Patent GB-581641-A (GB)
Title: Improvements in or relating to controllers for electric towing winch motors
IPC: B66C13/24
Filed: 1943-11-08
Abstract: 581,641. Control of D.C. winch motors. IGRANIC ELECTRIC CO., Ltd., (Cutler- Hammer, Inc.). Nov. 8, 1943, No. 18523. [Class 38 (iii)] A control system for a shunt motor driving a towing winch includes, in addition to the usual cable paying-out and reclaiming controls, means controlled by tension cable for automatically controlling the motor connections and speed-torque characteristics in a manner which avoids conditions which would result in excessive tension. The motor Af shown is controlled by a master controller MS operating in conjunction with a cable tension switch TS, cable reclaiming switch RS and a friction switch 25. Switch TS, which has normally closed contacts 22 and normally open contacts 23, actuates both'when the cable tension exceeds a predetermined value during paying-out and a higher predetermined value during reclaiming. The reclaiming switch has normally open contacts 27 and normally closed contacts 28, 29, the former of which is actuated by the cable drum after a definite amount of payout of the cable and the others sequentially after two further amounts of the pay-out, the contacts returning to normal, in reverse order, as the cable is reclaimed. The contacts of switch 25 are opened or closed according as to whether cable is being paid-out or reclaimed. The motor is started in pay-out direction by moving the handle of the master controller from "off" to "reset" and then back to "manual payout," the first movement energizing a transfer relay TR, over contacts 49, 51, to contact the fixed contacts 45 of the controller to supply line L1 over contracts TR37. Contacts TR39 establish a hold-in circuit for TR. The second movement energizes a switch E to cut out resistor 13 from the field circuit F and energization of a brake release relay B, and "reverse" contactors 1R, 2R in the armature circuit follows automatically. The motor thus starts in the payout direction and the subsequent dropping out of relay 1CR causes acceleration by permitting energization of switches 1A, 2A which cut out resistors 7, 8, in the armature circuit. Further acceleration follows the sequential closure of switches 2A-5A under the control of a relay 2CR (energized over contacts 1R1 and TS22) and series relays 3SR-5SR. If the motor now races a voltage relay 1VR connected across its armature responds, opening the circuit of transfer relay TR which switches control over to "automatic tension" even though the master controller remains in the "manual pay-out" position, the contact arm 37 of the relay shifting over and interrupting the supply of power to contact 45 of the controller and thus deenergizing contactors 1R, 2R. Relay 1CR consequently becomes energized to open the accelerating switches 1A, 2A and the motor stops. If, however, the tension switch operates during this operation its contact TS23 provides for the continued energization of switch E and relay B whilst the opening of its contact TS22 de-energizes relay 2CR. Reversing switches 1F, 2F thus become energized over contacts TR35, 36, and the motor reverses to provide a torque opposing pay-out, with the switches 3A-5A open. Switches 1A, 2A may close, with time delay, after closure of 1F2, depending upon whether or not the load actuates series relays 1SR1, 1SR2. If tension continues to increase the pullout speed of the motor is raised by the successive actuation of relays 11SR-14SR which carry the armature current, the relays energizing in turn switches (1FS-4FS) for inserting resistors 14-17 in the field circuit. Excessive pullout speed causes voltage relay 2VR to pick up and latch out, whereby switch E is de-energized followed by de-energization of contactors 1F, 2F and brake relay B. The motor thus stops. If, however, the tension decreases the resistors 14-17 are progressively cut-out and the eventual release of relays 2SR1, 1SR1 operates accelerator switches 1A, 2A to cut-out armature resistors 7, 8, when the motor will start to wind in the cable. Friction switch 25 closes in consequence, energizing relay 2CR which permits the sequential cutting out of armature resistors 9-11 by accelerating switches 3A-5A. A cushioning resistor 12 remains in the armature circuit permanently. Reclaiming of the cable continues until contacts 27 of switch RS (which have been engaged during pay-out) open to de-energize switches EB, 1F and 2F. Contacts 28, 29 of the reclaiming switch control the energization of field accelerator switches 3FS, 4FS and tend to maintain the paid out length of cable within limits. When control MS is moved to the "manual heave" position transfer relay TR is momentarily energized by contacts 49b and its self-maintaining circuit established over contacts TR39 so that contact 45 of controller is connected to supply line L1 and switch E and relay B thus energized. Reversing contactors 1F, 2F close upon pick up of B, the motor starts in the reclaiming direction and armature accelerators 1A. 2A close under the control of relay 1CR. Friction switch 25 also closes and the armature accelerator' switches 3A-5A close sequentially. Field accelerating relay FA is then energized over contacts 5A1 and 2F1, causing the progressive closure of its contacts 18-21 and the consequential energization of some or all of switches 1FS-4FS which insert resistors 13-17 in the field circuit.