US20060273650A1

US20060273650A1 - Foam cushion having a progressively increasing spring constant

Info

Publication number: US20060273650A1
Application number: US11/142,577
Authority: US
Inventors: James Embach
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2005-06-01
Filing date: 2005-06-01
Publication date: 2006-12-07

Abstract

A foam member for use within a vehicle seat exhibits a progressive spring effect along a vertical section therethrough. Preferably, the vertical section has a top and a bottom, with a spring constant of the foam increasing from top to bottom. In another aspect of the invention, the foam member has a top and a bottom, and includes an upper layer at the top of the foam member, and a lower layer at the bottom of the foam member. The lower layer is configured to resist a load applied to the foam member more than the upper layer. At least one of the layers may include an upper surface having a vertical component, thereby imparting a contoured shape thereto.

Description

TECHNICAL FIELD

The present invention relates to vehicle seats, and, more particularly, to vehicle seats including a foam member having a progressively increasing spring constant to maximize occupant comfort.

BACKGROUND OF THE INVENTION

A vehicle seat generally comprises a seating surface with a seat back attached thereto. The seating surface typically includes a seat cushion, side bolsters, and a front bolster. Similarly, the seat back usually includes a backrest cushion with a headrest extending therefrom, side supports, and a lumbar cushion. These various sections generally include an underlying foam substructure covered by a trim cover material, such as fabric, leather, etc. Additionally, there may also be a rigid frame structure and/or a suspension beneath the seating surface to support the vehicle seat within a vehicle.

SUMMARY OF THE INVENTION

A foam cushion for use within a vehicle seat includes a foam member according to the present invention. A vertical section taken through the foam member has a top and a bottom. A first foam portion at the top of the vertical section has a first spring constant, while a second foam portion at the bottom of the vertical section has a second spring constant greater than the first spring constant. Therefore, the foam member exhibits a progressive spring effect along the vertical section. Preferably, the second foam portion has a higher density and/or a higher firmness than the first foam portion to provide the difference in spring constant. A third foam portion having a third spring constant greater than the first spring constant and less than the second spring constant may also be disposed along the vertical section between the first and second foam portions. The foam member preferably includes a plurality of layers bonded together to create a laminate.
In another aspect of the invention, a foam cushion for use within a vehicle seat includes a foam member having a top for providing a load surface for a seat occupant, and a bottom opposite the top. The foam member includes an upper layer at the top of the foam member, and a lower layer at the bottom of the foam member, with the lower layer configured to resist a load applied to the foam member more than the upper layer. The cushion may also include a middle layer disposed between the upper and lower layers, with the middle layer configured to resist a load applied to the foam member less than the lower layer and more than the upper layer. At least one of the layers may include an upper surface having a vertical component, thereby imparting a contoured shape thereto. For instance, the upper surface may be characterized by a generally centrally located protuberance, or by at least one generally laterally located protuberance.
The foam member according to the present invention may be used as a vehicle seat cushion, a vehicle seat back, or a vehicle seat headrest. Additionally, the foam member may be used to integrally provide a vehicle seat back, vehicle seat side bolsters, and a vehicle seat front bolster. Similarly, the foam member may be used to integrally provide a vehicle seat back, side supports, and a lumbar cushion. The layers may be manufactured from any type of foam as known in the art, including but not limited to a conventional urethane foam or a viscoelastic memory foam.
In a further aspect of the present invention, a foam member for use within a vehicle seat includes an upper layer having a lower surface at least partially defining a first contour, a lower layer having an upper surface at least partially defining a second contour, and a middle layer having an upper surface at least partially defining a third contour complementary to the first contour, and a lower surface at least partially defining a fourth contour complementary to the second contour. The upper layer has a first spring constant, the lower layer has a second spring constant, and the middle layer has a third spring constant greater than the first spring constant and less than the second spring constant. The upper, lower and middle layers interlock such that the first contour mates with the third contour and the second contour mates with the fourth contour. The upper, lower and middle layers are bonded together to form the foam member. Preferably, at least one of the layers is provided by casting.
The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic perspective view of a vehicle including a vehicle seat;
FIG. 2 shows a schematic vertical cross-section of a first embodiment of a foam member for use within the vehicle seat of FIG. 1;
FIG. 3 shows a schematic vertical cross-section of a second embodiment of a foam member for use within the vehicle seat of FIG. 1;
FIG. 4 shows a schematic vertical cross-section of a third embodiment of a foam member for use within the vehicle seat of FIG. 1; and
FIG. 5 shows a schematic vertical cross-section of a fourth embodiment of a foam member for use within the vehicle seat of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, a vehicle seat 10 for use within a motor vehicle 12 includes a seating surface 14 with a seat back 16 attached thereto. The seating surface 14 includes a seat cushion 18, side bolsters 20, and a front bolster 22. Similarly, the seat back 16 includes a backrest cushion 24 with a headrest 26 extending therefrom, side supports 28, and a lumbar cushion 30. Additionally, there is typically a rigid frame structure (not shown) beneath the vehicle seat 10, and sometimes a suspension (not shown). The parts of the vehicle seat 10 listed herein are shown covered by a trim material. However, one skilled in the art will recognize the various portions of the vehicle seat 10.
FIG. 2 shows a first embodiment of a foam member 32 according to the present invention. The vehicle seat 10 of FIG. 1 includes at least one foam member 32. While the foam member 32 shown in FIGS. 2 through 5 is preferably used as the vehicle seating surface 14, the foam member 32 may be used with any part of the vehicle seat 10 without changing the inventive concept. The foam member 32 preferably has a top 34, which defines a load surface for a seat occupant, and a bottom 36 opposite the top 34. For example, if the foam member 32 is used as the backrest cushion 24 of FIG. 1, the top 34 of the backrest cushion 24 preferably defines a load surface for a seat occupant's back.
The foam member 32 preferably includes an upper layer 38, a middle layer 40 and a lower layer 42, with the layers 38, 40, 42 bonded to one another using adhesive sprays, transfer tape films, thermal bonding, or another type of bonding recognized by those skilled in the art to create a laminate. Each layer is preferably formed from any type of cast or skived foam material, such as a urethane foam, a viscoelastic memory foam, or another alternative elastomeric foam material. However, the present invention may be practiced using only an upper layer 38 and a lower layer 42, or without any distinct layers. The present invention may also be practiced using more than three layers, with comfort increasing with an increasing number of layers. It matters only that the foam member 32 exhibits an increasing spring constant k from top 34 to bottom 36, thereby providing the foam member 32 with a progressive spring effect. Assuming the use of multiple layers 38, 40, 42, the spring constant, k, can be defined for each layer 38, 40, 42 using the distance (d) the layer 38, 40, 42 deflects in response to the application of a load (F) on the foam member, wherein k=F/d. It can be seen that the higher the spring constant k, the less deflection (d) within the layer in response to the load (F). Additionally, resistance can be defined as the tendency of a layer to oppose a load applied to the foam member. The higher the spring constant k, the more resistance a given layer will exhibit.
