US3553617A

US3553617A - Magnet structure and magnet support structure in an electromagnetically operated switch

Info

Publication number: US3553617A
Application number: US844034A
Authority: US
Inventors: Merlin Y Turnbull; Harold E Whiting
Original assignee: Square D Co
Current assignee: Schneider Electric USA Inc
Priority date: 1969-07-23
Filing date: 1969-07-23
Publication date: 1971-01-05
Anticipated expiration: 1988-01-05
Also published as: GB1294186A

Abstract

A MULTIPLE CONTACT ELECTROMAGNETICALLY OPERATED SWITCH HAVING A HOUSING THAT PROVIDES AN ENCLOSURE FOR THE ELECTROMAGNET OPERATOR OF THE SWITCH. THE HOUSING INCLUDES AT LEAST ONE METAL PART THAT HAS A HIGH COEFFICIENT OF THERMAL CONDUCTIVITY SO THE HOUSING ACTS AS A HEAT SINK AND A RADIATOR FOR HEAT GENERATED WITHIN THE ELECTROMAGNET WHEN A MAGNET COIL OF THE ELECTROMAGNET IS ENERGIZED. THE HEAT SINKING CAPABILITY IS ACCOMPLISHED BY SUPPORTING A PORTION OF A MAGNET CORE FOR THE ELECTROMAGNET OF THE METAL HOUSING BY A PAIR OF EARS THAT ARE LOCATED ADJACENT THE POLE FACES OF THE MAGNET CORE TO MIXIMIZE THE TRANSFER OF HEAT BETWEEN THE MAGNET CORE AND THE HOUSING. THE EARS EXTEND FROM A MEMBER THAT IS CENTRALLY LOCATED IN THE STACK OF LAMINATED PIECES OF MAGNETIC IRON FORMING THE MAGNET CORE. A MEMBER PROVIDING THE CONNECTION BETWEEN THE ARMATURE AND A BELL CRACK LEVER EXTENDS CENTRALLY IN THE STACK OF LAMINATED PIECES OF MAGNETIC IRON FORMING THE ARMATURE SO THE SUPPORT FOR THE MAGNET CORE AND THE OUTPUT OF THE ARMATURE ARE COPLANAR WITH RESILIENT MEMBERS CARRIED BY THE MEMBER PROVIDING THE CONNECTION BETWEEN THE ARMATURE AND BELL CRACK ABSORBING THE SHOCK WHEN THE ELECTROMAGNET IS DE-ENERGIZED.

Description

197i M. Y. TURNBULL ETAL 3,553,61?

MAGNET STRUCTURE AND MAGNET SUPPORT STRUCTURE IN AN ELECTROMAGNETICALLY OPERATED SWITCH Filed July 25, 1969 2 Sheets$heet N VI JNI HQ. MERLIN Y. TURNBULL HAROLD E. WHITING Jan 5, 1971 M TURMBULL ET AL 3553,61?

MAGNET STRUCTURE AND MAGNET SUPPORT STRUCTURE IN AN I ELECTROMAGNETIC/LY OPERATED SWITCH Filed July 25, 1969 2 Sheets-Sheet 2 MERLIN Y. TURNBULL HAROLD E.WH|T|NG nited tes atent 3,553,617 Patented Jan. 5, 1971 3,553,617 MAGNET STRUCTURE AND MAGNET SUPPORT STRUCTURE IN AN ELECTRUMAGNETICALLY OPERATED SWITCH Merlin Y. Turnbull, Brooktield, and Harold E. Whiting, Milwaukee, Wis., assignors to Square D Company, Park Ridge, lll., a corporation of Michigan Filed July 23, 1%9, Ser. No. 844,034 Int. Cl. Hillh 45/04 US. Cl. 335-202 10 Claims ABSTRACT OF THE DISCLOSURE A multiple contact electromagnetically operated switch having a housing that provides an enclosure for the electromagnet operator of the switch. The housing includes at least one metal part that has a high coeflicient of thermal conductivity so the housing acts as a heat sink and a radiator for heat generated within the electromagnet when a magnet coil of the electromagnet is energized. The heat sinking capability is accomplished by supporting a portion of a magnet core for the electromagnet of the metal housing by a pair of cars that are located adjacent the pole faces of the magnet core to maximize the transfer of heat between the magnet core and the housing. The ears extend from a member that is centrally located in the stack of laminated pieces of magnetic iron forming the magnet core. A member providing the connection between the armature and a bell crank lever extends centrally in the stack of laminated pieces of magnetic iron forming the armature so the support for the magnet core and the output of the armature are coplanar with resilient members carried by the member providing the connection when the electromagnet is de-energized.

