WO2018068907A1

WO2018068907A1 - Grommet for sealing a tube, electric device, and method for sealing a tube of an electric device

Info

Publication number: WO2018068907A1
Application number: PCT/EP2017/063875
Authority: WO
Inventors: Ales FILIPEC; Radim Sotkovsky
Original assignee: Continental Automotive Gmbh
Priority date: 2016-10-10
Filing date: 2017-06-07
Publication date: 2018-04-19
Also published as: GB2554752A; GB201617140D0

Abstract

The invention is concerned with a grommet (20) for sealing a tube (16) and supporting at least one wire (14) that is arranged inside the tube (16), the grommet (20) comprising a sealing body (20') for filling a part of a space between the at least one wire (14) and an inner wall (30) of the tube (16), wherein the sealing body (20') comprises a separate through-hole (21) for each wire (14). At least one sealing ring (25) is provided for sealing a remaining space (38) between the sealing body (20') and the inner wall (30), wherein each sealing ring (25) is arranged at an outer circumference (24) of the sealing body (20') and wherein each sealing ring (25) is made of an elastic material.

Description

Grommet for sealing a tube, electric device, and method for sealing a tube of an electric device

The invention is concerned with a cable grommet - or short grommet - for sealing a tube and for supporting at least one wire that is arranged inside the tube. The invention is also directed to an electric device that comprises the inventive grommet. Finally, the invention is concerned with a method for sealing a tube, in which at least one wire is to be arranged. The sealing is achieved by means of the inventive grommet.

In an electric device, especially a thermocouple-based tem- perature sensor, an electronic circuit may be connected to a sensor element, like, e.g. a thermocouple, by means of extension wires or extension cables. The wires of such an interface cable may be located inside a tube, e.g. a steel tube. The imper^¬ meability or tightness against humidity and gases is fundamental for this ensemble in order to avoid parasitic electrical connections and water intrusion into the tube, especially in the case of a thermocouple. The tightness is generally ensured by an element that is called cable grommet or short grommet. The grommet is compressed between the wires and the tube. To this end, the grommet is made of an elastic material, like e.g. silicone. The basic shape of a grommet is that of a cylinder. Parallel through-holes are provided for arranging the wires inside the grommet. The cylindrical outer shape of the grommet fits inside the tube .

For sealing the tube with the grommet arranged inside, com^¬ pression is achieved by mechanically deforming the tube, e.g. by crimping. However, mechanically deforming the tube for the sealing can have a deteriorating effect on the water tightness regarding the region between the inside wall of the tube and the outside surface of the grommet. Further, crimping the tube is an additional production step that takes time and needs special tools . ^

It is an object of the present invention to seal a tube in which at least one wire is arranged, wherein the wire is aligned in parallel to an axis of the tube.

The object is achieved by the subject matter of the independent claims. Advantageous developments with convenient and

non-trivial further embodiments of the invention are specified in the following description, the dependent claims and the figures.

The invention provides a grommet for sealing a tube and supporting at least one wire that is arranged inside the tube and that is aligned in parallel to an axis of the tube. The method comprises a sealing body for partially filling a space between the at least one wire and an inner wall of the tube. The sealing body may have a basic outer shape of a cylinder. Like is known from conventional grommets, the sealing body comprises a separate through-hole for each wire. In other words, each wire may be passed through one separate through-hole of the sealing body. The sealing body may be made from e.g. silicone. An axis of each through-hole can be arranged in parallel to the axis of the tube. In other words, each through-hole is oriented parallel to a longitudinal axis of the sealing body. Thus, with the at least one wire arranged or stuck through a respective through-hole of the sealing body, the sealing body may be pushed or arranged inside the tube.