Within the foam member 32, the upper layer 38 has a first spring constant, k₁, the lower layer 42 has a second spring constant, k₂, and the middle layer 40 has a third spring constant, k₃, wherein k₁<k₃<k₂. Therefore, if a load is applied to the foam member 32, the upper layer 38 will deform more and resist less than both the lower layer 42 and the middle layer 40. Additionally, the middle layer 40 will deform more than the lower layer 42 but less than the upper layer 38. Conversely, the middle layer 40 will resist the load less than the lower layer 38 but more than the upper layer 42. Finally, the lower layer 42 will deform less and resist more than both the upper layer 38 and the middle layer 40. A vertical section taken anywhere through the foam member 32 will include a first foam portion at the top of the vertical section, and preferably within the upper layer 38, having a first spring constant (i.e. k₁for the upper layer 38), and a second foam portion at the bottom of the vertical section, preferably within the lower layer 42, having a second spring constant greater than the first spring constant (i.e. k₂for the lower layer 42). Since the first embodiment of the foam member 32 includes a middle layer 40, the vertical section will also include a third foam portion disposed along the vertical section between the upper and lower foam portions, and preferably within the middle layer 40, with the third foam portion having a third spring constant (i.e. k₃for the middle layer 40).
As described herein, the spring constants k₁, k₂, k₃increase from the top 34 of the foam member 32 to the bottom 36, such that the foam member 32 provides a progressive spring effect. That is, as the load on the foam member increases, i.e., with increasing seat occupant weight, the foam member 32 resists the load more and deforms less. The upper layer 38 is at the top 34 of the foam member 32, and therefore nearest a seat occupant. As such, the upper layer 38 has the lowest spring constant k₁to maximize seat occupant comfort. The lower layer 42 has the highest spring constant k₂, to provide firmer support as the load increases. Additionally, the lower layer 42 may cover vehicle substructure, and therefore should have a higher spring constant k to prevent a seat occupant from contacting the vehicle substructure. For example, it the foam member 32 is used in a seat cushion 18, the lower layer 42 will cover the rigid frame structure and/or suspension if present beneath the seat 10. By using a foam member 32 wherein the spring constants k₁, k₂, k₃increase from the top 34 of the foam member 32 to the bottom 36, seat manufacturers can provide maximum comfort and support to a seat occupant using less overall material. For example, k, can be chosen such that the mass and surface area of the 5^thpercentile deflects the foam member 32 to the middle of the upper layer 38, k₂can be chosen such that the mass and surface area of the 50^thpercentile occupant (male or female) deflects the foam member 32 to the middle of the middle layer 40, and k₃can be chosen such that the mass and surface area of the 95^thpercentile male deflects the foam member 32 to the middle of the lower layer 42. This sort of human accommodation strategy made possible by the spring constant gradient present within the foam member 32. Additionally, use of the foam member 32 according to the present invention may decrease the overall thickness of the vehicle seat part in which it is used, without sacrificing comfort or support.
To vary the spring constant from the top 34 to the bottom 36 of the foam member 32, a variety of techniques may be used. First, a different density of foam having the same firmness may be used for each layer 38, 40, 42, with the density of each layer increasing from the top 34 of the foam member 32 to the bottom 36. For instance, the upper layer 38 may have a density of 1 lb/ft³, the middle layer 40 a density of 2 lb/ft³, and the lower layer 42 a density of 4 lb/ft³, with the firmness of each layer being 325 N. As another option, the firmness may be increased from the top 34 of the foam member 32 to the bottom 36, and a constant density foam may be used. Alternatively, both the firmness and the density may vary from layer to layer. The present invention also contemplates using different types of foam for one or more layers to vary the spring constant. Additionally, the present invention may not require a multi-layer approach. Specifically, gravity may be used to settle a liquid suspension such that a single piece of cast foam exhibits a density gradient from top to bottom. If such techniques are used, defined layers would not be necessary to create a vertical section having varying spring constants at the top and bottom. It should be apparent to one skilled in the art that the present invention thus contemplates any foam member exhibiting an increasing spring constant from top to bottom.
Each foam layer 38, 40, 42 may be contoured, thereby allowing a single foam member 32 to be used to integrally provide a vehicle seat cushion 18, vehicle seat side bolsters 20, and a vehicle seat front bolster 22, as shown in FIG. 1. Additionally, a single foam member 32 may be used to integrally provide a vehicle backrest cushion 24, vehicle seat side supports 28, and a lumbar cushion 30. In general, each layer 38, 40, 42 includes an upper surface 43, 44, 45, respectively, which may have a vertical component, thereby imparting a contoured shaped to the layer 38, 40, 42. Each layer 38, 40, 42 also preferably includes a lower surface 51, 53, 55, respectively, which also may have a vertical component, thereby imparting a contoured shape to the layer. Specifically, the lower surface 51 of the upper layer 38 defines a first contour, and the upper surface 45 of the lower layer 42 defines a second contour. The upper surface 44 of the middle layer 40 defines a third contour complementary to the first contour, while the lower surface 53 of the middle layer 40 defines a fourth contour complementary to the second contour. The layers 38, 40, 42 interlock such that the first contour mates with the third contour and the second contour mates with the fourth contour, and bond together to create the foam member 32. Providing layers having matable contours allows the foam member 32 to be manufactured in a plurality of ways. For example, all three of the layers may be provided by casting, and subsequently interlocked and bonded. This is the preferred method of manufacture. Alternatively, one or more of the layers may be cast, with the remaining layers insert molded to the casted layer or layers, such that the contours are mated and bonded during the insert molding process.
As shown in FIG. 2, the upper layer 38 includes a plurality of generally centrally located upper protuberances 46 and a pair of laterally located upper protuberances 48. The centrally located upper protuberances 46 increase comfort for a seat occupant, while the laterally located upper protuberances 48 may replace the separate side bolster cushions conventionally used in vehicle seats. The protuberances 46, 48 impart the vertical component to the upper surface 43 of the upper layer 38. Similarly, the middle layer 40 includes a pair of generally laterally located middle protuberances 50, with the protuberances 50 imparting the vertical component to the upper surface 44 of the middle layer 40. Finally, the lower layer 42 includes a pair of generally laterally located lower protuberances 52, with the protuberances 52 imparting the vertical component to the upper surface 45 of the lower layer 42.
Referring now to FIG. 3, a second embodiment of a foam member for use within a vehicle seat is generally shown at 32′. The foam member 32′ preferably includes a top 34′ defining a load surface for a seat occupant, and a bottom 36′ opposite the top 34′. The foam member 32′ further preferably includes an upper layer 38′, first and second middle layers 40′, 41, and a lower layer 42′, with the layers 38′, 40′, 41, 42′ made from foam and bonded to one another as described with respect to the first embodiment 32. Within the foam member 32′, the upper layer 38′ has a first spring constant, k₁′, the lower layer 42′ has a second spring constant, k₂′, the first middle layer has a third spring constant, k₃′, and the second middle layer has a fourth spring constant, k₄, with k₁′<k₃′<k₄<k₂′. Therefore, if a load is applied to the foam member 32′, the upper layer 38′ will deform more and resist less than the first and second middle layers 40′, 41 and the lower layer 42′. Additionally, the first middle layer 40′ will deform more and resist less than the second middle layer 41 and the lower layer 42′, while deforming less and resisting more than the upper layer 38′. Similarly, the second middle layer 41 will deform more and resist less than the lower layer 42′, while deforming less and resisting more than the upper layer 38′ and the first middle layer 40′. Finally, the lower layer 38′ will deform less and resist more than the upper layer 38′ and the middle layers 40′, 41.
A vertical section taken anywhere through the foam member 32′ will include a first foam portion at the top of the vertical section having a first spring constant (i.e. k₁′, since the top of the vertical section will be disposed within the upper layer 38′), and a second foam portion at the bottom of the vertical section having a second spring constant greater than the first spring constant (i.e. k₂′, since the bottom of the vertical section will be disposed within the lower layer 42′). Since first and second middle layers 40′, 41 are utilized in this embodiment, the vertical section will also include third and fourth foam portions disposed along the vertical section between the upper and lower foam portions. The third and fourth foam portions have third and fourth spring constants (i.e. k₃′, k₄, since the third and fourth portions will be disposed within the first middle layer 40′ and the second middle layer 41, respectively). The spring constants k₁′, k₂′, k₃′, k₄thus increase from the top 34′ of the foam member 32′ to the bottom 36′, such that the foam member provides a progressive spring effect.
Each foam layer 38′, 40′, 41, 42′ may be contoured as described with respect to the first embodiment 32. Generally, each layer 38′, 40′, 41, 42′ includes an upper surface 43′, 44′, 47, 45′, respectively, and a lower surface 51′, 53′, 57, 55′, respectively, which may have a vertical component to give a contoured shape to the layer 38′, 40′, 41, 42′. As shown in FIG. 3, the upper layer 38′ is two separate pieces, each defining a generally laterally located upper protuberance 48′, with the protuberances 48′ imparting the vertical component to the upper surface 43′ of the upper layer 38′. Additionally, the first middle layer 40′ includes a plurality of generally centrally located middle protuberances 49, with the protuberances 49 imparting the vertical component to the upper surface 44′ of the first middle layer 40′.
Referring now to FIG. 4, a third embodiment of a foam member for use within a vehicle seat is generally shown at 32″. The foam member 32″ preferably includes a top 34″ defining a load surface for a seat occupant, and a bottom 36″ opposite the top 34″. The foam member 32″ further preferably includes an upper layer 38″, a middle layer 40″, and a lower layer 42″, with the layers 38″, 40″, 42″ made from foam and bonded to one another as described with respect to the first embodiment 32. Within the foam member 32″, the upper layer 38″ has a first spring constant, k₁″, the lower layer 42″ has a second spring constant, k₂″, and the middle layer has a third spring constant, k₃″, with k″<k₃″<k₂″. Therefore, if a load is applied to the foam member 32″, the upper layer 38″ will deform more and resist less than the middle layer 40″ and the lower layer 42″. Additionally, the middle layer 40″ will deform more and resist less than the lower layer 42″, while deforming less and resisting more than the upper layer 38″. Finally, the lower layer 38″ will deform less and resist more than the upper layer 38″ and the middle layer 40″.
