SHREDDER

FIELD OF THE DISCLOSED TECHNIQUE

The disclosed technique relates to shredders in general, and to methods and systems for shredding paper or plastic containers, in particular.

BACKGROUND OF THE DISCLOSED TECHNIQUE

Since the tremendous rise in consumer products during the last century, municipal authorities are forced to deal with the problem of solid waste management. Solid waste is daily transported to local waste sites and landfills, and incinerated by a combustion process which introduces vast amounts of carbon dioxide and other toxic substances to the atmosphere, thereby damaging the ozone layer and increasing the temperature of the Earth. A large portion of this solid waste is beverage plastic bottles, which have to be disposed of in some way. Plastic bottles can be either recycled for production of new plastic articles, or converted to usable energy. Environmentally concerned bodies in the US have lobbied a large number of bills to the House, which have turned into acts of Congress. The principal federal law governing management of solid and hazardous waste is the Solid Waste Disposal Act which was passed in 1965, and amended eight times since, as the Resource Conservation and Recovery Act (RCRA).

Many devices are in use today, to enable the consumers and municipal authorities to comply with federal and state laws concerning solid waste management. One of these types of devices is a shredder which either cuts or shears plastic bottles one at a time. The shredded material can then be delivered to a waste management plant for further

treatment. Such a shredder generally includes a set of rotating cutting elements which rotate on a shaft, and interleave with a matching set of stationary cutting elements. In this device, the thin wall plastic bottle is essentially sheared between every pair of rotating cutting element and a stationary cutting element. Another example is a device which includes two sets of rotating cutting disks, each having a plurality of cutting teeth (similar to a gear). The two sets of rotating cutting disks rotate in opposite directions and mesh together, like a gear set, and as the plastic bottle is fed to the rotating cutting disks, the thin wall material of the plastic bottle is caught between opposite cutting teeth, and cut into pieces.

Devices for shredding paper are known in the art. One of these is known as the cross-cut or confetti-cut shredder, which uses two contra-rotating drums to cut rectangular, parallelogram, or diamond-shaped shreds. Another type is the strip-cut shredder which uses rotating knives to cut narrow strips as long as the original sheet of paper. A further type is the pierce and tear shredder which uses a plurality of rotating blades which pierce the paper and then tear it apart.

US Patent No. 4,923,126 issued to Lodovico et al., and entitled "Machine for Cutting Disposable Containers", is directed to a machine which includes a feeding section, a cutting section and a dispersing section. The feeding section includes two feeding shafts. Each of the feeding shafts includes three paddles having a plurality of teeth. The cutting section includes a first cutting shaft, a second cutting shaft, a set of first cutting wheels, a set of second cutting wheels, a set of first combers, a set of second combers, a first pair of rods, a second pair of rods, a set of first pair of rod spacers, a set of second pair of rod spacers, a set of first spacer rings and a set of second spacer rings. Each of the first cutting wheels includes a set of first cutting teeth. Each of the second cutting wheels includes a set of second cutting teeth. The dispersion section includes a rotating shaft and a pair of dispersion paddles.

The set of first cutting wheels, the set of first combers and the set of first spacer rings are alternately located on the first cutting shaft. The set of second cutting wheels, the set of second combers and the set of second spacer rings are alternately located on the second cutting shaft. Each of the spacer rings of the set of first spacer rings separates the adjacent cutting wheels of the set of the first cutting wheels. Each of the spacer rings of the set of second spacer rings separates the adjacent cutting wheels of the set of the second cutting wheels. Each of the cutting wheels of the set of first cutting wheels is separated by an adjacent cutting wheel of the set of second cutting wheels. Each of the rod spacers of the set of first pair of rod spacers is located on the first pair of rods. Each of the rod spacers of the set of second pair of rod spacers is located on the second pair of rods.

The rod spacers of the first set of rod spacers separate between the cutting wheel of the set of first cutting wheels and the adjacent comber of the set of first combers. The rod spacers of the second set of rod spacers separate between the cutting wheel of the set of second cutting wheels and the adjacent comber of the set of second combers. The distance between the first cutting shaft and the second cutting shaft is less than a root diameter of the cutting wheels of the set of first cutting wheels and of the set of second cutting wheels.

