Fuse Holder

Abstract

A fuse holder has a fluid-tight housing with external terminals that are internally connected to the fuse by annular coil springs. A fuse handling rod carries an expansible sleeve device at one end for connecting it to the fuse and a second expansible sleeve device at the other end for sealing the end of the housing.

Description

BRIEF SUMMARY OF THE INVENTION

It is the purpose of the invention to provide a fuse-holding structure for use in protecting electrical apparatus, especially transformers, from damage caused by overload or short circuits.

The invention accomplishes this purpose by means of a fuse holder that has a hermetically sealed housing which is adapted at one end to be mounted on the top or the side of a transformer tank at the desired attitude with respect to the dielectric fluid in the tank. The housing includes spaced external electrical terminals which have internal contact surfaces that are connected to the fuse terminals by means of electrical connectors, preferably in the form of garter springs. A non-conductive rod is used as a holder for inserting or removing a fuse from the one end of the housing and it has a gripping means whereby it is releasably secured to the fuse, the other end of the rod preferably carrying an expansible sleeve means, operated by a handle that is pivoted on an extension of the rod, which can close and seal the one end of the housing.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross section through a fuse holder embodying the invention and shows the device in closed position with a fuse in place; and

FIG. 2 is an enlarged view, partly in section, showing the gripping means whereby the fuse holder rod is releasably attached to the fuse.

DESCRIPTION OF THE INVENTION

The fuse holder 1 has a tubular housing 3 which is of substantially uniform internal diameter. The housing 3 includes three metal current conducting sleeves 5, 7, and 9 located at the outer or top end, the mid portion, and the bottom or internal end, respectively. The housing 3 is preferably formed by winding glass fibers into the tube shape and around the exterior of the three sleeves 5, 7, and 9. Hermetic sealing of the fibers with the sleeves is achieved by means of the grooves 11 which are machined into the outer circumference of the sleeves and which enable the glass fibers to close and seal them in place. The glass fibers are suitably coated and cured to form a rigid tubing capable of withstanding the stresses and temperatures to which it is subjected during use in an electrical transformer.

The sleeve 5 has a flange 13 welded to it which serves as a means for mounting the fuse holder in the top or in the wall of a transformer tank. With the illustrated arrangement of the flange, that is, at right angles to the longitudinal axis of the housing 3, the fuse holder will be vertically disposed if mounted in the cover of a transformer tank and horizontally disposed if mounted in the side wall of a tank. If desired, the flange 13 can be welded at an angle to the axis of the housing 3 so that the fuse holder will extend at an angle to both the vertical and horizontal when it is secured in place in a transformer tank. U. S. Pat. No. 2,918,557 shows such an angular disposition of a transformer circuit breaker.

The central sleeve 7 has a stud 15 welded to it which projects through an opening 17 formed in the non-conductive glass fiber wall of the housing 3 to form an external electrical terminal. A second external terminal is provided by a threaded stud 19 that projects from a plate 21 which is welded across the bottom of the sleeve 9 to form a permanent closure for the internal end of the housing 3. The screws or studs 15 and 19 and their sleeves 7 and 9 form electrical terminal means extending outside of the housing which have contact surfaces on the inside of the housing and as a part of the uniform diameter inside wall of the housing, such contact surfaces being provided by the inner walls of the sleeves. Since the terminals 15 and 19 are located remote from the flange 13 and carry the high potential current, the mounting sleeve 5 and its flange 13 are at relatively low tank potential.

