Improvements in or connected with Sifters for Flour and other Materials.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in or connected with Sifters for Flour and other
Materials.
I, FREDERICK JOHN GRIFFIN RAINBOW, of Pilton Bakery, Barnstaple, in the
County of Devon, Master Baker, do hereby declare the nature of this invention
to be as follows:-
My invention relates to a new or improved sifter for flour or other materials.
As is well known when flour or other comminuted material has to be sifted
through more than one sieve it is convenient to arrange the sieves vertically
one over another so that what passes through one sieve may drop on to the one
below it. By this means the necessity of carrying or transferring the material
from a sieve at one place to a sieve at another is avoided. Inasmuch however as
the second sieve is for practical purposes made of finer mesh than the first sieve
and the third sieve than the second sieve and so on there is a danger of the under
sieves becoming clogged and of the material accumulating thereon.
My invention is designed to overcome this drawback and I do so by the means
hereinafter set forth.
I shall now proceed to describe the nature of my invention with reference
to a form in which two sieves, hereinafter termed the upper and the lower sieve
respectively, are employed. The lower sieve is of finer mesh than the upper.
I place these sieves a suitable distance apart and in order to prevent accumulation
of material on the lower sieve I cause it to be reciprocated or jogged at a higher
speed than the upper. This may be effected by any convenient mechanical means
as for example by attaching the sieves by means of rods or links or the like to
eccentrics or jogging cams so arranged or speeded that the eccentric or jogging
cam which drives the lower sieve shall move or rotate at a higher speed than that
which moves the upper sieve. Or I may produce this higher speed of the lower
sieve by causing the jogging to be effected by means of studs or projections
on a rotating drum or wheel with a larger number of studs or projections adapted
to jog the lower sieve than that number adapted to jog the upper sieve.
When there are more than two sieves I cause the third to move faster than the
second and so for the fourth if four are employed and so on.
I may also employ a clearing brush for clearing or sweeping the surface of a
sieve. Such a brush is conveniently mounted upon the inner end of a rod traversing
a race or other guiding arrangement by means of which the brush is deflected
from contact with the sieve at or near the inner end of its course. For example,
the arm or rod which carries the brush may be furnished with a cross-head the
ends of which travel in grooves, the said grooves being bent away from the surface
of the sieve at or near their inner ends.

page_text: Improvements in or connected with Sifters for Flour and other
Materials.
I, FREDERICK JOIN GRIFFIN RAINBOW, of Pilton Bakery, Barnstaple, in the
County of Devon, Master Baker, 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:-
-
My invention relates to sifting machines of that type in which two or more
sieves capable of reciprocating movement are arranged vertically one above
another, the mesh of the said sieves being of increased fineness the lower its
position in the vertical series.
In sifting machines of this class there is a danger of the lower sieves becoming
clogged and of the material to be sifted accumulating thereon.
My invention is designed to overcome this drawback and I do so by means as
hereinafter set forth.
In carrying my invention into effect I employ an indefinite number of sieves
placed vertically one over another; but for purposes of description I shall herein-
after chiefly refer to machines with two sieves only, and these I shall distinguish
as the upper sieve and the lower sieve respectively. The lower sieve is of finer
mesh than the upper. I place these sieves a suitable distance apart and in order
to prevent accumulation of material on the lower sieve I cause it to be moved at
a higher speed than the upper. This may be effected by any convenient
mechanical means as for example attaching the sieves by means of rods or links
or the like to eccentrics or to jogging cams so arranged or speeded that the
eccentric or jogging cam or other device which drives the lower sieve shall move
or rotate at a higher speed than that which moves the upper sieve. Or I may
produce this higher speed of the lower sieve by causing the movement to be effected
by means of studs or projections on a rotating drum or wheel with a larger number
of studs or projections adapted to jog the lower sieve than the number adapted to
jog the upper sieve.
I desire it to be understood that I do not limit myself to the herein described
means employed for moving the sieves; nor do I limit myself to any specific
means employed for causing such movement to take place at a differing speed.
Having now described in general terms this part of my invention, I shall proceed
to describe by way of types or examples certain means by which my invention
is to be or may be practised, and for this purpose I shall refer to the accompanying
drawings which illustrate in a more or less diagrammatic manner the features
of my invention.
In the said drawings,
Figure I is a vertical longitudinal section of a flour sifter constructed under
my invention.
Figure II is a plan of a sieve and connected parts.
Figure III is a detail view showing sieres operated by jogging cams..
Figure IV is a detail view showing sieves operated by jogging studs.
Figure Vis a plan view of the parts shown in side elevation in Figure IV.
In Figures I and II I illustrate a form of my invention in which the sieves
are operated by eccentrics mounted on separate shafts, one of these shafts being
a driving shaft and the other a driven shaft. The power being transmitted from
one to the other by means of pulleys and a driving belt.
The upper sieve 1 and the lower sieve 2 are carried on rods 3, 3, sliding in
blocks 4,4, fixed on the main framework of the machine. The sieves are worked

