Abstract: In order to improve a method for monitoring movable elements, in particular windows and sunroofs in motor vehicles, such that an object clamped between the movable parts and the part at rest is detected in a reliable fashion, the force acting upon such objects is maintained at the lowest possible value and the direction of the window is inverted as rapidly as possible. In order to ensure a reliable protection, a cutoff threshold consists of a constant component and a variable component, with the size of the difference (Dn) between the cutoff threshold and the instantaneous value of the rotation time (tu) influencing the switching signal.

Abstract: A welding backup shoe apparatus that comprises a double-acting fluid cylinder having a piston rod extending from it. A first retainer shoe is attachable to the piston rod and a second retainer shoe is opposed to the first retainer shoe. A first backup shoe to be received by the first retainer shoe and at least two other backup shoes are received by the first retainer shoe and by the second retainer shoe. The backup shoe is arcuate externally to be a close fit within a pipe. A guide is attached to the first retainer shoe, slidably engaging the second retainer shoe to guide the movement of the retainer shoes relative to each other. A release device is attached to the cylinder to abut the first backup shoe; and cables attach the two other backup shoes to the cylinder.

Abstract: The dry distillation of oil shale and like volatilizable materials as carried out by intimately mixing it with a fine-grain hot heat-transfer medium. According to the invention the hot distillation residue is passed in direct heat exchange with a cooling gas and the latter is utilized as one component of a preheating mixed gas which is passed in uniflow with the devolatilizable material through at least one riser. Hot combustion gases can make up other components of these mixed gases.