Abstract:
An apparatus for dissipating shock load in a parachute delivery system has at least one strip of material having a first end, a second end opposite the first end, and a predetermined length. The apparatus also has a piercing member having a first portion for piercing through the strip of material and a second portion that defines an opening. The strip of material passes through the opening in the piercing member. The first end of the strip of material is configured to be attached to parachute suspension lines. In a preferred embodiment, the strip of material is a strip of woven webbing. When a predetermined tensile force acts upon the strip of material and the piercing member such that the first end of the strip of woven webbing is pulled in one direction and the piercing member is pulled in an opposite direction, tension is produced which causes the piercing member to stretch and break the lateral fibers of the strip of woven webbing. In one embodiment, the apparatus includes a lanyard that has a first end attached to the piercing member and a second end adapted for attachment to a payload.

Description:
STATEMENT OF GOVERNMENT INTEREST 
   The invention described herein may be manufactured and used by the U.S. Government for Governmental purposes without the payment of any royalties thereon. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to an apparatus for dissipating the shock and related forces that occur during parachute opening. 
   2. Description of the Related Art 
   When a parachute completely opens during descent, shock loads are produced due to the weight of the payload attached to the suspension lines of the parachute. If large enough, such shock loads can rip or tear the parachute or parts thereof causing a catastrophic failure of the parachute system. Furthermore, if the payload consists of a person, that person could suffer severe injuries as a result of relatively large shock loads. 
   What is needed is an apparatus for use with a parachute that can safely dissipate the energy of a shock load that occurs when the parachute opens. 
   SUMMARY OF THE INVENTION 
   In one aspect, the present invention is directed to an apparatus for providing a velocity differential between a parachute and a payload to reduce shock load. In one embodiment, apparatus comprises at least one strip of material having a first end, a second end opposite the first end, and a predetermined length. The apparatus further comprises a piercing member having a first portion for piercing the strip of material and a second portion that defines an opening. The strip of material passes through the opening in the piercing member. The apparatus further comprises a device adapted for attaching the first end of the strip of material to the parachute suspension lines. When a predetermined tensile force acts upon the strip of material and the piercing member such that the first end of the strip of material is pulled in one direction and the piercing member is pulled in an opposite direction, tension is produced which causes the piercing member to longitudinally tear through at least a portion of the predetermined length of the strip of material. 
   In a related aspect, the present invention is directed to an apparatus for providing a velocity differential between a parachute and a payload to reduce shock load. In one embodiment, apparatus comprises at least one strip of material having a first end, a second end opposite the first end, and a predetermined length. The apparatus further comprises a piercing member having a first portion that is pierced through the strip of material and a second portion that defines an opening. The strip of material passes through the opening in the piercing member. The apparatus further comprises a device adapted for attaching the first end of the strip of material to the parachute suspension lines. When a predetermined tensile force acts upon the strip of material and the piercing member such that the first end of the strip of material is pulled in one direction and the piercing member is pulled in an opposite direction, tension is produced which causes the piercing member to longitudinally tear through at least a portion of the predetermined length of the strip of material. 
   In another aspect, the present invention is directed to a parachute delivery system, comprising a parachute having a canopy, suspension lines that extend from the canopy, and at least one strip of woven webbing. The strip of woven webbing has a first end, a second end opposite the first end, a predetermined length, a plurality of lateral fibers throughout substantially the entire length of the strip of woven webbing, and a plurality of longitudinal fibers extending for substantially the entire predetermined length of the strip of woven webbing. The parachute delivery system further comprises a device for attaching the first end of the strip of woven webbing to the parachute suspension lines. The parachute delivery system further comprises a piercing member which has a first portion that is pierced through the strip of woven webbing and a second portion that defines an opening. The strip of woven webbing passes through the opening in the piercing member. The parachute delivery system includes a lanyard having a first end attached to the piercing member and a second end adapted for attachment to a payload. When a predetermined tensile force acts upon the strip of woven webbing and the piercing member such that the first end of the strip of woven webbing is pulled in one direction and the piercing member is pulled in an opposite direction, tension is produced which causes the piercing member to stretch and break the lateral fibers of the strip of woven webbing. 
