High flow high capture side rails for comminutor

Abstract

An apparatus for comminuting solid waste material is provided. The apparatus includes a casing and a comminutor assembly including a plurality of cutting elements mounted on said first shaft in interspaced relationship with a plurality of second cutting elements mounted on said second shaft. The casing includes laterally opposed side rails each having a wall extending parallel to the flow direction of the liquid through the comminution chamber, a plurality of planar fins projecting outwardly of said rear wall in the direction of said stack, aligned with the flow direction of the liquid and being spaced from each other in a vertical direction to form slots therebetween, and the planar fins having a leading edge extending from the wall upstream a rearward edge, the rearward edge extending from an outermost portion of the leading edge toward the wall, and the fins have a path ratio greater than 1.55 to 1.

Claims

1. An apparatus for comminuting solid waste material comprising: a casing defining a comminution chamber and being open on opposite sides thereof for permitting the flow of liquid therethrough bearing solid waste material; said casing including an underlying base and an overlying head; a comminutor assembly including cooperating parallel first and second shredding stacks comprising: first and second parallel shafts mounted for rotation at opposite ends within said base and said head respectively; a plurality of cutting elements mounted on said first shaft in interspaced relationship with a plurality of second cutting elements mounted on said second shaft, said cutting elements being positioned between and separated in an axial direction by spacers which are coplanar with the cutting elements of the adjacent stack such that a cutting element from one stack and a spacer from the other stack form a pair of interactive shredding members, and wherein said casing includes laterally opposed side rails extending between the base and said head to the outside of respective stacks for controlling the flow of the liquid through the comminution chamber from one side to the other and for causing the solid waste to be deflected into the path of rotating cutting elements of said stacks; each of said side rails comprises: a side wall extending parallel to a flow direction of the liquid through the comminution chamber, a plurality of planar fins projecting outwardly of said side wall in the direction of said stack, aligned with the flow direction of the liquid and being spaced from each other in a vertical direction to form slots therebetween, wherein the planar fins having a leading edge extending from the side wall upstream a rearward edge, the rearward edge extending from an outermost portion of the leading edge toward the side wall, and the planar fins have a path ratio greater than 1.55 to 1.

2. The apparatus for comminuting solid waste material according to claim 1, wherein the planar fins have a path ratio ranging from 2.05-4.26 to 1.

3. The apparatus for comminuting solid waste material according to claim 1, wherein the leading edge has a rake angle, as defined with respect to a perpendicular from the side wall surface between the planar fins, within a range of 55 to 70 degrees.

4. The apparatus for comminuting solid waste material according to claim 1, wherein the leading edge of the planar fins are disposed upward in the flow direction from the cutting elements.

5. The apparatus for comminuting solid waste material according to claim 1, wherein the leading edge of the planar fins is adjacent the cutting elements.

6. The apparatus for comminuting solid waste material according to claim 4, wherein a clearance is formed between the rearward edge of the planar fins and the cutter elements, the clearance being within the range of 0.10-0.15 inches, inclusive.

7. The apparatus for comminuting solid waste material according to claim 5, wherein a clearance is formed between the leading edge of the planar fins and the cutter elements, the clearance being within the range of 0.10-0.15 inches, inclusive.

8. The apparatus for comminuting solid waste material according to claim 1, wherein the plurality of planar fins includes two rows of fins extending vertically, one row downstream in the flow direction from another row.

9. The apparatus for comminuting solid waste material according to claim 8, wherein the planar fins of the one row and aligned with the slots of the other row.

10. The apparatus for comminuting solid waste material according to claim 8, wherein the planar fins of the one row are aligned with the planar fins of the other row.

