Patent Publication Number: US-2012042524-A1

Title: Cast removal device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 61/151,601, filed Feb. 11, 2009, entitled APPARATUS AND METHOD FOR REMOVING A CAST, incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains to methods and apparatus for cutting through a material, and in particular to methods and apparatus for cutting through an orthopedic cast. 
     BACKGROUND 
     Casts used to set broken bones or other injuries to limbs generally consist of a hard outer shell, a sleeve, and an internal fabric or wrapping. The outer shell is typically made of layers of fiberglass or plaster. The inner wrappings are typically made from flexible woven or non-woven materials, such as cotton, polyester or other fibers. The hard outer cast shells typically are removed by using powered oscillating saws, which can be noisy and may create substantial fine debris. In order to prevent injury to patients, oscillating saws are usually operated at high frequency and low amplitude. However, oscillating saws can still cause burns or abrasions, and in many cases cause fear in many patients, especially small children. 
     What is needed are improved methods and apparatus for removal of a cast. Various embodiments of the present invention provide this in novel and unobvious ways. 
     SUMMARY OF THE INVENTION 
     Various aspects of the present invention pertain to methods and apparatus for cutting a layer of material. 
     One aspect of the present invention pertains to an apparatus for cutting a layer of material. Some embodiments include an electric motor and a gear train receiving the output of the motor. Still other embodiments include a first wheel including a first plurality of teeth arranged about a rotational axis, the first wheel being rotationally driven by the gear train, and a foot having a top surface and a sharp edge. Rotation of the first wheel presses the material against the top surface and move the material toward the sharp edge. 
     Another aspect of the present invention pertains to a method for cutting a layer of material. Some embodiments include providing a first plurality of teeth arranged about an axis and a foot having a shearing surface and a top surface. Other embodiments further include engaging the material with at least one tooth from the first plurality, rotating the first pattern about the axis, moving the engaged material by rotating toward the shearing surface and above the top surface, and cutting the material with the shearing surface by rotating. 
     Yet another aspect of the present invention pertains to an apparatus for cutting a layer of material. Some embodiments include a wheel including a plurality of teeth equally spaced about a rotational axis, each tooth having a concave side and a convex side, the wheel being rotationally driven. The convex side of each tooth leads the concave side of the same tooth during rotation. Still other embodiments further include an elongated foot having a top surface and a sharp edge, wherein during rotation the teeth press the material against the top surface and move the material toward the sharp edge. 
     Still another aspect of the present invention pertains to an apparatus for cutting a layer of material. Some embodiments include a gear train having a driving member rotating in a direction about a first axis. Still other embodiments include a cutting assembly including a first wheel and a second wheel, the first wheel and the second wheel each being adapted and configured to be rotationally driven by the driving member. Rotation of the first wheel and the second wheel moves the material over a toe and toward a sharp edge. The cutting assembly is adapted and configured to be mounted on the apparatus in either of two positions, the first position being one half revolution revolved about a second axis relative to the second position, the second axis being substantially perpendicular to the first axis, for cutting material in either of two directions. 
     It will be appreciated that the various apparatus and methods described in this summary section, as well as elsewhere in this application, can be expressed as a large number of different combinations and subcombinations. All such useful, novel, and inventive combinations and subcombinations are contemplated herein, it being recognized that the explicit expression of each of these combinations is excessive and unnecessary. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view of a cast removal system according to one embodiment of the present invention. Various aspects of the figure are semi-transparent. Other aspects of the figure include modeling lines. 
         FIG. 2  is a front end view of the apparatus of  FIG. 1  as taken along line  2 - 2  of  FIG. 1 . 
         FIG. 3  is a view of the apparatus of  FIG. 1  with one of the housing covers removed. 
         FIG. 4  is a view of the apparatus of  FIG. 3  with the other housing cover removed. 
         FIG. 5  is a view of a portion of the apparatus of  FIG. 4 . 
         FIG. 6  is a left side, top, and semi-exploded perspective of a portion of the apparatus of  FIG. 5 . 
         FIG. 6.5  is a left hand, top perspective, exploded view of a motorized cutting assembly according to another embodiment of the present invention. 
         FIG. 7  is a left side and frontal perspective view of a portion of the apparatus of  FIG. 6 , with some components shown with modeling lines and/or semi-transparent. 
         FIG. 8  is a frontal and left side exploded view of the apparatus of  FIG. 7 . 
         FIG. 9A  is a front planar view of a portion of the apparatus of  FIG. 8 . 
         FIG. 9B  is a front planar view of a portion of the apparatus of  FIG. 8 . 
         FIG. 9C  is a front planar view of a portion of the apparatus of  FIG. 8 . 
         FIG. 10A  is a perspective view of portions of the apparatus of  FIG. 8 . 
         FIG. 10B  is an end view of portions of the apparatus of  FIG. 8 . 
         FIG. 10C  is a perspective view of portions of the apparatus of  FIG. 8 , on the opposite side of the respective components relative to  FIG. 8 . 
         FIG. 11A  is a right side elevational view of a portion of the apparatus of  FIG. 8 . 
         FIG. 11B  is a top and frontal perspective view of the apparatus of  FIG. 11A . 
         FIG. 11C  is an exploded perspective view of a cutting assembly according to another embodiment of the present invention. 
         FIG. 11D  is a bottom view of the assembled apparatus of  FIG. 11C . 
         FIG. 11E  is an end elevational view of the apparatus of  FIG. 11D . 
         FIG. 11F  is a top plan view of a portion of the apparatus of  FIG. 11G  as taken along line  11 F- 11 F of  FIG. 11G . 
         FIG. 11G  is a front planer view of a portion of the apparatus of  FIG. 11C . 
         FIG. 11H  is an orthogonal cut-away view of the apparatus of  FIG. 11G  taken along the center line. 
         FIGS. 11I ,  11 J, and  11 K are top, end, and frontal orthogonal views, respectively, of a portion of the apparatus of  FIG. 11C . 
         FIG. 11L  is a close-up of a portion of  FIG. 11K . 
         FIG. 11M  is a front planer view of a portion of the apparatus of  FIG. 11C . 
         FIG. 11N  is a cross-sectional view of the apparatus of  FIG. 11M  as taken along the center line. 
         FIG. 11O  is a close-up of a portion of the apparatus of  FIG. 11M . 
         FIG. 12  is a left side, top, and frontal perspective of a portion of the apparatus of  FIG. 6 . 
         FIG. 13  is a left side elevational view of the apparatus of  FIG. 12 . 
         FIG. 14  is a right side elevational view of the apparatus of  FIG. 12 . 
         FIG. 15  is a bottom planar view of a portion of the apparatus of  FIG. 12 . 
         FIG. 16  is a left side and frontal perspective view of a portion of the apparatus of  FIG. 4 . 
         FIG. 17  is a left side and top perspective view of a portion of the apparatus of  FIG. 4 . 
         FIG. 18  is a right side and rear perspective view of the apparatus of  FIG. 17 . 
         FIG. 19  is a left side exploded perspective view of the apparatus of  FIG. 17 . 
         FIGS. 20A and 20B  are front, left side perspective views of a cutting assembly according to another embodiment of the present invention, shown both shaded only and shaded with lines, respectively. 
         FIGS. 21A and 21B  are right side perspective views of the cutting assembly of  FIGS. 20A and 20B , shown both shaded only and shaded with lines, respectively. 
         FIGS. 22A and 22B  are left side perspective views of the cutting assembly of  FIGS. 20A and 20B , shown both shaded only and shaded with lines, respectively. 
         FIG. 23  is an exploded, perspective view of the apparatus of  FIG. 21A . 
         FIG. 24  is a view of the apparatus of  FIG. 20A , as taken along line  24 - 24 , except rotated 180 degrees. 
         FIG. 25  is a cross-sectional view of the apparatus of  FIG. 24  as taken along line  25 - 25 . 
         FIG. 26  is a frontal view of a portion of the apparatus of  FIG. 20A . 
