Today in 1915, US Patent 1138251 A was issued, an invention of Joseph Schaefer, for his “Mash-Filter Plate.” There’s no Abstract, although in the description it includes this summary:

My invention relates to mash filters adapted for use in the arts of brewing, distilling or in the manufacture of compressed yeast, and in part is a continuation of my sugars and soluble matter are more completely removed from the lower part of the grains cakes because of the greater water pressure in the lower part of the frames. This results in the loss of more or less of the valuable sugars unless an excessive amount of water is used. The use of too much water is not desirable since this dilutes the wort to such an extent, that, to remove the excess of water, extended boiling is required which, it should be understood, is expensive and detrimental to the final product. To overcome these objections I have arranged the water chambers so that the grains cakes formed there between will be thicker at the bottom than at the top, or substantially trapezoidal in shape. It has been found that with cakes of this shape the sparging 18 more thorough, and with the use of a given quantity of water-the soluble sugars are more formaly and completely removed from the grains cakes.

Another object of my invention is .to facilitate the removal of the grains cakes from their frames when the sparging process is completed, and the series of frames are separated for this purpose. The frame as ordinarily constructed is provided with a flat floor or bottom from which ‘it is difficult to dislodge that part of the cake resting on the bottom, it usually being necessary’ for the workman to scrape it of with a paddle or other device. With my improved construction I overcome this objection by constructing the bottom or floor of each grains cake frame, wedge-shaped or like a tool edge in cross-section. This construction is adapted to save the time of the workman for, as the grains cakes are friable, it will be seen that a mere tap of a hammer will cause the bottom of the grains cake to separate and slide down on each side of the wedge-shaped bottom of the cake frame, and thus leave the frame clean without any further effort on the part of workman.