JP2000071852A - Cargo receiving table elevating device for cargo handling vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of vibration and noise due to the impact at the time of stopping a vehicle by interposing a brake device for gradually restricting the flow of the hydraulic fluid from a pressure oil supplying source to a hydraulic cylinder after a cargo receiving table reaches near the upper limit position so as to smoothly stop the raising operation between the pressure oil supplying source and the hydraulic cylinder. SOLUTION: When a hydraulic cylinder is contracted and a cargo receiving table is positioned at the lower limit position, a push bolt 54 dose not abut on a spool valve 34, and the spool valve 34 is held at a progressing position by a valve spring 35, and a passage cross sectional area of an opening of an output port 31 becomes the maximum. When a pressure pump is operated so as to raise the cargo receiving table, the discharged oil is supplied to the hydraulic cylinder so as to raise the cargo receiving table. When the cargo receiving table reaches near the upper limit position, the push bolt 54 abuts on the spool valve 34 so as to move the spool valve 34 backward, and flow of the hydraulic fluid from a hydraulic pump to the hydraulic cylinder is gradually restricted, and the cargo receiving table on the way of rising is smoothly stopped at the upper limit position. With this structure, impact at the time of stopping the cargo receiving table is relaxed so as to prevent the generation of vibration and noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loading / unloading device for a loading / unloading vehicle, and more particularly to a loading / unloading device supported on a vehicle body so as to be able to move up and down.
The present invention relates to a lifting / lowering device provided with a hydraulic cylinder disposed between the receiving table and the vehicle body and capable of driving the receiving table upward, and a hydraulic supply source for supplying hydraulic oil to the hydraulic cylinder.

[0002]

2. Description of the Related Art The above-mentioned lifting / lowering device for a loading / unloading vehicle is disclosed in, for example, Japanese Utility Model Publication No. 50-43856 and 51-44487.
It is conventionally known as described in Japanese Patent Application Publication No.

[0003]

In the above-described conventional loading / unloading device, the ascending loading / unloading device suddenly decelerates and stops when the ascending loading device reaches the upper limit position. In addition, there is a problem that the load is likely to shift and the load on the load receiving table may be shifted.

In order to solve such a problem, for example, a flow of hydraulic oil from a hydraulic supply source to a hydraulic cylinder in a rising process of the receiving tray is linked with the receiving tray after the receiving tray reaches a position near the upper limit position. It is conceivable to stop the loading table in a buffered manner by gradually squeezing the brake valve device. In this case, the change rate of the throttle flow rate of the hydraulic oil with respect to the operating stroke of the brake valve device (ie, the upward displacement of the loading table). Is constant, there are the following inconveniences. For example, if the constant change rate is set relatively large (that is, the flow of the hydraulic oil is rapidly reduced), the load receiving platform is not at an upper limit because the brake valve device cannot exhibit a sufficient damping effect. When the impact at the time of reaching the position is relatively large, while the rate of change is set relatively small (that is, the flow of the hydraulic oil is set to be gradually reduced), it is difficult to obtain a sufficient buffer effect. It is necessary to use a brake valve device with a long working stroke, which increases the size of the brake valve device, and furthermore, it is necessary to reduce the speed of the ascent of the loading cradle earlier in the process of ascending, thereby increasing the time required for ascending. I will.

[0005] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a lifting and lowering device for a cargo receiving platform of a cargo handling vehicle, which can solve the above-mentioned problem.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, a first aspect of the present invention is to provide a load receiving pedestal supported on a vehicle body so as to be able to move up and down, and provided between the load receiving table and the vehicle body. In a loading / unloading device for a loading / unloading vehicle including a hydraulic cylinder that can be driven up and a hydraulic supply source that supplies hydraulic oil to the hydraulic cylinder, the loading cradle is raised between the hydraulic supply source and the hydraulic cylinder. In the process, a brake valve device for buffering the lifting operation of the receiving cradle by intermittently reducing the flow of hydraulic oil from the hydraulic supply source to the hydraulic cylinder after the receiving cradle reaches the vicinity of the upper limit position is provided. It is characterized by that.

