Patent ID: 8460598

Claim:
A method for recycling blowing air from a blow moulding apparatus for blow moulding plastic material containers, said apparatus including: moulds provided with blowing cavities, first blowing means for blowing primary air in the cavities of said moulds, comprising a primary air tank, second blowing means for blowing secondary air in the cavities of said moulds, comprising a secondary air tank, first recycling means for recycling the blowing air exiting from said cavities, in a first step of discharging the air from the containers, wherein said first recycling means are configured so as either to allow an input of primary air into a first blowing stage within the cavities of said moulds or to allow an input of a part of secondary air into a second blowing stage, said method comprising the following stages: a) at a predetermined starting time t 0 of a blowing cycle, blowing the air into the containers contained in the cavities of the moulds at a first predetermined pressure P 1 , by means of the first blowing means, and maintaining the air at such a first pressure in the containers contained in the cavities up to a first time t 1 , in which said air is defined primary; b) blowing the air into the containers contained in the cavities of the moulds at a second predetermined pressure P 2 , by means of the second blowing means, said second predetermined pressure being higher than the first pressure P 1 , and maintaining the air at said second pressure up to a second time t 2 , in which said air is defined secondary; c) discharging the air from the containers contained in the cavities until a third pressure P 3 is reached in the containers, such a third pressure having a value comprised between said first pressure P 1 and second P 2 pressure, and recycling the air at said third pressure P 3 by means of the first recycling means, wherein said third pressure P 3 has a value in the range between 20 and 28 bar, this stage having a duration in the range between 0.05 and 0.15 sec, c′) discharging and recycling the air from the containers contained in the cavities until a fourth pressure P 3 ′ is reached in the containers with a value between 12 and 14 bars, and transferring the recycled air in a recycling tank or other dedicated storing means, this stage having a duration in the range between 0.05 and 0.10 seconds; and d) discharging the remaining air contained in the containers contained in the cavities at atmospheric pressure.