Difference between revisions of "Honeywell v. Hamilton Sundstrand Brief for Defendant-Appellee (Potter)"

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BRIEF FOR DEFENDANT-APPELLEE
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BRIEF FOR THE DEFENDANT-APELLEE
  
Honeywell’s claims infringement of its ‘893 patent for a compressor bleed air control apparatus and method by Hamilton Sundstrand’s APS 3200 is invalid under the doctrine of equivalentsBy applying the doctrine to each element of the claims in question, it can be seen that the ‘893 patent and the APS 3200 accomplish the same function in different waysThis conclusion is furthered by an examination of the ‘893 patent’s file-wrapper, in which Honeywell specifically narrowed its claims to avoid rejection based on obviousness.  By including the use of IGV position to establish a set point, Honeywell forfeited its claims to other methods of establishing a set point, leaving them available for public use.  
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The plaintiff Honeywell claims infringement of its ‘893 patent for a compressor bleed air control apparatus and method by the APS 3200, manufactured and sold by the defendant, Hamilton SundstrandThe ‘893 patent covers a “more efficient” APU surge control system in which it evaluates a minimum flow set point and adjusts said set point as a function of IGV positionThe system measures a designated flow parameter “substantially independent of temperature” and compares it to the position of the IGVs to generate an error, which is used in proportional integral control of the bleed valve to optimize bleed airflow.
  
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The APS 3200 utilizes a surge control system that adjusts the bleed valve according to the error between the flow parameter DELPQP and a set point based on air inlet temperature.  This method, however, produces an ambiguous signal at high flow conditions, referred to as the “double solution problem,” which the APS solves by using IGV position to determine whether the compressor is experiencing high or low flow.
  
The doctrine of equivalents teaches that a product may be deemed equivalent and infringing on a patent if the differences between the two devices are insubstantial (Graver Tank)This was refined in the case of Warner-Jenkinson v. Hilton Davis by the court’s holding that the doctrine of equivalents must be applied to each element of an invention rather than the invention as a whole because the elements of the claims are what define and limit the scope of the patent.  The differences between the Honeywell patent and the APS 3200 are more than insubstantialFocus on the method that is used to control the bleed valve setting and prevent surgeThe Honeywell patent evaluates a set point based on the error between a designated flow parameter and the position of the IGVs.  The set point is continuously evaluated as a function of the IGV position.  The APS 3200 utilizes a surge control system that compares DELPQP to a set point that is based on inlet temperature, not IGV position.  The position of the IGVs is used only to determine whether the compressor is experiencing high flow or low flow in order to solve the double solution problem presented by the DELPQP analysisThe system does not determine the set point as a function of IGV position, as is clearly expressed in the ‘893 patent.  The differences between the two systems are substantial and thus the doctrine of equivalents does not apply.  While they may accomplish essentially the same function, the way in which it is accomplished is different.
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The plaintiff seek to collect damages by relying on the doctrine of equivalents to claim that the APS 3200 is an infringement of the ‘893 patent, since there is no literal infringementIt is unnecessary to dispute whether or not the systems would be considered equivalents because the plaintiff is unable to argue equivalency due to prosecution history estoppel.  The claims of ‘893 were amended during the patent process in order to avoid rejection as obvious in light of the prior art.  The rejected independent claims had no mention of the use of IGV position to evaluate the flow set point; this was only added later as limitation to the claims.  The PTO asserted, correctly, that Honeywell could not claim all methods of evaluating flow to establish a set pointBy narrowing its claims in order to satisfy non-obviousness requirements, Honeywell forfeited its rights to claim other similar methods of surge control.  An inquiry into the state of the art at the time of Honeywell’s claimed invention, around 1982-83, shows that Sundstrand’s method of evaluating DELPQP and using IGV position to solve the double solution problem would have been foreseeable.  The technology of the time and relevant teachings in the prior art would have presented said method as obvious to anyone skilled in the art.  The L1011 APU surge control system was developed in the 1970s and also evaluated flow by measuring DELPQP.  And although the L1011 distinguished between high and low flow by means of a shock switch, it was common knowledge that IGV position was related to the level of airflow through a compressor, and any competent engineer could deduce that IGV position could have been used to determine whether a compressor was experiencing high or low flow in order to solve the double solution problem.  Honeywell’s own corporate representative, James Clark, even admitted that Honeywell engineers could have solved the double solution problem by measuring IGV position.
  
