Involute-Channel Blower Fan for Powered Respiratory Masks

The problem

In powered respiratory masks, traditional blower units often produce turbulent airflow and significant mechanical noise. When air is forced through a straight or uniform cross-section channel, the transition from high-pressure compression at the impeller to low-pressure delivery at the outlet can be inefficient. This inefficiency requires higher motor speeds to achieve adequate ventilation, which increases power consumption and drains batteries quickly. Furthermore, uneven airflow exiting the mask can cause discomfort around the nose and mouth, leading users to adjust their fit frequently or discontinue use due to irritation. The challenge is to create a compact fan assembly that delivers sufficient air volume for breathing comfort without excessive noise or energy loss.

The solution

1. The housing consists of a front cover (1) and a rear lid (2). The front cover contains a central air inlet (11), sized larger than the inner diameter of the fan blades but smaller than the outer diameter.
2. The rear lid forms a cavity (21) that acts as the air channel. A fan (3) with a motor is mounted in the middle of this cavity.
3. The key feature is the sidewall (22) of the cavity, which is shaped as an involute. It gradually widens from the edge of the fan in the direction of the fan’s rotation. One end near the outlet is closest to the fan edge, while the opposite end is furthest.
4. At the top of the sidewall, there are air outlets (23, 23’). These outlets may include notches (231) to facilitate smooth air release.
5. Inside the outlet area, curved baffles are installed. A first curved baffle (24) and a second curved baffle (24’) form a V-structure. These baffles divert the wind, splitting it into two streams that flow toward the sides of the nose.
6. Arc flanges (211) are placed at the ends of the sidewall near the outlets to further control the wind direction.

Who it is for

• Respiratory device manufacturers seeking to improve the ergonomics and battery life of powered air-purifying respirators (PAPRs) or smart masks.
• Medical equipment brands developing lightweight, low-noise ventilation aids for patients requiring assisted breathing in non-clinical settings.
• Consumer electronics companies entering the personal health market with wearable air quality solutions that prioritize user comfort.
• OEM integrators looking for a pre-engineered blower module that reduces acoustic testing requirements by leveraging passive aerodynamic noise reduction.

How it works

The main parts

Operating Steps

1. Intake: Air enters through the circular air inlet (11) on the front cover. The inlet size is calibrated to allow active draught without turbulence.
2. Compression & Expansion: The fan (3) rotates, pushing air into the cavity (21). Because the sidewall (22) follows an involute curve, the channel volume increases gradually in the direction of rotation. This expansion converts kinetic energy into static pressure efficiently.
3. Diversion: As the air approaches the outlets (23), it encounters the V-shaped baffles (24, 24’). These curved surfaces split the single stream into two distinct flows.
4. Delivery: The split streams are guided by the arc flanges and baffles toward the user’s nostrils, providing balanced and gentle ventilation.

Applications

Smart Respiratory Masks

Wearable masks equipped with small blowers need to operate quietly to avoid social embarrassment. The involute channel reduces the motor speed required for adequate airflow, lowering noise levels for public use.

Medical Ventilation Aids

For patients using portable oxygen concentrators or CPAP-like devices, consistent airflow is critical. The V-baffles ensure air is delivered evenly to both nostrils, preventing dry spots and improving compliance with therapy.

Industrial Dust Protection

Workers in dusty environments require powered respirators that run for long shifts. The energy-efficient design extends battery life, allowing for longer periods of protection between charges.

Automotive Cabin Air Systems

Compact blowers can be adapted for localized air circulation in vehicle interiors. The directional baffles help focus airflow to specific zones, such as the driver’s face, without wasting energy on the entire cabin.

Where it is less suitable

• High-volume industrial ventilation: This design is optimized for low-power, compact applications like masks, not for moving large quantities of air in factory settings.
• Static-only filtration: If no motor is present, the involute channel provides no benefit over standard passive vents.
• Extreme temperature environments: Plastic housings and standard motors may degrade faster in very hot or cold conditions compared to metal-bodied industrial fans.