Abstract:
A breakaway buckle has a keeper attachable to a first strap and a secure attachable to a second laterally disposed strap. The secure has a tongue releasably retained in the keeper by overlapping interlocked locking surfaces on both components. Cam surfaces on the secure and keeper coact in response to lateral and/or torsional forces exerted on the secure to reduce the area of overlap between the locking surfaces and thereby facilitate separation of the secure from the keeper.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of U.S. Ser. No. 10/354,720 filed Jan. 30, 2003, which in turn is a continuation-in-part of U.S. Ser. No. 10/103,264 filed Mar. 21, 2002, now U.S. Pat. No. 6,637,083. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to buckles of the type employed to interconnect manually releasable straps on backpacks and the like, and is concerned in particular with the incorporation of a breakaway release feature in such buckles.  
         [0004]     2. Description of the Prior Art  
         [0005]     Shoulder straps on backpacks tend to spread apart and slip off the shoulders of the wearer as he or she walks or moves about. As a solution to this problem, it is known to employ a length of web strap spanning over the sternum to connect the shoulder straps. The “sternum strap” is anchored to the face of each shoulder strap with friction fittings that can be adjusted vertically as desired. This configuration typically includes a side-release buckle that allows the wearer to connect or part the sternum strap as needed to don and doff the backpack.  
         [0006]     The known side-release buckles suffer from a number of problems, including, inter alia, lack of durability, difficulty in accessing release mechanisms, resistance to releasing under heavy loads, etc. Most of these problems have been addressed by the lanyard-releasable buckle disclosed in U.S. Pat. No. 6,637,083.  
         [0007]     There remains, however, a problem stemming from the buckle&#39;s inability to open unless its release mechanism is manually operated or it breaks under heavy loading. Thus, when employed as a sternum buckle, injury, particularly to the throat area and larynx, may result if the wearer attempts to doff the backpack without first releasing the buckle.  
         [0008]     There exists a need, therefore, for a buckle that is not only readily releasable by manually activating its release mechanism, but that also is automatically releasable in a “breakaway” fashion if the sternum strap is subjected to lateral and/or torsional forces. This typically will be the case in emergency situations where the wearer is prevented or distracted from manually releasing the buckle.  
       SUMMARY OF THE INVENTION  
       [0009]     A breakaway buckle in accordance with the present invention includes a keeper attachable to a first strap which typically will comprise the shoulder strap of a backpack or the like, and a secure attachable to the end of a second laterally extending strap, typically a sternum strap providing an interconnection between two shoulder straps.  
         [0010]     The keeper has a bottom wall cooperating with side walls to define a receiving channel extending from an open front end to a rear end closed by a back wall. A lever overlies the channel. The lever has a first downwardly convex locking surface and first cam surfaces, and is resiliently deflectable between a normally closed lowered position and an open raised position.  
         [0011]     The secure has a tongue with a second upwardly convex locking surface and second cam surfaces. The tongue is configured and dimensioned for insertion into the keeper channel through its open front end, and into a seated position against the keeper back wall and beneath its lever. The lever is deflectable upwardly from its closed position by entry of the tongue into the keeper channel. When the secure arrives at its seated position, the cover snaps downwardly into its closed position, placing its first locking surface in an interlocked abutting relationship at an area of overlap with the second locking surface on the secure. The first and second cam surface are arranged to coact in response to lateral and/or twisting movement of the secure relative to the keeper by decreasing the area of overlap between the interlocked locking surfaces, thereby facilitating axial withdrawal of the secure tongue from the keeper channel.  
         [0012]     Other features and advantages of the present invention will now be described in greater detail with reference to the accompanying drawings, wherein: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a perspective view of a breakaway buckle in accordance with the present invention, the buckle being depicted in its operative position providing a releasable connection between an adjustment strap on the shoulder pad of a backpack and a sternum strap;  
         [0014]      FIG. 2  is a plan view of the buckle shown in  FIG. 1 ;  
         [0015]      FIG. 3  is a plan view similar to  FIG. 2  showing the secure withdrawn from the keeper;  
         [0016]      FIG. 4  is a sectional perspective view taken along line  4 - 4  of  FIG. 2 ;  
         [0017]      FIG. 5A  is a sectional view taken along line  5 - 5  of  FIG. 2 ;  
         [0018]      FIG. 5B  is a view similar to  FIG. 5A  showing the secure in the process of being disengaged from the keeper as a result of lateral and/or torsional forces being exerted on the sternum strap;  
         [0019]      FIG. 6  is a perspective view of the keeper; and  
         [0020]      FIG. 7  is an enlarged sectional view taken through a detachable end of one of the side bars on the keeper, with the end hook particularly received in the housing socket.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]     With reference initially to  FIGS. 1-3 , a breakaway buckle in accordance with the present invention is generally depicted at  10 . In its operative position as shown, the buckle provides a releasable connection between a “first” adjustment strap  12  sewn to the shoulder pad  14  of a backpack (not shown), and a “second” sternum strap  16  extending along an axis “X” disposed laterally with respect to strap  12 .  
         [0022]     The buckle  10  is a two part assembly consisting of a keeper  18  attachable to strap  12 , and a secure  20  attachable to strap  16 . As shown in  FIG. 3 , when the buckle is released, the secure  20  is separated from the keeper  18 .  
