Patent GB-636203-A (GB)
Title: Improvements in or relating to glass level indicating and/or recording apparatus
IPC: G01F23/24
Filed: 1947-03-20
Abstract: 636,203. Level indicators for molten-glass furnaces. HARTFORD-EMPIRE CO. March 20, 1947, No. 7685. Convention date, March 21, 1946. [Class 51 (ii)] [Also in Group XXXVIII] In apparatus for indicating and recording the level of molten glass in a melting tank or the like, an electrode is vertically reciprocated by a reversible electric motor controlled by a relay combination which limits the downward stroke by completion of a circuit through the electrode and the glass surface and the upward stroke by interruption of the circuit through the electrode and the connecting thread of glass drawn out thereby. The reciprocating member is coupled mechanically to level indicator and electrically to the transmitter of a remote level recorder through a lost motion device. In Fig. 1, 2 a refractory conductive vertically dependent electrode 3 carried by a vertical rod 4 is reciprocated relatively to the surface of an earthed body of molten glass 2 in a melting tank, by a tubular shaft 10 movable in guides 11, 12 by a rotary threaded shaft 21 engaging a nut 20 secured to shaft 10 which is prevented from rotating by guides 25, 26. The shaft 21 is driven through reduction gearing by a reversible 3-phase A.C. motor 23a and may be rotated by a disengageable handwheel 111. When the electrode 3 contacts the glass surface, relay 86, Fig. 4, is A.C. energised by the secondary of transformer 93 through conductor 27 to close contacts 104, 105 to illuminate lamp 109 and contacts 88,89 to energize relay 98 which switches motor 23a to lift the electrode from the glass surface, pulling out a filament therefrom. When this breaks, relay 86 is de-energized, extinguishing lamp 109, de-energizing relay 98 and energizing relay 100 through contacts 89, 90 to switch the motor to lower the electrode to contact the glass surface, when the cycle is repeated. Excessive vertical reciprocatory movement causes cam surfaces 79, 80 to open a normally closed switch 75 which disables relays 98, 100. The downward excursion of the electrode, 3 indicates the glass level, and a tape 40 transmits the vertical reciprocations to rotate a hub 38 carrying a pointer 34 against a coil spring 42 so that the pointer swings over a dial 33, the starting point of each swing corresponding to the scale zero when the glass level is normal, and deviating in from zero in either direction with variations in level. The reciprocations of shaft 10 are coupled to an adjustable mechanical lost motion device comprising a yoke 56 carried by rod 58 and embracing a block 62 clamped to a stem 50 sliding through a threaded sleeve 53 engaging the lower arm of the yoke. When the glass level is normal the lost motion device just absorbs the reciprocations of shaft 10 without moving the stem 50, but on variations of level operates a transmitter in which the stem moves an iron core 45 upwardly or downwardly within two co-operating adjacent vertical reactance coils 47, 48, a spring- loaded braking element 51 pressing on the stem 50 and preventing any vertical movement of the latter except that derived from the lost motion device. The reactance coils are A.C. energized and are electrically connected to a known rotary level recording instrument 69 in which a pivoted stylus 71 co-operates with a rotary chart 70. Other forms of recorder may be used, and the apparatus may operate a batch feeder or the like to control the amount of glass in the melting tank. In a modification, Fig. 5 (not shown), the lost motion device comprises a casing attached to the reciprocating shaft and containing an expansible bellows which is briefly distended by a pneumatic pulse released by a relay energized by each reversing surge of the motor and collapsed by a spring when the motor completes its reversal to de-energize the relay. The piston of the bellows bears on the end of a rod, linked to the level indicator and the recorder transmitter, which passes through the casing on the inside of which a flange attached to the rod abuts when the glass level is normal. A fall in level depresses the rod, and a rise allows the bellows to be expanded upwards by the pneumatic pulse to raise the rod, thus operating the indicator and the recorder transmitter.