US2378162A - Electric switch - Google Patents

Description

June 12, 1945. STAPLETQN 2,378,162

ELECTRIC SWITCH Filed Nov. 25, 1941 3 Sheets-Sheet 1 June 12, 1945; G STAPLETQN 2,378,162

ELECTRIC SWITCH Filed Nov. 25, 1941 3 Sheets-Sheet 2 if v /6 gwuwflm y 'J MSJW 6 a K June 12, 1945. STAPLETON 7 2,378,162

ELECTRIC SWITCH Filed Nov. 25, 1941 S Sheets-Sheet 3 Patented June 12, 1945 ancc'rmo swrron George M. Staplet'on, New York, N. Y., assignor to Ward Leonard Electric Company, a corporation of New York Application'November 25, 1941, Serial No. 420,327 7 Claims. (Cl. 200-104) This invention relates to electric switches adapted for general use and for control purposes and is of the magnetically operated contacting type although certain features of this improvement are applicable to other types of switches.

Certain of the improvements disclosed herein and not claimed are the inventions of Frank G. Logan and are described and claimed in his pending United States application Serial No. 417,990, filed November 6, 1941.

Certain disclosures of this application not claimed herein are covered in a divisional application of this case, Serial No. 446,324; flied June 9, 1942. f

The improvements described and claimed herein relate to features of construction of various parts and their relationship to each other for the general object of obtaining a compact form of switch which may be conveniently manufactured and assembled and be durable and dependable under long continued use. One particular object is to provide a supporting frame which may be simply formed and serve a number of different functions and also to avoid the necessity and expense of machining the parts to close clearances. It is adapted to conveniently support at its upper portion the fixed contact head so that it is readily I removable together with the fixed contacts for inspection, renewal or cleaning of the parts. The frame likewise serves to restrain the movable constrains on the parts during and after the closing action of the switch.

Other objects and advantages of this invention will be understood from the following description and accompanying drawings which illustrate one embodiment of the invention.

Fig. 1 is a vertical central section in a plane at right-angles to the back of the switch; Fig. 2

is a top plan view with the connecting terminals 1 shown in section; Fig. 3 is a horizontal section on the line 3-4 of Fig. 1; Fig. 4 is a horizontal section on the line 4-4 of Fig. 1; Fig. 5 isan enlarged side view,'partly in section, of one of the fixed contacts; Fig. 6 is an enlarged perspective view of one of the arc chambers or shields; 'Fig. 7 is a vertical section on the line 1--'| of Fig. 1; and Fig. 8 is a horizontal section on the line 8-8 of Fig. 7. g

The apparatus is supported by a frame or base of sheet metal having a general U-shaped' form. The base of the U extends vertically and the two side portions extend forwardly from the base portion. The rear portion of the frame is corrugated for strength, the projecting ribs la which extend vertically along the back, being forced forwardly from the metal sheet before it is cut and bent to the desired form. At about the middle of the back portion, two of the ribs la are further tact head from abnormal displacement under I pressed forwardly forming projecting ribs I b, as

shown in Figs. 1 and 4, for a purpose later ex-.

plained. The back portion is providedwith openings ie at the top and bottom, as shown in Figs. 1 and 7, for the purpose of securing the frame toa supporting panel. The forwardly'extending side portions id are provided with a number of openings ie as shown in Figs. 7 and 8 for the purpose of ventilation and accessibility during assembly,

self-adjusting upon closing the switch; and a further object is to so relate the parts which loosely support the non-actuated portion of'the magnet to the actuated portion of the magnet in a manner that such parts will also serve as guiding means for permitting freedom of movement and self-adjustment of the-actuated portion of the magnet' during'the closing action. Another object is to provide a supporting frame which is so formed as-to be of light weight'and occupy small space while insuring sufficient strength and stiffness of the parts.

