Maria Montessori (1870-1952), the famous Italian educational reformer, had a number of patents for inventions for teaching aids. Although her two American patents have been noted elsewhere, I don't think her eight British patents have been listed. All are available for free online.
Her first application for a patent was in 1908 and was patented in France, Switzerland, Austria and in the USA as US 1103369, Educational device. It was to help children to write.
Her second American patent was applied for in 1913 as US 1173298, Cut-out geometrical figure for didactical purpose. It was a method of teaching geometry.
In Britain, she had patented her first of the eight patents with GB 1912/6706, Apparatus for use in teaching children. That link includes the amended version, from 1916, after a hearing before Justice Sargent where one claim was lost. This probably means someone took her to court but I have not traced the action. It has complex ideas on writing and mathematics and is perhaps in reality two or three separate inventions. The main drawings are given below.
Next there was GB 1914/14481, Apparatus for teaching children geometry. It is similar or identical to the second US patent mentioned above. Below are the main drawings.
Then there is GB 1913/17890, Apparatus for teaching children arithmetic. It is for an abacus with each row having differently coloured beads, to be used in conjunction with cards. Below is the main drawing.
After World War I the British system changed to numeration from 100,001 onwards so the numbers look different. Based on an Italian filing in 1918 is GB 141053, Device for teaching grammar (Italian patents are not available online, and only the Swiss equivalent patent to her first US patent is in Italian). A box contains compartments which are used to house cards of different colours for different parts of speech.
In 1929 Montessori applied from Spain (as for the following British patents) for GB 330422, Teaching young children elementary mathematics. Again it involves different colours, for strips of paper of different widths, each with a number on one side and adhesive on the other.
Also from 1929 is GB 330788, Artificial lighting. A hollow porcelain column has a light at the bottom and a transparent cover at the top. The idea was to provide shadowless light for a children's nursery. It is illustrated below.
Also from 1929 are two patents with the same titles, Teaching young children elementary mathematics. These are GB 332726 and GB 334319. This second patent is again based on the abacus idea and is illustrated below.
Once again this shows how much can be found in patents. In Montessori's case it is probable that books or journal articles cover the same ground, but this is not so for numerous inventors who have put forward their ideas. There are for example 79 British patents between 1914 and 1950 on the principle of teaching counting as listed here.