US789083A - Safety device for electric currents. - Google Patents

Description

PATENT ED MAY 2, 1905.

, MGKELVEY URITES.

SAFETY DEV-ICE FOR ELECTRIC CURRENTS.

APPLICATION FILED DBO. 27, 1904.

2 SHEETSSHEET 1.

No. 789,083. PATENTED MAY 2, 1905 MOKELVEY GRITBS.

SAFETY DEVICE FOR ELECTRIC GURRENTS.

APPLICATION FILED 1330.27, 1904.

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E J IV] 71711515731; 5 W7 LYI' TOR) I 1; Y WM. Mp /4/4i UNITED STATES Patented May 2, 1905.

PATENT OFFICE. I

MOKELVEY CRITES, OF CLEVELAND, OHIO, ASSIGNOR OF TW'O-THIRDS TO WVILLIAM S. ROGERS AND OSCAR TEXTOB, OF CLEVELAND, OHIO.

SAFETY DEVICE FOR ELECTRIC CURRENTS.

SPECIFICATION forming part of Letters Patent No. 789,083, dated May 2, 1905. Application filed December 27, 1904. Serial No. 238,377.

To (tZZ whom it may concern:

Be it known that I, McKELvnY CRITEs, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented a certain new and useful Improvement in Safety Devices for Electric Currents, of which the following is a full, clear, and exact description, reference being had to theaccompanyingdrawings.

IQ My invention relates to safety devices for electric currents, and particularly to cut-offs to be employed with rheostats or controllers for motors. In the employment of such rheostats or controllers it is of the utmost impor- 5 tance that there shall be a reliable safety device, which when the current from the main has been out off will positively prevent the current from flowing to said motor until and unless the switch-lever has been moved to dead or starting position. In my application Serial No. 225,417, filed September 22, 1904, there is disclosed a safety device of this character which will automatically and positively break the circuit through the rheostat or con- 2 5 troller to the motor and which will maintain the circuit open until the switch-lever has been moved to or near its initial position. I find, however, that in operation it is important that means shall be provided for automatically moving the switch-lever to its initial position when the current to the rheostat or controller has been cut ofi. WVhen such means for returning the lever to its initial position is used without a positive automatic cut-off, there is 3 5 more or less danger that the said means (generally a spring) may deteriorate or that sufiicient residual magnetism may remain in the electromagnet, which is employed to hold the lever in full-current position against the ac- 4 tion of such means to prevent the return of said lever to its initial position, or that improper handling of the device, causing the fusing together of the lever and the contacts of the rheostat or controller, may prevent such return of the lever. As a consequence the subsequent turning on of the current will rcsult in the burning out of fuses or of the motor-armature, w1th resultant danger to life and property.

The object of my invention is to provide 5 such a safety device for use with rheostats or controllers as will embody the advantages of the automatic means for returning the switchlever to its initial position when the currentsupply has been cut off with a positive and re liable cut-ofi' additional to such lever-operating means, thereby rendering the device thoroughly safe and reliable in operation.

Referring to the drawings, Figure 1 represents a plan view of one embodiment of my invention, showing the same applied to a rheostat or controller for a shunt-wound motor, with the parts in the position which they assume when the switchlever is at its initial position. Fig. 2 represents a similar view show- 5 ing the switch-lever in position to supply the full current to the motor-armature, with the other parts in the position which they assume when the current has been cut off; and Fig. 3 represents a side elevation of the contact meni- 7 bers.

Describing the parts by reference-numerals, 1 designates the ordinary bed-plate of a rheostat or controller. Pivoted to said bedplate is a switch-lever 2, having the ordinary operating-handle 3 and adapted to engage successively the contacts 4. At its lower end the switch-lever is provided with an extension or cam 5 for a purpose to be hereinafter described. The first of these contacts is a dead-point, as will 30 appear from an inspection of the drawings, and the second contact ll is the first live or rheostatic contact. The bed-plate is provided with a connection 6 for the conductor from the main and with connections? and 8 for the 5 field and armature, respectively, of a shuntwound motor which receives its current through the rheostat or controller. The armature connection is connected with the last contact of the rheostat or controller. 9

Supported by the bed-plate in any convenient position with reference to the switchlever is an electromagnetic device 9. This device isasolenoid having upper and lower iron heads 10, a brass tube 11 between said heads, a suitable winding 12, said winding being shown diagrammatically in Fig. 2 for clearness of illustration, and a movable core 14.

