Plastic latche for tool chest(box)

[jacekm]

Hello guys

I am designing palstic tool chest(box). Most of job regarding the design is already done, however I am still confused about right variant of plastic latch I should pick up.

There are two size variants of box: 20 and 22 inches big. Biggest is up to 25 kg.

I chose 4 types of latches I am interested in(visible on the picture.

What pros and cons they have and what should I consider before selecting the final variant?

What are the equations regarding stress, and forces, and special areas I should really check out?

 

[Paulkuklych]

Have you considered purchasing the 4 tool chests and doing product failure testing on them? That way you can see which latch will suit your application.

The blue latch has a manufacturing advantage in that it is just one piece the other have 2 pieces.

Hope this helps.

Paul Kuklych

http://www.improve-your-injection-molding.com

 

[MikeHalloran]

I wouldn't trust 25kg of tools to any plastic latch I have ever seen.


The best plastic toolbox on the market today is the Stanley FatMax.

http://www.walmart.com/ip/Stanley-FatMax-23-Toolbox/14146170

http://www.walmart.com/ip/Stanley-FatMax-28-Toolbox/14146171

Both sizes have metal latches. Test those to destruction; that's your standard.



My next choice would be the Stanley 18700 APV.

http://www.stanleytools.com/default...CT&PARTNUMBER=18700&SDesc=All+Project+Vehicle

I don't think they're in production any more. It's a wheeled thing that looks sort of like R2D2. It has large plastic latches. So far mine has not failed, but I don't think it's ever been loaded to 25kg.




Mike Halloran
Pembroke Pines, FL, USA

 

[jacekm]

I am keen to use tension latch because of tolerance.

Have any of you ever calculated or designed such latch?

 

[MikeHalloran]

No, I haven't designed an overcenter latch, but I will attempt to answer your questions.

What you have called initial interference is pretty much arbitrary. It's just there to keep the latch from sliding open.

Allowable load can be calculated from the geometry and material properties of the individual components, with consideration for the internal loads induced during latching.

Opening and closing force can be calculated from the toggle geometry, with consideration for deflection of the individual components, including the box itself.

I.e., I can conjecture how to do it. I'd start with a set of sketches and an initial material selection. I'd probably end up with a huge spreadsheet, with pretty much every dimension as an input, and stresses at various locations as outputs. If I had a parametric CAD system, I might be tempted to try using that, but I'd allow at least a month to screw around with the design possibilities, and another month just to get used to working with the parametric CAD.

If I didn't have two months to blow on the latches, I'd just call Southco and get a catalog and some advice.



Mike Halloran
Pembroke Pines, FL, USA