Patent Publication Number: US-11661792-B2

Title: Rolling shutter slat

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/578,934, filed Oct. 30, 2017, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to rolling shutters and, in particular, to a slat for a rolling shutter that minimizes the profile of the retracted rolling shutter and that may be formed from sheet metal. 
     Rolling shutters are commonly used in commercial, retail and residential applications as doors or to cover windows or other openings. The rolling shutter is made of a series of linked slats that hang from a spindle to cover a doorway, window or other opening of a building or fixture. When not in use, the rolling shutter is retracted by winding the slats about the spindle to form a roll. 
     The shutter slats typically have an upper edge with a hook-shaped engagement track, and a lower edge with a receiving track that forms a pocket for receiving the engagement track. The receiving track commonly comprises a branched structure with two elements—a complementary hook-shape for engaging the hook-shaped engagement track, and a guard that restricts the disengagement of the engagement track from the receiving track. The shutter slats are linked by the slidable engagement of the hook-shaped engagement track of a first slat in the pocket of the receiving track of a second slat, to form a loosely articulated hinge between the slats. An example of a shutter slat design is described in U.S. Pat. No. 8,944,137 to Miller, which is incorporated herein by reference. 
     The opening that is covered by the rolling shutter may be framed by guides or side tracks that keep the slats aligned and secure the rolling shutter within the opening. The rolling shutter incorporates an end retention system for engaging the side tracks. A cavity or a receptacle is typically formed within or adjacent to the receiving track for receiving an end retention device. An example of an end retention system is described in U.S. Pat. No. 8,616,261 to Miller, which is incorporated herein by reference. 
     Shutter slats are commonly manufactured by extrusion to produce the complex geometry and branched structure of the engaging and receiving tracks. Consequently, shutter slats are often made of plastic or relatively soft metals, such as aluminum. It would be preferable to produce the shutter slats from sheet metal, such as sheet steel which is significantly less expensive than aluminum as well as stronger and more resistant to damage. However, steel is difficult to work and the sheet metal cannot readily be formed into the complex profile of the shutter slat. Thus, it would be desirable to develop a shutter slat design and method for producing the slat using sheet metal, such as sheet steel. 
     SUMMARY OF THE INVENTION 
     A slat for a rolling shutter is disclosed, that comprises a single walled, continuous bent sheet that includes a curved body having first and second ends, and first and second sides. An engaging track is formed at the first end, having a first hook-shaped portion comprising a first bend curving toward the second side of the body. A receiving track is formed at the second end, that comprises a guard member and a lip member. The guard member includes a portion of the sheet that is bent over on itself. The lip member extends from the guard member and has a second hook-shaped portion comprising a second bend curving toward the first side of the body. The guard member and the lip member are spaced apart to define an aperture that is sized and shaped to receive the engaging track of another slat. 
     In another embodiment, a slat for a rolling shutter comprises a single walled, continuous bent sheet that includes a curved body having first and second ends, a first side with a convex curvature and a second side with a concave curvature. An engaging track is formed at the first end, having a first hook-shaped portion comprising a first bend curving toward the second side of the body. A receiving track is formed at the second end, comprising a guard member and a lip member. The guard member includes a portion of the sheet that is bent over on itself to form a base and an outer guard wall. The lip member extends from the base of the guard member and has a second hook-shaped portion comprising a bend curving toward the first side of the body. The guard member and the lip member are spaced apart to define an aperture that is sized and shaped to receive the engaging track of another slat. 
     In another embodiment, a slat for a rolling shutter comprises a single walled, continuous bent sheet that includes a curved body having first and second ends, a first side with a convex curvature and a second side with a concave curvature. An engaging track is formed at the first end, having a first hook-shaped portion comprising a first bend curving toward the second side of the body. A receiving track is formed at the second end, comprising a base extending from the second end, and a guard member extending from the base. The guard member includes a portion of the sheet that is bent over on itself. The lip member extends from the guard member and has a second hook-shaped portion comprising a bend curving toward the first side of the body. The base and guard member define an interior space. The guard member and the lip member are spaced apart to define an aperture that is sized and shaped to receive the engaging track of another slat. 
     In another embodiment, a slat for a rolling shutter comprises a single walled, continuous bent sheet that includes a curved body having first and second ends, a first side with a convex curvature and a second side with a concave curvature. An engaging track is formed at the first end, having a first hook-shaped portion comprising a first bend curving toward the second side of the body. A receiving track is formed at the second end, comprising a guard member extending from the second end, and a lip member extending from the guard member and having a second hook-shaped portion comprising a bend curving toward the first side of the body. The guard member and the lip member are spaced apart to define an aperture that is sized and shaped to receive the engaging track of another slat. A separately formed receptacle is coupled to the body adjacent to the receiving track, the receptacle having an interior space. In a further embodiment the first end of the body has a portion that is configured to be complementary to the shape of the receptacle. 
     In another embodiment, a slat for a rolling shutter comprises a bent, unbranched sheet that includes a body having a curvature with a convex side and a concave side, and opposite first and second ends. An engaging track is disposed at the first end of the body, and a receiving track is disposed at the second end of the body. The receiving track includes a guard member and a lip member that are spaced apart to define an aperture that is sized and shaped to receive an engaging track. The receiving track includes a portion of the sheet that is folded over on itself. 
     In another embodiment, a slat for a rolling shutter comprises a bent, unbranched sheet that includes a body having an outward facing side and an inward facing side, and opposite first and second ends. An engaging track is disposed at the first end of the body, and a receiving track is disposed at the second end of the body. The receiving track includes an aperture that is sized and shaped to receive an engaging track. A separately formed receptacle that is sized and shaped to receive an end retention device is coupled to the inward facing side of the body. 
