Abstract:
A two piece helmet with optional airbag is split along a vertical axis between the sides of the helmet to ease removal in the event of an injury. A series of aligned orifices in the helmet portions are joined by a removable cable. The cable ends are attached to each other to secure the helmet portions or to each of the helmet portions. The cable is accessed through removable panels that may also be used to tension the cable. Alternate means for joining the helmet portions include a series of lateral exterior latches opened by the cable. The helmet liner has two overlapping portions to minimize noise and improve weather sealing. An optional inflatable air bag is fitted to a lower perimeter of the helmet. A proximity sensing system will inflate the airbag when the vehicle is in motion and the helmet is displaced a certain distance from the vehicle.

Description:
FIELD OF INVENTION 
     The invention pertains to protective headgear. More particularly, the invention relates to helmets designed for easy removal after injury to the wearer. 
     BACKGROUND OF THE INVENTION 
     Various types of helmets have been developed for protection of the wearer. Nearly all provide some degree of cushioning from impacts and shock resistance and many incorporate novel systems to provide for ease of removal. U.S. Pat. No. 5,787,513 issued to Sharmat et al provides for a helmet that splits along a vertical axis, having a hinge at the top portion of the helmet and fastening means at either side. 
     U.S. Pat. No. 3,987,495 issued to Holley, discloses a motorcycle helmet designed to split along a central vertical plane running from the front to the rear of the helmet. The design is intended to provide a helmet that can be easily stored in a narrow space, such as a motorcycle saddlebag. U.S. Pat. No. 5,390,367, issued to Rush III discloses a one-piece helmet combined with an inflatable protective means attached to the lower circumference of the helmet. The protective means is instantly inflated upon impact with the crown of the helmet. 
     U.S. Pat. No. 4,324,005 is sued to Willis does not include a helmet, but rather employs a series of inflatable flaps that are inflated by a gas cylinder or manually by mouth when so desired by the wearer. U.S. Pat. No. 4,955,089 issued to Beale describes a hard hat that splits along a horizontal axis, requiring a series of fasteners along the joint between the upper and lower portions of the hard hat. U.S. Pat. No. 4,274,161 issued to Littler includes a one-piece helmet with manually inflatable collar attached to the lower circumference of the helmet. U.S. Pat. No. 5,133,084 issued to Martin discloses an inflatable safety collar that is actuated by a ripcord fastened to the vehicle of the user. 
     While other variations exist, the above-described designs for protective headgear are typical of those encountered in the prior art. It is an objective of the present invention to provide a helmet that will protect the wearer from impacts, punctures, crushing and abrasive forces. It is a further objective to provide a helmet that may be quickly and easily removed from the head with minimum injury to the wearer. It is a still further objective of the invention to provide a means for stabilizing the neck of the helmet wearer with respect to his head and body in the event of an accident. It is yet a further objective to provide a means to determine the appropriate time to deploy such stabilizing means based upon the relative position of the helmet wearer with respect to his vehicle. Finally, it is an objective of the invention to provide means to easily remove the stabilizing means when required for further care of the wearer. 
     While some of the objectives of the present invention are disclosed in the prior art, none of the inventions found include all of the requirements identified. 
     SUMMARY OF THE INVENTION 
     The present invention addresses many of the deficiencies of prior art protective headgear and satisfies all of the objectives described above. 
     A helmet providing the desired features may be constructed from the following components. A rigid, outer shell is provided. The outer shell includes a front portion and a mating rear portion. Each of the front and rear portions have a lower surrounding edge. The front portion includes an opening to provide forward visibility for a wearer. Means are provided for removably attaching the front portion to the rear portion. A resilient, padded inner liner is provided. The liner includes a first portion and a mating second portion. The first portion is sized and shaped to fit within the front portion of the outer shell. The second portion is sized and shaped to fit within the rear portion of the outer shell. Means are provided for securing the helmet to a head of the wearer. 
     In a variant of the invention, the means for removably attaching the front portion to the rear portion further includes a series of mating orifices in the front portion and in the rear portion. The orifices are located adjacent to an intersection between the front portion and the rear portion. A flexible cable is provided. The cable has a first predetermined cross-section, a first end and a second end and is sized and shaped to fit slidably through the mating orifices. The cable is threaded through the mating orifices and secures the front portion to the rear portion. Means are provided for removably attaching the first end to the second end. Means are provided for withdrawing the cable from the mating orifices. When the first end of the cable is detached from the second end, the cable may be withdrawn from the mating orifices and the front portion separated from the rear portion. 
