US2267202A - Fuse box construction - Google Patents

Description

Dec. 23, 1941. M. K. HOLMES ETAL FUSE BOX CONSTRUCTION Filed Nov. 13, 1959 4 Sheets-Sheet 1 680 eFMCMQ/w/Z, LA fiazmsegy.

4 Sheets-Sheet 2 In z/enzam 114020215. .floZm e5 M. K. HOLMES ETAL FUSE BOX CONSTRUCTION Filed Nov. 13, 1939 Dec. 23,. 1941. M. K. HOLMES ETAL F'usn BOX cons'muc'rzon 1 I 0 w w, w aw w Ma m w .x, m mflgn I w fiMQ a m m 4 a a Filed Nov. 13, 1939 Jmrucanwv Dec. 23, 1941. M. K.HOLMES ETAL FUSE BOX CONSTRUCTION 4 Sheets-Sheet 4 Filed Nov. 13, 1939 Patented Dec. 23, 1941 FUSE BOX CONSTRUCTION Minot K. Holmes, Muncie, Ind., and George F.

McMahon, Chicago, and Allan Ramsey, Evanston, Ill., assignors to Schweitzer & Conrad, Inc., Chicago, Ill., a. corporation of Delaware Application November 13, 1939, Serial No. 303,944

25 Claims.

Our invention relates generally to housed or box type cutouts and switches for use outdoors on high voltage transmission and distribution circuits, and it has particular relation to the construction of the housing or box itself and the provision of means for securing various fittings thereto. I

Ordinarily the housing or enclosure comprises integrally formed top, side and rear walls and provision is made for hinging a cover to close the open front. When the housing encloses a fuse tube, the tube is usually mounted on the cover and it is provided with suitable contact members for engaging line terminals that are mounted on the rear Wall of the housing. In such a construction it is essential that the line terminals and the hinge support for the cover be properly spaced so that the cover can accurately register with the front of the housing and also so that the contact members of the fuse tube can accurately register both horizontally and vertically with the line terminals on the rear wall. It is a relatively simple matter to properly space the hinge parts on the cover and the contact members on the fuse tube that is carried by the cover. However, it is not so simple a matter to maintain the proper spacing of the hinge niounting and line terminals on the housing. Yet this spacing must be provided in order to furnish a satisfactory operating device.

According to present practice, housings for electrical devices for use on high voltage circuits are made of insulating material in order to provide the requisite amount of dielectric material between the line terminals. It is customary to provide cavities or openings in the walls of these housings into which fittings can be cemented or bolted as the case may be. It will be understood that these fittings are provided for mounting thereon the line terminals, contact clips, the fuse or switch and door supports. and the mounting bracket or other means that is employed for securing the housing or boxon a cross arm or the like.

The housings or boxes that are employed in present commercial practice are formed of porcelain. The boxes are molded from suitable ceramic materials as is well understood in the porcelain art. As indicated. the box comprises top. side and rear Walls, being open at the front and bottom. ,It is present practice to mold the boxes with cavities in the side and rear walls into which inserts may be secured by 171:?15 of cement .g the fitnce with standard practice the molded box is fired in a kiln until it has been entirely vitrified In such a process it is usual to find that considerable shrinkage takes place. For example, the finished box after it comes from the kiln may have shrunk as much as one inch in twelve inches from its original dimensions prior to firing.

Since the boxes are employed for housing dropout fuses and disconnecting switches, it is necessarythat provision be made for accurately mounting these mechanisms, as set. forth hereinbefore, so that they will be capable of performing their intended functions properly. At first thought it might seem to be advisable to mold inserts in the porcelain so that they would be integrally formed therewith when the box is removed from the kiln. Obviously, such a procedure is impractical because of the shrinkage which takes place in the kiln. Therefore, the cavities are provided in the walls of the box during the molding process. which are much larger than the inserts which may be accurately spaced by means of jigs and which are secured in the cavities as described. The cavities generally have sand imbedded in the porcelain to furnish a rough surface. A thin coat of resilient compound is applied to this surface to allow for expansion of cement or alloy during temperature or other changes.

The box as received from the kilns of the porcelain manufacturer is provided with the cavities as described. Some cavities are located, for example, in the front side of the rear wall for receiving inserts for mounting the line terminals and hinge bracket, while one or more cavities are provided in the back side of the rear wall for receiving inserts for mounting the box on a cross arm or the like. The cavities in the front side. of the rear wall are partially filled with Portland cement and the inserts are held in position in the cement filled cavities by means of a jig. With the inserts held in position by the jig, the assembly is placed in a steam room for approximately twenty-four hours in order to permit the cement to properly set. The box is then removed from the steam room and the jig detached. The cavity or cavities in the rear wall are then filled with cement and the inserts, held in position in the cement by a suitable jig, after which the box is again placed in a steam room, this time for approximately forty-eight hours.

