US2921166A - Electric relays - Google Patents

Description

Jan. 12, 1960 w, FEW Em 2,921,166

ELECTRIC RELAYS Filed Jan. 23, 1956 2 Sheets-Sheet 2 i l 5 INVENTORS Wi/b'rzm Few Dav/d Bakers Ara /d 8. Pearson United States Patent ELECTRIC RELAYS William Few, Goshen, Ind., Arald B. Pearson, Old Bridge, NJ., and David Dakers, Cleveland Heights, Ohio, assignors to The Clark Controller Company,

Cleveland, Ohio, a corporation of Ohio Application January 23, 1956, Serial No. 560,655

21 Claims. (Cl. 200-104) This invention relates to subject matter classified as devices that make and break electric circuits at electric contacts; such devices being known in the art as switches, contactors, relays etc.

In the various arts such devices are utilized to make and break the main circuits of electrical apparatus, and others to make and break control circuits thereof; the control circuit current in the latter case being of small amperage of the order of say amperes, and the devices in such cases being generally known in the art as relays.

The present invention is applicable to main circuits but is particularly applicable to control circuits; and may be embodied in a manually operable form, but is particularly adapted to be operated by an electromagnet. -In order to disclose the invention in a concrete embodiment -thereof as required by law, it has been chosen to illus- 'trate and describe it herein as an electromagnetic control relay as defined above; and it will be so referred to hereinafter, although, it is to be understood that the actual invention is that set forth in the appended claims, and is not limited to this specifically defined embodiment.

An electric control may require the making and breaking of a single control circuit, or the simultaneous mak- :ing and breaking of a plurality of circuits; and in the case of the more recent type of control identified by the term automation there may be as many as twelve or more control circuits, to be simultaneously made and broken, or some'of them made and others broken and 'vice versa.

The electromagnetic relay in the embodiment thereof fully described herein comprises, in general, an electro magnet mounted on a base; and a make and break contact unit, so constructed that only one or any number thereof, selectively, up to the maximum that may be re- --quired, may be mounted on the base to be operated by the magnet.

' The contact unit comprises a complete set of parts including make and break contacts all assembled with a housing; whereby the unit may be made in quantities and at low cost; and whereby the number of units to be I mounted on the base with the magnet may be selected at 11 the time of making the complete assembly of the relay.

The said unit, in more detail, comprises a rod element i of insulating material, guided for reciprocation in the unit housing which is also made of insulating material.

The housing carries a pair of spaced stationary elec- Ztric contacts, and contact terminals for making external t connections to the circuit ,to be controlled.

.The rod element carries a contact bar for bridging the 'stationary contacts and the bridging contact may be as- -sembled with the rod element in either of two positions whereby the contacts may be either normally open or "normally closed.

In the preferred position of use, the rod elements reciprocate vertically, and the magnet is below the units.

A number of units may be mounted on the base in a transverse series side by side, and the rod elements are formed to have a quick detachable connection with a a transverse operating head of the magnet.

2,921,166 Patented Jan. 12, 1960 ice Other units may be mounted in another transverse series above the first series, the lower and upper units thereof then being in tiers, and the rod elements in each tier are formed to have quick detachable connection with each other. I

The transverse series of units may in some cases be wider than the magnet and overlaps it on each'side, and, in such cases, other units may be mounted on each side of the magnet with their rod elements connected to the magnet operating head.

The units are each of small dimension transversely, the general contour thereof defining a thin rectangular block; so that, as in the illustrative example described in detail hereinafter, a multi contact relay may be assembled as described without excessive overall width, having two transverse series or decks of six units each, one above the other, and two at the sides of the magnet, or a total of fourteen units, and as will become apparent hereinafter, even more than fourteen units may be provided if needed.

Each unit is independently mounted on the base and may be removed forwardly for replacement or to change its contacts from normally open to normally closed.

Each unit has its own are chamber for its contacts, formed by housing walls or barriers.

In a series of units, there are no exposed parts except the said terminals, all parts being enclosed by walls of the unit housings; and an opening is provided in the front wall through which the contacts may be viewed to inspect them or to determine whether they are normally closed or normally open.

The contacts in each unit are spring pressed in closed condition by a spring individual to the unit; and lost motion is provided in the said connections between rod elements in a tier and between the magnet head and the rod elements; whereby vibrations or shock to which the relay base may be subjected, will not be communicated to the spring pressed contacts.

