US3453569A

US3453569A - Electromagnetic switching device

Info

Publication number: US3453569A
Application number: US664796A
Authority: US
Inventors: Marvin E Ostby
Original assignee: Cutler Hammer Inc
Current assignee: Cutler Hammer Inc
Priority date: 1967-08-31
Filing date: 1967-08-31
Publication date: 1969-07-01
Anticipated expiration: 1986-07-01
Also published as: GB1167702A

Description

M. E. OSTBY July 1', 1969' ELECTROMAGNETI C SWITCHING DEVICE Sheet r4 Filed Aug. 31, 1967 July 1, 1.969 M. E. OSTBY ELECTROMAGNETIC SWITCHING DEVICE Filed Aug. 31, 1967 EWQ July 1,1969 M. E. OSTBY ELECTROMAGNETIC SWITCHING DEVICE Filed Aug. 31, 1967 7 w United States Patent 3,453,569 ELECTROMAGNETIC SWITCHING DEVICE Marvin E. Ostby, Brookfield, Wis., assignor to Cutler- Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Filed Aug. 31, 1967, Ser. No. 664,796 Int. Cl. H01h 6'7/02 US. Cl. 335-132 12 Claims ABSTRACT OF THE DISCLOSURE SUMMARY OF THE INVENTION This invention relates to electromagnetic switching devices such as contactors and relays. A primary object of the invention is to provide a device of this type which is compact in size to take up a minimal panel'area and yet effectively handle current loads of high designated ratings.

Another object of this invention is to provide a device of the type described wherein the parts which require service are readily accessible, easily replaceable, and formed to be replaced in only the proper orientation.

It is still another object of this invention to provide a device of the type described wherein removal of the stationary contacts may be accomplished without disturbing the terminal Wiring.

It is a further object of this invention to provide a device of the type described which has provisions for mounting an electrical interlock switch to either of two sides of the device, and wherein the interlock switch may be readily removed from one side and mounted on the other side of the device maintenance personnel in the field.

It is a further object of this invention to provide a device of the type described wherein the same provisions utilized for mounting the electrical interlock switch may instead be used for mounting a mechanical interlock member of the devie and to an adjacent device of the same type.

These and other objects will become more apparent in the following description when read in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIGURE. 1 is a top plan view of an electromagnetic switching device constructed in accordance with the invention;

FIG. 2 is a front elevational view of the device of FIG. 1;

FIG. 3 is a right-hand side elevation-a1 view of the device as viewed in FIG. 2;

FIG. 4 is a view of the underside of the device as viewed in FIG. 2 but in a disassembled relationship to show a removable cover, magnet housing assembly and base assembly;

FIG. 5 is a front view of the device with the cover and certain magnet components removed;

FIG. 6 is a front view of the base assembly of the device with the magnet housing assembly removed;

FIG. 7 is a sectional view taken along line 77 of FIG. 2;

FIG. 8 is a sectional view taken generally along the irregular line 8-8 of FIG. 2;

FIG. 9 is a sectional view of an auxiliary switching device taken along the line 99 of FIG. 7;

FIG. 10 is an exploded isometric view of a stationary contact and wiring terminal assembly and a fragment of the base;

FIG. 11 is a fragmentary view showing the armature mounting;

FIG. 12 is an isometric view of the underside of the coil member;

FIG. 13 is a front elevational view with portions broken away, of a pair of the devices mounted side-by-side and a mechanical interlock member mounted therebetween; and

FIG. 14 is a sectional view taken generally along the line 14-14 of FIG. 13, showing one of the devices in an energized state.

DESCRIPTION OF THE PREFERRED EMBODIMENT The particular embodiment of the device incorporating the invention is shown in the drawings as a three pole electrical contactor. The contactor comprises three basic molded, insulating sections, or components, which consist of a cover 2, a magnet housing 4, and a base 6. A metal mounting plate 8 is secured to the rear of the base 6 and is suitably apertured to facilitate mounting the contactor to a control panel or the like. Since such panels are generally in a vertical plane, the contactor has been shown in a position relative to being mounted on such a panel, even though the latter has not been shown.

