One-piece vented piston

Abstract

A vented piston (1) comprises a plunger (2) having a front side and a rear side, a venting passage (4) extending between the front side and the rear side, and a cap (7) located adjacent the front side. The cap is resiliently-biased by a spring (8) towards an open position in which air can pass through the venting passage from the front to the rear side of the plunger, and is movable from the open position into a closed position in which the cap closes the venting passage. The piston may be used in a storage chamber (10) of a dispensing system whereby air can be removed from the storage chamber by moving the plunger in the direction of a substance (12) stored in the chamber.

Description

[0001] Cross references to related patent applications [0002] This application claims priority from UK Patent Application No. 0721774.8, filed 7 November 2007. technical field [0003] The invention relates to a piston of the type that enables air to be expelled from the chamber in which said piston is arranged. Background technique [0004] In particular the invention relates to a piston suitable for use in a dispensing system which also serves to store the substance to be dispensed until it needs to be used. Dispensing systems of this type are known, for example, in the field of dentistry where dental materials (such as impression materials, restorative materials, filling materials) are often supplied in cartridges comprising a storage chamber in which The above-mentioned material or a certain component of the material is contained in it. A sealed dispensing outlet may be provided at the front end of the cartridge; and a piston for closing the storage chamber may be p...

AI Technical Summary

Problems solved by technology

[0006] When filling a substance into a dispensing system in which it is to be stored, the problem often arises of removing air from the storage chamber and ensuring that no voids or air bubbles are trapped in the stored substance

The presence of air can adversely affect the shelf life of the stored substance, and the presence of voids or air bubbles can adversely affect the accuracy of dosing of the substance that can be dispensed

A traditional way of dealing with this problem is to assemble the dispensing system in a vacuum environment, but this leads to the evaporation of some components of the substance to be stored, resulting in a change in its composition

Another way to deal with this is to populate the system with its assigned outlets, but this can only be used with reasonably configured systems

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