Patent Publication Number: US-2023144821-A1

Title: Axe and a method of manufacturing an axe

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application claims the benefit of priority to European patent application number 21206671.6, filed on Nov. 5, 2021, the complete disclosure of which is hereby incorporated by reference in its entirety. 
     FIELD 
     This invention relates to an axe and to a method for manufacturing an axe. 
     BACKGROUND 
     Previously there are known axes that have axe heads connected to axe handles. In these known solutions the axe handle has either a straight profile and/or is solid. The known solutions of axe handles are focused on securing the grip of the user with various configurations of widenings, protrusions, recesses, and surface materials, instead of the ergonomics of the user&#39;s grip viewed in light of the user&#39;s wrist position. 
     The above mentioned known axes are traditionally manufactured by inserting a separately manufactured straight handle through a hole in an axe head, thus securing said parts together. These separately manufactured handles are traditionally manufactured by i.e. carving wood, casting metal, or injection molding plastic. Known ways to utilize above mentioned manufacturing methods in axe handle manufacturing either restrict the shape of the handle, or the construct of the handle forcing the handle to be solid. 
     A disadvantage with an axe handle as described above is that a straight handle forces the user&#39;s wrist to be in a disadvantaged position when using the axe. This can make the use of the axe less efficient or cause unnecessary stress on the user&#39;s body when frequently used over a long period of time. Additionally, the weight of solid axe handles makes the axe less user friendly and less portable. Also, the manufacture of a solid axe handle requires more raw materials, and increases the throughput time of the process. 
     SUMMARY 
     An object of the present invention is to solve the above mentioned disadvantages and to provide an axe which has excellent properties during use and is easy to manufacture reliably. These and other objects are achieved with an axe according to independent claim  1  and with a manufacturing method according to independent claim  10 . 
     When the gripping end of an axe handle comprises a tubular curved portion according to the characterizing part of the independent claim  1 , the gripping end is in an advantageous position for use resulting in improved usability and ergonomics. 
     Preferred embodiments of the invention are disclosed in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following the present invention will be described in closer detail by way of example and with reference to the attached drawings, in which 
         FIG.  1    illustrates a perspective view of an embodiment of the invention, 
         FIG.  2    illustrates a back view of the embodiment of  FIG.  1   , 
         FIG.  3    illustrates a side view of the cross section B-B of the  FIG.  2   , 
         FIG.  4    illustrates a side view of the embodiment of  FIG.  1   , 
         FIG.  5    illustrates a back view of the cross section A-A of the  FIG.  4   , 
         FIG.  6    illustrates a back view of the embodiment of  FIG.  1   , with a curved core still inside the handle, and 
         FIG.  7    illustrates a side view of the cross-section B-B of the  FIG.  6   . 
         FIG.  8    illustrates a flowchart of an example method for manufacturing an axe. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1  to  5    illustrate an embodiment of an axe  1  comprising a handle  10  with a first gripping end  10   a , and an axe head  20  in a second end  10   b  of the handle  10 , the axe head  20  comprising an edge  21  defining the striking direction of the axe  1 . The edge  21  and the striking direction further define a striking plane, in respect to which the axe  1  is preferably symmetrical. The handle  10  further comprises a straight tubular portion  11  comprising a filling, and a curved tubular portion  12  which is curved on the striking plane defined by the striking direction of the axe  1 . The curvature of the curved tubular portion  12  is in the striking plane and preferably towards the striking direction. Consequently, the curved tubular portion extends from the straight tubular portion  11  as a curve towards the striking direction. The tubularity of the curved portion  12  without a filling allows the axe  1  to be lighter, and the curvature of the curved portion  12  allows the user to grip the handle  10  with a more advantageous wrist position. Another advantage of the curved tubular portion  12  is that the center of gravity of the axe  1  is moved further along the handle  10  of the axe  1  towards the axe head  20  making the axe more efficient and more maneuverable. 
