NFPA How fluid power technologies are Speaks out...

A SUPPLEMENT TO DESIGN NEWS DECEMBER 2010

NFPASpeaks out on:

How fluid power technologies are providing effective solutions impacting the performance and energy efficiency of a wide range of applications.

How Caterpillar Applies Electro-Hydraulics for Efficiency

Machine Tooling with Compact Hydraulic Power Packs

Pneumatics in Small Medical Devices

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F2 FLUID POWER / A SUPPLEMENT TO DESIGN NEWS DECEMBER 2010 [www.designnews.com]

FLUID POWER

A n increasing corporate focus on energy effi -ciency is a signifi cant design trend aff ecting mobile hydraulics based on the belief that fuel costs will continue to rise and there will

continue to be upward pressure on fuel prices as global demand for energy increases. End users’ interest in sustainability and the impact of greenhouse gas regula-tions adds this focus on energy effi ciency.

For a company such as Caterpillar — a manufacturer of construction and mining equipment, diesel and natural gas engines, and industrial gas turbines — looking specifi -cally at the fuel burned in the aggregate of all its machines, around 60 to 70 percent of that fuel used is consumed by the hydraulic system. So as Caterpillar looks to control owning and operating costs of its machinery, a major area to hone in on is hydraulic system effi ciency.

Tana Utley, vice president and chief technology of-fi cer at Caterpillar Inc., says that, “We view hydraulics as an important part of our future because it’s hard to fi nd a technology with greater power density that is continuously variable. Hydraulics will be part of our future platforms for a long time because the technology allows a very fl exible routing of power.”

KEY AREAS OF FOCUSTo understand Caterpillar’s energy-conscious approach to hydrau-lics, let’s fi rst look at the three “hows” driving Caterpillar plans.

According to Utley, the fi rst “how” is thinking about hydraulic system effi ciency and it starts with attention to details such as all of the bends, leak sources, radii and transitions in fl ow that can be targeted to improve effi ciency at the component level.

Th e second “how” entails looking at the system architecture, and how the components are put together. Beyond that, Cater-pillar looks at how to control this architecture, which includes

the integration of electronics into hydraulic systems.Th e fi nal “how” is to enable capabilities for even greater

owning and operating cost benefi ts. Hydraulics, and especially electro-hydraulics, is the platform for semi-autonomous and fully autonomous functions on Caterpillar machines.

Th ere are six key areas where Caterpillar is focusing to in-crease hydraulic system energy effi ciency:

• minimizing metering losses;• improving component and system effi ciency;• recycling lost energy;• reducing parasitic losses;

Tana Utley, vice president and chief technology offi cer at Caterpillar Inc., discusses how energy use and EPA Tier 4 emissions regulations puts the company’s design focus squarely on hydraulic system effi ciency.

BY AL PRESHER, CONTRIBUTING EDITOR, AUTOMATION & CONTROL

How Caterpillar Applies Electro-Hydraulics for Effi ciency

The Caterpillar M-series motor-grader uses high-tech Triple-P (propor-tional, priority, pressure) compensating electro-hydraulic valves to imple-ment proportional control. Use of the priority and pressure compensation controls allow the motor-grader operator to use two joysticks, rather than a series of eight knobs, to control the blade.

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• optimizing engine operating points; and• improving operator and worksite effi ciencyTo minimize metering losses, one area of focus is the inte-

grated electro-hydraulic valve control that enables intelligent control of valve position to minimize restrictions. “We are do-ing that today in our hydraulic systems,” says Utley.

Another area of focus is hydraulic excavators that use a cross-sensing system with two separate hydraulic implement pumps. Th is system enables Caterpillar to separate the circuits and the pressures during certain operations to control metering losses.

Th ough fi xed and variable displacement piston pumps have been around for a long time, another issue Caterpillar is work-ing on is the next generation of variable piston pumps, with a focus on volumetric and mechanical effi ciency. Utley says the objective here is to be able to deliver higher pressure and quicker response times. “We are also developing this family of pumps in concert with our engines of the future so that our engines will run at their optimum operating points,” she adds.

