US2686240A - Line fuse - Google Patents

Description

Aug. 10, 1954 J. c. RosE 2,686,240-

LINE FUSE Filed July 2l, 1950 55 .3/ gf 9 v 23 2 04, sa 5g 75@ f@ *T622 2'/ TTO/P/VEV.

Patented Aug. 10, 1954 LINE FUSE J ess C. Rose, North Holl J. G. McAlister, Inc.

poration of California Application July 21, 1950, Serial No. 175,062 8 Claims. (Cl. 20D-415.5)

This invention relates to a fused conductor connector, and more particularly to a connector between the free ends of two iiexible conductor cables, which is both a connector and a loadlimiting circuit interrupter.

While the'principles of'the'invention have application iny a Wide field' of electrical circuitsl of many different types it has particular application to conditions such` as obtain in moving picture and television studios; In these studies portable lights drawing currents of heavy amperageare used'. Insulatedflexible conductor cables lead from each lighting device to any, one of a number. of` conveniently located buss bars or other current distributors, each distributor supplying currentf'or anumber ofsuch lamps.

When, as `is usually the case, the source of` supply is froma center tapped'single phase, 220'volt, transformer secondary, or a 110-220 voltA three wire direct current source, the three power line wires are. connected to a three terminal distributor, to the outside. legs of which the-one wire of several of the two wire lamp cables vare connected in approximate balance, the returny wires of. the cables from allthevlamps being connected to the grounded middle leg. of4 they distributor. These connections for thesake of,` rapidity of operation are made at. the ends of` each ofx the wires of the cables byv terminal. clamps. The three feed wires to the distributor areY provided with circuit interrupters, either fuses or circuit breakers, of a size to protect the feeder lines from the load of allthe lamp connections supplied bythe distributor, but the protection oftheindividual lamps and individual lamp circuits fromv overloads caused by a1 short circuit in thelamp or between the two cable wires or otherwise, has presented a problem, of which this invention-provides a solution.

The problemi is made difficultv bythe conditions-in the studios. The lamp cables from the buss bar. or other distributor lie on the iioor or are strung around the studio in frequently changed locations, usually: in exposed positions wherer they are subject to trampling by vehicles and4 to other hardusage. If each lamp cable is ya single two wire line without distributing connections to other lamps between the distributor and the one lamp, a separate cablel is provided fbr each lamp; For proper overload protection of both the lamp and cable, the/expensive provision of a' numbery of individual fused outlets at each distributor becomes necessary in lieu of the customary rapidly operated' and convenient clamps;

ywood, Calif., assignor to Los Angeles, Calif., a cor- Since two single wire connections are made at the distributor for each lamp, it follows that if the system of terminal clamps is to be used, the logical place to fuse a lamp and lamp circuit is in the ho-t wire of the cable between the point at which it emerges from the cable and the terminal clamp which secures that wire to the buss bar terminal. The entire lamp circuit is then positively assured of overload protection.

This invention provides such a single wire combination connector and fuse for use close to the buss bar terminal. It is an object of the invention to provide a fused connector for a single flexible conductor, which shall be compact, readily operated, inexpensive of manufacture, capable of withstanding hardusage, and of simple construction.

It isanother object to provide such a connector, which shall be quickly and inexpensively re-fused.

It is another object to provide such a connector constructed for ready assembly and disassembly with two slidably joined parts, the conductors of the connector being incapable of making a conducting contact until the two parts are joined together to provide a completely enclosed chamber for the fuse.V This prevents the fuse from blowing, by reason of a pre-existing short circuit, as the two partsare being brought together, before they have moved toward each other sufficiently to enclose the fuse, eliminating any fire hazard or injury to persons from names blown outside the casing;

It is also an object of the invention toV provide a fused connector which will completely enclose the fuse in a substantially gas tight chamber, but provide forvslow escape of the gases, generated by the blowing of the fuse, over a baiiied course so as to prevent the jetting of llame into the ambient.

The invention is herein disclosed as embodied in a fused connector for use with illuminating equipment of moving picture and television studios, but the principles of the invention are applicable wherever overload protection is desired. Under different conditions, such protection may be conveniently associated with a line connector having utility other than as a mounting for the fuss` element. Or a fused connector embodying the principles of the invention may be usedv toprotect both sides of the circuit, providing two connections and two fuses in the same casing. The invention, therefore, is not limited to theparticular embodiment shown in the-drawings andA set forth in the following description, but embraces any device which comes within the spirit of the invention as defined in the appended claims.

