US3371297A

US3371297A - Electromagnetic control device having a predetermined radial air gap which remains substantially constant independently of the wear of the armature and associated stationary magnetic structure

Info

Publication number: US3371297A
Application number: US571583A
Authority: US
Inventors: James L Ridings
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1966-08-10
Filing date: 1966-08-10
Publication date: 1968-02-27
Anticipated expiration: 1985-02-27
Also published as: GB1123535A

Description

Feb. 27, 1968 J. L. RIDINGS 3,371,297

ELECTROMAGNETIC CONTROL DEVICE HAVING A PREDETERMINED RADIAL AIR.GAP WHICH REMAINS SUBSTANTIALLY CONSTANT INDEPENDENTLY OF THE WEAR OF THE ARMATURE AND ASSOCIATED STATIONARY MAGNETIC STRUCTURE Filed Aug. 10. 1966 2 Sheets-Sheet 1 IE I34 I32 FIG.2.

WITNESSES INVENTOR WWW James L. Ridings ATTORNEY 3,371,297 ETERMINED LLY Feb. 27, 1968 I J. momss ELECTROMAGNETIC CON TROL DEVICE HAVING A FRED RADIAL AIR GAP WHICH REMAINS SUBSTANTIA CONSTANT INDBPENDENTLY OF THE WEAR OF THE ARUIATURE AND ASSOCIATED STATIONARY IIAGNE'I'IC STRUCTURE 2 Sheets-Sheet 2 Filed Aug. 10, 1966 FIG.4.-

i Has; A

Fl sza United States Patent assignor to Westinghouse Pittsburgh, Pa., a corporation of This invention relates to electrical control devices, such as circuit interrupters or circuit breakers, relays and contactors, and more particularly to electromagnetic structures which form part of such devices.

In the construction of certain types of electrical control devices, an electromagnetic structure is provided which includes a movable armature or plunger that is actuated between different operating positions with respect to an associated stationary magnetic structure. In certain applications, the rnovable armature of such a device may include different portions which are disposed either to engage or to be actuated into closely spaced relation with corresponding portions of an associated stationary magnetic structure in at least one operating condition of the overall device. In such applications, it has been found that the operating characteristics of an electrical control device may vary during repeated operations due to the wear of the parts or due to the tolerances of the parts which make up the electromagnetic structure in such a device and the corresponding changes in the spacing or gaps between the different parts of the electromagnetic structure in at least one operating condition of the overall electrical control device. It is therefore desirable to provide an improved electrical control device of the type described including an electromagnetic structure in which variations in the operating characteristics of the device in at least one operating condition due to the wear of the parts or the tolerances of the parts which make up the electromagnetic structure is substantially eliminated. V

It is an object of this invention to provide a new and improved electrical control device including an electromagnetic means.

Another object of this invention is to provide an improved electromagnetic structure for electrical control devices including means for maintaining the relative positions of a movable armature and an associated stationary magnetic structure in at least one operating condition of the magnetic structure.

A more specific object of this invention is to provide an improved electromagnetic structure including a movable armature or plunger with means for insuring that different portions of the armature are properly positioned with respect to the associated stationary magnetic structure during the operation of the electromagnetic structure.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a front elevational tion and partly cut away, of a contactor embodying the principles of the invention with the contact means of the contactor being shown in the open circuit position;

FIG. 2 is a side elevational view, in section, of the contactor shown in FIG. 1, taken along the line IIII of FIG. 1;

FIG. 3 is a partial plan view, in section, of the conview, partially in sectactor shown in FIG. 1, taken along the line IIIIII of FIG. 1;

FIG. 4 is a diagrammatic view illustrating the operation of the electromagnetic structure which forms part of the contactor shown in FIG. 1 with the electromagnetic structure being shown in the operating condition which corresponds to the open circuit condition of the contactor;

FIG. 5 is a diagrammatic view, similar to FIG. 4, illustrating the operating condition of the electromagnetic structure which forms part of the contactor shown in FIG. 1 which corresponds to the closed circuit condition of the contactor; and

FIG. 6 is a diagrammatic view illustrating the electrical connections of the contactor shown in FIG. 1 in a typical application.

Referring now to the drawings and FIGS. 1 and 2 in particular, there is illustrated an electrical control device, more specifically a contactor 10 embodying the principal features of the invention. In general the contactor 10 comprises a stationary magnetic structure 30 on which an energizing or operating coil or winding means 50 is inductively disposed to control the actuation of a movable armature or plunger 60 which is operatively connected or coupled to a contact carrier assembly 70 to, in turn, control the opening and closing of the separable contacts of the contactor 10.

