Spring Jaw Fuse Clip and Integrally Retained Fuse Puller

This invention relates to spring jaw clips for receiving blade type fuses. In particular it relates to fuse clips of the aforementioned type having a fuse removal device incorporated therewith.

Spring jaw fuse clips for receiving blade type fuses are well known in the art. The contact pressure necessary to affect efficient current transfer between the fuse blade and spring jaws increases in proportion to the size and current rating of the fuse. For large fuses, the amount of pressure from the spring jaws is so substantial as to render insertion or removal of the fuse from the clip extremely difficult. Moreover, upstanding insulating barriers are commonly provided between adjacent fuses to achieve adequate electrical insulation between the adjacent fuses. The space between these barriers and the fuses is relatively small and adds to the difficulty of fuse removal.

Various devices have been provided on or in association with fuse clips to assist in fuse removal, one such device being a bell crank lever pivotally mounted to the fuse clip or to the insulating base to have one leg underly the blade at one end of the fuse. By pivoting the opposite end of the bell crank, the first mentioned leg will pry the fuse blade upwardly from between the spring jaws of the clip. This design has the disadvantage of requiring additional mechanical assembly and provision of additional formations on the base or fuse clip to accommodate the pivotal mounting of the bell crank. Another approach to solving this problem is to provide a fuse puller, or handle, directly on the fuse to project upwardly above the barriers. A disadvantage in this approach is that the fuse puller must be removed from the old fuse and placed onto the new fuse each time a fuse is changed. Still another approach to the problem is to provide a fuse puller in the molded base of the switch or device to which the fuse clip is mounted. Such fuse puller comprises a loop of insulating material guided for vertical movement within guideways molded in the switch base and limited in vertical movement by formations on the base and on the insulating loop. This approach has the disadvantage that each fusible device must be designed to include the guideways and limit stop configuration for the insulating loop fuse puller. Many present design fusible devices lack adequate space for this provision.

The invention disclosed herein provides a spring jaw fuse clip for a blade type fuse which has a fuse puller integrally mounted therewith and which requires no special modification to accommodate the fuse puller. This fuse clip and puller combination may be used anywhere that a fuse clip without the puller may be used. The puller stays with the fuse clip at all times and therefore need not be removed from or assembled to the fuse when it is changed. No modification of the fuse clip or special assembly operations are required to incorporate the puller with the fuse clip, and the clip is fully usable without the fuse puller.

The invention provides a spring jaw fuse clip having a fuse puller integrally retained thereto which comprises a base, a pair of spaced legs extending upwardly from the base and having transversely aligned vertical slots open to the upper ends of the respective legs, a backup spring engaging outer surfaces of the legs for biasing the legs inwardly, the spring having a portion spanning the respective slot in at least one leg, an insulating loop comprising a planar U-shaped lower portion disposed in the slots transversely of the legs and an upper handle portion extending above the upper ends of the legs, the bight of the U-shaped lower portion extending across the space between the legs and being disposed in proximity to the lower ends of the slots for positioning below the fuse blade inserted between the legs, the bight driving the fuse blade from engagement between the legs when the insulating loop is pulled upwardly and the bight abutting the backup spring at the portion thereof which spans the respective slot to limit upward movement of the insulating loop.

FIG. 1 is a plan view of a fuse holder assembly with a fuse installed incorporating the spring jaw fuse clip and integrally retained fuse puller of this invention;

FIG. 2 is a longitudinal sectional view of the fuse holder assembly of FIG. 1 taken substantially along the line 2--2 thereof;

FIG. 3 is a perspective view of the spring jaw fuse clip and integrally retained fuse puller of this invention;

FIG. 4 is a cross-sectional view of the fuse clip of FIG. 3 taken substantially along the line 4--4 of FIG. 3 and showing a fuse blade installed therein; and

FIG. 5 is a side elevational view of the fuse puller of this invention.

An exemplary embodiment of a fuse holder assembly is shown in FIGS. 1 and 2. An insulating base 2 is provided at opposite ends with fuse clip assemblies 4 and 6 which receive a blade type fuse 8 therebetween. The assembly of FIGS. 1 and 2 represents one phase of a multi-phase protected circuit device which would have similar fuse holder assemblies for each phase and located on opposite sides of that assembly shown in the drawings. For simplification of the description, the base 2 is broken away on opposite sides of the fuse holder assembly and only the single assembly will be described.

