Tennant Case 2: Hotchkiss v. Greenwood (1850)

In this case, the plaintiffs (Hotchkiss et al.) had filed for a patent for a new doorknob made of clay or porcelain and were granted one. They then filed a suit against the defendants (Greenwood et al.) for a violation of patent rights. Greenwood and his codefendants claimed that the doorknob was not, in fact, a new invention and thus was not patentable. The plaintiffs were then required to submit documentation proving that their invention was new, and that it was indeed patentable. The lower courts had ruled that no verdict could be given because the doorknob was not new, and therefore the patent was void.

The issue derives from the nature of the doorknob design. The basic structure and components of the doorknob were already known and in use; the only "novel" aspect of the design was that the knob itself was made of clay or porcelain and not metal or wood. Yet even the concept of a clay knob was not new, as it had been in use before. Had the knob been made of an entirely new "composition of matter," then the design would certainly have been protected by a patent. However, the concept was not new and the assembly and function of the doorknob as a whole did not change, and so the patent was void.

According to the ruling, the novelty would consist in:

• New composition which leads to practical use in daily life;
• A new manufacture, because the general process and function of the doorknob design had been previously known.

While the substitution of a new material may make the doorknob better or cheaper, it does not make an entirely new invention. The improvement is derived from a higher quality material, which is not new. The improvement takes no ingenuity or invention, but rather is an adaptation of an existing process which makes it almost entirely the same as before. Instead of inventing a new doorknob, the defendants rather had mechanically altered an existing one.