US2135164A - High tension expulsion fuse - Google Patents

Description

2% mix INVENTOR. ARNOLD E BROCK rill/WWII Ill/ll ll 1 Filed Jan. 11, 1937 A E BROCK HIGH TENSION EXPULSION FUSE Nov 1, 1938 Patented Nov. 1, 1938 UNITED STATES PATENT OFFICE HIGH TENSION EXPULSION FUSE fornia Application January 11, 1937, Serial No. 120,007

7 Claims.

The present invention relates generally to fuses, and more particularly to a new and improved construction for high tension expulsion fuses which will greatly increase the current interrupting range thereof.

An object of the invention is to provide a high tension expulsion fuse which will successfully operate to interrupt a circuit over a wider range of currents than has heretofore been possible with fuses of this character.

Another object of the invention is to provide a fuse of the expulsion type which will operate successfully to interrupt a circuit at its normal capacity rating and also withstand and successfully interrupt currents far in excess of its rated capacity.

Another object of the invention is to provide in an expulsion fuse of the character described, a new and novel form of gas pressure relief means which will become operative upon the occurrence of an excessive gas pressure within the fuse containing chamber.

In the construction of expulsion fuses of the character contemplated by this invention, it is necessary, in order that the fuses successfully operate at low and normal current values, to provide a constricted or small bore chamber through which the fusible element is extended, and fur ther, to disrupt any are formed within said chamber upon a fusion of the fuse element, it is desirable that the walls of this constricted chamber be formed or a more or less combustible material which will produce a deionizing gas to assist in the interruption of any are established therein. While a fuse of this construction has been found to operate in a very successful manner in the interruption of currents up to the normal rated capacity of the fuse, such a construction is open to the objection that when the fuse is subjected to a high overload current or a short circuit, the

pressures generated often burst the fuse containing chamber.

The above described characteristics are obtained, in accordance with the present invention, by confining the fuse in an enclosing body member having a constricted or small bore chamber of fibre or other deionizing gas producing material, and the objections thereto are overcome by providing an auxiliary gas outlet which is adapted to become operative to discharge gas from the fuse containing chamber upon the occurrence of an excessive pressure such as might be caused by the interruption of a high overload current are within said fuse enclosing body member.

For a better understanding of the present invention reference should be had to the accompanying drawing, wherein there is shown by way of illustration and not of limitation, preferred embodiments thereof.

In the drawing, wherein like numerals refer to like parts throughout the several views;

Figure 1 is a side view of a complete fuse of the type contemplated by this invention,

Figure 2 is a vertical sectional view of the fuse shown in Figure l, with the central insulating portion broken away to foreshorten this figure of the drawing,

Figure 3 is a fragmentary view of a fuse similar to the fuse shown in Figure 2 of the drawing, having two pressure responsive vents,

Figure 4 is a horizontal sectional View of the fuse taken along line IVIV of Figure 3, looking in direction of arrows, and

Figure 5 is a horizontal sectional view of the fuse taken along line V-V of Figure 2, looking in direction of arrows.

For the purpose of illustrating the invention there is shown in the drawing a fuse of the expulsion type having an open end through which the gases generated upon a blowing of the fuse are expelled to extinguish the arc and interrupt the circuit, as is well understood by those skilled in the art.

As shown, the fuse comprises a body member, designated generally by the numeral IE], to one end of which there is securely attached a ferrule if having a removable cap 32 for the insertion of a renewable fuse link 53. At the other end of the body member ii) there is securely attached an open ended ferrule i4 having a fuse link terminal it with a clamping screw If). The ferrules H and i l have a contact making portion which is adapted to be inserted in suitable fuse supporting clips to which the conductors of the protected circuit are connected. In some installations these fuse clips will be adapted to hold the fuse structure until it is removed from the circuit by an operator, and in other installations it is contemplated that the fuse illustrated may be used with the so-called drop-out type of fuse support which will permit the fuse to swing out of engagement with at least one of the contact clips upon a melting of the fuse link l3 due to an overload current.

