Patent Publication Number: US-8974003-B2

Title: Rear seat cushion sound reduction mat

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention generally relates to automotive seating. More specifically, the invention relates to a construction for the rear seat of an automotive vehicle. 
     2. Description of Related Art 
     One perception of a higher end automotive vehicle is the low level of noise occurring in the passenger compartment of the vehicle as the vehicle is being driven along a roadway. The noise generated from the rear floor panels of a vehicle contribute to the overall noise levels within the interior cabin of the vehicle. The panels themselves vibrate in a range of frequencies that produce noise, which has the negative side effect on the perception of the quietness of the vehicle. 
     Various means have been devised to insulate the passenger compartment from noise or to dampen the noise being transmitted into the passenger compartment. For example, the metal surfaces of automotive floor panels, door panels and roof panels have been coated with compositions of fillers dispersed in binders so as to provide the desired level sound deadening. In other examples, sheet materials have previously been heated, softened and applied so as to conform to the surfaces to similarly provide the desired sound deadening capabilities. In addition to coating or covering the metal surfaces of structural components of the vehicle, another method of providing for the deadening sound within the automotive vehicle is formation of an acoustically insulating carpet assembly that incorporating features and materials that enhance the attenuation properties of the carpet. However, incorporating such carpeting over the entire interior of the vehicle, and specifically in locations where carpeting is not visible, is a poor implementation of such systems in that it is expensive and undesirable. 
     SUMMARY 
     With the present invention, a mechanism has been developed to block a significant portion of the noise intruding upon the interior cabin of the vehicle through the floor panels, and thereby improve the noise comfort of the interior cabin. The present invention provides a seat assembly that is suitable for use in an automotive vehicle and which has deliberate sound-deadening characteristics such that the transmission of sound, particularly roadway noise, into the passenger compartment of the vehicle through the floor of the vehicle is reduced by the seat. This reduction is tunable within the construction of the seat itself. 
     The seat assembly, according to one aspect of the present invention, includes a seat back assembly that is located adjacent to and extends generally upward from a seat bottom assembly. The seat bottom assembly is configured to be mounted to the floor pan of the vehicle and has a width that extends laterally relative to the longitudinal axis of the vehicle. Preferably, the seat bottom assembly defines at least two passenger seating locations and has a construction that includes several distinct layers. One such layer is a seat base. The seat base has a non-planar, 3-dimensional contour upper surface. Located over the seat base is a sound-blocking layer. The sound-blocking layer is a non-porous resilient layer that extends substantially, continuously over the seat base, including the seating locations. Additionally, the sound-blocking layer has a shape that substantially conforms to the shape of the upper surface of the seat base. Located over the top of the sound-blocking layer, is a resilient seat cushion, and provided over the seat cushion is a trim layer. 
     In another aspect of the invention, the sound-blocking layer is in surface-to-surface contact with the upper surface of the seat base. 
     In an additional aspect of the invention, the sound-blocking layer is freely resting on the upper surface of the seat base. 
     In still another aspect of the invention, the seat base defines a base thickness, the seat cushion defines a cushion thickness and the sound-blocking layer defines a blocking layer thickness, wherein the thickness of the blocking layer is less than the thickness of the seat base and less than the thickness of the seat cushion. 
     In another aspect of the invention, the sound-blocking layer is completely covered by the seat cushion and in direct contact therewith. 
     In a further aspect of the invention, the sound-blocking layer extends uninterruptedly across substantially the entire width of the rear seat assembly. 
     In another aspect of the invention, the sound-blocking layer is formed of ethylene vinyl acetate. 
     In a further object of the invention, seat base is formed of expanded polypropylene. 
     In still another aspect of the invention, the seat cushion is a resilient foam cushion. 
     Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings in the claims that are appended to and form a part of this application. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a rear seat assembly incorporating the principles of the present invention; 
         FIG. 2  is a cross-sectional view through a portion of the seat bottom of the rear seat assembly seen in  FIG. 1 ; 
         FIG. 3  is a perspective view of the sound-blocking layer in surface-to-surface engagement with the seat base; and 
         FIG. 4  is a perspective view of the sound-blocking layer isolated from the seat base. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, directional terms are to be understood relative to an automotive vehicle and its direction of travel. The forward direction is therefore towards the front of the vehicle; the rearward direction is toward the rear of vehicle; the lateral directions are toward the sides of the vehicle; the upward direction is toward the roof of the vehicle; and the downward direction is toward the bottom of the vehicle 
     Referring now to the drawings, a rear seat assembly embodying the principles of the present invention is illustrated therein and generally designated at  10 . As its primary components, the rear seat assembly  10  includes two subassemblies, namely a seat back  12  and a seat bottom  14 . The seat back  12  is located adjacent to a rearward end of the seat cushion  14  and extends generally upwardly therefrom. Collectively, the seat back  12  and the seat cushion  14  cooperate to define a number of seating locations, generally designated at  16 , for passengers of the automotive vehicle. The rear seat assembly  10  seen in  FIG. 1  defines three such seating locations  16 . 
     In the vehicle, sound is transmitted into the passenger compartment through various structural components. One such structural component is the floor of the vehicle. In the rear passenger compartment of an automotive vehicle, the rear seat assembly  10  often rests directly on a floor pan  18 . Since the floor pan  18  is covered by the seat bottom  14 , in this area the floor pan  18  is not and need not be covered with carpeting. Carpeting in such an instance is an added, and therefore unwanted, expense. 
     During operation of a vehicle, vibration and/or road noise (sound) tends to be transmitted into the rear passenger compartment area through the floor. One measure that is taken in an attempt to attenuate this sound is the provision of a damp mat  20  on the floor pan  18 . However, while the damp mat does operate to attenuate some sound, in more luxury-branded vehicles, this sound attenuation may not be sufficient. 
     With the present invention, a higher level of sound attenuation or blocking is achieved and, therefore, the invention will have application in luxury-branded vehicles, but could be employed in any vehicle. 
     Seen in  FIG. 2  is a seat bottom  14  embodying the principles of the present invention. The seat bottom  14  is mounted to the floor pan  18  of the vehicle through engagement of a mounting hook  22 , formed as part of the seat bottom  14 , with a mounting catch  24  in the floor pan  18 . In essence, the mounting hook  22  is received within the mounting catch  24  and retained therein by well-known means. This engagement between the mounting hook  22  and the mounting catch  24  retains the seat bottom  14  in position on the floor pan  18 . The mounting hook  22 , itself, is part of a seat base  26  of the seat bottom  14  and may be formed of a metal rod or stamping. 
     The seat base  26  extends the width of the rear seat assembly  20  (as seen in  FIG. 3 ) and may be provided in a variety of constructions. The seat base  26  may have a traditional metal frame and spring construction. Alternatively, the seat base  26  may be formed with a 3-dimensional contoured upper surface  31  from which the remaining portions of the seat bottom  14  are built up. In an effort to reduce weight in automotive vehicles, the seat base  26  illustrated in the figures is not formed of a metal construction. Rather, the seat base  26  is formed as a molded, non-metal material that not only provides the support for the seat bottom  14 , but which also provides the internal suspension or a spring rate for the seat bottom  14 . One preferred material for such a seat base  26  is expanded polypropylene (EPP). 
