A detached leg spring energizer (also known as Fishback Spring or Fish Back Spring) is a spring loading element specifically developed for applications requiring minimal preload, responsive sealing force, and excellent flexibility under limited installation space. Unlike conventional cantilever or helical spring designs, the legs of the spring are separated from each other, allowing each spring arm to deflect independently.
This independent leg movement provides highly responsive sealing force with reduced contact pressure, making detached leg springs particularly suitable for low-pressure sealing, sensitive dynamic systems, and applications requiring extremely low breakaway torque.
Installed inside PTFE, filled PTFE, UHMWPE, PEEK, and other polymer jackets, detached leg springs continuously energize the sealing lips while generating minimal drag and gentle sealing load. Their flexible geometry allows effective compensation for dimensional tolerances, thermal expansion, and component misalignment.
Detached leg spring energizers are commonly used in semiconductor equipment, analytical instruments, medical devices, cryogenic systems, vacuum equipment, and precision motion applications.
Provides some of the lowest friction characteristics among spring energizer designs, making it suitable for precision and sensitive sealing systems.
Each spring arm deflects independently, providing highly responsive sealing force and excellent dynamic response.
Minimizes starting torque and stick-slip behavior, ensuring smooth motion in precision systems.
Excellent performance in vacuum environments and precision applications including semiconductor and medical equipment.
Typical Load Behavior: Detached leg spring energizers typically generate relatively low and stable spring loads throughout the operating deflection range. The independent movement of each leg helps reduce force spikes during compression while maintaining sufficient sealing contact.
Compared with helical springs, detached leg designs generally produce lower preload force and reduced friction, making them particularly suitable for precision instruments and vacuum applications where sealing force must be carefully controlled.
Detached leg springs are often selected when sealing force must be carefully controlled and friction must be minimized.
Detached leg springs provide the lowest friction and most responsive load characteristics among all spring energizer designs.
Unlike helical, canted coil, or cantilever designs where spring arms are connected, the independent leg geometry of detached leg springs eliminates load interaction between adjacent spring arms. Each leg responds individually to the sealing surface, resulting in:
Lowest Friction Lowest Breakaway Force Most Responsive
Minimal Stick-Slip
Best for Precision
Vacuum CompatibleThis makes detached leg springs the preferred choice for semiconductor wafer handling, analytical instrumentation, and high-precision medical devices.
Detached leg spring energizers occupy a unique position for ultra-low friction applications. With the lowest friction, lowest breakaway force, and excellent dynamic response, they are particularly suited for precision motion, vacuum, and semiconductor applications.
| Comparison Item | Helical | Canted Coil | Cantilever V | Cantilever U | Full Contact | Detached Leg |
|---|---|---|---|---|---|---|
| Spring Structure | Helical coil | Slanted coil | V-shaped cantilever | U-shaped cantilever | Continuous contact | Independent legs (Fishback) |
| Load Level | High | Medium | Low-Medium | Low-Medium | Medium-High | Very Low |
| Friction | Moderate | Low | Low | Low | Moderate | Very Low |
| Dynamic Performance | Moderate | Excellent | Excellent | Good | Moderate | Excellent |
| Compensation Ability | Moderate | Excellent | Excellent | Good | Excellent | Excellent |
| Breakaway Force | High | Low | Low | Low | Medium | Very Low |
| Vacuum Capability | Excellent | Excellent | Good | Good | Excellent | Excellent |
| Cryogenic Service | Excellent | Excellent | Good | Good | Excellent | Moderate |
| High Pressure | Excellent | Good | Moderate | Moderate | Excellent | Limited |
| Motion Systems | Moderate | Excellent | Excellent | Good | Moderate | Excellent |
| Seal Stability | Excellent | Excellent | Good | Good | Excellent | Good |
| Typical Applications | High-pressure static sealing | Dynamic and low-friction sealing | Reciprocating dynamic sealing | General-purpose sealing | Vacuum and cryogenic sealing | Precision motion and vacuum systems |
When minimal friction and precise motion control are critical, detached leg spring energizers are often the preferred choice for advanced sealing applications.