In the drawings:

Figure l is a schematic View of a circuit embodying the invention. ln this view the connector is shown in top plan view.

Figure 2 is an exploded View of the connector, showing the two parts of the casing pulled apart for examination or replacement of the fuse element.

Figure 3 is a vertical sectional view of the connector showing some parts in side elevation.

Figure 4 is a fragmentary top plan view of one end of the connector with the adjacent part of the casing horizontally sectioned to show the terminal structure within the casing.

Figure 5 is a fragmentary sectional View showing an alternative form of spacer ring.

Figure 6 is a sectional view taken along the line 6 6 of Figure 3.

In Figure l there is shown schematically a simple circuit in which the fused connector of this invention is used. A conductor l l is connected to one of the terminals at one end of the buss bar l2 and to the connector i3 at its other end. Conductor lil leads from the connector E3 to a lamp indicated diagrammatically at i5 and is sheathed in the cable IS with a return conductor lli which connectsthe lamp i5 with the center terminal of the buss bar, completing a standard l le volt lamp circuit. The ends of conductors i i and It are usually equipped with terminal clamps by which they may be rapidly connected or disconnected to the buss bar terminals. Conductors ill and IE5 at the lamp end of the cable itl are plugged into a suitable terminal receptor on the lamp structure.

The fused connector le comprises a two part casing Il made of insulating material and two terminal structures i8 and i9, the structure i8 being rigidly mounted and secured in the left- Yward casing part 2t, and the structure i9 being rigidly mounted and secured in the rightward casing part 2 l The casing is in the general form of a hollow closed end cylinder, providing a cylindrical interior chamber in which the terminal structures, including the fuse element 22, are mechanically protected, are insulated electrically from surrounding objects outside the casing, and by which the fuse is prevented when it blows from setting re to iniiammable objects or injuring the studio personnel. The left end of the casing shell has secured to it by the retaining screws 23 an insulating end closure plug 25 which has a central aperture 25 for the reception of the insulated conductor ld. The right end of the casing shell similarly has secured to it by retaining screws 2B an insulating end closure plug 2l which has a central aperture 28 for the reception of the insulated conductor I i. The inner end of each closure plug is of reduced diameter to provide an annular recess over which the cylindrical shell of the casing fits, giving the casing a smoothly contoured cylindrical exterior surface. The closure plugs are rounded at their outer ends, this feature and the smooth exterior surface of the shell enabling the connector to be dragged over the studio iioor and other surfaces without danger of being caught and torn loose from the conductors.

The rightward part 3Q of the shell has a telescopically sliding connecting joint at 3l with the rightward part 32. The outside diametersof the parts are the same. The rightward part 32 has an inwardly projecting skirt 33, providing a shoulder 3', against which the rightward end part of the shell abuts when the two parts are pushed into home position. rIhe retaining screw 35 holds them immovably in this position.

The leftward terminal structure i8 is permanently and rigidly mounted on the leftward part 2!) of the casing and when the two casing parts are pulled apart at the joint 3l, this terminal structure stays intact in leftward casing part 20. This terminal structure comprises a socket member 3e of brass or other conducting material which is formed with a central recess 3l on its left end into which the wire core of the conductor Il! is soldered, and with a ngered socket 38 on its right end for the reception of the contact pin 39 of the rightward terminal structure. The leftward terminal structure is completed by the ring fill, preferably of insulating material, which is fastened to the socket member 3e by the screw i I, this ring being in turn secured to the casing shell part 3Q.

The rightward terminal structure l@ comprises the contact pin member 42, the conductor connecting member d3, both of brass or the like, and a connecting bridge or dielectric frame member fill of insulating material, which is rigidly secured by the two bolts 5 to the two lugs 45 respectively on the juxtaposed ends of the pin member [i2 and cable connecting member lit. The fuse element lll is also secured or mounted by means of these bolts to the lugs 4i6 but on the side of the lugs opposite the bridge liti. The lugs are preferably threaded to receive the threaded Shanks of the bolts. Since each nut is disposed at the fuse end of its bolt and the bolts are held in position by reason of their threaded relation to the lugs, this mounting means permits the nuts to be removed and the fuse replaced without disassembling the pin member 52, the bridge or frame ifi and the conductor connecting member 63, simplifying and shortening the ire-fusing operatio'n.

