The Shaking Grate: Turn It to Sift the Ash, Tilt It to Dump the Fire

"My invention relates to a novel form and arrangement of circular grate for air-tight and other heating-stoves, which grate is rendered capable of being shaken horizontally about its axis for precipitation of its ashes, or, by a slight change of location, of being tilted into a vertical position for the purpose of dumping the spent fuel into the ash-pit." "Extending transversely athwart the upper part of the ash-pit is a horizontal bar, C, which supports a circular grate, D, having, at the centre of its under side, a socket, E, for a stud or teat, F, on the top of the bar C. A handle, G, which projects from the edge of the grate, in the plane of the latter, enables the grate to be shaken or vibrated about its axis for precipitating the ashes in the common way." "Projecting from the edge of the grate, nearly opposite to its handle, is a pivot, H, upon which, in conjunction with the handle, the grate can be tilted at one extremity of its stroke or vibration".

Stand a coarse wire mesh sieve over a box fan blowing upward, on its lowest speed. Measure the air speed just above the mesh with an anemometer. Sprinkle a spoonful of fine sand evenly over the mesh (the 'ash') and measure again; repeat until the reading has halved. Now give the sieve a few sharp turns back and forth about its centre, as Caven's handle does, and measure again. Record how much of the flow each shake restores. Wear safety glasses against blown sand.

**William Caven** of Cincinnati received US 81,139, dated 18 August 1868 (no filing date is printed on patents of that period), for grates in the "cannon" stoves of the day. **Honest limits.** The patent gives no rates. The clogging time, restored fraction and angle of repose in the notebook are examples; the sand-and-fan test is a model, not a fire.