US2750470A - Electric fuse - Google Patents

Description

June 12, 1956 J. R. MCBRIDE ELECTRIC FUSE Filed Jan. 28, 1954 INVENTOR JOSEPH ROBERT MQBRIDE BY m@ ATTORNEY assumo conducting element 28 by any suitable means is a conductor 30 which in Figure 1 is shown extending out of the lower extremity of the fuse tube 25. Conductor 30 is electrically connected to the terminal element 22 by suitable means such as a clamping screw (not shown).

From the above description it will be understood that terminal element 22 is retained in the position shown in Figure 1 by means of conducting means in the form of the conductor 30 and parts associated therewith. Furthermore, it will be understood that contact brush 18 is constructed so as to bias the contact element 19 into firm contact making engagement with the contacting portion 22A of terminal element 22.

Secured to the upper extremity of the conducting element 27 is a conductor 31 which in Figure 1 is shown secured by means of the clamping screw 32 to the terminal element 33. Terminal element 33 is provided at its lefthand extremity with a contacting portion 33A against which the contact element is biased by means of the brush 9. Terminal element 33 is pivotally mounted by the pin 34 to a metallic link 35 which in turn isV connected by pin 36 to the collar 37 mounted by means of the screw 38 to the fuse tube 25. Thus it will be understood that the conductor 31 and parts associated therewith serve to maintain the parts associated with terminal element 33 in the positions represented in Figure 1. The structure just described which forms the upper terminal assembly of the cutout is more fully described and claimed in U. S. Patent No. 2,172,143 granted September S, 1939, upon an application of George N. Lemmon and assigned to the assignee of this invention.

Upon the occurrence of a fault or overload condition, the fusible element comprising elements 27-29 is ruptured and the terminal element 22 rotates about trunnions 21 in a clockwise direction. This motion of terminal element 22 allows the pivot 23 to move in a clockwise direction about the trunnions 21 thereby to move the fuse tube downwardly. Simultaneously, the contacting portion 33A is released from the latch 12A formed within the sleet hood 12 thereby to allow the fuse tube and the collar 37 together with the parts associated therewith to swing in a clockwise direction about the trunnions 21. Simultaneously, the terminal element 33 is free to disengage the upper end of the fuse tube 25, all as explained more fully in the above-mentioned Patent No. 2,172,143.

The internal construction details of the fuse tube 25 and parts associated therewith can be best seen from Figure 2.A Tube 25 is of conventional construction and is prof vided with an inner lining element 39 formed of fiber or other suitable insulating material.

The fuse link as constructed in accordance with this invention and as shown in Figure 2 comprises a tubular element 40 of insulating material in which the conductt ing elements 27, 28, and solder connection 29 are disposed. The upper extremity of tubular element 40 is closed by closure element 41 which is securely affixed to the conductor 31 as by crimping or other suitable means and which is also securely atlixed within the tubular element 40 by cement or other suitable means as indicated at 42. While I have found it desirable to construct element 41 with a flange 43, it is obvious that this flange is not an essential feature.

It is Well-known that certain materials in the presence of an electric arc are capable of emitting gas, steam, or other suitable substances which are of value in eecting the prompt extinguishment of the arc. Such a substance is boric acid powder 44 which is shown in Figure 2 as being disposed Within the tubular element 40 and surrounding the fusible element comprising the parts 27 29. Thus when a fault or `overload condition develops, the soldered connection 29 melts to establish an Aarc in close proximity to the boric acid powder 44 thereby 4 to initiate the rapid emission of arc quenching gas which aids in interrupting the arc in known manner.

As already explained, it is possible for a fault or overload condition to develop which may rapidly increase the temperature of conducting elements 27 and 28 to an excessive value without appreciably increasing the temperature of the soldered joint 29 until an appreciable time later. Should a circuit interrupter such as an electric circuit breaker eiect the interruption of current through the fuse link, it is possible for the soldered joint 29 to melt after the cessation of liow of current through the fusible element. Should this occur there would be no arc established within the region of the boric acid powder 44. If no arc is established, no pressure will be established within the tubular element 40. In cutouts using fuse links which are sealed against moisture with a seal which is unyielding, this condition probably would not result in performance of a dropout operation by the cutout and there would be no visible indication that the fuse link had been ruptured.

In order to insure that the dropout operation will occur, yieldable sealing means for one extremity of the fuse link is provided in accordance with this invention. For example, the lower extremity of the tubular element 40 is closed by means of a viscous fluid generally designated -by the numeral 4S together with a retaining element in the form of sleeve 46. One suitable material for use as viscous fluid 45 is silicone paste and preferably the retaining sleeve 46 is provided with a flange 47 for engaging the lower extremity of the tubular element 40.

For the purpose of maintaining the retaining element 46 and the paste 45 in their tube closing relationship under normal conditions, means are provided for interrelating sleeve 46 with the fusible element comprising parts 27-29. As is indicated in Figure 2 this means may be in the form of the collar 48 secured by crimping or other means to the conductor 30. Obviously, collar 48 at its upper extremity is in engagement with the lower portion of sleeve 46.

