Abstract:
An actuator mechanism for window coverings, such as, Venetian blinds that eliminates the use of pull cords and tilting wands is provided. The actuator mechanism includes a stop member engageable with at least one of the slats to stop tilting movement thereof and a clutch arrangement between a drive axle and a tilt control mechanism, responsive to the stop member engaging at least one of the slats, to disengage the tilting force applied to a ladder cord supporting the slats.

Description:
TECHNICAL FIELD OF INVENTION 
     This invention relates to an improved window covering. More particularly, this invention relates to an improved window covering having the ability to tilt, raise or lower the slats of the window covering by operation of its bottom rail. 
     BACKGROUND OF THE INVENTION 
     Venetian blinds are a type of window covering comprising horizontal slats, one above another. The slats are typically suspended between an upper rail and a bottom rail by cords. One cord, the ladder cord, is used to control the rotation of the blinds. The other cord, the raising cord, is used to raise and lower the slats. The ladder cord allows the slats to rotate or tilt approximately 180 degrees in either direction. At one extreme the slats are rotated such that they overlap with one side of the slats facing inward and the other sides of the slats facing outward. At the other extreme, the opposite sides of the slats face inward and outward. When the lift cord is pulled, the bottom rail moves towards the upper rail, causing the slats to be stacked one on top of the other. 
     In most prior art Venetian blinds, an external tilting wand is used to control an operating mechanism that causes the rotation of the slats and an external lift cord is used to control the height of the bottom rail. These components are visible and not aesthetically pleasing. Moreover, the cords pose a choking or strangulation hazard for children. While some prior art Venetian blinds have removed the external tilting wand or lift cord, no such prior art devices have eliminated the needs of the external tilting wand, as well as the external lift cord without severely limiting the function of the blind. Therefore, it is desirable to provide an aesthetically pleasing and safe window blind that does not include either an external tilting wand or an external lift cord. 
     Therefore, there is a need for an actuator mechanism for controlling the movement of a window covering, such as a Venetian blind, that overcomes the foregoing problems. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a cordless actuator mechanism that is suitable for use with a window covering that does not require the use of conventional pull cords to raise or lower the window covering. The present invention is particularly suitable for use with a Venetian blind which includes a head rail, a plurality of slats, a raising cord, and a bottom member suspended from the raising cord to impart vertical adjustments thereto by a user. Other possible window coverings are cellular shades that include adjustable vanes within the cells. 
     With a Venetian blind a ladder extending from the head rail is provided, which is attached to and supports the plurality of slats for tilting movement thereof. A stop arrangement adapted to limit vertical movement of the ladder cord and the slats suspended therewith, a rotatable drive axle disposed within the head rail having a winding drum member mounted therewith, and a raising cord upper end portion secured with the winding drum member whereby vertical adjustment of the raising cord cooperates with the drive unit for rotation of the winding drum member and the drive axle are also provided. The stop arrangement can take various forms as will be discussed in greater detail below. 
     A tilting member is rotationally fixed with the drive axle, while an upper portion of the ladder is secured to the tilting member such that rotation of the tilting member applies a tilting force to the ladder to cause the ladder to tilt the slats. A clutch arrangement is provided between the drive axle and the tilting member, which is responsive to the stop arrangement arresting vertical movement of the ladder cord, to disengage the rotational or tilting force from the drive axle from being applied to the ladder. 
     In one embodiment, the tilting member comprises an outer drum about which the ladder cord is attached. The actuator mechanism further comprises an inner drum member circumferentially mounted about and rotationally fixed to the drive axle, and a collar member, such as a coil spring, comprising the clutch arrangement. The coil spring is circumferentially mounted about the inner drum and has a tightened state whereby the coil spring is engaged with the inner drum, and an expanded state whereby the coil spring is disengaged from the inner drum. 
     The outer drum is circumferentially mounted about the coil spring. The coil spring is biased toward the engaged condition. The coil spring is moved to the engaged condition by rotation of the winding drum member and the drive axle in response to vertical adjustment of the raising cord, by upward or downward manipulation of the bottom member, which enables a force to be transmitted from the drive axle to the coil spring. 