According to a second aspect of the present invention, in addition to the features of the first aspect of the invention, the brake valve device includes an input port and an output port connected to a hydraulic supply source and a hydraulic cylinder, respectively.
A valve box having a cylinder hole with both ports opened, and a predetermined forward position and a retracted position fitted to the cylinder hole so as to form a communication passage between the two ports with the cylinder hole. A sliding valve that can slide between the sliding valve and a valve spring that constantly urges the sliding valve to the forward position side, and the outer peripheral portion of the sliding valve has a gradually decreasing diameter toward the rear of the valve. A tapered portion formed so as to gradually narrow the communication path during the retreating process from the advance position to the retreat position of the valve, and the tapered portion rear end is formed at the rear end of the opening of one port during the retreat process. Is provided between the sliding valve and the loading tray, and the sliding valve is retracted from the forward position to the retracted position in conjunction with the loading tray rising from the vicinity of the upper limit position to the upper limit position. An interlocking mechanism is provided.

According to a third aspect of the present invention, in addition to the features of the first aspect of the present invention, the brake valve device includes an input port and an output port connected to a hydraulic supply source and a hydraulic cylinder, respectively.
A valve box having a cylinder hole with both ports opened, and a predetermined forward position and a retracted position fitted to the cylinder hole so as to form a communication passage between the two ports with the cylinder hole. A sliding valve that can slide between the sliding valve and a valve spring that constantly biases the sliding valve toward the forward position; An annular step for rapidly narrowing the communication passage through the opening of one of the ports in the process of retracting to the position, and the valve formed further in front of the annular step and further retracted from the intermediate retracted position; In the process, there is provided a taper portion for gradually narrowing the communication path, and a sliding valve is interposed between the sliding valve and the loading tray in conjunction with the loading tray rising from the vicinity of the upper limit position to the upper limit position. An interlocking mechanism for retracting from the forward position to the retracted position is provided, According to a fourth aspect of the present invention, in addition to the above feature of the third aspect of the present invention, an annular concave portion which forms the communication passage between the sliding valve and the cylinder hole is provided on an outer peripheral portion of the sliding valve. It is characterized by being formed continuously on the rear side.

In the present invention, the side on which the sliding valve moves in conjunction with the rise of the loading table is defined as the rear side of the sliding valve, and the opposite side is defined as the front side of the same.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below based on embodiments of the present invention illustrated in the accompanying drawings.

In the accompanying drawings, FIG. 1 is a longitudinal sectional side view of a rear portion of a vehicle showing one embodiment of the present invention, FIG. 2 is a hydraulic control circuit diagram of the embodiment, and FIG. 4, FIG. 4 is a side view as viewed from the arrow 4 in FIG. 3, FIG. 5 is an overall longitudinal sectional view of the brake valve device in a state where the sliding valve is in the forward position, and FIG. FIG. 7 is a graph showing the relationship between the operation stroke of the brake valve device and the throttle flow rate, and FIG.
FIG. 6 is a diagram corresponding to FIG. 6 showing a modification of the brake valve device, and FIG.
FIG. 9 is a sectional view taken along line 9-9 of FIG.

First, in FIG. 1, a pair of left and right brackets 2 are fixedly provided at both left and right ends of a rear portion of a vehicle body 1 of a cargo handling vehicle T, respectively. The parallel link mechanism 4 includes a pair of left and right hydraulic cylinders 5 having piston rods 6 of a pair of right and left hydraulic cylinders 5 rotatably supporting bases at appropriate places of the vehicle body 1 (for example, the bracket 2 or another bracket). The tip is rotatably connected and supported. Thereby, each parallel link mechanism 4 is operated according to the expansion and contraction operation of each hydraulic cylinder 5, and the load receiving table 3 can be rotated up and down.

