Tubing device

Abstract

The present invention provides a tubing device equipped with a control means capable of effectively suppressing the tilt of the lifting frame that occurs during the pushing operation. [Solution] A tubing device equipped with a control means 19 for controlling the lifting frame horizontally, wherein four lifting cylinders 13A to 13D are arranged at the four corners of a virtual rectangle along the outer edge of the lifting frame 14 in a plan view, and are hydraulic cylinders capable of contraction operation that applies a pushing force to the casing and extension operation that applies an pulling force, and the control means includes a tilt sensor 23 that detects the angle of change of inclination of the lifting frame with respect to the horizontal state, four variable throttle valves 24 paired with each of the four lifting cylinders and provided in the flow path 21 of the hydraulic fluid flowing out of each lifting cylinder in the contraction operation state of the lifting cylinder, and a control unit 25 that individually adjusts the degree of throttle of each variable throttle valve based on the change angle detected by the tilt sensor.

Description

[Technical Field]

[0001] The present invention relates to a tubing device, and more specifically, to a tubing device used for pushing and pulling casings into the ground during foundation work in buildings and civil engineering. [Background technology]

[0002] In general, tubing devices used in foundation work have a lifting frame mounted above a base frame via four lifting cylinders, and the lifting frame is equipped with a motor-driven chuck mechanism. The casing is gripped by the chuck mechanism through a through-hole in the center of each frame, and the rotational movement by the motor and the lifting movement by the lifting cylinders are transmitted to the casing (see, for example, Patent Document 1).

[0003] As shown in Figure 10, the lifting cylinder 101 has hydraulic circuits connected to the rod-side oil chamber 101a and the head-side oil chamber 101b, respectively. When the switching valve 102 is operated to supply hydraulic fluid from the hydraulic pump 103 to the rod-side oil chamber 101a, the chuck mechanism 105 and the lifting frame 106 descend together, and the casing 104 equipped with the drilling bit 104a at its tip is pushed into the ground. Therefore, in the pushing operation of the casing 104, the weight Wa of the casing 104, the weight Wb of the chuck mechanism 105 and the lifting frame 106, and the pushing force (output in the contraction direction) F of the lifting cylinder 101 are applied relative to the drilling bit 104a. A ,F B ,F C ,F D The sum of these two factors acts as the casing indentation force Fcp.

[0004] The pushing force Fi(i=A,B,C,D) of each lifting cylinder 101 is calculated using the following equation 1.

[0005] Fi = P1 × A1 - P2 × A2 ... Equation 1

[0006] In Equation 1, Fi is the cylinder pushing force (hereinafter simply referred to as "cylinder pushing force"), P1 is the primary side pressure, A1 is the primary side pressure-receiving area, P2 is the secondary side pressure (back pressure), and A2 is the secondary side pressure-receiving area. Here, the hydraulic pressure (primary side pressure) P1 supplied to the rod side oil chamber 101a is adjusted by changing the relief set pressure value of the relief valve 107. For this reason, the minimum casing pushing force Fcp acting on the drilling bit 104a is approximately equal to the sum of the weight Wa of the casing 104 and the weight Wb of the chuck mechanism 105 and the lifting frame 106, even when the relief set pressure value of the relief valve 107 is set to 0 (zero), as shown in Figure 11. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2006-348565 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the tubing device described above, if a portion of the casing tip (excavation bit) comes into contact with an underground obstacle such as a boulder (indicated by the symbol R in Figure 10) during the pushing operation, a difference in the reaction force received by the casing tip occurs between the contacted and non-contacting portions, resulting in a problem where the lifting frame tilts. For this reason, a control method that uses a groundable horizontal jack to provide a counter-influence in the opposite direction of the tilt can be considered, but such a control method that directly adjusts the level makes it difficult to effectively suppress the tilt of the lifting frame that occurs during the pushing operation, and was therefore not sufficient as a control means.

