The classificatory mechanism by pneumatical action at the taker-in cylinder part of the flat carding engine (D-type) consists of centrifugal, curved and climbing air current, so the lints and trashes can be classified by centrifugal force, gravity, inertia force and buoyancy.As a result of the qualitative investigations using the smoke-stream line, the following were observed:1. Air current within the limits less than 100mm from the inside of the both frames is to be excluded from the ordinary pneumatical action.2. As a result of this investigation concerning each variable time, it is possible to regard these streams as the quadric co-ordinatins streams.An example of the measuring values of the speed of currents concerning the centrifugal currents around the taker-in cylinder and the currents along the back surface of the mote knife, are showed by Fig. 6. As a results of those measuring under the experimental conditions, the following were observed:1. The tangential velocity of the centrifugal currents Vt is calculated from the following experimental formula;where, U0, Lc and hc are circular velocity of taker-in cylinder, circular length from gauge point between dish plates nose and taker-in cylinder, and distance from surface of taker-in cylinder respectively.4. Vr, the radial velocity of the centrifugal currents, is calculated from the following experimental formula;3. Vs, the component of velocity in the direction of the back surface of the mote knife concerning the currents along its back surface, is calculated from the following experimental formula;where, h, α2, β3 and V_??_ are distance from back surface of mote knife, coefficient and exponent concerning circular velocity of taker-in cylinder and length from gauge point of mote knife, and component of velocity in direction of back surface of mote knife on line between centrifugal currents and currents along back surface of the knife.4. θs, the angle to the back surface of the mote knife, of the currents along the back surface of the knife, is calculated from the following experimental formula;where, k2 and m2 are coefficient and exponent concerning circular velocity of taker-in cylinder and length from gauge point of the mote knife.