US2606233A - Switchboard - Google Patents

Description

W. H. SCHYMIK Aug. 5, 1952 SWITCHBOARD 7 Sheets-Sheet 1 Filed May 5, 1948 8 Far 0 INVENTOR. W Maw BY WC M W. H. SCHYMIK Aug. 5, 1 952 SWITCHBOARD 7 Sheets-Sheet 2 Filed May 5, 1948 g- 1952 w. H. SCHYMIK 2,606,233

SWITCHBOARD Filed May 5, 1948 7 Sheets-Sheet 3 INVENTOR. d/fw M flw u 5, 1952 w. H. SCHYMIK 2,606,233

SWITCHBOARD Filed May 5, 1948 7 Sheets-Sheet 4 JNVENTOR.

BY Mi /C M W. H. SCHYMIK Aug. 5, 1952 SWITCHBOARD 7 Sheets-Sheet 5 Filed May 5, 1948 OIIIIIIII I!! IN VEN TOR.

w. H. -SCHYMIK SWITCHBOARD 7 Sheets-Sheet 6 Filed May 5, 1948 INK/EN TOR.

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Aug. 5, 1952 w. H. scHYMIK SWITCHBOARD 7 Sheets-$heet '7 Filed May 5, 1948 Patented Aug. 5, 1952 SWITCHBOARD Walter Haines S chymik, Oreland, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application May 5, 1948, Serial No. 25,295

11 Claims.

The present invention, which is related to application Serial No. 539,336, filed June 8, 1944, now Patent No. 2,441,485, relates to circuit breaker mounting means and more particularly to means for mounting a plurality of thermal magnetic circuit breakers in a switchboard.

This invention contemplates the arrangement of the circuit breaker mounting means in such a manner that individual circuit breakers may readily be attached or removed from the switchboard from the front thereof with complete safety for the operator and in the simplest possible manner.

Heretofore, most switchboards have been so arranged that it has been necessary to obtain access to the rear of the switchboard and to work among the bus bars thereof to disconnect any particular circuit breaker and remove the same. This ordinarily requires a complete shut-down of the switchboard, or, at least, that entire section in which an operator is working in order to prevent injury to the operator.

This novel arrangement of the circuit breaker mounting means, so that the circuit breaker may be removed from the front of the switchboard, requires only that the particular circuit breaker which is to be removed be set at the off position prior to the removal.

This invention also contemplates the arrangement of the circuit breaker itself so that it may readily be handled during removal without danger to the operator.

Ordinarily in small circuit breakers which are mounted on a switchboard, the terminal members are so arranged that they may inadvertently be contacted by the operators fingers during removal. This is so because circuit breakers are not always back connected and must be arranged to permit front connection where necessary. When opposite terminals are thus contacted, the circuit breaker, even though it is in the off position, is Icy-passed by the body of the operator who may then be injured or electrocuted. This invention includes specific means inserted in the circuit breaker itself to prevent any such inadvertent contact with the terminal members of the circuit breaker.

Thus, a primary object of this invention is the provision of simplified mountingmeans for circuit breakers in a switchboard wherein the circuit breakers may be attached, removed or exchanged from the front of the switchboard.

Another object of this invention is the incorporation of safety features in the mounting means which will prevent injury to the operator while working on the switchboard.

Another object of this invention is the incorporation of further safety means in the circuit breaker itself to prevent injury to the operator while removing or replacing a, circuit breaker on the switchboard.

Another object of this invention is the ar- '2 rangement of the mounting means for circuit breakers on a switchboard insuch a manner that the mounting means may readily be adjusted to any slight variation in the surfaces or dimensions of any particular circuit breaker housing or part.

A further object of this invention'is to provide a totally enclosed safety switchboard, with circuit breakers that are removable from the front without disturbing the circuit breaker connections and in addition the circuit breaker is completely enclosed in insulation material with no exposed live parts.

Still another object is to provide a safety type switchboard wherein each circuit breaker or group of circuit breakers is mounted in a steel enclosed compartment so as to reduce to a minimumthe possibility of communicating ionized gas, either due to circuit breaker operation or even circuit breaker failure, into the other sec tions of the switchboard such as the bus compartment.

These and many other objects of this invention will become apparent in the following description and drawings in which:

Figure 1 is a view in perspective, partly broken away, of a dead front switchboard including the novel mounting means and novel circuit breakers of this invention.

Figure 2 is a view in perspective showing the manner in which safety to the operator is assured while the circuit breaker is being removed or replaced.

