Non-resiliency body-contact protective helmet interface structure

Abstract

Shock-absorbing, load-cushioning interface structure for use inside, and in operative cooperation with, the shell of a helmet for operative interposition such a shell and the head of a wearer. This structure is characterized with features and performances including (a) compression-deformation-and-slow-return viscoelasticity, (b) non-springy (anti-rebound) during a return from deformation, (c) acceleration-rate(strain-rate)-sensitivity, and (d) a durometer associated with an ILD number which is no less than about 15-ILD.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a human-body protective, cushioning helmet interface (shock-absorbing) structure which is designed especially to combine with a rigid protective helmet-shell barrier structure to protect the head from a blunt-trauma-type impact injury. More particularly, it relates to such structure (a) which lacks any springy (spring-back or rebound) resiliency, (b) which possesses acceleration-rate (syn., strain-rate)-sensitivity, and (c) which is designed to be interposed the body and a cooperating rigid barrier structure such as a helmet shell which is worn on the head, and through which rigid barrier structure (shell) and cushioning interface structure various kinds of shock loads may be delivered. The invention also relates to a helmet structure per se which includes a rigid barrier shell and cushioning interface structure of the type just generally outlined.

While there are many helmet applications wherein the structure of the present invention can offer distinct advantages, one preferred embodiment of the invention is described herein specifically in the setting of a military helmet, with respect to which the invention has been found to furnish particular utility.

From the important underlying disclosure history which illustrates and describes the invention focused upon herein, cross-referenced above in the forms of related cases, one particular patent of special interest has issued. This patent, U.S. Pat. No. 6,467,099, issued Oct. 22, 2002 for “Body-Contact Cushioning Interface Structure”, directs attention to an embodiment of the invention which is a specifically designed for use in environmental settings where moisture saturation, as by immersion in water, could present a problem by entering the cushioning structure material and diminishing the load-cushioning qualities of that material per se which is directly responsible for effecting non-springy, viscoelastic, acceleration-rate(strain-rate)-sensitive response to an impact (shock) event. To deal with that moisture-related issue, the embodiment of the invention featured there includes a cushioning core structure suitably coated with a gas-breathable, moisture-impenetrable barrier layer. The presently focused-upon embodiment of the invention addresses another kind of environmental situation wherein immersion moisture is not expected to become a problem.

Very specifically, the present invention embodiment points attention to the originally disclosed (in the underlying prior patent applications) core load-cushioning structure per se, and the direct cooperative relationship between that structure and a rigid helmet shell, without necessary reference being made to the presence or absence of a moisture-impervious outer barrier layer. Even more specifically, the invention set forth herein focuses, inter alia, on a special load-cushioning structure which is intended for combinational assembly and performance directly with a rigid protective-barrier helmet shell which first receives a shock impact against which the invention is designed to protect. There is no intervening, other load-handling structure interposed this load-cushioning structure and a helmet shell, though, if desired, the load-cushioning structure of the invention may be received in an envelop structure which deals with moisture wicking and/or attachment to a helmet shell. This load-cushioning structure possesses important, combined “core characteristics” which include (a) compression-deformation-and-slow-return viscoelasticity, (b) non-springiness, (c) acceleration-rate(strain-rate)-sensitivity, and (d) a durometer which is associated with an ILD (Identation Load Deflection) number which is no less than substantially 15-ILD. The invention also focuses attention on a helmet structure per se whose outer shell is appropriately lined, or otherwise internally equipped, with an insert, or inserts, of such load-cushioning structure.

Thus, one should read and understand the presently addressed invention by directing special attention toward the structure and use, per se, of a material combinable directly with an outer, rigid helmet shell, and interposable that shell and a wearer's head, which structure is, collectively, non-springy, viscoelastic with a minimum defined ILD number, and acceleration-rate(strain-rate)-sensitive.

With reference to a conventional military helmet, such an environment is vividly demonstrative of the issues that are successfully addressed by the present invention. For example, the current U.S.-issue military infantry helmet utilizes in its outer shell an internal webbing system combined with a removable leather liner to suspend the helmet on the wearer's head. Airspace between the webbing and the shell of the helmet contributes somewhat to the ballistic, and significantly to the cooling, capabilities of the helmet, but such a webbing system has proven consistently (a) to do a poor job of cushioning shock loads delivered to the wearer's head through the subject helmet, and (b) to be quite uncomfortable, and thus to be the source of many complaints from users.

