US2289944A

US2289944A - Plug fuse

Info

Publication number: US2289944A
Application number: US368333A
Authority: US
Inventors: Hoorn Fred G Von
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1940-12-03
Filing date: 1940-12-03
Publication date: 1942-07-14
Anticipated expiration: 1959-07-14

Description

July 14, 1942. F. G, VON HOORN 2,289,944

PLUG FUS E Filed Dec. 3, 1940 Irwvevtof: Fred @1A/Oh Hoorn,

b )VW KfW/ZM y H is Atto? may.

Patented July 14, 1942 UNITED STATES PATENT OFFICE General Electric Com New York pany, a corporation of Application December 3, 1940, Serial No. 368,333

(Cl. 20o- 130) 3 Claims.

My invention relates to electric fuses, and more particularly to plug fuses of the type which are adapted for use in residence wiring systems.

An object of my invention is to provide a new and improved fuse of the type described, in which the number and arrangement of the parts have been greatly reduced and simplified resulting in a fuse which may be manufactured at low cost.

Another object of my invention is the provision of an improved indicating arrangement within the fuse structure to designate the rating of the fuse.

In the accompanying drawing Fig. l is a View of a plug fuse constructed in accordance with my invention; Fig. 2 is a plan view of the top of the fuse; Fig. 3 is a cross-sectional view through the fuse body; and Fig. 4 is a perspective View of a portion of the fuse structure showing the indicating arrangement.

Referring to the drawing, my fuse is similar to a standard plug fuse capable of being inserted in any standard fuse receptacle such as employed in residence wiring systems. The fuse includes a body of insulating material IU, a fusible element or link I I, a screw-threaded shell I2 and a center contact I3. The latter two elements form a Contact means for making an electrical connection between the fuse and the contacts of the fuse receptacle.

The body I of the fuse is formed of insulating material and, in the instant case, is formed of a transparent insulating material. Examples of such a material are glass, or a molded plastic material. I prefer to make the body of glass. At one end the fuse body is provided with knurled sections I4 for gripping the fuse to thread it into a fuse receptacle. At the other end the fuse body is formed with a recess I5 which extends inwardly to a point adjacent the top of the body. The bottom wall I6 of the recess forms, in eect, a window through which the interior of the fuse body may be Viewed. The window is formed with an arcuate surface I'I on the top of the fuse body which acts as a lens to magnify the size of the fuse elements positioned within the body.

At its open end the recess I5 is closed by means including a disk I8 resting on a plate I9. These elements are held in position by a screw-threaded shell 20. Both the disk I8 and the plate I9 are formed of insulating material, for example, a relatively inexpensive insulating material such as sheet liber. The plate I9 carries the aforementioned center contact I3. In mounting the contact on the plate the contact is rst inserted through an opening 2l and the end of the contact is then peened over, as shown at 22, to secure it rigidly in position on the plate. The threaded screw shell 20 is secured to the body I0 by frictional engagement with serrations 23 formed on the outside perimeter of the body III conforming substantially to the configuration of the threads on the screw shell. At one end the threaded screw shell is provided with an inwardly turned ange 24 for engaging the plate I9 so that as the disk I8 and the plate I9 are positioned to close the recess I5 the threaded screw shell holds these elements in position when mounted on the fuse body. The center contact I3 extends through an opening 25 formed by the rim o f ange 24 so that this contact is eiectively insulated b y the plate I9 from the iiange of the screw shell.

As shown more particularly by Fig. 4, the disk I8 is provided at diametrically opposite sides with slots 26 for receiving the fusible element in a manner to be described later. The center of the disk is punched upwardly to form an offset portion 2'I which carries indicia 28 Corresponding to the rating of the fuse. As shown by Fig. 3, when in assembled position the offset portion 21 forms a space or chamber 28 for receiving the peened-over end 22 of the center contact I3 so that the disk I8 will lie flat against the plate I9 when held in assembled position by the screw shell.

