United States Patent 6,004,297: Scope, Claims Architecture, and US Landscape
What is the core invention claimed in US 6,004,297?
US 6,004,297 claims a mechanical injection syringe that meters “set doses” from a medicated cartridge using a thread-based dose setting mechanism coupled to a piston drive. The claim set centers on a specific bidirectional control problem: preventing unwanted piston movement during dose dialing while enabling controlled distal piston transport during the injection stroke.
Across independent Claim 1 and dependent Claims 2-8, the invention’s scope is defined by four technical blocks:
- Piston rod anti-rotation with axial translation
- The piston rod has a not circular cross-section and works with a piston rod guide that permits axial displacement but blocks rotation.
- Self-locking piston rod drive
- A not axially displaceable nut member in the housing has an inner thread that forms a self-locking thread connection with an outer thread on the piston rod.
- Dose setting mechanism driven by rotation of an injection button
- A dose setting element is rotated relative to the housing to screw outward from the proximal end by an amount determined by rotation angle.
- Axial returning of the injection button transforms axial motion into rotation of one piston drive element relative to the other.
- Unidirectional coupling with initial reluctance
- The key differentiator: a unidirectional coupling between the nut member and the piston rod guide that:
- allows relative rotation only in the direction that transports the piston rod distally
- prevents rotation in the opposite direction
- requires overcoming an initial reluctance large enough to resist a torque exerted on the coupling by dose setting
Dependent claims then specify implementation details (click coupling feel; pawl-and-wheel geometry; helical dose scale drum thread geometry; alternative thread couplings; mounting variants using a driver tube that rotates with the piston rod).
How do the claims map to specific mechanical components?
The claims operate as a mechanical architecture. The “claim coverage” is the intersection of these features. The following claim-to-element map clarifies what must be present for infringement.
Claim 1 (independent): full system definition
Claim 1 requires all of the following elements:
In practical terms, Claim 1 protects a two-mode behavior:
- Dose dialing mode: injection button movement and/or dose scale adjustment occurs without advancing the piston drive by resisting torque through a one-way coupling with threshold
- Injection mode: once threshold is overcome, motion couples into piston distal transport via permitted rotation path
Claim 2 (dependent): user interface click resistance
- Adds a click coupling providing moderate resistance against rotation in either directions between:
- housing and
- the element rotated relative to the housing to set a dose
Claim 3 (dependent): pawl and pawl wheel one-way mechanism
- Unidirectional coupling is:
- pawl sliding over a pawl wheel
- pawl wheel teeth have a steep front edge
- and a ramp shaped trailing edge
Claim 4 (dependent): tooth geometry for pawl engagement
- Specifies:
- trailing edges of pawl wheel teeth have a depression
- depression engages a mating protrusion on the pawl
Claim 5 (dependent): dose scale drum with helical track/rib
- Adds:
- a dose scale drum with a helical track on its surface
- engaged by a helical rib inside the housing
- This forms a not self-locking thread connection between the housing and the dose scale drum
- The dose scale drum is coupled to the injection button such that it is moved axially with the button
Claim 6 (dependent): dose lift thread connection defined
- Specifies that the thread connection lifting the injection button by dose setting is:
- the thread connection between the dose scale drum and the housing
Claim 7 (dependent): alternative thread coupling inside injection button
- Specifies:
- element rotated relative to the housing is the injection button
- not self-locking thread connection determining lifting is:
- an inner thread in a bore in the injection button
- engaging an outer thread on a part with enlarged diameter of the piston rod
Claim 8 (dependent): driver tube mounting variant
- Specifies:
- piston rod guide mounted in a driver tube
- piston rod is axially displaceable in driver tube but is rotated with the tube
- not self-locking thread connection determining lifting provided between:
- driver tube and
- a part axially displaceable with the injection button
Where is the real claim leverage: what makes it hard to design around?
The strongest coverage is not the general concept of dose dialing by screw translation. It is the combination of:
-
Unidirectional coupling location and function
- specifically between the nut member and the piston rod guide
- controlling relative rotation direction
-
Initial reluctance threshold
- designed so torque from the dose setting does not cause rotation
- rotation only occurs after threshold is overcome
This pairing is difficult to bypass without replacing the entire energy-transfer logic. A design-around that keeps dose dialing but removes “unidirectional coupling between nut member and piston rod guide” will likely avoid Claim 1. But many practical devices use ratchets, pawls, or one-way clutch arrangements. If those are located elsewhere (for example, between injection button and drive screw rather than nut member and guide) the infringement analysis changes.
Dependent Claims 3 and 4 further restrict the one-way coupling to a pawl-and-wheel geometry with steep front edge and ramp trailing edge, plus tooth depression/protrusion engagement.
Dependent Claims 5-8 restrict the dose scale and/or thread path. Those are not required for Claim 1 but become mandatory for infringement of those dependents.
What is the patent landscape relevance: how this fits into mechanical injection device families
US 6,004,297 belongs to the mechanical injection device space where patent portfolios often concentrate on:
- dose setting by rotation-to-translation
- prevention of “back driving” of the piston during dose selection
- tactile “click” user feedback
- one-way clutches or ratchets converting injection-button return into piston advancement
In this landscape, independent Claim 1 sets a clear differentiator: the unidirectional coupling with initial reluctance large enough to resist torque from dose setting. That detail maps to a common practical problem: dose dialing generates torque that can inadvertently turn the drive train. Threshold one-way coupling approaches are a known strategy, but the specific placement and threshold requirement narrow the claim scope.
