JP2009073618A - Mast device in forklift - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mast device in a forklift capable of enhancing an yield of material blanking for a sheet material of a tilt bracket by facilitating both the improvement of welding strength in the tilt bracket and the shortening of a welded part. <P>SOLUTION: The mast device in the fork lift has a pair of outer masts 11 (right-left) tilted in a back-and-forth direction and the tilt bracket 17 for pivoting the rod end 28a of a tilt cylinder 28. The tilt bracket 17 is formed of a flat sheet material and has a bracket upper surface 18 and a bracket lower surface 19 which are parallel with each other and a bracket front surface 20 in which the welded part 29 for fixing the tilt bracket 17 to the outer masts 11 is formed. The bracket front surface 20 has a continuous curved surface 21 for forming a recessed part H toward a bracket rear surface 24 side. The welded part 29 is formed along the continuous curved surface 21 and a welded end 29a is positioned near the end of the continuous curved surface 21. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a mast device in a forklift, and more particularly to a mast device in a forklift having a tilt bracket fixed to an outer mast by welding.

As a conventional technique of a mast device in a forklift, for example, a tilt cylinder mounting structure for a forklift disclosed in Patent Document 1 is known.
In this tilt cylinder mounting structure, the support plate is joined to the outer surface of the outer mast by welding.
The support plate is a member for rotatably mounting a piston rod, which is a front end portion of the tilt cylinder, to an intermediate portion between a pair of left and right outer masts that can tilt forward and backward.
The support plate is formed in a substantially rectangular shape, and has a step portion having a horizontal surface and a linear inclined surface on the upper end surface side, and includes an upper end that includes at least the entire front end surface and the upper end surface of the support plate. The weld end on the part side is set on an inclined surface.

According to this technique, stress concentrates on the weld end, and stress also concentrates on the intersection of the inclined surface and the horizontal plane.
By forming two stress concentration portions, the stress concentration of the welded portion on the upper end surface side is distributed to two points, so that the stress concentration generated at the weld end portion is halved compared to the conventional case.
JP-A-4-148799 (page 1-4, FIG. 1-2)

However, in the prior art disclosed in Patent Document 1, the welded portion for fixing the support plate corresponding to the tilt bracket to the outer mast tends to be long.
The length of the welded portion is required to be as short as possible while considering the welding strength.
In the prior art, it is considered that the support plate is formed of a flat plate material having a flat plate surface. However, since the shape of the support plate has a stepped portion on the upper end surface, it is compared with a simple rectangular plate. And the yield of the material removal with respect to a flat plate material is low, and it is the shape which is not considered about the effective use of material.
For this reason, when taking a material from the flat plate material, there is a possibility that the yield of the material taking is lowered and the waste of the surplus member is increased.

  The present invention has been made in view of the above problems, and an object of the present invention is to improve the welding strength of the tilt bracket and shorten the length of the welded portion, and to provide a material for the plate material of the tilt bracket. It is in providing the mast apparatus in the forklift which can improve the yield of taking.

  In order to achieve the above object, the present invention provides a pair of left and right outer masts, which are provided at the front of a vehicle body and tilted back and forth by a tilt cylinder, and are fixed to the outer surface of the outer mast by welding. A tilt bracket for pivotally supporting a mast device in a forklift, wherein the tilt bracket is formed of a flat plate material having a flat plate surface, the bracket upper surface and the bracket lower surface parallel to each other, and the tilt bracket A bracket front surface on which a welded portion to be fixed to the outer mast is formed; a bracket rear surface facing the tilt cylinder; and a shaft support portion that pivotally supports the rod end, and the bracket front surface has a recess toward the bracket rear surface side. A continuous curved surface to be formed; Along the curved surface are continuously formed, welded end of the weld, characterized in that located towards the end portions of the continuous curved surface.

