Abstract:
Making a spear gun shaft includes selecting a solid steel drill rod of desired length; wrapping the rod with thermo-setting polymer impregnated carbon fiber sheet; covering rod with compression wrapper; curing the resin coated rod in an oven; removing the covering; machining the cured resin to the desired diameter with ends exposing drill rod; affixing a spear tip-carrying member to an end of the rod; affixing a trigger-engaging member to opposite end of the rod; affixing collars over the joints formed between rod and members to reinforce the shaft at the respective joints; mounting a sliding collar onto rod; and affixing the collars with metal adhesive to waterproof and seal the respective joints covered by the collars.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   Not Applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable. 
   REFERENCE TO A MICROFICHE APPENDIX 
   Not Applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a shaft for a spear gun and to a method of manufacturing the shaft and particularly to the use of composite materials in such shafts. 
   2. Relevant Art 
   A number of spear gun shafts are known to the prior art. Because the shafts are used in a marine environment the materials necessary are quite expensive and typically are formed by stainless steel rods. Accordingly, less expensive spear gun shafts are desired without sacrificing the inherent characteristics of stainless steel shafts. Additionally, the need for a reduction in weight of the shaft would result in an increase in the velocity of the spear and thus enhance the performance of the spear. Further, the shaft should be no greater in weight and as strong, as stainless steel shafts, for use in undersea fishing. None of the prior art shafts meet all the desired specifications, as does the shaft made in accordance with this invention. 
   BRIEF SUMMARY OF THE INVENTION 
   In one aspect of the present invention there is provided a method of making a spear gun shaft by the steps of selecting a straight solid steel rod of the desired length; wrapping the rod with a composite material; affixing the composite material onto the rod; attaching a trigger-engaging member to one end of the shaft; and attaching a spear tip-carrying member to the other end of the shaft. Additional steps include affixing a collar bridging over the joint formed between the rod and the trigger-engaging member attached thereto; affixing a collar bridging over the joint formed between the rod and the spear tip-carrying member attached thereto; and mounting a sliding collar onto the rod. Further steps include wrapping the rod with a ribbon of epoxy resin impregnated carbon fiber cloth; covering the composite material with a removable compression wrapping; curing the epoxy resin in an oven; removing the compression wrapping applied after the resin is cured; and machining the surface of the cured composite material to provide the shaft with the desired diameter. 
   Other steps include forming a passageway into one end of the trigger-engaging member; removing material from one end of the rod to form a boss sized to fit within the passageway formed affixing the boss into the passageway; forming a passageway into one end of the spear tip-carrying member; removing material form one end of the rod to form a boss sized to fit within the passageway formed; and affixing the boss into the passageway. 
   In another aspect of the present invention there is provided a method of making a spear gun shaft by steps of selecting a hardened carbon steel drill rod of the desired length; wrapping the rod with an epoxy impregnated carbon composite material to a predetermined diameter; curing and affixing the composite material onto the rod; machining the composite material to the desired shaft outer diameter and its opposite end portions down to the steel drill rod; attaching and sealing a trigger-engaging member having substantially the same shaft outer diameter to one end of the shaft; and attaching and sealing a spear tip-carrying member having substantially the same shaft outer diameter to the other end of the shaft. Other steps include affixing a collar over the joint formed between one end of the rod and the trigger-engaging member attached thereto; affixing a collar over the joint formed between the another end of the rod and the spear tip-carrying member attached thereto; and mounting a sliding collar onto the rod between the collars affixed. 
   Further steps include wrapping the rod with a ribbon of epoxy resin impregnated carbon fiber cloth; wrapping the wound ribbon with a removable compression wrapping; curing the epoxy resin in an oven; removing the compression wrapping applied; machining the surface of the cured composite material to provide the rod with the desired diameter without exposing the surface of the rod; forming a passageway into one end of the trigger-engaging member having a diameter substantially equal to the diameter of the rod; removing the composite material from one end of the rod to form a boss substantially sized to fit within the passageway formed; and affixing the boss into the passageway. 
   Other steps employed include forming a passageway into one end of the spear tip-carrying member having a diameter substantially equal to the diameter of the rod; removing the composite material from the other end of the rod to form a boss substantially sized to fit within the passageway formed; and affixing the boss into the passageway. 
   In a further aspect of the present invention a metal tube is affixed over the shaft covered with the cured composite material. At least one band-engaging notch is cut into the metal tube and a trigger-engaging notch is also cut into the tube at a location approximately 180° apart from the band-engaging notch. A metal or plastic end cap is affixed to the end of the shaft. 
