JPH0358999B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a clutch cylinder that engages a winding drum clutch that is always energized to disconnect, a brake cylinder that releases an automatic brake of the winding drum that is always energized to tighten, and a brake cylinder that connects both cylinders together. This invention relates to a crane such as a truck crane that is equipped with a switching valve device that is switchably connected to a tank and has a free fall position for a suspended load, and a hoist brake that is always activated to be released.

In such cranes, the braking force of the hoisting drum increases as the footbrake pedal pressure increases, which has the advantage of making it easier to adjust the free-falling speed of the suspended load. In this case, the automatic brake of the winding drum must be released after the winding drum clutch has been disconnected and the winding drum has been substantially restrained by the foot brake, and then the foot brake must be released to allow the suspended load to fall freely. In order to achieve this, an auxiliary switching valve that is switched in conjunction with the foot brake is provided, and when the foot brake is completely released to increase the free descent speed of the suspended load, the automatic brake of the winding drum is activated. As a result, the crane boom is subjected to a large impact, which may damage the boom and other parts of the crane.

The present invention deals with this problem by providing a switchable system in the oil path between the switching valve device 1 and the brake cylinder 2 so that the brake cylinder, which normally communicates with the tank, is directly connected to the hydraulic pressure source 3. A brake control valve 4 is inserted, and means for issuing a switching signal for the brake control valve when the foot brake 5 is substantially tightened is provided on the foot brake side, and the switching valve device is switched to the free lowering position of the suspended load. A device that connects the switching signal transmission path of the brake control valve 4 only at certain times, and a device that receives the switching signal and holds the brake control valve 4 in the switching position while the switching valve device 1 is in the free-lowering position of the suspended load. It is characterized by having been established.

An embodiment of the present invention applied to a truck crane will be described below with reference to FIGS. 1 to 3. Reference numeral 6 indicates a brake band wound around a brake drum 7 that is integrated with the winding drum. One end of the brake band 6 is fixed to a base 8, and the other end is attached to a brake lever 10 which is pivotally connected 9 to the base. Connected to the terminal. The foot brake 5 is a master cylinder 11 operated by a pedal.
A power cylinder 13 is connected to the brake system through an oil passage 12, and a piston rod 14 of the power cylinder is constantly urged to contract by a compression spring 15 to the brake release position shown in the figure. Also, the brake cylinder 2 is
The piston rod 16 is constantly urged to extend to the illustrated brake tightening position by a compression spring 17, and the brake cylinder 2 and power cylinder 13 are
They are attached to the base side on both sides of the brake lever 10 so as to tighten the brake band 6 when each is extended.

18 is a hydraulic motor for driving the winding drum, 19 is a directional control valve that controls this, 20 is a hydraulic pump,
When the directional control valve 19 is switched to the right position from the neutral position shown in the figure, the oil passage 21 becomes the high pressure side and drives the hydraulic motor 18 in the hoisting direction, and when the directional control valve 19 is switched to the left position The oil passage 22 is on the high pressure side and drives the hydraulic motor 18 in the reverse direction. Note that 23 is a tank, and 24 is a counterbalance valve inserted into the oil passage 21.

The winding drum clutch has one end of both side clutches 26 pivotally connected 27 to a winding drum drive shaft which is interlockingly connected 25 to the output shaft of the hydraulic motor 18 , and a clutch cylinder 28 is connected between the other ends of the both clutches 26 , 26 .
At the same time, both clutches 26, 26
A tension spring 29 for clutch disconnection is provided in between.

Similar to the device devised in Utility Model Publication No. 57-15906, the switching valve device 1 releases the automatic brake of the winding drum after engaging the winding drum clutch when the winding drum starts driving, and tightens the automatic brake when the winding drum stops. In order to prevent the suspended load from accidentally slipping off by disconnecting the winding trunk clutch after the operation, a manually operated main switching valve 30 is provided.
Includes pilot-operated auxiliary switching valves 31 and 32.
As shown in FIG. 1, the auxiliary switching valve 31 has a constant position where the brake cylinder 2 is connected to the tank 23 via the oil passage 33, and when hydraulic pressure from the oil pressure source (accumulator) 3 is supplied to the pilot oil passage 31a. It is switched to the upper position in the figure to connect the oil passage 33 to the oil passage 34 to the main switching valve 30.

