GB965624A - Improvements in or relating to the manufacture of footwear - Google Patents

Abstract

965,624. Manufacture of footwear. H. LUDWIG. Dec. 13, 1962 [Nov. 24, 1962], No. 47048/62. Heading B5A. In a process for injection moulding soles of plastics material or rubber to uppers, the sole material is injected into the mould at a comparatively low internal pressure, e.g. 3 atmospheres, and shortly after injection e.g. 15-30 seconds, an increased pressure e.g. 8-10 atmospheres is produced in the mould. The control system consists of a double acting pneumatic piston drive 23, comprising a piston 24, which divides the cylinder 26 into two pressure chambers 27 and 28, and a connecting rod system 25. The chamber 27 is connected to a pressure source 31 by a pressure medium pipe 29 in which a valve 33 is incorporated, the valve having position I in which the pipe is not interrupted, so producing full pressure in the chamber 27, and position II in which there is no excess pressure in the chamber 27. The upper chamber 28 is connected to the source 31 by a pressure medium pipe 30 in which a pressure reduction valve 34 and valve 35 is incorporated. In position I the valve 35 connects the chamber 28 to the reduced pressure source, and in position II to the atmosphere. A multiple part mould 10 comprising two frame sections 13, displaceably mounted on a table 14 and having a sealing lip 15, on which the last 12 may be mounted is supplied to an injection unit 11. The mould also has a bottom ram 17 actuated by the piston drive 23 and having an exchangeable attachment member 18. The valves 33, 35 are placed in the I position and the ram 17 is moved upward by the pressure difference between chambers 27, 28, the correct injection position being given by a stop nut 46. The piston via rods 40, 41 releases a switching element 42 which causes the injection passage 20 to be exposed. The injection continues until the pressure of the material becomes great enough to move the ram downwards causing the passage to be closed via switch 42, and the mould is then moved from the injection unit. The valve 35 is moved to position II so the chamber 28 communicates with the atmosphere and a higher pressure is thus applied to the ram and hence the sole. When set the valve 33 assumes position II and the shoe is removed from the last.