GB2048980A

GB2048980A - Drainage inspection chambers

Info

Publication number: GB2048980A
Application number: GB8012616A
Authority: GB
Original assignee: Reed International Ltd
Current assignee: Reed International Ltd
Priority date: 1979-05-04
Filing date: 1980-04-17
Publication date: 1980-12-17
Also published as: GB2048980B

Abstract

In a collapsible plastics drainage inspection chamber formed in three or more sections, base section 1, which incorporates the drainage channels, is stowable (e.g. by inverting as in Fig. 1, not shown) wholly within telescopic wall sections 2, 3. The wall section 2 has external ribs 8 engageable by radially-retractable pins 6 on the section 3. In a modification the retractable pins 6 are replaced by fixed projections engaging bayonet slots in the ribs 8. A seating ring 11 is provided. <IMAGE>

Description

SPECIFICATION Improvements relating to drainage inspection chambers This invention relates to inspection chambers of prefabricated 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.

Normally 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 drainage inspection chambers is their bulk volume which results in very expensive storage and transportation costs. It is already known to make up the height of a drainage inspection chamber by superimposing 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 onepiece drainage inspection 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.

According to the present invention a drainage inspection chamber comprising a base and at least two separately formed side wall sections is characterised in that the base has a maximum external dimensioning such that it can be stowed within one side wall section and said one side wall section has a maximum external dimensioning such that it can be stowed within the other side wall section, and is further characterised in that, the two side wall sections in the assembled condition of the drainage inspection chamber are located vertically relatively to one another by projections on one of said side wall sections locating between ribs formed on the other side wail section.

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 of a first embodiment of drainage inspection chamber in its stowed condition, Figure 2 shows a partial sectional elevation of the drainage inspection chamber of Figure 1 in its assembled condition, Figure 3 shown in section and to a larger scale than Figure 2 how two side wall sections are fitted together when assembling 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 on 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, 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.

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 the 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 moulding of plastics material e.g. polypropylene. The base 1 is of the construction described in our Patent Application No.

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 4 rests on internal rib 5 of section 2. The lower side wall section 2 is located relatively 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 the space between annular ribs 8 formed on the outside of the lower side wall section 2. There are three bosses 7 symmetrically disposed at 1 200 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 wall sections of adjacent drainage inspection chambers 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 base 1 may be stowed the right way up and located within section 2 by small protrusions on the internal 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 wail section is then placed over the base 1 so that its internal 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 other 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 of the pins between adjacent ribs 8. The ribs 8 are interrupted at three positions symmetrically spaced from each other at 1 200 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 sufficient 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 height 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 height is reached, section 3 is rotated to move the bosses 21 out of the passageways and into position between the ribs 8 to set the height.

Furthermore, extremely 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 further side wall section of suitably larger diameter could be fitted on the side wall section 3 if desired. The ribs 8 and 10 also serve for strengthening the side wall sections 2 and 3.

A resilient sealing ring 11 (Figure 3) of 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 chamber, the pins are drawn part way out of the bosses from the position shown in Figure 2 to the retracted position shown in Figure 3.

Referring more particularly to Figure 3, the pins 6 have two snap fitting positions in the bosses 7 so that they cannot be readily withdrawn from the bosses 7. For this purpose the pins 6 are provided with spaced projections 1 2 and 13 which have a sloping leading face 14 terminating at radial shoulder 1 5. The bosses 7 have a sleeve portion 16 with a tapered lead-in 18, and shoulders 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 1 2 snap behind the shoulder 1 9. The pin is then in its retracted position (Figure 3) with the leading end of the pin lying within the sleeve portion 1 6 and the rear projections 1 3 then lie within the lead-in 18. Further movement of the pins 6 into the bosses 7 causes the projections 13 similarly to snap behind the shoulder 1 9 and the pins are then in the extended position shown in Figure 2 in which their projecting ends can engage between the ribs 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 again referenced 2 and 3 respectively and are formed by injection moulding of plastics material. The base 1 is not shown in Figures 5 to 8 but stows within the side wall section 2 and is assembled on the side wall section 2 in exactly the same manner as shown in Figures 1 to 3, the side wall section again being provided with the internal rib 5 for these purposes.