It is also present practice to secure the inserts in the cavities by means of a low fusing point alloy. The steps for securing the inserts in place in this manner are somewhat similar to those outlined above for cementing them. in place. The inserts must be placed in position on one side of the rear wall first and the alloy permitted to cool, and then the box is turned over for receiving the other inserts. Jigs are employed for accurately alining the inserts.

It will be observed that the prior methods of manufacturing boxes for fuses and switches of the type described are open to many serious objections. They are due principally to the fact that it is not possible to accurately mold porcelain to the desired shapes. A large number of operations is required in order to properly mount the inserts on both sides of the box. This involves considerable expense of handling. Moreover, because of the requirement of curing the cement considerable manufacturing space is required ifthe boxes are to be handled in any large quantities. Extreme care must be exercised in locating the fittings or inserts and in placing thecement or low melting point alloy in place. If this is not done they may become loose and the fittings associated with the line terminals'may be the source of radio interference. In some cases, after a long period of time, the cement may swell and crack the box, and in others the pouring of hot alloys around the inserts sometimes cracks the porcelain.

Sandin Patent No. 2,011,654, suggests that glass can be employed instead of porcelain for making the housing or enclosure and poirts out that metallic inserts can be molded in glass while they must be secured in porcelain by cementing or babbitting them in place. However, this patent only goes so far as to suggest that, when the housing is formed of glass. inserts can be molded in the back side of the rear wall to which a mounting bracket can be secured. For mounting the line terminals relatively large inserts are disclosed as being cemented or babbitted in cavities on the front side of the rear wall, there being one insert for each terminal. Possibly it was intended that these large inserts should be molded in place in the event that the housing is formed of glass. At any event, we have found that it is not feasible to mold large inserts, such as disclosed by Sandin, in glass for several reasons.

When relatively large single inserts are employed they tend to become loose in the glass on cooling because of the large amount of concentrated shrinkage. This causes the inserts to separate slightly from the glass and provide a source of electrostatic stress concentration that often results in radio interference. Obviously both looseness and radio interference are objectionable.

Because of the relatively great thermal capacity of large single inserts the molten glass first coming into contact with them is quickly cooled. It is then not possible to have the glass fiow into intimate contact with all portions of the surface of such inserts which are embedded in the glass. The resulting air spaces promote looseness and radio interference.

When the line terminals are bolted to relatively large single inserts and when an electrical device, such as a fuse or switch, is moved into or out of engagement therewith the stresses incident thereto are not uniformly distributed. Because of this non-uniformity of stress distribution the glass around the inserts may be cracked or shattered.

The foregoing are possibly some of the reasons why the construction disclosed in the Sandin patent embodying glass rather than porcelain has accuses never gone into commercial use in so far as we are aware.

The object of our invention generally stated is to provide an improved form of housing or box for fuses or switches that can be readily and economically manufactured and onto which the necessary parts may be accurately assembled with a minimum of time and expense.

An important object of our invention is to reduce the number of operations that are now required in the manufacture of an enclosed fuse or switch device.

An object of our invention is to accurately aline the various parts of a fuse or switch in a -"housing for the same without requiring many of the steps or operations that have previously been necessary.

A further object of our invention is to manufacture a fuse or switch box out of a material, such as glass, in which the fittings or inserts for receiving the lire terminals, fuse or switch and door supports, and the mounting bracket, are integrally embedded in the glass in proper alinement for their intended purposes.

Still another object of our invention is to employ a number of relatively small inserts embedded integrally in a fuse or switch housing of glass for distributing the stress incident to the mounting thereon of line terminals, etc.

A still further object of our invention is to equalize the pressure between the slightly irregular. surface of the glass and the fittings secured thereon by providing pads of yielding material therebetween.

Another object of our invention is to so mount the fittings that pressure resulting from tightening them is applied to the glass and not onto the adjacent surfaces of the inserts.

Other objects of our invention will, in part, be obvious and, in part, appear hereinafter.

