US2458954A - Automatic control system for electric circuits - Google Patents

Description

Jan. 11, 1949. N. MARQUEZ AUTOMATIC CONTROL SYSTEM FOR ELECTRIC CIRCUITS 3 Sheets-Sheet 1 Filed Nov. 6, 1945 Jan. 11, 1949. MARQUEZ 2,458,954

AUTOMATIC CONTROL SYSTEM FOR ELECTRIC CIRCUITS Filed Nov. 6, 1945 3 Sheets-Sheet 2 Jan. 11, 1949. N. MARQUEZ 2,453,954

I AUTOMATIC CONTROL SYSTEM FOR ELECTRIC CIRCUIT S Filed Nov. 6, 1945 3 Sheets-Sheet 3 24 Fig. 3

man J. 11, 1949 AUTOMATIC CONTROL SYSTEM ELECTRIC CIRCUIT FOR 8 Nemesio Marquez, Buenos Aires, Argentina, as-

signor to Francisco Ardila Cardenas, Rio de J aneiro, Brazil Application November .s, 1945, Serial No. 021,029 In Argentina February 23, 1945 12 Claims. 1

My present invention relates to electric control systems for the security. Protection and operation of all kinds of electrically operated apparatus and appliances, including electric motors, comprising temperature -responsive automatic switch means adapted to be operated by electric heat-producing means included in the same circuit 01' electric current which is to be controlled by said automatic switch.

One object of my invention resides in providing a new automatic temperature-responsive switch, comprising a glass bulb containing a body of mercury and having at least two vertical stems for permitting expansion of said mercury body and for housing a movable metallic contact member in each of said stems, connection means for including these contact members and said mercury body in the same electric circuit which is to be controlled by said switch, by means of electric heat-producing means also included in said circuit, in such a. manner that said switch responds to all kinds of fluctuationsin voltage and intensity of the electric current in said circuit.

A further object of the invention is to provide a new automatic mercury security switch for electric control systems adapted to protect all kinds of electrically operated apparatus and appliances, including electric motors, against undue and undesired fluctuations in voltage and intensity of the electric current supplied to said apparatus and appliances.

Still another object of my invention consists in providing a new automatic temperature-responsive security switch for electric control systems,

said switch comprising at least one bellows-forming container for containing a gas of high expansion coeilicient, exposed to electric heat-generating means included in the electric circuit to be controlled by said system, and adapted to protect all kinds of electrically operated apparatus and appliances, including electric motors, against undue and undesired fluctuations in voltage and intensity of the electric current supplied to said apparatus and appliances.

An additional object of the invention is to provide an electric control system for all kinds of electrically operated apparatus and appliances, including electric motors, comprising an automatic mercury security switch adapted to interrupt the current supply to said apparatus and appliances, when undue fluctuations in voltage and intensity occur in said current.

Another object of this invention is to provide an electric control system for all kinds of electrically operated apparatus and appliances, in-

cluding electric motors, comprising an automatic mercury security switch adapted to interrupt a three-phase current supply to said apparatus and appliances, in case of failure and of excessive load 01' any of the three phases of said current.

A further object of the invention is to provide an electric control system for all kinds of electrically operated apparatus and appliances, including electric motors, comprising an automatic heat-responsive security switch, including at least one bellows-forming container for containing a gas of high expansion coemcient, exposed to electric heat-generating means included in the electric circuit to be controlled by said system, and adapted to interrupt the current supply to said apparatus and appliances, when undue fluctuations in voltage and intensity 01 said current occur and in case of failure or current as well as of excessive load.

Another object of my present invention consists in providing a new automatic heat-responsive overload and under-power switch for electric control systems, comprising a double stem mercury bulb with a movable metallic contact member in each stem, said switch being adapted to operate as voltmeter and to automatically break the electric circuit to be controlled by said system, when predetermined overload and underpower limits are reached.

