Method for injection molding helical and straight gear

• US 6,663,810 B1
• Filed: 11/16/2000
• Issued: 12/16/2003
• Est. Priority Date: 06/02/1998
• Status: Expired due to Fees

• Current Assignee: New Bright Industrial Co., Ltd.
• Original Assignee: New Bright Industrial Co., Ltd.
• Inventors: Lee, Keung
• Primary Examiner(s): Heitbrink, Jill L.
• Application Number:
  US09/712,975
• Time in Patent Office: 1,125 Days
• Field of Search: 264/219, 264/318, 264/328.1, 264/334, 425/556, 425/577, 425/DIG.58, 249/57, 249/59
• US Class Current: 264/219
• CPC Class Codes: B29C 45/4005 Ejector constructions; Ejector operating mechanisms B29C45/44 takes precedence
• CPC Class Codes: B29L 2015/003 Gears
• CPC Class Codes: F16H 1/225 with two or more worm and worm-wheel gearings
• CPC Class Codes: F16H 2057/02034 Gearboxes combined or connected with electric machines structural association with electric machines H02K7/116
• CPC Class Codes: F16H 2057/02095 Measures for reducing number of parts or components
• CPC Class Codes: F16H 55/17 Toothed wheels worm wheels F16H55/22; chain wheels F16H55/30
• CPC Class Codes: F16H 57/021 Shaft support structures, e.g. partition walls, bearing eyes, casing walls or covers with bearings
• CPC Class Codes: F16H 57/029 characterised by means for sealing the gearboxes, e.g. to improve airtightness
• CPC Class Codes: F16H 57/032 characterised by the materials used
• CPC Class Codes: F16H 57/039 Gearboxes for accommodating worm gears
• CPC Class Codes: Y10T 74/19679 Spur
• CPC Class Codes: Y10T 74/2186 Gear casings

Abstract

A helical gear is disclosed that is formed by an injection molding process in which the mold cavity is formed of mirror finished hardened stainless steel. The helical gear is disclosed in a gear box that entirely encase the gears, and may be integral with the housing of the toy. Furthermore, an “L” axle for gears is disclosed that provides a straight shaft portion that extends through the axle bearing aligned with the centerline of the gear and a bent portion that is seated in a slot recess in the wall of the gear box.

Claims

1. A method for forming a helical gear having a helical gear disk and a smaller straight gear disk comprising:

a. forming a mold cavity for the helical gear having a moving mold section that defines the helical gear disk and a stationary mold section that defines the straight gear disk;

b. injecting liquid plastic into the mold cavity;

c. allowing the injected plastic to cool and solidify in the mold cavity to form the helical gear;

d. separating the mold cavity by splitting the moving mold section from the stationary mold section, and removing the helical gear from the stationary mold section by moving the moving mold section away from the stationary mold section without rotating the moving mold section relative to the stationary mold section;

e. maintaining the helical gear fully in the moving mold section during step (d);

f. ejecting the helical gear from the moving mold section by moving a non-rotating ejector out from the moving mold section and along an axis of the helical gear, wherein an ejection speed is used for the ejector that enables the gear to rotate during ejection from the moving mold section so that helical gear teeth on the helical gear are not damaged during ejection.

2. A method for forming a helical gear as in claim 1 wherein the mold cavity has a mirror smooth surface finish.

3. A method for forming a helical gear as in claim 1 wherein the mold cavity is formed of corrosion resistant, stainless steel.

4. A method for forming a helical gear as in claim 1, further including providing a mold pin that protrudes at least partially through the mold cavity to define a gear shaft aperture in the helical gear.