Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Reexamination Certificate
2000-02-04
2001-05-01
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
C174S1520GM
Reexamination Certificate
active
06225562
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sealing agent to be filled into a grommet, a method of sealing a wire harness with the sealing agent, and a sealing construction of the wire harness. More particularly, in order to waterproof the wire harness reliably, the present invention is intended to allow the sealing agent to have a high degree of penetration performance to fill gaps between groups of electric wires of the wire harness inserted into the grommet. Further, the present invention is intended to harden the sealing agent in a short period of time to accomplish a waterproof operation with high efficiency.
2. Description of Related Art
According to the conventional art, a wire harness W/H is positioned by penetrating it through a through-hole formed on a car body panel (P), as shown in FIG.
5
: An operator inserts the wire harness W/H into a grommet
1
made of rubber to bring it into close contact with a small-diameter section
1
a
of the grommet
1
. An engaging groove
1
c
formed on the peripheral surface of a large-diameter section
1
b
of the grommet
1
fits into the peripheral wall of a through-hole
2
of the car body panel (P), and a lip
1
d
formed on a part of the grommet
1
to be installed on the car body is brought into close contact with the car body panel (P). In this manner, the operator seals the wire harness W/H.
In inserting the grommet-installed wire harness W/H into an engine room and placing it at position, it is necessary to waterproof the wire harness W/H. To this end, referring to
FIG. 6
, inside the grommet, electric wires (w) constituting the wire harness W/H are not tied into a bundle with a tape but separated from each other. In this state, a sealing agent
3
is injected from the large-diameter section
1
b
of the grommet
1
into the gaps between the adjacent electric wires (w) and the gaps between the electric wires (w) and the inner peripheral surface of the grommet
1
.
The above-described conventional art has, however, a problem that the sealing agent
3
is incapable of penetrating readily into all the gaps, because the gaps between the adjacent electric wires (w) are small and in addition, the viscosity of the conventional sealing agent
3
is as high as 1,000 cps-2,000 cps.
A sealing agent having a low viscosity may be used to improve its flowability and hence its penetration property. But the problem is that it takes more than 15 minutes to harden. Thus, in that period of time, the sealing agent
3
flows downward from the grommet-installing region of the wire harness and is thus incapable of completely filling the gaps between the adjacent electric wires (w) inside the grommet.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described problems. It is accordingly an object of the present invention to provide a sealing agent having a low viscosity and improved penetration properties.
It is another object of the present invention to prevent the sealing agent from flowing downward from a grommet-installing region of a wire harness and further, reduce a sealing operation period of time by providing a sealing agent which hardens in a short period of time.
To achieve the above objects, a sealing agent of the present invention is filled into gaps between adjacent groups of electric wires and gaps between the groups of the electric wires and an inner peripheral surface of a grommet. The sealing agent is a two-liquid reactive hardening type and includes a hardening agent and a main agent containing a viscosity depressant mixed in a predetermined ratio with hardening accelerators. The sealing agent has a viscosity of 200 cps (centipoise)-500 cps in a grommet-to-wire assembly environment, such as an environment that has a temperature of from about 10° C. to about 40° C. and gels in three to seven minutes.
The mixing weight ratio between the main agent and the hardening agent of the sealing agent may be set to a range of 5.5:1-1:1. The main agent includes polyether polyol, triethanolamine and dibutyltin dilaurate both used as the hardening accelerators, a low-molecular weight aromatic hydrocarbon used as a viscosity depressant, and an anti-oxidant. The hardening agent includes polyisocyanate.
The sealing agent of the present invention has a viscosity in the range of 200 cps-500 cps in a grommet-to-wire assembly environment, such as an environment that has a temperature of from about 10° C. to about 40° C. More favorably, the viscosity of the sealing agent may be set to 300 cps, whereas the viscosity of a conventional agent is 1,000-2,000 cps. That is, the viscosity of the sealing agent is about ⅓-⅙ as low as that of the conventional one. Thus, the sealing agent of the present invention has a higher degree of flowability than the conventional one. Therefore, the sealing agent is capable of sufficiently penetrating into gaps between adjacent groups of electric wires and gaps between the groups of the electric wires and the inner peripheral surface of the grommet. The gelling time period is set to three-seven minutes. More favorably, it may be set to five minutes. Thus, the sealing agent gels before it flows downward from the grommet-installing region. Thus, there is no possibility that the sealing agent flows downward from the region which should be filled with the sealing agent. Further, the part of the groups of the electric wires positioned below the grommet-installing region is tightened to minimize the gaps between the groups of the electric wires. Therefore, the sealing agent being gelled can be prevented from flowing downward from the region which should be filled with the sealing agent.
According to another aspect, a method of sealing a wire harness according to the present invention comprises: mounting a large number of electric wires constituting the wire harness on a spacer for spacing groups of the electric wires at regular intervals so that a sealing agent fills into gaps between the groups of the electric wires; inserting the wire harness into a rubber grommet having a small-diameter section to be brought into close contact with a peripheral surface of the wire harness and a large-diameter section having a part to be mounted on a car body; bringing the spacer installed on the wire harness into close contact with an inner peripheral surface of the grommet; winding a tape around a leading end of the small-diameter section and the peripheral surface of the wire harness to fix the grommet to the wire harness at a predetermined position thereof; and injecting a sealing agent into the erected grommet from an opening positioned at an upper end of the large-diameter section, with the large-diameter section turned at an upper side of the grommet to fill the gaps between the groups of the electric wires and gaps between the groups of the electric wires and the inner peripheral surface of the grommet with the sealing agent.
The sealing agent has a low viscosity and a high flowability, thus penetrating sufficiently into narrow gaps between the adjacent groups of the electric wires without widening the gaps. To further ensure that the gaps are filled with the sealing agent, the spacer is installed in the grommet, thus waterproofing the wire harness securely.
According to another aspect of the invention, there is provided a sealing construction of a wire harness in which gaps between groups of electric wires and gaps between the groups of the electric wires and an inner peripheral surface of a grommet are filled with a sealing agent. The sealing agent is of a two-liquid reactive hardening type and includes a hardening agent and a main agent containing a viscosity depressant mixed in a predetermined ratio with hardening accelerators. The sealing agent has a viscosity of 200 cps-500 cps in a grommet-to-wire assembly environment, such as an environment that has a temperature of from about 10° C. to about 40° C. and gels in three to seven minutes.
According to still another aspect of the present invention, there is provided a sealing construction f
Fujishita Mikio
Kato Takahiro
Nguyen Chau N.
Oliff & Berridg,e PLC
Reichard Dean A.
Sumitomo Wiring Systems Ltd.
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