A ROLLER BLIND HAVING A STOP DEVICE WITH A CYLINDRICAL CAM

Abstract: A roller blind comprises: - a horizontal roller (2) which can rotate freely about its own axis, - a blind (4) having an upper edge fixed to the roller (2) and a free lower edge (5), - a fixed shaft (6), - a resilient biassing device (11) interposed between the fixed shaft (6) and the roller (2), for biassing the roller (2) towards a position in which the blind (4) is rolled up, and - a stop device (13) for locking the blind (4) in any lowered position against the action of the resilient biassing device (11). The stop device (13) comprises a stop body (21) fixed to the shaft (6) and a sleeve (16) which can slide and rotate relative to the shaft (6). The track (17) of a cylindrical cam is formed in the lateral surface of the sleeve (16) and is engaged by an entrainment pin (18) fixed to the roller (2). The track (17) of the cylindrical cam is formed so that the sleeve (16) is drawn into the stop position each time the blind (4) is rolled back by the resilient device (11) after it has been lowered from its most raised position. The track (17) causes the sleeve (16) to move away from the stop position when the blind (4) is lowered by a predetermined distance from the position in which it has been stopped.

Description: The present invention relates to a roller blind of the type comprising: a horizontal roller which can rotate freely about its own axis, a blind having an upper edge fixed to the roller and a free lower edge, a fixed shaft, a resilient biassing device interposed between the fixed shaft and the roller, for biassing the roller towards a position in which the blind is rolled up, and a stop device for locking the blind in any lowered position against the action of the resilient biassing device. More particularly the invention relates to a roller blind according to the pre-characterising portion of claim 1, which is known from EP-A-O 087 146. This document shows a stop device for a roller blind, comprising a coil spring brake mounted on the fixed shaft on which the roller carrying the blind is rotatable mounted. A cam sleeve has a Y-shaped cam groove engaged by a cam pin connected to the roller. The cam pin relatively moves along the cam groove and pushes the cam sleeve to loosen the coil spring brake when the blind is drawn and when it is released after drawn from a lowered position. The spring brake fastens the cam sleeve to the fixed shaft when the blind is released after drawn from the uppermost position. Moreover, from GB-A-189 412 a roller blind is known having a stop mechanism including a ring having two oppositely disposed pawls which are adapted to co-operate with a ratchet and are maintained in contact therewith by a spring. The present invention has the object of providing a stop device more functional and reliable than devices used hitherto. According to the present invention, this object is achieved by a roller blind according to claim 1. Further characteristics and advantages of the present invention will become clear from the detailed description which follows with reference to the appended drawings, provided by way of non-limiting example, in which: Figure 1 is a partially-sectioned perspective view of a roller blind according to the present invention, Figure 2 is a section taken on the line II-II of Figure 1, Figure 3 is an exploded perspective view of a stop device according to the present invention, Figure 4 is a development in a plane of the detail indicated by the arrow IV of Figure 3, Figure 5 is a perspective view of the detail indicated by the arrow V of Figure 3, from a different angle, Figure 6 is a section taken on the line VI-VI of Figure 1, Figure 7 is a section of a variant corresponding to Figure 6, and Figure 8 is an exploded perspective view of some components according to the variant of Figure 7. In Figure 1, a roller blind according to the present invention is generally indicated 1. The blind 1 includes a horizontal roller 2 which can rotate freely about its own axis and is supported at its ends by two brackets 3 fixed to the wall by means of screws. A blind 4 is rolled onto the roller 2 and has an upper end (not shown in the drawings) which is fixed to the roller and a free lower end provided with a stiffening rod 5. The roller 2 has a hollow interior and carries within it a fixed shaft 6 (Fig. 3 ). The shaft 6 has a flattened end, indicated 7, which projects from the roller 2 and is supported by the bracket 3 which is on the left in Figure 1. A spacer tube 6a is supported on the end of the shaft 6 which faces inwardly of the roller 2 (Figs. 3 and 6), and has a terminal cross-shaped support 8 which is mounted for free rotation on the tube 6a. A longitudinal rib 9 is formed on the inside of the roller 2 and engages one of the arms 10 of the cross-shaped support 8, making the latter fast for rotation with the roller 2. Fixed to the support 8 is the end of a helical spring 11 the other end of which is fixed to a larger-diameter part 12 of the shaft 6. Thus, helical spring 11 and the support 8 together constitute a device which constantly biasses