Abstract:
A method of manufacturing a cranial shock absorption system. The method is comprised of forming a first layer of elastomer, positioning a thin layer of material on top surface of elastomer such that the top surface is exposed around the entire exterior of the layer of material, allowing the first layer to partially set, positioning a tubular stem or valve on the first layer adjacent to the layer of material, forming a second layer of elastomer, allowing the first layer and second layer of elastomer to fully set around the thin layer of material, removing the thin layer of material from between the first and second layers of elastomer and then introducing a fluid into the chamber through the tubular stem.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     Not applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to protective head covering. More specifically, the present invention is a shock absorption system and that includes at least one silicone or thermoplastic elastomer bladder. 
     2. Description of the Related Art 
     Shock absorption systems are used for a variety of purposes, including safety equipment, helmets, body armor, padding, and other devices that are intended to reduce or prevent bodily injury. Conventional techniques and methods include molded plastics, foam, rubber, or other solid or semi-solid materials that absorb concussive forces or shock. For example, law enforcement helmets, military ballistic helmets, sports helmets, motorcycle helmets, riot helmets, and safety helmets often use expanded polystyrene or permeable foam covered with a hardened shell or other exotic fibers that, after being subjected to an impact or concussive force, must be replaced or repaired. The materials in the helmets reduce or eliminate trauma to the human skull and cranial regions by dissipating the force of a blow throughout the material, which often breaks apart or is severely weakened as a result. 
     Conventional shock absorption systems are inefficient because they must be replaced or repaired after an impact or concussive force is sustained. The inner protective rubber, foam, or other padding lining of a crash helmet may be significantly damaged, regardless of whether the hard outer layer is damaged by impact or concussive force. Structural damage to the inner lining eliminates the material strength and shock absorption and dissipation capabilities of convention systems. Further, conventional techniques do not evenly dissipate energy from impact or concussive force. 
     One particular industry interested in the development of such systems is the United States military. In November 2007, the Army issued a request for information seeking a technology solution that would increase blunt impact protection over the then-current performance standard. At the time, the testing standard for blunt impact protection required that a helmet dropped at a speed of 10 feet per second be able to diminish the force to which the wearer&#39;s head accelerates to under 150 g. The request for information called for the same degree of protection at a drop speed of 14.1 feet per second, with the ultimate objective of increasing this drop speed to 17.3 feet per second. As of July 2009, no manufacturer had developed a pad system passing the 14.1 feet per second test. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention presents a cranial shock absorption system that improves on existing technology due to its capability to withstand higher concussive forces and meet the United States military standards referenced above at a drop speed of 14.1 ft/sec. The inventor has found that the system described herein provides an improvement over existing technology in preventing head trauma resulting from concussive impact in that it absorbs and dissipates impact energy and concussive forces without the limitations of conventional techniques. 
     One aspect of the present invention is a cranial shock absorption system comprising a helmet shell having an interior surface, and at least one bladder secured to the interior surface of the shell. The bladder comprises silicone- or thermoplastic-elastomer first and second layers that are connected to form at least one chamber therebetween. The chamber contains a volume of fluid pressurized to between five to fifteen psig, inclusive. By forming elements of the system using a silicone or thermoplastic elastomer, the bladder is resistant to break down resulting from perspiration, oil, grease, and other agents likely to be found in the environments where the invention is likely to be used. 
     Another aspect of the present invention is a method of manufacturing a shock-absorbing bladder for use in a protective helmet. The method includes forming a first layer of elastomer having a top surface; positioning a thin layer of material on the top surface of the first layer of elastomer, wherein the surface area of a bottom surface of the thin layer of material is less than the surface area of the top surface of the first layer of elastomer material, and wherein the thin layer of material is positioned such that a portion of the top surface is exposed around the entire exterior of the layer of material; allowing the first layer to partially set; positioning a portion of a tubular stem or valve on the first layer adjacent to the layer of material to provide a communication path through the tubular stem; forming a second layer of elastomer over the first layer, the thin layer of material, and the portion of the stem positioned on the first layer; allowing the first layer and the second layer to fully set around the thin layer of material and the tubular stem portion; removing the thin layer of material from between the first layer and the second layer through the tubular stem to form a chamber between the first layer of elastomer and the second layer of elastomer; and introducing a fluid into the chamber through the tubular stem. 
     Yet another aspect of the present invention is a cushioning system for a protective helmet that comprises at least one silicone- or thermoplastic-elastomer body having a sealed interior chamber that is pressurized with a fluid; at least one layer of foam padding secured to an exterior surface of the elastomer body forming at least one cushion assembly, with the cushion assembly being shaped for attachment to the interior surface of a protective helmet. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a bottom elevation view of a system having the features of the present invention and comprising a plurality of silicone elastomer bodies formed as bladders. 
         FIG. 2  is a top partial sectional view of one of the bladders shown in  FIG. 1 , with a cutaway portion showing the chamber. 
