Cord-winding device for venetian blind

A cord winding device for a Venetian blind includes a receiving unit, a resilient driving unit mounted in the receiving unit, a braking unit mounted in the receiving unit and adjacent to the resilient driving unit, and a unidirectional damping unit mounted in the receiving unit. Through cooperation between the braking unit and the resilient driving unit, during winding and unwinding of pull cords, a bottom rail can be descended slowly and stopped conveniently at any desired height.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a Venetian blind, and more particularly to a cord winding device for a Venetian blind.

2. Description of the Related Art

Referring toFIGS. 1 and 2, a Venetian blind disclosed in U.S. Pat. No. 406,995 includes a head rail1, a bottom rail2, a plurality of slats3disposed between the head rail1and the bottom rail2, two pull cords4connected to the head rail1and the bottom rail2and extending through the slats3, and a cord winding device5mounted in the head rail1.

The cord winding device5includes a support6fixed in the head rail1, a resilient driving unit7mounted on the support6, and a braking unit8.

The resilient driving unit7includes first and second reels701,702, a driving wheel703disposed between the first and second reels701,702, a spring winding wheel704disposed between the driving wheel703and the second reel702, and a spiral spring705disposed between the driving wheel703and the spring winding wheel704. Four gears706are connected respectively to the first and second reels701,702, the driving wheel703, and the spring winding wheel704. Any two adjacent gears706mesh with each other.

The braking unit8includes a braking wheel801and a braking mechanism802disposed between the braking wheel801and one of the pull cords4for controlling geared connection between the braking wheel801and the first reel701.

The bottom rail2can be stopped at any desired height. However, if the size of the Venetian blind is comparatively large such that the total weight of the slats3and the bottom rail2is greater than the return force of the spiral spring705, since the bottom rail2is not braked during lowering of the bottom rail2, downward movement speed of the slats3and the bottom rail2is relatively quick so that the bottom rail2may cause damage to a person or an article disposed under the Venetian blind, thereby affecting adversely safety during use.

To overcome this drawback, in an improved Venetian blind disclosed in CN202788572, the applicant proposes to add a unidirectional clutch and a damping unit to the Venetian blind disclosed in U.S. Pat. No. 406,995, so as to retard downward movement of the bottom rail2, thereby increasing safety during use. However, since a relatively large space is required for operation of the braking mechanism, its volume needs to be reduced.

SUMMARY OF THE INVENTION

The object of this invention is to provide a cord winding device for a Venetian blind, which can retard downward movement of slats and a bottom rail to promote safety during use, and which has the advantages of simple structure, and easy manufacture and assembly.

According to this invention, a cord winding device for a Venetian blind includes a receiving unit, a resilient driving unit mounted in the receiving unit, a braking unit mounted in the receiving unit and adjacent to the resilient driving unit, and a unidirectional damping unit mounted in the receiving unit. Through cooperation between the braking unit and the resilient driving unit, during winding and unwinding of pull cords, a bottom rail can be descended slowly and stopped conveniently at any desired height.

As such, downward movement of the slats and the bottom rail can be retarded by the unidirectional damping unit to promote safety during use.

Preferably, the unidirectional damping unit is located at a side of an assembly of a first reel and the braking unit, so that the total length of the cord winding device can be reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIGS. 3 and 4, the preferred embodiment of a cord winding device according to this invention is used in a Venetian blind. The venetian blind includes a head rail (not shown), a bottom rail (not shown), a plurality of slats (not shown) disposed between the head rail and the bottom rail, and first and second pull cords100connected to the head rail and the bottom rail and extending through the slats. The cord winding device includes a receiving unit10, a resilient driving unit20mounted in the receiving unit10, a braking unit30mounted to the receiving unit10and adjacent to the resilient driving unit30, and a unidirectional damping unit40mounted to the receiving unit10.

The receiving unit10is mounted fixedly in the head rail, and includes a receiving seat11and an upper cover12disposed above and covering the receiving seat11. The receiving seat11extends along a longitudinal direction (X), and has a first end111and a second end112that is opposite to the first end111along the longitudinal direction (X). The upper cover12is formed with a position limiting slot121.

