Patent GB-701108-A (GB)
Title: Improvements in and relating to churns for the production of viscose
Inventor: STOKES WILLIAM HENRY
IPC: D01F2/08
Filed: 1950-10-11
Abstract: <PICT:0701108/IV (a)/1> A churn for the production of viscose comprises a container, one end of the container being mounted on a shaft rotatably mounted in a bearing, the other being mounted for rotation in a second bearing, a stirring mechanism fixed to the shaft and extending within the container over at least half the axial length of the container, driving means for rotating either the shaft or the container and a free wheel mechanism of which one part is connected to the shaft and the other part to the container so that on rotation of the container in one direction the stirring mechanism is caused to rotate at the same speed as and with the container and on rotation of the stirring mechanism in the same direction the container remains substantially stationary.  As shown a churn 1 comprises a container 2 surrounded by a jacket 3. A free-wheel 4 having gear teeth round its periphery is fixed to one end of the churn 1 by its outer member, and a hollow trunnion 5 is fixed at the other end of churn 1.  A shaft 6 held in two bearings 7, 8 in the frames 9, 10 respectively passes through and is fixed to the inner member of the free-wheel 4, and the hollow trunnion 5 is held in a bearing 11 in a third frame 12 so that the churn 1 is capable of rotation about its horizontal axis.  The free-wheel 4 is fitted with a gland (not shown) between the inner and outer members to prevent the escape of liquid or vapour from the container 2.  A paddle 13 is mounted on the end of shaft 6 within the container 2 and may be rotated by a pulley 14 splined to the shaft 6.  The pulley 14 can be driven through a driving belt 15 which is shifted off an idler pulley 25 by a belt shifting fork 16 when required.  The churn 1 may be rotated by shifting the belt 15 by means of the fork 16 on to a third pulley 17 mounted on a sleeve 18 surrounding the left-hand end of the shaft 6.  A gear-wheel 19, also mounted on the sleeve 18, drives the free-wheel 4 through a reduction gear train 20 and an idler gear-wheel 21.  When the churn is rotated, the shaft 6 and paddle 13 are also rotated by free-wheel 4, so that there is no relative motion between the paddle 13 and the churn 1.  When the paddle 13 is being directly driven through the pulley 14 and the shaft 6, the churn 1 receives no drive and remains substantially stationary by virtue of the "free-wheeling effect" of the free-wheel 4.  To prevent the churn 1 "creeping" due to its having insufficient inertia and/or to its contents having a high viscosity, a brake 22 fitted to the sleeve 18 is operated by fork 16 when moving the belt 15 on to the pulley 14, or by a brake pedal 23 fitted to the frame 9.  In the manufacture of viscose, alkali cellulose crumbs are charged into the churn 1 through a charging door 26 from a shoot 27, the door 26 closed and air evacuated from the container 2 through a non-rotating pipe 28 passing through the centre of the hollow trunnion 5 and communicating with a chamber 29 in a column 30 having an opening 31.  A running gland (not shown) is provided between the pipe 28 and the hollow trunnion 5 to prevent the escape of liquid or vapour from the container 2.  Carbon disulphide is now delivered to the container 2 by means of a second pipe 32, a second chamber 33 in the column 30 and a nozzle 34.  The second pipe 32 passes through but does not communicate with the pipe 28.  The churn 1 and paddle 13 are now rotated for the duration of the xanthation period by shifting belt 15 on to the pulley 17 and the belt 15 is then shifted to the pulley 25 and the churn braked by the pedal 23.  Dilute aqueous sodium hydroxide solution is now admitted to the container 2 through a third pipe 35 passing through but not communicating with the pipe 28, the chamber 33 and the nozzle 34. The belt 15 is then shifted on to the pulley 14 and the paddle 13 rotated while the churn 1 is held stationary by the brake 22.  When the cellulose xanthate has been dissolved, the belt 15 is shifted back on to the pulley 25 and the churn 1 rotated by means of the hand-wheel 24, until the door 26 is positioned over a discharge shoot 36 in the churn room floor 37.  The door 26 is removed and the solution discharged into the shoot 36.  The residual solution in the churn is washed out by passing a further quantity of dilute sodium hydroxide solution through the nozzle 34 and the churn 1 thus rendered ready for the cycle to be repeated.  The temperature of the container 2 is controlled by passing a heating fluid into a space 38 between the container 2 and the jacket 3 by means of an inlet pipe 39 communicating through a circumferential channel 44, sealed by a running gland, with a duct 40 within the collar 41 of the hollow trunnion 5 which opens into the space 38.  The fluid passes out of the space 38 by a second duct 42 communicating with an outlet pipe 43 through a second circumferential channel 45, sealed by a running gland, in the collar 41.  Due to the paddle rotating with the churn during xanthation churns constructed in accordance with the invention require only small power for rotation during xanthation and have a low fire hazard when the vacuum is broken on the completion of xanthation.  Specifications 549,250 and 656,872 [both in Group II], are referred to.