More specifically, the stationary magnetic structure 30, as best shown in FIGS. 1 and 3, comprises a pair of spaced upper and

lower plates

42 and 44, respectively, which are formed from a suitable soft magnetic material, such as iron. As illustrated in FIG. 3, each of the

plates

42 and 44 is generally rectangular in configuration with the

plates

42 and 44 being disposed in substantially parallel relationship. The stationary magnetic structure 30 also includes a central leg member or portion 45 which is also formed from a suitable soft magnetic material, such as iron, and which projects upwardly from the lower plate 44 for only a portion of the distance between the

plates

42 and 44, as shown in FIG. 1. The central leg member 45 may be formed integrally with the lower plate 44 or may be provided as a separate member which is secured to the lower plate 44 by suitable means, such as a bolt. It is to noted that in one operating position of the movable armature 60, as shown diagrammatically in FIG. 5, the lower end of the armature 60 seats against or engages the top or upper surface of the central leg member 45. In the other operating position of the armature 60, the lower end of the armature 60 as shown in FIGS. 1 and 2 is spaced away from the top or upper surface of the central leg member 45 by a predetermined distance or gap, as indicated at 63 in FIGS. 1 and 2.

i In order to permit the armature 60 to pass through the upper plate 42 of the stationary magnetic structure 30 and to permit the coupling of the armature 60 to the contact carrier assembly 70, the upper plate 42 includes a central opening 42B through which the armature 60 passes. In order to guide the reciprocating or rectilinear movement of the armature 60 between a first operating position which is shown in FIGS. 1 and 2 and a second operating position which is shown diagrammatically in FIG. 5, a tubular member or sleeve 65 may be provided as shown in FIGS. 1 and 2 which extends from the central opening 423 in the upper plate .42 downwardly to. the lower magnetic plate 44 to enclose the central leg member 45. The sleeve 65 is formed from a suitable non-magnetic material, such as brass and forms a non-magnetic gap between the armature 60 and the upper plate 42 around the opening 4213. The upper magnetic plate 42 also includes a raised or shoulder portion 42A which projects upwardly from the plane of the main portion of the plate 42 around the opening 42B and functions as a seat which is engaged by the ring-shaped member 64 of the plunger 60 in the operating position of the plunger 60 shown diagrammatically in FIG. to thereby bridge the nonmagnetic gap formed by the sleeve 65. It is to be noted that the shoulder portion 42A also acts as a retainer for the spring 72, whose purpose will be explained hereinafter.

In order to provide a magnetic path having a relatively low reluctance between the

magnetic plates

42 and 44 outside the operating coil means 50, the stationary magnetic structure 30 includes a pair of outer

magnetic leg members

34 and 35 which are disposed between the

plates

42 and 44 at the diagonally opposite corners of the

plates

42 and 44, as shown in FIG. 3, and which are formed from a suitable soft magnetic material, such as iron. In order to provide a predetermined nonmagnetic gap in each of the magnetic paths which are provided by the

outer leg members

34 and 35, a nonmagnetic washer or spacer member 38 formed of a suitable material, such as brass, is disposed, as illustrated, between the upper end of each of the

outer leg members

34 and 35 and the upper magnetic plate 42, as best shown in FIGS. 1 and 2, for a purpose which will be explained hereinafter. It is to be noted that each of the

outer leg members

34 and 35 is generally hollow cylindrical in configuration, as illustrated, and that the

outer leg members

34 and 35 may be maintained in assembled relationship with the associated

plates

42 and 44 by suitable means, such as the nonmagnetic bolts 92, which pass through aligned openings in the associated plates and leg members.

' In order to magnetically latch the plunger 60 in the operating position shown in FIG. 5 which, in the case, corresponds to the closed position of the separable contacts in the contactor 10, the stationary magnetic structure 30 also includes a pair of

permanent magnet members

32 and 34 which are disposed between the

magnetic plates

42 and 44 at the other diagonally opposite corners of said plates, as shown in FIG. 3, and which are generally hollow cylindrical in configuration to permit assembly with the

associated plates

42 and 44 by suitable means, such as the nonmagnetic bolts 92. It is to be noted that the

permanent magnet members

32 and 33 are disposed with like magnetic poles adjacent to the respective

magnetic plates

42 and 44, as best shown in FIGS. 4 and 5.