The feeding shafts rotate in opposite directions, to enable the paddles to feed a thin wall material of a bottle to the cutting section. The cutting shafts rotate in opposite directions, to enable the set of first cutting teeth and the set of second cutting teeth to entrap the thin wall material and to cut the thin wall material to small pieces. The rotating shaft rotates the dispersion paddles to disperse the small pieces.

US Patent No. 6,533,200 B2 issued to Paper and entitled "Arrangement of Seats for Knives on a Cutting Shaft in a Shredding Machine", describes a shredding machine for shredding wood, metal parts, plastic material, garbage and other waste materials. The shredding

machine includes a cutting shaft, a cutting plate and an electromotor. The cutting shaft is octagonal or polygonal in shape and includes a plurality of cutting tools, which are attached to the cutting shaft in a thread-like manner. In the following description, a first edge refers to a flat surface of the cutting shaft, and a second edge refers to another flat surface adjacent to the first edge. The cutting shaft includes a plurality of recesses. Each of the cutting tools is located within the respective recess, and fastened to the cutting shaft. Each set of the recesses extends from the first edge to the second edge, following in the direction of rotation of the cutting shaft. Each of the recesses includes a base and a contact surface. Each of the bases deepens uniformly relative to a cutting shaft surface of the cutting shaft, over the entire longitudinal extension of the cutting shaft. Each of the bases forms a right angle with the respective contact shaft surface. The height of the contact shaft surface between the second edge and the base corresponds to a diagonal extension of the respective cutting tool. The cutting tools engage with the cutting plate, while the cutting shaft rotates relative to the cutting plate by the action of the electromotor.

US Patent No. 6,520,435 B1 issued to Robinson and entitled "Plastic Bottle Shredding Assembly", describes a housing which includes a rotatable shaft, a motor, a loading door, a shelf, and a rod. The rotatable shaft includes a plurality of shredding heads. Each of the shredding heads includes a cutting line which extends radially outward from the respective shredding head, to cut a plastic bottle when the shredding heads are rotated. The rod includes a plurality of tines, and a handle portion. The handle portion extends outwardly from the housing. The motor rotates the rotatable shaft. The rod is slidably located in a pair of slots of the housing, to provide movement of the rod in a direction parallel to the shelf, toward and away from the rotatable shaft. The tines are spaced such that each of the shredding heads is aligned with an associated gap between an adjacent pair of tines, for

preventing the shredding heads to contact the tines. A user opens the loading door and inserts the plastic bottle into an interior space of the housing. The plastic bottle rests on the shelf. The user activates the motor to rotate the rotatable shaft, and pushes and rotates the rod by the handle portion, to force the plastic bottle toward the rotatable shaft, as the rotatable shaft shreds the plastic bottle.

US Patent No. 4,871 ,118 issued to Maloney and entitled "Machine for Densifying Plastic Containers and the like", is directed to a machine for shredding plastic bottles. The machine includes a feeder, a shredder, a motor, a motor pulley, a first chain drive and a second chain drive. The feeder includes a first shaft, a first pulley, a plurality of radial vanes, and a plurality of scraper blades. The shredder includes a second shaft, a second pulley, a plurality of rotary shredder elements, a plurality of stationary shredding elements, and a plurality of spacer disks. The radial vanes and the first pulley are connected with the first shaft. The rotary shredder elements and the second pulley are connected with the second shaft. The motor pulley is connected with the motor. The first pulley is connected with the motor pulley by the first chain drive. The second pulley is connected with the motor pulley by the second chain drive. Each of the rotary shredder elements includes a central hub from which extends a knife. Each of the knives includes a pair of cutting edges oppositely spaced 180 degrees apart. The knives are angularly spaced about the second shaft, at 90 degrees to each other. The spacer disks separate the rotary shredder elements. An anvil is formed by the stationary shredding elements spaced apart a distance from one another, greater than the thickness of the rotary shredding elements, wherein the rotary shredding elements pass between the stationary shredding elements, in close tolerance, to provide a cooperative cutting action.

Each of the scraper blades is stationary and is located in a respective slot between every respective pair of the radial vanes. When the motor operates, the first shaft rotates and the radial vanes pull a

plurality of plastic bottles toward the shredder. The motor rotates the second shaft to provide a scissoring action at the anvil, for shredding the plastic bottles.

