US Patent 6,681,768: Scope, Claim Architecture, and US Landscape for Tangential-Flow Dry Powder Inhalers
What is the core claim scope of US 6,681,768?
US Patent 6,681,768 covers a dry powder inhaler (DPI) architecture built around a tangential (swirl/cyclone-like) particle flow inside a circulation chamber with powder-laden air discharge coaxial to the chamber, and—across multiple dependent claim paths—sheath air and helical-flow disruption features. The claims also include variants that refine geometry (openings, wall segmentation) and a modular system (interchangeable top plates).
Independent claim set (broadest technical anchors)
- The document presents multiple independent compositions of matter/inhaler apparatus variants that share the same core inhaler fluid mechanics:
- Tangential powder injection via a first supply channel into a circulation chamber.
- Powder-free tangential air via one or more “second” air supply channels positioned symmetrically about a central axis.
- Common rotational direction for air streams to produce generally circular flow in the chamber.
- Coaxial discharge channel providing powder-laden air discharge.
- Independent claim coverage also spans:
- Wall geometry constraints (height less than diameter; planar segmented wall sections arranged in long/short sets).
- Discharge channel top-wall traversal for certain embodiments.
- Baffle member inside the discharge channel to disrupt helical flow and align particles parallel to the central axis.
- Modularity via multiple top plates and removable mouthpiece for configuration selection.
How do the claims define the technical features (element-by-element)?
Below is a claim-structured decomposition that tracks claim language across claims 1, 7, 12, 16, and 17, then extends through the dependent features (sheath air, baffles, wall segmentation, rectangular openings, modular plate interchange).
A. Circulation chamber geometry (recurring across claims)
The DPI has:
- Circulation chamber wall
- Top wall and bottom wall defining a circulation chamber with:
- Central axis
- Chamber height = distance between top and bottom walls
- Chamber diameter
- Constraint: chamber height is less than chamber diameter
- This establishes a squat chamber profile supporting swirl flow and allowing internal coaxial discharge.
B. Tangential air and powder introduction (swirl generation)
The system has:
C. Coaxial discharge channel (particle exit path)
The DPI includes:
- Discharge channel positioned substantially coaxially with the circulation chamber
- First end and second end
- First end defines an inlet
- Second end defines a discharge opening
In some embodiments (claims 1 and 7), the discharge channel:
- Has a portion extending through the top wall (claim 1 explicitly; claim 7 explicitly via “extending through said top wall”)
And in other embodiments:
- The discharge channel interior cross section is defined as substantially circular (claim 17).
Also, claim 1 specifies a separation geometry:
- Discharge channel portion inside the chamber has an outer perimeter spaced radially inwardly from the circulation chamber wall.
D. Sheath air around the discharge channel outlet (de-agglomeration/entrainment control)
In multiple dependent claim paths, a third air supply channel provides:
- Powder-free air
- Outlet positioned coaxially with the discharge channel second end
- The outlet forms an annular opening surrounding an exterior surface of the discharge channel at the outlet region
- This supplies a sheath of powder-free air surrounding powder-laden air discharged from the discharge opening
This is explicitly stated in:
- Claim 1
- Claim 9
- Claim 13
- Claim 21
E. Discharge-channel baffle to disrupt helical particle flow
A distinct feature set appears in claims 17-20:
- A baffle member positioned in the discharge channel
- Disrupt helical flow of particles through the discharge channel
- Directs particles in a direction substantially parallel to the central axis
Dependent refinements:
- Claim 18: baffle has plurality of ridges projecting radially inwardly, ridges extend parallel to the central axis; ridges project inwardly a distance less than discharge diameter.
- Claim 19: baffle comprises plurality of baffle frameworks extending between diametrically opposite sides at spaced locations along the central axis.
- Claim 20: frameworks are cross-shaped.
