JPH07257899A - Oil-hydraulic lifter - Google Patents

Abstract

PURPOSE:To quicken the sinking speed of a lifter when no load exists and retard when a load exists. CONSTITUTION:A hydraulic circuit 14 for sending a return oil of a hydraulic cylinder 6 when a table 4 is sunk is composed of a high speed circuit part 14A having a small flow path resistance and a low speed circuit part 14B having a large flow path resistance. The flow path resistances are set by throttle valves 18A, 18B. These circuit parts are opened selectively by solenoid-operated selector valves 19A, 19B. The table 4 is fitted with a sensing means 12 which senses existence of load. In conformity to the sensing signal given b the sensing means 12, the selector valves 19A, 198 are controlled by a changeover control device 20 so that the circuit part 14A is opened when no load exists and the circuit part 14B is opened when a load exists.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic lifter such as a table lifter used for loading sheet metal and various other loads.

[0002]

2. Description of the Related Art Due to the characteristics of its hydraulic circuit, a table lifter that hydraulically drives a table up and down has a fast descending speed when there is a load and a descending speed when there is no load. slow. That is, in a general table lifter, during the lowering operation, the pump is stopped and the hydraulic oil in the cylinder is discharged by the load on the table. The descending speed is adjusted by a throttle valve interposed in the return passage. The flow rate through the throttle valve is greater as the pressure difference across the valve is greater, so that the greater the load, the faster the descent rate.

However, considering the descending operation of heavy objects,
When there is a load, it is necessary to keep the descending speed low in order to prevent the collapse of the load, improve the accuracy of the stop position, and alleviate the impact at the time of stopping. Therefore, it is desirable to accelerate the descending speed to shorten the operation time. In particular, when performing a frequent lifting operation, it is desired to shorten the cycle time by shortening the descent time when there is no load as described above. For example, in a sheet metal processing line, a pallet loaded with material sheet material and a pallet loaded with product sheet material are replaced on the table lifter in the stocker for each sheet material processing in the sheet material processing machine, and the sheet material is placed at the same position. There is one that is configured to perform loading and unloading on a processing machine. At the time of replacement, the table lifter is moved up and down. In such equipment, when the processing time for one plate material is short, it may be necessary to wastefully wait the plate material processing machine depending on the replacement time of the pallets on the table lifter.
It is an important issue to reduce the fall time of the table lifter when there is no load.

An object of the present invention is to provide a hydraulic lifter capable of variably setting the descending speed according to the load. Another object of the present invention is to provide a hydraulic lifter that can decrease the descending speed quickly when there is no load and can slow it when there is a load, and can shorten the required operation time while preventing load collapse and improving stopping accuracy. is there.

[0005]

A hydraulic lifter of the present invention comprises a hydraulic lifter for raising and lowering a table by means of a hydraulic cylinder, wherein a hydraulic circuit for flowing return oil of the hydraulic cylinder in response to a descending operation of the table is provided with a flow resistance. It is configured by a plurality of different circuit parts, and circuit switching means for selectively opening the circuit parts is provided. The flow path resistance of each circuit portion is set by, for example, a throttle valve or the like. This hydraulic lifter may be provided with detection means for detecting the load condition on the table.

According to another aspect of the hydraulic lifter of the present invention, the hydraulic circuit on the return oil side is composed of a high-speed circuit portion having a small flow path resistance and a low-speed circuit portion having a large flow path resistance. A detection means for detecting the presence or absence is provided.
Further, a switching control device is provided which controls the circuit switching means so as to open the high-speed circuit portion when there is no load and the low-speed circuit portion when there is a load in response to the detection signal from the detection means.

[0007]

When the table is lowered, the supply of the hydraulic pressure to the hydraulic cylinder is stopped, and the circuit switching means selects and opens one of the plurality of circuit parts in the hydraulic circuit on the return side. As a result, the return oil flows at a flow rate that corresponds to the flow path resistance of the circuit portion and the load on the table, and the hydraulic cylinder operates toward the lower side of the table at a speed proportional to the flow rate. Therefore, by selecting the circuit portion of the flow path resistance according to the load state on the table, the table can be lowered at a desired speed according to the load state.
When the load state detection means on the table is provided, the detection result can be used for the selection of the circuit portion by the circuit switching means, and the selection can be automated.

