US Patent 5,891,086 (Needle-less Injector Actuator): Claim Scope, Coverage Boundaries, and US Patent Landscape
Executive summary: US Patent 5,891,086 claims a gas-pressurized actuator for a needle-less injector using a cartridge with a free piston acting on a liquid, with an impact member restrained by a latch until a firing position is reached. The independent claim is tightly structured around: (i) constant gas force communication with the impact member, (ii) a latch that prevents impact member movement despite gas force, and (iii) an actuator-cartridge mechanical interface where impact drives the piston to expel a single fixed dose. Dependent claims broaden into residual gas venting, air as the gas, trigger by contact force, and multi-dose language (claim 9), and further into mixing/multi-component cartridges (claims 10 and 23) and specific materials (glass body; PTFE and fluorinated polymers for the free piston, claims 17-22).
Below is a practical claim-by-claim scope map, then the US freedom-to-operate implications and the likely competitive patent landscape around needle-less injector actuators, cartridge-free-piston architectures, gas-latched firing, and on-cartridge mixing.
What does US Patent 5,891,086 claim cover for needle-less injector actuators?
Core coverage (independent claim 1): An actuator used with a prefilled cartridge to form a needle-less injector, where:
- The cartridge has:
- a liquid outlet
- a free piston inside the cartridge in contact with the liquid
- The actuator has:
- (a) a housing connectable to the cartridge
- (b) an impact member movable from a first position toward the forward portion to strike the free piston, then continue moving to expel a dose through the liquid outlet
- (c) a sealed/closed chamber (within the housing) prefilled with pressurized gas that is in constant communication with and constantly exerts force on the impact member, normally urging it toward the outlet
- (d) a latch within the housing that engages the impact member to prevent its movement toward the forward portion in response to the gas force, and is movable to a firing position where it permits movement
Claim-structure implication: Claim 1 is not just “gas-powered needle-less injection.” It is specifically a gas-as-continuous-bias + latch-as-shot-determiner architecture, where the gas force exists while the latch restrains the actuator until firing.
How strong is claim 1’s “latch despite constant gas force” limitation
This is a high-leverage limitation because many needle-less injectors use one of these variants:
- gas pressure only applied/valved at firing (no “constantly in communication” feature)
- springs used for stored energy rather than a constantly acting pressurized gas bias
- gas reservoirs that do not maintain constant force on the impact member before firing (or communication is not “constant”)
The “latch engages to prevent movement in response to said force” language ties infringement to a mechanism where the force is present and the latch counters it until firing.
Which elements in claim 1 are most likely to be required for infringement?
Most required elements (high certainty):
- Actuator + housing that connects with the cartridge
- An impact member that strikes the free piston and continues to drive it to expel liquid
- A gas-pressurized chamber in the actuator that:
- is prefilled
- is constantly in communication with and constantly exerts force on the impact member
- A latch that:
- engages the impact member to prevent motion due to the gas force
- moves to a firing position that releases the impact member
Material/format limitations are not in claim 1 (they appear in dependent claims 17-22 and claim 23).
What does claim 2 add: residual gas outlet and sealed chamber?
Claim 2
Adds a gas outlet in the chamber for allowing residual gas to escape after the dose is expelled.
Practical scope: Coverage extends to designs that include a vent/escape path so the pressurized chamber does not remain pressurized post-shot.
Claim 11 (sealed chamber)
Adds that the chamber is sealed.
Boundary effect: Designs that require open communication to atmosphere prior to firing may fall outside claim 11 but can still fall within claim 1 if other limitations are met. Claim 2 and claim 11 operate as dependent limitations.
How do claims 3 and 7 define latch actuation mechanisms?
Claim 3 (cam engageable with camming surface)
Introduces a cam structure that moves the latch to the firing position.
Design around: If the firing mechanism uses an electromagnet, piezo, solenoid release, or direct mechanical trigger without a cam-to-camming-surface function, claim 3 may not be met though claim 1 still might.
Claim 7 (resilient latch member)
Adds resilience to the latch member.
Boundary effect: A latch made of rigid non-resilient structure may avoid claim 7 but still infringe claim 1.
What does claim 4 require about pressurized gas (air)?
Claim 4 narrows to pressurized gas being air.
Design around: Use nitrogen, CO₂, or another gas would typically avoid claim 4. Broader claim 1 covers “pressurized gas” generically, and only claim 4 restricts to air.
How does claim 5 trigger firing: contact force vs direct user action?
Claim 5
Adds trigger means that operates the latch to initiate injection in response to a predetermined contact force between:
- the liquid outlet of the cartridge
- and the subject
This maps to “contact-actuated firing” (safety interlock against accidental discharge).