As best seen in Figure 6 the external rib formation on the side wall section 2 is different from 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 1200 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 passageways being shown at 24 in Figure 6. Each of the passageways is bounded on one side by a vertical rib 23 and on the other side by the end portion 25 of ribs 22. The end portions 25 are provided with 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 1 200 to each other about 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 locating in the passageways the slide wall section can be slid along the side wall section 2 to adjust the height of the drainage inspection chamber. After such adjustment the side wall section can be rotated to move the projections out of the passageways and between the end portions 25 of the ribs 22. The first part of this rotation will cause the projections 30 to ride up the sloped faces 28 of the projections 26 until it drops behind the shoulders 29 of the projections 26, 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 for stowing or for initial temporary height setting. For the final positioning of the sections 2 and 3, the section 3 is further rotated so that the projections 30 are in the position shown at 30" in Figure 6 between the shoulder 29 of the projection 27 and the adjacent vertical rib 23.

Claims

1. A prefabricated drainage inspection chamber comprising a base and at least two separately formed side wall sections is characterised in that the base has a maximum external dimensioning such that it can be stowed within one side wall section and said one side wall section has a maximum external dimensioning such that it can be stowed within the other side wall section and is further characterised in that the two side wall sections are located vertically relatively to one another by projections on one of said side wall sections locating between ribs formed on the other side wall section.

2. A prefabricated drainage inspection chamber according to Claim 1, wherein said base stows within the adjacent side wall section and said adjacent side wall section stows within the next upper side wall section.

3. A prefabricated drainage inspection chamber according to claim 1 or 2, wherein in the stowed condition the base rests on an internal location of the side wall section receiving it and the two side wall sections interfit through the location of said projections between said ribs

4. A prefabricated drainage inspection chamber according to Claim 1, 2 or 3, wherein said projections are spaced around the side wall section carrying them and the other side wall section has a series of said ribs spaced from each other along it, vertically extending passageways being provided through said ribs for receiving said projections, said projections being able to pass along said passageways to enable one of said side wall sections to be slid along the other side wall section to adjust the height of the drainage inspection chamber and relative rotation of said side wall sections causing said projections to move out of said passageways and locate between adjacent ones of said ribs.

5. A prefabricated drainage inspection chamber according to any preceding claim, wherein said projections comprise separately formed pins located in sleeve portions of bosses formed integrally with the side wall section carrying said pins.

6. A prefabricated drainage inspection chamber according to Claim 5, wherein said pins have a first snap-fitting position in said sleeve portions in which their leading ends lie within the sleeve portions of the bosses and a second snap-fitting position in which the leading ends of the pins project beyond the sleeve portions.

7. A prefabricated drainage inspection chamber according to Claim 4, wherein said ribs have end portions adjacent said passageways provided with at least one upwardly extending projection so that as said side wall sections are rotated relatively to each other said first mentioned projections ride over said upwardly extending projections on said rib end portions and become trapped behind them.

8. A prefabricated drainage inspection chamber according to Claim 7, wherein each of said rib end portions has two said upwardly extending projections, one being at the extremity of the rib end portion adjacent the passageway and the other being part way along the rib end portion so that the first mentioned projections have a first location between said two upwardly extending projections and a second location beyond the upwardly extending projection part way along the rib end portion.

9. A prefabricated drainage inspection chamber according to Claim 8, wherein said second location is between said upwardly extending projection part way along said rib end portion and a vertically extending rib on the side wall section.

10. A prefabricated drainage inspection chamber substantially as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.

11. A prefabricated drainage inspection chamber substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.

12. A prefabricated drainage inspection chamber substantially as hereinbefore described with reference to Figures 5 to 8 of the accompanying drawings.

New claims or amendments to claims filed on 5th September 1 980.

Superseded claims 1.

New or amended claims:

1. A prefabricated drainage inspection chamber comprising a base and at least two separately formed side wall sections is characterised in that the base has a maximum external dimensioning such that it can be stowed within one side wall section and one side wall section has a maximum external dimensioning such that it can be stowed within the other side wall section and is further characterised in that the two side wall sections are located vertically relatively to one another by projections on one of said side wall sections locating between ribs formed on the other side wall section.