Motors: expansible chamber type – With motive fluid valve – Contracting chamber exhaust valve controlled by expanding...
Patent
1989-06-16
1990-09-25
Look, Edward K.
Motors: expansible chamber type
With motive fluid valve
Contracting chamber exhaust valve controlled by expanding...
91433, 91415, 91392, F15B 1108
Patent
active
049585487
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a hydraulic drive mechanism for a machine element such as, for example, a punching or embossing tool executing, during a course of a machining cycle of a workpiece, a rapid feed movement toward the workpiece, thereupon with the same travel direction the working stroke, and subsequently thereto a rapid retraction movement leading back into the starting position.
A number of drive mechanisms of the aforementioned type have been proposed; however, problems are encountered in such drive mechanisms in the load-responsive switchover of the differential hydrocylinder, provided as the drive element, from rapid feed operation, wherein a large as well as small working areas of the drive piston are pressurized but wherein the maximally attainable feeding power is reduced by the ratio of the small to the large piston area, into the under-load feed operation wherein only the larger piston area is acted upon by the initial pressure of the pressure supply unit but the small piston area is pressure-relieved, which is necessary if the feeding power deployable in rapid feed operation is insufficient, for example, for penetrating the workpiece in a punching operation. When choosing a distance-dependent control of the transition from rapid feed operation to under-load feed operation, the disadvantage arises that in cases where the feeding power deployable in rapid feed operation would be adequate, and thus operation could be continued in rapid feed mode, too long cycle times must be tolerated. In order to be able to obtain a time saving in this respect, the choice is thus frequently to switch over from rapid feed operation to under-load feed operation in dependence upon the operating pressure. In other words, once the pressure in the drive pressure chambers of the differential cylinder has exceeded a threshold value, switchover is effected by an area switching valve that is pressure-controlled from rapid feed operation to under-load feed operation. However, in such a case, care must be taken that the under-load feed operation is maintained for a sufficient period of time to ensure that the pressure-controlled valve does not switch over "too early" again to rapid feed operation which could lead to undesirable vibrations and, in the extreme case, to an approximate standstill of the tool.
In order to overcome the above-mentioned problem, consideration could be given to equipping the pressure-controlled valve with an electromagnetic holding control unit in such a way that it additionally includes a control magnet maintaining the valve as soon as the latter has been switched over in dependence upon the pressure from rapid feed operation to under-load feed operation for a defined period of time in the functional position providing for under-load feed operation. However, in order to be able to utilize optimally short cycle periods, this procedure would have the consequence that the delay time during which the valve, to be switched in dependence upon the pressure, is maintained in its under-load operation function mode would have to be adapted in each case to the material thickness of the material to be worked upon. This would not only entail a considerable time consumption but also, in many cases, would result in erroneous settings which, in turn, would lead to unnecessarily long cycle times.
Therefore, it is an object of the present invention to improve a hydraulic drive mechanism of the type discussed hereinabove so that a need-responsive switchover of the drive mechanism from rapid feed operation to under-load feed operation and from the latter again to rapid feed operation and, respectively, final rapid retraction operation is made possible, independently of the thickness of a workpiece to be machined.
In accordance with advantageous features of the present invention, the hydraulic drive mechanism for a machine element such as, for example, a punching tool or an embossing tool, executing, during a course of a machining cycle of a workpiece, a rapid feed movement leading to th
REFERENCES:
patent: 4205591 (1980-03-01), Mickelson
patent: 4256017 (1981-03-01), Eastman
patent: 4445421 (1984-05-01), Walker et al.
patent: 4461449 (1984-07-01), Turner
patent: 4597557 (1986-01-01), Krieger et al.
patent: 4716812 (1988-01-01), Koerner et al.
patent: 4727797 (1988-03-01), Haussler
patent: 4765227 (1988-08-01), Balazs et al.
patent: 4771674 (1988-09-01), Hugdahl
Denion Thomas E.
Look Edward K.
LandOfFree
Hydraulic drive mechanism does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic drive mechanism, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic drive mechanism will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-323690