How does a wheel drive work?

A drive for wheels uses compressed air as an energy source. The devices used transform the energy of the compressed air into mechanical movement. In this way it is possible to control the movement in the wheels.

Pneumatic actuators, the base in the drive for wheels

In a pneumatic system, the pneumatic actuators are those that are responsible for transforming the energy of the compressed air into mechanical work. We can classify the pneumatic actuators in two groups: Cylinders and Motors.

Pneumatic Cylinders

The function of the pneumatic cylinders in the wheel drive is to transform pneumatic energy into mechanical work. It generally consists of forward movement and recoil movement.

The pneumatic cylinder is composed of a circular tube closed at the ends by two caps. Between them, a piston slides between two cameras. The piston is attached to a piston, which exits through one of the caps. In this way, the force that the cylinder develops when acting on the plunger surfaces can be used. Depending on how the retraction of the shank is performed, the cylinders can be divided into:

Single effect cylinders

E l single acting cylinder works in one direction. The displacement of the piston, due to the pressure of the compressed air, is in one direction only. In this case, the return to its initial position is carried out by a recoil spring that carries the built-in cylinder. By means of this recuperator spring, the movement of the single effect cylinders is limited. For practical reasons, they are small in diameter, and their greatest advantage is their reduced air consumption. For this reason they are usually applied as auxiliary elements in automations.

Double effect cylinders

The double-acting cylinders, on the other hand, are built in the form of a piston cylinder. They also have two intakes for the compressed air, which are located on both sides of the piston. When pressurized air is applied in the rear chamber and the anterior chamber is communicated with the atmosphere, the cylinder performs the advance stroke. This communication is possible thanks to a valve. The recoil movement is carried out by introducing air under pressure in the anterior chamber, and communicating the posterior chamber with the atmosphere. This also happens through a valve for the evacuation of the air contained in that cylinder chamber.

Pneumatic Motors

The function of pneumatic motors consists of transforming pneumatic energy into mechanical energy of rotation. This process is developed in an inverse manner to that of compression. Pneumatic motors convert the compressed air into mechanical work by means of linear or mainly rotary movement. The main characteristics of these engines, can be summarized in the following:
  • They are very light and compact       
  • Both starting and stopping are fast, they can work with variable speed and torque without needing complex control.       
  • They have a low inertia       

Types of drives for wheels and translation

The drives for wheels and translation or pneumatic drives, make it possible for the orders of movement of a machine to be executed. In the case, for example, of wheel drives, this is possible using compressed air as an energy source.

What are the types of drive for wheels and translation?

There are motors that in addition to drives for wheels , also have hydraulic and electrical drives. Each type of engine has well-defined characteristics. In general, they are classified according to the power, control capacity, volume, weight, precision, speed, cost and maintenance .

Drive with pneumatic cylinders

In this type of drive, the displacement of a piston or piston, enclosed in a cylinder, is executed. This displacement occurs as a result of the pressure difference on both sides of the cylinder. On the other hand, pneumatic cylinders can be either single acting, or double acting.

In those with a simple effect, the piston moves in one direction as a consequence of the thrust exerted by the pressurized air. To move in the other direction requires a spring, which returns the piston to its resting position.

In the double effect, however, it is the pressurized air that pushes the piston in both directions. The air can be arbitrarily introduced into either of the two chambers.

Drive with pneumatic motors

In pneumatic motors, the rotation of the shaft is carried out by means of compressed air. The two types of pneumatic motors most used are: rotary vane and axial piston motors . The axial piston motors work by means of a turning axis integral with a drum. Said drum is forced to rotate between the forces exerted by several cylinders. The cylinders, in turn, rest on an inclined plane. Another method of obtaining rotational movements by means of pneumatic actuators, is using cylinders whose piston is coupled to a pinion-rack system.

Within the drives for wheels and translation, the pneumatic motors have important advantages . First, they have a high thrust force and speed, with minimal friction. On the other hand, their small installation height and nominal command signal margins make them very manageable.

Other points to take into account in the drives for wheels and translation

The drives generally have two possible safety positions. These security positions vary depending on the execution. In particular, they are very effective when the membrane is discharged from pressure, or also in case of auxiliary power failure. These two positions are: either the rod moves to the lower end position, or enters the drive pushed by the springs or springs.

