Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to inspection chambers of prefab-
ricated construction for use in drainage or sewerage systems and
of the kind having a base with at least one channel in the base
extending between an inlet opening and an outlet opening. Normal-
ly there is a main channel extending across the base between an
inlet opening and an outlet opening and a number of branch channels
each extending across the base from a respective inlet opening to
the main channel.
One of the problems associated with prefabricated drain-
age inspection chambers is their bulk volume which results in veryexpensive storage and transportation costs. It is already known
to make up the height of a drainage inspection chamber by supèr-
imposing one or more separately formed side wall sections on the
base of the inspection chamber. However, because the wall sections
have always been arranged in vertically abutting relationship in
the assembled condition of the drainage inspection chamber, the
total bulk volume remains the same as a one-piece drainage inspec-
tion chamber~
One object of the present invention is therefore to
provide a drainage inspection chamber made up from a base and one
or more side wall sections, and which can be stored and transported
with a bulk volume less than the drainage inspection chamber in
its assembled condition.
A further object is to provide a drainage inspection
chamber which is variable in height.
A prefabricated drainage inspection chamber according to
the invention comprises a base and at least two separately formed
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vertically extending side wall sections. One side wall section
has an internal location which in the assembled condition of the
inspection chamber rests upon the base to support the one side
wall section on the base, and the side wall sections locate
vertically relatively to each other by projections on one locating
between ribs on the other, so that one side wall section extends
higher than the other. The base has a maximum external dimen-
sioning such that in the disassembled condition of the inspection
chamber it can be stowed in the one side wall section by inserting
it, inverted, through the top of the one side wall section until
it rests on the internal location.
Embodiments of drainage inspection chamber in accordance
with the invention will now be described by way of example with
reference to the accompanying drawings in which:
Figure 1 shows a sectional elevation o a first embodi-
ment of drainage i~spection chamber in its stowed condition,
Figure 2 shows a partialsectionc~ el~vation of the
drainage inspection chamber of Figure 1 in its assembled condition,
Figure 3 shows in section and to a larger scale than
Figure 2 how two side wall sections are fitted together when assem-
bling the drainage inspection chamber of Figure 1,
Figure 4 shows in section a modification of the fitting
arrangement of Figure 3,
Figure 5 shows a partial sectional elevation of the line
V-V of Figure 6 showing how the two side wall sections are fitted
together in accordance with another embodiment of the invention,
Figure 6 shows a partial elevation of the lower side
wall section of the drainage inspection chamber of Figure 5,
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Figure 7 shows a plan view of the upper side wall
section of the drainage inspection chamber of Figure 5, and
Figure 8 shows a detail looking in the direction of
arrow VIII of Figure 7.
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Throughout the drawings the same reference numerals
have, as far as possible, been used to designate corresponding
parts.
Referring now to Figures 1 to 3 of the accompanying
drawings tlle drainage inspection chamber comprises a base 1, a
lower cylindrical side wall section 2 and an upper cylindrical
side wall section 3, all formed by injection mouldin~ of plastics
material e.g. polypropylene. The base 1 is of the construction
described in our Canadian Patent No. ltl20,513,
The maximum external dimensions of the base 1 and side
wall section 2 are such that they can both be stowed within the
side wall section 3, with the base 1 within the section 2.
As can be seen from Figure 1 the base 1 is stowed upside down in
the section 2 and its rim ~ rests on internal rib 5 of section ~.
The lower side wall section 2 i5 located rclatively to the upper
side wall section 3 by plastics pins 6 which pass through bosses 7
on the upper side wall section 3 and whose inner ends locate in
thc space betwcen annular ribs $ fornl~d on the outside of the
lower side wall section 2. There a.re three bosses 7 syn~etrically
disposed at 120 to each other about the axis of the side wall
section 3.
As shown in chain-dotted line in Figure 1 a series of
inspection chambers can be stored in the stowed condition one
on the other with the adjacent upper side w~ll sections of
adjacent drainage inspection chan~bers locating on one another.
The second outer and inner side wall sections shown in chain-dotted
line in Figure 1 are referenced 21 and 31,
If preferred the hase 1 may be stowed the right way up
and located within section 2 by small protrusions on the internal
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wall of section 2. When assembling, the base is pressed down
beyond the protrusions and retained in position.
To assemble the drainage inspection chamber shown in
Figure 1, the base 1 is lifted out of the side wall section 2
and inverted. The side wall section is then placed over the base 1
so that its in-ternal rib 5 rests on the rim 4 of the base 1.
The upper side wall section 3 is then fitted to the lower side
wall section 2 as will now be described.
The side wall section 2 is provided with a series of the
aforementioned external annular ribs 8 which are regularly
spaced from each o~her along the length of the side wall section 2,
the spacing between adjacent ribs 8 being just slightly greater
than the diameter of the pins 6 to permit location oE the pins
be.tween adjacent ribs 8. The ribs 8 are interrupted at three
positions symmetrically spaced .Erom each other at 120 about the
axis of the side wall section 2, to form three linear passageways
through the .ribs 8 along the length of the side wall section 2.
