US2144707A - Cut-out - Google Patents

Description

A. RAMSEY Jan. 24, 1939.

CUT-OUT originl Filed June 9, 1934 gu 6/ D' ll Patented Jan. 24, 1939 CUT-OUT Allan Ramsey, Evanston, Ill., assigner to Schweit- Vler Conrad, Inc., Chicago, lll., a corporation of Delaware Original application June 9, 1934, Serial No. 730,075. Divided and this application July 22, 1937, Serial No. 154,973

55 Claims. (Cl. 20o-117) elfe My invention relates to cutouts for electrical circuits.

This application constitutes a division of my copending application, Serial No. 730,075, filed crete understanding of the present invention will be more apparent from the following detailed description taken in connection with the accompanying drawing, in which:

June 9, 1934, and assigned to the assignee of this Figure 1 is a view illustrating my imprOVed 5 application, now Patent No, 2,108,993, form of cutout mounted upon a cross arm and The fuse link assembly which I employ is of adapted to receive a fuse member;

the type described and claimed in my copending Figures 2 andk 3 are parts of a longitudinal application Serial No. 671,660, flied May 18, 1933, sectional view through the fuse member adapted now Patent No. 2,091,453, with certain improveto be mounted in the cutout shown in Figure 1 l" ments to make it universal or adapt it for use (Figure 3 is to be laid below Figure 2 With the with the fuse deviceconstituting a part of the dot and dash line a-a of Figure 3 on the dot plug of the cutout of the present invention, and and dash line a-a of Figure 2); and

with the dropout type ejector cutout box of my Figure 4 is a fragmentary elevational view of copending application Serial No. 734,262, nled the upper end of the fuse link assembly showing 15 July 9, 1934. the same removed from the retraction spring This fuse link assembly also embodies an imand cable assembly and another form of termiproved visual indicator feature and other imnal button applied directly t0 the upper fuse provements which will hereinafter appear. terminal thereOf t0 provide fOl universal appli- An object of my invention is to provide an cation. 20 improved combination of an insulating outer The cutout of my present invention comprises sleeve having metallic ferrules constituting outer an outer socket member 2, which carries the terminals, a pair of inner terminals within and main contact terminals, and the removable plug adjacent one end of the outer sleeve and conmember 4, Which bears the fuse device fOI intelnected electrically with the outer terminals, one rupting the circuit in case of overload or short 25 of the inner terminals being movable toward the circuit. It will be noted that the Plug member 4 other end of the sleeve, with a fusible element is adapted for insertion in the top of the socket between the inner terminals and an inner sleeve member 2, this arrangement bearing Particular of insulating material closely surrounding the relation to the type 0f fuse employed, aS Will inner terminals and closed by and attached to hereinafter appear. 30 the movable inner terminal to move therewith The socket member 2 principally consists of a toward the other end of the outer sleeve when tubular member 0f Wet DIOCeSS DOICelain, 01 the fusible element fuses. other suitable insulation, finished with a choco- A further object of my invention is to secure late glaze inside and out, and formed externally the fuse tube of a replaceable fuse link to one and intermediate its ends with two longitudinal 35 of a pair of relatively infusible terminals that spaced annular shoulders 5 5, between which are interconnected by fusible means, the other engage a split clamp 6. The clamp 6 is gripped terminal being sudably mounted within the fuse tightly about the body of the Socket 2 by a pair tub and unattached thereto. of bolts 'I extending through the sides of the 40 Still another object of my invention is to so clamp and engaged in Suitable nuts. One end of 40 construct the terminals of a replaceable fuse one side of the clamp 6 is extended and bent link that they may be deformed onto the fusible laterally to form a mounting tongue 8 Which 1S means interconnecting them. secured, for example, to the cross-arm I 0 of a A further object of my invention is to provide transformer pole or other point of disconnection for deforming one end of a terminal of a fuse by a bracket i. The holes through the Clamp 45 link onto a fusible element and a strain element part having the extending tongue 8 for the bolts or a fusible element alone and the other end 'I are preferably of square or polygonal form, Onto n f1eXble lead Comprising a plurality of and the bolts 1 preferably have corresponding strands of wire. square or polygonal portions engaging therein so Another object of my invention is to provide to prevent turning of the bolts in drawing up a silver fusible element in the present combinathe nuts. tion with the outer insulating sleeve and the The bracket II comprises four bracket parts inner insulating sleeve closely surrounding the I2, I3, I4 and I5. The part I2 ts the top of inner fuse terminals and closed by and attached the cross-arm I0 and has one end turned down to the movable inner terminal to move therewith along one side of the cross-arm. The part I5 55 toward the other end of the outer sleeve when fits against the opposite side of the cross-arm the fusible element fuses, whereby the silver and has yits lower portion onset or turned in fusible element is excluded from toovfree access beneath the bottom of the cross-arm. These to atmosphere. parts I2 and I5 have outwardly directed flanges I6 at their opposite ends. The parts I3 and Il 50 Further features and advantages and a conare interchangeable. The tongue 8 of the clamp 6 is swiveled between the extending end of the clamp part I4 and the flange on the adjacent end of the clamp part I3 upon a carriage bolt I1 which may be loosened to permit the cutout to be adjusted or swung to any angular position about the axis of the bolt I1, and tightened to clamp the cutout firmly in the position in which it is arranged. Carriage bolts I8 pass through the other pairs of spaced anges I6 for gripping the bracket tightly in place about the cross-arm I0. The socket member 2 is provided with suitable openings I9 and 20 to permit insertion of suitable line conductors to connections to the main control terminals therein in a manner fully described in my copending application, of which this is a division.