         FIG. 3  is a side sectional view through section line  3 - 3  of  FIG. 2 . 
         FIG. 4  and  FIG. 5  show a preferred method of manufacturing the silicone elastomer bladders. 
         FIG. 6  is a top partial sectional view of a second-described embodiment of a cushion assembly of the present invention. 
         FIG. 7  is a side sectional view of through section line  7 - 7  of  FIG. 6 . 
         FIG. 8  is a top elevation of an alternative embodiment of a cushion assembly of the present invention. 
         FIG. 9  is side sectional elevation through section line  9 - 9  of  FIG. 8 . 
         FIG. 10  is a bottom elevation of a cushioning system positioned in a protective combat helmet. 
         FIG. 11  is a bottom elevation of yet another embodiment of the present invention incorporated into a sports helmet. 
         FIG. 12  is a bottom elevation of an alternative embodiment of a cushion assembly of the present invention. 
         FIG. 13  is a side sectional view through section line  13 - 13  of  FIG. 12 . 
         FIG. 14  is a top partial sectional view of a yet another alternative embodiment of a cushion assembly of the present invention. 
         FIG. 15  is a side sectional view through section line  15 - 15  of  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is bottom elevation view of a protective combat helmet  16  having features of the preferred embodiment of the present invention. The helmet  16  has a front end  18  and a rear end  20 , and comprises an outer shell  22  formed of a composite material and shaped for placement on a soldier&#39;s head. Anchor points  24  for straps are fixed to an interior surface  26  of the shell  22 . In this embodiment, a helmet cushioning system preferably is composed of five generally rectangular silicone-elastomer cushion assemblies  28 , each comprising a bladder  29  (see  FIG. 2 ) that is a silicone elastomer body and a foam padding layer  60  (see  FIGS. 6-7 ). Each assembly  28  is substantially enclosed by a fire retardant covering  30  and secured to the interior surface  26  with circular “hook” fasteners  32 , such as those that typically used in hook-and-loop type fastener. The outer surfaces of the coverings  30  behave like “loop” in a hook-and-loop type fastening mechanism. This cushioning system further comprises a generally-circular cushion assembly  34 , also comprising a silicone elastomer bladder and foam padding layer, and is substantially enclosed by a generally circular fire retardant covering  36 . The covering  36  is secured to the crown area of the interior surface  26 . Although this embodiment discloses six cushion assemblies (five rectangular assemblies  28  and one circular assembly  36 ), it is anticipated that other embodiments could incorporate a fewer or greater number of cushion assemblies of different shapes and sizes depending upon the shape, size and intended use of the helmet. 
       FIG. 2  and  FIG. 3  show a bladder  29  of a generally rectangular cushion assembly  28  of the preferred embodiment shown in  FIG. 1 . The bladder  29  comprises a first layer  36  of silicone elastomer integrally formed with a second layer  38  of silicone elastomer to form a chamber  40 . In this embodiment, the integral formation between the first and second layers  36 ,  38  forms a sidewall  42  around the chamber  40 . However, it is anticipated that the integral formation of the layers  36 ,  38  of silicone elastomer may form various shapes. For example, the layers  36 ,  38  may be integrally formed into a pointed or rounded edge. 
     A tubular stem  44  protrudes through the sidewall  42  at an end of the bladder  29 . The stem  44  is sealed with a plug  46  to substantially isolate the pressure within the chamber  40  from the pressure exterior of the bladder  29 . In alternative embodiments, a one-way fill valve may be substituted for the stem  44  and plug  46 . 
     Preferably, the chamber  40  is pressurized with a fluid (e.g., air) to between ten and twelve psig (inclusive) causing the chamber  40  and bladder  29  to inflate and expand. It is anticipated, however, that the range of pressure in the bladder  29  could be between five to fifteen psig (inclusive). “Fluid,” as used herein means a gas, a liquid, or some combination of the two. When the chamber  40  and bladder  29  are not inflated, the first and second layers  36 ,  38  each have a preferred thickness of one-fifth of an inch. It is anticipated, however, that each of the layers  36 ,  38  have a thickness between one-eighth of an inch and one-quarter of an inch, inclusive. 
     The fluid is selected so as to not be absorbable or otherwise reactive with the silicone elastomer layers  36 ,  38 . Liquid silicone oil, for example, is not suitable for this application because it can be absorbed by the silicone elastomer layers  36 ,  38 , which causes both degradation of the layers as well as pressure alteration of the chamber  40  over time as the silicone oil is absorbed. 
     In this embodiment, the silicone elastomer is a platinum cure silicone compound having the following characteristics: (a) mixed viscosity (ASTM D-2393) of 30,000 cps; (b) specific gravity (ASTM D-1475 of 1.08 g/cc; (c) specific volume (ASTM D-1475) of 25.7 cu. in./lb.; (d) pot life (ASTM D-2471) of forty five minutes; (e) cure time of sixteen hours; (f) tensile strength of five hundred to one-thousand psig, (g) a Shore A hardness of 10 to 30 A; (h) 100% modulus (ASTM D-412) of 86 psig; (i) a percentage of elongation at break of 364% to 1000%; (j) Die B Tear Strength (ASTM D-624) of 108 pli; and (k) shrinkage (ASTM D-2566) of less than 0.0001 in./in. 
     In the preferred embodiment, an antibacterial agent is added to the silicone elastomer in a preferred ratio of antibacterial agent to silicone elastomer of 1:40 by volume. The antibacterial agent is polychloro phenoxy phenol. It is anticipated, however, that there may be no antibacterial agent or other antibacterial agents could be used in varying volumes. 
     As shown in  FIG. 4 , the bladders  29  described with reference to  FIGS. 1-3  are preferably formed in the following manner. Initially, the first layer  36  of silicone elastomer, such as a platinum cure silicone compound, is poured into a mold  35  having a cavity  37  of desired shape (e.g., rectangular, keystone, circular). Although shown as having a definite form in  FIG. 4  for clarity, the first layer  36  is initially in a liquid state. Only after pouring into the cavity  37  does the first layer take the form shown in  FIG. 4 . 