[0009] Therefore, the present invention aims to provide a tubing device equipped with a control means capable of effectively suppressing the tilt of the lifting frame that occurs during the pushing operation. [Means for solving the problem]

[0010] To achieve the above objective, the tubing device of the present invention comprises a base frame installed on the ground, a lifting frame provided above the base frame so as to be able to move up and down via four lifting cylinders, a chuck mechanism that moves up and down according to the lifting frame, a rotation transmission mechanism that applies rotational force to a casing gripped by the chuck mechanism, and a control means for controlling the lifting frame to be horizontal, wherein the four lifting cylinders are hydraulic cylinders arranged at the four corners of a virtual rectangle along the outer edge of the lifting frame in a plan view, and capable of contraction operation that applies a pushing force to the casing and extension operation that applies an pulling force, and the control means is characterized by comprising a tilt sensor that detects the angle of change of inclination of the lifting frame with respect to a horizontal state, four variable throttle valves paired with each of the four lifting cylinders and provided in the flow path of the hydraulic fluid flowing out of each lifting cylinder in the contraction operation state of each lifting cylinder, and a control unit that individually adjusts the throttle degree of each variable throttle valve based on the angle of change detected by the tilt sensor.

[0011] Furthermore, the control unit is characterized by adjusting the throttle degree of each variable throttle valve based on the angle of change so as to increase the flow cross-sectional area of ​​the hydraulic fluid flowing out from the upper-side lifting cylinder and decrease the flow cross-sectional area of ​​the hydraulic fluid flowing out from the lower-side lifting cylinder, which are two lifting cylinders located diagonally opposite each other in the virtual rectangle.

[0012] Furthermore, the variable throttle valve is characterized in that, in the initial state when the retraction operation of the lifting cylinder begins, it has an intermediate throttle degree that is in the middle of the adjustment range. [Effects of the Invention]

[0013] According to the tubing device of the present invention, even if the lifting frame is tilted during the pushing operation, the secondary pressure (back pressure) of the lifting cylinder can be regulated and the required cylinder pushing force (output in the contraction direction) can be obtained by simply adjusting the throttling degree of each variable throttle valve individually. In other words, when correcting the tilt of the lifting frame, an indirect control method is used to adjust the cylinder pushing force hydraulically, thereby applying a large casing pushing force only to the part of the casing that is in contact with an underground obstacle. As a result, the tilt of the lifting frame is corrected to horizontal, and the pushing operation can be continued while ensuring the verticality of the casing.

[0014] Furthermore, by focusing on two diagonally positioned lifting cylinders and regulating their respective secondary pressures as a pair, it becomes possible to determine the required cylinder pushing force at two points on each of the two diagonally opposite axes (on the x-axis and y-axis) (a total of four points). This not only reduces the number of control parameters to consider but also simplifies the setting and verification of values.

[0015] Furthermore, since the variable throttle valve has an intermediate throttle degree in its initial state, it is possible to secure the necessary cylinder pushing force when the lifting frame is horizontal, while maximizing the range of change in the cylinder pushing force required when it is inclined (upward and downward range). This allows for stable pushing operations in accordance with the diverse geological structures of the site. [Brief explanation of the drawing]

[0016] [Figure 1] This is a front view showing a schematic configuration of a tubing device in one embodiment of the present invention. [Figure 2] This is also a plan view. [Figure 3] This is also a schematic diagram of the control system. [Figure 4] This diagram shows a model of four lifting cylinders. [Figure 5] This is a diagram showing the x, y, and z axis coordinate system defined on the upper surface of the lifting frame. [Figure 6] This figure also shows the tilt in the x-axis direction (θAC) and the tilt in the y-axis direction (θBD) of the lifting frame. [Figure 7] This is a diagram illustrating how to correct the tilt of the lifting frame. [Figure 8] This graph also shows the relationship between primary pressure and cylinder indentation force. [Figure 9] This is a block diagram showing the control flow by the control unit. [Figure 10] This is a hydraulic system diagram illustrating the casing pushing operation in conventional technology. [Figure 11] This graph also shows the relationship between relief set pressure and casing compression force. [Modes for carrying out the invention]

[0017] Figures 1 to 9 show an example of one embodiment of the tubing device of the present invention. As shown in Figures 1 to 3, the tubing device 11 is generally configured to include a base frame 12 installed on the ground, a lifting frame 14 mounted above the base frame 12 so as to be able to move up and down via four lifting cylinders 13A, 13B, 13C, and 13D, a chuck mechanism 16 supported so as to be able to move up and down by four chuck cylinders (only one is shown in the figure) 15 erected on the lifting frame 14 and moving up and down in accordance with the lifting frame 14, a rotation transmission mechanism 18 that applies hydraulic rotational force to the casing 17 gripped by the chuck mechanism 16, and a control means 19 for controlling the lifting frame 14 horizontally. Furthermore, casing insertion holes 20 that penetrate vertically are formed in the central parts of the base frame 12, the lifting frame 14, and the chuck mechanism 16.

