US 3020566 A
Description (OCR text may contain errors)
Feb. 13, 1962 H. T. ANDERSON ETAL 3,020,566
SELF-TUCKING FITTED SHEET Filed Jan. 12, 1960 2 Sheets-Sheet 1 FIG. 3.
. INVENTOR- wdw/ W War; CLJWW 1962 H. T. ANDERSON ET AL 3,02
SELF-TUCKING FITTED SHEET Filed Jan. 12, 1960 2 Sheets-Sheet 2 FIG. 6.
INVENTORS 7 United States Patent 3,020,566 SELF-TUCKING FITTED SHEET Hattie T. Anderson and Martin Anderson, both of 1-H Gardenway, Greenbelt, Md. Filed Jan. 12, 1960, Ser. No. 2,797 4 Claims. (Cl. 5--334) This invention relates in general to fitted sheets or the like. In particular it relates to a fitted sheet having tensioned elastic means whereby the sheet will be self-tucking. More specifically it relates to a fitted sheet having differentially tensioned elastic means.
Sheets, or the like, of relatively inelastic material, manufactured to conform to the approximate contour of a distortable rectangular parallelopiped, as exemplified by a mattress, have been most commonly designed so as to furnish end, or corner, pockets into which the mattress is forced by mutual distortion of mattress and sheet. In order to reduce this mutual distortion, various provisions have been made for incorporating elastic inserts, gussets, and similar elastic elements into the sheet construction, particularly in the corners. While such constructions have facilitated fitting of the sheets, it has often been with the result of positioning elastic elements at the points of greatest strain. Sheets of this type, even when fully extended at the mattress bottom enfolding periphery, usually only with difliculty encompass the periphery of the mattress itself, and the strain of the repeated operations of fitting often seriously shortens the lifetime of the sheet.
It is also known to construct fitted sheets, or covers, conforming to the top, sides and ends of a mattress, or the like, with the peripheral side and end skirts dependent below the mattress and having an elastic band attached entirely around their common periphery and under such tension as to enfold the bottom of the mattress when placed thereon. When fully extended such a sheet should ideally have the approximate form of an open box. Thus, the fitting of such a sheet will ordinarily require no deformation or distortion of the mattress. This advantage is offset, however, by the tendency of such sheets to bag at the sides, especially, and at the ends, and also by the ease with which the sheet corners may creep, or be displaced, over the mattress corners. This latter disadvantage may be of potentially serious nature in sheets designed for baby cribs. The tendency to creep may be reduced by increasing the elastic tension, but this expedient is often at the cost of rendering the sheet irremovable except by distortion of the mattress. Also, the bagging at the sides cannot be decreased by increase of elastic tension, resulting as it does from the excess sheet edge liberated by the enfolding, by the sheet, of the mattress bottom. The smaller the edge perimeter upon the mattress bottom, the greater will be this edge excess.
This invention is directed towards an improvement in that form of sheet or cover which conforms to the top of the approximately rectangular object to be covered and has a peripheral skirt depending below the object to he covered, when placed thereupon, and urged inwardly upon the bottom thereof by elastic means attached to, or extending about, the free edge of the skirt. We have discovered that by differential tensioning of the elastic means in the extended corners of such a sheet during its fabrication there will result an improved sheet difficult to displace, self-tucking, non-creeping, relatively close fitting and free from bagging at the sides, subject to lessened strain at points of greatest tension during fitting operations, and fittable without distortion or deformation of the mattress. It is thus one purpose of this invention to provide a fitted sheet having differentially tensioned elastic means extending about its mattress bottom enfolding periphery. Another purpose of this invention is to provide a method of fabrication of such a sheet. An additional purpose of this invention is to provide a sheet having elastic means attached under tension to the corner segments of the skirt edge, the tension being suflicient to take up in comer gathers the excess enfolded skirt edge when the tensioned elastic means are relaxed, in cooperation with the skirt edge, upon a mattress.
In the drawings:
FIGURE 1 is a perspective view of one embodiment of our invention and shows, as applied to a mattress, a sheet having differentially tensioned elastic means with the elastic means shown as fully extended;
FIGURE 2 is a perspective view of the sheet and mattress of FIGURE 1 with the differentially tensioned elastic means shown as relaxed, with the sheet, upon the mattress;
FIGURE 3 is a perspective view illustrative of one mode of fabricating the differentially tensioned elastic means of our invention;
FIGURES 4 and 5 are perspective views illustrating two modes of fabricating sheets to which the differentially tensioned elastic'means of our invention may be applied; and
FIGURE 6 shows, in diagram, a preferred mode of fabricating the differentially tensioned elastic means of our invention.
