Directional-control valve

Details Directional-control valve Directional-control valve

1999-10-07

2001-03-13

Michalsky, Gerald A. (Department: 3753)

Fluid handling

With indicator, register, recorder, alarm or inspection means

Position or extent of motion indicator

C137S625640, C251S051000

Reexamination Certificate

active

06199585

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a directional control valve with an axially displaceable control piston in the interior of a valve housing and a travel sensor to detect the position of the control piston. The travel sensor has a pressure-tight travel sensor tube sealed at one end, with a directional transmitter rod telescoped in the opening at the other end. The rod is fastened to the control piston and extends in the direction of its axial displacement through a passage connecting the valve housing interior chamber with the travel sensor tube.
BACKGROUND OF THE INVENTION
A proportional modular valve, with an axially displaceable control piston and a travel sensor for the control piston, is manufactured by the Mannesmann Rexroth Aktiengesellscaft, and is commercially available under the reference 3WRC. Such valves preferably adjust the volume of hydraulic oil flows, for instance with forging equipment, power press cylinders, dye casting machinery and the like.
These valves are characterized by simple construction, because the travel sensor by virtue of its pressure-tight construction can be mounted directly in the passage of the valve housing. The directional transmitter rod extends out of the valve housing interior chamber and into the opening of the travel sensor tube. Since with this type of structure the user pressure prevailing in the passage is also effective in the pressure-tight travel sensor tube, the danger exists that, in cases wherein high pressure peaks with steep gradient sides occur in the user pressure, plastic bulging or expanding of the pressure-tight travel sensor tube can occur. This frequently leads to disturbances in position detection, especially in the case of the use of inductive travel sensors with coil bodies positioned on the travel sensor tube. The winding can tear, leading to breakdown of the associated control electronics, and with that the breakdown of the valve.
SUMMARY OF THE INVENTION
Objects of the present invention are to provide a directional control valve with an axially displaceable control piston and a travel sensor for detecting the control piston position that is an improvement in comparison with other such valves because of a higher quality of operation.
The foregoing objects are basically attained according to the present invention with a directional control valve, comprising a valve housing having an interior chamber and a passage, a control piston axially displaceable in the interior chamber, and a travel sensor mounted on the housing to detect positions of the control piston. The travel sensor has a travel sensor tube and a directional transmitter rod. The sensor tube is connected to the interior chamber through the passage, is sealed pressure-tight at one end thereof and has an opening at a second end thereof. The transmitter rod is telescopically displaced in the opening, is fixedly coupled to the control piston and extends in direction of axial displacement thereof through the passage. A seal is in the passage between the interior chamber and the opening of the travel sensor tube. The seal controls opening dimensions of a dampening gap and forms a throttle point allowing oil flow into the travel sensor tube. The seal includes a check valve blocking oil flow into the travel sensor tube.
The throttling of the oil flow in the travel sensor tube provided according to the present invention dampens the volume of hydraulic oil flow occurring when a pressure peak occurs in the user pressure. This sufficiently throttles the flow in the direction of the travel sensor that rising pressure in the travel sensor tube no longer leads to plastic deformation of the tube, and consequently to impairment of the function of the position detection of the travel sensor.
With one preferred embodiment, the seal mounted in the passage forms the dampening gap. With the check valve, oil which is expelled with the telescoping movements of the directional transmitter rod in the travel sensor tube can flow back over the check valve to the interior chamber of the valve housing. Thus, even the occurrence of compression pressure peaks in the travel sensor tube resulting from telescoping movements of the directional transmitter rod is avoided.
Preferably the dampening gap is provided on the valve body of the check valve.
This valve body can be constructed in an especially advantageous embodiment as a perforated disk having a central passage opening. Its side facing the travel sensor tube can cooperate with a shoulder surface serving as valve seat surface, constructed on a setoff of the passage. The perforated disk with its passage opening can be guided on the directional transmitter rod with a degree of play forming the dampening gap.
Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.


REFERENCES:
patent: 3551620 (1970-12-01), Hoover
patent: 4342331 (1982-08-01), Bartholomaus et al.
patent: 4478245 (1984-10-01), Bender
patent: 4593719 (1986-06-01), Leonard
patent: 4850394 (1989-07-01), Imhof et al.
patent: 4938118 (1990-07-01), Wolfges et al.
patent: 5553827 (1996-09-01), Perkey
patent: 3236636 (1984-04-01), None
patent: 3420400 (1985-12-01), None
patent: 9015899 (1991-02-01), None
patent: 0124242 (1984-11-01), None

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