Improvements in and relating to the manufacture of cellulose xanthate

摘要

PICT:0775893/IV(a)/1 PICT:0775893/IV(a)/2 In an apparatus in which the manufacture of cellulose xanthate is carried out in a series of steps under automatic control, the start of each step being initiated by a signal indicating the completion of the previous step, there is provided a member controlling the steps comprising a movable member having a number of actuators for initiating the operations performed in each step, a driving member for advancing the member intermittently, a signaling mechanism for indicating the completion of a step and a switching mechanism energized by the signal mechanism causing operation of the driving mechanism. As shown, alkali cellulose is supplied to a wet churn 31 equipped with a stirrer 38 and is therein converted to cellulose xanthate and formed into a slurry with aqueous sodium hydroxide. The alkali cellulose is supplied from a hopper 69, equipped with flap doors 68, to an inlet 32 provided with a sliding door 39. Carbon disulphide and aqueous sodium hydroxide are supplied to the churn 31 through pipes 34, 36. The churn 31 may be placed under a vacuum through a pipe 33 and vented to atmosphere through a pipe 35. The pipes 33, 34, 35, 36 are PICT:0775893/IV(a)/3 controlled by piston-operated valves 71, 72, 73, 74. The cellulose xanthate solution may be withdrawn through a pipe 37 controlled by a piston-operated valve 78. The sliding door 39 is operated by a double-acting piston 41, the compressed air for which is supplied through a valve 44 operated by a cam 16. The door 39 is held closed when compressed air is supplied through pipe 42 to the piston 41, pipe 43 being vented to atmosphere through a vent 49. On rotation of the cam 16 the salient 50 depresses the plunger 45 to the right, compressed air is supplied to the pipe 43 and the door 39 is opened. A projection 54 on the piston rod 40 operates switches 58, 60 through the medium of compressed-air valves 52, 53. The cam 16 is mounted on a shaft 47, Fig. 2, together with cams 17, 18, 19, 20, 21, 22, 23 which operate, through valves 61-67 respectively, pistons, similar to the piston 41, for operating the hopper flap 68, valve 33, valve 34, the paddle mechanism, valve 35, valve 36 and valve 78 respectively in the order named. Upon an extension of the cam shaft 47 are mounted rotary switches 84, 85, 86 provided with studs 1-15, 11-151 and 111-1511 and contact brushes 87, 88, 89 respectively. The brushes 88, 89 are connected to a positve bus-bar 90 and the studs 11-151 and 111-1511 to a negative bus-bar in a direct current supply. The brush 87 is connected to the negative bus-bar through a solenoid 92 and switch 93 and the studs 1-15 are connected to the bus-bar 90, each connection including a switch as shown in Fig. 5. The studs 11-151 are connected through warning lights 95 and additionally studs 71, 81, 101, 111 131, 141 are connected through timing mechanisms arranged in parallel with the lights 95. The studs 111-1511 are connected to the negative bus-bar through time-check mechanisms 96. A ratchet wheel 79 driven by a pawl 80 is mounted on the cam shaft 47. The pawl is mounted on a piston 81. At the commencement of the opertion, doors 68 and 39 are closed, the apparatus being in the position shown in Figs. 1 and 2. A push switch 91 is closed, thus energizing solenoid 92 which opens valve 83 to give a one-step rotation of the cam shaft 47. Projection 50 on cam 16 co-operates with piston 45 to cause the opening of door 39. An isolating switch 93 breaks the circuit and is re-set on the return stroke of the piston 81. The studs 2, 21, 211 are now contacting the brushes 87, 88, 89 and the projection 54 (Fig. 1) closes switch 60 to initiate the next step rotation of the shaft 47, which causes cam 17 to operate the hopper doors 68, whereby a charge of alkali cellulose is delivered to the churn. A switch 99, operated by pneumatic means, not shown, is closed when the hopper 69 is empty. This causes a further rotation of cam shaft 47 which brings cam 16 into a position whereby the door 39 is closed, and by means of the projection 54 the switch 58 is closed, thus causing a further rotation of the cam shaft and, through cam 18, a vacuum is applied to the churn. Pneumatic means detect when the vacuum is at a sufficient level and closes switch 102 to cause a further step rotation of the cam shaft. The succeeding steps of the cam shaft initiate rotation of the paddles 38, delivery of carbon disulphide, venting of churn 31 to atmosphere, delivery of sodium hydroxide and opening of delivery valve 78. The delivery of the full charge of carbon disulphide is detected by pneumatic means, not shown, whereby the solenoid circuit is closed and the next step commences. The xanthation period, period of venting to atmosphere, formation of a slurry with aqueous sodium hydroxide and removal of the slurry are all governed by timing mechanisms T1, T2, T3, T4 operating switches t1, t2, t3, t4. After the timed closure of the removal valve 78, further sodium hydroxide is admitted to the churn for rinsing, the paddles 38 are rotated and, after a time, stopped, and the valve 78 opened to remove the rinsing liquor and then closed under the influence of timing mechanisms T5 and T6 and further pneumatically operated switches 104 and 105. In the event of any operation not being completed in a given time the check timing units throw a switch 97 which connects an alarm 98. The lights 95 indicate the position at any given time. The rotary switch 84 may be overridden by a switch 106.