US2542264A - Electrical timing apparatus - Google Patents

Description

Feb. 20, w s n- ELECTRICAL TIMING APPARATUS Filed Feb. 7, 1949 INVENTOR. JAMES W. SMITH ATTORNEY Patented Feb. 20, 1951 ELECTRICAL TIMING APPARATUS James W. Smith, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application February 7, 1949, Serial No. 74,938

9 Claims.

The present invention is concerned with an electrical timing apparatus. More particularly, the present invention is concerned with a timing apparatus of the type which is cyclic in operation and is operative to control a relay so that during a first interval the relay will be oberative in a first position and during a second interval the relay will be operative in a second position.

In certain automatic controls, it is desired to have a pair of electrical circuits operated through recycling timing periods of adjustable length. The present invention accomplishes this recycling t min by using an electronic circuit whose current flow is regulated by the charging and discharging of a timing condenser and by a controlled relay which alternately connects the timing condenser in a discharging and charging circuit. In order that the apparatus operate consistently over a range of adjustment, it is necessary that the linear portion of the charging and discharging curve of the timing condenser be utilized in controlling the conductivity of the controlled electron discharge device. This is accomplished in the present invention by operating the control electrode of the discharge device at a voltage that is positive with respect to its associated cathode.

It is therefore an object of the present invention to provide a recycling timing apparatus which is controlled by a charging and discharging condenser while operating on the linear portion of the charging curve of that condenser.

A further object of the present invention is to provide a recycling timing apparatus of the type using an electron discharge device whose current flow is controlled by a charging and discharging condenser operating on the linear portion of the charging curve.

Still another object of the present invention is to provide a recycling timing apparatus having an electron dischargev device with a cathode and a control electrode which are connected to a direct current biasing source tending to cause the control electrode to go positive as an associated timing condenser is alternately charged and discharged by a controlled relay.

These and other objects of the present invention will be understood upon a consideration of the accompanying specification, claims and drawing of which:

The single figure shows diagrammatically the timing apparatus as it may be employed for cyclically operating a controlled relay.

Referring to the single figure, the numeral l represents the main control relay of the apparatus and this control relay may be used in any desired manner to operate to close and open an electrical circuit in a recycling manner as determined by the rest or the control apparatus.

This relay Ill comprises a relay winding II, and switch blades l2 and I3 normally biased into engagement, by means not shown, with contacts l4 and 16 respectively. Switch blade 13 is normally biased out of engagement with switch contact l5 when the relay is deenergized. A pilot relay is indicated by the numeral 20 and this relay comprises the relay winding 2|, a pair of switch blades 22 and 23 and a pair of switch contacts 24 and 25. The switch blades 22 and 23 are normally biased, by means not shown, out of engagement with their associated contacts 24 and 25 respectively. A suitable by-pass or filter condenser is connected across the relay winding 2| and functions in the normal manner to by-pass the alternating current flowing in the relay circuit.

Controlling the current flow through the relay winding 20 is an electron discharge device indicated by the numeral 30. This discharge device may be one section of a twin triode vacuum tube. The device comprises an anode 3i, a control electrode 32 and a cathode 33.

A further electron discharge device 35 is included in the electrical circuit for providing a direct current operating voltage. This device comprises an anode 36, a control electrode 37 and a cathode 38. This device may be the other section of the above-mentioned twin triode tube with its control electrode connected to the cathode. Located in the output circuit of this device is a filter network comprising a resistor 40 and a condenser 4|. A pair of resistors 42 and 43 form a voltage dividing network across the output of the filter condenser 4|.

A timing condenser 45 is utilized to control the potential difference between a cathode 33 and control electrode 32 of the discharge device 30 and this timing condenser is alternately connected in a discharging circuit and a charg ing circuit by the control relays. Located in the discharging circuit is an adjustable rheostat 41 while a further adjustable rheostat 48 is located in the charging circuit of condenser 45.

Supplying power to the apparatus is a suitable power transformer 50 which has a primary winding 5| connected to a suitable source of power and a pair of secondary windings 52 and 53. A main power switch 55 is provided in the main power lines for initiating operation of the apparatus.

The size of the components of the apparatus may obviously be varied without departing from the scope of the invention. The values of one particular set of components in the device where it operated satisfactorily are as follows: Condenser 4| was 12 mfds., condenser 26 was 12 mfds. and condenser 45 was 2 mids. The potentiometers 46 and 41 were 2 and 5 megohms respectively. The resistors 40, 42 and 43 were 3 15,000, 27,000, and 100,000 ohms respectively. The vacuum tube was a twin triode tube known commercially as a IZSN'IGT.

