Abstract:
A fitted sheet that fits on mattresses of various thicknesses by having a construction that is elastic along the side edges of the sheet. The sheet includes an insert extending from one side portion of the sheet to another. The insert is placed such that the side edge of the fitted sheet is formed by the insert. This allows the fitted sheet to fit more elastically over the corner of a mattress.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to bed linens, and more particularly to fitted bed sheets configured to accommodate mattresses of varying thicknesses. 
       BACKGROUND OF THE INVENTION 
       [0002]    Fitted sheets are advantageous for the bottom sheet of a set because they hold themselves on the mattress. A fitted sheet is less likely to separate from the mattress than a flat sheet that is merely tucked under the edges of the mattress. Accordingly, the fitted sheet is less likely to leave a user lying directly on the mattress after a restless night&#39;s sleep. The advantage of a fitted sheet comes from its shape, which is convex and corresponds to the mattress it is designed to cover. Unlike a flat sheet, a fitted sheet is shaped like an open ended box. It has a top portion and four side portions that are each connected to the top portion and two neighboring side portions. Four corners are formed at each of the junctions where the top portion and two side portions meet. Advantageously, the sides fit snugly around the sides of the mattress. 
         [0003]    To further secure the fitted sheet to the mattress, many fitted sheets include elastic around at least a part of the opening. The elastic assures that the opening of the fitted sheet is smaller than the mattress when in a relaxed state. Thus, the sides of the fitted sheet wrap around and slightly under the mattress. This construction provides pockets in the ends of the fitted sheet which encircle the ends of the mattress. The elastic must be stretched to remove the sheet from the mattress. 
         [0004]    A typical construction of a fitted sheet is shown in  FIGS. 1   a  and  1   b . Sheet  100  is made of a single piece of textile material. The piece of textile material is formed from a rectangular piece with four identical sections cutout from each corner, as shown in  FIG. 1   a . The resultant shape includes a central section which serves as the top panel  102  of the fitted sheet  100 . The top panel  102  is surrounded by four extensions which serve as side panels  104  of the sheet  100 . Each side panel has two ends  106  and one bottom edge  107 . Fitted sheet  100  is constructed by attaching end  106  to an adjacent end  106  using a hem  108 . Thus, a corner fold is formed where the ends meet. The hem  108  is usually very strong, such as a 5-thread over-lock stitch, so that the hem will not fail quickly. A result of the described construction is a fitted sheet  100  with the form of a box having an open side defined by the four bottom edges  107 . The constructed sheet is shown in  FIG. 1   b . Frequently elastic is included along the bottom edges  107 . 
         [0005]    The pockets formed in the ends of the fitted sheet should fit snugly around the mattress; superfluous fabric is considered unattractive. However, mattresses come in a variety of thicknesses and therefore a fitted sheet that can adapt to fit mattresses of various thicknesses is desirable. Accordingly, even if the fitted sheet is marketed for a mattress of a specific thickness, it is desirable for the fitted sheet to be flexible to adjust for thick mattress pads, feather beds or other accessories. If the fitted sheet is too tight it is difficult to put on the mattress. Pulling the corner folds of the fitted sheet around the corners of the mattress can be very difficult. Further, if the sheet fits too tightly it is more likely to pop off the mattress at the corners, leaving the user lying directly on the mattress. Thus, it is advantageous for a fitted sheet to be elastic, especially at the corners, such that it can adapt to mattresses of various thickness. 
         [0006]    Many textile materials are somewhat elastic, and articles made from textile materials have a certain degree of elasticity. This is advantageous for fitting the sheet onto the mattress. However, the prior art construction has limitations and the elasticity of the material is not fully utilized. The strength of hem  108  along the corner folds at ends  106  prevents the corner fold from having any degree of elasticity. In order to fit over the corners of the mattress, elasticity is most important along the corner fold of the sheet. Thus, the prior art construction of fitted sheets produces sheets that lack elasticity in the area where it is needed most. 
         [0007]    Thus, a fitted sheet without a hem located along the corner fold of the sheet is desirable. Further, a fitted sheet which has increased elasticity along the corner folds of the sheet is also desirable. 
       SUMMARY OF THE INVENTION 
       [0008]    In one aspect of the invention, a fitted sheet is configured to fit snugly over mattresses of various thicknesses by having a construction that is elastic along the corner folds of the sheet. The sheet includes a triangular insert extending from one side panel of the sheet to another. The triangular insert includes two insert side edges and a bottom edge. The triangular insert is disposed between two adjacent side panels by attaching each insert side edge to an end of the side panel. The insert is placed such that the corner fold of the fitted sheet extends from the bottom edge of the insert to a point on the body of the sheet. Accordingly, the fitted sheet does not include an inelastic hem along each corner fold. Thus, the fitted sheet fits more elastically over the corners of a mattress by utilizing the elastic properties of the fabric insert. 
