Patent Application
20080128097
This invention relates to suspension system for a window covering. The suspension system provides a mechanism for control of the window covering without use of a pull cord.
Window coverings, such as honeycomb window shades, Venetian blinds, and Roman shades typically have a head rail and a window cover material, such as pleated fabric, a plurality of slats, or blind members, which are controlled by cords, whereby a pull cord coupled to the slats, blind members, or fabric can be adjusted to raise or open the window covering. The pull cord extends from a headrail and is manipulated by a user to adjust the position of suspension cords and to thereby adjust the position of the window cover material. One shortcoming of such pull cords is that they require peripheral members that distract from the window cover material and can lessen the aesthetic appearance of the window covering. In addition, pull cords also present a potentially dangerous situation in that they are of relatively long lengths and may be mishandled by certain persons, especially children, such that accidental choking or hanging may occur.
There have been various developments in window coverings that do not utilize a lifting cord with a cord lock. One such patent is U.S. Pat. No. 2,420,301, issued May 13, 1947 to Cusumano for “Venetian Blind” which utilizes a cone-shaped member with grooves and a coil spring. This window covering design includes a counterbalance to enable positioning of the blind slats as desired without a lock. Another attempt includes U.S. Pat. No. 2,324,536 issued to Pratt and titled “Closure Structure” and utilizes tapes and coil springs to raise and lower a blind in which the bottom bar and the slats ride in tracks as they move upwardly and downwardly.
One issue that has been presented in other so-called cordless window coverings is that as a window covering is raised, increasing amounts of the window cover material are gathered and supported on the bottom rail, thereby increasing the weight suspended by the suspension cord. One patent directed to addressing this problem is U.S. Pat. No. 5,133,399, issued to Hiller et al. and titled “Apparatus by Which Horizontal and Vertical Blinds, Pleated Shades, Drapes and the Like May Be Balanced for No Load Operation.” In this device, a variable, upwardly directed force is applied to the cord structure with the force being substantially equivalent at all times to the combined weights of the lower rail and the blind members supported on the lower rail when the lower rail is above its lowermost operative position. The apparatus for applying the force includes a conical member coupled to a constant force spring or a variable force leaf spring. Other patents include U.S. Pat. No. 5,482,100, issued to Kuhar and titled “Cordless, Balanced Venetian Blind or Shade with Consistent Variable Force Spring Motor.”
In one version, a variable force spring is wound on drums whereby spring force imparted to a coiled spring is transferred from one drum to another. With these variable force spring motors, the force exerted is at its greatest when the blind or shade is fully raised such that the cords are supporting most or all of the weight for the bottom rail and the window cover material. The spring force is at its lowest point when the window covering is fully lowered such that only the bottom rail is supported by the suspension cord. In another embodiment, a constant force spring is utilized with a friction imparting device to accommodate the variable weight of the window covering between the raised and lowered positions.
One shortcoming of the previous attempts, however, is the complexity of the designs in that a substantial number of interconnected parts are required. The present invention provides a cordless window covering and does so in a more efficient manner.
The present invention is directed to a window covering that does not require the use of pull cords. In a preferred embodiment, the present invention includes a window covering suspension system that includes a head rail, at least one suspension cord, a control module and a friction member or reaction member. The suspension system can be combined with a window cover member that includes a window cover material and a weighted element, such as a bottom rail, to form the window covering.
The head rail preferably includes a transverse channel. A rotary axle is disposed within the channel and defines a longitudinal axis. At least one control module is positioned in the channel and the rotary axle extends through the control module. Preferably, more than one control module is positioned about the axle so that they operate together to evenly open and close the window covering.
The control module includes a support structure, such as a housing, into which a rotary winding drum and a spring are positioned and supported by the support structure. The spring is preferably a constant force flat spiral spring. The winding drum and spring are operatively connected to one another such that the spring exerts a rotational force on the winding drum. Preferably, the winding drum and spring are connected by a rotary spindle, and each of the winding drum, rotary spindle, and spring are positioned about the rotary axle. These components of the control module may be coaxial with one another. A friction member or reaction member is also provided for reasons discussed in further detail below.
