Spring devices – Fluid – Time delay
Patent
1993-11-26
1995-07-25
Oberleitner, Robert J.
Spring devices
Fluid
Time delay
267119, F16F 500
Patent
active
054355303
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an arrangement for a gas spring consisting on the one hand of a cylinder closed at both ends by means of end walls with a piston capable of axial displacement inside the fluid-filled inner space of the cylinder, which piston divides the latter into two sub-spaces, of which a first is bounded by a first end wall, the piston and an interjacent part of the cylinder wall, and the second sub-space is bounded by the second end wall, in which a piston rod operatively connected to the piston is mounted in a sliding and sealing fashion, the piston and an interjacent part of the cylinder wall, and on the other hand of an enclosed space so arranged as to communicate with the aforementioned first sub-space via a first openable and closable valve.
A gas spring of the kind referred to above, which, after compression, exhibits a delayed return to its original length, is described in more detail in WO90/15267 (SE-B-462 726). Also described in the aforementioned publication is an application for such a gas spring with a delayed return, namely for the purpose of ejecting a pressed component from a pressing tool.
Although a gas spring of the kind referred to above has an entirely satisfactory function, there is a general wish to have available a gas spring with smaller installation dimensions for otherwise unchanged characteristics. A further wish is to have available a gas spring which operates exclusively with gas. The gas spring referred to by way of introduction, however requires a gas/oil mixture; the use of gas alone in a gas spring according to WO90/15267 would permit the piston rod to execute undesirable overspringing movements.
The object of the present invention is to make available a gas spring of the kind referred to by way of introduction, which has smaller installation dimensions than previously disclosed gas springs, and which operates exclusively with gas. This is achieved in accordance with the invention in that the second sub-space is so arranged as to communicate with the aforementioned first sub-space via a second openable and closable valve, and in that the arrangement comprises a control device for actuating the aforementioned openable and closable valves so arranged as to enable the second valve to open when a force acting upon the end of the piston rod from an initial position close to the second end wall, in which the spring exhibits its original length, has forced the piston in a direction towards the first end wall and into a predetermined position, as to close the second valve again after a period of sufficient duration for pressure equilibrium to have been achieved between the aforementioned sub-spaces, as to enable the first valve to open for a period of sufficient duration to permit pressure equilibrium to be achieved between the second sub-space and the enclosed space and, after a predetermined period has elapsed after the force acting against the end of the piston rod has ceased to be applied, as to open the aforementioned second valve, when the piston returns to its initial position, and, once the piston has reached its initial position, as to open the first valve. The ability of the gas spring in accordance with the invention to operate without oil has environmental advantages on the one hand, in that the risk of oil leaks is entirely eliminated, and on the other hand has service/technical advantages.
An especially compact and installation-friendly design is achieved, as may be appreciated from one particular characteristic of the invention, in that the aforementioned enclosed space constitutes an extension of the cylinder and, as such, is bounded by the first end wall, a third end wall and an interjacent part of the cylinder wall.
By executing a first communicating line between the first sub-space and the enclosed space in the form of a channel in the first end wall, the advantage is achieved that the aforementioned first line lies entirely protected inside the gas spring.
An entirely protected second line between the first sub-space and the second sub-spac
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Oberleitner Robert J.
Schwartz Chris
Stromsholmens Mekaniska Verkstad AB
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