Abstract:
A hammock includes a bed made of a rectangular piece of fabric, whose ends are gathered together and secured to ropes which can be tied to respective trees. A ridge cord extends between the gathered ends, this cord being shorter than the fabric bed, so that the bed sags somewhat no matter how much tension is applied to the ropes. An entrance slit extending about half the length of the hammock allows one to enter from below. The hammock has a lozenge shape when it is viewed from the top and may be covered by a lozenge-shaped canopy.

Description:
This application is a division of U.S. patent application Ser. No. 09/262,448, filed Mar. 4, 1999, now U.S. Pat. No. 6,185 763. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to hammocks, particularly a hammock having a ridge cord providing a predictable sag in the hammock fabric. 
     BACKGROUND OF THE INVENTION 
     For camping and other recreational activities, different hammocks have been developed to provide shelter from insects, ground dwelling creatures and inclement weather. Being suspended above the ground, hammocks provide a more comfortable, dry, warm and clean surface than do tents. 
     Existing hammocks are entered by climbing over one side. This is difficult and sometimes dangerous, because the hammock is out of balance when a person enters it. The potential occupant pushes down one of the sides of the hammock, as low as possible, towards its longitudinal axis of symmetry, to allow his access. As soon as the occupant sits down and his weight comes off his feet, the hammock swings back into its original position, tumbling the occupant backwards, and sometimes out of the hammock. 
     The entrance in an enclosed hammock, which is usually between the bed and insect net, is normally closed by a zipper. The zipper is tensioned and is easily damaged, if it is not fully opened before entry. If the zipper is damaged the hammock can no longer provide protection from insects. It is known also that a zipper in an enclosed hammock is its most vulnerable feature. In known hammock designs, where each suspending rope is attached to the hammock through a sewn sleeve at each end, all of the occupant&#39;s weight is transmitted to the stitches of the sewn sleeve. If one or several stitches are overloaded, they can fail and the entire stitching can unravel under the weight of the occupant. If the stitching is stronger than the fabric fibers, concentration of tension at one point may cause the material to fail, starting a tear which can open quickly and not stop until the occupant reaches the ground. 
     Hammock sag until now had to be adjusted by trial and error, by adjusting the suspending ropes while tying them to their anchors. If the suspending ropes at each end of the hammock are attached so that too much slack is present, the resulting sag will also be increased. In this situation, the occupant will be bent, and hence in an uncomfortable position. If the suspending ropes at each end of the hammock are pulled too tightly, the sag will be reduced too much. In this situation, trying to climb into the hammock is difficult and dangerous. 
     Hammocks of rectangular and trapezoidal shape are known. They allow a relatively to restricted movement of occupant&#39;s arms and hands and they do not comply with the requirement that at the middle of the hammock, where the occupant is wider, the hammock must be wider as well. Attempts have been made to address and solve the above existing concerns. But it is apparent that up to the present time, there remains important shortcomings in hammocks. 
     U.S. Pat. No. 5,038,428 discloses a pillow and a slit added to an otherwise conventional hammock. The pillow is mounted atop the hammock, adjacent to the longitudinal edge mid-length of the hammock, so that the transverse axis of symmetry of hammock bisects the pillow. The incision has a predetermined longitudinal extent and is also positioned mid-length of the hammock and is bisected by the transverse axis of symmetry. The pillow and slit are on opposite sides of the longitudinal axis of symmetry of the hammock. A first individual standing in the incision may massage a second recumbent individual, whose head is supported by the pillow and whose feet may extend below the hammock or may rest atop the hammock on opposite sides of the first individual. The disclosed hammock is not designed for general use, but for a very specific one. The central location of the incision on one side of the longitudinal of symmetry of the hammock, does not allow a proper entry for the occupant. 
     U.S. Pat. No. 4,686,720 discloses a hammock comprising a lower support which is sewn to an upper cover. The lower support is cut in a trapezoidal shape and the wide part is intended to accommodate occupant&#39;s head and shoulder, the narrow lateral end being slightly gathered. A strip of fabric is sewn to the gathered fabric. The strip as well as the material of the lower fabric support, at the wide end, is folded over twice, sewn down and grommets are placed at intervals in the folded strip. A shortcoming of this hammock is that the trapezoidal form of the lower support does give the occupant a sense of space in the middle of the hammock and restricts movement of his arms and hands. 
     U.S. Pat. No. 4,001,902 discloses a combination comprising a hammock, an insulated sleeping bag and a tent. The hammock consists of a cloth of rectangular shape with a pocket, loop or similar device at each end, to accommodate a spreader bar of rigid material, such as wood or light metal. Attached at two or more points to each spreader bar is a stringing assembly of approximately 4′ to 5′ in length which leads to a single point, such as a metal ring, which, in turn, is attached by a rope to a tree. The tent is held in position over the hammock and sleeping bag by a separate ridge cord attached to the same trees. As can be seen, the manner of attaching the combination bed and shelter, by using a pocket or loop at the end of the hammock, a spreader bar and a stringing assembly, is complicated. 
