Abstract:
The present invention provides a ring binder mechanism comprising a housing having a top portion and an open bottom generally opposed to the top portion; hinge plates supported by the housing for pivoting motion relative to the housing; rings for holding loose-leaf pages, each ring including a first ring member and a second ring member, the first ring member being mounted on a first hinge plate and moveable with the pivoting motion of the first hinge plate relative to the second ring member between a closed position and an open position, in the closed position the two ring members forming a substantially continuous, closed loop for allowing loose-leaf pages retained by the rings to be moved along the rings from one ring member to the other, and in the open position the two ring members forming a discontinuous, open loop for adding or removing loose-leaf pages from the rings; and a travel bar disposed between the top portion of the housing and the hinge plates and having a plurality of projections, at least one of the projections having a structure to block the hinge plates from pivoting upward relative to the housing and at least other one of the projections having a structure to allow the hinge plates to pivot upward relative to the housing. The ring binder mechanism according to the present invention may be opened by pulling only a pair of particular ring members and closed by pushing any pair of ring members, thereby reducing the risk of paper&#39;s falling out thanks to unintentional opening of the mechanism.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to a ring binder mechanism for retaining loose-leaf pages, and in particular to an improved mechanism for opening and closing ring members and for locking closed ring members together.  
       BACKGROUND OF THE INVENTION  
       [0002]     Conventionally, a ring binder mechanism typically retains loose-leaf pages, such as hole-punched papers, in a file or notebook. The ring binder mechanism comprises generally a plurality of rings each consisting of two ring members which may be selectively opened to add or remove papers, or closed to retain papers while allowing them to be moved along the ring members. The ring members are attached to two adjacent hinge plates. The two hinge plates are supported loosely within an elongate housing in joined relation for pivoting motion relative to the housing. The housing is generally narrower than the joined hinge plates when they are in a coplanar position (180°). So as the hinge plates pivot through the coplanar position, they deform the housing and cause a spring force that urges them to pivot either upward or downward away from the coplanar position. Ring members mounted on the hinge plates move with the pivoting movement of the hinge plates to open or close. When the ring members close, the spring force blocks the movement of the hinge plates and retains the ring members together. Similarly, when the ring members open, the spring force retains them apart. The user may pull or push manually the ring members to overcome the spring force, thereby open or close the ring members. Furthermore, the user may open or close the ring members by operating a lever disposed at one end or two ends of some ring binder mechanisms to move the hinge plates through the coplanar position.  
         [0003]     One drawback to the conventional ring binder mechanism is that when the ring members close, the ring binder mechanism may open by pulling the closed ring members of any one ring to pivot the hinge plates through the coplanar position. Such the ring binder mechanism may open easily and unintentionally under an external force, especially when it falls onto the ground or other surfaces, thereby causing the papers to fall out. Accordingly, it would be desirable to provide an improved ring binder mechanism.  
       SUMMARY OF THE INVENTION  
       [0004]     One object of the invention is to provide a ring binder mechanism which may be opened by pulling only a pair of particular ring members and closed by pushing any pair of ring members, thereby reducing the risk of paper&#39;s falling out thanks to unintentional opening of the mechanism.  
         [0005]     Accordingly, the present invention provides a ring binder mechanism comprising:  
         [0006]     a housing having a top portion and an open bottom generally opposed to the top portion;  
         [0007]     hinge plates supported by the housing for pivoting motion relative to the housing;  
         [0008]     rings for holding loose-leaf pages, each ring including a first ring member and a second ring member, the first ring member being mounted on a first hinge plate and moveable with the pivoting motion of the first hinge plate relative to the second ring member between a closed position and an open position, in the closed position the two ring members forming a substantially continuous, closed loop for allowing loose-leaf pages retained by the rings to be moved along the rings from one ring member to the other, and in the open position the two ring members forming a discontinuous, open loop for adding or removing loose-leaf pages from the rings; and  
         [0009]     a travel bar disposed between the top portion of the housing and the hinge plates and having a plurality of projections, at least one of the projections having a structure to block the hinge plates from pivoting upward relative to the housing and at least other one of the projections having a structure to allow the hinge plates to pivot upward relative to the housing.  
