Appliance components do double duty

By: 
April 08, 1996

What do steam cleaners and leaf blowers have in common? Breadmakers and
file cabinets? What about refrigerators and small boats? They're all examples of
how engineers brought a winning technology from appliance design to a new arena.

The need for manufacturing flexibility is universal. As you'll see in the following examples, engineering approaches tailored to appliance component design can also answer a need in an unrelated application. These cases demonstrate how a simple yet elegant installation, a smaller footprint, or a complex materials process can launch an idea into an entirely new engineering domain.

Lean, mean cleaning machines. At first glance, a steam cleaner from Regina Consumer Products Co., Long Beach, MS, and a leaf blower from Poulan/Weed Eater might not look like cousins. But beneath their enclosures, you'll see something other than cleaning ability that these products share: Each product gets its power from electric motors designed at Ametek's Lamb Electric Division, Kent, OH.

"The motors are for completely different applications," says Lamb Electric's Director of Marketing Daniel Wilks. "But they both take advantage of our 'World' lamination."

The new lamination is more efficient as well as being more cost-effective to manufacture, says Project Engineer Gary Barnhart. At 2.50 x 25/8 inches, it has a smaller footprint than Ametek's popular three-inch-square lamination. Yet it has been designed to maximize the magnetic efficiency for the amount of steel used. "It does everything that it has to do very efficiently, so it can be smaller," says Barnhart.

To create the lamination, design engineer Mike Gilliland and other Ametek engineers concentrated on the flow of the electrical field generated in the motor's coils. "They re-designed the back end of the field to make a completely uniform magnetic path," explains Barnhart.

The Regina steam-cleaner motor was the first motor in production with the World lamination. Ametek and Regina team members worked closely together throughout design, and continue to have almost daily contact as product improvements roll out, says Barnhart. For example, to meet UL safety guidelines, many motors are designed with thermal cut-outs, or TCOs. A bit like a fuse, this feature trips a main circuit and prevents catastrophic failure if the motor reaches a high temperature for any reason--such as a blocked cooling inlet path.

"It took us--Regina and ourselves--a long time to work that feature out," recalls Barnhart. "We went through a gamut of testing until we felt confident the motor would perform properly."

The World lamination's smaller footprint contributes to a 20% weight loss over the previous design, but doesn't sacrifice performance. It can be produced on the same manufacturing line and is interchangeable with the three-inch version, which adds valuable production flexibility.

The lamination's small size gave engineers leeway in the winding configuration, says Barnhart. "We fine-tuned it to the customer's current-level tolerances; It's so forgiving, it allowed us to hit right where we wanted to hit and give long life." The motor easily meets its life requirement, he adds.

Previously, Regina required two different motors to suit the varying current levels of their three cleaner models. "The World lamination's performance allows them to use one motor for three different cleaners--and that reduced their inventory," says Barnhart.

Since the design of the World lamination, Ametek engineers have continued to work closely with Regina. Originally, Ametek supplied the OEM with a skeleton motor, to which Regina added an aluminum disk-and-ring "working" fan to create the vacuum that pulls water off the floor.

Recently, Ametek engineers added manufacturing fixtures that allow them to install more components on the motor prior to delivery. For example, they now install the working fan as well as a molded ABS vent cap for the fan that cools the motor. It's a direct response to customer needs, says Barnhart. "We deliver a complete unit to Regina and they just drop it in the cleaner."

Of course, Ametek engineers weren't about to hide their World lamination under a bushel. Lamb Electric Project Engineer John Lebo recognized it could likewise benefit his customer, Poulan/Weed Eater, Shreveport, LA. Today, Lamb Electric makes three variations of a motor for Poulan's Super Blower(TM) leaf blowers. Like the Regina motor, all the Super Blower(TM) motors are designed around the new World lamination and use double ball-bearing construction.

"The high efficiencies of the World lamination allowed Poulan to come out with a line of leaf blowers with more performance and life than previously available," says Lebo. The motor helped Poulan raise the performance of its product from 185 to 195 mph, while tripling life.

Poulan also tooled a new leaf blower for Sears that uses Lamb Electric motors. The Sears Craftsman leaf blower is offered in a high-powered model that blows air at 200 mph, as well as a medium-performance (1 hp) leaf blower that blows air at 150 mph. Poulan uses the motors in leaf blowers they make for Husquavarna and Paramount, as well as models sold in Europe.

From kitchen to office in a snap. Like any consumer product, appliances demand robust access hardware. That's why engineers at West Bend Co., West Bend, WI, consulted with engineers at Southco, Concordville, PA, for the design of their new bread maker. To fasten the door of their Baker's Choice(TM) bread and dough maker, West Bend engineers wanted to use a magnetic catch. The difficulty: Conventional catch housing materials didn't withstand the machine's high operating temperatures.

In the off-the-shelf version, the catch's housing was polypropylene. After testing, engineers selected a glass-reinforced nylon for the housing. "With a small modification, we were able to make the catch with a heat-resistant housing," recalls Dee Richardson, Southco International Market Manager.

The solution exemplifies the benefits an experienced supplier can bring to component design, says Corporate Engineering Manager James Grady. "Typically, a Southco field sales engineer will sit down with the customer and propose a host of alternatives for an application, then work with the customer to select the more appropriate one. Then the customer can test to come up with the final configuration." Southco's assembly consists of pole pieces of zinc-plated 1010 steel; the magnet is barium ferrite.

Part of the beauty of this part is that it simply snaps into the assembly, says Grady. Projecting ears allow it to adjust to different cabinet or frame thicknesses. The magnet requires a steel strike, or can function with the door itself if it's steel. "Low installed cost is a big concern for our customers," he adds. "This is a tamper-resistant installation--once it's snapped in, it's difficult to remove. There's no concern over loosening screws or weakening rivets."

Of course, easy installation and a smooth finish do more than answer the pleas of appliance designers. Simple modifications of color, shape, size, and housing material help the catch work in file cabinets from All Steel Inc., West Hazelton, PA. The catches also go into automotive storage compartments, electronic enclosures, and telecommunications equipment. Southco can tailor the catch to a variety of disengage-load requirements, from four to almost 12 pounds.

"With its low profile, it's hardly visible," comments Richardson. "Because it's a consumer product, aesthetic appeal has to be an issue. This catch is flush and part of the housing of the breadmaker."

Co-extrusion cools fridge, adds structure. Great ideas are born from adversity. Just ask engineers at Whirlpool or Maytag. For them, recent government mandates to eliminate CFC-based blowing agents and refrigerants meant re-thinking just about every aspect of design.

Large-appliance makers weren't alone in their struggle, and many engineering teams enlisted the help of suppliers such as polyurethane foam and plastics specialists at Bayer Corp., Pittsburgh, PA.

"We saw the challenge the refrigerator industry faced in making the conversion away from CFCs as opportunities," recalls Cathleen Johnson, Bayer's industry director for plastics in major appliances. "From the polyurethane foam perspective and from the plastics perspective, we wanted to get in and address this as an engineering problem to solve."

On the plastics side, rather than trying to take standard materials currently used for refrigerator liners, Bayer engineers decided to develop inherently chemically resistant materials. "We wanted to solve the problem, not try to work around it. That's why for us, joint programs with foam suppliers were very important," says Bayer Major Appliance Research Manager Glenn Hilton. "We needed chemical compatibility, and to be able to test under real circumstances."

Adds Bob King, vice president of Bayer's Technical Insulation group: "At the same time, the foam people were trying to figure out the right blowing agent." The engineers' biggest problem was trying to come up with foam that would not only insulate well, but also maintain the structural integrity of the cabinet. To add to the challenge, they had to meet opposing EPA and Department of Energy regulations. "The EPA said no more CFC-11; the DOE said you have to have the same insulation properties," laughs King. "It was a tug-of-war."

