Abstract:
A hammock having a self-closing bottom entrance slit is constructed with the slit substantially offset to one side of the center line of the hammock. This improves comfort by enabling one to lie in the hammock out of contact with the slit, and facilitates the addition of an insulating panel to the hammock.

Description:
FIELD OF THE INVENTION 
     This invention relates to hammocks, particularly to a jungle hammock having a bottom entrance opening. 
     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. 
     Traditional hammocks were entered by climbing over one side. That was difficult and sometimes dangerous, because the hammock was out of balance when a person entered it. The potential occupant pushed down one of the higher sides of the hammock, as low as possible, towards its longitudinal axis of symmetry, to gain access. As soon as the person sat down and his weight came off of his feet, the hammock swung back into its original position, tumbling the person backward, sometimes out of the hammock. 
     In my U.S. Pat. No. 6,185,763—the disclosure of which is incorporated herein by reference—I described a hammock which had a partial entrance slit running from one end of the hammock about half the hammock length, so that one could enter the hammock simply by standing up through the slit from directly beneath one end of the hammock, and then reclining on the unslit portion of the bed. The person&#39;s weight induced lengthwise tension in the fabric, which closed the slit so well that he or she could lie right on the slit and not fall out. I thought at the time that the slit must extend along the longitudinal center plane of the hammock, where the tension forces are the greatest. 
     My U.S. Pat. No. 6,865,757—which is also incorporated herein by reference—discloses a different hammock which is asymmetrical so as to encourage one to lie not along the tension axis established by the ropes at either end, as one does in most hammocks, but rather diagonally across the tension axis. This improves comfort by enabling one to lie diagonally across the tension axis. 
     I have combined the features of these two concepts, by making hammocks which have a bottom entrance slit and which are asymmetrical. These hammocks work as expected, but some users have reported that—particularly in asymmetrical versions where they lie diagonally to the longitudinal direction—lying across the tensioned slit is uncomfortable. 
     Knowing that fabric tension under load is the greatest along the center line of a hammock, I had thought that the slit would have to be centered in the hammock material for it to work; however, I have discovered that, when the occupant changes position from the longitudinal axis to lie on a diagonal axis, tension of the bottom fabric is spread over a wider area, allowing the entrance slit to remain under tension even when offset to one side of the longitudinal axis of the hammock. Moreover, the offset slit will remain closed under tension against all but deliberate opening maneuvers. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to improve the comfort of a hammock having a bottom entrance slit. 
     This and other objects of the invention will be apparent from the drawings and the following description, augmented by the description contained in U.S. Pat. No. 6,185,763, which is incorporated by reference herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a perspective view of a hammock having an entrance slit which bisects the hammock fabric and extends along the tension axis as shown in my U.S. Pat. No. 6,185,763; 
         FIG. 2  is a laid-out view of the fabric portion of the symmetrical  FIG. 1  hammock, showing the centered location of the entrance slit; 
         FIG. 3  is a top plan view thereof, showing the ends gathered and attached to suspending ropes, with a person lying diagonally across the entrance slit; 
         FIG. 4  is a laid-out view of a the fabric portion of a symmetrical hammock according to the present invention, showing a laterally offset entrance slit; 
         FIG. 5  is a top plan view of thereof, again showing the ends gathered and attached to suspending ropes, with a person lying diagonally on the symmetrical hammock but not across the entrance slit; 
         FIG. 6  is a laid-out view of the fabric portion of a modified form of the invention, wherein the slit extends on a bias angle to the length of a symmetrical hammock; 
         FIG. 7  is a top plan view thereof, showing the ends of the fabric gathered and attached to suspending ropes, with a person lying diagonally on the symmetrical hammock but not across the entrance slit; 
         FIG. 8  is a laid out view of the fabric portion of an asymmetrical hammock embodying the invention; and 
         FIG. 9  is a top plan view thereof, showing a person lying diagonally on the asymmetrical hammock. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A hammock  10  embodying the invention comprises a bed  12 , an insect net  14  which is located above the bed and is attached along its edges  16  to longitudinal sides  18  of the bed. Each end  20  of the bed is connected by a suspending rope  22  to one of a pair of spaced anchors  24  such as trees. 
