| 摘要 |
A dispensing cartridge for a relatively precise dispensing of various fluids having a relatively wide range of viscosities is disclosed. The dispensing cartridge in accordance with the present invention is relatively simpler in configuration than known dispensing cartridges while minimizing leakage of the fluid and eliminating problems associated with chemical attack of the O-ring by the fluid in the dispensing cylinder. In particular, the dispensing cartridge in accordance with the present invention includes a cylinder; a piston with a central bore and a bleed plug. In order to simplify the design, the air vent is configured as a tortuous path, for example, a spiral path, defined by a spiral bleed plug, which in a pre-staged position, allows air to freely escape along the spiral path along the circumference of the plug. As the piston contacts the fluid, the forward motion of piston is resisted by the high back pressure created by the small effective diameter and relatively long length of the spiral path. Once the piston contacts the fluid, the spiral plug is pushed into the piston closing the spiral path. By controlling the fluid flow by way of a tortuous path, the amount of fluid backflow through the piston is minimized if not eliminated, thus eliminating the need for an annular overflow chamber, thereby simplifying the design of the piston. In order to minimize problems related to the sealing of the piston within the dispensing cartridge, the piston may be provided with one or more radially extending sealing lips. These sealing lips are used in lieu of or in conjunction with an O-ring. The sealing lips further simplify the design by eliminating the O-ring as well as the need for an annular chamber adjacent thereto as well as problems relating to chemical attack of the O-ring by the fluid within the dispensing cylinder. In an alternative embodiment for use that is particularly adapted with non-aggressive fluids, the piston is provided with a single sealing lip and an O-ring.
|
