Airtac SAILB Rear Lock Cylinder SAILB40X125S
The AirTAC Airtac SAILB Rear Lock Cylinder SAILB40X125S is a genuine double-acting ISO 15552 profile cylinder with a Ø40mm bore, 125mm stroke and a built-in spring-applied, air-released mechanical lock in the back cover — it holds the load at the retracted (rod-in) stroke end even when air is lost.
- BoreØ40 mm
- Stroke125 mm
- Port sizeG1/4
- Lock positionBack cover
- Rod threadM12×1.25
- UnlockAir + manual
About the Airtac SAILB Rear Lock Cylinder SAILB40X125S
The AirTAC SAILB40X125-S is a double-acting ISO 15552 profile cylinder equipped with a spring-applied, air-released mechanical lock in the back cover. Because the lock engages when the piston reaches the retracted stroke end, it holds the rod safely in place without requiring live air pressure. Featuring a 16mm carbon steel rod and a 1/4 PT port, this bore 40 unit delivers 879N of push force at 0.7 MPa.
This model includes a magnetic piston (-S) for direct compatibility with AirTAC CMSE reed and DMSE solid-state sensors. The variable air cushion at the locker end is 20mm, intentionally shorter than the 27mm cushion on the free end to accommodate the lock mechanism. Remember that the cushion only decelerates the load near stroke end; the lock is the true static holding device.
Airtac SAILB Rear Lock Cylinder SAILB40X125S Technical Specifications
| Model | Airtac SAILB Rear Lock Cylinder SAILB40X125S |
|---|---|
| Series | SAIL ISO 15552 cylinder with lock |
| Bore size | Ø40 mm |
| Stroke | 125 mm |
| Acting type | Double acting, with lock |
| Port size | G1/4 |
| Rod thread | M12×1.25 |
| Lock type | Spring-applied, air-released (back cover) |
|---|---|
| Unlock | Automatic (air) & manual |
| Operating pressure | 0.15 – 1.0 MPa |
| Temperature | -20 to +70 °C |
| Speed range | 30 – 800 mm/s |
| Cushion | Adjustable (27 mm free end / 20 mm lock end) |
| Max stroke | Up to 1200 mm |
Specifications follow the official AirTAC SAIL datasheet (ISO 15552). Confirm against the product label before installation. Port options: PT / G.
How the Lock Holds
The lock is spring-applied and air-released: a spring drives a lock pin into the rod when the release air is removed, so the load is held at the retracted (rod-in) stroke end without live pressure. Supply air to the release port to unlock automatically, or use the manual release lever.
The lock engages only when the piston reaches the stroke terminal on the back-cover side — it is a static end-of-stroke hold, not a mid-stroke clamp and not a moving-rod brake. For locking at any position along the stroke, choose a BSAI clamp-lock instead.
Theoretical Output Force (Ø40mm)
| Pressure | Push force | Pull force |
|---|---|---|
| 0.5 MPa | 628 N | 528 N |
| 0.7 MPa | 880 N | — |
| Max (@1.0 MPa) | 128 kgf | |
Cylinder thrust is separate from the lock's holding capability. Actual usable force is lower than theoretical due to friction and back-pressure — size with a margin.
Where the Airtac SAILB Rear Lock Cylinder SAILB40X125S Is Used
Vertical Retract Hold
Secures a lifted vertical load in the retracted position automatically when air pressure drops, preventing sudden falls.
Power Failure Safety
Keeps a clamped workpiece held at the rod-in stroke end during a compressed air failure until release air is restored.
Gate Stop Hold
Maintains a gate or diverter firmly in the retracted home position without consuming continuous air pressure.
Is the Airtac SAILB Rear Lock Cylinder SAILB40X125S the Right Lock Cylinder?
Choose this back-lock model when your application requires the load to be held at the rod-in position; select a SAILF variant if you need the load held at the extended end. If your process requires clamping at an arbitrary mid-stroke point rather than a stroke end, the AirTAC BSAI clamp-lock cylinder is the correct choice. For higher force needs, stepping up to a bore 50 cylinder provides 1374N push at 0.7 MPa.
The lock is a static holding brake that engages after the cylinder stops, not a dynamic brake for a moving rod. To ensure the lock never releases unintentionally, avoid using a fast-exhaust valve and use an independent-exhaust solenoid valve, as back-pressure on the locker side can lift the lock pin. If human safety depends on the load staying retracted, add an independent safety measure. Replacement requires matching the 40mm bore, 125mm stroke, back lock position, PT port, and -S magnet.
Quick checklist
- ✓ Hold needed at the retracted (rod-in) end?
- ✓ Or lock anywhere → use BSAI
- ✓ Independent-exhaust valve fitted
- ✓ Port/thread type (PT/G)
- ✓ Extra safety measure for people
Airtac SAILB Rear Lock Cylinder SAILB40X125S FAQ
At 0.5 MPa it provides 628N push and 528N pull. At 0.7 MPa the push force is 879N, and at 0.9 MPa it is 1130N.
The spring-applied lock engages automatically at the retracted stroke end to hold the rod statically without live pressure. It unlocks by supplying air to the release port or via the manual lever. It does not clamp at mid-stroke.
Related AirTAC Lock & Standard Cylinders
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