US2357592A - Switch structure - Google Patents

Description

Sept. 5 1944. E, w LANDMElER 2,357,592

' SWITCH STRUCTURE Filed July 21 1941 EEEE e o o o e 25 2 j I 2! mm a 41 59 z .s 1! I! 46 1 a 1 F 1/ A! l Patented Sept. 5, 1944 SWITCH STRUCTURE Edwin W. Landmeier, Cin to The Wadsworth E Company, Kentucky cinnati, Ohio, assignor lectric Manufacturing Covington, Ky., a corporation of Application July 21, 1941, Serial No. 403,289

13 Claims.

This invention relates to electrical devices embodying electric switch facilities, electric fuse facilities, and to unitary structures embodying both in combination;

The devices of the invention are adapted particularly to be used in panel cabinets for distribution circuits, either singly or in multiple, depending upon the number of distribution circuits to be accommodated. For example, in a typical installation, a panel board may be equipped with say five or ten of the individual switch and fuse block units. These are placed side by side and are in electrical connection with the primary conductors from which electrical energy is furnished. The individual branch circuit conductors in turn are connected to the block unit terminals. The switches provide for control of the branch circuits and the fuses provide protection against overloading and short-circuiting of them.

In the preferred structure of the present invention, as shown in the drawing, each unitary block is comprised of a pair of fuses and a pair of switches. However, the invention also is directed to unitary blocks involving a single fuse and switch therefor. This modified form is adapted to be used particularly in instances where the space available for installation of a cabinet containing the unit is of minimum width, for example, in the channel trough of a building column.

One of the principal objects of the present invention has been to provide individual blocks embodying a fuse socket and a switch or a pair of fuse sockets and switches therefor in a simplified arrangement which is inexpensive to construct and simple to install.

A further object of the invention is to provide arrangements for simple, direct connection of the individual unitary blocks to the main electrical feeders of the panel.

Another object is to provide improved pushpull type switches having effective snap or friction means for holding the switches firmly in one position or the other, so as to protect against unintentional switch operation. It is also an object to construct the switches in such manner that the arcing incidental to switch opening and closing is reduced to a minimum.

A still further object of the invention is to incorporate the fusing and switching provisions as well as the provisions for direct connection of the blocks to the primary feeders in a structure which, besides being well insulated, is very compact in order that it; occupy less space than the devices heretofore available; this feature enables a plurality of the devices to be installed in a smaller panel cabinet requiring less wall area for its installation.

The preferred structure of the present invention providing all these features is built around an elongated base block which is adapted to be fastened to the back wall of the panel cabinet. Fuse receptacles for either plug or cartridge fuses are installed in cavities at one or both end of this block and a slidable element or a pair of them constituting the movable members of pushpull switches are positioned in the central part of the block. Each block is arranged to straddle the electrical feeders to which it is to be connected and also to support them. Thus, in the preferred arrangement, the fuses flank the switches and the switches, in turn, flank the feeders. When a plurality of the block units is arranged in side by side relationship the feeders are protected and concealed against accidental contact since the blocks are superimposed over.

them.

For switching purposes the unitary blocks carry a pair of stationary contacts for each switch and a slidable switch element therefor is arranged to move intermediate the contacts of the pair. The slidable elements, in turn, are equipped with contacts adapted respectively to be positioned between the respective pairs of stationary contacts for switch closure, the latter contacts being relativel loosely mounted so as to be self-aligning when interposed between the stationary contact members. Thus, when the slidable elements are moved, for example, in an outward direction, the switches are closed, and when they are pushed inwardly the bridging contacts are moved out of engagement with the stationary contacts and the switches are opened. One stationary contact of each pair is connected to a feeder member and the other to a distribution circuit terminal either directly or through a fuse contained in the base block.

