Category Archive: Power Transmission Components

Torque Limiter Sprockets Offer Maximum Protection from Torque Overload


When your equipment and machinery approach torque overload, you’ll be thankful you have a Torque Limiter to protect critical drive components.
Torque Limiters are often used in conjunction with sprockets, which guide the rotational movement of equipment and machinery, and serve as an automatic safeguard against torque overload. They are usually sold separately, but U.S. Tsubaki now offers user-friendly, cost-effective Torque Limiter Sprockets, which come pre-assembled and can be made in various sizes and tooth counts for any application.

How does the Torque Limiter Sprocket work?

The Torque Limiter Sprocket works by transmitting torque via two composite friction disks, which are compressed by disk springs against the ground face of the hardened tooth sprocket. The end-user sets the torque limit by tightening the adjusting nut on the device.

During normal operation, when no torque overload is occurring, the Torque Limiter will transmit torque from the driven shaft to the sprocket via the friction disks. As the drive shaft runs, the spring will compress the friction disks against the sprocket. This creates a frictional force that transmits the power from the drive shaft to the sprocket.
When a torque overload occurs, such as during a mechanical jam, the transmitted power will exceed the set torque point, causing slipping between the friction disks and sprocket. If slipping occurs, the frictional force will no longer be strong enough to transmit the torque from the drive shaft to the sprocket. The drive shaft will continue to run, but no torque will be applied to the sprocket. Once the torque overload is removed, the Torque Limiter will automatically reset and resume transmitting torque.

Applications and Uses for Torque Limiter Sprockets

Torque Limiter Sprockets can be used for a variety of applications where continual movement of the machine is important, including conveyors, gearboxes and motors. The slipping of the friction disks allows the machine to power through temporary jams and load increases without incurring damage. Without a torque limiting device, critical drive components are at risk of failure or breakage from torque overload.

Torque Limiter Sprockets parts

By combining the Torque Limiter and sprocket into one product, customers now have access to a complete torque limiting solution that can be customized for specific applications and machinery.

U.S. Tsubaki offers a wide selection of mechanical protection devices and Torque Limiters for any application. To learn more about Torque Limiter Sprockets and select the right configurations for your facility, contact us today.

What is a Torque Limiter?


overload protection relaysCritical drive components can fail or fracture from just a single moment or action. This incidence, called mechanical overload, is when a rotating component experiences torques beyond what the system is designed to handle. Any rotating operation can develop a lot of torque and, if there is any kind of malfunction, all of that force can break affected components including, but not limited to, the couplings, the drive or motor shafts, and/or the gearing.

Mechanical overload protection devices like the Tsubaki Torque Limiter can help reduce the risk of critical component failure.

Simply put, these devices protect rotating components from the risk of mechanical overload. Clutches, brakes, and Torque Limiters all fall under this classification. Torque Limiters, specifically, work by slipping during torque overload to prevent driven components from experiencing excessive torque loads. If a torque overload occurs, the Torque Limiter is able to protect critical equipment by disconnecting the driving shaft from the driven components.

How Does a Torque Limiter Work?

Torque Limiters ensure that torque-based forces never exceed the set point. By limiting torque forces to what the rotational components can safely handle, these parts reduce mechanical overload and failures. They can work independently or in congruence with electronic sensors. Sometimes, mechanical torque limiters are called overload clutches.

During normal operation, when no torque overload is occurring, the Torque Limiter transmits torque from the driven shaft to the driven member (sprocket, gear, pulley, etc.) via friction disks. The friction disks are compressed against the face of the driven member by disk spring and the frictional force is high enough to transmit the torque from the shaft to the member. The Torque Limiter spring force is manually variable via adjusting nut.

When a torque overload occurs, the transmitted torque will exceed the set torque point of the Torque Limiter. When this occurs, the frictional force is no longer strong enough to transmit the torque from the driving shaft to the driven member, and the driven member slips between the friction disks. When the torque overload is removed, the Torque Limiter automatically resets and resumes transmitting torque.

Torque Limiter Applications

Torque Limiters can be used to protect any machinery with rotating components. If there is any risk of a drive shaft transmitting too much torque to the driven shaft or tangential parts, a Torque Limiter can ensure torque never reaches critical levels. The components couple the two rotating bodies and introduce a disconnect method.

shock guardIndustries that commonly use Torque Limiters to protect their machinery include:

  • General machining and manufacturing
  • Packaging and assembly services
  • Printing and converting industries
  • Textile manufacturing
  • Forest products

Specific applications for Torque Limiters include:

  • Conveyors: If the conveying system jams, the Torque Limiter will disconnect the driving motor from the conveyor to protect critical components.
  • Gearboxes: This additional safety mechanism prevents excess torque from reaching vulnerable components in the driven system.
  • Generators: Power outages can cause sporadic moments of excess torque. A Torque Limiter can prevent that force from damaging the equipment.
  • Motors: The Torque Limiter can disengage the motor shaft from the driven system in the event it generates too much torque for the machinery to handle.
Torque Limiter

Torque Limiter Sprockets by U.S. Tsubaki

Our Torque Limiters offer excellent protection from excessive torque and the risks of mechanical overload. U.S. Tsubaki now offers a factory pre-assembled Torque Limiter Sprocket to help further improve our customer experience.

shock relaysTsubaki also produces the following overload protectors:

  • Shock Guard®
  • Mini Keeper
  • Torque Keeper
  • Shock Relay
  • Shock Monitor

Browse our wide selection of mechanical protection devices and Torque Limiters here. You can also contact us today to request specific information from our team.

All About Zip Chain Actuators®


Zip Chain Actuators—also commonly referred to as meshing chains, rigid chains, linear chains, and push-pull chains—are used alongside other material handling equipment to facilitate push and pull applications. These actuating units consist of two chains that interlock like a zipper to form a rigid column and are available with a wide range of features and performance characteristics to suit different applications. Typical uses range from motorized opening and closing of windows in buildings to heavy-duty industrial applications like platform lift operators and automated assembly lines.

How Do Zip Chain Actuators Work?

Zip Chain Actuators (ZCA) have a motor-driven shaft which turns a specially designed sprocket that converts the motor’s rotation into linear motion. When the motor rotates in one direction, it zips the ZCA segments and locks the chains’ links to form a straight, rigid chain; when the motor rotates in the other direction, the sprocket disengages the links and the chain retracts and coils back into a compact housing.

Zip Chain Actuator System Performance

The unique design of the ZCA significantly influences its performance. Compared to conventional linear actuators, such as electric screw-type, hydraulic, and pneumatic cylinders, they offer several advantages, such as:

  • Easier maintenance. Unlike a hydraulic actuator, the ZCA uses grease for lubrication, eliminating the risk of oil leakages due to faulty units and leaking lines. Additionally, they do not require pneumatic/hydraulic lines as they are connected solely through the use of cables, further reducing the number of parts requiring repair and maintenance.
  • Faster operation. ZCAs can move at higher speeds than other linear actuators. They are 3 to 10 times faster than hydraulic lift cylinders. For example, zip chain model ZCA45 can attain a maximum operating speed of 500 millimeters/second while models ZCA25 and ZCA35 can reach 1000 millimeters/second.
  • Greater control. When used with a servo motor, the motor’s rotational position can be precisely controlled to make the ZCA capable of precise multi-stop positioning.
  • Broader setup configurations. The retracting-chain design and compact housing enables ZCA to be mounted or suspended horizontally or vertically to suit a wide range of customer needs, even in limited-space environments.
  • Lower energy usage and costs. The ZCA can return energy savings of up to 50% compared to hydraulic and pneumatic cylinders because the use of a brake motor allows it to hold loads in place without any need for electrical power.
  • Longer service life. The ZCA demonstrates excellent resistance to wear and chain elongation. These qualities allow it to achieve an expected lifetime travel distance of approximately 4,000 kilometers. 

Zip Chain Product Options

Zip Chain Actuators are available with a hypoid motor or Tsubaki TERVO reducer for servo motors.

  • A ZCA with a hypoid gear motor is available in every size to accommodate a wide range of customer requirements. With fewer components, this ZCA facilitates an easier assembly and selection and all fits in a compact, integrated footprint.
  • A ZCA with a Tsubaki TERVO reducer for servo motors is a compact solution that provides more precise high-speed positioning and unlimited cycling frequency.

Zip Chain Actuator Applications

As mentioned above, the design of a ZCA makes it suitable for operating at high speeds and frequencies with precise multi-stop positioning and freedom of direction of installation. They are widely used for stacking and unstacking materials, horizontal and vertical push/pull operations, and high-speed sorting applications.

