Pumps – With condition responsive pumped fluid control – Responsive to pump created drive motor condition
Patent
1994-02-15
1996-05-28
Bertsch, Richard A.
Pumps
With condition responsive pumped fluid control
Responsive to pump created drive motor condition
417 46, 417297, 417403, 417509, 417900, F04B 1502, F04B 4903
Patent
active
055205216
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a hydraulic control device for a viscous fluid pump that includes at least one feed cylinder drivable by means of a hydraulic cylinder.
BACKGROUND OF THE INVENTION
Hydraulic control devices such as are known from German Patent Document DE 38 33 845 A1 are used to control two-cylinder viscous fluid pumps. The feed cylinders of these pumps are each driven by a hydraulic linear cylinder, work in a push-pull operation. In other words, one cylinder feeds, while the other--in the so-called suction stroke--is loaded with material to be transported, for example with concrete. The alternating opening of the feed chambers of the two feed cylinders toward the storage container containing the material to be transported and the alternating connecting of the feed chambers to a feed line is done by a tube switch. This switch controls both the function of an inlet valve for the feed cylinders which, through a changeover of the tube switch, moves into a communicating connection with the storage container, and also the function of an outlet valve for the feed cylinder carrying out the feeding stroke, the feed chamber of which feed cylinder being connected to the extended feed line. To changeover the tube switch to the two alternative feed paths, hydraulic linear cylinders acting in opposite directions are provided. The pistons of these cylinders are kinematically positively coupled with one another through the tube switch and can be reversed through an alternating pressure loading and pressure relief of the bottom-side control chambers of the two linear cylinders.
The feed line, which can be connected alternatingly to the feed chambers of the feed cylinder through the tube switch, can be blocked from the tube switch by means of a shutoff device controlling the function of the outlet valve. This shutoff device is a seated valve which can be moved into its blocking position by a bottom-side pressure loading of a hydraulic control cylinder, in which blocking position the feed line is blocked off from the tube switch. After the pressure relief of the bottom-side control chamber toward the tank of the pressure-supply plant, this valve is moved into its open position connecting the tube switch to the feed line by the pressure developing during the feeding operation in the respective feed cylinder in its feed chamber. To control the feeding operation of the viscous fluid pump, a sequence control is provided which reacts to hydraulic or electrical outlet signals from the end-position indicators which monitor the positions of the drive cylinders of the feed cylinders, the control cylinders for the tube switch and the control cylinder of the shutoff device. This sequence control ensures that the feed cylinders are actuated to carry out the feeding or loading stroke until after the tube switch has been moved into the operating position suited for the feeding and loading operation of the feed cylinders. The flow path, through which the pressure loading of the control cylinder in the sense of a closing movement of the shutoff device occurs, leads through a check valve, which is loaded in an opening direction by the high control pressure. The relief path, through which pressure medium can discharge from the bottom-side drive chamber of the control cylinder, is guided through a pressure-limiting valve which is connected in parallel to the check valve. This pressure-limiting valve is set in its open position as soon as the pressure--during the feeding operation--exceeds an adjustable presettable value. This is supposed to occur so that the shutoff device opens only when the pressure in the feed chamber of the respective feed cylinder operating in the feeding operation corresponds approximately to the pressure existing in the feed line in order to achieve a desired pre-compression of the material being transported in the feed chamber and to avoid uneven operation of the pump caused by the pressure differences between the feed chamber and the feed line.
This type of changeover of the shutof
REFERENCES:
patent: 3205906 (1965-09-01), Wilkinson et al.
patent: 3494290 (1970-02-01), Schaible
patent: 5222872 (1993-06-01), Marian et al.
patent: 5316453 (1994-05-01), Schwing
Benckert Hartmut
Muenzenmaier Werner
Renz Hans
Bertsch Richard A.
Putzmeister-Werk Maschinenfabrik GmbH
Wicker William
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