I believe drawings in patents are usually not subject to copyright. Sometimes they are, but the patent application has to have a notice in the specification of the copyright claim. Look at the second paragraph of US 5,715,314 for an example.
According to the USPTO, patents are published as part of the terms of granting the patent to the inventor. Subject to limited exceptions reflected in 37 CFR 1.71(d) & (e) and 1.84(s) , the text and drawings of a patent are typically not subject to copyright restrictions. The inventors' right to exclude others from making, using, offering for sale, or selling the invention throughout the United States or importing the invention into the United States for a limited time is not compromised by the publication of the description of the invention. In other words, the fact that a patent's description may have been published without copyright restrictions does not give you permission to manufacture or use the invention without permission from the inventor during the active life of the patent.
37 CFR 1.71 relates to the specification
(d) A copyright or mask work notice may be placed in a design or utility patent application adjacent to copyright and mask work material contained therein. The notice may appear at any appropriate portion of the patent application disclosure. For notices in drawings, see § 1.84(s). The content of the notice must be limited to only those elements provided for by law. For example, "©1983 John Doe"(17 U.S.C. 401) and "*M* John Doe" (17 U.S.C. 909) would be properly limited and, under current statutes, legally sufficient notices of copyright and mask work, respectively. Inclusion of a copyright or mask work notice will be permitted only if the authorization language set forth in paragraph (e) of this section is included at the beginning (preferably as the first paragraph) of the specification.
37 CFR 1.84 relates to drawings
(s) Copyright or Mask Work Notice. A copyright or mask work notice may appear in the drawing, but must be placed within the sight of the drawing immediately below the figure representing the copyright or mask work material and be limited to letters having a print size of.32 cm. to.64 cm. (1/8 to 1/4 inches) high. The content of the notice must be limited to only those elements provided for by law. For example, " ©1983 John Doe" (17 U.S.C. 401) and "*M* John Doe" (17 U.S.C. 909) would be properly limited and, under current statutes, legally sufficient notices of copyright and mask work, respectively. Inclusion of a copyright or mask work notice will be permitted only if the authorization language set forth in § 1.71(e) is included at the beginning (preferably as the first paragraph) of the specification.