Patent Abstract:
An article of bedding for disposition over the top, side and end surfaces of a mattress comprises a substantially inelastic web of textile material which includes a top panel, side and end panels, and corner seams. The article further comprises a stretchable corner member overlying each corner seam, an additional seam aligned axially with each corner seam, and a stretchable border member secured to the peripheral edges of the side panels. This construction allows the article to accommodate the contours of mattresses of varying thicknesses within each given peripheral mattress size classification. Methods of making such articles are also disclosed.

Full Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119(e) of prior U.S. Provisional Patent Application Ser. No. 61/820,366 filed May 7, 2013. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to articles used for bedding, and in particular, to bed sheets, blankets, quilts, duvets or duvet covers. More specifically, this invention relates to an improved bedding product that is placed on a mattress and is configured to fit the contours of the mattress tightly. Although the invention will be described in relation to a fitted bed sheet, it is to be understood that it could be used for other bedding articles as well 
     BACKGROUND OF THE INVENTION 
     Fitted sheets, which are also referred to as “bottom” sheets, are conventionally formed of fabric and are used to cover and protect a mattress. A fitted sheet typically comprises a top panel, two side panels and two end panels, and in general, the top panel is disposed over the top surface of the mattress, while each of the four side and end panels extends from the top panel and covers a sidewall or endwall, and at least a portion of the bottom surface, of the mattress. Further, each side panel is usually joined to each adjacent end panel at their respective edges by seams, in a manner to form corners adapted to conform to the shape of the mattress. A fitted sheet may also include some arrangement for securing the fitted sheet to the mattress and/or for keeping the fitted sheet in place on the mattress. 
     Nevertheless, fitted sheets often become displaced during use, which causes a disheveled look, and which may also cause discomfort to the user. Moreover, although nowadays mattresses are available commercially in several popular sizes, having width and length dimensions that are standardized within the bedding industry (e.g., “king,” “queen,” “full,” “twin,” etc.), in fact the dimensions of mattresses do vary from manufacturer to manufacturer, and even among the various mattress lines or models of the same manufacturer, particularly with respect to the thickness of the mattress. In other words, there is no “standard” mattress thickness dimension; rather, the thickness of particular mattresses may vary, depending on a number of factors such as the type or manufacturer of the bed, and the preferences of individual users. Therefore, fitted sheets designed for use on a mattress of a particular size, such as a “queen” size mattress, may not fit snugly on all mattresses of that size. Moreover, over time, an individual mattress may tend to change its size and shape, due to a variety of factors such as age and/or excessive use and/or environmental factors. 
     Accordingly, there is a need for a fitted sheet capable of remaining in place during use, and which, at the same time, can accommodate and fit snugly on mattresses of varying thicknesses, and can also adapt to any changes in mattress size and shape, while continuing to appear smooth and neat, at least along the top surface and sidewalls of the mattress. Although efforts have been made in the prior art to provide fitted sheets that can overcome these problems, such as those described in U.S. Pat. Nos. 5,287,574, 7,398,570 and 8,171,581, those efforts have not been completely satisfactory. 
     Most of these prior art solutions involve blending stretchable and non-stretchable portions into the fabric that forms the side panels of the sheet, such that the stretchable fabric portions are located at or near the corners. However, this solution may lead to undesirable consequences, such as differential shrinkage of the sheet after laundering, as well as a “mottled” appearance due to slight differences in the coloration of portions of the sheet, either initially or after laundering. These undesirable consequences are a direct result of blending stretchable and non-stretchable yarns into portions of the fabric, as these portions are assembled of yarn fibers having different characteristics. Since such blending is common to all of these prior art solutions, it is a fundamental flaw of the prior art. 
     It is therefore the principal object of the present invention to provide improved fitted bed sheets which are capable of remaining in place during use, which can fit the contours mattresses of varying thicknesses, and which, at the same time, do not exhibit the undesirable effects caused by the incorporation into the side panels of the sheet of both stretchable and non-stretchable portions of fabric. 
     SUMMARY OF THE INVENTION 
     This and other objects of the present invention are achieved by providing an improved fitted sheet including a top panel and side and end panels that are continuous and made from the same fabric, using any standard fabric construction process such as weaving or knitting. A special seam is provided at the corners to insure that the sheet fits snugly over the mattress and does not pop up during usage. In addition, flexible and stretchable strips or tapes, which stretch when pulled, are used at those corner seams and also along the free peripheral edges of the side panels. 
     Thus, one aspect of the present invention generally concerns improved articles for use as bedding materials, while another aspect of the present invention concerns methods for fabricating such articles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects, features, objects and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description of the presently most preferred embodiments thereof (which are given for the purposes of disclosure), when read in conjunction with the accompanying drawings (which form a part of the specification, but which are not to be considered as limiting its scope), wherein: 
         FIG. 1  is a top plan view of a substantially flat rectangular web of fabric from which the fitted sheet of the invention may be formed; 
         FIG. 2  is a view substantially similar to  FIG. 1 , illustrating in phantom lines the portions of the fabric web which are to be cut away and removed, so as to form side and end panels; 
         FIG. 3  is a view substantially similar to  FIGS. 1 and 2 , illustrating diagrammatically how the edge of each respective side panel is drawn towards the edge of an adjacent end panel, prior to stitching; 
         FIG. 4  is a bottom plan view of the fabric web of  FIG. 3 , after the side and end panels have been joined to form corner seams, thus forming a bed sheet; 
         FIG. 5  is a top plan view of the bed sheet of  FIG. 4 ; 
         FIG. 6  is a bottom plan view of the bed sheet of  FIG. 5 , after a flexible and stretchable strip has been added at each corner seam, and after an additional special seam has been formed adjacent each corner; 
         FIGS. 7 and 7A  are a bottom plan view, partially broken away, and a side perspective view, respectively, of the bed sheet of  FIG. 6 , after a flexible and stretchable strip has been stitched to the free peripheral edges of the side and end panels, thus forming the fitted bed sheet of the invention shown covering the top surface, the sidewalls and endwalls, and at least a portion of the bottom surface of a mattress; 
         FIG. 8  is a flow diagram depicting the process by which the fitted bed sheet of  FIG. 7  is formed, in accordance with the invention, from the rectangular web of fabric of  FIG. 1 ; 
         FIG. 9  is top plan view showing the fitted bed sheet of the invention covering the top surface of a mattress; 
         FIG. 10  is a diagrammatic bottom plan view, partially broken away, and substantially similar to  FIG. 7 , illustrating the fitted bed sheet of the invention covering a portion of the bottom surface of a mattress; and 
         FIGS. 11-13  are diagrammatic bottom plan views depicting several fitted bed sheets of the prior art. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment of the present invention will now be further described. As stated above, although the invention will be illustratively described hereinafter with reference to the formation of a fitted bed sheet, it should be understood that the invention is not limited to the specific case described, but extends also to the formation of other bedding items, such as blankets, quilts, bedspreads, duvets and duvet covers. 
     Referring first to  FIGS. 1-3  and to the flow diagram of  FIG. 8 , the process of forming the fitted bed sheet of the present invention begins with a flat web of material  10 , usually, although not necessarily, rectangular in shape, and preferably formed from a non-stretchable textile fabric that is woven or knitted from cotton, silk, wool, rayon, polyester, viscose and/or other types of threads, yarns or fibers, and combinations thereof, as is conventional in the bedding industry. To form the fitted bed sheet, initially the four corners of web  10  are cut, substantially along the lines  12 , as shown in  FIG. 2  (step  100  in  FIG. 8 ), forming generally square corner portions  14 ,  16 ,  18 ,  20  that are removed. The resulting modified web  22  is still flat, and as shown in  FIG. 3 , it includes a top panel  24  having a peripheral edge  26 , two opposed side panels  28 ,  30 , as well as two opposed end panels  32 ,  34 . Each of side panels  28 ,  30  and end panels  32 ,  34  has two respective side edges  35   a , as well as a distal edge  35   b.    
     Generally, the dimensions of top panel  24  are selected so as to be sufficient to be disposed over, and to cover, the top surface of a mattress (not shown), and the dimensions of side panels  28 ,  30  and end panels  32 ,  34  are selected to be sufficient to cover the sidewalls and endwalls, respectively, of the mattress, but they also extend a sufficient distance from the peripheral edge  26  of top panel  24  so as to cover at least a portion of the bottom surface of the mattress as well. In general, no matter what absolute dimensions are chosen for the side and end panels (such dimensions will depend upon the design, configuration, thickness and contours of the mattress on which the fitted bed sheet of the invention is to be used), opposed side panels  28 ,  30  will have a dimension L that will correspond substantially to the length dimension of the mattress, while opposed end panels  32 ,  34  will have a dimension W that will correspond substantially to the width dimension of the mattress; thus, opposed side panels  28 ,  30  will be substantially congruent, and similarly, opposed end panels  32 ,  34  will also be substantially congruent. 
     Referring now to  FIG. 4  in addition to the aforementioned  FIGS. 1-3  and  8 , the adjacent side edges  35   a  of side and end panels  28 ,  30 ,  32 ,  34  are then brought together as indicated by the arrows A in  FIG. 3 , and are joined, two by two (step  102  in  FIG. 8 ), to form corner seams  36 ,  38 ,  40 ,  42 , respectively, thus resulting in a bed sheet  44 . Preferably, a five thread lock stitch is used to join these edges, as illustrated schematically in  FIG. 4 . This lock stitch uses multiple threads that are interlocked with each other to provide strength for the seams, and this stitch allows bed sheet  44  to accommodate the shape of a mattress at the corners, and maintains the sheet on the mattress.  FIG. 4  comprises a reverse view of bed sheet  44  (as compared with  FIG. 3 ), so as to illustrate the positions and orientations of the stitches forming the corners seams. Each of corner seams  36 ,  38 ,  40 ,  42  has a proximal end  43   a  and a distal end  43   b . As will be apparent, the distal edges  35   b  of the side and end panels  28 ,  30 ,  32 ,  34  together form the peripheral free edge of bed sheet  44 . 
     Referring next to  FIGS. 5 and 6  in addition to the aforementioned  FIGS. 1-4  and  8 , an additional special seam is made (step  104  in  FIG. 8 ) in the fabric of top panel  24  of bed sheet  44  in the general vicinity of each of the corners, along lines  45 , each of which, as shown best in  FIG. 5  (a view of bed sheet  44  from above), is formed along a line which is an extension of one of the corner seams. Each of these additional seams  46 ,  48 ,  50 ,  52  is preferably about 1.5 inches in length, and each one extends diagonally, from peripheral edge  26  of top panel  24  towards the center of top panel  24 , along the same longitudinal axis as the adjacent one of corner seams  36 ,  38 ,  40 ,  42  ( FIG. 7A  shows the position of these additional seams when the fitted bed sheet of the invention is installed on a mattress). The purpose of these additional seams  46 ,  48 ,  50 ,  52  is to gather some of the fabric material of the bed sheet adjacent to the corners, and they help to insure that at each corner, the top panel  24  and each respective intersecting pair of side and end panels  28 ,  30 ,  32 ,  34 , do not form a narrow pocket, but instead fit over the mattress corner snugly and assume the shape of the mattress. These additional seams  46 ,  48 ,  50 ,  52  can be formed using conventional sewing techniques, such as Daug stitching or using lock stitching placed at all four corners. 
     As previously mentioned, even though mattresses have nominal standard (length×width) sizes, their actual dimensions may vary somewhat. This is particularly true of their thicknesses, which is also referred to herein as their heights. For example, some mattresses may have a height of 7 inches, while others may be as high as 18 inches. It would be inconvenient to manufacture a separate fitted sheet for mattresses of every possible height in each of the standard (length×width) mattress sizes. Therefore, in order to accommodate different heights, the fitted bed sheet of the present invention is provided with flexible and stretchable corner members  54 ,  56 ,  58 ,  60  (step  106  in  FIG. 8 ), one at each corner. 
     Corner members  54 ,  56 ,  58 ,  60  may be fabricated of any conventional tightly woven elastic material, having a stretch ratio ranging from about 1:2.75 to about 1:3, and may be provided on either surface of the sheet, but preferably they are provided on the surface which will become the inner surface of the sheet, that is, the surface which will be adjacent to the mattress when the sheet is in use. Each corner member is positioned overlying one of the corner seams  36 ,  38 ,  40 ,  42 , respectively, as illustrated in  FIG. 6 , and is secured, preferably via conventional lock stitching; the corner members  54 ,  56 ,  58 ,  60 , when the fitted bed sheet of the invention is installed on a horizontally-positioned mattress ( FIG. 7A ), are generally oriented vertically. 
     Each corner member  54 ,  56 ,  58 ,  60  is preferably provided in the form of a narrow strip or tape, about 8-12 mm wide, and its length is preferably smaller than the dimension chosen for the length of the side edge  35   a  of each of the side and end panels  28 ,  30 ,  32 ,  34 ; most preferably, the length of each corner member, before it is secured to bed sheet  44 , is chosen to be less than one-half of the length of the side edge  35   a  of the side and end panels  28 ,  30 ,  32 ,  34 . It is to be understood that, while the length of the corner members, as specified in the preceding sentence, is measured while each corner member is in a relaxed or “unstretched” condition, each corner member is secured to the sheet in “stretched” condition, that is, prior to securing each corner member to a respective corner seam, each corner member is stretched out, so that it essentially covers the respective corner seam from end to end. The elastic material from which corner members  54 ,  56 ,  58  and  60  may be formed is commercially available from a wide variety of sources, such as M/s. Shree Shyam Industries of Bhiwandi, Maharashtra, India and Mahendra Trading Company of Mumbai, Maharashtra, India. 
