US Patent 8,517,997: Claim Scope, Patent Strength, Expiration Risk, and Dispenser-Assembly Landscape

US Patent 8,517,997 protects a plastic dispenser assembly built around a one-piece hollow plunger with a radially flexible sealing lip. The central claim concept is a lip whose relaxed outer diameter exceeds the barrel diameter, but which flexes inward during axial movement and provides the primary, and in several claims the sole, sliding contact with the barrel.

The patent is directed to a mechanical dispenser, syringe, applicator, or similar container-and-plunger system. The claims do not cover a drug compound, therapeutic method, dosage regimen, biologic, or pharmaceutical formulation. They instead cover the device architecture, material pairing, sealing geometry, and operation of the plunger within the barrel.

What does US Patent 8,517,997 protect?

The patent has four independent claim groups: claims 1, 10, 20, and 23. Each group covers a related but distinct formulation of the same technical concept.

Independent claim	Principal protected subject matter	Key additional limitations
Claim 1	Barrel and elongated plunger with hollow tip and flexible sealing lip	Lip is oversized in the relaxed state, flexes inward during actuation, and provides the sole plunger-barrel contact
Claim 10	One-piece elongated plunger with hollow cylindrical body and circumferential sealing lip	Barrel and plunger use different plastics with different translucence
Claim 20	Barrel with inner cylindrical wall and plunger shaft with circular sealing lip	Lip engages the barrel wall during actuation; different plastic materials and translucence
Claim 23	One-piece plunger with circumferential lip and air gap	Air gap between the lip and hollow tip diminishes during actuation

The claim set is therefore layered. Claim 1 is the broadest independent formulation in functional terms, while claims 10, 20, and 23 create alternative enforcement routes focused on one-piece construction, material contrast, barrel-wall engagement, and the air-gap structure.

How does the sealing-lip mechanism work?

The sealing lip is formed around the hollow tip of the plunger. In its relaxed state, the lip has an outer diameter greater than the barrel's internal diameter. The plunger therefore cannot pass through the barrel without deformation.

During axial actuation, the barrel and plunger force the lip to flex radially inward. The lip remains biased outward, creating a seal against the barrel's inner wall. The claims characterize the lip as the sole contact, sole sliding contact, or entire circumferential engagement depending on the claim.

The operating sequence is:

The plunger is inserted into the open end of the barrel.
The oversized lip contacts the inner cylindrical wall.
Axial movement causes the lip to flex inward against its outward radial bias.
The lip maintains circumferential engagement with the barrel.
The hollow tip and shaft allow the lip to deform into an air gap or internal space.
The plunger moves without a separate elastomeric gasket or secondary sliding structure.

Claim 23 gives the air-gap feature its clearest legal significance. The air gap is between the sealing lip and hollow tip. It diminishes when the plunger moves, and the lip may flex inward to reduce that space.

What are the key elements of claim 1?

Claim 1 requires all of the following:

Element	Claim requirement
Barrel	Elongated barrel with an internal cross-sectional diameter
Plunger	Elongated plunger
Hollow tip	Hollow tip portion positioned within the barrel
External body	Body extends from the tip and terminates at an upper end outside the barrel
Finger grip	Body is outwardly flared at the upper end to form a flange
Hollow cylinder	Body is a hollow circular cylinder
Internal volume	Hollow tip and hollow cylinder define an interior volume opening through the flared upper end
Flexible lip	Lip is formed on the hollow tip
Oversized relaxed diameter	Lip outer diameter exceeds barrel internal diameter when relaxed
Actuation behavior	Lip flexes inward when barrel and plunger move axially relative to each other
Contact relationship	Lip provides the sole contact between plunger and barrel

The "sole contact" limitation is important. A product with a separate plunger guide, secondary rib, lower stabilizing ring, or other barrel-contacting structure may fall outside literal claim 1 even if it uses the same flexible lip.

