Screen-positioning device for use in roll blind

Abstract

 A screen-positioning device for use in a roll blind com. prising a fixed shaft (20) sustained by a bracket (12) for rotatably supporting the screen-roll (10), an extension shaft (21) secured to the fixed shaft (20) and formed with a drum portion (22) and a screw-bolt portion (23), a torsional spring (25) having one end thereof fixed to the drum portion (22) and the other end loosely turning around the screw-bolt portion (23), a screw-nut (26) mounted on the screw-bolt portion (23) and formed with a conical surface (28) for fitting engagement with the spring (25). When the screen (30) is raised to a predetermined height, the conical surface (28) is so engaged with the free end portion of the spring (25) that the spring (25) is caused to tighten on the drum portion (22) Whenever the screw-nut (26) is engaged with the spring (25). it undergoes the spring-back force to be rotated in the direction in which the screen (30) is lowered
The fixed shaft 120) is supported by the bracket (12) with the intervention of a one-way clutch mechanism comprising a brake drum (38) secured to the bracket (12). a brake coil spring (36) wound around the brake drum (38). a sector (34) secured to the fixed shaft (20) and fitted on the brake coil spring (36), a slit (35) formed in the periphery of the sector (34) to receive opposite ends (36a, 36b) of the brake coil spring (36), a dial-ring (40) loosely fitted on the sector (34) and provided with an inner projection (41) put in between the both ends (36a, 36b). The roll-up height of the screen is determined by an axial position of the screw-nut (26) on the screw-bolt portion (23). The axial position is easily adjusted by use of the dial-ring (40), which is rotatable together with the fixed shaft (20) or extension shaft (21) to move the screw-nut (26) along the screw-bolt portion (23).

Description

[0001] The invention relates to a screen-positioning device for use in a roll blind of the type having both brackets, a fixed shaft supported by one of the brackets, a screen-roll rotatably supported by the fixed shaft and the other bracket, a screen wound on the screen-roll, and a spring-motor interposed between the screen-roll and the fixed shaft to roll up the screen.

[0002] The device as disclosed by JP Y 58-21919 allows the spring-motor to roll up the screen to a predetermined height and stop the same without shock when the screen is released. It comprises a screw-bolt coaxially connected to the free end of the fixed shaft, a screw-nut mounted on the screw-bolt for rotation with the screen-roll, and a stopper attached to the screw-bolt to prevent a further axial movement of the screw-nut toward the stopper or rotation of the screen-roll. The stopper is composed of a first disc secured to the screw-bolt, a second disc axially movably but non-rotatably mounted on the screw-bolt to catch the screw-nut, and a plurality of belleville springs interposed between the first and second discs.

[0003] The known device has disadvantages one of which is that the screen is somewhat heavy to be lowered from the roll-up height. The reason for this is that the second non-rotatable disc frictionally resists the rotation of the screw-nut when the screen is lowered.

[0004] Another disadvantage is that it is not easy to adjust the axial position of the screw-nut or roll-up height of the screen, because the screw-nut can not be adjusted unless the screen-roll is removed from the brackets. In the case of a plurality of parallel roll blinds, it is impossible to raise all the screen-ends in a line without many trials each needing removal of the screen-roll from the brackets.

[0005] The invention as claimed is intended to provide a remedy. The device according to the invention comprises a fixed shaft, an extension shaft having a drum portion secured to the fixed shaft and a screw-bolt portion, a screw-nut fitted on the screw-bolt portion and formed with a conical surface, and a torsional spring in the form of a coil having an end portion secured to the drum portion and the other free end portion loosely turning around the screw-bolt portion for fitting engagement with the torsional spring. When the torsional spring is frictionally engaged with the screw-nut, it is so twisted as to prevent a further rotation of the screw-nut without bringing any shock and have a spring-back force to rotate the screw-nut or screen-roll in the direction in which the screen is lowered. Therefore, it is very smooth to lower the screen from the roll-up position.

[0006] In preference, the fixed shaft is supported by a bracket with the intervention of a mechanism comprising a dial-ring coaxially fitted on a sector, a brake drum secured to said bracket and coaxially contained within said sector, and a coil spring fitted on said brake drum, said dial-ring having an inner projection disposed between the both ends of said coil spring in a slit which is formed in the sector. Whenever the sector is rotated by the extension shaft or fixed shaft, the inner projection pushes one of the both ends of the coil spring in the direction in which the spring tightens on the brake drum, resulting in that the sector can not rotate. On the other hand, whenever the sector is rotated by the dial-ring, the inner projection pushes the end of the brake coil spring in the direction in which the spring loosens from the brake drum with the result that the dial-ring can rotate the sector as well as the screw-bolt. Upon rotation of the dial-ring, the screw-bolt portion rotates in either direction. This means that the axial position of the screw-nut is exactly adjusted by rotating the dial-ring. The dial-ring is easily rotated by fingers while the screen-roll remains supported by the both brackets.