Figure 3 is a view partly in cross section taken on line 3-3 of Figure 2 looking in the direction of the arrows and showing the specific mounting means for the circuit breaker. I

Figure 4 is an expanded view partly in cross section of the rear of the mounting means of'this invention.

Figure 5 is a view in perspective of the rear of a portion of the switchboard again showing the specific mounting means.

Figure 6 is a view in perspective showing a slight modification of the switchboard of Figure l.

Figure 7 is a view in perspective showing a further modification of this novel switchboard.

Figure 8 is a circuit diagram showing the circuit arrangement of circuit breakers in this novel switchboard.

Referring now to Figure 1, I have here shown my novel dead front switchboard I0 (the top and side plates being removed), which comprises vertical U-shaped supporting posts H and i2 of structural steel arranged with their flanges running parallel to the front of the switchboard and horizontal connecting members I4 and I5 also of structural steel inter-connecting the vertical posts H and I2 to form a complete framework. The framework is provided with suitable supports of insulated material for supporting the various bus bars 20, which are fed from a source of supply, not shown.

Current is taken from the bus bars 20 by the bus taps 2|, 2| and is led to the various circuit breakers 25. After passing through the circuit breakers 25, current then passes out through the cables 26 to the various loads to which the cables are connected.

A top finishing piece or cornice is secured across the upper ends of the front part of the framework to provide a finished appearance for the front of the switchboard; and steel panels 3|, 3|, having appropriate openings 32, 32 registering with the operating handles 33 of. the circuit breakers 25, are removablysecured to the front. frame. by the screws 35 which enter appropriate. tapped openings inthe frame members. Gircuit breakers 25 may be of any'well-known construction such as. shownin co-pending, application Serial No- 454,163, filed. Auguste, 1942, nowabandoned.

Flanges3-5 on the-panels 3| serve to spacethe panels appropriately from the" frame supporting membersto provide-clearance for the frontends of the circuit breakers 25 so that only the handle .33 thereof may project through theopenings 32.

The front of the switchboard, by reason of the panels 3|, the flanges 36 of which-are in contact with each other,.forms adead front or grounded front which will serve as a low resistance bypass protecting theoperator from any fault Whichmay occur at anyone circuit breaker A plurality ofhorizontal channel 40 are provided supported between the vertical front post members |2 by the bolts 40a to support the mounting means forv the circuit breakers hereinafter described. A channel is provided for each row of terminals. Thus, where, as seen in Figure 1,.flve rows-of circuit breakers are provided, each circuit-breaker having terminals atgthe top and 14 bottom ends, ten such horizontal: channels 40 must be provided.

Referring now to Figure 2, there-is here shown a'portion of the switchboard of Figure 1 with the front panels 3| removed, so that access may be obtained to the circuit breakers 25.

As-seen-in Figure 2, the normal method of removal of the circuit breakers is tograsp thetop and bottom end of any particular circuit breaker simultaneously and. pullthe same straight out.

1n the ordinary construction of circuit breakers, adapted either for front or back mounting,.the terminal members are accessible through the top and bottom openings 41 oneach circuit breaker.

Thus, the circuit breakers 25 are ordinarily constructed so that a connection may be made thereto through the top and bottom openings This is so even though additional back connecting members are provided. This becomes more obvious from Figure 3, where it will be seen that the end terminal member 42 is accessible through the openings 4| Instead, however, of taking the connection out directly through the opening 4|,

through his body and suffer a severe shock. This invention contemplates, therefore, the insertion of fiber pieces 45 in the openings 4| to cover the terminal members 42 and the other elements connected thereto, so that the operators fingers cannot contact the terminal members to by-pass the current through his body.

In Figures 2, 3, 4 and 5, there is also shown the mounting means for the circuit breakers in greater detail.

The mounting means comprises a mounting block individual to each end of each circuit breaker. This mounting block 50 is formed of a piece of molded Bakelite or similar insulating material designed to fill up the channel 40 in which it is positioned.

The mounting block also carries integral therewith a plurality of tubular extensions 5| (see Figure 3) having the cylindrical openings 52 therein to position the. draw-out lugs 53 hereinafter. described.

Thebackof the channelfiil, as seeninphantom in. Figure 4 and in solid in Figure 5, is providedwithan oblong cut-out 55 at each circuit breaker position to permit the tubular extensions 5| and the draw-out lugs 53' thereof to project therethrough to the back of the switchboard.

