FIELD OF THE INVENTION

[0001] This invention is generally directed to a wood shredding machine for reducing waste timber, logs, lumber, tree limbs, roots and other wood matter into mulch. The invention has particular application to a portable, on-site wood shredding machine that may be easily hauled to various locations to reduce wood matter to usable mulch at the work site.

BACKGROUND

[0002] In view of the increasing problem of waste disposal, it has become paramount that various waste products be processed into usable or recycled materials. To this end, landfills in many areas have begun rejecting the disposal of various types of materials including, for example, grass clippings, pruning debris, timber cuttings, and the like. Special processing centers are available for reducing organic fibrous materials including, for example, tree branches, tree trunks, tree roots, discarded lumber, and the like, into a shredded material which may be utilized as mulch. Many local townships, however, have ordinances that prohibit the production or storage of mulch because of its strong odors. Once the mulch has been produced, it often remains in large repositories that ferment and produce strong odors that pervade the immediate surroundings. These large mulch repositories may also pose the hazard of a difficult-to- extinguish fire. As a result, resident complaints complicate business for mulch producers and not all areas have the processing centers to convert wood waste to useful mulch products.

[0003] Also, the use of special processing centers requires that materials be hauled to the processing site. This is not always practical or cost effective, especially when dealing with

individuals that do not have access to machinery and vehicles that are adequate for hauling such waste materials. Generally, for ease of transport, wood matter is converted into wood chips on- site and transported by truck to a processing location for shredding the wood chips into mulch.

[0004] In addition, the large, industrial sized mulching machinery such as tub grinders, wood hogs, or horizontal grinders that are used to produce mulch at the processing centers is extremely large and expensive, often costing between $250,000 - $500,000. The various mulching machines convert even large wood matter into mulch by shredding the wood matter into longitudinal strips of wood fiber. This increases the surface area that is exposed to the action of bacteria and fungi that degrade the cellulose and lignin that constitutes the bulk of wood matter. Often, the mulching process involves multiple passes through a mulching machine to achieve fine shredded mulch, particularly if the starting material consists of large logs rather than wood chips. The resulting mulch is then distributed to customers, which adds to the cost of the process. The process of wood waste removal, transport, processing into mulch, and redistribution is an inefficient and expensive process. As a result, there is a need for wood shredding machines that can be easily moved to various job sites to convert wood waste into usable mulch on-site..

[0005] Furthermore, removal of organic waste such as grass clippings, pruning debris, and timber cuttings robs the soil of essential nutrients. The action of bacteria and fungi that are normally found in dead plant matter, such as leaves, grass clippings, timber cuttings, and shrub trimmings, leads to degradation of the wood waste into soil that replenishes and enriches the top soil. Undesirably, most of the wood waste that is generated on suburban residential properties is removed to processing centers by property owners, gardeners, landscapers, and tree services. The removal of organic matter breaks the normal cycle of soil utilization, organic matter degradation, and soil replenishment. Balance between these processes provides the basis of a normal ecology in wooded environments. Disruption of this balance leaves soil depleted of organic nutrients and more vulnerable to erosion. As a result, plants are less well nourished and

become more vulnerable to parasites and diseases. To rectify this situation as well as beautify their property, property owners typically purchase mulch to replenish the top soil on their property. In view of the foregoing, it is desirable to have a wood shredding machine that can be transported to residential or other types of property, and can convert wood matter into usable mulch on-site.

[0006] Numerous inventions that are directed to providing mobile chipping machines have been described. Conventional wood chippers have been developed to reduce tree limbs and branches to wood chips. U.S. Patent No. 5,005,620 to Morey discloses a wood chipping apparatus having a rotatable drum carrying knives angularly spaced about its circumferential wall. These chippers only reduce, wood matter to large wood particles because the wood chippers use cutting mechanisms instead of shredding mechanisms. Chipping eliminates environmental concerns associated with burning wood waste since the chips may be used as a landscaping element. Unfortunately, wood chips, while reduced in size, are still too large to support the timely degrading action of bacteria and fungi that is necessary for proper soil formation. If wood chips are used instead of proper shredded mulch, the wood chips degrade into soil too slowly and are subject to weathering processes (i.e., drying and bleaching) by sunlight. This leads to a graying of the wood chips that property owners find unattractive. As a result, property owners replace the wood chips before the wood chips have a chance to decay further. The conventional wood chipping machines are deficient in that the wood chips they produce are unable to support the timely action of bacteria and fungi and the ultimate transformation of the processed product into top soil without further processing.

