Patent ID: 8162790

Claim:
A rolling ball type two-stage low speed changer device comprising: a stationary disc, one outer surface of which has a hypo-based groove defined along a hypocycloidal curve in a circumferential direction of said stationary disc, said hypo-based groove having a first number of lobes; an eccentric disc, one outer surface of which has an epi-based groove defined along an epicycloidal curve in a circumferential direction of said eccentric disc, said epi-based groove opposing said hypo-based groove of said stationary disc and having a second number of lobes, the other surface of said eccentric disc having a hypo-based groove defined along a hypocycloidal curve in a circumferential direction of said eccentric disc and having a third number of lobes; an output disc, one outer surface of which has an epi-based groove defined along an epicycloidal curve in a circumferential direction of said output disc, said epi-based groove opposing said hypo-based groove of said eccentric disc and having a fourth number of lobes; an eccentric shaft interposed between said stationary disc and said output disc, and having one end portion, a middle portion and other end portion, said one end portion rotationally secured to a central portion of said stationary disc, said middle portion having an eccentric portion rotationally mounted on a central portion of said eccentric disc to pivotably support said eccentric disc, and said other end portion rotationally connected to a central portion of said output disc; first rollable balls rollably placed between said stationary disc and said eccentric disc to partly engage with said hypo-based groove of said stationary disc and to partly engage with said epi-based groove of said eccentric disc; second rollable balls rollably placed between said eccentric disc and said output disc to partly engage with said hypo-based groove of said eccentric disc and to partly engage with said epi-based groove of said output disc; each of said first, second, third and fourth number of lobes being an integer, said first number of lobes being greater than said second number of lobes, and said third number of lobes being greater than said fourth number of lobes, each difference between said first and second number of lobes and between said third and fourth number of lobes being two with said third number of lobes equal to an integral multiple of half of said second number of lobes; and a rotational input given to said eccentric shaft eccentrically rotating said eccentric disc to roll said first rollable balls along said hypo-based groove of said stationary disc and said epi-based groove of said eccentric disc so as to implement a first stage speed change, while at the same time, rolling said second rollable balls along said hypo-based groove of said eccentric disc and said epi-based groove of said output disc so as to implement a second stage speed change.