A clamping plate 55 (Figures 3, 4 and 5) which is wider than the oblong cut-out 55, has a central opening 51 adapting it to be fitted over the central tubular extension 5|. The clamping plate 56 is made of Bakelite or any other suitable insulating material and is backed up by a sheet of manganese steel 58 in order to give strength thereto. Since manganese steel is non-magnetic, the use of this type of material for reinforcement prevents heating at this point.

Clamping, plate 5658 is. provided with apair of opposite openings 58, through which the bolts 6|, 6| pass.

When the clamping plate is placed in position, as shown in Figures 3 and 5, so that the central opening 51 thereof is over the central extension 5| of the mounting block 55, the clamping, plate bridges the cut-out 55 in the channel 45. The bolts 6| are then threaded into the tapped openings 65 in the metal inserts 55 of the mounting block-59.

The tightening of the bolts 6| clampsv the back portion of the channel 49 betweenthe mounting block 50 and the clamping plate 55.

The threaded insert 66 may, as will be seen from Figure 3, extend slightly out of the back end of the mounting block 50 at 68, so that a rigid metallic member may be providedfor the clamp? ing operation.

While the mounting block 55 is primarily designed to fill the channel 40 on which the circuit' breakers 25' are mounted, it further serves as a means of adjusting the draw-out lugs 53 to accurately align the same with the separable contacts 70 of the circuit breakers. This adjust.- ment can be obtained by hand tightening the bolts 6| in the upper and lower mounting blocks 50 and then putting the breaker 25 in place (as hereinafter described), after which the clamping ing bolts 6| may be fully tightened. Thus, during this operation, partial tightening of the clamping bolts 6| positions the mounting block 50 in place but permits it to be shifted slightly until the circuit breaker 25 is aligned with. the draw-out lugs 53.

After this alignment is obtained, then the clamping bolts 6| may be tightened fully to secure the mounting block 59 permanently in place. When this final adjustment has been made, two self-tapping screws 72 are threaded through appropriate openings in the back of the channel 40 (see Figures 4 and 5) and intothe material of the mounting block 50 to anchor the mounting block 50 in position and to prevent any possible movement.

When the circuit breaker is mounted in position, mounting screws 14 may be inserted through the openings 75 of the circuit breaker and threaded into the front end of the tapped metal insert 66 to holdthe circuit breaker firmly in position.

It will thus be obvious that the clamping bolts or screws Si and the circuit breaker mounting bolts 14 are threaded into opposite ends of the same metal insert 66, so that these opposite bolts sharethe same metal insert.

By this arrangement, the plastic material of the mounting block i relieved of strains since the bolts BI and 14, being diametrically opposite and in the same piece, exert their forces in opposite directions neutralizing each other in their relation to the Bakelite of the mounting block 50. While the utilization of metal inserts in molded material is not new, it is believed that this arrangement for relieving strains is entirely novel.

The draw-out lugs 53 are made of copper and have hexagon head 89 which cooperate with similarly shaped hexagonal recesses 82 in the front of the mounting block 55. This prevents the turning of the draw-out lugs 53 when cables or bus bars are being mounted thereon.

The rear ends of the draw-out lugs 53 are provided with nuts 83 on the threaded ends 84 to facilitate the securement of cables or bus bars thereto. The front ends of the draw-out lugs 53 are smooth members which cooperate with separable contacts T0 of the circuit breaker 25.

The terminal 42 of the circuit breaker is provided with an opening, not shown, through which the bolts 23 pass.

The rear end of each bolt 43 is provided with the dumbbell shaped separable contact supporting member El of conductive material secured thereto in any appropriate manner.

A metal insert 89 is used to support the bolt 43 and to fill the opening 90 in the back of the circuit breaker.

The base of the circuit breaker is provided with depressions i l registering with the openings 99 to provide a space for the separable contacts l0 and the ends 85 of the draw-out lugs 53.

Terminal 42 is conductively related to the bolt 43 by the nut 53 which is held in position by the lock nut 94.

' The separable contact H! is held in position on the dumbbell shaped terminal end 81 by the garter spring 9'1. This separable contact member 10 is a flexible conducting member, which is well known in the art.

The rear ends of the separable contact members T8 are provided with the flaring portion 98, adapting them to slip readily over the ends 85 of the draw-out lugs 53, and are held in efficient current conducting relation with the ends 85 of the draw-out lugs by the garter springs 99.