the roller 2 towards the position in which the blind 4 is completely rolled up. A stop device, generally indicated 13, is arranged on the shaft 6 for enabling the blind 4 to be locked in any lowered position against the biassing action of the helical spring 11. The device 13 includes a bush 14 situated within the roller 2 in correspondence with its end which is on the left in Figure 1. The bush 14 is connected for rotation with the roller 2 by means of a longitudinal groove 15 which is formed in its lateral surface and engages the longitudinal rib 9 of the roller 2. The end of the bush 14 which faces inwardly of the roller 2 bears against a larger-diameter part 16 of the shaft 6. A portion of the shaft 6 passes through the bush 14 and projects from the roller 2 for insertion, as stated, in the left-hand bracket 3. A sleeve 16 is arranged within the bush 14 for rotation relative thereto and is free to slide along its own axis. A track 17 of cam mechanism is formed in the internal surface of the sleeve 16. The track 17 is engaged by an entrainment pin 18 which is fixed to the lateral wall of the bush 14 and is directed radially inwardly of the bush 14. The end of the sleeve 16 which faces outwardly of the roller 2 is provided with saw-teeth 19. The teeth 19 face corresponding teeth 20 formed on the portion of a stop body 21 which faces inwardly of the roller 2. The body 21 is bored internally and its inner surface carries a projection 22 which is engaged in a longitudinal groove 23 formed in the shaft 6, making the body 21 fast to the shaft 6. A resilient ring 24 is engaged in a seat 25 on the shaft 6 and prevents axial movements of the stop body 21. The sleeve 16 is mounted for rotation on a hollow cylindrical body which is in turn mounted for sliding on the shaft 6. The body 26 carries an internal projection 27 which engages the groove 23 of the shaft 6 and prevents the body 26 from rotating relative to the shaft 6. The lateral surface of the body 26 has a set of circumferential teeth 30 which are snap-engaged by a resilient tongue 31 carried by the sleeve 16, for preventing the sleeve 16 from rotating relative to the shaft 6 when the sleeve 16 is not positively entrained in rotation. The end of the body 26 which faces outwardly of the roller 2 has a circumferential projection 28 which engages an internal abutment 29 of the sleeve 16 to prevent axial movements of the sleeve. A resilient ring 32 engages a seat 33 for the axial restraint of the sleeve 16. In an alternative embodiment, instead of the circumferential teeth 30, the cylindrical body 26 carries a helical spring 34 wound with radial intereference around its lateral surface. The ends of the spring 34 are bent radially towards the outside of the spring to form two stalks 35. The stalks 35 engage opposite sides of a pin 36 which projects axially from the sleeve 16. When the sleeve 16 is entrained in rotation relative to the cylindrical body 26, the pin 36 applies a force to the stalks 35 which tends to open the spring 34, enabling the sleeve 16 to rotate freely. The following is a description of the operation of the stop device 13, starting from the configuration in which the blind 4 is completely rolled onto the roller 2. In this configuration, the entrainment pin 18 is in the position indicated P1 in Figure 4, relative to the track 17. In this configuration, the tips of the teeth 19 are at a distance c=a+b from the base of the teeth 20. When the blind 4 is lowered,the roller 2 rotates in the sense indicated by the arrow in Figure 3. The pin 18, which is fixed to the roller 2, therefore moves relative to the track 17 in the sense indicated by the arrow Y of Figure 4. At first, the sleeve 16 remains stationary, until the pin 18 reaches the position P2, and, at this point, if the blind 4 is lowered further, the pin 18 causes the sleeve 16 to move in the direction indicated by the arrow Z and is brought into the position indicated P3. The sleeve 16 is moved towards the stop body 21 by a distance a but the teeth 19 and 20 are not yet engaged. The pin 18 remains in the position P3 as long as the blind 4 continues to be lowered. When the blind 4 reaches the desired position, the blind is released and is rolled back by the helical spring 11. The pin 18 is thus moved in the opposite direction from the arrow Y and is brought to the position P4, causing a further movement of the sleeve 16 in the direction Z by a distance b. In this condition, the teeth 19 and 20 mesh with each other and are kept in contact by the biassing force of the helical spring 11. In order to release the blind 4 and enable it to be rolled back onto the roller 2, the blind 4 is lowered from the position in which it was locked. This brings the pin 18 into the position P5, moving the sleeve 16 away from the stop body 21 and disengaging the teeth 19 and 20. After the downward travel of the blind 4, the roller 2 is free to rotate in the sense in which the blind is rolled up and the entrainment pin 18 is brought to the starting position P1. It is clear from the above description that the operation of the stop device is precise and reliable.

