Hydraulic Buffer Device

Abstract

A damped spring unit housed in a cylindrical casing having one closed end and having a centrally located inner cylindrical wall supported from this closed end. A force transfer member is slidably supported in the cylindrical casing and includes an inner piston portion slidably supported in the inner cylindrical wall. A second piston portion is slidably supported at the outer end of the cylinder casing. A plurality of ports are formed at the inner end of the cylindrical wall to place the inner chamber in communication with the outer chamber. The outer chamber is filled with a mixture of a compressible fluid and non-compressible fluid and the inner chamber is filled with a non-compressible fluid. An external spring is connected between the closed end of the casing and a stationary frame member to absorb residual forces remaining after the damped spring unit reaches its "hard stop" condition.

Description

BACKGROUND OF THE INVENTION

This invention is directed to a buffer or shock-absorbing device which combines a compressible and non-compressible fluid medium to provide a hard stop for use on such items as guns, forges, punch presses, automobiles and aircrafts.

The object of this invention is to provide a hydraulic buffer device which is compact in size and relatively inexpensive to manufacture.

One of the critical design features of shock-absorber devices for use with such products as guns, punch presses and automobiles is to provide a compact unit which is capable of absorbing relatively large shock forces. It is also desirable in designing such a shock-absorber device to have a relatively simple design that is inexpensive to manufacture and easy to assemble.

SUMMARY OF THE INVENTION

A hydraulic buffer device embodying the principles of this invention includes a damped spring unit housed in an elongated casing closed at one end and having an inner cylindrical passageway. An inner cylindrical wall or shell is supported axially from the closed end wall. A forced transfer member is slidably disposed in the cylindrical passageway such that its inner piston portion extends axially into the outer end of the inner cylindrical wall and its outer piston portion is slidably supported by the inner cylindrical passageway. The inner piston portion and inner cylindrical wall define a first expandable and contractable chamber, and the outer piston portion and cylindrical passageway define a second expandable and contractable chamber. Port means are provided at the inner end of the inner cylindrical wall to place the first and second chambers in communication. The outer chamber is filled with a mixture of compressible and non-compressible fluids, and the inner second chamber is filled with a non-compressible fluid. An external spring is mounted between the closed end wall of the elongated casing and the associated frame member in order to absorb all forces exerted against the force transfer member after the force transfer member has reached the "hard stop position."

DESCRIPTION OF DRAWING

For a better understanding of this invention, reference may be made to the accompanying drawing in which:

FIG. 1 is a cross-sectional view of a hydraulic buffer device embodying the principles of my invention with the operating components shown in the original static position;

FIG. 2 is a hydraulic buffer device identical to FIG. 1 with the various operating components shown in the "hard stop position"; and

FIG. 3 is a hydraulic buffer device identical to FIG. 1 with the operating components shown in the over-travel position.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring to FIGS. 1 through 3 there is shown the preferred embodiment of my invention comprising a damped spring unit 10 and an external spring means 11.

The damped spring unit 10 is housed in an elongated casing 12 having a cylindrical body portion 14, a closed end wall 16 and an apertured end wall 18. End wall 16 is secured to cylindrical body portion 14 as by a weldment at 19. An inner cylindrical wall 20 is supported by the closed end wall 16 and extends axially of the inner cylindrical passageway 22, which is defined by the inner surfaces of the elongated casing 12.

A force transfer member 24 is slidably disposed in the inner cylindrical passageway 22 and comprises an elongated inner piston portion 26 and outer piston portion 28. The forward end 30 of the inner piston portion has a diameter slightly less than the inner cylindrical wall 20 and projects into the inner end of this cylindrical wall to define a first expandable and contractable chamber 32 therein. The outer piston portion 28 is formed with a central circular disc 34 and a cylindrical skirt 36 having a diameter slightly less than the diameter of the inner cylindrical passageway 22 to define the outer expandable and contractable chamber 38.

The outer chamber 38 is at least partially filled with a compressible fluid, such as air, and the remaining part of the outer chamber 38 and all of the inner chamber 32 are filled with a non-compressible fluid, such as oil. A passage for the fluid medium between chambers 32 and 38 is provided by means of a plurality of ports 42 formed at the inner end of inner cylinder wall 20. These ports 42 are made relatively large to avoid any metering of the fluid during the compression stroke so that the damped spring unit will quickly reach its "hard stop" position of FIG. 2. To prevent the escape of fluid from chamber 38, seal means 44 in the form of a plurality of O-rings are provided between the skirt 36 and the inner cylindrical passageway 22. Likewise, seal means 46 in the form of several O-rings provided around the forward end 30 of inner piston portion 26, prevent any leakage of the fluid medium outwardly between the inner cylindrical wall 20 and inner piston portion 26.

