Method for controlling the bell of a blowing nozzle

A method for controlling the bell of a blowing nozzle comprising two parts, which nozzle is arranged in a moulding unit intended to be associated with an installation for manufacturing containers of the bottle type, by a stretch blow-moulding operation of preforms arranged in appropriate moulds of the jack-knife type or the like, which unit comprises:

• on the one hand, a stretching rod borne by a slide which is mobile along the axis x-x′ of the mould with which the rod is associated, under the action of an actuator device, over a distance C which is greater than the depth H of said mould, between an inactive position where a free end of the rod is held at a sufficient distance from an inlet surface of said mould to permit the passage of the means for transferring the preform and the moulded container, and an active position where the free end reaches the bottom of said mould,
• on the other hand, a nozzle comprising a body attached to the support structure of said mould carrier unit, which nozzle also comprises a telescopic sealed extension, in the form of a bell, which bell is mobile under the action of said actuator device for passing from an inactive position where a free edge of the bell is held substantially at the same level as the free end of the stretching rod to a sealed active position where said free edge is sealingly applied against said inlet surface to close the circuit of the blowing fluid,
• wherein said bell comprises a manoeuvring member which cooperate with said slide to permit said bell to pass from the sealed active position to the inactive position with the same law of motion as said stretching rod,
• said method comprising:
• applying said bell against the inlet surface of the mould to close the circuit of the blowing fluid,
• and simultaneously driving the stretching rod to shift the free end from the inactive position corresponding substantially to that of said bell, to the active position for stretching the preform,
• wherein, after the blowing operation, causing said bell to be manoeuvred by the drive means of said stretching rod, at the end of a return travel, over a length which corresponds to a distance d separating the inlet surface of the mould and the free end of said stretching rod, when it is in the inactive position, thus shifting said bell from its active position for closing the blowing circuit to its inactive position, with a law of motion which corresponds to that of said stretching rod,
• and wherein said manoeuvring member which cooperates with the slide to shift the bell from the sealed active position to the inactive position comprises a bar which is attached at one end to said bell and which comprises at the other end a stop, which stop cooperates with a support formed on said slide so as to be driven thereby during the return of said stretching rod to the inactive position, said bar being parallel to said stretching rod.