Motors: expansible chamber type – With signal – indicator or inspection means
Reexamination Certificate
2002-09-26
2004-11-09
Look, Edward K. (Department: 3745)
Motors: expansible chamber type
With signal, indicator or inspection means
Reexamination Certificate
active
06813987
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Description
The invention concerns an electrohydraulic monitoring device for a dual effect (bi-directional) hydraulic cylinder.
The invention concerns an electrohydraulic monitoring device for a dual effect hydraulic cylinder, wherein the cylinder is divided into two pressure spaces by a cylinder piston, wherein the piston of the hydraulic cylinder and the cylinder housing are configurable into two alternative operating configurations for different functions by the alternative application and relief of pressure to the pressure spaces, and wherein—for example—for safety reasons, the maintenance of a defined operating pressure is necessary, and having the further generic features set forth below. The monitoring device of this type is known from DE-PS 23 10 193.
2. Description of the Related Art
The above-mentioned known monitoring device is realized with an integrated construction, with a pressure reduction valve for adjusting the operating pressure configured in such a manner that functional elements of the pressure reduction valve are also used as functional elements of the monitoring device. The pressure reduction valve is received in a central segment of a borehole extending centrally through a longitudinally extending block-shaped housing. The pressure reduction valve includes a basically cylindrical pot shaped housing part sealed laminarly against the housing borehole, within which a valve piston is sealed laminarly and moveable by pressure within the housing part and supported via a radial flange against the free ring end surface of the cylinder jacket of the pot shaped housing part. A compression helical spring acts on the side of this piston opposite the valve housing, while for its part the pressure reduction valve opposing end is supported against a piston provided slideably pressure-tight in the housing borehole, of which the position within the housing borehole is variable in defined manner for adjustment of a defined pretension of this valve spring by means of a spindle drive means, of which a spindle nut provides the closure of the central borehole on the end of the housing block opposite to the valve. On the side of the pressure reduction valve opposite to the valve spring the central borehole is closed off by a cylindrical pot shaped housing closure part seated in the borehole in the base area fixed to the housing for closing the central borehole, wherein the ring end face of the tubular shaped jacket of the housing closure part facing the movable housing of the pressure reduction valve provides a housing fixed abutment for the valve housing, which demarks at the same time the zero setting or normal position of the valve housing as well as the end position, in which the valve housing of the pressure reduction valve is biased or pushed by the effect of the its valve spring. In this zero position of the valve housing a pushrod or tappet shaped projection of an “inner” sensor piston projects—extending through a central borehole of the base part of the housing closure part and sealed off thereagainst by means of a housing fixed ring seal—and seated pressure tight yet slideable within the inside of a tubular shaped segment of the housing closure part, and extending so far axially out of the housing closure part, that an electrical switch provides an electrical output signal characteristic of the position of the housing of the pressure reduction valve. This sensor piston is supported on the valve housing via a short axial rod-shaped projection on the valve housing, supported on the valve housing side. Between the flange shaped sensor piston setting off or delimiting the two rod shaped projections from each other and the base of the housing closure part, the pushrod shaped piston projection provided for switch operation is surrounded by a ring piston, which is sealed radially inwardly by a further ring seal against the pushrod shaped projection of the flange shaped piston and radially outwardly sealed by means of a sealing flange against the inner cylindrical jacket surface of the housing closure part, wherein this sealing flange on the one hand forms the axial—moveable—border or limit of a sensor chamber, which is bordered housing fixed by the base of the housing closure part, and at the other hand is bordered or limited by the axial border of a second sensor chamber, bordered by a flange shaped sensor piston supported directly on the valve housing and axially moveable. The housing internal space extending between the base of the valve housing and the sensor piston supported thereupon and the receiving space for the valve spring are in communication with each other via housing fixed channels and are thus under the same pressure as the central return flow circuit of the hydraulic system returning to the supply reservoir, which may be lower than that of the operating pressure to be coupled into the monitored hydraulic cylinder of the pressure reduction valve, however may be subjected to significant oscillations or pressure fluctuations of several bar, for example 5 bar. This type of pressure fluctuation could be suppressed by a special leak oil line, which however would be associated with additional expense and complexity. The sensor chambers separated pressure tight from each other by the ring piston are each individually connected to one of the pressure or operating spaces of the double acting hydraulic cylinder, which, depending upon operating mode of the hydraulic cylinder, are alternatively acted upon by the exit or output pressure of the pressure reduction valve, respectively, depending upon the switch position of the operating mode selection valve. The ring surfaces, upon which the sensor pistons are acted upon by the operating pressure existing in the hydraulic cylinder, are so dimensioned, that, as soon as in one of the sensor chambers an operating pressure of a defined high proportion of, for example, 80% of the setting of the valve spring as predetermined by presetting of the valve spring, is reached, which causes the flange shaped sensor position supported on the valve housing to slide relative to the valve housing, whereby the valve housing is axially deflected out of its base position or starting position relative to the housing closure part and with significant increase of the pretension of the valve spring, executes a deflection stroke a to a second position marked or defined by an inner abutment ring of the housing, which corresponds to a control position of the valve piston, in which the pressure supplied or coupled in to the cylinder is slightly higher than that pressure, which corresponds to the valve spring pretension, which was preset during the adjustment operation of the pressure reduction valve.
Independent there of which operating mode the main cylinder is being operated in, that is, in which of its operating or pressure spaces the operating pressure needs to be built up, this coupling in into one of its two sensor chambers always leads thereto, that the valve housing reaches its end position deflected by the stroke a relative from its “pressureless” starting position. There in there is, depending upon in which sensor space the monitored pressure is coupled in, either the valve housing closest sensor piston alone is forced towards the valve housing and the other against the base of the housing closure part, or both sensor pistons are collectively pushed towards the valve housing. In both cases the rod shaped pushrod projection of the sensor piston on the valve side lifts off from the operating element of the switch, whereupon this, after the valve housing has carried out approximately a/2 of the deflection stroke, returns to its starting position, in which the switch starting signal indicates, that the operating pressure in the main cylinder is achieved, that is, the hydraulic device is operating as normal. If the actuating or operating pressure is not achieved for reason of some malfunction or defect, then this signal does not occur, and a signal combination remains established, which for
Hartmann & Laemmle GmbH & Co. KG
Leslie Michael
Look Edward K.
Pendorf & Cutliff
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