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Hydraulic Retracting Turn-Clamp Cylinder


Area of application

The hydraulic automatic turn-clamp cylinder, type HDHSZ, is designed for medium- to large-sized machines exerting a force of up to about 1,200 tons. It is mainly used for bottom die clamping (with and without clamping edge). For this purpose, T-slots or lock plates in the dies to be clamped are required.

The clamp cylinder is fitted in recesses in the press bed (or press ram) where it is fixed.

The clamp cylinder places little demand on the periphery of the machine. Its control can be easily combined in the existing machine control system.

Mode of operation

The double-acting hydraulic cylinder, hydraulically controlled , actuates the clamping process. In so doing, the tie rod is advanced from the housing of the clamp cylinder until it reaches the clamping position. The tie rod pinion, and hence the tie rod head, is rotated by means of a toothed rod until (by means of an edge bore) the clamping stroke is carried out.

The release process is carried out by reversing the hydraulic valve. After releasing the tie rod, the latter is rotated through 55° and then returns to the housing of the clamp cylinder.

Movement sequence for applying the clamping force:

Distinguishing features

The hydraulically operated clamping cylinder directly produces the necessary clamping force. In so doing, the hydraulic pressure must be maintained throughout the clamping process (optional equipment with non-return valves and pressure switches recommended).

By installing the cylinder in recesses provided for it in the press bed/ram, the surface of the clamp cylinder ends flush with the surface of the press bed or the ram. In addition, the tie rod is withdrawn to the idle position below the surface of the ram or bed, thus avoiding any difficulty in changing dies.

Electrical control of the following functions (switches):

Technical data

Switch: 2 inductive proximity switches; p-n-p normally open contact
Supply voltage: 10-30 V DC
Cable length: ca. 3 m

The clamp cylinder type HDSZ can be used for operating at temperatures of up to 70°C, and a maximum operating pressure of 400 bar.

The clamp cylinder has a manually operated emergency actuation device.



  • Fully automatic, purely hydraulic operation
  • Large clamping thickness tolerance
  • Central control
  • Highest standard of safety due to electrical control
  • Low installation cost
  • Low maintenance cost
  • High clamping force, despite compact dimensions of the clamp cylinders


The clamp cylinder has a gunmetal-finish housing and a gunmetal-finish tie rod.

It is secured by four bolts, of strength class 10.9 according to DIN 912 (not included). The thread dimension depends on the type (see technical drawing).

Dimensional diagrams

Technical specs