FLEXIBLE SEAL FOR A CABLE THROUGH HOLE BACKGROUND OF THE INVENTION [0001] The invention relates to a flexible seal for a cable through hole, to be mounted in an opening in a wall, particularly a wall of an electrical and electronics enclosure, the seal comprising a seal collar and a locking shoulder for receiving the wall sealably therebetween at the edge of the opening, a first end and a second end, and a tapering section between the first and second end, the tapering section comprising an outer surface, a wide end and a narrow end, whereby the narrow end of the tapering section is provided with a bead, which is turnable from a first position to a locking position, closer to the first end of the seal, to provide pull-off, in which locking position the seal surrounds the cable sealably. In this context, a cable refers to any electrical conductor, but particularly to such a conductor that has a circumferential sheath and typically contains multiple conductors. In this connection, the ex- pression'locking shoulder'also includes locking means in the form of lugs.

[0002] The above mentioned seals are known to be used when an opening, or a so-called through hole, of a wall need to be sealed, through which opening a cable is led through the wall.

[0003] Finnish Patent 60797 discloses a flexible seal of a type mentioned above. One end of the seal is provided with a bead, which, by roll- ing towards the wide end, provides pull-off. The pull-off means the property of the seal of preventing the cable mounted in the seal from being pulled off through the seal.

[0004] The problem with known flexible seals is that it is laborious to mount them in a wall. It is difficult to push the seal into the wall such that the tapering section of the seal is inserted sufficiently deep into the through hole, so that the seal is properly and sealably in place. The seal need to be pressed with great force from the side wherefrom it is pushed into the opening. A fairly steep tapering section does not in practice make it possible that when the seal is mounted, the seal would simultaneously be pulled to its place, the pulling making the mounting simpler. The seal must often be pressed from different sides so as to make sure that the mounting has been successful.

[0005] Stiff, plastic, screwable two-piece seals are also known, and their mounting is easy, but slow. Due to their structure, they are rather expen- sive. They provide an efficient pull-off.

BRIEF DESCRIPTION OF THE INVENTION [0006] It is an object of the present invention to provide a new flexi- ble seal for a cable through hole, which has no above drawbacks. To achieve this, the seal is characterized in that the bead is in the region of the narrow end of the tapering section and forms a projecting gripping shoulder at the outer surface of the tapering section to facilitate the pulling of the seal to its place in the wall. The gripping shoulder formed by the bead makes the mounting of the seal considerably easier.

[0007] The bead is preferably formed at the narrow seal end to a point which is very close to the first end of the seal. Thus the seal is made compact and short, which is important when the seal is used in enclosures, because there is not much room in the interior of the enclosures, and it is ad- vantageous that the seal takes as little room as possible inside the enclosure.

[0008] The bead is preferably an annular member, whereby it is easy to grip and pull the gripping shoulder with fingers. The tapering section close to the bead is preferably made of a thin material, so that the bead can be turned inwards, closer to the first end of the seal, to a locking position such that it presses against the cable surface and that its distance X from the first end of the seal is shorter than the distance Y from the outer surface of the turning point between the wide and narrow ends of the tapering section to the first end of the seal. Such a bead turned to the locking position presses against the cable surface, so that great friction is generated between the bead and the cable sheath, which efficiently prevents the cable from being pulled out of the through hole, i. e. the seal, whereby the bead provides an efficient pull-off.

[0009] According to a preferred embodiment of the invention, at its narrow end, the tapering section comprises a clamping surface for receiving a fixing means and for pressing the seal by means of the clamping surface firmly against the cable. Great compressive force can be achieved by means of a common cable tie, for example, which is fastened against the clamping sur- face. Due to the gripping shoulder, the cable tie (or some other tightening ele- ment) remains securely fastened to the seal and it does not slide off from the tapering section. Thus, the use of the clamping surface and of the gripping shoulder for mounting the cable tie (or other tightening element) and keeping it in its place is another way of providing an efficient pull-off in the seal of the invention.

[0010] The preferred embodiments of the seal according to the in- vention are disclosed in the attached claims 2 to 8.

[0011] The major advantages of the seal according to the invention are that it is easy and fast to mount. The mounting does not require use of tools either. In addition, the seal provides an efficient pull-off and it is not ex- pensive to manufacture.

BRIEF DESCRIPTION OF THE DRAWINGS [0012] In the following the invention will be described in greater detail by means of two preferred embodiments and with reference to the at- tached drawing, in which [0013] Figure 1 is a side view of a seal, [0014] Figures 2 and 3 show the seal from the opposite ends, [0015] Figure 4 is a section along the line IV-IV of Figure 1, [0016] Figure 5 illustrates how the seal is mounted, [0017] Figures 6 and 7 show the seal in two different operating po- sitions, and [0018] Figure 8 is a sectional view of a second embodiment of the seal.

DETAILED DESCRIPTION OF THE INVENTION [0019] A seal shown in Figures 1 to 4 comprises a first, wide end 1 with a large diameter, and a second, narrow end 2 with a small diameter. Be- tween the ends there is a tapering conical section 3 comprising an annular narrow end 4 with a small diameter, and an annular wide end 5 with a large diameter.

