GB310855A - Improved process and apparatus for coating finely divided and like material - Google Patents

Abstract

310,855. Maynes, H. F., and Maymes, E. C., (Assignees of Zebulske, E. A.). May 1, 1928, [Convention date]. Coatings for medicines; pillmaking appliances.-A process for coating finely divided material with a liquid coating comprises forming a spray of the coating liquid by means of compressed air, introducing the divided material into the spray, and maintaining the coated particles in suspension until the coating has dried or hardened. The application of the process to coating medicinal pills or pellets with chocolate, sugar, or other suitable coating material is referred to. As shown in Figs. 1 and 2, the apparatus is designed for coating a dried mixture of milk and sugar contained in a receptacle S, with chocolate that is liquified in a pressure kettle K. The liquified chocolate is forced by air under pressure through a pipe 9 to the inner nozzle 26 of a mixing device N, the powdered material being supplied through a pipe 2 to the mixing chamber 36. Compressed air from the pipe 15 is supplied to the kettle through a pipe 11, and to the member N through pipes 13, 14. When the valves 42, 43 are opened to admit compressed air through the pipes 14, 13 to the mixing nozzle, the needle valve 44 being open, the molten chocolate delivered through the tube 26 is converted into a fine spray by the compressed air issuing from the tube 21, this spray being carried out of the nozzle through orifices 30, 37. The cut-off valve 48 of the pipe 2 is then opened, and the partial vacuum that exists in the mixing chamber 36 induces a flow of material to be coated from the container 1. The supply of this material is regulated by the provision of openings 38 through the mixing chamber to the atmosphere, As the spray of coated material leaves the mixing chamber 34, 36 a converging annular blast of air delivered through the pipe 41 to the sleeve 39 surrounding the cap 35 serves to narrow the stream of spray and avoid its contact with the walls of the drying chamber D before the chocolate has become dried or set. The velocity of the stream of spray is reduced owing to the diverging walls 54 of the chamber D and the dried coated material is received by the canveyer 55. In the mixing nozzle N the tube 26 is centred by a screw 27 having a spring mounting 28, and the tube 21 is provided with openings 31 through which the compressed air passes to the interior of the cap 29. The injector action of the nozzle may be used to supply the granular material and the coating material without a gravity feed for the material in the container 1 or the use of compressed air to the chocolate container K. According to a modified arrangement which is illustrated, the mixing and spraying nozzle N is arranged horizontally, the coated material being sprayed into a hopper supplied with compressed air by rotary blower and received in a separator.