The piston rod of the piston-cylinder
The pressing units are piston-cylinder units which are arranged substantially in a vertical position, and that the pressing units are each arranged on a holder or mount which is pivotable about a substantially vertical axis. This arrangement offers the essential advantage that the extruder-head unit, not separable during operation, is now no longer connected with the calender during operation, so that the distance between the extruder and the calender can be varied during operation and hence the knead forming in the nip can be given an optimal size and shape. More important still is the advantage that the extruder can be used also without the calender. This advantage leads to a better utilization of the machine and is apparent whenever the extruder is operated sometimes with or sometimes without a calender.
It must be regarded as another special advantage of the invention that a standard extruder thus designed can be operated together with virtually every standard calender, and that, moreover, when an extruder head with exchangeable plates limiting the flow path of the extruded product in different ways is being used, a standard extruder head can be used. The use of such standard equipments increases their usability and lowers the prime cost. Calenders already existing in a plant can be made use of jointly with the extruder according to the invention, but also, when a new acquisition is made, first the extruder with the extruder head can be procured, then using the latter together with a calender purchased much later. This arrangement leaves the piston-cylinder units in a place where they do not hinder the installing and cleaning operations, where they do not affect the weight of the bottom part, and allow the piston-cylinder units to be universally usable for all replacement extruder heads, it being assured that the extruder head and following calender are completely independent of each other.
This arrangement can be realized in an especially simple and advantageous manner in that the two parts to be pressed together with the pressing units have a recess on both sides, that the piston rod of the twin screw extruder carries an abutment at its end, and that in the operating state of the extruder head the piston rod is in this recess.To assure contactless insertion of the pressing units into the operating position, it is of advantage if the pressing unit and/or its holder is mounted for vertical displacement. It is very easy to construct this apparatus if the holder embraces a journal by its one end and if at the end of the journal a piston-cylinder unit for lifting the holder is provided. For easy pivoting and displaceability of the machine parts to be moved, it is advantageous if the holder is provided on its end surrounding the journal with a ball beating against which the piston rod of the piston-cylinder unit pushes for the lifting of the holder.