Machine element or mechanism – Gearing – Yieldability in gear trains
Reexamination Certificate
1999-11-10
2003-11-18
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Gearing
Yieldability in gear trains
C074S450000
Reexamination Certificate
active
06647818
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a gear designed, so that a rotational-power transmitting member can be fitted into a gear body, whereby a power can be transmitted through such member to a desired device, and more particularly, a gear in which a shock force produced at the start and stoppage of the rotation of the gear can be moderated to reduce a noise during rotation of the gear, while reducing the number of parts, the number of operations and the cost which are required for producing the gear.
DESCRIPTION OF THE RELATED ART
This type of the conventional gear is conventionally comprised of a rim integral with a plurality of teeth at an outer peripheral surface thereof, a boss disposed concentrically inside the rim, and a plurality of ribs disposed radiately between the rim and the boss and connected at their opposite ends to the rim and the boss. The rim, the boss and the ribs are integrally formed in the gear, and fitting sections are provided between the boss and the rim, so that the rotational power of a gear body can be transmitted to the disk-shaped rotational-power transmitting member, while a predetermined amount of a shock generated with the rotation of the gear body, by fitting a portion of a disk-shaped rotational-power transmitting member to the fitting sections.
A conventional example of this type of the gear is shown in FIG.
1
. The gear body
10
includes teeth
11
, a rim
12
, a boss, a web
14
and ribs
15
. The cylindrical rim
12
is integral with the plurality of teeth
11
at its outer peripheral surface. The boss
13
is disposed concentrically with the rim
12
. The rim
14
is connected to the rim
12
and the boss
13
. The plurality of ribs
15
extend radiately from the boss
13
toward the rim
12
and is connected to the outer peripheral surface of the boss
13
, the inner peripheral surface of the rim
12
and the web
14
. The teeth
11
, the rim
12
, the boss
13
and the web
14
are integrally formed by pouring a molten material comprising a synthetic resin into a mold.
The fitting sections
16
are formed separately from the rim
12
, the boss
13
, the web
14
and the ribs
15
, using a rubber which is soft as compared with the synthetic resin for forming the gear body. The fitting sections
16
are partitioned by the ribs
15
; smoothly or tightly inserted in spaces defined in the gear body
10
by the rim
12
, the boss
13
and the web
14
; and fixed using a fixing means such as a screw which is not shown, or an adhesive.
A notch or recess
16
a
is defined in each of the fitting sections
16
, so that a disk-shaped rotational-power transmitting member can be fitted in the notch or recess
16
a.
One example of the disk-shaped power transmitting member is shown in FIG.
2
. The disk-shaped power transmitting member
17
has projections
17
a
provided on one side thereof and each having such a shape that the projections
17
a
can be fitted into the notches or recessed
16
a
of the fitting sections
16
mounted to the gear shown in FIG.
1
. Thus, the disk-shaped power transmitting member
17
is adapted to be rotated coaxially with the gear by fitting the projections
17
a
into the notches or recesses
16
a.
A shaft
17
b
is provided on the other side of the disk-shaped power transmitting member
17
. The shaft
17
b
is formed into, for example, a rectangular box-shape as shown in
FIG. 2
, or as a serration shaft, so that any of various power transmitting members such as various gears and, pulleys can be connected to the shaft
17
b.
Thus, when the gear body
10
is rotated, the rotational force thereof is transmitted through the fitting sections
16
to the disk-shaped rotational-power transmitting member
17
to rotate the rotational-power transmitting member
17
, and further, the rotational power of the power transmitting member
17
is transmitted to another power transmitting member.
Now, when the rotation of the gear is started, and when the rotation is stopped, an excessive load is applied to the teeth of the gear and the disk-shaped rotational-power transmitting member
17
rotated along with the gear. For this reason, there is a possibility that the meshing of the teeth is degraded, and the loudness of a noise produced during rotation of the gear is increased and in its turn, an adverse affection is exerted to the life of the gear.
Therefore, in the conventional gear of this type, a fitting section
16
made of a rubber separately from the gear body is mounted to the gear body to function as a buffering member for absorbing a shock produced with the rotation of the gear by the elastic deformation of the fitting portion
16
, thereby improving the meshing of the teeth of the gear for a period from the start of the rotation of the gear to the stoppage of the rotation to reduce the noise generated during rotation of the gear.
However, when a buffering member made of a rubber separately from a gear body is mounted to the gear body as in the conventional gear, the number of parts are increased correspondingly and moreover, the operation for mounting the buffering member is complicated; the labor required for producing the gear is increased; the efficiency for producing the gear is lowered; and the producing cost is increased. In addition, when buffering member made of the rubber separately from the gear body is mounted to the gear body, there is a possibility that an operator may forget the mounting of the buffering member, and it is difficult to enhance the yield of a product having a good quality. When a buffering member made of a rubber is not mounted to the gear body, and a recess, into which a projection of a disk-shaped rotational-power transmitting member can be fitted, is defined directly in the gear body, an excessive shock produced at the start and stoppage of the rotation of the gear is transmitted, as it is, to the disk-shaped rotational-power transmitting member and the gear body and as a result, the meshing of the teeth of the gear is degraded, and the noise generated with the rotation of the gear cannot be reduced.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a gear wherein the labor for mounting the buffering member made of the rubber to the gear body can be eliminated, thereby enhancing the efficiency of production of the gear and reducing the producing cost.
To achieve the above object, according to the present invention, there is provided a gear comprising a gear body which includes a rim integral with a plurality of teeth at an outer peripheral surface thereof, and a boss disposed concentrically inside the rim, and at least one fitting section which is formed from a material having a low hardness and a low flexural strength as compared with a material for forming the gear body and which is provided between the rim and the boss, so that the gear with a rotational-power transmitting member fitted into the fitting portion is rotated, whereby the rotational power of the gear body is transmitted to the rotational-power transmitting member, while elastically deforming the fitting section to absorb a predetermined amount of a shock produced with the rotation of the gear body, wherein the gear body and the fitting section are formed integrally with each other by a two-color molding process.
Preferably, the fitting section is formed to fill a space which is comprised of a recess defined by at least the rim, the boss and a web formed between the boss and the rim, and a bore portion communicating with the bottom surface of the recess and defined into such a shape that the sectional area at a predetermined location spaced apart from the bottom surface of the bore portion is larger than the sectional area at a location of connection to the bottom surface of the recess.
Preferably, the bore portion comprises a groove defined in the web on the opposite side from the side in which the recess is defined, and a through-bore having a sectional area smaller than the sectional area of the bottom surface of any of the recess and the groove.
Preferably,
Akiyama Koji
Takeuchi Youichi
Enplas Corporation
Fenstermacher David
Koda & Androlia
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