms

67, 68, 69 and 70 to contact the `

open contacts

72, 91, 8S, and 86 respectively.

Modified form of Figure 4 In Figure 4 there is shown a modified form of the invention which differs from the form shown in Figure 2 in the provision of a resistor 112 connecting the plate 80 of the condenser 79 directly to the positive terminal of the source of electrical energy 32.

Under the latter arrangement the condenser 79 charges through the diode and resistor 112 rather than through the electronic valve 56. Under the latter arrangement the valve 56 is directly deionized through the resistor 112 during the charging operation. The charging and discharging circuits are indicated in Figure 4 by solid and dotted arrows respectively.

There is further provided a condenser 113 connected in parallel to the stepper relay coil 12 for momentarily maintaining the coil 12 energized upon the switch 24 openmg.

The operation of the form of the invention of Figure 4 is otherwise substantially the same as described for the form of Figure 2 and therefore a further detail description is not believed necessary.

Modified form of Figure 5 In the modified form of the invention shown in Figure 5, there is provided a motor in the plate circuit instead of the stepper relay coil 12. The motor 120 has an armature 121 and lield winding 122 connected to the plate 55 by conductor 54 and to the positive terminal of the source of electrical energy by the conductor 53.

The armature 121 drives a shaft 123 indicated by dotted lines to which there is atiixed a cam 124 and gear 125 driving a gear train 126 which connects the shaft 123 to a second shaft 127 to which there is affixed the

switch arms

26 and 28, as shown, together with a second cam 128.

The came 128 operates an oli? normal switch 52 connected across the switch 64 previously described with reference to Figure 2, while the cam 124 operates a switch 130 having make before break contacts in which a contact 131 is normally closed by a switch arm 132 having a contact 13'3 normally open in relation to a second switch arm 134. The cam 124 has a cam surface 135 so arranged that upon initial energization of the motor 120 and rotation of the shaft 123 the switch arm 134 is actuated so as to first close the switch contact 133 and then actuate the switch arm 132 so as to open the contact 131. Upon continued rotation of the shaft 123 the surface causes the switch arm 134 to actuate the switch arm 132 so as to first close contact 13'1 before the switch arm 134 opens the contact 133.

The switch arm 132 and contact 133 are connected to conductor 61 leading to the negative terminal of the 9 source of electrical energy 32 through the off normal switch 52 or the switch 64 and conductor 62..

The contact 131 is connected by a conductor 131A leading to Ithe cathode 57. The switch arm 134 is connected to a conductor 136 leading to the conductor 54 which connects the plate 55 and the :motor 120 as previously described. A conductor 13'7 leads from the conductor 13.6 to a contact 138 controlled by the switch arm. 67.

In the operation of the latter modified form of the invention when electronic valve 56 fires either upon clos- V'ing switch 64 or upon discharge of the condenser 79 connected across the cathode 57 and grid 58, a circuit 'is completed from the negative terminal of the source of electrical energy 32 through conductor 62, switch 64, or switch 5,2, conductor 61,switch 130, conductor 131A, cathode 57, plate 55, conductor 54, motor 120, and conductor 53 returning to the positive terminal of the source of electrical energy 32. The motor 120 rotates in a counterclockwise direction driving the cam 124 so as to causekswitch arm 134 of switch 130 to close contact 133 whereupon the electronic valve is shunted through conductor 136 and the motor is energized through conductor 136. Continued rotati-on causes switch arm 134 to actuate switch arm 132 so as lto open contact 131.

Upon opening the contact 131 the condenser 79 is charged by an electronic flow from the negative terminal of the source of electrical energy 32, through the diode 100 tothe plate 78, and from the plate 80 through the resistor 1 12 to the positive terminal as previously eX- plained with reference to the form of Figure 4.

Energization of the motor 120 causes shaft 123 to continue to rotate until cam 124 once again causes switch arm 134 to actuate arm 132 so as to close contact 131 and cause arm 13410 open contact 133 at which point the

arms

26 and 28 have been adjusted through shaft 127 and gear train 126 to the next succeeding contact. Since `condenser 79 is now charged, a negative bias will be applied to the grid 58 by the condenser 79 preventing the tube 56 from tiring until the condenser 79 has discharged through the resistor 51, as previously explained with reference to the forms of Figures 2 and 4. The operation then repeats until the shaft 123 driven by the motor 120 causes the

switch arms

26 and 28 to contact the contacts 26L and 28L, respectively at which point the cam 128 causes the off normal switch 53 to open.