         [0009]    In another exemplary construction, the fitted sheet may include a body having a top panel that serves as a top portion of the sheet and four side panels extending downward therefrom. Four triangular inserts can be included, each attached between a neighboring pair of side panels. The apex of the triangular insert is positioned next a point on the body of the fitted sheet, optionally where the top panel and the side panels all meet each other. It is not a requirement of the invention that the fitted sheet include four triangular inserts. A single insert can be used to provide one flexible corner fold. Such a configuration is still an advantage over the prior art because the flexible corner fold can be placed over the mattress after the other corner folds. 
         [0010]    Another construction of the fitted sheet may include a body of the sheet with a top panel and two side panels. The two side panels are directly opposite one another. An elongated insert may be included extending from one side panel of the sheet to the opposite side panel. This elongated insert extends over an entire side of the sheet and includes two corner folds. If the sheet is rectangular, the elongated inserts may be included along the short sides of the sheet. One elongated insert may be used by itself, if desired. 
         [0011]    The fitted sheet is made of a textile material which may be woven or knit fabric. The textile material includes some natural flexibility and may be flexible along both the weft and the warp. A bias direction of the material is at an angle between the direction of the weft and the warp. Specifically, the bias direction may be at 45 degrees between the weft and the warp. The elasticity of the textile material is greatest along the bias direction. To utilize this elasticity, the textile material may be oriented within the insert to take advantage of the elasticity of the bias direction. To provide maximum elasticity, the bias direction may be aligned or substantially aligned with the corner folds of the sheet, for example, within 5 degrees. Alternatively, the bias direction may be less strictly aligned with the corner fold, such as within 30 degrees. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    These and other objects and features of the invention will become more apparent by referring to the drawings, in which: 
           [0013]      FIG. 1   a  illustrates the material construction of a prior art fitted sheet; 
           [0014]      FIG. 1   b  shows an enlarged corner fold construction of the sheet of  FIG. 1   a;    
           [0015]      FIG. 2  is a perspective view of part of the fitted sheet of the invention including an insert; 
           [0016]      FIG. 3  illustrates a bias direction within a textile material; 
           [0017]      FIG. 4  illustrates a possible orientation of the bias direction within the insert shown in  FIG. 2 ; 
           [0018]      FIG. 5  is a perspective view of the invention including an alternative insert; 
           [0019]      FIG. 6  is a perspective view of the invention including another alternative insert; 
           [0020]      FIG. 7   a  is a plan view of the material construction of a fitted sheet in accordance with the present invention; and 
           [0021]      FIG. 7   b  shows the contrast between the bias directions of a body of the sheet and an insert. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    The fitted sheet embodying the present invention includes several geometric features that are consistent throughout the different embodiments of the invention. These features are labeled in  FIG. 2 . The fitted sheet  1  includes a top panel  10  and four side panels  12  attached thereto. Four edges  14  of the top panel are included at the locations where the top panel  10  meets the side panels  12 . Four corner folds  16  are also included along the corners of the sheet. Sheet corners  18  are formed at the junction where the top panel  10  and the corner folds  16  meet. This construction forms a box shape that is open at the bottom. The bottom edge  15  may include elastic thereon. 
         [0023]    The fitted sheet  1  may be rectangular in shape. Accordingly, sheet  1  can include two long sides  22  and two short sides  24 . Likewise, the top panel  10  of sheet  1  can include two long edges  26  and two short edges  28 . 
         [0024]    Sheet  1  includes at least one insert  50 . A corner fold  16  extends from a bottom edge  54  of the insert  50  to the body  30  of the sheet.  FIG. 2  shows a fitted sheet  1  of the invention with a triangular insert  60  included at the corner fold  16  of the fitted sheet  1 .  FIG. 2  only shows a single insert  50  included in the fitted sheet  1 . However, for simplicity, the fitted sheet  1  shown in  FIG. 2  will be described in the following as including four triangular inserts  60 . A complete plan view of sheet  1  including all four triangular inserts  60  is shown in  FIG. 7   a . Further, a bias direction of the material in both the body  30  and the inserts  50  is shown in  FIG. 7   b . The term “triangular” has its ordinary meaning which includes shapes that are of, or related to, a triangle, e.g. a boomerang has a triangular shape, without being a triangle. 
