The Proximity Fuze: Whose Brainchild?

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The Proximity Fuze

Whose Brainchild?

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The month was May, the year 1940.

Poland had been crushed. The French ^nes at Sedan and on the Meuse had been broken, the Battle of France rumbled relent­lessly to its dismal finish. The agony and glory °f Dunkirk loomed as the British nation sum­moned Winston Churchill to lead it to its ^rendezvous with destiny. Scientific brain­power as well as manpower would play an 'niportant role in the mortal struggle. During the ominous interlude of the fleeting English ^sPring presaging the Battle of Britain, Britons forged the weapons for the coming conflict ^which Churchill would one day characterize ^as “the Wizard War.”

At the Air Defense Experimental Establish­ment, Christchurch, England, William A. S. huteinent, Edward S. Shire, and Amherst H. Thomson conceived a fuze which would detonate at closest approach to its target. By mid-May, they had prepared a secret mem- °^randum to the British Ministry of Aviation ^escribing the basic concept of their inven- ^tlQn. In their words:

The fuze is designed to operate on the in­tensity of the reflected radio wave received horn the target aircraft, a transmitter in­corporated in the fuze providing the radiation °f RF energy. In practice the function of transmitter and receiver are combined in one ^valve [tube] in a manner to be described. The aerial which is also common to the two func­tions is the outer case of the entire projectile. The frequency being chosen so that the pro­jectile with fuze resonates as a full-wave aerial. The frequency is about 125 megacycles but since the aerial has low Q, variation of ,¹⁰% in frequency shows neglibible differences ^ltl performance. The polar diagram of the aerial is used to obtain the correct “firing dia­gram” round the target for the fragmentation ²°ne of the shell. The power supply for the ap­paratus is from batteries within the fuze and switching on projection is accomplished by in­ertia switches operating on the acceleration of the projectile. The shell is detonated by means of an electric fuze connected in the anode of a thyratron which is caused to strike by the re­ceived signal.

Theoretical calculations indicated that a projectile proximity fuze could be arranged to set off an explosive charge upon reception by the receiver of radio frequency energy transmitted from the aerial and reflected from the target.

Within days of the conception, a “bread­board” circuit was constructed by the inven­tors and crudely but successfully tested in the laboratory by waving a piece of tin sheet to simulate a target. A circuit was then coupled to a thyratron trigger operating a camera and mounted on a tower. Aircraft were flown past to determine the distance at which triggering took place. Encouraged by the results of these tests, arrangements were made in early June for the procurement of a number of fuzes for test purposes from Electrical and Musical Industries, Ltd. Fuzes incorporated into unrotated projectiles were fired at targets supported by captive balloons with additional encouraging results. The principle was proven.

Sir John Douglas Cockcroft, Assistant Di­rector of Research, Ministry of Supply, and Director of British research in radar and elec­tronics, was kept informed of weekly progress.

President Franklin D. Roosevelt had estab­lished in the United States the National Defense Research Committee (NDRC) to apply the scientific talent of the nation to the problem of revitalizing a war capability that some feared had lain too long dormant. Recognizing the common peril, Roosevelt and Churchill entered into an understanding providing for exchange of scientific informa­tion. Despite the informal nature of this un­derstanding (or, perhaps because of it), in­formation exchange was full and effective. The British scientific mission, headed by Sir Henry Tizard, came to the United States in late August 1940 for the purpose of com­municating information which would further the war preparedness of the United States and assist defense efforts in Great Britain.^[1]

Professor Cockcroft was a member of this mission. He carried with him the secret de­tails of the radio proximity fuze work in Eng­land. On 17 September 1940, he briefly de­scribed the invention to Captain Wilford B. E. Goulett, Electronics Officer at the Naval Research Laboratory. Two days later, he ex­plained it in detail to Dr. Merle A. Tuve of the Carnegie Institute and Chairman of Sec­tion T, Division A, NDRC. Tuve was briefed on the latest results of the British fuze work at Christchurch.^[2] Excited by the possibilities of such a fuze, he instructed his associate, Dr. Richard B. Roberts, to duplicate the circuitry tested in Britain. When bench-tested, it again operated successfully. Thereafter, with co­workers, Henry H. Porter and Dr. Robert B. Brode, Roberts devoted his full time to de­velopment of the fuze.

