JP7494658B2 - Grommet - Google Patents

Description

The present invention relates to a grommet for waterproofing the exit of a cable connected to an electronic device from its housing.

Electronic devices installed outdoors must be waterproof, and ideally the entire device should be covered in a case. However, because cables must be routed out of the electronic device to connect to a power source, network, etc., some sort of waterproof structure is required for the cable outlet of the case.
As a waterproof structure for waterproofing a cable outlet portion of a housing, a grommet as shown in Patent Document 1 and Patent Document 2 is generally known. The grommet is usually made of a rubber material and has a cable insertion portion.

In the initial state, the hole through which the cable passes is often blocked by a lid. When using this type of grommet, a hole is drilled in the lid or the lid is cut off to allow the cable to pass through. In addition, in conventional grommets, the periphery of the lid is sometimes made thin so that the thin part can be easily cut by pressing the lid with a screwdriver or the like, making it easier to drill a hole.

JP 2005-110427 A JP 2018-182986 A

In conventional grommets as described above, if the cable moves relative to the housing after it is attached to the housing of an electronic device and a cable is passed through it, the cable insertion portion of the grommet cannot follow the cable, and a gap may occur between the cable and the grommet.
Furthermore, if the periphery of the cover that covers the cable insertion portion is made thin to make it easier to drill a hole in the cable insertion portion, the thin portion that remains after drilling may get inside the cable insertion portion and become pinched between the cable and the grommet, resulting in a gap between the cable and the grommet.

To prevent gaps from forming between the cable and the grommet, one idea is to insert the cable into the grommet and then inject caulking material into the grommet to seal the gap between the cable and the grommet. However, with conventional grommets, no consideration is given to the injection of caulking material, making this method difficult to work with and making it difficult to fill the gap sufficiently with caulking material.

The object of the present invention is to provide a grommet that allows the cable to be easily moved relative to the grommet and has excellent waterproofing properties that prevent water from entering the housing of an electronic device through the seal portion having the grommet.

To achieve this objective, the grommet of the present invention comprises a plate-shaped mounting portion that is attached to the housing of an electronic device, a gutter-shaped filling portion that protrudes from the mounting portion toward the outside of the housing, and a tubular cable insertion portion that has a cable insertion opening that is large enough to insert a cable and opens toward the inner space of the filling portion and is formed in the mounting portion so as to extend from the cable insertion opening toward the inside of the housing, and a recess that opens toward the inside of the housing is formed on the back surface of the mounting portion that faces the inside of the housing and is at the boundary with the cable insertion portion so as to surround the periphery of the cable insertion portion.

In the grommet of the present invention, the cable insertion portion has a connection portion that is connected to the mounting portion to form the cable insertion opening, and a seal portion that extends from the connection portion toward the inside of the housing, and the thickness of the seal portion may be thinner than the thickness of the connection portion.

In the grommet of the present invention, a lid that closes the cable insertion portion is provided at the tip of the cable insertion portion located opposite the cable insertion opening, and the lid is composed of a thin-walled portion connected to the cable insertion portion and a plate-shaped pressure-receiving portion that is formed thicker than the thin-walled portion and cooperates with the thin-walled portion to close the cable insertion portion, the thin-walled portion is disposed inside the housing from the tip surface of the cable insertion portion that faces the inside of the housing and inside the outer cylindrical wall surface of the cable insertion portion, and the boundary between the cable insertion portion and the lid may be composed of a first corner that is the boundary between the inner cylindrical wall surface of the cable insertion portion and the thin-walled portion, and a second corner that is the boundary between the tip surface of the cable insertion portion and the thin-walled portion.

In the grommet of the present invention, the cable insertion port may be formed in a tapered shape with a gradually decreasing diameter from the inner space of the filling portion toward the inside of the housing.

