| 摘要 |
A pump mechanism for delivering ink or the like writing fluid from a reservoir to a point of utilization such as a writing device. The mechanism includes a piston slidable in a cylinder for drawing ink into the cylinder during a suction stroke and discharging the ink during a pumping stroke. The cylinder is formed by a cylinder wall which includes a frusto-conical portion tapered inwardly in a direction away from the piston. The piston comprises a single plastic member having a forward end portion which faces and cooperates with the tapered portion of the cylinder wall and which has an outside diameter which is greater than the smallest diameter of the tapered cylinder wall portion, whereby the forward end portion of the piston engages the tapered cylinder wall portion as the piston moves forward during a pumping stroke. The front or forward wall of the piston is recessed to enable the forward end portion of the piston to deform and slidingly engage the tapered cylinder wall in sealing engagement as the piston moves forward in a pumping stroke. The forward end portion moves out of engagement with the tapered cylinder wall portion as the piston moves backward during a suction stroke. |
