Ever experience the bone jarring, teeth rattling pounding from riding in a boat? Pounding so abrupt and hard you just know your lumbar spine was hammered closer to your cervical spine? The times when you felt like you needed to say to your friends you had a great time, but in truth you were glad to be back on land? Now, imagine going even faster—hitting the waves even harder, and with more frequency...

Gliding on Waves

Covering the vast coastlines of our waterways, the military must at times endure the extreme harshness of fast speed and unnerving demands for control. In order to provide greater safety and control, Clippard's value added team, working in concert with Shockwave engineers, has developed a custom engineered system that provides a much safer, smoother ride.
 

Shockwave Seats, a division of Professional Components, Sidney BC, Canada, has developed products that have been used in numerous markets, including; military and law enforcement, rescue and patrol, racing and performance, cruising and fishing, and much more. According to president David Smith, Professional Components was awarded the single largest shock mitigation seat contract by the United States Coast Guard to supply seats for Homeland Security patrol vessels.
 

"The Coast Guard wanted a simple solution to enable them to adjust the air shock absorber for varying payloads and sea conditions. We had a rough idea of what we needed and built a crude working prototype. Clippard took the idea and ran with it, and within a short period of time we had the slick, robust version we call the RCC or Ride Control Center.The Coast Guard likes it, and we have enjoyed our working relationship with Clippard."
 

It is a very straight forward solution. First, the system is pressurized by pumping the stainless steel cylinder the necessary number of times to allow for the weight of the passenger. It is then locked (stowed) in position. From here, it is a matter of personal preference as far as the cushion of the ride is concerned—the easily accessible ride control valve enables the passenger to adjust the amount of air/ how fast the air can pass through the air volume tank. The more air that is allowed to escape, the more cushy the ride.
 

Clippard's control system includes a stainless steel cylinder, special aluminum manifold, four cartridge stem valves, a ride control valve, mufflers, knobs, and a pressure gauge.

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CASE STUDY

liquid level sensing

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In the early years of process controls, engineers were forced to rely on flow meter tubes and needle valves to control gas flows. Many applications require critical, precise variations of gas control, prompting an ever-growing need for more accurate and repeatable ways of controlling flow and/or pressure of a gas.

The first attempts at electronically controlling gases were electronic units controlled with an analog signal to a board controlling various valves. These units featured greater control when compared to the needle valves, but still had problems with accuracy. Process engineers now have more accurate, reliable solutions with advancements in flow and pressure sensors coupled with new valve technologies.

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The terms mixers, blenders and proportioners are synonymous when it comes to mixing two gases. Mixers are used in many applications across many industries; medical, welding, heat treating and food packaging to name a few. In the medical industry, O2 mixers are use to mix oxygen with other gases, including ambient air, for patient treatment. The mixers allow the doctor to go from a mixture of oxygen, typically from 21% to 100%. Most manufacturers are accomplishing this with modified needle valves that they manufacture.

easy replacement
needle valves

Clippard has been manufacturing and supplying needle valves for a wide variety of applications for over 50 years. We now offer a cartridge style needle valve—the GNV Series—that is especially well-suited for these types of mixing applications. The standard GNV stem will allow knobs to be put onto the end, and added mounting features make it an easy replacement in most situations.

Need help incorporating a Clippard needle into your product? Since we're the manufacturer, modifications are no problem.

proportional control for advanced mixing

For more advanced mixing, Clippard offers two electronic proportional valves. The EVP Series is a #10-32 ported valve and is small in size. The EVP provides air or gas flow control and varies the output flow based on the current input to the solenoid. The consistent gain of the valve provides a high degree of control for mixing applications. The typical flow capabilities for this valve are 0 bubble tight to a maximum flow of about 23 l/min, based on pressures up to 100 psig.

Controllability and overall value are the main features of the EVP Proportional Series valves. The EVP Proportional valve may be controlled by using DC current, open or closed-loop control and even PWM (pulse with modulation).

For higher flow applications we have developed an innovative stepper-controlled needle valve, the SCPV Series. The flow of this valve is again 0 bubble tight to 300 l/min based on 100 psig inlet pressure. The flow resolution is 0.56 slpm per step, with a position resolution of 0.001 per step.

