System and method for fractionating grain

Abstract

A sieving apparatus for fractionating a grain product comprises a top chamber separated from a bottom chamber by a sieve; a top chamber cover defined by a plurality of openings that allow substantially vertical entry of an air stream into the top chamber when the interior of the sieving apparatus is under vacuum via first exit port in a side wall of the bottom chamber for exit of air; an inlet port in a sidewall of the top chamber, the inlet port configured for feeding of dry grain particles into the top chamber and for substantially horizontal entry of air into the top chamber; and a first exit port in a sidewall of the bottom chamber for exit of air and exit of a first grain fraction from the bottom chamber when the interior of the sieving apparatus is under vacuum via the exit port.

Claims

1. A sieving apparatus for fractionating a grain product, the sieving apparatus comprising: a. a top chamber separated from a bottom chamber by a sieve; b. a top chamber cover defined by a plurality of openings that allow substantially vertical entry of an air stream into the top chamber to create air turbulence in the top chamber when the interior of the sieving apparatus is under vacuum via first exit port in a side wall of the bottom chamber for exit of air; c. an inlet port in a sidewall of the top chamber, the inlet port configured for substantially horizontal entry of air with dry grain particles under vacuum into the air turbulence in the top chamber; d. a first exit port in a sidewall of the bottom chamber for exit of air and exit of a first grain fraction from the bottom chamber when the interior of the sieving apparatus is under vacuum via the exit port; e. a second exit port in the sidewall of the top chamber, the second exit port for exit of air and exit of a second grain fraction from the top chamber when the sieving apparatus is under vacuum via the second exit port and inducing the horizontal entry of air into the top chamber; and f. a vacuum producer operably connected to the first exit port and operably connected to the second exit port, wherein the vacuum producer is configured to draw air horizontally through the inlet port.

2. The sieving apparatus of claim 1, further comprising nozzles installed in the sidewall of the top chamber for pulsing a high pressure air stream into the top chamber horizontally above the sieve surface.

3. The sieving apparatus of claim 1, wherein the openings of the top chamber cover define a total void space between about 0.20% to about 0.30% of the total surface area of the top chamber cover.

4. The sieving apparatus of claim 1, wherein the openings are substantially evenly distributed over the surface area of the top chamber cover and individually have a diameter sufficiently small relative to an applied vacuum to induce vertical airflow within the top chamber.

5. The sieving apparatus of claim 1, wherein the openings in the top chamber cover are circular.

6. The sieving apparatus of claim 5, wherein the circular openings in the top chamber cover each have a substantially identical diameter.

7. The sieving apparatus of claim 6, wherein the diameter of the top chamber is about 40 inches and the circular openings in the top chamber cover each have a diameter of about 0.5 inches and are arranged with one central opening, five openings substantially equi-spaced in a first circle around the central opening and eleven openings substantially equi-spaced in a second circle around the first circle.

8. The sieving apparatus of claim 1, wherein the sieve is supported by a sieve bed dividing the top chamber from the bottom chamber.

9. The sieving apparatus of claim 8, wherein the sieve bed is a metal screen with circular openings greater than about 4 inches in diameter.

10. The sieving apparatus of claim 1, wherein the sieve is defined by openings less than about 100 m in diameter.

11. The sieving apparatus of claim 1, wherein a horizontal tube with a hopper for loading a grain product is connected to the inlet port.

12. The sieving apparatus of claim 11, wherein the horizontal tube has an outer opening provided with a removable cap.

13. The sieving apparatus of claim 11, further comprising a valve in the horizontal tube between the hopper and the inlet port.

14. The sieving apparatus of claim 1, wherein the top chamber is removable from the bottom chamber.

15. The sieving apparatus of claim 14, further comprising a seal and a clamp to attach the top chamber to the bottom chamber.

16. The sieving apparatus of claim 1, wherein the bottom chamber is provided with a pressure gauge for measurement of the pressure state within the interior of the bottom chamber.

17. The sieving apparatus of claim 1, wherein at least a portion of the bottom chamber is conical-shaped or frustoconical-shaped and the bottom of the bottom chamber is defined by a bottom port which is capped when the sieving apparatus is in operation and which is uncapped during cleaning and/or maintenance of the bottom chamber.

18. The sieving apparatus of claim 17, wherein the bottom port is provided with a rotary airlock valve for continuous emptying of fine particulates from the bottom chamber while under vacuum.

