Injection-molding press

Injection-molding press for overmolding by injection-molding a second part on a first part, comprising:

• a movable portion and a fixed portion,
• at least a first mold element arranged on one of the portions of the press and at least a second mold element arranged on the other portion of the press so as to form a cavity between the first and second mold elements when the press is closed,
• the first mold element being provided with a first support surface and the second mold element being provided with a second support surface, the first and second support surfaces being disposed in their respective mold elements so that, in the closed position of the press with a first part inserted in the first mold element, at least a portion of a front end of the first part is clamped between the first and second support surfaces so as to form a tight seal for the cavity,
• wherein the first support surface is movable in the first mold element and the first support surface is movable between a retracted position and an advanced position, called working position, so that in the closed position of the press with a first part inserted into the first mold element and with the first support surface in the advanced position, at least a portion of the front end of the first part is clamped between the first and second support surfaces so as to form a tight seal for the cavity during the entire duration of injection,
• wherein the first mold element comprises a core and the second mold element is constituted by a matrix,
• wherein the core comprises a hollow cylindrical part and a valve disposed partially inside the cylindrical part, the valve being movable relative to the cylindrical part between a retracted position and an advanced position in which, when the press is closed, the first support surface is pressed against the second support surface with the interposition of at least a portion of the front end of the first part.

Method for overmolding a second part on a first part in a press,

• wherein the press is an injection-molding press for overmolding by injection-molding a second part on a first part, comprising:
• a movable portion and a fixed portion,
• at least a first mold element arranged on one of the portions of the press and at least a second mold element arranged on the other portion of the press so as to form a cavity between the first and second mold elements when the press is closed,
• the first mold element being provided with a first support surface and the second mold element being provided with a second support surface, the two support surfaces being disposed in their respective mold elements so that, in the closed position of the press with a first part inserted in the first mold element, at least a portion of a front end of the first part is clamped between the first and second support surfaces so as to form a tight seal for the cavity,
• wherein the first support surface is movable in the first mold element and the first support surface is movable between a retracted position and an advanced position, called working position, so that in the closed position of the press with a first part inserted into the first mold element and with the first support surface in the advanced position, at least a portion of the front end of the first part is clamped between the first and second support surfaces so as to form a tight seal for the cavity during the entire duration of injection,
• wherein the first mold element comprises a core and the second mold element is constituted by a matrix,
• wherein the core comprises a hollow cylindrical part and a valve disposed partially inside the cylindrical part, the valve being movable relative to the cylindrical part between a retracted position and an advanced position in which, when the press is closed, the first support surface is pressed against the second support surface with the interposition of at least a portion of the front end of the first part,
• wherein the method comprises the following steps:
• a. opening the press;
• b. positioning a first part on or in the first mold element;
• c. closing the press;
• d. injection-molding the second part onto the first part in the cavity formed between the first and second mold elements;
• e. opening the press;
• f. ejecting the finished object and returning to step (b),
• wherein, in step (c) or during a step (c1) following step (c) and prior to step (d)), at least a portion of the front end of the first part is clamped between the first support surface and the second support surface so as to form a tight seal for the cavity, and in step (e) or during a step (d1) following step (d) and prior to step (e), the clamping of the front end portion of the first part is removed,
• wherein at least one of the clamping of step (c) or (c1) and the removal of this clamping in step (e) or (d1) is obtained by moving the valve relative to the cylindrical part.