         [0025]    Sheet  1 , shown in  FIG. 2  is formed of a body  30  and four inserts  50 , specifically triangular inserts  60 . The body  30  includes a top panel  32  and four side panels  34 . In the described embodiment the side panels  34  are integrally formed with the top panel  32 . However, they may be formed as separate pieces. Each side panel  34  includes a panel bottom  39  and two panel ends  37 . If sheet  1  is rectangular, the body  30  may include two opposite long side panels  36 . Triangular inserts  60  may be attached between the ends  37  of adjacent side panels  34 . Each insert side edge  52  of the triangular insert  60  can be stitched to a panel end  37 . The stitching forms a hem  80  at each intersection of the side panels  34  and the insert section  50 . Preferably, the triangular insert  60  is shaped and disposed between the side panels  34  such that the insert bottom edge  54  is flush with the panel bottom  39 . Accordingly, a continuous bottom opening  15  is formed around the fitted sheet  1 . An apex  64  of the triangular insert  60  may be positioned to correlate with the top corner  18  of fitted sheet  1 . 
         [0026]    Fitted sheet  1  is made of a textile material which may be woven or knit fabric. The insert  50  and the body  30  may be formed of the same textile material or of different textile materials. The textile material can have a first elasticity in the direction of the warp and a second elasticity in the direction of the weft. However, the maximum elasticity of the material is along the bias direction  55  which is at an angle between the directions of the warp and the weft. The bias direction is illustrated in  FIG. 3 . The angle is typically approximately 45 degrees. In the bias direction, the textile material may stretch about 20% its normal size. 
         [0027]    To utilize the elasticity of the textile material or fabric in the bias direction  55 , the material can be oriented within the insert  50  to take advantage of the stretch of the bias direction. As shown in  FIG. 4 , the material within the insert  50  may be oriented such that the bias direction  55  is substantially aligned with the corner fold  16  of the sheet  1 . For maximum stretch along the corner fold  16 , the bias direction  55  of the material may be parallel, or almost parallel, to the corner fold  16 . Alternatively, a large quantity of stretch can be achieved within a 5 degree angle of the corner fold. Additionally, a less strict alignment of the bias direction  55 , say within a 30 degree or greater angle, of the corner fold  16  will result in less stretch. 
         [0028]    Another embodiment of the fitted sheet of the invention is shown in  FIG. 5 . The illustrated fitted sheet  1  includes an insert  50  that is an elongated insert  70 . The elongate insert extends from one side of the fitted sheet to a second side and continues to a third side. Thus, the elongate insert  70  shown makes up one entire side  12  of the fitted sheet  1  and includes two of the corner folds  16 . One embodiment may include two elongate inserts  70  at opposite ends of the fitted sheet. In this embodiment, the body  30  of the fitted sheet  1  only includes two opposite side panels  34 . Each insert side edge  52  is stitched to an end  37  of a side panel  34  with a hem  80 . Additionally, the insert top edge  72  is stitched directly to the top panel  32  of the body  30  along an edge  14  of the fitted sheet  1 . 
         [0029]    If the fitted sheet  1  is rectangular, the elongate inserts  70  may be disposed either along the long side  22  or the short side  24 . In the illustrated embodiment, the elongate insert  70  is disposed along the short side  24 . Accordingly, the insert top  72  is attached to body  30  along the short top edge  28 . 
         [0030]    The embodiments shown in  FIGS. 2 ,  4  and  5  have the insert side edge  52  angled with respect to the corner fold  16  of the fitted sheet. This provides an advantage that the hem  80  formed along the interconnection between the insert  50  and the body  30  is not aligned with the desired stretching direction of the fitted sheet  1 . For example, since it is desirable to stretch fitted sheet  1  lengthwise along corner fold  16 , angling insert side edges  52  with respect to side edge  16  lessens any impact hem  80  has on the stretching direction, if any. The hem used to attach the insert  50  to the base section  30  may be a bias hem. Although the angled insert side edges  52  are advantageous, the invention may be formed with an insert of any shape, such as that shown in  FIG. 6 . 
         [0031]    Thus, while there have been shown, described, and pointed out fundamental novel features of the invention as applied to several embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the illustrated embodiments, and in their operation, may be made by those skilled in the art without departing from the spirit and scope of the invention. Substitutions of elements from one embodiment to another are also fully intended and contemplated. The invention is defined solely with regard to the claims appended hereto, and equivalents of the recitations therein.