Respondent brought this action against petitioner for infringement of United States Patent No. 3,055,280 covering 'Means for Treating Bituminous Pavement.' The patent was assigned to respondent by one Neville.

Bituminous concrete—commonly called asphalt or 'blacktop'—is often laid in strips. The first strip laid usually has cooled by the time the adjoining strip is to be laid, creating what is known as a cold joint. Because bituminous concrete is pliable and capable of being shaped only at temperatures of 250 to 290 F., the cold joint results in a poor bonding between the strips. Water and dirt enter between the strips, causing deterioration of the pavement.

Respondent's patent sought to solve the problem of the cold joint by combining on one chassis (1) a radiant-heat burner for heating the exposed edge of the cold strip of pavement; (2) a spreader for placing bituminous material against that strip; and (3) a tamper and screed, for shaping the newly placed material to the desired contour and surface.

The standard paving machine in use prior to respondent's claimed invention combined on one chassis the equipment for spreading and shaping the asphalt, and it is unquestioned that this combination alone does not result in a patentable invention. Petitioner's alleged infringement resulted from its placing of a radiant-heat burner on the front of a standard paving machine, thus allowing its machine to perform the same functions with the same basic elements as those described in respondent's patent.

The use of a radiant-heat burner in working asphalt pavement dates back to a patent issued in 1905 to one Morcom, United States Patent No. 799,014. The value of such a heater lies in the fact that it softens the asphalt without burning the surface. The radiant-heat burner on respondent's claimed invention is essentially the same as that disclosed in a patent issued in 1956 to one Schwank, United States Patent No. 2,775,294. Thus the burner, by itself, is also not patentable.

The placement of the radiant-heat burner upon the side of a standard bituminous paver is the central feature of respondent's patent. The heater is used in this way for continuous paving along a strip to prevent a cold joint, whereas previously radiant-heat burners had been used merely for patching limited areas of asphalt. The operation of the heater is, however, in no way dependent on the operation of the other equipment on the paving machine. It is hung on the paver merely because that is a convenient place for it when heating the longitudinal joint of the pavement. A separate heater can also be used in conjunction with a standard paving machine to eliminate the cold joint, and in fact is so used for heating the transverse joints of the pavement.

Respondent claims that its patent involves a combination of prior art which produces the new and useful result of eliminating the cold joint. Its claim of unobviousness is based largely on the testimony of two individuals who are knowledgeable in the field of asphalt paving, expressing their doubts to the inventor Neville that radiant heat would solve the problem of cold joints. The District Court rejected respondent's claim of infringement, finding the patent invalid. The Court of Appeals, by a divided vote, reversed. For reasons that follow, we reverse the judgment of the Court of Appeals.

Each of the elements combined in the patent was known in the prior art. It is urged that the distinctive feature of the patent was the element of a radiant-heat burner. But it seems to be conceded that the burner, by itself, was not patentable. And so we reach the question whether the combination of the old elements created a valid combination patent.

The District Court said: 'All that plaintiff (respondent) has done is to construct four elements known in the prior art on one chassis.' That is relevant to commercial success, not to invention. The experts tendered by respondent testified that they had been doubtful that radiant heat would solve the problem of the cold joint.1 But radiant heat was old in the art. The question of invention must turn on whether the combination supplied the key requirement. We conclude that the combination was reasonably obvious to one with ordinary skill in the art.

There is uncontested evidence that the presence of the radiant-heat burner in the same machine with the other elements is not critical or essential to the functioning of the radiant-heat burner in curing the problem of the cold joint. For it appears that a radiant-heat burner operating in a tandem fashion would work as well. The combination of putting the burner together with the other elements in one machine, though perhaps a matter of great convenience, did not produce a 'new or different function,' Lincoln Engineering Co. of Illinois v. Stewart-Warner Corp., 303 U.S. 545, 549, 58 S.Ct. 662, 664, 82 L.Ed. 1008, within the test of validity of combination patents.

A combination of elements may result in an effect greater than the sum of the several effects taken separately. No such synergistic result is argued here. It is, however, fervently argued that the combination filled a long felt want and has enjoyed commercial success. But those matters 'without invention will not make patentability.' Great A. & P. Tea Co. v. Supermarket Corp., 340 U.S. 147, 153, 71 S.Ct. 127, 130, 95 L.Ed. 162.

The patent standard is basically constitutional, Article I, § 8, of the Constitution authorizing Congress '(T)o promote the Progress of * * * useful Arts' by allowing inventors monopolies for limited times. We stated in Graham v. John Deere Co., 383 U.S. 1, 6, 86 S.Ct. 684, 688, 15 L.Ed.2d 545, that under that power Congress may not 'enlarge the patent monopoly without regard to the innovation, advancement or social benefit gained thereby. Moreover, Congress may not authorize the issuance of patents whose effects are to remove existent knowledge from the public domain, or to restrict free access to materials already available. Innovation, advancement, and things which add to the sum of useful knowledge are inherent requisites in a patent system which by constitutional command must 'promote the Progress of * * * useful Arts.' This is the standard expressed in the Constitution and it may not be ignored.'

In this case the question of patentability of the combination turns on the meaning of 35 U.S.C. § 1032 which the Court reviewed in the Graham case, supra, at 13—17, 86 S.Ct. at 691—693. We said:

'We believe that this legislative history, as well as other sources, shows that the revision was not intended by Congress to change the general level of patentable invention. We conclude that the section was intended merely as a codification of judicial precedents embracing the Hotchkiss3 condition, with congressional directions that inquiries into the obviousness of the subject matter sought to be patented are a prerequisite to patentability.' Id., at 17, 86 S.Ct. at 693.

Obviousness, as an issue, is resolved as follows:

'Under § 103, the scope and content of the prior art are to be determined; differences between the prior art and the claims at issue are to be ascertained; and the level of ordinary skill in the pertinent art resolved.' Ibid.

We admonished that 'strict observance' of those requirements is necessary. Id., at 18, 86 S.Ct., at 694.

We conclude that while the combination of old elements performed a usefulfunction,4 it added nothing to the nature and quality of the radiant-heat burner already patented. We conclude further that to those skilled in the art the use of the old elements in combination was not an invention by the obvious-nonobvious standard. Use of the radiant-heat burner in this important field marked a successful venture. But as noted, more than that is needed for invention.

Reversed.

THE CHIEF JUSTICE took no part in the decision of this case.