The phrase "closed interior volume that opens through the flared upper end" should be understood as a cavity substantially enclosed by the hollow tip and cylindrical body but communicating through the upper end. It does not require an absolutely sealed volume.

How do claims 10, 20, and 23 differ?

Claim 10: one-piece plunger and material translucence

Claim 10 requires a one-piece elongated plunger with:

a body portion;
a flared proximal portion forming a finger grip;
a hollow distal tip;
a circumferential sealing lip;
an oversized lip in the relaxed state;
inward reduction of the lip diameter during actuation; and
a barrel and plunger made from different plastic materials with different translucence.

The claim is narrower than a generic flexible-lip dispenser because it combines mechanical geometry with optical material properties. The barrel must be more translucent than the plunger. The dependent claims further narrow this to a substantially translucent barrel and substantially opaque plunger.

Claim 20: barrel-wall engagement and material pairing

Claim 20 omits the flared finger-grip requirement and focuses on a shaft extending from a hollow tip to an external upper end. The lip has a circular outer perimeter and engages the barrel's inner wall during axial actuation.

This claim can cover a plunger without the specific flange architecture in claim 1 or claim 10. It still requires the different-material translucence relationship:

first plastic material for the barrel;
second plastic material for at least the lip and shaft;
second material less translucent than the first.

Claims 21 and 22 add full-perimeter engagement and insertion from the open barrel end toward the discharge opening.

Claim 23: air-gap architecture

Claim 23 requires:

a one-piece elongated plunger;
a hollow tip;
a circumferential sealing lip;
an air gap between the lip and hollow tip;
a hollow circular cylindrical body;
an interior volume opening through the upper end; and
the different-plastic, different-translucence relationship.

Claims 24 through 27 focus on air-gap reduction, sole sliding contact, inward flexing, and outward radial bias.

The air-gap limitation may be a significant distinction over conventional plungers that use a solid tip, a separate elastomeric gasket, or a lip supported directly by a solid core.

How many patents or claim clusters cover the same invention?

The supplied claims contain four independent claim clusters and 27 dependent claims attached to those clusters. Claims 28 through 31 add the specific material combination of polypropylene for the barrel and polyethylene for the plunger.

Claim cluster	Claims	Primary scope
First lip-and-barrel architecture	1-9, 28	Flexible oversized lip, flared grip, sole contact, optional polypropylene/polyethylene
One-piece plunger and translucence	10-19, 29	One-piece plunger, material contrast, lip deformation
Shaft and full perimeter engagement	20-22, 30	Circular lip, inner-wall engagement, insertion path
Air-gap structure	23-27, 31	Air gap, lip flexure, sole sliding contact, material pairing

The claims appear designed to preserve multiple infringement theories around one commercial product. A defendant may avoid one independent claim by changing the flange, omitting the air gap, or adding a secondary contact point, but still face another independent claim.

What formulations and delivery systems are covered?

The patent does not claim a pharmaceutical formulation. Its device claims could be relevant to products using:

liquid oral dispensers;
prefilled syringes;
unit-dose applicators;
topical or ophthalmic applicators;
nasal or mucosal delivery devices;
diagnostic sample dispensers;
veterinary dosing devices; and
non-drug fluid dispensers.

The claims do not require a needle, luer fitting, drug reservoir, sterilization process, dose marking, locking mechanism, or specific discharge orifice. A product may therefore fall within the claims even if it is marketed as an applicator rather than a syringe, provided the claimed barrel, hollow plunger, and flexible-lip geometry are present.

A device with a conventional elastomeric stopper is less likely to satisfy the literal claims because the patent emphasizes a flexible lip formed on the hollow tip, generally in a one-piece plastic plunger.

What materials are specifically protected?

Claims 28 through 31 expressly identify polypropylene for the barrel and polyethylene for the plunger.

Component	Claimed material
Barrel	Polypropylene
Plunger	Polyethylene

The broader claims do not require those exact polymers. They require different materials and, in claims 10, 20, and 23, a translucence relationship in which the plunger material is less translucent than the barrel material.

