Abstract:
A tilter system for a window blind permits a portion of the blind to selectively tilt closed while the balance of the blind remains tilted open. Various arrangements are disclosed for achieving this effect. One includes a lag mechanism in a two-piece tape drum which moves as a single unit during part of its rotation and as two independent drums during the balance of the rotation, with the ladder tape of the blind attached to one of the drums and an actuator cord attached to the other drum. The actuator cord is also anchored to the one of the tilt cables of the ladder tape at a desired point where the selective tilting closed of the blind is to be effected.

Description:
This application claims priority from U.S. Provisional application Ser. No. 60/312,570, filed Aug. 15, 2001. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to coverings for architectural openings, and, more specifically, to horizontal blinds, such as Venetian blinds, designed to selectively tilt open or tilt closed portions of the blind. 
   Typically, a Venetian blind has a top head rail or other frame member, which both supports the blind and hides the mechanisms used to raise and lower or open and close the blind. The raising and lowering is done by a lift cord attached to the bottom rail (or bottom slat). The slats, which are supported from the head rail, may be allowed to tilt so as to open the blind to allow a maximum of light through the blind, or to close the blind with the room side down (the edge of the slats which is closest to the room is facing down, which means that the other edge of the slats, the edge which is closest to the window or the wall, will be facing up), or to close the blind with the room side up. 
   Tilting the blind closed may be done for the purpose of blocking out light, or for obtaining privacy, or both. In order to obtain the optimum performance from the blind, it may be desirable to open one portion of the blind while closing another portion of the blind. For instance, it may be desirable, in an office setting, to tilt closed the lower portion of the blind in order to block the glare of sunlight on a computer screen, or to provide privacy so someone standing outside the window cannot stare through the window and see what is on going on inside the room. However, at the same time, it may be desirable to have the upper portion of the blind tilted open to allow some natural light and/or ventilation into the room. Another instance of an application for such a “split” blind design may be in a home where the floor of the house is at a higher elevation than the ground outside. A person standing in the house could freely see outside, but a person from the outside could not effectively see inside except for the uppermost reaches as allowed by the open section of the blind. 
   In addition to the issue of privacy and glare elimination, the light control feature of the split blind design is also beneficial in that it minimizes the ultraviolet light deterioration resulting from sunlight impacting on interior furnishings, rugs, hardwood floors, etc. while still maintaining indirect lighting from the outside as well as a clear view of the outside. This is particularly practical and applicable in buildings with a roof overhang over the window area or where the windows are recessed into the wall, creating an overhang. 
   Japanese Patent Application Number S63-55595 shows a design in which one portion of the blind can be closed while another is open. This reference seems to require at least 450 degrees of rotation of the tilt rod to complete one entire cycle, from one extreme position to the other extreme position of the blinds. There are two sets of tilt cords per tilt station, with the first set of tilt cords attached to a drive drum portion and the second set of tilt cords attached to a driven drum portion. The drive drum must rotate a full 360 degrees before it engages the driven drum, and it must then rotate an additional amount (probably no less than an additional 90 degrees and possibly another 360 degrees) to actuate the second set of tilt cords attached to the driven drum. By then, the first tilt cords are wrapping over themselves onto the drive drum, resulting in a shortening of these tilt cords, which raises the bottom rail away from the window sill, causing an undesirable daylight gap at the bottom of the blind. The overwrapping also may cause a problem with the cords tangling. In addition, the drive drum must rotate a full 360 degrees once it reverses direction before it can engage the driven drum in the opposite direction. 
   SUMMARY OF THE INVENTION 
   One objective of the present invention is to provide a blind system, which allows the user to tilt open or tilt closed the entire blind, as well as to selectively tilt open one portion of the blind while another portion of the blind is tilted closed. 
   The present invention achieves this goal without the need for overwrapping of the cords and without lifting the bottom of the blind to create a light gap between the blind and the window sill. 
   Various embodiments of the present invention provide a drive drum portion and a driven drum portion, with tilt cables and actuator cords connected to the various drum portions. Since both the tilt cables and the actuator cords serve to actuate the slats of the blind, the terms may be used interchangeably. The embodiments provide various means for effecting a lag between the rotation of the drive drum portion and the driven drum portion. The lag mechanism is similar to a clutch, which engages the driven drum portion to the drive drum portion during part of the rotation of the drive drum portion, and disengages it for the balance of the rotation. In some embodiments, the driven drum portion has extensions, which contact a fixed member (such as the mounting cradle), which serve as limit stops, limiting the rotation of the driven drum portion. The driven drum portion, in turn, limits the extent of rotation of the drive drum portion, which prevents the over wrap condition of the Japanese Patent. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partially broken away, perspective view of a blind system made in accordance with the present invention, with an exploded perspective view of one of the tape drums also shown above the blind; 
       FIG. 2A  is a perspective view of one of the tape drums of  FIG. 1 , showing its position and that of the tilt cables corresponding to the full blind in the tilted closed position as shown in  FIG. 2C ; 
