Full opinion text
OPINION PER CURIAM: This patent suit concerning servomechanisms presents several separate issues. Trial Judge Colaianni has filed a thorough and careful report giving his rulings and finding the relevant facts. Plaintiff has sought review of significant parts (but not of all) of the adverse aspects of the trial judge’s decision, and the defendant asks review of all the decision adverse to it. We have heard oral argument en banc and considered the briefs and record. Our conclusion is that the trial judge is correct on all points except his ruling that defendant’s overhaul of the 5"/38 single Mk 30 gun mounts at NOS Louisville during the 1967 to 1971 period amounted to impermissible reconstruction for which plaintiff should be compensated. We hold, on the contrary, that such overhaul amounted to permissible non-compensatory repair. On that issue we do not adopt the trial judge’s opinion but set forth our own differing views in Part II, infra, of this per curiam opinion. In Part I, infra, we adopt as our own, and set forth, the trial judge’s opinion on the other aspects of the case (with minor supplementation and modification by the court). Our ultimate conclusion is that plaintiff is not entitled to recover and the petition is dismissed. PART I. Trial Judge Colaianni’s opinion (except for the part dealing with overhaul at NOS Louisville, and also including minor supplementation and modification by the court) is as follows: COLAIANNI, Trial Judge. In this patent suit under 28 U.S.C. § 1498, plaintiff contends that various claims of three of its patents have been used or made by or for defendant without license or lawful right. Plaintiff, accordingly, seeks reasonable and entire compensation for such unauthorized acts. Defendant pleaded a whole host of defenses. Indeed, the validity of each of the patents is attacked on a variety of grounds. In addition, defendant alleges that it does not infringe any of the patents at bar. Plaintiff is the owner by assignment of the entire right, title and interest in the patents here in suit. The parties have agreed to the deferral of the issue of accounting until after final resolution of the question of liability. For reasons hereinafter stated, it is concluded that the claims at issue in the United States Letters Patents 2,550,514 and 2,414,-685 are invalid. It is further concluded that claims 7 and 17 of United States Letters Patent No. 2,679,138 are invalid. It is also concluded that claim 8 of patent No. 2,679,-138 is valid. Patent No. 2,550,514 United States Letters Patent No. 2,550,-514 (hereinafter referred to as the ’514 patent) was issued to Dr. Ernst F. W. Alexan-derson on April 24, 1951, for an invention entitled “System for Reproducing Position” and was based on an application filed on May 19, 1932. The invention relates to position followup control systems or servomechanisms. Generally, such systems are characterized by a pilot device and a driven object. An objective is to have the driven object follow the positional movement of the pilot device accurately and in a stable manner. An example of such a system is a shipborne gun and turret which is driven to follow the position of a telescope. Conventionally, well-known induction devices, commonly referred to as selsyns, are connected between the telescope and gun such that a voltage signal is generated which is representative of the positional departure of the gun from the telescope. Amplifiers are used to amplify the voltage or error signal for actuation of a direct current (hereinafter sometimes referred to as “d. c.”) motor which in turn controls the movement of the gun towards correspondence with the telescope. As the gun approaches positional agreement with the telescope, the error signal is proportionally reduced, eventually reaching zero when correspondence is achieved. Basic position control systems such as that described above were known prior to the invention of the ’514 patent. Positional servomechanisms of the above kind encounter problems of oscillation, commonly known as hunting, due to the inertia of the objects involved and the inherent time lags due to the servo components. Hunting can basically be described as oscillation of the gun back and forth about the point of correspondence. Due to the inductance of the servo components, the error signal is constantly lagging the actual departure of the gun from correspondence. As a result, the corrective action also lags the actual departure at any given moment, thus causing the gun to continually overshoot the desired position. Such a phenomena is clearly undesirable in many systems where speed and accuracy of position are critical. Traditionally, one approach to servo control involved increasing the system gain in an effort to eliminate hunting. The gain of a system is defined as the ratio of output power, current or voltage, to input power, current or voltage, respectively. Such an approach is unsatisfactory, however, since instability is encountered once a certain gain level is reached. Thus, there is a trade-off in any servo system between gain and stability. The prior art of record in this action discloses various techniques of position control aimed at eliminating or preventing the problem of hunting. Plaintiff’s Patented System The invention of the ’514 patent is drawn to a position control system of the above variety wherein hunting is eliminated or prevented. At col. 2, lines 28 to 38, of the ’514 patent, Dr. Alexanderson broadly describes one approach to anti-hunting: In carrying the invention into effect in one form thereof, changes in the torque or synchronizing force are utilized for modifying the synchronizing force in such a manner as to anticipate the final position and to bring the interconnected devices into correspondence without hunting or oscillation. In a system in which an electric motor is employed to drive an object into positional agreement with a control object, changes in the torque of the motor are so utilized. Figure 1 of the ’514 patent, reproduced in the findings, synthesizes this concept. In the patented system a pair of selsyns are connected between a gun and telescope for generating a voltage representative of the error or positional disagreement. This error signal is applied to a thyratron control amplifier and, following amplification, is supplied to a direct current motor for driving the gun into correspondence with the telescope. In order to avoid hunting by the gun, circuitry is provided for generating a modifying signal that combines with the error signal applied to the thyratron amplifier for driving the direct current motor. As disclosed, the circuit includes an anti-hunting means, described as being composed of a magnetic saturable core reactor having a plurality of direct current-supplied control windings and a plurality of alternating current-supplied reactive windings which are inductively related to each other. The control windings are connected in series to form a bridge and the reactive windings are connected in parallel to form a bridge. One diagonal of the reactive winding bridge is connected to a source of alternating current while the other diagonal is connected to the control windings of an output transformer, which applies the bridge output to the control circuit of the thyratron amplifier. One diagonal of the control winding bridge is connected to a source of direct current while the other diagonal is connected to the secondary