When a patent is for an improvement of an existing machine or
contrivance, the patentee in a suit for damages for infringement
must either show by reliable, tangible proof that the value of the
machine or contrivance as a whole is due to the use of his patented
invention or he must separate and apportion, by proof of the same
character, the part of the defendant's profits which are derivable
from the use of it in order to establish a claim for more than
nominal damages.
This was a suit in equity for infringement of a patent for an
improved mop head. The sole question raised was whether the
evidence of damages warranted a judgment for more than nominal
damages.
MR. JUSTICE FIELD delivered the opinion of the Court.
In this case the court below sustained the plaintiff's patents,
adjudged that the defendants were infringers, and directed a
reference to a master to ascertain and report the profits and gains
made by the defendants. The master reported that no proof was
presented to him that they had made any profit or
Page 111 U. S. 121
that the plaintiffs had suffered any damages. The court
sustained the report, and the decree allowed the plaintiffs only
nominal damages. From this decree the appeal is taken.
Garretson v. Clark, 15 Blatchford 70.
The patent was for an improvement in the construction of mop
heads, which may be described with sufficient accuracy as an
improvement in the method of moving and securing in place the
movable jam or clamp of a mop head. With the exception of this mode
of clamping, mop heads like the plaintiff's had been in use time
out of mind. Before the master, the plaintiff proved the cost of
his mop heads and the price at which they were sold, and claimed
the right to recover the difference as his damages. This rule was
rejected, and, no other evidence of damages being offered, the
master reported as stated. When a patent is for an improvement, and
not for an entirely new machine or contrivance, the patentee must
show in what particulars his improvement has added to the
usefulness of the machine or contrivance. He must separate its
results distinctly from those of the other parts, so that the
benefits derived from it may be distinctly seen and appreciated.
The rule on this head is aptly stated by Mr. Justice Blatchford in
the court below: "The patentee," he says,
"must in every case give evidence tending to separate or
apportion the defendant's profits and the patentee's damages
between the patented feature and the unpatented features, and such
evidence must be reliable and tangible, and not conjectural or
speculative, or he must show by equally reliable and satisfactory
evidence that the profits and damages are to be calculated on the
whole machine, for the reason that the entire value of the whole
machine, as a marketable article, is properly and legally
attributable to the patented feature."
The plaintiff complied with neither part of this rule. He
produced no evidence to apportion the profits or damages between
the improvement constituting the patented feature and the other
features of the mop. His evidence went only to show the cost of the
whole mop and the price at which it was sold. And, of course, it
could not be pretended that the entire value
Page 111 U. S. 122
of the mop head was attributable to the feature patented. So the
whole case ended, the rule was not followed, and the decree is
therefore
Affirmed.