In the preferred structure, to restrain the switch plates once they are moved to open or closed position, one or a pair of members having yieldable ends is installed in a recess of the base block intermediate the movable switch elements with the respective ends pressing frictionally against the switch plates, one friction member thus serving both of the plates. The yieldable ends of the friction member preferably press against one or both edges of the switch plates while the latter has notches cut into it, corresponding to switch open position and switch closed position. The force required to unseat a yieldable detent from seated position in a notch is of suchan order that it is practically impossible thereafter to stop the movement of the switch plate until the detent engages the next notch. This feature makes it substantially impossible for the switch plate to reside in a position other than the open or the closed position.

In instances in which the unitary block contains a single movable switch member instead of a pair of them a detent or a pair of them may be mounted on the block with the free yieldable end or ends arranged for engagement with the switch plate as described.

From the foregoing description of the principal features of construction of the present invention and from the following detailed description of the drawing which shows a preferred embodiment, those skilled in the art will comprehend the various modifications to which the invention is susceptible.

Other objectives of the invention and other features are disclosed in the following description and in the drawing in which:

Figure l is a perspective view of an individual fuse block with the cove over the central cavity removed to show the details of the switch detention members.

Figure 2 is a face view showing a plurality of the switch and fuse blocks of the present improvement arranged upon a panel backing.

Figure 3 is a sectional view taken on the line 33 of Figure 2.

Figure 4 is a fragmentary view taken on line 44 of Figure 6 showing the switch in open position.

Figure 5 is a view, similar to Figure 4, showing the switch in closed position.

Figure 6 is a fragmentary sectional view taken on the line 66 of Figure 3.

Figure '7 is a sectional view taken on the line 1-1 of Figure 2.

Figure 8 is a top plan view of the insulating washer provided for the fuse shell.

Figure 9 is a top plan View of the metallic lock washer provided for the fuse shell.

Figure 10 is a side elevational view of the lock washer shown in Figure 9.

The present invention embodies feature of physical structure such as thos through which compactness and simplicity are obtained, as well as features of electrical structure such as those by which directness of connection and appropriate safety are obtained through installation.

For purposes of clarity the mechanical structure is described first, then the electrical.

In the drawing, the panel board and cabinet have not been illustrated. These may be of the conventional type embodying a sheet metal case having a front cover. The unitary switch and fuse blocks may be mounted directly to the back wall of the panel member or, better still, they may be mounted upon a false back panel provided with offset feet, as disclosed in the drawing. The space provided by the offset feet intermediat the back panel and the false back provides clearance for screw heads and the protrusion of screw ends, and simplifies assembly operations.

Mechanical construction The base of each unit is a block of non-conducting material indicated generally at I, with cavities 2, located, at one or both ends of the block, for the reception of fuse shells 3. The block preferably is made in one piece though it may be made in sections if desirable, and of suflicient width to accommodate one, or two or more switch members. The portions of the block beneath the fuse receptacles are recessed as at 6 to enlighten the structure a well as to provide for the seating of switch contacts.

The outward face of the block contains a cavity as indicated at 1 (see Figure 1) intermediate the switch plates. This recess extends down through the block about halfway, and beneath it an opening, or pair of openings 88 comprising passageways which extend transversely of the block to permit the body to straddle supply conductors S--9. In the device disclosed, a hollow leg I0 is positioned in th transverse bottom opening between the two conductors to maintain positive separation of them and a wall ll extends above the leg Ill and within the central cavity 1 to provide reenforcements of the side walls l2 of the cavity and, more particularly, to provide a seat for the switch detents and cover plate which are described at a later point in the specification. Several buttress walls l3 extend into the cavity 1 from the side walls 12 thereof at spaced distances from the cross wall II, to reenforce the side walls I2. The tops of the buttress walls are configurated so that the switch detent members may rest on them or be fastened to them if desirable.

