US777246A - Rheostat. - Google Patents

Description

PATENTED DEC. 13

H. H. CUTLER.

RHEOSTAT.

APPLICATION FILED NOV. 21, 1902.

2T" EBTS-SHEBT l hide/1hr:

PATENTED DEC. 13

H. H. CUTLER.

RHEOSTAT,

APPLICATION FILED NOV.21,1902.

2 SHBETSSHEBT 2.

N0 MODEL.

y W Am UNITED STATES Patented December 13, 1904.

HENRY H. CUTLER, OF MILWAUKEE, WISCONSIN.

RHEOSTAT.

SPECIFICATION forming part of Letters Patent No. 777,246, dated December 13, 1904.

Application filed November 21, 1902. Serial No. 132,255. (No model.)

To (LU whom it may concern.-

Be it known that I, HENRY H. CUTLER, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented a certain new and useful Improvement in Rheostats, of which the following is a full,elear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to means for protecting rheostats to prevent injury thereto by the heating effect of an abnormal current through its resistances.

In rheostats employed for starting motors means is usually provided for cutting out the resistance slowly, and it often happens that the'attendant after partially cutting out the resistance will neglect to fully operate the device to cut out all of the resistance. In this case the remaining sections of the resistance in the main circuit are liable to become abnormally heated, since they are ordinarily not designed to carry the abnormal working current. This heating may rise to such an extent as to destroy the rheostat and possibly cause destructive fires. Also in rheostats employed for regulating a portion of its resistance is intended to be always included in the circuit. These resistances are therefore designed to withstand the normal working cur rent for any length of time, but in case of an abnormally strong current they are likewise liable to become heated and destroyed.

My invention is therefore designed to thus protect rheostats from overheating; and it consists in providing a thermostat in associa tion with the parts so liable to become heated which is arranged to control such safety devices as may be employed in connection with the particular rheostat or that it may be desired to employ.

My invention is illustrated in the accompanying drawings, in which the same reference characters indicate like parts throughout the several views, and in which- Figure 1 is a front elevation of a rheostat embodying my'invention. Fig. 2 is a side elevation of the same. Fig. 3 is a diagram showing how the circuits may be arranged. Fig. 4 is a diagram of still another arrangement, and Fig. 5 is a diagram of a difi'ei'ent rheostat.

The rheostatic device shown in Figs. 1 and 2 is the same as that shown in my Patent No. 702.409, dated June 17, 1902, although it will be understood that the invention is applicable to any other type of rheostat. This device is, moreover. only generally indicated in Figs. 1 and 2, since reference may be had to the said patent for a full disclosure of the details thereof. It comprises a suitable insulating base 2, upon which are located a plurality of interlocking hand-levers 3 3, &c., which are pivoted at their lower ends upon a rod 4:, supported at its ends in bearings 5, suitably secured to the face of said insulating-base. In the brackets supporting the bearings 5 and beneath the rod 4. a second rod 6 is located, said levers 3 being provided with downwardly extending ends 7, which are adapted to strike against the rod 6 to serve as stops for the said levers when they are opened. These levers carry bridging-contacts 8, which when closed, as shown in Fig. 2, engage the common contact-bar 9 at their lower ends and the individual contactblocks 10 at their'upper ends. The resistance of the rheostat is divided into sections 11, the first section being that at the left and is included between the common eontact-bar 9 and the individual contact 10 with which the second lever engages. The remaining sections of the resistance are included between the successive individual contacts. The first lever 3 of the series may be provided with laterally-extending arms 12, which carry carbon contacts 13, adapted to engage like contacts mounted upon the bar 9 and the first contact 10. These levers are provided with interlocking catches 14: 14:, &c., by means of which it is impossible to close the levers in any except the desired order that is, beginning with the first one at the left and then the others successively toward the right, and when the first lever of the series is released all of the others are likewise released and fall away from the front of the plate. The first lover of the series is provided with a pin 15,

which is adapted to engage in the notch of the catch 16 of the armature 17 of the releasingmagnet 18 when the said lever is closed. This armature is pivoted at its lower end upon the pivot 19, so that when the magnet is deenergized it opens by gravity, and thereby releases the pin 15. This armature is also arranged to fall out of the magnetic field of the magnet 18, so that it cannot be raised until the lever 3 is closed and strikes the armature 17 and carries it to the position shown in Fig. 2. It is then attracted and maintains the lever closed until the current is cut elf from the magnet.