Operation In considering the operation or the apparatus, it will be assumed that the apparatus as shown upon the drawing is in the completely deenergized position with the power line switch 55 in the open position so that no alternating current power is supplied to the control apparatus. When such is the case. the control relays 20 and 10 will be in the deenergized position and the associated discharge devices Ill and 35 will be nonconducting. The timing condenser 45 will also be completely discharged. Upon the closing of the main power line switch 55, alternating current will be supplied to the primary winding Ii 01' the power transformer. This will mean that the secondary winding 53 will be applying an alternating current voltage to the rectifier circuit which includes the discharge device 35 and filter network comprising the resistor 40 and condenser 4|.

As soon as current flows in the rectifier circuit there will be a voltage drop across the filter condenser such that the upper terminal will be positive and its lower terminal will be negative. The circuit for this current flow may be traced from the upper terminal of secondary 53 through conductor 50, resistor 42, resistor 43, conductor 6|, resistor 40, anode 35, control electrode 31 and cathode 33, and conductor 52 back to the lower terminal of secondary 53. With the energization or secondary winding 52, the electron discharge device 35 will also become conductive and the conductive circuit for the discharge device 30 may be traced from the upper terminal 01' secondary 52 through conductor 53, relay winding 21, anode 3|, cathode 33, conductor 54 and conductor 55 back to the lower terminal of secondary 52.

The reason the discharge device 35 will be conductive is that the timing condenser 45 will not have accumulated a charge and the control electrode 32 will be effectively connected to a direct current voltage which is positive with respect to the cathode 33. This will be seen when it is noted that the cathode 33 is connected by way 01' conductors 54 and 55 to a tap 51 where the resistors 42 and 43 are joined. The control electrode 32 is eflectively connected to the positive terminal 33 on the network connected across the filter condenser 41. This connection may be traced from the control electrode 32 through conductors 53, 10, and 1|, switch contact 14, switch blade i 2, conductor 12, rheostat 41 and conductor 13 to terminal 53.

When the discharge device 30 becomes conductive, the pilot relay 20 will become energized and switch blades 22 and23 will move into engagement with their respective contacts 24 and 25. When contact 23 engages contact 25, an energizing circuit is completed to the control relay l and this circuit may be traced from the input power line 14, through conductor 15, switch contact 25, switch blade 23, conductor 16, and relay winding II back to the other input power line 11. When the relay l0 becomes energized the switch blade 12 will be moved out of engagement with its associate contacts l4 to open the control electrode connection of discharge device 30 to the tap 53. When the relay 20 becomes energized, the switch contact 22 engages contact 24 and connects the timing condenser 45 in a charging circuit to terminals 33 and 15 of the output voltage divider connected across the filter condenser 4|. This charging circuit may be traced from the terminal 63, which terminal is positive, through conductor 10, condenser 45. conductors 50 and 10, switch contact 24, switch blade 22, conductor 3|, rheostat 45, and conductor 32 to tap 18 o! the voltage divider. With these last named connections completed, the timing condenser 45 will begin to assume a negative potential on its upper terminal and a positive potential on its lower terminal such that the control electrode 32 will tend to go negative with respect to the cathode 33. Inasmuch as there is a resistor in the form of rheostat 45 in the last traced circuit the charging 0! this timing condenser will be dependent upon the size of the condenser and the amount of resistance in the charging circuit. The latter may be adjusted by means of rheostat 45.

After a predetermined time the control electrode 32 will become biased sufliciently negative with respect to cathode 33, because of the charge on the condenser 45, that the current flow through discharge device 30 will no longer be capable of maintaining the control relay 20 energized. When the relay becomes deenergized the switch blade 22 will move out of engagcment with switch contact 24 to open the charging circuit for the timing condenser 45 and the switch blade 23 will move out of engagement with its associated contact 25 and open the energizing circuit for relay It. When this relay becomes deenergized the first timing interval will have been completed. When the relay 10 becomes deenergized the switch blade l2 will move into engagement with switch contact 14 and the closure of the electrical circuit resulting in this engagement will connect the timing condenser 45 in a discharge circuit that may be traced from the lower terminal of condenser 45 through conductor 19, conductor 13, rheostat 41, con-- ductor 12, switch blade 12, switch contact l4, and conductors 11, 10 and 30 to the upper terminal oi condenser 45.

As the condenser 45 discharges the control electrode 32 will have a voltage thereon which is progressively becoming lass negative with respect to cathode 33. Since there is a resistor in the form 01' rheostat 41 in the discharging circuit of this condenser the discharge will take a predetermined amount or time which again will be dependent upon the size of the resistance and the size of the timing condenser 45, and which time can be adjusted by means of rheostat 41. As soon as the control electrode 32 has reached a predetermined potential with respect to the cathode 33, which potential may be equal to or slightly less than that of the cathode, the current flow in the discharge device 30 will be such as to energize the control relay 20 and when this relay becomes energized the second timing interval will have been completed and the first timing interval will have been started over again.

