US3177318A

US3177318A - Protectors for electric circuits

Info

Publication number: US3177318A
Application number: US201A
Authority: US
Inventors: John C Lebens
Original assignee: McGraw Edison Co
Current assignee: McGraw Edison Co
Priority date: 1960-01-04
Filing date: 1960-01-04
Publication date: 1965-04-06
Anticipated expiration: 1982-04-06

Description

April 6, 1965 J. c. LEBENS PROTECTORS FOR ELECTRIC CIRCUITS 2 Sheets-Sheet l Filed Jan. 4, 1960 flVVE/VTOE JOHN C. LEBE/VS April 1965 J. c. LEBENS 3,177,318

PROTECTORS FOR ELECTRIC CIRCUITS Filed Jan. 4, 1960 2 Sheets-Sheet 2 v//v z s/v roe JOHN C- LEBE/VJ United States Patent 0 3,177,318 PROTECTORS FOR ELECTRIC CTRCUITS John C. Lehens, University City, Mo, assignor to Mc- Graw-Edison Company, Elgin, Iil.,- a corporation of Delaware Filed Jan. 4, 1969, Ser. No. 201 6 Claims. (Cl. 200-429) This invention relates to improvements in protectors for electric circuits. More particularly, this invention relates to improvements in electric fuses and in holders for those fuses.

It is therefore an object of the present invention to provide an improved electric fuse and a holder for that fuse.

Electric fuses are made in different sizes; and one determinant of fuse size is the voltage in the circuit with which the fuse is to be used. Thus, small fuses are customarily used with circuits wherein the voltages do not exceed one hundred and twenty-five volts, larger fuses are customarily used with circuits wherein the voltages exceed one hundred and twenty-five volts but do not exceed two hundred and fifty volts, and still larger fuses are customarily used with circuits wherein the voltages exceed two hundred and fifty volts but do not exceed six hundred volts. In some instances, the size and cost of the still larger fuses, used with circuits wherein voltages exceed two hundred and fifty volts but do not exceed six hundred volts, constitute serious drawbacks to the use of those fuses. Accordingly, it would be desirable to have an electric fuse that was no larger than electric fuses customarily used with circuits wherein the voltages do not exceed two hundred and fifty volts but that could be used with circuits wherein the voltages exceed two hundred and fifty volts. The present invention provides such a fuse; and that fuse can be used with circuits wherein the voltages exceed two hundred and fifty volts but do not exceed three hundred volts. It is therefore an object of the present invention to provide an electric fuse that is no larger than fuses which are used with circuits wherein the voltages do not exceed two hundred and fifty volts but that can be used with circuits wherein the voltages exceed two hundred and fifty volts but do not exceed three hundred volts.

The fact that the electric fuse provided by the present invention is to be used with circuits wherein the voltages exceed two hundred and fifty volts makes it imperative that the installers of that fuse be kept from touching any electrically live parts of that fuse. The present invention keeps the installers of the electric fuse, provided by the present invention, from touching electrically live parts of that fuse by using a hollow knob of insulation to embed and insulate the end face and the greatest portion of the sides of the outermost terminal of that fuse. That hollow knob projects both axially and radially outwardly beyond the end face and the sides of that outermost terminal of that fuse and thereby keeps the installers hands from accidentally coming into engagement with that outermost terminal. In this way, the present invention keeps the installers from accidentally touching the outermost terminal of the electric fuse provided by the present invention. It is therefore an object of the present invention to provide a hollow knob of insulation that embeds, and that projects both axially and radially outwardly beyond, the end face and sides of the outermost terminal of the electric fuse provided by the present invention.

The fuse holder, provided for the electric fuse of the present invention, has a fixed electrical contact which coacts with ears on the outermost terminal of that fuse to provide a bayonet-joint lock. That electrical contact can be electrically live; but that electrical contact is spaced an appreciable distance inwardly of the outer face of that fuse holder. Consequently, an installer is not likely to have his thumb or any of his fingers come into engagement with that electrical contact. It is therefore an object of the present invention to provide a fuse holder with a fixed contact that is spaced an appreciable distance in wardly of the outer face of that fuse holder.

