GB1596438A - Fuse-mate or carrier for a cartridge-type electrical fuse - Google Patents

Description

(54) FUSE-MATE OR CARRIER FOR A CARTRIDGE-TYPE ELECTRICAL FUSE (71) We, FISCHER & PORTER COM- PANY, a corporation organised and existing under the laws of the State of Pennsylvania, of Warminster, Pennsylvania 18974, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates generally to cartridge-type electrical fuses, and more particularly to a mating or carrying device which facilitates insertion of such fuses into a fuse holder and the removal thereof, the fusemate or carrier also carrying out other useful functions.

A fuse is a protective device containing a short length of special wire that melts when the current therethrough exceeds the rated value for a given period. Because the fuse is inserted in series with the circuit to be protected. it opens this circuit automatically in the event of an unacceptable overload.

The fuse commonly used in conjunction with electronic equipment is of the so-called cartridge type. This is constituted by a tubular casing of glass or other clear insulating material whose ends are enclosed by metal terminal caps, the fuse wire extending through the casing and bridging the caps.

Since the fuse wire is visible through the transparent casing, should an overload occur which melts the wire, the blown condition of the fuse the becomes evident. In some cases, the casing is of opaque or ceramic material.

Cartridge fuses are socketed in holders formed by an insulating base on which a pair of metal spring clips is mounted to engage the terminal caps of the fuse, the circuit connections being made to the clips. In many instances, an array of parallel holders are formed on a common base so that the fuses are then very close to each other. Normally, to install a fuse, one grips the casing thereof between the thumb and fore-finger and then pushes the fuse into the holder clips. And to remove a fuse from the holder, one again grips the casing with the fingers to pull the fuse from the holder clips.

To insure efficient electrical contact between the holder clips and the fuse terminal caps, the clips are designed to apply a substantial clamping pressure on the caps.

These pressures make insertion and removal of the fuse quite difficult, which difficulty is compounded when the fuses are small or where a family of fuses are very close to each other. Moreover, because at least one holder clip is alive, and the gripping fingers are quite close to the terminal caps, there is a danger of shock, particularly if resistance is experienced in removing or inserting a fuse in the course of which the fingers are shifted toward the caps.

Because of problems encountered in removing cartridge type fuses, the use of screw drivers to pry the fuse from the holder is not uncommon. This can lead not only to fracture of the relatively delicate fuse casing, but it may also result in the short-circuiting of adjacent fuse holders.

To overcome these difficulties, various forms of cartridge-type fuse extractors have heretofore been proposed, all of which include some means to grip the fuse casing and a handle to pull the clamped fuse out of the holder. Thus U.S. Pat. 1,380,242 shows a fuse extractor having a pair of jaws adapted to receive and retain a cartridge fuse, with a long handle to isolate the user from the fuse terminals. The extractor is designed so that after a fuse is inserted in its holder, the jaws can be disengaged therefrom. Other forms of fuse extractors or pullers adapted to engage, and then release the fuse, are disclosed in U.S. Patents 2,454,870; 3,215,006; and 3,654,824.

In fuse extractors or pullers of the type heretofore known, the tool is only put to use when a fuse is in need of insertion or removal, so that under normal circumstances, the cartridge fuses in a given piece of electronic equipment are socketed in their holders with their live terminals exposed.

These fuses are disregarded unless an overload occurs which renders the equipment inoperative. It is only when this happens that one has occasion to check the several protective fuses to see which one is blown and in need of replacement.

Because all of the live terminals are exposed, in seeking to extract a given fuse, one may accidentally make contact with an adjacent live terminal. And since the fuse wire usually has a silver-like appearance and is enclosed within a clear casing, it is difficult to discern the condition of the wire in each fuse, especially when the fuses are in a closely packed array. Hence it may be necessary to extract the fuses one at a time with a suitable extractor and to examine each fuse in a good light, if one is available, to see whether it is blown. Finally. when the blown fuse is located, one must then replace this fuse with a fresh fuse having the same rating.

This sometimes presents a problem, especially with small cartridge fuses whose ratings are inscribed on caps and are hard to make out.

