US2009601A - Electrical timing mechanism and system - Google Patents

Description

July 30, 1935- J. w. ANDERSON ELECTRICAL TIMING MECHANISM AND SYSTEM Filed Jan. 26, 1931 IN VENTOR.

John W Anderson Patented July 30, 1935 ELECTRICAL TILIING MECHANISM AND SYSTEM John W. Anderson, Gary, Ind.

Application January 26,

22 Claims.

This invention relates to electric control systems and apparatus, and particularly to electrical systems and apparatus for measuring and/ or indicating time.

It is one of the objects of my invention to provide an improved electrical system and apparatus and method for indicating the passage of time.

Another object is to provide an improved system and apparatus for effecting and/or controlling the time-periodic operation of apparatus.

Another object is to provide such a system and apparatus having improved means for adjustably varying the time periods thereof.

Another object is to provide an improved electrical system and apparatus operative to energize an electric circuit periodically, for efi'ecting and/or controlling the time-periodic operation of apparatus, and provided with improved means for adjustably varying the rate or periodicity of the energization of the circuit.

Another object is to provide in a thermally actuated electric system and apparatus in which a thermo-responsive means periodically effects the energization of an electric circuit, an improved means for automatically compensating the thermo-responsive means for changes of ambient or local temperature.

Other objects will be apparent to those skilled in the art to which my invention appertains.

My invention is fully disclosed in the following description taken in connection with the acccmpanying drawing, in which:

Fig. 1 is a diagrammatic representation of an electrical apparatus and system of connections therefor embodying my invention;

Fig. 2 is a view similar to Fig. 1 showing modifications.

Referring to the drawing, I have shown at I a bimetallic thermostatic element of rectilinear form, rigidly secured at one end to a stationary base 2, and at its free end carrying a contact 3 engageable with a contact 4 on the free end of a second bimetallic thermostatic element 5, preferably identical with the element I and mounted, at the end thereof opposite the contact 4, upon a base 6, which in turn is secured as by rivets I'! to a preferably resilient arm 8 rigidly connected at one end to a base 9 and adjacent its free end It being engaged by the end of an adjusting screw II threaded in a stationary base I2.

The base 9 is preferably disposed adjacent the contact 4 and the end I of the arm 8 disposed remote from the contact 4 whereby a longitudinal movement of the screw I I will efiect a much smaller movement of the contact 4. Thus a very 1931, Serial No. 511,311

sensitive micrometer adjustment of the position of the contact 4 toward and from the contact 3 may be effected by turning the screw II, the resilience of the arm 8 maintaining its end I0 always in contact with the end of the screw II.

The material of the elements I and 5 is so disposed that when responding to changes of temperature, they both tend to bend, in portions thereof remote from their bases 2 and 6 respectively, in the same direction.

The element I is provided with a heating winding I3 thereon or disposed adjacent thereto.

At I4 I have shown a thermostatic bimetallic element of generally linear form rigidly secured at one end to a base I5 and at its opposite free end carrying a contact I6, contactingly engageable with a contact H on the free end of a bimetallic thermostatic element I8 preferably identical with the element I4. The element I8 is mounted on the end opposite the contact II upon a base I9 secured as by rivets to one end of a preferably resilient arm 2I rigidly connected to a stationary base 22, and at its end 23 remote from the base 22 engaged by the end of an adjusting screw 24, threaded into a stationary base 25. The element I4 has a heating winding 26. The parts I4 to 26 inclusive are generally similar to the parts I to I3 inclusive, above described, except for differences which will presently appear.

A source of electric energy such as a battery, 27, is connected by a wire 28 to the base 6. One end of the winding I3 is connected to the base 2, and the other end by wire 29 and a wire 30 is connected to the base I9. The winding 25 is connected at one end to the base I5, and its other end is connected by a wire 3| to the source 21.

Current may flow from the source 21 by way of the element 5 through the contacts 34, element I, heating'winding I3, wire 29, element I8, contacts I6I'I, element I4, winding 26, wire 3| back to the source 21. The current in the winding I3 heats the element I causing it to bend and break the circuit at 34, whereupon the winding l3 being de-energized, the element I cools oif, returns to its original position and closes the contact 34, and this action continues. Thus a succession of current impulses is sent from the source 21 over the circuit above described, which current heats the element I4 by means of the winding 26, causing the element I4 to bend and break the circuit at the contact I6--II.

