Seat cushion

[0001] This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/377,417 filed May 3, 2002.

[0002] This invention was developed under Naval Air Systems Command Contract No. N00019-96-C-0043. The United States government may have certain rights in this invention.

[0003] This invention relates generally to the field of cushioning structures and more particularly seat cushions that offer the user protection from potentially injurious impacts.

[0004] It is well known that injuries sustained in aircraft crashes or so-called “hard landings” can result in serious injury and/or death to the occupants. For example, when an aircraft such as a helicopter experiences power reduction and/or loss and lands, significant forces are transmitted to the passengers and crew. Research has shown that spinal injuries can be expected when forces exceed 9.5 Gs which results in 2500 lbs of spinal loading. In addition, to injuries sustained in aircraft, spinal injuries can occur in vehicles when the ride is bumpy such as motor/speed boats, race cars, all-terrain vehicles, military ground vehicles (humvees and tanks), farm and construction equipment as well as gravitationally based amusement park rides. The foregoing spinal injuries can collectively be referred to as “impact injuries”. Proper seat design can help protect the occupants by attenuating impact acceleration thereby decreasing the injury producing forces. One way to achieve this goal is to extend the duration of the impact pulse, thus reducing the peak acceleration to safe levels.

[0005] When the spine suffers an impact injury, the injured party may become permanently or temporarily disabled to varying degrees, but the economic losses to the employer can also be great. For example, a helicopter or jet pilot represents a multi-million dollar investment when all of the training costs and experience are considered. In response to the foregoing, some attempts have been made to improve existing seating. These systems rely on foams and crushable materials for comfort, but provide only a minimum level of protection from impact energy. Even the advanced foams utilize the foam properties as the only means of protecting the occupant. These advanced foams are expensive and provide only a minor improvement in energy dissipation and, in fact, studies have shown that when foam cushioning “bottoms out” the body is exposed to dynamic overshoot and the potential for spinal injury actually increases. In view of the foregoing, it would be of great commercial value to provide a means of reducing impact injuries to the spine.

[0006] It is accordingly an object of the present invention to provide cushioning device that overcomes the above noted problems associated with the prior art devices.

[0007] Another object of the present invention is to provide a cushioning device that minimizes impact injuries by dissipating impact energy before it is transmitted to the human body.

[0008] A further object of the present invention is to provide a cushioning device that improves the survival rate of persons involved in aircraft crashes.

[0009] Still another object of the present invention is to provide a cushioning device that is re-useable.

[0010] Yet another object of the present invention is to provide a cushioning device that reduces loading on the spine.

[0011] A still further object of the present invention is to provide a cushioning device that is relatively inexpensive and easy to install.

[0012] A related object of the present invention is to provide a cushioning device that does not bottom out upon impact.

[0013] In accordance with the present invention, there is provided a cushioning device adapted to support a load and to reduce damage to the load as the result of externally applied impact forces. The apparatus comprises a first impact energy absorbing layer adapted to be placed beneath the load and to spread the impact energy substantially in the plane of the impact energy absorbing layer. The impact energy absorbing layer comprises a plurality of cells of pliable material having a first durometer, the cells being in fluid communication with each other to provide a valved fluid transfer between cells.

[0014] A second impact energy absorbing layer is positioned beneath the first impact energy absorbing layer and is adapted to spread the impact energy substantially in the plane of the second impact energy absorbing layer. Further, the second impact energy absorbing layer comprises a plurality of cells of pliable material, the cells are in fluid communication with each other to provide a valved fluid transfer between cells. The second impact energy absorbing layer differs structurally from the first impact energy absorbing layer. The structural difference is selected from one or more characteristics selected from the group consisting of durometer, fluid communication, impact energy absorbing layer thickness, cell shape and cell size.

[0015] A third impact energy absorbing layer may be positioned beneath the second impact energy absorbing layer and is adapted to spread the impact energy substantially in the plane of the third impact energy absorbing layer. The third impact energy absorbing layer comprises a plurality of cells of pliable material, the cells being in fluid communication with each other to provide a valved fluid transfer between cells. The second impact energy absorbing layer differs structurally from the first impact energy absorbing layer. The structural difference is selected from one or more characteristics selected from the group consisting of durometer, fluid communication, impact energy absorbing layer thickness, cell shape and cell size. As a result, the cushioning device absorbs impact energy force thereby reducing or eliminating damage to the supported load.

[0016] In the preferred embodiment, the respective impact energy absorbing layers are substantially identical, except that the durometer of the third impact energy absorbing layer is less than the durometer of the second impact energy absorbing layer which is less than the durometer of the first impact energy absorbing layer.

[0027] While the present invention will be described more fully hereinafter, it is to be understood at the outset that persons of skill in the art may modify the invention herein described while still achieving the favorable results of this invention.

[0028] Referring now to the drawings and specifically to FIG. 1, illustrated therein is a typical seat S which has positioned therein the cushioning material according to the present invention, generally indicated at 100, positioned therein. As will be more fully explained hereinbelow, the cushioning material comprises preferably three overlying impact energy absorbing layers 200a, 200b and 200c, each of which is essentially identical, except that each has a different durometer. With reference to the description that follows, the impact energy absorbing layers are generically referred to as layer 200. The seat S and the impact energy absorbing layer(s) are attached to a frame F by conventional mean, well known to those skilled in the art.

[0029] Turning now to the details of the impact energy absorbing layer 200, it is disclosed in U.S. Pat. Nos. 5,030,501 and 5,518,802 titled Cushioning Structure which are incorporated herein by reference. As best shown in FIGS. 2 through 4B, the impact energy absorbing layer comprises a plurality of cells 76 which are in fluid communication with each other to provide a valved fluid transfer between cells. As shown in FIGS. 3 and 4B, the cell members 35 are of hexagonal shape in cross-sectional plan. In the finally assembled condition, the sides of the individual hexagonal cells 35 are bonded to the top stratum 37 and bottom stratum 38 at edges 33 and 34 at one side and at edges 36 at the opposite side, respectively. The bond formed at the edges 36 and 33, 34 is a substantially hermetically sealed connection so that in the assembled condition the matrix includes a plurality of generally hexagonal cells 35 separately sealed one from the next, except as specifically otherwise provided and as hereafter defined.

[0030] Since the materials are heat sealable the various seals described herein may be accomplished by conventional heat sealing means. Adhesive or other suitable means could also be used.

[0031] The layer 200 is hermetically closed at the periphery and an inlet (not shown) may be provided for the admission of a fluid such as air or other gas which may be at a pressure above surrounding atmosphere or environment in which the structure is placed. The layer 200 is constructed of generally pliable materials, usually plastics, including vinyl and/or polyethylene type films.

[0032] Dimensionally it is conceived that the layer 200 could be between about one (1) and thirty (30) centimeters “thick”, i.e., the distance from the outside of one stratum to the other, depending upon application. The thickness of the sheet materials from which the strata 20 and 21 and matrix cells wall elements 22 are formed may be between about 0.01 and 100 mills.

[0033] In the embodiment shown in FIGS. 2 and 4B the matrix cells comprise hexagonal polygons. Such shape has been chosen because of the unique form of hexagon that permits complete nesting of the vertical surfaces of the cell one to the next. Nevertheless, other forms of polygons may provide the advantages of this invention and are to be considered as within the concepts worthy of further evaluation and usefulness in the application of the principles that are embodied in the layer 200.

[0034] For instance, the contacting wall between polygons may be sloped rather than vertical providing tapered or truncated polygons, rather than rectangular polygons as shown in FIG. 2. In this embodiment a plurality of cells 35 have substantially upstanding sides 36 bonded to an upper planar sheet like stratum 37 and a similar lower stratum 38.

[0035] Still other forms of polygons are within ready conception, for instance, pentagons or cones.

[0036] Referring to FIGS. 5A and 5B a structure 50 includes an upper stratum 51 to which is bonded a lower cellular matrix 52 on which is formed a plurality of downstanding/upstanding truncated polygon cells 53 selectively arranged in mutually supporting and equally load distributing relationship across the surface of the stratum 51.

[0037] In another aspect of this invention as shown in FIG. 6, a passage way conduit or aperture 30 is provided from a polygon to each of the adjacent cells through which the fluid is conducted to pass from one cell to the next. By the proper selection of the size of such conduits, the rate of fluid flow may be controlled and serve to “valve” the rate of the fluid passage from one cell to the next. Thus, the impact energy absorbency of each layer may be engineered as needed for a particular application. Such conduits 30 may be provided by allowing unbonded areas between the end of a cell 60 and the stratum 61. This controlled venting of the compressed air acts as a spring within the impacted cell and serves to maximize the absorption of the impact energy while minimizing the energy available for rebound. The difference in pressure between the impacted and the unimpacted, adjacent cells aids the controlled reinflation of the impacted cell in order to provide protection from repeated impacts.

