Patent Publication Number: US-7581500-B2

Title: Payload delivering ring airfoil projectile

Description:
FIELD OF THE INVENTION 
   The present invention relates to ring airfoil projectiles, and more particularly to an improved ring airfoil which is configured to deliver a payload. 
   BACKGROUND OF THE INVENTION 
   A need exists for a safe and effective means of delivering materials, such as suppression agents, to a remote individual. For example, it is desirable to provide a safe and effective means of delivering a suppression agent from a law enforcement officer to a criminal or terrorist, such as in the case of a mob or riot, when apprehending such individuals when fleeing, and where such individuals are engaged in a crime. 
   Of course, a variety of weapons are known which are designed to invoke lethal results. Non-lethal weapons are also known, such as tear gas grenade launchers and stun guns. In the case of stun guns, the user must be generally located within reach of the target. This increases the risk to the user and also prevents use of the gun in many instances. Tear gas grenades are not designed to deliver agent to a particular individual, but to an area. In addition, the grenades and grenade launchers are not extremely accurate over long distances. Over long distances, the grenades must be launched so that they travel a parabolic flight path. 
   Ring airfoils are known for their ability to travel long distances along a very flat and straight trajectory. For example, U.S. Pat. No. 3,982,489 to the inventor herein details a ring airfoil projectile which is useful as a non-lethal projectile. In this case, however, the energy imparted to the target (e.g. criminal) is the “payload” which is delivered by the ring airfoil. Some attempts have been made at creating a ring airfoil which is capable of delivering an agent. For example, U.S. Pat. Nos. 3,898,932 and 3,951,070 both detail ring airfoils having a hollow interior space containing a control agent. The projectile is configured to rupture at impact and deliver the control agent. 
   Unfortunately, several problems arise when considering a ring airfoil configured for payload delivery. Foremost is that introduction of the payload into the ring airfoil moves the center of gravity CG thereof. This affects the flight characteristics of the ring airfoil, generally increasing the dispersion of the ring airfoil from a straight trajectory. This is, obviously, undesirable because it decreases the likelihood that the payload will reach the intended target. 
   An improved payload delivering ring airfoil projectile is desired. 
   SUMMARY OF THE INVENTION 
   The present invention is a ring airfoil projectile. The ring airfoil projectile is preferably configured to deliver a payload to a target. The ring airfoil projectile is designed with improved flight characteristics. 
   In one embodiment, the ring airfoil projectile comprises a generally annular body which defines a central passage. The body is constructed so that a center of pressure is coincident or substantially coincident with a center of gravity thereof. In this manner, the ring airfoil projectile has no static stability or, stated another way, has neutral stability. 
   The body is preferably constructed of a nose section and tail section, the nose section comprising a material having a higher density than the material forming the tail section. In one embodiment, the nose section is constructed of rubber and the tail section is constructed of foam. 
   The nose and tail sections may be selectively connected and disconnected. In one embodiment, the nose section has a groove in a rear face thereof for accepting an outwardly extending key in a front face of the tail section. 
   The ring airfoil projectile is configured to deliver a payload to a target. In one embodiment, a plurality of cavities extend inwardly from the outer surface of the airfoil, preferably in the nose section. The cavities are spaced apart around the ring airfoil, each cavity separated from the next cavity by a dividing wall. 
   The cavities accept payload or a strip containing payload. In one embodiment, the payload is located in the cavities and then enclosed with a covering. In another embodiment, the payload is associated with a payload strip which is connected to the ring airfoil projectile. The ring airfoil projectile is preferably configured to deform upon impacting a target, thereby delivering or releasing the payload at the target. 
   In a preferred embodiment, the ring airfoil projectile is launched with spin. Preferably, the rotational velocity of the ring airfoil projectile when launched is not greater than about 0.2 of the forward velocity of the projectile. This rotational velocity imparts gyroscopic stability to the projectile during flight. 
   In one embodiment, the ring airfoil projectile is mounted to a sabot. The sabot engages rifling in a barrel of a launcher, thus imparting rotation to the sabot and the ring airfoil projectile. After the forward and rotational velocity is imparted to the sabot and ring airfoil projectile during launch, the sabot is stripped from the ring airfoil projectile, which then travels towards the intended target. 
