US1721995A - Electromagnet - Google Patents

Description

J. HARRIS ELECTROMAGNET July 23, 1929.

Filed Sept. 18, 1924 Inventor Jesse Harris M- W dlttorney.

Patented July 23, 1929.

UNITED STATES PATENT OFFICE.

JESSE HARRIS, OF LA FAYETTE, INDIANA, ASSIGNOR T0 DUNCAN ELECTRIC MANU- FACTURING COMPANY, OF LA FAYETTE,

INDIANA, A CORPORATION OF ILLINOIS.

ELECTROMAGNET.

Application filed September My invention relates to electro-magnets and resides in so constructing and relating the armature as to delay or prevent the opera tion or actuation of the armature load instantly after the energization of the ma net. To this end, I construct the armature o? the magnet with two sections in lost motion relation. the magnet pulling upon one armature section and, through the medium of this section, upon the other section, these armature sections being so related that the first section moves before moving the second. The two sections of the armature desirably thereafter move together to jointly operate or actuate the armature load which is coupled with the second armature section that is the later to move.

The magnet of my invention is of particular service when employed to operate a circuit breaker. It frequently happens that a surge of current flows over a line that does no ma .crial damage, be 'ause of its extremely short duration, although it may be of a high value. If the breaker should open. on such short time overloads, it would add an increased burden to the maintenance of the service, necessitating frequent resetting of the circuit breaker. If the operating magnet of the circuit breaker is constructed in accordance with my invention, a predetermined interval of time may intervene before the lucakcr operates to enable the surges calculated for to subside.

The accompanying drawing illustrates the employment of the preferred form of magnet of my invention as the operating magnet of a circuit breaker, a circuit to which the breaker may be applied being diagrammatically illustrated.

The circuit illustrated includes a generator of alternating current 1, to which the inven tion is not to be limited, however. Current supplied from the generator to the load 2 by way of the mains 3, 4. The circuit breaker switch is included in the main 3, this switch having two metallic complemental contacts, one in the form of a contact block 5 and the other in the form of a switch arm 6, composed of a plurality of curved spring blades. The circuit breaker operating electro-magnet 7 has its winding serially included in the main 3. The armature of this magnet, later to be fully described, is in loose connection with one end of a link 8 Whose other end is connect 18, 1924. Serial No. 738,513.

ed with a toggle link 9 which is pivoted upon a bracket 10. A second toggle link 11 connects the link 9 with the switch arm 6. A hand lever 12 is fixed upon the link 9 on the other side of its pivot therefrom. The switch is closed by the handle and is automatically opened when excessive current flows in the circuit for a sufficient length of time, this excessive current increasing the energization of the magnet to cause the magnet ar mature to operate upon the link 8 which, in turn, operates upon the toggle link 9 to break the toggle and open the switch.

The magnet of my invention, as it is preferably constructed, has its winding disposed about the closed or imperforate hollow cylinder or casing 13 which is preferably made of non-magnetic material, such as brass. The armature is composed of two sections, the section 14 being in the form of a floating iron core which is contained within the interior of the casing 13 and is movable longitudinally thereof. The motion of this armature section is mechanically retarded as by means of the oil 15 which, together with said armature section, substantially fills the interior of said casing. The thickness of the oil and the clearance between the core and the casing delay the movement of the core, which with its casing constitutes one form of dash pot. The remaining section 16 of the armature is an iron bar pivoted between its ends upon the lower end of the bracket 10, the link 8 passing through this armature section and having av head 17 which is engaged by the armature section 16, when the armature is attracted, to open the circuit breaker switch. The urinature section 16 has an elliptical hole 18 through which the lower end of the casing projects. The core 14 normally projects be low the bottom face of armature section 16 to such an extent as to permit the core 14 to be moved upwardly alone an appreciable distance before the flux will cause the armature section 16 and the armature section 1-1 to thereafter move upwardly together. The bottom of the casing 13 constitutes a support or abutment holding the armature section 14: in position to be moved part way alone, that is, without initially moving the armature section 16, when the magnet is energized. An appreciable period intervenes between the energi'zjat-ion of the magnet and the movement of the load operating section 16 of the 311113 ture, the length of the period being determined by the design of the instrument and the character of overload.

From the description hitherto given it will be understood that the armature section 1'-l responds before the armature section 16. lhis is due to the fact that the armature section 16 is outside of the range of the mag net coil, directly, the field established by the magnet coil acting upon the armature section 16 through the inermediation of the armature section 14, the dash pot 13 bei g of nonmagnetic material. It will also be observed that the armature section 1% passes through the plane of the armature section 16, when the magnet is deenergized, and projects below the armature section 16 as well above it. hen the magnet is initially energized the magnetic flux generated by the magnet winding operates, in part, to lift the armature section 1 1, a portion of this fiux passing through the armature section 1 1 and straying from the bottom thereof to draw downwardly upon the armature section 16 to over come any tendency on the part of the armature section 15L to instantly draw the armature section 16 upwardly when the section 14: responds to the magnetic pull of the mag net. When the magnet is deenergized and the armature is unattracted, the armature section 14 has a portion in the space between the energizing portion of the magnet and the armature section .16 so that when the magnet is energized, the armature section 14 will be initially materially subject to greater pull that the armature section 16.

Changes may be made without departing from my invention.

Having thus described my invention, 1 claim 1. An electro-magnet including the winding thereof;a casing of non-magnetic material about which said winding is disposed and having one end projecting beyond one end of the winding, the hollow interior of the casing being also surrounded by the winding and extending, with the aforesaid casing end, beyond the aforesaid end of the winding; and an armature formed in two individually and relatively movable sections, one of whicn is contained within the aforesaid casing and is movable along the axis of the winding within and with respect to the casing and which is constrained to have its outer end in proximity to the aforesaid projecting end of the casing when the magnet is deenergized, the inner end of this armature section being within the range of the magetic field due to the magnet winding when the magnet is energized, the other armature section being upon the exterior of the aforesaid casing that extends outwardly from the winding beyond this armature section and being positioned to be further from the influence of the winding than the first armaturesection when the magnet is initially energized, the first armature section extending away from the winding beyond the sec ond armature section when the magnet is deenergized to enable the first armature section to be moved throughout a part of its range of movement without appreciably moving the second armature section when the magnet is initially energized and to enable the first armature section in completing its movement to move the second armature section upon continued energization of the magnet.

2. The structure of claim 1 wherein a motion retarding fiuid is also contained within the casing and of sufiicient quantitv to retard the movement of the armature section that is within this casing.

In witness whereof, I hereunto subscribe my name. i JESSE IARRIS.

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