[0007] The advantages offered by the invention are mainly that the screen is lightly lowered from its roll-up position. The roll-up height of screen is exactly adjusted by fingering the dial-ring while the screen-roll is kept supported by the brackets. Each trial of pulling and releasing the screen for an adjustment of the roll-up height needs no removal of the screen-roll from the brackets, so that it is very quick and easy to adjust the roll-up height of the screen. It is easy to adjust a plurality of parallel blinds in a manner that all the screen-ends are levelled.

[0008] One way of carrying out the invention is described in detail below with reference to drawings which illustrate preferred embodiments, in which:-

FIG. 1 is a longitudinal section of the relevant portion of a roll blind equipped with the device according to the invention, illustrating the device when the screen is fully pulled down;

FIG. 2 is a view similar to FIG. 1, illustrating the device when the screen is rolled up to a desired height;

FIG. 3 is a view of another embodiment, similar to FIG. 1; and

FIG. 4 is a section taken along the line IV-IV of FIG. 3.

[0009] The figures show one end portion of a roll blind equipped with the device according to the invention.

[0010] As seen in FIG. 1, a screen-roll 10 has one end portion rotatably supported by a fixed shaft 20 passing through the end cap 14 of the screen-roll. The fixed shaft 20 has its outer end fixedly sustained by a bracket 12 and the other end pinned to an extension shaft 21, which is composed of an outer drum portion 22, an intermediate screw-bolt portion 23 and an inner end portion 24. A non-illustrated spring-motor is interposed between the opposite fixed shaft (not shown) and the screen-roll 10 to rotate the screen-roll 10 in the direction in which the screen 30 is rolled up. The drum portion 22 is slightly tapered toward the screw-bolt portion 23 and coupled with a torsion spring 25 in the form of a coil which has an end secured to the drum portion 22 and the other free end loosely turning around the screw-bolt portion 23. A screw-nut 26 is screwed on the screw-bolt portion 23 and circumferentially formed with splines 27 which are coupled with axial projections 16 on the inner circumference of the screen-roll 10. This means that the screw-nut 26 moves back and forth along the screw-bolt portion 23 as the screen-roll 10 rotates to wind up and down the screen 30. The inner end portion 24 is rotatably supported by a rotary collar 29, which is peripherally splined to couple with the axial projection 16 for rotation with the screen-roll 10. The screw-nut 26 has a conical surface 28 for fitting engagement with the spring 25, the inner diameter of which is larger than the minimum diameter of the conical surface 28 but smaller than the maximum diameter thereof.

[0011] As seen in FIG. 2, when the screen-roll 10 is rotated to raise the screen 30 to a predetermined height, the conical surface 28 is so engaged with the free end portion of the spring 25 that the spring 25 is caused to tighten on the drum portion 22. Thus, the spring 25 allows no further rotation of the screw-nut 26 as well as the screen-roll 10 and absorbs a shock when the screen 30 stops at the height.

[0012] Whenever the spring 25 is engaged with the screw-nut 26, it has a spring-back force to rotate the screw-nut 26 or screen-roll 10 in the direction in which the screen 30 is lowered. This ensures that the screen 30 is lightly lowered from the roll-up position.

[0013] In comparison with the known device in which it is somewhat heavy to lower the screen from the roll-up height because the screw-nut undergoes a frictional resistance whenever it is rotated to separate from the stopper, the inventive device allows the screen to be lightly lowered because the screw-nut always receives a spring-back force to rotate the screen-roll in the direction in which the screen is lowered whenever it is engaged with the stopper in the form of a torsional spring.

[0014] As seen in FIG. 3, the roll blind is provided with the screen-roll 10 one end portion of which is rotatably fitted on a cylindrical portion of the fixed shaft 20. The fixed shaft has an angular portion 20a fitted in an angular bore of a collar 32, which is secured to a sector 34 by set screws. The sector 34 coaxially contains a brake coil spring 36 around a brake drum 38. The brake drum 38 is rivetted to a bracket 50, which is fixed to a ceiling or the like by set screws. A dial-ring 40 is somewhat loosely fitted on the sector 34.

[0015] As seen in FIG. 4, the sector 34 has its periphery partly cut off as a slit 35 into which the opposite ends 36a, 36b of the brake coil spring 36 are inserted. The both ends 36a, 36b are not crossed but open when axially viewed. The dial-ring 40 has an inner projection 41 put in a space between the both ends 36a, 36b. The collar 32 is fitted on the angular portion 20a of the fixed shaft and rotatably contained within the brake drum 38.

[0016] As seen in FIG. 3, a snap ring 33 is mounted within the brake drum 38 to prevent the collar 32 from slipping out of the brake drum 38. The collar 32 is fixed to the sector 34 by set screws so that the sector 34 is also prevented from axially slipping out of the the brake drum 38 and always kept on the outer periphery of the brake coil spring 36.

[0017] As seen in FIG. 3, when the dial-ring 40 rotates in either direction, the inner projection 41 pushes one of the ends 36a, 36b in the direction in which the brake coil spring 36 is loosened to rotate together with the dial-ring 40 and then cause the sector 34 or fixed shaft 20 to turn. However, the fixed shaft 20 can not cause the dial-ring 40 to rotate, because the fixed shaft 20 or sector 34 always pushes the end in the counter direction in which the brake coil spring 36 is tightened on the brake drum 38 to stop the rotation of the sector 34 or fixed shaft 20.