A prime consideration in the design of such control devices is that the devices be readily serviceable in the field. To this end the molded cover 2 is provided with a pair of captivated round head screws 10 which may be loosened from the front of the device to allow the cover to be removed linearly toward the front to expose the magnet components of the device. An armature 12 is received between the outer ends of a pair of

push bars

16 and 18. The ends of armature 12 seat within

respective slots

16a and 18a formed on the inner surfaces of the

push bars

16 and 18, the slots being open to the upper surfaces of the respective push bars as seen best in FIG. 11. It may also be seen in FIG. 11 that the opening of slot 18a is smaller than the corresponding opening of slot 16a and is also smaller than the larger end of the armature 12. This insures that the armature always be assembled in the correct orientation to the device.

Each of the

push bars

16 and 18 are further provided with an opening 161; .and 18b which communicates between the respective slots, 16a and 18a, and exterior surfaces of the bars as seen in FIGS. 7 and 8. An armature retaining spring 20 is provided with upturned ends which extend through the

openings

16b and 18b and engage exterior surfaces of the push bars to position the spring 20 over the armature 12. The spring 20, being deformed by the armature, presses armature 12 tightly against the inner edges of the

slots

16a and 18a. Additionally, spring 20 serves as an effective cushion member for the protection of impact forces delivered in operation of the relay by allowing the

slide bars

16 and 18 to compress the ends of the spring further towards the armature 12 when it seats upon a core 22. The inner edges of the slots have outwardly extending tabs adjacent the open ends thereof to keep the armature from sliding upwardly out of the slots. To remove the armature 12 from the

push bars

16 and 18, the armature must be tipped outward against the bias of spring 20 to clear the projecting tabs and then slid upwardly through the free ends of the slots. The spring 20 may then be removed from the push bars.

Upon removal of the armature 12 and spring 20 a coil element 14 may next be removed from the magnet housing 4 by pulling it outwardly toward the front of the device. The coil element 14 is an encapsulated, twin coil member having a pair of openings 14a which each receive one leg of a laminated C-shaped core 22.

The coil element is further provided with a pair of blade terminals 14b (FIG. 12) which electrically engage respective ones of a pair of spring clip terminals 24 mounted on the base 6 when the coil is inserted in the device.

With reference particularly to FIG. 7, it may be seen that the coil element 14, when inserted in place, seats against an inner wall of magnet housing 4. The molded cover 2 has a plurality of helical compression springs 26 extending from its rear surface which bear against the front surface of coil element 14 to maintain the coil element firmly in place upon replacement of the cover. Cover 2 is further provided with an offset portion 2a along its upper edge to expose a portion of the coil 14 to view to reveal various coil ratings and other such indicia imprinted thereon. The front surface of the cover 2 is also provided with a pair of rectangular openings 2b into which project rectangular bosses 16c and 180 formed on the extreme outer ends of

push bars

16 and 18 to give a visual indication of the operative state of the contactor. In its unoperated state, the outer ends of the bosses 16c and 180 are substantially flush with the outer cover surface. When the contactor is operated, the bosses are withdrawn within the housing to indicate the energized condition.

In further keeping with the consideration of ready serviceability in the field, the contactor is designed to provide direct access to the contacts independently of the removal of the cover. The entire magnet housing 4 with the cover 2 secured thereto may be removed by loosening a pair of captivated screws 28 from the front of the device and pulling the magnet housing 4 linearly toward the front. To afford a visual distinction between screws and 28, the latter have been provided with hexagonally shaped, slotted heads. Upon removing the coil element from the device the blade terminals 14b of the coil element are disengaged from the terminal clips 24 which eliminates disconnecting any wires from the coil.

