ladder failures

Ladder Failures

Per Reinhall

Ladder cases• More than half a million people in the United

States suffer ladder-related injuries every year • More than 300 people die each year in the U.S.

from ladder injuries • The principles of product liability hold

manufacturers, distributors, suppliers and retailers responsible for injuries caused by their products. A product liability claim is usually based on design defects, manufacturing defects of insufficient warning documentation, often termed as "failure to warn."

•Federal Reform Attempts

The closest the U.S. Congress has ever come to enacting broad-scope product liability reform was in 1998. In that year, Congress passed the Federal Product Liability Fairness Act. This bill would have limited punitive damage awards to the greater of $250,000 or twice compensatory damages.

It would have also:

• Required plaintiffs to present a stronger case by raising the standard of evidence to "clear and convincing" from the current "preponderance of the evidence.“

• Required plaintiffs to show that a manufacturer acted with a "conscious and flagrant indifference to the safety of others" in order to prevail.

• Abolished the application of "joint and severable liability," thus ending the practice of suing "deep pocket" defendants with little or no liability.

Design Flaws– A single motion of the release bar can unlock both

hinges at a joint while loaded– The release bar is shaped such that it can be kicked

by the user. This can cause collapse of the ladder by unlocking both hinges in a joint.

– A low level of force on the release bar can unlock both hinges in a joint even when the ladder is fully loaded.

– The release bar can snap into locked position with an audible noise without total engagement of the locking pins. It is therefore possible for a user to get the impression that a joint is properly locked when it is not.

Zinc Hinge 1

0500

10001500200025003000350040004500

0 0.3 0.6 0.9 1.2 1.5 1.8

Displacement (inch)

Forc

e (lb

f)

Series1

Steel Hinge 1

0500

10001500200025003000350040004500

0 0.3 0.6 0.9 1.2 1.5 1.8

Displacement (inch)

Forc

e (lb

f)

Series1

LADDER SATISFYING THE ANSI A14.2 STANDARD

WITH ONE MIDDLE HINGE UNLOCKED

Torque=11,000 in-lb1000 lb

75.5 degrees

Torque=11,000 in-lb 355 lb

52 degrees

CONCLUSION

A ladder satisfying the ANSI A14.2 standard can easily support the weight of a 230 lb person when the ladder is at 52 degrees and one middle hinge unlocked

THE SUBJECT LADDER

WITH ONE MIDDLE HINGE UNLOCKED

Torque=5,805 in-lb

518 lb

75.5 degrees

Torque=5,805 in-lb187 lb

52 degrees

CONCLUSION

The subject ladder cannot support the weight of a 230 lb person when the ladder is at 52 degrees and one middle hinge unlocked

Moment in Middle Hinge While Climbing

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10000

12000

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RUNG

Mom

ent (

lb in

)

Moment While ClimbingStrength Specified by StandardKrause Multimatic (Zinc)

ANSI Standard

Krause Multimatic