Chair shell with integral hollow contoured support

[0001] The present invention relates generally to molded chairs, and more particularly, to a molded chair shell having an integral support member between the seat and the back.

[0002] Molded chair shells have been well known in the art for some time. A typical example of a molded chair shell is disclosed in U.S. Pat. No. 3,669,496, which includes a single, molded piece that forms the seat and the seat back. The chair further requires a frame, i.e., a back support, to which the molded piece is attached.

[0003] Another example of a molded chair is disclosed in U.S. Pat. No. 3,751,109, which shows a single, molded piece with legs attached at the bottom. This chair does not have a back support and therefore may be prone to material failure. Specifically, when a user sits in the chair and exerts a force on the back portion by leaning back on the back portion, the stress and strain resulting from the force will be concentrated primarily in the area that joins the seat to the back of the chair. Thus, after repeated use, this area ultimately may be prone to material failure. In such a situation, the back portion may not provide adequate support due to the degradation of the material joining the seat to the seat back, or in extreme cases, the back portion may ultimately break away from the seat portion.

[0004] There is thus a need for a molded chair shell that does not require an external frame to provide back support, which delays material failure, and has an increased life-span over prior art designs.

[0005] It is an object of the present invention to provide a high strength, one-piece molded chair shell that has an increased lifespan over prior art designs. It is another object of the invention to provide a chair shell that includes a reinforcement or support which functions to distribute stress throughout the chair shell, to avoid material failure after repeated use. It is a further aspect of the invention to provide a molded chair shell with a hollow reinforcement or support, which is integral with the shell and which is formed during the molding process.

[0006] Therefore, in accordance with one aspect of the invention, a molded chair component is in the form of a shell having a seat portion having a top side and a bottom side and a back portion which extends upwardly from the seat portion. The back portion has a front side and a rear side. The chair shell includes a hollow support member between the seat portion and the back portion. The hollow support member includes a cavity that is formed by cavity walls extending along the bottom of the seat portion and the rear of the back portion.

[0007] In accordance with another aspect of the present invention, a molded chair component includes a seat portion, a back portion extending upwardly from the seat portion at a junction area, and a cavity defined by the junction area. The cavity is formed by a series of cavity walls located at the junction area, which cooperate to form a reinforcement or support for the back portion.

[0008] In accordance with a still further aspect of the present invention, a molded chair component includes a seat portion having a top side and a bottom side and a back portion joined to the seat portion at a junction. The back portion defines a front side and a rear side. The molded chair component further includes a cavity located at the junction, which is formed by a first U-shaped cavity wall that extends upwardly into the back portion, and a second U-shaped cavity wall that extends forwardly into the seat portion.

[0009] Other aspects, features, and advantages of the invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

[0019] FIG. 1 illustrates one embodiment of a chair assembly 10 incorporating the chair shell of the present invention. The chair assembly 10 includes a chair shell 20 in accordance with the present invention, and a series of legs 12 attached to the chair shell 20. The chair assembly 10 may use any variety of leg designs known in the art, but preferably the chair assembly features four legs 12 as shown in FIG. 1. The chair shell 20 may be made using any suitable material, e.g., polypropylene, acrylic, polycarbonate, nylon, etc. but preferably it is molded plastic material.

[0020] Generally speaking, the chair shell 20 has a seat portion 22 and an adjacent pack portion 24. The seat portion 22 and the back portion 24 are connected together at a junction area 26. As is well known, the seat portion 22 provides a platform for sitting while the back portion 24 provides support for the user's back. The angle between the seat portion 22 and the back portion 24 be any satisfactory angle, and desired to accommodate user preferences.

[0021] The back portion 24 and the seat portion 22 may be any size and shape that may provide a suitable sitting surface, though in the illustrated embodiment the back portion 22 and the seat portion 24 are generally the same size. The back portion 24 and the seat portion 22 preferably taper near the junction area 26, as shown in FIGS. 1 and 3, which is the narrowest portion of the chair shell 20. In addition, the edges of the back portion 24 and the seat portion 22 are preferably rounded.