In the present invention, the cylindrical cable insertion portion is capable of swinging about one end portion adjacent to the inner space of the filling portion, and is also capable of translational movement in a direction perpendicular to the direction in which the cable extends. This allows the cylindrical cable insertion portion to reliably follow the tilting and translational movement of the cable, thereby maintaining waterproofing.
Because the cable insertion portion is easily deformed in this way, force is less likely to be transmitted from the cable to portions other than the cable insertion portion, such as the grommet attachment portion, the filling portion, etc. This makes it possible to maintain a high level of sealing in the gap between the portions other than the cable insertion portion and the housing of the electronic device, thereby preventing water from entering or insects from entering through this gap.
Therefore, according to the present invention, it is possible to provide a grommet that allows the cable to be easily moved relative to the grommet and has excellent waterproofing properties that prevent water from entering the housing of an electronic device through the seal portion having the grommet.

FIG. 1 is a perspective view of a housing of an electronic device using a grommet according to the present invention. FIG. 2 is an exploded perspective view showing the housing of the electronic device. FIG. 3 is an exploded perspective view showing the housing of the electronic device with the housing cut away. FIG. 4 is a front view of the grommet. FIG. 5 is a perspective view of the grommet as viewed from the outside of the housing. FIG. 6 is a perspective view of the grommet as viewed from the inside of the housing. FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. FIG. 8 is an enlarged cross-sectional view showing a main portion of the grommet. FIG. 9 is an enlarged cross-sectional view showing a main portion of the grommet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a grommet according to the present invention will now be described in detail with reference to FIGS.
The electronic device 1 shown in Fig. 1 has a box-shaped housing 2. This housing 2 can be installed outdoors. When installing this electronic device 1 outdoors, the bottom surface 2a of the housing 2, which is located on the lower right side in Fig. 1, is placed downward, and the front surface 2b of the housing 2, which is drawn largest in Fig. 1, faces forward of the electronic device 1.

The housing 2 is formed into a box shape by combining a lower case 3 and an upper case 4 .
A protrusion 5 that protrudes downward further than other portions is provided at the lower end of the housing 2. As shown in Figure 2, the protrusion 5 is formed by a protrusion 3a of the lower case 3 and a cover portion 4a of the upper case 4 that covers the protrusion 3a.

A hole 6 is formed on the underside of the protrusion 5. A cable 7 is passed through this hole 6. The cable 7 is a cable for connecting the electronic device 1 to a power source, a network, etc. The hole 6 of the protrusion 5 is formed as a notch in the cover portion 4a of the upper case 4. As shown in FIG. 2, a waterproof structure 11 is provided inside the protrusion 5. The waterproof structure 11 is for sealing the cable penetration portion 12 where the cable 7 penetrates the housing 2, and is composed of a bottom wall portion 13 that protrudes from the lower case 3 toward the inside of the housing 2, a grommet 14 attached to the bottom wall portion 13, a cover portion 4a of the upper case 4 that is placed over the grommet 14, and a caulking material 15 filled between the grommet 14 and the cover portion 4a.

3, the lower wall portion 13 is formed in a plate shape and has a box-shaped enclosure portion 16 that protrudes downward (toward the lower right in FIG. 3). A first notch 17 is formed in the front portion of the lower wall portion 13 for passing a part of a grommet 14, which will be described later.
The enclosure 16 is formed into a bottomed rectangular tube shape together with a part of the bottom wall 13. The opening of the rectangular tube constituting the enclosure 16 faces the front of the electronic device 1. A second notch 18 is formed on the bottom surface of the enclosure 16 for passing a part of a grommet 14 described later.

The grommet 14 is made of a rubber material and formed into a predetermined shape, and as shown in Figures 4 to 6, it has a plate-shaped mounting portion 21, a gutter-shaped filling portion 22 that protrudes from the mounting portion 21 toward the outside (downward) of the housing 2, and a cylindrical cable insertion portion 24 (see Figures 6 and 7) that includes a cable insertion port 23 that opens in the center of the mounting portion 21.