         [0023]     With reference additionally to  FIGS. 4-7 , it will be seen that the keeper  18  comprises a bottom wall  22  cooperating with side walls  24  to define a receiving channel  26  alignable with the axis “X”. The receiving channel extends from an open front end to a rear end closed by a back wall  28 . The bottom wall  22  is interrupted by an opening  30  adjacent to the front end of receiving channel  26 , and the back wall  28  has an abutment  32  projecting therefrom into the receiving channel.  
         [0024]     A lever  34  is integrally joined to and projects from the back wall  28  to overlie the receiving channel  26 . The lever is resiliently deflectable between a normally closed lowered position and a raised open position. Manual deflection of the lever from its closed to its open position is facilitated by a lanyard strap  36  looped through a transverse slot  38  at the forward lever end.  
         [0025]     A generally rectangular opening  40  in the lever is bordered by the back wall  28 , an opposite front wall  42 , and connecting side walls  44 . The front side of wall  42  is configured to provide a first ramp surface  46  (See  FIG. 4 ), and the back side of wall  42  is configured to provide a first locking surface  48 . When viewed in plan ( FIGS. 2 and 3 ), the first locking surface  48  is concave, and when viewed in a direction transverse to channel  26  ( FIGS. 5A and 5B ), the first locking surface is downwardly convex. The outer surfaces of the side walls  44  are configured to provide inwardly inclined first cam surfaces  50 .  
         [0026]     External side bars  52  are integrally joined at their proximate ends to the keeper side walls  24  as at  54 , and are provided at their distal ends with hook-shaped noses  56  configured to be snap fitted into side wall sockets  58 . The side bars  52  cooperate with the keeper side walls  24  to define slots  60  for accepting the adjustment strap  12 . The strap  12  may either be threaded through the slots  60  before being sewn to the shoulder pad  14 , or if the strap is already sewn in place, it can be laterally inserted in the slots by first disengaging the noses  56  from their respective sockets  58 .  
         [0027]     The secure  20  includes an externally ribbed base portion  62  and an integral forwardly projecting tongue  64 . The base portion  62  has an interior opening  66  bridged by a rib  68  over which an end of the sternum strap  16  is looped and thus connected. The tongue  64  comprises parallel laterally spaced legs  70  projecting from the base portion  62 . The distal ends of the legs  70  are connected by a front rib  72 , and a middle leg  74  joins the front rib  72  to an intermediate rib  76 .  
         [0028]     The intermediate rib  76  is configured to provide a second locking surface  78 . As viewed in plan ( FIGS. 2 and 3 ), the second locking surface is convex, and as viewed in a direction transverse to the receiving channel  26 , the second locking surface is upwardly convex.  
         [0029]     As can be best seen in  FIGS. 5A and 5B , the side legs  70  of the tongue  64  are provided with second cam surfaces  80  arranged to coact with the first cam surfaces  50  of the keeper. The width of the tongue is smaller than the width of the receiving channel  26 , thus providing side clearances as at  82 .  
         [0030]     As is best shown in  FIG. 4 , the middle leg  74  of the tongue  64  is configured to provide a second ramp surface  84 . As the tongue enters the receiving channel, the second ramp surface coacts in sliding engagement with the first ramp surface  46  to gradually deflect the lever  34  upwardly from its normally closed position. When the intermediate rib  76  passes beyond the front lid wall  46 , the tongue  64  is seated with its front rib  72  bearing against abutment  32  on back wall  28 , and the lever snaps downwardly, resulting in the first locking surface  48  coacting in an interlocked relationship with the second locking surface  78  on the tongue  64  at an area of overlap “A” (See  FIGS. 5A and 5B ).  
         [0031]     The resilient downward force of the lever  34  acts via the inclined interfaces between the first and second cam surfaces  50 ,  80  to center the tongue  64  in the channel  26 . Moreover, when the sternum strap  16  is tensioned in the direction of axis X (socalled “straight line” loading), the concave/convex relationship (as viewed in plan) of the first and second locking surfaces  48 ,  78  further serves to urge the tongue  64  centrally in the channel  26 . Centering the tongue  64  in the channel  26  maximizes the area of overlap A between the locking surfaces  48 ,  78 , which in turn maximizes the ability of the buckle to remain securely closed under heavy straight line loading.  
         [0032]     The buckle may be manually released by pulling on the lanyard  36  to raise the lever  34  and thus reduce the area A of overlap between the locking surfaces  48 ,  78 . The buckle may also be released in a breakaway mode by subjecting the sternum strap  16  and the secure  20  to which it is connected to lateral and/or torsional forces. As shown in  FIG. 5B , when this occurs, the tongue  64  will be urged from its position in the center of the channel  26  into an offset position, with the result that one or the other of the pairs of cam surfaces  50 ,  80  will coact to push the lever upwardly and thereby decrease the area of overlap between the locking surfaces  48 ,  78 . This reduction in overlap will facilitate a pulling apart of the secure from the keeper.  
         [0033]     Preferably, as shown in  FIG. 4 , the keeper  18  will additionally include external front and rear bars  86 ,  88  defining slots through which an auxiliary strap  90  can be threaded and looped around the shoulder pad  14  to stabilize the keeper  18  against movement relative to the secure  20 .