Still another object of the invention resides in providing a new automatic heat-responsive overload and under-power switch for electric control systems, comprising two bellows-forming containers for containing a gas of high expansion coefllcient, and being adapted to operate as voltmeter and to automatically break the electric circuit to be controlled by said system, when predetermined overload and under-power limits are reached.

A fiu'ther object of my invention is to provide and employ an electric control system for all kinds of electrically operated apparatus and appliances, including motors, comprising an automatic heat-responsive overload and under-power switch, as set forth in any of the two preceding paragraphs, adapted to automatically interrupt the current supply to said apparatus and appliances, when predetermined overload and under-power limits are reached.

Finally, in accordance with the objects as hereinbefore set forth, my present invention refers to improved combined electro-physical, thermic and electro magnetic control systems, for use in connection with all kinds of electric motors and electrically operated apparatus and appliances,

lighting and power plants, electronic and electric control circuits, radio electric systems, telephone and telegraph service stations, etc, said control system being adapted to efilciently and automatically protect said appliances, disconnecting the same in case of danger due to failure and excessive load or to any kind of fluctuations in voltage and intensity of the supplied current.

According to one feature of my invention, the new mercury control switch is operated by electric heat-generating means, such as a radiator lamp. suitably mounted in an adjustable manner outside the mercury containing bulb, this heatgenerating' means being provided with means for regulating its distance from said bulb and with suitable heat reflecting and concentrating means adapted to emciently provoke the expansion of the mercury body contained in said bulb; this expansion of the mercury body within the glass bulb and the vertical stems thereof being used for connecting and disconnecting all kinds of electric circuits, by establishing upon expansion of said mercury body, a physical contact between the latter and at least one movable metallic contact member, this contact member and said mercurybody being included by suitable connection means in the electric circuit to be controlled by, said switch, and due to that electric heatgenerating means is also included in the same circuit and responds to any fluctuations in voltage and intensity of the current in said circuit, said control switch, by means of the expansion of the said mercury body, also controls theelectric circuit with regard to said fluctuations as well as to overload and under-power limits in mercury containing glass bulb provided with two vertical hollow stems and a movable metallic contactmember in each stem, these contact members being disposed at difierent levels in said stems, thereby permitting to switch on a motor, apparatus and appliance, first by star connection and then by delta connection or vice versa.

According to still another feature of this invention, the new mercury control switch operates in combination with an eiectro-magnet having two separate coils with opposite windings, one of which coils is always connected whereas the other is connected by means of said switch for the purpose of neutralizing the magnetic field of said electro-magnet and breaking the circuit normally closed by said electro-magnet.

With these objects in view and others which will become evident from the following specification of certain practical embodiments of my present invention, wherein reference is made to the accompanying drawings, which illustrate said embodiments by way of examples only, and on which:

Figure 1 is a schematic view of a control system for electric circuits, comprising an automatic mercury security switch applied to three-phase current;

Figure 2 is a schematic view of a control system for electric circuits, comprising an automatic heat-responsive overload and under-power switch applied to three-phase current;

Figure 3 is a schematic view of a control system for single-phase current circuits, comprising the security switch as shown in Figure-l;

Figure 4 is a schematic view of a control system for single-phase current circuits, comprising the overload and under-power switch as employed in Figure 2.

Referring to the accompanying drawings and more particularly to Figures 1 and 2, the control system for electric circuits according to my in- I vention, comprises a temperature-responsive control switch which may comprise a glass bulb I for containing a mercury body 2, having two vertical hollow stems 3 for the purpose of forming upon expansion of the mercury body 2, two columns of mercury for establishing physical contact with two movable metallic contact members 4 and 4'-see Figure 1. Instead of the mercury bulb having two vertical stems, the temperature-responsive switch may also comprise two bellowsforming containersBO, (Fig. 2) filled with a gas such as ethyl oxide, of high expansion coefficient, and provided with indicator needles 8|, 8| adapted to move over the scales 82, 82. The extensions 83, 63' of the containers 80, 80' act in this case as the mercury columns 3 and establish circuit closing contacts with the screw-bolts 84, 84' acting as contact members. This control switch may be advantageously used in control systems for the security and protection of electric motors and all kinds of electrically operated apparatus and appliances, as will be hereinafter more particularly described.

