The present invention relates to a sealing to be laid between two surfaces and preventing a liquid or gaseous medium from flowing out from the gap between the surfaces, the sealing being made of a plastic material.

Sealings are employed in various pipe joints and also in other devices assembled of parts for the pre- vention of escape of liquid within said pipe joint or device through such joints. Sealings are either sheet¬ like, cut in various ways and into various shapes, or strip-like or cord-like sealings to be wound on the thread of a threaded joint when the joint is produced. Sheet-like sealings are manufactured from dif¬ ferent materials, such as plastic, impregnated paper etc., and their sealing capability is based on the fact that they are compressed between opposite sur¬ faces with bolts or other similar clamping means. For sealing threaded joints of pipes, a solution is known where pipe putty is applied to the juncture and flax tow is wound in the thread, so that when the pipe joint is tightened these means seal the gaps between the threads. Furthermore, today a teflon sealing strip that is wound on the thread of the pipe joint prior to tightening of the joint is commonly used.

Installing flax tow by means of pipe putty is dirty and cumbersome, wherefore it has largely been abandoned. A sealing employing a teflon band is prob- lematic in that if it is not seated correctly in the thread upon winding, it will not provide tight seal¬ ing, but water or gas can issue therefrom. Teflon band also has the drawback that, being insensitive to liquids and gases - i.e. not interacting with liquid or gas - it cannot seal a leaking spot through swell-

ing or similar.

It is an object of the present invention to pro¬ vide a sealing that affords easy and simple sealing while the sealing properties are good. The sealing of the invention is characterized in that sealing fibers that expand or swell upon contact with the medium to be sealed are laid during manufacture on the surface of and/or inside the plastic material that forms the sealing, thus increasing the sealing effect of the sealing.

The essential idea of the invention is that the sealing material is a thin plastic film, such as pre¬ ferably teflon, and during manufacture, fibers of a suitable fibrous material are attached within and/or to the surface of the teflon, so that fiber is pro¬ vided at the entire joint to be sealed, and thus the liquid or steam tending to escape through the joint will come into contact with the fiber. Specifically, when the sealing is shaped to be strip-like similarly as the known teflon band, the fibers are preferably laid in the longitudinal direction of the strip, and thus when the sealing strip so obtained is wound on the surface of the thread in the threaded joint, the fiber material is similarly wound, and when the joint is tightened, the fiber material is compressed in bet¬ ween the joint. Further, an essential idea of the invention is that the fiber material expands or swells under the action of the sealed medium, and thus the possible gaps remaining between the surfaces of the teflon or other plastic material and the joint are sealed by the expansion or swelling of the fiber material on the action of the liquid or steam. Thereby the threaded joint is made mechanically strong, and even though the joint is slightly loosened, it still remains tight.

The advantage of the invention is that sealing is easy to effect by employing a strip-like sealing material and by winding it on the thread, while a fiber material that swells in the thread on the action of the sealed medium is obtained, and this material finishes the sealing of the joint if small leaks remain in said joint. The solution is simple but con¬ siderably more efficient and reliable than the solu¬ tions presently employed. Further, the invention has the advantage that when a sheet-like sealing is used, the sealing is made more reliable and secure, without excessive tightening of the bolts of the sealing flange, for instance.

The invention will be explained in more detail in the accompanying drawings, in which

Figure 1 is a schematic perspective view, partly in section, of a sealing strip according to the inven¬ tion,

Figures 2a and 2b are schematic views of differ- ent alternatives for laying the fiber relative to the sealing strip,

Figures 3a-3e show different possible embodi¬ ments for laying the fibers in the transverse direc¬ tion of the material, and Figures 4a and 4b are exemplary views of a sheet-like sealing material according to the invention viewed from the surface direction of the sheet and showing a cross-section of the sheet.

Figure 1 is a perspective view, partly in sec- tion, of a sealing according to the invention, formed as a sealing strip 1. The sealing strip comprises a strip portion 2 made of a plastic material, such as teflon or other plastic material suited to the medium to be sealed, within which sealing fibers 3 are fed during the manufacture of the strip 2 shown in Figure

1. The sealing fibers 3 are either natural fiber or suitable synthetic fiber, selected on the basis of the purpose of use, i.e. primarily on the basis of the medium to be sealed, as it is essential that the fibers 3 either expand or swell if they come under the influence of the medium, such as liquid, steam or gas, flowing within the pipe to be sealed with the sealing strip 1. In constructing the joint, the sealing strip 1 is wound on the threaded portion provided on the outer surface of the pipe in such a way that it is tightly pressed onto the root of the thread. In that connection, the sealing fibers 3 are also wound around the thread. When the threaded joint is tightened, it is typical that the strip portion 2 is cut into parts on the action of the sharp edge of the thread crest, said parts remaining between the threads as sealing. In this situation, also the sealing fibers 3 become partly visible. If the sealing effected by the strip portion 2 between the threads of the joint is not tight enough, the medium in the pipe can flow in the joint outwardly, whereupon it comes into contact with the sealing fibers 3. When the sealing fibers 3 are so selected that the effect of the medium flowing in the pipe causes them to expand or swell as the medium per- meates the fibers, in this situation the sealing fibers will consequently fill the gap between the threads more closely than in the assembly of the joint, and thus maintain the joint tight under the continuous effect of the medium. In addition to Figure 1, Figures 2a and 2b show typical alternative ways of laying the sealing fibers 3 in the strip 2. In the solution shown in Figure 1, the sealing fibers 3 run substantially longitudinally of the strip portion 2. In Figure 2a, on the other hand, the sealing fibers 3 are laid to run wavily back