   The configuration of the ring airfoil projectile allows the ring airfoil to carry a payload and at the same time travel with minimum path dispersion. When the ring airfoil projectile impacts the desired target, the payload is delivered to the target. 
   Further objects, features, and advantages of the present invention over the prior art will become apparent from the detailed description of the drawings which follows, when considered with the attached figures. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a ring airfoil projectile in accordance with an embodiment of the invention; 
       FIG. 2  is a cross-sectional side view of the ring airfoil projectile illustrated in  FIG. 1  taken along line  2 - 2  therein; 
       FIG. 3  is an exploded perspective view of the ring airfoil projectile illustrated in  FIG. 1  showing a nose and tail section thereof separated from one another; 
       FIG. 4  is a perspective view of the tail section of the ring airfoil projectile seen from the opposing side than as shown in  FIG. 3 ; 
       FIG. 5  is a partial cross-sectional side view of a ring airfoil projectile containing a payload in accordance with the invention; 
       FIG. 6  is a perspective view of a payload strip for loading to a ring airfoil projectile in accordance with another embodiment of the invention; and 
       FIG. 7  is a partial cross-sectional side view of a ring airfoil as illustrated in  FIG. 5  being filled with agent. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention is a ring airfoil projectile. In the following description, numerous specific details are set forth in order to provide a more thorough description of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without these specific details. In other instances, well-known features have not been described in detail so as not to obscure the invention. 
   In general, the invention is a ring airfoil projectile. The ring airfoil projectile is preferably constructed to deliver a payload such as a suppression agent. Further, the ring airfoil projectile is configured with improved flight characteristics, with a center of gravity CG and center of pressure CP thereof are substantially coincident. In a preferred embodiment, the ring airfoil projectile is of a two-piece construction, a fore or nose section of the ring airfoil constructed from a material having a substantially higher density than a material used to construct a tail or aft section of the ring airfoil. 
   A preferred embodiment of the invention will be described with reference to  FIGS. 1-4 .  FIG. 1  illustrates a ring airfoil projectile (RAP)  20 . The ring airfoil projectile  20  has a front or nose  22  and a rear or tail  24 . Referring to  FIG. 2 , the ring airfoil projectile  20  defines a central passage  26  through which air flows in the direction of the front  22  to the rear  24  when the ring airfoil projectile  20  is traveling. 
   The ring airfoil projectile  20  is defined by a body. As is known in the art, the body comprises a generally annular or ring-shaped element. In a preferred embodiment, the body comprises a forward, nose or front section  28  and a rear, tail or aft section  30 . 
   In a preferred embodiment, the nose section  28  of the ring airfoil projectile  20  is configured to deliver a payload. Referring to  FIG. 3 , the nose section  28  of the ring airfoil projectile  20  defines the nose  22  of the ring airfoil projectile  20  and has an opposing rear face  34 . The nose section  28  has an outer surface  36  and an inner surface  38 . As illustrated, the nose section  28  is generally circular in shape and hollow, with the inner surface  38  defining a portion of the central passage  26  through the ring airfoil projectile  20 . 
   In one embodiment, a plurality of depressions or cavities  40  are formed in and extend inwardly from the outer surface  36  of the nose section  28  between the nose  22  and rear face  34 . In one embodiment, each cavity  40  comprises a somewhat cube-shaped area in the nose section  28 . As illustrated, the cavities  40  are located in annular fashion around the nose section  28 , the cavities  40  separated from one another by dividing walls  42 . The number of cavities  40  may vary. There may be as few as one cavity, and that cavity may extend as a slot or trough entirely around the nose section  28 . There may also be a plurality of cavities  40 , as illustrated. 
   As described in more detail below, the depressions or cavities  40  in the nose section  28  are preferably configured to hold a payload of material to be delivered by the ring airfoil projectile  20 . For this reason, the cavities  40  are preferably arranged symmetrically about the nose section  28  so that when filled with payload, the mass of the payload does not affect the flight characteristics of the airfoil, including the spin thereof. 
     FIGS. 3 and 4  illustrate a tail section  30  of the ring airfoil projectile  20 . As illustrated, the tail section  30  has a front face  50  and defines the rear edge  24  of the ring airfoil projectile  20 . The tail section  30  has an outer surface  52  and an inner surface  54 . The tail section  30  is again generally circular in shape, with the inner surface  54  thereof defining a portion of the central passage  26  through the ring airfoil projectile  20 . 