   Other objects, features and advantages of the present invention will be apparent from the ensuing description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing features of the present invention will become more readily apparent and may be understood by referring to the following detailed description of an illustrative embodiment of the present invention, taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a side elevational view of a parachute delivery system that uses the apparatus of the present invention; 
       FIG. 2A  is a view of the apparatus of the present invention taken along line  2 A- 2 A in  FIG. 1 ; 
       FIG. 2B  is a partial, front view of the apparatus of the invention, similar to the view of  FIG. 2A , showing the piercing member tearing the latitudinal fibers of the strip of woven webbing; 
       FIG. 3  is a side elevational view of a parachute delivery system that uses an alternate embodiment of the apparatus of the present invention; and 
       FIG. 4  is a side elevational view of a parachute delivery system that uses a further embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , there is shown parachute delivery system  10  which utilizes apparatus  11  of the present invention. Parachute delivery system  10  includes canopy  12  and suspension lines  14 . The function of parachute delivery system  10  is to safely deliver payload or cargo  16 . Apparatus  11  generally comprises strip of material  20 , piercing member  22  and ring or loop  24 . In one embodiment, piercing member  22  comprises a rip hook. Strip of material  20  has an upper portion  20 A and lower portion  20 B. Strip of material  20  and suspension lines  14  are attached to ring or loop  24 . In one embodiment, ring  24  is fabricated from metal. In another embodiment, ring or loop  24  is fabricated from the same material used to fabricate suspension lines  14 . Other suitable devices can be used to attach strip of material  20  to suspension lines. 
   Referring to  FIGS. 1 and 2A , piercing member  22  has top portion  26  and bottom portion  28 . Bottom portion  28  defines through-hole  30  through which strip of material  20  passes. In a preferred embodiment, top portion  26  is pierced into a starter-hole (not shown) in strip of material  20  during the assembly of apparatus  11 . Piercing the strip of material  20  with top portion  26  increases the size of the starter-hole so as to form relatively larger opening  32 . 
   Referring to  FIG. 1 , apparatus  11  includes lanyard  40  that has one end attached to piercing member  22 . Piercing member  22  includes through-hole  42  through which lanyard  40  passes. Lanyard  40  has an opposite end that is attached to ring or loop  43 . Tie lines  44  are attached to and between ring or loop  43  and payload  16 . In an alternate embodiment, other suitable devices can be used to implement the function of lanyard  40 . 
   Referring to  FIGS. 2A and 2B , strip of material  20  is preferably fabricated from fibers or fill yarns of woven webbing. For purposes of example, the ensuing description is in terms of strip of material  20  being configured as a strip of woven webbing. Specifically, the strip of woven webbing has latitudinal or lateral fibers  50  and longitudinal fibers  60 . For purposes of simplicity, fibers  50  and  60  are partially shown in  FIGS. 2A and 2B . When parachute delivery system  10  and payload  16  are released or dropped from an aircraft, parachute delivery system  10  accelerates due to gravity. Upon initial disreefing, the inflation of the parachute canopy  12  and the accelerating payload  16  cooperate to produce a tensile force on apparatus  11 . Specifically, the gravitational force produced by payload  16  causes a downward force, and the disreefing of the canopy  12  causes an opposite, upward force. Thus, device  24  is pulled upward in one direction and piercing member  22  is pulled downward in an opposite direction. This tensile force causes top portion  26  of piercing member  22  to begin ripping or breaking the lateral fill yarns or fibers  50  of strip of woven webbing  20  causing slit  70 . This ripping or breaking process continues as piercing member  22  moves downward along the length of strip of woven webbing  20 . As a result of the aforesaid ripping or breaking process, opening  32  in strip of woven webbing  20  (see  FIG. 2A ) merges into slit  70  (see  FIG. 2B ). The passage of strip of woven webbing  20  through opening  30  in bottom portion  28  of piercing member  22  controls and insures continuous breaking or ripping of the lateral fill yarns  50  in strip of woven webbing  20 . As piercing member  22  moves downward upon the strip of woven webbing  20 , the energy of falling payload  16  is dissipated through the heat and drag produced by piercing member  22 . As a result, falling payload  16  decelerates without a single shock or repeated shocks to payload  16 . 