The fuse construction which I employ in my improved cutout is of the type described and claimed in my copending application Serial No. 671,660, filed May 18, 1933, and embodies a number of improvements in this type of fuse, as will hereinafter appear. This fuse clears minor or low current faults as positively as it clears more severe faults, as during a short circuit or heavy overload; its operation does not require explosive action, but in all cases the instantaneous collapse of the coil spring establishes a definite and suicient gap regardless of the amount of fault current. At thesame time short circuit and heavy overload faults are cleared without attendant danger that excessive pressure may cause destruction of the equipment. Heavy pressures occur within a small cylinder or chamber which is a part ofthe fuse link, and the tube proper is freely vented. Pre-heating or corrosion does not deteriorate and result in causeless operation of the fuse element, because this element is made of a pure metal which has proved to be vastly superior from the standpoint of its resistance to corrosion and its ability to operate at a higher percentage of its melting point without deterioration. It is not necessary to replace unblown fuse links after an over-current has blown other fuses in the same circuit, and a permanent and exceptional accuracy of fuse ratings is obtained. The time delay characteristic and short arcing time make the fuse exceptionally suitable for selective operation.

Referring particularly to Figures 2 and 3, the universal fuse link shown generally at 69 is enclosed in a tube designated 10 in its entirety which is preferably formed of grade X rolled Bakelite or phenol condensation product tubing 1| rolled on a fiber liner 12, or other suitable insulating material. At its upper end the outer diameter of the tube 1| is reduced at 13 to receive the upper ferrule 14 which is preferably formed of brass rod or other suitable material. At its upper end 65 the ferrule 14 is threaded for mounting in a suitably threaded aperture in the plug member 4, Figure 1. At its lower end. the outer diameter of the tube 1| is reduced at 15 to receive the lower ferrule 16 which is preferably formed of cast hard bronze or other suitable material. 'I'he extreme ends of the tube 1| are preferably chamfered slightly, as illustrated. The upper reduced end of the tube 1I is provided with an external groove 11, and the inner surface of the ferrule 14 is provided with a downwardly aring or generally conical groove 18 which, when the ferrule is in place upon the reduced upper end ofthe tube with its lower end in engagement with the shoulder 19, registers with the groove 11. A conical spring snap ring 80, rformed of seamless brass tubing (half hard) and split at 8|, engages the shoulder at the upper end of the groove 11 and the shoulder at the lower end of the groove 18, and anchors or secures the ferrule 14 rmly to the tube without screws or the like and at lower cost, and in a small space. lAt the same time, an exceptionally strong joint is provided between the tube and ferrule. In assembling these parts, the snap ring 80 may be applied to the groove 11 before placing the ferrule upon the tube. Then as the ferrule is passed down over the upper end of the tube, the larger lower end of the snap ring may be pressed into the groove 11 to permit passage of the ferrule into place, whereupon the ring 80 will spring out into the conical groove 18 and, by its engagement with the shoulder at the lower end of this groove, will anchor the ferrule iirmly in place upon the tube. The lower reduced end 15 of the tube 1| is provided with a groove 82 similar to the groove 11, and the inner surface of the ferrule 16 is provided with an upwardly flaring or generally conical groove 83 corresponding with the groove 18. A spring snap ring 84 split at 85, similar to the ring B0, and engaging in the grooves 82 and 83 in a similar manner, locks or secures the lower ferrule 16 rmly in place upon the lower reduced end of the tube 1|. This ring 84 and the ferrule 16 may be applied in the manner described in connection with the ring 80 and the ferrule 14, and the upper end of the ferrule 16 engages the annular shoulder 86 vat the upper end of the lower reduced portion 15.

The upper cable terminal and spring fastener 90, which is preferably formed of brass rod or other suitable material, is flanged or headed to form a button 9| which seats upon the upper end of the ferrule 14. The reduced portion 92, depending integrally from'the button 9|, has a helical groove into which the upper few turns of the coiled fuse-spring 93 are threaded, and an integral depending socket 94 receives the upper end of the stranded cable 95 and is pressed secure-` ly thereon. 'I'he stranded cable 95, which is preferably of stranded copper or other suitable material, is connected to the lower cable terminal and spring fastener 96 by rigidly securing it in the socketed part 91 thereof, as by inserting it in the socket and pressing or flattening the socket firmly thereon and into secure engagement therewith. The terminal and fastener 96 has a helical groove for threaded engagement with the lower few turns of the spring 93.

The terminal 96 is knurled externally at 98 and is tapped or threaded internally at 99 for receiving the threaded upper end of the upper fuse terminal of the fuse link 69, which terminal is formed of copper or other suitable or preferred material. The lower fuse terminal |0| of the fuse link 69 is formed of similar material, and this terminal and the terminal |00 are connected by a strain wire or tensile element |02 arranged to bear the mechanical stress. 'I'he upper end of the wire |02 is inserted in a socket or opening in the lower `end ofthe terminal |00, and is secured rigidly in place as by punching at |04 the stock of the terminal |00 into firm binding engagement with the wire, or by flattening the socket firmly upon the wire. The lower end of the wire |02 is inserted in a socket or opening in the terminal |0I, and is secured rigidly in place as by punching at the stock of this terminal into firm binding engagement with the wire, or, as before, by flattening the socket upon the wire. The fuse I I0 preferably is of silver, and the strain wire |02 preferably is of nickel chromium wire. 'I'he upper end of the fuse wire I l0 is inserted in an opening in the terminal and is secured rmly in place therein as by punching the adjacent side of the terminal into firm engagement therewith, or flattening the same thereon. The lower end of the wire H0 is inserted in an opening in the terminal |0| and may be secured firmly in place therein as by punching the adjacent sides of the terminal |0| into firm engagement therewith, or flattening the same thereon. Intermediate its ends, the fuse wire H0 is coiled about the strain wire |02.

