AU604133B2 - Tank construction - Google Patents

Description

Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-62 %COMPLETE SPECIFICATION

(ORIGINAL)

0 41 FOR OFFICE USE: Ap'plication Number: Lodged: 00 "in6plete Specification Lodged: 0 C Accepted: 0 Published: Class Int. Class c,qlaleed Art: 0 4 0 3 .0 Name of Applicant: Ad~esof Appicant: Actual Inventor: Address for Service.

TO BE COMPLETED BY APPLICANT JOHN LESLI,", GRAH~AM McNAB and KEITH EDWARD OPIE both of 23 Commercial Street, Marleston, State of South Australia, Commonwealth of Australia JOHN LESLIE GRAHAM McNAB and KEITH EDWARD OPIE Care of R.K. MADDERN ASSOCIATES, 345 King William Street, Adelaide, State of South Australia, Commonwealth of Australia.

Complete, Speciflcatior, for the Invention entitled: "TANK CONSTRUCTION" Tho following statement Is a [Lull description of this Invention, Including the fbest'method of performilng lt' k~nown to me, us.

CANBERRAAC.T. ACCETED AND AMU)lY-LI FB 4826 IM Q/77 JS This invention relates to an improved construction for a tank, for example, for a septic tank.

It has been found that space limitations frequently require that tanks have a generally rectangular shape in plan, and a cylindrical tank having its cylinder axis 3 vertical is likely to be too wide for many sites.

Large diameter vertical cylindrical tanks are cos-- Soo effective with respect to materials used for the volume 0 Q0 C, 0 0°o contained with respect to tensil.r stresses, providing 0 000 0 0 0 .oo 10. what is often calleC hoop strength, but are liable to 00D o local buckling under compression forces which cen be 000 applied externally, if made of thin wall somi-flexibie material such as fibreglass reinforced plastics.

0 0 9 0o°o Rectangular tanks with generally flat sides can 0 9o 0 oo 15. meet many space limitations, however forces on the sides So of such tanks require the sides to have enough material of sufficient strength to provide the required stiffness to prevent distortIon, -nis being much greater than nieeded for cylindrical tanks.

The effects of stresses in flat sided tanks can only be withstood by flexible materials such as plastics Sif large amounts of plastics material, or ribbed wallsr are used for cunstruction. Rigid materials such as steel, cement and masonary have considerable mass, but for that reason handling and installing are more difficult than tanks made of lightweight flexible plastic i materials such as glass reinforced polyest- resins.

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Thin wall fibreglass reinforced plastics material must be made sufficiently rugged to withstand the hydraulic pressures imparted, and if that occurs with the previously used configuration or tank-shape, the material costs become excessively high. An object of this invention is to provide an improvement in the design of the shape of a tank such that it need not necessarily be wholly cylindrical, or have excessively thick walls.

Another object of this inr-ntion is to provide a tank which has a generally rectangular shape and which uses the advantages of circular form and thus can be manufactured from flexible materials without elaborate stiffening. It follows that there would also be cost savings in using rigid materials although there would be extra mass compared to most plastic materials.

Since appropriately selected plastic material can also provide resistance to corrosion and chemical attack, it is more suited to many tank applications.

As said above, a circular tank has much greater strength because of its "hoop strength" than say a vessel having flat sides, and in an embodiment of this invention advantage is taken of this phenomenon, in that a fibreglass tank comprises upwardly-extending side walls, and horizontally-extending base wall and lid, characterised in that the side walls comprise two parts which, in plan, are substantially C-shaped, and which intersect face-to-face, to thus form two upwardly-extending inwardly-directed ribs.

-3- The inwardly *Lirected ribs, in being flanked by the side walls z;zrving oul-wardly therefrom, constitute shallow beams which res4.st deflection, and this can be enhanced by a load member (which can be the lid itself) joining the ribs at thair upper ends. The load member must be able to function either as a tension, or as a 1.".pression member.

V Since the side wall upper portion of the container i~ C.,port-izn is constrained by the load member against inward VCK 10. or outward deflection due to hydraulic pressures, and the lower portion also constrained by the base of the container, the hoop strength will be elf ecti .re cver most if not all of the depth of the container portion, even though some of the depth may not benef it as much as the base or mouth.

An embodimant of the invention is described hereunder in some detail with reference to, a.nd is illustrated in, the accompanying drawings, in which: Fig. 1 is a plan view of the container portion of a tank, Fig. 2 is an "exploded" sectional. view showing a central section through the container walls and also through the tank lid, taken on line 2-2 of Fig. 1, and J Fig. 3 is a perspective view of the container portion.

In this embodiment, a septic tank comprises a container portion 10 and a lid 11, The container portion.

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and lid 11 both locate over an irlet tube 12 at one end, and an outlet baffle 13 exists at the other.

Both the container portion 10 and lid 11 are provided with outstanding flanges respectively designated 14 and 15 at tne mouth of the container portion 10, and these flanges become contiguous when bolted together by fasteners, or cemented together.

I T h The shape of the container portion 10 and lid 11 000 iI 0o both include part circular portions designated 18, and 0" 10. these intersect in upwardly extending inwardly directed ribs 19, on a plane P-P which is a chordal plane to both 0"Q"00 the part round portions. The base 20 at thef location of the chordal plane also has an upwardly projecting rib 21, j oo while the lid 11 has a tension member 22 extending c C C 15. transversely across it, which effectively joins the upper ends of the ribs 19.

The hoop strength of the part round portions would Sbe lost if it were not for the base 20 and its rib 21 Sat the lower portions of the container walls, and for the tension member 22 extending across the upper portion, but the existence of these two very inexpensive moulded portions preserve most although not all of the hoop strength of the part circular container portions 18 which make up the tank. A baffle plate 24 extends between opposite side walls of the tank.

Since these mechanical properties are preserved, for design purposes the tank will approximate two separate and independent circular tanks and therefore 5

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the need for excessive thickness of the walls of the tanks is averted.

One of the problems which has been encountered heretofore has been the cost of transport, but this can be reduced if the side walls of the container portion are upwardly divergent as shown. The inlet tube 12 and baffle 13 can be separate and can be positioned on 0g site.

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Claims (4)

1. A septic tank having upwardly-extending side walls, and horizontally-extending base wall and lid, characteri'ed in that the side walls comprise two parts which, in plan, are substantially C-shaped, and which intersect face-to-face, to thus form two upwardly-extending inwardly-directed ribs, I a transverse rib extending across the base of the tank between lower ends of the upwardly-extending ribs, and a load member extending across the tank and Soo"a effectively joining the upwardly-extending ribs at th .r upper 00 0 o ends. 0 0 oo on S2. A septic tank according to claim 1 further comprising o0 0 0o 2 outstanding flanges on both the tank and the lid, and fasteners for securing the flanges together face to face, said load member extending between flanges of the lid.

3. A septic tank according to claim 1 or claim 2 wherein the side walls diverge in an upward direction.

4. A septic tank according to any preceding claim further comprising an inlet tube, being partly engaged by a tank wall and partly engaged by the lid, and an outlet baffle extending into the tank from a tank wall, said inlet tube and said outlet baffle being positioned at opposite ends of the tank, distal from the open faces of the substantially C-shaped parts. 7 1,I '3 T ?0- I duscribul with r:u~ronce to aunc3 asu ii ~ctld accompanyingj dra~wingjs. DATD thio 24thi dayj o~ Juno, I§@ B hoir a ont truo R..MDBU& SCAL'

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