The opinion
MARTIN, Judge,
dissenting, with whom WORLEY, Chief Judge, joins.
Clamer specifies that “the heating effect upon a charge within an inductor coil carrying alternating current is dependent upon and is very nearly proportional to the frequency as well as the square of the ampere turns. 1 ” The reference specifically suggests heating, as is apparent from the following passages:
“Thus, it will be seen that I may choose between the use of stirring with or stirring without appreciable heating effect. If I desire the heating effect for a given number of ampere turns, the frequency should be increased, otherwise I will employ low, preferably commercial frequency.
“ * * * unless I desire to heat the charge during treating, I will use relatively low amperage and low frequency.”
Clamer also specifies that “[m]elting of the charge preliminary to its treatment may be effected * * * by the induction furnace in which it is to be treated.”
*476 Clamer thus teaches that the amount of heating will increase proportionally with increase in frequency from his “low, preferably commercial frequency” to some higher frequency which he uses if he intentionally heats the charge. Moreover, Clamer teaches that the ampere turns, as well as the frequency, are kept at a minimum to hold down heating effect. 2 I think that teaching, along with the statement quoted above that heating effect increases with increase in ampere turns, suggests to a person skilled in the art that a heating effect sufficient to melt a metal charge could be obtained at a particular “low” frequency 3 by increasing the current without further increasing the frequency.
Appellant himself establishes that those relationships taught by Clamer were in fact followed in prior art induction furnace design by using high currents at low frequencies as an alternative to lower currents at high frequencies. Thus, appellant’s application states:
“Coil currents somewhat higher than used in prior known induction melting practices are required to overcome heat loss because of the low temperature of the crucible wall. In prior practice coil currents of the order of 6000-7000 amperes at 60 cycles per second, and of 300-500 amperes at 2000 cycles per second are usual. * * * ” [Emphasis supplied.]
Appellant makes other references in his application to low frequency induction furnaces as known prior to his invention, referring, for example, to “prior known low-frequency coreless [induction] furnaces.”
Thus the issue seems to be whether constructing the crucible of Clamer of electrically insulated, water cooled, metal sections, for use in melting metals at frequencies known in the prior art, would be obvious. In my opinion, Rossi’s disclosure of insulated mold sections for the purpose of avoiding induction currents in the casing and of water cooling the sections would clearly suggest use of a corresponding construction in Clamer. It would also seem obvious to cool the crucible to a low enough temperature to prevent alloying of the crucible material with the melt. Such water cooling also would obviously cool the outside of the crucible.
A bottom member for the crucible is required only by claims 8 and 9. Where one was making a crucible of insulated conductive segments in line with Rossi’s teachings, it would seem but an obvious expedient to make the bottom in the form of a separate insulated disk-shaped member.
For the foregoing reasons, I would affirm the decision of the Board of Appeals.
. Ampere turns are the product of the number of turns in the coil and the number of amperes of current therethrough.
. Thus the patent states:
“As I wish usually to obtain stirring without great heating effect I will normally maintain the ampere turns at a minimum, as well as use low frequency.’’
. The Clamer patent, issued in 1933, does not specify the number of cycles considered “low, preferably commercial” frequency or “high” frequency. Appellant, in his application, refers to ordinary commercial power frequency as usually 60 cycles per second in the United States, and defines “low” frequency as the frequency range “below about 1000 cycles per second.”