[0007] Other chipper devices have been developed to further reduce wood chips. For example, U.S. Patent No. 4,824,034 to Baker discloses a wood chipper and/or shredder device. However, to achieve a desired particle size, a screen must be employed, which retains material not capable of passing therethrough for further chipping. The use of such screening is

undesirable since clogging of the device may occur. Also, additional time is required for further reducing the material to enable it to pass through the screen.

[0008] Also, chipper/shredder devices have been developed to first reduce wood matter into wood chips and then further reduce wood chips into finer particles. U.S. Patent No. 5,390,862 to Eglin discloses a portable commercial scale chipper/grinder for first chipping and then grinding tree limbs. The Eglin device first cuts the limbs into small wood chips that are then fed into a subsequent chamber that has flailing hammers to further reduce the size of the wood chips. The problem with this type of design is that it chips first, and then hammers. In this type of arrangement, it is likely that some of the wood chips will escape the hammering process owing to their shape or size, thereby creating a final product that contains wood chips that are not amenable to the action of soil-forming bacteria. Some chipper/shredder machines of this type, as disclosed in U.S. ^' Pat. No. 4,824,034 to Baker, employ a screen to prevent wood chips from being integrated into the final product, but these screens are subject to clogging problems. Therefore, it is desirable to have a simple shredding machine for reducing large wood matter into usable mulch.

[0009] A number of small scale wood shredders are commercially available that are effective for processing yard waste, such as grass cutting, leaves and twigs, into a mulch-like product that will support the action of bacteria to form soil. U.S. Patent No. 5,267,697 to Holecz discloses an apparatus for shredding yard waste material. While these units are satisfactory for comminuting yard waste materials having stems or stalks up to about an inch in diameter, they are not designed for disposing larger wood matter, such as large tree trunks, limbs or branches that result from larger scale operations of tree services on a property.

[0010] In addition, there have been some attempts at providing portable wood shredders that process large wood matter into mulch. U.S. Patent 5,402,950, U.S. Patent 5,265,811, and U.S. Patents 5,379,951 and Re. 36,486 are such examples. The final mulch product of these machines is limited by the cutting elements and the single comminuting process they use. These

machines employ cutting elements and comminuting processes that produce shredded fibers of varying lengths that are not regarded as usable mulch because of the inferior aesthetics and biodegradability of the resultant mulch. Usable mulch is a shredded wood product having sufficient surface area exposed to sustain the action of soil forming bacteria and fungi and a substantially uniform fibrous strand length, thereby facilitating the timely degradation of the shredded wood product into soil and resulting in a more aesthetic appearance.

[0011] U.S. Patent 4,355,670 to Ohrberg et al. employs auxiliary fragmenting means to further reduce particle size in large scale land clearing operations for commercial forestry. But the arrangement of the auxiliary fragmenting means with respect to the primary fragmenting means is inefficient. The arrangement relies on the primary fragmenting means to act on wood waste that is on the ground and to fling the fragmented wood in a forward and upward direction and eventually into the path of the auxiliary fragmenting means. This arrangement requires additional structure to block and deflect the flying fragmented wood toward the auxiliary fragmenting means that is located above and behind the primary fragmenting means. Some fragmented wood is likely to be flung away from the auxiliary fragmenting means or is likely to fall to the ground. As a result, such an arrangement cannot ensure that the fragmented wood created by the primary fragmenting means is further reduced by the auxiliary fragmenting means. Moreover, the apparatus exemplified in Ohrberg et al is not suitable for reduction of wood waste on home sites in suburbia, owing to the size and complexity of the mobile, self -feeding machinery. Residential properties in suburbia and elsewhere, require the use of wood waste reduction machinery that is more compatible with the safety requirements of these locations, owing to their smaller size and the proximal location of home and other structures. In particular, more precise operator controlled feeding of wood waste into a stationary wood reduction device reduces the chance of damage to structures on or near the work site by the mobile self-feeding wood waste reduction machinery. '

[0012] Therefore, it is desirable to have a portable wood shredder that addresses the aforementioned problems in the prior art.

