Abstract:
An umbrella device which has a shank, an umbrella-like cap formed as a membrane and a driver. The membrane is connected to the shank and is caused by the driver to move from a position of rest where it droops limply around the shank to an open position where it is essentially horizontal due to the centrifugal forces of the membrane produced by the rotation of the membrane by the driver.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an umbrella device having a shank and an umbrella-like cap which can rotate around the shank and opened up. 
   BACKGROUND OF THE INVENTION 
   Umbrella devices in the form of umbrellas and parasols are known, whose umbrella-like cap is provided with ribs, one end of which is linked to a ring arranged at the upper end of a shank and the other end at a sleeve, which can be displaced and fixed in place along the shank for spreading the umbrella cap. 
   These ribs are required for supporting the cover material used as the covering. In case of umbrella devices of larger dimension, the ribs already constitute a large proportion of the dead weight of the umbrella device. With a filigreed weight-reducing design they are prone to buckling when strained by wind. The controlled folding up of the cover material and of the rod produces strain has been shown to be technically difficult with umbrella devices of large surface areas, and poses the danger of damage to the thin cover material of low flexural strength in the contact points between the cover and the ribs. 
   An umbrella device having a shank and an umbrella-like cap which can rotate around the shank and opened up is known, for example, from U.S. Pat. No. 5,020,557 and from European Patent No. EP-A 0 382 122. In the first case, the umbrella-like cap is rotatingly held for absorbing and compensating wind forces. In the second case, the umbrella-like cap has two elements arranged on top of each other, wherein the upper cap element can be manually rotated with respect to the lower, fixed-in-place cap element by preselected degrees of angle for filtering out undesirable sunlight components. Such umbrella devices with a manually rotatable cap are relatively expensive to produce and elaborate in use, since they can be opened up-only over provided ribs, which moreover have a considerable weight. 
   SUMMARY OF THE INVENTION 
   It is the object of the present invention to provide an umbrella device of the type mentioned at the outset which, while avoiding the above mentioned disadvantages, can be opened up and folded again in a simpler, and in particular automatic way. 
   According to the present invention, the umbrella-like cap can be motor driven and includes a membrane of low flexural strength, but with tensile strength. The membrane has a circular base surface which can be erected by means of centrifugal forces resulting from the rotation from a position of rest, where it droops limply around the shank to an opened, essentially horizontal position. 
   A light-weight umbrella device which can be automatically opened up is created by means of the steps in accordance with the present invention, which can be mechanically simplified and can be produced with a large area in particular. The umbrella device moreover provides an active ventilation of the space underneath the umbrella-like cap. 
   A preferred arrangement of the motor drive and of the holder of the membrane on the power take-off shaft results from fixing the shank at the head of the shank against relative rotation, and the use of an electric motor. 
   In a preferred manner, the motor drive can be realized either by means of an electric motor of small dimensions, a pneumatic or also a hydraulic drive mechanism. The energy supply for the motor drive is received in the shank for achieving a weather protection for it and/or to avoid spoiling the appearance. As an energy supply for a pneumatic drive mechanism, the shank itself can constitute the air-conducting tube. 
   The membrane can have a pagoda-shaped cut-out shape, matched to the specific influencing variables suitably employed for improving the aerodynamic stability of the umbrella device. For example, a shape of the cap can include ballast which can be useful. 
   Providing the membrane with radially and/or annularly arranged cords is also advantageous for improving the aerodynamic stability of the umbrella device. Favorable embodiments thereof ensue from a membrane provided with additional masses on the outer circumference of the membrane, such as a cord at the edge, individual weights, doubling of the membrane, or the like. 
   A further option for improving the aerodynamic stability and/or the unfolding process of the umbrella-like cap of the umbrella device results, from a membrane having a flat, pillow-like shape, which may be divided into radially and/or annularly arranged air chambers connected with a blower, or a pneumatic drive, from having the inside of the membrane, which is at rest, charged with compressed air, and from providing the shank with outlet openings in the area of the membrane when at rest. 
   Further details of the present invention can be taken from the description which follows, in which the present invention is described in greater detail and explained by means of the exemplary embodiments represented in the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B , illustrate an umbrella device in accordance with a preferred exemplary embodiment of the present invention in an opened-up operating position in a schematic perspective view or a schematic lateral view, 
       FIG. 2 , illustrates the umbrella device in accordance with  FIG. 1  in a schematic lateral view, but in the folded-up position of rest, 
       FIG. 3 , illustrates a representation corresponding to  FIG. 1B , but in accordance with a second embodiment of the present invention, 
       FIGS. 4A , B to  8 A, B, illustrates representations corresponding to  FIG. 1A , or partial enlargements in accordance with the circles IV to VIII, but in accordance with further exemplary embodiments of the present invention, 
       FIG. 9 , illustrates a representation of a further embodiment corresponding to  FIG. 1B , 
       FIG. 10 , illustrates a representation of a further embodiment corresponding  FIG. 1B , 
       FIG. 11 , illustrates still another embodiment of the present invention during the opening-up process in a schematic lateral view. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The umbrella device  10 ,  110  or  210  represented in the drawings has a ribless, umbrella-like cap  11 ,  111  or  211 , which is rotatably maintained at the upper end of a shank  12 ,  112  or  212  and can be rotatably driven in such a way, that the umbrella-like cap  11  can be opened-up from a drooping, limp position of rest into an umbrella-like operating position, can be maintained opened up and stabilized by the centrifugal force resulting from its rotation. 