     In a second embodiment, the tilting member includes a winding pulley having a hub located between a pair of pulley sidewalls to define a generally V-shaped recess for confining a loop of the ladder cord as the ladder cord is wound about the hub. The pulley sidewalls are responsive to the stop member engaging at least one of the slats to stop tilting movement thereof so as to increase force on the ladder cord loop, causing the ladder cord loop to engage the pulley sidewalls, moving the ladder cord away from the hub so as to disengage the tilting force applied to the ladder cord. In a related embodiment, the hub comprises a plurality of ribs to provide increased engagement with the ladder cord. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a Venetian blind shown in an open configuration, and including an actuator mechanism according to a preferred embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of part of a tilt control mechanism of the actuator mechanism shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of a coil spring of the tilt control mechanism shown in  FIG. 2 ; 
         FIG. 4  is a perspective view of the tilt control mechanism shown in  FIG. 2 ; 
         FIG. 5  is a top view of an actuator mechanism of the embodiment shown in  FIG. 1 ; 
         FIG. 6  is a perspective view of the actuator mechanism of the embodiment shown in  FIG. 5 ; 
         FIG. 7  is a cross-sectional view of the Venetian blind shown in  FIG. 1 , taken along line  7 - 7  and shown in a fully retracted configuration; 
         FIG. 8  is a cross-sectional view similar to  FIG. 7 , but shown in a first closed configuration; 
         FIG. 9  is a cross-sectional view similar to  FIG. 7 , but shown in an open configuration; 
         FIG. 10  is a cross-sectional view similar to  FIG. 7 , but shown in a second closed configuration; 
         FIG. 11  is a perspective view of a second embodiment of an actuator mechanism according to the present invention; 
         FIG. 12  is an exploded perspective view of the actuator mechanism shown in  FIG. 11 ; 
         FIG. 13  is a fragmentary perspective view of the actuator mechanism shown in  FIG. 11 ; 
         FIG. 14  is a perspective view of the actuator mechanism shown in  FIG. 11 ; 
         FIG. 14A  is a cross-sectional view of the actuator mechanism shown in  FIG. 11 ; 
         FIG. 15  is a side elevational view of the winding drum assembly of  FIG. 6 , shown partly in cross-section; 
         FIG. 16  is a fragmentary side elevational view of an actuator mechanism with an alternative tilt winding pulley; 
         FIG. 17  is a perspective view thereof; 
         FIG. 18  is a front elevational view of the tilt winding pulley; 
         FIG. 19  is a side elevational view thereof; 
         FIG. 20  is a fragmentary side elevational view of an actuator mechanism with another tilt winding pulley; 
         FIG. 21  is a perspective view thereof; 
         FIG. 22  is a front elevational view of the tilt winding pulley; 
         FIG. 23  is a side elevational view thereof; 
         FIG. 24  is a fragmentary side elevational view of an operating mechanism with an actuator mechanism with an alternative clutching arrangement; 
         FIG. 25  is an exploded view of the actuator mechanism of  FIG. 24 ; and 
         FIG. 26  is a perspective view of the actuator mechanism of  FIG. 24 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention disclosed herein is, of course, susceptible of embodiment in many different forms. Shown in the drawings and described herein below in detail are preferred embodiments of the invention. It is 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. 
     For ease of description, actuator mechanisms for Venetian blinds embodying the present invention and utilizing a novel drive clutch arrangement, embodied as either a coil spring or a pulley wheel, is described herein below in their usual assembled position as shown in the accompanying drawings, and terms such as upper, lower, horizontal, longitudinal, etc., may be used herein with reference to this usual position. However, the actuator mechanisms may be manufactured, transported, sold, or used in orientations other than and described and shown herein. 
     A preferred embodiment of the present invention is shown in  FIGS. 1 through 10 . Referring to  FIG. 1 , Venetian blind  10  is shown in a fully extended position with its slats opened. The blind  10  includes head rail  12 , bottom rail  16 , a plurality of slats  70  and actuator mechanisms  20  and  21 . Head rail  12  has a rectangular plinth-like shape and includes a bottom side  15  and a substantially open top side  13 . The inside of head rail  12  forms a substantially hollow channel  14 . As shown in  FIGS. 7-10 , bottom side  15  of the head rail  12  includes a stop member or first bottom edge  11  (see  FIGS. 8 and 10 ) and a second bottom edge  19  (see  FIG. 7 ). Head rail  12  may be secured to a window or similar surface by means known in the art. It may also include decorative facing without departing from the spirit of the invention. 
     Referring again to  FIG. 1 , bottom rail  16  includes top side  17  and bottom side  18 . Preferably, the area of top side  17  is substantially equal to the longitudinal area of each individual slat  72 , although this is not required. The shape of the bottom rail may vary without departing from the spirit of the invention. 
     The slat array or plurality of slats  70  comprises a plurality of individual slats  72 . Each slat  72  includes a top portion  73  and a bottom portion  74 . Top portion  73  and bottom portion  74  are connected together by border  75 . Border  75  includes a first edge  76 , a second edge  77 , a third edge  78  and a fourth edge  79 , the third and fourth edge  78  and  79  extending along the width of each slat  72 . In the preferred embodiment, the cross-sectional shape of each slat  72  is substantially rectangular. Other shapes may be utilized, however. The number of slats included is determined based on the size of the slats and the desired length, or vertical extent, of the blind. 
