AU637048B2 - Improvements in or relating to a storage tank, panel member and die half for forming the same - Google Patents

Description

OPI DATE 29/11/89 AOJP DATE 04/01/90 APPLN- ID 36846 89 PCT NUMBER PCT/AU89/00205

PCT

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 4: (11) International Publication Number: WO 89/10883 90/02, E04H 7/30 Al (43) International Publication Date: 16 November 1989 (16.11.89) (21) International Application Number: PCT/AU89/00205 (81) Designated States: AT (European patent), AU, BE (European patent), CH (European patent), DE (European pa- (22) International Filing Date: 12 May 1989 (12.05.89) tent), FR (European patent), GB (European patent), IT (European patent), KR, LU (European patent), NL (European patent), SE (European patent), SU, US.

Priority data: PI 8188 12 May 1988 (12.05.88) AU Published With international search report.

(71) Applicant (for all designated States except US): G.G.M.T.

PTY LTD [AU/AU]; Unit 2, 3 Cressall Road, Balcatta, W.A. 6021 (AU).

(72) Inventor; and Inventor/Applicant (for US only) GILLETT, Graham [AU/ 6 3 7 0 AU]; Unit 2, 3 Cressall Road, Balcatta, W.A. 6021 (AU).

(74) Agents: HARWOOD, Errol, John et al.; Wray Associates, P.O. Box 6292, East Perth, W.A. 6004 (AU).

(54) Title: IMPROVEMENTS IN OR RELATING TO A STORAGE TANK, PANEL MEMBER AND DIE HALF FOR FORMING THE SAME (57) Abstract A storage tank (11) having a circumferential wall (13) formed of a plurality of overlapping and interconnected panel members The panel members (15) are particularly formed to include an expensive portion which is divided into a plurality of discrete regions (22) by the provision of outwardly projecting horizontally disposed rib portions (19) and a plurality of outwardly projecting and vertically disposed corrugations (21) which intersect with the rib portions (19) and auxiliary rib portions (25) at each intersection between a rib portion (19) and corrugation The corrugations (21) and auxiliary rib portions (25) are formed by a specially formed die half (33a) pressing a sheet member provided with preformed rib portions (19) against a complementary die half (33b). The die half (33a) is provided with a series of transverse slots (41) to receive the rib portions (19) and an associated auxiliary die means (39) to form the auxiliary ribs The bottom edge (37) of the die half (33a) provides a die face with a rectangular groove (51) therein for forming a corrugation and the auxiliary die means (39a) is provided with a die face having an outwardly projection nose (49) for forming the auxiliary rib (25) in the rib portions (19) substantially contemporaneously with the formation of the corrugations.

WO 89/10883 1 PC/AU'89/00205 "IMPROVEMENTS IN OR RELATING TO A STORAGE TANK, PANEL MEMBER AND DIE HALF FOR FORMING THE SAME".

THIS INVENTION relates to improvements in or-relating to a storage tank, panel member and die half for forming the same and also to methods of forming the storage tank and panel member. Moreover, the invention relates to improvements in storage tanks and panel members of the kind particularly disclosed in co-pending Australian Patent Application No. 62098/86.

In storage tanks and panel members of the kind disclosed in the aforementioned co-pending Australian Patent Application, a difficulty arises in the formation of a corrugation or further rib portion of the panel member at the point of intersection with the outwardly extending transverse rib portion thereof, wherein buckling and twisting of the panel member occurs in the region of the intersection, particularly along the rib portion.

Such deformation of the panel member in the region of the intersection is not only displeasing aesthetically but also produces points of weakness in the structure of the panel members and the wall of the storage tank as a whole.

Accordingly, it is an objection of the present invention to obviate or at least mitigate the aforementioned buckling and twisting of the panel member in the region of the intersection of a rib portion and corrugation thereof.

