Evolution of the Cable Locking System and an Alternative Plan

When the idea of the cable locking system first came to me, it was to assemble and disassemble the means of holding the beams for the deck of a suspension bridge. How it was to be produced and what that might cost were of secondary consideration then. After working out just how I would have it made, I found a manufacturer that would do the job, and it was a reasonable cost.

It was a long process getting the patent for the cable locking system, but once that was accomplished we set about writing a book – Building a Small Cable Suspension Bridge with the Cable Locking System. The book was meant to promote the cable locking system and talk about all the steps we took to build the bridge.

I never thought there was much of a market for small suspension bridges, after all, how many people have a creek or ravine that they need to cross on their property? But after we published the book, there was a fair amount of interest in the cable locking system, mostly in the United States, but also from around the globe. And we had put in the book, and on our website, “contact us if you are interested in the CLS.”

About a year later, some people were asking about purchasing CLS components. We had three companies that could do the job, but we were only considering about 50 “units.” After some waiting they gave quotes on 100 or 300 units. The prices seemed expensive, and after informing the interested buyers, we heard no more from them.

The cost of production seemed to be a problem and we weren’t willing to buy and store parts in case someone ordered them. So I wondered: Can I simplify the CLS so that it could be produced more cheaply, and by just about anyone, with a minimum of tools? I came up with a possible answer.

The “inverse” CLS employs the cable locking system but places it somewhat in reverse of the
original application. It eliminates some of the materials and simplifies the manufacturing process while still using the patented cable locking system. Here’s a drawing:


The new system has some drawbacks, in that it has to be placed beneath the beam during assembly as opposed to slipping the beam into the original CLS. Also, the beam has to be pre-drilled and a PVC tubing should be inserted to protect the cable from corrosion. But overall, assembly is not all that different from the original cable locking system design.

Picture a swing: hung by two ropes (chains, cables, etc) one on each side. To assemble the “inverse” system, while cradling the beam in your lap, grasp the first of the two suspender cables, push it through the pre-drilled hole ( with tube protector) such that the cable can be inserted through the “inverse” CLS. Pull tight. Proceed to other side and repeat. A screw through the side of the inverse will lock it to the beam so that it can’t move about. I actually use a screw in my original design, if you noticed in the book.

Hopefully this design will be something more affordable and something that people can have made locally without a lot of hassle. I prefer the original set-up for ease of assembling “on the fly” and less intrusion to the beam, but this is an option for you to consider.

Thanks for stopping by! Be sure to check out the book. It includes some cool ideas that apply to other projects, like how to put a really tall post into a deep hole when you aren’t that tall. Amazon has the book on sale for about $12.00 right now. Here is the link:

Building a Small Cable Suspension Bridge with the Cable Locking System

Images, diagrams, and text copyright 2013 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.

Patent for Sale!

We’ve been, off and on, trying to market the patent for my cable locking system. If you don’t know what that is, please visit http://www.wildcatman.com for information about the integral part of my suspension bridge. We had minor interest from Bridges to Prosperity (http://www.bridgestoprosperity.org/), but that’s about it so far. So, if you know anyone who wants to manufacture a cool cable locking system and send me a percentage of the profits, let me know!

Here’s a video Robin created about the system – http://www.youtube.com/watch?v=cLXrzC9K5wQ

Here’s the history of how I wound up with a patent for sale. It all started when I decided to apply for a utility patent. With no knowledge or experience in patents, Robin and I hired a patent attorney to do the initial search. They determined that it had never been done and, it also passed the test for being “unobvious” and therefore was patentable, in their expert opinion.

We knew that hiring an attorney to actually write the patent would cost more money than we had, but when we talked to these people on the phone they assured us that we could write it ourselves and do the drawings and they would charge a much smaller fee to help from that point on.

However, once the search was done, they wanted another $3-5,000 to pursue the patent for us. They denied ever telling us they would simply assist in some capacity. So we told them no thanks and bought David Pressman’s book, Patent it Yourself, (http://www.amazon.com/Patent-It-Yourself-Step-Step/dp/1413317197) and got to work. It took us a full month to get it all done to the best of our knowledge and understanding of the process. We wrote a check to the USPTO and sent them our specs, abstract, drawings, and claims – the main components of a patent application. Then we waited about 18 months (which they promise is typical). We did file online so could check in to see if any action had been done.

The eighteen months passed and our patent was rejected, with a “non- final” action. Our $500.00 patent search had failed to turn up another patent that the USPTO found and decided was too much like my invention. I looked at it and said no way, so the games began. We answered with revised claims, and it was rejected again. We filed a continued patent examination (get David’s book if you want more information) and tried again.

We got some help from the USPTO help-line who assured us that patent examiners are told to help people who weren’t using a patent attorney. That is, if we were lucky enough to get someone who was sympathetic. While our examiner did appear to be on our side, her letters always suggested that we needed to hire an attorney and she didn’t seem all that sympathetic. Considering that the attorney we did hire blew it on the patent search, we weren’t willing to spend the money even if we had it. I called the examiner and we had a few long conversations. It finally all came down to including the cable in the claims. Without it, my system did not lock.

Finally the examiner agreed to show our new claims to her supervisor. We waited some more, then one morning there was a message on our answering machine from the examiner. Her supervisor had told her she should not have rejected our most recent claim. She offered to rewrite it to include some things she felt needed to be there. We still have that recording.


On November 15, 2010, the cable locking system was allowed for a U.S. patent. It took almost three years and about $2,000. An attorney would have cost far more. For instance, had we hired the one who did the search, they would have charged $3-5,000 for the initial patent application. Then when it was rejected for the same reasons ours was rejected, they would have dinged us another several thousand to rewrite it and argue with the examiner. They all have the disclaimer that they can’t guarantee the initial patent search is thorough. All we can say about the entire patent process for the do-it-yourselfer is, “Good luck, and don’t give up!”

You can read more about all this in my book, Building a Small Cable Suspension Bridge. There is a link to purchase it on my website: http://www.wildcatman.com.

Images, diagrams, and text copyright 2013 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.