US 3371442 A
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March 5, 1968 R. l.. CARLSON DAMPED SPRING MEANS Filed March 24 1966 United States Patent Gte 3,371,442 Patented Mar. 5, 1968 3,371,442 DAMPED SPRING MEANS Robert L. Carlson, Chicago, Ill., assignor to W. H. Miner, Inc., Chicago, Ill., a corporation of Delaware Filed Mar. 24, 1966, Ser. No. 537,206 3 Claims. (Cl. 42-74) ABSTRACT F THE DISCLOSURE A normally extended damped spring operably connected between the relatively movable stock and buttstock boot of a shotgun or the like to absorb and dissipate the shock of recoil with the damped spring having a closed chamber filled with a compressible solid fixed to one of the relatively movable members and a piston rod iixed to the other and havin-g a piston provided with orice means disposed in the closed chamber, the compressible solid providing a damping and spring force on the piston as the rod moves into the chamber and reduces the volume of the compressible solid while forcing same through the orifice means with the expansion of the compressible solid after each recoil serving as the sole force for returning the damped spring to its normally extended condition.
My present invention relates generally to damped springs means and more particularly to damped spring means adapted to be incorporated in Shotguns, rifles and the like for absorbing recoil shock forces.
As is well kno-wn, when a firearm, such as a shotgun or ritie is discharged, the energy released in igniting the cartridge not only sends the bullet out of the barrel but also drives the gun sharply rearward. This recoil thrust passes through the gun and slams into the shooters shoulder and cheek, often causing injury or discomfort to the shooter. Prior eorts to absorb recoil shock have consisted of providing the butt end of the gun with rubber pads or spring arrangements. These devices yhave often resulted in clumsy stock structures and have not proved very effective. Most recently, hydraulic shock absorber arrangements have been installed inside the gun stock. In the main, such devices are complex in design, are diicult to seal, and require constant maintenance.
It is an object of my present invention t0 provide damped spring means between the :gun stock and a relatively movable buttstock boot for absorbing recoil forces. In general, damped spring means comprises casing means with a primary chamber therein, a piston rod extending outwardly of the primary chamber for receiving shock forces, and a piston at the end of the piston rod within the primary chamber. The piston provides axial orifice means, and the primary chamber is filled with a compressible solid. Preferably, the casing means is secured to the buttstock boot and the piston rod is secured to the gun stock. As the piston rod moves into the primary chamber in response to recoil forces, the reduction in volume of the compressible solid, and the throttling effect produced by the compressible solid being forced through the orice means, impose a damping and spring force on the piston rod and piston. Damped spring means of this type are easily sealed and require minimum maintenance.
It is another object of my present invention to provide a firearm construction, as described, wherein the buttstock boot slidably receives the gun stock and serves to enclose the damped spring means.
It is a further object of my present invention to provide damped spring means which is compact in construction and relatively simple in design. In this connection, the damped spring means of my present invention preferably has an elongated body portion of generally oblong cross section with the axis of the primary chamber coinciding with the longitudinal axis of the casing. Additionally, the primary chamber communicates with an auxiliary chamber which is lgenerally C-shaped in configuration. The leg portions of the auxiliary chamber are arranged on opposite sides of the prim-,ary chamber and the axes thereof lie in the plane of the major cross sectional axis of the casing. Thus, for a given size of damped spring means, optimum damping and spring characteristics are alorded.
It is a still further object of my present invention to provide damped spring means, as described, which includes means for varying the initial pressure of the compressible solid in the primary and auxiliary chambers.
Now in order to acquaint those iskilled in the art with the manner of constructing and using devices in accordance with the principles of my present invention, I shall describe in connection with the accompanying drawing a preferred embodiment of my invention.
In the drawing:
FIGURE l is a view, partly in elevation and partly in section, of a gun stock, a relatively movable buttstock boot and damped spring means, arranged in accordance with the principles of my present invention;
FIGURE 2 is a vertical longitudinal median sectional view, on an enlarged scale, of the damped spring means of my present invention;
FIG-URE 3 is an elevational view of one end of the damped spring means of FIGURE 2; and
FIGURE 4 is a sectional view, taken substantially along the line 4 4 in FIGURE 2., looking in the direction indicated by the arrows.
