GB2106338A - Fuse holder - Google Patents

Abstract

The holder for cartridge fuses has spring clips (2) which are a snap-in fit, allowing limited rotation to facilitate fuse insertion without breakage. Insulating walls (5) partially shroud the clips from accidental contact. The metal rivet normally used to secure a fuse clip to a base is eliminated, permitting a lower fuse holder profile for a given voltage requirement. Optional subsequent hot-forming of a clip-engaging post (9) on the base provides extra pull strength to the structure. <IMAGE>

Description

SPECIFICATION Fuse holder This invention relates to fuse holders for electrical cartridge fuses.

Conventional clip-in fuse holders for cylindrical cartridge fuses exhibit certain deficiencies with respect to high voltage insulation protection.

Such holders typically consist of a pair of spring clips mounted on a base and configured to engage the end terminals of a cylindrical cartridge fuse by pressing insertion. The clips, together with unitary or separate terminal lugs, are normally secured to the base by a metallic rivet passing through a hole in the clip base and through a matching hole passing through the mounting base. Since the rivets are in electrical contact with the clips, a short circuit can occur through the fuse terminals if the bottom faces of the rivets are exposed below the mounting base to contact any conducting surface on which the fuse holder may be mounted.

One solution involves provision of a separate insulating spacer inserted between the fuse mount base and the supporting surface. This solution is undesirable, since it requires an extra part, raises the overall height of the fuse structure and, thus, wastes space and poses tailoring problems for multiple fuse mount arrays of differing numbers of fuses.

An alternative solution is to provide a relatively thick fuse mounting base and to counterbore the rivet hole at the lower face of the mounting base to place the lower end of the rivet higher in the structure. This solution has the drawback that the surface walls of the counterbore walls serve as surface flashover paths at high voltages unless the base thickness is appropriately increased, again resulting in increased overall height of the fuse mount. Additionally, the rivets are extra parts in the assembly, and thus add materially to the manufacturing inventory. Accordingly, it is an object of one aspect of the invention to provide an inexpensive, easily assembled fuse holder with less parts and without conducting passages through the base so as to achieve a reduced structure height for a given voltage rating.

It is frequently observed that low-priced snapin cartridge fuses have their end terminals oriented significantly off-axis. Such structures are typically rather fragile, owing to the customary method of end terminal attachment, and as a result the terminals frequently break off when such fuses are inserted into conventional fuse holders with rigidly coaxially aligned fuse clips.

Accordingly, it is an object of one aspect of this invention to provide for self-aligning clips as a feature of the fuse mount to accommodate offaxis end terminals without such breakage.

In accordance with one of the features of the invention, an improved fuse holder for cartridge electrical fuses has snap-in terminal clips insertably lockingly engaged with a unitary insulating base. Protective insulating barrier wails partially shroud the terminal clips and the terminals of the engaged fuse from accidental touching contact with external objects. The terminal clips preferably lock to the base by locking engagement with the barrier walls, and thus do not require a conventional metal attaching rivet passing at least partially through the base. By eliminating the conducting rivet and its attendant potential for high voltage flashover to the surface on which the base is mounted, e.g.

a fuse box wall, the base may be made thinner, resulting in an overall lower profile and reduced space requirements. Further, by reducing the number of components and replacing a riveting operation with a snap-in operation, manufacturing costs are reduced.

According to a specific aspect of the feature invention, the snap-in engagement is secured by unitary tabs on the interior faces of the barrier walls engaging suitably shaped contours of the clip jaws.

According to another specific aspect of the invention, additional clip securing means is achieved by a pair of posts unitary with said mounting base and extending therefrom to engage matching holes in the bases of each clip upon clip insertion. The combination of tab engaging means to press the clip against the mounting base and a capture post to prevent lateral travel on the base provides an inexpensive easily-manufactured way of making a reliable fuse holder assembly.

According to still another specific aspect of the invention, additional strength is achieved in the assembly by configuring the posts to pass through and beyond the clip bases. The extended portion of each post may be crowned over by conventional hot-forming techniques after clip insertion, thereby imparting additional pull strength protection during fuse removal.

According to a further specific aspect of the invention, by configuring the clip jaws and locking tabs for loose engagement, the mounted clips are able to pivot on the mounting base to provide a self-aligning feature during fuse insertion. This provides for a maximum interfacial contact between the fuse terminals and the clip, thereby reducing contact resistance.

According to a still further aspect of the invention, the barrier walls are disposed in close proximity to the clips so that the clips are effectively secured against excessive rotation on the base, thereby preserving clip alignment for ease of insertion.

The fuse holder according to the invention may take the form of a pair of generally aligned, electrically conductive, generally channel section clips to receive respective end terminals of a cartridge fuse, and a unitary, electrically insulating mounting base which receives the clips, the clips being a snap-fit with portions of the base to lock the clips to the base.

