Frangible Detent Pin for Secure Holding and Smooth Retraction
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Solution Overview
Problem
Conventional spring-loaded detent pins are limited in their ability to securely hold parts in place due to the force required to retract the pin head into the bore, which can exceed the shear strength of the parts or result in frictional locking, preventing relative movement.
Innovation Solution
A frangible detent pin with a base, pin head, and elastic member, where the pin head is interconnected with the base through a frangible connection, allowing the pin to transition from a rigid stage to a spring-loaded stage when a compression load exceeds a predetermined threshold, facilitating relative movement between parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the outward bias of the pin head is increased to hold parts more securely, then the holding strength is improved, but the lateral force required to depress the pin head increases, which may exceed the shear strength of the parts or cause frictional locking
Solution Approach 1:
The detent pin is segmented into two functional stages: a rigid stage where the pin head is rigidly positioned relative to the base for secure holding, and a spring-loaded stage where the pin head can move relative to the base for smooth retraction. This segmentation allows the system to provide strong holding force when needed while reducing the force required for movement.
Solution Approach 2:
The detent pin transitions from a static rigid structure to a dynamic system with two distinct operational states. The pin head can be rigidly fixed to the base during the holding phase, then become movable during the retraction phase when lateral forces are applied. This dynamic behavior resolves the contradiction by providing strength when stationary and ease of movement when actuated.
2Force
If the angle of the inclined plane is decreased to reduce the lateral force required, then the force to depress the pin head is reduced, but the axial force on the pin head increases, which may still exceed part strength
Solution Approach 1:
The force transmission path is segmented through the frangible connection and spring mechanism. The inclined plane transfers lateral force to axial compression on the pin head, which then compresses the spring rather than directly exceeding part strength. This segmentation of the force path allows gradual energy absorption and prevents catastrophic failure.
Solution Approach 2:
The spring member is pre-installed between the pin head and base to provide cushioning before the axial force can exceed part strength. When lateral forces are applied, the spring compresses to absorb the axial force, preventing it from exceeding the shear strength of the parts. This beforehand cushioning resolves the contradiction by providing force reduction mechanisms in advance.
3Reliability
If a conventional spring-loaded detent pin is used, then the pin can be biased outward to hold parts in place, but the force required to retract the pin head may cause frictional locking or exceed the shear strength of the parts
Solution Approach 1:
The detent pin system is segmented into a rigid positioning stage and a spring-loaded transition stage. During normal operation, the rigid connection provides reliable secure positioning. During transition, the frangible connection fails and the spring-loaded stage engages, providing smooth movement. This segmentation allows the system to maintain reliability during positioning while enabling ease of operation during transitions.
Solution Approach 2:
The system changes its mechanical parameters between two stages: in the rigid stage, the pin head has fixed position relative to the base for secure holding; in the spring-loaded stage, the pin head gains mobility relative to the base for smooth retraction. This parameter change from rigid to compliant behavior resolves the contradiction between secure positioning and ease of operation.
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 frangible detent pin effectively secures parts in place without requiring excessive force for retraction, allowing for smooth transition between configurations while maintaining secure positioning, thus overcoming the limitations of conventional detent pins.
Implementation Method 1
an elastic member configured to bias the pin head away from the base
Data Source
Figure 1
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AI summary
A frangible detent pin comprising a base a pin head and an elastic member. The base is configured to be secured within a bore. The pin head and the base are interconnected through a frangible connection. The elastic member is configured to bias the pin head away from the base. The frangible detent pin has a rigid stage in which the pin head is rigidly positioned relative to the base and a spring-loaded stage in which the pin head is moveable relative to the base under a compression load between pin head and the base. The frangible detent pin is configured to transition from the rigid stage to the spring-loaded stage in response to the compression load exceeding a predetermined threshold sufficient to cause the frangible connection to fail.