Information on Linear Actuators

The modern times can be characterized as the era of digitization. Numerous gadgets and smart devices have become an integral part of an ordinary person’s life. People often forget about the simpler but not less important devices utilized in the daily practice. Some of them even have a mechanical drive, which the young generation can consider as an outdated technology. Anyhow, such devices or mechanisms do exist and occupy their niche in the whirl of the state-of-the-art innovations. The present article is dedicated to the range of products named linear actuators and their practical usefulness.

WHAT IS AN ACTUATOR?

A synonym to the word “actuator” is a “mover”. Actuating means inducing a movement. When we talk about a linear actuator, we mean a device inducing a motion in a straight line. The word "motion" can envisage different meanings: closing/opening, lifting/descending, pushing/pulling, blocking/ejecting etc.

Such mechanisms are widely used at industrial facilities and in household applications. Everything set in motion is impossible without an actuator. So, this product deserves a title of a significant device in the modern life.

TYPES OF ACTUATORS

Based on the energy type, the actuators are divided into various types. The categorization of actuators depends on the type of energy applied to cause a motion. Currently, this mechanism can convert mechanical energy, power from electricity, air, and liquid into a motion. Different types of actuators have different advantages and disadvantages. Let’s have a look at each one separately.

Electro-Mechanical Actuators

An electromechanical drive usually consists of the DC electric motor and the reducer. When the electric motor is on, the rotation is transmitted through the coupling to the motion screw. The nut moves linearly through the screw by transferring the force. In fact, the structure is similar to the mechanical analog plus the electric motor. This type is applied in robots with cyclic, position and planimetric management.

Electro-Mechanical Actuators

An electric linear actuator is used to move the clamp mechanisms at clipping and releasing the processed parts. This function is realized on turret machines, milling machines, modular machines and automatic transfer lines.

Advantages

- Low cost

- Maintainability

- Operating process can be automated

- Position feedback.

Disadvantages

- High wear and tear of parts

- Low electrical safety

- High dimensions

At the same time, a range of electromechanical linear actuators consists of multiple types and models including industrial, mini-tube, miniature, high speed, and track models of mechanisms. Efficiency and performance of an actuator usually depend on the quality. Despite the market diversity, linear actuators by Progressive Automations have earned a reputation of trustworthy devices that are widely applied in household mechanisms and for industrial purposes in automotive and marine automation, construction machinery, industrial equipment and automation, advanced robotics and other complex projects and facilities. Currently, all models are represented by the 12 volt actuators. The quality of products is supported by the 18-month warranty. Each actuator model undergoes numerous testing procedures to achieve the top-rated quality.

If you failed to find a suitable product for your needs, there is a full custom option providing an opportunity to build a actuator that will correspond to your specific requirements. Almost any characteristic of a customized device can be altered and driven to your criteria on dimensions, voltage, length of stroke etc.

You will not face any concern related to the installation of a 12 volt linear actuator since each device has mounting holes and can be supplied with mounting brackets of special design. The strongest materials used in their structure guarantee a firm mounting of a device.

Micro Linear Actuator

PA-07-4

Our smallest actuators small size fits perfectly for applications requiring limited space. The PA-07 model linear actuator is a great solution when you do not need high force and long stroke. This smallest representative of Progressive actuators provides 5 lbs of force output. Its moderate values of speed (0.59 in per sec) and stroke (0.5 to 12 in) are in high demand in robotics and miscellaneous manufacturing automation.

Mini Tube Linear Actuator

PA-11-1

Can you guess a meaning of a value 1.18 inches related to a 12v electric actuator? You won’t believe it but this is the diameter of the most compact model, our PA-11-D30. This unit is not packed with force (33 lbs) or speed (0.44 in per sec) but its attractive dimensions are highly appreciated by customers involved in marine and automotive automation, as well as robotics.

Mini Linear Actuator

PA-14-2 (2)

This model is larger than the previous one but still is a compact solution. The application range includes an automation in various areas like a production of furniture or robotics. Depending on your needs, the PA-14 electric actuator is available in three versions with different force values (35, 50, and 150 lbs). Stroke size is one for all versions and reaches 40 in. At the same time, the most powerful version has the lowest speed and vice versa. Speed values are 0.59, 1.18, and 2.00 in per sec.

