AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Standard Patent Applicant(s): Graf Plastics GmbH Invention Title: Underground tank The following statement is a full description of this invention, including the best method for performing it known to me/us: - 2 UNDERGROUND TANK The present invention relates to an underground tank according to the preamble of claim 1. In this connection it is to be noted that an underground tank 5 is a tank which is normally installed in the earth, and only in certain circumstances could be used above ground as well. Such underground tanks e.g. are known from the catalogue R26, edition 2005, "System for Using Rainwater" or the brochure "GARANTIA" 2006, respectively distributed by the company Otto 10 Graf GmbH Kunststofferzeugnisse, D 79331 Teningen, with the designations DIAMANT, COLUMBUS and CRISTALL. These underground tanks e.g. are manufactured by rotation moulding processes and with the already unitarily integrated tank dome which significantly protrudes beyond the adjacent contour. 15 Piping connecting ports then are formed at predetermined positions into the tank dome. A lid, or a prolonged dome shaft having a lid, or a dome shaft and an intermediate piece, or the intermediate piece is selectively inserted directly into the tank dome. The integrated tank dome leads 20 to relatively large transport dimensions of the underground tank or tank part, because the tank dome protrudes relatively far from the contour of the underground tank. Pipings which lead to the tank dome when the underground tank is installed have to be adapted to the given positions of the connecting 25 ports. As the installation position of the underground tank has to be selected e.g. accordingly to the conditions on site and can be adapted only extremely rarely to planned or already present pipings, the pipings have to be installed accordingly such that they lead to the connecting ports. 30 This means cumbersome excavation work and might result in flow obstructions in the pipings. Furthermore, the tank dome consists of the material of the underground tank N:\Melbourne\Cases\Patent\72000-72999\P72732.AU\Specis\P72732.AU GH Speci as filed.doc 27/08/07 -3 although there might be other material requirements valid for the tank dome, different from the material requirements for the underground tank itself. Finally, the shaping of the tank dome is dictated by the possibilities as given in the 5 moulding tool for the underground tank itself. The underground tank known from US 2003/0136789 A has two circular openings formed with distance in longitudinal direction of the underground tank. Both openings are substantially flush with the adjacent outer contour of the 10 underground tank. Either a lid or a tank dome then is mounted in the respective opening. In mounted position, the lid or the tank dome is fixed in a predetermined rotary position by means of a bayonet system having four bayonet elements distributed in circumferential direction. The tank 15 dome does not have any piping connecting ports for laterally approaching pipings. The storage tank known from GB 24 21 064 A has a tank dome which is integrally formed as a vertical collar having an upper circumferential U-shaped insertion groove. A 20 container- shaped piece is mounted with a lower edge in the insertion groove. Pipings which have to be connected laterally extend through the wall of the piece, the outer dimensions of which are substantially larger than the inner dimension of the tank dome. 25 A rainwater collecting tank known from DE-A-19 91 1009 is a substantially cylindrical tank body having an integrally formed tank dome which protrudes beyond the adjacent outer contour of the tank body. Inwardly protruding thread engagement elements are formed within the opening of the 30 protruding tank dome. An insertion piece is inserted into the tank dome. The outer wall of the insertion piece is formed as a thread. By rotating the insertion piece within N:\Melbourne\Cases\Patent\72000-72999\P72732.AU\Specia\P72732.AU GH Speci as filed.doc 27/08/07 the tank dome the height position of the upper opening of the insertion piece is adjusted in relation to the tank body. s It is an object of the invention to provide an underground tank having minimum transport dimensions and in some embodiments optimal placement of the pipings which either lead to the tank dome or extends away from the tank dome. 10 This object is achieved by the features of claim 1. As the tank dome is produced as a separate part, this separate part can be produced irrespective of the material of the underground tank from a material which specifically 15 is selected with a view to the requirements existing for the tank dome, and also can be shaped without restrictions dictated by the moulding tool for the underground tank itself. The transport dimensions of the underground tank are minimised because of the elimination of a protruding 20 tank dome. The possibility to turn or rotate the tank dome in the mounted position relative to the underground tank into selectable rotary positions allows to optimally place and install pipings which lead to the tank dome, because the respective optimum rotary position of the tank 25 dome may be