Full opinion text
OPINION and ORDER MELLOY, District Judge. In this patent infringement action, the plaintiff, Engineered Products Company (“EPC”), asserts patent and trade dress claims against the defendant, Donaldson Company (“Donaldson”), arising from Donaldson’s creation and sale of two air filter indicator devices — the Air Alert, sold from 1997 to 1999, and the NG Air Alert, sold from 1999 through the present. (Doc. no. 1). EPC claims that both devices infringe its patent, U.S. Patent Number 4,445,456 (“the ’456 patent”). Donaldson concedes that the Air Alert infringed the ’456 patent, but, as to that claim, asserts affirmative defenses of estoppel, waiver, laches, and patent invalidity. As to the newer device, the NG Air Alert, Donaldson disputes EPC’s allegation of patent infringement, arguing that its device falls outside the scope of the patent, and, alternatively, asserting the affirmative defense of patent invalidity. Currently before this Court are the parties’ cross motions for summary judgment as to the following: 1) Donaldson’s asserted equitable defenses of estoppel and lach-es; 2) the validity of EPC’s patent; and 3) infringement of EPC’s patent by Donaldson’s original Air Alert and the NG Air Alert. (Doc. nos. 69 and 74). Also before the Court is Donaldson’s motion for summary judgment on EPC’s trade dress claim, (doc. no. 74), and EPC’s motion for summary judgment on Donaldson’s false advertising and unfair competition counterclaims based on alleged misrepresentations by EPC in publications and product demonstrations (doc. nos. 8 and 69). Both parties have filed opposition and reply briefs on the relevant issues. (Doc. nos. 80, 83, 89, 92, and 94). On September 21, 2000, a Markman hearing was conducted and oral arguments were heard on the summary judgment motions. (Doc. no. 106). Part One of this opinion addresses those issues as to which construction of the patent claim is not essential, namely: equitable estoppel and laches; invalidity of the patent; trade dress violations; and false advertising and unfair competition. In Part Two, the Court construes the patent claim and addresses the cross-motions on infringement. Summary Judgment Standard The standard for granting summary judgment is well-established. A motion for summary judgment may be granted only if, after examining all of the evidence in the light most favorable to the nonmov-ing party, the court finds that no genuine issues of material fact exist and that the moving party is entitled to judgment as a matter of law. See Fed.R.Civ.P. 56(c); Montgomery v. John Deere & Co., 169 F.3d 556, 559 (1999); Matsushita Elec. Indus. Co. v. Zenith Radio Corp., 475 U.S. 574, 587, 106 S.Ct. 1348, 89 L.Ed.2d 538 (1986); Celotex Corp. v. Catrett, 477 U.S. 317, 327, 106 S.Ct. 2548, 91 L.Ed.2d 265 (1986). A fact is material if it might affect the outcome of the suit under the governing substantive law. See Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 255, 106 S.Ct. 2505, 91 L.Ed.2d 202 (1986). The party moving for summary judgment bears the “initial responsibility of informing the district court of the basis for its motion and identifying those portions of the record which show lack of genuine issue.” Celotex, 477 U.S. at 323, 106 S.Ct. 2548. Once the moving party has carried its burden, the opponent must go beyond the pleadings and designate specific facts-by such methods as affidavits, depositions, answers to interrogatories, and admissions on file-that show that there is a genuine issue for trial. See Fed.R.Civ.P. 56(e); Celotex, 477 U.S. at 324, 106 S.Ct. 2548. The evidence of the nonmoving party is to be considered as true, and justifiable inferences arising from the evidence are to be drawn in his or her favor. See Anderson, 477 U.S. at 255, 106 S.Ct. 2505. If the evidence of the nonmoving party is “merely colorable,” or is “not significantly probative,” summary judgment may be granted. Id. at 249-50, 106 S.Ct. 2505. Thus, the nonmoving party does not have to provide direct proof that genuine issues of fact exist for trial; rather, the facts and circumstances that the nonmoving party relies upon must “attain the dignity of substantial evidence and must not be such as merely to create a suspicion.” Metge v. Baehler, 762 F.2d 621, 625 (8th Cir.1985), cert. denied, 474 U.S. 1057, 106 S.Ct. 798, 88 L.Ed.2d 774 (1986). In essence, the evidence must be “such that a reasonable jury could find a verdict for the nonmoving party.” Anderson, 477 U.S. at 248, 106 S.Ct. 2505. Where the litigants concurrently pursue summary judgment, each summary judgment motion must be evaluated independently to determine whether there exists a genuine dispute of material fact and whether the movant is entitled to judgment as a matter of law. See, e.g., Wermager v. Cormorant Township Bd., 716 F.2d 1211, 1214 (8th Cir.1983) (“[T]he filing of cross motions for summary judgment does not necessarily indicate that there is no dispute as to a material fact, or have the effect of submitting the cause to a plenary decision on the merits.”); A. Brod, Inc. v. SK & I Co., L.L.C., 998 F.Supp. 314, 320 (S.D.N.Y.1998) (when faced with cross-motions, court must consider each motion independently of other, must in each instance view facts and draw all reasonable inferences in favor of nonmoving party, and is not required to grant summary judgment for either side); see generally, 11 James Wm. Moore et at, Moore’s Federal Practice ¶ 56.10[6] (3d ed.1997). Thus, a cross-motion for summary judgment operates exactly like a single summary judgment motion. Background EPC and Donaldson are the only domestic manufacturers of graduated or progressive air filter restriction indicators, and, therefore, the companies are generally aware of each other’s products and position in the industry. The disputed facts will be discussed as relevant to the various claims, and this brief background section serves only to give a general context to the current action. A. EPC’s Filter Minder: a progressive air restriction indicator with lock-up feature In the mid-1970s, Joseph Nelson, of Waterloo, Iowa, invented a device to indicate the level of restriction, i.e., the amount of clogging, in the air filter of a combustion engine, and inform the vehicle operator how soon the air filter would need to be changed. Mr. Nelson sought to invent a device that would indicate the progressive levels of air restriction that occurred, rather than a gauge that merely indicated when it was time to change the filter, i.e., a “go/no go” or “single position” gauge. In the late 1970s, Mr. Nelson added a “lockup” feature to his graduated air restriction gauge, which would indicate the highest level of air restriction attained even after the engine is turned off. The lock-up feature locks the moving indicator part at a point corresponding to the level of air restriction that occurs while the engine is running. Thus, Mr. Nelson’s invention allows the operator to see how much restriction is present in the air filter without having to operate the vehicle at the same time. Mr. Nelson named the product that incorporated his lock-up invention the “Filter Minder.” In November of 1977, Mr. Nelson and Ike Leighty incorporated EPC, which worked to further develop Mr. Nelson’s ideas and sell his inventions to original equipment manufacturers (“OEMs”), such as John Deere, CAT, Mack, International Harvester, etc. After four years, EPC was selling indicators to most of the OEMs in the United