[0038] In the embodiment of FIG. 6, an internal matrix structure 60 is sandwiched between an upper stratum 61 and a lower stratum 62 and bonded there between at the surfaces 63 and 64.

[0039] Referring to FIG. 6, the internal matrix structure 61 is provided with substantially upstanding walls that may also be designed to provide a one-way valve-like aperture 32 between the walls of the two mating hexagonal structures that aids the reduction of rebound energy. The apertures 32 open upon an impact due to the columnar buckling of the cell walls and pass fluid from the impacted area to adjacent areas when the pressure on the one side increases to a valve higher than the pressure on the other side. When the pressure equalizes during the structural rebound, the resilience of the material in the member 61 causes the valved opening to close or partially close thereby restricting the reverse flow by allowing the pressure to gradually equalize.

[0040] In prototype that was tested, it was determined that the durometer of the first impact energy absorbing layer 200a (positioned closest to the load) should be greater than the durometer of the second impact energy absorbing layer 200b (the middle layer) which should be greater than the lowest impact energy absorbing layer 200c. Specifically, the durometers were selected as follows:

[0041]

Impact Energy Absorbing Layer	Durometer Range	Optimal Durometer
200a	45-55	50
200b	37-47	42
200c	25-35	30

[0042] In tests that were conducted a 40% reduction in lumbar load was observed as compared with both the injury criteria and a competitive product as shown in FIG. 7. In the tests a test dummy as subjected to a lumbar load with a 23 g pulse and the loading was reduced from about 2600 pounds experienced by a competitive foam product to about 1800 pounds with the present invention, which is well below the injury criteria of 2500 pounds. The model that was constructed was for a specific application in an existing helicopter seat and only three inches of space was available to receive the cushioning device 200. It is believed that further reductions in impact force could be achieved were this not a retrofit application.

[0043] In view of the foregoing, it will be appreciated that for a specific application, the thickness, valve dimensions and durometer will have to engineered depending on the weight of the load and the type of impact forces expected.

[0044] Notwithstanding the foregoing, it will be recognized that the respective impact energy absorbing layers may be engineered for other applications. As such, the respective impact energy absorbing layers 200 may differ structurally from each other in a number of characteristics such as durometer (previously discussed), the fluid communication, impact energy absorbing layer thickness, cell shape and cell size. With respect to fluid communication, the diameter (or other characteristic) of the channels may be varied to obtain the desired degree of fluid transfer between cells.

[0045] When using the cushioning structure 200 to support a load or passenger, a first impact energy absorbing layer 200a is positioned beneath the load. The impact energy absorbing layer 200a is designed to spread the impact energy substantially in the plane of the impact energy absorbing layer 200a. The layer 200a is comprised of a plurality of cells of a pliable material and the cells 35 are in fluid communication with each other to provide a valved fluid transfer between cells 35 by means of channels 80.

[0046] A second impact energy absorbing layer 200b is positioned beneath the first impact energy absorbing layer 200a to spread the impact energy absorbing layer substantially in the plane of the second impact energy absorbing layer. The second impact energy absorbing layer 200b comprises a plurality of cells 35 of pliable material and the cells are in fluid communication with each other to provide a valved transfer between cells. The first layer 200a differs structurally from the second layer 200b. The structural difference between the respective layers 200a, 200b is selected from the group consisting of durometer, fluid communication, impact energy absorbing layer thickness, cell shape and cell size, depending on application.

[0047] In addition, a third impact energy absorbing layer 200c is positioned beneath the second impact energy absorbing layer 200b to spread the impact energy absorbing layer substantially in the plane of the second impact energy absorbing layer. The second impact energy absorbing layer 200b comprises a plurality of cells 35 of pliable material and the cells are in fluid communication with each other to provide a valved transfer between cells. The second layer 200b differs structurally from the third layer 200c. The structural difference between the respective layers 200a, 200b is selected from the group consisting of durometer, fluid communication, impact energy absorbing layer thickness, cell shape and cell size, depending on application.

[0048] In the illustrated embodiment, the respective layers differed from each other in durometer, the successively lower layers having lower a lower durometer.

[0049] While the embodiments of the invention shown and described is fully capable of achieving the results desired, it is to be understood that these embodiments have been shown and described for purposes of illustration only and not for purposes of limitation. Other variations in the form and details that occur to those skilled in the art and which are within the spirit and scope of the invention are not specifically addressed. Therefore, the invention is limited only by the appended claims.