     In another embodiment, a slat for a rolling shutter comprises a bent, unbranched sheet that includes a body having a curvature with opposite outward facing and inward facing sides, and opposite first and second ends, where the outward facing side has a convex curvature and the inward facing side has a concave curvature. An engaging track disposed at the first end of the body and a receiving track disposed at the second end of the body. The receiving track includes an articulation space that is sized and shaped to receive an engaging track through an articulation space aperture, a receptacle sized and shaped to receive an end retention device, and a receptacle aperture. The receptacle aperture and the articulation space aperture open towards opposite facing sides of the body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the disclosure will now be explained in further detail by way of example only with reference to the accompanying figures, in which: 
         FIG.  1    is a side section view of a rolling shutter slat; 
         FIG.  2    is a detail view of the engaging track of the slat of  FIG.  1   ; 
         FIG.  3    is a detail view of the receiving track of the slat of  FIG.  1   ; 
         FIG.  4    is a side section view of two slats according to  FIG.  1   , of a rolling shutter in an extended position; 
         FIG.  5 A  is a side section view of a plurality of slats according to  FIG.  1   , of a rolling shutter in a retracted position; 
         FIG.  5 B  is a side sectional view of a plurality of slats of an alternate embodiment of a rolling shutter in a retracted position; 
         FIG.  6    is a side section view of another embodiment of a rolling shutter slat; 
         FIG.  7    is a detail view of the engaging track of the slat of  FIG.  6   ; 
         FIG.  8    is a detail view of the receiving track of the slat of  FIG.  6   ; 
         FIG.  9    is a side section view of two slats according to  FIG.  6   , of a rolling shutter in an extended position; 
         FIG.  10    is a side section view of a plurality of slats according to  FIG.  6   , of a rolling shutter in a retracted position; 
         FIG.  11    is a side section view of an alternative embodiment of a rolling shutter slat; 
         FIG.  12    is a side section view of an embodiment of a rolling shutter slat having a separately formed receptacle for an end retention system; 
         FIG.  13    is a side section view of another embodiment of a rolling shutter slat for use with a separately formed receptacle; and 
         FIG.  14    is a side sectional view of a rolling shutter slat according to  FIG.  5 B . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS.  1 - 5   , an embodiment of a shutter slat  1  is shown that comprises a single walled slat formed from a continuous, bent unbranched sheet that includes a curved body  2  with an outward facing side  4 , an inward facing side  6 , a first edge or end  8 , and a second edge or end  10 . As shown in  FIG.  1   , curved body  2  may be configured with outward facing side  4  having a convex curvature and inward facing side  6  having a concave curvature. A hooking or engaging track  12  is formed at first edge  8  of body  2 , and a receiving track  14  is formed at second edge  10  of the body. 
     As shown in  FIG.  2   , engaging track  12  includes a hook-shaped portion that comprises a shank  12   a , a bend  12   b , a barb  12   c  and a point  12   d . Bend  12   b  curves back toward inward facing side  6  of body  2 . Engaging track  12  may also include a base  12   e  that extends from first edge  8  at an angle to body  2 . In the embodiment shown in  FIG.  2   , base  12   e  is configured such that engaging track  12  projects beyond (above) the convex curvature of outward facing side  4  of body  2 , and barb  12   c  does not project beyond (below) the concave curvature of inward facing side  6  of the body. In an alternative embodiment, engaging track does not have a base  12   e , and shank  12   a  may simply extend from first edge  8  along the curve of body  2  (not shown). 
     In examples where the engaging track  12  includes a base  12   e  that extends from the first edge  8 , the shank  12   a  extends from the base  12   e , the bend  12   b  extends from the shank  12   a , the barb  12   c  extends from the bend  12   b , and the point  12   d  is the end of the barb  12   c  and/or the terminus of the engaging track  12 . The point  12   d  may also be a first end of the sheet forming shutter slat  1 . 
     In further examples, the engaging track  12  includes a first face  13   a  disposed on the same side of the shutter slat  1  as the outward facing side  4  of the curved body  2 . In some examples, the first face  13   a  extends from the point at which the outward facing side  4  of the curved body  2  ends, for example, at the first edge  8 . The engaging track  12  may also include a second face  13   b  disposed on the same side of the shutter slat as the inward facing side  6  of the curved body  2 . In some examples, the second face  13   b  extends from the point at which the inward facing side  6  of the curved body  2  ends, for example, at the first edge  8 . The point  12   d  marks the place at which the first face  13   a  transitions to the second face  13   b , and vice versa. As can be seen in  FIG.  2   , as the first face  13   a  travels from the first edge  8  and approaches the point  12   d , at least a portion of the first face  13   a  faces the same direction as the inward facing side  6  of the curved body  2 . Similarly, as the second face  13   b  extends from the first edge  8  and approaches the point  12   d , at least a portion of the second face  13   b  faces the same direction as the outward facing side  4  of the curved body  2 . 
     In examples where the base  12   e  extends from first edge  8  at an angle to body  2 , a base angle  12   f  is formed between the outward facing side  4  (i.e., convex curved side) of the curved body  2  and the portion of the first face  13   a  extending along the base  12   e . For example, there may be a bend in the metal sheet between the base  12   e  of the engaging track  12  and the first edge  8  of the body  2 , which forms the base angle  12   f . In some examples, the base angle  12   f  is less than 180°. In further examples, the base angle  12   f  is between about 90° and about 180°. In even further examples, the base angle  12   f  is about 110° to about 140°. 
     As shown in  FIG.  3   , receiving track  14  forms a pocket for receiving the engaging track  12  of another slat, and includes a guard member  16  and lip member  18 . Guard member  16  extends from edge  10  of body  2 , and includes a portion of sheet  1  that is bent over or folded on itself to form an outer guard wall  20 . In one embodiment, the portion of sheet  1  that is bent over on itself forms a bulge or bead, such as terminal loop  22  having a guard articulation surface  24 . In a preferred embodiment, outer guard wall  20  extends along the same convex curvature defined by outward facing side  4  of body  2 , and more preferably, outer guard wall  20  and outward facing side  4  of body  2  form a continuous convex curvature. 
     Lip member  18  extends from guard member  16 , and includes a hook-shaped portion comprising a shank  18   a , a bend  18   b , a barb  18   c  and a point  18   d  that are sized and shaped to engage the engaging track  12  of another slat. Bend  18   b  curves back toward outward facing side  4  of body  2 . In the embodiment shown in  FIG.  3   , lip member  18  extends from the portion of the sheet that is folded on itself, at a point that is proximal to end  10  of body  2 . The hook-shaped portion of lip member  18  has a base  18   e  that is configured such that the lip member projects beyond (below) the concave curvature of inward facing side  6  of body  2 , and barb  18   c  does not project beyond (above) the convex curvature of outward facing side  4  of the body. 
     In some examples, point  18   d  may be the second end of the sheet forming shutter slat  1 . In some examples, the shutter slat  1  is comprised of a single continuous, unbranched sheet extending from point  12   d  of the engaging track  12  to point  18   d  of the receiving track  14 . This is accomplished, in part, by the portion of the guard member  16  that is bent over or folded on itself, which allows the shutter slat  1  to be made of a single continuous sheet of material—e.g., steel—and bent into the desired shape, rather than being manufactured by extrusion. 
     In further examples, the receiving track  14  includes a first face  15   a  disposed on the same side of the shutter slat  1  as the outward facing side  4  of the curved body  2 . In some examples, the first face  15   a  extends from the point at which the outward facing side  4  of the curved body  2  ends, for example, at the second edge  10 . The receiving track  14  may also include a second face  15   b  disposed on the same side of the shutter slat as the inward facing side  6  of the curved body  2 . In some examples, the second face  15   b  extends from the point at which the inward facing side  6  of the curved body  2  ends, for example, at the second edge  10 . The point  18   d  marks the place at which the first face  15   a  transitions to the second face  15   b , and vice versa. As can be seen in  FIG.  3   , as the first face  15   a  travels from the second edge  10  and approaches the point  18   d , at least a portion of the first face  15   a  faces the same direction as the inward facing side  6  of the curved body  2 , for example, as the first face  15   a  traverses the bulge  22 . Similarly, as the second face  15   b  extends from the second edge  10  and approaches the point  18   d , at least a portion of the second face  15   b  faces the same direction as the outward facing side  4  of the curved body  2 . 
     In some examples, where the guard member  16  is bent over on itself, portions of the second face  15   b  may face one another. In further examples, where the guard member  16  is bent over on itself, the second face  15   b  may be bent over in such a way that a portion of the second face  15   b  contacts another portion of the second face  15   b  at a contact point  17 . In further examples, where the guard member  16  is bent over on itself, the bulge  22  is formed by leaving a portion of the second face  15   b  open at a gap  19  between the two points at which the second face  15   b  comes in contact with itself. For example, when the guard member  16  is bent over on itself the portion of the second face  15   b  traversing the guard articulation surface  24  is open such that the gap  19  is formed where the second face  15   b  does not contact itself. 
     Lip member  18  and guard member  16  are spaced apart to form an aperture  26  that is sized and shaped to receive the engaging track  12  of another slat. In one embodiment, point  18   d  of the hook-shaped portion of lip member  18  and guard articulation surface  24  of guard member  16  are spaced apart to form aperture  26 . 
     Lip member  18  and guard member  16  define an interior space within receiving track  14 , that comprises an articulation space  28  formed between the lip member and guard member, that is sized and shaped to receive the hook-shaped portion of the engaging track  12  of another slat. In one embodiment, the interior space within receiving track  14  also includes a receptacle  30  formed between the lip member and guard member, that is sized and shaped to receive an end retention device, such as the screw and washer of an end retention system as described in U.S. Pat. No. 8,616,261. In a preferred embodiment, shank  18   a  of lip member  18  has an interior surface  32 . A shoulder  34  on interior surface  32  divides or separates the interior space within receiving track  14  into articulation space  28  and receptacle  30 , as shown in  FIG.  3   . Shoulder  34  may include a shoulder surface  36  that forms a bearing surface for the movement of the engaging track  12  of another slat within articulation space  28 . In one embodiment, shoulder  34  is formed by an indentation of the sheet in shank  18   a . In some examples, the interior surface  32  of shank  18   a  is a portion of the first face  15   a  of the receiving track  14 . The receptacle  30  may be separated from articulation space  28  by the bulge  22  and the shoulder  34 . In further examples, the receptacle  30  is defined by the portion of the first face  15   a  extending from the bulge  22  to the shoulder  34 . 
     Referring to  FIGS.  4 - 5   , slats  1 ′ and  1 ″ are shown linked together by the engagement of track  12  of slat  1 ″ in receiving track  14  of slat  1 ′ to form a loosely articulated hinge  38 . Guard member  16  of slat  1 ′ limits the movement or articulation of the engaging track  12  of slat  1 ″ within hinge  38  and prevents the accidental disengagement of the two slats. Guard articulation surface  24  of slat  1 ′ (in combination with shoulder surface  36 ) provides a bearing surface for the articulation of engaging track  12  of slat  1 ″ within hinge  38 . Outer guard wall  20  of slat  1 ′ includes a portion of the sheet that is bent over on itself, which provides additional strength and resistance to deformation of guard member  16  from the stress caused by articulation of hinge  38  and provides additional security from external forces that may be applied to hinge. 
     In one embodiment, engaging track  12  and receiving track  14  are configured to reduce the profile of hinge  38  when the rolling shutter is in the retracted position. As shown in  FIGS.  2  and  3   , the shank portion  12   a  of the engaging track  12  has a thickness A. Barb  18   c  of lip member  18  may be offset from guard member  16  by a distance B that is approximately the same as thickness A. As shown in  FIG.  5   , when the linked slats  1 ′ and  1 ″ are wound about a spindle  40  in the retracted position, the offset B allows shank  12   a  of the engaging track  12  of slat  1 ″ to rest at or below (i.e. does not project beyond) the curvature C of outer guard wall  20  of guard member  16  (and outward facing side  4  of body  2 ) of slat  1 ′. This configuration minimizes the height of hinge  38  and reduces the diameter of the roll when the shutter slats are in the retracted position. 
