Abstract: The intermittent electrolysis of a portion of the used ammoniacal etching solution generates oxygen at the anode which is mixed into the remainder of the circulated etching solution for reoxidation and regeneration before it is returned to the etching chamber. The portion of the solution which goes through the electrolysis cell, and has its metal content reduced, is returned to the beginning of the circulation loop rather than to the etching chamber, in order that the metal content of the circulated solution may be quickly reduced. This reduction is quickly picked up by a metal content measuring device in the branch supplying solution to the electrolysis cell.

Abstract: An electro-thermal actuating element. The element includes a container closed by a deformable element. The container holds a liquid and a positive thermal coefficient heating element. The heating element has a temperature/resistance curve having a sharp upward bend in a predetermined temperature range. The evaporation temperature of the liquid corresponds to the bend in the curve so that when the liquid is vaporized, the heating element is essentially switched off. The vaporization of the liquid deforms the membrane which is used for actuating external devices.

Abstract: The electro-magnetic valve includes a hydraulic pilot control consisting of an inlet and outlet with a concentric valve seat, sealable by a flexable diaphragm. The inlet and outlet are both arranged on one side of the diaphragm and a hydraulic pressure is arranged on the other side of the diaphragm. A filling aperture from the inlet to the pressure chamber and a central pressure relief aperture from the pressure chamber to the outlet are provided, the central pressure relief aperture being connected to a bypass in the valve body. An electro-magnetic means for opening the pressure relief aperture is also included.

Abstract: In addition to catalyzing the reoxidization of spent alkaline etching age the suspension of activated carbon powder in the etching solution also increases the speed of etching when the etching solution is recirculated in the etching of printed circuit boards. The ammonium sulfate etching solution is set to a pH of about 9 by the addition of ammonia gas. In the recirculation of the etching solution, a part of the solution can be freed by filtration from suspended carbon particles and passed through the cathode and anode chambers of an electrolysis cell for the recovery of the etched metal by deposition on the cathode. The activated carbon powder for this purpose is calcined before use, at a temperature of between 900.degree. and 1200.degree. C. in vacuum or in an atmosphere that is inert, reducing, or only slightly oxidizing as in the case of an atmosphere containing carbon dioxide, water vapor or both, in a concentration that does not appreciably oxidize the carbon particles.

Abstract: A circulator pump for a plant for the utilization of solar heat including a first heat exchanger for collecting heat at a high level disposed within a solar collector, a medium for receiving heat collected in the first heat exchanger, a second heat exchanger for collecting heat at a lower level with respect to the first heat exchanger and a circulator pump for circulating the medium through the first and second heat exchangers. The circulator pump is a prime mover driven by a pressure difference between the first and second heat exchangers and is a charger pump. The prime mover and charger pump operating in a push-pull manner as differential piston pumps having a common piston rod operatively disposed within a chamber including control ducts, which load an auxiliary control slider member. The auxiliary control slider member is reciprocated within a chamber and upon reaching end portions of the differential piston switch the chambers of the two differential piston pumps to effect oppositely directed movement.