By this means, therefore, a simplified dead. front switchboard is provided which is simple in construction, facilitates replacement and repair, and permits the circuit breakers to be accessible entirely from the front for tests and adjustment operations and protects the operator.

Many modifications of the novel switchboard structure should now be obvious to those skilled in the art. Thus, as shown in Figure 6, an additional steel panel H0 may be provided between the circuit breakers and the buses along the en- 6 tire height and width of the switchboard-this increases the safety feature of the switchboard. so equipped by preventing any breakdown in: the circuit breakers from spreading to the bus bars or the cables.

The steel panel H0 is supported between the horizontal frame members [4, l4 and is appropriately spaced from the front horizontal frame members l5 by the spacing plates HI which are provided with the small flange HZ secured in any suitable manner, as, for instance, by welding, to the steel plate H9 and in any suitable manner to the front frame members 15.

This construction, in addition to the added safety feature, obviates the necessity for utilizing a plurality of separate channel members it shown in Figure 1. That is, the steel plate I 10 has the appropriate mounting blocks 56 secured thereto in the same manner as the mounting blocks 58 are secured to the channels of Figures 3, 4 and 5; and the steel plate H0 has a cut-out similar to the cut-out 55 at each mounting block position.

The steel plate H0 may, however, be reinforced atthe mounting block positions by additional rigidifying U plates H5, H5 which are of channel shape only for the purpose of rigidity and to reinforce the conductive plate .I IE1 at the point where the mounting blocks for the circuit breaker are supported.

In Figure '7, there is shown a switchboard with top plates i3 and side plates it broken away. This switchboard has essentially the same construction as that provided in Figure 6, except that, in addition to the steel panel H0 between the circuit breakers and the bases, a steel partition H l is provided to separate groups of buses and their associated circuit breakers into cubicles. Only a single horizontal partition H! is shown to separate the switchboard into two sections; any number of vertical and horizontal partitions l1 and HI may be used to form any desired number of separate cubicles. 1

By this means, the board is divided into two sections and in the case of a fault, causing fire, prevent the spread of that fire from one section to another. Likewise any break down in the circuit breaker is prevented from spreading to the bus work by the grounded metal barrier I In.

These particular panel boards and their application to Navy vessel, presented some special problems that might not arise commercially.

It is frequently desirable under battle condi tlons, to lock circuit breakers in against their normal function. This is done to maintain maximum service as long as practical regardless of the possible damage to equipment.

Under some circumstances, with breakers locked closed, it is inevitable that in the event of a fault or a short circuit, that some of the smaller breakers will be taxed beyond their capacity and therefore break down. In such cases it is desirable to prevent the fire caused by this break down from spreading to other parts of the panel board, therefore, it is desirable to segregate groups of breakers and the bus Work feeding them.

This will be obvious from the circuit diagram of Figure 8 representing a standard circuit breaker arrangement on a vessel. Circuit breaker 4 is the main breaker which takes power from the transformer or other source and protects the feeder breakers 3. Eachbreaker 3 is connected to a bus from which current is taken from subsidiary feeders. Subsidiary feeders are protected by circuit breakers 2, each of which is connected to abus from which thaloads; protected by circuitbreakers-l, obtaincurrent. Itwill be clear. that if each subsidiary feeder breaker 2. and its associated load breakers l and their related buses and cables are contained'in. a single compartment or cubicle. Any firein that compartment will be confined to that subsidiary feeder breaker 2- and its associated load. breakers; I only. In less elaborate systems. or switchboards, eachmain feeder breaker 3 and its associated subsidiary feeder breakers '2. and load breakers 1 maybe in one compartment; inthatlcase, the switchboard for the: system of Figure 8 would have four compartments The locking feature .44; Figure 2, on thecircuit breakers provides means for 'holding'the: circuit breakers closed during battle conditions to prevent false tripping under physical shock or to permit equipment to continue to operate during a'battle even though fault conditions occur. The use of 'thislocking feature makes the. cubicle or compartment structure of Figure 7 important to prevent spread of the fire even though circuit breakers are destroyed by excess current;

The disconnecting elements 85l0 (Figure 3) are in front of the barrier H of Figures 6 and '7 and are protected by the Bakelite of the circuit breaker casing.

An additionaland desirable feature of this invention is the location of prod'holes 45a (Figure 2), for test purposes, in the front of the breakers. These holes are carried through the front of the panelboard (at34 of Figure '7). Provision is thus made for testing circuit breakers without sacrificing any of the safety features already described. Itmight be well to note that while these holes are: provided at both the line and load side of the circuit breaker casing they need only be carried through the panel board on the load side.

