Keyboard Switch Curved Cam Profile for Smooth Tactile Feedback
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Solution Overview
Problem
Mechanical keyboard switches, particularly metal contact and foam element switches, suffer from rapid wear and corrosion, leading to fatigue in users due to sharp force impulses during prolonged typing, as they lack effective tactile feedback mechanisms.
Innovation Solution
A keyboard switch design featuring a plunger with a curved cam profile that gradually changes force during actuation, incorporating a coil spring and flexible electrical contactor, providing smooth tactile feedback and reducing fatigue by distributing force more evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a sharp force impulse is used for tactile feedback in metal contact and foam element switches, then clear tactile response is achieved, but user fatigue increases during prolonged typing
Solution Approach 1:
The cam profile is designed with a curved geometry instead of a linear or sharp profile. The curve includes a first portion with a first radius of curvature and a second portion with a second radius of curvature, creating a smooth transition that distributes force gradually. This curved cam profile transforms the sharp force impulse into a progressive force application, maintaining tactile feedback clarity while reducing the sudden impact that causes user fatigue during extended typing sessions.
Solution Approach 2:
The invention changes the force application parameters by varying the radius of curvature along the cam profile. The transition from a first radius of curvature to a second radius of curvature modifies the force-travel curve characteristics, transforming the force delivery from impulsive to progressive. This parameter change allows the switch to provide adequate tactile feedback while distributing the mechanical load over time, thereby reducing muscle fatigue in the user's fingers.
2Ease of operation
If metal contact and foam element switches are used for tactile response, then good tactile and audible response is achieved, but contact wear and corrosion increase
Solution Approach 1:
The cam acts as an intermediary mechanical element between the plunger and the contactor. Instead of the plunger directly actuating the contact with a sharp impulse, the cam mediates the force transmission through its curved profile. This intermediary mechanism allows the contactor to be actuated smoothly and progressively, reducing mechanical shock and wear on the electrical contacts while maintaining the tactile and audible feedback characteristics associated with mechanical switches.
3Ease of manufacture
If a linear cam profile is used for switch actuation, then simple manufacturing is achieved, but smooth tactile response is reduced
Solution Approach 1:
The cam profile incorporates curved geometry with varying radii of curvature to achieve smooth tactile response. While more complex than a linear profile, the curved cam can still be manufactured using standard CNC machining or molding processes. The curvature design provides a progressive force application that creates a smoother tactile experience, balancing manufacturing feasibility with operational comfort for extended typing sessions.
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 switch design enhances tactile feedback and reduces user fatigue by smoothing the force-travel curve, extending the lifespan of the switch and improving typing comfort over long periods.
Implementation Method 1
a coil spring coiled about an exterior surface of the spring guide and the upstanding sleeve so as to resist the downward longitudinal movement of the plunger and promote upward longitudinal movement of the plunger
Implementation Method 2
The cam has a curved profile that incorporates a concave arc which uniquely changes the amount of force experienced by the typist at different points of the downward motion of the plunger
Implementation Method 3
a flexible electrical contactor extending from the top surface of the bottom portion of the base into the recess of the plunger and positioned within the recess proximate to the top portion of the stationary contact
Data Source
AI summary
A keyboard switch for a keyboard includes a base secured to a plunger that reciprocates with respect to the base and is biased away from the base. An electrical contact assembly is positioned within a cavity defined by the base and the plunger. The electrical contact assembly remains in an electrically open state when the plunger is furthest from the base, but the electrical contact assembly enters an electrically closed state when the plunger is longitudinally moved downwardly by force towards the base. In this regard, a cam protruding from a side portion of a body of the plunger has a profile surface that contacts the electrical contact assembly as the plunger is longitudinally moved towards the base. A curved profile of the cam that incorporates a concave arc uniquely changes the amount of force experienced by the typist at different points of the downward motion of the plunger.