It has been found that silver, as used in devices of this sort, has unusual characteristics. First, there is not an appreciable absorption of oxygen until temperatures close to the melting point are reached, and this oxygen is released again upon a slight drop in temperature. Even if there is some oxidation, the oxide has conducting properties similar to those of silver. Also, it has been found that under certain circumstances, silver will form undesirable compounds with other elements on blowing. In some of the experiments and tests made on fuses under various conditions, the blowing of the fuse appeared to be more violent than the power current would seem to account for.

This applicant, by a combination of the silver fusible element with the outer insulating sleeve and the inner insulating sleeve closely surrounding the inner fuse terminals excludes the silver fusible element from too free access to atmosphere, and maintains this exclusion upon blowing of the fuse. The highly advantageous character of the silver, namely, that it appears to produce less metallic vapor for a given rating; that it will retain its form up to a very high temperature; that it will not oxidize and change its rating for the oxide appears to be conductive, and that the time-current characteristic, which is an all-important factor under certain circumstances, can readily be maintained over long periods, is utilized. Furthermore, because of the provision of the terminals |00 and |0| in relatively massive form and, therefore, relatively infusible, as compared to the strain wire |02 and the fuse wire H0, the arc formed on blowing is confined substantially only to the space between these terminals, and consequently it is possible to more readily extinguish it.

The fuse wire ||0 of silver or other fusible.

conducting material, preferably whose oxide is a conductor, and the comparatively high resistance strain wire |02, both are completely enclosed and shielded from atmosphere, gases and moisture, by a tube H2 formed of fiber or other insulating material. 'Ihe upper end of the tube |I2 closely surrounds the upper fuse terminal |00 beneath the integral ange lll thereon, and is shrunk or crimped at I5 into the annular groove I6 to close the upper end of the tube ||2 against access of atmosphere to the silver fusible element and to secure the tube ||2 to the upper fuse terminal |00. The lower end of the tube ||2 passes freely over and closely surrounds the lower fuse terminal |0| and extends down to a position beneath this terminal and from the lower end of the fuse tube, as illustrated in Figure 3. The tube |I2 offers no impairment to free separation of the terminals |00 and |0| upon blowing of the fuse, yet, at the same time, it is rigid throughout its length and by its engagement at the upper endy with the terminal |00 and its cooperation .with the terminal |0| holds the terminals |00 and |0I rigidly against relative lateral movement, such as otherwise might result in movement or even crimping or twisting of the fuse wire ||0 and/or strain wire |02.

For the purpose of providing electrical connection to the lower terminal |0| of the fuse link v39 and setting the fuse and holding the same set, the lower end of the terminal I0| is provided with an extension formed of stranded conducting cable or other suitable material which forms a part of the fuse link 69 and is replaceable therewith. Several strands of copper cable, preferably tinned, or depth cable are employed in the illustrated embodiment, although this may, of course, vary widely. The upper end of this cable is inserted in a socket H8 on the lower end of the terminal I 0I, and this socket is flattened into firm engagement with the cable to secure the same therein. Within its length, the stranded cable is provided with a conical bushing I20-securely anchored in position upon the cable as by flattening the upper end of the bushing into firm engagement withthe cable at |2I. The lower conical part of the bushing |20 is engageable with a clip |22 to hold the fuse in set position. The clip |22 is formed by the outstanding and slightly hooked sides |23 of a conical socket |24 in the lower end of a tongue |25 formed integral with the lower ferrule 16 and depending therefrom, the integral sides |23 rounding or being. hooked outwardly from the base of the tongue |25 at the lower extremities of the sides |26 which round outwardly from the depressed portion |21.

The extension or stranded cable |I1 constitutes a tail extension which, when the spring 93 is retracted, extends down below the lower end of the fuse casing 'l0 and ferrule 16 so that it may be gripped conveniently for setting the fuse and placing the spring 93 under tension. With the spring 93 retracted, the setting of the fuse is accomplished by grasping the downwardly extending tail extension and pulling the same downwardly against the tension of the spring 93 until the conical bushing |20 is positioned below or clear of the bottom of the clip |22. The cable above the bushing |20 is then passed through the open side of the clip |22. Then, upon releasing the tail extension the spring 93 draws the bushing up firmly against the conical socket |24 in the clip |22, and this cooperation of the bushing |20 with the hooked sides of the clip holds the spring 93 extended and the fuse in set position. A circuit is thus established from the ferrule 14, upper cable terminal and spring fastener 90, stranded conductor 95, lower cable terminal and spring fastener 96, upper fuse terminal |00, fuse wire H0 and strain wire |02 in parallel, lower fuse terminal |0I, stranded conductor |I'|, bushing |20, and clip |22, to the lower ferrule 16 through the tongue |25. The tail extension below the conical bushing |20 may be cut off or otherwise removed after the fuse is set, as above described, but it is to be understood that this removal of a part or all of the tail eX- tension for setting the fuse or anchoring the lowering end of the fuse element assembly tothe lowerferrule on the fuse casing is not necessary within the scope of the present invention.