The present invention provides a fusemate or carrier of insulating material adapted to be coupled to a cartridge-type fuse having a fuse wire disposed within a cylindrical casing whose ends are enclosed by terminal caps, said caps being engageable by the spring clips of a fuse holder, said fusemate facilitating the insertion or extraction of said fuse and comprising a shield dimensioned to protectively cover said fuse and having a length which is at least equal to that of the fuse so as to overlie the caps and the spring clips; a socket secured to the underside of said shield, said socket being constituted by laterally projecting resilient jaws defining an inlet opening facing sideways relative to the shield, the opening being normally narrower than the diameter of the casing and leading to a channel, the jaws being dilatable at the opening to permit said casing to enter said channel whereby said jaws then damp onto and conform to said casing, said jaws having a length shorter than that of said casing so that they are interposed between said end caps; and a block secured to the upper side of said shield forming a handle for said fuse-mate. the arrangement being such that the lower jaws acts to hold the fuse in the channel when an outward force is applied to the handle to extract the fuse from a holder.

In a preferred embodiment of the invention. the fuse-mate is configured to define a block-like socket having a longitudinallyextending channel therein adapted to accommodate the tubular casing of a cartridge fuse and lateral inlet jaws which are dilatable to permit the casing to be snapped into the channel and to be held therein.

The upper surface of the socket is integral with the underside of a rectangular shield which extends over the terminal caps of the socketed fuse and protectively covers the entire fuse and the "live" clips of its holder.

Formed on the upper side of the shield is à handle having concave sides to define finger depressions and a face which lends itself to marking.

Because the lower surface of the socket serves as a shelf underlying the fuse held in the channel, an outward pulling force will not dislodge the fuse from the socket even if the fuse is tightly gripped by the holder clips and will serve to withdraw the fuse from the holder.

A preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a perspective view of an array of standard holders for cartridge-type fuses, some of the holder having fuses therein which are coupled to a fuse mate or carrier in accordance with the invention Fig. 2 shows in perspective a single fuse coupled to a fuse mate; Fig. 3 is a transverse section taken through a fuse held by spring clips of a holder; Fig. 4 shows in transverse section the fusemate coupled to the fuse; Fig. 5 is a side view of the fuse mate; Fig. 6 is a perspective view of the fuse mate as seen from the bottom.

Referring now to Fig. 1, there is shown an array of standard fuse holders, generally designated by numeral 10, one directly against the other so that the cartridge-type fuses 11 retained in the holders are in close proximity to each other. As previously explained, in a typical piece of electronic equipment having several protective fuses in a range of ratings appropriate to the equipment, an array of this type is not uncommon and presents difficulties in removing and replacing individual fuses.

Each holder 10 is constituted by a rectangular insulating base 12 on which is mounted a pair of metal clips 13 and 14 at spaced positions. These clips are formed with spring fingers adapted to engage and to electrically connect with the terminal caps 15 and 16 enclosing the ends of the transparent casing 17 of the cartridge fuse. A fuse wire 19 is disposed within the casing, the wire bridging end caps 15 and 16.

Clips 13 and 14 are electrically "live," since they are connected to the electrical circuit which is to be protected against an excessive overload. In the event of an excessive overload-that is, one exceeding the rating of the fuse-the wire is caused to melt to break the circuit and interrupt the flow of current therethrough.

The one-piece mate for the fuse is generally designated as F-M and is molded of a synthetic plastic material, such as polyethylene having good insulating qualities and some degree of resilience together with adequate structural strength. Fuse mate F-M is configured to define a block-shaped socket 19 of a square cross-section having a longitudinal channel 20 formed therein, which is contoured to conform to the cylindrical surface of fuse casing 17. The channel is provided with a laterally facing inlet formed by upper and lower jaws 21 and 22. The length of the jaws is slightly shorter than the length of the casing between end caps 15 and 16, so that the jaws may be clipped onto the casing between these caps. When, as shown figure in 4, the fuse casing is forced between the jaws, the jaws yield to permit entry of the casing into channel 20, the jaws then clamping onto the casing surface. Jaw 21 is provided with a leading edge ramp 21 A to facilitate the admission of the fuse.

The upper surface of socket 19 is integral with the underside of a rectangular shield 23 whose length is somewhat greater than the length of the cartridge fuse clamped between the jaws and whose width is somewhat greater than the width of the fuse so that the shield acts to protectively cover the fuse, overlying the end caps 15 and 16 and the "live" holder clips thereunder.

Formed on the outer surface of shield 23 is a handle 24, the width of the block being the same as that of the shield, the length of handle being shorter than that of the shield and being centered thereon. The opposing sides 24A and 24B of the handle and its opposing ends 24C and 24D (see Figures 4 and 5) are concave to form finger depressions to facilitate handling of the fuse-mate from any direction. Handle 24 is provided with a slightly convex (as shown) or flat face 24E onto which one may adhere a label bearing rating and other data which is then readily viewable by the user. The rating may alternatively be marked on shield 23.

