Good food – by design

Steel drive tape in grill design provides user-friendly, consistent cooking.

The moment when specialised equipment began replacing short-order cooks signalled a major turning point in the fast food industry. Since then, the list of possible applications has grown to cover everything from grills, ovens and fryers to soft-serve dispensers and drink makers. Not only is speed maintained throughout an entire shift but, also, the quality of the food remains consistent. As in industrial-scale food processing plants, these machines have to tolerate long periods of running time in high and low temperatures, be easily cleaned and robust. That being said, steel belts offer food equipment designers the ability to automate food processing knowing that the steel belt will stand up to extreme temperatures, is corrosion resistant, will not fray or impart taste if the belt is used as the cooking surface.  Sanitizing of steel belts can be accomplished using heated high pressure wash, chemical sprays and ozone or steam pressure. No other belting offers these distinct advantages to automate a food process.

Grilled to taste

One of the major U.S. manufacturers of equipment for the fast food industry was approached by one their top customers with a design challenge. This was to add automation to a cooking process that was to achieve three objectives:

Remove the manual decisions and opportunity for error with regard to a critical function of the cooking process.

Create a solution that would enable end users to set all cooking parameters with a 'one touch' button.

Maintain quality and consistency in the cooked product while reducing staff training, maintenance and repair costs.

Achieving these goals meant the restaurant could expand its menu without adding unnecessary equipment, labour or maintenance costs while improving the quality and appearance of their products.

In developing design options for the new commercial grill system, the equipment manufacturer employed an in-house multifunctional team for design engineering, manufacturing engineering, field service and marketing. This team was responsible for the engineering of the grill, building of the prototypes, modification of the designs and writing of the performance reports. Part of the testing phase included the set-up of a  simulated quick service restaurant where food could be cooked as though it was in an actual customer kitchen.

A critical component of the design is in the positioning of two cooking platens, one on top of the other. By actuating a precise movement, a programmable, repeatable distance can be set between the two platens. Ideally, the end user envisioned positioning the upper platen within 0.002" of a number of various stop positions above the lower platen. This would achieve the objective of setting a critical feature of the cooking process for a multitude of products without complex operator involvement. Three techniques were considered: cables, inclined planes and steel belts. For design assistance, the project engineer contacted Belt Technologies Inc, the US parent company of Washington based Belt Technologies Europe.

Stainless tape, medium-well

In a food-processing environment, stainless steel offers cleanliness and exceptional performance, especially in a hot environment. As an added benefit, the steel provides a low mass belt that performs well without lubrication.

A steel drive tape, a derivative of endless steel belts, was envisioned. Drive tapes are ideal in applications where rotary motion needs to be converted to linear motion. Similar drive tapes are used in robotic arm actuators, carriage positioning systems or mirror positioning systems for military or satellite use. For durability, the drive tape is most often fitted with reinforced end tabs thus ensuring that a firm and secure contact is maintained where the tape is terminated. Specifically, the use of steel drive tapes in this application could provide near-zero backlash, no stretch and the repeatability desired by the customer.

According to the equipment manufacturer, the steel drive tapes were a "clear winner" early in the design phase. In comparison to inclined planes, the drive tapes were less complex in design and offered a significant advantage in space and weight. Furthermore, it was stated that the incorporation of the steel drive tape was a "very intuitive design" offering the benefits over cable in manufacturing simplicity and field service. Due to the non-stretch nature of the steel drive tape, consistent, predictable results in the performance of the grill were possible. The final design incorporates the steel drive tape, terminated to both the upper cooking platen and a drive pulley. The drive assembly moves the upper platen to the required precise position by means of a single button on the operator control panel.

Done to perfection

Implementation of the design was not without challenges, however. Although the initial performance of the prototype drive tapes was encouraging, improvements to the design were needed to achieve optimum life cycles. According to Rich Lunden – Belt Technologies' manager of new product development – the change resulted in lower bending stress with ample strength to carry the load of the cooking platen. Lunden states: "We like to see a significant ratio of pulley diameter to drive tape thickness. With the original design, we would have needed a pulley diameter that would have exceeded the available space. By changing the belt thickness, we kept the pulley diameter within the customer's design requirements and achieved the life cycle we were all looking for." A slight modification to the location of the pulleys in relation to the termination point of the drive tape was the final correction. The re-designed system was tested to three million cycles after which a review by an independent metallurgist showed no signs of fatigue.

The company considers the project an absolute success, with the grill receiving "approved and released" status from their customer. "The steel belts allowed us to achieve results that were not possible with other alternatives" says the Engineering/Technical Services Vice President. Lunden agrees: "the opportunity for Belt Technologies to work with the engineers at our customer's location, early in the design phase, was important to the success of the project."

Belt Technologies Europe

www.belttechnologies.co.uk
www.belttechnologies.de