The mounting portion 21 is formed in a shape that fits into the above-mentioned surrounding portion 16 of the housing 2. At one end of the mounting portion 21 (the upper end in FIG. 4, the end on the front side of the electronic device 1), a first thin portion 25 is formed that is thinner with a step than other portions of the mounting portion 21. At both ends of the first thin portion 25, as shown in FIG. 2, protrusions 25a are provided that overlap the opening edge of the surrounding portion 16 from the front side of the electronic device 1.
A step 26 is formed between the first thin-walled portion 25 and the filling portion 22 so as to be thicker than the mounting portion 21. A first corner 27 located on the front side of the step 26 constitutes a line that serves as a guide for the appropriate amount of caulking material 15 to be injected into the filling portion 22, and is the front maximum limit position of the caulking material 15.

As shown in FIG. 6, a convex wall 28 is provided in the center of the left-right direction on the back side of the mounting portion 21, on the front side of the electronic device 1 (the upper side in FIG. 6), so that the thickness is greater than other parts of the mounting portion 21. This convex wall 28 is inserted into a first notch 17 of the lower wall portion 13 when the mounting portion 21 is inserted into the enclosure portion 16 of the lower case 3. The first notch 17 is formed so that a cable insertion portion 24, which will be described later, can pass through. Therefore, the front side of the center of the mounting portion 21 corresponding to the first notch 17 is no longer supported by the lower wall portion 13. However, in this embodiment, the convex wall 28 is provided in this portion, so this portion can be reinforced.

The back surface 21a of the mounting portion 21 facing the inside of the housing 2, which is at the boundary with the cable insertion portion 24, has a recess 31 that opens toward the inside of the housing 2 and surrounds the cable insertion portion 24.

As shown in Figs. 4 and 5, the filling section 22 is formed with a U-shaped cross section that opens toward the front of the electronic device 1 when viewed from below. Therefore, the filling section 22 has a first opening 32 that opens toward the outside of the housing 2 (downward), and a second opening 33 that opens in a direction perpendicular to the direction toward the outside of the housing 2 (to the front of the electronic device 1). When the mounting section 21 of the grommet 14 is inserted into the surrounding section 16 of the lower case 3, the filling section 22 is inserted into the second notch 18 of the surrounding section 16.

The first opening 32 constitutes a line that indicates the proper amount of caulking material 15 to be injected into the filling portion 22 and represents the lower limit of the maximum amount of caulking material 15 .
The second opening 33 is closed by the cover portion 4 a of the upper case 4 when the upper case 4 is attached to the lower case 3 to which the grommet 14 is attached.
The second opening 33 constitutes a line that serves as a guide for the proper amount of caulking material 15 to be injected into the filling section 22 and is the front lowest limit position of the caulking material 15.

At the lower end of the filling section 22, a second thin-walled section 34 is formed, which is thinner than the other parts of the filling section 22 at a step. A second corner 35, which is the boundary between the second thin-walled section 34 and the other parts of the filling section 22, forms a line that serves as a guide for the appropriate amount of caulking material 15 to be injected into the filling section 22, and is the lowest limit position on the lower side of the caulking material 15.

The cable insertion opening 23 is large enough to allow the cable 7 to be inserted and opens toward the inner space of the filling section 22. As shown in FIG. 7, the cable insertion section 24 having this cable insertion opening 23 is formed in the mounting section 21 so as to extend from the cable insertion opening 23 toward the inside of the housing 2 (to the right in FIG. 7), with the cable insertion opening 23 being one end. In this embodiment, the cable insertion section 24 is formed in a cylindrical shape that tapers away from the cable insertion opening 23.

In more detail, the cable insertion portion 24 has a connection portion 41 that is connected to the attachment portion 21 to form the cable insertion opening 23, and a seal portion 42 that extends from the connection portion 41 toward the inside of the housing 2. The connection portion 41 is formed in a tapered shape that gradually becomes smaller in diameter as it approaches the inside of the housing 2. Therefore, the cable insertion opening 23 is formed in a tapered shape that gradually becomes smaller in diameter as it approaches the inside of the housing 2 from the inner space of the filling portion 22.