     In a further variant, the means for removably attaching the first end of the cable to the second end includes first and second cable terminators. Each of the cable terminators has a first end, a second end and a cross-section no larger than the first predetermined cross-section. The first cable terminator is fixedly attached at its first end to the first end of the flexible cable and the second cable terminator is fixedly attached at its first end to the second end of the flexible cable. Each of the second ends of the first and second cable terminators includes a notch. 
     A retaining clip is provided. The retaining clip is formed of rigid material, has a U-shaped cross-section, is sized and shaped to fit frictionally over the cable terminators and includes a pair of protruding tabs. The tabs are sized, shaped, and located to removably engage the notches in the second ends of the terminators. When the second ends of the first and second cable terminators are placed adjacent each other and the retaining clip is pressed downwardly over the terminators, with the protruding tabs engaging the notches in the second ends of the cable terminators, the first and second cable ends will be removably attached. 
     In yet another variant of the invention, the means for removably attaching the first end of the cable to the second end includes first and second cable terminators. Each of the cable terminators has a first end, a second end and a cross-section no larger than the first predetermined cross-section. The first cable terminator is fixedly attached at its first end to the first end of the flexible cable and the second cable terminator is fixedly attached at its first end to the second end of the flexible cable. Each of the second ends of the first and second cable terminators includes a central stem and a securing portion attached to the stem. 
     A retaining clip is provided. The retaining clip is formed of rigid material, has a U-shaped cross-section, is sized and shaped to fit frictionally over the cable terminators and includes two pair of protruding tabs. The tabs are sized, shaped, and located to removably surround the central stems of the second ends of the cable terminators, drawing the securing portions of the terminators together. When the second ends of the first and second cable terminators are placed adjacent each other and the retaining clip is pressed downwardly over the terminators, with the protruding tabs surrounding the central stems of the second ends of the cable terminators, the first and second cable ends will be removably attached. 
     In still another variant, the means for removably attaching the first end of the cable to the second end includes an adhesive container. The container is sized and shaped to constrain the first end of the cable in close proximity to the second end of the cable. An adhesive is provided. The adhesive is poured into the adhesive container and over the first and second ends of the cable and allowed to dry. When the adhesive has dried, the first and second ends of the cable will be removably attached until sufficient tension is directed to separate the first end of the cable from the second end of the cable and the adhesive fails to grip either of the first and second ends of the cable. 
     In yet another variant of the invention, the means for removably attaching the front portion to the rear portion includes a series of mating, overlapping panels. The overlapping panels are fixedly attached to the front portion and the rear portion adjacent the intersection between the front and rear portions. The mating, overlapping panels serve to increase structural strength of the helmet and provide improved weather sealing. 
     In yet a further variant, the first and mating second portions of the resilient, padded inner liner include mating, interlocking edges, thereby providing improved weather sealing. 
     In still a further variant, the helmet includes a flexible, inflatable collar. The collar is removably attached to the lower surrounding edge of the front and rear portions of the rigid shell. Means are provided for rapidly inflating the collar as are means for deflating the collar. When the collar is inflated it will provide increased stability for the head and neck of the wearer by bearing against shoulders of the wearer. 
     In another variant of the invention, the means for rapidly inflating the collar and the means for deflating the collar include a pressurized gas cylinder, a control valve connected to the cylinder and tubing connecting the control valve to the inflatable collar. The cylinder contains sufficient gas to fully inflate the collar. The control valve includes a pressure relief valve and is capable of maintaining pressure in the collar until the relief valve is activated. Means are provided for activating the control valve. 
     In yet another variant, the means for activating the control valve further includes a position sensing system. The system is capable of determining if a helmet wearer&#39;s vehicle is in motion and a relative position of the helmet with respect to the vehicle. The system is capable of opening the control valve to inflate the collar upon sensing that the wearer&#39;s vehicle is in motion and the helmet is not within a first predetermined distance of the vehicle. The head and neck of the helmet wearer will be stabilized by the inflated collar in the event the wearer is separated from the vehicle by the first predetermined distance while the vehicle is in motion. 
     In still another variant, the helmet further includes means for rapidly removing the flexible cable to separate the front portion of the helmet from the rear portion. 
     In a yet another variant of the invention, the means for rapidly removing the flexible cable includes a first removable access panel. The first access panel covers the means for removably attaching the first end of the cable to the second end and a second removable access panel covers a portion of the flexible cable and an indentation in one of the front and rear portions of the helmet. The indentation provides means to apply tension to the cable for its removal. 