The auxiliary switching valve 32 is inserted into an oil passage 35 that connects the accumulator 3 to the main switching valve 30, and in the normal position shown in the figure, the oil passage 35 on the main switching valve side is connected to the tank 23, but the pilot oil Road 32
a is connected to oil passages 21 and 22 of the hydraulic motor circuit via a shuttle valve 36. Therefore, when one of the oil passages 21 and 22 becomes a high pressure side when the hydraulic motor 18 is driven, the pilot oil pressure switches the auxiliary switching valve 32 to the upper position in the drawing, thereby making the oil passage 35 conductive.

The brake control valve 4 inserted into the oil passage 33 is also a pilot-operated switching valve, and normally communicates with the oil passage 33. When the hydraulic pressure for release is supplied, the brake control valve is switched to the upper position in the diagram, and the brake cylinder 2 is sequentially connected to the accumulator 3 via the oil passage 33, the brake control valve 4, and the oil passage 37. , release the automatic brake on the winding drum. Note that 3p indicates a hydraulic filling device for the accumulator.

The main switching valve 30 is a three-position switching valve, and when it is in the neutral position shown in FIG. The oil passages 34 are each connected to a return oil passage 40 to the tank 23 via a main switching valve 30. Therefore, the brake control valve 4 and the auxiliary switching valve 31 are always in the position.
The brake cylinder 2 is connected to the tank 23, so that the drum clutch is disconnected by a spring 29 and the automatic brake is tensioned by a spring 17.

From this state, when the main switching valve 30 is switched to the free lowering position of the suspended load shown in FIG.
9 and 34 remain connected to the tank 23 to maintain the winding drum clutch and automatic brake in the neutral position, but the oil passage 42 connected to the oil passage 33 via a check valve 41 and the oil An oil passage 44 connected to the passage 12 via a check valve 43 is connected in parallel to the pilot oil passage 4a.

Therefore, by depressing the operating pedal of the master cylinder 11 and extending the power cylinder 13,
When the foot brake 5 tightens the winding drum, the check valve 4
1, the hydraulic pressure of the foot brake is transmitted only to the pilot oil passage 4a via the check valve 43 and the oil passage 44, so that the pressure signal causes the brake control valve 4 to operate as described above. is switched to the upper position, and the hydraulic pressure of the accumulator 3 acts on the brake cylinder 2 to release the automatic brake.

Once the automatic brake is released in this way, even if the signal pressure generated by the foot brake decreases by relaxing the pedal pressure on the master cylinder 11, the automatic brake release oil pressure (accumulator oil pressure) in the oil passage 33 will be applied to the check valve 41 and Since the brake control valve 4 acts on the pilot oil passage 4a through the oil passage 42, the brake control valve 4 is maintained in the upper position.
The automatic brake will not activate unexpectedly. Furthermore, since the transmission of the accumulator hydraulic pressure from the oil passage 42 to the oil passage 12 is also prevented by the check valve 43, there is no fear that the accumulator hydraulic pressure will interfere with the release of the foot brake.

Therefore, the foot brake 5 can be completely released to allow the suspended load to freely fall, or the pedal depression force of the master cylinder 11 can be freely increased or decreased to increase or decrease the descending speed of the suspended load.

Furthermore, when the main switching valve 30 is switched from the neutral position to the drum driving position shown in FIG. 35, but
The oil passage 4a remains in communication with the tank 23. Therefore, the clutch cylinder 28
9, the winding drum clutch is engaged, and the auxiliary switching valve 31 is switched to the upper position as shown in the figure.

Therefore, when the direction selector valve 19 is switched to the required right or left winding drum drive position and the hydraulic motor 18 is activated, the hydraulic pressure in the high pressure side oil passage is transferred to the shuttle valve 36.
Since the oil pressure is transmitted to the oil passage 32a and switches the auxiliary switching valve 32 to the upper position, the hydraulic pressure of the accumulator 3 is sequentially supplied to the brake cylinder 2 through the switching valves 32, 30, 31, and 4, releasing the automatic brake. It enables driving of the winding drum, that is, lifting or lowering the load.

Although the case where the switching signal of the brake control valve is transmitted by hydraulic pressure has been described above, the present invention also includes the case where the switching signal is transmitted electrically.