In accordance wi2h one aspect of the present invention, there is provided a storage tank comprising a circumferential 'wall formed of a plurality of overlapping interconnected panel members, each comprising an expansive portion, an outwardly projecting rib portion formed integrally with said expansive portion, and an outwardly projecting corrugation also formed integrally with said expansive portion and disposed, so as to intersect with WO 89/10883 2 PC/AU89/00205 said rib portion; said rib portion being arranged to substantially span a panel member transversely and combine with said corrugation so 'as to divide said expansive portion into a plurality of discrete regions adjacent to said rib portion and said corrugation; said tank being characterised by the provision of an auxiliary rib at the intersection between a said rib portion and corrugation, said auxiliary rib extending from said intersection radially along said rib portion.

In accordance with another aspect of the present invention, there is provided a panel member for forming a storage tank of the kind defined in the preceding aspect of the invention, comprising: an expansive portion, an outwardly projecting rib portion formed integrally with said expansive portion, and an outwardly projecting corrugation also formed integrally with said expansive portion and disposed so as to intersect with said rib portion; said rib portion being arranged to substantially span said panel member transversely and combine with said corrugation so as to divide said expansive portion into a plurality of discrete regions adjacent to said rib portion and said corrugation; said panel member being characterised by the provision of an auxiliary rib at the intersection between said rib portion and said corrugation, said auxiliary rib extending from said intersection radially along said rib portion to accommodate the outward projection of said corrugation at said intersection.

In accordance with a further aspect of the present invention, there is provided a method of forming a panel member for a storage tank of the kind defined it, the first aspect of the invention, comprising the steps of:integrally forming a longitudinal rib portion extending WO 89/10883 3 PCT/AU89/00205 outwardly from a substantially flat sheet member so as to substantially span the sheet member transversely; pinching said rib portion along part of its length so that its sides are disposed in juxtaposition to each other and extend radially outw;rdly substantially orthogonal to the general plane of said sheet member; pressing an auxiliary rib out from said rib portion near the point of intersection between said rib portion and the intended location of said corrugation; and pressing a corrugation out from said sheet member in intersecting relation with said rib portion and said auxiliary rib.

Preferably, said corrugation and said auxiliary rib are formed substantially contemporaneously by bringing a die half of the kind defined in the subsequent aspect of the invention and a complementary die half into mutual engagement with said flat sheet member provided with said rib portion.

In accordance with a further aspect of the present invention, there is provided a, die half for forming the corrugation and auxiliary rib defined in the preceding aspects of the invention when said die half is pressed against a sheet member disposed between said die half and a complementary die half, said die half comprising:an elongated body having an outwardly projecting die face shaped for pressing said corrugation into said sheet member when said die, halves are brought into mutual engagement with said sheet member; a transverse slot opening outwardly at said die face to accommodate said rib portion of said sheet member when said die hal-ves are brought into mutual engagement with said sheet member; and WO 89/10883 4 PCIr/AU8900205 auxiliary die means having a die face disposed within said slot moveable longitudinally of said body from one defining face of the slot towards the opposite defining face of the slot, said auxiliary die means being provided to progressively press said die face thereof into said rib portion to form said auxiliary rib from the inner extent of said rib portion radially outwardly thereof, contemporaneously with, or before, the formation of said corrugation.

Preferably, said auxiliary die means comprises a depending leg member pivotally mounted at a pivoting end to a side of said body and said die face of said auxiliary die means comprises a foot portion of said leg member, distally disposed relative to said pivoting end so as to be accommodated within said slot; said leg member including a heel portion extending marginally beyond said outwardly projecting die face of said body when said die halves are not in mutual engagement with said sheet member, and said -heel portion causing pivotal movement of said leg member inwardly of said body upon engaging said sheet member when said die halves are brought into mutual engagement with said sheet member, thereby simultaneously causing progressive inward and longitudinal movement of said foot portion within said slot relative to said body.

Preferably, said die face of said elongated body comprises a recessed groove extending rectilinearly along said body, and said die face of said auxiliary die means comprises a nose projecting longitudinally within said slot relative to said body towards said opposite defining face of said slot and tapering inwardly along said foot portion relative to sa-id body.

