Patent Publication Number: US-6709319-B2

Title: Sharpener assembly for a food slicer and related method

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application division to application Ser. No. 09/225,934 filed Jan. 6, 1999 now U.S. Pat. No. 6,261,161. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a sharpener assembly for a food slicer and, more particularly, to a sharpener assembly configured for enabling pivotal movement of a sharpening wheel and a truing wheel toward opposite sides of a knife of a food slicer. 
     BACKGROUND OF THE INVENTION 
     Typical food slicers have a base with a rotatable, circular or disc-like slicing knife mounter thereon, a gauge plate for determining the thickness of the slice and a carriage for supporting the food as it is moved past the cutting edge of the knife during slicing. The cutting edge of the knife tends to dull from use and therefore a sharpener is needed to sharpen the knife to maintain a good cutting edge for efficient slicing. Sharpening stones are typically brought against the knife&#39;s cutting edge as the knife rotates in order to provide such sharpening. A variety of sharpening devices have been used in the past to provide such sharpening. 
     Many existing sharpening devices suffer from using complex arrangements to convert a rotational movement into two translational movements. Other existing sharpening devices require two steps, a first in which a sharpening wheel or stone is brought into contact with one side of the knife to sharpen, and a second in which a truing wheel or stone is brought into contact with the opposite side of the knife to debur the knife edge. 
     U.S. Pat. No. 5,591,072 which is assigned to the assignee of the present application provides a sharpening device which overcame the problem of having to move the sharpening device between an inactive or stowed position and an active or sharpening position. However, the construction provided is relatively complex and includes a large number of parts adding to the expense of manufacture. Canadian Patent No. 630,702 describes a slicer with a knife sharpener which includes sharpening wheels which can be positioned on opposite sides of a knife for sharpening, but as mentioned above, requires the sharpener to normally be stored in an inactive position when not in use and in such inactive position the sharpening wheels are not positioned on opposite sides of the knife. Further, the sharpener requires two handles to be operated in order to sharpen the slicer knife. 
     Another disadvantage of known knife sharpeners is that the sharpening stones or wheels typically need to be more abrasive than the truing stones or wheels used. This requirement adds to parts cost of sharpeners and requires a more exacting manufacturing process in order to assure that the wheels of appropriate abrasiveness are placed properly during manufacture. 
     Further, certain food slicers are adapted for use with more than one type of slicer knife, and different knives can have different attributes such as knife edge thickness. Many existing sharpener assemblies lack the ability to account for such differences between knife types. 
     Accordingly, it would be desirable and advantageous to provide a relatively simple sharpener assembly which is always positioned for sharpening when attached to a food slicer. It would likewise be desirable to provide a sharpener assembly operable to provide sharpening and truing simultaneously by a single rotational motion. Further, it would be desirable and advantageous to provide a sharpener assembly configured to permit the sharpening wheel and the truing wheel to have substantially the same abrasiveness while still providing effective sharpening. Still further, a sharpener assembly which enables adjustment of the amount of sharpening which is performed would also be advantageous. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention a method of sharpening and truing a rotating slicer knife of a food slicer involves providing a rotatable sharpening wheel and a rotatable truing wheel on opposed sides of the slicer knife, the sharpening wheel and the truing wheel connected for pivotal movement toward the slicer knife upon rotation of a handle member. The handle member is rotated such that both the sharpening wheel and the truing wheel contact the slicer knife causing the sharpening wheel and the truing wheel to rotate. Relative rotation between the sharpening wheel and the slicer knife results in a sharpening grain acting inward along a cutting edge of the knife and relative rotation between the truing wheel and the slicer knife results in a truing grain acting outward along the cutting edge of the knife. The inward acting sharpening grain provides a more aggressive grinding action as desired for sharpening and the outward acting truing grain provides a less aggressive grinding action as desired for truing. 
     In another aspect of the present invention a sharpener assembly for a food slicer having a rotatable knife includes an assembly mount head having a recessed slot, the mount head including a through hole to the recessed. A frame having first and second spaced mount arms with a connecting member extending between the mount arms is provided, each mount arm including a through passage along its length. At least a portion of the connecting member is positioned within the mount head slot in alignment with the through hole. A first shaft extends through the through passage of the first mount arm and has a sharpening wheel connected to a first end thereof and a second shaft extends through the through passage of the second mount arm and has a truing wheel connected to a first end thereof. A handle is operatively connected to the frame connecting member through the through hole of the mount head for pivoting the frame. The subject assembly is preferably detachably connected to the base of the food slicer such that the sharpening wheel and truing wheel are normally positioned on opposite sides of the knife to facilitate sharpening as necessary by turning the handle to pivot the wheels into contact with the sides of the knife. Thus, a simple one-step rotation operation provides both sharpening and truing and there is no need for moving the assembly to an inactive position when it is not in use for sharpening and truing. 
