Expansible chamber devices – Displacement control of plural cylinders arranged in... – Having motor-operated adjustment
Reexamination Certificate
2003-05-16
2004-06-01
Look, Edward K. (Department: 2855)
Expansible chamber devices
Displacement control of plural cylinders arranged in...
Having motor-operated adjustment
C092S013700
Reexamination Certificate
active
06742440
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to apparatus, and an accompanying method for use therein, that utilizes first (working) and second (stopping) servo-controlled hydraulic pistons wherein the second piston acts as a controlled mechanical stop for the first piston. Advantageously, the apparatus can controllably stop the first piston, traveling at relatively high speeds, in a very short time and over a very short distance while advantageously inducing very little, if any, elastic strain into the apparatus.
2. Description of the Prior Art
Metallic materials play an indispensable role as an essential component of an enormous number of different products. Such materials are produced
typically in large ingots or other shapes and are controllably deformed by, e.g., rolling, forging or extruding into readily useable and conventional sheet, plate, coil or wire form for subsequent machining or forming. These deformations typically occur on a repeated incremental basis, such as through a multi-stand rolling mill where the material is repeatedly passed through successive pairs of rolls. Each pass incrementally compresses, i.e., deforms, the material into thinner stock. Typically, each pair of rolls is spaced equal distance from the next pair but has a smaller inter-roll spacing (“roll bite”) than the next pair. Hence, as the material becomes thinner it travels at a faster rate through successive roll pairs and this decreases the time occurring between each compression. Extrusion, forging and braking operations also typically involve incremental deformations until the material is properly sized.
In production environments, small incremental deformations are typically produced at high rates. However, correctly configuring a mill, forge or brake to properly deform production stock and impart a desired amount of strain to the material along with other physical/metallurgical characteristics can be a tedious, time-consuming and expensive process—particularly since such a machine needs to be taken out of productive use for an extended time to properly adjust its operational parameters. Consequently, to avoid the need for costly downtime, thermodynamic material testing systems are employed to simulate rolling, extruding, braking and forging processes on relatively small metallic specimens. Resulting simulation data is then used to properly set various operating parameters of production equipment and, by doing so, minimize its non-productive downtime. Illustrative simulators of this type include the “Gleeble” and “Hydrawedge” systems manufactured by Dynamic Systems Inc. (DSI) of Poestenkill, N.Y., which is the present assignee hereof (with “Gleeble” and “Hydrawedge” being registered trademarks owned by DSI).
Systems which deform metallic materials, particularly including material testing systems, often utilize linear motion of a piston/anvil combination produced by servo-controlled hydraulic systems, and particularly those which accelerate and stop pistons at very high speeds. Such movement is necessary to impart a desired amount of deformation to the material, situated, e.g., between a pair of anvils, at a desired strain rate and over as much of a resulting deformation as possible. In these environments, linear piston systems moving with velocities up to 10 meters per second are frequently used, with velocities of 1 to 2 meters per second being quite common.
In particular, in such testing systems, a fundamental problem arises in that a piston, while traveling at such a high relative velocity, must often be stopped in a manner, essentially immediately, through which its velocity does not decrease even over a small distance, else the strain rate imparted to the specimen will decrease over a stopping distance of the piston. Further, those systems typically utilize mechanical mechanisms of one sort or another to stop the piston which, while the piston is being stopped, disadvantageously introduce some strain into various structural components of the system itself. This added strain, by effectively compressing a frame of the system, tends to slightly elongate the stopping distance and thus adversely impact the resulting deformation of the specimen.
Another area in which high-speed deformation is becoming increasingly important is sheet metal processing. Here, a need to reduce production costs requires that press brakes used to deform metallic material, i.e., bend metal sheets, operate at increasingly high speeds. Conventional bending machines have a set of shaped dies in which the material is held and then formed or bent. The dies are mounted in rather large, heavy beam structures. Usually, one beam is mounted rigidly, while another is mounted on linear sliding ways. Traditional brakes rely on producing linear motion for the ways through a large flywheel and suitable connecting/pivoting arms mounted between one beam and the flywheel. Relatively modern brakes control the motion of the die/beam using hydraulic servo-controlled piston/cylinder systems. A precision with which the material can be bent depends upon how quickly the die can be stopped at a bottom of its stroke (travel). As the speed of the die increases, its stopping distance becomes increasingly arbitrary. Given this, the stroke often has to be disadvantageously run at a decreased speed to consistently stop the die at a precise location. Additionally, the metal being deformed often provides a variable load to the die. This variable load causes the control system to compensate while the dies are being stopped at a desired position, but again generally necessitates that reduced speeds are used to obtain precise bends in pieces then being processed. Such decreased speeds disadvantageously reduce material throughput. Hence, to consistently deform material at relatively high speeds and increase throughput, the stroke has to be accurately controlled both in terms of its velocity, throughout the stroke length, as well as its stopping distance.
In situations, be it in material testing systems or in production equipment, where material is being deformed at high-speeds, mechanical stops are often used to stop a high-speed anvil, ram or die at a precise position. Unfortunately, a position of such a mechanical stop has to be changed each time the desired amount of travel is changed.
Therefore, apparatus is needed to stop motion of, e.g., an anvil, a ram or die in an exact position even at very high speeds in order to provide consistent results. Such a stop should impart very little, if any, strain in the apparatus so that the stopping position remains the same regardless of the changes in a load then being deformed. This entails that an end of a high-speed stroke must be precisely controlled as well as being easily and rapidly changeable.
U.S. Pat. No. 5,092,179 (issued to H. S. Ferguson on Mar. 3, 1992) describes one such thermodynamic material testing system. As shown in
FIG. 5
thereof, a stroke of piston
509
and shafts
540
and
545
are stopped by stop disc
543
. A position of specimen material
570
, being deformed, is advanced by hydraulic cylinder
590
, piston
592
, wedge combination
585
/
582
, shaft
575
, load cell
574
, plate
568
, anvil base
565
and anvil
560
′. Each time specimen
570
is advanced by the wedge combination toward the left, anvil
560
is retracted and then rapidly advanced to the right, thus deforming specimen
570
until stop plate
543
hits cross-stop
550
. A drawback inherent in this system is that, during each hit, an amount of strain occurs elastically in an entire wedge assembly that supports a load on the right side of the specimen (load cell side). This elastic strain allows anvil
560
to move in the direction of deformation, thus decreasing the amount of deformation in the specimen and slightly compromising a final thickness of the specimen after each deformation. Once the system has been used to deform a particular specimen at a certain temperature, a computer-controlled deformation schedule (deformation program) that controls the system can be modifi
Chen Wei Chang
Ferguson Hugo S.
Dynamic Systems Inc.
Leslie Michael
Look Edward K.
Michaelson Peter L.
Michaelson & Associates
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