[0018] The four lifting cylinders 13A to 13D are double-acting hydraulic cylinders equipped with hydraulic fluid supply and discharge ports in the rod-side oil chamber 13a and the head-side oil chamber 13b, respectively. As shown in Figure 2, they are arranged at the four corners of a virtual rectangle VR along the outer edge of the lifting frame 14 in a plan view. Furthermore, the four cylinders are connected in parallel in the hydraulic circuit, and the hydraulic pressure (primary side pressure) P1 based on the relief set pressure value is configured to act equally on all four cylinders. For this point, please refer to Figure 10 and the conventional configuration described in Patent Document 1.

[0019] The pushing action that applies a pushing force to the casing 17 supplies hydraulic fluid to the rod-side oil chambers 13a of each lifting cylinder 13A to 13D, causing each lifting cylinder 13A to 13D to contract simultaneously. At this time, within the lifting cylinders 13A to 13D, the movement of the pistons pushes out the hydraulic fluid in the head-side oil chamber 13b, which flows out into the head-side flow path 21. This hydraulic fluid then merges and is returned to a tank (not shown). As a result, the chuck mechanism 16 and the lifting frame 14 descend together, and the casing 17, equipped with a drilling bit 17a at its tip, is pushed into the ground.

[0020] On the other hand, the pulling operation that applies pulling force to the casing 17 supplies hydraulic fluid to the head-side oil chambers 13b of each lifting cylinder 13A to 13D, causing each lifting cylinder 13A to 13D to extend simultaneously. At this time, within the lifting cylinders 13A to 13D, the movement of the pistons pushes out the hydraulic fluid in the rod-side oil chamber 13a, which flows out into the rod-side passage 22. This hydraulic fluid then merges and is returned to the tank. As a result, the chuck mechanism 16 and the lifting frame 14 rise together, and the casing 17 is pulled out of the ground.

[0021] The control means 19 is additionally mounted as a component of the main body of the tubing device 11 and its hydraulic unit (hydraulic power source device). As shown in FIG. 3, it includes an inclination sensor 23 that detects the change angle of the inclination of the lifting frame 14 with respect to the horizontal state, four variable throttle valves 24 provided in each head-side flow path 21 in pairs with each of the four lifting cylinders 13A to 13D, a control unit (CPU) 25 that individually adjusts the throttle degree of each variable throttle valve 24 based on the change angle detected by the inclination sensor 23, and a storage unit (such as a memory) 26 that stores the control program executed by the control unit 25. The control unit 25 and the storage unit 26 are incorporated, for example, in a controller 27 equipped with various I / O interfaces.

[0022] The inclination sensor 23 is, for example, a two-axis inclination sensor installed on the lifting frame 14, and it detects the inclination of the lifting frame 14 with respect to the horizontal state as an absolute angle. In this embodiment, as shown in FIGS. 4 to 6, with the intersection points of the central axes of the four lifting cylinders 13A to 13D that exert a cylinder pushing force (output in the contraction direction) F A ,F B ,F C ,F D and the upper surface of the lifting frame 14 being A, B, C, D respectively, an x-axis is taken on the diagonal line connecting the two points A and C as the first pair, a y-axis is taken on the diagonal line connecting the two points B and D as the second pair, and a z-axis extending vertically from the intersection point of the x-axis and the y-axis is taken (FIGS. 4, FIG. 5).

[0023] Based on the xyz-axis coordinate system defined on the upper surface of the lifting frame 14 in this way, the inclination sensor 23 detects the inclination angle in the z-axis direction in the x-axis direction of the lifting frame 14 as θ AC and the inclination angle in the z-axis direction in the y-axis direction as θ BD respectively (FIG. 6). The change angles (actual angles) θ AC ,θ BD detected by the inclination sensor 23 are transmitted to the controller 27 and used for hydraulic control to correct the inclination of the lifting frame 14 in the control unit 25.

[0024] The variable throttle valve 24 is incorporated into an electromagnetic proportional control valve that changes the throttle degree in accordance with an electrical control signal from the controller 27, for example. Increasing the throttle degree reduces the flow path cross-sectional area (throttle diameter), decreasing the flow rate of hydraulic fluid passing through. Conversely, decreasing the throttle degree increases the flow path cross-sectional area (throttle diameter), increasing the flow rate of hydraulic fluid passing through. In this embodiment, the attached solenoid is energized by adjusting the current value to initiate the contraction operation of the lifting cylinders 13A to 13D, in other words, at the start of the pushing operation of the casing 17, which has an intermediate throttle degree (a state in which the flow path area is narrowed to the middle), which is in the middle of the adjustment range. On the other hand, in the initial state when the extension operation of the lifting cylinders 13A to 13D is initiated, in other words, at the start of the pulling operation of the casing 17, it has the minimum throttle degree (a state with no throttle, where the flow path area is widened to the maximum).

