New toroidal bearing enables enhanced performance in commercial washersHospitals, hotels, theme parks, cruise ships, prisons, blue jeans manufacturers and many other institutions and enterprises have a common challenge: literally tons of laundry. Sharing that challenge are commercial washer designers charged with assuring long-term reliability. Today, a new bearing innovation from SKF is enabling significant enhancements in reliability and performance, and is opening doors to innovative new commercial washer designs.
   Commercial laundries and in-house laundry facilities for businesses and institutions handle a staggering amount of laundry. An average home washing machine handles about 18 pounds of laundry and may run a few times a week. Commercial washers, which often run around the clock, can handle from 40 – 800 pounds of dry laundry, depending on the machine model. (Add water, and you’ve got an incredibly heavy load.) What’s more, many commercial washing operations need not one, but many, machines to handle a volume that can easily reach more than 100 tons of laundry a week.
   Everyone has experienced the vibration and movement that occurs when a washing machine load becomes unbalanced. But, the problem is enormously magnified when hundreds of pounds of wet laundry clump to one side in a commercial machine. It is this consistent out-of-balance situation, coupled with extreme weight, high loading and high moisture levels, that have traditionally challenged design engineers working to enhance commercial washer reliability and performance. Today, with the aid of SKF’s Compact Aligning Roller Bearings (CARB), designers are achieving their performance objectives, and customers are enjoying significantly higher levels of productivity.
A cycle of wash and wear
Washing machines present a unique dual challenge for design engineers – and for the bearings that are at the heart of machine operation. That’s because the nature of the washing operation creates machine loads that impact the bearings at both the inner and outer ring.
   Figures 1 and 2 illustrate the unique loading situation in a washing machine. During the wash cycle, as water fills the wash cylinder and the cylinder moves slowly back and forth, the shaft rotates and the predominant load is the downward pull of gravity. So, an interference (tight) fit is required between the inner ring of the bearing and the shaft. During the extract cycle, the load spins at high speeds. The centrifugal force causes the clothes to shift to one side, and an out-of-balance load predominates. During this out-of-balance period the outer ring of the bearing needs to be held tight in the housing.
   Unfortunately, because most bearings are unable to handle both axial displacement and structural misalignment, it has not been feasible for bearings to be installed with an interference fit on both the inner and outer ring. Washer designers have been faced with the dilemma of where to compromise in the bearing arrangement, and are typically forced to choose between several evils. If one bearing ring is made loose on its housing to accommodate thermal expansion, fretting corrosion and creep are likely to damage the shaft, make dismounting difficult and restrict axial freedom.
   If all the bearing rings are tight, fretting corrosion and creep can be eliminated but the designer must choose between two options:

1. Using two spherical roller bearings that accommodate misalignment but do not have adequate axial displacement capability and thus potentially accept mutually opposed thrust loading, or
2. Using a spherical roller bearing in combination with a cylindrical roller bearing that allows axial displacement but does not have adequate misalignment capability, thus accepting uneven raceway load distribution.

Whatever path the designer chooses, the result is bearing bore/shaft wear and reduced bearing life from misalignment – which leads to compromises in reliability, productivity and cost-effective operation.
The CARB solution
Major commercial washer manufacturers are finding the solution they need in the new CARB bearing from SKF. A unique toroidal design that combines some of the best aspects of spherical, cylindrical and needle roller bearings, CARB has a single row of broad rollers with a slightly curved profile. This design enables the bearing to find the best position to distribute the load evenly. According to SKF senior application engineer Gill Detweiler, “In a toroidal bearing, when a force is applied to one edge or the other, the roller slides to a new position in order to escape edge loading, finding a place where the stress is minimized. This enables the bearing to accommodate both angular misalignment and axial displacement internally and without frictional resistance or reduction in service life.”
   CARB is intended for use at the non-locating end of a two-bearing arrangement. In a commercial washer application, the ideal arrangement is a CARB bearing used in combination with a spherical roller bearing. This enables all four bearing rings to be mounted with an interference fit that eliminates fretting corrosion and creep. With this configuration, the bearings can accommodate load-induced angular misalignment resulting from unbalanced loads, so shaft bending and support structure movement will not result in uneven raceway load distribution. And, because the CARB bearing can accommodate axial displacement internally, mounting inaccuracies and thermal expansions will not yield mutually opposed thrust loading.