   The actual length of the strip of woven webbing  20  depends on the deceleration force produced by its fill yarns and/or the strength of the individual fill yarns. In order to reduce the length of the strip of woven webbing  20  and yet produce a relatively larger deceleration force, woven webbing  20  is fabricated from relatively higher strength woven webbing. 
   In an alternate embodiment, strip of material  20  comprises a woven tape. Other suitable materials can be used to realize strip of material  20 . 
   In an alternate embodiment, parachute delivery system  10  further includes stop line  80  which controls the distance piercing member  22  moves along strip of woven webbing  20 . Stop line  80  is attached to and between rings  24  and  42 . The length of stop line  80  is shorter than the length of the strip of woven webbing  20  so as to prevent piercing member  22  from completely tearing or ripping its way through the entire length of strip of woven webbing  20 . Thus, when all shock load energy is dissipated, payload  16  is actually carried by stop line  80  and the remaining portion of the strip of woven webbing  20  that was not ripped by piercing member  22 . 
   Although the foregoing description is in terms of apparatus  11  being configured so that top portion  26  of piercing member  22  is pre-pierced through strip of material  20 , it is to be understood that apparatus  11  can be configured so that top portion  26  is not pre-pierced through strip of material  20 . In such a configuration, the user of the parachute system will pierce strip of material  20  with top portion  26  during the process of packing the parachute system. 
   Referring to  FIG. 3 , there is shown parachute system  100  that uses apparatus  102  in accordance with another embodiment of the present invention. Parachute delivery system  100  comprises canopy  104  and suspension lines  106 . Apparatus  102  generally comprises strips of material  108  and  110  that are attached together in an overlapping relationship. Strips of material  108  and  110  are attached to suspension lines  106  via ring or loop  111 . In a preferred embodiment, strips of material  108  and  110  are fabricated from woven webbing as described in the foregoing description. In one embodiment, strips of material  108  and  110  are stitched together. However, other suitable techniques may be used to attach strips of woven webbing material  108  and  110  together. Apparatus  102  further comprises piercing member  112 . Piercing member  112  has generally the same structure as piercing member  22  (see  FIGS. 1 ,  2 A and  2 B) and generally functions in the same manner as piercing member  22 . Piercing member  112  has an opening (not shown) that is similar to opening  30  in piercing member  22  (see  FIG. 2A ) through which both strips of woven webbing  108  and  110  pass. Piercing member  112  is pierced through both strips of woven webbing  108  and  110 . Apparatus  100  also includes lanyard  114  that has one end attached to piercing member  112  and an opposite end attached to load  120 . Specifically, one end of lanyard  114  passes through through-hole  130  in piercing member  112 . The other end of lanyard  114  is attached to ring or loop  116 . Tie lines  118  are attached to and between ring or loop  116  and payload  120 . Since two strips of material  108  and  110  are used, the length of the strips of material  108  and  110  do not have to be long as the length of strip of material  20  shown in  FIG. 1 . Deceleration begins when piercing member  112  and lanyard  114  are placed in tension by parachute canopy  104  and accelerating load  120 . Specifically, piercing member  112  begins ripping or breaking the horizontal or lateral fill yarns of strips of woven webbing  108  and  110 . This ripping or breaking process continues as piercing member  112  moves downward along the length of strips of woven webbing material  108  and  110 . As piercing member  112  moves downward, the energy of falling load  120  is dissipated through the heat and drag produced by piercing member  112  as it tears its way through strips of woven webbing  108  and  110 . As a result, falling load  120  decelerates without a single shock or repeated shocks to load  120 . The rate of dissipation of the energy depends upon the particular structure and strength of each strip of woven webbing  108  and  110 . 