   In another aspect of the invention a trigger-engaging cap member with a trigger-engaging notch therein and a pair of spaced band-engaging members in the form of collars are rigidly mounted onto the rear end of the shaft. 
   Preferably, the carbon fibers used in the composite material are aligned longitudinally with the long axis of the spear gun shaft. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The novel features believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which: 
       FIG. 1  is a pictorial cross-sectional view of the wrapped and coated steel rod in an early step of a method in accord with one embodiment of the present invention; 
       FIG. 2  is an enlarged detail of a portion of the rod prior to the step of curing in accord with the present invention; 
       FIG. 3  is an exploded view of the major components of the spear gun shaft in accord with the present invention; 
       FIG. 4  is a pictorial view of the completed spear gun shaft in accord with the present invention; 
       FIG. 5  is a pictorial view of the spear shaft in accord with a second embodiment of the present invention; 
       FIG. 6  is a pictorial view of the spear shaft in accord with a third embodiment of the present invention; 
       FIG. 7  is a pictorial view of the spear shaft in accord with a fourth embodiment of the present invention; 
       FIG. 8  is a cross-sectional view of the spear shaft in accord with a fifth embodiment of the present invention; and 
       FIG. 9  is a cross-sectional view of the spear shaft in accord with a sixth embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Introduction 
   The basic steps involved in making the spear gun shaft according one embodiment of the present invention are as follows.
     A. A straight preferably solid steel rod of the appropriate length is selected.   B. The rod is covered or wrapped in a helical fashion with a composite material cloth that will be sealed to the shaft by the appropriate technology.   C. The wrapping or sleeve is then reduced in diameter to the desired dimensions by grinding, machining or other suitable means.   D. The sleeve is removed from the ends of the shaft over a short length.   E. A short length of stainless steel rod is prepared with an elongate axial hole equal to the diameter of the naked rod drilled at one end. In addition, notches for engagement with a spear gun trigger apparatus are cut into the rod.   F. The notched rod portion is glued onto the rearward stripped end of the shaft rod.   G. At the forward stripped end of the shaft rod another stainless steel rod member has an axial hole drilled therein at its rear portion equal in diameter to the diameter of the naked rod portion.   H. The other front end of the stainless steel rod is machined to have a diameter equal to that of the naked rod and has external threads formed thereon to accept a standard spear gun spear tip. This rod is also glued onto the front end shaft.   I. A stainless steel collar is fitted over and bridging the rear joint near the trigger-engaging member. The length of the collar is chosen to reinforce the joint and prevent it from failing in use.   J. A movable capture slip bushing is placed on the shaft forward of the collar.   K. A stainless steel support collar is glued to support and bridge the forward joint and to limit the forward travel of the capture slip bushing.
 
Construction Details
   

   A method of manufacturing the spear gun shaft according to an embodiment of the present invention with reference to  FIGS. 1-3  is as follows.
     A. To make a 5/16″ shaft  9 , a 3/16″ hardened solid steel drill rod  10  of the desired length is chosen.   B. The rod  10  is wrapped with a graphite coating preferably formed from an epoxy resin impregnated carbon fiber cloth  11  to produce a diameter slightly larger than the final 5/16″ diameter desired. The carbon fibers are situated longitudinally with respect to the shaft length to increase the stiffness of the completed shaft.   C. A removable compression layer of material  12  is wrapped over carbon fiber cloth  11 . The layer  12  holds cloth  11  on the rod  10  in the proper shape for further processing.   D. The unit ( 10 ,  11 ,  12 ) is placed in a furnace or an oven (not shown) operating at a predetermined temperature for a predetermined time period for curing of the resin in cloth  11  which is preferably a thermo-set epoxy resin to thereby affix the composite material to the rod  10 .   E. After the curing process, the compression material  12  is removed from shaft  9 .   F. The shaft  9  is then centered in a lathe or other machine to grind down the shaft  9 .   G. At each end  13 ,  14 , of the shaft  9 , the carbon fiber material  11  is ground down to the steel core of rod  10 . The preferred length ground down is 1.5″ to expose bosses  25  and  26 .   H. A short trigger-engaging member  15  of 5/16″ OD type 17-4 heat-treated stainless steel round stock is provided. Member  15  has forward and rearward end portions  16 ,  17  respectively. A passageway or bore  18  (of 3/16″ diameter and 1.5″ in length) is drilled in end  16  and appropriate notches  19  are cut into the member  15  and are used to engage the trigger mechanism of a spear gun (not shown). These notches  19  vary for different spear guns. Member  15  is affixed to main rod  10  via a strong and waterproof metal adhesive.   I. A front short spear tip carrying member  20  of 5/16″ type 17-4 heat treated stainless steel round stock has a drilled passageway or bore  24  (of 3/16″ diameter and 1.5″ in length) in the end rear portion  21  thereof. The end forward portion  22  includes an externally threaded termination portion  23  for engagement with complemental internal threads of a spear tip (not shown). The front member  20  is affixed to the main rod  10  with a strong and waterproof metal adhesive.   J. A slip fit stainless steel rear collar  27  is placed over the joint  30  formed between rearward end  26  and front portion  16  of member  15  and is glued by a strong and waterproof adhesive to reinforce the completed shaft  32  at the joint between shaft end  14  and member  15 .   K. A capture slip bushing  28  is fitted over shaft  10  and will ultimately be connected to a tether line (not shown) of a spear gun.   L. A slip fit stainless steel front collar  29  overlies the joint  31  formed by and between forward end  25  of shaft  9  and rearward end  21  and bore  24  of member  20  and glued in place by a strong and waterproof adhesive to reinforce the completed shaft  32  at the joint  31 . Slip bushing  28  is slideable along shaft  9  between collars  27  and  29 .   