         [0010]     Additional features and advantages of the inventions will become apparent to those skilled in the art upon consideration of the attached drawings in conjunction with the following description of the drawings, which exemplifies the best mode of carrying out the invention as presently perceived, or can be learned through practice of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a side view of a ring binder mechanism of a first embodiment of the present invention;  
         [0012]      FIG. 2  is a top view of the ring binder mechanism of  FIG. 1 ;  
         [0013]      FIG. 3  is a bottom view of the ring binder mechanism of  FIG. 1 ;  
         [0014]      FIG. 4  is an end view of the ring binder mechanism of  FIG. 1 ;  
         [0015]      FIG. 5  is an exploded perspective view of the ring binder mechanism of  FIG. 1 ;  
         [0016]      FIG. 6  is a top perspective view of the ring binder mechanism of  FIG. 1  with the ring members in the closed and locked position;  
         [0017]      FIG. 7  is a bottom perspective view of the ring binder mechanism of  FIG. 1  with the ring members in the closed and locked position;  
         [0018]      FIG. 8  is a side view of the ring binder mechanism of  FIG. 1  with the ring members in the closed and locked position and with the housing removed to show internal construction, in which the detail structure is also shown with two partially enlarged views;  
         [0019]      FIG. 9  is a top perspective view of the ring binder mechanism of  FIG. 1  with a pair of particular ring members just opened and other ring members closed;  
         [0020]      FIG. 10  is a bottom perspective view of the ring binder mechanism of  FIG. 1  with a pair of particular ring members just opened and other ring members closed;  
         [0021]      FIG. 11  is a view similar to  FIG. 8 , showing internal state of the ring binder mechanism of  FIGS. 9 and 10 ;  
         [0022]      FIG. 12  is a top perspective view of the ring binder mechanism of  FIG. 1  with the ring members in the opened position;  
         [0023]      FIG. 13  is a bottom perspective view of the ring binder mechanism of  FIG. 1  with the ring members in the opened position;  
         [0024]      FIG. 14  is a view similar to  FIG. 8 , showing internal state of the ring binder mechanism of  FIGS. 12 and 13 ;  
         [0025]      FIG. 15  is an exploded perspective view of a ring binder mechanism of a second embodiment of the present invention;  
         [0026]      FIG. 16  is a top perspective view of the ring binder mechanism of  FIG. 15  with the ring members in the closed and locked position;  
         [0027]      FIG. 17  is a side view of a ring binder mechanism of a third embodiment of the present invention;  
         [0028]      FIG. 18  is a top view of the ring binder mechanism of  FIG. 17 ;  
         [0029]      FIG. 19  is a bottom view of the ring binder mechanism of  FIG. 17 ;  
         [0030]      FIG. 20  is an end view of the ring binder mechanism of  FIG. 17 ;  
         [0031]      FIG. 21  is an exploded perspective view of the ring binder mechanism of  FIG. 17 ;  
         [0032]      FIG. 22  is a top perspective view of the ring binder mechanism of  FIG. 17  with the ring members in the closed and locked position;  
         [0033]      FIG. 23  is a bottom perspective view of the ring binder mechanism of  FIG. 17  with the ring members in the closed and locked position;  
         [0034]      FIG. 24  is a bottom perspective view of the ring binder mechanism of  FIG. 17  with the ring members in the closed and locked position and with part of a housing broken away and some ring members and a hinge plate removed to show internal construction;  
         [0035]      FIG. 25  is a side view of the ring binder mechanism of  FIG. 17  with the ring members in the closed and locked position and with the housing removed to show internal construction, in which the detail structure is also shown with two partially enlarged views;  
         [0036]      FIG. 26  is a top perspective view of the ring binder mechanism of  FIG. 17  with a pair of particular ring members just opened and other ring members closed;  
         [0037]      FIG. 27  is a bottom perspective view of the ring binder mechanism of  FIG. 17  with a pair of particular ring members just opened and other ring members closed;  
         [0038]      FIG. 28  is a view similar to  FIG. 25 , showing internal state of the ring binder mechanism of  FIGS. 26 and 27 ;  
         [0039]      FIG. 29  is a top perspective view of the ring binder mechanism of  FIG. 17  with the ring members in the opened position;  
         [0040]      FIG. 30  is a bottom perspective view of the ring binder mechanism of  FIG. 17  with the ring members in the opened position;  
         [0041]      FIG. 31  is a view similar to  FIG. 25 , showing internal state of the ring binder mechanism of  FIGS. 26 and 27 ;  
         [0042]      FIG. 32  is an exploded perspective view of a ring binder mechanism of a fourth embodiment of the present invention; and  
         [0043]      FIG. 33  is a top perspective view of the ring binder mechanism of  FIG. 32  with the ring members in the closed and locked position; 
     
    
       [0044]     Corresponding reference numerals indicate corresponding parts throughout the views of the drawings.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0045]     Referring now to the drawings,  FIGS. 1-14  show a ring binder mechanism  1  according to a first embodiment of the invention. The ring binder mechanism  1  generally includes a housing indicated generally at  11  and three rings  13  supported by the housing  11 . The rings  13  retain loose-leaf pages on the ring binder mechanism  1 . By operating the particular ring  13  as described later, the ring binder mechanism  1  may be opened and closed to add or remove pages. Referring to  FIG. 2 , the housing  11  is elongate with a uniform, generally trapezoid cross section having at its center a raised plateau  15 . The two longitudinal ends of the housing  11  are generally closed. Bent under rims  17  extend from one longitudinal end of the housing to the other along two longitudinal edges of the housing  11  respectively. It is understood that a ring mechanism with a housing of other shapes (for example, a housing with an arc-shaped cross section) including irregular shapes does not depart from the scope of the invention.  
