This patent dispute, one of the final patent cases to be considered by this court, involves a device for transporting large, compacted haystacks and cotton modules. Returning special verdicts, the jury found the patent to be valid and infringed, and determined the factual basis for damages. The district court entered judgment assessing damages and enjoining defendant Anel. Anel appealed (our docket number 81-1157), posting a supersedeas bond for the money damages. After this appeal was noticed, plaintiffs charged Anel with violations of the injunction. The district judge refused to adjudge Anel guilty of contempt. Plaintiffs appealed this decision (our docket number 81-1384), and the two appeals were consolidated. Finding no error in either case, we affirm the district court.

This case involves a truly intriguing device which reconfirms the accuracy of the adage that necessity is the mother of invention. The device at issue is commonly called a "chain-type" or "chain-beam" haystack mover. The haystacks involved are not the wigwam-shaped piles brought to mind by references to Little Boy Blue or to searching-for-a-needle-in, but are large, tightly packed bales measuring 15 by 24 feet and weighing up to 10 tons. The chain-type mover has been adapted to handle the cotton module, a recently developed cotton bale similar to the haystack but heavier.

The device, mounted on a trailer or truck, is designed to load, transport, and unload the enormous bundles of hay or cotton, using only one operator, who need not exit the cab during the procedure. The driver merely backs the equipment to the load, lowers the rear end of the bed to ground level, engages the drive which operates a chain located in the center of the bed and the drive which moves the vehicle, and sits back and watches. The two drive means are synchronized so that they operate in opposite directions simultaneously and uniformly; as the truck moves backward the chain moves forward. Within moments, without any forward or backward motion of the load but only an upward tilt, the trailer is positioned entirely under the load. The chain drive is stopped and the bed is returned to the transport position. The vehicle is then driven to the new location, where the procedure is reversed and the load is placed on the ground. For all practical purposes, the trailer is driven under the load as it is lifted and is driven out from under the load as it is lowered.

Before the advent of the chain-type mover, haystacks were moved in a slow, cumbersome, dangerous and difficult fashion by a mechanism using a winch, cable and sling. One person alone could not perform that operation. The chain-type mover received wide and rapid acceptance, replacing its predecessor. Quicker, easier, safer and cheaper to operate, the device revolutionized the movement of haystacks.

Farmhand, Inc. holds the rights to the chain-type mover under U.S. Patent No. 3,298,550 (the '550 patent); Reynolds Module Systems, Inc. is a licensee. Reynolds adapted the device, in order to move cotton modules, by adding attachments, strengthening the mechanism, and increasing its capacity. Anel Engineering Industries, Inc. began building chain-type cotton movers in truck and trailer models in 1977. Anel did not seek authorization from the '550 patent-holder, and the instant suit followed.

Boyd Schiltz, a South Dakota farmer and haystack mover, applied for the '550 patent on April 6, 1964; it was issued on January 17, 1967. Boyd's brother Bruce, recipient of U.S. Patent No. 3,209,932 (the '932 patent), claims to be the inventor of the chain-type mover. The '932 patent reads on claim 10 of the '550 patent.

Bruce Schiltz applied for the '932 patent on October 22, 1963. Eleven days before, on October 11, 1963, Boyd Schiltz assigned his '550 patent interests to Farmhand. Bruce Schiltz was present during the assignment.

When considering the validity of the '550 patent, the jury was confronted with the adverse claims of inventorship. Conflicting evidence was presented, including evidence that Boyd Schiltz had reduced his invention to practice before Bruce Schiltz filed his application.

Anel contends that the jury's finding that the '550 patent was valid was based on erroneous instructions and directions, primarily as relates to the issues of inventorship and novelty.1

Instructions are considered adequate if the jury is given an appropriate understanding of the controlling law and of its role in the decision-making process:

In the review of jury instructions, a challenged instruction should not be considered in isolation but rather as part of an integrated whole. If, viewed in that light, the jury instructions are comprehensive, balanced, fundamentally accurate, and not likely to confuse or mislead the jury, the charge will be deemed adequate.

Scheib v. Williams-McWilliams Co., Inc., 628 F.2d 509, 511 (5th Cir.1980) (citing Vezina v. Theriot Marine Service, Inc., 554 F.2d 654 (5th Cir.1977)). The instructions challenged in the instant case must be reviewed in light of the total charge and the trial setting.

