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Engineering and Technology News |
| Torq TenderŽ From Zero-Max Provides Torque Limiting Overload Protection | |
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Depew, New York: Protecting motion and assuring smooth, continuous operation in filler systems has very large implications for bottlers when it comes to system downtime. Over the years, all types of devices have been incorporated into automated filling systems to guard against overloads and other system jam ups including shear pins, electronic limit switches and various types of mechanical stopping devices. All are workable options but with limitations for minimizing costly system down time and repairs.
At ElmarŽ Industries, one of the largest manufacturers of these filler systems in the world, mechanical torque limiters are utilized on certain applications because of their simplistic, fail-safe operation. Elmar Industries offers over 100 different model filler systems, from 6 to 72 stations including rotary piston, bottom fill, gravity and pocket modules for filling liquids, high viscosity and solid particulates into plastic, glass, composite and metal containers, narrow neck through wide mouth, with volumes ranging from ˝ oz. (15 ml) to 5 gallon (12 liters). On its Monoblock filler/capper systems, Elmar utilizes two different Zero-Max Torq TenderŽ torque limiting devices to safeguard two different machine functions in these customized bottle filling systems. "First, we use a H-TLC torque limiter (Model 500) in the motorized height adjustment mechanism, which raises and lowers the center column to adjust for different bottle heights," reports Russell Wozniak, project engineer for Elmar. "The second unit used is a Torque TenderŽ (TTXJF sprocket mount model) which connects to the primary drive train that moves the bottles through the system for filling. Both torque limiting devices provide fail-safe jam-up protection without having to rely on electrical devices." H-TLC Torque Limiter Prevents Over-Travel Of Filler Heads The motor driven height adjuster assembly has a rotating shaft that connects to the elevation device at one end and the H-TLC torque limiter at the motor end. Mechanical stops are positioned at the high and low point of travel of the filler head. Prior to use of the HTLC unit, the mechanical stops alone were insufficient to halt the upward travel of the adjusting column with every cycle. At times, the upward force would overpower the mechanical stops, jarring them loose and even knocking them off the system. The downward motion could develop too much force if the limit switch failed and the column bottomed out causing it to jam up. "What's critical is to be able to control both upward and downward travel so both of these problems are avoided even if the over-travel switches failed. The HTL-C solves both problems," reports Wozniak. Prior to using the HTL-C, Wozniak said various types of electronic stopping devices that employed sensors were evaluated. "The problem we encountered with sensors was complexity and unreliability. To achieve the protection required, multiple sensors were needed involving some complicated wiring and location issues. The sensors were expensive and we just didn't feel long term they would provide the 'fail-safe' protection our customers expect from our filler systems. We settled on Zero-Max's H-TLC torque limiter because it provided a solution that worked 100 percent of the time and wasn't dependent on electricals for actuation. Operating at up to 100 rpm in this application, the H-TLC is adjustable to handle different torques in addition to being corrosion resistant so it handles the harsh environment it operates in. Its a cost-effective solution that's relatively simple to install." Straight forward in design, the H-TLC is located between the motor that powers it and the shaft leading into the height adjuster mechanism. It operates on a spring-loaded convex pin and detent design, which reacts to pre-determined overloads. When the preset amount of overload is experienced, a pin disengages from the detent, shutting down the system. Once the overload condition is corrected, the H-TLC can be reset quickly and the system restarted. If higher or lower overload protection is needed, the H-TLC can be adjusted quickly for changes in torque. "We liked the fact that the H-TLC is repeatable as well as dependable," said Wozniak. "You install it and forget it. There's nothing electrical to adjust if a shutdown occurs. When assembling, it connects quickly without any special tools or devices such as alignment lasers. It's impervious to corrosives because of its Nylatron GSŽ and DelrinŽ housing design and it doesn't require any special maintenance or lubrication." Torq-TenderŽ Protects Filler System Main Drive Gears The second torque limiting device used in the filler system is a Zero-Max face mount Torque TenderŽ model. This device is a positive drive coupling which protects the timing screw mechanism in the main gear drive of the system, also from any kind of jam up. A timing screw in the drive sends bottles into the system for filling. If this rotation is stopped due to a downed bottle or jammed bottle, the Torq TenderŽ instantly disengages the timing screw drive, shutting down the filler. Wozniak said the Torq TenderŽ was chosen for this application in the system because of its rugged, steel construction, ability to mount to a sprocket and its compact size. It operates up to 200 rpm acting as a positive drive coupling during normal machine operation. Input power transfers to the central assembly through the rigidly held pawl and rotates the outer drive housing and the driven shaft to which it is connected. If a jam-up or some other malfunction causes an unacceptable load to occur, excessive torque on the pawl overpowers the springs and the pawl rotates out of its detent. The central assembly is thereby disconnected from the outer drive housing and cuts power in the system, shutting it down.
Elmar Worldwide, 200 Gould Avenue, P.O. Box 245, Depew, New York 14043-0245.
Zero-Max, 13200 Sixth Avenue North, Plymouth, Minnesota 55441-5509. Fax: 763-546-8260. Outside US and Canada call 763-546-4300. Modified by Administrator at Sun, Sep 17, 2006, 08:29:17 03/07/2005, 13:01:08 Edit |
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