Lens manufacturing apparatus and lens manufactured thereby

A lens manufacturing apparatus includes a first mold, a second mold, a first core, and a second core. The first mold defines a first compartment therein. The second mold defines a second compartment therein. The first core is inserted into the first compartment of the first mold, and includes a first mold surface with a first half-mold cavity and a conic ring surrounding the first half mold cavity. The second core is inserted into the second compartment of the second mold, and includes a second mold surface with a second half-mold cavity. The second half-mold cavity includes a bottom which connects to the periphery of the second mold surface by an acclivitous surface. The acclivitous surface is parallel with the outermost conic surface of the conic ring.

BACKGROUND

1. Technical Field

The disclosure relates to a lens manufacturing apparatus and a lens manufactured thereby.

2. Description of Related Art

Injection molding method is currently one of the best choice for mass production of lenses. Molten material is injected into a mold cavity of a mold apparatus under a high pressure. When the molding cavity is full, the cooled down and solidified molten material is shaped to produce a lens. Generally, a lens includes at least one convex or concave surface for converging or diverging transmitted light, which gives the lens a cross-sectional thickness varying from the periphery to the center. The varied cross-sectional thickness means that the molten molding material in the mold cavity is cooled down at different rates, where the thinnest parts are cooled before the thickest parts; as a result, this causes “sinks” in the lens, which produce molded-in stress that make the lens quite brittle.

Therefore, it is desirable to provide a lens manufacturing apparatus that can overcome the above problems, and a lens manufactured thereby.

DETAILED DESCRIPTION

Referring toFIG. 1, a lens manufacturing apparatus200according to one exemplary embodiment includes a first mold210, a second mold220, a first core230and a second core240.

The first mold210includes a first cylindrical body212having a first parting surface212aand an opposite first end surface212b. The first body212defines a first compartment214spanning from the first parting surface212ato the first end surface212b, for receiving the first core230. A first half sprue216defines in the first parting surface212a.

The second mold220includes a second cylindrical body222having a second parting surface222a, and an opposite second end surface222b. The second body222defines a second compartment224spanning from the second parting surface222ato the second end surface222b, for receiving the second core240. A second half sprue226is defined in the second parting surface222for forming a whole sprue together with the first half sprue216, through which the molten material is channeled into a mold cavity. The second parting surface222afurther defines an annular cutout228communicating with the second half sprue226around the second compartment224.

The first core230includes a first base232received in the first compartment214of the first mold210. The first base232includes a first mold surface232aon which a first half-mold cavity234and a conic ring236surrounding the first half-mold cavity234are formed. The bottom234aof the first half-mold cavity234is either aspherical or spherical whichever has a shorter radius of curvature.

The second core240includes a second base242received in the second compartment224of the second mold220. The second base242includes a second mold surface242ain which a second half-mold cavity244forms. The bottom244aof the second half-mold cavity244is as substantially flat as a horizontal plane by having a substantially large radius of curvature. The bottom244aconnects to the periphery of the second mold surface242aby an acclivitous surface244b. The acclivitous surface244bis approximately parallel with the outermost conic surface of the conic ring236.

In assembly, the first and second cores230and240insert into the first and second compartments214and224correspondingly. The first and second parting surfaces212aand222acontact, and the first and second cores230and240align with each other. The first mold surface232ais slightly lower than the first parting surface212aof the first mold210as viewed when the first mold210is detached and held upside down, while the second mold surface242ais coplanar with the bottom of the cutout228. A mold cavity forms between the first and second mold surfaces232aand242awhere molten material molds to a predefined shape. The depth at the periphery of the mold cavity changes little and is approximately constant, and is of slight difference as compared with the depth at the center of the mold cavity, as such to reduce the molded-in stress, and thereby equalizing the cooling rates of the molded material in the mold cavity.

Referring toFIG. 2, a lens100manufactured by the lens manufacturing apparatus200is shown. The lens100includes a circular center portion110, an annular middle portion120, and an annular outer portion130interconnected to the center portion110by the middle portion120.

The center portion110includes a first surface112and an opposite second surface114coaxial with the first surface112. The first surface112has a center portion with a larger radius of curvature and an acclivitous periphery surrounding the center portion. The second surface114is convex relative to the periphery thereof and has a shorter radius of curvature compared with the center portion of the first surface112. The second surface114is designed to be either aspheric or spherical according to different situations or needs. The outer radius of the first surface112is larger than that of the second surface114.

The middle portion120surrounds the center portion110. The middle portion120slopes radially outwardly from the periphery of the center portion110. The middle portion120includes a third surface122connected to the first surface112of the center portion110, and an opposite fourth surface124connected to the second surface114of the center portion110in parallel.

The outer portion130surrounds the middle portion120, and includes a fifth surface132connected to the third surface122and an opposite sixth surface134connected to the fourth surface124in parallel. The fifth and six surfaces132and134are both approximately parallel to the first and second surfaces112and114. The thickness of the middle portion120, i.e., the distance from the third surface122to the fourth surface124, is equal to the thickness of the outer portion130, i.e., the distance from the fifth surface132to the sixth surface134.

The lens100in the present disclosure has a middle portion120that smoothes the interconnection between the center portion110and the outer portion130, as such, in the molding process, the molten material can thereby easily flow into the center portion of the mold cavity to form the lens with little molded-in stress and without a “sink” problem.