Excavating – Digging edge – Specific material
Reexamination Certificate
2002-02-11
2003-11-18
Pezzuto, Robert E. (Department: 3671)
Excavating
Digging edge
Specific material
C037S452000, C172S701300
Reexamination Certificate
active
06647648
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a bucket tooth which is attached to a bucket of construction equipment or the like and is used mainly for a work of excavating or loading earth and sand and a method of manufacturing the bucket tooth.
RELATED BACKGROUND ART
Hitherto, the most common bucket tooth used for construction equipment or the like is of a type in which the bucket tooth is fit in an adapter fixedly provided on a bucket side and is fastened by a pin or the like. A bucket tooth of a type which is directly fastened to a bucket by using a bolt is also known.
FIGS.
23
(
a
1
) and
23
(
a
2
) through FIGS.
23
(
d
1
) and
23
(
d
2
) show examples of the bucket tooth of the latter type. In each of bucket teeth
50
A,
50
B,
50
C, and
50
D, the tip side opposite to a base portion having a plurality of bolt holes
51
is formed with a step, or the base portion is formed in a forked shape. The inner portion of the step or the inner space of the forked portion is placed in contact with the tip of a bucket lip (not shown) and the bucket tooth is fixed to the bucket lip by being bolted.
Another example of the bucket tooth of the bolting type is, as shown in FIGS.
24
(
a
) and
24
(
b
), a bucket tooth
60
of a shape having edges
61
at both one end and the other end and two bolt holes
62
,
62
in the center. The bucket tooth
60
can be used twice in such a manner that when the edge
61
at one end is worn and becomes short to the limit, the bucket tooth
60
is turned and the edge
61
at the other end is used.
In the conventional bucket teeth shown in FIGS.
23
(
a
1
) and
23
(
a
2
) through
23
(
d
1
) and
23
(
d
2
), however, when the tip of each of the tooth becomes useless by wear, the bucket teeth
50
A to
50
D have to be replaced by new bucket teeth. Consequently, there is a problem such that the life is relatively short due to the wear, and since the weight of the worn portion with respect to the weight of the whole tooth is small, the yield is low.
On the contrary, in the conventional bucket tooth shown in FIGS.
24
(
a
) and
24
(
b
), even when one of the edges
61
is worn out, the tooth is turned and the other edge
61
can be used. Consequently, it has advantages such that the life is relatively longer in spite of the wear and the yield is higher as compared with the bucket teeth shown in FIGS.
23
(
a
1
) and
23
(
a
2
) through FIGS.
23
(
d
1
) and
23
(
d
2
). On the other hand, the bucket tooth has a problem which is common to bucket teeth of the bolting type, such that a fastening bolt is easily loosened due to vibration, shock, and the like applied to the bucket tooth during operation.
The present invention is achieved in order to solve such problems. An object of the present invention is to provide a bucket tooth to be attached by being fastened by a bolt which is prevented from being loosened during operation, and to provide a method of manufacturing the bucket tooth, which can prevent a bolt from being loosened.
SUMMARY OF THE INVENTION
In consideration that a direct cause of loosening of a fastening bolt attaching a bucket tooth to a bucket lip is reduction in axial force of the bolt during operation, the present invention has been achieved by finding out effective means which prevents the reduction in axial force.
According to a first aspect of the present invention, there is provided a bucket tooth attached to a bucket lip via a fastening bolt, comprising axial force fluctuation absorbing means for absorbing fluctuations in axial force of the fastening bolt after attaching the bucket tooth to the bucket lip.
In the present invention, preferably, after the bucket tooth is attached to the bucket lip, fluctuations in axial force of the fastening bolt are absorbed by the axial force fluctuation absorbing means. Even when fluctuations in axial force occur in the fastening bolt in association with fluctuations in a load applied to the bucket tooth during operation, the fluctuations in axial force can be absorbed, thereby enabling reduction in axial force of the fastening bolt to be prevented. Obviously, according to the bucket tooth of the present invention, by providing a bolt fastening portion in the center portion, when the tip of the tooth becomes useless due to wear, the bucket tooth is turned and the other tip of the tooth can be used. Therefore, the bucket tooth having the increased life in spite of the wear and the improved yield can be achieved.
In the present invention, preferably, the axial force fluctuation absorbing means allows the bucket tooth to generate a resilient return force by causing a warp by resilient deformation so that one face side becomes a concave face and performing bolting in a state where the one face side is positioned on the bucket lip side. In such a manner, the fastening force at the time of bolting works as an action force in the direction of canceling the warp caused in the bucket tooth, the resilient return force is generated in the bucket tooth by the action force, the fluctuations in axial force of the fastening bolt during operation are absorbed by the resilient return force, and the reduction in axial force can be prevented.
In the present invention, preferably, the warp created in the bucket tooth is caused around a bolt hole into which the fastening bolt is inserted as a center, and an amount s of the warp is set to a value satisfying an equation of 2 mm/m≦s≦15 mm/m. Specifically, when the amount s of the warp increases, an effect of preventing the reduction in axial force of the fastening bolt can be obtained. A value equal to or lower than 10% is obtained as an axial force reduction rate which does not cause any problem in practice in the case where the amount s of the warp is set to 2 mm/m or larger. When the amount s of the warp exceeds 15 mm/m, it is not preferable since an excessive tensile stress works around the bolt hole at the time of bolting and it causes delayed fracture.
In the present invention, preferably, the axial force fluctuation absorbing means allows the bucket tooth to generate a resilient return force by spot facing the circumference on the side facing the bucket lip, of a bolt hole in which the fastening bolt is inserted. In such a manner, the spot facing portion around the bolt is resilient deformed in the direction so as to be in contact with the bucket lip by the fastening force at the time of bolting, thereby generating the resilient return force in the spot facing portion. By the resilient return force, the fluctuations in axial force of the fastening bolt during operation are absorbed and the reduction in axial force can be prevented. The present invention is effective even when the bolt hole is not in the center portion of the bucket tooth. When one side of the bucket tooth of a type in which the bolt hole is in the center portion is worn, the bucket tooth is turned and the other side is used.
In the present invention, preferably, the axial force fluctuation absorbing means allows the bucket tooth to generate a resilient return force by causing a warp by resilient deformation so that one face side becomes a concave face, spot-facing the circumference on the side facing the bucket lip, of a bolt hole in which the fastening bolt is inserted, and performing bolting in a state where the one face side is positioned on a bucket lip side. By warping the bucket tooth and forming the spot facing portion around the bolt hole in such a manner, by a synergistic effect of them, a larger resilient return force can be generated and the effect of absorbing the fluctuations in axial force of the fastening bolt can be increased.
Preferably, a ratio (z) of a depth L of the spot facing to a diameter D of the spot facing (=L/D) is set to a value satisfying an equation of 2 mm/m≦z≦18 mm/m. More specifically, when the spot facing amount (z) is increased, an effect of preventing the reduction in axial force of the fastening bolt can be obtained. However, a value equal to or lower than 10% is obtained as an axial force reduction rate which does not cause any
Amano Masaharu
Okawa Kazuhide
Armstrong Westerman & Hattori, LLP.
Komatsu Ltd.
Mammen Nathan
Pezzuto Robert E.
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