Abstract:
A damper for an air gun has a gas spring at least partially disposed within a compression tube. The damper includes a damping component contacting the gas spring and the compression tube. The damping component damps vibrations in the air gun when the gun is fired.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. application Ser. No. 12/194,615, filed Aug. 20, 2008, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to air guns and more particularly to a vibration damper for the force producing/charging assembly of a gas spring air gun. 
     BACKGROUND 
     Air guns use compressed air to discharge a pellet. Some air guns use a firing piston in a compression tube defining a compression chamber. In a gas spring-type air gun, the air gun is charged by moving this compression piston toward the trigger to compress a gas contained within a gas spring&#39;s cylinder behind the compression piston. 
     The gas spring is mounted between the compression piston and a trigger mechanism. The compression piston is retracted to cock the trigger and to compress the gas contained within the gas spring. The gas within the gas spring is compressed by a second piston, hereinafter, the spring piston. When the trigger is released, the gas spring launches the compression piston toward the barrel to compress the air in the compression chamber. The compressed air then propels the pellet through the barrel. One problem with air guns using a gas spring is that the rapid deceleration of both the compression piston and the spring piston produce an excessive amount of vibration shock, harmonics, and harshness (hereinafter collectively referred to as “vibration”) upon firing. 
     These gas-powered air guns suffer from inaccuracy due to the vibration resulting from the rapid movement, then rapid deceleration of the pistons during firing. There is therefore a need for an improved air gun charging system damper that overcomes these and other drawbacks of prior art designs and techniques. 
     SUMMARY 
     A damper for an air gun is provided that advantageously damps vibrations in a gas spring both during and after firing. The air gun has a compression tube and an axially movable compression piston in the compression tube. The damper includes a gas spring that has a gas spring body defining an interior chamber, and a gas spring piston movable relative to the interior chamber. A portion of the gas spring piston engages the compression piston. A vibration damping material contacts a portion of the gas spring body. A sleeve contacts an outer surface of the gas spring body and a portion of the compression tube to locate the gas spring body relative to the compression tube. 
     In one embodiment, a damper for an air gun has a gas spring at least partially disposed within a compression tube. The damper includes a damping component contacting the gas spring and the compression tube. The damping component damps vibrations in the air gun when the gun is fired. 
     In one embodiment, a damper for an air gun has a tubular compression piston, a barrel, and a gas spring mounted at least partially within the tubular compression piston. The damper includes a substantially tubular sleeve that receives and abuts the gas spring. The sleeve is effective to damp vibrations in the air gun after firing of the air gun. One advantage of the sleeve is that it provides a large surface area to abut and absorb vibrations from the gas spring. 
     One advantage of the damper is that it improves projectile velocities and accuracies by damping the vibrations caused by the gas spring. Further, when the damping component is a layer of damping material on the gas spring, the damping component remains free from contact with the moving portions of the gas spring during the firing sequence. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description refers to the accompanying drawings in which like reference characters refer to like parts throughout the several views, and in which: 
         FIG. 1  is a partially exploded, partially cut-away side view of an improved gas spring along with a conventional skirted compression piston; 
         FIG. 2  is a side sectional view of the improved gas spring gun in a cocked position within a compression piston; 
         FIG. 3  is a side sectional view of the improved gas spring gun in a post-firing position within a compression piston; 
         FIG. 4  is a perspective view of the vibration damping liner; 
         FIG. 5  is a sectional view of one of the guide sleeves; 
         FIG. 6  is a side sectional view of an alternate embodiment of the gas spring&#39;s liner with the gas spring in a post-firing position; 
         FIG. 7  is a side sectional view of another alternate embodiment of the gas spring&#39;s liner with the gas spring in a cocked position; 
         FIG. 8  is a side sectional view of still another embodiment of a gas spring having a liner mounted on both the inner and outer surface of the gas spring cylinder; 
         FIG. 9  is a side sectional view of the embodiment illustrated in  FIG. 8  in a post-firing position; 
         FIG. 10  is a side sectional view of yet another embodiment of a gas spring having a liner mounted to the outer surface of the gas spring cylinder; 
         FIG. 11  is a side sectional view of still yet another embodiment of the present invention having a slidable counter-weight mounted to the outer surface of the gas spring cylinder, shown in a cocked position; and 
         FIG. 12  is a side sectional view of the embodiment illustrated in  FIG. 11  in a post-firing position. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIGS. 1-3 , a gas spring  10  is shown along with a tubular shaped or skirted compression piston  12  for an air-powered pellet gun. The compression piston  12  is conventional and has a front end or head  13  having a dynamic seal or gasket  14  which creates an air-tight seal between compression piston  12  and the inner surface of the air gun&#39;s compression tube (not shown). In a typical air gun, the compression tube and compression piston  12  are substantially in-line with the air gun&#39;s barrel (not shown), such that once the air gun&#39;s trigger is pulled, the compression piston  12  moves toward the barrel and compresses the air in the compression tube in front of the piston head  13  expelling a projection, e.g., a pellet, out of the barrel. 