19. The sieving apparatus of claim 1, wherein the top chamber is cylindrical or ovoid.

20. A system for fractionating a grain product under vacuum, the system comprising: a. a sieving apparatus as defined in claim 1; b. wherein the vacuum producer is configured to draw air vertically through the plurality of openings of the top chamber cover; c. a first vessel for collecting fine grain particles that pass through the sieve and exit the bottom chamber via the first exit port under vacuum provided by the vacuum producer, the first vessel operably connected to the first exit port; and d. a second vessel for collecting coarse grain particles that do not pass through the sieve, the second vessel operably connected to the top chamber via the second exit port, under vacuum provided by the vacuum producer, the second vessel operably connected to the second exit port.

21. The system of claim 20, further comprising a pair of valves to alternate the vacuum suction between top and bottom chambers of the device and airlock valves to facilitate continuous emptying of course and fine particulates from the collection vessels.

22. The system of claim 21, further comprising an automated valve opening and closing sequencer for operation of the pair of valves.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention are described with reference to the accompanying figures.

(2) FIG. 1 shows a sieving apparatus 12 as part of a system 10 for fractionating a grain product (G) into a fine particulate fraction G1 and a coarse particulate fraction G2.

(3) FIG. 2 shows a top view of a top chamber cover 20 which is defined by a plurality of holes 22.

DETAILED DESCRIPTION OF THE INVENTION

(4) An example embodiment of a sieving apparatus and system for fractionating grain will now be described with reference to the drawings. Alternative embodiments employing alternative features will be briefly described during the course of the description of the embodiment of FIG. 1. Features of the top chamber cover are shown in FIG. 2.

(5) One embodiment of a sieving apparatus and system is described with reference to FIG. 1. Grain fractionating system 10 includes a sieving apparatus 12 which may be formed of food-grade stainless steel or other similar materials known to those skilled in the art. The apparatus 12 includes a bottom chamber 14 separated from a top chamber 16 by a sieve 18. In certain embodiments, the bottom chamber 14 has a generally cylindrical upper portion and a frustoconical lower portion and the top chamber 16 is also generally cylindrical with a diameter substantially similar to the diameter of the upper portion of the bottom chamber 14. Advantageously for the purpose of fractionating grain products, the sieve 18 has openings with diameters less than about 100 micrometers (m). This sieve 18 serves to fractionate a mixture of grain particles G into a fine fraction G1 (i.e. particles with smaller diameters than the diameter(s) of the sieve openings) and a coarse fraction G2 (i.e. particles with larger diameter(s) than the diameter(s) of the sieve openings).

(6) The top chamber 16 is provided with a cover 20 which generally covers the entire diameter of the top chamber 16. The top chamber cover 20 is provided with a plurality of openings 22. One embodiment of the top chamber cover will now be briefly described with reference to FIG. 2 which shows a top view of cover 20. This particular embodiment of the top chamber cover is a circular cover 20 with a central opening 22a. Five additional openings 22b are disposed in a circle located radially outward from the central opening 22a. The openings 22b are substantially equi-spaced from each other and from the central opening 22a. Eleven additional openings 22c are disposed radially outward from openings 22b and substantially equi-spaced from each other. This arrangement of openings 22 is useful for generating air currents when the apparatus 12 is under vacuum suction as will be described in detail hereinbelow. Advantageously, the cover 20 may be formed of substantially transparent hard plastic, plexiglass or other hard transparent material which allows the operator to visualize the movement of grain particles within the top chamber 16 when the system 10 is operating.

(7) Returning now to FIG. 1, the bottom chamber 14 is provided with a bottom exit port 24 through which vacuum suction is applied to the bottom chamber 14. Particles of the fine fraction G1 also pass through bottom exit port 24 for collection.

(8) The top chamber 16 is provided with an inlet port 26 for feeding of the mixture of grain particles G via a hopper 36 and horizontal tube 38 and for allowing passage of air when the system is operating. The horizontal tube 38 is provided with a removable cap 40 to cover its outer opening, and to allow access to the interior of the tube 38 to facilitate maintenance. In certain cases, opening of the cap 40 may provide a means to increase airflow into the top chamber 16 when the system 10 is operating. The top chamber 16 is also provided with a top exit port 28 for evacuation of the coarse fraction of grain particles G2 which is collected in the top chamber 16.

