Abstract: A vibratory dry-shaver comprises a shear foil having two longitudinal edges, and respective means to clamp the two longitudinal edges in place to cause the shear foil to assume a natural curvature, the tangents to such curvature at the two clamping means forming an acute angle with each other. A cutter is reciprocatingly movable along and adjacent to the shear foil, the cutting edge of the cutter having a curvature corresponding to that of the clamped, curved shear foil. The curved shear foil and the cutting edge of the cutter each have a hyperbolic cosine curvature according to the formula:y=c.multidot.cosh x/cwhere y indicates the distances of the individual cutting edge points from the x-axis, x is the coordinate in the direction of the width of the cutter, and c is a constant derived from the width 2b of the clamped shear foil and the height of the curvature h of the clamped shear foil.

Abstract: A heat pump, in which there is arranged in a circuit between an absorber (7) and a generator (1) a liquid pump (9) comprising a piston (35) which is displaceable in a cylinder (33) and forms the separation between a gas chamber (37) and a liquid chamber (39) in which simultaneously prevails a pressure of comparatively low level during the suction stroke and a pressure of comparatively high level during the delivery stroke. A guide member (47) secured to the cylinder (33) encloses with the piston (35) an auxiliary chamber (51) of variable volume in which liquid of comparatively low pressure at least during the delivery stroke is constantly present. The gas chamber (37) is connected to alternately a lead of low and high gas pressure (69 and 71, respectively) in the heat pump, while the liquid chamber (39) is connected synchronously therewith alternately to a lead of low and high pressure (11a and 11b, respectively) in the heat pump.

Abstract: Apparatus for sharpening knives, scissors, and the like comprises a housing forming an enclosure having two oppositely disposed walls each provided with an opening, such openings being coaxially aligned. A motor is mounted on the outer side of one of these oppositely disposed walls, the motor having a shaft extending through the opening in the one wall into the enclosure. A second shaft extends through the opening in the other oppositely disposed wall. A grinding wheel is fastened to the end of the second shaft positioned outside the enclosure. Provision is made for connecting the motor shaft to the other end of the second shaft to rotatably drive the second shaft and to enable axial movement of the motor shaft and the second shaft with respect to each other. A pair of axially spaced radial flanges is mounted on the second shaft within the enclosure.

Abstract: A device for charging a rechargeable electric power source comprises a first section and a second section capable of being assembled in two positions relative to each other, one of such positions being a rest position and the other of such positions being a charging position, the first section being formed to receive a rechargeable electric power source. Electric components are arranged in the second section as a charging circuit for charging a rechargeable electric power source. Connector pins are provided on the second section for cooperating with an electric mains socket, the connector pins being connected to the electric components of the charging circuit. In the rest position the connector pins are covered by the first section. In the charging position the connector pins are clear of the first section, and the rechargeable electric power source in the first section is electrically connected to the electric components of the charging circuit in the second section.