[0025] In the tubing device 11 configured in this way, if a part of the tip of the casing 17 (drilling bit 17a) comes into contact with an underground obstacle such as a boulder (see symbol R in Figure 10) during the pushing operation, a difference in the reaction force received by the tip of the casing 17 will occur between the contacted and non-contacted parts. As a result, drilling will stall in the part of the casing 17 tip where the resistance acting on the drilling bit 17a is large, while drilling will progress on the opposite side where the resistance acting on the drilling bit 17a is relatively small. Consequently, as shown in Figure 7(a), the lengths (strokes) of the four lifting cylinders 13A to 13D become uneven, causing the lifting frame 14 to tilt.

[0026] Therefore, the control unit 25 detects the change angle θ detected by the tilt sensor 23. AC ,θ BDBased on this, in the x-axis direction, for example, the throttling degree of each variable throttle valve 24 is adjusted so as to increase the flow cross-sectional area of ​​the hydraulic fluid flowing out from the upper-side lifting cylinder 13A, which is located on the upper side of the incline and is to be pushed firmly, and so as to decrease the flow cross-sectional area of ​​the hydraulic fluid flowing out from the lower-side lifting cylinder 13C, which is located on the lower side of the incline and is not to be pushed as hard, with respect to the x-axis direction. Similarly in the y-axis direction, the throttling degree of each variable throttle valve 24 is adjusted so as to increase the flow cross-sectional area of ​​the hydraulic fluid flowing out from the upper-side lifting cylinder 13D, which is located on the upper side of the incline and is to be pushed firmly, and so as to decrease the flow cross-sectional area of ​​the hydraulic fluid flowing out from the lower-side lifting cylinder 13B, which is located on the lower side of the incline and is not to be pushed as hard, with respect to the x-axis direction.

[0027] For example, focusing on the upper-side lifting cylinder 13A, as shown in Figure 3, the throttle of the variable throttle valve 24 is controlled to decrease from the intermediate throttle, and as a result, the flow area through which the hydraulic fluid that has flowed out into the head-side flow path 21 passes is widened, and the secondary pressure (back pressure) P2 of the lifting cylinder 13A decreases. Then, the cylinder pushing force F A As shown in the calculation formula (see formula 1 in the explanation of background technology), the secondary force (P2 × A2) that opposes the primary force (P1 × A1) becomes smaller, resulting in the cylinder pushing force (output in the contraction direction) F A This increases the force applied to the casing, allowing a large casing-pressing force Fcp to be applied to the contact area with the underground obstacle, thereby firmly pressing the casing 17 into place.

[0028] Furthermore, focusing on the lower-side lifting cylinder 13C, the throttle of the variable throttle valve 24 is controlled to increase from the intermediate throttle, resulting in a narrower flow area for the hydraulic fluid flowing out into the head-side passage 21, and an increase in the secondary pressure (back pressure) P2 of the lifting cylinder 13C. Then, the cylinder pushing force F C As shown in the calculation formula, the secondary force (P2 × A2) that opposes the primary force (P1 × A1) becomes larger, resulting in the cylinder pushing force (output in the contraction direction) F CThis reduces the force applied to the casing. This allows a small casing pressing force Fcp to be applied to the non-contact portion of the underground obstacle, preventing the casing 17 from being pressed too deeply.

[0029] In this way, the lifting cylinders 13A and 13C located on one diagonal and the lifting cylinders 13B and 13D located on the other diagonal are considered as pairs, and a control target is given to make the tilt of the lifting frame 14 0 (zero) (horizontal). The tilt sensor 23 detects the tilt of the lifting frame 14, and control is performed to individually adjust each variable throttle valve 24 provided in the head-side flow path (secondary flow path) 21 of each lifting cylinder 13A to 13D according to the tilt. In this case, as shown in Figure 8, the hydraulic pressure (primary pressure) P1 supplied to the rod-side oil chamber 13a of each lifting cylinder 13A to 13D is constant, but P2 changes according to the degree of throttle of the variable throttle valve 24, and as a result the cylinder pushing force F A ,F B ,F C ,F D This value fluctuates within a predetermined range, increasing or decreasing according to the degree of throttling of the variable throttle valve 24.

