US2104850A

US2104850A - Glass top plug fuse

Info

Publication number: US2104850A
Application number: US74633A
Authority: US
Inventors: Sears B Condit
Original assignee: Chase Shawmut Co
Current assignee: Chase Shawmut Co
Priority date: 1936-04-16
Filing date: 1936-04-16
Publication date: 1938-01-11
Anticipated expiration: 1955-01-11

Description

. Jan. 1933. s. B. CONDIT 2,104,850

GLASS TOP PLUG FUSE Filed April 16, 1936 waw air/r Patented Jan. 11, 1938 UNITED STATES PATENT OFFICE GLASS TOP PLUG FUSE Scars B. Condit, Boston, Mass., assignor to The Chase Shawmut Company,

Newburyport,

12 Claims.

This invention relates to electric fuses of the socalled plug type.

A plug fuse comprises a chambered body of insulating material having an exteriorly screwthreaded metal terminal shell thereon, a center contact member on one end of the fuse between which and the shell the fuse link is connected, a window in the end of the plug body opposite the center contact through which the fuse link can be inspected, and a rim at the top or window end of the body which is adapted to be grasped between the fingers to screw the fuse into and out of a receptacle.

This invention relates particularly to a plug fuse wherein the insulating body, the window and the rim are integral and are composed of glass or equivalent material.

A glass top plug fuse is quite common in the art and large numbers are sold yearly to householders. The public utilities, however, and other concerns using and installing fuse plugs that are adapted to be removed and replaced by individuals not in direct control of the concerns are hesitant to use the common glass top fuse because the glass rim is liable to be chipped as by the accidental dropping of the fuse on a hard surface, so that the fuse presents exposed sharp edges which can cut the fingers of the person removing and replacing this type of fuse in its receptacle.

It is an object of the present invention to pro vide a glass top fuse of such nature as to prevent the exposure of chipped or sharp edges to the direct contact of the fingers of a person rotating the fuse intoor out of its socket or receptacle.

It isa further object of the invention to enclose the finger engageable rim of a glass top fuse with a band of tough material capable of withstanding without rupture such impact as might chip or splinter the rim enclosed therein to retain the chips or splinters in place and to cover any sharp edges that might be formed, whereby to present a safe surface to be engaged by the fingers.

For some purposes the band is transparent, or substantially so but, when desired, can have a distinctive color, including black and white, to give a readily visual indication of the capacity of the fuse, one color denoting, say, a certain range of capacities and another color a different range of capacities. A fuse having such a colored band constitutes a further object of the invention.

A further object is generally to improve the construction of electric fuses.

Fig. 1 is a side elevation of a glass top plug fuse embodying the present invention.

Fig. 2 is a plan view of the fuse of Fig. 1.

Fig. 3 is a longitudinal section taken along line 3-3 of Fig. 1.

Fig. 4 is a plan view of a rim enclosing band prior to its application on the rim.

As herein illustrated the fuse comprises a plug body It, having an eXteriorly screw-threaded cylindrical section 52, a peripherally outstanding flange or rim M at the upper end thereof, and a transparent window 15, the parts l2, l4, and It; being integral and formed of a transparentglass or equivalent material. The plug body has an internal chamber l8 therein which is open at the lower end opposite the window I 6. An insulating bushing has an outstanding flange 22 that is seated upon the end of the plug body and is held in place by an exteriorly screw-threaded metal terminal shell 24 that 'is screw-threaded on the screw threads of the plug body. The bushing 25 has a center contact member 26 to which one end of a fusible link 28 is electrically connected. The other end of the link is connected to the bottom flange 39 of the screw shell. The fusible link has a weakened portion 32 that is adapted to fuse upon overload. Said weakened or readily fusible portion is disposed under the win- 25 dew IS in position to be viewed through the window. The particular fuse herein illustrated is described and claimed in a copending application of Morris B. Wood, Serial No. 18,275 filed April 26, 1935.

In accordance with this invention the rim I4 is protected so that it is not so liable to chip or splinter when dropped upon a hard surface and the chips and splinters are retained in close proximity to the body and the sharp edges resulting from the fractures are enclosed and shielded from contact with the fingers of a person engaging the rim to screw the fuse into or out of its socket receptacle.

The rim protecting means comprises a band or envelope 34 which closely encircles the rim l4 and has top and

bottom parts

36 and 38, respectively, which overlie the top and bottom edges of the rim and the plug faces there-adjoining for a suflicient distance to completely enclose the region that is liable to present sharp edges when chipped. The band can be composed of a material that is transparent or nearly so, so that light can pass through the band and through the plug body thereunder and into the link containing chamber l8 to illuminate the link so that it can be readily viewed through the window l6. However, where the construction of the fuse is such that the link is sufiiciently well illuminated otherwise, as is herein the case, the band need not have good light transmitting property and can have a color, including black and white, that readily identifies the capacity of the fuse.

The band is in tight non-slipping engagement with the rim and preferably is shrunk on the rim. The rim is provided with teeth 40 to improve the finger grip on the rim; and the band when shrunk in place conforms approximately to the configuration of the teeth so that the banded rim provides good engagement for the fingers and the teeth hold the band in positive non-rotating engagement with the rim.

The band is composed of a material sufficiently strong to withstand without injury blows that cause the chipping of the glass rim and the band is sufiiciently elastic for this purpose. The band is not materially affected by the temperatures to which the fuse is ordinarily subjected and also is not deleteriously affected by normal moisture conditions. The band preferably is somewhat hydroscopic so as to enhance its strength under normal conditions of use, although the band when dry has good strength when in place on the rim.

