Brake Pad options

That's a term I'll have to remember.

"The expensive bit was broken by uncommanded motion into the workholding vise."

Ned, You should consider existing brakes first. Reinventing the wheel rarely makes economic sense. Check out Kobelt Manufacturing...they are excellent. Steve

How about a safety latch system. Real simple design. First weld a stop rack to the column. Only needs to be 1/2" thick or so. Then for the stop a simple rocker that is spring loaded. On the rocker you place two sprockets that will engage the chain. The chain running between the two sprockets holds the latch off the track. If the weight drops on the chain the weight of the latch drops it into place.

I OI I IO I

I is your chain, The Os are the sprockets. With weight on the chain the sprockets stay in this position.

I O/ / /O I

Chain fails and the sprocket and mount rock down and the latch drops into the track.

Wouldn't need to use sprockets if the space is tight. Simple nylon or UHMW plastic could be used as rubbing blocks.

Simple, Safe and easy.

Great description of those safeties. I think the cable grippers you are referring to are these:

Interesting how terminology changes, I never heard of "uncommanded motion". I like the term "uncommanded motion".

Simple, higher pump output.

Exactly, in the new application you'd replace the basic hydraulic power pack normally mounted on the column, with a "real" industrial hydraulic power unit with a large tank and probably 10HP+ motor rated for continuous duty.

Thanks to everyone who responded. I still have to do some tweaking and check proportions and strengths of the various components, but this should be pretty close.

If the chain goes slack: the stack of Belleville washers (magenta) pulls the chain rod (gray) down; as the collar on the rod (gray) falls the arm (green) rotates CW; allowing the torsion spring to rotate the collar (gray) CCW; the pawl (green) rotates along with the collar and engages the slotted track (orange).

There was something very similar in one of the patents I looked at. Unfortunately, I have about .050" between the attachment points for the chain and the column.

I'd be surpised if it was that simple. At 1+ ft/sec an appropriately sized cylinder would be borderline for oil velocity with standard ports and full-size plumbing to match. Considering that the lift business is very competive, I doubt that the mfrs run 3/4" lines if

economic sense. Check out Kobelt

Thanks, Steve, I looked and didn't see anything I could use now. Quite likely there's something there that would have worked if the safety was designed in from the start, but as I mentioned elsewhere, this was a supposed to be a prototype and only to be run to prove out a concept. Not so anymore.

Take a look at an actual lift. There is no flow divider, there is a "T" connecting the two cylinders. Synchronization is provided by steel cables and pulleys much like on a drafting table.

Looks good. Not sure where the chains are attaching, but you may want to look at the lower spring loaded one and see if it should be a rigid mount, i.e. not spring loaded with different types of springs at each connection point.

Looks like a good solution. You might think of making the lower portion of the threaded rod as smooth as it can be. If the chain breaks it is likely to fly away and pull the threaded rod into a bind. A smooth, lubricated rod would probably not bind if pulled sideways.

Paul

There's a considerable amount of difference between locking the load in place once it has come to a stop and having the lifting gear fail (cable or chain break) if this load is already descending at a pretty good clip.

The chain runs in a loop, with the drive sprocket overhead and an idler at the bottom. The bottom spring protects the drive if the car overtravels in the down direction as a result of operator error or a control malfunction. The normal down position is about 1/2" over the floor. The spring allows the chain drive a couple extra inches of travel before the frame starts to lift if the car bottoms out on the floor.

And thanks for aiming me at the garage lifts.

That one of the required tweaks -- the originals are made from alloy threaded rod, and I just lengthened one for the layout. The new ones will need to have only enough thread on the lower end to adjust the chains.

Tim, having spent a lot of time living in or around the maintenance world, I'd say your suspicion is very well founded. The quality of maint techs and the safety ethos of management varies widely.

Wes

Does the number of belleville washers provide the travel you need? I'm used to seeing a large number of those things in drawbars to provide a small amount of travel.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

There are exactly enough Bellevilles in the model to convince my customer it'll work. If they decide to go ahead I'll figure out many are really needed, along with a few other things.