The resilient driving unit20is mounted in the receiving seat11, and includes a first reel21disposed rotatably in the receiving unit10, a second reel22disposed rotatably in the receiving unit10, and a reel driving member23rotatable to drive rotation of the first and second reels21,22. The first and second pull cords100,100′ are wound respectively the first and second reels21,22. The first reel21includes a first cord receiving wheel211connected with the first pull cord100, and a first gear212connected to and coaxial with the first cord receiving wheel211. The second reel22includes a second cord receiving wheel221connected with the second pull cord100, and a second gear222connected to and coaxial with the second cord receiving wheel221. The reel driving member23is disposed between the first and second reels21,22, and includes a spring winding wheel231, a spiral spring232wound on the spring winding wheel231and fastened to the spring winding wheel231at one end of the spiral spring232, a driving wheel233connected to the other end of the spiral spring232, and two driving gears234connected respectively to the spring winding wheel231and the driving wheel233and meshing respectively with the first and second gears212,222. The driving gears234are coaxial respectively with the spring winding wheel231and the driving wheel233. In this embodiment, rotating axes of any two adjacent ones of the first and second reels21,22, the spring winding wheel231, and the driving wheel233are misaligned with each other along the longitudinal direction (X). The rotating axes of the first reel21and the spring winding wheel231are aligned with each other along the longitudinal direction (X). The rotating axes of the second reel22and the driving wheel233are aligned with each other along the longitudinal direction (X).

The braking unit30is mounted in the receiving seat11, and is adjacent to the first reel21. In this embodiment, the braking unit30includes: a braking plate31contactable with the first reel11to stop rotation of the first reel11; a braking shaft32connected fixedly to the braking plate31and adapted for contact with the first pull cord100such that, upon movement of the first pull cord100, the braking shaft32is rotated by the first pull cord100; a straight slide slot33formed in the receiving unit10; and a position limiting pin34disposed movably in the slide slot33. The first pull cord100extends into the receiving unit10to contact frictionally the braking shaft32, and is wound on the first reel21. The braking plate31is rotatable in the receiving unit10about a vertical axis (L) perpendicular to the longitudinal direction (X), and has a plurality of teeth311rotatable to mesh with the first reel21, a bottom surface312perpendicular to the vertical axis (L) and abutting against the receiving unit10, and a guide slot313formed in the bottom surface312. With further reference toFIG. 5, which illustrates a braking state of the braking unit30and a unidirectional idle rotation state of the unidirectional damping unit40, the guide slot313has a curved slot section314extending around the vertical axis (L), a first stop slot section315connected to and disposed downstream of the curved slot section314, a second stop slot section316connected to and disposed downstream of the first stop slot section315, a third stop slot section317connected to and disposed downstream of the second stop slot section316, and a return slot section318connected between the third stop slot section317and a middle portion of the curved slot section314. When the teeth311of the braking plate31engage the first reel21, the first stop slot section315extends from the curved slot section314away from the first reel21and toward the vertical axis (L), the second stop slot section316extends from the first slot section315toward the first reel21and the vertical axis (L), the third stop slot section317extends from the second slot section316away from the first reel21, and the return slot section318extends from the third stop slot section317into the curved slot section314away from the first reel21and the vertical axis (L). Movement of the first pull cord100results in conversion of the teeth311of the braking plate31between an engaging state, where the teeth311mesh with the first reel21, and a disengaging state, where the teeth311are spaced apart from the first reel21. The cross-section of the braking shaft32has an arc that is adapted for contact with the first pull cord100and that has an angle not greater than 180°. The position limiting slot121has opposite closed first and second ends122,123, which are closed ends. The braking shaft32is provided with a position limiting rod321extending movably into the position limiting slot121. The position limiting rod321is vertical, and is disposed above and connected to the braking shaft32. However, to illustrate the guide slot313, inFIG. 3, the position limiting rod321is shown to be horizontal such that the bottom surface312of the braking plate31is vertical.