The right-hand fuse clip assembly 4 comprises a connector plate 10 and a pressure type wiring connector 12 secured to the right-hand end of base 2 by a bolt 14 extending upwardly through aligned holes in the base 2, connector plate 10 and connector 12 to receive a conical washer and nut assembly 16 at the upper or front side of connector 12. Suitable provisions are made to establish correct longitudinal alignment between the right-hand fuse clip assembly 4 and the left-hand fuse clip assembly 6. For example, base 2 may be provided with upstanding bosses 2a (FIG. 1) disposed on opposite sides of the connector plate 10 to cooperate with the bolt 14 for establishing proper alignment of the assembly 4. A spring jaw fuse clip 18 completes the fuse clip assembly 4. The clip 18 has a base portion which is positioned upon the upper surface of connector plate 10 and includes an offset mounting foot portion 18a. A pair of clearance holes are provided in mounting foot 18a to receive thread cutting screws 19 which threadably engage aligned holes in connector plate 10 to secure fuse clip 18 to the connector plate 10. Base 2 is provided with a recess in proximity to the aligned holes in plate 10 to permit the screws 19 to project below the connector plate 10.

Fuse clip 18 has a pair of spaced legs 18b which are formed upwardly from the base portion as may best be seen in FIGS. 3 and 4. The fuse clip illustrated in FIGS. 3 and 4 includes a fuse puller member 20, but the fuse clip per se is the same at either end of the assembly. The legs 18b converge in the upward direction to provide a spring biased gripping engagement with a blade inserted therebetween. The upper or free ends of legs 18b may be flared outwardly to facilitate insertion of a fuse blade therebetween. Each leg 18b contains a centrally located vertical slot 18c which effectively bifurcates the leg into two individual contact segments for enhanced engagement with a fuse blade inserted therein. Near the vertical midpoint of the legs 18b, the slot 18c is provided with arcuate recesses 18d which define a cylindrical opening in each leg for purposes of receiving a Class R fuse pin in a manner well known to those skilled in this art. Near the base of the fuse clip the legs 18b are provided at their outer edges with aligned notches 18e which are formed inwardly at right angles to the edge of the legs 18b.

A backup spring 22 is assembled to the fuse clip 18 to encircle the fuse clip and bear inwardly upon the outer surfaces of the legs 18b near their upper end. The spring 22 provides additional inward bias for the legs 18b and functions to limit outward movement of the legs 18b beyond a critical elastic limit thereof due to abnormal forces which may be exerted on the legs. The spring 22 comprises a first inverted U-shaped segment comprising a pair of upwardly extending legs 22a joined at their upper ends by a bight portion 22b which engages the respective leg 18b at a point just below the outward flare of the leg 18b and spans the slot 18c in that leg. At the opposite side of fuse clip 18, the spring 22 comprises a pair of upstanding legs 22c which are formed as a mirror image of legs 22a but which do not have a connecting bight portion at the upper ends thereof. The lower ends of legs 22a and 22c are joined by transversely extending horizontal segments 22d. Segments 22d are received within the aligned notches 18e to locate and retain the spring 22 assembled to the fuse clip 18.

The fuse clip assembly 6 at the left-hand end of the fuse holder assembly shown in FIGS. 1 and 2 comprises essentially the identical components as the fuse clip assembly 4 at the right-hand end, but additionally includes a fuse puller member 20 assembled to the fuse clip 18. The connector plate 10 of the fuse clip assembly 6 is reversely oriented with respect to the same plate for the assembly 4 in order to provide the holes for thread cutting screws 19 to be aligned on the same side of the longitudinal center line of the fuse assembly as are those for the fuse clip assembly 4. Referring additionally to FIGS. 3 through 5, the fuse puller 20 comprises a molded insulating loop 20 which is essentially a flat or planar member disposed within the slots 18c of the fuse clip 18. The lower portion of puller 20 is essentially U-shaped, the bight portion 20a thereof extending transversely between the legs 18b and extending out opposite sides thereof through the slot 18c. The thickness of loop 20 is nominally less than the width of slots 18c to guide the loop 20 for vertical movement within the slots. The height, or vertical dimension, of bight 20a cooperates with the width of slots 18c and the thickness of the loop to maintain vertical orientation of puller loop 20a with respect to the fuse clip 18, preventing it from pivoting or rocking over in the plane containing the longitudinal dimension of the fuse. Moreover, the height of bight 20a is greater than the diameter of the rejection pin opening formed by arcuate recesses 18d, preventing the loop from pivoting in the pin opening and thereby rocking over in the aforementioned plane when the loop is raised to align the bight with the pin opening. A handle portion 20b of the loop is angularly offset out of the plane of the lower portion.