“With what we are facing with EPA’s Tier 4 regulations, hy-draulics and how we tune our hydraulics are beginning to have an important infl uence, not just on overall machine perfor-mance, but also in how we address those regulatory challenges,” Utley says. “We use computational fl uid dynamics (CFD), a mathematical model of how fl uid fl ows through a system, to know — before we cut any iron — the complete design of the system and we can analyze how the fl uid fl ows through the circuits. Th e designer is able to see expansion and losses as the hydraulic fl uid expands, quantify the losses, and change the orifi ce size and the resulting fl uid fl ow.”

To enable the recycling of lost energy, Caterpillar has begun using regeneration circuits in its hydraulic excavators including both the boom and the stick that save energy during the boom-down and stick-in operations. According to Utley, this increases effi ciency, and reduces cycle times and pressure losses that result in lower fuel costs.

“Our wheeled excavator uses a dedicated variable displace-ment piston pump and a fi xed displacement hydraulic piston motor to power the swing mechanism,” Utley says. “Th is pro-vides a recuperative technology with a closed hydraulic circuit that allows us to maximize swing performance without reduc-ing power to the other hydraulic components. Swing braking energy is transferred directly back to the engine where it can be used in other circuits.”

OTHER ENERGY IMPROVEMENTSFans consume a lot of energy, so Caterpillar has begun using hydraulic demand fans which are electronically controlled. Th e units can vary fan speed to cool the engine as needed, thus saving fuel.

“We also carefully design lines and tubes to make sure that the fl uid fl ow is very smooth and is as linear as we can possibly make it, especially at connection points and transitions,” says Utley. “Computation fl uid dynamics also helps us to understand where losses occur, and to improve our design to reduce losses.”

One of Caterpillar’s goals is to reduce the top engine rpm, especially in applications such as hydraulic excavators.

“Historically we have had a high engine operating speed to accommodate the heavy hydraulic demands that we get in

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DN101208_003 3 12/10/10 3:44:54 PM


FLUID POWER

those applications and to ensure we have suffi cient pump response,” says Utley. “Instead of tuning the engine to run all of the time at a high rate of speed, we are now tuning the en-gine at a lower rpm, which enables us to optimize the engine performance. It also produces the very best fuel consump-tion at a lower engine rpm where it more naturally runs at a sweet spot.”

Another energy question continually facing Caterpillar is how to supply the right kind of power for a heavy transient de-mand in a hydraulic system. Currently, Caterpillar believes the answer is to speed the engine up temporarily which allows it to run at the sweet spot most of the time and provide the transient power only when needed.

HYDRAULIC EFFICIENCYLooking beyond direct hydraulic effi ciency, Caterpillar also considers the effi ciencies of what the hydraulic system itself en-ables. Th is includes technologies such as Caterpillar’s Accugrade system, which uses electro-hydraulic systems as a fundamental building block. Accugrade and auto-dig features rely on the ability of the machine to sense the position of the blade and control it based on the diff erence between what the computer thinks is the blade’s ideal position and the actual position.

Utley says it is not uncommon using Accugrade technology to see a 20 to 30 percent improvement in the effi ciency of an earth-moving job. “In hydraulic effi ciency, a fi ve or 10 point improvement is tremendous,” she says. “We have achieved 20 percent with a basic electro-hydraulic system; adding the po-sitioning technology has enabled us to implement innovations such as Accugrade to drive additional improvement gains.”

Hydraulics are not just used by Caterpillar to power machine work, but also for operator comfort.

“Th ink of the geometry of these machines when the operator is carrying a load and must drive over bumpy surfaces,” explains Utley. “On a tough worksite, the machine begins to bounce, which can cause the operator to slow down and even start dumping out the contents of the machine’s bucket.”

One of the technologies Caterpillar uses on its 938H wheel loader is a ride control system that off ers an option of using four nitrogen-charged accumulators set to diff erent pressures that enables the machine’s hydraulics to provide optimum cush-ioning over uneven terrain at all loads and speeds. “Since hy-draulics is a means of distributing power,” says Utley, “it takes hydraulic energy to do that. But in order to optimize energy consumption, we activate the system only when the operating speed is greater than 3 mph and the operator is in carry mode.”

For more information, go to www.caterpillar.com

The Caterpillar M-series motor-grader used for fi nish grading is an example of advanced electro-hydraulics includ-ing fl y-by-wire technology and joystick controls.

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Très chic: the designer pump.

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FLUID POWER

T hrough the use of leakage-free seated valves, two-way pressure reducing valves and a higher effi ciency radial piston pump,

Schwaebische Werkzeugmaschinen GmbH has been able to achieve energy savings of 73 percent on its BA 400 machining centers.

“One of the main ways to save energy with a machine tool is to control the creation of heat, so you don’t need to cool the tool down again,” says Ullrich Breuner, sales manager with Hawe Hydraulics, which worked with Schwae-bische Werkzeugmaschinen to increase the effi ciency of its BA 400 machining centers. “Working with Schwaebische Werkzeugmaschinen, we started de-veloping seated valves that are leakage free, which is a very diff erent function compared to spool valves."

Breuner says the compact hydraulic power packs used to revamp the BA 400 help save energy in three ways. Th e fi rst, and most obvious way, is by using the leak-free seated valves to eliminate permanent leakage. A second way is the use of two-way pressure-reducing valves to control the diff erent pressures for diff erent functions required by the machine tool while also limiting the leakage rate. Th e

third way involves use of a radial piston pump, which is more effi cient than a gear pump.

“A major benefi t in developing these ma-chines has been the realization that if you reduce the leakage rate, the application can use a smaller pump,” says Breuner. “If you don’t have the permanent leakage rate and the need to re-fi ll, it’s possible to use a 10-liter rather than a 15-liter pump. You are still able to achieve the same clamping time but use a smaller power unit because you have eliminated the leakage. And by using a submersible mo-tor, it helps create a compact system that limits the amount of oil needed.”

RADIAL PISTON PUMP EFFICIENCYTh e BA 400 series machining center is used for small to medium-sized work-pieces, as well as ferrous metal machining. Th e machining center is available with two or four spindles and provides torque up to 200 Nm. It is designed for clamp-ing blanks while workpieces are machined on the opposite worktable; it can also be used for multiple workpiece clamping on

a double swivel table with three linear axes and two rotary axes. Th e workpiece han-dling is done via robots or linear gantries.

Before implementation of the Hawe solution, the machine was fi tted with standard hydraulic controls, but Schwae-bische Werkzeugmaschinen was looking for a solution that would yield substan-tially more energy savings.

Th e Hawe system eliminates use of a gear pump to generate hydraulic energy and replaces it with a radial piston pump, which off ers a higher effi ciency than gear pumps or vane pumps. Th e choice of the pump’s power pack (HK series) also comes with a submerged motor for the drive.

Combining a horizontal machining center with compact hydraulic power packs and 8W seated valve technology in “storage mode” is helping Germany-based Schwaebische Werkzeugmaschinen create a new generation of energy-saving machines.


Machine Tooling with Compact Hydraulic Power Packs

A key advantage is a smaller motor that keeps the power pack compact, and loses less power in idle mode than a standard air-cooled motor.

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FLUID POWER

One key advantage is that the sig-nifi cantly smaller motor keeps the overall dimensions of the power pack compact; and it loses less power in idle mode than a standard air-cooled motor. Plus, at peak demand, submerged motors generate up to twice the rated output where a standard motor would break down due to ther-mal reasons. In a submerged motor, after approximately 30 min, the oil reaches a steady-state temperature, which is consid-ered an ideal condition for operating ma-chining tools. And because the HK power pack is built into an extruded aluminum casing with cooling gills, it allows unhin-dered heat transfer, as the air fl owing by can easily dissipate the low thermal energy.

