Obviousness

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

To determine whether the claims of US9151557 would have been obvious to a person having ordinary skill in the art (POSA) at the time of the invention, we must consider the scope and content of the prior art, differences between the prior art and the claims at issue, and the level of ordinary skill in the pertinent art. We also consider any secondary considerations of non-obviousness, although no such considerations have been provided in this analysis.

The patent US9151557 broadly concerns an automatic sear assembly for large-bore rifles, enabling full-automatic or burst-firing capabilities while aiming to reduce complexity and improve reliability compared to existing solutions. A key aspect is the bidirectional articulation of the sear lever, where movement away from the automatic sear has no effect, but movement towards it causes the sear to trip, initiating a subsequent firing cycle (Claim 1). The invention also details specific spring types (helical torsion and helical double-torsion) and a bushing/pin assembly for rotational mounting and component retention (Claim 20).

Definition of a Person Having Ordinary Skill in the Art (POSA):
A POSA in this field would likely be a firearms engineer or designer with several years of experience in the design, development, and manufacturing of small arms, particularly rifle mechanisms. This individual would be familiar with various firing mechanisms, sear designs, selector switches, and the mechanical interaction of components within a rifle, including springs, pins, and bushings. They would also understand the challenges associated with achieving selective-fire capabilities in large-bore rifles and relevant military specifications like MIL-W-13855.

Prior Art References:
The patent itself lists several prior art keywords: "sear," "automatic," "rifle," "assembly," and "lever." While no specific prior art patents or publications are explicitly identified in the "Prior art keywords" section as being cited against US9151557, the "Definitions" section of the patent's full text mentions MIL-W-13855 (Weapons: Small Arms and Aircraft Armament Subsystems, General Specification For) multiple times. This military standard is identified as a general specification covering requirements for small arms weapons, aircraft armament subsystems, attachments, accessories, equipment, and parts.

The absence of specific patent references in the "Prior art keywords" from the provided patent text limits the scope of this obviousness analysis to general knowledge in the field as represented by the description in the patent and the MIL-W-13855 standard. For a comprehensive obviousness analysis, a full review of the patent's prosecution history and cited prior art would be necessary. However, based on the provided information, we will proceed with the general understanding of the prior art.

General Understanding of Prior Art based on the patent's Background and Description:
The patent's background section states that "existing large-bore rifle designs which have selective-fire capabilities use a large and heavy sear lever for tripping the rifle's sear to provide the rifle with a full-automatic firing mode." It further notes that "that lever, which is suspended in the rifle's bolt carrier, adds moving mass to the bolt carrier, is prone to failure through the pin which permits the sear lever to pivot, and causes damage to the surface of the lower receiver and receiver extension tube of the host rifle." This suggests that prior art automatic sear mechanisms for large-bore rifles existed, but suffered from issues of size, weight, reliability (pin failure), and potential for damage to the rifle. The invention aims to overcome these limitations with a design that does not suspend the sear lever in the bolt carrier.

MIL-W-13855, as a general specification for small arms and aircraft armament, sets forth requirements for materials, drawings, dimensions, tolerances, and interchangeability of parts. A POSA would be intimately familiar with this standard and its implications for firearm component design and manufacturing. While MIL-W-13855 doesn't describe specific sear assembly designs, it dictates the engineering and quality standards that such components must meet.

Analysis of Obviousness:

Given the information, an obviousness challenge would need to combine elements from general knowledge in the field and potentially other specific prior art references (not explicitly listed here but generally referenced in the patent's background) that address similar problems or mechanisms.

Combination 1: General knowledge of existing automatic sear mechanisms + MIL-W-13855

• Motivation to Combine: A POSA, faced with the known problems of existing large and heavy sear levers causing increased moving mass, prone failure, and damage in large-bore selective-fire rifles (as described in the background of US9151557), would be motivated to design a more reliable and efficient automatic sear assembly. The general requirements outlined in MIL-W-13855 would guide the POSA in selecting appropriate materials, ensuring dimensional compliance, and adhering to quality standards for any newly designed or modified components.

• Reasoning for Obviousness: If prior art already disclosed automatic sear assemblies (even with the mentioned drawbacks), a POSA would know the basic components involved: a sear, a sear lever, and springs to control their movement in relation to a hammer and selector switch. The inventive step in US9151557 lies in the bidirectional articulation and the specific arrangement that allows the sear lever to operate independently in one direction and conjunctively in another. Without specific prior art disclosing a similar independent/conjunctive operation or a sear lever not suspended in the bolt carrier but operating adjacent to the automatic sear, it's difficult to argue that the precise mechanism of Claim 1 would be obvious. The patent emphasizes the novel bidirectional articulation where rotational deflection in a first direction causes the sear lever to rotate out of physical contact with the sear (without imparting rotation to the sear), and deflection in a second direction imparts rotation to the sear. This differential interaction, particularly when driven by a bolt carrier, is presented as a solution to the prior art's deficiencies.

  However, if prior art existed that showed any form of sear lever disengagement during part of the bolt carrier's cycle and engagement during another, a POSA might be motivated to optimize this interaction to achieve selective fire and improve reliability. The use of springs to bias mechanical components and facilitate controlled movement is fundamental to firearm design and would be well within the knowledge of a POSA. The specific helical torsion and helical double-torsion springs in Claim 20, while detailed, are common mechanical components, and their application to bias a sear lever and interface with a selector switch might be considered an engineering choice if the underlying functional concept (bidirectional articulation) were known. Similarly, the use of a bushing and pin for rotational mounting and retention, with slots and grooves for spring legs (Claim 20), represents standard mechanical design practices for firearm components that need to pivot and be retained.

Conclusion on Obviousness based on limited prior art provided:

Based solely on the provided "Prior art keywords" and the general context of existing automatic sear designs for large-bore rifles as described in the patent, a strong argument for obviousness of the entirety of Claim 1, Claim 16, or Claim 20 is difficult to make without specific prior art references that explicitly teach or suggest the novel bidirectional articulation and the specific independent/conjunctive operation of the sear lever as claimed.

However, a POSA would be motivated to improve upon existing large-bore automatic firing mechanisms to address issues of weight, reliability, and potential damage. If prior art existed that, for example, showed a sear lever moving independently of a sear during some portion of a firing cycle, and also showed a sear lever engaging a sear during another portion of the firing cycle to achieve automatic fire (even if imperfectly), a POSA, guided by MIL-W-13855 for material and manufacturing standards, might be motivated to refine such a system to achieve the benefits described in US9151557. The specific spring types and bushing/pin retention details of Claim 20 would likely be considered routine mechanical design choices to implement the desired functionality, rather than inventive steps in themselves, assuming the core functional concept was already known or obvious.

To provide a more definitive obviousness analysis, specific prior art references that illustrate or suggest the following would be crucial:

1. Automatic sear assemblies for rifles (especially large-bore) that include a sear and a sear lever.
2. Mechanisms where a sear lever interacts with a bolt carrier.
3. Mechanisms where a sear lever can move independently of the sear in one direction but engage and move the sear in another direction.
4. The use of torsion springs or double-torsion springs in sear assemblies.
5. Standard mounting techniques for pivoting firearm components using pins and bushings with retention features.

Without such specific references, a definitive assertion of obviousness against the detailed claims of US9151557 is not possible with high confidence. The patent appears to distinguish itself by the specific "bidirectional articulation" and independent/conjunctive operation, which, if truly novel, would not be obvious from general knowledge alone.