Detect-a-Finger® for Welders (RKC500)



Product Manual

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Product Description

The Detect-A-Finger is a cost-effective solution to help protect the operator’s fingers from pinch-point hazards. The Detect-A-Finger® drop-probe device reduces accidents at the point of operation where an operator’s fingers can enter. The key components of this device are a sensing probe module with the rod shaped to fit over or around the work piece, and a control module. When the operator initiates a machine cycle, the sensing probe is released and drops by gravity over or around the work piece. If the operator’s fingers are still in the hazard area, the sensing probe will not reach its preset position and will not allow the spot welder to start its cycle. If there are no obstructions to prevent the sensing probe from dropping, when it reaches its preset position, the control unit will allow the machine to cycle.

The compact design of the sensing probe module allows it to be attached to the welder arm. The drop-probe stroke is 1 5/8″.

Each unit is furnished with two plain 18″ aluminum drop-probe rods. These rods are to be shaped by the user to specific requirements. To prevent welding splash, additional lightweight clear plastic shielding can be attached to the rod.

Typical Applications

Press-Type Resistance Welder


This Detect-A-Finger® drop-probe assembly may be mounted either to the moving member of a welder (upper arm), like the rocker-arm type illustrated at right above, or may be mounted to a fixed part of a welder, like the press-type illustrated at left above. Depending on the type of welder, a single-stage or a two-stage foot switch may be required.


The Detect-A-Finger® may also be applied to mechanical foot pedal-type welders. To convert from a mechanical operation, the mechanical pedal must be removed and replaced with an air cylinder to operate the arm and foot switch. The cylinder bore and stroke (push- or pull-type) can be determined from actual machine measurements, and the method and location of attachment to the welder linkage. The air cylinder can be controlled by a three-way normally closed 115-V AC solenoid air valve. Adjustable flow control valves may be employed to smooth the welder arm movement, and an air filter-regulator-lubricator assembly may also be required.


As shown, the Detect-A-Finger® device for spot welders consists of two components, the control box (mounted on the frame of the welder) and the drop-probe assembly (mounted on the upper arm).

The control box provides interface of the Detect-A-Finger® device to the spot welder’s control system.

If the drop-probe unit is never allowed to complete its preset downward travel, the welder will not start its stroke. Insulated mounting hardware for the probe unit is also included.

Complete installation instructions and a maintenance manual are provided with each assembly.

Part No. CTD-011 – Foot Switch
This foot switch is protected from unintentional operation. A die-cast cover protects the top and both sides, and the front is protected by a hinged flap. The flap must be lifted with the toe before the foot may enter the switch. The electrical contact arrangement is 1 NO and 1 NC.

Our new, premium solution – the UNITROL SOFT TOUCH Pinch-Point Safety System – is the first and only fully passive safeguarding equipment designed to prevent a pneumatic riveter, welder or other small machine from applying full force if it detects fingers in the machine’s point-of-operation area by measuring electrical continuity between electrodes. If anything other than metal is present between the electrodes, their sensors will not detect continuity and the electrodes will open automatically. Click HERE for more information on the UNITROL Soft Touch for Welders.