         FIG. 27  is a cross-sectional view of the apparatus of  FIG. 26  as taken along line  27 - 27 . 
         FIG. 28  is an enlargement of a portion of the apparatus of  FIG. 26 . 
         FIG. 29  is a view from the rear of a portion of the apparatus of  FIG. 20A . 
         FIG. 30  is a cross-sectional view of the apparatus of  FIG. 29  as taken along line  30 - 30 . 
         FIGS. 31A and 31B  are front, left side perspective views of a cutting assembly according to another embodiment of the present invention, shown both shaded only and shaded with lines, respectively. 
         FIG. 32A  is a cross sectional view of a portion of the apparatus of  FIG. 31A  as taken in a plane through the centerline as shown by line  32 - 32  of  FIG. 31A  (housing removed). 
         FIG. 32B  is a cross sectional view of the apparatus of  FIG. 31A , as taken along a vertical plane passing through the rotational centerline, and showing schematically a material M being advanced. 
         FIG. 33A  is an exploded perspective view of the apparatus of  FIG. 31B . 
         FIG. 33B  is a perspective view of the support of the apparatus of  FIG. 31A . 
         FIG. 34  is a front, left side perspective view of a cutting assembly according to another embodiment of the present invention, shown shaded with lines. 
         FIG. 35  is a view of the apparatus of  FIG. 34  with the front half of the housing removed. 
         FIG. 36  is a cross sectional view of the apparatus of  FIG. 34  as taken along line  36 - 36  of  FIG. 34 . 
         FIG. 37  is a cross sectional view of the apparatus of  FIG. 34  as taken in a plane represented by line  37 - 37  of  FIG. 34  (housing removed). 
         FIG. 38  is an exploded perspective view of the apparatus of  FIG. 34 . 
         FIG. 39  is a perspective view of one of the advancing wheels of  FIG. 38 . 
         FIG. 40  is a perspective view of the other advancing wheel of  FIG. 38 . 
         FIG. 41  is a perspective view of a portion of an apparatus for cutting a layer of material. 
         FIG. 42  is a perspective view of the apparatus of  FIG. 39  with the housing, keel, and one advancing wheel removed. 
         FIG. 43  is a side elevational cutaway view of the apparatus of  FIG. 41  as taken along a vertical plane passing through the centerline. 
         FIG. 44  is an exploded view of the apparatus of  FIG. 41 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. At least one embodiment of the present invention will be described and shown, and this application may show and/or describe other embodiments of the present invention. It is understood that any reference to “the invention” is a reference to an embodiment of a family of inventions, with no single embodiment including an apparatus, process, or composition that must be included in all embodiments, unless otherwise stated. 
     The use of an N-series prefix for an element number (NXX.XX) refers to an element that is the same as the non-prefixed element (XX.XX), except as shown and described thereafter. As an example, an element  1020 . 1  would be the same as element  20 . 1 , except for those different features of element  1020 . 1  shown and described. Further, common elements and common features of related elements are drawn in the same manner in different figures, and/or use the same symbology in different figures. As such, it is not necessary to describe the features of  1020 . 1  and  20 . 1  that are the same, since these common features are apparent to a person of ordinary skill in the related field of technology. Although various specific quantities (spatial dimensions, temperatures, pressures, times, force, resistance, current, voltage, concentrations, wavelengths, frequencies, heat transfer coefficients, dimensionless parameters, etc.) may be stated herein, such specific quantities are presented as examples only. Further, with discussion pertaining to a specific composition of matter, that description is by example only, and does not limit the applicability of other species of that composition, nor does it limit the applicability of other compositions unrelated to the cited composition. This application incorporates by reference PCT application No. PCT/US08/83453, filed Nov. 13, 2008, titled CAST REMOVAL SYSTEM. 
     Various embodiments of the present invention pertain to apparatus and methods for cutting a layer of material with a quiet, clean, motorized shearing (or splitting or severing) action. The apparatus and methods described herein are applicable to cutting many different types of material, such as plaster, fiberglass, wood, sheet metal, and other preferably thin layers of material. In several embodiments, there are apparatus adapted and configured for cutting and removing a plaster, cloth, fiberglass, or polyester orthopedic cast placed around a limb of a patient, or casts fabricated from any type of material and used for any purpose. 
     Some embodiments include an arm that extends around one side of the splitting or shearing wheel, the end of the arm having an elongated foot that extends under the wheel. In those embodiments directed toward removal of orthopedic casts, this foot is located between the splitting wheel and the patient, such that the cast material is directed between the foot and the splitting wheel. In some embodiments, the foot is elongated in the direction of travel of the material. 
     In some embodiments, the foot includes a shearing surface that extends upward toward the splitting or shearing wheel, and is located such that a face of the splitting or shearing wheel is in sliding contact with the shearing surface. In such embodiments the shearing action occurs by the action of the shearing sector pressing against the material that is being supported along the top of the shearing surface. In some embodiments it is advantageous for this top edge of the shearing surface to have a squared off edge having a relatively small radius of curvature, so as to support the material to be cut as closely as possible to the face of the cutting wheel. In yet other embodiments, the leading edge of the foot has a razor-type surface to assist in advance cutting of the soft material on the inside of the cast. In yet other embodiments, the heel portion of the arm (where the foot connects to the arm) has a razor-type edge for assistance in cutting the soft material that has already been split. 
     Yet other embodiments of the present invention pertain to a hand-held, battery operated cutting device that shears a material with a high torque, low speed shearing action. In one embodiment, the material is automatically advanced through a scissors-type shearing action at about 0.8 inches per second, although other embodiments of the present invention contemplate material flow speeds of as high as about 3 inches per second. In some embodiments the torque applied to the shearing wheel (which produces the scissors-type action) is about fifty to one hundred and fifty foot-pounds (force). It has been found that a quiet, low dust-generating shearing action within these ranges provides acceptable performance in shearing an orthopedic cast. However, other embodiments of the invention are not so constrained, and as an example, in those applications where sheet metal is sheared, the shearing speed ranges as low as about two-tenths of an inch per second. 
     In some embodiments, the means for automatically advancing the material is accomplished at a substantially constant velocity. Velocity is generally maintained by an electronic controller (preferably operating a software algorithm) that automatically adjusts the power provided by the motor as the toughness of the material being cut varies (such as for an orthopedic cast of varying thickness, or a layer of wood of varying thickness). 
     In another embodiment of the present invention, there is a hand-held, motorized shearing assembly that operates at one of a plurality of predetermined material flow velocities. In one embodiment, there is a trigger switch preferably operated by a finger of the operator. Over a first range of switch movement, the linear velocity of the shearing wheel (and in some embodiments, further of the advancing wheel) is held substantially constant at a first linear velocity. Further movement of the switch into a second, predetermined range of movement operates the shearing wheel (and possibly the advancing wheel) at a second, higher, “boost” speed. This latter, second, boosted speed can be useful in the shearing of orthopedic casts, especially when the path of the shearing wheel is relatively straight along the cast, with the slower speed being helpful when the cutting device must follow a curved path (such as for a cast that holds an arm of a patient bent at the elbow). 
     In another embodiment of the present invention, there is an advancing wheel having a plurality of teeth that are adapted and configured for pressing contact, and in some embodiments, penetration into the outer surface of an orthopedic cast having an external woven material. As one example, some orthopedic cast have an exterior of a cross woven fiberglass matte, with a standard spacing between adjacent threads, which thus establishes a “hole pattern” or “line pattern” in the woven material. In some embodiments, the linear distant between adjacent teeth of the advancing wheel are adapted and configured to be even multiples of this hole pattern. Such spacing increases the likelihood that as a tooth penetrates into the outer surface of the cast, and then moves the cast, that the next tooth will not necessarily fray the woven material which would be the case if the tooth pattern were not a multiple of the weave pattern. However, the present invention is not so constrained and further, various embodiments of the present invention are adapted and configured for shearing any variety of orthopedic cast material, including Goretex®. 