     In a further variant, the means for removably attaching the front portion to the rear portion of the helmet further includes a series of mating orifices in the front portion and in the rear portion. The orifices are located adjacent an intersection between the front portion and the rear portion. A flexible cable is provided. The cable has a first predetermined cross-section a first end and a second end. The cable is sized and shaped to fit slidably through the mating orifices. The cable is threaded through the mating orifices and secures the front portion to the rear portion. Means are provided for removably attaching the first end to either of the front and rear portions of the rigid, outer shell. Means are provided for applying tension to the second end of the cable and withdrawing the cable from the mating orifices. When the first end of the cable is detached from the shell, the cable may be withdrawn from the mating orifices and the front portion separated from the rear portion. 
     In still a further variant, the means for removably attaching the first end of the cable to rigid, outer shell includes a cable terminator. The cable terminator has a first end, a second end and a cross-section no larger than the first predetermined cross-section. The cable terminator is fixedly attached at its first end to the first end of the flexible cable. The second end of the cable terminator includes a notch. 
     A retaining clip is provided. The retaining clip has a first end and a second end. The retaining clip is fixedly attached at its first end to the rigid outer shell. The retaining clip is formed of rigid material, has a U-shaped cross-section, is sized and shaped to fit frictionally about the cable terminator. The retaining clip includes a pair of protruding tabs. The tabs are sized, shaped, and located to removably engage the notch in the second end of the terminator. When the cable terminator is pressed into the second end of the retaining clip, with the protruding tabs engaging the notch in the second end of the cable terminator, the first end of the cable will be removably attached to the shell. 
     In another variant of the invention, the means for removably attaching the first end of the cable to the rigid, outer shell includes a cable terminator. The cable terminator has a first end, a second end and a cross-section no larger than the first predetermined cross-section. The cable terminator is fixedly attached at its first end to the first end of the flexible cable. The second end of the cable terminator includes a central stem and a securing portion attached to the stem. 
     A retaining clip is provided. The retaining clip has a first end and a second end. The retaining clip is fixedly attached at its first end to the rigid outer shell. The retaining clip is formed of rigid material, has a U-shaped cross-section, is sized and shaped to fit frictionally about the cable terminator. The retaining clip includes a pair of protruding tabs. The tabs are sized, shaped, and located to removably surround the central stem of the second end of the cable terminator. When the cable terminator is pressed into the second end of the retaining clip, with the protruding tabs surrounding the central stem of the second end of the cable terminator, the first end of the cable will be removably attached to the shell. 
     In still another variant, the means for removably attaching the first end of the cable to the rigid, outer shell includes an adhesive container. The container has a first end and a second end and is fixedly attached at its first end to the rigid, outer shell. The second end of the container is sized and shaped to constrain the first end of the cable. An adhesive is provided. The adhesive is poured into the second end of the adhesive container and over the first end of the cable and allowed to dry. When the adhesive has dried, the first end of the cable will be removably attached to the rigid, outer shell until sufficient tension is directed to the second end of the cable to separate the first end of the cable from the adhesive container, thereby permitting removal of the cable from the helmet. 
     In yet another variant, the means for removably attaching the front portion of the helmet to the rear portion includes a series of mating orifices in the front portion and in the rear portion. The orifices are located adjacent an intersection between the front portion and the rear portion. A flexible cable is provided. The cable has a first predetermined cross-section, a first end and a second end and is sized and shaped to fit slidably through the mating orifices. 
     At least one securing latch is provided. The securing latch has a first portion, a mating second portion and means for removably attaching the first portion to the second portion, thereby securing the front portion of the helmet to the rear portion. The first portion has an inner end and an outer end and is fixedly attached to the front portion of the shell. The second portion has an inner end and an outer end and is fixedly attached to the rear portion of the shell. The first and second portions including mating openings that are collinear when the first portion is located adjacent the second portion. The cable is threaded through the mating orifices and the mating openings. The cable includes means for unfastening the means for removably attaching the first portion of the securing latch to the second portion. 
     Means are provided for removably attaching the first end of the cable to the rigid shell as are means for withdrawing the cable from the mating orifices and the mating openings. When the first end of the cable is detached from the rigid shell, the cable may be withdrawn from the mating orifices and the mating openings, thereby unfastening the means for removably attaching the first portion of the securing latch to the second portion and permitting the front portion of the helmet to be separated from the rear portion. 