     In another embodiment, engaging track  12  and receiving track  14  are configured to reduce the profile of the hinge  38  when the rolling shutter is in the vertical or extended position. As shown in  FIG.  2   , engaging track  12  may include a base  12   e  that extends from first edge  8  of body  2  at an angle to outward facing side  4 . As shown in  FIG.  4   , when the linked slats  1 ′ and  1 ″ are in an extended position, the angle between base  12   e  of engaging track  12  and outward facing side  4  of body  2  (i.e., base angle  12   f ) may be configured such that engaging track  12  of slat  1 ″does not project beyond the curvature D of outer guard wall  20  of guard member  16  (and outward facing side  4  of body  2 ) of slat  1 ′. In a preferred embodiment, hinge  38  has approximately the same curve as body  2  of slat  1 ′—e.g., as shown in  FIG.  4   , where base  12   e  of engaging track  12  of slat  1 ″ extends approximately along the same curvature D as outer guard wall  20  of guard member  16  and the convex curvature of outward facing side  4  of slat  1 ′. This configuration minimizes any projections or other discontinuities created by hinge  38  in the outer surface of the rolling shutter, that may provide a point for water or debris to collect and intrude into the hinge, or that may reduce security by providing a point to force apart slats at the hinge. 
     The slats are preferably configured such that the hinges of a set of slats wound about a spindle  50  are nested with adjacent hinges  48  to reduce the profile of the rolling shutter in the retracted position. For example, when a set of slats are wound about a spindle  50 , there are multiple windings of slats with each successive winding increasingly distal to the spindle. In the example depicted in  FIG.  5 B  an innermost (or first) winding is comprised of a first series of slats  5 ′, where an engaging track  52 ′ of each slat in the first series of slats  5 ′ couples to the receiving track  54 ′ of the preceding slat, forming a first hinge  48 ′. A second winding is comprised of a second series of slats  5 ″, where the engaging track  52 ″ of each slat in the second series of slats  5 ″ couples to the receiving track  54 ′,  54 ″ of the preceding slat, forming a second hinge  48 ″. The engaging track  52 ″ of the first slat in the second series of slats  5 ″ may be coupled to the receiving track  54 ′ of the last slat in the first series of slats  5 ′. 
     In some examples, the second hinges  48 ″ are nested adjacent to the first hinges  48 ′, that is, each second hinge  48 ″ is positioned circumferentially adjacent to the adjacent first hinge  48 ′ rather than sitting radially adjacent to the first hinge  48 ′. In such examples, the receiving track of a hinge on an outer winding (e.g., the second winding comprised of the second series of slats  5 ″) is adjacent to either the receiving track of a hinge on the immediately preceding winding (e.g., with respect to the second winding, the immediately preceding winding is the first winding comprised of the first series of slats  5 ′) or the engaging track of a hinge on the immediately preceding winding. For example, in the example depicted in  FIG.  5 B , the second hinge  48 ″ is positioned circumferentially adjacent to the first hinge  48 ′ such that the receiving track  54 ″ of the second hinge  48 ″ is adjacent to the receiving track  54 ′ of the first hinge  48 ′. In further such examples, the lip member  518 ″ of the receiving track  54 ″ of the second hinge  48 ″ is adjacent to the base  546 ′ of the receiving track  54 ′ of the first hinge  48 ′ (see further description below of alternative slat embodiment depicted in  FIG.  14   ). Alternatively, as depicted in  FIG.  5 A , the location of the second hinge  38 ″ (assuming an engaging track of another slat were coupled to the receiving track) is positioned circumferentially adjacent to the first hinge  38 ′ such that the receiving track of the second hinge  38 ″ is adjacent to the engaging track of the first hinge  38 ′. In further such examples, the lip member  18 ″ of the receiving track of the second hinge  38 ″ is adjacent to the base  12   e ′ or shank  12   a ′ of the engaging track of the first hinge  38 ′. Alternatively, as depicted in  FIG.  10   , the location of the second hinge  138 ″ (assuming an engaging track of another slat were coupled to the receiving track) is positioned circumferentially adjacent to the first hinge  138 ′ such that the second edge  110 ″ of the second hinge  138 ″ is adjacent to the engaging track of the first hinge  138 ′ (e.g., the second edge  110 ″ of the second hinge  138 ″ is adjacent to the base or shank of the engaging track of the first hinge  138 ′). In other examples, the receiving track of hinge of an outer winding may be disposed between the body of a slat in an immediately preceding winding and the body of a slat in an immediately successive winding. For example, in the example depicted in  FIG.  5 B , the receiving track  54 ″ of the second hinge  48 ″ (i.e., the hinge in the second winding) is disposed between the body of a slat in the first series of slats  5 ′ (i.e., a slat in the immediately preceding first winding) and the body of a slat in an immediately successive third winding. The concepts described above may be expanded to cover sets of slats with any number of windings about a spindle  50 . Additionally, the concepts described above may apply to sets of slats with the same or a different number of slats in each winding and/or where the slats in a given winding have the same or varying lengths. 
     In some examples, the rolling shutter may comprises slats of different lengths to facilitate tight nesting of first and second hinges  48 ′,  48 ″. Those of skill in the art will appreciate that each successive winding of the rolling shutter will increase in circumference. In the example depicted in  FIG.  5 B , the slats in the second series of slats  5 ″ are longer than the slats in the first series of slats  5 ′. In some examples, increasing the length of a slat comprises increasing the length of the body of the slat. In a one embodiment, each winding is comprised of slats of the same length. Furthermore, each winding preferably comprises the same number of slats. However, those of skill in the art will appreciate that alternative rolling shutter configurations are possible where each winding comprises slats of different sizes and/or different numbers of slats. In examples where the hinges in a set of slats are configured to nest, such as the example depicted in  FIG.  5 B , the resulting fully wound set of slats (including all windings in the set) will have a smaller diameter than a set with the same number of slats but with hinges not in a nesting configuration. The smaller diameter, nested configuration, saves manufacturing cost for the housing in which the fully wound set of slats is stored by its ability to be in a smaller housing, which is also more visually appealing than a larger housing. 