If the switch arm 67 is set at single cycle operation by adjustment so as to close contact 66, then of course the operation ceases until started again by closing switch 64, but if the switch arm 67 is adjusted for automatic operation as shown in Figure 5, then the operation repeats upon the condenser 79 discharging through the resistor 51L. Y

The

switch arms

67, 68, 69 and 70 may be mechanically connected together so as to operate from a single manually adjustable knob 71 as previously described with reference to Figure 2, or the same may be separately operable so as to vary the effects produced thereby.

In the case of switch arm 67, it will be noted that upon the same closing contact 138 as in the off position, motor 120 will drive without

delay shafts

123 and 127 until cam 128 opens the off normal switch 52. During the latter operation, with switch arm 70 turned to its off position in which it contacts the open contact 86, the boot Valve operating solenoids will not be energized.

Although only three embodiments of the invention have been illustrated and described, various changes in the form and relative arrangements of the parts, which will now appear to those skilled in the art, may be made without departing from the scope of the invention. Reference is, therefore, to be had to the appended claims for a definition of the limits of the invention.

y What is claimed is:

1. A time delay circuit controlling apparatus compris- .ins an electronic valve having an anode and cathode connected in said time delay circuit and a control grid, a capacitor connected between the grid and the cathode, electromagnetic means connected in said time delay circuit and energized upon said valve closing said time delay circuit, a second circuit for charging said capacitor and a third circuit for discharging said capacitor, a switch member in said time del-ay circuit and said third circuit, said Iswitch member opened by said electromagnetic means upon the energization thereof, a diode in the second charging circuit for said capacitor and effective upon the opening of said switch member to complete the charging circuit for said capacitor, and s-aid electromagnetic means arranged to close said switch member after the charging of said capacitor, a resistor effective upon the closing of said switch member to complete the third circuit for discharging said capacitor, said capacitor arranged upon discharging to supply a negative bias to said grid for restraining said electronic valve from closing said time delay circuit, the resistor in said third circuit retarding the discharge of said capacitor whereby said capacitor continues to apply a negative bias to said grid for a predetermined delay period so as to restrain said electronic valve from closing said time delay circuit during said delay period.

2. A time delay circuit controlling apparatus comprising an electronic valve having an anode and cathode connected in said time delay circuit and a control grid, a capacitor connected between the grid and the cathode, charging and discharging circuits for said capacitor, electromagnetic means controlled by said time delay circuit for alternately elfecting said charging and discharging circuits for said capacitor, means in said charging circuit conductive to electronic flow in one direction only, said capacitor supplyin-g a bias to said grid during the discharge thereof for controlling the operation of said valve, variable means for retarding the discharge of said capacitor, and said variable means controlled by said electromagnetic means.

3. A time delay circuit controlling apparatus comprising an electronic valve having an anode and cathode connected in said time delay circuit and a control grid, av

capacitor connected between the grid and the cathode s o as to control said valve, charging and discharging circuits for said capacitor, an electromagnetic winding in said time delay circuit for alternately effecting said charging and discharging circuits, a source of electrical energy for said circuits, and said charging circuit including said electronic valve, said electromagnetic winding, and a resistor connected between the anode of said electronic valve and the negative terminal of the source of electrical energy, said resistor providing means for controlling the inductive voltage rise across the electromagnetic winding upon the opening of the time delay circuit.

4. A time delay circuit controlling apparatus comprising an electronic valve having an anode and cathode connected in said time delay circuit and a control grid, a capacitor, charging and discharging circuits for said capacitor, said capacitor so arranged as to supply a bias to said grid during electronic discharge therefrom, means including another electronic valve in the charging circuit conductive to electronic flow in the ch-arging direction only, said iirst mentioned electronic valve connected at One side of said capacitor and the other electronic valve connected at the opposite side of said capacitor, said electronic valves serially connecting said capacitor in Said charging circuit, and electromagnetic means controlled by said time delay circuit for alternately effecting said charging'and discharging circuits for said capacitor.