Thus when a fuse 11 is coupled to a fusemate F-M in the manner shown in Figs. I and 2, it becomes possible to insert the fuse into a standard holder therefor or to extract the fuse from the holder without difficulty and without any danger of finger contact with the "live" clips of the holder; for the fingers are well isolated from the end caps of the fuse and the holder clips. One may therefore insert or remove a fuse in poor light without fear of shock.

Because the lower surface of socket 19 forms a shelf under fuse casing 17, an outward pulling force applied to the fusemate in order to extract the fuse from its holder will not act to dilate jaws 21 and 22 of the lateral inlet and dislodge the fuse, even if the fuse is tightly gripped by the holder clips; for in order to effect such dilation, one must insert a fuse into the jaws in a direction normal to the outward pulling force. Hence even if the holder clips are tight and resist extraction, a heavy pulling force can be used to overcome this resistance without disengaging the fuse-mate from the fuse.

Even though the fuse holders are directly adjacent each other in the array shown in Fig. 1, the width of the fuse-mate is substantially less than the width of holder base 12; hence there is adequate room between the couples to permit the insertion of fingers therebetween.

Fuse mate F-M is formed of opaque material which may be white or in different colors. Hence, rather than label the ratings of the fuses on the fuse-mate, the fuse-mates may be color-coded to represent different ratings, such as red for 0.25 amps, green for 0.50 amps, and so on. When, as shown in Fig.

2, one wishes to examine the condition of fuse wire 19 in the fuse to determine whether the fuse is blown, one then sees this wire within the clear casing 17 against the opaque background of the mate, and its state is therefore more readily discernible.

It may be desirable in some instances to be able to pull out all fuse couples in a row thereof, so that one can examine the fuses to see which one has blown. To this end, one can provide a bridging strip having a row of tracks on the underside which clip onto the several handles of the fuse-mates, the strip having a handle thereon making it possible to pull out all of the couples simultaneously.

In practice, one may use a single fuse-mate as a tool to insert fuses into holders or to extract fuses therefrom; in which event, when a blown fuse is located and extracted, it must be detached from the mate and a fresh fuse coupled thereto. However, since the fusemates can be fabricated in quantity at very low cost, the fuse-mates may be coupled at the factory to appropriate fuses and supplied to users as couples; in which event the couples are installed in the fuse holders and remain therein until it is necessary to replace a blown fuse, in which case the blown couple is removed and discarded and a fresh couple put in place.

Since fuse cartridges come in various diameters and lengths, their companion fusemates must be dimensioned accordingly. It is also to be noted that cartridge fuses in large ratings often come with casings made of fibrous material rather than glass or clear plastic, and that one can provide fuse-mates appropriate to these sizes.

WHAT WE CLAIM IS: 1. A fuse-mate or carrier of insulating material adapted to be coupled to a car

