Abstract: Cupola-shaped plastic pieces with a flat, unwarped rim can be produced from an equally large blank without trimming of the rim, by heating an optionally preheated plastic sheet by radiant heat. The radiant heat acts only on the area surrounded by the rim area until the area exposed to the radiant heat has reached a temperature just below the softening temperature of the plastic. Up to this point, the rim is left without tension, or at most a low clamping pressure is applied which allows a thermal movement of the rim. Then, but before the beginning of the forming, the clamping pressure is increased so that the rim is held tight. The radiation activity continues until the area exposed to the radiant heat has exceeded the softening temperature, the radiation activity is then stopped, and the area heated to the forming temperature is formed.

Abstract: In a drive-in apparatus for driving fasteners such as clips, nails, tacks, staples and the like in a workpiece, a solenoid for actuating impact blade which ejects the fastener is movably arranged in the apparatus housing. The solenoid includes an exciter coil formed with a central opening in which a cylindrical armature connected to the impact blade is magnetically accelerated in forward direction and returns to the starting position by a resetting spring. The exciter coil is also movably guided within the housing and spring biased in the forward direction by another biasing spring having a progressive elasticity characteristic. Depending on the steepness of the characteristic line of the second biasing spring, the backstrokes of the apparatus and the force necessary for tacking operation can be adjusted in broad range.

Abstract: A hand-held motor-driven percussion tool comprises a piston driven over an air cushion and acting over an axially movable anvil on the inner end of a tool axially movable in a tool receiver provided at one end of a tool housing. The anvil has an annular collar located in the cavity of an impact body which is movable in the direction of the impact of the piston against a cushioning ring. The impact body has an abutment face adapted to be engaged by a collar of the anvil when the latter is driven by the piston. A face of the impact body facing away from the cushioning ring is directed toward a part fixedly connected with the tool housing. The mass of the impact body is for instance 10% greater than that of the anvil. If the tool during operation is withdrawn from a workpiece, then the flange of the anvil impinges upon the abutment face of the impact body and accelerates the latter towards the cushioning ring.

Abstract: A power driven hammer drill has a tool impacting mechanism, a wobble unit for reciprocating the tool striking mechanism and having a drum member which can be releasably coupled with an intermediate shaft driven by a motor, wherein a switching device is provided outside of a hammer drill housing and arranged so as to disengage a coupling element of the intermediate shaft out of a coupling element of the drum member of the wobble unit against the action of a spring.