A relay may be made up of upper units operatively connected to lower units, and the upper and lower units operatively connected to a magnet below the units; and all mounted on a common base; and each unit and the magnet may be detached from the base by individual attaching means accessible from the front, and then removed from the 'base by-forward withdrawing movement; and such movement automatically disconnects the upper and lower units from each other and disconnects the magnet from the units.

In general, each unit has a chamber closed at one side and open at the other side, and when assembled in a series as referred to the closed side'of each successive unit closes the open side of the preceding unit, and the contacts of each unit are then completely surrounded'by chamber walls and isolated from the contacts of other units.

Also, a second like complete relay comprising a series of units may be placed 'side-by-side with a first relay, Without providing insulation or space therebetween, since the closed side of the first unit of the second relay constitutes the closing wall of the last unit of the first relay.

The objects of the invention are to provide a relay having features such as those mentioned in the foregoing general description, singly or in combination.

An embodiment of the invention in several forms is fully described in the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is a front elevational view of a relay embodying the invention, in a form comprising twelve make-and break contact'units operated by an electromagnet;

Fig. 2 is a side elevational view from the plane 22 of Fig. 1, inwardly of a cover plate of Fig. 1;

' units.

. 3 2 Figs. 3 and 4 are fragmentary sectional views from the planes 3-3 and 4-4 respectively of Fig. 2;

Fig. 5 is a fragmentary sectional view from the plane 5-5 of Fig. 2;

7 Figs. 6 and 7 are fragmentary sectional views from the planes 6-6 and 7-7 of Fig. 2; I Figs. 8 and 9 are top and side views of a bridging contact element shown separately;

Fig. 10 is a fragmentary sectional view from the plane 7 Fig. is a front elevational view of a fragment of'a relay in modified form.

Referring to the embodiment of the invention ofFigs. 1 and '2, there is showngenerally at 1, a mainwbase, upon which is mounted an electromagnetindicated-generally at 2, and comprising a forwardly open E-form core secured to the base 1 by screws 3-3 screwed into the 'base through 7 feet 5 on side plates of the core one of which is shown in Fig. 2; and having a winding 6 on the middle leg of the core. The winding is held inplace by leaf springs 37-7 depending from ears 8 on side plates of thecore.

The said base 1 is preferably a die-casting whereby it may have a true front plane upon which parts may be accurately positioned for operation by the 'magnetras will be described.

A non-magnetic armature ;post 9 extends through a vertical bore in the middle leg of the 'core and at its lower end goes through a bore in an armature 10 with substantial clearance to provide some looseness, and armature 10 is secured on the post 9 by a readily removable pin 11 going through the armature and post.

A transverse bar 12 is mounted on the upperend of the post 9 above the magnet.

When the winding 6 is energized, the armature-10 moves upwardly as viewed and the post 9 raises the bar the open ends of the legs of the core; and upon de-energizing the winding, the armature'10 falls'to the position shown, dropping the bar '12 said predetermined distance; thus providing a predetermined up and down stroke for the bar 12.

A washer 13 of cushioning material surrounds the post 9 between the bar 12 and the magnet core, and serves as a cushion stop to stop downward movement of the bar. The bar 12 and armature '10 are prevented from'rotatmg by a finger 14 on the rear side of the bar, having a perforation therein slidingly engaging a vertical pin 15 on the magnet core.

Attached to the upper side of the bar 12 is a transversely elongated head 16, molded from electrical insulating material, and provided with sixhorizontal flanges 17-17 projecting forwardly from the head; and for greater strength the flanges at their right side as viewed are vertically thickened, making them of generally inverted L-shape.

In Figs. 1 and 2 vertically aligned with each of the head flanges .17 and in a tier, thereabove, is a pair of contact units as referred to hereinbe'fore. For reference hereinafter,-one of thepairs is designated as A and 'B, and another pair as C and D. There is thus provided an upper and a lower transverse series or deck of contact units, each dec'k comprising six units transversely or a total of twelve As will be described more fully, eachof'the units compri'ses a housing closed by 'a base on .its left side, and

ing being closed by the base of the next adjacent housing; and the housings of the last units at the right side, are

, closed by a plate 18 of insulating material secured on said units by screws 19-19.

All of the saidtwelve units have in general the same construction. A full description of the unit A of Figs. 1 and 2 will first be given from which a simple description of other units will suffice.

