Patent GB-379772-A (GB)
Title: Improvements in electrical operating and controlling apparatus for bulkhead doors, sluice gates and the like
IPC: H02P1/12
Filed: 1931-06-08
Abstract: 379,772. Electrically operating doors. STONE & CO., Ltd., J., Deptford, London, ASH, A. L., Inglenook, Acacia Drive, Thorpe Bay, Essex, and WATKINS, W. P., 54, Roseneath Road, London. June 8, 1931, No. 16677. [Class 65 (i).] Bulkhead doors, sluice gates, and the like are operated by an electric motor through a clutch which is engaged automatically upon the attainment of a predetermined motor speed. The armature or rotor of the motor is adapted to move axially with variation of speed either by magnetic interaction with the field system or by a separate means such as a centrifugal governor, or by a combination of these means ; the axial movement of the armature is used to cause engagement of the clutch and to vary the strength of the field in which the armature is rotating so as, for example, to give rapidacceleration at starting and maximum power at the working speed. Fig. 1 shows the arrangement for driving a vertically-moving bulkhead door by a two-pole direct current motor. The door a is driven by rack-and-pinion gear through a gear-box f and a clutch h from the armature 3 of the motor. A governor 12, which may be dispensed with, has its lower arms connected to the shaft j of the motor and its upper arms connected to a collar free to rotate but not to slide axially on the shaft of the gear box f. The governor preferably has a substantial flywheel effect. The armature of the motor is normally held out of register with the poles by a spring 8, Fig. 2, giving a weak field at starting, but is drawn into a central position between the poles, either by magnetic action or by the governor or both, when a predetermined speed is reached, so as to obtain the necessary lifting power through a strong field. The commutator 9 is lengthened to allow of the required axial movement relative to the brushes. Auxiliary brushes 11, Fig. 1, are provided at 90‹ to the main brushes. The motor has substantially series characteristics, but subsidiary shunt field windings are provided. The clutch is of a type capable of resisting a heavy impact, such as a dog clutch, so that when the speed of the motor has attained a predetermined value the engagement of the clutch causes an impact to be transmitted to the door from the moving parts, which have considerable momentum. If this impact is insufficient to commence the movement of the door, the speed will fall off and the clutch will disengage, allowing the motor to accelerate again for another impact on the door. The motor controller, Fig. 4, has two sets of moving contacts such as 41, 47, mounted on and insulated from a shaft 23 ; contacts which require insulation from one another are fixed to the shaft at different points in its length. The spindle has fixed to it a beam 22, which may be moved in either direction from the " off " position shown by the operation of one or other of the solenoids 20, 21, to bring either set of moving contacts into engagement with fixed contacts such as 42 ; the beam is normally held in mid-position, and is returned to that position after operation, by springs 24 surrounding the solenoid core rods. The solenoids are controlled from a main switch 25, Fig. 1; such main switches may operate through relays, and may each control one or more motor controllers. The control switches preferably have additional contacts which close before the main contacts to give warning of the operation of the doors. The solenoid or relay circuits include limit switches 26, 27, by means of which the controller is returned to its normal position to de-energize the motor when the door completes its movement. A suitable arrangement of contacts and connections for the controller is shown in Fig. 1. A mechanical device may be provided to enable local operation of the controller, but should be spring-controlled to return the controller to the position corresponding to the control switch when released. The door closes under its own weight, started by the motor, and its fall may be checked by a magnetic brake energized from the motor acting as generator or by regenerative braking; in the latter case it is necessary to have a doordetecting switch similar to the limit switch 27 at some point in the path of the door, or to provide shunt-field contacts on the controller adapted to close a certain time after the controller is set to the door-closing position. The limit switch 27 opens a little before the door reaches its bottom position and returns the controller to the " off " position, in which a contact 50 short-circuits the auxiliary brushes 11 to cushion the fall, the motor being excited momentarily as a generator by the shunt field windings. The controller may be adapted to cut out the shunt field during the raising of the door, as its braking effect is not then required.