Patent Application
20250001456
This application relates to sifters for flour or other items that are to be sorted by size.
Many items, such as flour, coffee beans, or other products need to be sorted by size. In the case of powdered goods, a sifter may be used. An improved sifter is described hereinbelow.
In one aspect of the invention, a sifter includes a screen including a cylindrical portion. A helix is positioned within the cylindrical portion and extends between a first end of the helix and a second end of the helix. The helix defines a volume extending between the first end of the helix and a second end of the helix and extending inwardly from an inner surface of the helix by at least 25 percent of an inner diameter of the inner surface of the helix, the volume being available to receive particles sifted by the sifter.
In some embodiments, the volume is an annular gap extending between the first end and the second end and extending inwardly from the inner surface of the helix by at least 35 percent of the inner diameter. The annular gap contains no structure of the sifter and is completely available to be occupied by the particles sifted by the sifter. In some embodiments, the annular gap extends inwardly from the inner surface of the helix by at least 40 percent of the inner diameter.
In some embodiments, the helix has at least 5 loops between the first end and the second end. In some embodiments, the helix has at least 10 loops between the first end and the second end.
In some embodiments, the screen is perforated with openings no larger than a screen diameter, a gap between the helix and the screen being less than two times the screen diameter.
In some embodiments, a shaft extends through the helix, the helix being mounted to the shaft. The helix may be mounted to the shaft only at the first end and the second end of the helix. The shaft may define a first opening and a second opening, the second opening being non-parallel to the first opening, a first end portion secured to the first end of the helix extending into the first opening and a second end portion secured to the second end of the helix extending into the second opening. In some embodiments, the first opening and the second opening are substantially perpendicular to one another. The first opening and the second opening may be substantially perpendicular to an axis of symmetry of the shaft. The helix may be a metal rod bent to form a helix, the first end portion and the second end portion being end portions of the metal rod. In some embodiments, a motor is coupled to the shaft.
In some embodiments, the screen defines an opening, the helix configured to urge a portion of the particles that do not pass through the screen out of the opening.
In some embodiments, a first end cap is secured over a first end of the cylindrical portion and a second end cap is secured over a second end of the cylindrical portion, the first end cap defining an opening and the helix configured to urge a portion of the particles that do not pass through the screen out of the opening.
In some embodiments, the screen includes a first portion secured to a first side of the cylindrical portion and a second portion secured to a second side of the cylindrical portion, the first and second portions being oriented tangent to the cylindrical portion. In some embodiments, the first portion and the second portion are perforated.
In some embodiments, the screen is mounted within a chute including one or more legs configured to hold the chute elevated above a support surface. In some embodiments, the screen defines a rim extending outwardly therefrom and the chute defines one or more projections configured to engage the rim.
Preferred and alternative examples of the present invention are described in detail below with reference to the following drawings:
Referring to
The sifter assembly 10 includes a screen 14. The screen 14 is perforated, such as a regular or random arrangement of openings 16. The openings 16 have a first size corresponding to the maximum size of a particles that are permitted to pass through the screen 14 with larger particles being blocked by the screen 14 from passing therethrough. For example, for a screen 14 configured to sift flour, the openings 16 may be circles with a diameter of between 0.5 mm (e.g., for flour) and 8 mm (e.g., for coffee beans), though other sizes may also be used. The separation between the openings 16 may be between 1 and 16 mm, measured from center to center of the openings 16. Note that larger sizes for the openings 16 may be used where larger items are to be sorted. For example, stated generally, the openings 16 may be between 0.001 and 0.05 times the diameter of the cylindrical portion 18 and may have a separation from center to center that is between 0.002 and 0.1 times the diameter of the cylindrical portion.
The screen 14 may include a cylindrical portion 18. The cylindrical portion may conform to a cylinder having an axis of symmetry substantially (e.g., within 3 m of) centered on and substantially (e.g., within 5 degrees of) parallel to the longitudinal direction 102a. The length of the cylindrical portion 18 along the longitudinal direction 102a may be sufficient to achieve a desired amount of throughput of particles when sifting. For example, the cylindrical portion 18 may have a length of between 3 and 10 times the diameter of the cylinder. The openings 16 may be distributed over 75 percent, 80 percent, 90 percent, or 95 percent of the area of the cylindrical portion 18.
