Torque Impulse Wrench Coupling for Play-Free Rotor Alignment
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Solution Overview
Problem
The existing torque impulse wrenches with a rigidly interconnected motor rotor and pulse unit suffer from poor coupling rigidity leading to misalignment and reduced torque efficiency, and require cumbersome disassembly for pulse unit service, necessitating a more stable and service-friendly connection.
Innovation Solution
A coupling design featuring a thread connection and conical surfaces between the motor rotor and inertia drive member, along with guide and support sections, ensures a play-free and rigid connection, allowing for easy removal of the pulse unit without disassembling the motor or housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a combined hexagon and splines coupling clamped axially by a central screw is used to connect the motor rotor and inertia drive member, then the coupling can be assembled, but radial and rotational play occurs during operation reducing torque efficiency
Solution Approach 1:
The patent employs a conical friction surface instead of flat axial clamping surfaces. The conical geometry converts axial clamping force into radial friction force that prevents radial and rotational play. The friction surface (36, 37) is inclined at an angle alpha, creating a self-locking effect that maintains rigid connection under torque loading without requiring complex multi-directional fastening mechanisms.
Solution Approach 2:
The patent changes the geometric parameters of the coupling interface by introducing a conical surface with specific inclination angle alpha. This parameter change transforms the force transmission mechanism from direct axial contact to friction-based radial constraint, eliminating play while maintaining assembly simplicity. The conical angle is optimized to provide sufficient friction force to prevent rotation and radial movement.
2Ease of repair
If the central screw axially clamping the coupling is made accessible from inside the motor rotor for service, then the coupling can be disassembled, but the motor and rear bearing must be removed from the housing making service awkward and time consuming
Solution Approach 1:
The patent segments the coupling assembly into two independent parts: the motor rotor assembly (motor and rear bearing) and the pulse unit with inertia drive member. The coupling connects these segments but allows the pulse unit to be removed independently by accessing the screw from the housing exterior through the pulse unit side, eliminating the need to disassemble the motor rotor assembly for service.
Solution Approach 2:
The housing acts as an intermediary that provides external access to the coupling screw without requiring disassembly of the motor rotor. The screw passes through the housing structure, allowing service personnel to access and operate the coupling fastening mechanism from the outside, thereby enabling easy removal and installation of the pulse unit for maintenance.
3Reliability
If a rigid connection between motor rotor and inertia drive member is implemented to prevent play, then torque impulse efficiency is optimized, but the structure becomes more complex requiring more than two bearings
Solution Approach 1:
The patent applies local quality by concentrating the rigidity requirement at the critical interface between motor rotor and inertia drive member through the conical friction surface. The friction-based connection provides localized rigid coupling exactly where needed for torque transmission, while the rest of the system maintains the simplified two-bearing arrangement. The conical surface geometry ensures rigidity only at the coupling point without requiring additional bearings throughout the system.
Data Source
AI summary
An impulse wrench includes a housing, an electric motor with a rotor, a hydraulic pulse unit with an inertia drive member and an output shaft, and a coupling rigidly connecting the rotor to the inertia drive member to form an integrated rotating structure. The coupling includes a male coupling portion on the inertia drive member and a female coupling portion on the rotor, such that the male coupling portion is received in the female coupling portion to form the coupling. The male and female coupling portions have external and internal threaded sections, respectively, where an axial clamping force is accomplished at relative rotation of the rotor and the inertia drive member. The male coupling portion and the female coupling portion are provided with mating conical surfaces which are brought together by the axial clamping force to form a rigid connection between the rotor and the inertia drive member.