   Referring primarily to  FIG. 2 , the nose section  28  and tail section  30  of the ring airfoil projectile  20  preferably contribute to an overall ring airfoil “wing” shape. In particular, the nose section  28  defines a generally rounded nose  22  leading to an area of increased body thickness towards the rear face  34  thereof. The tail section  30  has an area of increased thickness at the front face  50 , and tapers towards the tail  24  of the ring airfoil projectile  20 . Preferably, the thickness of the tail section  30  at its front face  54  and the thickness of the nose section  28  at its rear face  34  are the same, so that the two sections define a generally smooth inner and outer surface of the ring airfoil projectile  20 , at their interface, as illustrated in  FIG. 2 . 
   The nose section  28  and tail section  30  as illustrated are configured to meet at a plane which is substantially perpendicular to a centerline through the ring airfoil projectile  20 . The nose section  28  and tail section  30  may have other configurations. For example, the rear face  34  of the nose section  28  and the front face  50  of the tail section  30  may be slanted, meeting along a plane which extends at an angle between 0 and 90 degrees from a horizontal plane containing the centerline. Of course, the particular aerodynamic shape of the ring airfoil projectile  20  may vary depending upon desired characteristics. 
   Means are provided for selectively connecting the nose section  28  and tail section  30  of the ring airfoil projectile  20 . In one embodiment, this means is a mechanical interlocking mechanism. Referring to  FIG. 3 , the rear face  34  of the nose section of the ring airfoil projectile  20  includes a slot or groove  60 . In one embodiment, the slot  60  has a generally square or rectangular cross-sectional shape, and extends completely around the rear face  34 . 
   The front face  50  of the tail section  30  includes a corresponding raised key  62 . This key  62  is located and shaped to mate with the slot  60  in the rear face  34  of the nose section  28  when the nose section  28  and tail section  30  are connected to one another. 
   In one embodiment, the key  62  engages the slot  60  in a mechanical locking arrangement, this interlocking maintaining the nose section  28  connected to the tail section  30 . The key  62  may include one or more tabs  64  for engaging one or more insets  66  for aligning the nose section  28  with the tail section  30  in a particular position or orientation. Alternatively, the tabs  62  and insets  66  may be configured to permit a mechanical interlock where the tabs  62  are rotated into a locking position with the insets  66 . 
   In one embodiment, the nose section  28  and tail section  30  may be additionally secured to one another with additional or by other means, such as a chemical bond. For example, adhesive may be utilized to bond the key  62  into the slot  60 . Other mechanical locking configurations are also contemplated. For example, the slot and key may be shaped in other fashions. Pins may extend outwardly from the tail section  30  for engagement with mating apertures in the nose section  28 . The tail section  30  could also be heat bonded to the nose section  28 . 
   Importantly, in accordance with the present invention, the ring airfoil projectile  20  is constructed so that its center of gravity CG coincides or is located proximate to, its center of pressure CP. In one embodiment, this is accomplished by controlling the mass of the nose section  28  and tail section  30 . In a preferred embodiment, this is accomplished by the selection of materials used to form those sections, the materials having different densities. With the center of gravity CG substantially coincident with the center of pressure CP, the ring airfoil projectile  20  has static stability, or stability which is “neutral.” Preferably, the projectile  20  is configured so that the center of gravity CG and center of pressure CP are substantially coincident when considering a payload which the ring airfoil projectile  20  is to carry. 
   In a preferred embodiment, the nose section  28  is constructed of a material having a higher density than that of the tail section  30 . Preferably, the materials which are used are also selected to meet additional criteria. In particular, because the ring airfoil projectile  20  is configured to deliver a chemical payload, it is desired that the ring airfoil projectile  20  not contain any metal. Second, because the ring airfoil projectile  20  is preferably configured to impact a human target in a manner minimizing injury, it is desired that the ring airfoil projectile  20  not be constructed of a material which is unyielding and would thus concentrate the impact force and/or pierce the target. In a preferred embodiment, the nose section  28  is thus constructed of a rubber material. More preferably, the rubber material has a durometer value of around  30 . In a preferred embodiment, the tail section  30  comprises inert, low density foam, such as polyethylene or polystyrene. The use of rubber for the nose section  28  has the advantage that the nose section  28  will deform so that the impact surface area of the airfoil  20  enlarges when the nose section  28  impacts a target. This spreads the impact force over a larger area, reducing harm or injury. The use of foam material for the tail section  30  has the advantage that the material is lightweight and useful in moving the center of gravity CG of the ring airfoil projectile  20  forward. 
