US6155695 specifies decorative lighting. Would a similar product that serves a clearly non-decorative purpose have any risk of infringing this patent?
Would a non-decorative version be patentable?
To infringe on a patent, you need to implement every part of at least one claim. In the cited patent here is the first claim.
In combination, a decorative light and a light cover placed thereover, said combination comprising:
a light bulb having a filament for producing light of a first color;
a light bulb base connected to said light bulb for supporting said bulb;
at least one conductor communicating with said filament for providing a source of power thereto; and
a flexible light cover of a desired color placed over said light bulb, said light cover having a continuous side wall in frictional contact with said light bulb, and extending over said light bulb, and an integral cap attached to said continuous side wall, said light cover causing said light of a first color to be changed in color to a second different color;
a receptacle having an opening for receiving said light bulb base; and
at least one insulated wire electrically connected to said receptacle.
I would guess that non-decorative applications would be clear of this claim, but there are quite a few steps listed and avoiding any of them would likewise avoid infringement. Of course, you need to consider the other claims particularly 5 and 6 which are the other independent claims.
As for whether a non decorative use would be patentable, it really depends on two questions. Is the new application novel and is it non-obvious. To be novel, you have to have some inventive step. In my mind just taking an existing patent and removing the word "decorative" would not sufficiently novel. You could also be blocked from patenting on the grounds of obviousness. This means would someone skilled in the field find the new application obvious to implement given the prior art. I am not a patent lawyer, but my guess is that obtaining such a patent would be unlikely. Also, you need to evaluate whether there are other related patents and prior art to consider.