In the structure of claim 3, the descending operation is performed as follows. That is, the detection means detects the presence or absence of a load on the table, and when the load is present, the circuit switching means opens the low-speed circuit portion having a large flow resistance in response to the detection signal indicating that the load is present. This causes the table to descend at a low speed. When there is no load, the circuit switching means opens the high-speed circuit portion having a small flow path resistance in response to the loadless detection signal of the detection means. This causes the table to descend at high speed. As described above, since the load is lowered at high speed when no load is applied, the cycle time can be shortened. On the other hand, when the load is lowered at low speed, load collapse and reduction in stop accuracy can be prevented, and shock at the time of stop can be reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. The hydraulic lifter 1 is composed of a table lifter, and includes a lifter body 2 in which a table 4 is installed on a pantograph type lifting mechanism 5 driven by a hydraulic cylinder 6, and a hydraulic circuit 3 of the hydraulic cylinder 6.

As shown in FIG. 2, the elevating mechanism 5 has two sets of link mechanisms 7 in which a pair of intersecting links 7a, 7b are connected to each other at the intersections.
And the links 7b and 7b are connected by connecting members 8 and 9, respectively. The lower end of one link 7a in each link mechanism 7 is rotatably connected to the base plate 10, and the upper end of the other link 7b is rotatably connected to the table 4, and the link 7a
At the upper end of the free roller 11 contacting the lower surface of the table 4
In the lower end of the other link 7b, a free roller 11b that is in contact with the upper surface of the base plate 10 is rotatably attached. The hydraulic cylinder 6 has two link mechanisms 7, 7
Is arranged inside and is connected between the upper and lower connecting members 8 and 9. A ram cylinder or a single-acting cylinder is used as the hydraulic cylinder 6. On the side edge of the table 4, the table 4
A load detecting means 12 for detecting that the pallet P has been placed is provided. The detection means 12 is a proximity switch, but may be a limit switch, a photoelectric switch, a load cell, or the like.

The hydraulic circuit 3 comprises an oil supply side circuit 13 and a return side circuit 14, and the return side circuit 14 is composed of two circuit portions 14A and 14B having different flow path resistances. The refueling side circuit 13 is a main flow path 13 connected to the hydraulic pump 15.
a is connected to the bottom side oil chamber of each hydraulic cylinder 6, 6 by branching into two branch flow passages 13b and 13b at the tip, and a check valve 17 is interposed in the main flow passage 13a and A branch passage 13c with a relief valve 16 interposed is provided upstream of the stop valve 17. The hydraulic pump 15 is driven by the motor M.

Each circuit portion 14A, 14 of the return side circuit 14
B is composed of a circuit in which variable throttle valves 18A and 18B and electromagnetic switching valves 19A and 19B, which are circuit switching means, are connected in series, and both circuit portions 14A and 14B are arranged in parallel with each other and the reverse of the main flow path 13a. It is connected to the upstream side portion of the stop valve 17. The outlet ports of the switching valves 19A and 19B are opened to the tank 21. The variable throttle valves 18A and 18B are capable of manually adjusting the throttle amount. One circuit portion 14A is a high-speed circuit portion having a small flow passage resistance by reducing the throttle degree of the variable throttle valve 18A, and the other circuit portion 14B is made by increasing the throttle degree of the variable throttle valve 18B. It is a low-speed circuit part with large resistance. Instead of the variable throttle valves 18A and 18B, other types of flow rate adjusting valves may be used.

Both of the electromagnetic switching valves 19A and 19B are two-port, two-position directional switching valves, which are in the non-returned state at the normal position and open at the driven position. The switching drive device 20 is a means for outputting a control signal corresponding to the detection signal b of the load detecting means 12 to the switching valves 19A and 19B in response to the input of the descending command a, and performs the control shown in FIG. . A circle mark in the figure indicates an ON state. The switching drive device 20 is composed of a part of an electric circuit that controls the entire hydraulic lifter 1.