Anel argues that the trial judge's instructions and interrogatories incorrectly placed on it the burden of proof on the question of inventorship. If Bruce Schiltz invented the chain-type mover first, then the '932 patent is anticipatory prior art under 35 U.S.C. Sec. 103,2 obviously affecting the validity of the '550 patent.Presumption of Validity

The '550 patent, like every patent properly issued, carries with it a presumption of validity. The burden of showing the invalidity of a patent therefore rests upon the challenging party. 35 U.S.C. Sec. 282. "The burden on one who would invalidate a patent is a heavy one." Ludlow Corp. v. Textile Rubber & Chemical Co., Inc., 636 F.2d 1057, 1059 (5th Cir.1981).3

The impact of the presumption is measurably weakened when it is shown that the Patent Office, in making its decision on issuance, did not consider pertinent prior art. Cathodic Protection Service v. American Smelting & Refining Co., 594 F.2d 499 (5th Cir.), cert. denied, 444 U.S. 965, 100 S. Ct. 453, 62 L. Ed. 2d 378 (1979); Parker v. Motorola, Inc., 524 F.2d 518 (5th Cir.1975), cert. denied, 425 U.S. 975, 96 S. Ct. 2175, 48 L. Ed. 2d 799 (1976). The trial judge correctly declined an instruction diluting the presumption of validity of the '550 patent. The Patent Office, in approving the '550 patent, had considered the controversy between the Schiltz brothers and the prior art nature of the '932 patent.4

The presumption in favor of the '550 patent is further supported by prior adjudications and consent decrees testing and affirming its validity.5 See American Home Products Corp. v. Lockwood Manufacturing Co., 483 F.2d 1120 (6th Cir.1973) (another circuit's finding of validity against different infringer enhances presumption); Robertson Rock Bit Co. v. Hughes Tool Co., 176 F.2d 783 (5th Cir.1949) (another circuit's finding of validity deserves "comity," especially when patent has withstood lengthy challenges and infringers are shown to have deliberately copied), cert. denied, 338 U.S. 948, 70 S. Ct. 487, 94 L. Ed. 585 (1950).

At trial, evidence of the prior cases upholding the validity of '550 was offered as a factor for the jury's consideration in determining patent validity. Such evidence, like the factor of commercial success, was not dispositive, as such, but was relevant. Allowing the jury to consider this evidence was not error. See Illinois Tool Works, Inc. v. Foster Grant Co., 547 F.2d 1300 (7th Cir.1976) (same court, different infringer); Columbia Broadcasting System, Inc. v. Zenith Radio Corp., 391 F. Supp. 780 (N.D.Ill.1975), (different court, different infringer), rev'd on other grounds, 537 F.2d 896 (7th Cir.1975).6

The district judge properly cited the presumption of validity of the challenged '550 patent in placing the burden on Anel. The instructions, considered "as part of an integrated whole," were "comprehensive, balanced, fundamentally accurate, and not likely to confuse or mislead the jury" and therefore pass appellate scrutiny.

Likewise, the judge's instruction placing upon Anel the burden of showing that the '550 patent, as a combination patent, does not produce a synergistic result is not error. While Sakraida v. Ag Pro, Inc., 425 U.S. 273, 96 S. Ct. 1532, 47 L. Ed. 2d 784 (1976), set out the standards by which a combination patent is to be judged, it did not remove the statutory presumption of validity from combination patents. See 35 U.S.C. Sec. 282. Assignment to Anel of the burden on this element cannot be said to conflict with the requirements of Sakraida.

Nor is the '550 patent invalid as a matter of law because its elements can be found in the prior art. In reviewing a combination patent, the essential inquiry is whether there is "an unexpected, unusual or synergistic result." Huron Machine Products, Inc. v. A. & E. Warbern, Inc., 615 F.2d 222, 224 (5th Cir.1980). See Whitley v. Road Corp., 624 F.2d 698, 701 (5th Cir.1980) ("Simply stated, in this instance the whole is no greater than the sum of its parts."). In the instant case, we are persuaded that ample evidence supports the jury's finding that the practical effect of the chain-type haystack mover constitutes a gestalt, producing a novel and nonobvious combination result. We affirm the finding that the '550 patent is valid.

Anel argues that its machines, intended to transport cotton modules, cannot infringe the '550 patent, since that patent describes a machine for moving "hay" and "haystacks." We are not convinced.

