Valves and valve actuation – Fluid actuated or retarded – Pilot or servo type motor
Patent
1997-07-03
1999-11-09
Lee, Kevin
Valves and valve actuation
Fluid actuated or retarded
Pilot or servo type motor
251 3003, 13759616, F16K 1710
Patent
active
059798629
DESCRIPTION:
BRIEF SUMMARY
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a pilot-operated proportional pressure limiting valve. The invention also relates to a method of operating a pressure limiting valve.
Pilot-operated proportional pressure limiting valves are known. One known proportional pressure limiting valve is described in the book "Der Hydraulik Trainer", Vol. 2, published by Mannesmann Rexroth GmbH, Lohr/Main, pages B20 and B21.
From DE 38 24 089 A1 a pilot-operated proportional pressure limiting valve having a control oil nozzle arranged in a main piston is known. In order to obtain a very small adjustable pressure, the outlet of a control oil nozzle for the feeding of control oil to a pilot-operated valve is brought directly out of the main piston by connecting means.
The proportional pressure limiting valve in accordance with DE 38 24 089 A1 tends under certain circumstances to vibrate in the region of small volumetric flows and high pressure. Therefore, a damping nozzle is already provided in the main piston in the valve according to DE 38 24 089 A1. Since, however, within the above-indicated range, the control stroke of the main piston is very small and thus the volume of control oil displaced via the damping nozzle from the control space is also very small, the damping action of the damping nozzle on the control stroke of the main piston is too weak and the valve cannot be prevented from vibrating within this region.
SUMMARY OF THE INVENTION
The object of the present invention is, therefore, to avoid the disadvantages of the prior art, in particular also in the region of small volumetric flows and high pressure, to obtain an excellent damping of the main piston in order, in particular, to prevent the valve from vibrating.
BRIEF DESCRIPTION OF THE DRAWINGS
With the above and other objects and advantages in view, the present invention will become more clearly understood in connection with the detailed description of preferred embodiments, when considered with the accompanying drawings of which:
FIG. 1 diagrammatically shows a longitudinal section through a pilot-operated proportional pressure limiting valve according to a first embodiment of the present invention;
FIG. 2 diagrammatically shows a longitudinal section through a pilot-operated proportional pressure limiting valve according to a second embodiment of the present invention;
FIG. 3 diagrammatically shows a longitudinal section through a pilot-operated proportional pressure limiting valve according to a third embodiment of the present invention;
FIG. 4 diagrammatically shows a longitudinal section through a pilot-operated proportional pressure limiting valve according to a fourth embodiment of the present invention; and
FIG. 5 diagrammatically shows a pilot-operated proportional pressure limiting valve in accordance with the prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The valve 1 of FIG. 5 consists of a main valve 2 and a pilot valve 3. A pump is designated 5 and a tank 6. The pilot valve 3 has a proportional magnet 8 which can act via a magnetic ram 11 on a pilot cone 13.
The main valve 2 has a bushing 14 inserted into a recess in a housing 12 closed by a cover 4, a main piston 16 which is urged by a closure spring 17 against its seat being arranged in said bushing. Within the bushing 14 there is an axially extending inlet hole 18 as well as several radially extending outlet holes 19. The pump 5 is in communication via a line 21 with the inlet hole 18, while the outlet holes 19 are in communication with the tank 6 via a line 20. The pressure in the inlet hole 16 urges the main piston 16 in opening direction.
In order to produce a precontrol or pilot pressure, the inlet hole 18 is connected via a control oil nozzle 7 and a damping nozzle 9 to the spring or control chamber 22. A pressure in the control chamber 22 urges the main piston 16 in closing direction. The point of connection 25 of the two nozzles 7 and 9 is connected, via another nozzle 12 which also has the function of a damping nozzle, with a pressur
REFERENCES:
patent: 5328147 (1994-07-01), Stobbs
Der Hydraulik Trainer, vol. 2, published by Mannesmann Rexroth GmbH, Lohr/Main, Germany, pp. B20 and B21, Jan. 1986.
Farber Martin A.
Lee Kevin
Mannesman Rexroth AG
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