Impact Tool Washer Positioning for Compact Hammer Stroke
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Solution Overview
Problem
Conventional impact tools have a large axial dimension due to the need to position the hammer stroke to avoid interference with the washer receiving the coil spring's rear end, limiting their downsizing potential while maintaining a sufficient hammer stroke.
Innovation Solution
Incorporating a positioner between the carrier portion and the washer, with chamfers and engaging members, allows the washer to be coaxially positioned with the spindle, ensuring a long hammer stroke without interference and reducing the axial dimension by utilizing the space inside the coil spring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the hammer stroke range is positioned forward of the washer to avoid interference, then the hammer can have sufficient stroke length, but the axial dimension of the impact tool becomes large
Solution Approach 1:
The patent changes the spatial arrangement by moving the washer from a forward position (which would interfere with hammer stroke) to a rearward position on the carrier portion. This dimensional repositioning in the axial direction allows the hammer stroke to extend forward without interference, while the washer is relocated to the rear to receive the coil spring, thereby resolving the contradiction between sufficient hammer stroke length and reduced axial dimension.
2Ease of manufacture
If the washer is positioned forward to receive the coil spring, then the coil spring can be properly mounted, but the hammer stroke is interfered with and axial dimension increases
Solution Approach 1:
The washer is repositioned to the rearward side of the carrier portion, changing its axial position from forward to backward. This allows the coil spring to be mounted on the rearward washer without interfering with the forward hammer stroke, enabling both proper coil spring mounting and sufficient hammer stroke length to coexist.
3Length of stationary object
If the hammer is allowed to contact the washer for compact design, then axial dimension is reduced, but the hammer stroke becomes insufficient
Solution Approach 1:
By relocating the washer to the rearward position on the carrier portion, the patent creates spatial separation between the hammer stroke path (forward) and the washer position (rearward). This dimensional separation allows the hammer to achieve full forward stroke without contacting the rearward washer, ensuring sufficient stroke length while maintaining compact axial dimension through optimized component layout.
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
This configuration enables a downsized impact tool with a sufficiently long hammer stroke without increasing radial dimensions, ensuring reliable positioning of the washer and reducing the tool's overall size.
Implementation Method 1
a coil spring whose front end portion is inserted into an annular groove on a rear surface of the hammer and biases the hammer to an advanced position of the hammer
Implementation Method 2
balls fitted in and between cam grooves on the spindle and cam grooves on the hammer
Implementation Method 3
The impact mechanism transmits rotation of the spindle to the anvil as a rotational impact force
Data Source
AI summary
To ensure that a hammer can retract by a sufficient amount without interfering with a washer receiving a rear end of a coil spring, there is disclosed an impact driver having a washer receiving a rear end of a coil spring biasing a hammer of an impact mechanism to an advanced position. The washer is annular with an inner diameter larger than an inner diameter of an annular groove disposed on a rear surface of the hammer, and includes a frontward extended portion disposed at an inner circumference of the washer. Between a carrier portion of the spindle and the washer, there is disposed a positioner that positions the washer coaxially with the spindle.