The structure of the present invention offers appreciable improvements in these areas of concern regarding helmet performance. This structure, in the preferred form of the invention described herein, features a novel cushioning structure which offers the very important cooperative characteristics of compression-deformation-and-slow-return viscoelasticity, non-springiness, and what is known as acceleration-rate(strain-rate)-sensitivity.

According to the invention, it features what is referred to herein as a load-cushioning instrumentality formed from one, or a plurality of, body(ies) of a material which responds acceleration(strain)-rate-resistantly to shock-produced, rapid acceleration, with a resistance to compression deformation that generally rises in a somewhat direct relationship to the level or magnitude of acceleration. This kind of acceleration-rate(strain-rate)-sensitivity is somewhat analogous to the phenomenon known in the world of fluid mechanics as shear-resistant fluid dilatancy. This behavior, in the “world” of a helmet shell, causes a shock load to be transmitted to, and borne by, the wearer's head over a relatively wide surface area, and thus generally reduces the likelihood of serious injury. The rate-sensitive material proposed by the structure of this invention also responds to (and following) an impact event by recovering slowly from compression deformation to an undeformed condition—thus avoiding any dangerous “rebound”, spring-back activity. In point of fact, the load-cushioning material employed in accordance with the invention is decidedly non-springy in character. As will be further mentioned, the load-cushioning material proposed by the invention, in order to be capable of dealing most effectively in direct combination with a rigid helmet shell in the protection against head impacts, possesses a durometer with a minimum ILD number of about 15-ILD.

The association which exists between the load-cushioning structure and a helmet shell (rigid), is that the helmet shell converts whatever kind of specific impact occurs to it from the outside to a broad-area, blunt-trauma kind of event which is delivered directly to the load-cushioning structure without there being any interposed, other load-managing material, such as any material with springy rebound (resilience) behavior. Such a blunt-trauma event presented through the shell to the load-cushioning structure takes maximum advantage of the cushioning capabilities of the load-cushioning structure, and results in significant anti-injury impact delivery to the head of a helmet wearer.

With the load-cushioning (shock-absorbing) structure of this invention incorporated for use in conjunction with an operatively associated helmet shell, a load-transmission path exists between that shell and the head of a wearer. In this path, compression deformation and return response to a shock load delivered to the outside of the shell is solely determined by the characteristics of the invention's load-cushioning structure. Northing in this path introduces any form of a springy, spring-back, rebound response.

The structure of this invention is easily rendered in a variety of specific configurations, and thus is readily usable in a host of different helmet settings. It is relatively easy and inexpensive to manufacture, and it can be introduced very conveniently in a wide range of helmet “retrofit” situations. For example, it can be employed within, and in conjunction with, a helmet shell as a distribution of plural load-cushioning pads. It can also be implemented, if desired, as a large, singular helmet-shell insert. Overall structure thickness can be selectively chosen to be different for different circumstances. A single, or more than two, rate-sensitive sublayer(s) can be employed. Within a relatively wide range set forth below herein, a different specific durometer value (or values in a stack of sublayers) for the rate-sensitive sublayer(s) can be chosen.

All of the special features and advantages mentioned above that are offered by the present invention will now become more fully apparent as the description which follows below is read in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation (with certain portions broken away to reveal details of internal construction) of a military helmet whose outer shell is equipped on its inside with plural pad-like expanses (seven in total number) of cushioning interface structure constructed in accordance with the present invention.

FIG. 2 is a side elevation (also with portions broken away to reveal internal construction) of the helmet of FIG. 1, on about the same scale as and taken generally from the right side of, FIG. 1, with load-cushioning structure which is contained within the shell of this helmet being illustrated in a condition tilted slightly toward the viewer in this figure.

FIG. 3 is an enlarged-scale, fragmentary detail taken generally in the area of curved arrows 3-3 in FIG. 2, showing in cross section one of the several load-cushioning interface structures of the invention employed in the shell of the helmet of FIGS. 1 and 2.

FIG. 4 is a view showing a modified form of load-cushioning structure constructed in accordance with the invention.

FIG. 5 is a simplified view, somewhat like FIG. 2, showing a single helmet-shell insert version of the load-cushioning structure of the invention.

In FIGS. 3 and 4, but not in FIG. 5 wherein no ancillary jacketing structure specifically appears, certain outside jacketing structures (ancillary structures) for the illustrated load-cushioning structures of the invention are shown.

