Abstract:
Uncontrolled take-up of a shade and often unexpected noise development are perceived as disturbing by the operator. Therefore, it is provided that a shade arrangement with a length of shade material ( 10 ) and a take-up roll ( 12 ) to which the length of shade material is attached and which is pretensioned by spring force in the take-up direction of the length of shade, has a pressure volume ( 46 ) coupled to the free end ( 16 ) of the length of shade material ( 10 ) such that, when the length of shade material is unrolled from the take-up shaft ( 12 ), a pressure is built up in the pressure volume which, when the length of shade material is released from a position in which it is at least partially unrolled from the take-up roll, the take-up motion of the length of shade is braked.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a shade means with a length of shade material and a take-up roll to which the length of shade material is attached and which is pretensioned by spring force in the take-up direction of the length of shade. Furthermore, this invention also relates to a motor vehicle roof with such a shade arrangement. 
         [0003]    2. Description of Related Art 
         [0004]    Shade means of the initially named type are used for numerous applications, especially for shading purposes, for example, on buildings or in automotive construction, especially as cargo space covers and trunk covers, and also as covers, for example, for cabinets or chests. 
         [0005]    To activate such a shade arrangement, the length of shade material is unrolled from the take-up roll against the force of a return spring and is fixed in at least the partially unrolled state, for example, hung. In order to then uncover the shaded area, the free end of the length of shade material is unfixed so that the length of shade material automatically is taken up under the action of spring force. 
         [0006]    Even if provision is made for the length of shade material to be guided as it moves, for example, by a pull being attached to the free end of the length of shade material and being guided in lateral guide rails, uncontrolled take-up of the shade in which the shade snaps back under the action of a spring force has proven disadvantageous, on the one hand, since high take-up speeds can cause damage to part of the shade means, and on the other hand, uncontrolled take-up of the shade due to the associated jerky motion of the shade and the unwanted and often unexpected noise development when the pull strikes a stop are perceived as disturbing by the operator. 
         [0007]    German Utility Model DE-U-92 03 450 proposes, especially for a freezer chest means, a shade means in which the take-up shaft is connected to a rod with one end projecting into a space which is filled with a highly viscous fluid. Because, when the rod turns within the highly viscous fluid, shear of the fluid occurs along the surface of the rod located in the fluid, the rotation of the rod at higher speeds of the take-up shaft is braked. Aside from the fact that, in this approach, only rather limited damping can be produced, in the implementation of such a shade system in which a moving component is guided out of a liquid filled chamber, inherent sealing problems arise. 
         [0008]    Furthermore, German Patent DE 44 22 842 C1 proposed damping elements to brake the motion of the movable part. Similarly to DE-U 92 03 450, in this connection, a hollow chamber is filled with a viscous material, especially oil, in order to dampen the motion of the component turning in the hollow chamber. 
         [0009]    To brake spring shades, damped stops have also been used which a pull connected to the free end of the length of shade material strikes when the shade is completely opened, i.e., is taken up as far as possible onto the take-up shaft. By using these buffers, the problems associated with snap-back of the shade can be mitigated only to a limited extent, but in no case can they be eliminated. Since the buffer is used only in the very last part of the opening motion of the shade, with buffers, the unduly rapid recoil motion of the shade which often leads to startling of the operator cannot be influenced, and moreover, the impact of the pull or the sliders guiding the pull leads to unwanted noise development and to wear phenomena on the shade means. 
       SUMMARY OF THE INVENTION 
       [0010]    Therefore, it is the object of this invention to devise a shade means of the initially named type in which, when the length of shade material is released from a position which is at least partially unrolled from the take-up roll, the take-up motion of the length of shade material is effectively damped. 
         [0011]    This object is achieved in a shade means of the initially named type in that a pressure volume is coupled to the free end of the length of shade material such that when the length of shade material is unrolled from the take-up roll, a pressure is built up in the pressure volume which brakes the take-up motion of the length of shade material when the length of shade material is released from the position which is at least partially unrolled from the take-up roll. 
