US1930332A

US1930332A - Indicating fuse plug

Info

Publication number: US1930332A
Application number: US584413A
Authority: US
Inventors: Alden Milton
Original assignee: Individual
Current assignee: Individual
Priority date: 1932-01-02
Filing date: 1932-01-02
Publication date: 1933-10-10
Anticipated expiration: 1950-10-10

Description

Oct. 10, 1933. M. ALDEN 1,930,332

INDICA'IING FUSE PLUG Filed Jan. 2, 1932 MLTON A DEN, FW

Patented Oct. 10, 1933 UNITED STATES PATENT OFFICE My invention relates to protective devices for electric circuits commonly termed fuse plugs.

The main object of my invention is to provide a simple, inexpensive but effective construction which will indicate unmistakably when it has blown.

Another object is to provide a construction of this character which is safe and reliable.

I particularly sought to provide indicating means which can be tested by feeling even when the plug can not be seen.

In its preferred form the invention includes an insulating body formed of two parts connected by a screw shell and containing a fusible link or strip. An indicating plunger is connected to this fuse strip and normally held entirely within the plug under pressure of a spring. When the fuse blows the plunger is released and one end of it propelled outside the plug where it can be seen and felt.

Fig. 1 is a front view of a plug embodying my invention.

Fig. 2 is a longitudinal sectional view showing the parts in the normal position for use.

Fig. 3 is a cross sectional view on the plane of the line 3-3 of Fig. 2 but omitting the spring.

Fig. 4 is a longitudinal sectional view similar to Fig. 2 but showing the parts in the position which they would occupy when the fuse blows.

Fig. 5 is a detail view showing one method of securing the screw shell in place and venting the chamber.

Fig. 6 is a perspective view showing the fuse strip and indicating device.

The main body consists of the front portion 7 and the rear portion 8. These are formed of suitable insulating material. The front portion, for instance, may be formed of a molded phenolic condensation product and the rear portion may 40 be formed of glass. A screw shell 9 connects these two parts of the body and this may be formed of metal such as brass. Preferably this shell has a flange 10 imbedded in the part 8. The outer end of the shell may be orimped or bent inwardly at 11 into a number of recesses 12 in the wall 13 of the part 7. The front part 7 and the sleeve 13 are preferably molded'in one piece in such a way that they can be made by a two part die.

The recess 12 has an entrance 14 at the front which communicates with the interior of the sleeve 13 so as to provide a passage for the escape of gases due to combustion of the fuse. This passage 14 may be made of any suitable size and the crimped portion 11 of the'shell 9 may be relied upon to close this passage to any desired extent so that the passage may serve as a relief vent and yet prevent the passage of any substantial flame. The center contact disc 15 may have a central tubular portion 16 riveted in the glass disc 8.

. The fuse strip 17 has the end 18 soldered or otherwise suitably connected to the shell 9 and the other end 19 soldered to the center contact disc 15 by a drop' of solder 20. An intermediate portion 21 of the fuse strip may be reduced in size to serve as the point of maximum resistance and consequently the point at which the fuse will blow.

The indicating plunger 22 is mounted in position to slide through opening 23 in the front of the body of the plug, which passage may serve as the means for permitting the escape of pressure from the interior of the plug if desired. An arm 24 has a slot 25 to receive the inner end 26 of the indicating plunger. This arm 24 also has a notched portion 27 adapted to receive the reduced 76 portion 21 of the fuse strip when turned edgewise. When the strip is then turned to the position shown in Fig. 3 it is locked in this notched portion of the arm.

A spring 28 is mounted on the inner end 26 80 of the indicating plunger and presses against one end of the arm 24 was to bias the plunger toward the front of the plug. The fuse strip 17, however, normally resists this pressure of the spring and consequently the tip of the plunger 22 is normally flush with the outer sur-- face of the plug indicatingthat the plug is in its normal operative condition.

When the fuse blows the plunger is released and the spring shoots the plunger outwardly where it protrudes as shown in Fig. 4, thus indicating that the fuse has been blown.