The seal portion 42 is a portion that adheres liquid-tightly to the outer surface of the cable 7. The seal portion 42 in this embodiment is formed in a tapered shape with a gradually decreasing diameter toward the inside of the housing 2 so that the change in diameter is smaller than that of the connection portion 41, in other words, so that the taper angle is smaller. The thickness of the seal portion 42 is thinner than the thickness of the connection portion 41. In addition, the seal portion 42 protrudes toward the inside of the housing 2 beyond the attachment portion 21.

A lid 43 that closes the cable insertion portion 24 is provided at the tip of the seal portion 42, in other words, at the tip located on the opposite side of the cable insertion opening 23 of the cable insertion portion 24. The lid 43 is formed in a circular shape when viewed from the longitudinal direction of the cable insertion portion 24. The lid 43 in this embodiment is composed of a thin-walled portion 44 connected to the cable insertion portion 24 and a plate-shaped pressure-receiving portion 45 that is formed thicker than the thin-walled portion 44 and cooperates with the thin-walled portion 44 to close the cable insertion portion 24. The thin-walled portion 44 is disposed inside the housing 2 from the tip surface 24a of the cable insertion portion 24 that faces the inside of the housing 2, and inside the outer cylindrical wall surface 24b of the cable insertion portion 24.

As shown in FIG. 8, a first corner 46 is formed at the boundary between the inner cylindrical wall surface 24c of the cable insertion portion 24 and the thin-walled portion 44. A second corner 47 is formed at the boundary between the tip surface 24a of the cable insertion portion 24 and the thin-walled portion 44. These first corner 46 and second corner 47 form the boundary between the cable insertion portion 24 and the lid 43. In this embodiment, the first corner 46 and second corner 47 are formed at approximately the same position in the longitudinal direction of the cable insertion portion 24.

Next, the procedure for assembling the grommet 14 to the housing 2 will be described. In order to assemble the grommet 14 to the housing 2, first, a hole is drilled in the cable insertion portion 24 of the grommet 14. This drilling operation is performed by inserting a tool such as a screwdriver into the cable insertion opening 23 and using the tool to push the lid 43. When the lid 43 is pushed by the tool, the first corner 46 opens and the lid 43 is bent so that the second corner 47 narrows, as shown in FIG. 9. When the lid 43 is strongly pressed by the tool, stress is concentrated at the first corner 46 and the second corner 47. This stress concentration causes cracks to occur starting from the first corner 46 or the second corner 47, causing the thin portion 44 to break, and the lid 43 to come off from the cable insertion portion 24. At this time, it is considered that the cracks occur as shown by the two-dot chain line A and the two-dot chain line B in FIG. 9.

After a circular hole is thus created in the cable insertion portion 24, the cable 7 is inserted into the cable insertion portion 24 from the cable insertion opening 23. The mounting portion 21 of the grommet 14 is then fitted into the enclosure portion 16 of the lower case 3. After that, the caulking material 15 is injected into the filling portion 22 of the grommet 14. The caulking material 15 is injected from the first opening 32 of the filling portion 22 toward the inner space of the filling portion 22. After the caulking material 15 has been filled into the filling portion 22, the upper case 4 is attached to the lower case 3.

In the grommet 14 according to this embodiment, a recess 31 is formed on the rear surface 21a of the mounting portion 21 so as to surround the cable insertion portion 24, allowing the cylindrical cable insertion portion 24 to swing about one end adjacent to the inner space of the filling portion 22 and to move parallel to the direction perpendicular to the extension direction of the cable 7. This allows the cylindrical cable insertion portion 24 to reliably follow the tilting and parallel movement of the cable 7, thereby maintaining waterproofing.

Since the cable insertion portion 24 is easily deformed in this manner, force is less likely to be transmitted from the cable 7 to portions other than the cable insertion portion 24, such as the mounting portion 21 and the filling portion 22 of the grommet 14. This makes it possible to maintain a high level of sealing in the gap between the portions other than the cable insertion portion 24 and the housing 2 of the electronic device 1, thereby making it possible to prevent water from entering or insects from entering through this gap.
Therefore, according to this embodiment, it is possible to provide a grommet that allows the cable 7 to be easily moved relative to the grommet 14 and has excellent waterproofing properties that prevent water from entering the housing 2 of the electronic device 1 through the seal portion 42 having the grommet 14.

