Expansible chamber devices – With guide or seal on cylinder end portion for piston or... – Non-metallic seal means between piston or member and end...
Reexamination Certificate
2002-03-18
2003-12-09
Look, Edward K. (Department: 3745)
Expansible chamber devices
With guide or seal on cylinder end portion for piston or...
Non-metallic seal means between piston or member and end...
C277S583000
Reexamination Certificate
active
06658987
ABSTRACT:
The invention relates to a sealing device for a piston subjected to a pressure medium in a working cylinder, with a piston rod guide being arranged in or at the working cylinder and said rod guide comprising annular recesses and with elastic sealing rings as well as guide means being respectively disposed in the recesses according to Patent Application 199 26 450.3.
From the German Laid Open Patent Application DT 26 14 263 a dynamically adjustable sealing and guide device for pistons and piston rods is known which comprises at least two chamber rings arranged in series in the axial direction, and at least one sealing ring of an elastic material, which is located between them.
The piston has projections and recesses formed in the longitudinal direction, which are surrounded by a guide ring. A space is left between the guide rings for the accommodation of a sealing ring. The sealing ring rests against a groove in the piston via a further elastic ring, so that a certain adjustability is given due to the elasticity of the further ring.
The guide and sealing device for a piston subjected to a pressure medium in a working cylinder according to the German Patent DE 24 30 573 C3 is intended to prevent an axial displacement of the guide rings for an optimisation of the sealing effect and for reducing wear. For this purpose, the known positive fit of groove and collar with piston seals is utilised. Thereby, the disadvantageous deformation of the guide rings is to be prevented, on the other hand, however, the sealing effect between the rings and the piston is to be increased. The pressure build-up which is required at the spreader ring is to be enabled by openings in the piston.
According to the known teaching, a compression force is introduced through the openings to act on provided inclined surfaces. The provided elastic ring deflects the pressure in an upward direction so that all further rings can be biased towards a cylinder barrel (not shown).
Messrs Hunger DFE GmbH, Würzburg, also introduced a sealing system which can be biased externally. In this rod sealing system the sealing body has an integrated pressure duct via which the seal can be additionally biased by means of a contact pressure device. For this purpose the sealing body is penetrated by a hollow needle and additional pressure medium is supplied, adjustable to a fixed value, from the biasing device into the sealing body. This is to enable the balancing of the sliding or sealing behaviour, respectively, of the sealing elements in the installed hydraulic cylinder, with the lowest seal bias required for sealing being adjustable. The bias which is influenced by wear or fatigue after an extended service period can be changed, i.e. increased via the biasing device in order to increase the service life of the sealing system. As field of application for the presented sealing system which can be externally biased, hydraulic cylinders in machines and plants such as e.g. press cylinders, rolling mill cylinders, cylinders of civil engineering hydraulics equipment and so forth are known.
The cited solution, in particular, of the sealing system which can be externally biased by Messrs Hunger DFE GmbH requires a special sealing ring with the necessary pressure duct as well as an expensive clamping device with hollow needle and pressure accumulator. Thus, the known arrangement as a whole is expensive and cannot—or at least not economically—be employed as an emergency operation or quasi standby sealing device.
It was found that for example with so-called hydraulic upper piston die presses in the repair case, an upper hydraulic oil reservoir must be completely drained upon the exchange of one of the hydraulic cylinders or hydraulic pistons, respectively. Even after draining the hydraulic reservoir residual oil in a non-negligible quantity remains in the piston volume, which must be collected during the disassembly of the respective hydraulic cylinder, which makes the work considerably more difficult. For the above described case it would be desirable to provide the possibility of additional sealing in order to be able to exchange damaged primary seals which are located in the piston rod guide. Moreover, there should be the possibility to activate additional seals over a certain period of time, in order to ensure emergency operation properties of the relevant machines and equipment which employ hydraulic cylinders.
From the aforesaid it is therefore the object of the invention to specify an advanced sealing device for a piston subjected to a pressure medium in a working cylinder, with a piston rod guide known per se being provided in the or at the working cylinder and the rod guide comprising annular recesses, as well as elastic primary sealing rings as well as guide means being located in each recess, and with the device being provided with the possibility to ensure emergency operation properties in the emergency and/or repair case without having to rely on expensive special seals or extensive constructive modifications in the hydraulic cylinder system. In addition, it is to be ensured that the applied hydraulic pressure itself provides for the activation of an emergency seal.
The object of the invention is solved by means of a sealing device according to the characteristics as defined in claim 1, with claims 13 and 14 specifying special applications of such a device. The dependent claims comprise at least suitable embodiments and developments of the teaching described in the main claim.
The basic idea of the invention is to form at least one groove in the rod guide or in a cylinder ring downstream of the pressure chamber and concentrically surrounding the piston rod for the accommodation of a further quasi elastic emergency sealing ring, and to additionally provide means with the aid of which forces acting from the outside and radially to the piston rod can be applied to same, if required, so that the sealing ring is deformed similar to a crimp seal and brought into contact with the piston rod surface so that the desired sealing effect is ensured.
The elastic ring is to be a standard ring of the most simple construction, e.g. a so-called O ring, which is economically available. Due to the fact that only relatively low requirements with respect to long-term stability are to be met by the further sealing ring it is not necessary to employ expensive special materials.
In a first embodiment of the invention the additionally provided cylinder ring is located in a circumferential recess in the rod guide and more precisely at its upper end. The cylinder ring represents a supporting part which at least partially accommodates the elastic sealing ring, but, on the other hand, enables a lateral escape of the elastic sealing ring towards the piston rod in the case of the application of a force.
The supporting part can be adjusted in the axial direction of the piston rod, thereby driving the further elastic sealing ring and pressing same against an opposite stop face, so that the desired deformation of the sealing ring and the pressing or urging against the surface of the piston rod will result.
The mentioned stop face can be part of an mounting piece for accommodating one of the piston rod guide bands so that the additional constructive expenditure is kept within reasonable limits.
For the preferred application in a hydraulic upper piston die press, a plurality of sealable supply holes is provided in the rod guide, each of which enabling the actuation of a screw bolt by means of which the supporting part can be moved towards the cylinder frame.
In the case in which the guide rod must be disassembled for exchange purposes, e.g. of the primary seals, the supporting part is first moved via the screw bolt connection towards the stop face so that the further seal moves from a rest position into a sealing position towards to piston rod. This securely seals the working chamber of the hydraulic cylinder and the rod guide can be removed. Any hydraulic oil or similar fluid remaining in the working chamber need not be removed, collected and/or disposed of so
Kershteyn Igor
Log Hydraulik GmbH
Look Edward K.
LandOfFree
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