JPH085628B2 - Cylinder support beam structure of lift cylinder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mast device for a forklift truck, and more specifically, to the left and right sides of the mast arranged behind the mast.
Cylinder support beam structure for supporting a lift cylinder of a book.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional cylinder support beam structure of a conventional forklift truck, which is particularly found in large vehicles. As shown, a conventional cylinder support beam 20 for supporting a lift cylinder has a structure in which it is directly welded to the rear surfaces of the left and right outer masts 21 having a U-shaped cross section, and ribs are provided to secure the strength of the joints. It is reinforced by 22. In a large vehicle, in order to increase the allowable load (to arrange the mast device as close to the vehicle body side as possible), the cylinder support beam 20 is arranged at a substantially intermediate portion between the mast support 23 and the tilt support 24 as shown in the figure. It is usually set to.

By the way, in the mast device, when the load is applied (when a load is placed on the fork), a forward rotation moment M acts on the outer mast 21 via a lift roller (not shown), which causes a rear surface of the mast. Is subject to tensile stress. On the other hand, if a welded joint is present on a smooth surface where tensile stress acts, the strength is significantly reduced due to stress concentration due to a sudden change in cross-sectional shape, stress concentration at the joint due to the weld bead shape, metallographic change due to welding heat, etc. It is known. Even in the above-described conventional cylinder support beam structure, since the cylinder support beam 20 is welded to the highly stressed rear surface of the outer mast 21, stress is generated in the vicinity of the connecting portion of the outer mast 21 with the cylinder support beam 20 in the portion A in the figure. In the case of a large vehicle that concentrates, and in particular, the mounting position of the cylinder support beam 20 is set above the mast support 23 that serves as a fulcrum of the moment, there is a problem that the life is shortened under severe usage conditions. .

Therefore, an object of the present invention is to prevent the strength reduction of the outer mast by eliminating the welding of the cylinder support beam to the rear surface of the outer mast.

[0005]

In order to solve the above problems, the present invention is configured as follows. That is, according to the present invention, the mast support provided at the lower end portion of the outer mast and the tilt support projecting in the middle portion of the outer mast are provided slightly closer to the tilt support than the middle portion, and the left and right standing upright at the rear of the mast. A cylinder support beam structure for supporting two lift cylinders, which includes left and right support plates that are fixed to the side surfaces of the left and right outer masts by welding and project toward the rear of the mast, and between the left and right support plates. A support beam is installed horizontally, and the welding portion of the support plate with respect to the side surface of the mast is set at a certain distance from the rear surface of the mast.

[0006]

Therefore, according to the above structure, since there is no welded portion on the rear surface of the mast, which has a high tensile stress at the time of loading, the problem of stress concentration on the rear surface of the mast caused by this is avoided. That is, in the present invention, the cylinder support plate is welded to the side surface of the outer mast, and the support beam is installed over the side surface of the outer mast, so that the strength of the outer mast can be prevented from decreasing and the durability can be improved.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) FIGS. 1 to 4 show Embodiment 1 of the present invention. As shown in FIG. 1, a pair of left and right outer masts 1 having a U-shaped cross section are connected by a lower cross beam 2 at the lower end of the rear surface, and are connected by an upper cross beam at the upper end of the rear surface (not shown). The outer mast 1 is attached to the front axle (not shown) so as to be tiltable in the front and rear direction via the left and right mast supports 3 fixed to the rear surface of the lower cross beam 2, and is welded to the side surface of the mast slightly below the middle portion. Tilt support 4 fixed by and projecting rearward
Is supported by a tilt cylinder (not shown).

A cylinder support beam 6 for supporting two left and right lift cylinders 5 standing upright at the rear of the mast.
Is composed of a pair of left and right support plates 7 fixed to the side surfaces of the mast, and a support beam 8 horizontally installed between the support plates 7, and is slightly tilted from the intermediate portion between the mast support 3 and the tilt support 4. It is installed near the support 4.

The support plate 7 is formed in a horizontally long rectangle, and its contact peripheral edge portion is welded to the rear side of the mast while being abutted on the side surface of the mast.
In this case, the welded portion 9 applied to the contacting peripheral edge portion of the support plate 7 is provided at a position separated from the rear surface of the mast by a constant distance B (about 10 to 30 mm), as shown in FIG.

As shown in FIG. 2, the left and right support plates 7 are each provided with a square hole 7a.
As shown in FIG. 3, the fitting surface of each of the support shafts 8 is welded with the square shafts 8a provided at the left and right ends of the support beam 8 fitted therein. The support beam 8 of this embodiment is formed of a square bar, and has hole portions 8b for fitting and supporting the lower end portion of the lift cylinder 5 on the left and right upper surfaces.

