US2329957A - Fuse - Google Patents

Description

Sept 21, 1943- H. A. TRlPLET-r 2,329,957

FUSE

Filed June 28, 1957 Patented Sept. 2l,

FUSE

Hugh A. Triplea, wumette, nl., assigner to Schweitzer & Conrad, Inc., Chicago, IIL, a corporation of Delaware Application June 28, 1937, Serial No. 150,667

14 Claims.

My invention relates, generally, to fuse devices and it has particular relation to replaceable fuse links adapted to be mounted in a fuse tube or housing of the expulsion type.

In the copendingapplication of Allan Ramsey, Serial No. 559,846, filed August 28, 1931, and assigned to the assignee of this application, now Patent No. 2,091,452, a fuse housing arranged for receiving a replaceable fuse link and adapted for mounting in a box is illustrated and described. The box is formed of a suitable insulating material, such as porcelain, and it is adapted to be mounted on a cross arm or the like and is provided with terminals to which line conductors may be connected.

The fuse housing or tube itself is arranged to be detachably mounted on a cover that is hinged to the box and serves to close the same. The fuse tube is formed of suitable insulating material and it has ferrules at its ends from which spring wire contact fingers project for contact engagement with stationary terminals in the box.

Different types of replaceable fuse links are illustrated in this application. Generally these links comprise a terminal that is arranged to be connected to a movable terminal inside, of the fuse tube to which is attached a coil tension spring that serves to bias the movable terminal toward the normally closed end of the fuse tube.

. The fuse link is mounted adjacent the open end of the fuse tube and is provided with a flexible lead that serves as a connection to the terminal adjacent the open end of the fuse tube. Between the terminal and flexible lead of the replaceable fuse link a fusible element, for example, a silver wire, is provided to electrically interconnect the two parts. In order to relieve this fusible element of the stress that would otherwise be imposed thereon by the coil spring in the fuse tube, a strain wire mechanically interconnects these two parts. The fusible and strain elements are disposed between a pair of generally semicylindrically shaped pieces of insulation, such as cork, which are securely held together and in position by a suitable tube, such as a waterproofed paper tube.

On flow of suflicient current to melt the fusible element the current flow is transferred to the strain element which is immediately fused :and releases the movable terminal in the fuse tube for movement toward the closed end under the biasing force of the coil spring. 'Ihe arc is drawn at the open end of the fuse tube, thereby permitting the rapid evolution of gases generated thereby without building up dangerous pressures in the fuse tube. By drawing the arc in the fuse tube toward the closed end, advantage may be taken of the expulsion action of the device and arc extinguishing vapors or gases that are evolved from the inner lining of the fuse tube to rapidly extinguish the arc.

The object of the present invention, generally stated, is to provide an improved form of replaceable fuse link over that shown in the copending application of Ramsey which will be efficient in operation and which can be readily and economically manufactured and installed.

An important object of my invention is to improve the arc extinguishing characteristics of a replaceable fuse link.

Another object of my invention is to provide non-vegetable material in a fuse link which is replaceable therewith and which is capable of evolving an arc extinguishing medium on the blowing of the fuse link that will assist in extinguishing the arc.

Still another object of my invention is to place a mass of inorganic are extinguishing material in a spring tensioned renewable fuse link in such position that it will be acted upon by the heat of the arc and evolve therefrom a gaseous medium, the combined action of the spring tension and the gaseous medium evolved from the inorganic arc extinguishing material serving to effect rapid interruption of relatively small fault currents. i

Other objects of my invention will, in part, be obvious and, in part, appear hereinafter.

Accordingly my invention is disclosedgin the embodiment thereof shown in the accompanying drawing and it comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of my invention reference may be had to the following detailed description taken in connection with the accompanying drawing in4 which:

Figure 1 is a longitudinal sectional view of a fuse housing or tube that is adapted to receive the novel fuse link of the present invention;

Figure 2 is a longitudinal sectional view of the fuse link shown in Figure l, the terminal and flexible lead being shown in elevation;

Figure 3 is a longitudinal sectional view, similar to that shown in Figure 2, but taken at night angles thereto for the purpose of showing the arrangement of the fusible and strain element;

Figure 4 is a detailed sectional view, at an enlarged scale, taken along the line 4--4 of Fig- IU is provided with a. metal ferrule I2 that is secured in position by screws I3 and I4 which project into suitably threaded apertures, as shown.

