Abstract: The described apparatus for needling a nonwoven web comprises at least one needle beam carrying a needle board, a rocker for guiding the needle beam, and a slider-crank mechanism for actuating the needle beam. For a first-order mass balancing it is proposed that the slider-crank mechanism comprises two parallel crankshafts or eccentric shafts, which are adapted to be driven to rotate in mutually opposite senses, and associated connecting rods, which are connected by connecting rods to a link, which is pivoted to the rocker, and the arrangement is such that when the slider-crank mechanism is in a mid-position at the middle of its strike the plane of symmetry between the two crankshafts or eccentric shafts is at least approximately at right angles to a plane which contains the instantaneous overall center of gravity of the oscillating masses and the pivotal axis of the rocker.

Abstract: A screw rotor profile for both male and female rotors is generated from a single rack in which each individual rack segment includes four discrete circular arc segments and two discrete straight line segments. The leading and trailing flanks of the lobes of both the male and female rotors generated by the rack include involute portions disposed between tangent circular-arc-generated portions. A method for developing the rack is also disclosed.