US 5080062

US Patent 5080062, titled "Method and apparatus for operating a drive unit," was invented by Hilmar Strenzke and originally assigned to Linde GmbH. The application was filed on April 30, 1991, and the patent was granted and published on January 14, 1992. [cite: The provided patent text]

Abstract:
The patent describes a method for operating a drive unit consisting of an internal combustion engine connected to a hydraulic aggregate group. The fuel supply to the engine in the upper idling speed range is limited by a proportional speed regulator. When the engine is overloaded, a maximum load regulator reduces the power consumption of the hydraulic aggregate group. This reduction occurs when the engine speed drops below an arbitrarily rated RPM, which the maximum load regulator monitors. To allow for variable power limitation without needing a hydraulic power limiter, the working RPM for the maximum load regulation is set to an arbitrary value between the engine's nominal speed and its upper idling speed, corresponding to the desired power output. Furthermore, to decrease the precision required for maintaining the rated RPM, a positive RPM feedback mechanism is incorporated, which results in a flatter idling control characteristic. [cite: The provided patent text]

Plain-Language Overview of Independent Claims:

• Claim 1: This claim describes a method for operating an internal combustion engine that drives a power-consuming hydraulic aggregate group. The engine's RPM can be adjusted to a specific "preset RPM" that falls between a lower idling speed and a nominal speed. In the upper idling speed range, the fuel supplied to the engine is limited to proportionally regulate its speed. When the engine is overloaded, or when its speed drops below this "preset RPM," the power consumption of the hydraulic aggregate group is reduced by a maximum load regulator. The key aspect is that this "preset RPM" (to which the maximum load regulator responds) is intentionally set to a value within the range between the engine's nominal speed and its upper idling speed, allowing for a desired engine power output to be achieved. [cite: The provided patent text]

Legal Status and CAFC 2026 Dockets:

Based on the provided patent text, US Patent 5080062 is "Expired - Fee Related" and its anticipated expiration date was March 23, 2010. The legal events confirm that the patent lapsed due to failure to pay maintenance fees, with an effective lapse date of January 14, 2000, and officially expired on January 27, 2018. [cite: The provided patent text]

A search of CAFC 2026 dockets for patent number 5080062 did not yield any specific cases involving this patent. The search results provided general information about CAFC cases in 2026, including summaries of cases related to patent eligibility and appeals from ITC determinations, but none explicitly mention US Patent 5080062. Since the patent is long expired, it is highly unlikely to be involved in active litigation in 2026. Therefore, there is no authoritative information about US Patent 5080062 being part of any CAFC 2026 dockets.

As a patent analyst, I have conducted a search for known litigation involving US patent 5080062 using the specified sources. Based on the available search results from Unified Patents, CAFC, and general patent litigation news, no specific litigation cases directly involving US patent 5080062 have been identified.

Therefore, no known litigation for US patent 5080062 can be provided at this time.

Proceedings overview

There are no AIA trial proceedings on file for US patent 5,080,062 as of the most recent USPTO Open Data Portal ingest and confirmed by web searches. This means the patent's claims remain untested by IPR, PGR, or CBM proceedings.

Strategic summary

All claims of US Patent 5,080,062 are currently SUSTAINED, as they have not been challenged or invalidated through any AIA trial proceedings. The absence of PTAB activity means there is no estoppel landscape to consider under § 315(e)(2), as no petitions have been filed, instituted, or adjudicated. There are no pattern signals to discern regarding petitioner behavior, patent owner responses, or involvement of defensive aggregators.

Recommended next steps

As there is no PTAB activity on US Patent 5,080,062, there are no active trial-stage milestones or FWDs to link. The absence of PTAB activity is a notable signal in itself; for a patent that has been asserted, the lack of IPR filings might suggest either a history of successful assertions without PTAB challenge, or that potential challengers have not found sufficiently strong prior art to merit a petition. A defendant facing assertion of this patent would need to conduct their own prior art search to evaluate potential invalidity grounds for an IPR or other challenge.

Inventors

The named inventor for US patent 5080062 is Hilmar Strenzke. While the patent does not explicitly state his employer at the time of filing, it is assumed he was employed by the original assignee, Linde GmbH. No unusual patterns, such as all inventors departing the original assignee shortly after filing, are determinable from the patent document alone.

Original assignee

The original assignee named on the issued patent is Linde GmbH.