Slots 14 extend through the body of the block at opposite ends of the central cavity, the spacing and dimensions of the transverse openings 8-8 at the bottom of the block being such as to leave walls l5l5 for isolating the slots M from the openings 3. At the bottom of the unit, the slot passageways M are further delineated by the walls IB-IB which extend toward one another from the opposite side walls of the recesses 66. Slidable switch elements I! of flat, plate-like configuration are positioned in the slots l4. Each switch plate is of nonconducting material, for example, fiber board of suitable thickness, and is provided with a handle or hook [8 at its upper end by which it may be manipulated for switch operation.

Each slot M has abutment lugs l9 extending inwardly'from its opposite edges, as can be seen best in Figures 4 and 5, while the switch plates I! are provided with shoulders 20 for engagement with the abutment lugs I9 to limit the travel of the switch elements. As a practical matter, in the assembly of the units, the switch plates are inserted into the slots from the underneath side and the handles iii are then attached as by riveting,

The movable switch plates of the present apparatus are operated by pulling them outwardly or pushing them inwardly. While this general type of switch, as distinguished from the toggle type of switch, has been proposed in the past, it ha been difiicult to prevent operators unintentionally from moving the plates only part way in one direction or the other, and in obtaining th quick switch action which is requisite. If

th plates are moved only partly through their range of movement there is danger that the bridging contacts which they carry, as subsequently described, will reside in only partial engagement with their cooperating stationary contacts. When faulty contact of this sort occurs heat is generated through the flow of electricity because of the increased resistance and there is danger either that the contacts themselves or the insulation surrounding them will be burned 9r charred.

n the other hand, it is desirable that a positive "snap action be incorporated in the apparatus so that contact completion and contact rupture take place quickly. This feature is desirable to avoid undue arcing which occurs at the moment the contacts are moved into or out of engagement. These features are provided in the present apparatus by the positive detent action of which the description follows:

Notches in spaced relationship are formed in the switch plates IT at their opposite edges and these notches are arranged to cooperate respectively with the endwise portions of detention springs or clips indicated generally at 2| in Figure 1. The spring clips extend along the side walls of the cavity 1 and are seated upon the upper surfaces of the buttress walls i3 while the central portions of them reside in slots 22 which are out into the central wall ll. These clips are so formed that when the central portion of each clip is restrained against outward movement the endwise portions press against the edges of the switch plates. When the ends of the spring clips are seated in the notches of the switch plates it will be seen that the switch plates are detained against accidental movement and can be manipulated only upon exertion of a force which is sufficient to spring the ends of the clip outwardly to unseat the ends of the clip from the notches to permit the plates to slide. A positive snap action movement is thus obtained.

As will be seen, the two spring clips disclosed in the drawing serve eight detention notches since each clip acts upon both switch plates. When one of the switches is operated the clips are held against canting since they are supported by the buttress walls at the opposite sides of the transverse wall H.

To obtain the desired resiliency in the clips the central portion of them is offset form the ends thereof, while the ends are cupped to fit the con tour of the notches. However, it will be understood that simple bowed springs may be used in place of those disclosed.

To hold th spring clips against withdrawal from their seats when either of the switch plates is pulled outwardly a cover plate 23 is installed over the central cavity 1, being held in position by means of a bolt 24 which passes through an aperture in the central wall i i. The nut 25 carried by the bolt is seated against the upper surface of the wall I l (to hold the bolt against turning) and an acorn nut 26 is used to fasten the cover plate in position.

Cover plate 23 closes the central cavity and prevents the switch operator from accidentally coming into contact with th live screws residing within the cavity by which electrical connection of the unit is made with the bus bars. The unit is therefore a dead front unit in that no electrically energized parts are exposed to the operator, the plug fuses residing in the fuse receptacles preventing access to the contacts at these portions of the apparatus, and the terminals at the ends of each plug being concealed by a trim panel in the usual manner.

Cover plate 23 additionally carries numbers or other indicia for identifying the switches or the branch circuits they control, and instructions of operation of the switch.

In the structure disclosed straps 21 are sheared or struck from the cover plate so that a piece of paper may be inserted between the straps and the cover plate to carry the indicia, as shown in Figur '7.