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Original Article, January 2015
By Alan Hitchcox

Applications in food processing plants can really be tough on machine components—especially air cylinders. That's because government agencies require frequent washdown of equipment that comes in direct or incidental contact with food products. These regulations are enacted not only to protect our food supply, but also to protect workers at the food processing plants.

Because bacteria can be found in almost any food-handling scenario, OSHA standard 1910.141(h) specifies that, "In all places of employment where all or part of the food service is provided, the food dispensed shall be wholesome, free from spoilage, and shall be processed, prepared, handled and stored in such a manner as to be protected against contamination." To comply with this and other OSHA and FDA standrads, the food industry—from production to processing—relies on chemical washdown processes to eliminate bacteria.

Chemicals used in washdown processes typically are corrosive or caustic, characteristics that damage metals. According to Dana Johnson, of Birko Corp., a specialty chemical company, "General-purpose cleaners, foaming acids, and self-foaming chlorinated caustic cleaners and sanitizers such, as chlorine, are the most common chemicals used in washdowns." Another compound used solution is sodium hydroxide, which can be a strong caustic.

"Stainless steels have a proven record of being inert and are easily cleaned and sanitized, explained James D. Fritz, PhD, of TMR Stainless, a service provider to the stainless steel industry. "These properties, combined with the ease of fabrication, make stainless steels well suited for food processing applications. Typically, other materials—such as aluminum, copper alloys and coated carbon steels—do not have the same resistance for food processing and cleaning environments." Furthermore, at temperatures below 95° C (203° F), SAE types 304 and 316 stainless steel are resistant to highly concentrated sodium hydroxide.

Clippard's new line of All-Stainless Steel Cylinders resist corrosion and are designed and manufactured for high performance and long life.

In response these challenges, Clippard Instrument Laboratory, Cincinnati, recently introduced a line of stainless steel cylinders intended for use in a broad range of applications, including those in washdown and caustic environments. The quality cylinders are constructed of SAE 303 and 304 stainless steel and are available in bores from 3/4 to 2 in., with standard strokes from 1 to 32 in. on some models. They include a Nitrile rod wiper to keep potential contaminants from penetrating inside the cylinder.

• Maximum pressure rating of 250 psig
• Nitrile U-cup piston seals for full-power, low-friction
  and long-life operation
• Nitrile U-cup rod seals for leak-proof operation
• SAE 303 stainless steel end caps
• FDA Compliant Rulon rod bushing
• FDA Compliant Rulon clevis bushing on all
  universal mount cylinders
• Dimensionally interchangeable with other common brands
  of round-body cylinders
• FDA-compliant grease lubrication and wipers standard
• Temperature range from -20 to 230° F (-29 to 110° C)
• Cylinders have SAE 304 stainless steel tubes with polished bore
  low breakaway friction
• Precision-rolled construction for a solid, leakproof cylinder
• Rods are threaded, bonded, and orbit-formed to pistons
• Ground, polished and roller burnished SAE 303 stainless steel rods
  exhibit a smooth finish that prolongs rod seal life
• Full piston area breakaway to ensure full power from the beginning
  of each stroke
• All stainless steel air volume tanks (accumulators) available

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Original Article, January 2011
By Al PRESHER, CONTRIBUTING EDITOR

Pneumatics in Small Medical Devices

    With the design of medical devices moving toward smaller sizes, a hospital-to-home treatment model and reduced power consumption, electro-pneumatic device makers are seizing the opportunity by providing more potent, miniaturized control solutions. By using proportional control to precisely profile the delivery of air, for example, pneumatic devices are solidifying their position as a low cost technology ideal for a wide variety of handheld and portable medical devices.

    “There is a lack of awareness of how pervasive the pneumatic solutions are in medical applications,” says Ed Howe, president of Enfield Technologies. “Most people don’t realize how much pneumatics is used in surgical and life support equipment. In the artificial 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.”nd FDA standards, the food industry—from production to processing—relies on chemical washdown processes to eliminate bacteria.

Rise of Proportional Control
    One 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 profile 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 expensive devices,” says Howe. “The unit uses a proportional servo valve with embedded electronics and software, and it has a very specialized shape to the orifice and poppet - all together these carefully control the air flow.”

    Another application using proportional 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 flexible membrane and pulsing the membrane, stresses and pulls the cell. It’s not certain how growth is encouraged 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. This is an example of pneumatics bringing real benefits to the medical field by doing things that couldn’t be done before. In this case, we are substantially increasing yields.”

Growth of Pneumatics
    The 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 sophisticated, along with better design tools and mathematical modeling. 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 profile the air and deliver it in a more natural way,” says Howe. “Along with the air pressure profiling, systems consume less air by only providing what is needed and lower the wear on components, but the big developments are linked to therapeutic contribution.”

    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 compressor 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. These more sophisticated ventilators provide pressure control or PEEP (positive endexpiratory pressure), which allows the ventilator to be more effective 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 effective by using proportional controls to vary the pressure as the ventilator expands the lungs,” says Rob Clippard, vice president, sales & marketing for Clippard Instrument Lab. “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. This is an example of pneumatics bringing real benefits to the medical field by doing things that couldn’t be done before. In this case, we are substantially increasing yields.”

    Electro-pneumatic systems are also being used in automated blood pressure monitoring devices where a valve both inflates the cuff and controls the rate of deflation. The 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 sophisticated blood pressure monitoring devices not only recognize systolic and diastolic pressures, but actually measure the point at which the blood begins flowing.

    “When the cuff is inflated, the blood vessels are restricted and create a tourniquet,” says Clippard. “When the pressure is slowly released, there is a point at which some of the blood vessels release and blood starts to flow.”

    Sophisticated devices use techniques to notice how quickly the blood flow recovers and use that information to diagnose different maladies with the patient. The devices use very precise pressure control, versus a device which turns on and off, and provide a gross control. The proportional valve allows the application to inexpensively add fine pressure control at the point where those blood vessels are just beginning to open and blood is beginning to flow.

Designers Focus on Size and Power
    In pneumatics for medical applications, the trends are mirroring 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 getting 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 device 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 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. “The flow 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. The 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 effective 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 five pounds and less and the size of the pneumatics internally is a huge consideration.

    “The 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 battery 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 specific to applications. The device manufacturer comes with requirements, schematics and a willingness to consider more highly integrated pneumatic modules. Often these modules include flow control, filtration, switching valves, fittings and safety relief valves all manufactured specifically 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 consumption,” says Richard McDonnell, piezo products program manager for Parker Hannifin 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 efficient 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 technology 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 amplification 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 profile the delivery of compressed air or gases while minimizing power consumption,” says McDonnell. He says that there is also significant interest in energy recovery and ultra-low-power technology with energy harvesting to create energy independent systems. 

Original Article, NOVEMBER 2013
By ROB SPIEGEL, SENIOR EDITOR

The Many Faces of Manufacturing Efficiency

North American plants are becoming more efficient. While the term lean manufacturing once had a very specific meaning at plants like Toyota with its quality circles, now the term has come to mean any technique that brings efficiency and optimization to the manufacturing process. This goal is to improve throughput while reducing waste, to improve uptime while reducing energy consumption, to improve safety while reducing work stoppages.

Gains in manufacturing efficiency and automation means that logistics play a larger role in choosing a location for a plant. If your manufacturing is efficient in Ohio, you will be less likely to locate your plant in China. What you save in cheap overseas labor will be eaten up by shipping. The idea of keeping your manufacturing close to home works only if you can make sure your processes are very lean. We’re seeing new progress on a wide range of plant processes.

Less hardware and more software

One of the trends we’re seeing in lean processes is an increase of reliance on software and the trimming down of hardware. “How can you do more with less? If you have more functions with one controller instead of manycontrollers, you’ll be more efficient,” Graham Harris, president of Beckhoff Automation, told Design News. “You can control a machine with three axes with one controller. The synchronization is easier with one controller because all the data is on one CPU. That also saves cabinet space.”

The savings in hardware can include everything from PCs and controllers to wires. “You have less hardware and more software now. That’s efficient,” Harris told us. “You have only one cable, while traditionally, it was dual cables. So you have less material. Safety is now integrated into the same Ethernet bus as the controller. That offers savings in set-up.”

Safety and simulation

Safety has become significantly more efficient. For one, you can run safety on the same wire as control and power. For another, safety breeches don’t have to bring down the whole plant. “We have safety in zones now. We have the ability to just stop the zone when there is a safety infraction,” Patrick McDermott, regional manager at B&R Industrial Automation, told Design News. “We don’t have to stop everything. We’re going to programmable safety.” 

Simulation has also brought efficiency to plant processes. Changes can now be worked out in simulation before you turn on machines that might crash into each other if you don’t work out the configuration ahead of time in software. “Technology also means I’m not rewiring when I make a change. I’m changing the code instead. It’s configuration, not design and rewiring,” said McDermott.

The simulation means changes can be made both accurately and quickly. “One factor is time-to-market. Simulation allows machine builders to minimizing time on the machine,” McDermott told us. “You can spend your programming time up front. That minimizes time on the machine.”

Employee buy-in

Another way to make sure efficiency really takes hold in a plant is to get employee buy-in. You get the buy-in by involving employees in the efficiency process. “It starts with getting people to understand there is always room for improvement. You have to embrace all employees,” Jim Coshnitzke, a manager at Clippard, told Design News. “You get people in production, supervision, and management, and you map the current cycle. You model it and get input from everyone.”

“That input from everyone can be as little as changing the work set-up to make production movements more efficient. It may not seem like much when you save a handful of seconds, but they can add up to real savings. You look at what steps you can change. You rearrange tools to make movements up and it saves hours,” said Coshnitzke. “You work on those ideas. But in order to get the employees’ ideas, you have to have employee buy-in.”

The employee input can be as little as saving movement or as large as changing the fundamental manufacturing process. “In one instance, we compared batch to process. We had been doing batch. So we took all of the employees and took them through a Lego exercise,” said Coshnitzke.“We did batch, and then we did flow. We saw a 300-percent improvement with flow. Everyone was involved, so we have the buy-in to switch from bath to flow.”

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Original Article, JULY 2014 BY KEN KORANE

Here's how engineers used advanced software and innovative manufacturing techniques to produce a next-generation, high-flow valve.

Like most everyone today, machine builders want more for less. That certainly holds for users of pneumatic valves, who are clamoring for higher flow capacity, but not at the expense of buying a larger valve. At Clippard Instrument Laboratory, Cincinnati, such demands have spurred the development of a new line of two-way solenoid valves called the DV. Its unique construction builds on technology developed for the company's proven and reliable EV valves. But it provides five to six times more flow in an equally compact design. And, its rated life exceeds 1 billion cycles.

Engineering Challenges
Like its predecessor, the DV consists of three basic subassemblies: housing and solenoid; a base with a nozzle that channels flow; and a "spider" spring assembly that includes a poppet, overmolded seal, and puck-shaped magnet. Development of the DV was challenging, to say the least, admits Clippard Design Engineer Dave McBreen. His objective was upgrading this basic layout to substantially increase flow capacity, without markedly changing the valve's overall dimensions.

Though a serious design constraint, small size is a must because users rely on banks of these valves to handle a variety of tasks, he explains. "They're used in packaging equipment, medical devices, analytical instrumentation, and many other places. Industrial applications typically have multistation manifolds where valves are mounted as close together as possible to minimize space requirements. Thus, the DV valve's OD couldn't exceed three-quarters of an inch."

The first obstacle for the Clippard engineers was designing a solenoid coil that fit the available envelope and could generate sufficient power to shift the valve at high pressures — or determine it was impossible. Product specs called out maximum size, minimum power levels, and maximum flow at standard pressures of 100 psi. And response time had to be in the 10 to 15-msec range to permit high-speed operation.

The question was, how much magnetic force could a coil generate, and how big a magnetic puck was needed to pull against a half-pound preload? "With coil design, it's all about amp-turns," explains McBreen. "You get the most bang for your buck by wrapping out and growing your diameter, as opposed to growing taller." Coil technology hasn't advanced much since the days of the EV's development, so McBreen found no magic bullet in the latest generation of solenoids. "It's still wrapping wire around a spool," he says. They did consider voice-coil actuators, but found them too expensive and with unproven long-term reliability. "It was in our design's best interest to stay with a standard wound coil," says McBreen.

Faced with so many variables, and so many iterations, Clippard engineers developed a Coil Calculator software program to streamline the design process. It let them optimize the coil in relatively short order.

"We're basically designing a bobbin," says McBreen, "and we know the inner and outer diameter of the spool, how tall it is, and the wall thicknesses. The software lets us plug in the geometry and then enter different wire gauges. It shows us how many amp-turns we can get with a 34-gauge wire, a 32-gauge wire, and so on. We key in on the combination that gets us close, then make finite changes to the bobbin geometry to tune it in."

They chose to develop the program in-house, rather than rely on off-the-shelf software, because they had very specific goals. It's like buying an FEA package with lots of options that you don't need, and isn't well suited to your problem, he explains. "The Coil Calculator gave us exactly what we were looking for, it was obviously the way to go."

Engineers used the calculator in tandem with EMS, a 3D electromagnetic field simulator program from Montrealbased ElectroMagneticWorks. It let them tweak the resulting magnetic circuit, with impressive results. "I was shocked at the accuracy," admits McBreen. The first prototype met all physical requirements and performed to within 5% of predictions, which is in line with standard coil tolerances.

Higher Flow
The next engineering hurdle was designing flow passages that upped the valve's capacity, but not its size. "If you look at the nature of a two-way valve, especially a manifold-mount valve, air enters through the bottom, flows into the valve, then makes a 180° turn and travels down through the outlet holes and back into the manifold. That alone creates restrictions that you have to design around, to get the necessary flow," explains McBreen.

They examined many different orifice and channel shapes in the quest to maximize flow. For example, certain nozzle geometries, and radii on the nozzle edges, gave smoother, more-laminar conditions that resulted in consistent and higher flow. An added benefit was lower friction between the orifice and mating nozzle seal, which reduced preload and wear.

The DV is a normally closed valve. The poppet with an overmolded seal presses against the nozzle and closes off flow. Energizing the solenoid lifts the magnetic puck towards the core until it bottoms out against the bumper. In the manifold-mount version, air then flows through the #10-32 port, through the orifice, and into the internal chamber. A series of slotted holes surround the molded nozzle, permitting air to flow out to the manifold.

Engineers relied on both computational fluid dynamics analysis, in this case Flow Simulation CFD from Dassault Systémes SolidWorks, based in Waltham, Mass., as well as on physical testing—validating concepts with machined prototypes. CFD proved to be an excellent tool for modeling flow through individual valves and examining various options, says McBreen. However, simulating a bank of manifold-mounted valves was rather time consuming, he admits, as there are so many pathways to consider.

Spider Spring
Perhaps the most visually interesting component within the DV is the spider, an unusual spring that shifts the valve when the solenoid deenergizes. Developed by Clippard engineers, the unique configuration lets it generate sufficiently high force from an extremely compact spring with very little movement—the DV has only 0.018 in. of stroke and about 0.018 in. of spring preload. Minimal stroke is necessary, says McBreen, to ensure precise control and maximum flow at operating frequencies as high as 32 Hz.

Getting the configuration just right required intensive FEA analysis in SolidWorks on various spider designs. "We wanted the legs as long as possible, to get the longest stroke within our space limitations," says McBreen. Thus, the number, shape, length, and layout of the legs, the radii of transitions, and many other factors were studied and adjusted to come up with the proper stroke and spring rate—while keeping stress levels sufficiently low to ensure extremely long life.

