Prior art — US Patent 9060561

To identify the most relevant prior art for US patent 9060561, I will examine the "Citations" section of the patent, which lists documents cited by the applicant or the examiner during prosecution. The goal is to identify references that describe elements of the claimed invention, particularly those related to multiple shell layers and energy-absorbing transformer layers.

Here's an analysis of the cited prior art from US9060561, focusing on relevance to claims 1, 10, and 18:

Claim 1 (Helmet with Three Shell Layers):

A first shell layer.
A second shell layer connected to the first through a first energy transformer layer with first absorptive/dissipative material allowing sliding.
A third shell layer connected to the second through a second energy transformer layer with second absorptive/dissipative material for absorbing energy from forces imparted through the outer layers.

Claim 10 (Helmet with Two Shell Layers and a Lining):

A first shell layer.
A second shell layer connected to the first through a first energy transformer layer with absorptive/dissipative material allowing sliding.
A lining layer connected to the second shell layer, configured to conform to a human head.

Claim 18 (Protective Gear with Three Shell Layers):

A first shell layer.
A second shell layer connected to the first through a first energy transformer layer with first absorptive/dissipative means allowing sliding.
A third shell layer connected to the second through a second energy transformer layer with second absorptive/dissipative means for absorbing energy from forces imparted through the outer layers.

Analysis of Prior Art Citations:

1. US7076811B2 (Puchalski)

Full Citation: US7076811B2, "Protective head covering having impact absorbing crumple or shear zone," issued to Ione G. Puchalski on July 18, 2006 (filed September 9, 2002).
Brief Description: This patent describes a helmet with a shell consisting of three (or more) discrete panels that are firmly coupled but move relative to one another upon impact, creating a "crumple zone" or "shear zone" to dissipate and redirect forces.
Potential Anticipation/Obviousness (35 U.S.C. § 102): This reference is highly relevant to Claims 1, 10, and 18, particularly regarding the concept of multiple layers/panels that move relative to each other to absorb and dissipate impact and shear forces. The "discrete panels that are physically and firmly coupled together providing rigid protection under most circumstances, but upon impact the panels move relative to one another" directly addresses the idea of relative sliding movement between layers for energy absorption.
- Claim 1, 18: The three discrete panels could be considered analogous to the "first, second, and third shell layers." The relative movement and "crumple/shear zone" function as "energy transformer layers" with "absorptive/dissipative means" allowing sliding.
- Claim 10: The concept of multiple, relatively moving layers for energy absorption is present, potentially anticipating the shell and energy transformer layer combination.

2. US5815846A (Calonge)

Full Citation: US5815846A, "Resistant helmet assembly," issued to Calonge on October 6, 1998 (filed November 27, 1996).
Brief Description: This patent describes an impact-resistant helmet assembly with a first material layer coupled to a second material layer, defining a gas chamber in between for impact dampening. It also includes a fluid chamber with a viscous gel to provide resistance against disbursement from an impacted region, enhancing impact distribution and dampening.
Potential Anticipation/Obviousness (35 U.S.C. § 102): This reference is highly relevant to Claims 1, 10, and 18, especially concerning fluid or gel-filled layers for impact absorption and distribution.
- Claim 1, 18 (and dependent claims 2, 3, 5, 6): The "first material layer" and "second material layer" can be seen as shell layers. The "gas chamber" and "fluid chamber" containing a "viscous gel" or "fluid" directly anticipate the "first energy transformer layer" (and second) with "absorptive/dissipative material" comprising a "gel" or "fluid."
- Claim 10 (and dependent claims 11, 12): The same reasoning applies for the two-shell system with a gel/fluid transformer layer.

3. US5956777A (Popovich)

Full Citation: US5956777A, "Helmet," issued to Popovich on September 28, 1999 (filed July 22, 1998).
Brief Description: This patent describes a helmet with a rigid inner shell, a resilient spacing layer disposed outside and in contact with the inner shell, and an articulated shell (with discrete rigid segments coupled by resilient members) outside the resilient spacing layer.
Potential Anticipation/Obviousness (35 U.S.C. § 102): This reference is relevant to Claims 1, 10, and 18 by demonstrating a multi-layered helmet design with relative movement and energy absorption features.
- Claim 1, 18: The "rigid inner shell," "resilient spacing layer," and "articulated shell having a plurality of discrete rigid segments" can be mapped to the three shell layers and the energy transformer layers. The "resilient spacing layer" and "resilient members which couple adjacent ones of said rigid segments" can act as the "energy transformer layers" allowing for movement and absorbing energy.
- Claim 10: The "rigid inner shell" and "articulated shell" separated by a "resilient spacing layer" presents a two-layer system with energy absorption.

4. US6434755B1 (Halstead)

Full Citation: US6434755B1, "Helmet," issued to Halstead on August 20, 2002 (filed June 4, 1999).
Brief Description: This patent describes a football helmet with liner sections of different thicknesses and densities. Thicker, softer sections handle less intense impacts by crushing, while thinner, harder sections prevent bottoming out during more intense impacts.
Potential Anticipation/Obviousness (35 U.S.C. § 102): This reference is relevant for the concept of varying material properties within protective layers for impact management. While it doesn't explicitly describe sliding layers or electro/magneto-rheological fluids, the idea of tailored energy absorption within multiple layers (even if contiguous) is present.
- Claim 9, 10, 19, 20: This reference is particularly relevant to the lining layer (Claim 9, 10, 19) and the use of foam (Claim 20) with different properties for cushioning and energy absorption. The "liner sections of different thicknesses and densities" for impact attenuation could be considered a type of cushioning device within a lining layer.

