These hinge assemblies which were previously used in laptop computers have been designed into the sleekest cell phones, personal digital assistants (PDA) and small handheld digital cameras over the past few years.
Basically, the hinge assembly connects the cell phone base to the folder unit which contains the display screen. From the simple open-snap-close mechanism, the latest hinge mechanism now can control the angle of opening. Free-stop designs, where the folding stops at any angle, and 2 degree-of-freedom hinge assembly is in vogue. This flip-and-twist hinge assembly combines 2 rotary hinges with perpendicular axes, letting the clamshell cell phone flip open then twist 180 degress.
Each tiny custom hinge comprises a guide pin, shaft, cam, spring and housing. Advancing from the classic hinge components which were made from polyoxymethylene, the latest complicated hinge components are designed and manufactured from metals to provide stronger rotary hinge joints. These hinge components are manufactured using the metal injection molding (MIM) process or cnc machining. The former process, which is suitable for complex solid net-shape components, allows the mass production of hinge components competitively. However, with the recent shortening of product cycle in the competitive cell phone market, especially in Japan, more and more cell phone manufacturers are working with competent precision machining companies capable of machining these hinge components.
Leading Japanese companies in developing and selling sophisticated hinge units include Strawberry Corporation, Sugatsune Kogyou Co., Ltd, Omron Corporation and Yamamoto Precision Co., Ltd.
