The Precedent: Federal Circuit Confirms Limits on Claim Scope in Magnolia Med. Techs., Inc. v. Kurin, Inc.

Authored by Graham Christian

In this edition of The Precedent, we outline the decision in Magnolia Med. Techs., Inc. v. Kurin, Inc.

Overview

In Magnolia Medical Technologies, Inc. v. Kurin, Inc., the Federal Circuit affirmed a judgment of noninfringement on two patents covering devices that reduce contamination in blood cultures.  For one patent, the Federal Circuit held that independently recited “vent” and “seal member” elements must be separate structures, which Kurin’s device did not have under Magnolia’s trial theory.  For the other, the Federal Circuit agreed that “diverter” is a means‑plus‑function term and that Kurin’s different internal mechanism does not satisfy that limitation.

Issues

1. Did the district court properly grant judgment as a matter of law (JMOL) to Kurin of no infringement of claim 1 of Magnolia’s ’483 patent?
2. Is “diverter” in Magnolia’s ’001 patent a means‑plus‑function term limited to the structure disclosed in the specification and equivalents, and does Kurin’s device include such a structure?

Holdings

1. Claim 1 of the ’483 patent requires separate “seal member” and “vent” structures. Magnolia’s infringement case, which mapped both to a single porous plug, cannot support the jury’s verdict.  JMOL was therefore proper.
2. “Diverter” in the ’001 patent invokes means‑plus‑function treatment. By stipulation, Kurin’s device lacks the corresponding structure and equivalents, so the ’001 patent is not infringed

Background and Reasoning

Technology and The Kurin Lock

Blood culture tests can be falsely positive when the first portion of a blood draw carries skin bacteria into the sample bottle.  Magnolia’s patents describe devices that automatically trap this initial blood volume and allow only later blood to reach the collection container.

Kurin’s “Kurin Lock” is a small in‑line device.  Internally, blood entering the device reaches a junction leading to:

• a U‑shaped side channel that ends at a porous plug in a cap; and
• a main channel that leads toward the collection bottle.

At the start of the draw, air escapes through the dry porous plug so the initial blood flows into the side channel and displaces air.  When blood reaches the plug, it is absorbed, the plug swells and its pores close, thereby sealing the side channel and trapping the initial blood.  Once the downstream tubing is opened, subsequent blood flows only through the main channel to the bottle.  Thus, the same porous plug acts first as a vent for air, then as a seal for blood.

‘483 Patent: “Vent” and “Seal Member” Must Be Separate

Claim 1 of the ’483 patent recites a reservoir “at least partially defined by a seal member” and “a vent … configured to allow air to exit the housing as blood enters the fluid reservoir.”  At trial, the parties did not ask for a specific construction of the “vent” and “seal” limitations.  The jury thus applied plain meaning and found infringement.

On Kurin’s post‑trial motion for JMOL, the district court held that the claim language requires separate structures for the “vent” and “seal” limitations, thereby granting Kurin’s motion.  It relied on Becton, Dickinson & Co. v. Tyco Healthcare Group, which explains that separately listed elements ordinarily refer to distinct components.  Claim 1 uses “comprising” followed by “a … seal member” and “a vent,” joined by “and.”  The specification likewise shows a plunger serving as the seal and separate vents for air escape.

Magnolia challenged the district court’s grant of JMOL by first arguing that the district court improperly adopted a late claim construction but the Federal Circuit viewed it as a clarification inherent in the plain‑language reading.  Magnolia then argued that the separate-structure construction was incorrect, pointing to a dependent claim that mentions the seal preventing air flow “through the vent,” arguing that this would be redundant if claim 1 already required distinct structures.  The Federal Circuit disagreed, explaining that the dependent claim simply adds a specific functional relationship between the already separate seal and vent.

Finally, Magnolia argued that the jury had sufficient evidence to find infringement even under the separate-structure construction by recasting the umbrella valve of the Kurin Lock as the seal and the porous plug as the vent.  At trial, however, Magnolia’s expert testified that the porous plug alone was both the “seal member” and the “vent.”  The Federal Circuit, therefore, declined to entertain this new theory since Magnolia had not presented it to the jury.  Under the correct construction and Magnolia’s trial mapping, no reasonable jury could find infringement.  The Federal Circuit affirmed judgment as a matter of law of noninfringement for the ’483 patent.

‘001 Patent: “Diverter” as Means-Plus-Function

The related ’001 patent claims an apparatus with a reservoir and “a diverter having an inlet, a first outlet in fluid communication with the reservoir, and a second outlet.”  The diverter operates in a first mode where initial blood flows to the reservoir and in a second mode where subsequent blood bypasses the reservoir to the second outlet while the initial volume is prevented from flowing farther.

The key question was whether “diverter” is a means‑plus‑function term.  Such terms describe what something does, not what it is, and are limited to the structure disclosed in the patent for performing the function and equivalents.

Magnolia argued that “diverter,” combined with the recited inlets and outlets, connotes sufficient structure to overcome a means-plus-function construction.  Kurin argued that the claim does not explain how the device directs blood flow.  The district court agreed with Kurin and the Federal Circuit affirmed.  It noted that “diverter” here is a functional label.  The inlets and outlets define paths, not structural features actively directing the fluid behavior.  By contrast, the specification describes specific internal components of the claimed “diverter” that physically redirect blood flow in addition to the claimed inlets and outlets.

The Federal Circuit concluded that, in context, “diverter” does not name a particular structure and, therefore, falls under the means‑plus‑function statute.  In the district court, the parties had stipulated that, under a means‑plus‑function construction of “diverter,” Kurin’s Kurin Lock lacks the required structure and equivalents.  Once the Federal Circuit agreed that “diverter” is a means‑plus‑function term, that stipulation compelled affirmance of noninfringement for the ’001 patent.

Takeaway

Magnolia illustrates two recurring themes.  First, when claims recite elements separately, courts will expect separate physical structures unless the patent clearly teaches otherwise.  Building an infringement case on one component doing double duty can be risky.  Second, using broad functional nouns like “diverter” without describing the concrete mechanism invites means‑plus‑function treatment and can confine claim scope to the specific structures shown in the specification.  Thoughtful claim drafting and early claim‑construction strategy can prove critical.