JPH036115B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a system for controlling a hoisting drum in a truck crane, etc., and in particular, for supplying or discharging hydraulic pressure to a brake release cylinder of a hoisting drum brake that is constantly tightened, depending on whether the hoisting drum is driven or stopped. The present invention relates to a winding drum control device in which a master cylinder of the brake release cylinder that can be manually controlled is inserted into an automatic power brake control circuit.

With such a device, a suspended load below the free-fall limit load (a fraction of the normal rated load or permissible lifting load) can be freely lowered by the action of gravity, but if the detected load of the suspended load reaches the free-fall limit load. If a safety device is provided to prevent the free-falling operation when the free-falling operation occurs, the free-falling limit load can be increased compared to the conventional method. As this safety device, when a hoisted load is lifted from its original position at a high place to a free-fall starting position by a hoisting drum, when the hoisting load reaches the free-fall limit load, the hoisting drum is automatically driven. If a device is installed to stop the load, the safety device will be activated when the detected load of the suspended load exceeds the free-fall limit load due to lateral loads caused by gusts of wind or inertia caused by the rotation of the crane swivel platform. will no longer function. To avoid this, when the suspended load reaches the free-fall limit load at the free-fall start position, the brake release cylinder is directly connected to the tank to tighten the drum brake and prevent free-fall. This makes it impossible to lower the suspended load at the free fall start position to the original position.

The present invention deals with this problem, and includes a detection device that issues a signal when the suspended load reaches the free-fall limit load, and a signal issued by the detection device that causes the master cylinder to be placed in a non-operating position during manual operation. The present invention is characterized in that it includes an actuator for restoring power, and is provided with means for normally maintaining the actuator in a state in which the master cylinder can be operated manually.

An embodiment of the present invention will be described below with reference to FIG. 1 is a winding drum driven by a hydraulic motor; 2 is a brake release cylinder for the winding drum brake which is constantly biased by a spring 3; 4 is a brake release cylinder for the winding drum brake which is attached between the winding drum 1 and its driving hydraulic motor shaft; 6 is a control circuit for the winding drum drive hydraulic motor;
Reference numeral 7 indicates a master cylinder for pedal operation, and an oil chamber 1 between the main and sub pistons 8 and 9 of the master cylinder 7.
0 and its output side oil chamber 11 are connected via a mechanically operated check valve 12 provided in the main piston 8, and both the main and sub pistons 8, 9 are connected by the hydraulic pressure acting on the oil chamber 11 side. When returned to the illustrated position, the check valve 12 loses its backflow prevention function and the oil chambers 10, 1
This enables forward and reverse flow of oil between 1 and 2.

The control circuit 6 automatically supplies oil pressure to the oil passage 13 and the oil passage 14 to the clutch engagement cylinder 4 when the winding drum 1 is driven forward or backward by a hydraulic motor, and also controls the driving of the winding drum. When the engine is stopped (or when a clutch operation valve is provided, when it is switched to the clutch disengagement side), the oil passage 13 communicates with the tank, which is the same structure as in the past. The oil passage 14 is a pilot operated switching valve 1.
5 and an oil passage 16 sequentially to the oil chamber 10 of the master cylinder 7, regardless of whether the master cylinder is in operation or not. The switching valve 15 connects the oil chamber 10 to the tank T.
It is always energized to return to the right position shown in the figure, which communicates with the pilot oil passage 17, and when oil pressure acts on the pilot oil passage 17, it is switched to the left position and communicates the oil passages 14 and 16.

Also, the output side oil chamber 11 of the master cylinder 7 is connected to the oil passage 1.
It is directly connected to the brake release cylinder 2 via 8.