The fixed electrical contact of the fuse holder provided by the present invention is located at the inner end of a recess, and that recess has a diameter which is just slightly larger than the diameter of the hollow knob that embeds and insulates the end face and the greatest portion of the sides of the outermost terminal of the electric fuse provided by the present invention. As a result, there is only a very narrow annular space between the periphery of that knob and the portion of the fuse holder which defines that recess; and that space will resist any efforts to pass a metallic tool or wire through it. This means that it is not likely that a metallic tool or wire can be placed in engagement with the fixed contact of the fuse holder Whenever the fuse is set in position within that fuse holder. It is therefore an object of the present invention to provide a fuse holder with a fixed contact that is set within a recess which has a diameter that is just slightly larger than the diameter of the hollow knob which embeds and insulates the end face and the greatest portion of the sides of the outermost terminal of the fuse provided by the present invention.

The fixed contact of the fuse holder provided by the present invention has ears that can be bent around a partition in that fuse holder. To effectively accomplish the bending of those ears around that partition, ready access to the outer face of that fixed contact and to those ears must be provided. The present invention provides such access by providing the fuse holder with a large diameter portion which projects forwardly and rearwardly from the partition around which the ears of the fixed contact are to be bent. The forwardly projecting part of the large diameter portion of the fuse holder defines the recess in which the fixed contact is set, and thus provides ready access to the outer face of that fixed contact. The rear- Wardly projecting part of the large diameter portion of the fuse holder defines recesses that are in register with the ears on the fixed contact and thus provides ready access to those cars. As a result, a tool can pass through the forwardly projecting part of the large diameter portion of the fuse holder to holdv the fixed contact, while other tools can pass through the rearwardly projecting part of the large diameter portion of the fuse holder to engage and bend the ears of that fixed contact.

The hollow knob of insulation that projects both axially and radially outwardly beyond the outermost terminal of the electric fuse provided by the present invention will keep the installer from seeing the ears on that outermost terminal as he rotates that knob. Yet, that installer must aline those ears with complementary notches in the fixed contact in the fuse holder before he can remove the fuse from that fuse holder. Because that hollow knob of insulation overlie-s and conceals the ears on the outermost terminal of the fuse, it would be desirable to provide some means by which the installer could know when the ears on that terminal were close to the complementary notches in the fixed contact. The present invention provides such a means, and that means consists of stops which limit rotation of the fuse relative to the fuse holder. Those stops are so disposed that when they halt rotation of the fuse, the ears on the outermost terminal of the fuse are close to the complementary notches in the fixed contact. As a result, when the installer rotates the fuse as far as it will go, he knows that the ears on the outermost terminal of that fuse are immediately adjacent the complementary notches in the fixed contact; and he can then turn the fuse back a few degrees and withdraw it from the fuse holder.

Other and further objects and advantages of the present invention should become apparent from an examination of the drawings and accompanying description.

In the drawings and accompanying description a preferred embodiment of the present invention is shown and described but it is to be understood that the drawings and accompanying description are for the purpose of illustration only and do not limit the invention and that the invention will be defined by the appended claims.

In the drawings, FIG. 1 is a perspective view of one form of fuse and fuse holder made in accordance with the principles and teachings of the present invention,

FIG. 2 is a front elevational view of the molding which is used as the body of the fuse holder of FIG. 1,

FIG. 3 is a sectional view through the molding of FIG. 2, and it is taken along the plane indicated by the line 33 in FIG. 2,

- FIG. 4 is a rear elevational View of the molding of FIG. 2,

FIG. 5 is another sectional view through the molding of FIG. 2 and it is taken along the plane indicated by the line 5-5 in FIG. 2,

FIG. 6 is a front elevational view of the fixed contact for the fuse holder of FIG. 1 and of the conductor associated with that fixed contact,

FIG. 7 is a side elevational view of the fixed contact and conductor of FIG. 6,

FIG. 8 is a rear view of the fuse of FIG. 1,

FIG. 9 is a rear View of a lock nut usable with the fuse holder of FIG. 1,

FIG. 10 is a sectional view through the lock nut of FIG. 9, and it is taken along the plane indicated by the line lib-10 in FIG. 9,

FIG. 11 is a side elevational view, on an enlarged scale, of the fuse of FIG. 1,

FIG. 12 is a vertically-directed, longitudinally-extending section, on the scale of FIG. 11, through the fuse of FIG. 11, and

FIG. 13 is a vertically-directed, longitudinally-extending section, on a still larger scale, through the fuse and fuse holder of FIG. 1.