11. An apparatus for comminuting solid waste material comprising: a casing defining a comminution chamber and being open on opposite sides thereof for permitting the flow of liquid therethrough bearing solid waste material; said casing including an underlying base and an overlying head; a comminutor assembly including cooperating parallel first and second shredding stacks comprising: first and second parallel shafts mounted for rotation at opposite ends within said base and said head respectively; a plurality of cutting elements mounted on said first shaft in interspaced relationship with a plurality of second cutting elements mounted on said second shaft, said cutting elements being positioned between and separated in an axial direction by spacers which are coplanar with the cutting elements of the adjacent stack such that a cutting element from one stack and a spacer from the other stack form a pair of interactive shredding members, and wherein said casing includes laterally opposed side rails extending between the base and said head to the outside of respective stacks for controlling the flow of liquid through the comminution chamber from one side to the other and for causing the solid waste to be deflected into the path of rotating cutting elements of said stacks; each of said side rails comprises: a side wall extending parallel to the flow direction of the liquid through the comminution chamber, a plurality of planar fins projecting outwardly of said side wall in the direction of said stack, aligned with the flow direction of the liquid and being spaced from each other in a vertical direction to form slots therebetween, wherein the planar fins have a leading edge extending from the side wall upstream a rearward edge, the rearward edge extending from an outermost portion of the leading edge toward the side wall, and the leading edge has a rake angle, as defined with respect to a perpendicular from the side wall surface, within a range of 55 to 70 degrees.

12. The apparatus for comminuting solid waste material according to claim 11, wherein the planar fins have a path ratio ranging from 2.05-4.26 to 1.

13. The apparatus for comminuting solid waste material according to claim 11, wherein the leading edge of the planar fins are disposed upward in the flow direction from the cutting elements.

14. The apparatus for comminuting solid waste material according to claim 11, wherein the leading edge of the planar fins is adjacent the cutting elements.

15. The apparatus for comminuting solid waste material according to claim 13, wherein a clearance is formed between the rearward edge of the planar fins and the cutter elements, the clearance being within the range of 0.10-0.15 inches, inclusive.

16. The apparatus for comminuting solid waste material according to claim 14, wherein a clearance is formed between the leading edge of the planar fins and the cutter elements, the clearance being within the range of 0.10-0.15 inches, inclusive.

17. The apparatus for comminuting solid waste material according to claim 11, wherein the plurality of fins includes two rows of planar fins extending vertically, one row downstream in the flow direction from another row.

18. The apparatus for comminuting solid waste material according to claim 17, wherein the planar fins of the one row and aligned with the slots of the other row.

19. The apparatus for comminuting solid waste material according to claim 17, wherein the planar fins of the one row and aligned with the planar fins of the other row.

20. An apparatus for comminuting solid waste material comprising: a casing defining a comminution chamber and being open on opposite sides thereof for permitting the flow of liquid therethrough bearing solid waste material; said casing including an underlying base and an overlying head; a comminutor assembly including cooperating parallel first and second shredding stacks comprising: first and second parallel shafts mounted for rotation at opposite ends within said base and said head respectively; a plurality of cutting elements mounted on said first shaft in interspaced relationship with a plurality of second cutting elements mounted on said second shaft, said cutting elements being positioned between and separated in an axial direction by spacers which are coplanar with the cutting elements of the adjacent stack such that a cutting element from one stack and a spacer from the other stack form a pair of interactive shredding members, and wherein said casing includes laterally opposed side rails extending between the base and said head to the outside of respective stacks for controlling the flow of liquid through the comminution chamber from one side to the other and for causing the solid waste to be deflected into the path of rotating cutting elements of said stacks; each of said side rails comprises: a side wall extending parallel to the flow direction of the liquid through the comminution chamber, a plurality of planar fins projecting outwardly of said side wall in the direction of said stack, aligned with the flow direction of the liquid and being spaced from each other in a vertical direction to form slots therebetween, wherein a clearance in the vertical direction between the slots is greater at slots disposed above slots disposed at a lower part of the side wall.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other features and aspects of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

(2) FIG. 1 is a comminutor in the related art;