     SUMMARY OF THE INVENTION 
     The present invention is directed, broadly, to a hammock which includes a bed having an entrance slit, situated in the same vertical plane as its longitudinal axis of symmetry and located on one side of its center of symmetry. 
     This bed includes as well a self-closing feature for the entrance slit, located at midpoint of its short side, where said entrance begins. 
     This bed comprises as well a bundle of gathered folds, situated at both ends and made of each short side of a rectangular sheet which forms the bed. The bundle of gathered folds is used to fasten the hammock by suspending ropes to anchors. 
     This bed includes a ridge cord for adjusting the sag of the hammock. The ridge cord extends in the vertical plane, which contains the longitudinal axis of symmetry, and goes through each opposite bundle of gathered folds, where it is connected to each suspending rope. 
     A side adjustment cord of the rectangular sheet has one end attached to the middle of each longitudinal side of the rectangular sheet, the other end being fastened to a fixed element, one side adjustment cord being provided at each side of the hammock. 
     This hammock has a lozenge shape as viewed from the top. This shape is formed when opposite side adjustment cords are outwardly stretched and opposite suspending ropes are tensioned. This bed has a canopy cut in a lozenge form from a sheet of material. At each side of the canopy, where two concurrent edges of the lozenge form intersect the transversal axis of symmetry, an adjustably extending cord is attached. 
     In one aspect of this invention, the hammock has a bed which includes an entrance slit, situated in the same vertical plane as its longitudinal axis of symmetry and located on one side of its center of symmetry. The entrance slit extends from one of the short sides of the rectangular sheet of the flexible material from which it is made to a point short of its center of symmetry. The above disclosed bed of this hammock comprises as well a self-closing feature which is obtained by folding together several times, and then, holding in place, the edges of the entrance slit close to the corresponding short side of the substantially rectangular sheet of material, where the slit extends. 
     In another aspect of the invention, the hammock has a bed including a number of gathered folds, situated at both of its ends and made of each short side of a substantially is rectangular sheet which forms the bed. The bundle of gathered folds is used to fasten the hammock by suspending ropes to anchors. The bundle of gathered folds is made of each short side of the substantially regular sheet, which short side is folded several times parallel to the longitudinal axis of the rectangular sheet. The first fold is made towards the longitudinal axis and consists essentially of two layers, followed by a second fold of four layers, then eight layers and, finally, sixteen layers. Two resulting bundles of sixteen layers are folded together to form one bundle of gathered folds of thirty two layers of material, which are fastened together permanently, and in which one or more holes for suspending ropes are made. An accordion type of folding is an alternative solution. The folds of this accordion type of folding are fastened permanently and provided with one or more holes for attaching suspending ropes In another aspect of the invention, the hammock comprises a bed which includes for adjusting its sag, a ridge cord extending in a vertical plane, which plane includes the hammock&#39;s longitudinal axis of symmetry and going to the hammock ends, where is adapted to be attached individually to suspending ropes. 
     In another aspect of the invention, the hammock comprises a bed which includes for adjusting its sag, a ridge cord extending in a vertical plane, which plane includes the hammock&#39;s longitudinal axis of symmetry and going to the hammock ends, where it is adapted to be attached individually to suspending ropes. In another aspect of this invention, the hammock comprises a bed including, for adjusting its sag, a ridge cord extending in a vertical plane, which plane includes the hammock&#39;s longitudinal axis of symmetry and, after passing throughout each of the hammock&#39;s ends, where it is fastened, continues as a suspending rope. 
     This bed has, for altering its sag, according to individual comfort requirements, a workable adjustable length. The adjustment is obtained by untying one end of the ridge cord and retying again to a shorter or longer length. An adjustment device is used in combination with a part of the ridge cord which is intended as a slacked portion. This part is unwrapped or wrapped accordingly around the sag adjustment device, when the ridge cord is not under tension. This way, the extension of the slacked portion and consequently, the resulting number of subtracted or added wraps determines the workable length of the ridge cord. 
     In another aspect of this invention, the hammock comprises a bed including a side adjustment cord attached at one end to the middle of each longitudinal side of a substantially rectangular sheet from one which the bed is made, the other end being fastened to a fixed element. The adjustment cordis provided at each side of the hammock. 