The spider spring, with its long, narrow and curving legs, would be difficult to machine or fabricate by stamping, but it is pretty simple to etch, he notes. The process starts with a flat sheet of 0.020-in.-thick 17/7-PH stainless steel, which is then chemically etched to the final configuration. A finishing operation removes stress risers and gives it a glasslike surface. The process holds tolerances on some features to ±0.001 in., so there is little variation from part to part. That helps ensure consistent performance from one valve to the next.

Testing, Testing
Engineers tested several evolutions of the valve to prove out the design, evaluate different manufacturing techniques, and ensure the DV's durability. And given the billion-cycle intended life, that required some patience—as it involves running the valves at 32 Hz and 24/7 for a year. The test rig required solid-state relays because mechanical contactors would burn up under such demanding conditions. Units are tested at various pressures ranging from 0 to 100 psi, response time was regularly monitored, and valves were checked for leaks and seal wear every 50 million cycles.

McBreen's main concern was that the overmolded poppet seals would peel off the base metal over time, but that was never an issue. However, one unforeseen dilemma on an early prototype was the appearance of fretting corrosion between the magnetic puck and housing.

The initial design mandated an extremely small gap between the two parts, to take full advantage of the available magnetic field, McBreen explains. "Apparently, it was a bit too close."

The compact DV is a two-way solenoid valve that provides five to six times the flow of previous versions.

The spider spring shifts the valve when the solenoid deenergizes and has a stroke of only 0.018 in.

Fixing the problem wasn't a simple as merely widening the gap, however. "If you make the clearance too big, then you lose a percentage of your magnetic force." He again turned to the EMS software to refine dimensions and ensure the puck stays centered and glides with minimal friction—all while maintaining the needed magnetic-field strength.

Such setbacks are inherent to engineering, says a pragmatic McBreen. "It's part of the optimization process. Analysis only shows you so much and gets you in the right ballpark. That's why you test it, to find out what relative changes you can make to improve the end product."

Manufacturing Issues
Because the DV has a number of working components, and an extremely short stroke, part tolerances could have been a nightmare. "If you're not careful, the tolerance stack-up will match the stroke and the valve won't work. The battle is how to control those tolerances without driving manufacturing costs through the roof," states McBreen. "It gets a little tricky, but there are certain features we can control very tightly, so it eliminates some of the stack," he says. That's why parts are manufactured at Clippard's facilities in Cincinnati. "One of our niches is being very good at machining parts with very tight tolerances. We have the right equipment, we've been doing it for a long time, and it's less costly than using outside vendors."

Ensuring the DV is easy to manufacture and assemble was also a prime concern from the beginning. One example McBreen cites is opting for a molded nozzle, versus a machined one. Machining small orifices in stainless steel and holding extremely tight tolerances is difficult, and the parts take too long to make. Instead, a key supplier molds the nozzles from dimensionally stable Ultem and holds ±0.001 in. on the ID and other critical dimensions. And they tightly control the process to ensure excellent repeatability, he says.

The plastic nozzle also lets manufacturing personnel pop in a radial seal by hand, and it seats against the housing and nests in proper relation to the spider. The subassembly gives the necessary preload with near-zero friction on liftoff.

Assembling the DV involves simple press fits with no shimming. The three subassemblies are put together using simple tools, and every valve is automatically tested prior to shipping to the customer. Compared to the EV valve, the DV's streamlined manufacturing procedures save several minutes of production time for each part – which adds up to sizable time savings in highvolume production.

Product Specs
The DV is rated for flows of 100 lpm at 50 psi with a 0.070-in. orifice, and 100 lpm at 100 psi with a 0.052-in. orifice.

It's suitable for service with air and other compatible gases, and it is currently being tested with water. The valve base is made of 303 stainless steel, and all the magnetic components are 430F stainless steel. Other "wetted" materials include Ultem and polyphenylene sulfide (PPS). Ultem is a thermoplastic polyetherimide resin with outstanding elevated thermal resistance, high strength and stiffness, and broad chemical resistance. PPS, in similar fashion, has outstanding chemical resistance as well as thermal and dimensional stability. Seals in the DV are typically Buna, but FKM, silicone, and EPDM are available on request.

The valve has rather large flow passages and is quite dirt tolerant, says McBreen. It runs fine on air filtered to 40 μm and offers an important user-friendly feature: the valve is easy to disassemble and clean.

