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Eccentric Locking Mechanism

Eccentric Locking Mechanism

Eccentric Locking Mechanism

I am trying to design a mechanism that will lock two rollers against each other. One roller is driven by a motor and its position is fixed. The second roller is a pinch roller that needs to contact the drive roller during operation so it is driven. The pinch roller also needs to be able to be adjusted away from the drive roller to run a label web through. Both rollers are 8 inches long and need to fully contact each other along the entire height (driven roller is rubber and pinch is knurled aluminum).

Currently this is done with constant force springs on the pinch roller and a threaded adjustment that brings the roller into and away from the drive roller. I would like to simplify this and I think it can be achieved with an eccentric cam, just not sure the best way to do this.

One idea I had was to have a pressed pin mounted eccentrically at each end of a rod. The pins would be supported by bushings on top and bottom plates. A knob "keyed" with the pin would be turned which would then rotate the rod. The pinch roller would be mounted on the rod with bearings to allow it to rotate. The only thing I'm not sure about is if the rotating "eccentric cam" so that the pinch roller is pressed against the drive roller would hold it there. I feel that it would want to turn eccentrically on its own away from the drive roller. Something to lock the knob in place could fix this.

Would my idea work? Any other suggestions, would also be much appreciated.


RE: Eccentric Locking Mechanism

A sketch would be a tremendous help to understand your proposed configuration.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: Eccentric Locking Mechanism

There are dozens of ways to do this And you haven't given any information that would help choose one over the other. You haven't really even said what is wrong with what you have. Why change if it works?

RE: Eccentric Locking Mechanism

Not quite sure what you are trying to do but I think you'll need some springiness in the load path to keep the rollers in contact as parts wear out.

RE: Eccentric Locking Mechanism

You have a slight advantage, you can see it; we can’t see it from here. And, you haven’t given us a clue what you are really trying to do. Without some drawings, photos, etc. your description is less than helpful, imagine the dozens of sketches which could be drawn, generally meeting your description, but being no where near the true picture. But, I’ll guess too, I think this has to go over there, and that has to be right above it, except off to the right of left. smile

RE: Eccentric Locking Mechanism

So, you are designing a better nip roller for a labeling machine.

The problem is that the cam will not be dynamic, it will not float and provide the constant force required to keep the labels moving without slipping.

You said you wanted to simplify this, and I don't see how you are doing that by adding so much complexity. The spring allows easy replacement of the labels. People want a fast way to change the label roll, and if you make them adjust a knob to get the right pressure to drive the labels, then you are making them work harder. I used to design labeling machines, and the customer always demanded quick set up time to change label rolls.

Each change in label thickness will require a different set up. Labels do change in thickness and the spring loaded nip is the best way to do that. As the rubber drive on the servo wears, the spring adjusts dynamically.


RE: Eccentric Locking Mechanism

See basic drawing below. Basically the web path is pinched between the drive and pinch roller which causes it to be fed. I need to design a way to engage both roller aswell as disengage them easily.

I found this online. Does anyone have any idea how this could work? The pinch/nip roller is engaged by turning that handle with the black ball tip.

By simplify this I meant I wanted to simplify it for the customer to changeover labels. I did not describe the current system well. The nip roller is in a guideway and is adjusted in and out with a handle. There is a spring both on top and bottom so that the pressure remains constant. The problem with this is the handle needs to be turned quite a bit to spread the rollers apart. It is not difficult to use but some of our customers have seen other brand labelers with a quick release and engage knob. I have not seen it myself, but basically a knob is turned 90º and the rollers engage with each other. I assumed this was done with a cam but I might be wrong.

How did you bring the nib roller into and away from the drive roller?

RE: Eccentric Locking Mechanism

Look at the other brand machines to find out why your customers like the mechanism, then improve on that.


RE: Eccentric Locking Mechanism

The Nip roller is on a pivot, and a spring keeps it in compression. When a label roll is changed, simply push the nip roller over center.

No knobs, no levers. The only caveat is that the roller is cantilevered so it has to be strong.
The spring is not shown, but it goes between the two spring retainers; one on the arm and the other on the base.


RE: Eccentric Locking Mechanism

You can see the spring here. The grey drive roller is stationary. The white roller is pushed down until it locks over center, and the roll can be changed. There is nothing easier and this is used by most label manufacturers,

RE: Eccentric Locking Mechanism

It amazes me that someone is designing products for a company and has never seen the competitors' products. Go to their websites and go to YouTube and watch videos of similar machinery. Initially it may seem difficult to figure out design details by simple visual observation without someone explaining what you are seeing. With experience, it is amazing what can be learned from studying one picture, or several, and by pausing videos.

RE: Eccentric Locking Mechanism

Amazing ....

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