In Figure 2 the reference numeral 3| indicates an electro-magnet, the magnetic field of which is formed by the three phases of a three-phase current circuit; the three phases giving a compensated magnetic field total when the electric current is caused to operate a motor or to become otherwise operative on a load as indicated at 32. The closure of the circuit may be effected in any known manner by star, delta or other suitable connection.

The three magnet cores which compose the electro-magnet 3| have three windings, one for each phase. The magnetic field, when completed, serves for maintaining intensely attracted a lever 33 which in its attracted position closes the resulting magnetic field, but in case of failure of any of the three phases, the magnetic field is not compensated and said lever 33 of soft iron is removed from the electro-magnet by a spring 34 engaging a connecting member 35 and being adjustable by means of a screw or like device 36. The mechanic pull of the spring 34 on the lever 33 causes the latter, when being left unattracted by the electro-magnet 3|, to move a vertical rod 31 in upward direction. This rod is providedwith a wedge-like portion 38 and when moving upwards, by means of this wedge-like portion moves a slidably mounted rod 39 from the left to the right, by causing said wedge-like portion to act upon a small loose roller 40 of said rod 39. This lateral movement of the rod 39 opens the contacts 4| and thereby causes the interruption of the electric circuit and the current supply to the motor or other load indicated at 32. In this way the failure of one of the three phases in the electric-magnet 3| automatically causes 4 the "interruption of the three-phase current supply. The vertical rod 31 is movably mounted in suitable brackets 42, and the slidably mounted rod 33 is provided with a push button 43, by means of which in case of necessity and emergency the motor or other load 32 may be also disconnected by hand.

The slidably mounted rod 39 interrupts the current supply to the motor or other load 32 only in the following cases, viz: when in case of emergency the push button 43 is operated by hand; when in case of failure of anyof the three phases in the electro-magnet 3|, the rod 33 is operated by the spring 34, lever 32 and vertical rod 31; and finally when any of the three phases of the supplied current is excessively loaded. This lastmentioned case may be explained as follows:

' Each of the three phases of the current passes through one of the three bi-metallic blades 44 adjustably secured by means of screws 45 to suitable brackets. The blades 44 are of relatively high expansion coefficient, and when bending upon expansion, the same co-operate with stop plates 43 of the slidably mounted rod 39, the arrangement being such that as soon as any of the three phases is excessively loaded, the heat developed thereby causes the expansion of the respective blade 44 bending the latter in such a way that by engaging the respective stop plate 46 said blade 44 moves the rod 39 to the right against y the pull of the spring 41, and thus opens the contacts 4! and interrupts the current supply to the motor or other load 32.

The arrangement of parts as hereinbefore described with reference to Figure 2 is more or .0! said currentexceed predetermined limits of minimum and maximum overloads, said control system comprising an automatic mercury security switch which as already stated comprises a glass bulb I containin a body of mercury 2 and having two vertical hollow stems 3 with a movable metallic contact member 4; 4' in each stem. These contact members 4, 4 and the mercury body 2the latter by means of a metallic electrode 5-are included by way of suitable connection in the electric circuit of the control system.

The heat-generating means for causin the mercury body 2 to expand within the bulb I and its stems 3 comprise two incandescent lamps 52 supported by a concave reflector 5i, and a lens 53 so arranged that a pencil of heat rays 54 is concentrated upon the mercury body 2. These heat-generating means together with the mercury bulb i are disposed within a suitable casing (not shown) conveniently made of heat-insulating material, with the advantages that changes of the room temperature do not substantially interfore in the operation of the device, that radiation of heat of the lamps 52 is virtually uniform, and that finally the device may be readily adjusted in such a manner that. the same will be operative only at temperatures substantially higher than the usual maximum room temperature of the place where the device is used.