In order to seal the space between the outer surface of the sealing body on one side and the inner wall of the tube on the other side, the inventive grommet comprises at least one sealing lip or sealing ring. Preferably several sealing rings are provided. The at least one sealing ring is for sealing the remaining space between the sealing body and the inner wall of the tube. Each sealing ring is arranged at an outer circumference of the sealing body. Each sealing ring is made of an elastic material, like the already mentioned silicone. Each sealing ring is a ridge or edge encompassing the sealing body. Each sealing ring has a thickness or spatial extent along the axis of the at least one through-hole that is smaller than the spatial extent of the sealing body along the same direction. In other words, the sealing body is longer than each sealing ring is thick. Thus, each ring forms a sealing lip that is arranged around the outer circumference of the sealing body.

The invention provides the advantage that the sealing body of the grommet may be pushed inside the tube without the sealing body blocking this move, as the sealing body can have a diameter that is smaller than the inner diameter of the tube. Only the sealing ring or the several sealing rings touch the inner wall of the tube. As the at least one sealing ring as a whole is softer than the whole sealing body (due to the lesser or smaller extent along the axis) , the at least one sealing ring may be bent or deformed with less force than is needed to deform the whole sealing body.

In other words, the inventive grommet can be used for the following method for sealing a tube in which at least one wire is to be arranged. The at least one wire is pushed or threaded through a respective through-hole of the sealing body of the grommet. Then, the grommet is pushed inside the tube, whereby the at least one sealing ring at the outer circumference of the sealing body is elastically bent and/or compressed, such that an outer contour of each sealing ring is adapted to a contour of the inner wall of the tube. In other words, the sealing of the tube is achieved by means of bending and/or compressing, that is deforming the at least one sealing ring by pushing the grommet inside the tube. The invention also comprises optional embodiments that provide additional features which afford additional technical ad^¬ vantages .

Preferably, one sealing ring or two or three or more than three sealing rings are provided. The spatial extent of each sealing ring along the axis is less than 20%, in particular less than 10%, of the spatial extent of the sealing body. This allows for the deformation of each sealing ring with a force, can be applied easily with e.g. a finger.

Preferably, in a cross section (along the axis) each sealing ring comprises a triangular shape with one broad side of the triangular shape facing the outer circumference of the sealing body and an opposite tip of the triangular shape forming an outer rim of the sealing ring. In other words, each sealing ring is thinner and/or softer at the outside as compared to the inside. In other words, the thickness of each sealing ring is a function of the radial distance with regard to the axis, wherein the sealing ring is thinnest at the largest radial distance. Thus, the outer rim of each sealing ring is the softest part of the sealing ring. This allows for a reliable adaptation of the contour or shape of the outer rim with regard to the inner wall of the tube.

In order to provide an elastic sealing ring, the already mentioned elastic material preferably comprises or is made of silicone or PTFE ( Polytetrafluorethylene or Teflon) . These materials have proven to provide reliable sealing properties even at high temperatures around 270°C.

Each sealing ring may be a part of the sealing body itself. In other words, the sealing body and the at least one sealing ring may formed as one piece made of the same material. In other words, the grommet may be made of one body of a basic cylindrical shape, wherein the diameter of the body varies along the axis peri^¬ odically as a function of position along the axis in order to provide several sealing rings. Preferably, the profile or contour of the surface of the inner wall of each through-hole is of the shape of a sawtooth.

Another aspect of sealing the tube regards the space between each wire and the inner wall of the through-hole of the sealing body. Inside each through-hole preferably at least one elastic inner sealing ring is provided. The spatial extent of each sealing ring along the axis is smaller than a spatial extent of the through-hole along the same direction. Each inner sealing ring is thus thinner or flatter than the sealing body as a whole. In other words, at least one section of each through-hole provides a diameter of the through-hole that varies as a function of the position along the axis. Preferably, the profile or contour of the outer surface of the sealing ring is of the shape of the comb or a sawtooth. Thus, at least one inner sealing ring or sealing lip is provided inside each through-hole such that the sealing ring or sealing lip seals the space around the wire that may be arranged or pushed through the through-hole.

Accordingly, the inventive method for sealing the tube comprises that at least one inner sealing ring is provided inside each through-hole and each sealing ring is elastically bent and/or compressed (that is overall deformed) by the pushed-in wire such that an inner contour of each sealing ring is adapted to an outer contour of the wire.