Upon referring to Figures 2 and 3 of the drawing it will be seen that the fuse link l3 has an enlarged buttonlike head which is adapted to be secured at its upper end in good contact making engagement with the end of the ferrule H by forming member :8 th is preferably of horn fibre. In practice the Join fibre lining member i8 is tightly fitted within the outer refractory tubular n ember El extends throughout the entire length thereof. Wh this construction it will be seen that the hOli fibre lining member i 8 provides a constricted chamber through which the fuse 13 will extend in close proxlrm't" with the walls thereof, and w le horn fibre is specified as a preferred material, it is to be understood that this lining member !8 may be formed of any material which, upon volatilization or burning, is capable of producing a deionizing gas that will create a high pressure and expel the lower end of the fuse link from the chamber and at the time extinguish any are formed therein. This operation of the fuse is in the nature of an explosion in which the pressures generated are more or less proportional to the current flowing in the are up to its point of interruption, and conseq iently it often happens, upon a high current overload or a short circuit on the protected line, that unless means are provided to relieve this pressure, the fuse body forming member is subjected to a bursting strain. In the past, to avoid the building up of a bursting pressure with in the body forming member or" the fuse, it has been the practice, where high currents interrupted, to enlarge the size of the bore through which the fuse extends. This provides for a free escape of the gases and thus prevents the building of a bursting pressure within the fuse body forming memb r, but resort to this exped ent n cessarily locates the fuse link 53 more remote in the deionizing gas producing lining l8 and thus reduces the gas generating capacity of the fuse to such an extent that it will not always operate successfully at its normal or low current values.

To overcome the above disadvantages and at the same time provide a constricted fuse link containing chamber of small diameter, the ferrule l l, as shown in Figures 2 and 4 of the drawing and in accordance with one embodiment of t-is invention, is provided with a pressure relief outlet 59 through which the generated gases produced by an are within the fuse enclosing chamber are permitted to escape before the pressure reaches a value which might burst the body forming member id. In its preferred form the pressure relief outlet is has a shouldered and threaded portion into which a closure disc 29 and a tubular securing plug El are adapted to be inserted. The closure disc 253 may be made of any material, such as fish paper or from lead sheet of any desired thickness, depending upon the pressures involved.

In a modified form of the invention, the ferrule ll may be provided with more than one of these pressure relief outlets I9, as illustrated in Figure 3 of the drawing. Where more than one pressure outlet 59 is provided, the closure discs 20 thereof may be constructed so as to be responsive to different pressures and/or they may be made of different materials. In the latter event, for example, a fish paper closure disc 20 might be made responsiveto a predetermined definite pressure, and a lead closure disc 20 might be used in conjunction therewith, which is responsive to both heat and pressure, the heat generated by a sustained arc serving to weaken the lead disc and eventually cause it to rupture and provide an additional outlet for the escape of gases from within the fuse link enclosing chamber. In practice it is contemplated that these pressure relief outlet closure discs 29 will be proportioned so as not to rupture below a pressure which is necessary to a successful and efficient interruption of the are at the normal rated current capacity for which the fuse link is designed. In order to provide a plurality of pressure relief outlets having different pressure response characteristics, it is also contemplated that the pressure relief outlets l9 might be made of different diameters, and that these outlets of different diameters might be likewise provided with closure discs 20 of the same or different materials.

Figures 4 and 5 of the drawing more clearly illustrate the close proximity of the fuse link I3 with the lining member l8 of the body forming member 58, and the latter figure also illustrates more detail the terminal l5 and its clamping screw l6, which serve, on one form of fuse, as a connection for the looped lower end of the fuse link.

In conclusion it may be added that the present invention, in addition to providing a constricted enclosing chamber with a pressure relief means which will prevent bursting of the fuse enclosing body member I0 upon the generation of an excessive pressure therein, also by a location of the pressure relief means at the upper end of the fuse, greatly reduces overstrain upon the fuse supporting clips, prolongs their life when they are of the drop-out character and prevents a complete dislodgment of the fuse from its support, as now often happens in the interruption of an are under short circuit and heavy overload current conditions.

While I have, for the sake of clearness and in order to disclose the invention so that the same can be readily understood, described and illustrated specific devices and arrangements, I desire to have it understood that this invention is not limited to the specific means disclosed, but may be embodied in other ways that will suggest themselves to persons skilled in the art. It is believed that this invention is new and it is desired to claim it so that all such changes as come within the scope of the appended claims are to be considered as part of this invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is- I. In an expulsion fuse of the character described, the combination of a body forming member of insulating material having a normally closed contact making ferrule at one end and an open ended ferrule at its other end through which the arc disrupting gases are discharged under normal operating conditions, fuse link connecting means carried by each of said ferrules for attaching a fusible link therebetween, a fusible link extending through said body forming member and connected to said ferrules, said normally closed contact making ferrule having a gas discharging aperture formed therein, and means for closing said aperture operable under abnormal operating conditions to open said aperture and form an auxiliary gas discharge outlet upon the occurrence of a predetermined excessive gas pressure within said body forming member, said aperture and its closing means being positioned upon the normally closed contact making ferrule remote from the fuse link connecting means thereof, whereby the fuse link may be replaced after a normal operation of the fuse Without disturbing said means for closing said aperture.

