Machine Design

From the Safety Files: Was a manufacturer at fault for a mower without advanced safety features?

A man was pushing a mower across a slope when he slipped and caught his foot under the machine, sustaining serious injuries. The injury was just one of the thousands caused by personal lawn mowers each year.
Last month’s Safety Files (“Mower design flaws spark deadly fire,” Machine Design, Sept. 9, 2010, looked at a fatality related to a riding mower. This month, the machine in question is a self-propelled push mower.

At the time of the accident, the operator was crossing a short, 25° slope in the front yard of his rental property. When he slipped, he let go of the mower, and it stopped its self-propelled forward motion. However, the blade continued to spin.

The man got his foot wedged under the rear of the mower. A hard plastic guard hinged to the mower deck prevented his foot from going all the way under the mower, but his toes entered the blade circle and were seriously injured.

The plastic guard was meant to prevent objects from being thrown toward the operator, to keep feet out, and to comply with industry safety requirements. However, when the man’s foot pushed the guard’s bottom edge inward toward the blade, a 1.5-in. gap opened between it and the ground.
Investigators concluded the accident could have been prevented by a better guard design that truly excluded feet and objects from the blade circle.

Operator-presence controls (OPCs) would have also prevented the accident. OPCs are fail-safes that stop the motion of the mower blade within 3 sec when the operator loses contact with the mower. Current mower designs commonly require the operator to squeeze a bar to the mower frame to keep the engine from shutting off and the blade from stopping.

The Consumer Product Safety Commission (CPSC) has mandated OPCs on riding and walk-behind power lawn mowers sold since 1982. The mower in this case was a 1981 model. It had a clutch release that disengaged the self-propelling drive when the operator lost contact. The release didn’t kill the engine or disengage the blade drive.

CPSC had announced the upcoming OPC requirement at least three years before it went into effect, and other mower manufacturers were offering OPCs as early as 1980. OPC technology for lawn mowers had been available in some form since 1947.

Was the mower manufacturer negligent in failing to apply state-of-the-art safety measures to the mower or justified in waiting for the mandate? Weigh in by e-mailing [email protected] or in the comments section of this article on

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