Telemecanique Limit Switch Heads: Roller Lever, Plunger & Swing Rod
The head decides whether the switch survives. How to choose between roller lever, roller plunger, plain plunger and swing rod — and why the OsiSense XC range lets you change the head without changing the switch.
Telemecanique Limit Switches We Stock
A selection of the OsiSense XC and OsiSwitch bodies and heads we supply across India.
The head decides the switch
Most people choose a limit switch by its body — XCKP, XCKM, XCKJ — and treat the head as an afterthought. It is the wrong way round. The body decides how long the switch survives its environment; the head decides whether it works at all, and it is where nearly every premature failure starts.
Get the head right and a cheap plastic-bodied switch runs for years. Get it wrong and the most expensive metal switch in the catalogue shears off in a fortnight.
Roller lever
The most common head in the Telemecanique range, and the right default for side approach — anything travelling parallel to the switch body. A cam, a carriage, a pallet running along a guide rail.
Fixed roller lever
One lever length, set at the factory. Use it when the geometry is known and repeatable. It is the cheapest option and there is nothing to work loose.
Variable (adjustable) length roller lever
The lever length can be set on site. Worth the small premium during commissioning, when the exact mounting position is still moving, or on a line that runs several product sizes. It also saves re-drilling brackets later.
Lever length is a trade-off. A long lever needs less force to operate and tolerates a sloppier approach, but it needs more overtravel space and is easier to bend. A short lever is precise and robust but demands accurate mounting.
Plunger and roller plunger
Plunger heads are actuated from directly above rather than from the side. The operating travel is short, so mounting accuracy matters much more than it does with a lever.
Roller plunger
A roller on top of the plunger lets the target slide across it without tearing the head off. Use it where the approach is from above but with some lateral movement — a descending gate, a diverter arm, a lifting section.
Plain plunger
No roller, so the target must come straight down onto it. In exchange you get the highest switching repeatability in the range, which is why plain plungers are the usual choice for homing a machine axis. Do not use one where the target may drift sideways — it will bend the plunger.
Metal or steel plunger
Where the plunger takes repeated impact or the environment is hot, a steel plunger outlasts a thermoplastic one considerably. Telemecanique offer both across the compact and classic ranges.
Swing rod and cat-whisker
These are the heads for targets you cannot predict. A swing rod operates when pushed from almost any direction; a cat-whisker (spring rod) will operate from any direction at all, including from above.
They are the right answer for irregular, fragile or loosely presented products — sacks, bundles, hanging components, anything that arrives at a slightly different angle each time. The trade-off is precision: the switching point is approximate, so never use them where position accuracy matters.
Telemecanique offer both plastic and metal swing rod versions. Plastic tolerates being knocked about and springs back; metal survives heat and abrasion better.
Choosing by approach direction
| Approach | Head | Typical use |
|---|---|---|
| From the side, consistent | Fixed roller lever | Cams, carriages, pallets on a guide rail |
| From the side, varying | Variable length roller lever | Mixed product sizes, commissioning |
| From above, some sideways movement | Roller plunger | Gates, diverters, lifting sections |
| From above, straight down | Plain plunger | Axis homing, precise end stops |
| Unpredictable angle | Swing rod | Sacks, bundles, irregular products |
| Any direction | Cat-whisker (spring rod) | Fragile or hanging items |
The head is replaceable — and that changes your spares strategy
The OsiSense XC range is modular. A switch is a body plus a head, and the heads are sold separately under ZC references — ZCK-D15 and ZCK-D21 roller levers, ZCY18 for the OsiSwitch bodies, and so on.
Two practical consequences:
- Repair instead of replace. A bent lever or a worn roller means a new head, not a new switch. On a plant with dozens of switches that is a meaningful saving.
- Stock fewer part numbers. Hold one or two body types and a handful of heads, and you cover far more machine positions than stocking complete switches for every variant.
Frequently asked questions
Which Telemecanique head should I use for side approach?
A roller lever. Use a fixed lever where the geometry is consistent and a variable length lever where product size varies or the mounting position is not final.
Roller plunger or plain plunger?
Roller plunger if the target slides across the head at all; plain plunger if it comes straight down. The plain plunger gives better repeatability but will bend under sideways load.
Can I change the head on a Telemecanique limit switch?
Usually yes. The OsiSense XC range is modular and heads are sold separately under ZC references. Confirm compatibility against your specific body before ordering.
What is a cat-whisker limit switch used for?
Detecting targets that arrive at an unpredictable angle or are too fragile for a lever — sacks, bundles, hanging parts. It operates from any direction but gives an imprecise switching point.
Why does my limit switch lever keep bending?
Almost always the approach direction or overtravel. A lever struck from behind bends instead of rotating, and a lever with nowhere to travel after operating takes the full force of the moving part.
Not sure which head you need?
Send us the approach direction, the target size and a photograph of the mounting position — or the part number you are replacing — and we will confirm the right head or complete switch, with availability and lead time. GST invoicing and pan-India dispatch.
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