As was already explained, by using a grommet with outer sealing rings and preferably inner sealing rings as well, the shape of the tube can stay unchanged for the sealing. In other words, no crimping is performed at the tube.

The invention also comprises an electric device that is sealed using the inventive grommet. The electric device comprises a tube and at least one wire arranged inside the tube. Each wire is oriented in parallel to a longitudinal axis of the tube. An embodiment of the inventive grommet is provided, wherein the at least one wire is stuck through a respective through-hole of the grommet and the grommet is pushed inside the tube. Thus, the tube with the wires arranged inside is sealed against water and/or gas without the need of deforming the tube.

In a preferred embodiment, the electric device is a thermo-sensor with at least one wire connecting a thermocouple wire with an electronic circuit. Thus, the thermocouple wires stay dry and sealed inside the tube, while the electric wires may be led through the grommet to the outside of the tube. Fig. 1 a schematic illustration of an electric device ac^¬ cording to an embodiment of the invention;

Fig. 2 a schematic illustration of components of the electric device of figure 1; and

Fig. 3 schematic illustration of a grommet used for sealing tube of the electric device of figure 1. The embodiment explained in the following is a preferred em^¬ bodiment of the invention. However, in the embodiment, the described components of the embodiment each represent individual features of the invention which are to be considered inde^¬ pendently of each other and which each develop the invention also independently of each other and thereby are also to be regarded as a component of the invention in individual manner or in another than the shown combination. Furthermore, the described em^¬ bodiment can also be supplemented by further features of the invention already described.

In the figures elements that provide the same function are marked with identical reference signs.

Fig. 1 shows an electric device 10. The device 10 can be, for example, a thermo-sensor . The device 10 can comprise a mineral insulated cable 11 in which two thermocouple wires can be arranged. The so-called hot end 12 of the thermocouple wires can be arranged inside a zone a temperature of which must be de^¬ termined. For determining the temperature, an electronic circuit 13 can be provided. The electric device 10 can be arranged inside a motor vehicle for measuring the temperature of, e.g., ex^¬ haustion gas .

For connecting the thermocouple wires of the mineral insulated cable 11 with the electronic circuit 13, electric wires 14 can be provided for extending the thermocouple wires. The electric wires 14 can be arranged inside a braiding 15 for elec- tro-magnetically shielding the wires 14. Welding joints between the wires 14 and the thermocouple wires can be protected or arranged inside a tube 16. The tube 16 can be made of metal, e.g. steel . For fixing the mineral insulated cable 11 such that the hot and 12 is arranged inside the zone, a screw 17 and an olive ring can be provided.

Fig. 2 shows the components as they can be arranged inside the tube 16. Additionally, Fig. 2 illustrates the thermocouple wires 18 reaching out of the mineral insulated cable 11.

A separator 19 may be provided for preventing the thermocouple wires 18 and/or the wires 14 from touching. This makes the electric device 10 robust against vibrations, such as they may be caused inside a motor vehicle.

In order to prevent water and/or humidity and/or gas from intruding the tube 16 and from reaching welding joints 18' that connect the wires 14 and the thermocouple wires 18, a grommet 20 can be provided.

The grommet 20 is illustrated in Fig. 3 in more detail. The grommet 20 can be based on a sealing body 20' that provides one through-hole 21 for each wire 14. A middle axis of each through-hole 21 is aligned along or parallel to an axis 22 of the tube 16. Through each through-hole 21, one of the wires 14 can be pushed or threaded through. For sealing the tube 16 with the wires 14 arranged inside, the grommet 20 can be pushed into the tube 16 along a pushing direction 23 which points along the axis 22. At an outside or outer circumference 24 of the sealing body 20', several sealing rings 25 may be arranged. The sealing rings 25 are made of a flexible material. An outer diameter 26 of the sealing rings 25 is larger or greater than an inner diameter 27 of the tube 16. On the other hand, an outer diameter 28 of the sealing body 20' is smaller than the inner diameter 27 of the tube 16. A spatial extent Wl of each sealing ring 25 along the axis 22 is smaller than a spatial extent WO of the sealing body 20' along the same direction.

When pushing the grommet 20 along the pushing direction 23 into the tube 16, the soft, flexible and/or elastic sealing rings 25 are deformed as is illustrated in Fig. 3 by dashed lines. The adapted or deformed sealing rings 29 have an outer shape or contour that corresponds to the contour of an inner wall 30 of the tube 16. The adapted sealing rings 29 have their adapted shape only when arranged inside the tube 16. Fig. 3 shows the adapted rings 29 outside the tube 16 only for illustration purposes.

A basic outer shape of the sealing body 20' can be that of a cylinder. The basic shape of a cross section of each sealing ring 25 can comprise the shape of a triangle with one broad base side 31 attached to the sealing body 20' and the opposite tip 32 forming an outer rim 33 of each sealing ring 25. As shown in Fig. 3, in the longitudinal section of the grommet 20, an overall outer shape of the sealing rings 25 can be that of a comb or sawtooth.

Additionally, in each through-hole 21, inner sealing rings 34 may be provided for sealing a space between the wire 14 arranged inside the through-hole 21 and an inner wall 35 of the through-hole. Fig. 3 shows reference signs for one through-hole 21 only.

By pushing the wire 14 through the through-hole 21, the inner sealing rings 34 are elastically deformed, i.e. compressed and/or bent. The inner contour 36 of each sealing ring 34 is thus adapted to an outer contour 37 of the wire 14. A spatial extent W2 of each inner sealing ring 34 along the axis 22 is smaller than a spatial extent W0 of the through-hole 21 along the same direction. The shape of the inner surface of the sealing rings 34 in the longitudinal cross-section as shown in Fig. 3 can be that of a sawtooth.

Water and/or humidity and/or gas cannot reach the welding joints 18' from the far end side of the wires 14, i.e. from the direction of the electronic circuit 13. The space 38 between the sealing body 20' and the inner wall 30 of the tube 16 is sealed by the sealing rings 25. The space 39 between the wires 14 and the inner wall 35 of each through-hole 21 is sealed by the inner sealing rings 34.

The inner diameter 41 of each through-hole 21 in regions outside the sealing rings 34 is larger than the outer diameter 42 of the wires 14. An inner diameter 43 of each sealing ring 34 is smaller than the diameter 42, in the case that no wire 14 is pushed through the sealing ring 34.

As only the outer tips 32 of the sealing rings 25 are touching the inner walls 30, the pressure or force which deforms the sealing rings 25 is greater compared to a grommet with a constant diameter 28.

As only the inner tips 40 of each inner sealing ring 34 are touching the wires 14, the pressure or force which deforms the sealing rings 34 is greater compared to a grommet with a constant diameter 41. Thus, each wire 14 is only blocked by the tips 40 of each sealing ring 34. Thus, the pressure or forces concentrated at the tips 40 which provides a reliable sealing inside each through-hole 21.

The grommet 20 with the sealing body 20' and the sealing rings 25, 34 may be produced or provided as one piece. The material for providing the grommet 20 can be silicone or PTFE, for example. The grommet 20 provides all the deformation needed for sealing the tube 16. Thus, the tube 16 does not need to be changed in shape after the grommet 20 is positioned inside the tube. To allow for the deformation of the grommet 20 in a reliable manner, the structure of the contact surface between the grommet 20 and the inner wall 30 of tube 16 is a surface with lips or rings. The lips are also around the wires 14 inside the through-holes 21.

Additionally, instead of providing the separator 19, the grommet 20 can provide an axial prolongation 44 for covering the wires 14 and/or 18 and protecting them against a short circuit. Overall, a more robust design results which is less sensitive to irregularities of the inner wall 30 of the tube 16 regarding inner surface structure. Also, temperature driven changes of the compression of the grommet 20 by the tube 16 are also compensated by the sealing lips 25. As no separator is needed with the prolongation 44, a simpler manufacturing concept with less number of parts is possible. Also, as no deformation of the tube 16 is required, crimping of tube 16 is also unnecessary.

