Anti-Theft Door Handle Invention Field This invention offers a type of door handle, especially refers to a type of anti-theft door handle. Background Technical Information Currently, there are various door handles on the market. Some are connected with door locks; some are separated with door locks. However, no- matter connected types or separated types, most of them do not have the anti-theft function. Their anti-theft results are achieved through the function of door locks. But, thieves act according to the structures of door locks. They use a so-called "universal key" to commit crimes everywhere. Thieves with superb skills can unlock any locks with a universal key within two hours. Why it is possible for them to do so? This results from the exposed keyholes of door locks. Function of This Invention On account of the above fact, this invention adds a protective cover over door locks. It prevents the keyholes of door locks from direct outside exposure. So it will be very difficult to unlock door locks without special keys. The purpose of this invention is to provide a type of anti-theft handle, which can be installed over the keyholes of door locks so that thefts can be prevented. Another purpose of this invention is to provide a type of anti-theft handle which is of simple structure and it is easy to make and install. This invention of an anti-theft door handle consists of: The handle's body. A fan-shaped key slit part, which takes the form of a fan. The edge of its fan-shaped side is fixed with the upper side of the inner arc of the handle's body. 1 A keyhole cover, the two ends of which are fixed with an upper position and a lower position at the inner arc of the body of the handle. It is fixed on one side with the fan-shaped key slit part. The anti-theft door handle's body is of an arc shape. On its body, about one-fourth from the upper end, there is a rectangular upper keyhole. There is a bending part at each of the two ends of the handle's body. The bending parts take the form of rectangular plates. There is a rectangular slot opened on each surface side of the two bending parts. There is a round hole at the center of each of the two rectangular slots. The fan-shaped key slit part is composed of one piece of folded plate. A fan-shaped key slit is formed inside the folded plate. The keyhole cover is of a bar-type. In the middle of the bar, there is a round keyhole cover plate with extended bar arms. A rectangular lower keyhole is opened along with the bar in the middle of the keyhole cover plate. The handle's body is of a round ring-shape with an opening. The two ends at the opening are fixed with the body of a lock. Brief Explanation on Attached Diagrams In order to give further explanations on the features and functions of this invention, diagrams and application drawings are attached as follows: Diagram I is the solid schematic diagram of this invention. Diagram 2 is the solid schematic diagram of the fan-shaped key slit part in Diagram 1. Diagram 3 is the solid schematic diagram of the keyhole cover in Diagram 1. Diagram 4 is the schematic diagram for the way of usage and the unlocking procedure of this invention. Diagram 5 is the schematic diagram of the structure of another application of this invention. Best Way to Realize This Invention First of all, please refer to Diagram 1 to Diagram 3. These are the solid schematic diagrams and part drawings of this invention. They show the handle's body 10. The handle's body 10 is in an arc shape. Its cross section is of a rectangular shape or 2 an arc shape. There is a bending part 101 at each end of the handle's body 10. This bending part 101 is of a rectangular shape. The planes of the two bending parts 101 are horizontal. There is a rectangular slot 12 opened on the surface of each bending part 101. In the middle of each rectangular slot 12 there is a round hole 121 for a screw 122 to go through. The rectangular slot 12 is for the setting-in of the rectangular head 123 at the end of the screw 122. In the handle's body 10, about one-fourth from the upper end, there is a rectangular upper keyhole 11. This is for the insert of the door key. A fan-shaped key slit part 20 (Diagram 2) is folded into shape with one piece of plate. A fan-shaped key slit 22 is formed inside the folded plate. One side of this slit part and the fan-shaped side of it both have openings. Only the bottom side of the part is sealed. The fan-shaped side of the key slit part 20 is fixed with the upper side of the inner arc of the handle's body 10. The thickness of the fan-shaped key slit part 20 is less than that of the handle's body 10. A keyhole cover 30 (Diagram 3) is of a bar-type. It is composed of the keyhole cover plate 33 and the two extended arms 32 of the keyhole cover plate. In the middle of the keyhole cover 30, there is a round keyhole cover plate 33. This round keyhole cover plate 33 in the keyhole cover 30 can be made with specifications of different diameters according to need. The larger is the diameter, the better is the anti-theft function, but relatively, the longer is the time required for the unlocking with a key. The round keyhole cover plate 33 has an extended arm 32 at each side. A rectangular lower keyhole 31 is opened along with the bar in the middle of the keyhole cover plate. The ends of the two arms 32 of the keyhole cover 30 are fixed with an upper side point and a lower side point of the handle's body 10. And one side of the keyhole cover 30 is fixed with one side of the fan-shaped key slit part 20. The joining side of the fan-shaped key slit 22 and the joining side of the keyhole cover plate 33 are horizontal. Industrial Feasibility Please refer to Diagram 4. It is the schematic diagram to show the way of usage and the unlocking procedure of this invention. It shows that the handle's body 10 is fixed onto the door 50 with the screw 122 and covers the lock 302. So the lower keyhole 31 aligns with the keyhole 301 in the door lock 302. When unlocking, insert the key 40 into the upper keyhole 11 in the handle's body 10 first. The head of the key 40 goes through the fan-shaped key slit 22 in the fan-shaped key slit part and then protrudes the lower keyhole 31 (Position A of the key 40 in Diagram 4) in the keyhole cover plate 33. Then, the key 40 free-falls onto the bottom of the fan-shaped key slit 22 (Position B of key "40" in Diagram 4). As the head of the key protrudes the lower keyhole 31, one can use fingers to hold the head of the key 40 and 3 insert it into the keyhole 301 in the door lock 302. Once the key 40 touches the bottom of the door keyhole, the tail of the key will be just out of the lower keyhole 31. It will be in the unlocking space 60 in Diagram 4. This makes it possible for a human hand to turn the key 40 and unlock the door lock 302. After unlocking, to get out the key 40, first, we need to move the key 40 back to the very end. Now the head of the key 40 will be left a bit out of the lower keyhole 31. We then press the head of the key 40 down, so the tail of the key 40 will turn upwards to the position of the upper keyhole 11 (back to the original Position A). We can use the other hand to take the key 40 out. Or, we can fix a string at the tail of the key 40. We move the key 40 to the very back with our fingers and then pull it out with the string outside the upper keyhole 11. Further explanations: when the key 40 is in the upper keyhole 11, as the fan-shaped key slit 22 is just a bit larger than the thickness of the key 40, the key 40 will not fall sidelong. Also, as the bottom length of the fan-shaped key slit 22 is shorter than the length of the key 40, the head of the key 40 will surely protrude the lower keyhole 31. Please also refer to Diagram 5. This is another application of this invention. The general structure is the same as the above application. So we do not elaborate on it. The difference is that the handle's body 80 is in a round ring-shape with an opening. The two ends of the opening are directly fixed with the door lock 70. That is to say the handle's body 80 forms one with the lock. In comparison with the current techniques, this invention can prevent the theft with a universal key without changing the current structures of locks. This invention is also characterized by its simple structure and its easiness to make. 4