Structure to join cylinder lifting cargo-handling tool

Details Structure to join cylinder lifting cargo-handling tool Structure to join cylinder lifting cargo-handling tool

1998-08-28

2001-02-27

Olszewski, Robert P. (Department: 3652)

Elevator, industrial lift truck, or stationary lift for vehicle

Industrial lift truck or required component thereof

Having extensible vertical guide for load support

Reexamination Certificate

active

06193015

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a structure to join a cylinder lifting a cargo-handling tool, more specifically to a structure to join a cylinder which is joined to a connecting member which connects a pair of right-hand and left-hand second masts to each other, and which is used for vertically moving the cargo-handling tool provided on the pair of right-hand and left-hand second masts being vertically moved with respect to a pair of right-hand and left-hand first masts provided on a forklift truck
2. Description of the Related Art
Cargo-lifting mechanisms of a type having a structure as schematically shown in
FIG. 1
are known, that is, a cargo-lifting mechanism having three pairs of masts provided with a free lift. The foregoing lifting mechanism incorporates a pair of right-hand and left-hand (in a direction perpendicular to the surface of a drawing sheet) outer masts
1
secured to a front portion of the forklift truck. A pair of right-hand and left-hand middle masts
3
are provided for the outer masts
1
such that vertical movement of the middle masts
3
is permitted. Moreover, a pair of right-hand and left-hand inner masts
5
, which are capable of moving vertically, are provided for the middle masts
3
. The inner masts
5
are provided with a fork
7
serving as a cargo-handling tool on which a cargo is placed such that vertical movement of the fork
7
is permitted.
A cargo-handling-tool lifting cylinder (a full-free cylinder)
9
for vertically moving the fork
7
is secured to a position adjacent to the inner masts
5
. The fork
7
and the inner masts
5
are connected to each other by dint of a chain
15
through a chain sprocket
13
disposed at the top end of a cylinder rod
11
of the cargo-handling-tool lifting cylinder
9
. When the cargo-handling-tool lifting cylinder
9
is operated, the fork
7
is vertically moved with respect to the inner masts
5
.
On the other hand, mast-lifting cylinders
17
for vertically moving the middle masts
3
and the inner masts
5
are disposed at positions adjacent to the outer masts
1
. The outer masts
1
and the inner masts
5
are connected to each other by dint of a chain
21
through chain sprockets
19
disposed on the upper portions of the middle masts
3
. When the middle masts
3
are moved vertically because of the operation of the mast-lifting cylinders
17
, the inner masts
5
are moved vertically with respect to the outer masts
1
for a distance that is twice that of the middle masts
3
is vertically moved.
FIG. 2
is a plan view showing a specific structure of the above-mentioned lifting mechanism. The lower ends of the pairs of the right-hand and the left-hand outer masts
1
, middle masts
3
and the inner masts
5
are connected to each other by an outer-mast lower beam
23
, a middle-mast lower beam
25
and an inner-mast lower beam
27
. The pair of right-hand and left-hand mast-lifting cylinders
17
for vertically moving the middle masts
3
are elongated vertically on the outer-mast lower beam
23
disposed in the rear of the outer masts
1
. On the other hand, the cargo-handling-tool lifting cylinder
9
for upwardly moving the fork
7
is elongated vertically on a cylinder support
29
which is disposed between the right-hand and left-hand inner masts
5
and which forwards projects over the inner-mast lower beam
27
.
The fork
7
is joined to the front surface of a carriage
33
secured to the leading ends of a pair of carriage brackets
31
disposed on the inside of the inner masts
5
. Mast rollers
35
are joined to the side surfaces of the upper and lower ends of the carriage brackets
31
. When the mast rollers
35
vertically roll with respect to the inner masts
5
, the carriage brackets
31
, the carriage
33
and the fork
7
are vertically moved with respect to the inner masts
5
. Mast rollers (not shown in
FIG. 2
) are disposed between the outer masts
1
and the middle masts
3
and between the middle masts
3
and the inner masts
5
(for example, mast rollers
36
are disposed in the lower portions of the inner masts
5
as shown in
FIG. 3
to be described later).
Lift-mechanism support brackets
37
for mounting the foregoing lifting mechanism on the forklift truck (a front axle shaft) are disposed at the right and left ends of the outer-mast lower beam
23
. The distance from the joining center of each of the lift-mechanism support brackets
37
to the carriage
33
is a front overhang (FOH). When the FOH is reduced, the distance from the forklift truck to a portion for holding a cargo can be shortened. Thus, a cargo-handling operation can stably be performed.
FIG. 3
is a perspective view showing the inner masts
5
and the cargo-handling-tool lifting cylinder
9
which is joined to the inner masts
5
. A threaded hole
29
a
is formed in the upper surface of the cylinder support
29
provided for the inner-mast lower beam
27
. A bolt
39
is screwed in the threaded hole
29
a
. On the other hand, a locating recess
9
a
into which the head of the bolt
39
is introduced is formed in the lower surface of the cargo-handling-tool lifting cylinder
9
.
In a state in which the locating recess
9
a
of the cargo-handling-tool lifting cylinder
9
is received by the head of the bolt
39
jointed to the upper surface of the cylinder support
29
, brackets
41
disposed at positions relatively upper than the central portion of the cargo-handling-tool lifting cylinder
9
are secured to a center beam
43
with two bolts
45
, the center beam
43
establishing the connection between intermediate portions of the inner masts
5
in the vertical direction. Thus, the cargo-handling-tool lifting cylinder
9
is joined to a position adjacent to the inner masts
5
.
FIG. 4
shows an example in which two cargo-handling-tool lifting cylinders
9
are employed. The cylinders
9
are disposed at positions adjacent to the right and left inner masts
5
. In the foregoing example, pins
47
disposed on a cylinder support
29
are received by recesses
9
a
formed in the lower surface of the cargo-handling-tool lifting cylinder
9
. In the foregoing state, brackets
41
provided for the cargo-handling-tool lifting cylinder
9
are secured to the center beam
43
with bolts
45
.
The example of the structure for joining a cylinder for lifting a cargo-handling tool of the type shown in
FIG. 3
has the arrangement that the cargo-handling-tool lifting cylinder
9
is disposed at an intermediate position between the right and left inner masts
5
. Therefore, forward visibility is unsatisfactory for an operator of the forklift truck to efficiently perform the cargo handling operation. The example shown in
FIG. 4
incorporates the two cargo-handling-tool lifting cylinders
9
disposed at the right and left positions. Therefore, the forward visibility is improved as compared with the example shown in FIG.
3
. However, the cargo-handling-tool lifting cylinders
9
are disposed between the carriage brackets
31
shown in FIG.
2
. Therefore, the visibility for the forklift operator is obstructed. Thus, further improvement in the visibility is required.
To improve the forward visibility, a structure is disclosed in Japanese Utility-Model Applications Laid-Open No. 57-155198 and Laid-Open No. 59-123096. The structure is formed such that cargo-handling-tool lifting cylinders
9
are disposed adjacently to inner masts
5
at positions in the rear of the inner masts
5
.
When the cargo-handling-tool lifting cylinders
9
are disposed adjacently to the inner masts
5
at positions in the rear of the inner masts
5
, a structure may be employed in which brackets
41
for securing the cargo-handling-tool lifting cylinders
9
are, as shown in
FIG. 5
which is a plan view, secured to the center beam
43
by dint of bolts
45
from front positions of the forklift truck. To improve the forward visibility by disposing the cargo-handling-tool lifting cylinders
9
at further outer positions in the widthwise direction of the forklift truck, heads of the bolt

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