adapted irrespective of the installation position of the underground tank on site to the placement of the pipings. A substantial aspect of the invention is to stow the later mounted tank dome within the opening of the underground tank in order to achieve a compact 30 transport unit having minimised transport dimensions, and such that the tank dome which is put in the transport position into the opening offers additional stowing space for further equipment parts as for example a filter which has to be integrated later into the underground tank. In 35 this case it is particularly advantageous if the tank dome can be put so deep into the opening that the tank dome in the transport position does not N \Melboume\Cases\Patent\72000-72999\P72732. AU\Spes\P72732.AU Specification 2009-4-2.doc 14/04/09 -5 significantly protrude beyond the adjacent contour of the underground tank. A stepless rotatability over 3600 of the tank dome even improves the flexibility of the system of the underground 5 tank and the tank dome. Mounting the tank dome is particularly easy when the tank dome is snapped together with the underground tank or the tank part. For mounting the tank dome no additional fixation elements or even special tools are needed. The 10 necessary tightness is also achieved by the snapping-in of the tank dome. In a structurally simple way the opening already is prepared by the collar and the shoulder for a comfortable mounting of the tank dome. Only the snap hooks have to be snapped in 15 during mounting. The desired rotary position of the tank dome, expediently, is selected already before the snap hooks are snapped in. Since normally, the at least one inserted sealing anyhow is provided with grease or is wettened, it is even possible to turn the already snapped in tank dome into 20 the desired turning position, or to later change a previously selected rotary position in order to match the pipings. The snap in action, expediently, is achieved by means of the foot part of the tank dome. In this case it may be expedient to first produce the 25 underground tank or tank part such that the opening is closed with a disc. This has advantages for the production. This disc later is removed along a predetermined separation line. This separation then sets the collar used for snapping in the tank dome. This can be carried out already at the site of 30 the producer of the underground tank. N:\Melbourne\Cases\Patent\72000-72999\P72732.AU\Specis\P72732.AU GH Speci as filed.doc 27/08/07 -6 In an expedient embodiment the tank dome has a cross-section which is, except the foot part, not round. In the course of this cross-section flat regions may be prepared for providing piping connecting ports. Preferably, at least subterranean 5 teething depression is provided which hinders a later rotation of the tank dome when the underground tank is installed in the earth, because then an engagement is achieved between the tank dome and the earth. Expediently, the foot part has an outer flange provided at 10 the wall of the tank dome and an insertion ring which protrudes from the outer flange and is substantially coaxial with the axis of the tank dome. The outer flange is put over the opening when the insertion ring penetrates into the opening. In this fashion, the tank dome is stably supported 15 on the underground tank. At least one sealing receiving groove may be provided in the outer flange at the outer side of the foot region of the insertion ring. A sealing frame may be inserted into the sealing receiving groove. Alternatively, a sealing ring 20 placed around the opening of the underground tank then is introduced into the sealing receiving groove. The necessary sealing force is produced by the snap-in action of the tank dome. Expediently, the edge of the opening of the underground tank 25 or tank part has double walls and ribs in order to assure high strength in this region. Along the circumference of the insertion ring, expediently, several resiliently returning snap hooks are provided which automatically are hooked behind the shoulder of the 30 underground tank when the insertion ring is introduced. If needed, the snap-in connection later can be released by manipulation from above and through the tank dome. N:\Me1bourne\Caees\Patent\72000-72999\P72732.AU\Specis\P72732.AU GH Speci as filed.doc 27/08/07 -7 In a preferred embodiment the snap hooks are provided along the circumference of the insertion ring in several groups. Between the groups regions are formed which are free of snap hooks. In this fashion, the insertion ring can be made very 5 strong over a large part of the circumference. Furthermore, during the snap-in action form-fit connections and force-fit connections will result at many locations along the circumference. A transition between the outer flange and the wall of the 10 tank dome ought to be placed maximally on the outer diameter of the insertion ring, such that the tank dome can be put as deep as possible into the opening, when being placed in the transport position. Expediently, even a stacking shoulder is pre-formed at the 15 tank dome by which stacking shoulder the tank dome is supported stably on the opening edge when being placed in the transport position. In a simple fashion, e.g., the stacking shoulder is formed by the bottom of the sealing receiving groove. 