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TECHNICAL FIELD OF THE INVENTION 
     The present invention generally relates to a hinged slide rail structure for cabinets, and more particularly to a hinged slide rail structure that comprises a buffering device arranged between a hinge and a rail to reduce the noise induced in closing a cabinet door and protect a user from being clamped and hurt by a closing door. 
     DESCRIPTION OF THE PRIOR ART 
     Offices, laboratories, or various work sites are often provided with cabinets or lockers for storage and organization of articles. The cabinets are often provided with a door, which can turn upward or sideways, or slide sideways, for covering and closing a storage space inside the cabinet in order to realize protection and storage of the article. 
     A regular cabinet that is mounted to a wall uses a hinge connecting between the cabinet door panel and the cabinet body to allow the door panel to turn upward for opening. However, the door panel may be caused to swing downward due to gravity acting thereon, leading to undesired inconvenience of use. To overcome such a problem, a hinged slide rail is available in the market. As shown in  FIG. 1  of the attached drawings, a hinged slide rail  10  comprises a rail  11  that has a movable plate  111  to which a hinge  12  is mounted. The rail  11  is mounted to an inside surface of a door panel  21 . The hinge  12  has a movable blade  121  that is mounted to an access opening of the cabinet body  20  so as to connect the hinge  12  between the door panel  21  and the cabinet body  20 . With the hinge  12 , the door panel  21  may turn upward with respect to the cabinet body  20 . After the door panel  21  is lifted upward, the door panel  21  can slide on a surface of the cabinet body  20  in order to horizontally position on the cabinet body  20 , preventing the door panel  20  from falling and thus causing inconvenience of use. However, the operation of the hinged slide rail  10  is still disadvantageous. When the door panel  21  is pulled out, it is still subjected to the action of the gravity and thus falls down to induce a noise of impact and clamp and hurt the user. 
     To solve the problem, Taiwan Utility Model No. M352378 discloses a slide rail slow descending device, which is shown in  FIG. 2  of the attached drawings. The slide rail slow descending device  30  comprises a hinge  31 , a fixed rail  32 , a telescopic buffering device  33 , a movable rail  34 , and a swinging element  35 . The hinge  31  has an end fixed to a cabinet  40  that has an access opening. The fixed rail  32  has an end fixed to an opposite end of the hinge  31 . The telescopic buffering device  33  has an end fixed to an opposite end of the fixed rail  32  and an opposite end fixed to the hinge  31 . The movable rail  34  is reciprocally and slidably mounted to the fixed rail  32  and is connected to a door panel  41 . The swinging element  35  is rotatably coupled between the hinge  31  and an outer side of the movable rail  34 . The swinging element  35  comprises a friction section (not labeled) to abrade the outside surface of the movable rail  34 . The outside surface of the movable rail  34  that corresponds to the friction section forms a recess (not shown). Through the buffering effect provided by the telescope buffering device  33  and the friction force between the swinging element  35  and the movable rail  34 , the opening of the door panel  41  is made easy and convenient and effect of silencing and slow descending is realized in the closing of the door panel to avoid clamping and thus hurting users. However, the operation smoothness of sliding of the slide rail slow descending device  30  is heavily dependent upon the friction force between the swinging element  35  and the movable rail  34 , and the movement stroke of the telescopic buffering device  33  imposes a great influence on the opening degree of the door panel  41 . In the opening degree is over-limited or over-excessive, then inconvenience may be caused for the use and operation thereof, or even leading to damage of the door panel  41  or the cabinet body  40 . 
     Thus, the present invention aims to provide a hinged slide rail with buffering function, which is provided with a movement limiting structure to control the opening angle of a door panel to eliminate any possible inconvenience caused in the operation thereof, so as to overcome the above discussed problems. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a hinged slide rail with buffering function for enhancing the convenience of use. 
     Another objective of the present invention is to provide a hinged slide rail with buffering function, which provides an effect of slow descending in closing a door panel so as to protect a user from being clamped and hurt and to eliminate the generation of noise. 
     To achieve the above objectives, the present invention provides a hinged slide rail comprising a rail, a hinge, a retention frame, and a buffering device. The rail comprises a fixed plate, a balled plate, and a movable plate. The balled plate and the movable plate are accommodated in the fixed plate, while the fixed plate is mounted to an inside surface of a door panel. The hinge comprises a movable blade and a fixed blade that are rotatably coupled to each other. The fixed blade is fixed to an end of the movable plate. The movable blade has an end to which a pull bar is mounted. The retention frames mounted to an end of the fixed blade of the hinge and defines therein an accommodation space. The retention frame has an end opposite to the accommodation space and forming two parallel limiting slots. The buffering device is selected among a pneumatic device, a hydraulic device, and a pneumatic/hydraulic device. The buffering device comprises an active rod having an end forming a limiting block that is slidably received in the limiting slots of the retention frame. The limiting block is coupled to the pull bar of the movable blade. 
     To install, the fixed plate of the rail is mounted to an inside surface of the door panel and the movable blade of the hinge is attached to an access opening of a cabinet body. When the door panel is being opened, the door panel is turned upward rotated as being supported by the pivot between the fixed blade and the movable blade of the hinge. The pull bar of the movable blade drives the limiting block to extend the active rod outward, so that the limiting block is caused to slide to an end of the limiting slots of the retention frame, making the door panel parallel to a top surface of the cabinet body. The door panel may then be pushed toward the rear side of the cabinet body so as to realize opening and stowing the door panel in a space above the top of the cabinet body. The operation is convenient and the door panel does not unexpectedly close when an article is being removed out of the cabinet, making it safe in operation and use. To close the door panel, the door panel is first pulled forward and the door panel is acted by a downward force induced by gravity. The buffering device functions to slow down the downward movement of the door panel and to allow the door panel to close gently, so as to eliminate the problem of noise generation and clamping and hurting users. 
     The foregoing objectives and summary provide only a brief introduction to the present invention. To fully appreciate these and other objects of the present invention as well as the invention itself, all of which will become apparent to those skilled in the art, the following detailed description of the invention and the claims should be read in conjunction with the accompanying drawings. Throughout the specification and drawings identical reference numerals refer to identical or similar parts. 
     Many other advantages and features of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view illustrating the installation of a conventional hinged slide rail. 
         FIG. 2  is a schematic view illustrating the installation of a device disclosed in Taiwan Utility Model No. M352378. 
         FIG. 3  is an exploded view of a preferred embodiment of the present invention. 
         FIG. 4  is a perspective view of the preferred embodiment of the present invention in an assembled form. 
         FIG. 5  is a schematic view illustrating the operation of the preferred embodiment in an initial phase of opening a door panel. 
         FIG. 6  is a schematic view illustrating the operation of the preferred embodiment in a subsequent phase of opening a door panel. 
         FIG. 7  is a schematic view illustrating the operation of the preferred embodiment of closing a door panel. 
         FIG. 8  is a perspective view illustrating another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following descriptions are exemplary embodiments only, and are not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention as set forth in the appended claims. 
     Referring to  FIGS. 3 and 4 , which shows exploded and perspective views of the present invention, the present invention comprises the following constituent components: 
     A rail  50  comprises at least a fixed plate  51 , a balled plate  52 , and a movable plate  53 . The balled plate  52  is interposed between the movable plate  53  and the fixed plate  51  to enhance lubrication effect between the movable plate  53  and the fixed plate  51  so as not only to allow the movable plate  53  to do reciprocal sliding movement with respect to the fixed plate  51  but also making the sliding movement smooth. The rail  50  comprises a roller  54  set at one end thereof. 
     A hinge  60  comprises a movable blade  61  and a fixed blade  62  that are rotatably coupled to each other so that the movable blade  61  is reciprocally rotatable with respect to the fixed blade  62 . The fixed blade  62  is fixed to an end of the movable plate  53  of the rail  50 . The movable blade has an opposite end to which a pull bar  611  is rotatably mounted. The movable blade  61  of the hinge forms a plurality of fixing holes  612 . 
     A retention frame  70  has a central portion forming a cylindrical accommodation space  71  of which two sides forming lugs  72  extending therefrom to be substantially parallel to each other. The lugs  72  form at least one fixing hole  721  and one limiting slot  722  and the two limiting slots  722  are substantially parallel to each other. By inserting screws  73  through the fixing holes  721 , the retention frame  70  is fixed to the movable plate  53  of the rail  50 . 
     A buffering device  80  is selected from a group consisting of a pneumatic device, a hydraulic device, and a pneumatic/hydraulic device. In the instant embodiment, the buffering device  80  comprises a pneumatic/hydraulic device. The buffering device  80  is received in the accommodation space  71  of the retention frame  70  and has an end forming an active rod  81 . The active rod  81  has an end forming a limiting block  82  that is slidably received in the limiting slots  722 . The limiting block  82  is coupled to the pull bar  611  of the movable blade  61  to have the active rod  81  of the buffering device  80  set in a normally contracted condition and set the limiting block  82  at an innermost end of the limiting slots  722 . 
     When the movable blade  61  of the hinge  60  is doing reciprocal rotation, the active rod  81  of the buffering device  80  is driven to extend/contract and thus causing the limiting block  82  to reciprocally slide within the limiting slots  722 , so as to control an opening range of the hinge  60 . (In the instant embodiment, the movable blade  61  of the hinge  60  can take a relative rotation of 0-90 degrees with respect to the fixed blade  62 .) 
     Referring to FIGS.  3  and  5 - 7 , the present invention can be installed on a locker or cabinet  90  mounted on a wall. The fixed plate  51  of the rail  50  is mounted to an inside surface of a door panel  92  and the movable blade  61  of the hinge  60  is attached to an access opening of a cabinet body  91 . Thus, when the door panel  92  is opened, the door panel  92  is rotated upward as being supported by the pivot between the fixed blade  62  and the movable blade  61  of the hinge  60 , thereby causing the movable blade  61  to rotate upward. The pull bar  611  of the movable blade  61  drives the limiting block  82  to slide outward and extends the active rod  81  of the buffering device  80  (under the action of air pressure inside the buffering device  80 ), so that the limiting block  82  is caused to slide to an end of the limiting slots  722  of the retention frame  70 , making the door panel  92  parallel to a top surface of the cabinet body  91 . Afterwards, a user may push the door panel rearward, and the movable plate  53  of the rail  60  is caused to slide with respect to the fixed plate, moving the door panel  92  toward the rear side of the cabinet body  91 . In this way, opening and stowing the door panel  92  in a space above the top of the cabinet body  91  is realized. The operation is easy and the door panel  92  does not unexpectedly close when the cabinet is being accessed, making it safe in operation and use and also effort-saving. To close the door panel  92 , the door panel  92  is first pulled forward and the door panel  92  is acted by a downward force induced by gravity to overcome the hydraulic force of the buffering device  80  so as to slowly close. The present invention uses the buffering device  80  to reduce the downward moving speed of the door panel  92  to make the door panel  92  closed in a gentle manner. Thus, no noise and damage to a user may occur. 
     Referring to  FIGS. 5-8 , in another embodiment, to enhance the practicability of the present invention and to provide the convenience of effort-saved operation, a tension spring  55  is arranged between the fixed blade  62  of the hinge  60  and the fixed plate  51  of the rail  50 . The fixed blade  62  comprises a retention peg  621 . One side of the fixed plate  51  forms a retention peg  511 . Opposite ends of the spring  55  are respectively attached to the two retention pegs  621 ,  511 . When the door panel  92  is pushed rearward, the returning spring force of the spring  55  helps reducing the force needed in pushing the door panel  92  rearward. 
     Having been described the present invention above, it is apparent that the present invention offers the following advantages: 
     (1) The present invention arranges a buffering device  80  between the rail  50  and the hinge  60  to buffer the downward movement and force of the door panel  92  in order to eliminate the problems of clamping and hurting people and generation of noise. The buffering device  80  also helps saving effort for opening the door panel  92 . 
     (2) The present invention provides a retention frame  70  that forms limiting slots  722  for limiting the distance range that a limiting block  80  coupled to the hinge  60 , so as to control the opening range of the door panel  92 . 
     (3) The present invention arranges a tension spring  55  between the rail  50  and the hinge  60 , which helps reducing the force needed in pushing the sliding movement of the door panel  92 . 
     It is noted that what described above shows only a preferred embodiment of the present invention and does not intend to limit the scope of the present invention. For example, modification made on the type of the rail  50  or the type of the hinge  60  or the buffering device  80  is considered within the scope of the present invention. Thus, any modification that can be readily achieved by those having ordinary skills, such as replacing the pneumatic/hydraulic device of the buffering device  80  with a regular pneumatic device or a hydraulic device, is considered within the scope of the present invention as defined in the appended claims. 
     While certain novel features of this invention have been shown and described and are pointed out in the annexed claim, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention.

Summary:
A hinged slide rail with buffering function, which includes a rail to which a hinge is mounted. The hinge has a movable blade and a fixed blade between which a buffering device is coupled. The buffering device is housed in a retention frame. The retention frame has an end forming a limiting structure. The buffering device has an active rod coupled to the limiting structure. The movable blade includes a pull bar that is connected to the limiting structure. The hinged slide rail is installed between a door panel and a body of a cabinet to remarkably enhance the convenience of operation and eliminates the potential problems of generating noise and clamping and hurting users.