Patent Publication Number: US-8522852-B2

Title: Suspension system for a cordless window covering

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of application Ser. No. 11/591,718 filed Nov. 2, 2006 now U.S. Pat. No. 7,975,748, the disclosure of which is incorporated by reference. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     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. 
     BACKGROUND OF THE INVENTION 
     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. 
     SUMMARY OF THE INVENTION 
     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, u-shaped 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, 
         FIG. 1  is a perspective view of a preferred embodiment of the present invention with a window covering in a lowered position; 
         FIG. 2  is a perspective view of the embodiment of  FIG. 1  with the window covering in a partially raised position; 
         FIG. 3  is a front view of a preferred embodiment of the present invention in a partially raised position with the head rail and housing of the control module cut away and suspension cords shown in phantom; 
         FIG. 4  is a side elevated view of a preferred control module of the present invention with portions shown in cross section; 
         FIG. 4A  is an enlarged view of the friction member of the control module of  FIG. 4 ; 
         FIG. 5  is an end view of the control module of  FIG. 4 ; 
         FIG. 6  is an exploded view of the control module of  FIG. 4  and the axle; 
         FIG. 7  is an enlarged view of an alternate preferred embodiment of a friction member; and 
         FIG. 8  is an enlarged view of another alternate preferred embodiment of a friction member. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     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  FIG. 1 , a preferred embodiment of the present invention is shown. Window covering  10  includes a head rail  12 , a pair of control modules  14 ,  16  positioned within a channel  18  of the head rail  12  about axle  20 . A window cover member is also provided comprising window cover material  22  and weighted element, such as bottom rail  24 . As shown, the window covering  10  is in a lowered position such that the window cover material  22  is extended to cover a window space. In this particular embodiment, the window cover material  22  is shown as a double cell cellular material, however, other materials may also be used including honeycomb materials, Venetian blinds, Roman shades, Roman style shades, or the like. Also shown in this embodiment in engagement with the axle  20  is a clutch mechanism  19 . Any clutch mechanism as is known in the art may be utilized. For example, clutch mechanism  19  may be configured such that it locks the axle when engaged. By pulling down on bottom rail  24  slightly, the clutch member is disengaged from the axle to permit rotation of the axle  20 . When the window covering is in the desired position, the bottom rail  24  is again pulled down slightly to engage the clutch mechanism  19 . 
     Shown in  FIG. 2  is the window covering  10  of  FIG. 1  in a partially raised position. As the window covering  10  is raised, window cover material  22  is gathered and supported by bottom rail  24 . This is more clearly shown in  FIG. 3 . Suspension cords  26 ,  28  extend from control modules  14 ,  16 , respectively, pass through window cover material  22 , and are connected with bottom rail  24 . In this preferred embodiment, the suspension cords  26 ,  28  are connected directly to bottom rail  24 , however, other methods of operatively connecting the bottom rail to the suspension cords may also be utilized. For example, fastener modules may be used to enable the bottom rail to be easily replaced. In certain applications, a panel of material may be combined with a bottom rail such that the suspension cords are connected to the bottom rail by way of attachment to a connected panel of material. While the weighted element has been described thus far as a bottom rail, it is not limited to a straight elongated structure; instead, any weighted member can be utilized. Also, while two control modules  14 ,  16  are shown engaged with axle  20 , it should be understood that any number of control modules can be used. 
     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  FIGS. 4-6 . Referring to  FIG. 4 , control module  16  is shown. Control module  16  includes a support structure, such as housing  38 . Positioned within housing  38  are a winding drum  40  and a spring  42  (shown in cross section). The winding drum  40  and spring  42  are operatively connected to one another such that the spring  42  exerts a rotational force, i.e., torque, on the winding drum  40 . In this embodiment, the winding drum  40  and spring  42  are connected by a rotary spindle  44  that is integrally formed with the winding drum  40 . Referring to  FIG. 5 , the spring  42  is secured at an end  46  to spindle  44 . Preferably, spring  42  is a constant force spring that provides a constant amount of force or torque throughout the range of extension of the spring. Each of the winding drum  40 , rotary spindle  44  and spring  42  are positioned about the rotary axle  20 , which also defines a longitudinal axis  48 . It is preferred that winding drum  40 , rotary spindle  44  and spring  42  are coaxial with one another. The axle  20  inserts through the drum  40  and spindle  44  as the control module  16  is mounted on the axle  20 . This simple assembly permits easy and flexible mount of many control modules for wider window covering requiring more suspension cords. 
     Referring again to  FIG. 4 , suspension cord  28  is secured at a first end  50  to a post  52  formed on winding drum  40 . When window covering  10  ( FIG. 3 ) is raised, the suspension cord  28  is wound on winding drum  40  rotated by the torque from spring  42 . Referring to  FIG. 4A , the suspension cord  28 , in this embodiment, is passed through hole  54  formed in housing  38 . Suspension cord then travels a path though hook  56 , and then exits housing  38  through hole  58 . As such, the suspension cord  28  travels a path including three turns between the winding drum  40  and the window cover member including window cover material  22  and bottom rail  24 . The engagement with the housing  38  as the suspension cord  28  passes though holes  54  and  58 , as well as the engagement with the hook  56  generate a static friction force on the suspension cord  28  that resists movement when the window covering  10  is stationary, i.e., not being adjusted. The housing  38  and the hook  56  also provide a reaction force on the suspension cord  28 . 
     Referring again to  FIG. 4 , the spring  42  exerts a rotational force on winding drum  40  that, because the first end  50  of the suspension cord  28  is secured to winding drum  40 , is translated to a force (F 1 ) on the suspension cord  28 . Yet another force that is applied to suspension cord  28  when the window covering  10  is stationary is the weight (G) of the window cover material  22  the portion of the cord which is unwound, and the bottom rail  24 . The amount of cord unwound from the winding drum  40  contributes to the overall weight to a relatively small degree while the bottom rail  24  preferably provides most of the weight (G). Also, as discussed, in some window coverings, the window cover material  22  itself may contribute a force F 2  (not shown) to the bottom rail  24  opposite to the force of gravity. This force F 2  is significantly smaller than the force F 1 . In other words, the downward weight exerted on the suspension cord  28  is lighter for vertically lower positions of the bottom rail  24 . In these configurations, the sustaining force exerted by the spring  42  may exceed the downward weight and adversely cause an upwardly biased displacement of the bottom rail  24 . 
     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 1  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 F static  that is greater than or equal to the difference between the total gravitational force G and the sum of Force F 1  and F 2  regardless of the position of the window cover  10 . In other words:
 