According to our invention the housing or box for mounting a dropout lose device such as shown in the copending application of Allan Ramsey et al., SerialNo. 115.690, filed December 14, 1936, or the switch device shown in the copending application. of Allan Ramsey, Serial No. 115,691, filed December 14, 1936, is formed of glass rather than of porcelain. Glass is employed rather than porcelain since its dielectric properties are suitable for the intended purpose and principally for the reason that it does not shrink appreciably when it is cast. preciably. sets of relatively small metal inserts for receiving the various terminal and support fittings may be embedded in the material forming the box at the time that the molten glass is molded, a set being provided for each terminal and support fitting, with the result that they will be in the necessary accurate alinement when the box is cooled and is removed from the mold. A predetermined mass of glass is placed in the mold, which in itself contains some of the properly spaced inserts and also removable cores forming apertures in the side walls for receiving the line conductors. Then a plunger, with other inserts in place. is pushed into the mold, forcing the glass around the inserts. When the glass has hardened sufiiciently, the plunger is removed allowing the inserts to remain in the glass. The cores are withdrawn and the box is then removed from the mold. When the box is formed in this manner no further manufacturing steps are necessary to place it in condition for receiving the terminal and bracket fittings other than to grind Since glass does not shrink apoff certain of the surfaces which may be slightly rough.

For a more complete understanding of the na-- ture and scope of our invention reference may be had to the following detailed description taken in connection with the accompanying drawings, in which,

Figure 1 is a view in front elevation of a fuse box constructed in accordance with the present invention;

Figure 2 is a longitudinal sectional view taken along the line 2-2 of Figure 1;

Figure 3 is a view in rear elevation of the box shown in Figure 1;

Figure 4 is a detail sectional view taken along the line 4-4 of Figure 1;

Figure 5 is a view, on an enlarged scale, of one of the fittings or inserts shown in Figures 1-, 2 and 3;

Figure 6 is a view taken along the line 66 of Figure 7 and similar to that of Figure 2 showing a dropout fuse device disposed in operative position in the fuse box;

Figure 7 is a view similar to that of Figure 1; showing the terminal and hinge fittings in place;

Figure 8 is a view in front elevation of the thimble that is secured to the back side of the rear wall of the box and to which the mounting bracket may be secured for supporting the box on a cross arm or the like;

Figure 9 is a detail sectional view taken along the line 9-9 of Figure 7; and Figure 10 is a view, on an enlarged scale, of a modified form of insert.

While our invention is disclosed specifically in combination with a dropout fuse device of the type shown in the copending application of Ramsey et al. referred to hereinbefore, it will be understood that it may also be employed in conjunction with a disconnecting switch of the type shown in the copending application of Ramsey also referred to hereinbefore. In both of these embodiments one\of the requisites is that the various parts be capable of accurate alinement so that the fuse can drop out or the switch can be operated in the intended manner.

Referring now particularly to Figures 1, 2, 3 and 4 of the drawings, it will be observed that the reference character l0 designates generally a housing or box in which a dropout fuse device may be mounted. The box I0 is provided with an integrally formed top wall side walls l2 and I3, and a rear wall H. The box I0 is preferably formed of translucent colored glass that is amber or chocolate brown in appearance. When glass of this type is employed the light emanating from an electrical discharge. inside of the box or within the body of the glass, such as occurs when a faulty box is subjected to high voltage tests, is difused and rendered more readily visible than is the case if the glass were clear and not colored. If the glass were clear and transparent, a faint sparking would not develop the contrast which would be the case with a dark colored body. This feature makes it a comparatively easy matter to detect faulty insulating conditions.

As a result of the molding process ridges l5 protrude from the rear wall. These ridges are formed in the base of overflow chambers into which excess glass flows during the molding process in order to make certain that there will be suiiicient glass to completely fill all of the mold cavities. I

In the front side l6 of the rear wall l4 several sets of metal inserts are located. The upper set comprising three metal inserts i7 is provided for receiving the upper line terminal. Another set comprising two inserts I8 is provided for receiving the lower line terminal. On the lowermost portion of the rear wall I three inserts l9 are provided for receiving a hinge bracket. On the back side 20 of the rear wall N there is formed a raised portion 2| having a cavity 22 extending therethrough and a substantial distance into the rear wall H. The cavity 22 is provided for receiving the boss of a thimble as will be described hereinafter. Four metal inserts 23 are embedded in the back side 20 of the rear wall H to which the thimble may be secured. It will be observed that a slight generally rectangular recess 2| is provided in the raised portion 2| and that a recess 23" individual to each of the inserts 23 is provided in the bottom of the recess 2| for reasons which will be presently apparent.