   The center of pressure CP of the ring airfoil projectile  20  depends on the shape or aerodynamic profile of the ring airfoil projectile  20 . Thus, the densities (and thus total mass) of the nose section  28  and tail section  30  may need to be adjusted so that the center of gravity CG coincides with the center of pressure CP when the shape of the ring airfoil projectile  20  differs. For example, if the center of pressure CP is farther forward, it may be necessary to substantially lighten the mass of the tail section  30  to correspondingly move the center of gravity CG forward. In one embodiment, this may be done by forming the tail section  30  with “lightening” holes  59  (as illustrated in  FIG. 2 ). These holes comprise voids in the tail section  30 , reducing its mass. 
   As indicated above, the ring airfoil projectile  20  is preferably configured to deliver a payload of material to an intended target. In one embodiment, as illustrated in  FIG. 7 , payload material  70  may be located in the cavities  40 . The payload material  70  is then preferably enclosed with a covering  74 , such as illustrated in  FIG. 5 . The covering  74  may be a strip which extends entirely around the ring airfoil projectile  20  and covers all of the cavities, or individual coverings may be configured to cover each cavity. In either case, the covering  74  is preferably configured to tear, release or open when the ring airfoil projectile  20  impacts a target (but not during normal transport, loading, storage and handling), thus allowing the payload material  70  to escape. 
   In a preferred embodiment, the ring airfoil projectile  20  is configured to accommodate the covering  74 , whether comprising a simple cover or as part of a payload strip  72  including payload containing elements  75 , while retaining a smooth and continuous exterior aerodynamic profile. As best illustrated in  FIGS. 1 and 2 , the nose section  28  has a step  58   a  associated with a change in thickness or outer dimension of the nose section. Likewise, the tail section  30  has a similar step  58   b  associated with a change in thickness or outer dimension of the tail section  30 . As illustrated, these steps  58   a,    58   b  face one another, thereby defining an inset  57  in the outer surface of the ring airfoil projectile  20 . 
   Referring to  FIG. 5 , this inset  57  is designed to accommodate the covering  74 . Preferably, the inset  57  has a depth which is generally the same as the thickness of the covering  74 , such that when the covering is mounted to the ring airfoil projectile  20 , the combination thereof defines a smooth outer surface of the projectile  20 . In addition, the covering  74  preferably has a width which is equal to the distance between the two steps  58   a,    58   b,  whereby it substantially fills the inset  57 . 
   In one embodiment, the covering  74  may be of a lightweight, low shear material such as a paper covering. In order to increase the probability of rupture of the covering  74 , the covering may include one or more stress risers or areas of reduced shear and/or tensile strength, such as in the case of perforations (not shown) formed therein. Concentrated force upon these stress risers or areas of reduced strength cause the covering to rupture upon impact. 
   As illustrated in  FIG. 6 , the payload  70  may instead be associated with a payload strip  72 . The payload strip  72  preferably comprises a cover or supporting strip  74 , and a number of payload containing areas  75  corresponding to the cavities  40  in the ring airfoil projectile  20  into which they are inserted. In this configuration, the payload strip  72  may be pre-manufactured and then conveniently associated with any of a variety of ring airfoil projectiles in accordance with the invention. In one embodiment, the payload strip  72  is preferably again configured to rupture when the ring airfoil projectile impacts its target. In addition, the payload strip  72  may be secured to the ring airfoil projectile  20 , such as with adhesive or the like, to ensure that it does not become disassociated with the ring airfoil projectile during its flight. Further, the cover  74  portion of the strip  72  preferably engages the insert  57  as illustrated in  FIG. 5 . 
   The payload carried by the ring airfoil projectile  20  of the invention may comprise any of a variety of materials or agents. The agents may have a variety of chemical compositions and may be liquid, powder or of other forms. 
