Patent GB-190620369-A (GB)
Title: Improvements in or relating to Switches for use in Electric Circuits.
Inventor: BROADBENT FRANK
Filed: 1906-09-13
Granted: 1907-09-05
Abstract: 20,369. Broadbent, F. Sept. 13. Switches.-In automatic motor-starting switches of the type having a single operating solenoid for both the main switch arm and the rheostat arm, and also having a retaining-magnet for holding the main switch arm in the closed position, a pilot switch arrangement in shunt to the main circuit is provided in connexion with the operating- solenoid and the hold on' magnet. This form of control is particularly adapted for use with printing and like machinery where an inching-on motion is required. When two pilot swithes are employed, one for the solenoid and one for the hold on magnet, the motor, after having been stopped for any reason, cannot be restarted until the proper pilot switch is actuated. In the arrangement shown in Fig. 2, the closing of the normally open pilot switch h<1> causes the solenoid f to lift the rheostat arm. b, which pushes before it the main switch-arm a by means of a buffer b<2> till the main circuit is closed at c through the motor-armature B, all the resistances r, the arms b and a, the contact c, and the blow-out magnet k. A shunt circuit is established through the field B<1>, and another branch circuit through the retaining-magnet g and the normally closed pitot switch h<2>. As the arm a comes into the position in which it held by the retaining-magnet, it opens a switch i in the circuit of the solenoid f, which is thus de-energized and allows the arm b, checked by a dash-pot e, to fall, and cut out gradually the resistances r. The pilot switch h<2> enables the motor to be stopped at any instant. The circuits may be modified as shown in the dotted lines, the two pilot switches h<1>, h<2> being replaced by a single pilot switch h<3> which remains normally closed, in order to keep the retaining- magnet g energized. In this case accidental restarting is not avoided. In a further modification, the retaining-magnet is placed in the branch circuit containing the field-winding; both of the pilot switches, in this case, being normally open. To give the magnet time to acquire strength enough to hold up the main switch arm before the circuit of the lifting solenoid is broken, a switch such as the one shown in Fig. 4 may be provided instead of the switch i, Fig. 2. The movable contact is carried'on an armature i<3> with an adjustable retracting spring, and is moved by the attraction of the fixed core i<4> to break the circuit only when the magnet g has acquire a certain strength. In the modification shown in Fig. 5, the closing of the pilot switch h<1> completes circuit at first only though a part of the windings f<2> of the solenoid f. The main switch arm at is then closed and leads current through the motor armature B with all resistances in series, through the fieldwinding B<1> in shunt, an also through the solenoid coils f, f<2> in series. The lower core f<1> is thus attracted and lifts the rheostat arm over its contacts. This, on reaching the top, throws over a quick break switch h<4>, and puts resistance lamps l in the circuit of the solenoid f, in order to render the solenoid too weak to operate the main switch a should the latter have been opened by pressing the pilot switch h<2>. A resistance r' in series with the pilot switch h<1> serves to prevent shortcircuiting the solenoid coils f, through the accidental closing of the switch. In the modification shown in Fig. 6, the winding solenoid has only one winding, and is caused, through the arrangement of the magnetic yokes a<0>, f<0>, to operate first the upper core and next the lower core, owing to the diminished air-gap produced by the first movement. The cores are respectively connected to the switch arms, as shown in Fig. 5. In another modification shown in Fig. 7, the first movement'of the core of the solenoid f lifts the arm b, and an insulated end b<3>, acting under a projecting tooth a<5> on the main switch lever a, closes the latter and pushes, the tooth out of the way, leaving the arm b free to continue its upward movement 'over the resistance contacts d. Specification No. 4801, A.D. 1899, is referred to in the Provisional Specification.