The details of construction of one embodiment of the inserts is shown more clearly in Figure 5 of the drawings. This insert can be formed from square bronze rod stock by suitable screw machine operations. Grooves 24 are provided to form flanges 25 around which the molten glass can flow and which serve to secure it in position in the glass when it solidifies. The insert is threaded as indicated at 26 for receiving suitable screws to fasten the appropriate fitting thereto.

Instead of employing a single large insert for each of the line terminals and the hinge bracket with its attendant disadvantages, as previously described, a number of inserts is employed in order to reduce the strains on .cooling of the glass and to more uniformly distribute the stresses incident to the tightening of the various parts by the screws. Strength tests have been made showing that the multiple insert feature in glass is equal to, and in most cases superior to, the securing of a single large insert by Portland cement in a cavity, formed in porcelain for example. The glass around a small insert is not broken until considerable stress has been exerted. When the stress is sufliciently great, the glass crumbles around a small insert, which then be comes loose. Contrary to general belief, the box itself does not crack clear through the walls or fall apart.

It is important to select a material for the inserts which has a coefficient of thermal expansion that is substantially greater than the coefficient of thermal expansion of the glass. If the coeiiicients of expansion are substantially the same or if the coefilcient of expansion of the inserts is less than the coefficient of expansion of the glass then the latter on cooling may be cracked as the result of the'presence of the inserts. The coefiicients of expansion should be such that substantially no residual stresses will be present in the glass after it has cooled because of the presence of the inserts. We have found that it is desirable to have an extremely slight clearance between the inserts and the glass in which they are molded when the glass is finally cooled. While this might result in the inserts being somewhat loose in the glass, such actually is not the case when the line terminals are assembled thereon. The screws which serve to hold the line terminals to their respective inserts also serve to tighten the inserts in the glass, with the result that there is no apparent looseness of the inserts and consequently no radio interference.

At the same time that the inserts are embedded in the rear wall H of the box l0, apertures 2'! and 28 are formed n the side walls 12 and I3, respectively. These apertures 21 and 28 are formed by the flow of molten glass around cores which are carried by the side plates of the mold and project into the core or inner part of the mold. The apertures 21' and 28 are in alinement with the terminal fittings that are mounted on the inserts i1 and [8 for the purpose of receiving the'line conductors from either side.

In order to increase the creepage distance between the upper and lower terminals a barrier 29 is integrally formed in the front side l6 of the rear wall l4, and, as illustrated, it projects outwardly therefrom a substantial distance. Likewise, a barrier 30 is integrally formed in the front side l6 of the rear wall [4 between the lower terminal mounted on the inserts i8 and the hinge bracket mounted on the inserts I9 to increase the creepage distance therebetween and to prevent accidental engagement of the lower line terminal by the hinge when the fuse device is removed or placed in operation.

In Figures 6, 7 and 9 of the drawings the manner in which the line terminals, contact clips, fuse device and cover are mounted in the box is shown in detail. As there illustrated, an upper line terminal, shown generally at 35, is secured by suitable screws 36 to the upper set of inserts l1. A cushion gasket 31, preferably formed of lead, is placed between the under side of the line terminal 35 and the front side l6 of the rear wall l4. Similarly, a lower line terminal, shown generally at 38, and including a terminal casting 39, is secured by screws 40 to the inserts IS. The terminal 38 also includes a clip 4|, the purpose of which will be presently set forth, that is held in position by a screw 42. There is provided a lead cushion gasket 43 between the underside of the terminal casting 38 and the front side of the rear wall of the box I0. A hinge bracket 44 is secured by screws 45 to the lower set of inserts IS. A lead cushion gasket 46 is provided between the underside of the hinge bracket 44 and the front side of the rear wall l4. The lead cushion gaskets 31, 43 and 46serve to prevent the concentration of force on possible irregularities in the adjacent glass surface by readily conforming thereto and thereby substantially uniformly distributing the stresses incident to tightening the terminals 35 and 38, and the hinge bracket 44 in place.

As shown more clearly in Figure 7, pins 41 project inwardly from the opposite ears of the bracket' 44 for receiving hooks 48, one of which is shown in Figure 6, that form a part of a sleeve bracket 49 which is secured by screws 50 to a door 5|. The door 5| may be formed of suitable insulating material, such as Bakelite," and is provided with an integrally formed eye 52 to facilitate operation of the door to the open and closed positions.