[0020] The end 1 of the seal is provided with a hole 6 for a cable 7 (cf. Figures 2,4 and 5) or the like.

[0021] In Figure 5, the seal is mounted in an opening in a wall 11.

At the edge of the opening, one surface of the wall 11 is set against a locking shoulder 15 and the opposite surface of the wall against a seal collar 16, so that the seal collar is set sealably against the edge of the opening. The seal collar 16 presses slightly against the wall 11 when it is in its place, which en- sures a through hole impermeable to liquid or air. In Figure 1, the seal collar 16 is free from outer strain, and therefore its shape slightly differs from the shape shown in Figure 5.

[0022] The seal can very easily be passed to its final position shown in Figure 5 by pushing it 1 in the direction of arrow A and by simultane- ously pulling from a bead 10 at the end 2 in the direction of arrow A. During the pulling, the diameter of the wide end 5 decreases and a cylindrical surface 20 is inserted into the opening in the wall 11. The bead 10 can be easily gripped with fingers, and during the pulling, the nails can be set against a pro- jecting gripping shoulder 12 formed by the bead. The gripping shoulder formed by the bead 10 forms a sharp discontinuous point at an outer surface 13 of the tapering section 3. The projecting gripping shoulder 12 at the outer surface of the seal substantially facilitates the mounting of the seal.

[0023] At the end 2 there is an annular reduction means 8 which is inside the bead 10 and in the form of a material reduction. The material reduc- tion 8 defines the breaking point from which the material breaks when the ca- ble 7 is pushed in the direction of arrow A against a cylinder part 9 inside the material reduction, cf. Figure 5. The breaking point can be removed with rather a small amount of force, whereby an opening for the cable is formed.

[0024] After the cable 7 has been pushed through the ends 1 and 2 of the seal, the cable is pulled backwards in the direction of arrow B, so that the bead 10 turns by rolling inwards to a locking position shown in Figure 6.

Said turning is possible, because the tapering section 3 is made of a thin ma- terial. In the locking position, the bead 10 presses the seal sealably against the surface of the cable 7, and a friction force is generated, preventing the ca- ble from being pulled outwards from the wall 11, i. e. in the direction of arrow B.

Thus, the bead 10 provides an efficient pull-off. The tapering section 3 bends as in Figure 6, so that a turning point 14 is formed, and the more the seal is pulled in the direction of arrow B, the more the turning point presses the cable 7. The bead 10 and the turning point 14 provide a very efficient pull-off, which is due to the great friction forces against the surface of the cable. In most ap- plications, it is sufficient to perform the pull-off only by means of the bead 10, but the turning point 14 further improves the pull-off. In the locking position, the distance X between the bead 10 and the end 1 of the seal is shorter than the distance Y between the outer surface of the turning point 14 and the end of the seal.

[0025] Figure 5 shows that the tapering section 3 comprises two ta- pering conical surfaces 17 and 18, which are at different angles (X and P, re- spectively, to the axial direction of the seal. The conical surface 17 forms, if

desired, a clamping surface for a cable tie 19 or the like, cf. Figure 7. Com- pared to Figure 6, an alternative way of pressing the seal against the cable 7 is implemented by means of the cable tie 19 and the clamping surface 17. The use of the seal according to Figure 7 also provides an efficient pull-off. The use of Figure 7 is particularly suitable for multicore cables. Since the angle a is small, preferably about 0 to 30°, more preferably 0 to 20°, the cable tie 19 can be firmly tightened to its place. When the angle is bigger than the angle a, the total length of the seal is small, which is an advantage.

[0026] In Figure 7, the wall 11'is thicker than the wall 11, but the seal is the same as in Figure 5. The same seal can be used for wall thick- nesses of 1 to 5 mm, because it comprises a cylindrical surface 20, which is about 5 mm, i. e. 4 to 6 mm, wide. The flexible seal collar 16 bends so that it presses the wall 11,11', regardless of the wall thickness within the range of 1 to 5 mm. The width of the cylindrical surface 20, i. e. the length in the axial di- rection, varies typically between 4 to 6 mm.

[0027] Figure 8 shows a second embodiment of the seal. The em- bodiment of Figure 8 differs from the embodiment of Figures 1 to 6 in that the material reduction 8'is formed at the wide end 1'of the seal, in which case there is a ready-made hole 6'at the narrow end 2'of the seal, the hole in a way corresponding to the hole 6 of Figure 4.

[0028] In the above, the invention is described only by means of examples, and therefore it is to be noted that the details of the invention can be implemented in a variety of ways within the scope of the attached claims.

Thus, for example, the shape of the bead and gripping shoulder formed by the bead can vary from an annular member; and the bead need not necessarily be at the second end 2 of the seal, even though it is advantageous, when the compactness and small size of the seal are considered, but it may be posi- tioned at a short distance from it. If the bead is further away from the end 2 of the seal, the diameter of the seal must be greater compared to the situation where the bead is at the point shown by the figures. The gripping shoulder formed by such a bigger bead cannot be gripped so well. Furthermore, it would not provide such a gripping shoulder that could function as stopping means for the cable tie tightened around the clamping surface 17, because the cable tie could not be made to tighten around the cable. The seal can also be fastened to a wall other than an enclosure wall.