   Referring to  FIG. 4 , there is shown a further embodiment of the present invention. Parachute delivery system  200  uses apparatus  202  in accordance with a further embodiment of the present invention. Parachute delivery system  200  includes canopy  204  and suspension lines  206 . In accordance with this embodiment, apparatus  202  functions to force payload  210  to maintain specific velocity decay. Apparatus  202  generally comprises strips of material  212 ,  214  and  216  that are attached together and arranged in a layered relationship. Strips of material  212 ,  214  and  216  are attached together. In one embodiment, stitching is used to attach strips of material  212 ,  214  and  216  together. However, other suitable techniques can be used to attach strips of material  212 ,  214  and  216  together. Strips of material  212 ,  214  and  216  have progressively longer lengths. For example, the length of strip of material  212  is less than the length of strip of material  214  and the length of the strip of material  214  is less than the strip of material  216 . The upper ends of strips of material  212 ,  214  and  216  are attached to parachute suspension lines  206  via ring or loop  215 . In a preferred embodiment, each strip of material  212 ,  214  and  216  are fabricated from woven webbing as described in the foregoing description. Apparatus  202  further comprises piercing member  220 . Piercing member  220  has the same structure as piercing member  22  (see  FIGS. 1 ,  2 A and  2 B) and generally functions in the same manner as piercing member  22 . Piercing member  220  has an opening (not shown) that is similar to opening  30  in piercing member  22  (see  FIG. 2A ) through which all strips of woven webbing  212 ,  214  and  216  pass. Piercing member  220  is pierced through all three strips of woven webbing material  212 ,  214  and  216 . Apparatus  200  also includes lanyard  222 . Lanyard  222  has one end attached to piercing member  220  at through-hole  224 . Lanyard  222  has an opposite end attached to payload  210  via ring or loop  230 . Tie lines  232  are attached to and between ring or loop  230  and payload  210 . Deceleration begins when piercing member  220  and lanyard  222  are placed in tension by accelerating payload  210 . Specifically, piercing member  220  begins ripping or breaking the horizontal or lateral fill yarns of strips of woven webbing  212 ,  214  and  216 . This ripping or breaking process continues as piercing member  220  moves downward along the length of strips of woven webbing  212 ,  214  and  216 . As piercing member  220  moves downward, the energy of falling payload  210  is dissipated through the heat and drag produced by piercing member  220 . As a result, falling payload  210  decelerates without a single shock or repeated shocks thereto. The rate of dissipation of the aforesaid energy depends upon the particular structure and strength of the strips of woven webbing  212 ,  214  and  216 . 
   In an alternate embodiment, connecting devices such as rings or loops  24 ,  111  and  215  are not used. Instead, the end or ends of the strips of woven webbing are knotted to the parachute suspension lines. 
   A plurality of apparatuses  11 ,  102  or  202  may be used if a parachute delivery system is to deliver a very heavy load. For example, a pair of apparatuses  11  may be used in parallel in order to provide a velocity differential between the parachute and a heavy payload in order to substantially dissipate or minimize the effects of shock load. 
   Thus, the apparatus of the present invention safely provides a velocity differential between a parachute and a payload so as to substantially dissipate or minimize the effects of shock load. 
   Although the present invention has been described as being configured for use in a parachute delivery system, it is to be understood that the apparatus of the present invention can be used in other systems or situations wherein a payload is dropped or released from an elevation and shock load dissipation is needed. 
   The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein should not, however, be construed as limited to the particular forms disclosed, as these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the spirit of the invention. Accordingly, the foregoing detailed description should be considered as exemplary in nature and not limiting the scope and spirit of the invention as set forth in the attached claims.