Patent Publication Number: US-9895922-B2

Title: Ring binder with interlocking ring members

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to Chinese Patent Application No. 201510063445.9, filed Feb. 5, 2015, the entire contents of which are incorporated by reference. 
     FIELD OF THE INVENTION 
     Aspects of the present invention generally relate to a ring binder mechanism for retaining loose-leaf pages. More particularly, aspects of the present invention relate to a ring binder mechanism with ring members having interlocking formations for securing the ring members in a closed position. 
     BACKGROUND OF THE INVENTION 
     Ring binder mechanisms having rings for selectively retaining loose-leaf pages are well known. These mechanisms are commonly fastened to other structures such as notebook covers, files, clipboards, and the like to enable the rings to retain loose-leaf pages. The rings of ring binder mechanisms typically include two ring members that are selectively movable between an open position for receiving loose-leaf pages and a closed position for retaining loose- leaf pages. Conventionally, the ring members are hingedly connected to a base for pivoting movement relative the base. When the ring binder mechanism retains loose-leaf pages in the closed position, it is preferable for the rings to remain secured in the closed position. For certain types of ring binder mechanisms, when the rings are in the closed position, the rings are biased by a spring force towards the closed position to prevent unintended opening of the rings. The ring members of these and other types of ring binder mechanisms can also include interlocking formations that secure the ring in the closed position. However, known interlocking formations can be prone to disengagement in response to forces urging the ring members to pivot toward their open position. For example, if a ring binder loaded with paper is dropped, the ring members can be subject to lateral forces in the same direction as the ring member naturally opens. Some interlocking formations may be inadequate to resist such forces. 
     SUMMARY OF THE INVENTION 
     In one aspect, a ring binder for use in holding loose-leaf pages comprises an elongate base. Rings for retaining loose leaf pages include first and second ring members movable relative to one another between a closed position in which the first and second ring members together form a substantially continuous closed loop and an open position in which the first and second ring members form a discontinuous open loop. At least one of the first and second ring members are hingedly connected to the elongate base for selective pivoting movement toward the open and closed positions. A retaining system is configured to selectively and releasably hold the first and second ring members in the closed position. The retaining system comprises first and second interlocking formations adjacent ends of the first and second ring members, respectively. The first and second interlocking formations are selectively movable relative to one another between a retaining position in which the retaining system holds the first and second ring members in the closed position and a non-retaining position in which the retaining system does not hold the first and second ring members in the closed position. The first interlocking formation comprises a projection having a free end. The free end has a void configured and arranged to permit resilient bending of portions of the free end of the projection in a first direction as they engage the second interlocking formation when the interlocking formations are moved from the non-retaining position to the retaining position. Said portions of the free end of the projection are arranged relative the void so that in the retaining position said portions are substantially inhibited from bending in a second direction in response to the pivoting movement of said at least one of the ring members. 
     In another aspect, a ring binder for use in holding loose-leaf pages comprises an elongate base having a length and opposite longitudinal sides and rings for retaining loose leaf pages. Each ring includes first and second ring members movable between a closed position in which the first and second ring members form a continuous closed loop and an open position in which the first and second ring members form a discontinuous open loop. Each ring member includes a proximal end connected to the base and an opposite distal end. The first ring member comprises a first interlocking portion adjacent the distal end thereof and the second ring member comprises a second interlocking portion adjacent the distal end thereof. The first interlocking portion comprises a first interlocking formation, and the second interlocking portion comprises a second interlocking formation. The interlocking formations are configured to selectively and releasably engage one another for holding the ring members in the closed position. The interlocking formations are selectively movable relative to one another between a retaining position in which the interlocking formations engage one another to hold the first and second ring members in the closed position and a non-retaining position in which the interlocking formations do not engage one another to hold the first and second ring members in the closed position. The first interlocking formation comprises a projection extending along an axis generally lengthwise of the elongate base and having a free end. The free end of the projection comprises a single elongate slot having opposite sides and extending transverse to the axis of the projection and between the opposite longitudinal sides of the elongate base in the retaining position. The projection comprises a finger adjacent each of the opposite sides of the elongate slot. The fingers are adapted to engage the second interlocking formation and resiliently bend inward toward the slot as the interlocking formations are moved from the non-retaining position to the retaining position and configured to resist bending in a transverse direction between the opposite longitudinal sides of the elongate base in the retaining position. 
     Other objects and features will be in part apparent and in part pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top side perspective of a ring binder mechanism in an open position attached to the spine of a three-ring notebook; 
         FIG. 2  is a top side perspective of the ring binder mechanism in a closed position; 
         FIG. 3  is a bottom side perspective of the ring binder mechanism in the closed position; 
         FIG. 3A  is an enlarged view of a portion of  FIG. 3 ; 
         FIG. 4  is a top plan view of the ring binder mechanism in the open position; 
         FIG. 5  is a top plan view of the ring binder mechanism in the closed position; 
         FIG. 6  is an elevation of the ring binder mechanism in the open position; 
         FIG. 7  is an enlarged, fragmentary top plan view of the ring binder mechanism in the open position; 
         FIG. 8  is an elevation of the ring binder mechanism in the closed position; 
         FIG. 9  is an enlarged, fragmentary top plan view of the ring binder mechanism in the closed position; 
         FIG. 10  is an enlarged fragmentary perspective of the ring binder in a position between the open and closed positions; 
         FIG. 11  is a section taken in the plane of  11 - 11  of  FIG. 9 ; 
         FIG. 12  is an enlarged, fragmentary elevation of an interlocking portion of the ring binder mechanism; 
         FIG. 13  is an enlarged, fragmentary elevation of another interlocking portion of the ring binder mechanism; 
         FIG. 14  is a section taken in the plane of  14 - 14  of  FIG. 9 ; and 
         FIG. 15  is an enlarged, fragmentary top plan view of the ring binder mechanism in a closed, but non-retaining position. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the drawings. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 and 2 , a ring binder mechanism is generally indicated at reference number  10 . In the illustrated embodiment, the ring binder mechanism  10  is configured for attachment to the spine of a three-ring notebook  12 . The ring binder mechanism  10  generally includes an elongate base  20 . Three rings generally indicated at reference  30 , each comprising first and second ring members  32 ,  34 , are hingedly connected to the base  20  for pivoting movement relative thereto. For each of the rings  30 , the ring members  32 ,  34  are selectively movable between an open position ( FIG. 1 ) and a closed position ( FIG. 2 ). In the open position illustrated in  FIG. 1 , the first and second ring members  32 ,  34  form a discontinuous, open loop for adding loose-leaf pages to or removing loose-leaf pages from the rings  30 . In the closed position illustrated in  FIG. 2 , the first and second ring members  32 ,  34  together form a substantially continuous, closed loop for allowing loose-leaf pages retained by the ring  30  to be moved along the ring from one ring member to the other. As will be discussed in greater detail below, each ring  30  includes a retaining system, generally indicated at reference number  40 , for securing the ring in the closed position. The illustrated retaining system  40  provides interlocking engagement that resists the pivoting movement of the ring members  32 ,  34  relative the base  20  away from the closed position. The number of rings and ring members may be other than shown. 
     With further reference to  FIGS. 1 and 2 , the base  20  extends lengthwise along a longitudinal axis A 1  between opposite ends  50  and widthwise along a lateral axis A 2  between opposite longitudinal sides  52 . In the illustrated embodiment, the base  20  is a one piece body of molded plastic material. However, in other embodiments, the base can be made from different materials and have different constructions without departing from the scope of the invention. Referring to  FIGS. 3 and 3A , the bottom of the base  20  includes three pairs of bearing members  54  spaced apart from each other along the length of the base. Each of the bearing members  54  defines an axially extending arcuate recess. As discussed in further detail below, each of the bearing members  54  is configured to receive a pivot shaft  60  of a respective one of the ring members  32 ,  34  in the arcuate recess to secure the ring member to the base. In addition, the bearing members  54  are configured to permit rotation of the pivot shaft  54  in the arcuate recess about its longitudinal axis. 
     Referring to  FIGS. 1 through 5 , each of the ring members  32 ,  34  is connected to and supported by the base  20  for pivoting movement relative the base between the open and closed positions. The ring members  32 ,  34  are each a one piece body of plastic material formed separately from one another and the base  20 . However, it will be understood that the ring members can be made from different materials and have different constructions without departing from the scope of the invention. For example, it is contemplated that the ring members could be formed together with the base as an integrally formed, one piece body. Each ring member  32 ,  34  has a proximal end  64  that is connected to the base and an opposite distal end  66  that is a free end when the ring  30  is in the open position. In the illustrated embodiment, the pivot shaft  60  is located near the proximal end  64  of each ring member  32 ,  34 . 
     A curved arm portion  68  extends between the proximal and distal ends of each of the ring members  32 ,  34 . The curved arm portion  68  of each ring member  32 ,  34  has a substantially circular cross sectional shape. When the ring members  32 ,  34  are in the closed position, the curved arm portions  68  form a loop having a generally circular shape ( FIG. 2 ). It is understood that ring members could form loops in the closed position having different shapes without departing from the scope of the invention. For each ring  30  in the closed and open positions, a loop plane P ( FIGS. 4 and 5 ) bisects the arm portions  68  of the ring members  32 ,  34  as each extends distally from the respective pivot shaft  60  to the respective distal end  66 . Thus, each of the rings  30  is understood to be oriented in a respective one of the loop planes P. In the illustrated embodiment the loop planes P are oriented substantially orthogonal to the longitudinal axis A 1  of the base  20 . 
     Referring again to  FIGS. 3 and 3A , for each of the ring members  32 ,  34 , the pivot shaft  60  extends axially from the proximal end of the respective curved arm portion  68  in opposite directions along a hinge axis A 3  oriented parallel to the longitudinal axis A 1  of the base  20  and transverse (preferably substantially orthogonal) to the loop plane P. Each pivot shaft  60  is received in the arcuate recess defined by the respective bearing member  54  on opposite sides of the curved arm portion  68 . The pivot shaft  60  is received in the respective bearing member  54  for rotation about the respective hinge axis A 3  therein in the opening direction D 1  and the closing direction D 2 . Each of the ring members  32 ,  34  is, thus, hingedly connected to the base  20  for pivoting movement in the opening and closing directions D 1 , D 2  relative to the base about the hinge axis A 3 . It will be understood that the ring members could be hingedly connected to the base for pivoting motion relative to the base in other ways without departing from the scope of the invention. For example, it is contemplated that the ring members could be integrally formed with the base and hingedly connected to the base at a living hinge for pivoting motion relative the base. Likewise, although both of the ring members  32 ,  34  are configured for pivoting movement relative the base  20 , it is contemplated that only one of the ring members could be configured for pivoting movement relative the base while the other is fixed relative the base without departing from the scope of the invention. 
     The ring binder mechanism  10  does not bias the ring members  32 ,  34  toward either of the open or closed positions. Without the retaining system  40 , the ring members  32 ,  34  would be substantially free to pivot in the opening direction D 1  from the closed position. As discussed in greater detail below, the retaining system  40  secures the ring members  32 ,  34  in the closed position to prevent unintended opening of the rings  30  during use, particularly in response to forces urging movement of the ring members in the opening and closing directions D 1 , D 2 . Though ring members  32 ,  34  are not biased toward either of the open or closed positions, it is contemplated that the ring members could be biased toward the open and closed positions as is well known in the art without departing from the scope of the invention. 
     Referring to  FIGS. 6-10 , the retaining system  40  is operable to selectively and releasably hold the ring members  32 ,  34  in the closed position. The retaining system  40  includes a first interlocking portion  82  adjacent the distal end  66  of the first ring member  32  and a second interlocking portion  84  adjacent the distal end of the second ring member  34 . The first interlocking portion  82  is located at a distal end portion of the first ring member  32  and extends proximally away from the distal end  66  of the first ring member generally parallel to the loop plane P. Likewise, the second interlocking portion  84  is a distal end portion of the second ring member  34  and extends proximally away from the distal end  66  of the second ring member generally parallel to the loop plane P. When the ring  30  is closed, first and second interlocking portions  82 ,  84  are substantially aligned in face-to-face relationship ( FIGS. 8 and 9 ). 
     When the ring  30  is closed, the interlocking portions  82 ,  84  of the first and second ring members  32 ,  34  overlap one another. As shown in  FIG. 11 , a substantially planar facing surface  86  of the first interlocking portion  82  is substantially flush with a substantially planar facing surface  88  of the second interlocking portion  84  when the ring members  32 ,  34  are closed. In a preferred embodiment, the substantially planar facing surfaces  86 ,  88  are oriented substantially parallel to the loop plane P and are positioned adjacent thereto when the ring members  32 ,  34  are closed. 
     Referring to  FIGS. 6-11 , the first and second interlocking portions  82 ,  84  of the first and second ring members  32 ,  34  include first and second interlocking formations  92 ,  94 , respectively. The first interlocking formation  92  is located adjacent the distal end  66  of the first ring member  32 , and the second interlocking formation  94  is located adjacent the distal end of the second ring member  34 . The first interlocking formation  92  is operable to engage the second interlocking formation  94  such that the formations limit the relative movement of the interlocking portions  82 ,  84  of the ring members  32 ,  34  away from the closed position. As discussed in greater detail below, the ring members  32 ,  34  are selectively movable from a non-retaining position in which the retaining system  40  does not hold the ring members  32 ,  34  in the closed position to a retaining position in which the first interlocking formation  92  engages the second interlocking formation  94  to hold the ring members in the closed position. Moreover, in the retaining position, the first and second interlocking formations  92 ,  94  are configured for particularly strong interlocking engagement against the pivoting movement of the ring members  32 ,  34  in the opening and closing directions D 1 , D 2 . 
     Referring to  FIGS. 10-12 , the first interlocking formation  92  includes a projection extending along a projection axis A 4  from the facing surface  86  of the first interlocking portion  82 . The projection axis A 4  is oriented generally parallel to the longitudinal axis A 1  of the base  20  and generally orthogonal to the loop plane P. The second interlocking formation  94  includes an opening extending axially through the second interlocking portion  84  of the second ring member  34  in a direction parallel to the longitudinal axis A 1  of the base  20  and orthogonal to the loop plane P. The opening  94  is operable to releasably capture the projection  92  when the projection is inserted into the opening. 
     The projection  92  includes radially spaced apart top and bottom fingers  100 ,  102  that collectively form an axially extending post. Each finger  100 ,  102  has opposite lateral sides  96 , which are respectively spaced apart from one another along an axis oriented generally parallel to the lateral axis A 2  in the closed position. The radially outward surface of each finger  100 ,  102  also defines a radial end  98  of the projection  92 . The radial ends  98  of the projection  92  are vertically spaced apart from one another (i.e., along an axis that extends transverse to the longitudinal and lateral axes A 1 , A 2 ) in the closed position. When the ring  30  is closed, the top finger  100  is positioned above the bottom finger  102  relative the base  20  (i.e., the top finger  100  is spaced apart from the base  20  a greater distance than the bottom finger  102 ). The first and second fingers  100 ,  102  define the entire radial extent of the free end of the projection  92 . The two fingers  100 ,  102  are connected at their bases to the first interlocking portion  82  of the first ring member  32  and remain separate from one another along the entire axial extent of the projection  92 . The fingers could also be separate from one another at the free end of the projection and together at the base of the projection without departing from the scope of the invention. 
     Each of the fingers  100 ,  102  has an arcuate radially outer surface and a substantially planar radially inner surface that extend axially between the base and free end of the finger. When the ring  30  is closed, the substantially planar radially inner surface of each of the fingers  100 ,  102  is positioned in a respective plane oriented generally parallel to by the longitudinal axis A 1  and lateral axis A 2  of the base  20 . The radially outer surface of each of the fingers  100 ,  102  forms a radially outwardly extending lip  104  at the free end of the respective finger. As discussed in greater detail below, the lip  104  is configured to engage an opposed surface of the second interlocking portion  84  when the ring members  32 ,  34  are closed to inhibit the projection  92  from sliding out of the opening  94  in response to forces causing the first interlocking portion  82  to move away from the second interlocking portion in a direction parallel to the projection axis A 4 . 
     A single elongate slot  110  (broadly, a void) of generally rectilinear cross-sectional shape is formed in the free end of the projection  92 . The slot  110  is configured and arranged to permit resilient bending of the free ends of the fingers  100 ,  102  radially inwardly in a bending direction D 3  along bending axes A 5 , A 6  into the slot. The bending direction D 3  is a vertical direction oriented transverse to the longitudinal and lateral axes A 1  and A 2  in the closed position. The bending axis A 5 , A 6  of each finger  100 ,  102  is generally parallel to the lateral axis A 2  of the elongate base  20  in the retaining position. Moreover, the slot  110  is configured and arranged relative the fingers  100 ,  102  to substantially inhibit the fingers from bending in a direction transverse to the bending direction D 3  when the ring members  32 ,  34  pivot in the opening and closing directions D 1 , D 2  from the retaining position. As explained below, in the retaining position, the retaining system  40  thus provides robust interlocking engagement against the pivoting movement of the ring members  32 ,  34  in the opening and closing directions D 1 , D 2 . 
     The slot  110  extends laterally through the projection from one side  96  to the other. The slot  110  also extends axially through the projection  92  from the free end through the entire axial extent of the projection and further into the first interlocking portion  92  (see  FIG. 11 ). However, in other embodiments the slot can extend through a portion of the lateral or axial extents of the projection without departing from the scope of the invention. The slot  110  has opposite longitudinal sides that are bounded by the radially inward surfaces of the first and second fingers  100 ,  102 . The longitudinal sides of the slot  110  extend transverse to the projection axis A 4  and between the opposite longitudinal sides  52  of the base  20  when the ring  30  is closed. In the illustrated embodiment, the longitudinal sides of the slot  100  extend generally perpendicular to the projection axis A 4 . In the closed position, the longitudinal sides of the slot  110  are oriented generally parallel to the lateral axis A 2  of the base  20 . 
     As shown for example in  FIG. 13 , the opening  94  has a slightly elongate cross-sectional shape corresponding to the shape of the projection  92 . Opposite sides  116  of the opening  94  are spaced apart from one another and oriented vertically (i.e., transverse to the longitudinal and lateral axes A 1 , A 2 ) in the closed position. Top and bottom radial ends  118  of the opening are vertically spaced apart from one another in the closed position. The opening  94  is suitably sized to compress the projection  92  radially inward in the bending direction D 3  as the projection is inserted into the opening (i.e., moves from a non-retaining position to the retaining position). 
     Referring further to  FIG. 13 , the opening  94  is bounded by an axially extending wall  120  of the second interlocking portion  84 . The wall  120  includes a radially inwardly extending lip  122  configured and arranged to engage the radially outwardly extending lips  104  of the upper and lower fingers  100 ,  102  when the ring members  32 ,  34  are in the closed position. The lip  122  of the opening  94  extends radially inward of the lips  104  of the projection  92 . As the projection  92  is inserted into the opening  94 , the wall  120  is configured to engage the free ends of the fingers  100 ,  102  and bend the fingers radially inwardly about the bending axes A 5 , A 6  until the lips  104  are positioned radially inward of the lip  122 . After the lips  104  pass over the lip  122 , the fingers resiliently return (i.e., snap) radially outwardly to hold the ring members  32 ,  34  in the closed position. Referring to  FIGS. 11 and 14 , when the ring members  32 ,  34  are in the retaining position, the wall  120  engages the radial ends  98  and sides  96  of the projection  92 . The lips  104  of the projection  92  engage the lips  122  of the opening to inhibit unintentional disengagement when the ring members  32 ,  34  move away from one another in a direction parallel to the projection axis A 4 . 
     In the retaining position, the fingers  100 ,  102  are arranged relative the slot  110  to substantially inhibit bending in a direction transverse to the bending direction D 3  (i.e., along an axis oriented transverse to the bending axes A 5 , A 6 ) in response to the pivoting movement of either of the ring members  32 ,  34  in the opening and closing directions D 1 , D 2 . Furthermore, the projection  92  is configured to resist bending of any portion thereof in a direction substantially parallel to a direction in which the projection is urged to travel in response to forces tending to cause pivoting movement of the first and second ring members  30 ,  32  in the opening and closing directions D 1 , D 2 . The fingers  100 ,  102  substantially fill end portions of the opening  94  adjacent the radial ends  118  thereof. The fingers  100 ,  102  each extend laterally across the opening from one of the sides  116  to the other and have no voids formed between their opposite sides  96 . As a result, the fingers  100 ,  102  are each a solid piece of material that is substantially inhibited from bending toward or away from the sides  116  of the opening  94  in response to relative movement of the first and second interlocking portions  82 ,  84  in a direction transverse to the bending direction D 3 . By comparison, the slot  110  forms a void in the projection  92  that separates the fingers  100 ,  102  between the radial ends  118  of the opening  94 . The fingers  100 ,  102  are, therefore, substantially free to resiliently bend radially inward into the slot  110  along the bending axes A 5 , A 6  and substantially inhibited from bending along axes oriented transverse to the bending axes. 
     In the retaining position, attempts to pivot the ring members  32 ,  34  in the opening and closing directions D 1 , D 2  causes the first and second interlocking portions  82 ,  84  to try to move relative one another in a direction generally parallel to the lateral axis A 2  and in the loop plane P. When either of the ring members  32 ,  34  tries to pivot in the opening or closing direction D 1 , D 2 , a side wall  96  of the projection  92  engages a side wall  116  of the opening  94 . However, since the fingers  100 ,  102  fill the distal ends  118  of the opening  94  from one side  116  to the other, they do not bend radially inward toward or away from either side in response to the engagement with the sidewalls. Accordingly, the projection  92  and opening  94  are arranged and configured to substantially inhibit movement relative one another in response to attempts to pivot either of the ring members  32 ,  34  in the opening and closing directions D 1 , D 2 . 
     As shown in  FIG. 15 , in an exemplary method of closing the rings  30  of the binder mechanism  10 , the ring members  32 ,  34  are moved to an overlapping position so that the projection  92  is aligned with the opening  94 . From the open position, the ring members  32 ,  34  pivot toward one another in the closing direction D 2  and move away from one another in a direction generally parallel to the longitudinal axis A 1  of the base  20 . As illustrated in  FIG. 15 , the ring members are in a non-retaining position in which the retaining system  40  does not hold the ring members  32 ,  34  in the closed position. To insert the projection  92  into the opening  94 , the interlocking portions  82 ,  84  are moved toward each other in a direction generally parallel to the longitudinal axis A 1  of the base  20  (and also parallel to the projection axis A 4 ). When the facing surfaces  86 ,  88  of the interlocking portions  82 ,  84  are positioned substantially flush with one another as shown in  FIGS. 8-9, 11, and 14 , the interlocking formations  92 ,  94  are in a retaining position in which the retaining system  40  holds the first and second ring members  32 ,  34  in the closed position. 
     As the ring members  32 ,  34  move from the non-retaining position to the retaining position, the radial ends  98  of the free end of the projection  92  engage the wall  120  defining the opening  94 . The radial ends  118  of the opening  117  engage the radial ends  98  of the free ends of the fingers  100 ,  102  and apply a radially inwardly oriented force on the fingers in a direction parallel to the bending direction D 3 . As the interlocking portions  82 ,  84  are moved from the non-retaining position to the retaining position, the fingers  100 ,  102  resiliently bend radially inwardly toward the slot  110  in the bending direction D 3 . The fingers  100 ,  102  bend radially inwardly until the lips  104  are positioned radially inwardly of the lip  122 . As the projection  92  is inserted further into the opening  94 , the fingers  100 ,  102  resiliently return radially outwardly until the ring members  32 ,  34  reach the retaining position. 
     The arrangement of the fingers  100 ,  102  and the slot  110  substantially inhibits bending about an axis oriented transverse to the bending axes A 5 , A 6  as the ring members  32 ,  34  move from the non-retaining position to the retaining position. As the ring members  32 ,  34  move from the non-retaining position to the retaining position, both sides  96  of the fingers  100 ,  102  engage the sides  116  of the opening  94 . Since no voids are formed in the fingers  100 ,  102  between the opposite sides  96  thereof, the fingers do not bend inwardly in response to the engagement with the sides  116  of the opening. Moreover, since the fingers  100 ,  102  are sized to simultaneously engage both sides  116  of the opening  94  as they are inserted into it, they cannot bend side to side in a direction generally parallel to the lateral axis A 2  within the opening. 
     In the retaining position, the projection  92  extends axially into the opening  94  so that the radial sides and ends  96 ,  98  engage the opening wall  120  to inhibit movement of the projection  92  relative the opening  94 . The radially inwardly extending lip  122  of the opening wall  120  engages the radially outwardly extending lips  104  of the fingers  100 ,  102  to resist movement of the first interlocking portion  82  away from the second interlocking portion  84  in a direction parallel to the projection axis A 4 . In addition, the fingers  100 ,  102  substantially fill the radial ends  118  of the opening  94  from one side  116  to the other. Though the fingers  100 ,  102  are relatively free to bend radially inwardly into the slot  110  in the bending direction D 3 , the fingers are substantially inhibited from bending in the loop plane P in a direction transverse to the bending direction. Moreover, as discussed above, in the retaining position, the fingers  100 ,  102  are substantially inhibited from bending in response to the pivoting movement of the ring members  32 ,  34  in the opening and closing directions D 1 , D 2 . 
     To open the rings  30 , the ring members  32 ,  34  are moved away from one another in a direction generally parallel to the longitudinal axis A 1  of the base  20  (and parallel to the projection axis A 4 ) to remove the projection  92  from the opening  94 . As the projection  92  is removed from the opening  94 , the radial ends  98  of the projection  92  engage the wall  120  defining the opening and apply a radially inwardly oriented force on the fingers  100 ,  102 . The fingers  100 ,  102  resiliently bend inward about their bending axes A 5 , A 6  in response to the engagement until the radially outwardly extending lips  104  are disposed radially inwardly of the radially inwardly extending lip  122 . The radially outwardly extending lips  104  pass over the radially inwardly extending lip  104  and the projection  92  is removed from the opening  94 . Subsequently, the ring members  32 ,  34  can be pivoted in the opening direction D 2  until they reach the open position. 
     It is preferable for a ring binder mechanism to have a retaining system that securely holds the rings in the closed position. In the illustrated embodiment, the ring members  32 ,  34  close by pivoting in the closing direction D 2  and moving parallel to the projection axis A 4  in an insertion direction. Accordingly, it is preferable for the retaining system  40  to substantially inhibit the ring members  32   34  from unintended movements in directions opposite the closing direction D 2  and insertion direction. The retaining system  40  provides interlocking lips  104 ,  122  on the projection  92  and opening  94 , respectively, to inhibit movement of the ring members in a direction opposite the insertion direction. However, the interlocking lips  104  of the projection  92  extend radially outwardly beyond the radially inward end of the lips  122  of the opening  94 . Accordingly, to enable insertion of the projection  92  into the opening  94 , the lips  104 ,  122  must be radially deformable relative one another. Because the ring members  32 ,  34  are designed to pivot in the opening and closing directions D 1 , D 2 , it is preferable to enable the necessary deformation without adversely affecting the interlocking engagement provided by the retaining system  40  against the pivoting movement of the ring members. The illustrated retaining system  40  achieves the necessary radial deformation of the projection  92  relative the opening  94  without adversely affecting the strength of the interlocking engagement for inhibiting the pivoting movement of the ring members  32 ,  34  by arranging the slot  110  relative the fingers  100 ,  102  so that the fingers bend radially inwardly in the bending direction D 3  and are substantially inhibited from bending in a direction transverse to the bending direction. 
     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. 
     As various changes could be made in the above apparatuses, systems, and methods 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.