The stems 3 of the bulb I are suitably provided with scales bearing marks for volt measuring, with the advantage that the mercury control switch according to my invention, at the same time constitutes an automatic mercury control voltmeter, which operates with a maximum exactness, in view of that, as hereinbefore pointed out, changes of the room temperatures do not affect the operation of the device, provided the same is adjusted so as to operate at substantially higher temperatures than the usual maximum room temperature.

The adjustment referred to is effected, on one hand, by regulating the levels of the lower ends of the contact members 4, 4' and, on the other hand, by regulating the distance between the lamps 52 and the mercury bulb l and/or more or less efllcient heat-generating lamps 52.

The operation of the control system, according to the invention, employin the mercury security switch as hereinbefore referred to, will now be described together with the arrangement of other component parts of the'system which have not yet been mentioned.

I. Mechanical operation of the control system.

(a) The three-phase current circuit is closed by hand by means of a starter push button.

The reference numeral 56 indicates a starter push button, mounted on a slidable rod 51, which after being moved by the operation of said push button. by means of a spring 58 is returned to its normal inoperative position. The rod 51 at its end opposite to said push button is operatively connected with the vertical rod 31 and with a second vertical rod 8| adapted to operate a series of switches 60, whereas said rod 51 in its centre portion is provided with a'toothed edge adapted to operate by means of a sprocket and crossed belt connection 83 a resistance for voltage measurement 5!. Consequently when pushing the button 58, the slidable rod 51- performs four different operations, viz: (1) it pulls the rod 31 downwards and moves the lever 33 to its position in contact with the electro-magnet 3 I, thereby completing the magnetic field of the same; (2) it pushes the rod Bl downwards which in turn moves the switches 60 into their closing positions, thereby supplying electric current to the lamps 52 and to the resistances 62 adapted to regulate the intensity of heat production of said lamps: (3) by means of the sprocket and chain connection 63, the said rod 51 operates the resistance for voltage adjustment 59in such a manner that the resistance offered by the same to the electric current is momentaneously reduced for the reason that the major part of the resistance is put out of circuit and that thus more current is allowed to operate the lamps 52 and to produce more heat in less time; (4) the said rod 51 momentaneously closes a series of contacts 64 for the purpose of thereby supplying an initial current in excess to the motor or other load 32 :to facilitate starting as soon as upon expansion of the mercury body 2 an electric contact is established thereby with the contact member 4. In this starting operation the bimetallic elements 44 do not operate at all, due to that the same are placed in shunt by,

virtue of the contacts 64, but the same will be operative when excess of current occurs during operation of the device, as will be hereinafter explained (b) The three-phase current circuit is broken by hand by means of the push button 43.

Asalready explained, the push button 43, when operated, moves the slidably mounted rod 39 4| of a coil 65 of an electro-magnet I! which operate the connection and disconnection of the motor or other load 32.

11. Electrical operation of the control system.

(a) Connection of the electro-magnet 65.

This connection is eilfected by operating the starter push button 56, which as explained closes the switches 60 and lights the lamps 52. The heat generated by these lamps causes the mercury body 2 to expand until its level establishes contact with the contact member 4', the lower end of which isadjusted at a lower level than that of the lower end of the contact member 4. Upon establishment of said contact, an electric current passes through the electrode to the coil ll, thereby energizing the electro-magnet 63 and causing the same to attract the bar 63 and to close the contacts 61. After completing this connection, the starter push button 56 may be allowed to return to its normal inoperative position.

(b) Disconnection due to excess of voltage.

