Hso (and a couple of the lawyers on staff) know more about this than I do, but let's look at the difference between patents and just one other type of intellectual property, the trade secret. To quote:
A well-kept trade secret could theoretically last forever. But there is a risk. Unlike with patents, it is perfectly legal to reverse engineer and copy a trade secret. A patent lasts only 20 years, but during that period, the protection is far stronger: independent invention is no defense in a patent suit.*
Now, again, most knife designs aren't patented, but if made in a country where intellectual property rights are acknowledged, knives that are too close to a competitor's product in design or appearance can lead to a suit against the copied product.
There was a lawsuit from Spyderco towards Benchmade about 2005 over the use of the round ("Spyder") hole on the AFCK, but since a legal agreement was reached, it's difficult to find details now.
(Interestingly enough, Benchmade won a patent infringement case of its own in 2011.)
Though some of the case is about mislabeling counterfeit knives, the fact that visual characteristics of a knife can be intellectual property is clearly explained here.
*the difference between these two would be particularly important on the particulars of a process like making INFI steel, whereas Cold Steel's branding of steel "Carbon V" is just applying their own brand name to whichever inexpensive but decent-performing steel they're using now. So, a competitor using identical steel wouldn't be breaking intellectual property laws by using the same steel, but he would be in trademark violation if he called any steel he used "Carbon V" without permission from Cold Steel.
A well-kept trade secret could theoretically last forever. But there is a risk. Unlike with patents, it is perfectly legal to reverse engineer and copy a trade secret. A patent lasts only 20 years, but during that period, the protection is far stronger: independent invention is no defense in a patent suit.*
Now, again, most knife designs aren't patented, but if made in a country where intellectual property rights are acknowledged, knives that are too close to a competitor's product in design or appearance can lead to a suit against the copied product.
There was a lawsuit from Spyderco towards Benchmade about 2005 over the use of the round ("Spyder") hole on the AFCK, but since a legal agreement was reached, it's difficult to find details now.
(Interestingly enough, Benchmade won a patent infringement case of its own in 2011.)
Though some of the case is about mislabeling counterfeit knives, the fact that visual characteristics of a knife can be intellectual property is clearly explained here.
*the difference between these two would be particularly important on the particulars of a process like making INFI steel, whereas Cold Steel's branding of steel "Carbon V" is just applying their own brand name to whichever inexpensive but decent-performing steel they're using now. So, a competitor using identical steel wouldn't be breaking intellectual property laws by using the same steel, but he would be in trademark violation if he called any steel he used "Carbon V" without permission from Cold Steel.