The band can be formed of any suitable material but preferably is composed of a cellulose derivative as cellulose Xanthate or viscose, which is capable of shrinking on drying, so as snugly to conform to the periphery of the rim. The band can be applied in many ways. The band forming material can be in a solution. The rim of the fuse may be dipped in the solution and the fuse rotated to apply the solution to the periphery of the rim. The coated fuse can then be dried to evaporate the liquid and leave a deposit of the material in a band on the rim. It is more convenient, however, to use a preformed band which can be formed in any suitable manner as by forming a long tube of the material by dipping a mandrel sufficiently repeatedly into a solution of the material, with dryings between each dipping operation, and afterwards stripping the cylinder off the mandrel and cutting the cylinder into bands of suitable width. The bands can be stored, until use, in a preservative liquid, as water, to keep them limp and free from shrinkage.

Fig. 4 illustrates such a band prior to its application on the rim of the fuse. The internal diameter of the band preferably is not greatly larger than the diameter of the rim so that the band will retain itself on the rim. When the band dries it contracts or shrinks. The shrinkage is relatively great in all directions and for some bands is approximately 30%. A cellulose xanthate band can have a shrinkage of 30% or more. This relatively great shrinkage causes the band to forcibly grip the rim and to conform to the surface irregularities such as the teeth 63 thereof, and also to cause the edges of the band to draw over and upon the substantially right angularly related faces of the plug body at the top and bottom edges of the rim.

The band material can be made substantially transparent or nearly so to pass light therethrough into the interior of the plug body. The band also can be substantially opaque. The lower edge 4'2 of the band is spaced materially above the top edge of the screw-threaded shell 24 so that there is a clear transparent space 44 around the periphery of the plug body through which light can pass into the interior. Fuses of a certain capacity, or within a certain ran e of capacities, can have bands of one distinctive color, as blue or black, while fuses of a certain other capacity or within a certain other range of capacities, can have bands of a different color as red or white.

I claim:

1. A glass top plug fuse having a closed top plug body provided with a transparent window at one end and a rim that is integral with the body and window, said plug body and rim being composed of glass, and a protective band enclosing and gripping said rim and overlying and enclosing a possible sharp edge thereof and overlying face portions of said body on opposite sides of the rim.

2. A glass top electric fuse comprising a glass body having as integral parts thereof a transparent Window and outstanding rim, and a chip-retaining edge-shielding band enveloping and gripping said rim.

3. A glass top electric fuse having a glass body provided with a transparent window and a rim that are integral with the body, said rim having a series of projections by which the rim is adapted to be firmly engaged by the fingers and the fuse rotated, and a protective band snugly encircling and enclosing said rim and conformed to the surface configuration and to said projections thereof.

i. A glass fuse comprising a cylindrical plug body having an integral chamber open at one end, a window closing said other end, an outstanding rim at the window end of said body, an insulating bushing on the open end of said body, a screw-threaded metal terminal shell on said body and overlying a part of said bushing, a

center contact member carried by said bushing,

a fusible member in said chamber connected between said center contact member and said terminal shell, said plug body and said rim and window being integral and composed of glass, and a protective band snugly enveloping and grip ping said rim and overlying a possible sharp edge thereof and overlying face portions of said body on opposite sides of said rim.

5. A glass top plug fuse comprising a one-piece glass body having a window therein and an outstanding rim integral with said body and window, and a chip-enclosing band of electrically insulating material encircling and enclosing said rim and faces of said body on opposite sides of said rim.

6. A glass top plug fuse comprising a one-piece glass body having a window therein and an outstanding rim integral with said body and window, and a rim-enclosing envelope of electrically insulating material encircling and enclosing said rim and shrunk thereon.

'7. A glass top plug fuse comprising a one-piece glass body having a window therein and an outstanding rim integral with said body and window, and a band of electrically insulating material encircling and enclosing said rim, said band being composed of a transparent material.

8. An electric plug fuse comprising a plug body having a screw-threaded terminal shell thereon, a center contact member and a fuse link connected between said terminal shell and center contact member, said plug body having a part projecting beyond an end of said terminal shell and said part having a window and an outstanding rim, said plug body, said rim and said window being formed of transparent material of the nature of glass, and a protective electrically insulating envelope enclosing and gripping said rim, an edge of said envelope being spaced from the confronting edge of said terminal shell to provide an uncovered region of said transparent body therebetween to admit light into the interior thereof.

. 9. A glass top plug fuse comprising a glass plug body having integral therewith a transparent window and an outstanding rim, and a rim protecting band of tough electrically insulating relatively transparent material encircling and snugly engaging said rim and overlying face portions of said body on opposite sides of said rim.

10. A plug fuse comprising a plug body having a glass rim, and a shrunk-on rim protective cap of viscose encircling and enclosing said rim.

11. A plug fuse comprising a glass body having integral therewith a rim, and a colored tough envelope enclosing and gripping said rim.

12. A plug fuse comprising a transparent glass body having a window and outstanding rim at the top and an internal chamber open at the bottom, an insulating member on the open end of said body, a center contact member carried by said member, a screw-threaded shell on the exterior of said body, and a colored tough envelope enclosing and gripping said rim, said envelope being terminated short of said shell and there being a transparent section of said glass body exposed between said envelope and shell.

SEARS B. CONDIT.