As seen in FIG. 6, the removal of the magnet housing 4 exposes three pairs of stationary contact assemblies 30 for inspection. Replacement of a contact assembly 30 may be made by removing a single screw 32 as seen particularly in FIG. 10. The contact assembly 30 comprises a substantially Z-shaped metal bar 30a having a pair of outwardly extending Wings 30b along its vertical portion. The upper horizontal leg of the bar 30a has a clearance opening 300 for the screw 32 while the lower horizontal leg has a contact tip secured thereto. Contact 30 is further provided with a hole 30d formed in the vertical leg portion (FIG. 10) into which a tool may be inserted to facilitate removal of the contact from the base. Also depicted in FIG. 10 is a fragment of the base 6 showing a stationary contact mounting pocket 6a which receives the wings 301g of the stationary contact assembly. A shelf is provided in base 6 at the upper end of each pocket 6a and has a threaded opening 6b to receive the screw 32. Each shelf is provided with a pair of side walls which extend to the front surface of the base 6, and one of these walls has a vertical keyway 60 formed therein.

A wiring terminal 34 is shown in FIG. 10 and is merely representative of the various wiring terminals used on the device. The wiring terminals 34 are all substantially Z-shaped, having a clearance hole 34a for screw 32 in one leg and a threaded hole 34b in the other leg to receive the wire securing means. The leg of the terminal member which contains the clearance hole 34a also has a key tab portion 340 formed thereon to project outwardly of one side or the other, the exact side and location of the key determining into which pocket of base 6 the terminal may be placed. The connecting portion of the terminals 34 which joins the two legs thereof together may be of short length as in FIG. 10 or longer as seen in "the lower part of FIG. 8. Also, a plural terminal may be used as shown in the upper part of FIG. 8 wherein a second terminal is welded to the connecting portion of the first terminal.

To replace a faulty contact assembly 30, the screw 32 is removed, the contact assembly is lifted or flipped out of the slot 'by inserting a screw driver tip or the like into the hole 30d and a new contact is slid in. It is not necessary to disconnect the wiring terminal 34 nor to remove the terminal from the pocket. However, in the event the terminal is removed from the pocket, the key 340 and keyway 6c combinations will insure that the proper terminal and wire are replaced in the proper pocket. It can be seen that the contact assembly 30 overlies the wiring terminal 34 within the pocket and the two members are held securely in place by the screw 32 which is tightened into hole 6b.

The movable bridging contacts 36 of the contactor are mounted in a contact carrier 38 which is removed as a part of the magnet housing 4 and may easily be examined by inspection. The contact carrier 38 is secured between the inner ends of push bars 16 and 18 by pairs of screws 50 which pass through clearance holes in the push bars to take into threaded openings in the ends of the carrier 38. The contacts 36 are maintained in their operational position by conventional retaining clips 40 which may be disengaged from the contacts to replace the latter.

The U-shaped magnet core member 22 is held within a pocket of the magnet housing 4 by a steel strap 42 which is secured to the housing to overlie the bight of the core. A pair of screws 44 (FIG. 5) pass through clearance openings in the housing from the rear surface thereof to take into threaded openings of the strap to tighten the strap against the housing. A leaf spring 46 is disposed between the core 22 and the rear surface of the pocket to bias the core outwardly against the strap 42 and to provide a second cushioning means for the device upon operation.

Magnet housing 4 is further provided with a pair of

openings

4a and 4b which communicate between the front and rear surfaces of the housing along two sides thereof and which receive the push bars 16 and 18, respectively. The opening 4b is made larger than the opening 4a to accommodate the larger push bar 18, the latter of which will not fit into the smaller opening 4a. Thus the push bars must always be replaced in the same position from which they were removed which insures that the armature 12 will always be oriented the same with respect to the core 22.

