Leg vise Parallel Guide Adjuster by Ancora Yacht Service

[Jack Curtis]

Doing a search for prior "art" is very time consuming, and a huge job for an individual. Made somewhat easier by the internet, but still a lot of work.

[David Bird]

(To the best of my layman's knowledge) under current US patent rules, the inventor must disclose prior art of which he is aware. But he is under no obligation to search for prior art that he doesn't know about. The USPTO will do their own search.

The risk to the inventor of not searching is that the Patent Office will find prior art, so the inventor loses his investment in preparing the application. Or worse, a challenger turns up valid prior art after the patent has issued, so the inventor loses his investment in the whole process.

A thorough search for prior art in the US patent record can be expensive. But a cursory search is easy. I do it all the time.

[Carl Beckett]

A provisional US patent can be filed for $110. The gives you a year to advance the art.

The USPTO is piloting a program for small business via the SBIR program. They wont write the patent for you but will assist with expedited review. (they recognize there is a problem with small/big business collaboration and first to file issues, so are wanting to help even the playing field some for the little guys).

I dont think an exhaustive search on prior art is a requirement. Of course its in your own best interest to do some, so that your claims arent completely redundant (read - worthless) over whats out there. At the end of it all it will come down to the few unique claims of your invention. (and remember, a patent doesnt give you the right to do anything - only prevents others from profiting from your idea - so to some extent if you are going to make a commercial product you should be doing a prior art search anyway because if you use any feature of someone elses claims then they can block you or lay claim to profits). This is part of the problem with the patent system - kinda a 'veto' system which doesnt always motivate someone to GO DO and advance a technology (way too much just buried in the corporate coffers)

So start a patent by listing the 'claims'. Meaning, what are the key elements that are unique to this invention. List these out. Then you can write background and body of the invention, and reference prior art on the non-unique aspects.

My experience is you can patent about anything if you want (it can come down to the shape of the bracket being unique). Which might not be all that useful from a commercial standpoint, but then again most patents arent (and sometimes a patent on a very minor detail is useful just to prevent an offshore manufacturer from using the VERY SAME MOLDS/CASTINGS to produce a knockoff, after the original company has PAID for these molds!

[Derek Cohen]

I wrote:

First, I noticed that the parallel guide moved more smoothly when the tension on the chain was relaxed. So I relaxed the chain progressively until it was floppy. Then very floppy.

Then it became apparent that the chain tensions itself when the chop is holding a board. This is the important part because the chain must position and lock the chop in the same way as the cross bar in a hole. And it appears to do so , regardless of how floppy the chain is set.

And Jim replied ..

Derek the floppier the chain is more out of parallel the jaw will be when tension is applied. There should be just enough tension on the chain so the jaw is parallel at the optimum clamping strength. You might try lightly clamping a piece of wood, measure the parallelism of the jaw then adjust the nuts to correct. I think you might be able to turn the nuts without unclamping but give it a go.

Hi Jim

The best way to examine what I described is to do so visually. So here I a bunch of pictures.

This is what I meant by a floppy chain ..



Here is the position of the chop - just slightly open. The chop looks fairly parallel, but admittedly it is not doing any work. Still, it opens parallel.



Now if I insert a thin board ...



... the chain tightens up ..



Here is a wider board. I am attempting to assess for parallel. The easiest way is to see if both the sides of the board are held evenly ..



This board is easier to see. I would say it is perfectly parallel (where it counts - at the chop) ..



Here is another example. With the chop closed down but not tightly, it is apparent that the top is toed in slightly. The chain is loose, indicating that there is no tension ..



Now I add a quarter turn on the screw. The chain tensions, and the chop pulls square ...



Throughout this process, the leg vise is working very sweetly.

What do you think?

Regards from Perth

Derek

[Paul Incognito]

What do you think?

