Abstract:
Apparatus, systems and methods related to sharpening blades for rotary cutters. In one illustrative embodiment, a power sharpener system secures a rotary cutting blade between upper and lower columns that form a rotating axle in contact with upper and lower sharpening stones, each positioned at an appropriate angle to contact a cutting edges of the rotary blade for sharpening. The upper column may be rotatably attached to an upper cover or lid and the lower column rotatably disposed in a base. After the rotary blade is secured, an electric motor is used to rotate the column, contacting the edges of the blade against the stones to simultaneously sharpen both edges of the blade. In some embodiments, a retractable plate may be disposed around the lower column for placement of the rotary blade thereon and a lifting lever may be used to facilitate blade removal.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to honers and sharpeners for blades, and in particular, to devices aid methods for sharpening blades for hand held rotary cutters. 
       BACKGROUND 
       [0002]    Rotary cutters are used for cutting fabric in quilt making and hobby sewing, among other uses. Such rotary cutters come in many different designs, each of which includes a handle portion and a “wheel blade” or rotary cutting blade. The various designs for rotary cutters include differing handle shapes, for ease of use or user preference, with a rotary cutting blade rotatably mounted near one end. Various designs include differing blade guard features which are intended to reduce the potential for injury to a user. 
         [0003]    The rotary cutting blades for such cutters typically come in three standard sizes, a 28 mm diameter rotary cutting blade, a 45 mm diameter rotary cutting blade, and a 60 mm diameter rotary cutting blade. One known problem with rotary cutters is the relatively high replacement cost of the blades for these popular fabric, craft, and hobby cutting tools. Additionally, as noted in the prior art, many rotary cutting blades lack perfect roundness. 
         [0004]    Known sharpeners for rotary cutting blades include sharpeners for the large rotary blades of commercial cutters for meat slicing and the like, which are used with the motor driven blade of the cutter. Also, known are smaller manual sharpeners for hand held rotary cutters, such as those disclosed in U.S. Pat. Nos. 7,238,096, 5,660,582 and 5,499,943, the disclosures of each of which are incorporated by reference herein. However, these types of manual sharpener require the wheel blade to be removed from the cutter and secured within the device, following which the user rotates a portion of the device by hand to rub the cutting edge of the blade against an abrasive grit. This requires a significant effort on the part of the user, which may be problematic for some customers. 
         [0005]    One attempt to address these shortcomings has resulted in the RBS-61 Rotary Cutter Blade Sharpener available from inventive Circles, LLC. However, such sharpener requires a rotary blade to be bolted to in place on an open top, then a rotating; head positioned thereover which rotates an abrasive disk against the blade, rotating the blade. A complete sharpening requires removing and replacing the blade to sharpen both edges twice, once with a “diamond disc”, and once with an “ultrafine disc”. Such a sharpener is relatively bulky and harder to transport. Further, the continual exposure of the rotary blade during sharpening and the additional handling of the blade required to complete sharpening increase the likelihood of injury to a user. 
         [0006]    Accordingly there exists a need for assemblies and devices that address these problems. A system or assembly that allowed for a rotary blade to be honed or sharpened quickly with reduced chance of injury to a user would be an improvement in the art. Such a sharpener that was easily portable and relatively inexpensive would be further improvement in the art. 
       SUMMARY 
       [0007]    Apparatus, systems and methods in accordance with the present invention are related to sharpening blades for rotary cutters. In one illustrative embodiment, a power sharpener system secures a rotary cutting blade between upper and lower columns that form a rotating axle in contact with upper and lower sharpening stones, each positioned at an appropriate angle to contact a cutting edge of the rotary blade for sharpening. The upper column may be rotatably attached to an upper cover or lid and the lower column rotatably disposed in a base. After the rotary blade is secured, an electric motor is used to rotate the column, contacting the edges of the blade against the stones to simultaneously sharpen both edges of the blade. In some embodiments, a retractable plate may be disposed around the lower column for placement of the rotary blade thereon and a lifting lever may be used to facilitate blade removal. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0008]    It will be appreciated by those of ordinary skill in the art that the elements depicted in the various drawings are not necessarily to scale, but are for illustrative purposes only. The nature of the present invention, as well as other embodiments of the present invention may be more clearly understood by reference to the following detailed description of the invention, to the appended claims, and to the several drawings attached hereto. 
