US2361240A - Electrical apparatus - Google Patents

Description

Oct. 24, 1944.

H. L. RAWLINS ETL ELECTRICAL APPARATU Filed Feb. 15, 1941 2 Sheets-Sheet l 6 Eage H. Fischer. q ATTOR;

Odi. 24, 1944. H L. RAWLlNs ET AL 2,361,240

ELECTRICAL AAPPARATUS Filed Feb. l5, 1941 2 Sheets-Sheet 2 .Patented Oct. '24,. 1944l l UNITED STATES ATENTfoFFic-E Herbert L. Rawlins, Wilkinsburg, and Eugene H. Fischer, Derry, Pa., assignors to Westinghouse Electric & Manufacturing Company,v East Pittsburgh, Pa., acorporation of Pennsylvania Application February 15, 1941, Serial No. 379,076

21 Claims.

This invention relates generally to electrical apparatus, and more particularly to high voltage fusesand the support or enclosure therefor.

High voltage fuses are commonly supported in insulating boxes, to not only protect the fuse machining operations `after taking them from from the elements but also to act as a support the molds, for example, as by applying an abrafor the fuse and its terminal clips. This invensive material such as steel wool, and by drilling tion relates to fuse boxes made of anew type or cuttingnThis further increases the time, labor of porcelain which has the advantage over woodand expense necessary to produce a finished fuse en boxes used formerly as fuse enclosures, in lo box, vso that by the time glaze has been applied, that due to the fact that such fuse enclosures and the box fired, several days may have been are usually supported exposed to the elements, required to manufacture iustone fuse box. the life of a wooden box is short, and they are Furthermore, due to deterioration of the plas relatively larger in size and more complex than ter of Paris molds necessitating a subsequent the box of this invention because it was necessmoothing operation which must be performed sary to employ lead-in bushings for the conducby hand, it has been impossible to obtain a unitors, and to have relatively large dimensions to formproduct. This has added to the cost of provide the necessary insulation. making these boxes because of the large number The box of this invention also has the advanof spoiled and rejected boxes. Even in boxes tege over porcelain fuse boxes mede by the so- 2o which are put in service. difculty has been excalled vdry process, which, while being some perienced in obtaining a good fit of the covers improvement over the old wooden boxes, were and fuse Clips. because the COVerS being 0f 8 nevertheless limited in application due to the composition material and the clips being'of metal, relatively high porosity of porcelain made by this are of substantially uniform size and often fail process as compared to the boxes of this invento properly t the boxes because of the impostion, which limited the voltage at which they sibility of obtaining a uniform product by' the could be used, besides limiting the mechanical Wet casting DIOCeSS- This 1S ObjectiODB/ble bestrength thereof, thus rendering such boxes unnt cause unless the covers fit properly, foreign matfor high voltage applications. ter 4can enterA the boxes and might cause elec- It was then found that an improved enclosure trieel failure 0I' improper Operation end 0f OOUISe was obtainable by the use of a wet process porimPIOper location oi the clips will Tender propel celain. This type of porcelain is identified in electrical and mechanical engagement withaluse the art as "wet process porcelain," but in order carried by the door extremely difllcult. to obtain a porcelain which is suillciently dense The doors for cutout boxes are usuallyjsup-v and non-porous to provide the necessary nigh ported on pivot pins'carried. respectively. by opdielectric and mechanical strength especially in posite Side Weils 0f the. bOX. In Order to get the irregular form of a fusebox, this porcelain anywhere near accurate alignment 0f the 110188 has in the past been obtainable only by` a wet for these pivot pins in a fuse box made by the casting process. This process consumes a great wet process casting method, it has been n'cesdeal of time and involves a great many opera- 4o sary either to provide removable cores in the tions, thereby rendering -the resulting product mold or to provide an additional drilling operarelatively expensive, as compared to the new typetion after casting, with the latterv method heini of box herein disclosed. preferable for the greatest accuracy. It can be In the wet casting process of making porcelain.- appreciated that the alignment of such pivot absorbent molds are used, into which -a liquid pin'supporting apertures is very important in clay mix is poured. A head of the clay mix is obtaining agood fit of fusebox doors. maintained on the mold for insuring thedeposit Another disadvantage of fuse boxes made by of clay in the mold as the moisture content of the wet casting process, is that it has been found the clay mix is gradually absorbed by` the mold that a certain percentage. of the boxes willv be until a solid article is formed. It takes from warped and distorted in firing, probably due to two to four hours before a completed fuse box can be formed inthe mo1d`which is sufficiently stiffto permit its removal and handling. Inasmuch as the absorbent molds are in practice short' life, and even deteriorate so much during sary to subject the fuse boxes to smoothing and the casting method wherein the'box is progressively built up in a mold, to thereby further in-` crease the spoilage and expense of manufacture.

