A New Hook Design, Phase 1: Idea Collection

[Daniel Paulsen]

2/18/08

Phase 1: Idea Collection

Idea collection Phase is in full swing! Here are some of the hook ideas I have collected so far

1) Adjustable or Selectable Prehension. This is an old idea where the user can adjust the pinch force on a VC device. This would allow users to handle both heavy and delicate objects.

2) Detachable third finger. This would allow different modules to attach directly to the device such as a knife holder or different tools.

3) Non-preportional Spring Action. Instead of the device becoming more difficult to open the farther the device opens, it could maintian constant closing force or could become easier as it opens.

4) I read on Darryl's blog that he desires a nail holder. Why not.

Do you have any hook ideas? Let me know, and I will add them to the list. A little note about brainstorming. I am a strong beleiver in brainstorming without discrimination and negativity. So feel free to give me your craziest ideas, no matter how impractical.

I am also collecting concepts concerning the hook cosmetics. If there are any artists out there I would love to see sketches on what you think a hook in the 21st century should look like.

1/1/08

I interviewed a prosthetist who used to be a professor at Northwestern and he had an interesting point of view. He helped me get a better understanding of the different prehension modes and pointed out that the Dorrance Hook excels at lateral, tip, and hook prehension, but performs poorly for the palmer prehension (aka three jaw chuck). He also noted that the palmer prehension is the most commonly used prehension pattern in able bodied humans. I asked him why the Ottobock adjustable prehension hook was so unpopular, and he pointed out that the tines didn't have the neoprene coating and also noted that the adjustment snapped loudly and dangerously between settings.

I also just finished reading Harold Sears' (the founder of Motion Control) PHD dissertation on hook tine design. Dr. Sears did extensive patient trials on multiple designs which helped me gain a greater respect for hook design in general. One thing that struck me is that every person that participated in the patient trials wanted something different. Also every time time a feature was added, removed, or modified, some patients liked it and others hated it. There were a few exceptions to this where the patients all agreed that the hated certain features. According to his research the most well recieved ideas were his innovative cylindrical grips and his knife holder. I can definately see the importance of prototyping and feedback early in the design phase.

Here are a few more ideas to add to the list.

5) A slip over hand cosmesis
6) Palmer prehension pattern
7) Cylindrical grips

9/7/08

It seems that I am not a very persistant blogger. Well I have had a very nice summer vacation and now it's back to the grind.

Since I last posted I have studied the shortcomings of products currently available and I have interviewed a few users. I have also compiled a huge list of crazy ideas most of which are not worth mentioning. As of this point I have compiled a list of desirable qualities in a terminal device:

1) Robustness
2) Lightweight
3) Efficient (Low Friction)
4) Good Visibility
5) Versatile grasping patterns
6) Adjustable Grip Force
7) Cosmetic Appearance
8) Non-damaging tines

Next I will sketch several concepts I have and try to come up with a few more new concepts.

[Wolf Schweitzer]

Fingers on hook:

- I have one hook for clean daily use including office, kitchen, eating. That one was fitted with OB's rubbery (material?) "gloves" and that avoids scratches or slips of very thin objects such as single paper sheets.

- I am about to get a second hook (same build) without rubbery gloves. That one is for real work (forensic pathology) and meant to grip tissue or other at times slippery items. There, the metal hook grip surface is better than rubbery.

I guess these are universal hook / finger problems though.

[Daniel Paulsen]

Very clever idea for adding adjustability to the low force setting.

[Daniel Paulsen]

Thanks for the comments Wolf. I have heard that many users don't like the metal fingers on the Otto Bock spring lever hook because they can easily damage and scratch sensitive objects. What do you think?

[Wolf Schweitzer]

http://www.swisswuff.ch/tech/?p=30

New hook by Otto Bock after an intensive history of troubleshooting (see other posts on http://www.swisswuff.ch/tech/).

- stable hinge / joint
- cable fray problem technically solved
- mainly constant closing force (spring setting 1) / increasing force (setting 2)

[Wolf Schweitzer]

re. 3):

Otto Bock spring lever hooks are great and I am getting my OT to modify mine.

For one, I got my initial aluminum hook upgraded to the oblique steel hook - and wow, what a smooth ride that is.

Check out my spring / screw modifications for improved spring pull, and the new hook:

http://picasaweb.google.com/swisswuff/Arm2

The "low force" lever position causes an almost uniform force throughout the whole open/close way. For both the aluminum hook I had bevore and the steel hook I have now.