Designing a bottom door mechanism 1

[trazimcalvina]

I have been having trouble with a problem that looks really easy, I need to design a mechanism which can open the bottom doors( marked blue on the picture ) on this steel box in order to empty its contents, and of course keep it closed when the mechanism is not activated, the mechanism has to be activated on the side of the box so that it is easily reachable. It does not have to have a real closing function, that can be done manually.
Also, it really has to be basic because it is supposed to have no need of any real maintenance.
I sort of have an idea with a spring and a lever but I feel like I'm missing a simpler solution.
Dimensions of the box (1000mm x 1000mm x 700mm).

Thanks for any insights!

 

[desertfox]

hi
well whats being carried in the box? and how heavy are the doors?
You could have a simple shoot bolt mechanism manually operated but depending on what is being dropped out of the box and how heavy the doors are to re-close by hand will have a bearing on my suggestions.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[robyengIT]

manual operation looks like quite impossible because of the weight on the the doors and because the material will be discharged suddenly all together with impact on the receiver. You need something to open the doors slowly and capable to stop the opening operation if needed. Something like a steering wheel and a gear mechanism

 

[Jboggs]

Do the doors have to operate simultaneously or can they operate separately?
Are we talking manual actuation only? (Meaning no electric, pneumatic, or hydraulic)
What kind of load do they have to withstand from above?
Will there be any load on them when they are closing?
When opening do they have to travel a full 90 degrees? Can they stop at 45 degrees or some other position?
Do they have to create a full seal when closed (air tight, water tight, powder tight)?
How often will they operate? What is the duty cycle?

 

[JStephen]

Look at the doors on railroad hopper cars.
Here's a site showing some details:

https://www.aldonco.com/store/p/222-5-ft-pry-bar-for-swing-doors-on-open-top-hopper-cars.aspx

Note that they open more energetically with a full hopper, and you need to be at the side, not in line of the swing.
From long-ago memory, they had little cams that you normally tapped into place and opened with a short-handled 8-lb sledge. If I remember right, you could swing them shut with your foot, then had to lock them in place by tapping the cam back into place with the hammer.

 

[Compositepro]

Think how a cardboard box is designed. There are two sets of flaps (doors). The innerset holds the load and the outer set basically only holds the inner set closed. You can do the same thing with a piano hinge at the side of your doors. One leaf of the hinge folds over the doors, holding them closed. A single latch holds this leaf in place. Pull the latch, the hinge leaf swings out of the way and allows the doors to open.

 

[r13]

Would you consider this with some modifications.

 

[trazimcalvina]

Hi everyone, sorry for the late reply, I really appreciate all the answers.
As for your questions:
@desertfox
The box is to be used to transport ash with a forklift, the forklift would lift the box and a huge bag would be attached to the bottom through hooks on the side of the box (not visible on the sketch model) followed by the opening of the bottom through a mechanism activated on the side of the box (the bottom is not accessible due to the bag). I don't really know the type of ash but apparently its not too heavy, the customer specified that 4mm sheet metal doors are okay. They weigh around 30 kg (15 each).

@robyengIT
Sudden discharge is not a problem.

@Jboggs Sorry for the incomplete info
Do the doors have to operate simultaneously or can they operate separately? Not important, whatever is easier to pull off mechanism wise.
Are we talking manual actuation only? (Meaning no electric, pneumatic, or hydraulic) Yep, manual only is the current focus, but if its too complicated and expensive we would have to of course consider a pneumatic or hydraulic solution.
What kind of load do they have to withstand from above? I will have to check with the customer because i dont have the exact density of the ash involved, but as with the duty cycle i think the loads are not very significant.
Will there be any load on them when they are closing? No
When opening do they have to travel a full 90 degrees? Can they stop at 45 degrees or some other position? 45deg might be a problem, 60 looks good, 90 ideal.
Do they have to create a full seal when closed (air tight, water tight, powder tight)? Not really, its not a clean factory, and the ash could leak a bit.
How often will they operate? What is the duty cycle? Not sure, but not that often that it would be relevant. I would say once a week.

