Patent Publication Number: US-2023148101-A1

Title: Sharpening Sheath Adapted To Receive A Knife, And Combination Of Such A Sheath And A Knife

Description:
TECHNICAL FIELD 
     The present invention relates to the field of blade sharpeners and relates in particular to sheaths for scissors and kitchen knife blades, incorporating a sharpener. 
     STATE OF THE ART 
     There are various manual systems for sharpening kitchen knives. The first knife sharpeners were simple stones or steels requiring the user to have a certain mastery and manual dexterity to sharpen the blade, and requiring knowledge of the sharpening angles. 
     There are more complex knife sharpeners that are designed to be simpler and easier to use by a novice user while allowing for more precise sharpening. 
     For instance, document FR2576537 describes a sharpening sheath associated with a knife that makes it possible to simplify the sharpening operation. 
     However, such a device has the disadvantage of being unsuitable for knives with very different blade heights. In particular, such a device does not enable optimized sharpening of knives with highly curved blade profiles and/or with blade heights that vary significantly from one end of the blade to the other. Indeed, knife blades can have a curvilinear profile on generally all, or at least part, of the cutting edge of the blade. It is therefore difficult and challenging to sharpen a curved or curvilinear shape. The existing sharpeners only sharpen a portion of the cutting edge and do not reach the most curved part of the blade profile, unless the user imparts the adequate curvilinear motion to keep the blade in contact with the sharpener. 
     Moreover, with these existing devices sharpening is only partial and not very precise, resulting in a difference in the cutting performance of the knife between the tip and the heel of the blade. 
     SUMMARY OF THE INVENTION 
     The present invention is intended to remedy this disadvantage. 
     The technical problem behind the invention is to provide a sharpening sheath that guarantees good sharpening quality on knives irrespective of their curve and/or blade height. 
     To this end, the invention aims to provide a sharpening sheath, designed to receive a knife to be sharpened or stored, comprising a cavity for receiving a blade, an access opening at one end of the cavity, the sheath comprising, preferably in the vicinity of the access opening, an upper part equipped with a device for guiding the back of the blade and a lower part comprising a sharpening device onto which the cutting edge of the blade is intended to be applied when inserting the blade in the sheath or removing it therefrom, characterized in that the sharpening device is supported by an arm comprising a first longitudinal end rotatably mounted on a stand, the arm being returned by recoil means in the direction of the guiding device, and in that the sharpening device is rotatably mounted at a second longitudinal end of the arm and suspended from this second longitudinal end of the arm. 
     Such a sharpening sheath has the advantage of having a sharpening device that is rotatably mounted on an arm, which is itself rotatably mounted on a stand. The pivoting movement of the arm relative to the stand allows the sharpening device to move vertically in the sheath to accommodate different blade heights. The mobility of the sharpening device at the end of the arm allows the sharpening device to pivot and follow the curve of the blade so that it is always positioned at the same angle of attack relative to the cutting edge of the blade, such that the blade is optimally sharpened irrespective of the curve of the blade. 
     Advantageously, a sharpening sheath according to the invention is capable of sharpening a knife blade along the entire length of its cutting edge, whether straight or curved, without the user having given an input orientation to the blade. 
     Advantageously, a sharpening sheath according to the invention is capable of sharpening several knife sizes, and accordingly several blade profiles (for example, S-shaped blades such as machetes or scalpels), efficiently without depending on the strength or skill of the user. 
     The device may also have one or more of the following features, taken alone or in combination. 
     According to an advantageous feature of the invention, the first longitudinal end is mounted on the stand so as to pivot around a first axis and the sharpening device is mounted on the arm so as to pivot around a second axis, the first and second axes being parallel to one another. 
     According to an advantageous feature of the invention, these first and second axes are perpendicular to the longitudinal axis of the sheath. 
     This construction offers the advantage of being simple and economical to make and of enabling both a secure attachment and substantial displacement of the sharpening device along the cutting edge of the blade. 