Each parallel link mechanism 4 has a pair of upper and lower swing links 7 and 8 which are parallel to each other, and a horizontal end for rotatably supporting the base ends of the respective swing links 7 and 8 to the bracket 2. It is composed of support shafts 9 and 10, an upright column 11 extending in the vertical direction, and horizontal pins 12 and 13 for rotatably connecting the ends of both swing links 7 and 8 to the upright column 11.
The base ends of the swing links 7 and 8 are fixed to support shafts 9 and 10, and the support shafts 9 and 10 are rotatably supported by the bracket 2. Further, an arm 14 is integrally formed on one of the support shafts 9 so as to protrude outward in the radial direction, and the end of the arm 14 is rotatable with the end of the piston rod 6 of the hydraulic cylinder 5. Linked to

At the lower end of the upright support 11, the base end of the loading table 3 is rotatably supported via a shaft 15 parallel to the pins 12, 13. Moreover, the upper part of the upright support 11 and the tip of the load receiving table 3 are connected via a resilient support link 16, and the load receiving table 3 is in a horizontal posture when the support link 16 is in an extended state. It is to be noted that between the upright support 11 and the loading tray 3, although not shown, a driving means for forcibly rotating the loading tray between the horizontal position and the vertical position, and a holding device for holding the loading tray in the vertical position are required. It is installed according to.

Thus, when the hydraulic cylinder 5 is contracted while the support link 16 is extended and the load receiving table 3 is held in a horizontal posture, the operation of the parallel link mechanism 4 causes the load receiving table 3 to move.
Is lowered to the ground as shown by the chain line in FIG. 1, and conversely, when the hydraulic cylinder 5 is extended, the parallel link mechanism 4
As a result, the load receiving platform 3 rises to the upper limit position 3U where it contacts the rear edge of the loading platform 17 on the same plane as the loading platform 17 of the vehicle body 1 as shown by the solid line in FIG.

In FIG. 2, a hydraulic pump 19 as a hydraulic supply source for pumping hydraulic oil from an oil tank 18 is connected to a discharge oil passage 21, and a pair of connection oil passages 21 is provided downstream of the discharge oil passage 21. _1, 21 ₂ are connected in parallel, that the two connecting oil passage 21 _1, 21 _2, the hydraulic chamber 5a of the pair of left and right hydraulic cylinders 5, which are each composed of single acting cylinder
Are respectively connected. In the middle of the discharge oil passage 21, a check valve 20 that allows the flow of hydraulic oil from the hydraulic pump 19 to the hydraulic cylinder 5 side and the brake valve device V of the present invention are arranged in series in this order from the upstream side. Be mounted.

From a discharge oil passage 21 between the check valve 20 and the brake valve device V, a release oil passage 23 for returning hydraulic oil in each hydraulic chamber 5a to the oil tank 18 is branched. In the middle of the release oil passage 23, a release valve 26 that can open and close the passage 23 is interposed. The release valve 26 normally closes the release oil passage 23 by the check valve 22, and can be opened at any time in response to an input operation to the operation member 25. It can be adjusted arbitrarily.

Further, from a discharge oil passage 21 between the check valve 20 and the hydraulic pump 19, a relief oil passage 28 for returning the discharge oil of the pump 19 to the oil tank 18 is branched. A conventionally well-known relief valve 24 that responds to the discharge pressure of the hydraulic pump 19 is connected in the middle of the relief oil passage 28 so that the discharge pressure of the hydraulic pump 19 can be limited to a predetermined pressure or less by the relief action. .

Referring also to FIGS. 3 and 4, the brake valve device V is fixed to a support plate 27 fixed to the bracket 2 and is configured to operate according to the operating state of the parallel link mechanism 4. You.

