TECHNICAL FIELD The present invention relates to a bottle cap, and more particularly, to a bottle cap that prevents contents from being refilled in a bottle by displaying an opened state in such a manner that a wing hung in the bottom of the cap by rack and pinion is taken out when the cap is opened.

BACKGROUND ART Generally, there are different kinds of bottle products filled with contents such as liquid. The most general bottle is sealed with a cap after being filled with contents. The bottle is made of glass, plastic, or metal . Such a bottle includes a main body of a cap. There are different kinds of bottle caps. That is, there is a simple bottle cap that can be opened using an opener. There is another bottle cap that can be opened by turning the cap through a screw. In this case, the screw is formed on an outer surface of a nozzle of the bottle and is engaged with a screw'formed in the bottle. The products based on the above bottle caps do not have any special problems in case that they contain cheap contents. However, in case that they contain expensive contents, problems are likely to occur. That is, the expensive contents may be exchanged with the cheap contents . To prevent such a problem, various methods for sealing a bottle cap are being contrived but there is no method for solving the problem at present. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: Fig. 1 is a front view illustrating the state that a bottle cap according to the present invention is opened; FIG. 2 is an exploded perspective view of a bottle cap according to the present invention; Fig. 3 is a sectional view illustrating the state that a bottle cap according to the present invention is closed; Fig. 4 is a sectional view illustrating the state that a bottle cap according to the present invention is opened; Fig. 5 is a sectional view illustrating a bottle cap according to the present invention, which is opened, taken along line V-V of FIG. 2; FIG. 6 is a sectional view illustrating the state that a bottle cap is inclined at FIG. 5; FIG. 7 is a front view of a pinion that is an element of a bottle cap according to the present invention; FIG. 8 is a plane view of a case according to other embodiment of the present invention; and FIG. 9 is a sectional view of a bottle cap according to other embodiment of the present invention, taken along the same direction as that of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL PROBLEMS Accordingly, the present invention is directed to a bottle cap that substantially obviates one or more of the problems due to limitations and disadvantages of the related art . An object of the present invention is to provide a bottle cap that prevents contents from being refilled in a bottle in such a manner that a wing is hung in the bottle by rack and pinion.

TECHNICAL SOLUTIONS To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a bottle cap according to the present invention includes a cap covering a nozzle of a bottle in a state that it is engaged with a screw formed on the outer surface of the nozzle, having a rod provided with a rack on the 'outer surface, a pinion engaged with the rack formed in the rod of the cap and rotated by straight movement of the rod, a driving gear engaged with the pinion, and a wing having a rack engaged with the driving gear at the upper portion, driven in a straight direction by rotation of the driving gear. The pinion, the driving gear and the wing are supported by a case of the cap fitted into the nozzle, and the case has a middle hole of a predetermined depth, into which the rack of the cap is inserted. The pinion includes an inner gear that rotates the pinion only in one direction. The wing includes a hanging portion at the side, which prevents the wing from being inserted into the case again after it is taken out from the case. The case includes a connection path connected from the upper portion to the middle hole, the connection path has a heart shaped space at the middle portion, and the heart shaped space is provided with a control ball. The connection path includes a check valve having elasticity.

APPLICABLE ADVANTAGES The bottle cap according to the present invention has the following advantages. Since the wing is taken out from the case and is then hung in the cap, the user can recognize that the cap has been opened at least once. This prevents the contents from being refilled in the bottle. While the present invention has been described and illustrated herein with reference to the preferred embodiments thereof, it will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents .

BEST MODE FOR CARRYING OUT THE INVENTION Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. As shown in FIG. 1, a rod 10b having a rack is formed at the center inside a cap 10. The rod 10b is detached from middle holes 21a and 22a of a case 20 fixed in a nozzle of a bottle 1. A screw engaged with a screw 10a formed in the inner wall of the nozzle Ia is formed on the outer surface of the nozzle Ia. Since the cap 10 is detached, a wing 30 is protruded from the case 20 and is hung in a neck of the bottle 1. FIG. 2 is an exploded view illustrating the structure that the wing 30 is protruded. As shown in FIG. 2, the case 20 fitted into the nozzle Ia includes two opposing semi-cylindrical members 21 and 22 fixed to each other by tightening screw into holes 21c and 22c at four corners. Middle holes 21a and 22a are formed in the middle portion of the case 20. The rod 10b of the cap 10 is inserted into the middle holes 21a and 22a. The middle holes 21a and 22a have smooth surfaces without having any screws and are not connected with the lower end of the case. Therefore, if the case 20 is fixed, the bottle 1 is sealed by the lower end of the case 20. The semi-cylindrical members 21 and 22 have cut portions 21b and 22b into which the wing 30 is inserted, and cut portions 21d and 21f into which a pinion 40 and a driving gear 50 are inserted. The cut portion 21d is connected with the cut portion 21b. The driving gear 50 is inserted into the cut portion 21d so that it is to be hung in a rack 30a of the wing 30. The cut portion 21f is connected with the middle hole 21a. The pinion 40 is inserted into the cut portion 21f so that it is engaged with the rack of the rod 10b. Rotary shafts 42 and 51 of the pinion 40 and the driving gear 50 are respectively inserted into the holes 21e and 21g that support the pinion 40 and the driving gear 50. Since the cut portion 21f is engaged with the pinion 40 to allow the pinion 40 to be hung in the rack of the rod 10b, the contents in the bottle may be leaked out. To avoid such leakage, a packing may be provided between the cut portion 21f and the middle hole 21a. The wing 30 is provided at both sides of the case 20. The rack 30a engaged with the driving gear 50 is formed at the upper portion of the wing 30. A hanging portion 30b having elasticity is formed at the side of the wing 30 and unfolded by its elasticity if the wing 30 is extended from the case 20 at a certain length. Thus, the hanging portion 30b can be hung in the outer surface of the case 20. The driving gear 50 is engaged with the rack 30a of the wing 30 and at the same time is engaged with a longitudinal gear 41 of the pinion 40. FIG. 7 shows an enlarged view of the pinion 40 viewed at left sides of FIG. 3 and FIG. 4. Referring to FIG. 7, the rotary shaft 42 is formed at the center of the pinion 40. The longitudinal gear 41 is rotated along with the rotary shaft 42. The longitudinal gear 41 has an inner gear 43 that is hung in one way hanging portion 40a formed therein. The longitudinal gear 41 having such an inner gear is well- known. The longitudinal gear 41 is rotated along the pinion 40 only if the pinion 40 of FIG. 7 is rotated clockwise. If the pinion 40 is rotated counterclockwise, the inner gear 43 is not hung in the hanging portion 40a. Thus, the longitudinal gear 41 is not rotated. Protrusions 21k and 22d are formed at the outer surface of the case 20 as shown in FIG. 2, and are tightly fitted into a groove formed inside the nozzle Ia. FIG. 3 and FIG. 4 are sectional views of the pinion 40 and the driving gear 50 cut along the front side. As shown, FIG. 3 shows the state before the cap 10 is opened and FIG. 4 shows the state after the cap 10 is opened. Once the cap 10 is turned and starts to be removed from the nozzle Ia, the rod 10b descends. Since the pinion 40 is engaged with the rack of the rod 10b, the longitudinal gear 41 is rotated along with the pinion 40. The driving gear 50 engaged with the longitudinal gear 41 is also rotated so that the wing 30 having the rack 30a engaged with the driving gear 50 is driven and advances in a straight direction toward the outside of the case 20. This structure is shown in FIG. 4. Once the wing 30 advances toward the outside of the case at a predetermined distance, the hanging portion 30b is hung in the outer surface of the case 20. Thus, the wing 30 does not return to the case 20. Finally, viewing the wing 30 taken out from the case 20, the user can recognize that the cap 10 has been opened at least one time. Once the cap 10 is reversely turned to close, the wing 30 cannot return to the