Patent Publication Number: US-6220128-B1

Title: Shock absorbing handle of hand impact tool

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation-in-part application of U.S. patent application Ser. No. 09/304,698 filed on May 4, 1999, which is now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a handle of a hand impact tool, e.g., a hammer, and more particularly to a hammer handle that may absorb shock by allowing the whole handle to deform. 
     2. Description of the Related Art 
     Hammer have been used for a long time and are still popular. The user&#39;s hand is subjected to shock when hammering. U.S. Pat. No. 4,331,193 to Tudisco issued on May 25, 1982 discloses a hammer handle made of a spring strip formed into an oblong closed figure and a synthetic resin handle body molded around the frame. The handle is allowed to flex for reducing the shock resulting from striking a workpiece. Nevertheless, formation of such a hammer handle is troublesome. U.S. Pat. No. 4,738,166 to Yamaguchi issued on Apr. 19, 1988 discloses a hammer having a pair of axially extending passages in a grip thereof to absorb shock by allowing the grip to deform when the hammer head strikes an object. As can be seen from FIGS. 3 and 4 of said patent, the radially extending openings are not communicated with axially extending passages and thus have an unsatisfactory shock absorbing result. U.S. Pat. No. 5,280,739 to Liou issued on Jan. 25, 1994 discloses a hammer with a hand grip having a pair of holes to allow the hand grip to be compressible and deformable such that vibrations and shocks transmitted to the hand grip can be absorbed. Nevertheless, the shock-absorbing effects provided by the hammer handles disclosed in both U.S. Pat. Nos. 4,738,166 and 5,280,739 are not satisfactory, as the shock is only transmitted and absorbed along the axial direction. U.S. Pat. No. 811,390 to Foreman issued on Jan. 30, 1906 discloses a tool handle including channels 5, orifices 7, and recesses 4 in which air entering the recesses 4 may escape via the orifices 7. The shock occurring during hammering is mainly in the vertical direction that is parallel to the longitudinal axis of the hammer head. Nevertheless, the recesses 4 and the channels 5 are too small for they are arranged along a peripheral edge of the tool handle and thus fail to provide satisfactory shock-absorbing effect. The present invention is intended to provide an improved hammer handle that mitigates and/or obviates the above problems. 
     SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to provide a handle of a hand impact tool that may absorb shock more effectively by providing at least one axial passage in the handle and at least one transverse slot that is located in an outer periphery of the handle and communicated with the axial passage. The axial passage is located in an upper end portion or a lower end portion of the handle. In addition, the axial passage is substantially semi-circular or crescent shaped in cross section. 
     In accordance with an aspect of the invention, a handle of a hand impact tool comprises a pair of axial passages defined therein. A row of axially spaced first transverse openings defined in an outer periphery of the handle communicates with one of the axial passages. A row of axially spaced second transverse openings defined in the outer periphery of the handle communicates with the other axial passage. The handle further comprises two rows of axially spaced third transverse openings respectively formed on two sides of the row of axially spaced first transverse openings, each third transverse opening being defined in the outer periphery of the handle and communicated with said one of the axial passages. Two rows of axially spaced fourth transverse openings are respectively formed on two sides of the row of axially spaced second transverse openings, each fourth transverse opening being defined in the outer periphery of the handle and communicated with the other axial passage. The axial passages are substantially semi-circular or crescent shaped in cross section. 
     By such an arrangement, when hammering an object, the handle deforms not only in the axial direction but also in the radial transverse direction due to the provision of the transverse openings. Thus, shock as a result of hammering may be effectively absorbed not only in the axial direction but also in the radial direction. 
     Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a hand impact tool with a handle in accordance with the present invention; 
     FIG. 2 is an exploded perspective of the hand impact tool; 
     FIG. 3 is a perspective view of a portion of the handle in accordance with the present invention; 
     FIG. 4 is a perspective view of another portion of the handle in accordance with the present invention; 
     FIG. 5 is a side view of the hand impact tool; 
     FIG. 6 is an end view of the handle; 
     FIG. 7 is an end view of handle illustrating the shock-absorbing operation, and 
     FIG. 8 is a view similar to FIG. 7, illustrating a modified embodiment of the handle in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings and initially to FIGS. 1 and 2, a handle  10  in accordance with the present invention is provided to a hand impact tool, e.g., a hammer having a head  20  with a stem  21 . The handle includes  10  a compartment  11  (FIG. 2) for securely receiving an end of the stem  21 . The handle  10  comprises a pair of axial passages  12  defined therein. The axial passages  12  are respectively located in upper and lower end portions of the handle  10 . The axial passages  12  are substantially crescent or semi-circular (FIG. 8) shaped in cross section. In addition, at least one transverse opening is defined in an outer periphery of the handle  10  and communicated with one of the axial passages  12 . In this embodiment, the transverse opening is the one (see opening  16 ) defined in an end of the handle  10  adjacent to the head  20  of the hammer. 
     In a preferred embodiment of the invention, a row of axially spaced transverse openings  13  is defined in the outer periphery of the handle  10  and communicated with the upper axial passage  12 , and another row of axially spaced transverse openings  13  is defined in the outer periphery of the handle  10  and communicated with the lower axial passage  12 . Furthermore, two rows of axially spaced transverse openings  14  are respectively formed on two sides of the row of axially spaced transverse openings  13 , each transverse opening  14  being defined in the outer periphery of the handle  10  and communicated with the upper axial passage  12 , as shown in FIG.  3 . Two further rows of axially spaced transverse openings  15  are respectively formed on two sides of the row of axially spaced transverse openings  13  on the lower side of the handle  10 , each transverse opening  15  being defined in the outer periphery of the handle and communicated with the lower axial passage  12 . 
     FIG. 5 is a side view of the hammer and FIG. 6 is an end view of the handle. FIG. 7 is an end view of the handle illustrating the shock-absorbing operation. When hammering an object, the handle deforms not only in the axial direction but also in the radial direction due to the provision of the transverse openings  13 ,  14 ,  15 , and  16 . Thus, shock as a result of hammering may be effectively absorbed not only in the axial direction but also in the radial direction. The number of the transverse openings  13 ,  14 ,  15 ,  16  is chosen in response to material of the handle. More openings  13 ,  14 ,  15 , and  16  may be provided if the handle  10  is rigid, and less openings  13 ,  14 ,  15 , and  16  are provided if the handle  10  is made of a softer material. It is noted that the provision of the axial passages  12  in the upper and/or lower portions of the handle  10  may provide better shock-absorbing effect, as it meets the optimal ergonomic design when taking the holding situation of the hammer by a user&#39;s hand. Namely, a user usually holds the handle completely such that the shock is mainly in the vertical direction (i.e., the usual hammering direction that is parallel to the longitudinal axis of the hammer head  20 ). The axial passages  12  defined in the upper and lower end portions of the handle  10  may be sufficiently large for providing satisfactory shock-absorbing function. In addition, the crescent or semi-circular cross sectional configuration of the axial passages  12  assists in the shock-absorbing effect. This is because the crescent or semi-circular cross sectional configuration of the axial passages  12  provides the largest sectional area and volume for the limited space in the handle of the impact tool. Namely, the axial passages  12  will have the largest volume when they have a crescent or semi-circular shape in cross-section, thereby providing the best shock-absorbing effect. In addition, the axial passages are respectively defined in the upper end portion and the lower end portion of the handle, which further assists in shock-absorption. In conclusion, the crescent or semi-circular cross sectional axial passages defined in the upper end portion and the lower end portion of the handle are an ergonomic design that provides the best shock-absorbing effect. 
     Although the invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.