Referring to the drawings in detail, the numeral 10 generally denotes the body of a fuse holder that is made in accordance with the principles and teachings of the present invention. That body is preferably formed as a molding of plastic material, such as phenolic resin; and it has a small diameter cylindrical portion 12 at the rear thereof and a large diameter cylindrical portion 14 at the front thereof. An axially-extending boss 16 is provided at the rear edge of the large diameter cylindrical portion 14, and that boss is coextensive with a part of the small diameter cylindrical portion 12. The numeral '18 denotes a tapered portion at the rear of the small diameter cylindrical portion '12.

The numeral 2t? denotes an elongated, constant-diameter cylindrical recess within the body 10 of the fuse holder. A shorter, smaller-diameter passage 22 is'provided in the right-hand end of the body 10 of the fuse holder, and that passage is contiguous with the recess 20.

The numeral 24 denotes a shallow recess which is contiguous with the recess 2i and which is disposed outwardly of that recess; and the recess 24 has a diameter which is slightly larger than the diameter of the recess 2%. Protuberances 26 are provided in the recess 24, and those protuberances are triangular in end view. Those protuberances are at the opposite ends of a diameter of the recess 24.

The numeral 28 denotes a shallow recess which is contiguous with the recess 2d and which is disposed out wardly of that recess; and the recess 2-3 has a diameter which is slightly larger than the diameter of the recess 24. The recess 28 coacts with the recess 24 to provide an annular shoulder fit) for the body It? of the fuse holder.

The numeral it? denotes a deeper recess in the body in which is contiguous with the recess 23 and which is disposed outwardly of that recess; and the recess til has a diameter which is slightly larger than the diameter of the recess 23. The recess 4th coacts with the recess 23 to provide an annular shoulder 2? for the body it of the fuse holder. The shoulder 29 is spaced at short distance inwardly of the front ed e of the large diameter portion '14.

Two notches 32 are formed in the shoulder 29, and those notches project radially outwardly from the recess 28. Those notches are at opposite sides of the recess 23, and those notches communicate with openings 34 in a partition 3n in the large diameter portion 14 of the body 10 of the fuse holder. Those openings communicate with the rear of the large diameter portion 14 by means of two recesses 45 in that large diameter portion.

The recess 28 is also contiguous with a passage 38 that is formed in the large diameter portion 14 and in the boss 16 of the body It). That passage is circular'in cross section and it places the recess 28 in communication with the atmosphere at the rear of the boss 16. The axis of the passage 38 is parallel to the axes of the

recesses

20, 24, 2 3 and 4i 7 The numeral 44 generally denotes a fixed contact that is dimensioned to fit within the recess 28 of the body it). That fixed contact has a central opening 48 and has oppositely disposed notches 46 which project radially outwardly from that opening. The opening 48 is set in register with the recess 20, and the diameter of that opening is slightly larger than the diameter of the recess 20. The fixed contact 44 also has an opening 47 therein, and that opening is set in register with the passage 38 in the body it of the fuse holder; The diameter of the opening 47 is smaller than the diameter of the passage 33. The opening 47 accommodates the insulation-free outer end of a conductor 42, and that outer end will be suitably held within that opening, as by solder. The rear part of that conductor will be passed rearwardly through the passage 38 and will project beyond the rear face of the boss 16. That rear part of the conductor 42 will preferably be connected to the load side of the circuit to be protected.