A vertically oriented rib 20c is centrally disposed on bight 20a to extend in opposite directions therefrom. The length of rib 20c, i.e. in the longitudinal direction of the fuse, is greater than the thickness of slots 18c to retain the lower portion of loop 20 centered between the legs 18b, thereby preventing the lower end of the loop 20 from skewing out to either side of the clip 18. The transverse thickness of rib 20c is nominally less than the corresponding thickness of a fuse blade to be received by the clip, and is preferably less than the space between the legs 18b at their wider base portion so as to be loosely engaged by the interior surfaces of the legs at the upper edge of the rib when the loop is in its lowest position within the slots 18c. This engagement maintains the loop 20 vertically oriented with respect to the clip 18 to prevent the upper end of the loop from rocking, or tipping over, transversely of the clip 18. In the lowest position of loop 20, the bottom edge of rib 20c also engages with the base of clip 18 to further aid in maintaining the loop 20 oriented vertically in the longitudinal direction.

The loop 20 may be pulled upwardly within the slots 18c by means of the handle 20b. Upward travel of the loop is limited by engagement of the left-hand side of bight 20a (FIG. 4) with the portion 22a of backup spring 22 which spans the slot 18c in the left-hand leg 18b of the clip. To obtain maximum upward travel of loop 20 in the clip, the portion of bight 20a to the left of rib 20c (FIG. 4) is recessed below the height of bight 20a on the right side of rib 20c. Although loop 20 is primarily a fuse puller, as will be described more fully hereinafter, it also serves to faciliate insertion of a fuse blade into the clip. By pulling handle portion 20b, the loop 20 is moved to its upward limit position whereby the rib 20c cams the blades 18b apart to the approximate dimension of the fuse blade. The latter may thereby be easily inserted without requiring the penetrating edge of the blade to initially cam the legs 18b apart. As the blade is inserted, it drives the loop 20 to its lower position in the clip.

Referring again to FIGS. 1 and 2, the base 2 is provided with a pair of vertically upstanding ribs 2b which may extend along the entire fuse assembly or may extend only in the areas of the fuse clip assemblies 4 and 6 as desired. Such ribs are provided to increase the over the surface distance between adjacent fuse holder assemblies to achieve the necessary insulation requirements for devices of the type employing such fuse holder assemblies. The ribs 2b are spaced closely to the fuse in order to render the device as compact as possible, and do not permit a large amount of access to the sides of the fuse for removal thereof. For this purpose the fuse puller 20 has been incorporated in the fuse clip 18 of the left-hand fuse clip assembly 6 which is the line side of the fusible device. The fuse clip 18 is oriented with respect to the fuse assembly such that the offset upper handle portion 20b is angularly disposed toward the opposite end of the fuse assembly to overlie the fuse 8. The line side end of fuse 8 may be removed from fuse clip assembly 6 by pulling upwardly on the handle portion 20b of puller 20 to cause the upper surface of rib 20c to engage the lower surface of the fuse blade and drive it upwardly out of engagement with the legs 18b of the fuse clip as shown in dotted lines in FIG. 2. When the line side end of the fuse 8 is pivoted out of the fuse clip 18, the upper portion of puller 20 may be deflected free of the end of the fuse blade and the fuse then pivoted further in the clockwise direction as viewed in FIG. 2 to enable the workman to subsequently pull the other end free from fuse clip assembly 4. It is a common practice for fuse holder assemblies to be vertically oriented as opposed to the horizontal orientation shown in the drawings in FIGS. 1 and 2. When vertically oriented, the line side fuse clip assembly 6 is customarily disposed at the upper end of the fuse assembly. In this orientation, the angular displacement of the puller handle portion 20b serves also to prevent the fuse from falling completely out of the device in the event that the blade is freed from the fuse clip with unexpected momentum.

The spring jaw fuse clip with integrally retained fuse puller described in the foregoing specification represents a simple, economical approach to providing a fuse puller for fusible devices. The fuse puller disclosed herein facilitates both insertion and removal of the fuse. The offset handle portion of the puller serves as a retainer for the fuse to prevent the fuse from falling completely out of the fusible device during removal. While a single and preferred embodiment of the spring jaw fuse clip with integrally retained fuse puller has been disclosed herein, it is to be understood that this invention is susceptible of various modifications without departing from the scope of the appended claims.