US2497257A - Tensioned fuse construction - Google Patents

Description

Feb. 14, 1950 H. M. CHASE TENSIONED FUSE CONSTRUCTION 2 Sheets-Sheet 1 Filed March 2, 1946 Feb. E45 1950 H, M CHASE 2,497,257

TENSIONED FUSE CONSTRUCTION Filed March 2, 1946 2 Sheets-Sheet 2 A l f .l A Ima will ,y

jizz/@mier Patented Feb. 14, 195) UNITED STATES PATENT OFFICE TENSION ED` FUSE CONSTRUCTION Harold M- Chase, Chicago, lllassigner to S t G Electricl Company, a corporation of Delaware Application March 2, 1946 Serial No. 651,559

(Cl. 200e-117) l Claims. 1

My invention relates, gener-ally, to fuses and it has particular relation to low current fuses, although it is not limited thereto.

My invention, as herein disclosed, constitutes an improvement over the fuse construction disclosed in Patent No. 2,200,698., issued May 14, 1940, to Hugh A. Triplett and assigned to the assignee of this application. In this patent there is disclosed a fuse construction which is particularly adapted for use in protecting capacitors to which the current flow is relatively small and where the fault current likewise may be relatively small under certain conditions `and relatively great under other conditions.

The fuse there disclosed comprises, generally, ,Y

two parts connected in series circuit relation. One part comprises a resistor' in the form ci' a coil of tungsten wire which is embedded in a filling of marble dust. T is resistance element has the property of substantially increasing its resistance in the event that it is heated to a rc1- atively high temperature as takes place on the flow thereto oi relatively high fault current. The other section comprises a fuse wire of relatively small cross section which is arranged to be melt.- ed or fused on iiow thereto of relatively small fault current.

The construction of the fuse ls such that the fuse wire always blows whether the fault current is small or large. In the event that the fault current is relatively small the tungsten resistor remains unaffected. However, when a relatively large fault current flows, the tungsten resistor is heated thereby and it reacts with the marble dust to provide in the circuit a high resistance path which serves to limit the flow of fault current. The action takes place rapidly, the fiow of fault current being interrupted usually within one-half cycle of the alternating current.

On the ow of low fault current, difculty has been encountered in obtaining suiiiciently rapid terminal separation and elongation of the arc so as to effect satisfactory circuit interruption. Because of this a low current arc may hang on for several cycles and may cause substantial damage not only to the fuse itself, which is of no particular consequence, but the disturbance may extend 'to adjacent apparatus which is undesirable and should be avoided.

In fuses of this type only limited space is available for the mechanism which is used to extend and extinguish the low fault current arc. The situation is further complicated by the necessity of providing a relatively inexpensive construction for this apparatus since, after the fuse 2 blows, it is usually completely discarded and replaced with an entirely new fuse.

Accordingly, an object of my invention, generally stated, is to provide a, fuse for low current operation which shall be simple and ehicient and which may be readily and economically manufactured.

Another object is to provide forv translating a relatively short throw of a member released for movement on blowing of the fuse into a relatively great movement to elongate and thereby extinguish the arc incident thereto.

A further object is to provide for retrieving a iiexible conductor in a fuse to extend and extinguish the arc incident to operation thereof as a result of a relatively small movement of an operating mechanism.

Still another object is to Wrap the flexible conductor around a. rotatable drum that is bodily movable endwise of the fuse for rotating the drum by externally applied torque. i

A still further object is to cause rotation of the drum as a result of its translatory movement by unwinding therefrom a flexible tension member, one end of which is anchored to the fuse structure.

Another object is to anchor the flexible tension member to the drum and to provide good electrical connection between it and the flexible conductor of the fuse and with the associated fuse terminal.

