CRANE HAVING A CLOSED HYDRAULIC CIRCUIT

Abstract

A crane, in particular a mobile crane, having a closed hydraulic circuit in which a hydraulic pump is hydraulically connected to at least one hydraulic motor via a feed and a discharge, and in which the feed is hydraulically connected to the discharge via at least one bypass which bypasses the at least one hydraulic motor, wherein the at least one bypass includes a continuously adjustable valve for variably controlling the fluid flow bypassing the at least one hydraulic motor. In addition, a corresponding control device and a corresponding crane control program for actuating a closed hydraulic circuit of a crane are provided.

Claims

1-10. (canceled)

11. A crane having a closed hydraulic circuit in which a hydraulic pump is hydraulically connected to at least one hydraulic motor via a feed and a discharge, and in which the feed is hydraulically connected to the discharge via at least one bypass which bypasses the at least one hydraulic motor, wherein the at least one bypass comprises a continuously adjustable valve for variably controlling the fluid flow bypassing the at least one hydraulic motor.

12. The crane according to claim 11, wherein the at least one bypass comprises a closing valve which is configured to close the bypass to the fluid flow in at least one flowing direction.

13. The crane according to claim 11, wherein the feed is hydraulically connected to the discharge via two bypasses which are connected in parallel and respectively comprise a continuously adjustable valve and a closing valve for variably controlling the fluid flow for the opposing slewing directions of the at least one hydraulic motor.

14. The crane according to claim 11, wherein at least one continuously adjustable valve is a proportional valve.

15. The crane according to claim 11, wherein at least one closing valve is a unidirectional valve.

16. The crane according to claim 11, wherein the delivery flow of the hydraulic pump is able to be variably adjusted.

17. The crane according to claim 11, wherein the volumetric displacement of at least one hydraulic motor is able to be variably adjusted.

18. The crane according to claim 11, further comprising a control device which is in contact with the hydraulic pump and the at least one continuously adjustable valve via at least one interface and is configured to actuate the hydraulic pump and the at least one continuously adjustable valve during crane operations in a co-ordinated way.

19. A control device for actuating a closed hydraulic circuit of a crane according to claim 11, wherein the control device is in contact with the hydraulic pump and the at least one continuously adjustable valve via at least one interface and is configured to actuate the hydraulic pump and the at least one continuously adjustable valve during crane operations in a co-ordinated way.

20. A crane control program for actuating a closed hydraulic circuit of a crane, according to claim 11.

Description

[0020] In the following, a preferred embodiment of the present invention is described in more detail by referring to the enclosed FIGURE. The invention can comprise any of the features described here, individually and in any expedient combination.

[0021] FIG. 1 shows a hydraulic circuit diagram of a closed hydraulic circuit 1 of a crane, in which two hydraulic motors 3, 9 can be supported on the regulatable hydraulic pump 2 both via their shared feed 4 and via their shared discharge 5. It should be noted at this juncture that if the slewing direction of the motors 3, 9 is reversed, the feed 4 performs the function of the discharge, while the discharge 5 performs the function of the feed 4.

[0022] In addition to the hydraulic motors 3, 9 which are connected in parallel, the circuit 1 comprises two bypasses 6A, 6B in opposite directions, which are connected in parallel and bypass the two motors 3, 9. The hydraulic fluid can only flow anti-clockwise through the bypass 6A due to the unidirectional valve 8A and only clockwise through the bypass 6B due to the unidirectional valve 8B. Each of the bypasses 6A, 6B is thus responsible for exactly one slewing direction of the slewing mechanism of the crane (not shown), and the hydraulic fluid flows through it as soon as the proportional valve 7A, 7B assigned to it is opened. As can be seen in FIG. 1, the proportional valves 7A, 7B are held in their closed base position by means of a spring and can be non-incrementally opened by means of an operating member which is not indicated in greater detail. The valves can however also be designed inversely, i.e. opened when there is no flow and then proportionally closed. Depending on the degree to which the respective proportional valve 7A, 7B is open, a portion of the hydraulic fluid will flow through the relevant bypass 6A, 6B and will consequently not be available to drive the motors 3, 9.

[0023] In the following, different operational states of the hydraulic circuit shown in FIG. 1 are described in more detail.

[0024] In an open hydraulic circuit 1, when the joystick is moved, the proportional valve 7A (and/or 7B) assigned to the slewing direction is opened, wherein the hydraulic pump 2 which is configured as an axial piston pump increases the volumetric flow of hydraulic fluid by pivoting out, and the slewing mechanism accelerates as in known closed circuits. Hydraulic fluid does not flow through the proportional valve 7A (and/or 7B), since the higher pressure in the feed 4 acts to close the unidirectional valve 8A.

[0025] When coasting, the proportional valve 7A continues to be open, whereupon the hydraulic pump 2 pivots in and thus reduces the volumetric flow of hydraulic fluid delivered. The load side of the hydraulic motors 3, 9 changes, and circumferential coasting arises, similar to the coasting in previous closed circuits. When controlled in the opposite direction, the proportional valve 7A (and/or 7B) is closed using a ramp function, which increases the pressure in the discharge 5. This ramp function can be controlled or regulated. Once the resting position has been reached, the proportional valve 7B (and/or 7A) of the opposing bypass 6B (and/or 6A) is opened, and the hydraulic pump 2 drives in the other slewing direction. The crane accelerates in the opposite direction.

[0026] The brake pedal (not shown) is coupled to the two valves 7A, 7B, wherein slewing direction recognition defines which of the valves 7A, 7B is to be operated. The corresponding proportional valve 7A, 7B is proportionally closed, and the pump is pivoted in, which reduces the volumetric flow of hydraulic fluid delivered. The braking pressure increases, and the slewing mechanism slows. In order to re-accelerate, the proportional valve 7A, 7B is controlled to open and the hydraulic pump 2 is pivoted out (increasing the volumetric flow). As soon as the driving load pressure is higher than the pressure in the respective discharge 5, the unidirectional valve 8A, 8B closes.