Scissor Key Structure With Limit Stop for Short-Stroke Tolerance Control
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Solution Overview
Problem
Conventional key structures with short strokes face challenges in tolerance control due to the narrow allowable range of hook positions, making precise alignment difficult.
Innovation Solution
A key structure design incorporating a protrusion and a limiting member to control tolerances, where the protrusion abuts against the limiting member at maximum height to restrict the keycap's position, eliminating the need for precise hook positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the distance from the base plate to two hooks is increased to reduce horizontal displacement of the inner frame, then the vertical displacement of the keycap is restricted and the height of the keycap is reduced, but the allowable tolerance range of the position of the hook becomes extremely narrow and tolerance control becomes difficult
Solution Approach 1:
A limiting member is introduced as an intermediary element between the inner frame and the base plate. The limiting member includes a limiting portion that restricts the movement of the inner frame, replacing the need for precise hook positioning. This intermediary structure allows for greater tolerance in manufacturing while achieving the same height-reduction effect.
Solution Approach 2:
The connection structure is segmented into separate functional elements: the hook for attachment, the inner frame for structural support, and the limiting member for position control. This segmentation allows each component to be manufactured independently with relaxed tolerances, while the assembly achieves the required precision through the interaction of these elements.
2Ease of operation
If the horizontal displacement of the moving end of the inner frame is reduced to restrict vertical displacement of the keycap, then the height of the keycap is reduced, but the position of the hook must be precise making tolerance control difficult
Solution Approach 1:
The limiting member acts as a mediator that provides the position restriction function without requiring precise hook alignment. The limiting portion of the limiting member engages with the inner frame to control its movement, decoupling the position control function from the hook positioning and allowing for easier manufacturing and assembly.
3Volume of moving object
If conventional key structures with short strokes are used to reduce keycap height, then the keycap height is reduced, but the allowable tolerance range becomes narrow making production difficult
Solution Approach 1:
The limiting member is introduced as a dedicated component that handles the position restriction function. This allows the hook and inner frame to be manufactured with standard tolerances, while the limiting member provides the precise position control needed for short-stroke operation, significantly improving ease of manufacture and assembly.
Solution Approach 2:
The design changes the control parameter from hook position (which requires narrow tolerance) to limiting member position (which can have wider tolerance). By shifting the control function to a different parameter that is easier to control during manufacturing, the patent achieves short-stroke operation with improved manufacturability.
Data Source
AI summary
A key structure includes a base plate, a keycap, a connecting assembly, a protrusion and a limiting member. The connecting assembly includes a first frame and a second frame pivotally connected to each other. Two opposite ends of the first frame are movably connected to the base plate and the keycap, respectively, and two opposite ends of the second frame are movably connected to the base plate and the keycap, respectively, to drive the keycap upward and downward relative to the base plate. The protrusion is disposed on a sidewall of the first frame or a sidewall of the second frame. The limiting member corresponds in position to the protrusion. When the keycap is at a maximum height, the protrusion abuts against the limiting member.