JPS6026594A - Hydraulic circuit for crane - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to hydraulic circuits for cranes, and more particularly to hydraulic circuits for preventing engine stalling under severe load conditions.

The present invention provides a hydraulic circuit which prevents the engine of a crane, particularly an offshore crane, from stalling under worst-case loads. Crane engines are sized in terms of horsepower to provide sufficient power to operate under the loads normally encountered by the engine.

In order for a crane to perform all its functions, rotating, booming, and lifting at the same time, it requires a large engine, which makes it economically unviable when used under normal conditions. resulting in waste. To prevent the engine from stalling when a suitably sized engine is overloaded, the present invention automatically transfers hydraulic power from one of the pumps being driven by the engine to a reservoir. The present invention provides a circuit for automatically changing direction, thereby reducing the load on the engine and preventing the engine from stalling. In addition, a boom limiting device is provided that utilizes the load reduction sideway feature to prevent sudden movements that would cause the boom to list at an angle that would damage the crane. .

Referring to Figure 1, a platform-mounted crane is indicated by the designation number (10);
It comprises an upper working part (12) rotatably mounted on a stand (14) fixed to a platform on the T. A rotary table provided between the upper working part (12) and the stand (14) allows the upper working part (12) to rotate about 1 μ axis with respect to the stand (14).Ring gear and a pinion driven by a hydraulic rotary motor provides rotational force to the upper working part (12) in a conventional manner.A boom (18) is rotatably mounted to the upper working platform (12). The angular position of (18) corresponds to the composite rope ring (20) attached to the tip of the boom by means of a suspender (22) and the bail (20) rotatably attached to the top of the figure-of-eight support (26). The winch (28) is mounted on the support (26) and is adjusted by a wire rope that is stretched between the boom winch (28) and the boom winch (28). It is driven by a pressure motor (30).

A rope (54) is wound around the auxiliary winch (32), and the rope (64) is connected to the hook (38) via an extension (66) at the tip of the boom. This winch (
32) is also mounted on the support (26) and is driven by a hydraulic motor (40). The main hook block (42) is supported by a wire rope (44), which is wound around the main winch (46) via a ring at the tip of the boom. This main winch (46) is also mounted on the support (26) and is driven by a hydraulic motor (48). Pressurized fluid power for these motors is provided by an engine (
Three pumps (50), (56) driven by
2), given by (54).

Referring to FIG. 2, the engine (56) has three load reduction pumps (56) with pressure sensitive load reduction valves (58).
0 people (52), (54) are shown schematically as ya. Three pumps (50), (52), (54
)N load reduction valve (58) and its associated circuitry are included in block (60), which is commercially available as a unit. The valve (58) is normally placed in the state shown;
In this state, the pressurized flow from the pump (52) is transferred to the conduit (62).
). However, when fluid flows through the pilot passageway (64), a pressure zone is created at the orifice (66).

When the pressure acting on the right side of the load reduction valve (58), i.e. to the left of the valve, exceeds the pressure acting on the left side, i.e. the right side of the valve, and the resultant force of the compression spring, the valve (58)
turns to the left. When the valve (58) is thus switched, the flow from the pump (52) is routed through the conduit (70) to the liquid l'i! 1 (78). The relationship between this load reduction valve and the booster circuit will be described later. - Output fluid from the main pump (50) is directed via conduit (72) to a pair of center-open, double-acting hydraulic valves (74), (76). The valve (74) controls the main winch hydraulic motor (48) by returning one selective fluid to the reservoir via a conduit (82).A spring-loaded pressure motor (48) with a one-way ratchet A release brake (84) prevents the winch from rewinding when pressure is not applied. The brake (84) is connected to the conduit (82) and is connected to the valve (84).
Pressure exerted on the conduit (82) by 74) rotates the motor (48) in a direction that loosens the rope (44) wrapped around the hydraulic motor (48).