Each of the openings, 4a and 4b have a pair of projections 4c formed on the side walls of the openings in an opposed relationship. The push bars 16 and 18 are further provided with

windows

16d and 18d (FIGS. 7 and 8) which have inwardly extending projections at their opposite ends for positioning helical compression springs 48 within the windows. The inner ends of springs 48 rest upon the projections 4c within the

openings

4a and 4b. Inward movement of the push bars compresses the springs 48 between the outer end of

windows

16d and 18d and the projections 4c to provide an outward bias to the push bars and the connected armature 12 and carrier 38.

An electrical maintaining interlock 52 is provided for the contactor and consists of a molded housing 54 with a cover 56 secured thereto by rivets 58 or the like. Housing 54 has a pair of bosses 60 extending to one side which fit into recesses 6d of contactor base 6. The bosses 60 are provided with clearance openings for a pair of screws 62 which pass therethrough to take into threaded holes 6e in the recesses 6d to secure the interlock 52 to the base 6. The recesses 6d and screws 62 are covered by the magnet housing 4 when it is assembled to the contactor base 6 to thereby prevent removal of the interlock with= out first removing the magnet housing.

With reference particularly to FIG. 9, which is a view of the interlock 52 taken at the juncture of the housing 54 and the cover 56, it can be seen that there is provided two pairs of stationary contact and

terminal assemblies

64 and 66. An insulating movable contact carrier 68 is mounted within the housing 54 for reciprocal movement therein. Carrier 68 has two bridging

contact members

70 and 72 mounted within a window 68a to bridge

stationary contacts

64 and 66, respectively.

A pair of insulating retaining members 74 are provided to interfit with the bridging contact members and the edges of openings 68a to maintain the bridging members in position within the opening in a manner well known in the art. The retaining members 74 also have domed projections formed thereon to serve as seats for the ends of a helical compression spring 76 which coacts therebetween to bias the bridging

members

70 and 72 against the ends of the opening 68a.

A second helical spring 78 is provided to coact between one end of carrier 68 and an insulating spring seat 88 placed in the housing 54 to bias the carrier outwardly of the housing. The inner end of carrier 68 is guided for linear movement within the housing 54 by a pair of H- shaped bearing inserts 82 formed of nylon or other suitable bearing material. The outer end of carrier 68 is provided with an L-shaped hook portion 86b which receives a complementally formed hook on the carrier of an auxiliary switch (not shown) which may be mounted upon the outer surface of the interlock 52. Threaded inserts 84 (FIGS. 2 and 9) are trapped within openings of the housing 54 to receive the mounting screws of the auxiliary switch unit.

The electrical interlock 52 is operated by an extension 680 of the contact carrier 68 Which extends into the contactor base 6 through an opening 6 formed in the sidewall thereof to be engaged by the inner end of slide bar 16 (FIG. 7). The interlock 52 may be mounted to either side of the contactor, openings 6 being provided in both side walls of base 6 to allow the portion 68c to extend therethrough. A plug 86 is provided to close the unused opening 6f by sliding it into the opening from the front surface of the base 6. The sidewalls of the openings 6] contain V-shaped grooves and the edges of plug 86 have lateral complementary V-shaped edges to provide a tongue and groove arrangement for retaining the plug 86 within the opening 6 To operate the contactor disclosed herein, the windings of the coil element 14 are energized to cause the armature 12 to be attracted to the core 22. The movement of the armature forces the push bars 16 and 18 inward against the bias of springs 48. The push bars in turn drive the contact carrier 38 inwardly to cause the contact 36 to bridge the respective stationary contacts 30-. The lower end of push bar 16 also engages projection 680 of the electrical interlock contact carrier 68 after a predetermined amount of inward travel and moves the carrier 68 inward to open the circuit between the contacts 64 and to close the circuit between the contacts 66. This operated position may be seen in the left-hand contactor of FIG. 14. The springs 48 effect the reverse movement of the armature, push bars and contact carrier upon deenergization of the coil element 14 to restore the device to its initial condition. In addition to restoring the electrical interlock switch to its initial condition, the spring 78 also aids the springs 48 in returning the armature, push bars and carrier during the early part of their travel.