     In yet another aspect of the invention a sharpener assembly for a food slicer having a rotatable knife includes a frame having first and second spaced mount arms with a connecting member extending between the mount arms. A first shaft extends from the first mount arm and has a first abrasive wheel connected to an end thereof and a second shaft extends from the second mount arm and has a second abrasive wheel connected to an end thereof. A first biasing member is positioned on the first shaft for biasing the first abrasive wheel away from the first mount arm and a second biasing member is positioned on the second shaft for biasing the second abrasive wheel toward the second mount arm. In the preferred embodiment one abrasive wheel is a sharpening wheel and the other abrasive wheel is a truing wheel and the force exerted by one of the biasing members on the sharpening wheel is greater than the force exerted by the other biasing member on the truing wheel. Such preferred construction facilitates using wheels having substantially the same abrasiveness for both the sharpening wheel and the truing wheel. 
     In a further aspect of the present invention a food slicer includes a base with a disc-like slicing knife mounted for rotation on the base and having a peripheral cutting edge. A knife guard extends about a portion of the peripheral cutting edge of the knife and includes first and second side portions extending along respective first and second sides of the knife. A sharpener assembly is detachably mounted to the base and includes a frame having first and second spaced mount arms with a connecting member extending between the mount arms, a first shaft extending from the first mount arm and having a first abrasive wheel connected to an end thereof, and a second shaft extending from the second mount arm and having a second abrasive wheel connected to an end thereof. The first abrasive wheel is positioned on the first side of the knife and the second abrasive wheel is positioned on the second side of the knife. The first side portion of the knife guard includes a first open region alignable with the first abrasive wheel and the second side portion of the knife guard includes a second open region alignable with the second abrasive wheel. This configuration provides a slicer with a sharpener assembly which is always in a ready position for sharpening. 
     The abrasive sharpening or truing wheels incorporated in to the sharpener assemblies may preferably be formed by a disc-shaped member having a knife engaging side which includes a recessed area surrounded by an annular abrasive surface, wherein the annular abrasive surface is frusto-conical in shape such that a central axis of the frusto-conical annular abrasive surface coincides with a central axis of the abrasive wheel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a typical food slicer; 
     FIG. 2 is an exploded perspective view of one embodiment of a sharpener assembly; 
     FIG. 3 is a side view of the assembled sharpener of FIG. 2 with the housing removed; 
     FIG. 4 is a bottom view of the sharpener of FIG. 3 with the housing included; 
     FIGS. 5 and 6 show sharpening and truing grains respectively; 
     FIGS. 7-10 show the frame member of the sharpener of FIG. 2; 
     FIG. 11 shows an enlarged cross-sectional view of one embodiment of an abrasive wheel of the present invention; and 
     FIGS. 12 and 13 show alternative configurations of a blade guard adopted for use with the present invention. 
    
    
     DETAILED DESCRIPTION 
     A typical food slicing machine  100  is shown in FIG.  1 . It has a rotatable circular or disc-like slicing knife  102  mounted on a housing  104 . The knife is mounted for rotation on a fixed axis shaft. The slicer  100  conventionally uses a ring guard (not shown) fastened thereto for the protection of the cutting edge of the slicing knife  102 . The slicer  100  includes a cover plate  108  which is placed over the knife  102  and ring guard so that only a small portion of the knife blade is exposed. The slicer also includes a gauge plate  110  used to guide the food to be sliced and alter the thickness of the slices. The food is supported on carriage  112  which reciprocates in front of the blade. 
     In a typical embodiment of the present invention, a sharpener assembly which is mountable on a food slicer and a base assembly is provided. The sharpener preferably includes two abrasive stones which opposingly engage the front and rear sides or faces of the knife simultaneously to grind and hone a fine edge on the knife. The main abrasive stone is on the back side of the knife, i.e., the side opposite the food, and comprises a circular or disc-shaped abrasive stone mounted for rotation on a shaft. A similar abrasive stone carried on another shaft acts as a truing stone and comes into contact with the front side of the knife to debur the sharpened knife edge. 