The numeral 50 denotes two oppositely-disposed ears on the fixed contact 44, and those cars extend rearwardly from that fixed contact. The ears 50 will be set in the openings 34 in the partition 35, and a tool will be used to press the fixed contact back against the annular shoulder 30. At this time, suitable tools can be passed forwardly through the recesses 45 and into engagement with the ears 5d of the fixed contact 44. Those tools can then be manipulated to force the ears 50 into solid engagement with the rear face of the partition as. Those ears will conact with the partition 36 to solidly lock the fixed contact 44 in position within the recess 28. Y

The partition 36 is approximately midway between the front edge and rear edge of the large diameter portion 14 of the body 10'. This is desirable because it spaces the crimped ears 50 of the fixed contact 44 forwardly and away from the rear edge of the large diameter portion 114, and it also spaces the fixed contact 44 rearwardly and away from the front edge of that large diameter portion.

The numeral 52 denotes a locking nut of the split-sleeve type which can be used to lock the body It in position within an opening 57 in a panel 58. That locking nut has a radially-extending flange 55, and it has axiallydirected ears 56 that are formed at the inner periphery of the flange 55 and that project rearwardly from that flange. The rear edges of those ears are sharp, and they are spaced apart a distance less than the diameter of the small diameter portion :12 of the body 1d. The cars 56 have small protuberances 59 that project outwardly from the outer faces of the cars 56. In assembling the body It) with the panel 58, the locking nut 52 can be telescoped part way onto the tapered portion 18 of the small diameter portion 12 and that tapered portion and the ears Sd-can be set within the opening '57 of panel 53. Thereafter, rearwardly-directed pressure can be applied to the front edge of the large diameter portion 14 of the body 10. As that pressure is applied, the ears 56 on the locking nut 52 will pass rearwardly through the opening 57 until the flange 55 engages and is held by the front face of the panel 58. Thereafter the small diameter portion 12 will spread the ears 56 apart and ease rearwardly between then until the rear edge of the large diameter portion 14 engages and is held by the front face of panel 58. At such time, the protuberances 59 will abut the rear face of the panel 53, and the flange 55 will abut the front face of that panel; and the flange 55 will keep that locking nut from moving rearwardly, while the protuberances 59 will keep that locking nut from moving forwardly. Also at such time, the rear edge of the large diameter portion 14 will keep the body 1t) from moving rearwardly, and the sharp rear edges of the ears 56 will bite into the small diameter portion 12 and keep the body from moving forwardly. In this way the locking nut 52 fixedly holds the body 10 in assembled relation with the panel 58.

The tapered portion 18 of the small diameter portion 12 of the body 10 plays an important part inthe successful assembling of the body 10 with the panel 58. Without that tapered portion, the protuberances 59 on the ears 56 would have to be bent inwardly as the body 10 was moved rearwardly to cause those protuberances to pass through the opening 57; and the forces needed to bend those protuberances inwardly are so great that the small diameter portion 12 could be pressed completely between the ears 56 without effecting the required inward bending of those protuberances. As a matter of fact, where the body 10 has been made without the tapered portion 18, the flange 55 of the locking nut 52 has frequently been forced inwardly and forwardly of the rear edge of the large diameter portion 14; and in that position the locking nut is useless. However, where the tapered portion 18 is provided, the locking nut 52 can be set part way on that tapered portion and the protuberances 59 can be easily passed through the opening 57 in the panel 53. Thereafter the body 10 can be pressed rearwardly without any risk of the locking nut entering the space that is inward and forward of the rear edge of the large diameter portion 14.

When the body 10 of the fuse holder is fully seated within the opening 57 of panel 58, the boss 16 will be disposed within a D-portion of that opening. The boss 16 will coact with that D-portion to prevent rotation of the body 10 relative to the panel 58.

The numeral 82 denotes a helical compression spring that is disposed within the recess 20 of the body 10. One end of that spring abuts the right-hand end wall of the recess 20, and the other end of that spring presses against the rear face of a movable contact 80. That movable contact has a diameter which is smaller than that of the recess 20 so it can move freely relative to that recess. The shank of that movable contact is telescoped within the spring 82, and that shank is suitably connected to one end of a flexible conductor 78. That conductor passes outwardly through the passage 22 and will preferably be connected to the hot side of the electric circuit. The outer diameter of the insulation on the conductor 78 is less than the diameter of the passage 22 so the conductor 78 can move freely relative to that passage.