     In yet other embodiments, the apparatus includes a support member that places a downwardly extending arm with a forward extending foot around the back (aft) periphery of the shearing wheel. After the material is split by the means for shearing the material (which can be any of the shearing or splitting devices shown herein), the split material progresses aftward and goes past on either side of the arm. The forward-projecting foot reaches under the shearing wheel, such that the material flowpath (and the locus of the shearing operation occurs between the edge of the shearing wheel and the top of the foot). The bottom of the foot thus protects the patient. 
     In some embodiments, the foot includes a shearing surface that projects upward and is generally parallel to a face of the shearing wheel. This upwardly projecting surface has the appearing of a “shark fin” or “camel back.” Preferably, the top surface of the shark fin has a sharp, right-angle edge, so as to provide good shearing action relative to the cutting sectors. In yet other embodiments, the forward edge of the shark fin has a sharp surface, and in some embodiments a razor-type surface, for partial, advance cutting of the underside of the layer of material. In yet other embodiments, the aft portion of the foot (the “heel” or where the foot connects to the arm) is further adapted and configured to have a sharp edge, and in some embodiments, a razor-type edge, to complete, if necessary, the cutting of any soft material that was not sheared apart by the coaction of the shearing sectors against the shearing surface. In yet other embodiments, these razor-type edges are replaceable, and are held in by means such as one or more set screws. 
     In some embodiments, the fin extends upwardly from the top surface of the foot. As the advancing wheel moves the material over the fin and toward the shearing edge, the fin places the material in bending prior to being sheared. This bending creates a state of stress in the material that facilitates the shearing process. In some embodiments, there are advancing wheels on opposing sides of the fin, such as the fin places the top outer surface of the material being cut in a state of tension. Therefore, when the tensioned material is sheared, less shearing force is required to sever the material because of the pre-shear tensile state. 
     Broadly, described here are material severing devices and specifically, devices for cast removal from humans and animals. Unless otherwise stated, the term “animal” includes human beings. One embodiment described here comprises an assembly included a housing containing an electric motor, a mechanical gearing transmission component, a cutting mechanism designed to pierce and sever the cast and advance along the cast while cutting it, and a leg and foot mechanism whereas the foot extends along the underside of the cast to prevent the cutter from making contact with the skin. 
     The mechanical gearing transmission component would be designed to provide a slow rotation of the cutter while providing sufficient torque so as to pierce and sever a pathway down the length of a cast. While one embodiment would utilize a gearing transmission component, any means of conveying rotary motion might be utilized such as, for example, pulleys and belts or chains and sprockets. The cutter described could also provide for the deformation of the cast at the severed pathway allowing for a clear pathway, and providing easy separation of the cast upon completion of the cutting. In one variation the cutter could also shear the soft underlying wrapping through the use of increased torque combined with insertion of the cutter blade or serrations into an aperture within the foot that is traversing beneath the hard cast cover and underlying soft wrapping on a parallel path to the cutter mechanism. 
       FIGS. 1 and 2  show external views of an apparatus  20  according to one embodiment of the present invention. Apparatus  20  includes a mid-positioned handle  24  adapted and configured to be grasped by the hand of a human operator. One end of handle  24  includes a battery adapter  28  that couples to a battery assembly  80 . The other end of handle  24  is attached to an enclosed motorized cutting assembly  30  housed within a motor enclosure  26 . As seen best in  FIG. 1 , handle  24  preferably includes a plurality of rounded projections for improved gripping by the palm of the operator&#39;s hand. Further, handle  24  includes various curved surfaces that are adapted and configured for improved gripping by the fingers of the operator. 
     As best seen in  FIG. 2 , a cutting assembly  50  is mounted on the front end of apparatus  20 . Cutting assembly  50  preferably splits, shears, and advances a layer of material along a path  50 . 1 . Referring to  FIG. 1 , handle  24  preferably establishes a support axis  24 . 1  that is generally orthogonal to material path  50 . 1 . The arrow along  50 . 1  indicates a cutting assembly  50  oriented for movement of material in the direction of the arrow. An operator holding apparatus  20  by handle  24  is ergonomically encouraged to move apparatus  20  from side to side (from the operator&#39;s right to left or left to right). In those embodiments relating to removal of a cast from a limb of a patient, the material path  50 . 1  is generally parallel to the length of the limb. The orientation of axis  24 . 1  and  50 . 1  therefore permits an operator such as a surgeon, paramedic, or other health care professional to comfortably stand alongside the cast of the patient. Further, cutting assembly  50  is preferably symmetrically coupled to apparatus  20 , such that the direction along path  50 . 1  (from right to left or from left to right) can be changed by removing cutting assembly  50 , turning it around, and reattaching it to the front end of apparatus  20 . 
       FIGS. 3 and 4  show apparatus  20  with the right and left housing covers  22 . 1  and  22 . 2 , respectively, removed. Cover  22 . 2  is removed in  FIG. 3 . Covers  22 . 1  and  22 . 3  are removed in  FIG. 4 . Apparatus  20  includes a motorized cutting assembly  30  comprising a motor  32 , gear reduction  40 , and cutting assembly  50  supported by handle  24  and located in or on enclosure  26 . A handle assembly  60  is located within handle  24 . A battery assembly  80  is supported on one end of handle  24 . Handle assembly  60  and battery  80  are in electrical communication, and power from battery assembly  80  is provided through one or more electrical contacts  66 . Additionally, handle assembly  66  is in electrical communication with motorized cutting assembly  30 , and provides conditioned electrical power to motor  32 . 
     It is understood that apparatus  20  is not constrained to the placement of components shown in  FIGS. 3 and 4 , nor is it constrained to the type of components shown in  FIGS. 3 and 4 . As one example, apparatus  20  does not require a battery assembly and other embodiments of the present invention contemplate the use of electrical power from a cord that plugs into a wall socket. Additionally, the splitting and shearing apparatus and methods described herein can be powered by means other than electric motor including operation based on hydraulic power or pneumatic power, as examples. 
       FIGS. 5 and 6  show portions of motorized cutting assembly  30 . Referring to  FIG. 5 , motorized cutting assembly  30  includes a motor  32 , gear train assembly  40  and cutting assembly  50 , all supported relative to each other by a support assembly  34 . Briefly referring to  FIG. 3 , it can be seen that support assembly  34  is located within housing halves  22 . 1  and  22 . 2  by one or more channels, or in any other manner. In one embodiment, motor  32  is a brushless DC motor, such as a model DIH  23 - 30 - 013 Z as fabricated by BEI Kimco Magnetics. 
     Referring again to  FIGS. 5 and 6 , support assembly  34  includes front and rear support members  34 . 1   c  and  34 . 1   b . A pair of triangularly shaped webs  34 . 1   d  provide bracing for front plate  34 . 1   c  relative to central platform  34 . 1   f . A pair of projecting ears  34 . 1   a  bearingly support a portion of gear reduction assembly  40 . One or more stationary axles  34 . 1   e  are coupled to either front plate  34 . 1   c  or rear plate  34 . 1   b  to bearingly support portions of gear train  40 . In some embodiments, the various components of support assembly  34  are fabricated from aluminum or steel, and welded together. In yet other embodiments, support assembly  34  is fabricated from a plastic material, and the individual components are welded together ultrasonically, or adhered together, as examples. In yet other embodiments, support  34  is a one piece or multi piece molding. The aforementioned methods of fabricating support  34  are provided as examples only. 
     Referring to  FIG. 6 , a plurality of dowel pins  34 . 3  extend from a face of central support member  34 . 1   f , and align the driving axis of motor  32  with the input worm gear of gear train  40 . The front face  34 . 1   c  of support  34  include a pair of locating dowels  34 . 2  that are received within corresponding dowel holes  52 . 2  to align cutting assembly  50  relative to gear train  40 . Also shown in  FIG. 6  are a plurality of alignment pins  51 . 6  that align together front adapter  51 . 41  and rear adapter  51 . 42 , which are shown in  FIG. 8 , and which will be discussed later. 
