Bridging in vibratory feeding of cans 1

[cheapshot]

I am attempting to feed " tuna style " cans from a vibrating stainless tray mounted on a pivot to produce a ramp, onto a conveyor. The tray is a right triangle with a base of 36 inches and a side adjacent of 48 inches. A four inch opening at the top allows the cans to flow out. The cans will flow for a short time and then bridge.So far, no combination of fingers on the sides of the tray will break up the geometry and stop the bridging. Increasing the degree of the ramp only increases the pressure on the bridge. Any help in this matter will be greatly appreciated.
Cheapshot Charles W. Ames, Ames Mechanical Development

 

[CESSNA1]

CHEAPSHOT: I do not understand what you mean by "bridging", can you psot a photo or two

Regards
Dave

 

[bklauba]

By bridging, I believe you mean the classic jamming of material, by having it form a bridge, i.e., a stiff, unbending "structure".

This system used to work? or was it conveying different material?

I am wondering whether it is old, and worn out, or, if new, the wrong vibration frequency or amplitude is being used.

Can you supply some of these details?

 

[cheapshot]

In response to bklauba, this system is new. The pan or tray has one inch sides and can be loaded with about 30 cans with toweletts already in place ready for solvent to be dispensed into them. The trick is to get the cans to flow to the narrow end of the tray and glide onto a small conveyor which will carry the cans to the solvent dispensing station and then on to the sealer which is done manually. As the air activated vibrator moves the cans toward the discharge end of the tray, they will bridge at whichever point the cans form a line of ,2,3, on more cans between the sides of the tray. Adding cams on the sides or pins much like those in the table of a pinball machine to break up the bridging so far has been unsuccessful. The cans can always find a geometric combination to bridge. I am now getting ready to try wedges in the tray to direct the flow and break any bridges that try to form. It appears that when a bridge of more than 4 or more cans forms, it is weak and will buckle. I hope this makes my problem a little clearer.
Charles W. Ames

 

[ivymike]

Can you add a roller (rotation about vertical axis) to cause the bridging cans to "drive away" from each other when they come in contact?

 

[bklauba]

The most successful feeder trays I have seen that deal with this problem have rails on the sides of the "exit chute", which do not extend to the bottom of the tray. This keeps a separation between the bottom lip of the cans and the tray walls, where such "bridging" (the right term is likely to be jamming, since bridging normally refers to (hopefully) dry bulk mat'ls, i.e., sand, flour, wood chips, soy meal, etc. ) Sometimes these rails are polished or coated with Teflon, and sized so as to minimize their friction, and allow the turning and sliding (which ivymike also offered a possible solution, but rollers can jam and cause the problem to be far worse, or so I have seen).

In addition to the rails (which perhaps your feeder design includes), small, hi-freq, air driven, turbine vibrators can help overcome the starting/jamming friction that the cans experience. These should be mounted on the rails, not on the feeder, and are usually most effective in the 8-10 VKBM speed range.

bk

 

[bklauba]

Cheapshot,

Can you give us any fdbk on how you made out??

BK

 

[cheapshot]

To bklauba,
We have installed a spring wire finger attached to one of the vibrator mounting screws in the vicinity of the jamming. It appeared to work once in the shop but didn't work when we tried to use it in production. We do not have a ridge at the bottom of the can like you would see on soup or tuna cans. Instead we have a flange of about 1/8" at the top which is rolled over during the cover sealing operation. This is not helping us either. Our problem continues.
Cheapshot

 

[bklauba]

Can you post a drawing or photo of the app? Our firm has resolved a variety of problems such as this. Material flow, both original design or selection of material flow aid devices, is one of our firms market niches.

BK