In the present invention, the continuous curved surface on the front surface of the tilt bracket forms a recess that faces the rear surface of the bracket.
The load acting on the tilt bracket from the rod end of the tilt cylinder generates stress in the welded portion of the tilt bracket.
Since the welded portion is continuously formed along the continuous curved surface, the stress in the welded portion is distributed along the continuous curved surface.
Since the weld end of the weld is located near the end that is the front side of the continuous curve line, the weld end moves away from the shaft support, and stress concentration on the weld end is unlikely to occur.
The stress acting on the weld end decreases as the position of the weld end moves away from the shaft support toward the bracket front side.
According to the present invention, it is possible to achieve both the improvement of the welding strength in the tilt bracket and the shortening of the length of the welded portion only by providing the welded portion only on the front surface of the bracket.
Further, since the welded portion only needs to be provided on the front surface of the bracket, the upper surface of the bracket and the lower surface of the bracket can be made parallel to each other.
By using a tilt bracket in which the bracket upper surface and the bracket lower surface are parallel to each other, the tilt bracket can be formed into a shape suitable for improving the yield of material removal with respect to the plate material of the tilt bracket.

In the present invention, in the mast device in the forklift described above, the continuous curved surface may have a linear upper inclined surface portion that coincides with the axial center direction of the rod.
In this case, since the inclination direction of the upper inclined surface portion coincides with the inclination direction in which the stress in the welded portion acts, stress concentration at the weld end can be made difficult to occur, and as a result, the length of the welded portion is shortened. It becomes possible.

In the present invention, in the mast device in the forklift, the continuous curved surface may be vertically symmetric in the vertical direction between the bracket upper surface and the bracket lower surface.
In this case, since the continuous curved surface is vertically symmetric, the tilt bracket can be fixed to the outer mast in a state where the top surface of the bracket upper surface and the bracket lower surface are reversed.
For this reason, the manner of fixing the tilt bracket can be changed according to the type of the mast device, and the versatility of the tilt bracket for fixing the outer mast can be increased.

  According to the present invention, in the mast device in the forklift described above, the tilt beam may be fixed to the rear surface of the bracket, and the shaft support portion may be disposed below the tilt beam.

When the shaft support is disposed below the tilt beam, a greater load is applied to the tilt bracket than when the shaft support is disposed above the tilt beam.
However, since the welded portion along the continuous curved surface is continuously formed to improve the weld strength of the tilt bracket as compared with the conventional art, the tilt bracket can resist the stress based on the load.
Therefore, the shaft support portion can be arranged above or below the tilt beam according to the conditions of the mast device, and the design freedom of the mast device is improved.

  ADVANTAGE OF THE INVENTION According to this invention, improvement of the welding strength in a tilt bracket and shortening of the length of a welding part can be made compatible, and the yield of the material picking with respect to the plate-shaped material of a tilt bracket can be improved.

Embodiments according to the present invention will be described below with reference to FIGS.
1 is a schematic perspective view showing a mast device in a forklift according to an embodiment of the present invention, FIG. 2 is a side view showing a main part of the device, and FIG. 3 is an enlarged side view showing a tilt bracket, FIG. 4 is an explanatory view for explaining the material removal of the tilt bracket.
A mast device (hereinafter simply referred to as “mast device”) in a forklift according to this embodiment is provided at the front of the vehicle body of the forklift.

As shown in FIG. 1, the mast device 10 has a pair of left and right outer masts 11.
The outer mast 11 constitutes a part of the mast device 10 together with an inner mast (not shown) provided to be movable up and down inside the outer mast 11.
The right back side in FIG. 1 is the front of the mast device 10, and the left front side is the back.
The inner mast is provided with a lift bracket (not shown), the lift bracket is located at the front of the mast device 10, and the vehicle body (not shown) is located at the rear side of the mast device 10.

The outer mast 11 according to this embodiment has a substantially L-shaped cross section.
The outer mast 11 is mainly composed of a main wall portion 11a and a rear wall portion 11b.
The main wall portion 11a has an outer surface and an inner surface, and these surfaces are substantially parallel to the front-rear direction.
The rear wall portion 11b is a portion provided in a direction perpendicular to the main wall portion 11a at the rear end of the main wall portion 11a, and has a front surface looking forward and a rear surface facing the rear.

The pair of left and right outer masts 11 are connected by an upper stay 12 disposed horizontally near the upper end thereof.
The end portions of the upper stay 12 are connected by welding to the outer surface of the main wall portion 11a and the rear surface of the rear wall portion 11b in each outer mast 11.
The upper stay 12 has a substantially U-shaped form in plan view so as to protrude to the rear of the outer mast 11.

An intermediate stay 13 is provided at a distance from the upper stay 12 downward.
The intermediate stay 13 has substantially the same configuration as the upper stay 12, and the upper stay 12 and the intermediate stay 13 are intended to improve the rigidity of the mast device 10.
At the lower part of the outer mast 11, a mast bracket 14 having a shaft part 15 is welded to the rear wall part 11 b, and a lower beam 16 is welded to the rear part of the mast bracket 14.
The lower beam 16 increases the rigidity of the mast device 10 in the same manner as the upper stay 12 and the intermediate stay 13.
Since the shaft portion 15 of the mast bracket 14 is pivotally supported by the front portion of the vehicle body, the mast device 10 is tiltable back and forth with the shaft portion 15 as a fulcrum.

In the outer mast 11 between the intermediate stay 13 and the mast bracket 14, a tilt bracket 17 is fixed to the outer surface of the main wall portion 11a of the outer mast 11 by welding.
The tilt bracket 17 is a flat plate material whose both plate surfaces are uniformly flat, and is formed of a metal plate having a sufficient thickness that satisfies the welding strength.
In a state where the tilt bracket 17 is fixed to the outer mast 11, the rear portion of the tilt bracket 17 protrudes rearward from the outer mast 11.
A shaft hole 25 as a shaft support portion is formed on the lower side of the rear portion of the protruded tilt bracket 17.
The tilt cylinder 28 shown in FIG. 2 has a rod 28a that advances and retreats, and a shaft portion that is supported by the shaft hole 25 is provided at the end of the rod 28a.

The tilt bracket 17 has a bracket upper surface 18 and a bracket lower surface 19, and the bracket upper surface 18 and the bracket lower surface 19 have flat surfaces parallel to each other.
A bracket front surface 20 is formed between both front ends of the bracket upper surface 18 and the bracket lower surface 19.
A bracket rear surface 24 facing the tilt cylinder 28 is formed between both rear ends of the bracket upper surface 18 and the bracket lower surface 19.
For convenience of explanation, in FIG. 3, points A to G are set on the outer periphery of the tilt bracket 17, the bracket upper surface 18 (between points AB), the bracket lower surface 19 (between points CD), and the bracket front surface 20 (between points AC). ), The range of the bracket rear surface 24 (between the points BD) is clearly shown.

The bracket rear surface 24 is formed with a tilt beam fixing surface 24a (between points BG in FIG. 3) forming a surface perpendicular to the bracket upper surface 18.
Near the end of the tilt beam 27 is fixed to the tilt beam fixing surface 24a by welding.
The tilt beam 27 is formed of a long flat plate member, and connects the pair of left and right tilt brackets 17 to increase the rigidity of the mast device 10.
A connecting surface 24b (between points DG in FIG. 3) including an arc surface along the shaft hole 25 is formed between the lower end of the tilt beam fixing surface 24a on the bracket rear surface 24 and the rear end of the bracket lower surface 19.

2 and 3, the bracket front surface 20 occupies most of the bracket front surface 20, and includes a continuous curved surface 21 that forms a recess H toward the bracket rear surface 24, a continuous curved surface 21 and a bracket upper surface 18. The upper arc surface 22 to be connected and the lower arc surface 23 to connect the continuous curved surface 21 and the bracket lower surface 19 are formed.
The continuous curved surface 21 is a substantially C-shaped surface in a side view when the tilt bracket 17 is fixed to the outer mast 11.
A welded portion 29 that fixes the tilt bracket 17 to the outer mast 11 is continuously formed along the continuous curved surface 21.

The welded portion 29 has a predetermined width, and weld ends 29 a and 29 b that are end portions in the longitudinal direction of the welded portion 29 are positioned closer to the end portion of the continuous curved surface 21.
In particular, the occurrence of high stress on the weld end 29a can be suppressed by positioning the upper weld end 29a as far forward as possible on the continuous curved surface 21.
The tilt bracket 17 is fixed to the outer mast 11 only by the welded portion 29 along the continuous curved surface 21, and no welded portion is formed on the tilt bracket 17 at other portions.

Here, the continuous curved surface 21 will be described in detail with reference to FIG.
The continuous curved surface 21 includes a linear upper inclined surface portion 21a extending obliquely from the upper end (point E) toward the rear center, and from the lower end (point F) to the rear central portion. A straight lower inclined surface portion 21b extending obliquely, an intermediate vertical surface portion 21c forming a surface perpendicular to the bracket upper surface 18 between the upper inclined surface portion 21a and the lower inclined surface portion 21b, and an upper inclined surface portion 21a and an intermediate The upper curved surface portion 21d that connects the vertical surface portion 21c and the lower curved surface portion 21e that connects the lower inclined surface portion 21b and the intermediate vertical surface portion 21c are formed.

When the tilt cylinder 28 holds the outer mast 11 in an upright position, the inclination direction of the upper inclined surface portion 21a of the continuous curved surface 21 (shown by a one-dot chain line Q) and the axial direction of the rod 28a of the tilt cylinder 28 (one-dot chain line P). Are substantially coincident with each other.
The axial center direction of the rod 28a is the same as the forward / backward direction of the rod 28a that moves forward / backward by the operation of the tilt cylinder 28.
By making the inclination direction of the upper inclined surface portion 21a substantially coincide with the axial direction of the end of the rod 28a, generation of high stress in the welded portion 29 can be suppressed, and as a result, the length of the welded portion 29 can be shortened. Become.
It is preferable that the curvatures of the upper curved surface portion 21 d and the lower curved surface portion 21 e in the continuous curved surface 21 are set as large as possible in order to disperse the stress acting on the welded portion 29.

The operation of the mast device 10 according to this embodiment will be described.
The mast device 10 is tilted back and forth by the operation of the tilt cylinder 28.
At this time, a load acting on the axial direction of the rod 28 a is generated in the tilt bracket 17 of the mast device 10 via the rod 28 a end of the tilt cylinder 28.

When a load in the axial direction of the rod 28 a is generated in the tilt bracket 17, a stress corresponding to the load is generated in the welded portion 29, and this stress is distributed along the welded portion 29.
Since the vertical length of the welded portion 29 is formed continuously along the continuous curved surface 21 including the upper curved surface portion 21d and the lower curved surface portion 21e, a part of the stress acting on the welded portion 29 is Dispersed in the upper curved surface portion 21d and the lower curved surface portion 21e, excessive stress concentration is avoided in both the curved surface portions 21d and 21e.
Since the inclination direction of the upper inclined surface portion 21a coincides with the inclination direction in which the stress in the welded portion 29 acts, the portion of the welded portion 29 along the upper inclined surface portion 21a has a stress that matches the inclination direction of the upper inclined surface portion 21a. This stress can be counteracted even if the height is high, and excessive stress concentration at the weld end 29a is avoided.

In addition, the stress which acts on the welding end 29a reduces as the position of the welding end 29a moves away from the shaft hole 25 which becomes the load input source.
Furthermore, since the welded portion 29 along the continuous curved surface 21 is formed continuously, stress based on the vertical and forward loads on the tilt bracket 17 as well as the axial direction of the rod 28a acts on the welded portion 29. However, the welded portion 29 resists this stress, and the tilt bracket 17 maintains a state of being firmly fixed to the outer mast 11.

Next, the material removal at the time of manufacture of the tilt bracket 17 of this embodiment is demonstrated.
As shown in FIG. 4, the tilt bracket 17 is obtained by punching or cutting out a rectangular metal plate M as a plate-like member.
If the length of one side of the metal plate M is set to the same length as the distance between the bracket upper surface 18 and the bracket lower surface 19, excess portions m1 and m2 that are wasted as shown in FIG. , M3 (each area shown by hatching in FIG. 4) occurs.

The surplus portion m <b> 1 is a surplus portion generated by forming the continuous curved surface 21, the upper arc surface 22, and the lower arc surface 23 that constitute the bracket front surface 20.
In addition, the surplus portion m2 is a surplus portion generated by forming the connection surface 24b on the bracket rear surface 24 in the tilt bracket 17, and the surplus portion m3 is a surplus portion generated by forming the shaft hole 25.
In this embodiment, the bracket upper surface 18 and the bracket lower surface 19 are parallel to each other, and the ratio of the total area of the surplus portions m1 to m3 to be tightened to the total area of the metal plate M is an excess generated when a conventional tilt bracket is manufactured. Compared with the part, it can be lowered, and waste of material is suppressed.

