Abstract:
A cord lock for window coverings has one or more cams adjacent a surface over which a one or more lift cords travel. The cams are spring biased to a locked position in which they press the lift cords against the surface. A cam lock with a release cord is provided which engages and moves the cams from a locked position to an unlocked position in which the lift cords are free to move through the cord lock. The cord lock is always in a locked position whenever neither the lift cords are being pulled to raise the blind nor the release cord is being pulled to lower the blind.

Description:
FIELD OF INVENTION  
       [0001]     The present invention relates to a cord lock for window blinds which are raised and lowered by lift cords such as venetian blinds.  
       BACKGROUND OF THE INVENTION  
       [0002]     Venetians blinds have a headrail, a bottom rail and a set of slats carried on ladders that extend from the headrail to the bottom rail. Lift cords extend from the bottom rail through or adjacent the slats and into the headrail. The lift cords may be wound and unwound on an axle within the headrail, but more commonly pass through a cord lock in the headrail and exit the headrail at one end. Conventional cord locks will restrain the lift cords when the blind is in a fully raised, or partially lowered, position. But, typically those cord locks do not lock the cords in place when the blind is fully lowered. Consequently, anyone can grasp a lift cord of a fully lowered blind and pull the lift cord away from the blind until the end of the lift cord, which typically has a tassel, reaches the end of the headrail. When a lift cord is pulled in this way a loop is formed. Children have been known to do this. Indeed, some children have become entangled in a cord loop created in this way and have been strangled. Consequently, the industry has been encouraged to provide safety devices on venetian blinds to prevent cords from being pulled away from the slats. A similar problem can also occur in pleated shades and roman shades.  
         [0003]     One solution to this problem that some manufacturers have adopted is to attach a cord stop to each lift cord. One type of cord stop has a donut shape. The lift cord is passed through the center hole and around the body. This type of cord stop is disclosed in U.S. Pat. No. 6,453,971. Another type of cord stop is a ball with a slot that snaps onto the cord. Even though the cord stops that have been used are made from clear plastic, they are quite noticeable and detract from the appearance of the blind. Furthermore, one stop must be attached to each lift cord by the installer after the blind has been mounted on the window. This adds several minutes to the installation of a single blind. Fabricators and installers who install cord stops on their blinds must spend more time on each job thereby increasing the cost of the installation.  
         [0004]     There is a need for a mechanism that can be used in venetian blinds and other window coverings that will prevent lift cords from being pulled away from a fully lowered blind. That mechanism should not detract from either the operation or appearance of the blind.  
         [0005]     U.S. Pat. No. 5,275,222 discloses a cord lock and release system for blinds having a stationary member and a moveable member between which the lift cords pass. In the preferred embodiments a spring biases the moveable member toward the stationary member to restrain the lift cords. A linkage, which typically is a release cord, is attached to the moveable member. The operator pulls the release cord to move the movable member away from the stationary member to release the lift cords. Since the moveable member is biased to the locked position the cords will normally be restrained. The patent also teaches that a spring is not required and that gravity could keep the moveable member in a locked position. But, without the spring, the moveable member is free to rotate 360° and become stuck in a release position. Even the spring biased system permits rotation of the moveable member through an arc greater than 90°. Another shortcoming of this system is that a single moveable member is provided to restrain all of the lift cords. Lift cords often vary in diameter within a single blind by a few thousandths of an inch. If two lift cords in a blind vary in diameter the movable member in a locked position will restrain the larger diameter cord but may allow the smaller diameter cord to slip past the moveable member. Consequently, there remains a need for a cord lock or other system that will prevent lift cords from being pulled away from a fully lowered blind and not detract from either the operation or appearance of the blind.  
       SUMMARY OF THE INVENTION  
       [0006]     We provide a cord lock that retains the lift cords in a manner so that no lift cord can be pulled away from the window covering material in a fully lowered blind. Yet, the cord lock readily releases the cord when an operator pulls on the lift cords to raise the blinds. To lower the blind an operator pulls a release cord that extends from the cord lock.  
         [0007]     Our cord lock has a generally rectangular housing containing at least one cam spaced apart from a surface over which one or more lift cords pass. In the preferred embodiments the surface is a wheel and there is one cam and one wheel for each lift cord. The cams can rotate about a first axis from at least one unlocked position to a locked position, and from the locked position to the unlocked position. The surface is spaced apart from the cam such that a cord passing over the surface will be pressed against the surface and restrained when the cam is in the locked position, and the cord can freely pass over the surface in at least one direction when the cam is in the at least one unlocked position.  