Next, based on FIGS.
Will be described. The brake valve device V includes input and output ports 30 and 31 connected to the hydraulic pump 19 and the hydraulic chambers 5a of the left and right hydraulic cylinders 5, respectively.
A valve housing 33 having a cylinder hole 32 in which the output ports 30 and 31 are opened at intervals in the axial direction;
2 and a spool valve 34 as a sliding valve which can slide between a predetermined forward position A (solid line position in FIG. 5) and a retracted position C (dashed line position in FIG. 5). And a valve spring 35 constantly biased to the position A side. The valve spring 35
Is a cover plate fixed to the outer surface of the valve box 33 by screws 36 so as to cover the inner end of the blind hole 34b formed in the rear end surface of the spool valve 34 and the open end of the blind hole 34b with a space. The spool valve 34 is held in an elastically compressed state between the valve 34 and a suitable stopper means St provided between the valve 34 and the valve box 33 (in the illustrated example, the rear end of the valve 34). (A circlip or the like that is locked to the outer periphery and can be engaged with the rear end of the valve box 33).

A communication passage 40 is formed between the spool valve 34 and the cylinder hole 32 for always connecting the input and output ports 30 and 31 to each other. In the illustrated example, output ports 31 are formed on the upper and side portions of the valve box 33 so as to distribute and supply hydraulic oil from the brake valve device V to the pair of left and right hydraulic cylinders 5. The two connection oil passages 21 ₁ and 21 ₂ are respectively connected.

The spool valve 34 has a pair of front and rear land portions 34Lf, 34Lr which are slidably fitted in the cylinder holes 32 via seal rings S, respectively. Between 34Lr, there is provided an annular recess 34g that forms the communication passage 40 between the cylinder passage 32 and the cylinder passage 32. Further, a tapered portion 34t having a conical taper shape having a gradually decreasing diameter toward the rear is formed on a rear outer periphery of the front land portion 34Lf, and an annular step portion 34s is formed at a rear end of the tapered portion 34t. The annular concave portion 34g is continuous with the rear side of the step portion 34s.

In particular, as shown in FIG. 6, the tapered portion 34t is in the middle of the retreating process of the spool valve 34, that is, at a predetermined intermediate retreat position B, the rear end of the tapered portion 34t is a front port (the output port 31 in the illustrated example). (In other words, the rear end of the tapered portion 34t is located forward of the rear end of the opening 31a at the forward position A of the spool valve 34, and In the retracted position C, the opening 31
a so as to be located on the rear side of the rear end). Therefore, until the rear end of the tapered portion 34t passes through the rear end of the opening 31a of the front port 31 in the process of retreating the spool valve 34 (that is, the valve 34 moves from the advance position A to the intermediate retreat position B). The tapered portion 34t gradually narrows the portion of the communication passage 40 directly facing the opening 31a in the sliding direction of the valve 34, and after the passage (that is, the valve 34 is moved from the intermediate retracted position B to the retracted position C). During this time, the tapered portion 34t can gradually narrow the portion of the communication passage 40 behind the opening 31a in the radial direction of the valve 34, so that the communication passage 40 is divided into two types by the tapered portion 34t. It is possible to gradually stop down in a stop mode.

6 and 7, when the spool valve 34 is retracted from the advance position A to the predetermined intermediate retreat position B, the annular step 34s is moved to the front port 3
1 through the opening 31a.
(Particularly, the portion directly facing the opening 31a) can be rapidly squeezed, and then the spool valve 34 is moved to the intermediate retracted position B
In the process of further retreating, the tapered portion 34t can narrow the communication path 40 slowly. Further, an annular recess 34 which forms the communication passage 40 in cooperation with the cylinder hole 32
By continuously forming g on the rear side of the annular step portion 34s, forward and backward thrust exerted on the spool valve 34 by the operating oil pressure from the hydraulic pump 19 can be balanced (canceled). Spool valve 34
Can smoothly slide.