   To further assure optimum operation of CARB bearings, SKF also offers a lubricant innovation called System 24. System 24 attaches to the CARB housing and releases lubricant automatically as needed. SKF is working with washer manufacturers to develop a warning system with a sensor that lights up to tell the operator when it’s time to replace the lubricant cartridge.
Successful test applications
Several leading commercial washer companies are finding success with CARB.
   IPSO USA, a manufacturer of on-premise laundry equipment, was the first to test CARB. The company now uses CARB in all new machines and has more than 1,000 in service.
   “We initially tried cylindrical bearings,” says IPSO engineering manager Tony Fitzsimmons, “but in testing conditions, they lasted less than 200 hours. They could not accommodate angular misalignment caused by the shaft deflection. The inner races of the bearing were actually broken.” IPSO then tried a bearing arrangement using a spherical bearing and a CARB. “In our first test of the CARB bearing, we ran 900 hours with no failure,” he said.
Benefits beyond bearing life
Customers using CARB-enhanced washers in their commercial laundry operations are reaping benefits that go far beyond bearing life. CARB reliability is enabling higher productivity and lower costs in traditional machines, and opening doors to new machine capabilities.
Extracting water and costs
For commercial laundries, the greatest operational cost is the energy expense related to drying operations. The more moisture present in the clothes when they hit the dryer, the more energy it takes to evaporate the water. The best way to reduce moisture is to more effectively extract it from the clothes during the wash operation. This can be accomplished by spinning the clothes faster during the extract cycle. IPSO has recently created the means to do this through a patented speed enhancer called SmartSpin^TM – an electronic feature that measures the unbalance and then changes the speed of the extract cycle.
   “With new innovative design features like CARB and Smart Spin, IPSO offers a high-performance machine that is an industry leader,” says Tony Fitzsimmons.
   The enhanced extraction capability made possible by CARB is also contributing to increased productivity in terms of operational efficiency. In commercial laundries, one important measure of productivity is timing. The ideal situation is for the washers and dryers to be working on the same cycle. But the washers are often ahead of the dryers because it takes so long for the clothes to be dried. According to IPSO sales and marketing coordinator Bobby Dewrell, “Our new machines extract at such a high force that there is far less moisture in the load when it gets to the dryer. This requires less drying time, so the dryers can get on the same rhythm as the washers. This cuts down on time, and for some customers, it has enabled them to run fewer shifts.”
   CARB enables a one-step downsize in machine size, a benefit that can result in savings related to material costs, and better compatibility with the size and configuration of
customer facilities. This is because CARB is designed to carry the load across the entire surface of one roller, as opposed to traditional bearings that use two rollers. The one-roller design results in a smaller bearing that can carry the same load as larger bearings. The smaller bearing size enables a corresponding downsizing of other machine components.
High-temperature performance
Bleaches work best at a temperature of 180°F. While commercial washers are capable of running at these temperatures, the high heat contributes to shorter bearing life. CARB enables the machine to be less sensitive to high temperature, so laundries can run bleaches at high heat without compromising long-term bearing performance.
Extended machine life
With traditional bearing arrangements, bearing life could range anywhere from 5 – 30 years, depending on the operating conditions. Replacing the bearings can be a huge job, requiring a complete teardown of the machine and several days’ work.
   For laundry operations, productivity is interrupted.
   For manufacturers, service becomes a major part of the business.
   Many manufacturers are selling more than 100 machines a day and have been doing so for many years. “When you consider these manufacturers have been in business for quite a few years, it eventually means that they could be servicing machines all the time,” explains Gill Detweiler. “CARB significantly extends machine life. So customers don’t experience downtime, and manufacturers can get out of the service business.”
Outstanding customer acceptance
CARB’s unique capabilities are helping commercial washing machine manufacturers enhance both performance and customer satisfaction. “Our customers are very happy with our new CARB-enhanced machines,” says IPSO’s Bobby Dewrell. “We have yet to hear from a customer who has installed one and wanted something else. They can’t believe the output and throughput they’re getting.”