         [0012]    This approach is advantageous in several respects. On the one hand, here, differently than with the stop buffers known from the prior art, the braking action of the shade which is being taken up as a result of the spring force of the take-up roll occurs not only at the end of the take-up motion, but beforehand, and in particular, provision can be made for the damping action to increase with rising take-up speed. In particular, snap-back of the shade, as can be observed in known shades, is thus effectively prevented. Furthermore, since the pressure in the pressure volume is built up only when the length of shade material is unrolled from the take-up roll, there is a system which is unpressurized at rest, and which works without wear and in a maintenance-free manner. 
         [0013]    While the pressure volume can fundamentally be operated with any pressure fluid, i.e., liquid or gas, it is preferably operated with air in order to make the build-up as simple as possible. 
         [0014]    To actuate the pressure volume, the latter is preferably coupled via a sheathed cable arrangement to the free end of the length of shade. The positioning motion of the shade in this connection via the sheathed cable arrangement in the pressure volume builds up a pressure and brakes the take-up motion when the length of shade material is moving in the opposite direction. 
         [0015]    Preferably, there is a pull on the free end of the length of shade material which provides for uniform and wobble-free movement of the length of shade. In this connection, laterally from the length of shade, there can be guide rails in which the pull is directly guided or in which sliders connected to the pull are movably guided. 
         [0016]    Preferably, the pressure volume is provided by a pressure cylinder which is coupled to the free end of the length of shade material and in which, preferably, there is a movable pressure piston which determines the size of the pressure volume. If, when the length of shade material is being taken up and unrolled its free end is moved, the pressure piston coupled to the free end or to a pull provided on it or to the sliders connected to the pull moves back and forth accordingly in the pressure cylinder. 
         [0017]    While the coupling between the length of shade material and the pressure piston, in this connection, can take place fundamentally in any manner, the structure is especially simple when the pressure piston is coupled via a sheathed cable arrangement to the free end of the length of shade. Sheathed cables can be any elements, such as, for example, cables, cords, wire ropes, chains and the like, with tensile strength, preferably with tensile and compressive strength, which are still preferably flexible. Alternatively, the pressure piston located in the pressure cylinder could also be actuated by means of a connecting rod coupled to the free end of the length of shade. 
         [0018]    The shade means can be made in this connection such that the pressure piston is shifted in the take-up motion of the length of shade material between a first end position in which the pressure volume is minimum, and a second end position in which the pressure volume is maximum. The arrangement can be made here such that the take-up motion of the length of shade material is damped either by means of a negative pressure produced in the pressure volume or by means of an overpressure produced in the pressure volume. If the damping is to take place by means of negative pressure, the shade means is preferably made such that the pressure piston is in the first end position, i.e., in the position in which the pressure volume is minimum when the length of shade material is unrolled to the maximum degree from the take-up roll, so that the pressure piston when the length of shade material is being taken up, when it is shifted in the direction to the second end position, produces a negative pressure by increasing the pressure volume. In this configuration of the shade means the pressure cylinder preferably has an air inlet opening and an air outlet opening provided with a one-way valve, the air inlet and outlet openings being arranged such that the pressure volume in movement of the pressure piston in the direction to the first end position being vented via the air outlet opening, during displacement of the pressure piston in the direction to the second end position in the pressure volume by increasing the pressure volume into which air cannot flow through the now closed one-way valve a negative pressure is produced, and air can flow into the pressure volume through the air inlet opening when the pressure piston reaches the second end position. In this configuration of the shade means the pressure cylinder provides for damping of the winding motion of the length of shade material as soon as the shade is released from the at least partially unrolled position, since by moving the pressure piston the closed pressure volume is enlarged. Only when the second end position is reached, in which the shade is completely taken up, can air flow into the pressure cylinder through the air inlet opening so that the pressure volume becomes unpressurized again. Moreover in this configuration of the shade means, the damping of the winding motion increases with the progressing motion of the shade. In particular, since the negative pressure produced in the pressure volume will be maximum shortly before reaching the second end position at the end of the take-up motion, at the end of the take-up motion maximum damping is achieved, while at the start of the take-up motion, proceeding from the unpressurized pressure volume which is “pumped empty” via the one-way valve, the length of shade material is not braked. 