The numeral 60 generally denotes a glass tube fuse, and that fuse has a terminal 62 which can engage the movable contact 80. That fuse also has a terminal 64 which is equipped with radially-directed ears 66. Those ears are dimensioned to pass freely through the notches 46 of the fixed contact 44; but those ears can respond to rotation of the fuse 60 relative to the body 16 of the fuse holder to lodge under those portions of the fixed contact 44 which are spaced from the notches 46. At such time the fuse 60 can not be separated from the fuse holder. As a result, the ears 66 on the terminal 64 of the fuse 60 coact with U the notches 46 of the fixed contact 44 to joint lock.

The numeral 68 generally denotes a hollow knob of insulating material that embeds and insulates the end face and the greatest portion of the sides of the terminal 64 of the fuse 60. That knob has a knurled head '70 and has a reduced diameter shank 72. The reduced diameter shank 72 has a cylindrical recess 74 therein which is provided with an inner diameter that is substantially equal to the outer diameter of the terminal 64 of the fuse 60. As a result, the greatest portion of the terminal 64 of the fuse 60 can be pressed into the recess 74; and once it has been pressed into that recess, that greatest portion can not be removed from that recess. Further, that greatest portion of that terminal can not be rotated relative to that recess. In this way, the knob 68 is fixedly and permanently secured to the fuse 60.

It will be noted that the ears 66 on the terminal 64 of the fuse 60 are spaced a short distance inwardly from the inner face of the reduced diameter shank 72 of the knob 68. This spacing must be great enough to enable the ears 66 to move inwardly beyond the inner face of the fixed contact 44, in the fuse holder 10, so those ears can then be turned to underlie the portions of the fixed contact 44 which are intermediate the notches 46. Yet, the inner face of the reduced diameter shank 72 must be immediately adjacent the outer face of the fixed contact 44 when the fuse 60 is held in assembled relation with the body 10. Without this latter relationship, the installer could have difiiculty setting the ears 66 in the proper axial position to effect the required bayonet joint locking.

As shown by FIG. 2, the stops 26 are displaced a few degrees from a diameter that extends between the openings 34, which receive the ears 46 on the fixed contact 44. The diametric spacing between the apexes of those stops is less than the diametric distance between the outer edges of the ears 66. As a result, the fuse 60 can be turned only until its ears engage the stops 26. This means that the fuse 60 can be turned about ninety degrees in the clockwise direction after it has been set in position within the fuse holder, but it can be turned only a few degrees in the counterclockwise direction from its inserting and removing position. As a result, when an installer wants to replace a fuse 60, he need only rotate that fuse as far as it will go in the counterclockwise direction and then rotate that fuse a few degrees in the clockwise direction.

The outer diameter of the knurled head of the knob 68 is just slightly smaller than the diameter of the recess 40; and hence an annular gap of only about one hundredth of an inch can exist between the periphery of that head and the outer periphery of recess 40 when the fuse 60 is seated within the fuse holder. Furthermore, the outer diameter of the knurled head 70 of the knob 68 is almost a tenth of an inch larger than the inner diameter of the shoulder 29 defined by the

recesses

28 and 40. The overall result is that the knurled head 70 of the knob 68 coacts with the shoulder 29 to substantially prevent contact of any metallic tool or wire with the fixed contact 44 when the fuse 60 is seated within the fuse holder.

The numeral 84 denotes a metal clip that has been pressed onto the conductor 78 at a point which is spaced a short distance from the passage 22. That clip is generally U-shaped, and its legs are long enough to prevent the passage of that clip through the passage 22. As a result, unlimited movement of the conductor 78 relative to the body 10 is prevented.

The fuse 60 provided by the present invention can safely be used with circuits wherein the voltages exceed two hundred and fifty volts but do not exceed three hundred volts. The knob 68 projects both axially and radially beyond the terminal 64 and beyond the ears 66 and thereby adequately and fully prevents accidental contact between the terminal 64 and the installers hands. The knob 68 coacts with the large diameter portion 14 of the body 10 provide a bayonet to substantially completely prevent contact between a metallic tool or wire and the fixed contact 44 when the fuse 60 is disposed within the fuse holder. Also the large diameter portion 14 of the body projects forwardly beyond the fixed contact 44 and keeps the installers thumb or fingers from accidentally engaging that contact. Furthermore, that large diameter portion spaces the fixed contact 44 far enough from the panel 58 to avoid leakage paths to that panel. Yet, the total overall length of the body 10. is less than two and three-eighths inches and the total overall diameter of the large diameter portions is less than seven-eighths of an inch.