     This hammock has a lozenge shape, viewed from the top, formed when opposite side adjustment cords are outwardly stretched and opposite suspending ropes of the hammock are tensioned. In another aspect of this invention, the hammock comprises a bed which includes a canopy made in a lozenge form from a sheet of substantially synthetic material, to which canopy an adjustably extending cord is attached with one end where two concurrent edges of the lozenge intersect the transverse axis of the sheet from which the canopy is made. The other end of the adjustably extendible cord is joined to a fixed feature. Each two concurrent edges of the lozenge form sheet, at their point of intersection with the longitudinal axis of the sheet, is attached to a suspending rope of the hammock. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The concept and practical aspects of the invention are apparent from the purely exemplary, and therefore not restrictive, embodiments illustrated in the following examples, in which; 
     FIG. 1 illustrates schematically a side elevation of the hammock comprising the bed, insect net and canopy; 
     FIG. 2 illustrates schematically a top view which depicts the lozenge form of the bed, insect net and canopy; 
     FIG. 3 illustrates schematically a plan view of the bed with its lozenge form and the initial rectangular sheet of material, from which the bed is made; 
     FIGS. 4 to  9  illustrate a sequence of end view schematic elevations depicting the operational steps for making the bundle of gathered folds; 
     FIG. 10 illustrates a schematic side elevation of the bundle of gathered folds provided with holes; 
     FIGS. 11 to  13  illustrates schematically side elevation of the bed using different adjustments of the ridge cord for modifying the sag of the bed; 
     FIG. 14 illustrates schematically a side elevation of the sag adjustment device; 
     FIG. 15 illustrates schematically a side view elevation of the adjustment device with a slacked portion of the ridge cord before wrapping; 
     FIG. 16 illustrates schematically a side elevation view of the sag adjustment device wherein a portion of the ridge cord is pre-wrapped at the factory; and 
     FIG. 17 illustrates schematically a side elevation view of the sag adjustment device with wraps added by the occupant to shorten the ridge cord, hence to increase the sag. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIG. 1, a hammock  10  comprises a bed  12 , an insect net  14 , which is located above bed  12  and is attached along its edge  16  to longitudinal sides  18  of bed  12 . Each end  20  of the bed  12  is joined with a suspending rope  22  to a spaced anchor  24  such as a tree. A canopy  26  overhangs the insect net  14 . Bed  12 , dimensioned to provide accommodation for one or more persons, is made from a substantially rectangular sheet  23  (see FIG. 3) of flexible, breathable material. It must be of sufficient strength and resilience to withstand an appropriate load and repeated use under varying conditions. Nylon, polyester or a synthetic material with similar qualities is used. 
     An entrance slit  30 , situated in the same vertical plane as bed  12 &#39;s longitudinal axis of symmetry A, extends from one of the short sides  32  of a substantially rectangular sheet  28  to a point short of the center of symmetry of bed  12 . The short side  32 , opposite the entrance slit  30 , of rectangular sheet  28  (see FIGS. 4 to  9 ) is folded several times parallel to the longitudinal axis A of sheet  28 . The first fold of two layers of material is made towards the longitudinal axis of sheet  28  (see FIG.  5 ). Then, in the same manner, rectangular sheet  28  is folded in four layers (FIG.  6 ), then in eight layers (FIG. 7) and then, sixteen layers(FIG.  8 ). Finally, each bundle of sixteen layers is folded together to form one bundle of gathered folds  33  (thirty-two layers of material), which is held by a clamp  34  (FIG. 9) and fused by heat or bonded by an adhesive. Then, one or more holes  36  (FIG. 10) are cut or obtained by melting an aperture through the final bundle. A grommet  38  is provided for each hole  36 . 
     Alternatively, an accordion-type of folding can be used. Attachment of each bundle of folds  33  to each suspending rope  22  is achieved by joining a suspending rope  22  directly to its respective bundle  33  with a knot. At the short side  32 , corresponding to entrance slit  30 , the process of folding is somewhat different, including an additional set of folds which provide a self-closing entrance slit  30 . This self-closing is activated and maintained by the weight of the occupant. Here, the sequence of folding is the following: edges  40  of entrance slit  30  (FIG.  3 ), close to the corresponding short side  32 , are folded together several times and held in place. Next, one follows the same operational steps (FIGS. 4 to  9 ), described for short side  32 , opposite to entrance slit  30 . This folding, as described, of edges  40 , prior to the folding of short side  32 , produces, under the weight of the occupant, the self-closing of entrance slit  30 . 
     The operation of the entrance through slit  30  takes place as follows: The occupant either enters head first and turns around inside the hammock, or backs into the entrance slit until the back of his knees contact the low end of entrance slit  30 . Then, the occupant sits down on bed  12 , whose  28  becomes tensioned. As the occupant reclines against bed  12  and, as he lifts his legs off the ground, his entire weight is transmitted to bed  12 . Lastly, the occupant lifts his legs through entrance slit  30 , which closes, providing a bug-proof environment. The edges  40  of entrance slit  30  are folded together and held folded by the weight of the occupant. 
