Abstract:
A method for fastening a tool handle to a tool shaft includes the following steps. First, providing a tool shaft comprising an elongated body having a proximal end and a distal end. Next, providing a tool handle comprising a distal end, a proximal end and a socket formed at the distal end. Next, inserting the proximal end of the tool shaft into the socket of the tool handle, and then staking the proximal end of the tool shaft to the tool handle from two opposite directions.

Description:
CROSS REFERENCE TO RELATED CO-PENDING APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application Ser. No. 61/558,008 filed on Nov. 10, 2011 and entitled METHOD FOR FASTENING A TOOL HANDLE TO A TOOL SHAFT which is commonly assigned and the contents of which are expressly incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to an ergonomic tool handle, and to a method of fastening the tool handle to a tool shaft. 
       BACKGROUND OF THE INVENTION 
       [0003]    A conventional tool handle  50  usually includes a cylindrical body  10  having a proximal end  10   a  and a distal end  10   ba.  The distal end surface includes a socket  20 , which is usually shaped and dimensioned to receive the proximal end  30   a  of an elongated tool shaft  30 . The distal end  30   b  of the tool shaft usually has a specific tool shape or is attached to a tool end effector (not shown). The proximal end  30   a  of the elongated shaft is either permanently or removably attached to the socket  20  of the tool handle. Some of the attachment methods include welding, press-fitting of the shaft end into the socket, or screwing the threaded shaft end  30   a  into a threaded socket. Most of these attachment methods require high precision manufactured components or specialized production methods and tools, which increase the overall cost of the tool. 
         [0004]    It would be desirable to use a tool handle attachment method that does not require high precision manufactured components or specialized methods and tools. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides a tool handle attachment method that does not require high precision manufactured components or specialized methods and tools. A tool shaft is inserted into a tool handle opening and is subsequently attached to the tool handle via staking from two opposite directions. 
         [0006]    In general, in one aspect, the invention features method for fastening a tool handle to a tool shaft including the following steps. First, providing a tool shaft comprising an elongated body having a proximal end and a distal end. Next, providing a tool handle comprising a distal end, a proximal end and a socket formed at the distal end. Next, inserting the proximal end of the tool shaft into the socket of the tool handle, and then staking the proximal end of the tool shaft to the tool handle from two opposite directions. 
         [0007]    Implementations of this aspect of the invention may include one or more of the following features. The distal end of the tool handle includes first and second opposite recesses extending from the top and bottom surface of the tool handle, respectively, toward the socket wall and being oriented perpendicular to the socket axis. Each recess includes conical side walls and a flat bottom surface. A thin layer of material separates the flat bottom surfaces of the recesses from the socket wall. The staking includes inserting first and second stakes into the first and second opposite recesses, and punching the first and second stakes into the first and second recesses, respectively, thereby forcing the flat bottom surfaces of the recesses toward the socket wall without breaking the thin layer of material, and creating matching indentations in the flat bottom surfaces and the outer surface of the tool shaft, respectively. Each stake includes a cylindrical body terminating into a conical end and the conical end includes a conical base and two flat inclined surfaces terminating into a common narrow front flat surface. The cylindrical body includes a recess cutout surface extending longitudinally along the stake axis and the recess cutout surface is oriented perpendicular to the common narrow front flat surface. The first and second stakes are punched simultaneously into the first and second recesses, respectively. The tool handle includes a cylindrical body with a rounded rear surface and a flat front surface, and the cylindrical body includes a concave central section and flutes arranged around the perimeters of the proximal and distal ends. The distal end of the tool handle includes a conical outer surface that is angled relative to the outer surface of the cylindrical body. The tool shaft terminates in an end effector or tool tip. 
         [0008]    In general, in another aspect, the invention features a device including a tool shaft comprising an elongated body having a proximal end and a distal end, and a tool handle comprising a distal end, a proximal end and a socket formed at the distal end. The tool handle is fastened to the tool shaft by inserting the proximal end of the tool shaft into the socket of the tool handle and then staking the proximal end of the tool shaft to the tool handle from two opposite directions. 
