Gear Mechanism in the Mechanical Actuation system.

Gear

Gear trains are the mechanism which is very widely used to transfer and transform rotational motion. they are used when a change in speed or torque of a rotation device is needed. For example, the car gearbox enables the driver to match the speed and torque requirement of the terrain with the engine power available.

Gear can be used for the transmission of rotary motion between the parallel shaft and for the shaft which has axes inclined to one another. When two gear is in mesh, the larger gear wheel is often called the spur gear and the smaller one the pinion. 

Gear Train

The term gear train is used to describe a series of the intermeshed gear wheel. the term simple gear train is used for a system where each shaft carries only one gear wheel, the overall gear ratio is the ratio of the angular velocities at the input and output shaft.

The terms compound gear train is used to describe a gear train when the two wheels are mounted on the common shaft.

Rotational to translational motion

The rack and pinion is another form of gear, being essentially two intermeshed gears with one having a base circle of infinite radius. such gear can be used to transform either linear motion to rotational motion or vice versa. Another method that has been used for converting rotary motion translational motion is the screw and nut system. With the conventional form of screw and nut, the nut is rotated and moved along the stationary screw.

Ratchet and pawl mechanism

A ratchet is a device that allows linear or rotary motion in only one direction.it is used in rotary machines to index air operated the indexing table. the ratchet pawl mechanisms are consist of a wheel called ratchet, with saw-shaped teeth which engage with an arm called a pawl. the arm is pivoted and can move back and forth to engage the wheel. 

The shape of the teeth is such that rotation can occur in only one direction.rotation of the ratchet wheel in a clockwise direction is prevented by the pawl and can only take place when the pawl is lifted. the pawl is normally spring loaded to ensure that it automatically engages with the ratchet teeth.

Belt and chain drives

Belt drives are essentially just a pair of rolling cylinders with the motion of one cylinder being transferred to the other by a belt. belt drives use the friction that develope between the pulleys attached to the shaft and belt around the arc of contact in order to transmit a torque. the transmitted torque is due to the differences in the tension that occurs in the belt during operation. this differences results in a tight side and a slack side for the belt.

As a method of transmitting power between two shafts, belt drives have the advantages that the length of the belt can easily be adjusted to suit a wide range of shaft to shaft distances and the system is automatically protected against overloaded because slipping occurs if the loading exceeds the maximum tension that can be sustained by frictional forces.

Types of belts.

1. Flat belt: It is in rectangular in shape and cross-section. flat belt has an efficiency of 98% and produces little noise. it can transmit power over the long distance between pulley centre.
2. Round belt: it has a circular cross-section and is used with groove pulleys.
3. V-belt: V belt is used with grooved pulleys and is less efficient than the flat belt.
4. Timing belt: timing belt requires toothed wheels, having teeth which fit into the grooves on the wheels.