The present invention relates to electromagnetic type switching devices and more particularly to the constructional details and the arrangement of the components of a multiple contact electromagnetically operated switching device.

Electromagnetic switching devices of the type with which the present invention is concerned are commonly known as contactors and are furnished as devices of varying sizes having ratings in accordance with standards promulgated by the National Electric Manufacturers Association, commonly known as NEMA. An example of a contactor construction which is particularly suited to control loads of 50 amperes or less, which corresponds to a NEMA Size 2 device, is disclosed in United States Patent No. 3,354,415, which was granted on Nov. 21, 1967 to the inventors Joseph I. Gribble, Kenneth J. Marien and Harold E. Whiting.

While the proportions of the device shown in the Gribble et a1. patent may be increased to control currents greater than 50 amperes, economic and physical size limitations dictate that additional features should be incorporated therein if currents having a magnitude two or three times 50 amperes are to be controlled by the device. The stucture according to the present invention provides increased pressures between the switching contacts and a greater contact mass to enable the device to conduct the higher current values without overheating and without increasing the contact bounce characteristics of the device than was included in the structure disclosed in the Gribble et al patent. Thus while the device according to the present invention incorporates the desirable features and advantages included in the device as disclosed in the Gribble et a1. patent, it additionally includes a novel support arrangement for supporting the magnet core portion of the electromagnet which will cause the heat generated within the electromagnet to be more readily dissipated and reduce the impact shock which is imparted to the heat dissipating portion of the housing when the electromagnet is tie-energized.

It is an object of the present invention to provide an electromagnetically operated switch with a magnet structure which will reduce the shock when the electromagnet is de-energized and to support the magnet core on a housing part for the switch so the housing will act as a heat sink and dissipate heat generated within the electromagnet when the electromagnet is energized.

Another object is to support a magnet core of an electromagnet on portions of a metal part of a housing in an electromagnetically operated switch structure so the metal part will act as a heat sink and aid in dissipating the heat generated within the electromagnet when the electromagnet is energized and to reduce the shock to the metal part when the armature moves to a de-energized position when the electromagnet is de-energized.

A further object of the present invention is to provide an electromagnetically operated switch with a housing that has one metal part formed of a material that has a high degree of thermal conductivity and forms the external walls and the internal walls of a cavity within the housing and to support a magnet core and provide a connection between the armature and a bell crank lever in the switch by members which extend in a common plane centrally in a stack of laminated magnet metal pieces that form the magnet core and the armature so that the forces between the magnet core, the armature and the bell crank lever react along a linear plane to minimize wear of the parts and provide an efficient mag net structure and connection between the armature and the bell crank lever and to support the magnet core on a pair of ears that are formed on the magnet core member to extend laterally at the pole face portions of the magnet core which ears are arranged to rest on ledges formed on the walls of the housing part so that an efiicient heat transfer path is provided between the magnet core and housing part whereby the heat generated within the electromagnet will be efiiciently dissipated by the housing part when the electromagnet is energized.

