Inventions, just lke succeeding in any business requires taking calculated risks.
Should you disclosure your idea to others? Well, you can't make any money keeping it secret. In order to succeed at anything in life you have to take risks. The trick is to minimize risks.
A good first step is filing a patent application so you have your invention "on file" at the U.S. Patent Office. This gives you a filing date and a serial number for your invention.
Note that you do not get "patent rights" (i.e. the right to stop or exclude others from making, using, selling, or importing your invention in the issuing country) until a patent issues on your invention.
This is subject to a "retroactive damages" provision of patent law when your patent application is published and a party is put on notice wht they are curently doing will infringe your patent when issued. Note also that patents differ in "breadth of coverage" which affects what products are covered by your patent.
You can also ask the companies to sign Non-Disclosure Agreements (NDA) but don't be surprised if they say "NO!" What, after all, is in it for them (except the opportunity to get sued). Most companies will not sign an NDA, and if they will, they will sign only their form (which is really more of a disclosure agreement, not an NDA).
So, you are left with three choices: 1) keep your idea secret and wait until a patent issues (if ever.. not a certainty) on your invention, taking no risks, and making no money; 2) disclose your invention after you have taken the precautions lasted above to minimize your risk.
The first choice does not make sense in most situations. If a patent does not issue or has a limited breadth of coverage, you cannot stop copiers anyways. It can take years to get a patent. By then, the technology of your invention might be obsolete.
I suggest that prior to disclosing your invention to potential manufacturers or distributors that you file a patent application and then try to have them sign a non-disclosure agreement. This should help prevent those that you do disclose to from taking the idea further without your permission.
Also, be aware that others can "knock off" a product while it is pending. It is only after your patent issues that you can go after the "knock off" artists provided that there is a case of infringement. However, marking your products for which you have a patent appication filed as "Patent Pending" or "Patent Applied For" tends to discourage "less savvy" persons and companies from copying them.