The caps or cover plates extending across the central cavity have flanges bent downwardly to reside adjacent the side walls i 2 of the cavity and the spring detent members rest against these side flanges so that the outward pressure exerted by the spring detents is carried by the cap instead of being applied upon the side walls; the latter, in an instance where the base block is constructed of a material like Bakelite, may, therefore, be quite thin, whereas otherwise the walls would have to be sufficiently heavy to resist being cracked or split through the pressure exerted upon them by the detent springs.

While it is desirable, for purposes of compaction and concealment of the mechanism, to locate the spring detents in the central cavity of the block, it will be seen that these detents need not necessarily be located at this area but may reside at the upper portion of the block. It is also to be understood that while two spring detents arranged at opposite sides of the switch plates have been shown in the drawing, only one may be employed if desirable. In this instance the single spring detent may be arranged for frictional engagement with notches provided in the faces or edges of the switch plates, while the opposite faces or edges are supported to hold the plates against displacement due to the pressure exerted by the detent.

Electrical structure The lower portions of the switch plates l1 contain apertures in which contact elements 28 are located. These preferably are flat-sided tubular pieces of copper, brass or other suitable material and are of such length as to fit loosely within the apertures, their width being somewhat greater than the thickness of th switch plates in order that they readily may be engaged, at each side, by the stationary contact elements 29 and 33. Just above each contact element 28 each switch plate contains a slot 55 which is so positioned that when the bridging contact is fully out of engagement with its cooperating stationary con-- tacts the slot will be in alignment with them. The stationary contacts are therefore separated by an air gap in such manner that, if during the life of the apparatus the switch plate itself becomes charred or burned, or carbonized, its decreased insulating properties still will not permit short circuiting to take place between the stationary contact members.

The meeting faces of the walls l6, which serve to delineate slot M at the bottom of the base block of the structure, are spaced apart a dis" tance which is slightly greater than the length of the bridging contacts 28 carried by th switch plates, so that the bridging contacts readily may be inserted therethrough into their cavities in the switch plates. However, in order to keep the contacts from falling out of the cavities, shields or sheaths 3| are fitted into the lower portions of the slots l4 and extend upwardly a distance sufficient to prevent escape of the bridging contacts from the switch plates when the latter are in switch open position.

In the preferred structure supplemental slots 32 extend beyond the opposite walls of the slots l4 and the shields are dimensioned so that their edges may fit within the supplemental slots. In this manner the shields are located in position so that they do not in any way interfere with the sliding operation of the plates. The bottoms of the shields are exposed to rest upon the surface of which the base block may be mounted.

Contacts 30 are in the form of clips electrically connected with the bus bars 9, while contacts 29 are electrically connected with the center buttons in the fuse receptacles. The shells 3 of the fuse receptacles in turn are in electrical connection'with the output terminals 33 which are located atthe opposite ends of the unitary assembly. In general, the contact elements 28, which are movable with the switch plates 51, serve to bridge the stationary contact elements 29 and 39 as the switch plates are drawn outwardly, so that current flowing in the bus bars may pass through the switches and fuses located in the fuse receptacles to distribution circuits connected to the terminals 33.

In more particular detail, contacts 30 extending from the bus bars 9 are metallic pieces having flat seat portions 34 which reside against the ceilings of the passageways B. Hollow metallic grommets or rivets 35 extend through the ceilings and pass through bores in the fiat seat portions of the contacts 33, and the extended ends of the grommets are spun over to clamp the contacts to the ceilings. However, it is to be noted that the seat portions of the contacts are recessed slightly in order that the spun ends of the contacts do not extend beyond the exposed faces of the contact seat portions. This permits full contact to be made between the seat portions of the contacts and the bus bars. Screws 33 pass through the bores of the grommets and into threaded bores in the bus bars to clamp the bus bars firmly to the contacts and to the block. The contacts areheld against movement by this additional clamping and good electrical connection is insured.