States. Mr. Nelson was issued U.S. Patent Number 4,445,446 (“the ’456 patent”) for his mechanical air restriction indicator with the lock-up feature on May 1,1984. Mr. Nelson died in 1984, and his wife retired from the company in 1987. In 1997, Mr. Leighty, over eighty years old, sold the assets of EPC and its name to a group of the employees and a private investment group. That sale was completed in February of 1998. EPC is still located in Waterloo, Iowa, and Mr. Nelson’s Filter Minder remains the company’s best-selling product. B. Donaldson develops progressive air filter indicators with lock-up feature In the late 1970s, Donaldson began manufacturing and selling a line of air restriction indicators, including a progressive indicator with a lock-up feature sold under the trade name “Informer.” The Informer competed directly with, but was consistently outsold by, EPC’s Filter Minder. EPC considered the Donaldson Informer indicator to be an inferior product and not a substantial threat to EPC in the marketplace. In the mid-1990s, General Motors (“GM”) decided to add a progressive air restriction indicator to its light truck platform (the “GMT-800 platform”), which includes large passenger vehicles typically with four-wheel drive, such as sport utility vehicles (“SUVs”). This platform was expected to become the largest platform in the history of the auto industry, and represented a unique opportunity to manufacturers of progressive air restriction indicators, such as Donaldson and EPC. In 1995, concurrent with the industry’s growing awareness of the significant opportunity with GM, key Donaldson personnel, including vice president Nick Priadka, had a lunch meeting with EPC’s Mr. Leighty, during which Mr. Leighty was informed that Donaldson would be interested in purchasing EPC should Mr. Leighty ever decide to sell. Mr. Leighty informed Donaldson that he did not wish to sell EPC and suggested instead that Donaldson enter into a license with EPC for EPC’s Filter Minder. There was apparently no follow-up by either party. In April of 1996, as expected, GM published a request for quote (RFQ) for a progressive air restriction indicator for the GMT-800 platform. Donaldson responded to the RFQ by offering first a single-position indicator and then its Informer. Both were rejected. At about this time, Mr. Priadka telephoned Mr. Leighty ánd informed him that Donaldson would be upgrading the Informer, presumably to better compete for the GMT-800 platform. The result of this upgrade was the Donaldson Air Alert, and based on the Air Alert design Donaldson was awarded the GMT-800 contract. The Air Alert was manufactured and sold from 1997 to 1999, at which time it was replaced by the Next Generation Air Alert. EPC filed the present suit on November 20, 1998. PART ONE I. Equitable Defenses Donaldson does not dispute that its original Air Alert infringed EPC’s ’456 patent, but argues here that EPC is equitably estopped from enforcing that claim and, alternatively, that laches bars any claim for damages accrued prior to this suit. In support of this claim, Donaldson contends the following: (1) that EPC has known for years that Donaldson’s Informer indicator infringes the ’456 patent but never took any action regarding that device; (2) that EPC knew that Donaldson would be investing substantial resources to upgrade its Informer indicator but never informed Donaldson that it would take action to enforce its ’456 patent against any new or improved device; and (3) that in reliance on that misleading silence, Donaldson invested over $500,000 in developing the Air Alert, and would suffer both economic and evidentiary prejudice were EPC allowed to pursue an infringement claim at this time. In reply, EPC contends that there was no unreasonable delay in filing suit once it had concluded that the Air Alert infringed its ’456 patent. EPC further asserts that it engaged in no conduct that would reasonably imply that it had abandoned its ’456 patent rights, and that, moreover, Donaldson’s decision to develop and manufacture the Air Alert in no part relied upon conduct by EPC. The parties have filed cross-motions for summary judgment on these defenses, and thus, guided by the standards discussed above, the Court will review each party’s motion in turn. A. Equitable Estoppel Estoppel is cognizable under 35 U.S.C. § 282 as an equitable defense to patent infringement claims. See Aukerman v. R.L. Chaides Constr. Co., 960 F.2d 1020, 1028 (Fed.Cir.1992). As an equitable defense, estoppel is a matter committed to the sound discretion of the trial court, see id., and “is not limited to a particular factual situation nor subject to resolution by hard and fast rules.” Id. at 1041. Where established, it may bar all relief on a claim. See id.; ABB Robotics, Inc. v. GMFanuc Robotics Corp., 52 F.3d 1062, 1063 (Fed.Cir.1995). There are three essential elements to an equitable estoppel claim: 1) The patentee, through misleading conduct, leads the alleged infringer to reasonably infer that the patentee does not intend to enforce its patent against the alleged infringer. “Conduct” may include specific statements, action, inaction, or silence where there was an obligation to speak. 2) The alleged infringer relies on that conduct. 3)Due to its reliance, the alleged in-fringer will be materially prejudiced if the patentee is allowed to proceed with its claim. Aukerman, 960 F.2d at 1028; Gasser Chair Co., Inc. v. Infanti Chair Mfg. Corp., 60 F.3d 770, 775 (Fed.Cir.1995). Even where the three elements are established, the trial court must, in exercising its discretion and deciding whether to allow the defense to bar the suit, take into consideration any other evidence and facts respecting the equities of the parties. See Aukerman, 960 F.2d at 1043. And where a determination is made at the summary judgment level, the burdens must be allocated correctly by the court. See id. at 1044. Here, Donaldson bears the burden of establishing every element of its asserted defense by a preponderance of the evidence, see id. at 1046, and thus EPC is entitled to summary judgment if Donaldson does not meet its burden on even one element. The Court will first analyze the record pursuant to EPC’s motion, and then, to the extent necessary, the Court will discuss Donaldson’s cross-motion. (1.) EPC’s motion for summary judgment on equitable estoppel defense In reviewing EPC’s motion for summary judgment, the Court must view all evidence and justifiable inferences therefrom in favor of Donaldson to determine whether there are no genuine issues of material fact and EPC is entitled to judgment as a matter of law. See, e.g., Montgomery, 169 F.3d at 559. EPC does not bear the burden of persuasion at trial, and thus can show presumptive entitlement to summary judgment if it points to the absence of any factual support for an essential element of Donaldson’s claim. See Celotex, 477 U.S. at 322-24, 106 S.Ct. 2548 (so holding); Anderson, 477 U.S. at 250-253, 106 S.Ct. 2505 (holding that court must consider burden of persuasion at trial in determining strength of material submitted with motion). If EPC makes this showing, Donaldson must then, to preclude summary judgment, introduce specific facts showing a need for trial. See id. Thus, EPC is entitled to summary judgment if, after allocating the burdens as above, Donaldson cannot raise at least a triable issue as to every element of its estoppel claim. The Court will address each element in