Therefore, when switching the three-position directional control valve in the control circuit 6 from the illustrated winding drum stopped state to the winding drum driving position, hydraulic pressure is automatically or selectively supplied to the clutch engaging cylinder 4 from the oil passage 13 to start winding. When the body clutch is engaged, at the same time, the hydraulic pressure automatically supplied to the oil passage 14 enters the oil chamber 10 through the switching valve 15, which is switched to the left position in the figure, and the oil passage 16 in sequence. Furthermore, since the pressure is transmitted from the oil chamber 11 to the brake release cylinder 2 through the check valve 12, the winding drum brake is released, allowing the winding drum to be driven. If the directional switching valve is returned to the neutral position and the drum drive hydraulic motor is stopped, the check valve 12 has lost its backflow prevention function, and the switching valve 15 returns to the illustrated position and opens the oil passage 16. Since it communicates with the tank T, the hydraulic pressure in the brake release cylinder 2 passes through the master cylinder 7 and is discharged to the tank, and the winding barrel brake is tightened by the spring 3, and the winding barrel clutch is activated automatically or by clutch operation. Disconnected by operating the valve.

In this state where the winding drum is stopped, the driver depresses the drive pedal 21a of the brake lever 21 whose intermediate portion is pivoted 19 to the crane swivel table and whose lower end is connected to the piston rods of the main and sub pistons 8 and 9 via a link 20. When the main piston 8 is pushed to the right in the figure, the check valve 12 prevents backflow, and the oil in the output side oil chamber 11 is supplied under pressure to the brake release cylinder 2, releasing the drum brake and suspending it. Free fall of the load is possible.

Reference numeral 22 denotes an actuator (single-acting hydraulic cylinder) mounted on the crane slewing table in parallel with the master cylinder 7, and the tip of its piston rod 23 is always opposed to the actuating arm 20a for returning the master cylinder, which is fixed to the link 20 and protrudes from the actuator 22. A space is formed between the working arm and the piston rod 23 in the retracted position, in which the working arm 20a moves through the operation of the master cylinder 7. Hydraulic cylinder 22 is constantly biased to contract by spring 24 and has a stroke that pushes master cylinder 7 back to the non-operating position shown.

Reference numeral 25 denotes a crane overload prevention detection device, which includes a storage device 26 that stores the lifting allowable load (rated load) and outputs the lifting allowable load according to the elevation, expansion and contraction of the telescopic boom, and the actual lifting load. It includes a detector 27 for detecting the load, and the output sides of the memory 26 and the detector 27 are connected to bipolar changeover switches 28 and 29, respectively, and when the changeover switch is closed to the contact A side, the memory The outputs of 26 and detector 27 are connected to conductors 30 and 3, respectively.
1 to a comparator (not shown) which issues a signal if the two outputs are equal. As in the prior art, the signal issued by this comparator operates a device for stopping the operation of the crane operating equipment in the direction of increasing the crane overturning moment.

When the changeover switches 28 and 29 are closed to the contact B side, the output of the memory 26 is reduced by a percentage to the output corresponding to the free fall limit load.
is transmitted to the comparator 33 along with the output of the detector 27. The comparator 33 emits a signal when the detector output becomes equal to or higher than the calculator output, and the signal emitted by the comparator 33 is transmitted to the switching valve 35 through its transmission path 34, and At the same time as switching to the right position in the figure, an alarm device 38 such as a buzzer is activated. The switching valve 35 is inserted into an oil passage 37 connecting the single-acting hydraulic cylinder 22 and the hydraulic power source 36, and is always activated to return to the illustrated position communicating the hydraulic cylinder 22 with the tank T. When this occurs, the hydraulic cylinder is communicated with the hydraulic power source 36.

The figure shows a crane operator selectively switching the changeover switches 28 and 29, but in the case of a crane equipped with a clutch operation valve for controlling engagement and disengagement of the hoisting drum clutch in the control circuit of the clutch engagement cylinder 4. The changeover switch normally closes the contact A side, and when the clutch operation valve is switched to the disengagement side of the winding drum clutch, the changeover switches 28 and 29 close the contact B side in conjunction with this. It can also be done.

