Machine Design

Proper Training, Protective Gear, and Design Essential to Mower Safety

A man was mowing his lawn when the mower’s grass-collecting bag came loose. He reached down to pull it back into place, and a flying object hit him in the eye, injuring him.

The man had rented the self-propelled walk-behind unit earlier that day. A rental-center employee had shown the man how to operate the mower and attach the grass-collecting bag before loading the assembly into the renter’s car. At the mowing site, the renter mowed a few passes before he got injured.

The mower moves forward and its blade keeps spinning as a spring-loaded lever is held against the mower’s handle. During the incident, the renter continued to hold the lever down with one hand and walk behind the mower while attempting to reattach the grass-collecting bag.

A plastic frame that slides into slots on the mower’s chute holds open the inner end of the bag. A steel rod inserted into a hole in the mower body hooks into the outer corner of the bag, keeping it off the ground.

Investigators found that both the design of the grass-catching system and actions of the rental-center employee contributed to the accident.

The design made it easy to misassemble the rod and bag assembly. Friction between the rod and hole on the mower body into which it inserted was enough that a user might think he or she had correctly inserted the rod when it still had about 1.5 in. of travel before it was securely mounted. The rod would appear secure but could work itself loose under motor vibrations or travel over uneven ground.

When the rod was not properly installed, it rubbed against the mower body. A 1-in.-long strip of rust where paint had rubbed away indicated this was not the first time the rod was misinstalled.

Another set of design flaws hid critical warnings on the mower’s body from the operator. Some were obscured by the grass-collection bag, and some were molded into the grass chute in a noncontrasting color that was difficult to read.

The rental-center employee should have confirmed the renter’s understanding of the mower’s assembly and use by having him repeat these actions. The rental center should also have provided an owner’s manual and safety documentation with the mower.

Finally, because it was reasonably foreseeable that the renter would not have the right personal-protective equipment, the rental center should have provided safety glasses and hearing protection like those OSHA requires for power-mower operation in industrial settings.

Better training might have taught the renter to let go of the lever that kept the mower operating before bending down, and eye protection might have minimized his injuries.

This month’s safety violation comes from the files of Lanny Berke, a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a safety violation to share? Send your images and explanations to [email protected].

Edited by Jessica Shapiro

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