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Stop fittings serve as mechanical end-position limiters in pneumatic systems, ensuring the switching and positioning of cylinder pistons. The variants offered by Parker Legris combine proven Push-In technology with high-quality materials such as nickel-plated brass, stainless steel, and technical plastic blends to ensure lasting tightness and high resistance to dirt, vibration, and temperature fluctuations. Typical applications include assembly machines, handling technology, injection molding peripherals, and industrial presses.

Construction, Materials, and Surfaces

Legris stop fittings are available in several designs: straight, 90° angled, and compact variants for confined spaces. Housings made of nickel-plated brass offer high corrosion resistance and electrical conductivity, while stainless steel versions (AISI 316/304) provide increased chemical and temperature resistance. Plastic housings made of PBT or PA are lightweight, oil-resistant, and reduce vibration transmission. Connection threads according to ISO, BSPP, and NPT, as well as metric threads, allow direct integration into existing components. Internal running and valve components often consist of hardened brass or stainless steel to minimize wear.

Sealing Technology and Tightness

Tightness is central to stop fittings. Legris uses various elastomers such as NBR, FKM (Viton), and EPDM depending on the medium and temperature range. NBR is suitable for general compressed air applications up to approximately 90 °C, EPDM for steam and higher temperatures, FKM for oil and fuel-laden environments up to ~200 °C. Double seals and precision-machined valve seats achieve hermetic shut-off with minimal leakage rates. Products undergo tightness tests according to internal test cycles and relevant standards, ensuring consistent function even under fluctuating inlet pressure.

Operating Principle and Variants

The basic function is simple: upon reaching an end position, the piston is mechanically blocked by means of a bolt or actuating pin, or the pneumatic flow at the end of the cylinder is shut off. There are two main principles: mechanical stop (physical blockage of the port path) and pneumatic stop (valve closes pressure supply). Mechanical stop fittings are robust against contamination and are suitable for long-term use in an open environment. Pneumatic stop fittings offer finer controllability and are useful in combination with pressure path sensors for precise positioning systems.

Connection Options and Integration

Legris offers Push-In connections for quick assembly without special tools, as well as fittings with compression rings and flat seals for repeatable disassembly. Push-In systems reduce assembly time and minimize leak sources through precise manufacturing of the tube and hose receptacles. For fixed pipe connections, press-fit and screw-in variants are available. Connection diameters range from 4 mm to 12 mm for compact systems and up to 1/2" for larger pneumatic lines. Electrical variants with switching signals (NO/NC) are available to transmit stop states to PLCs or safety controls.

Operating Parameters and Service Life

The operating pressure range of typical Legris stop fittings is between 0 and 10 bar, with specialized versions up to 16 bar. Temperature ranges vary depending on the sealing material: NBR up to ~90 °C, EPDM up to ~120 °C, FKM up to ~200 °C. Service life is influenced by the number of cycles, particle load, and pressure surges; under clean conditions, high-quality versions achieve several million switching cycles. To increase service life, the integration of filters, pressure stabilizers, and shock absorbers in adjacent circuit sections is recommended.

Practical Example 1: Assembly Line with End Position Monitoring

In an assembly line with pneumatic grippers, stop fittings are used at the cylinder ends to mechanically fix the end position of the gripper jaws when parts are inserted. The choice fell on a nickel-plated brass straight version with NBR seal and 6 mm Push-In connection. Thanks to Push-In technology, installation could be carried out without special tools, which reduced downtime. In combination with an electronic proximity switch, the stop fitting ensured double status monitoring: mechanical lock at the end position and electromagnetic signal to the PLC. Result: Reduced repositioning and consistent product quality.

Practical Example 2: Injection Molding Peripherals with High Temperature Stress

In an injection molding tool, stop fittings with FKM seals and stainless steel housings were used to limit the pistons of the demolding cylinders. The high short-term temperature and aggressive environment required materials with high chemical resistance and low thermal expansion. The fittings enabled reliable switching cycles under elevated temperatures and minimized downtime due to corrosion.

Practical Example 3: Offshore Application

For a system on a floating platform, corrosion-resistant stop fittings made of AISI 316 stainless steel were chosen, combined with EPDM seals for saltwater-resistant properties. The fittings were installed in pipelines exposed to multiple vibrations and splash water. Due to the robust construction, leaks were avoided, and maintenance intervals could be extended. Details on similar components and system solutions can be found at https://maku-industrie.de/technik and specific application cases at https://maku-industrie.de/anwendungsbeispiele.

Selection Criteria for the Right Stop Fitting

Choose the design, sealing material, and connection suitable for the medium, temperature range, and installation space. Consider cyclic load and particle load of the environment. Compatibility with existing thread standards and the possibility of integrating electrical switching signals are also crucial. For applications requiring increased tightness, double sealing systems and hardened valve seats are recommended.

Maintenance and Error Prevention

Regular visual inspection, cleaning of connection and seating surfaces, and replacement of elastomer seals according to manufacturer specifications ensure long-term operation. In case of increased contamination, regular integration of inline filters and cycle dampers is recommended. Should repeated leaks occur, check for wear on the valve seat and damage to the actuating pin; abrasive particles are often the cause. Document the installation location and number of cycles to establish planned replacement intervals.

Safety and Standard Notes

Stop fittings are components in the safety area and must be evaluated according to machine directives and, if applicable, the operating instructions of the overall machine. Electrical variants must be connected in such a way that the safety functions of the control system are maintained. Observe material and temperature limits to prevent material failure and loss of seal.

Scope of Delivery and Documentation

Deliveries generally include the fitting itself, sealing rings, and assembly instructions. Technical data sheets with pressure-temperature curves, leakage rate specifications, and material lists are available. Use the product data pages in the shop to select suitable replacement seals and mounting accessories to order compatible components directly.

Recommended Product Selection (Brief Overview)

* Straight Push-In versions made of nickel-plated brass for general industrial applications * Stainless steel variants for corrosive or temperature-stressed environments * Electrical switching versions for feedback to control systems

Frequently Asked Questions (FAQ)

1. Which seal is suitable for applications with oil and high temperatures?

For oil and fuel-laden environments as well as higher temperatures, FKM (Viton) is recommended. FKM offers temperature resistance up to approximately 200 °C and good chemical resistance to mineral oils. Pay attention to the compatibility of the other materials in the system.

2. Are Push-In connections suitable for high cycles?

Yes, Push-In connections from Parker Legris are designed for industrial applications with high cycle numbers, provided the hoses are properly installed and the system remains free of abrasive particles. For extremely high loads or frequent disassembly, compression ring or screw-in variants are recommended.

3. How do I recognize if a stop fitting is leaking?

Leaks are indicated by audible leakage noises, dropping system pressure, or visible air bubbles at connection points when moisture is applied. Check seating surfaces, seals, and connection fittings. If internal wear is suspected, replace the fitting or the seal to prevent consequential damage.