A key advantage of this design is its low oil volume which, depending on the size of the power pack, can be kept between 0.8 to 4 gal (3 to 15ℓ). Lower oil demand brings down the costs of exchanging oil as well as the strain on the environment. For the machining center, the power pack’s selected size holds 4 gal (15ℓ) of oil. Using its radial piston pump, the power pack supplies pressur-ized oil for operating pressures of up to 10,000 psi (700 bar).

Breuner says those pressures are unusual for machining tools because the majority of applications operate at pres-sures between 2,200-4,400 psi (150-300 bar). But because Hawe manufactures all of its pressurized components from steel, such high operating pressures are not problematic because the components can withstand these loads over long periods. Seated valves made from steel wear less than slide valves in cast housings.

A cooling wheel mounted at the top of the power pack cools both the oil and motor, which means that an additional external cooling unit is avoided by using Hawe’s modular construction kit system. Due to the size of the motor, low oil vol-ume and compact dimensions, the power pack can be built into the machine and integrated into the machining center.

MACHINE OPERATION WITH THE NEW PUMPTh e machining center’s working mode varies depending on the workpiece. Many applications work with a mixture of diff er-ent workpieces, so that both the machine and hydraulics supply must be able to handle everything from continuous opera-

tion to machine set-up time. At standstill, the Hawe system operates in storage mode and saves additional energy which can be used in the machining center.

A smooth switching accumulator charge valve recharges the storage when-ever the duty switch point is reached. Because storage is charged when the machine is started, the machine con-trol monitors this operation constantly. Once the predefi ned pressure has been attained, the valve will switch itself into depressor circulation. At the slightest pressure, oil is re-fed into the tank.

Hawe’s modular system provides op-tions for the input block, such as pressure and return fi lters or TÜV-certifi ed valves. A variety of fi lters and valves can be combined with the BA block to achieve highly customized specifi cations.

Th e BA 400 machining center comes with a combination of sub-plates and a seated valve block (NBVP 16), which again increases the machine’s effi ciency. Because the seated valves are pre-controlled, they work with minimum switching capacity. Th e directional seated valve provides a maximum volume fl ow of 5.3 gal/min (20 ℓ/min) and maximum operating pressure of 5,800 psi (400 bar).

Th e use of directional seated valves saves considerable electric power during opera-tion of the machining center. A machine with 15 spool valves and/or 3-way pressure reducers accumulates a leakage of ap-proximately 0.4 gal/min (1.5 ℓ/min) at 2,200 psi (150 bar), and the confi guration requires an additional drive input of 375W compared to a solution with seated valves.

In a two-shift operation, each with eight hours per day and 200 working days per year, this adds up to 1,200 kWh for each machine. Plus, the heat gener-ated by the additional energy input also needs to be lowered, which means that the power saved doubles once more.

“Th e hydraulic power pack system has been available for more than 10 years,” says Breuner. “But, until recently, few compa-nies were thinking about energy savings. Now companies are thinking more about the total lifecycle, not only the initial investment but also ongoing operational costs. If you need 1,200 kilowatts less per year to run the machine and there are 10 machines, the savings are signifi cant.”

For more information, go to www.hawe-hydraulics.com.

Select Wire-ReinforcedHoses Based on WorkingPressure Requirements

Hydraulic hose reinforcement varies with itsrated working pressure.

Hoses with low working pressures normallyuse fabric reinforcement, while those handlinghigher pressures use high-strength steel wire.

Steel wire reinforced hoses come in two types:wire braid and spiral wire.

Wire braid hoses can handle working pressures up to 6,000 psi, depending on size.These “two-wire” braid hoses are frequentlyfound in high-pressure hydraulic applicationson construction equipment. Operating pressuresrange from 6,000 psi for 3/16” I.D. to 1,825 psifor 2” I.D. hoses.

By contrast, spiral wire hoses generally handleup to 5,000 psi in larger diameter sizes, up to2” I.D. Typically, "four-wire" and "six-wire"spiral hoses are used where extremely high-impulse pressure surges are encountered.