     The slats in the rolling shutter preferably have engaging and receiving tracks that are the same size—e.g., the engaging track  52 ′ for each slat in the first series of slats  5 ′ is the same size as the engaging track  52 ″ for each slat in the second series of slats  5 ″ and the receiving track  54 ′ for each slat in the first series of slats  5 ′ is the same size as the receiving track  54 ″ for each slat in the second series of slats  5 ″—such that the same tooling can be used to form all engaging and receiving tracks of all slats in the rolling shutter. The use of the same tooling for an entire set of slats allows for simpler and less-costly manufacturing procedures. 
     One factor that allows for the nesting configuration described above is the provision of a slat where a portion of the receiving track is formed to receive and/or enclose an end retention device. In conventional slat designs, a receptacle for receiving an end retention device must be coupled to the slat. In such examples, the space or volume taken by the end retention device is accounted for in the design of the receiving track, whereas in examples where the end retention device is otherwise coupled to a portion of the slat, the end retention device may interfere with a tightly nested configuration. For example, the receptacle  30  depicted in  FIG.  3    (as well as the receptacle  130  depicted in  FIG.  8   , the receptacle  230  depicted in  FIG.  11   , and the receptacle  530  depicted in  FIG.  14   , discussed in further detail below) is a portion of the receiving track  14  formed to receive and/or enclose an end retention device. Alternatively, the slat can be designed to leave space for a separately formed receptacle capable of receiving an end retention device while still nesting with the hinges formed by coupled slats (for example, the separately formed receptacle  330  for coupling to the receiving track  314  in  FIG.  12    and the well  452  for receiving a separately formed receptacle in  FIG.  13   ). 
     In some cases, the configuration of the shutter slat may allow water to intrude into receiving track  14 . In the embodiment shown in  FIG.  4   , the portion of sheet  1  that is bent over on itself to form an outer guard wall  20  creates a channel  42  on the inward facing side  6  of body  2 , behind the outer guard wall. Water and debris may collect in channel  42 , particularly when the rolling shutter is in the vertical or extended position. For example, condensation on the inward facing side  6  of the shutter slat may collect in channel  42  and infiltrate into guard member  16 , between the bent over portions of outer guard wall  20 . Multiple freeze/thaw cycles may cause expansion and deformation of outer guard wall  20 , which may weaken hinge  38  or otherwise interfere with the operation of the rolling shutter. 
     Referring to  FIGS.  6 - 10   , an alternative embodiment of a shutter slat comprising single walled slat formed from a continuous, bent unbranched sheet  101  is shown that includes a curved body  102  with an outward facing side  104 , an inward facing side  106 , a first edge or end  108 , and a second edge or end  110 . Body  102  may be configured substantially as described above, with outward facing side  104  having a convex curvature and inward facing side  106  having a concave curvature. An engaging track  112  is formed at first edge  108  of body  102 , and a receiving track  114  is formed at second edge  110  of the body. The configuration of engaging track  112  is substantially as described above, as shown. 
     Receiving track  114  is configured to reduce the infiltration of water into the guard member. As shown in  FIG.  8   , receiving track  114  includes a guard member  116  and a lip member  118 . Guard member  116  extends from edge  110  of body  102 , and includes a portion of sheet  101  that is bent over or folded on itself to form an outer guard wall  120  and a guard base  121 . A bulge or bead, such as terminal loop  122  may be formed in outer guard wall  120 , as described above. In a preferred embodiment, outer guard wall  120  extends approximately along the same convex curvature E defined by outward facing side  104 , as shown in  FIG.  6   . 
     Receiving track  114  has the same general configuration and relationship to body  102  as previously described. In the embodiment shown in  FIG.  8   , lip member  118  extends from guard member  116 , and includes a hook-shaped portion comprising a shank  118   a , a bend  118   b , a barb  118   c  and a point  118   d  that are sized and shaped to engage the engaging track  112  of another slat. Bend  118   b  curves back toward outward facing side  104  of body  102 . Lip member  118  projects below the concave curvature of inward facing side  106  of body  102 , and barb  118   c  does not project above the convex curvature of outward facing side  104  of the body. Lip member  118  and guard member  116  are spaced apart to form an aperture  126 , preferably between point  118   d  of the hook-shaped portion of lip member  118  and guard articulation surface  124  of guard member  116 . Barb  118   c  may be offset from outer guard wall  120  to minimize the height of hinge  138 . Lip member  118  and guard member  116  also define an interior space within receiving track  114 , comprising an articulation space  128  and a receptacle  130  for receiving an end retention device. A shoulder  134  on the interior surface  132  of shank  118   a  separates articulation space  128  and receptacle  130 . Shoulder  134  may also provide a shoulder surface  136  that forms a bearing surface with guard articulation surface  124 , for the movement of the engaging track  112  of another slat within articulation space  128 . 
     To reduce the accumulation of water, second edge  110  is positioned proximal to or at approximately the point  143  where lip member  118  extends from guard member  116 , as shown in  FIG.  8   . This configuration effectively eliminates channel  42  of the embodiment shown in  FIG.  4   . When the rolling shutter is in the extended position as shown in  FIG.  9   , any water accumulating on the inward facing side  106  of the shutter slat will be diverted onto lip member  118 , rather than collecting behind and infiltrating into guard member  116 . As shown in  FIGS.  9  and  10   , this configuration does not significantly alter the profile of hinge  138  in comparison to the embodiment of  FIGS.  4  and  5   , in either the extended or retracted positions. 
     In one embodiment, edge  110  is formed with a curve having a greater degree of curvature than the curve of body  102  (e.g., as shown in  FIG.  9   ). This configuration allows outer guard wall  120  to extend approximately along the same convex curvature E defined by outward facing side  104  of body  102 , while edge  110  is positioned at point  143  where lip member  118  extends from guard member  116 . In an alternative embodiment, edge  110  is formed with a curve having approximately the same degree of curvature than the curve of body  102  (not shown). For example, edge  110  and shank  118   a  of receiving track  114  may extend approximately along the concave curvature of inward facing side  106  of body  102 , and preferably edge  110 , shank  118   a  and inward facing side  106  of body  102  form a continuous concave curvature. In this alternative configuration, guard member  116  and lip member  118  project above the convex curvature E of outward facing side  104  of body  102 , such that outer guard wall  120  no longer extends along convex curvature E of outward facing side  104  of body  102 . 