I prefer to provide guard flanges 29 on opposite sides of the plunger to serve as a protection to the springand also as bailies to prevent the direct passage of flame from the interior of the chamber through the passage 23. These flanges also provide means for centering or positioning the plunger and the spring in the assembly of the parts.

In assembling the plug the arm 24 is slipped onto the tail end 26 of the plunger 22. The contracted portion 21 of the fuse strip is then slipped sideways into the notch 27 and turned 90 degrees. The plunger and the fuse strip are then inserted into the front portion of the body of the plug, leaving the end 18 extending outwardly through the slot 30 at one side. The spring is then placed on the inner end of .the plunger and the screw shell and disc 28, which have been previously assembled, are slipped on until the outer end of the sleeve 9 abuts against the flange 31.

The plunger 22 is pressed inwardly until its outer end is flush with the front of the plug, whereupon the end 19 of the fuse strip is soldered in place so as to hold the indicating plunger in the retracted position. The outer edge of the screw shell 9 is then crimped into a connection with one or more of the recesses 12 and the outer end 18 of the fuse strip may be soldered in place if desired.

The flange 31 serves as a hand grip and may be knurled or of any suitable shape or design.

The outer surface of the plug is preferably recessed as at 32 to provide a kind of finger-guide convenient for locating the passage 23 when the fuse is in working condition or locating the indicator when the fuse has blown.

The end 19 of the fuse link may be flat and the center contact disc 15 may be provided with a slot of appropriate shape and size to accommoate it.

The tubular sleeve 13 may be provided with a threaded portion to receive the threaded sleeve 9 as is frequently done in fuse plug construction.

This fuse plug not only provides a positive indication of its condition but the spring tension on the fuse strip aids in rupturing the arc since it pulls the fuse apart as soon as it is softened by heat. The arm also provides an insulating barrier between the parts of the ruptured fuse link.

I claim:

- 1. A fuse plug comprising a tubular insulating body part having interior flanges forming bai'lies substantially parallel to the axis of the plug, a plunger mounted between the said baflies having one end adapted to protrude in an opening in the front of the plug and an arm extending from between the bai'iies, a fuse strip connected to said arm and normally holding said plunger in position and a spring for actuating the plunger when the fuse blows.

v 2. A fuse plug comprising an insulating body part having a tubular sleeve together with in- 1,aso,es2

terior flanges forming baiiles, a'plunger mounted between the said bafiies and having one end adapted to protrude in an opening in the plug, a fuse strip normally holding said plunger in position and a spring holding said fuse strip under tension for actuating the plunger when the fuse blows.

3. A fuse plug comprising an insulating body part having a hand grip portion, together with flanges forming baflies substantially parallel to the axis of the plug, a plunger mounted between the said baffles having one end adapted to pro trude through the front of the plug and an arm extending from between the bailies, a fuse strip connected to said arm and normally holding said plunger in position and a spring engaging said arm between said baflies for actuating the plunger when the fuse blows.

. 4. A fuse plug comprising an insulating body part having a tubular sleeve and a hand grip portion, together with interior flanges forming bailles substantially parallel to the axis of the sleeve, a plunger mounted between the said bafiies and having one end adapted to protrude through the front of the plug, a fuse strip normally holding said plunger in position and a spring engaging said plunger between said baffles for actuating the plunger when the fuse blows.

5. In a construction of the character described, a plug having a body portion, a plunger adapted to protrude from the front thereof, an insulating arm secured to said plunger and hav-- ing an open notched end, and a flat fuse strip having a reduced portioninterlocked with the notched end of said arm, said arm being interposed between the parts of the fuse when it blows.

6. A fuse plug having a body portion, a plunger adapted to protrude therefrom and having an open notched portion of insulating material, a flat fuse strip having a reduced portion interlocked with the notched end of said arm and a spring holding the inner end of the strip under tension and tending to protrude the end of the plunger when the fuse blows.

MILTON ALDEN.