Integrally formed with the door 5| is a guide 55 having a suitable aperture therein through which a fuse tube 56 can slide. At its upper end the fuse tube 56 is provided with an upper terminal, shown generally at 51, which is arranged to have contact engagement with the upper line terminal 35. The fuse tube 56 is also provided with a lower terminal, shown generally at 58, which is in conducting relation to the sleeve bracket 49 and which is arranged to have contact engagement with the clip 4| of the lower line terminal 38.

The fuse tube 56 is biased downwardly by end of the fuse tube 56.

means of a coil compression spring 59 that reacts between the sleeve bracket 49 and the lower A flipper or lever 50, pivoted at '6! on the sleeve bracket 49, serves to hold the fuse tube 56 against the downward movement caused by the spring 59. A fuse link in the fuse tube 56, the flexible lead 62 of which extends over the flipper or lever 69 and around the stud 63 and clamped to the sleeve bracket 49 by the knurled nut 64, is arranged to hold the flipper or lever 60 in the position shown in the drawings.

When the fuse link in the fuse tube 56 blows, the flipper or lever 60 is released and the spring 59 is free to move the fuse tube 56 downwardly through the guide 55 and the sleeve bracket 49. The upper fuse terminal 51 is then disengaged from the upper line terminal 35 and the door 5| carrying the fuse tube 56 is then free to swing about the hinge pins 41 to the open position. The fuse tube 56 is then re-fused and replaced in service in the usual manner.

The sets of inserts l1, l8 and [9 must be accurately spaced because of the relatively close tolerances that are required for proper operation of the fuse device. mines the position of the door 5| and the parts carried thereby. The door 5| should accurately interfit with the groove provided therefor around theopen side of the box In so that it can be readily moved into and out of position and further so that it will fully close the open side to prevent entrance of rain, snow, sleet, etc. The terminals 51 and 58, carried by the fuse tube 56, should accurately register with their respective line terminals 35 and 38 to provide proper contact pressure and to permit disengagement of the upper terminal 51 from the upper line terminal 35 when the fuse link blows.

With a view to providing for mounting the fuse box ID on a suitable support bracket such as a cross arm hanger bracket, a thimble, shown generally at 66 in Figures 6 and 8, is provided having an integrally formed boss 61 which projects into the cavity 22 in the back side 20 of the rear wall 14. The thimble 66 is provided with an integrally formed flange 68 that overlies the inserts 23 to which it is secured by screws 69 extending through suitable countersunk apertures, as shown.

It is desirable that no moisture enter between the underside of the thimble 66 and the adjacent back side 20 of the rear wall 14. A collection of moisture therebetween might result in cracking or breaking of the rear wall in the event that it should freeze. To obviate the possibility of any entrance of moisture a sealing compound 10 comprising a waterproof plastic is provided in the recesses 2 l' and 23, as illustrated, underneath the thimble 66 when the screws 69 are tightened into place. The thimble 66 is effectively sealed to the box It) and all likelihood of the entrance of moisture therebetween is obviated. A lead cushion gasket between the glass and thimble 66 is not required, as the thin layer of sealing compound 10 provides all of the cushioning that is required between the adjacent surfaces and, by conforming to any irregularities that may be present in the adjacent glass surface, it substantially uniformly distributes the stress incident to tightening the thimble 66 in place.

It will now be apparent thatthe recess 2! provides a space for receiving the sealing compound 10 and for readily holding the same in The hinge bracket 44 deterplace while; the thimble is being clamped in place and the compound is solidifying.

By providing the recesses 23, the outer faces of the inserts .23 are always below the surfaceof the glass at the bottom of the recess 2 I Therefore, on tightening the screws 69, force is applied directly to this surface of the glass and cannot be applied directly to the outer faces of the inserts, as would be the case if these faces were flush with this surface. It would then not be possible to tighten the screws 69 further and the inserts 23 might become loosened, resulting in possible radio interference.

If desired, the inserts IT, IS and I! in the front side l5 of the rear wall ll can be molded in place so that their front faces will be slightly below the adjacent surface as are the inserts 23. This would further reduce the likelihood of the inserts in the front side of the rearwall becoming loose and causing radio interference.

The sealing compound Hi may be a high melting point but somewhat tacky asphaltic substance, known as Korite. The sealing compound is first melted and poured into the cavity in back of box, being careful not to fill adjacent screw holes in the inserts 23. The thimble i6 is then inserted and pulled into position by screws 69. Excess compound flowing outward around the edges, is later removed.

As illustrated, the thimble 66 is provided with a centrally located tapped aperture H for receiving a cap screw or the like of the hanger bracket. Obviously, if desired, a stud could be integrally formed with the thimble 66 or threaded into the aperture H.