A further object of the present invention is to provide an electromagnetically operated switch with a housing that has one metal part formed of a material that has a high degree of thermal conductivity and forms the external walls and the internal walls of a cavity within the housing and to support a magnet core and provide a connection between the armature and a bell crank lever in the switch by members which extend in a common plane centrally in a stack of laminated magnet metal pieces that form the magnet core and the armature so that the forces between the magnet core, the armature and the bell crank lever react along a linear plane to minimize wear of the parts and provide an efficient magnet structure and connection between the armature and the bell crank lever and to support the magnet core on a pair of cars that are formed on the magnet core member to extend laterally at the pole face portions of the magnet core which ears are ar ranged to rest on ledges formed on the walls of the housing part so that an etficient heat transfer path is provided between the magnet core and housing part whereby the heat generated within the electromagnet will be etficiently dissipated by the housing part when the electromagnet is energized and to position a pair of elastomeric members at a surface on the armature that is remote from the pole faces on the armature by the member which provides the connection with the bell crank lever to absorb the shock which occurs when the electromagnet is de-energized and the armature moves to a dc-energized position as the elastomeric members are compressed between the armature and a wall of the housing part.

Further objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended drawings illustrating certain preferred embodiments in which:

FIG. 1 is a side view partly in section of an electric switch incorporating an electromagnet structure and support therefor according to the present invention.

FIG. 2 is an end view partly in section of the switch in FIG. 1 taken in the direction of arrows 2--2 in FIG. 1.

FIG. 3 is a top view of the switch in FIG. 1 with a cover removed.

FIG. 4 is an exploded view showing in perspective the components of an electromagnet as used in the switch shown in FIG. 1 with a portion of the armature structure broken away to illustrate the connection of a shock absorbing member with the remainder of the armature.

Referring to the drawing, and particularly to FIG. 1, there is shown an electromagnet switch assembly having a plurality of components that are stacked one upon the other. The components of the assembly include a metal mounting plate 22, an insulating sheet-like member 24, an insulating base 26, an insulation barrier 28, a metal housing 30, and a cover 32, each of which is disclosed and described in an application for US. Pat. Ser. No. 844,148, which was filed concurrently herewith.

The metal mounting plate 22 is formed of a stamped metal part and provides a means to secure the switch assembly 20 to a vertical panel and the like, not shown. When the plate 22 is secured to a panel, an edge 34 becomes a bottom edge of the plate 22 and a surface 36 the front surface of the plate 22. The plate 22 has a pair of rearwardly extending indentations 38 along its bottom edge 34, providing a pair of spaced mounting feet having openings 39 therein. The plate 22 also has an identation 40 extending across its top edge which provides an elongated mounting foot having an opening 41 therein. The mounting

feet

38 and 40 with the

openings

39 and 41 therein are provided for the purpose of securing the plate 22 to a vertical panel. The plate 22 also includes an indentation 42 which extends from the bottom edge 34 rearwardly in the front surface 36 to the indentation 40. The indentation 42 is provided to permit passage of control wires, not shown, from the upper to the lower ends of the switch 20 in the space provided by the indentation. The control wires may be connected in circuit with the switching contacts of a device known as an overload relay, in a manner well known to those skilled in the art. The plate 22 also is provided with suitably located threaded openings which act as mounting holes which are used to secure the insulating sheet-like member 24 and base 26 to the plate 22.

The sheet 24 is preferably formed as a molded insulating part having a relatively thin cross section having a flat rear surface engaging the front surface 36 to cover a central portion of the indentation 42 so as to act as a cover for the wire trough. The sheet 24 is provided with a pair of circular ribs 44 which are raised on the front surface of the sheet 24 on opposite sides of a vertical center of the plate 22. The ribs 44 act as spring seats, as will be later described. The sheet 24 also is provided with portions 46 which are formed along the top and bottom edges of the sheet 24 in alignment with the indentation 42. The portions 46 act as scoops and aid in directing the wires in the portion of the wire trough disposed between the sheet 24 and the plate 22.

As disclosed in the application for United States Patent, Serial No. 844,148, the base 26 and the barrier 28 are formed of a molded insulating material having arc suppressing capabilities and cooperate with each other to provide a cavity which is divided into three compartments 48 having equal widths. The base 26 has a rear surface 50 positioned on the insulating sheet 24 and the plate 22 in a secured position by suitable screws which pass through openings in the base 26 and the sheet 24 and are threadedly received in the housing holes in the late 22. Extending into the material of the base 26 forwardly of the rear surface 50 and through the side walls of the base 26 is a slot 52. The slot 52 is centered on a center-line equidistant between a top wall 54 and a bottom wall 56 of the base 26 and is exposed to each of the compartments 48 by an opening. The compartments 48 each extend between the top wall 54 and the bottom wall 56 and each have a pair of terminal and stationary contact assemblies secured therein.