made of plaster of Paris. they haves relatively 66 This invention relates specifically to a fuse box made of a new type of porcelain which is order of 10%.

free of the above-mentioned defects of fuse boxes made in the above described manner of what is known as wet process porcelain, and which furthermore may be manufactured for aboutV one-half the cost of wet process porcelain boxes. This invention also relates to a novel fuse box structure which is especially adapted to this new type of porcelain, and to-novel fuse supporting and engaging means for the box.

Accordingly, one object of this invention is to -These and other objects of this invention will become more apparent, upon consideration of the following detailed description of a preferred embodiment. thereof, taken in connection with the attached drawings, in which:

Figure l is a central, longitudinal section of a fuse box constructed in accordance with this invention, and showing a fuse, door and contacts in elevation; f

Fig. 2 is a transverse section vie'w of the box taken on the line II-II of Fig. l with the fuse and upper contact in plan;

Fig. 3 is a top,view of the lower contact, of Fig. 1;

Fig. 4 is a top view of the lower contact supporting bracket of Fig. l; v

Fig. 5 is a side elevation of a slightly modified form of fuse box; and

Fig. 6 is a section taken on line VI-VI of Fig. 5.

'In the drawings, there is illustrated a fuse box 2, which in accordance with this invention, is of a new type of porcelain. As previously stated, in the past, it has been possible to obtain a dense porcelain in the irregular form of a fuse box, only by the wet casting process, which however, has

, porcelain is formed from the usual clay mix which is preferably comparatively dry, preferably not more than 17% moisture, and preferably having a relatively small percentage of ball clay, on the This dry mix is then placed in the metal die cavity of a die lpress. An important feature of the invention is the arrangement of the clay mix in the die before pressure is applied.

It has been found that in order to obtain a dense porcelain at least as good as that obtained by' the weil casting method, it lsessential to remove the entrapped air from the mix and ycause intimate engagement of the clay particles. In making porcelain in accordance with this invention, entrappedy air is removed, andthe clay particles are forced into intimate engagement by means of three main operations all carried out by use of the die press.`

less dense portions of the pile. The purpose of initially compacting portions of the pile, is to initiallyfcreate relatively dense portions and cause the lateral sliding movement of the clay particles to take place under relatively high presusre, to

, fill the voids in the less dense portions of the pile.

and thereby create a -porcelain article having a relatively uniform high density. It has been found that best results are obtained if the portions of the pile manually compacted correspond to the deepest parts of the die. Thus, in making a fuse box such as that shown on the drawings in a die press which is formed to exert pressure in a direction substantiallyat right` angles to the open front 8 and rear wall I0 of the box, the portions of the clay-piled over those parts of the die adapted to form side walls 4, 6 and skirt I2 (Figs. 5 and 6), should be higher and should be initially manually compacted, so that when the'press is closed, lateral sliding movement of the clay particles will occur from these portions into rear wall I 0, and form a box of high uniformly dense porcelain.

