Double acting cylinders
Double acting cylinders
An actuator is a device that changes the energy of the working medium into mechanical energy. We include this element of machines in the executive devices, i.e. the part that occurs in the control systems. The actuator is a controlling component because it acts on the device being controlled. By transferring mechanical energy to the control object, it makes it operational. For this reason, actuators are considered to be very important elements of devices used primarily in heavy industry.
Pneumatic actuators are mechanical devices that work with compressed gas. By converting air energy into mechanical energy, pneumatic actuators set the mechanisms in motion. They are considered very universal. They are widely used in many industries. Double-acting cylinders are most often used.
It is worth knowing that pneumatic cylinders are constructed very simply. The piston and piston rod (which most often acts as an actuator) are located in the actuator cylinder. The elements are placed on sleeves which define their path of movement. Appropriate seals are also very important parts of each cylinder. It is a key element of the actuator, especially when the mechanism is to be used in difficult conditions, for example in contact with caustic substances, oils or high temperature. In such situations, it is advantageous to use special, stronger seals, made of materials such as Teflon or Viton - this type of strong, synthetic rubber allows the actuator to work safely in difficult conditions. Thanks to the use of high-quality seals, we can be sure that the actuator will be operational for a long time.
Some of the elements with double-acting pneumatic cylinders are most often made of high-quality stainless steel and acid-resistant materials, thanks to which they are resistant to unfavorable working conditions. The fact that the actuators are made of high-quality materials allows the mechanisms to work in contact with sea water, food products or other substances that could lead to the destruction of essential components of the actuator. In the case of particularly difficult working conditions, steel covers are also used. They are important where there is a high risk of mechanical damage to the actuator. However, in most cases the actuator covers are made of anodized aluminum or similar materials that adequately protect the internal actuator mechanism.
A double-acting pneumatic cylinder is not a complicated device. Its operation is based on the performance of a working movement thanks to the pressure of compressed air, which is supplied to two chambers. The construction of the actuator with two chambers forces the mechanism to send air alternately to the two sides of the piston. For this reason, the double-acting cylinder is equipped with spool valves which are used to control the mechanism. Pneumatic cylinders are characterized by a high speed of movement of the piston rod, which is particularly noticeable in the case of a double-acting cylinder.
We can also find single-acting pneumatic cylinders on the market. If you are faced with choosing the right cylinder, it is worth familiarizing yourself with the functions of a single-acting and double-acting cylinder. The first major difference is the number of chambers. Single-acting cylinder, as the name suggests, only performs the working movement in one direction. There are single-acting pulling and pushing cylinders, which are often equipped with a spring that helps the actuator to function efficiently. Thanks to it, the movement of the device in both directions is smooth. On the other hand, a double-acting pneumatic cylinder, thanks to the presence of two chambers, is able to perform a working movement in both directions.
This fact overcomes limitations that exist with single-acting cylinders, such as a limited stroke range. The simplest definition of a stroke is the distance between the extended and retracted end of the piston rod. The small range of the stroke causes some barriers to the dynamics of the work. Too low a stroke causes the actuator movement to be decelerated quickly. This is due to the need to amortize the actuator. The damper seal makes it impossible for air to escape from the cylinder when the damper sleeve enters. Thanks to this, the durability of the mechanism is longer, however, the dynamics of work may be disturbed. This only applies to single-acting cylinders. In the case of a double-acting pneumatic cylinder, the stroke of the cylinder usually depends only on the size of the entire mechanism, and the shock absorption mechanism does not translate into the dynamics of the cylinder's operation. However, it is worth noting that this state of affairs also has its drawbacks. A double-acting long-stroke cylinder has a higher mechanical stress on the cylinder. This, in turn, necessitates the use of longer slip rings and larger bearing diameters, which translates into an increase in the size of the entire mechanism.
Double-acting pneumatic cylinder - application and advantages
The double-acting cylinder is widely used in industries such as metallurgical, chemical, machinery, stone, automotive, wood, but also in the paper and food industries. What's more, pneumatic actuators are also used in everyday objects. They are used, among others, in automatically opening gates. It is thanks to the pneumatic actuators that it is possible to operate the doors in the car or the unloading platforms used in the trucks. Pneumatic actuators are also used in spreaders and cutters, which are used by emergency services.
As you can deduce, pneumatic actuators are widely used in the world around us. No wonder, because due to the mechanism of its operation, the double-acting actuator is very easy to use and environmentally neutral, which is increasingly important for companies operating in the industry. Compressed air mechanisms not only do not have a negative impact on the climate, but are also much cheaper than other types of mechanisms because they only use air.
It is worth knowing that due to their popularity, double-acting cylinders are available in many varieties. These types of actuators can be easily found even in non-standard dimensions. Their versatility is a huge advantage, as it allows anyone looking for a double-acting cylinder to quickly find the perfect model for themselves. Their great versatility also translates into the specification of specific models, for example in relation to the previously discussed cylinder stroke. A double-acting cylinder has a stroke limited only by the design solutions for this particular mechanism. A huge advantage of double-acting pneumatic cylinders is the fact that with a long stroke, the cushioning mechanism does not adversely affect the dynamics of the cylinder, so work with a double-acting cylinder can be performed quickly. A double-acting pneumatic cylinder performs a large number of cycles thanks to the working movement in both directions, so its speed (measured in meters per second) is higher than in the case of single-acting cylinders.
The double-acting cylinder in the pneumatic version is distinguished by a very proven design. Similar devices have been known to mankind for several hundred years and their operation has not changed dramatically since then. As the history of industrial technology and automation shows, sometimes simple solutions are the most efficient. In addition, the advantage of this type of devices is also the fact that it is easy to service and maintain, as well as the purchase of any replaceable parts, for example gaskets. Due to the wide availability of double-acting pneumatic cylinders, you do not have to worry that you will end up in a spot in the event of a cylinder failure. In addition, failures do not happen too often, because thanks to their simple design, double-acting cylinders are considered to be of low failure. Additionally, the actuators are assessed against strict standards. Our double-acting pneumatic cylinders meet the ISO 6432 standard, so they are trustworthy devices.
Double acting cylinder - how to use it?
If you are wondering how to connect a double-acting actuator, you should pay attention to the issue of the aforementioned valves. In the case of double-acting actuators, we regulate their work with throttle-check valves that can be mounted directly in the actuator connection. Due to the fact that the air that leaves the chamber of a double-acting cylinder is choked, it is worth paying special attention to installing the valves in the right direction.
Connecting a double-acting actuator to the control object is very simple. However, before selecting and connecting the actuator, carefully check the compatibility of this element with the rest of the pneumatic system. Only by selecting the appropriate actuator for the parameters of our installation, we can count on the efficient functioning of the system. Failure to adjust the actuator to the installation parameters may result in dangerous failures. For this reason, before the purchase, the actuator must be carefully matched to other pneumatic components.
If we are sure that our actuator is properly selected, most often it is enough to connect it to the pipes on one side, which allows receiving compressed air, and on the other - to the working element. The assembly details may differ slightly from each other due to differences in the construction of pneumatic installations.
Before purchasing a double-acting cylinder, check the materials it is made of and familiarize yourself with the stroke length of the cylinder. It is also good to pay attention to the markings. It is worth knowing which image you can search for a double-acting cylinder - the symbol of this type of device is quite characteristic. The diagram shows a rectangular mechanism with a clearly marked piston rod. The designations of some types of double-acting cylinder differ from each other, as some of them show double-acting pneumatic cylinders with one-sided braking, and others - with double-acting. Thanks to this, we can obtain information about the technical details of a given actuator just by the symbol.