Reaction Bar Lock Nut for Power Wrenches
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Solution Overview
Problem
In power wrenches, the torque reaction bar can unintentionally loosen during screw joint tightening operations, posing safety risks due to the lack of a reliable lock mechanism for the clamping nut assembly, which may lead to uncontrolled wrench movement and potential injuries or equipment damage.
Innovation Solution
A manually operable lock mechanism is integrated into the nut assembly, allowing it to be shifted between a lock and release position using a maneuver ring and lock pins that interact with the splines coupling, ensuring the reaction bar is securely locked against rotation without requiring special design features on the wrench housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clamping nut is used to secure the reaction bar to the wrench housing, then the reaction bar is held in position, but the nut may unintentionally loosen during operation, creating safety hazards
Solution Approach 1:
The lock mechanism applies a preliminary counteracting force against the loosening tendency of the nut. The lock pin is positioned to engage with the splines coupling before operation begins, creating a pre-loaded locking condition that actively resists any rotational movement that would cause loosening. This preliminary anti-action prevents the harmful effect before it can occur.
Solution Approach 2:
The lock pin serves as an intermediary element between the nut assembly and the splines coupling. Rather than directly modifying the nut or housing, the lock pin mediates the connection by engaging with the existing splines coupling structure, transferring and securing the clamping force while preventing unintended loosening through its locking engagement.
2Reliability
If a lock mechanism is added to prevent unintentional loosening, then safety is improved, but the device complexity increases
Solution Approach 1:
The lock mechanism is merged with the existing nut assembly rather than being a separate independent system. The lock pin is integrated into the nut structure, and the locking function is combined with the clamping function. This merging approach adds the safety feature while minimizing the increase in overall device complexity by utilizing existing structural elements.
Solution Approach 2:
The splines coupling serves multiple functions: it provides the angular positioning of the reaction bar, enables torque transfer, and simultaneously serves as the locking surface for the lock pin. This multi-functionality reduces the need for separate locking structures, thereby limiting the increase in device complexity while achieving the safety objective.
3Reliability
If the reaction bar is rigidly secured to minimize accident risks, then safety is improved, but the ability to manually operate and position the reaction bar is reduced
Solution Approach 1:
The lock mechanism transitions from a static clamped state to a dynamically lockable state. During positioning, the maneuver ring allows the reaction bar to be freely adjusted. Once positioned, the lock pin engages with the splines coupling to create a rigid locked state. This dynamic transition between flexible and rigid states allows both easy positioning and secure operation.
Solution Approach 2:
The locking action is performed preliminarily before operation begins. The user positions the reaction bar using the maneuver ring, then engages the lock pin to secure it in the desired position. This preliminary locking action ensures the reaction bar is rigidly secured before torque application begins, maintaining safety while preserving ease of positioning during the setup phase.
Data Source
AI summary
A power wrench has a housing with a forwardly extending tubular neck portion, a rotation motor, an output shaft extending coaxially through the neck portion, and a torque reaction bar supported on the neck portion via a splines coupling. The reaction bar is axially locked to the housing by a nut assembly co-operating with a threaded section of the neck portion. The nut assembly includes a nut element, a maneuver ring supported on the nut element, and lock pins extend through axial bores in the nut element and are arranged to positively engage the keyways of the splines coupling in a lock position to rotationally lock the nut assembly relative to the housing. The lock pins are secured to the ring, and a spring is arranged between the nut element and the ring to bias the ring and the lock pins towards the lock position.