According to this embodiment, the following effects are produced.
(1) Since the welded portion 29 is continuously formed along the continuous curved surface 21, the stress in the welded portion 29 can be distributed along the continuous curved surface 21. Since the weld end 29a of the welded portion 29 is located closer to the end that is the front side of the continuous curved surface 21, and the inclination direction of the upper inclined surface portion 21a matches the inclination direction in which the stress in the welded portion 29 acts, the weld end 29a. It is possible to make it difficult for stress concentration to occur. Further, excessive stress concentration in the welded portion 29 can be avoided.

(2) By only providing the welded portion 29 along the continuous curved surface 21 on the bracket front surface 20, it is possible to achieve both the improvement of the welding strength in the tilt bracket 17 and the shortening of the length of the welded portion 29.

(3) Since the welded portion 29 only needs to be provided on the bracket front surface 20, the bracket upper surface 18 and the bracket lower surface 19 of the tilt bracket 17 can be made parallel to each other. By making the bracket upper surface 18 and the bracket lower surface 19 into the shape of the tilt bracket 17 that is parallel to each other, the tilt bracket 17 can be made into a shape suitable for improving the yield of material removal with respect to the plate-like material.

(4) When the shaft hole 25 is disposed below the tilt beam 27, a larger load acts on the tilt bracket 17 than when the shaft hole 25 is disposed above the tilt beam 27, but the continuous curved surface 21. Since the weld strength of the tilt bracket 17 is improved as compared with the conventional case, the tilt bracket 17 can resist stress based on the load. Therefore, the shaft hole 25 can be arranged above or below the tilt beam 27 according to the conditions of the mast device 10 and the like, and the degree of freedom in designing the mast device 10 is improved.

(5) In the mast apparatus 10 of this embodiment, the welding strength in the tilt bracket 17 is improved by forming the welded portion 29 along the continuous curved surface 21, and welding is performed on parts other than the bracket front face 20 as in the conventional mast apparatus. There is no need to provide a section. For this reason, the working time concerning welding work can be reduced.

(6) Since the welded portion 29 along the continuous curved surface 21 in the tilt bracket 17 is formed, the length of the welded portion 29 can be made shorter than before, and the labor and time required for welding work can be suppressed. it can. Moreover, since it is the continuous curved surface 21 including a curved surface with a large curvature, it is relatively easy to employ welding work by automatic welding using a welding robot or the like.

(7) The tilt bracket 17 according to this embodiment can be obtained by punching or cutting out the metal plate M whose both plate surfaces are flat, and at least does not require bending of the metal plate M and uses other parts. As a result, the tilt bracket 17 is easier to manufacture than before.

(Another example)
Next, the case where the tilt bracket 37 according to another example is used will be described.
FIG. 5 is a side view showing a tilt bracket 37 according to the second embodiment.
Here, the same reference numerals are used for elements that are common to the above embodiment, and the description of the above embodiment is used.
As shown in FIG. 5, a tilt bracket 37 is fixed to the outer surface of the main wall portion 11 a in the outer mast 11.

The tilt bracket 37 has a bracket upper surface 38 and a bracket lower surface 39 which are parallel to each other.
The tilt bracket 37 includes a bracket front surface 40 having a continuous curved surface 41, an upper arc surface 42, and a lower arc surface 43, and a bracket rear surface 44 facing the tilt cylinder 28 and having a tilt beam fixing surface 44a and a connection surface 44b.
This another example is characterized by a continuous curved surface 41 forming the bracket front surface 40, and the continuous curved surface 41 is vertically symmetric in the vertical direction between the bracket upper surface 38 and the bracket lower surface 39 as shown in FIG.
That is, the continuous curved surface 41 is vertically symmetric about the horizontal axis R set for convenience of explanation in FIG.

Accordingly, it is possible to use the tilt bracket 37 for another type of outmast in which the tilt cylinder 28 is disposed above the tilt beam 27.
Even if the top and bottom of the tilt bracket 37 is reversed and fixed to another type of outer mast, the lower inclined surface portion 41b, the intermediate surface portion 41c, the lower curved surface portion 41e, and the lower arc surface 43 are arranged on the upper side, and these 41b, 41c, 41e Is the same position as the upper arc surface 42, the upper inclined surface portion 41a, and the upper curved surface portion 41d when the top and bottom are not reversed.
When the tilt bracket 37 is turned upside down and fixed to another type of outer mast, the lower inclined surface portion 41b is positioned on the upper side, and the inclined direction of the lower inclined surface portion 41b coincides with the axial center direction of the rod 28a.
The welded portion 49 is formed along the continuous curved surface 41, the weld end 49 a is located near the upper arc surface 42, and the weld end 49 b is located near the lower arc surface 43.