[0018] The fixed shaft 20, passing through the end cap 14 of the screen-roll 10, is pinned to an extension shaft 21, which has a drum portion 22, a screw-bolt portion 23 and an end portion 24. The end portion 24 is loosely supported by a rotary collar 29, which is peripherally coupled with the screen-roll 10 by an axial projection 16. The drum portion 22 is slightly tapered toward the screw-bolt portion 23. A closely coiled spring 25 is coaxially put on the drum portion 22, having one end fixed to the drum portion and the other free end loosely turning around the screw-bolt 23 portion. A screw-nut 26 is threadedly fitted on the screw-bolt portion 23. The screw-nut 26 is peripherally formed with grooves 27, which is coupled with the axial projection 16 on the inner periphery of the screen-roll 10. This means that, as the screen-roll 10 rotates to wind up or down the screen 30, the screw-nut 26 rotates together with the screen-roll 10 and moves back and forth along the screw-bolt portion 23. The screw-nut 26 is formed with a conical surface 28 for frictionally fitting engagement with the closely coiled spring 25. The inner diameter of the coiled spring 25 is larger than the minimum diameter of the conical surface 28 but smaller than the maximum diameter of the same.

[0019] When the screen-roll 10 winds up the screen 30 to a predetermined height, the screw-nut 26 has its conical surface 28 engaged with the free end of the coil spring 25 in a manner that the conical surface 28 rotates the coil spring 25 to tighten on the brake drum 22. Thus, the coil spring 25 allows no further rotation of the screw-nut 26 or screen-roll 10 to stop the screen 30 at the predetermined height. The spring-back force of the coil spring 25 acts on the screw-nut 26 in the direction in which the screw-nut 26 or screen-roll 10 rotates to wind down the screen. The roll-up height of the screen is determined by an axial position of the screw-nut 26 on the screw-bolt portion 23. The axial position is easily adjusted by the use of the dial-ring 40, which is rotatable together with the fixed shaft 20 or extension shaft 21 to move the screw-nut 26 along the screw-bolt portion 23. The dial-ring 40 is easily operated by fingers to adjust the axial position of the screw-nut 26 or roll-up height of the screen while the _'screen-roll is kept supported by the brackets.

[0020] The device of the invention ensures that the roll-up height of the screen is exactly adjusted by a finger operation to move the screw-nut along the screw-bolt portion while the screen-roll remains in the brackets. It is most suitable for use in a roll blind to be required to raise a screen not fully but half. In the case of a plurality of roll blinds which are mounted side by side, the device can easily make all the screen-ends in a line when they are raised, because each trial of pulling and releasing the screen for an adjustment of the roll-up height needs no removal of the screen-roll from the brackets, so that it is very quick and easy to adjust the roll-up height of screen.

Claims

1) A screen-positioning device for use in a roll blind comprising a fixed shaft (20) fixedly supported by a bracket (12) for rotatably supporting a screen-roll (10) on which a screen (30) is wound, a screw-bolt (23) coaxially secured to said fixed bolt (20), a screw-nut (26) fitted on said screw-bolt (23) and engaged with said screen-roll (10) for rotation therewith, and a stopper (25) attached to said screw-bolt (23) for braking engagement with said screw-nut (26), characterized in that said fixed shaft (20) is joined with an extension shaft (21) having a screw-bolt portion (23) and a drum portion (22) secured to said fixed shaft, that said screw-nut (26) is fitted on said screw-bolt portion (23) and formed with a conical surface (28), and that said stopper comprises a torsional spring (25) in the form of a coil having one end thereof fixed to said drum portion (22) and the other free end loosely turning around said screw-bolt portion (23) for engagement with said conical surface (28).

2) The device as claimed in claim 1, wherein said torsional spring (25) is closely coiled around said drum portion (22) in a manner that said torsional spring (25) tightens when rotated in the same direction as said screen-roll (10) winds up said screen (30).

3) The device as claimed in claim 2, wherein said corsional spring (25) has an inner diameter larger than the ninimum diameter of said conical surface (28) but smaller _Lhan the maximum diameter of said conical surface (28).

4) The device as claimed in claims 1 to 3, wherein said fixed shaft (20) is supported by said bracket (12) with the intervention of a mechanism comprising a brake drum (38) secured to said bracket (12), a brake coil spring (36) wound around said brake drum (38), a sector (34) secured to said fixed shaft (20) and fitted on said brake coil spring (36), a slit (35) formed in the periphery of said sector (34) to receive both ends (36a, 36b) of said brake coil spring (36), a dial-ring (40) loosely fitted on said sector (34) and provided with an inner projection (41) put in between said both ends (36a, 36b).

5) The device as claimed in claim 4, wherein said sector (34) is prevented from axially slipping out of said brake drum (38) by a collar (32) which is fixed to said sector (34) and mounted within said brake drum (38) by a snap ring (39).

Drawing