The unit A comprises a housing 20 molded from electrical insulating-material and consisting of a rectangular base wall 21, on'the left side as viewed in Fig. 1, having an upper wall 22, a lower wall 23, a back wall 24 and a front wall 25, all rising from the base 'wall21; and terminating substantially in a common plane identified at 26 in Fig. 1.

All of the parts of the unit are either this common plane or between it and the base wall, sothat the overall form of the ,unit is that of a thin rectangular block, with all of the parts contained within and mounted upon the housing *walls.

The back wall 24 extends upwardly beyond the upper wall 22 in a flange 27 having a screw hole therethrough for mounting the housing on the main base 1 by a screw 28, accessible by a screw driver from the front of the device, whereby the unit may be removed forwardly at any time for repair or replacement.

The front wall 25 has a recess :29 .t herein providing a window therethrough fora purpose to be described.

The upper wall 22 has an upper conducting bar30, secured thereon by a screw 31 going through the bar'and screwed into the upper wall, and :the wall is recessed to receive the bar, which zpositions it and also disposes all parts thereof including the screw 3.1;in or below the said common plane 26 of the walls. I

The upper conducting bar 30 at its left end as viewed in Fig. 2 extends forwardly beyond the front wall25 and lower wall 23 byascrew 39j and intermediate of its ends I terminates in-an electric terminal 32 of anysui-table form to which a conducting wire of a control circuit may be secured, by ascrew 33 accessible from the front of the device. v b

At its rear 'end, the upperconducting barfitl extends downwardly vertically as zit-'34, see Fig. 4, to a ,point approximately half-way betweenthe upper and lower housing walls 22and 23, and has a horizontal terminal foot 35 extending toward the base wall 21 carrying onits upper and lower sides a pair-oftcontact .tips36 and 37.

1 Alowerjconducting bar- 38 is -mounted-similarly onthe has a portion 40 extending upwardlysee Fig. 3,:terminating in a-foot 4lon the-upper and lowersides of which are contact tips 42 and-=43; and-thelower bar 38 terminates at its left end in an electric terminal 44 like the terminal 32 of the upper ,conductingjbar 39.

The. contact tipsr36 and 3.7 arein horizontal alignment withzthe contact :tips 42and43and1spaced therefrom.

"A vertically Ire'ciprocable :plunger48 to :be more fully described carries a bridging contact element '45 see Figs.

8-9 having lcontact' tips {46-47 on its ends, which, in the unit A, normally engage and bridg'e .the' upper stationary-contact tips 3 6 and 42, normally closing a. control circuit connected to the terminals '32 and 44.

This normal engagement of the tips iisbestshown in Figs. 3 and 4 for the unit A; but -the tips 46-47 :on .the

contact and the stationary :tips36-37 and 42-43 may also be more clearly seen in Fig.2 for the-unit B where they are shown normallydisengaged:as'willbe described'for the unit B. i

The upper arid-lower walls 22 and23 have respectively deep upper and lower recesses 49 and 50 therein, covered or'bridged-respectively'by theconducting bars '30 and 33,

' whichfpro'vides upper and lower apertures 49-50. in -which"the plunger 48 is guided for verticalreciprocatory movementyseeFigs. 6 and '7.

The 51unf er 48 is moldedfrem electrical insulating material, preferably nylon. It is generally of cylindrical form, and to keep it from rotating in said guiding apertures 4950 it is provided with a tongue 51 on its back side as viewed in Fig. 2 and as shown in Fig. 6 and the tongue is disposed in a groove 52 at the bottom of the aperture 49 of the upper wall 22.

The plunger 48 has an L-shaped aperture 53 open at its back side as viewed in Fig. 2, and as shown in Fig. 5, comprising a horizontal slit 54 and a vertical slot 55. The said movable bridging contact element 45 Figs. 8-9 is made from a strip of flat sheet metal having an intermediate neck 56 provided by a notch 57.

To mount the contact element 45 on the plunger 48 as in Fig. 2, it is presented edgewise to the slit 54 with the notch 57 toward the slit, Figs. 11-12, with the tips 4647 on its under side; and the neck 56 is then slid edgewise into the slit 54, and then moved flatwise downwardly into the slot 55, in which it has a sliding fit at all times.