SUMMARY

[0013] The present invention relates to a portable, on-site wood shredder that is capable of processing large wood matter into usable mulch for property owners, hi one preferred embodiment, the wood shredder is mounted onto a trailer and can be easily transported to residential or other types of property, where the wood shredder can process large bulk wood matter, such as branches and cut or whole tree trunks, and deliver the homeowner usable mulch. Furthermore, the wood shredder of the present invention offers a simple shredding mechanism that does not require the wood matter to first pass through a wood chipping mechanism. The present invention shreds large wood matter to produce a usable mulch product that is amenable to degradation by bacteria and fungi to ultimately form new soil to replenish depleted top soil in areas where the mulch is distributed. Usable mulch is a shredded wood product having sufficient surface area exposed to sustain the action of soil forming bacteria and fungi and a substantially uniform fibrous strand length, thereby facilitating the timely degradation of the shredded wood product into soil and resulting in a more aesthetic appearance.

[0014] The portable wood shredder in accordance with one embodiment of the present invention includes a feed chute, a shredding chamber and a discharge chute. The feed chute, shredding chamber, and discharge chute are mounted onto a trailer along with an engine that powers the shredding mechanism and cutting mechanism.

[0015] The feed chute includes a feed system comprising means for conveying wood matter in a wood chipper or shredder, such as feed rollers, hi a preferred embodiment, the feed rollers are spring loaded, vertically arranged opposite each other, and counter-rotating. The spring loaded feed rollers are displaced with respect to each other to accommodate different size wood matter, while maintaining proper pressure to convey the wood matter. Wood matter that is

introduced into the feed chute is conveyed into the shredding chamber by the feed system. In another aspect of the invention, the wood can be fed into the feed chute by a winch or hoist that helps lift larger pieces of wood and feed it into the feed chamber. .

[0016] The shredding chamber includes a shredding mechanism having shredding teeth and a floor positioned in close proximity below the shredding mechanism that provides resistance against the shredding action of the shredding teeth and ensures proper shredding of the wood matter. In one embodiment, the shredding mechanism includes a shredding drum having an outer surface fitted with shredding teeth extending radially from the outer surface of the shredding drum, hi another embodiment, the shredding mechanism includes a plurality of discs, each fitted with shredding teeth extending radially from the outer edge of the discs and each arranged in a parallel relationship on a shaft, hi another embodiment, the plurality of blades can be arranged in a space-apart relationship of the shaft.

[0017] In another embodiment, the shredding chamber further includes a cutting mechanism, placed following the shredding mechanism, having cutting blades to further reduce the size of the shredded wood to produce a mulch with more uniform fibrous strand lengths, hi a preferred embodiment, the cutting mechanism is arranged in series with the shredding mechanism along a linear path, such that both the shredding and cutting mechanisms act against the floor of the shredding chamber, hi one preferred embodiment, the axis of rotation of the shredding mechanism and the axis of rotation of the cutting mechanism are aligned parallel to each other along a common horizontal plane to facilitate feeding and processing of the wood matter. Some wood shredding operations produce long fibrous strands that are aesthetically unappealing. Therefore, in this embodiment the cutting blades further reduce long fibrous strands into smaller strands, thereby producing a usable mulch in a single pass of the wood matter through the shredding chamber.

[0018] hi another embodiment, the shredding mechanism can be disengaged from its normal shredding position and lifted to a position above the wood processing path. The

advantage of this embodiment is that it allows the present invention to perform as a shredder or a chipper at the operator's discretion. .

[0019] The force of the spinning shredding and cutting mechanisms propel the shredded material into the discharge chute. Preferably, the discharge chute includes an enclosure that is funneled toward its discharge end to better direct the propelled mulch. Preferably, the shredding and cutting mechanisms spin with sufficient speed to propel the shredded material completely through the discharge chute. Preferably, the discharge chute has substantially smooth surfaces and tapers gradually from the shredding chamber to the discharge end. Alternatively, a conveying mechanism, such as a blower, vacuum or conveyor belt may be used to assist with the movement of the shredded material through the discharge chute.