WO 89/10883 5 PCT/AU8100205 The invention will be better understood in the light of the following description embodying the various aspects of the present invention. The description is made with reference to the accompanying drawings, wherein: Fig la is a side elevation of a die half for forming the corrugation and auxiliary rib of the panel member; Fig Ib is a side elevation of the die half showing the transverse slots with the auxiliary die means removed; Fig 2 is a close up view of a section of the die half at Fig 1 showing the leg member in the extended position engaging a sheet member shown in dotted outline; Fig 3 is the same view as Fig 2 but showing the leg member fully retracted to form the auxiliary rib whilst the die face of the body is engaging the sheet member shown in dotted outline to form the corrugation; Fig 4 is a sectional end view of Fig 3 taken along section 4-4; Fig 5 is a cross-sectional view through a rib portion of a sheet member prior to formation of an auxiliary rib and corrugation in intersecting relation therewith; Fig 6 is a similar view to Fig 5, but showing the rib portion after formation of an auxiliary rib and corrugation therein; Fig 7 is a close up perspective view of a section of the panel member showing the provision of the auxiliary rib at the intersection between the rib portion and corrugation; WO 89/10883i 6 PCT/AU89/00205 Fig 8 is an inverted view of Fig 7; Fig 9 is a view of the storage tank as a whole; Fig 10 is a similar view to Fig 7, but on a smaller scale; Fig 11 is a similar view to Fig 8, but on a smaller scale; Fig 12 is a perspective view of the exterior side of a panel member; and Fig 13 is a perspective view of the inside of the panel member shown at Fig 12.

The storage tank 11 is shown at Fig 9 of the drawings and generally consists of a circumferential wall 13 formed of a plurality of ove2rlapping, interconnected panel members best shown at Figures 10 and 11 of the drawings.

Each panel member 15 generally comprises a curved planar expansive portion 17 having a plurality of outwardly projecting rib portions 19 and a plurality of corrugations 21 arranged in an intersecting manner with each other to divide the expansive portion into a plurality of discrete regions 22 adjacent to and between the rib portions 19 and the corrugations 21. The rib portions 19 are disposed outwardly on the convex side of the panel member and span the panel member in its transverse direction which, as shown in the drawings, is generally horizontal when the storage tank is erected. The corrugations 21 also project outwardly on the convex side of the panel member, but span the panel member longitudinally which, as shown in the drawings, is generally vertical when the storage tank is erected. The rib portions 19 and the corrugations 21 are disposed orthogonally to each othe. and 14' WO 89/10883 7 PCT/AU89/00205 consequently define a series of intersections 23 which form a matrix over the expansive portion of the panel members.

An auxiliary rib 25 is provided at each intersection of a corrugation 2 and rib portion 19, and extends radially outwardly of a panel member along the rib portion 19 from an intersection 23, as best shown at Figures 7 and 8 of the drawings.

The rib portion 19, corrugations 21 and auxiliary ribs are all integrally formed with the expansive portion 17 of the panel members by a pressing operation which shall be described in more detail later.

The rib portions 19 have two juxtaposed sides 27a and 27b both of which project outwardly substantially orthogonal to the expansive portion 17. Accordingly, the rib portion 19 is generally U shaped in cross-section as shown at Figures 5 and 6 of the drawings and is provided to improve the strength characteristics of the panel members by opposing lateral forces derived from the contents of the storage tank interior when in operation. The juxtaposition of the opposing sides 27 extends from near one longitudinal edge 29a of the panel member entirely to the other longitudinal edge 29b of the panel member. At the one longitudinal edge 29a of the panel member the opposing sides 27 of each rib portion are marginally spaced apart to define a slot for accommodating the end of a rib portion disposed at the other longitudinal edge 29b of an adjoining panel member, so as to provide for marginal overlapping and interconnection between adjacent panel members.

WO 89/10883 8 PCT/AU89/00205 The rib portions 19 of a panel member are provided at sequential spaced apart locations extending from one transverse edge 31a of the panel member to the other transverse edge 31b of the panel member to provide strengthening of the panel member at successive locations along its length. Furthermore, the rib portions are more closely spaced towards the one transverse edge 31a of the panel member which is to be disposed at the base of the storage tank when in the erected position, than at the other transverse edge 31b. This arises due to the characteristics of the contents of a storage tank where the lateral forces provided by the contents are greater at the bottom of the tank than at the top of the tank. Thus, the innate strength of the panel members can be increased to enable large capacity tanks to be constructed by simply using additional and/or more closely spaced rib portions at the appropriate locations.