' Another object is to relate the actuated portion of the magnet to the driving connection of the movable head so that such portion has relative movement with reference to the driving connection for thepurpose of aiding in the selfalignment of the parts and avoiding unnecessary and in repair or adjustment of the parts. A number of projecting portions extend from the side portions and are bent inwardly at right-angles at the front of the frame for forming supports for various parts. A pair of these projections If, .shown in Figs. 1 and ,2, forms a support for a front plate 2 which may be utilized for supporting auxiliary control apparatus or parts and also serves another function to be described later. The plate 2 is also secured to a pair of inwardly turned projections lg of the frame which extend vertically along a considerable portion of the frame. A

pair of similar projections l h are positioned below the projections lg, as shown in Fig. 1', and serves, together with the projections lg, to support another front plate 3 which may be utilized for supporting auxiliary control apparatu or parts. A pair of similar projections Ii from the frame are positioned below the projections In and serve to support another plate 4, the pu p se oi which will be later explained. The extensions lg carry at their upper middle portions a pair of projections 17', as shown in Figs. 1 and 3, which are curved inwardly and outwardly and serve a purpose later explained. They are opposite the projections lb of the rear portion of the frame. The main frame and its various extensions and projections not only serve for supporting various parts but also accomplish other objects, as later described.

In describing the construction of the switch and the relationship and operation of its parts, the upper portion will first be described and the description continued by reference to the other parts inprogressive steps downwardly. The fixed contacts and inter-connections thereto are supported by a block of insulating material molded to the desired form. It extends horizontally across the upper portion of the switch and is supported at its sides by resting upon the side portions Id of the frame, as shown in Fig. '7 and upon the front projection if as shown in Figs. 1 and 2. The front tie plate 2 is provided at its upper part with a pair of inwardly extending projections 2a which extend over the front edge of the insulating block 5 and thereby serves to hold the front portion or the block in fixed position. The rear portion of the block 5 is held in place by a cross-pin 3 which extends over the rear part of the block, as shown in Fig. 1. This pin extends through slots He in the side portions of the frame. The outer ends oi. the pins are formed with circumferential grooves which are engaged by spring clip So, as shown in Fig. 2, for preventing endwise movement of the pin. When it is desired to remove the block 5, it is merely necessary to remove one of the clips Ba and then move the pin 6 endwise a short distance so as to clear the inside of a side portion of the frame and then by raising the free end of the pin and after removing the other clip 5a, the pin can be withdrawn from the other side of the frame. The slots lie permit this tilting and their final removal from either side of the frame as may be desired. Of course, the pin may be removed by pulling it out longitudinally after removing one 01' the pins to but where a number of these switches are stacked side by side closely in a row,v

the above described tilting method of removal of the pin can be accomplished even though another switch is mounted closely on each side. After removal of the pin the rear end of the block 5 is free to be raised from the frame and thus permit the front edge of the block to be withdrawn from under the clamping extensions 2a after first loosening the screws holding the plate 2. Thus the insulating block 5 may be readily removed and replaced, together with the parts carried by it, for inspection, cleaning or adjustment of the parts.

The block or head i is provided on its upper surface with ribs 50, as well shown in Fig. '7, which extend from front to back and also an upwardly extending rear cross-rib 5b, asgshown in Fig. 1. These ribs are for the purpose of strengthming the block and for also separating the upper portions of the fixed contacts whichportions lie in the valleys between the ribs. The fixed contacts are in the form of downwardly extending metal rods 1, the lower ends of which form the contacting faces of the fixed contacts which faces are preferably formed .of silver, or alloys of silver, or other suitable material, for obtaining good con tact surfaces. The upper endmof the contact rods or cylinders I are of reduced diameter and project upwardly through openings in the head 5, being secured to the head by washers and nuts la on the upper threaded ends of the contact rods. The upper ends of the contact rods are slotted so that they may be held by a screwdriver from turning while the clamping nuts 1a are turned tightly for locking the parts in fixed position. The lower portion of each fixed contact rod is encircled somewhat above its lower end by a ring 8 of insulating material, as shown in Fig. 1 and more particularly in Fig. 5. This insulating ring may be secured to the rod in any suitable manner but, as shown in Fig. 5, is held in place by spinning or upsetting a portion of the metal rod 1, as shown in Fig. 5, against the upper and lower inner edges of the insulating ring. This ring acts as a spacer on each fixed contact for preventing engagement with adjoiningparts and likewise as a barrier, although permitting free escape of the gases upwardly around its outer rim. In the particular switch shown, there are twelve fixed contacts 1 in three rows of four each. The front and rear contacts of each row are adapted to be connected to the controlled circuit, or circuits, by terminal connections in the form of flat strips 812 which are bent to extend under the clamping nuts la and locking washers on the contact posts and are provided at their outer ends with screws to and locking washers for receiving the conducting leads. The inner two contact posts of each row are connected by a metal link 8 which lies on the top of the contact head and extends under the clampin nuts 1a and washers of the two contact posts. The two front contact posts of each row are adapted to be bridged by a movable contactor, as indicated in Fig. 1, and the two rear contact posts of each row are adapted to be bridged by a contactor. Thus the circuit may be traced from the outer terminal 8a of one row through the front contact post and bridgi contactor to the second contact post and then through the link 9 to the next contact post and thence through the rear bridging contactor to the rear contact post and rear terminal Be. When the circuit of each row is opened there are thus secured four breaks in the circuit in series with each other which tends to reduce the arcing at each contact. The provision of the terminals affords means for connecting the switch in any way desired to the outside circuit and by locating the links 9 at the top of the insulating head, they are conveniently accessible and removable if desired for replacement by the connection of overload controlling devices between the inner terminals or the different rows, or by the connection of amrneters or other devices for particular purposes.

