Impingement mixing device with pressure controlled nozzle adjustment

DETAILED DESCRIPTION It is an object of the invention to provide an impingement mixing apparatus which continuously monitors component pressure and automatically adjusts the nozzles needle gap in order to maintain the appropriate pressure.
The nozzle needle gap can be adjusted by axially adjusting the nozzle needle position.
The axial movement of the nozzle needles can overcome the effects of changes in the pressure due to thermal expansion of the impingement components, built-up residue, deterioration of the nozzles, or a partial blockage of the impingement port.
The interaction between volume and pressure of each component further enables changing the component mixing ratio by affecting the pressure of only a single component or by modification of the component pressure of each component independent of the component pressure of the other components.
Changing the component mixing ratio will effect the characteristics of the product produced.
Particularly, the density or hardness of foam produced in a polyurethane mixing system can be effectively altered by adjusting the nozzles for a single component during the course of a shot.
This procedure enables production of multiple density pieces utilizing only a single mixing head.
Previously, multiple density pieces require the use of multiple mixing heads, duplex mixing devices such as described in U.
S.
Pat.
No.
4,175,874 or complicated mechanical hydraulic adjustments as shown in U.
S.
Pat.
No.
4,378,335 the disclosure of which is incorporated herein.
By altering the setting pistons of the adjustable pumps or the pressure of both components the component flow rate or volume can be changed without effecting the mixing ratios.
This a particularly useful feature when the cross-sectional area of the part in production varies.
During production the mixing heads are normally carried on robot arms and moved over a mold at a constant speed during the course of a shot.
Especially during the production of larger parts such as car seats it is important to pour more of the mixed components in the portion of a mold which defines a deeper area of the product than that which defines a shallower area