Does this clutch exist?

A cone clutch. The outer ring moves axially to engage or disengage. If you want rotation relative to a fixed frame to engage it, you could use a helical clutch shaft like a Maytag washing machine.

The centrifugal clutch in a chainsaw, snowmobile, go-kart etc might give you some ideas.

jsw

scritch fired this volley in news:jtkp6o$jpf$1 @speranza.aioe.org:

When the outer ring moves at all, or when it reaches a certain speed?

If you mean "at all", no. Not unless you provide a separate mechanical action to cause engagement of the elements.

The traditional "one way clutch" bearings use needle rollers that are held snug to the shaft and ramps in the outer race with small springs. When the inner shaft is rotated against the compression of the springs, they move up into the wider part of the ramp, and disengage from the shaft. When the inner shaft is rotated in the direction to allow the springs to extend, the rollers jam between the narrowing ramp and the shaft, locking the two together.

There are centrifugally-engaged clutches that will engage once the outer (or inner) race reaches a certain speed.

I can envision a sort of clutch that spring-centered on helical ramps, but causing it to engage in either direction would require that turning the outer race also cause some sort of deflection of the outer race along the axis of the driven shaft. That would be easy enough to do with cam followers on the outer race ends and a friction-delayed cam on each end that lagged in rotation. It would require some significant backlash before driving would occur, and would require reversal back into the neutral position to disengage.

Here's a patent depicting that kind of method.

LLoyd

I had to go out back and look. The reel drive clutch on my 1950's lawnmower engages outward like a centrifugal clutch when the conical end of a sliding shift sleeve pushes out a clutch shoe actuating lever.

jsw

I just happened to be looking for the same thing today for the feed on a machine tool. I was hoping for a passive device that would allow a handwheel to override the power feed. The description of the device at the top of this page is interesting, but there doesn't appear to be any more info online.

I also turned up a few patents with a search for "overrunning bidirectional clutch" but nothing that looked promisisng and I haven't waded thru them yet.

Some old GMN literature in my files shows some bidirectional sprags, but they seem to need some outside intervention to switch. Again, I haven't studied them carefully yet.

I may be stuck with a dog or face gear clutch actuated manually, pneumatically or magnetically. If you find something I'd love to see it.

If i understand you correctly, you're looking for the system found on gravely commercial lawn tractors. My units have two clutches. One unit goes low-neutral-high for speed on the PTO or mower. The other clutch unit goes forward-nuetral-reverse.

The interior design on this is very clever, you're just moving a ring with tapered surface back and forth to tighten against a mating drive surface. The clutch is on the outter diameter with the gearing in the middle.

karl

I think I remember a manual input clutch that engaged when handwheel rotation cammed a cone (or dog?) clutch axially. There was a friction drag on the cam follower's shaft bearing that had to be carefully adjusted. IIRC the cam resembled a Hirth coupling with the center bolt loose:

jsw

Not without some type of mechanical device to assist.

What are you attempting to do? That might help with suggestions.

Magic

Now, that would be telling my secret! Actually, you guys have told me what I need to know, and I have a idea now based on your comments. Thanks!

Now, about that birth certificate ...

I was getting nowhere searching for stock "face gears." "Hirth coupling" turned up a couple leads. Thanks.

I'm afraid the downside may be that Hirth coupling seems to imply a level of accuracy that I really don't need. I'm waiting on a price now, hoping it's better than the $600-1200 price for a pneumatic or magnetic tooth clutch in the capacity I need.

I've seen them used on an old Snowbird snowblower that I had, but I never knew that those couplings had a name. Good info!