ain machine, other claims
may be drawn for the combinations constituting the operative
sub-machines, and claims may be drawn covering the minor useful
combinations of elements found within the sub-machines. Each claimed
combination must be operative. But secondary claims cannot be made for
sub-machines or sub-combinations which are for divisional matter or
matter which should be made the subject of separate patents.

MECHANICAL EQUIVALENTS.

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