It is one of the important elements of my invention, that the elements I and I4 respond differently to the heat of the current impulses flowing in the circuit described, to effect a relato notch the ratchet wheel 43 ahead step at a tively rapid periodic make-and-break at the contacts 3-4 and a relativelyslow make-andbreak at the contacts I6--I1.

Thus a number of impulses must be sent over the circuit by the contacts 3--4 before the element'I4 will bend sufliciently to break the circuit at the contacts Iii-I1. When the contacts l6I1 are opened, all current in the circuit ceases flowing until they close again, whereupon the relatively rapid impulses from the contacts 3-4 begin again.

This result may be efiected in a number of ways. For example, the windings I3 and 26 may be alike, but the heat storage capacity, of the element I4 may be greater than that of the element I, requiring a longer period of time for it to heat sufliciently to bend it to the contact breaking degree. Again, the heating efiect of a currentimpulse in the winding 26 may be less than that in the winding I3, whereupon again, a number of impulses will be required. to break the contact at I6--I1 whereas one is enough to break contact at 3-4. Other means will occur to those skilled in the-art for effecting the result sought, namely that with the contacts 3-4 and I6-'-I1 in the same circuit, the contacs 34 will close and open periodically a number of times, sending a number of impulses to the winding 26 before the contacts I6I1 will be opened and the current to both windings thereupon be discontinued.

A second circuit is controlled by the contacts I 6I1 and comprises the winding 32 of a magnet 33, the circuit preferably including a. local source of current 34, a wire 35 connected to the base I 9, and a wire 36 connected to-the base I5.

The magnet 32-33 operates a switch arm 31 controlling the energization of a circuit comprising a local source 38, and an electro-magnet 39. The magnet 39, upon being energized, operatively moves an arm 40 normally retracted by a spring 4| and longitudinally pulls a pawl 42 engaged with the teeth of a ratchet 43,rotatably mounted on a. shaft 44.' Successive energizations of the magnet 39 will cause the pawl 42 time in a well known manner. The magnet 39 will be energized by the switch arm 31 upon each energization of the winding 32 which occurs uponveach closure of the contacts I6--l1, energization for the winding 32 flowing from the source 34 by wire L ra-through element I8, contacts I1 and i6, through element 04 and wire 36.

Switches 45, 46 and 41 may be provided to control the several circuits above described, and when these are closed, the operation 'of the system is as follows;

The element I is repeatedly bent by the heat from its winding I3, continuously opening and closing the contacts 3-4, and the current flowing through these contacts and through the winding 26 heats the element I4, and after a suitable predetermined number of impulses have flown through the winding 26, the element I4 bends sufliciently to break the contacts Iii-I1, whereupon the flow of current ceases. Thereupon also, the switch arm 31 moves to switch-open position as, for example, by a retracting spring 48, the winding 32 now being de-energized at the contacts I6--I1. Thereupon also, the spring 4I retracts the arm 40 and moves the pawl 42 to a new notch on the ratchet 43. After an interval of time, the element I4 cools ofi and causes the contacts I6-I1 to close, whereupon current flows through the winding 32, attracts the switch arm 31, energizes the winding 39, attracts the arm v40 and notches the ratchet wheel 43 ahead one notch. The operation just described continues, and the ratchet wheel 43 is notched ahead one notch at the end of each period of time determined by the periodicity of the element I4.

The efiect of ambient or local temperature upon the elements I and I4 is respectively neutralized or compensated by the elements and I8, any tendency of the local temperature to bend the elements I or I4, say, toward the left as viewed in Fig. 1, is compensated for by the same tendency of the elements I8 and 5 to move toward the left.

The amount of heat energy supplied to-the ele ment I4 to bend it is the integration of the heat from a number of current impulses. The amount of current which flows in the circuit and through the heating windings will be determined by the voltage of the source 21, but when once established, the movement of the element I4 will be unaffected by variations of the voltage source 21.

. For example, if the voltage of the source 21 should decrease, the actual value of current flowing will be less but this will result in less heating efiect in the winding I3 and in maintaining the contacts 3-4 closed for longer periods of time and will thus cause impulses of longer duration to flow to the winding 26. Thus on a decrease of voltage, and in a given length of time, fewer current impulses will flow to the winding 26, but they will be of longer duration, and the time current integration thereof will be constant at all voltages of the source 21.