The sheet shown in FIGURE 1 may be constructed by any manner practicable so as to have a top portion, 1 (as shown in FIGURES 3, 4, and 6), substantially conforming to the top of a mattress, 4, and a skirt portion, 2, substantially conforming to the periphery of mattress, 4, and depending in depth below it. To the free edge, 3, of skirt, 2, differentially tensioned elastic means, 3a, are attached, and, in FIGURE 1, are shown as fully extended in the application of the sheet to mattress, 4. As illustrated in FIGURE 2, when differentially tensioned elastic means, 3a, are relaxed, in cooperation with skirt edge, 3, upon mattress, 4, the major portion (which may be 60-100 percent, but which is illustrated in FIGURE 2 as being percent) of excess enfolded skirt edge is in gathers, 5, in the corners of the substantially rectangular periphery, 6, formed by the relaxation of skirt edge, 3, of FIGURE 1, and the enfolding by the depending portion of skirt, 2, of the bottom of mattress, 4. By substantially rectangular it is to be understood we mean to include the rounded corners which will be present and including the excess gathered sheet edge. The gathers, 5, shown in FIGURE 2, will substantially disappear from any corner upon full extension, as shown in FIGURE 1, of that corner. The sheet may thus be fitted or removed without substantial distortion or deformation of mattress, 4, by stepwise, or simultaneous, extension of one or more corners.
A preferred mode of fabrication of the differentially tensioned elastic means of our invention is illustrated in FIGURE 3. A length of elastic band, or the like, 7, is chosen so that its relaxed length is less than the length around the substantially rectangular periphery, 6, of FIG- URE 2, and having an extendable length greater than the the peripheral length around skirt edge, 3. Relaxed corner segments, 8, of elastic band, 7, are extended, as shown by the arrows, and attached to corresponding segments, 9, of skirt edge, 3. The lengths of relaxed corner segments, 8, are so chosen that: when they are extended to correspond to skirt corner segments, 9, attached thereto, 'and in cooperation therewith are relaxed upon mattress, 4, as shown in FIGURE 2, the major portion of excess enfolded skirt edge will be in gathers, 5. A procedure by which the relaxed and extended corner segment lengths, respectively 8 and 9, may be calculated will be described in detail hereinafter, and these calculations can form the basis of choosing particular corner segments, 8 and 9, for particular applications of this invention.
Still referring to FIGURE 3, the remaining side, 10, and end, 11, segments of elastic band, 7, are stretched to correspond to remaining side, 12, and end, 13, segments of skirt edge, 3. These side and end segments, extended and relaxed, may arbitrarily follow from the positioning of the corner segments. However a more exact procedure for the calculation of the lengths of all the segments and their relative positioning will be considered below in further detail.
While the general teachings of our invention may be applied empirically, the following discussion is offered to enable those skilled in the art to more fully understand our teachings, and to practice them without further experimentation. This discussion is, however, not intended to limit the scope of our invention but is merely illustrative of a preferred mode of practice thereof.
Consider that sheets, covers, or the like are to be fabricated for substantially rectangular parallelepipeds, exemplified, as above, by a mattress having in this case dimensions, length width, and depth, respectively, of X, Y, and Z, and a peripheral length about its sides and ends of L. These dimensions are taken as measured through the midpoints of the plane areas: top, bottom, sides, and ends; and the effect on these calculations of rounded corners, edges, etc. can be regarded as immaterial or insignificant, especially as we are concerned only with approximations which yield, as these do, operationally practicable results. Further, all consideration of hem and seam allowances, etc. is omitted as these can be added to the results of the following calculations by those skilled in the art and according to their own needs. Also, discussion of all means of attachment: stitching, binding, hemming, seaming, etc. will be omitted since they form no part of the present invention and their use will be apparent to those skilled in the art.
A preferred mode of fabricating the sheet to which the differentially tensioned elastic means of our invention may be applied, as illustrated in FIGURE 4, is to prepare a blank, 1, the top of the sheet, substantially conforming to the top of the mattress, and having length and width, respectively, of approximately X and Y, and having also slightly rounded corners. A second blank, 2, the sheet skirt, is also prepared of length L, sufficient to encompass mattress periphery L, and of width (Z+N) where Z is the mattress depth and N the excess depth of skirt depending below the mattress. Blanks 1 and 2 are then attached to each other, as shown in FIGURE 4, starting preferably at the midpoint of one end of blank 1. The differentially tensioned elastic means may be attached to skirt, 2, at edge, 3, either before or after this operation.