The cable insertion portion 24 of the grommet 14 according to this embodiment has a connection portion 41 that is connected to the mounting portion 21 to form the cable insertion opening 23, and a seal portion 42 that extends from the connection portion 41 toward the inside of the housing 2. The thickness of the seal portion 42 is thinner than the thickness of the connection portion 41. Therefore, even if the wire diameter of the cable 7 used varies, and even if the cross-sectional shape of the cable 7 is round or rectangular, the seal portion 42 can be reliably in contact with the cable 7.

In this embodiment, the boundary between the cable insertion portion 24 and the lid 43 is formed by a first corner 46 that is the boundary between the inner cylindrical wall surface 24c of the cable insertion portion 24 and the thin-walled portion 44, and a second corner 47 that is the boundary between the tip surface 24a of the cable insertion portion 24 and the thin-walled portion 44. Therefore, the fracture trace of the thin-walled portion 44 of the lid 43 is not formed so as to be convex inside the cable insertion portion 24, so that it is possible to reliably prevent a gap from being formed between the grommet 14 and the cable 7.

The cable insertion port 23 in this embodiment is formed in a tapered shape with a gradually smaller diameter from the inner space of the filling section 22 toward the inside of the housing 2. This prevents the connection section 41 of the cable insertion section 24 from moving toward the inside of the filling section 22 when the caulking material 15 is injected. In addition, since the space between the cable 7 and the cable insertion port 23 is widely open, the workability when injecting the caulking material 15 is improved, and the caulking material 15 flows smoothly, preventing the occurrence of a gap between the grommet 14 and the caulking material 15.

1...electronic device, 2...housing, 7...cable, 21...mounting section, 21a...rear surface, 22...filling section, 23...cable insertion port, 24...cable insertion section, 24a...tip surface, 24b...outer tube wall surface, 24c...inner tube wall surface, 31...recess, 41...connection section, 42...seal section, 43...lid, 44...thin section, 45...pressure receiving section, 46...first corner section, 47...second corner section.

Claims (3)

A plate-shaped mounting portion that is attached to a housing of an electronic device;
a gutter-shaped filling portion protruding outward from the housing on the mounting portion;
a cable insertion opening having a size allowing a cable to be inserted therethrough and opening toward an inner space of the filling portion, the cable insertion opening being tubular and formed on the mounting portion so as to extend from the cable insertion opening toward the inside of the housing,
a recess that is open toward the inside of the housing is formed on a back surface of the mounting portion that faces inwardly into the housing and is at a boundary with the cable insertion portion so as to surround the cable insertion portion ,
a cover for closing the cable insertion portion is provided at a tip end of the cable insertion portion opposite to the cable insertion opening,
The lid is
a thin-walled portion connected to the cable insertion portion;
a plate-shaped pressure receiving portion that is formed thicker than the thin-walled portion and cooperates with the thin-walled portion to close the cable insertion portion,
the thin-walled portion is disposed inward of the housing with respect to a tip end surface of the cable insertion portion that faces the inside of the housing and inward of an outer cylindrical wall surface of the cable insertion portion,
The boundary between the cable insertion portion and the lid is
a first corner portion that is a boundary between an inner cylindrical wall surface of the cable insertion portion and the thin-walled portion;
A grommet comprising a second corner portion which is a boundary between the tip surface of the cable insertion portion and the thin-walled portion . 2. The grommet according to claim 1,
The cable insertion portion is
a connection portion connected to the mounting portion to form the cable insertion opening;
a seal portion extending from the connection portion toward the inside of the housing,
A grommet, wherein the thickness of the sealing portion is thinner than the thickness of the connection portion. The grommet according to claim 1 or 2 ,
The grommet is characterized in that the cable insertion port is formed in a tapered shape such that the diameter gradually decreases from the inner space of the filling portion toward the inside of the housing.

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