Abstract:
A mounting buckle for a safety helmet includes at least one mating member configured for attachment to a V-shaped strap having an apex, the apex of the strap being substantially flush with the abutment surface. This configuration channels the tension in the straps along continuous lines, rather than allowing the tension to dissipate in an intervening length of strap.

Description:
RELATED APPLICATION 
   The present application claims priority to, and the benefits of, U.S. Provisional Application Ser. Nos. 60/765,144, filed Feb. 4, 2006, and 60/842,074, filed on Sep. 1, 2006, the entire disclosures of which are hereby incorporated by reference. 

   FIELD OF THE INVENTION 
   This invention relates generally to safety helmets and, in particular, to helmet straps and their adjustment. 
   BACKGROUND OF THE INVENTION 
   Helmets for head protection are worn in a variety of environments and for various purposes. Helmets are often secured to a wearer&#39;s head by a flexible chin strap. The chin strap may include multiple segments of flexible strap material that are secured at either side of the helmet and pass below the chin, where the segments are releasably joined. In some helmets the strap segments on either side of the helmet are attached to the helmet at two positions, in front of and behind the wearer&#39;s ear. When joined, the two strap segments form a single strap that may be adjusted in length. Many of the available approaches to connecting the strap segments are cumbersome and lack security. In some cases, for example, the wearer must pass one end of the strap through a buckle or a pair of “D-rings” with a return loop, making it difficult to quickly remove the helmet in an emergency. In other cases, a quick release “snap” lacks security due to the possibility of accidental release. Two-finger release mechanisms, while more secure, typically attach to the ends of the strap segments and thus require intervening length in line with the straps. This makes it difficult to place the fastener near the chin, which can be important to the stability of the helmet. 
   Simplifying the strap arrangements may reduce the awkwardness of disengagement, but often at the price of reduced helmet stability. For example, single-strap systems may allow play in the helmet when worn. Indeed, even multiple-strap systems can allow helmet movement if the straps are not aligned so as to maintain consistent lines of tension. 
   SUMMARY OF THE INVENTION 
   The present invention provides practical and reliable solutions to the foregoing problems. In various embodiments, the invention provides a secure retention system for protective helmets that facilitates easy adjustment. In particular, the stability of a protective helmet is improved when the straps that connect to the helmet on each side have substantially straight, continuous lines of tension extending through the buckle that joins them. Accordingly, in preferred embodiments, two V-shaped strap segments are drawn into an “X” configuration that channels the tension in the straps along continuous lines, rather than allowing the tension to dissipate in an intervening length of strap. 
   For example, a releasable two-part buckle in accordance with the invention may comprise a male component attached at one end to a flexible strap segment and having at least two fingers extending from the other end of the component, which can snap-engage a female component. The engagement can be released by simultaneously pressing the two fingers. In a preferred embodiment, the female component has a pass-through area along its underside, parallel to the direction of introduction of the male component, through which a second flexible strap segment may be passed. Flush abutment between flat surfaces of the male and female components without significant intervening linear space helps maintain tension between the strap components. 
   In one embodiment, a system of flexible straps comprises a chin-holding component having one strap segment passing below the chin and another strap segment passing between the chin and the lower lip; retention components on left and right sides of the helmet having one strap segment connecting to the front portion of the helmet and another strap segment connecting to a rear portion of the helmet; and a connecting device of the present invention joining the chin-holding component to the retention component on one side of the wearer&#39;s head such that the strap segments intersect substantially in the shape of the letter “X”. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which: 
       FIG. 1  is a plan view of the male and female components of a buckle in accordance with the present invention. 
       FIG. 2A  is an upper plan view of the buckle of  FIG. 1  in the connected position. 
       FIG. 2B  is a lower plan view of the buckle of  FIG. 2A . 
       FIG. 3  is an exploded view of the buckle of the present invention showing the flexible straps to which the male and female components are to be connected. 
       FIG. 4  shows another embodiment of the present invention in plan view. 
       FIG. 5  shows the two embodiments of the female component of the buckle taken from  FIG. 1  and  FIG. 4  to illustrate the critical geometry of the present invention. 
       FIG. 6  is a side view of a protective helmet with straps connected at the chin using a buckle constructed according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to  FIG. 1 , a buckle in accordance with the present invention comprises a male component  51  and a female component  54  coupling together flexible straps comprising, with respect to male component  51 , strap segments  57   a ,  57   b , and with respect to female component  54 , strap segments  60   a ,  60   b . Male and female components  51 ,  54  are preferably molded from a strong, flexible, resilient plastic material such as Nylon or Delrin. The fingers  63   a ,  63   b  and guide member  66  are received within a receptacle area  69  of the female component  54  using normal manual pressure. During this coupling movement, fingers  63   a  and  63   b  deflect laterally toward guide member  66  until engaging features  72   a ,  72   b  have cleared surfaces  75   a ,  75   b  of the female component  54 . At this point, the flexibility of the fingers  63   a ,  63   b  cause them to return outwardly to their uncompressed position, so that surfaces  75   a ,  75   b  resist return movement of engaging features  72   a ,  72   b , thereby preventing separation of the male component  51  from the female component  54 . The female component  54  has openings  78   a ,  78   b  that afford access to fingers  63   a ,  63   b  following insertion of the male component  51  into the female component  54 . 