and forth in the transverse direction of the strip portion 2, the fibers being relatively lengthy or, if made of a suitable material, continuous. Figure 2b, on the other hand, shows shorter sealing fibers 3 laid in crosswise relation obliquely to the strip portion 2. The fiber paths of both Figure 1 and Figures 2a and 2b can be applied to fibers on the surface of, and like¬ wise within, the sealing strip, and different fiber paths can be employed simultaneously, if more than one layer of fibers are provided.

Figures 3a-3e show different alternatives for laying the fibers in the structure of the sealing strip 1 in its transverse direction. Figure 3a shows a solution in which the sealing fibers 3 are disposed on the surface of the strip portion 2, in which case they are most preferably attached to the strip portion 2 by the actual strip portion material in connection with the manufacture of the strip portion. Figure 3b again shows a solution in which relatively thick fibers 3 are fed within a strip portion of molten material during manufacture of the strip material. Figure 3c further shows a solution in which relatively thick fibers 3 are suitably laid within the strip portion 2 and also on its outer surface, in which event the same fiber can occasionally be within the strip portion and occasionally on its surface, and likewise the paths of the separate sealing fibers 3 in the strip portion 2 can be in accordance with Figures 1 and 2a-2b, for example. Figure 3d shows a solution in which several relatively thin sealing fibers, arranged for example in two clearly distinct layers, are laid within the strip portion 2. Figure 3e again shows a solution in which a large quantity of very thin sealing fibers 3 randomly disposed within the strip portion 2 without forming any separate distinct layers are laid within

the strip portion 2.

If the sealing is formed as a sealing strip, it must be relatively easy to cut when used. This can be accomplished by disposing a roll of sealing strip in a separate stand; such stands are typically used for cutting tape. The stands can be provided with a cutt¬ ing edge of the material of the stand, if it is suffi¬ ciently hard and if sufficiently sharp cutting teeth can be produced therein. Likewise, the cutting edge can be formed of a separate gap-toothed metal strip, so that long tabs are produced at the end of the seal¬ ing strip, which is of advantage in use.

The sealing fiber employed in the sealing of the invention can be natural fiber, such as flax which is capable of swelling considerably on the action of water, or other fiber behaving in this way. Further, suitable synthetic fibers can be used in sealing vari¬ ous oil-based mediums; such a medium has an expanding or swelling action on said synthetic fibers, thus en- abling a sealing comprising the most suitable sealing fiber for instance in the form of a sealing strip for different uses to be produced. The material of the strip portion 2 can be teflon, which is well suited for this purpose, but also other plastic-based mater- ials that can otherwise be used as a sealing material for a given medium are possible.

One particular embodiment of the invention is a sheet-like sealing material, which is shown in Figures 4a and 4b. In this case, sealing fibers 3 are laid crosswise on the surface of and within a sheet-like plastic material so as to form a web structure. In this solution, the density of the sealing fibers form¬ ing the web can vary depending on the purpose of use, and thus for example an annular sealing for flange joints or the like can be formed of the sheet-like

sealing material. The thickness of such a sheet-like sealing may typically be 0.5-5 mm, and sealing fibers 3 can be provided therein in separate layers, said fibers thus providing effective sealing while the cut ends of the fibers allow the medium flowing within the sealed joint to come into contact with the sealing fibers and thereby to make them to expand or swell to enhance the sealing effect.

Furthermore, the sealing can be formed as a pre- fabricated annular sealing, in which case the sealing fibers can also be disposed annularly in one or more layers and preferably in the transverse direction of the annular sealing as several successive sealing fiber layers. This provides a particularly useful sol- ution for a flange construction. Further, the material can be a combination of synthetic fiber and teflon or plastic or similar.

The invention has been described in the fore¬ going specification and drawings by way of example only, and it is in no way limited to the examples given. The essential fact is that the sealing is cons¬ tituted by a plastic sealing which may be shaped into a strip portion or a sheet-like material and within which and/or on the outer surface of which sealing fibers are provided, said fibers expanding or swelling on the action of the sealed medium, thus enhancing the sealing effect of the sealing and the mechanical strength of the joint.