(9) In this particular embodiment, the sieve 18 rests upon a sieve bed 30 which may be constructed of a metal screen. In certain embodiments, the metal screen has openings which are greater than about 4 cm in diameter. The sieve bed 30 rests upon a ledge 32 which is formed in or attached to the inner side wall of the bottom chamber 14. The sieve 18 and sieve bed 30 may also be held in place by a seal 35 such as an o-ring, or gasket in combination with a clamp 34 for locking the top chamber 16 in place above the bottom chamber 14.

(10) Additional optional features of the bottom chamber 14 include a bottom port 42 with a removable cap 44. This feature is provided for maintenance and cleaning of bottom chamber 14 as well as evacuation of the fine particle fraction G1 if necessary. In addition, the bottom port 42 can be attached to a rotary airlock valve (instead of the removable cap 44) that can continuously empty the fine particles collected in the bottom chamber. The bottom chamber 14 also optionally contains a pressure gauge 46 for measurement of air pressure within the interior of the bottom chamber 14.

(11) Apparatus 12 as described above is shown in FIG. 1 as part of system 10 which also includes a vacuum producer 48, and a series of vacuum conduits that connect the vacuum producer 48 to the bottom exit port 24 and top exit port 28. Accordingly, in the embodiment shown in FIG. 1, vacuum producer 48 is operably connected to bottom exit port 24 of the bottom chamber 14 via conduit sections 50, 52, 54, 56, 60 and 64. Likewise, vacuum producer 48 is operably connected to top exit port 28 of the top chamber 16 via conduit sections 50, 52, 54, 58, 62 and 66.

(12) A first cyclone separator vessel 68 is connected between conduit sections 60 and 64 for the purpose of collecting the fine grain fraction G1 via vacuum suction provided by the vacuum producer 48. Likewise, a second cyclone separator vessel 70 is connected between conduit sections 62 and 66 for the purpose of collecting the coarse grain fraction G2 which accumulates in the top chamber 16. These cyclone separator vessels 68 and 70 advantageously operate in conjunction with respective valves 72 and 74 which permit or block vacuum suction from the lower chamber 14 and top chamber 16 respectively, as will be described in more detail hereinbelow. The cyclone separator vessels 68 and 70 may be conical in shape with a dispensing opening at the apex of the cone. The apex of the cone may be provided with rotary airlock valves in a construction which is known in the art to be effective for continuous dispensing of grain products.

(13) The system embodiment shown in FIG. 1 has optional components including a particulate filter 76 disposed between conduit sections 50 and 52 for the purpose of preventing fine particles from entering and damaging the vacuum producer 48. Vacuum conduit pressure gauge 78 is connected to conduit section 54 for the purpose of monitoring pressure in the conduit system. This conduit pressure gauge 78 may be configured to effect closure of a safety valve 80 if the pressure exceeds a pre-determined value, which may occur if blockages occur in any of the upstream conduit sections or cyclone separator vessels.

(14) The operation of system 10 of FIG. 1 will now be described. Valve 74 is closed and valve 72 is opened (safety valve 80 is also in its normally open position). The vacuum producer 48 is switched on and vacuum suction is applied to the vacuum conduit sections 50, 52, 54, 56, 60, and 64. As a result, air is pulled from the atmosphere into the top chamber 16 via holes 22 in the top chamber cover 20 and through the inlet port 26. Without being bound to any particular theory, it is believed that the plurality of air streams generated by holes 22 in the cover 20 moving substantially vertically downward towards and substantially perpendicular to the surface of the sieve collide with the substantially horizontal stream of air entering the top chamber 16 through the inlet port 26 and that this collision of air streams generates turbulent air currents within the top chamber 16 above the sieve 18. These turbulent air currents thoroughly stir and fluidize the unfractionated grain product G which enters the upper chamber 16 after feeding via the hopper 36 through the inlet port 26. This thorough stirring and fluidization of the grain product G prevents blockage of the openings of the sieve 18. In an alternative embodiment, high pressure air streams enter horizontally into the top chamber through nozzles (not shown) that are installed on the side wall of the top chamber and just above and parallel to the sieve surface. The pulsing of high pressure air stream done through one nozzle at a time. The air stream sweeps the sieve surface.

