Abstract:
The specification describes a roll up cine projection screen comprising struts for holding it taut in the extended condition for use. It is adapted to be held on a rolling up rod or a tubular casing on a carrier and in the case of which the struts are adapted to pivot with the cine projection screen held taut by them about a horizontal axis. The screen can be secured in several angular positions by means of two pivot bearings having vertical and horizontal axis respectively.

Description:
BACKGROUND OF INVENTION 
     1. Field to which invention relates 
     The present invention relates to cine projection screen. 
     2. The prior art 
     A roll up cine projection screen has already been proposed which is adapted to be held taut in the extended condition for use by means of struts and is adapted to be hung by means of either of its roll up rod or its tubular casing on a carrier. Furthermore, the struts with the cine projection screen held taut on them are pivoted on the carrier about a horizontal axis parallel to the plane of the screen and are adapted to be locked in several angular positions. 
     With this arrangement it is possible, more particularly for the purposes of overhead projection, though also for other types of projection, to arrange for any desired oblique positioning of the plane of the screen with respect to the vertical plane and thus to produce such a setting with respect to the optic axis of the projector that distortion owing to converging lines are prevented. A condition for distortion-free projection is, however, also an alignment between the projector and the cine screen in the horizontal plane in such a manner that the optic axis of the projector passes perpendicularly through the screen plane in its diagonal point of intersection. Accordingly in the case of prior art cine screens the position of the projector in the room was fixed. It is, however, often necessary or desired to arrange the projector at another place in the room, for example in order to avoid furniture, so that the optic axis runs obliquely through the room towards the projection screen. 
     SUMMARY OF THE INVENTION 
     One aim of the present invention is to make possible the production of distortion-free pictures in the case of such lateral oblique projection. 
     The present invention consists in a roll up cine projection screen comprising struts for holding it taut in the extended condition for use and which screen is adapted to be held on a roll up means, namely a rod or a tubular casing which is in turn supported on a carrier. The struts are adapted to pivot, with the cine projection screen held taut by them, about a horizontal axis running parallel to the plane of the screen and can be locked in several angular positions. Between one pivot bearing that has a horizontal axis and the carrier is located another a pivot bearing with a vertical axis. Owing to this additional possibility of pivoting movement it becomes possible to turn the cine screen even in the extended condition towards the auditorium or to the viewers who are locate to the right and to the left. It is thus possible for example even in the case of the use of an opaque cloth to arrange the screen on the window side of a room without the light shining on it giving rise to a disturbing effect. 
     The pivot joint in accordance with the invention with a vertical axis provides for central hanging up means which can be used for attachment to the ceiling or to the wall and only requires very little space. In the case of the construction in accordance with the prior art two massive lateral rods had to be arranged on the wall or on the ceiling respectively. The carrier in accordance with the invention with the double pivot bearings is of small dimensions comparatively speaking when the tubular casing is removed and the carrier does not appear bulky. 
     In accordance with a preferred embodiment of the invention for a carrier, use is made of a tube, preferably of rectangular cross-section, which is provided with a vertical through hole and it is stretched as a wall arm or is constructed as a covering arm with an L-shape. The hole in the carrier has a threaded pin inserted in it so that the pin can rotate. The carrier is secured by being screwed into place by the threaded pin. The threaded pin carries a pivoting sleeve with a vertical axis, and in this sleeve a pivot pin runs which has attachment means for the screen. 
     By the use of suitable friction brakes in the vertical and horizontal axis bearings, fixation of the screen in any desired position becomes possible without it being necessary to slacken off and tighten up clamping screws. 
     In accordance with a further embodiment of the invention the cine screen is provided with a drawing out handle, which is arranged at the lower weighting tube at the bottom end portion of the screen and the handle is screwed, on a thread and can be tightened subsequently in the best possible fashion in order to hold the cine screen securely in all conditions. For this purpose the spring controlled winding and unwinding roller of the screen roll up means can be fixed against rotation by a screen motion run up brake so that it can no longer yield on subsequent tightening. 
    
    
     LIST OF SEVERAL VIEWS OF DRAWINGS 
     In what follows an embodiment of the invention will be described with reference to the accompanying drawings. 
     FIG. 1 shows a partly broken away view of the cine screen suspension means in accordance with the invention with the cine screen drawn out. 
     FIG. 2 shows on a larger scale a sectional view of the double joint arrangement of the suspending or carrying means. 
     FIG. 3 is a side view of a cine projection screen suspended on a wall arm in the drawn out condition. 
     FIG. 4 shows a cine projection screen suspended on a ceiling arm in the rolled up condition. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     As a carrier for the cine screen use is made of a single carrying arm or carrier 10, which in accordance with FIG. 3 is constructed for wall mounting as an extended arm and in accordance with FIG. 4 is constructed for attachment to the ceiling as an L-shaped arm. This carrying arm can for example be constructed as a rectangular tube and be provided with an end cap. By means of a joint arrangement 12, which will be described further below in conjunction with FIG. 2, the screen sleeve or tube or roll up means 14 is carried on the carrier 10. This tube 14 encloses the screen 16 when latter is in the wound up. In accordance with FIG. 1 the screen is drawn out of the tube or roll up means 14. The lower end of the screen 16 is mounted in a slotted tube 18. The drawn out screen is held taut by a spreading strut arrangement in the form of two arms 20 and 22. 
