GB1169533A - Improvements in or relating to Drying Machines - Google Patents

Abstract

1,169,533. Steam heated drying machines. E. W. HUDSON Ltd. 20 Oct., 1966 [21 Oct., 1965], No. 44650/65. Heading F4U. The heating chamber of a platen of a leather drying machine is, during drying, connected to suction means and to a source of saturated steam, and the supply of steam is regulated so as to maintain the pressure in the heating chamber substantially at that value at which the boiling point of water is equal to the required drying temperature. In the illustrated embodiment, the steam supply is controlled in accordance with the temperature of the heating chamber to maintain that temperature constant, and it is stated that, since both saturated steam and condensate are present in the chamber, the required constant pressure will be maintained. As illustrated, the platen chamber 104 is connected to the source of saturated steam through a valve 114 which is controlled through an air line by a unit 118 operating in response to platen temperature sensed at 119. The air line includes a valve 115 which interrupts control by the unit 118 and closes the steam valve 114 if platen pressure sensed by a pressure switch 120 exceeds a safety pressure. The platen is connected to vacuum by two parallel lines, one of which includes a valve 105 and the other of which includes a valve 113 and a flow restricting orifice 112. A hood 106 which covers leather stretched over the platen is connected through a valve 107 to vacuum to lower the pressure on the leather during drying and thereby aid evaporation of moisture from the leather. Flood valves 116 and 117 are provided to enable the platen and hood to be connected to atmosphere. At the beginning of a drying operation, a timer 110, acting through a valve 109 and a relay RA/2, closes the flood valves 116 and 117 and opens the vacuum connection valves 105 and 107. The platen 104 is pumped down until a pressure switch 121 senses a predetermined platen pressure, when the switch 121 acting via a contact RB2 and a relay RB/4, closes the vale 105 and opens the valve 113 so that the platen is connected to vacuum through the restricted line. Since the platen pressure will then be below the safety pressure at which the switch 120 is set, the valve 115 will be opened to allow the supply of steam to the platen under the control of the unit 118. At the end of the drying operation, the timer 110 de-energizes the relays so that the flood valves are opened and the steam and vacuum valves are closed.