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Shooting Stars

Shooting Stars

In a modified version of the football team huddle, engineers from Smart Parts Inc. and Humphrey Products Company convened in a conference room in Loyalhanna, PA, last year to draw up a game plan for dominating the competition in a vastly different sport: tournament paintball.

When they broke, they had a strategy for developing a new solenoid valve that they felt would set a new standard in paintball markers-the guns players use to splatter opponents with tiny balls of paint.

But this was to be no ordinary valve. It had to be backward compatible so it would match the footprint of an existing valve. It had to be easy to maintain. And, it had to perform better than existing valves. How much better? A lot. For one key aspect of the valve-operating pressure-the engineers aimed for about a 125 percent improvement.

They hit their target. The new valve, the result of intense collaboration between Smart Parts, pneumatic-technology supplier Humphrey, and Humphrey's Japanese partner Koganei, could well surprise the market with its capabilities. It's a 7V device that provides a higher rated pressure (225 psig vs. 100 psig) than competitors' models, faster firing rate (an expected 28 balls per second vs 24), and shorter cycle (or, on-off) time than the previous valve. Humphrey engineers say their tests show that despite the 225-psig rating, the valve actually seals at 300 psig. The valve also has fewer parts than the one Smart Parts used previously, and weighs less. Though Smart Parts won't disclose the actual valve weight, the company says it is 1.1 gm lighter than the previous valve.

Smart Parts will use the valve in a new version of its Nerve marker that debuts in November.

The solenoid valve plays a critical role in the operation of a paintball marker. It allows incoming pneumatic pressure to flow through the porting, causing the shaft of the pneumatic cylinder within the marker to extend or contract. The extension and contraction of the firing cylinder cycles the marker. The valve also vents any pneumatic pressure on the opposite side of the cylinder from the previous firing cycle.

Fun Gun: The new Nerve marker consists of a stainless steel barrel, a special grip, and a pressure tank, among other components. The valve is rated for 225 psig, but seals at 300 psig.

Fits and Starts

The 12-month design project-six months shorter than usual for such an effort, Humphrey says-was filled with the usual fits and starts. But the numerous iterations resulted in some interesting innovations.

For one example, when the Humphrey team delivered the first prototype, Smart Parts reported that the valve misfired. Perplexed, the Humphrey team asked Smart Parts Project Engineer Ed Telford and his crew to share with them the details of the control circuitry. "Once we studied the circuitry, we redivided the wave form to lengthen the 'on time'-the length of time the coil sees the energy needed to pull the plunger in," says Rich McDonnell, Humphrey's director of business development.

That effort, plus changes to the coil windings and Humphrey's other steps to optimize the spring, armature, and piloting spool, shortened the overall cycle time. The result: Humphrey anticipates its design will reduce the overall cycle time from 39 msec to 36 msec. The details of the optimization are proprietary.

Among other design decisions that resulted from collaboration efforts, the Humphrey team moved the seals from the spool to the valve body to prevent leakage and seal failure. During the valve-design project, Humphrey engineers found that when the seal was on the spool, it came off under high pressure due to valve shifting. "We considered several alternatives, including bonding," McDonnell says, "but found that the best solution was placing the seal in the valve body and letting the spool ride on the seal."

Valve Assembly: The solenoid valve allows incoming pneumatic pressure to flow through the porting, causing the shaft of the pneumatic cylinder within the marker to extend or contract. The valve also vents the pneumatic pressure.

Integration Is Key

Further, they included a tamper-proof seal to prevent users from taking the marker apart and reassembling it and thereby voiding the warranty.

Beyond those innovations, Smart Parts asked Humphrey to correct an expensive element of the old valve design that caused difficulties in installation, maintenance, and repair: the soldering of the valve to the printed circuit board. Smart Parts wanted a female connector compatible with the male connector they had specified. That would eliminate the need for soldering. Humphrey engineers complied, but then, they and Smart Parts' team had rigidity concerns-they feared customers might accidentally snap the connector off the valve assembly. Solution: Humphrey integrated the connector into the solenoid housing. The company also developed a pilot housing and valve body cover machined from aluminum rather than the traditional injection-molded plastic, which, Telford says, is perceived by the market as a better alternative.

Backward Compatability

Footprint was another design issue. Smart Parts wanted a footprint for valve porting that would match the previous valve. To accomplish that, Humphrey engineers reversed all port locations on its valve body, using AutoCAD software to match the interfaces. The biggest lesson from this project, says Telford: "Find a supplier who will provide exactly what you need, rather than one that who wants you to change."

Contact National Editor Paul E. Teague at [email protected].

Required Specs For The Solenoid Valve
Operation Indirect action
Valve structure Soft spool and poppet
Operating pressure range 70-225 psi
Proof pressure (Actual max pressure before leakage) 300 psi
Cv value (Flow characteristics) 0.11
Power consumption 1.3W
Control voltage 7V dc
Seal compatibility Compatible with compressed air, carbon dioxide, nitrogen
Min. life cycle Three to five years of play
Design Partners
Smart Parts Ed Telford, project engineer
Hans Semelsberger, engineering manager
Associated product-development staff
Humphrey Rich McDonnell, director, business development;
Steve Hart, regional manager
Scott Industrial Systems Mark Ashton, district manager
Koganei Corp. Nori Yoda, U.S. country manager
Kazuya Okamoto, pneumatic valve engineer
Hiro Miyata, overseas manager


Web Resources
//Check out the links below for more info//

Humphrey Products: http://rbi.ims.ca/3858-556 Autodesk: http://rbi.ims.ca/3858-557 Share your experience with solenoid valves. Network with engineers involved in valve applications below, using the TalkBack function.
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