Friction Plunger Churn: Cream Pumped Through Openings You Close a Little More as It Thickens

"By causing the cream to pass and repass through contracted openings, and with considerable force, the friction of the cream against the edges of the openings has the effect of rapidly separating the butter from the whey at the same time the constant change in the course of the cream agitates the latter as effectually as the ordinary dashers."

Cut an 18 mm plywood base 750 x 400 mm. Stand a hardwood column 70 x 70 mm, 643 mm tall, on it 290 mm from where the bucket's middle will be, glued and screwed from under the base. Saw a slot 24 mm wide and 100 mm deep in its top and bore it 12.4 mm across 40 mm below the top for the pin h.

Screw the bucket's floor to the base. Drill a 20.4 mm hole in its side 30 mm above the floor, facing away from the column, and two 4.4 mm holes 19 mm either side of it. Lay a 30 x 2 mm O-ring in the inner half's groove, fit the halves inside and outside the wall and draw them together with two stainless M4 screws and lock nuts. Fill the bucket with water to check the box does not leak, then empty it.

Press an M6 nut into plate J's boss. Lay J on plate I between its flanges and stand I on its legs in the middle of the bucket's floor. Cut 170 mm of M6 stainless threaded rod, bend 40 mm of one end to an L for a handle, push the straight end in through the stuffing box with a 6 mm O-ring in its bore and screw it into J's nut. Turn K both ways: J slides until its openings line up with I's, and closes them after 8 mm.

Stack the four rings on plate I, the notched one at the bottom over rod K. Cut the flange from 12 mm plywood, a ring 304 mm across with a 154 mm hole, and bore a 16 mm hole 125 mm from its middle for the vent. Set it on the bucket's rim over the cylinder's top. Fit four stainless U-bolts through the bucket wall just under the rim, two each side, and drive two tapered hardwood wedges, 340 x 30 mm and 16 mm at their thick end, through them over the flange so it presses the cylinder down on the plates. Push the vent tube into its hole and its cover on top.

Cut two 153.9 mm discs of 3 mm food-grade silicone sheet and bolt them between the plunger plates through the middle, hub up; the silicone's edge is the packing e and should slide in the cylinder with a light drag. Saw a slot in each end of a 22 mm hardwood dowel 470 mm long between pin centres and pin its lower end to the plunger's hub with a 6 mm stainless bolt. Make the arm G from hardwood 40 x 22 mm, 930 mm long, bore it 12.4 mm 30 mm from one end for the pin h and 6.4 mm 290 mm from that for rod F, then bolt it into the column's slot with a 12 mm bolt and pin rod F to it.

With plate J slid so all the openings are open, pour about 10 litres of heavy cream at about 15 °C into the bucket, checked with the thermometer. Work the arm about once a second, timing it. As the cream thickens, give rod K a turn now and then to close the openings a little. Lift the vent's cover now and then to let the gas out. When the butter comes, knock the wedges out, lift out the flange, the cylinder and the plunger, pour off the buttermilk, wash the butter in cold water until it runs clear, work in a pinch of salt and weigh it.

**John J. Lehaye** of Reading, Pennsylvania, assignor to himself and John Tucker of Philadelphia, US 25,162, 16 August 1859, "Churn". He claimed the vessel B, cylinder C and plunger E in combination with means for enlarging or contracting the openings between the cylinder and the vessel. He gives no sizes, so every size here is ours; the U-bolts are his staples a, the O-ring box his stuffing box, and silicone his packing. His Fig. 4 alternative, projections on the cylinder's foot and on a ring in the vessel's bottom, turned to open or close the gaps, is not built. He also offered the machine as an egg beater and for mixing curds.