Stacking and Unstacking Materials

The typical operating characteristics of zip chains used in stacking and unstacking operations are:

  • Lifting weight: 204 kilograms for stacking and unstacking
  • Lifting speed: 30 meters/minute for stacking and unstacking
  • Stroke: 1,000 millimeters for both stacking and unstacking

Horizontal or Vertical Push/Pull

Horizontal and vertical zip chains for push/pull applications can utilize servo motors to aid their operations. Both types may offer the following operating characteristics:

  • Lifting weight: 102 kilograms
  • Lifting speed: 60 meters/minute
  • Stroke: 1000 millimeters and 1 second/cycle

High-Speed Sorting

High-speed sorting zip chains may have the following:

  • Lifting weight: 102 kilograms
  • Lifting speed: 60 meters/minute
  • Stroke: 750 millimeters

Zip Chain Actuator System Performance

Quality Zip Chain Actuators From Tsubaki

Since its founding in Japan in 1917, Tsubakimoto Chain Company (Tsubaki) has designed, manufactured, and supported many types of bulk material handling equipment. Zip Chain Actuators are the latest material handling solution in a long line of linear motion products designed and developed by Tsubaki.

At Tsubaki, we strive to offer the highest level of quality products and services for optimizing plant operations. From clutches & backstops, to power cylinders, to sprockets, to Zip Chain Actuators, Tsubaki offers a wide range of high-quality power transmission and motion control products. Learn more about Zip Chain Actuators and our other products by contacting us today.

Guide to Overload Protection Relays


overload protection relaysElectric motors see wide usage in machines with rotating components. Motors are often quite expensive, so it is important to prevent them from failure caused by carrying more electric current than their rated amperage. Electrical overload can sometimes develop from ground faults (short-circuits in the motor windings or peripheral cables), but more commonly occurs due to jamming or improper operation.

Overload protection relays prevent motor damage by monitoring the current in the motor circuit and breaking the circuit when an electrical overload or a phase failure is detected. Since relays are much cheaper than motors, they provide an affordable way of protecting motors.

Benefits and Features of Overload Protection Relays

There are different types of overload protection relays. Examples are fuses, thermal relays, electromechanical relays, and electronic relays. Fuses are widely used for protecting low-current devices like household appliances. Thermal, electromechanical, and electronic relays are used for protecting high-current machines like industrial motors. The main benefits of using relays are:

overload protection relays

Dependable Protection

Overload relays cut off current to the motor when a high-current situation develops due to a ground fault, short circuit, phase failure, or mechanical jamming. They are an inexpensive way of avoiding downtime for repair or replacement of failed motors from excessive current.

Proper Matching with Contractors

Contractors carry the high operating currents of the main circuit. They have inbuilt mechanisms to suppress arcing caused by the interruption of heavy motor currents. When contactors are properly matched with thermal relays, the combination provides a good motor starting circuitry.

Starters are Easy to Operate

Manual motor starters are used for turning motors on and off. These electromechanical devices are easy to install and to reset after they trip.

Mounting Kits

Application-specific mounting kits are available for various types of overload protection relays.

Overload protection relays have adjustable current setting ranges to control their activation threshold. In addition to preventing electrical overload, they can also detect and protect against phase failures. Since these relays often operate in hot environments, they provide ambient temperature tolerances up to 60° C.

Relays also come with automatic or manual resets that are sealable to protect them from the hazardous environments they operate in. Relays also incorporate stop and test functions to check their operational integrity while not carrying an electrical current.

View Our Catalog of Overload Protection Devices

Overload Protection Relay Product Considerations

Overload protection relays protect against the following fault situations:

Current Overload

Motor coils degrade when they carry currents greater than their designed limit and burn out after prolonged exposure.  When currents go above set limits, the overload protection relay trips to avoid damage.

Phase Loss

This is an important fault category since it is the leading cause of motor failures. It is caused when one of the phases of the electrical supply to the motor fails.


This miscellaneous category covers a variety of situations like ground faults, stalling or jammed motors, load imbalances (including under load), and voltage fluctuations.

Overload Protection Relay Products by U.S. Tsubaki

U.S. Tsubaki offers the following devices to protect against surges in electrical currents or torques:

  • Electronic Shock Relays: These relays protect against surges in electrical currents—under loads as well as overloads. Using them will prevent downtimes from unanticipated failures and expensive repairs. They help to keep your overall maintenance costs low.
  • Mechanical Shock Guards: These mechanical relays protect against surges in mechanical torque. Torque surges can occur in dusty, humid, and high-temperature environments. These devices disengage when the torque exceeds the threshold value and will reengage when the torque surge disappears.

U.S. Tsubaki Power Transmission, LLC is a leading manufacturer and supplier of motion control and power transmission products and is a subsidiary of the Tsubakimoto Chain Company, headquartered in Japan.  With over 100 years of manufacturing experience, Tsubaki prides itself on excellence in quality, reliability, and customer service and strives to be the manufacturer who provides the best overall value to customers.

Contact us for all your overload protection relay requirements.