With a View to providing for connecting the ferrule I2 to a terminal (not shown), it is provided with two pairs4 of arms I5, only one of each being shown, which are apertured at their outer ends for receiving transverse pins, such as the pin I6. Contact engagement with the stationary terminal isprovided by flexible spring wires I1, the outer ends of which are looped around the pin I6 and spaced apart by suitable washers I8. The ferrule I2 is provided with a hook I9 for mounting it on the cover (not shown) of the fuse box, as will bel readily-understood.

The upper enld of the ferrule I2 is threaded for receiving a cap screw 22. On its underside the cap screw 22 is provided with an integrally formed boss 23 having a helical groove 24 for receiving one end of a tension coil spring 25. The other end of the coil spring '25 is disposed in a suitable helical groove 26 in a movable terminal 21. The cap screw 22 and the movable terminal 21 are provided with socket portions 28 and 29 respectively for :receiving therein the ends of a flexible conductor 30. It will be observed now that the cap screw 22 closes the upper end of the fuse tube Ill and that electrical connection between the ferrule I 2 and the movable terminal 21 is provided by the flexible conductor 30 so that the spring 25 is not called upon to conduct current; Furthermore, it will be noted that the coil spring 25 serves to bias the movable terminal 21 from the lower open end of the fuse tube I toward the upper and closed end.

Adjacent the lower open end of the fuse tube I 0 a second ferrule 33 is provided. This ferrule is of split construction and is arranged to be clamped to the fuse tube I Il by means of suitable bolts 34. The manner of electrically connecting the ferrule 33 to the corresponding stationary terminal (not shown), is similar to that for ferrule I2. The ferrule 33 is provided with two pairs of arms 35, only one of each being shown,

' and pins, such as the pin 36, extend transversely therebetween for receiving the looped outer ends of flexible spring wire fingers 31, these looped outer ends being spaced apart by suitable washers 38.

With a viewto electrically interconnecting the movable terminal 21 and the ferrule 33, a replaceable fuse link, shown generally at 40, is provided. As shown, the fuse link 40 is positioned at the lower open end of the fuse tube I0 so that the gases generated on blowing thereof may be readily vented to the atmosphere. At one end the fuse link 40 lis provided with a fuse link terminal 4I and at the other Iend with a flexible lead 42. The fuse link terminal 4I is preferably forme-d by flattening a short length of copper tubing for 'a purpose that will be presently apparent. The

flexible lead 42 is preferably formed by a. relatively thin copper strap that is tinned. The link terminal 4I is placed on a attened portion 43 of the movable terminal 21 and over a stud 44 on which is threaded a nut 45. The stud 44 may be secured in position in the movable terminal 21 by a pin 46. It Will be observed that the exible lead 42 extends out of the lower end of the fuse tube Ill and over a stud 41 that is threaded into the ferrule 33. A nut 48 is provided for securing the end of the flexible lead 42 in position and in proper contact engagement with the ferrule 33.

With the exception of the fuse link 40, the apparatus just described and shown in Figure 1 of the drawing is fully described in the copending application of Ramsey, hereinbefore referred to, and, therefore, a further description thereof will not be set forth herein.

The details of construction of the replaceable fuse link 4I) are illustrated more clearly in Figures 2, 3, and 4 of the drawing. As there shown. the fuse link terminal 4I is provided with a suitable aperture 5I for fitting over the stud 44 on the movable terminal 21. Likewise, the flexible lead 42 is provided with anaperture 52, preferably oblong in shape, for tting over the stud 41. The flexible lead 42 is provided with a tail 53 that may be grasped by the han'd for pulling the fuse link 40 attached to the movable terminal 21 to the position shown in Figure l of the drawing and positioning the end over the stud 41. A series of small holes 54 is pro-vided to facilitate breaking oi of the tail 53 when the device has been re-fused.