According to this alternative example, since the continuous curved surface 41 of the tilt bracket 37 is vertically symmetric, the connection surface 44b of the tilt bracket 37 is at the upper position, and the tilt beam fixing surface 44a is at the lower position. By using the tilt bracket 37 upside down, the tilt bracket 37 can be applied to another type of outmast in which the tilt cylinder 28 is disposed above the tilt beam 27.
For this reason, the method of fixing the tilt bracket 37 can be changed according to the type of the mast device 10, and the versatility for fixing the tilt bracket 37 can be increased.

The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the gist of the invention. For example, the following modifications may be made.
In the above embodiment, the continuous curved surface includes the upper and lower curved surface portions and the inclined surface portion. However, the continuous curved surface may be formed by a single arc surface, or a combination of a plurality of arc surfaces having different curvatures from each other. It may be. In this case, it is preferable that the length of the weld formed along the continuous curved surface is shortened as much as possible.
In the above embodiment, the case where the tilt bracket is provided with the shaft hole as the shaft support portion and the rod end of the tilt cylinder has the shaft portion inserted into the shaft hole has been described. However, the tilt bracket is provided with the shaft portion and the rod end A shaft hole into which the shaft portion is inserted may be provided.

It is a schematic perspective view which shows the mast apparatus in the forklift which concerns on embodiment. It is a side view which shows the principal part of the mast apparatus in the forklift which concerns on embodiment. It is an enlarged side view which shows the tilt bracket which concerns on embodiment. It is explanatory drawing explaining the material removal of the tilt bracket which concerns on embodiment. It is a side view which shows the mast apparatus using the tilt bracket which concerns on another example.

Explanation of symbols

10 Mast device 11 Outer mast 17, 37 Tilt bracket 18, 38 Bracket upper surface 19, 39 Bracket lower surface 20, 40 Bracket front surface 21, 41 Continuous curved surface 21a, 41a Upper inclined surface portion 21b, 41b Lower inclined surface portion 21c, 41c Intermediate vertical surface portion 21d 41d Upper curved surface portion 21e, 41e Lower curved surface portion 22, 42 Upper circular arc surface 23, 43 Lower circular arc surface 24, 44 Bracket rear surface 25 Shaft hole 27 Tilt beam 28 Tilt cylinder 28a Rod 29, 49 Welded portions 29a, 29b, 49a, 49b Weld end H Recess M Metal plate m1, m2, m3 Surplus part

Claims (4)

In a forklift having a pair of left and right outer masts that are provided at the front of the vehicle body and tilted back and forth by a tilt cylinder, and a tilt bracket that is fixed to the outer surface of the outer mast by welding and pivotally supports the rod end of the tilt cylinder. A mast device,
The tilt bracket is formed of a flat plate material having a flat plate surface, a bracket upper surface and a bracket lower surface that are parallel to each other, a bracket front surface on which a weld portion that fixes the tilt bracket to the outer mast is formed, and the tilt cylinder A bracket rear surface that faces the shaft, and a shaft support portion that pivotally supports the rod end,
The bracket front surface has a continuous curved surface that forms a recess toward the bracket rear surface side,
The said welding part is continuously formed along the said continuous curved surface, The welding end of the said weld part is located near the edge part of the said continuous curved surface, The mast apparatus in the forklift characterized by the above-mentioned. 2. The mast device in a forklift according to claim 1, wherein the continuous curved surface has a linear upper inclined surface portion coinciding with the axial center direction of the rod. The mast device in a forklift according to claim 1 or 2, wherein the continuous curved surface is vertically symmetrical in the vertical direction between the bracket upper surface and the bracket lower surface. The mast device in a forklift according to any one of claims 1 to 3, wherein the tilt beam is fixed to a rear surface of the bracket, and the shaft support portion is disposed below the tilt beam.

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