The screen 14 may also include portions 20 extending outwardly from the cylindrical portion 18. The portions 20 may be tangent to the cylindrical portion 18 at a point of attachment to the cylindrical portion 18. The portions 20 may include openings 16 formed thereon or may be un-perforated. When perforated, the openings 16 may be distributed over 75 percent, 80 percent, 90 percent, or 95 percent of the area of the portions 20.
The cylindrical portion 18 and portions 20 may be a single piece of perforated material shaped, such as by bending, to include the cylindrical portion 18 and portions 20 or may be secured to one another by means of welding, screws, adhesive, or other fasteners.
The portions 20 in the illustrated embodiment, are substantially (e.g., within 3 mm of) planar and are substantially (e.g., within 5 degrees of) parallel to the longitudinal direction 102a and vertical direction 102c. The separation between the portions 20 in the horizontal direction 102b may be substantially (e.g., within 5 percent of) equal to the diameter of the cylinder. The portions 20 may extend outwardly from the cylindrical portion in the vertical direction 102c between 0.5 and 2 times the diameter of the cylindrical shape defined by the cylindrical portion 18, such as between 0.5 and 1 times. In other embodiments, the portions 20 are curved or planar and flare outwardly from the cylindrical portion 18 in a plane perpendicular to the longitudinal direction 102a. In such embodiments, the portions 20 may or may not be tangent to the cylindrical portion 18 at points of attachment to the cylindrical portion 18.
The sifter assembly may include end caps 22a, 22b. The end caps 22a, 22b are offset from one another along the longitudinal direction 102a and extend between the portions 20 and across each end of the cylindrical portion 18. The end caps 22a, 22b in the illustrated embodiment are unperforated, i.e., lack openings 16. The end caps 22a, 22b may be planar and substantially (e.g., within 5 degrees of) parallel to one another and may be parallel to the horizontal direction 102b and vertical direction 102c. In other embodiments, the end caps 22a, 22b may be planar or curved and flare outwardly in a plane parallel to the longitudinal direction 102a and vertical direction 102c. The end caps 22a, 22b may secure to edges of the screen by means of welds, adhesive, screws, or other fastening means.
At least one of the end caps 22a defines an opening 24. The opening 24 may extend over the axis of symmetry of the cylinder defined by the cylindrical portion 18. A shaft 26 is positioned within the cylindrical portion 18 and may have an axis of symmetry thereof substantially (e.g., within 3 mm of) colinear with and substantially (e.g., within 5 degrees of) parallel to the axis of symmetry of the cylindrical portion 18. The shaft 26 may extend outwardly through the opening 24 or may be accessible through the opening 24. The shaft 26 may be coupled to a motor 28, such as an electric, hydraulic, or pneumatic motor 28. In the illustrated embodiment, the shaft 26 includes a non-cylindrical feature configured to engage the motor, such as the illustrated square opening 30a, an external square or flattened surface, or other feature.
The end of the shaft 26 opposite the end that engages the motor 28 may be rotatably mounted to the end cap 22b. The shaft 26 may be rotatably mounted to the end cap 22b by passing through an opening in the end cap 22b, extending into a bearing mounted to the end cap 22b, or some other means. In the illustrated embodiment, the shaft 26 defines an opening 30b that receives a pin 30c mounted to the end cap 22b, the pin 30c being rotatable relative to the opening 30b.
Referring to
The helix 32 may be made of steel, stainless, steel, or other material. The helix 32 may have a thickness that is selected to both (a) avoid deformation during use and (b) provide sufficient area to move particles along the inner surface of the screen 14. For example, the diameter of a metal rod used to form the helix 32 may be between 0.01 and 0.1 times the diameter of the cylindrical shape defined by the helix 32. The pitch of the helix 32, i.e., the separation between each loop of the helix 32 along the axis of symmetry of the cylindrical shape, may be between 0.1 and 0.5 times the diameter of the cylindrical shape defined by the helix 32. In some embodiments, the helix 32 includes at least 5 loops, at least 10 loops, or at least 15 loops.