The terminal and stationary contact assemblies in each of the compartments 48 are arranged so that the contact assemblies of each pair are spaced equidistantly on opposite sides of the slot 52 and face in opposite directions. Each of the contact assemblies includes a terminal member 58 and a contact member 60. When the pairs of terminal and contact assemblies are secured at the opposite ends of the compartments 48, the terminal members 58 will have a wire connecting portion 62'extending external of the top wall 54 and the bottom wall 56 and the contact members will have an inclined stationary contact surface 64 positioned on opposite sides of the slot 52.

As disclosed in an application for United States Patent, Ser. No. 844,148, the barrier 28, the metal housing 38 and cover 32 define an internal closed cavity 66 wherein an electromagnet 68 is included. The electromagnet 68 operates a bell crank lever 70 which has a pair of arms 72 connected to a movable U-shaped contact carrier 74 that has a bight portion indicated by the numeral 76 in the drawings. The bight portion 76 is movable forwardly and rearwardly in the slot 52. The movable contact carrier 74 including the bight portion 76 is most clearly disclosed in an application for United States Patent, Ser. No. 844,100, concurrently filed herewith which has been assigned by the inventors Merlin Y. T urnbull and Harold E. Whiting to the assignee of the present invention. The barrier 28 has a body portion 78 which provides a front wall for the compartments 48 and suitable ribs, not shown provide side walls for the compartments. Extending from the body portion 78 are ears 80 that are arranged to seat upon the forward ends of a pair of posts 82 at the top and

bottom walls

54 and 56. The posts 82 each have a threaded insert molded therein and each of the ears 80 has an opening therein which permits the barrier 28 to be removably secured to the front surface of the base 26 by screws 84 which pass through the openings in the ears 80 into the threaded inserts in the posts 82. It is readily apparent that the removal of the screws 84 will permit the assembly including the barrier 28, the housing 30 and the cover 32 to be detached from the base 26 to permit access to the stationary and the movable contacts within the compartments 48 in the event the contacts require inspection or replacement.

The movable contact carrier 74 which is partly shown in FIG. 2, is preferably formed as a U-shaped molded part that includes the bight portion 76. The bight portion 76 is received in the slot 52 while arms, 86, which extend from opposite ends of the bight portion 76, extend externally of the side walls of the base 26 have free ends received in channels 88 in the housing 30 defined by portions 90 on the housing 30. The free ends of the arms 86 each receive a bearing 75 on a terminal end on an arm 72 of the bell crank lever 70. Extending forwardly of the bight portion 76 are a plurality of spaced projections 92 each of which extends into one of the compartments 48. The bight portion 76 has a rear surface 94 and each of the projections 92 has a front surface whereon a movable contact member 96 is positioned, in a manner disclosed in an application for United States Patent, Ser. No. 844,- 151, which has been filed by the inventor Merlin Y. Turnbull concurrently herewith.

The housing 30 preferably is formed as a cast metal part which has a high thermal conductivity. While aluminum may be used to form the housing 30, in that it posesses high thermal conductivity and is light weight, because of its resistance to impact, the housing part 30 is preferably formed of a zinc die cast material to have a bottom wall 98, a top wall 100 and a pair of side walls 102 and 104 which have a rear edge 106 resting on a front surface 108 of the barrier 28 and an open front wall 110 which is closed by the cover 32. The front surface 108 and the

walls

98, 100, 102 and 104 define the cavity 66 which has a front side closed by the cover 32. The cover 32, when removed, provides access to the electromagnet 68 that is positioned within the cavity 66 for inspection and for service purposes. Extending inwardly at each of the four corners of the housing 30 into the cavity 66 are suitably located ledges each of which has an opening therein and is arranged to rest upon the front surface 108 while the openings therein provide a passage for screws 112, one of which is illustrated in FIG. 1, which are threaded into suitably located threaded inserts that are embedded in the barrier 28 to secure the housing 30 to the barrier 28.