The corrugations 21 are more gradually contoured than the rib portions 19.and project outwardly from the expansive portion 17 a substantially lesser distance than the corresponding outward projection of the rib portions 19 so as to lie more within the general plane of the expansive portion of a panel member. The corrugations 21 enable a fixed curvature to be induced into the panel members about a longitudinal axis and also supplement the strength characteristics of the rib portions 19.

The auxiliary ribs 25 project outwardly along the rib portions in a tapered manner so that the broadest part of the transverse extent of the rib is disposed at the intersection 23 between a rib portion and corrugation of a panel member and is commensurate in size to the transverse extent of the corrugation, and converges to a point as the auxiliary rib extends radially from the WO 89/10883 9 PCT/AU89/00,05 intersection. In this manner, the auxiliary rib functions as a tuck to accommodate buckling or puckering of the panel member in the region of the intersection and the rib portion, which would otherwise occur during formation of the corrugations as a result of inducing a curvature to the panel members. Consequently, the auxiliary ribs are preferably disposed at each intersection 23.

The rib portions 19 of each panel member are arranged so that one rib portion is coincident with the intended upper edge of the panel member. The auxiliary ribs 25 which are provided along this one rib portion have a concave face on the upper side and a convex face on the lower side of the rib portion so that no sharp edges face upwardly along the upper side and outer end of the rib portion which could otherwise damage a plastic liner fitted within the storage tank and which was secured to the upper side of this one rib portion of the panel members. Conversely, the auxiliary ribs of the other rib portions of each panel member have their convex face on the upper side and concave face on the lower side of the rib portions. In this manner, rain or water impinging upon the upper faces of the rib portions falls off the rib, whereas if the concave face of the auxiliary rib was disposed on the upper face, a hollow would be provided which would retain water impinging upon the upper face possibly causing corrosion problems.

In order to form the storage tank, the panel members are arranged adjacent to each other in a contiguous manner so that one panel member overlaps marginally with its adjacent panel member. As previously described, the marginal spacing provided between the sides of the rib portions at the one longitudinal edge 29a accommodate the overlapping end of the rib portion of the adjacent panel WO 89/10883 10 PC1/AU89/00205 member. In order to fixedly interconnect the panel members, the opposite ends of each rib portion 19 of the panel member are provided with a pair of holes (not shown) which can be respectively aligned with corresponding holes of an adjacent panel member so as to receive a fastening means such as a nut and bolt arrangement to connect the overlapping ends of the panel members together. This fastening is provided around the entire circumference of the storage tank in order to form a closed wall 13 as shown at Fig 9 of the drawings.

The panel members are formed by initially obtaining a planar sheet member of generally rectangular shape and of the required size. This sheet member is initially pressed within a suitable die to form the rib portions 19 at spaced apart locations along the longitudinal extent of the sheet member so that each rib portion transversely spans the sheet member, At this stage, the rib portions generally adopt a V-shape in cross-section and are required to be pinched together to form the U-shaped cross-section as shown at Fig 5 of the drawings.

Consequently the rib portions are pinched together within a press so that the opposing sides 27a and 27b repose in juxtaposition to each other along a substantial part of their length except for the marginal portion disposed at the other longitudinal edge 29b of the panel member as previously described.

After completing this pinching process, a. further pressing operation is performed to form the corrugations 21 and auxiliary ribs 25 of the panel members and so induce a curvature to the panel members. This further pressing operation is performed in a progressive manner whereby the corrugations and auxiliary ribs are provided at successive spaced apart locations along the panel members extending WO 89/10883 11 PC/AU9/00205 from one of the transverse edges 31 to the other. The spacing between the corrugations determines the amount of curvature of a panel member whereby the more closely spaced the corrugations are, the lesser the effective radius of curvature of the panel member. Conversely, the further spaced apart the corrugations are, the greater the radius of curvature. In this manner, it is possible to construct panel members having a radius of curvature commensurate with the desired curvature of the wall of the storage tank and hence the diameter of the proposed storage tank.

