Low-Force Activation Buttons

Source

Longmate, Arthur R., 1996, Johnson & Johnson, Ergonomic Control Measures in the Health Care Industry, Occupational Ergonomics.

Task Prior to Abatement (Description)

Workers had to fully depress the welder activation buttons at the welding station, which were located in the front plate of the welder base. The task include getting the assembled stapler from a tray and putting it into the welder nest. Then the worker had to fully depress and hold the cycle activation buttons with both hands until contact of the vibratory horn. Finally, the worker had to get the instrument from the nest and put it into a finished instrument tray.

Task Prior to Abatement (Method Which Identified Hazard)

Increasing medical cases of thumb tendinitis among workers.

Ergonomic Risk Factor (Force)

Workers had to apply 5 lbs. of force with their thumbs to fully depress the welder activation button. More than 5 lbs. was actually applied by workers to overcome the 5 lb. force quickly.

Ergonomic Solution (Engineering Controls)

1. A modified push button switch was developed. The main compression spring was removed in order to reduce the required activation force to approximately 1 lb. An additional spring was built into the contact set in order to provide sufficient force for returning the button to its original position.
2. A standard low-force pushbutton switch requiring 2 lbs. of finger or thumb force was developed for application of two contact sets.

Ergonomic Solution (Benefits)

• All workers that perform this task now have reduced exposure to thumb tendinitis.
• There was an 80% reduction in required force for once contact set.
• There was a 60% reduction in required force for two contact set.

Ergonomic Solution (Method Which Verified Effectiveness)

Reduction in medical cases of thumb tendinitis.

Comments

Before implementing the new pushbutton design, the company experienced several options including presence-sensing, captive-coupled activation buttons, and photo-electric light beam sensor activation controls to address the injury issues. There were several undesirable ergonomic considerations and cost issues which came up but were not practical.