     According to an advantageous feature of the invention, the sharpening device is suspended at the second longitudinal end of the arm, advantageously suspended by its axis of rotation. In other words, the sharpening device is suspended at the second longitudinal end of the arm by its axis of rotation. This advantageous arrangement gives the sharpening device a pendular or swinging motion. The resulting pendular swing allows the sharpening device to adapt to all blade curves. 
     According to an advantageous feature of the invention, the center of gravity of the sharpening device is positioned under the second axis of the arm and under the second longitudinal end of the arm. This feature makes it possible to sharpen from the tip of the blade and continuously along the entire length of the blade edge. Indeed, the sharpening device remains in contact with the edge of the blade for the entire movement of the blade when the knife is inserted into or removed from the sheath. 
     According to an advantageous feature of the invention, the sharpening device comprises two sharpening elements arranged in a “V” shape. 
     This feature allows for balanced sharpening on both sides of the blade. 
     According to an advantageous feature of the invention, the second axis of the second longitudinal end of the arm is positioned above the two V-shaped sharpening elements. 
     According to an advantageous feature of the invention, the two sharpening elements are arranged in two offset planes parallel to each other and perpendicular to the longitudinal axis of the sheath. 
     This arrangement makes it possible to reduce the width of the sharpening device. 
     According to an advantageous feature of the invention, the guiding device comprises a V-shaped groove. 
     According to an advantageous feature of the invention, the V-shaped groove of the guiding device is positioned opposite the two V-shaped sharpening elements, such that the combination of the V-shaped sharpening elements and the V-shaped groove define a diamond-shaped opening into which the end of the blade is inserted when the knife is placed in the sheath. 
     This feature ensures that the blade is correctly guided and centered on the two sharpening elements. Advantageously, this facing characteristic allows the sharpening angle to remain symmetrical and constant throughout the sharpening process, in other words, while the blade is rubbing against the sharpening elements. 
     According to an advantageous feature of the invention, the recoil means comprise a return spring, advantageously helical, positioned between the arm and a stand. 
     This construction has the advantage of being simple and economical to achieve. 
     According to another advantageous feature of the invention, the arm is pivotally mounted on the stand between an upper position in which the return spring is fully extended and a lower position in which the return spring is fully compressed. 
     According to another advantageous feature of the invention, the recoil force applied by the return spring to the arm takes place from bottom to top. 
     This construction advantageously allows the sharpening device to be pushed permanently towards the cutting edge of the blade. The sharpening elements are always in close contact with the cutting edge and at the correct sharpening angles in order to sharpen the blade with every movement thereof. 
     According to an advantageous feature of the invention, the sharpening device is positioned adjacent to the access opening. The sharpening device thus forms the blade entrance of the sheath. 
     This feature allows the blade to be sharpened substantially along the entire length that is inserted into the sheath. 
     According to an advantageous feature of the invention, the sheath comprises a sleeve that is removably mounted on the stand. 
     This feature makes it easier to clean the inside of the sheath. 
     The invention also relates to a combination of a sharpening sheath as previously described and a knife intended to be sharpened or stored in this sheath. 
     Such a feature allows the knife to be stored. Advantageously, simply inserting the blade into its sheath or removing it therefrom makes it possible to sharpen the knife blade, with no need to adjust or direct the angle of the blade. 
     According to an advantageous feature of the invention, the sheath comprises a locking element cooperating with a safety notch provided on the back of the blade to longitudinally immobilize the knife in the sheath when the knife occupies a storage position in which the blade is inserted into the sheath. 
     Advantageously, the invention makes it possible to achieve precise sharpening of the cutting edge of the knife blade, along its entire length, without the user having any sharpening skills. The sharpening sheath can thus be used by anyone who is new to sharpening. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The purposes, aspects and advantages of this invention, according to the description given below of a particular embodiment of the invention presented by way of non-limiting example, will be better understood by referring to the attached drawings in which: 
         FIG.  1    is a perspective view of a sheath and of a knife according to a particular embodiment of the invention; the knife being shown outside the sheath. 
