Patent GB-878770-A (GB)
Title: Improvements in or relating to electrically operated sootblowers
Inventor: JONES CHARLES EDWARD
IPC: F28G3/16
Filed: 1957-08-28
Abstract: 878,770. Control of several motors; controllers. JONES, TATE & CO. Ltd. Feb. 28, 1958 [Aug. 28, 1957], No. 27180/57. Class 38 (3). Apparatus for sequentially controlling the operation of several electrically-driven soot blowers comprises means whereby each driving motor is connected as required to a power supply through a common main switch. A distributer is provided with a number of positions in each of which the control circuit of one sootblower is completed, the distrubuter being operated to complete each circuit in turn, and the main switch being opened before the distributer passes from one position to the next. As shown, the distributer comprises seven rings of contact-pairs, each ring consisting of eighteen pairs. A pressure bar 13 closes all the contacts of any row simultaneously, since it has parallel rollers 14 extending the length of the seven rings. The bar 13 is actuated by a ratchet 15 which is secured to arm 17 and rotated by solenoid 16, energization of the solenoid causing link 23 to move arm 22 clockwise, whereby a pawl pivoted to the bar engages a tooth in the ratchet. A further pawl is pivoted to a fixed member 21 for preventing reverse rotation of the ratchet, and both pawls are spring-urged to the engagement-position. A three-limbed member, Fig. 1 (not shown), prevents over-shooting of the pressure bar 13. When the ratchet has reached a desired position, one limb engages a fixed stop, and any further tendency for the bar to rotate causes another limb to engage a tooth of the ratchet. A spring is connected to the third limb for disengaging the second limb from the ratchet. The arm 22 is adapted to operate a heavy-duty switch which always opens before the distributer contacts to interrupt the motor-circuit. The arm also actuates a time-delay switch for ensuring that successive movements of the pressure-bar have an adequate time-delay between them. Each sootblower has its own motor M3, two-position sequence switch S3 for determining whether the sootblower is to be operated or by-passed, indicating lamp B3, and limit switch L3, the distributer D being shown in the condition at which the operation of the third sootblower is initiated. If the pressure bar is lying along the eighteenth row of contacts, the sequence is started by closing switch E to energize relay R, so causing solenoid O to move the pressure bar on to the first row. Contacts O1 open to disconnect the main contactor P, and contacts 02 open subsequently to de-energize relay R, contacts R1 remaining closed for a period sufficient to ensure that the solenoid completes the movement of the bar. When the contacts R1 open, solenoid O is de-energized and contacts O1 02 are allowed to close. If the sequence switches for the first and second sootblowers are in the " by-pass " positions, the pressure bar is automatically stepped on to the third row of contacts. With switch S3 in the position shown, contactor P is energized to start motor M3 whereby limit switch L3 is operated to energize relays T and t. Relay Q is then operated to provide an alternative circuit for the main contractor so that operation of the sootblower will continue even if the switch S3 is moved to the " by-pass" position during the course of such operation. When the sootblower reaches the end of its motion, the limit switch operates relay T to de-energize relay Q, contacts t1 being closed for a short period to complete a circuit for relay R. This causes the main contactor P to open before the solenoid O becomes effective to rotate the pressure arm of the distributer. An alarm circuit comprises a synchronous timing motor V which becomes effective, if the sootblower does not complete its operation within a predetermined period, to actuate an audible alarm AK and a flasher relay Y for lamp B3. When a fault has been indicated, switch S3 is returned to the " by-pass " position and push-button EA is actuated to move the distributer on to the next row of contacts. Relays F1, F2, F3 are provided to prevent energization of the contactor P if there is a fault in any of the phases of the main supply. In a modification, a circuit is provided for operating reciprocating sootblowers, the forward and return motion of each blower being controlled from one row of contacts on the distributer D. Two limit switches for each sootblower generate control currents of short duration at the beginning and end of the movement of the sootblower in each direction, and one motor drives the sootblower in both directions, a relay employed in turn for all the motors being used to reverse the direction of operation, Fig. 5 (not shown). The distributer may complete a control circuit of a sootblower in each of its positions, a relay being provided whereby, after the distributer has moved through all its positions back to the first, it does not move automatically again through all its positions until a manual switch has been actuated, Fig. 6 (not shown). In a further embodiment, two groups of sootblowers each having a separate distributer, are provided, and blowers of each group are operable simultaneously. The distributers are steppedon together only when two simultaneouslyoperated sootblowers have completed their operation. Some blowers of each group may be operated singly whilst the other group is inoperative, the distributers being automatically stopped and started for this purpose, Figs. 7, 8 (not shown). The control circuits for all the sootblowers of a group may be completed by two or more distributers, a second distributer being automatically started when a predetermined position on the first distributer is reached, Fig. 9 (not shown).