GB1088544A - - Google Patents

Abstract

1,088,544. Measuring linear displacement electrically. GULLICK Ltd. Sept.16, 1965 [Oct.31, 1964; Jan. 29, 1965], Nos.44499/64 and 3990/65. Heading G1N. [Also in Division G4] In a hydraulic ram, Fig. 2, the position of a piston 26 relative to a cylinder 25 in which it moves, controls the value of an electrical signal produced by a device which is contained within the ram and is fixed to the cylinder, a part or parts of the device being operated magnetically by movement of the piston. A magnet, 41, contained in the piston, draws an armature 42 along the inside of a tube 28, which lies in a bore in the piston 26 and piston rod 27, and is sealed against the hydraulic fluid, the armature 42 causing a contact to slide along a potentiometer track 29. The tube 28 may alternatively be filled with a conductive fluid which then takes the place of the track, and the armature may then take the form of a small mass (55, Fig.10, not shown) connected by a coiled electrical conductor (56) to a terminal (37). Instead of the potentiometer track or the conductive fluid, a series of resistors, inductors or capacitors may be used Figs. 5-8 (not shown), each having an associated reed switch (44), magnetically operated as the piston moves past it, the switches being arranged to switch the impedance elements into or out of a circuit, thereby constituting a step by step potentiometer. The switches (44, Fig. 5 not shown) may be operated by a magnet (41) in the piston, or by a pair of magnets (45, 46, Fig. 6, not shown) associated with each switch and arranged to actuate the switch when the piston is in a position to complete the magnetic circuit between the two magnets of a pair. Alternatively, each switch may be held closed by an associated bar magnet (48, Fig. 7, not shown) which has its flux diverted by the piston to allow the contacts to open. In a further embodiment Fig. 8 (not shown) each switch (44) has an associated magnet (50) slidable in a tube (49) between a first position in which it holds the switch closed and a second position in which the switch remains open, the magnet (50) being moved from one position to the other, by a magnet (41) contained in the piston (26), according to which way the piston is moving.