Randomized chain sprocket and method for making a sprocket

1. A method for making a sprocket with reduced noise and vibration for a chain and sprocket drive, comprising:

selecting a uniform chain having pins interconnected by links, each pin having a central axis and a chain pitch defined as a distance between the central axis of adjacent pins, the chain pitch being constant;

selecting a uniform sprocket having a plurality of uniform teeth and uniform tooth gaps spaced about the periphery of the sprocket, each of the uniform tooth gaps being located between adjacent teeth, each of the uniform tooth gaps having a tooth gap radial location defined as a distance between the center of the uniform sprocket and a point along the uniform tooth gap closest to the center of the uniform sprocket in a radial direction, each uniform tooth gap having the same tooth gap radial location,

drawing a pitch circle, having a radius defined as a distance between the center of the uniform sprocket and the central axis of a pin in one of the uniform tooth gaps;

positioning a uniform sprocket polygon inside the pitch circle, every vertex of the polygon touching the pitch circle and each side of the polygon equal to the chain pitch;

forming a first random sprocket polygon by altering the vertices between the sides of the uniform polygon while maintaining the length of each side;

determining a first vertex angle in a vertex of the first random polygon and a first supplementary angle of the first vertex angle;

forming a second random sprocket polygon, different than the first random polygon, by altering the vertices between the sides of the uniform polygon while maintaining the length of each side;

determining a second vertex angle in a vertex of the second random polygon and a second supplementary angle of the second vertex angle;

making a random sprocket having a plurality of random teeth and random tooth gaps spaced about the periphery of the random sprocket segment, one of each of the random tooth gaps being located between adjacent random teeth, each of the random tooth gaps having a tooth gap radial location defined as a distance between the center of the random sprocket and a point along the random tooth gap closest to the center of the random sprocket in a radial direction; and

at least one set of four consecutive random tooth gaps being defined as a first tooth gap, a second tooth gap, a third tooth gap and a fourth tooth gap, in that order, wherein

the first tooth gap and the fourth tooth gap have the same tooth gap radial location, and the second tooth gap and the third tooth gap have a different tooth gap radial location from each other and from the first and the fourth tooth gap, and

the set of four consecutive random tooth gaps have two different link angles, including a first link angle defined by an angle between a first link center line and a second link center line and a second link angle defined as an angle between the second link center line and a third link center line, the first link center line being defined by the central axis of a pin in the first tooth gap and the central axis of a pin in the second tooth gap, the second link center line being defined by the central axis of a pin in the second tooth gap and the central axis of a pin in the third tooth gap, and the third link center line being defined by the central axis of a pin in the third tooth gap and the central axis of a pin in the fourth tooth gap, and

one of the two different link angles equal to the first supplementary angle and the second of the two different link angles equal to the second supplementary angle.

2. The method of claim 1 , wherein

the first tooth gap radial location and the fourth tooth gap radial location are the same, the second tooth gap radial location being less than the first tooth gap radial location and the third tooth gap radial location being greater than the first tooth gap radial location.

3. The method of claim 1 , wherein

there is more than one set of four adjacent random tooth gaps.

4. The method of claim 1 , wherein

the first tooth gap radial location and the fourth tooth gap radial location are the same, the second radial location is greater than the first tooth gap radial location and the third tooth gap radial location is less than the first tooth gap radial location.

5. The method of claim 1 , wherein

the chain has a roller-type chain configuration.

6. The method of claim 1 , wherein

the chain has an inverted tooth-type chain configuration.

7. The method of claim 1 , wherein

the chain has a bush-type chain configuration.