Joints and connections – Articulated members – Pivoted
Reexamination Certificate
1999-08-19
2001-08-14
Browne, Lynne H. (Department: 3629)
Joints and connections
Articulated members
Pivoted
C403S150000, C403S157000, C403S155000, C403S161000, C403S163000, C403S014000
Reexamination Certificate
active
06273632
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Art
This invention relates to a joint pin lock mechanism or system for use on a pivotal pin joint which connects a pair of mechanical structural members pivotally relative to each other through a joint pin, and more particular to a joint pin lock mechanism which can lock a joint pin securely and safely in position in a fixed state against undesired rotational movements and against spontaneous axial movements as well if necessary.
2. Prior Art
In the manufacture of machines such as construction machines, for instance, it has been well known to connect two mechanical structural parts through a pivotal pin joint to permit pivotal movements relative to each other. As for example, shown in
FIG. 10
is a hydraulic power shovel which employs pivotal pin joints of this sort. Basically, the hydraulic power shovel is constituted by a vehicular body having a crawler type base carrier
1
and an upper rotary body
2
which is rotatably mounted on the base carrier
1
. Provided on the upper rotary body
2
is an operator's cab
3
and a front working mechanism
4
which is arranged to do predetermined jobs. The front working mechanism
4
usually includes a boom
5
which is lifted up and down, an arm
6
which is pivotally connected to the fore end of the boom
5
for swinging movements in a vertical direction, and a front attachment, for example, a bucket
7
which is pivotally supported at the fore end of the arm
6
.
In the case of a hydraulic power shovel as shown, normally hydraulic motors are employed for driving the vehicular base carrier
1
and for rotation of the upper rotary body
2
. In addition, the front working mechanism
4
are driven by hydraulic cylinders
8
to
10
. The boom
5
is lifted up and down by a boom operating cylinder
8
which is connected between the boom
5
and the upper rotary body
2
. Namely, one end of a cylinder tube
8
a
of the boom operating cylinder is connected to the upper rotary body
2
and a rod
8
b
which is projected from the other end of the cylinder
8
a
is connected to the boom
5
. A cylinder tube
9
a
of the arm cylinder
9
is connected to the boom
5
, and a fore end portion of its rod
9
b
is connected to the arm
6
. Further, a cylinder tube
10
a
of the bucket cylinder
10
is connected to the arm
6
, and its rod
10
b
is connected to the bucket
7
. In connecting the cylinders
8
a
to
10
a
and rods
8
b
to
10
b
of the respective drive cylinders
8
to
10
in this manner, two mechanical parts at each connecting point are connected through a pivotal pin joint which permits relative rotational movements of connected mechanical parts about a joint pin and also permits separation of the two connected parts upon extraction of the joint pin whenever necessary.
In this regard, Japanese Laid-Open Patent Application H6-300033 discloses a pivotal pin joint construction which connects hydraulic cylinders
8
to
10
rotatably relative to and separably from a cooperating mechanical part. Shown by way of example in
FIGS. 11
to
14
is the just-mentioned prior art pivotal pin joint construction which is used to connect a cylinder tube
9
a
of an arm operating cylinder
9
to a boom
5
.
More specifically, shown in
FIGS. 11 and 12
are a schematic outer view of the prior art pivotal pin joint and a sectional view taken on line Y—Y of
FIG. 11
, respectively. In these figures, indicated at
11
L and
11
R are brackets which are securely fixed to the boom
5
by welding or other suitable means. Supported between the brackets
11
L and
11
R (hereinafter a common reference numeral “
11
” is used for the two brackets for the convenience of explanation) is a connecting portion
12
of the cylinder tube
9
a
of the arm operating cylinder
9
. A joint pin
13
is passed across the two brackets
11
through the connecting portion
12
thereby to support the arm cylinder
9
pivotally relative to the brackets
11
on the part of the boom
5
. For this purpose, pin receptacle holes
11
a
and
12
a
are formed in the bracket
11
and connecting portion
12
, respectively. A bush
14
is fitted in the pin receptacle hole
12
a
for sliding contact with the joint pin
13
.
As the arm cylinder
9
is actuated, the arm
6
is turned up or down relative to the boom
5
to vary the angle between the arm cylinder
9
and the boom
5
. At this time, the connecting portion
12
is subject to a force which acts to turn the connecting portion forcibly about the joint pin
13
. If the joint pin
12
is caused to turn relative to the brackets
11
under the influence of the forced rotation of the connecting portion, it will hinder smooth movement of the boom
5
and could result in accelerated wearing of the joint pin
13
itself. Therefore, in addition to prevention of axial movements of the joint pin
13
which might result in disengagement from the connecting portion
12
and brackets
11
, it is necessary to prevent rotational movements of the joint pin
13
relative to the brackets
11
.
In the particular case shown, a joint pin lock structure
20
is formed on the pivotal pin joint upon inserting the joint pin
13
. The joint pin lock structure
20
includes a collar portion
21
which is securely fixed to the joint pin
13
by welding and extended in a direction perpendicular to the axis of the joint pin
13
. The just-described collar portion
21
function to lock the joint pin
13
in a fixed state in both rotational and axial directions.
In order to fix the collar portion
21
in position, a U-shaped anti-rotation plate
22
is securely fixed on the outer side of one of the paired brackets
11
, for example, on the outer side of the bracket
11
L, and the extended end of the collar portion
21
is arrested in a recess
22
a
of the U-shaped anti-rotation plate
22
. By engagement of the collar portion
21
with the U-shaped anti-rotation plate
22
, the joint pin
13
which is connected with the collar portion
21
is blocked against rotational movements. Further, the joint pin
13
is locked against movements in the axial direction by a stopper plate
23
which is provided with apertures (not shown) and fixed on the rotation blocking plate
22
by threading screws into screw holes in the rotation blocking plate
22
through apertures in the stopper plate
23
.
The pin receptacle hole
11
a
is bored into the bracket
11
L, and the anti-rotation plate
22
is fixed to the bracket
11
, for example, by welding, in separate stages of a fabrication process. Consequently, difficulties are often encountered in fixing the anti-rotation plate
22
in position with strict accuracy relative to the center of the pin receptacle hole
11
a,
due to errors occurring under the influence of the heat of welding operation or errors occurring in a machining stage. In order to engage the fore end of the collar portion
21
of the joint pin
13
in the recess
22
a
of the anti-rotation plate
22
without failure despite such positioning or dimensional errors, it is necessary to form the recess
22
a
in a broader width as compared with that of the collar portion
22
, providing a play or adjustment gap spaces &dgr; on the opposite sides thereof to absorb possible dimensional or positioning errors when the collar portion
22
is placed in the recess
22
a.
In this manner, arrangements have to be made to ensure that the collar portion
21
can be fitted in the recess
22
a
without failure despite positional deviations of the anti-rotation plate
22
relative to the pin receptacle hole
11
a.
As described above, it is inevitable to provide adjustment gaps
2
&dgr; between the recess
22
a
of the anti-rotation plate
22
and the collar portion
21
to compensate for errors in fabricating or machining stages although the anti-rotation function is impaired to a degree which corresponds to the width of the adjustment gaps
2
&dgr;. Besides, as the connecting portion
12
is turned repeatedly relative to the bracket
11
L, the collar portion
21
is each time collided against wall surfaces of the recessed port
Hasegawa Toshio
Kurosaka Hiroshige
Suzuki Ryohei
Takahashi Ei
Browne Lynne H.
Garcia Ernesto
Hitachi Construction Machinery Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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