The pressing operation is performed by interposing a flat sheet member with rib portions 19 previously formed thereon between two die halves, one being complementary to the other, and subsequently bringing the respective die halves into mutual engagement with opposite sides of the sheet member to form a single corrugation 21 extending the entire longitudinal extent of the sheet member in intersecting rel.ation to the rib portions, and auxiliary ribs 25 at each of the points of intersection between the rib portions 19 and the corrugation. The die halves are then brought apart and the sheet member is moved so that the next prescribed location for the provision of a corrugation is disposed betieen the die halves. The pressing operation is repeated and the process cotinued until all of the required corrugations and auxiliary ribs are formed at their required locations.

One of the die halves 33a for this pressing operation is of a form shown at Figures 1 to 4 of the drawings, generally comprising an elongated body 35, a series of transverse slots 41 and a series of auxiliary die means 39 associated with the slots positioned along the length of the body.

WO 89/108C3 12 PC/AU9/00205 The body... 35 has an upper longitudinally extending male edge 36 for being fixedly retained within the upper jaw of a press (not shown) and a lower outwardly projecting die face disposed oppositely to the male edge 36.

The outwardly projecting die face 37 is provided with a rectangular groove 51 along its terminal face which extends rectilinearly from one end of the body 35 to the other and which co-operates with a convexly shaped ridge provided on the die face of the complementary die half 33b for pressing a single corrugation into the sheet member when the die halves are bought into mutual engagement with the sheet member.

The transverse slots 41 are disposed at precise locations along the length of the body to correspond to the location of successive rib portions 19 along the length of the sheet member. Moreover, the slots 41 are of sufficient size to accommodate the rib portions of the sheet member when it is interposed between the die halves and during the time that the die halves are being brought into mutual engagement with the sheet member.

The auxiliary die means 39 associated with the slots 41 are each provided with a die face which is actually disposed within the corresponding slots. The die face is movable longitudinally with respect to the body within a slot 41 from one defining face 43a of the slot to the opposite defining face 43b of the slot whilst the die halves are being bought into mutual engagement with the sheet member.

In order to "achieve this longitudinal m.ovement, the auxiliary die means 39 is in the form of a depending leg WO 89/10883 13 7C/AU9/00205 member 45 which is generally U-shaped having a pair of pivoting ends 45a defining the distal ends of the U, pivotally mounted to the opposite sides of the body and spaced longitudinally from the slot. Furthermore, the die face of the auxiliary die means 39 is in the form of a foot portion 45b defining the bridge of the U, and which is distally disposed relative to the pivoting end of the leg member. The foot portion 45b is accommodated within the associated slot 41 adjacent to the leg member and is movable inwardly and outwardly of the slot relative to the body upon pivotal movement of the leg member. The leg member 45 also includes a heel portion 47 which is disposed so as to extend marginally beyond the terminal face of the die face 37 when the leg member 45 is at its maximal depending position as shown at Fig 2 of the drawings. The one defining face 43a of the slot is truncated outwardly to provide a flared opening which accommodates the heel portion 47 of the auxiliary die when the leg portion is pivoted to its maximal inward position relative to the body 35 so that the heel portion is coterminus with the die face of the body at this position.

The bottom of the foot portion 45b is provided with a central rectangular recess within the slot to coincide with the rectangular groove 51 which, extends rectilineally along the outwardly extended die face 37, when the leg member is in the raised position, as shown at Figures 3 and 4 of the drawings. The foot portion is also provided with a nose 49 disposed centrally above the recess 53 and which projects longitudinally within the slot relative to the body 35 from the face of the foot portion towards the opposite defining face 43b of the slot. Additionally, the nose 49 tapers inwardly along the foot portion relative to the body 35 from the top of the recess 53 so that it is spaced marginally above the distal end of the WO 89/10883 14 PCT/AU89/00205 heel portion 47. The breadth of the nose 49 at its broadest point is commensurate to the breadth of the recess 53 to form an auxiliary rib of similar transverse extent to a corrugation. Consequently, upon upward pivotal movement of the leg member 45, the nose 49 has a component of movement which is longitudinal relative to the body within the slot to engage one of the opposing sides 27a of the rib portion 19 and press the auxiliary rib therein.

