Reciprocating Saw Scotch Yoke Notch for Longer Stroke
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Solution Overview
Problem
Existing reciprocating saws face limitations in efficiently translating rotary motion into reciprocating motion, particularly in providing clearance for the driving gear during operation, which affects the reciprocating stroke length and even wear of components.
Innovation Solution
A power tool design featuring a scotch yoke mechanism with a pin extending from the driven gear, offset from the rotation axis, and a yoke with a notch that provides clearance for the driving gear, allowing for increased reciprocating stroke length and reduced uneven wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a conventional scotch yoke mechanism is used without a notch in the yoke, then the structure is simpler, but the driving gear cannot have sufficient clearance during reciprocating motion, limiting the stroke length and causing uneven wear
Solution Approach 1:
The yoke is segmented by introducing a notch that divides the yoke structure into distinct regions. This segmentation allows the driving gear to have clearance space within the notch during reciprocating motion, enabling increased stroke length without requiring complete redesign of the yoke structure.
Solution Approach 2:
A notch is extracted or removed from the yoke structure to create clearance space. This extraction of material from the yoke provides the necessary gap for the driving gear to move freely during reciprocating motion, directly enabling increased stroke length while maintaining overall structural integrity.
2Reliability
If the driving gear operates without sufficient clearance in the yoke, then the structure remains compact, but uneven wear occurs on the driving gear and driven gear components
Solution Approach 1:
The notch in the yoke segments the contact area between the driving gear and yoke, creating distinct zones that allow for more uniform distribution of wear. This segmentation prevents concentrated stress on single points, reducing uneven wear on both the driving gear and driven gear.
Solution Approach 2:
By extracting material to form the notch in the yoke, clearance space is created that prevents direct continuous contact between the driving gear teeth and the yoke surface. This reduction in contact stress and friction minimizes uneven wear on the gear components.
3Productivity
If the pin is positioned at the center of the driven gear, then the structure is more symmetric and simpler, but the scotch yoke mechanism cannot effectively translate rotary motion into reciprocating motion
Solution Approach 1:
The pin is deliberately positioned asymmetrically, offset from the center of the driven gear. This asymmetric positioning is essential for the scotch yoke mechanism to function, as it creates the necessary eccentric motion path that translates rotary motion of the driven gear into linear reciprocating motion of the yoke and spindle.
Solution Approach 2:
The offset pin position introduces a dimensional transformation by converting the rotational motion (circular path) of the driven gear into linear reciprocating motion of the yoke. The offset distance creates an eccentric mechanism that effectively transforms the motion type and direction.
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
The solution enhances the reciprocating motion efficiency and extends the stroke length while minimizing wear on internal components, improving the overall performance and usability of the saw.
Implementation Method 1
a pin extending from the driven gear and offset from the rotation axis and a spindle having a yoke coupled to the pin to translate rotation of the driven gear into reciprocating motion of the spindle
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
A power tool including a housing having a handle configured to be grasped by a user, a motor supported by the housing, a driving gear rotated by the motor, and a driven gear engaging the driving gear to be rotated by the driving gear about a rotation axis. The power tool also includes a pin extending from the driven gear and offset from the rotation axis and a spindle having a yoke coupled to the pin to translate rotation of the driven gear into reciprocating motion of the spindle. A notch is formed in an outer periphery of the yoke to provide clearance for the driving gear as the spindle is driven by the pin.