초록 ▼

In the illustrative embodiment of the invention disclosed, a pressurized gas spring is arranged to provide three different damping-rate states as the piston rod is progressively urged axially outward of the cylinder. A first damping-rate stage is provided by an axially movable ring carried by the pi

In the illustrative embodiment of the invention disclosed, a pressurized gas spring is arranged to provide three different damping-rate states as the piston rod is progressively urged axially outward of the cylinder. A first damping-rate stage is provided by an axially movable ring carried by the piston structure, a second stage is provided by an axially movable sleeve member slidably mounted on the piston rod for engagement at its inner end with the piston structure, and a third stage is provided by entry of the outer end of the sleeve member into a damping cylinder mounted adjacent the end wall of the cylinder through which the piston rod extends. The three damping-rate stages act cumulatively increasingly to slow outward movement of the piston rod. In the disclosed embodiment, the gas spring is mounted so as to be in the rod-down orientation when the piston rod is fully retracted, and the sleeve member is moved by gravitational force into engagement with the piston structure, thereby initiating the second damping-rate stage, when the gas spring moves to the rod-up orientation during use.

대표청구항 ▼

1. In a gas spring including a cylinder member having an axis and two end walls and defining a fluid-tight cavity therein; a piston rod member extending through one end wall in sealed relation thereto for axial movement inward and outward of said cavity between an innermost position and an outermost