Under certain control applications utilizing contactors of the above mentioned type, it is desirable to cause adjacent contactors to be interlocked in a mechanical manner so that both may not be operated simultaneously. While such contactor pairs are usually factory assembled on a single mounting plate it is sometimes necessary to convert two individual units into an intenlocked pair in the field, and this has been shown in FIGS. 13 and 14. Since the contactors shown in these figures are identical 6 to the earlier described contactor, like numerals have been applied to the same parts with certain numerals to specific portions of these parts omitted for the sake of clarity.

The contactors are shown as they would appear in normal installation on a panel. To add a mechanical interlock 88, a maintenance person would 'loosen the hex head screws 28 of each contactor to remove the complete magnet housing assembly 4 of each device, thereby exposing the screws 62 and the plugs 86. It is to be understood that prior to the conversion the right-hand contactor of FIGS. 13 and 14 had its electrical interlock 52 mounted on the left-hand side in the normal position as described before.

The plugs 86 are slid out of the right-hand openings 61 of the two contactors and the screws 62 are removed from the right-hand contactor to remove the electrical interlock 52 therefrom. This interlock is then remounted on the right-hand side of the contactor using the same screws 62 as shown in FIGS. 13 and 14.

A mechanical interlock 88 is provided which comprises a pair of identical insulating housing halves 90 secured together by some conventional means. Each housing half has a pair of bosses 90a extending outwardly of the side thereof identically to the bosses 60 of electrical interlock housing 54. The interlock 88 is inserted between the two contactors so that the four bosses 90a fit into the recesses 6d of the adjacent sides of the two contactors and is secured thereto by additional screws 62a which take into the threaded openings 6e of the bases.

The two housing halves 90 of the interlock 88, when secured together, form a cavity in which is trapped a rectangular adjusting block 92 made of nylon or the like. The adjusting block is afforded some linear movement within the cavity and may be adjusted forwardly and rearwardly of the device from the exterior thereof by an adjusting screw 94. An integral collar formed on screw 94 is entrapped in a circular cavity formed in the interlock housing to permit the screw 94 to be rotated without moving linearly. The threaded shank portion of the screw engages a threaded opening in the rectangular adjusting block 92, the block being restrained from rotation but permitted linear travel. Rotation of the screw 94 therefor causes the block 92 to be adjusted inward or outward within the housing according to the direction of rotation of the screw.

A T-shaped roller assembly 96 is pivotally mounted to a depending tongue portion of the adjusting block 92. Assembly 96 has freely rotatable rollers 98 secured at the ends of the cross bar member of the T which extends through openings 90b in the interlock housing halves 90 and openings 69 in the contacter bases 6 to lie within the devices as shown in FIG. 13. With respect to FIG. 14, it may be seen that when one contractor is operated, the lower edge of the push bar adjacent the mechanical interilock side of the device engages the respective roller 98 to pivot the roller assembly 96 out of its path of travel and into the path for the respective push bar of the other contactor, thus preventing operation of the latter. It is desirable that the roller assembly 96 not be pivoted to an extent which would cause jamming between the two contact carrier assemblies and thus the interlock is adjusted so that with one device operated, a small amount of movement is afforded the carrier of the other before it engages the roller 98. After this adjustment is made a plastic plug 100 may be inserted into the hole around the exposed end of adjusting screw 94.

Mechanical interlock 88 is further provided with a pair of wiring terminals which are trapped between the housing halves to extend outwardly of the upper and lower surfaces of the housing. These wiring terminals function solely as tie points as would a terminal block attached to the device, and in so doing utilize an otherwise void area of the device.

While the contactor has been disclosed in a preferred embodiment, it is to be understood that the novel features herein presented are susceptible of various modifications without departing from the scope of the appended claims.