'I'he fuse link terminal 4I and the iiexible lead 42 are electrically interconnected by a fusible element 55, preferably in the form of a silver wire or it may be composed of zinc or tin. It will be understood that different sizes and lengths of fusible element 55 may be provided depending upon the ampere rating of the fuse link. In order to relieve the fusible element 55 of the stress that would otherwise be imposed thereon by the coil spring 25, a strain elem-ent 56, formed preferably of high tensile strength wire such as nickelchromium, is provided for mechanically interconnecting the fuse link terminal 4 I and the flexible lead 42. 'Ille strain element 56 is formed into a generally rectangularly shaped loop with the upper ends 51 turned inwardly and crossed as illustrated. The ends 51 of the strain element 56 and the upper end of the fusible element 55 are disposed inside of the link terminal 4I which is then collapsed thereon to the position shown. Indentations 58 are made in the fuse link terminal 5I, as shovm, in order to secure the ends 51 of the strain element 56 in position. A sleeve 59, formed preferably of tinned copper, and initially in tubular shape, surrounds the lower ends of the fusible and strain elements 55 and 56 and the upper end of the flexible lead 42. Suitable indentations 60 are provided in the sleeve 59 for securely fastening the lower end of the strain element 56 in place. It will be noted that the copper tubing forming the terminal 4I and the upper end of the flexible lead 42 with the sleeve 59 therearound form relatively infusible terminals for the fusible and strain elements 55 and 56, thereby confining the vaporization of metal on blowing substantially to these two elements.

The fusible and strain elements 55 and 56 are encased in a housing that is formed by a pair of generally semi-cylindrically shaped members 65 that are preferably formed of cork. These two members 65 are secured in position by a sleeve 66 that may be formed of paper that has b'een suitably water-proofed. v

In the copending application of Ramsey, hereinbefore referred to, the members 65 are solid throughout their entire length. I have found that the arc extinguishing ability of the fuse link I may be improved by providing cavities, such as the cavities 61, in these members 65 and then filling the same with a suitable arc extinguishing material 68, such as calcium carbonate or lithium carbonate in powdered form. When the cavities 61, which may be formed by drilling the members 66 with a suitably shaped drill, are filled with the arc extinguishing material 66, the fusible and strain elements 55 and 56 are embedded therein. In this position the arc that is formed on blowing of the fusible and strain elements immediately contacts the arc extinguishing ma terial 68 and, due to the heat of the arc. an arc extinguishing medium is evolved therefrom that is capable of materially assisting in extinguishing thearc. When the filling 68 is of calcium carbonate or lithium carbonate, carbon dioxide is evolved which is capable of assisting in extinguishing the arc. It will be observed that the arc extinguishing material 68 is kept from contact with the atmosphere by the members 65 and the sleeve 66.

Under certain operating conditions it has been possible, by the use of the arc extinguishing material 68 in the fuse link 40 itself, to materially decrease the number of cycles of alternating current during which an arc is maintained once it is formed with respect to the number of cycles that are required to extinguish the same when this material is not used. That is, when the members 65 are made solid, as is the case in the copending application of Ramsey, considerably more time is required to extinguish the arc than is the case when these members are provided with the cavities 61 and they are filled with arc extinguishing material such as calcium carbonate or lithium carbonate. This is particularly true in the interruption of relatively small fault currents because of the combined action of the spring 25 in extending the arc drawn on blowing of the fusible and strain elements 55 and 56 and the gaseous medium such as carbon dioxide, that is evolved from the arc extinguishing material With a view to preventing one of the members 65 from being expelled while the other is not under certain relatively low fault current conditions. a washer Il having a suitable centrally located slotted opening is placed around the flexible lead 42 immediately below the members 65 and is secured in position by a cotter pin 12. On formation of an arc between the terminals of the fuse link 40 the are extinguishin-g material 68 is retained in close proximity thereto, especially for low fault currents, and it is possible to take full advantage of it which might not be the case if one of the members 65 were expelled.

It will be obvious that certain changes may be made in the above construction and that different embodiments of the invention may be made without departing from the scope thereof. Therefore, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

l. A replaceable fuse link adapted for mounting under tension in a fuse housing comprising,

in combination, a pair of terminal members, a fusible element electrically interconnecting said terminal members, non-vegetable arc extinguishing material carried by the fuse link and replaceable therewith from which by action of an arc drawn on blowing of said fusible element a gaseous arc extinguishing medium is evolved, and a strain element mechanically interconnecting said terminal members for relieving said fusible element of stress otherwise imposed thereon by the tension in the fuse housing.

2. A replaceable fuse link adapted for mounting under spring tension in a fuse housing comprising, in combination; a terminal, a flexible lead, a fusible element electrically interconnecting said terminal and said flexible lead, a strain element mechanically interconnecting said terminal and said flexible lead for relieving said fusible element of stress otherwise imposed thereon by the spring tension in the fuse housing, and inorganic arc extinguishing material carried by the fuse link, replaceable therewith and closed to the atmosphere from which by action of an arc drawn on blowing of said fusible and strain elements a gaseous arc extinguishing medium is evolved.