Other objects of my invention will, in part, be obvious and in part appear hereinafter. I 4 A My invention is disclosed in the embodiments thereof shown in the accompanying drawings and it comprises the features of construction, combination of elements and arrangement'` ofparts which will be exemplied in the constructions hereinafter Set forth and the scope of the anplication of which will be indicated in the appended claims. I A

For a more complete understanding of the nature and scope of my invention reference, may be had to the following detailed description tagen together with the. acfompanying drawings, in which:

Figure 1 is a View. in. Side elevation. of a fuse in which my invention is incorporated;

Figure 2 is a longitudinal sectional view of the fuse shown in Figure l;

Figure 3 is a View, similar to that in Figure 2 but taken at right angles thereto, showing only the upper end portion of the fuse;

Figure 4 is a view, similar to Figure 3, showing `end of the fuse tube.

the retrieving mechanism as it appears after the fuse is blown;

Figure 5 is a detail sectional view taken along the line 5-5 of Figure 2;

Figure 6 is a view, in side elevation, of the drum over which the flexible conductor is trained;

Figure 7 is a detail sectional view of the drum showing how the flexible conductor and the flexible tension member are anchored thereto; and

Figure 8 is a detail sectional view of a modication of the fuse construction shown in Figure 2 in which additional spring means is provided for pre-loading the fusible element.

Referring now particularly to Figures 1 and 2 of the drawings, it will be Vnoted that the reference character Il) designates, generally, a fuse of the character here under consideration in which the present invention is incorporated. 'Ihe fuse IU comprises a composite fuse tube formed by an outer shell Il of insulation, such as a .phenolic condensation product and a liner I2 of ber. At the ends of the fuse tube are positioned Screws I1 lfrom the bodies of the terminals I3 and I4 for `the purpose of holding the same in place.

It will be noted that the central portion I9 of the-terminal I3 forms a closure for the upper Reference will be made hereinafter to this closure in connection with VIV.the operation of the retrieving mechanism. The compositeY fuse tube has a filling 22 of marble dust in which is embedded a resistor ele- `ment 23 in the form of a coil of tungsten wire. As set forth hereinbefore, Ythe function of the ,resistor 23 is to -prevent the rise of current flow through the fuse on the occurrence of a fault by reaction with the `filling 22 of marble dust to insert in the circuit a relatively high resistance. The lower end of the resistor 23 is secured to va terminal 24 which is deformed thereon. The

,'head of the terminal 24 projects through a gen,- ,erally U-shaped terminal support 25 into the upper ends of which the screws I8 arethreaded,

of marble dust. Y

1 With a view to providing an indication that ythe fuse I IJ has blown, an indicator ring 39 is provided around the boss I5 of the upper terminal I3. The ring 39 is carried by a U-shaped indicator lguide 3I, formed for example of hard drawn copper wire. The upwardly extending armsrof the guide 3| are slidably'mounted in slots 32,

shown more clearly in Figure 5, that are formed in a ferrule 33 which is located in the upper end 'of the liner I2 and abuts the closure portion I9 of the terminal I3. The ferrule 33 is formed of good conducting material such as brass or copper. Flat headed screws 34 project through the upper end of the liner I2, as shown more clearly in Figure '3, and into and through the walls of the ferrule 33 to provide a stop, the function of which will be set forth presently.

On the lower intermediate portion of the indicator guide 3l there is rotatably mounted a pulley or drum, shown generally at 35. The drum 35 is preferably machined from a brass rod of .suitable diameter and comprises relatively small drum portions 36 on opposite sides of a relatively large drum portion 31. Suitable anges are provided, as illustrated, on the ends of the small and large drum portions to prevent slipping off of flexible members wrapped thereon.

With a view to biasing the indicator guide SI upwardly for the purpose of moving the indicator ring 30 to its alternate position and for the purpose of elongating the arc incident to the operation of the fuse, a coil compression spring 39 is provided in the ferrule 33. It will be observed that the spring 39 bears against the underside of the indicator guide 3l and the bottom of a groovel 40 in the frerrule 33. In order to ina-ke maximum use of the force exerted by the spring 39 it is assembled so that the convolutions thereof are engaged or the spring is solid until it is releasved.

A flexible conductor 44, formed of a number of strands of copper wire, is trained over the relatively large diameter drum portion 31 in the peripheral groove and the end extends through an aperture 45, which is more clearly shown in Figures 6` and 7 of the drawings. A metal sleeve 46 is deformed onto the end of the flexible conductor 44 and serves to anchor the same against a shoulder at one end of the aperture 45.

