Patent GB-931872-A (GB)
Title: Improvements relating to processes and machines for making asbestos-cement or like pipes
Inventor: WHITFIELD WILLIAM HENRY
IPC: B28B21/48
Filed: 1961-02-08
Abstract: 931,872. Making asbestos-cement &c. pipes. TURNERS ASBESTOS CEMENT CO. Ltd. Jan. 26, 1962 [Feb. 8, 1961], No. 4707/61. Class 99(2). In a process for the manufacture of pipes by causing an endless band 1 to pick up a layer of material containing fibres from at least one rotary cylindrical sieve 2 and carry the material to the nip between a rotary mandrel 7 and an anvil roller 8 to coat the mandrel, the latter being changed for another when the coating has been formed on it to the desired thickness, the band moves continuously in contact with the sieve or sieves but the anvil, roller is stopped while the mandrel is being changed, and a loop formed in the band in the length thereof running from the anvil roller to the sieve or first sieve is reduced in length at a relatively fast rate to provide a length of band travelling in contact with the sieve or sieves throughout the period in which the anvil roller is stopped, and this loop is reformed at a relatively slow rate while the anvil roller is rotating again during the production of the next pipe. As shown, the band passes from the sieve 2 over a roller 5 and a suction box 6, which draws some of the water out of the layer carried by the band, and to the mandrel 7 and from the latter over rollers 12, 13 and 14 and a suction box 15. From the roller 14, the band passes over a roller 16 to squeeze rollers 17, a guide roller 20 and rollers 19, 21 and 22, the roller 21 being free to move up and down to lengthen or shorten the band between the rollers 19, 22. Driving of the band is effected through the roller 8 which is driven by a variable speed motor 23, and the roller 5, mounted to reciprocate towards or away from the sieve, is driven by a variable-speed reversible motor 25 pre-set to run in each direction on the receipt of a starting signal and at a predetermined speed for a predetermined period of time. As shown in Fig. 2, screwthreaded shafts 30 carry brackets 31 on which is mounted the roller 20, raising and lowering of the latter being effected by the turning of a handwheel 61, and the roller 21 is carried in bearings 33 slidable in guide slots 34 in a vertical frame 35. The roller 5 is carried at each end thereof in bearing blocks 37 slidable on rails 38 at the ends of each of which are sprocket wheels 39 and 40 around which an endless chain passes, the wheels 40 being interconnected by a counter-shaft 42 driven by the motor 25 through a coupling 69, gearing 70 and a chain 43; by turning the motor in the appropriate direction, the roller 5 can be moved from one end of the rails to the other. The speed of the motors 23, 25 is controlled throughout the operation of making a pipe and during the changing of a mandrel so that the sieve speed remains substantially constant. In a modification, a rear roller 66, Fig. 5, equivalent to the roller 5 is mechanically connected to a loop-forming roller 51 so that both rollers move backwards and forwards together, the rollers being carried in bearing blocks 52 slidable in rectilinear guides 53 and connected by rods 54. The blocks carrying the rollers 66 are tapped for traverse screws 58 driven from the motor 25. In other modifications, one or both of the loop-forming rollers can be oscillated instead of being reciprocated, and the roller 21 may be subjected to hydraulic or pneumatic pressure and move in a line other than vertical; also, there may be more than two loop-forming rollers for changing the path of the endless band.