Double bull&#39;s-eye device
FIELD OF THE INVENTION 
     The present invention relates to a double bull&#39;s-eye device, and more particularly to a double bull&#39;s-eye device incorporated within a dart game without any securing part. 
     BACKGROUND OF THE INVENTION 
     A dart game is an interesting exercise equipment which has a dart panel including a bull&#39;s-eye and many concentric annular regions and radially divided into many sectorial blocks each of which is related to a specific score. 
     Early dart games or devices had only one bull&#39;s-eye. Afterwards, people developed a dart device having double bull&#39;s-eyes by defining a smaller region inside the original bull&#39;s-eye so as to make two concentric circular regions; generally, the inner bull&#39;s-eye&#39;s score is higher than the outer bull&#39;s-eye&#39;s in order to challenge the player&#39;s darting accuracy and to advance the interest of the game. 
     Relative references found about double bull&#39;s-eye device include R.O.C. Utility Model No. 192,984, U.S. Pat. Nos. 4,586,716 and 5,193,817. The U.S. Pat. No. 4,586,716 disclosed a double bull&#39;s-eye device formed by engaging an ax/al key way provided on the outer bull&#39;s-eye and an extension provided on the rib of the inner bull&#39;s-eye. The R.O.C. Utility Model No. 192,984 and the U.S. Pat. No. 5,193,817 correspondingly disclosed a similar double bull&#39;s-eye device which is formed by sleeving an inner circular target plate onto an annular support member sleeved onto an outer circular target plate and then securing the annular support member on a target frame with screws; but, such a dart device would have a higher cost due to the tedious assembly with screws. 
     References: 
     1. R.O.C. Utility Model No. 192,984 issued to Pan, Jong-Haw on Oct. 11,1992. 
     2. U.S. Pat. No. 4,586,716 issued to Brejcha et al. on May 6, 1986. 
     3. U.S. Pat. No. 5,193,817 issued to Pan on Mar. 16, 1993. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a double bull&#39;s-eye device capable of being incorporated within a dart game or device without any securing part. 
     In accordance with the present invention, a double bull&#39;s-eye device adapted to be incorporated within a circular rib formed on a dart frame comprises a base having a top end and a bottom end engagable with the circular rib, an outer bull&#39;s-eye sleeved from the top end on the base; and an inner bull&#39;s-eye passing from the top end through the base to be mounted on the base. 
     In accordance with the present invention, the base is a tubular member provided with at least one inner axial groove and at least one inner circumferential indentation, and including an intermediate shoulder and a bottom flange having a plurality of projecting parts which respectively have a plurality of through holes. 
     In accordance with the present invention, the bottom flange has three projecting parts. 
     In accordance with the present invention, the base has two inner axial grooves and two inner circumferential indentations. 
     In accordance with the present invention, the outer bull&#39;s-eye has an annular wall having a plurality of axial indentations for respectively receiving therein the plurality of projecting parts and a plurality of feet for respectively passing through the plurality of through holes. 
     In accordance with the present invention, the circular rib has a plurality of indentations for respectively engaging with the plurality of axial projecting parts. 
     In accordance with the present invention, the inner bull&#39;s-eye further includes a hollow cylinder having a top end and at least one bottom projection for being inserted along the at least one inner axial groove and then to be retained respectively in the at least one inner circumferential indentation; and a ring provided on the top end of the hollow cylinder and protruding above the outer bull&#39;s-eye. 
     The present invention may best be understood through the following description with reference to the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing the disassembled parts of a double bull&#39;s-eye device according to the present invention; 
     FIGS. 2A and 2B are sectional views schematically showing a process of assembling the inner bull&#39;s-eye of a double bull&#39;s-eye device according to the present invention; 
     FIGS. 3A, 3B and 3C are perspective views schematically showing a process of assembling a double bull&#39;s-eye device according to the present invention; and 
     FIG. 4 is an exploded view showing a double bull&#39;s-eye device of another preferred embodiment according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the present double bull&#39;s-eye device 10 is adapted to be incorporated within a circular rib 11 formed on a dart frame 1, which includes a base 101 having a top end 1015 and a bottom end 1016 for being engagable with the circular rib 11, an outer bull&#39;s-eye 102 sleeved from the top end 1015 on the base 101 and an inner bull&#39;s-eye 103 passing from the top end 1015 through the base 101 to be mounted on the base 101. 