     In still another variant of the invention, the means for removably attaching the first portion of the securing latch to the second portion and the means for unfastening the means for removably attaching the first portion of the securing latch to the second portion includes a pivot pin. The pivot pin is fixedly attached to the second portion between its inner end and its outer end perpendicular to a long axis of the second portion. A latching element is provided. The latching element has a first end, a second end, a first edge, a second edge, a top surface, a bottom surface and an orifice extending from the first edge to the second edge. The latching element is rotatably mounted at the orifice to the pivot pin. 
     A resilient engaging finger is provided. The finger extends downwardly from the bottom surface of the latching element. A receiving notch is provided. The notch is located in the first portion between its inner end and its outer end so as to frictionally engage the resilient finger when the latching element is rotated to a first, closed position. An unfastening protrusion extends downwardly from the bottom surface of the latching element and is located to obscure a portion of the mating openings when the latching element is rotated to the first, closed position. 
     A dislodging element is provided. The dislodging element has a cross-section greater that the first predetermined cross-section, and is capable of fitting slidably within the mating openings in the securing latch. The dislodging element is fixedly attached to the flexible cable at a point where the dislodging element will pass through the mating openings of the securing latch when the cable is withdrawn from the helmet. The dislodging element bears upon the unfastening protrusion as the cable is withdrawn from the helmet, thereby causing the latching element to pivot upwardly to a second, open position dislodging the resilient engaging finger from the receiving notch. This permits the first portion of the securing latch to be separated from the second portion and the front portion of the helmet to be separated from the rear portion. 
     In a final variant of the invention, the first removable access panel further includes at least one tensioning element. The tensioning element is attached to an underside of the first access panel and is sized, shaped and located to engage a portion of the flexible cable. The tensioning element imparts tension to the cable while securing the first access panel to the helmet. 
     An appreciation of the other aims and objectives of the present invention and an understanding of it may be achieved by referring to the accompanying drawings and the detailed description of a preferred embodiment. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the preferred embodiment of the invention; 
     FIG. 2 is an exploded perspective view of the preferred embodiment of the invention illustrating the front and rear portions of the helmet and the flexible cable joining them; 
     FIG. 3 is a detailed perspective view of the first and second cable ends, cable terminators and the retaining clip attaching the terminators together; 
     FIG. 4 is a detailed perspective view of a second embodiment of the first and second cable ends, cable terminators and the retaining clip attaching the terminators together; 
     FIG. 4A is detailed side view of an end of a first embodiment of a flexible cable; 
     FIG. 5 is a detailed perspective view of a third embodiment of the first and second cable ends, cable terminators and the retaining clip attaching the terminators together; 
     FIG. 6 is a perspective view of the mating, overlapping panels attached to the front and rear portions of the helmet; 
     FIG. 7 is a perspective view of the mating, first and second portions of the resilient, padded inner liner of the helmet; 
     FIG. 8 is a perspective view of the FIG. 1 embodiment further including a flexible inflatable collar attached to the lower surrounding edge of the front and rear portions of the shell; 
     FIG. 9 is a cutaway perspective view of the FIG. 8 embodiment illustrating the pressurization and control mechanisms for the helmet; 
     FIG. 10A is a perspective view of the FIG. 8 embodiment in conjunction with a wearer and a motorcycle illustrating the helmet proximity sensing system with the wearer properly mounted; 
     FIG. 10B is a perspective view of the FIG. 8 embodiment in conjunction with a wearer and a motorcycle illustrating the helmet proximity sensing system with the rider with the wearer dislodged so as to activate the pressurization and control mechanisms for the helmet; 
     FIG. 11 is a perspective view of the FIG. 8 embodiment illustrating the flexible cable in place in the helmet; 
     FIG. 12 is an exploded perspective view of the FIG. 8 embodiment illustrating the first and second removable access panels; 
     FIG. 12A is a side view of a first embodiment of the first access panel illustrating tensioning elements; 
     FIG. 12B is a side view of a second embodiment of the first access panel illustrating alternate tensioning elements; 
     FIG. 12C is a plan view of a first embodiment of the first access panel illustrating tensioning elements, the flexible cable and the means for retaining the second end of the flexible cable; 