20 In order to allow to comfortably put the tank dome into the underground tank, it may be expedient when the wall of the tank dome, beginning at the outer flange, is inclined obliquely inwards and terminates at an inwardly extending shoulder surrounding the receiving seat. This design also 25 results in high strength of the tank dome in its upper region. In an expedient embodiment a dome shaft which fits the dome is provided with a seat for a lid or an intermediate piece. An annular flange, preferably having stiffening ribs at the 30 lower side, is formed at the outer side of the seat. The outer diameter of the annular flange at least corresponds with the outer diameter of the insertion ring. In the Ni\Melbourne\Cases\Patent\72000-72999\P72732.AU\Specis\P72732.AU GH Speci as filed.doc 27/08/07 - 8 transport position the stowed dome shaft can be introduced completely into the tank dome, will be centred there, and will be supported on the insertion ring. In an expedient embodiment the underground tank consists of 5 two identically manufactured tank parts. The disc is removed only from the opening of one tank part. In this opening the tank dome will be mounted later and first will be put in for transporting the transport unit. Using identical tank parts for assembling the underground tank allows an 10 optimum use of one and the same tool, e.g. of an injection moulding tool or an injection moulding and embossing tool. Using injection moulding methods or injection moulding and embossing methods allows to produce the tank parts from fair cost material in smaller tools than have to be used for 15 rotation moulding processes, and with higher production rates. Since the tank dome is produced in a separate tool, the tool for the underground tank tank part does not have to be adapted to the shape and design of the tank dome. According to a further important aspect the tank parts are 20 separably joined by means of quick connectors which are mounted from the outer side along a seam region. This allows to even further reduce the transport dimensions, because both tank parts can be transported stacked within each other and such that the tank dome and further accessory 25 devices can be laid into the shell cavity. Mounting the underground tank and the tank dome are carried out on site. By using the same tank parts, however, in another embodiment, e.g. already at the site of the producer, a monolithic underground tank can be assembled by welding the tank parts 30 to each other along the seam region. For transporting the monolithic underground tank and for reducing the transport dimensions then first one opening is made free. The tank N:\Melbourne\Case\Patent\72000-72999\P72732.AU\Specia\P72732.AU GH Speci as filed.doc 27/08/07 - 9 dome is then put into this opening. The stowing space constituted by the inserted tank dome then is useable to stow further equipment components there. Finally, it may be expedient to produce the tank parts and at 5 least the tank dome respectively unitarily and as plastic material injection moulded parts. Of particular advantage are injection moulded and embossed form parts, because they can be produced by applying a lower forming pressure. Embodiments of the invention will be explained with the help 10 of the drawings. In the drawings is: Fig. 1 a perspective view of an underground tank in installed position, Fig. 2 a perspective partial view of the underground tank of Fig. 1, 15 Fig. 3 the underground tank of Fig. 1 as a transport unit and in a perspective view, Fig. 4 a perspective partial view of a detail, Fig. 5 a section in a sectional plane V-V in Fig . 4, Fig. 6 a section in the sectional plane V-V of Fig. 5 20 illustrating the underground tank as a transport unit according to Fig. 3, and Fig. 7 a section in the sectional plane V-V of Fig. 4, showing the underground tank, e.g. according to Fig. 1 in the installed position. 25 An underground tank E shown in Fig. 1, expediently, consists of plastic material and is joined in the shown embodiment from two tank parts 1, 2 along a seam region 5 by means of quick connectors 4 applied from the outer side. N:\Melbourne\Cases\Patent\72000-72999\P72732.AU\Specia\P72732.AU GH Speci as filed.doc 27/08/07 - 10 Expediently, both tank parts 1, 2 are identical and are produced in one and the same moulding tool. The tank parts 1, 2 e.g. are injection moulded form parts or injected moulded and embossed form parts. The underground tank E is 5 joined first on site by means of the quick connectors 4, meaning that the tank parts 1, 2 can be stacked within each other during transport. Alternatively, the underground tank E can be joined already at the site of the producer and can be transported in ready condition to the site of the 10 installation. Alternatively, it is indicated that both tank parts 1, 2 can be joined without quick connectors along the seam region 5, as indicated by the reference number 3, by welding them to a monolithic underground tank, e.g. already at the site of the producer. Each tank part, at least the 15 tank part 1 which is the upper one in Fig. 1, has a dome boss 6 which is substantially flush with the adjacent contour. Fig. 1 shows the underground tank E already in installed position M. In this case a tank dome D is mounted in the dome boss 6 which tank dome D protrudes beyond the contour. 