Contacts 39 terminate in upwardly extending U-shaped prong portions or clips 31 which extend from the bus bars toward the switch plates respectively and are yieldable so that they may press firmly against the bridging contacts 28 of the switch members. The base block is appropriately configurated to provide cavities 38 within which the U-portions of the prongs 31 may reside.

At the respective opposite sides of the bridging contacts 28 prongs 39 extend from the stationary contacts 29 for similar engagement with the movable contacts. These prongs 39 likewise are yieldable so that as the switch plates are pulled outwardly the opposite faces of the bridging contacts are engaged by the prongs and are aligned thereby to insure good electrical connection.

The clips 39 of the contacts 29 extend across the ceilings of the recesses 6 and are held in position by means of the screws 49. It is desirable that recesses be provided in the ceilings for reception of the clips so that they may be held securely.

As shown in the drawing, the U portions of the contacts 39 face downwardly toward the bottom of the prong and the U portion contacts 29 face upwardly. This arrangement facilitates contact of the clips over substantially the entire surface of each bridging contact 28, since the bridging contacts 28 are relatively loosely mounted in the switch plate and align themselves flatly against the faces of the stationary contact members.

Screws 49 have heads forming the button contacts of the fuse receptacles and the shanks of the screws extend through the bottom walls of the fuse cavities for threaded engagement with the clips 29, while the head portions also serve to clamp the fuse shells 3 and terminal clips 33 to the base block. The fuse shells 3 are of the usual type, threaded at their upper portions as at M to Lil receive conventional fuse plugs and have portions of their bottom walls and contiguous portions of their side walls cut away for clearance purposes.

The terminal clips 33 are comprised of forked portions 42 which are seated upon the bottom walls of the fuse shells and connector portions 43 which extend outwardly to receive terminal connector screws 44. Lugs 45 may be struck from the connector portions 43 so as to facilitate the attachment of wires to the terminals.

The fuse receptacles are seated upon the floors of the fuse cavities 2, and theforked portions 42 of the connector clips rest on the base portions of the receptacles and form. electrical contact therewith, while fiber insulating washers 46, and metallic washers 41 above them, are placed intermediate the heads of the screws 49 and the forked portions of the connector clips. As the screws 40 are tightened, the clips 29, the fuse shells 3 and terminals 33 are clamped firmly to the blocks, with the fiber washers 46 forming the electrical insulation between the shells of the fuses and the button contacts of them.

The metallic washers 41 are of double lock formation having cleats 56 struck to extend from their one face for engagement with the fiber washer 45 and other cleats or tangs 51 struck from the other face for engagement with the heads of the screws 43. The cleats 56 are sufficiently blunt that they do not bite through the fiber washer 46 or tend to rupture it. The tangs 51 bite into the screw head 40 and prevent it from turning relative to the fiber washer. In order to prevent each fiber washer itself from turning and thereby indirectly permitting the screw 40 to become loosened, it can be provided with a tail 58 which extends through the cut-away portion 59 of the fuse shell and into the recess 48. By this structure all of the parts are held and locked against movement during the life of the apparatus. These features are disclosed in more particular detail, and claimed, in my copending application Serial No. 405,329, now issued as United States Patent No. 2,326,370.

The terminals 33 extend endwisely from the fuse receptacles through apertures 48 cut in the end walls of the fuse cavities and rest on ledges 49, so that the terminals are supported against downward movement when wires are attached to the terminal screws. Appropriate recesses 59 are provided in the terminal ledges 49 for clearance of the depending portions of terminal screws.

The apparatus of the present invention may embody both switching and fusing facilities, or either alone, that is, the improvements relating to the switch organization may be used independently of fuse receptacles or vice versa, if desirable. It is to be noted that one switch plate may be employed in a block and the other omitted if single instead of double switching facilities are requisite.