         [0009]    Among the advantages of this invention may be one or more of the following. The tool handle has an ergonomic design that includes a concave central section, stabilization flutes and a spherical end. The concave central section of the tool handle facilitates grasping the tool handle from a flat surface and the stabilization flutes prevent rolling of the tool handle on a flat surface. The stabilization flutes also provide visual and tactile means for orienting the tool tip or end effector during use. The spherical rear surface of the tool handle allows it to rest comfortably in the user&#39;s palm and to be easily rotated and manipulated with the user&#39;s fingers. The tool handle attachment method does not require any additional mechanical components, high precision equipment or process. The method is economical and fast. The thin layer of material that separates the handle from the shaft does not break through and remains intact after the staking. This maintains a seal between the handle and the shaft and prevents contaminants from entering the tool handle opening during use. This provides benefits in cleaning and sterilization of the tool handle. There is no visible discoloration or damage of the tool handle after the attachment, and therefore the handle does not require any subsequent polishing or finishing. Preliminary mechanical testing results indicate that the attached tool handle exceeds the strength requirements for most surgical tool applications. 
         [0010]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and description below. Other features, objects and advantages of the invention will be apparent from the following description of the preferred embodiments, the drawings and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Referring to the figures, wherein like numerals represent like parts throughout the several views: 
           [0012]      FIG. 1  is a schematic diagram of a prior art tool handle; 
           [0013]      FIG. 2  is side elevational view of a tool handle attached to a tool shaft, according to this invention; 
           [0014]      FIG. 3  is a front elevational view of the tool handle of  FIG. 2 ; 
           [0015]      FIG. 4  is a cross-sectional view of the tool handle of  FIG. 2 ; 
           [0016]      FIG. 5  is a detailed view of area A of  FIG. 4 ; 
           [0017]      FIG. 6  is a detailed view of area A during the staking process; 
           [0018]      FIG. 7  is a the top view of the tool handle of  FIG. 2  prior to the staking process; 
           [0019]      FIG. 8  is a the top view of the tool handle of  FIG. 2  after the staking process; 
           [0020]      FIG. 9  is a cross-sectional view of the tool handle of  FIG. 2  after the staking process; 
           [0021]      FIG. 10  is perspective view of the tool shaft after the staking process; 
           [0022]      FIG. 11  depicts a front elevational view of the tool handle with typical dimensions; 
           [0023]      FIG. 12  depicts a side elevational view of the tool handle with typical dimensions; 
           [0024]      FIG. 13  is a detailed view of area A prior to the staking process with typical dimensions; 
           [0025]      FIG. 14  is top elevational view of the tool handle; 
           [0026]      FIG. 15  is a bottom elevational view of the tool handle; 
           [0027]      FIG. 16  is a front elevational view of the stake used in the staking process with typical dimensions; 
           [0028]      FIG. 17  is a side elevational view of the stake used in the staking process with typical dimensions; 
           [0029]      FIG. 18  is a detailed side view of the stake tip; 
           [0030]      FIG. 19  is a top view of the stake tip; 
           [0031]      FIG. 20  is a perspective view of the tool handle; 
           [0032]      FIG. 21  is a top view of the tool handle of  FIG. 20 ; and 
           [0033]      FIG. 22  is a bottom view of the tool handle of  FIG. 20   
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    The present invention provides a tool handle attachment method that does not require high precision manufactured components or specialized methods and tools. A tool shaft is inserted into a tool handle opening and is subsequently attached to the tool handle via staking from two opposite directions. 
