Note: Descriptions are shown in the official language in which they were submitted.
~78996
FUSE HOLDER BLOCK
Technical Field
The subject matter of the invention is an
improved clip-in holder for electrical fuses.
5 Background of Prior Art
Conventional clip-in fuse holders for
cylindrical cartridge fuses exhibit certain deficien-
cies 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 throuah 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
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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
5 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 sur-
10 face flashover paths at high voltages unless the basethickness is appropriately increased, again resulting
in increased overall height of the fuse mount. Addition-
ally, the rivets are extra parts in the assembly, and
thus add materially to the manufacturing inventory. Ac-
15 cordingly, it is an object of the invention to provide
an inexpensive, easily assembled fuse mount 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 snap-
in 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 fre-
25 quently break off when such fuses are inserted into
conventional fuse holders with rigidly coaxially aligned
fuse clips. Accordingly, it is an object of this inven-
tion to provide for self-aligning clips as a feature of
the fuse mount to accommodate off-axis end terminals
30 without such breakage.
1178996
The present invention resides in an open frame
fuse holder for insertable electrical cartridge fuses having
cylindrical coaxial end terminals, the holder including an
insulating unitary mounting base having a major inner face
and a major outer face, the inner face including a pair of
spaced apart clip base support areas disposed thereon
proximate to opposite edge portions of the inner face, and a
pair of electrically conducting spring clips on the mounting
base, each of the clips including a terminal lug means on
the clip, a clip base mounted on one of the clip base
support areas, and two spaced apart upstanding clip jaws
with major jaw surfaces facing one another, portions of each
of the clip jaws configured with contours to springingly
lockingly engage a cylindrical fuse terminal pressed between
the jaws. Insertion pressure actuated engaging means is
provided for locking the clips to the cli.p support areas by
pressing the bases of the clips against the clip support
areas and into snap-in engagement with portions of the
mounting base, portions of the clips and the portions of
2~ the base configured for mutual snap-in engagement. The
jaws of the pair of clips are configured to place the
engagement axis of each clip when mounted on the mounting
base substantially coaxial with respect to each other.
Pivot means is provided for allowing rotation of at least
one of the clips engaged by the pressure actuated engaging
means about an axis of rotation passing through the clip
support area associated with the at least one clip, the
rotation providing a self-aligning feature of the at least
one clip during fuse insertion to reduce mechanical stress
on the engaged fuse terminal and to reduce electrical contact
resistance therewith.
According to a specific embodiment of the invention,
insulating barrier walls 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,
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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 the self-aligning feature during
fuse insertion. This provides for a maximum interfacial
contact between the fuse terminals and the clip, thereby
reducing contact resistance.
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il~78996
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.
Other objects, advantages, and features of the
invention will become apparent upon making reference to
the description to follow, the drawings, and the claims.
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1178996
Brief Description of Drawings
_
Figs. lA, lB, lC, and lD 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. 6~ is a similar view of a conventional riveted fuse
clip structure with the same metal-to-base insulation distance,
showiny 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. 7A is a cross-sectional view of the form shown in
Fig. 7 as seen from the line 7A-7A;
Fig. 8 is front elevation of an alternative version of
the fuse holder shown in Fig. lC, wherein the terminal lugs extend
upward and away from a mounting surface.
Figs. 9A and 9B are side and end elevations respectively
of an alternative form of clip locking means.
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il78996
Detailed ~escription of Invention
The exemplary form of the invention is shown
in Figs. lA, lB, lC and lD, and consists of a unitary
insulation mounting base l and two conducting fuse hold-
5 ing clips 2, the base and the clips being configuredto 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 connect-
ing lugs 3 unitary with each clip 2 extend away from
lO the mounting base 1. The clips 2 are partially shroud-
ed 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
a fuse holder with a cartridge fuse 6 installed. Fig. 8
15 shows an alternative of the fuse holder assembly shown
in Fig. lC, 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
20 clip 2 positioned for insertion. The clip 2 is mounted
on the base by pressing the clip downward between t~o
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
25 are then engaged by inward motion of the locking tabs,
securing the clip to the base. A unitary post 9 extend-
ing up from the base l engages a hole lO in the base of
the clip 2 to secure the clip against lateral motion.
Referring to Fig. lC, it will be noted that
30 the engaging slots 8 are configured longer than the
width of the locking tabs 7, thereby permitting the
clips to rotate about the mounting posts 9 as shown in
Fig. 5. The amount of rotation is restrained by close
proximity of the interior surface of each of the walls 5
35 (Fig. 5) to the base of the clip ll, thereby holding
117899~;
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
5 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
10 similar mounting base wherein a clip 2' is secured to the
base by a conventional metal rivet 13. This method of
attachment places a conductor contacting a clip in
closer proximity tG whatever mounting surface on which
the fuse holder is attached, and thus reduces the maximum
15 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 mount is achieved
for a given base thickness and overall height, and may
be seen by comparing Fig. 5B with Fig. 6A, wherein
20 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 conven-
tional fuse holders of similar type. The assembly is
25 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 holAer is shown in Figs. 7 and 7A . In this ver-
sion the clips 2" have tabs 14 on their jaw ends compliantly
30 engaging configured interior shoulders 15 on the walls 16.
A capture post of the type previously described may
optionally be employed, however, a high degree of compli-
ance is necessary in the tabs 14 if significant rotation
about the post is to be allowed. Figs- 9A and 9B are
35 side and end elevations respectively of another
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1~7899~
alternative form of cli~-in locking means wherein a
clip 17 is secured to a mounting base 1~ by a single
central tab 19, and is captured by an engaging
ridge 20 on the base engaging an appropriately config~red
5 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
10 and, therefore, this invention shall be limited only
by the scope of the appended claims.
