Abstract: A machine for forming stacks of bags from a web of synthetic thermoplastic material has feeding rollers for feeding the web to welding jaws which form transverse welds in the web. There is a first motor for operating the feeding rollers and a second motor for operating the welding jaws. A central processing unit controls operation of the respective motors and includes a controller for the first motor for operating the first motor for an increased time and at a reduced speed during feeding of a leading bag in a stack as compared with the time and speed of operation of the first motor during feeding of remaining bags in the stack. This facilitates the removal of a previously formed stack of bags from a machine.

Abstract: An apparatus for controlling machines for making bags or sacks severed by welding from continuous tubular or semitubular films of synthetic thermoplastics has at least one pair of pinch rollers for feeding the continuous film. The pinch rollers are driven via a transmission by a first motor. A pair of welding jaws provides the continuous film with seam welds, transverse seam welds or severed transverse seam welds. A second motor actuates the welding jaws via a drive mechanism. A central processing unit controls the motors in such a manner that the motor for the pair of welding jaws is energized at a time when the motor for driving the pair of pinch rollers is still driving the pinch rollers, and after a standstill phase of the motor for driving the pair of pinch rollers the latter motor is energized even before the motor for driving the pair of welding jaws has stopped.

Abstract: A Stirling heating pump has a working piston acting upon a compression chamber and actuated by a crank drive accommodated in a housing, and a diaphragm bellows surrounding the working piston for sealing the compression chamber from the housing and having an inner hollow communicating with the former. Pressure variations in the interior of the diaphragm bellows are compensated by a pressure throttling element arranged between the compression chamber and the inner hollow of the diaphragm bellows, and a compensating diaphragm expansible in the housing and having an inner hollow communicating with the inner hollow of the diaphragm bellows serves to form a closed flow circuit.