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If, as Honeywell claims, the APS 3200 is an equivalent to the claims of the ‘893 patent, it is difficult to find clearer evidence that such an equivalent was foreseeable in light of the prior art.  Thus, if Honeywell had wished to claim said equivalent, it could have done so explicitly in the drafting of the patent.  Failure to do so results in surrender to public use.  The original claims may have encompassed such a method, but prosecution history estoppel prevents the plaintiff from attempting to reclaim those elements that it surrendered during the patent amendment process.
  
There are many different ways in which to evaluate compressor flow, prevent surge and optimize bleeding.  If Honeywell were allowed to claim equivalence between its patented method and the method employed by the APS 3200, which are substantially different, it would follow that they could also claim equivalence in just about any other evaluation method.  This would clearly undermine the purpose of the patent claims, which is to limit the scope of patent protection for an invention.
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There are many different ways in which to evaluate compressor airflow, prevent surge and optimize bleed flow rate.  If Honeywell were allowed to claim equivalence between its ‘893 patent and the APS 3200, then they would likewise be able to argue equivalence with almost any method of controlling bleed airflow that utilized IGV position in any way.  This would undermine the authority of the PTO, as its initial rejection of the ‘893 application prevented Honeywell from such a broad scope of patent protection.  A decision of equivalency would substantially broaden the claims of the ‘893 patent, contrary to the conditions under which it was awarded.  This would put undue burden on the industry, as manufacturers would be hard pressed to design around such a broad patent claim.  It has long been well known in the industry that IGV position is important in evaluating compressor airflow, and such information is commonly used in a number of ways.  The ‘893 patent and the APS 3200 both involve the use of IGV position in relation to surge control, but in substantially different ways.  If Honeywell were allowed to claim equivalence between the two methods, many other systems in the industry would be endangered.  
  
The Honeywell patent was originally rejected as obvious and only patented after the addition of terms that define the use of IGV position in evaluating the set point.  The PTO clearly – and correctly – asserted that Honeywell could not claim all methods of evaluating flow to establish a set pointThe addition of IGVs into the patent claims limited the scope to include only the method of evaluating the set point based on IGV position, leaving other methods, such as that employed by Sundstrand, available to the publicHad the broad language of the original patent application been maintained, the courts could assume that the APS 3200 fell within the scope of the claims, according to the precedent set forth in CSC Fitness, for example.  But the amendments to the patent claims introduced the limiting language that was absent from the CSC patent, and Honeywell has conceded its benefit of the doubtUpon rejection of their broader claims, Honeywell could have chosen to patent additional specific methods but did not.  In narrowing their claims, Honeywell excluded any method that did not use IGVs to establish a set point.  If they had wished to claim a method of establishing a set point based on inlet temperature, they could have.  
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In summary, during the patent application process, Honeywell narrowed its claims in the ‘893 patent through an explicit description of its bleed flow optimization methodIn doing so, it forfeited its right to other methods of surge controlPrior art teachings show that the techniques used in the APS 3200 would have been foreseeable at the time that the ‘893 patent was draftedThus, when it narrowed its claims, if Honeywell had wished to claim such techniques as equivalent, it must have included them in its claims. By failing to do so, it forfeited those processes to the publicThus, Honeywell is barred from claiming infringement under the doctrine of equivalents by its prosecution history estoppel and the foreseeability of such an equivalent.
 
 
 
 
This is not to say that no equivalents could be drawn from the ‘893 patent.  For instance, if the APS 3200 compared DELPQP to Honeywell’s set point based on IGV position, this could be considered an equivalent because the only difference would be the substitution of DELPQP for Honeywell’s chosen flow parameterSince the set point would have been evaluated in the same way, the differences would be insubstantial.  The difference in evaluation method is significant, however.  The file-wrapper shows that the narrowing of these particular claims was demanded by the PTO, which is clear evidence that the patent, once granted, was never intended to exclude from public use all methods of surge control and bleed flow optimization based on comparison of a flow parameter to a set point.
 