   Finally, the metal adhesive used underneath collars  27  and  29  provide a waterproof seal for the rear and front joints  30 ,  31  respectively, thereby sealing the rod  10  against seawater and the rest of the marine environment. 
   With respect to  FIG. 5 , a second embodiment of the spear shaft includes connection assembly  33  that omits the use of collars. Shaft  34  fits into a spear tip assembly member  35  including a slightly flared portion  35 A having a recess  36  into which shaft  34  fits and is secured via a metal adhesive  36 A. Threads  37  are used to secure an appropriate spear tip. 
   A trigger engaging member  38  includes a flared portion  38 A with recess  39  therein having a metal adhesive  39 A for securing shaft  34 . 
     FIG. 6  illustrates a third embodiment of the spear shaft, which includes connection assembly  40  wherein shaft  41  fits with trigger engaging member  45  having flared portion  45 A with recess  46  and adhesive  46 A all similar to the embodiment of  FIG. 5 . 
   At the other end of the shaft  41  a spear tip assembly  43  includes an integral spear tip adapter  44 . Recess  42  in flared portion  43 A includes metal adhesive  42 A as before. 
     FIG. 7  illustrates a fourth embodiment  48  of a collar-like device  49  having first and second recesses  50 ,  51  separated by a circular boss or flange  53  defining a passageway  52  therethrough. 
   Shaft  55  includes a reduced end portion  54 , which may be the same diameter of rod  10 , passes through connector passageway  52  and then into passageway  57 . Tip adapter member  56  is nested in recess  51  and the end of shaft  55  is nested in recess  50  of connector  49 . Metal adhesive is used to secure the members together as before. 
     FIG. 8  illustrates a fifth embodiment of the shaft according to the invention. The trigger-engaging end of any shaft  9 ,  34  or  41  is constructed as follows. A metal tube  58  of approximately 9″ is slideably positioned over the shaft and the cured composite material leaving a short section to accommodate a sealing cap  61 . The tube  58  is used for a trigger-engaging member and is made of stainless steel or anodized aluminum and is affixed in place via a waterproof metal adhesive as understood in the art. 
   Band latch notches  59  are machined through tube  58  and into, but not through, the composite material  11 . A gun latch notch  60  is machined into a metal or plastic cap  61 , which is secured via a waterproof metal adhesive or other appropriate adhesive to the end of the shaft/tube assembly, identified generally at numeral  62 . 
   The particular construction of  FIG. 8  provides a lighter trigger-engaging end to the shaft, than those of the other embodiments, which results in a “truer” motion of the spear when fired. 
     FIG. 9  illustrates a sixth embodiment of the spear shaft  63  in accord with the present invention. Rod  65  is covered by composite material  64  provided as before. A trigger-engaging member in the form of a cap  66  is affixed with adhesive as before and includes a trigger-engaging notch  67  cut therein. Two band-engaging members or collars  68 ,  69  are affixed to one end of the shaft  63  by mounting them over the composite material  64  and are attached with the appropriate adhesive. Arcuate portions  70 ,  71  form notches and may be of any appropriate shape for differing spear guns and their operating characteristics. Preferably, both collars  68  and  69  are identical in size and shape and are normally spaced apart. 
   While the invention has been described with respect to certain specific embodiments, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended therefore, by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention. 
   What is claimed as new and what it is desired to secure by Letters Patent of the United States is: