Valves and valve actuation – Hermetic flexible wall seal for actuator – Bellows
Reexamination Certificate
1999-08-27
2001-03-20
Shaver, Kevin (Department: 3754)
Valves and valve actuation
Hermetic flexible wall seal for actuator
Bellows
Reexamination Certificate
active
06202984
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a shut-off device for pipes comprising a spindle communicating with a shut-off device arranged in a housing, whereas the spindle is borne in an upper part of the housing so as to be axially slidable, the upper part of the housing being provided with a cover resting on the housing, whereas the interior space of the cover is communicating with the medium led through the housing.
2. Description of the Prior Art
A shut-off device of the type mentioned above has been manufactured for quite a few years. Shut-off devices for pipes, and more particularly stop slide valves, yet proved to often require big strokes as opposed to globe valves which get on well with relatively small strokes. In shut-off devices of the type mentioned above, it is indeed always necessary to completely remove the actual shut-off device, that is the key, from the open cross section of the pipe. Considerable efforts were therefore necessary to seal up the shut-off device for pipes against its environment, particularly when dealing with big nominal diameters.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide a shut-off device for pipes of the type mentioned above by means of which tubes of big nominal diameters, that may be locked by slide valves, may be sealed up against their environment in a durable and reliable way so that the medium led inside the pipe conduit is securely prevented from leaking out. This is of particular interest when the medium led in the pipes is aggressive or toxic.
The solution of the invention is to provide the spindle at its lower end facing the shut-off device with a ring carrying at least two compactly arranged, preferably metallic expansion bellows that are placed in concentric arrangement, whereas the inner expansion bellows is communicating with the spindle and the other outer expansion bellows is communicating with the upper end, that is with the flange of the cover. The flange is provided with a boring through which the spindle may pass. Additionally to the flange, the cover also has a sleeve-type cover element attached to the flange. The two expansion bellows, that are concentric to each other and to the spindle, are for example soldered by their lower end to the ring. The inner expansion bellows continues to be compactly connected to the spindle by being for example soldered to it. The outer expansion bellows is connected by its upper end with the flange of the cover by being soldered or otherwise connected in a compact way. A hollow space is thus provided between the exterior side of the inner expansion bellows' wall and the inner side of the outer expansion bellows' wall, whereas said hollow space is not communicating with the medium contained in the housing. Said hollow space is however communicating with the boring of the spindle through the flange of the cover. It is thus guaranteed that, in case of intact expansion bellows, no medium can escape through the boring between cover and spindle. Thanks to the arrangement of two concentrically borne expansion bellows in a pipe-like cover, the overall height of the spindle itself as well as of the expansion bellows to be sealed up can be kept small.
As already mentioned at the beginning, the sealing of shut-off devices for pipes by means of slide valves in housings having a big diameter is very complicated. Long expansion bellows could not be used for sealing, since the longer the bellows the easier they tend to buckle or, at the slightest inner pressure, to bulge. As already explained and thanks to the arrangement of two concentrically borne expansion bellows, the length of each single bellows is reduced so that they are no more bulging under inner pressure nor buckling due to excessive length. As also already mentioned above, the overall height of the spindle itself can thus be reduced, which is advantageous from the manufacturing point of view.
As already explained, the inner bellows is connected to the spindle. The inner bellows is hereby preferably provided at its upper end with a transition ring for its connection with the spindle. This is necessary, since the bellows, which is for example made of metal, has a relatively small material cross section, whereas the spindle has a big mass. In order to prevent the expansion bellows from glowing out while connecting the bellows with the spindle in a compact way, for example by soldering, the transition ring is provided, the size of its cross section lying between the cross section of the spindle and that of the expansion bellows.
According to another characteristic of the invention, the ring is arranged or guided in an axially slidable way on the spindle on one side and in the cover, that is in the sleeve-type cover element, on the other. The spindle is hereby advantageously provided with a bearing surface for the ring, said bearing surface being for example designed as a circumferential shoulder. Thanks to the axially slidable arrangement of the ring on the spindle as well as in the sleeve-type cover element, the inner expansion bellows is first expanded when for example the key is taken out of the pipe, the spindle then creeping axially upwards. When a determined expansion of the inner bellows is achieved, the ring also creeps upwards according to the spindle's movement. In a more detailed description, this process is the following: the spindle is provided with a holder for the shut-off device. This holder is hitting the ring at a determined vertical displacement of the spindle and is thus taking it along. Accordingly, the distance to be covered between the two bellows during the axial deformation of the expansion bellows is apportioned so that each bellows only has to cover a determined, relatively short distance. The use of relatively short bellows is thus made possible with all the advantages already explained.
According to another characteristic of the invention, the inner expansion bellows is impinged by the inner pressure of the medium, whereas the outer expansion bellows is impinged by the outside pressure of the medium. That means that the shorter expansion bellows is impinged from the inside, which is not relevant, since it does not tend to bulge thanks to its short length. The strain exerted by the medium's pressure onto the outer circumference of the outside expansion bellows is not relevant either since the expansion bellows can withstand relatively high external pressures. Therefore, the ring is provided with a passage leading to the inner space of the inner expansion bellows and with a passage leading to the space between the inner wall of the sleeve-type body of the cover and the outer wall of the outer expansion bellows, both passages guaranteeing that infiltrated medium may flow out again. These passages are therefore also called relief borings.
If, for all that, an expansion bellows happens to be damaged, a gland encompassing the spindle is provided in the housing cover, said gland serving as additional securing means intended to keep the medium away from its environment. The gland itself is arranged in a gland casing arranged in the cover. An advantage thereof is that the outer expansion bellows is fastened onto the gland casing in the way described above.
According to another advantageous characteristic, the spindle is secured against torsion. Such a safety device against torsion prevents the expansion bellows from torsioning, which would directly destroy them. The upper part of the housing has a housing bridge for the guidance of the spindle, whereas the housing bridge is connected with the cover by several pillars, said pillars undertaking the function of safety device against torsioning. The safety device against torsioning itself consists of a plate that encompasses the spindle so as to rotate in unison with it but so as to be axially slidable relative to it, and that is arranged as a bearing thrust on the pillars between the cover and the bridge of the housing. The housing bridge is provided with a thread for the
Fichtner Lothar
Rosam Markus
Hanrath James P.
Keasel Eric
Prazisionsarmaturen Ostfalenpark Barieben GmbH
Shaver Kevin
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