I008 AGRICUl/rURAL MACHINERY 



the other long and connected to the edges B of the lower screen, which im- 

 parts a rocking movement to it. The screen A is not perforated at its end 

 p p' lying below the discharge aperture of the hopper, so that the material 

 from the latter has to pass over to p' before dropping through to the bottom 

 screen. Through a regulator placed against the vertical wall of the hopper, 

 and by which the fan box may be turned, the fan outlet apertiire may be 

 raised or lowered so as to enlarge either the part c which blows on to the 

 screen A, or the part c' which blows helow the same screen. From p' to 

 s the latter is perforated, not by punched holess, but by small arched not- 

 ches with convex edge bent downwards spoonwise, so as to facilitate the 

 entry of the current of air from below upwards and the descent of the small 

 grain and seeds, while the large grains fall from s into the inclined plane 

 d and the small straw, empty grains, etc., are expelled from the machine by 

 the air current. 



During the drop from A to B, the grains are struck by the air current 

 c' and compelled to follow an inclined path which brings them near the end 

 w" of the lower screen. The latter is supported laterally by the wooden 

 edges B to which is fixed the shaft /receiving the movement of the 4 springs 

 .Y and .v' supporting the screen as a whole. The result is that the latter, 

 which under the action of the connecting rod c f tended to perform a per- 

 fectly vertical alternating movement, is compelled on the contrary to 

 shift along 2 arcs of a circle wdth radii w^hich are respectiveh^ equal in the 

 lower part to the lever arm x' and in the upper part to the lever arm x. 

 In consequence of the impetus thus given b}' the screen to the grains cover- 

 ing it, the latter are thrown upwards, and in accordance wdth the law of 

 uniformly varied movement, they describe a parabolic path, falling on the 

 screen at a point farther up. They thus make small successive intermit- 

 tent advances, passing up along the screen until they pass through the 

 meshes or fall at .s^^', where they are collected. 



The screen is generally made of sheet iron perforated on the space n' 

 n" with small holes for separating the earth and small seeds ; on the space 

 n n' with larger holes separating the bad seeds; a sheet-iron apron with a 

 double slope placed below collects the screenings of s" and s"", while the sto- 

 nes, which cannot rise owing to their weight, fall from s' into the inclined 

 plane d. In the aperture q through which the cereal descends there is an 

 inclined plane q s^^' which, by means of the lever i maj^ be inclined right or 

 left and thus feed the cereal into either of the 2 sacking inlets with which 

 the appliance is fitted, so as to allow of continuous fall of the cereal during 

 the connecting up and taking away of the sacks. 



Thus the speed of conveyance of the cereal does not only depend on 

 the lever arm e of the elbow-joint, but also on the mutual position and the 

 length of the screens x and x' , and still more on the rapidity of alternative 

 movement. The effective conveyance momentum acquired by each grain 

 weighing p must not onh' be capable of overcoming the frictional resistance 

 against the screen and raising the grain, but also of enabling it to describe 

 such a path that when it falls back into the screen it cannot descend again. 