The space within the housing 3 between the sleeves 7 and 9 comprises a chamber 23 for the fuse 25. The fuse 25 is a type that is available on the open market and has an elongated uniform diameter body 27 which may or may not have a reduced diameter end sections 29 from which project electrical terminals 31 in the form of a metal current conducting sleeves. In accordance with this invention the exterior surface of the terminal sleeve 31 at each end of the fuse 25 is electrically connected to the inner surface of the sleeves 7 and 9 by means of coil springs which are arranged in annular form, i.e., as toroids or garter springs 33 and 35. The springs 33 and 35 have a relaxed outer diameter which is less than the inner diameter of the housing and a relaxed inner diameter which is less than the outer diameter of the contact sleeves 31. However, when the sleeves 31 are forced inside the springs, they are expanded into good electrical contact with the inner walls of sleeves 7 and 9. The change in diameter between the body portion 29 and the terminal 31 of the fuse provides a radial shoulder 37 against which the spring 33 is seated as indicated in FIG. 1. The other face of the spring 33 presses against a guide washer 39 which is carried by a fuse gripping means 41 on the inner end 43 of a non-conductive fuse holding rod 45. As will become apparent hereinafter, the rod 45 is releasably connected to the terminal sleeve 31 and thus to the fuse 25 so that it may be used to insert and remove the fuse. By virtue of the shoulder 37 and washer 39 the spring 33 is carried along with the rod and fuse when these parts are removed through the top end of the housing. During such movement the spring will readily slide along the wall of the chamber 47 within the housing 3 between the sleeves 5 and 7.

The lower contact spring 35 bears against the bottom plate 21 and may be held there by a retainer washer 49 which has a force fit inside of the contact sleeve 9 so that upward movement of the fuse 25 allows the bottom terminal 31 to simply withdraw from the internal opening in the spring 35. A guide washer 51 similar to the guide washer 39 has a force fit on the bottom sleeve terminal 31 and is therefore removed with the fuse 25. The two washers 39 and 51 are just slightly smaller in diameter than the housing 3 and serve as guides for the assembly of fuse and rod to center them within the housing 3 and facilitate insertion of the lower sleeve 31 into the inner opening of the spring 35.

The gripping means 41 at the inner end of the rod 45 comprises a sleeve 53 of rubber or rubber-like material which in relaxed state will slide easily inside of the fuse terminal 31. The rubber sleeve 53 has a flange 55 which engages the washer 39 that is mounted on the sleeve. A dished metal cover 57 is disposed around the flange 55 and a metal sleeve 59 is secured to the cover 57 and extends within the sleeve 53 to form a wear-resistant bearing for the bolt 61 which threads into a threaded aperture 63 in the bottom end of the rod 45. The bolt 61 has a pressure plate or shoulder 65, which may be convex as indicated, that engages the bottom face 67 of the sleeve 53. After the sleeve 53 is inserted inside of the sleeve 31, rotation of the rod 45 relative to the screw 61 will cause the shoulder 65 to move toward the bottom face 69 of the rod therefore axially compressing the sleeve 53 and causing it to radially expand and grip the inner wall to the terminal 31. Conversely, when it is desired to disconnect the rod 45 from the fuse 25 the rod is rotated in a reverse direction to lengthen the exterior portion of the screw 61 and relieve pressure on the rubber sleeve 53 so that it can be withdrawn from the terminal. The friction between surfaces 65 and 67 serves to prevent the screw 61 from rotating with the rod 45.

The outer or top end of the rod 45 is enlarged in a conical section 71 which also serves to guide and center the assembly of rod and fuse in the housing 3. The top end 73 of the rod 45 is preferably convex as illustrated and engages the bottom face of a hollow rubber sleeve or body 75 and serves as a pressure face for applying longitudinal compression, with an outward radial component, to cause the rubber body 75 to tightly grip the wall of the tubing 3 at its outer end and form a fluid-tight closure. The body 75 has a top wall and flange 77 that engages the annular top end face 79 of the housing 3 and a bottom wall 81 which engages the pressure face 73 of the rod. A metal cover of shallow cup shape 83 extends over the flange 77. The cover 83, flange 77, and wall 81, have aligned apertures through which extends a support rod 85 that is firmly embedded within the end 71 of the rod 45 to project from the rod and form a rigid extension of the rod. This support rod 85 is preferably constructed of metal to give it greater hardness and strength than is possessed by the non-conductive material from which the rod 45 is formed. Pivoted on a pin 87 to the outer end of support rod 85 is a cam member 89 to which is welded a lever or handle 91. The cam 89 has a flat cam face 93 which can engage the cover or pressure plate 83 to longitudinally compress the sleeve 75 against the pressure face 73 on the rod to radially expand the sleeve into tube closing position. The cam member 89 also has a cam face 95 which is located closer to the pin 87 so that upon rotation of the handle 91 to a vertical position, as fragmentarily illustrated by the phantom lines at 97, the pressure on the rubber body 75 will be released whereby the rod and fuse 25 can be readily removed from the housing 3. It will be noted that the support rod 85 in conjunction with the cam 89 provides a direct connection between the handle and the rod 45 to facilitate either pulling of the rod 45 during removal or pushing on the rod 45 during insertion.

