The present invention concerns an adaptor plate for connecting a cover plate to a plurality of piston housings of an injection molding machine, wherein the adaptor plate has a first fluid passage and a second fluid passage for feeding a first and a second control fluid into the piston housings, wherein the first fluid passage has at least one first fluid passage inlet for receiving the first control fluid and a plurality of first fluid passage outlets for discharge of the first control fluid to the piston housings and the second fluid passage has at least one second fluid passage inlet for receiving the second control fluid and a plurality of second fluid passage outlets for discharge of the second control fluid to the piston housings.