A vertical section taken anywhere through the foam member 32″ will include a first foam portion at the top of the vertical section having a first spring constant (i.e. k₁″, since the top of the vertical section will be disposed within the upper layer 38″), and a second foam portion at the bottom of the vertical section having a second spring constant greater than the first spring constant (i.e. k₂″, since the bottom of the vertical section will be disposed within the lower layer 42″). Since the middle layer 40″ is utilized in this embodiment, the vertical section will also include a third foam portion disposed along the vertical section between the upper and lower foam portions. The third foam portion has a third spring constants (i.e. k₃″, since the third portion will be disposed within the middle layer 40″). The spring constants k₁″, k₂″, k₃″ thus increase from the top 34″ of the foam member 32″ to the bottom 36″, such that the foam member provides a progressive spring effect.
Each foam layer 38″, 40″, 42″ may be contoured as described with respect to the first embodiment 32. Generally, each layer 38″, 40″, 42″ includes an upper surface 43″, 44″, 45″, respectively, and a lower surface 51″, 53″, 55″, which may have a vertical component, thereby giving a contoured shape to the layer 38″, 40″, 42″. As shown in FIG. 4, the upper layer 38″ includes a plurality of generally centrally located upper protuberances 46″ imparting the vertical component to the upper surface 43″ of the upper layer 38″. Additionally, the upper layer 38″ includes a pair of laterally located upper protuberances 48″ imparting the vertical component to the upper and lower surfaces 43″, 51″ of the upper layer 38″. The middle layer 40″ includes a pair of generally laterally located middle protuberances 50″, with the protuberances 50″ imparting the vertical component to the upper and lower surfaces 44″, 53″ of the middle layer 40″. Finally, the lower layer 42″ includes a pair of generally laterally located lower protuberances 52″, with the protuberances 52″ imparting the vertical component to the upper surface 45″ of the lower layer 42″.
Turning now to FIG. 5, a fourth embodiment of a foam member for use within a vehicle seat is generally shown at 32′″. The foam member 32′″ preferably includes a top 34′″ defining a load surface for a seat occupant, and a bottom 36′″ opposite the top 34′″. The foam member 32′″ further preferably includes an upper layer 38′″, a middle layer 40′″, and a lower layer 42′″, with the layers 38′″, 40′″, 42′″ made from foam and bonded to one another as described with respect to the first embodiment 32. Within the foam member 32′″, the upper layer 38′″ has a first spring constant, k₁′″, the lower layer 42′″ has a second spring constant, k₂′″, and the middle layer has a third spring constant, k₃′″, with k₁′″<k₃′″<k₂′″. Therefore, if a load is applied to the foam member 32′″, the upper layer 38′″ will deform more and resist less than the middle layer 40′″ and the lower layer 42′″. Additionally, the middle layer 40′″ will deform more and resist less than the lower layer 42′″, while deforming less and resisting more than the upper layer 38′″. Finally, the lower layer 42′″ will deform less and resist more than the upper layer 38′″ and the middle layer 40′″.
A vertical section taken anywhere through the foam member 32′″ will include a first foam portion at the top of the vertical section having a first spring constant (i.e. k₁′″, since the top of the vertical section will be disposed within the upper layer 38′″), and a second foam portion at the bottom of the vertical section having a second spring constant greater than the first spring constant (i.e. k₂′″, since the bottom of the vertical section will be disposed within the lower layer 42′″). Since the middle layer 40′″ is utilized in this embodiment, the vertical section will also include a third foam portion disposed along the vertical section between the upper and lower foam portions. The third foam portion has a third spring constants (i.e. k₃′″, since the third portion will be disposed within the middle layer 40″). The spring constants k₁′″, k₂′″, k₃′″ thus increase from the top 34′″ of the foam member 32′″ to the bottom 36′″, such that the foam member provides a progressive spring effect.
Each foam layer 38′″, 40′″, 42′″ may be contoured as described with respect to the first embodiment 32. Generally, each layer 38′″, 40′″, 42′″ includes an upper surface 43′″, 44′″, 45′″, respectively, and a lower surface 51′″, 53′″, 55′″, respectively, which may have a vertical component, thereby giving a contoured shape to the layer 38′″, 40′″, 42′″. As shown in FIG. 5, the upper layer 38′″ includes a plurality of generally centrally located upper protuberances 46′″, which impart the vertical component to the upper surface 43′″ of the upper layer 38′″. Additionally, the upper layer 38′″ includes a pair of laterally located upper protuberances 48′″, which provide the vertical component to the upper and lower surfaces 43′″, 51′″ of the upper layer 38′″. Additionally, the middle layer 40′″ includes a pair of generally laterally located middle protuberances 50′″, with the protuberances 50′″ providing the vertical component to the upper and lower surfaces 44′″, 53′″ of the middle layer 40′″. The lower layer 42′″ includes a pair of generally laterally located lower protuberances 52′″, and also a generally centrally located lower protuberance 54, with the protuberances 52′″, 54 imparting the vertical component to the upper surface 45′″ of the lower layer 42′″. The generally centrally located lower protuberance 54 is preferably designed to increase central support for a seat occupant, and specifically to the seat occupant from contacting the suspension and vehicle seat hardware disposed underneath the vehicle seat of FIG. 1, when the foam member 32′″ is used as the vehicle seating surface 14 of FIG. 1. However, one skilled in the art will recognize that both the centrally located protuberances 46′″, 54 and the laterally located protuberances 48′″, 50′″, 52′″, both in this embodiment 32′″ and the other embodiments presented herein 32, 32′, 32″ could be configured in a different manner than specifically described or shown herein to provide differing support of a seat occupant.
While the best modes for carrying out the invention have been described in detail, it is to be understood that the terminology used is intended to be in the nature of words and description rather than of limitation. Those familiar with the art to which this invention relates will recognize that many modifications of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced in a substantially equivalent way other than as specifically described herein.