The opposite defining face 43b of the slot is provided with a recess (not shown) to accommodate the nose 49 in its maximally longitudinally extended position as shown at Fig 3 of the drawings which coincides with the heel portion 47 of the leg member being brought into alignment with the outwardly projecting die face 37 of the body upon the die face engaging the expansive portion 17 of the sheet member. Importantly, the bottom of the nose 49 is approximately aligned with the innermost point of the rectangular gropve 51 when the leg member is fully retracted so that when the auxiliary rib 25 is pressed into the rib portion 19, the auxiliary rib is contiguous with the outermost point of the corrugation which is formed by the rectangular groove 51.

The auxiliary die means 39 associated with the transverse slots 42 are arranged so that the die face provided on the foot portion 45b thereof is movable in a generally longitudinal direction upon inward pivotal movement of the leg portion of the auxiliajry die means in the direction towards that end of the body 35 which accommodates the slots of the greater spacing, that is the end of the body which corresponds to the upper end of the panel member, all except for-one auxiliary die means 39a associated with the end transverse slot 41a which receives the uppermost WO 89/10883 15 PCr/AU89/00205 rib portion 19 coincident with the upper end of 31b of the panel member. This auxiliary die means 39a is arranged so that the die face provided on the foot portion thereof is disposed within the end transverse slot 41a so that it is movable in a generally longitudinal direction with respect to the body upon inward pivotal movement of the leg portion, opposite to the general longitudinal direction of movement of the die faces of the other auxiliary die means. In this manner, the one auxiliary die means 39a forms an oppositely curved auxiliary rib in the intended upper rib portion of the panel member than is the case with the auxiliary ribs formed in the other rib portions.

Now describing the operation of the die halves 33 in more detail, as previously mentioned the die half 33a is attached to the upper jaw of the press along the male edge 36 and the complementary die half 33b is fixedly attached to the bottom jaw of the press. By operation of the press, one of the die halves may be bought towards mutual engagement with the other die half to perform the pressing operation on a piece of sheet material interposed between the respective die halves. In the present embodiment, the top die half 33a is actually moved relative to the bottom complementary die half 33b. A flat sheet of material such as sheet metal having its rib portions previously formed therein is positioned between the die halves so that the rib portions 19 are aligned for axial movement within the slots 41 of the die half 33a. As should be noted from Fig 1, the slots 41 and their associated leg members 45 are more closely spaced at one end of the die half than the other so as to coincide with the required spacing of the rib portions upon. a panel member.

WO 89/10883 16 PCTr/AU89/00205 The press is then operated so that the die half 33a travels slowly towards the sheet member and complementary die half 33b whereupon the rib portions 19 simultaneously enter the respective slots 41 without impediment from the leg members 45. This is achieved when the leg members are in their fully depressed positions thereby causing the respective foot portions 45a thereof to be disposed alongside the respective defining faces 43a of the slots to open the slots and allow unimpeded access of the rib portions to the slots. In this fully depressed position the nose 49 of each leg member is actually disposed outside of the confines of the slot thereof and behind the general line of the defining faces 43a facilitating entry of the rib portions to the slots.

Upon progressive downward movement of the die half 33a, a point is reached where, the heel portions 47 of the respective leg members engage the adjacent expansive portions of the sheet member so that upon further movement of the die half, the leg members commence to rise in a pivotal manner about the pivoting ends 45a thereof.

Simultaneously, the foot portions 45b of the leg members begin to rise within the respective slot 41 and introduce a component of movement to each nose 49 from tihe defining face 43a of a slot towards the opposite defining Eace 43b of the slot. Thus, the bottom tip of each nose 49 commences to engage the rib portions 19 of the sheet member whilst it is being accommodated within the slot at a point along the rib portion which coincides with the intended top of the corrugation as determined by the location of the nose 49 above the heel portion 47 of the leg member as shown at Fig 2 of the drawings. Upon further downward movement of the die half 33a, the nose moves further- in the longitudinal direction within the slot relative to the body 35 and combines with the WO 89/1 F0883 17 PCr/AU89/00205 complementary recess on the opposing defining face 43b of the slot to impress the auxiliary rib 25 into the rib portion.

