US3460079A - Polarized electromagnet - Google Patents

Description

ug- 5, 1969 e. DI MARCO 3,460,079

' POLARIZED ELECTROMAGNET Filed July '7. 196? 2 Sheets-Sheet l All@ 5 1969 B. DI MARCO 3,460,079

POLARI ZED ELECTROMAGNET Filed July 7. 196'? 2 Sheets-Sheet 2 4/ -/d, lf I z l r 31 ,C ...E I a- .5. M4# 1 l l if? Jr A l# L JA L 4Z im Q 55.5.4 //f /5/ Mik-i Wu fm W@ @M5/Q A M United States Patent O 3,460,079 POLARIZED ELECTROMAGNET Bernard Di Marco, Lincoln Park, Mich., assignor to I-T-E Imperial Corporation, Philadelphia, Pa., a corporation of Delaware Filed July 7, 1967, Ser. No. 651,912 Int. Cl. H01f 7/08 U.S. Cl. 335-230 8 Claims ABSTRACT OF THE DISCLOSURE An electromagnet unit biased to open position is maintained in closed position by a permanent magnet that is part of the yoke assembly. The latter is generally E-shaped and consists of a first generally U-shaped stack of lamination providing the outer legs of the E, and a second generally I-shaped stack of lamination providing the center leg of the E. E-shaped non-magnetic stainless steel retainers maintain the lamination stacks in operative positions, with these operative positions being such that the stacks and retainers cooperate to form a pocket wherein a slablike ceramic permanent magnet is retained. The armature is constructed of a Hat sheet of steel.

This invention relates to electromagnets in general and in particular relates to a novel construction of an electromagnet that can be energized and deenergized by the application of instantaneous voltage signals and will remain in the position dictated by the last applied signal even if all power is removed from the operating coil.

Copending application Ser. No. 568,249 filed July 27, 1966, entitled Industrial Control Relay with B. Di Marco et al. as inventors and assigned to the assignee of the instant invention, discloses an electromagnetic contactor of a type often referred to as an industrial control relay. Briey, an electromagnetic contactor is a multi-pole switch having biasing means urging the switch arms to a iirst position and an electromagnet which when energized acts against the biasing means to operate the switch arms to a second position. For the most part, prior art electromagnetic contactors are so constructed that the operating coil must be continuously energized to maintain the switch means in the second position.

This often leads to undesirable conditions. In particular, by momentary loss of control power, the magnet coil will be deenergized and the switch means will not be maintained in its second position. Further, continuous currents flow through the magnet operating coil requiring excessively large winding size to prevent overheating.

In order to overcome these disadvantages, for some applications the prior art has provided mechanical latches and permanent magnet latches to maintain the switch arms in the second position against the force of biasing means urging the switch arms to the first position. The instant invention is concerned with the permanent magnet type latch for electromagnetic contactors.

In particular, the device of the instant invention includes a novel construction for an E-shaped magnet yoke assembly including a permanent magnet. High strength permanent magnets of convenient shapes are readily constructed of ceramic material. In the case of a magnet of sheet-like or slab-like shape, the magnetization axis may be perpendicular to the plane of the slab as in the device of the instant invention. The E-shaped yoke assembly provides a pocket for the slab without lshorting the magnet by utilizing non-magnetic retainer plates constructed of stainless steel to maintain two stacks of lamination in operative positions. The rst stack is generally U-shaped and provides the relatively narrow outer legs of the E while 3,460,079 Patented Aug. 5, 1969 the second stack is generally I-shaped and provides the relatively wide center leg ofthe E about which the electromagnet operating coil is wound. The armature is simply a flat sheet of steel secured to means for connecting the armature to a movable contact carrier.

Accordingly, a primary object of the instant invention is to provide a novel construction for an electromagnet device having a permanent magnet latch.

Another object is to provide an electromagnet of this type having a novel yoke assembly construction including a ceramic permanent magnet.

Still another object is to provide an electromagnet of this type in which the yoke assembly includes two stacks of lamination maintained in operative positions by nonmagnetic sheet-like members with the stacks and sheetlike members cooperating to form a pocket wherein a plate-like permanent magnet is disposed.

These objects as well as other objects of the instant invention will become readily apparent after reading the following description of the accompanying drawings in which:

FIGURE 1 is an exploded perspective showing the main assemblies of an electromagnet constructed in accordance with the teachings of the instant invention.

FIGURE 2 is an exploded perspective of the yoke assembly of FIGURE l.

FIGURE 3 is a side elevation of the yoke assembly.