We shall designate by E the length of relaxed elastic band, 7, of FIGURE 3, which is also the peripheral length of skirt edge, 3, when fully relaxed, off the mattress, in cooperation with the elastic means. The length of the substantially rectangular periphery, 6, of FIGURE 2, shall be designated as A. It can be then appreciated that the excess enfolded skirt edge, the major portion of which is in corner gathers, 5, of FIGURE 2, will be (L-A). The skirt edge when fully relaxed off the mattress in cooperation with the elastic means will contain an additional excess of skirt edge (AE) distributed, in gathers, about its periphery, but substantially disappearing when the sheet is relaxed upon the mattress. The excess gathering (L-A), predominantly in gathers, 5, of FIGURE 2, will in turn substantially disappear upon full extension of the sheet. To accomplish this a length of elastic E of segments: a, each corner; b, each side; and 0, each end, is differentially extended and attached to the corresponding segments of skirt perimeter, L respectively: Pa, each corner; Rb, each side; and Re, each end, whereby the respective dimensions when relaxed upon the mattress about periphery A, will be Qa, Qb, and Qc.
4 symbolically then: (1) E=4a+2b+2c (2) L=4Pa+2Rb+2Rc and (3) A=QE=4Qa+2Qb+2Qc where P, in this illustration, is the maximum extensibility of the elastic, i.e., the ratio of the maxlmum extension of E to E; Q is the ratio,
where K is the decimal percent of excess (L'-A) taken up in corners a and will have a value within the range .60 to 1.0, although preferably it will lie between .90 and While arbitrarily the segments b and 0 may be positioned between corners a, it is also useful to calculate them by Equations 7, below, which will determine each a as symmetrical at each corner:
Y c= a where X and Y are equal, respectively, to (X -2N and (Y2N) In a preferred form of this invention wherein each a is asymmetrically positioned, the side and end segments can be calculated by Equations 8, below:
The peripheral length A, necessary for the above calculations, may be approximately predicted, and so used, by the formula,
In the fabrication of the differentially tensioned elastic means as constructed by this mode of practice of our invention, then, there is selected a length of elastic E of lesser relaxed length than A, and with extensibility P such that PE is greater than L. The calculated corner, side, and end segments of E: a, b, and c, are then stretched, respectively, to lengths: Pa, Rb, and Re, and attached to equal and corresponding segments of skirt edge length L. For highly elastic hands it may in some cases be found desirable to use as the working value of P a value P which will be, while still sufiicient to ensure that PE will be greater than L, somewhat less (in general, up to 10 percent) than the actual maximum extensibility of the elastic, thus decreasing the strain upon the elastic during fitting and removal of the sheet. In either case the elastic at the extended corners will be under maximum relative tension with respect to the side and end segments. The differentially tensioned elastic means formed by this operation will, when relaxed upon the mattress, have peripheral length A with corner, side, and end segments, respectively, of lengths Qa, Qb, and Qc. One manner of practicing this teaching is illustrated in FIGURE 6 to be referred to below,
The differential tensioning thus is apparent upon fitting of the sheet, upon its removal from the mattress, or, in fact, upon any displacement from the position of equilibium when upon the mattress. When relaxed upon the mattress the elastic means is under substantially equal extension (Q) throughout. Stress and strain will be equally distributed throughout peripheral length A. The gathering in the corners comprising the major portion of the excess enfolded sheet edge tends to form non-creeping corner pockets very resistant to displacement. By means of this gathering the bagging at the sides is largely eliminated and the sheet will be very close fitting. The corner gathering and the elastic means also cooperate to cause the sides to be reliably self-tucking. Upon extension of the corners, the gathering substantially disappears and the sheets are readily fitted or removed without distortion or deformation of the mattress and may indeed even be applied with a person lying on the mattress, as is necessary in a sheet for hospital use. Since the potential extensibility is predominately in the corners, the extension necessary for removal is not evenly dis tributed about peripheral length A but is concentrated at the corners being manipulated, where the excess gathering cooperates to relieve strain upon the relatively nonextensible sheet material. Conversely, when the corners are fully extended, the elastic at the corners, which is under maximum relative extension, cooperates With the adjacent side and end elastic segments to urge itself with maximum relative tension to revert to the relaxed position upon the mattress. As as additional advantage, this results in the corners being resistant to displacement by tugging as, for example, by an infant in a crib.