     After pouring, the first layer  36  is allowed to partially set. A typically partial setting time is approximately thirty minutes, with the objective being that the first layer  36  will support a thin layer of material placed on its top surface while still allowing an additional layer of silicone elastomer to integrally form with the first layer  36 . An antibacterial agent, such as polychloro phenoxy phenol, may optionally be mixed with the silicone elastomer. 
     After pouring and partially setting, the first layer  36  of silicone elastomer will have a top surface  39  that is not in contact with the mold  35 . A thin layer  41  of material is thereafter positioned on the top surface  39  within an interior surface area  51 . 
     The thin layer  41  of material is preferably geometrically similar in shape to the top surface  39  of the first layer  36  of silicone elastomer, but has a bottom surface  33  with a smaller surface area than the top surface  39  so that, an outer surface area  52  remains exposed around at least a substantial portion of the perimeter of the thin layer  41  of material. 
     In this preferred method of formation, the thin layer  41  also has a tab  43  having an end positioned at an edge  45  of the top surface  39 . Except for where the tab  43  is in contact with the top surface  39 , the outer surface area  52  entirely surrounds the inner area  51  and is not in contact with the thin layer  41  of material. Ends  54  of the outer surface area  52  are adjacent to the tab  43 . 
     Minimizing the thickness of the thin layer  41  of material allows the combined thickness of the first and second layers  36 ,  38  to approach the total thickness of the bladder  29 . Preferably the thin layer  41  of material is a biaxially-oriented polyethylene terephthalate, or boPET, film, which is commonly sold under the trade name MYLAR, and has a thickness of between thirty eight and forty five ten-thousandths of an inch. It is anticipated, however that other suitable materials may be used. 
     The second layer  38  of silicone elastomer is thereafter poured into the mold  35  over the first layer  36  and the thin layer  41  of material. Although shown as having a definite form in  FIG. 4  for clarity, the second layer  38  is initially in a liquid state. The first and second layers  36 ,  38  are then allowed to completely set with the second layer  38  integrally forming with the first layer  36 . 
     As shown in  FIG. 5 , as the first and second layers  36 ,  38  set, the placement of the tab at the edge of the top surface causes a rectangular opening  47  between the integrated first and second layers  36 ,  38  of material. After the first and second layers  36 ,  38  completely set, the thin layer  41  of material (not shown) is removed by pulling the thin layer  41  of material through the opening  47 . Removal of the thin layer  41  of material leaves a chamber  40  between the first and second layers  36 ,  38  of silicone elastomer. The resulting chamber  40  has the same negligible thickness (as compared to the thickness of the first and second layers  36 ,  38 ) and shape as the thin layer  41  of material at the time the second layer  38  was poured, and the chamber  40  is in fluid communication with the exterior of the bladder through the opening  47 . A tubular stem  44  is coated with a silicone epoxy and pressed into the opening  47  to provide a fluid communication path to the chamber  40  from the exterior of the bladder  29 . A first end  31  of the tubular stem  44  is exposed to the exterior of the bladder  29  and the second end  49  is exposed to the chamber  40 . 
     A fluid, which is preferably air, is then introduced into the chamber  40  under pressure. In the preferred embodiment, the chamber pressure is increased to between ten to twelve psig, which causes the first and second layers to expand outerwardly. The stem  44  is then sealed with a plug  46  to maintain the pressure within the chamber  40 . In alternative embodiments, the chamber pressure may be increased to a range between five and fifteen psig (inclusive), and a one-way fill valve (such as those used to inflate tires) may be substituted for the stem  44  and plug  46 . 
       FIG. 6  and  FIG. 7  show a cushion assembly  28  of the preferred embodiment substantially enclosed by a fire retardant covering  30 . A foam padding layer  60  is adhered to the first layer  36  of the bladder  29  using a suitable bonding agent. The foam padding layer  60  is made of ethylene vinyl acetate (EVA) cut to match the shape of the bladder  29 . The thickness of the foam padding layer  60  is preferably one-half inch. It is anticipated, however, that the thickness could be with a range of between one-eighth inch and three-quarters of an inch thick (inclusive). It is further anticipated that the foam padding layer could be formed any number of suitable foam materials, including closed-cell extruded polystyrene foam or expanded rubber. 
     The fire retardant covering  30  has a closed end  48 , and an open end  50  through which the cushion assembly  28  may be inserted. In the preferred embodiment, the covering  30  is made of a flame resistant meta-aramid material. Alternative embodiments contemplate the cushion assembly  28  used without the fire retardant covering  30 . 
     When the helmet  16  takes a concussive blow, the bladders  29  absorb at least a portion of the force of the helmet that would otherwise act on the head of the wearer. The configuration of the bladder  29  as described above, and in combination with the properties of the silicone elastomer, cause compression and lateral expansion of the bladder  29  to dissipate the kinetic energy of the blow, and its elastic properties return the bladder  29  to its initial shape. The foam padding layer  60  further serves to lessen the forces of the concussive impact on the wearer&#39;s head and adds comfort for the wearer. 
     The following table shows test results for this embodiment of the invention. A helmet having the features of the invention was mounted to a Size C magnesium headform for testing and secured using a retention system. The position of the headform was adjusted to allow for impact of the helmet at the desired location, including the front, crown, back, and side. All testing was done using a hemispherical anvil. The drop height was adjusted to achieve the desired impact velocity, which was measured just prior to impact. During testing, the peak acceleration for each impact was recorded: 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 Test 
                 Peak 
                 Impact Velocity 
               