Tuve recognized that his Section T might obtain valuable assistance from the elec­tronics experts at the National Bureau of Standards. He invited Harry Diamond and Wilford S. Hinman, Jr., of NBS to take charge of a group to work on the project indepen­dently but in parallel with other groups. In mid-December 1940, Diamond was briefed on the project he was about to undertake and brought up to date on the previous work of the British. Up to this time the radio en­gineers at NBS had done no work on the proximity fuze.

Lloyd Berkner of Tuve’s staff had already set to work on a variation of the fuze using separate tubes for transmission and reception, which had the theoretical advantage that the transmitter could be as powerful as desired and the receiver adjusted independently' Diamond chose to pursue the Berkner ap­proach not only because of the advantages de­rived from being able to make the receiver separately adjustable from the transmitter but also because it was thought that sufficient attention was being given by Roberts to the j combined oscillator-detector circuit approach Hinman and Diamond proceeded to develop and build fuzes which, though modified, con­tained in combination the elements of the British invention. Six bombs containing the modified Diamond-Hinman fuze were sue- j cessfully tested against water targets on 6 May 1941.

The May test did not resolve difficulties as­sociated with anti-aircraft fuzes. The twh problems of microphonics and failure of tubes caused by vibration and acceleration re­quired detailed testing of components to de­velop an operational fuze for such shells- Many scientists contributed improvements which were incorporated into the ultimate solution. Components were improved but the basic concept of the invention remained. De­velopment of special rugged tubes was aug' mented by a contract with Bell Telephone ¹ Laboratories. Marshall, of Raytheon, and Dr- Dave Mitchell, of Columbia, also contributed to the studies. The University of Virginia ’ loaned its centrifuge to subject the tube fila' ments to simulated flight conditions. (A larger centrifuge was eventually built speci­fically for the program). Guns to fire the tubes vertically were built and vertical shots to test; tubes and components commenced in Decent' j ber 1940 at a farm in Vienna, Virginia.

The fuze for anti-aircraft shells was con- sidcrcd next in importance to the develop' ment of radar and ahead of all other prob' | lems being considered by NDRC. A high <R' gree of secrecy therefore surrounded the ffiz^e work. Every effort was made to prevent every' one except key personnel in Section T, NDRG from associating the electronics work with ordnance devices. Despite the highly secU¹ * nature of the invention, the U. S. and U. j groups were in continual contact and reports | of tests and suggestions for improvements wef^e j exchanged and discussed.

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Interference. On 31 August 1953, the Pateflj Office declared a three party “Interference proceeding between Butement, Shire, an¹ Thomson and Merle A. Tuve of NDRC, a'¹⁰ Russell Varian to determine priority of i”' ventorship of the fuze.

one year subsequent to the foreign applica­tion, and the foreign patent was granted, no patent could thereafter be obtained in the United States. On 30 August 1945, the Com­missioner of Patents issued a so-called “Gen­eral Rescinding Order” which abolished all such orders of secrecy imposed upon wartime patent applications, except those which the Commissioner specifically excepted by written notice prior to 30 November 1945. This date passed without notification. The American attorney for the applicants therefore notified the British authorities that the U. S. Patent Office had declassified the application. The British patent application was declassified and then “accepted” and published on 25 Feb­ruary 1947 as the final steps preparatory to the grant of the British patent. This publica­tion affords the public an opportunity to bring to the attention of the Patent Office addi­tional factors bearing on the patentability of the invention.

The prosecution of the U. S. patent ap­plication continued until the Patent Office also notified the inventors that the invention was patentable. However, three days before this notification, on 27 June 1947, the As­sistant Commissioner of Patents “excepted” the Secrecy Order from the provisions of the General Rescinding Order and restored it to full force and effect. The inventors’ attorney argued against reiinposition of secrecy since that the invention had been fully described in the published British application. The Patent Office, nonetheless, maintained the classified status of the U. S. application.

Recognizing that the grant of a British patent would destroy the right to obtain an American patent, officials of the Ministry of Supply took steps to delay the British grant. At the same time, the American attorney saw a means of escape. The Boykin Act of 1946 operated to prevent loss of patent rights owing to delays caused by war. The Act extended until February 1948, the statutory one-year period during which an applicant would be permitted to claim the date of his first for- eign-filed application as his effective filing date in the United States. The benefits of the Act were duly claimed and the inventors were granted the effective filing date of the British application.

