US2602888A - Electronic timer - Google Patents

Description

July 8, 1952 AUDIER 2,602,888

ELECTRONIC TIMER Filed Sept. 4, 1945 VOLTAGE TIME Patented July 8, 1952 UNITED STATES PATENT OFFICE ELECTRONIC TIIWERY Mark Audieig Milwaukee, Wis.; assignor t'o' Cutler Hammer, Inc.,-Milwaukee,1Wis.'-, its-corporation of Delaware Application'september 4, 1945 Serial jIN'oI614l',' l'," 4jiv 3. Claims; (Cl. 250%27') This invention. relates to improvements in electric timing systems of the condenser type.

Condensers have heretofore been employed in timing. systems but not to full advantage, the prior uses having been such as to necessitate a relatively'large condenser where a substantial time. element is needed. The time element ob tained has been an exponential function of the change. involtageof the condenser and as a con-' sequence: the condenser capacity has not been employed efficiently.

The present invention has among its objects to provide a system wherein the condenser is so utilized that the potential change of which timing is a function is linear and whereby the condenser capacity is more efficiently employed- Another object is to provide a timing system which is of increased accuracy and which affords with use of a condenser of given capacity a longer timing period.

Another object is to provide a timing system of the condenser type wherein such more advantageous use of the condenser is enabled by a readily accomplished coordination of the condenser and an electron tube.

Another object is toprovidea timingsystem of the characteraforeindicated which aiiords ad-v justment over a wide range of the time element provided thereby.

Another object is to provide a timing system having numerous advantageous applications including timing of circuit commutations for motors andother translating devices.

Other objects and advantages will hereinafter appear.

The invention comprehends a system in which the potential of a circuit element is :varied substantially linearly as a function of lapse of time following initiation of a given condition of the circuit whereby an effect is produced upon the circuit as such potential attains a given value. A more specific example is raising linearly with the lapse of time'the potential of the cathode of an electron tube supplied with energy byvaryingthe potential of the control electrode of the tube with respect to the cathodein accordance with the change of the cathode potential.

The-accompanying drawing is illustrativeof anembodiment of the invention, it beingunderstood that the embodiment illustratedis susceptible of various modifications without departing; from the scope-of the appended claims. a

Fig. 1 is a connection diagram showing1the timing system applied to control -.of an electric;

motor. and Y 2 Fi'g-e2 isa curve of-the potential of certain elements of the system shown in Fig. 1.

The system as shown-in Fig. 1 comprises a 'positive bus bar IIl'and-a negative busbar II of a direct current supply which furnishes electrical energyto the armature I2 ofa directcu'rrent' motorwhoseshunt field winding I2 m'ay be energized in any suitable "manner;

One terminal ofthe armature'IZ is connected to the bus bar-l0 througha normally open'main contact I3 of an electromagnetic switch I 3 which is provided with an energizing winding I 3!? and normallyopen auxiliary contacts I3"and"f I3 The 7 other "terminal of the armature I2 is con'-' nected through a starting resistor I4 to'the'b us bar I I. The starting resistor I 4 may be short cir cultedby the'normally open contact" I5 of an electromagnetic switch I 5 which is provided with an energizing winding I5 Oneterminal-of the winding I 5 is connected to the anode I 6' of an electron tube ISWhlCh also has a cathode I S and acontrol electrode-I62 A highva'cuum electron tube ITis provided-with a cathode Il an, anode IT, and a'control electrode I1; The cathode'll is connected through a resistor "I 8 to'the bus bar I I ,The'anode I'Ib is'connected to one terminal of the-winding-IE andals'oto one=terminal of contact I3 The second terminal of contact I3 is connected 'to bus bar III. A resistor Isis-interposed between the cathode I! and the control electrode -I 7, and the control electrodel 1 is also connected througha condenser 20 to the bus "bar I I. The cathode IB is connected to the movable" contact 2 I or a voltage divider 2|, which inturn 1s connected across the bus bars I0 and I I. The

control electrode I6 is connected tothebus bar" When the bus bars "are energized and the field winding- I 2 of the 'motor -is excited, the push'but ton'switch-id maybe'momentarily closed thereby completing a circuit from bus bar I0 through the contacts of the push button switches-25 and 24 to and through thetenergizing winding I3 to bus barf'I I. Thereupon the switch I3 is energized to close theicontacts I3 so that now the push but- 2 ton switch may beare1eased; -th'e winding 3 re'-' maining energized. In responding, the switch [3 also closes the contacts 13* and [3a Closure of contact 3 connects the motor armature ill to the bus bars i9 and ii in series with the resistor l4 and the motor begins to accelerate. Closure of contacts 13 connects the tube ll across the bus bars [6 and i i in series with the resistor 18.

Before closure of the contact l3 the potential of the cathode ll' and also of the control electrode il was that of the bus bar H, and as no current flowed through tube H the voltage drop contact 2 l in the resistors i8 and i5, and the potential across the condenser 29 were zero. At the instant When the contact 13 closes the tube ll becomes conducting, which produces a voltage drop across the resistors 18 and i9, resistor l9 producing a biasing potential of the control electrode I! with respect to the cathode H This biasing potential controls the impedance of the tube i1 and therefore the voltage drop through the resistor H3. The voltage drop across resistor it determines the final chargin potential applied to the condenser 29, the rate of charge of said condenser and the rate of rise of its potential being limited by the resistor 59. As the charge of the condenser 52G :reases, the potential of the control electrode ll becomes increasingly positive and this in turn increases the current flowing through the resistor i8 and the voltage drop therethrough. The voltage drop across the resistor it continues to exceed the voltage drop across condenser 2i] by an amount which is equal to that control electrode potential necessary to produce the voltage drop in the resistor it. This action in turn produces a substantially linear rise of the potential or the condenser 28 and of the voltage drop across the resistor l8 and therefore of the potential of the cathode ll.