               
                   
                 Test No. 
                 Location 
                 Acceleration (g) 
                 (ft/sec) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1 
                 Crown 
                 58 
                 14.21 
               
               
                   
                 2 
                 Crown 
                 61 
                 14.21 
               
               
                   
                 3 
                 Crown 
                 79 
                 17.04 
               
               
                   
                 4 
                 Crown 
                 79 
                 17.03 
               
               
                   
                 5 
                 Front 
                 113 
                 14.23 
               
               
                   
                 6 
                 Front 
                 82 
                 14.20 
               
               
                   
                 7 
                 Front 
                 111 
                 17.05 
               
               
                   
                 8 
                 Front 
                 112 
                 17.05 
               
               
                   
                 9 
                 Rear 
                 125 
                 14.22 
               
               
                   
                 10 
                 Rear 
                 114 
                 14.23 
               
               
                   
                 11 
                 Rear 
                 156 
                 17.04 
               
               
                   
                 12 
                 Rear 
                 150 
                 17.04 
               
               
                   
                 13 
                 Left Side 
                 97 
                 14.22 
               
               
                   
                 14 
                 Left Side 
                 61 
                 14.23 
               
               
                   
                 15 
                 Left Side 
                 92 
                 17.07 
               
               
                   
                 16 
                 Left Side 
                 124 
                 16.08 
               
               
                   
                   
               
             
          
         
       