The construction shown and described herein is a spring type expulsion fuse. A surrounding sectionalized cork (not shown) and an outer enclosing tube of waterproof paper, gummed paper or the like, may be placed around the insulating tube |I2 as in my copending application Serial' ferrule 14. 16v

No. 671,660, now Patent No. 2,091,453, and this tube and the fuse link 69 may be modified in accordance therewith. In the case of an ordinary air-type expulsion fuse as disclosed in my said copending application, Serial No. 671,660, now Patent. No. 2,091,453, or in the case of the drop out type ejector cutout box of my copending application Serial No. 734,262, filed July 9, 1934, the spring and cable assembly 93, 95 and the associated terminals 90 and 96 may be removed by unscrewing the upper fuse terminal |00 of the fuse link 69 from the tapped or threaded socket in the lower end of the terminal 96. Then, by merely threading the upper end of the upper fuse terminal |00 into. a button |35 of suitable conducting material and flanged radially as shown in Figure 4, the same fuse link 69 is adapted for use with the ordinary air type expulsion fuse or with the drop out type ejector cutout box of my rcopending application, Serial No. 734,262.V This makes the fuse link 69 universal, in that it is adapted for use in different types of fuse housings or mountings.

The cylinder or tube ||2, which encloses the fuse element 0 and strain wire |02 of the fuse link 69, in addition to confining the arc in a very small space and preventing charring and metal spattering on the tube liner 12, and with its upper end closed to prevent too free access of atmosphere to the fusible link and maintain the closure upon fusing of the link, serves, by its downward extension below the ferrule 16 to perform the additional function of giving a visual indication when the fuse has been blown. Since the upper end of the tube or cylinder ||2 is secured to the upper fuse terminal |00 by crimping or shrinking into the groove ||6, it will be apparent that this tube I2 will move upwardly with the upper fuse terminal |00 and lower cable terminal and spring fastener 96 upon retraction of the spring 93. Consequently, the absence of the projection of the lower end of the tube |2 down from the bottom |40 of the'ferrule 16 gives a visual indication that the fuse has blown and the spring 93 retracted. However, the presence of the lower end of the tube l2 beneath the bottom |40 of the ferrule 16 indicates visually that the fuse has not blown and that the device is in operative relation. The lower end of the tube I2, the absence or presence of which gives this indication, is indicated at |42 in Figure 3.

The current of my invention is set in operative relation by assembling the fuse parts as shown in Figures 2 and 3, and then screwing the upper threaded end 65 of the upper ferrule 14 into the plug member 4. The plug 4 is then inserted into the socket 2, as illustrated in Figure 1.

The upper ferrule 14 is provided with an annular groove |50 having spaced ventv openings |52 therein that are normally closed by a pressure band |54 which is held in place by a coiled lock spring |56. On blowing of the fuse link 69, Suilicient pressure is generated within the tube 'l0 to lift the band |54 and force the spring |56 outwardly into a suitable groove in the socket member 2, thereby locking the tube and plug 4 to the socket member 2, as is more fully described in my copending application of which this application is a division.

To renew the fuse link or reload the device, the plug 4 is rst withdrawn from the socket 2. The fuse tube 10 is then removed from the plug 4 by unscrewing the threaded upper end 65 of the 'I'he spring and flexible lead assembly are withdrawn from the tube 10 and then the remains of the blown fuse link 69 are then removed by unscrewing the upper fuse terminal |00 from the cable terminal and spring fastener 96, whereupon a new fuse link 69 is applied by screwing the upper terminal thereof into the tapped opening in the terminal 96. The fuse link 69 and spring and cable assembly are then inserted into the fuse tube 10 through the upper end of the upper ferrule 14. The tail extension ||1 is then grasped and drawn downwardly against the tension of the spring 93 and the conical bushing |20 engaged in the clip |22, whereupon the excess tail extension below the bushing |20 may be cut off with a pair of pliers.

While I have shown and described my invention with reference to the particular details of construction of one embodiment, it is to be understood that the invention may appear in different forms and with numerous modifications and variations such as will suggest themselves to one skilled in the art, and it is to be further understood that I consider all such modifications and variations to be included within the scope of my invention.

I claim:

1. In a device of the class described, a movable system including a movable terminal member, a coil spring normally under tension and connected to said terminal member, a fuse link having a fuse terminal for connection with the terminal of said'movable system, and a second fuse terminal, a rigid tubular insulatingJ envelope secured to the fuse terminal for connection with the terminal of the movable system and `being movable therewith and fitting telescopically over the other fuse terminal, and a fusible element within said envelope, said tubular envelope being out of contact with the fusible element.

2. In combination, an outer sleeve, a pair of fuse terminals within said sleeve, a fusible link between said terminals, an inner sleeve closely surrounding said inner terminals and said fusible link and projecting from said outer sleeve, and means to retract the inner sleeve when the link is fused.