The claims of the patented invention are paramount. Thus "we must first turn to the claims of the patent because the scope of every patent is limited to the invention described in its claims, read in the light of the specifications." Ziegler v. Phillips Petroleum Co., 483 F.2d 858, 868 (5th Cir.), cert. denied, 414 U.S. 1079, 94 S. Ct. 597, 38 L. Ed. 2d 485 (1973). However, an inventor is not limited to the literal scope of his claims in every respect; as Judge Learned Hand once suggested: "[H]e is not charged with a prophetic understanding of the entire field of [the invention's] usefulness." B. G. Corp. v. Walter Kidde & Co., 79 F.2d 20, 22 (2d Cir.1935). Exceptions to patent limitations have developed, including the concept of pioneer patents and the doctrine of equivalents.7

The district judge properly instructed the jury on the question of infringement, including file wrapper estoppel and the doctrine of equivalents. The jury reasonably could have concluded that the '550 patent should be defined by its unique operation rather than by the specific load or product upon which it was originally designed to operate, especially since use of the cotton module did not develop until several years later. The finding that the '550 patent is infringed by Anel's machines was based on a proper understanding of a patent's reach and limitations.8

When the district court issued its permanent injunction,9 Anel had fifteen infringing machines. Anel subsequently purchased Craven Welding Company, thereby acquiring the license to sell chain-type movers which Craven had purchased from Farmhand. After Anel attempted to sell and in fact sold some of its machines, Farmhand and Reynolds sought a contempt citation. The motion was denied by the district judge.

Generally, when an appeal is noticed the district court is divested of jurisdiction; the matter is transferred immediately to the appellate court. The rule, however, is not absolute. The district court maintains jurisdiction as to matters not involved in the appeal, such as the merits of an action when appeal from a preliminary injunction is taken, see Ex parte National Enameling & Stamping Co., 201 U.S. 156, 26 S. Ct. 404, 50 L. Ed. 707 (1906), or in aid of the appeal, as by making clerical corrections. See 16 C. Wright, A. Miller, E. Cooper & E. Gressman, Federal Practice and Procedure Sec. 3949, at 359 (1977). The district court maintains jurisdiction for other matters, such as ordering stays or modifying injunctive relief.10 The Ninth Circuit in Hoffman v. Beer Drivers & Salesmen's Local, 536 F.2d 1268, 1276 (9th Cir.1976), upheld the district court's "continuing duty to maintain a status quo" in recognizing the jurisdiction of the trial court to issue further contempt orders while an appeal from the first contempt order was pending.

We have recognized the continuing jurisdiction of the district court in support of its judgment, as long as that judgment has not been superseded. In Brown v. Braddick, 595 F.2d 961 (5th Cir.1979), a patent interference action, the district court held contempt hearings on violations of its discovery orders. Jurisdiction was sustained:

Since Braddick failed to ask the district court for a stay pending appeal and to post supersedeas bond as required by F.R.C.P. 62(d), the district court retained power to enforce its order by civil contempt proceedings. See Sekaquaptewa v. MacDonald, 544 F.2d 396, 406 (CA 9, 1976), cert. denied, 430 U.S. 931, 97 S. Ct. 1550, 51 L. Ed. 2d 774 (1977).

Id. at 965. The Brown court distinguished United States v. Roundtree, 420 F.2d 845 (5th Cir.1969), as involving criminal contempt proceedings.

Anel did not seek a stay of the injunction nor post a supersedeas bond relative thereto.11 The district court, accordingly, maintained jurisdiction to supervise its injunction--to execute its unsuperseded judgment--and properly entertained the motion for contempt. See Sirloin Room, Inc. v. American Employers Insurance Co., 360 F.2d 160 (5th Cir.1966) (order to enforce unsuperseded money judgment may be entered by district court even after appeal noticed); International Paper Co. v. Whitson, 595 F.2d 559 (10th Cir.1979) (same).

In reviewing the propriety of the district court's substantive decision on the contempt issue, we find that the record supports the determination that Anel did not violate the injunction. Farmhand and Reynolds would have an indelible taint apply to all machines manufactured by Anel before it acquired a valid license. The district court did not interpret its injunction to apply in that fashion nor do we. "We see no basis for substituting our judgment for that of the district judge in interpreting his own order." Securities & Exchange Comm'n v. Sloan, 535 F.2d 679, 681 (2d Cir.1976), cert. denied, 430 U.S. 966, 97 S. Ct. 1646, 52 L. Ed. 2d 357 (1977).

The judgment of the district court is, in all respects, AFFIRMED.