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Hydro-Mechanical Block Clamp


Area of application

The hydro-mechanical block clamp unit type HBS is designed for medium-sized and large presses exerting a pressure of ca. 500 tons upwards. It is particularly suitable for bottom die clamping and rolling bolster clamping. It is also being used increasingly for top die clamping.

The clamp unit can be fixed to the bed or ram surface or on the inside of the press frame in the case of bolster clamping.

Its use requires dies that have straight clamping edges.

Mode of operation

A hydraulically actuated mechanically locking clamping wedge mechanism transmits its clamping force to a clamping jaw.

In the clamping process, the jaw is forced out of the housing, and clamps the die to the surface of the bed or the slide. The movement sequence is internally controlled.

Movement sequence for applying the clamping force:

Distinguishing features

The clamp unit is fitted with a clamping wedge mechanism. In this system, the clamping force required is transmitted by mechanical components which are actuated by low hydraulic pressure only during the clamping or release process. The clamping wedge mechanism ensures that the clamp unit is mechanically self-locking when clamping. Nevertheless, a pilot-controlled non-return valve in both the clamping and release ports must secure the clamp unit against vibrations occurring during the production process. Thus, the hydraulic power unit can be switched off in clamped or released condition. Because of this, the clamping force is independent of the compressibility of the compression media, the operating temperatures and the line losses.

In the parked position, the clamping jaw is completely retracted into the housing, and thus protected from damage. The clamping edge of the die is released, and changing dies without interference is assured.

In the case of the dies used, maximum thickness tolerances of ±1.0 mm are permitted.

Electrical control of the following functions (switches):



  • Mechanical self-locking
  • Occupies little space, due to compact dimensions
  • Large clamping thickness tolerance
  • Central control
  • Hydraulic pressure required only during the clamping or re lease process
  • High mechanical load capacity


The individual components of the clamp unit are made from high-strength steels. The element is secured by two bolts of strength class 10.9 (not included). The thread dimension depends on the type (see technical drawing).

Technical data

Type HBS 50 HBS 100 HBS 200
Nominal clamping force kN 50 100 200
Max. load capacity kN 80 160 320
Max. operating pressure bar 110 110 110
Die thickness tolerance mm ± 1.0 ± 1.0 ± 1.0
Oil volume required (each process) clamping cm3 12 54 58
Oil volume required (each process) release cm3 20 79 73
Delivery rate per element l/min. 0.2-0.3 0.6-1.2 0.6-1.2
Weight kg (ca.) 25 30 50
Hydraulic connections G 1/4 G 1/4 G 1/4
Max. operating temperature °C 70 70 70
Pressure medium Hydraulic Oil Standard 3448
ISO Vce (DIN 51519)
Viscosity 25 - 60 cST/40 °C
Filter 20 - 25 µm

1) If a pump with a higher delivery rate than necessary is used, the oil flow must be reduced
by means of flow regulating valves or oneway restrictors.


Precision position switches

  • 2 inductive proximity switches
  • PNP contact
Hydraulic Circuit DiagramHydraulic Circuit Drawing

Dimensional diagrams

Specs table