3. In a device of the class described, a fuse tube, a movable system within said tube including a movable terminal member, a coil spring normally under tension and connected to said terminal member, a fuse link having a fuse terminal for connection with the terminal of said movable system and a second fuse terminal, a rigid insulating envelope secured to the fuse ter-- minal for connection with the terminal of the movable system, said envelope fitting telescopically over the other fuse terminal and extending from the end of the fuse tube for indicating the condition of the fuse, and a fusible element with'- in said envelope.

4. In combination, a fuse tube, a movable system within said tube including a movable terminal and a coil spring normally under tension and connected to said terminal, a fuse link assembly for connection to said terminal, and means for connection to the movable system and projecting from the end of the fuse tube when the spring is under tension and retracted from the end of the fuse tube upon retraction of the spring to indicate the condition of the fuse.

5. In a fuse, an insulating outer sleeve having metallic ferrules constituting outer terminals, a pair of inner terminals within and adjacent one end of the outer sleeve and connected electrically with the outer terminals, one of said inner terminals being movable toward the other end of the sleeve, a fusible element between the inner terminals, and an inner sleeve of insulating material closely surrounding the inner terminals and the fusible element and closed by and attached to the movable inner terminal adapted to move therewith toward the other end of the outer sleeve when the fusible element fuses.

6. In a fuse, an insulating outer sleeve having metallic ferrules constituting outer terminals, apair of inner terminals within and adjacent one end of the outer sleeve and connected electrically with the outer terminals, one of said inner terminals being movable toward the other enel of the sleeve, a fusible element between the inner terminals, and an inner sleeve of insulating material closely surrounding the inner terminals and the fusible element and closed by and attached to the movable inner terminal adapted to move therewith toward the other end of the outer sleeve when the fusible element fuses, the other inner terminal being adapted for relative movement through the inner sleeve and out of the end thereof.

7. In a fuse, an insulating outer sleeve having metallic ferrules constituting outer terminals, a pair of' inner terminals within and adjacent one end of the outer sleeve and connected electrically with the outer terminals, one of said inner terminals being movable toward the other end of the sleeve, a fusible element between the inner terminals, an inner sleeve of insulating material closely surrounding the inner terminals and the fusible element and closed by and attached to the movable inner terminal, and a spring for retracting the movable terminal and the inner sleeve toward the other end of the outer sleeve when the fusible element fuses.

8. In a fuse, an insulating outer sleeve having metallic ferrules constituting outer terminals, a pair of inner terminals within and adjacent one end of the outer sleeve and connected electrically with the outer terminals, one of said inner terminals being movable toward the other end of the sleeve, a silver fuse link between the inner terminals, and an inner sleeve of insulating material closely surrounding the inner terminals and the fusible element and closed by and attached to the movable inner terminal adapted to move therewith toward the other end of the outer sleeve when the fusible element fuses.

9. In a fuse, an outer insulating member having a bore of relatively large diameter, an inner insulating member having a bore of relatively small diameter, terminals and a fusible element closely surrounded by the bore of the inner member, one terminal forming a permanent closure for one end of the bore of the inner insulating member, and means for moving said latter terminal and the inner insulating member when the fusible element fuses to lengthen the arc within the inner bore.

10. In a fuse, an outer insulating member having a bore of relatively large diameter, an inner insulating member having a bore of relatively small diameter, terminals and a fusible element closely surrounded by the bore of the inner member, one terminal forming a permanent closure for one end of the bore of the inner insulating member, and means for moving said latter terminal and the inner insulating member when the fusible element fuses to lengthen the arc rst within the bore of the inner insulating member and later within the bore of the outer insulating member.

11. In a fuse, an outer insulating member having a bore of relatively large diameter, an inner insulating member having a bore of relatively small diameter, terminals and a fusible element closely surrounded by the bore of the inner member, one terminal forming a permanent closure for one end of the bore of the inner insulating member, and means for moving said latter terminal and the inner insulating member when the fusible element fuses to lengthen the arc irst within the bore of the inner insulating member and later within the bore of the outer insulating member, one terminal and the adjacent end of the arc being closely surrounded by the relatively small diameter bore of the inner insulating member throughout the duration of the arc.

l2. In a fuse, an outer insulating member having a bore of relatively large diameter, an inner insulating member having a bore of relatively small diameter, terminals and a silver fuse link closely surrounded by the bore of the inner member, one terminal forming a permanent closure for one end of the bore of the inner insulating member, and means for moving said latter terminal and the inner insulating member when the fusible element fuses to lengthen the arc Within the inner bore.

13. An article of manufacture comprising a renewable unit for a fuse comprising a pair of fuse terminals, a stress sustaining link connecting said terminals, a fusible link connected at its ends to said terminals and having its intermediate portion formed into a coil and independent of said sustaining link, and an insulating sleeve closely surrounding the fuse terminals but being out of contact with the fusible link and the stress sustaining link and being closed by and attached to one of said inner terminals.

14. A renewable unit for a fuse comprising a pair of fuse terminals, stress sustaining and fusible links connecting said terminals, an insulating sleeve closely surrounding the fuse terminals and the stress sustaining and fusible links and closed by and attached to one of said terminals, and means interchangeably attachable to said latter terminal for adapting the unit for use in an ordinary air expulsion fuse and in a retraction fuse having means for moving one of said terminals.

15. In combination, an outer sleeve, a pair of fuse terminals within said sleeve, a fusible link between said terminals, and an inner sleeve closely surrounding said inner terminals and said fusible link and projecting from said outer sleeve, said inner sleeve being adapted to be drawn into said outer sleeve upon fusing of said link.