Potentially relevant material combinations include:

translucent polypropylene barrel with opaque polyethylene plunger;
transparent or translucent polyolefin barrel with an opaque polyolefin plunger;
a barrel made from one plastic and a plunger made from another plastic with lower light transmission.

Claims 13 and 20 require, in different ways, that the barrel or plunger be made entirely, or at least substantially, from the identified material. A multi-material plunger may create a non-infringement argument if the accused lip or shaft does not use the claimed second material. That argument depends on the exact claim construction and prosecution history.

What design-around strategies could avoid literal infringement?

The strongest design-around options target limitations repeated across the independent claims.

Use a lip that is not oversized in the relaxed state

A lip with an outer diameter equal to or smaller than the barrel diameter in the relaxed state could avoid claims requiring an oversized relaxed diameter. A separate elastic seal could then expand into contact after insertion.

Add a second plunger-barrel contact structure

Claims 1 and 24 require sole contact or sole sliding contact in specified circumstances. A guide rib, stabilizing ring, bearing surface, or other contact element could create a non-infringement position. The added structure would need to be engineered without recreating an equivalent circumferential sealing function.

Use a solid plunger shaft

The hollow circular-cylinder limitation appears repeatedly. A solid shaft with a flexible peripheral seal could avoid claims requiring the hollow cylinder and interior volume.

Eliminate the air gap

A solid-supported lip, foam-backed lip, or lip joined directly to the tip may avoid claims 23 through 27. This design would still need to address claims 1, 10, and 20.

Use the same material for barrel and plunger

Claims 2, 10, 12, 13, and 20 emphasize different materials or different translucence. Using the same polymer, or using a plunger that is not less translucent than the barrel, could avoid those limitations. This would not necessarily avoid claim 1 if the product otherwise meets its structural and functional elements.

Change the lip orientation

Claim 9 and claim 18 expressly require an axially directed lip. A radially oriented or differently shaped sealing element may avoid those dependent claims, although the broader independent claims may remain relevant.

Use a separate elastomeric gasket

A conventional plunger stopper can avoid the one-piece hollow-tip architecture. The risk is lower if the elastomeric stopper is mechanically separate from the plunger body and the plunger has no claimed circumferential flexible lip.

How strong is the patent estate based on the claims?

The claim estate has moderate structural breadth but substantial element density.

Strengths

Four independent claims cover different descriptions of the same device.
The central lip concept is repeated across the claim set.
Claims cover both structure and operation.
Polypropylene and polyethylene are expressly identified.
The claims address one-piece construction, circumferential engagement, radial bias, air-gap reduction, and material translucence.
Claims 20 and 23 omit some of the flange-specific limitations in claim 1.

Vulnerabilities

The claims contain many limitations that may be difficult to prove from an assembled commercial product.
"Sole contact" can be defeated by a secondary guide or contact surface.
The material and translucence limitations may exclude products using clear or similarly translucent plunger materials.
The exact meaning of "closed interior volume that opens" may be contested.
"Actuated axially relative to one another" requires evidence of actual movement and deformation.
Claims 1, 10, and 23 appear to overlap heavily, increasing potential validity and double-patenting scrutiny.
Conventional syringes with flexible one-piece plastic seals may present novelty or obviousness challenges depending on the cited prior art.

The most defensible commercial position would likely focus on a product that uses all of the following: a one-piece hollow plastic plunger, a circumferential oversized lip, radial inward flexure during insertion and actuation, no other sliding contact, and a more opaque polyethylene plunger inside a more translucent polypropylene barrel.

What prior-art categories are most relevant?

The relevant patent landscape is likely concentrated in five technical categories.

Conventional elastomeric syringe stoppers

These references disclose a barrel and plunger with a sealing member. Their principal distinction is usually a separate rubber or elastomeric stopper rather than an integral plastic sealing lip.