Referring now to FIGURE 1, the stock of a shotgun is designated generally by the reference numeral 10. The gun stock 10 has an internal recess or cavity 12 opening rearwardly thereof. The recess 12 is adapted to house a recoil shock absorbing damped spring unit which incorporates the principles of my present invention and which is indicated generally by the reference numeral 14. The construction, mounting and operation of the damped spring unit 14 will be described in detail hereinafter. It will be appreciated that the unit 14 is shown incorporated in a shotgun for illustrative purposes only and that the principles of my present invention can be used with any firearm which is tired from the shoulder.
As shown in FIGURES 2, 3 and 4, the recoil shock absorbing clamped Spring unit 14 includes a casing 1b comprised of an elongated body portion 18 of generally oblong or tiattened cross section, a forward wall 20 and a rear wall 22. Viewing FIGURE 4, the dot A indicates the longitudinal 'axis of the body portion 18, an imaginary horizontal line passing through the longitudinal axis corresponds to the minor cross sectional axis, and an imaginary vertical line passing through the longitudinal axis corresponds to the major cross sectional axis.
Projecting inwardly from the forward casing wall 20 are inner longitudinal web portions 24 and 26 which terminate short of the rear wall 22. The web portions 24 and 26 serve to define with the other portions of the casing 16 and inner cylindrical primary chamber B and an auxiliary generally C-shaped chamber C. The axis of the primary chamber B coincides with the longitudinal axis A of the casing 16, and the leg portions of the auxiliary chamber C are arranged on opposed sides of the primary chamber B with the axes thereof lying in the plane of the major cross sectional axis of the casing 16.
The forward casing wall 20 is formed with an opening 28 which is coaxial of the longitudinal casing axis A, and an inwardly facing annular shoulder 30 is defined at the inner end of the opening 28. Extending through the opening 28 and projecting into the chamber B is a piston rod 32. The piston rod 32, intermediate of its ends, is formed with a collar portion 34 that is engageable with the casing 3 shoulder 30 'to limit movement of the piston rod 32 out- =wardly of the casing 16. The piston rod 32 is also provided, at its inner end, with a piston 36. The periphery of the piston 36 is spaced from the interior cylindrical surface of the chamber B to dene therewith axial orifice means in the form of an annular orifice. Additionally, the inter-communicating chambers B and C are filled with a compressible solid or elastomer 38 such as silicone rubber. To prevent the escape of compressible solid past the piston rod 32, an annular seal 40 is mounted in the forwardwall 20.
To permit the admission of compressible solid into the casing 16, a iller plug 42 is provided in the rear wall 22. Additionally, a screw 44 is threaded through the forward casing wall 20 for effecting preloading of the cornpressible solid 38. As the screw 44 is threaded axially inwardly or outwardly, the initial pressure of the compressible solid is varied due to the change in the effective volume ofthe chambers B and C.
The casing 16 is slidably mounted within a sleeve member 46 having a forward end wall 4S. The forward end of the piston rod 32 is suitably secured, as by a threaded connection, to the forward end wall 48. The sleeve 46 and the forward end wall 48 thereof are ixedly mounted in a conventional manner within the recess 12 of the gun stock 10. During movement of the gun stock l relative to the casing `16, corresponding movement is imparted to the piston rod 32 while the sleeve member 46 slidably guides the casing 16.
As is evident from FIGURE l, the rear portion of the casing 16 projects rearwardly out of the gun stock 10. To 'house the above-mentioned projecting portion of the casing 16, and also to provide a cheek protector, a buttstock boot 50 is provided for the gun. The buttstock boot 50 comprises a housing 52, a spacer 54, and a butt plate 56. The housing 52, which is preferably fabricated of a plastic material, is in the shape of a conventional buttstoclc boot and is arranged to slidably engage the rear portion of the gun stock that extends into the housing. The spacer 54 is of the same material as the housing 52 and provides additional cushioning means for the shoulder of the gunner. The spacer 54 is secured to the rear casing wall 22 by means of bolts 58, and bears against shoulders 59 and 60 formed in the housing 52. The butt plate 56, also of a plastic material, is adapted to t over the rear end of the housing 52 and is removably snapped into position.
