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Gallery, Projects and General => The Design Shop => Topic started by: raynerd on September 15, 2013, 03:58:33 PM

Title: Box release mechanism ? - ideas or suggestions?
Post by: raynerd on September 15, 2013, 03:58:33 PM
Hello guys

I could do with some suggestions and ideas to make my concept work.

I would have a box made up - say 60x60x80mm in clear Perspex. Coins drop into the box and are stored - when the 50th coin drops into the box, all the coins are dumped from the bottom of the box.

I can deal with the coin counting, that isn`t a problem. However, I don`t know how to design the release AND reset method!! The other issue is to ensure ALL the coins get dumped.


A few of my thoughts - place a diagonal piece in the box so that the coins slope towards one corner. Use a small push/pull solenoid to open a slide bottom. The logistics around this are sketchy - how would I smoothly run the bottom trap door open and closed - just in slots? How would I magnify the travel of a small solenoid (7-10mm) to ensure the trap door slides open enough.  A much better method would be a hinged trap door but I`ve no idea how you could easily reset the door! You could easily release a hinged door using a solenoid to act as a "lock" but I can`t imagine how the trap door could be lifted back up to reset. 

Any help appreciated!    :proj:

Chris

Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: SemiSkilled on September 15, 2013, 04:16:57 PM
How about a wheel with with a quarter or more cut out, on  the 50th coin the wheel rotates the cutout allow the bottom of the box to drop emptying the box, as the wheel continues to rotate the solid part closes the box, wheel stops.

Lee
Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: srm_92000 on September 15, 2013, 05:15:33 PM
How about pivoting the base along its centre and driving it round slowly 180 deg.
Micro-switch situated to cut the motor once level, activating pulse just needs to be long enough to move the door/some sort of cam, off the switch. A bit like car wipers parking setup.  :thumbup: I see another wiper motor finding a new home. :coffee:
Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: vtsteam on September 15, 2013, 07:57:32 PM
How about just a wheel, no box. The wheel is like a water wheel but only two "buckets". In other words it has just a single divider. It rotates 180 degrees to simultaneously empty the contents of one side and bring the other side up for filling with coins. When that side fills, it rotates another 180 degrees -- etc.

Actually it can be any shape, not just a wheel, as long as there are two of them, they face opposite directions, and the whole rotates 180 degrees to empty and bring the other side up for filling. Could even be a pair of boxes.

And actually, actually, (double actually) it doesn't even have to be two boxes. Could be only one box with an open top that rotates 360 degrees slowly and then stops upright again after having dumped the coins -- ready to receive more.
Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: clevinski on September 15, 2013, 09:58:24 PM
Hi, Chris,

I'm not sure how much space you have, but I was thinking a horizontal "floor" to your box that is pivoted at one corner.  Upon receipt of the 50th coin, you activate a motor to rotate your floor around this pivot point.  (The "floor" will always remain... what's the term when something is parallel in two dimensions?  Anyway, the floor does not tilt; the coins on it are pushed off by the lack of clearance between the floor and the side wall.) 

The length of the activation pulse is relatively short, because you latch the motor using a cam and a microswitch.  When the "floor" has turned through approx. 360, the cam deactivates the microswitch and the motor stops, with your floor closed again.  The advantage of this technique is that you don't have two separate "empty" and "reset" functions; there is only one "rotate floor" function.

BTW, we do something very similar with some of our paper cutter devices (used as components in other equipment).  This ensures that the cutter blade rotates 360 and provides closed-loop feedback so that it stops in the same place every time.
Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: raynerd on September 16, 2013, 01:57:17 PM
How about a wheel with with a quarter or more cut out, on  the 50th coin the wheel rotates the cutout allow the bottom of the box to drop emptying the box, as the wheel continues to rotate the solid part closes the box, wheel stops.

Lee

I like the idea of this... It sounds simple turning a wheel but I can't figure out how it would actually open and then latch the bottom. I get your idea of using a rotating cutout disk, but don't get how it will actually release and gather.
EDIT - I understand now! However, the spinning mechanism would need to be mounted to the bottom of the box which wouldn't be ideal as mentioned in the last paragraph of this post.  Guess you could use spur gears but that seems an added problem.

How about pivoting the base along its centre and driving it round slowly 180 deg.
Micro-switch situated to cut the motor once level, activating pulse just needs to be long enough to move the door/some sort of cam, off the switch. A bit like car wipers parking setup.  :thumbup: I see another wiper motor finding a new home. :coffee:

I could actually use a stepper motor and simply spin the motor slowly 360!! I do very much like this..it is simple. I'm just wondering how much torque I'd need. I said 50 coins but actually I probably only do 35 or even 25 - not sure how much torque I'd need!  Also I haven't got much room behind the whole thing for the motor but then you can get quite "short" stepper motors.

How about just a wheel, no box. The wheel is like a water wheel but only two "buckets". In other words it has just a single divider. It rotates 180 degrees to simultaneously empty the contents of one side and bring the other side up for filling with coins. When that side fills, it rotates another 180 degrees -- etc.

Actually it can be any shape, not just a wheel, as long as there are two of them, they face opposite directions, and the whole rotates 180 degrees to empty and bring the other side up for filling. Could even be a pair of boxes.

