From an entry in the 1874 work, Wiley's American iron trade manual of the leading iron industries of the United States: "Planing machines". It is entirely possible that these planing machines are for metalworking rather than woodworking.
Do not confuse this maker with Thomas Robinson & Son, a very large English manufacturer of woodworking machinery.
Information Sources
A Photo Index entry shows a 24-inch planer with "Wm. Robinson & Co. Lowell Mass / No. 3" cast into the cutterhead cover. The "3" is upside down.