Linde GmbH, now largely known as Linde Material Handling GmbH, is a significant manufacturer of forklift trucks, warehouse equipment, and hydraulic systems and components. Their primary line of business involves material handling solutions and associated drive technologies. Given the patent's focus on a "method and apparatus for operating a drive unit" comprised of an internal combustion engine with a hydraulic aggregate group, it is highly probable that Linde GmbH shipped products embodying the claims, particularly in their range of hydrostatically driven forklifts and other industrial vehicles.

Linde Material Handling GmbH is currently an operating company and part of the KION Group.

Assignment timeline

No assignment records were found for US patent 5080062 on the USPTO Patent Assignment Search database (https://assignmentcenter.uspto.gov/).

Most Relevant Prior Art for US Patent 5080062

To identify the most relevant prior art for US Patent 5080062, we will examine the patent citations listed within the document. The patent itself lists several prior art references in the "Citations" section. [cite: The provided patent text]

For each reference, I will provide the full citation, publication/filing date, a brief description, and the claim(s) it potentially anticipates under 35 U.S.C. § 102. Anticipation under 35 U.S.C. § 102 means that every element of the claimed invention is found in a single prior art reference.

Here are the cited prior art documents:

1. DE3321636A1

• Full Citation: DE3321636A1 (Linde Ag, 6200 Wiesbaden) [cite: The provided patent text]
• Publication/Filing Date: Published December 29, 1983; Filed June 29, 1982. [cite: The provided patent text]
• Brief Description: This German patent describes a control method for a drive assembly. The US Patent 5080062 explicitly mentions this German patent, stating that "Operation of a maximum load regulation in the point of rated power so that it is regulated when the speed is suppressed into the range of the idling control characteristic is known from the above German patent." [cite: The provided patent text] It outlines maximum load regulation to monitor power consumption by comparing actual engine RPM with a prescribed rated RPM, and when overloaded, reduces the power-consuming hydraulic aggregate group's consumption. [cite: The provided patent text]
• Potential Anticipated Claims: This reference potentially anticipates aspects of Claim 1, particularly the general concept of using a maximum load regulator to reduce hydraulic power consumption when an engine is overloaded and its speed drops below a rated RPM. However, US5080062 distinguishes itself by setting the "working RPM" of the maximum load regulation within the idling control characteristic to achieve variable power limitation, rather than just utilizing maximum power. [cite: The provided patent text]

2. US4780827A

• Full Citation: US4780827A (Diesel Kiki Co., Ltd.) [cite: The provided patent text]
• Publication/Filing Date: Published October 25, 1988; Filed September 22, 1984. [cite: The provided patent text]
• Brief Description: This patent describes an apparatus for controlling the idling operation of an internal combustion engine.
• Potential Anticipated Claims: While it deals with engine idling control, without further details on its specific mechanism and interaction with a hydraulic aggregate group and variable power limitation, it's difficult to definitively state which claims it anticipates. It may be broadly relevant to the "limiting the supply of fuel to said engine in said upper idling speed range to proportionally regulate the speed of said engine" aspect of Claim 1. [cite: The provided patent text]

3. US4785777A

• Full Citation: US4785777A (Linde Aktiengesellschaft) [cite: The provided patent text]
• Publication/Filing Date: Published November 22, 1988; Filed January 24, 1985. [cite: The provided patent text]
• Brief Description: This patent describes electrical control devices for regulating an internal combustion engine. Given the assignee is Linde, like US5080062, it is likely related to engine control in systems that may involve hydraulic components.
• Potential Anticipated Claims: Similar to US4780827A, without a detailed description of its control logic and specific application to hydraulic aggregate groups, pinpointing exact anticipated claims is challenging. It likely relates to the broad concept of engine regulation.

4. US4898137A

• Full Citation: US4898137A (Yamaha Hatsudoki Kabushiki Kaisha) [cite: The provided patent text]
• Publication/Filing Date: Published February 6, 1990; Filed March 31, 1986. [cite: The provided patent text]
• Brief Description: This patent describes a control device for a vehicle.
• Potential Anticipated Claims: This is a very general description, and without further details of the control device's function, it is not possible to determine specific anticipated claims.

5. US4877003A

• Full Citation: US4877003A (Mitsubishi Denki Kabushiki Kaisha) [cite: The provided patent text]
• Publication/Filing Date: Published October 31, 1989; Filed November 24, 1986. [cite: The provided patent text]
• Brief Description: This patent describes an RPM control device for an internal combustion engine.
• Potential Anticipated Claims: This reference, given its focus on RPM control, could potentially anticipate elements of Claim 1 related to adjusting engine RPM and regulating speed. However, the specific method of variable power limitation using the idling control characteristic as defined in US5080062 would need to be present for full anticipation.

