Brushless DC Motor Orientation for Circular Saw Compactness
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Solution Overview
Problem
Current circular saws are hindered by the large weight and volume of their motors, which restrict size and weight reduction, and the motor overhang interferes with using a 2x4 piece of lumber as an edge guide, limiting depth of cut and tool compactness, especially in corded power tools where high power demands require large transformers.
Innovation Solution
A circular saw design with a brushless DC motor having a reduced size and weight ratio, allowing a 2x4 lumber edge guide on either side of the footplate, utilizing a high voltage motor that eliminates the need for a transformer and incorporates a flywheel for energy storage and a cooling fan for minimal weight increase, enabling full depth cuts and beveling in both directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a smaller lighter motor is used to reduce size and weight, then the motor size and weight are reduced, but the motor may not have enough power to drive a circular saw with acceptable performance
Solution Approach 1:
The patent changes the voltage parameter of the brushless DC motor from conventional low voltage (12V, 18V, 36V) to high voltage (120VAC rectified to approximately 170VDC). This parameter change enables a dramatically smaller and lighter motor (about 400g, 40mm diameter, 82mm length) to deliver the same or greater power output than much larger low-voltage motors, resolving the contradiction between motor size/weight and motor power.
2Ease of operation
If the motor overhang is reduced to enable edge guide use, then edge guide compatibility is improved, but the motor design becomes more constrained
Solution Approach 1:
The high voltage parameter change enables extreme motor miniaturization, which naturally reduces the motor overhang to less than 25% of the footplate width. This eliminates the need for complex positioning mechanisms or compromises in edge guide design, as the motor simply occupies minimal space by virtue of its reduced dimensions.
3Adaptability or versatility
If a transformer is included to enable corded operation with low voltage motor, then corded power tool functionality is achieved, but the size and weight savings of the brushless DC motor are negated
Solution Approach 1:
The patent changes the motor voltage parameter to high voltage (120VAC compatible), which eliminates the need for a transformer in corded operation. The motor can be directly powered from standard AC outlets through rectification, removing the heavy transformer component and preserving the size and weight advantages of the brushless DC motor design.
4Volume of moving object
If the motor extension beyond the upper guard is reduced to reduce overall tool size, then tool compactness is improved, but the motor mounting options are limited
Solution Approach 1:
The high voltage parameter enables extreme motor miniaturization with dimensions of approximately 40mm diameter and 82mm length. This small size allows the motor to be mounted with minimal extension beyond the upper guard (less than 25% of guard radius), achieving compact tool design without sacrificing mounting flexibility, as the motor can be positioned in various locations within the constrained space.
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 results in a compact, lightweight circular saw with enhanced operational stability and power efficiency, allowing full depth cuts and dual beveling capabilities without the need for a transformer, while maintaining high torque and resistance to binding during use.
Implementation Method 1
a DC brushless motor drivingly coupled to the saw blade... The invention may enable the size and weight of the motor on a working device to be dramatically reduced
Implementation Method 2
incorporates a flywheel for energy storage and a cooling fan for minimal weight increase, enabling full depth cuts and beveling in both directions
Implementation Method 3
a cooling fan for minimal weight increase, enabling full depth cuts and beveling in both directions
Data Source
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AI summary
A circular saw (10) includes a footplate (18) and an upper guard (26) coupled to a saw blade (12). The footplate (18 has a width (130) between two lateral edges (132a, 132b) in a direction perpendicular to the saw blade (12). The upper guard (26) has a radius extending from the axis of the blade (12) to the outermost surface of the upper guard (26) in the radial direction. A DC brushless motor (16) is drivingly coupled to the saw blade (12) and is disposed above the footplate (18). The motor (16) has a rotational axis within forty five degrees of parallel to the width of the footplate (18), or within forty five degrees of parallel to the radius of the upper guard (26). The motor (16) extends towards one of the lateral edges (132a, 132b) of the footplate in the width direction (130), or towards the outermost surface of the upper guard (26) in the radial direction.