turn. a). Misleading conduct To establish estoppel, Donaldson must first prove that EPC’s misleading conduct led Donaldson to reasonably infer that EPC did not intend to enforce its ’456 patent against Donaldson. See Aukerman, 960 F.2d at 1028. As noted above, “conduct” may include specific statements, action, inaction, or silence where there was an obligation to speak. See id. Where “a patentee’s ‘misleading conduct’ is essentially misleading inaction ... [that] inaction must be combined with other facts respecting the relationship or contacts between the parties to give rise to the necessary inference that the claim against the defendant is abandoned.” Id. at 1042 (citations omitted). In the typical estoppel case, the paten-tee first informs the alleged infringer of its concerns and intention to enforce its patent rights against an accused device and then fails to follow through on those threats. See Hottel Corp. v. Seaman Corp., 833 F.2d 1570, 1574 (Fed.Cir.1987) (“In the cases that have applied intentionally misleading silence in the patent infringement context, a patentee threatened immediate or vigorous enforcement of its patent right but then did nothing for an unreasonably long time.”), quoted in Meyers v. Asics Corp., 974 F.2d 1304, 1309 (Fed.Cir.1992). This inaction on the pat-entee’s part can become “misleading conduct” if at some point it leads the alleged infringer to reasonably infer that the pat-entee has abandoned its previously expressed claim. See id. at 1308. EPC filed the present suit on November 20, 1998, and it is undisputed that prior to that EPC had never approached Donaldson with concerns about the ’456 patent and any Donaldson products, including the allegedly Ion standing infringement by Donaldson’s Informer indicator. EPC argues that it is therefore entitled to summary judgment because a defendant relying on misleading silence to show estoppel must, at a minimum, show that the paten-tee gave the defendant notice of infringement and then delayed taking action for an unreasonably long time. See, e.g., Asics Corp., 974 F.2d 1304 (finding no basis for applying equitable estoppel on summary judgment because Meyers did not have any contact with Asics prior to filing suit); Meyers v. Brooks Shoe, Inc., 912 F.2d 1459, 1464 (Fed.Cir.1990) (finding no misleading conduct where defendant could not show that patentee “threatened immediate or vigorous enforcement of his patents but then did nothing for an unreasonably long time”) see also, Hottel Corp., 833 F.2d at 1574 (listing cases and concluding, “In the cases which have applied intentionally misleading silence in the patent infringement context, a patentee threatened immediate or vigorous enforcement of its patent right but then did nothing for a long time.”). Donaldson argues, however, that in light of the history between the parties and events that transpired prior to and during Donaldson’s development of the Air Alert, EPC’s silence and inaction can be deemed misleading conduct under Aukerman. This Court recently addressed this precise issue in another patent case and concluded that the absence of prior communication or threat by the patentee is not necessarily fatal to an estoppel claim. In that opinion, the Court explained: Like [plaintiff], this Court has been unable to find any federal [circuit] cases where misleading conduct was established absent a prior communication by the patentee to the alleged infringer regarding potential enforcement. However, the federal circuit has not expressly held, and this Court is not prepared to say, that the absence of such prior communication is necessarily fatal to an es-toppel claim. Aukerman and subsequent case law have emphasized that equitable estoppel “is not limited to a particular factual situation nor subject to resolution by simple or hard and fast rules.” Aukerman, 960 F.2d at 1041; accord, James River Corp. v. Hallmark Cards, Inc., 915 F.Supp. 968, 981 (E.D.Wis.1996) (rejecting narrow reading of misleading silence that would require prior express threat, the court found that “focus is properly on all the factors that may bear on what inferences [the alleged infringer] could reasonably draw from [the patentee’s] silence”). Therefore, the Court finds that it is not dispositive that [plaintiff] never expressly communicated to [defendant] its infringement concerns about the ... patent and the [accused device]. Rather, the proper inquiry under Aukerman is whether [plaintiffs] inaction, combined with other facts respecting the relationship or contacts between the parties, gave rise to the necessary inference that the claim against [defendant] was abandoned. See ABB Robotics, 52 F.3d at 1064 (“[T]hat an immediate threat of force may be the most common scenario does not mean that it is the only set of facts which can support a finding of misleading silence.”); Scholle Corp. v. Blackhawk Molding Co., Inc., 133 F.3d 1469, 1472 (noting that “course of dealings” between patentee and alleged infringer may in some cases reasonably imply patent right abandonment absent a statement to the contrary). The quantity and quality of communications between the parties is one factor, albeit a significant one, to be considered in that analysis. Order, Cedarapids v. CMI, No. 98-110 MJM (November 2, 2000). Applying these principles, the Court notes the following undisputed facts: EPC and Donaldson are the only two domestic manufacturers of graduated indicators; EPC’s first graduated indicator, the Filter Minder, for which it applied for and received the ’456 patent, was developed and manufactured in the late 1970s and has been on the market ever since; Donaldson also introduced a graduated indicator, the Informer, in the late 1970s to the early ’80s which, since then, has competed in the marketplace with EPC’s Filter Minder; EPC’s Filter Minder has consistently significantly outsold Donaldson’s Informer; and both companies were aware of, and competing for, the new business opportunity presented by GM’s decision to include graduated indicators in its light truck and SUV platform. Viewing the evidence in the light most favorable to Donaldson, the nonmoving party, the Court finds the following facts also relevant: Nick Priadka, vice president of Donaldson, worked at EPC from 1980 to 1986 before moving to Donaldson where he has been ever since; the companies have a generally amicable relationship as evidenced by their occasional sharing of customer information and periodic visits between the companies’ personnel at trade shows and industry events; in 1995, Mr. Priadka and other key Donaldson employees had an amicable, informal meeting with EPC founder, Ike Leighty, at which Donaldson indicated that it would be interested in purchasing EPC should Mr. Leighty ever decide to sell; and shortly thereafter, Mr. Priadka informed Mr. Leighty that Donaldson would be improving its Informer product. One could reasonably infer from these facts that both EPC and Donaldson were aware that Donaldson’s long selling Informer infringed EPC’s ’456 patent. A jury could further find that EPC knew that Donaldson’s upgrade was intended to make it more competitive with regard to the GM bid, and that to succeed Donaldson would have to improve (or arguably, “better-infringe”) the already infringing Informer. A jury could then conclude that it was reasonable for Donaldson to infer that if EPC had never taken action to enforce its ’456 patent against Donaldson’s Informer, it would not now take action