     FIG. 13 is an exploded perspective view of an alternative embodiment of the invention, illustrating the first end of the flexible cable being attached to the helmet and the second end being attached to a means for applying tension to the second end; 
     FIG. 14 is a detailed perspective view of the means for attaching the first end of the cable to the helmet; 
     FIG. 14A is detailed side view of an end of a second embodiment of a flexible cable; 
     FIG. 15 is a detailed perspective view of a first alternative means for attaching the first end of the cable to the helmet; 
     FIG. 16 is a detailed perspective view of a second alternative means for attaching the first end of the cable to the helmet; 
     FIG. 17 is an perspective view of an alternative embodiment of the invention, illustrating a securing latch for attaching the front portion to the rear portion of the helmet; and 
     FIG. 18 is a detailed perspective view of the securing latch in open position as activated by the flexible cable; and 
     FIG. 19 is a detailed perspective view of the securing latch in closed position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 and 2 illustrate a helmet  10  providing the desired features that may be constructed from the following components. A rigid, outer shell  14  is provided. The outer shell  14  includes a front portion  18  and a mating rear portion  22 . Each of the front  18  and rear  22  portions have a lower surrounding edge  26 . The front portion  18  includes an opening  30  to provide forward visibility for a wearer  34 . Means  38  are provided for removably attaching the front portion  18  to the rear portion  22 . A resilient, padded inner liner  42  is provided. The liner  42  includes a first portion  46  and a mating second portion  50 . The first portion  46  is sized and shaped to fit within the front portion  18  of the outer shell  14 . The second portion  50  is sized and shaped to fit within the rear portion  22  of the outer shell  14 . Means  54  are provided for securing the helmet  10  to the head  32  of the wearer  34 . 
     In a variant of the invention, illustrated in FIG. 2, the means  38  for removably attaching the front portion  18  to the rear portion  22  further includes a series of mating orifices  58  in the front portion  18  and in the rear portion  22 . The orifices  58  are located adjacent to an intersection  62  between the front portion  18  and the rear portion  22 . A flexible cable  66  is provided. The cable  66  has a first predetermined cross-section  70 , a first end  74  and a second end  78  and is sized and shaped to fit slidably through the mating orifices  58 . The cable  66  is threaded through the mating orifices  58  and secures the front portion  18  to the rear portion  22 . Means  82  are provided for removably attaching the first end  74  to the second end  78 . Means  86  are provided for withdrawing the cable  66  from the mating orifices  58 . When the first end  74  of the cable  66  is detached from the second end  78 , the cable  66  may be withdrawn from the mating orifices  58  and the front portion  18  separated from the rear portion  22 . 
     In a further variant, illustrated in FIG. 3, the means  82  for removably attaching the first end  74  of the cable  66  to the second end  78  includes first  90  and second  94  cable terminators. Each of the cable terminators  90 ,  94  has a first end  98 , a second end  102  and a cross-section  106  no larger than the first predetermined cross-section  70 . The first cable terminator  90  is fixedly attached at its first end  98  to the first end  74  of the flexible cable  66  and the second cable terminator  94  is fixedly attached at its first end  98  to the second end  78  of the flexible cable  66 . Each of the second ends  102  of the first  90  and second  94  cable terminators includes a notch  110 . 
     A retaining clip  114  is provided. The retaining clip  114  is formed of rigid material, has a U-shaped cross-section, is sized and shaped to fit frictionally over the cable terminators  90 ,  94  and includes a pair of protruding tabs  118 . The tabs  118  are sized, shaped, and located to removably engage the notches  110  in the second ends  102  of the terminators  90 ,  94 . When the second ends  102  of the first  90  and second  94  cable terminators are placed adjacent each other and the retaining clip  114  is pressed downwardly over the terminators  90 ,  94 , with the protruding tabs  118  engaging the notches  110  in the second ends  102  of the cable terminators  90 ,  94 , the first  74  and second  78  cable ends will be removably attached. 
     In yet another variant of the invention, illustrated in FIG. 4, the means  82  for removably attaching the first end  74  of the cable  66  to the second end  78  includes first  114  and second  118  cable terminators. Each of the cable terminators  114 ,  118  has a first end  122 , a second end  126  and a cross-section  130  no larger than the first predetermined cross-section  70 . The first cable terminator  114  is fixedly attached at its first end  122  to the first end  74  of the flexible cable  66  and the second cable terminator  118  is fixedly attached at its first end  122  to the second end  78  of the flexible cable  66 . Each of the second ends  126  of the first  114  and second  118  cable terminators includes a central stem  132  and a securing portion  134  attached to the stem  132 . 
