| 摘要 |
A first hollow elongated cylinder has a first inner diameter. One end of the first cylinder is open. The opposite end of the first cylinder is provided with sealed tip adapted to detachably receive a hypodermic needle. A second hollow elongated cylinder has a second and larger inner diameter. One end of the second cylinder is open. The opposite end of the second cylinder has centered therein a circular port with a diameter equal to the first diameter. The cylinders are disposed end to end along a common cylindrical axis. The opposite end of the second cylinder is secured to the open end of the first cylinder with said port being coincident with the open end of the first cylinder. A sealing disc is centered on said axis and is slidable back and forth in said cylinders along said axis, said disc having a diameter equal to said first diameter and when disposed in said first cylinder engaging the inner surface thereof with a liquid tight seal. A bushing is disposed in the open end of the second cylinder and has a circular opening centered on said axis, said opening having a third diameter smaller than said first diameter. An elongated cylindrical piston extends slidably through said opening, there being a liquid tight seal between said piston and said bushing. One end of said piston is disposed outside of the second cylinder and is enlarged, said piston being aligned with and centered on said axis, the length of the piston being longer than the combined lengths of said first and second cylinders. Cooperating detachably engagable means are on said disc and on the opposite end of the piston whereby said opposite piston end can be detachably secured to said disc.
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