5. US8533869B1 (Noggin Group LLC)

Full Citation: US8533869B1, "Energy absorbing helmet underwear," issued to Noggin Group LLC on September 17, 2013 (filed February 19, 2008).
Brief Description: This patent describes energy-absorbing helmet underwear. The details of the energy absorption mechanism would require reviewing the full patent.
Potential Anticipation/Obviousness (35 U.S.C. § 102): Without the full text, it's harder to assess specific anticipation. However, the title suggests a focus on energy absorption, likely within a layer adjacent to the head, making it potentially relevant to the lining layer and its energy-absorbing functions in Claims 9, 10, 19, and 20. If it describes layered structures for energy absorption, it could also be broadly relevant to the transformer layers.

6. US20130019384A1 (Brainguard Technologies, Inc.)

Full Citation: US20130019384A1, "Biomechanics aware protective gear," published January 24, 2013 (filed July 21, 2011).
Brief Description: This is an earlier publication by the same assignee, Brainguard Technologies, Inc., and is a parent application to US9060561. It likely discloses similar or identical subject matter regarding biomechanics-aware protective gear with multiple layers and energy/impact transformers.
Potential Anticipation/Obviousness (35 U.S.C. § 102): As a parent application with an earlier priority date, this document is highly likely to anticipate or render obvious many, if not all, of the claims of US9060561 under 35 U.S.C. § 102. It serves as "prior art by the same inventive entity" (or common assignee) and would typically disclose the core concepts of multi-shell layers and energy-transforming layers for rotational and shear forces.

7. WO2013013180A1 (Robert Knight)

Full Citation: WO2013013180A1, "Biomechanics aware protective gear," published January 24, 2013 (filed July 21, 2011).
Brief Description: This is a PCT application, also by Robert Knight (the inventor of US9060561), with the same priority date as US20130019384A1. It describes biomechanics-aware protective gear.
Potential Anticipation/Obviousness (35 U.S.C. § 102): Similar to US20130019384A1, this document, sharing the same priority date and inventor/assignee, is highly likely to anticipate or render obvious the claims of US9060561.

8. EP2734071A1 (Brainguard Technologies, Inc.)

Full Citation: EP2734071A1, "Biomechanics aware protective gear," published May 28, 2014 (filed July 21, 2011).
Brief Description: This is a European patent application by the same assignee, Brainguard Technologies, Inc., with the same priority date as the aforementioned related applications. It also describes biomechanics-aware protective gear.
Potential Anticipation/Obviousness (35 U.S.C. § 102): Again, sharing the same priority date and assignee, this European application would likely anticipate or render obvious the claims of US9060561.

9. US8863319B2 (Brainguard Technologies, Inc.)

Full Citation: US8863319B2, "Biomechanics aware protective gear," issued October 21, 2014 (filed July 21, 2011).
Brief Description: This is another U.S. patent by the same assignee and sharing the same priority date. It explicitly states it is related to "biomechanics aware protective gear."
Potential Anticipation/Obviousness (35 U.S.C. § 102): As a direct continuation or related application claiming the same priority date, this patent would certainly anticipate or render obvious the claims of US9060561. It is likely that US9060561 is a divisional or continuation of this patent or a common parent.

Other citations (e.g., US3946441A, US4352484A, US5713082A, US6103641A, US6145348A, US6378140B1, US6658671B1, US6728969B2, US20030088906A1, US6996856B2, WO2004032659A1, US7254843B2, US20060059605A1, US20110004980A1, US8176574B2):
These patents broadly relate to safety helmets, energy absorption, blunt trauma reduction, impact absorbing products, or layered constructions. While they contribute to the general state of the art, their relevance for direct anticipation of the specific multi-shell, sliding layer, and electro/magneto-rheological element features of claims 1, 10, and 18 of US9060561 would require a detailed claim-by-claim comparison of their disclosures. Many appear to address the broader concept of impact absorption in protective gear.

Specifically for electro-rheological/magneto-rheological elements (Claim 4, 13, 14, 15):
The provided patent text for US9060561 explicitly mentions electro-rheological and magneto-rheological elements as part of the energy and impact transformer layers. If any of the cited prior art explicitly discloses the use of such "smart fluids" in multi-layered protective gear for viscosity changes in response to impact, it would be highly relevant to these specific dependent claims. However, none of the brief descriptions for the cited patents explicitly mention these materials, though Calonge (US5815846A) discusses viscous gels which could be a precursor. Further examination of the full text of all cited patents would be necessary to definitively determine anticipation or obviousness for these specific features.

Overall Most Relevant:
The most relevant prior art for US9060561 are the Puchalski (US7076811B2), Calonge (US5815846A), and Popovich (US5956777A) patents, as they directly address multi-layered helmet structures with mechanisms for relative movement and energy absorption to mitigate impact forces, including potentially shear forces. Furthermore, the multiple family members by Brainguard Technologies, Inc. and Robert Knight (US20130019384A1, WO2013013180A1, EP2734071A1, US8863319B2) are essentially the same inventive concept filed earlier and therefore would be highly anticipatory.