467,210. Liquid-break switches; arc-rupturing in switches. REYROLLE & CO., Ltd., A., LEESON, B. H., and WILD, R. W. Dec. 14, 1935, No. 34734. [Class 38 (v)] In a liquid-break alternating-current circuitbreaker of the kind having an arc-control device comprising an enclosure of insulating-material within which the arc is drawn, the pressure developed by the arc causing a blast of deionizing fluid to be discharged through the arc path and out from the enclosure at one side thereof, the arc gases are discharged from the enclosure through a series of aligned short vents leading into a common discharge passage so shaped that the discharge of fluid through one vent sets up a suction at the other vents. In the construction shown in Figs. 1 and 4, the arc-control device is enclosed in a metal casing consisting of two parts A, A<1>. The upper part A is directly con. nected to the lead-in conductor B passing through the insulator B<1> and is formed with a flat face A<8> which constitutes the main fixed contact co-operating with a group of spring- mounted contact blocks C<1> carried by the movable bridging-member C. The lower part A<1> of the casing is cup-shaped with a central hole at its lower end, and is formed at its upper end with inclined lugs A<2> which co-operate with lugs A3 on the part A of the casing to constitute a breech-block joint for securing the two parts of the casing together. To prevent relative rotation between the two parts when they are secured together, a catch A<4> pivoted to the upper part A engages a recess in the upper edge of the part A<1>, the catch being released by a spring-controlled button A<6> when it is desired to separate the parts. The insulating structure within the casing is in the form of a longitudinally divided hollow block D with a projection D<1> which fits within a slot in a projection A<7> of the part A of the casing, the block being bored with a shaped discharge passage D2 which communicates with the hollow interior of the block, the vertical dividing plane between the two halves of the block passing centrally through the discharge passage. Each half of the block is provided with ribs D<3> for supporting shaped baffles E at the inner end of the discharge passage, thus dividing the throat of the passage into a series of vertically aligned vents E<1> . . . E<4>. The block D has a central projection D4 which passes through the hole in the bottom of the part A<1> of the casing, and is bored to receive the rod-like arcing contact F carried by the bridging member C. A cupshaped ring G of insulating material covers the lower part of the casing. The contact rod F engages fixed arcing contacts H carried by spring blades H<1> secured to the upper part A of the casing, one of the contacts being made longer than the others so that it forms an arcing tip H<2> which is shaped to constitute a portion of the wall of the uppermost vent E<1>. The interior of the block D is arranged to constitute an oil-filled enclosure J on the side of the rod F remote from the vents, the walls of the enclosure being smooth and curved in conformity with the curves of the walls of the discharge passage D<2>. In the closed position, the rod F substantially closes the vents, but it is provided with one or more ducts F<1>, F<2>, which may be in the form of grooves or holes, as described in Specification 467,211, to allow liquid to be ejected through some or all of the vents before the arc is drawn past the vents. In a modification the upper part of the metal casing is insulated from the fixed contacts, and the insulating block within the casing is divided longitudinally into three parts M, M<1>, M<2>, Fig. 6, in order to enable an insert N of soft iron, preferably made in two parts for convenience of assembly, to be provided around the back of the vents, the distortion of the magnetic field thus produced causing the arc to be drawn towards the vents. The common discharge passage M3 is formed in the part M of the block, and the baffles E are held in position by engagement with slots in two side plates O, O<1>. A cup-shaped ring P of insulating material surrounds the three parts of the block to insulate the iron insert N from the metal casing. In another construction, Fig. 7, a single structure is used for two arccontrol devices in series. The moving contact rods Q move in line with one another in opposite directions, and co-operate with a single central fixed contact comprising a group of spring- pressed segmental contact blocks R. The insulating structure of each arc-control device is longitudinally divided into three parts, the two parts S being separated in a plane passing through the discharge passage T which is formed in the third part S<1>. Baffles T<1>, held by insulating plates T2, are mounted in the throats of the discharge passages, and the two passages lead to a single outlet orifice T<3>, The six parts of the two devices are held in position by an insulating tube formed in two parts U, U<1> which are bolted together by metal reinforcing bands U<2>. The structure is mounted horizon-. tally at the top of a central supporting pillar and enclosed, together with the actuating mechanism, in an outer insulating casing. Specifications 435,250 and 435,308 also are referred to.