     The receiving track  114  also includes a first face  115   a , a second face  115   b , and a gap  119  which have the same general configuration and relationship to body  102  and guard member  116  as the previously described first face  15   a , second face  15   b , and gap  19 . In examples where the second edge  110  has a curve with a greater degree of curvature than the curve of body  102  (e.g., as shown in  FIG.  8   ), a transition point  125   a  between the outward facing side  104  and the first face  115   a  of the guard member  116  will not be along the same general curvature of the curved body  102 . For example, the transition point  125   a  forms a transition angle  125   b . In some examples, the transition angle  125   b  is less than 180°. In further examples, the transition angle  125   b  is less than 90°. In even further examples, the transition angle  125   b  is between about 20° and about 70°. 
     In some examples, the guard member  116  is bent over or folded on itself much like the guard member  16  described and disclosed with respect to  FIGS.  1 - 5   . In examples where the edge  110  has a curve with a greater degree of curvature than the curve of body  102  (e.g., as shown in  FIG.  8   ), a contact zone  117  is formed where the second face  115   b  of the bent over guard member  116  comes in contact with itself. For example, a portion of the second face  115   b  traversing the outer guard wall  120  comes in contact with a portion of the second face  115   b  traversing the shank  118   a.    
     The rolling shutter may comprise individual slats having bodies with different lengths and curves. As shown in  FIGS.  5  and  10   , the rolling shutter in the retracted position typically comprises a series of linked slats  1 ′,  1 ″, etc. ( 101 ′,  101 ″, etc.), that are wound about a spindle  40  ( 140 ) in a plurality of successive windings. In a preferred embodiment, each winding will generally have the same number of slats, and the slats within each winding will have bodies with approximately the same length (measured from first to second edge) and with approximately the same curve. In a further preferred embodiment, the bodies of the slats in each successive winding will generally have increasing length and curves with a decreasing degree of curvature. The number of slats in each winding may vary according to the application and/or size of the rolling shutter. In one embodiment, each winding of the rolling shutter has at least 5 slats, and more preferably has six slats. Those of skill in the art will appreciate that it is possible for a rolling shutter to have a different number of slats in each winding, slats of different lengths in each winding and/or slats that do not strictly increase in length with each successive winding. However, such configurations generally will not permit rolling shutter designs that have the most compact configuration in the retracted position. 
     The shutter slat may be formed of various materials as are known in the art, including plastic and aluminum as are used in conventional extruded shutter slats. However, the shutter slat is designed to be formed as a single walled, continuous bent, unbranched sheet, which allows the use of materials that are not readily extruded. In one embodiment, the shutter slat is produced from a sheet of material, and preferably sheet steel. Various manufacturing techniques or combinations of techniques for forming or bending sheet metal may be used, as are known in the art, including punch and die, wiping die edge bending, rotary die bending, air bending, offset bending, single or multiple die bending, hemming, and roll forming or roll bending. Different tooling may be used for different slats within a winding and/or between windings of a rolling shutter. Similarly, different gauges of sheet metal thickness may be used for different slats within a winding and/or between windings of a rolling shutter. 
     Referring to  FIG.  11   , another embodiment of a shutter slat is shown having an alternative configuration of the guard member. The shutter slat  201  comprises a single walled, continuous bent, unbranched sheet having the same general configuration as the slats of  FIGS.  1  and  6   —e.g., including a curved body  202  with an outward facing side  204  having a convex curvature, an inward facing side  206  having a concave curvature, a first edge or end  208 , and a second edge or end  210 . A hooking or engaging track  212  is formed at first edge  208  of body  202 , and a receiving track  214  is formed at second edge  210  of the body. 
     As shown in  FIG.  11   , engaging track  212  projects toward the outward facing side  204  of body  202 , and includes a hook-shaped portion that comprises a base and/or shank  212   a , a bend  212   b , a barb  212   c  and a point  212   d . In one embodiment, engaging track  212  does not project beyond the convex curvature F of outward facing side  204 . Preferably, at least a portion of a bend  212   b  is positioned approximately along the convex curvature of outward facing side  204 . In a further embodiment, edge  208  of body  202  may have a greater degree of curvature than the curve of body  202 , to form an acute interior angle between base  212   a  and edge  208  of the body. This configuration preferably allows base  212   a  to follow more closely the bend of the lip member when engaged in the receiving track of another slat. 
     In some examples, the first edge  208  forms a first edge bend  209 . In such examples, the first edge bend  209  forms an interior angle  211   b  between the engaging track  212  and the convex side (i.e., outward facing side  204 ) of the body  202 . In some examples, the interior angle  211   b  formed by the first edge bend  209  is less than 180°. In other examples, the interior angle  211   b  formed by the first edge bend  209  is between about 45° and about 135°. In further examples, the interior angle  211   b  formed by the first edge bend  209  is about 90°. In further examples, the interior angle  211   b  formed by the first edge bend  209  is an acute angle. In some examples, a first face  213   a  of the engaging track  212  is disposed on the same side of the shutter slat  201  as the outward facing side  204  (i.e., the convex side) of the body  202 . In examples where the convex curvature of the outward facing side  204  has a greater degree of curvature at the edge  208  (e.g., forming a first edge bend  209 ), a transition point  211   a  between the outward facing side  204  and the first face  213   a  of the engaging track  212  will not be along the same general curvature of the curved body  102 . For example, the transition point  211   a  forms a transition angle (i.e., the interior angle  211   b ). In some examples, the transition angle is less than 180°. In further examples, the transition angle is less than 90°. In even further examples, the transition angle is between about 20° and about 70°. In some examples, such as the example depicted in  FIG.  11   , the transition point  211   a  extends in the inward direction such that it is disposed on the inward side of point  212   d  (i.e., is disposed on the inward side of a vertical plane G defined by the location of the point  212   d ). In other examples, the transition point  211   a  extends in the inward direction such that it is disposed on the outward side of point  212   d  (i.e., outward side of vertical plane G). In other examples, the transition point  211   a  extends in the inward direction such that it is disposed an inward amount about equivalent to that of the point  212   d.    
