Pneumatic Torque Limiter Provides Overload Protection

Nexen announced their TL Series pneumatically engaged, single-position torque limiters, delivering overload protection for industrial machinery. The TL Series uses a ball/detent interface and proximity sensor to immediately disengage the machine shaft when excessive torque or a machine jam occurs, effectively protecting downstream equipment and product from damage and decreasing downtime. Upon detecting the overload condition, the sensor instantly sends a signal to the torque limiter’s control valve, exhausting the air and disengaging the unit for a clean disconnect of power to the driven components.

By utilizing pneumatic actuation, TL Series units facilitate remote trip-out torque adjustment via an air regulator, allowing operators to optimize overload protection while the machine is in use-thus eliminating the need for inconvenient onsite adjustments. Each torque limiter’s interface has five ball/detents arranged in an asymmetrical pattern, assuring each engagement occurs in the same position and affirming machine components are accurately synchronized. The unique hard-chromed detent interface decreases drive-ring wear when the balls are pressed against the face during jog-to-position engagement, extending operational life as well as ensuring complete disengagement every time-without premature re-engagement.

Semi-open and totally enclosed, nickel-plated TL Series units are available. Semi-open units are sealed to keep contaminants out of the ball/detent area, while enclosed units are designed to protect the ball/detent and spline areas in washdown or other manufacturing environments where liquids are present. A variety of ball/detent sizes are available to provide a range of torque capacities, making the TL Series well suited for a broad application base, including packaging machinery, food processing, bottling, material handling and newspaper presses.

Several additional features of the TL Series ensure its long-lasting, dependable operation:

• The air chamber is sealed with o-rings to eliminate air leakage and minimize repairs, with backup rings to prevent o-ring dislocation, decreasing wear and extending the component’s operational life.

• Internal springs separate the ball and detent interfaces, preventing the ball from being forcefully removed from the detent-extending life and eliminating detent distortion, as well as preventing the torque limiter from re-engaging until the machine stops.

• The proximity sensor features an LED that illuminates to indicate when the torque limiter is engaged.

• Single-flex or double-flex couplings are available to deliver high shaft misalignment protection with zero backlash and excellent torsional rigidity.

http://www.nexengroup.com/nexen/index.jsp

Servo Torque Limiter from R+W America

Protection of an electromechanical system from torque overload is often assumed to be guaranteed by the current limits set in the drive parameters. But in the case of hard stops, impacts and other situations where overload occurs very rapidly, sufficient energy to do damage often exists in the rotating inertia driving the load.

R+W servo-rated torque limiters are accurate to +/-5% release torque and positively disengage the motor or gearbox shaft in 1-3 milliseconds. Patented pre-loads and a specially designed spring system remove backlash and guarantee a very low profile for higher release torques.

R+W America
www.rw-america.com/torque-limiters/index.html

Torque Limiters Tag-team to Prevent Overloads

For bottlers, protecting motion and assuring smooth, continuous operation in filler systems are critical in preventing system downtime. To guard against overloads and other system jam-ups, automated filling systems incorporate all types of devices including shear pins, electronic limit switches, and various types of mechanical stopping devices. These options may get the job done, but when they require repair, the systems must go down.

Elmar Worldwide Monoblock filler systems have speeds to 600 containers per min. The Company offers over 100 different models, from six to 72 stations, including rotary piston, bottom fill, gravity, and pocket modules. It uses Zero-Max torque limiters to protect from overloads.

For Elmar Industries, mechanical stops alone could not sufficiently halt the upward travel of the adjusting column with every cycle on one of its 100+ models – the Monoblock custom filler/capper
systems. At times, the upward force would overpower the mechanical stops, jarring them loose and sometimes knocking them off the system. The downward motion could develop too much force if the limit switch failed and the column bottomed out. This would jam-up the system. “What’s critical is to be able to control both upward and downward travel to avoid both of these problems even if the over-travel switches fail,” said Russell Wozniak, project engineer for Elmar.

Wozniak’s team turned to an alternative method for overload protection. Elmar now uses mechanical torque limiters because of their simplistic, fail-safe operation. On its Monoblock filler/capper systems, two different Zero-Max Torq Tender torque-limiting devices safeguard two separate machine functions. Both devices provide fail-safe jam-up protection.

The Zero-Max H-TLC torque limiter provides overload protection in the bottle height adjuster mechanism.

“We use the H-TLC-500 torque limiter in the motorized height adjustment mechanism, which raises and lowers the center column to adjust for different bottle heights,” reported Wozniak. This device prevents over-travel of filler heads. At the high and low point of travel of the filler head are mechanical stops. 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. 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 load reaches the preset limit, a pin disengages from the detent, shutting down the system. Once the overload condition is corrected, the torque limiter can be reset fast and the system restarted. The H-TLC can quickly be adjusted for changes in torque as needed.

The Zero-Max face-mount Torq Tender is the second torque-limiting device in the system.  It
connects to the primary drive train that moves the bottles through the system for filling, and protects the timing screw mechanism in the main gear drive from any kind of jam-up. Steel springs within the unit force metal slides against each side of a hardened cast steel pawl, holding it rigid with one end seated in a detent on the outer drive housing. During normal machine operation, the Torq Tender functions as a positive drive coupling. Input power transfers into the central assembly through this pawl. The outer drive housing and its driven shaft then rotate.

1. During normal machine operation, a hardened cast steel pawl is held rigidly between metal slides, with one end seated in a detent on the outer drive housing. 2. The pawl rotates out of its detent when excessive torque overpowers the springs.

When a load exceeds the rating determined by the precision tempered torque springs, excessive torque overpowers the springs, and the pawl rotates out of its detent. The central assembly is disconnected from the outer drive housing. This cuts power in the system, shutting it down.

Wozniak said that prior to the Torq Tender, a shear pin protected the feed screw drive. This was a problem because it required time to replace it following a jam-up. The Torq Tender, however, re-starts quickly, and it does not require tools. “You can manually re-set the torque springs of the Torq Tender with a simple full turn of the device. This puts the pawl back in its detent, and it re-engages the drive shaft. What’s more, Wozniak reported, “Once installed, you can forget about the Zero-Max torque limiters because they never need service. Ours have performed without problems for over five years with many installations operating twenty-four hours a day, seven days a week.”

Zero-Max
www.zero-max.com

Elmar Worldwide
www.elmarworldwide.com