Abstract: A block of stacked green films provided with internal electrodes is laminated, at least one actuator is separated from the block, the actuator obtains its shape by means of a machining operation, is then sintered, and the sinter skin produced by the sintering is used as an insulating layer. The sinter skin is abraded at the points where the internal electrodes are connected to the external electrodes.

Abstract: In piezoceramic multilayer actuators, the head region and the foot region consist of inactive, that is to say electrode-free, piezoceramic layers. Due to the arrangement of the metallic electrodes and the layers of the piezoceramic materials, the shrinkage of the piezoceramic material, in particular in the passive head region and foot region, is influenced during the sintering process and can cause the formation of cracks. Different expansion behavior of the active and of the passive region during operation also lead to stresses which favor crack formation, in particular at the boundary between both regions. According to the invention, it is therefore proposed that a transition region (11), whose shrinkage and expansion behavior lies between the shrinkage and expansion behavior of the active region (10) and the shrinkage and expansion behavior of an inactive region (8, 9) which are electrode free, adjoins the active region (10) up to the inactive head region (8) and up to the inactive foot region (9).

Abstract: The material silicon carbide possesses not just extraordinarily good thermal, chemical and mechanical properties, as a result of an adjustable porosity it is also possible to apply the material in conditions with difficult tribological relationships. As the porosity influences not only the friction between two workpieces, but also the rigidity of a material, a careful selection of pore diameter, number of pores per unit volume of material and the distribution of the pores in the material is necessary. According to the invention, with a porosity of the sintered silicon carbide body of 2 to 12 vol. %, comprised of non-communicating closed pores, evenly distributed in the material, the pores are spherical and have a nominal diameter of from 10 ?m to 48 ?m.

Abstract: The invention relates to a monolithic multilayer actuator comprising a sintered stack of thin films, made from piezo-ceramic with inlaid metallic inner electrodes which extend from the stack on alternate sides and are electrically wired in parallel with external electrodes (3, 4) and are provided with connector wires (5). According to the invention, the actuator may be supplied with nominal voltage over a long period of time, without a change in the properties thereof, whereby the multilayer actuator (1) is sealed within a metallic or ceramic housing (8, 11, 16), the connector wires (5) are integral parts of the housing base (11) and the housing (8, 11, 16) is filled with a water-absorbing medium (14) and a water-transporting, electrically-insulating medium (15).

Abstract: The invention relates to a monolithic multilayer actuator comprising a sintered stack of thin films, made from piezo-ceramic with inlaid metalic inner electrodes which extend from the stack on alternate sides and are electrically wired in parallel with external electrodes (3, 4) and are provided with connector wires (5). According to the invention, the actuator may be supplied with nominal voltage over a long period of time, without a change in the properties thereof, whereby the multilayer actuator (1) is sealed within a metallic or ceramic housing (8, 11, 16), the connector wires (5) are integral parts of the housing base (11) and the housing (8, 11, 16) is filled with a water-absorbing medium (14) and a water-transporting, electrically-insulating medium (15).

Abstract: For the manufacture of multilayer actuators, the laminate is split into several actuators, which are pyrolized and then sintered. Because lamination in the unsintered body often produces non-homogeneity in the density, and the shrinkage during the firing of the ceramic is not of a constant value, the final geometry of the actuators can only be accurately obtained by the hardening of the sintered actuators. But in this case the internal electrode layers deposited in the actuators are thereby also processed, which can cause electrical flashovers and leakage currents during operation.

Abstract: In piezoceramic multilayer actuators, the head region and the foot region consist of inactive, that is to say electrode-free, piezoceramic layers. Due to the arrangement of the metallic electrodes and the layers of the piezoceramic materials, the shrinkage of the piezoceramic material, in particular in the passive head region and foot region, is influenced during the sintering process and can cause the formation of cracks. Different expansion behaviour of the active and of the passive region during operation also lead to stresses which favour crack formation, in particular at the boundary between both regions.

Abstract: For the manufacture of multilayer actuators, the laminate is split into several actuators, which are pyrolized and then sintered. Because lamination in the unsintered body often produces non-homogeneity in the density, and the shrinkage during the firing of the ceramic is not of a constant value, the final geometry of the actuators can only be accurately obtained by the hardening of the sintered actuators. But in this case the internal electrode layers deposited in the actuators are thereby also processed, which can cause electrical flashovers and leakage currents during operation.

Abstract: In the permeable structure, which is built up of sheets, continuous channels are arranged in rows and between the rows of channels are formed flow spaces which at opposite sides are bounded bit cover plates. In the flow spaces (4) at least two successive transverse bridges (6) are arranged on the same level, the transverse bridges (6) in at least half of the sheets having a different length (B) and the channels (1) extending essentially perpendicular to the flow spaces (4).

Abstract: In the heat exchanger module, produced by stacking sheet cards provided with openings and subsequently joining the individual cards of the card stack, each sheet card (2) or group of sheet cards of the stack is arranged rotated about a common axis by an angle .alpha. of between 0.degree. and 30.degree. with respect to the preceding sheet card (2) or group of sheet cards, the openings (3) forming helical channels (4).