JPH04148799A - Tilt cylinder fitting construction for fork lift - Google Patents

Abstract

PURPOSE:To reduce stress concentration generating on a welded part to half and improve durability of a supporting plate by providing a stepped part having a horizontal face and a linear slope on the upper end face side of a supporting plate, and welding so as to position the welding end part on the slope. CONSTITUTION:When a mast 1 is bent as shown with a virtual line by application of moment in the forward tilting direction on an outer mast 1 at a cargo handling work, as for a welding part 10 on the upper end face side of a supporting plate 7, except stress is concentrated on the welding end part A, stress is concentrated on the point of intersection part B between a slope face 7b and a horizontal face 7a. Namely, by forming the upper end face of the plate 7 out of not only the horizontal face 7a but the continued slope 7b, two points of stress concentration parts can be formed, as a result of this, stress concentration on the welding part 10 on the upper end face side can be dispersed to two points. Hereby, stress generating on the welding end part A can be reduced to half compared with the customary one.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a structure for attaching a tilt cylinder to an outer mast, which is attached to the outer mast for tilting the mast unit of a forklift truck back and forth.

(Prior Art) As shown in FIG. 5, the left and right outer masts ll of the mast unit in a forklift have their lower ends connected to the lower front end of the vehicle body, specifically, to the front axle 12 via mast brackets 13, so that they can be tilted forward and backward. installed. The left and right tilt cylinders 14 for tilting the mast unit back and forth have rear end portions of the cylinder bodies rotatably pivoted to the vehicle body via cylinder brackets 16, and extend diagonally upward in front. The front end of the piston rod 15 is rotatably connected via a pivot 18 to a support plate 17 joined to the intermediate portion of the outer mast 11.

The conventional support plate 17 is generally formed into a substantially rectangular shape, and the entire front end surface, a portion of the upper end surface, and a portion of the lower end surface are joined by welding while superimposed on the outer surface of the outer mast. There is. Note that the left and right support plates 17 have tilt beams 19 on the lower rear end surfaces.
are connected by.

(Problem to be Solved by the Invention) However, in the conventional case described above, during actual use, the welded end of the welded part 20 joining the support plate 17 to the outer mast 11, especially on the upper end surface side. Stress is concentrated at point A, which may cause cracks or peeling, and if left as is, this problem will progress one after another and lead to damage. This is because, during cargo handling work, a moment load acts on the outer mast 11 as shown in the imaginary line, causing it to deflect forward about the pivot shaft 18, which is the point of force application of the tilt cylinder 14, and due to this deflection. This is thought to be caused by external force acting intensively on the welded end A in a manner that pulls it.

In view of the above-mentioned problems, the present invention provides an improved forklift tilt cylinder mounting system that can reduce stress concentration occurring at the welded portion that joins the support plate to the outer surface of the outer mast, particularly at the welded end on the upper end surface side. Its purpose is to provide structure.

(Means for Solving the Problems) In order to solve the above problems, the present invention is configured as follows.

In other words, the front end of a tilt cylinder whose rear end is rotatably supported by the vehicle body and extends diagonally upward forward is placed approximately in the middle of an outer mast whose lower end is attached to the lower front end of the vehicle body so as to be tiltable forward and backward. The mounting structure for rotatably mounting the tilt cylinder includes a support plate that is stacked on the outer surface of the outer mast and joined by welding in order to rotatably mount the front end of the tilt cylinder. The plate is formed into a substantially rectangular shape, and has a step 1 having a horizontal surface and a linear inclined surface on the upper end surface side.
and a mounting structure in which the welding end on the upper end side of the welding part that is applied to at least the entire front end surface and the upper end surface of the support plate is set on the inclined surface. . , (Function) With the above configuration, when the outer mast bends forward during cargo handling work, the stress in the weld on the upper end surface of the support plate is concentrated at the weld end, and also on the inclined surface and horizontal Also concentrate on the intersection with the part. That is, regarding the welded portion on the upper end surface side of the support plate, there are two stress concentration portions, which can be reduced by half compared to the conventional case where stress concentration was concentrated at the welded end.

(Example) Hereinafter, an example of the present invention will be specifically described based on FIGS. 1 and 2. The left and right outer masts l of the mast unit in a forklift are attached to the lower front end of the vehicle body, specifically the mast bracket 3 to the front axle 2, as in the past.
It is attached so that it can be tilted forward and backward. Further, the left and right tilt cylinders 4 extend obliquely upward in front with the ends of the cylinder bodies rotatably attached to the vehicle body via cylinder brackets 6, and their piston rods 5 is rotatably connected via a pivot 8 to a support plate 7 joined to the outer surface of the outer mast l.

The support plate 7 is formed into a rectangular shape, and
At approximately the midpoint in the vertical direction of the outer mast l, the rear end side partially protrudes from the rear end of the outer mast l and overlaps the outer surface of the mast, and in this state, the entire front end surface and
A portion of the upper end surface and a portion of the lower end surface are joined by welding, and are connected to the piston rod 5 of the tilt cylinder 4 by a pivot shaft 8 at the upper side of the rear end portion. Note that the left and right support plates 7 are connected to each other by a tilt beam 9 at their lower rear ends.

In this embodiment, the upper end surface side of the support plate 7 has a front portion formed in a horizontal plane 7a, and a portion located approximately in the middle in the front-rear direction and in front of the connection point with the tilt cylinder 4. It is formed on the inclined surface 7b of the trailing end, which is substantially perpendicular to the line of action of the force.