A first end of the suspension cord is connected to the winding drum such that as the winding drum is rotated by the rotational force provided by the spring, the suspension cord is wound thereon. As discussed, the spring is preferably a constant force spring that provides a substantially constant amount of torque throughout the range of extension for the spring. Suitable constant force springs are known in the art. With such springs, the force exerted by the spring to resist uncoiling is constant since the change in the radius of curvature is constant.
A second end of the suspension cord is connected to weighted element, e.g., a bottom rail of the window cover member, such that as the suspension cord is wound on the winding drum, the bottom rail is raised and window cover material is gathered on the bottom rail. The suspension cord travels a path that engages the friction member or reaction member, such as a hook that may take the form of a standard hook, and eyelet, horseshoe-shaped member, unshaped member, or other piece through which the suspension cord may pass. The support structure may also be configured to form the friction member or reaction member by offsetting surfaces formed within the support structure such that the suspension cord is caused to travel a path including a plurality of turns, and preferably at least three turns, thereby increasing the force required to overcome the static friction force on the cord. Similarly, by including a plurality of turns, the reaction force on the cord by the reaction member is increased. The suspension system may also include a combination of such friction members or reaction members.
In use, the spring is configured to exert a rotational force on the winding drum. The rotational force is translated by the winding drum to an upward force on a portion of the suspension cord as the window covering is moved between a lowered position and a raised position. For example, as the cord is wound on the winding drum, the tangential force of the winding drum is the upward force on the cord. At the same time, the suspension cord supports the weight of the window cover material and bottom rail. As discussed, the total weight supported by the cord increases as the window covering is raised from a lowered position to a raised position due to the increasing amount of window cover material supported by the bottom rail. The amount of cord also contributes to the overall weight, but only to a relatively small degree. An additional force opposite the gravitational force may come from the window cover material itself in that the material, such as found in a honeycomb or cellular shade, may possess an inherent spring force. For example, a honeycomb or cellular window cover material, when stretched, will tend to retract as a result of memory in the material.
The friction member provides a static friction force to the cord and is configured to provide sufficient static friction such that the difference between the weight of the window cover member and cord versus the sum of the window cover material spring force and the spring upward force are offset, thereby maintaining a desired position for the window covering. In other words, when the window covering is stationary or not being adjusted, the static friction force offsets the net result of the other upward and downward forces on the suspension cord such that the window cover member is not unintentionally raised or lowered. This friction member engages the cord, and is preferably positioned downstream of the winding drum. In other words, the friction member is positioned to engage a portion of the cord that is not wound on the winding drum.
The amount of friction can be adjusted depending on the weight of the window cover member and the cord texture and thickness by configuring the friction member, such as the hook member, to cause the suspension member to travel a path that includes a plurality of turns. The distances between turns, the angles of the turns, and the amount of contact between the friction member and the cord can all be adjusted to provide the desired amount of static friction suitable for a particular application. A higher static friction allows the same control module to be used over a greater range of window covering lengths.
The hook may also be a reaction member designed to prevent undesired movement of the bottom rail and ensure a stationary position (e.g., no movement between the cord and the hook). A reaction force exerted by the hook on the cord, or other offset surfaces, contributes to counteract the force of the spring to keep stationary the cord when the bottom rail is positioned at the desired height.
As discussed, however, the winding drum and spring in the control module are preferably in a coaxial relationship with one another and are engaged with the axle which is guided through the winding drum and spring. In this manner, multiple similarly configured control modules may be utilized to accommodate different weight window cover members and different size window coverings. Such modularity provides substantial advantages over the prior art.
A clutch mechanism may also be included in the suspension system to provide even greater flexibility in design. Clutch mechanisms, such as utilized in roller shades are generally known, and are designed to engage a rotating axle to releasably lock the axle. With the present invention, a clutch mechanism may be employed along with the control module.
In the drawings,
The invention disclosed herein is susceptible of embodiment in many different forms. Shown in the drawings and described hereinbelow in detail are preferred embodiments of the invention. It is to be understood, however, that the present disclosure is an exemplification of the principles of the invention and does not limit the invention to the illustrated embodiments.