     A tilt control mechanism  30  for tilting the plurality of slats  70  is provided, and is shown in greater detail in  FIGS. 2-6 . The tilt control mechanism  30  includes an inner drum  40 , a clutch arrangement that includes a coupling member, such as coil spring  50 , and a tilting member  60  that, in this embodiment, is an outer drum. As shown, the inner drum  40 , coil spring  50  and tilting member  60  are comprised of individual components, although other combinations of parts is possible. Inner drum  40  is preferably provided as a monolithic plastic molding and includes an outer surface portion  44  that is generally cylindrical. First and second flange portions  42  and  46  respectively protrude from the outer surface  44  of the inner drum  40  at two axially opposite sides thereof. Through hole  48  is defined by inner drum  40 . Through hole  48  is configured to accept insertion of drive axle  24  such that the inner drum  40  is tightly mounted on the drive axle  24  and also rotationally fixed relative to the drive axle. The inner drum  40  can also define a slit  45  cut through the second flange  46  and a portion of the outer surface  44  proximate to the second flange  46 . Slit  45  can add some resiliency to the end portion of the inner drum  40  for facilitating its assembly through the tilting member  60 . 
     The tilting member  60  is hollow and generally cylindrical in shape. The tilting member  60  includes an outer surface  61 , and defines a recess  63  having an inner surface  68 . The inner surface  68  of recess  63  further defines a slot  62 . Formed axially on the outer surface  61  is a groove  64 . Groove  64  is sized to receive retainer segment  66  that includes clipping tabs  65  and  67  for securely fixing end portions of ladder cord sections  22   a  and  22   b  ( FIG. 5 ), which are front and rear ladder cord sections, to tilting member  60 . In this embodiment, the retainer segment  66  and the tilting member  60  are separate components. In other embodiments, retainer segment  66  may also be integrally formed on the tilting member  60 . Retainer segment  66  can be shaped to match the radius of curvature of the tilting member  60 . 
     As more clearly shown in  FIG. 3 , coil spring  50  comprises end portions or prongs  52 , which extend in a substantially radial outward direction. The coil spring  50  can have two states, referred to herein as tightened and expanded states. Coil spring  50  is configured such that in a tightened state, it is firmly mounted by way of friction on the outer surface portion  44  of the inner drum  40  between the first and second flange portions  42  and  46 . Provided with the coil spring  50 , the inner drum  40  can be inserted into recess  63  of the tilting member  60  with the prongs  52  being lodged in the slot  62  thereof. When the coil spring  50  is in the tightened state, the coil spring  50  tightly presses around the outer surface  44  of the inner drum  40  so that the inner drum  40 , coil spring  50  and tilting member  60  rotate in unison. When the coil spring  50  is in the expanded state, the coil spring  50  expands so that it no longer tightly grips on the outer surface  44  of the inner drum  40 . The inner drum  40  is thus&#39; able to rotate along with the drive axle  24  independent of the coil spring  50  and tilting member  60 . 
     Referring to  FIGS. 2-6 , the tilt control mechanism  30  includes the coil spring  50  mounted around the inner drum  40 . Inner drum  40  and coil spring  50  are mounted within recess  63  of the tilting member  60  with the prongs  52  of the coil spring  50  placed within the slot  62 . The height of the first and second flange portions  42  and  46  is preferably sized so as to prevent axial shifting of the coil spring  50  or the tilting member  60  from the inner drum  40 . To drive the tilt control mechanism  30 , the drive axle  24  is mounted through the hole  48  of the inner drum  40 . 
     With reference to  FIGS. 1 ,  5  and  6 , two ladder cord sections  22   a  and  22   b  are engaged with the clipping tabs  65  and  67  on the retainer segment  66 . It will be understood by skilled practitioners that one ladder cord section  22   a  can extend at the front of the Venetian blind  10  and connect with one side edge of the plurality of slats  70  (e.g., fourth edge portion  79 ), whereas the other ladder cord section  22   b  can extend at the rear of the Venetian blind  10  and connect with an opposite side edge of the plurality of slats  70  (e.g., third edge portion  78 ). Each of the ladder cord sections  22   a  and  22   b  has an upper end secured with the tilt control mechanism  30 , and a lower end secured with the bottom rail  16 . Ladder cord sections  43  are secured at one end to another tilt control mechanism  31  and at the other end, to bottom rail  16  in a manner similar to ladder cord sections  22   a  and  22   b . The plurality of slats  70  can be thereby suspended from ladder cord sections  22   a ,  22   b  and  43 . Raising cord  25  extends from the winding drum assembly  29  of the actuator mechanism  20 , through an aperture in head rail  12 , through the plurality of slats  70 , and is fixed at a lower end to bottom rail  16 . Raising cord  26  similarly extends from the winding drum assembly of another actuator mechanism  21  similar to the actuator mechanism  20 , through an aperture on head rail  12 , through the plurality of slats  70  and is secured with bottom rail  16 . As will be seen, the bottom rail  16  may be pulled or pushed by a user to impart vertical adjustments to the raising cord and adjust the inclination of, i.e., tilt, the plurality of slats  70 . 
     Referring to  FIGS. 5 and 6 , the actuator mechanism  20  includes the winding drum assembly  29  and tilt control mechanism  30 . The winding drum assembly  29  and tilt control mechanism  30  is mounted with the drive axle  24 . In the same manner, actuator mechanism  21  is also mounted on the drive axle  24  and includes a winding assembly and tilt control mechanism similar to those of actuator mechanism  20 . The use of a common drive axle  24  to connect multiple actuator mechanisms also provides for a simple and reliable means for synchronization and balancing of the actuator mechanisms to promote even lifting and tilting of the blind. In the embodiment disclosed, two actuator mechanisms are mounted on the drive axle  24 . The number of actuator mechanisms utilized depends on the weight and width of the blind, and may vary as needed. 
       FIG. 15  is a cross-sectional view illustrating one embodiment of the winding drum assembly  29  used for operating the raising cord  25  (for clarity, the tilt control mechanism has been omitted in  FIG. 15 ). As shown, the winding drum assembly  29  includes a support structure, such as housing  138 . Positioned within the housing  138  are a winding drum  140  and a motor spring  142  (shown in cross section) axially spaced apart from each other. In this embodiment, the winding drum  140  includes a spindle  144  that is integrally formed with the winding drum  140 . The drive axle  24 , which defines a longitudinal axis  48 , is inserted through and secured with the spindle  144  such that the winding drum  140  and drive axle  24  rotate together. It is preferred that the winding drum  140 , spindle  144  and motor spring  142  are coaxial with one another. More specifically, the motor spring  142  can be a spiral spring having a first end fixedly secured on the housing  138  and a second end fixedly secured on the spindle  144 . The motor spring  142  exerts a rotational force, i.e., torque, on the drive axle  24  and the winding drum  140  in a direction that winds the raising cord  25  around the winding drum  140 . Preferably, the motor spring  142  is a constant force spring that provides a constant amount of force or torque throughout the range of extension of the spring. As each winding drum assembly is mounted on the same drive axle  24 , additional winding drum assemblies may be incorporated in a simple and convenient manner for a wider window covering that requires greater lifting force. 
     The raising cord  25  is secured at a first end  150  to a post  152  formed on the winding drum  140 . When the bottom rail is raised, the raising cord  25  is wound around the winding drum  140 , which is rotated by the torque from the motor spring  142 . When the bottom rail  16  reaches a desired height and the pulling force thereon is removed, a counterbalancing force to the torque from the motor spring  142  enables the bottom rail and plurality of slats to remain in position. This counterbalancing force can include internal friction, and the weight load exerted by the bottom rail and slats stacked thereon on the raising cord  25 . 
     Reference now is made to  FIGS. 7 through 10  to describe an operation of the Venetian blind  10 . Shown in  FIG. 7  is the Venetian blind  10  of  FIG. 1  in a fully raised position. In this configuration, the plurality of slats  70  are stacked on top of each other and rest on the top portion  17  of bottom rail  16  in a substantially horizontal position. The top slat  72  abuts the second bottom edge  19  of head rail  12 . In this configuration, coil spring  50  is in its tightened state wherein coil spring  50  tightly holds onto the inner drum  40 . Additionally, raising cord  25  is also wound up around winding assembly  29 . 
       FIG. 8  shows Venetian blind  10  of  FIG. 1  in a lowered first closed position. In this position the plurality of slats  70  are in a substantially vertical position wherein bottom portion  74  of the individual slats  72  faces forward. When it is desired to lower the Venetian blind  10 , the bottom rail  16  is grasped and lowered from the fully raised position as shown in  FIG. 7  toward the position in  FIG. 8 , i.e. the bottom rail  16  is pulled away from head rail  12 . As the bottom rail  16  is pulled away from the head rail  12 , the raising cord  25  is unwound from the winding assembly  29 , which causes rotation of the winding drum  140  and the drive axle  24  (e.g., in a counterclockwise direction). Rotation of the drive axle  24  causes rotation of the inner drum  40 . The rotation of the inner drum, in this configuration is transmitted via the coil spring  50  to the tilting member  60 . As a result, one of the ladder cord sections  22   b  is pulled upward while the other ladder cord section  22   a  is moved downward which causes the plurality of slats  70  to tilt in a first direction until each individual slat  72  reaches a first maximum inclination, which may be stopped when fourth edge portion  79  of the top slat  72  abuts the first bottom edge  11  of head rail  12  and/or third edge portion  78  of each individual slat  72  abuts against an adjacent lower slat  72 . In one embodiment, the bottom edge  11  of the head rail  12  can thus be engageable with the top slat to act as a stop arrangement to restrict vertical movement of the ladder cord sections  22   a  and  22   b  and to stop tilting movement at a maximum inclination of the plurality of slats  70 . This maximum inclination may correspond to a closed position of the Venetian blind  10  where no or a minimal amount of light is allowed to pass through the plurality of slats  70 . When tilting of the plurality of slats  70  is stopped at the first maximum inclination, rotation of the tilting member  60  is blocked, and further rotation of the drive axle  24 , which is imparted directly to the inner drum  40 , causes the coil spring  52  to rotate slightly such that one of the prongs  52  of coil spring  50  presses against a sidewall of the radial slot  62  of the rotationally blocked tilting member  60 . As a result, the coil spring  50  expands to an expanded state whereby the inner drum  40  is allowed to rotate as the drive axle  24  continues to rotate, whereas the tilting member  60 , coil spring  50  and ladder cord sections  22   a  and  22   b  remain rotationally stationary relative to the drive axle. Because the end portions of ladder cord sections  22   a  and  22   b  are secured to the outside of the tilting member  60 , no frictional movement occurs between the ladder cord sections  22   a  and  22   b  and the tilting member  60 , thereby preventing wear damage to the ladder cord sections  22   a  and  22   b . The configuration of the components also allows the drive axle  24  to continue to rotate, thereby allowing the raising cord  25  to be unwound from winding drum assembly  29  and allowing the plurality of slats  70  to be deployed. As a result of the construction of Venetian blind  10 , the plurality of slats  70  tilt in one direction and travel downward during this stage of operation. 
     Shown in  FIG. 9  is Venetian blind  10  adjusted to an open and lowered position. In this position, the plurality of slats  70  is in a substantially horizontal position. To reconfigure window blind  10  from the lowered closed position as shown in  FIG. 8  to the lowered open position in  FIG. 9 , bottom rail  16  is slightly lifted towards head rail  12 . As this occurs, drive axle  24  rotates clockwise, and prong  52  of the coil spring  50  previously pressed against the corresponding sidewall of the radial slot  62  is no longer urged against thereto. As a result, the coil spring  50  recovers its tightened state on the inner drum  40 , such that clockwise rotation of the drive axle  24  again causes the rotational force on the inner drum  40  to be transmitted via the coil spring  50  to the tilting member  60 . Accordingly, rotation of the tilting member  60  pulls upward one of the ladder cord sections  22   a  and extends downward the other ladder cord section  22   b . This action causes the plurality of slats  70  to tilt in a second direction. When the desired amount of tilt is achieved, upward lifting of the bottom rail  16  can be discontinued, and the slats come to rest as shown in  FIG. 9 . 
       FIG. 10  illustrates an operation for raising the Venetian blind  10  of  FIGS. 7-9 . When the bottom rail  16  is raised, the drive axle  24  and winding drum assembly  29  are driven in (e.g., clockwise) rotation by action of the motor spring  142 , which winds the raising cord  25  around the winding drum assembly  29 . The clockwise rotation of the drive axle  24  is imparted to the inner drum  40  and transmitted via the coil spring  50  to the tilting member  60 . As a result, the ladder cord sections  22   a  and  22   b  raise and lower, respectively, and cause the plurality of slats  70  to rotate or tilt in a second direction opposite to the first direction until a second maximum inclination of the plurality of slats  70  is reached. The second maximum inclination of the plurality of slats can occur when the slats  72  contact with one another or the third portion edge  78  of the top slat  72  abuts against the first bottom edge  11  of head rail  12 . Once the second maximum inclination of the plurality of slats  70  is reached, rotation of the tilting member  60  is blocked. As the bottom rail  16  continues to rise, which causes continued rotation of the drive axle  24 , another one of the prongs  52  of the coil spring  50  presses against a corresponding sidewall of the radial slot  62  of the rotationally blocked tilting member  60 . As this occurs, the coil spring  50  again expands, thereby allowing rotation of the inner drum  40  with the drive axle  24  relative to the tilting member  60  and the coil spring  50 , which will remain substantially rotationally stationary as the drive axle  24  and inner drum  40  continue to rotate. As the drive axle  24  continues to rotate, the raising cord  25  is wound around the winding drum assembly  29  so that the plurality of blinds slats  70  may be progressively raised and stacked on the bottom rail  16 . With this construction of Venetian blind  10 , the plurality of slats  70  can thus tilt in one direction and slide upward at the same time. 
     Certain variations in the above are to be understood as being within the scope of the present invention. For example, the directions of rotation of components within the header rail described above may be reversed. Also, the above description of  FIGS. 7-10  specifically refer to actuator mechanism  20 , however, the description is equally applicable to actuator mechanism  21  as actuator mechanisms  20  and  21  are identical and operate simultaneously because they are both connected to drive axle  24 . As will be appreciated, coil spring  50  functions as a clutch arrangement between the drive axle  54  and the tilting member  60 , responsive to a stop arrangement which in this embodiment is the bottom wall of the head rail body, engaging the top slat to stop tilting movement of the slats, causing the coil spring to loosen, discontinuing the tilting force applied to the ladder cord sections. 
     Although the clutching arrangement used to transmit torque between the inner drum  40  and tilting member  60  is preferably embodied as the coil spring  50 , the clutching arrangement may comprise other types of known mechanisms wherein the inner drum and the tilting member rotate together and, with sufficient force, is allowed to rotate relative to the tilting member. 
     For example, the clutching arrangement may be a sleeve that is rotationally secured with tilting member, and thereby frictionally engaged with the inner drum. Upon application of sufficient torque from the drive axle, the static coefficient of friction between the inner portion of the sleeve and the outer surface of the inner drum may be overcome, thereby allowing for relative rotational movement between the tilting member and inner drum. When the torque is discontinued, the static friction again causes the tilting member and inner drum to rotate in conjunction with each other. 
     As yet another alternative, referring to  FIGS. 24-26 , the outer surface portion  320  of inner drum  302  may fit snugly within an inner portion  306  of the tilting member  304  such that the inner drum  302  is frictionally engaged with the tilting member  304 . In such a configuration, no separate intermediate member between the inner drum  302  and the tilting member  304  is necessary. Rather, the static friction between the inner drum  302  and the tilting member  304  are sufficient to enable the inner drum  302  and the tilting member  304  to rotate together. When the static friction is overcome by sufficient force from the drive axle  24  the inner drum  302  may be rotated independent of the tilting member  304 . 
     Another embodiment of the present invention is shown in  FIGS. 11-14A . Actuator mechanism  80  includes a winding drum  100 , shaft sleeve  109 , coil spring  110  having out-turned ends or prongs  112 , tilting control mechanism  90 , ladder cord sections  84  and raising cord  86 . Actuator mechanism  80  is mounted in the head rail  81  with the drive axle  82 . Actuator mechanism  80  may replace the actuator mechanism described previously in reference to  FIGS. 1-10 . As such, actuator mechanism  80  is used to raise, lower and tilt a plurality of blind slats. 
     Shown in  FIG. 12  is a portion of actuator mechanism  80  wherein the parts are unassembled. In this embodiment, winding drum  100  includes a substantially hollow cylindrical body  104  having a cord-winding barrel  108 , and a shaft sleeve  109  extending at one side of the cord-winding barrel  108  and having a diameter smaller than the cord-winding barrel  108 . The shaft sleeve  109  has a substantially cylindrical shape and is adapted to mount around the drive axle  82 . An inner surface of the cord-winding barrel  108  also includes a radial slot  106  adapted to engage with the prongs  112  of the coil spring  110 . 
     In this embodiment, the tilting control mechanism  90  includes a pulley  98 , and a sleeve portion  94  adjoined at one side of the pulley  98 . Pulley  98  includes radial ribs  92  for increased gripping of each ladder cord section  84  by the tilting control mechanism  90 , which facilitates displacement of the ladder cord sections  84  for tilting the slats. 
     In conjunction with  FIGS. 11 and 12 ,  FIG. 13  is an enlarged view of the tilting control mechanism  90  assembled with the winding drum  100   FIG. 14  is a perspective view of the actuator mechanism  80 , and  FIG. 14A  is a cross-sectional view of the actuator mechanism  80  shown in  FIG. 14  (for clarity, the drive axle and cord elements are not shown in  FIG. 14A ). As shown, the coil spring  110  is tightly mounted around the sleeve portion  94  of the tilting control mechanism  90 . The shaft sleeve  109  of the winding drum  100  is then mounted through the sleeve portion  94  of the tilting control mechanism  90  provided with the coil spring  110 , and the prongs  112  of the coil spring  110  are engaged with the slot  106 . As with the previous embodiment, the coil spring  110  has two states. In its tightened state, the coil spring  50  tightly fits around the sleeve portion  94 , so that the winding drum  100 , coil spring  110  and tilting member  90  can rotate together. In its expanded state, the coil spring  110  expands so that the coil spring  110  loosens its grip on the tilting control mechanism  90 . When the coil spring  110  is in the expanded state, as the winding drum  100  is rotated by the drive axle  82 , the tilting control mechanism  90  and coil spring  110  remain rotationally stationary relative to the drive axle  82 . In this manner, the coil spring  110  acts as a clutch arrangement for coupling and uncoupling rotational movements of the winding drum  100  and tilting control mechanism  90 . 
     Each ladder cord section  84  is engaged with one side of the plurality of blind slats (e.g., one ladder cord section at the front side, and another one at the rear side), and has an upper portion secured about pulley  98 . The end portions of the two ladder cord sections  84  are secured together by clip  85  at a location between the ribs  92  of the pulley  98 . As shown in  FIGS. 14 and 14A , the actuator mechanism  80  can be mounted in a casing  88  having a first compartment  88 A, a second compartment  88 B, and a third compartment  88 C between the first and second compartment  88 A and  88 B. The first compartment  88 A of the casing  88  can house a motor spring  130  used for sustaining the bottom rail  16  in equilibrium at a desired height. In one embodiment, the motor spring  130  includes a constant force spiral spring having a first end secured with the drive axle  82  via an adapter sleeve  132 , and a second end secured with the casing  88 . The second compartment  88 B houses the winding drum  100  coupled with the raising cord  86 . In turn, the third compartment  88 C houses the tilting member  90  coupled with the ladder cord sections  84 , at a position between the cord-winding barrel  108  and the motor spring  130 . The drive axle  82  is assembled through the interior of the casing  88 , and passes respectively through the winding drum  100 , the tilting member  90 , and the motor spring  130 . With this construction, the actuator mechanism  80  can be assembled in a compact and modular manner, which can be easily mounted with the drive axle  82 . 
     The actuator mechanism  80  may replace the actuator mechanism  20  previously in connection with  FIGS. 1-10  for operating the Venetian blind. During operation, the motor spring  130  exerts a force on the drive axle  82 , which is converted into an upward force via the winding drum  100  and raising cord  86  for sustaining the weight of the bottom rail  16  and any slats  72  stacked thereon. 
     When a user wants to tilt the plurality of slats  70  in a first direction, he or she pulls down slightly on the bottom rail  16  within a limited range of displacement. The raising cord  86  is then pulled downward causing rotation of the winding drum  100 , which causes the coil spring  110  in its tightened state and the winding drum  100  to rotate. As a result, the tilting member  90  moves the two ladder cord sections  84  in opposite directions to tilt the plurality of slats  70  in the first direction. The plurality of slats  70  continue to rotate and tilt in the first direction as the bottom rail  16  moves downward. Once the plurality of slats  70  reach the desired inclination, the user releases the bottom rail  16 . The sum of all the forces applied on the raising cord  86  (including the lifting force generated by the motor spring  130 , the weight of the bottom rail  16  and slats stacked thereon, and internal friction force) acts to keep the bottom rail  16  and plurality of slats  70  in equilibrium at the desired inclination. 
     If the user wants to tilt the plurality of slats  70  in a second direction opposite to the first direction, he or she applies an upward force on the bottom rail  16 , which causes rotation of the drive axle  82  and winding drum  100  driven by the motor spring  130 . This motion of the winding drum  100  is imparted to the tilting member  90  via the coil spring  110  being in a tightening state. As a result, the tilting member  90  moves the two ladder cord sections  84  in opposite directions to tilt the plurality of slats  70  in the second direction. The plurality of slats  70  continuously tilts in the second direction as the bottom rail  16  rises. Once the plurality of slats  70  reach the desired inclination, the user can release the bottom rail  16 . 
     When a user wants to lower the Venetian blind and deploy the plurality of slats  70  (as shown in  FIG. 8 ), the bottom rail  16  is grasped and lowered away from the head rail  12 . As the bottom rail  16  is pulled away from head rail  12 , the raising cord  86  is pulled downward, which causes rotation of the winding drum  100  and drive axle  82  (e.g., in a counterclockwise direction). Rotation of the winding drum  100  is transmitted to the tilting member  90  via the coil spring  110  such that one of the ladder cord sections  84  is pulled upward while the other ladder cord section  84  is extended downward, which causes the plurality of slats  70  to tilt in the first direction until they reach a first maximum inclination in the first direction. Tilting of the plurality of slats is stopped when fourth edge portion  79  of the top slat  72  abuts the first bottom edge  11  of head rail  12  and/or third edge portion  78  of each individual slat  72  abuts against an adjacent lower slat  72  ( FIG. 1 ). When the plurality of slats  70  are stopped at the first maximum inclination, further rotation of the tilting member  60  is blocked, and further rotation of the winding drum  100  causes one of the prongs  112  of the coil spring  110  to press against one sidewall of the radial slot  106  and cause the coil spring  110  to move to an expanded state. As a result, the coil spring  110  and winding drum  100  are permitted to rotate as the bottom rail  16  is lowered and the raising cord  86  unwinds, whereas the tilting member  90  and the ladder cord sections  84  held thereon are kept stationary at the first maximum inclination of the slats  70 . 
     When a user wants to raise the Venetian blind and retract the plurality of slats  70  (as shown in  FIG. 10 ), a slight upward force (e.g., less than the weight load on the raising cord  86 ) can be applied on the bottom rail  16 . As a result, the motor spring  130  acts to rotate the drive axle  82  and winding drum  100  (e.g., in a clockwise direction) to wind the raising cord  86  and raise the bottom rail  16 . Rotation of the winding drum  100  is imparted to the tilting member  90  via the coil spring  110 . As a result, the ladder cord sections  84  causes the plurality of slats  70  to tilt in the second direction opposite the first direction until they reach a second maximum inclination, which may be stopped when the third edge portion  78  of the top slat  72  abuts the first bottom edge  11  of the head rail  12  and/or fourth edge portion  79  of each individual slat  72  abuts against an adjacent lower slat  72  ( FIG. 1 ). When the plurality of slats  70  are stopped at the second maximum inclination, rotation of the tilting member  60  is blocked, and further rotation of the winding drum  100  causes one of the prongs  112  of the coil spring  110  to press against one sidewall of the radial slot  106  and force the coil spring  110  to loosen its grip on the blocked tilting member  60 . As a result, the coil spring  110  and winding drum  100  continue to rotate as the bottom rail  16  rises and the raising cord  86  winds around the winding drum  100  driven by the motor spring  130 , whereas the tilting member  90  and the ladder cord sections  84  held thereon are kept stationary at the second maximum inclination of the slats  70 . The bottom rail  16  can be thereby raised until it reaches a desired height. 