Parallel end edges 5858 are provided at the ends of the notch 57; and the plunger is provided with parallel flat faces 59-59. When the contact element has been mounted as just described, these end edges and flat faces are mutually engaged with small clearance, which, while allowing free loose movement of the contact element on the plunger longitudinally in the slot 55, limits rotational movement of the contact element around the axis of the plunger, whereby the contact tips 4647 of the contact element will always be maintained in vertical alignment with the stationary contact tips 36 and 42 above described.

In the closed contact condition of unit A referred to, and here being described, a spring 60 surrounding the plunger 48 and abutting at its upper end upon the upper wall 22 and at its lower end upon the contact element 45, holds the contact tips 46 and 47 of the contact element upon the upper stationary contact tips 36 and 42, see Figs. 3 and 4, independently of the plunger 48 in the normal down position of the plunger, as indicated in-Fig. 5 by the intermediate position of the neck in the slot 55.

The plunger 48 of the unit A extends below the lower housing wall 23 and has a laterally open notch 61 therein, giving it, in general, the form of a hook 62.

Now as to the unit B, it is substantially like the unit A above described, except as to its plunger 63, and except that it is shown assembled to be in the normally open contact condition as referred to. It has stationary contact tips and terminals like the unit A.

Its plunger 63 extends upwardly beyond its upper wall 22 and has a laterally open notch 64 therein, giving it in general the form of a hook 65; and the hooks 62-65 of the plungers of the units A and B are hooked together or interlocked making in effect one continuous plunger, as best shown in Fig. 5.

The plunger 63 extends below the lower housing wall 23 and has a hook 66 thereon, like the hook 62 of the upper unit A, and the hook 66 is interlocked with that one of the flanges 17 of the head 16, immediately under it.

The plunger 63 has an L-shaped aperture 67 therethrough comprising a slit 68 and a slot 69, and is like the L-shaped aperture 53 of the unit A except that the slot '69 extends above the slit 68 whereas in unit A the slot extends below the slit 54, and except that the aperture 53 of the unit A is in its upper part and the aperture 67 of the unit B is in its lower part.

Another bridging contact element 45 is assembled in the aperture 67 of the plunger 63 by the process described for the unit A and its plunger 48, except that in this case the contact element is turned over so that its tip 4647 are on top, see Fig. 2; and the assembly operation may be identified as like that described for the plunger 48 by comparing Figs. 12 and 14.

The plunger 63 has an annular flange 70 thereon, and

4647 of the contact element 45 are below the lowerv stationary tips 3743, as indicated in Fig. 2, that is, in normally open contact condition.

In this case the contact element 45 will move upwardly in unison with the plunger 63 until its tips 4647 engage the stationary tips 3743, and then move farther, leaving the tips held in engagement by the spring 71, and freed from the plunger.

As described, the head 16 has up and down movement of predetermined extent; and from the foregoing it will be seen that in its down position, a contact element 45 on the unit A is freed from the plunger'48 and held in closed contact condition solely by the spring 60, and that in its up position a contact element 45 of the unit B is freed from the plunger 63 and held in closed contact condition solely by the spring 71.

Any accidental vibration or shock communicated to the relay which might give vibratory up or down movement to the head 16 and plungers 48 and 63 of the units A and B, will not disturb the current carrying engagement of the contact tips of these units.

The unit A is shown in Fig. 2 to be normally in closed contact condition; and the unit B in normally open contact condition. This is for description purposes.

It is an important part of the invention that the unit A may be the one in normally open contact condition, and the unit B may be the one in normally closed contact condition; or that both units may be in normally closed or both in normally open condition; to correspond to requirements of the control circuits connected to the terminals.

This is made possible selectively by alternatively assembling the bridging contact elements 45 on the respective plungers 48 and 63 in different positions thereon; and to this end, the plunger 43 of unit A is provided with another L-shaped aperture 72 disposed with a slot 73 extending upwardly from a slit 74 and therefore corresponding to the aperture 67 of the unit B as illustrated; and the unit B is provided with another L-shaped aperture 75 disposed with a slot 76 extending downwardly from a slit 77 and therefore corresponding to the aperture 53 of the unit A. The plunger 48 also has an annular flange 70 thereon like that of plunger 63.

With this provision contact elements 45 may be as sembled selectively in the apertures of either of the units, as described, to be in position to normally engage or normally disengage the stationary contact tips; and this as will be understood applies to all of the twelve units of the relay of Fig. 1.

