with reference to fig1 , a helmet shell 100 is shown from the right side of the wearer &# 39 ; s head ( the left side having symmetrical features and configuration ). flexible straps 102 , 104 , 106 form a “ y ” configuration and are joined with matching straps ( not shown ) on the opposite side of the helmet and attached at the neck or chin with an adjustable buckle 110 of conventional design . the middle junction point 112 of the retention straps is fixed by a clip or by sewing the straps 102 , 104 , 106 together such that they can flex , but cannot slide relative to one another . the retention strap 104 is secured to an attachment - mechanism coupling 115 at a point forward of the wearer &# 39 ; s ear . the other upward strap 106 is secured to the helmet 100 at a rearward attachment point 117 behind the wearer &# 39 ; s ear ; engagement of strap 106 to the helmet at point 117 preferably occurs at the inside surface the helmet shell 100 by means of , for example , a rivet or other retention element . an adjusting strap 104 ′ slidably engages a head - retention element 120 and extends forward through the coupling 115 and then downward , where it is secured to strap 104 by means of an adjustment mechanism 122 . when strap 102 is pulled downward , strap 104 ′ slides around the coupling 115 and , due to the geometry of its path , pulls the head - retention element 120 forward and upward until it presses against the nape of the wearer &# 39 ; s neck . when strap 102 is secured to the corresponding strap on the opposite side of the helmet and joined at the chin coupling 110 , the combination of the forward and upward tension on the head - retention element 120 created by strap 104 ′ and the downward tension on the helmet shell 100 created by straps 104 , 106 provides a secure fit . with reference to fig2 , one embodiment of the attachment mechanism coupling 115 is shown separated from the helmet ( the right - side coupling is illustrated ; the left - side coupling has symmetrical features ). the illustrated embodiment of attachment mechanism 115 is formed with curved engagement surfaces 130 , 132 that secure it to or within the side of the helmet shell 100 . angular features 132 and / or holes 134 are provided so that the attachment mechanism 115 can be co - molded with the plastic of the outer shell 100 . these features 132 , 134 serve as a scaffold into which plastic may flow during fabrication , thereby imparting mechanical strength to the attachment . alternatively , the attachment mechanism 115 can be secured to the outer shell 100 by conventional means such as by rivet or bolt . the path of the retention strap through the open area 140 and over a smooth rounded surface 142 is best understood in connection with fig1 and 3 , the latter illustrating a section of a preferred embodiment of the right - side attachment mechanism 115 . the portion of the retention strap 104 ′ coming from the head - retention element 120 is shown schematically as it passes over the angled element 142 and downward to adjustment mechanism 122 and attaches to a pin 144 . a second portion of the retention strap 104 extending from the middle junction point 112 passes upwards through adjustment mechanism 122 and attaches to a pin 148 . in using the present invention , the wearer places the helmet on his / her head and adjusts the straps 104 , symmetrical on left and right sides of the helmet , by means of adjusting buckle 110 to fit snugly at the chin . the wearer then pulls downward on adjustment mechanism 122 by placing pressure on the locking tab 150 , thereby causing adjustment mechanism 122 to slide downward along strap 104 , pulling strap 104 ′ due to its fixed attachment at pin 144 . the pulling action on strap 104 ′ tightens the head - retention element 120 at the back of the wearer &# 39 ; s neck . the wearer then lowers and attaches straps 104 at the chin . in this downward orientation strap 104 is forced against strap 104 ′ at the angled surface 152 of locking tab 150 . this contact by surface 152 cooperates with a fixed pin 154 to frictionally engage straps 104 , 104 ′ and thereby prevent strap 104 ′ from sliding back from the position obtained from the tightening pull . fig4 and 5 illustrate another embodiment of the attachment mechanism coupling 115 . in this embodiment , straps 104 and 104 ′ are different portions of the same continuous strap and will be denoted as 104 – 104 ′ ( where the reference numeral 104 refers to the end of the strap going to the chinstrap and 104 ′ refers to the end connecting to the head - retention element 120 ). the element of the retention strap 104 – 104 ′ coming from the head - retention element 120 is shown schematically as it passes over the rounded surface 142 and extends downward to pass around a pair of guide bars 160 , 162 . bar 160 has an angular profile terminating in an angled projection 164 facing outwardly with respect to the helmet . the strap 104 – 104 ′ passes over this angled profile and then around bar 162 , and finally to the chinstrap buckle 110 ( see fig1 ). this outward end of strap 104 – 104 ′ can be pulled by the wearer in the direction of the “ free ” arrow , or downward in the direction of the “ lock ” arrow . in using the present invention , the wearer places the helmet on his / her head and pulls the strap 104 – 104 ′ ( symmetrical straps on left and right sides ) away from the head in the direction of the “ free ” arrow . at this angle the strap is able to freely slide over the surface 142 and bars 160 , 162 , and the pulling action tightens the head - retention element 120 at the back of the neck ( see fig1 ). the strap 104 – 104 ′ is then lowered in the direction of the “ lock ” arrow and attached at the chin . in the downward “ lock ” position , strap 104 – 104 ′ is forced against itself and angled surface 164 of bar 160 . this contact frictionally engages the strap so it cannot slide back from the position obtained in the tightening pull . fig6 , 7 a and 7 b illustrate yet another embodiment of the attachment mechanism coupling 115 . in this embodiment , straps 104 and 104 ′ are different portions of the same continuous strap and once again will be denoted as 104 – 104 ′. the portion of the retention strap 104 – 104 ′ coming from the head - retention element 120 is shown schematically as it passes over the angled element 142 and then extends downward to pass around a pivotable pin 170 and through a pair of guide posts 172 , 174 . pin 170 and guide posts 172 , 174 are part of a rotating assembly 176 that rotates about a pivot point 180 . assembly 176 is shown in a “ free ” position in fig7 b and a “ lock ” position in fig7 a . the strap 104 – 104 ′ passes through a narrow passage 182 between pins 142 , 170 . in using the helmet incorporating this attachment mechanism , the wearer places the helmet on his / her head and pulls the strap 104 – 104 ′ on left and right sides of the helmet away from the head in the direction of the “ free ” arrow . the angle of this pulling action causes the assembly 176 to rotate outward to the position shown in fig7 b . in this position , the strap 104 – 104 ′ is free to slide over the pins 142 , 170 and the pulling action tightens the head - retention element 120 at the back of the neck ( see fig1 ). the strap 104 – 104 ′ is then lowered in the direction of the “ lock ” arrow and attached at the chin . this downward motion rotates the assembly 176 to the “ lock ” position shown in fig7 a , in which strap 104 – 104 ′ is pinched in the narrow space 182 . this pinching action frictionally engages the strap , preventing it from sliding back from the position obtained in the tightening pull . 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 .
an improved retention system for a protective helmet comprises slide / coupling mechanisms on opposite sides of the helmet shell , and a movable element at the rear of the helmet . fastening of the chinstrap secures the helmet in the downward direction and tightens the movable element against the nape of the neck , thereby securing the helmet in the area of the occipital lobe .