Whereas the drawings and accompanying description have shown and described a preferred embodiment of the present invention it should be apparent to those skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof.

What I claim is:

1. In combination, a glass tube electric fuse that has terminals at the opposite ends thereof, radially-projecting ears on one of said terminals adjacent the inner edge of said terminal, a knob of insulation that fixedly embeds and insulates the end face and the greatest portion of the sides of said terminal and thereby permanently interconnects said fuse and said knob, said knob having a knurled head that projects axially and radially beyond said terminal and said radially-projecting ears, said knob having a reduced diameter shank that extends toward but stops short of said radially-projecting ears on said one terminal, a fuse holder with an elongated recess therein that is adapted to accommodate the other of said terminals and the inner end of said fuse, a second recess in said fuse holder that is disposed outwardly of the first said recess but that is contiguous to the first said recess, said second recess being adapted to receive said radially-projecting ears on said one terminal of said fuse and to permit rotation of said fuse relative to said fuse holder, stops in said second recess that are in register with said radially-projecting ears on said one terminal of said fuse and that limit rotation of said fuse relative to said fuse holder, a third recess in said fuse holder that is disposed outwardly of said second recess but that is contiguous to said second recess, said third recess being adapted to receive the inner face of said reduced diameter shank of said knob and to receive a fixed contact, said fixed contact having a central opening therein to accommodate said other terminal and said inner end of said fuse, said central opening in said fixed contact having a diameter less than the diametric distance between the outer edges of said radiallyprojecting ears on said one terminal of said fuse, said fixed contact having notches therein that are contiguous with said central opening and that are dimensioned to accommodate said radially-projecting ears on said one terminal of said fuse whereby said radially-projecting ears on said one terminal of said fuse can pass through said notches and can then be rotated to underlie and abut those portions of said fixed contact which are. intermediate said' notches and can thereby hold said fuse in assembled relation with said fuse holder, said fixed contact being dimensionedso the inner face of said reduced diameter shank of'said knob is closely adjacent the outer face of said fixed contact whenever said radially-projecting ears on said one terminal of said fuse underlie'and abut said portions of said fixed contact which are intermediate said notches, a fourth recess in said fuse holder that is disposed outwardly of said third recess but that is contiguous with said third recess, said fourth recess being adapted to receive the inner face of said knurled head and being dimensioned to coact with said knurled head to define a small annular gap that will substantially completely keep metallic tools or wire from engaging said fixed cont-act when said fuse is disposed within said fuse holder, said fuse holder having a small diameter cylindrical portion that is adapted to extend through an opening in a panel,

and alocking nut of the split sleeve type that is adapted to secure said fuse holder to said panel, said small diameter cylindrical portion of said fuse holder having a tapered portion adjacent the rear thereof to initially accommodate said locking nut and thereby facilitate the mounting of said fuse holder in said opening in said panel, said locking nut snugly fitting said small diameter cylindrical portion of said fuse holder and being adjacent one face of said panel to hold said fuse holder and said panel in assembled relation whenever said small diameter cylindrical portion of said fuse holder is mounted in said opening in said panel, said radially-projecting ears on said one terminal of said fuse underlying said portions of said fixed contact which are intermediate said notches to hold said other terminal and said inner end of said fuse within said first recess and to hold said inner face of said knurled knob within said fourth recess whenever said fuse is assembled with said fuse holder.