     Preferably, apparatus  20  includes a switch  36  for changing the polarity of electrical power provided to motor  32 . This change in polarity also changes the direction of rotation of motor  32 , gear train  40 , and cutting welds  56  and  54 . This feature is useful in conjunction with the removal, swapping from end to end (such as about the vertical axis shown on  FIG. 7 ), and reattachment of cutting assembly  50  so as to affect a change in the direction of material path (as previously referenced relative to  FIG. 2 ). 
       FIG. 6.5  shows an exploded perspective view of a motorized cutting assembly  33030  according to another embodiment of the present invention. A brushless, DC motor  33032 , having a wireloom  33032 . 1  providing output signals for motor sensors and further providing input power to power the motor, is coupled to a worm  33042 . 1  of first worm pair  33042 . This first worm pair is coupled to a second worm pair  33044 , which further drives a pinion set  33046 . The output torque of gear train  33040  is provided at an output drive  33046 . 3  that is supported by a bearing  33047 , which in one embodiment is a roller bearing. The output drive axis further includes a thrust ball  33047 . 1  and a thrust disc  33047 . 2  to provide an axial load on the output shaft. A pair of molded housings  33034 , front and rear, provide support and enclosure for gear train  33040 , as well a mounting surface for alignment and coupling of motor  33032 . 
       FIGS. 7 and 8  show assembled and exploded views, respectively, of cutting assembly  50 . A housing  51  comprising front and rear halves  51 . 1  and  51 . 2 , respectively, statically retain between them a keel  52 . Housing  51  and keel  52  both include alignment holes to accept dowels  34 . 2 . 
     Further included within housing assembly  51  are front and rear driving adapters  51 . 4  aligned relative to each other by pins  51 . 6  previously seen in  FIG. 6 . Front adapter  51 . 41  and rear adapter  51 . 42  further include an interior driven interface  51 . 45  that have a shape complimentary to, and are driven by, adapter drive  46 . 3  of gear train  40  (which is shown in  FIGS. 12 and 13 ). 
     Referring again to  FIGS. 7 and 8 , adapters  51 . 4  include (either individually, or together) a cutting assembly drive surface  53  that is complimentary in shape to, and drives, driven interfaces  54 . 1  and  56 . 1  of wheels  54  and  56  (as shown in  FIGS. 9   a  and  9   c ). 
     Cutting assembly  50  further includes a socket screw  58  comprising a threaded shaft and a centrally located cylindrically-shaped central abutment. The abutment is captured within an internal pocket formed by the coupling of front adapter  51 . 41  to rear adapter  51 . 42 . The threaded portion of socket screw  58  is received within a threaded receptacle  46 . 4  of adapter drive  46 . 3  (as best seen in reference to  FIG. 12 , the threaded receptacle not being shown in  FIG. 12 ). A tightening of socket screw  58  into adapter drive  46 . 3  results in compression of the abutment feature of socket screw  58  against an inner wall of rear adapter  51 . 42 . If the operator desires to change the direction of material flow as indicated along path  50 . 1  of  FIG. 2 , then socket screw  58  is loosened, and adapter drive  46 . 3  can be removed from driven interface  51 . 45 . Cutting assembly  50  can then be rotated 180 degrees about the vertical axis shown in  FIG. 7 , and realigned with dowel holes  52 . 2 . Socket screw  58 , still captured but loose within the coupled adapters  51 . 41  and  51 . 42 , is then tightened such that the central abutment feature now holds adapter  51 . 41  in compression against adapter drive  46 . 3 . 
     Cutting assembly  50  further includes a means for biasing shearing wheel  54  toward contact with flat surface  52 . 5  of keel  52 . In one embodiment, and as shown in  FIG. 8 , a wavy spring  51 . 5  is placed between a ledge of front adapter  51 . 41 , and biases a part adapter drive  51 . 41  and surface  54 . 8  of splitting wheel  54  (referring to  FIG. 10   b ). This biasing action places a load along the rotational axis of wheel  54  so that flat surface  54 . 4  of wheel  54  is in sliding contact with flat surface  52 . 5  of keel  52 . As best seen in  FIGS. 10A and 10B , wheel  54  has a sharp-edged perimeter  54 . 3  that extends around flat surface  54 . 4 . 
       FIGS. 9 ,  10 , and  11  show various views of the splitting or shearing wheel  54 , the advancing wheel  56 , and keel  52 . The splitting wheel  54  is shown in  FIGS. 9A ,  10 A,  10 B, and  10 C. Wheel  54  includes a plurality of shearing or splitting sectors  54 . 2  arranged in a generally cylindrical pattern. Preferably, there are anywhere from about 4 to about 14 sectors equally spaced around the periphery of the wheel. Each sector preferably includes a splitting edge  54 . 5  which, for the embodiment shown in  FIG. 9A , is preferably linear. The beginning of the shearing sector includes a concave transitional section  54 . 7  that begins (taking into account the direction of rotation shown on  FIG. 9A ) with a lead in portion that extends radially inward toward the center of the wheel  54 . Transitional section  54 . 7  then curves from the radially inward direction to alignment with splitting edge  54 . 5 . Edge  54 . 5  is canted aft an outward angle relative to its tangency with the end of transitional section  54 . 7 . Splitting edge  54 . 5  thereby has a component of motion (when wheel  54  is rotating) that is generally radially outward from the center of wheel  54 . Each splitting sector  54 . 2  is closed out with a section  54 . 8  that transitions from a point of tangency with the end of splitting sector  54 . 5  toward a tip or apex  54 . 6 . From apex  54 . 6 , the next splitting sector  54 . 2  begins with the concave transitional portion  54 . 7 . Wheel  54  further includes a driven interface  54 . 1  for rotating wheel  54  and transmitting the torque required to shear the layer of material. As best seen in FIGS.  10 B and  10 C, wheel  54  includes a substantially flat surface  54 . 4  that, during operation, slides against flat surface  52 . 5  of keel  52 . The side of wheel  54  opposite of flat surface  54 . 4  has a surface adapted and configured to receive a biasing force from spring  51 . 5 . 
     Advancing wheel  56  can be seen in  FIGS. 9C ,  10 A,  10 B, and  10 C. Wheel  56  has a driven interface  56 . 1  adapted and configured to receive a rotational input and a torque input from an adapter  51 . 4 . Wheel  56  includes a pattern of teeth  56 . 2  that are arranged in a generally cylindrical pattern about the center line of wheel  56 . In one embodiments, each tooth includes a generally convex-shaped side  56 . 4  that meets a concave-shaped side at an apex or tip  56 . 6 . As best seen in  FIGS. 10A and 10B , each tooth in pattern  56 . 2  is asymmetrically shaped, as best seen in edge-on-view  FIG. 10B . Each tooth  56 . 2  has a surface  56 . 7  that is spaced away from the keel (as best seen in  FIGS. 1 and 5 ). The side  56 . 5  opposite of the keel side is substantially flat. Referring to  FIG. 5 , wheel  56  has teeth  56 . 2  that are axially spaced apart from the portion of the material being split. This axial spacing is adapted and configured to provide that each tip  56 . 6  is able to come into contact with portions of the material being cut that are not at the frayed or weakened split line of the material. However, other embodiments of the present invention contemplated advancing wheels having teeth that are symmetric, or biased toward the keel. However, some of these embodiments are adapted and configured to provide spacing between the split interface of the material and the portion of the material being contacted by advancing wheel  56 , so that advancing wheel  56  is able to contact a portion of the material strong enough to advance the material. 
     In one embodiment, the tips  56 . 2  have sharp edges. Further, the axis of wheel  56  is located relative to the path of material along foot  52  such that the tips  56 . 2  press firmly against the surface of the material. In some embodiments, teeth  56 . 2  make indentations on the material as it is driven. In other embodiments, teeth  56 . 2  penetrate the top surface of the material. Further, yet other embodiments of the present invention contemplate the use of an advancing wheel  56  that relies on friction to advance material being cut. In one such embodiment, wheel  56  includes a rubber coated periphery that comes into frictional contact with the surface of the material. In yet other embodiments, the periphery of wheel  56  has a plurality of ridges which improves the frictional contact by establishing a frictional contact patch that is a narrow contact line. 