     A retaining clip  138  is provided. The retaining clip  138  is formed of rigid material, has a U-shaped cross-section, is sized and shaped to fit frictionally over the cable terminators  114 ,  118  and includes two pair of protruding tabs  142 . The tabs  142  are sized, shaped, and located to removably surround the central stems  132  of the second ends  126  of the cable terminators, drawing the securing portions  134  of the terminators together. When the second ends  126  of the first  114  and second  118  cable terminators are placed adjacent each other and the retaining clip  138  is pressed downwardly over the terminators  114 ,  118 , with the protruding tabs  142  surrounding the central stems  130  of the second ends  126  of the cable terminators  114 ,  118 , the first  74  and second  78  cable ends will be removably attached. 
     In still another variant, illustrated in FIG. 5, the means  82  for removably attaching the first end  74  of the cable  66  to the second end  78  includes an adhesive container  146 . The container  146  is sized and shaped to constrain the first end  74  of the cable  66  in close proximity to the second end  78  of the cable  66 . An adhesive  150  is provided. The adhesive  150  is poured into the adhesive container  146  and over the first  74  and second  78  ends of the cable  66  and allowed to dry. When the adhesive  150  has dried, the first  74  and second  78  ends of the cable  66  will be removably attached until sufficient tension is directed to separate the first end  74  of the cable  66  from the second end  78  of the cable  66  and the adhesive  150  fails to grip either of the first  74  and second  78  ends of the cable  66 . 
     In yet another variant of the invention, illustrated in FIG. 6, the means  38  for removably attaching the front portion  18  to the rear portion  22  includes a series of mating, overlapping panels  154 . The overlapping panels  154  are fixedly attached to the front portion  18  and the rear portion  22  adjacent the intersection  158  between the front  18  and rear  22  portions. The mating, overlapping panels  154  serve to increase structural strength of the helmet  10  and provide improved weather sealing. 
     In yet a further variant, illustrated in FIG. 7, the first  46  and mating second  50  portions of the resilient, padded inner liner  42  include mating, interlocking edges  162 , thereby providing improved weather sealing. 
     In still a further variant, illustrated in FIG. 8, the helmet  10  includes a flexible, inflatable collar  166 . The collar  166  is removably attached to the lower surrounding edge  26  of the front  18  and rear  22  portions of the rigid shell  14 . Means  170  are provided for rapidly inflating the collar  166  as are means  174  for deflating the collar  166 . When the collar  166  is inflated it will provide increased stability for a head  32  and neck  182  of the wearer  34  by bearing against shoulders  186  of the wearer  34 . 
     In another variant of the invention, illustrated in FIG. 9, the means  170  for rapidly inflating the collar  166  and the means  174  for deflating the collar  166  include a pressurized gas cylinder  190 , a control valve  194  connected to the cylinder  190  and tubing  198  connecting the control valve  194  to the inflatable collar  166 . The cylinder  190  contains sufficient gas to fully inflate the collar  166 . The control valve  194  includes a pressure relief valve  202  and is capable of maintaining pressure in the collar  166  until the relief valve  202  is activated. Means  206  are provided for activating the control valve  194 . 
     In yet another variant, illustrated in FIG. 10, the means  206  for activating the control valve  194  further includes a position sensing system  210 . The system  210  is capable of determining if a helmet wearer&#39;s vehicle  214  is in motion and a relative position of the helmet  10  with respect to the vehicle  214 . The system  210  is capable of opening the control valve  194  to inflate the collar  166  upon sensing that the wearer&#39;s vehicle  214  is in motion and the helmet  10  is not within a first predetermined distance  218  of the vehicle  214 . The head  32  and neck  182  of the helmet wearer  34  will be stabilized by the inflated collar  166  in the event the wearer  34  is separated from the vehicle  214  by the first predetermined distance  218  while the vehicle  214  is in motion. 
     In still another variant, illustrated in FIG. 1, the helmet  10  further includes means  222  for rapidly removing the flexible cable  66  to separate the front portion  18  of the helmet  10  from the rear portion  22 . 
     In a yet another variant of the invention, also illustrated in FIG. 1, the means  222  for rapidly removing the flexible cable  66  includes a first removable access panel  226 . The first access panel  226  covers the means  82  for removably attaching the first end  74  of the cable  66  to the second end  78  and a second removable access panel  230  covers a portion of the flexible cable  66  and an indentation  234  in the front portion  18  of the helmet  10 . The indentation  234  provides means  238  to apply tension to the cable  66  for its removal. 