5. A time delay circuit controlling apparatus comprising an electronic'valve having an anode and a cathode connected in said time delay circuit and a control grid, a capacitor for controlling the operation of said electronic valve, a source of electrical energy, first means connecting said source in circuit with said capacitor for charging the same, second means including a switch in said time delay circuit and connecting said source in circuit with said capacitor for discharging the same, an electromagnetic winding in the delay circuit, and a fourth circuit, including a resistor shunting said electronic valve so as to permit a controlled inductive voltage rise across the winding upon the opening of said time delay circuit by said switch element so as to effect an increase in the electrical charge on said capacitor.

6. ln a time delay circuit controlling apparatus of the class including an electronic valve having an anode and cathode connected in said time delay circuit and a control grid, a capacitor connected between the grid and the cathode, a circuit for charging said capacitor and a circuit for discharging said capacitor, said capacitor applying a bias to said grid for controlling said electronic valve, and an electromagnetic means connected in the time delay circuit; the improvement comprising a single switch element in the time delay and discharging circuits and operated by said electromagnetic means to open said last mentioned circuits so as to effect a transfer of said capacitor from the discharging to the charging circuit upon cnergization of said electromagnetic means, said discharging circuit including variable resistance means for retarding the discharge of said capacitor, and means operably connecting said electromagnetic means to said variable resistance means.

7. ln a time delay circuit controlling apparatus of the class including an electronic valve having an anode and cathode connected in said time delay circuit and a control grid, a capacitor connected between the grid and the cathode, a circuit for charging said capacitor and a circuit for discharging said capacitor, said capacitor applying a bias to said grid for controlling said electronic valve, and an electromagnetic means connected in the time delay circuit; the improvement comprising a single switch element in the time delay and discharging circuits and operated by said electromagnetic means soy as to effect a transfer of said capacitor from the discharging to the charging circuit upon energization of said electromagnetic means, and said switch element effective upon such energization of the electromagnetic means for directly opening said time delay and discharging circuits.

8. In a time delay circuit controlling apparatus of the class including an electronic valve having an anode and cathode connected in said time delay circuit and a control grid, a capacitor connected between the grid and the cathode, a circuit for charging said capacitor and a circuit for discharging said capacitor, said capacitor applying a bias to said grid for controlling said electronic valve, and electromagnetic means connected in the time delay circuit; the improvement comprising a rst switch element in the time delay and discharging circuits and operated by said electromagnetic means to open said discharging circuit so as to effect a transfer of said capacitor from the discharging to the charging circuit upon energization of said electromagnetic means, and a second switch element effective upon the energization of said electromagnetic means for shunting said cathode and anode and said first switch element so as to maintain energization of said electromagnetic means while said charging circuit is applied to the capacitor, and means driven by said electromagnetic means for returning said second switch element to its original relationship to effect deenergization of said electromagnetic means.

9. In a time delay circuit controlling apparatus of the class including an electronic valve having an anode and cathode connected in said time delay circuit and a control grid, a capacitor connected between the grid and the cathode, a circuit for charging said capacitor and a circuit for discharging said capacitor, said capacitor applying a bias to said grid for controlling said electronic valve, and electromagnetic means connected in the time delay circuit; the improvement comprising a first switch element in the time delay and discharging circuits and operated by said electromagnetic means to opensaid discharge circuit so as to effect a transfer of said capacitor from the discharging to the charging circuit upon energization of said electromagnetic means, a second switch element effective upon the energization of said electromagnetic means for shunting said cathode and anode and first switch element so as to maintain energization of said electromagnetic means while said charging circuit is applied to the capacitor, means driven by said electromagnetic means for returning said first and second switch elements to the original relationship.

l0, In a time delay circuit controlling apparatus ofthe class including an electronic valve having an anode and cathode connected in said timedelay circuit and a control grid, a capacitor connected between the grid and the cathode, a circuit forA charging said capacitor and a circuit for discharging said capacitor, said capacitor applying a bias to said grid for controlling said electronic valve, and electromagnetic means connected in the time delay circuit; the improvement comprising a first switch element inthetime delay and discharging circuits and operated by said electromagnetic means to open the discharging circuit and effect a transfer of said capacitor from the discharging to the charging circuit upon energization of said electromagnetic means, a second switch element effective upon the energization of said electro- ".agnetic means for shunting said cathode and anode and first switch element so as to maintain energization of said electromagnetic means while said charging circuit is applied to the capacitor, means driven by said electromagnetic means for returning said first and second switch elements to the original relationship, and other means driven by said electromagnetic means for opening said time delay circuit after a predetermined cycle of operation.