A motor is indicated at 20, which has its armature-circuit closed by means of conductor 21 to the first of the individual contacts 10, and thence when the first lever is closed through the contacts thereof to the common bar 9, and thence through the sections of the resistance to the last contact 10, and thence by conductor 22 to the opposite side of the circuit. The releasing-magnet 18 is, as shown, connected between the first contact 10 by means of a conductor 23, and thence by conductor 24 to the shunt field-winding 25 of the motor, and thence to the other side of the circuit, the releasing-magnet being therefore connected in series with the shunt field-winding of the motor. T/Vhen, therefore, the current on the power-circuit fails, the releasing-magnet will be deenergized and the first lever 3 will be opened, which will permit all of the others to open. This will open the armature-circuit and prevent its closure except through the said resistances.

In case the device is employed as a starting resistance, that being the purpose of the spe cific construction shown in Figs. 1 and 2, and the attendant should for any reason fail to close all of the switches or levers 3 the last section or sections 11 of the resistance would remain in circuit. The continued flow of current would therefore be at such remaining sections, and unless some measure was taken to protect them they would soon be destroyed. For this purpose l employ the thermostat 26, which is not shown in Fig. 1 and which, as shown in Fig.

2, is located within the box in the rear of the base-plate 2, containing the rheostatic resistances. The resistances, which are only shown diagrammatically in Fig. 1, are in practice formed as shown in Fig. 2 and are composed of fiat metallic strips 11, suitably connected in circuit and mounted within the casing or box 27. The thermostat 26 is placed adjacent a section of the resistance, preferably near the last section of the series, so that it can be affected by the rise in temperature of the said resistance to close the contacts 28 and 29. These contacts are included in series with the windings of the magnet 30, which is adapted when energized to close the contact 31, carried by its armature and the stationary contacts 32 in a shunt of the releasing-magnet 18, said shunt comprising the conductors 33 and 3&. hen the shunt is thus closed, the releasing-niagnet is deprived of operating-current and releases the levers 3.

The thermostat 26, it will be understood, may be of the usual or any desired pattern and may be arranged in any desired way to control the safety devices. The thermostat shown in Fig. 2 consists merely of a straight bar formed of different materials having different coefficients of expansion and carries at its free end the contact 29, which is adapted normally to be free from the contact 28, but when the temperature rises to be carried into engagement with contact 28.

The diagram of this apparatus is shown more clearly in Fig. 1, in which the thermostat 26 is seen to be in series with the extra magnet 30, together with a resistance-coil 35, which may be the shunt field-winding of the motor or an external resistance, as desired. The contact 31 of the armature of the extra magnet 30, as is observed, closes when raised the shunt composed of the conductors 33 and 3 1 of the releasing-magnet 18, which latter may be included across the line with the resistance 25, which may also be a shunt lieldwinding of the motor or other resistance. It is here clearly shown that when the thermostat is operated by the heating of the resistances it closes the circuit of magnet 30, which is actuated to close the shunt of the releasing magnet which releases the levers 3 and opens the circuit of the motor.

The arrangement of the thermostat may be varied in many ways, one variation being shown in Fig. 3, in which the releasing-magnet 18 is connected with a resistance 36 across the line, which resistance may be the shuntfield of the motor. The thermostat 26 arranged when closed by the heat of the resistance 11 to directly shunt the magnet 18, and thereby cause its denergization and the release of the levers 3.