Feedback Linear Actuator

PA-14P-1

At first glance, there is no difference between characteristics of PA-14 and PA-14P. However, the latter model of linear electric actuator offers a sought-after feature called a potentiometer. This device lets you know the positioning of an actuator. The scope of application is endless since the actuator is rather convenient for different purposes.

Mini Industrial Actuator

PA-09-3

What will be if we take the model Pa-14 and increase its power? We obtain a high-performance unit providing 330 lbs but keeping its small dimensions. For this reason, the device accomplishes tasks requiring much power but less space. The PA-09 is quite popular among customers engaged in such areas as manufacturing, robotics, marine automation etc. Reduced speed (0.27 in per sec) is another difference of this industrial actuator from its donor model.

Linear Actuator with IP-66 rating

PA-04-2

Ingress Protection 66 envisages the maximum dust protection and the water splash protection. So, the 12 volt linear actuator withstands pressure 100 kPa. The PA-04 is a rather forceful device available in two versions (400 and 100 lbs). The mentioned protection rating makes the actuator a fit to the application in marine automation and robotics.

Linear Actuator

PA-03-1

The model index is fewer than of the previous actuator but it does not stipulate a reduced force. On the contrary, the PA-03 model provides an increased value – 600 and 200 lbs versions. However, stroke value is fewer and ranges from 4 to 24 in. The model will be a great solution for automation of manufacturing process in any industry.

High Force Industrial Actuator with IP-66 rating

pa-13-1-

The above-mentioned benefits of IP-66 rating do not require explanation. At the same time, this feature is not the major advantage of PA-13. In fact, this model is the most powerful device among the Progressive linear actuators. Despite a low speed of 0.25 in per sec, the mechanism is capable to provide 3000 lbs of force. As a rule, such requirements are essential for construction and manufacturing applications where this model has been successfully used.

Heavy Duty Linear Actuator

PA-17-1

A combination of force and performance is a hallmark of the PA-17 model. Force values provided by this linear actuator are lesser than of the previously mentioned unit. However, 2000 and 850 lbs (two version available) are considerable values that are required for construction, industrial, manufacturing purposes, and boat automation. Protection class is IP-65 proving a heavy duty characteristic of the device.

High Speed Linear Actuator

PA-15-1

Even the fastest model among the above-mentioned ones cannot be compared with this lightning-fast unit. It is not a joke because nine inches per second is a considerable speed in the world of linear actuators. At the same time, the speed increase is available due to the reduction of force. Thus, the most powerful unit provides 33 lbs at 3.15 in per sec. The fastest PA-15 (9.05 in per sec) can carry only 11 lbs. Such characteristics are unpopular for industrial purposes. Anyhow, automation in marine and automotive industries is the target area of use of high-speed actuators.

Track Linear Actuator

PA-18-1

The main advantage of this model of 12v actuators is its structure. As a rule, when choosing a linear actuator, it is necessary to consider its dimensions in extended and initial positions. PA-18 releases you from such concerns since its design does not stipulate any additional space. This model can be encountered as a part of sliding chalkboards or large moving displays. In addition, force parameters are also impressive. A moderate force value of 150 lbs for the largest share of applications and an incredible 900 lbs for special needs. Stroke size is also considerable (from 2 to 60 inches).

Mini Track Linear Actuator

PA-08-2

If you liked the structure of a track linear actuator, you would appreciate the particular model that combines features of PA-14 and PA-18. No extended size is the major peculiarity of PA-08. In addition, small dimensions allow it fit in tight space that is really necessary for various types of automation purposes. Moreover, the mini track actuator can boast of sufficient force (50 lbs).

Mechanical Actuators

mechanical-actuator-1

To get a linear motion at a mechanical actuator, a rotary motion is required. The different mechanism types enable such conversion of mechanical power. These include cam, screw, and wheel plus axle. The working principle is simple. A user has to rotate or apply force in another way to an external mechanism to move the shaft. A car jack is a decent example of a mechanical actuator. Yet, despite the apparent outdatedness, this type of mechanism is used often for the exact positioning of an item. Such fields as working with lasers or optics require an accurate adjustment.