The Boykin Act contained two additional

A graduate of the University of Rochester in 1953, Doctor Brennan received his Juris Doctor degree from Georg^e' town Law Center in 1958. H^e studied at the Institute fo^f Foreign and International TradeLawat the University d Frankfurt, Germany, during the academic year 1959-1960’ He was the Director of th* U. S. Navy’s European Patent Program in London from 1961 to 1965 when he began his current assign' ment as Staff Attorney, Assistant Chief of Naval R^e" search for Patents.

provisions: No patent issued under the Ac¹ could extend for a longer term than 20 yeah from the filing date of the first foreign ap' plication. The second proviso was of mor^e immediate concern. No patent issued unde’ the Act could serve as a basis for a claii” against the U. S. government. Although th^e British Government had granted rights to th^e U. S. government for use of the fuze during World War II, it had not granted any righ¹ to use the invention after the war. Postwar royalties could amount to a great deal.

During the period 1947-1953, the British government repeatedly attempted to have the U. S. application declassified. In 1953, th^e British and American Governments agreed ^t0 grant reciprocal royalty-free licenses for d^e' fense purposes in any patents which they owned. Thus, the prospect of licensing U- ^ governmental use of the invention evaporated-

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Faced with an expensive interference cd¹' test and having no prospect of royalty incd”^e from the U. S. government by virtue of 1953 Patent Interchange Agreement (a^,lC| the special provision in the Boykin Act), ^ British government offered the U. S. gover¹¹' ment title to the application if in return it ^a5’ sumed the costs of its prosecution.

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The Proximity Fuze: Whose Brainchild? 77

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partment attorney in charge of the case elected to proceed in the Interference on the basis of the Butement application. The Tuve application was withdrawn from the contest and the broad claims deleted. Tuve was then ’ssued a patent containing claims directed to the specific improvements he contributed.

From December 1953, until the Secrecy Order was finally rescinded in January 1959, the case lay dormant in the Patent Office. However, government attorneys were me­thodically searching government archives and fequesting that records be located and pre­served for use in the coming contest. In at­tempting to prove that Butement et at were the first inventors, the government was pre­^Sented with a monumental task. The burden °f proof on Butement, Shire, and Thomson tfas unusually onerous. Varian had filed a H. S. patent application prior to the date of their British application. They were required to prove that they had first conceived the in­tention and had been diligently attempting t° “reduce it to practice” continuously from ^a time just prior to Varian’s entry into the ^beld until they had actually reduced the in­tention to practice in 1942.

Furthermore, proof of conception in Britain tt^s meaningless under U. S. law. It had to be Proven that the concept was introduced into ^tbc United States at an early date and that, ^a^^er introduction of the concept into the J-mited States, Tuve and his associate had ^ecn diligent in attempting to reduce the in- ^ntion to practice. In addition, it had been °^ne on behalf of the British inventors. The Pain of evidence was unusually long and the ^abure of any link would be fatal. If the government lost the contest, liability to Brian’s assignee could run into millions of

dollars.

In preparing the government’s case, Mr.

‘ ^lchael VVerth, the Justice Department at- _s^0rney, travelled throughout the United ^ates and Britain. He interviewed scores of ^^ltr>esses taking testimony and depositions. ^e inspected thousands of pages of records d reports. The case record included af- j, ^avits of 40 witnesses totalling 600 pages. ^^uPporting these affidavits were 824 exhibits d records of the Navy, the British govern­al I*¹' and universities and corporations ^lch assisted in the project. The affidavits of

all the contributors, both British and Amer­ican, confirmed that the concept originated with the British inventors; that their trans­atlantic co-workers refined the concept, and that this magnificent team effort finally re­sulted in the “actual reduction to practice” of the invention in the Chesapeake Bay.