The operation of the above configuration will be described. When raising the table 4, as shown in FIG. 3, each switching valve 19A,
The motor M is turned on in the off state of 19B. As a result, the pressure oil discharged from the pump 15 is supplied to both the hydraulic cylinders 6 and 6, and the hydraulic cylinders 6 and 6 extend to raise the table 4. When the inside of the circuit becomes equal to or higher than the set pressure, such as when reaching the rising end, excess pressure oil is discharged from the relief valve 16. When the table 4 is stopped, the motor M is turned off and both switching valves 19A and 19B are kept off.

When lowering the table 4, the motor M
Is turned off and one of the switching valves 19A and 19B is opened.
At this time, the switching control means 20 responds to the descending command a and switches the switching valves 19A, 1A according to the load detection state of the detection means 12.
9B is selected, and the descending speed is automatically selected. That is, in the unloaded state in which the pallet P is not placed on the table 4, the detection means 12 including the proximity switch is in the off state, and at this time, the solenoid of the first switching valve 19A is driven to drive the high speed circuit. Open part 14A. As a result, the return oil of the hydraulic cylinder 6 is discharged to the tank 21 side at a flow rate according to the flow path resistance set by the variable throttle valve 18A, and the table 4 descends at high speed.

When the pallet P is placed on the table 4, the detecting means 12 consisting of a proximity switch detects the iron pallet P and is turned on. At this time, the solenoid of the second switching valve 19B is driven. And circuit part 1 for low speed
Open 4B. Thereby, the return oil of the hydraulic cylinder 6 is
The flow is discharged to the tank 21 side at a flow rate according to the flow path resistance set by the variable throttle valve 18B, and the table 4 descends at a low speed.

As described above, since the load is lowered at high speed when there is no load, the cycle time can be shortened even when the raising / lowering operation is frequently repeated. On the other hand, since the load is lowered at a low speed when loaded, even if the load on the pallet P is a heavy load or a large number of plate materials are loaded, the load can be lowered without a problem of load collapse, and a shock at the time of stoppage. Is also small. Also, it is possible to prevent the accuracy of the stop position from decreasing.

In the above embodiment, the lowering speed is controlled to the second speed, but as shown in FIG. 5, both switching valves 19A and 19B are opened to control the third speed when there is no load. good. In this case, in the hydraulic lifter having the configuration shown in FIG. 1, in addition to the pallet detecting means 12, a detecting means 22 for detecting a load (for example, a loading plate material) on the pallet P is provided, and the switching control device 20 controls the detecting means 12 and 22. The control shown in FIG. 5 is performed according to the detection state. The luggage detection means 22 is
The lifter main body 2 is composed of a photoelectric switch installed in a frame (not shown) around the lifter main body 2 or a plate material presence / absence data input means provided in a control system of a transfer facility including this hydraulic lifter.

The lowering operation of this structure will be described. When the pallet P is not placed on the table 4 and there is no load, the first
Both the second and second switching valves 19A and 19B are opened, and both circuit parts 14 in the return side circuit 14 in the parallel state are connected.
The return oil of the hydraulic cylinder 6 is made to flow to A and 14B. As a result, the table 4 descends at a higher speed than when only the high-speed circuit portion 14A is opened.

When only an empty pallet P is placed on the table 4, the pallet detecting means 12 is turned on and the load detecting means 22 is turned off. In this case, the switching control device 20 opens only the first switching valve 19A, and the return oil of the hydraulic cylinder 6 is discharged from the circuit portion 14A on the high speed side.
Therefore, the table 4 descends at a high speed to some extent, though it is slower than when there is no load. When the pallet P on which the plate materials are stacked is placed on the table 4, the pallet detecting means 12 is turned on and the load detecting means 22 is turned off.
In this case, the switching control device 20 opens only the second switching valve 19B, and the return oil of the hydraulic cylinder 6 is discharged from the low speed side circuit portion 14B. Therefore, the table 4 descends at a low speed.

