Apparatus for the production of plastic pipes with transverse grooves

In apparatus for the production of plastic pipes with transverse grooves, in which half-shells each provided with a mold recess, are arranged on a machine bed and driven in a cycle so that respective pairs thereof complete a mold on a molding path, an injection head of an extruder being located at the start of the molding path, and furthermore the half-shells being each provided with vacuum channels communicating with the respective mold recess, said channels joining into vacuum connections formed in the machine bed in the molding path, and the half-shells being provided with cooling channels which join into cooling water inlets and outlets formed in the machine bed in the molding path, the improvement comprising:

• said cooling channels and said vacuum channels being completely separated from each other in the respective half shells, said cooling channels joining with cooling water return channels provided separately in the machine bed from the vacuum connections, said cooling water return channels being likewise subjectable to vacuum, and
• means for automatically regulating the temperature of said half-shells including at least one means for sensing the temperature of a half-shell on the molding path and means for governing the quantity of cooling water per unit time flowing to said cooling water inlets,
• said regulating means actuating said governing means to control the quantity of flowing cooling water when said sensed temperature exceeds a predetermined temperature,
• the temperature of the half-shell being governed only by the quantity of flowing cooling water and maintained at a constant value during the molding operation,
• said temperature sensing means contacting a smooth external surface of said mold half-shell on the molding path by means of a shoe.