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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to a junction block for use with electric
circuits in automobiles and in particular to an improvement on such
junction block whereby it is made possible to prevent occurrence of
leakage currents or short circuits at the inner junction through
connectors with associated circuitry (wire harnesses).
2. Description of the Prior Art
With an ordinary junction block, it has commonly been designated that for
securing mating connectors in their fixed connected positions within a
connector housing of a junction block, the connector housing be provided
with lock means composed of a lock chamber and a retainer pawl. When
fabricating a lower casing and housing of such design by plastic moulding,
the housing will necessarily be formed with an opening in its bottom wall
through which the core is to be removed for withdrawal of the finished
moulding from the pattern.
In the event, therefore, water should once soak or filter, from outside,
into the casing through a lock portion of the upper and lower casings, for
example, it flows, through the bus bar distribution board and through that
opening, onto the bottom wall of the housing. The water then travels
spreading along the bottom wall of the housing until it moistens the tabs
and female terminals in the connector. This may cause leakage currents or
short circuits to occur between the adjoining bus bars or female terminals
in the casing. This objectionable problem arises frequently since the
junction block usually is disposed within the engine room of the
automobile where during the car washing, water under pressure tends to get
in there may occur, within the junction block, dew condensation due to
significant temperature differences between high and low.
Furthermore, with a junction block accomodating a number of connectors, it
is usual in design that the connector housing may have some tab holes
unused or left open without corresponding tabs being inserted
therethrough. In that case, the same problem as described above may arise
since external water may enter the connector housing through this unused
hole and cause leakage currents or short circuits between the connector
elements.
SUMMARY OF THE INVENTION
The invention, therefore, is directed to settle the above described
problems by providing an improved junction block which is capable of
effectively preventing occurrence of leakage currents or short circuits at
the interconnections of the mating terminal elements in the connector
within the block.
In order to achieve the above object, a junction block according to the
invention comprises an upper casing and a lower casing forming in it a
housing for receiving mating connectors and a bus bar distribution board,
the bus bar having integral tabs which extend perpendicularly to the bus
bar and into the connector housing through respective holes formed in the
bottom wall of the connector housing, the improvement being that there is
provided at least one deflecting barrier member adjacent an opening formed
in the bottom wall of the housing, which opening has necessarily been
formed in the bottom wall of the housing by the necessity of core removal
in the moulding operation for the housing, or adjacent an unused hole,
which otherwise would receive an associated tab, formed in the bottom wall
of the housing, in such manner that the deflecting barrier member
prohibits any water or water drops which have soaked in through the
opening in the bottom wall of the housing or has been produced within the
junction block due to dew condensation, from reaching the tab base zone in
the housing.
The invention will now be described in further detail with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a secional view of an essential portion of a junction block
construction according to an embodiment of the invention;
FIG. 2 is a perspective view, partly cut away, of a connector housing of
FIG. 1 junction block with a deflecting barrier member of the invention
and a not-shown opening for core removal formed in the bottom wall of the
housing;
FIG. 3 is a perspective view showing the connector housing and its mating
connector according to the prior art arrangement in separation from each
other;
FIG. 4 is a sectional view showing the two parts in FIG. 3 being coupled
with each other; and
FIG. 5 is an enlarged sectional view of a portion of the FIG. 4 assembly.
DETAILED DESCRIPTION OF THE INVENTION
Before describing the invention which is illustrated in FIGS. 1 and 2, a
prior art junction block will first be described with reference to FIGS.
3, 4, and 5 throughout which drawings like parts carry like reference
numerals.
Reference numeral 1 indicates an upper casing of the junction block and 2
its lower casing. On the lower casing 2 is integrally formed a connector
housing 3 for receiving a connector 10 attached to the distal end of a
wire harness 13. The connector housing 3, as shown in FIGS. 3 and 4, is
formed at its outer side with an expanded lock chamber 4 for accommodation
of a lock arm 11 formed on the connector 10. The lock chamber 4 in turn is
provided on its inner wall with a retainer pawl 4a which is adapted for
engagement with a cooperating retainer pawl 11a formed at the extremity of
the lock arm 11 on the connector 10. Reference numeral 5 indicates a bus
bar distribution board housed in the casing, consisting of a number of bus
bars 6 having selected circuit patterns and an insulating base plate 7.
Tabs 8 extend perpendicularly to the bus bar and into the housing 3
through respective holes 3b. It is intended that these tabs 8, when the
connector 10 is fitted in the housing 3, make electric contact with their
mating female terminals 12.
With the thus arranged prior art junction block, it is necessary to provide
lock means in the form of the lock chamber 4 and its retainer pawl 4a for
the purpose of securing the mating connector 10 locked in position within
the connector housing 3. When manufacturing the lower casing 2 and housing
3 by plastic moulding, accordingly, the housing 3 as finished is
necessarily formed in its bottom wall 3a with an opening 3c through which
the core for formation of the retainer pawl 4a is to be removed.
If water should once enter the casing from outside through, for example,
the locking portions (not shown) of the upper and casings, it (as shown in
FIG. 4 and at W in FIG. 5) soaks through the bus bar distribution board 5
onto the bottom wall of the housing 3 via the opening 3c. The water then
creeps spreadingly along the bottom wall 3a until it moistens the tabs 8
and female terminals 12. This may cause occurrence of short circuits or
leakage currents between the adjoining bus bars 6 and 6 or female
terminals 12 and 12 of the connector 10.
Furthermore, this is the case, too, where the soaking of water specified
above takes place via an unused hole 3b with no tab inserted therethrough.
According to the invention, however, as shown in FIGS. 1 and 2, in a
junction block comprising upper and lower casings 1 and 2 having on
integral connector housing 3 for the receipt of the mating connector 10
and a bus bar distribution board 5, the bus bar having tabs 8 extending
perpendicularly to it and into the housing 3 through respective holes in
the bottom wall 3a of the housing 3; the improvement is that there is
provided a deflecting barrier member 9 in the form of an elongate
rectangular bar disposed adjacent the opening 3c in a manner to isolate
the tab base zone S (See FIG. 2) from the opening 3c for creeping passage
of water or water drops along the bottom wall 3a of the housing 3
therebetween, while directing water or water drops, which have been
accumulated around the opening, downwardly to facilitate their discharge
outside from the function block.
Alternatively, the connector housing 3 may be formed in separation from the
lower casing 2 and the two members may be secured together by means of
screws. Though this deflecting barrier member is shown as an elongate
rectangular bar, it may be shaped otherwise, e.g. into a curved or
C-shaped bar, an annulus, a ring of various sections, etc. This depends on
the relative location of the junction block in the automobile, especially
in the engine room, and its attitude as installed. The barrier member also
is preferred to be of 1 mm and over in height, more preferably 3 mm to 5
mm, from the inner surface of the bottom wall 3a of the connector housing
3.
With this arrangement of the invention, any water or water drops which have
entered from outside or been internally generated due to dew condensation,
find no way to creep along the bottom wall 3c of the housing 3 into the
tab base zone S because of the deflecting barrier member 9 which serves to
conduct the water or water drops in the discharging direction indicated at
W in FIG. 1.
Hence, it is assured to avoid occurrence of short circuits or leakage
currents between the bus bars 6 and 6 or between the contact terminals 12
and 12 of the connector 10, which otherwise could lead to operational
troubles such as malfunction of the relays, overheating of the
distribution wire boards, etc.
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