Spindle Bearing Arrangement for Power Tool Rotational Stability
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Solution Overview
Problem
Existing rotary power tools with planetary-type transmissions and torque limiting clutches face limitations in spindle bearing arrangements, which affect the tool's rotational stability and torque distribution.
Innovation Solution
The power tool incorporates a dual bearing system, comprising a front bearing and a rear bearing, to support the output spindle for rotation about the spindle axis, with the rear bearing indirectly supporting the spindle's rear end and the front bearing directly supporting the spindle's front end, enhancing rotational stability and torque management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single bearing supports the output spindle, then the device complexity is reduced, but the rotational stability and torque distribution deteriorate
Solution Approach 1:
The bearing support function is segmented into two separate bearings: a first bearing supporting the rear end of the output spindle and a second bearing supporting the front end of the output spindle. This segmentation allows each bearing to handle specific loads independently, improving rotational stability and torque distribution while maintaining manageable device complexity through functional division.
2Device complexity
If a single bearing supports the output spindle, then the device complexity is reduced, but the torque distribution deteriorates
Solution Approach 1:
The torque support function is segmented between two bearings positioned at different locations along the output spindle. The first bearing handles torque at the rear end while the second bearing handles torque at the front end, creating optimal torque distribution across the spindle length and improving overall force management.
Solution Approach 2:
The bearing support is extended from a single-point support to a distributed support along the axial dimension of the output spindle. By positioning bearings at both the rear and front ends, the system transforms a one-point force application into a distributed force system, improving torque distribution and reducing stress concentrations.
3Device complexity
If rearward thrust loads are allowed to affect the spindle rotation, then the device complexity is reduced, but the rotational stability deteriorates
Solution Approach 1:
The thrust load management is segmented by positioning the first bearing to specifically counteract rearward thrust loads on the output spindle. This separate bearing arrangement isolates thrust load effects from the rotational motion, preventing thrust-induced instability while maintaining simple device architecture through dedicated functional elements.
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 improves the rotational stability and torque distribution of the power tool, allowing for more efficient operation and user control by preventing rearward thrust loads from affecting the spindle's rotation, thereby enhancing the tool's overall performance.
Implementation Method 1
The front bearing and rear bearing, which are disposed on opposite sides of the spindle lock, support the output spindle relative to the housing for rotation about a spindle axis
Data Source
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AI summary
A power tool with a motor (60), a housing (12), a transmission (82), an output spindle (18), a front bearing (210) and a rear bearing (190). The motor has an output shaft (64). The transmission is disposed in the housing and receives a rotary input from the output shaft. The transmission includes an input planetary stage (110), which has an input planet carrier (124), and an output planetary stage (112). The output spindle is driven by the transmission and has a first end (170), which extends at least partly through the input planetary stage, and a second end (172) opposite the first end. The front bearing is disposed between the output spindle and the housing to support the second end of the output spindle for rotation about the spindle axis. The rear bearing indirectly supports the first end of the output spindle in the housing for rotation about the spindle axis.