           [0009]      FIG. 1  is a perspective view of an illustrative embodiment of a power sharpening system in an open position in accordance with the principles of the present invention. 
           [0010]      FIG. 2  is a front view of the embodiment of  FIG. 1 . 
           [0011]      FIG. 3  is a top view of the embodiment of  FIG. 1 . 
           [0012]      FIG. 4  is a side view of the embodiment of  FIG. 1 . 
           [0013]      FIG. 5  is a front cutaway view of an alternative embodiment of a power sharpening system in accordance with the principles of the present invention. 
           [0014]      FIG. 6  is a side cutaway view of the embodiment of  FIG. 5 , 
           [0015]      FIG. 7  is a front perspective view of another alternative embodiment off portion of a power sharpener with the present invention. 
       
    
    
     DESCRIPTION 
       [0016]    For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment 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. 
         [0017]      FIGS. 1 through 4  depict a first illustrative embodiment of a power sharpening assembly  10  in accordance with the principles of the present invention. An outer case  100  surrounds and contains the remaining components of the system  10  and includes an upper cap portion  102  which is connected by a hinge H to a lower portion  110 . Upper cap portion  102  may be generally formed as a rounded sidewall and closed top forming an encircled wall having an open bottom. A securing latch L may extend from the sidewall as a protrusion that interacts with a corresponding latch receiver LR on lower portion  110 . 
         [0018]    A number of structures are disposed in the well of upper cap portion  102 . An upper column  122  is rotatably attached to the upper cap portion  102  by a mounting bracket  124 . As depicted, in  FIGS. 1 through 4 , the upper column  122  and mounting bracket  124  may comprise an axle and bearing type of structure. Alternatively, as depicted in  FIG. 6 , upper column  122 A may be formed as an outer member  622  with a circular planar bottom having encircling sidewall extending at a right angle from the edges thereof to an outer flange  624 , which is disposed on a hub  623 , on which it can be rotated, and protrudes through a hole in the mounting bracket  124 A face, retained thereon by the flange  624 . A circular pad  123  formed of a resilient material, such as a silicone or rubber may be mounted on the face of the upper column  122  for contacting the surface of an inserted rotary blade. It will be appreciated that although depicted as having a rounded cross section, a structure having any cross sectional shape may be used so long as it can be rotated. 
         [0019]    Structures for aligning the upper cap portion  102  with lower portion  110  when the system  10  is closed are also disposed on the upper cap portion  102  and include alignment rods  130 A and  13 AB extending from the closed top of upper cap portion  102 . These rods may be hollow rod, such as rod  130  which has a lower opening (which may be formed by an extension of only a portion of the rod  130 ) Upon closure, alignment rod  130  may receive a corresponding column located within lower portion  110  within its open bore to facilitate accurate alignment of the upper and lower portions. Alternatively, the rod may be a solid protrusion, having a polygonal, rounded, or other cross sectional shape, which is received in a corresponding receiver in the lower portion  110 . 
         [0020]    Additionally, in some embodiments, the alignment rod  130  interaction with a lower column may engage a cut-off switch to complete a circuit that allows the sharpener  10  to be operated, but prevents operation when the sharpener is open. It will be appreciated that in other embodiments, a cutoff switch which completes a circuit that allows the sharpener  10  to be operated, but prevents operation when the sharpener is open, may be constructed in other manners. For example, in  FIG. 1 , a closure tab  145  disposed at the rear surface of the sidewall of upper portion  202  presses push bar  206  into recess of the sidewall at the rear of the front section  200  of tower portion  110 , engaging a switch. 
         [0021]    Additional alignment structures may include one or more alignment flanges  132 , formed as extensions of the outer rim of upper cap portion  102  sidewall that reside inside the sidewall of lower portion  110  upon closure. Alignment flanges  132  may encircle a portion of the upper cap portion  102  and may includes one or more notches that correspond to tabs  152  inside the sidewall of lower portion  110  for increased accuracy of alignment. In addition to facilitating alignment, the flanges  132  may contact retractable plate  150 , pushing it downwards and allowing sharpening of an inserted rotary blade to occur, as discussed in further herein. 