Overall, the example shows how a sealing of wires in a tube is made possible by the invention.

Claims

1. Grommet (20) for sealing a tube (16) and supporting at least one wire (14) that is arranged inside the tube (16), comprising a sealing body (20') for filling a part of a space between the at least one wire (14) and an inner wall (30) of the tube (16), wherein the sealing body (20') comprises a separate through-hole (21) for each wire (14) and wherein each through-hole (21) is oriented parallel to a longitudinal axis (22) of the grommet (20) , c h a r a c t e r i z e d b y

at least one sealing ring (25) for sealing a remaining space (38) between the sealing body (20') and the inner wall (30), wherein each sealing ring (25) is arranged at an outer circumference (24) of the sealing body (20') and wherein each sealing ring (25) is made of an elastic material and wherein a spatial extent (Wl) of each sealing ring (25) along the axis (22) is smaller than a spatial extent (W0) of the sealing body (20') along the same direction .

2. Grommet (20) according to claim 1, wherein one sealing ring (25) or two or three or more than three sealing rings (25) are provided and/or wherein the spatial extent (Wl) of each sealing ring (25) along the axis (22) is less than 20 percent, in particular less than 10 percent, of the spatial extent (W0) of the sealing body (20') .

3. Grommet (20) according to any of the preceding claims, wherein in a cross section each sealing ring (25) comprises a triangular shape with one broad side (31) of the triangular shape facing the outer circumference (24) of the sealing body (20') and an opposite tip (32) forming an outer rim (32) of the sealing ring (25) .

4. Grommet (20) according to any of the preceding claims, wherein the elastic material comprises or is silicone or PTFE.

5. Grommet (20) according to any of the preceding claims, wherein the sealing body (20' ) and the at least one sealing ring (25) form one piece made of the same material.

6. Grommet (20) according to any of the preceding claims, wherein inside each through-hole (21) at least one elastic inner sealing ring (34) is provided and wherein a spatial extent (W2) of each inner sealing ring (34) along the axis (22) is smaller than a spatial extent (WO) of the through-hole (21) along the same direction .

7. Grommet (20) according to claim 6, wherein in a longitudinal section along the axis (22) each inner sealing ring (34) comprises an inner diameter (43) for pushing through a wire (14) and an outer diameter (41) attached to the sealing body (20')_/ wherein the inner sealing ring (34) is thinnest at the inner diameter (43) and is broadest at the outer diameter (41) .

8. Electric device (10) comprising

- a tube (16) and

- at least one wire (14) arranged inside the tube (16) in parallel to a longitudinal axis (22) of the tube (16),

c h a r a c t e r i z e d b y

a grommet (20) according to any one of the preceding claims, wherein the at least one wire (14) is stuck through a respective through-hole (21) of the grommet (20) and the grommet (20) is pushed inside the tube (16) .

9. Electric device (10) according to claim 8, wherein the electric device (10) is a thermo-sensor with at least one wire (14) connecting a respective thermocouple wire (18) with an electronic circuit (13) .

10. Method for sealing a tube (16), in which at least one wire (14) is to be arranged, wherein

the at least one wire (14) is pushed through a respective through-hole (21) of a sealing body (20') of a grommet (20) according to any one of claims 1 to 7 and the grommet (20) is pushed inside the tube (16), whereby at least one sealing ring (25) at an outer circumference (24) of the sealing body (20') is elastically bent and/or compressed, such that an outer contour of each sealing ring (25) is adapted to a contour of an inner wall (30) of the tube (16) .

11. Method according to claim 10, wherein at least one inner sealing ring (34) is provided inside each through-hole (21) and wherein each inner sealing ring (34) is elastically bent and/or compressed by the pushed-in wire (14) such that an inner contour

(36) of each inner sealing ring (34) is adapted to an outer contour

(37) of the wire (14) .

12. Method according to claim 10 or 11, wherein a shape of the tube (16) stays unchanged for the sealing.