Application of McKenna, Patent Appeal No. 5956.

• Citation: 97 USPQ 348,203 F.2d 717
• Decision Date: 15 April 1953
• Docket Number: Patent Appeal No. 5956.
• Parties: Application of McKENNA et al.
• Court: United States Court of Customs and Patent Appeals

97 USPQ 348, 203 F.2d 717 (1953)

Application of McKENNA et al.

Patent Appeal No. 5956.

United States Court of Customs and Patent Appeals.

April 15, 1953.

Clarence B. Des Jardins and Albert F. Robinson, Cincinnati, Ohio (Watts T. Estabrook, Washington, D. C., and Des Jardins, Robinson & Keiser, Cincinnati, Ohio, of counsel), for appellants.

E. L. Reynolds, Washington, D. C. (Clarence W. Moore, Washington, D. C., of counsel), for Commissioner of Patents.

Before GARRETT, Chief Judge, and O'CONNELL, JOHNSON, WORLEY, and COLE, Judges.

JOHNSON, Judge.

This is an appeal from the decision of the Board of Appeals of the United States Patent Office affirming the holding of the Primary Examiner rejecting as unpatentable claims 24 to 27, the only remaining claims in appellants' application for a patent on a "Process for the Explosive Pressing of Powdered Compositions."

The appealed claims relate to a process in the field of powder metallurgy. They are directed to an allegedly novel method of forming and compacting articles to a desired shape from powdered metal mixtures, particularly the hard carbides, nitrides and borides of various metals.

In carrying out the process, the powder mixture, or a loosely compacted mass of powder, is placed in a fluid-impervious sheath, and the sheath is then placed in a pressure chamber filled with fluid. The pressure chamber is designed so that an explosion had having a movable piston may be coupled thereto in sealed relationship, with one end of the movable piston resting against the fluid in the chamber. A charge of powder is placed in the explosion head adjacent the other end of said piston. When the powder is ignited, the resulting explosion drives the piston against the fluid in the pressure chamber, thus creating a pressure which is transmitted by the fluid uniformly in all directions to the sheath-enclosed article in the pressure chamber, thereby uniformly compacting it. The amount of fluid displacement which the piston has made in the pressure chamber, is of course, a measure of the amount that the article has been compacted as a result of the explosion. According to appellants' specification, the best range of pressure for molding hard carbide metal compounds, such as tungsten carbide or other carbides, is between 60,000 to 70,000 pounds per square inch, and the maximum pressure for best results should be developed within the range of 25 to 50 milliseconds. The article thus formed is later "sintered," in a manner well known in this art, to a firmly coherent or cemented condition.

Claims 24 to 27 read as follows:

"24. The improvement in the art of powder metallurgy comprising the surrounding of a powder compact with a body of liquid and subjecting said body of liquid to explosive pressure transmitted thereby uniformly to said compact from all directions, to condense said compact uniformly.

"25. The improvement in the art of powder metallurgy comprising the surrounding of a powder compact with a body of liquid and subjecting said body of liquid to pressure developed to a maximum within the range of 25 to 50 milliseconds, said pressure being transmitted by said liquid to the compact from all directions to condense said compact uniformly.

"26. The process of claim 25 in which the powder compact is separated from the liquid by a pliable rubber envelope enclosing the compact.

"27. The process of claim 26 in which the rubber envelope is evacuated."

The references relied on by the Patent Office are: Johnson (Great Britain) 21,840 A. D. 1897; Madden 1,081,618 Dec. 16, 1913; Duryea et al. 1,371,671 March 15, 1921; McKenna 2,220,018 Oct. 29, 1940.

The Madden patent discloses a process for preparing billets from powdered refractory metals such as tungsten and molybdenum. The powdered metal is put into a closed rubber tube which is placed in a pressure chamber. Water or other fluid is then forced into the chamber under great pressure by a pump and the pressure maintained for a brief period. The pliable tube permits the uniform application of the high fluid pressure to the powdered material in substantially all directions, so that the powdered material is compacted into billets having a high degree of uniformity and strength.

The patent to McKenna, one of the joint applicants herein, discloses a method of compacting articles having tortuous shapes from powdered carbides, nitrides, and borides of metals. That method, insofar as it is pertinent here, is similar to the above-described process disclosed by Madden. The powdered metal is placed in a rubber sheath which is shaped and then placed in the chamber of a hydraulic press, so as to be entirely submerged. It is then subjected to a pressure of 5,000 to 30,000 pounds per square inch to compact the powder into an article having a relatively dense body. The article so formed is then sintered in the usual way.

Duryea et al. discloses a process for briqueting fragmentary matter such as iron borings. The borings are fed into a cylindrical die closed at one end, a close fitting plunger is entered into the open end of the cylinder, and a preliminary mild pressure is applied thereto to partially compress the borings. Then an explosive charge is fired in the cylinder, by a means not disclosed, so as to drive the plunger further into the die, thereby compacting the material therein under high pressure. It is also suggested that steam or compressed air may be used instead of an explosion to suddenly raise the pressure used to drive the plunger. The reference states that the sudden and practically explosive application of increased pressure causes the individual fragments or particles to slide one upon another and the friction thus occasioned creates an intense heat at the proximate surfaces of the fragments and thereby fuses, welds or coheres those fragments into one mass.

The Johnson patent shows the application of an explosion to drive a piston against a body of liquid which engages a solid metal sheet or tube to press it into an embossing die or to expand portions of it into recesses. Upon oral argument, the Solicitor for the Patent Office conceded that the Johnson reference is somewhat remote, but asserted that it does disclose a means which could be used to carry out the process taught by Duryea et al.

The examiner rejected claims 24 to 26 as unpatentable over either Madden or McKenna in view of either Duryea et al. or Johnson. He noted that the only difference between applicants' claimed process and those shown by Madden and McKenna was that the fluid in the pressure chamber was subjected to explosive pressure in order to compact the powdered matter in the sheath. He held that it would not constitute invention to substitute the explosive pressure developing means taught by Duryea et al. or Johnson for the pump type pressure means used in either Madden or McKenna. The examiner also rejected claim 27 on the sole ground of being vague and indefinite. The latter rejection will be discussed in more detail below.

The board affirmed the examiner's rejections of claims 24 to 27, with one member filing a dissenting opinion as to the affirmance of the rejection of claims 24, 25 and 26. The majority of the board concurred with the examiner's view that no invention was involved in making the "obvious substitution" of explosive forces used in the secondary...