Delmar, Ake (Ehrner & Delmar Patentbyrå AB Box 10316 S-, 100 55, SE)
|1.||Apparatus for facilitating extracting of supply con duits (4) for thermosetting resin from a mould cavity being under vaccum and partly filled with reinforcing material for producing composite pipes, the mouths of said supply conduits are placed initially at the lowest part of said mould cavity and is then progressively moved upwards in a position just below the surface of the introduced resin, c h a r a c t e r i z e d i n that a friction reduction means (1) is placed around each supply conduit (4).|
|2.||Apparatus according to Claim 1, c h a r a c t e r i z e d i n that the friction reduction means (1) is made of a substance which is soluble in the thermosetting resin used.|
|3.||Apparatus according to Claim 1 or 2, c h a r a c t e r i z e d i n that the surface of the friction re duction means (1), which is directed against the supply conduit (4), is proveded with a lubricating substance.|
A method for vacuum moulding of objects of thermo- setting resin is known from SE-9002066-0, in which the resin is supplied through at least one hose, which its sealingly inserted through a wall in the upper portion of the mould cavity sufficiently deep into the mould cavity so that its free end is positioned in the lower part of said cavity, and the hose or hoses are then progressively pulled upwards at such a speed that the free end of said hose or hoses is positioned just below the surface of the resin.
An apparatus for supplying thermosetting resin through at least one supply conduit is known from PCT/SE96/01057, said supply conduit for producing molecu- lar friction in the thermosetting resin, which is trans- ported through said supply conduit, is an elongated, thin pipe or cannula of metal.
This apparatus is particularly used for producing composite pipes, which are made of a thin inner liner of metal, a sheath or intermediate load-carrying layer of reinforced thermosetting resin and possibly an external pipe of metal.
When producing such composite pipes with a length of up to 12 metres and a thickness of material of about 3-30 mm the liner of metal is first provided with a suit- able reinforcement and to the desired thickness at the same time as a suitable number of supply conduits for the thermosetting resin are placed in the reinforcement, in such a way that the mouths of said supply conduits are placed in the lower part of the ready mould. The inner liner and the reinforcement is then provided externally with a closing mould part in the form of an elastic or rigid mould part or an external pipe. Vacuum is then applied and the supply of thermosetting resin through the supply conduits is started, whereupon said supply conduits are pulled out of the mould at such a speed that the mouths of said supply conduits are placed just below the surface of the rising resin.
There is now a need for producing such composite pipes with a length of up to about 40 metres. However, when producing such long pipes by means of the above de- scribed supply conduits the friction between said conduits and the reinforcement will be too large. Simply, it is not possible to extract the supply conduits without breaking the same. The supply conduits used have an external dia- meter of 1-3 mm and a wall thickness of 0,2-0,5 mm and a tensile strength of 900 kN.
Increasing the wall thickness of the supply conduits while maintaining the same inner diameter will lead to that the external diameter has to be increased. This is not an acceptable solution, since ridges and cavities will then appear in the reinforcement after the supply con- duits, which in the ready-made composite pipe will be filled with thermosetting resin.
The object of the invention is to eliminate the above-mentioned drawbacks.
According to the invention this object is achieved in that a friction-reduction means is arranged around each supply conduit.
The invention will now be described in more detail with reference to the attached drawing, which is a broken perspective view of the friction reduction means according to the invention together with a supply conduit.
Preferably, a friction reduction means 1 is made as a thin, elongated stripe or foil, which is folded in the middle of the longitudinal direction of the stripe for producing a V-shaped stripe with two stripe halves 2,3 between which a supply conduit 4 is placed. The stripe halves 2,3 has such a width that they completely cover the supply conduit 4 when they are folded against each other. When producing composite pipes with a length of up to about 40 metres the supply conduits 4 together with friction reduction means 1 are placed in the reinforcement in the same way as described above.
The friction reduction means 1 shall be made of a substance soluble in the thermosetting resin used, which is supplied by means of said supply conduits, so that no foreign substances, layers or marks from the friction re- duction means will appear in the finished laminate of the composite pipes. The surfaces of the stripe halves 2,3 which are directed towards the supply conduit can be pro- vided with a lubricating substance, such as e. g. wax, in order to further reduce the friction between the supply conduit 4 and the stripe 1.
By arranging such friction reduction means 1 around each supply conduit within the mould it is now possible to produce composite pipes with a length of up to 40 metres by means of thin, elongated supply conduits and without ridges or cavities being formed in the reinforcement of the finished composite pipe.