In assembled position one end of the fusible element or link II extends through one of the recesses 26 in the disk I8 and the end is then bent backwardly into a recess 29 formed in the outer wall of the insulating body and secured in any suitable manner, such as by solder 30, to the upper edge of the screw-threaded member I2. Within the recess I5 the fuse link extends upwardly in a loop to a point adjacent the window I6 and the looped portion of the link is provided with indicia 3l corresponding to the rating of the fuse at a point adjacent the window I6. The indicia are readily visible through the window and are enlarged by the lens effect resulting from the use of the curved surface I'I. The opposite end of the fuse link extends through the other of the recesses 26 in the disk I8 and then passes into the chamber 28 where it i s secured to the center contact I3 in any suitable manner such as by solder 32.

The indicia 28 are readily visible through the Window I6 at one end of the fuse body, even though they are positioned at the opposite end of the body on the disk I8 which forms a portion of the closure for the recess I5. This means that it is unnecessary to position additional indicating means, such as a piece of indicia bearing paper within the recess I to indicate the rating of the fuse. Since the entire insulating body of the fuse is formed of transparent material, a very large light gathering area is attained so that the interior of the plug fuse is clearly visible for easy reading of the indicia 28. The disk lil and the plate I9 form an exceptionally strong closure for the recess I5 and are well able to withstand the pressures incident to volatilization of the fuse link upon short circuit. Since the disk and plate are formed of relatively llow cost material, such as sheet fiber, it will be apparent that the overall cost of the fuse is considerably reduced without sacrificing strength or interrupting capacity of the fuse. The offset portion 21 of the disk I8 forms in effect an arch which greatly strengthens the disk and prevents it from being ruptured or blown out upon short circuit. Venting of the interior of the fuse body will be effected through the -recesses 126 'in the disk I3 'and the spaces formed by the clearances between the screw shell and the threads 23 of the fuse body. Some of the -gases will also pass through the passage 29. Upon short circuit, the resulting arc cannot travel along the fuse link to the center contact I3 inasmuch as it will be snu'ifed out vat the point where the link passes through the 4left-hand groove -25 in the disk I8 before it can enter 'the chamber 28.

While I prefer to make vthe insulating 'body of the lfuse of Ytransparent material in order to render the rating indicia of the disk I3 clearly visible, it should be manifest that in some cases the body of the 'fuse may be made of opaque .insulating material with a separate transparent window-at the top Vfor viewing of the indicia.

What I claim as new and desire -to secure by Letters Patentof Athe UnitedStates is:

1. vA plug fuse comprising a'body of insulating material having a recess extendingfrom one end thereof, a fusible element disposedlin'said'recess, a disk of insulating material resting on theend Wall of said body closing said recess, said disk having a central arched portion extending slightly into said recess, a plate of insulating material adjacent said insulating disk and having a center contact mounted therein and a threaded screw shell mounted on said base and having a flange engaging said insulating plate to secure said disk and plate in position on said base, one end of said fusible element being electrically connected to said screw shell and the other end being connected to said center contact.

2. Aplug fuse comprising a body of insulating material having a recess extending from one end thereof, a fusible element disposed in said recess, a disk of Vinsulating material having an offset center portion disposed at the said one end of the body to close said recess, a plate of insulating material adjacent said insulating disk and having a center contact mounted therein, and a threaded screw shell mounted on said base and having a flange engaging said insulating plate fto secure said plate and disk in position on said base, one end of said fusible element being electrically connected to said screw shell and the other end being connected to the center contact in the space between the disk and plate formed by the offset portion of said disk.

3. A plug fuse comprising a body of insulating material having a recess extending from one end thereof, a fusible element disposed in said recess, a disk of insulating material having an offset portion, said disk vbeing disposed at the said one end of the body closing said recess, said disk being provided with opposite slots, a plate of insulating material adjacent said insulating disk and having a center Contact -mounted thereon, and a threaded screw shell mounted on said base and having a `flange engaging said insulating plate to secure said plate and disk in position on said base, one end of said fusible element extending through one of the slots in said insulating disk and being electrically connected to `said screw shell, the other end of said fusible element extending through the other .of said .slots and being connected to said .center contact in the space between said plateand disk formed by the offset portion of said disk.

FRED' G. voN HOORN.