Manhole Cover Lock with Self-Returning Bolt
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Solution Overview
Problem
The existing locking and unlocking device for manhole covers often results in the key being secured to the cover, making it difficult to use the key to unlock another cover, and there is a risk of the bolt being left in an unlocked position, leading to security issues and confusion about the lock's functionality.
Innovation Solution
Incorporating a torsion spring and strut mechanism that elastically holds the lock in a locked position, ensuring the bolt is automatically returned to its locked state, and using a key with a cylindrical sleeve and rotor design that allows for secure engagement and automatic return to the locked position, preventing manual misalignment of the bolt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the key is inserted into the lock and the bolt is rotated to the locking position, then the cover is securely locked to the frame, but the key becomes held prisoner in the opening of the cover and cannot be removed
Solution Approach 1:
The bolt is designed to rotate dynamically between two positions: a locking position where it engages the striker and captures the key, and an unlocking position where it disengages and releases the key. This dynamic rotation allows the same component to provide both secure locking and key removal functionality
Solution Approach 2:
The L-shaped opening is pre-configured with its second branch positioned to receive and guide the key arm during rotation. This preliminary design of the opening geometry ensures that when the bolt rotates to the unlocking position, the key arm automatically aligns with and can be withdrawn through the predetermined path of the L-shaped opening
2Ease of operation
If the operator manually rotates the bolt to the unlocked position to apply the cover to the frame, then the cover can be installed, but the operator may forget to lock the bolt, leaving the cover unlocked and creating security issues
Solution Approach 1:
The lock mechanism is designed to be self-locking through the spring-loaded bolt. When the cover is applied to the frame, the bolt automatically engages with the striker under spring pressure, eliminating the need for the operator to remember to manually lock it. The system serves itself by automatically securing the cover in place
Solution Approach 2:
The spring continuously exerts a locking force on the bolt, pre-positioning it in the locked state. This preliminary anti-action counteracts any tendency for the bolt to remain unlocked, ensuring that the cover is automatically secured as soon as it is applied to the frame, preventing the security issue of forgotten locking
3Adaptability or versatility
If the bolt is left in the unlocked position, then the key socket cannot engage with the rotor, but this may lead operators to think the lock no longer works normally
Solution Approach 1:
Instead of the key determining whether locking is possible, the system is inverted so that the bolt position and spring force determine the locking state. The L-shaped opening configuration is inverted in logic: rather than allowing key insertion to indicate functionality, the inability to insert the key (when bolt is locked) becomes the indicator of proper operation, while the unlocked position with spring pressure indicates readiness to lock
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
Ensures the key can be easily transferred between covers while maintaining secure locking and unlocking functionality, preventing accidental unlocking and enhancing user experience by automatically returning the bolt to its locked position.
Implementation Method 1
a return means in the form of a torsion spring (30) arranged concentrically on the rotor (13)
Implementation Method 2
The end of the torsion spring opposite to that resting under the buffer is resting on a strut fixed transversely to the rotor to elastically urge the free end of the strut resting under the buffer so as to hold the lock in its position of lockdown.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The lock for a manhole cover (1) comprises a rotor (13) carrying a bolt (14) which engages with a catch on the frame. A helical spring (30) attached to the rotor biases it towards the locked position, from which it can be moved using a key.