       FIG. 2B  is the same view as  FIG. 2A  but with the tape drum mounted on its cradle; 
       FIG. 2C  is a perspective view of the blind system of  FIG. 1 , when the tape drum is in the position depicted in  FIG. 2A ; 
       FIG. 2D  is a section view along line  2 D— 2 D of  FIG. 2B  (with the tilt cables removed for clarity); 
       FIG. 2E  is the same view as  FIG. 2D  but with the cradle removed for clarity; 
       FIG. 3A  is a perspective view of the tape drum of  FIG. 1 , showing its position and that of the tilt cables corresponding to the full blind in the tilted open position as shown in  FIG. 3C ; 
       FIG. 3B  is the same view as  FIG. 3A  but with the tape drum mounted on its cradle; 
       FIG. 3C  is a perspective view of the blind system of  FIG. 1  in the fully open position, when the tape drum is in the position depicted in  FIG. 3A ; 
       FIG. 3D  is a section view along line  3 D— 3 D of  FIG. 3B  (with the tilt cables removed for clarity); 
       FIG. 3E  is the same view as  FIG. 3D  but with the cradle removed for clarity; 
       FIG. 4A  is a perspective view of the tape drum of  FIG. 1 , showing its position and that of the tilt cables corresponding to the lower part of the blind being in the tilted closed position, and the balance of the blind being in the tilted open position as shown in  FIG. 4C ; 
       FIG. 4B  is the same view as  FIG. 4A  but with the tape drum mounted on its cradle; 
       FIG. 4C  is a perspective view of the blind system of  FIG. 1  with the lower part closed and the upper part open, when the tape drum is in the position depicted in  FIG. 4A ; 
       FIG. 4D  is a section view along line  4 D— 4 D of  FIG. 4B  (with the tilt cables removed for clarity); 
       FIG. 4E  is the same view as  FIG. 4D  but with the cradle removed for clarity; 
       FIG. 5A  is a perspective view of the driven drum portion (the left half) of the drum of  FIG. 1 ; 
       FIG. 5B  is an opposite-end perspective view of the driven drum portion of  FIG. 5A ; 
       FIG. 5C  is a side view of the driven drum of  FIG. 5A ; 
       FIG. 5D  is an end view of the driven drum of  FIG. 5A ; 
       FIG. 6A  is a perspective view of the drive drum portion (the right half) of the drum shown in  FIG. 1 ; 
       FIG. 6B  is an opposite-end perspective view of the drive drum of  FIG. 6A ; 
       FIG. 6C  is a side view of the drive drum of  FIG. 6A ; 
       FIG. 6D  is an end view of the drive drum of  FIG. 6A ; 
       FIG. 7  is a perspective view of the drum cradle of  FIG. 1 ; 
       FIG. 8  is an opposite-side perspective view of the drum cradle of  FIG. 7 ; 
       FIG. 9A  is a side view of the cord-to-tape attachment clip shown in  FIG. 1 ; 
       FIG. 9B  is a perspective view of the cord-to-tape attachment clip of  FIG. 9A ; 
       FIG. 10A  is a perspective schematic depicting the first step in attaching the cord to the tape using the cord-to-tape attachment clip of  FIG. 9B ; 
       FIG. 10B  is the same schematic as in  FIG. 10A  but showing the cord-to-tape attachment clip already installed; 
       FIG. 11A  is an exploded, perspective view of the drive drum portion and driven drum portion, the tilt rod, the tilt tapes and the tilt cord (or actuator cord) of  FIG. 1 ; 
       FIG. 11B  is a perspective view of the assembled components from  FIG. 11A , shown in the position corresponding to the fully closed blind as shown in  FIG. 12A ; 
       FIG. 11C  is the same view as  FIG. 11B  except that the position corresponds to the fully open blind as shown in  FIG. 12B ; 
       FIG. 11D  is the same view as  FIG. 11B  except that the position corresponds to the lower portion of the blind being fully closed while the upper portion of the blind is fully open, as shown in  FIG. 12C ; 
       FIG. 12A  is a schematic cross-sectional view of the blind of  FIG. 2C  (with the tilt station cradle removed for clarity), when the blind is in the fully closed position; 
       FIG. 12B  is a schematic cross-sectional view of the blind of  FIG. 3C  (with the tilt station cradle removed for clarity), when the blind is in the fully open position; 
       FIG. 12C  is a schematic cross-sectional view of the blind of  FIG. 4C  (with the tilt station cradle removed for clarity), when the upper portion of the blind is in the fully open position, and the lower portion of the blind is in the fully closed position; 
       FIG. 13A  is a schematic cross-sectional view of a blind, similar to the schematic view of  FIG. 12A , but for a second embodiment of the present invention showing the upper portion of the blind fully open and the lower portion of the blind fully closed room side up; 
       FIG. 13B  is the same view as in  FIG. 13A , but with the tape drum rotated 270 degrees to the position corresponding to the blind in the fully open position; 
       FIG. 13C  is the same view as in  FIG. 13A , but with the tape drum rotated 405 degrees to the position corresponding to the blind in the fully closed position room side down; 
       FIG. 14  is a perspective view of the one-piece tape drum used in the second embodiment of the present invention, depicted in  FIGS. 13A ,  13 B, and  13 C; 
       FIG. 15  is a schematic exploded perspective view of a two-piece tape drum used in a third embodiment of the present invention; 
       FIG. 16A  is a schematic perspective view of the assembled tape drum of  FIG. 15 , including the tilt cables, and the actuator cord, in the position corresponding to the fully closed blind depicted in  FIG. 16B ; 
       FIG. 16B  is a schematic cross-sectional view of a blind, similar to the schematic view of  FIG. 13A , but using the tape drum of  FIG. 15 , showing the blind fully closed room side down; 
       FIG. 17A  is the same view as  FIG. 16A  but with the tape drum rotated 90 degrees to the position where the blind is in the fully open position; 
       FIG. 17B  is the same view as  FIG. 16B  but showing the fully open position, with the tape drum in the position shown in  FIG. 17A ; 
       FIG. 18A  is the same view as  FIG. 16A  but with the tape drum rotated 270 degrees to the position where the upper portion of the blind is fully open and the lower portion of the blind is fully closed room side up as shown in  FIG. 18B ; 
       FIG. 18B  is the same view as  FIG. 16B  but showing the upper portion of the blind open and the lower portion of the blind closed room side up, corresponding to the tape drum position shown in  FIG. 18A ; 