The contact pin member i2 carries the contact pin 39 sized to snugly mate with the fingered socket 38. The socket iingers are rounded at their outer ends to facilitate the entry of the pin 39. The Contact pin member d2 is centered in the leftward shell part 20 by an insulating ring i9 secured to the pin member by a set screw 5d. This ring slides along the bore surface of the shell part 2t and is of a diameter to give it a slight clearance with respect to this bore surface for two reasons. The gases formed when the fuse blows may escape through this clearance to the chamber to the left of the ring, from which chamber the gases may slowly bleed through very small bleeder holes 52 in the casing shell around this chamber. The second advantage will appear from a consideration of the manner in which terminal structure I9 is mounted in the rightward shell part 2 i.

The conductor connecting member 43 is soldered to the wire core of the conductor ll in the same manner as has been described above for conductor hi. The member d3 has fastened to it an insulating ring 53 by the set screw 54, which in turn is secured to the rightward casing shell portion by the retaining screw 55. lt is then clear that the casing part 2| and the entire rightward terminal structure E@ from the contact pin 39 to the conductor l l, including the rings e9 and 53, the fuse Lil, bridge .te and conductor ll move bodily as a single substantially rigid sub-assembly, when the retaining screw 35 is removed and the two parts of the casing are pulled apart. Similarly the leftward terminal structure moves with itsrseveral associated parts asa single subassembly with the leftward casing partZQ.

These two subassemblies are related to each other in the same fashion as are the two parts of an ordinary plug and socket connector, and the addition of the fuse to one subassembly does not destroy the similarity. rhe use and fuse holder are secured to, and are removable with, the one end of the connector, a feature of construction which simplies the handling of the device when a fuse is to be replaced.

For easier fabrication and greater strength the retaining screw is of a length to be threaded into the ring 53. When the two parts of the connector are moved toward each other for inal assembly, the pin 3S and ring le are first to enter the shell of the leftward' part of the connector. The slight clearance between the ring 119 and the leftward shell facilitates the entry movement. Since the length 54 of the telescopic joint between the shell parts is greater than the distance 55 between the extreme left end of the contact pin 39 and the extreme right end of the fingered socket 38, the chamber surrounding the fuse between rings i9 and 53 will be formed and Iclosed prior to the making of contact between the ccntact pin and ngered socket. Ii, then, there is an undiscovered short which has not been corrected at the time the casing parts are being slid into their home position, the fuse will olow, but this will not happen until the fuse chamber has been formed, andthe danger of ire to surrounding objects' and injury to the operator are thereby eliminated.

Figure 5 shows a modification of the contact pin member. Instead of the single insulating ring 49 of Figure 3, a triple finned brass ring 55 is formed integrally with the remainder of the contact pin member. The rim surfaces of this triple ring 55 have a substantially close sliding t' with the bore surface of the casing. Small drilled bleeder holes 5l are then provided transversely through the rings, the holes in one ring being in staggered relation to the holes in the other rings, The rings then act like ba'le plates to break up jets of flame from a blown fuse, while yet permitting the passage of the gases from the disintegrated fuse through the rings to relieve the gas pressure in the inner fuse chamber.

The foregoing description of the fused connector reveals its uses, the manner in which it is re-fused and the advantages which come from its incorporation in an electrical circuit in the way described.

I claim:

1. A connector for connecting two insulated electrical conductors comp-rising: a rst rigidly and permanently assembled terminal fixture mechanically and electrically adapted to be secured to a free end of one of said conductors; a second rigidly and permanently assembled terminal xture adapted to be mechanically and electrically secured to the free end or" the other of said conductors; said nxtures each comprising a casing tube or" insulating material having an aperture at its outer end, and a conductor terminal structure permanently and rigidly secured within the tube, the casinfy tubes slidaoly telescopically engaging each other at their inner open ends, and providing a substantially gas tight envelope of insulating material for the terminal structures, said free ends1 oi the insulated conductors entering the casing tubes through the apertured outer ends thereof respectively for securement to the terminal structures respectively, the terminal structures having pin and socket electrical contacts for engagement with each other when the tubes are moved toward one an.- other into telescoped position, and one of the terminal structures having mounting means interposed in its conductance path for supporting an overload fuse; interengaging means on the tubes and terminal structures for constraining the fixtures and consequently the tubes and terminal structures to move in parallel straight lines, each with respect to the other, while they are being telescopically joined; and means for securely fastening the casing tubes together when telescopically joined.