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. to break the circuit and interrupt the flow of current therethrough. The one-piece mate for the fuse is generally designated as F-M and is molded of a synthetic plastic material, such as polyethylene having good insulating qualities and some degree of resilience together with adequate structural strength. Fuse mate F-M is configured to define a block-shaped socket 19 of a square cross-section having a longitudinal channel 20 formed therein, which is contoured to conform to the cylindrical surface of fuse casing 17. The channel is provided with a laterally facing inlet formed by upper and lower jaws 21 and 22. The length of the jaws is slightly shorter than the length of the casing between end caps 15 and 16, so that the jaws may be clipped onto the casing between these caps. When, as shown figure in 4, the fuse casing is forced between the jaws, the jaws yield to permit entry of the casing into channel 20, the jaws then clamping onto the casing surface. Jaw 21 is provided with a leading edge ramp 21 A to facilitate the admission of the fuse. The upper surface of socket 19 is integral with the underside of a rectangular shield 23 whose length is somewhat greater than the length of the cartridge fuse clamped between the jaws and whose width is somewhat greater than the width of the fuse so that the shield acts to protectively cover the fuse, overlying the end caps 15 and 16 and the "live" holder clips thereunder. Formed on the outer surface of shield 23 is a handle 24, the width of the block being the same as that of the shield, the length of handle being shorter than that of the shield and being centered thereon. The opposing sides 24A and 24B of the handle and its opposing ends 24C and 24D (see Figures 4 and 5) are concave to form finger depressions to facilitate handling of the fuse-mate from any direction. Handle 24 is provided with a slightly convex (as shown) or flat face 24E onto which one may adhere a label bearing rating and other data which is then readily viewable by the user. The rating may alternatively be marked on shield 23. Thus when a fuse 11 is coupled to a fusemate F-M in the manner shown in Figs. I and 2, it becomes possible to insert the fuse into a standard holder therefor or to extract the fuse from the holder without difficulty and without any danger of finger contact with the "live" clips of the holder; for the fingers are well isolated from the end caps of the fuse and the holder clips. One may therefore insert or remove a fuse in poor light without fear of shock. Because the lower surface of socket 19 forms a shelf under fuse casing 17, an outward pulling force applied to the fusemate in order to extract the fuse from its holder will not act to dilate jaws 21 and 22 of the lateral inlet and dislodge the fuse, even if the fuse is tightly gripped by the holder clips; for in order to effect such dilation, one must insert a fuse into the jaws in a direction normal to the outward pulling force. Hence even if the holder clips are tight and resist extraction, a heavy pulling force can be used to overcome this resistance without disengaging the fuse-mate from the fuse. Even though the fuse holders are directly adjacent each other in the array shown in Fig. 1, the width of the fuse-mate is substantially less than the width of holder base 12; hence there is adequate room between the couples to permit the insertion of fingers therebetween. Fuse mate F-M is formed of opaque material which may be white or in different colors. Hence, rather than label the ratings of the fuses on the fuse-mate, the fuse-mates may be color-coded to represent different ratings, such as red for 0.25 amps, green for 0.50 amps, and so on. When, as shown in Fig. 2, one wishes to examine the condition of fuse wire 19 in the fuse to determine whether the fuse is blown, one then sees this wire within the clear casing 17 against the opaque background of the mate, and its state is therefore more readily discernible. It may be desirable in some instances to be able to pull out all fuse couples in a row thereof, so that one can examine the fuses to see which one has blown. To this end, one can provide a bridging strip having a row of tracks on the underside which clip onto the several handles of the fuse-mates, the strip having a handle thereon making it possible to pull out all of the couples simultaneously. In practice, one may use a single fuse-mate as a tool to insert fuses into holders or to extract fuses therefrom; in which event, when a blown fuse is located and extracted, it must be detached from the mate and a fresh fuse coupled thereto. However, since the fusemates can be fabricated in quantity at very low cost, the fuse-mates may be coupled at the factory to appropriate fuses and supplied to users as couples; in which event the couples are installed in the fuse holders and remain therein until it is necessary to replace a blown fuse, in which case the blown couple is removed and discarded and a fresh couple put in place. Since fuse cartridges come in various diameters and lengths, their companion fusemates must be dimensioned accordingly. It is also to be noted that cartridge fuses in large ratings often come with casings made of fibrous material rather than glass or clear plastic, and that one can provide fuse-mates appropriate to these sizes. WHAT WE CLAIM IS:

1. A fuse-mate or carrier of insulating material adapted to be coupled to a car

tridge-type fuse having a fuse wire disposed within a cylindrical casing whose ends are enclosed by terminal caps, said caps being engageable by the spring clips of a fuse holder. said fuse-mate facilitating the insertion or extraction of said fuse and comprising: A a shield dimensioned to protectively cover said fuse and having a length which is at least equal to that of the fuse so as to overlie the caps and the spring clips; B a socket secured to the underside of said shield, said socket being constituted by laterally projecting resilient jaws defining an inlet opening facing sideways relative to the shield. the opening being normally narrower than the diameter of the casing and leading to a channel, the jaws being dilatable at the opening to permit said casing to enter said channel whereby said jaws then clamp onto and conform to said casing, said jaws having a length shorter than that of said casing so that they are interposed between said end caps; and C a block secured to the upper side of said shield forming a handle for said fusemate, the arrangement being such that the lower jaw acts to hold the fuse in the channel when an outward force is applied to the handle to extract the fuse from a holder.

2. A fuse-mate as set forth in claim 1, wherein said shield, said socket and said handle are integral with each other and are fabricated from a single, molded piece of synthetic plastic material.

3. A fuse-mate as set forth in claim 1, wherein said casing is of transparent material and said fuse-mate is of opaque material whereby the wire in said casing may be readily seen against an opaque background to determine its condition.

4. A fuse-mate as set forth in claim 1, wherein the sides and ends of said handle are concave to define finger depressions.

5. A fuse-mate as set forth in claim 4, wherein said handle has a substantially flat or slightly convex face to receive a marking label.

6. A device for the insertion and removal of a cartridge-type fuse substantially as described with reference to and as illustrated in Figures 1 to 6 of the accompanying drawings.