According to the above configuration, in order to freely lower the suspended load, the changeover switches 28 and 29 are closed in advance to the contact B side as shown in the figure, and then the hoisting drum 1 is controlled to lift the suspended load to the free-fall starting position. After stopping as shown in the figure and disengaging the winding barrel clutch automatically or manually, when the pedal 21a is gradually depressed,
If the hanging load is below the free fall limit load and the comparator 33 does not issue a signal, the hydraulic cylinder 22
As shown in the figure, the cylinder is connected to the tink T through the switching valve 35 and maintained in a contracted state, so that the hoisting drum brake can be released to freely lower the suspended load as described above, and the suspended load can be lowered. If the load is equal to or greater than the free fall limit load and the comparator 33 is emitting a signal, the switching valve 35 is switched to the right position in the figure in advance to connect the hydraulic cylinder 22 to the hydraulic source 36, and Since the piston rod 23 extends as shown by the chain line in the figure and restrains the operating arm 20a, that is, the brake lever 21 and the main and sub pistons 8 and 9 in the illustrated positions, the master cylinder cannot operate. to prevent the free fall of the suspended load.

On the other hand, if the load detected by the detector 27 reaches the free-fall limit load due to a lateral load due to gusts of wind or inertia caused by the rotation of the crane swivel table, the load detected by the comparator 33 will be The signal causes the contracted hydraulic cylinder 22 to expand as described above, returning the master cylinder 7 to the illustrated state, thereby tightening the hoisting drum brake and preventing the suspended load from freely falling. Therefore, depending on whether the lateral load generation phenomenon disappears or continues, the suspended load can be freely lowered again by operating the master cylinder 7, or the suspended load can be suspended by the hoisting drum 1.

Above, we have explained the case where the actuator is a single-acting hydraulic cylinder 22 and the actuating arm 20a and the piston rod 23 are separable in order to reduce the operating resistance of the master cylinder 7. However, the actuator is a hydraulic motor that can rotate in forward and reverse directions. In addition, a rack that meshes with a pinion attached to the output shaft can function similarly to the piston rod 23.

According to the present invention, when the detected load of the suspended load reaches the free fall limit load in response to the start of its free fall, of course,
Even when some kind of lateral load acts during free descent and the free descent limit load is reached, the master cylinder 7 is forcibly pushed back to the non-operating position and the drum brake is tightened, so the lateral load does not occur. This has the advantage that the winding drum brake can be controlled by human power or power in response to the disappearance or continuation of the phenomenon.

[Brief explanation of the drawing]

The figure is a circuit diagram of one embodiment of the present invention. 1... Winding drum, 2... Brake release cylinder, 4
...Clutch engagement cylinder, 6... Control circuit for the winding drum drive hydraulic motor, 7... Master cylinder, 8,
9... Main and sub piston, 20... Link, 20a...
... Master cylinder return activation arm, 21... Brake lever, 22... Actuator, 23... Piston rod, 25... Crane overload prevention detection device, 26... Memory device, 27... Lifted load detector , 32...Calculator for free fall limit load, 33...
...Comparator, 35...Switching valve, 36...Hydraulic power source.

Claims (1)

[Scope of Claims] 1. A power brake control circuit that automatically supplies or discharges hydraulic pressure to a brake release cylinder of a winding drum brake, which is always tightened, in response to drive or stop of the winding drum, In the winding drum control device in which a master cylinder of the release cylinder that can be controlled manually is inserted, there is a detection device that emits a signal when the suspended load reaches the free fall limit load, and a detection device that outputs a signal when the hoisted load reaches the free fall limit load. 1. A safety device for freely lowering a suspended load, comprising an actuator for power-returning a master cylinder to a non-operating position, and a means for normally maintaining the actuator in a state in which the master cylinder can be operated manually. 2. The freedom to hang a load as set forth in claim 1, wherein the actuator is a single-acting cylinder in which the tip of a piston rod is separably abutted and engaged with the return actuation arm of the actuator to push the master cylinder back to the non-operating position. Descent safety equipment.