against a mere upgrade of that infringing product. Essentially, a jury could reasonably find that, at some point after Donaldson informed EPC about the planned enhancement of the Informer, EPC should have at least advised Donaldson that EPC would enforce its ’456 patent against an infringing upgrade, and that its failure to do so constituted misleading conduct under Aukerman. b). Substantial reliance The second essential element of equitable estoppel requires Donaldson to show that it substantially relied on the misleading conduct of EPC in connection with taking some action. See Aukerman, 960 F.2d at 1042-43. Donaldson contends that decisions in the mid-1990s regarding the development, manufacture, and mass production of the Air Alert were made in substantial reliance on its reasonable inference that it would not be sued by EPC for patent infringement. EPC counters that no reasonable jury could conclude that Donaldson substantially relied on EPC’s conduct. Rather, EPC contends, Donaldson never even considered EPC’s patent when it decided to develop the Air Alert and Donaldson’s actions were solely driven by its desire to capture the extraordinary new business opportunity represented by the GM light truck platform. Initially, the Court notes some discord in the parties’ briefs, and in the ease law, as to what must be shown to establish the substantial reliance element. In Auker-man, the court explained this element as follows: Reliance is not the same as prejudice or harm, although frequently confused. An infringer can build a plant being entirely unaware of the patent. As a result of infringement, the infringer may be unable to use the facility. Although harmed, the infringer could not show reliance on the patentee’s conduct. To show reliance, the infringer must have had a relationship or communication with the plaintiff which lulls the infringer into a sense of security in going ahead with the plant. Id. at 1042-43. Although this oft-cited example clearly recognizes a causal element in distinguishing reliance from prejudice (the third element of equitable estoppel), it arguably suggests, as Donaldson asserts, that the infringer can demonstrate rebanee in some cases by showing little more than already established under the misleading conduct element, i.e., the facts supporting a finding of misleading conduct can also prove reliance. In contrast, EPC argues that only affirmative proof of actual reliance should be considered. The Court agrees with EPC that reliance cannot be construed so broadly as to impermissibly conflate the reliance and misleading conduct elements. The federal circuit’s opinion in ABB Robotics, 52 F.3d 1062, supports an analysis that falls somewhere between those proposed by the two parties. In ABB Robotics, the patentee argued that the trial court had improperly decided whether the abeged infringer could have relied on the patentee’s silence instead of using the correct standard, whether the alleged infringer actually relied on the patentee’s conduct. See id. at 1064. The appellate court rejected the patentee’s position, finding it “clear that the trial court did not consider abstract theoretical possibilities, but rather, looked at the conduct of the parties and decided that the infringer had a relationship with the patentee that lulled the infringer into a sense of security that it would not be sued.” Id. Thus, ABB Robotics clarifies that while the misleading conduct analysis looks mainly to the conduct of the patentee to determine what reasonable inferences flow from its actions, the reliance factor focuses on the conduct and communications of both parties in determining whether the infringer substantially relied on the patentee’s conduct. Under ABB Robotics, it is clearly not enough for Donaldson to show that, given EPC’s conduct, it would have been reasonable for Donaldson to be lulled into a sense of security. To demonstrate substantial rebanee, as opposed to misleading conduct, Donaldson must do more — it must show that it was, in fact, so lulled. In support of its position, EPC points to deposition testimony by at least five key Donaldson employees, each of whom clearly and affirmatively denied any consideration whatsoever of EPC or EPC’s patents during the relevant time period. Among these deponents were: Nick Priadka, vice president of Donaldson; Stan Koehler, the “quarterback” of Donaldson’s plan to pursue GM’s light truck market; Richard Canepa, director of the New Business Unit, who had previously worked at EPC; and Val Peterson, director of the Automotive Business Unit and the person accountable for all major customers. Mr. Priadka’s deposition is exemplary, and undisputably damaging. In that testimony, Mr. Priadka affirmatively attests that, prior to EPC filing suit, he was unaware of any analysis at Donaldson relating to the validity, scope or enforceability of EPC’s patents and that, moreover, he had never been a party to any discussion about nor had he seen any documents pertaining to EPC’s patents. EPC also submits internal strategic mem-oranda by Donaldson that link development of the Air Alert to the potential GM opportunity and which make no mention of any litigation risks regarding EPC’s patents. EPC has clearly met its burden as the summary judgment movant and were this evidence uncontested the Court would agree that no reasonable jury could find substantial reliance on Donaldson’s part. Here, however, there is some evidence to support a different perspective. Thus, the Court will review that evidence to determine whether, granting all justifiable inferences in Donaldson’s favor, a jury could reasonably find in favor of Donaldson on this element. Although Donaldson does not dispute the evidence offered by EPC. Rather, it maintains that EPC’s version of the facts is incomplete and far less conclusive than EPC represents. Donaldson contends that the evidence actually shows that, although the employees cited by EPC did not review or consider EPC’s patents, it was simply because it was not the job of those employees to do so. Donaldson argues that EPC’s evidence merely reflects that in a company the size of Donaldson it is not the job of design engineers and salespeople to consider patent infringement matters. Moreover, Donaldson argues, additional testimony by Richard Carlson, a manager in Donaldson’s intellectual property department, shows that during the relevant time period Donaldson did review the status of EPC’s patents and consider the litigation threat posed by them. Specifically, Mr. Carlson testified regarding conclusions conveyed to Donaldson designer, Larry Nepsund, after Mr. Carlson had reviewed, in 1996 or ’97, copies of EPC’s ’456 patent in relation to design work on the Air Alert. His testimony, in relevant part, is as follows: Q. And again correct me if I misstate anything. You and Larry mentioned the Informer as a possible reason why these patents might be invalid? A. Potentially, but it was more than that. Q. What was “more than that”? A. Well we looked at these patents and we kind of talked generally about what these patents were all about, and Larry had read the patents, I believe he told me that he had read them, and I looked at them and we were, Larry said well what do these patents mean? I said well we have to cite them as prior art to your calibration wheel patent, and we did note that they were older patents relative to the time we’re talking about, this was about in 1996 or ’97.... And that the