         [0008]     We further provide a cam lock within the housing that is capable of assuming a first position in which the cams are in the locked position, and at least one additional position in which the cams are engaged by the cam lock and in an unlocked position. The cam lock limits the travel of the cams through an arc that preferably is less than 90°. The cam lock can be variously configured. In one embodiment the cam lock is a box-like carriage. In another preferred embodiment the cam lock is a pair of interlocking drums. In yet another embodiment the cam lock is a single wheel having a slot into which the cams are fitted. In still another embodiment the cam lock is a U-shaped housing that extends around the pivoting end of the cams.  
         [0009]     A release cord is attached to the cam lock in a manner so that pulling the release cord moves the cam lock to engage and move the cams from the locked position to a release position in which the lift cords can freely move through the cord lock. One or more springs are attached to the cam lock, to the axle carrying the cams or directly to the cams, biasing the cams to the locked position. The spring has a strength that enables the cams to move from the locked position to the unlocked positions when an operator pulls the lift cords to raise the blind or pulls the release cord to lower the blind.  
         [0010]     Other objects and advantages of our cord lock will become apparent from a description of certain present preferred embodiments shown in the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a perspective view of a first present preferred embodiment of our cord lock.  
         [0012]      FIG. 2  is a sectional view along the line II-II of  FIG. 1  showing the cord lock in a locked position and having no release cord.  
         [0013]      FIG. 3  is a sectional view similar to  FIG. 2  showing the cord lock in a first unlocked position.  
         [0014]      FIG. 4  is a sectional view similar to  FIGS. 2 and 3  showing the cord lock in a second unlocked position or release position.  
         [0015]      FIG. 5  is a sectional view taken along the line V-V of  FIG. 1  showing the cord lock in the unlocked position shown in  FIG. 4 .  
         [0016]      FIG. 6  is a sectional view taken along the line VI-VI in  FIG. 1 .  
         [0017]      FIG. 7  is a sectional view similar to  FIG. 2  of a second present preferred embodiment of our cord lock in a locked position.  
         [0018]      FIG. 8  is a sectional view similar to  FIG. 7  of the second present preferred embodiment of a cord lock in a first unlocked position.  
         [0019]      FIG. 9  is a sectional view similar to  FIGS. 7 and 8  showing the second present preferred cord lock in a second unlocked position or release position.  
         [0020]      FIG. 10  is a sectional view similar to  FIG. 7  of the third present preferred embodiment of our cord lock in a locked position.  
         [0021]      FIG. 11  is a top plan view of the third present preferred embodiment shown in  FIG. 10 .  
         [0022]      FIG. 12  is a perspective view of a fourth present preferred embodiment of our cord lock in a locked position.  
         [0023]      FIG. 13  is a perspective view similar to  FIG. 12  of the fourth present preferred embodiment of a cord lock in a first unlocked position.  
         [0024]      FIG. 14  is a perspective view similar to  FIGS. 12 and 13  showing the fourth present preferred cord lock in a second unlocked position or release position.  
         [0025]      FIG. 15  is a front view of a portion of the cord lock shown in  FIGS. 12, 13  and  14  showing the ramp over which the lift cords pass.  
         [0026]      FIG. 16  is perspective view of a cam lock lift mechanism that can replace the ramp in the fourth present preferred embodiment shown in  FIGS. 12 through 15 .  
         [0027]      FIG. 17  is a top plan view of portion of a headrail into which two of our cord locks have been installed.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     A first present preferred embodiment of our cord lock  1 , shown in  FIGS. 1 through 6 , has a housing  2  formed from two spaced apart parallel sides  3  and  4  held together by front walls  5  and  6 , bottom walls  7  and  8  and spacer  9 . An inverted keyhole slot  10  is provided in the spacer  9  through which a release cord  11 , shown only in  FIG. 1 , passes. The cord lock shown in FIGS.  1  though  6  is configured to accommodate four lift cords  12 . As will be seen, other configurations could be provided to receive two, three, five, six or even more cords. However, for blinds having eight or more lift cords we prefer to use two or more cord locks.  