US Patent No. 4,678,126 issued to Prentice et al., and entitled "Shredder", describes a shredder which shreds material by the cutting action of an anvil means. The anvil means includes an arbor shaft, a plurality of grating members, a plurality of tooth bearing bodies and a plurality of spacers. Each of the tooth bearing bodies includes a pair of teeth, located opposite to a central portion of the tooth bearing body. The grating members are stationary. The spacers are mounted on the arbor shaft. The tooth bearing bodies are mounted on the arbor shaft such that they form a helical tooth pattern, whereby adjacent tooth bearing bodies are angularly displaced by 16.5 degrees. The spacers provide spacing between every two adjacent tooth bearing bodies. The tooth bearing bodies and the grating members are arranged, such that there is between 1/32 inch and 1/2 inch clearance between every tooth bearing body and the adjacent grating member.

SUMMARY OF THE DISCLOSED TECHNIQUE

It is an object of the disclosed technique to provide a novel method and system for shredding an object.

In accordance with the disclosed technique, there is thus provided a device for shredding an object. The device employs a shear assembly for shredding the object. The shear assembly includes a plurality of stationary cutters firmly coupled with a housing, and a rotary cutting assembly firmly coupled with a rotating shaft. The stationary cutters are located on a substantially flat stationary plane. Each of the stationary cutters has a stationary cutting edge. Each of the stationary cutting edges is defined by a stationary cutting edge profile as projected on the flat stationary plane. The stationary cutting edges are located along a substantially straight line.

The rotating shaft is coupled with the housing. A rotation axis of the rotating shaft is substantially parallel with the substantially flat stationary plane, and substantially parallel with the substantially straight line. A rotary cutting assembly axis of the rotary cutting assembly is substantially identical with the rotation axis. The rotary cutting assembly includes a plurality of rotary cutting edges divided among at least one rotary cutter. Each of the rotary cutting edges is defined by a rotary cutting edge profile as projected on a substantially flat rotary plane. The rotation axis is located on the substantially flat rotary plane. The rotary cutting edge profile is substantially complementary to the stationary cutting edge profile. The rotary cutting edge profile is defined by a rotary edge profile axis lying on a substantially flat rotary edge profile plane.

The rotation axis is substantially normal to the substantially flat rotary edge profile plane. Each adjacent ones of the rotary cutting edges, is shifted relative to one another, along respective substantially flat rotary edge profile planes, such that the rotary cutting edges align with respective ones of the stationary cutting edges, at different times. Each stationary cutter point on a respective stationary cutter, is associated with a

respective maximum distance from a center of a respective rotary cutting edge. The respective stationary cutter point is associated with a respective set of rotary cutter points located on the respective rotary cutting edge. Each rotary cutter point of the respective set of rotary cutter points, is associated with a respective distance from the center. Each of the respective distance is equal to or less than the maximum distance. The respective set of rotary cutter points defines a respective rotary edge profile axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technique will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: ' Figure 1 is a schematic illustration of a perspective view of a cutting assembly of a shredder, for shredding an object, constructed and operative according to an embodiment of the disclosed technique;

Figure 2A is a schematic illustration of a side view of a pair of rotary cutter and a respective stationary cutter of the cutting assembly of Figure 1 , when a rotary cutting edge of the rotary cutter initially makes contact with a stationary cutting edge of the stationary cutter;

Figure 2B is a schematic illustration of the side view of Figure 2A, in an advanced stage of rotation of the rotary cutter past the stationary cutter; Figure 2C is a schematic illustration of the side view of Figure

2A, in a further advanced stage of rotation of the rotary cutter past the stationary cutter;

Figure 3A is a schematic illustration of a detail view in perspective of the pair of the rotary cutting edge and the stationary cutting edge of Figure 2A;

Figure 3B is a schematic illustration of a detail view in perspective of the pair of the rotary cutting edge and the stationary cutting edge of Figure 2B;

Figure 3C is a schematic illustration of a detail view in perspective of the pair of the rotary cutting edge and the stationary cutting edge of Figure 3C;

Figure 4A is a schematic illustration of a front view of a rotary cutter of the cutting assembly of Figure 1 , constructed and operative according to another embodiment of the disclosed technique; Figure 4B is a schematic illustration of a cross section of the rotary cutter of Figure 4A ;

Figure 5 is a schematic illustration of a detail of a rotary cutting edge of the rotary cutter of Figure 4B;

Figure 6 is a schematic illustration of another detail of the rotary cutting edge of the rotary cutter of Figure 4B, constructed and operative according to a further embodiment of the disclosed technique;