     Receiving track  214  comprises a base  246 , a guard member  216 , and a lip member  218 . Base  246  extends from edge  210  of body  202 , and projects toward the inward facing side  206  of the body. Guard member  216  extends from base  246  and has a portion where sheet  201  is bent over on itself to form an outer guard wall  220   a , an inner guard wall  220   b , and a guard member end or point  222 . In the embodiment shown in  FIG.  11   , outer guard wall  220   a  extends from base  246 . Base  246  and outer guard wall  220   a  define an interior space or receptacle  230  for receiving an end retention device, such as the screw and washer of an end retention system as described in U.S. Pat. No. 8,616,261. An opening or aperture  248  into receptacle  230  may be formed between edge  210  of body  202  and guard member point  222 . In one embodiment, base  246  may form a lip  246   a  at edge  210  and/or guard member point  222  may form a lip  222   a , such that the width of aperture  248  is smaller than the interior width of receptacle  230  to assist in retaining an end retention device within receptacle  230 . 
     Lip member  218  extends from guard member  216  and includes a hook-shaped portion comprising a shank  218   a , a bend  218   b , a barb  218   c  and a point  218   d  that are sized and shaped to engage the engaging track  212  of another slat. Bend  218   b  curves back toward outward facing side  204  of body  202 . In the embodiment shown in  FIG.  11   , lip member  218  extends from inner guard wall  220   b . Lip member  218  and inner guard wall  220   b  define an interior articulation space  228  within receiving track  214 , that is sized and shaped to receive the hook-shaped portion of the engaging track  212  of another slat. Barb  218   c  and/or point  218   d  are spaced apart from inner guard wall  220   b  and/or end  222  to form an opening or aperture  226  into articulation space  228 , that is sized and shaped to receive the engaging track  212  of another slat. 
     In one embodiment, receiving track  214  does not project beyond the convex curvature F of outward facing side  204  of body  202 . Preferably, guard end  222  and/or at least a portion of a bend  218   b  are positioned approximately along the convex curvature F of outward facing side  204  of body  202 . Articulation space aperture  226  and receptacle aperture  248  open toward the outward facing side  204  of body  202 . Although the embodiment shown in  FIG.  11    has a receiving track  214  and an engaging track  212  that do not project beyond the convex curvature F of outward facing side  204  of body  202 , those of skill in the art will appreciate that the shutter slat may alternatively be configured with the reverse configuration—i.e. with a receiving track and/or an engaging track that do not project below the concave curvature of inward facing side  206  of the body. In this alternative configuration, articulation space aperture  226  and receptacle aperture  248  open toward the inward facing side  206  of body  202 . 
     Referring to  FIG.  12   , another embodiment of a shutter slat is shown having a separately formed receptacle, which reduces the complexity of the shutter slat design. Shutter slat  301  comprises a single walled, continuous bent, unbranched sheet having the same general configuration as slat  201  of  FIG.  11   —e.g., including a curved body  302  with an outward facing side  304  having a convex curvature, an inward facing side  306  having a concave curvature, a first edge or end  308 , and a second edge or end  310 . A hooking or engaging track  312  is formed at first edge  308  of body  302 , and a receiving track  314  is formed at second edge  310  of the body. 
     Receiving track  314  comprises a guard member  316  and a lip member  318 . Guard member  316  extends from edge  310  of body  302 , and projects toward the inward facing side  306  of the body  302 . Guard member  316  has an inward facing side  320   a  and an outward facing side  320   b . Lip member  318  extends from guard member  316 , and has a hook-shaped portion comprising a shank  318   a  extending from the guard member, a bend  318   b , a barb  318   c  and a point  318   d  that are sized and shaped to engage the engaging track  312  of another slat. Bend  318   b  curves back toward outward facing side  304  of body  302 . Lip member  318  and guard member  316  define an interior articulation space  328  within receiving track  214 , that is sized and shaped to receive the hook-shaped portion of the engaging track  312  of another slat. Barb  318   c  and/or point  318   d  are spaced apart from guard member  316  and/or edge  310  of body  302  to form an opening or aperture  326  into articulation space  328 , that is sized and shaped to receive the engaging track  312  of another slat. 
     In some examples, the second edge  310  forms a second edge bend  311  where the receiving track  314  extends from the second edge  310 . In such examples, the second edge bend  311  forms an interior angle  317  between the receiving track  314  and the concave side (i.e., inward facing side  306 ) of the body  302 . In some examples, the interior angle  317  formed by the second edge bend  311  is less than 180°. In other examples, the interior angle  317  formed by the second edge bend  311  is between about 45° and about 135°. In further examples, the interior angle  317  formed by the second edge bend  311  is about 90°. In some examples, the interior angle  317  conforms to the shape of a receptacle. 
     A receptacle  330  with an interior space  330   a  for receiving an end retention device, may be formed separately from body  302  and coupled to inward facing side  306  of the body, preferably adjacent to or near receiving track  314 . Receptacle  330  may be coupled to body  302  by various means known in the art, including welding, adhesive, or using a fastener. In the embodiment shown in  FIG.  12   , receptacle  330  is secured to body  302  by a fastener  350  such as a screw or rivet that passes through the body of the slat and into the receptacle. In an alternative embodiment, receptacle  330  may be similarly coupled to guard member  316  instead of or in addition to body  302 . In some examples, the interior angle formed by the second edge bend  311  conforms to the shape of the receptacle  330 . In further examples, the concave side of the body  302  (i.e., the inward facing side  306  of the body  302 ) at the second edge  310  of the body  302  and the receiving track  314  are sized and shaped to receive the receptacle  330 . 