The counterbalance valve (86) of the conduit (80) is also opened -C by the pressure of the conduit (82), thereby allowing the pressurized fluid to flow into the liquid reservoir (7).
Go back to 8). Valve (74) is diverted to direct pressure into conduit (80), thereby causing hydraulic motor (48) I
It is rotated in the direction of winding up the d-Loso (44). A check valve (88) diverts pressure to a balance valve (86). There is no need to release the brake (84) in order to wind up the rope (44), since a one-way ratchet built into the brake (84) prevents unwinding of the rope (44).

Conduit (90 people (92) installed valves (76) and motors (40)
- likewise controls the auxiliary winch (32).

A balance valve (96) of the conduit (90) and a spring biased one-way brake (94) are connected to the conduit (92), which is connected to the rope (64) of the winch (filter 2).
) is pressurized to unwind. A check valve (98) provides a bypass to the balance valve (96). Hydraulic motor (
The operation mode of the valve (76) that controls the valve (74),
This is the same as described for the motor (48).

The rotary motor (100) is controlled by a rotary valve (102) which receives pressurized fluid from a pump (54) via a conduit (104). Conduit (106), (1
o8) connects the valve (102) to the motor (IDO),
These conduits are pressurized and communicate with the liquid reservoir so as to determine the direction of rotation of the upper working part (12) with respect to the platform (14). A pair of check valves' (110), (112) directs makeup fluid into each conduit (106), (108) to prevent cavitation within the motor (100).

The boom lift valve (114) is connected to the second load reduction valve (58).
It receives pressurized fluid from conduit (62) only when in the position shown. The valve (114) is the conduit (116 people (
118> to a hydraulic motor (30) for lifting the boom. Conduit (IIA) is pressurized when the boom tip is lowered, ie when the rope is unwound from the winch (28). The pressure in conduit (118) is directed to a balance valve (120) which causes fluid to return to the reservoir via conduit (116). At the same time, the conduit (
118) is pressurized and pressurizes the pawl release cylinder (122) to disengage the pawl holding the winch (2B)' and the one-way ratchet pressure release brake (124). This lowers the boom. Check valve (j26)
causes the pressure in conduit (116) to bypass balance valve (120). Spring-loaded check valve (12
8) controls the pressurized fluid supplied by the pump (52) through the conduit (62) to the valve (114) whenever the pressure in the conduit (62) exceeds the pressure in the conduit (72) by a predetermined amount. , mixes with pressurized fluid delivered from pump (50) via conduit (72). Therefore, the main winch and the auxiliary winch are connected to the pump (50) and the pump (50) at least during part of the operating time so that both winches can operate faster.
52) Receiving coupling fluid from both. It turns out. The check valve (130) and the pressure release valve (132) are connected to the valve (114).
) to prevent cavitation from occurring and cause the cavity to reoccur when the boom is lowered.

When the load reduction valve (5B) is in the state shown, all functions of the machine are available to the operator.

However, if the hydraulic load on the engine (56) reaches such a level that it is likely to stall the ennon, the pressure in the pilot passage (64) will increase enough to divert the inner relief valve (134), thus causing the pilot passage ( 64) is connected to the liquid tank side of the pump.The fluid flow in the orifice (66) causes a pressure drop in the orifice area, so that the production control valve (58) is diverted to the left side.The pump ( The pressurized fluid flow from 52) is diverted to conduit (70) and conduit (62) is closed off. The load applied to the ennon by pump (52) is effectively removed and the engine stalls. Therefore, the engine can supply not only the maximum power required by the main hydraulic motor and the auxiliary motors (40) and (42), but also the maximum power required by the rotary motor (100). This prevents the vehicle from stalling.

Boom rise limit valve (156) and override valve (13B)
) are connected in series to a conduit (140) extending from the pilot passageway (64) to the liquid reservoir (78). Restriction valve (136
) is normally switched to close the conduit as shown in FIG. 2, and the override valve (13B) is normally open. When the boom tipping motion reaches an acceptable limit, the restriction valve is mechanically diverted to open the conduit (140) and direct fluid flow to the reservoir. This causes a pressure drop in the orifice (66). When there is a difference in pressure on either side of the load reduction valve (58), the valve (58) switches and the pump (
The pressurized fluid from 52) is redirected through conduit (70) towards the liquid tank and conduit (62) is closed. When the manual override valves (1 to 8) are operated, the boom raising circuit is activated again. Manually moving this valve (168) upwardly closes the conduit (140) again so that fluid no longer flows through the orifice, balancing the pressure on both sides of the valve (58) and causing a splash (68) ) again switches the valve (58) to the position shown in FIG.