winding of an input transformer. The manner of operation of the input transformer will be described in greater detail, infra, but generally can be described as permitting only changes of torque of the d.c. motor to initiate operation of the anti-hunting means. The primary winding of the input transformer is shunted by an unmarked resistor and connected across the armature of the direct current drive motor. No voltage is induced in the secondary winding of the input transformer when the drive motor current is steady. However, when the drive motor current is changing, a voltage is induced in the transformer secondary and applied to the anti-hunting means. In the absence of an input, the anti-hunting means is magnetically balanced. Any input unbalances the bridge, causing a proportionate output to be applied by way of the output transformer to the thyratron control amplifier. In turn, the operation of the amplifier will affect the direct current motor. The patent clearly teaches that no modifying signal is to be produced during constant current operation of the direct current drive motor. The self-imposed limitation of the anti-hunting operation by the patentee to only such times when the torque of the direct current drive motor is changing is emphasized at col. 8, line 61, to col. 9, line 3, of the ’514 specification: Thus it will be seen that a change in the direction of rotation of the motor * * * [12] produces a change or a reversal of the phase of the voltage supplied from the anti-hunting device to the control circuit of the electric valve apparatus. Furthermore, it will be observed that since the direct current control winding bridge is connected to the motor circuit through a transformer that the anti-hunting means 55 is responsive only to changes in the motor current and since the voltage which it supplies to the control circuit for the electric valve apparatus is roughly proportional to the motor current, the anti-hunting means 55 is in this sense responsive to the rate of change of motor current and since the motor current is a measure of its torque, the anti-hunting means is thus responsive to rate of change of torque. A further characteristic of the anti-hunting means is that it causes the modifying signal to lag changes in the drive motor current, as described in the specification at col. 12, lines 23 to 30: Due to the fact that the alternating current reactive coils of each arm of the bridge are short circuited upon each other, the anti-hunting means functions as a transformer with a short-circuited secondary, the large inductance of which causes the direct current magnetization to be considerably lagging with respect to the changes in motor current. However, the modifying signal applied by way of the output transformer to the thyra-tron amplifier causes the drive motor current to lead the actual departure from correspondence and operates to bring the gun into correspondence without overshoot. Scope of Claims Involved in Suit Plaintiff argues that the inventions defined by claims 35 and 36 of the ’514 patent have been used and/or manufactured by defendant without plaintiffs authorization. Claim 35, broken down into lettered sections element by element for ease of reference, reads as follows: 35. A follow-up control system comprising in combination (a) a pilot device, (b) a driven object, (c) driving means for said object, (d) control means for said driving means. (e) means responsive to positional disagreement of said pilot device and driven object for actuating said control means to control said driving means to drive said object toward correspondence with said pilot device, and (f) anti-hunting means responsive to the rate of change of torque of said driving means for actuating said control means. Claim 36, similarly broken down into lettered sections element by element, reads as follows: 36. A follow-up control system comprising in combination (a) a pilot device, (b) a driven object, (c) driving means for said object, (d) means for controlling the energization of said driving means, (e) means responsive to positional disagreement of said pilot device and driven object for actuating said control means to control said driving means to produce a torque for driving said object toward correspondence with said pilot device, and (f) anti-hunting means for actuating said control means in accordance with the rate of change of said torque. Both claims 35 and 36 are combination claims drawn to position follow-up control systems. Defendant asserts that both claims 35 and 36 are invalid under 35 U.S.C. § 102 (1970 & Supp. V 1975) and 35 U.S.C. § 112 (1970 & Supp. V 1975). Further, nonin-fringement is also asserted as a defense. In view of the conclusions reached with respect to Section 112, the court need not and does not reach the validity question under Section 102 or the infringement issue. As a prelude to a thorough consideration of Section 112, it is necessary to point out that the parties are in complete disagreement concerning the interpretation to be given element (f) of both claims 35 and 36. Defendant asserts that element (f) of claims 35 and 36 refers only to the anti-hunt means 55 shown in Fig. 1 of the ’514 patent. On the other hand, plaintiff contends that anti-hunt means 55, input transformer 81 and its unmarked shunt resistance, as well as output transformer 75, are all included within the phrase anti-hunting means of both claims 35 and 36. As the following analysis will reveal, defendant’s interpretation is the correct one. In Autogiro Co. of America v. United States, 384 F.2d 391, 397-98, 181 Ct.Cl. 55, 63 (1967), this court, in referring to the relationship between the claims of a patent and its specification, stated: In serving its statutory purpose, the specification aids in ascertaining the scope and meaning of the language employed in the claims inasmuch as words must be used in the same way in both the claims and the specification. U.S.Pat.Off. Rule 75(d). The use of the specification as a concordance for the claims is accepted by almost every court, and is a basic concept of patent law. [footnotes omitted] This precept takes on particular significance where the definition of a term appearing in a claim is disputed by the parties. Since the patentee is his own lexicographer, no genuine issue of fact as to the meaning of a claimed term can be found to exist where the meaning is made ineontrovertibly clear elsewhere in the patent or in the file wrapper. Duplan Corp. v. Deering Milliken, Inc., 370 F.Supp. 769, 772, 180 USPQ 373, 376 (D.S.C.1973), and cases cited therein. A careful review of the ’514 patent and its file wrapper provides invaluable insight as to the proper interpretation and meaning to be given to element (f) of claims 35 and 36. Turning first to the specification, col. 6, line 72, to col. 7, line 3, plaintiff emphasized that anti-hunting means 55 was to be responsive to transient conditions in the system: In order to prevent the gun 10 from hunting or oscillating about the position of correspondence with the telescope 11, anti-hunting means 55 are provided for modifying or controlling the voltage applied to the control circuit of the electric valve apparatus 14 in accordance with transient conditions in the system, (emphasis added) The structure referred to by the numeral 55 is subsequently referred to in the patent specification as the anti-hunting means 55, the anti-hunting device 55, or the anti-hunting detector 55, on