Latest revision as of 11:45, 6 April 2011

BRIEF FOR THE DEFENDANT-APELLEE

The plaintiff Honeywell claims infringement of its ‘893 patent for a compressor bleed air control apparatus and method by the APS 3200, manufactured and sold by the defendant, Hamilton Sundstrand. The ‘893 patent covers a “more efficient” APU surge control system in which it evaluates a minimum flow set point and adjusts said set point as a function of IGV position. The system measures a designated flow parameter “substantially independent of temperature” and compares it to the position of the IGVs to generate an error, which is used in proportional integral control of the bleed valve to optimize bleed airflow.

The APS 3200 utilizes a surge control system that adjusts the bleed valve according to the error between the flow parameter DELPQP and a set point based on air inlet temperature. This method, however, produces an ambiguous signal at high flow conditions, referred to as the “double solution problem,” which the APS solves by using IGV position to determine whether the compressor is experiencing high or low flow.

The plaintiff seek to collect damages by relying on the doctrine of equivalents to claim that the APS 3200 is an infringement of the ‘893 patent, since there is no literal infringement. It is unnecessary to dispute whether or not the systems would be considered equivalents because the plaintiff is unable to argue equivalency due to prosecution history estoppel. The claims of ‘893 were amended during the patent process in order to avoid rejection as obvious in light of the prior art. The rejected independent claims had no mention of the use of IGV position to evaluate the flow set point; this was only added later as limitation to the claims. The PTO asserted, correctly, that Honeywell could not claim all methods of evaluating flow to establish a set point. By narrowing its claims in order to satisfy non-obviousness requirements, Honeywell forfeited its rights to claim other similar methods of surge control. An inquiry into the state of the art at the time of Honeywell’s claimed invention, around 1982-83, shows that Sundstrand’s method of evaluating DELPQP and using IGV position to solve the double solution problem would have been foreseeable. The technology of the time and relevant teachings in the prior art would have presented said method as obvious to anyone skilled in the art. The L1011 APU surge control system was developed in the 1970s and also evaluated flow by measuring DELPQP. And although the L1011 distinguished between high and low flow by means of a shock switch, it was common knowledge that IGV position was related to the level of airflow through a compressor, and any competent engineer could deduce that IGV position could have been used to determine whether a compressor was experiencing high or low flow in order to solve the double solution problem. Honeywell’s own corporate representative, James Clark, even admitted that Honeywell engineers could have solved the double solution problem by measuring IGV position.

If, as Honeywell claims, the APS 3200 is an equivalent to the claims of the ‘893 patent, it is difficult to find clearer evidence that such an equivalent was foreseeable in light of the prior art. Thus, if Honeywell had wished to claim said equivalent, it could have done so explicitly in the drafting of the patent. Failure to do so results in surrender to public use. The original claims may have encompassed such a method, but prosecution history estoppel prevents the plaintiff from attempting to reclaim those elements that it surrendered during the patent amendment process.

There are many different ways in which to evaluate compressor airflow, prevent surge and optimize bleed flow rate. If Honeywell were allowed to claim equivalence between its ‘893 patent and the APS 3200, then they would likewise be able to argue equivalence with almost any method of controlling bleed airflow that utilized IGV position in any way. This would undermine the authority of the PTO, as its initial rejection of the ‘893 application prevented Honeywell from such a broad scope of patent protection. A decision of equivalency would substantially broaden the claims of the ‘893 patent, contrary to the conditions under which it was awarded. This would put undue burden on the industry, as manufacturers would be hard pressed to design around such a broad patent claim. It has long been well known in the industry that IGV position is important in evaluating compressor airflow, and such information is commonly used in a number of ways. The ‘893 patent and the APS 3200 both involve the use of IGV position in relation to surge control, but in substantially different ways. If Honeywell were allowed to claim equivalence between the two methods, many other systems in the industry would be endangered.

In summary, during the patent application process, Honeywell narrowed its claims in the ‘893 patent through an explicit description of its bleed flow optimization method. In doing so, it forfeited its right to other methods of surge control. Prior art teachings show that the techniques used in the APS 3200 would have been foreseeable at the time that the ‘893 patent was drafted. Thus, when it narrowed its claims, if Honeywell had wished to claim such techniques as equivalent, it must have included them in its claims. By failing to do so, it forfeited those processes to the public. Thus, Honeywell is barred from claiming infringement under the doctrine of equivalents by its prosecution history estoppel and the foreseeability of such an equivalent.