The Board of Patent Interferences con­cluded in 1965 that Butement had established introduction of the conception of the inven­tion into the United States in September 1940, by the disclosure of Cockcroft to Tuve. The Board also held that the work by Tuve and his associates in reducing the invention to practice was done on behalf of the original inventors in accordance with agreements at the highest level. In the Board’s words:

The evidence is not complete, in that it is not known what the President and the Prime Minister said to each other about the Tizard Mission either directly or through ambassa­dors, but we do not think it is necessary to know this. It is known that the British decided not to put the Mission on the basis of a formal agreement, in fact, to attach no conditions to the disclosure. But the purpose of the British government in offering the disclosure and the purpose of the government of the United States in accepting the disclosure and pro­ceeding to put it into practice seems plain enough. . . . Tuve did not forget the dis­closure made to him and then came up with the idea to work on it at a much later time on a project of his own. He went to work on it im­mediately as his commitment to the United States government required him to do. More­over, contact was maintained between Tuve and his coworkers on one hand and the source of the conception on the other. It included, according to documents, exchange of models.

Thus did the Patent Office grant priority of invention in the basic proximity fuze inven­tion to Butement and his co-workers.

Aftermath. The case was not yet closed. More than 20 years had passed since the initial filing of the British application in 1942, therefore the patent could no longer issue to the applicants under the Boykin Act. Follow­ing the decision of the Board of Patent Inter­ferences, the Patent Office rejected the patent application because of the Boykin Act pro­vision. The Navy withdrew the claim for the benefit of the Act inasmuch as the benefit of the act was not needed. Indeed, it had never been needed since the British patent was never permitted to issue because of the ad­verse effect it would have on the prosecution of the U. S. case.

The patent examiner refused to permit withdrawal. His position was that the patent could not issue under the Boykin Act and the applicants would not be permitted to issue it otherwise than under the Boykin Act.

There followed a petition to the Commis­sioner of Patents requesting him to direct the Examiner to permit the application to be examined in the customary manner without reference to the Boykin Act. The Commis­sioner refused to act. The Navy appealed the decision of the Examiner to the Patent Office Board of Appeals. Here, again, the decision of the Examiner was reaffirmed; this time by a vote of two-to-one.

The sole recourse was to sue the Commis­sioner of Patents in the District Court for the District of Columbia. Although the Depart­ment of Justice has authority to file such a suit against another government department, it is an unusual step, not taken lightly. None­theless, after reviewing the case with the at­torneys from the Navy Department, the suit was instituted. There were several reasons for following that unique course. First, if the patent application were abandoned, its ef­fectiveness as a defense in infringement suits against the government would be diminished. In view of the fact that the Varian patent ap­plication might issue with limited claims and that other applications unknown to the government might issue with broad claims, it was imperative to have the protection of this patent. In addition, the U. S. govern­ment had undertaken to prosecute the ap­plication in return for the assignment from the British government. To conform to the spirit of this undertaking, every attempt should be made to obtain a patent and there­by affirm the value of the British contribution.

The case in the District Court was not prolonged.

On 18 August 1967, Judge Alexander Holt- zoff, in an opinion from the bench after con­clusion of arguments, granted Summary Judgment to the inventors and ordered the Patent Office to withdraw the technical ob­jection to the granting of the patent.

The testimony and affidavits of the inven­tors, of Tuve, of Hinman, and of Cockcroft and others associated with the early work on the fuze in the United States and Britain es­tablished the inventorship of Butement, Shire, and Thomson. On 20 February 1968, the Patent Office issued U. S. Patent No- 3,369,487 for an invention which time and technology had long since passed by. Later- filed applications have matured into patents, have run their course, and have expired dur­ing the period this patent was pending. In the hands of a corporation, the patent might be worth millions even now because it is the basic patent covering the radio proximity fuze. All radio proximity fuzes would prob­ably infringe the broad claims of this patent-

Although they had already received an c* > gratia award from the Crown for their work, the grant of a U. S. patent and the acknowl' edgements of their inventorship in the af­fidavits of their American associates is an additional source of satisfaction to Butement, Shire, and Thomson. The patent document and the official files of the application w$ preserve the evidence that theirs was the genius that gave birth to the invention; was their brain child.

It has been assumed in the United State⁵ that the proximity fuze was an all-American j invention. It was not. It was born in Britain^ perhaps, however, it can be said to have reached maturity in the United States. Cer'. tainly, the invention would not have beef perfected in time to play a significant part if the war without the contributions of thoS^c who formed the international team. The if' ventors would not have won the interference if detailed records had not been maintained and preserved by their American associate⁵’' The issuance of this historic patent has p^ef' fected the government’s defense against p°' tential infringement suits and provides to th^e inventors official American acknowledgemef¹ of their contribution.