     Gas spring  10  includes an elongated tubular body  16 . A pair of end walls or plugs  18 ,  20  are fixed to body  16  to define a pressure chamber  22 , also referred to herein as a compression chamber. In the embodiment shown, plugs  18 ,  20  are fixed within the chamber  22  by roll forming annular projections  24  in body  16 . By roll forming the projections  24 , a small channel  25  is formed in the outer surface  26  of the body  16 . It should be appreciated that plugs  18 ,  20  may be affixed to body  16  in substantially any manner suitable to create and air-tight condition within pressure chamber  22  and may include a seal or gasket (not shown) between the inner surface  28  of body  16  and the plugs. 
     Front plug  18  includes a central opening  30 , which is preferably co-axial to the longitudinal axis of body  16 . Opening  30  includes a dynamic seal or o-rings  32  that are mounted within concentric channels formed in the cylindrical inner wall plug  18 . 
     Gas spring  10  further includes a piston  34 . Piston  34  has an elongated and rigid piston rod  36 . An enlarged retainer head  38  is mounted at one end of rod  36 . Piston  34  is mounted within body  16  and projects through opening  30  with retaining head  38  contained within chamber  22 . Dynamic seal  32  cooperates with rod  36  to create the airtight condition within chamber  22 . Piston  34  is movable axially from a cocked or ready to fire position, generally shown in  FIG. 2 , to a post-firing position shown in  FIG. 3 . As shown in  FIGS. 2 and 3 , the forward-most end of rod  36  engages a portion of the skirted compression piston  12 , e.g., the rearward wall of head  13 , such that movement of the compression piston  12  in the direction of arrow  5  (when cocking the air gun) will force rod  36  further into chamber  22 ; and such that movement of the gas spring piston  34  in the direction of arrow  6  (when the air gun is fired) will force the compression piston  12  toward the air gun&#39;s barrel. 
     An amount of pressurized gas  40 , such as air, is trapped within chamber  22  and the additional volume occupied by the piston  34  when it is in the cocked position further pressurizes the gas  40 . In the embodiment shown in the FIGs., an inlet valve  42  in rear plug  20  allows the pressure within chamber  22  to be adjusted. 
     Gas spring  10  further includes a liner or lining  44  of vibration damping or absorbing material. As shown, liner  44  is disposed within chamber  22  and abuts the inner wall  28  of body  16  face-wise. That is, the outer surface  48  of liner  44  conforms to and abuts substantially the entire surface of cylindrically-shaped inner wall  28 . Liner  44  also preferably runs the entire length of chamber  22  to maximize the surface area covered by the vibration damping or absorbing liner. Liner  44  is preferably formed from an elastomeric material, such as rubber, which is sufficiently rigid to remain in place against the inner wall  28  of body  16 , while still damping any vibrations that pass into the liner. 
     Importantly, liner  44  is relatively thin to leave an adequate gap  50  between its inner-most surface  52  and the radially projecting retaining head  38 . This clearance or gap  50  ensures that the piston  34  will not be slowed by liner  44  when the gas spring is cocked/compressed and while the piston  34  is traveling forward when the air gun is fired, i.e., toward the post-firing position shown in  FIG. 3 . 
     Referring now to  FIG. 4 , liner  44  is shown as a substantially contiguous sheet that may be rolled into the general shape of inner wall  28 . In the embodiment illustrated, liner  44  is a flat sheet that is rolled into a cylindrical shape leaving a mating line or gap  54  running the length of the liner. Liner  44  is sized to compress slightly when it is inserted into body  16 . This compressed fit within chamber  22  ensures the face-wise relationship between liner&#39;s outer surface  48  and inner wall  28 . In other embodiments, liner  44  may be tubular in shape (i.e., no mating line  54 ) and sized to abuttingly fit against wall  28 . 
     It should be appreciated that the inherently resilient nature of the vibration damping material, e.g., a rubber material, of liner  44  will cause it to press against innerwall  28  when liner  44  is compressed and inserted into chamber  22 . In other embodiments, liner  44  may be further held against inner wall  28  by adhesives or other fastening means. Liner  44  by continuously abutting the gas spring body  16  during firing, transfers any vibrations in the gas spring  10  to the internally mounted vibration damping material of the liner  44  to reduce the vibration created during the firing process. 
     Referring also now to  FIG. 5 , in the preferred embodiment, gas spring  10  further includes a pair of guide sleeves  56 ,  58  mounted to the outer wall  26  of body  16 . Each sleeve  56 ,  58  is generally ring-shaped having a cylindrical outer wall  62  and a concentric opening  64  defined by an inner wall  66 . As shown best in  FIG. 3 , the outer diameter of forward sleeve  56  is sized to slidably mate with the cylindrical inner wall  12   a  of the skirted compression piston  12 , while the rearward sleeve  58  is preferably the same diameter as the piston  12 . 
     Each sleeve  56 ,  58  is preferably a ring of durable and rigid material, such as a plastic. The outer wall  62  of sleeve  56  is preferably smooth and present little frictional resistance to the movement of skirted piston  12  relative to gas spring  10 . 
     Sleeves  56 ,  58  includes means to grip the outer wall  26  of body  16  and fix the sleeves  56 ,  58  in place along the body. In the preferred embodiment, sleeves  56 ,  58  include at least one annular ridge  68  that projects radially inwardly from the inner wall  66 . This ridge  68  is preferably shaped complementary to the roll formed channel  25  used to retain plugs  16 ,  18 . The ridge  68  cooperates with channel  25  to fix the sleeves along body  16 . It should be appreciated that other fasteners can be used in place of, or in addition to, the ridges/channels to hold the sleeves  56 ,  58  to the cylindrical body  16 . 
     When an air gun is fired, the unloading of gas spring  10  not only presses compression piston  12  forward, but also creates vibrations in the air gun, which reduces performance. Further, the rapid deceleration of pistons  12  and  34  create additional vibration in the air gun. Sleeves  56 ,  58 , by continuously abutting the skirted compression piston  12  during firing, transfers the vibrations in piston  12  to the liner damped gas spring  10  to reduce the vibration created during the firing process. 
     In one embodiment, shown in  FIG. 6 , the liner, denote  44 ′, includes an enlarged annular neck  70  at the forward-most end of the liner. This neck  70  is preferably formed  10  from the same vibration damping material as the rest of the liner and projects radially inward to defines an opening  72  that is concentric to opening  30  and rod  36 . 
     Opening  72  is sized to abuttingly and frictionally mate with the radially outer surface  38   a  of retaining head  38 . In one embodiment, opening  72  is slightly smaller than (approximately 0.01 inches) the diameter of head  38 . 
     As shown in  FIG. 6 , neck  70  only runs along the forward-most end of liner  44 ′, such that neck  70  will not restrict the movement of piston  34  until the piston  34  is substantially at the post-firing position illustrated. The reduced size of neck  70  frictionally restrains the movement of the axially sliding piston  34  and substantially prevents the piston  34  from bouncing back in the direction of arrow  5  after the air gun has been fired. 