     The base 101 is a tubular member provided with two inner axial grooves 1013, two inner circumferential indentations 1014, an intermediate shoulder 1012 and a bottom flange 1011 having three projecting parts 10111 each of which has one through hole 10112. The outer bull&#39;s-eye 102 has an annular wall having three axial indentations 1021 for respectively receiving therein the three projecting parts 10111 and three feet 1022 for respectively passing through the three through holes 10112. The circular rib 11 has three indentations 111 for respectively engaging with the three radial projecting parts 10111. The inner bull&#39;s-eye 103 includes a hollow cylinder 1031 having a top end, two bottom projections 10311 for being inserted along the two inner axial grooves 1013 and then retained respectively in the two inner circumferential indentations 1014 and a ring 1032 provided on the top end of the hollow cylinder 1031 and protruding above the outer bull&#39;s-eye 102. 
     To assemble the present double bull&#39;s-eye device 10, one will sleeve the outer bull&#39;s eye 102 onto the base 101, respectively engage the three axial indentations 1021 (shown in FIG. 1) with the three projecting parts 10111, then respectively pass the three feet 1022 of the outer bull&#39;s eye 102 through the three holes 10112 of the base 101 (shown in FIG. 2A), and finally mount the inner bull&#39;s-eye 103 on the circular tube of the base 101 by rotating the two bottom projections 10311 to engage with the two inner circumferential indentations 1014 of the base 101 (shown in FIG. 2B). The assembled double bull&#39;s-eye device 10 is incorporated in a circular rib 11 having three indentations 111 for respectively engaging with the three radial projecting parts 10111 so as to prevent the base 101 from turning. 
     Referring to FIGS. 2A and 2B, the dart device according to the present invention includes a dart frame 1 having a circular rib 11, a base 101, an outer bull&#39;s-eye 102, an inner bull&#39;s-eye 103, a conducting matrix device 21 and a bottom cover 22. After the double bull&#39;s-eye device is assembled in the dart device, the inner bull&#39;s-eye 103 cannot be disengaged. Also, referring to FIGS. 3A, 3B and 3C, if the inner bull&#39;s-eye 103 is to be taken out, then one will have to press the inner bull&#39;s-eye 103 in the direction toward the conducting matrix device 21 and then rotate the inner bull&#39;s eye 103 in order to disengage the two bottom projections 10311 from the two inner circumferential indentations 1014 of the base 101; but due to the fact that the assembled double bull&#39;s-eye device 10 is stopped by the conducting matrix device 21 which is supported by the bottom cover 22, the inner bull&#39;s-eye 103 has no space to be pressed down and accordingly cannot be disengaged. As a result, when the outer bull&#39;s-eye 102 is darted, then it will axially move a distance to contact the conducting matrix device 21 with its feet 1022 so as to generate a signal; while when the inner bull&#39;s-eye 103 is darted, then the inner bull&#39;s-eye 103 will axially move a distance to contact the conducting matrix device 21 with the foot 1033 of the inner bull&#39;s-eye 103 so as to generate a signal. 
     Preferably, the diameter 112 (shown in FIG. 1 ) of the outer bull&#39;s-eye 102 is larger than that of the circular rib 11 and the inner bull&#39;s-eye 103 is retained in the base 101 by its bottom projections 10311 so as to ensure that the double bull&#39;s-eye device is secured in the dart frame 1 when the dart is to be pulled out of the dart frame 1. 
     Referring to FIG. 4, another preferred embodiment of a double bull&#39;s-eye device 10 according to the present invention is similar to the previous preferred embodiment except that the base 101 is not provided with holes 10112 and the three feet 1022 of the outer bull&#39;s-eye 102 respectively project through the intermediate recesses formed by every adjacent two of the projecting parts 10111 of the base 101. 
     To sum up, the present invention provides a new double bull&#39;s-eye device which is adapted to be secured within a dart device without screws and can accordingly save the cost spent on the assembling procedure. 
     While the invention has been described in terms of what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention need not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.