Understanding Crank and Slotted Lever Mechanism Motion

The crank and slotted lever mechanism is a commonly used inversion of the single slider crank chain. It is primarily known for converting rotary motion into oscillating motion, and it's widely used in shaping machines and slotting machines to produce a quick return stroke.

How the Crank and Slotted Lever Mechanism Works

Let's break down the components and their motions:

• Link 1 (Frame): This is the fixed link.
• Link 2 (Crank): This is the input link. It rotates continuously about a fixed pivot on the frame.
• Link 3 (Sliding Block/Slider): This block is connected to the end of the crank (Link 2) and slides within a slot in Link 4.
• Link 4 (Slotted Lever): This is the output link. It pivots about a fixed point on the frame (different from the crank's pivot). The sliding block (Link 3) moves along a slot in this lever.
• Link 5 (Connecting Rod): This link connects a point on the slotted lever (Link 4) to the ram or cutting tool (Link 6). (Note: Some diagrams show Link 4 directly connected to a tool, but the most common setup includes Link 5 and 6).
• Link 6 (Ram/Cutting Tool): This link moves back and forth, typically in a straight line (translating motion), driven by the oscillating motion of Link 4.

As the crank (Link 2) rotates, the slider (Link 3) moves in a circular path relative to the frame and also slides within the slot of the slotted lever (Link 4). This causes the slotted lever (Link 4) to swing back and forth about its pivot point. This back-and-forth swinging motion is called oscillating motion or rocking motion.

Motion Produced by the Mechanism

The output link, which is the slotted lever (Link 4), produces an oscillating motion. This mechanism is specifically designed to achieve this type of motion, converting the continuous rotary input of the crank into an intermittent oscillating output of the lever.

Let's look at why other options are not correct for the primary output motion of the slotted lever:

• Rotatory motion: This is the motion of the input crank (Link 2), which rotates continuously in a circle. The slotted lever (Link 4) does not complete full rotations; it only swings through an arc.
• Translating motion: This is linear motion, like moving in a straight line. The ram or cutting tool (Link 6) often exhibits translating motion, but the slotted lever itself performs oscillating motion.
• Zig-zag motion: This is not a standard term used to describe fundamental kinematic motion types in mechanisms.

Therefore, the crank and slotted lever mechanism produces oscillating motion of the slotted lever.