Improvements in Grain Separating Screens for Thrashing Machines.
Year: 1895

page_text: Date of Application, 15th Oct., 1895-Accepted, 23rd Nov., 1895
COMPLETE SPECIFICATION.
Improvements in Grain Separating Screens for Thrashing Machines.
1, CHARLES CLOSZ, of Webster City in the County of Hamilton, and State of
Iowa, United States of America, Gentleman, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
In thrashing machines the long straw and grain are thrown out from the thrashing
cylinder upon a separating platform which carries off the long straw by a vibrating
movement, opening and shaking it, and separating the grain therefrom and delivers
it through openings in said platform.
The grain is thus delivered together with chaff weeds, heads and pieces of short
straw, forming a considerable proportion of light stuff mixed with the grain. For
cleaning this grain 1 have provided a sheet-metal platform screen, especially
suited for use with a primary separating platform and is mounted and operated
beneath it.
My purpose is to provide a chaffing screen of transverse rows of openings which
will give better effect to the air-blast in lifting and floating the light bodies from
and over the surface between the openings, while the grain passes freely from said
surface through the openings.
The precise improvement for this purpose I will point out in the concluding
claims in connection with the drawings, illustrating the same.
Referring to these drawings:-
Figure shows in top view so much of a sheet metal platform screen as illustrates
my improvement in the separating surface.
Figure 2 is a vertical longitudinal section of the same taken mediately of one of
the rows of transverse openings.
Figure 3 is a similar section taken on the line of Fig. 1, showing the scoop
form of the separating surface.
Figure 4 is a section on the line - of Fig. 1, showing the double scoop form
of the separating surface looking toward the outer end.
Figure 5 shows in perspective the double scoop formation of one of the transverse
strips
Figure 6 is a transverse section taken through one of the openings.
Figure 7 is a diagram of the shape of the opening.
In the drawings have shown the screening surface which is formed with
longitudinal corrugations a, and between them the surface is divided by transverse
cuts into strips which are struck up so as to form the separating surface and the
openings.
It will be understood that the platform is mounted to have an end wise vibratory
movement and an air-blast provided beneath it directed up through the openings
in the direction of the movement of the light stuff from the platform.
The openings join the corrugations at their base lines and the cuts by which
the openings are formed are of the shape of what is known in archery as
"enpids-bow."
The distance between the corrugations is about two and a half inches, more or
less, as may be desired and the distance between the openings is about an inch.

page_text: The surface between these openings is formed so that one edge stands upward about
on a level with the top line of the corrugations, and toward the outer end of the
platform, while the other edge stands downward below the base-line of the
corrugations and to an extent greater than the projection above said line, so that
the full area of the opening between the upper edge of one strip and the under
edge of the adjacent strip will be below the bottom of the corrugations and
the separating surfaces of all the strips will stand toward the inner end of
the platform to receive the blast from that direction. In the middle of
their length the strips are formed with a convex ridge, on the upper surface
which merges on each side into a concave scoop form which extends to the
base line of the corrugations and forms a double scoop surface, the concavity of
which increases in depth from the lower to the upper edge of the strip. The fines
of these scoop surfaces are regular and uniform from the point r. to the point d,
across the strip, and from the base of the corrugation at e, to its joining the
convex ridge in the length of the strip. The pitch of the rouvex ridge is straight
about forty-five degrees from a vertical line and the scoop surfaces on each side
give a free and foll action of the air-blast from edge to edge of the strip so that
the air acts to lift and float the light stuff over the edges and the openings, while
the grain freely passes down the scoop surfaces through the opening. The double
scoop surface and middle ridge gives the upper edge of the strip a concave set-
back, at the ridge and a sima reversa curve extending therefrom to the corrugation.
In the upper deepest part of the scoops this curve forms the lobes g,g, ou each
side of the middle sut-back curve. The middle ridge at the lower edge of the
strip joins the scoop-sur aces on level between the points c, c, and this "gives the
widest part of the opening between the upper set-back, and the lower points (9
so that the air-blast has its greatest volume between and within the scoop surfaces
and the grain has its freist passage from the surfaces of its flattened lower
edge c, c. From this flattened surface part the opening decreases in width equally
to each end. The hollows of the scoops are deep enough to give a slight holding
of the air volume the better to lift the chat particles and to carry them over the
edge and the straw and weeds over upon the flat surfaces j,j, along the corrugations
over which surfaces such matter slides to the next surface. These Hat surfaces
are of triangular shape and extend from the upper edge at each end of the opening
along the base of the corrugation for about one-half of the width of the strip as
seen in Fig. 1.
The form of the scoop surfaces and their relation to the middle ridge provides
an effective action to the air-blast upon the falling grain as it descends upon the
two scoups, while at the same time such form facilitates the lifting of the light
stuff and carrying it over the deepest parts of the scoops and this is one of the
important advantages of the twin scoop construction in the secondary separation.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, 1 declare that what I
claim ia :-
1. A sheet metal screen for separating grain having longitudinal corrugatious
and transverse openings between them, the strips providing said openings each
being formed with a transverse convex ridge mediately of its length and with
scoop-like hollows on each side of said ridge extending in continuous and unprokon
curves to the base of the corrugations and to the flat surfaces at the upper edges
and ends of said strips, the said median ridge having its greatest couvexity at the
upper edge and merging into a flat surface at the lower edge of the strip for the
purpose stated.
2. A sheet metal grain separating screen having longitudinal corrugations and
transverse openings between them, the strips providing said openings each being
formed with a convex ridge medintely of its length and having its greatest
convexity at the upper edge and merging into a flat surface at the lower edge, the

page_text: surface on each side of said ridge formed scoop-like with continuous and unbroken
curves extending to the corrugations, for the purpose stated.
Dated this 15th day of October 1895.
BOULT & WADE,
Agents for the Applicant.