Guaranteed advantages of hydraulic rod clamps:
  • Clamping and releasing without axial rod movement
  • clamping effect in case of a power failure
  • allowance- and wear-free locking
  • load capacity independent of direction
  • clamps all round rods
  • TÜV-certified

Application areas

There are many situations where rods have to be held in a certain position: For example to protect people, machines and tools in case of power failures or plant shutoffs. Or to fix axes during a manufacturing process. And also for all highly dynamic applications and test processes.
Here are some examples from practical experience:

Grinding machine > production

During the production process of ICE rail sleepers, extremely large and heavy concrete workpieces must be positioned for grinding safely and with an accuracy of 0.01 mm. Hänchen's hydraulic cylinders and Ratio-Clamp® clamping units are designed exactly for these requirements.

Aviation > testing technology

The setups for aviation tests have been refined to the last detail. Hänchen cylinders are used in different fields of testing, simulating ambient conditions and loads during different flight phases. Ratio-Clamp® clamping units are used to protect the intricately constructed and expensive systems.

Press > production

Hänchen lock cylinders guarantee safe movements of the press. Clamping units ensure safety during the pressing process in moulding and injection presses for the production of synthetic and rubber moulded parts in accordance with EN 289.

Railway technology > maintenance

For maintenance purposes, trains must be fixed in the raised state – the Ratio-Clamp® is ideally suited for this purpose. The clamping units hold the train securely in position until the work has been completed and it can return to the rails.

Profiling machine > production

Hänchen clamping units ensure precise machining and consistent quality in the production of metal profiles. During the production process, they facilitate the machining of the profiles by locking the forming tools in place. Ecological and efficient, purely with spring power.

The functional principle in detail

Hänchen's Ratio-Clamp® offers safety while saving energy costs. Thanks to its sophisticated functional principle, the hydraulic clamping device features some fundamental advantages when compared with other locking systems.

Ratio-Clamp® rod locks works mechanically by using frictional contact: The power is directed through springs to a clamping sleeve which holds the rod radially using friction. The load capacity of the fixation is not influenced by the direction. The hydraulic releasing pressure moves the locking piston against the spring power to unlock the clamp - the rod can be moved in both directions. When the hydraulic pressure drops, the power stored in the springs is released, and the rod is locked.

Video to functional principle of the clamping device Ratio-Clamp® on the example of a gantry milling machine.

Hänchen's clamping device Ratio-Clamp® offers safety while saving energy costs. Thanks to its sophisticated functional principle, the clamping device features some fundamental advantages when compared with other locking systems.
Locking and securing loads

If the releasing pressure drops, the force stored in the springs is released and causes the rod to clamp. Thus the load is secured and the Ratio-Clamp® is ready to take over the load.


Loading is possible immediately after clamping. No axial movement of the rod is required. In the clamped state, the forces in both directions can be kept free of play.

Ratio-Clamp® works mechanically by using frictional contact: The power is directed through springs to a clamping sleeve which holds the rod radially using friction.

The locking piston moves against the spring power by hydraulically releasing pressure and releases the clamping force. The rod can be moved in both directions.


Short-term overloading with slipping of the rod is possible without damaging the rod or the clamping unit.

Energy efficiency and precision for every case

Do you have an application where a round rod has to be held in a specific position? There are different ways to achieve this: by electronic control, shutting off all ports, locking with pivot pins or by using the clamping unit Ratio-Clamp®. The Ratio-Clamp® scores with numerous advantages.

  • Stepless clamping without energy supply
  • Fixes precisely at the desired positions
  • Holds position at temperature fluctuations
  • Savings in energy costs through clamping with spring power


Comparison of advantages and disadvantages of locking options for round rods

Pivot pin
Clamping unit
Energy efficiency + + +
Position accuracy + + +
Independence from
external influences
+ + +
Effort + +
Flexible positioning + + +

Regardless of hydraulics and electronics, Ratio-Clamp® will hold the piston rod in any position for any amount of time – no energy supply required.

Case example: The energy required for clamping a piston rod:

A hydraulic cylinder with an 80 mm bore is moved at 150 bar with a speed of 0.5 m/s. The drive power required is 38 kW.

Power loss when holding
When using an electronic control system with a controlled pump, the power loss to be expected at the pump is approx. 1.25 kW, plus a loss of approx. 1.25 kW at the control valve. So in this example, the total power loss with the controlled drive would be 2.5 kW. With a holding time of 5.000 hours a year, you'd lose 12.000 kWh.

Power loss when holding

Ratio-Clamp® uses spring power for holding, which is why there is no need for hydraulic or electric power.

Characteristics of hydraulic clamping devices

Releasing pressure

Basic design
The basic releasing pressure required for releasing the clamping unit is between the minimum pressure and the maximum admissible pressure of 160 bar.

Reduced design
For application cases with low supply pressure, a version designed with a reduced released pressure is available.


TÜV certification
Every Ratio-Clamp® is type tested by TÜV SÜD.