1. In a gas spring including a cylinder member having an axis and two end walls and defining a fluid-tight cavity therein; a piston rod member extending through one end wall in sealed relation thereto for axial movement inward and outward of said cavity between an innermost position and an outermost position; a piston unit carried by said piston rod member internally of said cylinder member and separating said cavity into first and second working chambers; fluid passage means extending through said piston unit for connecting said first and said second working chambers to permit fluid flow therebetween in response to axial movement of said piston rod member and said piston unit; a body of pressurized fluid within said cavity; and means for damping the rate of outward movement of said piston rod member; the improvement comprising: said damping means comprising first damping valve means and second damping valve means within said fluid passage means; said first damping valve means and said second damping valve means being arranged in series; both said first damping valve means and said second damping valve means being movable between a closed condition and an open condition, first throttled by-pass means and second throttled by-pass means by-passing said first damping valve means and said second damping valve means, respectively, in the respective closed conditions; said first throttled by-pass means and said second throttled by-pass means being connected in series when said first damping valve means and said second damping valve means are in said respective closed conditions, said first throttled by-pass means having a smaller cross-sectional area than said second throttle by-pass means; said second damping valve means comprising a piston ring engaging the inner cylindrical face of said cylinder member and being housed in a circumferential groove of said piston unit at an axially intermediate location of said piston unit, said circumferential groove having an invariable axial width larger than the axial width of said piston ring, said piston ring being axially movable within said circumferential groove between a first terminal position remote from said one end wall, in which first terminal position said second damping valve means are in said closed condition and a second terminal position closer to said one end wall, in which second terminal position said second damping valve means are in said open condition, said first terminal position occurring in response to outward movement of said piston rod member and said second terminal position occurrring in response to inward movement of said piston rod member; p1 said first damping valve means comprising a valve member axially movable with respect to said piston unit to a limited extent, said valve member cooperating with an end face of said piston unit remote from said circumferential groove and directed toward said one end wall so as to open and close, respectively, the exit of a fluid passage extending within said piston unit from said circumferential groove to said end face, said valve member being connected to a damping piston, said damping piston entering into a damping cylinder, provided within said cavity adjacent said one end wall thereof, as said piston rod member approaches said outermost position and defining therewith a damping chamber, and means defining a throttled fluid path between said damping chamber and said second working chamber adjacent said one end wall to further dampen the outward rate of further movement of said piston rod member, said valve member being held in a closing position with respect to said fluid passage when said damping piston enters into said damping cylinder. 2. The gas spring of claim 1, wherein said damping piston, when at said first terminal position, covers a part of the flow cross section of said fluid passage means so as to increase the flow resistance of said fluid passage means and thereby dampen outward movement of said piston rod member and, when at said second terminal position, uncovers said part of said fluid passage means so as to reduce the flow resistance of said fluid passage means, said damping piston thereby operating as a first damping valve means for controlling the rate of movement of said piston rod member. 3. The gas spring of claim 2, wherein: said damping piston includes a radially inward directed annular flange; said piston rod includes a first axial section of reduced diameter relative to an adjacent axially outward section of said piston rod, thereby defining a first shoulder at the juncture of said two sections of said piston rod member, said first shoulder being directed towards the other end wall; and said annular flange encircles said reduced diameter section and engages said first shoulder when said damping piston is in said second terminal position. 4. The gas spring of claim 3, wherein: said damping piston includes an end face directed towards said other end wall; and means carried by said piston rod member defines an abutment face directed towards said one end wall for engagement with said end face of said damping piston when said damping piston is in said first terminal position. 5. The gas spring of claim 4, wherein said abutment face defining means comprises a surface on said piston unit. 6. The gas spring of claim 5, wherein said fluid passage means includes second damping valve means responsive to outward movement of said piston rod member relative to said cylinder member for increasing the flow resistance of said fluid passage means and to inward movement of said piston rod member relative to said cylinder member for decreasing the flow resistance of said fluid passage means. 7. The gas spring of claim 6, wherein said first damping valve means effects an additional increase of the flow resistance of said fluid passage means when said damping piston is brought into said first terminal position as compared with the flow resistance already increased by said second damping valve means in response to outward movement of said piston rod member. 8. The gas spring of claim 7, wherein said damping piston is made of plastic material. 9. The gas spring of claim 7, wherein the flow resistance of said throttled fluid path defining means effects an additional damping of the rate of outward movement of said piston rod member when said damping piston enters said damping cylinder as compared to the damping already effected by said first and second damping valve means. 10. The gas spring of claim 2, wherein said damping piston is movable between said first and second terminal positions with respect to said piston rod member under its own gravitational weight in dependence upon the orientation of the gas spring. 11. The gas spring of claim 3, wherein said piston rod member includes a second axial section of reduced diameter relative to said first axial section, said second section being axially inward of and adjacent to said first section so as to define at the juncture of said first and second sections a second shoulder directed towards said other end wall; and said piston unit is axially fixed with respect to said piston rod member by said second shoulder, on the one hand, and means secured to the innermost end of said second section, on the other hand. 12. The gas spring of claim 1, wherein said pressurized fluid comprises at least in part a pressurized gas. 13. The gas spring of claim 12, wherein a small amount of liquid is present within said cavity. 14. A gas spring as set forth in claim 1, wherein the unit comprising said valve member and said damping piston is axially movable in response to the orientation of said gas spring in space such that said valve member closes said fluid passage when said piston rod member extends in an upward direction from said piston unit. 15. The gas spring of claim 14, wherein said throttled fluid path defining means comprises the annular gap between the interior circumferential face of said damping cylinder and the exterior circumferential face of said damping piston. 16. The gas spring of claim 15, wherein said exterior circumferential face of said damping piston is slightly conical and converges in the direction of said one end wall. 17. The gas spring of claim 14, wherein the outer circumferential surface of said damping cylinder is radially adjacent the inner circumferential surface of said cylinder member. 18. The gas spring of claim 17, wherein said damping cylinder is axially fixed between said one end wall and a radially inward directed abutment carried by said cylinder member. 19. In a gas spring including a cylinder member having an axis and two end walls and defining a fluid-tight cavity therein; a piston rod member extending through one end wall in sealed relation thereto for axial movement inward and outward of said cavity between an innermost position and an outermost position; a piston unit carried by said piston rod member internally of said cylinder member and separating said cavity into first and second working chambers; fluid passage means extending through said piston unit for connecting said first and said second working chambers to permit fluid flow therebetween in response to axial movement of said piston rod member and said piston unit; a body of pressurized fluid within said cavity; and means for damping the rate of outward movement of said piston rod member; the improvement comprising: said damping means comprising first damping valve means and second damping valve means within said fluid passage means; said first damping valve means and said second damping valve means being arranged in series; both said first damping valve means and said second damping valve means being movable between a closed condition and an open condition, first throttled by-pass means and a second throttled by-pass means by-passing said first damping valve means and said second damping valve means, respectively, in the respective closed conditions; said first throttled by-pass means and said second throttled by-pass means being connected in series when said first damping valve means and said second damping valve means are in said respective closed conditions, said first throttled by-pass means having a smaller cross-sectional area than said second throttled by-pass means; said second damping valve means comprising a piston ring engaging the inner cylindrical face of said cylinder member and being housed in a circumferential groove of said piston unit at an axially intermediate location of said piston unit, said circumferential groove having an invariable axial width larger than the axial width of said piston ring, said piston ring being axially movable within said circumferential groove between a first terminal position remote from said one end wall, in which first terminal position said second damping valve means are in said closed condition and a second terminal position closer to said one end wall, in which second terminal position said second damping valve means age in said open condition, said first terminal position occurring in response to outward movement of said piston rod member and said second terminal position occurring in response to inward movement of said piston rod member, said first damping valve means effecting an additional increase of the flow resistance of said fluid passage means when said damping piston is brought into said first terminal position as compared with the flow resistance already increased by said second damping valve means in response to outward movement of said piston rod member; said first damping valve means comprising a valve member axially movable with respect to said piston unit to a limited extent, said valve member cooperating with an end face of said piston unit remote from said circumferential groove and directed toward said one end wall so as to open and close, respectively, the exit of a fluid passage extending within said piston unit from said circumferential groove to said end face, said valve member being connected to a damping piston, said damping piston entering into a damping cylinder, provided within said cavity adjacent said one end wall thereof, as said piston rod member approaches said outermost position and defining therewith a damping chamber, and means defining a throttled fluid path between said damping chamber and said second working chamber adjacent said one end wall to further dampen the outward rate of further movement of said piston rod member, said valve member being held in a closing position with respect to said fluid passage when said damping piston enters into said damping cylinder.