case 20 as described above. Since the longitudinal gear 41 is structured to rotate only in one direction by the inner gear 43 and the hanging portion 40a, the longitudinal gear 41 is not rotated even though the pinion 40 engaged with the rack of the rod 10b is rotated. FIG. 5 and FIG. β are sectional views cut at a right angle along a direction different from that of FIG. 3 and FIG. 4. A connection path of contents in the bottle is shown in FIG. 5 and FIG. 6. Once the cap 10 is removed, the contents should be taken out from the bottle 1. In this case, the connection path is required because the lower portion of the case 20 is sealed. The connection path includes first paths 21h and 22e having a certain diameter, heart shaped spaces 21i and 22f inserted into a control ball 50' , and second paths 2Ij and 22g having a diameter smaller than that of the first paths 21h and 22e, connected with the middle holes 21a and 22a. The operation of the control ball 50' is shown in FIG. 6. The control ball 50' is positioned at the top of the heart shaped spaces 21i and 22f once the bottle 1 is inclined, so that the contents are easily moved to the second paths 21j and 22g. Also, the control ball 50' blocks the first paths 21h and 22e in a state that the bottle 1 is upright, thereby preventing the contents from being refilled. A check valve 60 having elasticity is formed in the first paths 21h and 22e to open only in one direction. Such a check valve has a similar structure to one widely used in a swimming tube. Meanwhile, the bottle cap according to the other embodiment of the present invention will be described with reference to FIG. 8 and FIG. 9. As shown in FIG. 8, a concave and convex portion is formed at a joint portion of two cylindrical members 21' and 22' constituting the case. The concave and convex portion is sealed by additive to prevent the case from being reused. Reference numerals 21X' and 22X' denote air vents, and 21a denotes a hole into which the rod is inserted. The concave and convex portion serves to enhance adhesion of the cylindrical members 21' and 22' and thus make disassembly of the case difficult. FIG. 9 is a sectional view of a bottle cap according to the other embodiment of the present invention, taken along the same direction as that of FIG. 5. Air vents 21X' and 22X' are shown in FIG. 9. In the same manner as the first embodiment of the present invention, liquid paths 21h' and 22e' including the first paths, the heart shaped spaces and the second paths are formed in the case. The air vents 21X' and 22X' are connected from the side of the case to its upper portion. A straw 70 is fitted into the air vents 21X' and 22X' and is extended to the side of the bottle. The straw 70 is then bent at the side of the bottle and extended to the bottom of the bottle. At this time, the heart shaped sections of the paths 21h' , 22e' , 21X' and 22X' are inclined as shown in the enlarged portion of FIG. 9. When the bottle is inclined, the ball of the air vents 21X' and 22X' is moved to the heart shaped space prior to the ball of the liquid paths 21h' and 22e' so that the contents in the bottle can easily be taken out. A bellows 70a is formed at the bent portion of the straw 70 fitted into the end of the air vents 21X' and 22X' . The bellows 70a serves to facilitate movement of air. Meanwhile, in the embodiments of the present invention, one screw is formed on the outer surface of the nozzle Ia and another screw engaged with the above screw is formed on the inner surface of the cap 10, so that the cap 10 is moved up and down. However, the screw engaged with the screw 10b may be formed in the holes 21a, 22a, and 21a' of the case without forming the screw on the outer surface of the nozzle Ia. In other words, half of the screw formed in the rod 10b is to be hung in the pinion in the same manner as the aforementioned embodiments, and the other portion of the screw is formed at the same pitch as that formed in the nozzle Ia. The screw is also formed in the holes 21a and 21a' of the case corresponding to the screw of the nozzle Ia, thereby opening and closing the cap 10. Further, the screw may be formed on the outer surface of the case at the same pitch as that of the screw of the case engaged with the rod 10b. Thus, the screw formed on the outer surface of the case may be engaged with the inner surface of the cap. Moreover, the case may be made of transparent material and the other parts such as pinion, rack and gear provided inside the case may be made of different colored materials, so that the driving operation of the parts can be viewed.