GB772668A - Thickeners - Google Patents

Abstract

772,668. Gravity-separation apparatus. STOKES, R. O. April 26, 1955 [April 27, 1954], No. 12230/54. Class 46. [Also in Groups XXIV and XXXII] In a centre-drive thickener having a reversible motor for raising and lowering the rake, the rake is driven by a worm 3, Fig. 2, engaging a worm-wheel (not shown). The thrust of the worm is supported by a spring (not shown) whereby the axial position of the worm varies a little in dependence on the resistance encountered by the rake. When the resistance rises above normal a double collar (not shown) on the worm 3 moves a stud 7, the direction being to the right as seen on Fig. 3, the stud rotating an arm 8 and, with it, an arm 25. A link 24, 24a is thereby raised and rocks a lever 21, Fig. 2, about a pivot 22 so that a switch contact 23 on the lever touches a contact 20 on a framework 18. The reversible motor is accordingly energized so as to raise the rake shaft through the worm-wheel until a lever 15, 17 connected to the rake shaft lowers the framework 18 and hence the contact 20 away from the contact 23 to stop the motor. When the resistance falls again the worm 3 moves the stud 7 to the left again, thereby causing the contact 23 to touch another contact 19 on the framework, the reversible motor thereupon lowering the rake shaft. Again the lowering stops when the lever 15, 17 raises the framework 18 and hence the contact 19 away from the contact 23. The parts 24, 24a of the link are connected by an arrangement of telescoping tubes 29, 30 and a spring (not shown) which is such that so long as the tension or compression in the link does not exceed the spring bias the link acts as a solid rod, but when the bias is exceeded the link lengthens or shortens respectively (see Group XXIV or XXXII). Specification 586,074 [Group XXXV] is referred to in the Provisional Specification.