subject matter of the patents was, of course, related to his restriction indicator work, which was also very much like that which was done earlier and resulted in the Informer.... And it occurred to us that, we did not dissect the claims in these patents, we kind of just glanced at them, we knew we had not been sued for patent infringement relative to the Informer. We knew that Larry’s current development work was kind of a carry-on of the Informer, and didn’t consider them much of a problem. ... Carlson depo., p. 65, line 12 through p. 67, line 2. According to Donaldson, this testimony shows that Donaldson, through its agent, reviewed the relevant EPC patent and recognized its similarity to the Informer. Mr. Carlson, as agent for Donaldson, then reasonably concluded that because EPC had never sued over the Informer, there was no threat regarding the Air Alert which was a “carry-on” of the Informer. Moreover, Donaldson contends, as manager of the intellectual property department it was Mr. Carlson’s job — and not that of Mr. Priadka, Mr. Canepa and the others — to make determinations of this sort and that his determination in this case was bolstered by factors discussed above in connection with the misleading conduct element — the limited industry size, the periodic interaction among the companies’ personnel, and the generally amicable relationship between the companies. Thus, Donaldson argues, Mr. Carlson’s review, combined with reasonable inferences drawn from the conduct and relationship between the parties during this period, resulted, in fact, in Donaldson being lulled into a sense of security that EPC would not enforce its ’456 patent against Donaldson. The Court concludes that, construing all evidence and justifiable inferences therefrom in Donaldson’s favor, a jury could reasonably characterize the evidence as Donaldson proposes. In so concluding, the Court does not discount the potentially persuasive weight of EPC’s evidence. Rather, the Court merely acknowledges that, where other evidence exists which, if believed by the jury, would support a contrary conclusion, a genuine issue of material fact exists which cannot be resolved at summary judgment. c). Prejudice The final essential element of equitable estoppel requires Donaldson to show material prejudice resulting from Donaldson’s reliance. See Aukerman, 960 F.2d at 1028. The prejudice may be a change of economic position or loss of evidence. See id. at 1043. Here, the Court finds that Donaldson has raised a triable issues as to material evidentiary prejudice. Mr. Nelson, the inventor of the Filter Minder and the ’456 patent, died in 1984; his workroom, and any relevant papers that may have been stored there have long since been disassembled. Further, as the record demonstrates, memories of potentially key witnesses have faded over the twenty-plus years since EPC’s graduated indicator was first developed. See id. at 1033 (“Evidentiary, or “defense” prejudice, may arise by reason of a defendant’s inability to present a full and fair defense on the merits due to the loss of records, the death of a witness, or the unreliability of memories of long past events, thereby undermining the court’s ability to judge the facts.”). d). Equity considerations Having found that Donaldson has met its burden of demonstrating triable issues as to each element of its estoppel defense, the Court will not address at length the equities considerations mandated by Auk-erman except to note that such considerations further support resolution of the estoppel claim at trial rather than summary judgment. See Aukerman, 960 F.2d at 1043 (directing that trial court “must, even where the three elements of equitable estoppel are established, take into consideration any other evidence and facts respecting the equities of the parties in exercising its discretion and deciding whether to allow the defense of equitable estoppel to bar the suit.”). Donaldson bears the burden of demonstrating that it did not engage in egregious conduct which, under equity principles, would preclude a determination of estop-pel. EPC contends that Donaldson’s willful infringement of the ’456 patent is the kind of egregious conduct which mandates summary judgment in EPC’s favor. See Gasser Chair Co., 60 F.3d at 775 (holding that willful infringement is one factor which may indicate a shift in the equities even where underlying elements established); Ryco, Inc. v. Ag-Bag Corp., 857 F.2d 1418, 1428-29 (Fed.Cir.1988) (explaining test for willful infringement as whether, under all the circumstances, a reasonable person would prudently conduct himself with any confidence that a court might hold the patent invalid or not infringed) (citing Central Soya Co. v. Geo A. Hormel Co., 723 F.2d 1573, 1577 (Fed.Cir.1983)). EPC presents a colorable claim that, in developing the Air Alert, Donaldson willfully infringed EPC’s patent. However, Donaldson does not concede this issue, and, if accepted as true, Mr. Carlson’s testimony may persuade a jury that, under the unique facts of this case, Donaldson’s less than extensive review of EPC’s patent was sufficiently prudent. Therefore, because the record as it stands would permit, but not require, a conclusion of willful infringement by Donaldson, the Court concludes that equity considerations are not determinative in resolution of EPC’s motion on estoppel. The Court will now briefly address Donaldson’s motion for summary judgment on the same issue. (2.) Donaldson’s motion for summary judgment on equitable estoppel defense After thoroughly reviewing the record, the Court concludes that Donaldson’s cross-motion on estoppel must similarly be denied. In evaluating Donaldson’s motion, the Court must view all facts in favor of the nonmoving party, EPC, and, as the above discussion makes clear, such an analysis demonstrates genuine issues of material fact as to whether Donaldson can prove every element of its affirmative defense. In brief, the record supports the following findings: both EPC and Donaldson were aware that the Informer infringed EPC’s patent; both companies were aware that the Informer posed no threat in the marketplace to EPC’s graduated indicator; and both companies knew that EPC was a much smaller company than Donaldson. From these facts, a jury could reasonably conclude that given the foreseeable costs involved in any patent action, EPC’s inaction regarding a poorly-copied and noncompetitive product did not reasonably imply that EPC would not take legal action were Donaldson to introduce an infringing product that posed a credible threat. Further, a jury could reasonably conclude that Richard Carlson’s testimony was outweighed by other conflicting testimony and evidence suggesting that Donaldson did not substantially rely upon EPC’s conduct or its patents when deciding to develop and manufacture the Air Alert. In sum, while the Court finds that Donaldson’s characterization of the facts was permissible, it was far from undisputed and thus summary judgment in Donaldson’s favor is unwarranted. See Aukerman, 960 F.2d at 1043-44 (“[0]n summary judgment, such an inference must by the only possible inference from the evidence.” (emphasis in original)). The Court will now turn to the parties’ cross-motions as to Donaldson’s asserted laches defense. B. Laches Unlike estoppel which may bar recovery altogether, laches bars recovery only of those damages arising prior to suit. See Aukerman, 960 F.2d at 1028; Gasser Chair Co., 60 