Find a solution for handling heavy hammers while making repairs on large boat propellers was the request. First we needed to know what the upper limits of the tool weight might be. Then we needed to know the spatial parameters for using these tools and the number of cycles or uses within a given time. Factor in the number of different tools and the challenge became more in focus.
There are lots of devises that have been designed for handling heavy tools. Problem is, either they cost way too much or were too limited in their application. We needed a solution that performed at or near the same speed as a human arm, could easily lift the tools necessary and had adequate manipulation to work within a 3 dimensional space. In other words it needed to work up/down, in/out and forward and back. It had to accommodate various hand tools and must be easy to change from one tool to the next. Last but not least; it would be great if it could be used for other lifting operations.
We knew going in what the solution would look like. It would most likely resemble other more traditional tool handlers. A cable extending from overhead with a retractable reel that could lift a few hundred pounds and be very nimble. Most tool handlers just can’t meet those specs so a high speed overhead crane seemed the next best answer. But cranes tend to be big and bulky, certainly overkill for this application. What if we just sized everything down and designed some very precise pivots into the crane? That is exactly what we did. The next challenge was finding a way to minimize the amount of force needed to manipulate the lifting component around the work area. Most cranes use a trolley or bridge that roll along a rail of some sort. While minimal, the force required to move a trolley would be more than this application would tolerate. After all, we’re trying to replace the lift and carry action of a human arm and shoulder. The next step in resolving this challenge would be the one that made this modification successful.
There are lots of devises that have been designed for handling heavy tools. Problem is, either they cost way too much or were too limited in their application. We needed a solution that performed at or near the same speed as a human arm, could easily lift the tools necessary and had adequate manipulation to work within a 3 dimensional space. In other words it needed to work up/down, in/out and forward and back. It had to accommodate various hand tools and must be easy to change from one tool to the next. Last but not least; it would be great if it could be used for other lifting operations.
We knew going in what the solution would look like. It would most likely resemble other more traditional tool handlers. A cable extending from overhead with a retractable reel that could lift a few hundred pounds and be very nimble. Most tool handlers just can’t meet those specs so a high speed overhead crane seemed the next best answer. But cranes tend to be big and bulky, certainly overkill for this application. What if we just sized everything down and designed some very precise pivots into the crane? That is exactly what we did. The next challenge was finding a way to minimize the amount of force needed to manipulate the lifting component around the work area. Most cranes use a trolley or bridge that roll along a rail of some sort. While minimal, the force required to move a trolley would be more than this application would tolerate. After all, we’re trying to replace the lift and carry action of a human arm and shoulder. The next step in resolving this challenge would be the one that made this modification successful.
While discussing this project with Bob Williams, a consultant for the Preferred Workers Program for the State of Oregon a solution was found. Williams asked if some kind of articulating arm could be used in place of the traditional crane boom. The answer was yes.
There were some technical issues that had to be addressed to insure the concept would work properly. For example; how the lifting cable would be routed so as not to be in the way or create a self closing apparatus, where should the hoist be mounted and how the operator would activate the hoist. These questions were answered later in a staff meetings at ERGOdynamics.A few weeks later a double knuckle overhead jib crane with single point lift wire had been designed and installed. The lift shadow of the crane included a 270 degree radius and the reach extended to nine feet. Lift capacity was 400 lbs. and the hoist was activated by a foot switch. Using a foot switch allowed the worker to keep both hands free for fine tool manipulation.
Bob Williams, working in concert with the employer, employee and the staff of ERGOdynamics found a great solution and helped keep a talented and loyal Oregon worker on the job.
ERGOdynamics has an extensive resume filled with unique and successful solutions for ergonomic issues facing America’s workers. For more information on this project or a concern of your own contact ERGOdynamics. 
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