Design around: A design that fires based on a timer, a user trigger switch independent of contact force, or a different sensed parameter may avoid claim 5.
What does claim 6 cover: relative movement between user-holdable portion and cartridge?
Claim 6
Introduces:
- actuator has a user-holdable portion
- cartridge mounting allows relative movement between user-holdable portion and cartridge
- trigger occurs by relative movement when the liquid outlet is urged into contact
- latch comprises a latch member movable to firing position by relative movement
This is a common mechanical safety architecture, and the claim text is structured to capture it specifically.
Claim 8 and dose size
- Claim 8: gas energy sufficient for a single dose
- Claim 9: gas energy sufficient for a plurality of successive doses
Inconsistency note for claim interpretation: The independent claim 1 describes expelling “a dose,” and claim 9 expressly anticipates multi-shot embodiments. If an accused product is single-use, claim 9 may be irrelevant; if multi-use, claim 8 may be narrower but still potentially asserted depending on how “energy stored … sufficient” is satisfied.
How do claims 10 and 23 extend to on-cartridge component mixing?
Claim 10
Actuator in combination with a cartridge including:
- separately held plurality of components to be mixed prior to injection
- a mixing member for mixing
- impact member includes a mixing means movable toward the outlet to strike the mixing member
- the strike triggers movement enabling component mixing
Claim 23 (expanded mixing + penetrating member through partition)
This is a more detailed mixing cartridge architecture. It adds:
- cartridge components separated by at least one partition
- cartridge has a penetrating member movable to a mixing position by penetration of the partition
- actuator impact/mixing means strikes the mixing member such that it moves penetrating member to the mixing position
High-value infringement hook: Claim 23 requires both (i) partition-separated components and (ii) a penetrating member moved into a mixing position by the mixing member struck by the actuator impact/mixing means.
Design around: If mixing is achieved by purely fluidic mixing, without a partition-penetrating member, or without partitioned compartments, claim 23 may be avoided.
What is protected by the specific material limitations in claims 17–22?
These are combination claims, where cartridge structure matters:
Claim 17–18: cartridge body glass (transparent)
- cartridge body comprises glass
- glass is transparent
Claim 19–22: free piston plastic, especially PTFE and fluorinated polymers
- free piston comprises plastics material
- plastic is a polymer/copolymer comprising a fluorinated hydrocarbon
- examples include polytetrafluoroethylene (PTFE)
- expanded list includes:
- tetrafluoroethylene-hexafluoropropylene copolymer
- tetrafluoroethylene-ethylene copolymer
- polychlorotrifluoroethylene
- poly(vinylidene fluoride)
- tetrafluoroethylene-perfluoro(propyl vinyl ether) copolymer
- hexafluoroisobutylene-vinylidene fluoride copolymer
Scope boundary: These dependent limitations narrow the infringement set to products matching those materials. Most products using elastomers (e.g., silicone rubber seals) or different polymer types would not satisfy these claims even if the actuator architecture is similar.
What does claim 24 cover: method of injecting using gas-latch impact?
Claim 24 is a method claim including the same structural-latent limitations:
- injector with:
- cartridge having free piston
- impact member movable from behind free piston to strike and then expel
- chamber prefilled with pressurized gas constantly contacting and exerting force in first position
- latch movable from restraining position to firing position (engages to prevent movement in response to gas force, then releases)
- method steps include causing latch movement to firing position so impact member moves, strikes free piston, expels a single dose
If litigated: Method claims often face easier proof of use in some fact patterns, but they still require the presence of the claimed injector architecture at the time of injection.
Claim 25
Adds disposing of the injector after the single dose.
What is the practical “claim estate map” across likely design choices?
Claim scope by design axis
| Design axis |
Claim coverage in US 5,891,086 |
Key limitation words |
| Gas actuator architecture |
Yes (claim 1) |
“prefilled with pressurized gas,” “constantly in communication,” “constantly exerts a force,” “normally urge” |
| Restraint until firing |
Yes (claim 1, 24) |
“latch … engages … prevent movement … in response to said force,” “movable out of engagement … to a firing position” |
| Contact-force actuation |
Yes (claim 5, indirectly claim 6) |
“predetermined contact force between … liquid outlet … and subject” |
| Dose sizing |
Yes (claims 8–12 implied by dose/venting) |
“sufficient to expel a single dose” vs “plurality of successive doses,” distance of travel (claim 13) |
| Dose metering by travel |
Yes (claim 13) |
“distance of travel … determines the dose” |
| Residual gas venting |
Yes (claim 2) |
“gas outlet … allowing residual gas to escape” |
| Mixing on-cartridge |
Yes (claims 10, 23) |
partition-separated compartments + penetrating member + actuator mixing means striking mixing member |
| Cartridge material constraints |
Yes (claims 17–22, and claim 23 depends on cartridge) |
glass transparent; PTFE and specific fluorinated polymers |
How might US 5,891,086 be used in litigation: claim charts likely focus on latch/gas communication/impact-to-piston interface?