     A canopy  26  overhangs the insect net  14 . Cords  58 ,  62  extending from the midpoint  56  of the bed and canopy, respectively, may be tied to anchors  60 ,  64  to keep the bed and canopy spread out. 
     The bed  12 , dimensioned to provide accommodation for one or more persons, is made from a substantially rectangular sheet  28  (see  FIG. 2 ) 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 fabric with similar qualities is used. 
     An entrance slit  30  extends from one of the short sides  32  of a substantially rectangular sheet  28  for about half the length of the bed. The short sides  32  of the rectangular sheet  28  are folded several times parallel to the longitudinal axis “T” of sheet  28 . This gathering of the bed material is described in detail in U.S. Pat. No. 6,185,763. 
     To enter the hammock, a person crouches or stoops so that he is directly below the hammock slit, and then stands up through the slit, either entering head first and turning around inside the hammock, or backing in until the back of his knees contact the low end of entrance slit  30 . Then, the person sits down on the unslit portion of the bed  12 , which tensions the sheet  28 , particularly the lengthwise (warp) threads. 
     As the person reclines against the bed  12 , lifting the legs off the ground, his entire weight is supported by tension in the fabric. Consequence, as the occupant lifts his legs through entrance slit  30 , the slit snaps close under tension, providing secure support and a bug-proof environment. 
       FIGS. 1-3  are labeled “PRIOR ART” because the entrance slit in each of them is centered on the fabric and extends along the tension axis “T” of the hammock, as taught by U.S. Pat. No. 6,185,763. The improvement provided by the present invention is depicted in  FIGS. 4-7 . Because the ends of the hammock fabric are gathered, in  FIG. 4  the slit appears to extend at an angle to the axis “T”, but as one can see in the layout of  FIG. 5 , actually it is cut parallel to, but laterally offset from, the axis “T”. Preferably, the slit lies to one side of at least 60% of the width “W” of the fabric, more preferably 60%-80%, most preferably about 70%. 
     In the example of  FIGS. 6 and 7 , the slit actually is cut at a bias, diagonally with respect to the tension axis and the warp threads of the fabric. The edges of the slit may have to be reinforced in this example to prevent fraying of the fabric edge. The slit in  FIG. 6  is shown to be offset to one side of the center line a substantial amount; however, the amount of offset may vary. 
       FIGS. 8 and 9  show the principles of the invention applied to an asymmetrical hammock. The hammock is termed asymmetrical because, if folded in the tension axis “T”, its sides are not aligned with one another. The asymmetrical shape encourages an occupant to lie diagonally across the tension axis, which provides good support for the lower back. In this case, the slit is offset to the side away from the natural position of the user&#39;s legs. 
     One advantage of the invention is that, as  FIGS. 5 ,  7  and  9  show, a person can lie on the hammock with improved comfort out of contact with the tensioned entrance slit. Another advantage is that an insulation panel  40 , if desired, can be installed diagonally across the bottom of the hammock, beneath the expected user location, without crossing the entrance slit. Both construction and use of an insulated version of the hammock are thus simplified: the insulation panel does not have to have a slit in it, and the user does not have to negotiate an opening in the insulation. 
     Although the hammock has been described above as being made of a woven fabric material, it should be understood that the inventive aspects do not depend on the nature of the material and thus the claims below refer to a “sheet” of material. The material could alternatively be a non-woven fibrous material, a film, foil or other thin, strong and preferably breathable material perhaps yet to be invented. 
     Inasmuch as the invention is subject to many variations and modifications, it is intended that the description and drawings shall be interpreted as merely examples of the invention defined by the claims below.