Seal disk for bearings

Details Seal disk for bearings Seal disk for bearings

1998-12-21

2002-06-11

Sandy, Robert J. (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Circumferential contact seal for other than piston

C277S586000

Reexamination Certificate

active

06402158

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to plastic or rubber seal disks for seal-type bearings, in particular bearings with seal grooves formed inside each of two shoulders of an outer ring. More specifically, this invention relates to an improved seal disk for bearings that can be fitted into the seal groove concentrically with the bearing and having the bearing axis as center. The seal disk of the present invention prevents enclosed lubricant from leaking out almost infallibly, even when the seal disk expands or shrinks under thermal stress and/or absorbs water or other liquids and swells.
BACKGROUND OF THE INVENTION
Seal-type bearings with lubricant enclosed therein are widely used in such fields as office equipment and household electric appliances. In bearings of this type, plastic and rubber seal disks are widely used because they provide high sealing performance and easy fitting. Examined Japanese utility model application No. 7-32985 discloses one widely known embodiment thereof.
The seal disk disclosed in Japanese utility model 7-32985 is illustrated in FIG.
19
. As shown, the seal disk is integrally formed and has a ring-shaped raised area
6
a
with a trapezoid-like section on the back side in the outer circumferential portion and a projection
6
b
with a triangular section on the face in the outer circumferential portion. Seal disk
6
is placed around an inside edge of the face of outer ring
7
and pressed uniformly into the U-shaped groove formed inside each shoulder of outer ring
7
, as shown in FIG.
20
. Seal disk
6
is caught in groove
7
′, with the inside flat top surface of ring-shaped raised area
6
a
in contact with the inner inside wall of seal groove
7
′ and projection
6
b
bent on the outer inside wall of seal groove
7
′.
Thus seal disk
6
is held in seal groove
7
′ tightly and firmly by the elastic force of projection
6
b
, with the gap between the outer ring and the inner ring securely sealed. That is, seal disk
6
has the outer peripheral portion in contact with inner inside wall
7
a
of seal groove
7
′ and elastically with outer inside wall
7
b
of seal wall
7
′, with a minute gap G defined between the bore edge of seal disk
6
and the inner ring. This prevents lubricant enclosed between outer and inner rings
7
and
8
from leaking out and keeps dust and other foreign matter from entering the space between the two rings.
In
FIG. 20
, reference numeral
9
indicates one of a plurality of free-rolling balls placed between outer and inner rings
7
and
8
, while reference numeral
10
is a retainer or separator, keeping balls
9
apart from one another at regular intervals. The bearing in which plastic or rubber seal disk
6
is used has the outer inside wall
7
b
of seal groove
7
′ designed so as to define an angle of inclination a of about 45 degrees with the face of outer ring
7
, as indicated in FIG.
21
.
With the outer peripheral portion of seal disk
6
held in seal groove
7
′ of outer ring
7
, projection
6
b
is bent toward the center of seal disk
6
, with an elastic reaction force N working in a direction indicated by the arrow, shown in
FIG. 21. A
component of this reaction force N works in the direction of the center of seal disk
6
from the circumference thereof. In
FIG. 21
, the angle of inclination &agr; of outer inside wall
7
b
of the seal groove
7
′ is large, and so is the component force working from the outer peripheral portion of seal disk
6
toward the bore or the center thereof. As a result, seal disk
6
when installed is automatically concentric with the bearing and has the axis of the bearing as a center. Gap G between the bore wall of seal disk
6
and inner ring
8
is maintained approximately uniform all around.
However, bearings with smaller angles of inclination &agr; will have smaller component forces working from an outer peripheral portion of seal disk
6
to the bore. When a conventional plastic or rubber seal disk
6
is placed in such a bearing, the elastic reaction force N will work more along the direction of the axis of the bearing, because of the smaller angle of inclination &agr;, as illustrated in FIG.
22
.
In bearings with small angles of inclination &agr; of the outer inside wall
7
b
of seal groove
7
′, the seal disk
6
can fail to be mounted concentrically with the bearing and have the axis as center. That is, a seal disk
6
may be installed eccentrically, with non-uniformity caused in the gap G between the seal disk
6
and the inner ring
8
. That can cause such problems as decreased sealing performance, dismounting of seal disk
6
off seal groove
7
′, and deterioration in the roundness of outer ring
7
.
These problems are especially evident with bearings in which a metallic seal disk or a metal-plastic combination seal disk is used. The seal grooves
7
′ in such bearings are designed so that the angle of inclination &agr; is less than approximately 17 degrees. In such bearings, a plastic or rubber seal cannot be used in place of metallic or metal-plastic combination seal disks, even though plastic and rubber seal disks are less expensive but excellent in durability.
Another problem relates to the lubricant that is normally enclosed within seal disk
6
of the bearing. Rotation of the bearing generates a centrifugal force that forces the lubricant outward. Leakage of the lubricant is blocked primarily by seal disk
6
with its raised area
6
a
in close contact with the inner inside wall
7
a
of seal groove
7
′. Contact seal performance at this point is a function of the contact pressure, the closeness of the contact, and the size of the contact area. Increasing the contact pressure and the size of the contact area can improve seal performance and minimize the possibility of lubricant leakage. However, there is a certain limit to the magnitude of the elastic reaction force that can be mounted in practice on a raised area
6
a
, because of such factors as the mechanical strength of the seal disk and the inside edge of the outer ring face as well as the resistance force to be overcome in mounting a seal disk
6
. Also, a certain limit is imposed on the size I of the contact area between inner inside wall
7
a
of seal groove
7
′ and raised area
6
a
, because of the thickness of the bearing outer ring
7
, the shape of the seal groove
7
′, and other considerations. Thus the size I of the contact area may not be expanded very much.
For those reasons, seal-type bearings using conventional plastic or rubber seals as shown in
FIG. 18
cannot completely keep the lubricant from leaking out. The centrifugal force of the rotating outer ring
7
will force some lubricant out of the seal disk
6
through seal groove
7
′, although the leakage may be very small. Leakage of the lubricant increases with a rise in the operating temperature of the seal-type bearing, because the viscosity of the lubricant rapidly lowers as the operating temperature exceeds 80° C.
A seal disk
6
itself undergoes great change in the crystal structure of its resin material as it is subjected repeatedly to a heating and cooling cycle and as it absorbs moisture from the atmosphere. This results in distortion or a change in dimension of the seal disk, with increased leakage of the lubricant.
SUMMARY OF THE INVENTION
The present invention addresses problems such as those described above. It is an object of the present invention to provide a bearing seal disk that can be fixed in the seal groove of an outer ring concentrically with the bearing and have the axis thereof as its center, irrespective of the angle of inclination formed by the outer inside wall of the seal groove in the outer ring. It is another object of the present invention to provide a bearing seal disk the sealing performance of which is so enhance as to prevent lubricant from leaking out almost completely, both in high temperature operation and in and after prolonged service.
FIRST EMBODIMENT
To achieve these objects, the presen

Affiliated with

Also associated with

Rating

Seal disk for bearings does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Seal disk for bearings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Seal disk for bearings will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2937654