         [0022]    Also disposed in the upper cap portion  102  is upper sharpening stone  140  which is removably disposed in upper stone mounting bracket  142 , which may be formed as a portion of mounting bracket  124 . As depicted, upper sharpening stone  140  may be formed as an elongated member having a square cross section that may be placed in the upper stone mounting bracket  142 , as between a fixed end clip at first end and a movable end clip or lever  143  at the opposite longitudinal end, or as in a recess formed by a first wall or clip at a first end together with opposite walls along the long edges thereof and retained therein by an end clip or lever at the second longitudinal end. Upon installation, one side of the stone is exposed towards the open bottom of upper cap portion  102 , at an angle A measured against a plane parallel to the surface of the face of upper column  122 . Angle A, when measured against the general plane of the base may be from about 5 to about 15 degrees, depending on the embodiment. In the depicted embodiment, the angle is at about 11 degrees and corresponds to the angle of the cutting edge of a rotary cutter blade. Upper sharpening stone  140  may be a natural or synthetic stone suitable for sharpening a blade, as known to those of ordinary skill in the art. It will be appreciated that by using an upper sharpening stone  140  with a square cross-section, as the exposed side of the stone is worn down by use, a user may rotate the stone in the mounting bracket  142  (by removing and replacing the stone) to allow all sides of the stone to be equally used. 
         [0023]    It will be appreciated that, as best depicted in  FIG. 2 , the upper stone mounting bracket  142  may be disposed on mounting bracket  124 . In other embodiments, upper stone mounting bracket may be independently disposed in the upper cap portion  102  on a separate bracket. 
         [0024]    Lower portion  110  of outer case  100  includes a rounded front portion  200 , which may be generally formed as a rounded sidewall and a closed bottom forming an encircled will having an open top, and a rear portion  202  which may be formed as an enclosed box of a desired shape attached to the front portion  200 . Latch receiver LR may be disposed on the front outer sidewall of front portion  200  for receiving latch L disposed on upper portion to secure the upper and lower portions in a closed position. Hinge H is attached to the rear portion  202 , which may include a recess in the top thereof for receiving hinge H or the rear surface of upper portion  102  when in an open position. An actuation switch, such as button  204  may be disposed in the rear portion  202 , as may be a receiving socket for a power cord. 
         [0025]    A retractable plate  150  is disposed within the open portion of the front section  200  of lower portion  110 . As depicted in  FIGS. 1 and 3 , the upper surface of the retractable plate  150  may be formed as a generally planar surface having a series of rounded downward steps of decreasing size. Each step  152  may be formed by a planar circular flat portion with an outer sidewall rise to the adjoining outer step. The spacing between the steps may correspond to the two standard sizes of rotary cutting blades, for handheld rotary cutters, for example the inner step  152 B may hold a 45 mm diameter rotary cutting blade on the flat portion thereof within its encircling sidewall while ringing step  152 A may hold a 60 mm diameter rotary cutting blade on the flat portion thereof within its encircling sidewall. Rotary cutting blades of differing diameters may be placed on the rotary plate  150  on whichever step  152  they fit into or on the retractable plate above the indicated steps, so long as the diameter falls within the coverage of the sharpening stones. 
         [0026]    A lifting lever generally indicated at  160  in  FIG. 1 , may be disposed in the retractable plate  150  to facilitate removal of a rotary blade after sharpening. As depicted lifting lever  160  may be formed as a member having a vertical portion  162  near an edge of retractable plate  150 , which is joined to a horizontal portion  164  corresponding to the upper surface of retractable plate ISO. The horizontal portion  164  of lifting lever  160  lies within an opening in the retractable plate  150  and the surface of the horizontal portion may match the upper surface of retractable plate  150  by completing the steps  152 . Lifting lever  160  may be hingedly attached to the retractable plate  150 , as by a hinge pin near the transition of vertical portion  162  and horizontal portion  164 , in order to allow lever  160  to be rotated by pressing the vertical portion  162  forwards and down, thereby raising the horizontal portion  164  to tip and lift a rotary blade disposed thereover. 