   In accordance with  FIG. 1B , the upwardly extending shank  12  is maintained fixed in place, for example fastened underneath the bottom-surface  13  on a block  14 . A motor drive  15  is fastened or flanged at the upper end of the shank  12 , whose vertically upwardly projecting drive shaft  16  is connected, fixed against relative rotation, with a lower disk  17  which, together with an oppositely located upper disk  18  is a part of a fastening device  19  for the cap  11 . 
   The umbrella-like cap  11  essentially consists of a membrane  21  made of a light material of low flexural strength, but having tensile strength. The membrane  21  has a circular base surface and is fastened around its center between the two disks  17  and  18  of the fastening device  19 , wherein the two disks  17  and  18  are typically arranged centered with respect to the circular peripheral edge  22  of the membrane  21 . Maintaining the membrane  21  on the fastening device  19  can be provided in a manner not represented, for example by clamping the two disks  17 ,  18  against each other. 
   In the position of rest represented in  FIG. 2 , the membrane  21  is arranged around the shank  12 , limply drooping down from the fastening device  19 . It should be understood that the ratio between the membrane diameter and the shank length can be selected in accordance with conventional umbrellas or parasols. If the motor drive  15  which, in the exemplary embodiment represented here is an electric motor drive, is switched on, the membrane  21  is caused to rotate, for example in the direction A ( FIG. 1A ), because of which the membrane  21  is raised in the direction of the arrows B because of the centrifugal forces acting on it, until it has attained the opened-up, here approximately horizontal operating position, represented in  FIGS. 1A and 1B . In this operating position, the rotation (arrows A) of the membrane  21  lasts as long as the umbrella-like cap  11  is intended to be kept opened up. The required size of the rotating speed is a function of various factors, such as weight, exterior effects, and the diameter of the membrane  21 , as well as the amount of the possible additional ballasting. To fold the membrane  21  into the position of rest or parked position in accordance with  FIG. 2 , the motor drive  15  is switched off or the speed of rotation is steadily reduced. 
   The embodiment in accordance with  FIG. 3  shows an umbrella device  10   a  with a pagoda-shaped cut-out shape of the umbrella cap  11   a  matched to the specific influencing variables. 
     FIGS. 4 to 8  show embodiments of umbrella devices  10   b  to  10   f , whose umbrella-like caps  11   b  to  11   f  or membranes  21   b  to  21   f  are equipped with ballasting  30  of different kinds. In accordance with  FIG. 4 , the membrane  21   b  is provided with annular cords  31  which, in accordance with  FIG. 4B  are covered and held by a strip  36  made, for example, from the material of the membrane. 
     FIG. 5  shows ballasting  30  in the form of radial cords  32 , which are maintained on the top or the underside of the membrane  21   c , for example also by means of strips  37 . 
     FIG. 6  shows an edge cord  33  as ballasting, which is held in an edge seam  38  of the membrane  21   d.    
   In the embodiment in  FIG. 7 , the ballasting  30  is formed by individual masses  34 , which are fastened in an evenly distributed arrangement on the outer edge  29  of the membrane  21   e.    
   Finally,  FIG. 8  shows ballasting  30  at the peripheral edge, for example by means of an annular doubling  35  of the material of the membrane  21   f.    
   An improvement of the aerodynamic stability and the opening process when the rotating process is started results from the ballasting. 
   The embodiment in accordance with  FIG. 9  shows an umbrella device  10   a ′ with a double-layered cap  11   a ′, whose upper,  25 , and lower layer  26  are each maintained at an upper,  19   a , and lower fastening device  19   b.    
   The umbrella device  110  represented in  FIG. 10  has a cap  111 , wherein the membrane  121  is embodied as a flat cushion with an upper membrane layer  41  and a lower membrane layer  42 , which are connected along the outer edge. The two membrane layers  41  and  42  are divided into individual chambers  44  by means of intermediate walls  43 . In the exemplary embodiment, the radial and/or ring-shaped chambers  44  are filled with air, wherein the interior pressure to be built up in the chambers  44  can be provided in different ways during start-up and during rotation in the operating position. For this purpose, the membrane  121  or its chambers  44  are connected in a manner not represented with a blower. The interior pressure built up in the chambers  44  can also be temporarily limited in the operating phase. It is for example possible to increase the interior pressure during the duration of external effects, such as increased wind strain, and to reduce it during phases of reduced effects, or even to evacuate the chambers  44 . 
   In the umbrella device  210  represented in  FIG. 11 , the shank  212  is provided with outlet openings  46  in its upper area covered by the membrane  212  in the position of rest, which are arranged in the wall of the hollow shank  212 , for example distributed over the circumference and at several heights. The hollow shank  212  is connected with a blower  47 . The compressed air generated by the blower  47  is conducted through the hollow shank  212  and can exit through the outlet openings  46 . It is possible by means of this compressed air flow  48  to effectively aid the opening process of the membrane  221 , which here has the shape of the membrane  21  in accordance with  FIGS. 1 and 2 , during the rotation of the membrane  221  (arrow A). After having attained the operating position of the membrane  221 , the blower  47  can be switched off. 
   While the motor drive  15  is represented as an electric motor in the exemplary embodiments shown in the drawings, whose electrical feed line can be conducted through the hollow shank  12 ,  112 ,  212 , it is provided in accordance with an embodiment not represented to design the motor drive  15  as a pneumatic drive. It is possible to use the blower  47  in accordance with  FIG. 10  for this, in which the underside of the fastening device  19  is embodied in the form of a wind wheel, for example. With this arrangement the outlet openings  46  are designed to be closable. It should be understood that such a pneumatic drive mechanism can also be advantageous in connection with the exemplary embodiment in  FIG. 10 .