Finally, when the outwardly extending die face 37 of the die half 33a comes into engagement with the expansive 'portion of the sheet member as shown at Fig 3 of the drawings, the leg members 45 are disposed at their uppermost positions and the noses 49 at their maximally longitudinally extended positions within the slot.

Further movement of the die half causes the convexly shaped ridge 55 of the complementary die half 33b to enter the confines of the rectangular groove 51 of the die half 33a so as to form the corrugation 21 into the sheet material, as shown at Figure 4. The movement of the die half 33a continues until full engagement with the complementary die half 33b is achieved with the sheet material interposed therebetween, whereupon the corrugation 21 is fully formed having an outward extent commensurate with the depth of the rectangular groove 51.

The die half 33a is subsequently retracted upwardly bringing the die halves and the interposed sheet material out of mutual engagement so that the sheet member can be moved for the formation of the next corrugation and auxiliary rib.

By providing auxiliary ribs to the panel members in this manner, the curving of the rib portions about a longitudinal axis with respect to the panel members which arises during formation of each corrugation is accommodated within the auxiliary ribs and so irregular buckling or wrinkling of the rib portions which arise otherwise, is -avoided.

WO 89/10883 18 PCT/AU9/00205 In another embodiment (not shown) the die face of the body is segmented into discrete die faces provided on discrete slidable members which are attached to the body. Each discrete slidable member and die face has associated therewith a locking means, a transverse slot and an auxiliary die means, whereby the members are slidably mounted upon the elongated body for separately adjustable slidable movement longitudinally of the body. In this manner, the tr.ansverse slots of each member can be independently located and locked into a prescribed position along the elongate body for precise alignment with a corresponding preformed rib portion of the panel member on which the corrugations and auxiliary ribs are to be formed. To provide longitudinal support to the discrete slidable members, and a continuous die face for tie die half, slidably spacer means having a die face corresponding to the die face of the slidable members may be interposed between adjacent slidable members and connected thereto by longitudinally extending dowels located within .axially aligned holes provided in the slidable members and spacer means. This arrangement of the die half provides for additional utility whereby the same die half can be used to form corrugations and auxiliary ribs in panel members having rib portions of different sets of spacings which may arise in constructing storage tanks of differing volumes and depths.

It should be appreciated that the scope of the present invention is not limited to the particular embodiment herein described. In particular, the die half described herein is only of a preferred form and can be embodied in other forms than that described without departing from the spirit from the present invention.

Claims (12)