It will be noted that the control electrode 32 is connected to a positive point in the direct current voltage source with respect to the cathode 33. This connection has the effect of overcoming the normal tendency of the control electrode to assume a potential that is slightly negative with respect to cathode 33, and causes the discharge voltage of condenser 45 to be effective over the linear portion or the discharging curve. For example, assume that the current flow through device 30 necessary to energize relay 20 is had when the control electrode 32 is at the same potential as cathode 33. If the circuit were arranged so that when condenser 45 was completely discharged, as where both cathode 33 and control electrode 32 were connected to terminal 68, the control electrode 32 would assume a potential which is slightly negative with respect to cathode 33 and the relay 20 would not become energized upon the timing condenser becoming fully discharged. The negative voltage on the control electrode is the result of several factors inherent in the construction of electron discharge devices. Some of these factors include the thermo electric effect of the dissimilar metals used 'in the making of the control electrode and cathode, and the initial velocities at which the electrons are forced from the cathode surface which in turn will be dependent on the work function of the cathode. Another factor is the leakage current and the interelectrode capacities of the tube. The combination of effects results in an accumulation of electrons on the control electrode and it will tend to hold the current flow in the tube at a much lower value than would be true if the effects were not present.

To overcome this tendency of the control electrode to be negative, it is effectively connected to tap 68 and cathode 33 is connected to tap 61 so that the control electrode tends to go to .a potential that is positive with respect to cathode 33. By selecting a proper voltage drop across the resistor 42, it is possible for the linear discharge portion of the discharge curve of condenser 45 to be efiective to control conduction of the device 30 as well as the operation of the relay 20. This further means that linear adjustment of the rheostat I! will result in substantially a linear t me adjustment on the operation of the apparatus on the discharging of the condenser 45.

It can thus be seen that the charging and discharging of the condenser 45 results in a recycling operation of the pilot relay 20 and the main control relay III with the timing period controlled by the time constants of the charging and discharge circuits of the condenser 45. If the relay I is recycled, the blade I3 will move alternately between the ccntacts l5 and I6 to open and close a pair of electrical circuits which may be used in any desired manner. While a specific embodiment of the invention has been shown, it is to be understood that it is for illustrative purposes only and the invention is to be limited solely by the scope of the appended claims.

I claim as my invention:

1. A recycling timing apparatus, comprising in combination, an electron discharge device having an anode, cathode and control electrode, relay means in circuit with said discharge device, a source of direct current control voltage, a timing condenser having one end connected to said control electrode and the other end connected to a positive terminal on said source, means including said relay m.ans for connecting said one end to a negative terminal on said source for a first time interval until said condenser is charged independently of any current flow in said discharge device to a potential which will render said discharge device nonconducting and said relay means inoperative, means actuated upon said relay means becoming inoperative to connect said condenser in a discharge circuit, and means connecting said cathode to an intermediate point on said direct current source so that as said condenser discharges said control electrode tends to go to a potential that is positive with. respect to said cathode, said discharge device when said control electrode reaches a predetermined potential with respect to said cathode rendering said relay means operative to terminate a second time interval and restart the first time interval by reconnecting said condenser to said source.

2. A recycling timing apparatus, comprising in combination, an electron discharge device having an anode, cathode and control electrode, relay means in circuit with said discharge device, a source of direct current control voltage, a timing condenser having one end connected to said control electrode and the other end connected to a positive t rminal on said source, means including said relay means for connecting said one end to a negative terminal on said source for a first time interval until said condenser is charged independently of any curr-nt flowing in said discharge device to a potential which will render said discharge device nonconducting and said relay means inoperative, a first adjustable resistor in said last named connection for det rmining the time duration of said first interval,

means actuated upon said relay means becoming inoperative to connect said condenser in a discharge circuit, means connecting said cathode to an intermediate point on said source so that as said cond.nser discharges said control electrode tends to go to a potential that is positive with respect to said cathode, and a second adjustable resistor connected in said discharge circuit to determine the rate of discharge, said discharge device when said control electrode reaches a predet rmined potential with respect to said cathode rendering said relay means operative to terminate a second time interval and restart the first time interval by connecting said condenser to said source.