The electromagnet 68 which is positioned within the cavity 66 includes a magnet coil 114, an armature 116 and a magnet core 118. The magnet coil 114 preferably is formed as a molded encapsulated coil body as is well known to those skilled in the art and has a rear end positioned against an elastomeric sheet-like member 120 that is positioned in a socket in the front surface 108 and its front end positioned against an elastomeric member 122 on an inner face of the cover 32 so as to be positioned within the cavit 66 by the cover 32 and the barrier 28 when the cover 32 is secured to the housing 30.

Extending inwardly along the opposite side walls 102, 104 are a pair of

ledges

124 and 126. The

ledges

124 and 126 each extend from the portions 90 into the channels 88 so as to present a forward facing surface 128 that is exposed to the cavity 66 and have a threaded opening 129 therein. The surfaces 128 are disposed to be adjacent and extend parallel to a center line indicated by a numeral 130 in FIGS. 1 and 2.

The magnet core 118 has an E-shape and includes an E-shaped central member 132 with an equal number of E-shaped magnet iron pieces stacked on the opposite sides of the central member 132. The E-shaped central member 132 and the stacked E-shaped magnet iron pieces, which are indicated by the

numerals

134 and 136, are laminated together and secured by rivets 138. The E- shaped central member and the E-shaped iron pieces provide the magnet core 118 with a central leg 140 and a pair of outer legs 142 with the leg 140 presenting a pole face 144 and the legs 142 presenting pole faces 146. The pole faces 142 and 144 all face in the same direction with the pole faces 146 having shading coils 148 that are shaped and sized and secured therein in a manner well known to those skilled in the art. Extending outwardly of the outer legs 142 adjacent the pole faces 146, and integrally formed on the central member 132 are a pair of ears 150, each of which has an opening 152 therein.

lhe ledges

124 and 126, the surfaces 128, the openings 129, the ears 150 and the openings 152 are arranged so that when the magnet core 118 is positioned within the cavity 66, the ears 150 will rest upon the surfaces 128, with the

openings

129 and 152 in alignment with each other with the central member 132 centered on the center line 130 and extending in a plane defined by the center line 130 that is perpendicular to the bottom wall 98 and the top wall 100. Further, when the magnet core 118 is thus positioned in the cavity 66, a top wall 154 of the E-shaped magnet core 118 including the E-shaped member 132 and the E-shaped

magnet iron pieces

134 and 136, will engage the portions of the top wall 100 facing the cavity 66. When the magnet core 118 is thus positioned within the cavity 66, the pole faces 144 and 146 will face the bottom wall 98. The magnet core 118 is maintained in the cavity 66 in the position described by a pair of fastening members 156, each of which has a portion extending through the openings 152 and threaded into the opening 129. The fastening members each have a head portion that tightly engages the ears and a threaded bore extending from a free end thereof. The free end may be provided with a suitable slot 162 which receives a top of a screw driver for the purpose of tighten ing the members 156 in the openings 129. As in conventional practice, a lock washer 162 may be positioned between the head portion and the ears 150.

If desired, the portions of the

magnet iron pieces

134 and 136 which define the central leg 140 may be formed as separate parts which are spaced from the remainder of the magnet core by a sheet 164 of a non-magnetic metal, such as brass, to provide the magnet core with a permanent air gap, as is well known to those skilled in the art. When the magnet core 118 is provided with a permanent air gap, the

portions

166 and 168 providing the central leg 140 are maintained in position by rivets 170 and a leg portion 172 formed integrally with the remainder of the central member 132.

