A rubber based sliding button design for Slidepad (27-Jan-2012)

Avago Technologies                                    

A rubber based sliding button design for Slidepad

Abstract

Described is an improved design for a top button module in a Slide pad application. Using a plastic button, silicone rubber gasket, and plastic rim, the improved composition eliminates problems associated with dust, moisture, water sealing, and poor cosmetic quality while maintaining low costs and high performance levels.

Description

A.           Prior solutions and their disadvantages

In Slide pad application, the top button module must be able to:

1.    Slide horizontally in all directions within a predefined 3mm distance from the origin

2.    Be pressed downward by an operator’s finger to activate a click

3.    Spring back (i.e., upward) to its original height after the finger releases

Figure 2: Parts of a button

In the current Slide pad design, the top button module consists of: button, button rim, and button spring. (Figures 1, 2) The button is attached to the button spring by ultrasonic welding. Then, the button spring is latched to the button rim.

The bottom surface of the button rim slides on a flat surface. The button spring supports the button vertically. The button spring provides flexibility for the button to move downward when the operator presses it with their finger. When the finger releases, a spring mechanism underneath the top button module pushes the button back to its original height. The button spring provides additional spring-back force.

The disadvantages to this approach are:

·         Complicated and high-cost assembly process

­   Ultrasonic weld of button to spring

­   Difficult to latch button spring onto button rim

·         Poor strength: arms of the button spring (stainless steel) tend to break in cyclic test, around 600k cycles, due to fatigue

Figure 3: Poor strength

·         Poor reliability against moisture, dust, and water; there is a gap between button and rim, which enlarges as the button moves down

Figure 4: Gap between button and rim

·         Poor cosmetic appearance: there are obvious ultrasonic welding marks left on the top surface of the button following the ultrasonic welding of the button to the spring

B.           Problems solved by the invention

This i...