Patent Publication Number: US-2022235573-A1

Title: Deployable and retractable cover

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application No. 62/863,296, filed Jun. 19, 2019, the entire contents of which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present subject matter relates to covers, like pavilions or sheds. More particularly, the present subject matter relates to deployable and retractable covers. 
     BACKGROUND 
     Covers, like pavilions, or sheds, made of flexible sheets, like canvas sheets, are occasionally used to cover open spaces, for example playgrounds festival areas, and other areas of outdoor activity, in order to protect the open spaces from direct sunlight, or rain. Covers are also used to protect the content of structures, like greenhouses, from direct sunlight. Assembly and disassembly of such covers is complicated and cumbersome. 
     In some occasions, there is a desire to temporarily retract the cover. For example, when there is a need to temporarily allow exposure of plants in a greenhouse to sunlight, and then deploy the cover again over the greenhouse in order to prevent further exposure of the plants to excess sunlight. Such practice of retraction and deployment of the currently available covers is also cumbersome and complicated. 
     SUMMARY 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this subject matter belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present subject matter, suitable methods and materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting. 
     According to one aspect of the present subject matter, there is provided a cover system comprising:
         at least one cover sheet having four edges;   a plurality of flexible rafters, each of the rafters is slidably connected to at least one of two opposite edges of the four edges; and   at least one roller provided on at least one of two other opposite edges of the four edges, wherein the roller is configured to rotate, and the cover sheet is configured to wrap around the roller and be released from the roller, depending on a direction of rotation of the roller.       

     According to one embodiment, the cover sheet has a square shape. 
     According to another embodiment, each of the rafters is slidably connected to at least one of two opposite longitudinal edges, and wherein the at least one roller is provided on at least one of two transverse edges. 
     According to yet another embodiment, the cover system further comprises at least one support configured to support each of the rafters. 
     According to still another embodiment, the support is in a form of a pole that is configured to hold the rafter above a surface of an open space. 
     According to a further embodiment, the support is a part of a structure that is covered by the support system. 
     According to yet a further embodiment, the structure is a greenhouse. 
     According to still a further embodiment, the rafter comprises:
         a tube;   a cable threaded within the tube and extending out of the tube; and   one, or two rails flexibly attached to the tube, wherein the rail is configured to hold a cover sheet, and allow sliding of the cover sheet along the length of the rail.       

     According to an additional embodiment, the rafter further comprising one, or two connectors, each connector is configured to connect the rail to the tube. 
     According to yet an additional embodiment, the connector is narrow. 
     According to still another embodiment, the connector allows bending of the rail relative to the tube. 
     According to another embodiment, the rail comprising a hollow along an entire length of the rail, and a slot along an entire length of the rail, wherein the slot is positioned distally from the tube to which the rail is attached. 
     According to yet another embodiment, the rail has a round profile, and with the slot has a substantially C-shaped profile. 
     According to still another embodiment, the cover sheet is flexible. 
     According to a further embodiment, a plurality of sliders is attached to at least one of two opposite edges of the four edges of the cover sheet, wherein the slider is configured to be threaded in the hollow of the rail, and slide along the rail, wherein the cover sheet passes through the slot. 
     According to yet a further embodiment, the plurality of sliders is attached to a longitudinal edge of a strip, wherein an opposite longitudinal side of the strip is attached to the at least one of two opposite edges of the four edges of the cover sheet. 
     According to still a further embodiment, a friction between a surface of the slider and an inner surface of the rail, facing the hollow, is minimal, thus allowing smooth sliding of the slider along the rail. 
     According to an additional embodiment, there is a gap between the sliders that are attached to at least one of two opposite edges of the four edges of the cover sheet. 
     According to yet an additional embodiment, a size of the slider is larger than a size of the slot, wherein the slider is confined within the hollow, and is configured to slide inside the hollow without being able to pass through the slot and disconnect from the rail. 
     According to still an additional embodiment, the cable is configured to attach to at least two supports and be stretched between the at least two supports. 
