| WO/2005/086893 | DURABLE SEALING CURTAIN |
| JP10205251 | OPENING/CLOSING DEVICE |
| JP2003211957 | PREASSEMBLED WINDOW SHADE COMPONENT GROUP |
SCHÖRLING, Stefan (Hälla, Fellingsbro, S-71041, SE)
| Claims 1. Roller blind with an operating mechanism in the form of an elongated pulling means (20, 23) running over a wheel (11) so as to form two strands (21 , 22; 24, 25), characterised in that the strands are open and the pulling means (20, 23) and the wheel (11) are adapted in such a manner that the cord slips on the wheel when one of the strands (21 , 22; 24, 25) is pulled except when a counterforce is applied to the other trailing strand. 2. Roller blind according to claim 1 , characterised in that the pulling means is a ball chain (20) and the wheel (11) has shallow depressions for the balls of the ball chain adapted in such a manner that the ball chain skips if no counterforce is applied. 3. Roller blind according to claim 1 , characterised in that the pulling means is a plain cord (23) having a winding angle of more than 180 degrees. 4. Roller blind according to claim 3, characterised in that the cord (23) has a winding angle of more than 270 degrees. |
Field of the invention
The invention relates to a roller blind with a pull cord running over a wheel.
Background of the invention and brief description of the invention
Roller blinds of this type usually have a ball chain in a closed loop. This loop constitutes a risk as young children can put their heads in the loop and be strangled. One aim of the invention is to eliminate this risk without increasing manufacturing costs. This is achieved in that the chain has open strands and the cord and the wheel are adapted in such a manner that the cord slips on the wheel when one of the strands is pulled except when a counterforce is applied to the other trailing strand. There is therefore no need for a closed loop.
Brief description of the drawings
Figure 1 is a perspective view of a roller blind.
Figure 2 is an exploded diagram corresponding to Figure 1.
Figure 3 is a perspective view of a roller blind slightly modified compared to that of
Figure 1.
Figure 4 is an exploded diagram corresponding to Figure 3. Description of illustrated embodiments of the invention
Figures 1 and 2 show one end of a roller blind. It has a wheel 11 with cogs 12 and an end journal 13 with a square hole 14 which matches a square peg (not shown) on a bracket 16 mounted on the wall. The cog-wheel 11 is non-rotatably fixed to the rod of the roller blind and has tangential play with respect to the end journal 13 except when it is rotated towards the limit of the tangential play and can then rotate freely relative to the stationary end journal. This locking mechanism for preventing unintentional rotation of the roller blind is conventional and is not described here.
A ball chain 20 lies over the cog-wheel 11 so as to result in two open strands 21 , 22. The cogs 12 of the cog-wheel form shallow depressions for the balls of the ball chain and the cogs are adapted in such a manner that the ball chain comes out of mesh when any one of these strands is pulled.
In order to rotate the cog-wheel and raise or lower the roller blind, one of the strands is pulled and a counterforce is applied to the other strand so that the ball chain does not come out of mesh. The other strand can then be returned to the starting position without a counterforce being applied without the cog-wheel rotating and then the action can be repeated in order to rotate the cog-wheel again.
As a result of the fact that the action can be repeated, there is no need for a closed loop on the chain and it is possible to use an open chain with relatively short strands.
Figures 3 and 4 show a modified embodiment in which a cord 23 having a circular cross section is used as a pulling means instead of a ball chain. Figure 4 shows the cog-wheel 11 removed from the end of the rod of the roller blind, whereas in Figure 2 it is shown inserted. The two strands 23 of the cord are designated by the reference numerals 24, 25. Otherwise, the same reference numerals used in Figures 1 and 2 are used here. The cord 23 is wrapped around the wheel, i.e. it has a large winding angle, in this case greater than 360 degrees. The winding angle is adapted to the cord and wheel combination so as to give the same function as that of the embodiment according to Figures 1 and 2, i.e. so that the wheel 11 is rotated when a counterforce is applied to the trailing strand. If the friction between the cord and the wheel is high, the winding angle does not have to be as large as that shown. In the extreme case, it is sufficient for the cord to lie over the wheel, i.e. to have a winding angle of 180 degrees, although a relatively large counterforce is then often required in order to rotate the wheel 11. This winding angle can be increased by applying a guide means to the underside of the wheel to control the two strands of the cord in such a manner that the winding angle is, e.g. 270 degrees or more.
Figures 3 and 4 show a lateral projection 26 on the end cover above the cogs 12 and this projection prevents the ball chain from skipping if it is desired to use a ball chain in a closed loop in the conventional manner instead of the cord 23. When a cord 23 is used, it is of course not necessary to use a cog-wheel and a smooth wheel can be used.
A cord or a ball chain has been shown by way of example for the pulling means. Alternatively, e.g. a flat belt can be used as the pulling means. Other modifications are also possible within the scope of the claims.