In the foregoing, this invention has been described only in connection with preferred specific embodiments thereof. Many variations and modifications of the principles of this invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein but only by the appended claims.

I claim:

1. A switchboard mounting for a circuit interrupter" comprising afirst metallic mounting plate; a second metallic plate, a support therefor; insulating supporting inserts secured to one of said plates; circuit connecting members carried by said insulating supporting inserts; said circuit connecting members projecting beyond said insulating supporting insert on opposite sides; the projections of said circuit connecting members on one side forming disconnect contacts for said circuit interrupter; means including said disconnect contacts for permitting automatic disconnection of said interrupter from its circuit on withdrawal of said interrupterfrom' said switchboard; the projections of said circuit connecting members on the other side each forming a connecting means to a circuit; an opening in said mounting plate; said insulating supporting insert and said projections on said other side of said insert extending through said opening.

2. A dead front. switchboard comprising a mounting for a plurality of circuit interrupters; each circuit breaker mounting comprising a metallic mounting plate; a support therefor; an insulating supporting insert secured to said plate; circuit connecting members carried bysaid insulating-supporting insert; said circuit connecting members projecting beyond said in"- sulating supporting insert on opposite sides; the projections of said circuit connectingmembers on one side forming disconnect contacts for said circuit. interrupter; the projections of said circuit connecting members on the other side each forming a connecting means to a circuit; an opening in said mounting plate; said projections on said other side of said insert passing through said opening; buses and connecting members for said buses to said circuit connecting means of said interrupters being housed in said switch.- board; said mounting plate being metallic and continuous and furnishing a continuous metallic support for a plurality of said circuit interrupters in the same plane; said continuous metallic plate extending between. the circuit interrupters and said buses and connecting members for said buses.

3. A dead front switchboard. comprising. a mounting for a plurality of circuit interrupters; each circuit breaker mounting comprising, a mounting plate; a support therefor; an insulating supporting insert secured to said plate; circuit connecting members carried by said insulating supporting insert; said circuit connecting members projecting beyond said insulating supporting insert on opposite sides; the projections of said circuit connecting members on one side forming disconnect contacts for said circuit interrupter; the projections of said circuit connecting members on the other side eachforming a connecting means to a circuit; an opening in said mounting plate; said projections on said other side of said insert passing through said opening; buses and connecting members for said buses to said circuit connecting means of said interrupters being housed in said switchboard; said mounting plate being metallic and continuous and furnishing a continuous metallic support for a plurality of said circuit interrupters in the same plane; said continuous metallic plate extending between the circuit interrupters and said buses and connecting members for said O buses; and additional metallic plates in said switchboard normal to said metallic mounting plate dividing said switchboard structure into cubicles separating sets of circuit interrupters and their associated buses and connecting members.

4. A dead front switchboard comprising a mounting for aplurality of circuit interrupters; each circuit breaker mounting comprising a mounting plate; a support therefor; an insulating supporting insert secured to said plate; circuit connecting members carried by said insulating supporting insert; said circuit connecting members projecting beyond said insulating supporting insert on opposite sides; the projections of said circuit connecting members on one side forming disconnect contacts for said circuit interrupter; the projections of said circuit connecting members on the other side each forming a connecting means to a circuit; anopening in said mounting plate; said projections on said other side of said insert passing through said opening; buses and connecting members for said buses to said circuit connecting means of said interrupters being housed in said switchboard; said mounting plate being metallic and contine uous and furnishing a continuous metallic support for a plurality of said circuit interrupters in the same plane; said continuous metallic plate extending between the circuit interrupters and interrupters and said buses and connecting accuses members for said buses; and a metallic sheet secured in front of said circuit interrupters; openings in said last mentioned metallic sheet to operate said circuit interrupters.

5. A dead front switchboard comprising a mounting for a plurality of circuit interrupters; each circuit breaker mounting comprising a mounting plate; a support therefore; an insulating supporting insert secured to said plate; circuit connecting members carried by said insulating supporting insert; said circuit connecting members projecting beyond said insulating supporting insert on opposite sides; the projections of said circuit connecting members on one side forming disconnect contacts for said circuit interrupter; the projections of said circuit con necting members on the other side each forming a connecting means to a circuit; an opening in said mounting plate; said projections on said other side of said insert passing through said opening; buses and connecting members for said buses to said circuit connecting means of said interrupters being hou ed in said switchboard; said mounting plate being metallic and continous and furnishing a continuous metallic support for a plurality of said circuit interrupters in the same plane; said continuous metallic plate extending between the circuit interrupters and said buses and connecting members for said buses; and a metallic sheet secured in front of said circuit interrupters; openings in said last mentioned metallic sheet to operate said circuit interrupter and additional small openings in said last mentioned metallic sheet forming prod holes for testing said circuit interrupters.