I claim:

1. An electromagnetic switching device comprising, in combination; an insulating base member; an insulating magnet housing secured to said base member and removable therefrom to expose an open end of said base member; an insulating cover member secured to said magnet housing and removable therefrom to expose an open end of said magnet housing; a pair of push bars, said push bars being mounted within openings at opposite side walls of said magnet housing for reciprocal movement therethrough, the opposite ends of said push bars extending into said cover member and said base member; a magnet core mounted within said magnet housing; a coil member disposed about said magnet core within said magnet housing; an armature secured between said push bars to overlie said magnet core; spring means bearing between said magnet housing and said push bars to bias said push bars and said armature away from said magnet core; an insulating movable contact carrier secured between said push bars to extend within said base member, said movable contact carrier having a plurality of windows formed therein; said windows having movable bridging contacts resiliently mounted therein; a plurality of stationary contacts mounted within said base member as alined pairs and wherein energization of said coil member causes said armature to be attracted to said magnet core to move said push bars and said movable contact carrier toward said base member, said movement causing said movable contacts to bridge respective alined pairs of said stationary contacts.

2. The combination according to claim 1 wherein removal of said magnet housing from said base member exposes said stationary contacts within the opening of said base member, said stationary contacts each being mounted upon individual shelf portions of said base member to extend within said opening of said base member, said shelf portions being formed in opposite side walls of said base member, recessed from the exposed end of said base member and extending between said opening and the respective exterior surfaces of said base member, together with wiring terminal members disposed over said shelf portions in alinement with said stationary contacts to extend outwardly of said respective external surfaces of said base member, the outer ends of said wiring terminals being provided with means for securing electrical wire leads thereto, and wherein a wiring terminal member and a stationary contact member are secured to an individual shelf portion by a threaded fastener which passes through alined clearance openings in said wiring terminal and said stationary contact to take into a threaded opening in said shelf portion.

3. The combination according to claim 2 together with cooperating key and keyway means provided between said wiring terminals and the respective recessed shelf portions, there being a different combination of said key and keyway means for each recessed shelf formed on the same side of said base member and wherein a noncooperating key and keyway combination provides an interference to prevent a non-conforming terminal from being fitted into the recessed shelf portion.

4. The combination according to claim 3 wherein said keyway is a groove in a side wall which is adjacent said recessed shelf and extends between said shelf and said exposed end of said base member, and said key is a projecting tab formed on a corresponding side of said wiring terminal.

5. The combination according to claim '2 together with contact pockets formed within said opening of said base aind proximate each recessed shelf portion, said pockets each comprising a pair of opposed projections spaced from and generally parallel to the Wall of said opening which is adjacent said recessed shelf portion, said projections extending from the inner wall of said opening toward said open end of said base member, and wherein said stationary contact is inserted into said pocket from said open end of said base, portions of said contact extending within the spaces between said adjacent wall and said opposed projections, said' contact further having a first offset portion formed to overlie said shelf portion and a second offset portion formed to extend between said opposed projections and into a central portion of said opening in said base.

6. The combination according to claim 1 together with openings provided through an opposite pair of side walls of said base, said openings also being open to the exposed end of said base when said magnet housing is removed therefrom; a pair of recesses in said opposite side walls, said recesses being located on either side of said openings and open to the respective external surface of said side walls and to the exposed end of said base member; a threaded hole provided in the inner surface of each of said recesses; an auxiliary switch unit comprising a housing with an opening in one side wall thereof, a switch actuator linearly movable within said housing and spring biased to a first position therein, said switch actuator having a projecting portion extending through said opening in said housing; a pair of outwardly extending bosses formed on said side wall of said switch housing and on opposite sides of said opening in said housing; said side of said housing of said auxiliary switch unit being placed against the external surface of one of said opposite pair of side walls of said base and said bosses extending within said recesses; said bosses having clearance openings therein which are in alinement with said threaded holes; threaded fasteners insertable through said clearance openings from said exposed end of said base to take into said threaded holes to secure said switch unit to said base; and wherein said projecting portion of said switch actuator extends through said opening in the side wall of said base to be engaged by a respective one of said push bars upon energization of said electromagnet to move said actuator to a second position within said switch housing.