In operation, the lineman inserts his "hot stick" in the eye of the lever 91 and pulls up on it so that the lever and cam 89 pivot on pin 87 to the upright position 97. This releases the longitudinal pressure on the rubber body 75 and unlocks the top end of the fuse holder body 3. With a smooth lifting motion, the lineman can pull the fuse 25 and connector rod 45 out of the housing 3. During this motion, the bottom connector spring 35 pulls off the terminal sleeve 31 and remains in place in the bottom of the fuse holder. In the event that the fuse holder 1 is horizontal, the disc 49 will serve to hold the spring in place whereas in the vertical position gravity will at least partially perform this function.

The spent fuse 25 is removed by rotating the insulated rod 45 in a loosening direction until the rubber sleeve 53 is relaxed sufficiently to slide out of the terminal sleeve 31. In attaching a new fuse to the rod the connector spring 33 and guide washer 39 are installed, the sleeve 53 is inserted into the sleeve 31, and the rod 45 rotated until it bottoms, there being a positive "feel" when the gripping means 41 is completely tightened up.

With the new fuse attached to the rod 45 and the lever 91 still in its upright position 97, the lineman can start the bottom of the fuse and rod assembly into the open top of the housing 3. He simply pushes down with a quick stroke and the assembly with the self-aligning features, due to washers 39 and 51 and the tapered head 71, guides itself into the housing 3. The handle 91 because of its direct attachment by means of rod extension 85 permits the forces from the hot stick to be transferred directly to the rod 45. As the assembly approaches the bottom of the housing, the lower fuse terminal 31 is guided into the center of the connector spring 35 to expand it into contact with sleeve 9. After the internal assembly is seated on the bottom end 21 of the housing, the lineman can pull the locking lever 91 to the full line position of FIG. 1 to close the top end of the fuse holder and seal it by expansion of the rubber body 75.

Modifications may be made in the specific construction that has been illustrated without departing from the spirit and scope of the invention.

Claims

I claim:

1. A fuse holder for a fuse of the type having an elongated body with electrical terminals at opposite ends in the form of longitudinally extending conductive sleeves, said fuse holder comprising a tubular housing closed at one end and open at the other end, closure means for the open end of the housing, said housing having a first electrical terminal means adjacent the closed end and a second electrical terminal means at a central location between said ends, said terminal means each including a contact surface on the inside of the housing, the space inside said housing between said first and second terminal means comprising a chamber for said fuse, first and second electrical connectors in said chamber engageable with the conductive sleeves for electrically connecting the conductive sleeves of the fuse to said contact surfaces, an elongated fuse holding rod inside said housing having a first end adjacent said closure means, said rod having a second end adjacent the fuse chamber, and releasable attachment means including threaded means carried entirely by the second end of the rod for removably securing said second end to an interior portion of one of the conductive sleeves of said fuse so that the fuse forms a longitudinal extension of the rod and the two are movable together as a unit through the open end of the housing, said rod and said fuse being rotatable, one relative to the other, to effect release of said rod from said fuse.

2. A fuse holder as set forth in claim 1 wherein said releasable attachment means also includes an attachment member fitting into said interior portion and expandable against a surface of said interior portion for connection to it.

3. A fuse holder as set forth in claim 2 wherein said attachment member comprises a rubber-like body, and said rotation causing said threaded means to compress said body to cause it to radially expand against said surface.

