Molding device for forming compact lens barrel

A molding device for forming a compact lens barrel includes a first mold part and a second mold part. The first mold part includes a generally cylindrical molding recess with an opening defined at an end thereof. The first mold part has a bottom surface facing toward the opening. A first protrusion is formed on the bottom surface. The first protrusion has a round, first top surface. The second mold part includes a core insert and a second protrusion formed on the core insert. The second protrusion has a round, second top surface. The second mold part is received in the molding recess with the second top surface contacting the first top surface. An annular surface portion of one of the first top surface and the second top surface is exposed. The annular surface portion has a width equal to or less than 0.005 mm.

BACKGROUND

1. Technical Field

The present disclosure relates generally to a molding device for forming a compact lens barrel.

2. Description of Related Art

Compact image pick-up apparatuses are used in a variety of consumer electronic devices, such as notebook computers, personal digital assistants (PDAs), and cellular telephones. The compact image pick-up apparatus includes a compact lens barrel, a number of optical lenses received in the compact lens barrel, and an image sensor. The compact lens barrel includes a light incident opening defined in the distal end thereof for allowing the outside light into the lens barrel. The compact lens barrel is usually formed by injection molding using a molding device. For forming a compact lens barrel, a very accurate molding device is demanded.

The molding device includes a first mold part and an opposite second mold part. The first and second mold parts cooperatively form a molding cavity in the shape of the compact lens barrel. The first mold part includes a concave portion, and the second mold part includes a convex portion inserted in the concave portion. The lens barrel is formed in the molding cavity. A first protrusion is formed on an end face of the convex portion, and a second protrusion is formed on an inner bottom surface of the concave portion. The first protrusion is in contact with the second protrusion for forming the light incident opening. A parting surface is formed between the end face of the convex portion and the inner bottom surface of the concave portion. A patching surface with a width greater than 0.02 millimeters (mm) is formed around the parting surface for preventing formation of burrs. However, this results in a very thin inner edge of the compact lens barrel in the light incident opening, thereby causing the inner edge become pervious to light, which may cause glare during image capture.

Therefore, there is a need for a molding device for molding a lens barrel, to overcome the above mentioned limitations.

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, a molding device10in accordance with an exemplary embodiment includes a first mold part11and a second mold part12. By injecting plastic materials into the molding device10, a lens barrel (a lens barrel30as shown inFIG. 4) is obtained.

The first mold part11has a molding recess15with an opening152. The molding recess15is generally cylindrical. The first mold part11has a round bottom surface11a. A first protrusion110is formed at the center of the bottom surface11a. The first protrusion110includes a first frustoconical portion113protruding from the bottom surface11a, and a second frustoconical portion114on top of the first frustoconical portion113. The second frustoconical portion114has a round, first top surface111facing away from the bottom surface11aand perpendicular to a central axis of the molding recess15. The first protrusion110tapers away from the bottom surface11a. A side surface of the first frustoconical portion113is in smooth connection with a side surface of the second frustoconical portion114. A cone angle of the first frustoconical portion113is greater than that of the second frustoconical portion114.

The second mold part12includes a core insert17, and a second protrusion120. The core insert17is generally cylindrical, and has an end face12a. The core insert17includes a first cylindrical insert part171, a second cylindrical insert part172, a third cylindrical insert part173, and fourth cylindrical insert part174sequentially stacked on one another in the described order away from the end face12a. The first to fourth cylindrical insert parts171,172,173,174are formed in a single body, are coaxial with each other, and have diameters increasing one after the other in the described order. The second protrusion120is formed at the center of the end face12a. The second protrusion120is frustoconical and tapers away from the end face12a. The second protrusion120has a round, second top surface121facing away from the end face12a. The second top surface121is perpendicular to a central axis of the core insert17.

The second mold part12is inserted in the molding recess15of the first mold part11. The first to fourth cylindrical insert parts171,172,173,174of the core insert17have diameters less than that of the molding recess15, thereby forming a molding cavity20in the molding recess15between the first molding part11and the second molding part12. The molding cavity20has a shape of the lens barrel30as shown inFIG. 4. The first top surface111is in contact with and coaxial with the second top surface121. Referring toFIG. 3, the second top surface121has a greater diameter than that of the first top surface111, thus an annular, patching surface129in the second top surface121is exposed to the molding cavity20. The patching surface129has a width W satisfying 0<W≦0.005 mm. In this embodiment, the width W is 0.005 mm.

Referring toFIG. 4, molding materials are injected into the molding cavity20of the molding device10and are then cured, thereby obtaining a lens barrel30. The lens barrel30includes a receiving hole33corresponding to the core insert17for receiving optical elements, such as optical lenses, and a light incident opening31corresponding to the first top surface111and the second top surface121. Four steps35are formed in the receiving hole33because of the first to fourth cylindrical insert parts171,172,173,174with different diameters. Optical elements received in the receiving hole33can contact with the steps35for being more firmly fixed to the lens barrel30. The patching surface129can prevent burrs forming on the lens barrel30. Also, because the patching surface129is narrow, the glare is reduced. In a glare test of the lens barrel30in this embodiment, glare almost disappears completely.

It is to be understood that the first top surface111can also have greater diameter than that of the second top surface121, thereby an annular patching surface within the first top surface around the second top surface121. In this situation, the width of the patching surface also satisfies 0<W≦0.005 mm.