(3) FIG. 2A is a side rail in the related art and FIG. 2B shows a segment of that side rail;

(4) FIG. 3A shows a flow direction view and FIG. 3B shows a orthogonal view of a segment of the side rail of FIG. 2B;

(5) FIG. 4A shows a top view of a related art fin on a side rail and FIG. 4B shows a perspective view of the same;

(6) FIGS. 5A and 5B show a top view and a perspective view of a fin on a side rail in accord with an embodiment of the present application;

(7) FIG. 6 shows a comparison between a fin according to an embodiment of the application (left side) compared to a related art fin (right side);

(8) FIG. 7 shows various fin shapes in accord with embodiments of the present application;

(9) FIG. 8 shows an embodiment with fins upstream of the cutter elements;

(10) FIG. 9 shows an embodiment with fins located downstream of the leading edge of the cutter elements;

(11) FIG. 10 shows an embodiment with fins located in an upstream and downstream position in a vertically staggered manner;

(12) FIG. 11 shows an embodiment with fins located in an upstream and downstream position in a vertically aligned manner;

(13) FIG. 12 is a table showing test results;

(14) FIG. 13 shows flow length path ratios of the fins shown in FIGS. 15 and 16;

(15) FIG. 14 shows flow length path ratios of the fins shown in FIGS. 17 and 18;

(16) FIG. 15 shows a prior art fin;

(17) FIG. 16 shows a half shield shaped fin in accord with an embodiment;

(18) FIG. 17 shows a cheese wedge shaped fin in accord with an embodiment;

(19) FIG. 18 shows a triangular shaped fin in accord with an embodiment;

(20) FIG. 19 shows a progressive side rail in accord with another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

(21) The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.

(22) An aspect of this application is to improve on existing designs by providing a side rail structure that directs more solids into the cutting elements (prevents bypass of solids) while reducing the stapling of solids on the rail structure. As shown in FIGS. 5A, 5B and 8, the new design consists of horizontal fins and slots, a highly-raked leading surface, shortened length of flow passage (FIG. 6) and smaller clearance (FIG. 6) between cutters and fins, resulting in higher flow capacity, improved capture effectiveness and minimized stapling.

(23) The highly-raked leading surface 230 and abbreviated trailing surface 250 create a fin 200 geometry where there is a shorter flow path tangent 220 to the cutter stacks 26, 28 and longer flow path away the cutter stacks. (FIGS. 15 and 16 show the difference in flow paths between old and new, and FIGS. 13-17 show a comparison between the paths.) The rake angle 225 can range from 55 to 75 degrees. In the embodiments shown in FIGS. 17 and 18, the rake angle is 61.5 degrees in the embodiments showing a constant rake angle. This geometry creates a length-of-path differential between the fins 200 and as a consequence a pressure gradient is developed between the rails 20 and the cutter stacks 26, 28. That is, due to this structure, the pressure in each slot 110 is lowest adjacent to the cutter stacks 26, 28 and highest away from the cutter stacks 26, 28. As a result, there is a lateral flow toward to the cutters of each stack (see FIGS. 5A and 5B). This lateral flow results in dramatically-reduced stapling and improves feeding of material into the cutter stacks 26, 28 (see FIG. 12).

(24) The new geometry reduces the overall surface area of each fin A lower average pressure drop through the comminutor promotes improved hydraulic capacity (see and compare FIG. 4A-5C). Because of the higher hydraulic efficiency, the gap 215 between the side rail and the cutter stack can be decreased as compared to the gap 210 in the related art, further reducing bypass (see FIG. 6).

