GB1588558A - Fixer cutting element - Google Patents

Description

(54) IMPROVED FIXED CUTTING ELEMENT (71) We, DOW BADISCHE CANA DA LIMITED, a corporation organized under the laws of Canada of P.O. Box 3156, Station C., Ottawa, Ontario, Canada K1Y 4J4 do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the comminution and granulation of solid material. It relates more particularly to a comminuting or granulating apparatus for polymeric and like material.

Solid material such as polymeric material is generally transported and sold in comminuted or granulated form. One major advantage therein is that the material in such a form can be readily fed into extrusion and like devices for subsequent forming operations. Moreover, the material in such a form can be easily measured by volume, and can be transported short distances by pressure or suction through conduits.

Of a large number of devices for cutting solid material such as polymeric material into very small pieces, the most satisfactory appear to be those comprising at least one fixed cutting element or bed knife positoned around the cutting circle of a rotary cutting element, which is often provided with a plurality of blades. Examples of such devices are those specified and depicted in the following U.S. patents: 3,661,332; 3,790,093; and 3,897,016. Notwithstanding the efficacy of this type of device, it is often found wanting in one very significant aspect, that is, the fixed cutting elements or bed knives are usually short lived. These bed knives, which are fabricated from construction metals and alloys of all kinds, as well as from very hard material such as ceramics, usually have to be removed for sharpening, or even complete replacement, after only a few days of use.Furthermore, the interruptions in operation caused by such sharpenings and replacements result in significant reductions in daily output.

In accordance with this invention there is provided a cutting element, adapted fdr use in an apparatus for comminuting polymeric and the like material, comprising a rigid polyhedron which has a substantially rectangular slot partially penetrating therein from the intersection of a first and second face thereof and extending along an edge of the polyhedron, the first face of the polyhedron and a line perpendicular to the longitudinal cross-sectional axis of the slot and passing through the intersection of the two faces of the polyhedron, forming an angle of between 20 and 70 degress and an insert fabricated from a ceramic material which is positioned within the slot and which substantially conforms to the configuration thereof, the insert being adhesively bonded to all surfaces of the slot, the surfaces of the insert projecting from the slot being ground so that such surfaces are substantially flush with the corresponding surfaces of the top and front faces of the polyhedron.

It has been found of especial advantage if, in the present invention, the angle formed by the intersection of the first face of the polyhedron and a line perpendicular to the longitudinal cross-sectional axis of the slot and passing through the intersection of the two faces of the polyhedron is between 40 and 50 degrees, most advantageously 45 degrees.

In contrast to the prior constructions, therefore, the cutting element in accordance with this invention has an advantage in that it has a substantially longer useful life which may be in the order of from many months to several years, the need for sharpening thereof being reduced.

The invention is further described hereinafter, by way of examply only, with reference to the accompanying drawings, in which: Figure I is a sectional view schematically illustrating a fixed cutting element in accordance with the present invention Figure 2 is a perspective view schematically illustrating the same fixed element shown in section in Figure 1; and Figure 3 is a schematic illustration of an apparatus for comminuting or granulating polymeric and like material employing a standard rotary cutting element cooperating with a fixed cutting element in accordance with the present invention.

Figure 1 illustrates a fixed cutting element (10) which comprises a polyhedron (11), having a top, bottom, front, back, and 2 side faces. Polyhedron (11) is quadrangular in cross-section, and is illustrated as being rectangular although other quadrangular cross-sectional configurations are useful, such as a square. Polyhedron (11) is fabricated from a rigid material of construction selected from commonly employed tool metals and alloys, such as hard tool stainless steel. To facilitate the positioning and securing of fixed cutting element (10) in proximity to the rotary cutting element with which it co-operates, and a hole (13) is drilled through the body of polyhedron (11) from top to bottom in proximity to each side face thereof, and bolts (not shown) are inserted through each of the holes (13).

Partially penetrating into polyhedron (11) is a slot (not visible) of substantially rectangular cross-section, which slot is subsequently substantially completely occupied by insert (12) having a substantially similar cross-sectional configuration. This slot penetrates into the polyhedron from the intersection of the top and front faces thereof and extends along the length of polyhedron (11) from one side face to the other side face. The exact extent of penetration of the slot into polyhedron (11) is not critical, the degree of ingress varying between wide limits with satisfactory results.

Advantageously the distance of penetration of the slot into polyhedron (11) is at least substantially equal to the height of the front face of polyhedron (11).

However, the angle of penetration of the slot into polyhedron (11) is critical. The slot should be positioned so that an angle a of between about 20 and 70 degrees is formed by the intersection of the top face of polyhedron (11) and a line perpendicular to the longitudinal cross-sectional axis of the slot and passing through the intersection of the top and front faces of the polyhedron (11). It has been found to be particularly advantageous if angle a is between about 40 and 50 degrees, especially 45 degrees.