Specific embodiments of the present invention will now be described by way of example, reference being made to the accompanying drawings, in which: Figs. 1 A, 1 B, 1 C, and 1 D are a perspective view, a top plan view, a front elevational view, and a side elevational view, respectively, of the preferred version of the improved fuse holder; Fig. 2 is a perspective view of the holder with a fuse inserted; Fig. 3 is an exploded perspective view showing one end of the fuse holder with a clip positioned for insertion from above; Figs. 4A and 4B are cross-sectioned side elevations showing details of the clip insertion and clip locking mechanism; Fig. 5 is a top plan view in cross section showing rotation limiting engagement of the base of a fuse clip with the walls;; Fig. 6A is a cross-section partial front elevation of one end of a clip assembly wherein the fuse post has been crowned for increased pull strength; Fig. 6B is a similar view to Figure 6A, but of a conventional riveted fuse clip structure with the same metal-to-base insulation distance, showing the reduced height achieved with the improved structure for comparison purposes; Fig. 7 is in perspective view of an alternative form of snap-in clip fuse mount; Fig. 8 is front elevation of an alternative version of the fuse holder shown in Fig. 1 C, wherein the terminal lugs extend upward and away from a mounting surface.

Fig. 9A and 9B are side and end elevations respectively of an alternative form of clip locking means.

Referring to Figs. 1 A, 1 B, 1 C and 1 D, a fuse holder assembly consists of a unitary insulation mounting base 1 and two conducting fuse holding clips 2, the base and the clips being configured to lockingly engage together under snap-in pressing engagement. A central hole 4 in the base 1 allows passage of a mounting screw (not shown). Two connecting lugs 3 unitary with each clip 2 extend away from the mounting base 1. The clips 2 are partially shrouded by insulating barrier walls 5, which provide a measure of protection against accidental electrical contact of external objects with the clip structure. Fig. 2 shows the fuseholder with a cartridge fuse 6 installed. Fig. 8 shows an alternative of the fuse holder assembly shown in Fig. 1 C, wherein the terminal lugs extend upward and away from a mounting surface.

The barrier walls 5 further serve as part of the clip anchoring assembly. Fig. 3 shows details of a clip 2 positioned for insertion. The clip 2 is mounted on the base by pressing the clip downward between two compliant wall-mounted locking tabs 7 (Figs. 4A and 4B), forcing them outward until the clip is fully seated on the base.

Locking slots 8 (Figs. 3, 4A, 4B) in the clip are then engaged by inward motion of the locking tabs, securing the clip to the base. A unitary post 9 extending up from the base 1 engages a hole 10 in the base of the clip 2 to secure the clip against lateral motion.

Referring to Fig. 1 C, it will be noted that the engaging slots 8 are configured longer than the width of the locking tabs 7, thereby permitting the clips to twist about the mounting posts 9 as shown in Fig. 5. The amount of twist is restrained by close proximity of the interior surface of each of the walls 5 (Fig. 5) to the base of the clip 11, thereby holding the clip in proper alignment for fuse insertion and insuring that no substantial motion of the lug 3 can occur to cause an accidental short circuit to adjacent structures. For additional pull strength during fuse removal the posts may be crowned after assembly by conventional hot-forming methods well known to the art. Fig. 6A shows a cross-sectional view of a fuse clip 2 engaged by such a crowned post 12.

Fig. 6B shows a cross-section view of a conventional mounting base wherein a clip 2' is secured to the base by a conventional metal rivet 1 3. This method of attachment places a conductor contacting a clip in closer proximity to whatever mounting surface on which the fuse holder is attached, and thus reduces the maximum allowable voltage that may safely be applied to a clip before high voltage flashover occurs. By eliminating the rivet 13, a higher voltage rating fuse amount is achieved for a given base thickness and overall height, and may be seen by comparing Fig. 6B with Fig. 6A, wherein the metal-to-mounting plane distance D of both structures is held to the same standoff distance.

The elements of the structure are all suited to well-known mass production techniques at competitive cost with respect to conventional fuse holders of similar type. The assembly is easily assembled, uses less parts by eliminating the rivets, and is self-aligning This accomplishes several of the objects of the invention. An alternate form of fuse holder is shown in Figs. 7 and 7A. In this version the clips 2" have tabs 14 on their jaw ends compliantly engaging configured interior shoulders 1 5 on the walls 16. A capture post of the type previously described may optionally be employed, however, a high degree of compliance is necessary in the tabs 14 if significant rotation about the post is to be allowed. Figs. 9A and 9B are side and end elevations respectively of another alternative form of clip-in locking means wherein a clip 17 is secured to a mounting base 18 by a single central tab 19, and is captured by an engaging ridge 20 on the base engaging an appropriately configured engaging contour on the clip.

While for the purpose of illustration, various forms of this invention have been disclosed, other forms thereof may become apparent to those skilled in the art upon reference to this disclosure without departing from the scope of the invention.