     While the seat base  26  extends the full width of the rear seat assembly  10 , in the illustrated embodiment, a recess  28  is provided within the area of at least two of these seating locations  16 , preferably the seating locations on the right and left sides of the rear seat assembly  10 . The recesses  28  serve several functions. One function is to facilitate registration or positioning of layers provided on top of the seat base  26 . Another function is to provide a centralized area having enhanced cushioning, by virtue of the omission of the seat base  28  in this area, for the comfort of the passenger sitting thereon. To provide for this comfort, the seat bottom  14  includes a seat cushion  30  positioned on top of the seat base  26  and over the recess  28 . The seat cushion  30  is typically a urethane foam material and, as seen in  FIG. 2 , as an increased thickness generally in the area of the recessed  28 . The increased thickness provides added padding for the comfort of the seat&#39;s occupant. When utilizing a traditional construction for the seat base, the seat cushion  30  may be molded such that the frame is substantially encapsulated by the foam. 
     According to the present invention, located between the seat cushion  30  and the seat base  26  is a sound-blocking layer  32 . As seen in the figures, the sound-blocking layer is configured in its free condition so as to exhibit a shape that substantially conforms to the upper surface of the seat base  26  over which it is to be installed. The sound-blocking layer installed on the upper surface  31  of the seat base  26  is seen in  FIG. 3 . As seen in  FIG. 4 , the sound-blocking layer  32  is shown isolated from the remaining portions of the seat bottom. Notably, the sound-blocking layer  32  extends substantially uninterruptedly across the entire width of the rear seat assembly  10  and, therefore, the seat base  26 . The sound-blocking layer  32  also extends over and bridges the recesses  28  formed in the seat base  26  at the left and right primary seating locations  16 . In these seating locations, the location of the recesses  28 , the sound-blocking layer  32  contacts a lower surface of the seat cushion  30  located thereabove, and may contact either the damp mat  20  (if provided) or the floor pan  18 , the latter situation occurring when no damp mat  20  is utilized in the vehicle. In a traditional construction, the sound-blocking layer  32  may be encased within the cushion  30  as a result of the molding of the cushion  30  about the seat base  26  or the sound-blocking layer  32  may be secured in surface-to-surface contact with an exterior surface of the cushion  30 , such as the underside/bottom surface of the cushion  30 . 
     Preferably, the sound-blocking layer  32  is formed of a material that is non-porous. One such preferred material is ethylene vinyl acetate (EVA). EVA is a rubber-like material and is available in a variety of thicknesses. Being available in various thicknesses, the employment of EVA sheets of different masses can be used to tune the spring rate of the seat base  26  and can therefore be used to improve transmission loss performance of the seat bottom  14  (attenuate the vibrations/sound being transmitted into the passenger compartment from the floor beneath the seat bottom  14 ) at specific frequencies or range of frequencies, such as 125-630 Hz. For example, in one implementation of the present invention, the sound transmission loss of the seat bottom  26  was increased by over 1 dB through the incorporation of a 1 mm EVA sound-blocking layer  32  having a mass of 1.5 kg into the seat bottom  26 . In another example, the sound transmission loss was increased by about 2 dB through the incorporation of a 2 mm EVA sound-blocking layer  32  having a mass of 2 kg into a seat bottom  26 , as compared to a similarly constructed seat bottom  26  without wither a 1 mm or 2 mm EVA sound-blocking layer  32 . It is anticipated that thicknesses for the sound-blocking layer will range from 0.5 to 10 mm depending upon the particular aspects of the application and design into which the invention is being incorporated. Accordingly, the effectiveness of the increase in sound transmission loss is perceived as being between 0.1-2.0 dB. 
     The sound-blocking layer  32  also preferably exhibits a depth, as measured from the front edge of the seat bottom  14  to the general location of the seat back  12  that is less than the depth of either the seat base  26  or the seat cushion  30 . In this way, the sound-blocking layer  32  can be registered with both the seat base  26  and the seat cushion  30 , by formation of a corresponding recess  38  in the lower surface of the seat cushion  30 . This further prevents the sound-blocking layer  32  from interfering with the fit of the seat cushion  30  on the seat base  26  and finish of a trim layer  34 , such as a leather material, over the seat cushion  30  and about the seat base  26  wherein it is secured by fasteners  36  and the like.