May 26, 2012 © Ron Katznelson & John Howells Inventing-around Edison’s incandescent lamp patent: evidence of patents’ role in stimulating downstream development Ron D. Katznelson1 and John Howells2 ABSTRACT We provide an anatomy of the influence of Edison’s incandescent lamp patent U.S. 223,898 on downstream development and show how subsequent inventor activity adjusts to the improved certainty provided by court decisions as to the boundaries of a patent’s claims. First, we show that court decisions upholding Edison’s patent generated a surge of patent filings in the incandescent lamp classes at the U.S. Patent Office. Second, by inspection of the specifications of these later patents we are able to categorize certain design-around efforts by their evasion of specific elements of the claims of Edison’s ‘898 patent. Third, by analysis of forward citation to these patents we show that regardless of these inventions’ commercial viability in the incandescent lamp market, some became important prior art for new technological fields and some laid the groundwork for the later successful substitute for Edison’s carbon filament. Fourthly, we show that the recent view that Edison’s patent gave the patent holder General Electric (GE) a dominant position in the incandescent lamp market is incorrect: we show that besides commercially-successful invention around the claims of this patent, data for GE’s market share, number of manufacturers in the field and lamp price erosion through the period of the Edison patent’s enforcement reveal GE’s market position to have been stable, even weakening through the period of patent enforcement. Lastly, we derive from our account criteria against which any allegation of development block should be assessed and illustrate their utility by refuting allegations that Edison’s patent blocked downstream development. Keywords: incandescent lamp, Edison, design-around, invention-around, downstream development, patent. Table of Contents 1 Introduction ................................................................................................................................................................................................. 2 2 Design around patents – an essential element of competition and innovation ........................................................................ 3 2.1 Certainty of patent claim boundaries is essential for design-around investments. ........................................................................ 5 2.2 Survey of empirical evidence of design-around outcomes and benefits ......................................................................................... 5 3 This study’s original contribution to empirical methods of evaluating design-around outcomes ...................................... 7 3.1 Data and methods .................................................................................................................................................................................. 9 3.2 The limitations of our study ................................................................................................................................................................ 11 4 Edison’s ‘898 pioneer patent – the historical and legal trajectory .............................................................................................. 11 4.1 The surge in non-infringing incandescent lamp development ....................................................................................................... 14 4.1.1 Stopper Lamps ............................................................................................................................................................................... 17 4.1.2 Lamps with no leading-in wires passing through the glass ....................................................................................................... 20 4.1.3 Gas-filled, or non-vacuum lamps ................................................................................................................................................. 22 4.1.4 Non-carbon filament lamps .......................................................................................................................................................... 23 4.2 The crowding field of electric incandescent lamp manufacturers .................................................................................................. 26 4.3 The price decline of incandescent lamps ........................................................................................................................................... 26 4.4 Edison/General Electric‘s incandescent lamp market share .......................................................................................................... 27 5 Improved certainty of Edison’s claim boundaries spurred design-around investments ...................................................... 28 6 Did Edison’s patent block downstream technology development? ........................................................................................... 29 6.1 A standard for determining whether patent-induced, downstream development block has occurred ..................................... 30 6.1.1 Whether commercial activity evidence supports a conclusion of blocking ........................................................................... 31 6.1.2 Whether the facts in alleged blocking cases lend themselves hypothetically to remedies purported to alleviate such blocking .................................................................................................................................................................................. 31 6.2 Commercial activity evidence in the Edison case shows that no downstream development block occurred ......................... 31 6.2.1 Close commercially feasible non-infringing substitutes were available ................................................................................... 31 6.2.2 The patent owner did not comprise the entire industry to which the patent pertained ....................................................... 32 6.2.3 The patent owner was not a ‗price maker‘ .................................................................................................................................. 33 6.2.4 The patent owner did not control technical advances in areas to which the patent pertained ........................................... 34 6.3 Was Edison‘s incandescent lamp patent a ‗blocking patent‘ in Great Britain? ............................................................................ 35 7 Conclusion - The study of Edison’s patent is the study of the patent system at work ......................................................... 37 Acknowledgements ........................................................................................................................................................................................... 38 References ............................................................................................................................................................................................................ 38 Appendix A – Electric lamp patent classifications ................................................................................................................................... 44 Appendix B – Downstream patents citing designs-around Edison’s patent .................................................................................... 46 1 Dr. Ron D. Katznelson is the president of Bi-Level Technologies, Encinitas, California, USA. [email protected]. No Company resources or funding were used for this work. Dr. Katznelson used his personal time and resources for this study. 2 Dr. John Howells is an Associate Professor at the Department of Business Administration Aarhus School of Business, Aarhus University, Aarhus, Denmark. [email protected]. 1 1 Introduction On November 4, 1879 Thomas A. Edison filed a patent application entitled ―Electric Lamp‖ with the U.S. Patent Office, which was granted as U.S. Pat. No. 223,898, on January 27, 1880 (hereinafter called ―the ‗898 patent‖). This patent was one of Edison‘s 424 patents on electric light and power generation3 and its significance was not readily apparent for several years. This paper presents an original analysis of the inventive activity directed at designing-around Edison‘s ‗898 incandescent lamp patent. We show that the attempt to enforce the Edison patent stimulated much downstream development work of varied commercial and technological significance. The originality of this study lies in the data we collect that reveals surges of patenting activity in the incandescent lamp patent classes after key events in the legal trajectory of Edison‘s patent; after his filing suit against an infringer in 1886 and especially after 1892 when the appeal court affirmed the 1891 decision and upheld the validity of Edison‘s patent. We analyze the patents that constitute the surge of patents after the 1891 court decision and find that much of the surge can be understood as a stimulated effort to design around particular elements captured in Claim 2 of Edison‘s patent – the then hardest claim in Edison‘s patent to circumvent. Furthermore, our novel forward-citation method and reading of a selection of these patents reveals that while some design-around work did not yield commercially viable alternatives to Edison‘s lamp, new technologies of later commercial significance were introduced to the public record,