     
       FIGS. 8-9  depict an alternative embodiment for a cushioning assembly. Because any pressurized body tends to depressurize over time or depressurizes due to the changes in atmospheric pressure or temperature, this embodiment includes a hand pump  114  in association with a one-way valve  115  to allow a wearer to re-pressurize the cushioning assembly  106  through tubing  113 . 
     As shown in  FIG. 8 , the cushion assembly  106  is circularly shaped. It is anticipated, however, that the cushion assemblies of the embodiment could vary in size and shape depending on the application. The cushion assembly  106  comprises a silicone-elastomer body  108  having a sealed interior chamber  134  that is pressurized with a fluid as described with reference to  FIGS. 2-3 . The cushion assembly  106  also includes a foam padding layer  110  secured to an exterior surface of the silicone-elastomer body  108 . A patch  116  of hook or loop material is adhered to the exterior surface of each of the silicone elastomer bodies  108  for securing to the corresponding hook or loop material adhered to the interior surface of a protective helmet. 
     As shown in  FIG. 9 , the cushion assembly  106  comprises a silicone elastomer body  108  formed as a bladder having a first layer  120  and a second layer  122 . In this embodiment, the first and second layers  120 ,  122  are integrally adhered at their outer edges forming a sidewall  126  to create the chamber  134  between the first and second layers  120 ,  122 . In an uninflated state, the first and second layers  120 ,  122  each have a thickness of approximately one-fifth of an inch, although the thickness will decrease as the chamber  134  is inflated causing the first and second layers  120 ,  122  to stretch. It is anticipated, however, that each of the layers  120 ,  122  have a thickness between one-eight of an inch and one-quarter of an inch, inclusive. The first and second layers  120 ,  122  and sidewall  126  are formed of a silicone elastomer mixed with an antibacterial agent (e.g., polychloro phenoxy phenol) in a ratio of 1:40 by volume. The tubular valve stem  128  having a one-way valve  129  protrudes through the sidewall  126  of the bladder. 
     The hand pump  114  and valve  115  are in fluid communication with the interior chamber  134  of the cushion assembly  106  through tubing  113 . The wearer may adjust the pressure of the cushioning assembly  100  by using the hand pump  114  and valve  115  with the valve  128  of the cushion assembly to be inflated or deflated. 
     The foam padding layer  110  is adhered to the first layer  120  using a suitable bonding agent. The foam padding layer  110  is made of ethylene vinyl acetate cut to match the shape of the silicone elastomer body  108 . The thickness of the foam padding layer  110  is preferably one-half inch. It is anticipated, however, that the thickness could be with a range of between one-eighth inch and three-quarters of an inch (inclusive). In alternative embodiments, hook-and-loop fasteners may secure the foam padding layer  110  to the first layer  120 . 
       FIG. 10  shows a bottom elevation of a cushioning system  100  placed in a combat helmet shell  132  having an interior surface  136 . The central cushion assembly  106  is positioned adjacent the crown area of the shell  132 . First and third cushion assemblies  101 ,  103  are orientated along the sides of the interior surface  136 . Second and fourth cushion assemblies  102 ,  104  are secured to the front portion  138  and rear portion  140  of the interior surface  136 , respectively. In this embodiment, the silicone elastomer bodies  108  contact and conform to the contour of the interior surface  136 . Although thus far described with the foam padding layers  110  of the various cushion assemblies  101 - 104  being positioned between the wearer of the helmet shell  132  and the silicone-elastomer bladders  108 , alternative embodiments contemplate the silicone-elastomer bladders  108  as being positioned between the wearer of the helmet and the foam padding layers  110  when worn. 
     Although thus far described with reference to a combat helmet, the present invention is useful in other applications as well, such as sports equipment. While the combat applications may require planning for fires and explosive events desiring in the use of a flame retardant materials, sports equipment contemplates no necessity for such materials, and may preferably replace the coverings described supra with a vinyl coating as either a single vinyl covering encloses all of the cushion assemblies a separate vinyl covering for each of cushion assembly. 