As described above, by controlling the third speed, the speed can be switched between the case where there is an empty pallet P on the table 4 and the case where there is no empty pallet P, and the stop position accuracy, the shock at the time of stop and the shortening of the descent time can be reduced. More appropriate operation can be performed in consideration. Moreover, the hydraulic circuit can be as simple as the two-speed control. Although the above description has been given of the case where the load on the pallet P is a plate material, the third speed control can be performed in the same manner as described above even when another load is loaded on the pallet P. Further, the load detecting means 22 and the pallet detecting means 12 can be combined into one sensor by setting two kinds of determination levels by using a weight detecting means such as a load cell.

In each of the above embodiments, the case where the circuit portions 14A and 14B in the return side circuit 14 are connected in parallel has been described, but both circuit portions 14A and 14B are connected in series to selectively open and close. A bypass path may be provided for either circuit portion 14A, 14B. Also by this, the descending speed can be controlled to the second speed or the third speed. Further, the return side circuit 14 may be configured such that a circuit portion similar to the circuit portion 14A is added in parallel to the configuration of FIG. 1 to control the third speed. Further, the present invention is not limited to the table lifter constituted by the pantograph type lifting mechanism 5, but can be generally applied to a hydraulic lifter for lifting and lowering a table by a hydraulic cylinder. The switching means of the circuit portion of the return side circuit is not limited to the switching valves 19A and 19B, but may be one switching valve or another configuration.

FIG. 6 shows a plate material storing and conveying apparatus equipped with the hydraulic lifter 1 of the present invention. The hydraulic lifter 1 may be that of the embodiment shown in FIG. 1 or the other various embodiments described above. This plate material storage / conveyance device is provided with a plate material stocker 4
The loader 41 and the unloader 42, which are of the one-in-one-out-one-out type, are assembled to the 0. In this type, the loading position and the unloading position of the plate material W are the same plate material loading / unloading position Q, and the plate material stocker 40 is arranged at the lowermost stage. Therefore, the pallets P are switched back and forth between loading and unloading as follows.

This will be described below. The stocker main body 44 of the plate material stocker 40 has a plurality of stages of loading shelves 43 on which the pallets P (P1, P2) loaded with the plate materials W (W1, W2) are placed.
And an elevator 45 for transferring the pallets P1 and P2 between the loading shelf 43 at an arbitrary stage and the plate material loading / unloading position Q at the lowest stage is provided on the front surface of the stocker main body 44. Each of the loader 41 and the unloader 42 has a suction pad and a gripper, and is movably installed on a common erection rail 46 extending cantileverly from the plate material loading / unloading position Q. A plate material processing machine (not shown) is arranged at the tip of the rail 46. At the plate material loading / unloading position Q, the hydraulic lifter 1 of the present invention for raising and lowering the pallet P is provided on the floor surface, and the rear position thereof, that is, the position opposite to the elevator 45 is the retreat position R of the pallet P. Further, at the plate material loading / unloading position Q, a stock conveyor 48 that opens the transport surface 48a and drops the product plate material W2 under the transport surface 48a is installed.

In the operation of carrying the material plate material W1 into the plate material processing machine, the product pallet P2 is retracted to the retreat position R as shown in FIG.
The material plate W1 on the pallet P1 is adsorbed by the loader 41 while being placed on the hydraulic lifter 1 of FIG.
The loader 41 is run to the plate material processing machine along. The unloader 42 approaches the plate material processing machine along the erection rail 46 after the loader 41, grips the product plate material W2 processed by the plate material processing machine, and pulls it out to the plate material loading / unloading position Q.
At this time, the material pallet P1 placed on the hydraulic lifter 1 is moved to the retreat position R, and the product pallet P2 at the retreat position R is moved onto the hydraulic lifter 1.

At this time, the stock conveyor 48 is
The unloader 42 waits for the return of the unloader 42 with the transportation surface 48a closed, and the product sheet material W2 delivered from the sheet material processing machine by the unloader 42 is received on the transportation surface 48a. After that, the transport surface 48a is opened, and the holding of the product plate material W2 by the unloader 42 is released, so that the product plate material W2 is dropped and stacked on the product pallet P2 on the hydraulic lifter 1. After that, the product pallet P2 and the material pallet P1 are again replaced between the plate material loading / unloading position Q and the retreat position R, and the loader 41 adsorbs the next material plate material W1.
By repeating such an operation, the plate material W is carried in and out.