Figure 7 is a schematic illustration of a further detail of the rotary cutting edge of the rotary cutter of Figure 4B, constructed and operative according to another embodiment of the disclosed technique;

Figure 8 is a schematic illustration of a top view of the cutting assembly of Figure 1 ;

Figure 9 is a schematic illustration of a top view of a cutting assembly of a shredder, constructed and operative according to a further embodiment of the disclosed technique;

Figure 10 is a schematic illustration of a top view of a pair of a rotary cutter, and a stationary cutter of a cutting assembly of a shredder, constructed and operative according to another embodiment of the disclosed technique;

Figure 11 is a schematic illustration of a top view of a pair of a rotary cutter, and a stationary cutter of a cutting assembly of a shredder, constructed and operative according to a further embodiment of the disclosed technique;

Figure 12A is a schematic illustration of a top view of a rotary cutter of a cutting assembly of a shredder, constructed and operative according to another embodiment of the disclosed technique; Figure 12B is a schematic illustration of a cross section of the rotary cutter of Figure 12A;

Figure 13 is a schematic illustration of the rotary cutter of Figure 12A, together with a matching stationary cutter; and

Figure 14 is a schematic illustration of a perspective view of the cutting assembly of a shredder, constructed and operative according to a further embodiment of the disclosed technique.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The disclosed technique overcomes the disadvantages of the prior art by employing a set of rotary cutters rotating relative to a set of stationary cutters, whose cutting profile is complementary to that of each of the rotary cutters. Each pair of a rotary cutter and a stationary cutter, shreds a plastic bottle or paper, by shearing a thin wall of the plastic bottle or the paper. Each cutting edge of the rotary cutters is shifted relative to that of an adjacent rotary cutter, such that the rotary cutter and the stationary cutter pairs, each shear a small portion of the paper or the thin wall of the plastic bottle, at different times. Each point on a stationary cutting edge of each of the stationary cutters, is associated with a maximum radius from a rotation axis of the respective rotary cutter. The radii of each set of points on a rotary cutting edge of the respective rotary cutter, which correspond the respective point on the stationary cutting edge, are equal to or less than the respective maximum radius. Each set of these points on the rotary cutting edge, defines a cutting profile axis, located on a plane perpendicular to an axis of rotation of the rotary cutters. This cutting profile axis can be either in the form of a curved line or a straight line. The cutting profile of each of the rotary cutters is in form of a recess, and the cutting profile of each of the stationary cutters is in form of a protrusion complementary to that of each of the rotary cutters. Alternatively, the cutting profile of each of the stationary cutters is in form of a protrusion, and that of each of the stationary cutters is in form of a recess. The terms "normal", "perpendicular", "parallel" and "flat", herein below, in the context of lines, axes, planes, orientations, and flatness, refers to substantially normal, perpendicular, parallel, and flat, respectively.

Reference is now made to Figure 1 , which is a schematic illustration of a perspective view of a cutting assembly of a shredder, generally referenced 104, for shredding an object, constructed and

operative according to an embodiment of the disclosed technique. Cutting assembly 104 includes a power transmission assembly 106, and a motor 108. Cutting assembly 104, power transmission assembly 106, and motor 108 are located within a housing (not shown). Cutting assembly 104 includes a plurality of rotary cutters 122, a plurality of stationary cutters 124, a shaft 126, cages 128 and 130, a plate 132 and bearings 134 and 136. Each of rotary cutters 122 is in form of a disk having one or more rotary cutting edges 138 on a periphery thereof. Each of stationary cutters 124 includes a stationary cutting edge 140 at an edge thereof. Each of rotary cutting edges 138 is defined by a rotary cutting edge profile complementary to a stationary cutting profile of each of stationary cutting edges 140, as described herein below. Power transmission assembly 106 (i.e., electric power transmission assembly) includes a shaft gear 142, an idler 144, and a motor gear 146. Alternatively, the power transmission assembly can include a belt and a pair of pulleys, to transmit power from the motor to the shaft to which the rotary cutters are coupled.

The housing is made of a rigid material, such as a metal casting, and the like. Each of cages 128 and 130 is in form of a rigid elongated plate. Plate 132 is coupled with cages 128 and 130. Bearings 134 and 136 are mounted in cages 128 and 130, respectively. Shaft 126 is assembled into bearings 134 and 136. Rotary cutters 122 are firmly coupled with shaft 126. Each of rotary cutters 122 is defined by a respective flat rotary edge profile plane (not shown), which is perpendicular to a rotation axis 156 of shaft 126. Rotary cutters 122 are mounted on shaft 126, such that each of rotary cutting edges 138 is shifted relative to an adjacent rotary cutting edge 138, along a respective flat rotary edge profile plane.