l1. In a time delay circuit controlling apparatus of the class including an electronic valve having an anode and cathode connected in said time delay circuit and a control grid, a capacitor connected across said cathode and grid for applying a bias to said grid for controlling said electronic valve, a circuit for charging said capacitor, a cir` cuit for discharging said capacitor, and a source ot` electrical energy for said circuits; the improvement comprising a single switch element in the time delay circuit and closing said discharging circuit so as to conduct a negative charge to the cathode for closing the time delay circuit, said charging circuit controlled by said single switch element, and said charging circuit arranged to apply a positive charge to said cathode for di-ionizing said valve upon said switch element being actuated so as to open the time delay circuit.

12. A time delay circuit controlling apparatus comprising an electronic valve having an anode and a cathode connected in said time delay circuit and a control grid, a capacitor for controlling the operation of said electronic valve, a source of electrical energy, first `means including said first mentioned electronic valve connected at one side of said capacitor and another electronic valve connected at the opposite side of said capacitor so as to serially connect said source in circuit with said capacitor for charging the capacitor, second means including a discharge circuit for said capacitor, a switch member alternately operable to open said discharge circuit to make effective the charging circuit of said first means and to close said discharge circuit so as to connect said capacitor in shunt relation to said other electronic valve and said source in circuit with said capacitor to discharge the capacitor.

13. A time delay circuit controlling apparatus comprising an electronic valve having an anode and a cathode -connected in said time delay circuit and a control grid, a

capacitor for controlling the operation of said electronic valve, a source of electrical energy, first means including said first mentioned electronic valve connected at one side of said capacitor and another electronic valve connected at the opposite side of said capacitor so as to serially connect said source in circuit with said capacitor for charging the capacitor, second means including a discharge circuit for said capacitor, a switch member alternately operable to open said discharge circuit to make effective the charging circuit of said first means and to close said discharge circuit so as to connect said capacitor in shunt relation to said other electronic valve and said source in circuit with said capacitor to discharge the capacitor, and an electromagnetic winding in the delay circuit for controlling the operation of said switch member to alternately make effective said charging and discharging circuits.

14. A -device of the character described, comprising, in combination, an electronic valve having an anode, a cathode and a :control grid, said anode and cathode connected in a control circuit, means applying a bias to said grid for controlling said circuit, motor means operated periodically under control of said circuit, a plurality of load devices, switching means actuated by -said motor means to sequentially affect said load devices, a manually operable switch means to simultaneously render said motor actuated switching means ineffective and to shunt said anode and cathode so as to effect independent energizat'ion of said motor means, and means actuated by said motor means for opening said shunt circuit at a predetermined position of the motor means.

15. An electronic timing system for controlling a plurality of external circuits in succession comprising means to accumulate an electrical charge, a charging circuit, a plurality of discharge circuits for discharging said charge accumulating means at different rates, and switching means including a plurality of switching elements and an electro-magnetic winding to operate said switching elements, one of said switching elements in the discharging circuit and operated by said electromagnetic winding to open the discharging circuit and make effective said charging circuit, other of said switching elements operable in step-by-step action by said electromagnetic winding in response to charging and discharging cycles to effect a repetition of said cycles with said different discharge circuits successively and to energize said external circuits successively.

16. An electronic timing system for controllingra plurality ,Of external circuits in succession comprising means toaccumulate an electrical charge, a charging circuit including a rectifier lconductive to electroni-c flow only in a direction for charging said, charge accumulating means, a plurality of discharge circuits for discharging said charge accumulating means at different rates, and switching means including a plurality of switching elements and an electromagnetic winding to operate said switching elements, an energizing circuit for said electromagnetic winding, one of said switching elements in both the energizing and discharging circuits, said one switching 'element operated by said electromagnetic winding to open both the energizing and discharging circuits and make the charging circuit effective through said rectifier upon energization of said electromagnetic winding, other of said switching elements operable in step-by-step action by said electromagnet winding to effect a repetition of said cycles with said different discharge circuits successively and to energize said external cir-cuits successively.