   With reference to  FIGS. 2 and 3 , fingers  63   a ,  63   b  are sufficiently exposed through the openings in the female component  54  to permit the wearer to pinch the fingers and flex them inwardly, thereby freeing the engaging features  72   a ,  72   b  from surfaces  75   a ,  75   b  and allowing the male component  51  to be withdrawn from the female component  54 . A flexible intermediate strap  81  passes through a slot  79  in male component  51 , and a flexible intermediate strap  87  is secured to female component  54  through a pass-through area  84 . 
   In the preferred embodiment, intermediate strap  81  is sewn or otherwise permanently affixed to the flexible strap components  57   a ,  57   b . As illustrated, the components  57   a ,  57   b  are part of the same single length of strap, which is folded to form a V-shaped configuration. Alternatively, however, components  57   a ,  57   b  can be separate strap segments that are joined to form the same configuration. In either case, the apex  88  of the V is substantially aligned (i.e., flush) with the abutment face  90  of male component  51 , which, when the male and female components are locked, makes contact with a complementary abutment surface  93  of the female component  54 . As a result, the edges of the V-shaped straps at their apices are substantially in contact along the entire apex  88  edge length. 
   Similarly, the pass-through area  84  in the female component accepts intermediate strap  87 , which is sewn or otherwise affixed to strap segments  60   a ,  60   b  and positioned so that the apex  89  of the V is substantially flush with the abutment surface  93 . The pass-through area  84  is oriented parallel to the direction of introduction of the male component  54 , and locates the tensioning region of the strap segments  60   a ,  60   b  adjacent the front surface  93  of the female component  54 , very close to the point where the female component joins the male component. 
   It is also possible to utilize the invention with single linear strap segments rather than V-shaped segments. In this case, the male component  51  may be connected to one of the single straps directly through the slot  79  (see  FIG. 2 ) instead of employing the intermediate strap  81 , and the female component  54  may be connected directly to the other single strap using the pass-through area  84 , thereby obviating the need for the intermediate strap  87 . Another alternative is to use one free, single strap and one V-shaped strap, in which case it is advantageous for the male component  51  to be connected to the single strap directly through the slot  79  and the female component  54  to be connected to the V-shaped strap via intermediate strap  87 . 
     FIG. 4  illustrates another embodiment  54 ′ of the female component. The component  54 ′ has many of the same features as the female component  54  shown in previous figures, including receptacle area  69 , surfaces  75   a ,  75   b , and openings  78   a ,  78   b  which cooperate with features of the male component  51  as described previously. Straps  60   a ,  60   b  are attached to the component  54 ′ via mounts such as the slots  95   a ,  95   b . This embodiment is particularly well suited to applications where two straps are joined at the female side with one or two straps on the male side. 
     FIG. 5  shows how both female components  54  and  54 ′ share the critical geometry that allows tension to pass through the buckle without being dissipated by intervening linear space. The dotted lines A-A′ and B-B′ follow the tension in the flexible straps  60   a ,  60   b  respectively. The slots  95   a ,  95   b  are angled toward each other so that the lines of tension A-A′ and B-B′ intersect each other at or very near the front surface  93  of the female component. As can be seen in  FIG. 5 , both embodiments  54  and  54 ′ of the female component provide this geometry. When the male and female components are engaged, these lines of tension are substantially continuous—that is, the lines A-A′ and B-B′ shown in  FIG. 5  are substantially congruent with complementary lines from the V-shaped strap of the male component. This is because when the male and female portions of the buckle are locked, the V-shaped straps come together to form the letter “X,” so that tension in the opposed straps are aligned. This has been found to substantially improve helmet stability. 
     FIG. 6  shows a system of helmet straps employing the buckle of the present invention to secure a protective helmet  96 . A chin-holding component comprises the strap segment  57   a , which passes between the chin and the lower lip, and the strap segment  57   b , which passes below the chin and is joined to the male component  51  of the buckle. The retention strap segment  60   a  is connected to the side of helmet toward the front, and the strap segment  60   b  is connected to the side of the helmet toward the rear. These are joined, as described above, to the female component  54  of the buckle. When the male component  51  is inserted into the female component  54 , the strap segments  57   a ,  57   b  and  60   a ,  60   b  abut to form the letter “X” because the buckle does not occupy significant space between them. The result is improved stability of the helmet  96  with respect to the wearer&#39;s head. 
   Having described certain embodiments of the invention, it will be apparent to those of ordinary skill in the art that other embodiments incorporating the concepts disclosed herein may be used without departing from the spirit and scope of the invention. The described embodiments are to be considered in all respects as only illustrative and not restrictive.