As best shown in FIGS. 1 and 2, the armature or plunger 60 is generally T-shaped in cross-section and comprises a first generally cylindrical member 62 and a second generally annular or ring-shaped member 64 which are both formed from a suitable soft magnetic material, such as iron. The major portion of the cylindrical member 62 is disposed in concentric relation with the sleeve or guide member 65 for reciprocating movement within the sleeve member 65 between the position shown in FIGS. 1 and 2 and the position shown in FIG. 5. The upper end of the cylindrical member 62 includes a portion of reduced cross-section, as indicated at 62B, around which the ring-shaped member 64 is concentrically disposed and along which the ring-shaped member 64 is axially movable during a portion of the travel of the plunger or armature 60, as will be explained hereinafter. The upper end of the cylindrical member 62 also includes a shoulder portion, as indicated at 62A, against which the ring-shaped member 64 is biased or held by the compression spring 74 which is disposed between the ring-shaped member 64 and a common movable contact support 112 which forms part of the contact carrier assembly 70 in one operating position of the armature 60 as will be described hereinafter. It is important to note that the ring-shaped member 64 of the armature 60 is disposed to move axially and seat against a first portion of the stationary magnetic structure 30 which is the shoulder portion 42A of the upper plate 42 prior to and independently of the lower end of the cylindrical member 62 of the armature 60 which subsequently seats against the upper surface of the central leg portion 45 when the armature 60 is actuated from the position shown in FIGS. 1 and 2 to the operating position shown in FIG. 5. Since the nonmagnetic gap formed by the upper end of the sleeve 65 is first magnetically shunted or bridged by the ring-shaped member 64, substantially all of the magnetic forces acting on the armature 60 are effective to close the air gap 63 between the lower end of the armature 60 and the central leg portion 45.

In order to provide a predetermined radial gap or spacing between the ring-shaped member 64 and the upper portion 62B of the cylindrical member 62, the cross-sectional area or diameter of the upper portion 623 is slightly smaller than the cross-sectional area or diameter of the central opening in the ring-shaped member 64 with the radial gap between the ring-shaped member andthe cylindrical member 62 being preferably of a relatively small size on the order of 0.001 inch. A predetermined radial gap is also provided between the outer periphery of the cylindrical member 62 and the portion of the upper plate 42 around the opening 423 by the thickness of the sleeve member 65 which is disposed concentrically between the upper plate 42 and the cylindrical member 62.

In order to operatively couple or connect the armature 60 to the contact carrier assembly 70, a nonmagnetic connecting shaft 122 may be provided which includes a threaded portion that projects into and engages an internally threaded central opening 62C in the cylindrical member 62 of the armature 60, as shown in FIGS. 1 and 2. The common movable contact support 112 may be secured to the connecting shaft 122 by suitable means such as the lock nuts 71, shown in FIGS. 1 and 2. In order to assist in guiding the reciprocating movement of the plunger or armature 60 within the sleeve member 65, the connecting shaft 122 may be extended or a separate guide pin 124 may be provided in the central opening 62C of the cylindrical member 62 which projects downwardly into an aligned central opening 453 in the central leg member 45 of the stationary magnetic structure 3.0 with the guide pin 124 being formed from a suitable nonmagnetic material, such as brass or nonmagnetic stainless steel. The armature or plunger 60 is biased generally upwardly away from the central leg member 45 of the stationary magnetic structure 30 by a suitable means, such as the compression spring 72, which is disposed between the upper magnetic plate 42 and the contact support 112 of the contact carrier assembly 70. with the biasing force from the spring 72 being transmitted through the contact support 112 and the connecting shaft 122 to the armature 60. The shoulder portion 42A of the upper magnetic plate 42 functions as a retainer for the spring 72, as previously mentioned, with the spring 72 being disposed in substantially concentric relationship with the compression spring 74.

