US2457477A - Fuse attachment for electric plugs - Google Patents

Description

Dec. 28, 1948. A.- LA RIZZA FUSE ATTACHMENT FOR ELECTRIC PLUGS 2 Sheets-$heet 1 Filed Aug. 9, 1947 FIG.4

F 5 INVENI'OR. KWTHONY LoRIZZA Dec. 28, 1948. I LA RIZZA 2,457,477

FUSE ATTACHMENT FOR ELECTRIC PLUGS Filed 'Aug. 9, 1947, 2 Sheets- Sheet 2 an SH INVENTOR. 1 1 ANTHONY LoRlZZA BY FIG. 9 dsnm ffil f ATTORNEYS Patented Dec. 28, 1948 (UNITEDSTATES PATENT OFFICE Anthony La Rizza, Revere, Mass.

Application August 9, 1947, Serial No. 767,671

provide a fuse attachment which can be mounted on one of the prongs of an ordinary electric plug thereby converting it intov a fused plug.

.Fused electric plugs are now commonly made with the fuse element built into the plug. With this construction if the fuse blows or melts, the plug becomes useless and must be replaced by another. plug.

With= my invention the fuse element can be applied to a prong of any ordinary plug, and if in use the'fuse-gives away, the fuse element may be removed from the prong of the plug and a fresh fuse element applied thereto. In other words, with inyinvention the blowing of the fuse does not render the plug itself inoperative, because in order to repair the damage, it is only necessary to remove the blown fuse element from the prong of the plug and replace it by a fresh fuse element.

"Moreover, my invention has the further advantagethat any ordinary plug can be converted into a fusedplug by merely mounting the fuse attachment on the prong of the plug, and if at any time the plug is tobe used under circumstances in which afu'se is not required, such fuse attachment can be demounted from the prong of the plug.

I In'order to give an understanding of the invention, 'I have illustrated in the drawings some selected embodiments thereof which will now be described after which the novel features will be pointed out in the appended claims.

In the drawings:

Fig. 1 is an enlarged view of an electric plug Fig. 7 is-a view similar to Fig. l but showing a Q differentembodiment of the invention. 7

Fig. 8 is a View of one of the retaining strips. Fig. 9 is a section on the line 99, Fig. .7. .Fig. 10 isa section on the line l0.l0, Fig. 7.

1115 an enlarged fragmentary sectional.

6 Claims. (01. 200f115-5) View showing a portion of the insulating strip and thefuse element.

Fig. 12 is a fragmentary sectional view showing a still different embodiment of the invention.

R-eferring first to the embodiment of the invention shown in Figs. 1 to 6, I indicates an ordinary electric plug provided with the prongs 2 and 3 and connected to the cord 4 leading to the appliance to which the plug is connected. These parts may be such as are usually found in electric plugs and constitute no part of my present invention, which, as stated above, is a fuse attachment adapted to be removably mounted on one of the prongs of the plug.

The fuse attachment shown in Figs. 1 to 6 comprises a retaining member 5 of insulating material which is provided with two openings 6 and 1 to receive the prongs 2 and 3 of the plug I. The attachment also comprises an insulating strip 8 made of paper or some other suitable insulating material which is provided at one end with a head portion 9. The insulating strip is assembled with the retaining member 5 by placing the head portion-9 beneath one end ID of the retaining member 5 and threading the strip 8 through the opening 6 'to form a loop ll adapted to embrace one of the prongs of the plug I, said strip 8 extending underneath the retaining member 5 and then being threaded through the two slots l2 with which the retaining member is provided as shown at l3 in Fig. 1.

The fuse attachment also includes a fuse element in the form of a strip M of conducting material which is provided at one end with a head portion l5. This fuse element l4 embraces the loop portion of the insulating strip 8 andthe head end of the fuse element extends through-the opening 6. The head l5 thereof underlies the retaining member 5 and is confined between the latter and the insulating strip 8.

The other end of the fuse element I4 also extends through the opening 6 of the retaining member, and then extends around the head 9 ofthe insulating strip as shown at I6, the end 3 can be easily applied to any electric plug l by placing the retaining member over the prongs of the plug and introducing one of the prongs into the loop ll of the insulating member 8.

When the device is thus applied to the plug, the portion of the fuse element l4 which embraces the prong 2 is insulated therefrom by the insulating strip 8, but the end portion I! of the fuse element which is located inside of the loop of insulating material will contact with the prong 2.