(3)' A relatively high press pressure should be used, for example, a minimum pressure of about 200 lbs. per square inch depending upon the complexity of the article to be formed. However, it has been found that while such high pressures are desirable, a mere sustained high press pressure is insuilicient to obtain the desired porcelain density, especially in making fuse boxes, and this (l) In o-rder to remove air from the mix, some N means should be provided for removing air from the die interior, such, for example, as by evacuation of the die when closed, by a vacuum pump or by the use of a heavier-than-air gas to displace" the air, or the like. f

(2) In order to provide for intimate engagement of the -clay particles they must not only be compressed into intimate association, but must desired density is obtainable onlyby causing the press to engage the mix with an impact. Such an impact will cause the lateral sliding of the clay Y particles described above, into intimate engagement under high pressure. The amount of moisture in the mix is suillcient to permit relative lateral movement of the clay particles, and may be considered as just sufficient to permit in effect. a plastic flow of the mix into the recesses of the dies. It has also been found that in order to obtain the desired densityof porcelain it is necessary that al plurality of successive impacts be dealt. Thus, for example, in making fuse boxes, the press is preferably operated to deal three successive impacts to the article being formed, and it has been found that a plastic'flow of the clay occurs on each impact and is usually'completed on the third impact.

Porcelain fuse boxes made.V by the above-described new method have a density and consequent dielectric strength at least as good, and will run generally better than boxes made by the old wet casting method. Probably more important however, is thefact that fuse boxes made of this new porcelain can be made to close tolerances so that no additional operations are necessary before rlring to obtain a uniform product. This makes it possible to form pivot apertures in the box by the pressing operation, and always obtain ay good fit of the door, thereby eliminating drilling,.scraping,` shaving or coring operations. Tolerances, for example, of one percent in the length of fuse boxes are obtainable, and tolerances in boxes made by the wet casting process s from this cause.

are entirely unpredictable and run, for example, from three to six percent. Also lit is found that there is negligible warping in firing of fuse boxes which are die-pressed, so that there is no spoilage For example, in the manufacture of several lhundred boxes to date, there has been no spoiled or rejected boxes.

From the foregoing, it is readily apparent that not only are `fuse boxes made of die-pressed porcelain better, from an electrical and mechanical standpoint, but that their cost of manufacture is much less than fuse boxes of cast wet process porcelain. The boxes can be pressed in a few minutes, for example about three minutes, and then ilred after a relatively short drying period without any other operations and with-1L out spoila'ge. and in the firing kiln in substantially less than 24 hours, and this should be contrasted to the several days time necessary to produce a cast `wet process porcelain fuse box, and its attendant high spoilage, as high at times as 20 to 30 per-l cent.

It is, of course, recognized that it is old to form porcelain articles by the application of pressure using various methods, such as extrusion, with a subsequent forming operation or hot pressing with a plaster mold; but heretofore no one has been able to press in a metal die a relatively large irregular article of porcelain such asa fuse-box,-

Thus a' fuse box may be pressed* The advantages of the die-pressed.`

the front of the box, so that a die may be inserted and withdrawn from the front of the box. At the same time, by using die-pressed porcelain, it is possible to form the exterior opposed surfaces of the box parallel, and also to form irregular surfaces on the exterior of the box by the use of a female die member having removable sides. Consequently, it can be seen that a die-pressed porcelain fuse box will present a particularly effective and regular exterior appearance, While permit-v ting the formation of irregularities or indenta.

tions in the outer surfaces in the same operation by which the box is formed.

Depressons 24 are provided on the inner surpression 24 by cement material 28, similar to the comprises a generally rectangular box Zhaving.

at opposite endsof the box. As shown in the drawings, the protuberance 9 is-provided with a socket 1 opening to the outer surface of rear wall I0, for receiving a bracket arm I4 for supporting `the box. Bracket arm I4 is secured in socket I 0 by any desired eementing material, such,

for example, as lead or the like, which is cast into the socket with bracket arm I4 in place, and the interior surface of socket 'I is preferably rough' cned, as by sanding, to secure a good bond with disposed leg 32 having in the outer end thereof,

inwardly extending slots 34 for receiving the shank of a screw 36 freely passing through an aperture in one leg 40 of a substantially U-shape'd clamping member, and threadedly received in the other leg 38 of the clamping member.

