Oil Pan Drain Plug Lock Ring to Prevent Cold-Weather Unscrewing
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Solution Overview
Problem
Existing drain plugs for oil pans in internal combustion engines are prone to accidental unscrewing due to brittle resilient stops, which can break, especially in cold climates, leading to potential engine damage.
Innovation Solution
A drain plug design featuring a lock ring that slides axially between locked and released positions, using catches and external stops to prevent rotation without requiring torque, and a retainer to maintain the locked position, ensuring robustness against breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resilient stops are used to prevent drain plug unscrewing, then the drain plug is protected from accidental loosening, but the stops become brittle and break in cold climates
Solution Approach 1:
The locking mechanism is divided into separate functional components: the lock ring with radial arms provides the locking action, while the retainer clip provides the resilient retention. This segmentation allows each component to be optimized for its specific function, with the retainer being the only resilient element that needs to flex, rather than the entire locking mechanism being made of brittle resilient material.
Solution Approach 2:
The retainer clip acts as an intermediary element between the lock ring and the drain plug body. It provides the necessary resilient retention force to hold the lock ring in place without requiring the lock ring itself to be made of brittle resilient material. The retainer mediates between the need for a secure locked position and the need for resilient retention.
2Reliability
If resilient stops are used to prevent drain plug unscrewing, then the drain plug is secured, but releasing the stops requires torque application that can cause breakage
Solution Approach 1:
The lock ring is designed to transition between two dynamic states: a locked position where the radial arms engage with the drain plug body to prevent unscrewing, and an unlocked position where the arms are disengaged. The retainer clip enables this dynamic transition through axial movement rather than requiring torque application, making the release operation simpler and less prone to causing breakage.
Solution Approach 2:
The locking and release mechanism operates in a different dimension than traditional torque-based locking. Instead of using rotational torque to engage and disengage the locking elements, the system uses axial movement of the retainer clip to control the locking state. This dimensional change from rotational to axial operation eliminates the risk of excessive torque causing breakage during release.
3Strength
If a lock ring with radial arms is used, then a robust structure resistant to breakage is achieved, but the device complexity increases
Solution Approach 1:
The lock ring integrates multiple functions into a single component: it provides the locking action through its radial arms, serves as a structural element connecting the retainer to the drain plug body, and defines the locked position through its geometry. The retainer clip, while a separate component, is simple in design and only provides retention functionality. This merging of functions reduces the overall complexity compared to having separate components for each function.
Data Source
AI summary
A drain plug for an engine collection pan has an external screw portion forming a threaded connection with the collection pan and a catch formed on the plug body. A lock ring axially slides on the plug body between a released position in which the lock ring does not interfere with rotation of the plug body relative to the collection pan to release the threaded connection and a locked position connected between the catch on the plug body and an external stop on the collection pan to prevent release of the threaded connection. A retainer on the plug body selectively retains the lock ring in the locked position. The lock ring is a robust structure, resistant to breakage even in colder climates. The axial sliding does not require any tool for application of torque to release the lock ring.