       FIG. 19  is a schematic exploded perspective view of a two-piece tape drum used in a fourth embodiment of the present invention; 
       FIG. 20  is a schematic perspective view of the upper ladder tape and the lower ladder tape used in the fourth embodiment; 
       FIG. 21A  is a schematic perspective view of the assembled tape drum of FIG.  19  and the ladder tapes of  FIG. 20 , in the position corresponding to the fully closed blind depicted in  FIG. 21B ; 
       FIG. 21B  is a schematic cross-sectional view of a blind, similar to the schematic view of  FIG. 13A , but for the fourth embodiment of the present invention, showing the blind fully closed room side down; 
       FIG. 22A  is the same view as  FIG. 21A  but with the tape drum rotated 90 degrees to the position where the blind is in the fully open position; 
       FIG. 22B  is the same view as  FIG. 21B  but showing the blind in the fully open position, with the tape drum in the position shown in  FIG. 22A ; 
       FIG. 23A  is the same view as  FIG. 21A  but with the tape drum rotated 180 degrees to the position where the upper portion of the blind is fully open and the lower portion of the blind is fully closed room side up as shown in  FIG. 23B ; 
       FIG. 23B  is the same view as  FIG. 21B  but with the upper portion of the blind fully open and the lower portion of the blind fully closed room side up, corresponding to the tape drum in the position shown in  FIG. 23A ; 
       FIG. 24A  perspective view of a driven drum, similar to that of  FIG. 5A , but for a fifth embodiment of the present invention, without the “catch” or detent present in the driven drum of  FIG. 5 ; 
       FIG. 24B  is perspective view of a drive drum, similar to that of  FIG. 6B , but for the fifth embodiment of the present invention; 
       FIG. 24C  is a perspective view of the torsional spring used in the fifth embodiment of the present invention; 
       FIG. 25A  is an exploded, perspective view of the drive and driven drums of  FIGS. 24A and 24B  as they are being mounted onto the tilt rod; 
       FIG. 25B  is a partially exploded view, similar to  FIG. 25A , but with the addition of the torsional spring; 
       FIG. 25C  is a partially exploded view, similar to  FIG. 25B , but with the addition of the cradle or tape roll support; 
       FIG. 25D  is a perspective view of the assembled tilt station of the fifth embodiment of the present invention; 
       FIG. 26A  is a schematic cross-sectional view of a blind, similar to the schematic view of  FIG. 12A , but for a sixth embodiment of the present invention, showing the blind fully closed room side down; 
       FIG. 26B  is the same view as in  FIG. 26A , but with the tape drum rotated 90 degrees to the position corresponding to the blind in the fully open position; 
       FIG. 26C  is the same view as in  FIG. 26A , but with the tape drum rotated 270 degrees to the position showing the upper portion of the blind fully open and the lower portion of the blind fully closed room side down; and 
       FIG. 27  is a perspective view of an alternate embodiment of the drive drum portion (the right half) of the drum shown in FIG.  1 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to  FIG. 1 , the blind  10  includes a head rail  20  and a plurality of slats  11  suspended from the head rail  20  by means of tilt cables  16  and their associated cross cords  17  (See FIG.  10 A), which together comprise the ladder tapes  18 . Lift cords  12  are fastened at the bottom of the bottom slat (or bottom rail)  21 , which typically is heavier than the other slats  11 . As is well-known in the art, the lift cords  12  are routed through rout holes in the slats  11 , through the head rail  20 , and out through a cord lock mechanism  22 . An operator tilt wand  24  is rotatable about its longitudinal axis to actuate tilt stations  30  via a tilt rod  26  and a tilter  28  as is also well known in the art. However, the tilt stations  30  of the present invention are different from those of the prior art, as will be described shortly. Not normally found in a blind is an actuator cord  14 , which runs parallel to the tilt cables  16  and attaches to the ladder tapes  18  via a clip attachment  32 , as will be described later. While a wand tilter  24  is shown, it is understood that the tilt rod  26  may be rotated by other means such as a cord tilter or a motorized tilter. 
   In order to cause certain portions of the blind  10  to open or close independently of the rest of the blind stack, the actuator cord  14  is activated separately from the tilt cables  16 . As will be appreciated from the following description, this separate means of activation of the actuator cord  14  may be the result of such actions as pulling separately on the actuator cord  14 , attaching the actuator cord or one of the tilt cables  16  to a stationary object (such as the head rail  20 ), or attaching the actuator cord  14  and the tilt cables  16  to a tape drum  30  which has a built-in lag when it pulls on these cords  14 ,  16  via such mechanisms as eccentric mounting of the cords  14 ,  16  and/or by selectively rotating driving and driven drums. In one embodiment, separate ladder tapes are used to control separate portions of the blind, instead of using an actuator cord. 
   Referring to  FIGS. 1 ,  2 A and  2 B, the tape drum  30  includes a drive drum portion  302 , a driven drum portion  304 , and a cradle  306 , which houses and rotatably supports the tape drum  30  in the head rail  20 . 
     FIGS. 6A-6D  show the drive drum  302 , which includes a hollow shaft  310  extending the full length of the drive drum  302 , with a non-circular cross-section inside surface  312 , which closely matches the cross-sectional profile of the tilt rod  26  such that, when the tilt rod  26  rotates, it drives the drive drum  302  as will be described in more detail later. A circular flange  314  is fixed to the shaft  310  and forms a flat shoulder  316  facing toward the left end  318  of the drive drum  302 . Extending from the circumferential edge of the flange  314 , a finger  322  projects to the left, and a truncated cylindrical projection  324  projects towards the right end  320  of the drive drum  302 . The truncated cylindrical projection  324  is concentric with the hollow shaft  310 , and it has a flat  326  which truncates the truncated cylindrical projection  324 . The flat  326  defines a slotted opening  328  into an internal cavity  330 , used for receiving and securing a tilt cable  16  or actuator cord  14  as will be described later. 
