Large cylindrical quick-connection 7

[random88]

I have been asked to design a quick connection between a "part" and a rotary positioner. Currently the parts connect on a flange with 6 screws (3/8" unc)on a 11.38" diameter.
The "part" is cantelevered and weighs less than 100lbs.

The "boss" wants something like a bayonet connection or someother twist and lock idea. (like how a camera lens ataches to a camera, but this is a mighty big "lens")

Are there any standards for giant bayonet connections?
How about standards for a giant screw thread? (I am thinking maybe with 3 starts).

Has anybody seen a quick cylindrical connection around 12" in diameter?

thanks
random88

 

[JStephen]

You might look up how a Victaulic coupling works on pipe. Probably not something you'd want to use directly (too heavily built), but the idea might be workable. There are also pressure-vessel manways with different kinds of quick-opening schemes.

 

[MintJulep]

How about something like a quick-connect air line coupler? Add a key if maintaining a specific orientation is necessary.

 

[unclesyd]

I would look at this type clamp with a toggle latch. There are quite a few variations on this theme used in vacuum service.

Another approach might be a multi-lead thread to make something like a quarter turn lock, Like a gallon milk carton cap (US).

A breech mechanism is a lot on machining.

http://www.clampco.com/products/flanges.asp

 

[arto]

Check out V-Band Clamps SAE AS1895, AS5355
quick & light & stronger than the tubee

http://www.vossind.com/

makes 'em

 

[MikeHalloran]

The Clampco flanges and Voss v-band clamps are not really that quick. On paper, they look good, but the bands never settle in the same orientation twice, so you'd be constantly fiddling with the t-bolt adjustment. Additionally, the band is a loose piece, and you probably don't want to deal with that, unless you have three hands.

Simplest thing to implement may be six studs, and fast-acting tooling nuts. Of course that's six loose pieces, but they're small and cheap enough to stock extras.

Next simplest thing is six ball-lock studs, which can be made captive with cables.

Or maybe some really big servo clamps.

Or just mill circumferential slots where the holes are now, so you can loosen the screws, rotate the flange and disengage it by lifting it 'over' the screw heads. The slots would have a counterbore at one end, and a through hole at the other end, both a little bigger than the screw heads.





Mike Halloran
Pembroke Pines, FL, USA

 

[unclesyd]

MikeHolloran,
We use the Clampco and similar products with over center latches for everyday applications and don't see the problems your mention. Our application pretty much assures that the approach of the two flanges are squared as they approach.

We also have a department that uses hundreds of Tri-Clamp T-handled fittings with no problem.

 

[MikeHalloran]

My experience is primarily with clamps on 6..12" nominal diameter exhaust pipes, in which service it can take several minutes to make up and tighten a v-band joint. Some of the difficulty probably has to do with squeezing out water glass or compressing a gasket. In this application, with no gasket, assembly might go a bit faster.

The v-bands are also not designed for a lot of mate/demate cycles; the Tri-Clamps might be a better choice from that perspective.

We don't yet know the requirements for repeatability or rotational location.







Mike Halloran
Pembroke Pines, FL, USA

 

[random88]

Thanks for all your varied suggestions.
I have been looking and thinking about the various suggestions. all having pluses and minuses.
The vclamps are great for piping but I worry about using them for a cantelevered support.

I really like some of Mikehallorans ideas but need clarification on others.

"Simplest thing to implement may be six studs, and fast-acting tooling nuts. Of course that's six loose pieces, but they're small and cheap enough to stock extras." So simple i am wondering why i never thought of this.

"Next simplest thing is six ball-lock studs, which can be made captive with cables." I confess I do not understand this one. What are ball-lock studs?

"Or maybe some really big servo clamps." again I do not know what a servo clamp is? But if it is anything like a servo valve i think it will be overkill for our application.

"Or just mill circumferential slots where the holes are now, so you can loosen the screws, rotate the flange and disengage it by lifting it 'over' the screw heads. The slots would have a counterbore at one end, and a through hole at the other end, both a little bigger than the screw heads." I like this idea the best and will encourage the "bosses" to try it out. While a bit slower than the camera lense type attachment I have been working on, It will be much, much less expensive! Thanks Mike.

 

[MikeHalloran]

By "ball lock studs", I meant "ball lock pins", which are fairly common in aircraft tooling and have MS numbers. You can get them and quick- release tooling nuts nuts from places like Reid Tool Supply. They're kind of light duty, and don't compress a joint in the way that you probably need.

Servo clamps are visually simple cantilevered clamps that pinch the mounting flange of a servomotor. I have never seen them as big as you need, but you could have them made as custom parts for not a lot of money.

The circumferential slots are sometimes referred to as keyhole slots; I was suffering a little brain fade and couldn't bring up the term.



Mike Halloran
Pembroke Pines, FL, USA

 

[EdDanzer]

You might want to look at machine tool quick change systems. Cam locks, cam screws, tooling plate locating locks, insert tool joints and wedge systems. MSC industrial has a broad listing of manufactures. We have built a bayonet system for an air cooled camera lens and would not recommend it for your application. We have built a cam lock system to replace a ¾” NC bolt but it has space and cost limitations. Another place to look is back hoe buckets for heavy duty ideas. 6 bolts are overkill for 100 lbs.

 

[random88]

EdDanzer
why do you not recommend the bayonet system?

 

[tygerdawg]

Are you required to go strictly mechanical?

Check out the tooling component companies like Carr-Lane, etc., for ideas of how to do quick-mount fixturing.

Something along the lines of EdDanzer's comment, look at using a robotic end effector quick change device from

http://www.ati-ia.com

or similar companies. That would give you a quick easy solution, but you'd have to have pneumatic power on the unit.

TygerDawg

 

[EdDanzer]

In order to twist the connection there must be clearance on a part that large this will be .010-.030. This clearance will make the assembly some what flexible. The any contamination in the clearance will make it difficult to assemble and disassemble.

 

[random88]

Thanks EdDanzer
I had expected the small clearance that is why i figured it would be very expensive to manufacture to small tolerances. I had not considered contamination. Now i have yet another support for the keyhole method. I got support from some of the "bosses" for the keyhole method yesterday. I am also thinking that since we don't need all 6 bolts we don't need 6 keyholes, that will speed up the equipment changing.

TygerDawg
pneumatics is not an option. thanks for the ideas anyway.