The angular shift of rotary cutting edges 138, relative to one another, has a random value (i.e., different between every pair of adjacent rotary cutting edges 138). Alternatively, this angular shift is of a predetermined value, as described herein below in connection with Figure

19. Each of stationary cutters 124 is firmly coupled with plate 132, along a

flat stationary plane (not shown), such that all stationary cutting edges 140 are located along a straight line (not shown).

Shaft gear 142 is coupled with shaft 126. Motor gear 146 is coupled with motor 108. Idler 144 meshes with shaft gear 142 and with motor gear 146, thereby transmitting the power from motor 108 to shaft 126. Shaft 126 rotates about rotation axis 156 in a direction referenced by an arrow 158.

In order to shred an object, such as paper, a plastic bottle, optic media, magnetic media, and the like, the user turns on a switch (not shown) to commence the shredding operation. Motor 108 rotates rotary cutters 122 in direction 158, through power transmission assembly 106. The paper or the plastic bottle is caught between a stationary cutting edge 140 of each of stationary cutters 124, and a rotary cutting edge 138 of a respective rotary cutter 122, to be shredded by a shearing action. The shredded particles are collected in a waste collection pan (not shown) located within the housing. The user removes the waste collection pan from the housing in order to dump out the shredded particles. Alternatively, the shredder can include a waste basket (not shown) for collecting the shredded particles. The waste basket is made for example, from Polyethylene Terephthalate (PET), and the like, or of a material substantially the same as the one which the shredded object is made of.

Further alternatively, the cutting assembly can include a sensor, such as a microswitch, proximity switch, magnetic switch, and the like, which senses the presence of the object, which the user feeds into the shredder, and thus turns on the motor. When the sensor stops detecting the presence of the object, the sensor turns off the motor, thereby automatically ending the shredding operation, without user intervention.

It is noted that in a shredder whose cutters shred a plastic bottle simultaneously, the motor which powers the shredder, experiences large momentary peaks of cutting load, which are well beyond the average load and close to the maximum load on the motor. The instantaneous power

consumed by this motor is close to the maximum power which the motor can provide. However, rotary cutting edges 138 of cutting assembly 104 are shifted relative to one another, and each pair of rotary cutting edges 138 and stationary cutting edges 140, make contact at a time, different than that of an adjacent pair. Therefore, motor 108 continuously experiences relatively small cutting loads, which are the same or smaller than the average load. Hence, the shredder can employ a motor which consumes much less power, weighs much less and costs less, than in the case of a shredder in which all cutters shred the plastic at the same time. Alternatively, the power transmission assembly can be a manual power transmission assembly, in order to enable the user to operate the cutting assembly manually, for example, by turning a handle, employing a foot pedal, and the like. It is noted that additionally, cutting assembly 104 can shred optic and magnetic media, such as compact disk (CD), low gage copper, aluminum, and the like, as well as paper and plastics.

Further alternatively, the rotary cutters can be coupled directly with a pair of gears, similar to shaft gear 142 at the two ends thereof, instead to the shaft. Each of these gears can be supported by three or more idlers, similar to idler 144. The idlers can be coupled to the two cages, and at least one idler at each end of the rotary cutters, can be rotated by the motor. The rotation of the idlers causes the two gears, and thus the rotary cutters to rotate.

Reference is now made to Figures 2A, 2B, 2C, 3A, 3B, and 3C. Figure 2A is a schematic illustration of a side view of a pair of rotary cutter and a respective stationary cutter of the cutting assembly of Figure 1 , when a rotary cutting edge of the rotary cutter initially makes contact with a stationary cutting edge of the stationary cutter. Figure 2B is a schematic illustration of the side view of Figure 2A, in an advanced stage of rotation of the rotary cutter past the stationary cutter. Figure 2C, is a schematic illustration of the side view of Figure 2A, in a further advanced stage of rotation of the rotary cutter past the stationary cutter. Figure 3A is a

schematic illustration of a detail view in perspective of the pair of the rotary cutting edge and the stationary cutting edge of Figure 2A. Figure 3B is a schematic illustration of a detail view in perspective of the pair of the rotary cutting edge and the stationary cutting edge of Figure 2B. Figure 3C is a schematic illustration of a detail view in perspective of the pair of the rotary cutting edge and the stationary cutting edge of Figure 3C.