The movable contact assembly is formed of two separable blocks of molded insulating material which are securely clamped together for holding the various associated parts in place. The lower insulating block In extends horizontally between the side portions of the frame. The upper block I l similarly extends horizontally between the side portions of the frame and is removably secured to the lower block by screws l2, well shown in Figs.

3 and 'l, which pass vertically down through the upper block'and lower blockand have a threaded engagement at their lower ends with a channel shaped sheet metal strip II to be later described. The lower insulating block II is provided with a number of vertical openings lfla each or which is below and opposite the previously described fixed contacts. These openings are for the pm 01 providing a free flow or air upwardly to and road the contacts to aid in extinguishing the arcs and in carrying away the hot gases. The upper block I I of the movable assembly is provided with twelve cylindrical openings I la which are opposite the contact posts I and these openings extend vertically downward and communicate with the openings Ila in the lower block it, as well shown in Figs.,1 and 7. A cylindrical arc shield r or barrier I4 is positioned within each of the openparticularly shown in Fig. 6 and aspaceitb is left-between the edges of the upper portion of the shield. The lower. portion of the shield is dared outwardly at No and, as well shown in Fig,

1, the adjoining portions of the insulating blocks I0 and H are shaped to receive these flared portions of the shields so that when the two -insulating blocks are clamped together by the screws I2,

the shields M will be held in fixed position. Pr0-.

vision isalso madefor insuring .that the shields are maintained in their proper positions with ref erence to the movable contacts. This is accomplished by formingvertical projections Hb on the insulating block I! which project within the openings Ha, as shown in Fig. 3. The width of each projection Hb corresponds with the opening .Hb of-each shield and. when the shield is passed intoits opening in the insulating block,

the Vertical edges of the upper portion of the shieldwlll engage the projection Nb and thereby insure that each shield is maintained in its proper position. The barriers or shields M may be formed of sheet metal and it should be noted that each of these shields'is individually insulated from- Metal shields I other portions 01 the apparatus. are desirable owing to their ability to resist objectionable disintegration from effects-of arcs;

and either magnetic ornon-magnetic metarmay be used, such as iron orv brass but the shields may be made of material other than metal which will retain its form and be capableof withstanding the eflects oi the arcs. 1 a Each of the movable contactsbridges a pair of fixed contacts, as shown in Fig. l, and is in the 3 term of a sheet metal channel piece Iii, as well shown in Fig.7 and is preferably made of copper:

and'this channel piece carries at each end a con-i tact l-Sa which is securely fastened to the piece I! as by riveting or otherwise. These contacts are preferably formed with a face of silver or silver alloy for insuring good contact with the fixed contacts when engaging them. Each of these bridging movable ,contact assemblies extends 1 through the cut-away portions Ha "of a pair of V shields so that the contact faces are centrally ceive the upper'ends of the strips in assembling the parts. Each bridging piece I! of the movable contacts is provided with a central slot of the same form as the cross section of the strip and is adapted to freely move along the guiding strip.

A spring ll encircles each guiding strip I6 andone end of the spring is positioned below each of the bridging pieces I! while the other end seats in an opening formed in the insulating block I.

