Patent GB-610042-A (GB)
Title: Improvements in machines for ironing or pressing moist fabrics
IPC: G05D22/02
Filed: 1945-07-30
Abstract: 610,042. Ironing-machines. PRESTON, J. E. July 30, 1945; No. 19495. [Class 138(ii)] [Also in Group XL(c)] An ironing-press comprises relativelymovable pressing members 2, 5, which are adapted to evaporate moisture from the work pressed between them, control means sensitive to the moisture content of the work for separating said members so as to end the pressing operation, and additional control means for causing separation of the members after a predetermined time interval, if they have not previously been separated by the first control means. The invention is applied to the operation of a press comprising a buck 2, which is moved vertically by a pivoted lever 3 under the action of a servomotor 4, and a head 5 supported upon a pivoted lever 6 which can be operated to close the press by a servomotor 7 and toggles 8; a shock-absorber 10 limits movement of the toggles 8 during closure of the press and serves to initiate press-opening movement by springs 9. Steam is circulated through either the buck or head, or both these members. The servomotors 4, 7 are controlled through the medium of a solenoid 23, which, when de-energized, permits the press to be closed by the manuals 13a, 14a of valves 13, 14 controlling the supply of pressure fluid to the servo-motor 7. When the head 5 is moved into pressing relation with the buck 2, the toggles 8 operate a valve 11 to permit relation with the buck 2, the toggles 8 operate a valve 11 to permit the supply of fluid to the servomotor 4 in order to apply pressure to the buck. A release valve 16 for causing the press to open is operated either by manuals 16a, 19a or by energizing the solenoid 23. The control circuit of the solenoid 23 comprises a circuit which includes three thermionic valves A, B, C, which are provided in their plate circuits with relays 49, 84, 107 operating respectively, armatures 51, 90, 113. The grid circuit of the valve A is provided with a standard resistance 56 and a variable resistance 57. In addition, a supplementary grid bias is imposed on the grid when the press is closed by the completion of a circuit 59, which includes the moist article in the press; in order to provide this circuit, the buck 2 carries a sheet 37 of wire gauze insulated from the buck by a pad 38 and covered by a muslin layer 39. The effect of this supplementary grid bias is to interrupt the plate current of the valve A so that the relay 49 is deenergized and its armature 51 makes contact at 53. This condition is maintained until the article dries to the point at which the grid bias becomes normal and plate current is again passed; the relay 49 is then energized and the armature 51 makes contact at 52. The resistance 57 can be adjusted to select the point at which plate current will energize the relay 49. Before closure of the press, and while plate current is flowing in valve A, the relay 49 causes a second armature 71 to make contact at 72, and, thereby, close a supplementary grid circuit, including a condenser 81 and variable resistance 82, for the second valve B. The over-biassing potential produced by this circuit stops the flow of plate current in the valve B and de-energizes the relay 84 so that the armature 90 makes contact at 92. When this supplementary grid circuit is broken at 72 by de-energisation of the relay 49 (i.e. when the wet article is placed in the press), the B valve will not function normally and pass plate current until the condenser 81 has had sufficient time to discharge its accumulated charge into the original grid circuit. The resistance 82 has the effect of delaying this discharge for several minutes, and it may be adjusted to provide the desired time interval. The effect of the above control is that, if the relay 49 should be energized because the wet article has reached the required degree of dryness, the presscontrolling solenoid 23 is energized, since it is then included in a closed circuit, which comprises the armature 113, contact 122, armature 51 and contact 52. On the other hand, if, before the relay 49 is actuated, the valve B acts to energize the relay 84 (because the prescribed time interval has elapsed), the solenoid 23 will still be energized since it is included in a circuit comprising the armature 113, contact 122, armature 90 and contact 91. The action of the valve C is to prevent closing of the press for a prescribed period after it has been opened. When the supplementary grid circuit for this valve is broken by the energization of relay 49 (and the press is opened), no plate current will pass in the valve C until the condenser 121 has discharged; the time for this is set by the variable resistance 120. Relay 107 is thereby energized so as to break contact between the armature 113 and contact 122, and de-energizes the solenoid 23. This results in the closure of the exhaust of the servomotor 4 so that the press may be closed by the manuals 13a, 14a. If desired, the opening of the press may be effected by the de-energization, instead of the energization, of the solenoid 23, and the circuit may be arranged to control two or more presses coupled for tandem or related operations. Specifications 564,606 and 610,041 are referred to.