Claims: A roller blind of the type comprising: a horizontal roller (2) which can rotate freely about its own axis, a blind (4) having an upper edge fixed to the roller (2) and a free lower edge (5), a fixed shaft (6), a resilient biassing device (11) interposed between the fixed shaft (6) and the roller (2), for biassing the roller (2) towards a position in which the blind (4) is rolled up, and a stop device (13) for locking the blind (4) in any lowered position against the action of the resilient biassing device (11); wherein the stop device (13) comprises: a stop surface (20) fast with the fixed shaft (6), a sleeve (16) which can slide and rotate on the fixed shaft (6), cam means (17, 18) for causing the sleeve (16) to slide along the fixed shaft (6) as a result of the rotation of the roller (2) of the blind, the cam means (17, 18) comprising a closed-loop track (17) and a cam-follower member (18) engaged therein, which are carried by the sleeve (16) and by the roller (2) of the blind, the cam track (17) being formed so that the cam-follower member (18) is moved relative to the cam track (17) always in the same sense along it as a result of the rotations of the roller (2) of the blind caused by the successive lowering and raising of the blind (4); characterised in that the stop surface (20) is constituted by end teeth of a stop body (21) connected to the fixed shaft (6), said teeth cooperating with corresponding end teeth (19) fixed to the sleeve (16), the sleeve (16) being adapted to slide towards and away from a stop position in which its end teeth (19) engage the teeth of the stop body (21) so as to prevent the sleeve (16) from rotating relative to the fixed shaft (6), the cam track (17) being formed so that it causes the sleeve (16) to slide into its stop position each time the blind (4) is rolled back by the resilient device (11) after it has been lowered from its most raised position, and to move away from the stop position when the blind (4) is lowered by a predetermined distance from a position in which it has been stopped. A roller blind according to Claim 1, characterised in that the slidable sleeve (16) is arranged for sliding within a bush (14) fixed to the roller (2) and carries the cam track (17) on its outer surface, the lateral wall of the bush (14) carrying a radial pin (18) which projects into the bush (14) and constitutes the cam-follower member (18). A roller blind according to any one of the preceding claims, characterised in that the sleeve (16) is mounted for rotation on a cylindrical body (26) which is in turn mounted for sliding on the fixed shaft (6) and is prevented from rotating relative thereto. A roller blind according to Claim 3, characterised in that the cylindrical body (26) has, on its lateral surface, a set of circumferential teeth (30) which cooperate with a resilient tongue (31) carried by the sleeve (16) for restraining the sleeve (16) against rotating during the stages in which it is not positively entrained for rotation by the roller (2) of the blind through the cam means (17, 18). A roller blind according to Claim 4, characterised in that the cylindrical body (26) has a portion which projects from one end of the sleeve (16) and on which a helical spring (34) is wound with radial interference, the spring having two radial end stalks (35) that engage opposite sides of an axial pin (36) which projects from the end of the sleeve (16) and, from time to time, applies to one of the two stalks (35) a force which tends to open the spring (34) when the sleeve (16) is entrained in either of the two senses of rotation, so as to enable the sleeve (16) to rotate freely relative to the cylindrical body (26).

Inventors: MOTTURA, SERGIO
Applicants: MOTTURA S.P.A.
Application year: 1989
Main classification: E06B9
IPC codes: E06B9