Positioned within the slot and conforming to the configuration thereof is insert (12), which is formed from a hard material such as one of the common ceramic or refractory materials well known and often employed in the art. Such are quite hard substances having a very low coefficient of friction, an example of which is "Henium," which is marketed by the Heany Industrial Ceramics Corporation of New Haven, Connecticut.

Before the positioning of insert (12) in the slot, any oil or other surface impurities are removed from the slot and insert (12) by the application thereto of a cleaning solvent such as acetone. This cleaning treatment is followed by evenly applying a thin layer of a standard refractory or ceramic adhesive (such as CTA 11, marketed by the 3M Company of Minneapolis Minnesota) to the entire surface of both the slot and insert (12), after which insert (12) is inserted into the slot and worked back and forth therein, in order to ensure the removal of any air bubbles and to facilitate uniform coverage and optimum bonding. After a curing at room temperature for a period of at least 24 hours, the surfaces of insert (12) which project from the slot are ground so that they are essentially contiguous with the corresponding surfaces of the top and front faces of polyhedron (11).Fixed cutting element (10) is now ready for positioning to cooperate with a rotary cutting element in an apparatus for comminuting or granulating polymeric and like material, an example of which is now set forth below.

Referring to Figure 3, there is shown a granulating apparatus (100), which includes a carrier means (14) supporting rotary cutting element (16), which is mounted for rotation thereon in proximity to inlet (15), through which polymeric and like material is fed, preferably in the form of rope-like strands or "spaghetti." A modified fixed cutting element (10) according to the present invention is positioned and securely mounted on carrier means (14) as shown, in proximity to rotary cutting element (16).

The free ends of a plurality of blades (17) of rotary cutting element (16) are separated from insert (12) of fixed cutting element (10) by a gap chosen in view of the degree of granulation or comminution desired. The drive means for rotary cutting element (16) includes an electric motor (18), also mounted on carrier means (14), and driving through a pulley belt transmission (19) a shaft which drives rotary cutting element (16) through pulley and belt transmissions (20) and (21).Strands of polymeric or like material, which have been introduced into inlet (15) and have passed through the gap between plural blades (17) of rotating rotary cutting element (16) and the exterior surface of insert (12) of modified fixed cutting element (10) according to the present invention, are sheared into granules or small particles, which are confined in hood (22) and directed thereby into a collection means (not shown) for accumulation and ultimate disposition.

WHAT WE CLAIM IS: 1. A cutting element, adapted for use in an apparatus for cominuting polymeric and the like material, comprising a rigid polyhedron which has a substantially rectangular slot partially penetrating therein from the intersection of a first and second face thereof and extending along an edge of the polyhedron, the first face of the polyhedron and a line perpendicular to the longitudinal cross-sectional axis of the slot and passing through the intersection of the two faces of the polyhedron forming an angle of between 20 and 70 degrees, and an insert fabricated from a ceramic material which is positioned within the slot and which substantially conforms to the configuration thereof, the insert being adhesively bonded to all surfaces of the slot, the surfaces of the insert projecting from the slot being ground so that such surfaces are substantially flush with the corresponding surfaces of the first and second faces of the polyhedron.

2. A cutting element as claimed in claim 1, in which the angle formed by the intersection of the first face of the polyhedron and the line perpendicular to the longitudinal cross-sectional axis of the slot and passing through the intersecton of the two faces of polyhedron is between 40 and 50 degrees.

3. A cutting element substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. and directed thereby into a collection means (not shown) for accumulation and ultimate disposition. WHAT WE CLAIM IS:

1. A cutting element, adapted for use in an apparatus for cominuting polymeric and the like material, comprising a rigid polyhedron which has a substantially rectangular slot partially penetrating therein from the intersection of a first and second face thereof and extending along an edge of the polyhedron, the first face of the polyhedron and a line perpendicular to the longitudinal cross-sectional axis of the slot and passing through the intersection of the two faces of the polyhedron forming an angle of between 20 and 70 degrees, and an insert fabricated from a ceramic material which is positioned within the slot and which substantially conforms to the configuration thereof, the insert being adhesively bonded to all surfaces of the slot, the surfaces of the insert projecting from the slot being ground so that such surfaces are substantially flush with the corresponding surfaces of the first and second faces of the polyhedron.

2. A cutting element as claimed in claim 1, in which the angle formed by the intersection of the first face of the polyhedron and the line perpendicular to the longitudinal cross-sectional axis of the slot and passing through the intersecton of the two faces of polyhedron is between 40 and 50 degrees.

3. A cutting element substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.