Churn con rodillo autogiratorio: rodillos acanalados que giran impulsados por una rueda fija mientras el batidor gira

Colver's improvement consisted "in giving the beaters of a churn dasher a revolving motion on their own axis." Lewis W. Colver of St. Louis, Missouri, received US 6,726, dated 18 September 1849, for a rotary churn-dasher of four horizontal beaters between a cross at one end and a round flat case at the other. Two are wedge beaters; the other two are fluted rollers with hook-shaped flutes, each between two edge-beaters whose inner faces curve in toward it. A belt from a large stationary pulley inside the case turns the rollers fast as the dasher goes round; "the granules of butter are drawn by the hooked flutes into the converging spaces between the rolls and the edge beaters, thus compressing them together." This rung works out the rollers' speed, then prints the fixed gear, rollers, beaters and end pieces, builds the dasher in a box, and makes butter.