       FIG. 11 , for example, shows another embodiment of a cushioning system positioned within a sports helmet such as a football helmet  216 , or a baseball, lacrosse, racing, hockey, horseracing, or equestrian helmet (not shown). The football helmet  216  has a front end  218  with a facemask  219 , a rear end  220 , and an outer shell  222  having an interior surface  226 . The shell  222  is formed of a composite material and shaped for placement on an athlete&#39;s head. 
     Five generally rectangular cushion assemblies  228 , each having a silicone elastomer bladder and foam padding layer as described above, are substantially covered by vinyl coatings  230  and secured to the interior surface  226  with circular hook-and-loop fasteners  232 . A generally circular cushion assembly  234  is substantially covered by a vinyl coating  236 , which is secured to the crown area of the interior surface  226  with a circular hook-and-loop fastener  232 . 
     When the football helmet  216  takes a concussive blow, the bladders  228 ,  234  absorb at least a portion of the force of the helmet  216  that would otherwise act on the head of the wearer. The configuration of the bladders  228 ,  234  as described above, and in combination with the properties of the silicone elastomer, cause compression and lateral expansion of the bladders  228 ,  234  to dissipate the kinetic energy of the blow, and its elastic properties return the bladders  228 ,  234  to their original shape. The foam padding layers further serve to lessen the force concussive impact on the wearer&#39;s head. 
       FIG. 12  and  FIG. 13  show a cushion assembly  328  of an alternative embodiment of the present invention. The cushion assembly  328  is shown in an uninflated state, but may be inflated through the one-way fill valve  345  positioned in the valve stem  344 . 
     The cushion assembly  328  comprises a bladder  329  having a first layer  336 , a second layer  338 , and a foam padding layer shaped as a collar  360  and adhered to the first layer  336  of the bladder  329  using a suitable bonding agent. Although not shown, the cushion assembly  328  is substantially enclosed by a fire retardant covering as described supra. Alternative embodiments of the cushion assembly  328  anticipate that a second foam padding collar identical to the foam padding layer  360  may be adhered to the second layer  338  of the bladder. 
     Preferably, the foam padding collar  360  is made of EVA foam with an opening  362  through its middle. The perimeter of the collar  360  substantially matches the shape of the perimeter of the bladder  329 . When the bladder  329  is inflated, the first layer  336  expands into and partially fills the opening  362  in the collar  360 . The thickness of the foam padding collar  360  is preferably one-half inch. It is anticipated, however, that the thickness could be within a range of between one-eighth inch and three-quarters of an inch thick (inclusive). 
       FIGS. 15-16  disclose another embodiment of a cushion assembly  400  of the present invention. The cushion assembly  400  comprises a bladder  402  having a first layer  404  of thermoplastic elastomer, a second layer  406  of thermoplastic elastomer, a chamber formed between the first layer  404  and the second layer  406 , and a foam padding layer  408  encapsulated within the chamber. The foam padding layer  408  is made of EVA foam and is generally-rectangular. The thickness of the foam padding layer  408  is preferably one-half inch. It is anticipated, however, that the thickness could be with a range of between one-eighth inch and three-quarters of an inch thick (inclusive). Although not shown inflated, the bladder  402  may be filled with a fluid, such as air, through a one way fill valve  412 . 
     Encapsulating the foam padding layer  408  within the bladder  402  decreases the time required for the cushion assembly  400  to return to its pre-impact shape after receiving a concussive impact. As the cushion assembly  400  is impacted, the bladder  402  dissipates a portion of the energy and compresses against the foam padding layer  408 . The remaining energy is absorbed by the combination of the elastomeric first layer  404  in contact with the foam padding layer  408 . 
     The present invention is described above in terms of preferred illustrative embodiments of specifically-described protective helmets, cushioning systems, and method of manufacture. Those skilled in the art will recognize that alternative constructions can be used in carrying out the present invention. Other aspects, features, and advantages of the present invention may be obtained from a study of this disclosure and the drawings, along with the appended claims.