' The U-shaped clamping member is provided with an offsetportion 42 in the leg 40 thereof, to provide an enlarged bight portion in line with conductor' apertures 44 in the side walls of the box. A`scrw 46 is threadedly engaged with offset portion 42 of the clamping member, to secure a `conductor in the bight portion of the clamping member. The fuse contact proper inducting material such, for example, as vcopper or the like, and a resilient backing strip 50 which may be of any desired resilient material such,

I'he outer end of contact strip 48 is slotted toV provide spaced contact arms` 52, and the outer end of resilient backing strip 50 is provided with a pair of spaced slots to form outer contact pressure arms 54, substantially aligned with the conthe cementing material I6. Bracket arm I4 may be secured to a hanger bracket 'or support I6 for mounting the same on a cross arm or the like, for example'as by a bolt 20. The outer surface of rear wall' I0 of the fuse box is provided about the opening of socket 1, with an annular depression 22 to increase the creepage distance t0 supporting bracket I4.

It will be ,noted that the fuse vbox illustrated is particularly adapted to be made by the diepressing method described, in that all inner faclng surfaces of the box diverge outwardly toward \It will be observed that the contact strip, 46, backing strip 50, and U-shaped clamps 36, 40, 42,k

tact arms 52 of the contact strip, and anV intermediate independently movable latching strip 56, positioned 'so that the outer end thereof overlies the slot in the end of the contact strip 48, and it has an inwardly bent latch portion 43 adapted to extend below contact strip 48.

are assembled by screws 36 so that they may be removed as a unitJ from supporting bracket arm 32 merely by loosening screws 36. When these parts are removed from'the supporting bracket,

y, they are maintained in supporting relationl by vcludes a contact strip 48 of any suitable cony tively easily mounted in position in the fuse box merely by slipping them over the leg 32 of la supporting bracket, and tightening screws 36. It should be noted that the inner end 41 of contact strip '48 extends beyond the inner end of backing strip 5G into the bight portion of the clamping member, so that a conductor in the bight portion, will be clamped against the contact strip by setscrew 46. With the contact in the position shown in Fig. 1 of the drawings, it is obvious that the contacting portions 52 of the contact strip are positioned to engage the upper terminal of a fuse, while latch portion 49 on leg 56 of resilient backing strip 50, is positioned to latch the fuse terminal in engagement with the contact strip. rhis particular arrangement insures that while the fuse terminal is moved into and out of engagement with the contact assembly, that the contact strip 48 and its resilient backing strips t 'will not be overstressed in latching the fuse terr nel in place. That is, the only part which is ovetressed by movement o the fuse terminal with the contact stri, ing strip which, as independently or so as not to effec The lower conteo many respects, id assembly and, theL applied to like p l avoid undue repetition.. t -will be noted t ie supporting bracket and U-shaped clamping member are identical with those used for the upper contact assembly, er.'- cept that the supporting bracket is rotated su'ostantially 130 from the position occupies in connection with the upper contact assembly, so that leg thereof extends downwardiv from leg 32 instead of upwardly as ln the upper contact construction. Also, the inner ends of contact strip E@ and resilient backing strip 6U which are received in the U-shaped clamping member, are substantially like the inner ends of contact strip 4S and resilient strip 50 for the upper contact, the only difference being that the outer ends of contact strip 58 and resilient backing strip 59 are substantially ocextensive and similarly formed with an arcuate recess 62 to receive the fuse tube The fuse box is preferably provided with a door te of any desired composition material, provided with an exterior handle 8S, and an interior integral apertured support Bl adjacent the upper end thereof for slidably receiving fuse i3. Support 58 is provided with a portion having a setscrew 69 threadedly engaged therethrough to secure the fuse I3 against longitudinal movement. Door 6I is also provided adjacent the lower end thereof with spaced, integral, longitudinally extending anges 10, having an integral connecting member 12 forming a channel for receiving the lower end of fuse I3. A lower terminal casting Il is adapted to be secured to door 'flanges l0, for example, as by rivets 18 or the like, and this terminal casting is, as shown, substantially trapezoidal in form, including an upper is the leg 5S of the bach viously stated, is movable 5t and the contact strip, t the contact pressure.