And actually, actually, (double actually) it doesn't even have to be two boxes. Could be only one box with an open top that rotates 360 degrees slowly and then stops upright again after having dumped the coins -- ready to receive more.

Problem with this method is the space needed on the front surface...  Also, would it be working by balance? I think if I was going with a rotating container, I'd simply turn a box pivoted from the centre as suggested above.
Hi, Chris,

I'm not sure how much space you have, but I was thinking a horizontal "floor" to your box that is pivoted at one corner.  Upon receipt of the 50th coin, you activate a motor to rotate your floor around this pivot point.  (The "floor" will always remain... what's the term when something is parallel in two dimensions?  Anyway, the floor does not tilt; the coins on it are pushed off by the lack of clearance between the floor and the side wall.) 

The length of the activation pulse is relatively short, because you latch the motor using a cam and a microswitch.  When the "floor" has turned through approx. 360, the cam deactivates the microswitch and the motor stops, with your floor closed again.  The advantage of this technique is that you don't have two separate "empty" and "reset" functions; there is only one "rotate floor" function.

BTW, we do something very similar with some of our paper cutter devices (used as components in other equipment).  This ensures that the cutter blade rotates 360 and provides closed-loop feedback so that it stops in the same place every time.

Very very clever and simple idea and would be really effective...however, am I right in thinking that your moving mechanism would be either above or below the box??  Only I'd have to have the mechanism hidden at the side of the box...

Perhaps I need to make that clear... The box will be stuck to a surface on one of its sides. The coins fall in from the top. Whatever opens the box needs to be hidden behind the fixed side. I'm very sorry to have wasted time, that should have been clear in my original message. The idea of rotating the full box 360 is a good one since I can pivot the box from the fixed side. The only issue will be that the boxes full weight will be hanging from the mount of the box to the motor. Then again, 25-50 coins isn't such a great weight - 50 coins would be 325g

Really interesting ideas and has got me thinking! Any more feedback welcome.
Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: raynerd on September 16, 2013, 02:10:41 PM
Your ideas inspired me into this... A rotating front. As mentioned, the slope causes cons to be pushed onto the front face, the front spins and when the cutout gets to the coins allows them to spil.

However, it is doomed to fail! Also, being Perspex I have to understand my limitations with playing and modelling the material. I'd fail cutting a circular front for a start. The square front wouldn't rotate well enough.

Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: DaveH on September 16, 2013, 03:19:28 PM
One way is to have rotating shelves - 4 is probably the easiest. The weight of the coins would cause to shelves to rotate. A "pin" operated by a solenoid can hold the shelves in place. By with-drawing the pin the  shelves will rotate and drop the coins. The pin when returned will stop the shelves from rotating.

Something like this.
 :beer:
DaveH
Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: raynerd on September 16, 2013, 03:29:34 PM
Dave, I like the idea for sure as it is easy to implement but there is an awful lot of dead space and consequently the compartments would have to be large to hold all 25-50 coins and with 3 of them empty at one time. Would it work in two halfs - issue would be ensuring there was an imbalance to one side to cause it to tip.

Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: DaveH on September 16, 2013, 04:03:19 PM
Hi Chris,
It could work with 'two halves' (I think). The main problem is getting back to the starting position. If one half was heavier (a small counter weight)  than the other half it would allow it to rotate back - a small stop will be required. One shelf could be much smaller than the other but one will need to be heavier to make it rotate back to the start.

Just needs a bit of thinking "outside the box"

Outside the box  :lol:  :lol:  :lol: I'm wasted on here  :lol:
 :beer:
DaveH

Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: raynerd on September 16, 2013, 04:11:57 PM
Ho ho ho  :doh:

Lol, yes I know what you mean. It would certainly be tricky to reliably get it back to the start.

I'm moving back towards a 360 deg rotation pivoted from the centre of one side
Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: BiggerHammer on September 16, 2013, 07:15:14 PM
My apologies if I have missed this somewhere in the thread. How about just using a solenoid to release the bottom panel. Spring load the bottom panel. Actuate the solenoid and hold. Bottom panel tilts all coins drop. Now that the weight is off of the bottom panel the spring should return it to the closed position. Just have the solenoid re-engage and bob's your uncle.
Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: raynerd on September 17, 2013, 07:39:56 AM
My apologies if I have missed this somewhere in the thread. How about just using a solenoid to release the bottom panel. Spring load the bottom panel. Actuate the solenoid and hold. Bottom panel tilts all coins drop. Now that the weight is off of the bottom panel the spring should return it to the closed position. Just have the solenoid re-engage and bob's your uncle.

For this idea I presume the mechanism would be working from the bottom and on show
Title: Re: Box release mechanism ? - ideas or suggestions?
Post by: TLGriff on September 30, 2013, 06:06:07 PM
You just need to ask a gunsmith.

The trigger of a gun works the same way. As pressure is increased, it holds hammer up until the very last instant and then drops it. To simulate this, your box would need a pan inside (the trigger), pivoted along one edge to catch the coins and linked to the bottom of the box, the hammer (also pivoted), to hold it closed. The pan would need a sear attached to it to engage a catch on the side of the box to hold everything shut. The coins would add more and more weight to the pan until the sear would no longer hold. Then the pan and bottom would release together, dropping the coins out the bottom.

Tom