Bill is right, technically there were no original "patch knives" only because they were not called a "patch knife" but rather a:
"Bag knife" - meaning any small knife carried in or on a possibles bag. Most had a sheath sewn to the back of the bag, but some on the side or front.
"Pouch knife" - same as bag knife.
"Poke blade" - same as bag knife with "poke" being another name for "bag".
"Strap knife" - only difference here is that the sheath was sewn to the front strap of the bag, pouch or poke.
There was no set style for this type of knife, they were generally any knife with a blade shorter than 6" and most commonly 3" to 5" and single edge. "The Kentucky Rifle Hunting Pouch" contains sever dozen pictures of original bags showing attached sheaths for small knives. The small knives were not used solely for cutting patches, they were used anytime the larger hunting knife would be impractical.