[0020] Among others, the portable wood shredder of the present invention includes one or more of the following advantages:

1) the portable wood shredder is smaller than industrial sized shredding equipment found at processing centers and can therefore be transported to temporary work sites, such as residential or other types of property;

2) the portable wood shredder is substantially cheaper than conventional shredding equipment, such as tub grinders, wood hogs and horizontal grinders that are found at processing centers; the price of the embodiments of the portable wood shredder are estimated to be in the range of currently marketed wood chippers, which are approximately one fifth of even lower priced tub grinders;

3) the portable wood shredder eliminates the need to haul bulk wood matter from a work site to a processing center;

4) the portable wood shredder eliminates the need to haul wood chips from a work site to a processing center;

5) the portable wood shredder processes wood waste so that it can be re-sold to the customer as usable mulch at the original work site without having the additional steps of removal, transport, processing and redistribution;

6) the portable wood shredder circumvents many municipal ordinances that prohibit the production of wood mulch at a central and permanent processing center; and

7) the portable wood shredder provides an economical and efficient means of restoring the normal balance between soil depletion and replenishment in the "urban forest."

[0021] The present invention satisfies a consumer need for removing unwanted wood waste, by providing wanted mulch for aesthetic and soil enrichment needs, and an ecological need for recycling organic material. Other options exist for removing and recycling wood waste, but are not as efficient or cost effective. For example, the portable wood shredder in accordance with the present invention is more effective than wood chippers, because the usable mulch produced decomposes faster than the larger wood chips and does not gray in the sunlight like wood chips. Also, the present the wood shredder in accordance with present invention is more efficient than conventional wood shredders, because it can produce, in a single pass, a usable mulch that is substantially uniform in size, readily biodegradable, and has a more aesthetic appearance. The wood shredder of the present invention is an improvement over the existing art because it provides a portable wood shredder that can be taken on-site, process large wood matter, and produce usable mulch that is aesthetically appealing and more readily biodegradable.

[0022] Additional features of the present invention are set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Fig. 1 is a perspective view of an exemplary embodiment of the portable, on-site wood shredder;

[0024] Fig. 2 is a side view of the embodiment of Fig. 1 with the side panel removed, illustrating the interior of the exemplary wood shredder;

[0025] Fig. 3 is a top view of the embodiment of Fig. 1 with the top panel removed illustrating the interior of the portable, on-site wood shredder;

[0026] Fig. 4 is another exemplary embodiment of a wood shredder having a shredding mechanism capable of moving out of the wood processing path, leaving just a cutting mechanism in the wood processing path;

[0027] Fig. 5 is another exemplary embodiment of a wood shredder having only a wood shredding mechanism and no wood cutting mechanism;

[0028] Figs. 6A and 6B are side and top views, respectively, of an exemplary shredding mechanism;

[0029] Figs. 7A and 7B are side and top views, respectively, of another exemplary embodiment of the shredding mechanism;

[0030] Figs. 8A and 8B are side and top views, respectively, of an exemplary cutting

drum;

[0031] Fig. 9A depicts wood chips produced by the cutting action of a conventional wood chipper;

[0032] Fig. 9B depicts shredded wood produced by the shredding action of a shredding mechanism that consists of shredding teeth mounted on a drum-like rotating mechanism; and

[0033] Fig. 9C depicts the usable mulch produced by the combination of the shredding mechanism and cutting mechanism of a portable on-site wood shredder in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0034] The present invention is directed to a portable wood shredder that is capable of processing large wood matter into usable mulch for property owners on-site. The wood shredder is portable, meaning that it can be easily transported to residential or other types of property where large wood matter, such as branches and cut or whole tree trunks, is present. For example, i in one preferred embodiment, the wood shredder is mounted onto a trailer. Once on-site, the machine can process wood matter, including large wood matter, on-site and leave the property owner usable mulch. Usable mulch is a shredded wood product having sufficient surface area exposed to sustain the action of soil forming bacteria and fungi and a substantially uniform fibrous strand length, thereby facilitating the timely degradation of the shredded wood product into soil and resulting in a more aesthetic appearance.

[0035] Furthermore, in one embodiment the wood shredder includes a simple shredding mechanism that does not require the prerequisite step of chipping large wood matter into wood chips. The portable wood shredder shreds large wood matter, such as branches and cut or whole tree trunks, to produce a usable mulch product that is amenable to degradation by bacteria to ultimately form and replenish soil.

[0036] Fig. 1 shows an exemplary embodiment of the portable, on-site wood shredder 1. As shown in Fig. 1, the wood shedder 1 includes a feed chute 5, a shredding chamber 6 and a discharge chute 7. As shown in the embodiment of Fig. 1, the wood shredder 1 can be mounted on a trailer 2 that can be hitched to a truck or automobile (not shown) for easy transportation to different job sites. The wood shredder 1 also includes a drive mechanism 4 enclosed by a housing 11 and an engine 3.