(15) The entry of the unfractionated grain product G into the apparatus 12 is also facilitated by the vacuum suction provided by the vacuum producer 48. If so desired, the horizontal stream of air may be increased or regulated by installing a valve on the horizontal tube 38 between the hopper 36 and the top chamber 16 of the apparatus 12. Other means of regulating the flow of air through the inlet port 26 may be provided in alternative embodiments.

(16) The grain product G in the top chamber 16 is then fractionated by the sieve 18. For the sake of clarity, in FIG. 1, the interior of the top chamber 16 is shown to contain only the coarse grain fraction G2 but it will be understood that initially, the unfractionated grain product G occupies the top chamber 16 until the fine particles G1 have passed through the openings of the sieve 18 and entered the bottom chamber 14, leaving the coarse grain fraction G2 in the top chamber 16. The particles of fine fraction G1 pass through the bottom exit port 24 and through vacuum conduit 64 for collection in the first cyclone separator vessel 68. When the fractionation of a dispensed amount of grain product G is judged to be complete, valve 72 is closed and valve 74 is opened. As a result, with continued operation of the vacuum producer 48, vacuum suction through conduits 60 and 64 is halted and vacuum suction through conduits 62 and 66 is initiated. This action has the effect of drawing air and coarse particles G2 from the top chamber 16 through the top exit port 28 and through conduit 66 for collection in the second cyclone separator vessel 70. In certain embodiments, both of the cyclone separator vessels 68 and 70 have rotary airlock valves installed at their bottoms, which are used to continuously empty the fine and coarse particulates collected in the vessel.

(17) In certain embodiments, the system may operate in a cyclical manner with the following briefly described steps: (i) a pre-determined volume of unfractionated grain product G is dispensed and fractionated under vacuum suction operating via conduits 64 and 60 with valve 72 open and valve 74 closed as shown in FIG. 1 (ii) fine particles G1 are evacuated to the first cyclone separator vessel 68; and (iii) coarse particles G2 are evacuated to the second cyclone separator vessel 70. Such a cyclical process may be optimized and automated. In addition to the valve automation, the installation of the rotary airlock valves at the bottom of the bottom chamber 35, as well as the bottom of the cyclone collector vessels 68 and 70, would facilitate a continuous particle classification, collection and dispensing process. By appropriately sizing all elements of this automated continuous system, a commercial scale operation is feasible.

(18) In certain embodiments, an automated valve opening and closing sequencer may be provided to provide a sequence of opening and closing of valves in order to achieve the required efficient grain material classification. Both valves should not remain closed as this will led to buildup of high vacuum in the conduits/tubes/vessels. The action of the sequencer may be controlled by conventional electronics, processors and programs known to the person skilled in the art.

(19) In certain embodiments, the rate of feeding of grain material into the hopper is synchronized with the operation. For example, when suction begins through the exit port of the bottom chamber, the feeder will initiate the feeding of the grain material into the hopper and the grain material will be sucked through the inlet port into the top chamber. After feeding defined amounts of grain material into the top chamber, the feeder will stop but vacuum suction through the exit port in the bottom chamber continues to operate for defined period of time in order to perform air current assisted sieving. Once the sieving process is complete, the coarse material is collected from the top chamber. To allow this step, suction through the exit port in the top chamber is started and suction through the exit port of the bottom chamber is halted. The valve that provides suction to the top chamber is opened first, before closing the valve that provides suction to the bottom chamber.

(20) The skilled person will recognize that the arrows indicating the direction of flow of air through the system 10 induced by the action of the vacuum producer 48 can be changed by closing the open valve 72 and opening the closed valve 74. This would cause air to flow out of the top exit port 28, and through conduit 66, through the second cyclone separator vessel 70 and through conduits 62, 58, 54, 52 and 50.

EXAMPLES

Example 1

Fractionation of Various Grain Products and Compositions

(21) Application of the process to finely milled barley and oat flours yielded coarse fiber concentrates which were enriched in beta-glucan (up to 33% and 22%, respectively) and produced a fine particulate stream enriched in starch (up to 72% and 69%, respectively) and protein (up to 19% and 16%, respectively).

(22) Application of the process to canola meal (13%, total dietary fiber and 37% protein) yielded a fiber enriched coarse particle fraction (up to 53% total dietary fiber) and a fiber-reduced protein meal which was slightly enriched in protein content (up to 41% protein). Similar trends were observed with soy meal.

