JPH036117B2 - - 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.

However, in the oil passage between the master cylinder and the brake release cylinder, there is a constant position where the oil passage is conducted.
Inserting a switching valve with a switching position that connects the brake release cylinder to the tank and tightens the hoisting drum brake when the hoisting load reaches the free-fall limit load would prevent the hoisting load from being lifted high by the hoisting drum. If the detected load of the suspended load reaches the free-fall limit load while it is being lifted from its original position to the free-fall starting position, the drum brake will be tightened and the suspended load will be lowered to its original position. If the master cylinder is used to release the hoist drum brake, lateral loads and vertical loads due to gusts of wind etc. will be added to the hoisted load that is freely falling, and the detected load of the hoist will exceed the free-fall limit load, and the hoist hoist will be suspended. When the brake is tightened to prevent free descent, it may become impossible to lower or raise the suspended load, which is extremely dangerous.

The present invention solves this problem by constantly returning the oil in the brake release cylinder to a position where it can be discharged into the tank, and by controlling the master cylinder by a valve switching signal that is issued when the master cylinder and the winding drum are driven. A valve device that can be switched to connect the output side to the brake release cylinder is connected between the master cylinder and the brake release cylinder, and a detection device is provided to issue a signal when the suspended load reaches a free fall limit load. The present invention is characterized in that a device is provided for blocking the transmission path of the valve switching signal when the master cylinder is driven by the signal generated by the detection device.

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; a clutch engagement cylinder of the winding drum clutch which is constantly biased to disconnect; 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 and 9 are connected to each other via a piston return spring 36 in the oil chamber 11. When the check valve 12 returns to the illustrated position due to its elasticity, the check valve 12 loses its backflow prevention function, allowing forward and reverse flow of oil between the oil chambers 10 and 11.

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 clutch operation valve is stopped (or when the clutch operation valve is switched to the clutch disengagement side if a clutch operation valve is provided), the oil passage 13 communicates with the tank, which is the same as the conventional structure. 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.
The pilot oil passage 17 is always energized to return to the right position as shown in the figure, which communicates with the pilot oil passage 17, and when hydraulic pressure acts on the pilot oil passage 17, it is switched to the left position and communicates the oil passages 14 and 16.

Therefore, assuming that the output oil chamber 11 of the master cylinder 7 is in direct communication with the brake release cylinder 2 through the oil passage 18, the three-position directional control valve in the control circuit 6 can be Automatically or selectively switch the oil path 1 to the drum drive position.
When hydraulic pressure is supplied from 3 to the clutch engaging cylinder 4 to engage the winding drum clutch, the hydraulic pressure automatically supplied to the oil passage 14 is simultaneously applied to the switching valve which is switched to the left position in the figure by the pilot hydraulic pressure. 15 and oil passage 16 in order to enter the oil chamber 10, and further through the check valve 12, the oil is transmitted from the oil chamber 11 to the brake release cylinder 2, so that the winding drum brake is released and the winding drum is driven. forgive. Furthermore, when 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.
Since the switching valve 15 returns to the illustrated position and communicates the oil passage 16 with the tank T, the hydraulic pressure in the brake release cylinder 2 is discharged to the tank through the master cylinder 7, and the drum brake is tightened by the spring 3. and the winding barrel clutch is disconnected automatically or by operating a clutch operating valve.

When the winding drum is stopped, the main and sub pistons 8 and 8 of the master cylinder 7 are activated by operating the brake pedal.
9 to the right in the figure to input drive the master cylinder, the check valve 12 prevents backflow.
The oil in the output side oil chamber 11 is transferred to the brake release cylinder 2.
is supplied under pressure to release the drum brake, allowing the suspended load to descend freely.

Reference numeral 19 denotes a valve device inserted into the oil passage 18. The valve device 19 has a normally closed valve 20 that opens in response to a valve switching signal (pressure signal) issued when the master cylinder 7 and the winding drum 1 are driven, and a normally closed valve 20 that opens the brake release cylinder 2. The normally closed valve 20 and the check valve 21 are connected in parallel in the oil passage 18. 22 and 23 are pilot oil passages (pressure signal transmission paths) whose one ends are connected to the oil passages 16 and 18, respectively;
The other ends of both pilot oil passages 22 and 23 are connected to a pilot operating portion of a normally closed valve 20 via a shuttle valve 24.

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 as shown in FIG. It is transmitted to the comparator 33 along with the output. This comparator 33 emits a signal when the output of the detector 27 becomes equal to or greater than the output of the calculator 32, and the signal is sent to the electromagnetic switching device inserted into the pilot oil passage 23 via its transmission path 34. The pilot operating portion of the normally closed valve 20 is connected to the tank T by switching the valve 35 from the right position (normal position) shown in the figure where the pilot oil passage is conductive to the left position.

The figure shows the crane operator selectively switching the changeover switches 28 and 29, but in the case of a crane equipped with a clutch operating valve for controlling the 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 drum clutch, the changeover switches 28 and 29 close the contact B side in conjunction with this. It can also be done.