2. In an expulsion fuse of the character described, the combination of an insulating open ended body forming member having a normally closed contact making ferrule at one end thereof and an open ended contact making ferrule at the other end thereof through which the arc disrupting gases are normally discharged, a removable cap means for closing the end of said normally closed ferrule and securing one end of a fusible link thereto, means carried by said open ended ferrule for securing the other end of said fusible link thereto with the link extending out through and around the open end thereof, and a pressure responsive vent located in the side of said normally closed ferrule independently of said removable cap means at the end of said ferrule adapted to open and permit a further discharge of gas from said body forming member at this point in the event of an excessive back pressure of gas during the interruption of are within said body forming member.

3. In a high tension expulsion fuse, the combination of a body forming member of highly refractory insulating material, contact engaging ferrules secured upon the ends of said body forming member, a lining of combustible material within said body member having deionizing gas producing properties, a fusible element connected to said ferrules extending through said body member and in close relation with said lining, one of said ferrules being open at its end to provide for the free discharge of the deionizing gas from said body member upon a normal fusion of said fusible link and the other of said ferrules having an auxiliary gas discharge outlet in one side thereof adjacent the arcing path of the fusible element, and a disc of heat sensitive rupturable material secured over said auxiliary gas discharge outlet adapted in the event of a heating and an excessive gas pressure to rupture and open said auxiliary gas discharge outlet during the interruption of an abnormal are within said body forming member.

4. In an expulsion fuse of the character described, the combination of a cylindrical body forming member of insulating material with a deionizing gas producing lining forming a confined expulsion chamber for a fuse element, an open ended contact engaging ferrule providing an elongated gas discharge outlet for a diameter greater than that of the expulsion chamber at one end of said body forming member, a second contact engaging ferrule secured to and forming a closure at the other end of said body forming member, means carried by said ferrules for securing the ends of a fuse thereto with the fuse extending through said expulsion chamber, said latter ferrule having an auxiliary gas discharge outlet in one side thereof adjacent the arcing path of the fusible element, and a closure means secured over said outlet adapted to rupture in the event of an excessive heat and gas pressure Within said expulsion chamber.

5. In an expulsion fuse of the character described, the combination of a cylindrical body forming member of insulating material having deionizing gas producing properties and forming a confined expulsion chamber for a fuse element, an open ended contact engaging ferrule providing an elongated open gas discharge outlet at one end of said body forming member, a second contact engaging ferrule secured to and forming a closure at the other end of said body forming member, means carried by said ferrules for secur ing the opposite ends of a fuse element thereto with the fuse element extending through said expulsion chamber, said latter ferrule having a plurality of gas discharge outlets of different diameters formed therein, and a fragile closure means secured over each of said outlets.

6. In an expulsion fuse of the character described, the combination of a cylindrical body forming member of insulating material having deionizing gas producing properties and forming a confined expulsion chamber for a fuse element, an open ended contact engaging ferrule providing an open gas discharge outlet at one end of said body forming member, a second contact engaging ferrule secured to and forming a closure at the other end of said body forming member, means carried by said ferrules for securing the ends of a fuse element thereto with the fuse element extending through said expulsion chamber, said latter ferrule having a plurality of gas discharge outlets formed therein, and a fragile closure means secured over each of said outlets, each of said fragile closure means being adapted to rupture at a different pressure than the other.

'7. In an expulsion fuse of the character described, the combination of a cylindrical body forming member of insulating material having deionizing gas producing properties and forming a confined expulsion chamber for a fuse element, an open ended contact engaging ferrule providing an elongated open gas discharge outlet of a diameter greater than that of the expulsion chamber at one end of said body forming member, a second contact engaging ferrule secured to and forming a closure at the other end of said body forming member, means carried by each of said ferrules for securing the ends of a fuse thereto with the fuse element disposed in said expulsion chamber, said latter ferrule having a gas discharge outlet formed in the side thereof remote from its end and adjacent the arcing path of the fusible element, and a fragile heat and pressure responsive closure disc disposed over and closing said outlet.

ARNOLD E. BROCK.

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