US20090265839A1

US20090265839A1 - Fluid Safety Liner

Info

Publication number: US20090265839A1
Application number: US12/296,843
Authority: US
Inventors: Laurence Young; Nicholas Chan; Jason Ruchelsman
Original assignee: Massachusetts Institute of Technology
Current assignee: Massachusetts Institute of Technology
Priority date: 2006-04-13
Filing date: 2007-04-12
Publication date: 2009-10-29
Also published as: WO2008063690A2; WO2008063690A3

Abstract

A fluid safety liner includes a liner of closed-cell foam that uses a series of channels and reservoirs to spread forces and distribute fluid contained within the liner throughout different areas of the liner. The liner is useable in protective gear such as a helmet and has a shape that conforms to the area of protection. The channel and reservoir system generally includes a mesh of coupled channels and reservoirs in the closed-cell foam. The channel and reservoir system also generally includes an incompressible fluid movable throughout the system for redistributing pressure and absorbing the force of any impact through viscous flow. The reduction in peak force and lengthening of the duration of the force reduces the biomechanical severity (e.g. HIC, Head Injury Criterion) of a blow to the protective gear.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from U.S. provisional application No. 60/792,287 filed Apr. 13, 2006, incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to safety liners that incorporate the use of fluids to disperse the force of an impact, in particular the use of fluid safety liners for protection of the head and other body parts.

BACKGROUND ART

It is known in the prior art to provide protective helmets that use primarily foam to cushion an impact. It is also known in the art to use fluids in the design of the helmet to absorb the energy of the impact. U.S. Pat. No. 5,815,846 to Calonge discloses a helmet assembly using a combination of a gas and a fluid (including a generally viscous gel) for impact distribution and dampening. U.S. Pat. No. 3,609,764 to Morgan discloses the use of interconnected flexible chambers that can increase and decrease in size and transfer fluid from a first chamber to an adjacent second chamber when an impact force is applied.

SUMMARY OF THE INVENTION

In a first embodiment of the invention there is provided a device, wearable on the body, for protecting a body part against a physical blow having a closed-cell foam member and fluid disposed within. The closed-cell foam member has an inner surface that conforms generally to the outer surface of a body part. The member has a plurality of conduits formed within where fluid is located. Upon receipt of a blow at a location, the blow will cause the fluid located in the conduits within the member to move away from that location to absorb energy from the blow and to redistribute the force from the blow away from the location.
In a related embodiment the closed-cell foam member is a liner for a helmet.
In another embodiment the closed-cell foam member has at least 4 conduits formed within that are coupled in such a way as to form a mesh.
In a related embodiment the conduits of the closed-cell foam member contain a fluid that is substantially incompressible.
In another embodiment there is provided a device wearable on the body for protecting a body part against a physical blow having a closed-cell foam member and at least one fluid channel in communication with at least two reservoirs within the member. The closed-cell foam member has a surface that conforms generally to an outer surface of the body part. The member has fluid within the channel and reservoirs that upon impact is urged away from the reservoir in the vicinity of the blow through the channel to another reservoir further from the vicinity of the blow to absorb energy and redistribute force from the blow.
In a related embodiment the closed-cell member is a liner for a helmet.
In a related embodiment the closed-cell member includes at least four channels and at least four reservoirs formed in the member. In the member the reservoirs are coupled to one another via the channels so as to form a mesh.
In a related embodiment the fluid within the member is substantially incompressible.
In another related embodiment the fluid within the member is a combination of incompressible fluid and compressible fluid.
In yet another related embodiment the fluid within the member is a shear-thickening fluid.
In yet another related embodiment the fluid within the member is a shear-thinning fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

FIG. 1 is a schematic profile illustrating distribution of force and pressurc, experienced on the head of a subject wearing a conventional helmet, upon impact of a blow to the helmet.

FIG. 2 is a schematic profile illustrating distribution of force and pressure, experienced on the head of a subject wearing a helmet, upon impact of a blow to the helmet, when the helmet incorporates a liner in accordance with an embodiment of the present invention.

FIG. 3 is a perspective view of an embodiment of the present invention incorporating a plurality of reservoirs in a liner of closed-cell foam, wherein the relative locations of the reservoirs are depicted.

FIG. 4 is a cross section of the liner of FIG. 3.

FIG. 5 is a perspective schematic view of the liner of FIG. 3, having the same orientation as that of FIG. 3, illustrating the outer surface of the liner in relation to the reservoirs disposed therein.

FIG. 6 is another perspective view of the liner of FIG. 3, again having the same orientation as that of FIG. 3, illustrating the outer surface of the liner.