numerous occasions. Significantly, there is not a single instance to which plaintiff can point where the specification refers to either transformer 81 or transformer 75 as the anti-hunting means. Equally significant is the lack of specification support for plaintiff’s position that the phrase anti-hunting means was intended to cover transformers 75 and 81 as well as the bridge connected control and reactive windings. A comparison of certain other claims of the ’514 patent with claims 35 and 36 further supports the conclusion that the term anti-hunting means as used in the claims at bar refers only to anti-hunting means 55. Significant evidence of the scope of any claim is the language employed in other claims of the same patent. Bethell v. Koch, 427 F.2d 1372, 1374, 57 CCPA 1233, 166 USPQ 199, 201 (1970). See aiso Stukenborg v. Teledyne, Inc., 299 F.Supp. 1152, 161 USPQ 10 (C.D.Cal.1969), aff’d, 441 F.2d 1069, cert. denied, 404 U.S. 852, 92 S.Ct. 90, 30 L.Ed.2d 92 (1971); and Leach v. Rockwood & Co., 273 F.Supp. 779, 154 USPQ 356 (W.D.Wis.1967), aff’d, 7 Cir., 404 F.2d 652 (1968). Reference to claim 34 sheds particularly relevant light on the scope to be afforded claims 35 and 36. Claims 34, 35 and 36 were all introduced into the ’514 patent simultaneously by an amendment during its pendency in the Patent and Trademark Office. Claim 34 reads as follows: 34. A follow-up control system comprising in combination (a) a pilot device, (b) a driven object, (c) driving means for said object, (d) means responsive to positional disagreement of said pilot device and driven object for controlling said driving means to drive said object toward correspondence with said pilot device, and (e) means responsive to the rate of change of torque of said driving means for controlling said driving means to prevent hunting, (emphasis added) The last element of claim 34 is couched in terms of a means-plus-a-function statement. In compliance with 35 U.S.C. § 112, this element must be interpreted as including all disclosed elements necessary to perform the stated function of preventing hunting. See also Technitrol, Inc. v. Control Data Corp., 394 F.Supp. 511, 185 USPQ 801 (D.Md.1975), vacated on other grounds, 550 F.2d 992 (4th Cir. 1977). By reference to the specification, it is clear that the claimed means includes input transformer 81 and its unmarked shunt resistance, anti-hunting means 55 and output transformer 75. As a cursory comparison of claim 34 with both claims 35 and 36 reveals, this last element is one of the distinctions between the claims in issue and claim 34. Claim 34 also recites a single means clause for determining the error and controlling the object drive means whereas claims 35 and 36 recite both a positional disagreement determining means and a control means for the drive means. Otherwise, claims 34, 35 and 36 are basically identical in language. To sustain plaintiffs position that element (f) of claims 35 and 36 structurally includes more than just anti-hunting means 55, would require the court to ignore the differences in language between the means to prevent hunting of claim 34 and the anti-hunting means of claims 35 and 36. The difference in language exists and cannot be regarded as meaningless, especially when the patentee himself has repeatedly used the phrase anti-hunting means to refer only to structure 55 of the Fig. 1 embodiment. When a “means” term is employed in a claim, it is ordinary and customary to interpret that language as an attempt to use means-plus-a-function terminology as allowed by 35 U.S.C. § 112. However, words used in a patent cannot be given their ordinary and accustomed meaning where it appears from the patent that the inventor has attached some different and/or specific meaning to them. Harrington Mfg. Co. v. White, 323 F.Supp. 1345, 1353, 169 USPQ 193, 200 (N.D.Fla.1971), rev’d on other grounds, 475 F.2d 788 (5th Cir.), cert. denied, 414 U.S. 1040, 94 S.Ct. 542, 38 L.Ed.2d 331 (1973). Claim 2 of the ’514 patent is also useful in establishing the meaning of terms used in, and the permissible scope of, coverage to be afforded to claims 35 and 36. That claim recites, inter alia: means responsive to changes in said current, and anti-hunting means controlled by said current change responsive means for modifying said alternating voltage and reducing the magnitude of said current in accordance with changes in said direct current as said devices approach correspondence. A careful study of the claims in light of the ’514 specification reveals that claim 2 especially recites and claims the transformer 81 and the anti-hunting means 55. Particularly, transformer 81 is characterized in claim 2 as “means responsive to changes in said current.” Accordingly, it is abundantly clear that the phrase “anti-hunting means” was not intended to include transformer 81. Plaintiff’s present argument that the phrase “anti-hunting means” is intended to cover transformer 81, anti-hunting means 55, and transformer 75 in claims 35 and 36 takes on a particularly hollow ring in view of the obvious intent that the phrase “anti-hunting means” covers something less than that combination of elements in claim 2. To be consistent with plaintiff’s own use of terms in other claims of the same patent, it is essential in interpreting claims 35 and 36 that the term “anti-hunting means” be restricted to the structure borne by the number 55 in Fig. 1 of the ’514 patent and not include transformer 81. In sum, it is concluded that element (f) of both claims 35 and 36 structurally cover no more than anti-hunting means 55 for to do otherwise would enable a patentee to define his invention in one way while seeking allowance of a patent from the Patent Office and in another way while seeking to have the patent enforced by the courts. Where, as in the instant case, the patentee has defined a term and the Patent and Trademark Office has accepted that definition as evidenced by the file wrapper, the same definition should be applied by the courts. Kaiser Industries Corp. v. McLouth Steel Corp., 400 F.2d 36, 49, 158 USPQ 565, 578 (6th Cir. 1968), cert. denied, 393 U.S. 1119, 89 S.Ct. 992, 22 L.Ed.2d 124. Interpreting claims 35 and 36 in light of the above analysis dictates that anti-hunting means 55 be directly connected to the direct current drive motor 12. Moreover, in such a combination, since transformer 81 would not be present to block steady start motor currents, the anti-hunting means 55 would generate a modifying signal regardless of whether or not the drive motor current was changing or constant. In other words, anti-hunting means 55 would respond not only to changes of torque, but to all currents supplied to the direct current drive motor. However, all claim limitations must be considered in determining the scope and manner of operation of a claim. As the following analysis will show, the limitations imposed in both claims 35 and 36 on anti-hunting means 55, i. e., that it be responsive to or actuated in accordance with the rate of change of torque of the direct current drive motor, requires that a modifying signal not be generated under constant drive motor current conditions. Turning again to the patent specification, it is necessary to reemphasize that col. 8, line 66, to col. 9, line 3, which was reproduced supra, during an earlier discussion of the ’514 patent, clearly states that anti-hunting means 55 is responsive to the rate of change of the drive motor torque. From this it