How does a cushion bowls work?

[wnydirtguy]

I know it maybe be a dum question but how does it work. the boss finally got some 627f's.:notworthy we have TS-14 so that is all I have ran. I have heard about them but never ran a scraper with one. So I am just wondering about them. And if anyone can give me some incite one the controls of the 627 that would be great. Got up in the cab and was not used to seeing all the switchs. the Terexs and cats are abit different. Thanks for any help.

 

[DPete]

In simple terms a cushion hitch has extra links and a ram to raise the neck off the tractor, the ram is hooked to an accumulator charged with Nitrogen so the oil in the ram while raised pushes against the nitrogen giving it the suspension and absorbing some of the shock load that would otherwise be transfered to the tractor. Load and dump with the hitch down, up for travel. On the F there should be a rocker switch on your right to raise and lower the hitch. If accumulator gets low on nitrogen pressure the hitch will seem solid in the raised position, they need charging from time to time, you should be able to see the flex of the neck suspension out the rear window. Hope this helps, grease that hitch often, we grease our 623's daily. Big big difference from ridgid to cushion hitch, you will appreciate it.

 

[alan627b]

Dirtguy, if you are talking about some of the new scrapers where the bowl lift cylinders have a cushion effect, I expect they work on a similar priciple to the nitrogen/hydraulic system on Cat cushion hitches or Terex suspended front axles, similar in construction to what is described above. A lot of newer wheel loaders also have a system like this for the loader lift arms, to reduce the tendency for the machine to "lope' during travel mode.

As best as I understand it, picture a selaed cylinder where the piston floats in the cylinder. Nitrogen gas above the piston and hydraulic oil under it...really like a big gas shock absorber. When the selector lever is placed in the locked down position, they oil is bled off and the cylinder compresses and has no cushion effect. When the travel mode is selected pressurized oil lifts the piston part of the way up the cylinder and nitrogen is in the space above it providing a cushioning affect. It's going to take a Cat mechanic to explain it better than I can..

From what I've read, Cat 627H series and Terex TS14G or current models have this priciple applied to the bowl lift cylinders also.
Hope this helps somewhat....I ran a 621G for a short while but generally I run 621/627 B models from the 70's and 80's, so I haven't been around the new stuff too much yet. And Terex is a bad word as far as scrapers are concerned around here (Nebraska, or at least my part of it!).

Alan

 

[stadamack]

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