I am not 100% up to speed on international patent laws and treaties but it seems that China is a signatory to the them
http://en.wikipedia.org/wiki/List_of_parties_to_international_patent_treaties
However the question is what is patented, copyrighted and has registered designs (the way something looks, for example you cannot patent a wheel loader as such but you can register the design of it, so that another manufacturer cannot make an exact copy).
So while ChengChong might not be breaching patents, they may be breaching registered designs. However they may make subtle design changes to side step these laws.
I guess the reason that Chinese manufactures don't see a problem with copying is that the rules are not that well enforced in China and they are trying to get up to speed/catch up with western manufacturing at a rate of knots. Japan did the same thing after WW2, lots of stuff made in the 50's was copied by Japan and eventually they learnt to make them better that the original manufacturer (a good example of this is British bikes). Why did Japan copy rather than design their own? Because they needed a product quick and R and D takes time and expertise, which Japan did not have in post WW2, also they where able to produce products that people in the west where familiar with. Which is perhaps one of the reasons Chinese equipment manufacturers are copying western equipment. People look at a Chinese loader and because it looks similar to a Cat or JD, they will be more willing to buy it, thinking they are getting Cat/JD quality at a bargain price.
Obviously this is not the case, long after the sweet taste of low price is forgotten, the bitter after taste of low quality remains (or something along those lines).
People need to factor in costs of breakdowns when they make a machinery purchase decision, no good buying a machine at half the price if it spends half it's working life sitting in the workshop, waiting for parts which may never turn up.