It will be observed that the line terminals 35 and 38 are provided with conductor receiving apertures 13 and 14 into which set screws 15 and 16 project for holding the line conductors therein. These conductor receiving apertures 13 and 14 are positioned in alinement with the apertures 21 and 28 in the side walls l2 and I3 of the box I0 so that the line conductors may be readily inserted in place from either side without requiring any bending of them as they enter the box.

In Figure 10 of the drawings there is shown a modified form of insert 80 which may be used instead of the inserts previously described and shown in detail in Figure 5. It will be observed that the insert 80 is generally conical in shape.

and that when a screw is inserted in the threaded aperture Bi and tightened against a terminal casting, for example the terminal casting 39, Figure 6, the insert 80 will be drawn tightly into uniform engagement with the surrounding glass. This avoids the presence of small and unsymmetrical air spaces around the insert which have been found to be a source of radio interference. If desired, the inner enlarged end of the insert 80 can be deformed somewhat from the conical form or champfered as indicated at 82 along one side in order to provide a shape that will resist turning in the glass when a screw is inserted.

As previously indicated, it might be considered feasible to embed a single large insert in the glass when it is molded but, at the present state of the art, this does not appear to be a satisfactory solution to the problem. If an attempt were made to embed in the glass an insert which would have the general dimensions of the terminal casting 39, of Figure 9, the net effects of relative expansion and contraction of the glass and the metal forming the insert would be so great that it would be difflcult to obtain a satisfactory product, either because the glass would be cracked, due to overstressing, or the insert would be loose rather than tightly held in the surrounding glass. On the other hand, if an attempt were made to mold the glass around several inserts rigidly attached to the terminal casting 39, then excessive strains would result in the glass not only because of the presence of a number of inserts but also because of their being rigidly held with respect to each other, thereby preventing any relative movement. In some cases the inserts would probably be tightly held in place but this would be due principally to the undesirable strains resultin from this method of manufacture.

Now instead of following either of these two procedures, it will be observed that, according to our invention, the inserts, such as the inserts I8, are embedded in the glass independently of each other so that the resulting stresses are only those which exist when the glass is molded around a single small insert. This is permissible and well within the limits of practical design possibilities. Because of the relatively small resulting residual stress when several small inserts are employed, they can be fairly accurately located during the molding process. The terminal casting, such as the casting 39, is then bolted or otherwise secured to the separately embedded inserts after all of the expansion and contraction effects have taken place. The lead cushion gasket, such as the gasket 43, then provides a. cushion pad for making the terminal casting and the inserts to which it is bolted tight relative to each other and also to the adjacent surface of the box l0.

Since certain further changes may be made in the foregoing construction and different embodiments of the invention may be'made without departing from the scope thereof, it is intended that all matter shown in the accompanying drawings or described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. An enclosure for an electrical device having terminals comprising, in combination, a molded vitreous box, and a plurality of sets of metallic inserts embedded inthe material forming said vitreous box, each set being individual to each terminal for supporting the same, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded.

2. An enclosure for an electrical device having terminals comprising, in combination, a vitreous box, a plurality of sets of metallic inserts embedded in the material forming said box, each set being individual to each terminal for supporting the same, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded, and a spacer forming a cushion between each terminal and the adjacent surface of the box.

3. An enclosure for an electrical device having terminals comprising, in combination, a molded vitreous box having integral side and rear walls, a set of metallic inserts embedded in the material forming the back side of said rear wall for supporting said vitreous box, and a plurality of additional sets of metallic inserts embedded in the material forming the front side of said rear wall and each set being individual to each terminal for supporting the same, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded.

4. An enclosure for a high voltage electrical device having terminals comprising, in combination, a molded vitreous box, a plurality of sets of metallic inserts embedded in the material forming said vitreous box, each set being individual to each terminal, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded, and threaded means for holding said terminals to the metallic inserts individual thereto, said threaded means on being tightened serving to securely hold said inserts in said vitreous box whereby radio interference is avoided.

5. An enclosure for an electrical device having terminals comprising, in combination, a molded vitreous box, a plurality of sets of metallic inserts embedded in the material forming said vitreous box, each set being individual to each terminal, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded and the coefficient of expansion of said metallic inserts being substantially greater than the coefficient of expansion of the material forming said vitreous box whereby on cooling substantially no stress is present in the latter due to the presence of the former, threaded means for holding said terminals to the metallic inserts individual thereto, said threaded means on being tightened serving to securely hold said inserts in said vitreous box whereby radio interference is avoided, and a compressible spacer between each terminal and the adjacent surface of the box forming a cushion therebetween.

