Flexible or portable closure – partition – or panel – Plural strip – slat – or panel type – Venetian blind type
Reexamination Certificate
2000-04-17
2001-12-04
Purol, David M. (Department: 3634)
Flexible or portable closure, partition, or panel
Plural strip, slat, or panel type
Venetian blind type
C160S193000
Reexamination Certificate
active
06325131
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application corresponds to and claims priority to European Application No. 99201187.4, filed Apr. 16, 1999. This European application is hereby incorporated by reference as though fully set forth herein.
BACKGROUND OF THE INVENTION
a. Field of the Invention
This invention relates to a cord spool for a cord driven mechanism for controlling the retraction and deployment of an architectural covering, especially a covering for an architectural opening, such as a window blind or shade. This invention particularly relates to a cord spool which counteracts the increasing downward force which must be applied to an operating cord to open a window covering—to overcome the increasing weight and/or frictional resistance of the covering, as it is opened. The invention quite particularly relates to a cord spool for a venetian blind which is raised by winding lift cords around a central shaft or on separate spools on the central shaft of the head rail of the blind.
b. Description of the Related Art
When raising a conventional Venetian blind to open it, its lift cords pull its bottom rail upwardly as a result of its operating cord or pull cord being pulled downwardly or of other means, such as a motor. As the percentage of the blind that is lifted increases, the weight of the blind, already lifted, pulls downwardly on the lift cords. The percentage of the blind that has not yet been lifted is supported by its ladder cords.) The force needed to continue to raise the blind has to overcome continuously the increasing weight of the amount of the blind already lifted. In this regard, the initial raising force overcomes the weight of the bottom rail. Subsequent raising forces are variable and are related to the percentage of the blind, already raised. This is because the weight, to be pulled up, increases as the percentage of the blind already raised increases. Additionally, friction in the cord system for raising the blind will also gradually increase as the blind is raised, thereby increasing the required raising forces.
Thus, there will normally be a significant gradient in the raising forces needed to open a Venetian blind. If a person is raising the blind by pulling downwardly on its operating cord, the person will experience the significant raising force gradient as the blind is opened. If the person is strong, he will often use excessive force to raise the last part of the blind. This can cause the bottom rail of the blind to slam into the head rail, thereby damaging the blind. Excessive raising forces pulling on the operating cord can also make it wear more quickly. By comparison, people with muscle-weakening diseases or rheumatism will often find it difficult to fully raise the blind comfortably because of the significant raising force gradient. If a motor is used, the motor will either be adapted to supply a constant force, which will raise the last part of the blind more slowly, or to supply extra force to compensate for the significant raising force gradient encountered in raising the blind. This often requires expensive electronic circuitry and/or elaborate automatic gear boxes in motor driven blinds.
Cord spools, which counteract the increasing raising forces needed to open such blinds, are known, for example from U.S. Pat. No. 13 251 (1855) and French patents 1 157 647 and 389 516. In such cord spools, an operating cord is wound around a threaded cone. As a blind is raised, the operating cord is wound around progressively larger diameters of the cone. The leverage effect of the larger diameters increases the raising forces to counteract the increasing weight of the percentage of the blind, already raised.
Such cord spools have several drawbacks. One drawback is that all the operating cord is stored on the cord spool, which takes up a lot of space. Another drawback is that there is no relation between the increasing weight of the percentage of the blind, already raised, and the increased raising force provided by the leverage effect caused by winding the operating cord on increasingly larger cone diameters. As a result, the increase in raising force can easily exceed the increasing weight of the percentage of the blind, already raised, resulting in excessive raising forces being exerted on the last part of the blind, to be opened. This can cause the bottom rail of the blind to slam into the head rail. The reason for this problem is that it is very difficult to correctly dimension such a cord spool in relation to the total weight of a blind. In this regard, the correct dimensions of the cord spool (i.e., its length, slope, and thread pitch) and the length of the operating cord would have to be calculated against the height, width, number of slats and total weight of the raised blind. These calculations would have to be made for each blind, since blinds are often made to measure. This would require, in effect, a differently dimensioned cord spool for each different blind which is highly undesirable in modern manufacturing where head rail mechanisms are typically designed for a wide variety of sizes and types of blinds.
SUMMARY OF THE INVENTION
In accordance with this invention, an improved cord spool is provided for a architectural covering, such as a Venetian blind, having a rotatable central shaft for opening and closing the covering; the cord spool comprising: a circumferential surface, about which an operating cord can be wound that can be driven in opposite directions to open and close the covering; means for regulating or preventing an F(pull) gradient when pulling on one end of the operating cord to open the covering; and a variable coupling means connected to the central shaft and the circumferential surface for automatically actuating the means for regulating or preventing an F(pull) gradient when the torque on the central shaft, exerted by the window covering, is greater than the torque on the circumferential surface, exerted by the operating cord as it is being pulled to open the covering.
Advantageously, the means for regulating or preventing an F(pull) gradient comprises means for increasing the diameter of the circumferential surface.
Also advantageously, the variable coupling means tightens when the torque of the window covering on the central shaft is greater than the torque on the circumferential surface of the operating cord, as it is being pulled to open the covering. It is especially advantageous that the variable coupling means comprises a spring, particularly a coil spring, having an inherent tightness that is intermittently less than the torque of the covering, exerted on the central shaft, minus the torque of the operating cord, exerted on the circumferential surface, during the raising of the covering.
In one advantageous embodiment, the means for regulating or preventing an F(pull) gradient comprises:
an outer cone having an outer surface that has: i) a first longitudinal end with a relatively small, first lateral diameter, ii) a second longitudinal end with a relatively much larger, second lateral diameter, and iii) an intermediate longitudinal section, between the ends of the outer cone and having progressively larger lateral diameters which increase longitudinally from the first end to the second end of the outer cone; the outer cone being rotatable about its longitudinal axis; the outer cone also having at least one longitudinally-extending slit between its first and second ends;
the operating cord being wound circumferentially about the outer surface of the outer cone in the first lateral direction and having a pair of depending end portions on laterally opposite sides of the outer cone;
an inner rod that is within the outer cone and has a first longitudinal end and a second longitudinal end, connected to the central shaft; an outer surface of the inner rod having a thread that is wound circumferentially in a first lateral direction and that advances from the first end to the second end of the inner rod; the inner rod being rotatable about its longitudinal axis; and
means for pushing the operating cord longitudi
Dekker Nicolaas
Horsten Antonius Johannes Josephus
Dorsey & Whitney LLP
Hunter Douglas Industries B.V.
Purol David M.
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