17. A time delay circuit controlling apparatus comprising, an electronic valve for controlling said circuit, a capacitor for controlling the operation of said electronic valve, an electromagnetic means in the time delay circuit controlled by the electronic valve, a switch member in the time delay circuit, said switch member alternately opened and closed by said electromagnetic meansa charging circuit for said capacitor effective upon the opening of the time delay circuit by the switch memberand a discharging circuit for said capacitor effective uponthe closing of the time delay circuit by said switch member, a source of electrical energy for said 14 circuits, said charging circuit including unidirectional conductive means, and said switch element in said time delay and discharging circuits and arranged to connect said capacitor in shunt relation to said unidirectional conductive means for discharging said capacitor.

18. For use with an apparatus for controlling a plurality of cyclically operable inflatable ice removing elements on airfoil surfaces of an saiucraft; the combination comprising electrical control means for timing the period of inflation of each of the ice removing elements, electric light means adapted to be connected to a source of electrical energy, means operated by said control means to periodically connect said electric light to said source means for visually indicating the interval of inllation of each ice removing element, and manually operable switch means for selectively connecting said light means to said operated means to indicate said intervals of inflation and across said source for indicating the electrical condition of the source.

19. For use with an apparatus for controlling a plurality of cyclically operable inflatable ice removing elements on airfoil surfaces of an aircraft; the combination comprising electrical control means for timing the period of inflation of each of the ice removing elements, electric light means adapted to be connected to a source of electrical energy, switch means operated by said control means to selectively connect said light means to said source for visually indicating the interval of inflation of eachice removing element, other electric light means, said switch means operated by said control means to selectively connect said other` light means to said source for visually indicating the period of inoperation of said elements between cycles ot operation, additional electric light means for.. visually indicating the electrical condition of the source, and other switch means cooperating with said first mentioned switch means for connecting all of said indicator lightmeansto said source, said other switch means manually yoperable to place said indicator light means out of operation irrespective of the operative condition ofsaid control means. l

2,0. For use with an apparatus for electrically controlling a plurality of cyclically operable inflatable ice removing elements for airfoil surfaces of an aircraft; the `combination comprising a unitary housing, a plurality of electric lights carried in said housing, first circuit means for electrically connecting said lights to said apparatus for visually indicating the indivudal interval of ination of each ice removing element, another electric light carried in saidhousing, second circuit means for electrically connecting said light to said apparatus t'or visually indicating the period of inoperation of said elem-ents between cycles of operation, an additional electric light, third circuit means for electrically connecting said additional lightto a source of' electrical energy for said apparatus for visually indicating the electrical condition of the control apparatus, and a manually operable control switch means in said ilrst, second and third circuit means for connecting said indicator lights to said source, said control switch means manually operable to open said circuits to place said indicator lights out of operation irrespective of the operative condition of said control apparatus.

2l. An electronic timing system for controlling a plurality of external circuits in succession comprising means to accumulate an electrical charge, a charging circuit, a plurality of discharge circuits for discharging said charge accumulating means at different rates, an electronic Vvalve having an anode, cathode andcontrol grid, a circuit including said anode and cathode, said grid biased by the charge accumulating means to control the current in said anode-cathode circuit, said charging circuit including means conductive to electronic flow in a charging direction only, control means for terminating the electron flow `through said conductive means, switching elements operable in step-bystep action to effect said diiferent discharge circuits successively and to energize said external circuits successively, and current responsive means in the anodecathode circuit, said last-mentioned means directly controlled by the current in the anode-cathode circuit for eiecting the operation of said control means and the aforesaid operation of said switching elements in response to the charging and discharging cycles.

22. The combination dened by claim 2l in which said conductive means includes a second electronic valve having an anode and a cathode connected in the charging circuit.

23. The combination defined by claim 2l in which said current responsive means includes an electromagnetic winding in the anode-cathode circuit for operating the switching elements in the step-by-step action.

24. The combination deiined by claim 2l in which said conductive means includes a second electronic valve having an anode and a cathode connected in the charging circuit, and said current responsive means includes an electromagnetic winding in the anode-cathode circuit of the first-mentioned electronic valve for operating both the control means and the switching elements.

25. In a time delay control the combination with a condenser, an electromagnetic relay having an operating winding and operative to pick up and to drop out at predetermined current values respectively in said winding, a tirst circuit for initially connecting said winding across a source of unidirectional voltage for energizing said winding at the pick up current value of said relay, and a second circuit for serially connecting said condenser and said winding across said source of unidirectional voltage for charging said condenser, of means for alternately effecting operation of said iirst and second circuits, a by-pass circuit connected in parallel with said condenser to provide an additional path for current flowing to said winding, the sum of the currents flowing to said winding through said second circuit during the charging period of said condenser and through said by-pass circuit being greater than the drop out current value of said relay, and a resistor in said by-pass circuit, the resistance of said resistor and of said relay winding being so related to the voltage of said source that the current flowing through said bypass circuit operatively increases the ux produced by said winding while remaining below the drop-out current value of said relay.