The potential of the cathode H is impressed through the resistor 23 upon the control electrode Et of the tube It. The potential of the control electrode iG with respect to the cathode 5 is controlled by adjustment of the contact 2 i The adjustment is such that initially the potential of the control electrode it prevents conduction of current by the tube i6. As the potential of the cathode ll rises, the potential of the control electrode 55 rises correspondingly so that ultimately the tube 56 becomes conducting, thereby energizing the relay winding i5 sui'ficiently t0 aiiord closure of contacts to short circuit the resistor Hi, whereupon the motor will further accelerate to full speed.

The accompanying diagram (Fig. 2) illustrates the potential variations just discussed. Before closure of the contacts 53 the potential of the cathode Il is that of the negative bus bar ll. When the contacts it close, the tube ['7 is conducting, as the potential of control electrode ll is the same as that of the cathode i'i under which conditions the tube is slightly conducting. The tube current passing through the resistor 18 renders the cathode it positive, its potential suddenly rising to the value A. The potential drop through resistor i5 is impressed on the parallel circuit comprising the condenser 25 and resistor 55, the latter controlling the rate of charge of the condenser 28. As a result the voltage of condenser 2d and with it the potential of the control electrode i'i rises linearly in accordance with the curve B. This in turn increases the conductivity of tube 17, thereby raising the potential of the cathode li linearly as indicated by curve A. The potential of the cathode i'i is impressed through the resistor 23 and the condenser 22 and the latter is charged exponentially at a very rapid rate. Thereafter its potential rises in accordance with the rise of the rising potential impressed upon it by the resistor It as shown by curve C. As the potential of the condenser 22 is impressed on the control electrode It, the tube It ultimately becomes conducting to energize the switch I 5 which short circuits resistor [4. The potential of the cathode I5 with respect to the control electrode l't may be varied by adjustment of the Thus the absolute potential of the control electrode i6 of the tube !6 affords energization of the switch i5 and therefore the time interval between closure of contacts 13 and response of switch it may be varied.

It will be apparent that the linearly varying voltage of the condenser 20, or the linearly varying potential of the cathode l'l may be impressed upon circuits other than that shown to produce commutation of such circuits after the lapse of a given time from the moment of initiation of conduction of the tube il. Furthermore, the tube it: may be of other than the-gaseous type.

It will also be obvious that the system may be used to control energization of the switch [5 or some other translating device from a circuit in which the voltage is normally insuificient to actuate the device, but increases to a higher value, whereupon the response of the device to said higher value is delayed in the manner aforedescribed.

I claim:

1. A timing circuit comp-rising, in combination with a constant potential unidirectional source oi current, a high vacuum tube having a cathode,

an anode and a control electrode, a first resistor connecting said cathode directly to said source, a second resistor connected to said cathode, a condenser connected in series with said second resistor and together therewith in parallel with said first resistor, a connection between the control electrode of said tube and the common terminal of said second resistor and said condenser, a switch to control the connection of said anode to said source, a second electron tube having a cathode, an anode and a control electrode, means to impress the voltage of said source upon the main conducting path of said second tube, a third resistor connected to the cathode of the first mentioned tube, a second condenser connected in series with said third resistor and together therewith in parallel with said first resistor, and a connection between the control electrode of said second tube and the common terminal of said third resistor and said second condenser.

2. A timing circuit comprising, in combination with a constant potential unidirectional source of current, a high vacuum tube having a cathode, an anode and a control electrode, a first resistor connecting said cathode directly to said source a second resistor connected to said cathode, a condenser connected in series with said second resistor and together therewith in parallel with said first resistor, a connection between the control electrode of said tube and the common terminal of said second resistor and said condenser, a switch to control the connection of said anode to said source, a second electron tube having a cathode, an anode and a control electrode, means nected in series with said third resistor and together in parallel with said first resistor, and a connection between the control electrode of said second tube and the common terminal of said third resistor and said second condenser.

3. A timing circuit comprising, in combination with a constant potential unidirectional source of current, a high vacuum tube having a cathode, an anode and a control electrode, a first resistor connecting said cathode directly to said source, a second resistor connected to said cathode, a condenser connected in series with said second resistor and together therewith in parallel with said first resistor, a connection between the control electrode of said tube and the common terminal of said second resistor and said condenser, a switch to control the connection of said anode to said source, a second electron tube having a cathode, an anode and a control electrode, means including a translating device to connect the main conducting path of said second tube to said source and further including a voltage divider for varying the potential impressed on the cathode REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,052,183 Lewis et al Aug. 25, 1936 2,129,036 Schlesinger Sept. 6, 1938 2,203,468 Martin June 4, 1940 2,279,007 Mortley Apr. 7, 1942 2,372,005 Kinsman Mar. 20, 1945 2,406,429 Mahoney Aug. 27, 1946 2,495,919 Brunn Jan. 31, 1959

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