In Fig. l, I have shown on the shaft 44 a clock hand 50 for which there may be provided a dial not shown. Thus the system at Fig. 1 may be employed to indicate the passage of time like a clock. The rate at which the hand 50 moves around the dial will of course be determined by the rate of vibration or periodicity of the element I4. This, of course, may be predetermined within limits by the design of the parts in a well known manner and, however, may be accurately adjusted by the following means.

Upon turning the screw I I to move the end ID of the arm 8 toward the left, Fig. 1, the contact 4 will be moved toward the contact 3 and put some bending pressure on the element I. This will require more heat in the winding I3 to break the contacts 3-4 and therefore cause impulses of longer duration to flow. correspondingly, the element I4 will be heated sufliciently to break the contacts I6I1 in a shorter period of time, thus increasing the periodicity of the element I4, and moving the hand 50 faster.

Again, if the screw 24 be turned to move the element 29 toward the left, and to advance the contact I1, for any given rate of impulses from the contacts 3-4, it will require more of these impulses to bend the arm I4 to the contact @reaking point and hence the periodicity of the elem'ent I4 will be slower and the hand 5!} will be nnved slower.

As shown in Fig. 1, the screw 24 may be provided with a dial 5| having calibration marks thereon cooperating with an index or pointer 53 stationary on the base 25. The dial 5| may be calibrated in seconds, minutes or other divisions of time, or may be calibrated in percentages of increase or decrease of periodicity of the element I4 effected by movement of the screw 24.

Similarly, the screw I I may be provided with a calibrated dial, although not shown in the drawing.

It will be understood, of course, that the ratchet wheel 43, which is adapted to turn the shaft 44, may be employed to operate or step up apparatus of various kinds other than a clock hand and thus cause any desired operative effect of an apparatus to be brought about periodically.

In a modification of my invention shown in Fig. 2, the contact 4 is connected directly to the arm 63 and the contact I1 is directly connected to an arm 64, the free ends of the arms 63 and 64 being adjustably movable by adjusting screws 65 and 66. The compensating thermostatic elements I8 and 5 are omitted in this form. The element I4 is replaced by an element 6| to the upper end of which is pivotally attached as at 61, a generally horizontally disposed pawl 68 engaged with teeth of a ratchet wheel 69. The operation is generally the same as that of Fig. 1. Current flows from the source 60, through the winding I3 of the element I, thence direct to the contact 3, thence to contact 4, through the arm 63 to a wire 10, to the arm 64, contact I1, contact I6, winding 62 and back to the source 60. A succession of impulses at the contacts 3-4 causes the contacts I6-I1 to open, moving the pawl 68 ahead to another notch. Upon cooling of the element 6|, it returns to its original position, closing the contacts I6-I1 and during its return movement turns the ratchet wheel 69 the distance of the pitch of the teeth. The periodicity of the elements I and 61 may be adjusted by the screws 65 and 66 as will be understood from the more detailed description of Fig. 1.

In this form of my invention, the ratchet wheel 69 is mounted on a shaft 1 I upon which is mounted a drum controller 12 having thereon one or more contacts 13-13 engageable by stationary contact fingers 14. A stationary finger 15 slides on the shaft H. An external circuit comprising wires 16 and 11 is connected respectively to the fingers 14 and 15. A step-by-step rotation of the ratchet wheel 69 and shaft 1| successively brings the contacts 13 into contact with the finger 14, and then current may flow from a local source 18 through the finger 15, shaft 1|, drum 12, contact 13, finger 14 and thence to an external circuit where an impulse of current thus sent out may be employed to actuate or control any desired and suitable apparatus. By the arrangement shown, two impulses will be sent out for each complete revolution of the ratchet wheel 69.

In the form of my invention shown in Fig. 2, a modified form of compensation for changes of ambient temperature is illustrated. In this form of my invention, it is presumed that the thermostatic elements I and 6| and their heaters I3 and 62 are disposed within an enclosing housing 90. Within the housing is also disposed a heating winding for heating the air therein and for maintaining it substantially at a constant temperature. The heating winding 80 is placed in series with a contact 8| on an adjusting screw 82,

a contact 83 engaging the contact 8|, a bimetallic on its free end and at its opposite end rigidly connected to a stationary base or support 85, the circuit being completed from the element 84 to the source 60 by a wire 86, and from the source to the winding 88 by a wire 81.

When the device is put in operation, current continuously flows from the source 60 through the winding 80 and contact 83--8I. When the interior of the housing attains the desired temperature, the element 84 bends sufficiently to break the contact at 83--8I and heating of the winding 80 is discontinued until the temperature falls below the desired value whereupon the element 84 again closes the contact 83-8I and supplies more heat to the winding 80.