Advantages

- Low cost

- Simple structure

- High maintainability

- Long durability.

Disadvantages

- Low speed

- Low accuracy

- Low specific capacity.

Hydraulic Actuators

This type of actuators is widely used to transfer high power and induce motion via the liquid. This function is performed due to the incompressibility of liquids. A simple structure of a hydraulic actuator consists of a hollow cylinder with an inserted piston. An applied pressure induces a motion along the piston axis. The ratio of the piston areas enables to operate the high forces. Thus, a smaller force can be transformed into the bigger one. This feature makes a hydraulic cylinder an irreplaceable mechanism for the various types of machinery. These include the building machines, rolling mills, pressure equipment. The car drivers are familiar with the hydraulic actuator used for the steering system. You can also encounter the device in the smaller equipment such as rock drills, grips etc.

Advantages

- High specific capacity

- Stepless speed regulation of an output element in a wide range

- High operation speed

Disadvantages

- Dependency on the operating conditions

- Structural frangibility

- Low KPI

- Low durability

Pneumatic Actuators

The working principle of this type of mechanism is identical to the above-mentioned hydraulic type. Yet, there is the major exception – a liquid is replaced with a compressed gas. A compressed gas delivered to a chamber generates force and causes motion of a piston. Thus, an air compressor acts as a power source. Thus, the pneumatic actuators the preferable solution for the number of industrial facilities.

The scope of use of pneumatic cylinders is similar to its hydraulic analogs. They can be encountered in the heavy machinery and equipment such as pneumatic grabs, mechanical arms (manipulators), pressure equipment, dividing mechanisms etc.

Advantages

- Simple structure

- Maintainability

- Fire safety

- Fail-safe performance in different operational conditions

- High-speed operation

- High durability

Disadvantages

- High cost of the pneumatic power

- Heaviness

- Large dimensions

- Low signaling speed.

Piezoelectric Actuators

If this term seems weird, you might be familiar with another notion of a piezoelectric actuator namely ultrasonic motor. The idea of this mechanism lies in the property of certain materials to expand when they are exposed to a voltage. A picture will be clearer if we explain the working principle. The key element is this structure is a piezoelectric element, which loses its shape upon electrical action. This element induces the ultrasonic vibrations creating a mechanical running wave that in turn moves a rotor. Although everything seems clear, you require huge efforts and sophisticated equipment to implement the principle.

The equipment requiring the minimum angular and linear movements may contain the piezoelectric actuators. They are widely utilized in astronomy devices, the charge particle accelerators, and robotics. The piezoelectric motors were the basis for the development of actuators in antennas and surveillance cameras, electric razors, cutting tools, tape drive mechanisms, electric drills, ceiling fans and other useful devices.

Advantages

- Possibility of a direct actuation for any rotation speed

- High operation speed

- Operation at various adverse conditions including high temperatures, vacuum, strong magnetic fields, and increased radiation.

Disadvantages

- Short actuator stroke

- High voltages required

- Expensive and fragile structure

- Effective for compression only.

TYPES OF LINEAR ACTUATORS

The above-mentioned types of linear actuators are differentiated on the basis of the energy used for their operation. The following categorization is different since it divides different actuators types by the structure type. We start with the most common type of linear actuators – screw type.

Screw Type

This linear actuator working principle envisages a movement of a screw shaft induced by the rotation of a nut. The screw type linear actuator is driven by electric or mechanical power. According to the thread type of a screw, another classification is offered.

Lead screw actuators

This structure stipulates the usage of a screw as a linkage. A linear motion is caused by turning a screw. This type of actuators is not designed for high power because of the large losses of the frictional area. The geometry of the thread differs resulting in another classification by the thread type. The more the friction the less the efficiency of the thread. Hence, the V-shaped threads have the smallest share of the lead screws among the competitors.

