The invention relates to a mould apparatus for moulding objects having a substantially uniform cross section, comprising a plurality of elongate, interconnectable link members provided with lining parts adapted to form a mould surface when the link members are interconnected. The invention is particularly intended for moulding a weight cap or coating around sub-surface pipes for the transport of oil or gas at sea. An example of a field in which the invention is particularly useful is the moulding of a weight coating made from a composite material consisting of crushed iron ore in a plastics matrix as described in the applicant's Norwegian patent No. 150 771 (corresponding to US patent No. 4 606 378) . According to this patent an outer plas pipe is utilized as a moulding for the composite material to form the weight coating. This is a rather expensive approach since in many cases the outer plastic mould pipe has proved unnecessary in the completed moulded structure.

GB patent application No. 2 052 362 discloses a mould for moulding of weight coatings on pipes, for example, consisting of elongate members of a circular segment-shaped section internally coated with replaceable lining parts such as wooden bars and adapted to be interconnected around the pipe to be coated. The prior mould according to the GB patent application can be adapted to pipes of different diametres only by removing all the installe lining bars, form new lining bars of a different thickness in accordance with the new pipe diameter, and installing the new lining bars in the mould. Apart from the fact that this represen a cumbersome and time consuming work, the possibility of varying the mould diameter of one and the same mould is rather limited, and the mould can only be utilized for external moulding of pipes. Furthermore the lining bars of the prior mould must be very accurately machined and installed in the mould in order to obtain a fairly tight continuous moulding surface.

As a further example of the prior art in the field it is referred to US patent No. 1 398 968 relating to a moulding form consisting of laterally interbolted, elongate, circular segment sectioned members provided with a lining material such as wooden bars. The members require cumbersome installing and there is no

possibility of conforming the members to varying curvatures of the article to be coated.

The object of the present invention is to provide a mould apparatus of the introductorily described type, which in a simple and rapid manner can be conformed to the circumference of objects, such as pipes, of very different sections, and which may be utilized for objects of concave as well as convex shape.

According to the invention this object is achieved by each link member of the mould apparatus having a protruding, substan¬ tially circular section head portion adapted to be laterally inserted- into a correspondingly circularly sectioned recess in the adjacent link member.

Thereby the radius of curvature of the mould apparatus may be varied through a very wide range, simply by inserting or removing link members in a number adapted to the purpose, without the necessity of replacing lining parts or other components. The structure according to the invention will secure that the edge portions of the lining parts are resiliently abutting each other to form a tight, continuous mould surface. The latter property is utilized in a particularly advantageous manner if at least an external portion of the lining parts consists of an elastomeric material, and particularly if it has a trapezoidal cross section.

An embodiment of the mould apparatus according to the invention is described in detail below with reference to the drawing, in which:

Fig. 1 shows a cross section of a link member in the mould apparatus according to the invention,

Fig. 2A and B show interconnected link members in two different conditions,

Fig. 3A and B show cylindrical mould cavities formed by means of the mould apparatus,

Fig. 4 shows a modified link member,

Fig. 5 is a partial view of a mould formed by the modified link member shown in fig. 4,

Fig. 6 and 7 show further modified members for the forming of corner mould surfaces,

Fig. 8 shows an end piece to be used in connection with the mould apparatus according to invention, and

Fig. 9 shows a connector to interconnect mould apparatuses according to the invention.

The mould apparatus according to the invention is releasably assembled from a number of elongate, profiled link members to form a flexible mould wall or mat. The basic shape of a such link member 2 is shown in cross section in fig. 1. It comprises a body 4 and a lining part 6 releasably secured to the body 4.

The body 4 has a central portion 8 being connected at one side via a neck portion 10 to a circular section head portion 12 and at its opposite side being provided with a circular groove 14 dimensioned to slidingly receiving the head portion 12 of an adjacent link member 2 and having an opening 15 providing clearence for the neck portion 10. The central portion 3 has a flat backing surface 16 parallel to a plane P through the centres of the circular head portion 12 and matching circular groove 14. The backing surface 16 forms a support surface for the lining part 6.

The lining part 6 consists of a similarly elongate, strip of an elastomeric material, such as rubber, with a trapezoidal cross section, for example. In the embodiment as shown the lining part 6 engages the backing surface-16 with its shorter longitudinal face which has a longitudinal slit opening 18. The lining part 6 is releasably locked no the body 4 by means of regularly spaced throughbolts 20 engaged in threaded apertures in an elongate metal plate 22 which is embedded or by other means secured in the elastomeric material of the lining part. In the drawing the larger width dimension of the lining part is indicated by B.

The "pitch" of the link members is determined by the spacing C between the centres of the circular link head portion 12 and the circular link groove 14.

The link members 2 are interconnected by laterally pushing the head portion 12 of the link body into the groove 14 of the adjacent member. Thus, when interconnected each link member may perform a limited pivot movement around the head portion of the adjacent member, an arcuate circumferencial portion 19 at the recess 14 in a link being displaced in a correspondingly arcuate recess 21 in the adjacent member during the pivoting movement. The pivoting movement is limited by the groove opening 15. In

fig. 2A is shown six interconnected links 2 in which the links are fully rotated (angularly displaced) relative to each others in one direction, i.e. until the circu ferencial portion 19 of one link bottoms in the recess 21 of the adjacent member against the neck portion 10. The facing edges of the elastomeric lining parts β will then be resiliently compressed and form a continuous, sealed, concave mould surface.