As Will be noted, the stationary contacts comprise both upper tips 36-42 and lower tips 37-43, and therefore can serve for normally closed or normally open contact condition; and that the bridging contact 45 has only one set of tips 46-47 which are made to cooperate with either of the upper or lower stationary tips by simply turning it over to put the contact tips 46-47 on its upper or lower side, at the time of mounting it on the plunger.

In mounting the units in a transverse series or deck as in Fig. 1, the base wall 21 of each unit is on the left side thereof, and rests upon or is closely adjacent to the said common plane of the housing walls of the next adjacent unit thus constituting a covering wall therefor.

With this in mind it will be apparent that the contacts in each unit are entirely surrounded by the base wall and side walls of the unit and the base wall of the next adjacent unit; thereby isolating them from the contacts of the other units, in arc chambers individual to the unit; whereby failure or short circuit in one unit willnot affect any other unit.

..r 7 The front wall .of each unit has said window 29 therein "located so that an observer can view the contacts of the unit and determine whether they have been assembled for normally open or normally closed condition, and therefore suitable for the requirements of the control circuit to be connected to the unit.

Upper and lower units in normally closed and normally open condition can be stacked, and a relay built up from them as needed for a control; or one already built up ;may be taken down and rebuilt; and to this end each upper unit is made readily attachable and detachable on the base 1 by a single screw 28; and upon removing it, a single screw 28 mounting the unit under itbecomes exposed for removing it. The entire relay is therefore serviceable from the front.

The magnet also may be assembled with or removed from the base 1 from the front, since the flanges 17 on the magnet :head 16'may be moved into or out of engagement with the hooks 66 of the plungers of the lower units, by rearward or backward movement of' the magnet.

The last units, at the right side of the relay, as in Fig. 1, may be provided with a covering wall or plate 18 of insulating material, mounted on the walls of the last unit by screws 19.

While twelve units are shown in Figs. 1 and 2, as exemplifying the multiplicity provided for by the unit construction, it will be apparent that any number of such units less than twelve can be used with the same unit construction.

Instead of mounting all of the relay units above the magnet head 16 to be operated thereby, two units may be mounted on the base on opposite sides of the magnet as shown in Fig. wherein to simplify the drawing the two units are shown at 7879 in outline and the magnet at 80 in outline. To this end, the top bar 81 of the magnet is provided with hook-like ends, 82 and 83 interlocked with the upper hooks 84-S5 on the plungers of the units 7879.

A relay with a total of fourteen units is provided by adding the units 78-79 to the relay of Fig. 1.

Also a small relay comprising only the magnet 80 and v the two units 78-79 on each side of it is made available,

as will-be understood.

A plurality of complete relays, say relays like that of Pig. 1, each operated by its own magnet may be mounted in a continuous horizontal series, in which case as will be apparent no insulation between adjacent relays will be necessary in addition to that provided by the unit housing themselves;

The topmost units, of the relay as in Fig. 1, are preferably provided with covers 86 integral with the top wall 22, covering the upper end of the plunger and the recess 49 in which it is guided, to keep out dust etc. which otherwise might fall through the recess into the housing; and such covers together with the top walls 22 themselves, provide a surface along which control circuit wires coming from the terminals may be grouped and laid and supported.

It is to be noted that in the total stroke of the plunger say the plunger 48 or 63, it moves part of the way in unison with the bridging contact element which it carries, and has only a short sliding movement relative to it, when freed therefrom as described.

The bridging contact is made of metal; and the plunger is by choice molded from nylon. It is well known that there will be little friction and a negligible amount of dust produced by sliding engagement between such materials. This together with the short sliding travel eliminates all danger of dust production and accumulation, which occurs in other constructions of relay having a long sliding, guiding movement using other materials.

What is claimed is:

1. An electric circuit making and breaking device comprising a base; a contact operating element reciprocably supported on the base; means on the base for reciprocating the contact operating element between normal and operated positions; a pair of spaced stationary contacts in permanently fixed-positions on the base; a contact element attached toithe operating element for connecting'and disconnecting the stationary contacts upon reciprocation of the operating element; two manually operable attaching means on the operating element for attaching the contact element thereto in either of two positions, selectively; the

two attaching means being spaced apart in the direction of reciprocation and the stationary contactsbeing diselement to operated position, the stationary contacts if connected will b e disconnected, and if disconnected will be connected. n l V 2. A device as described in claim 1, and in which, the reciprocable contact operating element is elongated in the direction of reciprocation; and the contact element comprises an elongated metal body with contacts on its ends; and the two attaching means comprises two apertures extending through the operating element spaced apart longitudinally thereof and having openings at the side of the operating element; and the contact element is attachable to the operating element-by manually inserting a middle portion of the contactelement into either aperture selec- 'tively,th rough the opening thereof.

