Clamping head for hydraulic presses, injection moulding machines, ...
Clamping unit as a safety component with DGUV Test Certification
Clamping heads are used worldwide in machines as a safety component for personal protection.
With the approval of the DGUV Test, the clamping head is approved for use on hydraulic presses - according to EN ISO 16092-1/-3 and on synthetic injection moulding machines - according to EN ISO 20430.
Both of our designs, safety catcher and Ratio-Clamp® locking unit, are suitable for applications where raised loads must be secured against falling or unintentional lowering/sinking.
- Activated in the event of a power failure
- Acceptance of the DGUV Test
- No damage to the clamping unit
- No damage to the clamped rod
Use as a safety component
Securing gravity-loaded axles
The safety catcher is a reliable technological solution if hazards due to external forces or loadsmust be taken into account in accordance with EN ISO 13849-1. In the case of fluctuation or loss of pressure energy, the clamping unit locks round rods under axial load.
The clamping head is used as a safety element as follows:
- As a secure position-holding element in case of a line break
- As a locking element when cylinders or valves have internal leakage, e.g. via throttle gap seals
- As a safety component in gravity-loaded axles, when hazards occur due to load, e.g. in lifting devices where there is a risk of dangerous sinking of a load.
The clamping unit is permissible as a safety component in accordance with EN ISO 13849-2. For a performance level that requires redundancy, it can be combined with a non-return valve as a secondary safety element, for example.
Functional principle of both clamping head versions
Personal protection for presses and injection moulding machines
Operating principle of the Ratio-Clamp®
The Ratio-Clamp® locking unit can be used horizontally or vertically. It secures round rods direction-independently via frictional contact, in which a spring triggers the clamping mechanism in the event of energy failure. The clamp is opened via hydraulic pressure directly at the same point, without the rod retracting.
Functional principle of the safety catcher
The safety catcher can be used vertically. It locks according to a self-energizing principle and can be loaded in tension or pressure, depending on the direction. The clamping is released by hydraulic or pneumatic pressure through a return stroke of the rod.
Technical data of the locking unit Ratio-Clamp®
Horizontal and vertical installation
| RATIO-CLAMP® AS A SAFETY COMPONENT |
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| + Release pressure + Locking + Sealing system + Certification |
Basic design With spring force Servocop® DGUV Test |
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| Rod-Ø (mm) |
Permissible load (kN) |
Release pressure min. (bar) |
Installation |
Installation-Ø (mm) |
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| 18 | 6,25 | 55 | 175 | 80 | ||
| 20 | 7 | 55 | 175 | 80 | ||
| 22 | 8,5 | 70 | 175 | 80 | ||
| 25 | 10 | 70 | 175 | 80 | ||
| 28 | 15,75 | 90 | 185 | 95 | ||
| 30 | 20 | 105 | 185 | 95 | ||
| 32 | 20 | 60 | 205 | 116 | ||
| 36 | 22,5 | 75 | 205 | 116 | ||
| 40 | 25 | 80 | 205 | 116 | ||
| 45 | 32,5 | 70 | 225 | 140 | ||
| 50 | 40 | 90 | 225 | 140 | ||
| 56 | 45 | 75 | 250 | 168 | ||
| 60 | 50 | 75 | 250 | 168 | ||
| 63 | 50 | 85 | 250 | 168 | ||
| 70 | 70 | 80 | 292 | 200 | ||
| 80 | 90 | 90 | 292 | 200 | ||
| 90 | 100 | 65 | 450 | 253,5 | ||
| 100 | 125 | 75 | 450 | 253,5 | ||
| 110 | 150 | 65 | 525 | 324 | ||
| 120 | 165 | 70 | 525 | 324 | ||
| 125 | 175 | 75 | 525 | 324 | ||
| 140 | 225 | 65 | 540 | 390 | ||
*The specified values apply to operation with mineral oil. When using other fluids such as HFC, the holding load may differ.
The holding forces of the locking unit Ratio-Clamp® correspond to at least twice the weight of the load to be secured.
In this Ratio-Clamp® variant with DGUV Test certification, the locked state is monitored and indicated by an inductive proximity switch. To monitor its function, this has an additional diagnostic output.
- Loadable regardless of direction
- Hydraulically released: min. see table, max. 160 bar
- Design key version up to Ø 100
- Factory check of the Ratio-Clamp® required after 1 million switching cycles
- Max. rod speed: 1 m/s with Servocop®
- Working temperature: -30 °C to +80 °C
- Fluids: Mineral oils or HFC*, others such as water or Skydrol® on request
Technical data of the safety catcher
Installation with tensile load or compressive load
| SAFETY CATCHER FOR VERTICAL AXLES |
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| + Locking + Certification |
Self-reinforcing DGUV Test |
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| Rod-Ø (mm) |
Permissible load (kN) |
Installation length1 (mm) |
Installation length2 (mm) |
Installation diameter |
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| 25 | 10 | 152 | 155 | 71 | ||
| 28 | 15 | 169 | 82 | |||
| 40 | 33 | 211 | 214 | 106 | ||
| 50 | 52 | 264 | 125 | |||
| 56 | 67 | 262 | 265 | 140 | ||
| 63 | 100 | 285 | 290 | 160 | ||
| 70 | 107 | 302 | 172 | |||
| 80 | 133 | 322 | 325 | 194 | ||
1 Compressive load without centering collar
2 Tensile load with centering collar
The values given apply to all fluids.
The holding load of the safety catcher for machines has a safety factor of at least 2, but does not exceed a safety factor of 2.8.
- Compressive load or tensile load
- Hydraulically released: min. 40 bar, max. 250 bar
- Pneumatically released: min. 4 bar, max. 10 bar
- Factory check of the safety catcher required after 2 million switching cycles
- Max. rod speed: 0.5 m/s
- Working temperature: 0 °C to +60 °C
- Fluids: mineral oils, HFC or compressed air, others on request
FAQ - Clamping unit - Clamping head
Questions on mechanical engineering fundamentals
- What is a clamping head?
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A clamping head is a component that serves as a safety element in machines. It fixates round rods in any position by automatically activating the clamping mechanism when energy fails. Due to this functional principle, clamping heads are frequently used to secure loads, especially to avoid hazards in the event of a power failure.
- How do you secure gravity-loaded axles in accordance with DGUV or the Machinery Directive?
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Gravity-loaded axles, for example, must be protected according to EN ISO 13849. Depending on the Performance Level (PLr) to be achieved, redundant protection is required. In the case of hydraulic axles, this can be achieved via a lock valve in combination with a clamping head or locking unit or safety catcher.
- What do "positive locking" and "frictional contact" mean, and how does the Hänchen clamping unit work?
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A positive locking connection holds because components interlock geometrically, for example, a pivot pin in a bore or a gearing. In contrast, a frictional contact connection holds through friction: a contact force, also known as normal force, generates sufficient friction force to prevent movement.
The Hänchen clamping units operate on the principle of frictional contact.
- What does the "DGUV Test" certification mean for my machine safety (CE)?
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The DGUV Test certification confirms that the clamping unit is approved as a safety component for personal protection in hydraulic presses (according to EN ISO 16092-1/3) and synthetic injection moulding machines (according to EN ISO 20430). The use of such a certified component significantly simplifies your risk assessment and the proof of conformity according to the Machinery Directive.
of the clamping head
- Is the clamping head a safety component according to EN ISO 13849?
The clamping head can be used as a safety component according to EN ISO 13849. For this purpose, we provide a B10D value upon request, which you can use to calculate your required MTTF value and determine the Performance Level.
- What is the difference between the "Ratio-Clamp® locking unit" and the "safety catcher"?
The Ratio-Clamp® locking unit fixes a rod independently of direction (for tension and pressure) and can be used both horizontally and vertically. The safety catcher is specifically designed for vertical, gravity-loaded axles and utilizes a direction-dependent self-energizing principle to achieve extremely high holding loads.
- How often should a clamping unit be inspected?
The clamping unit should be regularly inspected depending on the load. In particular, the tightness and the holding load must be checked according to the manufacturer's specifications. Additionally, an expert should inspect the condition and effectiveness of the clamping unit at least once a year; for applications as a load-holding device, statutory regulations must also be observed. Furthermore, for Ratio-Clamp® clamping units and Hänchen safety catchers, defined maximum clamping cycles apply, after which an inspection by Hänchen is recommended.