From the description above it will be understood that the viscous uid 45 and retaining sleeve 46 not only constitute a yieldable Weathertight sealing means for the lower extremity of tubular element 40, these parts in addition are particularly well adapted for retaining the boric acid powder 44 in position within the tubular element 40. Thus, if the junction between the closure member 41 and the upper extremity of tubular element 40 is also made weathertight, the fuse link is rendered entirely free of the adverse effects of changing weather conditions, and since the viscous fluid 45 and sleeve 46 are yieldable once the fusible element is melted it is clear that the fuse link allows the cutout to drop out under the action of gravity and the bias of brushes 9 and 18 even though no arc is established by the fusible element so that a visible indication of the fact that the fusible element is melted is always obtained.

Should a fault or overload condition develop, the boric acid powder 44 effects a rapid generation of arc quenching gas so as rapidly to elevate the pressure within tubular element 40 thereby to effect a prompt piston action of the conductor 30 and parts associated therewith and increase the arc length at a high rate, and also to rapidly scavenge the ionized products of arcing from the interior of tubular element 40.

While a particular embodiment of the invention has been shown and described, I do not wish to be limited thereto and intend in the appended claims to cover all changes and modifications as fall Within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. An electric fuse comprising a tubular element of insulating material,y a fusible element disposed Within said tubular element, a conductor extending out of at least one. end .ofsaid tubular element and electrically connectedwithsaid fusible element, theoutside. of saidcon.- ductor being substantially smaller than the inside of-said tube todelinea space therebetween2 andV yieldable sealing means including a. viscous duid and a retaining element normally disposed in said spacev in proximity to said conductor for rendering said one end of said tubular element weathertight, said retaining element being effective normal-ly to aidin holding said fluid within said tube and being releasable'in coordination-vJi-ththe rupture of said fusible element. l l

2. An electric fuse comprising. a, tubular enclosing structure of insulating material, a fusible element disposed withinsaid tubular structure, a powder inproximity to said fusible element for emitting.- arc extinguishingy iiuid in response to the establishmentof an are by said fusible element, and closure means forming a seal for each end of said enclosing structure, the closure. mea-ns for at least one end of said.. enclosing structure. comprising a viscous iiuid to aid in retaining said powder within said structure and arranged to yield so as. tol relieve the pressure developed within said structure due to the'formation` of an arc therein.`

3. An electric fuse comprising atubular. enclosing structure of insulating material, a fusible element disposed within said` tubular structure,.a powderin proximity to said. fusible element for emitting arc extinguishingfluid in response to the establishment of an are by said. fusible element, andy closure means. forming a. seal for eachend of'said. enclosing structure, the. closure. means for at least one end of said enclosing structure comprising a retaining element releasably maintained in its tube closing posi tion, and viscous material within said tubular structure, said retaining element being effective normally to aid in maintaining said viscous material Within said tubular structure.

4. An electric fuse comprising a tubular enclosing structure of insulating material, a fusible element disposed within said tubular structure, a first conductor connected with said fusible element and extending out of one end of said tubular enclosing structure, means secured to said one end of said enclosing structure and to said first conductor for securing said first conductor in position and for closing said one end of said enclosing structure, a second conductor connected with said fusible element and extending out of the other end of said enclosing structure, said conductors and said fusible element constituting a series circuit through said structure, a viscous uid in said other end of said enclosing structure, and a retaining sleeve mounted within said other end of said enclosing structure with said second conductor extending therethrough and operably related therewith to aid in holding said viscous iiuid within said enclosing structure, said viscous iiuid and said retaining sleeve constituting closure means for said other end of said enclosing structure, said closure means being yieldable in response to rupture of said fusible element.

5. An electric fuse comprising a tubular enclosing structure of insulating material, a fusible element disposed within said tubular structure, a first conductor connected with said fusible element and extending out of one end of said tubular enclosing structure, means secured to said one end of said enclosing structure and to said first conductor for securing said first conductor in position and for closing said one end of said enclosing structure, a second conductor connected with said fusible element and extending out of the other end of said enclosing structure, said conductors and said fusible element constituting a series circuit through said structure, n viscous iiuid in said other end of said enclosing structure, and a retaining sleeve mounted within said other end of said enclosing structure with said second conductor extending therethrough to aid in holding said viscous fluid within said enclosing structure, said viscous uid and said retaining sleeve constituting yieldable closure meansv for saidother endof, said. enclosing. structure, and holdingl means for securingsaid retainingsleeve. in position.. within saidotherend of said enclosing-structure, said holding means being releasablefin response. to. rupture. of said fusible element.