F.3d at 773. Laches may be defined as “the neglect or delay in bringing suit to remedy an alleged wrong, which taken together with lapse of time and other circumstances, causes prejudice to the adverse party and operates as an equitable bar.” Aukerman, 960 F.2d at 1028-29. “Courts of equity ... will not assist one who has slept on his rights, and shows no excuse for his laches in asserting them.” Id. (quoting Lane & Bodley Co. v. Locke, 150 U.S. 193, 201, 14 S.Ct. 78, 37 L.Ed. 1049 (1893)). To successfully invoke laches, a defendant must prove by a preponderance of the evidence: (1) that the plaintiff delayed filing suit an unreasonable and inexcusable length of time from the time the plaintiff knew or reasonably should have known of its claim against the defendant; and (2) that the delay resulted in material prejudice or injury to the defendant. See Advanced Cardiovascular Sys., Inc. v. SciMed Life Sys., Inc., 988 F.2d 1157, 1161 (Fed.Cir.1993); Aukerman, 960 F.2d at 1028. On summary judgment, the burden of proof on an issue must be correctly allocated, see Gossen Corp. v. Marley Mouldings, Inc., 977 F.Supp. 1346, 1350 (E.D.Wis.1997), and the moving party must also establish that there was no genuine issue of material fact as to either element. See Gasser Chair Co., 60 F.3d at 773. No fixed period of time has been classified as “unreasonable” delay per se; rather, that determination rests on the circumstances of the particular case. See Aukerman, 960 F.2d at 1032. However, a rebuttable presumption of laches arises where a patentee delays bringing suit for more than six years after the date the patentee knew or reasonably should have known of the alleged infringer’s activity. See id. at 1035; Hall v. Aqua Queen Mfg., Inc., 93 F.3d 1548, 1552-53 (Fed.Cir.1996). This presumption shifts to the patentee the burden of producing evidence which if believed would show that either the paten-tee’s delay was reasonable or excusable under the circumstances or the defendant suffered neither economic nor evidentiary prejudice. See Wanlass v. General Elec. Co., 148 F.3d 1334, 1337 (Fed.Cir.1998). Without the presumption, “the facts of unreasonable, inexcusable delay and prejudice must be proved and judged on the totality of the evidence presented.” Auk-erman, 960 F.2d at 1038. The period of delay is calculated from the time the patentee has actual or constructive knowledge of the defendant’s potentially infringing activities. See Wanlass, 148 F.3d at 1337-38 (quoting Eastman Kodak Co. v. Goodyear Tire & Rubber Co., 114 F.3d 1547, 1559 (Fed.Cir.1997) (“[D]elay begins when the plaintiff knew, or in the exercise of reasonable diligence should have known, of the defendant’s allegedly infringing activity.”)). “The availability of delay based on constructive knowledge of the alleged in-fringer’s activities imposes on patentees the duty to police their rights.... ‘[T]he plaintiff is chargeable with such knowledge as he might have obtained upon inquiry, provided the facts already known by him were such as to put upon a man of ordinary intelligence the duty of inquiry.’ ” Wanlass, 148 F.3d at 1338 (quoting Johnston v. Standard Mining Co., 148 U.S. 360, 370, 13 S.Ct. 585, 37 L.Ed. 480 (1893), and citing Advanced Cardiovascular Sys., 988 F.2d at 1162 (“Absent actual knowledge, the facts must support a duty of inquiry.”)). Even if a defendant establishes the laches elements, the defense remains an equitable judgment of the trial court in light of all the circumstances. See Auker man, 960 F.2d at 1036; Gasser Chair Co., 60 F.3d at 773. “A court must look at all of the particular facts and circumstances of each case and weigh the equities of the parties. Where there is evidence of other factors which would make it inequitable to recognize the defense despite undue delay and prejudice, the defense may be denied.” Gasser Chair Co., 60 F.3d at 773 (quoting Aukerman, 960 F.2d at 1036). In the present action, there are cross-motions before the Court, and where relevant the Court will discuss and construe disputed facts in favor of each party in turn. (1.) The parties’ cross-motions on laches Donaldson argues that the Air Alert is merely an upgrade of the Informer and thus it is appropriate to measure the lach-es delay period from EPC’s knowledge of infringement by the earlier device. Conversely, EPC contends that the Air Alert is a new product and therefore any conduct with regard to the Informer is irrelevant and cannot be “tacked on” for purposes of the laches inquiry. According to EPC, the relevant time period runs only from 1997 when EPC obtained and examined an Air Alert indicator. Thus, EPC contends, no presumption arises and the relatively brief delay in filing suit was neither unreasonable, inexplicable nor prejudicial. a). Establishing the “delay” period As the parties’ positions make clear, Donaldson’s laches defense turns predominantly on whether the delay period is measured from EPC’s constructive knowledge of infringement by Donaldson’s Informer. Thus, the critical inquiry is whether such “tacking on” is appropriate in this case or whether, as EPC asserts, Donaldson’s development of the Air Alert triggered an independent laches period for that product. The federal circuit has not, in the laches context, prescribed the standard to be applied in determining whether an alleged infringer may “tack on” delay periods from prior infringing activity, but Aukerman makes clear that consideration of altered conduct is relevant. In reversing the trial court’s grant of summary judgment to the alleged infringer, the Aukerman court noted, inter alia: Similarly, we believe the court erred in resolving the issue of whether the defendant’s infringing activities changed sufficiently to disrupt the laches period. It is not disputed that defendant’s conduct changed during the laches time frame both by its manufacturing its own slip-forming device and by greatly increasing the amount of asymmetrical wall it poured. It could not be inferred against the patentee that these changed circumstances should have been known to the patentee or were immaterial to the determination of laches. Aukerman, 960 F.2d at 1039; see also, Gasser Chair Co., 60 F.3d at 774 (“A court must consider any excuse for the delay offered by the plaintiff.”). Other courts have held that where the defendant alters the nature of its infringing activity, a new period of delay begins as to the altered conduct. See MGA, Inc. v. Centri-Spray Corp., 639 F.Supp. 1238, 1244 (E.D.Mich.1986) (listing supporting citations, and concluding that the court cannot, at summary judgment stage, resolve disputed issue of material fact as to whether defendant so altered the infringing activity); Jacuzzi Whirlpool Bath, Inc., 211 U.S.P.Q. at 232 (reversing district court conclusion that laches applies to the enforcement of a patent against the defendant generally rather than to particular instances of infringing conduct, and holding instead that defendant must establish that prior conduct was “the same or virtually the same” as the conduct later sued upon); Spalding & Evenflo Cos., Inc. v. Acushnet Co., 718 F.Supp. 1023 (D.Mass.1989) (citing MGA and finding two separate periods of infringement involving two separate infringing golf balls where paten-tee chose not to sue when defendant stopped infringing with first product but later sued within months after defendant introduced a new infringing product); North American Philips Corp. v. Taito America Corp., 1997 