must be concluded that the patentee intended to limit the operation of anti-hunting means 55 to situations wherein the drive motor current was changing. That plaintiff intended the ’514 invention to operate only in response to changes in the drive motor current is further gleaned from a review of the prosecution history. During the prosecution of the application upon which the ’514 patent is based, original claim 5 was rejected as fully met by United States Patent No. 1,684,137 to Mit-tag, United States Patent No. 1,684,138 to Nixdorff, and French Patent 703,178 to Sperry. In response to the rejection, the claim was amended to provide anti-hunting means responsive “only to changes in said direct current.” Counsel argued that the above change distinguished his invention over the references for the following reasons: In the Mittag patent the anti-hunting motor 63 is continuously responsive to the voltage of the driving motor 12 irrespectively of whether the voltage remains constant or changes. This is likewise true of the Nixdorff patent in which the coils 56-59 inclusive are connected across the field and armature terminals of the driving motor 12. Applicant’s system in which the anti-hunting means respond only to changes in the current supplied to the driving motor 12 is believed to be superior to the systems disclosed in the Mittag and Nixdorff patents and since this feature is clearly specified in claim 5 as amended, it is accordingly believed that this claim will be found to be clearly allowable. Apparently the patent examiner did not fully appreciate the meaning of plaintiff’s remarks, however, for he continued the rejection and noted that it would require no invention to make the anti-hunt device either current or voltage responsive since in Nixdorff voltage and current are proportional once motor speed is established. Claim 5 was additionally rejected as fully met by United States Patent No. 1,811,860 to Morton which showed a current-responsive anti-hunting device. In response, plaintiff again emphasized that the claim was drawn to anti-hunt means responsive only to changes in the motor current, thus excluding response to constant drive motor currents. Patent claims 34, 35 and 36, submitted during examination as application claims 36, 37 and 38, were added to the application by amendment. In describing the subject matter of the claims, plaintiff noted that: As pointed out on page 15, lines 10-20 inclusive, applicant’s anti-hunting system . is responsive to the rate of change of torque of the driving means. Each of the three added claims 36, 37, and 38 is limited to this specific feature, (emphasis added) Lines 10-20 of p. 15 of the application correspond to col. 8, line 66, to col. 9, line 3, of the issued patent, which describes the rate of change of torque in terms of the action of transformer 81. The clear import of the ’514 specification, as well as plaintiff’s actions during prosecution of the application through the Patent and Trademark Office, dictate that element (f) of both claims 35 and 36 is structurally limited to anti-hunting means 55. It is equally clear that anti-hunting means 55 was intended to generate a modifying signal only during changing drive motor current conditions. Claims 35 and 36 are Inoperative Having concluded the anti-hunting means of claims 35 and 36 is a specific recitation of anti-hunting means 55, which responds only to changes in the direct current drive motor current, the conclusion is inescapable that both claims 35 and 36 fail to comply with 35 U.S.C. § 112 and are accordingly invalid. Claims 35 and 36 fail to structurally recite, in any form, transformer 81. This element is an essential element of the combination for without transformer 81, or some equivalent means, the claimed combination is inoperative since there would be nothing to prevent the generation of a modifying signal by anti-hunting means 55 under constant current drive motor conditions. Since the combination as claimed is inoperative for its claimed purpose, the patentee has failed to distinctly claim the disclosed invention as required by the second paragraph of 35 U.S.C. § 112. Wilson v. Midwest Folding Products Mfg. Co., 175 USPQ 649, 656 (N.D.Ill.1972); Shelco, Inc. v. Dow Chemical Co., 322 F.Supp. 485, 517, 168 USPQ 395, 415 (N.D.Ill.1970), aff’d, 466 F.2d 613 (7th Cir.), cert. denied, 409 U.S. 876, 93 S.Ct. 125, 34 L.Ed.2d 129 (1972). Specifically, the anti-hunting means 55 cannot be and is not responsive only to the rate of change of the drive torque absent some element i. e., transformer 81, for restricting the drive motor inputs thereto. A claim to be valid must recite a structure that is capable of performing its purported function. Blohm & Voss AG v. Prudential-Grace Lines, Inc., 346 F.Supp. 1116, 1130, 174 USPQ 484, 496 (D.Md.1972), rev’d on other grounds, 489 F.2d 231 (4th Cir. 1973), cert. denied, 419 U.S. 840, 95 S.Ct. 70, 42 L.Ed.2d 67 (1974). Accordingly, claims 35 and 36 are invalid. Patent No. 2,414,685 United States Patent No. 2,414,685, hereinafter referred to as the ’685 patent, was issued to Dr. E.F.W. Alexanderson, Dr. Martin A. Edwards and Mr. Kenneth K. Bowman on January 21, 1947, on an invention entitled “Follow-Up Control System.” The invention relates to position control systems for maintaining two objects in positional correspondence. Such systems generally comprise a pilot device, a driven object, selsyns, or similar devices for detecting the positional disagreement between the pilot and object, and structure for responding to the detected positional disagreement or error and moving the driven object into correspondence with the pilot. The invention disclosed in the ’685 patent relates to electrical servomechanisms for position control which utilize a compensated armature-excited dynamo-electric machine, described in detail hereinbelow, for supplying current to a d. c. drive motor for moving the driven object into correspondence with the pilot. The dynamo-electric machine is used as an alternative to conventional electronic tube amplifiers. In one embodiment of the invention, high and low speed selsyn devices are connected between a pilot device and driven object for detecting and responding to the positional disagreement or mismatch therebetween. A Wheatstone bridge is suitably connected to the selsyn network such that a portion of the bridge is unbalanced in response to the direction and magnitude of the detected error. A voltage is thus generated across the bridge which is impressed on the control field winding of a compensated armature-excited dynamo-electric machine. The disclosed dynamo-electric machine is provided with a pair of load brushes arranged to commutate on a control or load axis and a pair of brushes arranged to commutate on a primary or short-circuit axis which is perpendicular to the control axis. The brushes on the control axis are connected across the armature of a d. c. motor which drives the driven object. The brushes on the short-circuit axis are short-circuited by an appropriate winding. The total flux on the control axis of the dynamo-electric machine is produced by the control field winding, the armature reaction of the current on the control axis, and a compensating field winding connected in series between the load brushes and the d. c. motor. The control axis flux gives rise to a voltage on the short-circuit axis which generates a short-circuit current. The total flux on the short-circuit