[0022] The seat portion 22 has a top side 30 and a bottom side 31. The bottom side 31 of the seat portion 22 may be configured to receive the legs 12, e.g., brackets 14 for receiving legs 12 may be attached to or integral with the bottom side 31 of the seat portion 22. See, e.g., FIG. 3. The back portion 24 similarly has a front side 32 and a rear side 33. As shown in FIG. 1, the front side 32 of the back portion 24 and the top side 30 of the seat portion 22 may combine to form a substantially continuous surface. The rear side 33 of the back portion 24 and the bottom side 31 of the seat portion 22 may similarly form a substantially continuous surface. See, e.g., FIGS. 5 and 6. Preferably, the back portion 24 and the seat portion 22 are contoured so as to provide a comfortable sitting surface. For example, the front side 33 of the back portion 22 and the top side 30 of the seat portion 22 may be slightly concave. See FIGS. 1 and 5.

[0023] The seat portion 22 and the back portion 24 are preferably solid. However, if so desired, either or both may be manufactured to be hollow, i.e., there may be space between the top side 30 and the bottom side 31 of the seat portion 22 and/or the front side 32 and the rear side 33 of the back portion 24.

[0024] As shown in FIGS. 5-7, the chair shell 20 of the present invention further includes an integral contoured reinforcement or support 39 at the junction area 26 between the seat portion 22 and the back portion 24. The reinforcement 39 extends throughout the width of junction area 26, and includes an internal cavity 40 between the back portion 24 and the seat portion 22. More specifically, the cavity 40 is positioned on the rear side 33 of the back portion 24 and on the bottom side 31 of the seat portion 22. The shape of the cavity 40 is illustrated in dotted lines in FIGS. 1, 3 and 4.

[0025] The reinforcement or support 39 is formed by cavity side walls 42 that extend along the rear side 33 of the back portion 24 and the bottom side 31 of the seat portion 22, in combination with a cavity outer wall 44 and a pair of cavity end walls, shown at 42c, 42d. The thickness of the cavity side walls 42 may be uniform, or the thickness may gradually decrease in a direction from the base of the cavity side wall 42, i.e., the portion proximate the chair shell 20, outward.

[0026] Preferably the cavity 40 is substantially enclosed by the cavity side walls 42, end walls 42c and 42d, and the cavity outer wall 44, but there may be openings in the cavity walls as desired. Additionally, the cavity 40 may be divided into a plurality of chambers or sections (not shown) by internal cavity walls, if desired.

[0027] As can be seen in FIG. 3, the cavity 40 preferably is positioned over the junction area 26 where the seat portion 22 and the back portion 24 are joined. More specifically, a first cavity wall 42a is located on the seat portion 22 and a second cavity wall 42b is located on the back portion 24 opposite the first cavity wall 42a. As noted above, cavity end walls 42c and 42d are located on both the back portion 24 and the seat portion 22, thus spanning the junction area 26 and extending between and joining cavity walls 42a, 42b. The outer wall 44 functions to closes the cavity 40, and is adjacent and supported by the various cavity walls 42. The cavity outer wall 44 is preferably convex, e.g., it may have generally the same curvature as the chair shell 20 in the junction area 26. Preferably, the cavity walls 42 and cavity outer wall 44 are integral with the chair shell 20 and formed during the molding process. Representatively, the shell 20 is formed in an injection molding process, and the cavity 40 is formed using a gas injection process that is carried out during the injection molding of shell 20. The cavity 40 preferably encompasses all or a substantial portion of the junction area 26.

