1,003,761. Valves. ROTORK ENGINEERING CO. Ltd. May 22, 1962 [May 23, 1961], No. 18602/61. Heading F2V. [Also in Division H2] An electrical control unit for a valve actuator includes a switch or pair of switches forming part of a control circuit operating the actuator motor, and each switch is selectively operable either as a limit switch, or as a torque switch, or as a combined limit and torque switch, and is operable in response to the output movement of the actuator and/or the output force, i.e. thrust or torque of the actuator control unit 20 is responsive to axial movement of the actuator motor shaft 11, through a shaft 21 loosely coupled with the motor shaft, and also the rotational movement of the output shaft 14, through a secondary shaft 17, to operate torque and/or limit switches 51 and also other limit switches 46, 47. Axial movement of shaft 21 against a strong spring 59 in response to an increase in torque is transmitted to another short shaft which has a helically threaded end 60 passing through a nut 61 such that the shaft is forced to rotate to operate a switch operating lever 62. The torque setting of switches 51a, 51b, is adjustable by screws 66 mounted in extensions of lever 62 and engageable by a further lever 63 resiliently mounted on the rotating end 60 of the short shaft. Secondary shaft 17 extends into the casing 19 surmounting the control unit and has an extension entering a hollow threaded spindle on which is threadedly mounted a nut 29 movable between pins 28, 32, at two extreme positions on the spindle. A spring 40 prevents nut 29 from rotating when shaft 17 rotates, the nut thus moving along the spindle until it engages pin 28 or pin 32 when it is forcibly rotated to cause a rotatably mounted plate 43 to actuate limit switches 46, 47. If removable screws 68a are inserted into plate 67, which is an extension of lever 62, then rotational movement of plate 43 causes a plate edge to engage a screw and thereby rotate plate 67 to operate the switch operating lever 62 independently os any axial movement of shaft 21, torque switchee 51 then acting also as limit switches. The coupling of shaft 21 with the motor shaft 11 if removable if switches 51 are required to act solely as limit switches. The lower portion of plate 43 has an extension 53 connected with an indicator device 54 of Specification 1,003,764, in which a pointer 55 moves across a dial 56 visible through a window 57 in the casing 19 to indicate the end positions of the valve. The adjustable stop nut 31 carrying pin 32, the flange 27 carrying pin 28, the travelling nut 29 and the threaded spindle therefor from the subjectmatter of Specification 1,003,765. Specification 1,003,766 relates to the frictional drive between the shaft 17 and the threaded spindle for nut 29. Specifications 842,581, 865,565 and 939,353 also are referred to.
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