Abstract:
There is provided a spring assisted electric motor driven lifting mechanism for lifting and lowering a blind which permits the quick and easy matching of the spring assist pre-rotation to the torque output of the electric motor. The device includes an elongated cylinder coupled to the blind such that rotating the cylinder about its axis lifts and lowers the blind. Coupled to the elongated cylinder is an electric motor which is configured to rotate the elongated cylinder about its axis. A torsion spring is coupled to the cylinder for biasing the elongated cylinder to at least partially neutralize the weight of the blind. The torsion spring is in turn coupled to a spring preload adjuster which is configured to adjust the tension on the torsion spring by moving an adjustment member. The spring preload adjuster is further configured such that the adjustment member extends perpendicularly away from the axis of the elongated cylinder.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates generally to adjustable spring assist mechanisms which are used in window coverings and awnings to partially neutralize the weight of the blind or awning. 
       BACKGROUND OF THE INVENTION 
       [0002]    Motorized blinds incorporate an electric motor to raise and lower the blind. These motorized blinds usually incorporate an elongated roller tube upon which either the blind (in the case of a roller blind) or the support chords (in the case of a roman, pleated, cellular or other blind) are wound. The electric motor is placed within the roller tube and, upon activation, causes the roller tube to rotate about its axis, either lifting or lowering the blind. The electric motor must be sufficiently large to apply sufficient torque to the roller tube to overcome the weight of the blind when the blind is fully lowered (in the case of a roller blind) or when the blind is fully raised (in the case of a roman, pleated or cellular blind). For a standard sized blind typically used for residential applications, a relatively small electric motor is sufficient. In the case of a large blind which is several meters in length, then a much larger electric motor is required since the blind would be correspondingly much heavier. Larger electric motors have several drawbacks. Firstly, they are generally larger and therefore require larger roller tubes. Also, they tend to be more expensive, and most significantly, they require more electric energy to operate. Since large electric motors require more electric energy to operate, they tend to require higher voltage wiring, usually 110 v or 220 v. This means that installing these larger electric blinds generally requires a licensed electrician. 
         [0003]    Spring assisted roller blinds have been in operation for many years. These roller blinds use an elongated torsion spring to partially or completely neutralize the weight of the blind, making the blinds easier to open and close. The tension of the torsion spring in the spring assist is preset so that the spring assist neutralizes the weight of the blind. The tension of the torsion spring is preset by pre-rotating the spring assist through several revolutions before the blind is fully assembled and installed. Combining an electric motor with a spring assist is not practical because it is very difficult to match the required pre-rotation of the spring assist when the spring assist is coupled to both the roller tube and the electric motor. If not enough pre-rotation is applied to the spring assist, then the electric motor will either not be able to operate the blind or the motor will draw too much current and potentially burn out. However, if too much pre-rotation is applied to the spring assist, then the electric motor will not be able to fully lower a raised roller blind, or in the case of roman, pleated or cellular blinds, the electric motor will not be able to fully raise the blind. As a result, correctly matching the pre-rotation of the spring assist to the electric motor is vital. Unfortunately, the only way to correctly preset the pre-rotation of the spring assist to match with the electric motor would be to repeatedly preset the spring assist pre-rotation, then assemble and mount the blind, then test the pre-rotation of the spring assist, then take down the blind again, disassemble it and reset the pre-rotation of the spring assist. This operation would have to be repeated over and over again until the correct pre-rotation for the spring assist is found. Furthermore, over time the tension of the torsion spring in the spring assist would change, requiring removal, disassembly and then further adjustment followed by further testing, removal and adjustment. As a result, spring assisted electrically driven blinds have not been available in the market. An improved spring assist mechanism in combination with an electric motor which makes it possible to accurately, precisely and quickly match the pre-rotation of the spring assist to the electric motor is therefore desired. 
       SUMMARY OF THE INVENTION 
       [0004]    In accordance with one aspect of the present invention, there is provided a spring assisted lifting mechanism for lifting and lowering a blind which permits the quick and easy matching of the spring assist pre-rotation to the drive mechanism for lifting and lowering the blind. The device includes an elongated cylinder coupled to the blind such that rotating the cylinder about its axis lifts and lowers the blind. Coupled to the elongated cylinder is a cylinder drive which is configured to rotate the elongated cylinder about its axis. A torsion spring is coupled to the cylinder for biasing the elongated cylinder to at least partially neutralize the weight of the blind. The torsion spring is in turn coupled to a spring preload adjuster which is configured to adjust the tension on the torsion spring by moving an adjustment member. The spring preload adjuster is further configured such that the adjustment member extends perpendicularly away from the axis of the elongated cylinder. 
         [0005]    With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the preferred typical embodiment of the principles of the present invention. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a long sectional view of a roller blind incorporating a motorized and spring assisted blind lifting device made in accordance with the present invention. 
           [0007]      FIG. 2  is a blown up portion of  FIG. 1  showing the spring assist portion of the present invention. 
           [0008]      FIG. 3  is a cross sectional view of the spring preload adjustment portion of the present invention. 
           [0009]      FIG. 4  is a front view of a portion of a roller blind incorporating a motorized and spring assisted blind lifting device made in accordance with the present invention and showing details of the tension adjustment portion of the present invention. 
           [0010]      FIG. 5  is a long sectional view of a roller blind incorporating a hand operated blind lifting drive and spring assist made in accordance with the present invention. 
           [0011]      FIG. 6  is an exploded view of the slip clutch portion of the roller blind shown in  FIG. 1 . 
           [0012]      FIG. 7  is a perspective view of a preload rotation counter for use with the spring assist mechanism made in accordance with the present invention. 
           [0013]      FIG. 8  is a top view of the preload rotation counter shown in  FIG. 7 . 
           [0014]      FIG. 9  is a side view of the preload rotation counter shown in  FIG. 8 . 
           [0015]      FIG. 10  is a front view, partly in cross section, of the preload rotation counter shown in  FIG. 8  being used in combination with spring preload adjustment portion of the present invention. 
       
    
    
       [0016]    In the drawings like characters of reference indicate corresponding parts in the different figures. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Referring firstly to  FIG. 1 , a blind incorporating an adjustable spring assisted blind lifting device made in accordance with the present invention is shown generally as item  10  and includes blind  12  having lower end  14  and upper end  16 . Upper end  16  is attached to drive mechanism  11  which includes elongated cylinder  18  having opposite ends  20  and  22  and axis  23 . Elongated cylinder  18  is preferably an elongated tube of the type generally used to construct roller blinds (often called roller tubes). Attached to end  20  of elongated cylinder (roller tube)  18  is spring assist mechanism  24  which consists of an elongated torsion spring  25  having opposite ends  26  and  28 . Spring assist mechanism  24  is configured to apply a biasing torque to elongated cylinder (roller tube)  18  to at least partially neutralize the weight of blind  12 . End  26  of torsion spring  26  is attached to coupling  30  which is in turn rotatably coupled to yoke  32  which is coupled to end  20  of roller tube  18 . Opposite end  28  of torsion spring  25  is attached to coupling  34  which is attached to roller tube  18 . Couplings  30  and  34  are dimensioned and configured such that torsion spring  25  is coaxially aligned with axis  23  or roller tube  18 . As roller tube  18  is rotated about axis  23 , blind  12  is lowered or lifted (depending on the direction of rotation) and torsion spring  25  is loaded or unloaded, respectively. Torsion spring  25  acts to partially neutralize the weight of blind  12 . As blind  12  is lowered, roller tube  18  rotates and torsion spring  25  is loaded. Ideally, tension spring  25  is preloaded (i.e. pre-tensioned) sufficiently such that the torsion spring counteracts the torsion applied by blind  12  when the blind is fully lowered. Torsion spring  25  is coupled to spring preload adjuster  36  via end  38  of coupling  30 . Spring preload adjuster  36  has an adjustment member  40  which when moved (i.e. rotated) changes the tension in tension spring  25  by rotating the tension spring about axis  23 . Hence, torsion spring  25  can be pre-tensioned by simply rotating adjustment member (worm gear)  40 . Spring preload adjuster  36  is attached to bracket member  42  which is in turn fixed to a wall or window frame (not shown). 
         [0018]    Drive mechanism  41  is coupled to the opposite end  22  of roller tube  18  via yoke  43 . Drive mechanism  41  may comprise any type of electrically operated or hand operated drive configured to raise or lower blind  12  by rotating roller tube  18 . Drive mechanism  41  is configured to apply a drive torque to roller tube  18  which, when combined with the biasing torque generated by spring assist  24 , is sufficient to raise and lower blind  12 . In the embodiment of the present invention shown in  FIG. 1 , drive mechanism  41  consists of an electric motor  44  having an end  46  which passes through yoke  43  and which is coupled to coupling  48 . Yoke  43  is mounted to roller tube  18  and is rotatably mounted to electric motor  44  to permit the roller tube to rotate relative to the electric motor. Coupling  48  is rigidly coupled to bracket  50  which is in turn fixed to a wall or window frame (not shown). Electric motor  44  has shaft  66  which is coupled to slip clutch  54 , which is in turn coupled to roller tube  18 . Electric motor  44  is coaxially aligned with roller tube  18  and activation of electric motor  44  causes shaft  66  to rotate which in turn causes roller tube  18  to rotate about axis  23 . When electric motor  44  is de-activated, shaft  66  does not rotate, thereby keeping roller tube  18  from rotating. As explained further below, slip clutch  54  permits roller tube  18  to rotate relative to shaft  66  when sufficient downward force is applied to blind  12 . 
         [0019]    Referring now to  FIG. 2 , spring preload adjuster  36  consists of a housing  37  which contains a circular gear  56  which is coupled to and coaxially aligned with end  38  of coupling  30 . Rotation of circular gear  56  causes a corresponding rotation in torsion spring  25 , which in turn either increases or decreases the tension on the spring depending on which direction the circular gear is rotated. Adjustment member  40  is preferably a worm gear which is rotatably mounted within housing  37  and oriented perpendicularly to circular gear  56  and axis  23 . Circular gear  56  has a peripheral edge  58  with teeth which are configured to intermesh with worm gear (adjustment member)  40  such that rotation of the worm gear causes a corresponding rotation in circular gear  56 . As best seen in  FIG. 3  adjustment member  40  consists of an elongated shaft having worm gear portion  62  which is configured to intermesh with teeth  60  of circular gear  58 . Adjustment member  40  has axis  66  which is perpendicular to axis  23 . End  70  of adjustment member  40  is positioned immediately adjacent opening  68  in housing  37 . End  70  is also configured such that it can be engaged by screw driver  72  (or by an allen key or similar tool). Opening  68  is dimensioned sufficiently to permit the end of screw drive  72  to engage end  70  of adjustment member  40  in order to allow the user (not shown) to rotate adjustment member sufficiently to rotate circular gear  56  and in turn adjust the tension of the torsion spring of the spring assist (see item  25  of  FIG. 2 ). 
         [0020]    Referring now to  FIG. 4 , orienting adjustment member  40  such that it extends perpendicular to axis  23  of roller tube  18  makes the drive mechanism of the present invention practical. By orienting adjustment member  40  perpendicular to axis  23 , the spring assist mechanism  24  can be pre-tensioned after blind  10  has been installed to wall  5 . It will be appreciated that if adjustment member  40  was coaxial to axis  23 , it would be impossible to adjust the pre-tension of the spring assist while the blind was mounted to wall  5  since the adjustment member would not be accessible. The present arrangement makes it possible to mount blind  10  to wall  5  (or immediately adjacent wall  5 ) and then adjust spring assist  24  to neutralize the weight of blind  12 . Since the blind is already mounted, precisely adjusting the spring assist to completely neutralize the weight of blind  12  is much easier. This removes the guess work associated with pre-tensioning the spring assist and speeds up the installation of the blind. 
         [0021]    Referring now to  FIG. 5 , the adjustable spring assist mechanism of the present invention can be coupled for use with a hand operated drive mechanism for lifting and lowering the blind. Roller blind  100  is virtually identical to the previously discussed roller blind and includes a roller tube  18  coupled to the spring assist mechanism  24  as discussed in the previous example. Blind  12  is coupled to roller tube  18 . Drive mechanism  110  consists of a roller clutch  114  which is coupled to roller tube  18  and to chain  112 . Pulling on chain  112  causes roller clutch  114  to apply a torque to roller tube  18  which, with the assistance of the torque applied by spring assist  24 , causes roller tube  18  to rotate in response and blind  12  to either lift or lower depending on how the chain is pulled. Roller clutch  114  is a standard roller clutch as commonly available in the market. Spring preload adjuster  36  is coupled to spring assist  24  as in the previous roller blind example. Roller clutch  114  may incorporate a slip clutch (not shown) there in to permit a user (not shown) to lower blind  12  by simply pulling on the blind with a force greater than the torque applied by spring assist  24 . 
         [0022]    Referring now to  FIG. 6 , slip clutch  54  consists of a hub member  62 , slip spring  64  mounted onto hub member  62 , and coupling  60 . Hub member  62  is configured to fit onto shaft  66  which extends from electric motor  44  so that the hub and shaft move together. Slip spring  64  has ends  68  and  70  which are spaced apart sufficiently such that protrusion  72  of coupling  60  fits between ends  68  and  70  when coupling  60  is coaxially mounted over hub  62 . Slip spring  64  is configured such that when hub  62  is rotated relative to coupling  60 , one of ends  68  and  70  of the slip spring are engaged by ends  76  and  74  of protrusion  72 , respectively, causing slip spring  64  to constrict more tightly onto hub  62 . Slip spring  64  and hub  62  are further configured such that when coupling  60  is rotated relative to hub  62  with a torsion force (slip torque) exceeding a predetermined level, slip spring  64  will rotate along with coupling  60  relative to hub  62  without damaging hub  62 . As mentioned above with reference to  FIG. 1 , electric motor  44  is configured to apply a motor torque to roller tube  18  and spring assist  24  is configured to apply a biasing torque to roller tube  18  sufficient to rotate the roller tube and lift blind  12 . Slip spring  64  and hub  62  are configured such that the predetermined level of the slip torque exceeds the combined motor and biasing torques to permit the user, not shown, to lower blind  12  simply by pulling down on the blind. 
         [0023]    Referring back to  FIG. 2 , it will be appreciated that accurately adjusting the biasing torque applied by the spring assist mechanism  36  is important to ensure that the spring assist mechanism neutralizes the weight of the blind  12 . As mentioned above, in order to ensure that the spring assist mechanism  36  neutralizes the weight of blind  12 , the spring assist mechanism must be preloaded by pre-rotating the elongated torsion (biasing) spring  25  through one or more rotations via several rotations of worm gear  40 . However, accurately pre-rotating the biasing spring may involve guess work, particularly if there is a large ration between worm gear  40  and circular gear  56 . Hence, if the user wished to rotate elongated biasing spring  25  by 4 rotations, and if the ratio between circular gear  56  and worm gear  40  was 9:1, then the user would have to rotate the screw by 36 rotations. Rotating worm gear  40  36 times is trivial if an electric screwdriver or drill is used; however, keeping track of the number of rotations through which worm gear  40  is rotated may be quite difficult. Therefore, precisely adjusting the pre-rotation of elongated biasing spring  25  to a specific number of pre-rotations may be difficult. 
         [0024]    Referring now to  FIGS. 7 ,  8  and  9 , a preload rotation counter, shown generally as item  200 , may be used to help precisely adjust the tension (i.e. pre-rotation) of elongated torsion spring  25  (see  FIG. 1 ). Preload rotation counter  200  consists of an elongated shaft  210  rotatably mounted to housing  212  and having opposite ends  214  and  216 . Elongated shaft  210  has threaded portion  220  with nut  222  threaded thereon. Housing  212  has protruding end  218  and face  215  with elongated slot  217  and indicia  226  formed thereon. But  222  is coupled to indicator  224  which projects through slot  217 . Nut  222  is configured such that as shaft  210  is rotated, nut  222  moves along threaded portion  220  and indicator  224  moves along face  215 . 
         [0025]    Referring now to  FIG. 10 , end  214  of shaft  210  is configured to couple to an electric screw driver or drill  230  and end  216  is configured to couple to worm gear  40  of spring preload adjuster  36 . Drill  230 , when activated, will cause the rapid rotation of shaft  210  of preload rotation counter  200 , which in turn will cause the rapid rotation of worm gear  40  and a corresponding slower rotation of circular gear  56 . As mentioned above, rotation of circular gear  56  causes a corresponding rotation in the elongated torsion spring  25  (see  FIG. 2 ) and therefore preloads the elongated torsion spring with tension. Also, as shaft  210  is rotated, indicator  224  moves. The treading of threaded portion  220  and the spacing of indicia  226  are configured such as shaft  210  is rotated through sufficient turns to cause circular gear to  56  to rotate through one full rotation, indicator  224  moves one full indicator number. Hence, the number of rotations of circular gear  56  is indicated by the indicia on preload rotation counter  200 . This provides a convenient and efficient means for accurately preloading the elongated torsion spring  25  (see  FIG. 2 ) by a set number of pre-rotations. Hence, if 5 pre-rotations are required, the user need only apply the drill to rotate shaft  210  until the indicia  226  reads 5. This takes the guess work out of pre-loading the spring biasing mechanism and decreases the likelihood that the spring biasing mechanism will be either pre-loaded too much or not pre-loaded enough to neutralize the weight of the blind. This also permits the rapid installation of several blinds. The first installed blind will require some level of testing before the correct pre-rotation is found to fully neutralize the weight of the blind. Once the exact number of pre-rotations is found, however, the remaining blinds (assuming they are of the same size and type) can simply be pre-rotated to the exact level as the first installed blind. Minor variations to the pre-rotation can then be done by hand. 
         [0026]    A specific embodiment of the present invention has been disclosed; however, several variations of the disclosed embodiment could be envisioned as within the scope of this invention. It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.