Bayonet feature dimensioning

[dgallup]

I've got a part with a bayonet feature on one end that another part will lock into. I'm not sure what is the best way to ensure proper position of these features to the ID bore and to each other. The mating part will slide in the bore and have a cross pin that has to slide in the slot on both sides and then rotate 45 degrees to hold the two parts together. The most important dimension is the the bottom surface of the locking lug because that will control squeeze on a seal. I want that directly toleranced from the opposite end but maybe the rest could just be a profile control? But there has to be something controlling the 180 degree symmetry between the two lugs.

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[3DDave]

One pin will hit the stop before the other. There doesn't need to be symmetry, just need to ensure there is enough travel.

 

[dgallup]

Sure one side will hit first but the second can't be too far out of position or it won't work at all.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[3DDave]

I'm referring to the rotational stop. Why would it not work at all if one side has a gap?

 

[dgallup]

I'm considering all the aspects of the slots, not just the stop. If the two start slots are off the mating part won't even start. And the horizontal legs need to be pretty co-planar or it won't turn.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[3DDave]

There are multiple requirements.

1) The vertical slots are both wide enough and deep enough to allow full engagement and compression of the seal.

2) The vertical slot walls have to be located relative to whatever restriction is placed on motion by what appears to be a cylindrical contraint that serves as both a rotational locator and linear guide

3) The bottoms of the horizontal slots have to be at least as deep as the vertical slots and are probably not intended as a cam surface and mainly serve to let the user feel a sudden increase in force so they know they should start turning while still pushing.

4) The tops (undersides in that view) of the horizontal slots have to be located so that the seal remains compressed with the mating pins engaging them. I don't detect any camming required.

5) The closed ends of the horizontal slots need to allow enough travel so the crosspin is unaligned with the vertical slots. From the description, only one closed end needs to be at 45 degrees of travel as long as the other is at least 45 degrees of travel.

All contacts appear to be one-side contacts, so profile of surface could be used for everything with correctly chosen nominal dimensions. Each surface group would likely have a different tolerance zone size.

 

[Compositepro]

"pretty co-planar". That all depends on you tolerances. Perhaps that is why ball-detent quick couplers are more common. It is also common practice on bayonet fittings for there to be a detent in the locked position so you have to push the fittings together before you can rotate them to decouple.

 

[dgallup]

The customer doesn't want a cam or detent feature. I was hoping some one could dig up a spec or example of a bayonet connection. But I can reinvent the wheel.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[Compositepro]

Maybe try modifying an off-the-shelf Chicago fitting to meet your needs.

https://www.bing.com/search?q=chica...806CDB3F58311A&ts=1712881426456&wsso=Moderate