FIG. 7 is a perspective view of an embodiment of the present invention incorporating a plurality of conduits in a liner of closed-cell foam, wherein the relative locations of the conduits are depicted.

FIG. 8 is a perspective schematic view of the liner of FIG. 7, having the same orientation as that of FIG. 7, illustrating the outer surface of the liner in relation to the conduits disposed therein.

FIG. 9 is a graph illustrating the effects a fluid liner has on the force profile over time due to an impact as compared to the effects a conventional foam liner has on the force profile over time due to an impact.

FIGS. 10 a and 10 b are graphs illustrating the pressure distribution over the corresponding liners area

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Definitions. As used in this description and the accompanying claims, the following terms shall have the meanings indicated, unless the context otherwise requires:
A “mesh” is a network of conduits within which fluid is displaced on receipt of a blow in such a manner that force associated with impact of the blow is distributed away from the vicinity of the blow and energy associated with impact of the blow is dissipated.
A “conduit” is a volumetric region in a deformable medium for holding fluid and conveying fluid. A conduit may serve as a channel for conveying fluid and in addition may serve as a reservoir of variable volume for fluid. Accordingly, in the course of deformation of the medium at a given location of a conduit, the conduit expels fluid from the given location. However, since the medium is deformable, the conduit conveys fluid away from the given location, and conduit portions located away from the given location will expand to receive fluid displaced as a result of the deformation.
A “reservoir” is a conduit in a deformable medium for holding, supplying, or receiving fluid.
A “channel” is a conduit in a deformable medium for conveying fluid.
FIG. 1 is a schematic profile illustrating a prior art distribution of force and pressure, experienced on the head of a subject wearing a conventional helmet, upon impact of a blow to the helmet. In FIG. 1, the force of the blow is represented by vector 11. The blow is imparted to prior art helmet 12, with which is associated a prior art liner 14. The force 11 is transmitted through the helmet 12 and through the liner 14 to produce force and pressure on the head 13 of the subject. The magnitude of the force is at a peak at the point of impact, and diminishes as distance from the point of impact increases. The distribution of force in a direction normal to the head is illustrated by vectors 15. It can be seen that, while the combination of helmet 12 and liner 14 achieves some distribution of force, nevertheless the distribution of force is highly localized.
FIG. 2 is a schematic profile illustrating distribution of force and pressure, experienced on the head of a subject wearing a helmet, upon impact of a blow to the helmet, when the helmet incorporates a liner in accordance with an embodiment of the present invention. Similarly, here the force of the blow is represented by vector 11. The blow is imparted to helmet 12, with which is associated a liner 21 in accordance with an embodiment of the present invention. Prior to the blow, the liner has a profile indicated by dashed line contour 22. The force 11 is transmitted through the helmet 12 and through the liner 21 to produce pressure on the head 13 of the subject. The liner 21 includes a number of conduits in which fluid is disposed. The blow causes fluid in the liner to flow away from the vicinity of the blow and the liner to deform into the shape having the profile indicated by solid line contour 23. The distribution of forces, in a direction normal to the head caused by the blow as transmitted by the helmet and liner is illustrated by vectors 25. Although here as in FIG. 1, the magnitude of the force is at a peak at the point of impact, and diminishes as distance from the point of impact increases, the magnitude of the force at the point of impact is here reduced and spread over a larger region. It can be seen that the combination of helmet 12 and liner 21 achieve a distribution of force over a greater area, in such a manner that the force in the vicinity of the blow has been reduced in comparison to the force in the vicinity of the blow in the case of the prior art embodiment illustrated in FIG. 1. In other words, the liner 21 has the effect, among other things, of distributing force of the blow away from the region of impact.
The liner responds to a blow by deformation triggering the flow of fluid within and also by causing propagation of a pressure wave through the fluid. In combination these processes cause distribution of force over a larger region compared to the prior art and also involves absorption of energy. Of course the liner material, itself, even independent of the pressure of fluid, accounts for some absorption of force and some absorption of energy.
It can also be seen that the blow in the embodiment of FIG. 2 has caused deformation of the liner 21. As will be described in further detail below, the liner contains fluid that is displaced as a result of the blow and propagates a pressure wave as a result of the blow. As previously discussed the processes are responsible in part for the deformation and also serve to absorb some energy from the blow.
In general, we can describe handling of the impact of the blow by this equation:
∫_A PdA=F _B (1),
where F_Bis the force of the blow, P is the local pressure at a given location of the head, and A is the area of the region, projected onto a plane normal to the force of the blow, over which the pressure is experienced.
FIG. 3 is a perspective view of an embodiment of the present invention incorporating a plurality of reservoirs in a liner of closed-cell foam, wherein the relative locations of the reservoirs are depicted. In FIG. 3, the peripheral reservoirs 33 are shown in their relative locations along the lower outer region of liner 21. The reservoirs 33 and 34 are coupled by channels 35 to form a mesh. (For convenience of illustration, the channels and reservoirs are not shown to scale.) The channels, for example, are here shown as lines, whereas in fact, the channels have a cross sectional area sufficient to convey fluid between reservoirs.
Although we have distinguished between reservoirs and channels, both reservoirs and channels are disposed in closed-cell foam, a deformable medium, so that the functions of reservoirs and of channels overlap one another—namely, the reservoirs serve also to convey fluid and the channels serve also to hold fluid. In this respect, we say that the reservoirs and the channels are both “conduits” as that term is defined above.
FIG. 3 also shows the interior reservoirs 34 arranged in an overarching pattern relative to peripheral reservoirs 33. On receipt of a blow, fluid flows through channels 35, causing a redistribution of fluid in the liner. As discussed previously, the fluid flow can absorb energy from the blow.