[0037] Fig. 2 is a side view and Fig. 3 is a top view of the exemplary embodiment of Fig.l with the side and top panels, respectively, removed to show the interior of the feed chute 5, the shredding chamber 6, the discharge chute 7 and the drive mechanism 4. The feed chute 5,

the shredding chamber 6 and the discharge chute 7 can be formed as a single unit or as separate units that are connected to one another.

[0038] The feed chute 5 includes a housing 15 and a feed mechanism 8. The housing 15 includes a top panel 16, a bottom panel 17, and two side panels 18. As shown, an opening 19 is provided in the front of the feed chute 5 for allowing wood matter to be fed into the wood shredder 1. The feed chute 5 may include one or more guides 20 for directing wood matter toward feed mechanism 8.

[0039] As shown in Figs. 2 and 3, the feed mechanism 8 includes two feed rollers 21, 22. As shown, the feed rollers 21, 22 are arranged vertically opposite one another. As shown, the top feed roller 21 is spring loaded and is displaced to accommodate different size wood matter introduced into the feed chute 5. Alternatively, the bottom feed roller 22, or both the top 21 and the bottom feed roller 22, may be spring loaded to allow various size wood matter to be fed into the shredding chamber 6.

[0040] In one embodiment, the feed rollers 21, 22 act in a counter-rotating manner to feed wood matter from the feed chute 5 into the shredding chamber 6. Preferably, the feed rollers 21, 22 feed the wood matter into the shredding chamber 6 at a constant feed rate. Having the feed rollers 21, 22 rotate at a constant rate while conveying wood matter into the shredding chamber 6 helps to achieve more consistent particle size. The feed rollers 21, _. 22 may be powered by a separate power source, or preferably, they are driven by engine 3.

[0041] As shown in Figs. 2 and 3 the shredding chamber 6 is enclosed by a housing 23 in communication with feed chute housing 15. As shown, the shredding chamber housing 23 includes a top panel 24, a bottom panel 25, and two side panels 26. The shredding chamber 6 receives the wood matter from the feed chute 5 via the feed mechanism 8. The bottom panel 25 of the shredding chamber 6 includes a floor 27, preferably formed by replaceable cutting plates or anvils (not shown).

[0042] As shown in the embodiment of Figs. 2 and 3, a shredding mechanism 9 is rotatably mounted on an axle 31 within the shredding chamber housing 23. As shown, the shredding mechanism 9 includes shredding teeth 30. Preferably, the shredding teeth 30 are replaceable, allowing for easy replacement if they are worn or damaged. The shredding mechanism 9 is positioned in close proximity to the shredding chamber floor 27 (or the cutting plates or anvils), creating only a small gap or clearance in order to produce a greater shredding force and to ensure proper shredding of the wood matter. In one embodiment, the gap or clearance is about 0.5,- 20 mm, measured from the distal end of the. shredding teeth 30 to the surface of the shredding chamber floor 27 (or the cutting plates or anvils). In .a preferred embodiment, the gap or clearance is in the range of about 0.5 — 4 mm, measured from the distal end of the shredding teeth 30 to the surface of the shredding chamber floor 27 (or the cutting plates or anvils). In a more preferred embodiment, the gap or clearance is about 1 mm. The cutting plates and/or anvils (not shown) are also preferably replaceable because the shredding action of the shredding teeth 30 against the cutting plates and/or anvils will typically cause wear.

[0043] Fig. 4 shows another embodiment of the wood shredder 1 that is substantially similar to the embodiment of Figs. 1, 2 and 3, but where the shredding mechanism 9 can be disengaged from its normal shredding position and lifted to a position above the wood processing path. The advantage of this embodiment is that it allows the present invention to perform as a shredder or a chipper at the operator's discretion, thereby serving the diverse needs of various land clearing operations.

[0044] hi the embodiment illustrated by Fig. 4, the shredding mechanism 9 moves out of its normal shredding position along a curved track 32. Preferably, the curvature of the track 32 that guides the upward displacement of the shredding mechanism 9 is sufficient to maintain a fixed relative distance between the axles 31, 35 of the shredding 9 and cutting mechanisms 10. Preferably, a fixed relative distance is maintained between the axles 31, 35 of the shredding 9 and cutting mechanisms 10 so that they can maintain proper tension in the drive belt 14.

