Abstract: A check valve (10) comprises, a flexible tube (11) having first and second end portions defining an inlet (13) and an outlet (14), respectively, and a rigid valve body (12) surrounding the flexible tube (11). The end portions of the flexible tube are sealingly fixed to the valve body (12) to define an enclosed space (17) between the exterior of the flexible tube and the interior of the valve body. A fixed volume of a substantially incompressible fluid is located in the enclosed space (17). When the pressure at the outlet (14) is greater than the pressure at the inlet (13), the flexible tube is substantially collapsed so as to close the valve or allow severely restricted flow. However when the pressure at the inlet is greater than that at the outlet, some of the fluid is displaced from the inlet area towards the outlet area so that the flexible tube (11) is expanded in the area adjacent the inlet and the tube is substantially open.

Abstract: A toner fill plug for a toner cartridge within an image forming device. The cartridge includes a toner reservoir having a port through which toner is input. The plug is sized to fit within the port and prevent toner leakage. The plug includes a reflector which aligns with an adjacently-positioned toner level sensor for determining the amount of toner remaining within the reservoir. The plug is removable to allow the user to refill the reservoir with new toner.