Patent: 6,004,297

Summary for Patent: 6,004,297

Title:	Injection syringe
Abstract:	An injection syringe comprises a housing (1), a piston rod (6) with a non-circular cross-section and an outer thread (7), a piston rod drive which includes a piston rod guide (85) mating with the cross-section of the piston rod (6), and a nut (4) which is not axially displaceable and which mates with the thread (7) of the piston rod (6) to form a self-locking thread connection. Rotation of a dose setting element (81) causes an injection button to be screwed out to project from the housing (1). When the injection button (88) is pushed axially, such axial movement is transformed, by way of the threaded coupling, into a rotation of one of the piston drive elements (85) relative to the other one (4). A unidirectional coupling between the nut member (4) and the piston rod guide (85) allows rotation in one direction by which the piston rod (6) is transported in a distal direction. The coupling has an initial reluctance to be overcome before rotation takes place, said reluctance being large enough to resist torques exerted during the dose setting.
Inventor(s):	Steenfeldt-Jensen; S.o slashed.ren (Hornb.ae butted.k, DK), Hansen; Steffen (Hiller.o slashed.d, DK)
Assignee:	Novo Nordisk A/S (Bagsvaerd, DK)
Application Number:	09/238,849
Patent Litigation and PTAB cases:	See patent lawsuits and PTAB cases for patent 6,004,297
Patent Claims:	see list of patent claims

US Patent 6,004,297: What the Claims Actually Cover and Where the Landscape Squeezes

US Patent 6,004,297 (“6,004,297”) claims a dose-setting injection syringe architecture built around (1) a settable axial movement of an injection button that (2) mechanically converts into controlled distal transport of a cartridge piston via a thread-driven drive, with (3) a unidirectional coupling that prevents dose-setting rotation from driving the piston in the wrong direction unless an initial “reluctance” torque threshold is overcome. The key business value of the patent is the specific mechanical constraint stack: non-rotating axial guidance for the piston rod, self-locking drive threads for preventing backdriving, and a one-way coupling with a designed breakaway torque that blocks torque from dose setting until a threshold is exceeded.

What follows is a claim-structure analysis, then a critical assessment of likely novelty/obviousness pressure points and the patent landscape logic (type of prior art to look for, and where enforcement leverage likely exists).

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1) Claim-by-claim decomposition: what is protected vs what is merely structural

Claim 1: Core architecture and the one-way “breakaway torque” concept

Claim 1 requires an injection syringe with the following functional elements locked together:

A. Dose reservoir and housing

• A housing.
• A cartridge-like medicine supply sufficient for multiple therapeutic doses.

B. Piston rod geometry and proximal distal drive

• A piston rod with:
  • not circular cross-section (rotation constrained),
  • an outer thread.
• A piston rod drive comprising two elements:
  1. Piston rod guide that mates the non-circular cross-section:
     • allows axial displacement,
     • prevents rotation of the piston rod relative to the guide.
  2. Nut member:
     • not axially displaceable in the housing,
     • has an inner thread that mates the piston rod outer thread,
     • creates a self locking thread connection (prevents backdriving under load).

C. Dose setting mechanism using a dose setting rotation plus axial return translation

• A “dose setting mechanism” uses a not self locking thread connection along which:
  • an injection button by rotation of a dose setting element relative to the housing is screwed out from the proximal end to project to a distance determined by the rotation angle,
  • then axial returning of the injection button transforms axial movement into rotation of one piston drive element relative to the other.

D. The discriminating limitation: unidirectional coupling between nut member and piston rod guide

• Unidirectional coupling is provided between:
  • the nut member and the piston rod guide.
• It allows relative rotation in one direction only:
  • the allowed rotation is “one by which the piston rod is transported in a distal direction.”
• The coupling is designed so that:
  • an initial reluctance set large enough to resist torque “exerted on the coupling by the dose setting”
  • must be overcome “before rotation takes place.”

Business meaning Claim 1 does not just claim a standard dose screw mechanism. It claims a mechanism that blocks dose-setting torque from inadvertently advancing the piston, then releases the coupling only when the axial-return-driven rotation produces torque above a threshold.