assembly and support in .with the upper contact ksurface adapted to engage contact strip 58, and

a lower side surface adapted to support a screw 18 for securing the tail 80 of a fuse link supported within the fuse to the terminal castingr 14. Fuse I3 is also provided with an upper terminal ferrule 82, to which the other end of the fuse link is adapted to be secured, for example, as by a terminal cap 8l removably engaged with terminal ferrule l2. The lower fuse terminal Vand out of engagementN casting 14 is also provided with a groove 88 forming a continuation of slots 86 in the sides of door 64, for receiving pivot pins supported respectively on side walls 4 and B of the fuse box.

From the foregoing, it is believed that it will oe readily apparent that fuse I3 is carried on door 64 for pivotal movement to and away from a closed position with respect to fuse box 2, and when door 64 is in its closed position, fuse I3 will have its terminals 54 and 14 engaged, re-

spectively, with contact strips 48 and 58. It will be noted that the contact strips have the outer ends thereof bent upwardly so that they and their resilient backing strips may be stressed to engage the fuse terminals with a predetermined pressure. Furthermore, the upper contact assembly is also adapted to latch the door and fuse in closed position, by means of an independently movable portion of the resilient contact backing strip, so that the Contact strip itself is not called upon to performfthis latching function and consequently will not be overstressed to weaken the same. The unitary assembly of the contact strips and their resilient backing strips with a. clamping means, for not only securing the Contact assembly in operative position in a fuse box 'out also to secure a line conductor thereto, is especially advantageous since it; greatly sur lines assembly and replacement of these l It should also be noted that the contacts, men in operative lposition, are rigidly secured. :ik fuse boi: so

- `outwardly on door handle Se and the fuse and door may then be pivotally moved, outwardly relative to the casing, and, when moved to a depending position with respect to the casing, these parts may be detached from the casing merely by moving the end of the door carrying terminal block 'l5 outwardly, to remove the boxpivot pins outof slots 86 and 8E?.

In Figs. 5 and 6 of the drawings, there is illustrated a fuse box which is like that shown in Figs. 1 to 4 of the drawings, with the exception that it is especially designed for higher voltages, and to this end is provided with e. substantially U-shaped skirt I2 on the outer surface of rear wall' I0 of the box, with the closed end of the skirt positioned Just'above socket 1 in rear wall III. This skirt provides additional creepage distance from the supporting bracket Il to both upper and lower conductor apertures 4I, and since the lower end is left open, there is no opportunity for foreign matter to accumulate within the skirt. It will be noted, by particular reference to Fig. 6, that the legs of skirt I2 are positioned substantially in alignment with side walls l and G, respectively, of the box so that when the box is formed of die-pressed porcelain with the die pressure being exerted in a. direction substantially parallel with the side walls of the box, the most; extensive, or thicker portions, of the box will be in alignment with the direction in which pressure is exerted, so that the initial compacting operation previously referred to may be carried out along the side edges of the dies, to secure a now of the porcelain mix laterally from these portions into the rear wall of the casing.

Both boxes shown in the drawings are preferably provided wlth annular grooves 5I! 'about conductor apertures Il, and with grooved portions 92 having straight end portions connected by intermediate curved portions, so l that these grooves will be positioned both between conductor porcelain,

