Agitating – Having specified feed means – Plural related feeders having separate outlets to mixing...
Reexamination Certificate
1999-10-06
2001-06-12
Cooley, Charles E. (Department: 1723)
Agitating
Having specified feed means
Plural related feeders having separate outlets to mixing...
C366S336000, C222S145600
Reexamination Certificate
active
06244740
ABSTRACT:
BACKGROUND OF THE INVENTION
Pasty multi-component masses, such as dental impression masses, are produced by means of mixing devices in which the individual components of the mass are simultaneously supplied from separate cartridge cylinders to a mixer which dispenses the mixed paste from a front end. The mixer may be a static mixer or a dynamic mixer (having a rotary mixer element). The paste exiting from the front end of the mixer may be supplied directly onto an impression spoon.
Depending on the viscosity and mixing ratio, the fact that the pressure builds up differently in the individual cartridge cylinders at the start of the device may cause the components to reach the mixer at different times. In such a case, the first length of paste exiting from the mixer has a mixing ratio which differs from a desired value and may therefore cure less perfectly or more slowly, or have other undesired properties.
In case one of the components is a base paste and the other is a catalyst of a dental impression mass, a typical mixing ratio of base paste to catalyst is 5:1. Due to the different properties and/or amounts of material and the differently sized inlet openings of the mixer, it can be observed that the mixing chamber is filled with the base paste before the catalyst arrives, so that a first length of approximately 3 cm of the final paste fails to have the desired mixing ratio.
Known is a static mixer for producing pastes from different amounts of components, which includes a housing having at its rear end an inlet opening for each component. A space provided between a mixing chamber and a plate, which has the inlet openings for the two components, is divided into two chambers by a partition wall extending in the axial direction of the mixer. One of the chambers forms a straight axial flow path for the component of the smaller volume proportion, whereas the other chamber covers the remaining cross-sectional area, which is substantially larger than the volume proportion of this component, and which is separated from the mixing chamber by a transverse wall. This other chamber thus forms a retaining volume which is filled by the component of the larger volume proportion before that component can pass a narrow passage provided in the transverse wall and reaching the mixer element. This is intended to ensure that the two different components reach the mixing chamber substantially simultaneously.
A problem exiting with this known device resides in the fact that the above-mentioned transverse wall with the narrow passage increases the flow resistance for the respective component considerably, thus rendering the overall device sluggish. As another disadvantage, the axial length of the device is significantly increased by the retaining space.
EP 0 302 819 A2 discloses a cartridge magazine for a flowable mass comprising two containers of different diameters for receiving different amounts of two components of the mass. Due to the fact that a common outlet pipe is offset from the axial center toward one edge of the cartridge system, the connecting channels between the cartridge outlets and the common outlet pipe have different lengths. In this known mixer, the above-mentioned problem of an improper mixing ratio at the beginning occurs at the second and each further application when there is no longer a time difference in time in the advancement of the components.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a mixer for producing multicomponent pastes, which is as smooth to operate and compact as possible and which permits the production of a pasty mixture that has a desired mixing ratio from the start.
To this end, a mixer for producing a paste by mixing nonequal amounts of components in accordance with the present invention comprises a housing having a longitudinal axis, a rear end provided with separate inlet openings for each component, and a front end provided with a dispensing opening, a mixing chamber formed in the housing, and a delay chamber formed in the housing between one of the inlet openings and the mixer chamber, the delay chamber extending along an arc about the longitudinal axis so as to increase the length of the path to be followed by the component applied to the one inlet opening. The deviation channel may have the same cross-section throughout its length as the corresponding inlet opening so that the overall flow resistance is hardly increased. Moreover, the deviation channel is so disposed that it does not substantially increase the overall dimensions of the mixer.
In a preferred embodiment of the invention, the mixer is a dynamic mixer, with a mixer element provided in the mixing chamber and supported in the housing for rotation about the longitudinal axis.
For producing pastes from two components, it is preferred that the positions at which the components enter the mixing chamber are offset from each other by less than 180° about the longitudinal axis. This is specifically advantageous because both components are supplied to the mixer element at closely adjacent positions, thus rendering each mixing process effective from the start.
In an embodiment of a mixer for producing dental impression masses from a base substance and a catalyst substance, the deviating channel is preferably disposed between the inlet opening passed by the base substance and the mixing chamber. This structure is useful for typical base-catalyst substances. Moreover, since a certain excess of catalyst only results in slightly faster curing without substantially altering the properties of the final paste, the structure advantageously ensures that the mixing chamber is first wetted by the catalyst to produce a paste that is properly mixed from the start.
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Brandhorst Gerd
Peuker Marc
Wagner Ingo
Wolf Christina
Connolly Bove & Lodge & Hutz LLP
Cooley Charles E.
Espe Dental AG
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