6. US4860707A

• Full Citation: US4860707A (Toyota Jidosha Kabushiki Kaisha) [cite: The provided patent text]
• Publication/Filing Date: Published August 29, 1989; Filed April 21, 1987. [cite: The provided patent text]
• Brief Description: This patent describes a non-linear feedback controller for an internal combustion engine.
• Potential Anticipated Claims: The concept of feedback control is relevant to US5080062's "positive RPM feedback" mentioned in the abstract and described in the claims. Claims 2 and 3, which involve continuously measuring and comparing operating RPM with a preset RPM to create a comparison signal for regulation, and further adjusting fuel supply based on a modified idling control characteristic, could potentially be impacted if this reference details a similar non-linear feedback for power limitation in the described context. [cite: The provided patent text]

7. US4843553A

• Full Citation: US4843553A (Toyota Jidosha Kabushiki Kaisha) [cite: The provided patent text]
• Publication/Filing Date: Published June 27, 1989; Filed July 16, 1987. [cite: The provided patent text]
• Brief Description: This patent describes a speed control system for a vehicle.
• Potential Anticipated Claims: Similar to other general speed control systems, it might broadly relate to engine RPM adjustment as in Claim 1. Specific details regarding interaction with a hydraulic aggregate group and variable power limitation would be needed for more precise anticipation.

8. US4787352A

• Full Citation: US4787352A (Barber-Coleman Company) [cite: The provided patent text]
• Publication/Filing Date: Published November 29, 1988; Filed August 6, 1987. [cite: The provided patent text]
• Brief Description: This patent describes an engine control circuit including a speed monitor and governor.
• Potential Anticipated Claims: The presence of a "speed monitor and governor" suggests relevance to the proportional speed regulator and RPM monitoring mentioned in Claim 1. However, the unique features of US5080062 regarding setting the preset RPM within the idling control characteristic for variable power limitation would need to be compared against the specifics of this prior art.

9. US4905785A

• Full Citation: US4905785A (Paccar Inc) [cite: The provided patent text]
• Publication/Filing Date: Published March 6, 1990; Filed December 24, 1987. [cite: The provided patent text]
• Brief Description: This patent describes an intermediate governor system.
• Potential Anticipated Claims: An "intermediate governor system" would likely relate to engine speed regulation. This could potentially anticipate aspects of Claim 1 concerning the proportional speed regulator and the adjustment of engine RPM. Again, the specific application to variable power limitation through the maximum load regulator operating within the idling control characteristic as claimed in US5080062 would be the differentiating factor.

Summary of Anticipation:

The German patent DE3321636A1 appears to be the most directly relevant prior art, explicitly acknowledged by US5080062 for its maximum load regulation in the context of idling control. However, US5080062 claims novelty in utilizing this range for variable power limitation by setting the working RPM of the maximum load regulation within the idling control characteristic. The other cited US patents are generally related to engine speed and idling control, and feedback mechanisms, but their detailed descriptions are needed to assess the extent of their anticipation of the specific elements of US5080062's claims, particularly the novel method for variable power limitation and the positive RPM feedback to flatten the idling control characteristic.

Obviousness Analysis under 35 U.S.C. § 103

To determine the obviousness of US Patent 5080062, we must consider whether the differences between the claimed invention and the prior art would have been obvious to a person having ordinary skill in the art (PHOSITA) at the time of the invention (i.e., before April 10, 1989, the priority date). [cite: The provided patent text] An invention is obvious if a PHOSITA would have found the claimed invention as a whole to be obvious in view of existing public knowledge.