In the valve box 33, on one side of the spool valve 34, the communication port 40 is bypassed.
A bypass path 41 for short-circuiting between 0 and 31 is formed.
A check valve 37 of a ball valve type that allows only the flow of hydraulic oil from the output port 31 to the input port 30 side (that is, return oil from the hydraulic cylinder 5 to the oil tank 18) is interposed in the bypass passage 36. The set pressure for opening the check valve 37 is
It can be adjusted arbitrarily by adjusting the set load of the valve spring 38 by appropriately rotating the adjusting screw 39 also serving as a spring receiving means for supporting the return spring 38 of the valve 37.
The check valve 37 is used by the hydraulic cylinder 5 when the load receiving table 3 has a heavy load in the lowering process of the load receiving table 3 executed by arbitrarily opening the release valve 26.
The flow of return oil to the oil tank 18 from the
The valve opening operation is performed in response to an increase in the differential pressure between the input and output ports 30 and 31 in order to avoid a delay caused by the restriction by the (taper portion 34t). Can be performed smoothly.

In addition, between the spool valve 34 and the loading tray 3, the loading tray 3 is moved from 3 U ′ near the upper limit position U to the upper limit position 3.
An interlocking mechanism I is provided to move the spool valve 34 from the forward position A to the retreat position C in conjunction with the upward movement toward U. The interlocking mechanism I includes a support arm 52 fixed to the outer end of the support shaft 9 of the parallel link mechanism 4 and extending outwardly of the support shaft 9. An outer end 34a extending outside the valve housing 33
And a lock nut 53 capable of fixing a screwing position of the bolt 54 with respect to the support arm 52.
Is screwed. Thus, the pressing bolt 54 comes into contact with the outer end 34a of the spool valve 34 to cause the valve 34 to move backward only when the load receiving table 3 is at the upper limit position 3U or the vicinity 3U 'shown by a solid line in FIG.

Next, the operation of the above embodiment will be described. When the hydraulic cylinder 5 is contracted and the load receiving table 3 is at the lower limit position as shown by the chain line in FIG. 1, the pressing bolt 54 is not in contact with the spool valve 34. (See the solid line in FIG. 5), and in this state, the cross-sectional area of the opening 31a of the output port 31 (therefore, the communication path 40 between the ports 30, 31) is the largest.

Here, when the hydraulic pump 19 is operated to raise the load receiving table 3, a large amount of the discharged oil is supplied to the hydraulic cylinder 5 through the discharge oil passage 21, whereby the hydraulic cylinder 5 is quickly extended. Then, the loading table 3 linked with the extension operation via the parallel link mechanism 4 moves up quickly.

When the receiving table 3 reaches 3U 'near the upper limit position 3U, the push bolt 54 of the interlocking mechanism I is moved to the spool valve 34.
Abuts the outer end of the valve 34, whereby the valve 34 starts a retreating operation. The spool valve 34 retreats in conjunction with the further rise of the loading tray 3, but with the retraction,
Since the communication passage 40 (the flow of hydraulic oil from the hydraulic pump 19 to the hydraulic cylinder 5 side) is gradually reduced, the ascending loading tray 3 can be bufferedly stopped at the upper limit position 3U. Therefore, since the generation of an impact at the time of the stop is suppressed, the generation of vibration and noise due to the impact can be effectively prevented, and the displacement of the load on the load receiving table 3 can be effectively suppressed.

In this case, the communication path 40 (therefore, the flow of the hydraulic oil toward the hydraulic cylinder 5) is controlled by the spool valve 3
In the process of retracting from the forward position A to the predetermined intermediate retreat position B (section A → B in FIG. 7), the valve 34 is rapidly throttled mainly by the annular step portion 34s, and then the valve 34 is moved to the intermediate retreat position B. Further retreating process (section B → C in FIG. 7)
In this case, the valve 34 is gradually narrowed by the tapered portion 34t, so that the brake valve device V exerts a necessary buffer effect to reduce the impact when the cargo receiving platform 3 arrives at the upper limit position 3U. The stroke can be made as short as possible, and the size of the brake valve device V can be reduced accordingly. In addition, the lifting speed does not need to be specially reduced until the loading tray 3 reaches the vicinity 3U 'of the upper limit position 3U during the lifting process of the loading tray 3, so that the time required for lifting is shortened as much as possible to improve the work efficiency. .