         [0046]     Three rings  13  of the ring binder mechanism  1  are substantially identical and have roughly circular profile. As shown in the drawings, the rings  13  each include two roughly semi-circular ring members  21   a ,  21   b  formed from a conventional, cylindrical rod of a suitable material such as steel. The ring members  2 la,  21   b  have respective fee ends  23   a ,  23   b . The free ends  23   a ,  23   b  are formed so that they may securely hold the ring members together against misalignment (relative to the longitudinal axis of the ring members) when in the closed position of the rings. The D-shaped rings known in the art also fall within the scope of the invention. Furthermore, the ring members having different cross-sections (for example, elliptical cross-section) or formed from different materials do not depart from the scope of the invention.  
         [0047]     As shown in  FIG. 5 , the ring binder mechanism  1  includes two mirror image hinge plates  25   a ,  25   b  each supporting respective ring members  21   a ,  21   b . Each of the hinge plates  25   a ,  25   b  is thin and rectangular in shape. The hinge plates  25   a ,  25   b  are slightly shorter than the  25   a ,  25   b  along the inner edge of the hinge plates  25   a ,  25   b . The cutouts  27   d  are longer than other three cutouts  27   a - 27   c  in the longitudinal direction of the hinge plates  25   a ,  25   b . The hooked portions  29  are formed on the inner edge of the hinge plates  25   a ,  25   b  adjacent the cutouts  27   d . The use of the cutouts  27   a - 27   d  and the hooked portions will be described later.  
         [0048]     As shown in  FIG. 5 , the ring binder mechanism  1  also includes an elongate and substantially flat and rectangular travel bar  31 , which is oriented in a substantially vertical plane as shown by the drawings to lock the ring members  21   a ,  21   b  together while they close. The travel bar  31  includes three inverted L-shaped projections  33   a   33   c  extending integrally and downward from the travel bar  31  within the plane of the travel bar. The projections  33   a - 33   c  are spaced from each other along the longitudinal direction of the travel bar  31  so that two projections  33   a ,  33   c  thereof are adjacent to each longitudinal end of the travel bar  31  respectively and other projection  33   b  is slightly offset from the center of the travel bar  31 . It is understood that a travel bar having different shapes and more or less than three projections does not depart from the scope of the invention.  
         [0049]     The projections  33   b ,  33   c  have the same shape and include a suspending portion  35  extending downward from the bottom surface of the travel bar  31 , a shoulder portion  37  extending perpendicularly to the suspending portion  35  and a sloping portion  39  extending upward and slopingly from the shoulder portion  37  toward the bottom surface of the travel bar  31 . The projection  33   a  is slightly different from the projections  33   b ,  33   c  in shape. Specifically, the projection  33   a  includes a suspending portion  35 ′ extending downward from the bottom surface of the travel bar  31  and a sloping portion  39 ′ extending upward and slopingly from the suspending portion  35 ′ toward the bottom surface of the travel bar  31 . The travel bar  31  and the integral projections may be formed in a single step.  
         [0050]     A hooked portion  41  projecting downward is disposed between the projections  33   b ,  33   c  having a relatively large space. Preferably, a plurality of corresponding horizontal extensions  43  are formed on the top surfaces of the travel bar  31 . The width of the horizontal extensions  43  is slightly narrower than that of the raised plateau  15  of the housing  11  so that the travel bar  31  may move smoothly along the raised plateau  15  of the housing  11  without changing the moving direction laterally of the housing  11 .  
         [0051]     Referring to  FIGS. 6-8 , the assembled ring binder mechanism  1  is described now, wherein the ring members  21   a ,  21   b  are shown to be in closed and locked position. As shown in the drawings, the travel bar  31  is disposed within the housing  11  below the raised plateau  15  of the housing  11 . The travel bar  31  extends longitudinally along the housing  11  and orients substantially parallel to the longitudinal axis of the housing so that the projections  33   a - 33   c  face away from the housing  11 .  
         [0052]     As shown in  FIGS. 5 and 6 , the hinge plates  25   a ,  25   b  join together in parallel arrangement under the travel bar to form a central pivoting hinge  47  having a pivotal axis. This is achieved in a known way in the art. As described later, the hinge plates  25   a ,  25   b  may pivot upward or downward on the central hinge  47 . Respective four cutouts  27   a - 27   d  in each of the hinge plates  25   a ,  25   b  align with each other to form four openings in the interconnected hinge plates. The interconnected hinge plates  25   a ,  25   b  are supported in the housing  11  under the travel bar  31  The outer longitudinal edges of the hinge plates  25   a ,  25   b  are supported loosely by the bent under rims  17  to be moveable within the bent under rims when the hinge plates pivot.  
         [0053]     The ring members  21   a ,  21   b  extend through the respective openings  19  formed along the opposite longitudinal sides of the housing  11  to be mounted respectively on the upper surface of the respective hinge plates  25   a ,  25   b  with the free ends  23   a ,  23   b  facing toward each other. The ring members  21   a ,  21   b  are mounted rigidly to the hinge plates  25   a ,  25   b  in a known way and move with them when the hinge plates  25   a ,  25   b  pivot. Although in the illustrated mechanism  1  in which the ring members  21   a ,  21   b  of each ring  13  are mounted respectively to the hinge plate  25   a ,  25   b  and move with them, a ring binder mechanism with only one ring member of each ring movable and the other one fixed (for example, a ring binder mechanism with only one ring member of each ring mounted on a hinge plate and the other ring member mounted for example on the housing) does not depart from the scope of the invention.  
         [0054]     As shown in  FIGS. 7 and 8 , the travel bar  31  disposed between the raised plateau  15  of the housing  11  and the hinge plates  25   a ,  25   b  connects with the hinge plates through a spring  45  so that three projections  33   a - 33   c  on the travel bar  31  align respectively with the openings formed by three cutouts  27   a - 27   c  on the respective hinge plates  25   a ,  25   b  with the spring  45  substantially located in the opening formed by the cutouts  27   d  on the respective hinge plates  25   a ,  25   b . One end of the spring  45  connects to the hooked portion  29  on the hinge plate and the other end to the hooked portion  41  formed on the travel bar  31  so that the spring  45  is in a tensioned state. Thus, the spring  45  has a potential energy to pull the travel bar  31  toward the right side of  FIGS. 7 and 8 . Preferably, correspondingly with the sloping portion of each projection, a sloping protrusion  27   a ′- 27   c ′ is formed at one side of three cutouts  27   a - 27   c  facing toward each sloping portion to guide the sloping portion of each projection to slide along it, thereby facilitating the operation of the ring binder mechanism  1 .  
         [0055]     If necessary, a through hole  51  may be provided at the housing  11  adjacent to one or two of its ends. A fixture  53  such as a rivet may extend through the through hole  51  to secure the ring binder mechanism  1  to the cover of a file or a notebook.  
         [0056]     Referring to  FIGS. 6-15 , the operation of the ring binder mechanism  1  will be described. As known, the hinge plates  25   a ,  25   b  may pivot upward or downward relative to the housing  11  and move the ring members  21   a ,  21   b  mounted thereto between a closed position and an open position. The hinge plates  25   a ,  25   b  are slightly wider than the housing when they are in a coplanar position (180°). So as the hinge plates pivot through the coplanar position, they deform the housing and cause a spring force that urges the hinge plates  25   a ,  25   b  to pivot either upward or downward away from the coplanar position. When the hinge plates  25   a ,  25   b  pivot downward (i.e. the hinge  47  moves away from the housing  11 ), the ring members  21   a ,  21   b  close; when the hinge plates  25   a ,  25   b  pivot upward (i.e. the hinge  47  moves toward the housing  11 ), the ring members  21   a ,  21   b  open.  
         [0057]     In  FIGS. 6-8 , the ring binder mechanism  1  is shown to be in closed and locked position. The hinge plates  25   a ,  25   b  are hinged downward away from the raised plateau of the housing so that the ring members  21   a ,  21   b  of each ring  13  close together to form a continuous loop for retaining loose-leaf pages. As shown in  FIG. 8 , at that time, the projections  33   a - 33   c  on the travel bar  31  align with the hinge  47  above the hinge plates  25   a ,  25   b  so that all of the suspending portions  35 ,  35 ′ of the projections  33   a - 33   c  are positioned in the openings formed by three cutouts  27   a - 27   c  on the respective hinge plates  25   a ,  25   b  while the shoulder portions  37  of the projections  33   b ,  33   c  engage with the upper surfaces of the hinge plates  25   a ,  25   b  and the sloping portion  39 ′ of the projection  33   a  abuts against the edge of the opening formed by the cutouts  27   a on the respective hinge plates  25   a ,  25   b . If an operator attempts to pull the rings  13  adjacent to the projections  33   b ,  33   c  apart, the projections  33   b ,  33   c  on the travel bar  31  between the hinge plates  25   a ,  25   b  and the raised plateau  15  of the housing block the hinge plates  25   a ,  25   b  from pivoting upward, thereby being incapable of opening the rings  13 .  
         [0058]     However, if the operator attempts to pull the particular ring  13  adjacent to the projection  33   a  apart as shown in  FIGS. 9-11 , the force to make the hinge plates  25   a ,  25   b  pivot upward causes the sloping portion  39 ′ of the projection  33   a  to slide along the sloping protrusion  27   a ′ on the hinge plates  25   a ,  25   b  so that the travel bar  31  moves toward the left side of the drawings relative to the housing  11  until the shoulder portions  37  of the projections  33   b ,  33   c  move out of the hinge plates  25   a ,  25   b  and into the positions corresponding to the openings formed by the cutouts  27   b ,  27   c . When the hinge plates further pivot through the coplanar position, they deform the housing and cause a spring force that urges the hinge plates  25   a ,  25   b  to pivot upward away from the coplanar position. The travel bar  31  moves toward the left side of the drawings so that the sloping portions  39  of the projections  33   b ,  33   c  slide along the sloping protrusion  27   b ′,  27   c ′ on the hinge plates  25   a ,  25   b  until the ring members  21   a ,  21   b  separate fully from each other to open the rings  13 , as shown in  FIGS. 12-14 .  
         [0059]     To close and lock the ring members  21   a ,  21   b , the operator may push manually the ring members  21   a ,  21   b  of any ring  13  to close them. At that time, the hinge palates  25   a ,  25   b  pivot downward and the travel bar  31  moves toward the right side of the drawings under the tension force of the spring  45  so that the sloping portions of the projections slide along the sloping protrusion on the hinge plates  25   a ,  25   b  to move the projections  33   b ,  33   c  out of the corresponding openings. When the hinge plates further pivot downward through the coplanar position, the shoulder portions  37  of the projections  33   b ,  33   c  engage with the upper surfaces of the hinge plates  25   a ,  25   b  and the sloping portion  39 ′ of the projection  33   a  abuts against the edges of the opening formed by the cutouts  27   a  on the respective hinge plates  25   a ,  25   b , thereby causing the ring binder mechanism  1  in the closed and locked position.  
         [0060]     Therefore, the ring binder mechanism according to the present invention may be opened by pulling only the ring members of the particular ring. Otherwise, it is impossible to open the ring binder mechanism according to the present invention. It should be understood that one of the projections  33   b ,  33   c  may have the same structure as the projection  33   a . In this case, the ring binder mechanism according to the present invention may be opened by pulling the ring members of the ring adjacent to the projection  33   a  or other projection having the same structure.  
         [0061]      FIGS. 15 and 16  illustrate a second embodiment of the ring binder mechanism of the present invention. The mechanism of this embodiment is generally designated by reference numeral  101 . Parts of the mechanism of this second embodiment corresponding to parts of the mechanism of the first embodiment are indicated by the same reference numerals, plus “100”. This embodiment is substantially similar to the first embodiment except that the structure of the ends of the housing  111  is different. In the second embodiment, a recess is formed at the two ends of the housing  111  respectively and a through hole  151  is formed in the bottom of the respective recess so that the ring binder mechanism may be attached to the cover of a file or a notebook.  
         [0062]      FIGS. 17-31  illustrate a third embodiment of the ring binder mechanism of the present invention. The mechanism of this embodiment is generally designated by reference numeral  201 . Parts of the mechanism of this third embodiment corresponding to parts of the mechanism of the first embodiment are indicated by the same reference numerals, plus “200”. This embodiment is substantially similar to the first embodiment except that the spring  45  in the first embodiment is replaced by a rotatable member  245 .  
         [0063]     Specifically, in the ring binder mechanism  201  according to the third embodiment, since it is unnecessary to provide with the spring  45 , neither the hooked portion  29  is formed on the hinge plates  225   a ,  225   b  nor the hooked portion  41  on the travel bar  231 . The rotatable member  245  in the ring binder mechanism  201  according to the third embodiment is substantially J-shaped and includes a main body  245   a , two arms  245   b  extending vertically upward from the main body  245   a  and spaced from each other and a hooked potion  245   c  extending from the lower end of the main body  245   a . A through hole  245   d  is formed in the main body  245   a  and two additional through holes  245   e  are formed in the vertically extending arms  245   b.    
         [0064]     At a position corresponding to the cutouts  227   d  on the hinge plates, two extensions  265  extend respectively downward from the bent under rims  217  of the housing  211  adjacent to the ring  213  used to open the ring binder mechanism  201  so that the rotatable member  245  may be received within a space defined by the two opposite extensions  265 . A through hole  267  is formed in the extension  265  respectively. Correspondingly, a through hole  241  is formed in the travel bar  231  adjacent to the projection  233   a.    
         [0065]     When assembled, the travel bar  231  is disposed in the space between two vertically extending arms  245   b  of the rotatable member  245  and connects with the rotatable member  245  via a hinge pin  261  extending through the through holes  245   e ,  241 . Next, the travel bar  231  and the rotatable member  245  assembled together are disposed between the raised plateau  215  of the housing  211  and the hinge plates  225   a ,  225   b  so that the rotatable member  245  is received within the space defined by the two opposite extensions  265  on the bent under rims  217  of the housing  211  and connects with the housing  211  via a hinge pin  263  extending through the through holes  267  and  245   d . The main body  245   a  and the hooked portion  245   c  of the rotatable member  245  extend through the opening formed by the cutouts  227   d  on the hinge plates to expose to the outside so that the free end of the hooked potion  245   c  abuts against the lower surface of the hinge plates  225   a ,  225   b . Except for the difference mentioned above, the assembly of the ring binder mechanism  201  according to the third embodiment is substantially similar to that of the first embodiment.  
         [0066]     Referring to  FIGS. 22-31 , the operation of the ring binder mechanism  201  will be described. The ring binder mechanism  201  is shown to be in the closed and locked position in  FIGS. 22-25 . The hinge plates  225   a ,  225   b  are hinged downward away from the raised plateau of the housing  211  so that the ring members  221   a ,  221   b  of each ring  213  close together to form a continuous loop for retaining loose-leaf pages. As shown in  FIGS. 24 and 25 , the projections  233   a - 233   c  on the travel bar  231  align with the hinge  247  above the hinge plates  225   a ,  225   b  so that all of the suspending portions  235 ,  235 ′ of the projections  233   a - 233   c  are positioned in the openings formed by three cutouts  227   a - 227   c  on the respective hinge plates  225   a ,  225   b  while the shoulder portions  237  of the projections  233   b ,  233   c  engage with the upper surfaces of the hinge plates  225   a ,  225   b  and the sloping portion  239 ′ of the projection  233   a  abuts against the edges of the opening formed by the cutouts  227   a on the respective hinge plates  225   a ,  225   b . If an operator attempts to pull the rings  213  adjacent to the projections  233   b ,  233   c  apart, the projections  233   b ,  233   c  on the travel bar  231  between the hinge plates  225   a ,  225   b  and the raised plateau  215  of the housing block the hinge plates  225   a ,  225   b  from pivoting upward, thereby being incapable of opening the rings  213 .  