Figure 6 shows the automatic activation of the boom rise limit valve (136).
- shows the equipment. The valve (136) is mounted on the two legs of the support (26). The valve (166) has a compression spring (14
4) has a spool (142) biased outwardly by.

A bell crank (146) is suspended one rotation from the support by a pin (148). Bell crank (
146) and the upper end of the upper arm (150) and the support (26)
) is tensioned between the tension springs (152) and the upper arm (1
50) is positioned so that it can be secured to the spool (142).

The tension spring (152) applies a force to the compression spring (144) that exceeds the force of the compression spring (144), so that the spool (
142) into the inward position, ie the position of the valve (136) shown schematically in FIG. Bell crank (146
) extends substantially at right angles to the arm (150) and has a roller (154) at its free end.
6) can be freely reprinted. Boom (18) Crab 1
When raised to a position where stress in the boom becomes excessive due to near vertical orientation, the boom (18) engages the rollers (56), causing the bellcrank (146) to move as seen in FIG. Rotate counterclockwise.

The upper arm (150) also rotates and pulls back (152)
The compression spring (144) therefore forces the spout (142) outwardly. As the spool moves outwardly, the valve (136) is diverted and the fluid flow into the conduit (140).
This leads to the results described above. A flexible connecting member or cable (158) is strung between the boom attachment (160) and the upper arm (150) attachment (162). This cable (15B) merely provides a tension force on the boom (18) and becomes loose when the boom is raised. However, when the boom lowers, the cable becomes taut. When the cable (158) is tensioned in this manner, the cable is attached to the upper arm (i
so) away from the spool (142) and the conduit (14
The valve (138) is diverted so that fluid flow is directed to 0). Valve (136) therefore functions to prevent the operator from inadvertently tilting the boom beyond the limits in two directions. Therefore, the load reduction valve (58) which diverts the flow path of the pump (52) that raises the boom is, according to the invention, only prevented from raising or lowering the boom beyond permissible limits. Therefore, it is effectively avoided that a load is applied to the engine that would cause the engine to stall inadvertently.

Although preferred embodiments of the present invention have been illustrated and described as described above, it is obvious that various changes and modifications can be made to the present invention without departing from the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a side elevational view of a bench-mounted version having a hydraulic circuit according to the invention, FIG. 2 is a schematic diagram of the hydraulic circuit according to the invention, and FIG. 3 is a boom lifting limit and lowering. FIG. 3 is a side elevational view of a limiting device for limiting limits;・ 50.52.54 ・Pump 5B, 74.76, 114... Valve 66... Orifice patent application agent Yuki Yamazaki F''IC1ml □1st-3 Procedural amendment 1 Matter A'1 Showa 59 (I Patent Application No. 133455 2 Name of the invention Liquid bar circuit for cranes 3 Relationship with the person making the supplement 1'1 Patent applicant name Name FMC Corporation 4 Agent

Claims (1)

[Claims] (1) A hydraulic circuit for a crane having an engine, which includes a plurality of pumps driven by the engine, and a system in which power from at least one of the pumps is always supplied when the power of the pump exceeds the permissible power of the engine. A hydraulic circuit for a crane comprising a load reduction valve connected to redirect the output to the input side. (2. In the hydraulic circuit for a crane according to claim (1), an orifice that creates a pressure differential in response to fluid flow; a diversion device that redirects the load reduction valve to redirect the output whenever a sufficient pressure difference occurs; C) A crane hydraulic circuit having a boom restriction valve for providing fluid flow. C) A crane hydraulic circuit as claimed in claim (2) coupled in series with the boom restriction valve for providing fluid flow to the orifice. A crane hydraulic circuit containing a manually convertible override valve to prevent