In this volume, we will look at an automation clever mechanism that converts crank rotation into linear motion and makes the linear motion stroke twice that of the original one.

[Fig.1] is a diagram of this mechanism.

In this structure, the slider used in the standard slider crank mechanism introduced in #251 is replaced by a toothed gear. In addition, the slider guide is separated into a fixed rack and a movable rack. The crank motion on the driving shaft is transmitted to the toothed gear. Then, the stroke of rolling motion (L) over the fixed rack increases by 100% (2L) when it reaches the gear top. This stroke (2L) acts on the movable rack installed on the gear top.

(1)Application examples

The structure tends to be longer than originally intended if a pneumatic cylinder and a slide way (linear guide) are used or if a structure where ball screws are used for connecting a motor is adopted. This automation clever mechanism is an effective solution for making the fixture short and compact.

Application examples

1.Oscillating motion of a processing machine
2.Reciprocating linear motion mechanism for one-piece flow production fixture
(printing, wiping, pressuring, and others)
3.Inspection jigs

(2)Tips on selecting appropriate standard components

All of the parts shown in [Fig.1] can be assembled by using the standard components. This section explains the assembly of gears and racks.

The Module value (m) in the catalog is used to determine a combination of gears and racks. The components are compatible if items with the same module value are mixed. (See the below figure.)

* Additional information (See [Fig.2]) Module (m): Designation indicating the tooth size of a gear When (d) represents the pitch circle diameter and (z) represents the number of teeth, the pitch (p) on the pitch circle, called the circular pitch, is calculated by using the following formula: Circular pitch p = Πd / z However, the above formula includes an irrational number Π, which is inconvenient for designs using integers. There, the formula with the module (m) is generally used for calculating the size of each tooth. p / Π = d / z = m