Abstract:
A baseball bat includes a wood bat body having a longitudinally extended center through hole, and a tubular core member made of composite material, metal or plastics and fitted into the center through hole of the bat body. The tubular core member has two inner threads in the two ends thereof. Two weights are respectively threaded into the inner threads in the two ends of the core member such that the weights are movable along an axial direction of the core member when the weights are driven to rotate by an external force so as to adjust the center of gravity of the baseball bat.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a wood baseball bat and, more particularly, to a high-strength and high-performance wood baseball bat, which allows the user to adjust the center of gravity thereof. 
     2. Description of the Related Art 
     Regular baseball bats include wood baseball bats and metal (aluminum) baseball bats. Using a wood baseball bat requires a higher batting skill than a metal baseball bat. However, some people prefer to use a wood baseball bat rather than a metal baseball bat because of the unique outer appearance of the wood baseball bat and the sound produced upon hitting against the ball. 
     However, a wood baseball bat has two major drawbacks that should be improved. One drawback of a wood baseball bat is its weak structural strength. The other drawback of a wood baseball bat is its poor batting performance (less power and not easy to control the hitting point). 
     Further, the center of gravity of a wood baseball bat is determined subject to its material and size (length and thickness). Because a conventional wood baseball bat is made of natural wood, it is difficult to control the density of the bat (either made of a wooden block by a lathe, or formed of wooden strips by compression). Wood baseball bats of the same size and same material may have a different center of gravity. The center of gravity different makes quality control difficult. Further, wood baseball bats made according to conventional techniques have their center of gravity limited to a narrow segment. Making a wood baseball bat having its center of gravity beyond such a narrow segment needs to change the size or proportion. The aforesaid drawbacks limit the flexibility in product design. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished under the circumstances in view. It is the primary objective of the present invention to provide a wood baseball bat, which has a strong structural strength, and does not break easily. 
     It is another objective of the present invention to provide a wood baseball bat, which provides a great moment when hitting the ball, and has a broad sweet spot for better performance. 
     It is still another objective of the present invention to provide a wood baseball bat, which allows adjustment of the center of gravity. 
     To achieve these objectives of the present invention, the baseball bat comprises a wood bat body having a handle at a first end thereof, a ball-hitting portion at a second end thereof, and a center through hole axially extended the first and second ends; a tubular core member made of a material selected from a group consisting of composite material, metal and plastics and fitted into the center through hole of the bat body, the core member having an inner thread corresponding in location to the ball-hitting portion of the bat body and a length shorter than the bat body; and a weight mounted inside the tubular core member and having an outer thread threadedly engaged with the inner thread of the core member such that the weight is movable along an axial direction of the core member when the weight is driven to rotate by an external force. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal sectional view of a wood baseball bat according to a first preferred embodiment of the present invention. 
     FIG. 2 is a cross-sectional view taken along line  2 — 2  of FIG.  1 . 
     FIG. 3 is similar to FIG.  2  and shows a cross-sectional view of a wood baseball bat according to a second preferred embodiment of the present invention. 
     FIG. 4 is similar to FIG.  2  and shows a cross-sectional view of a wood baseball bat according to a third preferred embodiment of the present invention. 
     FIG. 5 is a longitudinal sectional view of a wood baseball bat according to a fourth preferred embodiment of the present invention. 
     FIG. 6 is a cross-sectional view taken along line  6 — 6  of FIG.  5 . 
     FIG. 7 is a longitudinal sectional view of a wood baseball bat according to a fifth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, a wood baseball bat  10  is shown comprised of a bat body  12 , a tubular core member  24 , two weights  28 , and two end plugs  34 . 
     The bat body  12  is a bar of wood having a relatively thinner handle  14  at one end and a relatively thicker ball-hitting portion  16  at the other end. The total length of the bat body  12  is about 32˜35 inches. The diameter of the handle  14  is about ⅞˜1 inch. The diameter of the ball-hitting portion  16  is about 2˜2.5 inches. The aforesaid bat body size is the best choice; however it is not the limitation. The bat body  12  has a center through hole  18  axially extended through the two distal ends. According to this embodiment, the center through hole  18  has a uniform circular cross section. The diameter of the center through hole  18  is about ¾ inch. The bat body  12  further has two circular recesses  22  at the two distal ends around the center through hole  18 . 
     The tubular core member  24  is made of compound material (for example, carbon fibers). Alternatively, the tubular core member  24  can be made of metal, rigid plastics, or the like. The tubular core member  24  is shaped like a straight round tube, having a length slightly shorter than the axial length of the bat body  12  and an outer diameter fitting the diameter of the center through hole  18  of the bat body  12  (i.e., about ¾ inch). The tubular core member  24  is fitted into the center through hole  18  of the bat body  12 , keeping the two distal ends spaced from the two distal ends of the bat body  12  by a gap. According to this embodiment, the distal ends of the tubular core member  24  are respectively disposed in flush with the inner side (bottom wall) of the circular recesses  22 . The tubular core member  24  has two inner threads  26  respectively extended in the two ends. 