     Because the ladder cord sections  84  move along with the tilting member  90 , no frictional movement occurs between the ladder cord sections  84  and the tilting member  90 . When the bottom rail  16  is lowered to deploy the plurality of slats  70 , the stationary position of the tilting member  90  and ladder cord sections  84  can eliminate conventional wear damage to the ladder cord sections  84 . 
     Turning now to  FIGS. 16-19 , an alternative actuator mechanism  200  is shown. Actuator mechanism  200  includes a tilt control mechanism embodied as tilt winding pulley  204  made of molded plastic or other suitable material. Tilt winding pulley  204  has a central opening through which drive shaft  24  is passed for rotationally coupling the winding pulley  204  with the drive shaft  24 . As shown in  FIG. 18 , tilt winding pulley  204  includes a tilting cylinder or central hub  207  (see  FIG. 18 ) and sidewalls  206  that define an internal V-shaped recess  210 , that narrows toward the center of the tilt winding pulley  204 . Referring to  FIG. 16 , the upper end of ladder cord sections  22  is formed in a closed loop, and is inserted within recess  210  so as to contact the surfaces of tilt winding pulley  204  that define recess  210 . When the bottom rail is moved upward or downward for tilting the slats, the drive axle  54  can accordingly rotate to drive rotation of the tilt winding pulley  204 . Because the loop of ladder cord sections  22  is tightly fitted within the recess  210 , rotation of the tilt winding pulley  204  also causes displacement of the ladder cord sections  22  for tilting the slats. When the slats reach the maximum inclination and the drive axle  54  continues to rotate, the ladder cord sections  22  cannot move further and start to slip relative to the tilt winding pulley  204  rotating in unison with the drive axle  54 . 
       FIGS. 20-23  show another alternative tilt control mechanism  220 , which includes a tilting member embodied as tilt winding pulley  224  made of molded plastic or other suitable material. Tilt winding pulley  224  is substantially identical to tilt winding pulley  204  in construction and function, except for the addition of radially directed drive ribs  234  that extend from the central hub  235  to provide enhanced engagement with the ladder cord sections. 
     Tilt winding pulley  224  has a central opening through which drive shaft  24  is passed. As shown in  FIG. 22 , tilt winding pulley  224  includes side walls  206  that define an internal V-shaped recess  230  that narrows toward the center of the pulley  224 . Referring to  FIG. 20 , the upper ends of ladder cord sections  22  are joined to form a closed loop, and are tightly fitted within recess  230  so as to contact the inner surfaces of tilt winding pulley  204  that define recess  230 . When the bottom rail is displaced upward or downward for tilting the slats, the drive axle  54  can accordingly rotate to drive rotation of the tilt winding pulley  224 . Because the loop of ladder cord sections  22  is tightly fitted within the recess  230 , rotation of the tilt winding pulley  224  also causes displacement of the ladder cord sections  22  for tilting the slats. When the slats reach the maximum inclination and the drive axle  54  continues to rotate, the ladder cord sections  22  cannot move further and start to slip relative to the tilt winding pulley  224  rotating in unison with the drive axle  54 . With this construction, a separate clutch arrangement is not required, but is instead integrated into the tilt control mechanism. 
     The stop arrangement for limiting vertical movement of the ladder cord sections has been described as an engagement between and edge of a topmost slat with the head rail, or contact between adjacent slats tilted to their maximum inclination. However, the stop assembly may also take other forms. For example, another alternative stop arrangement is the inclusion of protrusions or other detent arrangements on the tilting drum that will engage a fixed catch structure within the head rail. 
     In addition to the clutching arrangements described above, other clutching arrangements may be suitable. For example, the winding drum and the tilt control mechanism may be engaged to one another by way of static friction, such as being positioned in an abutting coaxial arrangement. When sufficient force is exerted on the winding drum and rotation of the tilt control mechanism is stopped by the stop arrangement, the static friction could be overcome and the winding drum allowed to rotate independent of the tilt control mechanism. An adjustable spring can be incorporated to adjust or otherwise vary the amount of static friction between the winding drum and the tilt control mechanism. Yet another possible clutching arrangement would be similar to the embodiment shown in  FIGS. 16-19 , wherein the winding drum and the tilt control mechanism are an integral unit having a winding portion connected to the raising cord and a tilting portion connected to the ladder cord. 
     The foregoing descriptions and the accompanying drawings are illustrative of the present invention. Still other variations and arrangements of parts are possible without departing from the spirit and scope of this invention.