Light Curtain for forklift pick up

Leukic

Member
L
Join Date
Oct 2018
Location
Leesville
Posts
93
I am in the begining stages of a project and I was just looking for some opinions.
The gist of the operation is
1-Bricks are pushed down a long rollerbed via a pneumatic pusher
2-A forklift picks them up.

A- I need to create a light curtain BARRIER so when the fork lift is picking up the cubes of brick the PUSHER does NOT PUSH( thus smashing cubes into a moving cube thats on the forklift.
B- The light curtain needs to auto reset. As ONLY the foklift has access to the light curtain at the loading area and once in this area the foklift will be blockingthe light curtain the entire time.

Would this be considered a safety light curtain install? Or just a light barrier to momentarially pause a movement in the machine?
 
Leukic said:
I am in the begining stages of a project and I was just looking for some opinions.
The gist of the operation is
1-Bricks are pushed down a long rollerbed via a pneumatic pusher
2-A forklift picks them up.

A- I need to create a light curtain BARRIER so when the fork lift is picking up the cubes of brick the PUSHER does NOT PUSH( thus smashing cubes into a moving cube thats on the forklift.
B- The light curtain needs to auto reset. As ONLY the foklift has access to the light curtain at the loading area and once in this area the foklift will be blockingthe light curtain the entire time.

Would this be considered a safety light curtain install? Or just a light barrier to momentarially pause a movement in the machine?
Click to expand...

Is there risk of a human being harmed by a failure of this light curtain/barrier?

I will exclude "feelings of the plant manager that production has been affected" as possible harm.
 
A keyence light curtain should work fine for this using an AB Safety Relay wired to auto reset. As far as whether this would be considered a safe... would need to be established through the different layers of safety implemented and the results of a safety audit to identify safety risks.
 
mk42 said:
Is there risk of a human being harmed by a failure of this light curtain/barrier?

I will exclude "feelings of the plant manager that production has been affected" as possible harm.
Click to expand...


No as in there is nothing there now. Overhead of the brick there is a huge red light that comes on when the brick are being pushed. So when the light is off the forklift pics up the cubes, but if he is to slow or someone is training. the pusher will push cubes down to the cubes that are being pick up. Failure of this light curtain would be loss of finished brick.
 
rootcon said:
A keyence light curtain should work fine for this using an AB Safety Relay wired to auto reset. As far as whether this would be considered a safe... would need to be established through the different layers of safety implemented and the results of a safety audit to identify safety risks.
Click to expand...

Yes I read up on a few other light curtain threads and I have mentioned to one of our company engineers about a safety assessment before we proceed further with purchasing products.

I have already been on keyence site as we use a few different light curtains from them (y)
 
Leukic said:
Yes I read up on a few other light curtain threads and I have mentioned to one of our company engineers about a safety assessment before we proceed further with purchasing products.

I have already been on keyence site as we use a few different light curtains from them (y)
Click to expand...

Also if you want some great tips you can just ask keyence as well. They have sent their guys onsite with me to help set stuff up as well as offer insight into the applications. The are very knowledgeable.
 
rootcon said:
Also if you want some great tips you can just ask keyence as well. They have sent their guys onsite with me to help set stuff up as well as offer insight into the applications. The are very knowledgeable.
Click to expand...

That is a good Idea, I will contact them to see if they can make a recommendation for which type of light curtain to use.(y)
 
Leukic said:
No as in there is nothing there now. Overhead of the brick there is a huge red light that comes on when the brick are being pushed. So when the light is off the forklift pics up the cubes, but if he is to slow or someone is training. the pusher will push cubes down to the cubes that are being pick up. Failure of this light curtain would be loss of finished brick.
Click to expand...

Could someone just walk in when there is no forklift and somehow get hurt by the pusher?

Ultimately, it boils down to "if there is no risk to a person, you could potentially get away with a non-safety rated light curtain." You need a full safety analysis to be sure make the call.
 
Leukic,

what happens if the forklift does not get the pallet of bricks from the line?
does the conveyor system keep pushing the pallet of bricks into each other?
can the system push a pallet of bricks off the conveyor onto the floor? if the answer to this question is yes, then a proper risk assessment has not been done imho. someone can be standing at the exit and have the pallet pushed off the conveyor and onto them.

how far is it from the end of the pallet when it is pushed to the end of the conveyor?

we have a similar system with a chain driven conveyor and a 5500 lb pallet load. there is enough stations that we can stage the pallets. when the forklift gets the pallet at the end, a photo cell is cleared. after a time delay, we feed the next pallet.

several other options.
1. ab has a programmable fence. if you step inside the programmed area, the output turn the power to the pusher off. when you clear the area, the output resets.