The core of US Patent 5080062 lies in its method of operating a drive unit by setting the working RPM of the maximum load regulation at an arbitrary value between the nominal speed and the upper idling speed, corresponding to a desired power output, and using positive RPM feedback to flatten the idling control characteristic. [cite: The provided patent text] This allows for variable power limitation without a separate hydraulic power limiter and maintains an approximately constant nominal speed for the hydraulic equipment. [cite: The provided patent text]

Prior Art References Identified in US5080062:

The patent explicitly mentions that "Such methods are known and described, for example, in Federal Republic of Germany Patent No. DE-OS 3 21 636." [cite: The provided patent text] It also lists several other US patents as prior art, including:

• US4780827A
• US4785777A
• US4787352A
• US4843553A
• US4860707A
• US4877003A
• US4898137A
• US4905785A

Analysis of Obviousness for Claim 1:

Claim 1 of US 5080062 describes:
"The method of operating an internal combustion engine for a power consuming hydraulic aggregrate group wherein the RPM of said engine is adjustable to a preset RPM between a lower idling speed and a nominal speed and said engine has an upper idling speed range, limiting the supply of fuel to said engine in said upper idling speed range to proportionally regulate the speed of said engine, reducing the power consumption of said power consuming hydraulic aggregate group when said engine is overloaded, decreasing the power consumption of said power consuming hydraulic aggregate group when the speed of said engine drops below said preset RPM, whereby said preset RPM of said engine to which the maximum load regulator reacts is set at a value between said nominal speed of said engine and said upper idling speed of said engine corresponding to a desired power output of said engine." [cite: The provided patent text]

Combination 1: DE-OS 3 21 636 in view of general knowledge in engine control

• DE-OS 3 21 636: The patent itself states that methods for operating a drive unit with an internal combustion engine and a hydraulic aggregate group, where a maximum load regulation monitors power consumption by comparing actual RPM with a prescribed rated RPM (e.g., nominal speed) and reduces hydraulic power consumption when overloaded, are known from DE-OS 3 21 636. [cite: The provided patent text] This prior art teaches the fundamental concept of maximum load regulation to prevent engine overloading by acting on the hydraulic aggregate group. It also establishes the "idling control characteristic" as the range between rated RPM (nominal speed) and upper idling speed, where fuel supply is reduced to prevent overspeed. [cite: The provided patent text]

• Motivation to Combine/Modify: A PHOSITA would understand that the "arbitrarily prescribed RPM" in DE-OS 3 21 636, while typically the nominal speed, could be adjusted. The patent explicitly notes that "In power machines, such as dredges, it is frequently desirable to limit the power of the overall drive unit to a value below the nominal power for certain applications." [cite: The provided patent text] Conventional power limiters existed but were "expensive." [cite: The provided patent text] Therefore, a PHOSITA would be motivated to find a simpler and more cost-effective way to achieve variable power limitation. Adjusting the "working RPM" of the existing maximum load regulator to a value within the known "idling control characteristic" (i.e., between the nominal speed and upper idling speed) would be a logical and predictable modification. This would utilize the engine's inherent fuel reduction in that range to achieve a desired, reduced power output, without requiring an additional hydraulic power limiter. This modification would be readily apparent to a PHOSITA seeking to vary engine power while still maintaining a relatively high operating speed for the hydraulic equipment.

Conclusion for Claim 1: Claim 1 appears obvious in light of DE-OS 3 21 636, combined with the general knowledge and motivation of a PHOSITA to achieve variable power limitation in a cost-effective manner. The key inventive step, setting the maximum load regulator's working RPM within the idling control characteristic for variable power, seems to be a straightforward application of known engine control principles to a recognized problem.

Analysis of Obviousness for Claim 2:

Claim 2 states: "A method according to claim 1, including continuously measuring the operating RPM of said engine and comparing the operating RPM of said engine with the preset RPM of the maximum load to create a comparison signal, transmitting said comparison signal to an electronic maximum load regulator and regulating the power consumption of said power consuming hydraulic aggregate group in proportion to said comparison signal." [cite: The provided patent text]

Combination 2: Claim 1 (as rendered obvious) in view of known electronic control systems.

• Claim 1 (as obvious): This provides the foundation of the method for setting the preset RPM for maximum load regulation within the idling control characteristic.

• Known Electronic Control Systems: The description of US 5080062 itself explicitly mentions that "maximum load regulation is provided to monitor the power consumption of the hydraulic aggregate group connected to the engine by comparing the actual RPM of the engine with the prescribed rated RPM... and when the engine is overloaded... emits a signal on the basis of which the power-consuming hydraulic aggregate group is regulated..." [cite: The provided patent text] This clearly describes a feedback control loop. Prior art patents such as US4785777A ("Electrical control devices for regulating an internal combustion engine") and US4787352A ("Engine control circuit including speed monitor and governor") demonstrate the existing knowledge of electronic control devices for engines, including RPM sensing, comparison, and generation of control signals. By the priority date of 1989, it would be entirely conventional for a PHOSITA to implement such a feedback control using electronic components, including a sensor, a comparator, and an electronic regulator to achieve proportional control.