6. An enclosure for an electrical device having terminals comprising, in combination, a molded vitreous box having integral side and rear walls, a set of metallic inserts embedded in the material forming the back side of said rear wall, support means disposed to be secured to said metallic inserts in the back side of said rear wall, a plurality of additional sets of metallic inserts embedded in the material forming the front side of said rear wall and each set being individual to each terminal, the mass of eachinsert being relatively small as compared to the mass of the material in which it is embedded, and threaded means for holding said support means and said terminals to the set of metallic inserts individual thereto.

7. Means for mounting the terminals of an electrical device in insulated spaced relation comprising, in combination, a molded glass support,

and a plurality of sets of metallic inserts embedded in the glass, each set being individual to each terminal for supporting the same, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded.

8. Support means for mounting a device comprising, in combination, a molded glass support member, a plurality of metallic inserts embedded as a closely associated group in the glass when it is molded to provide for attachment of said device thereto under predetermined tension, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded, and a compressible spacer between said device and said inserts forming a cushion therebetween.

9. Support means for mounting a device comprising, in combination, a molded glass support member, and a plurality of metallic inserts embedded as a closely associated group in the glass when it is molded to provide for attachment of said device thereto, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded, the surface of the glass adjacent each insert being recessed to permit the force incident to the attachment of said device to said inserts to be applied to the surface of the glass and not to the adjacent faces of said inserts.

10. Support means for mounting a device comprising, in combination, a molded glass support member, a plurality of metallic inserts embedded as a closely associated group in the glass when it is molded to provide for attachment of said device thereto, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded, and compressible spacer means between said device and the adjacent glass surface to substantially uniformly distribute the force incident to the attachment of said device to said inserts, the surface of the glass adjacent each insert being recessed to permit said force being applied to the surface of the glass and not to the adjacent faces of said inserts.

11. Means for mounting the terminals of an electrical device in insulated spaced relation comprising, in combination, a molded glass support, metallic inserts embedded in said support for carrying the same and for mounting the electrical device thereon, the mass of each insert being relatively small as compared to the mass of the material inwhich it is embedded, and spacer means arranged and adapted to provide a cushion between the-adjacent surface of the glass and the parts mounted thereon.

12. An enclosure for an electrical device'having terminals comprising, in combination, a molded glass box having integral side and rear walls a plurality of metallic inserts embedded in the back side of said rearwall for supporting said glass box, and a plurality of additional separate inserts embedded in the front side of said rear wall and individual to each terminal for supporting the same, the mass of each insert being relatively small as compare to the mass of the material in which it is embedded.

13. An enclosure for an electrical device comprising, in combination, a molded glass box having integral side and rear walls, metallic inserts embedded in the back side of said rear wall for sup-porting said glass box, and additional metallic inserts embedded in the front side of said rear wall for mounting the electrical device thereon, the coefiicient of expansion of said metallic inserts being greater than the coefiicient of expansion of the glass and the mass of each insert being relatively small as compared to the mass of the material in which it is embedded.

14. A housing for supporting a high voltage electrical device having terminals comprising, in combination, a molded glass box, a plurality of sets of metallic inserts embedded in the glass, each set being individual to each terminal, the

mass of each insert being relatively small as compared to the mass of the material in which it is embedded, and threaded means for holding said terminals to the metallic inserts individual thereto, said threaded means on being tightened serving to securely hold said inserts in the glass whereby radio interference is avoided.

15. An enclosure for an electrical device having line terminals comprising, in combination, a molded glass box having integral side and rear walls, a set of metallic inserts embedded in the back side of said rear wall, support means disposed to be secured to said metallic inserts in the back side of said rear wall, and a plurality of additional sets of metallic inserts embedded in the front side of said rear wall, each set being individual to each line terminal, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded and the coeflicient of expansion of said metallic insertsbeing substantially greater than the coeflicient of expansion of the glass whereby on cooling substantially no stress is present in the latter due to the presence of the former, and threaded means for holding said support means and said terminals to the metallic inserts individual thereto.

16. An enclosure for an electrical device havingterminals comprising, in combination, a molded glass box having integral side and rear walls, a set of metallic inserts embedded in the back side of said rear wall, support means disposed to be secured to said metallic inserts in the back side of said rear wall, a plurality of additional sets of metallic inserts embedded in the front side of said rear wall, each set being individual to each line terminal, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded, threaded means for holding said support means and said line terminals to the metallic inserts individual thereto, and spacing means of yielding material between said support means and between said line terminals and the adjacent surface of the glass and adapted to form a cushion therebetween and to conform thereto.