26. A time delay control comprising an electronic flow resistance means, a switch operable when closed to connect one end of said resistance means to one side of a source of direct current, a condenser, means connecting said condenser between said one end of said resistance means and the one side of said source of current, a resistor connected between siad one side of said source and the other end of said resistance means, an electromagnetic device having an operating winding connected between said other side of said source and said other end of said resistance means, said winding when energized operating said device to open said switch so as to cause charging of said condenser by said source of current through said resistance means and operating winding, the sum of the current flowing to said winding from said condenser and the current flowing to the winding through said resistor during the charging of said condenser' is snticient to hold said device in operated position whereas the current flowing to said winding through said resistor is insucient of itself to hold said device in operated position.

27. A recycling timing apparatus comprising a condenser, relay means, an electron discharge device having said condenser connected to the input thereof and said relay means in the output thereof, a source of control voltage, circuit means for connecting said condenser to said source to charge said condenser` impedance means in said charging circuit for delaying the charging of said condenser through a tirst time interval, said relay means when energized by said discharge device effecting operation of said circuit means to charge said condenser for said first time interval, said condenser when approaching a maximum charged condition rendering said discharge device and thereby said relay means inoperative, means actuated by said relay means when inoperative to connect said condenser in a discharging circuit, impedance means in said discharge circuit for-delaying the discharge of said condenser-through a second time interval until said discharge device becomes operative to energize said relay means and thereby restart the rst charging interval.

28. A recycling timing apparatus comprising a condenser, relay means, an electron discharge device having an anode, cathode and control electrode, means connecting said condenser to said control electrode and said re- Ylay means in energizing relation to said anode, a source of direct current control vo-ltage, circuit means including an electrical resistance means for connecting said condenser to said source to charge said condenser, said relay means controlling said circuit means, said relay means when energized by said discharge device rendering said circuit means effective to charge said condenser through a tirst time interval until said control electrode renders said discharge device inoperative whereupon said relay means becomes de-energized, means actuated by said relay means when de-energized to connect said condenser in a discharging circuit, means connected in said discharge circuit for delaying the discharge of said condenser through a second time interval and until the voltage thereon renders said discharge device conductive to energize said relay means and thereby restart the charging of said-condenser for the first charging interval, said discharge device continuing conductive throughout the charging interval, and means for connecting said cathode to said source while said condenser is discharging during the second interval so that said control electrode will tend to go to a potential that is positive with respect to said cathode.

29. A recycling timing apparatus comprising a timing condenser, relay means, an electron discharge device having an anode, cathode and control electrode, said timing condenser being connected between said cathode and said control electrode and said relay means being connected in energizing relation to said anode, a source of direct current voltage having positive and negative terminals thereon, circuit means for connecting said condenser Vbetween opposite positive and negativeterminals on said source to charge said condenser so as to apply a negative bias to said control electrode, said circuit means including impedance means delaying the charging of said condenser, said relay means when energized by said discharge device rendering said circuit means etfective to charge said condenser until the negative bias on said control electrode increases to a value suicient to render said discharge device inoperative whereupon said relay means becomes de-energized, means actuated by said relay means when de-energized to connect said condenser in a discharging circuit and render said charging circuit means ineffective, means for effectively connecting said cathode to a negative terminal on said source while said condenser is discharging through said discharge circuit so that said control electrode will tend to go to a potential that is positive with respect to said cathode, means connected in said discharge circuit for delaying the discharge of said condenser until the negative bias on said control electrode decreases to a value sufficient to render said discharge device conductive for energizing said relay means so as to render said charging circuit means effective to charge said condenser, and said discharge device continuing conductive during the charging interval of the condenser.

30. The combination dened by claim 27 including a by-pass circuit connected in parallel with said condenser to provide an additional path for supplying current to said relay means, said relay means being energized and de-energized at predetermined current values, the sum of the currents owing to said relay means through said discharge device and said by-pass circuit during the charging of said condenser being greater than said energizing current value of said relay means so as to maintain the relay means energized when the current ilowing to said relay means solely through said discharge device falls below said energizing current value, a resistor in said bypass circuit, the resistance of said resistor being so related to the voltage of said source that the current flowing through said by-pass circuit increases the current to said relay means while remaining below the energizing -current value of said relay means.