page_text: to and fro by eccentrics 5 and 6 mounted on separate shafts 7 and 8. These
shafts are connected by a driving belt passing over pulleys 9 and 10 of such
relative size that the speed of the lower shaft is greater than that of the upper.
The relative speeds can be adjusted by altering the ratio of the sizes of the pulleys.
The material to be sifted is placed in the hopper 12 at the bottom of which is
a sliding door, not shown in the figure, and several transverse bars 13 to partly
carry the weight of the material and check to a certain extent its downward
flow when the sliding door is open. The material falls or flows on to the upper
sieve. Part passes through it on to the lower sieve and part is held on the upper
sieve. The material falling on the lower sieve is there further sifted and what
passes through it flows out through the opening 14 of the lower hopper shown.
In some cases I provide rubber buffers as shown at 21 (attached to fixed parts 24
of the framework) in Figure II so placed that the rods 3, 3, knock against them at
the end of every stroke. The effect of this is to jog the material in the upper
sieve and that which cannot pass through the meshes travels towards this end of
the sieve. I provide a transverse upwardly projecting strip 22 and opening 22
in the sieve so that this material (fluff, coarse lumps, fibre and the like) can pass
out and fall down over a chute 23. In this way I can automatically remove a
coarse or useless material from a sieve. The chute 23 may be dispensed with
and a sack or other receptacle be placed under opening 22".
The strip 22 is not a necessary feature of my invention and I may omit it when
desired. Thus, I have omitted it from the lower sieve shown in Figure I, where it
will be seen that the material jogged (by the sieve striking the buffers) towards
the fore end of the sieve falls through the opening 22b, without passing over a
strip or other obstruction, and passes down the chute 23ª.
It will be seen that the employment of such openings at the fore ends of the
sieves (either with or without strips 22) forms an excellent means of passing the
different grades of material separated by the sieve to different receptacles,
the graded materials being conducted by chutes 23, or other equivalent con-
veying devices, to the said receptacles which may be placed in any convenient
positions. By this means also I am able to run the sifting machine continuously,
the operations of sifting and grading being in other respects automatic.
Apart from fulfilling the functions of a sifting and grading machine, my
invention, particularly in its simpler forms, constitutes an excellent machine for
mixing flours in bakehouses.
In Figure III I illustrate a case in which a jogging movement is produced by
cams 15 and 16, the upper sieve being moved by a three-throw cam and the
lower by a four-throw cam, so that if the two cams rotate at the same angular
velocity the speed of reciprocation of the lower sieve bears to that of the upper
the ratio of four to three. Such ratio can be varied at will by varying the number
of teeth on the two cams. 25, 25 are rollers against which the cams bear,
and 26, 26 are counter-springs for producing the return stroke of the sieves.
In some cases I use a disc as shown at 17, Figure IV, carrying a number of
studs 18 on each side. These studs knock against arms 19, 20 fixed on the two
sieves. If there are, say, two studs on the one side (namely that whose studs
actuate the upper sieve) and three on the other side of the disc, to actuate the lower
sieve, the lower sieve will be moved oftener than the upper in the ratio of three to
two. The ratio of the speeds of the sieves may be altered at will by changing
the number of studs on the disc. 27 is a spring on rod 28 to prevent too great a
forward movement of the sieve as this might cause the parts to become jammed.
In the figures I have shown the sieves as being supported by rods sliding in
bearings, but any other supporting devices which will admit of reciprocation such
for example as rollers may be employed.
In Figure I, I show the bars 13 as attached to the bottom of the hopper 12. I
sometimes find it convenient to attach the said bars to the top of the sieve as
shown in Figure III where they are shown as stretching between cheeks 29
erected on the sides of the sieve.

page_text: I have not herein before spoken of any relation of speed of movement to size
of mesh but in practice I prefer to cause the speed of movement of the sieves to
vary directly with the fineness of the mesh, that is to say the finer the mesh the
greater the speed. Thus let us assume that we have a machine with three super-
posed sieves, the first or highest one having a mesh, and being moved at a speed
to suit the material thrown upon it, that the second sieve, namely that immediately
below the highest, has a mesh twice as fine as that of the first and that the third
or lowest sieve has a mesh twice as fine as that of the second and four times as fine
as that of the first or highest. In this case I drive the second sieve at twice (or
thereabouts) the speed of the first and the third sieve at twice (or thereabouts)
the speed of the second and four times the speed of the first: and I provide said
sieves with reciprocating devices to cause the said sieves to be moved accordingly.
It will be seen by a reference to Figures I and II that the movement of the
sieves in that case is not in one plane merely but that there is an up and down
movement (towards one end at least) as well as a to and fro movement and also that
the movement is a gentle and continuous one without jogging or knocking. In
Figures III, IV and V however it will be seen that the movement is a true jogging
movement accompanied by a knocking or sudden concussion. In practice the
movement to be given to the sieves depends upon the material to be sifted. Thus
with materials which have little or no tendency to segregate and clog a gentle
continuous movement may be employed whilst in the case of materials apt to
segregate and cause clogging a more or less violent jogging action may be required.
As a rule the more violent the jogging the greater the advantage of employing
buffers. Where however the violence of jogging is but slight the buffers may
be dispensed with as also in the case of a continuous reciprocating movement.
For purposes of definition in the Claims I shall speak of the first or highest
sieve of a series of superposed sieves as the upper sieve and those sieves which lie
below the said upper sieve, whether they be the second, third or what not, as
lower sieves.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. In sifting machines of the type specified, driving each lower sieve at a
speed higher than that of the sieve immediately above it.
2. In sifting machines of the type specified, driving each lower sieve at or
approximately at a speed as much higher than that of the sieve immediately above
it as its mesh is smaller than that of the sieve immediately above it.
3. In a sifting machine of the type specified the combination of two or more
sieves, each lower sieve being of finer mesh than the sieve immediately above it
and two or more reciprocating devices for said sieves, each lower reciprocating
device being adapted to cause more rapid movement of its sieve than the recipro-
cating device immediately above it substantially as set forth.
4. In a sifting machine of the type specified the combination with the parts
mentioned in Claim 3 of upwardly projecting strip 22 and opening 22" and either
with or without chute 23, substantially as and for the purpose set forth.
For the Applicant,
J. G. LORRAIN, M.I.E.E., M.I. Mech. E.,
Norfolk House, Norfolk Street, London, W.C.,
Chartered Patent Agent.