Valve for shutting off a flow

Valve for shutting off a flow having a housing wherein a plug member is movable in one stroke between "on" and "off" terminal positions;

• a rotary drive which is switchable off in the "off" terminal position of the valve;
• a resilient member for limiting an increase in torque generated by kinetic energy of the rotary drive in the "off" terminal position;
• and a torque control for the rotary drive, comprising means defining a given total angle of rotation of the rotary drive in both rotary directions of travel thereof, the total angle of rotation corresponding to one stroke of the plug member and being the sum of a first and a second partial angle of rotation, said first partial angle of rotation beginning at one terminal position and ending before a new terminal position is reached, said new terminal position being also preceded by part of said second partial angle of rotation;
• the rotary drive having an available starting torque (break-away torque) which is higher than the larges torque applicable by the rotary drive, a switching transmission located between the rotary drive and a rotatable threaded member for producing said starting torque, in said first partial angle of rotation, said starting torque being greater by at least a factor of 1.2 than said largest torque applicable by the rotary drive.