The movable contact assembly, as previously described is composed of two separable blocks of molded insulation fastened together and they support and carry the arc barriers or shields as well as the spring pressed bridging contacts. The fas-- tening screws I! serve as a common means, not

i only for holding the insulating blocks in and II together, but by engaging the metal-piece ii of U form, serve to hold .all parts of the movable contact head together.

The parts are shown'in the open position of the switch and when the part I3 is moved up-;

wardly upon the energization of the magnet, the

movable contact assembly including the arc chambers or shields I4, is moved upwardly and thereby cause the bridging movable contacts to engage After their respective pairs of fixed contacts 1. initial engagement and upon further upward movement of the parts, the movable bridging contacts are forced downwardly by their engagement with the fixed contacts along the guiding strips l6 againstthe pressure of the springs ll.

As the bridging contacts have a certain freedom v of movement on the guiding strips, they are self adjusting so that the pressure of the movable contacts against the fixed contacts is equalized, thereby insuring proper engagement and sumcient contact pressure of each ovable contact with its fixed contact. Also, by reason of the movable contact assembly being pivotally connected, as hereinafter explained with the actuated portion or the magnet, the movable contact -.the switch, the pressure'of the contacts and the head is capable of movement as a whole so as to be self-adjusting in relation to the fixed contacts in order to further insure equalization of "contact pressure in all parts.

When the magnet isdeenergized for opening springs ll' together with theweight of t e parts,

force the movable contact head downwardly witha quick opening movement. In this opening action the arc barriers are, of course, moved downwardly with the movable contact head andthis action results in constantly bringing freshsunfaces of the shields oppositethe arcs and thereby aid in cooling and extinguishing them. Furthermore, by bringing new surfaces opposite the arcs,

positioned W thin the shields and opposite a pair or fixed contacts, as shown in Fig. l. Each bridglug contact is kept in proper alignment by a contact guide II in the form of a metal strip of rectangular form, as shown in Figs. 1 and 3. The lower end of each of these guiding strips is knurled or roughened and is forced intoan opening in the insulating block l0 so as to be firmly retained in position by the block Ill. The strips are secured in position in the block ll before the block II is i'astenedthereto; and the openings formed in the insulating block I I for reception of the upper ends of these strips are of sufficient size to freely rethe arc chambers are less subject to deterioration from effects of the arcs, as compared with fixed arc barriers where the arcing effects are concentrated on the same portions of the barriers. Also, the free-spaces between the arc chambers and the fixed contacts and around the insulating rings s provide open passagesior the free flow of the hot. gases upwardly in their natural tendency of movement and out through the top of the chambers, this free passage of the hot gases upwardly and outwardly being assisted by the free 1 inflow of air through the openings lilo below each ofthe contacts. The are chambers also serve to cool the hot gases as they pass freely upwardly and out from the chambers.- The cut-away-portions of the chambers for the purpose of permitting the introduction of the movable contacts andv oi the bridging elements carrying them, do not lessen the eflectivenesspf the structure in extinguishing the arcs because, with reference to each pair of contacts, the currentpasses through a loop formed by one fixed contact, the bridging contacts and the other fixed contact which results in forcing the arcs outwardly from the loop always against the portions of the chambers which are not cut away. The cut-away portions of the chambers serve also to facilitate the inward passage of air to the chambers to aid in the upward and outward passage of the hot gases through the chambers.

The function of the inwardly pressed projections lb from the rear of the main frame and of the projections Id at the front portion of the frame on opposite ends of the movable contact head is for restraining the movement of the head under shocks and jars. The movable head is normally guided in its movement by parts hereinafter described but the projecting portions referred to serve as restraining means under unusual or severe conditions for preventing the movable head being jolted to an abnormal position, as one of the purposes of this improved switch is for adaptation to withstand severe shocks and jars as, for example, when used on naval vessels.