WL 543111 (N.D.Ill.1997) (noting the “sparse” case law on this issue, but concluding that defendant had not met its burden of showing that the facts met the Jacuzzi Whirlpool Bath standard or that a lower standard should be applied). Donaldson asserts that its Air Alert was merely an upgrade of its Informer indicator, and that under the case law it is proper to tack on the delay period attributable to the Informer because the modification did not change the nature of the infringing activity. The record supports constructive knowledge of the infringing nature of the Informer indicator dating back to 1980 when EPC requested the Patent and Trade Office (“PTO”) to amend EPC’s pending patent claim to specifically cover the Donaldson Informer indicator. Under this construction of the facts, the delay in bringing suit would run 14 years, from 1984 when the ’456 patent was issued, until 1998 when EPC filed this suit. See Aukerman, 960 F.2d at 1032 (delay period “does not begin prior to issuance of the patent”). The presumption would be established, and the burden would shift to EPC to produce sufficient evidence to put one of the underlying factors into genuine dispute. EPC rejects in toto Donaldson’s assertion that the Air Alert is merely a modification of the Informer. Rather, EPC argues, Donaldson’s development and manufacture of the Air Alert substantially changed the infringing activity and EPC’s inaction (or laches) regarding the Informer cannot be generalized to a substantially different activity. Therefore, EPC contends, the delay period commences only as of EPC’s constructive or actual knowledge as to the infringing nature of the Air Alert. This would date back no further than 1997 when EPC was able to obtain an Air Alert indicator. Approximately one year later, after examining the Air Alert indicator and seeking legal counsel as to its infringing nature, EPC filed this suit. Thus, no presumption arises, and alternatively no unreasonable or inexcusable delay can be established. The parties present diametrically opposed evidence and testimony in support of their positions, which must be accepted as true for purposes of the cross-motions. Thus, the Court concludes that where, as here, there is a material factual dispute as to whether the Informer and Air Alert designs are sufficiently similar as to warrant one rather than two delay periods, summary judgment in favor of either party is not appropriate at this time. See, e.g., MGA, Inc., 639 F.Supp. at 1244 (finding that dispute over similarity of subsequent infringing products precluded resolution of delay period and laches determination at summary judgment stage). II. Invalidity of EPC’s %56 Patent The parties have presented cross-motions for summary judgment on Donaldson’s affirmative defense that EPC’s ’456 patent is invalid under the statutory “on-sale bar” rule. Under 35 U.S.C. § 102(b), a patent is invalid if the claimed subject matter was “in public use or on sale in this country, more than one year prior to the date of the application for patent in the United States.” See, e.g., Pfaff v. Wells Elecs., Inc., 525 U.S. 55, 57 n. 1, 119 S.Ct. 304, 142 L.Ed.2d 261 (1998) (discussing statutory on-sale bar rule). However, “[t]he law has long recognized the distinction between inventions put to experimental use and products sold commercially,” id. at 64, 119 S.Ct. 304, and the on-sale bar is not triggered by those activities which can reasonably be deemed experimental use. See id. Here, the patent application was filed on June 19, 1978, and therefore June 19, 1977 constitutes the critical date for purposes of the on-sale bar of 35 U.S.C. § 102(b). At issue, then, is whether EPC activities prior to June 19, 1977 fall within the experimental use exception. A patent is presumed valid, and invalidity must be established with clear and convincing evidence by the challenging party. See 35 U.S.C. § 282; American Hoist & Derrick Co. v. Sowa & Sons, 725 F.2d 1350, 1360 (Fed.Cir.), cert. denied, 469 U.S. 821, 105 S.Ct. 95, 83 L.Ed.2d 41 (1984); Abbott Labs. v. Geneva Pharm., 182 F.3d 1315, 1318 (Fed.Cir.1999). To establish invalidity under 35 U.S.C. § 102(b), Donaldson must prove that all of the claims of the patent were ready for patenting and were in use or on sale before the critical date. See Pfaff, 525 U.S. at 67, 119 S.Ct. 304 (discussing conditions for application of on-sale bar). One way by which a party can demonstrate that an invention was “ready for patenting” is “by proof of reduction to practice before the critical date.” Id. When an actual embodiment of all of the elements of the claimed invention has been built, the invention has been reduced to practice. See id. at 57 n. 2, 119 S.Ct. 304 (quoting Corona Cord Tire Co. v. Dovan Chemical Corp., 276 U.S. 358, 383, 48 S.Ct. 380, 72 L.Ed. 610 (1928) (“A machine is reduced to practice when it is assembled, adjusted and used. A manufacture is reduced to practice when it is completely manufactured.”)); RCA Corp. v. Data General Corp., 887 F.2d 1056, 1061 (Fed.Cir.1989) (“Experimental use, which means perfecting or completing an invention to the point of determining that it will work for its intended purpose, ends with an actual reduction to practice.”) (citations omitted). Evidence such as memoranda, drawings, correspondence and testimony of witnesses may be used to establish that the embodiment was in fact the claimed invention. See RCA Corp., 887 F.2d at 1060. If Donaldson can demonstrate that the ’456 patent was reduced to practice, it must then prove that the prototype was in public use, on sale, or offered for sale prior to June 19,1977. The Court concludes that the parties’ positions on this issue reflect a material factual dispute that cannot be resolved at summary judgment. Before elaborating on this decision, however, the Court must resolve a distinct but relevant dispute between the parties wherein Donaldson has moved this Court to strike an amended interrogatory response by EPC. (Doc. no. 97). A. Donaldson’s motion to strike EPC’s amended interrogatory response In early August, 1999, EPC responded to Donaldson’s interrogatory regarding the dates of conception and reduction to practice of the invention embodied in the ’456 patent. In its response, EPC admitted its belief that the ’456 patent was reduced to practice prior to April 27,1977. (See doc. no. 77, tab 28, at 3-4). EPC apparently based this response on a letter dated April 27, 1977, written by Ike Leighty wherein Mr. Leighty discusses a handmade prototype that he and Mr. Nelson gave to a Mack Trucks engineer. The amended interrogatory response was submitted in August 2000, after Donaldson’s summary judgment motion raised the issue of on-sale bar, and recharacterizes the April 1977 events as part of the testing period. (See doc. no. 98, exh. A, p. 3-4). In it, EPC avers that although conception of the invention embodied in the ’456 patent proceeded April 27, 1977, the invention was not reduced to practice until late summer or fall of that year, “following testing that eventually confirmed that the invention would perform as intended.” (Id.). EPC contends that its amended answer relies on no new facts and merely corrects a premature and incorrect characterization of the facts that were in evidence. Donaldson argues that EPC’s amended answer is an unfair last-minute attempt to create a triable issue as to on-sale bar and contradicts deposition testimony of EPC’s President, Peter Simer, wherein he