Abstract:
A sheet anchoring system is provided to restrain the periphery of a fitted sheet on a bed, where the sheet anchoring system includes a plurality of pivotable clips each having a first end and a second end with engaging friction surfaces to grasp between the surfaces a portion of the periphery of the sheet without the need for a spring or other force-biasing mechanism. The second end also has engaging surfaces forced into engagement by the weight of the mattress on top of the second end when the second end is placed between the mattress and a box spring below the mattress.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application 61/622,344 filed on Apr. 10, 2012 which is incorporated by reference. 
     FIELD OF THE INVENTION 
     This invention relates to devices that can hold down bed sheets. 
     BACKGROUND OF THE INVENTION 
     The problem of bed sheets being pulled from underneath a mattress is well-known. Movement on the bed causes the bed sheets to collapse toward the movement, pull the bed sheet from under the mattress. 
     Prior to the disclosed invention devices that held down bed sheets required elaborate systems were ineffective at keeping sheets from moving or risked injuring the user. The present invention solves this problem with a scissor clamp. The prior art includes: U.S. Pat. No. 7,698,759 issued to Frasier; U.S. Pat. No. 7,152,260 issued to Ota; and U.S. Pat. No. 4,541,137 issued to Murray. 
     Frasier teaches a bed sheet securing assembly comprising a scissor clamp that locks and unlocks a clamp that secures a bed sheet to a bed post. Here the scissor clamp is not directly holding the bed sheet, rather a spring clamp is. Ota teaches buckle clamp that can be used to hold down a bed sheet but does not teach a scissor clamp. Murray teaches another variety of spring clamp, but does not teach a scissor clamp. 
     BRIEF SUMMARY OF THE INVENTION 
     In one embodiment of the invention, a sheet anchoring system is provided that is configured to restrain the periphery of a fitted sheet on a bed. The sheet anchoring system may comprise, for example, a plurality of pivotable clips each having a first end and a second end, the first end comprising engaging friction surfaces configured to grasp between the surfaces a portion of the periphery of the sheet, the second end comprising engaging surfaces configured to be forced into engagement when in use by the weight of the mattress on top of the second end when the second end is placed between the mattress and a box spring below the mattress, the pivotable clips configured to securely restrain movement of the sheet periphery during use without the need for a spring or other force-biasing mechanism to maintain the friction surfaces of the first end in engagement with the sheet therebetween, the friction surfaces comprising a material having a coefficient of friction sufficient to restrain movement of the sheet from between the surfaces of the first end when in use. The first end may be configured in any number of possible shapes. For example, the first end surfaces may comprise a generally arcuate shape. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  is a perspective view of an embodiment of the invention shown in use. 
         FIG. 2  is an exploded perspective view of an embodiment of the invention shown in use. 
         FIG. 3  is a perspective view of an embodiment of the invention. 
         FIG. 4  is an exploded perspective view of an embodiment of the invention. 
         FIG. 5  is a detailed section view of an embodiment of the invention taken along line  5 - 5  in  FIG. 1 . 
         FIG. 6  is a section view of an embodiment of the invention taken along line  6 - 6  in  FIG. 3 . 
         FIG. 7  is a side view of an embodiment of the invention shown in the open position. 
         FIG. 8  is a side view of an embodiment of the invention shown in the closed position. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention overcome many of the obstacles associated with holding down bed sheets, and now will be described more fully hereinafter with reference to the accompanying drawings that show some, but not all embodiments of the claimed inventions. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. 
       FIG. 1  shows sheet anchor  10  in use. User  38  sleeps on a bed that includes mattress  28  atop box spring  30 . Mattress  28  is covered by fitted sheet  32 . Fitted sheet  32  can be covered by flat sheet  34  and blanket  36 . User  34  desires to sleep on a bed without pulling fitted sheet  32 , flat sheet  34  or blanket  36  from between mattress  28  and box spring  30 . Sheet anchor  10  can accomplish this. 
       FIG. 3  and  FIG. 4  show sheet anchor  10  in more detail. Sheet anchor  10  comprises first anchor plate  12  rotationally coupled to second anchor plate  14  with rivet  22 . 
     First anchor plate  12  comprises first flat end  18 , where first flat end  18  is mechanically coupled to first flat end grip material  26 . First flat end  18  is mechanically coupled to a first shank offset by first offset section  16 . The remainder of the first shank is mechanically coupled to first curved end plate  20 . First curved end plate  20  is mechanically coupled to first curved end plate outer grip material  24  and first curved end plate inner grip material  24 . In some embodiments the curved end plates can be arcuate shaped. 