The flexible conductor 44 extends downwardly through a bore 41 in a liner 48 of arc extinguishing material, such as boric acid. The liner 48 is vpreferably placed in an inner fuse tube 49 of fiber or like material, the upper end of which rests in a cavity formed by a circular flange 50 extending downwardly from the ferrule 33. It will be noted lthat the bore 41 registers with an aperture 5I in the bottom of the rerrule 33 and that the flexible conductor 44 extends downwardly therethrough. At its lower end the flexible conductor 44 has a sleeve 54 of copper or the like deformed thereon. The sleeve 54 is also deformed on the upper end of a fusible element 55 which may be formed of nickel chromium alloy wire or other high strength wire. The lower end of the fusible element 55 has an anchor member 56 deformed thereon. It will be noted that the anchor member 56 is alsodeforrned onto the upper ond of the resistor 23. The anchor member 56 is provided with an integrally formed radial flange 51 which bears against the lower end of the fuse tube 49 and places the same in compression when the flexible conductor 44 is placed under tension by the spring 39.

When the fusible element 55 blows on the occurrence of an overload, the exible conductor 44 is no longer restrained and the spring 39 is released to move the indicator guide 3| upwardly vcarrying with it the drum 35. This upward movement is limited by the distance that the drum 35 can move toward the closure I9. Even if it were permitted to move sumciently far to engage the closure I9', the terminals of the arc formed on blowing of the fusible element 55 in some cases may not be separated sufficiently far to extinguish the arc as quickly as is desired.

Accordingly, provision is made for rotating the drum 35 by means external thereto so that, in addition to its bodily movement upwardly, it is rotated at the same time to wind the flexible conductor 44 thereon. For this purpose a flexible tension member 58 is wrapped around the relatively small drumrportions 36 in opposite directions and is threaded through an aperture 59, Figure 6, extending'through the relatively large drum portion 31. The ends of the flexible tension :member 58 extend through inclined aperture 69 ber. ,provided a metal .ferrule the lower end of in the bottom of the ferrule 33 and are held in place by copper sleeves 5l deformed thereon. The flexible tension member 58 is preferably formed of braided copper cable comprising a number of strands of small diameter copper wires.

In order that there will be no creep of the drum 35 and the indicator guide 3l due to the biasing action of the spring 39 prior to blowing of the fusible element 55, the flexible conductor 44 and the flexibie tension member 53 are prestretched before assembly in. the fuse. Then, when the pre-stretched members are .placed in position in the fuse under tension they will stretch no further.

When the fusible element 55 blows, as previously described, the spring 39 moves the drum 35 upwardly. At the same time since the ends of the flexible tension member 58 are held stationary with respect to the ferrule 33, they unwind from the small diameter drum portions 36 and cause the drum 35 to revolve. Therefore, the flexible conductor 44 is wrapped around the large diameter drum portion 31 at the same time that it is moved bodily Vupwardly so that the combnation of the two actions effects a greater separation of the arcter'minals than would otherwise be possible. As shown in Figure 4, the spring 39 moves upwardly until it engages the inner ends of the screws 34 which, as previously described, form a stop. In this position it will be noted that vthe large diameter drum portion 3l is spaced slightly from the closure i9 so that it is lfree to rotate in this position as a result of the kinetic energy imparted thereto by the spring 39 resulting from the flexible tension member 53 causing its rotation. The extent that the flexible conductor 4i is wrapped around the large diam- 'eter 'drum portion 37 will depend upon the rela- 'tive 'diameters of the portions 36 and 3l of the drum and on the number of turns of the flexible tension member 58 Varound the small diameter 'drum portions 33. Obviously these proportions may be varied as circumstances dictate.

In Figure 4 attention is directed to the position of the indicator ring 30. It will be noted that lts `alternate position, 'as there illustrated, shows that the fuse has blown and should be replaced.

The fuse construction, shown in Figure v'2 and describedas hereinbefore, is 'suitable for relatively small current ranges when the particular shapes and sizes ofthe parts there shown are used. For example, this construction is particularly adapted for use with the fusible element 55 in the 4range of from 1 to '5 amperes. In this range and with the design proportions used, the 'spring 3S is 'capable of providing the desired time-current characteristic. However, when it is desired to `employ the Vinvention in .connection with fuses-of higher current rating, such as the order of 5 to 10 amperes, it is desirable to provide additional spring tension for pre-loading the fusible element so `as .to afford the desired time-current characteristic.

Accordingly, for this purpose the construction shown in'Figure 8 of the drawings may be used.