2. A connector for use between the ends of two conductors, comprising: a two-part tubular casing, each part having a closed end, apertured to pass one of the conductors, and the two parts having a sliding gas-tight telescopic joint for holding them in relatively assembled position, a first terminal structure Xedly mounted and fastened in one casing part and arranged for securement to its associated conductor end, a contact element on said rst terminal structure, a second terminal structure having a rearward position xedly mounted and fastened in the other casing part, said second terminal structure having a forward portion including a contact element for making contact with said contact element on said nrst terminal structure when the two casing parts are assembled position, a dielectric frame member included in said second terminal structure connecting said forward and rearward portions, mounting means on said forward and rearward portions for connecting a fuse therebet reen, said other casing part having a length sufficient to enclose the entire length of space between said mounting means when the two casing parts are assemble-fl, the two terminal structures being mounted in their respective casing parts at such positions therealong that when the casing parts are placed in the initial position of their sliding telescopic joint the contact of the second terminal structure is out of electrical Contact with the contact of the i'lrst terminal structure, and when the two casing parts are in the home position of their joint the contact element of the second terminal structure is in electrical contact with the contact or" the first terminal structure.

3. A connector for use between the ends of two conductors, comprising: a two-part tubular casing, each part having a closed end, apertured to pass one of the conductors, and the two parts having a sliding gas-tight telescopic joint for holding them in relatively hired assembled position, a nrst terminal structure xedly mounted and fastened in one casing part and arranged for securement to its associated conductor end, a contact element on said rst terminal structure, a second terminal structure having a rearward position fixedly mounted and fastened in the other casing part, said second terminal structure having a forward portion including a contact element for making contact with said contact element on said nrst terminal structure when the two casing parts are in assembled position, a dielectric frame member included in said second terminal structure connecting said forward and rearward positions, mounting means at said forward and rearward positions for connecting a fuse therebetween, said terminal structures including annular spacers rigidly related to the terminal structures and extending outwardly to the bore surface of the casing, the nrst terminal structure having a spacer intermediate its connection to its associated conductor end and its place of contact with the second terminal structure, and the second terminal structure having one spacer adjacent its contact element and the other spacer adjacent its connection with its associated conductor end, whereby a substantially gas-tight chamber is provided for the contacting connection between the two terminal structures, and another substantially gas-tight chamber is provided for the space between said mounting means.

4. The combination dened in claim 3, in which transverse gas bleeder holes are formed in the one spacer of the second terminal structure, and gas bleeder holes are provided in the casing between the spacer of the rst terminal structure and the one spacer of the second terminal structure.

5. The combination defined in claim 3, in which the one spacer of the second terminal structure has a plurality of proximately adjacent, spaced, parallel ring-like walls, and in which transverse gas bleeder holes are formed in each of said walls, the holes in one wall being staggered with respect to the holes in an adjoining wall, whereby when the fuse blows iiame will not pass through the said parallel walls in single straight jets.

6. The combination defined in claim 5, in which further gas bleeder holes is provided in the casing between the spacer of the first terminal structure and the one spacer of the second terminal structure.

7. The combination dened in claim 3, in which the casing is of an insulating material, and the ends thereof are centrally formed with the said apertures for passage of the conductor ends, and the said terminal structures are each provided with a socket at its extreme outer end for soldering the associated conductor end.

8. The combination defined in claim 3, in which the one casing part extends inwardly a distance suicient to enclose the entire length of space between said mounting means when the two parts are in assembled relationship, and the second part has a telescopic gas-tight joint with the first part, the terminal structures being mounted in their respective casing parts at such positions along said casing parts that when the two casing parts are placed in the initial position of their telescopic joint the contact element of the second terminal structure is out of electrical Contact with the first terminal structure, and when the two casing parts are in the home position of their joint the contact element of the second terminal structure is in electrical Contact with the rst terminal structure, and in which the iirst terminal structure and the contact element of the second terminal structure are formed with pin and socket mating elements, the one spacer of the second terminal structure is of a diameter to slightly clear the bore surface of the casing, the other spacer of the second terminal structure engages the bore surface of the second casing part, both casing parts, including their ends are of dielectric material, the apertures for the conductor ends are disposed ycentrally of the casing ends, and the said terminal structures are each formed with sockets at their extreme outer ends for soldering their associated flexible conductor ends to said terminal structures.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,114,366 Knaui Oct. 20, 1914 1,604,373 Wyman Oct. 26, 1926 1,974,291 Reynolds Sept. 18, 1934 2,046,221 Thomas June 30, 1936 2,306,340 Lee Dec. 22, 1942 2,375,472 Hollins et al May 8, 1945

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