The winding, as shown, is in circuit with the field of the motor. The solenoid is preferably supported in a vertical position, so that when deenergized the movable core 14 may drop freely by gravity from said solenoid. For this purpose the axis of the solenoid may be actually vertical, or it may be slightly inclined from the vertical, as herein shown. 1 prefer the latter arrangement on account of cheapness of construction, as both heads may be of the same length and may be provided with squared ends. These heads engage the armature 45 on the lever 2 to retain said lever in full-current position when the solenoid is energized. The switch-lever is pivoted to a shaft 46. A spring 47 is wound around this shaft, with one end 48 suitably attached thereto and the other end engaging the lever, the spring being so arranged as to normally hold the lever in its initial position. (Shown inliig.

1.) At the upper end of the solenoid there is provided a short core 15, (shown in dotted lines in Fig. 2,) said core being of magnetic material and being connected to a plate 16, which rests upon the upper head 10. This plate is provided with perforations for the screws 17, said screws extending through said perforations and being threaded into the upper head. The screws are not set up against the plate 16, thereby permitting a slight longitudinal movement of the core and its attached plate. The movable core 14 is of sufficient length to extend to the lower surface of the lower head when the solenoid is energized, shown in Fig. 1. Below said solenoid are the spaced contact members 18. One of these members is connected with the connection 6 for the main and the other is connected with the switch-lever 2. Between these members there is placed a block 19 of insulating material. This block is provided with a perforation 190, which may be square or angular in cross-section, as shown and described in my application Serial No. 225,417, for the passage of the rod 20 of similar shape in cross-sectionand carrying the contact member 21, which is preferably'a laminated brush. W'hen the solenoid is energized, the brush 21 closes the circuit between the contacts 18, the shape of the rod and the corresponding perforation in the block 19 preventing the brush from turning out of position to bridge the gap between the contacts. hen the switch-lever is in starting position, it lifts the setting-lever 22 and, owing to the resiliency of the brush 21, will cause considerable impact between the movable core 14 and the short core 15. The slight movement permitted said latter core by the screw 17 and plate 16 will relieve this impact. When the solenoid is subsequently energized, the mutual attraction of the two cores sustains the lower core and its connected parts.

Nith the parts as above described it will be apparent that when the current-supply to the rheostat or controller is cut off, whether the spring 47 operates to return the lever to its initial position or whether through deterioration of the spring or the residual magnetism in they electromagnetic device, or both, the lever remains in full-current position, the circuit through said rheostat or controller will be positively broken. -In the event that the spring operates the lever will be at dead position. In the event that the spring does not operate the deenergizing of the electromagnetic device will permit the gravity-operated circuit-breaker 21 to drop and positively break the circuit through the rheostat or controller. ()wing to the weight of the core 14, the rod 20, and the brush 21, any small residual magnetism that may remain in the solenoid and its parts will be insufficient to sustain the core and such parts and the circuit will be broken.

Moreover, the drop ')ing of the core weakens the residual magnetism in the electromagnetic device and makes the operation of the spring more certain and effective. In order to close 2 the circuit after it has been broken, I preferably employ the arm or lever 22, said arm or lever being pivoted to the bed-plate and having at the free end thereof a' rubber pad 23 for engaging the shoe 24 on the under side of the brush 21. The lower rounded end of the switch-lever is provided with the projection or cam 5, hereinbefore referred to, said cam or projection being located as shown in the drawings and being of such shape as to hold.

the arm 22 elevated and the brush 21 in engagement with the contacts 18 until the switch-lever shall have been moved as far as the first rheostatic. contact 41. The body of the switch-lever is suliiciently elevated above the bed-plate to pass over the lever 22, as shown in Fig. 2.

The particular construction of the gravityoperated cut-off and the combination of such cut-off with a switch-lever without any means for automatically returning such lever to its initial position forms the subject-matter of my application, Serial No. 225,417, hereinbefore referred to. The invention in this case resides in the combination of such cutoff with a switch-lever having means for automatically returning it to its initial position when the current-supply to the rheostat or controller is cut off.

W hile I have described my invention in detail, it will be obvious that such details may be departed from more or less without avoiding the spirit of my invention, and I do not propose to be limited to such details except as they may be positively included in the claims or may be rendered necessary by the prior state of the art.

