# Symmetrical Coupler Curves

## Symmetrical Coupler Curves

 Symmetrical Coupler Curves are frequently useful. For example, you can find a coupler curve with two straight lines that may be useful for Dwell Mechanisms. Mechanisms with symmetrical coupler curves are easy to design with MechDesigner. Design Parameters of a Four-Bar Mechanism to give a Symmetrical Coupler-Curve. The four-bar mechanism to the left is defined by the Points: AoA (Crank), BoB (Output Rocker), AB (Coupler), Point K (Symmetrical Coupler Point on Part AB). Symmetrical Coupler Curves A Coupler Curve becomes symmetrical when: AB = BOB = BK Axis-of-Symmetry The Axis-of-Symmetry is the ray: BOJ The angle of the axis-of-symmetry, relative to the frame, from BO is: ∠AOBOJ(Θ)= ∠ABK / 2  (External Angle =∠ABK ) The Coupler Point is on the Axis-of-Symmetry when the Input Crank angle, α, is 0 and 180

Video of Symmetrical Coupler Curve and Axis-of-Symmetry

 It is worth watching this video two or three times to understand the mechanism design. In the video: •the 4-bar is stationary, as we edit the angle ABK from 0 to 360  •the Coupler-Curve is the path of K for a complete a rotation of the Crank, AOA•the Crank-Angle, α (BOAOA) is fixed at 180º .Because the lengths of AB, BOB, and BK are equal, the Coupler-Curve is be symmetrical. •the axis-of-symmetry ∠AOBOJ, increases as we increase ∠ABK Video of Symmetrical Coupler Curve. Symmetrical Coupler Curves Video of Symmetrical Coupler Curve.

Application of Symmetrical Coupler Curve with two straight lines: Geneva Indexer Symmetrical Coupler Curves Video of a Geneva Indexing Mechanism controlled with a Symmetrical Coupler Curve.