FIGS. 8 and 9 show a modification of the spool valve 34 as a sliding valve. That is, in the above embodiment, when the tapered portion 34t is provided in the spool valve 34, the outer periphery of the rear half of the land 34Lf on the front side of the valve 34 is formed as a conical tapered surface. The outer periphery of the second half of the land portion 34Lf has a cylindrical shape,
In addition, a tapered groove 34t whose passage cross-sectional area (groove width / groove bottom) gradually increases rearward on the outer peripheral surface thereof is formed in the front port 3
At least one line (a plurality of lines in the illustrated example) is formed corresponding to one opening 31a, and this is a tapered portion. Thus, according to this modified example, the same operation and effect as in the above embodiment can be expected.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and various embodiments are possible within the scope of the present invention. For example, in the above-described embodiment, an example is shown in which the present invention is applied to a cargo handling vehicle of a type in which the load receiving table 3 is supported on the vehicle body 1 via a parallel link mechanism 4 so as to be able to move up and down. The present invention may be applied to a cargo handling vehicle of a type in which a loading table is supported vertically vertically via a vehicle.

In the above embodiment, the output port 31 is disposed on the front side of the input port 30 so that the annular step portion 34s and the tapered portion 34t of the spool valve 34 sequentially pass through the opening 31a of the output port 31. What was done,
In the present invention, the input port 30 is disposed before the output port 31 so that the opening of the input port 30
The annular stepped portion 34s and the tapered portion 34t may sequentially pass.

Further, in the above-described embodiment, the annular step portion 34s is formed at the rear end of the tapered portion 34t provided on the outer periphery of the spool valve 34.
However, in the present invention (claims 1 and 2), the bottom surface of the annular concave portion 34g is made continuous with the rear end of the tapered portion 34t without interposing the step portion, and the annular step portion is omitted. May be.

[0035]

As described above, according to the first aspect of the present invention,
The flow of the hydraulic oil from the hydraulic supply source to the hydraulic cylinder during the ascending process of the load cradle is carried out between the hydraulic cylinder capable of driving up the load cradle and the hydraulic supply source for supplying the hydraulic oil to the hydraulic cylinder. After reaching the upper limit position, a brake valve device is provided to stop the ascending operation of the loading tray in a buffered manner by gradually squeezing, so that the throttling action of this brake valve device causes the ascending loading tray to reach the upper limit position. It can be stopped in a buffered manner, so that the impact at the time of the stop is reduced,
The generation of vibration and noise due to the impact can be effectively prevented, and the displacement movement of the load on the load receiving table can be suppressed.

According to a second aspect of the present invention, the brake valve device comprises a valve box having input and output ports connected to a hydraulic supply source and a hydraulic cylinder, respectively, and a cylinder hole having both ports opened. A sliding valve fitted in the cylinder hole so as to form a communication passage between the ports and the cylinder hole and capable of sliding between a predetermined forward position and a retracted position; A valve spring that is constantly biased to the position side, and is formed on the outer peripheral portion of the sliding valve so as to gradually decrease in diameter toward the rear of the valve, and the process of retreating the valve from the advanced position to the retracted position. A tapered portion that gradually narrows the communication path is provided such that the rear end of the tapered portion passes through the rear end of the opening of one of the ports during the retreating process, and is provided between the sliding valve and the loading tray. Rises from the vicinity of the upper limit position to the upper limit position Because interlocking mechanism is retracted to the retracted position from the forward position slide valve in conjunction is provided in that,
Until the rear end of the tapered portion passes through the rear end of the opening of one of the ports during the retreating process of the sliding valve (that is, while the rear end of the tapered portion is located forward of the rear end of the opening), the tapered portion communicates with the communication passage. The portion directly facing the opening is gradually narrowed in the sliding direction of the valve, and after passing therethrough (that is, after the rear end of the tapered portion has moved rearward from the rear end of the opening), the tapered portion of the communication passage is closed. The portion behind the opening can be gradually narrowed in the radial direction of the valve. As a result, the communication path is formed by the tapered portion (the flow of the hydraulic oil from the hydraulic supply source toward the hydraulic cylinder during the ascending process of the loading tray). Can be effectively squeezed in two kinds of squeezing modes, so that the brake valve device can exert a sufficient cushioning effect to effectively suppress the occurrence of impact when the load receiving platform reaches the upper limit position. The buffer characteristics can be diversified.