4. A fuse holder as set forth in claim 3 wherein said threaded means extends through said body and is threaded into the second end of the rod, said threaded means including a pressure shoulder operatively connected to a face of the body remote from said second end, relative rotation of the rod and threaded means serving to control the position of said shoulder and the degree of radial expansion of said body.

5. A fuse holder as set forth in claim 1 wherein said closure means includes a rubber-like sealing member inside the housing pressing against the first end of said rod and a compression member outside the housing for applying longitudinal compression to the sealing member to press it against the first end of the rod and radially expand it against the housing.

6. A fuse holder as set forth in claim 5 wherein said compression member is attached to the first end of the rod and includes a longitudinally movable pressure plate for applying pressure to the sealing member.

7. A fuse holder as set forth in claim 6 including a support rod at the first end of the rod and extending through the sealing member and pressure plate, said compression member being movably secured to said support rod and including cam means operative upon movement of the compression member for moving the pressure plate.

8. A fuse holder as set forth in claim 7 wherein said compression member is pivoted to said rod and said cam means is shaped to yieldably hold the compression member in respectively the compressed and released position, said compression member including handle means whereby the fuse holding rod and attached fuse and closure means may be handled as a unit for insertion into and removal from the housing.

9. A fuse holder as set forth in claim 1 wherein said housing comprises a non-conductive tubular member and three longitudinally spaced metallic sleeves integrated with said member, one of said metallic sleeves being located at said open end and the other two of said metallic sleeves forming said first and second electrical terminal means.

10. A fuse holder as set forth in claim 9 wherein said one sleeve has a mounting flange for the fuse holder secured to it.

11. A fuse holder as set forth in claim 1 wherein at least one of said electrical connectors comprises an annular coil spring having a relaxed state outer diameter less than that of the inner diameter of a said contact surface and a relaxed state inner diameter less than the outer diameter of a conductive fuse terminal sleeve, said spring being expandable into peripheral contact with the contact surface upon insertion of said terminal sleeve into the inner diameter of the spring.

12. A fuse holder as set forth in claim 1 wherein said electrical connectors comprise annular coil springs fitting on the outside of said conductive sleeves and expandable by said sleeves into contact with said contact surfaces.

13. A fuse holder as set forth in claim 12 wherein one of said springs is carried by said rod in contact with the second electrical terminal means and the other of said springs is in contact in the first electrical terminal means.

14. A fuse holder as set forth in claim 13 including means connected to the housing for holding the other coil spring at the closed end of the housing during movement of the rod to remove a fuse.

15. A fuse holder as set forth in claim 1 including guide washers connected to said conductive sleeves for centering said fuse in said housing.

16. A fuse holder as set forth in claim 15 including a tapered centering surface formed on said rod adjacent its first end and serving to guide and center said rod in said housing.

17. A fuse holder for holding a fuse of the type having an elongated body with electrical terminals at opposite ends in the form of longitudinally extending conductive sleeves, the holder comprising a tubular housing closed at one end and open at the other end, a movable closure for sealing the open end of the housing to make the housing fluid tight, said housing having a first electrical terminal means adjacent the closed end and a second electrical terminal means at a location intermediate said ends, said terminal means each having a contact surface on the inside of the housing, the space inside said housing between said first and second terminal means comprising a fuse chamber, first and second electrical connectors in said fuse chamber engageable with the conductive sleeves for electrically connecting a fuse in said chamber to said first and second terminal means, a fuse holding rod in said housing having first and second ends, said closure being connected to said first end of the rod, and selectively releasable connection means including threaded means mounted entirely on the second end of the rod for removably connecting it to an interior portion of one of the conductive sleeves of the fuse so that when connected together said fuse forms a longitudinal extension of the rod and the two are movable together as a unit, said rod and said fuse being rotatable, one relative to the other, to effect release of said rod from said fuse.

18. A fuse holder as set forth in claim 1 wherein said interior portion has a smooth surface for receiving said attachment means, said releasable attachment means being adapted to effect a retaining engagement with said interior portion.