Obviousness — US Patent 9347554

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

This analysis identifies combinations of prior art references that would render the claims of US Patent 9347554 obvious to a person having ordinary skill in the art (PHOSITA). The motivation to combine these references is also discussed.

General Understanding of Obviousness

Under 35 U.S.C. § 103, a patent claim is obvious if "the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains." The Supreme Court's decision in KSR International Co. v. Teleflex Inc. emphasized a flexible approach to obviousness, allowing for various rationales for combining prior art, not just explicit suggestions or motivations within the references themselves. These rationales include:

Teaching, Suggestion, or Motivation (TSM): The prior art itself suggests the combination.
Obvious to Try: A finite number of identified, predictable solutions exist, and a PHOSITA would have good reason to pursue the known options.
Common Sense/Ordinary Creativity: A PHOSITA would have arrived at the invention through ordinary innovation or common sense.
Design Need/Market Pressure: A known problem creates a design need or market pressure to combine existing elements in a known way to achieve a predictable result.

Prior Art References for US 9347554

The patent itself identifies European Patent Application No. 1,008,785 (EP '785) as relevant prior art. Additional cited patents are also considered.

EP 1,008,785 A2 (New Holland U.K. Limited): Discloses an automatic shifting arrangement for a hydraulic motor in a hydrostatic drive system. It monitors pressure in a working line, and when pressure exceeds a predetermined value, a controller signals a solenoid to shift a pilot valve, which then shifts a torque valve, adjusting the motor's swash plate to control speed. Conversely, a reduction in pressure below a certain point causes the system to return to previous positions. (Described in US9347554, "Definitions" and "BACKGROUND" sections)
US 3,271,955 A (Sperry Rand Corp): Titled "Power transmission." While not fully detailed in the provided text, the title suggests it relates to fundamental power transmission concepts relevant to hydrostatic drives.
US 3,319,419 A (Sundstrand Corp): Titled "Constant speed drive." This reference is highly relevant given the emphasis in US '554 on maintaining constant machine speed, acceleration, or deceleration.
US 4,766,779 A (Fabco Automotive Corporation): Titled "Hydrostatic transmission assembly and method of increasing the torque and speed range thereof." This patent explicitly addresses increasing the torque and speed range of hydrostatic transmissions.
US 6,272,950 B1 (Sauer-Danfoss Inc.): Discloses a "Drive train for a vehicle and method of controlling a drive train."
US 2006/0230920 A1 (Torsten Berg): Discloses a "Hydrostatic transmission."
US 7,390,282 B2 (Caterpillar Inc.): Discloses a "Directional shift in hydrostatic drive work machine."
US 2009/0145122 A1 (Michael Deeken): Discloses a "Hydraulic drive system."
US 2011/0178684 A1 (Kubota Corporation): Discloses a "Speed Change System for Work Vehicle."
EP 1,176,340 A2 (Schlumberger Technology B.V.): Discloses a "Differential hydrostatic transmission system" with a wide dynamic speed control range. It includes a hydrostatic motor, a variable-displacement hydraulic pump, and a two-position control device. The system can operate in normal and fine-speed control modes. In normal mode, motor speed is a function of pump displacement.
US 4,694,187 A (General Electric Company): Discloses an "Electromechanical constant speed drive generating system" with a mechanical differential and a variable speed input from an engine. It aims to maintain a constant output speed using a variable speed dynamoelectric machine, highlighting concepts of maintaining constant speed.

Obviousness Combinations and Rationale

The independent claims of US 9347554 (Claims 1 and 7) center on a controller adjusting pump and motor displacements to maintain constant machine speed, acceleration, or deceleration during shifting, specifically detailing an acceleration mode where motor displacement is first decreased (upshift) while pump displacement is adjusted to maintain current speed, followed by increasing pump displacement for constant acceleration.

Combination 1: EP 1,008,785 A2 in view of US 3,319,419 A and the general knowledge of a PHOSITA