According to a third aspect of the present invention, the brake valve device comprises a valve box having input and output ports respectively connected to a hydraulic supply source and a hydraulic cylinder, and a cylinder hole having both ports opened. A sliding valve fitted in the cylinder hole so as to form a communication passage between the ports and the cylinder hole and capable of sliding between a predetermined forward position and a retracted position; A valve spring that constantly urges the valve to the position side, and the outer peripheral portion of the sliding valve passes through the opening of one of the ports in the process of retreating from the advanced position to the predetermined intermediate retreat position. And a taper portion formed continuously with the front side of the annular step portion and gradually narrowing the communication path in the process of further retracting the valve from the intermediate retreat position. Between the receiving platform and the receiving platform, the The interlocking mechanism is provided to retreat the sliding valve from the advance position to the retreat position in conjunction with the upward movement of the hydraulic fluid. )
Can be rapidly throttled by the annular step of the sliding valve in the process of retracting from the advanced position to the predetermined intermediate retracted position, and then in the process of sliding the valve further backward from the intermediate retracted position. It can be squeezed slowly by the tapered portion. As a result, the operating stroke of the brake valve device can be shortened as much as possible while exerting a sufficient cushioning effect on the brake valve device to reduce the impact at the time of arrival at the upper limit position of the loading table, and the brake valve device can be downsized accordingly The lifting speed does not need to be specially reduced until the loading tray reaches the vicinity of the upper limit position during the lifting process of the loading tray, so that the time required for lifting is shortened as much as possible to improve the work efficiency.

According to the fourth aspect of the present invention, an annular recess which forms the communication passage between the sliding valve and the cylinder bore is formed continuously on the rear side of the annular step in the outer peripheral portion of the sliding valve. So
The axial thrust exerted on the sliding valve itself by the operating oil pressure can be balanced back and forth, and the sliding valve can slide smoothly accordingly.

[Brief description of the drawings]

FIG. 1 is a longitudinal side view of a rear portion of a vehicle, showing one embodiment of the present invention.

FIG. 2 is a hydraulic control circuit diagram of the embodiment.

FIG. 3 is an enlarged view of a part viewed from the arrow 3 in FIG. 1;

FIG. 4 is a side view as viewed from arrow 4 in FIG. 3;

FIG. 5 is an overall vertical sectional view of the brake valve device in a state where the sliding valve is at a forward position.

FIG. 6 is an enlarged view of a portion viewed in the direction of arrow 6 in FIG.

FIG. 7 is a graph showing the relationship between the operation stroke of the brake valve device and the throttle flow rate.

FIG. 8 is a view showing a modification of the brake valve device and corresponding to FIG. 6;

9 is a sectional view taken along line 9-9 in FIG.