(23) Application of the process to pulse flours enabled the production of a fiber enriched coarse particle fraction (up to 28% total dietary fiber content) and a fine particle fraction that is enriched in starch (up to 56%).

(24) Application of the process to debranned, tempered and milled wheat grain yielded white wheat flour (extraction rate 69%) and a bran concentrate.

(25) Application of the process to debranned, tempered and milled durum wheat grain yielded durum Atta wheat flour having a composition appropriate (69% starch, 14% protein and 4% dietary fiber) for the production of Indian and Arabic style flat breads

Example 2

Comparison of Grain Product Fractionation Methods

(26) An example embodiment of the method of the present invention was employed to fractionate three different grain products (barley flour, oat flour, milled oat bran) with the aim of obtaining coarse grain fractions with increased content of beta-glucans (Table 1). The results obtained from this embodiment are compared with existing air classification technology in Table 2. The results indicate that the beta-glucan content is increased to a greater extent using the present method. The yields provided by this embodiment of the method of the present invention are superior when compared to standard air classification technology, yet require significantly less initial capital investment, and require less ongoing operational costs.

(27) In Table 1, it can be seen that beta-glucan content (a soluble dietary fiber) is increased by up to 33% for barley flour and up to 22% for oat flour and milled oat bran. Thus, an increase in soluble dietary fiber greater than 296% in barley flour, 342% in oat flour and 243% in milled oat bran may be expected when fractionating barley and oat grain materials using embodiments of the present invention. The average total dietary fiber (TDF) of barley flour, oat flour and milled oat bran ranged between 12-13%, 11-13% and 16-19%, respectively (results not presented in Table 1). Because TDF includes soluble dietary fiber (SDF) and insoluble dietary fiber (IDF), TDF increased substantially in the coarse fraction (Table 1) when fractionating barley and oat grain material using embodiments of the present invention.

(28) Similar fractionation testing carried out on pulse flour and canola meal resulted in increases in total dietary fiber greater than 200%. Data obtained from these tests is shown in Table 3.

(29) The relationships between the major factors influencing the efficiency of particle separation and auto-sieve cleaning are shown in Table 4.

(30) TABLE-US-00001 TABLE 1 Production of beta-glucan enriched fiber concentrates from barley and oat grain/material using the air-current assisted particle separation technology (ACAPS) Grain material (Type, beta-glucan content and particle size) Beta-glucan Yield and composition of fiber concentrates produced through ACAPS technology content Flour particle Yield Beta- Starch Protein Lipid Ash TDF Type (%) size (%) glucan (%) (%) (%) (%) (%) (%) Barley Flour Sample 1 6.1 0.1 100% through 400 27.4 0.5 18.1 0.1 39.2 0.6 18.5 0.1 2.1 0.0 1.6 0.0 38.1 0.1 micron screen Sample 2 7.3 0.0 100% through 400 24.8 0.4 24.1 0.2 37.5 0.3 17.9 0.0 1.9 0.0 2.0 0.0 40.2 0.3 micron screen Sample 3 9.2 0.2 100% through 400 24.3 0.2 33.4 0.3 31.8 0.2 17.2 0.2 1.6 0.1 1.8 0.1 46.8 0.6 micron screen Oat Flour Sample 1 3.5 0.0 100% through 500 19.1 0.0 15.0 0.0 42.9 0.3 19.3 0.1 8.5 0.2 1.7 0.0 26.8 0.2 micron screen Sample 2 5.2 0.1 100% through 500 18.4 0.2 19.5 0.1 39.3 0.1 18.9 0.3 9.0 0.2 1.5 0.0 31.2 0.3 micron screen Sample 3 6.3 0.1 100% through 500 17.3 0.6 21.6 0.3 34.5 0.8 19.4 0.2 10.0 0.1 1.8 0.1 33.9 0.4 micron screen Oat bran (milled) Medium Oat bran 5.5 0.2 100% through 500 35.3 0.3 13.4 0.4 37.5 0.2 20.2 0.0 8.4 0.2 2.0 0.1 30.8 0.1 (MOB) micron screen Fine oat bran 8.7 0.1 100% through 500 28.8 0.4 21.5 0.2 25.2 0.3 19.5 0.1 8.9 0.1 1.8 0.0 43.8 0.2 (FOB) micron screen Values are means of three replicates SD; *ACAPS = Air current assisted particle separation technology