One-piece plastic plungers

These references may disclose molded plastic plungers with integral sealing rings or lips. They are the closest prior-art category because they can address the one-piece construction and circumferential seal.

Flexible-lip and bellows seals

References in this group disclose lips that bend, roll, or flex under axial pressure. The key comparison is whether the lip is oversized in the relaxed state and flexes inward against a radial outward bias.

Hollow-tip and air-gap designs

These references may disclose a hollow plunger tip that permits a sealing ring to deform into an internal cavity. They are especially relevant to claims 23 through 27.

Dual-material dispenser systems

These references address a translucent barrel paired with an opaque plunger, often for visual dose measurement or product presentation. They may be relevant to the material and translucence limitations even if they do not disclose the claimed sealing geometry.

A validity challenge would likely combine one reference showing a one-piece flexible-lip plunger with another showing the selected plastic materials or translucence contrast. The principal issue would be whether the combination supplies a reason to use the air gap, hollow body, oversized relaxed diameter, and sole-contact configuration together.

What is the Orange Book status of US 8,517,997?

US 8,517,997 is a device patent based on the supplied claims. The claims do not identify an active pharmaceutical ingredient, drug formulation, method of treatment, or dosage regimen.

The patent therefore should not be treated as an Orange Book drug patent merely because the claimed dispenser could deliver a drug. Orange Book listing generally concerns patents submitted for an approved drug product, including drug substance, drug product, or method-of-use patents. A device patent may be relevant to a drug-device combination product, but its listing status cannot be determined from the claim text alone (FDA, 2024; 21 C.F.R. § 314.53).

There is also no biosimilar claim scope in the supplied patent. Biosimilar litigation under the Biologics Price Competition and Innovation Act concerns biologic products and related patents, not the mechanical dispenser architecture claimed here (42 U.S.C. § 262).

When does US 8,517,997 lose exclusivity?

The claims supplied do not establish the patent's filing date, earliest effective priority date, patent-term adjustment, terminal disclaimer, reexamination history, or post-grant status. Those facts control the enforceable expiration date.

For a modern utility patent, the ordinary term is generally 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment and other statutory provisions (35 U.S.C. §§ 154, 156). Patent expiration should therefore be determined from the USPTO Patent Center record and the patent's front-page term information, not from the claim language.

The patent's exclusivity is also limited by:

claim validity;
written-description and enablement requirements;
prosecution-history estoppel;
terminal disclaimers;
maintenance-fee status;
reexamination or post-grant proceedings;
assignment and licensing rights; and
any litigation judgment or settlement.

What Paragraph IV risks exist?

A generic or follow-on applicant would face a Paragraph IV issue only if the dispenser patent is listed for the relevant approved drug product and the applicant's product is alleged to infringe. The patent claims alone do not establish such listing.

If listed, likely Paragraph IV positions would include:

Challenge theory	Relevant claim issue
Non-infringement	Product uses a separate stopper, solid shaft, or additional sliding contact
Non-infringement	Lip is not oversized in the relaxed state
Non-infringement	Plunger is not less translucent than the barrel
Non-infringement	No air gap exists between lip and tip
Invalidity	Flexible one-piece plastic lip was anticipated
Invalidity	Claimed geometry was obvious over syringe-seal references
Invalidity	Material and translucence limitations lack adequate inventive significance
Written description	Specific combinations were not adequately supported in the original disclosure

The most commercially important question would be whether a generic manufacturer can retain an equivalent dispensing performance while eliminating at least one repeated structural limitation.

What litigation and licensing issues matter?

The claim set supports litigation against manufacturers of molded plastic syringes and applicators, but the supplied information does not identify parties, complaints, settlements, licenses, or court rulings. No litigation or licensing conclusion should be drawn from the claims themselves.