[Explanation of symbols]

 1 ··· Body 3 ··· Load receiving stand 3U ··· Upper limit position 3U ′ ··· Near the upper limit position 5 ··· Hydraulic cylinder 19 ··· Hydraulic pump as hydraulic supply source 30 ··· Input Port 31: Output port (one port) 31a: Opening 32: Cylinder hole 33: Valve box 34: Spool valve as sliding valve 34g: Annular recess 34s: Annular stage Portion 34t Taper portion 35 Valve spring 40 Communication path A Advance position B Intermediate retreat position C Retreat position I Interlocking mechanism T ..Cargo handling vehicles V ... Brake valve devices

Claims (4)

[Claims] 1. A load receiving table (3) supported on a vehicle body (1) so as to be able to move up and down, and disposed between the load receiving table (3) and the vehicle body (1) to drive the load receiving table (3) upward. A loading cradle elevating device for a cargo handling vehicle comprising a hydraulic cylinder (5) to be obtained and a hydraulic supply source (19) for supplying hydraulic oil to the hydraulic cylinder (5), wherein the hydraulic supply source (19) and the hydraulic cylinder ( 5), the load receiving pedestal (3) moves the hydraulic oil from the hydraulic supply source (19) toward the hydraulic cylinder (5) during the ascending process of the load receiving pedestal (3). (3U '), a brake valve device (V) for buffering the lifting operation of the loading tray (3) by buffering by gradually squeezing the loading tray (3) is interposed, and the loading tray lifting and lowering of the cargo handling vehicle is performed. apparatus. 2. The brake valve device (V) has input and output ports (30, 31) connected to a hydraulic supply source (19) and a hydraulic cylinder (5), respectively, and both ports (30, 31) are open. A valve case (33) having a cylinder hole (32) to be closed and a communication passage (40) between both ports (30, 31) formed between the cylinder hole (32) and the cylinder hole (32). The slide valve (3) which is fitted to the slide valve and can slide between a predetermined forward position (A) and a backward position (C).
4) and a valve spring (35) that constantly biases the sliding valve (34) toward the forward position (A). The outer periphery of the sliding valve (34) is provided with the valve (34). The tapered portion (34) is formed so as to gradually decrease in diameter toward the rear of the valve (34), and gradually narrows the communication path (40) in the process of retreating the valve (34) from the advanced position (A) to the retracted position (C).
t) is provided so that the rear end of the tapered portion (34t) passes through the rear end of the opening (31a) of the one port (31) during the retreating process. Between (3) and (3), the sliding valve (3) interlocks with the rise of the load receiving table (3) from the vicinity (3U ') of the upper limit position (3U) to the upper limit position (3U).
The lifting / lowering device according to claim 1, further comprising an interlocking mechanism (I) for retreating 4) from the forward position (A) to the retreat position (C). 3. The brake valve device (V) has input and output ports (30, 31) connected to a hydraulic pressure supply source (19) and a hydraulic cylinder (5), respectively, and both ports (30, 31) are open. A valve case (33) having a cylinder hole (32) to be closed and a communication passage (40) between both ports (30, 31) formed between the cylinder hole (32) and the cylinder hole (32). The slide valve (3) which is fitted to the slide valve and can slide between a predetermined forward position (A) and a backward position (C).
4) and a valve spring (35) that constantly biases the sliding valve (34) toward the forward position (A). The outer periphery of the sliding valve (34) is provided with the valve (34). In the process of retracting from the forward position (A) to the predetermined intermediate retreat position (B), passes through the opening (31a) of the one port (31) and rapidly narrows the communication path (40). 34s)
And a tapered portion (3) formed continuously with the front side of the annular stepped portion (34s) and gradually narrowing the communication passage (40) while the valve (34) is further retracted from the intermediate retracted position (B).
4t) is provided, and between the sliding valve (34) and the loading tray (3), the loading tray (3) rises from the vicinity (3U ') of the upper limit position (3U) to the upper limit position (3U). The sliding valve (3
The lifting / lowering device according to claim 1, further comprising an interlocking mechanism (I) for retreating 4) from the forward position (A) to the retreat position (C). 4. An annular concave portion (34g) which forms the communication passage (40) between the sliding valve (34) and the cylinder hole (32) is formed on an outer peripheral portion of the sliding valve (34). 4. The loading / unloading device of a cargo handling vehicle according to claim 3, wherein the lifting / lowering device is formed continuously on the rear side.