End portions 34a, 34b secure to the helix 32 and bend inwardly into the cylindrical shape. For example, the helix 32 and end portions 34a, 34b may be embodied as a single metal rod bent into a helical shape with end portions 34a, 34b. The shaft 26 may define openings 36a, 36b offset from one another along the longitudinal direction 102a. The openings 36a, 36b may be non-parallel with respect to one another. For example, the openings 36a, 36b may be substantially perpendicular to one another, such as rotated between 80 and 90 degrees about the longitudinal direction 102a relative to one another. The end portions 34a, 34b insert within the openings 36a, 36b, respectively. The end portions 34a, 34b may be retained within the openings 36a, 36b by some or all of (a) the rigidity of the helix 32 and the fact that the openings 34a, 34b are non-parallel to one another, (b) set screws, (c) interference fit, (d) welds, adhesive, or (e) some other fastener.
As is apparent, an annular gap 38 is present between the helix 32 and the shaft 26. For example, the annular gap 38 may have a thickness perpendicular to the axis of symmetry of the shaft 26 of at least 0.25, at least 30, at least 35, or at least 45 percent of the inner diameter of the helix 32, i.e., the cylindrical shape defined by the inner surface of the helix as defined above. The gap 38 extends at least between the end portions 34a, 34b and may have a length along the longitudinal direction of between 0.7 and 1, such as between 0.9 and 1 times the separation between the end caps 22a, 22b along the longitudinal direction 102a. In some embodiments, no portion of the sifter assembly 10 extends into the annular gap 38 between the end portions 34a, 34b such that only particles being sifted using the sifter assembly 10 are present in the annular gap 38 during use.
In some embodiments, the shaft 26 is eliminated. For example, end portion 34a may engage the motor 28 and end portion 34b may be rotatably connected to the end cap 22b. In such embodiments the annular gap 38 has a thickness of up to 100 percent of the volume of the cylindrical shape and may be embodied as a cylindrical volume rather than annular gap 38.
One or both of the screen 14 and one of the end caps 22a, 22b defines an opening 40 that is larger than the openings 16, e.g., at least 2 times, at least 8 times, at least 16 times, or at least 32 times larger than the openings 16 in at least one of the directions 102a, 102b, 102c. In the illustrated embodiment, the opening 40 is an extension of the opening 24 providing access for the shaft 26 to couple to the motor 28. In the illustrated embodiment, the opening 40, or a separate opening, extends at least partially along the screen 14. For example, the opening 40 extends inwardly into the screen 14 along the longitudinal direction 102a, such as a distance that is between 0.05 or at least 0.5 times the diameter of the cylindrical portion 18. The opening 40, or a separate opening, may be positioned at the bottom of the screen 14, i.e., in the cylindrical portion opposite the portions 20 overlapping a midpoint of the cylindrical portion 18 between the portions 20. The opening 40 permits particles that are too large to pass through the openings 16 of the screen 14 to fall out of the sifter assembly 10.
Referring to
The support 42 may define a chute 48. The chute 48 may have sides substantially parallel to the vertical direction 102c or that flare outwardly with distance above the sifter assembly 10. The sifter assembly 10 may include a rim 50 or other structure extending outwardly from one or both of the screen 14 and the end caps 22a, 22b. For example, the rim 50 may be formed by bending outwardly the upper edges of the single piece of material forming the screen 14 or by securing separate pieces of material to upper edges of the portions 20 and extending outwardly from the screen 14. One or more protrusions 52 extend inwardly into the chute 48, sch as from a bottom edge of the chute 48. The one or more protrusions 52 engage one the rim 50 of the sifter assembly to maintain the sifter assembly 10 within the chute 48 and/or positioned to receive particles passing through the chute 48.
The chute 48 may be mounted to legs 54 configured to maintain the chute 48 elevated above a surface supporting the chute 48. For example, a rim 56 may extend outwardly from the chute 48 with the legs 54 being mounted to the rim 56.
During use, the motor 28, a hand crank, or some other source of torque, rotates the shaft 26 such that the helix 32 pushes the second particles that will not fit through the openings 16 to the opening 40. For example, for the right-handed helix 32 shown, the helix 32 may be rotated counter clockwise from the point of view shown in
The sifter assembly 10 provides various advantages, including without limitation the following:
While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.
