Apparatus for injection molding elongated objects
Injection molding apparatus includes: a mold structure having a main axis and a mold cavity; a core in the mold cavity, defining a mold envelope bounded by an inner sidewall, an inner endwall at one end of the inner sidewall, an outer sidewall spaced apart from the inner sidewall, and an outer endwall spaced apart from the inner endwall; a nozzle at an end of the cavity, including an interior channel communicating with the mold envelope; a pin in the nozzle, moveable between a closed position forming a part of the outer endwall and blocking flow between the interior channel and the mold envelope, and an open position permitting fluid flow; and a locking pin within the core and moveable between a retracted position free of the outer endwall, and an extended position received within the outer endwall, preventing relative lateral movement of the core and the mold cavity.
1. An injection molding apparatus having a main axis, comprising:
a mold structure including a mold cavity therein;
an elongated core disposed in the mold cavity such that a mold envelope is defined between the mold cavity and the core, the mold envelope being bounded by an inner sidewall, an inner endwall disposed at an end of the inner sidewall, an outer sidewall spaced apart from the inner sidewall, and an outer endwall spaced apart from the inner endwall;
a nozzle disposed adjacent the outer endwall, including an interior channel in fluid communication with the mold envelope;
a valve gate pin disposed in the nozzle and moveable along the main axis between a closed position in which it forms a part of the outer endwall and blocks fluid flow between the interior channel and the mold envelope, and an open position in which it permits fluid flow between the interior channel and the mold envelope; and
a locking pin disposed within the core and moveable along the main axis between a retracted position in which the locking pin is free of the outer endwall, and an extended position in which the locking pin is received within the outer endwall so as to prevent relative lateral movement of the core and the mold cavity.
2. The apparatus of claim 1 wherein the core includes an end face that defines the inner endwall of the mold envelope, the end face including a void that receives the locking pin.
3. The apparatus of claim 1 wherein an overall length of the mold envelope measured parallel to the main axis is about 100 times greater than a distance between the inner and outer sidewalls.
4. The apparatus of claim 1 further including a first actuator operable to move the valve gate pin between the open and closed positions.
5. The apparatus of claim 1 further including a second actuator operable to move the locking pin between the extended and retracted positions.
6. The apparatus of claim 1 wherein the mold structure includes:
a mold block which defines the outer sidewall of the mold envelope; and
a valve block positioned axially adjacent to the mold block and including an end cavity which defines the outer endwall of the mold envelope.
7. The apparatus of claim 6 wherein:
the valve block includes a chamber with an endwall opposite the end cavity; and
the nozzle is disposed in the chamber, with a nozzle end of the nozzle spaced a short distance from the endwall.
8. The apparatus of claim 1 wherein the mold structure includes an injection orifice defined in the outer endwall, the orifice being coaxially aligned with the valve gate pin and the locking pin.
9. The apparatus of claim 8 wherein a tip of the locking pin includes one or more shallow slots formed around its periphery.