Anyone can separate inventions into the following groups:
Level 1: Regular
Routine design problems solved (after a few dozen attempts) by methods well known within the specialty or inside a company (About 32% of the solutions occurred at this level.)
Example: The ability to change the size of weighted (lead) shoes for divers to fit different size feet by adjusting their length. (It is curious that this development occurred only in the 1960's, some 70 years after the invention of divers' shoes; i.e., for 70 years all divers used uncomfortable shoes of the same size.)
Level 2: Improvement
Development of the existing system, usually with non-common methods from the same industry with some knowledge additional to the inventor specialization (about 45% of solutions; a few hundred attempts)
Examples: (a) Potatoes can rot as a result of bacteria naturally present on their surface. Heating in boiling water kills the bacteria, but too much heat will cook the inside of the potatoes. The potatoes can be exposed for a short time (5 seconds) to a 700°C flame. This kills the surface bacteria without affecting the inside of the potatoes. (b) Welding two different metals together (such as copper and aluminum) can present a challenge. One useful technique is to use a spacer made of a metal which can be welded to both of the incompatible metals.
Level 3: Invention inside paradigm
Essential improvement of the existing system utilizing the methods / knowledge from other fields, sometimes far from the existing system’s industry (18%; dozens of thousand attempts)
Examples: (a) Cattle feed consists of various cut grasses which have been mixed with special equipment. Producing the grass mixture by sowing the various grasses together yields a crop which is difficult to till. Further-more, one grass species may suppress the others. The grasses can be sown in narrow parallel strips, and harvested across the strips. Thus, the grasses will get mixed in the receiving bin of the mower. (b) Commonly used methods for moving molten, chemically-active salts require the use of ex-pensive devices. A more economical method uses an air-fuel mixture that is pumped into the bottom of the boiling solution, forming bubbles. As the bubbles rise, they move the salts to the top. Since the bubbles also burn, the molten salts do not solidify. (c) An electromechanical relay element has a finite number of switching cycles. Substituting a cheap semiconductor relay element increases the number of switching cycles and decreases the switching time and weight of device.
Level 4: Breakthrough outside paradigm
Creating a new generation of the system, the solution usually cannot be obtained in technology, but can be found in science (4%; several hundred of thousand attempts)
Examples: Microscope, steam engine, photocopy machine, atomic force microscope.
Level 5: Discovery
Pioneer invention of an radically new system usually based on a major discovery in some basic (or new) science less than 1%, millions attempts) .
Examples: Discovery of x-rays, penicillin, DNA, laser, high-Tc superconductors.
The grade of similar inventions decrease with time, especially for levels 2-4.