DETAILED DESCRIPTION OF, AND BEST MODE FOR CARRYING OUT, THE INVENTION

Turning attention now to FIGS. 1, 2 and 3, indicated generally at 10 (FIGS. 1 and 2) is a military helmet including a shell 10a. In all respects, shell 10a is completely conventional in construction, and might have any one of a number of different specific constructions and configurations.

Fastened in one of a variety of appropriate manners on the inside, concave, dome-like surface of shell 10a is an installation 12 of shock-absorbing, load-cushioning interface structure constructed in accordance with the present invention. Installation 12, in the particular setting illustrated in these figures and now being described, includes seven, individual, multi-layer, load-cushioning, interface-structure pads 12a, 12b, 12c 12d, 12e, 12f, 12g, each of which includes one preferred form of a central, or core, load-cushioning instrumentality possessing certain characteristics which are key to the structure and functionality of the present invention. Pad 12a is joined to the inside surface of shell 10a in the frontal, central portion of that surface. Pads 12b, 12c are disposed on laterally opposite sides of pad 12a. Pads 12d, 12e are located in laterally spaced places on the inside, lower, rear portion of the inside surface of shell 10a. Pad 12f is positioned centrally between pads 12d, 12e. Pad 12g is disposed on the upper (or crown) portion of the inside surface of shell 10a.

With a brief digression made here to FIG. 5, this figure shows an installation in helmet shell 10a which takes an alternative invention form, one of many possible alternative forms, of a single load-cushioning insert 14 which is employed instead of plural, distributed pads. Insert 14 may be made to have the internal structure of any embodiment of the invention.

With regard to configuring a load-cushioning instrumentality as a singular insert for a helmet shell, as illustrated in FIG. 5, such an embodiment is visually similar to, but functionally and internally structurally very different from, a commercial product known as Zetaliner™ made by Oregon Aero based in Scappoose, Oreg. The Zetaliner™ product takes the form of a cloth-covered viscoelastic foam insert for installation within a plastically crushable, shell-like insert component which itself sits inside a helmet shell. The foam is of very low durometer and ILD number, less than 15-ILD, and is designed to create a tight, conforming and deforming fit with a wearer's head. The foam is thus normally substantially in a compressed and deformed state (to enhance fit) when it is in use, and it is the immediate outer, crushable shell-like insert which functions, non-reversibly, to respond with shock dissipation of an impact delivered to the associated helmet shell. The foam, in its normally substantially compressed and deformed state, is not poised for load-cushioning. It functions essentially for fitment purposes, rather than for load cushioning.

Returning to FIGS. 1-3, inclusive, the perimetral shapes and the locations of the illustrated seven pads, and indeed the specific number of pads chosen for use in helmet 10 in this form of the invention, are completely matters of choice, and are not part of the present invention. These specific shapes, locations, and this “pad-count” number, have been chosen in relation to equipping the shell of helmet 10 with one appropriate and versatile, overall interface structure that acts between a wearer's head and shell 10a. A description of a preferred internal construction for pad 12a which now follows, fully describes the construction of each of the other six pads in installation 12.

Accordingly, pad 12a includes a central, or core, load-cushioning structure, or instrumentality, 16 made up of two sublayers 16a, 16b. This core structure, viewed either individually as something which can be installed inside the shell of a helmet, or as part of a cooperative combination with the outer shell (10a) of a helmet, lies at the heart of the present invention.

Ancillary to this load-cushioning core structure, but nonetheless illustrated in FIGS. 1-3, inclusive, are an applied moisture-blocking, gas-permeable barrier layer 18, and a moisture-wicking outer layer 20. These two layers, while includable if desired, are not part of the present invention. The earlier mentioned, cross-referenced, historical background-case material describes materials which could be used for these layers if one chooses to include them.

Practical experience has shown that it is very useful, and thus desirable, to include at least outer wicking layer 20 which, while not affecting load-cushioning behavior, offers a certain wearing-comfort appeal. Such a layer, when employed, is distributed preferably in the form of an enclosure bag around core structure 16. This bag might typically take the form of a polyester fabric, such as fabric known as Orthowick made by Velcro Laminates, Inc., 54835 C.R. 19, Bristol, Ind. 46507.

The right side of pad 12a in FIG. 3 is referred to herein as the body-facing side, and the left side of the pad in this figure is referred to as the load-facing side. Each of the two sublayers (16a, 16b) which make up core structure 16 is formed, importantly, of a suitable acceleration-rate(strain-rate)-sensitive material, such as a viscoelastic urethane compression-deformation-and-slow-return material, which possesses, in technical terms known to those skilled in art, acceleration-rate(strain-rate)-sensitivity.