The extent of the interruptions is suff~icient to allow the passage
of the pins 6. Thus with the leading, i.e. projecting, ends
of the pins 6 locating in the passageways the side wall section 3
can be slid longitudinally along the side wall section 2 to adjust
the heigh-t of the drainage inspection chamber. After such
adjustment the upper side wall section 3 is rotated to move the
pins out of the passageways and between -the ribs 8.
As shown in Figure 4 another method of adjustment and
location includes bosses 21 moulded integrally with the side wall
of section 3. For height adjustment the bosses slide longitudinally
in the three linear passageways running through ribs 8. When the
required helght is reached, section 3 is rotated -to move the bosses
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21 out of -the passayeways and into position between the
ribs 8 to set the height.
Furthermore, ex-tremely accurate final height adjustment
may be achieved by having the ribs 8 forming a screw thread, it
being a three start thread to accommodate the three bosses 21.
The upper side wall section is also provided with a series
of external ribs 10 similar to the ribs 8. Thus a Eurther side wall
section of suitably larger diameter could be fitted on the side
wall section 3 i desired. The ribs 8 and 10 also serve for
strengthening the side wall sections 2 and 3.
A resilient sealing ring 11 (Figure 3) oE square section
is adhesively secured to the outside of the section 2 and seals
with the internal surface of the section 3 when the latter is
fitted. To permit the pins 6 to pass the sealing ring 11 when
assembling the drainage inspection ch~m~er, the p:Lns are drawn
part way out of the bosses from -the pOSitiOIl shown in Figure 2
to the retracted posi-tion shown in F`igure 3.
Referring more particularly to E`i~ure 3, the pins 6 have
two snàp fitting positions in the bosses 7 so that tlley cannot be
readily withdrawn from the bosses 7. ~or this purpose the pins
6 are provided with spaced projections 12 and 13 which have a
sloping lead~ng face 14 terminating at radial shoulder 15. The
bosses 7 have a sleeve portion 16 with a tapered lead-in 18, and
shouldexs 19 at their inner ends formed by gaps in the bosses 7.
Thus as the pins 6 are pushed into the bosses 7, the leading
projections 12 pass through the sleeve portion 16 and the pins
are stressed under their own resilience until the leading
projections 12 snap behind the shoulder 19. The pin is then
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in its retracted position(Figure 3)with the leading end o~ the
pin lying within the sleeve portion 16 and the rear projections 13
then lie within the lead-in 18. Further movement of the pins
6 into the hosses 7 causes the projections 13 similarly to snap
behind the shoulder l9 and the pins are then in the extended
position shown in Figure 2 in which their projecting ends can
engage between the xibs 8.
In Figure 2 the drainage inspection chamber is shown
fitted with a cover receiving plate 20. Not only can the total
height of the drainage inspection chamber be set by interfitting
of the side wall sections 2 and 3 as described above, but it can also
be set by cutting off a portion of the length of the upper section 3.
Referring now to Figures 5 to 8, the lower and upper
cylindrical side wall sections are a~ain referenced 2 and 3
respectively and are formed by inject:ion moulding of plastics
material. The base l is not shown i.n Figures 5 to 8 but sto~s
within the side wall section 2 and is assembled on the side wall
section 2 in exactly the same manner as shown in Figures l to 3,
the side wall section again being provided with the in~ernal rib 5
for these purposes.
s best seen in Figure 6 the external rib formation on
the side wall section 2 is different Erom that shown in Figures 1 to
3~ in that the series of horizontal ribs 22 are intersected by
a series of vertical ribs 23.
The ribs 22 are interrupted at three positions
symmetrically spaced from each other at 120 about the axis of the
side wall section 2 to form three linear passageways through the
ribs along the length of the side wall section 2, one of these
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passa~ew~ys bein~ shown at 2~ in Figure 6. Each of the
passageways is bounded on one side bv a vertical rib 23 and
on the other side by the end portion 25 of ribs 22. The end
portions 25 are provided wi-th upward projections 26 and 27 one
at the extremity of the end portion 25 and the other partway along
the end portion 25. Each of the projections 26 and 27 has a
sloping leading face 28 and a shoulder 29 forming the rear face.
The side wall section 3 is provided with three integral
U-shaped projections 30 on its internal surface. The projections
30 are symmetrically spaced at 120 -to each other abou-t the axis
of the side wall section 3. The width of -the through passageways
in the side wall section is sufficient to allow the passage of
the projections along them. Thus with the projections 30
locat~ng in the passageways the side wal.l sec-tion can be s].id
along the side wall sec-tion 2 to adjust tl-e hei~ht of the drainage
inspection chamber. After such ad; llS tment the side wall section
can be rotated to move the projecti.ons out of the passageways and
between the end portions 25 o:E the r:Lbs 22. The Eirst part of
this rotation will cause the project:Lons 30 to ride up the sl.oped
faces 28 of the projections 26 until it drops behind the shoulders
29 of the projections 2~, so that they are in the position shown
at 301 in Figure 6. This relative positioning of the side wall
sections 2 and 3 can be used Eor stowing or for initial temporary
height setting. For -the final posi-tioning of the sections
2 and 3, the section 3 is :Eurther rotated so that the projections
30 are in the posi.tion shown at 30" in Figure 6 between the shoulder
29 of the projection 27 and the ad-)acent ver-tical rib 23.