When the plug thus equipped with a fuse attachment is plugged into a socket connection, the portion of the fuse element which embraces the prong 2 will contact with the complemental contact elements of the socket connection and a circuit will be established through the fuse element inasmuch as the end thereof is contacting with the prong 2.

If, during use, abnormal current conditions arise which might injure the appliance to which the plug is attached, such abnormal current conditions will melt the fuse at the place IQ of reduced cross sectional area thereby breaking the circuit and preventing injury to the appliance.

The blowing of the fuse does not in any way effect the structure of the plug itself, for the plug with the blown fuse may be removed from the socket element and the fuse attachment removed from the plug and replaced by an attachment having a fresh fuse, thereby again putting the plug into condition for use.

In the construction shown in Figs. 1 to 6 the fusing point IQ of the fuse element is more or less exposed, and there is a possibility that when the fuse blows, the accompanying flash may blow out of the socket to which the plug I is connected.

In the embodiment shown in Figs. 9 to 12, I have shown a construction in which the fusing point of the fuse element is enclosed in a sealed casing, thus eliminating any possible danger from a flash occasioned by the blowing of the fuse.

In the form of the invention shown in Figs. 9 to 11, indicates the plug having the usual prongs 2 and 3 and 4 indicates the cord connecting the plug to the appliance.

The fuse attachment illustrated in Fig, 9 is provided with two retaining members 2|, 22 of insulating material which are spaced slightly from each other and are connected at their ends in any suitable way, as by means of cement 23. Each strip is provided with two openings 24, 25 to receive the prongs 2 and 3 of the plug, and each strip is also provided with an additional somewhat larger opening 25, the purpose of which will be presently described.

The fuse attachment shown in Fig. 9 also involves a strip 28 of insulating material similar to the strip 8 shown in Figs. 1 to 6. One end 29' of this strip is located between the two retaining members 2|, 22 and said strip of insulating material is bent into a loop 30 which extends through the alined openings 25 of the retaining members 2|, 22 and is of suflicient proportions to receive and embrace the prong 2 of the plug I. Thestrip 28 also has a portion 3| extending between the tworetaining members 2 22, the end 32 of which. is bent downwardly through the alined openings 26 of the retaining members as clearly seen in Fig. 9.

The fuse element is indicated at 34 and it is provided with a loop portion 35 that embracesithe loop 30 of the insulating strip, one end 36 of the fuse element is confined between the retaining members 22, 23 and overlies the end portion 29, of the retaining strip. Another portion 310i the fuse element is also confined between the retaining members 2|, 22 and overlies the portion 3| of the insulating strip. The fuse element is also provided with a loop portion 38 which embraces the down-turned portion 32 of the insulating strip and said fuse element further has a portion 39 located between the two retaining members 2 I, 22 and underlying the portion 3| of the insulating strip,.the end portion 40 of the fuse element being located between one leg of the loop 30 of the insulating strip and the prong 2 and having contact with said prong.

The fusing portion or the portion of the insulating strip of reduced cross sectional area where the fuse element will melt is shown at 42 and is located in the loop portion 38 of the insulating strip which embraces the down-turned leg 32 of insulating material.

The loop portion 38 of the fuse element which contains the fusing point 42 is enclosed in a sealed casing 43. Thiscasing may comprise a cylindrical shell of insulating material; the lower end of which isclosed by a cap member 44. In the combstruction: shown in Fig; 9 the cap 44 has a still: 45 anchored thereto which extends. through the shell' 43 and which has at its upper end a head 46 that engages the upper side of the top retaining member 2|. and which also closes and seals, the opening 26 in the retaining member.

The shell 43 is held tightl clamped against; the underside of the lower retaining member and by means of this construction, the loop portion 38 of the fuse element is located within a. sealed container.

The device shown in Figs. 7 to 11 operates in the same way as that shown in Figs. 1 to 6. The fuse attachment comprising the two retaining mem'aers 2| 22, the insulating strip 30, the fuse element 34, and the sealed casing 43 constitute i a unitary structure which can be readily applied A plug having. this to the plug I, the. fuse element will melt. at the point 42 thereby breaking the circuit to the appliance. With the device shown in Figs. 7 toll. any flash Which. might occur by the blowing of the fuse is contained entirely within the sealed. casing 43.

