Phase 3: Design Phase

[Daniel Paulsen]

4-16-09

Phase 3: Design Phase

In phase 3 I modeled my ideas in SolidWorks analyzed my ideas in Microsoft Excel and then used my final model to make a rapid prototype. Here are the results of my many hours and late nights:

Here are some of the features my design includes:

1. Wide opening in between fingers for increased visibility.
2. Curved grasping surface for excellent cylindrical grasping.
3. Direct force path from finger to stud or high robustness.
4. Slender fingertips for reaching into pockets.
5. Rubber grip surfaces for secure and nondamaging grip.
6. Sleek contours for modern appearance.
7. Narrow well mating tip for superior tip prehension.
8. Grip force setting is easily changed without the use of the opposite hand.
9. Long-lasting metal springs instead of rubber bands.
10. Four different grip settings to allow between 4 -- 10 pounds of adjustable grip force.
11. Use of ball bearings for smooth and efficient motion.
12. Easily replaceable fingers for serviceability and for different hook finger style options


After the CAD model and analysis I got a rapid prototype made of some parts and machined the smaller delicate parts. After a few modifications I was very excited when it actually worked!!!!!!!

[Daniel Paulsen]

As far as I know their is no electronic copy. I borrowed it from Harold Sears himself and I already gave it back. Also the copy I got was missing pages. When I get home I will try to find an image of his design.

[Wolf Schweitzer]

I wear some silicon tube over the hook claws; the hook is designed to be used without them as well though. Also where could I get a copy of the Sears thesis? Did someone scan it, are the 138 pages electronically available? Thank you very much in advance.

[Daniel Paulsen]

I agree that rubber inserts would be essential this design. I always meant to have them, only I didn't have time to model them.

You have a very good eye for hook designs. In fact my hook shape was heavily influenced by the Harold Sears Hook, the Dorrance 555, and also the contour hook.

I like the idea of letting anyone design there own finger replacements, I would be really excited to see what users come up with.

[Jon Kuniholm]

Daniel -

That looks like great work. I have a couple of comments, and a question.

I'd very much like to see some rubber inserts on the outsides of the hook, in order to allow stabilization of credit card receipts, etc. This is a constant annoyance to me and I'm sure many people.

It looks like you have incorporated many of the good features of Harold Sears' hook design, from his dissertation that you mentioned in a previous post. His hook is still unavailable, as far as I know, but we'd very much like to see it in production, in either a body powered or externally powered design (as well as this one).

You mentioned the easily replaceable fingers. This is a great feature that we have advocated as a way to use a single mechanism and offer the different shapes that people seem to like for their hooks (lyre, farmers' etc.). I know that we have had discussions about open source and architecture, and I'm curious what your intentions are with this design, and if you would consider, if not opening the design itself, opening the interface for the fingers.

If a mechanical interface were published in the form of an IGES or STEP model, for example, then it would be easy for folks to design finger replacements that added features that they were interested in that you might not be interested in going to the trouble to add yourself.

Anyway, looks like great work, and I'm looking forward to seeing if there's a way that we could help get it tested and help any with the design.

Jon

[Daniel Paulsen]

Thanks for the feedback. You are not the only one that has liked the replacable fingers.

One thing to consider is that I specifically designed this hook to target bilateral amutees, which is why I designed the adjustment to change without the use of the other hand.

The cylinder contains the beefy metal spring which supplies the pinch force.

[Wolf Schweitzer]

Nice job, but better to get some videos to see it in action.

In my view, the one big improvement over existing models (Hosmer, Otto Bock) that already cover points 1,2,3, 4, 5, 6, 7, 8, 9 (OB), 10 (OB: 2 settings, pretty sufficient) but hopefully not 11 (even when we modified my hook joint for stability, we decided to rebush it and not go for a ball joint that looks/sounds nice but does not stay sturdy) would be your number 12.

If you set up that hook with a set of different useful pliers, a pair of scissors, small precision scissors, one hook that specifically grips frying pan handles and irons (for ironing shirts etc), and make that an excellent set of claw options, that'd be a product with a lot of potential. The switch mechanism should be quick to operate and sturdy :-)

One grip I use the hook for, that causes issues, is grabbing a thin bar - when manually operating a screen, awning or when cleaning with a broom. I remember having had issues with that a number of times. So far there are just workarounds (stuffing a cloth or rubber piece in between). The more complex grip types you offer the more I can think of, actually ;-)

What is the cylinder thing (blue in your diagram) doing?