Torque limiters reduce machine down time

When a machine collision occurs, torque limiters will separate the drive from the driven elements within milliseconds.

When a machine collision occurs, torque limiters will separate the drive from the driven elements within milliseconds.

This is critically important to reduce down time and costly repairs.

This article introduces four styles of torque limiters within one standard design.

With the increased demand for factory automation, more and more systems are being designed and built, using servo and DC motor drives, with ever increasingly complex control systems.

Machines are getting larger, more rigid and designed for much higher production rates.

When a machine jam or collision occurs the costs can be very high, not only in terms of repair costs, but also in down time and lost production.

Today's design engineer must incorporate collision avoidance, and torque overload protection into the machine design.

R+W has developed a full line of torque limiters covering a large torque range.

Each torque limiter design offers four different styles of operation, single-position, multiposition, load holding and full disengage.

All four styles are available in the same dimensional package.

The result is more design flexibility for the engineer.

Based on a patented construction principle, all versions are absolutely backlash free, and are extremely compact with very low mass moments of inertia.

The R+W patented manufacturing process results in a 10% higher overall stiffness than other comparable ball detent systems.

All R+W torque limiters exhibit an extremely fast disengagement speed (1-2ms), often faster than the time needed for a motor controller to sense an overcurrent.

As it is a mechanical device, all of the working components are precision machined and hardened to withstand multiple disengagements without degradation of performance.

The system uses specially designed spring discs, which have a unique performance characteristic allowing for very sensitive adjustments with very little spring pressure after disengagement.

The standard version is the single-position engagement style.

When an overload is detected and the coupling disengages, it will automatically re-engage in the same position after rotating 360 degrees.

This is particularly useful in applications requiring precise registration: printing, die cutting and labelling for example.

The coupling will only re-engage if the speed and torque are reduced.

An actuation ring moves during disengagement allowing for a sensor to trigger system shutdown.

Multiposition versions operate similar to the single position version but will automatically re-engage at several positions, equally spaced, around the circumference of the coupling.

The standard is every 60 degrees, but custom designs with more or less positions are available.

The third style is the load holding version.

In this version the coupling will sense an overload but will not separate the drive from the driven elements.

The actuation ring will move, triggering the cutoff switch, and the coupling will rotate slightly but will continue to drive.

This version is particularly useful in lifting or hoisting applications where the load cannot be allowed to free-fall.

The load holding version will also automatically re-engage once the torque overload has been reduced.

The fourth version is the full-disengage.

When an overload is sensed, this coupling will disengage and remain disengaged.

Re-engagement of this coupling must be performed manually.

These are used in applications where there physically is no room to mount a sensor for the actuation ring, or in high speed applications where the drive speed cannot be reduced fast enough.

They are also used in situations where the machine designer wants to manually disengage a portion of the machine; like a print station in a printing press for example.

The reality in manufacturing today is that all machines will jam or crash at some point, often during peak production, or during the middle of the third shift.

Torque limiters are a form of cheap insurance against costly repairs and lost production.

They are compact, and can be easily incorporated into existing machine designs.

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