One mode of operation of the heating element 80 and its associated parts is to adjust the screw 82 so that at some high or maximum local temperature such, for example, as a summer temperature of 90, the contacts 83 and 8| will just be held open by the element 84. At any lower local temperature, the contacts 83-8I will close and stay closed until the heating winding 80 has raised the temperature in the casing up to the said 90".

By keeping the temperature within the casing at a constant value in this manner, the local or ambient temperature to which the elements BI and I are subjected does not vary and no compensation therefor is necessary.

It will be understood that the periodicity of the elements I and I4 of Fig. 1 or the elements I and 62 of Fig. 2 is not limited to any particular ratio. In the practice of my invention it is only necessary that the periodicity of the element I be greater than that of the element I4, or 6 I, as the case may be. I have therefore found it convenientto refer to the periodicity ratio of these elements as a ratio of one plus to one.

My invention is not limited to any particular type of casing for use in connection with the form of Fig. 2. At 90 I have indicated in cross-section an enclosing casing such as that referred to above in which all of the apparatus elements described hereinbefore are enclosed, the circuit wires 16 and 11 being led through the wall of the casing as indicated at 91. It will be understood, of course, that some of the elements of apparatus such, for example, as the current source 63 may be disposed outside of the casing.

Where the form of my invention shown in Fig. 1 is employed, it may be desirable to employ shields 9| and 92 respectively to shield the bimetallic element 5 from heat of the winding I3 and to shield the bimetallic element I8 from heat of the winding 26. The purpose of these shields is to render the-bimetallic elements 5 and I8 responsive only to ambient temperatures.

In both of the forms of Figs. 1 and 2, I have shown the circuits of the heating windings in series with each other and with the contacts controlled by the two thermostatic elements and with a common source of current, that is to say, all in a single continuous series circuit. My invention is not limited to this particular circuit arrangement. Those skilled in the art may devise circuits in which some of the elements referred to are in derived or parallel circuits without sacrificing the advantages of my invention. I have illustrated a single series circuit herein for purposes of description, that being the simplest circuit wherewith my invention may be practiced.

From the foregoing disclosure of my invention, it will be apparent that it may be employed variously in relation to the passage of time either to measure intervals of time and to indicate the same as, for example, on a clock dial, or to perform an initiating or controlling function periodically after the passage of preselected intervals of time. My invention furthermore may be adapted to perform other functions involving time than those mentioned. I have found it convenient to refer to all of the possible time related functions of my invention as timing functions.

My invention is not limited to the exact details of construction nor to the exact circuit connections hereinbefore illustrated and described, and

it wfll be understood that many changes and modifications other than those shown may be made without departing from the spirit of my invention or sacrificing its advantages.

I claim:

1 .In an electric timing system and apparatus, a current source, a first thermostat, an electric heater therefor, a second thermostat, an electric heater therefor, a contact set controlled by movement of the first thermostat, a. contact set controlled by movement of the second thermostat, and a, circuit connecting the source, the two heaters and the two sets of contacts in series relation.

2. In an electric timing system, a current source, a first thermostat, an electric heater therefor, a second thermostat, an electric heater therefor, a contact setcontrolled by movement of the first thermostat, a contact set controlled by movement of the second thermostat, and a circuit connecting the source, the two heaters and the two sets of contacts in series relation, the thermostats being movable responsive to an increase of temperature effected by their respective heaters to break the circuit at their respective contact sets.

3. In an electric timing system, a current source, a first thermostat, an electric heater therefor, a second thermostat, an electric heater therefor, a contact set controlled by movement of the first thermostat, a contact set controlled by movement of the second thermostat, anda circuit connecting the source, the two heaters and the two sets of contacts in series relation, the thermostats being movable to periodically make and break the circuit at their respective contact sets responsive to changes of heating effect of their respective heaters, and periodicity of one thermostat being greater than that of the other thermostat.

4. In an electric timing system, a current source, a first thermostat, an electric heater therefor, a second thermostat, an electric heater therefor, a contact set controlled by movement of the first thermostat, a contact set controlled by movement of the second thermostat, and a circuit connecting the source, the two heaters and the two sets of contacts in series relation, the thermostats being movable to periodically make and break the circuit at their respective contact sets responsive to changes of heating eifect of their respective heaters, the ratio of periodicity of the thermostats being as one plus to one, movable time indicating means and means transmitting movement of the thermostat of lower periodicity to the time indicating means.