FIGURE 3A is an end view of the yoke assembly looking in the direction of arrows 3A--3A of FIGURE 3.

FIGURE 4 is a side elevation of one of the non-magnetic retainer plates of the yoke assembly.

FIGURE 4A is a cross-section taken through lines 4A- 4A of FIGURE 4 looking in the direction of arrows 4A- 4A.

FIGURE 5 is a plan view of the armature assembly.

FIGURE 5A is a side elevation of the armature assembly looking in the direction of arrows SA-SA of FIG- URE 5.

FIGURE 6 is an electrical schematic illustrating a control circuit including the electromagnet of FIGURE l.

As best seen in FIGURE 1 electromagnet 10, constructed in accordance with the teachings of the instant invention, includes E-shaped yoke assembly 11, coil assembly 12 having aperture 12a to receive the center leg of yoke assembly 11, and armature assembly 13. With particular reference to FIGURE 2, itis seen that yoke assembly 11 consists of generally U-shaped lamination stack 14, generally I-shaped lamination stack 15, rectangular plate-like ceramic permanent magnet 16, E-shaped nonmagnetic stainless steel retainer plates 17, 17 and six rivets 18 for retaining elements numbered 14-17 together as a unitary structure.

Lamination stack 14 provides the relatively narrow outer legs 14a, 14b and base 14c of a generally E-shaped magnet yoke while lamination stack 15 provides the relatively wide center leg 15a of the magnet yoke. The lower ends of lamination stack 15 is provided with lateral projections 15b, 15C which, as best seen in FIGURE 3, extend beyond the shorter edges of permanent magnet 16 to act as a flux collector. However, projections 15b, 15e terminate a considerable distance from outer legs 14a, 14b so as not to short-circuit the flux generated by permanent magnet 16.

Permanent magnet 16 is slightly wider than lamination stacks 14, 15 in order to provide suflicient permanent magnet flux for magnetically latching electromagnet 10 against the force of return spring 34 (FIGURE 6). Thus, each retainer plate 17 is provided with a shallow generally rectangular recess 19 (FIGURE 4A) to receive the longer edges of permanent magnet 16. Shallow recess 20 (FIG- URE 3) wherein permanent magnet 16 is disposed is 3 formed through the cooperation of lamination stacks 14, 15.

As seen in FIGURE 5 armature assembly 13 consists of magnetic plate armature 40 with connecting member 41 welded or otherwise secured to the upper surface of armature 40. Central portion 41a of member 41 is formed away from the upper surface of armature 40 to provide a shallow passage 42 extending the full width of armature 40 at the center thereof. In a manner well-known to the art, aperture 42 is adapted to receive means (not shown) for mechanically connecting armature assembly 13 to the movable contacts of a contactor for operation thereof.

As seen in the schematic of FIGURE 6, coil assembly 12 includes ON coil 21, OFF coil 22 and semiconductor diode 25 paralleled by surge protective device 24. Coils 21, 22 are multiturned windings each having an end thereof connected to one electrode of diode 25 by conductor 26 internally of coil assembly 12. The other electrode of diode 25 is connected to terminal 30 extending externally of coil assembly 12 for connection to one terminal L-1 of an AC control power source (not shown). The other ends of coils 21, 22 are connected to insulation covered conductors 21a, 22a, respectively, which extend externally of coil assembly 12. Elements 21, 22, 24 and 25 are encapsulated in a suitable plastic material forming body 23 thereby providing coil assembly 12 as a unit which is highly resistant to mechanical shock and other harmful environmental conditions including high humidity.

Switches 28, 29 (FIGURE 6) are normally closed and normally opened, respectively. Switch 28 is interposed between lead 21a and one of the stationary contacts of ON control switch 31 Whose other stationary contact is connected to the other terminal L-2 of the AC control voltage source. Switch 29 is interposed between lead 2lb and one of the stationary contacts of OFF control switch 32 whose other stationary contact is connected to terminal L-2.

Operation of electromagnet proceeds as follows. Starting with armature assembly 13 in its released position remote from yoke assembly 11, having been moved there by return spring 34 (FIGURE 6), ON control 31 is closed to complete an energizing circuit for ON coil 21, such circuit extending from terminal L-l, through diode 25 acting as a halfwave rectifier, ON coil 21, switch 28 and control 31 to terminal L-Z. With this energizing circuit completed current flows through ON coil 21 in a direction generating flux which aids the liux generated by permanent magnet 16 and is of sufficient magnitude to operate armature assembly 13 against the force of return spring 34 toward yoke 11 to latched position. In moving to its latched position, armature assembly 13 opens switch 28, closes switch 29, and also operates additional switch units of the contactor (not shown).