In this construction there is provided a fuse tube B5 having a liner 66 Vlof Aboric acid or the like placed :therein and providing a bore v67| through which the flexible conductor 44 extends as previously described. As its lower end the fuse tube r65=iits into a metal ferrule B8 which joins it with an insulating tube 6 9 -thatformsan arcing chamyAt `the lower end of the tube 69 there is 'whichis closed by a `Washer 1|.

A terminal fitting 'l2 is located at the lower end of the flexible conductor 44 and the upper portions '-13 thereof is deformed onto the same while a lower portion 'I4 is deformed onto the upper end of a fusible element 15 which may be of nickel chromium alloy wire or the like. A terminal fitting I6 is deformed onto the lower end of the fusible element 15 and onto the upper end of a short length 'Il of flexible conductor the lower end of which has deformed thereon a tubular metal fitting '18 that is also deformed onto the upper end of the resistor 23.

Now in order to preload the fusible element '15, a coil compression spring 'I9 reacts between a fiange 8D extending from the ferrule 'lil and a washer 8| which bears against the upper end of the fitting 1B. The force applied by the spring T9 and the strength of the fusible element 'l5 are so correlated as to provide the desired time-current characteristic. In this manner the timecurrent characteristic of the fusible element 'l5 can be controlled independently of the spring 39.

Unless the force applied by the spring 39 is greater than that applied by the spring 19, the former has no effect on the tension which is applied. to the fusible element l5, This will be clear from a consideration of the manner in which these forces are applied.

In either of the modifications of the invention on low current faults the fusible elements and l5 fuse or melt. The arc incident thereto is immediately elongated by the withdrawal of the flexible conductor 44 resulting from the bodily movement and rotation of the drum 35. In the case of high current faults this action likewise takes place and in addition the resistance of the resistor element 23 is increased substantially instantaneously so as to insert in the circuit a relatively high resistance.

Since certain further changes can -be made in the foregoing-constructions and different embodiments of the invention can be made without departing from 4the spirit and scope thereof, it is intended that all matter shown in the accompanying vdrawings and described hereinbefore shall be Vinterpreted as illustrative and not in a limiting sense.

I claim as my invention:

l. `In a fuse device, incombination, a fuse tube, a conductor in said fuse tube including a fusible section and a flexible section, means for anchoring said conductor at one end of said fuse tube, `a rotatable drum at the other end of said fuse tube over which said iiexible section is trained and to which it is secured, means mounting said drum for movement bodily endwise Aof said fuse tube, means biasing said drum for said endwise movement to tension said conductor and restrained as long as said fusible section remains intact, and means operatively interconnecting said drum and said fuse tube for causing said drum to rotate as a result of said endwise movement on blowing of said fusible section to wind said flex- 4ible section thereon to an extent greater than twice the bodily endwise movement of said drum. 2. In a fuse device, in combination, a fuse tube, a conductor in said fuse tube including a fusible Lsection and a flexible section, means for anchorlong as said fusible section remains intact, and a 'flexible tension member wrapped around a portion of said drum and anchored at one end for causing said drum to rotate as a resultV of said endwise movement on blowing of said fusible sec- -tion to wind said flexible section thereon, the

'diameter of the portion of said drum around which said tension member is wrapped being sub- 'stantially different from the diameter of the portion around which said flexible section is wrapped whereby a motion multiplying effect is provided.

3. In a fuse device, in combination, a fuse tube, a conductor in said fuse tube including a fusible section and a flexible section, means for anchoring said conductor at one end of said fuse tube, a rotatable drum at the other end of said fuse tube having a relatively large diameter portion over which said iiexible section is trained and to which it is secured and a relatively small diameter portion, means mounting said drum for movement bodily endwise of said fuse tube, means biasing said drum for said endwise movement and Yrestrained as long as said fusible section remains intact, and a flexible tension member wrapped around said small diameter portion of said drum and anchored at one end relative to said fuse tube for causing said drum to rotate as a result of said 'endwise movement on blowing of said fusible section to wind said flexible section thereon.