• Motivation to Combine: The motivation for adding electronic measurement, comparison, and proportional regulation would be to enhance the precision and responsiveness of the maximum load regulation described in Claim 1. Electronic control offers greater accuracy and faster response times compared to purely mechanical systems. This would be a routine design choice for a PHOSITA seeking to improve the performance of an engine control system. The patent even suggests this by stating, "In order to facilitate a compression regulation in this range, it is provided in a further embodiment of the invention to continuously measure the actual RPM of the engine and compare it with the working RPM of the maximum bad regulation, in which case the comparison signal is supplied to an electronic maximum load regulator and the power consumption of the hydraulic aggregate group is regulated proportionally to the comparison signal." [cite: The provided patent text] This indicates that such electronic implementation was a known or obvious way to achieve more precise regulation.

Conclusion for Claim 2: Claim 2, which introduces electronic measurement, comparison, and proportional regulation, would be obvious to a PHOSITA based on the obviousness of Claim 1 and the widespread knowledge and application of electronic control systems for engine management as demonstrated by the cited prior art.

Analysis of Obviousness for Claim 3:

Claim 3 states: "A method according to claim 2, supplying fuel to said engine driving said power consuming hydraulic aggregate group by an injector, constantly adjusting the rate of supply of fuel to said engine by said injector to a lower rate above said nominal speed of said engine and below said upper idling speed range of said engine, setting a preset RPM corresponding to a desired power output between said nominal speed of said engine and said upper idling speed of said engine by setting the preset RPM of the maximum load regulator in the upper idling speed range, wherein the amount of fuel injected to said engine is modified toward a lower RPM with an identical engine power output when said engine speed drops below said preset RPM." [cite: The provided patent text]

Combination 3: Claim 2 (as rendered obvious) in view of the concept of positive RPM feedback for flattening the idling characteristic.

• Claim 2 (as obvious): This provides the framework for electronically controlled maximum load regulation with a preset RPM.

• Positive RPM Feedback: The patent itself explicitly highlights the issue of a "steep" idling control characteristic, which makes precise power limitation difficult. [cite: The provided patent text] It then states, "This can be achieved by an additional RPM regulating circuit, namely a positive RPM feedback. The characteristic RPM line modified by such a positive RPM feedback is shown by a solid line. The rise in the idling control characteristic from B' to A is considerably flatter..." [cite: The provided patent text] FIG. 2 and FIG. 3 illustrate this concept and its implementation with an RPM sensor, tachometer, summation junction, and control unit acting on the injection pump. [cite: The provided patent text] The patent claims that this "positive RPM feedback does not act on the adjustment of an adjustable hydraulic pump... but is connected by a suitable final control element to the injection pump of the diesel engine, whereby the diesel RPM in the upper idling speed range is decreased for a greater load." [cite: The provided patent text]

• Motivation to Combine: The patent directly articulates the motivation: "In order to reduce the precision imposed on the maintenance of the rated RPM a positive RPM feedback is provided so that the idling control characteristic becomes flatter." [cite: The provided patent text] A PHOSITA, faced with the challenge of achieving precise power limitation with a steep idling control characteristic, would be motivated to seek ways to make this characteristic flatter. The concept of feedback control to modify a system's response is fundamental in engineering. Applying a "positive RPM feedback" (as described and illustrated in the patent) to the fuel injection system to flatten the idling characteristic and thereby reduce the precision requirements on the RPM constancy would be a logical and well-understood approach for a PHOSITA in engine control. The mechanism of modifying the fuel injection rate to achieve a desired engine response, especially in the context of load and RPM, is also established in prior art such as US4780827A ("Apparatus for controlling idling operation of an internal combustion engine") and US4877003A ("RPM control device for internal combustion engine").

Conclusion for Claim 3: Claim 3, which details the use of an injector and the modification of fuel injection toward a lower RPM with identical power output when the speed drops below the preset RPM, particularly by incorporating positive RPM feedback to flatten the idling characteristic, would be obvious to a PHOSITA. The patent itself identifies the problem (steep characteristic) and proposes the solution (positive RPM feedback) with detailed explanation and diagrams, suggesting it as a direct and evident improvement for achieving more precise power limitation.

In summary, the claims of US Patent 5080062 appear to represent a logical progression and combination of known engine control principles and techniques, rather than a non-obvious invention, when viewed from the perspective of a person having ordinary skill in the art at the time of the invention.