The magnet core actuating the switch to closed position is composed of two similar laminated parts and on account of the fact that the part corresponding to the. usual fixed part is movable for the purpose of securing self-alignment and self-adjustment, it will be referred to herein as the non-actuated part of the magnet and the other part as thefactuated part of the magnet. Each part is built up of laminations of general E form and the laminae of each part are of the same size and shape which simplifies the stocking problem and the cost of assembly. The faces of the ends of the three legs of the E are ground, after assembly of the core parts, to lie in the same plane; and when the parts are in their attracted position, there is no air gap between the engaging faces of the core portions. This not only simplifies the cost of manufacture by permitting the grinding of the engaging faces by one operation in the same plane but the omission of any air gap results in the advantages of lower volt-ampere imput to the magnet coil, uniformity of' coil inductance and a slight time delay before actuation of the switch to open position, due to higher residual magnetization and higher induced secondary currents in the iron core, the last named advantage being particularly desirable in overcoming the opening of the switch when the circuit of the magnet coil is momentarily opened at auxiliarly control contacts by severe shocks on the apparatus.

Referring to Fig. 1, the three-legged form of the laminae 18 of the non-actuated portion of the magnet is shown as having the legs extending vertically downward and the three-legged The projections llb from the end plates loosely engage vertical slots 200 in the cross brackets 20 so as to permit considerable freedomof movement of the non-actuated portion of the magnet in alldirections for the purpose of self-adjustment, .as later explained, but is, of course, re-

strained by the slots from assuming extreme or abnormal positions. In assembling the core of the non-actuated portion of the magnet, the end plates 18a having. the projections [8b are permanently fastened to the laminae, as by riveting, and the pole faces afterwards ground. This eliminates possible distortion of the parts which might occur if the end plates or their supporting extensions were attached after grinding. The magnet coil 2| is carried by a spool 2la of insulating material and is held in place, as shown in Fig. '7 by a U-shaped strip 22 of metal, the base of the U passing over the top of the laminae I8 and the legs extending downwardly inside the magnet coil. The supporting strip 23 is provided with outwardly extending projections 23a at the lower ends of the legs which pass under and support the magnet coil.

The actuatedportion of the magnet comprising the laminae i9 is provided with end plates |9a which extend along opposite sides of the laminae and are bent at right-angles, as shown in Fig. 8, to pass inwardly over the ends of the laminae and again bent outwardly at rightangles to form extensions ISb. These end extensions are spaced from each other for receiving the driving rods 24 which latter are connected for actuation of the movable contact head. At the front portions of the end plates lea is secured a pair of angular pieces 25 which are bent at right-angles so as to extend toward the side portions of the main frame as shown in Fig. 8. In assembling the core structure of the actuated part of the magnet, the end plates 19a and the angular pieces 25 are permanently fastened together and to the laminae as by riveting the parts, after which the pole faces of this portion of the magnet are ground inia single opera tion in the same plane. This avoids possible distortion of this portion of the magnet which otherwise might occur if the end plates or pieces 25 were attached to the laminae after the grinding peration.

There are two drive rods 24, one in the back and one in the front portion of the apparatus,

for connecting the actuated portion of the magnet with the movable contact. head. These rods are of square cross section, as shown in Fig. 4, and are pivotally connected by pins 240. between the extensions I 9b of the end plates, as shown in Fig. 8. The drive rods extend upwardly from these pivotal connections and are loosely guided in their movement by the two brackets 20, as shown in Fig. 4, these brackets being bent at their middle portions to form vertical guiding laminae IQ of the actuated portion of the magnet is shown with its legs extending upwardly and, as already explained, the engaging faces of the legs are ground, after assembly, in the same plane so as to insure uniform good surface contact. The end plates. [8a of the non-actuated portion of the magnet core are shown in Fig. 4 as provided at each end with angular extensions lab which project rearwardly and forwardLv. These extensions respectively engage sheet metal brackets 20 which are bent to a desired shape, as shown, and provided with side portions 20a by which they are securely fastened to the side portions of the main frame by the screws 20b.

channels for the rods. The upper ends of the rods are riveted, or otherwise firmly secured to the ends of a metal strip or yoke 28 of channel form, the bent side portions extending upwardly, as shown in Fig. 7. These side portions fit freely within the downwardly extending side portions of the strip or yoke l 3 which has been previously described as being fixed to the movable contact head by the screws 12. The two yoke pieces are pivotally connected together at their middle portions by a pin 21, as shown in Figs. 1 and '7.