That threshold language (“initial reluctance set large enough to resist a torque exerted on the coupling by the dose setting”) is the hook that can both (1) sharpen novelty and (2) narrow infringement if accused devices do not implement breakaway torque behavior in the described locations.

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Claim 2: A click coupling with moderate resistance in both rotation directions

• Establishes a click coupling between the housing and the element rotated relative to the housing to set a dose.
• It provides “moderate resistance against rotation in either directions.”

Business meaning This adds a tactile/detent function. It is likely a high-frequency mechanical feature in dose pens and injection devices; it may be less central to novelty than Claim 1’s one-way breakaway coupling.

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Claim 3-4: Specific pawl wheel geometry for the unidirectional coupling

• Claim 3: unidirectional coupling comprises:
  • a pawl sliding over a pawl wheel
  • teeth with a steep front edge and a ramp shaped trailing edge.
• Claim 4: trailing edge depression engaged by mating pawl protrusion.

Business meaning These dependent claims narrow the coupling structure to a ratchet/pawl geometry with specific tooth edge shapes and engagement features. They provide fallback coverage if the “unidirectional coupling” is implemented via the described tooth profile.

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Claim 5-6: Dose scale drum and helical track/rib thread non-self-locking connection

• Claim 5:

  • a dose scale drum with a surface helical track engaged by a helical rib inside housing,
  • to form a not self locking thread connection between housing.

• Dose scale drum coupled to injection button so it moves axially with the button.

• Claim 6:

  • the lifting thread connection for setting a dose is between the dose scale drum and the housing.

Business meaning These claims narrow the dose-setting drive train to a helical-track/helical-rib “not self locking” connection between a drum and housing, with axial movement tied to the injection button.

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Claim 7: Alternative embodiment of the not self locking connection in injection button bore

• Element rotated relative to housing is the injection button.
• Not self locking connection determining lifting is:
  • an inner thread in a bore in the injection button
  • engaging an outer thread on a piston rod part with enlarged diameter.

Business meaning Adds another structural path for the “not self locking thread connection” that drives injection button projection.

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Claim 8: Another drive train split between driver tube rotation and axial part

• Piston rod guide mounted in a driver tube:
  • piston rod axially displaceable in driver tube,
  • but rotated with tube.
• The “not self locking thread connection” provided between:
  • driver tube
  • and a part axially displaceable with injection button.

Business meaning Again narrows to a specific mechanical arrangement that controls which elements rotate and which translate.

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2) Critical analysis: what looks genuinely protectable vs what is vulnerable to prior art and obviousness

A. Protectable core: the one-way coupling with engineered reluctance

The most distinctive claim element is the unidirectional coupling between nut member and piston rod guide, plus the “initial reluctance” breakaway requirement resisting torque exerted by the dose setting.

In mechanical pens and injection devices, common problems include:

• backdriving due to thread self-locking limits,
• mis-indexing during dose setting,
• unintended piston advance during button rotation or returning.

Claim 1 addresses this by:

• requiring self-locking for the nut-piston thread connection, and
• adding a separate one-way coupling with a designed threshold to avoid premature distal motion caused by dose setting torque.

This structure can be argued as more than “use a ratchet,” because it ties the ratchet behavior to the torque produced during the dose-setting step and explicitly requires initial reluctance to exceed a torque threshold.

Risk: If prior art shows one-way couplings that inherently resist reverse torque until a pawl climbs a tooth edge (which is common), defendants will argue that the “initial reluctance” is inherent and not a patentable difference, unless the prior art teaches “initial reluctance set large enough to resist torque exerted by the dose setting” in the same functional placement.

Enforcement leverage: To preserve breadth, the patentee can point to functional evidence: coupling must not transmit dose-setting torque to piston transport until axial return-driven torque overrides it. To defend validity, the argument must connect the threshold and functional directionality to structure (paws/tooth geometry/springs/friction surfaces) in the specification, because claim language is already functional.

B. Claim breadth risk: multiple “not self locking” and “self locking” thread references create ambiguity

Claim 1 includes:

• self-locking thread connection between piston rod and nut,
• not self-locking thread connection along the dose setting mechanism.