2. have a pb / light / horn station.
press the maintained button, a signal beacon starts and a horn sounds.
the pallet pusher is turned off.
the forklift driver gets the pallet of bricks and pulls out the maintained pb.
the light and horn goes off and the pallet pusher is enabled.
I would use an interface relay for this.

hope this helps,
james
 
My first thought is - what happens if someone walks past the light curtain? Is it possible for someone to be on the other side, have it auto-reset, and start pumping out bricks again while someone is inside?

If that is the case, I would want at minimum some kind of reset or acknowledge button after the fork operator picks up the bricks in addition to a pull-cord of some kind inside the area so someone stuck has a means of stopping the bricks from piling on.
 
Here is a super fast mspaint. It looks like **** but hey It gives an idea
The curtain is something like1ft away from the rollerbed rail maybe 20inches I havent measured.

efl95e.png
 
James Mcquade said:
Leukic,

what happens if the forklift does not get the pallet of bricks from the line?
does the conveyor system keep pushing the pallet of bricks into each other?
can the system push a pallet of bricks off the conveyor onto the floor? if the answer to this question is yes, then a proper risk assessment has not been done imho. someone can be standing at the exit and have the pallet pushed off the conveyor and onto them.

how far is it from the end of the pallet when it is pushed to the end of the conveyor?

we have a similar system with a chain driven conveyor and a 5500 lb pallet load. there is enough stations that we can stage the pallets. when the forklift gets the pallet at the end, a photo cell is cleared. after a time delay, we feed the next pallet.

several other options.
1. ab has a programmable fence. if you step inside the programmed area, the output turn the power to the pusher off. when you clear the area, the output resets.

2. have a pb / light / horn station.
press the maintained button, a signal beacon starts and a horn sounds.
the pallet pusher is turned off.
the forklift driver gets the pallet of bricks and pulls out the maintained pb.
the light and horn goes off and the pallet pusher is enabled.
I would use an interface relay for this.

hope this helps,
james
Click to expand...

The bricks come out strapped 4 different ways in a cube so there are no falling bricks or cubes.


Right now there are no safety systems installed for this set up. The forklift driver honks his horn when he is about to pick up a cube and the operator on the inside stops the pusher via a manual stop button then honnks again when done and the guy on the inside starts it back up.

So If the line is full of cubes the pusher will push and if it doesn't meet the extended LS in time it faults out. Which is the other part of the project is installing a PSC at the end of the conveyor for conveyor full don't push.
 
The way you describe current operation, it sounds to me like there should just be a photo-eye or a mat to tell when the fork driver is trying to pick up a set of bricks. That would be the 'automation' of the operator pushing the button to stop/start.

Without carnal knowledge of this system, this doesn't sound like a safety problem to me, just an automation one. A pair of photo eyes would probably be a lot cheaper than a light curtain and relay.
 
Rson said:
The way you describe current operation, it sounds to me like there should just be a photo-eye or a mat to tell when the fork driver is trying to pick up a set of bricks. That would be the 'automation' of the operator pushing the button to stop/start.

Without carnal knowledge of this system, this doesn't sound like a safety problem to me, just an automation one. A pair of photo eyes would probably be a lot cheaper than a light curtain and relay.
Click to expand...

I agree with this, except I think a light curtain is the correct device to use. I don't know of any fork-truck resistant mats, and a photo cell would need to be aligned carefully to ensure it always detected the leading edge of the truck (the forks which are likely to be in motion vertically).
 
I think you are over engineering this it is not a safety device a light curtain is over kill.
If I understand this correctly all you are looking to do in to prevent the pusher from advancing when the lift truck is present.
Why not use a simple photo beam that get blocked when the lift truck is at the pickup point.
Beam blocked pusher, advance stopped. No muting, no reset of the curtain.
The only issue I can see if a person walking in front blocking the beam will pause the pusher if it is moving. There should not be any personal in that area anyway.
if mount the photo eye at an angle it will catch the lift truck
Keep it simple
 
Last edited:

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