In order to actuate the armature plunger 60 between the ditferent operating positions previously described, the energizing or operating coil or winding means 50 is disposed between the

plates

42 and 44 around the central leg portion 45 of the stationary magnetic structure 30 and around the lower portion of the cylindrical member 62 of the armature 60 with the pair of

outer leg members

34 and 35 being disposed outside the operating coil means 50 at a first pair of diagonally opposite corners of the stationary magnetic structure 30 as shown in FIG. 3 and with the pair of

permanent magnet members

32 and 33 being disposed outside the operating coil means 50 at the other pair of diagonally opposite corners of the stationary magnetic structure 30, as shown in FIG. 3. The conductor turns of the operating coil means 50 may be wound on an insulating spool or bobbin which, in turn, is supported on the sleeve member 65 which may be conveniently employed as a coil form. The additional elec trically insulating

washers

52 and 54 may be disposed between the opposite ends of the insulating spool 56 and the adjacent upper and lower

magnetic plates

42 and 44, respectively, as best shown in FIGS. 1 and 2. As shown diagrammatically in FIG, 6, the operating coil or winding means 50 may include a first winding portion 50A and a second winding portion 5013 which may be separately energized from a source of unidirectional voltage, as indicated at the terminals T1, T2 and T3, to either actuate the plunger in one direction to close the contacts of the contactor or in the opposite direction to open the contacts of the contactor 10. More specifically, when a voltage is applied to the first winding portion 50A and current flows in the conductor turns of the first winding portion 50A, the magnetic flux which is produced may be in the same direction as the flux which is supplied to the armature 60 and the central leg portion 45 from the

permanent magnet members

32 and 33. On the other hand, when the voltage is applied to the second winding portion 50B and current flows therein, the magnetic flux which is produced thereby may be opposing in direction with respect to the magnetic flux supplied from the

permanent magnet members

32 and 33 to the armature 60 and the central leg portion 45 of the stationary magnetic structure 34), as will be explained in greater detail hereinafter.

Referring again to FIGS. 1 and 2, the contact carrier assembly 70 includes a common contact support 112 which is secured to the connecting shaft 122 and is operatively coupled to the armature 60 for reciprocating movement therewith by the shaft 122. As illustrated, the contact carrier assembly 70 includes a plurality of laterally spaced movable contact bridging members C1, C2 and C3 which are resiliently supported on a plurality of associated laterally spaced shafts or posts 132 which are secured to and project upwardly from the common contact support 112, as shown in FIGS. 1 and 2. Each of the contact bridging members C1 through C3 is slidably supported on the upper end of one of the shafts 132 between a pair of concentric

electrical insulating members

138 and 139, as best shown in FIG. 1. Each of the electrical insulating members 138 includes a flange portion at the lower end which is disposed between one of the contact bridging members C1 through C3 and a shoulder portion 132A which is provided on each of the shafts 132 to limit the downward movement of the associated contact bridging member on the shaft 132. A pair of contact members 144 are mounted on and disposed at the opposite ends of each of the contact bridging members C1 through C3, as best shown in FIG. 2. In order to provide contact pressure between the contact bridging members C1 through C3 and the associated stationary contacts as will be described hereinafter, a compression spring 136 is disposed between each of the contact bridging members C1 through C3 and a cup-shaped washer 134 which is secured to each of the shafts 132 adjacent to the upper end thereof to function as a spring seat for the upper end of each of the compression springs 136. Each of the insulating members 139 includes a flange portion which acts as a spring seat for the lower end of one of the associated compression springs 136.

In order to support a plurality of stationary contact members in the line of travel of the contact bridging members just described, the insulating terminal board 150 is provided and includes a plurality of spaced compartments. The insulating terminal board 159 is supported on a generally U-shaped bracket member 82 with the terminal board 150 being secured by suitable means to the bracket means 82, such as the bolts 163 shown in FIG. 1. The bracket member 82 in turn is mounted on and supported by the stationary magnetic structure 30 and is secured to the stationary magnetic structure by suitable means, such as the bolts 92. More specifically, the contactor 10 includes a plurality of pairs of spaced

contacts

146 and 148 which are disposed adjacent to and in the line of travel of the associated contact bridging members C1 through C3. The

stationary contacts

146 and 148 are electrically connected to the associated

terminal posts

162 and 164 respectively by the

electrically conducting members

147 and 149, respectively.