With regard to acceleration-rate(strain-rate)-sensitivity, the materials in sublayers 16a, 16b respond to compressive accelerations each with a compression-deformation resistance behavior that is likenable generally to the sheer-resistance behavior which is observed in certain fluids as a phenomenon known as fluid dilatancy. When compressive pressure is applied to these materials, if that pressure application is done at a very low acceleration rate, the materials respond very readily and fairly instantaneously with a yielding deformation response. However, if such a pressure is applied rapidly, i.e., with a rapid (large) acceleration rate, the materials tend to act very much like solids, and they do not respond rapidly with a yielding deformation action. Generally speaking, the higher the rate of acceleration associated with an applied compressing force, the more like a solid material do sublayers 16a, 16b behave. An important consequence of this acceleration-response characteristic is that the structure of the invention offers, in relation to prior art structures, a superior shock-cushioning action. It thus offers a significant improvement in injury avoidance. A contributing factor also in this regard is that the materials in sublayers 16a, 16b, after undergoing a compressive deformation, return relatively slowly toward their pre-deformation configurations.

The preferred two-sublayer make-up for core structure 16 is further characterized by the fact that the rate-sensitive, viscoelastic material in sublayer 16a has a lower durometer and Indentation Load Deflection (ILD) response number than does the material in sublayer 16b. Specifically, and in the construction now being described, sublayer 16a has a durometer with an ILD number (or rating) preferably no less than substantially 15-ILD, and preferably further in the ILD number range of about 15 to about 28. Sublayer 16b has a durometer with an ILD rating preferably in the range of about 42 to about 55. Sublayer 16a herein is made of a viscoelastic material designated as Confor CF-40, made by a company called EAR Specialty Composites in Indianapolis, Ind. Sublayer 16b is made of a viscoelastic material designated as Confor CF-45, also made by this same company.

The overall thickness of core structure 16, i.e. the dimension thereof measured laterally (or from left to right sides) in FIG. 3 (shown at T₁), is preferably about ⅞-inches. Sublayer 16a has a thickness pictured in FIG. 3 at T₂ (measured in the same fashion) preferably of about ⅜-inches, and sublayer 16b, a thickness pictured in FIG. 3 at T₃ preferably of about ½-inches. Different thickness dimensions may, of course, be chosen for various purposes, including for “sizing” purposes, to aid in achieving a proper and comfortable helmet fit.

Within the context of a two-sublayer make-up for core structure 16, and with respect to an overall core structure thickness which is greater than about ½-inches, it is preferable that the thickness of sublayer 16a be maintained at no less than about ⅜-inches. Where the overall thickness of core structure 16 is reduced to about ½-inches or less, it is preferable here that this core structure be made of but a single layer of “lower durometer type” viscoelastic material, but preferably with and ILD number which is no less than about 15-ILD.

Under all circumstances, it is preferable, where a multi-sublayer structure is employed for core structure 16, that the component thereof which is toward the body-facing side of the whole assembly have the lowest (in the case of more than two layers) durometer ILD number associated with it.

Another consideration regarding the structure of core structure 16 is that, preferably, it have a quite uniform thickness throughout. Uniformity of thickness plays an important role in maximizing the capability of this core structure to conform as precisely as possible with, in the case of a helmet, the topography of the wearer's head. My practice has been to create such a core structure with an overall thickness which lies within a tolerance range of about ±0.002-inches. This is the thickness tolerance which characterizes the core structure pictured in helmet 10.

Within the three-dimensional body of each of the two viscoelastic sublayers, there is no other structure present, save ambient and entrained gas. Accordingly, each such body responds to shock loads substantially uniformly, and omnidirectionally, throughout its entirety.

Pad 12a is suitably and preferably releasably anchored to the inside of helmet shell 10a through a two-component conventional hook-and-pile structure 24 typically sold under the name Velcro—a readily commercially available product made by Velcro USA, Inc., 406 Brown Avenue, Manchester, N.H. 03108-4806. One component of this hook-and-pile structure is suitably attached either directly to core structure 16, or to any outside-layer covering structure employed with this core structure, and is located on what was referred to earlier as the load-facing side of pad 12a. The other component of the hook-and-pile structure is suitably joined to the inside surface (at the appropriate location) of helmet shell 10a.