Gates newest advancement is its M-XP™

hydraulic hose, which combines the flexibilityof wire-braid construction with the strengthand performance of spiral-wire reinforcement.

M-XP hose has been tested at an industry-leading 1,000,000 impulse cycles – five timesthe SAE standard. This capability increasesservice life and makes Gates M-XP hose idealfor out-of-sight and hard-to-reach applicationslike boom arms and scissor lifts.

Gates M-XP hose is engineered with one-half the SAE bend radius requirement, whichreduces hose length requirements and allowsfor greater flexibility and easier installation inconfined spaces.

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DN101208_008 8 12/8/10 3:01:17 PM

M-XP™ hose brings together the best of spiral-wire and wire-braid.

Introducing a revolution in hose performanceand economy. Gates new M-XP hydraulic hosecombines the flexibility and economy of wire-braid construction with the strength and performance of spiral-wire reinforcement.

There are a million reasons to spec this hose.

Tested at 1,000,000 impulse cycles (fivetimes the SAE standard)at 212°F, M-XP hosecan handle 4,000 psi high-impulse applicationsin all sizes. It is ideal for out-of-sight and hard-to-reach applications like boom arms and scissorlifts used in mobile equipment, construction andother industrial markets.

And the benefits don’t stop there. M-XP hoseis engineered with one-half the SAE bend radiusrequirement for greater flexibility, easier handlingand reduced hose length. Plus, it can be fittedwith economical one-piece MegaCrimp® couplingsrather than more expensive spiral-wire fittings.

It all adds up to a hose assembly that delivershigh performance and low cost.

See what M-XP hose will do for your next hydraulic application. For more information,visit www.gates.com/mxp

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DN101208_009 9 12/8/10 3:01:22 PM


FLUID POWER

W ith the design of medical devices moving toward smaller sizes, a hospital-to-home treatment

model and reduced power consump-tion, electro-pneumatic device makers are seizing the opportunity by providing more potent, miniaturized control solu-tions. By using proportional control to precisely profi le the delivery of air, for example, pneumatic devices are solidify-ing their position as a low cost technol-ogy ideal for a wide variety of handheld and portable medical devices.

“Th ere is a lack of awareness of how pervasive the pneumatic solutions are in medical applications,” says Ed Howe, president of Enfi eld Technologies. “Most people don’t realize how much pneumatics is used in surgical and life support equipment. In the artifi cial heart made by SynCardia, for example, basically the whole drive system is pneumatic and some of the components are similar to what is being used in factory automation.”

RISE OF PROPORTIONAL CONTROLOne clear trend is the move to proportional control and electro-pneumatics for more precise control solutions. Howe says that with devices such as ventilators or respirators, the operation of units in the past has been largely on and off , pushing a breath in and taking a breath out. But now medical device manufacturers are using pneumatics to profi le the breath provided to the patient to be more natural and assist in the recovery process.

“We are working on a ventilator that will work with infants through adults, so that when it’s used in an ambulance, air care helicopter or within a hospital, there isn’t a need for two expen-sive devices,” says Howe. “Th e unit uses a proportional servo valve with embedded electronics and software, and it has a

very specialized shape to the orifi ce and poppet — all together these carefully control the air fl ow.”

Another application using propor-tional pneumatic controls is the process of growing cells either for biomedical research or transplants such as bone marrow cells. Grown in a Petri dish, the yields are very low. But researchers discovered that putting the cells on a fl exible membrane and pulsing the membrane, stresses and pulls the cell. It’s not certain how growth is encour-aged but the obvious theory is that cells recognize the motion and, surrounded by other cells, sense it is in a living host.

“Using a very smooth and fast valve, we are able to replicate the heartbeat

of the host animal rather than just turning the valve on and off ,” says Howe. “We are even able to perfectly replicate the heartbeat of a hummingbird. Th is is an example of pneumat-ics bringing real benefi ts to the medical fi eld by doing things that couldn’t be done before. In this case, we are substantially increasing yields.”

