Gas Strut Locking Tubes

Locking Tubes for Gas Springs

Locking tubes are mechanical safety devices for gas springs. They prevent a fully extended gas spring from being compressed unintentionally.

When the gas spring reaches its fully extended position, the locking tube automatically moves into its safety position. The gas spring can then no longer be compressed until the locking mechanism is released manually. This provides additional protection against the accidental closing of an open flap, bonnet, lid or cover.

Locking tubes are particularly suitable for applications where sudden closing caused by overloading, incorrect operation, wind or gas spring failure could endanger people. Typical applications include mobile sales vehicles, trailers, machine covers, maintenance flaps and access hatches.

Use the product table above to select a suitable locking tube by piston rod diameter, cylinder diameter, maximum stroke and material.

Meaning of the Specifications in the Product Table

The values R and T describe the size of the corresponding gas spring. A combination of R = 8 mm and T = 18 mm, for example, is intended for a gas spring with an 8–18 mm size.

The maximum stroke St should not be assessed solely from the physical length of the locking tube. The gas spring size, stroke and design must all be compatible with the locking tube.

How a Locking Tube Works

As the gas spring extends, the locking tube moves along the pressure tube. Once the gas spring reaches its fully extended position, the locking element automatically pivots or moves into a position where it is mechanically supported against the cylinder.

The gas spring can then no longer be compressed. The load is not held solely by the gas pressure but is additionally secured by the mechanical locking device.

To close the application, the locking tube is pressed out of its safety position manually using the thumb or hand. Only after the lock has been released can the gas spring be compressed again in a controlled manner.

The locking mechanism should always be released deliberately and carefully. The flap must be supported while unlocking so that it cannot drop suddenly.

Not a Position-Locking Gas Spring

A locking tube must not be confused with a position-locking gas spring.

The locking tube secures the gas spring only in its fully extended position. It cannot lock the application at intermediate positions.

A position-locking gas spring, by comparison, contains an internal valve system and can be locked at different positions within the stroke, depending on the design.

A locking tube is therefore suitable where a flap needs to be opened fully and secured mechanically in this end position. A position-locking gas spring is required for continuously adjustable height or angle positioning.

How to Select the Right Locking Tube

Proceed in the following order:

1. Identify the gas spring: Determine the manufacturer, article number and size of the existing or intended gas spring.

2. Check the piston rod diameter: The value R of the locking tube must match the piston rod diameter.

3. Check the cylinder diameter: The value T must match the outside diameter of the pressure tube.

4. Compare the stroke: Select a locking tube whose maximum stroke St is suitable for the gas spring stroke.

5. Check the installation space: The locking tube requires sufficient clearance throughout the complete movement.

6. Select the material: Consider humidity, corrosion, cleaning agents and other environmental conditions.

7. Check the movement: Make sure that the locking tube can engage completely and can be released safely by hand.

A locking tube should not be selected solely by the piston rod diameter. The cylinder diameter, stroke, mounting points and installation geometry must also match the gas spring.

Where compatibility is uncertain, the exact gas spring article number should be checked together with a dimensional drawing or photographs of the installation.

Steel or Stainless Steel

Steel locking tubes are suitable for many general applications in dry or moderately humid environments. The black surface coating provides limited corrosion protection and visually matches gas springs with a black-coated pressure tube.

Stainless steel locking tubes are intended for applications with increased requirements for corrosion resistance and cleanliness. Typical examples include humid industrial environments, outdoor areas, food processing equipment, medical technology and marine applications.

Even with a stainless steel version, suitability for seawater, chlorides, acids or aggressive cleaning agents must be assessed according to the actual operating conditions.

Ideally, the locking tube and gas spring should be selected in compatible material versions.

Installation and Safety Recommendations

The locking tube is a safety-related component and must be installed correctly and checked regularly for proper operation.

For reliable operation, we recommend:

• using only locking tubes intended for the corresponding gas spring,

• ensuring sufficient freedom of movement throughout the complete stroke,

• preventing the tube from tilting or becoming blocked laterally,

• testing the locking function several times after installation,

• checking that the tube is securely engaged before working beneath an open flap,

• replacing damaged, bent or heavily corroded components immediately,

• never disabling the locking mechanism with cable ties, wire or other objects.

The movable component must be supported securely before the locking tube is released. Heavy flaps in particular may generate a considerable closing force after unlocking.

The locking tube does not replace a load-bearing construction or correctly designed mounting points. The gas spring, end fittings, brackets, hinges and supporting structure must all be suitable for the forces involved.

For applications with an increased risk of injury, additional mechanical safety devices or a formal risk assessment may be required.

Typical Applications

Locking tubes are commonly used on:

• serving hatches on mobile sales vehicles,

• trailer and vehicle flaps,

• machine and safety covers,

• maintenance and access hatches,

• control cabinets and technical housings,

• agricultural machinery,

• construction and commercial vehicles,

• heavy lids and covers.

They are particularly useful where people may work or stand beneath or directly beside an open flap.

Maintenance and Functional Checks

Locking tubes are generally low-maintenance. Nevertheless, their function should be checked regularly.

In particular, check:

• whether the tube engages securely when the gas spring is fully extended,

• whether it can be released in a controlled manner without excessive force,

• whether deformation, corrosion or other damage is present,

• whether the tube can move freely,

• whether the mounting points and gas spring remain securely attached.

Dirt, paint, adhesive or heavy deposits may restrict movement. The locking tube should be kept clean but must not be modified or dismantled without authorisation.

Further information on selection, installation and safety can be found in our Gas Spring FAQ.

Frequently Asked Questions About Gas Spring Locking Tubes

When does the locking tube engage?

The locking tube engages when the gas spring reaches its fully extended position.

Can the locking tube hold intermediate positions?

No. It secures only the fully extended end position. A position-locking gas spring is required for holding intermediate positions.

How is the locking mechanism released?

The tube is pressed manually out of its safety position. At the same time, the flap must be supported so that it can be closed in a controlled manner.

Does every locking tube fit every gas spring?

No. The piston rod diameter, cylinder diameter, stroke and design must be compatible with the gas spring.

Does the locking tube replace the gas spring?

No. It supplements the gas spring with a mechanical safety device in the fully open position.