1. 2. A panel member as claimed in claim 1, wherein said auxiliary rib has a convex face on the upper side of said rib portion and a concave face cn the opposing lower side of said rib portion.
2. 3. A panel member as claimed in claim 1 or 2, wherein a plurality of rib portions are provided in parallel spaced apart relation along said expansive portion, one rib portion being coincident with the intended upper edge of is'aid panel member, whereby the auxiliary ribs of said one rib portion have a concave face on the upper side and a convex face on the lower side of said one rib portion, and WO 89/10883 20 PCT/AU89/00205 the auxiliary ribs of the other rib portions have a convex face on the upper side and a concave face on the lower side of said other rib portions.
3. 4. A panel member as claimed in any one of the preceding claims wherein said auxiliary rib is of a transverse extent approximately commensurate with the transverse extent 'of said corrugation at the point of intersection therewith and converges to a point as the auxiliary rib extends radially from said intersection. A panel member substantially as herein described with reference to the accompanying drawings where appropriate.
4. 6. A storage tank comprising a circumferential wall formed by a plurality of overlapping interconnected panel members as claimed in any one of the preceding claims.
5. 7. A storage tank substantially as herein described with reference to the.accompanying drawings where appropriate.
6. 8. A die half for forming the corrugation and auxiliary rib of a panel member as claimed in any one of claims 1 to when said die half is pressed against a sheet member disposed between said die half and another die half complementary thereto, said die half comprising: an elongated body having an outwardly projecting die face shaped for pressing said cori~gation into said sheet member when said die halves are brought into mutual engagement with said sheet member; a transverse slot opening outwardly at said die face to accommodate said rib portion of said sheet member when said die halves are brought into mutual engagement with said sheet member; and WO 89/10883 21 PC/AU89/00205 auxiliary die means having a die face disposed within said slot movable generally longitudinally of said body from one defining face of the slot towards the opposite defining face of the slot, said auxiliary die means being provided to progressively press said die face thereof into said rib portion to form said auxiliary rib from the inner extent of said rib portion radially outwardly thereof, contemporaneously with, or before, the formation of said corrugation.
7. 9. A die half as claimed in claim 8, wherein said auxiliary die means comprises a depending leg member pivotally mounted at a pivoting end to a side of said body and said die face of said auxiliary die means comprises a foot portion of said leg member, distally disposed relative to said pivoting end to be accommodatad' within said slot, said leg member including a heel portion extending marginally beyond said outwardly projecting die face of said body when said die halves are not in mvtual engagement with said sheet member, and said hell portion causing pivotal movement of said leg member inwardly of said body upon engaging said sheet member when said die halves are brought into mutual engagement with said sheet member, thereby simultaneously causing progressive inward and generally longitudinal movement of said foot portion within said slot relative to said body. A die half as claimed in claim 8 or 9, wherein said die face of said elongated body comprises a recessed groove extending rectilinearly along said body, and said die face of said auxiliary die means comprises a nose projecting longitudinally within said slot relative to Ssaid body towards said opposite defining face of said slot and tapering inwardly along said foot portion relative to said body. WO 89/10883 22 PCT/AU89/00205
8. 11. A die half as claimed in any one of claims 8 to wherein the die face of said elongate body is segmented into discrete die faces provided on discrete slidable members each having an associated locking means, transverse slot and auxiliary die means, said slidable members being mounted upon said elongate body for separately adjustable slidable movement longitudinally of said body to enable independent location and locking of the transverse slot thereof into a prescribed position for precise alignment with a corresponding preformed rib portion of said panel member.
9. 12. A die half as claimed in any one of claims 8 to 11, wherein a plurality of transverse slots and auxiliary die mieans are provided to accommodate a plurality of rib portions of said sheet member, whereby one end transverse slot and associated auxiliary die means for forming the auxiliary rib in the intended upper rib portion of saLd panel member, are arranged so that the die face of said associated auxil.iary die means is disposed with said one end transverse slot and is movable in a generally longitudinal direction with respect to said body opposite to the general longitudinal direction of movement of the die faces of the other auxiliary die means to form an oppositely curved auxiliary rib in said intended upper rib portion,
10. 13. A die half as claimed in any one of claims 8 to 12, wherein said one defining face of said transverse slot is truncated outwardly to provide a flared opening for accommodating the heel portion of said auxiliary die when said leg portion is pivoted to its maximal inward position relative to said body so that said heel portion is coterminous with the die face of said body at this position. WO 89/10883 23 PCr/AU89/00205 14, A die half substantially as herein describe with reference to the accompanying drawings where appropriate. A method of forming a panel member for a 'storage tank of the kind claimed in any one of claims 5 or 6, comprising the steps of:- integrally forming a longitudinal rib portion extending outwardly from a substantially flat sheet member so as to substantially span the sheet member transversely; pinching said rib portion along part of its length so that its sides are disposed in juxtaposition to each ,other and extend radially outwardly substantially orthogonal to the general plane of said sheet member; pressing an auxiliary rib out from said ri> portion near the point of intersection between said rib portion and the intended location of said corrugation; and pressing a corrugation out from said sheet member in intersecting relation with said rib portion and said auxiliary rib.
11. 16. A method as claimed in claim 15, wherein said corrugation and said auxiliary rib are formed substantially contemporaneously by bringing a die half of the kind claimed in any one of claims 8 to 14 and complementary die half into mutual engagement with said flat sheet member provided with said rib portion.
12. 17. A method of forming a panel member for a storage tank substantially as herein described with reference to the accompanying drawings where appropriate.