The general description set forth to this point is applicable to the manufacture of sheets, or covers, for mattresses, or the like, of all sizes. For a particular mattress it is necessary only to measure the dimensions X, Y, Z, and L; determine the value of P, for the elastic; and select the values N, K, and Q or E, in order to use the above equations in the construction of the sheet. As has already been stated, K, the decimal percent of excess (LA) gathered in the corners, may be in the range .60 to 1.0 and is preferably within the range .90 to 1.0. A value of .95 for K will be satisfactory for most purposes. The value for N should be less than A of Y, the width of the mattress, and is preferably within the range .11Y to .19Y with .15Y being generally satisfactory. Thus for the average crib mattress N Would preferably be Within the range 3 to 5 inches, with 4 inches being generally satisfactory. The value of Q will be determined within the limits defined by the requirements that E be less than A and that PE, or PE, be greater than L. Thus, broadly, Q must be greater than 1.0 and less than and, in general, we have found values of Q in the range 1.1 to 1.3 to be satisfactory, with a value of 1.2 being preferred. Discrepancies which may be introduced by rounded mattress corners and edges, slightly bulging tops and bottoms, etc., have been found to be negligible and will not seriously affect the validity of the calculations. The value of A, for example, calculated, according to Equation 9, as an intermediate value for subsequent calculations, has been found to agree very closely with the actual length of the substantially rectangular periphery, 6, of FIGURE 2, in sheets fabricated according to the teachings of this invention.
The following example which is presented to illustrate a specific embodiment of our invention will be described with reference to a crib mattress with slightly rounded corners and having dimensions: X equals 52 inches; Y equals 27 inches; Z equals 5 inches; and L equals 152.5 inches. As indicated above, and for purposes of clarity,
inclusion of hem and seam allowances, etc. is omitted, although it is to be understood that such allowances have been made and must be made in practice.
' A rectangular blank is prepared of area (LX (Z+N)) equal to 152.5 X9 inches, with -N selected as 4 inches. This will form the skirt of the sheet and it will be noted that here L equals L. A length of elastic band, B, equal to inches, and having an extensibility P of 1.8, is also prepared. Since, from Equation 9, A is 126 inches, Q will equal 1.2, a generally satisfactory working value from which E may conversely be calculated. K is selected to be .95 and the Working value of P, P, will be 1.7. From Equations 5, 6, and 8: a equals'9.4; Pa equals 16; b equals 23.5; Rb equals 30.8; c equals 10.2; and R0 equals 13.4 inches.
Reference should here be made to FIGURE 6 which illustrates schematically the process of differentially extending thelength E of elastic band, 7, to correspond to the length L of edge, 3, of skirt blank, 2. Since the skirt blank, in this embodiment of our inveniion, is to be attached to the top blank with the initial attachment being at the midpoint of one end, as shown in FIGURE 4, it is necessary to begin the differential extension of length E, 7, at the midpoint of an end segment 0. Accordingly, as shown in FIGURE 6 with the differential extending being indicated by arrows, and starting at one end: &0 inches of elastic are extended to /2Rc' inches and attached to /2 Rc' inches of skirt edge; the next a inches of elastic are extended to Pa inches and attached to the next Pa inches of skirt edge; the next b inches of elastic are extended to Rb inches and attached to the next Rb inches of skirt edge; and so forth until the differentially extended elastic is completely attached to the skirt edge. By means of suitable indicia, prepared beforehand upon skirt edge and elastic band, the matching and attachment of their respective lengths is very efficiently and rapidly performed. Continuous lengths may be prepared in this matter and then cut into individual skirt lengths.
A second blank is prepared conforming to the top plan of the mattress, 27 x 52 inches, and having slightly rounded corners so as to have an edge perimeter of 152.5 inches. To this top blank the skirt blank is properly positioned and attached, in the manner shown in FIGURE 4, and along the edge opposite the differentially tensioned elastic means. By use of contrasting colors or prints for skirt and top, and/or by use of a decorative tape to bind the top seam, aesthetically pleasing effects may be given to the sheet.
While the foregoing example describes a preferred embodiment, the teachings of this invention are applicable to other forms of sheet and cover construction, within the limitations of the present disclosure. (For example, a sheet of the conventional open box type may be made from a single rectangular blank with square cut-out corner portions, the fabrication of which is shown in FIG- URE 5, the elastic then being differentially extended and attached to the free edge, 3.