The unidirectional damping unit40is located at aside of an assembly of the first reel21and the braking unit30. With further reference toFIG. 6, the unidirectional damping unit40includes a unidirectional clutch41disposed pivotally on the receiving unit10, a fixed outer shell42sleeved around the unidirectional clutch41and fixed on the receiving unit10, and a damping fluid43disposed between the fixed outer shell42and the unidirectional clutch41. The unidirectional clutch41has a driven wheel411braking unidirectionally the first reel21, a rotating shaft412connected fixedly to the driven wheel411, a cylinder413sleeved rotatably around the rotating shaft412, and a plurality of braking members414disposed between the rotating shaft412and the cylinder413. The driven wheel111meshes with the first gear212of the first reel21. The cylinder413has a plurality of curved grooves416that are formed in an inner surface415thereof and that receive respectively and movably the braking members414. Each curved groove416has a deep end417and a shallow end418that is opposite to the deep end417such that, when the corresponding braking member414is disposed in the deep end417, the cylinder413is rotatable relative to the rotating shaft412, and when the corresponding braking member414is disposed in the shallow end418, the cylinder413is co-rotatable with the rotating shaft412.

With particular reference toFIGS. 5 and 6, when the bottom rail is suspended and fixed at a desired height, the teeth311mesh with the first gear212, the braking members414are disposed at the deep ends417of the curved grooves416, the position limiting rod321is disposed at the first end122of the position limiting slot121, and the position limiting pin34is disposed at an end of the curved slot portion314of the guide slot33.

With particular reference toFIGS. 4 and 5, when the slats are in a closed state such that the bottom rail is adjacent to the cord winding device, to open the slats, the bottom rail is first pushed to move upwardly slightly, so that a force applied to the spiral spring232by the weight of the slats and the bottom rail is removed. At this time, due to the return force of the spiral spring232, the driving wheel233is rotated clockwise to drive counterclockwise rotation of the first reel21. Hence, the braking plate31is rotated in a clockwise direction (I) until the first stop slot section315engages the position limiting pin34, the teeth311are removed from the first gear212, and the position limiting rod321is disposed at the second end123of the position limiting slot121, as shown inFIG. 7.

Next, with particular reference toFIGS. 8 and 9, the bottom rail is pulled downwardly to move the first and second pull cords100,100′ outwardly (i.e., unwind the first and second pull cords100,100′). At this time, due to a friction between the first pull cord11and the braking shaft32and cooperation between the position limiting pin34and the slide slot33, the braking shaft32is rotated in a counterclockwise direction (II) by a small angle to allow the second stop slot section316to engage the position limiting pin34. Upon continued outward movement of the first pull cord100, the first reel21is rotated clockwise to thereby drive counterclockwise rotation of the driven wheel411and the rotating shaft412of the unidirectional damping unit40, so that the braking members414are moved from the deep ends417to the shallow ends418, thereby rotating the cylinder413relative to the fixed outer shell42. Hence, rotation of the cylinder413, the rotating shaft412, and first reel21is retarded by the damping fluid43, thereby reducing downward moving speed of the slats.

Referring toFIG. 10, when the bottom rail is descended to a desired height, it is pushed upwardly slightly to rotate the driving wheel233clockwise and the braking plate31in the clockwise direction (I), until the third stop slot section317engages the position limiting pin34. Finally, the bottom rail is pulled downwardly slightly to rotate the braking shaft32in the counterclockwise direction (II). During counterclockwise rotation of the braking shaft32, since the return slot section318extends from the third stop slot section317into the curved slot section314away from the first reel21and the vertical axis (L), the braking plate31is returned to its original position (as shown inFIG. 5) so as to allow the teeth311to mesh with the first gear212, thereby stopping the bottom rail at the desired height.

Through the above operation, the bottom rail can be moved to and stopped at any desired position. Alternatively, a similar process may be provided to include the steps: pushing the bottom rail upwardly slightly, pulling the bottom rail downwardly slightly, pushing the bottom rail upwardly to a desired height, and pulling the bottom rail downwardly slightly. In this manner, the position limiting pin34also can pass through the first, second, third stop slot sections315,316,317and the return slot section318. Furthermore, during closing of the slats, since the first gear212is rotated counterclockwise to drive clockwise rotation of the driven wheel411and the rotating shaft412to thereby move the braking members414from the shallow ends418to the deep ends417, the slats can be closed quickly.

In view of the above, downward movement of the slats and the bottom rail can be retarded to promote safety during use. Furthermore, since the unidirectional damping unit40is located at a side of the assembly of the first reel21and the braking unit30, and since any two adjacent ones of the first and second reels21,22as well as the spring winding wheel231and the driving wheel233of the reel driving member23are misaligned from each other along the longitudinal direction (X), the length and volume of the cord winding device are reduced.

Alternatively, an arc of the braking shaft32in contact with the first pull cord100may have an angle not greater than 360°.