Patent GB-640223-A (GB)
Title: Improved method and means for moulding objects from a mouldable mass
IPC: B28B7/32
Filed: 1946-04-12
Abstract: 640,223. Molding concrete &c. SJODIN, O. V. April 12, 1946, No. 11361. [Class 87 (ii)] [Also in Group X] Plastic material such as concrete, asphalt concrete, is continuously moulded by means of a moulding-member comprising an envelope of flexible impermeable material having a continuously developable moulding surface supported by a rigid greased filling member or fluid pressure inside the envelope. For moulding pipes, sewers, channels, &c. continuously, the envelope 1 is used as an inner moulding member or core and is in the form of a tube turned half inside out with the ends then joined together to form a continuous surface. This envelope is filled with air, or partly filled with water when moulding open channels (Fig. 6b), and drawn forward by a rod 21. (Fig. 5a) or rope passing down its centre and frictionally engaging its surface. The moulding surface is continuously stripped from the moulded surface at the rear of the envelope and brought forth at the front while that part in contact with the concrete at any instant is stationary. In Fig. 5a (moulding a tunnel or sewer), a rigid premoulding member or shield 11 is used to give the desired form to the inside of the tunnel &c., fitting over the front of the member 1 and drawn forward at the same speed. An outer mould 10 is also used, concrete being supplied through the open top of this mould. This outer mould may be a sliding mould and in conjunction with a feeding device such as a screw and funnel the apparatus may be used in continuous moulding of pipe lines without cutting ditches by forcing the feeding device through the earth. When moulding channels &c. Fig. 6b, the envelope may be spaced from the surrounding surface by concrete blocks &c. 23. The envelope may be guided by any suitable guide device or guided in a free-floating manner in the concrete by pressing the pulling rope or cord vertically or laterally. When moulding articles of limited length the moulding member may comprise two flexible portions 1, 1 joined by a rigid portion 2, the centre part of the envelope passing over a roller 3 (Fig. 2a). Part of this centre part may be dispersed with and replaced by a rope. The rear half 1 may be dispensed with and replaced by a reservoir 2 (Fig. 3a) for fluid which may be introduced thereinto to advance the envelope. Liquid in the reservoir may be evaporated for the same purpose. In this arrangement the centre part of the envelope is closed and attached to a wire 4 wound on a roller 3. In the apparatus of Fig. 4, similar to Fig. 2a, for moulding pipes, an outer mould 10 is used and the envelope 1 has a premoulding member 11, with spacers 13. The envelope is advanced by applying fluid pressure behind the rear of the envelope 1 which is confined in a casing 6, open at the left end, in a larger casing 8. Fluid is introduced through opening 14 for this purpose. Annular reinforcement 17 may be provided and also longitudinal. The reinforcement may also be helical, anchored to pins 18 on end wings 19. The outer mould may be slotted to allow escape of excess water. After moulding the end of the mould may be closed and water introduced to strip the envelope from the mould. When the envelope reaches the end of the mould further movement is prevented and the water pressure increased to test the pipe. The envelope may be arranged upon an inner supporting cylindrical core 24, Fig. 8, which is useful in tunnels for removal of excavated material. The core is integral with a guide ring 11. Movement of the envelope relative to the core when advancing the envelope may be facilitated by introducing compressed air and rollers between them. The envelope may be used as an outer moulding member with a suitable shield 11 (Fig. 7a), when moulding beams, pipes and columns. The moulding material may be vibrated, e.g. by vibrating the member 11, Fig. 4. The moulding member may be used horizontally, vertically, or inclined. The moulded mass may be compressed by increasing the pressure in the envelope or by applying the envelope on a tapering core or by using a tapering tubular rigid member in the envelope. This increase of pressure may be utilized for the prestraining of longitudinal, annular, tubular sheet metal or helical reinforcement, the outer mould, if provided, being yieldable. With helical reinforcement any relation between longitudinal and annular prestraining forces may be obtained by suitably choosing the pitch of the helix. The envelope may be elastic radially for the purpose of applying pressure and reinforced with flexible wires longitudinally. The moulding material may be heated e.g. by heating the filling material. A heater 16 is shown in Fig. 4 for this purpose. A variation of the moulding section may be effected by manufacturing the envelope with a non- cylindrical shape, e.g. conical in longitudinal section. Apart from the means referred to above the envelope may be advanced by air pressure behind or vacuum in front. When a rod 21 is used, reintroduction of the rod into the opening in the centre of the envelope is effected by beating or vibrating it, and introducing compressed air between it and the envelope.