Fitted sheet with a mattress

Abstract: A sheet is provided for dressing a mattress. The sheet may be formed from a tube of knit fabric having spaced apart ends closed by end seams normal to the longitudinal axis of the tube. The tube is longitudinally open, from end to end, to provide an opening for application of the sheet to a mattress.

Description: The invention relates to a fitted bed sheet in combination with a substantially rectangular mattress according to the preamble of claim 1. Such as known from DE-A-2 829 873. Traditionally, fitted bottom sheets as defined above have been manufactured by cutting a pattern in a textile fabric, said pattern comprising rectangular notches cut in the corners of a rectangular sheet dimensioned to fit a mattress. The pattern is then sewn by the application of a seam in each notched corner corresponding to the corner edge of a mattress and the application of a band of elastic around each corner at the bottom edge of the textile fabric. An alternative method of construction in which a corner seam is sewn with elastic along its length is disclosed in applicant's issued U.S. Patent No. 4,912,790, dated April 3, 1990. The form of construction shown in that patent has succeeded in removing one step from the manufacturing process by combining the application of elastic with the sewing of the corner seam. However, the manufacturing of fitted bottom sheet remains a fairly labour intensive process. Because of the individual cutting of each corner and the individual application of elastic in each corner it has been infeasible to automate the manufacture of fitted bed sheets. US-A-3,380,086 issued to McCurry discloses a sheet based on a rectangular blank with folded side margins and glued along the transverse ends for a bassinet made in disposable non-woven fabric. While this is suited to automated manufacture, the design is not satisfactory as a fitted sheet. This prior art design fits very loosely having projecting ears of unfilled fabric at the corners and gaping marginal portions underneath the mattress. A bassinet has a light weight mattress which can be lifted and eased into such a sheet. Further the design is for newborn infants and will not be placed under the stresses of normal hospital use. Such a sheet on a full sized hospital mattress which lifts would quickly disengage. In addition, the loose fit would allow the sheet to wrinkle and move under the patient causing serious discomfort and problems to patients confined for long periods. Knitted fabric, which is quite inexpensive, and soft to the touch, is also useful for the manufacture of fitted sheets, but has traditionally required the use of more complex patterns, and more hand sewing. An example of a prior art pattern for a knitted fabric is shown in Figure 1. The knit fabric, which has a two-way stretch, is supplied in a tubular form, the tube having an axial direction indicated by arrow 1 . The corners, in a conventional pattern 4, are cut along one end of the tube and the tube slit along the side edge 5 between the corners. The corners are cut as a wide bevel, with a square notch 6 in the middle thereof, as shown in Figure 1, and the tube 4 is cut at the level of the corners. Conventionally, then, the tube is unfolded, and each corner brought together and hand sewn on a machine, from the vertex 2 of each notch to the edge 3 of the bevel. This bevel and notch pattern creates a small pouch-type of structure at each end of the sheet, which is required in a knitted fitted sheet, to prevent the ends of the sheet, which will exhibit stretch, from creeping up and over the end of a mattress. However, such a problem still exists for knitted sheets used on hospital beds, because the mattress of a hospital bed can be raised up at an angle. That is, when the end of a mattress is lifted, there will be a tendency for the fitted sheet, if it is at all stretched, to form a bridge between the ends of the mattress. This makes it easy for the end of the conventional knit sheet to slip over the end of the mattress. In view of the foregoing, it will be appreciated that knit fabrics are advantageous for use in making fitted sheets because of their low cost, and the attractive and comfortable fit achieved through the stretch characteristics of the fabric. However, to date the disadvantages associated with knit sheets, namely the high cost of hand labour to finish each corner thereof, and the tendency of the sheet to creep up and over the end of a hospital bed mattress, have tended to outweigh the advantages, such that there is only minimal usage of knit fabric fitted sheets in hospitals. Moreover, it will be understood that hospitals are a major market for sheets of any kind, since each bed in a hospital accounts for two or three sheets per year, on average. The document DE-A-2 829 873 discloses a sheet for a mattress which is provided with a transverse seam at both longitudinal ends thereof. At the underside of the sheet, when attached to a mattress, a longitudinal slot is provided between opposite edges of the sheet which terminate at the transverse seams with their respective ends, wherein the seams are provided well above the bottom plane of the sheet. The document US-A-3 789 441 discloses a sheet for a mattress made of knitted fabric which is focussing on the configuration of the side panels which are joined by a single seam along arcuately cut end edges. The document CA-A-2 101 108 discloses a fitted bed sheet which consists of woven material, and is not made of stretchable knitted fabric. The object underlying the present invention is to provide a fitted bed sheet in combination with a substantially rectangular mattress which can easily be manufactured and provides a suitable coverage of the corresponding mattress. According to the invention, this object is solved by a fitted bed sheet in combination with a substantially rectangular mattress as defined in the main claim. Advantageous further developments of the invention are specified in the subclaims. It is an advantage of the present invention that the fitted sheet of knit fabric fits the mattress tightly, while fully covering the upper surface and exposed sides. As a result, no undesirable wrinkling or movement of the sheet in use is encountered. An additional advantage of the improved fit is the economical use of less fabric than in prior art designs. Although the sheet does not describe a three dimensional volume, the stretch of the fabric accommodates the mattress as dressed with a closely conforming covering. Other prior art two dimensional designs leave undesirable ears, or unfilled fabric projections in the corner areas. Further, the flexibility offered by the stretch fabric enables a single sheet to accommodate a variety of mattress lengths as are frequently encountered in institutional use. In drawings that illustrate the present invention by way of example: Figure 1 a is a plan view of a typical prior art pattern for use in making fitted sheets from knit fabric; Figure 1b is a view of the underside of a prior art product; Figure 2 is a plan view of a fitted sheet made from knit fabric; and Figure 3 is an isometric view of the fitted sheet of knit fabric in use on a mattress illustrated from the underside of the mattress. Figure 2 illustrates a fitted sheet of knitted fabrics. Knitted fabric is produced in a tubular form, the tube extending in the direction of arrow 1. The tube is slit and finished on its edges 14 in a first step, and then folded back into its original tube configuration, with the finished edges meeting in the centre of the tube, as shown in Figure 2. The ends 15 'of the sheet are then cut and finished, in a single operation per end, to provide a finished product. The length of fabric between the ends of the sheet of Figure 2 is not critical, since the knit fabric will stretch. The maximum length of fabric will, however, be the length of a selected mattress plus twice the depth. Any longer, and the sheetwill not fit. The minimum length will depend on the stretch properties of the fabric being used, and selection of an appropriate length of fabric will be a matter of choice to one skilled in the art. However, the applicant has found that a length of fabric about equal to the length of the selected mattress to be dressed, plus up to about the depth thereof, is appropriate. Moreover, the applicant has found the best success with folding the sides of the fabric until they meet midway. This assists in preventing any creep of the sheet over the top of the mattress. As seen in Figure 3, substantially the full upper surface of the mattress M is covered by the sheet. Distortion between lateral and longitudinal stretch permits the ends of the sheet to fully enclose the ends of the mattress according to the present invention and results in the oval shaped opening defined by the longitudinal edges. Advantageously the edges 14 are bound to finish the raw cut fabric. A knit binding 16 , particularly having a more limited stretch property than the fabric, may serve to constrict the opening and better prevent disengagement in use. A binding of elastic material or overstitching may also be used. The applicant has determined that a sheet with no gap between the side edges will not creep up the ends of the mattress. The total width of knit fabric for any selected mattress should be the width of the mattress, plus about thrice the depth. However, it will be clearly understood that much wider variance in width is possible, because of the inherent stretchability of knit fabrics. Clearly, a fit is dependent on the stretch properties of the fabric. A preferred fabric has both longitudinal and lateral stretch. SleepKnit® fabric manufactured by Med-I-Pant Inc. has proven to have appropriate stretch qualities. Under weight tension SleepKnit® demonstrates a lateral stretch of 88 - 135% and a longitudinal stretch of 22 - 31%. This compares to 1 - 6% lateral stretch and 0 - 1% longitudinal stretch for a standard woven fabric under the same weight tension conditions. With such stretch properties, the finished sheet may have a width, in a relaxed condition, of 75 - 100% of the width of the mattress while still providing full coverage. The length of the finished sheet, in a relaxed condition, will be approximately the length of the mattress to about the length plus one times the depth of the mattress. It is to be understood that the examples described above are not meant to limit the scope of the present invention. It is expected that numerous variants will be obvious to the person skilled in the field of bed sheet manufacture without any departure from the scope of the invention as defined by the claims.

