Educational mechanical calculator

Claim 1

An educational mechanical calculator for use in teaching arithmetical concepts comprising: a base; register gears mounted on said base with their axes perpendicular to a common plane spaced above the base, said register gears spaced sufficiently far part that they do not engage one another, and each bearing marks representing the numerals 0, 1 . . . N, the marks being equally spaced around each of said register gears; a carry-over gear mechanically unattached to the aforementioned elements, and selectively insertable into and removable from said base by a user; said base including portions defining carry-over sockets located in such positions relative to said register gears that when said carry-over gear has been selectively inserted into one of said carry-over sockets, it engages two adjacent register gears; each of said register gears having a first set of teeth which extend perpendicularly from one side of said common plane and a second set of teeth which extend perpendicularly from the opposite side of said common plane; on successive register gears the first set of teeth and then the second set of teeth alternately consist of a single carry-over tooth, the remaining set of teeth on each register gear having N=1 teeth; the depths of successive carry-over sockets alternating so that when said carry-over gear is inserted into them in sequence its teeth will alternately engage the first sets of teeth of a first register gear and of an adjacent second register gear and then the second sets of teeth of said register gear and of an adjacent third register gear; said base further comprising a separate set of multiplying sockets associated with each of said register gears, the centers of successive multiplying sockets within each set being spaced from the center of the register gear with which the set is associated by amounts equal to N+1 times the radius of the associated register gear; and, a set of multiplying gears, mechanically unattached to any of the aforementioned elements and to each other, having radii equal to 1, 2 . . . N times the radius of said register gears, having teeth adapted to engage the teeth of said register gears, and having respectively 1, 2 . . . N times the number of teeth as said register wheels, said multiplying gears each bearing marks representing the same set of numerals 0, 1 . . . N as on said register gears, the marks being equally spaced around each of said multiplying gears, each of said multiplying gears individually selectively insertable into and removable from one of said multiplying sockets by a user, and when so inserted engaging a register gear.