16. In a fuse, an insulating outer sleeve having metallic ferrules constituting outer terminals, a pair of inner terminals within said sleeve, a

fusible element between the inner terminals, and

an inner sleeve of insulating material closely surrounding the inner terminals and the fusible element and closed by and attached to one of said inner terminals, said inner sleeve being appreciably longer than the distance between said inner terminals and relatively short with respect to the outer sleeve.

17. In a fuse, an insulating outer sleeve having ferrules constituting outer terminals, a pair of fuse terminals lwithin said sleeve, a fusible element between said terminals, an inner sleeve closely surrounding said terminals and said element for accumulation of pressure upon blowing of the fuse, one yfuse terminal being movable within the inner sleeve fer elongation of the arc within said sleeve and movable from the inner sleeve to release the pressure and permit an outward ow of gases from the sleeve, said inner sleeve and the other terminal being movable further to elongate the arc.

18. A renewable fuse link comprising a first terminal having a threaded stud at one end, an arcing tip at the other end, and having an intermediate groove, a second terminal comprising an arcing tip at one end and a flexible lead attached to the other end, a fusible element, said arcing tips having means for mechanically gripping the ends of said element and a fiber tube surrounding said terminals and the element and being anchored at one end to said groove, said exible lead extending out of the open end of the tube.

19. The combination with claim 18 of a stress sustaining link connected between the arcing tips to relieve the fusible element of tension, said tube being out of contact with the element and the stress sustaining link, said second terminal tting loosely in the bore of the tube, whereby it tends to be expelled upon the generation of gases by the arc.

20. In a fusible current interrupter, a link comprising the combination of a current sensitive element adapted to be fused upon the passage therethrough of current in excess of a. predetermined value for a predetermined period of time, a. relatively thin walled tubular en-y velope of substantially uniform bore surround-"v ing the said element but being out of contact therewith, rigid metal terminals for the element, said terminals being of a current carrying capacity high enough to remain unfused upon the passage therethrough of any value of current within the capacity for which the interrupter is designed, said tubular envelope extending beyond the ends of the element and telescoping with said terminals, one end of said tube being closed by the corresponding one terminal and the other terminal substantially lling and being slidable in the bore of the tubular envelope, said latter terminal being adapted to be moved out of the envelope upon fusing of said element.

21. The link of claim 20 further characterized by a coupling head forming a rigid extension of the said one terminal for supporting one end of the link, and a flexible lead joined to and extending from said other terminal.

22. A terminal for a fuseglink comprising a rodlikesection having a tubular socket on each end, a iiexible lead disposed in one socket, said one socket being collapsed upon the iiexible lead to connect the same mechanically and electrically, a fusible element disposed in the other socket, said other socket being collapsed upon the fusible element to form a good electrical and mechanical connection, said terminal being of sumcient mass and conductivity to serve as a. barrier for the arc between the fusible element and the flexible lead.

23. The combination of claim 22 wherein the collapsed sockets are of a maximum transverse dimension substantially not in excess of the maximum diameter of the rodlike section.

I24. The terminal of claim 22 wherein the second socket has localized indentations of the walls of the socket upon the element to produce localized deformations of the element and the socket to improve the mechanical and electrical connection of the same.

25. A terminal for a fuse link comprising a central rodlike section having sockets upon each end, a exible lead disposed in one socket, the walls of the socket being deformed to make connection mechanically and electrically between the terminal and the lead, a fusible element and a strain .element disposed in the second socket, said second socket having the walls thereof collapsed upon the fusible element and the strain element, the walls of the second socket being 1ocally deformed to produce localized deformation of the socket and the element to improve the mechanical and electrical connection of the elements with said second socket.

26. The method of joining a rodlike terminal to, a fusible element which comprises forming a socket in one end of the rodlike terminal of an internal diameter substantially in excess of the diameter of the fusible element, introducing the fusible element into the socket, collapsing. the walls of said socket into contact with the sides of the fusible element, and applying localized pressure to a wall of the socket adjacent the fusible element, whereby a localized deformation of the socket and the element is produced to improve the mechanical and electrical bond between the terminal and the element.

27. A fuse link comprising an outer cylindrical terminal member and an inner cylindrical terminal member, said members having sockets facing towards eachother, a strain wire and a silver fuse wire embraced within and held by said sockets, a small bore thin-walled ber tube anchored to and closed by the outer terminal and relatively closely embracing the inner terminal but permitting free expulsion of the inner terminal from the adjacent end of the tube, said inner terminal constituting a piston-like obstruction to the escape of gases generated by the arc produced upon melting of the fusible element, and a exible lead secured to the inner terminal member and extending out of the open end of the tube.

28. A replaceable fuse link comprising a fuse tube, a fuse terminal at one end of said fuse tube, a single flexible lead comprising a plurality of stranded conductors extending out of the other end of said fuse tube, a silver fusible element interconnecting said fuse terminal and said ilexible lead, and a strain'element also interconnecting said fuse terminal and said flexible lead.

29. A replaceable fuse link comprising a fuse tube, a fuse terminal at one end of said fuse tube, a flexible lead extending out of the other end of said fuse tube, a strain element interconnecting said fuse terminal and said flexible lead, and a silver fusible element surrounding said strain element and also interconnecting said fuse terminal and said flexible lead.

