Finding historical patents on the Web
If you are looking for patent data from the period prior to the mid 1970s then only a limited amount of searching can be carried out on the web.
For extensive and thorough historical searches you will need to visit a patent library where a full range of hardcopy and microform searching aids are available. The most extensive collection of this type of material in the United Kingdom is held at the British Library while the other member libraries of the United Kingdom's Patent Information Network are also an excellent starting point for historical patent research. The United Kingdom Patent Office does not deal with patent enquiries of an historical nature.
It is difficult to establish the exact extent of historical coverage in the Esp@cenet worldwide database and to be sure of what data becomes searchable at what date. If in doubt you should assume that comprehensive coverage begins in the early 1970s. A chart in the "help" pages of Esp@cenet gives an indication on country and date coverage. The following information may also be of use.
British patents on Esp@cenet
Coverage of British patents in the Worldwide database (unlike Esp@cenet's Great Britain database which starts from 1979) is good from 1920 onwards and you should be able to pull up a copy of British patents from this date by a patent number search. You should also be able to make a search using the European Classification and in some cases key words from the title and abstract. Inventors may not be indexed in the inventor name field. The names of inventors who filed patent applications independently (i.e. not as employees) may be present in the patent applicant field. The names of inventors working for a company or organisation may be present in the patent applicant field but this is not always the case. Searches sometimes turn up a British patent earlier than 1920 but the information available is likely to be very restricted and a copy of the specification may not be available.
Other countries on Esp@cenet
You will also find early material from the United States, Germany, France and Switzerland in the Worldwide database. The date of the earliest material covered varies, as do the elements which are searchable. For instance all US patents from 1836 are available in facsimile but they are not searchable by classification code (European Classification) until 1920. On the other hand all German patents from 1877 onwards are available in facsimile and all of them can be searched by European Classification code as well as number.
US Patent and Trademark Office database
The USPTO database (Patent Full-Text and Full-Page Image Databases) carries images of all US patents from 1790 to date. However patents earlier than 1976 can only be searched by current US classification codes and by number