         [0067]     However, if the operator attempts to pull the particular ring  213  adjacent to the projection  233   a  apart as shown in  FIGS. 27-28 , the force to make the hinge plates  225   a ,  225   b  pivot upward causes the sloping portion  239 ′ of the projection  233   a  to slide along the sloping protrusion  227   a ′ on the hinge plates  225   a ,  225   b  so that the travel bar  231  moves toward the left side of the drawings relative to the housing  211 . Moving the travel bar  231  toward the left side causes the rotatable member  245  to rotate anti-clockwise around the hinge pin  263  so that the free end of the hooked portion  245   c  of the rotatable member  245  further pushes the hinge plates  225   a ,  225   b  upward. The travel bar  231  further moves toward the left side relative to the housing  211  until the shoulder portions  237  of the projections  233   b ,  233   c  move out of the hinge plates  225   a ,  225   b  and into the positions corresponding to the openings formed by the cutouts  227   b ,  227   c . When the hinge plates further pivot through the coplanar position, they deform the housing and cause a spring force that urges the hinge plates  225   a ,  225   b  to pivot upward away from the coplanar position. The travel bar  231  further moves toward the left side so that the sloping portions  239  of the projections  233   b ,  233   c  slide along the sloping protrusion  227   b ′,  227   c ′ on the hinge plates  225   a ,  225   b  until the ring members  221   a ,  221   b  separate fully from each other to open the rings  213 , as shown in  FIGS. 29-31 .  
         [0068]     To close and lock the ring members  221   a ,  221   b , the operator may push manually the ring members  221   a ,  221   b  of any ring  213  to close them. At that time, the hinge palates  225   a ,  225   b  pivot downward and therefore push the free end of the hooked portion  245   c  of the rotatable member  245  downward so that the rotatable member  245  rotates clockwise around the hinge pin  263  to cause the travel bar  231  to move toward the right side of the drawings with the rotation of the rotatable member  245 . As a result, the sloping portions of the projections slide along the sloping protrusion on the hinge plates  225   a ,  225   b  to move the projections  233   b ,  233   c  out of the corresponding openings. When the hinge plates  225   a ,  225   b  further pivot downward through the coplanar position, the shoulder portions  237  of the projections  233   b ,  233   c  engage with the upper surfaces of the hinge plates  225   a ,  225   b  and the sloping portion  239 ′ of the projection  233   a  abuts against the edges of the opening formed by the cutouts  227   a on the respective hinge plates  225   a ,  225   b  , thereby causing the ring binder mechanism in the closed and locked position.  
         [0069]     Therefore, the ring binder mechanism  201  according to the present invention may be opened by pulling only the ring members of the particular ring  213 . Otherwise, it is impossible to open the ring binder mechanism according to the present invention. It should be understood that one of the projections  233   b ,  233   c  may have the same structure as the projection  233   a . In this case, the ring binder mechanism according to the present invention may be opened by pulling the ring members of the ring adjacent to the projection  233   a  or other projection having the same structure.  
         [0070]     To rotate smoothly the rotatable member  245  with the movement of the travel bar  231  or move smoothly the travel bar with the rotation of the rotatable member when the ring binder mechanism  201  is operated to open or close the ring members, a through slot  245   f  may be formed in the main body  245   a  of the rotatable member  245  so that the rotatable member  245  may be deformable to facilitate the rotation.  
         [0071]      FIGS. 32 and 33  illustrate a fourth embodiment of the ring binder mechanism of the present invention. The mechanism of this embodiment is generally designated by reference numeral  301 . Parts of the mechanism of this fourth embodiment corresponding to parts of the mechanism of the third embodiment are indicated by the same reference numerals, plus “100”. This embodiment is substantially similar to the first embodiment except that the structure of the ends of the housing  311  is different. In the fourth embodiment, a recess is formed at the two ends of the housing  311  respectively and a through hole  351  is formed in the bottom of the respective recess so that the ring binder mechanism may be attached to the cover of a file or a notebook.  
         [0072]     Components of the mechanism of the present invention according to the several discussed embodiments are made of a suitable rigid material, such as metal (e.g., steel). But mechanisms made of a nonmetallic material, specifically including plastic, do not depart from the scope of this invention.  
         [0073]     When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “up”, “down”, “upward”, “downward”, “upper”, “lower”, “left”, “right” and variations thereof is made for convenience, but does not require any particular orientation of the components.  
         [0074]     As various changes could be made in the above without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.