3. A replaceable fuse link adapted for mounting under spring tension in a fuse housing comprising, in combination, a pair of relatively infusible terminals, a flexible lead connected to one of said terminals, a fusible element electrically inter-connecting said terminals, a strain element mechanically interconnecting said terminals for relieving said fusible element of stress otherwise imposed thereon by the spring tension in the fuse housing, Aand a filling of powder embedding said fusible and strain elements and adapted to evolve an arc extinguishing medium due to the heat of-the arc formed on blowing of the fuse link. i l

4. A replaceable fuse link adapted for mounting under tension in a. fuse housing comprising,l in combination, a pair of terminal members. a fusible element electrically interconnecting said terminal members, a mass of lithium carbonate carried by the fuse link and replaceable therewith for evolving carbon dioxide on blowing of said fusible element to assist in extinguishing the arc, and a strain element mechanically interconnecting said terminal members for relieving said fusible element of stress otherwise imposed thereon by the tension in the fuse housing.

5. A replaceable fuse link adapted for mounting under tension in a fuse housing comprising, in combination, a pair of terminal members, a fusible element electrically interconnecting said terminal members, a mass of calcium carbonate carried by the fuse link and'replaceable therewith for evolving carbon dioxide on blowing of said fusible element to assist in extinguishing the arc, and a strain element mechanically interconnecting said terminal members for relieving said fusible element of stress otherwise imposed thereon bythe tension in the fuse housing.

6. A replaceable fuse link adapted for mounting under spring tension in a fuse housing comprising, in combination, a terminal, a flexible lead, a fusible element electrically interconnecting said terminal and said flexible lead, a strain element mechanically interconnecting said terminal and said flexible lead for relieving said fusible element of stress otherwise imposed thereon by the spring tension in the fuse housing, and a mass of lithium carbonate adjacent said fusible and strain elements for evolving said fusible and strain elements for evolving carbon dioxide due to the heat of the arc formed on blowing of the fuse link for assisting in extinguishing the arc.

8. A replaceable fuse link adapted for mounting under tension in a fuse housing comprising, in combination, a pair of terminal members, a fusible element electrically interconnecting said terminal members, a strain element mechanically interconnecting said terminal members for relieving said fusible element of the stress otherwise imposed thereon by the tension in the fuse housing, a sleeve of insulation surrounding said fusible and strain elements, and extending in overlapping relation with the adjacent portions of said terminal members, and a mass of inorganic arc extinguishing material within said sleeve of insulation and adjacent said fusible and strain elements from which by action of an arc a gaseous arc extinguishing medium is evolved.

9. A replaceable fuse link adapted for mounting under spring tension in a fuse housing comprising in combination, a terminal, .a flexible lead, a fusible element electrically interconnecting said terminal and said iiexible lead, a strain element mechanically interconnecting said terminal and said exible lead for relieving said fusible element of stress otherwise imposed thereon by the spring tension in the fuse housing, a sleeve of insulation surrounding said fusible and strain elements and extending in overlapping relation with the adjacent portions of said terminal and flexible lead, and a mass of powdered arc extinguishing material within said sleeve of insulation from which by action of an arc a gaseous arc extinguishing medium is evolved.

housing, a sleeve of insulation surrounding said fusible and strain elements and extending in overlapping relation with the adjacent portions of said terminal members, and a mass of lithium carbonate within said sleeve of insulation and4 adjacent said fusible and strain elements for evolving carbon dioxide due to the heat of the arc formed on blowing of the fuse link for assisting in extinguishing the arc.

11. A replaceable fuse link adapted for mounting under spring tension in a fuse housing comprising, in combination, a terminal, a flexible lead, a fusible element electrically interconnecting said terminal and said flexible lead, a strain element mechanically interconnecting said tery minal and said flexible lead for relieving said fusible element of stress otherwise imposed thereon by the spring tension in the fuse housing, a sleeve of insulation surrounding said fusible and extending in overlapping relation with the adjacent portions of said lead, and a mass of lithium arc formed on blowing of the fuse link for assisting in extinguishing the arc.

12. A replaceable fuse link adapted for mounting under tension in a fuse housing comprising, in combination, a pair of terminal members, a fusible element electrically interconnecting said terminal members, a strain element mechanically interconnecting said terminal members for relieving said fusible element of the stress othering said terminal and said flexible lead, a strain element mechanically interconnecting said terminal and said flexible lead for relieving said of stress otherwise imposed thereon by the spring tension in the fuse hous- HU GH A. TRIPLE'IT.

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