The magnet coil 114, when positioned within the cavity 66 by the

elastomeric members

120 and 122 after the cover 32 is secured to the housing 30, will present a rectangularly shaped opening 174 into which the leg 140 extends while a top wall 175 of the coil is positioned adjacent a wall 176 on the magnet core 118 from which the leg 140 extends. The coil 114 further has a pair of side walls 178 positioned adjacent the inner faces of the outer legs 142, a bottom wall 180 facing the bottom wall 98 and a portion 182 extending through a suitable opening in the cover 32 carrying terminals 184 for the windings within the coil. The armature 116 in the form shown in FIGS. 1 and 4, has a T-shape and includes a central member 186 that is preerably formed of a single metal piece to have a pair of T-shaped portions 188 in face-to-face engagement with each other with the interface therebetween extending in the plane defined by the center line 130 and an equal number of T-shaped magnet iron pieces stacked on the opposite sides of the T-shaped portions 188. The T-shaped portions 188 and the stacked T-shaped magnet iron pieces, which are indicated by the

numerals

190 and 192 are laminated together and secured by rivets 194. The T-shaped central portion and the T-shaped stacks of

iron pieces

190 and 192 provide the armature 116 with a central leg or stem 196 having a pole face 198 at its free end and a pair of pole faces 200 at the ends of the arms 202 which face and are arranged to engage the pole faces 146. The stem 196 extends into and is movable in the opening 174 when the armature 116 is positioned in the cavity 66. The armature 116 has a bottom wall 204 facing in the opposite direction from the pole faces 200. Extending downwardly from the wall 204 and spaced therefrom, the member 186 is provided with a portion 206 that is shaped to provide an operative connection with a bearing 208 that is mounted on an operating ar-m 210 of the bell crank lever 70. The portion 206 has a box-like cross section and has its opposite ends 212 spaced inwardly of the ends 214 of the armature 116. The box-like cross section provides a pair of spaced inner walls 216 and an opening 218 is provided in portions of the inner walls 126 and the rear wall 220 of the portion 206. The opening 218 is sized so an end portion of the operating arm 210 on the bell crank lever 70 may extend into the space between the walls 216. The arm portion 210 carries the bearing member 208 which is positioned between the walls 216 and is more clearly described in the application for United States Patent, Serial No. 8441100, supra. When the armature 116 is positioned within the cavity 66, the bearing member 208 will be positioned between the walls 216 while the central leg 196 of the armature 116 is received in and partly extends into the opening 174 of the coil 114.

Positioned at the opposite ends 212 of the box-like portion 206 are a pair of elastomeric members 222 which are preferably formed by butyl rubber, which is a ma terial well known for its ability to absorb shock without instantly rebounding. Each of the members 222 includies a shock absorbing portion 224 which is substantially rectangular in shape, having a fiat surface 226 positioned on the rear wall 204 and a flat surface 228 remote from the wall 204 extending downwardly beyond the square shaped portion 206 so as to engage the bottom wall 98 when the armature is in its de-activated position. The members 222 also include a portion 225 which is formed integrally with the portions 224 and is received within the interior of the square shaped portion 206 to position the shock absorbing portion 224 on the ends 212. A spring member having its opposite ends 232 formed to engage the outer surfaces of the shock absorbing portion 224 and a portion 234 connecting the ends 232 passing adjacent the wall 204 maintains the members 222 in position on the ends 212. The switch assembly also includes a pair of springs 236 which are positioned by the ribs 44 and engage the bight portion 76 to constantly urge the movable contact carrier 74 forwardly in the slot 52 and a spring 238 which is compressed as the movable contact 96 engages the stationary contact surfaces 64.

The mounting plate 22, the insulating member 24, the base 26, the stationary contacts assemblies, the movable contact carrier 74 with the movable contacts 96 thereon, the barrier 28, the housing 30 and the bell crank lever 72 which is positioned within the cavity 66 are all assembled in a manner disclosed in the application for United States Patent Serial No. 844,148, supra. After the foregoing mentioned parts are assembled, the electromagnet 68 is installed in the cavity 66 by assembling the armature 116, coil 114 and the magnet core 118 so that the stem 196 extends into the opening 174 from one side of the coil 114 and the central leg 140 of the E- shaped magnetic core 118 extends into the opening 174 from the other end of the coil 114. The electromagnet 68 is then installed within the cavity 66 by aligning the armature 116, the coil 114 and the magnet coil 118 so that the coil 114 is seated on the elastomeric member 120, the opening 218 permits the bearing 208 to be received between the walls 216 and the openings 152 on the ears 150 are aligned with the openings 129 so that the fastening members 156 may secure the electromagnet 68 in the cavity 66 as previously described with the shock absorbing portions 224 in engagement with the bottom wall 98. The cover 32 is then secured on the housing 30 by positioning the cover 32 on the open front 110 and tightening screws 240, which extend through suitably located openings in the cover 32, into the threaded bores 160. The cover 32, when secured to the housing 30, will cause the coil 114 to be properly positioned in the cavity 66 as the elastomeric member 122 is compressed against the front surface of the coil 114.

