Printed forms of margarine are generally made by an extrusion process wherein margarine, supercooled fluid form, is fed into a temperature controlled chamber under pressure for subsequent crystallization. Once crystallization or a "hardening" of the margarine has taken place, it can then be molded into the desired printed forms. The term "printed forms" or "prints" is a word of art that is used to define the shape of the margarine after it has been wrapped, and generally, refers to wrapped margarine having a rectangular bar shape.
In order to process margarine into print form, liquid margarine is taken from its mixing tank and pumped at a uniform rate to a heat exchanger where it is cooled to a paste-like consistency, and then to an expansion or compensating chamber or tube. From this expansion or compensating tube, the cooled margarine, which is still in a fluid state, is forced by the feed pump pressure into a retracted piston. Through the synchronous motion of a gear arrangement, the retracted piston and its cylinder are rotated 180.degree. and the piston is pushed forward to emit the collected margarine into a crystallization chamber. The piston is moved forward by new product being forced into the other side of the piston by means of the pressure head already established by the feed pump. The piston and cylinder are again rotated to emit the margarine into the crystallization chamber by the same process.
This step feeding process is continued until the crystallization chamber is filled with margarine. The margarine experiences a settling or crystallizing action which can be defined in terms of the time it takes a given amount of margarine to travel from the floating piston mechanism through the chamber and up to the molding or print chamber interface. It is during this time that the margarine crystallizes or solidifies and thus enables it to be molded into print forms. The crystallized margarine is forced into the mold chamber apparatus by the intermittent pressure built up in the chamber through the action of the floating piston in the step feeding process thereby causing the volume displacement of margarine into the mold.
The action of the floating piston is generally operated in synchronization with the molding operation, that is, the print mold chamber is in a receiving position to accept margarine when the piston is ejecting margarine into the crystallization chamber, hence the positive displacement of the margarine. Once the crystallized margarine is displaced into the mold, it is removed and forwarded to a synchronously operated wrapping apparatus and then onto a likewise synchronously operated packaging machine for assembling the wrapped prints into containers. This margarine processing operation is described in the brochure entitled "Lynch Morpac Model `CT`" put out by the Lynch Corporation of Anderson, Indiana.
One of the disadvantages of the above-identified system is that the functionality of the floating piston is severely limited, not only by its fixed dimensional size, but also because each piston must be externally adjusted for precise volume displacement of margarine into the mold. Hence, the volume displaced by each of the rotary floating pistons must be adjusted precisely to the volume of the mold chambers. Otherwise, excess margarine will be forced through the mold chamber vents, thereby reducing officiency and promoting maintenance problems due to leakage and subsequent margarine caking buildup outside of the system. Further complications exist in that sufficient margarine may not be available to fill the mold cavity thereby leading to the formation of incomplete or underweight prints.
Another disadvantage is that the 180.degree. rotation of the piston and its ejecting movement offers a mechanically complicated and expensive system that must be continually maintained. Leakages of the liquid margarine occur through the crevices of the piston and its chamber and eventually into the crevices formed by the chamber and housing thereby causing cleaning and sanitary problems.
More importantly, however, use of the free floating piston means for metering margarine offers the distinct disadvantage of limiting the length or capacity of the crystallization chamber because of the fixed mechanical drive arrangement operating from the molding apparatus main drive. Increasingly higher pressures are required to force the margarine emulsion into the piston chamber if higher operating speeds are desired, thus limiting the efficiency of the processing operation. Variations in crystallization chamber lengths caused by product and production demands are, therefore, restricted, especially when margarines are composed of the "softer" varieties of oils which require longer chamber lengths for crystallization.