2. In combination, an elongated electric fuse that has a terminal at one end thereof, an ear on said terminal, a knob of insulation that fixedly embeds and insulates the end face and the greatest portion of the sides of said te'rmial and thereby permanently interconnects said fuse and said knob, said knob projecting both axially and radially beyond said terminal and beyond said ear on said terminal, a fuse holder that is adapted to accommodate the inner end of said fuse, a recess in said fuse holder that is adapted and dimensioned to receive said ear on said terminal and to permit rotation of said fuse relative to said fuse holder, a stop in said recess that is in register with said ear on said terminal and that limits rotation of said fuse relative to said fuse holder, a fixed contact in said fuse holder that has an opening therein to accommodate the inner end of said fuse, said fixed contact having a notch that is contiguous with said opening and that is adapted and dimensioned to accommodate said car on said terminal, said notch in said fixed contact being adjacent but spaced an angular distance from said stop, whereby said stop indicates when said fuse has been rotated to a position closely adjacent its inserting and removing position, said ear on said terminal being adapted to pas through said notch and to be rotated to underlie and abut portions of said fixed contact that are displaced from said notch and thereby hold said fuse in assembled relation with said fuse holder, said fixed contact being dimensioned so the inner face of said knob is closely adjacent the outer face of said fixed contact whenever said ear on said terminal of said fuse underlies said portions of said fixed contact which are displaced from said notch, and an outer recess in said fuse holder that is disposed outwardly of said fixed contact, said outer recess being adapted to receive the inner face of'said knob and being dimensioned to coact with said knob to define a small annular gap that will substantially completely keep metallic tools or wire from engaging said fixed contact when said fuse is disposed within said fuse holder, said fuse holder and said fixed contact coacting with said fuse to releasably hold said fuse in assembled relation with said fuse holder.

3. In combination, an elongated electric fuse that has an electricaily-conducting terminal at one end thereof, an electrically conducting ear on said terminal, a knob of insulation that fixedly embeds and insulates the end face and part of the sides of said terminal and thereby permanently interconnects said fuse and said knob, said knob projecting both axially and radially beyond said terminal to prevent accidental engagement between said terminal and the hands of an installer, a fuse holder that is adapted to accommodate the inner end of said fuse, a recess in said fuse holder that is adapted and dimensioned to receive said ear on said terminal and to permit rotation of said fuse relative to said fuse holder, a fixed electrically-conducting contact in said fuse holder that has an opening therein to accommodate the inner end of said fuse, said fixed contact having a notch that is contiguous with said opening and that is adapted and dimensioned to accommodate said ear on said terminal, said car on said terminal being adapted to pass through said notch and to be rotated to underlie and abut portions of said fixed contact that are displaced from said notch and thereby hold said fuse in assembled relation with said fuse holder, said fixed contact being dimensioned so the inner face of said knob is closely adjacent the outer face of said fixed contact Whenever said ear on said terminal of said fuse underlies said portions of said fixed contact which are displaced from said notch, and an outer recess in said fuse holder that is disposed outwardly of said fixed contact, said outer recess being adapted to receive the inner face of said knob and being dimensioned to coact with said knob to define a small annular gap that will substantially completely keep metallic tools or wire from engaging said fixed contact when said fuse is disposed within said fuse holder, said fuse holder and said fixed contact coacting with said fuse to releasably hold said fuse in assembled relation with said fuse holder, said car on said terminal directly engaging said fixed contact to provide a direct engagement between said fuse and said fixed contact and thereby minimize local heating of said fuse.

4. In combination, an elongated electric fuse that has a terminal at one end thereof, an ear on said terminal, a fuse holder that is adapted to accommodate the inner end of said fuse, a recess in said fuse holder that is adapted and dimensioned to receive said car on said terminal and to permit rotation of said fuse relative to said fuse holder, a stop in said recess that is in register with said ear on said terminal and that positively limits rotation of said fuse relative to said fuse holder in one direction, and a fixed contact in said fuse holder that has an opening therein to accommodate the inner end of said fuse, said fixed contact having a notch that is contiguous with said opening and that is adapted and dimensioned to accommodate said ear on said terminal, said fixed contact being disposed outwardly of said recess and overlying said stop, said notch in said fixed contact being adjacent but spaced a short angular distance from said stop, whereby said stop indicates when said fuse has been rotated to a position closely adjacent its inserting and removing position, said fuse holder and said fixed contact coacting with said fuse to releasably hold said fuse in assembled relation with said fuse holder.