     Keel  52  can be seen in  FIGS. 9   b ,  11   a  and  11   b . Keel  52  includes a pair of dowel holes  52 . 2 , each on an opposite side of a central clearance hole  52 . 7 . Adapters  51 . 4  extend through clearance hall  52 . 7  to drive wheels  54  and  56 . A central structural web extends in between each dowel hole  52 . 2  and central passage  52 . 7 . Also extending from this central structural web is an arm  52 . 3  that extends downward toward the material path, and further supports a foot  52 . 1  adapted and configured to be located under the material path. As best seen in  FIG. 11   a , arm  52 . 3  jogs to the right (as shown in  FIG. 11   a ). This offsetting jog permits arm  52 . 3  to have on it a sharp edge  52 . 4  that performs any final shearing of fibers not otherwise sheared or split by wheel  54 . 
     Foot  52 . 1  has a substantially rounded and smoothed underside so as to not cause abrasions when this underside passes over a patient&#39;s skin, for those embodiments in which apparatus  20  is used as a cast removal device. The present invention also contemplates those embodiments in which an inventive apparatus is used to shear through paper, wood, sheet metal, or fabric, and in this embodiment the underside of foot  52 . 1  does not have to be rounded or curved. 
     As best seen in  FIGS. 11   a  and  11   b , a “shark fin” or flat surface  52 . 5  extends upwardly from the topside (material side) of foot  52 . 1 . One side of this projection has a substantially flat surface  52 . 5  that is adapted and configured to be in sliding contact with wheel surface  54 . 4 , and further to co-act with wheel  54  to split or shear the layer of material. In some embodiments, sharp edge  52 . 4  extends from arm  52 . 3  forward (opposite of the direction of the material flow) and along the upper edge of flat surface  52 . 5 . However, in yet other embodiments, the top surface of flat surface  52 . 5  is not a sharp edge. 
     Referring to  FIGS. 11   a  and  11   b , dowel holes  52 . 1  have a length that is adapted and configured to provide rigidity and precision in the mounting of cutting assembly  50  to dowels  34 . 2 . 
       FIGS. 11C to 11O  depict various views of a cutting apparatus  31050  according to another embodiment of the present invention. Cutting assembly  31050  is similar to assembly  50 , but with several changes. Assembly  31050  includes first and second advancing wheels  31056   a  and  31056   b , preferably stationed on opposite sides of splitting wheel  31054 . In addition, cutting assembly  31050  does not include a wavy spring for biasing the position of the splitting wheel. Further, each advancing wheel  31056   a  and  31056   b  incorporates apparatus similar in function to driving adaptors  51 . 4 . 
     As best seen in  FIGS. 11D and 11E , advancing wheels  31056   a  and  31056   b  are arranged on opposite sides of splitting wheel  31054  and further on opposite sides of arm  31052 . 3  of keel  31052 . The teeth of each advancing wheel are preferably displaced outwardly from the plane in which the material is cut, as best seen in  FIG. 11E . By spacing the ends of the advancing teeth away from the cut, there is less chance of the advancing teeth pressing against, and in some embodiments penetrating, the surface of the material too close to the frayed or weakened cut (split) edges of the material. However, the present invention is not so constrained, and further contemplates those embodiments in which the advancing teeth are roughly centered about a central plane of the corresponding advancing wheel, and also those embodiments in which the teeth are splayed inward toward the plane of the cut. 
       FIGS. 11F ,  11 G, and  11 H depict various views of keel  31052 . As seen best in  FIG. 11F , the shearing face  31052 . 5  of keel  31052  has a multifaceted face. A lead-in portion  31052 . 5 A is angled such that it falls away from the flat face  31054 . 4 , with reference to the direction  31050 . 1  of motion. A second facet of the flat surface of foot  31052 . 5  falls further away from contact with wheel  31054 , in an intermediate planar faceted section  31052 . 5 B. The distal-most portion of the shearing surface  31052 . 5  of foot  31052 . 1  is a third angled surface  31052 . 5 C that falls away at an angle less steep than angles A or B. In one embodiment, the first faceted surface is angled three degrees falling away from the advancing wheel. The intermediate cutting facet falls away by about four degrees. The final planar facet C falls away at about one degree. In one embodiment, the angular orientation of portion  31052 . 5 C helps create interference at the shearing interface to increase contact pressure between the face of the cutting wheel and the keel foot. The angular orientation of surface  31052 . 5 A establishes an angle at which the cutting sectors meet the top surface of the foot, and helps to create improved shearing action relative to the soft casting materials (such as the woven materials). 
       FIGS. 11I ,  11 J,  11 K, and  11 L depict various views of a cutting wheel  31054  according to one embodiment of the present invention. Referring to  FIG. 11L , a single cutting sector  31054 . 2  can be seen in detail. In one embodiment, each cutting sector begins (relative to the flow of material) from an apex  31054 . 6  for a short linear span of about three one-hundredths of an inch, and then blending tangentially into a transitional portion  31054 . 7  that is curved concave inwardly, and in some embodiments has radius of curvature of about one-tenth of an inch. This partly linear, partly curved transitional section  31054 . 7  tangentially blends into a substantially linear shearing section  31054 . 5  that, in one embodiment, is angled generally perpendicularly relative to the tip by less than about ninety degrees. The generally linear cutting section  31054 . 5  tangentially transitions to a curved close out section  31054 . 8  that is preferably curved concave outward, and ends in the tip  31054 . 6  of the next section. 
       FIGS. 11M ,  11 N and  11 O depict various views of an advancing wheel  31056  according to another embodiment of the present invention. Wheel  31056  incorporates integrally a driving adaptor  31051 . 4 . Wheel  31056  further incorporates a driven interface  31051 . 45  complementary in shape to a corresponding driving member  31046 . 3 . 
       FIGS. 12 ,  13 ,  14 , and  15  show various views of support assembly  34  and gear reduction assembly  40 . Gear reduction assembly includes a first worm drive  42  that drives a second worm drive  44 . Speed and torque from the output of second worm drive  44  is provided to a pinion pair  46 , and finally to an adapter  51 . 4 . 
     As seen in  FIGS. 13 and 14 , a rotational speed and torque from motor  32  is provided to a first worm gear  42 . 1 . Worm gear  42 . 1  is in engagement with the corresponding worm wheel  42 . 2 , the latter supported by support  34 . In one embodiment, worm gear  42 . 1  is preferably fabricated from a first, harder material, and in one particular embodiment is fabricated from steel of the grade SAE  1144 . In that embodiment, the worm  42 . 1  has an axial pitch of 0.133; has 2 threads; is a right hand helix with a lead angle of 10.9 degrees; a pitch diameter of 0.44 inches; a major diameter of 0.53; a minor diameter of 0.36 (all diameters in inches); and a pressure angle of about 20 degrees. The driven worm wheel  42 . 2  is preferably fabricated from a second material that is not as hard as worm  42 . 1 , and in one embodiment worm gear  42 . 2  is fabricated from a plastic material such as nylon 66. In one embodiment, worm wheel  42 . 2  has a diametral pitch of 23.57; a helix angle of 10.8 degrees; is a right hand helix; has a pitch diameter of about 0.89 inches; a major diameter of about 0.96 inches; a minor diameter of 0.79 inches; and a pressure angle of about 20 degrees. In one embodiment, worm gear  42 . 2  is coupled to its shaft by sliding splines. 