         FIG.  2    is an exploded perspective view of the sheath in  FIG.  1   ; 
         FIG.  3    is a perspective view of the sheath of  FIG.  1    with the knife inserted into the sheath, the sheath being shown in this figure without its outer sleeve in order to provide visual access to the sheath mechanism; 
         FIG.  4    is a longitudinal cross-sectional view of the sheath and of the knife in the position illustrated in  FIG.  3   ; 
         FIG.  5    is a bottom view of the removable sheath sleeve; 
         FIG.  6    is another perspective view of the sheath in  FIG.  1    without the knife; 
         FIG.  7    is a cross-sectional view along line VII-VII of  FIG.  4   ; 
         FIG.  8    is an exploded perspective view of the sharpening device equipping the sheath. 
     
    
    
     Only those elements required in order to understand the invention have been depicted. In order to facilitate interpretation of the drawings, the same elements are labeled with the same references across all the figures. 
     It will be noted that, in this document, the terms “horizontal,” “vertical,” “lower,” “upper,” “top,” “bottom,” “front,” “rear,” “longitudinal” and “transverse” are used to describe the sharpening device in use, when it is sitting flat on its base. 
       FIGS.  1 ,  3  and  4    depict a sharpening sheath  1  and a kitchen knife  2  comprising a blade  20  intended to be stored in the sheath  1 , the knife  2  typically comprising a handle  21  that protrudes from the sheath  1  when the blade  20  is stored in the sheath  1 . 
     As shown in  FIG.  2   , the sheath  1  comprises a stand  3  and a sleeve  4  which are attached to each other and are advantageously made of plastic. The stand  3  and the sleeve  4  have an elongated shape defining a cavity  40  intended to receive the blade  20  of the knife  2  for storage, the sheath  1  having a rear end provided with an access opening  10  through which the blade  20  of the knife  2  can be inserted into the cavity  40 . Upstream of the access opening  10 , the sleeve  4  has a guide skirt  41  that has walls that converge in the direction of the access opening  10  and allow the tip of the blade  20  of the knife  1  to be guided towards the access opening  10 . 
     The stand  3  comprises a base  30  comprising an underside intended to lie flat on a support and comprises a front end formed by a grid  31  that extends upwards from the base  30  at an angle of around 65° relative to the underside of the base  30 , the grid  31  closing the front end of the sheath  1  and advantageously being achieved by molding with the base  30 . 
     The sleeve  4  is advantageously removably attached to the stand  3  and has an inverted U-shaped cross-section, which can be seen in  FIG.  5   , comprising, at each of its ends, a ridge  42  that fits in a guide groove  32  arranged longitudinally on each side of the base  30  of the stand  3 . 
     As shown in  FIGS.  3  and  4   , the sheath  1  comprises a guiding device for the upper part of the blade  20  of the knife  2 , also referred to as the back of the blade  20 , comprising a guide piece  5  attached inside the sleeve  4 , at its curved part defining the top of the sleeve  4 , the guide piece  5  extending in the longitudinal axis of the sheath  1  from the open end of the sheath  1  to the grid  31  defining the front end of the sleeve  1 . 
     Preferentially, the guide piece  5  comprises an opening  51  in the vicinity of its front end, into which hooks a hook  45  mounted on the sleeve  4 , as seen in  FIGS.  2  and  4   , the front end of the guide piece  5  comprising an upwardly projecting head  52  that fits into a suitable recess  44  provided at the front end of the sleeve  4 . 
     Inserting the hook  45  into the opening  51  and fitting the head  52  into the recess  44  allows the front end of the guide piece  5  to be removably attached to the front end of the sleeve  4 . 
     The guide piece  5  is advantageously attached to the rear end of the sleeve  4  by clipping, the rear end of the guide piece  5  comprising a centering ring  50  that elastically snaps in between two locking clips  43  projecting from the edges of the access opening  10  of the sheath  1 . 
     As can be seen in  FIG.  2   , the head  52  of the guide piece  5  fits longitudinally into a notch  33  arranged at the upper end of the grid  31  when the sleeve  4  is placed on the stand  3 , the head  52  comprising an underside comprising a groove  53  into which a locking tab  34  positioned at the base of the notch  33  elastically snaps, enabling the sleeve  4  to be held in position on the stand  3 . 