F static G−(F 1 +F 2 ), where:
         G is the weight of the window cover material, bottom rail, and unwound portion of the cord;   F 1  is the linear force exerted by the spring on the suspension cord;   F 2  is the spring force of the window cover material on bottom rail; and   F static  is the static friction force of the friction member.       

     The suitable amount of frictional force can be determined depending on factors such as the weight of the window cover member and the cord texture and thickness, bottom rail weight, and spring force of the window cover material. By adjusting one or more of these factors, a sufficient amount of static friction force for the suspension cord can be included in the present invention. 
     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 F static  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 F 1  and F 2  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 F static  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 F static  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 F 1  and F 2 . 
     Referring to  FIG. 6 , a brief explanation of the various parts of the control module  16  is provided. The housing  38  includes a cover  60 , a base  62  and an end cap  64 . Hook  56  is also provided. Winding drum  40  is formed integrally with rotary spindle  44 . A separate spindle  68  is also provided which is configured to connect winding drum  40  to end  70  of housing cover  60 . Axle  20  is guided through control module  16 . 
     Referring to  FIGS. 7 and 8 , alternate embodiments of a friction member are shown. In  FIG. 7 , the suspension member  128  exits though hole  154  formed in housing  138 . The suspension cord also engages hook  156  extending over the hole  158 . Unlike the previous embodiment, however, the suspension member  128  does not engage hole  158 . As such, in this embodiment, the cord travels along a path having two turns. In  FIG. 8 , no hook member is included. In this embodiment, the suspension cord  228  interacts with the rims of the holes  254  and  258  through which it travels. 
     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.