Slotted Link Quick Return Shaper Drive Mechanism

Slotted Link Quick Return Shaper Drive Mechanism

Slotted Link Quick Return Shaper Drive Mechanism - The slotted link quick returns mechanism.

Slotted link mechanism	Principle of mechanism
A - Clamping nut B - Ram C - Link D D - Crankpin A E - Slotted crank B F - Bull Wheel G - Glot	A - Path of crankpin B - Length of stroke C - Cutting stroke D - Idle or return

Slotted link mechanism is very common in mechanical shapers. The mechanism is simple and compact. It converts the rotary motion of the electric motor and gearbox into the reciprocating motion of the ram.

The slotted link mechanism gives the rain a higher velocity during the return non cutting stroke than during its forward cutting stroke thereby reducing the time wasted during the return stroke. The bull gear is driven by a pinion which is connected to the motor shaft through a gearbox with four, eight or more speeds available. The bull wheel has a slot. The crank pin A is secured into this slot; at the same time it can slide in the slotted crank B.

When the bull wheel rotates, the crank pin A also rotates and side by side slides through the slot in the slotted crank B. This makes the slotted crank to oscillate about its one end C. This oscillating motion of slotted crank (through the link D) makes the ram to reciprocate. The intermediate link D is necessary to accommodate the rise and fall of the crank.

The position of the crank pin A in the slot in the bull wheel decides the length of the stroke of the shaper. The further it is away from the centre of bull wheel, the longer is the stroke.

The cutting stroke of the ram is completed while the crank pin moves from A to A₁ and the slotted link goes from left to right. Similarly, during return stroke crank pin moves from A₁ to A and the link changes its position from right to left. The time taken by cutting and idle strokes of the ram is proportional to the angles AZA₁ and A₁ZA respectively.

Cutting time/Idle time = angles of AZA₁/angles of A₁ZA .

Since the crank pin A rotates with uniform velocity and angles of A₁ZA is smaller, it is obvious that the idle return stroke is quicker than the forward cutting stroke and hence the slotted link mechanism is known as quick return mechanism.