How broad is Claim 1 vs dependent claim limitations?
Breadth in Claim 1
Claim 1 is broad relative to Claims 2-4 and Claims 5-8 because it does not require:
- a specific pawl wheel shape (Claims 3-4)
- a click coupling arrangement (Claim 2)
- a dose scale drum helical track (Claims 5-6)
- a particular injection button bore/thread geometry (Claim 7)
- a driver tube mounting variant (Claim 8)
Claim 1, however, is constrained to the specific system-level combination and functional requirement for the unidirectional coupling threshold.
Narrowing in dependent claims
- Claims 2 narrows to a click coupling with “moderate resistance against rotation in either directions.”
- Claims 3-4 narrow the unidirectional coupling mechanism to a specific pawl/wheel geometry.
- Claims 5-6 narrow the dose mechanism to a dose scale drum with helical track/rib and specify the lifting thread path.
- Claim 7 narrows the rotated element to the injection button and defines the internal thread coupling.
- Claim 8 narrows to a driver tube arrangement with defined axial displacement and rotation behavior.
Where would competitors likely land if they seek a design-around?
Within the scope boundaries described above, the most likely non-infringing routes are:
- Shift one-way coupling location
- Use an anti-backdrive device, but between different components than the “nut member and piston rod guide.”
- Replace threshold-throttled behavior
- Use a one-way clutch that allows rotation during injection without relying on an “initial reluctance” sized to resist torque from the dose setting.
- Keep the dosing mechanism but change thread path
- Use a different thread translation or conversion route for transforming injection-button return into drive rotation.
However, any alternative must still produce correct metering and injection performance. Portfolio strategy typically targets those engineering levers.
Claim coverage summary table
| Claim |
Mandatory scope additions beyond Claim 1 |
What gets constrained |
| 1 |
Unidirectional coupling between nut member and piston rod guide + initial reluctance threshold + one-way relative rotation to move piston distally |
System architecture for anti-backdrive and torque threshold behavior |
| 2 |
Click coupling between housing and dose-setting rotated element; moderate resistance in either direction |
User feedback interface and frictional resistance model |
| 3 |
Pawl sliding over pawl wheel; steep front edge + ramp trailing edge |
One-way coupling geometry |
| 4 |
Pawl wheel tooth depression engages mating pawl protrusion |
Tooth/pawl engagement geometry |
| 5 |
Dose scale drum with helical track + helical rib; not self-locking thread connection; coupled axially to injection button |
Dose scale construction and thread connection |
| 6 |
Injection button lifting thread is the dose scale drum-to-housing thread |
Specific thread path for the lift |
| 7 |
Injection button is rotated element; not self-locking thread via inner bore thread and enlarged-diameter piston rod part thread |
Thread mechanism and which element rotates |
| 8 |
Piston rod guide in driver tube; piston rod axially displaceable but rotates with tube; lifting thread between driver tube and axially displaceable part with injection button |
Mechanical mounting and thread conversion path |
How to read the claims for FTO diligence
For FTO or competitive freedom-to-operate analysis, Claim 1 is the primary gate. A device can avoid all infringement by failing at least one of these core requirements:
- piston rod anti-rotation via not circular cross-section + mating guide that prevents rotation
- piston rod drive with nut member not axially displaceable forming self-locking thread connection
- dose setting mechanism with not self-locking thread connection and injection button rotation and axial returning conversion step
- unidirectional coupling located between the nut member and piston rod guide that:
- permits rotation only for distal piston transport
- requires overcoming initial reluctance sized to resist torque exerted by dose setting
Dependent claim infringement depends on additional structural specifics.
Key Takeaways
- US 6,004,297 Claim 1 protects a mechanical injection syringe architecture that converts dose dialing motion into injection piston movement while preventing inadvertent piston advancement through a one-way coupling with an “initial reluctance” threshold between the nut member and piston rod guide.
- Dependent claims narrow the invention to click coupling feel (Claim 2), pawl-wheel geometry (Claims 3-4), and multiple dose setting thread/path variants using a dose scale drum (Claims 5-6), injection button internal thread (Claim 7), or a driver tube arrangement (Claim 8).
- The design-around levers implied by the claim language are: relocate the one-way coupling, remove or change the threshold behavior, or re-route the dose-to-drive torque conversion path so that it no longer matches the required mechanical and functional combination of Claim 1.
FAQs
-
What is the single biggest novelty in Claim 1?
The unidirectional coupling between the nut member and piston rod guide that allows distal transport rotation only and requires an “initial reluctance” threshold large enough to resist torque from the dose setting.
-
Does Claim 1 require a pawl and pawl wheel?
No. Pawl wheel geometry appears only in dependent Claims 3-4.
-
Is a click mechanism mandatory for protection?
No. The click coupling is in dependent Claim 2 only.
-
Do Claims 5-8 need to be present to infringe Claim 1?
No. Claims 5-8 are dependent, so they add narrowing features on top of Claim 1.
-
How should engineering teams interpret “not self locking” and “self locking” here?
Claim 1 uses self-locking for the nut-member/piston-rod thread connection in the piston drive, and not self-locking for the dose setting thread connection along which the injection button is screwed out.
References
[1] United States Patent 6,004,297. Claims 1-8 (as provided in prompt text).