     Referring now to  FIGS. 14 and 15 , located on the same shaft with worm wheel  42 . 2  is a second worm gear  44 . 1 . Worm gear  44 . 1  engages a worm wheel  44 . 2 . Worm wheel  42 . 2  is supported on a shaft along with a pinion drive gear  46 . 1  (with a bearing being placed in between these gears). In one embodiment, the second worm gear  44 . 1  is fabricated from a first, harder material, such as SAE  8620  and is case hardened in a specific embodiment, worm  44 . 1  has an axial pitch of about 0.16; has one thread; has a right hand helix; a helix angle of about 6.7 degrees; a pitch diameter of about 0.43; a major diameter of about 0.53; a minor diameter of 0.30; and a pressure angle of about 20 degrees. In one embodiment, the shaft that incorporates worm  44 . 2  includes a splined section to accept worm gear  42 . 2 . Worm wheel  44 . 2  is preferably fabricated from a softer material than worm  44 . 1 , and in one embodiment worm wheel  44 . 2  is fabricated from CA 673 bronze. In one specific embodiment, worm gear  44 . 2  has a diametral pitch of about 19.9; has 18 teeth; is a right handed helix; has a helix angle of about 6.7 degrees; a pitch diameter of about 0.91; a major diameter of about 0.98; a minor diameter of about 0.75; and a pressure angle of about 20 degrees. 
     Pinion drive gear  46 . 1  in turn drives a larger pinion driven gear  46 . 2 , as best seen in  FIGS. 12 and 15 . The driven pinion member  46 . 2  is located on the same shaft with adapter drive  46 . 3 , with a bearing  47  being interposed there between. In one embodiment, the overall gearing ratio from the output speed of the motor to the input speed of the motor to the output speed of drive  46 . 3  is about 330:1, such that gear train  40  has an output speed that is less than the input speed of motor  32 , and is driven with an output torque that is greater than the input torque of motor  32 . 
       FIG. 16  is a prospective view of a handle assembly  60  according to one embodiment of the present invention. Handle  60  includes a structural chassis  61  that supports a pivotal finger switch  62 . The interior end of finger switch  62  includes a pair of projections, each having on their surface a magnet. Located in between the magnets on these projections is a Hall sensor  64 , located on a circuit card  70 . A plurality of electrical contacts  66  located at one end of circuit card  70  provide an input for electrical power to circuit card  70 . 
       FIGS. 17 ,  18 , and  19  are various views of a battery assembly  80  according to one embodiment of the present invention. Battery assembly  80  includes a plurality of batteries  84  located within a housing  82 . In one embodiment, the batteries are of a nickel-metal hydride type. Power from the batteries is provided to a circuit card  90  that conditions the power as required. A plurality of electrical contacts  86  provide battery power to contacts  66  of handle assembly  60 . An assembly of five LEDs and corresponding light pipes  88  receive a signal from circuit card  90  pertaining to the state of charge of batteries  84 . Referring to  FIG. 17 , the LEDs  88  indicate to the operator whether or not there is sufficient charge to sever the cast of another patient. 
     Cover  82 . 4  of housing  82  includes dovetail grooves  82 . 3  that are grasped by complimentary-shaped grooves on the underside of battery adapter  28 . Battery assembly  80  further includes a spring-loaded sliding switch  82 . 1  that locks battery assembly  80  to handle  24 . A button  82 . 2  provides an actuatable switch by which the operator can request the status of batteries  84  to be displayed on LEDs  88 . 
       FIGS. 20-44  are scaled drawings, although one of ordinary skill in the art will appreciate that the scale can change from one figure to another. Further, it is appreciated that these drawings represent specific embodiments, and the relative dimensions of one feature to another are not to be construed as limiting. 
       FIGS. 20-30  depict a cutting assembly  150  according to another embodiment of the present invention. Cutting assembly  150  is the same as the cutting assemblies previously described, except for the changes shown and described hereafter. As one example, cutting assembly  150  is usable with cutting apparatus  20  previously described, and in some embodiments, cutting assembly  150  can be directly substituted for cutting assembly  50 . 
     Referring to  FIGS. 20 ,  21 , and  22 , cutting assembly  150  includes a supporting member  151  that is coupled to an apparatus such as apparatus  20 . Support member  151  supports a pair of advancing wheels  156 A and  156 B, the teeth of which are on opposing sides of the support member  151 . Front and rear housing covers  151 . 1  and  151 . 2 , respectively, (not shown) shield the user from portions of the advancing wheels. A keel  152  extends downward from one side and toward the other side from support member  151 . As best seen in  FIGS. 21 and 22 , a front splitting wedge  152 . 8  and a rear splitting wedge  152 . 9  extend from foot  152 . 1  of keel  152 , and are generally placed between advancing wheels  156 A and  156 B. 
       FIGS. 23 ,  24 , and  25  depict the assembled elements that comprise a cutting assembly  150  according to one embodiment of the present invention. A central support member  151  supports a pair of advancing wheels  156 A and  156 B that are coupled together by a pair of pins  151 . 6 . Each wheel includes a driven interface  156 . 1  that has a shape complementary with the shape of adaptor drive  46 . 3  of gear reduction assembly  40  (referring to  FIG. 12 ). Referring to  FIG. 25 , this driven interface (shown in  FIG. 20  as a substantially square interface) can drive either one of the advancing wheels. A hubscrew  158 , which threadably couples to a threaded pocket of adaptor drive  46 . 3 , can move toward either wheel along the drive axis, as permitted by the flange  158 . 1  located within a pocket  156 . 8  formed between wheels  156 A and  156 B. 
     As best seen in  FIGS. 23 and 25 , central support member  151  includes a pair of semi-circular pockets  151 . 5  scalloped onto either face. Each advancing wheel  156  is generally centered within a corresponding pocket  151 . 5 . In some embodiments, central support member  151  does not include enclosures that extend around the advancing wheel, although the present invention does contemplate a multi-part support member  151  similar to housing  51  that at least partly encloses the advancing wheels. 
       FIGS. 26 ,  27 , and  28  show an advancing wheel  156   b  according to one embodiment of the present invention. In one embodiment, wheel  156   a  is identical to wheel  156   b , although the present invention contemplates embodiments in which the wheels are different. 
     Wheel  156   b  includes a pattern of teeth  156 . 2  that extend in a repetitive pattern around the circumference of the wheel. Wheel  156   b  is adapted and configured to be rotated more than 360 degrees as the material is cut. 
     Referring to  FIG. 28 , the teeth of wheel  156   b  have a shape that is adapted and configured to have the tip  156 . 6  be the first point of contact with the cast material moving along path  150 . 1  as the wheel rotates. In one embodiment, the teeth comprise a convex side  156 . 4  and a concave side  156 . 3 , the two sides meeting at apex  156 . 6 . In another embodiment, the concave and convex sides are circular in shape and have the same radius. However, the present invention is not so limited and contemplates other shapes of teeth. As best seen in  FIG. 27 , each tooth of wheel  156 B has a generally constant cross sectional shape, such that tip  156 . 6  engages with the material to be cut with line contact. However, the present invention is not so constrained, and further includes those embodiments in which the cross sectional shape of the tooth narrows, such that contact with the material is more concentrated with subsequently higher bearing stresses in the material when contacted with the tooth. 
       FIGS. 29 and 30  depict frontal and cross-sectional views, respectively, of a support member  151  according to one embodiment of the present invention. Support member  151  is coupled to the front of an apparatus such as apparatus  20  in a manner similar to that of cutting assembly  50 . 
     Support member  151  includes a keel  152  that extends downward and from one side of support member  151 . Keel  152  includes an elongated foot  152 . 1  supported in cantilever-fashion by arm  152 . 3 . Keel  152  is elongated in a direction parallel with the movement of material. At the end of keel  152  opposite of arm  152 . 3  is a toe  152 . 11  that is adapted and configured to be located on the side of the material being cut opposite of advancing wheels  156 . Extending upwardly from foot  152  is a front splitting wedge  152 . 8  which has a generally triangular or wedge-shaped cross-section (as best seen in  FIG. 30 ). A sharp edge  152 . 4  extends along the top and front of wedge  152 . 8 . As best seen in  FIG. 29 , the front edge of wedge  152 . 8  slopes upward from the top surface of foot  152 . 1  to a maximum height, and then falls back at a 135 degree angle to the top surface of foot  152 . 1 . This sloping front edge and the lateral movement of the material being cut (from left to right in  FIG. 29 ) permit sharp edge  152 . 4  of front wedge  152 . 8  to apply progressively increasing splitting pressure onto a surface of the material. 