31. The combination of means for applying a resultant potential having positive and negative components, a relay, `an energizing circuit for said relay, a resistor, a capacitor, circuit control means operable to apply said negative component to said capacitor in response to energization of said relay and to apply said positive component through said resistor to said capacitor in response to deenergization of said relay, and means operable to deenergize said relay only While the charge of said capacitor is Within a range extending from its most negative value to approximately zero.

32. The combination of means for applying a resultant potential having positive and negative components, a relay, an energizing circuit for said relay comprising a gaseous conduction device provided with a control grid and an anode and cathode and connected to have said positive component applied through said relay between its anode and cathode, a capacitorv connected between said cathode `and grid, means for interrupting the current of said gaseous conduction device, a resistor, and circuit control means responsive to operation of said relay for applying said negative component to said capacitor in response to current conduction of said gaseous conduction device and for applying said positive component through said resistor to said capacitor in response to interruption of said current conduction.

33. An electronic sequence timer including at least one electric discharge device for controlling the sequencing of said timer, said device having associated therewith a timing network which when set times the operation of said device; characterized by a single control discharge device having conductive and non-conductive states connected in circuit with said network; means responsive to said control device when it passes from one state to the other to set said network and means responsive to said device when it passes from said other state to said one state to initiate the timing operation of said network.

34. In combination, a iirst electric discharge device having an anode, a cathode, and a control electrode; means including a capacitor cooperative with said control electrode and including a timing network which when set maintains said device in non-conductive condition during an interval in which the capacitor discharges and which timing network after a predetermined time interval renders said device conductive during an interval in which the capacitor charges; a second electric discharge device;

means for maintaining said second device non-conductive during the interval in which the capacitor discharges; means for rendering said second device conductive; means cooperative with said timing means and said second device for setting said timing means when said second device is rendered conductive and means for thereafter rendering said second device non-conductive to initiate the timing of said timing means.

35. An electronic timing device comprising means for supplying an energizing current and biasing voltage, an electron valve -having control grid, cathode and anode electrodes, a relay connected in series between said anode electrode and said current supply means, said relay operating responsive to flow of current in said valve, a charging circuit comprising a condenser and resistor in series, said condenser being connected between said control grid electrode and said cathode electrode, and means for connecting both said condenser and said control grid electrode to said biasing voltage supply means upon operation of said relay.

36. A timing device comprising a source of electrical energy; a tube of the electronic valve type with anode, cathode and control electrode; means to connect a controlled electromagnetic winding in series with said anode and cathode; a resistor and means to connect said resistor yacross said cathode and anode, said resistor providing means for controlling the inductive voltage rise across the electromagnetic winding when said tube is non-conductive with the electromagnetic Winding and resistor in series; and means to connect said anode and cathode to said source of electrical energy and to bring said control electrode to ring potential.

References Cited in the le of this patent UNITED STATES PATENTS 1,412,568 Mortensen Apr. 11, 1922 1,434,072 Taussig Oct. 31, 1922 1,943,185 Neville Jan. 9, 1934 1,980,146 Vingerhoets Nov. 6, 1934 2,032,746 Grant Mar. 3, 1936 2,061,011 Vingerhoets Nov. 17, 1936 2,144,033 Root Ian. 17, 1939 2,165,048 Gulliksen July 4, 1939 2,182,530 Baer Dec. 5, 1939 2,279,007 Mortley Apr. 7, 1942 2,288,458 JelTers June 30, 1942 2,299,501 Schneider Oct. 20, 1942 2,337,905 Livingston Dec. 28, 1943 2,339,750 Bartholoy Jan. 25, 1944 2,343,918 McCoy Mar. 14, 1944 2,373,255 McGoldrick Apr. 10, 1945 2,415,963 Olving Feb. 18, 1947 2,444,208 Taylor et al. June 29, 1948 2,444,209 Pond et al. June 29, 1948 2,467,944 Munson Apr. 19, 1949 2,471,834 McDowell May 31, 1949 2,506,394 Strange May 2, 1950 2,549,149 White Apr. 17, 1951