The closed-cell foam of the liner may be made of a wide range of materials. Indeed, various types of closed-cell foam may be employed in various embodiments of the present invention. Some types of closed-cell foam contemplated include EPS (Expanded Polystyrene) and EPP (Expanded Propylene). EPS is one-use only (permanently deforms) whereas EPP may be reusable, at least to some extent. In the latter category, is Cell-Flex NX210, available from Der-Tex Corp, Saco, Me. Additional materials of this type are available from Foam Fabricators Inc., Scottsdale, Ariz. Desirable performance characteristics of closed-cell foam for the liner are elastic deformability on receipt of a blow. Such characteristics enable the liner to experience local deformation on receipt of the blow to cause movement of fluid away from the area of impact, and also expansion of conduits in the liner in regions away from the area of impact. Also desirably in many cases, after impact the liner and conduits in the liner return generally to their original shapes and pressure of the fluid returns to pre-impact levels. Materials providing elastic deformation may be desirable in many cases in comparison to those providing plastic or permanent deformation because the former materials provide an opportunity for reuse of the liner.
A range of fluids may be employed in various embodiments of the present invention. The fluid may, for example, be non-Newtonian, including shear-thickening fluids and shear-thinning fluids. In some embodiments, the fluid is incompressible. Suitable fluids include those currently used in existing knee pads, for example, those manufactured by Fluid Forms, Inc., Boulder, Colo., under the 1002 Patella T trademark. Suitable fluids include liquid silicone oil (a polymerized siloxane), a product currently used, among other things, for impact absorption in shoes. Silicone oil is available in a wide range of viscosities from various suppliers, including Clearco Products, Bensalem, Pa. A silicone oil can be chosen to provide a desired viscosity and desired fluid flow characteristics for use in embodiments of the present invention. In further embodiments, one of the fluids employed may include gas or a substance that has more than one phase, such as a substance that is in a gas, liquid, and/or solid phase.
FIG. 4 is a cross section of the liner of FIG. 3. In this cross section view of liner 21 reservoirs 33 and 34 are located within the closed-cell foam. Reservoirs 33 and 34 are in the same configuration in FIG. 4 as was illustrated in FIG. 3. In FIG. 4 the closed-cell foam inner surface 41 that conforms generally to an outer surface of the body part can be seen. Reservoirs 33 and 34 are in the same configuration in FIG. 4 as was illustrated in FIG. 3. The reservoirs 33 and 34 are coupled by channels 35 to form a mesh as was illustrated in FIG. 3.
FIG. 5 is a perspective schematic view of the liner of FIG. 3, having the same orientation as that of FIG. 3, illustrating the outer surface of the liner in relation to the reservoirs disposed therein. Reservoirs 33 and 34 are in the same configuration in FIG. 5. as was illustrated in FIG. 3. The reservoirs 33 and 34 are coupled by channels 35 to form a mesh as was illustrated in FIG. 3.
FIG. 6 is another perspective view of the liner of FIG. 3, again having the same orientation as that of FIG. 3, illustrating the outer surface of the liner. The channels 35 illustrated in FIG. 3. are shown here, configured in a mesh without being coupled to reservoirs 33 and 34.
FIG. 7 is a perspective view of an embodiment of the present invention incorporating a plurality of conduits in a liner of closed-cell foam, wherein the relative locations of the conduits are depicted. On receipt of a blow, fluid flows through conduits 71, causing a redistribution of fluid in the liner. The conduits in the general embodiment must be in a deformable medium. In addition to absorption of energy caused by fluid flow, the flow of fluid throughout the liner also serves to redistribute the fluid for the purpose of expanding the area of closed-cell foam over which the net pressure is applied, thereby reducing the maximum magnitude of pressure experienced at a particular location.
The conduits 71 may have various shapes to meet the needs of the desired flow pattern and viscosity characteristics associated with the fluid employed. The conduits may include orifices, constrictions, baffles, and or valves. As FIGS. 1-8 indicate, the conduit path need not be in a straight line, and may be contoured to provide desired force distribution and energy absorption.
FIG. 8 is a perspective schematic view of the liner of FIG. 7, having the same orientation as that of FIG. 7, illustrating the outer surface of the liner in relation to the conduits 71 disposed therein.
FIG. 9 is a graph from a study conducted to illustrate the effects a fluid-filled liner has on attenuation of peak forces associated with a blow. Tn the study a fluid liner and a foam liner were constructed. The foam liner used conventional ski helmet foam found supplied from Der-Tex Corp. Saco, Me. The fluid liner was made from a slightly elastic and waterproof fabric used in the design of army tents. Each of the liners were wrapped around a steel cylinder and set up for a drop test in an Instron Dynatup 9250 drop tester. Each of the liners was dropped from a height of 1 meter and the impact force and velocity were measured as a function of time through the use of strain gauges and light sensors in the Dynatup machine. The pressure distribution was also recorded through the use of Pressurex strips (thin sheets that turn varying densities of red when pressure is applied). Curve 91 illustrates the magnitude of the force felt by the foam liner over time. Curve 93 illustrates the magnitude of the force felt by the fluid liner over time. The peak force 94 experienced by the fluid liner is substantially lower than the peak force 92 experienced by the foam liner. The time of impact for the fluid liner was almost twice as long as the impact time for the foam liner. The fluid liner also experienced a more uniformly applied force over its impact time as opposed to the foam liner that experienced a series of force peaks and dips during its impact.
FIGS. 10 a and 10 b are graphs from the same study discussed in connection with FIG. 9. FIGS. 10 a and 10 b illustrate the pressure distribution that results upon impact of a liner. FIG. 10 a represents the fluid liner. FIG. 10 b represents the foam liner. Impact forces are distributed over a larger area in the fluid liner as compared to the foam liner. In particular, it can be seen in FIG. 10 a that a maximum pressure of 100 PSI (pounds-per square inch) is experienced by the fluid liner, while FIG. 10 b shows that a maximum pressure of 115 PSI is experienced by the foam liner.

