Patent ID: 8496469

Claim:
A closure assembly for an injection unit of plastic material into a mould, comprising: a driving piston adapted to move along a respective axis; a closing rod, arranged coaxially to said driving piston, having a first end or head, associated with said driving piston, and a second end or tip, opposite to the first end and suitable for cooperating with an injection hole of said mould, said driving piston being adapted to drive an axial movement of said closing rod between an open position in which said closing rod opens said injection hole, and a closed position, in which said closing rod closes by the respective tip said injection hole, and micrometric regulation means for regulating axially in a micrometric way the closing rod in the respective said closed position, wherein said micrometric regulation means comprise at least one adjustment element provided with a thread having a fine pitch, with said adjustment element being adapted to be screwed or unscrewed in a corresponding threaded internal seat, formed in said driving piston, so as to adjust in a micrometric way, along said axis, the relative position of the closing rod with respect to the body of said driving piston and consequently regulate axially the closing rod in said closed position, wherein said adjustment element is entirely housed in said internal seat so as not to project from the body of said driving piston ( 15 ), wherein there are further provided fixing means, associated with said micrometric regulation means, for stably fixing said adjustment element ( 21 ) with respect to the body of said driving piston, once said closing rod has been regulated in said closed position, wherein said internal seat, in which said adjustment element is housed, comprises: a first upper portion, substantially cylindrical, formed adjacently to an upper side, spaced from the closing rod, of said driving piston, and provided along its internal cylindrical surface with a plurality of projections and notches; a second threaded intermediate portion, in which said adjustment element is adapted to be screwed or unscrewed in order to regulate said closing rod in said closed position; and a third lower portion, which houses the head of said closure rod; and wherein said fixing means comprise an elastic washer capable of rotating and moving axially jointly with said adjustment element and having along the external perimeter at least one protruding portion provided for cooperating elastically with the projections and the notches formed in said first upper portion of the internal seat of said driving piston, whereby, when said adjustment element is screwed or unscrewed, that is rotated in the two senses, in said internal seat for regulating micrometrically said closure rod in said closed position, said elastic washer is capable, by elastically cooperating through the respective protruding portion with said projections and notches, of firmly fixing said adjustment element, once said closing rod has been regulated in said closed position.