Control voltages are typically 12 and 24 Vdc, but many users design their own circuitry. One example is hit/hold actuation which energizes the valve momentarily with its rated voltage, and then reduces it by approximately 33% to hold the valve position. Some even run off rectified alternating current. Rated power consumption is 1.9 W.

Both manifold and cartridge mounting options are offered, and the valve has #10-32 ports and a 0.75-in. body. Clippard is also producing a metric version for marketing worldwide. It has M5 ports and a 19-mm body.

Markets & Applications
DV valves are suitable for many applications across a diverse range of industries. "We feel it's a very optimized valve," stresses McBreen. "It has a small package, with little heat rise, and low power consumption. They mount on three-quarter-inch centers, can flow a lot of air, and they're very price competitive."

He ticks off a list of potential applications, such as in medical devices like blood-pressure cuffs, for analytical instrumentation, gas chromatography, and leak-decay test systems. In manufacturing settings, banks of valves are well suited for controlling production machines and packaging operations—applications that tend to have lots of cylinders and actuators.

A fully ported three-way version of the DV is slated for introduction this fall, and a proportional valve is in the works.

OCTOBER 2013 Design Hardware & Software BY CABE ATWELL

Halloween is a time when kids and adults get the opportunity to step outside themselves and dress up in attire that would be deemed strange any other time of the year.

These attractions sure have come a long way from those back in the '80s when I was growing up. Back then, kids used their imaginations as we ventured through the local haunted houses, which were usually erected in a shopping plaza's parking lot. These were the kind that wwere built into several semi-trailers that were usually connected together to form several rooms.

The Raspberry Pi & air piston-based Scary Door.
Source: Cabe Atwell

The rooms were then outfitted with terrifying glow-in-the-dark ghosts, rubber serpents and spiders, and a host of teenagers made up to look like goblins that were going to drag us to their chamber of horrors.

The technology that made up those attractions is not in the same league as those found in cities across the U.S. in the 21st century. Most of the technology back then consisted of levers and pulleys that would move objects using fishing line. Sure, that’s not so scary, but factor in black lighting and strobe lights, and things seemed pretty frightening, especially being 12 to 14 years of age.

Fast-forward to today’s multi-million dollar haunts, and the difference in technology is night and day. The pulleys and fishing line have been replaced with pneumatic actuators that allow finely-detailed monsters to move. Gone are the simple black lights -- they’ve been replaced with IR (infrared) sensors and precision lasers that are able to detect movement and activate horrific props as patrons walk by.

All the technology these places feature (on a large scale) are controlled by a central hub or computer system, which controls everything from haunting sounds to incredibly realistic animatronic displays. For some of the bigger venues, fans are required to sign waivers as they proceed through the attraction, as well as required to wear an RFID bracelet that not only lets supervisors know your location, but are also used to trigger some of the displays themselves. Technology isn’t just centered on large attractions alone -- home-brew haunted houses are taking advantage of it as well.

My Scary Door project is a prime example of how new technology is being implemented in at-home attractions. The door was designed using a 24-inch monitor that displays Halloween-themed videos embedded in a creepy sheet-metal laden door. Outfitted behind the door is a system of pistons and solenoid valves that strike the sheet metal in time with the video being displayed to create the simulation that someone (or something) is beating on the door. Trick-or-treaters engage the door’s scariness by triggering a Seco-Larm Enforcer break-beam device situated several yards before getting to the door itself. Controlling the show are two Raspberry Pi SBCs, with one for controlling the video output and the other, combined with a PiFace, for implementing the relays that fire the pistons. C and C++ code bind everything together for a technology-based haunted device that is capable of scaring the most reserved children looking to get their Halloween candy.

It’s easy to understand why scaring people is big business, as the revenue generated each year for these haunted attractions can easily be in the billions. This creates healthy competition for those who design such attractions to be the scariest in the nation. It’s most assured that as technology advances, so will our fears, which seem to grow as Halloween draws near and we venture through the “Scary Door”!

Happy Halloween!

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