The operation of the switching device is as follows. While the switch 20 will operate when mounted on a horizontal support, it is particularly suited to be mounted on a vertical panel, not shown, so that the armature 116 will be moved by the combined forces furnished by gravity and the springs 236 to a position whereat the pole faces 200 of the armature 116 are separated from the pole faces 146 of the magnet core 118. The energization of the coil 114 through suitable wires connected to terminals 184 causes a mutual magnetic attraction to be generated between the armature 116 and the magnet core 118. The armature 116 is connected to the rotatable bell crank lever 70. The magnet core 118 is maintained in engagement with the top wall 110 by the ears 150 which are secured on the

ledges

124 and 126. It is well known that the magnetic attraction between the armature 116 and the magnet core 118 increases exponentially with the decrease in the distance between the pole faces of the armature 116 and the magnet core 118 and the magnet attraction increases to a maximum when the pole faces engage each other. The magnetic attraction between the armature 116 and the magnet core 118 causes the armature 116 to move upwardly toward the magnet core 118 and the bell crank lever 70 to rotate about its pivot. The rotating bell crank lever 70 causes the movable contact carrier 74 to move toward the plate 22 to a position wherein the movable contacts 96 engage the contact surfaces 64. The initial movement of the contact carrier 74 is opopsed by the force of gravity on the armature 116 and by the springs 236. The subsequent movement of the contact carrier 74 which occurs after the movablee contacts 96 engage the contact surfaces 64, is opposed by the force of gravity on the armature 116 and the springs 236 as well as the springs 238 which are associated with the movable contact member 96. Thus. the resistance to the movement of the armature 116 toward the magnet core 118 progressively increases as the springs 236 are compressed and markedly increases as the force required to compress the springs 238 is added to the force required to compress the springs 236. The magnet core 118 is rigidly supported in the cavity 66 by the ears to have its upper wall 154 tightly pressed against the top wall 110. It is well known that when an electromagnet is energized, the area of the magnet core which includes the shading coil operates at a higher temperature than the remainder of the magnet core. Thus the heat generated within the electromagnet 68 when the coil 114 is energized will be readily transmitted by the ears 150 which are located on the magnet core adjacent the shading coils 148 and the wall 154 to the metal housing 30 so the metal housing may serve as an etficient heat sink and dissipate the heat energy generated within the electromagnet 68. When the coil 114 is de-energized, the combined forces of the

springs

236 and 238 as well as the force of gravity on the armature 116 will cause the armature 116 to move downwardly toward the bottom wall 98. After the movable contact members 96 separate from the contact surfaces 64, the force of gravity on the armature 116 and the springs 236 causes the armature 116 to continue its movement toward the bottom wall 98 to a position wherein the elastomeric members 222 engage the bottom wall 98 and limit further movement of the armature 116. The members 222 each have a flat surface 226 resting on the rear wall 204 of the aramature 116 and a surface 228 arranged to engage the bottom wall 98. Thus as the armature 116 moves to its de-activated position, the members 222 will be compressed and absorb the shock which could otherwise damage the housing 30. Further, as disclosed in the Gribble et al. patent No. 3,354,415, supra, and in patent application Ser. No. 844,151, supra, as well as an application for US. Pat. Ser. No. 843,994, concurrently filed herewith, the movable contact and its supporting structure provides an arrangement will considerably reduce the bounce which accompanies the engagement between the movable contacts 96 and the stationary contact members 60.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

What is claimed is:

1. In an electromagnetically operated switch, the combination comprising: a housing including at least one metal part having a high coefficient of thermal conductivity, said part having a top wall, a bottom Wall and a pair of side walls defining an internal cavity within the housing and providing at least a portion of the external Walls of the housing and a pair of support ledges along side wall portions of the cavity, an E-shaped magnet core having a plate-like member and an equal number of E-shaped laminated magnet metal pieces stacked on opposite sides of the plate-like member to provide a pole face at the terminal end of each outer leg of the core, a shading coil secured adjacent the pole face on each outer leg and a pair of ears extending from the plate-like member at the pole face portions of the core, said ears being secured to the support ledges for mounting the core within the cavity so the plate-like member extends in a plane perpendicular to the top and the bottom walls and providing a path for conducting heat generated within the core to the metal housing part, an armature movably mounted in the cavity and having a central member extending in the plane of the plate-like member and an equal number of laminated magnet metal pieces stacked on opposite sides of the central member to provide a pair of pole faces on the armature that are engageable with the pole faces on the magnet core, and a magnet coil having an opening extending therethrough centered in the plane of the plate-like member and surrounding at least a portion of the middle leg of the E-shaped magnet core for inducing a magnetic flux in the core and causing the pole faces of the armature to engage the pole faces of the core when the coil is energized.

2. The electromagnetically operated switch in accordance with claim 1 including a bell crank lever having an actuating arm portion movable in the cavity and a boxlike portion on the central member centered in said plane and extending from a side of the armature remote from the pole faces on the armature, said box-like portion providing a connection between the armature and the actuating arm portion of the hell crank lever.

3. The electromagnetically operated switch in accordance with claim 2 wherein the armature is movable along said plane between two positions in the cavity and a yieldable means including a spring force reacting on the bell crank lever constantly urges the armature to a first of the said two positions and maintains the armature in the first position when the electromagnet is de-energized and the armature is moved against the force provided by the yieldable means to a second of the said two positions whereat the pole faces of the armature and the magnet core engage each other when the electromagnet is energized and wherein the switch includes a pair of resilient elastomeric members positioned at opposite ends of the b0x-like portion to engage the bottom wall of the metal part of the housing to reduce the shock to the housing when the armature moves from the second position to the first position. I

4. The electromagnetically operated switch in accordance with claim 3 wherein the armature, the magnet coil and the magnet core are positioned within the cavity so that the force of gravity acts on the armature and provides at least a portion of the force which constantly urges the armature toward the first position.

5. The electromagnetically operated switch in accordance with claim 3 wherein the armature is connected to a movable contact carrier through the bell-crank lever and springs reacting on the movable contact carrier provides a portion of the force which constantly urges the armature toward the first position.

6. The electromagnetically operated switch in accord ance with claim 1 wherein the magnet core is E-shaped and the armature is T-shaped.

7. The electromagnetically operated switch in accordance with claim 1 wherein the central portion of the box-like portion has spaced inner walls and an opening therein receiving a portion of the actuating arm portion of the bell crank lever so that a bearing member that is rotatable on a terminal end of the actuating arm is positioned between the inner walls of the box-like portion.

8. The electromagnetically operated switch in accordance with claim 3 wherein the elastomeric members each includes a shock absorbing portion that is positioned by the box-like portion to have surface portions engaging the side of the armature from which the box-like portion extends and surface portions extending from the box-like portion engageable with the bottom wall of the housing so that the elastomeric members are compressed between the bottom wall of the housing and the armature as the resilient members absorb the shock when the armature moves to the first position.

9. The electromagnetically operated switch in accordance with claim 8 wherein the box-like portion has an opening at each of its ends and each of the elastomeric members includes a portion extending from a side of the shock absorbing portion into the opening on the ends of the box-like portion for positioning the shock absorbing portion on the side of the armature.

10. The electromagnetically operated switch in accordance with claim 9 wherein a single spring-like member that has opposite ends engaging a side of the shock absorbing portion on each elastomeric member that is remote from the box-like portion maintains the position of the elastomeric members on the ends of the box-like portion.

References Cited UNITED STATES PATENTS 3,354,415 11/1967 Gribble 335132 HAROLD BROOME, Primary Examiner U.S. Cl. X.R. 335-432