Where an inventor produces a new mechanical device for the production
of a certain result, he can often see in advance that various
modifications of it can be made to bring about the same result, and
even if he does not see it he may in the future find competitors
getting at the result by a different construction. He analyzes the
competing structure, and determines that "it is the same thing only
different," and wonders what the legal doctrine of mechanical
equivalents means, and asks if he is not entitled to the benefits of
that doctrine, so that his patent may dominate the competing machine.
An inventor may or may not be entitled to invoke the doctrine of
mechanical equivalents, and the doctrine may or may not cause his
patent to cover a given fancied infringement. If an inventor is a
pioneer in a certain field, and is the first to produce an
organization of mechanism by means of which a given result is
produced, he is entitled to a claim whose breadth of language is
commensurate with the improvement he has wrought in the art. He cannot
claim functions or performance, but must limit his claim to mechanism,
in other words, to the combination of elements which produces the new
result. His claim recites those elements by name. If the new result
cannot be produced by any other combination of elements, then, of
course, no question will arise regarding infringement. But it may be
that a competitor contrives a device having some of the elements of
the combination as called for by the claim, the remaining elements
being omitted and substitutes provided. The competing device will thus
not respond to the language of the claim. But the courts will deal
liberally with the claim of the meritorious pioneer inventor, and will
apply to it the doctrine of mechanical equivalents, and will hold the
claim to be infringed by a combination containing all of the elements
recited in the claim, or containing some of them, and mechanical
equivalents for the rest of them. Were it not for this liberal
doctrine, the pioneer inventor could gather little fruit from his
patent, for the patent could be avoided, perhaps, by the mere
substitution of a wedge for the screw or lever called for by the
claim. The court, having ascertained from the prior art that the
inventor is entitled to invoke the doctrine of equivalents, will
proceed to ascertain if the substituted elements are real equivalents.
A given omitted element will be considered in connection with its
substitute element, and if the substitute element is found to be an
element acting in substantially the same manner for the production of
substantially the same individual result, and if it be found that the
prior art has recognized the equivalency of the two individual
elements, then the court will say that the substituted element is a
mechanical equivalent of the omitted element, and that the two
combinations are substantially the same. This reasoning must be
applied to each of the omitted elements for which substitutes have
been furnished. In this way justice can be done to the pioneer
inventor. But the courts, in exercising liberality, cannot do violence
to the language of the claim. The infringer will not escape by merely
substituting equivalents for recited elements, but he will escape if
he omits a recited element and supplies no substitute, for the courts
will not read out of a claim an element which the patentee has
deliberately put into the claim, and a combination of a less number of
elements than that recited in the claim is not the combination called
for by the claim.
It is seldom that the exemplifying device of the pioneer inventor is a
perfect one. Later developments and improvements by the original
patentee, or by others, must be depended on to bring about perfection
of structure. Those who improve the structure are as much entitled to
patents upon their specific improvements in the device as was the
original inventor entitled to his patent for the fundamental device.
These improvers are secondary inventors, and are not entitled to
invoke the doctrine of mechanical equivalents. The secondary inventor
did not bring about a new result, but his patent was for new means for
producing the old result. His patent is for this improvement in means,
and his claim will be closely scrutinized in court, and he will be
held to it, subject only to formal variations in structure. The
justice of thus restricting the claim of the secondary inventor must
be obvious, in view of the fact that if the doctrine of mechanical
equivalents were applied to his claim, then the fundamental device on
which he improved would probably infringe upon it, which would be an
absurdity. It is thus seen that the pioneer inventor may have a claim
so broad in its terms that its terms cannot be escaped; that he may
invoke the doctrine of equivalents and have his claim dominate
structures not directly responding to the terms of the claim; that the
secondary inventor, who improves only the means, is limited to the
recited means and cannot invoke the doctrine of equivalents. But
within this general view, sight is not to be lost of the fact that
secondary inventors may be pioneers within certain limits. They are
not the first to produce the broad ultimate result, but they may be
pioneers in radically improving interior or sub-results, and they may
thus reasonably ask for the application of the doctrine of equivalents
to their claims within proper limits. The matter often becomes quite
complicated, for it is sometimes difficult to determine as to what is
the result in a given machine, for many machines consist, after all,
of a combination of subordinate machines. Thus the modern
grain-harvesting machine embodies a machine for moving to the place of
attack, a machine for cutting the grain, a machine for supporting the
grain at the instant of cutting, a machine for receiving the cut
grain, a machine for conveying the cut grain to a bindery, a machine
for measuring the cut grain into gavels, a machine for compressing the
gavel, a machine for applying the band, a machine for tying the band,
a machine for discharging the bundle, a machine to receive the bundles
and carry them to a place of deposit, and a machine to deposit the
accumulated bundles. The machine would be useful with one or more of
these sub-machines omitted, and each machine may be capable of
performing its own individual results alone or in other associations.
Pioneership of invention might apply to the main machine, or to the
sub-machines, or even to the sub-organization within the sub-machines.
(To be continued.)
* * * * *
[Continued from SUPPLEMENT, No. 1172, page 18764.]