With reference to Figures 2A and 3A, stationary cutter 124 includes a stationary cutting edge 340. Stationary cutting edge 340 includes a convex stationary cutting edge profile 342, which is complementary to a concave rotary cutting edge profile 212, as described herein below in connection with Figure 4A. Convex stationary cutting edge profile 342 is in form of a portion 344 of a circle (not shown), which operates as a stationary shearing edge 346. Portion 344 intersects faces 348 and 350 of stationary cutter 124, at endpoints 352 and 354, respectively.

With reference to Figures 2A and 3A, as a rotary cutter 200B rotates in a direction 158 toward stationary cutter 124, endpoints 218 and 220 make contact with endpoints 352 and 354, respectively. With further rotation of rotary cutter 200B in direction 158, as in Figures 3B and 3C, the points of contact of stationary shearing edge 346 with rotary cutting edge 200B ₁ approach a point 356 located on a flat rotary edge profile plane 206, as described herein below in connection with Figure 4A. As these points of contact approach point 356, stationary cutter 124 and rotary cutter 200B, shear the object. A stationary cutter point 358 on stationary shearing edge 346 is associated with a plurality of rotary cutting points 228A, 228B, 228C, and 228D on concave rotary cutting edge profile 212. Rotary cutting points 228A, 228B, 228C, and 228D define a rotary edge profile axis 226, as described herein below in connection with Figure 5. Each of rotary cutting edges 200A, 200B, 200C, and 200D, and each stationary shearing edge

346 can be hardened (e.g., by heat treating, case hardening), in order to prolong the life of cutting assembly 104.

Reference is now made to Figures 4A, 4B, 5, 6, and 7. Figure 4A is a schematic illustration of a front view (view I) of a rotary cutter of the cutting assembly of Figure 1 , constructed and operative according to another embodiment of the disclosed technique. Figure 4B is a schematic illustration of a cross section of the rotary cutter of Figure 4A (cross section II-II). Figure 5 is a schematic illustration of a detail of a rotary cutting edge of the rotary cutter of Figure 4B (detail III). Figure 6 is a schematic illustration of another detail of the rotary cutting edge of the rotary cutter of Figure 4B, constructed and operative according to a further embodiment of the disclosed technique. Figure 7 is a schematic illustration of a further detail of the rotary cutting edge of the rotary cutter of Figure 4B, constructed and operative according to another embodiment of the disclosed technique.

With reference to Figures 4A, 4B, and 5, rotary cutter 122 includes a plurality of rotary cutting edges 200A, 200B, 200C, and 200D, and a bore 202 at a center 204 thereof. Shaft 126 passes through bore 202, and shaft 126 is rigidly locked with rotary cutter 122, for example, by an adhesive, set screw, key, and the like. Hence, rotation axis 156 passes through center 204. The term "flat rotary edge profile plane" herein below, referenced 206, refers to a plane which passes through approximately half a thickness A of rotary cutter 122, and which is normal to rotation axis 156. Hence, flat rotary edge profile plane 206 is a plane which is perpendicular to the drawing sheet of Figure 4A. Figures 4B, 5, and 6, are illustrations which are projected on flat rotary edge profile plane 206. The term "flat rotary plane" herein below, refers to a plane which passes through rotation axis 156, and which lies on the drawing sheet of Figure 4A. The flat rotary plane which is perpendicular to the drawing sheets of either of Figures 4B, 5, and 6, is referenced 208.

Rotary cutter 122 is in form of a disk made of a material which is harder than the material from which the plastic bottle or the paper is made of, such as metal (e.g., machined steel, machined stainless steel, cast iron, steel casting), ceramic, masonry, stone, and the like, of a radius r-i and thickness A. Rotary cutting edges 200A, 200B, 200C, and 200D are machined on rotary cutter 122, equilaterally, on a periphery 210 thereof. Alternatively, the rotary cutting edges are spaced apart on the periphery of the rotary cutter, at different angular locations. Each of rotary cutting edges 200A, 200B, 200C, and 200D includes a concave rotary cutting edge profile 212 machined therein. A projection of concave rotary cutting edge profile 212 on flat rotary plane 208 (Figure 4A), is in form of a portion

214 of a circle (not shown) having a center 216. Endpoints 218 and 220 of portion 214, intersect faces 222 and 224, respectively, of rotary cutter 122.