The fact that the fuse attachment is separate from the plug but can be readily mounted thereon makes it possible to convert any ordinary electric plug into a fused plug by simply mounting my improved fuse attachment on one of the prongs thereof The fuse attachment has the further advantage that it is relatively simple in construction and can be inexpensively manufactured.

Instead of using cement for uniting the retaining members 2|, 22, I may simply staple said members together as shown in Fig. 12 wherethey are connected by a staple element 50, the legs 5| of which extend through both retaining members and are bent or clinched over as shown at 52.

I claim:

1. The combination with an electric plug having prongs for insertion into a socket terof' a fuse attachment. therefore comprising a strip of insulating material adapted to embrace the sides and end of one of said prongs, and a fuse element embracing the insulating strip and provided with a fusible portion, one end of the fuse element being located between said insulating strip and said prong and in contact with the latter, said insulating strip insulating the remaining portion of said fuse element from said prong.

2. The combination with an electric plug having prongs for insertion into a socket element, of a fuse attachment for said plug comprising a strip of insulating material presenting a U-shaped formation to fit over one of said prongs, a fuse element embracing said U-shaped strip of insulating material, an end portion of the fuse element being bent around the end of the strip of insulating material and located on the inside of the U-shaped formation and in contact with said prong, the main portion of said fuse element being insulated from the prong.

3. The combination with an electric plug having a pair of prongs for insertion into a socket terminal element, of a fuse attachment therefor comprising a retainer member of insulating material having openings to receive said prongs, a strip of insulating material anchored at one end to said retainer and adapted to embrace one of said prongs, a fuse element in the form of a strip embracing the strip of insulating material and thus situated to contact the terminals of a socket element when the plug is plugged thereinto, one end of the fuse element being located between the insulating strip and the prong which it embraces and in contact with said plug, said 1-? having prongs for insertion into a socket terminal element, of a fuse attachment for said plug comprising a strip of insulating material adapted to embrace the sides and end of one of said prongs, a fuse element having a portion embracing the insulating strip and thus situated to contact the terminals of a socket element when the plug is plugged thereinto, one end of the fuse element being located between the insulating strip and the prong of the plug which it embraces, said fuse element having a fusible portion between said end thereof and the part which contacts with the socket element, and a sealed enclosure enclosing the fusible portion of the fuse element.

5. The combination with an electric plug having prongs for insertion into a socket terminal element, of a fuse attachment therefor comprising a two-part retainer member of insulating material having openings to receive said prongs, a strip of insulating material anchored at one end of said retainer and having a portion received between the two parts of the retainer and also having a loop portion which projects through an opening in one part of the retainer and embraces one of the said prongs and further having a laterally extended end portion, a fuse element in the form of a strip having a loop portion which embraces the loop portion of the insulating material and is thus situated to contact the terminals of a socket element when the plug is plugged thereinto, said fuse element having another portion embracing the laterally extending end portion of the insulating strip and provided with a fusible portion, the remaining portion of said fuse element being situated partly between the two parts of the retainer member and partly between one leg of said loop of insulating material and the corresponding prong of the plug, with which prong said fuse element has contact and a sealed casing enclosing the fusible portion of the fuse element.

6. The combination with an electric plug having prongs for insertion into a socket terminal element, of a fuse attachment therefor comprising a strip of insulating material having a portion which embraces one of said prongs, and a fuse element embracing said insulating strip and having one end interposed between the insulating strip and the prong and in contact with the latter, said insulating strip insulating the remaining portion of the fusible element from said prong.

ANTHONY LA RIZZA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 332,286 Pfannkuche Dec. 15, 1885 1,664,408 Frakes Apr. 3, 1928 FOREIGN PATENTS Number Country Date 345,199 Great Britain Mar. 12, 1931 Certificate of Correction Patent No. 2,457,477. December 28, 1948.

ANTHONY LA RIZZA It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

t Column 4, line 75, claim 1, for therefore reed therefor; column 5, line 35, claim 3, for the Word plug reed prong,- column 6, line 7, claim 5, for end of read and to;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 3rd day of May, A. D. 1949.

THOMAS F. MURPHY,

Assistant Gammz'ssioner of Patents.

Certificate of Correction Patent No. 2,457,477. December 28, 1948.

ANTHONY LA RIZZA It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 7 5, claim 1, for therefore read therefor; column 5, line 35, claim 3, for the Word plug read prong; column 6, line 7, claim 5, for end of read end to;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 3rd day of May, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents.

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