Prosthetic Hook History; Ray Trautman

[Jon Kuniholm]

As you may know, we have a special interest in the hooks developed by Ray Trautman, which were loved by many and have been unavailable for some time. While we've often focused on the 1912 Patent by David Dorrance, you'll notice that one of the distinguishing features of the modern hook is missing: the offset fingers.

It appears as if this feature, shown in the figure below, may have been invented by Ray Trautman in 1919.

Some of Trautman's patents (notably the one that describes the Trautman Hook backlock design) were assigned to Dorrance. It would be interesting to understand these business relationships. Many of these early patents should clearly never have been granted by modern standards, and there is often obviously applicable prior art in the patent literature, so we'd appreciate hearing about it if you've found any.

[Wolf Schweitzer]

To hold a broom, I find that the *width* of the opening has to match the diameter of the broom handle and if that works it does so regardless of the shape angle (as I can change the angle with the wrist). Freedom to move is brought about by having the handle squeezed by rubber/spring tension. The only difference between oblique and straight designs obviously - once you hold the claws parallel to the floor - is the angle of the spring / feather relative to the claw. So what it boils down to is that for oblique claws, you need somewhat higher spring / rubber tension to hold the same object (as the force vector of the rubber / spring only has a portion < 100% going in the squeeze direction). Where it becomes really apparent for me is when I am driving: both Hosmer work hook and Otto Bock Movohook have this claw shape offset and both really require harder cable pulls to readjust grip on the steering wheel while actually not holding it as firmly. The Hosmer 555 or V2P are more efficient as all rubber / spring seems to go into the grip squeeze. I think the only application where exactly that angle comes into play is when one (and only one) rotational position of the hook is used for most of the day and when that position also serves to hold a glass for drinking. Then it is rather exactly at the correct angle. Otherwise and in relation to all other grips I personally don't like the oblique design. - With the Hosmer work hook, there is yet a different thing to consider - it not only moves at an angle but also has an angular metal edge that closes well. This can be very useful to hold thin bags or plastic folders.

[Jon Kuniholm]

The offset also allows for swivel in situations such as using a broom or shovel, where you might want to similarly be able to account for different angles and give an object freedom to move. The work hooks made by Dorrance have a bit larger offset--one that might allow the use of larger-handled tools.

[Wolf Schweitzer]

I just tried it. Indeed a drinking glass fixes between two points and allows for a minimal and very useful swivel while drinking without falling out. My guess that was what it was an important design feature for before quick lock wrists allowed for repositioning without loosening of the terminal device.

[Wolf Schweitzer]

The Otto Bock Movohook also has offset fingers. I find it one of the most annoying features of this hook design. Either our modern lifestyle is different (other objects?), I am doing something wrong or my (competitively used) other hooks really evolved since those early designs emerged and in fact I am spoiled. I find the shape of the V2P (more similar to what was posted as "Trautman hook") or a Hosmer 555 far better. Maybe it was really an absent feature of early day wrists that did not allow for quick 30 degree supination to hold a drink - so the hook had to accomodate for this.