Blower Tube Motor Cooling Using Diffuser Pressure Differential
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Solution Overview
Problem
Existing handheld blowing apparatuses have a long overall length and complex designs, which hinder compact construction and efficient cooling of the drive motor.
Innovation Solution
A handheld work apparatus with a blower tube and motor compartment that directs the working air flow through an annular space, where the extraction opening for cooling air is placed downstream of the diffuser, creating a positive pressure to facilitate cooling without the need for an additional fan wheel, allowing the drive motor to be positioned near the impeller or diffuser, and using a closed motor compartment design for effective cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the drive motor is arranged upstream of the impeller, then the cooling air flow can be established, but the overall length of the blowing apparatus becomes very long
Solution Approach 1:
The patent inverts the conventional arrangement by placing the drive motor downstream of the impeller instead of upstream. This inversion allows the motor to be positioned in a compact configuration within the blower tube while still establishing effective cooling air flow through the motor housing, thereby reducing the overall length of the apparatus.
2Ease of manufacture
If the motor compartment is opened to the environment, then the construction is simpler, but the drive motor becomes contaminated in dirty environments
Solution Approach 1:
The patent employs a motor compartment housing that acts as a protective barrier, separating the drive motor from the dirty environment while allowing controlled air flow through designated openings. This enclosure protects the motor from contamination while maintaining the simplicity of construction through integrated housing design.
3Temperature
If an additional fan wheel is added for cooling air feed, then the cooling efficiency improves, but the device complexity increases
Solution Approach 1:
The patent utilizes the kinetic energy of the working air flow itself to drive the cooling air circulation. The working air flow passing through the blower tube creates a pressure differential that naturally draws cooling air through the motor housing and exhausts it through the rear opening, eliminating the need for an additional fan wheel or active cooling mechanism.
4Ease of manufacture
If the extraction opening is placed upstream of the diffuser, then the construction is simpler, but the pressure at the extraction opening is insufficient for effective cooling
Solution Approach 1:
The patent positions the extraction opening downstream of the diffuser where the working air flow has already been pressurized. This preliminary pressurization of the air flow before it reaches the extraction opening ensures that sufficient pressure is available to drive the cooling air circulation through the motor compartment without requiring additional complex pressure generation mechanisms.
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 compact, simple construction that ensures adequate cooling of the drive motor while avoiding contamination and minimizing flow resistance, allowing the apparatus to operate effectively in dirty environments.
Implementation Method 1
the extraction opening and the outflow opening being arranged such that during operation of the work apparatus a first pressure (p5) at the extraction opening is greater than a second pressure (p2, pa) at the outflow opening
Data Source
AI summary
A handheld work apparatus has a blower tube with a blower arranged therein. The blower conveys a working air flow through the blower tube and has an impeller rotatably driven by an electric drive motor. A diffuser is mounted in a stationary manner in the blower tube downstream of the impeller. The motor is arranged in a motor compartment in the blower tube. Downstream of the diffuser, the work apparatus has an extraction opening for cooling air for the drive motor, via which an annular space, formed between the blower tube and the motor compartment, is connected to the motor compartment. The motor compartment has an outflow opening for cooling air arranged upstream of the extraction opening. The extraction opening and the outflow opening are arranged so that during operation the pressure at the extraction opening is greater than the pressure at the outflow opening.