F. Circulation chamber wall segmentation (long and short planar segments / paired 135° segments)
Claims 7, 8, 12 define a more detailed chamber wall structure:
- The circulation chamber wall is defined by a plurality of wall segments
- Each wall segment is substantially planar
- Each has a height extending from bottom to top
- Long and short segment structure:
- Long segments have length no less than a first length
- Short segments have length no greater than a second length
- First length > second length
- Long and short segments alternate along circumference
- One short segment is positioned at an angle to and downstream of each long segment (relative to circular flow).
Dependent geometry:
- Claim 8: each long-short downstream pair is at approximately 135 degrees (angle between a long segment and the downstream short segment).
A different segmentation formulation:
- Claim 12: wall segments are arranged in pairs, each pair comprises two intersecting wall segments forming an angle of approximately 135 degrees
- The openings separate each pair from adjacent pairs.
G. Opening shapes and placement constraints
Claims 4 and 5 add specific opening geometry:
- Rectangular shape for the first opening and each second opening (claim 4).
- Each opening has:
- A top edge adjacent to the top wall
- A bottom edge approximately midway between top and bottom walls (claim 5).
Claim 6 adds discharge-channel penetration depth:
- Discharge channel extends into the circulation chamber by a distance greater than one half the chamber height
- Therefore inlet is positioned closer to the bottom wall than to the top wall.
H. Number of second openings and symmetry mapping
Claims constrain second openings for performance tuning and manufacturing consistency:
- Claim 2: seven second air supply channels.
- Claim 10: second openings are 3 to 8, symmetrically positioned; and counts of long and short wall segments align to the total number of openings and first opening.
- Claim 11: second openings consist of 3.
- Claim 14-15: second openings comprise 3 to 8, with dependent specifying 3.
I. Modular inhaler system (configurable top plates)
The patent includes system claims:
-
Claim 22: modular dry powder inhaler system
- Inhaler body has circulation chamber wall and bottom wall defining portion of chamber
- Removably mountable top plates form the top wall when mounted
- Each top plate defines discharge channel positionable coaxially with circulation chamber
- Different top plate configurations allow selection based on user requirements.
-
Claim 23: mouthpiece removably mountable securing a selected top plate to inhaler body and defining third air supply channel
- Third air supplies a sheath of powder-free air around discharge channel outlet.
-
Claim 24: top plate flange extends radially outward and defines passages forming portion of third air supply channel.
-
Claim 25: different top plates can define:
- Common discharge opening diameter
- Different inlet opening diameters (at first end).
-
Claim 26: at least one top plate includes a discharge channel and optionally includes a baffle member to disrupt helical flow when mounted.
What do the claim dependencies imply about design-around pressure?
The claim set is not limited to a single embodiment; it builds a feature tree where several functional components recur across variants:
1) Tangential multi-port swirl chamber (first tangential powder feed + symmetric tangential powder-free air)
2) Coaxial discharge channel
3) Optional annular sheath air (third channel)
4) Optional internal baffle (helical disruption)
5) Optional geometry tuning (rectangular ports, penetration depth)
6) Optional wall segmentation architecture (alternating long/short planar segments; 135° relationships)
7) Optional modularity (top plates and mouthpiece)
This structure narrows infringement risk for a competitor: even if a design avoids one dependent feature (for example, sheath air), other dependent features may still be captured if the competitor retains the tangential swirl + coaxial discharge channel architecture.
What is the patent landscape around US 6,681,768 (device class and likely prior art zones)?
A. Technology neighborhood: swirl/cyclone particle separation inside DPIs
US 6,681,768’s architecture sits in a family of DPI concepts that:
- accelerate powder-laden air,
- impart swirl/tangential flow to control particle trajectories,
- reduce wall deposition and entrainment variability,
- and stabilize exit flow by shaping inlet/outlet geometry.
The core elements (tangential channels, circular flow chamber, coaxial discharge) are the type of features that frequently appear in:
- cyclone-based separators,
- inhaler injectors using annular or sheathing flows,
- and DPI throat/orifice management designs.
B. Sheath air and annular powder-free flows
The sheath air concept appears as:
- a third powder-free air stream forming an annular opening surrounding the exterior of the discharge channel end, producing a concentric “sheath.”
This is in the broader area of:
- particle focusing,
- reducing powder agglomeration at the outlet,
- and controlling entrainment.
C. Discharge baffles to interrupt helical flow
Claim 17-20 cover baffle architectures to disrupt helical flow in the discharge channel and re-direct particles axially.
Landscape implication:
- In DPI devices that use swirl generation, downstream flow frequently carries rotation, so internal anti-rotation features or turning vanes often appear in later designs to reduce rotational dispersion.
D. Modular inhaler bodies with interchangeable top components
Claim 22-26 are consistent with modular product strategies:
- swapping geometries that tune resistance, plume characteristics, or airflow distribution,
- without re-engineering the main chamber body.
Landscape implication:
- Competitors who keep the tangential swirl chamber and coaxial discharge while swapping top plates still inherit much of the claim structure, unless the interchange changes delete or materially alter the defined coaxial discharge and inlet/outer perimeter relationships.
How broadly does the claim language cover variations (what is “must-have” vs “optional”)?
Must-have to hit broadest independent claim themes
Across independent claim groupings (claims 1, 7, 12, 16, 17, 22), the must-have structural spine is:
- a circulation chamber defined by top and bottom walls with height < diameter
- a first supply channel delivering powder + air tangentially into the chamber
- at least one second air supply channel delivering powder-free air tangentially
- air delivered in common rotational direction to form generally circular flow
- a coaxial discharge channel with inlet and discharge opening
- for sheath and baffle variants, the relevant elements are additional must-haves only if those dependent claims are invoked.
Optional features that narrow to dependent claims
- Sheath air via annular third outlet: dependent (claims 1/9/13/21; also claim 23 system-level)
- Baffle member disrupting helical flow: dependent (claims 17-20; also claim 26)
- Wall segmentation patterns and 135° relationships: dependent (claims 7-8 and 12)
- Rectangular ports and port edge placement: dependent (claims 4-5)
- Discharge channel penetration depth: dependent (claim 6)
- Specific second opening counts (3 to 8, exactly 3, or exactly 7): dependent (claims 2, 10-11, 14-15)
- Modular top plates and mouthpiece arrangements: independent system claim (claim 22) and dependent system features (claims 23-25; baffle in top plate claim 26)
US 6,681,768 claim-by-claim scope map
Claim 1
- Covers the full tangential swirl chamber + coaxial discharge + annular sheath air around discharge channel exterior.
Key scope binds:
- chamber height < diameter
- first tangential powder feed
- plurality of symmetrical second tangential powder-free feeds
- coaxial discharge channel with top-wall traversal and radially inward outer perimeter spacing
- third tangential powder-free sheath forming annular opening around discharge channel end.
Claims 2-6
- Add port count (seven second channels).
- Add top-wall flange with passages forming part of third air supply channel.
- Add rectangular first/second opening shapes; top edge at top wall and bottom edge midway.
- Add discharge channel penetration > half chamber height, pushing inlet closer to bottom wall.
Claims 7-11
- Cover tangential swirl + coaxial discharge but focus on segmented planar wall with long/short alternating arrangement and downstream short segment.
- Dependent claim 8 sets approximate 135° angle between long and downstream short segment.
- Dependent claim 9 reintroduces annular sheath air.
- Dependent claim 10 sets numerical constraints on openings and segment counts mapping.
- Dependent claim 11 specifies exactly three second openings.
Claims 12-15
- Alternative wall segmentation constraint:
- wall segments in pairs with ~135° intersecting walls
- openings separate adjacent pairs.
- Dependent claims 13 and 14-15 include sheath air and second-opening counts (3 to 8; optionally exactly 3).