3. A device as described in claim 1 and in which the reciprocable operating element is generally of rod form extending in the direction of reciprocation; and the contact element comprises a metal bar, withcontacts at its ends; and the two attaching means comprise two open apertures extending into the rod form operating element from the side thereof, and of generally L-form, comprising a transverse slit and a longitudinal slot, having a slot bottom; and the contact element is attached by sliding a middle portion of the bar inwardly in the slit to dispose it in the slot; and spring means is provided holding the bar yieldably toward the slot bottom.

4. An electric circuit making and breaking device comprising electric contacts and adapted to be convertible r from normally closed to normally open contact condition; the device comprising a single pair of spaced stationary contact elements in permanently fixed positions having contact portions on opposite sides thereof; a movable bridging contact element having spaced contact portions; a reciprocable carrier to which the movable contact element is attached, and means for reciprocating it; the carrier having a normal position in which the contact portions of the movable contact element are engaged with. the contact portions on one side of the stationary contact elements; manually operable means for detaching the movable contact element from the carrier and attaching it again to the carrier in another position thereon in which, with the carrier in the same normal position the contact portions of the movable contact element are spaced from the contact portions on the opposite side of the stationary contact elements; the means for attaching the bridging conof the aperture against the force of the spring means when the contacts of the bridging contact element are moved into engagement with the stationary contact elements, by reciprocatory movement of the carrier.

. A. elec r c q w m k and in i e c prising a main base having a front wall; a contact unit comprising a walled unit housing projecting forwardly from the base wall and fastened thereon by fastening means accessible from the front thereof; a pair of spaced stationary contacts permanently fixedly mounted in the unit housing and connected to circuit terminals accessible from the front of the housing; an elongated plunger supported in the unit housing for verticalreciprocation and carrying a movable bridging contact element in the unit housing, engageable and disengageable with the stationary contacts by reciprocation of the plunger; the plunger having a portion of book form projecting from the housing; a head supported on the base for vertical reciprocation; and operating means for reciprocating the head, fastened on the base wall by fastening means accessible from the front thereof; the head having a tongue engaged in the plunger hook form portion to reciprocate the plunger in unison with the head; the unit housing and operating means being each removable forwardly from the base upon unfastening the fastening means, and the tongue and hook portion being disengageable by said forward movement of either the unit housing or the operating means.

6. A device as described in claim and in which the unit housing is above the head, and the operating means is below the head, and the plunger hook portion extends downwardly out of the housing to engage the tongue on the head.

7. A device as described in claim 5 and in which the unit housing is at the side of the operating means and below the head, and-the plunger hook portion extends upwardly out of the housing to engage a tongue on the head.

8. An electric circuit making and breaking device comprising a main base having a front wall; a pair of contact units comprising respective walled unit housings projecting forwardly from the base wall and fastened thereon one above the other; stationary contacts permanently fixed in each housing connected to circuit terminals on the housings; upper and lower elongated plungers supported in the respective housings for vertical reciprocation and carrying movable contact elements in the respective housings engageable and disengageable with the stationary contacts by reciprocation of the'plungers; the upper plunger having a hook form portion projecting downwardly out of the upper housing; the lower plunger having an upper hook form portion projecting upwardly out of the lower housing; the said hook form portions being mutually engaged to cause the plungers to reciprocate in unison; the lower plungers having a lower hook form portion projecting downwardly out of the lower housing; a head supported on the base for vertical reciprocation, and operating means for reciprocating it fasened on the base wall; the head having a tongue engageable in the lower hook form portion of the lower plunger to reciprocate the plungers in unison with the head.

9. An electric circuit making and breaking device as described in claim 8 and in which the unit housings and the operating means are fastened on the base by fastening means accessible from the front and are each removable forwardly from the base upon unfastening the fastening means; and the mutually engaged hook form portions of the plungers' are arranged so that they are disengageable by forward movement of one housing relative to the other; and the lower hook form portion of the lower plunger is arranged so that it is disengageable from the tongue by forward movement of the lower housing or of the operating means.

