Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for other than internal combustion engine – or...
Reexamination Certificate
2003-03-10
2004-11-23
Pickard, Alison K. (Department: 3676)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal for other than internal combustion engine, or...
C277S552000, C277S928000, C464S175000
Reexamination Certificate
active
06820876
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a boot for a universal joint and, in particular, to a boot for a universal joint having a sealing structure that properly controls the flow of air or the like between the inside and the outside of the boot in response to a change in the inside volume of the boot based on a pressure fluctuation in the boot. The invention improves sealing performance against the intrusion of splashed water or muddy water.
2. Description of the Related Art
There has been conventionally known a boot for a universal joint having a structure which has a boot body made of an elastic material such as rubber and a boot adapter made of a plate such as a steel plate. One-end fitting portion of the boot body is fitted on the outer peripheral side of an inner shaft such as a propeller shaft or the like and the other-end fitting portion of the boot adapter is fitted on the outer race of the universal joint to prevent dust or muddy water from intruding into the universal joint.
Certain features of a boot for a universal joint are already known from a boot disclosed in Japanese Patent Application Laid-open No 8-28704. The foregoing boot
010
, as shown in
FIG. 9A
,
FIG. 9B
,
FIG. 10A
, and
FIG. 10B
, has a structure for coping with the pressure fluctuation in the boot
010
. There, an annular lip portion
01
b
is in contact with the inner shaft
03
of a propeller shaft or the like outside one-end fitting portion
01
a
of the boot
010
. A passage
01
D is present for making the inside of the boot
010
communicate with the outside thereof on the inner peripheral surface of the one-end fitting portion
01
a,
and a sealing structure is provided with discontinuous protrusions
01
c
for controlling the passage
01
D in response to the pressure fluctuation in the boot
010
in a circumferential direction of the inside of the annular lip portion
01
b.
The boot
10
controls the inflow or outflow of air or the like caused by the pressure fluctuation in the boot
010
via controlling the passage
01
D by the discontinuous protrusions
01
c,
to reduce a load applied to the boot
010
based on the pressure fluctuation thereby to improve the durability of the boot
010
.
In this respect, a part denoted by a reference symbol
0
B in the
FIG. 9A
is a fastening band used for fitting the boot
010
.
However, the boot provided with the sealing structure described above does not have sufficient measures against a detrimental effect produced by the pressure fluctuation in the boot. In particular, a pressure fluctuation may occur in the boot, for example, at a time when an abrupt pressure drop is caused in the boot by an abrupt increase in the inside volume of the boot, which is caused by the boot being expanded outward by the action of a centrifugal force produced by the rotation of the boot involved by the rotation of a shaft such as the propeller shaft or the like. In other words, the boot does not have sufficient measures against splashed water or muddy water intruding into the boot through the passage, along with the outside air being sucked into the boot when a negative pressure is produced by an abrupt pressure drop in the boot.
That is, in the sealing structure of the conventional boot
010
, as is evident from FIG.
10
A and
FIG. 10B
, when pressure in the boot
010
increases, as shown in
FIG. 10A
, air or the like in the boot
010
pushes up the lip portion
01
b
as shown by an arrow p and thus flows out. When the pressure in the boot decreases, as shown in
FIG. 10B
, the lip portion
01
b
is strongly pressed on the inner shaft
03
as shown by an arrow q to be bent inward, thereby to bring the discontinuous protrusions
01
c
formed in the circumferential direction on the inside of the lip portion
01
b
into contact with the inner shaft
03
. In this way, the lip portion
01
b
is supported by the protrusions
01
c,
and hence the tip portion of the lip portion
01
b
is raised up in such a manner to be separated from the inner shaft
03
as shown by an arrow r. This allows the air or the like to be smoothly sucked into the boot
010
through gaps between the discontinuous protrusions
01
c,
as shown by an arrow s, and hence raises the possibility that splashed water and muddy water will also intrude into boot along with the suction of the air or the like.
In particular, as described above, when negative pressure is produced by the abrupt pressure drop in the boot
010
caused by the boot
010
being expanded outward by the centrifugal force, a force for pressing the lip portion
01
b
in a direction shown by the arrow q is increased, to increase a tendency of raising up the tip portion of the lip portion
01
b,
as shown by the arrow r, thereby expanding a gap between the tip portion of the lip portion
01
b
and the inner shaft
03
. Further, the suction force of the outside air or the like applied to the tip portion, which is produced by the negative pressure abruptly produced in the boot
010
, raises the possibility that splashed water or muddy water will intrude into the boot
010
along with the suction of the air or the like.
The foregoing conventional boot, as described above, does not have a sealing structure which copes sufficiently with the splashed water or the muddy water intruding into the boot along with the suction of the outside air. The intrusion of splashed water or muddy water into the boot causes damage to the boot itself to reduce the durability of the boot. This also deteriorates the lubrication function of grease, which is a material lubricating the inside of the boot, thereby to wear the universal joint in the boot or to form rust over a short time of use, which results in significantly reducing the durability of the universal joint.
Thus, there has been a search for a boot having the sealing structure capable of properly coping with splashed water or muddy water intruding into the boot, but the fact is that there has not been developed a satisfactory boot provided with a sealing structure having a function properly coping with pressure fluctuation in the boot, and a function properly coping with splashed water or muddy water intruding into the boot.
Therefore, it is desired to quickly develop or improve a boot provided with a sealing structure capable of properly coping with the pressure fluctuation in the boot and effectively preventing splashed water or muddy water from intruding into the boot.
SUMMARY OF THE INVENTION
It is an object of the present invention, in a boot for a universal joint, to protect the universal joint and to improve the durability of the boot for the universal joint by properly controlling the flow of air between the inside and the outside of the boot caused by variations in pressure in the boot, to prevent splashed water or muddy water from intruding into the boot.
Under the circumstances, the invention provides the boot having a sealing structure capable of suitably coping with the pressure fluctuation in the boot. In particular, the invention relates to measures to remove a detrimental effect produced by a negative pressure generated in the boot by the action of a centrifugal force produced when the boot is rotated. To be more specific, the invention relates to the improvement of a boot in which a passage structure for making the inside of the boot communicate with the outside of the boot is improved from the viewpoint of preventing splashed water or muddy water from intruding into the boot when negative pressure is generated in the boot. The invention is a boot for a universal joint for coupling an input-side shaft to an output-side shaft of the type in which one end of the boot is fitted on one shaft of both the shafts via its one-end fitting portion, and the other end of the boot is fitted on the other shaft of both the shafts via its other-end fitting part, to cover the universal joint. The one-end fitting part of the boot has an annular lip portion, and the one-end fitting portion and the annular lip portion each have a partial passage. The partial pa
Orum & Roth
Pickard Alison K.
Showa Corporation
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