Claims (13)

Claims

1. An open frame fuse holder for insertable electrical cartridge fuses having cylindrical coaxial end terminals, said holder comprising an insulating unitary mounting base including a major inner face and a major outer face, said inner face including a pair of spaced apart clip base support areas disposed thereon proximate to opposite edge portions of said inner face, a pair of electrically conductive spring clips on said mounting base, each said clip comprising a terminal lugs means a clip base mounted on a respective one of said clip-base support areas, and two spaced apart upstanding clip jaws with major jaw surfaces facing one another, portions of each of said clip jaws being configured with contours and being sprung lockingly to engage a cylindrical fuse terminal pressed between said jaws, insertion pressure actuated engaging means for locking said clips to said clip support areas by pressing the bases of said clips against said clip support areas and into snap-in engagement with portions of said mountin base, portions of said clips and said portions of said base being configured for mutual snap-in engagement, the jaws of said pair of clips being configured to place the engagement axis of each clip when mounted on said mounting base substantially coaxial with respect to the other, and pivoting means on said base for allowing twisting of at least one of said clips engaged by said pressure actuated engaging means about an axis of twist passing through the clip support area associated with said at least one clip, to provide a self-aligning feature of said at least one clip during fuse insertion to reduce mechanical stress on the engaged fuse terminal and to reduce electrical contact resistance therewith.

2. A fuse holder as claimed in claim 1 wherein said pivoting means comprises an insulating post unitary with said mounting base, said post being disposed centrally within said associated clip support area and rising therefrom, the base of said at least one clip having a hole passing through the major face thereof and configured to accept and engage said post for twisting of that clip around the post.

3. A fuse holder as claimed in claim 2 wherein said post is configured to extend above the top face of the base of said at least one clip to allow crowning deformation of the top of said post after assembly.

4. A fuse holder as claimed in any preceding claim, wherein said mounting base includes a plurality of electrically insulating barrier walls unitary with said mounting base and extending away from said inner face thereof, said walls being disposed on opposite sides of each said clip support area to present a wall face opposite each outer face of each said clip jaw, each of said walls being configured in height and length to act as an insulating protecting shield for at least a portion of said clip jaw, said walls being configured to expose the central regions of an inserted fuse to side access, and said engaging means comprising portions of said walls configured lockingly to engage matching contoured regions on said clip jaws.

5. A fuse holder as claimed in claim 4 wherein said pressure actuated engaging means comprises a plurality of locking tab means unitary with said wails and a locking region on each said clip, and each said locking region being configured lockingly to engage by snap-in engagement the adjacent locking tab means when a clip base is pressed against a clip support area.

6. A fuse holder as claimed in claim 5 wherein each said locking region comprises an elongate slot in each said clip jaw configured to engage said tabs.

7. A fuse holder as claimed in claim 6 wherein each said slot is disposed with its major axis perpendicular to said axis of twist each locking tab engaging said at least one of said clips, being configured to engage only a portion of a slot length of the engaged slot to facilitate said twisting of said at least one clip on said associated support area.

8. A fuse holder as claimed in any one of claims 4 to 7 further including twist limiting means comprising at least a portion of the interior face of each said barrier wall adjacent said at least one of said clips configured and disposed to limit the twist of said at least one of said clips by arresting engagement with a portion of said clip.

9. An open frame fuse holder for insertable electrical cartridge fuses having cylindrical coaxial end terminals, said holder comprising an insulating unitary mounting base including a major inner face and a major outer face, said inner face including a pair of spaced apart clip base support areas disposed thereon proximate to opposite edges portions of said inner face a pair of electrically conductive spring clips on said mounting base, each said clip comprising a terminal lug means, a clip base mounted on one of said clip base support areas, and two spaced apart upstanding clip jaws with major jaw surfaces facing one another, portions of each of said clip jaws being configured with contours and being spring lockingly to engage a cylindrical fuse terminal pressed between said jaws; and insertion pressure actuated engaging means including clip engaging means on said base and base engaging means on said clip configured for mutual engagement to lock said clips against said clip base support areas by pressing the bases of said clips against said clip base support areas and into snap-in engagement with said base, said pressure actuated engaging means comprising portions of suid base configured lockingly to engage portions of said clips, the jaws of said pair of clips being configured to place the engagement axis of each clip when mounted on said mounting base substantially coaxial with respect to the other, said base including a plurality of electrically insulating barrier walls unitary with said mounting base and extending away from said inner face thereof, said walls being disposed on opposite sides of each said clip support area to present a wall face opposite each outer face of each said clip jaw, each of said walls being configured in height and length to act as an insulating protecting shield for at least a portion of said clip jaws, said walls configured to expose the central regions of an inserted fuse to side access.

10. A fuse holder as claimed in claim 9 wherein said clip engaging means on said base comprise clip engaging means unitary with said barrier walls and disposed on the interior faces thereof.

1 The fuse holder as claimed in claim 9 or 10 wherein the engaging means on one of said base and said clips is a tab means, and the other of same are slots configured to engage said tab means.

12. A fuse holder for electrical cartridge fuses having coaxial cylindrical end terminals, comprising a pair of generally aligned, electrically conductive, generally channel section clips to receive respective end terminals of a cartridge fuse, and a unitary, electrically insulating mounting base which receives the clips, the clips being a snap-fit with portions of the base to lock the clips to the base.

13. A fuse holder for electrical cartridge fuses, substantially as hereinbefore described with reference to and as iiiustrated in the accompanying drawings except Figure 6B thereof.