30. In a fuse link, a terminal having a knurled portion, and a sleeve of insulation vfrictionally engaging said knurled portion, said knurling extending longitudinally of said terminal and sleeve to prevent relative rotation thereof.

31. In a fuse link, a terminal having a peripheral groove and a knurled portion, and a sleeve of insulation frictionally engaging said knurled portion, said knurling extending longitudinally of said terminal and sleeve to prevent relative rotation thereof and said sleeve interfltting with said groove to prevent relative longitudinal movement between it and said terminal.

32. In a fuse link, a terminal having an attaching portion at one end, a fuse element receiving portion at the other end and a peripheral groove and a knurled portion intermediate said ends, and a fiber tube frictionally engaging said knurled portion and shrunk into said groove for preventing relative rotary and axial movement between said terminal and said sleeve.

33. In a fuse, in combination, an insulating outer sleeve, a pair of relatively infusible terminals within said insulating outer sleeve, a fuse wire interconnecting said relatively infusible terminals, and an inner sleeve of insulating material surrounding said relatively infusible terminals and attached to one of them, said inner sleeve of insulating material being appreciably longer than the distance between said relatively infusible terminals and relatively short with respect to said insulating outer sleeve.

34. A renewable fuse link comprising,in combination; a first terminal having support means at one end, an arcing tip at the other end, and a groove intermediate said ends; a second terminal comprising an arcing tip at one end and a flexible lead attached to the other end, a fusible element, said arcing tips having means for mechanically gripping the ends of said fusible element, and an insulating tube surrounding said first and second terminals and said fusible element and being anchored at one end in said groove, said flexible lead extending out of the other end of said insulating tube.

35. In a fuse link having a fusible element, a terminal for said fusible element having a current carrying capacity such that it remains substantially unfused upon flow of any value of current within the intended interrupting capacity of said fusible element, one end of said terminal being formed to receive one end of said fusible element and being collapsed and locally deformed thereon to provide mechanical and electrical connections thereto, and means at the other end of said terminal for connecting it in an electric circuit.

36. A replaceable fuse link comprising, in cornbination, a fuse tube, a relatively infusible terminal at one end of said fuse tube, a flexible lead extending out of the other end of said fuse tube, a strain element interconnecting said relatively infusible terminal and said flexible lead, and a fusible element surrounding said strain element and also interconnecting said relatively infusible terminal and said flexible lead.

37. A fuse link comprising, in combination, a ilrst terminal having an attaching portion at one end and a fusible element receiving portion at the other end, a tubular insulating member interiltting with said first terminal and hel-d substantially in alinement therewith, a second terminal movably mounted entirely within said tubular insulating member a`nd having a fusible element receiving portion at one end and a conductor receiving portion at the other end, a fusible element interconnecting said fusible element receiving portions, and a stranded conductor connected to said conductor receiving portion of said second terminal and extending out of the other end of said tubular insulating member.

38. A fuse link comprising, in combination; a. first terminal having an attaching portion at one end, a fusible element receiving portion at the other end, and a peripheral groove and a knurled portion intermediate its ends; a tubular insulating member at one end frictionally engaging said knurled portion and interfltting with said groove; a second terminal movably mounted in said tubular insulating member and having a fusible element receiving portion at one end and a conductor receiving portion at the other end; and a fusible element interconnecting said fusible element receiving portions.

39. A fuse link comprising, in combination.; a first terminal having an attaching portion at one end, a fusible element receiving portion at the other end, and a peripheral groove and a knurled portion intermediate its ends; a tubular insulating member at one end frictionally engaging said knurled portion and interfltting with said groove; a second terminal movably mounted entirely within said tubular insulating member and having a fusible element receiving portion at one end and a conductor receiving portion at the other end; a fusible element interconnecting said fusible element receiving portions, and a stranded conductor connected to said conductor receiving portion of said second terminal and extending out of the other end of said tubular insulating member.

40. A renewable fuse link for mounting in different types of fuse housings comprising, a tubular member of insulating material, a. fusible section in said tubular member, a flexible terminal connected to one end of said fusible section and extending out of one end of said tubular member, a rigid terminal connected to the other end of said fusible section and extending out of the other end of said tubular member, a xed head on the outer end cf said rigid terminal, and a removable head surrounding said fixed head.

4l. A renewable fuse link for mounting in different types of fuse housings comprising, a fuse tube, a terminal at one end of said fuse tube, a flexible lead extending out of the other end of said fuse tube, fusible means interconnecting said terminal and said flexible lead, and means interchangeably cooperating with said terminal for adapting said fuse link for use in said different types of fuse housings.

42. A renewable fuse link for mounting in different types of fuse housings comprising, a fuse tube, a terminal at one end of said fuse tube, a flexible lead extending out of the other end of said fuse tube, fusible means interconnecting said terminal and said flexible lead, and means interchangeably attachable to said terminal for adapting said fuse link for use in an ordinary air expulsion fuse housing and in a retraction fuse housing having means for moving said terminal.

43. A renewable fuse link for mounting in different types of fuse housings comprising, a fuse tube, a terminal at one end of said fuse tube, a flexible lead extending out of the other end of said fuse tube, fusible means interconnecting said terminal and said flexible lead, threaded means on said terminal, and an adapter threaded for engagement with said threaded means and having a flanged head for adapting said fuse link for use in different types of fuse housings.

