Abstract: The small a.c. motor which is intended in particular for the oscillating drive of a toothbrush fastened to the armature shaft, has as the armature a cylindrical permanent magnet (4) magnetized diametrically, a stationary coil surrounding this permanent magnet at a clearance along its whole length, its turns running essentially rectangularly, and a tubular stator case (1) surrounding the coil and of rectangular cross-section, to which the outer periphery of the coil being adapted. The coil is composed of two equal part-coils (2,3) and orientated with its axis perpendicular to the axis of the armature and its planes of winding lie essentially in parallel with the large sidefaces of the stator (1). The two part-coils (2,3) rest against one another at faces orientated in parallel with their planes of winding in a plane passing through the armature axis, and their edges running diametrically to the armature have in the center semi-circular recesses (2a,2b,3a,3b,) for the passage of the armature shaft (5).

Abstract: A hydraulic apparatus is provided which comprises a liquid-pulse generator, and hydraulic motor connected to said generator by a flexible pipe. The motor is driven by liquid pulses provided by the generator via the pipe. The pulses form standing waves within the pipes with a certain wavelength. In order to insure an efficient energy transfer, the length of the pipe is an odd multiple of the quarter-wavelength.

Abstract: A constant-volume increment pipetting arrangement for use particularly in connection with analysis of minute specimen volumes of biological fluids. The arrangement, which is designed to have a very low inertia factor, comprises a pumping unit having a pair of two-port valves with a duct running between a port from each valve, wherein at least a portion of the duct wall is movable to provide a variable volume pipetting chamber. The second port of one valve serves as the intake port for the fluid to be pipetted and the remaining port of the other valve serves as the delivery port. Three reciprocating drive elements are provided, connected one each to the valves and to the movable portion of the duct wall. Associated with the drive elements is a sequential control means, wherein the control means portion for the drive element connected to the moving portion of the duct wall constitutes an electromagnet arrangement energizable by a periodic supply.