CONTRIBUTORS
Safety catcher vs rod lock—what do i need?
SHANE HATFIELD

VP of Business Development—Rod Locks & Press Safety,
Machine Design Components

Office:

+1.815.316.5219

Email:

shane@ame.com

Safety catcher vs rod lock—what do i need?
NICK ROELING

Product Manager, Rod Locks & Press Safety

Office:

+1.815.316.5217

Email:

nickroeling@ame.com

Safety catchers and rod locks are very similar but they have different functions. Safety catchers are meant to do just that, catch a falling or sinking load. Implementing a safety catcher on a separate guide rod is vital to preventing catastrophic damage from a falling platen.


A rod lock system is designed to position and hold along a rod. So, it’s less about safety and more about the refined position, although rod locks can be added to a safety system in conjunction with a safety catcher for redundancy and simplify system recovery.


But, what is the real difference between a safety catcher and a rod lock, and how do you select the best option for your specific application?


  1. PNEUMATIC AMLOK RLN AND RCH SERIES ROD LOCKS | AMLOK position hold, power-off rod locking device is a double acting solution with springs that create the holding capacity as seen below (RLN and RCH). It holds load during a power or pressure loss and is designed to directly attach to your cylinder/actuator providing holding in both directions. It can also be used in stand-alone applications.


Safety catcher vs rod lock—what do i need?
Safety catcher vs rod lock—what do i need?
Safety catcher vs rod lock—what do i need?

SITEMA SAFETY CATCHERS | A safety catcher is single-acting, self-intensifying solution that functions similar to a finger trap where the load creates the holding—so more load equals higher holding forces.

Safety catcher vs rod lock—what do i need?

So which one is the correct device for you? Ask yourself, “Is my application a ‘position-and-hold’ or ‘gravity fall’ application?”


POSITION AND HOLD APPLICATIONS | Solution: AMLOK Rod Locks

Why: AMLOK units are bi-directional precision locking devices that hold in a precise location. The best solution for holding your rod or cylinder in place mechanically is the AMLOK. Whether you need to hold an external load in place or counteract the inherent issues with a cylinder (over travel, bouncing, drifting, and reverse travel) this is the best way to resolve these issues. If positioning is important to your team, then AMLOK is the solution.


Safety catcher vs rod lock—what do i need?

GRAVITY FALL APPLICATIONS | Solution: SITEMA Safety Catcher

Why: In the case of a falling load where you want a safe and reliable solution, a SITEMA safety catcher is the defacto standard. These are designed to decelerate and stop a falling load in the event of a gravity fall situation. The device is single acting. This creates a situation where the load is held until the power system is back online and functioning (you need to move the press upwards after power is restored to “reset” the SITEMA ensuring you are in a safe condition).

Safety catcher vs rod lock—what do i need?

HOW DO I CHOOSE THE CORRECT DEVICE?


If the application is a “position-and-hold” application, then use the AMLOK series units.


If the application is a “gravity fall” condition, then utilize the SITEMA Safety Catcher.


For special custom applications, consult with an engineer at AME.


AMROK ROD LOCK SITEMA SAFETY CATCHER
Releasing is possible, even under load, the load to be secured can therefore still fall down. Releasing under load is not possible, the unit is safe against unintended release.
Releasing is possible even when the load has not been taken over. A dangerous situation can result from this behavior. Releasing is not possible before the load has been taken off the clamping unit. Therefore, it is automatically made sure that the load has been safely taken over.
Depending on the cylinder pressure, the load will jump upwards or sink down during releasing. This also ensures a smooth releasing by use on a cylinder.
Clamping system always full strained. Clamping system strained only when necessary.
This results in a comparatively short service lifetime. This results in a high service lifetime.
Load cannot be lifted at pressure failure, trapped persons remain trapped. Safety factor > 2 already included.
Usually high holding forces are only possible with hydraulic clamping units. Loads up to 220kN can be secured with pneumatic clamping units.
Usually no DGUV approval. DGUV approval for all standard safety catchers and safety brakes.

THE SIMPLE WAY TO LOOK AT WHAT YOU NEED:

  1. Position and Hold: AMLOK
  2. Bi-Directional Movement: AMLOK
  3. On the End of a Cylinder: AMLOK
  4. Press Safety: Typically SITEMA
  5. Safety Solution for Press Applications: Typically SITEMA
  6. Gravity Fall Protection: SITEMA
  7. Braking Applications: SITEMA

At the end of the day, there can be some overlap on the different clamping solutions. Please consult the factory for any advice on your application.

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