[0030] For example, in response to the tilt of the lifting frame 14 as shown in Figure 7(a), the control unit 25 executes a control program to adjust the throttling degree of the variable throttle valve 24 paired with the lifting cylinder 13A to "small", the throttling degree of the variable throttle valve 24 paired with the lifting cylinder 13C to "medium", the throttling degree of the variable throttle valve 24 paired with the lifting cylinder 13B to "large", and the throttling degree of the variable throttle valve 24 paired with the lifting cylinder 13D to "minimum (none)". In this case, the cylinder pushing force F A ,F B ,F C ,F D The relative magnitudes are as shown in Figure 8, F D >F A >F C >F B The following relationship holds true. As a result, in the pushing operation of the casing 17, the cylinder pushing force F of the lifting cylinder 13D is mainly DThe increase in this force contributes to a large casing pressing force Fcp being applied only to the portion of the casing 17 that is in contact with the underground obstacle. As a result, a force acts to reduce the inclination of the lifting frame 14, that is, to make it horizontal, as shown in Figure 7(b).

[0031] Here, as shown in Figure 9, the control target for making the lifting frame 14 horizontal is θ AC0 =0, θ BD0 Setting = 0, the cylinder pressing force F A ,F B ,F C ,F D This is calculated using equations 2 through 7 below.

[0032] F A =(P AC +K AC )F0...Formula 2 F C =(P AC -K AC )F0...Formula 3 K AC =k AC (θ AC0 -θ AC )...Equation 4 F B =(P BD +K BD )F0...Formula 5 F D =(P BD -K BD )F0...Formula 6 K BD =k BD (θ BD0 -θ BD )...Equation 7 F0: Cylinder pressing force when no restriction is applied P AC : When the tilt is 0, the ratio of the pushing force of the two lifting cylinders 13A and 13C (0 <P AC <1) P BC : When the tilt is 0, the ratio of the pushing force of the two lifting cylinders 13B and 13D (0 <P BD <1) k AC: Control parameters for the diagonal AC direction (k AC >0, and P AC -K AC (Values ​​that are >0) k BD : Control parameters for the diagonal BD direction (k BD >0, and P BD -K BD (Values ​​that are >0) θ AC0 : Target angle (0) in the diagonal AC direction θ BD0 : Target angle (0) in the diagonal direction BD

[0033] For example, F0 = 1000N, P AC =0.5, k AC Assuming = 0.05, in the lifting frame 14 during the pushing operation, the diagonal AC (x axis) is tilted by 5 degrees (θ AC Assume that the lifting cylinder 13C is located on the upper side of the incline (=5 degrees) and the lifting cylinder 13A is located on the lower side of the incline. Here, P AC =0.5 is the setting value when the tilt of the lifting frame 14 is 0, i.e., horizontal, and you want to push with a force of 1 / 2 × F0, and it can be set arbitrarily by the operator. As a result, a pushing force of 500N per lifting cylinder is exerted when pushing in a homogeneous soil layer. K AC The angle of change is θ AC Based on this, the setting value for how much force to use in response is predetermined based on the specifications of the tubing device 11, construction conditions, etc.

[0034] Substituting each value into equation 4, K AC =0.05 × (0 - 5) = -0.25, which can be calculated. Then, substituting the values ​​into equations 2 and 3, we get F A =(0.5-0.25)×1000=250N and F C =(0.5+0.25)×1000=750N, and so on. This allows us to calculate F based on the inclination of the lifting frame 14, using a pressing force of 1 / 2×F0 as a reference. A and F CThey change (increase or decrease) in conjunction with each other, and a force acts so that the inclination of the elevating frame 14 becomes smaller.

[0035] Here, considering the inclination of the diagonal line AC (x-axis) and the inclination of the diagonal line BD (y-axis) in addition, using equations 5 to 7, F B and F D are calculated (for example, F B = 300 N, F D = 700 N). According to the inclination of the elevating frame 14, based on the pushing force of 1 / 2×F0, F B and F D change (increase or decrease) in conjunction with each other, and a force acts so that the inclination of the elevating frame 14 becomes smaller. Thus, the cylinder pushing forces F A , F B , F C , F D of the respective elevating cylinders 13A to 13D become the calculation results (F A = 250 N, F C = 750 N, F B = 300 N, F D = 700 N) obtained by using equations 2 to 7, and the throttle degree of each variable throttle valve 24 is adjusted so as to be this value, and based on this control, the pushing operation of the tubing device 11 is performed.