When ON coil 21 is deenergized by opening ON control 31, armature assembly 13 remains in latched position in that the flux of permanent magnet 16 is of sufficient strength to maintain armature 40` in engagement with lamination stacks 14, 15. Closing of OFF` control 32 at this time completes an energizing circuit for OFF coil 22, such circuit being from terminal L-1, through halfwave rectifier diode 25, OFF coil 22, the now closed switch 29, OFF control switch 32 to terminal lf2. Current flowing in OFF coil 22 generates liux in the magnetic frame comprising armature 40 and lamination stacks 14, 15, opposing the fiux of permanent magnet 16 with the net flux being of insufficient strength to maintain armature assembly 13 latched against the force of return spring 34. Thus, return spring 34 operates armature assembly 13 to its released position shown in FIGURE 6 and in so doing opens switch 29 and closes switch 28 so that upon subsequent operation of ON control 31 the energizing circuit for ON coil 21 may be completed.

It is noted that in FIGURE 6 the arrows for the respective coils are not to indicate current flow but rather to indicate that the fluxes generated by coils 21, 22 are in opposite directions through magnetic frame 14, 15, 40 when the respective coil energizing circuits are completed,

Thus, it is seen that the instant invention provides a novel construction for an electromagnet having a permanent magnet latch. In particular, the permanent magnet is a plate-like ceramic member in a plane perpendicular to and at the base end of the center leg of an E-shaped yoke. The magnetic frame and the permanent magnet elements of the yoke assembly are positioned and maintained as a unitary structure by stainless steel side plates.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. An electromagnetic device including a magnetic frame having a first and a second section; coil means mounted in magnetic coupling relation to said frame whereby a flow of electric current in said coil means generates magnetic flux in said frame; an assembly including said first section; biasing means urging said assembly and said second section away from each other to a released position; said assembly also including a permanent magnet of suflicient holding power to maintain said assembly and said second section adjacent to each other in a latched position when said coil means is deenergized; a iirst and second energizing circuit for said coil means; said first circuit when energized causing current fiow in said oil means in a direction generating a rst magnetic flux aiding a second magnetic flux of said permanent magnet with the resultant of said first and said second fluxes being of sufiicient strength to overcome said biasing means and operate said assembly and said second section to said latched position; said second circuit when energized causing current fiow in said coil means in a direction generating a third magnetic flux opposing said second iiux with the resultant of said second and said third fluxes causing said assembly and said second section to be released from each other enabling them to be operated by said biasing means to said released position; said first section being generally E-shaped with a base, relatively narrow outer legs and a relatively wide center leg; said legs extending generally in the same direction from said base, said magnet positioned at the base end of said center leg and interposed between said center leg and said center leg and said base; said magnet comprising a plate-like member magnetized perpendicular to the plane thereof; said legs being generally perpendicular to said plane, said first section comprising a first stack of generally U-shaped laminations including said base and said outer legs, and a second stack of generally I-shaped laminations including said center leg.

2. A device as set forth in claim 1 in which said second stack at the end thereof closer to said magnet includes first and second projections extending in opposite directions toward said outer legs but terminating short thereof.

3. A device as set forth in claim 2 in which said magnet is rectangular and said projections extend beyond the shorter sides of said magnet.

`4. A device as set forth in claim 1 in which said assembly includes retainer means for maintaining said stacks and said magnet in operative positions; said retainer means including first and second side plates of relatively low magnetic permeability with said stacks and said magnet positioned between said side plates.

S. A device as set forth in claim `4 in which each of References Cited said plates are constructed of stainless steel. UNITED STATES PATENTS 6. A device as set forth in claim 1 in which said stacks 2,876,397 3/1959 Wasson 335 230 are provided with formations cooperating to form a shal- 3 153 178 10/1964 Martin 335 234 low recess wherein said magnet is disposed.

7. A device as set forth in claim 1 in which said second FOREIGN PATENTS section includes an armature part having a at surface 245,088 1&0/ 1966 Austria. which engages said legs when said second section is in said 983,303 2/ 1965 Great Britain.

latched position.

8. A device as set forth in claim 7 in which said arma- 10 G' HARRIS Prlmary Exammer ture part comprises a single sheet of material having rela- U.S. Cl. X.R. tively high magnetic permeability. 317-150; 335-253

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