In order to totally enclose the operating parts of the contactor 10, a housing structure may be provided which includes the base member 102 which may be secured to the stationary magnetic structure 30 by suitable means, such as bolts (not shown), and a plurality of side wall members 104 which extend between the base member 162 and the lower portion of the insulating terminal board 150 which forms part of the overall housing structure. A cover member may be secured to the top of the insulating terminal board by suitable means, such as the bolts or screws 154. Where desired, the leads or wires from the operating coil or any wiring provided may pass through one of the side walls 104 through a suitable connector means, as indicated at 175. I

In order to prevent the simultaneous energization of the first and second winding portions 59A and 50B, respectively, of the operating coil or winding means 50 previously described, one or more auxiliary switches S1 through S4 may be mounted on top of the stationary magnetic structure 30 in the line of travel of the common contact support 112, as best shown in FIG. 2. A plurality of actuating members 172 and 174 may be mounted on the common contact support 112 to project downwardly from the common contact support to engage corresponding plunger members provided on top of the respective auxiliary switches S1 through S4 to thereby prevent the simultaneous energization of the first and second winding portions 58A and 50B respectively of the operating coil or winding means as indicated diagrammatically in FIG. 6.

Considering the overall operation of the contactor 10, it will be assumed initially that the separable contacts of the contactor 10 are in the open circuit position as shown in FIGS. 1 and 2 and that the movable armature 60 is in a corresponding position as shown diagrammatically in FIG. 4 with the lower end of the armature 60 being spaced from the central leg portion 45 of the stationary magnetic structure by a predetermined spacing or nonmagnetic gap, as indicated at 63. It will also be assumed initially that neither of the winding

portions

50A and 50B is initially energized and that substantially all of the magnetic flux from the

permanent magnet members

32 and 33 is concentrated in the magnetic paths which include the

outer leg members

34 and 35 with very little magnetic flux from the

permanent magnet members

32 and 33 flowing through the magnetic path which includes the armature 60 and the central leg portion 45. It is to be noted at this time that the armature 60 is held in the position shown in FIG. 4 by the biasing force applied to the plunger 60 by the compression spring 72 which tends to actuate the plunger 60 in an upward direction, as viewed in FIG. 4. It is also to be noted that in the initial operating position of the plunger 60, the relative reluctance of the magnetic path which includes the plunger or armature 60 and the central leg portion 45 is greater than that of the magnetic paths which include the

outer leg members

34 and 35 due to the greater magnetic gap present between the armature 60 and the central leg portion 45 of the stationary magnetic structure 30.

In order to close the separable contacts of the contactor 10, the first winding portion or closing coil 50A, as shownin FIG. 6, is energized from the input terminals T1 and T2 through the normally closed contacts of the auxiliary switches S1, as illustrated. Prior to the energization of the first winding portion or closing coil 58, it is to be noted that the magnetic flux supplied by the

permanent magnet members

32 and 33 travels through three parallel closed loops which extend from the upper end of each of the

permanent magnet members

32 and 33 through the upper magnetic plate 42, and then downwardly through the three separate magnetic paths which include the

outer leg members

34 and 35, the armature 60 and the central leg member 45 to the lower magnetic plate 44 and then back to the lower end of the respective

permanent magnet members

32 and 33. In the assumed operating condition prior to the energization of the first winding portion 50A, most of the magnetic flux supplied from the

permanent magnet members

32 and 33 will flow through the magnetic paths which include the

outer leg members

34 and 35, as previously mentioned. When the first winding portion or closing coil 50A is energized, the magnetic flux produced by the current flow through the first winding portion 50A will be in the same direction through the armature 60 and the central leg member 45 as the flux supplied from the

permanent magnet members

32 and 33 with the magnetic flux produced by current flow in the first winding portion 50A being opposing or in an opposite direction with respect to the magnetic flux supplied trom the

permanent magnet members

32 and 33 to the outer leg members 34- and 35. The magnetic flux supplied from the

permanent magnet members

32 and 33 will therefore be effectively shifted or transferred from the

outer leg members

34 and 35 to the magnetic path which includes the armature 60 in the central leg portion 45 of the stationary magnetic structure 30. The armature 60 will then be actuated or attracted downwardly by the magnetic flux from the

permanent magnet members

32 and 33 and by the magnetic flux produced by current flow in the first winding portion 50A until the lower end of the armature 69 seats against the top of the central leg portion 45 and the ring-shaped magnetic member 64 of the plunger or armature 60 seats against the shoulder portion 42A of the upper magnetic plate 42, as best shown diagrammatically in FIG. 5. Since the ring-shaped member 64 is resiliently mounted on the cylindrical member 62 of the armature 60, the ring-shaped member 64 will seat on the shoulder portion 42A of the upper magnetic plate 42 prior to and independently of the cylindrical member 62 of the armature 66, as shown in FIG. 5, since the cylindrical member 62 is free to move downwardly to seat against the top of the central leg portion 45 of the stationary magnet structure after the ringshaped member 64 comes to rest against the shoulder portion 42A of the upper magnetic plate 42 which acts as a stop for the downward travel of the ring-shaped member 64.

