| 摘要 |
1296486 Cooling granular material NATIONAL ENG CO OF CANADA Ltd 7 April 1970 [10 April 1969] 16489/70 Heading F4U Hot foundry sand is passed through a chamber in which it is cooled by a supply of water which is automatically controlled according to the electrical resistance of the sand in the chamber. The resistance depends on the moisture content of the sand and therefore, approximately, on the temperature of the sand. As illustrated, sand passes from a conveyor 12, through a chute 16, into the chamber 20, The sand is moved through the chamber to an outlet, Fig. 4 (not shown), by two rotary stirring assemblies 18 and 50 driven by a common motor 70. The current drawn by the motor is sensed and the resulting signal is used to control the position of a door at the outlet from the chamber. The motor current depends on the load on the motor and therefore on the level of sand in the chamber, and the control system is such that the door operates to maintain a constant sand level. The chamber 20 is bounded by a rubber sidewall 30 having apertures 48, formed by crossed slits, through which air is passed from a blower 46. The air aids in the cooling of the sand by the evaporation of water which is added from a header 100. The supply of water is governed by a valve 110 which is controlled by a system responsive to both the electrical resistance of the sand and the level of the sand. The resistance is measured by passing current between at least one pair of electrodes 130 mounted in the rubber wall 30. An electrode is illustrated in detail in Fig. 2 (not shown) and comprises a conducting disc hold in place on the inner surface of the wall by a bolt which passes through the wall for connection to a lead wire. The valve 110 is opened at regular intervals to admit water unless the resistance of the sand is such as to indicate that no cooling is required. The valve control system is also responsive to the motor current so that if the sand level falls below the level of the electrodes the valve is rendered inoperative. |