     In a further variant, illustrated in FIG. 11, the means  38  for removably attaching the front portion  18  to the rear portion  22  of the helmet  10  further includes a series of mating orifices  58  in the front portion  18  and in the rear portion  22 . The orifices  58  are located adjacent an intersection  62  between the front portion  18  and the rear portion  22 . A flexible cable  242  is provided. The cable  242  has a first predetermined cross-section  246 , a first end  250  and a second end  254 . The cable  242  is sized and shaped to fit slidably through the mating orifices  58 . The cable  242  is threaded through the mating orifices  58  and secures the front portion  18  to the rear portion  22 . Means  258  are provided for removably attaching the first end  250  to either of the front  18  and rear  22  portions of the rigid, outer shell  14 . Means  262  are provided for applying tension to the second end  254  of the cable  242  and withdrawing the cable  242  from the mating orifices  58 . When the first end  250  of the cable  242  is detached from the shell  14 , the cable  242  may be withdrawn from the mating orifices  58  and the front portion  18  separated from the rear portion  22 . 
     In still a further variant, illustrated in FIG. 13, the means  258  for removably attaching the first end  250  of the cable  242  to rigid, outer shell  14  includes a cable terminator  266 . The cable terminator  266  has a first end  270 , a second end  274  and a cross-section  278  no larger than the first predetermined cross-section  70 . The cable terminator  266  is fixedly attached at its first end  270  to the first end  250  of the flexible cable  242 . The second end  274  of the cable terminator  266  includes a notch  282 . 
     A retaining clip  286  is provided. The retaining clip  286  has a first end  290  and a second end  294 . The retaining clip  286  is fixedly attached at its first end  290  to the rigid outer shell  14 . The retaining clip  286  is formed of rigid material, has a U-shaped cross-section, and is sized and shaped to fit frictionally about the cable terminator  266 . The retaining clip  286  includes a pair of protruding tabs  298 . The tabs  298  are sized, shaped, and located to removably engage the notch  282  in the second end  274  of the terminator  266 . When the cable terminator  266  is pressed into the second end  294  of the retaining clip  266 , with the protruding tabs  298  engaging the notch  282  in the second end  274  of the cable terminator  266 , the first end  250  of the cable  242  will be removably attached to the shell  14 . 
     In another variant of the invention, illustrated in FIG. 14, the means  258  for removably attaching the first end  250  of the cable  242  to the rigid, outer shell  14  includes a cable terminator  302 . The cable terminator  302  has a first end  306 , a second end  310  and a cross-section  314  larger than the first predetermined cross-section  70 . The cable terminator  302  is fixedly attached at its first end  306  to the first end  250  of the flexible cable  242 . The second end  310  of the cable terminator  302  includes a central stem  318  and a securing portion  322  attached to the stem  318 . 
     A retaining clip  326  is provided. The retaining clip  326  has a first end  330  and a second end  334 . The retaining clip  326  is fixedly attached at its first end  330  to the rigid outer shell  14 . The retaining clip  326  is formed of rigid material, has a U-shaped cross-section, is sized and shaped to fit frictionally about the cable terminator  302 . The retaining clip  326  includes a pair of protruding tabs  338 . The tabs  338  are sized, shaped, and located to removably surround the central stem  318  of the second end  306  of the cable terminator  302 . When the cable terminator  302  is pressed into the second end  334  of the retaining clip  326 , with the protruding tabs  338  surrounding the central stem  318  of the second end  306  of the cable terminator  302 , the first end  250  of the cable  242  will be removably attached to the shell  14 . 
     In still another variant, illustrated in FIG. 15, the means  258  for removably attaching the first end  250  of the cable  242  to the rigid, outer shell  14  includes an adhesive container  342 . The container  342  has a first end  346  and a second end  350  and is fixedly attached at its first end  346  to the rigid, outer shell  14 . The second end  350  of the container  342  is sized and shaped to constrain the first end  250  of the cable  242 . An adhesive  354  is provided. The adhesive  354  is poured into the second end  350  of the adhesive container  342  and over the first end  250  of the cable  242  and allowed to dry. When the adhesive  354  has dried, the first end  250  of the cable  242  will be removably attached to the rigid, outer shell  14  until sufficient tension is directed to the second end  254  of the cable  242  to separate the first end  250  of the cable  242  from the adhesive container  342 , thereby permitting removal of the cable  242  from the helmet  10 . 