On the other hand, the pneumatic diaphragm actuators are suitable for control elements with a rotary plug. They are especially indicated for butterfly and shutter valves. While pneumatic rotary drives are usually single-acting drives with return springs. These are usually used in butterfly pistons and other control elements that have a rotary shutter.

What are the drives for rotation and winch?

The drives for rotation and winch  are key elements in the operation of certain machines. They must be compact because of the high power density they will support in the development of the task for which they are focused.

They are usually available as standard products or in customized versions. In combination with other larger bearings , they must form a perfectly harmonized system. This will be able to develop based on a reduced torsional game.

The drives for rotation and winch are designed to offer speed and capacity values ​​for the cable. They must have very good compact dimensions. Also a correct optimization of the drum and the sealing discs. The high degree of refinement of the safety devices of the drives for rotation and winch will guarantee reliable operation.

General characteristics of the drives for rotation and winch

The general characteristics of the drives for rotation and winch are those of a compact and high performance structure. They have a serrated root without groove, integrated disc brake and are usually suitable for various hydraulic motors.

A hydraulic motor is an actuator by means of pressurized water that, when properly connected to a system with general characteristics of the drives for rotation and winch, produces a rotating action. This can be unidirectional or bidirectional depending on the design of the system.

The motors are similar in design to the pumps only when a pump takes a rotary actuator to move the hydraulic fluid out of the unit. While a motor will take the flow into itself and put out a rotary actuator.

The drives for rotation and winch are designed to withstand high dynamic loads. Not surprisingly, the rotation devices of a conventional type excavator, usually use these robust transmissions . The gear teeth and bearings are individually adapted and specially designed for the rotation function.

For its part, a winch is a mechanical device, consisting of a roller or rotating cylinder. It is operated manually or by a person or by a steam, electric or hydraulic machine . It is also attached to the cylinder or roller by a cable, a metal rope or a cable.

What are the drives for wheels and translation?

The drives for wheels and translation  are also known as pneumatic drives. These are intended to enable the orders of movement, generated by the control unit to a machine, to be carried out.

In the case of wheel drives, the source of energy used is compressed air. Although they allow a great speed of action, their accuracy in this case is less than other types of drives.

We find motors that, in addition to wheel drives, can have hydraulic and electric drives. Each type has certain characteristics. We can classify them according to their power, control capacity, volume, but, precision, speed, cost and maintenance.

We have two types of drives for wheels

Pneumatic cylinders

In this case, the displacement of a piston enclosed in a cylinder is obtained by the different pressure that is on both sides of the cylinder. The pneumatic cylinders can be single or double acting. In the first, the piston moves in one direction pushing compressed air. For its part in the seconds, the movement occurs under the effect of a spring (which returns the piston to its resting position).

Pneumatic motors (rotary or axial piston fins)

In pneumatic motors, the rotation of an axis is done by compressed air. The two most commonly used types are rotary vane and axial piston engines .

It must always be borne in mind that the use of a robot with a certain type of pneumatic control must have a compressed air system, including: compressor, distribution system (tubes, electrovalves), filters, dryers, etc. The robot must be equipped with a compressed air system. However, these pneumatic systems are common and exist in many factories where a certain degree of automation has been implemented.

The pneumatic drives are membrane drives with a roller membrane and internal springs.

They have the following advantages :
  • dimensioned for control pressure up to 6 bar (90 psi)
  • small installation height
  • high pushing force and positioning speed
  • minimal friction
  • several nominal margins of command signal
  • change of the nominal margin of signal and inversion of the direction of movement without need of special tools

Other keys of the drives for wheels and translation

Security position

The drives have two possible safety positions according to the execution, which are effective when the membrane is released from pressure or in the event of failure of the auxiliary power:
  • Stem coming out of the drive (FA) : the actuator stem moves to its lower end position.
  • Stem entering the drive (FE) : the piston rod enters the drive by the force of the springs.

Pneumatic drive with rotary lever

Pneumatic diaphragm actuator suitable for control elements with rotary shutter, especially suitable for butterfly and shutter valves. Membrane with surface of 350 or 700 cm2. Optional with manual control. The Type 3204-7 drive is suitable for the integrated mounting of a positioner.

Rotary pneumatic drive

Single acting rotary drive with return springs for butterfly valves and other control elements with rotary shutter. Nominal rotation angle of 70° or 90°. Membrane with a surface of 160 or 320 cm2. Optional with manual control.