Patent GB-761158-A (GB)
Title: Production of filaments by melt-spinning
IPC: D01D1/06
Filed: 1954-03-26
Abstract: <PICT:0761158/IV(a)/1> <PICT:0761158/IV(a)/2> <PICT:0761158/IV(a)/3> Apparatus for the production of artificial filamentary products from comminuted fusible filament-forming materials comprises a chamber for receiving particles of material, a spinning jet adapted to be heated and disposed at an opening of the chamber, two or more rams within the chamber, each having a working face for applying mechanical pressure to urge the particles towards the opening of the chamber against the jet, and means for reciprocating the rams in such a way that the mechanical pressure is applied to the material continuously. As shown in Figs. 1 and 2, comminuted thermoplastic material from the hopper 12 passes by gravity into an elongated tamping chamber 17 supported by the hopper 12 and communicating, at its upper central portion 18, with the lower portion 19 of the hopper.  The material passes through the tapered lower portion of the chamber 17 and is forced out of a long slit-like opening 22 at the bottom of the chamber, and through the orifices 23 of a heated jet plate 24, by the reciprocating action of alternately operating tampers or rams 26, 26a, which are located within the chamber 17 and extend over substantially its entire length.  The jet plate 24 also extends along substantially the entire length of the chamber 17 and is mounted between a cover strip 27 and a supporting strip 28, both made of electrical insulating material, the whole assembly being secured to the bottom of the chamber 17 by means of a mounting member 29 attached to the bottom of the chamber by screws (not shown).  The jet plate 24 is adapted to be heated by the passage of a controlled electric current along its length to a temperature sufficient to melt the thermoplastic material forced against the plate by the reciprocating action of the rams 26, 26a.  This action also serves to distribute the material, which enters the central portion of the chamber 17, over the whole length of the chamber so that material is forced through the orifices of the plate 24 along its entire length. The rams comprise long horizontal bars 31, 31a (Fig. 3) having working faces 32, 32a, flat sides 33, 33a and thickened upper portions 34, 34a.  The bars 31, 31a are adapted to be mounted so that their working faces 32, 32a can be reciprocated in the guides 36 towards and away from the jet plate 24 with the flat sides 33, 33a in sliding contact with each other.  The bars 31, 31a are connected to means for reciprocating them by posts 37, 37a welded, brazed or soldered to the bars between their ends.  These posts comprise cylindrical heads 38, 38a, stems 39, 39a, and nipples 41, 41a adapted to be received in semicircular grooves 42, 42a in the bars 31, 31a, the grooves being so located that, when the bars are mounted between the guides 36, all the posts 37, 37a are in the same plane.  To enable the bars 31, 31a to be reciprocated without the posts of one bar fouling the other, a portion of each bar is cut out, as at 43, 43a, opposite the points where the posts are attached to the other bar.  The bars 31, 31a are bevelled, as shown at 44, 44a, 45, 45a, to permit the comminuted material to move more freely past the rams and towards the jet plate 24.  The posts 37, 37a are operatively connected to a drive shaft 46, situated at the top of the machine frame 11, by means of eccentrics 47, 47a, pins 48, couplings 49, connecting rods 51, lost-motion connections 52, tie rods 53 and collars 54.  The stems 39, 39a of the posts are mounted in sleeves 56 (Fig. 2) of packing glands 57, which are screwed into a cover 58 of the chamber 17, and the heads 38, 38a fit within the collars 54 and are held in the collars by removable pins 59 mounted on the collars below the heads.  The collars 54 are formed with internally threaded portions 60 adapted to receive threaded ends of the tie rods 53, which carry lock nuts 61.  The positions of the collars 54 along the tie rods 53 can be varied by loosening the lock nuts 61 and rotating the collars, such rotation of the collars being permitted by the connections between the collars and the heads 38, 38a of the posts 37, 37a.  The assembly of tie rods 53, collars 54 and rams 26, 26a is urged downwards by means of strong compression springs 62, whose lower ends abut against flanges 63 on the tie rods 53 and whose upper ends abut against adjustable nuts 64 mounted on threaded sleeves 66 fixed to an L-girder 67 mounted on the frame 11.  The lostmotion connections 52 comprise pins 69 carried by the tie rods 53 and fitting in slots 71 in the enlarged ends of the connecting rods 51, the rods 51 being slidably mounted in guides 72 in the sleeves 66. By virtue of these lost-motion connections the upward movement of the rods 51 lifts the tie rods 43 and the rams 26, 26a against the action of the springs 62, while the downward motion of the rods 51 permits the springs to urge the rams downwards to perform their tamping action.  