         [0027]    As best depicted in cross-sectional views of  FIGS. 5 and 6 , system  10  includes a number of features at least partially disposed in the interior of lower portion  110 . A lower column  220  is disposed in a central hole in retractable plate  150  to expose the top surface  222  thereof. As with upper column  122 , a circular pad  223  formed of a resilient material, such as a silicone or rubber may be mounted on the face of the lower column  220  for contacting the surface of an inserted rotary blade. It will be appreciated that although depicted as having a rounded cross section, a structure having any cross sectional shape may be used so long as it can be rotated. In some embodiments, the face of either lower column  220  or upper column  122  may include a projection that pass through the central hole of an inserted rotary blade and enters a corresponding receptacle on the opposite column upon closure to facilitate alignment. 
         [0028]    The top surface  222  of lower column  220  may be disposed coplanar with the top surface of the retractable plate  150  or at a lower point to enable a user to place a rotary blade on the retractable plate. Where a projection ( 228 .  FIG. 1 ) is present on the top surface of lower column  220 , it may project past the retractable plate  150  to facilitate alignment. 
         [0029]    From top surface  222  to a junction point  226  underneath the retractable plate  150 , lower column  220  may have a first portion with a relatively thicker cross section that corresponds to the central hole in retractable plate  150 . From junction point  226  to a lower end, the lower column  220  may comprise a shaft having a relatively narrower cross section (in comparison to the upper portion) which may be disposed in a receiver  230  which may comprise a column disposed on the bottom surface of the lower portion  110  that has a bore in which the shaft rotates. 
         [0030]    Extending from the thicker first portion of lower column  220  near junction point  226  is a radial flange  232  which enables the rotation of lower column  220  to be driven. In depicted embodiment, a medial section of the radial flange  232  extends laterally outward from the column  220  and a slanted portion  234  extends upwards at an angle from the medial section. As best depicted in  FIG. 5 , the outer surface of the slanted portion  234  may include a series of ridges  236 , which are spaced apart at regular intervals to allow the rotation to be driven. A medial shelf  240  which may include a lower shaped guide portion  242  or a separate shelf and guide may be used to maintain the column  220  in proper position. 
         [0031]    As best depicted in  FIG. 6 , an electric motor M having a shaft S is used to drive a gear element G 1 , having a slanted portion G 2  and a series of ridges G 3  that correspond to the slanted portion  234  and spaces between the ridges  236  of the medial flange  232  to rotate the lower column  220 . Presently, some embodiments use a nine volt motor which rotates the column  220  at a speed of approximately 600 RPM, although it will be appreciated that a motor having a different voltage or rotating the column at a different speed may be used, provided such motor and speed are sufficient to sharpen an inserted rotary blade. It will be appreciated that the motor may be provided power through a cord plugged into a receiving socket disposed in the case  100 , which may be attached through a transformer to a standard electrical outlet, or that a suitable battery or battery series may be used as known to those of skill in the art. 
         [0032]    Beneath its generally planar upper surface, retractable plate  150  has support structures that allow it to retract into bottom portion  110  when top portion  102  is closed and elevate when top portion  102  is opened. On either side of the retractable table  150 , a columnar leg  156  may extend downwards from the upper planar member. As depicted each leg  156  may be a hollow column formed from a surrounding sidewall  154  and may have an open or closed bottom. The lower end of each leg  156  is received in a receptacle  250  formed by a wall  252  projecting upwards from the bottom of the bottom portion  110  and the sidewall of the bottom portion  110 . The legs  156  are spaced outwards of the medial flange  230  of the lower column. A resilient member such as a spring may be disposed in the front portion of the bottom portion in contact with the retractable plate to urge the plate to an elevated position when the system  10  is open. For example, in some embodiment, such resilient members may be at least partially disposed in the receptacles  252  to provide an upwards force on the legs  156 . 
