Updated Split Hook

The split hook has been around since 1912 (at least), and is the most popular terminal device. Versions are made by Hosmer, RSLSteeper, Otto Bock, and others.

We'd like to update this time-tested design to include some features that would improve this classic, including making it out of polymers to lighten it, including rubberized inserts to aid in holding objects in place with the sides, and other improvements.

Other efforts have been made to make the hook cheaper to make, most notably this effort, at Arizona State, although no product is known to be available. OPP has unsuccessfully contacted the authors in an attempt to secure the donation of this design to the public domain.

The most popular design is the Hosmer-Dorrance 5x (shown at left).
This funky Otto Bock design (right) shares some characteristics.

The shadow box pictures at the bottom of this page were created by Open Prosthetics volunteer Chris Wescott, who has also taken a stab at modeling the hook.

Some extra info from Chris on the orientation of the pictures: "Each one was taken at a specific angle of rotation. For instance the first part one of the hook (one without the extra arm) was taken at 0, 90, 111.625 & 201.625 degrees. The other part of the hook (with extra arm) was taken at 0, 90, 105.75, and 205.75 degrees. You will notice that I took one picture with the bolt hole normal and then one perpendicular to the shot for both parts. The other two shots were taken where the flat side of the hook was parallel with the shot and then one 90 degrees from that point."

Produce a lower-cost all-polymer version of the standard split hook. Duplicate the functionality of the standard split hook, and add additional functionality as allowed by the material. Interface with existing wrist units OR a custom all-polymer rotating wrist unit.

We would like the device to:

• Be manufacturable for less than $150 (an injection-molded part ought to be possible for several dollars, even in high-quality materials),
  

• Be Sufficiently durable to daily long-term use,
  

• Include the useful asymmetry of the original hook's fingers to: indicate the direction of opening, capture curved objects from behind, serve as a hook in the unopened position, and secure irregularly shaped objects,
  

• Duplicate the grip surfaces on the interior, including the pen/cigarette notch (definition as needed),
  

• Have grip surfaces on the exterior of the hook (both sides) to aid in holding objects in place, e.g. signing a credit card receipt,
  

• Adapt to multiple quick-release wrist types, the standard 1/2"-20 thread, and/or a custom plastic rotating wrist unit,
  

• Be non-metalic to enable wearing through airline security (nice to have).

• Document current design - see pics below.
  

• Study materials selection possibilities
  

• Create design studies for candidate designs.