5. A fuse holder that is adapted to be mounted in an opening in a panel and that has a portion of large transverse dimension which is adapted to be located at the outer face of said panel, a recess in said large portion that opens to the front edge of said large portion, a second recess in said large portion that opens to the rear edge of said large portion, a partition in said large portion of said fuse holder that is intermediate the first said recess and said second recess and that is adapted to be set parallel to said outer face of said panel, a fixed contact for said fuse holder that abuts said partition and that is in communication with the first said recess, openings in said partition that are in communication with the first said and said second recesses and thus with the front and rear edges of said large portion of said fuse holder, and ears on said fixed contact that extend through said openings and that are bent around and into engagement with said partition to lock said fixed contact in position within said fuse holder, said large portion of said fuse holder projecting forwardly of said partition to prevent accidental engagement between said fixed contact and the thumb or fingers of an installer, said large portion of said fuse holder projecting rearwardly of said partition to prevent leakage paths between said fixed contact and said panel.

6. A fuse holder that is adapted to be mounted in an opening in a panel and that has a portion of large transverse dimension which is adapted to be located at the outer face of said panel, said fuse holder having a portion of smaller transverse dimension which is adapted to extend through said opening in said panel and to be located at the inner face of said panel, said smaller portion of said fuse holder having a tapered inner end, and a locking nut of the split sleeve type that is adapted to secure said fuse holder to said panel, said locking nut having a portion that can extend into said opening in said panel and having a second portion that can not extend into said opening but will abut and be held by the front face of said panel, said tapered inner end of said smaller portion of said fuse holder initially accommodating the first said portion of said locking nut while both said fuse holder and said locking nut are disposed forwardly of said panel and the first said portion of said locking nut initially being dimensioned to fit into said opening in said panel so said tapered end of said smaller portion of said fuse holder can be used to dispose the first said portion of said locking nut within said opening in said panel, said tapered inner end of said smaller portion of said fuse holder thereafter being movable through the first said portion of said locking nut to expand the first said portion of said locking nut and to fixedly secure said locking nut to said panel.

References Cited by the Examiner UNITED STATES PATENTS BERNARD. A. GILHEANY, Primary Examiner. RICHARD M. WOOD, Examiner.

Claims

4. IN COMBINATION, AN ELONGATED ELECTRIC FUSE THAT HAS A TERMINAL AT ONE END THEREOF, AN EAR ON SAID TERMINAL, A FUSE HOLDER THAT IS ADAPTED TO ACCOMMODATE THE INNER END OF SAID FUSE, A RECESS IN SAID FUSE HOLDER THAT IS ADAPTED AND DIMENSIONED TO RECEIVE SAID CAR ON SAID TERMINAL AND TO PERMIT ROTATION OF SAID FUSE RELATIVE TO SAID FUSE HOLDER, A STOP IN SAID RECESS THAT IS IN REGISTER WITH SAID EAR ON SAID TERMINAL AND THAT POSITIVELY LIMITS ROTATION OF SAID FUSE RELATIVE TO SAID FUSE HOLDER IN ONE DIRECTION, AND A FIXED CONTACT IN SAID FUSE HOLDER THAT HAS AN OPENING THEREIN TO ACCOMMODATED THE INNER END OF SAID FUSE, SAID FIXED CONTACT HAVING A NOTCH THAT IS CONTIGUOUS WITH SAID OPENING AND THAT IS ADAPTED AND DIMENSIONED TO ACCOMMODATE SAID EAR ON SAID TERMINAL, SAID FIXED CONTACT BEING DISPOSED OUTWARDLY OF SAID RECESS AND OVERLYING SAID STOP, SAID NOTCH IN SAID FIXED CONTACT BEING ADJACENT BUT SPACED A SHORT ANGULAR DISTANCE FROM SAID STOP, WHEREBY SAID STOP INDICATES WHEN SAID FUSE HAS BEEN ROTATED TO A POSITION CLOSELY ADJACENT ITS INSERTING AND REMOVING POSITION, SAID FUSE HOLDER AND SAID FIXED CONTACT COACTING WITH SAID FUSE TO RELEASABLY HOLD SAID FUSE IN ASSEMBLED RELATION WITH SAID FUSE HOLDER.