In an infringement posture, the highest-friction factual disputes are usually:
- Whether the gas force is “constantly in communication” with the impact member pre-firing
- Whether a latch restrains the impact member while gas pressure is acting
- Whether the latch “moves to a firing position” permitting movement
- Whether an impact member strikes a free piston (not a diaphragm, not a seal stack, not a different energy transfer element)
- Whether dose is metered by travel (claim 13)
- Whether the product has partition-separated components with a penetrating member (claim 23)
How does US 5,891,086 compare with common needle-free injection designs?
Typical competitors that could evade claim 1
- Spring-driven plungers where energy is stored mechanically rather than by constant pressurized gas acting on an impact member
- Gas valves that open at firing so pressure is not “constantly” exerted prior to release
- Solenoid/piezo release mechanisms where no latch “prevents movement in response to gas force”
- Cartridges where injection is driven by a rigid cartridge internal piston that is not struck by a separate impact member (or no impact member moving from a first position to strike)
Typical overlaps likely to increase infringement risk
- Cartridge with internal free piston in contact with liquid to outlet
- Actuator containing a gas reservoir connected to a movable impact member
- A mechanical safety latch that blocks movement until a contact-force trigger or relative movement triggers release
- Shot metering by piston travel distance
What does the independent claim likely cover commercially for needle-less injector platforms?
A broad reading of claim 1 covers a platform rather than a single formulation: it protects an actuator-cartridge system where:
- cartridges are prefilled with liquid
- an actuator drives a free piston via impact
- constant gas bias and latch release control firing
This aligns with common “single-use disposable cartridge + reusable actuator” models, and with disposable mixed-component cartridges.
What US patent landscape exists around gas-latch needle-less injectors and mixing cartridges?
Landscape structure that typically clusters around this claim:
- Actuator mechanisms for needle-free injection:
- gas reservoirs, pistons, impact members, latch/trigger interlocks
- Cartridge architectures:
- free pistons, prefilled reservoirs, seals and outlets, replaceable disposable cartridges
- On-cartridge mixing:
- multi-chamber compartments, partitions, penetrating members, mixing needles/rods, internal turbulence or plunger-driven mixing
- Dose metering:
- travel-distance metering, fixed stroke, volume control via stroke limits and seals
- Materials:
- low-friction fluoropolymers, transparent glass housings, barrier layers, chemical compatibility
Business implication: Claim 1 is a defensible hook for actuator architecture, while claims 10 and 23 extend the estate into mixing cartridge technology that can be valuable if the therapeutic is reconstituted at use.
Key takeaways
- US 5,891,086 is anchored on a latch-controlled release of an impact member that is constantly urged by prefilled pressurized gas toward a cartridge free piston.
- The strongest infringement vector is mechanism identity: constant gas force acting through communication with the impact member, restrained by latch until firing position.
- Dependent claims expand into contact-force triggered firing, residual gas venting, dose metering by impact member travel, and on-cartridge mixing using partition-penetrating members.
- The narrowest coverage is in cartridge materials (glass and specific fluorinated polymers like PTFE) in claims 17–22.
- The overall estate should be valued as a platform patent for needle-less injectors, with higher specificity when the design also incorporates internal mixing mechanics and specific polymer/glass constraints.
FAQs
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What part of US 5,891,086 is most likely to be required to prove infringement?
The gas chamber being prefilled and constantly communicating with the impact member while a latch prevents impact member movement until a firing position.
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Does US 5,891,086 cover contact-force triggered firing?
Yes. Claim 5 requires trigger means operating the latch in response to a predetermined contact force between the liquid outlet and the subject.
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Is on-cartridge mixing covered by this patent?
Yes. Claims 10 and 23 cover mixing where actuator-driven impact/mixing moves a mixing mechanism, including partition-separated components and a penetrating member moved into a mixing position.
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Do the fluoropolymer and glass limitations apply to every claim?
No. Those material limitations appear in dependent/combination claims (17–22, and the cartridge-specific portion of claim 23), not in claim 1’s actuator core.
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What design choices are most likely to avoid the broader actuator claims?
Architectures where gas pressure is not constantly exerted on the impact member pre-firing, or where firing is not controlled by a latch that restrains movement in response to that force, or where energy transfer does not involve striking a cartridge free piston.
References (APA)
- United States Patent and Trademark Office. (n.d.). U.S. Patent 5,891,086 (Needle-less injector actuator).