In the repetitive operation, the hydraulic lifter 1
When receiving the unloaded product sheet W2,
Each time one is received, the next rising height is lowered by one. The movement of the pallets P1 and P2 between the retracted position R and the plate material loading / unloading position Q is performed by a chain drive device (not shown).
Is carried out horizontally by the hydraulic lifter 1 on the pallets P1, P.
Raise and lower when replacing 2. At this time, when the hydraulic lifter 1 is lowered with the product plate material W2 placed thereon, stop accuracy is required for delivery with the chain drive device.

In this plate material storing and conveying device,
Hydraulic lifter 1 for pallets P1 and P2 for each processing
It is necessary to replace the pallets on the pallets, which requires frequent replacement operations, and the pallets P1 and P2 on which the plate materials are stacked are heavy items, and the stopping accuracy when moving up and down is also required. However, by using the hydraulic lifter 1 of the present invention, it is possible to improve the occurrence of useless waiting time due to the descending time of the hydraulic lifter 1, the cycle time can be shortened, and the required stopping accuracy can be secured. You can

[0029]

According to the hydraulic lifter of the present invention, the hydraulic circuit for flowing the return oil of the hydraulic cylinder in response to the descending operation of the table is constituted by a plurality of circuit parts having different flow path resistances, and these circuit parts are selectively selected. Since the circuit switching means for opening is provided, the table can be lowered at a speed corresponding to the load state by selecting the circuit portion of the flow path resistance according to the load state on the table. According to the invention of claim 2, since the detection means for detecting the load condition on the table is provided, the detection result can be utilized for the selection of the circuit portion by the circuit switching means,
The selection can be automated. According to a third aspect of the present invention, the hydraulic circuit that causes the return oil of the hydraulic cylinder to flow in response to the descending operation of the table is configured by a high-speed circuit portion having a small flow resistance and a low-speed circuit portion having a large flow resistance. The circuit switching means selectively opens both circuit parts, and responds to a detection signal of a detection means for detecting the presence or absence of a load on the table, the high speed circuit when there is no load, and the low speed circuit when there is a load. Since the switching control device for controlling the circuit switching means so as to open the portion is provided, the descending speed can be made fast when there is no load and can be made slow when there is a load, preventing load collapse, improving stopping accuracy, and mitigating shock when stopping. While trying, the cycle time can be shortened.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a hydraulic lifter according to an embodiment of the present invention.

FIG. 2 is a perspective view of the hydraulic lifter.

FIG. 3 is an explanatory diagram of a control operation of a switching control device in a hydraulic lifter.

FIG. 4 is a block diagram of a control system in another embodiment of the present invention.

FIG. 5 is an explanatory diagram of a control operation of the switching control device.

FIG. 6 is a front view and a side view showing a plate material storage / conveyance device in which the hydraulic lifter is used.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hydraulic lifter, 3 ... Hydraulic circuit, 4 ... Table, 6 ... Hydraulic cylinder, 12 ... Detection means, 14 ... Return side circuit, 14
A ... High speed circuit portion, 14B ... Low speed circuit portion, 18
A, 18B ... Variable throttle valve, 19A, 19B ... Electromagnetic switching valve (circuit switching means), 20 ... Switching control device

Claims (3)

[Claims] 1. In a hydraulic lifter for raising and lowering a table with a hydraulic cylinder, a hydraulic circuit for flowing return oil of the hydraulic cylinder with respect to a lowering operation of the table is constituted by a plurality of circuit parts having different flow path resistances. A hydraulic lifter provided with circuit switching means for selectively opening parts. 2. The hydraulic lifter according to claim 1, further comprising detection means for detecting a load state on the table. 3. A hydraulic circuit for flowing the return oil of the hydraulic cylinder in response to a descending operation of a table is constituted by a high-speed circuit portion having a small flow path resistance and a low-speed circuit portion having a large flow path resistance, and the circuit is provided. The switching means is designed to selectively open both circuit parts, and is provided with a detecting means for detecting the presence or absence of a load on the table. 2. The hydraulic lifter according to claim 1, further comprising a switching control device for controlling the circuit switching means so as to open a circuit portion for low speed.