Patent GB-903713-A (GB)
Title: Improvements in or relating to means for detecting the presence of unsafe working conditions in a process or equipment
Inventor: BURRIDGE FREDERICK JAMES
IPC: G01N23/08
Filed: 1958-03-11
Abstract: 903,713. Radiation sensitive detectors. WOODALL - DUCKHAM CONSTRUCTION CO. Ltd. Jan. 1, 1959 [March 11, 1958; June 9, 1958], Nos. 7762/58 and 18429/58. Class 40 (3). [Also in Group XII] Equipment for supervising or controlling the discharging of coke from a coke oven, of the kind described in Specifications 801,116 and 801,117, in which a transmitter located on a coke guide projects a beam of radiation through the oven to impinge on detection means located on a pusher machine, is characterized by the fact that the detection means comprises at least two detectors controlling individual control relays which have contacts connected in series in a control or supervision circuit, the contacts being closed only when the beam of radiation is not attenuated (i.e. when the coke-guide and pusher machine are correctly aligned, and the oven doors have been removed), and an auxiliary relay has contacts which open the control circuit if the states of the control relays are not identical. As shown, the transmitter 1 contains a source of γ-rays such as cobalt 60, the projection of the rays 2 being controlled by a shutter 4 under the control of the coke-guide operator; the operating circuit of a relay 6, which controls the energization of a thrustor 5 to actuate the shutter, includes interlock contacts 10, 11, which are closed only when the flopper plate of the coke-guide is in position and the travel controller of the coke.guide is in the " off " position. The detector unit 3 comprises two pairs of Geiger tubes 15, 16 and 17, 18, each pair being connected via an amplifier (not shown) to a control relay 19 or 20, which has contacts 21 or 22 in a circuit 23 which controls the advance of the pusher ram. An auxiliary relay 25, with contacts 24 in the circuit 23, is supplied from a source 28 via transfer contacts 29, 30, operated by the control relays 19, 20, respectively, so that the auxiliary, relay circuit is opened unless both control relays act together. Auxiliary relay 25 is slugged to allow for slight asynchronism. The de-energization of the relay 25 opens contacts 31 in the auxiliary relay circuit, so that the relay 25 is not re-operated by a subsequent identity in the states of the control relays 19, 20. A delay relay 27 has contacts 26 in the control circuit 23 which do not close until the amplifiers have had time to warm up. Preferably, the Geiger-tubes, amplifiers, and control circuit are energized from the source 28. A four-position switch (not shown) closes contacts 35-39, 48, 49, when-the switch is in the positions shown in parentheses. Closure of contacts 35 permits energization of relay 25 independently of contacts 29, 30, 31, and contacts 36 prevent the control circuit from being closed during such energization. Contacts 37, 38 shunt contacts 21, 22, respectively, and contacts 39 shunt transfer contacts 29, 30, so that the control circuit may be permitted to operate despite a fault affecting one of the control relays. When the relay 25 is deenergized, contacts 40 close to light one of two lamps 41, 42, via contacts 43, 44 of control relays 19, 20, to indicate which control relay is in the released condition. A visual or audible indicator 45 is energized via contacts 46, 47 of relays 19, 20, to indicate control circuit operation; switch-controlled contacts 48, 49 shunt contacts 46, 47 to allow the indicator 45 to operate when one control relay is out of action. The contacts in the control circuit 23 are shunted by interlock contacts 50 which close to allow the ram to be advanced to the open oven mouth, and by a normally open push-button switch 51. Interlock contacts 52 maintain the control circuit open unless the travel controller on the pusher machine is in its " off " position. The invention is also applicable to equipment utilizing light, X-rays, or R.F. radiation. Specifications 839,650 and 903,712 also are referred to.