Backpack Blower Mixed-Flow Impeller Design to Reduce Weight and Bulk
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Solution Overview
Problem
Backpack leaf blowers face a trade-off between maximizing blowing capacity and minimizing weight and bulkiness due to the use of internal combustion engines, which are heavy.
Innovation Solution
The design incorporates a housing with a motor and a mixed flow fan assembly, including a pair of mixed flow fans and an impeller with dual airflow paths, coupled via a ribbed coupler, to efficiently generate and direct airflow while minimizing weight and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an internal combustion engine is used to power the blower, then maximum blowing capacity is achieved, but the device becomes heavy and bulky
Solution Approach 1:
The patent replaces the internal combustion engine (mechanical system) with an electric motor (electrical system). The electric motor is coupled to the impeller through a coupling device that includes a hub and ribs, eliminating the need for a heavy combustion engine while maintaining the blowing capacity through efficient electrical-to-mechanical energy conversion.
2Productivity
If the housing cross-section is optimized for airflow, then blowing efficiency is improved, but the device becomes more bulky
Solution Approach 1:
The patent employs a non-circular cross-sectional shape for the housing, specifically with an axial height greater than the transverse width. This dimensional optimization allows the housing to define a chamber with a duct that efficiently guides airflow from the impeller to the nozzle, improving blowing efficiency while maintaining a compact form factor suitable for backpack mounting.
3Power
If a coupling device with multiple ribs is used to connect the impeller, then torque transmission is improved, but the device complexity increases
Solution Approach 1:
The coupling device is segmented into a hub and multiple ribs. The hub is connected to the drive shaft, and the ribs extend from the hub to engage with the impeller. This segmentation allows for effective torque transmission through the distributed rib structure while keeping each individual component relatively simple in design.
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 enhances airflow efficiency and reduces the blower's weight and bulk, allowing for increased blowing capacity with improved user comfort and reduced stress on the user's back.
Implementation Method 1
a motor supported by the housing and having a drive shaft defining an axis
Implementation Method 2
an impeller supported in the chamber and driven by the motor to generate an air flow
Data Source
AI summary
A blower including a housing at least partially defining a chamber, a motor including a drive shaft defining a rotational axis, an impeller driven by the motor to generate an air flow in the chamber, and a coupler operably connected between the drive shaft and the impeller. The chamber may have an axial height which increases from a position proximate a back plate to a position spaced from the back plate. The chamber may have a non-circular cross-section proximate a chamber outlet, and a tube assembly in fluid communication with the chamber may have a tube inlet with a non-circular cross-section. The impeller may define two separate airflow paths each having an inlet and an outlet.