In fig. 2B the same six links are shown in a relative rotational position in which the edges of the lining parts 6 just contact each other to form a continuous concave mould surface.

In fig. 3A and B there is shown how the link members 2 rray be interconnected to form a fluid tight cylindrical moulding or form work F, F' of minimum diameter, in which the angular position of the link members corresponds to that shown in fig. 2A, and of maximum diameter, in which the link members assume the relative angular positions shown in fig. 3B, respectively. Owing to the resilience of the elastomeric material of the opposed lining parts 6 of the link members the interconnected link members 2 automatically will assume the cylinder shape as shown having a substantially circular cross section. In the form according to _fig. 3A fifteen links are used, while in the form according to fig. 33 fortyfive links are used. Any desired mould diameter between the two limit cases of fig. 3A and 3B may be obtained by one and the same type of link members , i.e. link members having a given pitch C, by utilizing an appropriate number cf members between the above mentioned minimum and maximum numbers consistent with the desired diameter. If, on the other hand, one wishes to determine the pitch C for link members 2 based on a desired mould diameter D and a selected number of members n the pitch can be calculated by simple geometry

(C = (D+H) sin 360/2n, in which H is the distance between plane ? and the outer surface of the lining part as indicated in fig. 1) .

The mould apparatus according to the invention, in addition to concavεly curved mould surfaces as so far shown, may also be us to form flat or convexly curved mould surfaces. What matters is the ratio between the maximum width B of the lining part 6 and the pitch C of the body 4. B/C < 1 results in concavely curved mould surfaces as in fig. 2 and 3; if the ratio B/C = 1 flat

surfaces will result, and B/C > 1 results in convex mould surfaces. (Neglecting compression of the lining parts) .

In the latter case, in which the maximum width of the lining parts 6 must be larger than the pitch C, it may be an advantage to use a support plate 24 between the lining part 6 and body 4, as indicated for the link member 2' in fig. 4. This allows the same type of body 4 to be used for lining parts 6 of varying width B and will secure adequate support of lining parts with a wider base than the width of the backing surface 15 of the link body.

Fig. 5 is a partial view cf interconnected link members 2' with support plates 24, forming a convexly curved mould surface portion. Like in the previous example the link members 2' can be interconnected to form a closed cylinder form, e.g. to form the internal mould or form work in a steel pipe to be provided with an internal weight coating.

Fig. 6 and 7 show interconnected link bodies which, together with suitabl formed lining parts (not shown) , are modified to form an "internal" corner moulds-surface and an "external" corner mould surface, respectively, with orner angle equal to or larger than 90° .

Of course it is not essential for the lining part 6 to have a trapezoidal cross section as shown. Instead, It may ha ^τ* e C- shaped edges, for example, and the outer surface thereof may be corrugated rather than smooth. Generally it will be understood that by modifying the form and dimensions of the lining members 6 one and the same basic type of body 4 may be used, to obtain a mould cavity of almost any desired cross sectional shape.

For closing the ends of the mould cavity formed by the mould apparatus according to the invention suitably adapted end pieces are used. An example of this is shown in fig. 8 in which a pip- R is to be coated with a weight coating W. Here a schematically indicated mould apparatus F according to the invention is used consisting of link members 2 interconnected into a cylinder form in the same manner as shown in fig. 3A and B. An annular end collar E sealingly receives the end portion of the mould apparatu F while also sealingly engaging the surface of the pipe R, e.g. by means of an O-ring seal. The end collar E may be provided

with an.opening (not shown) for injecting moulding mass while an end collar in the opposite end of the mould apparatus may be formed with opening for evacuation of the mould cavity defined by the interconnected link members, the lining parts thereof pressing against each other to form an air tight seal around the pipe. The end collars E will be suitably split into two halves when they are used in connection with moulding of an external coating around pipes, the two halves being assembled around the pipe by means of bolts for example.

Similarly several mould apparatuses F of the invention may be axially interconnected, for example by means of suitably formed joint collars S of substantially T-shaped cross section as schematically indicated in fig. 9.

When the moulding of the required object, e.g. a cylinder as indicated in fig. 3, is completed in the mould apparatus of the invention the object easily detaches from the mould apparatus upon removing a l ^' ink member thereof by pushing it laterally outwards, the pinching effect between the compressed lining parts of the link memb-ers assisting in releasing the mould apparatus, and the rubber material from which the lining parts preferably are made having low adhesion to most of the moulding materials in question, e.g. to the composite material discussed in the Norwegian patent No. 150 771 referred to above. Suction between the mould surface of the lining parts and the surface of the moulded object is eliminated when the mould members are rolled off since air will leak in between the connections when the pinching effect seases.

It will be understood that although primarily the apparatus according to the invention is intended to form mould cavities for the moulding of objects, and consequently is denoted as a mould apparatus, if desired it may of course be used also in other applications such as to form a cavity (container) for storing liquids or bulk material. Also when used in such applications it will fall within the scope of the claims.

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