   In use, the ring airfoil projectile is launched from a launcher. Various types of launchers may be used to launch the ring airfoil projectile. In one embodiment, the ring airfoil projectile is mounted to a sabot (not shown). The sabot protects the ring airfoil projectile during launching. 
   Preferably, the sabot, and thus the associated ring airfoil projectile  20 , are launched with a spin. Most preferably, the ring airfoil projectile  20  is launched with a rotational velocity, that velocity not greater than about 0.2 of the forward velocity. Spin may be imparted by launching the sabot and associated ring airfoil projectile  20  through a barrel of a launcher, the barrel having internal rifling. After launched by a launcher, the sabot is preferably stripped from the airfoil projectile, which travels forward while spinning. 
   It is desired that the ring airfoil projectile  20  have sufficient structure integrity that it is not damaged when launched or during flight, and yet breaks up upon impact to deliver the payload. Launching with a sabot has the advantage that the rifling in the barrel does not mar the ring airfoil projectile, thus degrading its aerodynamic characteristics. In addition, the sabot protects the ring airfoil projectile from damage from the explosive charge or other means used to launch the projectile. 
   In the preferred embodiment, as stated above, the ring airfoil projectile has static stability. Gyroscopic stability is imparted via the rotation of the ring airfoil projectile. As such, if the ring airfoil projectile is launched without disruption (i.e. wobble or shake such as due to movement of the launcher), the ring airfoil projectile will travel with minimum dispersion (i.e. will not deviate from its intended straight path). In particular, the spin and the coincidence of the center of pressure CP and center of gravity CG of the airfoil contribute to its stability. 
   When the ring airfoil projectile reaches its intended target, the ring airfoil projectile impacts the target. Advantageously, the ring airfoil projectile deforms upon impact. As indicated above, this increases the impact surface area and thus spreads the force over a wider area. At the same time, the payload  70  is released. The combination of spin and forward momentum causes the payload  70  to be dispersed and move towards the target. Among other things, the spinning of the ring airfoil projectile results in a centrifugal force which causes the released payload to be dispersed radially outward. At the same time, the forward velocity causes the dispersed material to continue traveling forward to the target. 
   The ring airfoil projectile of the invention has numerous advantages. As indicated above, the ring airfoil projectile has a center of pressure CP and center of gravity CG which are coincident or nearly coincident, contributing to the stability of the ring airfoil projectile in flight. This enables the ring airfoil projectile to travel with minimal dispersion, increasing the probability that the intended target will be hit. 
   In accordance with the invention, the multi-part construction of the ring airfoil projectile allows the ring airfoil projectile to be custom configured. As indicated, different aerodynamic shapes may be utilized. At the same time, however, changes may be made to sections of the ring airfoil projectile to then ensure that the center of pressure and center or gravity for those different designs to be coincident. 
   Another advantage is that the ring airfoil projectile may deliver a payload. The ring airfoil projectile is configured to deliver a significant amount of payload. The particular payload configuration of the ring airfoil projectile of the invention has several advantages. One advantage is that the ring airfoil projectile is configured to deliver payload while maintaining its stable flight characteristics and without compromising structural integrity. Some hollow ring airfoil projectiles have been developed in the past. These designs have the disadvantage that the body thickness of the projectile is substantially reduced, allowing the projectile to deform in flight and suffer from other problems associated with its lack of structural integrity. Further, these configures are more difficult to use, in the sense that the payload must be contained entirely within the enclosed airfoil, substantially complicating manufacturing. 
   The ring airfoil projectile  20  may be constructed in other fashions and still be configured both so that the center of gravity CG and the center of pressure CP are nearly coincident and, if desired, so that the ring airfoil projectile  20  can deliver a payload. For example, the ring airfoil projectile may have more than two sections, such as three or more. It is also possible for the ring airfoil projectile to comprise one body, but have that body comprise two or more different materials. For example, the body might be molded as a single element comprising two different materials. 
   The ring airfoil projectile  20  may also be configured to fragment or break apart when impacting a target, thereby releasing the payload. 
   It will be understood that the above described arrangements of apparatus and the method therefrom are merely illustrative of applications of the principles of this invention and many other embodiments and modifications may be made without departing from the spirit and scope of the invention as defined in the claims.