Claims

1. A foam cushion for use within a vehicle seat comprising:

a foam member;

a first foam portion at a top of a vertical section taken through said foam member, said first foam portion having a first spring constant; and

a second foam portion at a bottom of said vertical section, said second foam portion having a second spring constant greater than said first spring constant, such that said foam member exhibits a progressive spring effect along said vertical section.

2. The foam cushion of claim 1, wherein said second foam portion has a higher density than said first foam portion.

3. The foam cushion of claim 1, wherein said second foam portion has a higher firmness than said first foam portion.

4. The foam cushion of claim 1, further comprising:

a third foam portion disposed along said vertical section between said first and second foam portions, said third foam portion having a third spring constant greater than said first spring constant and less than said second spring constant, such that said foam member exhibits a progressive spring effect along said vertical section from said top to said bottom.

5. The foam cushion of claim 1, wherein said foam member comprises a plurality of layers bonded together to create a laminate.

6. A foam cushion for use within a vehicle seat comprising:

a foam member having a top and a bottom, said top providing a load surface for a seat occupant;

an upper layer at said top of said foam member; and

a lower layer at said bottom of said foam member;

wherein said lower layer is configured to provide greater resistance to a vertical load applied to said foam member than said upper layer.

7. The foam cushion of claim 6, further comprising:

a middle layer disposed between said upper and lower layers, wherein said middle layer is configured to provide less resistance to vertical load applied to said foam layer than said lower layer and more resistance than said upper layer.

8. The foam cushion of claim 7, wherein at least one of said upper layer, said middle layer and said lower layer includes an upper surface having a vertical component.

9. The foam cushion of claim 8, wherein said upper surface is characterized by a generally centrally located protuberance.

10. The foam cushion of claim 8, wherein said upper surface is characterized by at least one generally laterally located protuberance.

11. The foam cushion of claim 6, wherein said foam member is used as at least one of a vehicle seat cushion and a vehicle seat back.

12. The foam cushion of claim 6, wherein said foam member integrally provides a vehicle seat cushion, vehicle seat side bolsters, and a vehicle seat front bolster.

13. The foam cushion of claim 6, wherein said foam member integrally provides a vehicle backrest cushion, side supports, and a lumbar cushion.

14. The foam cushion of claim 6, wherein said foam member is used as a vehicle seat headrest.

15. The foam cushion of claim 6, wherein at least one of said upper and lower layers comprise one of a conventional urethane foam and a viscoelastic memory foam.

16. A foam member for use within a vehicle seat comprising:

an upper layer having a first spring constant and a lower surface at least partially defining a first contour;

a lower layer having a second spring constant and an upper surface at least partially defining a second contour; and

a middle layer having a third spring constant greater than said first spring constant and less than said second spring constant, an upper surface at least partially defining a third contour complementary to said first contour, and a lower surface at least partially defining a fourth contour complementary to said second contour;

wherein said upper, lower and middle layers interlock such that said first contour mates with said third contour and said second contour mates with said fourth contour, and wherein said upper, lower and middle layers are bonded together to form said foam member.

17. The foam member of claim 16, wherein at least one of said upper, lower and middle layers are provided by casting.