     Support arm  152 . 3  further includes a rear wedging cross-section  152 . 9 , and a sharp front edge  152 . 4 . Material continuing to move under the action of wheel  156  is advanced over the sharp edge  152  of rear splitting wedge  152 . 9 , such that the splitting action continues along the upper thickness of the material being cut. 
     Referring to  FIGS. 25 and 20A , it can be seen that the material flow path  150 . 1  extends in a fashion similar to that of cutting assembly  50 . The material to be cut or split is advanced from the right to left, as seen in  FIG. 20A  under the action of the teeth of the advancing wheels. As advancing wheels  156 A and  156 B rotate in a clockwise direction, the descending teeth contact and press into the material positioned along flow path  150 . 1 . As the wheels continue to rotate, the teeth press progressively harder into the material, and further push and pull the material along the sharp edge  152 . 4  of front wedge  152 . 8 . The sharp edge  152 . 4  splits the material, both by the piercing of the material with the sharp edge and the wedging action that occurs as the pierced material is pushed along the wedge shape. The material continues to move from right to left along flow path  150 . 5  under the action of the teeth of the advancing wheel, and subsequently encounters the sharp edge  152 . 4  of the rear wedge  152 . 9  of keel  152 . Rear wedge  152 . 9  further includes a cross-sectional shape that increases similar in fashion to that of front wedge  152 . 8 , to thereby continue the splitting and wedging-apart action on the material. 
     In one embodiment, wheels  156 A and  156 B have equal numbers of teeth, and further the teeth of each wheel are equally angularly spaced about the centerline of the wheel. In still further embodiments, the wheels are interlocked to each other such that the tooth pattern of one wheel is offset relative to the tooth pattern of the other wheel by one-half of the tooth spacing. This is best seen in  FIGS. 20A and 20B . This interspaced interlocking of the wheels provides for more uniform movement of the material over the foot and onto the sharp edges. 
     In some embodiments of the present invention, the cutting assembly  150  includes a single wheel  156  that engages the material to be cut and moves it toward a sharp edge. However, yet other embodiments include a plurality of wheels, each of which has teeth in engagement with (or pressing against) the material to be cut. These wheels are spaced apart from one another so that their teeth engage different portions of the material being cut. 
       FIGS. 31 ,  32  and  33  depict different aspects of a cutting assembly  250  according to another embodiment of the present invention. Cutting assembly  250  operates in a manner similar to that of cutting assembly  150 , except for differences that will be explained. 
     As best seen in  FIGS. 31A and 32B , keel  252  extends downward from support  251  by an attachment arm  252 . 3 . An elongated foot  252 . 1  extends laterally from arm  252 . 3  and ends in a toe  252 . 11  that is located generally under teeth  256 . 2 . 
     The rotational movement of teeth  256 . 2  moves the material along path  250 . 1  toward the sharp surface  252 . 4  of rear shearing wedge  252 . 9 . In some embodiments, wedge  252 . 9  has a generally concave shape  252 . 12  that is open in the direction of accepting the material to be sheared and generally at the apex of the concavity (as best seen in  FIG. 33B ). Thus, wheels  256 A and  256 B press the material downward toward foot  252 . 1 , bend the material over fin  252 . 10 , and pull the material past the sharp edge  252 . 4  of rear cutting surface  252 . 9 . 
     Foot  252 . 1  includes a fin  252 . 10  that rises upward from the top surface of the foot and extends toward the centerline of advancing wheels  256 A and  256 B. This fin  252 . 10  preferably comes to an apex (which can be seen in  FIGS. 36 and 43  with regards to feet  352 . 1  and  452 . 1 , respectively). Referring again to  FIGS. 31B and 33 , it can be seen that this apex of the fin slopes upward toward the rotational centerline. Therefore, as teeth  256 . 2 A and  256 . 2 B move the material in direction  250 . 1 , the material to be cut is pressed downward by the teeth toward the top surface of foot  252 . 1 , and the portion of material in between the teeth is pressed upward by the top surface (or apex) of fin  252 . 10 . This motion places the material to be cut in bending, such that the topmost surface of the material tends to be in tension, and the bottommost surface (surface of the material in contact with the fin) is in a state of compression. 
       FIG. 32B  is a cross sectional view of a cutting assembly  250  that is cutting a portion of a material M. The material M is being moved toward the shearing surfaces of foot  252 . 1  in direction  250 . 1  by the action of the teeth of advancing wheels  256 A and  256 B. The apex of the teeth are generally in pressing contact with the material M, and in some embodiments can puncture the material. The material has been drawn by the teeth over the toe  252 . 11  (not shown in  FIG. 32B ), and a portion of material is on top of raised fin  252 . 10  of foot  252 . 1 . Fin  252 . 1  presses against the underside of material M. On either side of the fin the teeth of the advancing wheels push down on the material M, such that the material is bent in a downward U-shape. This bending places the top surface MT in tension, and the bottom surface MC in compression. This increased state of stress within the material reduces the amount of shearing force that needs to be applied by the sharp edge  252 . 4  within the concave cutting surface  252 . 12 . 
     Cutting assembly  250  further includes a plain bearing  257  located between a cylindrical alignment pilot  256 . 8 A and an inner diameter of support structure  251 . A second cylindrical alignment pilot  256 . 8 B is received within first pilot  256 . 8 A, as best seen in  FIG. 32 . Bearing  257  is preferably fabricated from a lubricious material (or has a lubricious coating on the material), and in one embodiment is fabricated from Polylube® MRP material provided by Polygon Company. Bearing  257  prevents galling between the outer diameter of pilot  256 . 8 A and the inner diameter of support structure  251 .  FIG. 33  further shows a pair of washers  251 . 9  located on either side of support  251 , and providing spacing and bearing functions pertaining to translational movement of wheels  256 A and  256 B along their rotational axis. Four alignment pins  251 . 6  limit movement of wheel  256 A relative to wheel  256 B. Further, these pins  251 . 6  impart driving torque from the driven wheel (i.e., wheel  256 A in  FIGS. 31A ,  31 B, and  32 ) to the other (or front) wheel  256 B. As stated previously for cutting assembly  50 , this driving torque is imparted to wheel  256 A by the driving surface  256 . 1 A from a driving member such as driving member  46 . 3  (as seen in  FIG. 12 ). 
     Wheels  256 A and  256 B include teeth that are oriented for advancing the material to be cut in a manner different than wheels  56  and  156 . Referring first to  FIGS. 20A and 20B , it can be seen that wheels  156  include teeth that have a concave surface on one side, and a convex surface on the other side. As the wheels  156  turn in their normal manner, the concave side leads the convex side in advancement along direction  150 . 1 . Thus, as teeth  156  rotate clockwise from a position closest to foot  152 . 1  (as viewed in  FIG. 20A ), the concave side of a tooth  156 . 2  grabs and “scoops up” the material being cut, and in some embodiments can act to lift the material as it is being sheared in rear cutting surface  152 . 9 . 
     In contrast, the orientation of the teeth  256 . 2  of cutting assembly  250  are oriented in an opposite direction. As wheel  256  rotates in its normal manner, the leading edge of a tooth is the convex side  256 . 4 , and the trailing side is the concave side  256 . 3 . Referring to  FIG. 31A , as wheel  256 B rotates to move material in direction  250 . 1 , there is less tendency to lift up the material, since the leading of the tooth is a convex surface. Therefore, as wheel  256  rotates, the convex side of the tooth nearest the apex first contacts the material, followed by the concave side which trails the apex. As the tooth continues to rotate and move upward and away from foot  252 . 1 , the convex leading edge of the tooth facilitates the sliding off of the punctured material from the tooth.  FIGS. 34-40  depict various views of a cutting assembly  350  according to another embodiment of the present invention. As will be appreciated by one of ordinary skill in the art, cutting assembly  350  is similar to cutting assemblies  50 ,  150 , and  250 , except for the differences that will be shown and described. 
