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Limited Slip Differential

Limited Slip Differential

Limited Slip Differential

I have invented (on paper) a limited slip differential that is completely geared and does not use any clutches, hydraulics, sensors, or electronics.  It is simply a very unique arrangement of gears that has 1 input and 2 outputs.  The outputs can spin at different speeds.  As one output slows down, the other speeds up by an equal amount.  The difference in the output speeds is limited to 50% difference (or a different percent--based on the gear ratios)--hence it is a limited slip.  Currently the design is just in my head, on paper, and i did a 3-d simulation to confirm that it would work.  Is this significant?  I have searched the US patent site and I can't find anything else that accomplishes this.  The Torsen system is kind of similar but that works on the principle of sending more torque to the side with the most resistance, and really isn't a limited slip (if one wheel is off the ground it spins freely, and the other wheel doesn't move).  All of the other designs I found use friction plates or electronics.  Patents cost a few thousand dollars--would this be worth patenting with the hopes that i could sell the patent?  I am an engineer, but in an non-automotive field.  Thanks for any advice.  

RE: Limited Slip Differential

I think computers might apply the brake to the spinning wheel in most cars with ABS in the near future. It will all be incorporated into the stability control system.


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RE: Limited Slip Differential

I for one am not impressed by systems that burn up your brakes & waste power to maintain traction but that does seem to be the trend these days since all the hardware is already there for ABS & stability control.  It costs the OEM nothing but a little software code.  It costs the owner in higher maintenance fees on non-warranty "wear items".

RE: Limited Slip Differential

I read that the Quaife has a spring in the middle of it...I'm not sure if thats true though.  My idea isn't the same as the Torsen (I found an animation of that) or the Quaife or Eaton Truetrac.  But it does have some similarities.  I don't know how similar it can be and still get a patent.  I know that my design would have a preset maximum percent speed difference between the two wheels (50% for example), which apparently the others don't do.  
The second poster mentioned electronically controlled limited slip by using the ABS controls to apply one of the brakes.  It has been around for at least 10 years now (I remember Mercedes using it on the M-class SUV in 98).  It works ok but has some limitations.  Audi and other high-end cars still use the Torsen so there must be an advantage to it.  

RE: Limited Slip Differential

I would suggest you talk to a patent attorney before you have any more public discussion. Take what you posted and the responses to the attorney with you. One or two hours of attorney time is not all that much money for the advice you will receive.
As to whether it is marketable, that is always a very difficult question to answer. Often inventors have to apply for a patent ($5K-$15K depending on complexity), and then pay for a working prototype. Then the patent attorney often has to argue your case to get the patent issued. This can take several years. Sometimes states have offices that help inventors bring their inventions to market. You can also talk to your local SCORE office, which is part of the SBA.
Dana, before bankruptcy, would evaluate geared inventions for no charge, and give you an opinion if they would like to joint venture or not. I do not know if they still offer this program, and I am not sure if they were liquidated as a business or not.
You can approach those companies that make limited slip differentials, and ask if they would be willing to review you invention. Make sure anything you supply is labeled proprietary, and talk to a patent attorney first. Many companies will not review data labeled as proprietary, as they feel it opens them up to unfair lawsuits.
Pursuing inventions is part of the American dream, but it is a very difficult road.

RE: Limited Slip Differential

Can you patent it in Mexico? or Cuba, or any Eastern European country? Make sure to have included in the list of applicable countries, USA! Few extra bucks, but quick and sure patent.

RE: Limited Slip Differential

Modern countries typically have their own patent processes. So if you want one for the USA, you have to file it to the USA.

RE: Limited Slip Differential


In most developed countries you can take out a local patent and apply to also register in many specified countries, at an extra cost of course.

I really doubt that this is worth the cost on several grounds, being:-

It sounds like it might not pass an innovation test.

It will be competing in the market with a large range of existing mechanical products, some of which offer similar performance.

It will also be competing with electronic devices at very little incremental increase to anything with ABS. These may not be technically nice, but they sound sophisticated and modern from a marketing standpoint and cost virtually nothing to include.

Most times such devices get so little actual use, that the increased running and maintenance costs get lost.


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