A blind which is provided with adjustable feedback energy to roll up a curtain autonomously is disclosed. The blind uses primarily a worm-gear pressure regulation device which can be adjusted manually, is assembled at a side of the blind and is exposed outward. The pressure regulation device acts indirectly onto a volute spring of a rolling system to determine a degree of winding of the curtain by the feedback energy. In addition, using introduction of feedback interference, a working speed at the maximum feedback energy can be damped effectively and a speed of rolling back the curtain can be moderated.

BACKGROUND OF THE INVENTION 
       [0001]    a) Field of the Invention 
         [0002]    The present invention relates to a blind with adjustable feedback energy, and more particular to a blind which allows a user to easily adjust and increase feedback energy at an exterior part of the blind, when the blind is elastically fatigued as it has been used for a long time. The blind is provided with a damping device to moderate a feedback speed in the beginning of rolling back a curtain and to facilitate adjusting the curtain to align to a middle position. 
         [0003]    b) Description of the Prior Art 
         [0004]    Referring to  FIG. 1  and  FIG. 2 , the working principle and the fundamental mechanism of the feedback operation of a blind are disclosed. For a blind  1  which stores energy to roll back a curtain  10 , a working axis S of a rolling system  2  is combined coaxially with an energy feedback device  3 . The energy feedback device  3  is provided with a volute spring  300  which results in a torque when the volute spring  300  changes radially. When a user is to pull down the curtain  10 , the force of the curtain  10  will drive the volute spring  300  through a reel  20  to store energy and when the user is to roll back the curtain  10 , the feedback energy will be outputted reversely from the volute spring  300  to roll up the curtain  10  immediately. 
         [0005]    The blind  1  is provided with a hanging beam  12 , two sides of which are provided with brackets  11 . The reel  20  is supported coaxially and indirectly by the brackets  11  using positioning holes  110  which are located on the brackets  11 , along a same axis of the reel  20 . Therefore, the reel  20  is able to rotate on the working axis S to roll up and down the curtain  10 . 
         [0006]    Referring to  FIG. 2 , it shows the working principle of the energy feedback device  3 . The energy feedback device  3  includes a positioning pivot  30 , an end of which is combined with a stopping pier  32  and the other end of which passes through a through-hole  310  provided by a movable round pier  31 . The positioning pivot  30  moves relatively to the through-hole  310 , whereas the movable round pier  31  and the stopping pier  32  are fixed respectively by two ends of the volute spring  300 . After passing through an angular restrictor  4 , the positioning pivot  30  is fixed at the positioning hole  110  at the left bracket  11 . The positioning pivot  30  can be positioned radially by the positioning hole  110  directly or by sheathing with an axial pier  21 . The axial pier  21  is a sheath unit which can deform elastically along an axial direction and an interior of the axial pier  21  provides for axial sliding of a relative end of the positioning pivot  30 . After the axial pier  21  has been pressed in by an external force, a vertical position of the corresponding bracket  11  is changed, which facilitates the rolling system  2  and the curtain  10  to escape entirely from the bracket  11  or to be combined with the bracket  11 . 
         [0007]    An outer circumference of the movable round pier  31  provides for fixing and combining with an inner circumference of the reel  20 . An outer surface of the reel  20  provides for combining with an upper end of the curtain  10  to roll the curtain  10 . An outer circumference of the stopping pier  32  is movably assembled with an inner circumference of a relative end of the reel  20  through a sliding ring  320 ; whereas, a cylindrical positioning disc  210 , which is assembled at the positioning hole  110 , is used to support a center between the reel  20  and the right bracket  11 . The positioning hole  110  can support an axis of the reel  20  and is overlapped with the working axis S. When the curtain  10  is brought downward, a component of force is produced to act onto the reel  20  and drive the reel  20  to rotate radially. When the reel  20  rotates, the movable round pier  31  is linked simultaneously to act onto a left side of the volute spring  300 ; whereas, a right side of the volute spring  300  is fixed by the stopping pier  32 . On the other hand, the stopping pier  32  is fixed and combined with the positioning pivot  30  and a radial angle at a left end of the positioning pivot  30  is restricted as the left end is fixed by the left bracket  11 . Accordingly, under a condition that the stopping pier  32  is fixed and the movable round pier  31  is driven to move, the volute spring  300  is twisted that an elastic force of the volute spring  300  is changed to store elastic energy. 
         [0008]    When a lower end  101  of the curtain  10  is pulled down to a certain height, it is stopped by the angular restrictor, allowing the lower end  101  of the curtain  10  to be positioned at any height. 
         [0009]    The angular restrictor operates the reel  20  so that the orientation of the reel  20  can be restricted transiently and the reel  20  is restricted from rotating again, when the lower rim of the curtain  10  is at any height. This restriction device uses a ratchet (not shown in the drawings) or any design that can be used to lock a rotation unit to lock a ratchet wheel, and can be operated to be unlocked when the device is locked. 
       SUMMARY OF THE INVENTION 
       [0010]    The primary object of the present invention is to provide a blind, wherein the feedback energy of the rolling system to the curtain can be increased by easily adjusting a pressure regulation device which manually adjusts a function of a worm gear set. The pressure regulation device is combined at a side of the bracket that is exposed out of the blind and is coaxially linked with the volute spring of the rolling system to respond to energy, thereby further interfering with a degree of winding of the curtain. 
         [0011]    In the present invention, an axial worm is used to act onto an end of the reel for stopping and an outer end of a positioning pivot, which is coaxially combined with the reel, is slidingly provided at the pressure regulation device along an axial direction, allowing the reel to displace transversally to be used to roll up a blind with a lift cord, especially a blind with a slat. 
         [0012]    To enable a further understanding of the said objectives and the technological methods of the invention herein, the brief description of the drawings below is followed by the detailed description of the preferred embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  shows a front view of a conventional blind. 
           [0014]      FIG. 2  shows an internal structural view of a conventional blind with feedback energy. 
           [0015]      FIG. 3  shows a three-dimensional view of a left end of a blind of the present invention. 
           [0016]      FIG. 4  shows a schematic view of an appearance of a pressure regulation device which is combined at an outer end of the blind of the present invention. 
           [0017]      FIG. 5  shows a cutaway view of the blind of the present invention after combining with the pressure regulation device. 
           [0018]      FIG. 6  shows a three-dimensional structural view of an angular restrictor of the present invention. 
           [0019]      FIG. 7  shows a structural view of the present invention which is provided with an adjustment knob for external adjustment by rotation. 
           [0020]      FIG. 8  shows a schematic view of the present invention which utilizes a slat and a worm to achieve a function of the pressure regulation device. 
           [0021]      FIG. 9  shows a structural view of the present invention which is added with a centrifugal damper. 
           [0022]      FIG. 10  shows a side view of a main unit of  FIG. 9 . 
           [0023]      FIG. 11  shows a schematic view of the present invention wherein the centrifugal damper is provided with an auxiliary magnetic damping device. 
           [0024]      FIG. 12  shows a relation diagram of the magnetic damping device with respect to magnetic elements, according to the present invention. 
           [0025]      FIG. 13  shows a relation diagram of the magnetic damping device with respect to elastic elements, according to the present invention. 
           [0026]      FIG. 14  shows a structural view of the present invention which is provided with an expansion damper. 
           [0027]      FIG. 15  shows an exploded view of the present invention which is provided with a positioning pivot, slidingly located at the pressure regulation device along an axial direction. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    Referring to  FIG. 3 , the present invention discloses a blind  1  with feedback energy that can be increased manually, wherein a bracket  11  is provided with a through-hole  111  allowing an axial pier  21  to pass through and rotate freely. 
         [0029]    Referring to  FIG. 4  and  FIG. 5 , the blind  1  that rolls up and down a curtain  10  is provided with a hanging beam  12 , two sides of which are provided respectively with the bracket  11 . An outer end of one bracket  11  is provided with a pressure regulation device  5 , an interior of the pressure regulation device  5  is provided with a link disc  50 , and a center of the link disc  50  is provided with a latch hole  51 . The latch hole  51  links with a positioning pivot  30  which penetrates from a reel  20  and a radial angle of the link disc  50  can be changed by adjusting an external force. The link disc  50  links synchronously with mechanisms inside the reel  20  to result in a change of feedback energy. 
         [0030]    The left bracket  11  (as shown in  FIG. 5 ) is combined outward with the pressure regulation device  5  and the latch hole  51  in the center of the pressure regulation device  5  provides for combining with a relative end of the positioning pivot  30  and restricts a radial angle to the entire positioning pivot  30 . A mechanical rigidity of the positioning pivot  30  is larger than the feedback energy and a right end thereof is combined with a stopping pier  32  which provides for combining with an end of a volute spring  300 ; whereas, the other end of the volute spring  300  is combined with a movable round pier  31 . A center of the movable round pier  31  is provided with a through-hole  310 , allowing the positioning pivot  30  to pass through. The positioning pivot  30  moves relatively to the through-hole  310  and an outer circumference of the stopping pier  32  is movably assembled with an inner circumference of the reel  20  through a sliding ring  320 . Therefore, axes of the stopping pier  32  and the reel  20  are overlapped with the working axis. In addition, an inner circumference at a right end of the reel  20  can be supported by a positioning disc  210  which is assembled at the through-hole  111  of the right bracket  11  through the axial pier  21 . An outer circumference of the movable round pier  31  provides for combining with the inner circumference at the relative end of the reel  20 , and an outer surface of the reel  20  provides for combining with an upper end of the curtain  10  to roll up and down the curtain  10 . 
         [0031]    A left end of the movable round pier  31  is assembled with an angular restrictor  4  as shown in  FIG. 6 . The angular restrictor  4  includes a rotary disc  41  which is assembled with a port of the movable round pier  31 . An interior of the rotary disc  41  drives a stator  42  of a centrifugal swing block  43  and the rotary disc  41  is assembled with the positioning pivot  30 . Besides, a radial angle of the rotary disc  41  is restricted. 
         [0032]    Regarding to the operation of the angular restrictor  4  (a height stopping device), the positioning pivot  30  moves relatively to the through-hole  310  and an outward end of the movable round pier  31  is connected with a rotary disc  41  of the angular restrictor  4 ; the rotary disc  41  provides for locking and fixing a relative end of the movable round pier  31  through a locking hole  47  and the rotary disc  41  and the movable round pier  31  can be seen as a same unit. A centrifugal swing block  43  swings by gravity and is pivoted at a shaft hole  46  on the rotary disc  41  by a shaft pin  44 . A tail end of the centrifugal swing block  43  is provided with a centripetal tooth  430 . After passing through the through-hole  310 , the positioning pivot  30  is combined with a stator  42  and an outer circumference of the stator  42  is radially provided with a tooth slot  420 . In addition, an outer end of the stator  42  is closed by an end sealing piece  45 . Therefore, the positioning pivot  30  and the angular restrictor  4  are combined longitudinally and the most tail end of the positioning pivot  30  can be sheathed by the axial pier  21 . 
         [0033]    As the stator  42  is combined with the positioning pivot  30 , the stator  42  is also stopped radially; whereas, the rotation of the movable round pier  31  drives the centrifugal swing block  43  to change angularly and when the movable round pier  31  rotates at a high speed, the centrifugal swing block  43  will swing outward by the centrifugal force, allowing the tooth  430  not to be engaged with the tooth slot  420 , which enables the movable round pier  31  to rotate freely. However, when the movable round pier  31  is stationary, under the action of gravity, the tooth  430  of the centrifugal swing block  43  will be engaged downward with the tooth slot  420  of the stator  42 . Thus, a radial angle of the movable round pier  31  will be stopped by the indirect engagement of the centrifugal swing block  42 , and this effect allows the curtain  10  to be stopped at any height 
         [0034]    When the volute spring  300  is elastically fatigued, the user can adjust the pressure regulation device  5  to drive the stopping pier  32  to rotate, which links the volute spring  300  to rotate toward a direction of pressurization, thereby increasing elastic energy of the volute spring  300 . The adjustment at this time is that the movable round pier  31  must be stopped and that stopping force can be exerted onto the reel  20  by a way that a lower end  101  of the curtain  10  can be fixed temporarily and thus the movable round pier  31  can be stopped. Under a condition that the movable round pier  31  is stopped indirectly and after the positioning pivot  30  has rotated, the right end of the positioning pivot  30  will drive the stopping pier  32  which drives synchronously the volute spring  300 , resulting in a change of radial angle at that end. Therefore, a body part of the volute spring  300  will form a change of elastic pressure, such as the increase of pressure. 
         [0035]    On the other hand, when the feedback energy of the volute spring  300  is too large, one can also adjust the pressure regulation device  5  to release the interior elastic pressure, thereby decreasing the feedback energy. 
         [0036]    In the present invention, the feedback energy adjustment method especially facilitates adjustment of an elastic torque when the volute spring  300  is elastically fatigued after being used for a long time and helps determination of the feedback energy of the volute spring  300  before leaving a factory without using a pre-determined value to avoid excessiveness or insufficiency; if the feedback energy is excessive, then the lower end  101  of the curtain  10  will hit machine parts at a lower part of the blind  1  when rolling back the curtain  10 , whereas if the feedback energy is insufficient, then the lower end  101  cannot be rolled back completely to a highest point. 
         [0037]    Using the pressure regulation device  5  of the present invention, there is no need to exercise setting a default torque to the volute spring  300  before leaving a factory. In addition, to the blind  1  to be installed, as different requirements of feedback energy will be available for different masses, the pressure regulation device  5  can be used to adjust proper feedback energy for the requirement of the feedback force corresponding to a specific mass; for example, if the feedback energy is adjusted that the curtain is rolled back to a highest point, then the feedback energy is reset to zero or to a small value, allowing the lower end  101  not to explicitly hit the lower part of the blind  1  and to be positioned correctly. Or, if the feedback energy is not adjusted excessively when leaving a factory, then the pressure regulation device  5  can reduce the feedback energy of the volute spring  300 . Therefore, for the blind  1  which is provided with autonomous feedback energy to roll back the curtain, the adjustment of the feedback energy by the pressure regulation device  5  will help simplifying a work procedure before leaving a factory or adjusting the feedback energy according to a practical requirement or increasing the feedback energy when the energy feedback device  3  is elastically fatigued. 
         [0038]    Referring to  FIG. 7  and  FIG. 8 , the pressure regulation device  5  of the present invention is assembled at an outer side of the bracket  11  to facilitate adjustment by the user. The through-hole  111  that is provided axially at the bracket  11  allows the positioning pivot  30  (or the axial pier  21 ) to pass through, wherein the axial pier  21  is sheathed with the positioning pivot  30  or can pass through the positioning pivot  30  directly to avoid sheathing with the axial pier  21 . An interior side of the bracket  11 , on the other hand, provides for coaxial assembly with a rolling system  2 . The reel  20  of the rolling system  2  is assembled with the angular restrictor  4  and the axial pier  21  which passes through the bracket  11  is latched in the latch hole  51  at the center of the link disc  50 . The pressure regulation device  5  is provided with a box unit  52  which is fixed and assembled with the bracket  11 . The link disc  50  will result in a change of radial angle through adjustment with an adjustment knob  500 . In a mean time, the link disc  50  will drive the axial pier  21  by the latch hole  51 , allowing the axial pier  21  to result in a change of angle. The axial pier  21  drives synchronously the positioning pivot  30  to rotate, thereby adjusting the feedback energy as described above. 
         [0039]    Referring to  FIG. 8  again, the pressure regulation device  5  is a worm gear set which utilizes a higher sliding rate to facilitate adjusting the feedback of a high torque. 
         [0040]    The worm-gear pressure regulation device  5  includes a box unit  52 , and an axial position is provided with a link disc  50 . An outer circumference of the link disc  50  forms a worm gear  532  which provides for gnawing with a worm  531  moving inside the box unit  52 . The worm  531  is supported by a seat  533 , allowing the worm  531  to keep gnawing with the worm gear  532 . The worm  531  is extended outward with an adjustment knob  500  for operation by the user. 
         [0041]    After adjustment with the pressure regulation device  5  (as shown in  FIG. 5 ), energy of an energy feedback device  3  can be increased and when the curtain  10  is pulled down to a lowest end, the feedback energy stored in the energy feedback device  3  is largest. In the beginning of rolling back the curtain  10 , the maximum power that is outputted by the energy feedback device  3  will roll up the curtain  10  rapidly and then slow down gradually. However, the momentum in the beginning will affect safety of operation elements and the user. 
         [0042]    The abovementioned issue is more explicit especially after the adjustment and pressurization through the pressure regulation device  5 , wherein in the beginning of roll-back operation, the kinetic energy is very large, causing the curtain  10  to ascend rapidly. To solve this issue, the present invention provides an interference means to slow down the roll-back speed, which is described below. 
         [0043]    Referring to  FIG. 9 , a space is yielded from an inner circumference at a right end of the reel  20  to be assembled with a shaft-type centrifugal damper  8 . The centrifugal damper  8  is provided with a bracket  11  which is fixed at a side through an axial pier  21 , with that a center line thereof is overlapped with the working axis S. An open end at a left side of a fixed barrel  80  is coaxially provided with a sheath barrel  81 , an outer circumference of which is fixed at and assembled with the inner circumference of the reel  20  to form a same unit. The sheath barrel  81  links rightward with a set of boosting device  82  along the same axis. The boosting device  82  then drives a set of friction device  83  to result in a damping effect. 
         [0044]    A right end of the sheath barrel  81  links with a first planetary disc  810  of the boosting device  82  and the first planetary disc  810  drives a first planetary gear  812 . A center of the first planetary gear  812  gnaws concentrically with a first sun gear  811  and an outer circumference of the first planetary gear  812  cuts at an inner gear ring  800  on an inner circumference of the fixed barrel  80 . As the inner gear ring  800  is fixed, a rotation speed of the first sun gear  811  is enlarged by 4 times. Moreover, the first sun gear  811  drives rightward a second planetary disc  820  which drives rightward a second planetary gear  822 . An outer circumference of the second planetary gear  822  also gnaws at the fixed inner gear ring  800  and a center of the second planetary gear  822  gnaws concentrically with a second sun gear  821 . If this second-stage rotation speed is also enlarged by 4 times, then by multiplying by 4 of the first-stage speed, the ratio of the rotation speed of the sheath barrel  81  to that of the second sun gear  821  will be 1:16, which largely increases the terminal speed. This high terminal speed is to meet the requirement of the boost of the centrifugal force. 
         [0045]    The high rotation energy acquired by the second sun gear  821  drives a rotation disc  830  which links coaxially at a right end. A periphery of the rotation disc  830  is radially divided by an equal angle with centrifugal swing blocks  831 ,  832  at an equal radius, of a same shape and a same mass. An outer surface of the centrifugal swing block  831  ( 832 ) corresponds to a friction surface  801  which is provided on the inner circumference of the fixed barrel  80 . The friction surface  801  is an inner annular surface with a friction effect and is also an elastic surface. 
         [0046]    Using the abovementioned structures (as shown in  FIG. 9  and  FIG. 10 ), the centrifugal damper  8  includes a fixed barrel  80  which is fixed by a bracket  11 . When the reel  20  is driven at a high speed in the beginning of rolling back the curtain, as described above, a rotation system, which links synchronously with the centrifugal damper  8 , will first drive the sheath barrel  81 . After the sheath barrel  81  has driven the boosting device  82 , by increasing the speed with the boosting device  82 , the rotation disc  830 , which links with the friction device  83 , will rotate at a high speed. The rotation disc  830  will then drive the centrifugal swing blocks  831 ,  832  to result in centrifugal swing. The centrifugal swing blocks  831 ,  832  are blocks and have masses, with that one end of the centrifugal swing block  831  is bridged at a radius of the rotation disc  830  by a pivot P and the other end is a free end and has a mass. A centrifugal force, which is related to the mass and the rotation speed, is resulted at the free end. The centrifugal force acts on the friction surface  801  of the fixed barrel  80  through the outer surfaces of the centrifugal swing blocks  831 ,  832  and the resulted friction force will reversely interfere with and consume the rotation energy of the reel  20 . Therefore, in the beginning of rolling back the curtain, the maximum energy of the reel  20  can be damped. 
         [0047]    Moreover, the size of the centrifugal force of the centrifugal swing block  831  ( 832 ) is proportional to the rotation speed of the reel  20 ; the higher the rotation speed of the reel  20  is, the larger the centrifugal force will be. Therefore, the friction force is also increased simultaneously. The abovementioned phenomenon is properly used in the damping of the reel  20  under high kinetic energy in the beginning of rolling back the curtain, in order to moderate the initial speed of roll back. On the other hand, before the curtain is rolled back to approach to the upper end, the feedback energy is almost depleted. At that time the rotation speed of the reel  20  is slow and the slight friction force is insufficient to reversely interfere with the rotation of the reel  20  again, enabling the reel  20  and the centrifugal damper  8  to correspond equally with each other, in accordance with the requirement of feedback energy. Hence, the centrifugal damper  8  is very well suitable for the blind which is provided with the feedback energy to roll back the curtain. 
         [0048]    To intensify the damping capability of the friction device  83 , two intensifying devices are implemented to the friction device  83 . Referring to  FIG. 11 , an outer circumference of the fixed barrel  80 , relative to the friction device  83 , is provided with a magnetic damping device  84 . The magnetic damping device  84  is assembled with the fixed barrel  80  through a provided connector  840  and is used to position locations of elements. The magnetic damping device  84  provides for assistance of the damping capability to the friction device  83 . 
         [0049]    Regarding to the abovementioned assisting system, the present invention proposes two concepts: magnetic or elastic interference. First of all, referring to  FIG. 12 , it discloses the magnetic interference system. A swing end of the centrifugal swing block  831  ( 832 ) is assembled with a movable magnetic unit  841 , and a circumference of the connector  840  of the magnetic damping device  84  is radially provided with corresponding fixed magnetic units  842  at an equal angle. The fixed magnetic units  842  are fixed indirectly by the fixed barrel  80 . The movable magnetic unit  841  is separated from the fixed magnetic unit  842  by a close distance at which magnetic lines of force can interact and magnetic poles of the two magnetic units are arranged to attract each other. 
         [0050]    The centrifugal swing block  831  ( 832 ) is driven to result in a centrifugal force, forming a friction force between the centrifugal swing block and the friction surface  801  of the fixed barrel  80  to serve as a first action force for reversely interfering with the reel  20 . In addition, a magnetic attractive force between the movable magnetic unit  841  and the fixed magnetic unit  842 , when the movable magnetic unit  841  rotates to meet with the fixed magnetic unit  842 , is used as a second action force for reversely interfering with the reel  20 . The second action force is added to the first action force, summing up with larger reverse interference energy to the reel  20 , which can be applied to the blind with high feedback energy. 
         [0051]    There is at least one fixed magnetic unit  842  that is provided at an equal angle to increase the magnetic attraction function. 
         [0052]    Referring to  FIG. 13 , another means of damping is to use elastic slashing to deplete kinetic energy of the source. 
         [0053]    In this method, the friction surface  801  of the fixed barrel  80  is provided with an elastic damping device  85  which is kept toward the working axis S. The elastic damping device  85  is provided with a friction block  851  and an end surface of the friction block  851  is deep into a radius of the friction surface  801 . After the centrifugal swing blocks  831 ,  832  have been driven, in addition to that the friction damping with the internal surface of the friction surface  801  is used as the first reverse interference action force, a slash action occurs when an outer friction surfaces of the centrifugal swing block  831  ( 832 ) cuts at the end surface of the friction block  851  that is deep into the friction surface  801 . The slash energy results from the rotation energy of the rotary disc  830  and thus becomes the second reverse interference action force. The second reverse interference action force is added to the first action force, summing up with the rotation energy to reversely interfere with the reel  20 , thereby moderating the initial power for rolling back the curtain. 
         [0054]    The abovementioned friction block  851  is radially distributed at an equal angle and is positioned on a relative location of the fixed barrel  80  by the connector  850 . The friction block  851  can penetrate into a through-hole which is opened at a corresponding position on the fixed barrel  80  and the end surface of the friction block  851  can enter deeply into the radius of the friction surface  801 , with that the depth allows the outer surface of the centrifugal swing block  831  ( 832 ) to slash and cut through. Besides, the friction block  851  can be fixed on the corresponding position of the fixed barrel  80  through an elastic element  852  which is connected with the connector  850  indirectly. 
         [0055]    The abovementioned damping method is an explicit dynamic centrifugal damping method. The present invention further provides a more static damping system, as shown in  FIG. 14  (in association with  FIG. 5 ). 
         [0056]    An interior of a Venetian blind  1  of the present invention is provided with an energy feedback device  3 . As the feedback energy can be increased and there is potentially large stored energy, the initial feedback energy will be larger. In addition, as the mass of the curtain is constant, when the user pulls down the curtain to the bottommost end, an interior of the energy feedback device  3  will be accumulated with great stored energy. At the initial moment when the user opens the curtain  10 , the power outputted by the feedback energy will be largest, allowing the curtain  10  to ascend rapidly. The last lower end  101  will also be driven toward and to hit the lower part of the hanging beam  12  at a high speed. Therefore, interference has to be exercised for higher feedback energy, so as to reduce the power at that time. However, the stored energy of the feedback device is largest when the curtain  10  is pulled down to the bottommost end, thus at the initial moment when the curtain  10  is opened, the working energy is the largest. In order to moderate the initial feedback power, the present invention further provides an expansion damper  9  which is used in a design to moderate the feedback energy when the energy is largest. 
         [0057]    In the present embodiment, an interior of another end of the reel  20  is provided with a shaft-type expansion damper  9 . The expansion damper  9  is provide with a fixed end and a working end, the fixed end is assembled at the bracket  11  on the corresponding side through a fixed barrel  93  and a root part of the fixed barrel  93  is provided with an annular shoulder unit  931 . An interior of the fixed barrel  93  is provided with a longitudinal slide rail  930 , allowing a corresponding end of a passive screw  91  to slide longitudinally. The other end of the passive screw  91  is a thread  910  which is cut at by a female thread  920  on an inner circumference of a link barrel  92 . The link barrel  92  is provided with an inner annular positioning slot  921  at a location corresponding to the abovementioned annular shoulder unit  931 . The inner annular positioning slot  921  moves relatively to the annular shoulder unit  931  and the link barrel  92  links with the reel  20  to from the working end. 
         [0058]    Accordingly, when the reel  20  rotates, it drives synchronously the link barrel  92  to rotate and the female thread  920  of the link barrel  92  will cut at the thread  910  of the passive screw  91 . In addition, another end of the passive screw  91  is radially restricted by the slide rail  930  and therefore, the passive screw  91  will not rotate. However, as the thread  910  is acted by the female thread  920  of the link barrel  92 , and thus, the passive screw  91  will displace leftward and rightward along an axial direction by being cut at obliquely. 
         [0059]    In the abovementioned process of left and right displacement, a bevel function of a cone unit  911  having a push edge is utilized to affect an elastic and frictional expansion ring  94  to result in a change of outer diameter. The change of outer diameter will friction onto a relative surface on an inner circumference of the link barrel  92 , forming a damping effect by the friction force and allowing the rotation speed of the link barrel  92  to be restricted. 
         [0060]    Using the introduction of the expansion damper  9 , the rotation speed of the reel  20  will be affected. The timing of that affection is when the stored energy of the energy feedback device  3  is largest, where the expansion damper  9  can produce the largest interference of rotation damping to the reel  20 . On the contrary, when the stored energy of the energy feedback device  3  has been released and weakening, the expansion damper  9  will gradually lose the expansion pressure to the expansion ring  94  due to the retreat of the cone unit  911 . Therefore, the interference of the outer circumference of the expansion ring  94  to the inner circumference of the reel  20  will be diminished gradually and by that the friction interference between these two elements is an alternate and progressive relation, the rolling speed of the curtain  10  can be more uniform during the process of rolling up. 
         [0061]    Referring to  FIG. 15 , the latch hole  51  in the center inside the pressure regulation device  5  provides for latching with the positioning pivot  30  of the rolling system  2 . In addition, the latch hole  51  can further provide for slidingly emplacing the relative end of the positioning pivot  30  along the axial direction. 
         [0062]    The pressure regulation device  5  is assembled at the outer surface of the bracket  11  through the provided box unit  52  and achieves similarly the adjustment to the angle of the positioning pivot  30  as described above. The right end of the positioning pivot  30  is also assembled with the stopping pier  32  and the outer circumference of the stopping pier  32  is connected indirectly with a sliding ring  320  which is movably assembled on the inner circumference of the reel  20 . On the other hand, the left end of the positioning pivot  30  is assembled with the stator  42  of the angular restrictor  4  and forms a longitudinal combination with the angular restrictor  4 , as shown in  FIG. 6 . An end of the provided rotary disc  41  is assembled with a corresponding end of the movable round pier  31  and an outer circumference of the movable round pier  31  provides for assembling with the reel  20 . 
         [0063]    The positioning pivot  30  can be slidingly provided at the latch hole  51  along the longitudinal direction. However, under a condition that the positioning pivot  30  is radially restricted by the latch hole  51 , the positioning pivot  30  can only move left and right that it is restricted radially. The restriction also enables the volute spring  300  to store and adjust the feedback energy as described above. 
         [0064]    In this design, the reel  20  rotates radially and can result in an axial displacement by any external force. This displacement allows the left and right edge of the curtain  10  to align to two side edges of a window, i.e., the curtain  10  can be adjusted to be at a center location vertically, which facilitates aligning the curtain  10  to the center. 
         [0065]    On the other hand, this axial movement also applies to the curtain  10  with a lift cord  102 . The curtain  10  can be the curtain  10  with a slat, a honeycomb blind, a pleated blind or a Roman blind, which is the curtain  10  that requires the lift cord  102 , wherein the lift cord  102  is wrapped around a coil  103  on the outer surface of the reel  20  and can be wound orderly. 
         [0066]    The axial displacement provided by the present invention is that the right end of the reel  20  is assembled with an end sealing piece  72 . A center of the end sealing piece  72  is provided with an inner thread  720  which is cut at by an axial screw  7  fixed on the right bracket  11  by a root part  71 . The distance of thread of the axial screw  7  is roughly the same as the cross section of the lift cord  102 , and therefore, when the reel  20  turns by one round, the axial screw  7  can provide a feed distance which is roughly the same as the cross section of the lift cord  102  to push the reel  20  to displace axially. Under a condition that the displacement is the same as the cross section of the lift cord  102 , the coil  103  after the lift cord  102  has been wrapped around will be next to each other without overlapping. 
         [0067]    In the abovementioned design, considering the requirement of detachment of the angular restrictor  4 , an axial location of movement of the reel  20  is correspondingly provided with a pre-stopper  200 . Using a reserved stroke of the pre-stopper  200 , when the curtain  10  is pulled down to the bottommost end when used normally, the added reserved stroke of the pre-stopper  200  can be utilized to further pull down the curtain  10 , thereby providing the unlocking stroke required by the angular restrictor  4 . 
         [0068]    The locking and release actions of the angular restrictor  4  have been disclosed as in  FIG. 6  and  FIG. 5 , wherein the unlocking action of the angular restrictor  4  is conducted by the stroke of further pulling down the curtain  10 . 
         [0069]    During the normal usage, the curtain  10  that has been pulled down completely can shade light from a window completely. In the normal usage, the user is accustomed to pull down the curtain  10  completely. However, before rolling back, the unlocking is required. If the curtain  10  has been already pulled down to the bottommost, then it cannot be pulled down further to acquire the unlocking stroke, that is, the curtain  10  cannot be rolled back. In the prior art, to enlarge the pull-down stroke of the curtain  10 , the curtain  10  will be over a lower rim of the window frame significantly to prevent the user from pulling down the curtain  10  to the lowest point. Yet, as the stroke is reserved significantly, the cost of material will be very high. 
         [0070]    To save the material and to solve the issue of lower dead spot, the present invention utilizes a segmentation method to reserve the unlocking stroke, allowing the user to add a unlocking stroke when the curtain  10  is accidentally pulled down to the lowest end. 
         [0071]    Regarding to the abovementioned method of adding the stroke, a pre-stopper  200  is provided. The pre-stopper  200  is fixed at the bracket  11  at a side and is provided with an elastic element  203  which is an elastic deformation unit and is fixed inside the bracket  11  by a support disc  201 . The support disc  201  is provided with an annular opening  202 , allowing the elastic element  203  to be sheathed. An axial deformation value of the elastic element  203  is an amount of increase of the axial displacement of the reel  20  required by the unlocking stroke and meets the rotation angle of unlocking required by the angular restrictor  4 . Therefore, under a normal condition, when the user is to open the curtain  10  completely to feel that the light is shaded completely, he or she will accustomedly pull down the curtain  10  completely. During the process of pulling down the elastic element  203 , the reel  20  will move right axially and the right end will first press on a relative end surface of the elastic element  203 , resulting in a touch message which can be sensed by a hand. Therefore, the user will feel that the curtain  10  has been pulled down completely and this is defined as the pre-sensing stop point in the present design. Under this condition, when the user is to roll up the curtain  10 , he or she can pull down the curtain  10  again to enter into the unlocking stroke and reversely operate the angular restrictor  4  to conduct the unlocking action. For this addition of the unlocking stroke, the force exerted should be intensified to resist the deformation force of the elastic element  203 , mainly the push force of the end surface of the reel  20  to the end surface of the elastic element  203 . After fulfilling the force to be exerted, the angular restrictor  4  will result in a relative change of radial angle and is unlocked. This addition of the unlocking stroke can widen the distance between the right end surface of the reel  20  and the relative inner surface of the bracket  11 . The abovementioned requirement can be also satisfied when the curtain  10  has been pulled down completely to the bottommost end, and the right end surface of the reel  20  or the axial stroke has not yet been interfered. 
         [0072]    It is of course to be understood that the embodiments described herein is merely illustrative of the principles of the invention and that a wide variety of modifications thereto may be effected by persons skilled in the art without departing from the spirit and scope of the invention as set forth in the following claims.