Patent GB-610041-A (GB)
Title: Improvements in machines for ironing or pressing moist fabrics
IPC: G05D22/02
Filed: 1945-07-30
Abstract: 610,041. Ironing-machines. PRESTON, J.E. July 30, 1945, No. 19494. [Class 138(ii)] [Also in Group XL(c)] Relates to an ironing- press comprising relatively-movable pressing members 2, 5 which are adapted to evaporate moisture from the work pressed between them, operating means for moving the members into pressing relation, and control means sensitive to the electric conductivity of the work for relieving the pressure between said members and terminating the pressing operation. According to the invention, additional control means is provided for preventing the application of further pressure between the members for a pre-determined period after the pressure relief. In the arrangement shown in Fig. 1, the buck 2 is moved vertically by a pivoted lever 3 under the action of a servo-motor 4, and the head 5 is supported by lever 6 which can be operated to close the press by a servo-motor 7 and toggles 8; a shockabsorber 10 limits movement of the toggles 8 during closure of the press and serves to initiate press-opening movement by means of springs 9. Steam is circulated through either the head or buck, or both these members. The servo-motors 4, 7 are controlled through the medium of a solenoid 23, which, when de-energized, permits the press to be closed by manuals 13a, 14a, controlling the supply of pressure fluid to the servo-motor 7. When the head 5 is in pressing relation with the buck 2, the toggles 8 operate a valve 11 to permit the supply of fluid to the servo-motor 4 in order to apply pressure to the buck. A release valve 16 for causing the press to open is operated either by means of manuals 16a, 19a or by energizing the solenoid 23. The control circuit of the solenoid 23 comprises two thermionic valves A, B, each of which is provided in its plate circuit with a relay 49, 67. The grid circuit of the valve A comprises 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, 60 which includes the moist article in the press; 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 the 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. At this time, the armature 70 of relay 67 is making contact at 72, so that the press-controlling solenoid 23 is then included in a circuit comprising armatures 51, 70; the solenoid 23 is, therefore, energized and the press is opened. The closure of the press is prevented for a pre-determined interval after it has been opened, by the operation of the valve B, the grid circuit of which normally includes a standard resistance 75, but, when the relay 49 is de-energized, also comprises a supplementary circuit in the form of a variable resistance 82 and condenser 81. When this supplementary circuit is in action, it prevents the passage of plate current in the valve B so that the relay 67 is de-energized. At the time when the circuit is broken at 53 by energization of the relay 49 (i.e., when the article has reached the required degree of dryness and the press is opened), the valve B will not function normally to pass plate current until the condenser 81 has had sufficient time to discharge its accumulated charge; at this stage, the valve B will again pass plate current, the relay 67 is energized, and the circuit of the solenoid 23 is thereby broken so as to permit closure of the press. Instead of using the valve B for delaying the closing of the press, an electro-mechanical timedelay relay unit (Fig. 2, not shown) may be used with the circuit comprising the valve A. In this case the solenoid 23 is again energized to cause opening of the press, consequent upon energization of the relay 49; at the same time, although the time relay unit is then energized, the delay unit incorporated with it prevents breaking the solenoid circuit until the lapse of the pre-determined time interval according to the setting of the delay unit. The control circuit shown in Fig. 3 comprises an additional valve C2 which delays the opening of the press after the normal opening point by an additional period of time determined by the discharge of a condenser 142a in the supplementary grid circuit of the valve. At the time when the article in the press reaches the desired degree of dryness, and the valve A2 acts to energize the relay 128, the circuit of the solenoid 23 is open at the relay 135, and is retained open for a period determined by the discharge of the condenser 142a. When after the discharge of this condenser, the relay 135 is energized, the solenoid 23 is included in a closed circuit, and becomes energized so as to effect the opening of the press. The energization of the relay 135 also breaks the supplementary grid circuit of the valve B2 and when, after a predetermined interval, the condenser 146 is discharged, the plate current of this valve is restored so that the relay 147 breaks the circuit of the solenoid 23 and permits the press to be closed. Specifications 564,606 and 610,042 are referred to.