Nested Volute Blower for CPAP Noise and Size Trade-off
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Solution Overview
Problem
Traditional CPAP systems with single-stage blowers are noisy and less responsive, while two-stage blowers are larger and more expensive, necessitating a solution for a compact, quiet, and responsive blower assembly for effective CPAP treatment.
Innovation Solution
A compact blower assembly with a double-ended design featuring nested volutes, vibrational isolation, and alternating shroud impellers made of polypropylene, which reduces inertia and noise through a combination of materials and design features such as tapered blades and flexible seals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single-stage blower is used, then the device size is reduced, but noise increases and pressure response time worsens
Solution Approach 1:
The single-stage blower is segmented into two independent impellers (first and second impellers) mounted on opposite ends of a common shaft, each operating at different speeds to perform different functions. This segmentation allows the first impeller to operate at higher speed for rapid pressure response while the second impeller operates at lower speed for quieter operation, resolving the contradiction between compact size and noise reduction.
Solution Approach 2:
The patent extends the blower design into the axial dimension by mounting impellers on both ends of the motor shaft, creating a double-ended configuration. This dimensional change allows two-stage pressurization within a compact footprint, achieving two-stage performance without the increased size typically associated with multi-stage blowers while reducing noise through optimized speed distribution.
2Loss of time
If a two-stage blower is used, then pressure response time improves, but device size increases
Solution Approach 1:
The common output shaft serves multiple functions: it transmits rotational power to both impellers, allows independent speed control of each impeller, and enables synchronized operation when needed. This multi-functionality allows the compact double-ended design to achieve two-stage pressurization with fast response time without requiring separate drive mechanisms that would increase size.
Solution Approach 2:
The patent merges two impeller stages into a single integrated motor assembly where both impellers share a common shaft and housing space. The first and second volutes are combined within the same motor body, creating a unified structure that achieves two-stage performance in a compact package, resolving the contradiction between fast response and small size.
3Loss of time
If a two-stage blower is used, then pressure response time improves, but device complexity increases
Solution Approach 1:
The control system automatically switches between single-stage and two-stage operation modes based on pressure requirements, and the system self-regulates impeller speeds to optimize performance. This self-service capability reduces the need for complex manual controls and external monitoring, achieving fast response time while keeping operational complexity manageable.
4Reliability
If traditional motor housing is used, then motor protection is improved, but blower size increases
Solution Approach 1:
The motor housing and first volute are merged into a single integrated structure, eliminating the need for a separate motor housing. The motor body itself forms part of the volute chamber, creating a compact design where the motor is protected while the overall blower size is reduced. This merging resolves the contradiction between motor protection and compact size.
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 provides faster pressure response, reduced noise, and increased reliability in a smaller package, enhancing the effectiveness of CPAP treatment for sleep disordered breathing.
Implementation Method 1
a first stage impeller enclosed within a first volute and a second stage impeller enclosed within a second volute, each for pressurizing gas
Implementation Method 2
vibrational isolation, and alternating shroud impellers made of polypropylene, which reduces inertia and noise
Data Source
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AI summary
Apparatus for generating a supply of air at positive pressure for treatment of a respiratory disorder, the apparatus comprising a chassis (238) enclosure including an interior wall (240), a blower motor assembly (200) structured to produce a flow of air at positive pressure along an air path and located within the chassis enclosure, and a flexible sleeve (202) substantially enclosing the blower motor assembly and including a bottom wall (206) and a peripheral side wall (204), wherein the flexible sleeve is structured and arranged to expand radially outwardly into at least partial engagement with the interior wall of the chassis enclosure when the air at positive pressure flows along a portion of the air path that is radially between the blower motor assembly and the flexible sleeve, thereby at least partially supporting the blower motor assembly in a manner that isolates vibration.