FIG. 4 and FIG. 5 show an example thereof, and in FIG. 4, members with the same reference numerals as in FIG. 1 are corresponding members. The main switching valve 30 has oil passages 31a, 3
The main switching valve is equipped with a micro switch 45 that closes only when the suspended load is switched to the free lowering position. The brake control valve 4 is configured as an electromagnetic switching valve that can be switched by conduction of a solenoid 4s. On the other hand, in the oil passage 12, there is a pressure switch 4 which is closed when the foot brake 5 is tightened.
6, and a pressure switch 47 that closes when the automatic brake is released is connected to the oil path 33, respectively, and the contacts of the pressure switches 46 and 47 are connected to the operating circuit of the solenoid 4s, which is turned on by the switch 45, as shown in FIG. are connected in parallel like. 48 indicates a battery.

For this purpose, as shown in FIG. 4, the main switching valve 30 is switched to the free-lowering position of the suspended load, the switch 45 is closed, the clutch cylinder 28 is connected to the tank 23, and the drum clutch is disconnected. When the foot brake 5 is tightened by depressing the operating pedal of the master cylinder 11, the pressure switch 46 closes due to the hydraulic pressure and the solenoid 4s is turned on.
Therefore, since the brake control valve 4 is switched to the upper position in the figure, the hydraulic pressure of the accumulator 3 is supplied to the brake cylinder 2 to release the automatic brake.
Since the pressure switch 47 is closed at the same time, even if the operating force of the master cylinder 11 is relaxed and the pressure switch 46 is opened, the solenoid 4s is self-maintained in a conductive state and the automatic brake is maintained in a released state. Therefore, the first thing is that the suspended load can be freely lowered while freely adjusting the braking force of the foot brake 5.
This is the same as the case shown in the figure.

Also, in the embodiment of FIG. 4, the pressure switch 47
Instead of providing a relay 49 shown in FIG. 6, the relay 49 is connected in parallel with the solenoid in the operating circuit of the solenoid 4s, and the self-holding contact CR of the relay is connected in parallel with the pressure switch 46. It is clear that the same function can be provided with the automatic brake release position, and in any of the embodiments, by switching the main switching valve 30 from the free-falling position of the suspended load to a position other than that, the function of holding the automatic brake release position of the hoisting drum disappears. do.

According to the present invention, when the suspended load is freely lowered, the automatic brake of the hoisting drum is not released unless the hoisting drum is almost completely restrained by the foot brake.
There is no risk of the suspended load accidentally slipping off, and once the automatic brake is released, the automatic brake will be activated inadvertently and impact will be applied to the crane boom, regardless of whether or not the hoisting drum is braked by the foot brake. Therefore, there is no need to control the descending speed of the suspended load while worrying about the operation of the automatic brake as in the conventional method, and there is an effect that the suspended load can be quickly and freely lowered.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment of the present invention, FIGS. 2 and 3 are circuit diagrams when switching the switching valve device,
4 and 5 are a hydraulic circuit diagram and an electric circuit diagram of another embodiment, respectively, and FIG. 6 is an electric circuit diagram of still another embodiment. 6... Brake band, 7... Brake drum, 10... Brake lever, 11... Master cylinder, 13... Power cylinder, 18... Hydraulic motor for driving drum, 19... Directional switching valve, 20...
...Hydraulic pump, 26...Clutch pump, 28...
...Clutch cylinder, 30...Main switching valve, 31,
32...Auxiliary switching valve, 41, 43...Check valve, 4
5... Micro switch, 46, 47... Pressure switch, 4s... Solenoid, 49... Relay.

Claims (1)

[Claims] 1. A clutch cylinder that engages the winding drum clutch that is always energized to disconnect, a brake cylinder that releases the automatic brake of the winding drum that is always energized to tighten, and the freedom to switch and connect both cylinders to the tank. In a crane equipped with a switching valve device provided with a lowering position and a foot brake of a winding drum that is always activated to be released, a switching valve device 1 and a brake cylinder 2 are provided.
A switchable brake control valve 4 is inserted into the oil path between the brake cylinders and the brake cylinder, which normally communicates with the tank, to connect directly to the hydraulic power source 3, and the switching signal of the brake control valve is transmitted to the foot brake. 5 is substantially tightened, on the foot brake side, and conducts the switching signal transmission path of the brake control valve 4 only when the switching valve device is switched to the free lowering position of the suspended load; A device for controlling the free fall of a suspended load, comprising a device that receives a signal and holds the brake control valve 4 in the switching position while the switching valve device 1 is in the free descent position of the suspended load.