axis is produced by the armature reaction of the current on the short-circuit axis and a shunt field winding. The short-circuit axis flux produces a voltage across the control axis which gives rise to a load current for application to the d. c. motor. Without the series compensating field winding on the control axis, the armature reaction flux of the load current, which opposes the control flux generated by the control field winding, would minimize the flow of current through the short-circuit path. However, since the flux generated by the compensating field winding is in line with the control flux, it opposes the armature reaction flux. In this manner, only a small residual of power input is required of the control field winding to generate an effective short-circuit current. The result is that the control field winding turns can be reduced relative to conventional dynamo-electric machines. Moreover, the inductance of the machine is reduced, thus improving the machine’s speed of response. A high-gain power output is also achieved. The amplified output from the dynamo-electric machine is applied to the armature of the d. c. motor for driving the object into positional correspondence accurately, quickly and in a stable manner. A second disclosed embodiment of the ’685 patent is quite similar to the system described above, with the exception that electronic tubes are substituted to perform the functions of the Wheatstone bridge arrangement. The Issues Plaintiff has alleged unauthorized manufacture and use by the defendant of the inventions defined by claims 7 and 11 of the ’685 patent. In response, defendant has asserted the defenses of invalidity and non-infringement of the ’685 patent, implied license to the inventions defined by the claims, failure to mark under 35 U.S.C. § 287 (1970), and, with respect to at least one of the accused devices, expiration of the statute of limitations. Since, as is explained more fully hereinbelow, it is concluded that the ’685 patent is invalid, it is not necessary to address the remaining defenses asserted. Defendant challenges the validity of claims 7 and 11 on the single statutory ground of obviousness, 35 U.S.C. § 103. For reasons which follow, it is concluded that the inventions defined by claims 7 and 11 of the ’685 patent would have been obvious to one of ordinary skill in the art at the time the inventions were developed and are therefore invalid. Scope of Claims 7 and 11 of the ’685 Patent The first necessary step in properly adjudicating the validity of patent claims is to establish their proper scope. It has long been recognized that the claims of a patent are the measure of the grant to the patentee. See Strumskis v. United States, 474 F.2d 623, 200 Ct.Cl. 668, cert. denied, 414 U.S. 1067, 94 S.Ct. 576, 38 L.Ed.2d 472 (1973). Nevertheless, the Supreme Court, in a series of cases stretching back to the early part of this century, has established that the claims of a patent are to be construed in light of the specification and both are to be read with a view to ascertaining the invention. See, e. g., Motion Picture Patents Co. v. Universal Film Mfg. Co., 243 U.S. 502, 510, 37 S.Ct. 416, 61 L.Ed. 871 (1917); United States v. Adams, 383 U.S. 39, 49, 86 S.Ct. 708,15 L.Ed.2d 572, 148 USPQ 479, 482 (1966). Indeed, this court, in Autogiro Co. of America v. United States, 384 F.2d at 396-97,181 Ct.Cl. at 61-2, explained the necessity for interpreting claims in light of the specification: Claims cannot be clear and unambiguous on their face. A comparison must exist. The lucidity of a claim is determined in light of what ideas it is trying to convey. Only by knowing the idea, can one decide how much shadow encumbers the reality. The very nature of words would make a clear and unambiguous claim a rare occurrence. . The dictionary does not always keep abreast of the inventor. It cannot. Things are not made for the sake of words, but words for things. The necessity for a sensible and systematic approach to claim interpretation is axiomatic. The Alice-in-Wonderland view that something means whatever one chooses it to mean makes for enjoyable reading, but bad law. Claims are best construed in connection with the other parts of the patent instrument and with the circumstances surrounding the inception of the patent application. Bearing these principles in mind, attention is focused on claims 7 and 11 of the ’685 patent, whose elements appear below in lettered subsections for ease of analysis and reference: 7. In a follow-up control system having (a) a pilot device and (b) driven object, the combination with (c) a direct-current electric motor for driving said object, of (d) an armature excited dynamo-electric machine for supplying current to said motor, said machine having (e) a control field winding, (f) a pair of load brushes connected to said motor and arranged to commu-tate on said control axis, (g) a pair of short-circuited brushes arranged to commutate on an axis at an angle with said control axis, and (h) a series compensating field winding on said control axis having ampere turns equal to between 75 per cent and 125 per cent of the armature ampere turns, and (i) means responsive to positional disagreement of said pilot device and driven object for supplying current to said control winding thereby to cause said motor to drive said object toward correspondence with said pilot device. * # * * * * 11. In a follow-up control system having (a) a pilot device and (b) driven object, the combination with (c) ' a direct-current motor for driving said object, of (d) an armature excited dynamo-electric machine having (e) a control winding and (f) a pair of load brushes arranged to commutate on the axis of said winding and connected to supply current to said motor, (g) a pair of short-circuited brushes arranged to commutate on an axis at an angle with said control axis and (h) a series field winding for compensating armature reaction on said control axis, (i) electric valve apparatus for supplying a control current to said control winding, and (j) means responsive to positional disagreement of said pilot device and driven object for controlling said valve apparatus to supply current to said control winding of a polarity depending upon the relative positions of said device and object thereby to cause said motor to drive said object toward correspondence with said pilot device. On its face, claim 7 is directed to a follow-up position control system comprising the combination of a pilot device and a driven object, a d. c. motor for driving the object, an armature-excited dynamo-electric machine equipped with a series compensating winding whose ampere turns range from 75 to 125% of the armature ampere turns for supplying current to the d. c. motor and means responsive to the positional error between the pilot and object for supplying current to the control winding of the dynamo-electric machine for elimination of the positional error. Claim 7 contains the only recitation of the percentage compensation afforded by the series field winding to be found anywhere in the ’685 patent. Similarly, claim 11 is directed to a followup position control system comprising the combination of a pilot device and driven object, a d. c. motor for driving the object, a compensated armature-excited dynamo-electric machine for supplying current to the d. c. motor, electric valve apparatus for supplying current to the control winding of the dynamo-electric machine