10. An electric circuit making and breaking device, comprising a main frame; a plurality of individual contract units each comprising stationary and movable contacts and the 'units mounted on the frame adjacent to each other, each by its own individual attaching and detaching means accessible from the front of the frame; an

'10 operating electromagnet mounted on the frame by attaching means accessible from the front of the frame; and an operating connection between the magnet and all of the movable contacts of the plurality of units; each unit when detached being removable forwardly independently of the others.

11. An electric circuit making and breaking device, comprising a main frame, a plurality of individual contact units each detachably mounted on the frame adjacent to each other and each comprising a walled housing and a set of stationary and movable contacts electrically isolated from those of the other units by being enclosed Within walls of the housings; and the movable contacts of the plurality of units all operatively connected to a single operating means on the main frame, by connections pass ing through openings in the respective housing wall; and each unit when detached from the frame being removable forwardly therefrom independently of others.

12. An electric circuit making and breaking device, comprising a main base, a plurality of individual contact units mounted in a horizontal series on the main base by attaching and detaching means accessible from the front and each contact unit when detached from the base being removable forwardly out of the series independently of the others in the series; each unit of the series comprising a main wall extending forwardly from the main base and side Walls rising laterally from the main wall, providing a chamber closed at one side and open at the other side; the units of the series being mounted adjacent to each other and the main wall of each unit constituting a wall for substantially closing the open side of the chamber of the next adjacent unit; stationary and movable contacts in each chamber, electrically insulated from those of the other chambers by the walls of the closed chambers; and contact operating means mounted on the base connected to the movable contacts of all of the units through openings in the chamber walls.

13. A device as described in claim 12 and in which, the open side of the chamber of the last of the series of units is closed'by a plate of insulating material mounted on the side walls of the last unit of the series.

14. A device as described in claim 12 and in which the main chamber wall at one end of the series of units and the side walls of the open chamber at the other end of the series are conterminous with opposite sides of the main base, whereby a number of devices of the same construction may be disposed in adjacent side by side relation with the main bases thereof mutually abutting and the main chamber wall of one device constituting a wall for substantially closing the open sided chamber of the next adjacent device.

15. A device as described in claim 12 and in which a window is provided in one of the side walls of each chamber through which the stationary and movable contacts may be viewed.

16. An electric circuit making and breaking'device, comprising a walled housing; a plunger of insulating material supported for reciprocating movement in apertures in spaced walls of the housing, and the apertures and the plunger formed to prevent rotation of the plunger, the plunger provided with an aperture therethrough having an opening at a side of the plunger; an elongated flat sheet metal contact element having a rectangular notch in one side edge thereof, and adapted to be mounted on the plunger by inserting its mid-portion edge- Wise into the aperture through the opening with the end edges of the rectangular notch then embracing opposite sides of the plunger; the embraced sides of the plunger having flat surfaces engaged by the notch end edges and preventing rotation of the contact element around the axis of the plunger.

17. An electric circuit making and breaking device comprising a main base having a planar front face; a horizontal series of contact units each comprising a housing molded from insulating material, consisting of a main bottom wall and open at the tops of the side walls; and

each unit mounted on 'th'e 'front'face of'the main base by a screw accessible from the front of the device and going through an upper extension of the back side wall with the main bottom wall extending forwardly from the front face; the units of the series being close together with the main bottom wall of each succeeding unit of the series close to the tops of the side walls of the preceding unit and constituting a chamber-closing wall of'the preceding unit; each unit having conducting elements mounted on the top and bottom walls respectively, terminating in circuit terminals at the front of each unit, and the conducting elements having respective portions extending into the chamber and spaced apart and carrying jointly a pair of upper and a pair of lower contact tips; with the pairs in horizontally spaced relation; an elongated plunger molded from insulating material slidably guided for vertical reciprocatory movement in aligned open recesses in the top and bottom housing walls and retained in the recesses by recess covering portions of the conducting ele ments; a metal contact element carried by the plunger and means for selectively mounting it on the plunger at either of two longitudinally spaced points; the plunger having a normal unoperated down position and reciprocable to an up position, and in said normal down position the contact element when mounted at said first point connecting the upper pair of contact tips and upon reciprocation to the up position disconnecting them; and the contact element when mounted at the second said point being spaced from the lower pair of contact tips and upon reciprocation to said up position connecting them; a spring surrounding the plunger and reacting between the contact element and the top housing Wall to yieldably hold the contact element toward the connected pairof contacts in the down positions of the plungerand being selectively movable to a position on the plunger at which it reacts between the contact element and a projection on the plunger to yieldably hold the contact element to ward the connected pair of contacts in the up position of the plunger; the contact element being horizontally elongated and comprising a mid-portion and contacts at its ends; and the selective mounting means for the contact element comprising two apertures through the plunger, each having an opening at the side of the plunger and spaced apart longitudinally, and the apertures being of opposite L-form and the apertures and mid-portion of the contact element formed so that the mid-portion can be inserted into either of the apertures through its opening and be retained therein; the plungers of the units of the series having each aportion of hook-form projecting downwardly through the said recess in the bottom housing wall; an electromagnet mounted on the said planar front face of the base by screw means accessible from the front, and