@JStephen
Interesting. A pry bar solution is really interesting here. It would enable activation from a distance, which would be useful or from the side which is a must. I will give it a look and try to come up with something less heavy duty.

@Compositepro
Another interesting idea, I thought about something similar but I couldnt figure out how to open the whole thing from the side of the box, as I said in a previous answer the whole bottom is not accessible when the box is to be opened. A sort of a bag will be attached on hooks that will be welded on the lower part of two sides of the box.

@r13
If the medium wasnt ash this would be a solid solution. But other than that the customer is currently demanding we exhaust all possible mechanical solutions before moving on to pneumatic or hydraulic.

 

[EdStainless]

I have seen hoppers that required manual reset of the doors. They had to be held in place by hand and then bars under the sides held them closed. A lever on the side simply pivoted the bars out of the way and allowed the bottom to drop open.
Very crude, manuel and no control. But functional.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[rb1957]

the box is carried on a fork lift. presumably the box has an open top ... to put the ash in the box. what about tipping the box ? that'd make for a better box.

you could build into the box something to hold onto the fork lift (a couple of rings ?) then a lug and a rope and you're done ... maybe a block and tackle. Use the other lower side (the other one is "fixed" to the fork list) and the box could be lifted (rotated) to vertical, then use the fork list arms to go beyond the vertical.

another day in paradise, or is paradise one day closer ?

 

[hendersdc]

You might be able to find something that fits your needs off the shelf. We used a lot of ones like rb1957 is describing for scrap metal. The last picture shows exactly what you are describing, search term is "bottom dump hopper". That one is from these guys:[URL unfurl="true"]https://ibullmfg.com/trash-hoppers/drop-bottom-hoppers/[/url]

 

[Jboggs]

You might also want to find some way to intentionally limit or control the flow of the ash into the bag. I can very easily picture a large cloud of dust almost exploding out the top of the box as the ash falls into the bag. Is the top of the box sealed at that time? You might do some research on how large commercial dust collector units handle emptying their collection bins.

 

[r13]

How about design the box as a hopper?

 

[chicopee]

I was thinking along the lines of hendersdc bottom picture but instead of the side mechanism to open and close the bottom hatch in his picture, install a counterweighted lever to keep the bottom door closed and to open the bottom door move the counterweight by hand but keep safety in mind with my suggestion.

 

[MJCronin]

If indeed you want to store and periodically dump coarse abrasive ash, consider the material handling solution used by the power plant industry.

For their coal fired power plants, ash is collected in sloped hoppers on equipment and blown into a common dump silo.

The ash dump silo typically has a hopper bottom with a powered rotary valve (also called Rotary Feeder) at the lower flange. Detroit Stoker makes some bullet proof equipment ... There are other vendors

http://www.detroitstoker.com/main/ash-handling-systems-overview/

https://www.acsvalves.com/?gclid=Cj...dS7W44sF6S-fcpniHv_yGu1Y3RAii1YxoCYlkQAvD_BwE

https://processbarron.com/ash-handling/rotary-feeders/

Rather than inverting the entire storage container, the rotary valve is actuated and ash is discharged pneumatically
...

MJCronin
Sr. Process Engineer

 

[trazimcalvina]

@EdStainless
Several solutions including bars underneath crossed my mind too, but i couldnt figure out how a lever would move them out of the way.
Could you perhaps go into more detail or even better produce a simple sketch.

@hendersdc
This is exactly what I had in mind, thanks so much I spent so much time looking for something like this on google and couldnt find it for the life of me,
sadly im not in the US (I'm in Europe) so this off the shelf solution wouldnt work, but I will research local options maybe someone is already making something like this.
But this will definitely serve as a great illustration of what I need.

@chicopee
I like the simpleness of what you suggested, but again, I cant really visualize it, could you perhaps sketch something, or go into more detail.
Nothing too detailed, but just so I can grasp what you had in mind

@MJCronin
I'm gonna suggest something like this to the customer even though i'm not sure how they would go about procuring it since they aren't in the US. But thanks!