Flexural Parallel-Motion Trackpad for Uniform Click Feel
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Solution Overview
Problem
Existing clickable trackpads in mobile computing devices face challenges in providing consistent tactile feedback across the entire surface due to varying force requirements for registering a click, especially near the mechanical hinged mechanism, and haptic trackpads increase costs without addressing space constraints.
Innovation Solution
A mechanical flexural parallel motion trackpad design using a printed circuit board assembly, touch sensor, flexure mechanisms, and torsion bars that allow for uniform click registration across the surface without mechanical hinged mechanisms, relying on a combination of flexure mechanisms and a dome switch for tactile feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical hinged mechanism is used for clickable trackpad, then tactile feedback is provided, but force consistency varies across the trackpad surface
Solution Approach 1:
The trackpad is divided into multiple independent flexural support structures (first, second, third, and fourth flexural supports) distributed across the surface. Each support independently manages local deformation and force distribution, ensuring uniform tactile feedback across the entire trackpad surface regardless of click location.
Solution Approach 2:
The patent modifies the mechanical parameters of the support structures by using flexible supports with controlled stiffness characteristics. These flexural supports have optimized geometric parameters (thickness, length, material properties) that enable them to provide consistent force feedback across different positions while maintaining uniform deformation characteristics.
2Reliability
If haptic trackpad is used to provide tactile feedback, then click feel is achieved, but device cost increases
Solution Approach 1:
The patent replaces complex haptic actuation systems with a passive mechanical flexural support system. The tactile feedback is generated through the inherent elastic deformation and recovery of the flexural supports, eliminating the need for motors, actuators, or complex haptic control systems while maintaining reliable click feedback.
Solution Approach 2:
The flexural support structures are designed to automatically provide tactile feedback through their own elastic properties. When pressed, they deform and provide resistance force, then return to their original position, creating natural tactile feedback without requiring external power sources or active control systems.
3Reliability
If traditional mechanical hinged mechanism is used, then clickable function is achieved, but space consumption increases
Solution Approach 1:
The patent employs thin flexural support structures that function as flexible mechanical elements. These thin-film-like supports provide the necessary mechanical function with minimal thickness, reducing the overall space requirement while maintaining the clickable functionality through their flexural properties.
Solution Approach 2:
The patent extracts and eliminates the traditional mechanical hinge mechanism from the trackpad design. By removing this bulky component and replacing it with distributed flexural supports, the design achieves clickable functionality with significantly reduced space consumption and structural complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design provides consistent tactile feedback with minimal variance in depression force, reduces component complexity and cost, and fits within the limited space of mobile devices, offering a reliable and predictable click feel without the need for haptic devices.
Implementation Method 1
Each of the flexure mechanisms includes a pair of bonding pads, each of the bonding pads fixed to an underside of the PCBA; a pair of rotatable linkages, each of the rotatable linkages to rotate in response to compression of an associated one of the flexure mechanisms
Implementation Method 2
The torsion bars rotationally link the flexure mechanisms. A combination of the flexure mechanisms and the switch defines an activation threshold force and a release threshold force for the touch sensor
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
Clickable trackpad designs generally aim to achieve a thin form factor with a minimized footprint that provides consistent user perception of click feel at scale within cost constraints. The clickable trackpad designs found herein adopt a mechanical depression mechanism that allows a user to register a click at any point on the trackpad surface with little variance in the depression force required to register the click. This provides a consistent click feel for the user. Further consistency of the click feel is achieved by establishing simultaneous travel of the entire trackpad surface, no matter where the click force is applied. This motion is a downward translation of the trackpad surface. An end user may press at any location of the trackpad surface to achieve a push button input (or click).