A closed-end washer applied to a guide wheel device is coupled to a wheel axis and includes a roller, transmission belt and closed-end washer, wherein the wheel axis has a notch. In assembly, the roller is first put around the wheel axis. After the transmission belt is looped about the roller, the closed-end washer is embedded into the notch of the wheel axis for preventing the transmission belt and the roller from coming off the wheel axis during rotation. In practice, the closed-end washer is made of the flexible materials, such as rubber or plastic. The embedding pieces forms on the inner side of the closed-end washer is the embedding portion for embedding into the notch of the wheel axis so that the closed-end washer is securely placed on the wheel axis.

DESCRIPTION OF THE PREFERRED EMBODIMENT From the forgoing, it is apparently seen that the traditional guide wheel structure can not just discard the roller cover due to the opening of the C-washer or E-ring by which usually cause the transmission belt get stuck. Therefore the present invention provides a closed-end washer without an opening. Referring to FIG. 8A, a top view of a closed-end washer according to an alternative preferred embodiment of the invention is shown. The circumference of the closed-end washer 800 is complete as a whole. The inner side of the closed-end washer 800 is the embedding portion 810 for embedding into the notch of the wheel axis. The closed-end washer 800 is securely placed on the top section of the wheel axis. In order to embed the embedding portion 810 into the notch, the closed-end washer 800 is made of a flexible material in practice. In the present embodiment, the embedding portion 810 further comprises several embedding pieces 815 forming on the inner side of the closed-end washer 800 . The embedding pieces 815 radiated from the center of the closed-end washer 800 . Since the closed-end washer 800 is made of flexible material, the assembly of the closed-end washer 800 only requires placing the closed-end washer 800 on the top section of the wheel axis and pressing the closed-end washer 800 on the wheel axis for embedding the embedding pieces 815 into the notch of the wheel axis. Thus, the closed-end washer 800 can be placed on the wheel axis securely. There are also other flexible or elastic materials suitable for forming the closed-end washer 800 , such like rubber, plastic or the like, without difficulty. In addition, the embedding pieces 815 are used for embedding into the notch to fix the closed-end washer on the wheel axis regardless of the number of the embedding pieces. An alternative closed-end washer according to the invention is shown in FIG. 8B . Referring to FIG. 9, a perspective view of a guide wheel device using the closed-end washer in FIG. 8A is shown. After putting the roller 210 around the wheel axis 410 and looping the transmission belt 130 about the roller 210 , the closed-end washer 800 is embedded into the notch of the wheel axis 410 . The assembly of the guide wheel device is then finished. The closed-end washer 800 positions the roller 210 and the transmission belt 130 and thus prevents the transmission belt 130 and the roller 210 from coming off the wheel axis 410 during rotation. The closed-end washer 800 with no opening will not cause the transmission belt 130 getting stuck even there is no roller cover. What needs to be noticed, the closed-end washer applied to a guide wheel device is not restricted on the scanner. It is suitable for any device equipped a guide wheel device to minimize the volume of the guide wheel device and economize materials. The closed-end washer and the guide wheel device according to the invention at least have the following advantages: Firstly, the wheel axis is shorter than before and the product corresponds to the trend of compactness. Secondly, it does require the roller cover and therefore economize materials and raise the competitiveness of the product. While the invention has been described by way of example and in terms of the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment. To the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.