An excess of voltage in the current supplied to the motor or other load 32, will cause the lamps 52 to generate more heat, and in case this excess is maintained for some time, the mercury body 2 will continue expanding and will reach the contact member 4, which as has been stated has its lower end situated at a higher level than the contact member 4', As soon as the mercury establishes contact with the contact member 4, a second current will pass to a, second coil 65" of the afore-mentioned load connecting and disconnecting electro-magnet 65, and as this coil 65" is connected in opposite direction with regard to the coil 65', the same produces an equal, but opposite magnetic fieldto that of the coil 65' and thereby destroys the effect of the electro-magnet 85 on the bar 69, which, therefore, under the action of suitable springs returns the contacts 61 to their circuit-breaking positions. This way the motor or other load 32 is disconnected by excess of voltage.

(0) Disconnection due to deficiency of voltage.

In case of deficiency or lack of voltage, the heat generated by the lamps 52 will decrease. The mercury body 2 will contract and if the lack of voltage persists, the contact between the mercury and the contact member 4' will be interrupted, with the result that the contacts 61 will be opened due to absence of current in the coil 65' of the electro-magnet 65.

III. Electro-mechanical operation of the control system. (a) Disconnection due to failure of a phase of the three-phase current. I

As already stated, the failure of one of the three phases in the electro-magnet 3|, causes the lever 33 to be removed therefrom by the spring 34. Said lever 33 moves the vertical rod 31 upwards and its wedge-like portion 38 pushes the slidably mounted rod 39 to the right and by means of the latter opens the contact 4| of the coil 65' of the electro-magnet 65, which in turn disconnects the contacts 61 of the motor or other load 32.

(b) Disconnection due to excess of current.

The current supplied to the motor or other load 32 passes through the bi-metallic blades 44, which under the influence of heat produced by excess of current become curved, with the result that their curved portions engaging the stop plates 48 provided on the slidable rod 39, move acaaou 8 this rod to the right and disconnect the'contacts 4| of the coil 65' of the electro-magnet 65, which in turn disconnects the contacts 61 of the motor or other load 32.

The operation of my control system according to Figure 2 is exactly the same as that of the embodiment according to Figure 1. In practice, the automatic temperature-responsive control switch provided with the two bellows-forming gas containers 80, may be more advantageously .used as automatic overload and under-power switch.

In Figures 3 and 4 I have shown some applications of my improved electric control systems according to Figures 1 and 2.

Figure 3 illustrates the control of a singlephase current circuit, by means of a double-stem mercury bulb adapted to automatically effect the disconnection of the circuit in case of failure or deficiency as well as in case of excess of voltage of the electric current, the reference numerals 24 and 25 indicate the conductors for the entering and outgoing currents, respectively.

Figure 4 shows the same control system of Figure 2 applied to a single-phase current circuit.

Figures 3 and 4 inclusive are sufflciently clear and self explaining regarding the further constitution and operation of the control systems as illustrated, so that no further explanations appear to be necessary.

It will be readily understood that the present invention is by no means restricted to the embodiments as described and shown, but that various amendments and modifications may be made therein and that such amendments are to be considered as falling within the scope of this invention as clearly outlined and set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. Automatic control device for electric circuits for the protection of electric motors and all kinds of electrically-operated apparatus and appliances, comprising a load circuit, a spring-loaded interruptor in said circuit, an electro-magnet having two coils with opposite windings for normally maintaining said interruptor in its circuitclosing position, a mercury body, a glass bulb containing said mercury body and having two vertical hollow stems, and an adjustably mounted metallic contact element'in each of said stems, a metallic electrode projecting through the bulb wall into said mercury body, electric conductors for connecting said electrode to said circuit, for connecting said contact elements with the two coils of said electro-magnet, and for connecting these two coils to said circuit, and electric heatgenerating means in thi circuit for acting upon said mercury body.

