Method of producing a die forming lens fisheye steps

• US 5,308,200 A
• Filed: 12/08/1992
• Issued: 05/03/1994
• Est. Priority Date: 12/13/1991
• Status: Expired due to Term

• Current Assignee: Koito Manufacturing Company Limited
• Original Assignee: Koito Manufacturing Company Limited
• Inventors: Otsuka, Yoshinori
• Primary Examiner(s): BRIGGS, WILLIAM R
• Application Number:
  US07/986,786
• Time in Patent Office: 511 Days
• Field of Search: 409/131, 409/132, 362/334, 362/335, 362/337, 362/338, 362/339, 362/340, 362/61, 362/80, 359/741, 359/742, 359/743, 359/751
• US Class Current: 409/132
• CPC Class Codes: B29C 33/424 Moulding surfaces provided with means for marking or patterning for injection moulding B29C45/372
• CPC Class Codes: B29D 11/00605 Production of reflex reflectors
• CPC Class Codes: Y10T 409/303808 including infeeding

Abstract

A method of producing a die for use in forming fisheye steps in an automobile lens having both straight and curved portions. The plurality of fisheye steps formed on the curved portion of the lens are divided into generally parallelogram-like sections. The die comprises plural concave portions that are arranged to form the fisheye steps when applied in a lens forming process. In the die producing method, the boundary lines between concave portions corresponding to the respective fisheye steps are connected to produce approximately a straight line, to thereby improve an appearance of the fisheye steps. Further, the concave portions that are divided by longitudinal lines extending in a first direction and lateral lines obliquely intersecting the longitudinal lines and extending in a second direction are produced by NC machining using an end mill. The end mill is controlled to have a locus generally in parallel with the longitudinal lines, in which vector control is added when the end mill passes a start side lateral line that is expected to become a boundary between the concave portions and passes an end side lateral line to enter the next concave portion so that the locus of the end mill becomes perpendicular to these lateral lines.

Claims

1. A method of producing from a die workpiece block a die to be used for forming, on a lens having a curved portion, a plurality of fisheye steps that are divided by boundary lines into generally parallelogram-like sections, said die being divided into a plurality of concave portions corresponding to the respective fisheye steps by a first group of boundary lines extending in a first direction and a second group of boundary lines extending in a second direction, said method comprising the steps of:

(1) entering a cutting tool into a divided section of said die block corresponding to one concave portion while controlling an entrance movement direction of said cutting tool so that is locus becomes perpendicular to a start side boundary line comprising a first one of said second group of boundary lines and specified to become a boundary of said divided section;

(2) moving said cutting tool relative to said die block so that said cutting tool proceeds generally in parallel with the boundary lines of said divided section belonging to said first group of boundary lines; and

(3) controlling a relative exit movement direction of said cutting tool so that the new locus of said cutting tool becomes perpendicular to a specified end side boundary line comprising a second one of said second group of boundary lines, wherein;

said second group of boundary lines is formed substantially as a straight line, said second group of boundary lines obliquely intersecting said first group of boundary lines.

2. In a method of producing from a die workpiece block a die to be used for forming, on a lens having a curved portion, a plurality of fisheye steps that are divided by boundary lines into generally parallelogram-like sections, said die being divided into a plurality of concave portions corresponding to the respective fisheye steps by a first group of boundary lines extending in a first direction and a second group of boundary lines extending in a second direction, wherein

continuous machining for a plurality of divided sections is performed by shifting, in the forming direction of said second group of boundary lines at very small intervals, said locus of said cutting tool that is generally in parallel with the forming direction of said first group of boundary lines, and wherein

said second group of boundary lines is formed substantially as a straight line, said second group of boundary lines obliquely intersecting said first group of boundary lines.

3. The method of producing a die as set forth in claim 2, wherein said continuous machining is performed by uniformly feeding said cutting tool in said first direction while controlling the entrance movement and exit movement of said cutting tool with velocity vector control.