GB968325A - A method and apparatus for producing a coated base - Google Patents

Abstract

968,325. Coated sheet material. S. F. REED. Aug. 17, 1960 [Aug. 17, 1959], No. 28508/60. Heading B2E. [Also in Divisions B6, G5 and H1] A method of coating a base material, e.g. a thermoplastic, is characterized in that a coating material is deposited on a rigid surface and applied to the base material whilst the latter is in a semi-solid state. In the apparatus of Fig. 1 a sheet of liquid base material, e.g. nylon, in the form of a web 12 is extruded on to a cylinder 14 rotating in association with a chilling cylinder 16 such that the material emerges at 20 as a printed solid web. Both cylinders are engraved with depressions 21 in accordance with the information to be printed on the web and the cylinder 16 carries a coolant, e.g. ethylene glycol. The depressions 21 are filled with small particles of pigment fed through hoppers 22 and 24 to applicators 26, 28. Scraper blades 30, 32 are provided and the pigment may be either in dry powder form or in a viscous suspension. The particles are embedded in both the surfaces of the solidified web resulting in the finished product as shown for example in Fig. 2b. Fig. 2c shows an electric cable comprising two identical sections each of which has four conductors 33 on each side of a base 31 and is made with the apparatus of Fig. 1. The cylinders 14, 16 have circumferential grooves fed with electrically conductive particles from the hoppers 22, 24. In an alternative apparatus the liquid web is fed from a well 34, Fig. 3, formed between two rotating chilling cylinders 36, 38. Strands of fibrous filling material may be used as a web strengthener being fed into the cylinder "nip" from a hopper 35. Alternatively a paper web may be used as a strengthener. In another embodiment the apparatus of either Fig. 1 or Fig. 3 is used with a web liquidized by solution in a highly volatile solvent. The apparatus is modified by the substitution of a heated cylinder or cylinders for the chilling cylinder(s). The cylinders may be of an electrically conductive material 42, Fig. 4a, having a removable shell 44 of non-conductive material. The grooves produced in engraving &c. extend through the shell 44 to expose the conductive material 42. The pigment particles are such that they are held in the grooves by electrostatic forces produced by opposite charges on the particles and the material 42, the latter being charged through a brush 45 and slip ring 46, Fig. 1. Alternatively, the cylinder of Fig. 4a may be used to provide particle adherence by magnetic attraction, the material 42 in this case being magnetized by a permanent or electromagnet. A further cylinder, Fig. 4b, has a smooth surface, the particles being attracted thereto in the desired pattern by either electrostatic or magnetic forces. Fig. 5 illustrates apparatus using electrostatic attraction for simultaneously embedding particles of various colours in the same web. Each colour pattern is fed to a cylinder 72, which is of the type shown in Figs. 4a or 4b, by apparatus comprising a light source in a rotating transparent cylinder 50 carrying a photographic transparency 52. Adjacent the cylinder 50 is a slit 54 focusing an image of the transparency 52 upon the surface of a rotating cylinder 56 coated with a material, e.g. selenium, which is responsive to light energy to cause deterioration of an electrostatic charge upon its surface produced by bombarding positive ions generated by a wire 58 running the length of the cylinder. The surface of the cylinder 56 thereby carries an image in the form of a selective distribution of positive ions which image is built up by the ejection from a nozzle 62 of negative charged particles of the colour required. A negatively charged electrode 68 accelerates particle flow to the cylinder surface whilst a positively charged electrode 70 extracts any particles remaining unattached to the cylinder. The cylinder 72 bears a still higher positive charge sufficient to pull all of the particles from the cylinder 56 and cause them to adhere to the cylinder 72. The particles may be transferred from cylinders 56 to 72 by magnetic attraction, in which event suitable magnetic particle material is used. In the production of pre-recorded magnetic tape the signal to be recorded is fed to terminals 110, Fig. 9, of an amplifier 112 which is in turn connected to a light source 114 the light from which is projected through lens 116 and focused in a narrow line 118 upon the surface of a cylinder 120 which is identical with cylinder 56, Fig. 5. Transposition to a cylinder 72 is as described above. A multi-colour apparatus comprises printing cylinder pairs such as 93, 95, Fig. 7, for each colour, the web material 105 remaining in a plastic state until it reaches chilling cylinders 107, 109. It may be necessary to heat each of the printing cylinders. Un-recorded magnetic tape may be produced by the apparatus of Fig. 8 by forming the depressions in the cylinders 98, 100 as circumferential grooves 102 and extruding liquid web material from nozzles 104 above the grooves. Cylinders 106 and 107<SP>1</SP> carry electrostatically charged particles. The apparatus of Figs. 1, 3 and 5 may be used to produce paper webs carrying parallel stripes of magnetizable material bonded thereto. In an apparatus for producing printed sheets a flat plate 122, Fig. 10, is provided with particle filled depressions 124 in accordance with the desired image and is reciprocated, a liquid sheet being extruded during the time the plate 122 is passing under it. The sheet 128 is carried forward to a chilling cylinder 130 which may also have particle filled depressions representative of an image desired to be printed on the opposite side of the sheet. The particles may be electrostatically or magnetically applied and held on the cylinder 130 and similarly applied to the plate 122. An apparatus for producing printed electrical circuits on a web 132, Fig. 11, comprises an anvil 134 and a printing unit 136 between which the web is located. The unit includes a heating element 138 which heats locally, by means of arms 142, the areas of the web into which conductive particles 140 are to be embedded. Between each of the arms 142 are anvils 144 which are chilled by means of a coolant to prevent the heating of the web except in the areas embedding the particles. Similar operations may be repeated in several stages in order to build up a completed printed circuit with each of the types of conductive particles which may be required for conductors, resistors, inductors and capacitors &c. The apparatus of Fig. 11 may be modified to permit the application of conductive particles by electrically or magnetically lowering the heating arms 142 into the web rather than being raised into it.