A recent court decision brings some traditional patent claim language into doubt.
By Kirk Teska
Ever
wonder exactly what your own or a competitor's patent really covers? Certain
long-held assumptions regarding patents are now being called into question.
In a recent case, Toro held three patents for a soil-aerating machine
that delivers water under pressure to a series of nozzles. Water slugs
ejected by the nozzles fracture the soil to encourage turf growth. Toro's
patents described an example where a mechanical cam-based system functions
to open and close a valve to deliver pressurized water to the nozzles.
John Deere entered the market with its own aerating machine. Instead of
using a cam-based system to control the valve, however, Deere's
design employed a solenoid.
Toro sued, but in the end, Deere successfully fended off the charge of
infringement, largely because Toro's patent claims recited "control
means" for delivering the pressurized water to the nozzles. One
rule concerning apparatus patent claims is that they must recite structural
elements—a minimum of one of which is new. But how does one protect
a cam-based subsystem for controlling the delivery of water to the nozzles
and also protect other equivalent subsystems that accomplish the same
result?
One specific patent law eases the burden of claim drafting in situations
like this by allowing the use of so-called "means plus function"
claim language. Basically, the idea is the use of special patent claim
language approved by Congress as a shorthand reference to specific structure
disclosed in the specification of the patent. So, instead of specifically
claiming a cam-based subsystem for controlling the delivery of water to
the nozzles, Toro's patent claims recited "control means"
or a "control mechanism."
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| The aerating machine, as drawn in Toro's patent. |
Building upon a series of cases where patent claims including "means"
clauses were found to be rather restrictive, the high patent court (the
Court of Appeals for the Federal Circuit in Washington, D.C.) in the Toro
case recently gave patent attorneys a good reason not to use the shorthand
"means plus function" language in patent claim drafting.
In the January 2004 case, Toro's patent claims recited the aerator's
pressurized water source, the nozzles, and "control means"
or a "control mechanism" connecting the pressurized water
to the nozzles in a controlled way.
Toro's patents disclose a gasoline engine-driven aerator and discuss
how slugs or jets of incompressible liquid such as water, liquid fertilizer,
or weed killer exit nozzles to penetrate the soil to reduce soil compaction.
To create the slugs of water, the valve controlling the delivery of the
liquid to the nozzles has to open and close very fast. To control the
valve, Toro implemented the cam-based subsystem and described that subsystem
as an example of the control means or mechanism claimed in the patents.
According to the Toro patents, the valve stem is normally closed, preventing
the fluid from entering a valve chamber and exiting an output connection.
The valve stem is connected to the plunger of a slide mechanism and a
compression spring biases the plunger and the stem toward the valve. The
slide mechanism is connected to the frame so that it can move in a vertical
direction only. The slide mechanism has a cam follower that rides in a
cam. The cam track has a cam follower actuator that moves the slide mechanism
into a downward direction with each revolution of the cam. The downward
movement of the slide mechanism pulls the valve stem away from the output
port and allows the high-pressure liquid from the fluid conduit to enter
the valve chamber and exit out of the output connection into a discharge
tube and, ultimately, through the output ports of the nozzles.
When John Deere came out with its own aerating machine that also used
pressurized water and nozzles, the only important difference was that
Deere employed an electrically operated solenoid as opposed to Toro's
cam subsystem to control the valve that delivered water to the nozzles.
Toro asserted that cams and solenoids can be used interchangeably and
that, when its patent claims recite "control means" or a
"control mechanism," a solenoid constitutes another infringing
example of a control means or mechanism.
Cams vs. Solenoids
However, because the same function—controlling the flow of water
to the nozzles—was carried out in different ways in the competing
machines, the court held that Toro's claimed "control means"
was a narrow patent restriction covering the cam system but not Deere's
solenoid. Cams and solenoids don't work the same way, the court
held: a mechanical lifter versus electromagnetism. According to the court,
"no reasonable fact finder" would see Deere's solenoid
system as the equivalent of Toro's cam-based system.
Thus, the downside associated with the convenience of using the special
means claim language is that you could be severely limited in any attempt
to put a stop to competing products, other than those configured exactly
as specified in the body of your patent. Until we are more sure, means
type language in patent application claims should be carefully scrutinized.
As Toro discovered, you may pay a high price for the convenience of employing
means plus function claim language in patent claims.
If drafting patent claims is difficult, interpreting them is more so:
Claim interpretation is not an exact science, say the courts. As a result,
the difference between what you and a court thinks your patents cover
may differ sharply. And remember, in one instance, Toro's patent
claims recited a control "mechanism." That's no different
from control means, held the court. So, be cautious, too, of claim language
that doesn't even include the word "means."
Kirk Teska is a patent attorney with the law firm
of Iandiorio & Teska in Waltham, Mass.