The device shown in Figs. 1 and 2 might with slight modilication be employed for regulating purposes, in which case the last sections of resistance would probably be in circuit most of the time. In Fig. 5 l have shown a different form of ordinary regulating-rheostats, in which a pivoted arm 4:0 is adapted to sweep over a series of contacts to cutout the sections 11 of resistance. This arm may be placed at any point to secure the desired speed of the motor, at which point it is held by the dog 41, carried by the armature 42 of the retaining magnet 43, said dog engaging the teeth of the ratchet-segment 14, secured to the lever 10. The thermostat 26 is arranged upon the heating of the resistance-sections remaining in the circuit to close the shunt of the magnet 13, and thereby cause it to release the arm 40, which is returned to normal position by a suitable coiled spring 45, thereby opening the circuit of the motor.

It is obvious that still other arrangements may be made without departing from the spirit of the invention, which broadly consists in protecting a rheostat by means of a thermostat.

Having described my invention, what I claim as new, and desire to secure by Letters Patent, is-

1. The combination with a rheostat, of the movable element thereof, a retaining-magnet for said movable element, means for returning the same to its initial position, and a thermostat responsive to the heat generated by said rheostat for deenergizing said magnet when the heat produced by the rheostatic resistance exceeds a prearranged temperature.

2. The combination with a rheostat, of the movable element thereof, a retaining-magnet for said movable element, means for returning the same to its initial position, and a thermostat responsive to the heat generated by said rheostat operating to close a shunt-circuit around said magnet to deprive the same of current when the heat produced by the rheostatic resistance exceeds a prearranged temperature.

3. The combination with a rheostat, of the movable element thereof, a retaining-magnet for said movable element, means for returning the same to its initial position, a thermostat responsive to the heat generated by said rheostat, and a switch controlled by said thermostat for closing a shunt-circuit around said magnet, when the heat produced by the rheostatic resistance exceeds a prearranged temperature.

4. The combination with a rheostat, of a contact-arm therefor, a retaining-magnet for said contact-arm, means for returning the same to its initial position, a thermostat responsive to the heat generated by said rheostat, and a switch controlled by said thermostat for closing a shunt-circuit around said magnet and thereby deenergize the same when the heat produced by the rheostatic resistance exceeds a prearranged temperature.

5. The combination with a rheostat, of a plurality of contact-arms therefor, a retaining-111agnetfor said arms, means for returning them to their initial positions, a thermostat responsive to the heat generated by said rheostat, and a switch controlled by said thermostat for closing a shunt-circuit around said magnet and thereby deenergizing the same when the heat produced by the rheostatic resistance exceeds a prearranged temperature.

6. he combination With an electric motor, of a rheostat therefor, a movable element for said rheostat, a retaining magnet for said movable element connected in parallel with the armature of the motor, a thermostat responsive to the heat generated by said rheostat for deenergizing said magnet when the heat produced by the rheostatic resistance exceeds a prearranged temperature.

7. In a rheostat, in combination, a resistance adapted to be included in an electric circuit, means for adjusting said resistance, a retaining-magnet for said means, a switch for controlling a shunt-circuit around said retaining magnet, a magnet for operating said switch, and a thermostatic element associated with said resistance and responsive to changes in the temperature thereof and controlling the circuit of the last mentioned magnet, whereby when said resistance becomes heated to a predetermined degree said retainingmagnet will be deprived of current by the closing of the shunt-circuit around the same and permit said means to return to the normal position.

8. In a rheostat, in combination, a resistance adapted to be included in an electric circuit, a plurality of arms for adjusting said resistance, a retaining-magnet for said arms, a switch for controlling a shunt-circuit around said magnet, a second magnet for operating said switch, and a thermostatic element associated with said resistance and responsive to the changes in the temperature thereof and controlling the circuit of the last-mentioned magnet, whereby when said resistance becomes heated to a predetermined degree said retaining-magnet will be deprived of current by the closing of the shunt-circuit around the same and permit said arms to return to their normal position.

- In witness whereof I have hereunto subscribed my name in the presence of two witnesses.

HENRY H. CUTLER.

Witnesses:

RoB'r. V. MORTIMER, F. R. BACON.

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