2. Automatic control device for electric cir cuits for the protection of electric motors and all kinds of electrically-operated apparatus and ap-- pliances, comprising a load circuit, a springloaded interruptor in said circuit, an electromagnet having two coils with opposite windings for normally maintaining said interruptor in its circuit-closing position, two bellows-forming gas containers containing a gas of relatively high expansion coefllcient, a contact element provided on each of these containers electrically connected to said'circuit, two adjustable contact elements arranged opposite the contact elements of said containers and electrically connected to they 9 A circuit, and electric heat-generating means included in this circuit for acting upon said gas containers.

3. Automatic control device for electric circuits for the operation, security and protection 01' electric motors and all kinds of electrically-operated apparatus and appliances, comprising a load circuit, a spring-loaded interruptor in said circuit, an electro-magnet having two coils with opposite windings for normally maintaining said interruptor in its circuit-closing position, a me chanically operated interruptor in said circuit and connected to one of the coils of said electromagnet for breaking said circuit, electro-magnetic means for operating said mechanically operated interruptor in case oi! phase failure in said circuit, bimetallic members for operating said mechanically operated interruptor in case of excess current in said circuit, a temperature-responsive switch device having two adjustable contact elements each connected with one of the two coils of said electro-magnet for causing said spring-loaded interruptor to become operative under the action of its spring in case oi excess voltage and under voltage in said circuit,

and electric heat-generating means included in this circuit for operating said temperature-responsive switch.

4. Automatic control device for electriccircuits for the operation, security and protection of electric motors and all kinds oi electrically-operated apparatus and appliances, comprising a load circuit, a spring-loaded interruptor in said circuit, an electro-magnet having two coils with opp site windings for normally maintaining said interruptor in its circuit-closing position, a mechanically operated interruptor in said circuit and connected to one of the coils of said electromagnet for breaking said circuit, electro-magnetic means included in said circuit for operating said mechanically operated interruptor in case of phase failure in said circuit, bimetallic members included in said circuit for operating the mechanically operated interruptor in case of excess current in said circuit, a mercury body, a glass bulb containing said mercury body and having two vertical hollow stems, and an adjustably mounted metallic contact element in each of said stems, a metallic electrode projecting through the bulb wall into said mercury body, electric conductors for connecting said contact elements to the two coils of said electro-magnet, an electric conductor for connecting said electrode to said circuit, and electric heat-generating means included in this circuit for acting upon said mercury body and causing the same to break said circuit in case of excess voltage or 01 under voltage.

5. Automatic control device for electric circuits for the operation, security and protection of electric motors and all kinds of electrically-operated apparatus and appliances, comprising a load-circuit, a spring-loaded interruptor in said circuit, an electro-magnet having two coils with opposite windings for normally maintaining said interruptor in its circuit-closing position, a mechanically operated interruptor in said circuit, electro-magnetic means included in said circuit for operating said meha'nically operated interruptor in case of phase failure in said circuit, bimetallic members included in said circuit for operating said mechanically operated interruptor in case of excess current in said circuit, two bellows-forming gas containers containing a gas oi relatively high expansion coefllcient, a contact element provided on each of these containers electrically connected to said circuit, two adjustable contact elements arranged opposite the contact elements of said containers and electrically connected to the two coils of said electro-magnet, electric conductors for connecting these two coils to said circuit, and electric heat-generating means included in said circuit for acting upon said gas containers and for causing the same to break said circuit in both cases of excess voltage and of under voltage.

6. Automatic control device for electric circuits for the operation, security and protection of electric motors and all kinds of electrically-operated apparatus and appliances, comprising a load circuit, a spring-loaded interruptor in said circuit, an electro-magnet having two coils with opposite windings for normally maintaining said interruptor in its circuit-closing position, a mechanically operated interruptor in said circuit, a slldable bar for operating this last-mentioned interruptor and means provided on this bar for imparting a sliding movement thereto, electro-m'agnetic means included in said circuit and adapted to act upon a spring-loaded lever and operatively connected to said slldable bar for operating said mechanically operated interruptor in case of phase failure in said circuit, bimetallic members included in said circuit and adapted to act upon said slldable bar for operating said mechanically operated interruptor in case of excess current in said circuit, a temperature-responsiv switch device having two adjustable contact elements each connected with one 01' the two coils of said electro-magnet for causing said spring-loaded interruptor to become operative under the action of its spring in both cases of excess voltage and of under voltage in said circuit, and electric heat-generating means included in this circuit for operating said temperature-responsive switch device.

