ES362445A1 - Workhead positioning means - Google Patents

Abstract

In a ballast-tamping vehicle comprising first and second tamping heads 21, 22 respectively straddling sleepers T1, T2, the loading head 21 is fixed on the vehicle chassis 24 while the head 22 is movable longitudinally by a motor 30, there being provided automatic first and second control means controlling the vehicle brakes and the motor 30 in response to photo-electric, magnetic or mechanical sleeper-sensing devices so that the machine is automatically stopped with the heads 21, 22 precisely over their sleepers irrespective of variations in sleeper spacing. As shown the movable head 22 is mounted on a wheeled sub-frame 25 actuated by a hydraulic cylinder fed by a pump 32 on the vehicle wheels 33. The control means shown comprises two photo-electric detectors 40, 41 (one for each head) which overlie different rails. Each detector has a light transmitter and a receiver responding to spots of paint which have been applied to the rails by a preceding car 10. The car 10 may be an independent inspection car or a satellite survey car and carrier for each rail a solenoid-valve-controlled paint applicator 13 so that paint spots may be applied - e.g. to alternate rails - either by an operator, or automatically by a sleeper-switch 18. The relative positions of the paint spots, detectors and tamping heads are chosen to allow for vehicle braking distances. As shown the detector 40 is telescopically adjustable in relation to the fixed head 21 to compensate for effects of gradient on braking distances. The paint spot and light detector may, in a modification be replaced by a metal sleepertack and magnetic detector. In an alternative control means dispensing with the car 10 the vehicle itself carries for each of the two tamping heads a sleeper indexing switch 50, Fig. 2, comprising a vertically retractable frame 51 carrying a pivotal sensing element 52 actuating a micro-switch FT1 through a cam and push rod. The two micro-switches are incorporated in respective counting and time delay circuits, Figs. 5, 6 (not shown) which are energised through contacts (CR1, CR2) closed by the raising of the tamping heads. The vehicle may be provided with automatic inching mechanism and with a third adjustable sleeper-sensing element to detect overshoot.