The clamping unit is also available with a DGUV Test certification (testing and certification system of the "Deutsche Gesetzliche Unfallversicherung"). Ratio-Clamp® has a B10D value according to EN ISO 13849-1 for use as a redundant safety component. The double safety requirement by the DGUV for the maximum holding load is already taken into account in the load specification.
learn more


Locking with spring power
Usually, energy stored in springs is used to clamp a rod. This means that the rod can be held for unlimited periods of time without any energy supply.

Hydraulic locking
When very high holding loads are required, the clamping unit can also be locked hydraulically. For the release, hydraulic pressure is used as usual.

Sealing system

Servocop®: compact seal, lip seal, wiper ring
The basic type of Ratio-Clamp® uses the frictionoptimised sealing system Servocop®. Here, the primary seal touches the rod. The maximum speed of the rod is 1 m/s.

Pressure piston seal, lip seal, wiper ring

For very sensitive applications, we recommend the design with pressure piston seal, where no pressurised seal touches the rod. Thus, the sliding friction is very low and remains constant regardless of the releasing pressure. The maximum speed of the rod is 2 m/s.
learn more

Accessories for the clamping device Ratio-Clamp®
Quality taken to the next level.

Hydraulic cylinders

Ratio-Clamp® can be combined with Hänchen hydraulic and standard cylinders and with all cylinders from other manufacturers.

A fixed flange is used for attachment to Hänchen hydraulic cylinders or cylinders pursuant to ISO 6020-1, ISO 6020-2 and other makes. For this purpose, the rod must be extended according to the length of the clamping unit. If attached separately, the clamping unit can also be loosely installed using a collar flange to compensate for axis misalignment.

Ratio-Clamp® can be combined with Hänchen hydraulic and standard cylinders and with all cylinders from other manufacturers.
Proximity switch

The respective state – rod locked or released – can be monitored via inductive proximity switches. The device for mounting a proximity switch is available as standard. On request, the clamping unit can be equipped with two proximity switches. When using the Ratio-Clamp® as a safety component or with required DGUV Test certification, it is obligatory to have a proximity switch with diagnostic output installed. This also monitors the function of the switch and supply line.

Proximity switch indicates whether the clamping device is locked released.
Control block

Used when Ratio-Clamp® is installed on a hydraulic cylinder. It provides correct and consistent control and thus reduces the complexity of the required wiring.

When controlling a Ratio-Clamp®, it must first be released by applying pressure to the releasing port – only then may the rod be moved. When using a clamping unit together with a hydraulic cylinder, it can be done by means of a hydraulic sequential control or by electronic monitoring. For example, in order to build up counterpressure, sensors in an electronic control system can measure the load on vertically installed cylinders. This prevents the rod from jolting when releasing.

This can also be achieved with a hydraulic control block: first the releasing pressure is built up, then the cylinder is pressurised. Matching valves locks the pressure in the cylinder so that the Ratio-Clamp® can be unlocked almost without jolts even when handling vertical loads.

More about the functions of the control block.

Control block ist Used when Ratio-Clamp® is installed on a cylinder.
Rod requirements

The round rod to be clamped shall have a hard surface and must meet the minimum requirements when installing the Ratio-Clamp®. A honed rod is recommended.

Technical drawings and CAD dataCAD data for the clamping unit can be found in our HÄKO or at Cadenas.

Technical data of hydraulic clamping device

  • for all round rods with hard surfaces
  • load capacity independent of direction
  • after 2 million switching cycles the Ratio-Clamp® shall be inspected at the factory
  • max. rod speed: 1 m/s for Servocop®, 2 m/s for pressure piston seal
  • max. releasing pressure: 160 bar
  • working temperatures: -30°C bis +80°C
  • fluids: mineral oils, others like water, HFC or Skydrol® on request
Technical data
Clamping unit
Here you can find all technical data for our clamping unit Ratio-Clamp® on an overview sheet

  + Releasing pressure
+ Locking
+ Sealing system
+ Certification
Basic design
With spring power
Reduced design
With spring power
  Rod Ø
holding load
Releasing pressure
holding load
Releasing pressure
   16  10     60     8     50     
   18  12,5  55     8     35     
   20  14     55     9     40     
   22  17     70     12     45     
   25  20     70     15     50     
   28  31,5  90     25     65     
   30  40     105     30     75     
   32  40     60     30     45     
   36  45     75     32     50     
   40  50     80     38     55     
   45  65     70     45     50     
   50  80     90     55     60     
   56  90     75     60     50     
   60  100     75     70     55     
   63  100     85     60     55     
   70  140     80     100     55     
   80  180     90     130     65     
   90  200     65         
   100  250     75         
   110  300     65         
   120  330     70         
   125  350     75         
   140  450     65         
   160  750     90         

Other holding forces and rod Ø on request.
Hydraulic locking is possible up to 2,000 kN holding load and 300 mm rod Ø.
The stated values apply to operation with mineral oil. The holding load may differ when using other fluids.