     In the embodiment of  FIGS.  1  to  5   , the filling of the straight tubular portion  11  is formed with a filling part  13  visible in  FIGS.  3 ,  5 , and  7   , which filling part  13  is separate and premade. Alternatively, instead of using a separate filling part  13 , the filling may also be filled during the manufacture process of the handle  10  using the same material as the material of the handle  10 . However, using a separate pre-fabricated filling part  13  is advantageous for surface quality of the handle  10 , as it allows the tubular portions of the handle  10  to have a substantially constant wall thickness t 1 . The curing time of the handle  10  is also shortened when a separate filling part  13  is used, as there is no need to wait for the filling to be cured. Additionally, as the filling part  13  remains hidden in regular use, waste material left over from other manufacturing may be used as the raw material for the filling part  13 . 
     In the embodiment of  FIGS.  1  to  5    said filling part  13  is positioned relative to the axe head  20  with mating positioning elements visible in  FIGS.  3 ,  5 , and  7   . In the embodiment the mating positioning elements are particularly compatible recess/protrusion elements delimiting relative movement of said parts. The filling part  13  having a recess receiving a protrusion of the axe head  20  visible in  FIG.  5   , restricting relative sideways movement of the parts, in respect to the striking plane. Respectively, as is visible in cross section B-B in  FIGS.  3  and  7   , the axe head  20  has a recess into which the filling part  13  protrudes, restricting the relative movement of the parts in striking direction. Other positioning elements may also be used such as conical elements or other generally known ways of aligning parts. These positioning elements allow the subparts to be easily positioned in accurate positions when the axe  1  is manufactured, making the process faster, more efficient, and more accurate. 
     In the embodiment of  FIGS.  1  to  5   , the filling part  13  is solid, which is visible in  FIGS.  3 ,  5 , and  7   . Advantages of using a solid filling part  13  is its ease of manufacture. Alternatively, the filling part  13  may have a hollow construct or have an infill. Such filling parts  14  with a hollow structure or an infill can be manufactured with for example additive manufacturing. These options would reduce the weight of the filling part  13 , and thus reduce the weight of the axe  1 . 
     In the embodiment of  FIGS.  1  to  5   , the tubular curved portion  12  comprises a section with a substantially constant wall thickness. Optionally, the wall thickness of all tubular portions of the handle  10  may have a substantially constant wall thickness. The more constant the wall thickness, the more evenly the handle  10  is cured, thus increasing quality of the handle  10 . 
     In the embodiment of  FIGS.  1  to  5   , the top line  16  of the curved portion  12  at least partially follows a circular path on said striking plane defined by the striking direction of the axe  1 . The curvature of the top line  16  allows the wrist to be set in a natural position when grabbing the axe  1 , as the wrist sits on the top line  16  when the axe  1  is used. Top line in this context means the side of the axe handle  10 , which faces away from the striking direction, and is on top when the axe is struck when the edge  21  of the axe head  20  faces down. Additionally, this following of the circular path makes it easier to design and manufacture accurately the curved molds and cores used for manufacturing the axe  1 . The angle between the first gripping end  10   a  of the handle  10  and the straight tubular portion  11  of the handle  10 , formed by the curvature, is preferably between 1° and 15°, more preferably between 5° and 11°, and most preferably 8°. 
     In the embodiment of  FIGS.  1  to  5   , the curved tubular portion  12  is hollow and an inner area al of the hollow curved tubular portion  12  of the handle  10  perpendicular to a longitudinal center axis X1 of the curved tubular portion  12  increases towards the first gripping end  10   a  of the handle  10 . This creates sort of a backstop for the handle  10  without needing to increase the wall thickness of the hollow curved tubular portion  12 . This backstop decreases the chance of the handle  10  slipping from the user&#39;s hand when using the axe  1 . 
