No, not necessarily. Patent applications are secret for at least 18 months (longer, if the applicant is not seeking foreign protection and requests non-publication) so there is at least an 18-month window during which you cannot have knowledge about pending applications. 1. You (or someone else) could ask the maker of the "similar product" if they have applied for patent protection. If not, then you might be free to make a competing product. If they tell you a patent application is pending, then you will need to see a patent attorney for help evaluating the risk of going forward and/or help you design-around the pending claims (designing around is completely lawful). 2. The safest course of action is to invest some time and money with a patent attorney (locally or anywhere in the country) who can do a formal search of the issued patents and published applications, to help evaluate the risks before you spend any more time and money on this new product design.
This comment is NOT LEGAL ADVICE and is posted for informational purposes only. I am not your attorney; you are not my client. Both you and any other person reading this comment SHOULD NOT RELY UPON this comment. Regardless of the information provided in this comment, any reader of this comment should CONSULT AN ATTORNEY to get the legal advice you are seeking.
Patent applications typically published 18 months after having been filed, but not always. So no patent search is every perfect. Plus, you need to worry about anything in the world -- patent or non-patent -- that could be like your concept.
I recommend having a patent attorney or patent agent do a patent search (preferably working with an established search company that has access to proprietary databases).
As to differences in design, it is hard to know the answer without taking a look at your invention and the one that you are worried about. Most attorneys, including myself, will talk to you for free.
Mr. Anderson's explanation is correct. I just wanted to add that you are in the clear unless and until a patent issues. If a patent application is pending, you are not prevented from practicing that which is disclosed in the patent. However, if a patent subsequently issues and what you are doing is covered by one or more of the claims in the issued patent, you would then be liable from infringement from the issue date forward. In addition, if the patent application is published at eighteen months and then a patent subsequently issues with the claims substantially identical to the claims as they were published, then you could be liable for pre-issuance damages (a reasonable royalty) to the extent you had actual notice of the published application. Either way, you should definitely speak with a patent attorney for a clearance search.
Disclaimer: This answer does not constitute legal advice and does not create an attorney-client relationship. You should not rely on this answer to resolve your particular legal issue, since different laws are applicable in each jurisdiction, and each set of facts are specific to a particular situation. As with any legal question, you should consult with an attorney licensed in the appropriate jurisdiction to evaluate your particular legal problem following a comprehensive consultation and review of all the facts and documents.
Design patents (as opposed to utility patents referred to by the other responders) do not publish unless and until a design patent issues. Thus, if there is a design patent on file, it would not publish at all until it is granted.
Your best bet is to speak with a patent lawyer about doing a clearance search to determine whether there is prior art that could immunize you against the possibility of being found to infringe a patent relating to your distinctive feature. The clearance will not likely be foolproof, but will give you a sense of the potential risk before you spend a lot of money marketing your design and may give you the opportunity to "tweak" your design now to further improve the chance of prevailing if you are later accused of infringing.
This information is intended to be general and educational in nature. It is not intended to be specific legal advice or establish an attorney-client relationship. I require a signed retainer agreement from a potential client to establish an attorney-client relationship and before I will provide specific legal representation.
You've already received very useful information from my colleagues [for free -- isn't this site great?].
I write only to note that most products in the marketplace are not protected by a patent. Which may be why you could not find a patent claiming the product that's similar to the design of your product.
Many times it does not make economic sense to spend money on patent protection for an invention embodied in a product that (1) won't be on the market for more than a few years or (2) undergoes design changes frequently.
Your own patent attorney should conduct a "freedom to operate" search of currently-in-force patents to make sure your product does not infringe anyone else's. If not, then you could discuss with him whether your product is patentable in light of all the other similar products that have ever been sold and, if yes, whether it makes economic sense for you to seek patent protection [or use that money for branding or manufacturing or distribution, etc].
The above response is general information ONLY and is not legal advice, does not form an attorney-client relationship, and should NOT be relied upon to take or refrain from taking any action. I am not your attorney. You should seek the advice of competent counsel before taking any action related to your inquiry.
Short Answer: Consult an Attorney
It appears that your invention concerns an aesthetic aspect of a product and you would thus be looking for protection of your invention as a design patent. The fact that you can't find a similar product is good news as far as patentability is concerned, but it is not enough. Remember, any prior work can potentially count against your and prevent you from obtaining a patent on your invention. I advise that you consult a patent attorney who will conduct a search of the prior art, identify the differences between your invention and the prior art and analyze as to whether the differences are enough to likely be patentable. Good Luck.