It will be readily observed by reference to the drawings that by the use of die-pressed porcelain for a fuse box, it is possible to obtain nearly any desired irregularities in the outer surfaces of the box while at the same time maintain a. symmetrical box structure having parallel exterior surfaces. Such constructions are extremely dimcult, if not impossible, to obtain by the old wet casting process porcelain, because of the necessity of providing for removal of the box from the mold after it has been formed.- Thus, a fuse boxy when made of die-pressed porcelain, will have mechanical and dielectric strength at least as good as that of the oid cast wet process porcelain box, and has the further advantages of generally bettering these characteristics. Thus, for example mechanically, it is possible with die-pressed porcelain to obtain a uniform product manufactured to close tolerances so that a good flt of the box doors is always insured as well as proper positioning of the contact supporting portions and barriers within the box. Also, due to the extreme accuracyfpossible with die-pressed porcelain, a great many economies may be made in manufacture of these irregularly shaped fusev boxes which are not necessarily applicable to any other type of porcelain product, so as to reducer the cost of the poreclain for fuse boxes approximately by one-half.

Having described preferred embodiments of the invention in accordance with the patent statutes,

it is desired that the invention be not limited to the paricular embodimens disclosed herein, inasmuch as it will be obvious, particularly to persons skilled in the art, that many changes and modifications may be made in these particular embodiinents withou departing from thei broad vspirit'and scope our invention. Accordingly,

it is desired that this invention be interpreted as f broadly as possible and that it be limited only by U-shaped flange around said recess with the closed end of said flange adjacent the top wall the prior art and by what is expresslyset' forth in thevfollowingv claims.

We claim as our invention: 1. A newl article of manufacture comprising an irregular shaped 'high voltage fuse box of uniformly dense, die-pressed porcelain. t r `2. A new article of manufacture comprising a high voltage fuse box lof initially compacted and vacuum die-pressed porcelain.

' 3. A new article of manufacture Acomprising an irregular shaped high voltage fuse box of dense, non-porous, cold die-pressed porcelain.

of said box, the leg portions of the flange being substantially in alignment with the side walls of said box, and said box being formed ofv a single unitary piece of die-pressed porcelain.

6. A fuse box including spaced side walls connected by integral top and rear walls to form a box having an open front, a recess in the outer surface of said rear wall for supporting a mounting bracket, an outwardly extending substantially U-shaped flange around said recess with the closed end of'said flange adj'acent the top wall of said box, said flange being outwardly tapered, the leg portions of the flange being substantially in alignment with the side walls of said box, and

`said box being formed of a single unitary piece of die-pressed porcelain.

7. A fuse box including spaced side walls connected by integral top and rear walls to form` a box having an open front, a contact supporting bracket having a slotted outer end on said Vrear wall, a contact strip, a substantially U-shaped clamp member, means connecting the legs of said clamp member to force them together, and adapted to be received in said bracket slot to secure said bracket and contact strip between the legs thereof, and means for securing a conductor in the bight portion of said clamp member.

8. A fuse box .including spaced side walls connected by integral top and rear walls to form a box having an open front, a contact supporting bracket having a slotted outer end on said rear wall, a contact strip, a substantially U-shaped clamp' member, means connecting the legs of said clamp member to force them together and adapted to be received in said bracket slot to secure said bracket and contact strip between the legs thereof, means for securing a conductor in the bight portion of said clamp member, and said contact strip adapted to extend into the bight portion of said clamp member so as to be engaged by said conductor.

9. A fuse box including spaced side walls connected by integral top and rear walls to form a box having an open front, a contact supporting bracket having'a slotted outer end on said rear wall, a. contact strip, a substantially U-shaped clamp member, means connecting the legs'of said clamp member to force them together and adapt-` ed'to be received in said bracket slot to securesaid bracket and contact strip between the legs 4. A fuse box including spaced side walls connected by integral top and rear walls to' forma box having an open front, confronting inner surfaces of theside walls of said box being flared outwardly, with opposed outer surfaces of saidN side walls being substantially parallel, and,said box being of a single unitary piece of die-pressed 5. A fuse box including spaced side walls connected by integral top and rear walls to form aH box having an open front, a recess in the outer surface of saidy rear wall for supporting a mountingbracket, an outwardly extending substantially thereof, means `for`securing a conductor in the bight portion of said clamp member, and saidv securing means extending-through an aperture in said contact strip, whereby said clamp member and contact strip are removable as a unit from said bracket.