     A ridge cord  42  (FIGS. 11 to  13 ) extends in a vertical plane which includes longitudinal axis A of bed  12  and goes through each opposite bundle of gathered folds  33  and is attached to each suspending rope  22  or, alternatively, the ridge cord  42  can be attached to at least one of holes  36 . Alternatively, when no holes are used, the ridge cord  42  could be attached directly to each bundle of gathered folds. Preferably, the ridge cord  42  continues beyond its points of attachment at each opposite bundle of gathered folds  33  as suspending rope  22 . In order to alter the sag of bed  12 , according to individual comfort requirements, the workable length of ridge cord  42  (FIGS. 11 to  13 ) is adjustable by untying one end of it and retying again to a shorter or longer length. As can be seen in FIGS. 11 to  13 , three examples illustrates a comparison of different adjustments. The distance between anchors  24  is constant. On the left side of all three figures (FIGS. 11 to  13 ), there is one vertical line which constitutes the line of reference. On the right side of all three figures are three vertical lines X, Y and Z. 
     The first example (FIG. 11) is a bed  12  with a ridge cord  42 , whose workable length has been preset at the factory for the comfort requirements of an average user. Notice that ridge cord  42  terminates at line X, between Y and Z. 
     The second example (FIG. 12) is a of bed  12 , where ridge cord  42  terminates at line Y. In this case, the workable length of ridge cord is shorter and the sag of bed  12  is increased. 
     The third example, (FIG.  13 ), is a bed  12  with a longer workable ridge cord  42 . Ridge cord  42  now terminates at line Z. Thus, its length is increased but the sag of bed  12  is reduced. 
     Alternatively, a sag adjustment device  44  (FIGS. 14 to  17 ) is provided. It has, in the presented embodiment, an elongated form with a circular cross section and two transverse holes  46 . The ridge cord  42  passes successively through both transverse holes  46  and a slack portion  48  of ridge cord  42  is left between exit  50  of first hole  46  and entrance  532  of second transverse hole  46 . The part of ridge cord  42 , which constitutes slacked portion  48 , is wrapped, when ridge cord  42  is not under tension, one or more times around either end of the sag adjustment device  44 . The extension of slacked portion  48  and, consequently, the resulting number of added or subtracted wraps has a direct influence on the final workable length of ridge cord  42  and the corresponding amount of sag of bed  12 . The adjustment, shown in FIG. 16, illustrates slacked portion  48 , pre-wrapped at the factory to allow existing wraps to be unwrapped from or to allow additional wraps to be wrapped around sag adjustment device  44 . The second adjustment, shown in FIG. 17, illustrates sag adjustment device  44  with additional wraps of ridge cord  42 , wrapped onto device  44  by the occupant of hammock  10 , to shorten ridge cord  42  and, hence, increase the sag of bed  12 . 
     At approximately the middle of each longitudinal side  54  of the rectangular sheet  28 , an attachment element  56  is secured. The attachment element  56  is normally provided with a grommet (not shown). A side adjustment cord  58  passes through the attachment element  56 . The inner end of side adjustment cord  58  can be provided with means for length adjustment for example a cord lock of known type (not shown). The outer end of side adjustment cord  58  is attached to a fixed element  60 . 
     The insect net  14  is formed from a sheet of substantially lozenge shape of synthetic mesh type material. Polyester or nylon are preferred. The edges  16  of the insect net  14  are attached to longitudinal edges  18  of bed  12 . When the opposite side adjustment cords  58  are outwardly stretched and the suspending ropes  22  are tensioned, the shape of bed  12 , viewed in plan, is a lozenge. The canopy  26  is cut in a lozenge form from a sheet of synthetic material such as nylon or polyester. 
     An adjustably extendible cord  62 , for each side of canopy  26 , is attached with one side where two concurrent edges of the lozenge intersect transverse axis B. The other end of the adjustably extendible cord  62  is joined to a fixed feature  64 . Each two concurrent edges of the lozenge form the sheet of canopy  26  at their point of intersection with longitudinal axis A is attached to a suspending rope  22 . Each length of side adjustment cord  62  can be independently adjusted. Either side of canopy  26  may be flipped over and secured to the other side, to provide coverage on one side only. From that position, both sides of canopy  26  may be rolled together and stored above ridge cord  42  and secured with a ring(not shown) slid from one end to the mid point of said canopy. 
     Since the invention is subject to modifications and variations, it is intended that the foregoing description and the accompanying drawings shall be interpreted as only illustrative of the invention defined by the following claims.