averred that “the factual statements contained in [the interrogatory responses] are true and accurate.” Rule 36(b) of the Federal Rules of Civil Procedure directs that “the court may permit withdrawal or amendment [of an admission] when the presentation of the merits of the action will be subserved thereby and the party who obtained the admission fails to satisfy the court that withdrawal or amendment will prejudice that party in maintaining the action or defense on the merits.” Fed.R.Civ.P. 36(b); FDIC v. Prusia, 18 F.3d 637, 640 (8th Cir.1994) (considering effect on litigation and prejudice to resisting party in determining whether to allow amendment of admissions). After reviewing the parties’ numerous briefs on the issue, the Court concludes that Donaldson’s motion to strike EPC’s amended interrogatory answer number 4 should be denied. In so doing, the Court notes that EPC initially responded to the interrogatory in August, 1999, relatively early in the discovery process, and expressly based its response on its “investigation to date.” (Exh. 1 to Sullivan aff., doc. no. 109). Potentially contradictory evidence — namely, the April, 1977 letter and Mr. Leighty’s deposition testimony — was in the record as of December 1999 at the latest and thus Donaldson had notice of the factual dispute throughout the discovery period. The Court notes further that in March and April 2000, Donaldson served 297 Requests for Admission on EPC, none of which, according to EPC, raised, explicitly or implicitly, an issue regarding the reduction to practice date. In light of these facts and the voluminous record in this case, EPC’s failure to “catch” what it alleges was a premature and incorrect interrogatory response is neither unreasonable nor inexplicable. The inherently factual nature of the reduction to practice inquiry further supports this Court’s conclusion that justice would not best be served by binding EPC to what could reasonably be deemed a premature mischaracterization of facts in evidence and known to both parties. See Prusia, 18 F.3d at 640 (directing courts to consider the effect upon the litigation and prejudice to the resisting party “rather than focusing on the moving party’s excuses for erroneous admission”). Moreover, Donaldson has not shown that it will be unduly prejudiced by a ruling that will permit this issue to go to trial. See id. (finding abuse of discretion in refusing to allow amended admission where the plaintiff moved to amend prior to district court’s hearing on summary judgment motion, and stating that “[a]lthough [defendant] may have difficulty finding evidence to establish [the facts represented in the original admissions], this difficulty derives from the inaccuracy of the admissions rather than the stage of the proceedings at which the [plaintiff] sought to amend its admissions”). Having resolved this preliminary matter, the Court will now explain its conclusion that neither party is entitled to summary judgment on the asserted invalidity defense. B. On-sale bar: ready for patenting and put in public use Donaldson argues that the record shows by clear and convincing evidence that the on-sale bar conditions were met because the ’456 patent had been reduced to practice and put into public use by, at the latest, April 1977, several months prior to the on-sale bar date of June 19, 1977. EPC refutes those allegations, asserting that the activity to which Donaldson is referring was for testing purposes only and thus falls within the experimental use exception to the rule. EPC contends that the invention was not reduced to practice until the completion of tests in August 1977 showing that the device worked as intended — that the device progressively locked up in use and sustained vibration. At issue are the justifiable inferences to be drawn from an April, 27,1977 letter by Ike Leighty memorializing a visit by Mr. Leighty and Joe Nelson to Mack Trucks. During the visit, Mr. Leighty and Mr. Nelson presented and discussed their available line of gauges, none of which included the lock-up feature of the ’456 patent. They also, however, apparently gave a handmade prototype of a progressive gauge indicator to Bill Baldwin of Mack Trucks’ Vehicle Development division. In dispute is whether in so doing EPC triggered the on-sale bar clock and rendered the patent invalid. The relevant portion of the letter, the last three paragraphs, reads as follows: [¶ 7] In the meantime, we hope you will be able to give the handmade prototype an accelerated test on a vehicle. As soon as it has proven itself, we would appreciate your mounting that same gauge directly on an engine so that it gets the ultimate vibration. [¶ 8] We are completing our own tests and expect to release for tooling within the next 80 to 60 days ... production 12 to 14 weeks after that. [¶ 9] We will keep in touch with you and in the meantime, if you discover anything in the tests that you think would be interesting to us, please let us know. EPC contends that the letter clearly shows that the prototype was still in the experimental stage and so had not been reduced to practice. It cites the plain language of the letter as well as deposition testimony by Mr. Leighty, in which he testified that neither EPC nor Mr. Nelson had the resources to independently test the prototype. According to EPC, without such testing it would be impossible to know if the gauge’s progressive lock-up mechanism actually worked as intended. Mr. Leighty testified that, in light of their lack of resources, it was EPC’s hope that Mack Trucks would assist them in this testing process. Mr. Leighty further testified as to his belief that the prototype given to Mack Trucks did not embody all of the features that were later included in the ’456 patent. And finally, Mr. Leighty testified that, despite the optimistic projections in the letter, it was not until August 1977 that the gauge had been sufficiently tested that it could be offered for sale. EPC contends that this latter date is the date at which the invention was reduced to practice and any events prior to August 1977, including the interaction and correspondence with Mack Trucks, were merely part of the experimental use phase. The Court agrees that this is a reasonable characterization of the evidence, and as such is sufficient to warrant denial of Donaldson’s motion for summary judgment. See Pfaff, 525 U.S. at 64, 119 S.Ct. 304 (“[A]n inventor who seeks to perfect his discovery may conduct extensive testing without losing his right to obtain a patent for his invention — even if such testing occurs in the public eye.”). That being said, however, the Court disagrees with EPC’s contention that the record as it stands necessitates summary judgment in its favor. The precatory language used by Mr. Leighty reasonably suggests that while EPC would be interested in Mack Trucks’ feedback regarding the prototype, EPC was in no way relying upon Mack Trucks as an integral part of any testing process. Mr. Leighty plainly says as much in paragraph 8. Viewed in that light, the request for Mack Trucks’ testing assistance could be construed as a sales ploy, similar to a suggestion by an auto dealer that a valued or sought-after customer test drive a new car. The predominant purpose of the request is not to acquire information about the tested product, but rather to get the customer to try it in the expectation that he or she will then be inclined to purchase it. There is nothing in the letter to