     According to another embodiment, the rail is configured to withstand a transverse force applied on the sliders that are within the hollow, and not bend in a manner that widens the slot and allows the sliders to be pulled out of the rail through the slot. 
     According yet another embodiment, the rail is configured to withstand a transverse force and prevent exit of the slider through the slot up to a certain threshold level, and when the level of the transverse force is higher than the threshold level, the rail is configured to become flexible and allow widening of the slot in a manner that allows exit of the slider through the slot. 
     According to still another embodiment, the cable is made of a single strand. 
     According to a further embodiment, the cable is made of a plurality of interwoven strands. 
     According to yet a further embodiment, the cover sheet comprises a plurality of sub-cover sheets that are attached one to the other along a length of the cover sheet. 
     According to still a further embodiment, the sub-cover sheets are different in their transparency. 
     According to an additional embodiment, a first roller is attached to one side of the cover sheet, and a second roller is attached to an opposite side of the cover sheet, wherein simultaneous rolling of the first roller and the second roller, in the same direction and velocity, causes changing of the sub-cover sheet that is practically used for covering. 
     According to yet an additional embodiment, the roller is manually operated. 
     According to still an additional embodiment, the roller is operated by a rotor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the embodiments. In this regard, no attempt is made to show structural details in more detail than is necessary for a fundamental understanding, the description taken with the drawings making apparent to those skilled in the art how several forms may be embodied in practice. 
       In the drawings: 
         FIG. 1  schematically illustrates, according to an exemplary embodiment, a cover system. 
         FIG. 2  schematically illustrates, according to an exemplary embodiment, a rafter of a cover system. 
         FIG. 3  schematically illustrates, according to an exemplary embodiment, cover sheets connected to a rafter. 
         FIG. 4  schematically illustrates, according to an exemplary embodiment, a cross-sectional view of a rafter connected to a cover sheet. 
         FIG. 5  schematically illustrates according to an exemplary embodiment, a cover system comprising three cover sheets connected through two rafters. 
         FIG. 6  schematically illustrates, according to an exemplary embodiment, a cover sheet comprising a plurality of different parts. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before explaining at least one embodiment in detail, it is to be understood that the subject matter is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The subject matter is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. In discussion of the various figures described herein below, like numbers refer to like parts. The drawings are generally not to scale. 
     For clarity, non-essential elements were omitted from some of the drawings. 
     The present subject matter provides a cover system, optionally comprises several covers, that allows easy and rapid deployment and retraction of at least one cover. The cover is deployed over an open space, which optionally can contain plants, trees, flowers, vegetables, or animals, for example in greenhouses, as well as children in playgrounds and army or industry equipment such as in hangars. 
     The cover system comprises: at least one cover sheet having four edges; a plurality of flexible rafters, each of the rafters is slidably connected to at least one of two opposite edges of the four edges; and at least one roller provided on at least one of two other opposite edges of the four edges, wherein the roller is configured to rotate, and the cover sheet is configured to wrap around the roller and be released from the roller, depending on a direction of rotation of the roller. According to one embodiment, the cover sheet has a square shape. According to another embodiment, each of the rafters is slidably connected to at least one of two opposite longitudinal edges, and wherein the at least one roller is provided on at least one of two transverse edges. 
     Referring now to  FIG. 1 , schematically illustrating, according to an exemplary embodiment, a cover system. According to one embodiment, the cover system  1  comprises: at least one cover sheet  110 -X (X refers to a number of an item in a plurality of items that are similar or identical) having two opposite longitudinal sides L and two opposite transverse sides T; a plurality of rafters  120 -X, wherein each longitudinal side L of the cover sheet  110 -X is movably connected to a rafter  120 -X; and at least one roller  130 , wherein at least one of the transverse sides  110 -T of a cover sheet  110 -X is connected to the roller  130 , and wherein the roller  130  is configured to rotate, and the cover sheet  110 -X is configured to wrap around the roller  130  and be released from the roller  130 , depending on the direction the roller  130  is rotated. The covers  110 -X are configured to move according to the arrow  902 -X. 
