The Hand-Housing Rubber Brush: Back, Teeth and a Hood for the Hand in One Moulding

"As stated, the brush comprising the back 1, teeth 2, and retainer 3, is a one-piece structure and is preferably formed of rubber molded or otherwise formed into the desired shape." "The edge portions of the retainer at their juncture of the back 1 are made thicker than the remaining portion and gradually taper in thickness as they recede from their juncture with the back, leaving the center portion comparatively thin and flexible, so as to yield slightly when a large hand is thrust into the retainer." "The thickened edge portions of the retainer provide ample protection against injury and resist wear incident to the striking of the edge portion of the retainer against any part of the stall or other object."

**Mould.** In CAD draw three parts and print them in PLA. A tray 16 × 10 cm oval inside, its floor pitted with tapering pockets 8 mm deep every 8 mm for the teeth. A core the shape of the space a flat hand fills: a half-oval dome 13 cm long, 8.5 cm wide and 3.5 cm high with a flat underside, standing 4 mm above the tray floor on a tab that runs out through the mouth. A shell whose inside follows the core 6 mm away at the edges, narrowing to 2.5 mm at the crown, with its open end cut on a slant toward the closed end, a pour hole at the crown and a vent at the closed end. **Cast.** Wipe every face with a thin film of petroleum jelly. Assemble tray, core and shell and clamp the core's tab. In gloves, weigh and mix the silicone rubber by its maker's instructions, stir slowly with a dowel, and pour in a thin stream into the pour hole until it rises in the vent. Leave it to cure as long as its maker says. Take off the shell, stretch the mouth and draw the core out, and peel the brush from the tray. **Test.** Slide your hand in and check that the mouth closes about the wrist. Dust a piece of wool felt with flour and count the strokes it takes to lift it.

**John S. Hickson** of Charlottesville, Albemarle County, Virginia, filed US 840,328 on 29 January 1906; it was patented 1 January 1907. The retainer 3's middle is spaced from the back 1 and joined to it at its edges, making a housing that completely encompasses the hand. In the most general construction the brush is oblong, and the teeth may be of any length and number. His claim covers a new rubber article of manufacture: a back with integral tapering teeth, a retainer integral with it that houses the hand, thickened at the joint with the back, and an entrance cut away on an incline toward the closed end, giving a contracted mouth and free play for the wrist. **Honest limits.** Cast silicone rubber in a printed mould stands in for his moulded rubber. The notebook compares stiffness only through thickness, for one rubber; its thicknesses are examples. The fit on your hand and your stroke counts are the result.