Fork Sensor Overview (9-1-2021)

Label application machines apply labels from a roll, one-at-a-time, by being able to use a sensor that can reliably detect the difference between the label material and its web material or backing.  Usually, a photoelectric sensor is used in the through-beam mode, which consists of a sender on one side, and a receiver on the opposite side of the web.  In this mode, the photo-eye attempts to pass its light beam through the gap between consecutive labels, and when the leading edge of the label arrives, the signal is attenuated, having to pass through both the web material and the label material.  If the application is appropriate for a photoelectric sensor, the sensor senses the difference between label and no-label, and switches its output to indicate the leading edge of each label.

While Tri-Tronics offers several other of their photoelectric sensors that can operate in this through beam mode using a pair of fiberoptic cables, one for sending, the other for receiving, the installation requires some fixturing of each fiber, along with the higher cost associated with using fiberoptic cables plus the cost of the sensor.  Depending on the physical constraints of the application, fiberoptic cables may be the only solution, since fiberoptic cables are available in relatively small sizes.  The use of fiberoptic cables also allows the sensor to be mounted in a more convenient location for periodic adjustment if needed.

Circa 2017-2018, Tri-Tronics introduced their FS Fork Sensor.  It is a single frame, housing both the sender and receiver components, and available in [8] different gap sizes, from 20 to 220 mm (span). This single unit makes the installation significantly easier than mounting 2 separate fiberoptic cables.  It also allows easy re-location of the Fork Sensor, should there be a change in label dimensions, requiring the sensing point to be moved accordingly.

The narrow profile of each Tri-Tronics FS Fork Sensor (10 mm), fits in areas where space is a premium.  It detects objects as small as 0.5 mm, and has a fast response time of 240 microseconds, with a repeatability of 120 microseconds.   It has a selectable light/dark operate, sensitivity control, and LED output indicator.  The LED light source is visible Red, and is standard with a 3-pin M8 Micro connector on its body.

While the sensor ideally can be used for label detection on a web material, it can be used to conveniently sense any object passing in its field of view within the gap.

Excel Automation/Eagle Sensors & Controls are Authorized Distributors for Tri-Tronics products since 1989 & 1978, respectively.  Contact us for technical, application, or sales support.