Patent GB-976489-A (GB)
Title: Typewriter ribbons with protective layers
IPC: B41J31/00
Filed: 1961-05-18
Abstract: 976,489. Ink-ribbons. COLUMBIA RIBBON & CARBON MANUFACTURING CO. Inc. May 18, 1961 [May 20, 1960], No. 18133/61. Heading B6F. An inked fabric typewriter ribbon of cotton, felt, silk or nylon which has been rendered clean to the touch has at least one surface thereof coated with a porous, spongy layer comprising a synthetic resin and a non-volatile material, which is a non-solvent for said resin. In one embodiment in Fig. 2 a conventionally inked typewriter ribbon 20 is coated on one side with a porous layer 10 comprising a honeycomb of synthetic resin material having pores 11, containing a non-volatile material such as a mineral oil, and colouring matter if desired, and the opposite side of the ribbon is coated with a protective, continuous inkimpervious layer 30 to prevent back transfer of ink to the type bars. In another embodiment in Fig. 1 (not shown) the ink impervious layer is dispensed with. In a further embodiment in Fig. 3 (not shown) the fabric ribbon is impregnated with a pore-forming resinous ink composition, containing pigment or dye and the thus impregnated ribbon is then coated on both sides with a similar pore-forming resinous composition but devoid of pigment or dye. The process of rendering the inked ribbon clean to the touch comprises the steps of applying to at least one surface thereof a layer of resinous composition including a non-volatile material and allowing the layer to set. The ribbon may be inked with a conventional ink or a resinous ink composition in which case it is essential that the non-volatile vehilces of the composition contain no solvents for the resin material of the coat layer 10 and in addition the ink softener should be compatible and miscible with the non-volatile material and both softener and the non-volatile material may be oils, e.g. mineral or vegetable oils. As the resin of the pore-forming compositions, which set to porous, spongy layers, unsaturated polymers, vinyl chloride-vinyl acetate copolymers, hydrocarbon polymers, polyurethanes and polamides may be used. As the non-volatile, non-solvent material mineral, vegetable and animal oil are satisfactory eg. naphthenic mineral oil, peanut oil, sperm oil &c. The resinous pore-forming material together with the non-volatile, non- solvent component and pigment or dye are dissolved in a 3:1 mixture of ethyl acetate and toluol, the mixture ground to a coating con sistency, which is then spread evenly over one or both surfaces using an apparatus or im mersing the ribbon in a vat containing themixture, and allowing it to cool and harden by evaporation of the volatile solvents, whereupon the ribbon is heated for a short period to a temperature of 150‹ C. to fuse the layer to the fabric. To avoid the use of highly volatile solvents the resinous material may be suspended as a finely divided dispersion in a completely non - volatile dispersing liquid. The inkimpervious layer comprises a synthetic resin, of any of the materials used above, dissolved in a volatile solvent, whereupon a thin film is applied to the unprotected side of the fabric and the solvent allowed to evaporate. The layer may also be applied by using selfsustaining films of the resinous pore-forming compositions referred to above and adhering them to the fabric by means of adhesives.