180¦ Air Powered Hinge Assembly 4

[engjeff]

My problem is the one beam has to flip on top using some sort of air or air/hydraulic a full 180° and then come back extended.

-The point of rotation is above the two beams
-when flipped the cylinder can not extend past the end of
the assembly. The point of flipping is to save length
for transport.
-The total weight of the extend moving part is 3,000#'s
distributed.

My question is what should I use for force, the beam can not slam up and down it may kill someone if it does. I have 120psi of air in that location and customer requires it be air powered.

What location should the points be to make the assembly rotate using a non cycling cylinder. As in when extended it must be flipped on top and when retracted it must be extended.

Thank you,

Jeff

 

[desertfox]

Hi engieff

Can you mount the cylinder vertical?if so you can then use
a bell crank lever to achieve what you require.

desertfox

 

[engjeff]

I could use this but, I do not see how I could get 180° of rotation from a single action. Could you explain?

http://www.flying-pig.co.uk/mechanisms/pages/bellcrank.html

 

[unclesyd]

You may want to look at pneumatic actuators though I've never seen one that can overcome the inertia in your layout without some additional mechanical advantage.

http://www.phdinc.com/products/default.asp?id=1

 

[engjeff]

What do you think about something such as this?

http://www.google.com/patents?id=S-o_AAAAEBAJ&dq=PREFABRICATED+FOLDING+BRIDGE

 

[dvd]

You could do this with a spur gear attached to a shaft (hinge pin) and a gear rack attached to a cylinder. Hydraulic looks safer than pneumatic because you will crossover on the forces from push to pull.

 

[engjeff]

Hydraulic in that location would be cost/customer prohibitive. Also, I am trying to avoid a crossover of force and somehow mechanically tie it so a single stroke can move the part 180°.

 

[handleman]

Jeff,
dvd's point is that it appears you are wanting the axis of rotation to be horizontal. That is, you're wanting to lift this 3000 lb beam from horizontal to vertical and then back down to horizontal with a single actuator. The "crossover of forces" he refers to is the fact that for half the stroke you will be pushing against gravity. As soon as you get past vertical, gravity will be pulling in the same direction as your actuator is pushing. If you are using some type of air cylinder, the compressed air that was doing the pushing will suddenly have nothing pushing back, and the 3000 lbs will come crashing down to the other side with the combined force of gravity and your air cylinder, destroying everything in its path. My opinion is that pure air is entirely out of the question. Air over oil is your only option here. And I really doubt you're going to be able to get 180 degrees of rotary motion out of a single actuation of a linear actuator without using a gear/rack mechanism.

 

[dvd]

Are the intermediate positions important to the mechanism? What about the initial position? It looks to me like there would be other ways to accomplish this. Why don't you explain a little more about what you are trying to do?

 

[SnTMan]

Worm gear powered by an air motor?

Regards,

Mike

 

[engjeff]

None of the positions except extended and retracted are important. This assembly is the rear auxiliary axle on a unique military truck that is C-130 air transportable. The extra 4 feet causes a problem.

The worm gear powered by an air motor would be a great option, any clue on who would make a gear that could sustain that weight and the air motor? I would love to do electric but batteries and air flight is a problem. I think they will allow Gel Cell Optima's I will run this by them... All I would need is a gear system so I could mount the motor in a unexposed location.

Thank you for all your help so far.

 

[zcp]

Can your break point be further in so you are less than 180? This would prevent the reversal of forces. May want to add a "lock" cylinder when in the stowed position so it does not come crashing down with a loss of air pressure. Air motor with cable / chain to winch it up looks like a good option

ZCP

http://www.phoenix-engineer.com

 

[engjeff]

Could you explain what you mean by bring it in further so that it will be less than 180°?

 

[budt]

Mount a clevis both ends cylinder vertically Rod Up below the rotation pivot center or vertically Rod down above the rotation pivot center and power the cylinder single acting so it pushes or pulls the load up and then goes the opposite direction to let the load down as it passes TDC.

The load must have momentum to pass TDC. The load will be accelerating as it moves to TDC and then decelerate to the end of stroke by exhausting air as it lays the part down.

Saw this design on a circuit somewhere in te past 40 years and it was slick. Not as heavy a part as I remember but very smooth operating.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[zcp]

If you have space, leave it at an angle instead of folding completely upon itself. Less degrees to transverse but you might have to get creative with the break points.

ZCP

http://www.phoenix-engineer.com

 

[engjeff]

Budt, I was trying to avoid moving from push to pull during the 180° rotation unless you know of a valve or controller kit that will make the transition smooth enough to get over the TDC.

zcp, I could have it at 179°- ~135° the issue still is to spin that pin/pivot past 90° seems to require a motor or a push then pull motion.

Thank you for your help so far.

 

[budt]

I know my explanation is not real clear but the cylinder would only have air on one side. This means it is pushing or pulling half way and exhausting for a portion of the other half of the 180 Deg. while lowering the load

A 3-Way 2 Position valve would shift to prssurize the cylinder until near TDC and then it would shift to Exhaust with flow restricted to decelerate and lower the load.

I could give you a rough sketch in MSWord if there is a way post it here or I could send it directly to you. I'm at fluidpower1**@**hotmail.com


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[Newmanite]

Have you thought about using an offset linkage at the pivot point and a set of gas struts to control the decent rate of the lid?Obviously whilst still using your air ram to shift the load you could apply twin air rams and gas struts or a single air ram

 

[sreid]

I like SnTMan's idea of a worm gear and an air motor. But change it to an air motor and a gear box with the required ratings and ratios.

 

[handleman]

Have you considered at all the size of pneumatic cylinder that would be required to do this? The absolute minimum bore air cylinder required for Bud's suggestion is going to be over 4". That is assuming that you attach one end of the cylinder clevis to the very end of the beam such that its load is only 1500 lbs, and the other end of the cylinder is attached to an infinitely long clevis so that its line of action is always vertical. Any mechanism that comes close to fitting into your design is going to require at least a 7" bore air cylinder. So far I think the best idea I've seen here is the worm gear. You can't beat the inherent braking function of the worm gear. I'm not sure where you're getting the 120psi air, but if the supply failed, coupling blew off, etc, the beam would come crashing down. With the worm gear, either the spur or worm gear would have to fail to let the beam fall.