comprising an armature connected to a bar above the magnet, movable by the armature from a normal down position to an up operated position; a head on top of the bar molded from insulating material and comprising a series of forwardly projecting flangesengaged respectively in the hook-form portions of the plungers, to reciprocate them all from normal to operated position in unison with the head; each of the unit housings and also the magnet being removable from the main base by forward withdrawal of either'thereof; and the hook-form portions of the plungers and the flanges disposed so that upon forward withdrawal of either, the hook-form portion is automatically disengaged from the corresponding 'flange.

each chamber; terminals connected to the stationary contacts; plungers reciprocably guided in the upper and lower apertures and carrying contacts movable therewith; operating means to reciprocate the plungers in unison to operate the contacts; a portion of each upper'chamber wall extending over and covering the upper aperture therein; the upper walls and covering portions of the series of housings providing a transverse shelf for supporting conductors leading from the terminals.

19. A contact unit, comprising walls of insulating material comprising a back wall and side walls rising from the back wall providing a chamber closed at the back 'and side walls and open at the front opposite the back wall; a pair of stationary contacts supported on the side walls; an elongated reciprocable element supported by opposite side walls for longitudinal reciprocation and 7' carrying contacts movable therewith to bridge and unbridge the stationary contacts; conducting elements provided with terminals and connected to the stationary contacts and supported on the side walls; making each unit a complete self contained assembly, the aforesaid parts all disposed inwardly of the tops of the side walls and exposed at the front of the chamber; whereby a like unit when placed with its back wall adjacent to the tops of the said side walls, will substantially cover the exposed parts, with the back wall of the like unit constituting a front wall of the chamber; the unit having a side wall formed to receive manually operable means for attaching the unit to a base surface with the back wall at right angles to the base surface and for detaching it therefrom.

20. A device as described in claim 1, and in which, the reciprocable contact operating element is elongated in the direction of reciprocation; and the contact element comprises an elongated metal body with contacts on its ends; and the two attaching means comprises two apertures in the operating element spaced apart longitudinally thereof and opening through the operating element; and the contact element is attachable to the operating element by manually inserting the contact element into either aperture selectively, through the opening thereof.

21. A contact unit to be mounted in side-by-side relationship with a plurality of like units on a common base, comprising walls of insulating material comprising a back wall and sidewalls rising from the back wall providing a chamber closed at the back and side walls and open at the front opposite the back wall; a pair of stationary contacts supported on the side walls; an elongated reciprocable element supported by opposite sidewalls for longitudinal reciprocation and carrying contacts movable therewith to bridge and unbridge the stationary contacts; conducting elements provided with terminals and connected to the stationary contacts and supported on the side walls; one side wall formed to receive manually operable means for attaching the unit to the base surface with the back wall at right angles to the base surface and for detaching it therefrom, whereby the terminals and manually operable means are accessible fromthe same direction.

Butler et al. June 6, 19 08 890,840 2,064,632 Schmitt Dec, 15, 1936 2,106,581 Unwin Jan. 25, 1938 2,273,545 Van Valkenburg Feb. 17, 1942 7 2,433,710 Schleicher Dec. 30, 1947 1 2,457,011 Walley Dec. 21, 1948 2,514,913 Tyrner July 11, 1950 2,589,167 Van Valkenburg et al. Mar. 11, 1952 2,616,998 Salsa. Nov. 4, 1952 2,672,536 Rosing et al.. Mar. 16, 1954 2,743,339 Taylor Apr. 24, 1956 2,811,617 Townsend Oct. 29, 1957 Q FOREIGN PATENTS 626,738 Germany Mar. 2, 1936

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