Abstract: Tire tread (1) is divided into central part (20) and edge parts (30), central part (20) having width Lc between 40% and 90% of total width W of the tread. Edge parts (30) do not have any transverse cuts. Central part (20) has a tread pattern with circumferentially oriented sipe (21) and transversely oriented sipes (22, 22?, 22?) distributed around the periphery of the tread, such sipes having a depth at least equal to 60% of thickness E of material to be worn away and being interconnected to form a network. Such sipes are continued by hidden channels (210, 220). Central part (20) is delimited axially by transverse sipes (22?, 22?), each of which ends in end channel (221?, 221?) that opens onto tread surface (10) and extends into the thickness of the tread, and each end channel (221?, 221?) is connected to the network formed by the hidden channels.

Abstract: The invention relates to a safety device for protection against the rise of pressure in a pneumo-hydraulic control circuit which includes, upstream, a pressure generator and downstream, a pneumo-hydraulic accumulator. The device is characterized in that it includes, between the generator (3) and the accumulator (1) a non-return valve (6), a first safety valve (4) capable of a discharge at least equal to that of the generator upstream from the non-return valve, a second safety valve (5) downstream from the non-return valve and means for the second safety valve to be subjected to only a small discharge. The invention applies in particular to the pneumo-hydraulic control of very high tension cut-out switches.

Abstract: A gas-blast circuit-breaker comprises arcing contacts provided with nozzles of the same diameter, operating means ensuring an original movement of a mobile one of the arcing contacts in the opposite direction to that of the mobile main contact at the opening of the device.