FIELD OF THE INVENTION

The invention relates to a valve having a valve housing, which has at least one pressure supply port, a first utility port, a second utility port and a return port. A control spool is guided in a longitudinally movable manner in the valve housing for controlling these individual ports. The fluid connections between the ports are interrupted in a central neutral position of the control spool. When the control spool moves from the neutral position in the direction of a first end position of the control spool, the pressure supply port is connected to the first utility port, and the second utility port is connected to the return port in a fluid-conveying manner. When the control spool moves from the neutral position in the direction of a second end position of the control spool opposite from the first end position, the pressure supply port is connected to the second utility port, and the first utility port is connected to the return port. The utility ports are separated from each other in the end positions of the control spool.

The invention further relates to a valve having a valve housing, which has a first utility port and a second utility port. A control spool is guided in a longitudinally movable manner in the valve housing for controlling these utility ports. A fluid connection between the utility ports can be established by moving the control spool from a neutral position.

BACKGROUND OF THE INVENTION

Such valves, which are used to operate hydraulic motors or differential cylinders, are known in the state of the art. In particular for differential cylinders, which lift or lower masses, it has proven to be advantageous to feed the hydraulic fluid displaced from one working chamber directly into the other working chamber when the piston moves, instead of letting the hydraulic fluid flow unused out of one working chamber in the direction of the tank and in parallel pumping it out of the tank into the other working chamber, thereby consuming a lot of energy.

For this purpose, valves have been developed in the past, which, in addition to the lift-neutral-lower positions, also feature a floating position, in which the piston of the differential cylinder can move freely, and a rapid traverse, in which the piston moves faster: DE 10 2008 008 092 A1 and DE 10 2007 054 137 A1. The rapid traverse is also called regeneration. The logic of the positions of the valve spool is lifting-neutral-lowering-regenerate-floating in DE 10 2008 008 092 A1. In the case of DE 10 2007 054 137 A1 the logic is regenerate-lifting-neutral-lowering-floating.

If the valves are additionally formed as load-sensing valves, in which a load pressure is detected in particular at one of the utility ports and is transmitted to an upstream individual pressure compensator valve and/or a hydraulic pump, it has been shown that a lot of energy is wasted during operation. Also, during parallel operation of several valves situations occur in which the valves consume a larger pump volume flow than the pump can supply. This condition is also known as undersaturation. There are two load cases during lifting and lowering loads using a differential cylinder, in which cases the behavior of the known valves is particularly energy inefficient: (1) lifting at low load and (2) lowering at high load.

In the first load case of “lifting at low load”, the valve connects a bottom side of the differential cylinder to a pump and its rod side to a tank. In that case, the pump has to provide all the hydraulic fluid needed to extend the piston, for which however only a small pressure is required. If now in a system further functions are operated in parallel, to which higher loads are applied, a pressure compensator valve has to be used to regulate the pump pressure down to a level that is appropriate for the low load. Hydraulic fluid then uselessly drains to the tank. A further problem is that in this case the valve may consume such a large pump flow that the functions operated in parallel cannot be adequately supplied, and therefore, become slower, although theoretically there is enough energy available to operate all the functions.

In the second load case of “lowering at high load,” the valve connects a highly pressurized bottom side to the tank and connects the rod side to the pump. In this case, the hydraulic fluid flows unused from the bottom side to the tank, and hydraulic fluid has to be supplied in parallel at the rod side. In this case, the self-weight of the load is usually sufficient to lower the load without requiring the support of the pump.

SUMMARY OF THE INVENTION

Based on this state of the art, the invention addresses the problem of providing an improved valve having a higher energy efficiency and a simpler structure.

This problem is basically solved by valves having, between the neutral position and one of the end positions, a regeneration position is provided, in which the utility ports are interconnected in a fluid-conveying manner, or a floating position is provided, in which the utility ports are interconnected in a fluid-conveying manner.

In this way, the more energy-efficient logics of neutral-regeneration-lifting or neutral-floating-lowering can be implemented, ensuring that the hydraulic fluid available in the differential cylinder is first used to move the load before the pump supplies additional hydraulic fluid. A very small pump volume flow is then required for the load case of “lifting at low load” and in the load case of “lowering at high load” it may even possible that no pump volume flow is required at all.

Particularly advantageously, in the regeneration position the first utility port is connected to the second utility port via the pressure supply port, preferably via at least two circumferential recesses at the control spool, in a fluid-conveying manner. Thus, compared to a conventional 4/3 directional control valve, a regeneration position can be provided by only one additional recess at the control spool. That regeneration position permits considerable savings in pump power. It is advantageous if the second utility port is exclusively connected to the pressure supply port in the regeneration position and, in that way, is separated from the return port.

In the floating position, the first utility port can be connected to the second utility port via the return port, preferably via two circumferential recesses at the control spool, in a fluid-conveying manner. Again, only one additional recess at the control spool is required to provide this functionality. The fluid can then flow from one utility port to the other utility port via the return port. It is advantageous if the second utility port is exclusively connected to the return port in the floating position and is in that way separated from the pressure supply port.

The regeneration position may be advantageously provided between the neutral position and the first end position of the control spool, in particular the end position for lifting. The floating position is provided between the neutral position and the second end position of the control spool, in particular the position for lowering. In this case the spool logic is built in such a way that the floating position and the regeneration position are arranged symmetrically around the neutral position. The pump power then can be reduced, both for lifting and for lowering.

In a particularly advantageous embodiment, the control spool can have two utility port recesses, which overlap with the utility ports and a further regeneration recess, which is located between the utility port recesses. In addition, or alternatively, the control spool may have a floating recess, which is located between a utility port recess and an adjacent free end of the control spool. In this way, the control spool does not have to be extended to form the functionalities. The recesses can be advantageously provided in an existing spool of a 4/3 directional control valve.

In the valve housing, a load-sensing line can also be provided, which is de-pressurized in the neutral position of the control spool via a recess of the control spool towards the return port. In particular, a groove in the control spool can connect a section of the load-sensing line, which opens out at the control spool, to the return port.

Advantageously, the load-sensing line is directly connected to one of the utility ports when the control spool is out of the neutral position. For this purpose, two sections of the load-sensing line between the utility ports can open out into a control spool bore. One of the sections each can be brought into connection with the assigned utility port by the control spool.

To switch the control spool to the correct positions, pressure sensors may be connected to the utility ports, which are connected to a control device that controls the motions of the control spool. In this way, the load situation can be determined before the valve is switched, i.e. whether it is possible to lift or lower the load in the regeneration position or the floating position. If this is not possible, it is immediately switched to one of the positions lifting or lowering.

The recesses of the control spool may have at least one proportional opening edge having at least one control groove. The control groove can be essentially triangular in shape. Furthermore, several control grooves may be distributed along the opening edge and arranged at the respective recess. The control grooves permit the load to move without jerking, and pressure peaks in the system are prevented.

For moving the control spool, an electromechanical actuator can be provided. This actuator permits the precise position control of the spool and a smooth transition between the control spool positions.

In a second solution of the problem, a valve is provided with a valve housing, which has a first utility port and a second utility port, and in which a control spool is guided in a longitudinally movable manner for controlling these utility ports. A fluid connection between the utility ports can be established by the motion of the control spool from a neutral position. This valve is characterized in that the fluid connection between the utility ports are interruptible by a further motion of the control spool in the same direction.

Each feature of the valve according to the invention can be used individually or in combination with others. The drawings are purely schematic and not to scale. In the Figures:

Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the drawings, discloses a preferred embodiment of the present invention.