ACME Screw 2

 

The most effective geometry for lead screw is the square and triangular shapes. Both types can boast of low friction and capacity to carry a high power. At the same time, most of the actuator manufacturers opt for the ACME thread geometry. The reason is the high manufacture cost of the triangular and square types. ACME type is also known as trapezoidal shape. Although this geometrical shape is less effective than the traditional square, it has a higher load-bearing capability. Thank these properties, ACME thread has a status of the most common thread form in the world.

Ball screws

Ball-Screw

The ball screw is the main alternative to the leadscrew. The main difference is a minimum friction achieved due to the ball bearings used as a screw. Such structure is perfectly applied when a high precision is required. For example, the control surfaces in missiles and airplanes are moved using the ball screws. Despite the considerable advantages, this type of screw loses to the ACME screw linear actuator. The latter has the better cost-effectiveness.

Planetary Roller Screw

Another screw-type actuator that can boast of minimum friction is called a planetary roller screw. It has a two-way function because it can induce both rotational and linear motion. In spite of a rather complex and therefore expensive structure, planetary roller screws can be encountered in many electro-mechanical linear actuator applications. The roller screw is a perfect solution for the high-precision and heavy-load applications.

roller-screw

Unlike the ball screw, the load transfer elements in a planetary roller screw are the rollers. They can be either threaded or grooved. Such structure provides a larger amount of bearing points resulting in a similar to ball screw efficiency at low speeds. At the same time, the efficiency grows along with the growth of the speed. The main advantages of the roller screws include precision, rigidity, load rating, acceleration, lifetime, and speed.

Belt Type

This type of actuator has a belt acting as a linkage. As a rule, a belt is made of a flexible material in a loop shape. It transmits force from the driving pulley to the following pulley. Due to the loop shape, the location of the pulleys is not defined strictly.

Belt Drives

The structure of any belt drive is similar with small differences in the type of a belt and location of pulleys. This drive type attracts with its simplicity and low price. They require minimum maintenance and no lubrication. The machine will not face any jams or overload if a belt drive is used. Besides, the efficiency of such drives is rather high. Unfortunately, everything has its flaw. In this case, the belt is the main hence the most vulnerable element of the structure. It can stretch or slip down unless a toothed belt is applied.

Geared Drives

The first thing coming to the mind when mentioning a geared drive is a gearbox in the motor vehicles. However, this drive type has multiple miscellaneous applications. The power is transmitted via the gears from the rotating driving element to the driven one. The torque and the transmitting power can vary due to the size of the input and output shafts. The application of the geared drives can be encountered in various types of equipment including industrial, agricultural, construction etc.

Direct Drives

Geared and belt drives stipulate a loss of power because of a linkage. A direct drive mechanism has no intermediate elements and does not lose power because of friction. The working principle is simple – the shaft for motor and the driven element is the same. A good example in the household application is a washing machine or a fan. Such structure has numerous advantages but depends completely on the motor type.

Rod Type

The operation principle of the rod types of linear actuators is based on the use of the metal hollow threaded tube as the pulling/pushing element of. The rod connects to the long screw fixed on the rotor by the screw gear. When the rotor rotates, the rod goes up or down (forward or backward) by virtues of the movement of the screw.

Rod style

A rod actuator is a perfect solution when you need to push or pull something. The electric and pneumatic cylinders represent the rod styles actuators.

Rodless style

Judging from the name, this type of actuators is free of a rod. Unlike the rod style mechanisms, the rodless devices do not pull or push but move along the carriage. Such type is represented by the electric, hydraulic, and pneumatic drives.

BASIC LINEAR ACTUATORS SPECIFICATIONS

Any device can be described by mean of the technical specifications. This information is necessary to detect the applicability of a certain mechanism to the established requirements or conditions. The following specifications are essential for the selection of the actuator applications.

Stroke Size

This notion describes the length of the actuator’s functioning namely the length of the extension. This value is not necessary to be high. A linear actuator long stroke is applied mainly at the industrial facilities. The smaller stroke sizes suit better to a more precise production.

Force or Load

As a rule, this value is expressed to understand the permissible weight of an item to move. The value is expressed usually in Newton (N). The largest force specifications are commonly found in pneumatic or hydraulic cylinders. A high force linear actuator suits for the heavy industries. The household or accurate actuator applications find it absolutely useless.