         [0035]    Referring to  FIG. 2 , instrument  60  includes an ergonomic tool handle  100  and tool shaft  65 . Tool shaft  65  terminates in an end effector or tool tip  70 . Tool handle  100  has a cylindrically shaped body  110  with a rounded rear surface  114  and a flat front surface  112 , shown in  FIG. 3 . The cylindrical body  110  has a concave central section  110   a  and flutes  116  arranged around the perimeters of the proximal end  110   c  and distal end  110   b.  The concave central section  110   a  facilitates grasping the tool handle  100  from a flat surface and flutes  116  prevent rolling of the tool handle on a flat surface. Flutes  116  also provide visual and tactile means for orienting the tool tip or end effector  70  during use. The spherical rear surface  114  of the tool handle  10  allows it to rest comfortably in the user&#39;s palm and to be easily rotated and manipulated with the user&#39;s fingers. The flat front surface  112  includes an axial opening (socket)  124  terminating at point  126 , as shown in  FIG. 5 , and  FIG. 6 . The distal end  110   b  of the tool handle has a conical outer surface that is angled relative to the outer surface of the cylindrical body  110 . The angled surface of the distal end  110   a  includes two opposite recesses  120 ,  122 , extending from the top and bottom of the tool, respectively, and being oriented perpendicular to the socket axis  90 , as shown in  FIG. 5 . In one example, the angle between the conical distal end surface and the cylindrical body surface is 30 degrees, as shown in  FIG. 11 . Recess  120  has conical side walls  120   a,    120   b  and a flat bottom end  121 . Similarly, recess  122  has conical side walls  122   a,    122   b  and flat bottom end  123 . A thin layer of material separates the flat bottom ends  121 ,  123  from the axial opening  124 . In one example, the thin layer of material has a thickness of about 0.06 inches. Typical dimensions of the tool handle  100  are shown in  FIG. 11-FIG .  15 . In one example, the handle  100  has a length of 4.4 inches, a radius of 0.56 inch, a circular front surface with a diameter of 0.3 inch, a spherical rear surface with a curvature radius 0.280 inch, concave central section  110   a  with a curvature radius 11.875 inch, an axial front opening  124  with a diameter of 0.117 inch and an opening length of 0.563 inch, top and bottom recesses  120 ,  122  having a bottom diameter of 0.125 inch and side walls angled by 20 degrees relative to axis  92 , shown in  FIG. 13 . 
         [0036]    Referring to  FIG. 6 , the process of attaching the toll handle distal end  110   b  to the proximal end of the shaft  65  includes the following steps. First, the proximal end of the cylindrical shaft  65  is inserted into opening  124  of the tool handle. Next, two stakes  130   a,    130   b  are placed into recesses  120 ,  122 , respectively, and the stakes  130   a,    130   b  are then punched down along directions  140   a,    140   b,  respectively. This staking process, forces the bottom surfaces  121 ,  123  of the recesses  120 ,  122 , respectively, into the cylindrical shaft  65 , and creates indentations  121   a,    123   a  in the bottom surfaces  121 ,  123 , respectively, and indentations  125   a,    125   b  in opposite sides of the cylindrical shaft  65 . Tool handle indentations  121   a,    123   a  match and cooperate with shaft indentations  15   a,    125   b,  respectively, to fixedly attach the tool handle  100  to the shaft  65 . The thin layer of material that separates the flat bottom ends  121 ,  123  from the axial opening  124  does not break through and remains intact after the staking. This is achieved by using stakes with specific geometric shape. 
         [0037]    Referring to  FIG. 16-FIG .  19 , stake  130   a  has a basically cylindrical body  132  with a conical tip  134 . Cylindrical body  132  includes a recess cutout  133  extending longitudinally along axis  135 , shown in  FIG. 17 . Recess cutout  133  is used for orienting conical tip  134  in the stacking fixture, in order to ensure proper orientation of the deformed material. Conical tip  134  includes a conical base  134   a  and two angled front surfaces  136   a,    136   b  meeting each other at a narrow font flat surface  138 , shown in  FIG. 17 . In one example, surfaces  136   a,    136   b  form 30 degrees angles with axis  135  and front surface  138  has a width of 0.0173 inch. The radius of the conical tip base is 0.1875 inch and the length is 0.250 inch. In this example, stake  130   a  has a length of 0.8 inch, a radius of 0.169 inch and the recess  133  has a length of 0.350 inch. 
         [0038]    The thin layer of material that separates the handle from the shaft does not break through and remains intact after the staking. This maintains a seal between the handle and the shaft and prevents contaminants from entering the tool handle opening during use. This also provides benefits in cleaning and sterilization of the tool handle. Furthermore, there is no visible discoloration or damage of the tool handle after the attachment and therefore, the handle does not require any subsequent polishing or finishing, as shown in  FIG. 7  and  FIG. 8 . Preliminary mechanical testing results indicate that the attached tool handle exceeds the strength requirements for most surgical tool applications. The mechanical testing included a pull test, a torsion test and a destructive test. In the destructive test, the handle was cut in half in order to observe the effect of the staking punch on the shaft and the tool handle opening, as shown in  FIG. 9  and  FIG. 10 . 
         [0039]    Several embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.