Derek Mack explains why more engineers than ever before are turning to Electro-Mechanical linear actuators as their first choice of actuation mechanism
The world of solid and bulk handling represents a demanding industrial environment where plant and machinery must be robust and reliable.
Bulk solid materials are almost certain to be dirty or dusty – or both. Further, they are fairly likely to be hard or heavy – or both. It’s little surprise that these materials are notorious for causing damage to handling machinery through shock loading, impact damage and ingress of dust and other fine particles.
As a result of these prevailing conditions, engineers designing and building bulk-handling machinery always go for an ultra-robust approach, using heavy gauge metals and design details that can cope with years of arduous duty. However, it is inevitable that in any machine design some parts will be more critical than others.
In bulk-handling machinery, the most fragile parts used to be the drive mechanisms that open and close gates, diverters and valves. Machinery designers had to go to great lengths to protect these from impacts and dust ingress.
A standard solution within the industry for delivering linear movement has been hydraulic cylinders – these are able to transmit heavy loads and have relatively few moving parts which make them more reliable. However, they do have several drawbacks which can make them cumbersome to install.
The hydraulic cylinders have to be supported with a power pack which consists of pump, motor, oil tank, regulators, filters etc. – all of which are then connected by piping to a control system. This creates additional expense and also requires a frequent regular maintenance schedule to prevent problems such as oil leak contamination particularly where food stuffs are handled.
Fortunately Tsubaki offers an alternative that provides a linear drive mechanism which can withstand the rigours of the bulk-handling environment. It is also easy to specify, easy to fit, requires little maintenance and is so versatile that it can be used in many configurations.
Linear actuators, such as the Power Cylinder range from Tsubakimoto Europe, are sealed, one-piece actuators that combine an electric motor and a ball screw. The motor drives the actuator mechanism via gears, which serve to step down the motor speed to the operating speed and enlarge power. It is also a standard to fit Power Cylinders with a simple overload protection device and with a brake that is automatically applied when the motor stops, thus holding the load safely in a fixed position.
Outwardly, they are designed to be robust and to have a high level of protection against ingress of dust, dirt and other contaminants. They may also include integral wiring, lubrication, end-stops and other elements to create a plug and play unit that can be fitted with a minimum of fuss, yet ensure a long and reliable running life. Furthermore, they are likely to include a means for easy mounting of position sensors so that they can be easily integrated into an existing control system.
The Tsubaki Power Cylinder range is ideal for the rigours of bulk handling with impressive performance across many different sizes. For instance, the available thrust ranges from 0.25kN to 882kN, stroke lengths are offered from 50mm to 2000mm and speeds vary from 8mm/s to 333mm/sec. They can be fitted with different types of motor to suit each application, including induction, stepper and servo motors.
In use, a power cylinder provides forwards and backwards’ linear motion up to a defined maximum stroke. This can be refined by fitting the cylinder with position sensors that have the capacity to stop at set-points along the stroke; alternatively an encoder can be used to give the ability to stop at any selected point.
Introducing electro-mechanical linear actuators to a design in place of more traditional hydraulic systems can provide a number of benefits. The self contained nature of these powerful components eliminates the potential for oil leaks, improving reliability and reducing maintenance time. The Tsubaki Power Cylinder range is extremely varied to cope with most industry requirements. To ensure that operation is both reliable and efficient it’s important that the correct size is selected, with load and stroke requirements taken into consideration.
When specifying linear actuators, it is important to consider the need of options, such as anti-rotation, potentiometers, encoders and other sensors, bellows to protect against dust and water ingress as well as mounting and fixing options. These decisions can be straightforward, but Tsubaki engineers are always available to carry out site visits or consult during design stages to offer any support that may be required.
Tsubaki Power Cylinders are easy to specify and provide a robust and reliable drive mechanism that is suitable for even the most demanding of bulk handling situations. This compares to the alternative of designing and building a complete hydraulic system that requires careful installation and commissioning, consideration for protecting the relatively delicate hydraulic drive cylinder and provision for addressing potential oil leaks and any subsequent contamination.
Derek Mack is with Tsubaki UK.