New technology could render pneumatics too expensive to run

With these objections in mind, Southend-based Direct Thrust Designs has developed ElectroPistons. These are a new alternative to air pistons claimed by the company to be 'The world's first linear electric piston'. The inventor is Hugh-Peter Kelly, whose track record includes the development of the tubular linear motor back in the late 1980s. And, as with this invention, the ElectroPiston – rather than using compressed air to provide the motive force – instead provides a combination of powerful magnetics and DC electrical power. Kelly describes the potential applications for this technology as being: "Any application where there's something that goes back and forth and where the user would prefer to use electricity rather than compressed air." He is keen to point out, however, that it is not a solenoid, a linear actuator or a linear electric motor but instead a, "controlled in-out motion, which does not require complicated, expensive control circuits". The advantages inherent to this technology include the fact that it is many times more efficient than pneumatics, offers no power drop off or time lag with multiple rams and has a very quick setup, high reliability and is virtually silent. However, the real selling point of this solution lie in the cost savings it can offer. These are fairly spectacular, although this is hardly surprising when one considers the sheer quantity of equipment eliminated by this development (compressors, air preparation, filtration, control valves, etc) as well as the electricity required to run them. In fact (based on figures given by a pneumatics supplier, Kelly admits), the five-year total of running this system is £1705.75 (capital cost £907.40, annual running cost £159.67), as opposed to £7422.50 for a four-cylinder compressor system. As Kelly puts it: "We think that this has the potential to render old-fashioned pneumatics simply too expensive to run." The pistons provide smooth continuous force over their entire stroke, exactly the same as pneumatic pistons, but without all the complications and expense associated with compressed air supplies. Using a novel and patented technology to obtain their linear and smooth powered movement, the forces they are capable of providing are many times that of conventional solenoids, making them useful for countless industrial applications. The ranges of ElectroPistons available from Direct Thrust Designs cover push/pull forces from a 1N up to 141N for the single block range and up to 282N for the double block range. It is important to select the correct specification unit for the intended job and duty cycle, especially when operating at the top end of performance. The product has only one moving assembly, and is therefore low-maintenance. Maintenance is confined to the checking of and occasional cleaning of the guidance rod surfaces and the unit itself. The moving part of the ElectroPiston (known as the "thrust rod") contains application specific permanent magnets. The stationary part (known as the "thrust block") contains especially configured electrical coils. When the coils are energised, a magnetic field is created which interacts with the powerful fields produced by the thrust rod. This causes linear movement of the rod to either end of its movement, the direction of travel simply depending upon the direction of the current flow. The force of the movement is similar to air systems, the greater the supplied current (akin to air pressure) the greater the push/pull thrust available. The force is equal in both directions. The pistons are built to withstand heavy industrial use, and can be installed to provide repetitive push / pull movements for virtually any type of machinery. Proprietary igus linear bearings are used to guide the bearing shafts on all three ranges. These have been selected as suitable for continuous, arduous industrial applications. Unlike air pistons, there are no air seals or valves to wear with age or use. Correctly used, the life of the magnetic components themselves is theoretically infinite. ElectroPistons are equipped with a rugged bearing system and each size of ElectroPiston in this range has been proof tested in free running (in line) direct push/pull mode to over 100,000,000 cycles. This is equivalent to one stroke per second over a 16 hour shift, five days per week for seven years. ElectroPistons have an extremely rapid response and can move end to end in a fraction a second, so potentially speeding up automation operations. With low inertia loads, they are capable, depending on the unit size, of speeds from 6 to 18 or more full cycles per second. With the benefit of the velocity control option, they are also able to move at slower speeds, so making possible various speed/stroke combinations such as 'slow in, fast out'. The operation of the ElectroPistons is virtually silent, the only associated sound being contact of the end plates with the body at the extremes of stroke. All the hissing and escaping air noises associated with conventional air pistons are avoided, so transforming the noise pollution suffered by air systems and the users operating them. Unlike pneumatic products, the force exerted by ElectroPistons in either direction of travel is the same, as opposed to that of the bi-directional air pistons in which the surface area of the piston reduces force in one direction of travel compared to the other. This system is also inherently clean. The pollutants associated with compressed air driven systems are absent, and for many applications they can operate without any external lubrication. For this reason they are an ideal choice for automation systems operating in hygienic environments, such as food processing, sensitive electronics or medical equipment. ElectroPistons instantly respond to the electrical power supplied to them. There is no mechanical lag, or need for pressure build up, regardless of the number of pistons installed in a particular system. With compressed air systems, a continually running compressor uses considerable electrical power. ElectroPistons only use electrical power when energised. A recent report by the UK based Carbon Trust states that on average only 20% of the electrical energy used by a compressed air system is expended in moving the air piston. With ElectroPistons, it is 100%. Another surprising facet of the ElectroPiston is revealed when Kelly places a 27kg weight on top of one, which it proceeds to lift easily. "That is just for people who think that linear actuators are weak," he smiles. That said, he does make clear that ElectroPistons are not suitable for providing very large forces. However, Kelly remains aware that it is going to be a challenge to shift people from the pneumatic systems they have been using for decades. He says: "The only way to really persuade people of the worth of this system is if they buy it and run trials. Obviously, the technological, environmental and – most importantly – cost arguments are very strong, but only by using them and seeing that they work will people ultimately be convinced.