(31) TABLE-US-00002 TABLE 2 Comparison of air-current assisted particle separation technology (ACAPS) and the traditional pin-milling and air-classification (PMAC) technology for the production of beta-glucan enriched fiber concentrates from barley and oat grain/material Fiber Concentrates produced through ACAPS* and PMAC* Process using embodiment of Process using traditional pin-milling and present Invention (ACAPS) air- classification technology (PMAC) Grain Material Beta- Beta-glucan Beta- Beta-glucan (Type, beta-glucan content and particle size) glucan extraction glucan extraction Beta-glucan Flour particle Yield content efficiency Yield content efficiency Type content (%) size (%) (%) (%) (%) (%) (%) Barley Flour Sample 1 6.1 0.1 100% through 400 27.4 0.5 18.1 0.1 81.4 0.2 14.1 0.2 21.2 0.3 49.0 0.2 micron screen Sample 2 7.3 0.0 100% through 400 24.8 0.4 24.1 0.2 84.9 0.1 16.2 0.4 22.4 0.2 49.7 0.3 micron screen Sample 3 9.2 0.2 100% through 400 24.3 0.2 33.4 0.3 88.2 0.2 19.0 0.6 23.1 0.1 47.7 0.2 micron screen Oat Flour Sample 1 3.5 0.0 100% through 500 19.1 0.0 15.0 0.0 75.2 0.0 11.2 0.0 16.6 0.2 53.1 0.1 micron screen Sample 2 5.2 0.1 100% through 500 18.4 0.2 19.5 0.1 73.2 0.1 12.6 0.3 20.6 0.4 49.9 0.3 micron screen Sample 3 6.3 0.1 100% through 500 17.3 0.6 21.6 0.3 59.3 0.4 12.0 0.6 21.2 0.2 40.4 0.3 micron screen Oat bran (milled) Medium Oat bran 5.5 0.2 100% through 500 35.3 0.3 13.4 0.4 86.0 0.2 20.3 0.4 14.2 0.1 52.4 0.2 (MOB) micron screen Fine oat bran 8.7 0.1 100% through 500 28.8 0.4 21.5 0.2 71.2 0.3 18.5 0.7 22.9 0.4 48.7 0.5 (FOB) micron screen Values are means of three replicates SD; *ACAPS = Air current assisted particle separation technology; PMAC = Pin-milling and air-classification technology

(32) TABLE-US-00003 TABLE 3 Yield and composition of fiber concentrates produced from pulse flour and canola meal using air-current assisted particle separation technology (ACAPS) Yield of fiber concentrate (%) Composition of the fiber concentrates produced through ACAPS technology Grain material type and particle size Produced (composition of the native flour/material given in brackets below each value) Particle size through ACAPS Starch Protein Lipid Ash TDF Type specification technology (%) (%) (%) (%) (%) Field pea flour 100% through 400 18.3 0.4 29.7 0.4 29.6 0.1 0.8 0.0 2.9 0.0 28.3 0.2 micron screen (48.2 0.6) (24.8 0.6) (0.9 0.0) (3.8 0.2) (6.5 0.6) Lentil Flour 100% through 400 20.1 0.6 28.9 0.5. 30.7 0.0 1.5 0.1 3.2 0.1 25.6 0.4 micron screen (51.3 0.8) (26.1 0.9) (1.1 0.2) (3.5 0.5) (6.2 0.3) Canola meal 100% through 400 24.2 0.3 n/a 34.2 0.2 1.2 0.1 8.7 0.1 52.9 1.5 (milled) micron screen (37.1 0.9) (3.3 0.5) (5.9 0.4) (13.3 0.7) Values are means of three replicates SD *ACAPS = Air current assisted particle separation technology

(33) TABLE-US-00004 TABLE 4 Relationships among the major factors influencing the efficiencies of particle separation (PSE) and auto sieve cleaning(ASCE) Distance between Vacuum Diameter of the hole Number of holes Velocity of the air top cover and Volume strength on the top cover (i.e. % void in through the holes sieve bed of air (Hg) (inches) the top cover) (m/s) (inches) (CFM) Vacuum strength X X X (inches Hg) Diameter of the X X holes on the top cover (inches) Number of holes X X (i.e. % void in the top cover) Velocity of air X X X through the holes (m/s) Volume of air X X X X (cubic feet per minute, CFM)
Concluding Statements

(34) Although the present invention has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the invention as understood by those skilled in the art.