Thus the actuated portion of the magnet is 'not only pivotally connected to the drive rods but there is .also a pivotal connection between the yoke of the drive rods and the yoke of the movablecontact'head. This gives a flexibility of movement between the parts and provides for the self-adjustment and alignment of the parts for insuring the proper seating of the pole faces of the magnet and aids in the proper seating and balancing of pressure of the contacts. The

axes of these pivotal connections are at rightangles ,to the side plates of the main frame and to the bridging movable contacts for permitting self-adjustment of the parts in planes perpenof the non-actuated part of the magnet in a:

fixed position, the non-actuated part of the mag-, net is mounted, as already described, so as to bemovable with reference to the supporting frame and movable with reference to other parts of the switch for securing proper alignment and engagement of the parts by self-adjustment. This avoids the time and expense otherwise required to machine the parts to close clearances and likewise avoids the time and care required in making refined adjustments after the assembly of the parts. Furthermore in the prior rigid and attempted perfectly aligned structures, the alignment is not permanent, especially when subjected to severe shocks, owing to the distor tion of the parts which inevitably follows pronounced shocks and jars. In the present form of construction the free floating and self-adjustment of the parts with reference to each other insures permanent and properrelationship of the parts which is not afiectedby distortion of the main support or other parts of the apparatus. Moreover, with this improved structure. the proper seating and self-alignment of the parts give continued quiet operation when energized and in fact becomes more quiet with continued use owing to continued improvement in the pole faces under continued use. These lag loops are applied to and secured lnplace on the two portions of the magnet before the final grinding operation of the polefaces.

Special. additional provision is made for preventing undesired opening or closing of the switch when-subjected to severe vertical shocks or to vertical components of shocks. This is accomplished by the provision of inertia controlled latches, the operation of which is dependent upon change of motion of the entire structure. One of the latches is for preventing the'switch from closing under severe shocks and the other is for preventing the switch from opening under severe shocks. One of these inertia latches is shown in the lower right-hand portion of Fig. 1.

It comprises a weighted body portion 29 which extends across the lower front portion of the main frame, as shown in- Fig. -8, and is provided I with a latch 29a at each end which extends up w-ardly-and is provided with an inwardly projecting hooked end. These two ends of the latches are normally positioned, as shown in Fig. 1, somewhat above and in front ofthe angular pieces secured to the actuated portion of the magnet core. The two latches are pivoted on a pin whichis supported at its ends in the side portions of the main frame. The weighted portion 29 of the latch being positioned outwardly fromythe pin 30', tends to maintain the latches inthe position'shown in Fig. 1 out oferigagementwith the angular pieces '25. .An adjustable screw 3| mounted on the tie-plate '4. limits the outward movement of the latches. The radius from the axis of the pin 30 to the center of gravity of the mass 29 is shorter than I the distance from the axis of the 'pin 30 to the hooked ends of the latches. It follows that any movement of the mass 29 about its pivot is amthe surface engagement of the parts the lon er the switch is used. 7 I

In assembling this improved structure, the

parts are connected together as described except that the screws 2011 which hold the crossbrackets 20 to the main frame are left to loosely in plan view in Fig. 8 and held in placeby upsetting portions of the edges of the laminae over the loop. As shown in Fig. 1, one of these l'ag loops is. provided on the outer pole face of the non-actuated portion of the magnet, while the other of the lag loops is provided on the face of the inner pole of the actuated portion of the piified in the movement of the hooked end of the latch inproportion to their relative dis tances from the pivot pin. Under normal con-- ditions the latchesare out of engagement with the angular-pieces 25 and thus energizing of the magnet coil will permit the switch to be closed in the manner already described. But if the switch is in the open position and the apparatus is subjected to a severe vertical shock, or to the in the present structure this is preferably in the T form of a rectangular copper loop 28, as shown v magnet. This relative arrangement insures that at least one of the two engaging faces of each ole of the magnetwill be a solid, smooth, face vertical component of such a shock, the actuated of movement referred to, the hooked ends of the'latches will be rapidly moved inwardly andengage the angular pieces 25 before the switch can close and thereby restrain and prevent the closing of the switch. After the passing of the shock the inertia latch will fall to its normal position so that the switch will be free to close upon eriergization of its magnet.