It is to be noted that in the operating position of the armature 60 shown in FIG. 5, the ring-shaped member 64 is actually spaced away from the shoulder portion 62A on the armature 60 and that a predetermined radial gap previously described will be present between the ringshapcd member 64 and the cylindrical member 62. It is important that the radial gap or spacing which exists between the ring-shaped member 64 and the cylindrical member 62 will remain substantially constant despite the wear of the parts that will result from the seating of the ring-shaped member 64 on the shoulder portion 42A of the upper magnetic plate 42 and from the seating of the lower end of the cylindrical member 62 of the armature 60 on top of the central leg member 45 of the stationary magnetic structure 30.

While the armature 60 is actuated downwardly to the operating position shown in FIG. 5, the contact bridging members C1 through C3 previously described will also be actuated in a downward direction to engage the associated pairs of

stationary contacts

146 and 148 of the contactor 10. When the plunger 60 is actuated from the position shown in FIG. 4 to the operating position shown in FIG. to thereby close the separable contacts of the contactor 10, the magnetic flux supplied from the

permanent magnet members

32 and 33, which was previously concentrated in the magnetic paths which include the

outer leg members

34 and 35, will be transferred to the magnetic path which includes the armature 6t) and the central leg member 45 of the stationary magnetic structure 30 and will remain concentrated in the magnetic path which includes the armature 60 and the central leg portion 45 since the reluctance of the magnetic path which includes the armature 60 will be relatively less than the reluctance of the magnetic paths which include the outer leg members 34 and since the lower end of the armature 60 is now seated against the top of the central leg portion to thereby substantially eliminate the gap 63 which previously existed between the armature 60 and the central leg portion 45 as shown in FIG. -4. When the armature 64) reaches the operating position shown in FIG. 5, the auxiliary switches S1 mounted on top of the stationary magnetic structure 30 will be actuated to the opposite operating positions to thereby deenergize the first winding portion or closing coil A since the contacts of the auxiliary switches S1 shown in FIG. 6 will be actuated to the open positions during the closing of the main separable contacts of the contactor 10. The magnetic flux supplied from the

permanent magnet members

32 and 33 will remain in the magnetic path which includes the armature shown in FIG. 5 even though the first winding portion is deenergized by the associated auxiliary switches at the end of the travel of the armature 60 because of the relatively lower reluctance which results in the magnetic path which includes the armature 69 as just described. In summary, the magnetic fiux supplied from the

permanent magnet members

32 and 33 will magnetically latch the contactor 10 in the closed circuit condition shown in FIG. 5 since the magnetic flux from the

permanent magnet members

32 and 33 will be substantially concentrated in the magnetic path which includes the armature 60 to thereby retain the armature 60 in the operating position shown in FIG. 5 against the force exerted on the armature 60 by the biasing spring 72.

In order to open the closed separable contacts of the contactor 10 and to actuate the armature 6th from the position shown in FIG. 5 back to the original operating position shown in FIG. 4, the second winding portion 50B shown in FIG. 6- may now be energized through the contacts of the auxiliary switches S1, which will now permit energization of the second winding portion or tripping coil 5013 from the terminals T1 and T3. When the second winding portion or tripping coil 50B is energized, the magnetic flux produced by the second winding portion or tripping coil 508 will be in a direction opposite to that of the magnetic flux produced in the armature 60 from the

permanent magnet members

32 and 33 to thereby transfer or shift most of the magnetic flux from the

permanent magnet members

32 and 33 from the magnetic path which includes the armature 6t and the central leg portion 45 back to the

outer leg members

34 and 35. When the magnetic flux is shifted from the path which includes the armature 60 and the central leg portion 45, the force exerted on the armature 60 by the biasing spring 72 is sutficient to actuatethe armature 60 upwardly from the operating position shown in FIG. 5 back to the operating position shown in FIG. 4 with the previously closed separable contacts of the contactor 10 being opened by the upward movement of the contact bridging members C1 through C3 back to the positions shown in F168. 1 and 2.

