Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41J—TARGETS; TARGET RANGES; BULLET CATCHERS
  • F41J5/00—Target indicating systems; Target-hit or score detecting systems
  • F41J5/06—Acoustic hit-indicating systems, i.e. detecting of shock waves

Definitions

• the present invention relates to a target of the type having an acoustic chamber within which microphones are arranged to receive the soundwaves generated by a fired projectile entering said chamber, the microphones being connected to means adapted to establish the hit position of the projectile on the basis of differences in the transit time of the soundwaves to said micro ⁇ phones.
• Fig. 1 is a front view of a known target
• Fig. 2 is an enlarged' sectional view of the lower part of this target.
• the known target has a front sheet 1 of rubber or plastics material so designed that the sheet 1 will not be torn open or become frayed when pierced by a projectile, but will close up again after each piercing.
• the target also has a rear sheet 2 of the same material as the front sheet 1.
• the sheets 1 and 2 which are im- permeable to sound, are stretched over a circumferential frame 3 defining, together with said sheets 1 and 2, an acoustic chamber 4.
• four microphones 5 are arranged to receive the sound ⁇ waves generated by a fired projectile entering said chamber 4.
• the propagation of these soundwaves in the chamber 4 is circular, the projectile being the centre.
• the microphones 5 are connected to means (not shown) adapted to establish the hit position of the projectile on the basis of differences in the transit time of the soundwaves to the four microphones.
• thin plastics films are provided on either side of the target to protect the sheets 1 and 2 against sunlight.
• Fig. 2 shows a projectile 6 fired at the target and its trajectory 7.
• the projectile 6 which is shown at the moment when its point enters the chamber 4, is here as ⁇ sumed to travel at supersonic velocity, and the soundwaves emanating from the point of the projectile therefore pro- pagate towards the target in the form of a cone whose front has been designated 8 and which has a cone angle 2 ⁇ .
• These external soundwaves do not enter the chamber 4 since they are stopped by the sheet 1 which is impermeable to sound.
• the propagation of the soundwaves generated by the projectile 6 is circular in the chamber 4, the projectile being the centre.
• These internal soundwaves reach the four microphones 5 at different times depending upon the hit position of the projectile, i.e.
• the hit position of the projectile is established by the above-mentioned means (not shown) to which the microphones 5 are connected.
• the established hit position is recorded, and the marksman is provided with an indication thereof on a screen or strip.
• the sheet 1 is of such a character that it closes up again each time it has been pierced by a projectile. This applies to pointed projec- tiles.
• a novel type of projectile or bullet has been introduced, especially in sport shooting, and this projectile has no point.
• This novel projectile or bullet which is called hollow-point ammunition, is provided in its front end with a concave hollow and punches a lasting hole in the sheet 1 during its passage therethrough. As a result of such holes, the sheet 1 can no longer be regarded as impermeable to sound and therefore may give rise to inaccurate hit position recordings.
• a target which is of the type mentioned by way of introduction and which is char ⁇ acterised in that the acoustic chamber is defined for- wardly by a sound-delaying wall of such thickness that the soundwaves generated by the projectile and passing through the wall will reach each optional point on the inner side of the wall, and thus each microphone, later than the soundwaves generated by the projectile as it enters the chamber, and this also when the said point is located in a hole previously punched into the wall.
• the wall is built up of small closed cells, preferably of plastics material.
• the wall has two surface layers defining between themselves a space which is filled with free cells.
• the wall is a panel consisting of cells bonded to one another.
• Fig. 1 is a front view of the above-mentioned known target.
• Fig. 2 is an enlarged sectional view of the lower part of this target.
• Fig. 3 shows a part section of a first embodiment of the target according to the present invention.
• Fig. 4 shows a part section of a second embodiment of the target according to the present invention.
• Figs. 5 and 6 are enlarged views of a portion V and VI, respectively, of the part sections in Figs. 3 and 4.
• the target shown in Fig. 3 has a front sheet 1 and a rear sheet 2 which may be of the same type as the front sheet 1 and the rear sheet 2 in the target shown in Figs. 1 and 2.
• the front sheet 1 also here is of such a character that it cannot be torn open or become frayed as a result of being pierced by pointed projectiles, but will close up again after it has been hit by a pro ⁇ jectile. Furthermore, it is impermeable to sound.
• each of the sheets 1 and 2 there is provided in this embodiment a further sheet la and 2a, respectively, the front sheet la preferably being of the same type as the sheets mentioned before, whereas the rear sheet 2a may be a plastics film protecting the sheet 2 against sunlight.
• an acoustic chamber 4 is defined, the lower part of which accommodates four microphones 5 in the same manner as in the target according to Figs. 1 and 2.
• the space between the sheets 1 and la is filled with small light-weight plastics cells 10 having a diameter which is at least equal to the diameter of the remaining bullet holes in the sheets and amounts to 2-3 mm.
• plastics cells which are tight so as not to absorb moisture and which preferably are filled with air, are not bonded to one another but may, as far as space is available, be entirely freely movable relative to one another.
• This filling of plastics cells forms a wall in which soundwaves penetrating thereinto will obtain, because of the cell structure, a far longer transit path. It will be appreciated, upon comparison with the prior art target shown in Fig.
• Fig. 4 distinguishes from the target of Fig. 3 merely in that the wall formed by the plastics film la, the cells 10 and the sheet 1 has been replaced by a panel 12 consisting of cells bonded to one another and preferably prepared from the polyethylene cellular plastics material which is being marketed by Dynamit Nobel AG, Troisdorf, Federal Republic of Germany, under the trade name TROCELLEN.
• the panel 12 has similar sound-delaying characteristics as the wall 10 of plastics cells, but distinguishes therefrom in that the cells bonded to one another are unable completely to fill up a hole produced by, for example, hollow-point ammunition.
• the cell material has been shown to form channels having extremely "fluffy” or uneven walls, as will appear from Fig. 6, and this means that these channels per se provide a sound-damping and sound-delaying effect.
• the panel 12 has a thickness such that the total path of the "external" soundwaves, which here naturally includes the distance a, as in the known case according to Fig. 2, will be considerably longer as compared therewith.
• the inter- nal soundwaves which propagate circularly from the projectile 6 and cover the distance to the hole 11 will reach the hole and any other optional point on the inner side of the panel 12 before the "external" soundwaves, also when this point is in a location where one or more projectiles on their way 13 through the panel 12 have completely pierced this panel.
• the panel thickness must be selected in dependence upon the hole diameter that may be expected, and this diameter naturally is dependent upon the ammunition employed. The greater the expected hole diameter, the greater should be the thickness chosen for the panel 12.

Landscapes

• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
• Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20357912

Family Applications (1)

Country Status (3)

Cited By (5)

Citations (1)

• 1984
  • 1984-11-27 SE SE8405960A patent/SE458719B/sv not_active IP Right Cessation
• 1985
  • 1985-11-25 EP EP19860900296 patent/EP0233886A1/en not_active Withdrawn
  • 1985-11-25 WO PCT/SE1985/000479 patent/WO1986003284A1/en unknown

Patent Citations (1)

Also Published As

Similar Documents

Legal Events