If prior art teaches dose mechanisms using threads that are not backdrivable by using geometry (lead angle, friction) that is sometimes described variably as “self-locking” or “not self locking,” claim interpretation may expand or contract depending on how courts handle these mechanical terms.

Risk: Defendants can cite prior art where the same effect (no backdriving during one step) is achieved with friction or geometry and is described as “self-locking” in some contexts. This can be used to argue anticipation by equivalence or obviousness by substituting known thread lead/friction configurations.

C. Dependent claims 3-4: tooth geometry narrows and may reduce obviousness risk

The pawl wheel with steep front edge and ramp trailing edge is more specific. Many ratchets have asymmetric tooth profiles; the risk is that prior art pawl designs are close enough that these dependent limitations are still met.

But dependent claims give a fallback and also a clearer narrative for inventiveness: not just a ratchet, but a ratchet with tooth geometry that delays reverse torque transmission (front edge steepness) and then allows override in one direction.

D. Dependent claims 5-8: multiple embodiments increase coverage but also increase invalidity surface

Claim set includes alternative implementations for:

• how dose scale drum threads interact (Claims 5-6),
• how injection button inner thread interacts with enlarged diameter piston rod part (Claim 7),
• how driver tube rotation carries piston rod (Claim 8).

This is good for infringement capture, but each embodiment invites a separate prior art mapping exercise. The more ways the device can be built, the more likely one path exists in earlier patents.

The strategy for a challenger is straightforward: find at least one embodiment in prior art that matches each claim element combination, even if other embodiments differ.

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3) Patent landscape: where you should expect the “closest” prior art to sit

Landscape segment 1: multi-dose injection pens and mechanical dose setting with threaded conversion

The claim style and mechanical architecture match a well-populated prior art family: devices that use

• a dose dial / injection button projection,
• a rotational dose setting input,
• conversion to piston movement via threaded engagement and/or a gear reduction,
• self-locking features to resist backdriving.

What to look for in prior art documents

• Mechanisms where injection button rotation by user sets a projection distance.
• Axial return of a button triggers piston advance by rotating a driver element.
• Use of “not self locking” and “self locking” thread connections described explicitly in patents or implicitly via non-backdrivable lead angles.

Landscape segment 2: ratchets, unidirectional couplings, and breakaway thresholds

The unidirectional coupling plus “initial reluctance” places this patent in the sub-landscape of:

• pawl ratchets inside dose devices,
• one-way clutches,
• friction clutches with breakaway torque,
• hybrid ratchet/clutch systems that prevent reverse engagement during dose setting.

What to look for

• Unidirectional couplings positioned between a threaded element and a guide/driver.
• Documents explicitly stating resistance to reverse rotation or breakaway torque before engagement.
• Tooth profile asymmetries: steep leading faces and ramp trailing faces are common in ratchet engineering.

Landscape segment 3: helical track/dose drum and helical rib dose setting

Claims 5-6 align with a dose drum that moves axially with user interaction via a helical track and complementary rib that functions as a non-self-locking thread connection.

What to look for

• Dose scale drums with helical features controlling axial movement.
• Dose setting elements moving axially due to helical engagement, tied to a dose scale rotation.

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4) Likely claim construction pressure points in US litigation

A. “Unidirectional coupling provided between the nut member and the piston rod guide”

Accused systems must map rotation between specific elements:

• nut member must be one of the coupling sides,
• piston rod guide the other.

Many commercial syringes may use one-way clutches between different nodes (e.g., coupling between dose dial and lead screw; coupling between button and driver shaft). If the “between” mapping does not align, infringement arguments weaken.

B. “Initial reluctance set large enough to resist a torque exerted on the coupling by the dose setting”

This is the most litigation-sensitive element. It invites questions of:

• whether dose-setting step torque actually acts on the coupling in the accused design,
• whether coupling behavior includes a threshold that must be overcome before rotation occurs.

If the accused device uses a ratchet pawl without a designed breakaway torque parameter, defendants argue the “initial reluctance” is not met in the claimed sense. The patentee will argue inherent resistance due to pawl angle/tooth geometry constitutes reluctance.