It is to be understood that the teachings of the invention may be applied to electromagnetic structures which employ other types of latching arrangements than the magnetic latching means as disclosed since the teachings of the invention may be applied generally to electromagnetic structure including a generally E-shaped stationary magnetic structure (with or without permanent magnet latching members) which cooperates with an associated generally T-shaped movable armature which is required to seat against different spaced portions of the stationary magnetic structure. It is also to be understood that the teachings of the invention may be applied to the electrical control devices including contacts which are normally closed rather than normally open as in the contactor 10 described. A single operating winding may also be employed in certain applications by applying currents of opposite directions to obtain magnetic fluxes of corresponding directions to actuate the armature 60 between the different operating positions.

The apparatus embodying the teachings of this invention has several advantages. For example, when the disclosed armature seats against the different portions of the associated magnetic structure as shown in FIG. of the drawings, a predetermined radial gap results which remains substantially constant or at a predetermined value independently of the wear of the parts of the armature and the associated stationary magnetic structure which engage one another during repeated operations of an electrical control device which incorporates an electromagnetic structure as disclosed. The operating characteristics of the electrical control device, including the disclosed electromagnetic structure having at least one operating condition in which the armature seats against the associated stationary magnetic structure, remains substantially constant during repeated operations of the device rather than varying due to the changes in the nonmagnetic gaps which result between the difierent portions of the armature and the associated stationary magnetic structure or varying due to the tolerances of the difierent parts of the device as in known constructions.

Since numerous changes may be made in the above-described apparatus, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. An electrical control device comprising stationary and movable contact means, and means for actuating the movable contact means between open and closed positions with respect to the stationary contact means, said actuating means including a stationary magnetic structure and a generally T-shaped armature coupled to the movable contact means and comprising a generally cylindrical magnetic member movable between a first position spaced away from and a second position adjacent to a first portion of the stationary magnetic structure and a generally annular magnetic member resiliently disposed around and adjacent to one end of the generally cylindrical magnetic member with a radial gap therebetween to engage a second portion of the stationary magnetic structure in the second position of the generally cylindrical magnetic member and to be spaced away from the second portion of the stationary magnetic member in the first position of the generally cylindrical magnetic member, the first and second portions of the stationary magnetic structure being spaced axially from one another with respect to the generally cylindrical magnetic member.

2. An electromagnetic structure comprising a generally E-shaped stationary magnetic structure including a central leg portion and at least two outer leg portions spaced laterally therefrom, coil means disposed around the central leg portion between the central leg portion and the outer leg portions, and a generally T-shaped movable armature disposed to move between a first position spaced away from and a second position adjacent to the stationary magnetic structure, said armature comprising a generally cylindrical magnetic member disposed to move reciprocally toward and away from the central leg portion and a generally ring-shaped magnetic member disposed in concentric relation around one end of the cylindrical magnetic member to engage the outer leg portions independently of the cylindrical magnetic member in one position of the armature and to be spaced away from the outer leg portions in the other position of the armature.

3. The combination as claimed in claim 2 wherein separable contact means are provided and operatively coupled to the movable armature to be actuated thereby between open and closed positions.

4. An electromagnetic structure comprising a stationary magnetic structure including first and second substantially parallel, spaced magnetic plates, at least two spaced outer magnetic leg members extending substantially between the plates and a central magnetic leg member extending from the second plate toward the first plate for only a portion of the distance therebetween, the first plate including a central opening substantially aligned with the central leg member, coil means disposed between the plates around the central leg member and a generally T-shaped armature disposed to move reciprocally with respect to the stationary magnetic structure between first and second predetermined positions, said armature comprising a generally cylindrical magnetic member disposed to pass through the opening in the first plate with one end disposed adjacent to the central leg member in the first position of the armature and a gen erally annular magnetic member concentrically disposed around the other end of the cylindrical member for limited movement with respect thereto to independently engage the first plate of the stationary magnetic structure in the first position of the structure.

5. The combination as claimed in claim 4 wherein stationary and movable contact means are provided with the movable contact means being coupled to the armature for actuation between open and closed positions with respect to the stationary contact means by the movement of the armature between the first and second predetermined positions.

6. The combination as claimed in claim 4 wherein a predetermined radial gap is provided between the other end of the generally cylindrical magnetic member and the generally annular magnetic member in both positions of the armature.

References Cited UNITED STATES PATENTS 3,091,725 5/1963 Huston 335-253 3,253,098 5/1966 Perry 335-l 3,310,762 3/1967 Goetz 335 BERNARD A. GILHEANY, Primary Examiner. H. BROOME, Assistant Examiner.