     The direct engagement of the vibration damping liner&#39;s neck  70  with piston  34  (which abuts the compression piston  12 ) provides an additional path for any vibrations in the pistons  12 ,  34  to travel into the vibration damping material of liner  44 ′ when the gas spring  10  is in the post-firing position. 
     Referring now to  FIG. 7 , yet another embodiment of the gas spring liner, denoted  44 ″, is shown as a plurality of individual elastomeric o-rings  72 , which are stacked adjacently and abuttingly along the entire length of chamber  22 . The o-rings  72  are preferably sized such that they are slightly compressed by wall  28  when inserted into body  16 . In another embodiment shown in phantom, the neck  70  shown in  FIG. 6  can be replicated by using o-rings  72   a  at the forward-most end of the tube having an appropriately sized inner diameter (i.e., using thicker o-rings). 
     Referring now to  FIGS. 8 and 9  an alternate embodiment is illustrated where a second liner  144  is mounted to the outer surface  26  of the cylinder. Liner  144  is substantially the same as liner  44  described above, but is abuttingly mounted to outer surface  26  between the sleeves  56 ,  58 . This second layer of vibration damping material acts to supplement the damping effects of the single liner  44  described above. 
     It should be appreciated that the outer liner  144  is sufficiently thin to ensure that there is clearance, shown as a gap  146 , between the liner  144  and the inner surface  12   a  of the piston. In this manner, the vibration damping outer liner  144  does not interfere with the firing and cocking operations of the air gun. 
     In another embodiment, shown in  FIG. 10 , the inner liner  44  may be eliminated and only the outer liner  144  operates to receive and damp any vibrations in the air gun. 
     Referring now to  FIGS. 11 and 12 , still another embodiment of invention showing a gas spring  10 ′ having an internal liner  44  as described above. In addition to the vibration damping liner  44 , gas spring  10 ′ includes a tubular-shaped counter-weight  150  that is slidably mounted around the outer surface  26  of the gas spring cylinder  16 . The inner diameter of the tubular counter-weight is such that a sliding fit exists between the outer surface  26  and the inner surface  152  of the counter-weight. 
     As shown, the forward portion of counter-weight  150  is sized to fit within the skirted portion of a piston  12 , while remaining free to slide axially along the gas spring surface  26  between the guides  56 ,  58 . The rearward end of the counter-weight terminates at an enlarged annular head  154 . Head  154  extends radially from the otherwise relatively thin profile such that the rearward end  12   b  of piston  12  may abuttingly engage a forward shoulder  155  of the head. 
     Counter-weight  150  is preferably formed from a high density material, such as tungsten carbide. In operation, the counter-weight  150  is pressed back adjacent to the rear guide sleeve  58  by the piston  12  when the air gun is cocked. Upon firing, the piston  12  moves rapidly away from the gas spring  16  and counter-weight  150 . Once the piston  12  reaches the forward-most point of its travel, it comes to an abrupt stop while causing the pellet in the air gun to fire and the air gun to recoil from the discharge of the pellet and the compressed air. This recoil effect causes the counter-weight  150  to slide axially along the gas spring and strike the rearward side  56   a  of forward guide sleeve  56  to counter the recoil effect of firing the air gun. In other embodiments, shoulder  155  strikes the rearward end  12   b  rather than the forward end of the counter-weight striking the guide sleeve. 
     In another embodiment, the rear guide sleeve  58  may be eliminated and replaced with counter-weight  150 . In this embodiment (not shown), the counter-weight may include, like sleeve  58 , means to frictionally mate with the rearward groove  25  in the cylinder  16 . In still other embodiments, the counter-weight  150  may be slidably mounted around a gas spring having a vibration damping outer liner  144 . 
     In still other embodiments, the liner may initially be a liquid elastomeric material, which is applied to the body&#39;s inner wall  28  (and/or its outer wall  26 ). In the preferred version of this embodiment, a layer of vibration damping material is sprayed onto the wall(s) as a liquid and allowed to cure or set to form a layer or liner  44 . 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.