     Second anchor plate  14  comprises second flat end  18 , where second flat end  18  is mechanically coupled to second flat end grip material  26 . Second flat end  18  is mechanically coupled to a second shank offset by second offset section  16 . The remainder of the second shank is mechanically coupled to first curved end plate  20 . Second curved end plate  20  is mechanically coupled to second curved end plate outer grip material  24  and second curved end plate inner grip material  24 . 
       FIG. 6  and  FIG. 7  show the assembled sheet anchor in motion. As a user separates first flat end  18  from second flat end  18 , first curved end plate  20  moves ultimate second curved end plate  20 . In one embodiment, first offset section  16  and second offset section  16  are slightly proximate first curved end plate  20  and second curved end plate  20  while being slightly ultimate first flat end  18  and second flat end  18  respectively in order to allow for greater force and leverage to be upon sheet  32  as shown in  FIG. 2 , and  FIG. 5 . In this regard, the first end is configured at an angle from the second end. 
     Usage of sheet anchor  10  is shown in  FIG. 2  and  FIG. 5 . User  38  inserts fitted sheet  32  between first curved end plate  20  and second curved end plate  20 . The user then compresses first curved end plate  20  toward second curved end plate  20  such that first curved end plate inner grip material  24  and second curved end plate inner grip material  24  hold sheet  32  firmly. Next, the user slides first curved end plate  20  and second curved end plate  20  into opening  36  between mattress  28  and box spring  30  such that first flat end grip material  26  and second flat end grip material  26  create friction against mattress  28  and box spring  30  sufficient to prevent user  34  from pulling sheet anchor  10  from opening  36 . 
     One of the useful features of sheet anchor  10  is the ability to utilize a variety of components to high coefficient of static friction (μ s ) with regard to both moving sheet anchor  10  from opening  36  (μ sa ) and moving flat sheet  32  from between first curved end plate  20  and second curved end plate  20  (μ ss ). In particular μ sa  can be maximized by using a first material for first flat end grip material  26 , second flat end grip material  26 , first curved end plate outer grip material  24  and second curved end plate outer grip material  24  where the coefficient of static friction of the first material against the material used to make the outer surface of mattress  28  and box spring  30  is at least 0.4. Likewise, μ ss  can be maximized by using a second material for first curved end plate inner grip material  24  and second curved end plate inner grip material  24  where the coefficient of static friction of the second material against the material used to make flat sheet  32  is at least 0.5. The first material and the second material, do not necessarily have to be the same material, but rubber has been effective for both materials in some embodiments. 
     A sheet anchoring system can be made by using at least one, and in some cases more sheet anchors  10 . For instance, a single sheet anchor  10  can be used at the foot of a bed. In another embodiment a first sheet anchor  10  can be placed in a first corner at the foot of a bed and a second sheet anchor  10  can be placed in a second corner at the foot of a bed. In another embodiment a first sheet anchor  10  can be placed in a first corner at the foot of a bed, a second sheet anchor  10  can be placed in a second corner at the foot of a bed, a third sheet anchor  10  can be placed in a third corner at the head of a bed and a fourth sheet anchor can be placed in a fourth corner at the head of a bed. 
     As shown in  FIG. 1 , a first sheet anchor  10  can be placed in a first corner at the foot of a bed, a second sheet anchor  10  can be placed in a second corner at the foot of a bed, a third sheet anchor  10  can be placed in a third corner at the head of a bed and a fourth sheet anchor  10  can be placed in a fourth corner at the head of a bed. Further, fitted sheet  34  and blanket  36  are held at a foot of the bed with fifth sheet anchor  10  and sixth sheet anchor  10 . 
     In an alternative embodiment, it may be desired to maintain the periphery of the sheet in a vertical orientation along the side of the bed, rather than tucked in between the mattress and the box-spring. In such an arrangement, the first and second ends of the clips may be oriented at an angle, preferably about or about 90 degrees, but other angles may be acceptable. In such an arrangement, when the second end of the clip is placed between the mattress and the box-spring (or whatever other physical unit is supporting the mattress), the weight of the mattress on the second end of the clip forces the surfaces of the first end to tightly grasp the periphery of the sheet in a generally vertical or other non-horizontal orientation.