     Finally, and referring now to  FIG. 7  in addition to the aforementioned  FIGS. 1-6  and  8 , a border member  62  is secured, preferably via twin needle lock stitching, to the outer edge or perimeter  64  of fitted bed sheet  44  (that is, to the free peripheral edges of the side and end panels  28 ,  30 ,  32 ,  34 ), as illustrated in  FIG. 7  (step  108  in  FIG. 8 ). Border member  62  is preferably provided in the form of a flexible and stretchable strip or tape comprised of a tightly woven elastic material, having a stretch ratio in the range of from about 1:175 to about 1:2, and is preferably about 1 inch (25 mm) wide. Preferably, the overall length of the border member  62  is shorter than the overall length of the perimeter  64  of sheet  44  (the length of perimeter  64  being the combined total of twice the value of dimension W and twice the value of dimension L, as illustrated in  FIG. 2 ) most preferably, the length of border member  62  is chosen to be approximately one-half of the length of perimeter  64 . 
     It is to be understood that, while the length of the border member  62 , as specified in the preceding sentence, is measured while it is in the relaxed or “unstretched” condition, the border member is secured to the sheet in “stretched” condition, that is, prior to securing the border member  62  to the perimeter  64  of sheet  44 , the border member  62  is stretched out, so that it essentially extends around the entire peripheral free edge of the sheet. Thus, due to the combined effect of flexible and stretchable corner members  54 ,  56 ,  58 ,  60  and flexible and stretchable border member  62 , the final fitted bed sheet  44  is formed with a peripheral free edge having an irregular shape (see  FIG. 7 ). The elastic material from which border member  62  may be formed is commercially available from a wide variety of sources, such as M/s. Shree Shyam Industries of Bhiwandi, Maharashtra, India and Mahendra Trading Company of Mumbai, Maharashtra, India. 
     The resulting fitted bed sheet  44  has several advantages over the prior art. Referring now to  FIGS. 7A ,  9  and  10  in addition to the aforementioned  FIGS. 1-8 , the additional seams near the corners insure that the sheet fits snugly and smoothly over the corners of the mattress, while the corner members  54 ,  56 ,  58 ,  60  and the border member  62  cooperate to hold the top panel  24  and side and end panels  28 ,  30 ,  32 ,  34  evenly and smoothly on the various corresponding surfaces of the mattress. Moreover, the fitted bed sheet  44  not only adjusts automatically to variations in the dimensions of a mattress, but can also be used for mattresses with varying heights, depending on the dimension chosen for the edges of the side and end panels  28 ,  30 ,  32 ,  34  (that is, the dimension chosen for the length of the lines  12  shown in  FIG. 2 ). For example, if 16 inches is chosen for that dimension, then the fitted sheet will accommodate mattresses with heights ranging from 7 inches to 18 inches, whereas if 14 inches is chosen for that dimension, then the fitted sheet will accommodate mattresses with heights ranging from 5.5 inches to 16 inches, while if 18 inches is chosen for that dimension, then the fitted sheet will accommodate mattresses with heights ranging from 9 inches to 20 inches. 
     Referring finally to  FIGS. 11-13  in addition to the aforementioned  FIGS. 1-10 , further advantages of the fitted bed sheet  44  of the present invention over the fitted bed sheets of the prior art become apparent. The known fitted bed sheet in  FIG. 11  (described in U.S. Pat. No. 5,287,574) is provided with the entirety of each end panel  66 ,  68  being made of a special stretchable (e.g., Lycra®) fabric, as indicated by the arrows B. This fitted sheet is expensive to make, and after a while the knitted fabric loses its flexibility (especially after repeated washing) and fails to maintain its stretching characteristics. In addition, although the outer peripheral edge  70  of this fitted sheet is provided with a circumferential tubular elasticized “cord,” this material is of insufficient size to insure that the sheet remains in place during use.  FIG. 12  shows another known fitted sheet (described in U.S. Pat. No. 8,171,581) that is provided with segments  72  of special stretchable (e.g., Lycra®) fabric positioned adjacent the corners. Again, this construction is expensive to manufacture, requiring special assembly, particularly near the corner seams, in order to join the stretchable fabric segments with the non-stretchable fabric making up the rest of the fitted sheet.  FIG. 13  shows yet another known fitted sheet (described in U.S. Pat. No. 7,398,570), similar to the one in  FIG. 11 , except that the end panels  74 ,  76  are “composites” of dual construction, in which a stretchable portion (as indicated by the arrows C) is attached to a non-stretchable portion. Again, this structure is expensive and time-consuming to assemble. 
     While there has been described what are at present considered to be the preferred embodiments of the present invention, it will be apparent to those skilled in the art that the embodiments described herein are by way of illustration and not of limitation. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. Therefore, it is to be understood that various changes and modifications may be made in the embodiments disclosed herein without departing from the true spirit and scope of the present invention, as set forth in the appended claims, and it is contemplated that the appended claims will cover any such modifications or embodiments.

Technology Classification (CPC): 3