Claims: A fitted bed sheet in combination with a substantially rectangular mattress having a width (W), a length (L) and a depth (D), the sheet (7, 11) being composed of a stretchable knitted fabric, the sheet (7, 11) in a relaxed state comprising a substantially rectangular main body panel defining an upper surface of a sheet, and a pair of congruent side panels extending from the main body panel, and folded under same, the side panels and the main body panel being sewn together along the end edges thereof, wherein the lateral edges of the side panels beneath the main body panel meet along the centre line of the main body panel, characterized in that the mattress is covered by the sheet (7, 11) with the ends of the mattress fully enclosed. The sheet according to claim 1, wherein the main body panel has a maximum length of L + 2D. The sheet according to claim 1 or 2, wherein the total width of the main body panel and the side panels is less than or equal to W + 3D. The sheet according to any of claims 1 to 3, wherein the length of the main body panel is in the range of L to L + D. The sheet according to any of claims 1 to 4, wherein the total width of the main body panel and the side panels is in the range of W + D to W + 3D. The sheet according to any of claims 1 to 5, wherein the length of the main body panel is about L + 1/2D, and the total width of the main body panel and the side panels is about W + 2D.

Inventors: MACDONALD ROBERT, MACDONALD, ROBERT
Applicants: MACDONALD ROBERT, MACDONALD, ROBERT
Application year: 1997
Main classification: A47G9
IPC codes: A47G9