     FIGS. 5A-5D  show the driven drum  304 , which has a substantially similar shape to that of the drive drum  302 . The driven drum  304  has a hollow shaft  332  extending the full length of the driven drum  304 , with a cylindrical internal surface  334 , which closely matches the cylindrical outside surface of the hollow shaft  310  extending out the left end  318  of the drive drum  302 , so the hollow shaft  310  of the drive drum  302  fits inside of the hollow shaft  332  of the driven drum  304 , and the driven drum  304  rides on and is rotatably supported by the left end  318  of the hollow shaft  310  of the drive drum  302 . A circular flange  336  on the driven drum  304  forms a flat shoulder  338  at the right end  340  of the driven drum  304 . A truncated cylindrical projection  344  projects toward the left end  342  of the driven drum  304 . The truncated cylindrical projection  344  is concentric with the hollow shaft  332 , and it has a flat  346 , which truncates the truncated cylindrical projection  344 . The flat  346  has two slotted openings  348  which connect the flat  346  to internal cavities  350 , used for receiving and securing the tilt cables  16  or a tilt cable  16  and actuator cord  14  as will be described later. The circumferential edge of the flange  336  has a first driven surface  352  and a second driven surface  354  approximately  180  degrees from the first driven surface  352 . These driven surfaces  352 ,  354 , are located so they will be contacted by the finger  322  of the drive drum  302  as the drive drum  302  rotates in order to drive the driven drum  304 . A shorter step  356  acts as a “catch” or detent and also provides driven surfaces against which the finger  322  of the drive drum  302  may act to drive the driven drum  304 . 
   When the drive drum  302  and driven drum  304  are assembled with their respective flat shoulders  316 ,  338  in direct contact with each other and the left end  318  of the hollow shaft  310  of the drive drum  302  inside the hollow shaft  332  of the driven drum  304 , and when the finger  322  of the drive drum  302  is “caught” between the first driven surface  352  and the step or detent  356 , the flats  326  and  346  are aligned with each other so as to be coplanar, as shown in FIG.  3 A. This position corresponds with the fully open position of the blind, as will be explained later. 
   On the driven drum  304 , a wing (or cradle-impacting member)  358  extends to the left, beyond the truncated cylindrical projection  344 , and this wing  358  contacts the cradle  306  and acts as a stop to limit the rotation of the driven drum  304  relative to the cradle  306 , as will be described later. 
   The cradle  306  (See  FIGS. 7 and 8 ) is a U-shaped bracket, used to mount the tape drum portions  302 ,  304  for rotation in the head rail of the blind. The cradle  306  has right and left arms  362 ,  364  connected together by an interconnecting bar  366 . Extending from the bar  366  and between the two arms  362 ,  364  is a foot  368 , which ends in two toes  370 . There are also two fingers  372  projecting upwardly from the arms  362 ,  364 . These toes  370  and fingers  372  are received in recesses (not shown) in the head rail  20  in order to securely mount the cradle  306  to the inside of the head rail  20 . The foot  368  also defines a slotted opening  374 , which matches with a similar slotted opening (not shown) in the bottom surface of the head rail  20  to provide a passageway for the ladder tapes  18  and the actuator cord  14  to enter the head rail  20  and reach the tilt station  30 . The arms  362 ,  364  are substantially J-shaped, with the crook  376  of the right arm  362  rotatably supporting the hollow shaft  310  of the drive drum  302 , and the crook  378  of the left arm  364  rotatably supporting the hollow shaft  332  of the driven drum  304 , as shown in  FIG. 2B. A  projection  380 , extending from the top of the arm  364  and at approximately a 45 degree angle from the left planar surface defined by the arm  364 , partially encloses the top of the hollow shaft  332  of the driven drum  304 , releasably securing the tape drum assembly  302 ,  304  to the cradle  306  while allowing rotation of the tape drum about its longitudinal axis (which coincides with the longitudinal axis of the tilt rod  26 , which is inserted through the mated hollow shafts  310 ,  332  of the drive and driven drums  302 ,  304  respectively). This is seen best in FIG.  2 B. As seen from the left end of the blind, the long leg  382  of the J-shaped left arm  364  provides a limit stop to the clockwise rotation of the driven drum  304  as the wing  358  on the driven drum  304  impacts against this long leg  382  as shown in  FIGS. 2B and 2D . The short leg  384  of the J-shaped left arm  364  provides a limit stop to the counter-clockwise rotation of the driven drum  304  as the wing  358  on the driven drum  304  impacts against this short leg  384  as shown in  FIGS. 3B and 3D . Thus, the driven drum  304  is restricted to rotation only along a pre-selected angular displacement (approximately a 90 degree angle in the present embodiment) before one or the other of the legs  382 ,  384  of the cradle&#39;s left arm  364  stops the rotation when it is contacted by the cradle-impacting member (or wing)  358  of the driven drum  304 . 
   Of course, while the wing  358  of this embodiment is made as a single member, extending along a defined rotational angle of the driven drum  304  and having two cradle-impacting surfaces, it could just as well be two separate members, each with its own cradle-impacting surface. 
     FIGS. 9A and 9B  show the cord-to-tape attachment clip  32 , which is used to attach the actuator cord  14  to the tilt cable  16  of the ladder tape  18 , as shown in  FIGS. 10A and 10B . The flat, substantially rectangular clip  32  defines upper and lower large slotted openings  386 , which open to the right and left sides of the clip  32 , respectively, a smaller slotted opening  388  in between the two larger openings  386  and opening to the right, and a fourth opening  390  at the upper end of the clip  32 .  FIGS. 10A and 10B  demonstrate how the clip  32  is mounted onto the ladder tape  18 , and how the actuator cord  14  is secured to the clip  32 . One of the tilt cables  16  of the ladder tape  18  is laced through the upper and lower large slotted openings  386  of the clip  32 , with a cross cord  17  received in the smaller slotted opening  388 . This secures the clip  32  to the ladder tape  18 . The end of the actuator cord  14  is fed through the fourth opening  390 , and a knot  392  is then tied at the end of the actuator cord  14  so that the cord  14  cannot pull back out of the hole  390 . Now, as the actuator cord  14  is pulled up, it also pulls the clip  32  and the lower portion of the tilt cable  16  to which the clip  32  is securely attached. 
   Assembly of the Tilt Station  30   
   In order to assemble the tilt station  30  of the present invention, the drive drum  302  and the driven drum  304  are assembled by inserting the hollow shaft  310  of the drive drum  302  into the hollow shaft  332  of the driven drum  304  so that the flat shoulders  316 ,  338  of the drive and driven drums  302 ,  304  are pressed together, the shafts  310  and  332  are mated together, and the finger  322  of the drive drum  302  is caught between the first driven surface  352  and the step  356  on the flange  336  of the driven drum  304 . The tape drum assembly  302 ,  304  is then inserted into the cradle  306  such that the leftwardly-projecting portion of the hollow shaft  332  of the driven drum  304  lies on the crook  378  of the left arm  364  of the cradle  306 , and the rightwardly-projecting portion of the hollow shaft  310  of the drive drum  302  lies on the crook  376  of the right arm  362  of the cradle  306 . The tilt rod  26  is then inserted through the mated hollow shafts  310 ,  332  of the drive and driven drum  302 ,  304  respectively. The cradle  306  is then snapped onto the head rail  20 , with the slotted opening  374  of the cradle  306  lining up with the matching slotted opening in the head rail  20  so that the tilt cables  16  and the actuator cord  14  may pass from the outside of the blind  10  to the inside of the head rail  20  and may then be attached to the tilt station  30  as described below. 
   There is one tilt station  30  for each ladder tape  18 . The two tilt cables  16  of the ladder tape  18  are fed through the slotted opening  374 -of the cradle  306 , knots or grommets are secured to the ends of the tilt cables  16 , and these ends are slid behind the slotted openings  348  of the driven drum  304  into the chambers  350 , such that the tilt cables  16  are secured to the driven drum  304 , with one of the tilt cables  16  lying on either side of the hollow shaft  332  of the driven drum  304 , as shown in  FIGS. 4B and 12B . The actuator cord  14  is similarly fed through the slotted opening  374  of the cradle  306 , and a knot or grommet is tied to its free end, which is then slid behind the slotted opening  328  of the drive drum  302  into the chamber  330 , so that the actuator cord  14  is secured to the drive drum  302  as shown in FIG.  3 B. The clip  32  is attached to the front tilt cable  16 , as has already been described and depicted in  FIGS. 10A and 10B , at the desired location, defining the “break” point  394 , between the separately-operated portions of the blind  10 . The other end of the actuator cord  14  is secured to the clip  32  by passing the actuator cord  14  through the hole  390  of the clip  32  and tying a knot on the end of the cord  14 , as has already been described. 
   Operation of the Tilt Station 
   Now, as the tilt wand  24  (or other actuator) is rotated fully in one direction, causing the tilt rod  26  to rotate clockwise (as seen from the left side of the blind of FIG.  1 ), the tilt rod  26  drives the drive drum portion  302  by means of its non-circular cross-section outer surface contacting the non-circular cross-section inner surface  312  of the hollow shaft  310  of the drive drum  302 . This Provides a non-slip positive engagement drive between the tilt rod  26  and the drive drum portion  302 . A driving surface of the leftwardly-projecting finger  322  on the drive drum  302  contacts the driven surface  352  on the driven drum  304 , providing a non-slip Positive engagement drive between the drive drum portion  302  and the driven drum portion  304 , causing the driven drum  304  to rotate in the clockwise direction. At this point, the drive drum  302  and driven drum  304  are rotating together in a clockwise direction. 
   During this time, all the slats of the blind are tilting together as shown schematically in FIG.  12 A. This continues until the wing  358  of the driven drum  304  contacts the long leg  382  of the left arm  364  of the cradle  306 , stopping the clockwise rotation of the driven drum  304 . Since the finger  322  on the drive drum  302  remains in contact with the driven surface  352  of the driven drum  304  and cannot rotate any further beyond that stopped driven surface  352 , the rotation of the drive drum  302  is also stopped. This clockwise-most stopped position is shown in  FIGS. 2A ,  2 B,  2 D,  2 E,  11 B and  12 A and corresponds to the position in which the blind  10  is tilted fully closed, room side down, as shown in  FIGS. 2C and 12A . 
   As the tilt wand  24  is rotated in the opposite direction, the tilt rod  26  turns counter-clockwise, causing the drive drum portion  304  also to rotate counter-clockwise. The finger  322  on the drive drum portion  304  then engages the surface of the detent (or step)  356  on the driven drum portion  304 , thereby providing a non-slip positive engagement between the drive drum portion  302  and the driven drum portion  304 , driving the driven drum portion  304  in the counter-clockwise direction. The drum portions  302 ,  304  continue to rotate together in the counter-clockwise direction until the driven drum portion  304  is stopped, when the wing  358  on the driven drum portion  304  contacts the short leg  384  of the left arm  364  of the cradle  306  (See FIG.  3 D). At this point, the tape drum assembly  302 ,  304  has rotated approximately 90 degrees from the closed position shown in  FIG. 12   a , and the blind is now in the fully open position, with the drum portions in the position shown in  FIGS. 3A ,  3 B,  3 D,  3 E,  11 C, and  12 B. The rear tilt cable  16  has dropped slightly and has unwound from its partially wrapped condition around the truncated cylindrical projection  344  of the driven drum  304 , while the front tilt cable  16  and the actuator cord  14  have been raised slightly, resulting in the entire blind  10  being in the fully open position as shown in  FIGS. 3C and 12B . 
   As the tilt wand  24  continues to be rotated in the counter-clockwise direction, the tilt rod  26  continues to turn counter-clockwise, driving the drive drum  302  in the same counter-clockwise direction (See FIGS.  4 D and  4 E). Since the driven drum  304  cannot rotate any further in the counter-clockwise direction (due to the limit stop caused by the contact of the wing  358  against the short leg  384  of the left arm  364  of the cradle  306 ), the finger  322  on the drive drum  302  skips over the detent  356  on the driven drum  304 , so that only the drive drum  302  continues to rotate for an additional pre-selected angular displacement (approximately 180 degrees in the present embodiment) until the finger  322  contacts the second driven surface  354  on the driven drum  304 . Since the driven drum  304  is stopped from further counter-clockwise rotation at this point, contact between the finger  322  of the drive drum and the second driven surface  354  of the driven drum also stops the drive drum  302 , thereby defining the counterclockwise-most position of the drive drum  302 . 
   At this point, the actuator cord  14  has lifted the lower portion of the front tilt cable  16 , thereby closing the bottom portion of the blind in the room-side up position while leaving the top portion open, as shown in FIG.  12 C. This condition is illustrated in  FIGS. 4A ,  4 B,  4 D,  4 E,  11 D, and  12 C. Since the driven drum  304  has not rotated any further, the tilt cables  16 , which are attached to the driven drum  304 , have not moved. However, the drive drum  302  has continued to rotate an additional 180 degrees, and this has wrapped the actuator cord  14  around the truncated cylindrical projection  324  of the drive drum  302 , pulling up on the clip  32 , and thus also pulling up on the front tilt cable  16  at the “break” point  394 , where the clip  32  is attached to the tilt cable  16 . As the front tilt cable  16  below the break point  394  is raised and the rear tilt cable  16  remains unaffected, the slats  11  below the break point  394  are tilted up to give the effect of a tilted closed blind, room side up, as shown in  FIGS. 4C and 12C . 
   Reversing the direction of rotation of the tilt wand  24  merely reverses the events described above. Namely, when starting from the position depicted by  FIG. 12C , as the tilt wand  24  is rotated, causing the tilt rod to rotate clockwise, the weight of the blind  10  on the tilt cables  16  prevents the driven drum  304  from rotating at first, until the drive drum  302  has rotated clockwise approximately 180 degrees lowering the actuator cord, and returning the blind to the open position shown in FIG.  12 B. Further rotation of the tilt wand results in the finger  322  contacting a surface of the detent  356  on the driven drum  304 , thus Positively driving both drum portions  302 ,  304  clockwise until the condition depicted in  FIG. 12A  is reached, where the wing  258  contacts the longer leg  382  of the left arm  364  of the cradle  306 , stopping the clockwise rotation of the driven drum portion  304 . Further rotation of the tilt wand  24  causes the finger  322  to skip over the detent  356  and forces the finger  322  against the first driven surface  352 , which brings the rotation of the entire tilt station  30  to a stop. 
   Alternate Embodiments 
   For ease in description, alternate embodiments of mechanisms for selectively tilting portions of a blind will be described by comparing and contrasting them with the first embodiment previously described and schematically illustrated in  FIGS. 12A ,  12 B, and  12 C. The cradle  306  has been deleted from all views, but it is understood that the cradle  306  would be present and would be providing the support for rotation and the limit stops, as required, when so indicated. In order to obtain further clarity and brevity in the description, all figures henceforth (where applicable) refer to front tilt cables  16   a  and rear tilt cables  16   b , front actuator cables  14   a  and rear actuator cables  14   b , and upper ladder tapes  18   a  and lower ladder tapes  18   b , where front refers to the room side of the blind  10  and back refers to the window or wall side of the blind  10 . (Of course, the directions front, back, left, right, etc. could be reversed in any embodiment without changing the functioning of the blind.) 
     FIGS. 13A ,  13 B, and  13 C show a second embodiment of a blind  10   a , which uses a single-piece tape drum  30 A, shown in FIG.  14 . This single-piece tape drum  30 A is in fact very similar to the two-piece tape drum  302 ,  304  of the first embodiment, even though the specific geometry of the truncated cylindrical projections  324 A,  344 A of the single-piece tape drum  30 A differ slightly from the corresponding surfaces  324 ,  344  of the two-piece tape drum  30  in order to account for the correct lag in pulling on the actuator cord  14 B. 
   In this second embodiment, the front tilt cable  16 A is secured to the head rail  20  (See FIG.  13 B), the rear tilt cable  16 B is secured to the rear slotted opening  348 B of the tape drum  30 A and extends only as far as the “break” point  394 , where it is terminated. The actuator cord  14 B is secured to the front slotted opening  328 B and extends all the way to the bottom rail  21 . The actuator cord  14 B is secured to the bottom rail  21  in a similar manner as the front tilt cable  16 A is secured to the bottom rail  21 . The actuator cord  14 B is also secured to all the ladders  17  supporting the slats  11  located at or below the break point  394  but is not connected to any of the ladders  17  supporting the slats  11  located above the break point  394 . So, the actuator cord  14 B effectively is one of the tilt cables for the lower portion of the blind. 
   The lengths of the tilt cables  16 A,  16 B and of the actuator cord  14 B are adjusted so that, when the tape drum  30 A is fully rotated clockwise (as seen from the vantage point of FIG.  13 A), the bottom portion of the blind  10 A is tilted closed room side up, and the upper portion of the blind  10 A is tilted open. As the tilt wand  24  is rotated so that the tilter  28  in turn rotates the tilt rod  26  and the tape drum  30 A counter-clockwise, the length of the rear tilt cable  16 B remains unchanged so that the upper portion of the blind  10 A remains tilted open. However, the actuator cord  14 B wraps around the surface  324 A of the tape drum  30 A and is thus shortened, bringing the lower portion of the blind  10 A to the tilted open position as shown in FIG.  13 B. This corresponds to a counterclockwise rotation of 270 degrees from the initial position of FIG.  13 A. Further counter-clockwise rotation of the tape drum  30 A to a position which is 405 degrees from the initial position results in both the rear tilt cable  16 B and the actuator cord  14 B wrapping on the surfaces  344 A,  324 A of the tape drum  30 A, respectively, thus shortening these cords  16 B,  14 B, bringing both the upper and lower portions of the blind  10 A to the tilted closed position room side down as shown in FIG.  13 C. As in the case of the first embodiment, reversing the direction of rotation merely reverses the events described above. 
   In this embodiment, the two portions  324 A,  344 A of the tape drum  30 A are positively driven together by the tilt rod  26 . This non-slip positive engagement drive is formed by the non-circular cross-section outer surface of the tilt rod  26  engaging the non-circular cross-section inner surface of the tape drum  30 A. 
     FIGS. 15-18B  show a third embodiment of a blind  10 B. This embodiment  10 B uses a two-piece tape drum  30 B as shown schematically in FIG.  15 . This two-piece tape drum  30   b , including the drive drum portion  302 B and the driven drum portion  304 B, is in fact very similar to the two-piece tape drum  302 ,  304  of the first embodiment, even though the specific geometry of the truncated cylindrical projections  324 B,  344 B of the tape drum  30 B differ slightly from the corresponding surfaces  324 ,  344  of the tape drum  30  in order to account for the correct lag in pulling on the actuator cord  14 A. The driven drum portion  304 B has a first projection  396 B, which engages the flat  326 B on the drive drum  302 B and a second projection  398 B which engages the short leg  384  of the arm  362  of the cradle  306  to serve as a first limit stop. The second projection  398 B engages the long leg  382  of the arm  362  of the cradle  306  to serve as a second limit stop. 
   In this third embodiment  10 B, the front tilt cable  16 A is secured to the head rail  20 , the rear tilt cable  16 B is secured to the driven drum  304 B, and the actuator cord  14 A is secured to the drive drum  302 B and extends down to the break point  394 , where it attaches to the front tilt cable  16 A via the clip  32  as has already been described. 
   The lengths of the tilt cables  16 A,  16 B and of the actuator cord  14 A are adjusted so that, when the tape drum  30 B is fully rotated clockwise, with the projection  398 B of the driven drum portion  304 B stopped against the cradle and the drive drum portion  302 B stopped against the driven drum portion  304 B, the entire blind  10 B is tilted closed room side down, as shown in FIG.  16 B. The flat  326 B on the drive drum  302 B pushes against the first projection  396 B of the driven drum  304 B, holding the rear tilt cable  16 B pulled up against the weight of the blind stack, and holding the blind in the closed position of FIG.  16 B. As the tilt wand  24  is rotated so that the tilter  28  in turn rotates the tilt rod  26  and the drive drum  302 B counter-clockwise to a new position which is 90 degrees from the position of  FIG. 16B , the driven drum  304 B also rotates counter-clockwise 90 degrees, forced open by the weight of the blind stack pulling on the rear tilt cable  16 B. This lengthens the rear tilt cable  16 B as it unwinds from the surface  344 B of the driven drum  304 B so that the entire blind  10 B is tilted open as shown in FIG.  17 B. The relative positions of the drive and driven drums  302 B,  304 B and of the tilt cables  16 A,  16 B and the actuator cord  14 A at this position are shown in FIG.  17 A. As the drive drum  302 B continues to rotate counter-clockwise, the second projection  398 B on the driven drum  304 B contacts against the leg  384  of the arm  362  of the cradle  306 , which stops the driven drum  304 B from further counter-clockwise rotation. 
   Further counter-clockwise rotation of the drive drum  302 B to a position which is 270 degrees from the initial position (initial position is shown in  FIG. 16B ) results in the actuator cord  14 A wrapping onto the surface  324 B of the drive drum  302 B, thus shortening this cord  14 A, bringing the lower portion of the blind  10 B to the tilted closed position room side up as shown in FIG.  18 B. The relative positions of the drive and driven drums  302 B,  304 B and of the tilt cables  16 A,  16 B and the actuator cord  14 A when the blind is in this position are shown in FIG.  18 A. As in the case of the other embodiments, reversing the direction of rotation reverses the events described above. 
     FIGS. 19-23B  show a fourth embodiment of a blind  10 C. This embodiment uses a two-piece tape drum  30 C, shown schematically in FIG.  19 . This two-piece tape drum  30 C, including drive drum portion  302 C and driven drum portion  304   c , is very similar to the two-piece tape drum  302 ,  304  of the first embodiment, even though the specific geometry of the surfaces  324 C,  344 C of the tape drum  30 C may differ slightly from the corresponding surfaces  324 ,  344  of the tape drum  30  in order to account for the correct lag in pulling on the different ladder tapes  18 A and  18 B of FIG.  20 . The driven drum portion  304 C has a projection  398 C, which engages the short leg  384  of the arm  362  of the cradle  306  to serve as a limit stop. The drive drum portion  302 C has a projection  396 C, which engages the flat driven surface  326 C on the driven drum portion  304 C. 
   In this fourth embodiment  10 C, there are two sets of ladder tapes  18 A and  18 B (See FIG.  20 ), each including cross cords  17 , supporting a set of slats  11 , with the cross cords tied to front and rear cables  16 A,  16 B, respectively. The first ladder tape  18 A is shorter than the second ladder tape  18 B, in that it only extends down as far as the break point  394  on the blind  10 C (See FIG.  22 B). The second ladder tape  18 B extends all the way down to the bottom rail  21 , but it does not have cross cords  17  above the break point  394 . The longer set of cables  16 A,  16 B, corresponding to the longer ladder tape  18 B is attached to the drive drum portion  302 C, and the shorter set of cables  16 A,  16 B corresponding to the shorter ladder tape  18 A, is attached to the driven drum portion  304 C such that, when the drive drum portion  302 C and the driven drum portion  304 C are in the initial position shown in  FIG. 22A , the entire blind  10 C is in the tilted open position of FIG.  22 B. 
   As the drive drum portion  302 C is rotated clockwise, the projection  396 C on the drive drum portion  302 C contacts the flat driven surface  326 C on the driven drum portion  304 C, driving the drum portions  302 C,  304 C clockwise 90 degrees, until the projection  398 C on the driven drum portion  304 C contacts the long leg  382  of the arm  362  of the cradle  306 , serving as a first limit stop. At this point, the entire tilting mechanism comes to a stop at the position shown in  FIGS. 21A and 21B , with the entire blind  10 C tilted closed room side down. The projection  396 C on the drive drum portion  302 C pushes against the flat driven surface  326 C of the driven drum portion  304   c , and the rear tilt cables  16 B of both ladder tapes  18   a ,  18 B are pulled up against the weight of the blind stack. 
   As the tilt wand  24  is rotated in the opposite direction, so that the tilter  28  in turn rotates the tilt rod  26  and the drive drum  302 C counter-clockwise 90 degrees, back to the initial position, the projection  396 C on the drive drum contacts a detent (not shown) on the driven drum  304 C to cause the driven drum  304 C to rotate counter-clockwise 90 degrees back to its initial position, returning to the initial position shown in  FIGS. 22A ,  22 B, with the entire blind open. 
   As the drive drum  302 C continues rotating counterclockwise, a projection from the driven drum  304 C contacts the cradle, stopping the driven drum  304 C in the open position, while the drive drum rotates 90 degrees counterclockwise from its initial position of  FIG. 22A  to the position shown in FIG.  23 A. At this point, the front tilt cable  16 A of the long ladder tape  18 B has wrapped onto the surface  324 C of the drive drum  302 C, thus shortening this long cable  16 A, bringing the lower portion of the blind  10 C to the tilted closed position room side up as shown in FIG.  23 B. Thus, with 90 degrees of rotation of the driven drum and 180 degrees of rotation of the drive drum, the blind can go from a position that is fully closed room side down, to an open position, to a position with the top portion open and the bottom portion closed room side up. As in the case of the other embodiments, reversing the direction of rotation merely reverses the events described above. 
     FIGS. 24A-25D  show a fifth embodiment of a blind  10 D. This embodiment uses a two-piece tape drum  30 D. This two piece tape drum  30 D is very similar to the two-piece tape drum  302 ,  304  of the first embodiment, with the difference being that the projection or catch  356  in the driven drum  304  has been eliminated, and a torsional spring  400  (See  FIGS. 24C and 25B ) is used instead, as is described below. 
   The torsional spring  400  has a first end  400 A and a second end  400 B. As shown in  FIGS. 25B ,  25 C, and  25 D, the spring  400  is mounted onto the shaft  332 D of the driven drum portion  304 D, with the first end  400 A engaging the wing  358 D of the driven drum portion  304 D, and the second end  400 B engaging the cradle  306  at the base of the projection  380 . The spring  400  biases the driven drum  304 D in the counter-clockwise direction. 
   Except for the absence of the detent projection  356  on the driven drum  304 , and the replacement of its function by the torsional spring  400  engaging the new driven drum  304 D, this fifth embodiment operates in the same manner as the first embodiment described above. Referring briefly to  FIGS. 12A ,  12 B, and  12 C, and considering the position of  FIG. 12B  to be the starting point, when the tilt rod  26  is rotated clockwise, it drives the drive drum  302  clockwise, and the driving surface on the projection  322  of the drive drum  302  engages the driven surface  352 D on the driven drum  304 D, forcing the driven drum  304 D also to rotate clockwise 90 degrees to the position shown in FIG.  12 A. This causes the end  400 A of the spring  400  also to rotate clockwise, compressing the spring  400 . At this point, the blind is closed, room side down, as seen in FIG.  12 A. 
   As the tilt rod  26  is rotated back counter-clockwise 90 degrees to the position shown in  FIG. 12B , the compressed spring  400  pushes against the wing  358 D of the driven drum  304 D, causing the driven drum  304 D to rotate counter-clockwise as well, and keeping the step  352 D of the driven drum  304 D pressed against the driving projection  322  of the drive drum  302 . When the blind reaches the open position depicted in  FIG. 12B , the wing  358 D on the driven drum  304 D contacts the leg  384  of the cradle  306 , stopping the driven drum  304 D. 
   Further counter-clockwise rotation of the tilt rod  26  results in rotation of the drive drum  302  only, for approximately 180 degrees. The actuator cord  14  wraps onto the drive drum  302 , until the projection  322  on the drive drum  302  hits against the second driven surface  354 D on the driven drum  304 D, causing the drive drum  302  to stop in the position depicted in  FIG. 12C , with the top portion of the blind in the open position and the bottom portion of the blind, below the “break” point  394 , in the closed position, room side up. As in the case of the first embodiment, reversing the direction of rotation of the tilt rod reverses the events described above. 
   The projection  322  on the drive drum  302  no longer has to “jump” over the detent on the driven drum  304 D, since there is no longer a detent  356  on the driven drum  304 D in this fifth embodiment. As a result, the user no longer experiences a sharp increase in force to engage or disengage the driven drum  304 D. 
     FIGS. 26A ,  26 B, and  26 C depict a sixth embodiment  10 E of a blind manufactured in accordance with the present invention. This embodiment  10 E is identical in its components to the first embodiment  10  onto the fifth embodiment  10 D described above. The difference is that the actuator cord  14  in this sixth embodiment  10 E is secured to the rear tilt cable instead of to the front tilt cable. The net effect is that, in one position of the tape drum  30 D, when it is rotated fully in the counter-clockwise direction (as seen from the vantage point of FIG.  26 C), the actuator cord  14  pulls up on the rear tilt cable  16  at the break point  394 , resulting in the lower portion of the blind  30 D being closed room side down (as shown in  FIG. 26C ) instead of being closed room side up (as shown in FIG.  12 C). 
   For all the embodiments described above, the use of the terms “front” and “back”, “inside” and “outside” with respect to the blind and slats are arbitrary, and it is obvious that the blind could be turned around, so that the front becomes the back, the inside becomes the outside, and vice versa. Also, the construction could be reversed, so that the entire blind closed with the inside edges up instead of down, and the lower portion closed with the inside edges down instead of up. 
     FIG. 27  illustrates an alternate embodiment of the drive drum  302 D, which may be used with any of the previously described embodiments using two-piece tape drums. The finger  322  in this drive drum  302 D has two radially directed slots  402 D on the flat shoulder  316  such that the finger  322  has some flexibility to spring out of the way when it hits against the detent  356  in the driven drum  304 . The jump by the finger  322  over the detent  356  is therefore easier, requiring the use of less force by the user who is thus less likely to interpret the detent  356  as a limit stop. 
   While several embodiments of the present invention have been shown and described, it is not practical to describe all the possible variations and combinations that could be made within the scope of the present invention. It will be obvious to those skilled in the art that modifications may be made to the embodiments described above without departing from the scope of the invention as claimed.