Although, for reasons of economy, sheets may be fabricated according to the teachings of our invention where in the end and side elastic segments are omitted, corner elastic segments only being employed to take up substantially all of the excess enfolded skirt edge, we have found that sheets so constructed are not as generally satisfactory as those described heretofore in this specification. In the fabrication of such an embodiment of our invention, Equation 6, above, may be used with the value K omitted or set substantially equal to 1.0. The remaining equations may then, if desired, be employed for purposes of positioning the corner segments.
It is within the scope of this invention, although particular reference has been made to fitted sheets, to provide covers, and a process of making them, for any solid object having, at the bottom to be enfolded by the cover, an approximately rectangular configuration. It is also within the scope of this invention to provide covers for objects more or less regular than mattresses, including pads, cushions, and seats.
1. A self-tucking cover for a mattress, or the like, comprising: a top substantially conforming to the top of said mattress; a skirt substantially conforming to the periphery of said mattress and depending in depth below said mattress, said skirt having a free peripheral edge; difierentially tensioned elastic means attached to said edge, said elastic means when fully extended in cooperation with said edge being of substantially equal peripheral length therewith; extensible corner elastic segments of said elastic means, and cooperating respectively therewith relative- 1y inextensible corner segments of said edge, each of said corner edge segments being of substantially greater length than the corresponding corner elastic segments when said corner elastic segments are fully relaxed, said corner elastic segments when fully relaxed in cooperation with corresponding corner edge segments being of relatively greater extensibility than the remainder of said elastic means when said remainder is fully relaxed in cooperation with the remainder of said edge, whereby said elastic means may be differentially extended in cooperation with said edge.
2. The structure of claim 1 in which said elastic means further includes extensible side and end elastic segments and said peripheral edge further includes relatively inextensible side and end edge segments respectively coop erating with said elastic segments, each of said edge segments being of substantially greater length than the corresponding extensible elastic segments when said extensible elastic segments are fully relaxed.
3. A self-tucking cover for a mattress, or the like, comprising: a top substantially conforming to the top of said mattress; a skirt substantially conforming to the periphery of said mattress and depending in depth below said mattress, said skirthaving a free peripheral edge; difierentially tensioned elastic means attached to said edge, said elastic means when fully extended in cooperation with said edge being of substantially equal peripheral length therewith; extensible corner, side, and end elastic segments of said elastic means, and cooperating respectively therewith relatively inextensible corner, side, and end edge segments of said edge, each of said edge segments being of substantially greater length than corresponding extensible elastic segments when said extensible elastic segments are fully relaxed, said corner elastic segments fully relaxed in cooperation with corresponding edge segments being of relatively greater extensibility than said extensible side and end elastic segments fully relaxed in cooperation with corresponding edge segments, whereby said elastic means may be differentially extended in cooperation with said edge, said elastic means when relaxed upon said mattress in cooperation with said edge being under substantially equal extension throughout the periphery thus formed, whereby the major portion of excess enfolded skirt edge will be gathered by said corner segments.
4. A self-tucking cover for a mattress, or thelike, comprising: a top substantially conforming to the top of said mattress; a skirt substantially conforming to the periphery of said matress and depending in depth below said mattress, said skirt having a free peripheral edge; differentially tensioned elastic means attached to said edge, said elastic means when fully extended in cooperation with said edge being of substantially equal peripheral length therewith; extensible corner, side, and end elastic segments of said elastic means, and cooperating respectively therewith relatively inextensible corner, side, and end edge segments of said edge, each of said edge segments being of substantially greater length than corresponding extensible elastic segments when said extensible elastic segments are fully relaxed, said corner elastic segments fully relaxed in cooperation with corresponding edge segments being of relatively greater extensibility than said extensible side and end elastic segments fully relaxed in cooperation with corresponding edge segments, whereby said elastic means may be differentially extended in cooperation with said edge, said elastic means when relaxed upon said mattress in cooperation with said edge being under substantially equal extension throughout the periphery thus formed, whereby 90100% of excess enfolded skirt edge will be gathered by said corner segments.
References Cited in the file of this patent UNITED STATES PATENTS 815,056 Leotard Mar. 13, 1906 2,528,313 Kessler Oct. 31, 1950 2,624,893 Harris Jan. 13, 1953 2,633,574 Dolan Apr. 7, 1953 2,696,872 Kurland et al Dec. 14, 1954