20 As an option, a dome shaft A is inserted into the tank dome D. The dome shaft A has an upper opening 7. The axis of the tank dome D is indicated by reference number X. The tank dome D, expediently, is a unitary injection moulded part or an injection moulded and embossed part, e.g. made from PP 25 or PET, which plastic material may be processed without reinforcement or may alternatively contain a mineral reinforcement or glass fibre reinforcement. If desirable, the tank dome D and/or the dome shaft A even may consist of metallic material, e.g. cast iron. 30 In the installed position M as shown in Fig. 1 the underground tank E is installed in the earth such that the opening 7 e.g. is substantially flush with the surface of a grassed area or the upper surface of the ground. In this N:\Melbourne\Cases\Patent\72000-72999\P72732.AU\Specia\P72732.AU GH Speci aa filed.doc 27/08/07 - 11 case at least one piping will be installed to the tank dome D. Fig. 2 illustrates the underground tank E in the installed position M with a piping 10 connected to the tank dome D. 5 As indicated by a double arrow 8 the tank dome D being manufactured separately from the underground tank E or the tank parts 1, 2 may be mounted in several selectable rotary positions in relation to the underground tank E, and such that the respective piping 10 can be placed optimally 10 irrespective of the mounted position of the underground tank E in the earth. Expediently, the tank dome D even may be turned over 3600 relative to the underground tank E. The tank dome D has a round foot part F including an outer flange 12 which outer flange 12 is fixed at the dome boss 6 15 of the tank part 1. Expediently, the tank dome D is fixed by a snapped-in connection. The outer contour of the tank dome D may not be round but e.g. has at least one flat region 9 for placing a piping connection port. In some cases, even a subterranean toothing recess 11 may be formed which hinders 20 a later turning of the tank dome D thanks to a toothing with the surrounding earth. Also, the dome shaft A may be turned in relation to the tank dome D. Fig. 3 shows the underground tank of Fig. 1 in a transport position D defining a compact transport unit G. This may be 25 the underground tank which is joined either by means of the quick connectors 4 or by welding. In this case the tank dome D is put into the opening in an inverse position compared to the mounted position shown in Figs 1 and 2. In some cases, even the dome shaft A may be stowed therein. 30 The inserted tank dome D or the dome shaft A offer a large stowing space S for equipment parts of the underground tank E. N:\Melbourne\Caees\Patent\72000-72999\P72732.AU\Speci8\P72732.AU GH Speci as filed.doc 27/08/07 - 12 Furthermore, it is indicated in Fig. 3 that the transport unit G has transport feed 15 put into feet 13 formed at the lower side, while the upper feet 13 are provided with eyelets 14 for hoisting gear. When inserted, the tank dome D 5 protrudes with the foot part F only slightly beyond the adjacent outer contour of the underground tank E. Fig. 4 e.g. illustrates a view of the lower tank part 2 (or the upper, identical tank part 1) prior to opening an opening K which is pre-shaped for mounting and stowing the tank dome. 10 The opening K is surrounded by a double wall opening edge 17 having radial ribs 18 being part of the dome boss 6. As shown, the opening K is closed by a potentially flat disc 16. The disc 16 is connected with the opening edge 17 along a predetermined separation line 19. In the case that the tank 15 dome D has to be mounted in this opening K, expediently already at the site of the producer, the disc is removed. The disc 16, however, in the other tank part remains and, for strength reasons, is provided with ribs. Fig. 4 also shows the transport feet inserted into the feet 13, as well as the 20 eyelet 14 for the hoisting gear. Fig. 5 illustrates in a form of a section in the sectional plane V-V in Fig. 4 that the opening K is closed by the disc 16 having the ribs 20, such that disc 16 is connected along the predetermined separation line 19 with a collar 29 of the 25 opening K. An undercut shoulder 22 is formed at the lower end of the collar 21. The collar 21 is stably supported by the opening edge 17 and the radial ribs 18. The dome boss 6 of the tank part 1 is formed by the disc 16, the collar 21 and the opening edge 17, such that the disc 16 or the collar 30 21 is substantially flush with the adjacent contour 23 of the tank part 1. N:\Melbourne\Cases\Patent\72000-72999\P72732.AU\Specie\P72732.AU GH Speci as filed.doc 27/08/07 - 13 Fig. 6 illustrates as a section a part of the transport unit G of Fig. 3. The opening K is made free in the tank part 1. The tank dome D is inserted with the receiving seat 26 leading into the opening K. In some case, even the dome 5 shaft A may be stowed within the tank dome D such that then further stowing space for additional equipment components is present in the interior. The tank dome