Each unit of the present invention may be attached to a panel board or false back member by means of screws 5|, and as many of the blocks may be arranged in side by side relationship as are necessary to accommodate the distribution circuits which are to be serviced through the panel board. Bus bars 9 extend centrally down through the group of blocks and these feeder lines terminate in connectors 52 which are appropriately insulated from one another by a porcelain insulator 53. 7

Thus, an entire assembly of fuse and switch blocks and bus bars may be assembled upon a panel and this panel then may be inserted in a conventional panel cabinet. The panel cabinet, however, may be of considerably smaller size than would be required to accommodate similar facilities embodying toggle type switches, since the latter, because of their construction, require considerably more space.

Having described my invention, I claim:

1. A unitary switch and fuse block structure comprising a non-conducting base member having a cavity, movable means including switch contacts located at opposite ends of the cavity, the said movable means having notches in opposite edges thereof, spring means extending along the cavity at opposite sides of said movable means, with the endwise portions of the spring means constituting detents arranged for respective engagement with the notches, and means for holding the spring means in the cavities, the said base including stationary electrical contacts for engagement with the switch contacts of said movable members.

2. An electrical switch comprising a block of non-conducting material, switch plate members located in spaced relationship, each movable within said block, pairs of stationary contacts carried by said block at opposite sides of the respective switch plates and movable contacts carried by said switch plate members for respective engagement with said stationary contacts, the said switch plate members having notches in opposite sidewise edges thereof corresponding to switch open and switch closed positions, and spring detent means extending along the block, with the opposite ends of said detent means arranged for engagement with said notches.

3. An electrical switch comprising a block of non-conducting material having pairs of stationary contacts in spaced relationship, switch plate members supported by theblock and movable therein intermediate said stationary contacts of the respective pairs, bridging contact members carried by the switch plate members for bridging the contacts of the pairs, and a spring detent member supported by the block and having its opposite ends yieldably associated with the respective switch plate members for frictional engagement therewith whereby the one spring detent member serves to hold two switch plates frictionally against unintentional movement.

4. An electrical switch comprising a base block of non-conclucting material, switch members residing within the block and extending transverse- 1y thereof, the said members being movable along their longitudinal axes, stationary contacts carried by the block respectively at opposite sides of said switch members, bridging contacts carried by the switch members and adapted respectively to be moved into engagement with said stationary contacts upon movement of said switch members, and means for frictionally restraining the said switch members to hold them in predetermined switch open and switch closed position subject to forcible movement out of position, comprising yieldable members extending along said base block and having their endwise portions respectively engaging the opposite sidewise edges of said switch members.

5. A device of the class described comprising a base member of non-conducting material having a cavity containing a fuse receptacle and having a transverse opening in its bottom face permitting the base block to straddle a bus bar, the said base block including a pair of stationary contacts one of which is located adjacent the said fuse receptacle and the other of which is located adjacent the said transverse opening, the latter of the said pair having a portion extending into said transverse opening of the base block for electrical connection with a bus bar straddled by the base block, and a switch memebr slidably carried by the base block and having a contact adapted to be moved intermediate the stationary contacts of the pair upon movement of said switch members.

6. An electrical switch comprising a base block of non-conducting material, switch plate members residing within the block in spaced relationship, the said members being movable along their longitudinal axes, stationary contacts carried by the block respectively at opposite sides of said switch members, bridging contacts carried by the switch plate members and adapted respectively to be moved into engagement with said stationary contacts upon movement of said switch members, and means for frictionally restraining the said switch members to hold them in predetermined switch open and switch closed position subject to forcible movement out of position, comprising yieldable members disposed adjacent the opposite sidewise edges of said switch plate, each yieldable member having its opposite ends each respectively engaging a sidewise edge of each switch :memebr.

