Heart Cam Switch Lock Pin Reverse Movement Prevention
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Solution Overview
Problem
Conventional cam-groove structures with a heart cam shape suffer from wear-out issues in the step-like part of the bottom surface, leading to unintended movement of the lock pin, which hinders the reliable operation of switches.
Innovation Solution
A heart cam mechanism with a cam groove featuring a heart-shaped path and surrounding cams, where the sliding end part engages with a concave part at a locking position, moving along a heart-shaped path with specific vertex positions, and a locking position guiding point, ensuring the lock pin remains in the correct direction even when the step-like part is worn out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a step-like part is provided on the bottom surface of the cam groove to prevent reverse movement, then the lock pin is prevented from moving in reverse direction, but the step-like part wears out due to repeated operations
Solution Approach 1:
The invention extracts the reverse movement prevention function from the bottom surface of the cam groove and transfers it to the side surface through a protrusion structure. The protrusion extends from the side surface of the cam groove toward the center, creating a mechanical barrier that prevents the lock pin from moving in reverse without requiring a step-like structure on the bottom surface.
Solution Approach 2:
The invention transitions from preventing reverse movement through a vertical step structure (bottom surface) to preventing it through a horizontal protrusion structure (side surface). This dimensional shift moves the constraint from the vertical dimension to the horizontal dimension, reducing wear while maintaining the same functional effect.
2Stability of the object's composition
If a step-like part is provided on the bottom surface to maintain locking position, then the lock pin remains stable, but repeated pressing operations cause wear and force reduction
Solution Approach 1:
The invention extracts the stability-providing function from the bottom surface step structure and relocates it to the side surface protrusion. The protrusion engages with the lock pin's side surface rather than the bottom surface, providing stable positioning without the wear problems associated with repeated contact on the bottom surface.
Solution Approach 2:
The protrusion acts as an intermediary element between the cam groove and the lock pin, providing a new contact interface that mediates the interaction. This intermediary structure reduces direct wear between the bottom surface and lock pin while maintaining the necessary mechanical constraint for stable operation.
3Reliability
If the end part of the lock pin is pressed against the bottom surface by a spring member, then the lock pin is prevented from moving in reverse, but the pressing force reduces over time due to wear
Solution Approach 1:
The invention extracts the reverse movement prevention function from the spring-pressed bottom surface contact mechanism and relocates it to the side surface protrusion engagement. This eliminates the need for continuous spring pressure against the bottom surface, maintaining reverse prevention through geometric constraint rather than continuous force application.
Solution Approach 2:
Instead of using a spring to press the lock pin against the bottom surface (force-based approach), the invention inverts the approach by using a protrusion that geometrically constrains the lock pin's movement (structure-based approach). The constraint is built into the geometry rather than being maintained by continuous force.
Data Source
AI summary
A heart cam mechanism of a switch includes a cam groove, which includes a heart cam and surrounding cams, and a lock pin. The heart cam has a concave part, a first vertex opposite the concave part, and second and third vertices on a concave-part side. While the switch is in a locked state, an upper end part of the lock pin is engaged with the concave part of the heart cam, and is positioned at a locking position. While the switch is pressed, the upper end part slides while pushing against a bottom surface of the cam groove located outside the heart cam, and moves along a heart-shaped path, which is depressed at the locking position. This configuration prevents an end part of the lock pin from moving in a reverse direction even when a step-like part of the bottom surface of the cam groove is worn out.