7. Automatic control device for electric circuits for the operation, security and protection of electric motors and all kinds of electrically-operated apparatus and appliances, in accordance with claim 6, characterized by the fact that the slldable bar for operating the mechanically operated interruptor is provided with spring means for normally maintaining the same in its inoperative position and with a push button for manually operating said interruptor.

8. Automatic control device for electric circuits for the operation, security and protection of electric motors and all kinds of electrically-operated apparatus and appliances in accordance with claim 6, characterized by the fact that the slldable bar for operating the mechanically operated in terruptor is provided with a small loose roller and by the fact that the spring-loaded lever acted upon by said electro-magnetic means at its fre end is connected with a rod having a wedge-like portion to act upon said loose roller for movin said slldable bar.

9. Automatic control device for electric circuits for the operation, security and protection of electric motors and all kinds of electrically-operated apparatus and appliances in accordance with claim 6, characterized by the fact that the slldable bar for operating the mechanically operated interruptor is provided with stop blades of insulating material adapted to be acted upon by said bimetallic members.

10. Automatic control device for electric circuits tor the operation, security and protection of electric motors and all kinds of electrically-operated apparatus and appliances in accordance with said bimetallic members is associated with a metallic spring means operatively connected to a manually operated slidable bar to shunt said bimetallic members by the operation of this slidable bar.

for the operation, security and protection of electric motors and all kinds of electrically-operated apparatus and appliances in accordance with claim 6, characterized by the fact that said bimetallic members are electrically connected to the movable contacts of said spring-loaded interruptor and are further electrically connected to said electric heat-generating means for acting upon said temperature-responsive switch device, and by the fact that each of said bimetallic members is associated with a metallic spring means operatively connected to a manually operated slidable starter bar to shunt said bimetallic members by the operation of this starter bar, which is provided with a push button for its operation, with a spring for normally maintaining the same in its inoperative position and with means for operatively connecting the same to a pair of movable rods for operating by means 01' one of these rods upon said mechanically operated interrupter and by means of the other of said rods a series oi switches for said electric heat-generating means.

12. Automatic control device for electric circuits for the operation, security and protection of electric motors and all kinds of electrically-operated apparatus and appliances in accordance with claim 6, characterized by the fact that a slidable starter bar operatively connected to a number of metallic spring means associated each with one of said bimetallic members and adapted to shunt 11. Automatic control device for electric circuits the latter upon operation of said starter bar, this starter bar including at its free end a push button for its operation and a spring for normally maintaining it in its inoperative position, whereas at its other end comprises an enlarged portion provided with grooves for operatively and movably connecting said starter bar with a pair of movable rods for operating by means of one of these rods the said mechanically operated interrupter and by means of the other rod a series of switches for said electric heat-generating means, said starter bar being provided with a toothed portion engaging a sprocket wheel operatively connected by a chain to another sprocket wheel which is provided with means for operating a variable resistance for controlling the current admitted to said electric heat-generating means.

NEMESIO MAR UEZ.

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

UNITED STATES PATENTS Number Name Date 1,297,945. Warden et al Mar. 18, 1919 1,488,952 Stoekle Apr. 1, 1924 1,845,227 Bower Feb. 16, 1932 1,932,808 Van Vaikenbury Oct. 31, 1933 2,063,898 Shipley Dec. 15 1936 2,150,050 Chilowsky Mar. '2', 1939 2,162,098 McCabe June 13, 1939 FOREIGN PATENTS Number Country Date 302,344 Great Britain Jan. 18, 1930

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