4. In a fuse device, in combination, a fuse tube, a conductor in said fuse tube including a fusible section and a fiexible section,` means for anchoring said conductor at one end of said fuse tube, a

' ferrule at the other end of said fuse tube, a rotatable drum mounted in said ferrule for movement Vbodily endwise of said fuse tube and having a pair of relatively small diameter portions and a relatively large diameter portion therebetween over which said flexible section is trained and to which it is secured, means biasing said drum for said endwise movement and restrained as long as said fusible section remains intact, and a flexible conductor threaded through said relatively large diameter portion of said drum and wrapped Y around said relatively small diameter portions thereof with the end anchored to said ferrule for causing said drum to rotate as a result of said Yendwise movement on blowing of said fusible section to wind said flexible section thereon.

5. In a fuse device, in combination, a fuse tube,

'a conductor in said fuse tube including afusible section and a flexible section, means for anchoring said conductor at one end of said fuse tube, a ferrule at the other end of said fuse tube, a U-shaped indicator member slidably mounted on said ferrule for indicating by change of its position that the fuse has operated, a drum rotatably mounted on the intermediate part of said indicator member and movable bodily therewith endaround said relatively small diameter portions thereof with the ends anchored to said ferrule for causing said drum to rotate as a result of said endwise movement on blowing of said fusible section to wind said flexible section thereon.

6. In a fuse device, in combination, a fuse tube,

.a conductor in said fuse tube including a fusible section and a flexible section, means for anchoring said conductor at one end of said fuse tube, a ferrule at the other end of said fuse tube, a closure for the outer end of said ferrule, a rotatable drum mounted in said ferrule for movement bodily endwise of said fuse tube toward said closure and having a pair of relatively small diameter portions and a relatively large diameter portion therebetween over which said flexible section is trained and to which it is secured, means biasing said drum for said endwise moveiment and restrained as long as said fusible section remains intact, a flexible conductor threaded Ythrough said relatively large diameter portion of said drum and wrapped around said relatively small diameter portions thereof with the ends anchored to said ferrule for causing said drum to rotate as a result of said endwise movement on blowing of said fusible section to wind said flexible section thereon, and stop means for limiting the action of said biasing means whereby said relatively large diameter portion of said drum in its outermost position is spaced from said closure and thereby is free to continue to rotate as a result of the kinetic energy imparted thereto by said biasing means to wind up said flexible section.

V'7. In a fuse, retrieving means for a flexible conductor comprising. in combination, a rotatable drum over which said flexible conductor is trained and to which it is secured, means mounting said drum for translatory movement and restrained by said flexible conductor, means for causing said drumto rotate as a result of said translatory movement when it is no longer restrained by said flexible conductor to wind the same thereon, and stop means cooperating with said drum for limiting the translatory movement of the same where the kinetic energy previously imparted thereto causes continued rotation thereof to wind up further said flexible conductor. Y

8. In a fuse, retrieving means for a flexible conductor comprising, in combination, a rotatable drum over which said flexible conductor is trained and to which it is secured, means mounting said drum for translatory movement and restrained by said flexible conductor, a flexible tension member wrapped around a portion of said drum and anchored at one end for causing said drum to rotate as a result of said translatory movement when it is no longer restrained by said flexible conductor to wind the same thereon, and stop means cooperating with said drum for limiting the translatory movement of the same Where the kinetic energy previously imparted thereto causes continued rotation thereof to wind up further said flexible conductor.

9. In a fuse device, in combination, a fuse tube, a conductor in said fuse tube including a fusible section and a flexible section, means for anchoring said conductor at one end of said fuse tube, spring means interposed between said anchoring means and said fuse tube for preloading said fusible section, a rotatable drum at the other end `of said fuse tube over which said flexible section is trained and to which it is secured, means mounting said drum for movement bodily end- Wise of said fuse tube, means biasing said drum for said endwise movement and restrained as long as said fusible section remains intact, the

" 'force exerted on said fusible section by said biasing means to move said drum endwise being less than the force exertedl thereon by said spring means which preloads the same, and means for causing said drum to rotate as a result of said endwise movement on blowing of said fusible section to Wind said flexible section thereon.