Thus each ram is raised to substantially the same predetermined position upon each revolution of the shaft 46.  This position is adjustable relative to the jet plate 24 by means of the threaded connections between the rods 51 and the couplings 49 and also by means of the threaded connections between the collars 54 and the tie rods 53.  The working faces of the rams may be lifted to about 5/16 inch above the upper surface of the plate 24.  The rams descend, however, only so far as the thickness of the layer of material lying over the plate will permit, the lost-motion connections 52 allowing the residual movement of the rods 51, under the influence of the eccentrics 47, 47a, to take place independently of the tie-rods and rams.  The lowest possible position of these is determined by the adjustment of the collars 54, which act as stops engaging the upper surfaces of the packing glands 57.  One pair of eccentrics 47 is mounted on the shaft 46 at a position 180 degrees removed from that of the other pair of eccentrics 47a so that, when both the eccentrics 47 are in their highest positions, both of the other eccentrics 47a are in their lowest positions. Accordingly, when the ram 26 is raised to its highest position, the other ram 26a is being pressed, under the action of the springs 62, against the comminuted material above the jet plate 24, and vice versa.  The lost motion connections 52 are so proportioned, and the parts are so adjusted, that a ram 26 or 26a is under the influence of its operating pair of eccentrics 47 or 47a for only a relatively small fraction, e.g. one sixth, of the cycle of operation, the rams being free to be urged downwards under the action of the springs 62 for the remainder of the time. Thus for a major portion of the cycle of operation both rams 26 and 26a are pressing against the powdered material above the plate 24, while for two spaced minor portions of the cycle the material is under the pressure of only one of the rams. The orifices 23 in the jet plate 24 are preferably arranged in staggered relationship in two spaced rows, the rows being, for example, 0.05 inch apart, and each row being directly under a working face 32, 32a. However, since the rams 26, 26a are side by side, the pressure of either ram, transmitted through the powdered material, urges the material over both rows of orifices 23 in a downward direction. In the operation of the apparatus there is a balance between the rate of withdrawal of the material in the form of filaments from the jet plate 24 and the rate of supply of fresh powdered material to the upper surface of the plate 24.  Thus if the material should enter the space created beneath the face 32 or 32a by the travel of the ram 26 or 26a to its uppermost position at a greater rate than that at which it is being drawn away from below the plate 24 in the form of filaments, the thickness of the layer of material on the plate 24 would increase, the clearance beneath the face 32 or 32a would decrease, and the rate of supply of fresh material would correspondingly diminish.  The material in the chamber 17 is preferably maintained at sub-atmospheric pressure.  To this end, the chamber 17 is provided with a vacuum line 76 connected to a vacuum pump (not shown), the opening 77 of the vacuum line being shielded by a baffle plate 78 so that the material will not be drawn into the vacuum line.  A second vacuum line 79 (Fig. 2) is provided in the upper portion of the hopper 12 to enable the pressure in the hopper to be reduced quickly, particularly when starting up the apparatus.  To aid in maintaining the sub-atmospheric pressure in the chamber 17 a seal 80 is provided in the gland 57.  Also, the hopper 12, the walls of the chamber 17 and the connection between the hopper and the chamber are all made substantially air-tight, and the hopper is provided with a removable air-tight cover (not shown).  Several spinning machines 10 are operated from a single shaft 46 and means are provided whereby the rams 26, 26a of any one machine may be disconnected from the shaft without interfering with its rotation. To this end, the apparatus includes a plate 81, supported at one side by a pair of pivot pins 82 mounted on the frame 11 and having apertures 83, adapted to receive the tie-rods 53, and projections 84, adapted to engage the undersides of the flanges 63 of the tie rods when the projections are moved upwards by the rocking of the plate. The other side of the plate 81 is supported on an eccentric cam 86 which is keyed to a shaft 87 journalled at the end of brackets 88 depending from the L-girder 67 of the frame 11. Rotation of the shaft 87, by means of a long handle 89 keyed thereto, causes the cam 86 to rotate, thus rocking the plate 81 to lift all the tie-rods 53 against the action of the springs 62. When the parts are thus lifted the rotation of the drive shaft 46, and the resulting reciprocation of the connecting rods 51, has no effect on the tie-rods 53