and means responsive to the positional error between the pilot and object for control of the electric valve apparatus to eliminate the positional error. The dynamo-electric machine of claim 11 does not require any particular degree of compensation on the control axis but only broadly calls for “a series field winding for compensating armature reaction * * *.” Plaintiff urges that claims 7 and 11 are narrower in scope than their plain language suggests. Specifically, the threshold question to be decided is whether claims 7 and 11 are drawn to a follow-up position control system utilizing an armature-excited dynamo-electric machine for current supply having full or 100% compensation on its control axis. Stated differently, the issue is whether claims 7 and 11 only cover an armature-excited machine with a series compensation winding whose ampere turns are equal to 100% or more of the armature ampere turns, or are broad enough to cover an armature-excited machine with a series compensating winding whose ampere turns are less than the ampere turns of the armature. This court has, to be sure, had occasion to apply a narrower interpretation to claims, when read in light of the specification, than the claim language would otherwise seem to require. See Roberts Dairy Co. v. United States, 530 F.2d 1342, 208 Ct.Cl. 830 (1976). However, having carefully reviewed the ’685 patent and its file history, we well as the contentions of plaintiff, it is concluded that claims 7 and 11 cannot properly be construed as limited exclusively to followup position control systems utilizing an am-plidyne, i. e., an armature-excited dynamo-electric machine with 100% or more compensation. The series compensating field winding is described in the ’685 patent specification at col. 3, lines 42-8: The series compensating field is used principally to reduce the control power. It is connected so that the series field ampere turns oppose the armature reaction turns along the control axis and leave only a small residual to be overcome by the control field. In this way the power amplification is increased many times. The performance of the disclosed dynamo-electric machine is discussed at col. 4, lines 7 to 13, of the ’685 specification: The predominant characteristics of machine 14 are rapid response, and low ratio of control watts to load watts, e. g. an amplification as high as 25,000:1. No percentages of compensation are disclosed, although the 75 to 125% figure of claim 7 was part of the original claim language and thus is part and parcel of the original disclosure. Bocciarelli v. Huffman, 232 F.2d 647, 43 CCPA 873, 109 USPQ 385 (1956). Nevertheless, this range of compensation, even when read into the ’685 specification, cannot be concluded to be any more than exemplary or preferred. There is no indication in any part of the ’685 patent which would justify treating the 75 to 125% limitation as exclusive or critical. Plaintiff urges, through its expert witness Dr. Chestnut, that the phrase “having ampere turns equal to between 75 per cent and 125 per cent of the armature ampere turns,” which appears in claim 7, is a technician’s manner of saying 100 ± 25% compensation. In other words, it is a compromise between the theorist who desires 100% compensation and the technician who realizes it is not always achievable. Such an interpretation cannot be gleaned from the patent or its file history. Indeed, if anything, a contrary interpretation is demanded from the above-quoted excerpts from the patent in suit. Plaintiff has failed to suggest any persuasive reasons for interpreting the 75 to 125% limitation that appears in claim 7 in any manner other than that dictated by its clear language. Specifically, this phrase is concluded to recite a range of compensation from 75 to 125% and, accordingly, claim 7 broadly covers partial, as well as 100% or greater, compensation. Plaintiff would have the court conclude that the disclosure of “an amplification as high as 25,000:1” is tantamount to stating that the dynamo-electric machine has 100% compensation on the control axis. Quite clearly, however, the prefatory language “as high as” dispels any notion that a specific percentage compensation is intended and suggests a degree of flexibility which results in a range of gains with a ceiling of 25,000:1. Plaintiff also points to the disclosure that the series field winding leaves “only a small residual to be overcome by the control field” as indicating 100% compensation. The phrase “a small residual” is relative. It is impossible to base a conclusion limiting claims 7 and 11 to 100% compensation on the sole basis of such a relative term, especially since plaintiff has not adequately demonstrated that partial percentages of compensation do not likewise leave what might be termed a small residual of power to be overcome by the control field. The patentees, through their own action during the prosecution of the application through the Patent Office, did not expressly limit the claims in suit to 100% series compensation. Moreover, of equal significance is the fact that the specification does not clearly disclose the intention of the patentees to require the use of a series compensating winding having ampere turns equal to those of the armature. Their assignee will not now be allowed to retreat to a narrower reading than that obviously urged during the prosecution of the patent by referring to the specification, especially when the specification does not expressly support the desired reading, and plaintiff is instead forced to rely upon an assortment of vague implications from the construction of a few sentences in the specification. Mueller Brass Co. v. Reading Indus., 352 F.Supp. 1357,1365,176 USPQ 361, 367 (E.D. Pa.1972), aff’d, 487 F.2d 1395, 180 USPQ 547 (3d Cir. 1973). Additional relevant factors militate against limiting the scope of claims 7 and 11 to require 100% or greater compensation on the control axis. To begin, it was established at trial that the amplidyne, a dynamo-electric machine which has 100% or greater compensation on the control axis, is characterized by a variable current output which responds to changes in the load. This variable current characteristic is not present in dynamo-electric machines which have less than 100% compensation (partial compensation), and such machines instead produce a constant current output independent of the load. The output current of partially compensated machines can only be varied by changing the ampere windings on the control winding of the machine. Project reports filed with the General Electric Co. patent department prior to the January 21, 1939, filing date of the ’685 patent demonstrate that the patentees, at that time, were fully aware of the difference in current output characteristics between partially and fully compensated machines. Nevertheless, the ’685 patent specification, while referring to the prior art problem of independent load voltage and current characteristics in dynamo-electric machines, does not contain any discussion of the load voltage and load current characteristics of the disclosed compensated machine. In other words, the variable current output characteristic of amplidynes is not mentioned or discussed in the patent claims, specification, or file history of the ’685 patent. Significantly, 5 months later, in an application entitled “Dynamoelectric Machine” which matured into United States Patent No. 2,227,992, hereinafter referred to as the ’992 patent, on January 7, 1941, Drs. Alexanderson and Edwards disclosed fully a dynamo-electric machine having variable current output characteristics, high amplification ratio and fast response time. The series compensating field winding in the ’992 patent was disclosed at p. 2, col. 2, lines 52-60, as— * * * arranged substantially to neutralize the magnetic back coupling of electric current in the secondary circuit of the armature with the primary armature circuit by substantially neutralizing the armature reaction flux along the secondary axis. This field exciting winding 29 is adapted to neutralize substantially the armature reaction 22 under all load conditions, * * *. Thus, couched in terms of substantial neutralization of the control axis armature flux and variable current output characteristics, it is clear that the series field winding of the ’992 patent was disclosed as providing 100% compensation of the control axis armature reaction flux and was, in essence, a disclosure of the amplidyne. As an aid in determining the true scope to be accorded claims 7 and 11 of the ’685 patent, it is useful to look to the subsequently filed ’992 patent to assist the court in understanding what it was that the inventors deemed of substantive importance in the earlier patent. Jacwil Mfrs. v. Batesville Casket Co., 311 F.2d 38, 42, 136 USPQ 42, 45 (7th Cir. 1962), cert. denied, 372 U.S. 942, 83 S.Ct. 937, 9 L.Ed.2d 968 (1963). Viewing the ’685 disclosure in the context of all the factors discussed above, as well as what was disclosed in the ’992 patent, it is concluded that the inventors’ intent in the earlier ’685 patent was to disclose a position follow-up control system utilizing a compensated armature-excited dynamo-electric machine for power amplification without limitation as to the percentage compensation. Such is concluded to be a reasonable construction of the ’685 specification, which, on one hand, talks of opposing armature reaction, achieving gains as high as 25,000 to 1 and leaving but a small residual of power to be overcome, but, on the other hand, fails to refer to 100% compensation per se or to substantial neutralization of control axis armature reaction flux, operating conditions clearly called for in the ’992 patent. This is especially meaningful where the inventors were aware of the distinctions prior to filing the ’685 application but made no reference to them in the ’685 application. It is, therefore, concluded that the compensation of the dynamo-electric machine set forth in claim 7 ranges from 75 to 125% while the compensation of the dynamo-electric machine set forth in claim 11 of the ’685 patent has no percentage limits. Obviousness Having established the scope to be afforded the claims in suit, attention is next directed to defendant’s argument that the claims are invalid because they fail to comply with the statutory standard set out by 35 U.S.C. § 103 (1970). The validity of claims 7 and 11 must be adjudged in the context of the guidelines enunciated in Graham v. John Deere Co., 383 U.S. 1, 17, 86 S.Ct. 684, 15 L.Ed.2d 545 (1966), wherein the Supreme Court formulated the test of obviousness based upon a consideration of the relevant prior art, the differences between the claims in issue and that prior art, and the level of ordinary skill in the relevant technological art. Defendant asserts the relevance of the following seven prior art references, only one of which, French Patent No. 812,451 to Japolsky, was cited by the patent examiner during the prosecution of the application which matured into the ’685 patent: U.S. Patent Re. 16,667 Hewlett, et al. French Patent 812,451 Japolsky U.S. Patent 1,684,132 Hewlett, et al. U.S. Patent 1,985,981 Edwards U.S. Patent 1,684,138 Nixdorff U.S. Patent 2,412,864 Bowman British Patent 420,167 Pestarini The pertinence of those references not considered during the examination process seriously weakens the usual presumption of validity afforded all patents under 35 U.S.C. § 282 (1970 & Supp. v 1975). Bolt, Beranek & Newman, Inc. v. McDonnell Douglas Corp., 521 F.2d 338, 340, 187 USPQ 142, 144 (8th Cir. 1975), cert. denied, 423 U.S. 1073, 96 S.Ct. 855, 47 L.Ed.2d 82 (1976); Ellicott Mach. Corp. v. United States, 405 F.2d 1385, 186 Ct.Cl. 655 (1969). In addition, it should be noted that all of the above patents, except Japolsky and Pestarini, were assigned to and owned by plaintiff corporation. Six of the references introduced into evidence by defendant provide ample insight into the general state of the position control art at the time the ’685 invention was developed. The French Patent 812,451, granted to Nicholas Japolsky on February 1, 1937, discloses a system for maintaining two objects in positional correspondence. Displacement recorders detect the positional disagreement between the two objects and forward an error signal to a dynamo-electric generator which amplifies and supplies current to a d. c. motor for driving one object into positional correspondence with the other. Dr. Martin A. Edwards taught a basic positional servo for maintaining two objects in positional correspondence wherein sel-syns provide a voltage signal indicative of positional error between the two objects which is converted to an amplified current by appropriate electric valves. The amplified current is then used to drive a d.c. motor for controlling the .movement of one object to achieve correspondence with the. other. United States Letters Patent No. 1,985,981 issued to Dr. Edwards on January 1, 1935. United States Reissue Patent No. 16,667 was issued to Edward M. Hewlett, et al., on July 5, 1927, for an invention entitled “Means for Reproducing Position.” The patent discloses yet another system for maintaining positional correspondence between two objects. A voltage signal indicative of positional error between the two objects is produced by a pair of induction or selsyn devices connected therebetween. The signal is amplified by a pair of electron discharge amplifier tubes and then impressed on the grid of a second pair of electron discharge tubes for supplying amplified current to the armature of a d. c. motor which drives one of the objects into correspondence with the other. The specification discloses that additional amplification of the control current may be obtained by the use of one or more electric generators for further amplification of the current output from the electric tubes. Hewlett, et al., Patent No. 1,694,132, issued on September 11,1928, discloses a position control system which teaches the same relevant position control apparatus as the Hewlett, et al., Reissue Patent. United States Patent No. 1,684,138 issued to Samuel P. Nixdorff on September 11, 1928. Nixdorff developed a position control system similar to those above. Disclosed in the patent was the teaching that, after amplification by a pair of electric tubes, the gain of a position control system could be further enhanced by using a pair of cascaded generators to further amplify the current from the electric tubes before application to the drive motor for the driven object. Yet another position control system is shown in United States Patent No. 2,412,-864, which issued to Kenneth K. Bowman on December 17, 1946. The patent is based on an application filed in the United States Patent and Trademark Office on August 20, 1937. As disclosed in the patent, a driven object is controlled by a d.c. motor which is in turn responsive to voltage signals from