     An exploded perspective view of a sharpener assembly in accordance with one aspect of the present invention is shown in FIG.  2  and includes a handle  10 , a handle shaft  12 , a housing  14 , a mount head  16 , a frame  18 , and a mount post or shaft  20 . The mount head  16  includes a recessed slot  22 , a through hole  24  which extends to the recessed slot  22 , and threaded holes  26 A,  26 B which extend laterally into the recessed slot  22 . The frame  18  includes spaced mount arms  28 A,  28 B with a connecting member  30  extending between the arms. Each mount arm includes a corresponding through passage  32 A,  32 B along its length. Each through passage receives a corresponding mount arm  34 A,  34 B to which the abrasive wheels  36 A,  36 B are rotatably attached. Housing  14  includes an opening  38  which aligns with mount head through hole  24  for permitting handle shaft  12  to extend to and connect to a handle receiving hole  40  in the connecting member  30  of frame  18 . A bottom side of mount head  16  also includes an opening  42  which receives the assembly mount shaft  20 , with the mount shaft being non-rotatably connected thereto. Holes  44  in housing  14  align with the corresponding holes  46  in mount head  16  to provide attachment of housing  14  to the mount head  16 . A leaf spring type biasing member  48  is connectable to one side of the connecting member  30  of frame  18 , such as by using aligned holes and screws. Although shown as separate attachable components, handle  10  and handle shaft  12  could be formed as an integral component with handle  10  being molded to handle shaft  12 . It is also anticipated that handle shaft  12  could be replaced with a torsion spring  12 ′, and use of such a torsion spring would act as a limit to the force applied by each abrasive wheel against the slicer knife  102  upon rotation of the handle  10  discussed below. 
     As best seen in the side elevation view of FIG. 3, when assembled, the abrasive wheels  36 A,  36 B are spaced from each other so as to be disposed on opposite sides of a slicer knife  102 . The free end of assembly shaft  20  mounted in a non-rotatable manner with respect to a food slicer base, and with the opposite end of assembly shaft  20  mounted in a non-rotatable manner with respect to mount head  16 , such as through use of a pin  21 . Thus, when handle  10  is rotated in a clockwise manner as indicated by arrow  50 , the frame  18  will likewise be rotated or pivoted within mount head slot  22  such that each abrasive wheel  36 A,  36 B moves toward the slicer knife  102  as indicated by arrows  52 A,  52 B until each abrasive stone contacts its corresponding side of the slicer knife  102  for sharpening and truing thereof. However, in the normal assembled position with handle  10  not rotated, biasing member  48 , which may be a leaf spring type member, urges the respective abrasive wheels  36 A,  36 B into the non-contacting positions shown in FIGS. 2-3 via contact with the side of the mount head  16 . 
     Advantageously, disposed on each shaft  34 A,  34 B is a biasing member  54 A,  54 B for urging the respective abrasive wheels  36 A,  36 B toward the slicer knife  102  as they engage the respective side of the knife  102 . In particular, biasing member  54 A (FIG. 2) may be a spring washer disposed about shaft  34 A at a location between abrasive wheel  36 A and an end  56  of mount arm  28 A such that as abrasive wheel  36 A contacts slicer knife  102  compression of biasing member  54 A urges the abrasive wheel  36 A into contact with the slicer knife  102  with a first predetermined force. Biasing member  54 B may be a compression spring disposed about shaft  34 B between an end  58  of mount arm  28 B and an end  60  of shaft  34 B. Thus, in the illustrated embodiment biasing member  54 A biases abrasive wheel  36 A away from mount arm  28 A and biasing member  54 B biases abrasive wheel  36 B toward mount arm  28 B. In order to facilitate use of similar abrasive wheels  36 A,  36 B having substantially the same abrasiveness, the force with which abrasive wheel  36 A is urged away from mount arm  28 A is preferably greater than the force with which abrasive wheel  36 B is urged toward mount arm  28 B, and abrasive wheel  36 A acts as a sharpening wheel and abrasive wheel  36 B acts as a truing wheel. 
     As best seen in the bottom view of FIG. 4, the pivot or rotation of frame  18  will be limited by the recessed slot  22  of mount head  16  because connecting member  30  of frame  18  will contact the sides of slot  22  after a predetermined amount of pivot or rotation. In order to provide adjustment of the amount of permitted rotation of frame  18  relative to mount head  16 , one or more threaded passages  26 A,  26 B are provided into which threaded members such as set screws  27 A,  27 B may be positioned with interior ends of such set screws extending into slot  22 . The set screws can be threaded further into slot  22  to reduce the permitted rotation of frame  18  or can be threaded further out of slot  22  to increase the permitted rotation of frame  18 . This feature permits the sharpener assembly to be used in a larger variety of food slicers having knives of different types or dimensions. 