     As shown in  FIGS.  5  and  6   , the centering ring  50  comprises an inverted V-shaped groove  54  for centering the back of the blade  20  relative to the sleeve  4  when the blade  20  is inserted into the sheath  1 . 
     The sheath  1  comprises, opposite the centering ring  50 , a sharpening device  6  advantageously carried by an arm  7  pivotally mounted on the stand  3 , the sharpening device  6  being returned in the direction of the centering ring  50  by a return spring  8  acting on the arm  7 . Preferentially, the arm  7  can be moved in the plane of the blade  20  between an upper position in which the return spring  8  is fully extended and a lower position in which the return spring  8  is fully compressed. 
     As shown in  FIGS.  2  and  3   , the arm  7  comprises a first or “front” end, pivotally mounted in the vicinity of the front end of the stand  3 , by means of a first axis  71  extending perpendicularly to the longitudinal direction of the stand  3 . In the particular embodiment illustrated in the figures, the first axis  71  is supported by two lateral partitions  35  extending vertically on either side of the front end of the arm  7 , these lateral partitions  35  contributing to the rigidity of the connection between the base  30  and the grid  31 . 
     The arm  7  comprises a second or “rear” end on which the sharpening device  6  is preferentially pivotally mounted around a second axis  72  extending parallel to the first axis  71 , the device being capable of pivoting relative to the arm  7  over an angular range of at least 15° and preferentially around 30°. 
     In the example shown in the figures, the arm  7  comprises two lateral lugs  73  that project towards the rear of the arm  7  and between which the sharpening device  6  is positioned, the second axis  72  being advantageously formed by cylindrical pins with circular cross-sections that project laterally from the sharpening device  6  and that fit into the circular openings provided in the lateral lugs  73 . The cylindrical pins of the sharpening device  6 , forming the axis  72 , are arranged in the upper part of the sharpening device  6 . 
     As can be seen more precisely in  FIG.  8   , the sharpening device  6  comprises a U-shaped body bearing two sharpening elements  60  positioned to form a V in a projection plane perpendicular to the longitudinal axis of the sheath  1 , i.e., when the sharpening device  6  is viewed along the direction in which the blade  20  is inserted into the access opening  10  of the sheath  1 , the two sharpening elements  60  being staggered on the longitudinal axis of the sheath  1  and each extending in a plane perpendicular to the longitudinal axis. 
     The two sharpening elements  60 , advantageously consisting of two cylinders made of ceramic material, are positioned in two housings  61  arranged to hold two sharpening elements  60  in the V-shaped arrangement, the device  6  comprising a slot  63 , arranged between the two U-shaped legs, enabling access to the space between the two sharpening elements  60 . The two sharpening elements  60  are immobilized by friction inside their housing  61  due to the pressure of a part of the body of the sharpening device  6 , not visible in the figures, against the end of the sharpening element  60 . Thus, the sharpening elements  60  do not rotate in their housing  61 , or only slightly, when they are subjected to the friction of the blade  20  as it is inserted into or removed from the sheath  1 . 
     In the particular exemplary embodiment shown in the figures, the return spring  8  is a coil spring positioned between the stand  3  and the underside of the arm  7 , in the vicinity of the rear end of the arm  7 . To ensure that the return spring  8  is held between the arm  7  and the stand  3 , the stand  3  comprises a cup  36  for holding the lower end of the return spring  8  and the underside of the arm  7  comprises a cup  74  for holding the upper end of the return spring  8 , the cup  74  facing the cup  36  when the arm  7  is brought towards the stand  3 . 
     Advantageously, the back of the blade  20  of the knife  2  comprises a safety notch  22 , preferentially positioned in the vicinity of the handle  21  of the knife  2 , into which a locking element  55 , constituted by the bottom of the groove  54 , clicks when the entire blade  20  is inserted through the sheath  1 , as illustrated in  FIGS.  3  and  4   . The insertion of the locking element  55  into the safety notch  22 , due to the effect of the thrust of the return spring  8  on the arm  7 , allows the knife  2  to be immobilized longitudinally in the sheath  1  in a storage position. 
