At present, on a common image forming device, such as a printer, a device for accumulating recording medium including papers etc. (in order to facilitate description, recording medium are hereinafter referred to as papers) is commonly installed, which is intended to avoid the printed pages from being taken away by users when the printing has not yet been finished and thus resulting in the loss of a part of the information. A printer with a medium accumulating device will not discharge the printed page from the printer until one sheet of printed page has been finished. However, a conventional printer with a medium accumulating device can only collect one piece of printed page at one time, i.e., after the printing of one piece of printed page has been finished, the piece of printed page will be discharged from the printer. However, when the printed contents are more than one sheet, users are not usually clear about how many pages are left behind, and thus often take the discharged printed pages away with those left behind being omitted, therefore resulting in a disclosure of users' information.
A device capable of accumulating a plurality of printed papers is disclosed in an international patent published in 2000 (Publication No. U.S. Pat. No. 6,077,030A). Referring to FIG. 1A, the device includes a drum cylinder 20 capable of receiving and accumulating a plurality of papers by means of predetermined portions in its periphery and a clamping means capable of clamping the front end of the paper, wherein the clamping mean includes at least a delivery roller 32 parallel to the drum cylinder, the delivery roller 32 clamps a predetermined portion of the printed paper and drives the printed paper to rotate with the drum cylinder. In this way, the printed papers are accumulated and clamped on the delivery roller 32. Also, the delivery roller 32 may discharge several pieces of printed papers out of the drum cylinder 20. This device, however, has the following disadvantages.
Firstly, the device needs to employ a clamping means to clamp the front edge of the paper by its pressure, such that the accumulating device can then operate normally. In this way, since it is necessary for the clamping means to open and close repeatedly, its clamping force will decrease gradually due to spring fatigue, which causes clamping failure, and thus the accumulating device fails to operate normally.
Secondly, as is shown in FIG. 1B, it is required for the device to rotate positively and negatively by means of two motors, i.e., with the reversible rotating of a first motor 66, the device controls the drum cylinder 20 to rotate reversibly and thus implements paper accumulating; with the reversible rotating of a second motor 82, the device controls the delivery roller 32 and pressing roller 36 to rotate positively and negatively and thus implement paper discharging. The structure involved is complicated and the cost for electric control is relatively high.