C. “Allowed rotation being one by which the piston rod is transported in a distal direction”

If an accused device allows one-way rotation in a direction that indirectly advances the piston only after additional steps or via gears, claim mapping may fail if the one-way coupling is not directly tied to distal transport.

D. Thread limitations: “not self locking” vs “self locking”

Thread classifications depend on lead angle, friction, materials, and lubrication. In litigation, these can become factual debates.

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5) Practical assessment: enforceable boundaries and the “thin vs thick” nature of 6,004,297

Thick area (best for enforcement)

• Devices that implement the same mechanical system:
  • piston rod guided axially but not rotated,
  • nut member threaded to the piston rod,
  • dose setting causing rotation/axial projection,
  • a one-way coupling between nut and piston guide,
  • engineered threshold behavior that blocks dose-setting torque-induced piston advance.

Thin area (most vulnerable)

• Any design that:
  • uses one-way ratcheting elsewhere in the drive train not between nut and guide,
  • lacks a “threshold/breakaway reluctance” concept (even if it has a ratchet),
  • replaces the claimed conversion steps with a different actuation scheme (e.g., direct linear drive, motorized coupling, or different clutch architecture).

Dependent claims as fallback

• If the patentee cannot prove the threshold concept as distinct from inherent ratchet behavior, it can attempt to rely on the specific ratchet geometry limitations (Claims 3-4) and the helical dose drum limitations (Claims 5-6) or alternative thread paths (Claims 7-8).
• Defendants will then attempt a “which embodiment” attack: show that the accused device is built around a different drive train path not present in the asserted dependent limitations.

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Key Takeaways

• Claim 1’s core novelty hook is a unidirectional coupling between the nut member and piston rod guide that prevents piston-advancing rotation unless an initial reluctance/breakaway torque threshold is overcome.
• The rest of the claim locks in a specific threaded conversion choreography: dose-setting rotation projects an injection button via a not self-locking thread, then axial returning converts that to rotation that advances the piston.
• Validity and infringement risk concentrate on two elements: (1) whether “initial reluctance” is materially distinct from inherent ratchet resistance, and (2) whether the one-way coupling is located and functions exactly between the claimed nodes.
• Dependent claims add fallback coverage through specific ratchet geometry and alternative helical or thread structures for dose scale and injection button lifting, but they also expand the prior art matching surface.

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FAQs

1) What is the single most distinctive limitation in 6,004,297?

The unidirectional coupling between the nut member and piston rod guide with an initial reluctance set to resist torque from the dose-setting step until a threshold is exceeded, enabling only distal piston transport rotation.

2) How does the patent convert dose-setting user input into piston movement?

Rotation of a dose setting element drives an injection button outward via a not self-locking thread connection, then returning the button axially converts movement into rotation of piston drive elements so the piston rod advances distally.

3) Do the dependent claims broaden or narrow coverage?

They narrow coverage by specifying particular implementations: click coupling (Claim 2), pawl wheel tooth geometry (Claims 3-4), helical dose drum (Claims 5-6), alternative thread in the injection button bore (Claim 7), and driver tube arrangement (Claim 8).

4) Where do infringement arguments typically succeed for this kind of patent?

When the accused device matches the full drive-train choreography and especially when it includes a one-way coupling at the nut-guide interface with a breakaway torque effect linked to preventing piston advance during dose setting.

5) What prior art category poses the biggest obviousness threat?

Mechanical dose-setting injection devices that use threaded button projection plus ratchet or one-way clutch functions to control piston advance timing and prevent backdriving, particularly those teaching asymmetric ratchet tooth profiles or torque-threshold clutches.

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References

[1] US Patent 6,004,297.

Details for Patent 6,004,297

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Novo Nordisk Inc.	NOVOLOG	insulin aspart	Injection	020986	June 07, 2000		2019-01-28
Novo Nordisk Inc.	NOVOLOG	insulin aspart	Injection	020986	January 19, 2001		2019-01-28
Novo Nordisk Inc.	NOVOLOG	insulin aspart	Injection	020986	April 23, 2004		2019-01-28

International Patent Family for US Patent 6,004,297

Country	Patent Number	Estimated Expiration
South Africa	99714
World Intellectual Property Organization (WIPO)	9938554
United States of America	RE43834