Referring to
Shown in
As the window covering 10 is moved from a lowered position to a raised position, the suspension cords 26, 28 are wound within control modules 14, 16 in a manner described in greater detail below. As the bottom rail 24 is brought closer to head rail 12, window cover material 22 is gathered and supported by the bottom rail 24. As shown, a gathered portion 30 of window cover material 22 is resting on the bottom rail, such that the weight of gathered portion 30 plus the bottom rail 24 are supported by the suspension cords 26, 28. The ungathered portion 32 of the window cover material 22 is suspended from head rail 12 and is not supported by the suspension cords 26, 28. As should be readily understood, the weight, supported by the suspension cords 26, 28 increases as the window covering 10 is moved to a raised position. In other words, the weight on the ends 34 and 36 of suspension cords 26, 28 increases as more window cover material 22 is gathered and supported by the bottom rail 24. Although not shown, in the context of a Venetian blind, the number of slats that would be supported by the suspension cords, as opposed to ladder cords, would increase as the Venetian blind is raised.
In this particular embodiment, two control modules 14, 16 are mounted about axle 20. As discussed, the number of modules in a particular window covering can vary as needed. Due to the modular nature of the control modules and the common axle, stock quantities of the control modules can be utilized rather than require adjustment of individual control modules that increases manufacturing costs and complexity. Also, given the nature of window coverings as often being customized for a particular window, modular control modules provide greater flexibility in manufacturing. The use of a common axle to connect the plurality of control modules also provides for a simple and reliable means for synchronization and balancing of the control modules to promote even lifting of the window covering, unlike the prior art.
Greater detail on the control modules is described with
Referring again to
Referring again to
In order to prevent the foregoing unintended movement, the friction member, which in this embodiment comprises the engagement locations with the housing 38 as the suspension cord passes through holes 54 and 58 and the hook 56, is put in contact with the cord to create the static friction force F Static that suitably balances the difference between the opposing forces applied to the cord 28. The forces that tend to move the window cover 10 to a raised position applied to the suspension cord 28 include the force F, from the spring 42 and the spring force of the window cover material 22. Counterbalancing these raising forces are the downward forces G caused by the weight of the window cover material 22 and the bottom rail 24, and to a minor degree the unwound portion of the suspension cord 28. The total weight on the suspension cord 28 increases as the window covering 10 is raised from a lowered position to a raised position due to increasing amount of the window cover material 22 supported by the bottom rail 24.
In order to prevent unintended movement of the window covering 10, the friction member is positioned downstream of the winding drum, which in this embodiment comprises the engagement with the housing 38 as the suspension cord 28 passes though holes 54 and 58 and the engagement with the hook 56, creates a static friction force Fstatic that is greater than or equal to the difference between the total gravitational force G and the sum of Force F1 and F2 regardless of the position of the window cover 10. In other words:
In order to raise window covering 10, a user exerts a force on the bottom rail opposite the force of gravity such that the static friction force Fstatic is overcome. Sufficient force by the user must be exerted such that the difference between the total gravitational force G and the sum of Force F1 and F2 is overcome. Similarly, in order to lower the window covering 10, a user pulls down on the bottom rail so that the static friction force Fstatic is overcome. As should be readily appreciated, this difference is intended to be such that only a moderate amount of force by the user is required.
One of the advantages of the present design is that the static friction is automatically adjusted to meet the needs of the window covering so it remains stationary. As the window covering is opened, the weight G on the cord increases and tends to make the window covering close. However, because the static friction force Fstatic is a function of the tension on the cord as it acts against the friction member, the static friction increases to counteract the increase in weight.
The relevant forces in the present invention may also be viewed from the perspective of reaction forces, and the friction member may be considered as a reaction member. This reaction member exerts a reaction force against the suspension cord to prevent undesired movement of the bottom rail and ensure a stationary position. This counterforce applied to the cord is a reaction force because it counterbalances the force of the suspension cord against the various surfaces. When viewed it in this context, it should be understood that the reaction force is at most equal to the difference between force G and F1 and F2.
Referring to
Referring to
The descriptions above have shown the control modules as being located in the head rail. Is some embodiments, the control modules may be located in the bottom rail, or a combination of the head rail and bottom rail. It may also be desired to exclude the head rail and secure the control modules directly to a window frame.
The foregoing descriptions are to be taken as illustrative, but not limiting. Still other variants within the spirit and scope of the present invention will readily present themselves to those skilled in the art.
