https://patentbrief.org/company/theophilus-van-kannel Plain-English explanations of patents assigned to Theophilus Van Kannel, newest first. en-us Sat, 13 Jun 2026 10:10:02 GMT https://patentbrief.org/patent/us/387571/revolving-door-van-kannel The 1888 patent for the revolving door, designed to keep buildings warm while allowing people to enter and exit easily. Tue, 07 Aug 1888 00:00:00 GMT https://patentbrief.org/patent/us/387571/revolving-door-van-kannel