# Latching mechanism for a tilting ramp

1. May 7, 2007

Hello all
I have attcahed a WORD file that has a diagram that exlains the problem.

When you open the file, you would see that I have a inclined part (called ramp) that pivots on a base. A ball (load) rolls up the ramp. The ramp is supported by a spring and some linkage. The linkage shown is not the final linkage, it's just there for representation. This linkage is the design problem. That is, I need to design a linkage such that when the ball rolls up to the point (shown by asterisk), the linkage will collapse such that ramp is now free to swing down and hit the base. For all other positions of the ball before that point A, the ramp should stay where it is.

I have put in a simple link that is blocked by a stopper. When the ball reaches certain point on the ramp, this link slips off the stopper and then the ramp falls down.

2 important criteria that it must meet:

1) The linkage needs to be a very simple link so tht the manufacturing is easy and cheap. I don't want to design a complicated multi-link mechanism.
2) The linkage should be load-independent and position-dependent. That is, the ramp must not fall down before the ball reaches point A, regardless of the weight of the ball. Therefore, it's the position, not the weight, of the ball that determines the movement of the ramp.

This whole assembly is laced inside a rectangular box that is shown in the 2nd picture. I have made the box transparent so that you can see the ramp. The linkage I want to design doesn't have to be like the linkage I have shown. It can be like a latch that engages in the side of the box. I just can't come up with any ideas.

I am looking for ideas to make this work. Eventually, i would want to do a force analysis of this linkage so that I can design the point A and load etc. Bu that will be later.

Thanks a lot for your help.

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2. May 7, 2007

### FredGarvin

Make it an electrical contact with the ball. The ball hits a certain spot, a contact is made and the linkage falls.

Now for the important questions:
- What are the materials involved?
- What spring are you using?
- What kind of scale are we talking?

3. May 7, 2007

### Danger

I'd consider just going with a simple straight bar pivoted to one side of the ramp and extending through a slot in the enclosure wall. When the ball hits it, it gets pushed ahead and disengages. (Think of hitting one blade of a propellor.) A light spring could return it to the loaded position once the ball has passed.

4. May 7, 2007

Thanks for the suggestion. But I am not very clear on it. can you please send me a sketch to help me visualize?
thanks

5. May 7, 2007

### Danger

I've been having no joy with ImageShack lately, but I'll try.

edit: Okay, here goes...

edit #2: Awww, crap. Still nothing. As much as I detest PC's, I'll try doing it up in Paint on my boss' computer tomorrow and repost it. Illustrator won't save in a format that ImageShack accepts, and apparently my Photoshop is screwing up jpg's.

edit #3: I just noticed something really weird. When I looked at the thumbnail on the ImageShack site, it turned out that I could see an extremely dim outline of the picture in the black square. When I double-clicked it, the full-size version came up fine (a bit lighter than originally drawn). Then I came back here and clicked on the link. Just black, but when I clicked on the square and dragged it away, the image showed up enough to be seen with effort. Maybe you can get enough from it that way. Let me know. (It's a top view of the apparatus in the 'before' and 'after' positions.)

Last edited: May 8, 2007
6. May 8, 2007

Tyanks for the effort. But I couldn't see the image when I clicked on link above. Internet Explorer opened up but there was a small square with a "x" mark in it, the kind that shows up when the image is not there or link is wrong or something. Can you please email it to me at bhootiya@lycos.com?
Thanks

7. May 8, 2007

### Danger

I'm not too good with working e-mails.
I've redrawn it in Paint and this link works. The quality sucks, but I guess it's good enough to get the idea across. Again, it's 'before' and 'after' top views.

edit: Oops! I guess that I shouldn't have resized it. Hang on for a larger version.

edit #2: Here goes again.

edit #3: Hmmmpppphhhh... that didn't do any good at all. I hope that you can see it.

edit #4: Okay, after a ton of screwing around, I got the original to upload as a tif. Behold:

Last edited: May 8, 2007
8. May 8, 2007

Thanks a lot for all the effort. Great picture, what did you use to make this picture? Nice shading etc.

I get some idea but I am not clear how this bar is holding the ramp up. If the bar is above the ramp, how does the ramp stay up? And also, I want to have such a thing that the ball doesn't have to push the bar all the way out of its way. As soon as the ball touches the bar, the ramp should fall. This is also because the ball is travelling at a very slow speed, rather in halts and jerks, not continuous motion, no fast travel.

I was thinking along the lines of some latch that is at the end of the ramp. this latch somehow holds the ramp up. then as soon as the ball pushes it ever so slightly, it disengages fro the ramp and lets the ramp fall...

any alternatives.
thanks again

9. May 8, 2007

### Q_Goest

Interesting problem. What’s it for? Can you be a bit more specific? Does it need to be completely mechanical or can you use electrical devices? What’s the overall size of this? What are you using it for? When designing things, it always helps to know what you’re designing for. If it’s an industrial application and you need precise control for example, then Fred’s comments about using an electrical interface to more precisely control the mechanism may be the right way to go. If this is a mouse trap you’re trying to catch small leprechauns in the woods with, then electrical controls would be overkill, and Danger’s approach may be the best solution.

Just to hitch-hike on Danger’s approach, and because you’re responding to his thoughts, I’d suggest the attached. The circles are hinges, rectangles are solid sections. This is just a dumb idea to get others thinking, but basically, the ball rolls up the ramp to the trap which pushes down on the second, smaller, hinged section shown. The smaller hinged section is over-centered such that it holds the trap up. Once the smaller hinged section goes over-center towards the left, it collapses, and the entire ramp falls.

You obviously need to modify this significantly. Drop the entire floor away to determine how low it falls. Put a stop on the trap so it only rotates so far. Lots of little details are not shown.

I’m sure there’s a million other ways to do it.

#### Attached Files:

• ###### Doc1.doc
File size:
27.5 KB
Views:
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10. May 9, 2007

### Danger

Off my back, you parasite! :tongue:

Your presentation is eloquent and practical, but seems to be overly complicated. That is not necessarily a bad thing, but I'm taking the 'minimalist' approach.

Ady, this was a very basic drawing in Illustrator CS. Thank you for the compliment, but it was really rudimentary. As for the 'why' of the ramp staying up, the short end of the bar extends through a slot in the side of the wall. The whole bar assembly is mounted at a height equal to the radius of the ball. If you want to make the trigger instantaneous, alter the angle between the two legs of the bar relative to the pivot. You can tune it to whatever 'hair-trigger' sensitivity you desire.

11. May 12, 2007

### Danger

It's probably too late now (sorry, I've been busy), but here's a drawing that I hope can clarify my idea.