Spring devices – Vehicle – Comprising compressible fluid
Patent
1996-09-05
2000-05-09
Graham, Matthew C.
Spring devices
Vehicle
Comprising compressible fluid
267113, 267119, 267224, F16F 902
Patent
active
060592737
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an arrangement for a gas spring comprising a cylinder, which at its one end is delimited by a fixed end wall, and at its other end has a first guide sealed against the inner will of the cylinder and against a piston rod capable of axial movement within the cylinder, in conjunction with which the end of the piston rod facing towards the end wall is executed with a second guide mounted in such a way as to be capable of sliding against said inner wall.
BACKGROUND OF THE INVENTION
A conventional gas spring operates in a similar manner to a helical spring, i.e it produces a spring resistance equivalent to the compression from the moment at which it is affected by a force.
In many applications this force is represented by a moving part of a machine, the movement of which requires to be contained and damped. Because of metal components which strike one another with full force, this gives rise to disturbing mechanical noise and din, which cannot be accepted under current working environment legislation. Attempts have been made to dampen the contact between the moving part of the machine and the gas spring with the help of helical springs or damping elements made of an elastic material. These attempts were not particularly successful, since helical springs do not give the desired effect, and the stresses on such damping elements are considerable and the service life of the elements is accordingly very limited. Both the purchase and replacement of damping elements also involve truly daunting costs.
SUMMARY OF THE INVENTION
The object of the present invention is to eliminate the aforementioned disadvantages and to bring about an acceptable noise level having regard for working environment legislation. This is achieved in accordance with the invention in that an annular piston sealed against the aforementioned inner wall and against the piston rod is mounted on the piston rod between the aforementioned guides in such a way that it is free to slide, which annular piston divides the inner space of the cylinder between the aforementioned first guide and the end wall into a first part space delimited by the first guide and the annular piston and into a second part space delimited by the annular piston and the end wall, in that, in an initial position in which the gas spring is unaffected, there is present in the first part space a pressure which is greater than the pressure present in the second part space, such that the annular piston is retained between the aforementioned guides through the effect of the pressure acting upon, on the one hand, one surface of the annular piston and, on the other hand, the other surface of the annular piston and the end surface of the piston rod. This means that, when the piston rod is actuated by an external increasing force acting in an axial sense to the end wall of the cylinder, which causes the piston rod to be inserted gradually into the cylinder, in conjunction with which from the initial position, in which the spring force of the gas spring is negligible, to a first position of the piston rod, in which the pressures in the two part spaces are identical, the pressure in the second part space gradually approaches the pressure prevailing in the first part space, the spring force of the gas spring remains negligible compared with the spring force prevailing after passing the aforementioned first piston rod position, and so that, as the force acting upon the piston rod reduces, after passing the aforementioned first piston rod position, the spring force is once more a fraction of the spring force that was present prior to passing the first piston rod position, only to become negligible once more in the initial position.
What is achieved through the characteristics of the invention is that the spring force is negligible at the moment when mechanical contact occurs between the part of the machine and the gas spring; only after mechanical contact has been established does the gas spring produce a spring force proportional to th
REFERENCES:
patent: 1214343 (1917-01-01), Matthews
patent: 2977146 (1961-03-01), Edwards et al.
patent: 3328019 (1967-06-01), Wilson
patent: 4270771 (1981-06-01), Fujii
Gustafsson Krister
Sand Gunnar
Graham Matthew C.
Stromsholmen AB
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