That is, the upper end surface side of the support plate 7 is formed into a stepped portion with a horizontal surface 7a on the front side and an inclined surface 7b at the intermediate position, and the intersection of both surfaces 7a and 7b forms an obtuse angle. Therefore, among the welds 10 applied to the support plate 7, the welds on the upper end surface side extend from the horizontal surface 7a to the inclined surface 7b, and the welded end A is connected to the inclined surface 7b.
stipulated in b.

Note that the line of action of the force on the tilt cylinder 4 fluctuates in the vertical direction as the outer mast l tilts, but in this embodiment, the inclined surface 7b is within the angular range of the tilt cylinder 4. It is set to form approximately a right angle in a specific direction, for example when the mast is tilted forward.

The tilt cylinder mounting structure of this embodiment is configured as described above. Therefore, during cargo handling work, a forward tilting moment acts on the outer mast 1, causing the outer mast 1 to move along the imaginary line shown in FIG. When the support plate 7 is bent forward as shown in FIG.
In addition to stress being concentrated at the welded end A, stress is also concentrated at the intersection B between the inclined surface 7b and the horizontal surface 7a. In other words, by making the upper end surface of the support plate 7 not only a horizontal surface 7a but also an inclined surface 7b connected thereto, two stress concentration parts can be formed, and as a result, the welded part 10 on the upper end surface side Stress concentration can be distributed to two points.

This makes it possible to reduce the stress generated at the welded end A by half compared to the conventional method.

Furthermore, in this embodiment, among the welded portions 10 on the upper end surface side of the support plate 7, the welded portions on the inclined surface 7b side that are approximately perpendicular to the line of action of the force of the tilt cylinder 4 are welded end portions. Since the tensile force due to the deflection of the outer mast 1 is evenly resisted between A and the intersection point B, stress concentration occurring at the welded end A is also reduced by this.

FIGS. 3 and 4 show an inclined surface 7b on the upper end surface as described above.
Regarding the support plate 7 of this embodiment, which is equipped with the outer mast 1. This figure shows the results of two examples in which the magnitude of the stress acting on the welded end A when a moment in the forward tilting direction is applied to II is measured using a strain gauge.

In addition, when measuring, the weld length of the upper end surface is set to be equal to the conventional horizontal surface weld length, which is the sum of the horizontal surface weld length and the inclined surface weld length in this example.
The conditions were the same except for this point.

Stress test example 1 shown in Fig. 3 and stress test example 2 shown in Fig. 4 differ in the thickness of the support plate and the thickness of the tilt beam, but otherwise the conditions are exactly the same. .

In stress test example 1 in Fig. 3, for the stress P kg/cri generated at the welded end A of the conventional support plate
The stress generated at the welded end A of the support plate 7 in this example is reduced to 0.45 Pkg/mm'. In addition, in stress test example 2 in FIG. 4, the stress generated at the welded end A of the support plate 7 of this embodiment is 0, whereas the stress generated at the welded end A of the support plate 7 of this embodiment is 0. .3 Q
kg/mtn 2.

This stress test also confirmed that the stress at the welded end A of the support plate 7 of this example was reduced compared to the conventional support plate 17.

In this embodiment, the case where the inclined surface 7b is approximately perpendicular to the line of action of the force of the tilt cylinder 4 has been described.
For example, when the mast is tilted forward, approximately 90 degrees with respect to the line of action of the force of the tilt cylinder 4.
There is no problem as long as it is within the range of 35 degrees to 35 degrees.

(Effects of the Invention) As detailed above, according to the present invention, when the support plate is joined to the outer surface of the outer mast by welding, the step portion having a horizontal surface and a linear inclined surface is provided on the upper end surface side. By adopting such a configuration and performing welding in such a manner that the welding end is located on the inclined surface, stress concentration occurring at the welding end can be halved compared to the conventional method. This makes it possible to improve the durability of the support plate and provide a highly safe tilt cylinder mounting structure.

[Brief explanation of drawings]

FIG. 1 is a side view showing a tilt cylinder mounting structure according to an embodiment of the present invention, FIG. 2 is an exploded perspective view showing main parts, and FIG.
4 and 4 are graphs showing the stress test results for the upper end surface side welded ends of the support plate according to the present invention and the conventional support plate, respectively, and FIG. 5 is a side view showing the mounting structure of the conventional tilt cylinder. be. l...Outer mast 4...Tilt cylinder 7
...Support plate 7a...Horizontal surface 7b...Slope surface 10...Welding part Applicant Toyota Industries Corporation Agent Patent attorney Hidehiko Okada (3 others) Figure 5

Claims (1)

[Scope of Claims] A tilt cylinder whose lower end is rotatably supported by the vehicle body and which extends diagonally upward at approximately the middle of an outer mast whose lower end is attached to the lower front end of the vehicle body so as to be tiltable forward and backward. A mounting structure for rotatably attaching the front end of the tilt cylinder, the support plate being superimposed on the outer surface of the outer mast and joined by welding in order to rotatably attach the front end of the tilt cylinder. The support plate is formed into a substantially rectangular shape, and has a stepped portion having a horizontal surface and a linear inclined surface on the upper end surface side, so that at least the entire front end surface and the upper end surface of the support plate are formed. A tilt cylinder mounting structure for a forklift, wherein a welding end on the upper end side of a welded part that is applied including the welding part is set on the inclined surface.