Alternatively, axle 31 may be disengaged when the shredder mechanism 9 is lifted out of the wood processing path.

[0045] As shown in the embodiments of Figs. 2, 3 and 4, the cutting mechanism 10 is positioned following the shredding mechanism 9. Preferably, the cutting mechanism 10 is positioned along a linear path relative to the shredding mechanism 9 such that both the shredding mechanism 9 and cutting mechanism 10 act against the floor 27 of the shredding chamber 6. hi one preferred embodiment, the axis of rotation of the shredding mechanism 9 and the axis of rotation of the cutting mechanism 10 are aligned along a common horizontal plane to facilitate feeding and processing of the wood matter. As shown, the cutting mechanism 10 can be a cutting drum 33. The cutting mechanism 10 of the present invention is not limited to a cutting drum 33 of the embodiment of Figs. 2, 3 and 4, and it is contemplated that the cutting drum 33 may be any other conventional cutting mechanism known to those skilled in the art.

[0046] The cutting mechanism 10 is rotatably mounted on an axle 35 within the housing 23 of the shredding chamber 6. Some wood shredding operations produce long fibrous strands that are aesthetically unappealing. Therefore, the cutting mechanism 10, fitted with cutting blades 34, can be used to further reduce long fibrous strands exiting the shredding mechanism 9 into smaller pieces or particles. The cutting mechanism 10 is fixed in close proximity to the shredding chamber floor 27 (or the cutting plates and/or anvils), creating only a small gap or clearance in order to ensure proper cutting of the shredded wood matter. Preferably, the gap or clearance between the distal ends of the cutting blades and the floor 27 is of the same order or size as described for the shredding mechanism 9.

[0047] Fig. 5 shows another embodiment of the wood shredder 1 that is substantially similar to the embodiments of Figs. 1, 2, 3 and 4, but where only a shredding mechanism 9 is used and there is no cutting mechanism 10 included in the wood shredder 1. This embodiment provides a simplified design with fewer parts that will be cheaper than the shredding-cutting embodiments illustrated by Figs. 1, 2, 3 and 4. This embodiment can be used for many

applications where the aesthetic requirement for uniform mulch fiber strand length is less important.

[0048] The force of the spinning shredding mechanism 9 and/or cutting mechanism 10 propel the shredded material into the discharge chute 7. Preferably, the shredding and cutting mechanisms 9, 10 spin with sufficient speed to propel the shredded material completely through the discharge chute 7. Alternatively, a conveying mechanism (not shown), such as a blower, vacuum or conveyor belt may be used to assist with the movement of the shredded material through the discharge chute. 7

[0049] Alternatively, a conveyor (not shown) or other suitable means can be incorporated into the area between the shredding mechanism 9 and the cutting mechanism 10 to feed the shredded wood matter being discharged from the shredding mechanism 9 into the cutting mechanism 10. >

[0050] As shown in Figs. 2 and 3, the discharge chute 7 is an enclosure in communication with the shredding chamber housing 23. Preferably, the discharge chute 7 includes smooth surfaces and a tapered design that gradually funnels toward its discharge end 36. The funneled discharge chute 7 directs the mulch propelled from the shredding chamber 6 to a

desired location.

[0051] As shown in Figs. I _^ 2, 3, 4 and 5, the drive mechanism 4 includes an engine 3 having a drive shaft 12, drive belts 13, 14 and axles 31, 35. hi the embodiments of Figs. 1, 2, 3, 4 and 5, the drive shaft 12 is connected to the axle 35 of the cutting mechanism 10 by the drive belt 13. Additionally, in the embodiments of Figs. 1, 2, 3 and 4, the axle 35 of the cutting mechanism 10 is connected to the axle 31 of the shredding mechanism 9 by drive belt 14. The drive mechanism 4 links the axles 31, 35 of the shredding 9 and cutting mechanisms 10 to the engine 3. As a result, the engine 3 drives the shredding 9 and/or cutting mechanisms 10 by way of the drive belts 13, 14 that are connected to the axles 31, 35. The drive mechanism 4 is enclosed by an external housing 11 so that its moving parts are not exposed. In the embodiment

of Fig. 4, the external housing 11 for the drive mechanism 4 is hinged at the position of the cutting mechanism's 10 axle 35 to permit the upward displacement of the shredding mechanism 10 along the curved track 32.

