Slotted-lever Quick-return Mechanism Explained: How It Works, Diagram, Parts, Formula and Uses

Posted by Robbie Dickson on

← Back to Engineering Library

For a normalized external-pivot slotted lever with center distance d=1, a selected return sweep θr determines r/d=cos(θr/2). The complementary work sweep is 360°−θr, and constant crank speed makes stroke-time fractions equal their input-angle fractions.

Slotted-Lever Quick Return · Normalized Tangent Geometry

Explore exact normalized tangent geometry and constant-speed timing for a selected return sweep.

0°

Cut Sweep
--
Time Ratio
--
Cut Time
--
Return Time
--

Equation Used

r/d=cos(θr/2); θwork=360°−θr; Q=θwork/θr; t=Tθ/360°.
Normalized input-angle and timing model only; absolute linkage dimensions and output kinematics are not predicted.
  • The crank pin follows a circle about a fixed center and the slotted lever pivots at an external point.
  • The selected return sweep is bounded between 0 and 180 degrees.
  • Input angular speed is constant.
  • Absolute dimensions, ram linkage, loads, wear and safety are excluded.
FIRGELLI Automations - Interactive Mechanism Calculators

The ratio r/d sets the crank radius relative to the distance between the two fixed pivots.

Same mechanism and inputs as the interactive calculator.

Normalized tangent construction

The crank pin follows a circle and the slotted lever passes through the external pivot and pin. Tangent lever positions define the two reversals. Absolute dimensions and the ram linkage are not supplied.

What the calculator determines

Select return sweep and total cycle time. The calculator reports complementary work sweep, constant-speed time ratio and the two exact time allocations.

Exact normalized identities

r/d=cos(θr/2); θwork=360°−θr; Q=θwork/θr; times=Tθ/360°.

Selected-input example

For θr=100° and T=4 s, work sweep is 260°, ratio is 2.60:1, work time is 2.889 s and return time is 1.111 s.

Normalized angle model only

No absolute crank radius, center distance, lever length, connecting rod or ram guide is supplied. Stroke, linear velocity, force, loads, wear and safety are excluded.

Questions

What does r/d mean?

It is the normalized crank-radius to center-distance ratio implied by the selected tangent sweep.

Where are the lever reversals?

The lever reverses where its centerline is tangent to the crank circle. For the selected return sweep, r/d=cos(θr/2).

References

Building or designing a mechanism like this?

Explore the precision-engineered motion control hardware used by mechanical engineers, makers, and product designers.

← Back to Mechanisms Index
Share This Article
Tags: