Abstract:
The buckle has a buckle body, and a lock mechanism for releasably locking two tongues insertable inside the buckle body in a longitudinal insertion direction; the lock mechanism includes a retaining rod movable, in a release direction perpendicular to the longitudinal insertion direction, between a lock position engaging retaining seats formed in the two tongues, and a release position disengaging the two tongues to permit expulsion of the tongues from the buckle body; the lock mechanism also includes a release button movable in the release direction to move the retaining rod into the release position; and the retaining rod is movable in the release direction independently of the release button, and is maintained in the lock position by a spring.

Description:
The present invention relates to a safety strap buckle, in particular for automotive child safety seats, as well as for push-chairs or prams. 
   BACKGROUND OF THE INVENTION 
   Safety strap buckles for automotive child safety seats are known, e.g. as described in European Patent Publication Number EP 0 867 131A1, comprising:
         a buckle body connected to a first strap portion; and   a click-on lock mechanism housed inside the buckle body and designed to releasably lock two tongues connected to a second and third strap portion.       

   In the embodiment described in the above patent application, the lock mechanism comprises a release button which is maintained, by a return spring, in an upper lock position in which the tongues are retained inside the buckle body by a rodlike retaining member engaging corresponding retaining seats defined by the two tongues. 
   The release button is movable, in a direction perpendicular to the insertion direction of the tongues and in opposition to the elastic force of the spring, into a lower release position, in which the retaining member is released from the seats on the tongues to permit expulsion of the tongues from the buckle body. 
   In the above known embodiment, the rodlike retaining member is supported by the release button, and so moves with the button between the two lock and release positions. As a result, when the tongues are inserted into the buckle body, thus moving the retaining member into the retaining seats, the release button is also moved with it and produces undesired noise. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a safety strap buckle designed to eliminate the above drawback of the known art. 
   According to the present invention, there is provided a safety strap buckle as claimed in the attached claims. 
   Very briefly, the basic idea underlying the invention is to provide a lock mechanism for a buckle of the above type, wherein the retaining member is a separate component part from the release button. Consequently, the lock stage only involves the retaining member, which engages the retaining seats on the tongues in the usual way, while the release buttons remains stationary in the rest position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described in detail, purely by way of a non-limiting example, with reference to the accompanying drawings, in which: 
       FIG. 1  shows an exploded view in perspective of a first embodiment of a safety strap buckle in accordance with the present invention; 
       FIG. 2  shows a schematic, partly cross sectioned view in perspective of a detail of the lock mechanism of the  FIG. 1  buckle; 
       FIG. 3  shows a schematic cross section of the  FIG. 2  detail; 
       FIG. 4  shows a schematic cross section of a portion of a second embodiment of a safety strap buckle in accordance with the present invention; 
       FIG. 5  shows a section along line V-V of the buckle portion in  FIG. 4 ; 
       FIG. 6  shows an exploded view in perspective of a release button and a rodlike retaining member of a third embodiment of a safety strap buckle in accordance with the present invention; 
       FIG. 7  shows a view in perspective, with parts removed for clarity, of a fourth embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the following description and accompanying drawings, only the part of the buckle containing the innovative lock mechanism is described and illustrated. For any other details, the reader is referred to the known art referred to in the introduction. 
   With reference to  FIG. 1 , number  10  indicates as a whole a safety strap buckle in accordance with the invention, in particular for automotive child safety seats, as well as for push-chairs or prams. Buckle  10  comprises a hollow body or shell  12  in turn comprising: a substantially flat bottom wall  12   a ; a substantially flat top wall  12   b ; two lateral walls  12   c ; a front wall  12   d ; and a fastening portion  16  on the opposite side to front wall  12   d  and having a slot  18  by which to attach body  12  to a first strap portion (not shown). 
   Two known tongues  20  and  21  are insertable inside body  12  through an opening  14  in front wall  12   d  and in a direction substantially perpendicular to front wall  12   d  (hereinafter referred to as the longitudinal direction). 
   Tongues  20  and  21  are attached respectively to a second and third strap portion (not shown) by means of respective slots  22  and  23 , and each comprise, in known manner, a stem portion  24 ,  25  having a downward-facing recess  26 ,  27  which acts as a retaining seat. As will be clear from the following description, a buckle in accordance with the invention may obviously also be used in retaining systems employing a different number of tongues (typically one or three). 
   Hollow body  12  houses the buckle click-on lock mechanism, which substantially comprises a rodlike retaining member  28  and a release button  29 , both shown in detail in  FIGS. 2 and 3 . 
   With particular reference to  FIGS. 2 and 3 , retaining member  28  comprises a rod  30  which extends in a direction (hereinafter referred to as the transverse direction) parallel to the plane of bottom wall  12   a  of body  12  and perpendicular to the insertion direction of tongues  20  and  21 , and engages retaining seats  26  and  27  in tongues  20  and  21  to retain tongues  20  and  21  inside body  12 . In the example shown, rod  30  has a rectangular cross section, but may obviously have a differently shaped, preferably circular, cross section. 
   Retaining member  28  also comprises two guide members  31  and  32  fixed to the ends of rod  30 , and which slide, in a direction perpendicular to the plane of bottom wall  12   a  (hereinafter referred to as the vertical direction), inside an appropriately shaped guide seat  34  formed in body  12 . Alternatively, one guide member—in this case, annular in shape—may be provided. 
   The two guide members  31 ,  32  (or one guide member) are preferably made of plastic material. Rod  30  may be made of plastic material—in which case, it is formed in one piece with guide members  31  and  32 —or of metal material—in which case, the two guide members are advantageously molded onto it. 