44. A renewable fuse link for mounting in different types of fuse housings comprising, a fuse tube, a relatively infusible terminal attached to one end of said fuse tube, a flexible lead extending out of the other end of said fuse tube, fusible means interconnecting said terminal and said flexible lead, a threaded stud on said terminal, and an adapter threaded at one end for attachment to said threaded stud and having a flanged head at the other end for adapting said fuse link for use in an ordinary air expulsion fuse housing and in a retraction fuse housing having means for moving said terminal.

45. A unitary fuse link structure adapted to be positioned in a fuse cartridge, said link structure comprising a tubular element, a conducting element carried bythe upper end of said tubular element for engagement with a terminal, conducting means extending from the other end of said tubular element and of sufficient length to extend out of the fuse cartridge for connection to a second terminal, and a fusible element electrically connecting said conducting means and said' first mentioned conducting element, said conducting means being unattached to the tubular element and movable relative to the lower end thereof after rupture of the fusible element.

46. A unitary fuse link structure adapted to be positioned in a fuse cartridge, said link structure comprising a tubular element, a conducting element carried by the upper end of said tubular element for engagement with a terminal, conducting means extending from the other end of said tubular element and of sulicient length to extend out of the fuse cartridge for connection to a second terminal, a fusible element electrically connecting said conducting means and said first mentioned conducting element, and resilient means tensioning said fusible element and acting to quickly increase the gap between the parts of the fusible element when the latter is ruptured by overload current, said conducting means being unattached to the tubular element and movable relative to the lower end thereof by the action of the resilient means after rupture of the fusible element.

47. A unitary fuse link structure adapted to be positioned in a fuse cartridge, said link structure comprising a tubular element, a conducting element carried by the upper end of said tubular element for engagement with a terminal, conducting means extending from the other end of said tubular element and of sufficient length to extend out of the fuse cartridge for connection to a second terminal, a fusible element electrically connecting said conducting means and said first mentioned conducting element, and coil spring means disposed within the fuse cartridge and externally of said tubular element and acting to quickly increase the gap between the parts of the fusible element when the latter is ruptured by overload current, said conducting means being unattached to the tubular element and movable relative to the lower end thereof by the action of said coil spring means after rupture of the fusible element.

48. In a fuse, an insulating outer sleeve having outer terminals adjacent its ends, a pair of inner terminals within said sleeve, one of said inner terminals being connected to one of said outer terminals and the other inner terminal including a iiexible lead for connection to the other outer terminal, a fusible element interconnecting said inner terminals, an inner sleeve of insulating material mounted on said one inner terminal and extending over said fusible element and said other inner terminal, said inner sleeve being appreciably longer than said fusible element and relatively short with respect to said outer sleeve, and spring means within said outer sleeve tensioning said fusible element and acting to quickly increase the gap between the parts of the fusible element when the latter is ruptured by overload current.

49. In a fuse, an insulating outer sleeve having outer terminals adjacent its ends, a pair of inner terminals within said sleeve, one of said inner terminals` being connected to one of said outer terminals and the other inner terminal including a flexible lead for connection to the other outer terminal, a fusible element interconnecting said inner terminals, an inner sleeve of insulating material mounted on said one inner terminal and extending over said fusible element and said other inner terminal, said inner sleeve being appreciably longer than said fusible element and relatively short with respect to said outer sleeve, and coil spring means disposed within said outer sleeve and externally of said inner sleeve and acting to quickly increase the gap between the parts of the fusible element when the latter is ruptured by overload current.

50. A replaceable fuse link comprising, a pair of relatively infusible terminals, fusible means interconnecting said terminals, and a sleeve of insulating material surrounding said terminals and said fusible means and being appreciably longer than the distance between said terminals.

51. A replaceable fuse link comprising, a sleeve of insulating material, a pair of relatively infusible terminals, one of said terminals being disposed at one end of said sleeve and the other being slidable therein, a fusible element interconnecting said terminals, and a flexible lead connected to the other of said terminals and extending out of the other end of said sleeve.

52. A replaceable fuse link comprising, in combination, a fuse tube. a relatively infusible terminal at one end of said fuse tube, a conductor extending out of the other end of laid fuse tube including a relatively infusible terminal and a flexible lead, a strain element interconnecting said terminals, and a fusible element surrounding said strain element and also interconnecting said terminals.

53. A replaceable fuse link comprising, a sleeve of insulating material, a pair of relatively infusible terminals, one of said terminals being disposed at one end of said sleeve and the other v being readily movable therein, a fusible element interconnecting said terminals, and conducting means including a flexible lead constituting an extension of the other of said terminals and extending out of the other end of said sleeve.

54. A replaceable fuse link comprising, in combination, a pair of relatively infusible terminals, fusible means interconnecting said terminals, a sleeve of insulating material surrounding said terminals and said fusible means and being appreciably longer than the distance between said terminals, one of said terminals being located at one end of said sleeve and the other being freely movable out of its other end, and conducting means connected to said other terminal and extending out of said other end of saidvsleeve.

55. A replaceable fuse link comprising, in combination, a fuse tube, a relatively infusible terminal at one end of said fuse tube, a conductor extending out of the other end of said fuse tube including a relatively infusible terminal and a. flexible lead, and strain andfusible elements lnterconnecting said terminals, said fuse tube being appreciably longer than the distance between said terminals and said conductor being freely movable out of said fuse tube on blowing of said strain and fusible elements.

ALLAN RAMSEY.

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