[0036] Thus, according to the tubing device 11 of the present invention, even when the elevating frame 14 inclines during the pushing operation, by a simple control of only individually adjusting the throttle degree of each variable throttle valve 24, the secondary side pressure (back pressure) of the elevating cylinders 13A to 13D is regulated to obtain the necessary cylinder pushing force (output in the contraction direction) F A , F B , F C , F D . That is, when correcting the inclination of the elevating frame 14, by an indirect control for adjusting the cylinder pushing forces F A , F B , F C , F D by hydraulic pressure, a large casing pushing force Fcp is applied only to the portion where the casing 17 contacts the underground obstacle, and as a result, the inclination of the elevating frame 14 is corrected to horizontal, and the pushing operation that ensures the verticality of the casing 17 can be continued.

[0037] Furthermore, focusing on the two diagonally positioned lifting cylinders (13A, 13C / 13B, 13D), the secondary pressure of each is regulated as a pair. Therefore, the required cylinder pushing force F is calculated at two points (a total of four points) on each of the two diagonally opposite axes (on the x-axis and y-axis). A ,F B ,F C ,F D This makes it possible to determine the parameters, which not only reduces the number of control parameters to consider but also makes it easier to set and verify the values.

[0038] Furthermore, since the variable throttle valve 24 has an intermediate throttle degree in its initial state, the cylinder pushing force F required when the lifting frame 14 is in a horizontal position is also present. A ,F B ,F C ,F D While ensuring the required cylinder pushing force F in the inclined state, A ,F B ,F C ,F D Because the range of change (upward and downward movement) can be maximized, the pushing operation can be stably performed in accordance with the diverse geological structures of the site.

[0039] It should be noted that the present invention is not limited to the above-described embodiments, and the control means can be configured to be incorporated into existing systems, and can be appropriately modified according to the specifications of the tubing device, and the arrangement of components is also arbitrary. For example, the configuration, arrangement, and setting conditions (e.g., adjustment of the aperture) of the tilt sensor and variable throttle valve are arbitrary, and the specifications of the control program are also arbitrary. [Explanation of symbols]

[0040] 11...Tubing device, 12...Base frame, 13...Lifting cylinder, 13a...Rod-side oil chamber, 13b...Head-side oil chamber, 14...Lifting frame, 15...Chuck cylinder, 16...Chuck mechanism, 17...Casing, 17a...Drilling bit, 18...Rotation transmission mechanism, 19...Control means, 20...Casing insertion hole, 21...Head-side flow path, 22...Rod-side flow path, 23...Tilt sensor, 24...Variable throttle valve, 25...Control unit, 26...Storage unit, 27...Controller

Claims

1. A base frame that is installed on the ground, A lifting frame is provided above the base frame so as to be able to move up and down via four lifting cylinders, A chuck mechanism that moves up and down according to the lifting frame, A rotational transmission mechanism that applies rotational force to the casing gripped by the chuck mechanism, A tubing device comprising control means for horizontally controlling the lifting frame, The four lifting cylinders are hydraulic cylinders that are arranged at the four corners of a virtual rectangle along the outer edge of the lifting frame in a plan view, and are capable of contraction, which applies a pushing force to the casing, and extension, which applies a pulling force. The control means is A tilt sensor detects the angle of change in the tilt of the lifting frame relative to its horizontal state, Paired with each of the four aforementioned lifting cylinders, four variable throttle valves are provided in the flow path of the hydraulic fluid flowing out of each lifting cylinder when the lifting cylinder is in a retracted state, A tubing device characterized by having a control unit that individually adjusts the degree of throttling of each variable throttling valve based on the angle of change detected by the tilt sensor.

2. The tubing device according to claim 1, characterized in that the control unit adjusts the throttle degree of each variable throttle valve based on the angle of change so as to increase the flow cross-sectional area of ​​the hydraulic fluid flowing out from the upper-side lifting cylinder and decrease the flow cross-sectional area of ​​the hydraulic fluid flowing out from the lower-side lifting cylinder, among the two lifting cylinders located diagonally opposite each other in the virtual quadrilateral.

3. The tubing device according to claim 2, characterized in that the variable throttle valve has an intermediate throttle degree that is in the middle of the adjustment range in the initial state when the retraction operation of the lifting cylinder is started.

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