   Retaining member  28  is movable, in the vertical direction defined above, between a lowered position, in which tongues  20  and  21  can be inserted and released inside body  12 , and a raised position (shown in  FIGS. 2  and  3 ), in which, once tongues  20  and  21  are inserted inside body  12 , rod  30  engages retaining seats  26  and  27  to prevent release of the two tongues. 
   Retaining member  28  is maintained in the raised lock position by a spring  35 —in the example shown, a leaf spring, the ends of which press on guide members  31  and  32 , on one side, and the central portion of which presses on bottom wall  12   a  of body  12 , on the other side. 
   Spring  35  may obviously be a different type, e.g. a helical compression spring; in which case, two springs are preferably used, and press on the two guide members  31  and  32  at the ends of rod  30 . 
   Button  29  comprises, in known manner, a top portion  36 , e.g. disk-shaped, which is pressed by the user to release the strap; and two guide members  38  and  39  joined to (e.g. formed in one piece with) top portion  36  and mounted to slide inside guide seat  34 . 
   The two guide members  38 ,  39  of button  29  advantageously comprise respective stop teeth  40 ,  41 , which slide in respective vertical grooves  42 ,  43  ( FIG. 3 ) in guide seat  34 , and cooperate with respective stop surfaces  44 ,  45  at the top ends of grooves  42 ,  43  to define a top limit position (lock position) of the button. 
   Button  29  is maintained in the lock position by a spring  46 —in the example shown, in the form of a cylindrical helical spring—interposed between disk-shaped portion  36  and a supporting surface  48  (shown schematically in  FIG. 3 ) defined by buckle body  12 . 
   Operation of the lock mechanism of the buckle according to the invention will now be described briefly. 
   When inserted inside buckle body  12  at the lock stage, tongues  20 ,  21  interact in known manner with rod  30  of retaining member  28 , so that rod  30  engages retaining seats  26 ,  27  on the tongues to retain the tongues inside the buckle. Retaining member  28  being a separate component part from button  29 , the button remains stationary in the lock position during the above operation, thus generating no noise. When button  29  is pressed at the release stage, on the other hand, guide members  38 ,  39  of the button push retaining member  28  into the lowered position, in which rod  30  disengages the retaining seats on the tongues, which are expelled in known manner from buckle body  12  by an ejector spring  50  (shown in  FIG. 1 ). 
     FIGS. 4 and 5  show a second embodiment of a safety strap buckle in accordance with the present invention, and in which parts identical or corresponding to those in  FIGS. 1 to 3  are indicated using the same reference numbers. 
   The second embodiment substantially differs from the first by the rodlike retaining member only comprising rod  30 , with no guide members. The ends of rod  30  slide inside respective guide seats  52  formed in hollow body  20  beneath guide seat  34  of button  29 . Rod  30  is moved downwards, to release the lock mechanism, by two bottom appendixes  54  (only one shown in  FIG. 5 ) formed by guide members  38 ,  39  and also sliding inside guide seats  52  of rod  30 . 
     FIG. 6  shows a third embodiment of a safety strap buckle in accordance with the present invention, and in which parts identical or corresponding to those in  FIGS. 1 to 5  are indicated using the same reference numbers. 
   The third embodiment substantially differs from the second by retaining rod  30  sliding inside two guide seats  56 ,  57  defined by slots in respective guide members  38 ,  39  of release button  29 . 
   In the second and third embodiment too, spring  35  acting on retaining rod  30  may be a leaf spring or any other suitable type. For example, two cylindrical helical springs pressing on the two ends of the rod may be used. 
     FIG. 7  shows a fourth embodiment of a safety strap buckle in accordance with the present invention, and in which parts identical or corresponding to those in  FIGS. 1 to 6  are indicated using the same reference numbers. 
   The fourth embodiment differs from the  FIG. 2  embodiment by two helical springs  35 , as opposed to one leaf spring, acting on the ends of rod  30  to keep rod  30  in the raised lock position; and each tongue  20 ,  21  (only one is shown in its entirety) is formed by molding plastic material onto a respective metal reinforcing insert  60  (only one shown in  FIG. 7 , without plastic material). Inserts  60  are embedded completely in the plastic material, and terminate, at one end, with respective annular portions  61  surrounding slots  22 ,  23 , and, at the other end, with respective appendixes  62  embedded in the teeth defining respective retaining seats  26 ,  27 . 
   Body  12  is also formed by molding plastic material onto a metal reinforcing insert  65  (shown partly). 
   Metal insert  65  is embedded completely in the plastic material, and comprises : an annular end portion  66  embedded in portion  16  about slot  18 ; a load-transfer portion  67  defined by two arms (only one shown) and extending, from portion  66 , along lateral walls  12   c  and beneath guide seats  52  (not shown in  FIG. 7  but similar to those to  FIG. 5 ) and therefore beneath rod  30  in the vertical or release direction; and two appendixes  68 , which define the ends of said arms, are aligned with the ends of rod  30  in the longitudinal direction, and are located opposite guide seats  52  (i.e. on the opposite side with respect to the retaining seats  26 ,  27  when tongues  20 ,  21  engage body  12 ) to assist in retaining rod  30  in the event of pull on buckle  10  in the longitudinal direction. 
   Clearly, changes may be made to the embodiments and details described and illustrated herein purely by way of non-limiting examples, without, however, departing from the scope of the invention as defined in the accompanying claims.