Patent GB-385447-A (GB)
Title: Consistency controlling mechanism for concrete mixers
IPC: B28C7/02
Filed: 1932-01-15
Abstract: 385,447. Concretemixing machines. THORNTON, A. A.; 7, Essex Street, Strand, London. - (Koehring Co.; 31st Avenue, Milwaukee, Wisconsin, U.S.A.) Jan. 15, 1932, No. 1254. [Class 86.] In a concrete-mixing apparatus a predetermined amount of water is added from a primary tank to the mix of aggregate and cement and the unknown moisture content of the aggregate is allowed for by determining the amount of water which is still required to be added to the mix from a supplementary tank. The resistance of the mixing drum to rotation is taken as a measure of the supplemental water to be supplied, and the device for regulating such supply is operated by the relative movement of the mixing drum and a flexibly connected driving mechanism. As shown, a shiftable rod 4 above the drum 3 is actuated by the charging skip during the charging operation. A pair of links, one of which 4a is shown in Fig. 3, is pivoted to the rod and connected to corresponding valves for connection respectively between the primary water tank and mixing drum, and between a source of supply and the primary tank. The valves are set so that when one is open the other is shut and vice versa, a snap-over mechanism being provided. Valves 10 .. 13 control a predetermined amount of water from the primary tank 9 to the mix. The rod 4 is threaded at 20a, Fig. 6, so as to be capable of engaging internal threads on a clutch member 19, which normally is interlocked by means of teeth 22 with a sprocket 21 loose on the rod. The sprocket is driven by a chain 28 from a sprocket intermittently rotated by a friction block 29 on the drum. A gear wheel 32 on the drum is driven through chain and sprocket gearing 31, 30, Fig. 2, from the main driving shaft and relative movement between it and the drum is determined by the resistance offered by the mix to the turning movement. The drum carries a number of supports 38 to each of which is attached one end of a compression spring 36, the other end being attached to a slotted part 35 of the gear wheel 32 with which a stud 33 engages. By means of cams 39 and a spring-pressed roller 40, the lost motion in the drive effects a lateral alteration of the position of a flanged ring 43. The ring operates an arm attached to a slidable rod 46 which by linkage 48 and gearing 49, 52, 53 sets the height of a four-way casting 56, which controls the discharge from the secondary tank 61. The intermittent movement of the sprocket wheel 21 causes the clutch member 19 to be rotated when the charging skip is lowered for filling with aggregate, thereby allowing the spring 40 to move the rod 4 to a position in which the clutch members engage to rotate and gradually move the rod 4 in a direction whereby the gear 20a is gradually unscrewed. In operation, the primary tank is filled, the valves 10 .. 13 adjusted, the charging skip loaded and hoisted to the position for charging the drum. The rod 4 moves in a direction to actuate the valves for interrupting connection between the supply and primary tank, and establishing connection between the said tank and mixing drum. The clutch member is also disengaged and valves actuated to fill the secondary tank. As the skip is lowered the rod is moved back to its initial position gradually, allowing the resistance mixture of aggregates and water to set the supplementary supply of water. When the supplementary water is discharged from the tank to the required amount a siphoning action breaks down.