Engineers were also charged with maintaining all the performance advantages of ABS, such as appearance, adhesion to the foam, moldability, and rigidity, as well as bringing resistance to the new HCFC-141b blowing agent--without a large cost hike.

"We went back to the basic polymerization to modify the ABS so it's inherently resistant to the blowing agent," says Hilton. Their ultimate solution: a two-layer co-extrusion. This unusual approach uses a cap layer of ABS to face the interior of the fridge, which retains high gloss and chemically resists fatty, oily foods. The second layer of the extrusion is an ABS substrate that directly contacts the polyurethane foam.

"This is a significantly modified ABS; a unique polymerization technology," explains Hilton. "We patented the composition and structure of the co-ex material with polyurethane foam containing the HCFC blowing agent."

Because fixturing trim and punching large holes after forming are inherent in the thermoforming process, the two ABS elements of the co-extrusion had to be fully compatible. Depending on the part geometry and the techniques a manufacturer chooses, as much as 50% of an original sheet is reground and must go back into the substrate layer.

Cyber Contacts
You can reach the following companies mentioned in this feature via the Internet. Please tell them that you were referred by Design News.
Bayerhttp://www.bayer-ag.de/english/0000home.asp
Whirlpool [email protected]

Some industry players toyed with the idea of a discrete third layer to accommodate this regrind, but Bayer engineers were keenly aware that refrigerator manufacturers had existing co-extruding equipment. So Bayer engineers created a two-layer system that would accept the regrind in the substrate layer. "We spent a considerable amount of time and effort on that aspect," reflects Hilton. "But it also reaps dividends at the end of the product life. Once recycle streams exist for ABS, it will be compatible."

"Our material is extremely good at processing from an extrusion and forming standpoint," adds Johnson. "It delivers uniform thin-wall parts and a very low scrap rate of thermoformed liners: the lowest industry-wide."

Depending on the equipment a refrigerator manufacturer has chosen, Bayer engineers tailor the resin formulas and the ratio of cap layer to substrate. That's where good supplier relationships and an application-specific focus are important, says Johnson. "How are the parts fixtured before they get foamed? How are the parts joined? All of that is fair game for us when we're doing a project. That approach lets us translate materials and also techniques to other industries."

Today, industries that didn't previously rely on ABS and polyurethane foam structures are considering the dynamic duo for new products. For example, Bayer technology now goes into spas and pool steps. In the future, engineers expect to apply it towards signs and personal watercraft.

"We've learned a lot about how foam and plastic meet, the mechanism of how they fail, thermoforming performance, and the ability to form detailed shapes with less scrap. This will allow engineers more design flexibility," says Hilton.

Ironically, appliance manufacturers are now charged with getting away from HCFCs, too. Says Johnson: "I think this has put us in an unprecedented position to take advantage of the systems we've got in place in foam and plastic. We have the tests and proven techniques for predicting performance. Now design engineers can push the limits."


Two functions are better than one

Sometimes, doing one job just isn't enough, especially in appliance design. To engineers at Southco, a single component that acts as both closure device and switch was a natural. Their Grabber(TM) catch with integral micro switch combines a latch and low-voltage micro switch in one installation.

For example, in a refrigerator, the two-for-one assembly can act as a latch and micro switch with toggle to activate the interior light. "You don't need separate wiring for the light," says Engineering Manager James Grady. "For our customers, it's a reduction in total installed cost. It's one installation instead of two, one vendor, one stocking part number, and one installation step. And it takes less real estate."

"It breaks the paradigm of 'I need a latch and a switch,'" adds Grady. The combination component is headed for new markets such as recreational vehicles, marine, and automotive consoles. It may also find its way into specialized equipment where it could be used to document access, such as environmental test chambers, or to activate a camera to record someone accessing an area.

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