6. An electric fuse. comprising atubularenclosing structure of insulating. material, a fusible element disposed within said. tubular structure, a first conductor connected with said fusible element and` extending out of one.. end of said tubular enclosing structure, means secured. to said one end of said enclosing structure and to said first .conductor for securing said first conductor in position and for` closing said: one end of said enclosing structure, a second conductor connected with said fusible element and extending out of the other end of said enclosing strucf ture, said conductors and'said fusibleelement constituting a series circuit through said structure, a-fpowd'er within said. structure for emitting an arcextinguishing fluid in response to the. establishment'ofi an arc by saidA fusible element, a viscousfluid. insaid other'en-d of said enclosing structure, and a retaining sleeve. mounted within said4 other end of said enclosing structure. with said second conductor extending therethrough to aid.' in holding said viscousfluid Within saidenclosing structure, .said viscous fluid andsaid retaining sleeve constituting yieldable. closure means. for said other end of said enclosing structure.

7'. An electric fuse. comprising an-insulatingitube; an elongatedA fusible. element disposed within said. tube, a first conductor connected with one end of saidfusible element and' extending out of one end of saidtube, means for securing said one conductor in position relative to said tube, a second conductor connected with the other end of said fusible element and extending out of the other end of said tube, the outside of said second conductor being appreciably smaller than the inside of said tube to define a space therebetween, viscous fluid means in the space between said second conductor and said tube and comprising yieldable sealing means for said other end of said tube, and means operably related with said fusible element for normally maintaining said iiuid within said tube.

8. An electric fuse comprising an insulating tube, an elongated fusible element disposed within said tube, boric acid powder inside said tube and in proximity to said fusible element, means for securing one end of said fusible element in position relative to said tube, means forming an external electrical connection for said one end of said fusible element, a conductor connected with the other end of said fusible element and extending out of the other end of said tube, the outside of said conductor being smaller than the inside of said tube to define a space therebetween, and viscous liuid sealing means in said space for retaining said powder in said tube and for normally rendering said other end of said tube weathertight, said fluid means being yieldable to relieve pressure formed within said tube due to the establishment of an arc therein by said fusible element.

9. An electric fuse comprising an insulating tube, an elongated fusible element disposed within said tube, means for securing one end of said fusible element in position relative to said tube, means forming an external electrical connection for said one end of said fusible element, a conductor connected with the other end of said fusible element and extending out of the other end of said tube, the outside of said conductor being smaller than the inside of said tube to define a space therebetween, silicone paste in said space, said paste being effective to render said other end of said tube weathertight and to relieve pressure formed within said tube due to the establishment of an arc therein by said fusible element, and means operably related with said fusible element for normally maintaining said paste within said tube.

l0. An electric fuse comprising an insulating tube, an elongated fusible element disposed within said tube, boric acid powder inside said tube and in proximity to aveogto said fusible element, means for securing one end of said fusible element in position relative to said tube, means forming an external electrical connection for said one end of said fusible element, a conductor connected with the other end of said fusible clement and extending out of the other end of said tube, the outside of said conductor being smaller than the inside of said tube to define a space therebetween, and silicone paste in said space for yieldably retaining said powder within said tube and for normally rendering said other end of said tube weathertight.

11. An electric fuse comprising an insulating tube, an elongated fusible element disposed within said tube, means for securing one end of said fusible element in position relative to said tube, means forming an external electrical connection for said one end of said fusible element, a conductor connected with the other end of said fusible element and extending out of the other end of said tube, the outside of said conductor being smaller than the inside of said tube to define a space therebetween, a retaining element disposed in said space and operably related with said conductor, and viscous fluid means in said space, said retaining element normally being effective to aid in holding said viscous fluid means within said space and being releasable in response to rupture of said fusible element.

12. An electric fuse comprising an insulating tube, an elongated fusible element `disposed within said tube, boric acid powder inside said tube and in proximity to said fusible element, means for securing one end of said fusible element in position relative to said tube, means forming an external electrical connection for said one end of said fusible element, a conductor connected with the other end of said fusible element and extending out of the other end of said tube, the outside of said conductor being smaller than the inside of said tube to define a space therebetween, and silicone paste in said space, said paste being effective normally to render said other end of said tube weathertight and to maintain said powder therein, and a retaining sleeve releasably maintained within said other end of said tube normally to aid in holding said paste within said space, the normal tension applied between said two external connections by associated mounting equipment being effective to eject said retaining sleeve and at least a portion of said paste from within said tube upon melting of said fusible element thereby to establish an exhaust path to atmosphere from within said tube.

References Cited in the le of this patent UNITED STATES PATENTS Re. 14,897 Schweitzer et al June 22, 197.0 871,851 Young Nov. 26, 1907 1,092,805 Weissberg Apr. 7, 1914 1,614,646 Bowie Jan. 18, 1927 1,952,734 Ten Brook Mar. 27, 1934 2,218,912 Huber Oct. 22, 1940 2,376,809 Rawlins et al May 22, 1945 2,572,901 Yonkers Oct. 30, 1951 2,650,283 Von Hoorn Aug. 25, 1953 2,651,695 Baker Sept. 8, 1953

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