If the comparator 33 does not emit a signal in the state shown in FIG. When activated, the normally closed valve 20 is switched to the lower position in the figure by the pilot pressure to conduct the oil passage 18, so that the drum brake can be released as described above.
Also, when the drive of the winding drum 1 or the master cylinder 7 is stopped, the pilot operating oil pressure of the normally closed valve 20 is changed to the oil path 2.
2 and the switching valve 15 into the tank T, or through the oil passage 23 and the switching valve 35 into the oil chamber 11 of the master cylinder. The hydraulic pressure in the brake release cylinder 2 passes through the check valves 21, 12 and the switching valve 15 in sequence and returns to the tank T, or returns to the oil chamber 11 through the check valve 21, and then The barrel brake is tightened by spring 3.

However, when the comparator 33 issues a signal and the switching valve 35 is switched to the left position, the normally closed valve 2
Since the transmission of the pilot pressure in the master cylinder side oil chamber 11 to the pilot operating section of When the cylinder 1 is driven, the normally closed valve 20 is activated as described above.
can be opened to release the barrel brake. Therefore, if the hanging load is more than the free fall limit load, the winding drum 1
It is possible to control the crane and other parts of the crane to lift the hoisted load at the original position to the starting position of free fall, and to disconnect the hoisting drum clutch automatically or manually, but the hoisting drum brake cannot be released manually. First, the free fall of the suspended load is prevented.

In addition, if a lateral load or vertical load due to a gust of wind etc. acts on the suspended load during free descent and the detected load of the suspended load by the detector 27 reaches the free descent limit load, the signal emitted by the comparator 33 Normally closed valve 2 as mentioned above
0 returns to the illustrated closed position, making it impossible to adjust the master cylinder 7 or the hoisting drum brake, so the operating force of the master cylinder is removed, the hoisting drum brake is tightened, and the free descent of the suspended load is stopped. Next, depending on whether the lateral load generation phenomenon described above disappears or continues, that is, whether the switching valve 35 returns to the illustrated position, the master cylinder 7 is operated to allow the suspended load to freely descend again, or the hoisting drum 1 All you have to do is drive the suspended load.

In the above embodiment, when the suspended load in free fall receives some kind of lateral load or vertical load and the detected load of the suspended load reaches the free fall limit load, this is stopped by closing the normally closed valve 20 or It is necessary to eliminate the operating force of the master cylinder 7 by detecting the activation of an alarm (buzzer) normally attached to the detection device 25, but if you want to avoid this, the valve device 19 in FIG. 1 can be switched as shown in FIG. 2. Valve 38 may be used. The switching valve 38 is always energized to return to the upper position shown in the figure, which connects the brake release cylinder 2 directly to the tank T, and when pilot pressure is supplied to the pilot operation part from the oil passage 22 or 23, the brake release cylinder is 2 to the lower position where it connects to the hydraulic oil chamber 11 of the master cylinder.

Therefore, as a result of the operation of the master cylinder 7, the hanging load that is freely falling receives some kind of lateral load, and the detected load of the hanging load reaches the free-falling limit load. When the switching valve 35 is then switched to the left position in the figure, the switching valve 38 returns to the upper position in the figure and directly communicates the brake release cylinder 2 with the tank T, so that the drum brake is automatically tightened. In FIG. 2, members with the same reference numerals as in FIG. 1 are corresponding members.

In each of the embodiments described above, the valve switching signal of the normally closed valve 20 or the switching valve 38 is a pressure signal, but it is clear that the valve switching signal can also be an electrical signal.

According to the present invention, when the suspended load reaches the free descent limit load when hoisting the suspended load from the original position to the free descent starting position, the release of the drum brake is automatically disabled and the free descent is resumed. In addition, if a lateral load or vertical load due to a gust of wind etc. is applied to the suspended load while the suspended load is free-falling, and the detected load of the suspended load reaches the free-fall limit load, at least The free fall of the load can be switched to powered suspension by the winding drum, which has the effect of eliminating the risk of the suspended load hanging in the air.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, and FIG. 2 is a circuit diagram of main parts of another embodiment. 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, 19... Valve device, 20...
Normally closed valve, 21...Check valve, 22, 23...Pilot oil passage for transmitting valve switching signal, 24...Shuttle valve, 25...Detection device for crane overload prevention, 3
5...Solenoid switching valve, 38...Switching valve.

Claims (1)

[Claims] 1. The brake release cylinder of the winding drum brake, which is always tightened, can be manually controlled in a power brake control circuit that automatically supplies or discharges hydraulic pressure according to the drive or stop of the winding drum. In a winding drum control device in which a master cylinder is inserted, the brake release cylinder is always energized to return to a position where the oil in the cylinder can be discharged to a tank, and the master cylinder is activated by a valve switching signal issued when the master cylinder and winding drum are driven. A valve device which can be switched to connect the output side of the brake release cylinder to the brake release cylinder is connected between the master cylinder and the brake release cylinder, and a detection device is provided to issue a signal when the suspended load reaches the free fall limit load. A safety device for freely lowering a suspended load, characterized in that a device is provided for blocking the transmission path of the valve switching signal when the master cylinder is driven by the signal emitted by the detection device.