Patent GB-822722-A (GB)
Title: Apparatus for melting synthetic organic linear high polymers for use in the production of filaments and films by extrusion of the melt
IPC: D01D1/09
Filed: 1956-04-03
Abstract: <PICT:0822722/IV (a)/1> Melt-spinning apparatus comprises a melting chamber, a device for feeding a synthetic organic linear high polymer to the chamber at a controlled rate, a device sensitive to variations in pressure, temperature or electrical conductivity of an element of the apparatus in accordance with variations in the level of the melt in the chamber, a metering pump for withdrawing the molten polymer at a constant rate from the melting chamber, and a device for feeding the response of the sensitive device to the feed control device, thereby to ensure a substantially constant and reproducible residence time of the polymer in the melting chamber.  Preferably the response feeding device comprises a make-and-break contact which is actuated by the response of the sensitive device and is connected to an electric relay which causes a small reversible electric motor to run either in one direction or the other according to whether the low voltage electric circuit is made or broken and thereby alter the gear ratio of an infinitely variable speed gear through which the controlled-feed device is driven by a constant-speed electric motor. As shown in the drawing, polymer to be melted, for example in the form of chips, passes from a container 1 and through a cock 2 into the bucket wheel controlled feed device 3 driven by a constant-speed electric motor 23 through the infinitely-variable speed power transmission gear 19 and a clutch.  From the bucket-wheel 3 the chips drop through a supply pipe 4 at one end of the melting chamber on to a roller 5 rotating at a constant speed in the direction of the arrow and fill a melting-chamber 6, which has a grid 7 preventing the chips from falling to the bottom of the chamber.  The chamber has a rectangular horizontal cross-section, is formed in a heated block 8, has a two-part cover 21 and can be evacuated through a pipe 22.  The rotation of the roller 5 dips the chips into the melt and accelerates their melting by causing them to move in the melt.  The melt is caused to move as a film in a helical path along the roller from the inlet to the outlet end of the melting chamber.  The eccentric position of the roller with respect to the curved bottom of the melting chamber 6 causes the melt to be drawn by the rotation of the roller into the wedge-shaped space 9 between the roller and the wall of the chamber and fed under pressure to a constant-speed metering pump 11 through a discharge bore 10 at the end of the melting chamber remote from the supply pipe 4.  The pump 11 meters the melt through a duct 12 to a spinning nozzle 13.  Arranged in the block 8 is a pressure-sensitive device 14 which communicates via a duct 15 with the melting-chamber 6 and the pressure in which varies according to the level of the melt in the chamber 6.  A rise in this level with consequent increase in the pressure beyond a predetermined value causes the make-and-break contact of a low voltage electrical circuit to close and close the relay switch of a higher voltage electrical circuit which causes a small reversible electric motor to run in one direction and drive the gear ratio control shaft 20 of the infinitely-variable speed power transmission gear 19 in a direction which lowers the output/input gear ratio.  The breaking of the contacts 16 reverses the above effects.  A disc on the gear ratio control shaft 20 is provided with limit switches (not shown) which limit the gear ratio variation to a predetermined range.  The speed of the motor driving the polymer feed device may alternatively be controlled by means of a diaphragm which is mechanically coupled to an infinitely variable electrical resistance of the carbon type and which is acted upon by the pressure in the wedge-shaped space 9 in the melting-chamber 6.  As the roller 5 rotates at a constant speed, an increase of the level of the melt in the chamber 6 increases the pressure in the space 9 and vice versa.  The carbon p  resistance controls the speed of an electric motor driving the polymer feed device.  The solid polymer may be in the form of filaments or strips produced by a continuous polymerization and extrusion process.  The polymer feed device may comprise oscillating metering troughs or oscillating metering troughs or oscillating shut-off members, the stroke of which may be automatically controlled by the sensitive device.  A device sensitive to variations in temperature or electrical conductivity, mounted just above the usual level of the liquid, may be used instead of a pressure-sensitive device.