         [0019]    Similar damping behavior can be achieved when the shade means is made such that the pressure piston is in the second end position, i.e., in the end position in which the pressure volume is maximum, when the length of shade material is unrolled from the take-up roll to the maximum degree. As a result, an overpressure is produced when the length of shade material is taken up onto the take-up roll with the corresponding motion of the pressure piston in the direction toward the first end position in the pressure volume. 
         [0020]    In this connection, the arrangement can be such that the pressure cylinder has an air passage opening which is arranged such that, when the pressure piston moves in the direction to the second end position, i.e., when the shade is unrolled, air can flow through the air passage opening into the pressure volume, and when the pressure piston is moved in the direction to the first end position, i.e., when the shade is being taken up, air from the pressure volume can escape through the passage opening. It goes without saying that, to produce an overpressure in the pressure volume, the air passage opening is dimensioned such that the amount of air flowing out through the air passage opening per unit of time is less than the amount of air displaced by the pressure piston (i.e., in order to produce a damping action, the area of the air passage opening must be smaller than the cross-sectional area of the pressure cylinder). In order to achieve a suitable damping action, in this connection, the air passage opening as compared to the cross-sectional area of the pressure cylinder will be small, and by the dimensioning of the air passage opening, the degree of damping can be set at will. 
         [0021]    If the pressure piston is actuated via a sheathed cable arrangement, in another configuration of the invention, the shade means is made such that the pressure piston can be moved in both directions by the sheathed cable arrangement so that compressively stiff elements need not be provided as the sheathed cable elements, but only elements, such as, for example, cables, with tensile strength, can be used. In this case, the cable can be attached on either side of the pressure piston, for example, by means of hooks, or in a preferred configuration of the invention, can penetrate the pressure piston. In particular, the pressure piston can have an axial slot into which the cable is inserted. 
         [0022]    Furthermore, the pressure piston can be attached to the cable by means of clamping, cementing, welding, crimping and/or by separate holding elements. In these embodiments, since the cable runs through the pressure volume, it goes without saying that, on the end of the pressure volume facing away from the pressure piston, there should be a corresponding sealing element in order to seal the moving cable relative to the pressure cylinder. The pressure piston itself can be sealed relative to the pressure cylinder in the conventional manner by means of seals which run circumferentially around the outside of the piston, for example, O-ring seals. 
         [0023]    If a sheathed cable arrangement is used to move the pressure piston, it can have a revolving cable, especially an inherently closed revolving cable which is coupled, on the one hand, to the free end of the length of shade material and to which, on the other hand, a pressure piston is attached. To equalize production and mounting tolerances, there can be a compensation element, for example, a tension spring, in the revolving cable. 
         [0024]    To dampen the take-up motion of the length of shade material, there can be one or more pressure cylinders. For example, there can be a pressure cylinder which is coupled on each side to the free end of the length of shade, especially to a pull which is provided on the free end of the length of shade material or to a slider which is connected to the pull. Alternatively, on either side of the length of shade material, there can be a respective separate pressure cylinder, with pressure pistons which are coupled to one end of the pull and to a slider which is connected to the pull. 
         [0025]    While shade means of the above explained type can be used in numerous applications, especially for shading of window openings, to separate spaces, to close cabinets and chests and the like, an especially preferred application is in automotive construction where these shade means can be used as cargo space covers, for example, as trunk lids or for covering the cargo bed of pickups, but mainly for shading a sunroof which has a transparent or translucent cover. 
         [0026]    With the concept described here, in which the opening process of a manually actuated, spring-tensioned shade, a so-called spring shade, is damped in a specific manner, on the one hand, the ease of operation of the shade means is increased since snap-back of the shade is prevented, the shade slides back gently and unwanted noise as occurs when the known shade strike a buffer are avoided, and on the other hand, the stress on the components is reduced as a result of the damped return of the length of shade. Compared to known shade means in which the length of shade material snaps back in an uncontrolled manner, an increased value of the system is achieved by the damped return motion of the length of shade. 
         [0027]    Preferred embodiments of the invention are explained in detail below with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a schematic perspective view of a shade means in accordance with the invention; 
           [0029]      FIGS. 2 to 5  show views of one embodiment of a pressure cylinder which works with negative pressure in different operating positions of the pressure piston; 
           [0030]      FIGS. 6 to 9  show views of a pressure cylinder which works with overpressure in different operating positions of the pressure piston; 
           [0031]      FIGS. 10  A &amp;  10 B show detailed end and side views of a sealing element for sealing the pressure cylinder; 
           [0032]      FIGS. 11A , B &amp;  12 A, B show detailed side and end views of embodiments of the pressure piston; 
           [0033]      FIG. 13  is a schematic perspective view of an alternative embodiment of the shade means in accordance with the invention in which there is only one pressure cylinder for damping of the take-up motion of the length of shade; 
           [0034]      FIG. 14  is a schematic perspective view of another embodiment of a shade means which works with a pressure cylinder; 
           [0035]      FIG. 15  is a schematic perspective view of a configuration of a shade means which operates with a pressure cylinder and in which there are two pressure cylinders in the pull; 
           [0036]      FIG. 16  is a sectional view through a guide rail for use with a shade means in accordance with the invention; and 
           [0037]      FIGS. 17 to 19  show another version of a pressure cylinder which is used in the shade means in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0038]      FIG. 1  shows a shade means in which the length of shade material  10  is taken up onto a take-up shaft  12  which is pretensioned by means of a spring  14  in the take-up direction of the length of shade material  10 . The length of shade material  10  can be preferably lengths of fabric which, depending on the application, can also be provided with a light reflecting or heat reflecting layer. 
         [0039]    In the embodiment shown in  FIG. 1 , there is a pull  18  on the free end  16  of the length of shade material  10  that is provided with a handle  20  for actuation by the operator. Each end of the pull  18  is connected to a slider  22 . Sliders  22  are guided in guide rails  24  (such as that shown in  FIG. 16 ) and which are run parallel to the drawing direction of the shade. 
         [0040]    To draw the length of shade material  10 , the operator pulls the pull  18  on the handle  20  in a direction away from the take-up shaft  12 , as a result of which the length of shade material  10  is unrolled from the take-up shaft  12  against the reset force of the springs  14 . In order to keep the length of shade material in a position which is at least partially unrolled from the take-up shaft  12 , the free end of the length of shade material is locked in the pertinent position. For this purpose, laterally of the length of shade material  10 , there can be several catch hooks, or as shown in  FIG. 1 , there can be a locking mechanism  28  which interacts with an engagement part  26  which is provided in the pull  18  and which locks the pull in its end position which completely stretches the length of shade material  10 . 
         [0041]    If the length of shade material is to be taken up, the locking is released so that the pull  18  is drawn back under the action of the force of the spring  14 . In order to damp this return motion of the pull  18  and especially to prevent the shade from snapping back, there is a pressure cylinder  30  on each side of the length of shade  10 . While, in the illustrated embodiment, the pressure cylinder is an elongated component with a circular cross section, it goes without saying that the pressure cylinder can be any hollow profile with a uniform cross section which can have any cross sectional shape, for example, round, oval, angular, etc. In the pressure cylinder  30 , there is a pressure piston  32  which is coupled via a revolving (endless) cable to the slider  22  which bears the pull  18 . 
         [0042]    In this embodiment, the cable  34  runs axially through the pressure cylinder  30  and is deflected via deflection rollers  36  to form a closed loop. Instead of concomitantly turning deflection rolls  36 , deflection can also take place via a stationary component, for example, a metal pin. Furthermore, in the embodiment shown in  FIG. 1 , the deflection roll  36  located nearer the take-up roll can be located on the axle  38  of the take-up shaft  12  or deflection of the cable  34  can take place directly via the axle  38 . 
         [0043]    In order to equalize tolerances in the production and mounting of the shade means and especially of the sheathed cable system thereof, in the cable  34  which can be, for example, a plastic-jacketed wire rope, there can be an equalization element  40 , for example, a tension spring. 
         [0044]    With reference to  FIGS. 2 to 5 , an embodiment of the pressure cylinder  30  is explained below in which the take-up motion of the length of shade material is damped by the build-up of a negative pressure. If the pull  18  is moved in the direction to the take-up shaft proceeding from the completely closed position of the shade ( FIG. 5 ), the pressure piston  32 , which is located in the pressure cylinder  30  and which is attached, for example, by means of crimp elements  42  on the cable  34 , is moved to the right in  FIG. 2 . While the end of the pressure cylinder  30  shown at left in  FIG. 2  can be open, the other end  44  of the pressure cylinder  30  is closed in order to form a variable pressure volume  46  between the cylinder and the pressure piston  32 . In this connection, the pressure piston  32  is sealed relative to the inside wall of the pressure cylinder  30 , preferably, by means of a plurality of O-rings  48 . Furthermore, on the closed end  44  of the pressure cylinder  30 , there is a sealing element  50  which provides for sealing between the movable cable  34  and the pressure cylinder  30 . Adjacent to the closed end  44 , or the sealing element  50  located therein, the pressure cylinder  30  has an air outlet opening  52  which is sealed by means of a one-way valve  54  such that air can escape from the interior of the pressure cylinder, but no air can travel through the air outlet opening into the pressure cylinder. 
         [0045]    If the pressure piston  32  is moved from the position shown in  FIG. 2  into the position shown in  FIG. 3 , air is compressed in the pressure volume, but can escape via the air outlet opening  52 . As soon as the shade is closed to a length enough that the air dammed in the pressure volume  46  can escape sufficiently via the air outlet opening  52 , the pressure between the pressure chamber  46  and the outside space surrounding the pressure cylinder  30  is equalized via the one-way valve  54 . 
         [0046]    If the free end of the length of shade material proceeding from the closed position of the length of shade material shown in  FIG. 3  is released, the pressure piston  32  on the cable  34  within the pressure cylinder  30  is pulled to the left in  FIG. 3 . By increasing the pressure volume  46 , a negative pressure is formed in the pressure volume  46  since the one-way valve  54  seals the air outlet opening  52 , and thus, the pressure cannot be equalized. As a result of the negative pressure in the pressure volume  46  a compressive force F D  which is directed against the tensile force F S  of the cable  34  acts on the pressure piston  32  and becomes greater with increasing displacement of the pressure piston  32  in the direction to be opened, i.e., the completely taken-up position of the shade, and thus, causes an increasing damping action. 
         [0047]    When the completely taken-up position of the length of shade material  10  is reached, in which the pressure piston  32  is in the end position shown in  FIG. 5 , the pressure between the pressure chamber  46  and the outside space surrounding the pressure cylinder  30  can be equalized by the air inlet opening  56  which is arranged such that it is cleared by the pressure piston  32  shortly before reaching its second end position. 
         [0048]      FIGS. 6 to 9  show a modified embodiment of the pressure piston  30  in which damping of the take-up motion of the length of shade material is effected by producing an overpressure in the pressure cylinder. In the version of the pressure cylinder  30  shown in  FIGS. 6 to 9 , it is, in turn, made as a half-open hollow section with one end  44  sealed in order to define a pressure volume  46  between the aforementioned end or a sealing element  50  located adjacent to the closed end  44  and the movable pressure piston  30 . The end  60  of the pressure cylinder opposite the closed end  44  can be completely opened or can have air passage openings (not shown) which are made correspondingly large. 
         [0049]    If the shade is closed proceeding from the opened, i.e., completely taken up position shown in  FIG. 9 , the pressure piston  32  moves to the right in  FIG. 6 , until it reaches its end position shown in  FIG. 7 , in which the shade is closed, i.e., is unrolled to the maximum degree from the take-up shaft. Since the pressure volume  46  is enlarged during the motion of the pressure piston  32  into the closed position, air is sucked by the negative pressure which forms here from the outside space surrounding the pressure cylinder through an air passage opening  58  located near the closed end  44  of the pressure cylinder  30  into the interior of the pressure cylinder. As soon as the shade remains long enough in the closed position, pressure equalization between the interior of the pressure cylinder  30 , i.e., the pressure volume  46  and the outside space surrounding the pressure cylinder, is established via the air passage opening  58 . 
         [0050]    If the shade is opened proceeding from the completely closed position shown in  FIG. 7 , i.e., its free end is unlocked, the length of shade material  10  is pulled back by the force of the spring  14  of the take-up shaft  12  and the pressure piston  32  is moved to the left in  FIG. 8 . Since the area of the air passage opening  58  is small relative to the cross sectional area of the pressure cylinder  30 , when the pressure piston  32  moves to the left in  FIG. 8 , an overpressure or compressive force F D  forms in the pressure volume  46  which counteracts the tensile force F s  of the cable  34 , and thus, brakes the take-up motion of the length of shade. Since the force of the spring of the take-up shaft continues to act until the length of shade material  10  has been completely taken up, in this connection, air will escape from the pressure volume  46  through the air passage opening  58  until pressure equalization between the interior and exterior of the pressure cylinder  30  has been established. 
         [0051]      FIG. 10  shows a detailed view of a preferred embodiment of the sealing element shown in  FIGS. 2 to 9 . The sealing element  50 , on the one hand, must provide for sealing of the pressure cylinder  30  in order to enclose the pressure volume  46  between the sealing element  50  and the pressure piston  32 , and on the other hand, it must allow a displacement motion of the cable  34  to which the pressure piston  32  is attached. In order to simplify installation of the shade arrangement, the sealing element  50  preferably has an axially running slot  64  which extends to the middle  62  of the cylindrical sealing element  50  and into which the cable  34  is inserted when the shade means is installed, the center recess  62  of the sealing element  50  being dimensioned such that the it rests against the cable  34 , but does not prevent its motion. 
         [0052]      FIGS. 11 &amp; 12  show detailed views of preferred embodiments of the pressure piston  32  shown in  FIGS. 1 to 9 . While the pressure piston  32  can be attached on either end to the cable  34  by the pressure piston  32  being provided with a continuous hole  65  for the cable as shown in  FIGS. 11 &amp; 12 , on the ends of which the cable  32  is attached by means of cementing or welding, by crimping or by separate holding elements. Analogously to the sealing element  50  from  FIG. 10 , the pressure piston  32  could also be provided with a slot which extends as far as the center hole  65  and into which the cable  32  is inserted and clamped, and optionally, fixed by additional measures, such as cementing, welding, crimping, etc. 
         [0053]    After installing the pressure piston on the cable  34 , the pressure piston  34  is preferably provided with O-ring seals in order to seal it relative to the inside wall of the pressure cylinder  30 . For this purpose, as is shown in  FIG. 11 , the pressure piston  32  can be provided with circumferentially running grooves  66 , in which O-rings  68  are locked after being slipped over the pressure piston  32 . 
         [0054]    Alternatively, the pressure piston  32  and can be made in one piece with seals  70  by, as is shown in  FIG. 12 , the seals being molded, for example, injection molded, in one piece onto the pressure piston  32 . Preferably, in this connection, the pressure piston  32  and the pressure cylinder  30  are made of the same material, for example, of plastic, since they are then subjected to the same thermal expansion, and thus, possible tightness problems caused by temperature fluctuations can be precluded from the start. If different materials are used for the pressure cylinder and the pressure piston, the embodiment shown in  FIG. 11  will be provided with separate O-ring seals since here different thermal expansions of the pressure cylinder and pressure piston can be easily equalized by the corresponding elasticity of the O-rings  68 . 
         [0055]    Alternatively to the embodiments in which there is a respective pressure cylinder on each side of the shade, with reference to  FIGS. 13 &amp; 14 , versions of the shade means are proposed in which there is only one pressure cylinder are explained. 
         [0056]    In particular,  FIG. 13  shows an embodiment of the shade means in which a pressure cylinder  30  is located parallel to the take-up shaft  12  such that the length of shade material  10  can be stretched between the take-up shaft  12  and the pressure cylinder  30 . On the free end of the length of shade material  10 , in turn, a pull  18  is attached which is guided laterally by means of sliders  22  in guide rails  24 , of which only one is partially shown in  FIG. 13 . The sliders  22  and  22 ′ of the pull  18  are coupled to the pressure piston  32  which is located in the pressure cylinder  30  and which can be moved via sheathed cables. In particular, the first slider  22  is connected to the pressure piston  32  via a cable  72  which is deflected via a deflection roll  76 . The second slider  22  is also connected likewise to the pressure piston  32  via an circulating cable  74  which is guided in a loop via deflection rolls  76 ,  78  and  80 . 
         [0057]    While  FIG. 13  shows one embodiment in which, when the length of shade material  10  is stretched, the pressure volume is minimized and damping of the take-up motion by a negative pressure produced in the pressure chamber  46  is achieved (as was explained in detail with reference to  FIGS. 2 to 5 ), it goes without saying that, in this embodiment, by the corresponding alignment of the pressure cylinder  30 , the version explained with reference to  FIGS. 6 to 9  could be implemented with damping by overpressure. 
         [0058]      FIG. 14  shows a version of the shade means similar to that from  FIG. 13 ; however, here the pressure cylinder  30  is not located parallel to the take-up roll, but laterally relative to the drawn length of shade. Analogously to the embodiment as shown in  FIG. 13 , in this connection the first slider  22  of the pull  18  is connected via a unilaterally acting cable  72  which is guided via the deflection rolls  76 ,  78  to the pressure piston  32  on which a circulating cable  74  additionally acts which is connected to the second slider  22 ′. Similar to the embodiment from  FIG. 1 , in the embodiments as shown in  FIGS. 13 &amp; 14 , the deflection roll  80  can be located on the axle  38  of the take-up shaft  12  or can be formed by it. Moreover, in the embodiment as shown in  FIG. 14 , instead of the two separate deflection rolls  78 ,  82  there can be a common deflection roll via which both the cable  72  and also the cable  74  are deflected. 
         [0059]      FIG. 15  shows another version of the shade means in which two pressure cylinders are integrated into the pull  18  of the shade means. In this connection, the pull  18  is in turn guided via lateral sliders  82  in guide rails (not shown) which are located along the length of shade. 
         [0060]    In the pull  18 , are a first pressure cylinder  88  and a second pressure cylinder  90  with pressure pistons  92 ,  94  which are coupled via cables  86 ,  84  to the sliders  82 ,  82 ′ of the pull  18 . Different from in the above described embodiments, in which the cable length between the pressure pistons and the sliders is the same in all positions of motion of the shade means, in the version as shown in  FIG. 15 , the cables  84 ,  86  are not fixed with respect to the sliders  82 ,  82 ′, but are attached to a frame  96  which surrounds the shade means and which, for example, can be formed by the fixed surface of a vehicle roof or of a roof frame located underneath, such a roof surface. As is shown in  FIG. 15 , the cables  84 ,  86  are guided around the deflections rolls  98  attached to the sliders  82  such that they cross on one of the sliders (in  FIG. 15 , at slider  82 ). 
         [0061]    In the version of  FIG. 15 , the pressure cylinders  88 ,  90  are designed as pressure cylinders which work with negative pressure damping, as was explained with reference to  FIGS. 2 to 5 . However, it goes without saying that the pressure cylinders  88 ,  90  can also be designed as pressure cylinders which work with overpressure, as was explained with reference to  FIGS. 6 to 9 . Furthermore, one of the two pressure cylinders  88  or  90  can be omitted, still preferably, two sheathed cables being used according to the sheathed cables  84 ,  86  in order to avoid skewing of the pull  18 . 
         [0062]    With repeated reference to  FIGS. 2 to 9 , it goes without saying that the shade means proposed here can be diversely modified. In particular, in an especially simplified version of the embodiment shown in  FIGS. 2 to 5 , the openings  54 ,  56  can be entirely omitted, and then, provision should be made for preferably normal pressure or a slight negative pressure instead of an overpressure prevailing in the pressure volume  46  in the position of the length of shade material in which the pressure volume  46  is minimum, which position is shown completely opened in  FIG. 3 , i.e., the taken-up position. Then, if the shade, in this position, is released so that the pressure piston  32  moves to the left in  FIG. 3 , in the pressure volume  46 , a negative pressure, and thus, a braking force F D  arise which counteracts the cable force F S  caused by the spring of the take-up shaft, and thus, brakes the take-up motion of the length of shade. While in such a simplified version a corresponding damping behavior would be achieved, here however, the pressure volume  46  is not relieved when the shade reaches its taken-up end position. 
         [0063]      FIGS. 7 &amp; 9  show another version of the shade means in which the damping behavior of the pressure cylinder  30  has been modified by making providing another air passage opening  100 . In embodiments with several air passage openings, as is explained below relative to the example with two air passage openings  58 ,  100 , in the first part of the take-up motion proceeding from the completely closed position of the shade in  FIG. 7 , greater air escape through the air passage openings  58 ,  100  takes place, and thus, lower damping than in the second part of the take-up motion in which the pressure piston  32  has passed the air passage opening  100 , and therefore, air can escape from the pressure volume  46  only through the air passage opening  58 . It goes without saying that the damping behavior of the pressure piston  30  can be further modified by providing additional air passage openings. 
         [0064]    When the pressure cylinder or cylinders  30  is or are located laterally parallel to the drawing direction of the length of shade material  10 , as is illustrated in  FIGS. 1 &amp; 14 , the pressure cylinders  30  can be integrated together with the guide rails  24  for the sliders  22  in a profile component, as is illustrated in  FIG. 16 . In particular,  FIG. 16  shows a section through the roof frame as can be used especially in a motor vehicle in which a shade means is used in order to limit light incidence through a transparent or translucent cover. The guide rail  24  can have guide channels  102 ,  106  in this case, in which sliders of the shade means and sliders of a movable cover for closing the roof opening are supported. The guide rail  24  also has a hollow profile section  106  in which a pressure piston  32  is located, and which is thus used as a pressure cylinder  30 . 
         [0065]    Furthermore, the guide rail  24  can have fastening and/or stabilizing elements and can be integrated in one piece in the roof frame which surrounds the roof opening. 
         [0066]      FIGS. 17 to 19  schematically show another version of a pressure cylinder. Different from the pressure cylinders which are shown in  FIGS. 2 to 9  and which are closed on only one side by a sealing element  50  to form the pressure volume  46 , in the pressure cylinder  108  shown in  FIG. 17 , there is a sealing element  50  at each end of cylinder  108 , the cable  34  being able to move through the sealing elements  50 , but escape of air through the sealing elements  50  being largely prevented. In the pressure cylinder  108 , a pressure piston  110  is movably located, and in turn, it is sealed by O-rings  112  relative to the inside wall of the pressure cylinder  108  and the cable  34  is attached to it on both sides. 
         [0067]    As is indicated in  FIGS. 18 &amp; 19 , the pressure piston  110  contains a valve the functions to pass air more quickly in one direction, but more slowly in the other direction in order to cause a braking action. For this purpose, there can be a valve ball  114  in the pressure piston  110  which works in the manner of a return or flash valve which prevents air from flowing through in one direction, but allows flow in the other direction. For example, the pressure piston  110  can have a first air channel  116  and as shown in  FIG. 19 , or as shown in  FIG. 18 , several second air channels  118  which each discharge into a chamber  120  in which the valve ball  114  is located to be able to move freely. The geometry of the chamber  120  and of the air channels  116 ,  118  is chosen here such that, when in the motion of the pressure piston  110  in one direction (to the right in  FIG. 17 ) air flows in through the first air channel  116 , the valve ball  114  rests against a first stop surface  122 , and in doing so, enables the passage of air through the air channel or channels  118 . Conversely, if the pressure piston  110  moves in the other direction, the valve ball  114  is displaced by the air flowing in through the air channel or second air channel or channels  118  such that it rests against a second stop surface  124 , and in doing so, blocks air passage through the first air channel  116 . 
         [0068]    The design shown in  FIGS. 17 to 19  has the advantage that penetration of dirt particles or lubricants into the pressure cylinder is prevented by the bilateral encapsulation of the pressure cylinder  34 .