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I have a medical device I am designing which will lie under the patient bed.

I need to add a "connector/joint" on this device to permit the attachment of some consumable.

Here is a quick overview of the process:

basic assembly schema

  • Blue part is low cost injected plastic disposable part that will be assembled and disassembled only 2-3 times before being disposed.
  • Orange part is the device, can contain more complex parts (springs...).
  • Orange part must last thousands of assembly/disassembly.
  • Orange part is not movable, only blue part can be moved when assembling.
  • When assembled, it must resist to at least 100N force in all direction, including rotation around the "snap axis".
  • Orange part must be around 3cm which is a good side to apply pressure with two fingers.
  • Disassembly pressure force should be low as only two fingers will be use, other hand will retain blue part.
  • It should be easy to assemble/disassemble with "closed eyes" as the device will be under a bed and there might be no visibility on the device itself.

As my drawing might be a bit confusing, here is a common device that is similar (aka a buckle).

buckle

The main problem with buckle design is the require pressure force for disassembly which is way too high, it's also too hard to assemble and not robust enough. But it is a good example for the "general principle".

What I am looking for is not for someone to design the assembly for me, but I am looking for exiting systems that are an alternative to a snap in joint and any pointer that would help me design it.

Nicolas Goy
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2 Answers2

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I would use a collar lock with a slide action locking gate. Solves the durability issues and can be used thousands of times. The collar can be square and slide into a dual keyway to support the blue item while a cylindrical gate (spring loaded or not) shuts behind it. Collar thickness determines load bearing capacity.

Rhodie
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For a circular attachment, then a groove and matching balls held with a spring loaded collar. Used on brake lines for trailer and also much higher pressure/flow rates in hydraulic fittings.

Image from https://hydraulicmegastore.com/product-category/hydraulic-products/quick-release/

enter image description here

Solar Mike
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