     The abrasive wheels  36 A,  36 B each contact the slicer knife  102  so as to result in a preferred sharpening or truing grain as the case may be. Referring to FIGS. 5 and 6, with abrasive wheel  36 A acting as the sharpening wheel, contact between the wheel and the slicer knife  102  is shown at  62 A. Arrow  64  indicates the direction of rotation of slicer knife  102  and arrow  66 A indicates the direction of rotation of wheel  36 A upon contact with the slicer knife  102 . The velocity vector V K  of the knife and the velocity vector V W  of the wheel combine to provide a relative velocity vector V R  (of the wheel relative to the knife) which provides a sharpening grain in the direction indicated by arrow  68 A, inward along the knife edge which make grinding more aggressive as desired for sharpening. In FIG. 6, contact between wheel  36 B and slicer knife  102  is indicated at  62 B. The direction of rotation of slicer knife  102  is again indicated by arrow  64  and the direction of rotation of wheel  36 B is indicated by arrow  66 B. The velocity vector V K  of the knife and the velocity vector V W  of the wheel combine to provide a relative velocity vector V R′  (of the wheel relative to the knife) which provides a truing grain in the direction indicated by arrow  68 B, outward along the knife edge which makes grinding less aggressive as desired for truing. Accordingly, this feature also facilitates use of wheels  36 A,  36 B having similar abrasive properties. It is recognized that the direction of the sharpening grain and the truing grain may vary depending upon the exact configuration of the knife as well as other factors. 
     An enlarged view of the frame  18  is depicted in FIGS. 7-10. Referring to FIG. 7, a perspective view of frame  18  is shown in which the frame is upside down relative to its position shown in FIG.  2 . In this enlarged view it is apparent that the mount arms  28 A,  28 B are angled in relation to each other in order to facilitate proper contact of the respective abrasive wheel with the sides of the slicer knife  102 . A lateral opening  70  is shown for receiving a pin or set screw to connect the handle shaft  12  to the frame  18 . Also shown are threaded holes  72  for securing the leaf spring type biasing member  48  thereto. 
     In FIGS. 8-10 line  74  represents a plane which runs parallel to the axis of the handle shaft  12  and is used to define the angular relationship between mount arms  28 A and  28 B. As shown in FIG. 8 mount arm  28 A intersects plane  74  at an angle A and as shown in FIG. 10 mount arm  28 B intersects plane  74  at an angle B. In one embodiment of the invention angle A might be on the order of about 19 degrees and angle B might be on the order of about 6 degrees. However, it is recognized that such angles could vary depending upon the exact configuration of the slicer knife  102  as well as other factors including the exact configuration of the abrasive wheels  36 A,  36 B. 
     With respect to the configuration of abrasive wheels  36 A,  36 B, reference is made to FIG. 11 showing an enlarged cross-sectional side view of a representative abrasive wheel. As shown, in a preferred embodiment the abrasive wheel is a generally disc shaped member having a knife engaging side  76  which includes a recessed area  78  which is surrounded by an annular abrasive surface  80 . Surface  80  may, for example, include an abrasive coating of cubic boron nitride. Abrasive surface  80  is preferably frusto-conical in shape as shown, with a central axis of  82  of the frusto-conical abrasive surface coinciding with an axis  84  of rotation of the wheel. Further, a line  86  extending from and parallel to the annular surface  80  at a point thereabout and to the axis of rotation  84  intersects the axis of rotation  84  at a non perpendicular angle. In particular, angle C of such intersection is preferably in the range of about 80 to 84 degrees. However, it is recognized that such angle could vary depending up the exact configuration of the slicer knife  102  as well as other factors including the angular relationship between mount arms  28 A and  28 B. 
     With respect to attachment of the sharpener assembly to the food slicer, mount shaft  20  is used as previously mentioned. The mount shaft  20  includes an opening  90  at the bottom thereof for positioning on a mount boss (not shown) of a food slicer base. The opening  90  (FIGS. 2 and 3) and the mount boss may be appropriately configured to prevent rotational movement of the mount shaft  20  relative to the mount boss. It is recognized that other manners of connecting the sharpener assembly to the slicer are possible. 
     Referring to FIGS. 12-13, a knife guard  118  is preferably configured for facilitating the positioning of the abrasive wheels  36 A,  36 B on opposed sides of the slicer knife  102 . In this regard, the knife guard  118  typically includes side portions  120 A,  120 B which extend along opposed sides of the slicer knife  102 . In order to provide access to the sides of the slicer knife  102 , each side portion of the knife guard  118  preferably includes a respective open region aligned with the abrasive wheel adjacent thereto. As shown in the side view of FIG. 12, such open regions may take the form of radially recessed regions  122 A and  122 B. In another embodiment shown in the top view of FIG. 13, the open regions may take the form of laterally spaced regions  122 A′ and  122 B′ of side portions  120 A and  120 B respectively. Such configurations allow the sharpener assembly to be located in a sharpening position at all times while permitting the sharpener assembly to be easily removable from the food slicer. 
     Although the invention has been described and illustrated in detail it is to be clearly understood that the same is intended by way of illustration and example only and is not intended to be taken by way of limitation. For example, the respective functions (sharpening or truing) of the abrasive wheels could be reversed as needed depending upon the knife configuration and the mounting location of the assembly. Further, a sharpener assembly could utilize a sharpening wheel of different abrasiveness than the truing wheel without departing from the broader aspects of the present invention. Accordingly, the spirit and scope of the invention are to be limited only by the terms of the appended claims.