A PULLING CORD DEVICE FOR VENETIAN BLINDS AND THE LIKE

Abstract: The desire to take a cord or ball chain through the side of an upper profile commonly requires friction reducing means for supporting the string. According to the invention this is obtained by a combination of cord pulleys consisting of a pulley (3) directly fitted to the shaft (2) and two further pulleys (4 and 7) which are freely rotating and which guide the cord in a compact manner so that pulling the other end causes rotation of the shaft (2) in the opposite direction.

Description: A pulling cord device for Venetian blinds and the like. The invention relates to a mechanism in a toprail for an actuating cord for Venetian blinds and the like comprising a driven cord pulley and friction reducing means at the exit of the cord from the mechanism. It is known to control the angular position and lifting of the slats of Venetian blinds by means of a cord which is fitted round a pulley which creates friction with respect to the cord. Both ends of the cord may be pulled, whereby the slats may be tilted in both directions. It is similarly known to use an endless cord or ball chain which is fitted round a pulley so that e.g. a roller blind, folded blind, or Venetian blinds may be lifted or lowered by repeated pullingin the same side of the string. These constructions have been provided with a pulley with an axis perpendicular to the top rail and a transmission, such as conical gears or a worm gear to transmit the movement to the desired rotational axis which is along the lenght of the upper rail. This solution is complicated because the gear transmission has to be provided with good bearings. Another solution is to pull directly with a cord pulley on the actuating shaft, but in this case the desire to take the cord or ball chain out of the side of the top rail creates problems with friction between the cord and guide surfaces, because the cord enters at the top of the pulley which is simple, but it also enters at the bottom, where the cord has to bent around a small radius of curvature, so that small rollers or special friction reducing surfaces in glide channels have to be provided. This creates a considerable difference in the pulling force which has to be exerted by the user in order to operate a Venetian blind or other blinds, in particular when worn. Furthermore it frequently creates confusion as to 2 which cord has to be pulled when a particular adjustment is desired. It is the purpose of the invention to provide a mechanism which guides the cord in a friction reducing manner without the use of special glide channels. This is obtained in a construction which is particular in that the ends of the cord exit from the mechanism at the top side of two pulleys which are fitted to one and the same shaft which is parallel to the top rail, in which one pulley is mounted freely rotatable on the shaft and the other pulley is fixed to the shaft, in which there is fitted between the two pulleys a freely rotatable third pulley on a shaft perpendicular to the shaft in the top rail. Thereby one end of the cord is caused to drive the shaft directly in one direction, and the other end of the cord to drive in the other direction on the first pulley, because the direction is changed by means of the second and third pulleys. The particular advantage of this solution is that the two ends of the cord exit next to each other at the same height in the side of the top rail, and that the string at no place is curved around a small radius of curvature with a support that creates friction. In an advantageous embodiment it is provided that the direct pull is used in the fixed pulley for lifting of the Venetian blind or roller blind, and that a pull in the other end of the cord is used for the lowering requiring less force. In this manner a further reduction occurs in the difference between pulling forces. The invention will be described in greater detail in the following with reference to the drawing, in which Fig. 1 shows a housing for the mechanism according to the invention with two cords in a three-dimensional representation, and 3 Fig. 2 shows the mechanism from behind in a similar three- dimensional representation. In Fig. 1 is seen a housing 1 which contains a shaft 2 and two pulleys 3 and 4, around which are wrapped two ends 5 and 6 of a cord. In this embodiment the cord is a ball chain, i.e. a thin and flexible cord with spheres cast around it at a fixed distances. The housing 1 is fitted into a top rail which is not shown, which is provided with openings for the cord ends 5 and 6 next to each other. The shaft 2 is connected to the further mechanism which acutates a roller blind, a folding blind, a Venetian blind or a similar screening device. The pulley 3 is fitted non-rotatably to the shaft 2, and a pull on the end 5 of the cord hence causes rotation in one direction (in the figure counterclockwise) of the shaft 2. In Fig. 2 the parts fitted into the housing are seen from behind, and it is seen that the ball chain has been placed around both pulleys as well as around a "reversing pulley" 7 fitted therebetween. This reversing pulley has its axis perpendicular to the shaft 2 and has the purpose to ensure that a pull in the end 6 of the cord is transmitted as a rotation in the opposite direction of the pulley 3 and hence the shaft 2. A further function of the reversing pulley is to increase the amount of wrap around the pulley 3, which is important for the transmission of forces in case a thick cord without spheres is used for the actuation. The pulley 4 is freely rotatable on the shaft 2. However, the friction may be further reduced and still further stability is obtained by an independent bearing for the pulley 4. During operation it is relevant to ensure that a pull against a resistance from e.g. gravity during lifting of a roller blind occurs directly by means of pulling the cord 4 end 5, because the pull in this case occurs directly on the pulley 3. The increased friction which is present in spite of the use of friction reducing bearing materials for the pulleys 4 and 7 is less disadvantageous during a corresponding lowering, because it may directly contribute to a weak braking of the movement. In case it is desired to use a thick cord without spheres, it may be advantageous to increase the wrap of the end 5 of the cord around the pulley 3, and this may be obtained in that the intermediate pulley 7 is fitted with a downwards directed vertical shaft instead of a horizontal shaft as shown in Fig. 2. Thereby the wrap may be increased to ca . 270 degrees (as opposed to 180 degrees as shown) , and this increase combined with a suitable profile for the cord pulley 3 will ensure a stable function.

Claims: 5 P A T E N T C L A I M S 1. A mechanism in a toprail for an actuating cord (5, 6) for Venetian blinds and the like comprising a driven cord pulley and friction reducing means at the exit of the cord from the mechanism c h a r a c t e r i s e d i n that the ends of the cord exit from the mechanism at the top side of two pulleys (3, 4) which are fitted to one and the same shaft (2) which is parallel to the top rail, in which a first pulley (14) is mounted freely rotatable on the shaft and the a second pulley (3) is fixed to the shaft, in which there is fitted between the two pulleys a freely rotatable third pulley (7) on a shaft perpendicular to the shaft in the top rail. 2. A mechanism according to claim 1, c h a r a c t e r i s e d i n that the bearing of the freely rotatable pulley (4) is fitted directly to the shaft (2) . 3. A mechanism according to claim 1, c h a r a c t e r i s e d i n that the bearing of the freely rotatable pulley (4) is fitted inside the housing (1! of the mechanism. 4. A mechanism according to any of the preceding claims, c h a r a c t e r i s e d i n that the direct pull is used in the fixed pulley (3) for lifting of the Venetian blind or roller blind, and that a pull in the other end (6) of the cord is used for the lowering requiring less force .

Inventors: JENSEN POUL CHRISTIAN, JENSEN, POUL, CHRISTIAN
Applicants: FABERS FAB AS C, JENSEN POUL CHRISTIAN, A/S CHR. FABERS FABRIKER, JENSEN, POUL, CHRISTIAN
Application year: 1999
Main classification: E06B9
IPC codes: E06B9