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

1. The combination of a rheostat 01' controller, aswitch-lever therefor, an electromag netic device adapted when energized to hold said lever in full-current position, means for moving said lever to its initial position when said device is deenergized, and means independent of said lever for positively breaking the circuit through the rheostat or controller when the current-supply thereto is cut oil, substantially as specified.

2. The combination of a rheostat or controller, a switch-lever therefor, an electromagnetic device in circuit with said rheostat or 6. The combination of a rheostat or controller having a switch-lever, an electromagnetic device adapted when energized to hold l said lever in full-current position, a verticallycontroller and adapted when energized to hold said lever in full-current position, means for moving said lever to its initial position when said device is deenergized, and means independent of said lever for positively breaking the circuit through the rheostat or controller when the current-supply thereto is cut ofi", substantially as specified.

3. The combination of a rheostat or controller, a switch-lever therefor, an electromagnetic device in circuit with said rheostat or controller and adapted and arranged to hold said lever in full-current position when current is supplied to said rheostat or controller, a circuit making and breaking device adapted to be held in circuit-closing position by said electromagnetic device when current is being supplied to said rheostat or controller and to positively break by gravity the circuit when the current-supply is cut off, and means for moving said lever to its initial position when the current-supply is so cut ofi, substantially as specified.

4. The combination of a rheostat or controller, a switch-lever therefor, an electromagnetic device adapted when energized to hold said lever in full-current position, a vertically-movable member operated by said device, a pair of spaced contacts below said lever, one of said contacts being connected to the lever and the other to the source of current-supply, a circuit-closer adapted to connect said contacts and carried by said movable member, and means for moving said lever to its initial position when the currentsupply to the rheostat or controller is cut off, substantially as specified.

5. The combination of a rheostat or controller, a switch-lever therefor, an electromagnetic device adapted when energized to hold said lever in full-current position, means for supplying current to the said rheostat or controller and said device, a device arranged to be held in position to close the circuit through the rheostat or controller when the electromagnetic device is energized and by its gravity to positively break the circuit when the electromagnetic device is denergized by a cessation of current-supply to the rheostat or controller, and means for moving said lever to its initial position when the currentsupply is cut ofl, substantially as specified.

movable member operated by said device, a pair of spaced contacts below said device, one of said contacts being connected to the lever and the other to the source of current-supply, a circuit-closer adapted to connect said contacts and carried by said movable member, means for moving said lever to its initial position on the cessation of current-supply to the electromagnetic device, and means carried by said lever for moving the circuit-closer into position to bridge the space between said contacts when said lever is at or near its initial position, substantially as specified.

7. The combination of a rheostat or controller, a switch-lever therefor, an electromagnetic device adapted when energized to hold said lever in full-current position, means for supplying current to said rheostat or controller and said electromagnetic device, a device arranged to be held in position to close the circuit through the rheostat or controller when the electromagnetic device is energized and by its gravity to positively break the circuit when the electromagnetic device is deenergized by a cessation of current-supply to the rheostat or controller, means for moving said lever to its initial position when said electromagnetic device is deenergized, and means operated by the lever for resetting such gravity device to close the circuit when said lever is at the dead position and to maintain it so closed until the lever is on the first rheostatic contact, substantially as specified.

8. The combination of a rheostat or controller havinga switch-lever, a spring tending to hold said lever in its initialposition, an electromagnetic device in circuit with said rheostat or controller and adapted to hold said lever in full-current position against the action of said spring, and means independent of said lever for automatically breaking the circuit through said rheostat or controller when said electromagnetic device is deenergized by a cessation of the current-supply to the rheostat or controller, substantially as specified.

9. The combination of a rheostat or controller, a switch-lever therefor having means for returning it to initial position, and a single electromagnetic device adapted, when energized, to hold said lever in full-current position against the action of said means and to release said lever when deenergized, said device having means for automatically and positively breaking the circuit through the rheostat or controller on the cessation of the current-supply thereto, substantially as specified.

10. The combination of a rheostat or controller, a switch-lever therefor, a spring tending to retain said lever in its initial position, current-supply thereto, substantially as speciand a single electromagnetic device adapted, lied. 1

when energized, to hold said lever in full-cur- In testimony whereof I afiix my signature rent position against the action of said spring in the presence of two witnesses.

5 and to release said lever when deenergized, MCKELVEY CRITES. I

said device having means for positively and Witnesses: automatically breaking the circuit through J. B. HULL,

the rheostat or controller 0n cessation of the B. W. BROGKETT.

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