     The weights  28  are metal cylindrical members, each having an outer thread  32  extended around the periphery. The weights  28  are respectively mounted in the tubular core member  24  and screwed up with the inner threads  26 . The screw joint between the weights  28  and the tubular core member  24  is properly adjusted to prevent rotary motion of the weights  28  relative to the tubular core member  24  upon batting of the bat body  12 . Each weight  28  further has a tool groove (not shown) disposed at an outer side (for the right-sided weight, the tool groove is disposed at the right side) for the positioning of a driving tool used to turn each weight  28  forwards/backwards along the corresponding inner thread  26  in the tubular core member  22 . The tool groove can be a straight groove, crossed groove, or hexagonal groove for the positioning of a keystone tip screwdriver, Phillips head tip screwdriver, or hex wrench. 
     The end plugs  34  are wooden members (preferably of the same wooden material for the bat body  12 ) bonded to the circular recesses  22  in flush with the distal ends of the bat body  12  to seal the distal ends of the center through hole  18 . 
     The wood baseball bat  10  has features and advantages as follows: 
     1. Similar to a conventional wood baseball bat, the wood baseball bat  10  has the same wooden appearance quality and produces the same sound when hitting the ball. 
     2. The insertion of the tubular core member in the axially extended center through hole of the bat body greatly reinforces the structural strength of the wood baseball bat to prolong its service life. The wood baseball bat does not break easily like conventional wood baseball bats when hitting the ball. 
     3. During production, the maker can use a tool to rotate the weights in the tubular core member to further adjust the center of gravity of the wood baseball bat (according to the aforesaid embodiment, the center of gravity of the wood baseball bat can be adjusted within the range of 10.5˜14.5 inches from the front end of the bat body). Therefore, the maker can calibrate the center of gravity of the wood baseball bats of the same lot as desired, preventing a variation of product performance due to wooden material density difference. The maker can also adjust same size wood baseball bats into different groups having different center of gravity. Therefore, the maker can provide a broad specification range without increasing the manufacturing cost. Further, the invention breaks the constrained relationship between size and center of gravity in conventional wood baseball bats, providing multiple choices to users. 
     4. The arrangement of the weights in the front and rear ends of the bat enables the bat to have a relatively broader sweat spot and to produce a relatively greater moment when hitting the ball. Therefore, the user can bat the ball with the sweet spot easily to drive the ball to fly faster and farther. 
     It is to be understood that the bat body of the present invention can be cut from a solid wooden block by a lathe (and then drill the desired center through hole for the mounting of the tubular core member). Alternatively, the bat body can be made in the same way as the conventional “compressive wood baseball bat” by means of fastening wooden strips to the periphery of the tubular core member by adhesive and compression. 
     FIG. 3 is a cross sectional view of an alternate form of the wood baseball bat according to the present invention. According to this embodiment, the bat body  44  is formed of two semicircular wooden bars  42 . The two semicircular wooden bars  42  each have a longitudinal groove  46 . When the semicircular wooden bars  42  bonded together, the longitudinal grooves  46  form a circular center through hole  52 , which accommodates the tubular core member, referenced by  48 . During fabrication, the tubular core member  48  is put in between the semicircular wooden bars  42 , and then the semicircular wooden bars  42  are bonded together. 
     FIG. 4 is a cross sectional view of another alternate form of the wood baseball bat according to the present invention. According to this embodiment, the tubular core member  52  has a plurality of longitudinal ribs  54  equiangularly spaced around the periphery and stopped against the peripheral wall of the center through hole  58  of the bat body  56 . The cross-section of the tubular core member  52  is shaped like a gear. This design of tubular core member  52  greatly reinforces the structural strength of the wood baseball bat. Further, the engagement between the longitudinal ribs  54  of the tubular core member  52  and the peripheral wall of the center through hole  58  prevents biasing of the tubular core member  52  when rotating the weights  59  to adjust the center of gravity of the wood baseball bat. 
     FIGS. 5 and 6 show still another alternate form of the wood baseball bat according to the present invention. According to this embodiment, the tubular core member  62  of the wood baseball bat  60  is extruded from aluminum, having two inner threads  64  in the two rounded ends of the inner diameter and radial ribs  68  supported on the inside and extended in longitudinal direction. According to this embodiment, there are four radial ribs  68  connected together, forming a crossed support to reinforce the structural strength of the tubular core member  62 . In addition, a solid cylindrical core member having two rounded hollow ends for receiving the weights may be used to substitute for the tubular core member. 
     FIG. 7 shows still another alternate form of the wood baseball bat according to the present invention. According to this embodiment, there is only one weight  74  mounted in the front end of the tubular core member  72  of the wood baseball bat  70 . The rear end of the tubular core member  72  is not provided with a weight. This embodiment achieves also the advantages of reinforcing the structural strength, improving the batting performance, and allowing adjustment of the center of gravity.