EP 1,008,785 A2 describes an automatic shifting arrangement for a hydraulic motor within a hydrostatic drive system. It explicitly teaches monitoring pressure to trigger shifts and adjusting the hydraulic motor's swash plate via a controller, solenoids, and valves to control speed. The patent mentions both increasing and decreasing pressure scenarios, implying both upshifting and downshifting operations. (Described in US9347554, "Definitions" and "BACKGROUND" sections)
US 3,319,419 A describes a "Constant speed drive." While the full details are not provided in the prompt, the title itself strongly suggests a focus on maintaining constant speed in a drive system. Similarly, US 4,694,187 A describes an "Electromechanical constant speed drive generating system" that aims to maintain a constant output speed despite variable engine input, further demonstrating the known art of constant speed control.
Rationale for Combination: A PHOSITA, faced with the automatic shifting system of EP '785, and possessing knowledge of constant speed drive systems as taught by US '419 and US '187, would have been motivated to combine these concepts to improve the smoothness and control during the automatic shifting process. The problem addressed by US '554—that conventional multi-speed hydrostatic drives cause "shock or jerks" during acceleration or deceleration, thereby decreasing efficiency—is a known problem in the art. (US9347554, "INDUSTRIAL APPLICABILITY" section) It would be obvious to a PHOSITA to integrate mechanisms for maintaining constant machine speed or controlled acceleration/deceleration during shifts, to mitigate these shocks. EP '785 already uses a controller to signal adjustments; incorporating logic to modulate pump displacement to achieve constant speed or acceleration/deceleration during the motor's displacement change would be a predictable improvement to achieve smoother operation. The control functionality described in EP '785 (controller, solenoids, pilot valves, torque valves) provides the basic framework for such an integration.

Specifically addressing Claim 1 elements:

"receive an input signal indicative of a current machine speed and a desired machine speed": EP '785's controller monitors pressure which is indicative of machine operation and indirectly speed, and the concept of desired speed is implicit in any shifting operation. Explicitly using input signals for current and desired machine speed is a common control paradigm in drive systems, as shown by various references describing control of machine speed (e.g., US 2011/0178684 A1, "Speed Change System for Work Vehicle").
"output a motor displacement command signal and a pump displacement command signal to selectively adjust a motor displacement of the hydraulic motor and a pump displacement of the pump... to maintain at least one of constant machine speed or constant acceleration or constant deceleration during adjustment of the pump displacement and the motor displacement": EP '785 already controls motor displacement via a swash plate. The addition of adjusting pump displacement to achieve constant machine speed, acceleration, or deceleration during the motor's displacement change is a logical extension for smoother operation, especially considering the teachings of US '419 and US '187 regarding constant speed control. EP 1,176,340 A2 also discusses variable-displacement hydraulic pumps and motors in a differential hydrostatic transmission system to achieve a wide dynamic speed control range, further reinforcing the concept of adjusting both.
Acceleration Mode Logic: The specific sequence of decreasing motor displacement while decreasing pump displacement to maintain current speed, then increasing pump displacement for constant acceleration, would be an obvious control strategy to a PHOSITA seeking to smooth out shifts in a hydrostatic drive. This is a common engineering approach to manage transient forces during gear changes (or, in this case, displacement changes) in powertrains. The stated problem of "shock or jerks" directly motivates this kind of controlled, phased adjustment.

Combination 2: EP 1,008,785 A2 in view of US 4,766,779 A and general control system knowledge

EP 1,008,785 A2: As above, provides the basis for automatic shifting of a hydraulic motor.
US 4,766,779 A: Explicitly teaches a "Hydrostatic transmission assembly and method of increasing the torque and speed range thereof." This patent directly addresses the performance aspects (torque and speed range) that are affected by shifting in hydrostatic systems.
Rationale for Combination: A PHOSITA would be motivated to combine the automatic shifting mechanism of EP '785 with the goal of increasing torque and speed range as taught by US '779. To achieve improved performance (increased torque and speed range) while also ensuring smooth operation, it would be a natural step to implement precise control over both pump and motor displacements during shifts. The control strategy of maintaining constant speed/acceleration/deceleration during displacement changes directly contributes to both smooth operation and optimal utilization of the extended torque/speed range. The general knowledge of how to electronically control hydraulic components, as described in US '554 (e.g., variable solenoid valves for swash plate control), would enable such a combination.

Conclusion on Obviousness

The independent claims of US 9347554, particularly Claims 1 and 7, appear to be obvious in light of the combination of EP 1,008,785 A2 with references like US 3,319,419 A, US 4,694,187 A, US 4,766,779 A, and general knowledge in the art of hydrostatic drive control. The primary inventive step claimed by US '554 is the coordinated adjustment of pump and motor displacements to maintain constant speed, acceleration, or deceleration during shifting. However, the concept of automatic shifting in hydrostatic motors (EP '785), the desire for constant speed control (US '419, US '187), and the aim to improve the operating range of hydrostatic transmissions (US '779) were all known in the prior art. A PHOSITA would have found ample motivation to combine these known elements and control strategies to achieve the predictable outcome of smoother and more efficient shifting in hydrostatic drive systems. The problem of "shock or jerks" during shifts was recognized, and applying known control principles to actively manage the machine's speed/acceleration during displacement changes would have been an obvious solution to a skilled engineer.