         [0029]     The operation of the cord lock can best be understood with reference to  FIGS. 2, 3 , and  4 . Within the cord lock housing  2  we provide four cams  13 ,  14 ,  15  and  16  on a common pin  17  that passes through the housing. There is one cam for each lift cord  12 . All of the cams rotate on a common axis defined by pin  17 . We prefer to provide teeth or a serrated edge  18  on each cam which engage a lift cord  12  when the cam is in a locked position shown in  FIG. 2 . A second pin  20  passes through the housing  1  and is parallel to pin  17 . Pin  20  carries a wheel or roller  21  over which the lift cord  12  rides. We prefer to provide a separate wheel for each cam, but a common roller could be used for all cams  13  through  16 . If desired, a spacer can be placed between adjacent wheels and adjacent cams. Those spacers could extend to the front walls  5  and  6  of the cord lock. Furthermore, the wheels  21  could simply be fixed curved surfaces that do not move as a lift cord  12  passes over them. The relative positions of the cams  13  through  16  and the wheels  21  define cord paths between them through which the lift cords travel. The lift cords  12  enter the cord lock  1  between front walls  5  and  6  after passing from the window covering material. They pass over spacer rod  24 , over wheel  21  and exit the cord lock between bottom walls  7  and  8 . When the cams  13  through  16  are in the locked position shown in  FIG. 2 , each lift cord is pinched between a cam and a roller and the teeth  18  on each cam press into the cord. If one pulls on a lift cord where the cord passes through the blind slats or other window covering material, the cord will not move. Hence, a child pulling a lift cord away from the window covering material in a fully lowered blind could not create a loop in the cord. The lift cord would not move. Furthermore, the bottom rail of the blind cannot be lowered when the cams are in the locked position shown in  FIG. 2 . To raise the blind an operator pulls on the portion of the cord below the bottom of the cord lock. As can be seen in  FIG. 3  that force turns wheel  21  and moves the cam to a first unlocked position. As the lift cords  12  are pulled to raise the blind, the cams ride on the lift cords. When the operator releases the lift cords the weight of the blind causes the lift cords to move in the opposite direction. As that motion begins the teeth  18  in the cams quickly engage the lift cords locking the blind in place. Once again the blind is in the locked position shown in  FIG. 2 . Teeth  18  should be angled to enable the cord to be easily released when pulled by the operator.  
         [0030]     A movable cam lock or carriage  30 , positioned between cams  14  and  15 , has a slot  32  that enables the carriage to move back and forth over pin  20 . A spring  34  is connected between pin  33  in the carriage and rod  24  biasing the carriage  30  to the locked position of  FIG. 2 . Pins  35  and  36  extend through the carriage  30  toward the sidewalls  3  and  4  of the housing  2 . The pins  35  and  36  are positioned to capture the cams  13 ,  14 ,  15  and  16  between them. Consequently, the cam lock limits the movement of the cams. Movement of the carriage from the locked position shown in  FIG. 2  to the release position shown in  FIG. 4  will engage and move the cams  13 ,  14 ,  15  and  16  to a second unlocked position. Since the cams are now away from the lift cords those cords are free to move in either direction. Unless the lift cords are being held by the operator, the weight of the shade will pull the lift cords through the cord lock until the bottom rail hits the window sill or is otherwise restrained. The carriage can be moved to the release position by pulling on the release cord  11  shown in  FIG. 1 .  
         [0031]     Having explained the operation of the cord lock, it should now be apparent how a blind equipped with our cord lock is operated. To raise the blind, an operator pulls the lift cords. To lower the shade, the operator pulls the release cord. It is not necessary to move the lift cords to one side through a plane parallel to the blind or through a plane perpendicular to the blind to lock or unlock the cord lock. This is another advantage over many conventional cord locks.  
         [0032]     In a second present preferred embodiment of our cord lock  40 , shown in  FIGS. 7, 8  and  9 , the cam lock contains a pair of locking drums  41  and  42  in place of the carriage  30  of the first embodiment. In this embodiment, pin  47  extends through the housing  39  and carries the first locking drum  41  and four cams  43 , two on each side of the locking drum  41 . A second pin  45  extends through the housing and carries second locking drum  42  and two wheels  46 , two on each side of the second locking drum. As in the first embodiment, a lift cord  12  passes between each set of cams and wheels. A slot  49  is provided in the first locking drum  41  which receives a pin  48  in the second locking drum  42 . This slot and pin arrangement causes the two locking drums to move together. A spring  50  extends from pin  51  on the first locking drum  41  to a pin  52  extending from the housing as shown in  FIG. 8 . This biases the locking drums to the locked position shown in  FIG. 7 . If desired the spring could be connected between the second locking drum and the housing. A release cord  56  extends from pin  54  on locking wheel  42 , passes over rod  53  and exits the bottom of the cord lock. The bottom  38  of the housing has a passage  60  through which the lift cords  12  pass. We prefer to provide guide pins  62  in the passage  60  to separate adjacent lift cords. Pulling the lift cords from below the cord lock moves the cams to an unlocked position shown in  FIG. 8 . Pins  51  and  57  extend through the first locking wheel  41  and capture the cams  43 . Pulling the release cord turns both locking wheels  41 ,  42  until pin  51  moves the cams away from the lift cords to an unlocked position or release shown in  FIG. 9 . The drums need not be round but could be a polygon or have an irregular or non-symmetric shape.  
         [0033]     Several variations could be made in the embodiments illustrated in  FIGS. 1 through 9 . In both versions of the cord lock a spring was connected between the housing and the cam lock, namely carriage  30  or locking drum  41  or  42 . In an alternative embodiment one could attach the spring indirectly to the cams by a connection to the rod carrying the cams, particularly if the cross section of the rod is a polygon. The spring could directly engage the cams or one could provide individual springs for each cam. The use of individual springs for each cam enables each cam to move independently, thereby compensating for variations in the diameters of the cords. However, use of multiple springs is more expensive than the single spring embodiments shown in the drawings.  
         [0034]     The third present preferred embodiment of our cord lock  70  shown in  FIGS. 10 and 11  is similar to the second embodiment. A cam lock wheel  72  is carried on axle  65  extending from housing  69 . A second axle  75  carriers wheel  76  over which one or more lift cords  12  travel. Again we prefer to have a separate wheel for each lift cord. Cams  73  are carried on pin  77  and captured within a slot  78  in the cam lock wheel  72 . As in the previous embodiment spring  50  biases the cam lock wheel  77  to the locked position shown in  FIG. 10 . Release cord  56  is attached to cam lock wheel  77  by pin  54  and travels around pin  53  before exiting the cord lock. As can be seen from the top view of the cord lock  70  in  FIG. 11  this cord lock can be quite narrow. Consequently, two or even three cord locks can be placed side by side within the headrail.  
         [0035]     A fourth present preferred embodiment of our cord lock  80  is shown in  FIGS. 12 through 15 . This cord lock  80  has a base  81  from which wall  82  extends. A second wall  83  is attached to the base  81  and wall  82 . As can be most clearly seen in  FIG. 15 , wall  83  has a slot through which the lift cords  12  pass. The bottom edge  93  of that slot is angled relative to the base  83  and serves as a ramp. Axle  84  extends from wall  83  an carries cams  85  as well as bell-shaped cam lock  86 . The cam lock  86  may be spring biased to the locked position shown in  FIG. 12  or may be configured so that gravity pulls the cam lock to the locked position. The cams  85  are sufficiently away from the leading edge of bell-shaped cam lock  86  and wall  83  that an operator may move the lift cords  12  up ramp  93  from the position shown in dotted line in  FIG. 15 . This motion causes the leading edge of the cam lock  86  to rise moving the cams to the release position shown in  FIG. 14 . As in the previous embodiments the cam lock  86  allows the operator to pull the lift cords to raise the blind. When that happens the cams will be positioned as in  FIG. 13 . This cord lock is configured to fit into the end of a headrail. We prefer to provide a cover  88  over the slot  92  through which the lift cords exit the cord lock.  
         [0036]     The cord lock shown in  FIGS. 12 through 14  could be alternately configured to have a release arm  90  shown in  FIG. 16 . A carrier  89  is attached to the top of wall  83 . Release arm  90  has a two bends that define a central portion  96  that is held by the carrier  89 . The front portion of the release arm has an eyelet  91  through which the lift cords  12  pass. The opposite end of the release arm is bent to provide a trip bar portion  94 . When the operator moves the lift cords to the left, the central portion of the release arm rotates within the carrier and the trip bar portion moves down engaging the cam lock. As indicated by the arrows in  FIG. 16 , this motion causes the leading edge of the cam lock  86  to rise moving the cams to the release position shown in  FIG. 14 .  
         [0037]     One could substitute a dog leg part for each of the cams in the illustrated embodiments. The cam configurations in those embodiments were selected over a dog leg because the selected cam configurations are shorter. One could also substitute a second cam for each roller. Then the lift cords would pass between two cams. If a second cam is used a stop should be provided to prevent the second cam from rotating 360°.  
         [0038]     When our cord lock  1 ,  40 , or  70  is installed in a headrail  100  as shown on  FIG. 17  we prefer to provide a guide pin  101 ,  102  for each pair of cords. The guide pins direct the cords to positions below one of the cams. When guide pins are used in the manner shown in  FIG. 17  it is unlikely that one lift cord will interfere with another lift cord or shift to a position in which two lift cords are adjacent a single cam. Two cord locks and associated pins are shown in  FIG. 10 , but any number of cord locks can be arranged in the headrail. When two or more cord locks are used the additional lift cords passing through one cord lock would be routed over or around the other cord locks. A single release cord (not shown) is connected to both cod locks.  
         [0039]     All of the components of the cord lock could be made of plastic or metal. We prefer that the cams be metal, preferably brass, so that the teeth in the cams will undergo less wear. The wheels, pins and locking drums also should be metal. The housing preferably is polycarbonate or other plastic.  
         [0040]     While we have shown and described certain present preferred embodiments of our cord lock it should be distinctly understood that our invention is not limited thereto but may be variously embodied within the scope of the following claims.