D e.g. is inserted until the tank dome D abuts with an external stacking shoulder 32 of the foot part F substantially on the collar 10 21. The tank dome D has, beginning at the foot part F, an inwardly obliquely inclined tank dome wall 24 extending over an inwardly extending shoulder 25 to the receiving seat 26. An outer flange 27 with a downwardly extending edge 28 15 extends outwardly from the tank dome wall 24. At the side of the outer flange remote from the receiving seat 26 an insertion ring 29 is formed which is substantially coaxial to the axis X of the tank dome D. Snap hook 30 are provided at the insertion ring 29. For example adjacent to the 20 insertion ring 29 a circumferentially continuous sealing receiving groove 31 is formed into the outer flange 27. The bottom of the sealing receiving groove 31 forms the stacking shoulder 32. The dome shaft A has a wall 33 extending to an opening 34 and 25 a seat 35 e.g. for a lid. The seat 35 is surrounded at the outer side by an annular flange 36, the outer diameter of which corresponds at least to the outer diameter of the insertion ring 29. The annular flange 36 is stiffened at the lower side by ribs 37. The dome shaft A, when inserted 30 into the tank dome D to define the transport unit G, is centred and positioned by means of the annular flange 36 and the ribs 37. N:\Melbourne\Cases\Patent\72000-72999\P72732.AU\Specis\P72732.AU GH Speci as filed.doc 27/08/07 - 14 Fig. 7 illustrates as a section the ready mounted installation position M e.g. also shown in Fig. 1. The tank dome D is inserted with the insertion ring 29 into the collar 21 until the snap hooks 30 are snapped in behind the shoulder 5 22. In this embodiment, the snap hooks 30 are arranged in groups along the circumference of the insertion ring 29, such that between the groups regions 41 are formed which are free of snap-in hooks. Each snap hook 30 is formed in the insertion ring 29 such that the snap hook resiliently returns 10 into a home position. A sealing 40 is inserted in the sealing receiving groove. The sealing 40 abuts on the collar 21 and seals tightly there. The downwardly extending edge of the outer flange grips over the opening edge of the opening K. 15 The dome shaft A is inserted from above into the receiving seat 26. A sealing 39 seals and holds the dome shaft A. The annular flange 36 protrudes outwardly beyond the tank dome D. A piping connection port 38 is cut out in the flat region 9 which piping connection port 38 precisely is aligned 20 to a straight, optimally short piping 10 as shown in Fig. 2, and by the selected rotary position of the tank dome D in relation to the tank part 1. The piping 10 can be installed in the ground or in the earth as straight as possible and irrespective of the position of the underground tank E in 25 relation to the tank dome D, because the rotary position of the tank dome D easily can be aligned with the piping 10. The concept to produce the tank dome D as a separate part and with respect to the chosen material and the design adapted to the special requirements of a tank dome, also may be 30 expedient for other underground tanks, e.g. for underground tanks which are produced monolithically by rotation moulding and having an opening for mounting and/or stowing the tank dome already formed during the production or cut out later. N:\Melbourne\Cases\Patent\72000-72999\P72732.AU\Specie\P72732.AU GH Speci as filed.doc 27/08/07 - 15 The opening K even could be arranged such that it is set inwardly in relation to the adjacent contour of the underground tank in order to avoid any protruding components of the underground tank which contribute to the transport 5 dimensions. However, even a somewhat higher placement of the opening in relation to the adjacent contour of the underground tank is feasible. As a further alternative the snap hooks even may be snapped in at the outer side of the dome boss. If required, the finally selected rotary 10 position of the tank dome may be fixed by a removable fixing element. Furthermore, the tank dome D also could be higher or lower in relation to the dimensions of the underground tank than is shown. In a case in which the underground tank is used for sewage water treatment or the like and is 15 equipped with one or several separation walls, several tank domes could be mounted as described above. The respective tank dome expediently is dimensioned such that it fulfils the function of a manhole. For example, steps or fixation assemblies for a ladder could be formed or provided in the 20 interior of the tank dome. Such an underground tank E may selectively be equipped with one tank dome or several tank domes which e.g. have different height dimensions or different shapes, e.g. in adaptation to the installation conditions or the respective purpose for the use of the 25 underground tank. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" 30 is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. N\Melbourne\Cases\Patent\72000-72999\P72732.AU\Specie\P72732.AU GH Speci as filed.doc 27/08/07 - 16 It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other 5 country. N:\Melbourne\Cases\Patent\72000-72999\P72732.AU\Specis\P72732.AU GH Speci as filed.doc 27/08/07