     Cutting assembly  350  includes a pair of advancing wheels  356 A and  356 B that include a modified means of providing torque from the wheel driven by the gear train to the other wheel. Referring to  FIG. 35 , driving torque from the gear train is provided to wheel  356 A. Wheel  356 A subsequently drives outermost wheel  356 B. 
     Referring to  FIGS. 39 and 40 , the hub of wheel  356 A includes an outermost diameter  356 . 11  that is received generally within the inner diameter  351 . 10  of support  351  (as best seen in  FIG. 38 ). Referring again to  FIG. 40 , wheel  356 A further includes an inner diameter  356 . 8 A that receives within it a piloting outer diameter  356 . 8 B of the hub of wheel  356 B (as best seen in  FIG. 39 ). However, the pilot of wheel  356 B is squared off on two edges so as to form a pair of partly cylindrical ears  356 . 9 B. The squared off surfaces of these ears are received within the mating flat surfaces  356 . 9 A of wheel  356 A. By the placement of these ears within a complementary-shaped pocket, a driving torque applied to driving surface  356 . 1 A is transmitted by surfaces  356 . 9 A to the ears  356 . 9 B of wheel  356 B. Likewise, if cutting assembly  350  is placed on apparatus  20  in the opposite direction (so as to cut material in a direction opposite that as indicated by arrow  350 . 1 ), then the driving torque imparted by the gear train to driven interface  356 . 1 B will be transmitted by ears  356 . 9 B to the walls of pocket  356 . 9 A of wheel  356 A. 
     Therefore, it can be seen that cutting assembly  350  includes a pair of advancing wheels that are keyed or interlocked to each other so as to impart torque directly from the structural web of one wheel to the structural web of the adjacent wheel. It is not necessary to transmit torque by pins  351 . 6 . Instead, these pins can maintain the location of one wheel relative to the other and prevent sliding apart along the axis of rotation. As seen best in  FIGS. 35 and 38 , each pin  351 . 6  is locked in place by a pair of spring clips  35 . 7  that fit within grooves on either end of the pin. 
       FIGS. 41-44  depict various views of a portion of an apparatus according to another embodiment of the present invention.  FIG. 41  shows a cutting assembly  450  placed in driving engagement with a drive adapter  446 . 3  extending on one end of the shaft that also includes driven gear  446 . 2  of a pair of pinion gears (similar to the pinion gears  46 . 2  and  46 . 1  shown in  FIGS. 12-15 ). Cutting assembly  450  is similar to cutting assemblies  50 ,  150 ,  250 , and  350 , except as will be shown and described. 
       FIG. 42  shows a portion of the apparatus of  FIG. 41 , except with housing halves  451 . 2  and  451 . 1  removed, and also with support structure  451  (including the keel and the foot) removed. It can be seen that pinion gear  446 . 2  is located on one end of a shaft, with the other end of the shaft including a squared-off driving section  446 . 3 . Driving member  446 . 3  has a length that is sufficient for it to extend completely through the hubs of the advancing wheels  456 A and  456 B. As best seen in  FIG. 43 , and as can be appreciated from  FIG. 42 , the driving portion  446 . 3  extends within advancing wheel  456 A. Therefore, drive adapter  446 . 3  can directly drive both wheels  456 B and  456 A. 
     Referring to  FIGS. 42 and 43 , it can be seen that these figures show cutting assembly  450  coupled to the drive adapter  446 . 3  in a second position that is different than the position of the cutting head  350 .  FIG. 42  shows that the wheel closest to pinion gear  446 . 2  is wheel  456 B, which includes a pair of driving ears  456 . 9 B. In a manner similar to that discussed with regards to cutting assembly  350 , these drive ears are received within a complementary-shaped driving pocket of wheel  456 A. Thus, in cutting assembly  450  the wheels  456  have features that interlock them so that they rotate in unison, and further these features (such as the ears) permit the transmission of torque. In addition, torque is transmitted directly to each wheel by the driving element  446 . 3  from pinion gear  446 . 2   
     In comparing  FIGS. 34 and 41 , it is evident that cutting assemblies according to various embodiments of the present invention can be located on a driving shaft in either of two positions.  FIG. 34  shows a first position in which the flow of material  350 . 1  is from right to left, and in which advancing wheel  356 B is the front-most advancing wheel and wheel  356 A is closest to the pinion gear. 
       FIG. 41  shows a cutting assembly  450  in which the assembly is oriented in a second position. This position is revolved about axis  451 . 12  by one-half turn. Referring to  FIG. 43 , it is seen that interchangeability axis  451 . 12  is generally perpendicular to rotational axis  446 . 5  of the advancing wheels. 
     Returning to  FIG. 41 , it is seen that after this change in position, the flow of material  450 . 1  is generally now from left to right, and further that the front-most advancing wheel is wheel  456 A, and wheel  456 B is comparatively closer to pinion  446 . 2 . Thus, the mounting and drive features of the cutting assemblies  50 ,  150 ,  250 ,  350 , and  450 , are adapted and configured to provide two different cutting directions based on placement of the cutting head in either of the two different positions. 
     Cutting assembly  450  and driving member  446 . 3  are further adapted and configured to provide easy releasability of cutting assembly  450  from drive adapter  446 . 3 , and subsequently easy reattachment in the same position (such as replacing a worn cutting edge) or in the other position (such as for cutting in the other direction). As best seen in  FIGS. 42 ,  43 , and  44 , driving member  446 . 3  and cutting assembly  450  are adapted and configured to accommodate means  459  for readily disengaging the cutting assembly from the driving member. In one embodiment, means  456  includes a push button  459 . 1  located within a collar  459 . 5 , both of which are in a bore of driving member  446 . 3 . A spring  459 . 4  biases push button  459 . 1  outward from the front face of cutting assembly  450 . 
     Referring to  FIG. 43 , collar  459 . 5  and driving member  446 . 3  are adapted and configured to receive a ball  459 . 3 . Ball  459 . 3  is pushed outwardly by a sloping, transitional detent  459 . 2  of button  459 . 1 . Therefore, button  459 . 1  is spring loaded to push ball  459 . 3  outward past the outermost surface of driving member  446 . 3  (as best seen in  FIGS. 42 and 43 ). This ball extends between the hubs of wheels  456 A and  456 B. Any attempt to slide the wheels off of driving member  446 . 3  will be obstructed by interference between the ball  459 . 3  and the innermost hub (the hub of wheel  456 A in  FIG. 43 ). Therefore, the location of cutting assembly  450  along rotational axis  446 . 5  is established by interference of the ball and the wheel hub, and further by the other end of the hub pressing against a shoulder of driving element  446 . 3 . 
     Removal of cutting assembly  450  is easily accomplished by pushing button  459 . 1  inward, such that ball  459 . 3  drops to a lower position and no longer interferes with the hub of the innermost advancing wheel. When ball  459 . 3  is in the lower position, cutting assembly  450  can be removed by translating it forward in a direction parallel to the rotational axis. Likewise, to engage cutting assembly  450  onto driving member  446 . 3 , the pushbutton is again pushed inward to lower the position of the ball, and the cutting head can be reinserted over the driving member and the dowels  34 . 2  (as seen in  FIG. 6 ). 
     Other embodiments of the present invention contemplate other means for readily engaging and disengaging the cutting assembly from the driving member. As seen with regards to other cutting heads described herein, another means for readily engaging and disengaging the cutting assembly is a central socket screw  58  or  158  that threadably engages a set of interior threads within driving member  46 . 3 . Further, yet other embodiments of the present invention contemplate a spring loaded, bayonet-type of engagement mechanism such as those used in some electrical connectors. Preferably, the engaging and disengaging means does not require a separate tool, and further in some embodiments can be accomplished with a single hand of the user. 
     While the inventions have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.