     Optionally or alternatively, the sheet can be moved and wrapped around an appropriate roller  130  that can be on either side of the cover  110 -X or only on one side. In case there are two rollers  130  operated on both sides of the cover, the cover  110 -X can be wrapped on each one according to the current needs. As an example, the cover  110 - 1  is shown in  FIG. 1  in a state in which it is partially wrapped on the corresponding frontal roller  130  so that a portion of the surface is covered and a portion  115  is uncovered while the volume beneath this portion  115  is exposed to sunlight, rain or the like. 
     According to one embodiment, the cover system  1  further comprises at least one support  140 -X configured to support each of the rafters  120 -X. According to another embodiment, illustrated in  FIG. 1 , the support  140 -X can be in a form of a pole that is configured to hold the rafters  120 -X in a predetermined height above a surface of an open space, for example above a sand on the beach, above a grass loan, above a paved surface, above an orchard or crops, and the like. According to yet another embodiment, the support  140 -X can be a part of a structure, for example a part of a roof of a greenhouse. 
     The ability and ease of the covers to deploy and retract is due to the structure of the rafters  120 -X and its connection to the cover sheet  110 -X. 
     Referring now to  FIG. 2 , schematically illustrating, according to an exemplary embodiment, a rafter of the cover system. According to one embodiment, a rafter  120  comprises a tube  122 , a cable  124  threaded within the tube  122  and extending out of the tube  122 ; and one, or two rails  126  flexibly attached to the tube  122 , wherein the rail  126  is configured to hold a cover sheet and allow the cover sheet to slide along the length of the rail  126  according to embodiments that are described hereinafter. The exemplary rafter  120  illustrated in  FIG. 2  comprises two rails  126  attached to opposite sides of the tube  122 . However, the rafter  120  can comprise one rail  126  attached to the tube  122 . The cable can be any type of cable that is configured to withstand relatively high strength. The cable can be entwined or unite. 
     According to one embodiment, the rafter  120  further comprises one, or two connectors  128 , each connector  128  is configured to connect the rail  126  to the tube  122 . As can be seen in  FIG. 2 , the connector  128  is attached to the rail  126  and the tube  122 , and resides between the rail  126  and the tube  122 . According to another embodiment, the connector  128  is narrow. According to yet another embodiment, the connector  128  allows bending of the rail  126  relative to the tube  122 . 
     As illustrated in  FIG. 2 , the rail  126  comprises a hollow  1262  along the entire length of the rail  126 , and a slot  1264  along the entire length of the rail  126 . The slot  1264  of the rail  126  is positioned distally from the tube  122  to which the rail  126  is attached. Thus, when the rafter  120  comprises two rails  126  attached to the tube  122 , the slots  1264  of the two rails  126  are directed opposite one to the other. 
     The rail  126  can have a profile in any shape that is suitable for allowing the cover sheet to slide along the length of the rail  126  according to embodiments that are described hereinafter. The exemplary rail  126  illustrated in  FIG. 2  has a round profile, and with the slot  1264 , it has substantially a C-shape profile. However, this shape of profile is only exemplary and should not be considered as limiting the scope of the present subject matter. For example, the rail can have a rectangular profile having a slot  1264 , a triangular profile having a slot  1264 , and the like. 
     According to one embodiment, the rafter  120  is flexible. In other words, the tube  122  is flexible, the cable  124  is flexible, and the rail  126  is flexible. According to another embodiment, the connector  128  is flexible as well. In this way, the rafter can be wind into a compact structure. 
     Referring now to  FIG. 3 , schematically illustrating, according to an exemplary embodiment, cover sheets connected to a rafter. The rafter  120  is shown to connect to two cover sheets  110 - 1  and  110 - 2  on both sides, which is a portion of the system  1  as shown in  FIG. 1 , in an enlarged view. According to one embodiment, the cover sheet  110 -X is flexible, and is made of a flexible material, like canvas, nylon, fabric, net, and the like. According to another embodiment, a plurality of sliders  112  is attached to a longitudinal edge L of the cover sheet  110 - 1  and  110 - 2 . The sliders  112  are configured to be threaded in the hollow  1262  of the rail  126 , and slide along the rail  126 . Thus, the slot  1264  of the rail  126  allows connection of the sliders  112  to the cover sheets  110 - 1  and  110 - 2 , when the cover sheets pass through the slot  1264 . 
     According to the aforementioned embodiment, the plurality of sliders  112  is directly attached to the longitudinal edge L of the cover sheet  110 . According to another embodiment, illustrated in  FIG. 3 , the plurality of sliders  112  is attached to a longitudinal edge of a strip  114 , when an opposite longitudinal side of the strip  114  is attached to the longitudinal edge L of the cover sheet  110 . According to still another embodiment, the strip  114  is adhered to the longitudinal edge L of the cover sheets. 
     As mentioned above, the plurality of sliders  112  is configured to be threaded in the hollow  1262  of the rail  126 , and slide along the rail  126 . According to one embodiment, the plurality of sliders  112  is configured to freely slide along the rail  126 . According to another embodiment, a friction between a surface the slider  112  and an inner surface of the rail  126 , facing the hollow  1262  is minimal, thus allowing smooth sliding of the slider  112  along the rail  112 . Such minimal friction between the surface of the slider  112  and the inner surface of the rail  126  can be achieved by making the slider  112  of a material having a low friction coefficient, or coating the surface of the slider  112  with a material having a low friction coefficient, or making the rail  126  of a material having a low friction coefficient, or coating the inner surface of the rail  126 , facing the hollow  1262 , with a material having a low friction coefficient, or any combination thereof. 
     The attachment of the plurality of sliders  112  to the longitudinal edge L of the cover sheet  110 -X, according to the aforementioned embodiments, retains the flexibility of the longitudinal edge L of the cover sheet  110 -X. For example, when there is a gap between the sliders  112 , it is possible to bring the sliders  112  close one to another, while somewhat folding the longitudinal edge L of the cover sheet  110 -X in the gap between two adjacent sliders  112 . This allows, for example, shortening of the length of the cover sheet  110 -X to some extent. This embodiment is different, and advantageous, compared to prior art cover sheets. The edges, for example longitudinal edges, of prior art cover sheets are supported by rigid frames, or rigid beams, which render the edges of the prior art cover sheets rigidity. 
     According to one embodiment, the shape and size of the slider  112  corresponds to the shape and size of the hollow  1262  of the rail  126 . For example, the rail  126  illustrated in  FIG. 3  has a tube-like structure having a round profile. Accordingly, the slider  112  has a ball-like shape having a round profile and a size that fits the size of the hollow  1262  of the rail  126 , in a manner that allows sliding of the slider  112  along the rail  126 , as described above. However, the embodiment illustrated in  FIG. 3 , regarding the size and shape of the slider  112  should not be considered as limiting the scope of the present subject matter. The slider  112  can have any size and shape as long as it enables threading of the slider  112  into the hollow  1262  of the rail  126 , and sliding of the slider  112  along the rail  126 . 
     According to one embodiment, the size of the slider  112  is smaller than the size of the slot  1264  of the rail  126 . Thus, the slider  112  can be confined within the hollow  1262 , and slide inside the hollow  1262  of the rail  126  without being able to pass through the slot  1264  and disconnect from the rail  126 . In other words, the plurality of sliders  112  are configured to maintain a connection between the cover sheet  110 -X and the rail  126 . 
     As illustrated in  FIG. 3 , the cable  124  is prone to longitudinal forces, designated with double arrow  905 . These longitudinal forces  905  are applied on the cable  124  when the cable  124  is stretched between two opposite supports  140  (as shown in  FIG. 1 ). Thus, according to one embodiment, the cable  124  is configured to withstand longitudinal forces  905  applied to the cable  124 . As further illustrated in  FIG. 3 , the cable  124  is prone to a first transverse force. An exemplary first transverse force is designated with a rightward arrow  904 . The first transverse force  904  is a pulling force applied by a first cover  110 - 1  that is connected to the rafter  120  according to embodiments described above. Similarly, the cable  124  is prone to a second transverse force. An exemplary second transverse force is designated with a leftward arrow  906 . The second transverse force  906  is also a pulling force applied by a second cover  110 - 2  that is connected to another side of the rafter  120  according to embodiments described above. It has to be mentioned that when only one cover sheet  110 -X is connected to the rafter  120 , then only one transverse force is applied on the cable  124 . Thus, according to another embodiment, the cable  124  is configured to withstand a first transverse force  904 , or a second transverse force  906 , or both a first transverse force  904  and a second transverse force  906 . 
     According to one embodiment, the rail  126  is configured to withstand a transverse force  904  or  906  applied by the cover sheet  110 -X connected to the rail  126  through the sliders  112 . The transverse forces  904  or  906  that is applied by the cover sheet  110 -X tend to pull the sliders  112  out of the rail  126  through the slot  1264 . Thus, according to a preferred embodiment, the rail  126  is configured to withstand the transverse forces  904  and  906  and does not bend in a manner that widens the slot  1264  and allows the sliders  126  to be pulled out of the rail  126  through the slot  1264 , and thereby disconnect the cover sheet  110  from the rafter  120 . According to another embodiment, the rail  126  is configured to withstand a transverse force  904  or  906  in a certain degree. Accordingly, a rail  126  can be made of materials and designed in a manner that allows the rail  126  to withstand a certain degree of transverse forces  904  and/or  906 . Thus, different rails  126  can be designed to withstand different degrees of a transverse force  904  or  906 . 
     According to one embodiment, the cable  124  is made of a single strand. According to another embodiment, the cable  124  is made of a plurality of interwoven strands. 
     Referring now to  FIG. 4 , schematically illustrating, according to an exemplary embodiment, a cross-sectional view of a rafter connected to a cover sheet.  FIG. 4  illustrates an exemplary embodiment of the rafter  120  in which a tube  122  is connected to a rail  126  with a connector  128 . Inside the tube  122  there is a cable  124 . The rail  126  comprises a hollow  1262  and a slot  1264 . Inside the hollow  1262  of the rail  126  there is a slider  112 . Since the hollow  1262  is cylindrical, the slider  112  has a ball-like shape having a circular profile that corresponds to a circular profile of the hollow  1262  of the rail  126 . All illustrated in  FIG. 4  is a gap between the slider  112  and an inner surface of the rail  126 . This gap allows the slider  112  to freely slide along the rail  126 . Nevertheless, as described above there are additional embodiments in which the ability of the slider  112  to freely slide along the rail  126  is represented. In addition, since  FIG. 4  illustrates a cross sectional view, only one of the plurality of sliders  112  that are illustrated in  FIG. 3 , is shown. 
     Another embodiment that is illustrated in  FIG. 4  is the size of the slider  112  that is larger than the size of the slot  1264  of the rail  126 . Thus, when a transverse force  906  is applied on the slider  112  and tends to pull the slider  112  out of the rail  126  through the slot  1264 , the slider  112  does not pass through the slot  112  and does not exit the rail  126 . 
     However, according to another embodiment, the rail  126  is configured to withstand a transverse force  904  and/or  906  and prevents exit of the slider  112  through the slot  1264  up to a certain threshold level, and when the level of the transverse force  904  and/or  906  is higher than the threshold level, the rail  126  is configured to become flexible and allows widening of the slot  1264  in an manner that allows the slider  112  to exit through the slot  1264 . This embodiment allows, for example, disconnection of the cover sheet  110 -X from the rafter  120  by pulling the cover sheet  110 -X and thereby applying a transverse force  904  and/or  906  on the slider  112  that is higher than the threshold level that the rail is configured to withstand. 
     Still another embodiment that is illustrated in  FIG. 4  is the connection of the slider  112  to the cover sheet. According to exemplary embodiment illustrated in  FIG. 4 , the slider  112  is connected to strip  114 , when the strip  114  is connected to the cover sheet (the cover sheet is not shown in  FIG. 4 ), as illustrated in  FIG. 3 . As can be seen in  FIG. 4 , the strip  114  is attached to the slider  112  and passes through the slot  1264  of the rail  126 . The strip  114  can be attached to the slider  112  by, for example, an adhering material, mechanical clamping, and the like. 
     Referring now to  FIG. 5 , schematically illustrating, according to an exemplary embodiment, a cover system comprising three cover sheets connected through two rafters.  FIG. 5  illustrates a first cover sheet  110 - 1  connected to a first rafter  120 - 1 ; a second cover sheet  110 - 2  connected in one side to the first rafter  120 - 1 , while in an opposite side, the second cover sheet  110 - 2  is connected to a second rafter  120 - 2 ; and a third cover sheet  110 - 3  also connected to the second rafter  120 - 2 , according to embodiments described above. Thus, the three cover sheets  110 -X that are connected by the two rafters  120 -X together form a cover system  1  that is configured to cover an open space, crops, or items, as described herein before. 
       FIG. 5  also illustrates an enlarged view of a part at an edge of the second rafter  120 - 2  and parts of the second cover sheet  110 - 2  and third cover sheet  110 - 3  that are connected to the second rafter  120 - 2 , according to some exemplary embodiments. The enlarged view illustrates the tube  122 , a cable  124  inside the tube  122  that also protrudes out of the tube  122 , a first rail  126 - 1  attached to one side of the tube  122 , and a second rail  126 - 2  attached to another side of the tube  122 . In the first rail  126 - 1  there is a plurality of second sliders  112 - 2  attached to the second cover sheet  110 - 2  through a second strip  114 - 2 . Similarly, in the second rail  126 - 2  there is a plurality of third sliders  112 - 3  attached to the third cover sheet  110 - 3  through a third strip  114 - 3 . 
     Also illustrated in  FIG. 5  are two opposite longitudinal forces  902 - 1  and  902 - 2  that can be applied on the cover sheets  110 - 2 . When, for example, a first longitudinal force  902 - 1  is applied on the second cover sheet  110 - 2 , the second cover sheet  110 - 2  can be pulled in the same direction of the puling force so that the cover sheet  110 - 2  can wind around the roller  130 . 
     One of the advantages of the cover system  1  of the present subject matter is the flexibility of the cover sheets  110 -X and the flexibility of the rafters  120 -X. For example, the cover sheets  110 -X and rafters  120 -X can be shipped in spools. This is advantageous particularly due to the large number of components, as well as their large sizes, that occasionally have to be shipped. Another advantage is the easy installation and handling of the cover system  1 . 
     Returning now to  FIG. 1 , illustrating an exemplary embodiment of the cover system  1 . The cover system  1  comprises a first rafter  120 - 1 , a second rafter  120 - 2 , a third rafter  120 - 3  and a fourth rafter  120 - 4 . The first rafter  120 - 1  is stretched over a first raw of supports, in a form of poles designated  140 - 1 ; the second rafter  120 - 2  is stretched over a second raw of supports  140 - 2 ; the third rafter  140 - 3  is stretched over a third war of supports  140 - 2 ; and the fourth rafter  140 - 4  is stretched over a fourth raw of supports  140 - 4 . 
     The first rafter  120 - 1  is connected to one cover sheet  110 - 1 , and the fourth rafter  120 - 4  is connected to one cover sheet  110 - 4 . On the other hand, the second rafter  120 - 2  is connected to two cover sheets  110 - 1  and  110 - 2 , and the third rafter  120 - 3  is also connected to two cover sheets  110 - 2  and  110 - 3 . Thus, according to one embodiment, the rafter  120 - 4 , as an example, can comprise one rail on an appropriate side, and as a result, rafter  120 - 4  is configured to connect to one cover sheet  110 - 3 . According to another embodiment, the rafter  120 - 3 , as an example, can comprise two rails, each on one side of the rafter, and as a result, rafter  120  is configured to be connected between two cover sheets  110 - 3  and  110 - 2 . 