         [0033]    Also disposed in the lower portion  110  is lower sharpening stone  340  which is removably disposed in lower stone mounting bracket  342 . Stone opening  157  is present in retractable table  150  and allows retractable table  150  to retract past the lower stone and bracket during operation. As depicted, lower sharpening stone  340  may be formed as an elongated member having a square cross section that may be placed in the upper stone mounting bracket  342 , as between a fixed end clip at first end and a movable end clip or lever  343  at the opposite longitudinal end, or as in a recess formed by a first wall or clip at a first end together with opposite walls along the long edges thereof and retained therein by an end clip or lever at the second longitudinal end. Upon installation, one side of the stone is exposed towards the open upper end of lower portion  110 , at an angle B measured against a plane parallel to the surface of the face of lower column  220 . Angle B, when measured against the general plane of the base may be from about 5 to about 15 degrees, depending on the embodiment. In the depicted embodiment, the angle is at about 11 degrees and corresponds to the angle of the cutting edge of a rotary cutter blade. Lower sharpening stone  340  may be a natural or synthetic stone suitable for sharpening a blade, as known to those of ordinary skill in the art. It will be appreciated that by using an lower sharpening stone  340  with a square cross-section, as the exposed side of the stone is worn clown by use, a user may rotate the stone in the mounting bracket  342  (by removing and replacing the stone) to allow all sides of the stone to be equally used. 
         [0034]    It will be appreciated that upper stone  140  and lower stone  340  may be disposed at any desired angle with respect to one another that facilitates placement in a system  10  in accordance with the present invention. For example, in the embodiment depicted in  FIGS. 1 through 4 , the stones are offset from one another in an angle of approximately 90 degrees measured around the rotational axis of the system, while in the embodiment depicted in  FIGS. 5 and 6 , the stones are offset from one another in an angle of approximately 180 degrees measured around the rotational axis of the system. 
         [0035]      FIG. 7  depicts an alternative mechanism for a sharpener system in accordance with the present invention which has a rotary blade RB disposed in the axle formed by upper column  722  and lower column  720 , and uses sharpening stones having a circular cross section and planar lower and upper faces. Such stones,  740  and  840  are mounted in mounting brackets  742  and  842  having a circular stone holding portion. In some embodiments of this type, the stones may be rotated by rotation of, or in, the mounting brackets during sharpening in order to obtain even wearing on the top surface of the stone. In other embodiments, a user may manually rotate the stones between sharpening as desired to obtain even wear. In either type of embodiment, the stones may be removed from the mounting brackets and replaced to expose the former lower surface as the new upper surface to allow both planar sides of the stone to be equally used. 
         [0036]    In operation, a user inserts a rotary blade for a hand held rotary cutter which needs to be sharpened into an open system  10  in accordance with the present invention by placing the rotary blade on or over the top surface  22  of the lower column  220 , as by placing the blade on the retractable plate  150  within a suitable step  152  centered over the lower column  220 . The upper portion  102  or cap of the system  10  is then closed, by rotating the upper portion on hinge H and engaging latch L with latch receiver LR. The alignment structures of the upper and lower portions engage to provide a proper alignment that brings the rotational axis of upper column  122  in alignment with that of lower column  220 , as the face of upper column  122  engages the upper surface of the rotary blade. Where present, the retractable plate  150  is retracted as it is pushed downwards by the structures in the upper portion  102  and cutoff switch  206  is engaged to allow the motor M to be engaged. 
         [0037]    The inserted rotary blade is now held in a rotating axle formed by the upper column  122  and lower column  220  and the cutting edge thereof is in contact with the upper and lower sharpening stones, at an appropriate angle for sharpening. The user then actuates button B to engage the motor M, causing the rotating axle to rotate and sharpening the blade. In some embodiments, actuation of the button B engages an automatic cycle, in which the blade is rotated against the stones for a fixed amount of time set in a control circuit to sharpen or hone the blade as desired. For example, a shorter sharpening cycle may be selected, or a longer honing cycle may be used where the cutting edge is nicked or the blade has strayed from the ideal planar shape to an unsuitable degree. In other embodiments, the button may simply engage the motor while pressed allowing the user individual control over the process. 
         [0038]    After the sharpening process is complete, the user opens the system  10  by releasing latch L from latch receiver LR and rotating top portion  102  upwards. Lifting lever  160  may then be used to tip up the exposed rotary blade for removal from the system  10  and replacement in a hand held rotary cutter. 
         [0039]    While the present invention has been shown and described in terms of preferred embodiments thereof, it will be understood that this invention is not limited to any particular embodiment and that changes and modifications may be made without departing from the true spirit and scope of the invention as defined and desired to be protected.