Abstract:
A tape rule with an automatic blade extension mechanism in which the internal ruler blade reel is not equipped with a center-wound, spiral retraction spring. The torsion developed by winding the steel ruler blade around the reel is of sufficient magnitude such that when the ruler blade is released, it automatically extends to facilitate taking measurements. As such, the present invention is of higher industrial and practical value.

Description:
BACKGROUND OF THE INVENTION 
     1) Field of the Invention 
     The invention herein relates to measuring hardware, specifically a tape rule with an automatic blade extension mechanism in which the torsion developed by winding the steel ruler blade around the reel is of sufficient magnitude such that when the ruler blade is released, it automatically extends. At the same time, the present invention is equipped with a gear train that enables the smooth retraction of the ruler blade to thereby further enhance the practical value of tape rule herein. 
     2) Description of the Prior Art 
     A conventional tape rule is comprised of a tape reel that consists of a center-wound, spiral spring at the interior section, a ruler blade wound on the exterior section, and a hook riveted to the front end of the ruler blade; the center section of the spiral spring on the said tape reel is inserted over the center shaft of the left case half; and the front end of the ruler blade is positioned in a bumper block which is secured inside the bottom section and front end of the left case half, with the other side of the said bumper block secured inside the bottom section and front end of the right case half; and a plurality of screws are inserted through the right case half and fastened into the center shaft and mounting posts of the left case half to thereby complete the assembly of the tape rule body. The conventional product is utilized by pulling out the ruler blade of the tape rule to an appropriate length during a measurement operation and then releasing the hook of the tape rule when measuring is finished. Since the tension of the spiral spring (similar to the type utilized in most tape rule spring mechanisms) inside increases in proportion to the length unwound and, therefore, the rewinding speed is faster when the length is greater; if the said ruler blade is constructed of metal, the user is susceptible to cutaneous injuries of the hand, which is an inconvenient shortcoming of the conventional product. Furthermore, if the rewinding speed is too rapid, the force of impact against the bumper block is intensified, the poor cushioning performance by the conventional bumper block often leads to the dislodging of the hook, a serious shortcoming that preludes further utilization. In the structure of the said conventional tape rule a spiral spring is installed in the tape rule to enable the forceful retraction of the ruler blade when the ruler blade hook is released after measurement is completed. Conversely, when the user wants to perform a measurement, the ruler blade must be pulled from the tape rule to an appropriate length, but such an operation is extremely inconvenient if done as a one-man operation. To innovate a more practical and convenient tape rule, the inventor of the invention herein conducted exhaustive research and development based on many years of professional manufacturing experience and, furthermore, subjected the results to extensive testing and further refinement to achieve an even higher level of practical value, which finally culminated in the tape rule with an automatic blade extension mechanism. 
     SUMMARY OF THE INVENTION 
     Therefore, the primary objective of the invention herein is to provide a tape rule with an automatic blade extension mechanism, wherein the torsion developed by winding the steel ruler blade around the reel is of sufficient magnitude such that when the ruler blade is released, it automatically extends and, furthermore, a rewinding gear train is built-in, thereby further improving the tape rule structure and increasing its practical value. 
     To enable the examination committee a further understanding of the structural features and content as well as the advantages and features of the present invention, the brief description of the drawings below are followed by the detailed description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric drawing of the invention herein. 
     FIG. 2 is an exploded drawing of the invention herein. 
     FIG. 3 is an exploded drawing of the reel  3  of the invention herein. 
     FIG. 4 is an exploded drawing of the reel  3  of the invention herein. 
     FIG. 5 is an exploded drawing of the rewinding gear train of the invention herein. 
     FIG. 6 is an exploded drawing of the rewind gear train of the invention herein. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, and FIG. 6, the tape rule with an automatic blade extension mechanism of the invention herein is comprised of a front case half  1 , a rear case half  2 , a reel  3 , a rewind hub  4 , a rewind gear  5 , a locking component  6 , and a gear cover  7 , of which: 
     The front case half  1  is of one-piece plastic construction; the said front case half  1  has a round opening formed in its posterior section and, furthermore, with a bearing rim  11  disposed towards the interior, a plurality of raised, inward facing threaded holes  12  along the circumference of the bearing rim  11 , and a groove  14  situated along the lateral inner side of the bearing rim  11 ; a plurality of elevated threaded holes  13  are distributed along the interior sides of the said front case half  1  and, furthermore, a prop rest  15  of a tubular shape extends inward near the forward edge of the said front case half  1 . 
     The rear case half  2  is of one-piece plastic construction; the said rear case half  2  has a locating ring  21  at the center of its interior side and a bearing surface  22  within the locating ring  21 ; a plurality of elevated fastening holes  23  are formed along the interior sides of the said rear case half  2 , a curved locating element  25  extends along the interior portion at the back of the said rear case half  2  and, furthermore, an arrestor button  26  is inserted into the forward edge of the said rear case half  2 . 