5. In an electric timing system, a current source, a first thermostat, an electric heater therefor, a second thermostat, an electric heater therefor, a contact set controlled by movement of the first thermostat, a contact set controlled by movement of the second thermostat, and a circuit connecting the source, the two heaters and the two sets of contacts in series relation, the thermostats being movable to periodically make and break the circuit at their respective contact sets responsive to changes of heating efiect of their respective heaters, the ratio of periodicity of the thermostats being as one plus to one, movable time indicating means, and mechanical means for transmitting movement of the thermostat or lower periodicity to the time indicating means.

6. In an electric timing system, a current source, a first thermostat, an electric heater therefore, a second thermostat, an electric heater therefor, a contact set controlled by movement of the first thermostat, a contact set controlled by movement of the second thermostat, and a circuit connecting the source, the two heaters and the two sets of contacts in series relation, the thermostats being movable to periodically make and break the circuit at their respective contact sets responsive to changes of heating effect of their respective heaters, the ratio of periodicity of the thermostats being as one plus to one, electrically actuable time indicating means and an energizing circuit having contacts therefor controlled by movement of the thermostat of lower periodicity.

7. In an electric timing system, a current source, a first thermostat, an electric heater therefor, a second thermostat, an electric heater therefor, a contact set controlled by movement of the first thermostat, a contact set controlled by movement of the second thermostat, and a circuit connecting the source, the two heaters and the two sets of contacts in series relatiomthe thermostats being movable to periodically make and break the circuit at their respective contact sets responsive to changes of heating efiect of their respective heaters, the ratio of periodicity of the thermostats being as one plus to one, electrically actuable time indicating means, and an energizing circuit and contacts therefor controlled by the contact of the thermostat of lower periodicity.

8. In an electric timing system, a current source, a first thermostat, an electric heater therefor, a second thermostat, an electric heater therefor, a contact set controlled by movement of the first thermostat, a contact set controlled by movement of the second thermostat, and a circuit connecting the source, thetwo heaters and the two sets of contacts in series relation, the thermostats being movable to periodically make and break the circuit at their respective contact sets responsive to changes of heating efiect of their respective heaters, the ratio of periodicity of the thermostats being as one plus to one, and thermostat periodicity adjusting means for at least one of the thermostats.

9. In an electric timing system, a current source, a first thermostat, an electric heater therefor, a second thermostat, an electric heater therefor, a contact set controlled by movement of the first thermostat, a contact set controlled by movement of the second thermostat, and a circuit connecting the source, the two heaters and the two sets of contacts in series relation, the thermo-- stats being movable to periodically make and break the circuit at their respective contact sets responsive to changes of heating effect of their respective heaters, the ratio of periodicity of the thermostats being as one plus to one, and thermostat periodicity adjusting means for both of said thermostats.

10. In an electric timing system, a current source, a first thermostat, an electric heater therefor, a. second thermostat, an electric heater therefor, a contact set controlled by movement of the first thermostat, a contact set controlled by movement of the second thermostat, and a circuit connecting the source, the two heaters and the two sets of contacts in series relation, the thermostats being movable to periodically make and break the circuit at their respective contact sets responsive to changes of heating effect of their respective heaters, the ratio of periodicity of the thermostats being as one plus to one, and thermostat periodicity adjusting means for at least one of the thermostats comprising a movable support for one of the contacts of the set and means for adjustably moving the support.

11. In an electric timing system and apparatus, a thermostat, an electric heater therefor, and automatic means including a variable source of current, a heater circuit, electrical connections for periodically energizing the heater from the source with successive amounts of electric heat energy to eifect periodic movement of the thermostat and compensating means for current variations, causing the cumulative value of the successive amounts of energy in a given interval to be sub stantially constant to cause the periodicity of the thermostat to be substantially constant.

12. In an electric timing system and apparatus, a thermostat, an electric heater therefor, and automatic means including a variable source of current, a heater circuit, electrical connections for periodically energizing the heater from the source with successive amounts of electric heat energy to effect periodic movement of the thermostat and heat responsive means operable by the current source causing the cumulative value of heating current supplied to the heater in a given interval to be substantially constant, a movable time indicating apparatus and means transmitting movement of the thermostat to the time indicating apparatus.

13. In an electric timing system and apparatus, a thermostat, an electric heater therefor, and automatic means including a variable source of current, a heater circuit, electrical connections for periodically energizing the heater from the source with successive amounts of electric heat energy to effect periodic movement of the thermostat and heat responsive means operable by the current source causing the cumulative value of heat energy supplied to the thermostat heater in a given interval to be substantially constant, and a time indicating apparatus operable by the movement of the thermostat.

14. In an electric timing system and apparatus, a thermostat, an electric heater therefor, and automatic means including a variable source of current. a heater circuit and electrical connections for'periodically energizing the heater from the source with successive amounts of electric heat energy to efiect periodic movement of the thermostat and for causing the cumulative value of the successive amounts of energy in a given time interval to be substantially constant to cause the periodicity of the'thermostat to be substantially constant, an electric time indicating apparatus and a circuit therefor controlled by movement of the thermostat.

15. In an electric timing system and apparatus, a thermostat, an electric heater therefor, and automatic means including a variable source of current, a heater circuit and electrical connections for periodically energizing the heater from the source with successive amounts of electric heat energy to effect periodic movement of the thermostat and for causing the cumulative value of the successive amounts of energy in a given time interval to be substantially constant to cause the periodicity of the thermostat to be substantially constant, and contacts controlled by movement of the thermostat for making and breaking the heater circuit.

16. In an electric timing system and apparatus, a thermostat, an electric heater therefor, and automatic means including a variable source of current, a heater circuit and electrical connections for periodically energizing the heater from source with successive amounts of electric heat energy to effect periodic movement of the thermostat and for causing the cumulative value of successive amounts of energy in like predetermined time intervals to be substantially equal to cause the periodicity of the thermostat to be substantially constant, contacts controlled by movement of the thermostat for making and breaking the heater circuit, and movable mechanical means for adjusting the position of one of the contacts to adjustably vary the periodicity of the thermostat.

17. In an electric timing system and apparatus, a thermostat, an electric heater therefor, and automatic means including a variable source of current, a heater circuit and electrical connections for periodically energizing the heater from the source with successive amounts of electric heat energy to effect periodic movement of the thermostat and for causing the cumulative value of successive amounts of energy in like predetermined time intervals to be substantially equal to cause the periodicity of the thermostat to be substantially constant, contacts controlled by movement of the thermostat for making and breaking the heater circuit, and movable mechanical means for adjusting the position of one of the contacts to adjustably vary the periodicity of the thermostat, and adapted to indicate by its position the said periodicity.

18. In an electric timing system and apparatus, a pair of thermostats, an electric heater for each thermostat, a current source, circuit connections for energizing the thermostats from the source, and contacts openable and closable by the movement of each thermostat to efiect energization and de-energization of both heaters concurrently.

19. In an electric timing system and apparatus, a pair of thermostats, an electric heater for each thermostat, a current source, circuit connections for energizing the thermostats from the source, and contacts openable and closable by the movement of each thermostat to effect energization and de-energization of both heaters, opening oi. the contacts being adapted to concurrently effect the de-energization of both heaters, the thermostats moving periodically responsive to the energization and de-energization of their heaters, the periodicity of one thermostat being greater than that of the other, a movable time indicating apparatus and means transmitting movement of the thermostat of lower periodicity to the time indicating apparatus.

20. In an electric timing system and apparatus, a pair of thermostats, an electric heater for each thermostat, a current source, circuit connections for energizing the thermostats from the source, and contacts openable and closable by the movement of each thermostat to effect energization and de-energization of both heaters, opening of the contacts being adapted to concurrently effect the deenergization of both heaters, the thermostats moving periodically responsive to the energization and de-energization of their heaters, the periodicity of one thermostat being greater than that of the other, a movable time indicating apparatus and means transmitting movement of the thermostat of lower periodicity to the time indicating apparatus.

21. In an electric timing system and apparatus, a pair of thermostats, an electric heater for each thermostat, a current source, circuit connections for energizing the thermostats from the source, and contacts openable and closable by the movement of each thermostat to effect energization and de-energization of both heaters, opening of either of said contacts being adapted to concurrently deenergize both heaters, the thermostats and contacts associated with each thermostat openable and closable by the movement of its associated thermostat to efiect energization and de-energization of both heaters, opening of either contact being adapted to de-energize both heaters, the thermostats moving periodically responsive to the energization and de-energization of their heaters, the periodicity of one thermostat being greater than that 01' the other.

JOHN w. ANDERSON.

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