Patent GB-701351-A (GB)
Title: Improvements in or relating to method and machine for making plastic venetian blind tape
IPC: B29C65/48
Filed: 1952-02-08
Abstract: 701,351. Plastic venetian blind tape. HUNTER DOUGLAS CORPORATION. Feb. 8, 1952 [Feb. 15, 1951], No. 3372/52. Class 20 (3) [Also in Group VIII] Plastic venetian blind ladders are made by forming tapes of plasticized resin having a plurality of longitudinally extending parallel filaments embedded therein, bringing two tapes together in spaced parallel relation, heating the tapes to the fusion temperature immediately before hanging them together in parallel relation, inserting plastic cross bars between the tapes at regularly spaced intervals with their ends abutting against the tapes whose adjacent surfaces are tacky, and pressing the ends of the cross bars against the tacky surfaces of the tapes until the latter are cooled below the fusion temperature. Two tapes are formed on endless bands 15, e.g. of stainless steel, which pass around wheels 13, 14 and 13<SP>1</SP>, 14' and are preheated in an oven 26, by spreading resin paste on the bands at 20, laying filaments on the paste layer at 54, heating in tunnel ovens 22 to fuse the resin and plasticizer, applying a second resin layer at 21 and heating in ovens 23. As the tapes pass around the driven wheels 14, 14' to assume a side by side position they are made tacky by heating, and cross bars 74 are severed at 24 from a continuous strip 74' of T-section and supported on a conveyer 73 between the tapes until they are joined thereto, whereupon the completed ladder is cooled at 25 and removed from bands 15. The resin paste preferably comprises fine particles of polyvinyl chloride suspended in a liquid plasticizer such as dioctyl or dinonyl phthalate, but other resins such as vinyl copolymers, e.g. vinyl chloride acetate, and vinyl chloride-vinylidene chloride, may be used. The applicators 30 for applying the resin each comprises a wedge shaped head 31 formed in two parts 32, 33 clamped together and secured to a support 34 by screws 35, forming a cavity 36 which opens through a narrow slot 40 at the pointed end and connects through a hole 41 with a supply pipe 42 from the resin container 43. High pressure air through line 44 forces the paste through the applicator. The bands 15 are guided at the upper and lower edges by grooved rollers and backed by a roller 45. At station 20 the band 15 is bent from its normal line by rollers 52, 53, the applicator 30 operating midway between these rollers, and the filaments 19 being applied immediately after this point. The threads 19 are unwound from cones in a housing 56 and fed through individual eyelets, converging dividers, and a comb to the roller 54, and come into contact with the resin directly opposite the roller 53. Suitable temperatures for ovens 22, 23 are 280-300‹ F. and 330-340‹F. respectively. The tapes are partially fused by contact with the heated rims 64 of wheels 14, 14<SP>1</SP> and directly by means of an electric heater. The strip 74', which has portions of reduced thickness to form hinge portions in the cross bars, is fed over a curved guide 81 on a support 85. Swingably mounted on a shaft 90 projecting from block 85 is an arm 91 having two vertically spaced parallel guide rods 92, and a head 93 slides on rods 92 and is engaged by a crank pin 94 on the end of a drive shaft 95. Shaft 95 rotates in block 85 parallel to shaft 90, and is driven from a motor through sprockets 96, 98 and chain 97. A block 100 fixed to the side of head 93 in alignment with guide 81 carries a knife 101 and pressure pad 102, and a block 103 attached to an arm 91 directly opposite block 100 carries a knife 104 and stripper plate 105. Pad 102 is mounted on a rod 106 slidable in a hole 107 and is urged outwardly by spring 110 in cavities 111, a limit stop 108 restricting the movement of the pad and positioning the face thereof beyond the edges of knife 101. Knife 101 has two sets of cutting edges 112, 113 which co-operate with the cutting edges 114, 115 of knife 104, edges 113 and 115 severing the strip 74', and the shorter edges 113, 114 cutting a slit in the cross bar 74 in which a blind slat may be inserted. The stripper plate 105 is mounted on rods 120 which slide in holes in block 103 and have a part 121 fixed to their projecting rear ends. Part 121 is slidably mounted on rods 122 projecting from block 103, and springs 123 encircling rods 122 urge the part 121 to the left (Figs. 12 and 16). As shaft 95 rotates clockwise the head 93 is carried by pin 94 and shifted back and forth along rods 92, and causes arm 91 to oscillate. During each cycle pad 102 engages strip 74' and pulls the strip down, the knives cut the strip, the pad yields against springs 110, and the stripper yields against springs 123, and when the head 93 moves to the left, knives 101 and 104 are withdrawn from each other and pad 102 and stripper 104 restored to their original positions. The cross bars 74 drop into the open jaws of conveyer 73, which comprises a plurality of links 130 connected by pivot pins 131 and is passed around wheels 132, 133 driven through a sprocket 136 and chain 140 from the motor driving bands 15 and mechanism 72. The cross bars, cut to a width slightly less than half the width of the tapes, are carried alternately high and low by conveyer 73 to stagger the cross bars on opposite sides of the centre line of the tapes and to space them laterally a distance sufficient to allow the blind lift card to be threaded therebetween. Links 130 therefore have long arms 141 terminating in flat shelves 142, while the alternate links 130<SP>1</SP> have short arms 141' and shelves 142'. Flat plates 143, 143' are fixed to the outer sides of arms 141, 141<SP>1</SP>. A bell crank 144 having a downward leg 145 and upward leg 146 or 146', is pivoted on each pin 131 between the side links 130. Flat plates 150, 150' are fixed to legs 146, 146' and co-operate with plates 143, 143' to clamp the cross bars. A spring 149 connects each bell crank 144 to the top edges of plates 143, 143', and tends to close plates 150 or 150' against plates 143, 143'. The outer end of the crank leg 145 rides on a flat horizontal track 151, and the angular position of the bell crank is determined by the level of the track 151 with respect to the centre of pin 131, and the latter is determined by side rails 152 on which the links 130 ride, see Fig. 11. The rails 152 rise from the sprocket 132 to a flat midway portion and then descend as they approach sprocket 133, causing the conveyer chain to rise slowly until the cross bars 74 are gripped between plates 143 &c. and brought into register with the tapes, to travel parallel with the tapes while the cross bars are secured to the tapes, and finally to descend so that plates 143, 143', 150, 150' are opened by springs 149 to clear the cross bars and pass around wheel 133. As the plates 143 &c. start to close the conveyer chain passes between rollers 153, 154 which align the cross bars, and when the plates have firmly gripped the cross bars the latter are heated by hot plates 155 to orepare the ends for fusion to the tapes. Specifications 619,143 and 660,947 are referred to.