[0052] Figs. 6A and 6B show an embodiment of the shredding mechanism 9. This particular embodiment is a shredding drum 28 having shredding teeth 30 fixed on an outer surface. In a preferred embodiment, the teeth are fixed such that the distance measured radially between the distal tip of the teeth and the surface of the drum is about 2 cm. Preferably, the shredding teeth 30 are replaceably fixed on the shredding drum 28 using conventional means, such as screws (not shown), hi one embodiment, the replaceable teeth 30 may be the commercially available Super Tooth® manufactured by Rayco®. The shredding teeth 30 are replaceable when worn out or damaged.

[0053] Figs. 7A and 7B ^' show an alternative embodiment for the shredding mechanism 9. The embodiment shown in Figs 7 A and 7B includes a plurality of shredding discs 29 mounted parallel to each other along an axle 31. The shredding discs 29 are fitted along their outer edge with shredding teeth 30, such as, for example, the commercially available Super Tooth® manufactured by Rayco®. hi a preferred embodiment, the teeth are fixed such that the distance measured radially between the distal, tip of the teeth and the outer edge of the discs is 2 cm. Again, the shredding teeth 30 are preferably replaceably fixed on the shredding discs 29 using conventional means, such as screws (not shown). The shredding teeth 30 are replaced when worn out or damaged.

[0054] The shredding teeth 30 of the shredding mechanism 9 may be Super Tooth® or any other similar conventional shredding element modified for application in the wood shredder 1. Super Tooth® and other similar shredding elements may be modified to be fixed in the shredding mechanism 9 of the wood shredder 1. The Super Tooth® or other similar shredding element is well suited for use with the wood shredder 1 because it is designed for shredding large

wood matter and is still small enough that it would not interfere with the portability of the wood shredder 1.

[0055] Figs. 8 A and 8B -show the details of an embodiment where the cutting mechanism 10 is a cutting drum 33. The cutting drum 33 is fitted with cutting blades 34 on an outer surface. The cutting blades 34 fixed on the cutting drum 33 may be conventional blades used in wood chipping or shredding machines. Preferably, the cutting blades 34 are replaceable when worn or damaged.

[0056] Figs. 9A, 9B, and 9C depict three different wood products alongside a ruler, which is shown for relative sizing and not actual sizing. Fig. 9 A depicts the usable mulch 37 produced by the combination of the shredding mechanism 9 followed by the cutting mechanism 10 of the portable wood shredder'l. The usable mulch 37 is readily biodegradable, because its fibers 38 are first shredded apart by the shredding mechanism 9. Further, the usable mulch 37 is characterized by its relatively small and uniform size (as compared to wood product resulting from a conventional shredder and/or chipper) resulting from the shredded wood next passing through the cutting mechanism 10. When the fibers 38 are shredded apart there is more surface area exposed to the action of bacteria and fungi that degrade the cellulose and lignin that constitutes the bulk of wood matter.

[0057] In contrast, Fig. 9B depicts the relatively long fibrous strands of shredded wood 39 that are produced by conventional wood shredders and the shredding mechanism 9of the portable wood shredder 1. The relatively long fibrous strands of shredded wood 39 are not uniform in size and are longer than the usable mulch 37, because there is no further wood reducing means, such as the cutting mechanism 10. As a result, the relatively long fibrous < strands of shredded wood 39 are slower to biodegrade and less aesthetically pleasing than the usable mulch 37.

[0058] Also in contrast, Fig. 9C depicts wood chips 40 produced by a conventional wood chipper and by the cutting means 10 of the portable wood shredder 1. The wood chips are

cut rather than shredded, so they laclc the shredded fiber characteristic of the long fibrous strands of shredded wood 39 and the usable mulch 37. Further, the woods chips 40 have a block-like appearance and are larger in size (e.g., width or diameter) than the long fibrous strands of shredded wood 39 and the usable mulch 37. As a result, the wood chips 40 are slower to biodegrade than the long fibrous strands of shredded wood 39 and the usable mulch 37 and are less aesthetically appealing than the usable mulch 37.

[0059] Although the invention has been described with reference to exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the true sprit and scope of the present invention.