7. A switch and fuse block structure comprising a base block having fuse receptacles at its opposite ends, a cavity at its upper face intermediate the fuse receptacles and a transverse opening at its bottom face enabling the block to straddle electrical conductors which reside in spaced parallel relationship to one another, pairs of conductors in spaced relationship carried by said base block respectively inwardly of said fuse receptacles, with one of the conductors of each pair being in electrical connection with a portion of said fuse receptacle and means connected with the other member of each pair extending into the said transverse opening for electrical connection with a conductor straddled by said base block, switch members slidable between the said pairs of contacts and carrying contacts adapted to bridge the contacts of the pairs when the plates are slid, and means common to the edges of both slidable switch plates for exerting yieldable pressure thereupon to frictionally hold them in predetermined positions into which they manually may be moved.

8. A unitary switch and fuse block structure comprising an elongated base block having cavities at its opposite ends for receiving fuse receptacles, a cavity at its upper face and a transverse opening at its bottom face enabling the block to straddle electrical conductors which reside in spaced parallel relationship to one another, pairs of conductors in spaced relationship carried by said base block inwardly of said fuse cavities, means connected with one of the conductors of each pair extending into the said transverse opening for electrical connection thereof with a conductor straddled by said base block, plate members respectively slidable between the said pairs of contacts and carrying contact members adapted to bridge the contacts of the pairs when the plate members are moved into contact closing position, and spring means common to both said plate members extending along said base block within the central cavity and at the opposite edges of said plate members the said spring means exerting yieldable pressure on said plate members to frictionally hold said plate members in predetermined positions into which they manually may he slid.

9. In a switch structure, a non-conducting base having a cavity therein flanked by slidable switch plates, detent means residing in the cavity with the respective ends of the detent means engaging the said switch plates for frictional detention thereof, a cover plate disposed over the cavity intermediate the switch plates, the said cover plate having a flange along at least one of its side edges residing in the cavity for supporting a central portion of the detent means disposed therein.

10. In a switch structure, a base having a cavity therein, a switch plate disposed at one end of the cavity and slidable relative to the base, detent means contained within the cavity and having a yieldable end for engagement with the switch plate for frictional detention thereof in predetermined positions, a, cover plate disposed over the cavity, means for attaching the cover plate to said base, said cover plate having its exposed surface recessed for reception of 'a sheet bearing indicia designating a circuit controlled by said switch plate.

11. The combination comprising a block having a cavity therein for reception of a fuse receptacle, a switch .plate residing in said block transversely thereof adjacent said fuse cavity and being slidable therein, a pair of stationary contacts disposed at opposite sides of said switch plate, the block having a transverse passageway in its bottom face, one of said contacts having a connector portion extending into said passageway and exposed therein for connection with an electrical feeder residing in the said passageway, .and screw means extending through the block and said connector portion for attaching the connector portion to an electrical feeder with the said switch plate carrying a bridging contact adapted to be interposed between the stationary contacts upon movement of the switch plate.

12. The combination comprising a block having connection with an electrical feeder residing therein, the said switch plate carrying a bridging contact adapted to be interposed between the stationary contacts upon movement of the switch plate, detent means for frictionally restraining the switch plate against movement when the bridging contact thereof is in full engagement with the stationary contacts and also when the bridging contact thereof is fully out of engagement with the stationary contacts, the said detent means constituting at least one member having one portion mounted in substantially fixed relationship and having its opposite end yieldable and in engagement with an edge of said switch plate.

' 13. A device of the class described, comprising a block of non-conducting material having a cavity therein flanked by a pair of contact carrier plates each being slidable within said block, bridging contact means carried by said contact carriers, stationary contacts supported by the block and positioned respectively for engagement with the contacts carried by said carrier, a pair of elongated spring clip members extending along said .cavity respectively adjacent the opposite edges of said contact plates, each clip member being common to the pair of contact carriers and having its endwise portions pressing upon oppo-' site sidewise edges of the contact carriers and arranged frictionally to maintain the contact carriers in predetermined switch open and switch closed positions, whereby snap action is obtained in moving the contact carriers manually from one position to the other.

EDWIN W. LANDMEIER.

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