Not sure which spring type fits your application? Contact our engineering team for selection support →
When installed inside the seal jacket, the separated spring legs apply independent radial or axial forces to the sealing lips.
During operation, each spring arm responds individually to:
This independent movement helps maintain stable sealing performance while minimizing friction and wear on the sealing jacket. The detached leg design also provides excellent load distribution across a wide deflection range, making it suitable for both static and dynamic applications.
Dimension Reference: L = Cross-section width | J = Cross-section height | K = Material Thickness
Custom dimensions available. Contact us for full specifications or specialized OD, strip thickness/width solutions.
All dimensions in inches. Custom dimensions available. Table shows a portion of our standard range.
| Part Number | F (in) | H (in) | J (in) | K (in) | L (in) |
|---|---|---|---|---|---|
| HDY-DLS-138 | 0.098 | — | 0.355 | 0.016 | 0.386 |
| HDY-DLS-141 | 0.039 | 0.221 | 0.256 | 0.020 | 0.433 |
| HDY-DLS-140 | 0.157 | — | 0.358 | 0.020 | 0.443 |
| HDY-DLS-139 | 0.125 | — | 0.410 | 0.020 | 0.526 |
| HDY-DLS-137 | 0.079 | 1.049 | 0.561 | 0.020 | 1.120 |
| Contact us for complete specification sheet and custom dimensions → | |||||
Materials
Material selection directly influences corrosion resistance, spring recovery, fatigue life, and sealing reliability.
Excellent corrosion resistance and fatigue performance for long-cycle dynamic and precision sealing applications. Available to AMS5833 and NACE MR0175.
Nickel alloy suitable for elevated temperature and demanding sealing applications up to 650°C.
Outstanding corrosion resistance in highly aggressive chemical and process environments.
Precipitation-hardening stainless steel balancing strength, elasticity, and manufacturability.
Material selection depends on operating temperature, corrosion resistance requirements, media compatibility, and expected service life. Additional alloys including Monel 400, Hastelloy C22/C2000, and Victrex™ PEEK are available upon request.
Detached leg spring energizers perform particularly well in applications requiring ultra-low friction, minimal breakaway force, and sensitive dynamic response. Actual performance depends on seal jacket design, operating media, and material selection.
Handa Spring manufactures custom detached leg spring energizers based on seal groove dimensions, required preload, friction requirements, operating temperature, media compatibility, pressure conditions, and motion type.
Each spring is manufactured using standard tooling. Minor variations to dimensions can be made with minor adjustments to tooling. More significant changes may require inquiry about non-standard cross-sections.
Rapid Prototyping: Custom prototypes available for fit, form, and function testing before full-scale production.
Applications
Semiconductor 
Medical 
Aerospace 
Analytical Instrumentation 
Robotics 
Cryogenics Vacuum Technology 
Precision Manufacturing 
Industrial EquipmentWhy Choose Us
Handa Spring manufactures custom detached leg spring energizers based on seal groove dimensions, friction requirements, and operating conditions. We work with seal manufacturers and OEMs to match spring geometry, load characteristics, and material to specific application requirements.
1. What is a Detached Leg spring energizer?
2. What is the advantage of detached legs?
3. Is it suitable for dynamic sealing?
4. Can it operate in vacuum?
5. Is it suitable for cryogenic applications?
6. Which materials are available?
Elgiloy, Inconel X-750, Inconel 718, MP35N, Hastelloy C-276, 17-7PH, 316, and 301 stainless steel are available. Monel 400 and Hastelloy C22/C2000 available upon request.
7. Can the load be customized?
8. Is it suitable for high pressure?
9. Can you manufacture welded rings?
10. What seal materials are compatible?
11. What industries use detached leg springs?
12. Can prototypes be supplied?
13. What information is required for quotation?
Contact Handa
Handa Spring manufactures custom detached leg spring energizers for low-friction sealing, vacuum applications, cryogenic equipment, and precision motion systems.
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