Switchable Torque Limiter in Electrical Screwdriver
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Solution Overview
Problem
Conventional screwdrivers transmit applied force directly to workpieces, risking damage when excessive torque is applied, and lack versatility for tasks requiring higher torque.
Innovation Solution
An electrical torque screwdriver with a torque limiter mechanism that includes a driving tooth, slipping block, pawl, and restoring element, which allows the screwdriver to slip when excessive force is applied, preventing damage and switching to general-use mode with an electrical switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a torque limiter is applied to the screwdriver to prevent workpiece damage from excessive force, then workpiece protection is improved, but the screwdriver cannot perform jobs requiring larger torque
Solution Approach 1:
The torque limiter mechanism is designed to be dynamically switchable between two states: engaged mode where the pawl engages with the driving tooth to limit torque and protect the workpiece, and disengaged mode where the electrical switch resists the restoring element to prevent engagement, allowing full torque transmission for high-torque tasks. This dynamic switching resolves the contradiction by making the torque limitation feature optional rather than fixed.
Solution Approach 2:
The screwdriver is designed with multi-functionality by integrating both torque limitation capability and full-torque capability through the switchable mechanism. The same basic structure serves dual purposes: protecting workpieces from damage when needed, and delivering full torque when required, making the tool universally applicable to both precision and heavy-duty tasks.
2Ease of operation
If the torque limiter mechanism is engaged to slip when excessive torque is applied, then force transmission control is improved, but the device complexity increases
Solution Approach 1:
The patent replaces a purely mechanical torque limiter with an electromechanical system. The electrical switch controls the engagement of the restoring element, which in turn controls the pawl's engagement with the driving tooth. This substitution allows for easier operation through electrical control while managing the complexity by using a straightforward on/off switching mechanism rather than a complex mechanical adjustment system.
Solution Approach 2:
The restoring element acts as an intermediary between the electrical switch and the torque limiter mechanism. When the electrical switch resists the restoring element, it prevents the pawl from engaging with the driving tooth, thereby controlling torque limitation without requiring direct mechanical connection between the switch and the torque limiter components.
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
Prevents workpiece damage by slipping when excessive torque is applied and allows for use as a general-use screwdriver for higher torque tasks by controlling force transmission through the torque limiter and electrical switch.
Implementation Method 1
The restoring element which is pivotally disposed on the handle and has a restoring force, wherein one end of the restoring element resists against the slipping block for pushing the pawl to be engaged with the driving tooth
Data Source
AI summary
An electrical torque screwdriver includes a handle, a shaft, a torque limiter, and an electrical switch. The shaft is disposed on the handle and rotatable but not movable linearly. The torque limiter includes a driving tooth, a slipping block, a pawl, and at least one restoring element. The driving tooth is disposed on the shaft. The slipping block is disposed on the handle. The slipping block is displaceable linearly but not rotatable. The pawl is disposed on the slipping block and engaged with the driving tooth. The restoring element is pivotally disposed on the handle and has a restoring force, wherein one end of the restoring element resists against the slipping block for pushing the pawl to be engaged with the driving tooth. The electrical switch is disposed on the handle for optionally resisting against the other end of the restoring element to stop the restoring element.