6. In a dead front switchboard, a removable front plate, a second metallic plate, circuit breakers mounted on said switchboard between said plates, said removable front plates being mounted in front of said circuit breakers, said circuit breakers having front connecting means and disconnecting contacts bus runs connectible to said disconnectin cont cts, vertical and horizontal metallic partitions for isolating adjacent circuit breakers from each other, said metallic partitions isolating said circuit breakers from said bus runs, and means whereby said circuit breakers are manually removable from the front upon removal of said front plates while protecting the operator from the circuit, said circuit breakers being totally enclosed in insulating material.

'7. In a steel enclosed safety type switchboard, a removable front metallic plate, a second metallic plate, circuit breakers mounted on said switchboard between said plates, said removable front plates being mounted in front of said circuit breakers; said circuit breakers having disconnect contacts and having front connecting means, bus runs connectible to said disconnecting contacts, vertical and horizontal metallic partitions for isolating adiacent circuit breakers from each other, said metallic partitions isolating said circuit breakers from said bus runs, and means whereby said circuit breakers are manually removable from the front upon removal of said front plates while protecting the operator from the circuit, said circuit breakers being totally enclosed in insulating material.

8. In a steel enclosed safety type switchboard, a removable metallic front plate, a second metallic plate, circuit breakers mounted on said switchboard between said plate, said removable front plates being mounted in front of said circuit breakers; said circuit breakers having disconnect contacts and being removable from the front upon removal of said front plates, bus runs connectible to said disconnecting contacts, vertical and horizontal metallic partitions for isolating adjacent circuit breakers from. each other, said metallic partitions isolating said circuit breakers from said bus runs, said circuit breakers being totally enclosed in insulating material, said front plates and circuit breakers being provided with registering holes to receive a test prod for checking the energy of the cirsuit.

9. In a steel enclose-cl safety type switchboard, a removable metallic front plate, a second metallic plate, circuit breakers mounted on said switchboard between said plates, said removable front plates being mounted in front of said cir= cuit breakers; said. circuit breakers having disconnect contacts and being removable from the front upon removal of said front plates, said circuit breakers being totally enclosed. in insulating material, means on said circuit breakers accessible from the front for holding the same in closed position against overload.

10. A metal enclosed safety type switchboard. means for mounting circuit breakers therein, circuit breakers having disconnect contacts to facilitate removal thereof from the front, removable front metallic plates arranged to cover the front of said circuit breakers; said circuit breakers being completely enclosed in insulated housings, said switchboard having a wiring compartment the back thereof and a grounded metallic barri r between said circuit breakers and the wiring compartment.

11. A metal enclosed safety type switchboard, means for mounting circuit breakers therein, said circuit breakers having disconnect contacts to facilitate removal thereof from the front, removable front metallic plates arranged to cover the front of said circuit breakers; said circuit breakers being completely enclosed in insulated housings, said switchboard having a wiring compartment in the back thereof and a grounded inetalic barrier between said circuit breakers and the wiring compartment, each group of circuit breakers and their associated connections therefor in the wiring compartment being fed from the same source and segregated into a grounded metal compartment.

WALTER HAINES SCHYMIK.

REFEBENQES CITEE The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 718,632 Johnson Jan. 20, 1903 1,119,718 Olley Dec. l, 191 1,141,359. Power June 1, 1915 1,166,149 Olley so. 28, 1915 2,041,112 Bucher May 19, 1936 2,050,378 Randall Aug. 11, 1936 2,086,424. Kcehler July 6, 1937 2,126,674 Stout Aug. 9, 1933 2,132,630 Jackson Oct. 11, 1938 2,2l0,696 West Aug. 6, 1940 2,225,791 Nau Dec. 2%, 1940 2,331,255 West Oct. 5, 1943 2,411,861 Dec. 3, 1946 2,438,025 'Ialiaferro Mar. 16, 1943 FOREIGN PATENTS Number Country Date 102,643 Austria Feb. 25, 1926

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