Speed

This value determines the time required by an actuator to move. Usually, the mechanically driven actuators are the slowest. Fast mechanisms are necessary for the constructional needs. At the same time, a slow speed is associated with the precise applications.

Duty Cycle

A linear actuator duty cycle means the frequency of the device operation. It is expressed in the amount of repetitions within the specified period (strokes a minute, minutes an hour, hours a day). The largest share of linear actuators require pauses between the operations to avoid overheating. Nevertheless, the heavy-duty mechanisms can boast of a higher duty cycle value.

Voltage

This value is applicable to the electric driven actuators and means the power supply options. In addition to the very value of voltage, the type of current (direct or alternate) is also essential. As a rule, the source of power depends on the motor requirements.

IP Rating

The full abbreviation expansion looks as Ingress Protection Rating. In simple words, the numeric IP shows the degree of protection of a linear actuator. The protection stipulates the ingress of foreign objects, liquids, and other materials that can interrupt the safe operation of the device. For example, an actuator with IP65 has the highest dust protection (6 – dust tight) and a protection from low-pressure water (5- water jets at 30 kPa).

APPLICATIONS OF A LINEAR ACTUATOR

In the scope of the present article, numerous types of application were mentioned. You can encounter the use of this mechanism in simple domestic appliances and in the heavy-duty machines on the mass productions. Yet, the devices differ in their specifications and structures they perform the similar functions.

Home and Office Application

home

Look around while sitting in an office chair. Many surrounding devices contain a linear actuator. Even the chair – most of them are equipped with pneumatic or mechanical actuators to regulate the lifting stroke. Usually, these mechanisms in the household application are introduced by the electric actuators.

Industry Application

media-20170828

It is impossible to imagine this area without the use of various types of actuators. In fact, to list all the practical applications on the industrial facilities, we will need several dozens of pages. Various equipment, processing machines, lathes, auxiliary devices, and other miscellaneous electrical and mechanical mechanisms are associated with the linear actuators in some or other way.

Medical Application

medical

Due to the need for precise operation and smaller sizes, the mechanisms used in medical area are introduced mainly by the electric and mechanical actuators. However, this area is so vast that you can encounter the hydraulic mechanisms either. Here is a small list of devices equipped with the linear actuators in the medical industry:

- treatment chairs

- dental chairs

- wheelchairs

- electric patient lifts

- electric couches/tables

- bath lifts

- hospital beds

- home care beds

- nursing home beds

- stretchers

- incubators.

FEATURES OF A LINEAR ACTUATOR

    • Wide Application Range

No doubt that the scope of application of the mentioned devices is almost unlimited. It can be an integral part of the complex mechanisms as well as a right hand for a person in the daily routine.

    • Relative Structure Simplicity

Naturally, there are complex devices designed to the certain industrial needs. At the same time, the largest share of the linear actuators includes the durable simple mechanisms. Besides, they are easily repairable.

    • Selectivity

Some of the types of actuators are irreplaceable. So, you have a choice what to opt for – mechanical, electric, piezoelectric, hydraulic or pneumatic type.

    • High Performance

In accordance with a wide choice of options, your production or business can be improved by the use of the proper type of the mentioned device.

    • Up-To-Dateness

The development of the linear actuators has not stopped on the simple mechanic drive with a threaded screw. Progress requires the implementation of complex solutions. Today you can opt for the innovative solution stipulating a remote control or timer for the effective operation.

    • Modesty

Naturally, the mechanism cannot experience the human feelings like pride. However, if they could, modesty would be the main attribute of the linear actuator. We face the benefits of this technology every day and do not even think about the usefulness granted by these devices.

    • Irreplaceable

Could you imagine the absence of the linear actuators in the life? For example, how would you lift a car to replace a broken wheel? There are many similar examples. And all they evidence the necessity of this mechanism for not only an industrial scale but also for the daily routine.

Conclusion

We hope that when you read this article you would be able to give an extended answer to the question “what is a linear actuator”. In fact, the world of these devices cannot be described on a couple of pages. They offer multiple interesting things for even a regular person not related to some industrial affairs. Yet, now you are aware of the practicality and usefulness of the mentioned technology.

 

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