     According to one embodiment, the degree of retraction of one cover sheet is independent of the degree of retraction of other cover sheets of the cover system. For example, referring now to  FIG. 1 , the first cover sheet  110 - 1  can be fully retracted, while the second cover sheet  110 - 2  and the third cover sheet  110 - 3  are fully extended. Another example is that the first cover sheet  110 - 1  and the second cover sheet  110 - 2  can be partially extended, while the third cover sheet  110 - 3  is fully retracted. This is to illustrate the flexibility of usage of the cover system  1  of the present subject matter. 
     According to one embodiment, the direction of movement of one cover sheet along the rafter or rafters, to which the cover sheet is connected, is independent of the direction of movement of other cover sheets of the cover system, along the rafters, to which the other cover sheets are connected. The directions of movements of the cover sheets and rafters are illustrated in  FIG. 1  with double-headed arrows  902 -X. Each cover sheet  110 -X can move in directions  902  independently of the other cover sheets. 
     Referring now to  FIG. 6 , schematically illustrating, according to an exemplary embodiment, a cover sheet comprising a plurality of different parts. In the aforementioned embodiments, the cover sheet  110  was regarded as uniform in its entirety, for example in terms of transparency. However, according to another embodiment, the cover sheet  110  can comprise a plurality of sub-cover sheets  105 -X that are attached one to the other along the length of the cover sheet  110 . According to yet another embodiment, the sub-cover sheets  105 -X are different in their transparency. For example,  FIG. 6  illustrates two sub-cover sheets of the cover sheet  110 —a first sub-cover sheet  105 - 1  and a second sub-cover sheet  105 - 2 . As will be understood hereinafter, this cover sheet  110  can comprise additional sub-cover sheets  105 -X that are not seen in  FIG. 6 . For example, the first sub-cover sheet  105 - 1  can be opaque and prevents passage of light through it, and the second sub-cover sheet  105 - 2  can be transparent and allows passage of light through the second sub-cover sheet  105 - 2 . 
     In addition,  FIG. 6  illustrates a first roller  130 - 1  attached to one side of the cover sheet  110 , and a second roller  130 - 2  attached to an opposite side of the cover sheet  110 . Simultaneous rolling of the first roller  130 - 1  and the second roller  130 - 2 , in the same direction and velocity causes changing of the sub-cover sheet  105  that is practically used for covering. Thus, the exemplary cover sheet  110  that is illustrated in  FIG. 6  can comprise additional sub-cover sheets  105  that are wrapped around the rollers  130 -X. For example, as illustrated in  FIG. 6 , the first sub-cover sheet  105 - 1  that is opaque is practically used for covering. When there is a desire to allow light to pass through the cover sheet  110 , the first roller  130 - 1  and the second roller  130 - 2  can simultaneously roll clockwise in the same speed. As a result, the first sub-cover sheet  105 - 1  is wrapped around the first roller  130 - 1 , and the second sub-cover sheet  105 - 2 , that is transparent, is released from the second roller  130 - 2  and practically used for covering, thus allowing passage of light through the cover sheet  110 . 
     It should be mentioned that the embodiments illustrated in  FIG. 6  are possible due to the structure of the cover system  1  of the present subject matter, namely the rafters  120 -X and the embodiments of connection of the cover sheet  110  with the rafter enables the aforementioned ability to change the type of sub-cover sheet  105 -X that is practically used for covering. 
     According to one embodiment, the roller  130  is manually operated. According to another embodiment, the roller  130  is operated by a rotor. 
     It is appreciated that certain features of the subject matter, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the subject matter, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub combination. 
     Although the subject matter has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.