[0028] Positioning the cavity 40 over the junction area 26 provides reinforcement and support to the junction area 26, which allows the use of a relatively thin material for the back portion 24 and the seat portion 22 of the chair shell 20. More specifically, the stress resulting from a force on the back portion 24 will be distributed throughout the cavity walls 42, 44 of the reinforcement or support 39. Accordingly, the junction area 26 is subjected to lower stress levels due to the presence of the hollow reinforcement or support 39

[0029] As shown in FIGS. 2 and 3, the reinforcement or support 39 preferably forms outer ribs 46 that extend upwardly along the edges of the rear side 33 of the back portion 24, and forwardly along the edges of the bottom side 31 of the seat portion 22. For example, the second cavity wall 42b and the cavity end wall 42c join together to form a rib 46. The first cavity wall 42a and cavity end wall 42d, the first cavity wall 42a and the cavity end wall 42c, and the second cavity wall 42b and the cavity end wall 42d similarly form ribs 46. The cavity 40 may extend through the ribs 46 or partially through the ribs 46 as shown in dashed lines in FIGS. 1-4, or the ribs 46 may be closed off, i.e., solid. In such a configuration, i.e., when a rib 46 is solid, the width of the rib 46 may be substantially uniform throughout the rib 46, or the width of the rib 46 may taper to the distal end of the rib.

[0030] The ribs 46 are positioned along the respective edges of the back portion 24 and the seat portion 22, and terminate below the top of the back portion 24 and rearwardly of the front of the seat portion 22. The ribs 46 function to further dissipate stress that would otherwise be concentrated on the junction area 26. The ribs 46 generally recede or taper into the respective surface, e.g., either the rear side 34 or the bottom side 32, i.e., the height of the rib 46 gradually decreases. See FIG. 2.

[0031] Using such a configuration for the ribs 46, the reinforcement or support 39 and the ribs 46 provide further support while still maintaining flexibility in the chair shell 20, e.g., the degree of flexibility in the back portion 24 may increase as the height and/or width of the ribs 46 decreases. Additionally, the flexibility of the back portion 24 with respect to the seat portion 22 depends on a variety of factors including, but not limited to, the material properties of the plastic used to form the chair shell 20, the height and width of the back portion 24, the thickness of the back portion 24 and the height and thickness of the cavity walls 42. These dimensions may all be adjusted in order to provide the desired degree of flexibility in the chair shell 20. As can be seen in FIGS. 6 and 7, the seat portion 22, cavity walls 42, cavity outer wall 44 and back portion 24 preferably have substantially the same thickness.

[0032] Thus, by using the preferred configuration for the ribs 46, i.e., positioning ribs 46 along the edges of the back portion 24 and the seat portion 22, it is possible to reduce or eliminate material failure of the chair shell 20 in the junction area 26 while providing a comfortable sitting experience to the user. More specifically, the material properties of the molded chair shell 20 may allow for the back portion 24 to move or flex with respect to the seat portion 22 when a force is exerted on the back portion 24 by a user leaning back in the chair. This flexibility in the back portion 24 may provide a more comfortable sitting experience for the user. Different degrees of flexibility may be achieved by using different materials and/or material thicknesses to form the chair shell 20.

[0033] As shown in FIGS. 2 and 3, the cavity 40 is preferably generally symmetrical about its center, in order to distribute stress evenly rather than concentrating stress at a certain point. As shown in FIGS. 3 and 4, the cavity walls 42 are preferably U-shaped with the walls 42 forming ribs 46 extending along the respective edges of the back portion 24 and the seat portion 22.

[0034] Additionally, the back portion 24 may feature an aperture that can serve as a handle 48, which may be useful for stacking, un-stacking or positioning like chair assemblies 10.

[0035] The chair shell 20 of the present invention is preferably formed of durable, lightweight plastic. This may allow for easy transportation and storage of the chair shell s 20 or chair assemblies 10. Preferably, the chair shell 20 is contoured so as to be easily stackable with another like chair shell 20, which may further allow for easy transportation and storage. The chair shell 20 of the present invention is a modular unit that may be able to be manufactured relatively inexpensively and mass produced efficiently. Further, the chair shell 20 may be manufactured to have any color as desired.

[0036] As will be appreciated by those skilled in the art, a product, e.g., a chair shell 20, formed by molding using a gas injection process will typically have a gate, shown at 50, which functions to enclose an opening through which gas is injected during manufacture. Though the location of the gate 50 may vary, the gate 50 may be located at the center of the cavity end wall 44, to provide the symmetrical shape of cavity 40 as shown and described.

[0037] Various alternatives and modifications are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.