(25) There are several embodiments of fin shapes that provides the benefits described above. FIG. 7 shows variants of leading edge 230 and trailing edge 250 designs that can provide the flow benefits described herein. The leading edge 230 can be a straight edge, a convex curve or a concave curve. In the case of a straight leading edge, the rake angle 225 is constant. However, the rake angle 225 need not be constant. For example, in the case of a convex curve shape, the angle can begin rather steep (55 degrees) and decrease to 75 degrees (the angle being measured from a perpendicular to the side wall). By contrast, in the case of a concave curve, the rake angle begins as at a maximum value of 90 degrees (e.g., 0 degrees from the flow direction) and decreases toward the cutter stack.

(26) In addition, the trailing edges 250 can take on a variety of shapes in combination with any of the leading edge variants to provide the flow advantages described above. Similar to the leading edge variates, the leading edge 250 can take a straight shape, a convex shape or a concave shape as shown in FIG. 7.

(27) In another aspect of the application, the fins can be positioned in various locations to improve the function of the cutter stacks 26, 28. In one embodiment as shown in FIG. 8, the fins 200 are arranged upstream of the cutter stacks 26, 28 and overlapping the front leading edge of the cutter stacks when viewed from a direction orthogonal to the direction of the flow. When positioned in this location, the trailing edge 250 of the fins 200 is placed within a predetermined clearance of the cutter elements (0.10-0.15). Alternatively, as shown in FIG. 9, the fins may be placed downstream of the leading edge of the cutter stacks. When positioned in this location, the leading edge 230 is placed within a predetermined clearance of the cutter elements (0.10-0.15).

(28) FIGS. 10 and 11 show other embodiments where fins 200 are placed both in the upstream position of FIG. 8 and the downstream position of FIG. 9. In FIG. 10, the upstream fins downstream fins are placed in a staggered manner. That is, the fins are staggered vertically so that the slot 210 of an upstream fin corresponds to a downstream fin and vice versa. Alternatively, as shown in FIG. 11, the upstream fins and the downstream fins may be placed so as to be aligned vertically. When positioned in this manner, the corresponding fins and slots are aligned in the horizontal direction.

(29) FIG. 12 shows the result of testing to determine how the new designs responded to stapling effects using 1 wide strips. The test was conducted by feeding 1 wide strips into a flow stream and counting how many of the strips stapled (wrapped) the fins and how many passed through the comminutor. The comparative production side rail using the fin of FIG. 15 realized stapling at a rate of 60% under the test conditions. In comparison, the cheese wedge fin of FIG. 17 and the half shield fin of FIG. 16 experienced no stapling under the testing conditions.

(30) FIGS. 13-14 show the path length ratios (amount of reduction in length per unit distance from the side rail side of the fin) of the fins of FIGS. 15-18. As is evidenced by these tables, the path length ratios decrease at a faster rate and begin decrease at locations closer to the side rail as compared to the conventional fins. The path ratio (path length ratio) is calculated by taking the maximum flow path length and dividing it by the minimum flow path length (Max FPL/Min. FPL). The maximum flow path length is defined as the longest parallel flow vector across the fins of the side rail from the leading edge to the trailing edge. (Sta.0 in FIG. 15, 16, 17, 18). The minimum flow path length is defined as the shortest parallel flow vector across the fins of the side rail from the leading edge to the trailing edge, that is tangent to the adjacent cutter outside diameter (OD) (Sta.9 in FIG. 16, 17, 18,) (Sta.8 FIG. 15). Flow paths inside of the tangent of the cutter OD can be assumed obvious that the particle would contact the cutter. Creating too large a ratio could have an adverse effect on flow capacity performance by creating unwanted surface friction.

(31) FIG. 19 is shows an embodiment according to another aspect of the application. This progressive side rail design, progressively improves flow performance as the waste stream's water level rises by increasing the open area of the side rail 20. The lower zone 300 of the side rail uses a 50% open area to capture solids and pass flow, as the water level rises to next zone 310 of the side, openings between the fins are increased to 66%. The final zone 320 of the side rail use a 75% to 100% open area to gain optimum flow performance. The progressive side rail improves the form of the solution to provide increased flow capacity without severely sacrificing solids capture performance.