A similar inertia latch or stop prevents theundsired opening of the switch under severe vertical shocks by a reverse manner of operation. A mass 32 is positioned at the lower cen-- tral portion of the switch, as shown in Fig. 1, and

extends crosswise between the side portionsof the main frame. The mass is provided near its ends with supporting plate 32a. which are pivotally mounted upon a pin 33 which extends between and'is supported byv the side portions of the inain frame. Between the extensionsflc is a cross-bar 32b, the upper portion of which is notched at Me. A spring J4 is connected at one end to the weight 32 .and at its other end to the pin III for normally holding this shock preventing means in the position shown in Fig. l. The mass 32 is provided with extensions 32d as shown Fig. 7 which normally engage the lower edges the side portions of the main frame for limiting the upward movement of the restraining means to the position shown in Fig. 1. When the switch is closed, the lower inside corner of the actuated portion of the core is positioned opposite and above the notch 32c of the inertia latch. When the apparatus is subjected to a severe vertical shock, or to a vertical component thereof, when the switch is closed, the opening of the switch is prevented because any tendency to open the switch will cause the mass 32 to move downwardly overcoming the tension of spring 3! and due to the amplified relative movement of the notch Me by reason of its distance from its axis from the pin 33 being greater than the distance from itsaxis to the center of gravity of the mass 32, the notched portion 320 will move under the lower inside corner of the actuated core portion of the switch before the switch has had time to open. This action will prevent the opening of the switch until the full effects of the shock or shocks have passed, after which the spring 34 will move the restraining means to the normal position shown in Fig. l where it will permit the normal opening of th switch when desired.

Although a particular embodiment of this imrovement has been shown and described, various modifications may be made therein for adaptation to particular requirements without departing from the scope of the invention.

I claim:

1. An electric switch comprising vertically extending side supports, a fixed insulating contact head supported at the upper portion of said supports, a movable insulating contact head, an electromagnet having an actuated portion and a, non actuated portion, cross bracket secured to and extending between said supports at their front and rear portions respectively, means for loosely supporting the non-actuated portion of the magnet by said cross brackets to permit movement in all directions of the non-actuated portion of the magnet with reference to the brackets, and mechanical driving means connecting the actuated portion of the magnet to said movable contact head.

2. An electric switch comprising vertically extending side supports, a fixed insulating contact head supported at the upper portion of said supports, a movable insulating contact head, an electromagnet having an actuated portion and a nonactuated portion, cross brackets secured to and extending between'said supports at their front and rear portions respectively, means for loosely supporting the non-actuated portion of the magnet by said cross bracketsto permit movement in all directions or the non-actuated portion of the magnet with reference to the brackets, and

mechanical driving means connecting the actusted portion of the magnet to said movable contact head, said brackets being formed to loosely guide said driving means.

3. An electric switch comprising vertically extending side supports, a fixed insulating contact head supported at the upper portion of said support, a movable insulating contact head, an electromagnet having an actuated portion and a nonactuated portion, cross brackets secured to and located between said supports atlthelr front and rear portions respectively, means for loosely supporting the non-actuated portion oi the magnet by said cross brackets to permit movement in all directions of the non-actuated portion of the magnet with reference to the brackets, and mechanical driving means comprising two upwardly extending drive rods connecting the actuated portion of the magnet to said movable contact head, said brackets being formed to loosely guide said drive rods respectively.

4. An electric switch comprising a frame having vertically extending side supports, a fixed insulating contact head supported at the upper portion or said supports, a movable insulating contact head, an electromagnet having an actuated portion and a non-actuated portion, cross brackets secured to and-extending between said supports at their front and rear portions respectively, means for loosely supporting the non-actuated portion of the magnet by said cross brackets to permit movement in all directions of the non-actuated portion of the magnet with reference to the brackets, and mechanical driving means connecting the actuated portion of the magnet to said movable contact head, said frame having projecting portions for restraining said movable head from abnormal displacement.

5. An electric switch comprising a frame having verticalhr extending side supports, a fixed insulating contact head supported at the upper portion of said supports, a movable insulating contact head, an electromagnet having an ac- I tuated portion and a non-actuated portion, cross brackets secured to and extending between said supports at their front and rear portions respectively, means for loosely supporting the non-actuated portion of the magnet by said cross brackets to permit movement in all directions of the non-actuated portion of the magnet with reference to the brackets, and mechanical driving means'connecting the actuated portion of the magnet to said movable contact head, said brackets being formed to loosely guide said driving means, said frame having projecting portions for restraining said movable head from abnormal displacement.

- GEORGE M.

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