GROWTH OF PNEUMATICSTh e underlying theme to this transition is the use of more proportional pneumatics and better use of control theory. Mechanical elements in the valves are becoming more sophisti-cated, along with better design tools and mathematical model-ing. Systems are using more sensors, electronics and advanced controls to manage pneumatic systems and compressed gases, which has always been the real challenge.

“Pneumatic systems are able to profi le the air and deliver it in a more natural way,” says Howe. “Along with the air pressure profi ling, systems consume less air by only providing what is needed and lower the wear on components, but the big devel-opments are linked to therapeutic contribution.”

Medical industry’s focus on portable, lightweight, low-power designs and more precise proportional control is a fi t for electro-pneumatics technology.


Pneumatics in Small Medical Devices

Specialty servo and electro-pneumatic medi-cal valves provide solutions for proportional control, and offer integrated controller and driver electronics.

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[www.designnews.com] DECEMBER 2010 FLUID POWER / A SUPPLEMENT TO DESIGN NEWS F11

Compared to the past where respirators used large glass tubes with bellows and were primarily electric systems, respirators now use compressed air in a small cylinder, or a small compres-sor and valves, to modulate a system where the devices have been miniaturized.

Another proportional valve application is controlling the pressure of a ventilator that is actually breathing for patients. Th ese more sophisticated ventilators provide pressure control or PEEP (positive end-expiratory pressure), which allows the ventilator to be more eff ective in the transfer of oxygen into the nodules of the lungs that complete the transfer of oxygen into enriched blood.

“With PEEP, the pressure control device makes the ventilator more eff ective by using proportional controls to vary the pres-sure as the ventilator expands the lungs,” says Paul Gant, sales manager for Clippard Instrument Lab.

Electro-pneumatic systems are also being used in automated blood pressure monitoring devices where a valve both infl ates the cuff and controls the rate of defl ation. Th e electronic valve is cycling on and off , and the pressure drops as the device exhausts the air in the cuff . Valves used on these more sophis-ticated blood pressure monitoring devices not only recognize systolic and diastolic pressures, but actually measure the point at which the blood begins fl owing.

“When the cuff is infl ated, the blood vessels are restricted and create a tourniquet,” says Gant. “When the pressure is

slowly released, there is a point at which some of the blood ves-sels release and blood starts to fl ow.”

Sophisticated devices use techniques to notice how quickly the blood fl ow recovers and use that information to diagnose diff erent maladies with the patient. Th e devices use very precise pressure control, versus a device which turns on and off , and provide a gross control. Th e proportional valve allows the ap-plication to inexpensively add fi ne pressure control at the point where those blood vessels are just beginning to open and blood is beginning to fl ow.

DESIGNERS FOCUS ON SIZE AND POWERIn pneumatics for medical applications, the trends are mirror-ing the changes in the medical devices themselves. One trend is portability and movement where in the past the focus was more on in-hospital treatment. Now there is a clear shift to more out-of-the-hospital and home clinical treatment.

“What we are seeing with medical devices is that they’re get-ting smaller and are often made to be ambulatory where they need to be disconnected from the wall for the patient to be able to move around,” says Randy Rieken, sales leader, Americas for Norgren Life Sciences.

In some cases, there is a need for the patient to take the de-vice home. A patient might use a ventilator in the hospital, and the same device might be taken home by the patient and used remotely. With the devices getting smaller and the requirements

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FLUID POWER

for pneumatics changing, components are getting smaller and power consumption is an important design issue. Audible noise levels are critical because, if a patient takes an O2 concentrator or ventilator home, they don’t want to hear the valves actuating.

“Because the components are smaller, issues such as accuracy and reliability are even more important,” says Rieken. “Th e fl ow capabilities of valves, even though they are getting smaller, are often the same as before. Medical device manufacturers are looking for higher performance components in a smaller package.”