Rotary edge profile axis 226 (Figure 3A), of concave rotary cutting edge profile 212, is defined by rotary cutting points 228A, 228B ₁ 228C, and 228D (Figure 3A). Rotary edge profile axis 226 is a curved line (e.g., a portion of a circle - not shown), having a radius r ₂ greater than /- _? . Each set of rotary cutting points similar to rotary cutting points 228A, 228B, 228C, and 228D, define a different rotary edge profile axis similar to rotary edge profile axis 226. Rotary cutting points 228A, 228B, 228C, and 228D are located at radii r ₃ , r ₄ , r ₅ , and r _δ , where r ₃ > r ₄ > r ₅ > r ₆ . Rotary cutting points 228A, 228B, 228C, and 228D correspond to stationary cutter point 358 (Figure 3A) on stationary shearing edge 346, and stationary cutter point 358 is associated with a radius r _maN from center 204, wherein 'max > '3 > ^; 4 > >'$ > ⁷ 6 ^•

A cross section of each of rotary cutting edges 200A, 200B, 200C, and 200D is in form of a beak (cross section II-II in Figure 5), being defined by two curved lines 230 and 232. Curved lines 230 and 232 emanate from points 234 and 236, respectively, on periphery 210, toward

direction of rotation 158, and meet at a vertex 238, to form a sharp end of the beak. A radius r ₇ of vertex 238 from center 204 is greater than r ₂ .

With reference to Figure 6, a rotary cutting edge 260 includes a concave rotary cutting edge profile 262, similar to concave rotary cutting edge profile 212, as described herein above, with the exception that a rotary edge profile axis 264 thereof, is in form of a straight line. A center (not shown) through which rotary edge profile axis 264 passes is seen as a plurality of sequential points 266A, 266B, 266C, and 266D, on a flat rotary edge profile plane similar to flat rotary edge profile plane 206 in Figure 5 (i.e., on section II of Figure 4A). Distances of points 266A, 266B, 266C, and 266D from a center 268 of a rotary cutter 270, are referenced di, d ₂ , d ₃ , and d ₄ , and the distance of a stationary cutter point on a stationary shearing edge similar to stationary cutter point 358 (Figure 3), is referenced <i _mas , where d _max > d _λ > d ₂ > J ₃ > d ₄ . Rotary edge profile axis 264 is sloped at a positive angle θ relative to a horizontal axis 274, in a direction opposite to direction 272, wherein horizontal axis 274 is normal to a flat rotary plane 276 similar to flat rotary plane 208 (Figure 5).

With reference to Figure 7, a rotary cutting edge 300 includes a concave rotary cutting edge profile 302, whose rotary edge profile axis 304 is in form of a straight line, sloped at an angle β similar to rotary edge profile axis 264 as described herein above in connection with Figure 6. A cross section of concave rotary cutting edge profile 302 projected on a flat rotary edge profile plane (not shown), similar to flat rotary edge profile plane 206 of Figure 4A (i.e., cross section II-II), is in form of a rectangle defined by two vertical sides 306 and 308 which emanate from points 310 and 312, respectively, of a periphery 314 of rotary cutter 300, and a horizontal side 316 which connects endpoints 318 and 320 of vertical sides 306 and 308, respectively.

Reference is now made to Figure 8, which is a schematic illustration of a top view (view IV) of the cutting assembly of Figure 1. A

plurality of substantially identical rotary cutters 122 are firmly coupled with shaft 126, such that rotary cutting edges 138 of adjacent rotary cutters 122 are shifted relative to one another, in a random manner. As shaft 126 rotates, each of rotary cutting edges 138 makes contact with a respective stationary cutting edge 140, in a random manner, thereby enabling cutting assembly 104 to shear the thin walls of plastic bottle 148.

Reference is now made to Figure 9, which is a schematic illustration of a top view (view IV) of a cutting assembly, generally referenced 390, of a shredder, constructed and operative according to a further embodiment of the disclosed technique. Cutting assembly 390 includes a rotary cutter 392, a plurality of stationary cutters 394, and a shaft 396. Rotary cutter 392 includes a plurality of rotary cutting edges

398. Each of stationary cutters 394 includes a stationary cutting edge 400.

Rotary cutter 392 is in form of a drum made of a material which is harder than the material from which plastic bottle 148 is made of, such as metal (e.g., machined steel, machined stainless steel, cast iron, steel casting), ceramic, masonry, stone, and the like. Rotary cutter 392 can be firmly assembled onto shaft 396. Alternatively, rotary cutter 392 and shaft 396 can be made of the same stock, and necessary machining performed on that stock, in order to provide operation of cutting assembly 390.