10. A fuse box including spaced side walls connected by integral top and rear walls to form` a.

box having an open front, a vcontact supporting bracket having a slotted outer end on said rear wall, a contact strip, a resilient backing strip,l

a substantially IU-shaped clamp member, means connecting the legs'of said clampy member to force them together and adapted to be received in said bracket slot to secure 'said bracket, r lient strip and contact strip between the legs t ereof, means for securing a conductordn the bight portion of said. clamp member, and said contact strip adapted to extend into the bight portion of said clamp member so as to be engaged by said conductor.

' ll. A fuse box including spaced side walls connected by integral top and rear walls to form a box having an lopen front, means on said. rear ritiri wall for supporting a latching contact, said contact including a conducting strip and a resilient backing strip, and said backing strip including an independently movable latch portion offset from at least an outer portion of said conducting strip and adapted to project therebelow to independently latch a fuse terminal in engagement with said conducting strip.

l2. Contact means for releasably engaging a fuse terminal or the like, including a contact strip having a forked outer end, and a. resilient backing strip having an independently movable latch portion adapted to overlie and at least in part extend through the space between the outer end portions of said contact strip.A Y

13. Contact means for releasablv engaging fuse terminal or the like, including a contact strip, and a resilient backing strip having an independently movable latch portion offset from at least anouter portion of said contact strip and adapted to project therebelow to independently latch said terminal in engagement with said contact strip.

i4. A new article of manufacture comprising irregular shaped high voltage fuse box of dienpressed porcelain having dielectric and vmechanical strength characteristics at least as good as Wet-process porcelain.

l5. A new article of manufacture comprising an irregular shaped 'nigh voltage fuse boxv of die-pressed porcelain having dielectric and mechanical strength characteristics at least as good as Wet-process porcelain, but having a greater degree of dimensional iidelity.

1G. A ruse box including spaced side walls, connected by integral top and rear Walls to form a box having an open front, spaced fuse contacts secured in said box to said rear wall, a door for the front of said box movably mounted thereon, a fuse carried by said door, spaced terminals carried by said fuse positioned to engage said contacts when said door is closed, and said box being or a single unitary piece of die-pressed porcelain having dielectric and mechanical strength characteristics at least as good as wetprocess porcelain, but having a. greater degree 'of dimensional fidelity, whereby proper engage- Cil connecting the legs of said clamp member to force them together for securing the unit in operative position on a support member, one end of said strip positioned between the legs of said clamp member and apertured to receive said securing means.

i8. A contact unit including a conta/ct strip, a substantially Ll-shaped clamp member, means connecting lthe legs of said clamp member to force them together for securing the unit in cperative position on a support member, one end or" said strip positioned between the legs of said clamp member apertured to receive said securing means, means for securing a conductor in the "night portion of said clamp member and said contact strip adapted to extend into the bight portion of said clamp member so as to be engaged by said conductor.

19. l Afuse enclosure comprising a box portion having spaced side Walls connected by integral tcp and rear Walls, and a door portion for the iront of said box movably mounted thereon, at

least one portion of said enclosure being of a single unitary piece of uniformly dense diepressed porcelain.

20. In a device of the type described, a support of insulating material, a bracket projecting from said support, a unitary' terminal assembly adapted to be mounted on said support, said assembly including a substantially U-shaped member and a terminal member having one end loosely held assembled therewith by clamping means, said assembly adapted to be mounted on said bracket with said bracket received in said U-shaped member' in engagement with said terminal member, whereby said clamping means is effective to secure said assembly to said bracket and to secure said terminal member against movement.

, 2l. In a device of the type described, a support of insulating material, a bracket projecting from said support, said bracket having at least one slot therein opening at one edge thereof, a contact strip, a substantially U-shaped clamp member, means connecting the legs of said clamp member to force them together, and adapted to be received in said bracket slot to secure said bracket and contact strip between the legs thereof.

HERBERT L. RAWLINS. EUGENE H. FISCHER.

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