Hi Bertho,
Yes, I find that really amazing! If that's all it takes to get a patent, my version would be easy to patent with all the changes I made. I wonder why they didn't think of soldering the balls to the board. That is way easier than soldering a wire to the balls. Since I am publishing my plans right here and very soon on a web page, I will declare my design as public domain. The way I understand it is, if you publish complete plans for something and declare it as public domain, nobody can patent it. I don't hold much stock in patents anyway. All a patent does is give you the right to sue anyone that you think is violating your patent. From what I hear, you can expect to lay out $25,000 up front just to begin a patent lawsuit. So, in my opinion, it isn't worth patenting unless you think you are going to have a market big enough to expect to make millions off it. I don't think the market for digitizing probes is that big. So, just for the sake of public domain, I hereby declare my design (and as much of it as I have already published here and on my site) to be in the public domain.
I think my idea of mounting the balls on the top side of the PC board (not to mention soldering them to the board) makes more sense. And also my idea to make the plane of the PC board adjustable to compensate for the misalignment of various probes is a good idea -- it makes it possible to align your spindle with what you are probing rather than to wherever the tip of the probe is in relationship to the axis of the spindle. Without the adjustment, the probe is useless as an x,y positioning instrument and only good for scanning. It would take incredible amounts of precicion to manufacture a probe that is completely concentric to the spindle of your machine, especially if you have different stylii, so make it adjustable and save the headache!
I am considering offering probes of my design for sale at a really low price compared to what is out there now. The cheapest I've seen on the web so far are around $295. I think I can produce and sell mine for maybe $150 or less.
I just looked at the Renishaw paper you linked to. They obviously have a lot of time into making a well-built probe. It's no wonder they charge so much for them. I wonder if their probe tips are always exactly on the axis of the spindle they are mounted in?
Here's a 0.25 inch square section of the back of a dime that I scanned with my latest prototype. The scan was done using 0.001" steps in the x and y axes for a total of 62,500 elevation samples. The point cloud generated by Mach3 (using the digitzing wizard that is included with those other wizards, not the add-on one that you download from Artsoft -- I can't get that one to work at all!), was taken into Global Mapper and displayed in a 3-D projection with "Atlas Shading" which applies colors according to elevation like maps in an atlas. I also added some vertical exaggeration to emphasize the elevation differences (exaggeration here is 5.5 times). You can see the red color indicates higher elevation as you move toward the right front corner. This is because the thickness of the dime is greater toward the edges. You may also notice that the scan is cleaner looking in about the first half of the scan (the half closet to you in the image). Up about 3/4 of the way you can see where there is a stripe where the elevations were sampled wrong and there is a valley cutting through the oak leaves. I think I may know what caused this -- not sure yet though -- not going to try to guess the real reason at this point. I think this image demonstrates a good degree of accuracy -- close enough for any practical use of the probe in my opinion. We're talking errors less than the thickness of oak leaves on the back of a dime!