I was going to borrow this machine for a couple days from a friend but there are issues with the bucket lock pins. This machine is manual locking. The pins are tapered and common sense would say they need to be flipped so you can connect up quick but then have to pull the levers to remove the bucket. The taper looks like its the wrong way? I mean think about this......pull on the bucket, taper on the pin will help it try to push up, and then there is nothing but spring force holding that pin down. Tell me this is all wrong? If not, how do I get the cleared up?
I think the idea of that taper is to more or less make the latch be self adjusting with the spring holding it in tight. This might not be the best image out of parts break down but you can see the taper on the back side of the latch pin. Without seeing it in person I would have to think that the problem might be overall wear or something not adjusted or binding. Might just need to be disassembled cleaned and adjusted. Spring looks like it is jammed with rust and dirt.
the first pic shows the problem the bucket is too loose on the coupler. it appears the tab that the pin goes into is bent down away from the coupler. I would bend that back so that is tight to the coupler and add a plate tying it back to the bottom of the bucket. the taper allows for wear in the mating surfaces not up and down movement. I suspect when your bucket comes off its being pushed up and unhooking from the top lip. you don't show any pics of the top lip but I would look there also for problems.
Looks like the pin is worn as well. Instead of bending it back straight, I would just replace them. And upon further looking, the pin don't appear to be coming down all the way, I think when the handle goes over center (lock) and the pin is down far enough so the angle ramp is completely below the hole in the plate. Check the linkage for sloppy connections as well.
I think i first wanted to see if things even look to be assembled right? the taper on the pins should face the operator? My issue with that is not only is this a taper, but there is just a spring holding it down! Pull on the bucket hard enough and the force rides that taper and pushes up on the pins. Never the less, i agree that the top side interface needs looked at because I am pretty sure all attachments fit pretty loose. They do jump over on the top side frequently.
Just my 2 cents. Our 1840 has a similar setup for attaching the bucket. Our parts are worn from years of use and one of the locks that holds the bucket on does the same thing. I've had the bucket come off once on me because it didn't stay tight. Turns out that the handle that you push down to keep it locked had a worn spring or something and the handle wouldn't lock down unless you really strong armed it. I jumped on it and it went way past where I thought it was supposed to be and locked it up nice. Old machines need TLC and some parts here and there. Keep a grease gun handy too.
Are you saying (for sure) that you or the owner has experienced the bucket coming loose regularly, or, you just 'think' that there would be a problem due to the orientation of the pin taper? From what I can see, that's how it should be, mine is the same way and I've never had any attachment come loose ...and I keep mine pretty well greased. The lower tab of the bucket in your picture looks about the same angle and distance as mine does, I just checked mine. The pin taper in the picture doesn't look too worn either. If an attachment has come loose, maybe the pin wasn't fully engaged, the spring is weak/broke, a rock or some object pushed the pin up, grease got on the taper face and the pin worked up, a problem with the attachment slot ...something along those lines.
I have personally had implements detach on this machine. We went over the mounts the other day and determined, for whatever reason, all attachments, brand new and old, are loose, having about .50" play up and down. This caused the pins to not have solid engagement and allow the implement to raise up and get off the angled lock on top. We decided to add filler plates on the top angles to make the implements ride about .50" higher in the "saddle", which got us good contact on the bottom, and better engagement of the pins. This seemed to fix 90% of the problem. We can now do some back drag work without issue BUT, during my tests, by putting the bucket on the ground and curling down, I could see the pins try to ride up. I did not push this to the point of making it come off but it sure looks like I could get there. The owner has already added washers to the pins springs to get them to stay down. They are not in bad shape but there is a bit of play in their sockets in the quick mount. Not sure what else to do. I sure like hydraulic locks though! Never had a CAT machine lose a bucket.....