7. The combination according to claim 1, wherein a pair of said electromagnetic switch devices are provided, each having openings provided through an opposite pair of side walls of said base, said openings also being open to the exposed end of said base when said magnet housing is removed therefrom; a pair of recesses in said opposite side walls, said recesses being located on either side of said openings and open to the respective external surface of said side walls and to the exposed end of said base member; a threaded opening provided in the inner surface of each of said recesses; together with a mechanical interlock unit comprising a housing with a central cavity and openings through opposite sides thereof, a T-shaped roller assembly pivotally mounted within said housing and having roller members extending outwardly of said housing through said openings; pairs of outwardly extending bosses formed on said side walls of said interlock housing and on opposite sides of said openings in said side walls of said housing, said interlock unit being disposed between an adjacent pair of said electromagnetic switching devices with the opposite sides of said unit against the respective external surfaces of said opposite side walls of said base members and with said bosses extending within said recesses, said bosses having clearance openings therein which are in alinement with said threaded openings; threaded fasteners insertable through said clearance openings from said exposed end of said base to take into said threaded openings to secure said interlock unit to said bases; and wherein said roller members extend through said openings in the side walls of said bases to be engaged by respective ones of said push bars of said electromagnetic switching devices, and wherein operation of one of said devices causes said push bar thereof to engage the respective roller member to pivot 9 i said roller assembly out of'the path of said push bar and into the path of the push bar of the unoperated device.

8. The combination according to claim 7 together with threaded means for linearly adjusting said T-shaped roller assembly along the path of travel of said push bars to vary the point at which the latter engage with respective ones of said roller members, said threaded means being accessible from the outer end of said devices for rotation in opposite directions to cause said linear movement of said assembly.-

9. The combination according to claim 1, wherein said armature is mounted within open-ended slots formed on the inner surfaces of the outer ends of said push bars which are exposed upon removal of said insulating cover member from said insulating magnet housing, said armature being biased against the inner edges of said openended slots by spring means, said armature further being retained within said slots by portions formed adjacent the open ends of said slots and extending from said inner edges substantially normal thereto, and wherein said armature may be removed from said open-ended slots of said push bars by moving said armature in a first direction against the bias of said spring means to clear said projections and then moving said armature in a second direction toward and through the open ends of said slots.

10. The combination according to claim 9, wherein one end of said armature is smaller than the opposite end, and wherein the opening of a corresponding one of said openended slots is smaller than the opening of the opposite open-ended slot, said corresponding one of said openended slots preventing said opposite end of said armature from being inserted therein to insure properly oriented replacement of said armature to said push bars.

11. The combination according to claim 9 wherein said coil member is removable from said magnet housing subsequent to the removal of said armature from said push bars, said coil member being linearly extractable through the exposed end of said magnet housing, and wherein said coil is provided with blade terminals which become separated from cooperating spring clip terminals upon said removal of said coil, said spring clip terminals being secured to said insulating base member.

12. The combination according to claim 11 wherein said spring clip terminals extend within openings formed in said magnet housing and said blade terminals also extend within said openings to be engaged by said spring clip terminal when said coil is assembled to said magnet housing, and-wherein removal of said magnet housing with said coil assembled thereto from said insulating base member causes said blade terminal to become separated from said spring clip terminals to effect electrical disconnection of the coil.

References Cited UNITED STATES PATENTS 3,202,785 8/1965 Jelley. 3,235,686 2/1966 Gribble 335-132 3,334,319 8/1967 Herrmann 335-132 BERNARD A. GILHEANY, Primary Examiner. H. BROOME, Assistant Examiner.