A spring member 48 is disposed between the closed end wall 16 and an axial cavity 50 formed in the forward end section 30 of piston portion 26 to assist in the return of the forced transfer member 24 to its original position of FIG. 1. After the spring 48 in force transfer member 24 is positioned within the cylindrical passageway 22, the apertured end wall 18 has internal threads in its outer skirt portion 52 for mounting on complementary threads at the outer end 54 of casing 12. The apertured end wall 18 has an enlarged central opening 60 to permit the buffer actuating member (not shown) to exert an axial inward force on the force transfer member 24 as diagrammatically depicted as force F.sub.1 in the drawings. The annular shoulder portion 62 defining the opening 60 further serves the function of providing a stop means to limit the outward travel of the forced transfer member 34 as shown in FIG. 1.

In operation, a recoil force F.sub.1 is directed in an axial inward direction of the force transfer member 24 causing the force transfer member to be displaced towards the left as viewed in the drawing. This displacement of the forced transfer member decreases the volumes of both chambers 32 and 38 with the resultant effect of compressing the compressible fluid. When the counteracting pressure of the compressible fluid becomes larger than the spring force exerted by external spring member 12, the force transfer member 24 is at its "hard stop position" (FIG. 2) and further residual components of recoil force F.sub.1 will be absorbed by the external spring 12. When the recoil force F.sub.1 is dissipated, the damped spring unit 12 returns to the original position of FIG. 1. One possible use of this return action of the damped spring unit from the position of FIG. 3 to the position of FIG. 1 would be the employment of the return force to actuate a feeder for a reloading purpose such as incoming ammunition.

From the foregoing description, it will be appreciated that the extent of travel of the force transfer member 24 to reach the hard stop position of FIG. 2 is proportional to the volume of compressible fluid, i.e., the more compressible fluid, the greater distance force transfer member 24 will travel for the same recoil force F.sub.1. Likewise, the degree of overtravel of the entire damped spring unit 12 is directly dependent on the spring constant of external spring member 12.

While I have shown and described what I believe to be a preferred embodiment of the 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.

Claims

I claim:

1. In a hydraulic buffer device, a damped spring unit comprising an elongated casing having a closed end wall and having an inner cylindrical passageway, an inner cylindrical wall supported axially on said closed end wall, a force transfer member slidably disposed in said outer casing having an inner piston portion extending axially into the outer end of said inner wall and having an outer piston portion with an outer diameter slightly less than the diameter of said inner cylindrical passageway, said inner piston portion and said cylindrical wall defining a first expandable and contractable chamber, said outer piston portion and said inner cylindrical passageway defining a second expandable and contractable chamber, port means at the inner end of said inner wall to place said first and second chambers in communication, a compressible fluid filling at least a portion of said second chamber, a non-compressible fluid filling the remaining portion of said second chamber and all of said first chamber, and sealing means disposed between the periphery of said outer piston portion and said inner cylindrical passageway to prevent any fluid leakage.

2. The combination of claim 1, further comprising means for mounting said outer casing on a frame member, said mounting means including a spring member disposed between said outer casing and said frame member to absorb residual forces exerted against said force transfer member after said force transfer member reaches its hard stop position.

3. The combination of claim 1, further comprising stop means at the outer end of said inner cylindrical passageway for limiting the outer movement of said force transfer member.

4. The combination of claim 1, further comprising an axial cavity provided in the inner end face of said inner piston portion, and a spring disposed between said closed end wall and said axial cavity.

5. In a hydraulic buffer device, a damped spring unit comprising a cylindrical casing having a closed end wall and an apertured end wall, an inner cylindrical wall supported axially on said closed end wall, a force transfer member slidably disposed inside said casing having an inner piston portion extending axially into the outer end of said inner wall and having an outer piston portion with a diameter slightly less than the bore diameter of said cylindrical casing, said inner piston portion and said inner cylindrical wall defining a first expandable and contractable chamber, said outer piston portion and the interior of said cylindrical casing defining a second expandable and contractable chamber, port means at the inner end of said inner wall to place said first and second chambers in communication, a compressible fluid filling at least a portion of said second chamber, a non-compressible fluid filling the remaining portion of said second chamber and all of said first chamber, and sealing means disposed between the periphery of said outer piston portion and said cylindrical bore to prevent any fluid leakage.

6. The combination of claim 5, further comprising means for mounting said casing on a frame member, said mounting means including a spring member disposed between said casing and said frame member to absorb residual forces exerted against said force transfer member after said force transfer member reaches its hard stop position.

7. In a device of the class described, a cylinder having a closed head at one end and an apertured head at the other end, a secondary cylinder concentric with and disposed in the main cylinder and having one end attached to the inside of the closed head of the main cylinder, a main piston fitting fluid tight in the main cylinder and adapted to lie radially outside of the secondary cylinder, an auxiliary piston attached axially to the inside of the main piston and disposed to lie inside the secondary cylinder, there being ports extending from the inside of the secondary cylinder to the inside of the main cylinder disposed adjacent the main cylinder head and a compression spring disposed between the auxiliary piston and the main cylinder head.