     The reel  3  consists of a left flange  31 , a right flange  32 , and a ruler blade  33 ; the said left flange  31  is disc-shaped and has a gear  311  projecting from the center of its outer side; the left flange  31  has tubular spool  312  extending from its inner side and, furthermore, a locating notch  313  is formed in the extremity of the tubular spool  312 ; the said tubular spool  312  has a T-shaped clip slot  314  in its body and, furthermore, a threaded post  315  extends through the center of the said tubular spool  312 . The said right flange  32  is disc-shaped and has a circular raised fitting  321  at its center and a locating block  322  extends from the said raised fitting  321 ; the said right flange  32  has a square member  323  projecting from the center of its inner side and, furthermore, a hole  324  is disposed through the center of the said square member  322 ; additionally, the said right flange  32  has a locating edge  325  on its outer side, with the said right flange  32  also consisting of a screw  34  that is inserted into the hole  324  and then fastened to the threaded post  315  at the center of the left flange  31  and, furthermore, the said locating block  322  is fitted into the locating notch  313  in the extremity of the tubular spool  312  at the inner side of the left flange  31 , following which the T-shaped catch end  313  of the ruler blade  33  is inserted and fixed into the T-shaped clip slot  314  in the body of the said tubular spool  312  on left flange  31 , and the entire ruler blade  33  is wound around the reel  3 . 
     The rewind hub  4  has a convex block  41  contoured as a split pair along its outer side and a linkage hole  42  is formed through the posterior side of the said convex block  41 ; the said rewind hub  4  has a square collar  43  projecting from its center; the said rewind hub  4  has a drive hole  44  through its center, with the said drive hole  44  being square at the outer lateral extremity of the rewind hub  4  and round at the inner lateral extremity of the rewind hub  4 ; and the said rewind hub  4  has a bearing rim  45  formed into the surface of its inner side; the rewind hub  4  also consists of a crank  46  having a linkage hole  47  through one end and the said crank  46  has a grip rod  49  projecting from its other end; the arrangement of the said crank  47  is such that a hinge pin  48  is inserted into the linkage hole  42  in the two convex blocks  41  and into the linkage hole  47  of the crank  46 , enabling the crank  46  to pivot 180 degrees around the axis of the hinge pin  48 . 
     The rewind gear  5  has a star-shaped serrated hole  51  formed in its center, with ring gear teeth  52  disposed along the interior sides of the said rewind gear  5 . 
     The locking component  6  is cylindrical along its center portion and has a square push button  61  at one extremity and a star-shaped serrated tip  62  flanging outward from its other extremity, with the locking component  6  having a hole  63  disposed in the center of the star-shaped serrated tip  62  for the entry of a spring  64 . 
     The gear cover  7  is disc-shaped and has a locating ring  71  projecting from the center of one side and, furthermore, a hole  72  disposed laterally to the locating ring  71 ; and the said gear cover  7  has a plurality of fastening holes  73  along its outer circumference. 
     The rewind hub  4  of the invention herein is placed into the bearing rim  11  and the groove  14  of the front case half  1 , the rewind gear  5  is then fitted onto the bearing rim  45  at the inner side of the rewind hub  4 ; the locking component  6  is inserted through the rewind gear  5  and into the drive hole  44  of the rewind hub  4  such that the square push button  61  at one extremity of the said locking component  6  extends through the rewind hub  4  drive hole  44 ; the star-shaped serrated tip  62  at the other end of the said locking component  6  is inserted into the star-shaped serrated hole  51  in the rewind gear  5 ; a respective plurality of screws  74  are inserted through the plurality of fastening holes  73  of the gear cover  7  and then secured into the threaded holes  12  of the front case half  1 ; the said reel  3  is inserted into the said gear cover  7  hole  72  by means of the gear  311  at the center of its left flange  31 , which is then enmeshed with the ring gear teeth  52  along the along the interior sides of the rewind gear  5 ; the front case half  1  and the rear case half  2  are placed together with the reel  3  cradled between the curved locating element  25  and the locating ring  21  of the rear case half  2 , a plurality of screws  24  are inserted through the rear case half  2  fastening holes  23  and secured into the front case half  1  threaded holes  13  to thereby assemble the present invention into a single structural entity. 
     As assembled from the said structural components, the tape rule of the invention herein functions such that under conditions of normal usage, the said crank  46  is postured against the front case half  1  and, furthermore, the grip rod  49  is situated in the prop rest  15 ; the crank  46  presses the push button  61  of the locking component  6  downward and the star-shaped serrated tip  62  at the opposite extremity of the locking component  6  is separated from the star-shaped serrated hole  51  in the rewind gear  5  such that the said rewind hub  4  and crank  46  cannot rotate the rewind gear  5 ; at the same time, since the reel  3  in the invention herein does not have a center-wound, spiral retraction spring, during measurements it is only necessary to move the arrestor button  26  upward to release the ruler blade  33  from its locked state, whereupon the ruler blade  3  extends automatically due to the torsion developed by the said ruler blade  33  when wound a number of turns around the reel  3 ; when the retraction of the ruler blade  33  is desired, the user folds the crank  46  outward by 180 degrees to the rotating position and the spring  64  in the other extremity of the said locking component  6  rebounds, causing the star-shaped serrated tip  62  of the locking component  6  to become inserted into the star-shaped serrated hole  51  in the rewind gear  5  such that turning the crank  46  drives the rewind gear  5  and rotates the reel  3  to enable the rapid and, furthermore, efficient retraction of the tape rule. 
     In summation of the foregoing section, since the tape rule with automatic blade extension mechanism herein is an original invention among this category of products that is capable of greater utility performance and possesses considerable practical value and, furthermore, no identical or similar article has been disclosed in the market, the invention herein is submitted to the examination committee for review and granting of the commensurate patent rights.