Bloom Socket: First Prototype, Design and Usage Feedback Requested

For discussion of arm designs.
User avatar
andreas
Posts: 31
Joined: Thu Feb 12, 2015 4:55 pm

Bloom Socket: First Prototype, Design and Usage Feedback Requested

Postby andreas » Mon Jun 01, 2015 1:42 am

Given that the vast majority of upper limb differences are transradial or transulnar, we know that there is a large population out there that isn't benefiting from our devices yet. The socket is a key foundation upon which to build out actuation systems and end effectors, so I took a crack at a socket system this weekend. Source files here

This is an early prototype, but I think it's underlying design segmentation shows promise: a "hub" to which the end effector attaches and a series of "petals" that can be individually modified and customized to fit each individual residual limb. The hub and petals join via an easily described interface of two screws and bolts. This will hopefully allow for a lot of compatibility across CAD tools as the salient dimensions can be sketched on a napkin.

My thoughts so far:
  • This prototype seems a bit small-- will scale up for the next revision
  • The bolts (even six M4s) add a bit of weight
  • The nut traps are a little loose-- easy fix for the next rev
  • Pipe threading on the hub may not be the most useful end effector attachment interface-- will look into cam-locking chucks for the next rev
  • Three petals is probably not the best solution. I suspect four petals, two narrow, two broader, will provide a better fit in transradial cases.
  • It seems that a lot of sockets incorporate features for cable attachment and guidance. Will research more and add to next rev.
  • I'm not sure the second strap slot solution I implemented is the better one. Will experiment more, but am still considering the "fold-out" slot seen in rev 1 of the petal.
  • I'm also working on a printable ratcheting mechanism for adjusting the circumferential compression via the strap running the perimeter of the socket. I'll probably integrate it into an individual petal that can be dropped in.
My Questions:
  • Would it be advantageous to allow the top edges of the petals to fasten together to create a continuous lip around the top of the socket?
  • Are there some standard end effector interfaces that could be printed or attached to the hub?
  • What do folks think about "sealing" the interior surface of the petal so that adhesive-backed foam can be easily used without lint etc. getting stuck to the adhesive where its exposed through the expansion mesh slots? I've modeled and will test this soon.



bloom1.JPG
Rev 1 hub and rev 1 petal
bloom1.JPG (1.06 MiB) Viewed 1446 times

bloom3.JPG
Petal attachment method
bloom3.JPG (905.83 KiB) Viewed 1446 times

bloom2.JPG
View into the socket-- planning on four petals for better fit in next rev
bloom2.JPG (690.9 KiB) Viewed 1446 times

bloom6.JPG
Pipe thread end effector interface in this proof of concept, but will incorporate something more functional soon
bloom6.JPG (664.05 KiB) Viewed 1446 times

bloom 5.JPG
As-printed flat petal
bloom 5.JPG (986.63 KiB) Viewed 1446 times

bloom4.JPG
Thermoformed petal v2
bloom4.JPG (924.35 KiB) Viewed 1446 times

AdamArabian
Posts: 32
Joined: Mon Feb 16, 2015 2:04 am

Re: Bloom Socket: First Prototype, Design and Usage Feedback Requested

Postby AdamArabian » Mon Jun 01, 2015 8:44 pm

I have a hard time determining what may happen - its such a nonstandard socket design that I don't know if any of us really have a sense for what a three-leaf design like that would do. It could be awesome, but it could also produce pinch points or abrasions at the edges. If you wore a sock underneath it it would help but then you're just relying on squeezing the living daylights out of your arm to keep it on which may not be ideal.

I can think of problems but none that wouldn't show up in very early testing so I'd suggest we try doing just that - some very early testing! I have an IRB that should get approved shortly which I think would allow me to use a socket like this and see what happens (if the prosthetist I'm working with is willing gto play along at least...)

My only recommendation before that would be to reverse curl the edges when thermoforming just to prevent sharp edges.

I'll defer to my elders/betters/wisers though if they have other ideas.

Another thought - the "hub" portion looks pretty long which limits its utility (requires moderate to short transradial amputees). Just in general the shorter you can make it the better it is.

davidcdietz
Posts: 2
Joined: Sun Jun 07, 2015 1:01 pm

Re: Bloom Socket: First Prototype, Design and Usage Feedback Requested

Postby davidcdietz » Sun Jun 07, 2015 1:39 pm

For the traditional transradial arm protheses, the movement of pronation and supination typically takes place at the wrist. On the human body pronation and supination taks place at the elbow the radius pivots around the ulna. Here is a discussion about the movement. http://www.researchgate.net/post/Is_pronation_supination_a_movement_part_of_the_wrist_or_the_forearm if this design was modified to pivot around the static residual limb socket I belive it could offer great stability and pressure relief at the residual limb. If the proximal edge of the "petals" is concave and can fit into a convex lip at the socket the TD could spin at from the elbow joint rather than at the wrist. The benifit would be better distribution of the load at the socket and better distributing pressure at the residual limb. basically a spinning functional fairing. Here is a neat drawing of the action of pronation and supination coming from the elbow. http://drawingbooks.org/lutz1/source/index.html#calibre_link-24

davidcdietz
Posts: 2
Joined: Sun Jun 07, 2015 1:01 pm

Re: Bloom Socket: First Prototype, Design and Usage Feedback Requested

Postby davidcdietz » Sun Jun 07, 2015 1:41 pm

So yes a contiuous concave lip spinning aorund the socket.

User avatar
Skip Meetze
Posts: 33
Joined: Mon Feb 16, 2015 9:33 am
Location: Webster, NY
Contact:

Re: Bloom Socket: First Prototype, Design and Usage Feedback Requested

Postby Skip Meetze » Tue Jun 09, 2015 10:21 am

For the Monette Modular Arm (soon to be published in the forum) we are connecting the modular elements using the O&P standard 1/2-20 (1/2 inch fine thread, M12 fine thread outside the US). We are thermoforming to capture a nut or bolt in a printed-in hexagonal recess. Perhaps your petals will sometimes be easier to form over a longer residual forearm than the Monette socket that Jeff Erenstone has been developing. I look forward to hearing about some testing results.

AdamArabian
Posts: 32
Joined: Mon Feb 16, 2015 2:04 am

Re: Bloom Socket: First Prototype, Design and Usage Feedback Requested

Postby AdamArabian » Wed Jun 17, 2015 6:30 am

Skip - whats the ETA on the arm? We're pretty eager to see the latest!

Jfwinston
Posts: 11
Joined: Tue Jun 13, 2017 1:03 am

Re: Bloom Socket: First Prototype, Design and Usage Feedback Requested

Postby Jfwinston » Wed Mar 28, 2018 3:45 pm

Andreas, has this prototype received testing since this post? Is there a newer version that you are working with?

The idea of a ratcheting mechanism similar to this https://vimeo.com/204128272 has been tossed around.
Co-lead at e-NABLE Portland, mechanical engineer, and no idea what I'm doing


Return to “Arms”

Who is online

Users browsing this forum: No registered users and 0 guests