Metal deforming – With means to drive tool – Including pneumatic- or fluid-actuated tool support
Reexamination Certificate
2000-02-03
2001-08-28
Jones, David (Department: 3725)
Metal deforming
With means to drive tool
Including pneumatic- or fluid-actuated tool support
C072S472000, C083S588000, C100S296000
Reexamination Certificate
active
06279370
ABSTRACT:
The present invention relates to an hydraulic arrangement for performing a secondary operation in a pressing tool for sheet metal forming.
The present invention further relates to a method for performing a secondary operation in a pressing tool for sheet metal forming.
In sheet metal forming operations, for example, it is usual to arrange a passive hydraulic system in the pressing tool. This is done in order to be able to shift some of the pressing force to another position and another direction, for example in order to be able to perform yet another operation in the same tool. Such a system can be achieved by arranging a primary hydraulic cylinder/piston unit in a lower tool half in such a way that the piston is pressed into the cylinder when the tool is closed. The oil flow from the primary hydraulic cylinder/piston unit can thus be used in order to produce a stroke in a secondary hydraulic cylinder/piston unit. The timing of the said stroke usually coincides with the closing of the tool but can also be delayed trough the use of a pressurised accumulator for storing the oil that flows from the primary hydraulic cylinder/piston unit, which after a predetermined time delay can be used to produce the stroke in the secondary hydraulic cylinder/piston unit. A device of the aforementioned kind is disclosed in U.S. Pat. No. 5,038 598.
The high pressures associated with the secondary operation of the known devices as well as the relatively large flows occurring for each stroke of the secondary hydraulic cylinder/piston unit requires a substantial amount of energy, which during each stroke is partially transformed into heat which must be removed from the system in order for it to operate satisfactorily.
One object of the present invention is to provide an arrangement , which generates less heat during operation and displays some or all of the advantages stated below.
Another object is to provide a method, which minimises the energy requirements during operation and displays some or all of the advantages stated below.
Preferred embodiments of the arrangement and method according to the present invention also comprise one or more of the characterising features according to the dependent claims.
The inventive design has several advantages in comparison with prior art systems: It generates less heat during operation, wherefore no cooling system is required; the absence of a cooling system makes that the system requires less space, is easier to install and maintain and use; has less pressure variation, which causes less stress to the components; smaller flows, which makes the use of smaller and more accessible components possible; the piston of the first accumulator, of the preferred embodiments, does not encounter a physical stop, which brings about less stress on the first accumulator and less pressure fluctuations in the system; the piston of the primary cylinder/piston unit does not encounter a physical stop, which brings about less stress on this unit. The method according to the invention allows for optimising the energy consumption and thus less heating of the operating fluid.
Preferred embodiments of the invention will be further explained below with reference to drawings enclosed, in which:
FIG. 1
shows a preferred embodiment of the arrangement in accordance with the invention;
FIG. 2
shows a second embodiment which is similar to the preferred embodiment but utilises a pressure controlled non-return valve, having the same function as the pressure controlled two way valve of the preferred embodiment;
FIG. 3
shows a third embodiment, which is also similar to the second embodiment and utilises a 3-2 , valve to control the work and return strokes of the secondary cylinder/piston unit;
FIG. 4
shows a fourth embodiment using a low and a high pressure accumulator and lacking some of the advantages of the embodiments in accordance with
FIGS. 1
to
3
.
REFERENCES:
patent: 4148209 (1979-04-01), Bessho
patent: 4209987 (1980-07-01), Kononov et al.
patent: 4321818 (1982-03-01), Bessho
patent: 5038598 (1991-08-01), Pitzer
patent: 5640877 (1997-06-01), Danly, Sr.
patent: 5855114 (1999-01-01), Runesson
Altera Law Group LLC
Jones David
Stromsholmen AB
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