Each of rotary cutting edges 398 has a concave rotary cutting edge profile 402 similar to concave rotary cutting edge profile 212 (Figure 4A), as described herein above. Each of stationary cutting edges 400 includes a convex stationary cutting edge profile 404, which is complementary to each of concave rotary cutting edge profiles 402. Concave rotary cutting edge profile 402 is similar to concave rotary cutting edge profile 212, as described herein above in connection with Figure 4A. Each of stationary cutters 394 is similar to stationary cutter 124 (Figure 1 ), as described herein above. Rotary cutting edges 398 are arranged on a surface (not shown) of rotary cutter 392 in a random manner, such that adjacent rotary cutting

edges 398 make contact with respective stationary cutting edges 400, at ^' different times. Rotary cutting edges 398 can be machined on rotary cutter 392, as a plurality of protrusions on the surface of rotary cutter 392.

Reference is now made to Figure 10, which is a schematic illustration of a top view of a pair of a rotary cutter, generally referenced 430, and a stationary cutter generally referenced 432, of a cutting assembly of a shredder, constructed and operative according to another embodiment of the disclosed technique. Rotary cutter 430 includes a rotary cutting edge 434. Stationary cutter 432 includes a stationary cutting edge 436. Rotary cutting edge 434 includes a concave rotary cutting edge profile 438. Stationary cutting edge 436 includes a convex stationary cutting edge profile 440, complementary to concave rotary cutting edge profile 438. Concave rotary cutting edge profile 438 has all the properties of concave rotary cutting edge profile 212, as described herein above in connection with Figures 2A, 3, 4, and 5, except that a contour thereof is in form of a triangle, instead of a portion of a circle.

Reference is now made to Figure 11 , which is a schematic illustration of a top view of a pair of a rotary cutter, generally referenced 460, and a stationary cutter generally referenced 462, of a cutting assembly of a shredder, constructed and operative according to a further embodiment of the disclosed technique. Each of rotary cutter 460 and stationary cutter 462 have all the properties of rotary cutter 122 and stationary cutter 124, respectively, as described herein above in connection with Figures 2, 3, 4, and 5, except that a contour of a concave rotary cutting edge profile 464 of a rotary cutting edge 466 of rotary cutter 460, is in form of a curve, instead of a portion of a circle.

Reference is now made to Figures 12A, 12B, and 13. Figure 12A is a schematic illustration of a top view of a rotary cutter, generally referenced 490, of a cutting assembly of a shredder, constructed and operative according to another embodiment of the disclosed technique. Figure 12B is a schematic illustration of a cross section (cross section

V-V), of the rotary cutter of Figure 12A. Figure 13 is a schematic illustration of the rotary cutter of Figure 12A, together with a matching stationary cutter, generally referenced 496.

With reference to Figures 12A, and 12B, rotary cutter 490 includes a rotary cutting edge 492. Rotary cutting edge 492 includes a convex rotary cutting edge profile 494, which has all the properties of concave rotary cutting edge profile 212, as described herein above in connection with Figures 2A, 3, 4, and 5, except that convex rotary cutting edge profile 494 is in form of a convex body instead of a concave body. With reference to Figure 13, stationary cutter 496 includes a stationary cutting edge 498. Stationary cutting edge 498 includes a concave stationary cutting edge profile 500, which is complementary to convex rotary cutting edge profile 494.

Reference is now made to Figure 14, which is a schematic illustration of a perspective view of the cutting assembly, generally referenced 620, of a shredder, constructed and operative according to a further embodiment of the disclosed technique. Cutting assembly 620 includes a plurality of rotary cutters 622 and a shaft 624. Cutting assembly 620 is similar to cutting assembly 104, as described herein above in connection with Figure 1 , except that adjacent rotary cutters 622 are shifted by a constant value, instead of a random value as in cutting assembly 104.

It will be appreciated by persons skilled in the art that the disclosed technique is not limited to what has been particularly shown and described hereinabove. Rather the scope of the disclosed technique is defined only by the claims, which follow.