Regards from Perth

Derek

I think I want one of these!
Please let us know when they'll be available for purchase.
Paul

[Carl Beckett]

I think I want one of these!
Please let us know when they'll be available for purchase.
Paul

Yes, what Paul says...... +1

[Jim Ritter]

Thanks again Derek you do have a knack for conveying information. That is definitely looser than my chain but the difference could be I have 18" between the screw and the chop and yours is 12". I most likely have a bit more flex in the chop. As long as it grips when you ask it to and tensions up parallel I think you found your sweet spot for your combination of chop, beam spacing, screw etc.

[Paul Erickson]

Derek, What size chain is that? It looks to be larger than a bicycle chain. I'm also wondering if there isn't a way of incorporating the internal wheel guide with the chain pulley? Perhaps with a grooved wheel?

cheers, Paul

[Jim Ritter]

Hi Paul, the chain is a #35 roller chain. It is much stronger than a bicycle chain,and has a little more room between the side plates. I tried to combine a sprocket and roller, just couldn't figure a good way to do it. The two different diameters would turn at different rates. I only have one roller on mine, it is on the inside of the leg on the underside. Placed on the inside the bulk of the weight of the chop etc wants to tip the works into the bench but the chain resist that force. Mine works very smooth, one finger operation. A friend on another forum is installing it in conjunction with BenchCrafted glide screw. Depending on the spacing between the screw and the top of the beam the forces on the chain can get pretty high. I measured 600# where Derek has his placed. Mine are further apart and the potential is 400#. I would discourage the use of a bicycle chain.
Jim

[Derek Cohen]

Hi Paul

I was hoping that Jim would answer first since he did all the work designing the mechanism.

What can I add? Well, I was initially a little concerned that a roller would not spin as smoothly as a sprocket. Jim has a sprocket on his leg vise which he hand made as there was nothing small enough on the market. When the production prototype came along, the solution was to use a roller since this would be significantly cheaper to make. I remained concerned that it would not work as well, but trusted Jim's judgement. I do not have a sprocket to compare, but the roller works very well, and I doubt that anyone would remain concerned after using it.

With regard the force on the chain, what I can offer is the experience of snapping the wooden dowel I was using when the parallel guide was tightened a touch more than I should have (and not nearly as much as it could have been). This dowel was 1/2" in diameter and made from Wandoo, a West Australian timber that rivals steel! It snapped as if it was made from Pine. Clearly there is a lot more power in a leg vise than one realises. Go with a thicker chain.

Regards from Perth

Derek

[Paul Erickson]

Thanks Jim and Derek,

Now I'll just have to find a local source for #35 roller chain.

cheers, Paul

[Paul Erickson]

Hi Derek,

I notice that you have what looks like leather in the inside faces of your vise. I am assuming that you install it with the rough side out for better holding, is that correct?

cheers, Paul

[Paul Erickson]

Hi Derek, I don't think you need to rush into this. I'll make up some brackets here and give it a try. On yours if you add spacers to move the sprocket out it will impinge on the working space of the vise. Unless your new beam is longer than I think. A spacer and longer screws might introduce a source of flex in that area that might be of some concern. Is there room to put a roller under the beam on the inside, like I fitted to mine? I would try that first.

Hi Jim,

Any chance of seeing a picture of how you have your roller setup? I am having trouble seeing how it doesn't want to cause the vise to tilt away from the bench.

cheers, Paul

[Jeff Wittrock]

Jim,

I would just like to say again that I think this is a very clever idea. I hope that you are able to successfully produce and market this as a product. I love having a leg vice on my bench. At least for the type of work I do, there are very few times when I find myself needing (wanting) a vice other than leg vice and wagon vice I have. I think anything that removes some of the inconvenience of using a manual pin in the parallel guide while not being overly complicated is going to be a winner.

Good luck

[Jim Ritter]

Paul check your PM. Here is a photo of the sprockets I'm having produced.



Derek.. I'll send you the production sprockets when they come in. I like them much better. They will be a straight replacement for what you have.