Fundamental Mechanical Mechanisms: Transmission and Motion Conversion

Mechanical Movement Systems: Transmission and Transformation

This section details the fundamental mechanisms used to transmit or transform movement within mechanical systems.

Mechanisms of Movement Transmission

Transmission mechanisms transfer motion and power from a driving element to a driven element. These include:

• Direct Transmission: Elements are in direct contact (e.g., friction wheels, gears).
• Indirect Transmission: Uses flexible elements (e.g., belt or chain).
• Auxiliary Mechanisms: Clutches, brakes, and turn reversers (inverters).

Direct Transmission Components

Axis (Axle)

A fixed support element around which another component, such as a wheel, rotates.

Shaft

A rotating element that transmits circular motion and power.

Coupling

An element that allows joining two shafts. Types include: Elastic (e.g., rubber gasket), Fixed (e.g., flange or thread), and Articulated.

Friction Wheels

Friction wheels are two wheels with completely smooth rims that are in direct contact with one another. The rotating driving wheel communicates movement to the driven wheel through friction.

• This system is primarily used to convey movement and small efforts.

Gear Systems (Engrenages)

Gears are toothed wheels that mesh without slipping, transmitting circular motion and power through direct thrust.

• The wheel with more teeth is typically called the Crown Wheel (or Gear).
• The wheel with fewer teeth is called the Pinion.
• The element that transmits the movement is called the Driver, and the element that receives the movement is called the Driven.

Belt and Pulley Transmission

This system consists of two pulleys connected by a flexible belt. The belt must be made of flexible material such as leather or rubber.

Mechanisms of Movement Transformation

Transformation mechanisms convert one type of motion (e.g., circular) into another (e.g., rectilinear).

Crank-Rod Mechanism

This mechanism transforms a continuous circular motion into an alternating rectilinear motion. It is composed of three main elements:

1. Slider (Plunger): The piece that moves within a guide, executing rectilinear movement.
2. Rod: Allows the articulated union between the crank and the slider.
3. Crank: A lever set by a rotation axis at one end and connected to the rod at the other end.

Cams and Eccentrics

These mechanisms transform the circular movement of a shaft into an alternating rectilinear motion.

• Cam: A piece, usually shaped with specific profiles (lobes), designed to actuate a follower element.
• Follower: The element that is actuated by the cam, resulting in alternating reciprocating movement.
• Eccentric: Functions similarly to a cam, where the axis of rotation is offset from the center of the circular element.

Other Transformation Mechanisms

• Rack and Pinion
• Endless Screw (Worm Gear)
• Maltese Cross

Speed Control and Auxiliary Mechanisms

Speed Changer (Shifter)

The speed changer is used to decrease or increase the number of revolutions per minute (RPM) between the motor shaft and the driven shaft.

Auxiliary Mechanisms

These mechanisms control the flow and direction of power:

• Clutches: Engage or disengage power transmission.
• Brakes: Stop or slow down movement.
• Turn Reversers (Inverters): Change the direction of rotation.

Transmission Ratio Formula

The relationship of transmission (i) is calculated using the following formulas:

Gears/Friction Wheels:

Chain/Belt (Strap) Drive:

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