a Wheatstone bridge. The bridge generates voltage signals indicative of positional disagreement between the driven object and a pilot device. Selsyn devices provide fine and coarse control and are connected to the two objects such that they provide a signal to the bridge indicative of the positional error. The error signal is modified by an anti-hunt network prior to application to the drive motor. Bowman, et al., essentially teach the same system shown by the ’685 patent except for amplification of the error signal by a dynamo-electric machine. Both Hewlett, et al., patents and the Nix-dorff patent thus teach a follow-up control system which includes a motor for driving an object into positional correspondence with a pilot device in response to a signal indicative of positional disagreement. However, these prior art patents all disclose the use of electric tubes or cascaded generators for supply of current to the drive motor whereas claim 11 calls for a compensated armature-excited dynamo-electric machine to perform that function. Similarly, all of the references previously discussed teach follow-up control systems which include a motor for driving an object, i. e., a gun or search light, into positional correspondence with a pilot device in response to a signal indicative of positional disagreement. The prior art, however, utilizes electronic tubes, cascaded generators, or a basic dynamo-electric machine for supplying current to the drive motor while claim 7 calls for a 75 to 125% compensated armature-excited dynamo-electric machine for such current supply. Resolution of the obviousness of claims 7 and 11 involves slightly different questions. With respect to claim 11, it is necessary to determine whether or not it would have been obvious to one of ordinary skill in the position follow-up control art, at the time the ’685 invention was made, to utilize an armature-excited dynamo-electric machine with any degree of compensation, for supplying current to the driving motor of a position control system such as shown by the Hewlett, et al., and Nixdorff references. With respect to claim 7, it must be determined whether or not it would have been obvious to one of ordinary skill in the position follow-up control art at the time of the invention of the ’685 patent to utilize an armature-excited dynamo-electric machine having either partial or 100% or greater compensation on the control axis for supplying current to the drive motor of a position control system such as those illustrated by any of the references described above. As will be seen, it is concluded that both claims 7 and 11 are invalid because they fail to meet the requirements of 35 U.S.C. § 103. An analysis of British Patent Specification 420,167 by Giuseppe Massimo Pestarini, received in the United States Patent and Trademark Office Library on January 8, 1935, shows that compensated armature-excited dynamo-electric machines were known in the art at the date of filing of the application which matured into the ’685 patent. The Pestarini machine is compensated on the control axis by a compensating field winding interposed in series between the load and load brushes. The effect of the winding is described at p. 4, lines 20 to 27, of the Pestarini patent: The coils [series compensating windings] are wound so as to excite a magnetic flux in a direction to assist the flux produced by the main field coils 14,15,16,17. This compensating winding partially neutralis-es [sic] the armature flux along the axis b, d and enables the ampere turns of the coils 14-17 to be reduced. The patent further states at p. 4, lines 95 to 103, that: The current in the load circuit 7, which passes through the coils indicated by C [series compensating windings] produces a flux which assists the flux produced by the windings indicated by SW [main field winding] and consequently reduces the amount of energy required to be supplied from the source connected to the terminals 8, 9 of the winding SW. Pestarini teaches an armature-excited dynamo machine having a series compensating winding which partially neutralizes the armature reaction flux. The result, as is the case in machine 14 of the ’685 patent, is a reduction in the number of ampere turns of the control winding of Pestarini’s motor. The reduction in ampere turns of the control winding reduces the inductance of the system to improve the system’s time constant or response. In addition, the system’s gain is greatly increased. As is the case generally, whenever a 35 U.S.C. § 103 obviousness test is being applied, it is critical to the analysis to deliberately guard against using the teaching of the patent in suit in arriving at the conclusions. The above observations regarding the Pestarini patent, as well as the following disclosures, insure against any misapplication of the process and guarantees the integrity of the results reached in this instance. While Pestarini does not teach specific applications of his machine, he does broadly suggest its utility “where high values of current are required in the consumption circuit.” Indeed, a machine for improving system gain, which finds particular use where high current outputs are needed, is disclosed. Certainly, the Pestarini patent discloses a solution to overcoming a number of the below-quoted prior art deficiencies outlined at col. 1 of the ’685 patent: Heretofore, follow-up systems have been utilized in which the motor was supplied from electric valves. Although such systems possess a sufficiently high degree of accuracy, they have other limitations, and there are many applications in which it is desirable that means other than electric valves, e. g., dynamo-electric machines, be utilized for supplying current to the driving motor. However, dynamo-electric machines have windings that contain inductance and inductance causes delayed or lagging currents. The result of this, especially in a follow-up system having several stages of amplification, is that the restoring force of the driving motor is still active when the driven object reaches correspondence with the pilot device, and this produces generation of self-excited mechanical oscillations usually referred to as “hunting.” Accordingly, a further object of this invention is the provision of a follow-up control system in which the driving motor is supplied from a dynamo-electric machine and in which means are provided for eliminating hunting without sacrificing sensitivity of the system. Plaintiff, in arguing against the obviousness of combining Pestarini with the position control references of record, points out that none of the prior art systems suggest the use of an armature-excited dynamo-electric machine for any purpose. Further, plaintiff urges that not only does Pestarini not suggest any specific application for a dynamo-electric machine, he clearly does not teach that it can be used as an amplifier in a position control system. The fallacy of these contentions is that they ignore the level of skill in the art as demonstrated by patents such as those issued to Hewlett, et al, and Nixdorff. Those patents illustrate that the general level of skill in the position control art had developed to the point where position control systems utilizing a variety of amplifiers for amplification of the positional disagreement signal were abundant. Moreover, it was during this time frame and in this technical environment that Pestarini disclosed his armature-excited dynamo-electric machine f