     In the embodiment of  FIGS.  1  to  5   , the second end  10   b  of the handle  10  partially surrounds the axe head  20  in a longitudinal direction X2 of the straight tubular portion  11  of the axe  1 , such that it delimits relative movement of said parts in said longitudinal direction X2. In other words, the second end  10   b  of the handle  10  is provided with an opening, and the axe head  20  protrudes through the opening. This allows the handle  10  to be manufactured around the axe head  20  with i.e. injection molding, instead of manufacturing said parts separately and then connecting said parts together. 
     In the embodiment of  FIGS.  1  to  5   , the curved portion  12  comprises a surface portion  30 . The surface portion  30  enhances the comfort of the handle  10  and improves the grip of the user. The surface portion  30  is preferably softer than rest of the handle  10 . The surface portion  30  may also further comprise surface texture, particularly in form or recesses or protrusions in order to improve the grip and to reduce the possibility of the user&#39;s hand slipping when using the axe  1 . 
     The material of the handle  10  is preferably a polyamide (PA) reinforced with 30-40% glass fiber. 
     The material of the filling or filling part  13  is preferably manufactured of similar polyamide (PA) with 30-40% glass fiber as the handle  10  of the axe. This is advantageous as it provides increased adhesion between the filling and the handle  10 . Other materials may also be used such as poly propane, available as waste plastic, for instance. 
     The material of the axe head  20  may be carbon steel, for instance. However, other axe head materials such as stainless steel may also be used. 
     The material of the surface part is preferably a thermoplastic elastomer (TPE), in particular styrene-ethylene-butylene-styrene (SEBS). 
     The axe  1  may be an axe intended for one-handed use. Such axes are generally smaller, than axes intended for two-handed use. In axes mainly intended for one-handed use, this curvature of the handle  10  is especially advantageous as it is the sole contact point between the user and the axe when the axe  1  is used. 
       FIG.  8    illustrates a flow chart of an embodiment of a manufacturing method for manufacturing an axe  1 . This method may be implemented for manufacturing the axe illustrated in  FIGS.  1 - 7   , for instance. For instance, an injection molding machine can be used for executing the manufacturing steps. The embodiment method comprises steps of A arranging the axe head  20  into a mold, arranging B a filling into the mold to contact the axe head  20 , arranging C a curved core  15  into the mold to contact the filling, introducing D a melt mass to the mold to form the handle  10  by surrounding the filling and the curved core  15  and to partially surround the axe head  20  with the melt mass. And removing E the curved core  15  from the formed handle  10  once the handle  10  is cured. With these steps an improved axe can be easily manufactured, with high quality and repeatability of the process. 
     The first steps illustrated in the flow chart requires a premade axe head  20 , a mold for the axe  1 , either arranging a suitable filling or providing a premade filling part  13 , and a curved core  15 . These required parts are then inserted to the mold accordingly into correct positions. Once the parts are in position inside the mold, the mold can be filled with the melt mass to fill the void spaces between the mold and the parts inside the mold. Once the mold has been filled, the axe  1  is allowed to cure before opening the mold and removing the axe  1  from the mold. 
     Preferably, the curved core  15  is removed by extracting the curved core  15  from the mold in a curved path corresponding with the curvature of the curved core  15 . 
     Preferably if a filling part  13  is used, the filling part  13  and axe head  20  are shaped to have compatible positioning elements improving the accuracy and throughput time of the manufacturing method, and to make sure the parts are aligned correctly. The filling part  13  may be locked to the axe head  20  with said positioning elements. 
     Optionally, also the curved core  15  and the filling may have compatible positioning elements improving the accuracy and throughput time of the manufacturing method, and to make sure the parts are aligned correctly. Correspondingly, the curved core  15  may be locked to the filling with said positioning elements. 
     Preferably, the mold and the curved core  15  are dimensioned to mutually obtain a wall thickness in at least a part of the curved portion  12 . This dimensioning ensures that the properties of the axe  1  are as intended, and that the curing of the handle  10  is even. 
     It is to be understood that the above description and the accompanying figures are only intended to illustrate the present invention. It will be obvious to a person skilled in the art that the invention can be varied and modified without departing from the scope of the invention.