GB609207A - Improvements in and relating to electric fluid blast switches - Google Patents

Abstract

609,207. Gas-blast switches. BRITISH THOMSON-HOUSTON CO., Ltd. Feb. 18, 1944, No. 3034. Convention date, Feb. 26, 1943. [Class 38 (v)] In order to meet the different gas-blast conditions required in opening and closing the switch, as described in Specifications 544,017 and 545,111, the blast valve is controlled from the switch - operating mechanism, which is provided with a lost - motion connection for supplying the opening blast before contactseparation and selectively discriminating between circuit-opening and closing conditions. A link 21 coupled to the fluid-motor 18 has a slot 29 engaging a pin 30 on a bell-crank lever 22 connected to the contact 12. In opening, link 21 moves to the left to cause roller 43 to engage the point 40 of a cam 31 pivoted to pin 30, so engaging a roller 33 and slightly opening the blast valve 15. On continued movement of link 21, the, lost motion at 29, 30 being taken up, the contact 12 is moved and the cam surface 41, 42 opens the valve 15 to its maximum, whereafter the valve closes. In closing, roller 43 moves with link 21 from high point 40 to the high point 44 of a cam 32, also pivoted on pin 30, the cam surface 45 of cam 32 engaging the roller 33 to provide a closing blast. The cam-contours can be selected for the different blast-conditions. In a modification, Fig. 5 (not shown), cam 32 is dispensed with and a cam-formation provided on the link 21 itself to effect a closing blast. In a further modification, Fig. 8 (not shown), a single cam 31 controls both blasts and is engageable at different points by roller 43 to vary the extent of opening of the valve. In Fig. 9, the lost-motion connection is provided by a pin 56 on a link 52 and slot 55 in a link 53. In opening, the links close up as permitted by the slot, and raise a further pivot 54 for the links whereby roller 57 engages cam 58 and provides a blast. In the closing movement, the links are separated as shown and roller 57 in its lower position opens valve 15 to a lesser extent to provide a smaller blast.