     In a preferred embodiment, receptacle  330  is coupled to body  302  at or near edge  310 . Body  302  and/or receiving track  314  may be configured to receive receptacle  330 . In one embodiment, the inward facing side  306  of body  302  and/or the inward facing side  320   a  of guard member  316  are configured to conform or be complementary to the size and shape of receptacle  330 . For example,  FIG.  12    shows a receptacle  330  with a rectangular or square cross-section. Inward facing side  306  of body  302  and inward facing side  320   a  of guard member  316  are configured to form a right angle that is complementary to the shape of the receptacle. 
     In another embodiment, the shutter slat may include a well that is configured to receive a separately formed receptacle. Referring to  FIG.  13   , a shutter slat  401  is shown that comprises a single walled, continuous bent, unbranched sheet having the same general configuration as slat  301  of  FIG.  12   —e.g., including a curved body  402  with an outward facing side  404  having a convex curvature, an inward facing side  406  having a concave curvature, a first edge or end  408 , and a second edge or end  410 . A hooking or engaging track  412  is formed at first edge  408  of body  402 , and a receiving track  414  is formed at second edge  410  of the body. Receiving track  414  comprises a guard member  416  and a lip member  418 . Guard member  416  extends from edge  410  of body  402 , and projects toward the inward facing side  406  of the body. Guard member  416  has an inward facing side  420   a  and an outward facing side  420   b.    
     Slat  401  forms a well  452  for receiving a separately formed receptacle, that is preferably positioned at or near edge  410  of body  402 . In the embodiment shown in  FIG.  13   , a rib  454  is formed in body  402  that projects toward the inward side  406  of the body. Rib  454 , inward facing side  406  of body  402 , and guard member  416  define well  452  that is sized and shaped to receive a separately formed receptacle. For example, the surface  454   a  of rib  454 , inward facing side  406  of body  402 , and inward facing side  420   a  may form well  452  as a rectangular channel for receiving a receptacle with a square or rectangular cross-section (e.g., receptacle  330 ). 
     The receptacle may be secured in well  452  in the same manner described for coupling receptacle  330  to body  302 . In another embodiment, well  452  may be configured to allow the receptacle to be friction fit within the well, in place of or in addition to other means of coupling the receptacle to the body  402 . For example, rib  454  and guard member  416  may be spaced apart by a distance that is slightly smaller than the width of the receptacle. In other examples, rib  454  and guard member  416  may be spaced apart by a distance that is about the width of the receptacle. 
     Referring to  FIG.  14   , another example shutter slat  501  is depicted. Shutter slat  501  comprises a single walled, continuous bent, unbranched sheet having the same general configuration as slat  201  of  FIG.  11   —e.g., including a curved body  502  with an outward facing side  504  having a convex curvature, an inward facing side  506  having a concave curvature, a first edge or end  508 , and a second edge or end  510 . A hooking or engaging track  512  is formed at first edge  508  of body  502 —the engaging track  512  having the same general configuration as slat  201  of  FIG.  11   —and a receiving track  514  is formed at second edge  510  of the body  502 . The receiving track  514  requires less forming stations (i.e., less bends to arrive at the final shape of receiving track  514 ) than other examples. 
     Similar to  FIG.  11   , the shutter slat  501  in  FIG.  14    includes a first edge bend  509  forming an interior angle  511   b  between the engaging track  512  and the convex side (i.e., outward facing side  504 ) of the body  502 , where a transition point  511   a  is formed between the outward facing side  504  and the engaging track  512 . In the example depicted as shutter slat  501  the transition point  511   a  is located on the outward side of point  512   d  (i.e., outward side of vertical plane G′). 
     Receiving track  514  comprises a base  546 , a guard member  516 , and a lip member  518 . Base  546  extends from edge  510  of body  502 , and projects toward the outward facing side  504  of the body. Guard member  516  extends from the base  546 . Base  546  and guard member  516  define an interior space or receptacle  530  for receiving an end retention device. An opening or aperture  548  into receptacle  530  may be formed between edge  510  of body  502  and the guard member  516  at a guard member point  522 . In some examples, base  546  forms a lip  546   a  at edge  510  and/or guard member point  522  may form a lip  522   a , such that the width of aperture  548  is smaller than the interior width of receptacle  530  to assist in retaining an end retention device within receptacle  530 . 
     Lip member  518  extends from guard member  516  and includes a hook-shaped portion comprising a shank  518   a , a bend  518   b , a barb  518   c , and a point  518   d  that are sized and shaped to engage with engaging track  512  of another slat. Shank  518   a  extends from guard member  516  in a generally vertical direction (i.e., in a direction similar to the length of the body  502 ). Bend  518   b  extends from the shank  518   a  and curves toward outward facing side  504  of body  502 . Lip member  518  and guard member  516  define an interior articulation space  528  within receiving track  514 , that is sized and shaped to receive the hook-shaped portion of the engaging track  512  of another slat. Barb  518   c  and/or point  518   d  are spaced apart from guard member  516  to form an opening or aperture  526  into articulation space  528 , that is sized and shaped to receive the engaging track  512  of another slat. In some examples, receiving track  514  does not project beyond (i.e., below or past the inward facing side of) the concave curvature H of the inward facing side  506  of body  502 . In further examples, guard member point  522  and/or at least a portion of shank  518   a  and/or bend  518   b  are positioned approximately along the concave curvature H of outward facing side  504  of body  502 . In further examples, engaging track  512  does not project beyond (i.e., above or past the outward facing side of) the convex curvature F′ of the outward facing side  504  of body  502 . Articulation space aperture  526  and receptacle aperture  548  open toward opposing sides of body  502 . For example, articulation space aperture  526  opens towards the outward facing side  504  of body  502  and receptacle aperture  548  opens toward the inward facing side  506  of body  502 . 
     Although described herein as embodiments of a rolling shutter, the term “slat” may also refer to a curtain, screen, grille, or other covering for an opening that is retractable by stacking the components, such as by coiling or winding. For example, the term “slat” may include the stacking links of a coiling grille. Further, while particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the present disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this disclosure.