Fuel Nozzle Interlock Failsafe Mechanism
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Solution Overview
Problem
Fuel nozzles can inadvertently dispense fuel even when the spout is not inserted into a fuel container due to interlock mechanism failures, leading to potential misuse and premature wear, as existing mechanisms lack a failsafe mechanism to prevent operation without proper engagement.
Innovation Solution
A failsafe interlock mechanism that ensures the nozzle remains disabled unless the spout is correctly inserted, combined with a lost motion mechanism to limit excessive movement and prevent over-travel, which includes a spring-biased interlock rod and resilient members to maintain the interlock in an engaged position upon failure, preventing fuel dispensing regardless of spout engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an interlock mechanism is used to enable fuel dispensing when the spout is inserted into a fuel container, then fuel dispensing control is improved, but the risk of mechanism failure leading to improper use increases
Solution Approach 1:
The patent inverts the traditional interlock logic by making the system inherently safe (interlock engaged) and requiring active disengagement for fuel dispensing. The resilient member biases the interlock toward the engaged position, and only when the spout is properly inserted and the operator actively overcomes this bias does the interlock disengage to permit fuel flow. This inversion ensures that any failure of the disengagement mechanism defaults to a safe state, preventing fuel dispensing misuse even if components fail.
Solution Approach 2:
The resilient member provides preliminary anti-action by continuously biasing the interlock mechanism toward the engaged position before any failure can occur. This pre-applied counter-force ensures that the interlock remains in the safe state unless actively disengaged, and if the resilient member or disengagement mechanism fails, the anti-action is already in place to prevent improper fuel dispensing.
2Ease of operation
If the interlock mechanism is allowed to move freely between engaged and disengaged positions, then operational flexibility is improved, but excessive movement accelerates wear and failure
Solution Approach 1:
The patent applies preliminary action by providing guide structure that pre-defines the movement path of the interlock mechanism between engaged and disengaged positions. This guide structure is built into the system before operation begins, ensuring that the interlock component travels only along the intended trajectory and cannot exceed predetermined limits. This prevents over-travel that would accelerate wear while maintaining smooth operational flexibility within the designed range.
3Object-affected harmful factors
If a failsafe mechanism is added to prevent fuel dispensing upon interlock failure, then safety is improved, but device complexity increases
Solution Approach 1:
The patent merges the failsafe function with the existing interlock mechanism components rather than adding separate failsafe systems. The resilient member serves dual purposes: it provides the biasing force for normal interlock operation and simultaneously acts as the failsafe element that defaults to the engaged position upon failure. The guide structure also serves both to enable smooth operation and to prevent over-travel. This merging approach achieves fuel dispensing prevention upon failure without proportionally increasing device 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 solution ensures the nozzle cannot dispense fuel unless properly engaged, preventing misuse and extending the interlock mechanism's lifespan by limiting excessive movement and maintaining the interlock in an engaged position upon failure, thus ensuring safe and reliable operation.
Implementation Method 1
a resilient member biased to maintain the interlock mechanism in the engaged position
Implementation Method 2
a lost motion mechanism to prevent excessive movement of the interlock mechanism
Data Source
AI summary
The present invention comprises a nozzle assembly for dispensing fuel into an inlet of a container comprising a body, a spout and a vapor collection sleeve fitted over the spout and compressing when the spout is inserted into the inlet of a container. An interlock mechanism prevents operation of the nozzle assembly unless the sleeve is at least partially compressed by insertion of the spout into the container inlet. The interlock mechanism includes structure to prevent the interlock mechanism from moving from the engaged position to the disengaged position in the event of a failure of the interlock mechanism whereby the nozzle assembly cannot dispense fuel regardless of whether the spout is engaged with the inlet of the container or not. An interlock actuator is mounted for movement within the body and coupled to the sleeve, while a lost motion mechanism limits movement of the interlock actuator into the body.