Obviousness

Obviousness Analysis under 35 U.S.C. § 103 for US Patent 9133837

This analysis considers combinations of prior art references that would render the claims of US Patent 9133837 obvious to a person having ordinary skill in the art (POSITA) at the time of the invention (priority date 2008-04-24). The patent itself discusses US Pat. No. 5,525,043, highlighting its complexity as a problem the current invention seeks to address. However, other prior art references cited by the examiner are also highly relevant.

Primary Reference: US 5,050,379 A to Kabushiki Kaisha Toyoda Jidoshokki Seisakusho (Toyoda)

US Patent 5,050,379 A, titled "Displacement of a variable displacemet hydraulic pump and speed of an engine driving the pump controlled based on demand," discloses a control method and system for a hydraulic work machine. This patent appears to teach all elements of the independent claims of US 9133837.

Obviousness of Independent Claim 1 (Method of controlling a hydraulic system)

Claim 1 of US 9133837 recites:
"A method of controlling a hydraulic system having a variable displacement pump operatively coupled to an engine, comprising:
detecting a speed of the engine;
determining a desired power value of the pump based on user input;
identifying an allowable power value that may be expended by the pump based on a map that indicates the allowable power value at the detected speed;
selecting a pump power value, the selected pump power value being the lower of the allowable power value and the desired power value; and
adjusting the pump to deliver the selected pump power value."

Toyoda discloses each of these elements:

• Detecting a speed of the engine: Toyoda teaches that "engine speed N is detected by engine speed sensor" (Col. 4, lines 52-53).
• Determining a desired power value of the pump based on user input: Toyoda senses "demand for the hydraulic pump" (Col. 4, line 49), which leads to the determination of a "target pump displacement Dd" (Col. 4, line 50), representing the desired power.
• Identifying an allowable power value that may be expended by the pump based on a map that indicates the allowable power value at the detected speed: Toyoda explicitly states that "permissible engine load Tp is determined based on the engine speed N by using a map" (Col. 4, lines 53-54). This "permissible engine load" functions as the allowable power value.
• Selecting a pump power value, the selected pump power value being the lower of the allowable power value and the desired power value: Toyoda teaches that "When the target pump displacement Dd causes the engine to be overloaded, a load control circuit... reduces the pump displacement from the target pump displacement Dd so that the engine load is restricted to the permissible engine load Tp." (Col. 4, lines 56-60). This directly corresponds to selecting the lower of the desired and allowable power values.
• Adjusting the pump to deliver the selected pump power value: Toyoda's "displacement control circuit... controls the pump displacement Dp" (Col. 4, lines 63-64) based on the output of the load control, thereby delivering the selected pump power value.

Therefore, Claim 1 of US 9133837 is rendered obvious by US 5,050,379 A.

Obviousness of Dependent Claims 2-10

Given the obviousness of Claim 1, the dependent claims would also be obvious when combined with common knowledge in the art.

• Claim 2: Toyoda's Figure 2, which plots permissible engine load versus engine speed, shows that allowable load (power) generally increases with engine speed, consistent with allowable power being less at lower engine speeds. (Col. 5, lines 34-36).
• Claim 3: A POSITA would understand that an "allowable power value" or "permissible engine load" (as in Toyoda) would naturally be a function of the maximum rated power of the pump and engine, as these are inherent physical limits.
• Claims 4, 5, 7, 8, and 18, 19: Toyoda explicitly discusses "target pump displacement Dd" (desired displacement) based on demand and restricting "pump displacement" to match the "permissible engine load Tp" (allowable displacement). (Col. 4, lines 49-60). A POSITA would understand that desired and allowable power are directly translatable to desired and allowable displacement for a variable displacement pump.
• Claims 6 and 20: Toyoda explicitly detects "pump discharge pressure P" (Col. 4, line 52). The calculation of allowable displacement as a function of allowable power (or torque) divided by detected discharge pressure (d_allowable = f(T_allowable / P_d)) is a fundamental hydraulic principle well-known to a POSITA.
• Claim 9: Toyoda's system is for "hydraulic actuators" (FIG. 1) on a "hydraulic work machine" (Col. 1, lines 6-7), clearly demonstrating an implement operable by the pump's fluid.
• Claim 10: Toyoda describes a continuous control system that repeatedly detects parameters and adjusts the pump, implying continuous readjustment in response to changes in engine speed or desired power. (Col. 4, lines 49-65).

Obviousness of Independent Claim 11 (Hydraulic system)

Claim 11 of US 9133837 recites a hydraulic system with specific components and a control system configured for the method steps.

• Engine, variable displacement pump, implement, and engine speed sensor: Toyoda explicitly discloses an "engine 1," a "variable displacement hydraulic pump 2," "hydraulic actuators 3a, 3b" (implements), and an "engine speed sensor 4" (FIG. 1, Col. 4, lines 52-53). The function of hydraulic power being a function of piston displacement is inherent to variable displacement pumps.
• Control system configured for identifying allowable power from a map, determining desired power, and adjusting displacement to deliver the lower of the two: Toyoda's "load control circuit 7" and "displacement control circuit 9" (FIG. 1, Col. 4) collectively constitute a control system that performs precisely these functions as detailed in the Claim 1 analysis above.