     In yet another variant, illustrated in FIG. 17, the means  38  for removably attaching the front portion  18  of the helmet  10  to the rear portion  22  includes a series of mating orifices  358  in the front portion  18  and in the rear portion  22 . The orifices  358  are located adjacent an intersection  362  between the front portion  18  and the rear portion  22 . A flexible cable  366  is provided. The cable  366  has a first predetermined cross-section  70 , a first end  370  and a second end  374  and is sized and shaped to fit slidably through the mating orifices  358 . 
     At least one securing latch  378  is provided. The securing latch  378  has a first portion  382 , a mating second portion  386  and means  390  for removably attaching the first portion  382  to the second portion  386 , thereby securing the front portion  18  of the helmet  10  to the rear portion  22 . The first portion  382  has an inner end  394  and an outer end  398  and is fixedly attached to the front portion  18  of the shell  14 . The second portion  386  has an inner end  402  and an outer end  406  and is fixedly attached to the rear portion  22  of the shell  14 . The first  382  and second  386  portions including mating openings  410  that are collinear when the first portion  382  is located adjacent the second portion  386 . The cable  366  is threaded through the mating orifices  358  and the mating openings  410 . The cable  366  includes means  414  for unfastening the means  390  for removably attaching the first portion  382  of the securing latch  378  to the second portion  386 . 
     Means (not shown) are provided for removably attaching the first end  370  of the cable  366  to the rigid shell  14  as are means (not shown) for withdrawing the cable  366  from the mating orifices  358  and the mating openings  410 . When the first end  370  of the cable  366  is detached from the rigid shell  14 , the cable  366  may be withdrawn from the mating orifices  358  and the mating openings  410 , thereby unfastening the means  390  for removably attaching the first portion  382  of the securing latch  378  to the second portion  386  and permitting the front portion  18  of the helmet  10  to be separated from the rear portion  22 . 
     In still another variant of the invention, illustrated in FIG. 18, the means  390  for removably attaching the first portion  382  of the securing latch  378  to the second portion  386  and the means  414  for unfastening the means  390  for removably attaching the first portion  382  of the securing latch  378  to the second portion  386  includes a pivot pin  418 . The pivot pin  418  is fixedly attached to the second portion  386  between its inner end  402  and its outer end  406  perpendicular to a long axis  422  of the second portion  386 . A latching element  426  is provided. The latching element  426  has a first end  430 , a second end  434 , a first edge  438 , a second edge  442  (not shown), a top surface  446 , a bottom surface  450  and an orifice  454  extending from the first edge  438  to the second edge  442 . The latching element  426  is rotatably mounted at the orifice  454  to the pivot pin  418 . 
     A resilient engaging finger  458  is provided. The finger  458  extends downwardly from the bottom surface  450  of the latching element  426 . A receiving notch  462  is provided. The notch  462  is located in the first portion  382  between its inner end  394  and its outer end  398  so as to frictionally engage the resilient finger  458  when the latching element  426  is rotated to a first, closed position  466 . An unfastening protrusion  470  extends downwardly from the bottom surface  450  of the latching element  426  and is located to obscure a portion of the mating openings  410  when the latching element  426  is rotated to the first, closed position  466 . 
     A dislodging element  474  is provided. The dislodging element  474  has a cross-section  478  greater that the first predetermined cross-section  70 , and is capable of fitting slidably within the mating openings  410  in the securing latch  378 . The dislodging element  474  is fixedly attached to the flexible cable  366  at a point  482  where the dislodging element  474  will pass through the mating openings  410  of the securing latch  378  when the cable  366  is withdrawn from the helmet  10 . The dislodging element  474  bears upon the unfastening protrusion  470  as the cable  366  is withdrawn from the helmet  10 , thereby causing the latching element  426  to pivot upwardly to a second, open position  486  dislodging the resilient engaging finger  458  from the receiving notch  462 . This permits the first portion  382  of the securing latch  378  to be separated from the second portion  386  and the front portion  18  of the helmet  10  to be separated from the rear portion  22 . 
     In a final variant of the invention, as shown in FIG. 12, the first removable access panel  226  further includes at least one tensioning element  490 . The tensioning element  490  is attached to an underside  494  of the first access panel  226  and is sized, shaped and located to engage a portion  498  of the flexible cable  66 . The tensioning element  490  imparts tension to the cable  66  while securing the first access panel  226  to the helmet  10 . 
     The two piece helmet with optional airbag  10  has been described with reference to particular embodiments. Other modifications and enhancements can be made without departing from the spirit and scope of the claims that follow.