     The operation of the sharpening sheath  1  will now be described. 
     When the user wants to put the blade  20  of the knife  2  back into the sheath  1  or to sharpen it, he or she brings the tip of the knife  2  in front of the diamond-shaped opening, seen in  FIG.  6   , formed by the groove  54  and by the two sharpening elements  60 , and then inserts the blade  20  of the knife  2  into the sheath  1  in a longitudinal movement. During this movement, the back of the blade  20  is centered in the bottom of the V-shaped groove  54  while the cutting part of the blade  20  is centered by the “V” formed by the two sharpening elements  60 . 
     This dual positioning of the cutting part of the blade  20  and the back of the blade  20  makes it possible to obtain a sharpening angle that remains symmetrical and constant for the entire path of the blade  20  in the sheath  1 , with no need for the user to manually direct the blade  20 . This ensures symmetrical sharpening and equal sharpening angles on both sides of the blade edge, resulting in even and centered wear of the blade  20 . 
     Moreover, when the blade  20  is inserted into or removed from the sheath  1 , the pivoting movement of the arm  7  allows the sharpening device  6  to follow the profile of the cutting part of the blade  20 , the sharpening device  6  exerting, under the effect of the return spring  8 , moderate pressure on the cutting part of the blade  20  when the tip of the blade is inserted into the access opening  10  of the sheath  1 , and then increasing pressure as the height of the blade  20  increases as the knife  2  is inserted into the sheath  1 . The high degree of friction between the cutting part of the blade  20  and the sharpening elements  60  causes the blade  20  to sharpen. Moreover, when the blade  20  is inserted into or removed from the sheath  1 , the guide piece  5  remains stationary and fixed inside the sleeve  4 , while the arm  7  performs a rotating movement and the sharpening device  6  performs a pendular movement. 
     Lastly, as the sharpening elements are positioned one behind the other in the direction of insertion of the blade  20 , the possible oscillation of the sharpening device  6  relative to the second end of the arm  7  allows the sharpening elements  60  to remain in permanent contact with the blade  20  and to remain correctly angled relative thereto, thus optimizing the sharpening of the blade  20 . 
     When the blade  20  of the knife  2  is fully inserted into the sheath  1 , the locking element  55  of the centering ring  50  is inserted into the safety notch  22  on the back of the blade  20  under the effect of the return spring  8 . The knife  2  is then held securely in the sheath  1 . To remove the knife  2  from the sheath  1 , the user must first exert downward pressure on the handle  21  of the knife  2  to pull the locking element  55  out of the safety notch  22 , and then pull the handle  21  of the knife  2  to remove the blade  20 . This manipulation prevents the knife  2  from accidentally falling out, for example when the sheath  1  is being handled for transport. 
     Furthermore, the sheath  1  thus achieved also has the advantage of allowing for easy cleaning of the inside of the sheath  1 . Indeed, the user can easily detach the sleeve  4  from the stand  3  by holding the stand  3  with one hand, after having removed the knife  2 , and then by exerting traction on the sleeve  4  such that the groove  53  pulls away, by elastic deformation of the head  52 , from the locking tab  34  located at the top of the grid  31 . The sleeve  4  can then be slid onto the stand  3 , with each guiding groove  32  of the stand  3  having an open longitudinal end on the side of the access opening  10  for the removal of the ridge  42  of the sleeve  4 . After the inside of the sheath  1  has been cleaned, the sleeve  4  can be reassembled on the stand  3  by carrying out the operations described above in reverse order. 
     Of course, the invention is in no way limited to the embodiment described and illustrated, since this embodiment was only provided by way of example. Changes can still be made, particularly with regard to the constitution of the various elements or by substituting technical equivalents, without departing from the scope of protection of the invention. 
     Thus, in an alternative embodiment not shown, the sleeve may not be removable from the stand, and the stand and the sheath sleeve may be made in one piece, for example.