Therefore, Claim 11 of US 9133837 is rendered obvious by US 5,050,379 A.

Obviousness of Dependent Claims 12-14

• Claim 12: Toyoda's system is for a "hydraulic work machine" (Col. 1, lines 6-7), making this claim obvious.
• Claim 13: User input for hydraulic machines is conventionally provided via levers. A POSITA would find it obvious to use a lever to direct the desired power signal to the control system.
• Claim 14: As discussed for Claim 10, Toyoda's continuous control operation inherently involves readjustment.

Obviousness of Independent Claim 15 (Method of operating a machine)

Claim 15 of US 9133837 is substantially similar to Claim 1, rephrased for operating a machine.

• Detecting a user input signal indicative of a desired power value: Taught by Toyoda's sensing of "demand for the hydraulic pump".
• Sensing a speed of the engine: Taught by Toyoda's "engine speed sensor".
• Choosing an allowable power value from a map: Taught by Toyoda's determination of "permissible engine load... by using a map".
• Adjusting the pump to direct a lower of the allowable power value and the desired power value: Taught by Toyoda's load control reducing pump displacement to restrict engine load to the permissible level.

Therefore, Claim 15 of US 9133837 is rendered obvious by US 5,050,379 A.

Obviousness of Dependent Claims 16-20

These claims are rendered obvious for the same reasons as the corresponding dependent claims of Claim 1, in view of US 5,050,379 A and common general knowledge in the art.

Alternative Reference: US 5,525,043 A to Lukich (Caterpillar Inc.)

US Patent 5,525,043 A, titled "Hydraulic power control system," is explicitly discussed in the background of US 9133837. While US 9133837 seeks to address the "complexity" and cost of Lukich's system, the method and system claims of US 9133837 are drafted broadly and do not inherently exclude such complexity or specify a "minimal number of operating parameters" as a claim limitation.

Lukich discloses:

• Detecting engine speed: Using an "engine speed sensor 58". (Col. 4, lines 60-61 of US5525043A).
• Determining desired power value based on user input: Responding to "operator input devices such as control levers 12" (Col. 3, lines 60-61 of US5525043A), which provide a "pump output control signal indicative of a desired implement demand" (Col. 4, lines 52-54 of US5525043A).
• Identifying an allowable power value from a map: Employing a "power limit curve (FIG. 3)" (Col. 5, lines 34-35 of US5525043A) which plots "pump output pressure versus engine speed at a maximum permissible load" (Col. 3, lines 16-18 of US5525043A). This power limit curve serves as a map for allowable power.
• Selecting the lower of allowable and desired power: Lukich's "pump output control logic 50" (Col. 4, line 43 of US5525043A) determines the pump output to accommodate the lowest of various pressure limiting signals, including the "maximum permissible load" (allowable) and the "desired implement demand" (desired). (Col. 4, lines 57-59 of US5525043A). The system reduces pump output when the load exceeds a predefined level. (Col. 3, lines 33-35 of US5525043A).
• Adjusting the pump: Lukich's system reduces the "displacement of the variable displacement pump" (Col. 3, lines 33-34 of US5525043A).

Motivation to combine with Lukich:
A POSITA would be motivated to use the teachings of Lukich, which addresses the same problem of preventing engine lug in hydraulic systems, to control a variable displacement pump. The "power limit curve" in Lukich is functionally equivalent to the "map" recited in the claims of US 9133837. Any additional details not explicitly mentioned in Lukich's claims (e.g., specific lever input for desired power, or the precise calculation of allowable displacement from allowable power and pressure) would be considered common knowledge in the hydraulic control art at the time of the invention.

Conclusion on Obviousness

All independent claims (1, 11, and 15) and their dependent claims (2-10, 12-14, 16-20) of US Patent 9133837 are rendered obvious by US Patent 5,050,379 A (Toyoda). Toyoda comprehensively discloses the method steps and system components for controlling a variable displacement pump based on engine speed, a map for allowable power, and desired user input, by selecting the lower of the allowable and desired power.

Alternatively, US Patent 5,525,043 A (Lukich), a prior art reference from the same assignee and discussed in the background of US 9133837, also renders the claims obvious. Lukich teaches the core elements of detecting engine speed, determining desired power from user input, identifying allowable power from a power limit curve (a map), selecting the lower of these values, and adjusting the pump displacement.

A POSITA would have been motivated to combine these teachings (from either Toyoda alone, or Lukich in combination with common knowledge) because they address the common and recognized problem of efficiently controlling hydraulic systems to prevent engine lug and stall. The methods and systems described in the prior art provide direct and analogous solutions to the problems addressed by US 9133837.