[0001] This invention relates to electrical systems and, in particular, fuse assemblies
therefor.
[0002] Where an electrical system is installed within a classified area, eg potentially
explosive and/or inflammable atmospheres, there is a requirement for fuse assemblies
used in the system to be fully protected to an explosion-proof/flame-proof British
Standard (BS 5501 Part 5). Thus, it is necessary for the fuse assemblies to be tested
and certified by an appropriate authority as complying with BS 5501.
[0003] In order to comply with safety regulations, it is the present practice to install
the individual fuse assemblies together within an explosion-proof/flame-proof enclosure.
This practice has the disadvantage that a suitable enclosure is large, heavy and expensive
to produce.
[0004] An object of the present invention is to provide an alternative fuse assembly for
use in hazardous atmospheres which does not suffer from the disadvantage discussed
above.
[0005] According to the present invention a fuse assembly for use in harzardous atmospheres
comprises an elongate enclosure which is explosion-proof/flame-proof and dimensioned
to accept a specified size of fuselink, the enclosure having an opening through which
the fuselink is fitted closable by a tightly fitting cover, electrical connectors
extending through end walls of the enclosure and supported in spaced relationship
within the enclosure and fixing means whereby the terminals of the fuselink can be
directly and fixedly connected to respective connectors.
[0006] Preferably, the cover is hinged at one end to the enclosure and has fixing means
at the other end.
[0007] Conveniently, the enclosure and cover would be moulded from a suitable plastics material
and would be of a thickness sufficient to ensure the integrity of the enclosure should
an internal spark or explosion occur.
[0008] In order that the invention may be readily understood, one embodiment will now be
described, with reference to the accompanying drawing, in which:
Figure 1 is a plan view of the enclosure, with its cover removed.
Figure 2 is a side view of the enclosure and cover, partly in section.
Figure 3 is a view similar to Figure 1 with the form of an elongate rectangular case
1 dimensioned to accommodate a cartridge fuselink manufactured to BS 88, Part 2. The
assembly comprises the elongate case 1 and cover 2, which are moulded from a suitable
plastics material, and of a suitable thickness, to ensure flameproof and explosion
proof integrity. The case 1 has an elongate opening 3 which is shaped and dimensioned
to enable the fuselink 6 to be passed through into the case. A pair of connectors
4 are provided, which are manufactured to BS 5501, Part 6, and have threaded holes
in their heads 5 located within the case 1 at opposite ends thereof, the threaded
holes in the heads being spaced a distance corresponding to the spacing of the apertures
(fixing centres) normally provided in the terminals 6a of the cartridge fuse link
6. The connectors 4 include limbs 7 which pass through suitable apertures in the respective
end walls of the case. Preferably, the connectors are fitted during moulding of the
case. The outer, external ends of the limbs 7 are provided with cable clamping facilities
in the form of screwed cable connectors 8.
[0009] The cover 2 is dimensioned and shaped to correspond to the wall of the case defining
the opening 3 and is hinged at one end via integral bosses 9 and 10 in the cover and
case respectively and a pin 11 therethrough. To prevent removal of the pin 11 it is
inserted fully within a blind hole, through the parts 9 and 10 and the insert end
is then sealed with expoxy resin. The other end of the cover is provided with a captive
screw 12 which can be screwed into a threaded aperture provided in a thickening 13
of the respective end wall, and thereby tightened down onto the case.
[0010] The fuselink 6 is fixedly connected via its terminals 6 directly to the heads 5 of
the connectors 4 via fixing screws 14.
[0011] As shown, the side walls of the enclosure 1 have spacer lugs 15 formed therein so
that a number of fuse assemblies can be mounted side-by-side on a fuseboard, or in
a further enclosure with a miniumum space defined between them. Conveniently, they
may be fitted squarely together on the fuseboard by providing a DIN rail on which
the assemblies are mounted via a shaped slot 16 in the bottom wall of each enclosure.
To retain each enclosure in position on the DIN rail, a plastics clip 17 is provided
which is slidably mounted in a bore 18 opening into the groove 16.
1. A fuse assembly for use in hazardous atmospheres comprising an enclosure which
is explosion proof/flameproof, characterised in that the enclosure (1) is dimensioned
to accept a single specified size of elongate fuselink (6), in that the enclosure
has an opening (3) through which the fuse link is fitted which is closable by a tightly
fitting cover (2), in that electrical connectors (4) extend through end walls of the
enclosure and are supported in spaced relationship within the enclosure, and in that
fixing means (14) are provided whereby the terminals of the fuselink can be directly
and fixedly connected to respective connectors.
2. A fuse assembly according to claim 1, characterised in that the cover (2) is hinged
(via parts 9 to 11) at one end to the enclosure (1) and has fixing means (12) at the
other end.
3. A fuse assembly according to claim 1, or 2 characterised in that the enclosure
(1) and cover (2) are moulded from a suitable plastics material and are of a thickness
sufficient to ensure the integrity of the enclosure should an internal spark or explosion
occur.
4. A fuse assembly according to any one of claims 1 to 3, characterised in that each
enclosure is formed with a transverse shaped slot (16) whereby a number of said assemblies
can be mounted side-by-side on a DIN rail.
5. A fuse assembly according to claim 4, characterised in that each enclosure is provided
with spacers (15) on its side walls to define a minimum clearance between the mounted
assemblies.