     The upper spreading or extending arm 20 is attached via a pivot joint 24 (see FIG. 3) in a pivoting manner on the double joint 12 and is connected with the lower spreading arm 22 via a knee joint 26. The spreading arms 20 and 22 consist of tubes of square cross-section. In the free end of the lower spreading or extending arm 22 a guide piece 21 can be slid axially, though it is suitably keyed by below described pin 27 to prevent guide piece 21 from turning. This guide piece 21 extends by means of a threaded pin 23 attached to it through the cap 25 that closes the free end of the arm 22. On the threaded pin 23 a tightening handle 28 with a female screw thread is screwed and this handle 28 rests axially on the tube end or on the cap 25 and serves for holding the screen taut, as will be described further below in detail. 
     The guide piece 21 carries a rectangularly projecting pin 27, which projects through a slot, extending along the lower spreading arm 22. Being able to pivot about its axis, pin 27 carries the slotted tube 18, which forms the weighting tube for the cine screen. The ability of pin 27 to pivot with respect to tube 18 permits arms 20 and 22 to fold as arm 22 pivots around pin 27. 
     Furthermore, on the guide piece 21 a projection 29 is attached, which also extends through the slot of the arm 22 and carries a spring plate 31 with a handle 33 that extends alongside handle 28. The spring plate 31 has a hole, through which the pin 27 projects. The spring plate 31 carries a detent pin 35, which fits into a detent hole of a detent plate 30, which plate is attached to the slotted tube 18. In the rolled up condition the slotted tube 18 closes the drawing out slot of the tube 14 and the joint 26 of the folded spreading or extending arms 20 and 22 is carried by a sheet metal joint holder 32, which is attached to the drawing out tube. 
     In order to ensure that the cine screen 16 can be drawn taut in the extended condition by means of the tightening handle 28, the rolling mechanism of the tube or roll up means 14 is provided with a screen unwinding brake. This consists of a disc 58 arranged in a nonrotary manner in the closing cap 56 and the disc 58 is guided by the thread of the roller threaded spindle 60 and can be axially moved by the latter. There is also a disc 62, which rotates with the roller threaded spindle 60, and which carries a run up pin 63. On drawing out the cine screen the roller threaded spindle 60 is turned and moves the nut 58 on the spindle 60 to the left until the pins 63 and 59, respectively, of the discs 62 and 58, respectively, engage each other firmly. 
     By gripping and pushing down the tightening handle 28 via the pivot pin 27 the slotted tube 22 is drawn out downwards and in the terminal position the pin 35 swings into the detent recess of the receiving plate 30. By turning the tightening handle the guide piece 21 within the tube 22 can be drawn downwards so that the slotted tube 18 connected with the guide piece 21 via the pivot pin 27 is also drawn downwards and tightens the cine screen, which in the upper tube is fixed by the screen unwinding brake. 
     The rolling up again of the cine screen is carried out in a simple manner by drawing on the spring handle 33 toward the tightening handle 28 so that the pin 35 comes out of its locked position and the spreading or extending joints 20, 22 can be folded and the cine screen with the slotted tube 18 is passed over the tightening handle 28. 
     The pivoting joint 12 has a vertical joint pin 34, which can be turned in a vertical hole of the carrying arm 10 and is supported by means of screwed on nuts 36 on the upper side of the carrying arm 10. The pivot pin 34 carries a bearing sleeve 38 with a horizontal axis. Between the carrying arm and the bearing sleeve an unstepped surface gripping plate 39 and an unstepped surface braking pad 40 are fitted so that when the nuts 36 are suitably tightened, frictional engagement is provided for which makes possible a swinging of the screen about the vertical axis but the screen is fixed in every pivoting position. The bearing sleeve 38 carries a pin 42, which in its center part carries a hub 44, on which a dovetail shaped carrying bearing 46 is attached while via an arm 48 a further dove tail-shaped carrying bearing 50 is attached for enabling pushing of elements 46, 48 along the tube 14. For passing through the arm 48 and the bearing 46 the sleeve 38 is slotted in the center part. The hub 44 is mounted in a non-rotary manner on the pin 42, which by means of the device described in what follows is guided with frictional engagement in the bearing sleeve 38. The pin 42 has a threaded bolt 47 passing through it, which is carried by closing caps 49, fixed in the bearing sleeve 38, at both ends and which is fixed in these caps by means of screws. Plate springs 51 placed on the threaded bolt 47 rest against the end caps and these springs act on the unstepped surface guiding discs 52 and press the discs against the unstepped surface braking discs 54, which come to engage the ends of the pin 42. In this manner the pin 42 is supported within the bearing sleeve 38 in a frictional manner and the friction is so adjusted by dimensioning of the springs 51 that the cine screen remains in the drawn out position at any desired angular setting.