17. A housing for supporting a high voltage electrical device having a pair of line terminals comprising, in combination, a molded glass box having integral side and rear walls, and a plurality of separate metallic inserts embedded in the front side of said rear wall and individual to each line terminal for supporting the same, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded, said side walls having apertures formed therein during the molding of said box in registry with said line terminals to permit insertion of line conductors.

18. A housing for supporting a high voltage electrical device comprising, in combination, a molded vitreous box having integral side and rear walls, insert means embedded in the material forming the back side of said rear wall,

,support means secured to said insert means for mounting said box on a cross arm or the like, and sealing means interposed between said support means and said rear Wall for preventing the entrance of moisture therebetween.

19. A housing for supporting a high voltage electrical device comprising, in combination, a molded vitreous box having integral side and rear walls, a plurality of inserts embedded in the material forming the back side of said rear wall, a plate secured to said inserts and adapted to have support means attached thereto, and waterproof sealing means between said rear wall and said plate for preventing the entrance of moisture therebetween,

20. A housing for supporting a high voltage electrical device comprising, in combination, a molded vitreous box having integral side and rear walls, said rear wall having a cavity therein opening outwardly of its back side, a plurality of metallic inserts embedded in the material forming the back side of said rear wall around said cavity, a thimble having a boss projecting into said cavity and a peripheral flange, retaining means projecting through said flange into said inserts for holding said thimble in place, and

waterproof sealing means around said boss and hinged to a hinge bracket on the rear wall and which is required to close one side of the enclosure and which has fuse terminals which are required to engage line terminals on the rear wall both with close tolerances comprising, in combination, a molded glass box having integral top, side and rear walls, a plurality of sets of separate metallic inserts embedded in the front side of the rear wall during the molding process each set being individual to each line terminal and to the hinge bracket to which the same can be secured, the mass of each insert being relatively small as compared to the mass of the material in which it is embedded, and apertures formed during the molding process in the side walls in register with the line terminals for receiving the line condoctors therethrough.

22. Method of making an enclosure, including a rear wall, for an electrical device which is adapted to move into and out of contact engagement with spaced apart line terminals each fastened to a set of metallic inserts embedded in the front side of the rear wall, it being required that the line terminals be located in predetermined spaced relation whereby the electrical device will accurately register with the line terminals, the method comprising: holding the sets of inserts in predetermined spaced relation in a mold cavity which is of the desired shape of the enclosure, and filling the mold cavity with molten glass thereby embedding the inserts therein.

23. Method of making an enclosure with integral top, side and rear walls for an electrical device mounted on a cover, the electrical device and cover being hinged on support means to permit movement of the electrical device into and out of contact engagement with spaced line terminals and the cover into and out of registry with the front side of the enclosure, the support means and line terminals each being fastened to a set of metallic inserts embedded in the front side of the rear wall, it being required that the support means and the line terminals be located in predetermined spaced relation both horizontally and vertically whereby the electrical device and the cover can be moved into accurate registry respectively with the line terminals and the front side of the enclosure, the method comprising: holding the sets of inserts and the inserts forming each set in predetermined spaced relation in the front side of the rear space of a mold cavity which is of the desired shape of the enclosure, and filling the mold cavity with molten glass thereby embedding the inserts therein.

24. Means for mounting the terminals of an electrical device in insulated spaced relation comprising, in combination, a molded glass support, and a plurality of sets of inserts embedded in the glass, each set being individual to each terminal for supporting the same, each insert com rising a generally rectangular metallic member having a centrally threaded aperture and one or more peripheral grooves into which the glass interfits for securely holding the inserts in place and the mass of each insert being relatively small as com- =25 aaczaoe pared to the mass of the material in which it is embedded.

25. Means for mounting the terminals of an electrical device in insulated spaced relation comprising in combination, a molded glass support, and a plurality of sets of inserts embedded in the glass, each set being individual to each terminal for supporting the same, each insert comprising a generally conical metallic member having a centrally threaded aperture and positioned so that on tightening of a screw in the aperture the conical surface is clamped tightly against the glass adjacent thereto and the mass of each insert being relatively small as compared to the mass of the material in which it is embedded.

' MINOT K. HOLMES.

GEORGE F. MCMAHON. AILAN RAMSEY.

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