Claims 16
- Reasserts tangential swirl + coaxial discharge + annular sheath air with top-wall flange passages feature.
Claims 17-21
- Tangential swirl + coaxial discharge + specific baffle in discharge channel to disrupt helical flow and align particles axially.
- Dependent claim 18 ridge-based inward projections.
- Dependent claim 19 framework-based baffles (cross-shaped at 20).
- Dependent claim 21 re-adds annular sheath air.
Claims 22-26 (modular system)
- Modular inhaler system with:
- inhaler body + removable top plates defining top wall
- each top plate forms discharge channel coaxial with the chamber
- different top plate configurations for user needs.
- Dependent claim 23: mouthpiece mounts top plate and defines third air channel with annular sheath.
- Dependent 24: top plate flanges define passages for third air supply.
- Dependent 25: common discharge opening diameter and different inlet opening diameters among top plates.
- Dependent 26: top plate discharge channel can include baffle member to disrupt helical flow.
Landscape takeaways for freedom-to-operate (practical infringement pressure points)
A competitor’s DPI design attempting to avoid US 6,681,768 should evaluate:
- Tangential swirl architecture is central. Removing tangentiality or switching to non-rotational straight flow is a major change versus minor geometry tweaks.
- Coaxial discharge channel and defined inlet/discharge relationship is also central. Moving exit away from coaxial alignment or fundamentally changing inlet geometry is a higher-risk area.
- Annular sheath air is a common additional feature. If included, it tracks directly with sheath-oriented dependent claims.
- Internal baffles that disrupt helical flow are captured. Anti-swirl downstream mechanisms are not automatically safe if they still disrupt helical flow in the discharge channel with ridges/frameworks as claimed.
- Segmented long/short 135° wall pairs is a specific narrowing path. If a design uses a different chamber wall construction without the alternating long/short or paired 135° intersection framework, it may avoid those dependent constraints while still facing independent tangential-swirl + coaxial-discharge coverage.
Key Takeaways
- US 6,681,768 claims a DPI defined by tangential multi-port swirl generation, coaxial discharge, and optional sheath air and anti-helical discharge baffles.
- The claim set is layered: independent coverage largely anchors the swirl chamber + coaxial discharge, while dependent claims tighten geometry (rectangular ports; port placement; segmented 135° wall constructs) and add downstream controls (annular sheath air; baffle frameworks/ridges).
- The modular system claims extend protection to interchangeable top plates that keep the core swirl chamber and coaxial discharge architecture while varying discharge channel/inlet geometry.
- Design-around effort must focus on altering one of the central anchors (tangential swirl, coaxial discharge architecture, or annular sheath/anti-helical mechanisms), not only on minor port shape or count.
FAQs
1) Is sheath air required to fall under the main concept?
Sheath air is not required to define the overall swirl + coaxial discharge concept because sheath air appears in specific dependent claim groupings. It does, however, become required where the specific dependent claims are asserted.
2) What is the most central structural limitation across independent claim themes?
The combination of a tangential powder feed into a circulation chamber, symmetric tangential powder-free air streams in a common rotational direction, and a coaxial discharge channel is the recurring spine.
3) Does the patent cover baffles in the discharge channel?
Yes. Claims 17-20 cover baffles positioned in the discharge channel to disrupt helical flow and redirect particles axially, including ridges and cross-shaped framework options.
4) Do the claims require a specific number of second openings?
Some dependent claims set specific counts (for example, seven; three; or a range). Other claims use “at least one” or “plurality” second channels without fixing a number.
5) What does the modular claim set protect?
Claim 22 protects a modular system built from an inhaler body plus removable top plates that define a discharge channel coaxial with the circulation chamber, with additional dependence for mouthpiece-driven air sheathing and top-plate geometry variations.
References
[1] United States Patent No. 6,681,768, “Dry powder inhaler.”
