Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for a pipe – conduit – or cable
Reexamination Certificate
1998-01-26
2001-07-17
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal for a pipe, conduit, or cable
C277S924000
Reexamination Certificate
active
06260852
ABSTRACT:
The invention relates to methods and devices for sealing an annular gap between two sealing surfaces of machine parts with the aid of a ring in contact on these two sealing surfaces, in particular on extrusion machines where this sealing is of significance, preferably in filter and tool-changing devices.
BACKGROUND OF THE INVENTION
In the interior of extrusion machines of the industry processing rubber and synthetic materials, the extrudable material or extrudate is under pressures, in particular at the end of the passage through the extrusion machine where the material is disintegrated and in a flowable state. At this place frequently a filter, also referred to as a strainer, is disposed in the path of the extrudate in order to remove parts and foreign bodies which cannot be disintegrated from the flow of the extrudate, conventionally directly following the extrusion device, which can be a screw extruder, ram extruder, toothed wheel or other extruder, before the extrudate leaves the discharge head disposed at the end of the extrusion device.
The strainers must be cleaned from time to time. In order not to interrupt the production operation for the cleaning, strainer-changing devices were developed which are installed in the extrusion system for example, between extruder and discharge head. These comprise discrete strainer cassettes or a slider with at least two strainers and means for a rapid displacement of this strainer cassette or this slider into their operating positions. Due to the high pressures occurring at the site of the strainer, problems are encountered to attain “perfect” sealing during operation with high contact pressures in the region of the seal, but to decrease briefly the high contact pressures for the displacement of the slider so far that the slider or the strainer cassettes without damage and without damaging the seal used can be slid in order to make them effective again immediately after the displacement of the slider with the strainers or the strainer cassettes.
Also, for the reason of not having to interrupt the production operation or only extremely briefly, similar apparatus are used in the discharge head region as tool changers.
Technology has developed a number of options of which, however, none is fully satisfactory.
In DE 3043217 C2, two meshing rings are hydraulically displaced and pressed against the slider. Since here an annular cylinder comprising two concentrically disposed corrugated pipes causes the hydraulic displacement, and the attainable contact pressures are not sufficient for many applications since the strength of the corrugated pipes fabricated of very thin material is highly limited.
In DE 1919269, the contact pressing takes place by means of a ring which is impressed upon by piston rods, acting obliquely upon it, of small hydraulic cylinders. The sealing of the cylindrical inner circumferential surface of this ring and the occurring transverse forces here represent problems.
In DE 1729396, the compacting pressure is not exerted onto annular surfaces but rather only on two opposing sites via wedge surfaces.
In DE 19615679, A1 mechanical displacement is achieved not with hydraulic forces but rather by rotation of a pressing ring provided with outer threads in an inner threading. High contact pressures, and thus sealing pressures, cannot be attained due to the high frictions and locally unequal contact pressing due to thread tolerances. The resetting with defined residual pressure is also not readily possible.
The invention avoids the disadvantages of the prior art. It is the task of the invention to create with simple means a unique sealing device which seals, for example, an extrusion machine even at very high pressures and yet is readily relieved of load if a machine part is to be displaced relative to the other.
SUMMARY OF THE INVENTION
The invention comprises that either a preferably substantially planar ring comprising an elastic but very strong material is used, which preferably projects unilaterally beyond its sealing surface, and that this ring through pressure onto the portion of the ring projecting on one side beyond this sealing surface is deformed such that it becomes arched and comes to rest in contact in the form of an annular line with its one marginal edge on the one sealing surface and becomes braced in the form of an annular line on the other sealing surface. Alternately, an arched or weakly-truncated cone-form ring comprising an elastic but very strong material is used, which at least on one side projects beyond the sealing surface, and that this ring under pressure is placed sealingly between the two sealing surfaces and is allowed to be in contact in the form of an annular line with its one marginal edge on the one sealing surface and is braced on the other sealing surface in the form of an annular line, and that by introducing force onto the portion of the ring projecting beyond the sealing surface deforms this ring such that losing its arching extends and therein loses the line-form contact position on the one sealing surface.
In both cases, the sealing attained through two annular line-form sealing surfaces at which the surface pressing and thus the sealing effect is very high. In the one case the ring is deformed in order to attain the sealing, in the other, the second case, the ring is deformed in order to cancel the sealing effect and the annular line-form contact pressing in order to be able to displace the strainer cassette or the slider.
This sealing can be applied wherever a gap must be sealed which is slightly greater than the thickness of the portion of the ring to be sealed.
The device according to the invention is realized such that the ring in the region between the two annular line-form contact surfaces is substantially planar and, by introducing force onto the portion projecting beyond the sealing surface, can be arched so that the two annular line-form contact surfaces of the ring are in contact on the sealing surfaces under pressure.
The previously cited two realization options also determine the devices for sealing an annular gap between two planar sealing surfaces of machine parts in particular on extrusion machines:
In the one embodiment, the device according to the invention is implemented such that the ring comprises an elastic but very strong material, that the ring projects at least on one side beyond its sealing surface, that the ring becomes deformed through the effect of force on the portion projecting on one side beyond its sealing surface such that it becomes arched, and that the ring with its one marginal edge is in contact in the form of an annular line on the one sealing surface and is braced in the form of an annular line on the other sealing surface.
The other realization option is distinguished thereby that the ring at least in the region between the two annular line-form contact surfaces is arched or has the form of a truncated cone, that the two annular line-form contact surfaces with the introduction of force are in contact on the sealing surfaces and through pressure onto the portion of the ring projecting beyond the sealing surface at least in the region between the two annular line-form contact surfaces is deformable in a plane and through introduction of force onto the portion of the ring projecting beyond the sealing surface this ring is deformed such that losing its arching extends and therein loses the line-form contact on the one sealing surface.
It is therein of advantage if the ring is fabricated of metal, a high-strength synthetic material or a metal composite material.
Depending on the type of application the portion of the ring intended for the force introduction can project outwardly or inwardly beyond the sealing surface: if a surface is to sealed toward the outside, the portion of the ring intended for the force introduction is disposed outside, if a breach or a hole is to be sealed, the portion of the ring intended for the force introduction is disposed inside in the hole.
The material of the ring can be of uniform thickness, however it is of advantage
Knight Anthony
Lackenbach Siegel Marzullo Aronson & Greenspan
Maschinenfabrik Paul Troester
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