Claims

1. A device, wearable on the body, for protecting a body part against a physical blow, the device comprising:

a closed-cell foam member, such member having an inner surface conforming generally to an outer surface of the body part, such member including a plurality of conduits and such member being deformable;

a fluid disposed in the conduits;

so that when the foam member experiences a blow at a location, the blow triggers a pressure wave in the fluid and flow of fluid in the conduits away from that location in such a manner as to absorb energy from the blow and to redistribute force from the blow away from the location.

2. A device according to claim 1, wherein the closed-cell foam member is a liner for a helmet.

3. A device according to any of claims 1 and 2, wherein the device includes at least four conduits and such conduits are in communication with each other to form a mesh.

4. A device according to any of claims 1 through 3, wherein the fluid is substantially incompressible.

5. A device, wearable on the body, for protecting a body part against a physical blow, the device comprising:

a closed-cell foam member, such member having an inner surface conforming generally to an outer surface of the body part, such member including at least one fluid channel;

wherein the at least one fluid channel is in communication with at least two reservoirs formed in the closed-cell foam member;

a liquid disposed in the at least one channel and in the reservoirs;

so that when the foam member experiences a blow in the vicinity of one of the reservoirs, the blow triggers a pressure wave in the fluid and flow of fluid in that onc of the reservoirs through the at least one channel to another one of the reservoirs in such a manner as to absorb energy from the blow and to redistribute force from the blow away from the vicinity.

6. A device according to claim 5, wherein the closed-cell foam member is a liner for a helmet.

7. A device according to any of claims 5 and 6, wherein such member includes at least four channels, at least four reservoirs are formed in the member, and the reservoirs are coupled to one another via the channels so as to form a mesh.

8. A device according to claim 5, wherein the fluid is substantially incompressible.

9. A device according to claim 5, wherein the fluid is a combination of incompressible fluid and compressible fluid

10. A device according to claim 5, wherein the fluid is a shear thickening fluid.

11. A device according to claim 5, wherein the fluid is a shear thinning fluid.