I shall now describe the operation of my recoil shock absorbing mechanism which is shown at rest in the drawing. When `the gun is fired, the gun stock 1t) is urged rearwardly and telescopes into the housing 52. This telescoping yaction moves the piston rod 32 and piston 36 rearwardly within the primary chamber B. During such movement, the volume of chamber B is reduced to the extent of displacement by the piston rod 32, thus increasing the pressure of the compressible solid 38 in both chambers B and C. Concurrently, the compressible solid 38 is forced through the annular orice surrounding the piston 36 thereby producing a throttling effect. The described volume-pressure change of the compressible solid, and the attendant throttling effect, impose a damping and spring force on the piston and piston rod, and thereby serve to dissipate the energy of the recoil shock force resulting from firing of the gun. The damped spring unit 14 will absorb up to 90 percent of the recoil force.
When the recoil shock force is fully dissipated, the pressure of the compressible solid 38, acting on the unbalanced area of the piston rod 32 within the chamber B, causes the piston 36 and piston rod 32 toy return to the position shown in FIGURE 2. During the return stroke of the piston rod 32, the compressible solid flows back through the annular orice -surrounding the piston 36 to lill the space being vacated by the latter. Correspondingly, the pressure of the compressible solid 38 returns to the normal preload pressure'. In this connection, engagement ofthe piston rod collar portion 34 with the casing shoulder 39 serves to establish the rest position of the piston rod 32. Finally, by reason of the arrangement of the chambers B and C in a common plane, desirable damping and spring characteristics are afforded in a compact construction. k Y
While I have shown and described what I believe to be a preferred embodiment of my present invention, it will be understood by those skilled in the art that various rearrangements and modifications may -be made therein without departing from the spirit and scope of my invention.
1. A gun stock and a relatively movable buttstock boot at the rear end thereof, a normally extended damped spring means acting between Said gun stock and said buttstock boot for dissipating the energy of recoil forces imposed on said gun stock, said normally extended damped spring means comprising a casing secured to said buttstock boot and having a primary chamber therein, a piston rod extending outwardly of said chamber and connected to said gun stock, a piston at the end of said piston rod within said chamber and providing axial orifice means, and a compressible solid lling said chamber for providing a damping and spring force on said piston rod and said piston as said piston rod moves into said chamber and reduces the volume of said compressible solid while the latter is forced through said orice means, said compressible solid expanding after each recoil and serving as the sole force for returning said damped spring means to its normally extended condition, and adjustable means for varying the initial pressure of said compressible solid.
2. The device of claim 1 wherein said primary charnber is cylindrical and wherein an auxiliary chamber is provided in said casing in communication with said primary chamber whereby to accommodate a greater volume of said compressible solid.
3. The device of claim 1 wherein said casing is provided with shoulder means adjacent one end of said pri-- mary chamber, and said piston rod istprovided with a collar portion that is engageable with said Shoulder means for limiting outward movement of said piston rod relative to said casing.
References Cited UNITED STATES PATENTS 2,668,049 2/l954 Taylor 267-63 XR 2,846,211 8/1958 Taylor 267-63 2,994,524 8/1961 Jarret et al. 267-1 3,152,798 10/1964 Iarret et al. 267-1 837,601 12/1906 Behr 42-74 2,731,753 l/ 1956 Mathieu 42-74 3,001,312 9/1961 Campbell 42-74 3,176,424 4/1965 Hoge 42-74 3,209,482 10/1965 Kuzma et al 42-74 3,300,889 1/l967 Baker 42-74 BENJAMIN A. BORCHELT, Priltary Examiner.
T. H. WEBB, Assistant Examiner.