10. In a fuse device, in combination, a fuse tube, a conductor in said fuse tube including a fusible section and a flexible section, means for anchoring said conductor at one end of said fuse tube, spring means interposed between said anchoring means and said fuse tube for preloading said fusible section, a rotatable drum at the other end of said fuse tube having a relatively large diameter portion over which said flexible section is trained and to which it is secured and a relatively small diameter portion, means mounting said drum for movement bodily endwise of said fuse tube, means biasing said drum for said endwise movement and restrained as long as said fusible section remains intact, and a flexible tension member wrapped around said small diameter portion of said drum and anchored at one end relative to said fuse tube for causing said drum to rotate as a result of said endwise movement on blowing of said fusible section to wind said flexible section thereon.

11. In a fuse device, in combination, a fuse tube, a conductor in said fuse tube including a fusible section and a flexible section, means for anchoring said conductor at one end of said fuse tube, a rotatable drum at the other end of said fuse tube over which said flexible section is trained and to which it is secured, means mounting said drum for movement bodily endwise of said fuse tube, means biasing said drum for said endwise movement to tension said conductor and restrained as long as said fusible section remains intact, means for causing said drum to rotate as a result of said endwise movement on blowing of said fusible section to wind said flexible section thereon, and stop means for limiting the endwise movement of said drum where the kinetic energy previously imparted thereto causes its continued rotation to wind up further said flexible section.

12. In a fuse device, in combination, a fuse tube, a conductor in said fuse tube including a fusible section and a flexible section, means for anchoring said conductor at one end of said fuse tube, a rotatable drum at the other end of said fuse tube over which said flexible section is trained and to which it is secured, means mounting said drum for movement bodily endwise of said fusetube. means biasing said drum for said endwise movement to tension said conductor and restrained as long as said fusible section remains intact. a flexible tension member wrapped around a portion of said drum and anchored at one end for causing said drum to rotate as a result of said endwise movement on blowing of said fusible section to wind said flexible section thereon, and stop means for limiting the endwise movement of said drum where the kinetic energy previously imparted thereto causes its continued rotation to wind up further said flexible section while said flexible tension member is unwrapped from said drum portion.

13. In a fuse device, in combination, a fuse tube, a conductor in said fuse tube including a fusible section and a flexible section, means for anchoring said conductor at one end of said fuse tube, a rotatable drum of good conducting material at the other end of said fuse tube over which said flexible section is trained and to which it isV secured and electrically connected, means mounting said drum for movement bodily endwise of said fuse tube, means biasing said drum for said endwise movement to tension said conductor and restrained as long as said fusible section remains intact, and a flexible tension member of good conducting material wrapped around Va portion of and electrically connected to said drum and anchored at one end for causing said drum to rotate as a result of said endwise movement on blowing of said fusible section to wind said flexible section thereon and to complete the circuit from said conductor to the anchor position of said flexible tension member.

14. In a fuse device, in combination, a fuse tube, a conductor in said fuse tube including a fusible section and a flexible section, means for anchoring said conductor at one end of said fuse tube, a rotatable drum of good conducting material at the other end of said fuse tube having a relatively large diameter portion over which said flexible section is trained and to which it is secured and electrically connected and a relatively small diameter portion, means mounting said drum for movement bodily endwise of said fuse tube, means biasing said drum for said endwise movement and restrained as long as said fusible section remains intact, and a flexible tension member of good conducting material wrapped around said small diameter portion of and electrically connected to said drum and anchored at one end relative to said fuse tube for causing said drum to rotate as a result of said endwise movement on blowing of said fusible section to wind said flexible section thereon and to complete the circuit from said conductor to the anchor position of said flexible tension member.

15. In a fuse device, in combination, a fuse tube, a conductor in said fuse tube including a fusible section and a flexible section, means for anchoring said conductor at one end of said fuse tube, a ferrule at the other end of said fuse tube, a rotatable drum of good conducting material mounted in said ferrule for movement bodily endwise of said fuse tube and having a pair of relatively small diameter portions and a relatively large diameter portion therebetween over which said exible section is trained and to which it is secured and electrically connected, means biasing said drum for said endwise movement and restrained as long as said fusible section remains intact, and a flexible conductor threaded through said relatively large diameter portion of and electrically connected to said drum and wrapped around said relatively small diameter portions thereof with the ends anchored to said ferrule for causing said drum to rotate as a result of said endwise movement on blowing of said fusible section to wind said flexible section thereon and to complete the circuit from said conductor to the anchor position of said flexible conductor.

HAROLD M. CHASE.

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