How do Locking Units Absorb Axial Forces in Both Directions?

Jun 28, 2018

Locking units are primarily used as functional clamps for precision locking. They also prevent unwanted movement and absorb axial forces in both directions.

The clamping system consists of a conical sleeve and a clamping ring. The sleeve is axially fixed in the housing and only allows radial movement. The clamping ring is guided by the housing and is forced in the axial direction over the sleeve to achieve the clamping action.

The clamping force of a locking unit is generated by some sort of spring action or fluid pressure. Depending on their type, the locking unit is unclamped by hydraulic or pneumatic pressure applied to the annular piston. A well-defined clearance ensures that the shaft can move without friction.

If an overload occurs, then the shaft slips through the clamping unit. This normally causes no damage. However, applications with recurring overload should be avoided due to the seizing potential that is dependent on the force-level, slipping speed, and rod quality.

Pressureless Locking Units

If the unit is pressureless, the rod is clamped by a spring force and the full nominal holding force can be carried. Proximity switch 1 signals “rod clamped”.

The 3/2-way valve gets electrically actuated during every cycle of operation and releases the locking unit. In all other operations, including power failures, emergency stops, etc. the locking unit is actuated, secures the rod, and stops the load. The shaft should not be moved unless proximity switch 2 signals “clamping released”.

Pressurized Locking Units

If the port within the locking unit is pressurized then the rod is clamped by force of the annular hydraulic or pneumatic piston, and it can hold a force proportional to the applied pressure.

Using the nominal pressure, the full nominal holding force is achieved and proximity switch 1 signals “rod clamped”.

Precision Locking for Various Applications

Locking units provide precision locking and prevent unwanted movement in a variety of applications including:

  • Machine tools -- Locking units hold the vertical axis of a machine tool in case of a power failure or emergency stop, providing safety for the worker and machine.
  • Linear drives -- Locking units provide safety on the z-axis of a machine tool.
  • Lathes -- For high-speed trains and the overhaul of wheel bogeys, locking units are fixated on the center sleeve of a lathe. 
  • Steelworks -- The necessary stepless locking of the drive on a high-performance roll stand is performed by locking units because the hydraulic wedge adjustment of the lower roll is not self-blocking. 
  • Suspension bridges -- Locking units fixate the hydraulic cylinders on the service cabin for the support cables of suspension bridges.

 

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