For diligence, the legally material records are:

USPTO Patent Center prosecution history;
assignment records;
maintenance-fee records;
Patent Trial and Appeal Board proceedings;
PACER and district-court dockets;
International Trade Commission investigations;
FDA product labeling and device descriptions; and
commercial product specifications.

A settlement could narrow enforcement rights without changing the issued claims. A license could also divide rights by field, customer, territory, or product type. Those arrangements are not visible from the claim language.

How does this patent compare with conventional syringe patents?

Issue	US 8,517,997 claim concept	Conventional syringe design
Seal type	Integral flexible plastic lip	Often separate elastomeric stopper
Plunger construction	Hollow tip and hollow cylindrical body	Often solid or separately assembled
Relaxed lip diameter	Greater than barrel diameter	May be equal to or below barrel diameter
Actuation	Lip flexes inward during axial movement	Stopper compresses or slides
Contact	Sole or sole sliding contact in several claims	Multiple guides or sealing surfaces may exist
Air gap	Expressly claimed in claim 23 group	Not necessarily present
Material contrast	Barrel more translucent than plunger	Not generally required
Polymer pairing	Polypropylene barrel and polyethylene plunger in claims 28-31	Broad range of glass, elastomer, and plastics

The patent's differentiation is strongest against all-plastic dispensers using the specific lip-and-cavity arrangement. Its differentiation is weaker against products using conventional rubber plungers or mechanically distinct sealing components.

Key Takeaways

US 8,517,997 is a device patent covering a plastic barrel and plunger assembly, not a drug or biologic patent.
The core invention is an oversized, circumferential, flexible sealing lip formed on a hollow plunger tip.
The lip flexes inward during axial actuation while remaining biased radially outward.
Claims 1, 10, 20, and 23 create four overlapping independent claim clusters.
Claims 10, 20, and 23 add different-translucence plastic materials, generally requiring a more opaque plunger than barrel.
Claims 28 through 31 specifically recite a polypropylene barrel and polyethylene plunger.
The strongest design-around routes are a separate elastomeric stopper, a solid shaft, an additional plunger-barrel contact, elimination of the air gap, or use of the same material and translucence for both components.
The patent does not establish Orange Book, biosimilar, Paragraph IV, litigation, settlement, licensing, or current enforceability status.
The exact expiration date cannot be derived from the claims and must be determined from the patent's term and maintenance records.
The principal validity risks are prior art involving one-piece plastic flexible-lip plungers, hollow-tip seals, air-gap deformation, and dual-material dispenser construction.

FAQs

Does US 8,517,997 cover a standard disposable syringe?

Not necessarily. A standard syringe with a separate elastomeric stopper may not contain the claimed one-piece hollow plunger and integral circumferential sealing lip. Infringement depends on the specific construction.

Can a transparent plunger avoid the patent?

It may avoid claims requiring the plunger material to have lower translucence than the barrel. It would not automatically avoid claim 1 if the remaining structural and functional limitations are satisfied.

Does the patent require a medication inside the barrel?

No. The claims recite the dispenser assembly itself and do not require a drug, active ingredient, formulation, or therapeutic use.

Is an air gap required for every claim?

No. The air-gap limitation is concentrated in claim 23 and its dependent claims. Claims 1, 10, and 20 do not expressly require the same air-gap configuration.

Are polypropylene and polyethylene mandatory materials?

No. They are expressly required only by claims 28 through 31. The broader claims use different-material and translucence limitations, depending on the claim.

References

35 U.S.C. § 154. Patent term.
35 U.S.C. § 156. Patent term extension.
35 U.S.C. §§ 112, 271, 282. Patent validity, infringement, and defenses.
42 U.S.C. § 262. Biologics Price Competition and Innovation Act.
21 C.F.R. § 314.53. Submission of patent information for approved drug products.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations.
U.S. Patent No. 8,517,997, claims 1-31. United States Patent and Trademark Office.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2003221794	⤷ Start Trial
World Intellectual Property Organization (WIPO)	03093108	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 8,517,997