FIG. 4 in the drawings illustrates a modified form of a load-cushioning pad 12a made in accordance with the invention. This pad differs from the pad as shown in FIG. 3 by the fact that core structure 16 here includes but a single, acceleration-rate(strain-rate)-sensitive, viscoelastic component, or instrumentality, shown at 16c. Component 16c has a thickness, indicated at T₄ in FIG. 4, of about ½-inches, and is formed generally of the same kind of viscoelastic material described earlier as having a durometer rating with an ILD number in the range of about 15 to about 28. Thus, component 16c herein is preferably made of the EAR Specialty Composites material designated as Confor CF-40.

There is thus provided by the present invention a unique, shock absorbing, load-cushioning structure which offers the various compression-and-slow-return, non-springy, acceleration-rate(strain-rate)-sensitive, viscoelastic benefits ascribed to it hereinabove—which benefits offer significant improvements over related prior art structures.

If and when a shock load is transmitted through the helmet shell to the head of the wearer, it emerges on the inside of the shell as a blunt-trauma-type event which is delivered to the inside-installed load-cushioning structure, 16. The rate-sensitive nature of structure 16 causes that structure to respond with the very effective behavior described earlier herein, namely, to act in an acceleration-resistant and anti-spring-back fashion that causes such an event to be further distributed over a very broad expanse, and to be managed without there being any negative and dangerous rebound repercussions.

Very specifically, within a helmet shell, the load-cushioning structure of the invention defines what is referred to herein as a load-transmission path between this shell and the head of a wearer. Such a path can be visualized by looking, for example, at FIGS. 3 and 4 in the drawings with the idea that a horizontal line passing generally vertically centrally through these fragmentary views essentially highlights such a path where it extends between the inside of the pictured helmet shell and the inner side of structure 16. Within this path, a shock load delivered to the outside of the helmet shell causes a compression deformation first response, and a subsequent slow return, or second, response, to occur in structure 16. This response behavior of structure 16 solely determines how the head of a wearer experiences the triggering shock load. In other words, there is no other compression-and-return material involved in this load-transmission path, and especially, no material in this path which can introduce any form of a springy, spring-back, rebound (resiliency) response. This behavior is strikingly contrastable with prior art behavior which seems always to focus upon achieving intentionally some form of such a springy reaction response.

This unique behavior of the present invention causes it to offer superior ballistic response capabilities in relation to preventing the likelihood of a serious head injury. The operational features of load-cushioning structure 16—compression deformation-and-slow-return viscoelasticity, non-springy anti-rebound, and acceleration-rate(strain-rate)-sensitivity—contribute significantly to the invention's superior behavior.

The invention, as proposed, may take the form, for example, as a shock-absorbing structure per se intended for use inside the shell of a helmet. It may also take the form of a combination of a shock-absorbing structure and a rigid helmet shell.

While the invention has been disclosed in particular settings, and in particular forms herein, the specific embodiments disclosed, illustrated and described herein are not to be considered in a limiting sense. Numerous variations, some of which have been discussed, are possible. Applicants regard the subject matter of their invention to include all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein.

Claims

1. Shock absorbing structure for use inside the shell of a helmet for operative interposition such a shell and the head of a wearer comprising a load-cushioning instrumentality which is structurally characterized with (a) compression-deformation-and-slow-return viscoelasticity, (b) non-springy (anti-rebound) behavior, (c) acceleration-rate(strain-rate)-sensitivity, and (d) a durometer which is associated with an ILD number of no less than about 15-ILD.

2. The shock-absorbing structure of claim 1, wherein said instrumentality is formed from plural, cooperative bodies of materials each individually characterized as expressed for the instrumentality set forth in claim 1.

3. Helmet structure, in operative condition comprising a shell, and shock-absorbing structure installed in said shell, disposed therein to act in a condition of operative interposition between said shell and the head of a wearer of the helmet structure, and taking the form of a load-cushioning instrumentality which is structurally characterized with (a) compression-deformation-and-slow-return viscoelasticity, (b) non-springy (anti-rebound) behavior, (c) acceleration-rate(strain-rate)-sensitivity, and (d) a durometer which is associated with an ILD number no less than about 15-ILD.

4. The helmet structure of claim 3, wherein said instrumentality is formed from plural, cooperative bodies of materials each individually characterized as expressed for the instrumentality set forth in claim 3.

5. The helmet structure of claim 3, wherein said shock-absorbing structure, within said shell, defines a load-transmission path between said shell and the head of a wearer, in which path compression deformation and return response to a shock load delivered to the shell is solely determined by the characteristics of said shock-absorbing structure.