Rieken says it used to be that miniature valves were 16 mm, and then 10 mm. But now many are 8 mm and there is work on valves in the 4 to 5 mm ranges. At some point as devices continue to get smaller and smaller, the actual technology may change but now valves are still using the same technologies. Th e current goal is to miniaturize and optimize designs to be smaller but, in the future, technologies such as shape metal alloys and piezo actuator technology may come to the forefront as devices get smaller.

One area where pneumatics continues to provide eff ective components for portable devices is ventilator products. We may think of a big ventilator next to a patient’s bed, but units are becoming smaller and some companies are targeting the C-PAP market (devices that help patients with sleep apnea breathe properly while asleep), where the patient can wear the ventilator on their waist or carry it in a small bag. With oxygen concentrators, devices often weigh fi ve pounds and less and the size of the pneumatics internally is a huge consideration.

“Th e design focus in on size and power, and there are things you can do with power,” says Rieken. “We actually have a PWM (pulse width modulation) valve with a processor that can detect when the plunger is moving to optimize the power but most design decisions are based on the size of the device and battery usage. An oxygen concentrator may need a 12-hour bat-tery life and, if there are four valves in the unit, they need to be extremely low power.”

One area where suppliers are concentrating to provide greater value to customers is engineering expertise specifi c to appli-cations. Th e device manufacturer comes with requirements, schematics and a willingness to consider more highly integrated pneumatic modules. Often these modules include fl ow control, fi ltration, switching valves, fi ttings and safety relief valves all manufactured specifi cally for the application and designed into a compact, optimized module that is fully assembled and tested.

ENERGY-EFFICIENT PIEZO SOLUTIONS“In handheld instrumentation and medical devices, power budgets are being scrutinized more than ever, as a result of a delicate balance between added functionality and power con-sumption,” says Richard McDonnell, piezo products program manager for Parker Hannifi n Corp.

As portable or handheld analyzers continue to shrink in size and device functionality continues to increase, customers are expecting next-generation products to operate longer between battery charges. In the past, instrument engineers might have considered using a hit-and-hold circuit to reduce a valve’s power consumption which uses a higher voltage to open the valve and then a lower voltage to hold it open. Power consumption is

decreased, but it is not as effi cient as piezoelectric valves.But McDonnell says that option is no longer good enough.

For example, one client cited that in an application of two 0.5W valves, the valve’s parasitic power loss was second only to the instrument’s cooling fans. New piezoelectric actuator tech-nology enables the valves to operate in the 100 mW range and, coupled with negligible heat generation, self-latching function and the ability to stay in position without power being applied, are reasons for growing interest in piezoelectric technology.

“How that relates in the world of pneumatics is to provide customers with multi-function valves. It was that idea that led us to developing advanced piezoelectric actuator technologies to augment or perhaps even replace solenoids in the future,” says McDonnell.

Parker has opted to develop its piezo technology around two types of actuators: a 25 mm round, short stroke, low force RLP actuator and its ViVa, a family of actuators with mechanical amplifi cation for applications requiring large displacement and high force. Either type can be used as an independent actuator or as an alternative to solenoid and voice coil type actuators.

McDonnell says Parker’s compliant actuator design increases the piezo displacement well beyond the traditional stack-type piezo, while generating more exploitable forces when compared with Bender-type piezo actuators.

“Because the ViVa actuator is inherently proportional, we can apply the technology in a variety of applications to precisely profi le the delivery of compressed air or gases while minimizing power consumption,” says McDonnell. He says that there is also signifi cant interest in energy recovery and ultra-low-power technology with energy harvesting to create energy indepen-dent systems.

A D V E R T I S E R SI N T H I S I S S U E

Advertiser Page

Bosch Rexroth Corp. 3

Cross Mfg. Inc. 11

Enfield Technologies 11

Gates 8,9

Hawe 5

HydraForce 4

Parker Hannifin Corp. 7

Swagelok 4

Publisher does not assume any liability for errors or omissions in this index.

DN101208_012 12 12/10/10 3:48:34 PM

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