As described above, in this embodiment, the support plate 7 of the cylinder support beam 6 is welded to the side surface of the mast so as to project rearward, and the support beam 8 for directly supporting the lift cylinder 5 is horizontally attached thereto. Since the outer mast 1 is installed on the outer mast 1, welding to the rear surface of the mast, which has a large tensile stress when a forward moment M is applied to the outer mast 1, is avoided. Therefore, even though the cylinder support beam 6 is welded to the outer mast 1, it is possible to prevent a decrease in mast strength due to welding. This is effective in a large vehicle in which the cylinder support beam 6 is set higher than the mast support 3 which is the center of the outer mast 1 in the front-rear direction. The tensile stress due to the moment M acting on the mast side surface of the outer mast 1 is much smaller than that on the rear surface of the mast. Therefore, even if there is a welded portion here, that is not a problem in terms of mast strength. I won't.

Further, in this embodiment, the support beam 8 is connected to the support plate 7 by a fitting method and the fitting surface is welded so that the load is received by the fitting surface. , Support plate 7
This is far more advantageous in terms of strength as compared with a joint structure in which the support beam 8 is placed on the upper end surface of and welded.

As shown in FIG. 4, of the intersection of the inner surface of the support plate 7 and the rear edge of the mast of the outer mast 1, the D range (corner Welding may be performed on a portion 10 to 30 mm apart from the portion.

(Embodiment 2) Next, Embodiment 2 of the present invention will be described with reference to FIG. In this embodiment, the support plate 7 of the cylinder support beam 6 is integrated with the tilt plate 4, and this is welded to the side surface of the outer mast 1. Other configurations are similar to those of the above-described first embodiment. Then, in this case, the welded portion 9 has a certain distance B (10 to 10) from the rear surface of the mast as in the first embodiment.
It is applied over the entire outer peripheral edge from a position separated by about 30 mm). Therefore, according to the second embodiment, not only the same effect of preventing the strength reduction of the outer mast 1 as that of the first embodiment can be obtained, but also the reduction of the number of parts and the reduction of the manufacturing man-hours and the welding man-hours due to the common use of parts. Can be planned.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention. In this embodiment, in addition to the integration of the support plate 7 and the tilt plate 4 described in the second embodiment,
The support beam 8 is formed of a round bar, and a flat support seating surface 8d is formed around the hole 8b for supporting the lift cylinder 5. Further, the support plate 7 and the support beam 8 are connected to the round hole 7b and the round shaft. 8c, and the structure is such that the fitting surfaces are welded together. Therefore, in the case of this embodiment, in addition to the same effects as those of the first and second embodiments, by adopting the circular fitting type, the stress concentration of the fitting portion that may occur in the case of the square fitting type is prevented. It is possible to avoid it and improve its durability.

Although not shown in the drawings, as another embodiment, the support beam is formed of a square member, and only the end portion is processed into a cylindrical shape to form a circular fitting type. It is possible to weld an iron plate, etc. instead of machining the surface.

[0017]

As described above in detail, according to the present invention, the cylinder support beam for supporting the lift cylinder is welded to the side surface of the outer mast to avoid welding to the rear surface of the mast, which has a high tensile stress during loading. As a result, the strength of the outer mast can be improved by suppressing the strength reduction of the rear surface of the mast due to the stress concentration in the welded portion, the change in the metal structure due to heat, the occurrence of residual stress, and the like. Also, by setting the welded part of the support plate to be welded to the side surface of the mast at a certain distance from the rear surface of the mast, it is possible to avoid the occurrence of stress concentration parts on the rear surface of the mast and to reduce the influence of welding heat as much as possible. Since it is possible, it is very useful for improving the strength of the outer mast.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cylinder support beam structure of a lift cylinder according to a first embodiment of the present invention.

FIG. 2 is a partial perspective view showing fitting of a support plate and a support beam.

FIG. 3 is a partial perspective view showing a welded portion of the support plate to the outer mast.

FIG. 4 is a partial perspective view showing a case where the inner side of the support plate is welded to the outer mast to enhance the welding strength.

FIG. 5 is a perspective view showing a cylinder support beam structure of a lift cylinder according to a second embodiment of the present invention.

FIG. 6 is a perspective view showing a cylinder support beam structure of a lift cylinder according to a third embodiment of the present invention.

FIG. 7 is a perspective view showing a cylinder support beam structure of a conventional lift cylinder.

[Explanation of symbols]

 1 Outer mast 3 Mast support 4 Tilt support 5 Lift cylinder 6 Cylinder support beam 7 Support plate 8 Support beam 9 Weld

Claims (1)

[Claims] 1. A mast support provided at a lower end portion of an outer mast and a tilt support projecting near an intermediate portion of the outer mast are provided slightly closer to the tilt support than an intermediate portion thereof and are provided upright at the rear of the mast. A cylinder support beam structure for supporting two left and right lift cylinders, the left and right support plates fixed to the side surfaces of the left and right outer masts by welding, and between the left and right support plates. And a support beam that is horizontally installed on the mast, and the welding portion of the support plate with respect to the side surface of the mast is set to be separated from the rear surface of the mast by a certain distance, and the cylinder support beam structure of the lift cylinder.