Patent GB-793971-A (GB)
Title: Improvements in and relating to the manufacture of asbestos cement tubes
IPC: B28B21/48
Filed: 1955-09-13
Abstract: 793,971. Tube-making machines. EXTERNIT SOC. PER AZIONI. Sept. 13,1955 [Sept. 16, 1954], No. 26202/55. Class 99(2). A machine for making asbestos cement tubes comprises two movable tube-forming units A, B arranged in series and operating alternatively, an inclined plane guide 4 over which mandrels 3 on which the tubes are formed are allowed to roll for feeding to, and unloading from, the units, and means 9d, 10 ... 13 for stopping the advancement of the individual mandrels. There is control means arranged to actuate the stopping means cyclically in such sequence in each cycle that during the formation of a tube in the unit B a mandrel 3b with a tube formed in the unit A and an unused mandrel 3c advance to the space between the units, while another unused mandrel 3d is placed under the unit A for the subsequent formation of a tube, and, during the formation of the tube in the unit A the tube 3a formed in the unit B and the tube 3b disposed between the units advance out of the machine while the mandrel 3c is placed under the unit B. As shown in Fig. 1, the units A, B include lower cylinders A 1 , B 1  over which passes a felt 16 carrying plastic asbestos-cement for application to the mandrels 3, members 6a, 6b for holding the mandrels in position during a tube-forming operation, and bars 7a, 7b, for depressing the mandrel-supporting members 5a, 5b. The members 9d, 10 ... 13 for arresting advancement of the mandrels down the guide 4 are raised and lowered by fluid-pressure, pistoncylinder devices controlled by cam-operated valves 14a ... 14f and a distributor valve 15. The figure shows the step in which a tube has been formed on the mandrel 3a in the unit B, a mandrel 3b carrying a tube which has been formed in unit A and an unused mandrel 3c respectively held by the members 12 and 11 intermediate the two units, a mandrel 3d held by the member 10 in the unit A for forming a tube in that unit, and unused mandrels 3e, 3f awaiting advancement into the units. Before the tube on the mandrel 3a has reached the desired thickness, the unit A is depressed and formation of the tube in that unit is started, and upon completion of the tube in the unit B the latter is lifted so that the member 5b reverts to the original position thereof to restore continuity of the guide 4. Manipulation of the valve 15 causes shifting of the appropriate valves 14 whereby (a) the members 12, 13 are depressed so that the mandrels 3a, 3b roll out of the machine, (b) the member 11 is lowered to permit the mandrel 3c to move into the unit B against the raised member 13, the member 5a is raised upon completion of the tube in unit A, (c) the member 10 is lowered thereby allowing the mandrel 3d and the tube formed thereon to come to rest against the raised member 12, the formation of a tube on the mandrel 3c meanwhile being commenced, (d) the member 9d is operated to release the mandrel 3e and to come to rest against the raised member 11, and (e) in the final stage of the operative cycle, the member 10 is raised to receive the mandrel 3f when released by the member 9d.