Obviousness

Obviousness Analysis of US Patent 9512025 under 35 U.S.C. § 103

This analysis examines the obviousness of US Patent 9512025, titled "Methods and apparatuses for reducing heat loss from edge directors," by considering the common knowledge in the field and readily available prior art principles. The patent aims to solve the problem of devitrification of molten glass near edge directors in a fusion draw glass forming process, which occurs due to heat loss from the edge directors to cooler downstream edge rollers. The claimed solution involves a replaceable heating cartridge with an inclined heat-directing surface that simultaneously heats the edge director and thermally shields it from the edge rollers.

Background and Problem Addressed

The patent acknowledges that glass forming apparatuses commonly use forming wedges to create glass ribbons, with edge directors at the ends of the wedge to manage ribbon width and edge characteristics. However, these edge directors can act as heat sinks, leading to devitrification of molten glass in their proximity. This issue is exacerbated by the presence of cooler edge rollers downstream, which draw heat from the edge directors, further reducing their temperature and promoting devitrification, ultimately causing defects and increasing production costs.

A person having ordinary skill in the art (PHOSITA) in glass manufacturing would be aware of the basic components of a fusion draw process (forming wedge, edge directors, edge rollers) and the challenges associated with maintaining precise temperature control to prevent devitrification.

Key Novel Elements of US9512025

The independent claims (Claims 1, 8, and 15) of US9512025 primarily introduce the following combination of features:

• A replaceable heating cartridge removably positioned in a housing port below the edge director.
• The cartridge has a heat directing surface inclined at an angle of less than about 90° with respect to a bottom surface of the enclosure.
• This surface includes at least one heating element.
• The heating cartridge is oriented such that the heat directing surface faces the edge director, ensuring a greater view factor (proportion of thermal radiation) at the edge director than at the edge rollers.
• Crucially, a lower edge of the heat directing surface and the bottom surface of the heating cartridge are at least partially positioned between the edge director and the plurality of edge rollers to thermally shield the edge director from the plurality of edge rollers.

Analysis of Obviousness

To demonstrate obviousness, one must show that the claimed invention, as a whole, would have been obvious to a PHOSITA at the time of the invention (i.e., before the May 15, 2014, priority date) in view of prior art references or combinations thereof, with a motivation to combine them.

Given the explicit problem articulated in US9512025 (devitrification due to heat loss from edge directors to cold edge rollers), a PHOSITA would have been motivated to find solutions that address both heating the edge director and preventing heat loss.

Combination of known elements:

1. Heating Elements in Glass Manufacturing: It is common knowledge in glass manufacturing to use heating elements (e.g., resistance heaters) to maintain precise temperatures in various parts of the glass forming apparatus, including near molten glass, to prevent defects like devitrification. The patent itself mentions the use of "refractory or metallic resistance heaters, induction heaters or other heating devices" as optional additional heaters. Thus, placing a heating element near the edge director to maintain its temperature would be a well-known approach.
2. Modular and Replaceable Components: The use of "replaceable" components, particularly in high-temperature industrial environments where maintenance and uptime are critical, is a standard engineering practice. Designing a heating element within a removable cartridge allows for easier maintenance and replacement, which the patent highlights as reducing "production losses and equipment downtime."
3. Directing Heat with Shaped Surfaces: The concept of using shaped or inclined surfaces to direct radiant heat towards a target area is a fundamental principle of thermal engineering. A PHOSITA, aiming to efficiently heat the edge director, would naturally consider shaping the heater's surface and orienting it to maximize heat transfer to the target (the edge director) and minimize loss to non-target areas. The patent notes that "the inclined angle of the heat directing surface allows heat to be more efficiently radiated towards the edge director."
4. Thermal Shielding: To prevent heat loss from a hot component to a cold component, thermal shielding or insulation is a well-established solution in high-temperature processes. The patent explicitly states that the "cooler edge rollers act as a heat sink, drawing heat from the edge directors." A PHOSITA, recognizing this problem, would seek to interpose a thermal barrier between the hot edge director and the cold edge rollers.

Motivation to Combine:

A PHOSITA facing the problem of devitrification at the edge directors due to heat loss to the cold edge rollers would be motivated to combine these known elements for a predictable improvement.

• Motivation to heat the edge director: The immediate problem is that edge directors are too cold, causing devitrification. Therefore, directly heating the edge director is an obvious first step.
• Motivation to use a heating cartridge: For practical reasons in an industrial glass-forming environment, such heating would ideally be delivered by a modular, replaceable unit to facilitate maintenance and minimize downtime.
• Motivation to incline the heat directing surface: To efficiently deliver heat to the edge director and avoid heating other components unnecessarily, it would be intuitive to shape and orient the heater's surface (e.g., incline it) to direct radiation towards the target (edge director) and away from other areas. The patent demonstrates that an inclined surface of 60° (less than 90°) significantly increased the edge director's temperature compared to a 90° angle, indicating a predictable improvement in heat delivery efficiency.
• Motivation to position the cartridge for thermal shielding: Recognizing that the edge rollers are actively cooled and act as heat sinks, a PHOSITA would be motivated to place a thermal barrier between the heated edge director and the cooling rollers. Placing the heating cartridge itself, especially its non-heating or insulated parts (e.g., the bottom surface and lower edge of its enclosure), to partially block the line of sight or radiative path between the edge director and the edge rollers would provide this shielding effect. The patent explicitly states that "the lower edge of the heat directing surface and the bottom surface of the heating cartridge are at least partially positioned between the edge director and the plurality of edge rollers to thermally shield the edge director from the plurality of edge rollers." This dual function (heating and shielding) from a single unit would be an efficient and desirable design choice to address the identified problem comprehensively. The patent highlights this "dual-functionality" as a key advantage.

Conclusion on Obviousness:

While US9512025 presents a practical and effective solution, the individual elements—heating elements, modular cartridges, shaped surfaces for directing heat, and thermal shielding—were known in the art of high-temperature processing, particularly in glass manufacturing. The specific problem addressed by the patent (devitrification at edge directors due to cold edge rollers) would have provided a strong motivation for a PHOSITA to combine these known elements. The combination of an inclined heat-directing surface within a replaceable cartridge, strategically positioned to both radiate heat to the edge director and provide a thermal shield against the edge rollers, would have been a predictable outcome of applying known engineering principles to solve an identified problem in the field. The result, a reduction in devitrification, is a predictable improvement in the art. Therefore, the independent claims of US9512025 would likely have been obvious to a PHOSITA at the time of the invention.