3. A recycling timing apparatus, comprising in combination, a condenser, relay means, an electron discharge device having said condenser connect d to the input thereof and said relay means in the output thereof, a source of control voltage, means including said relay means when energized by said discharge device connecting said condenser directly to said source through a timing resistor to charge said condenser through a first time interval to rend r said discharge de vice and said relay means inoperative, means actuated by said relay means when inoperative to connect said condenser in a discharging circuit, impedance means in said dischargecircuit for delaying the discharge of said condenser through a s.cond time interval until said discharge device becomes operative and starts the first interval, and means connecting said discharge device to said source so that said device is rendered operative and inoperative by charging and discharging potentials on said condenser which are on the linear portion of the charge and discharge curves of said condenser.

4. A recycling timing apparatus, comprising in terval until said control electrode renders said device inoperative and said relay means becomes deenergized, means actuated by said relay means when deenergized to connect said condenser in a discharging circuit, means connected in said discharge circuit for dJaying the discharge of said condenser until the voltage thereon renders said discharge device conductive to restart the first interval. and means connecting said cathode to said source so that when said condenser is discharging said control electrode will tend to go to a potential that is positive with respect to said cathode.

5. A recycling timing apparatus, comprising in V combination, a timing condenser, relay means,

an electron discharge device having an anode, cathode and control electrode, means connecting said condenser to said control electrode and said relay means in energizing relation to said anode, a source of direct current voltage having end terminals and a tap thereon, means including said relay means when energized by said discharge device connecting said condenser to an end terminal of said source to charge said condenser through a timing resistor until said control electrode renders said device inoperative and said relay means becomes deenergized to terminate a first time interval, means actuated by said relay means when deenergized toconnectsaidcondenser in a discharging circuit, means connected in said discharge circuit for delaying the discharge 01' said condenser until the voltage thereon renders said device conductive to terminate a second time interval and restart the first interval, and means connecting said cathode to said tap on said source so that when said condenser is discharging said control electrode will tend to go to a potential that is positive with respect to said cathode.

6. A recycling timing apparatus, comprising in combination, an electron discharge device having an anode, cathode and control electrode, relay means in circuit with said discharge device, a source 01' direct current control voltage comprising a further electron discharge device and a filter network connected in series with an alternating source of power, a timing condenser having one end connected to said control electrode and the other end connected to a positive terminal on said source, means including said relay means for connecting said one end directly to a negative terminal on said source through a timing resistor for a first time interval until said condenser is charged to a potential which will render' said discharge device nonconducting and said relay means inoperative, means actuated upon said relay means becoming inoperative to connect said condenser in a discharge circuit, and means connecting said cathode to an intermediate point on said direct current source so that as said condenser discharges, said control electrode tends to go to a potential that is positive with respect to said cathode, said discharge device when said control electrode reaches a predetermined potential with respect to said cathode rendering said relay means operative to terminate a second time interval and restart the first time interval.

7. A recycling timing apparatus, comprising in combination, an alternating source of power, an

electron discharge device having an anode, cathode and control electrode, relay means, means connecting said cathode to one terminal of said alternating source and said anode to another terminal oi said source through said relay means, a source oi direct current control voltage having a positive terminal, a negative terminal and a tap at an intermediate point, means connecting said cathode to said tap, a timing condenser having one end connected to said positive terminal and the other end connected to said control electrode, and means including switch contacts actuated by said relay means for alternatingly connecting said other end of said condenser to said positive and negative terminals of said direct current source so that said condenser will be charged and discharged to control the iiow of current in said discharge device in a recycling manner.

8. A recycling timing apparatus, comprising in combination, an alternating source of power, an electron discharge device having an anode, cathode and control electrode, relay means, means connecting said cathode to one terminal of said alternating source and said anode to another terminal of said source through said relay means, a source of direct current control voltage comprising a further electron discharge device connected to said alternating source of power and having in circuit therewith a filter network and a tapped output resistor which has a positive voltage on one end terminal and a negative voltage on the other end terminal, means connecting said cathode to a tap on said resistor, a timing condenser having one end connected to said positive terminal and the other end connected to said control electrode, and means including switch contacts actuated by said relay means for alternately con necting said other end of said condenser to said positive and negative terminals of said direct current source so that said condenser will be charged and discharged to control the operation 01' said relay means in a recycling manner.

9. A recycling timing apparatus, comprising in combination, an alternating source 01' power, an electron discharge device having an anode, cathode, and control electrode, first relay means, means connecting said cathode to one terminal 01' said alternating source and said anode to another terminal of said source through said relay means, a source of direct current control voltage having a positive terminal, a negative terminal and a tap at an intermediate point, means connecting said cathode to said tap, a timing condenser having one end connected to said positive terminal and the other end connected to said control electrode, a second relay means adapted to be energized by means including said first relay means, and means includingswitch contacts 01' said first and second relays i'or alternately connecting said other end of said condenser to said positive and negative terminals of said direct current source so that said condenser will be charged and discharged to control the operation of said first and second relay means in a recycling manner.

JAMES W. SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number

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