Metal deforming – With indication of condition or position of work – product,... – Work drawn or extruded through die
Patent
1997-01-08
1999-01-12
Jones, David
Metal deforming
With indication of condition or position of work, product,...
Work drawn or extruded through die
72 173, 72 215, 723893, 723895, B21D 502
Patent
active
058573666
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method of bending processing (i.e., bending) of works (i.e., workpieces) with a press brake and a press brake for use in the same method, and more particularly, to a method of bending processing in which, after bending angles at plural positions of a sheet-shaped work are measured by trial bending thereof, an engagement positional relation between the upper tool and lower die is corrected according to the measured actual bending angles to achieve accurate bending processing of the work at a target bending angle, and a press brake for use in the same method.
Further, the present invention relates to a bending processing apparatus, and more particularly, to a press brake comprising a control unit for calculating a D value of a distance from the bottom of a die to the tip of a punch so as to control the press brake.
BACKGROUND ART
As schematically shown in FIG. 6, a conventional press brake comprises a upper apron 7 (alternatively referred to as a upper table or a fixed table) fixed on a left and right side frame 5L, 5R respectively mounted on a base 3, and a lower apron 9 (or referred to as a lower table or a movable table) provided so as to oppose the upper apron 7, the lower apron being vertically movable.
Hydraulic cylinders 11L, 11R are provided on the left and right sides respectively to move the above lower apron 9 vertically. At appropriate positions of the lower apron 9, crowning cylinders 13 are provided to compensate for a downward curve in the lower apron 9 generated at the time of bending a sheet-shaped work W.
The same Figure shows a case in which two crowning cylinders 13 are provided, however crowning cylinders may be provided in the center of the lower apron 9 or the upper apron 7. That is, the crowning cylinders may be provided in an arbitrary number, and may be provided on either the upper apron 7 or the lower apron 9.
An upper tool 15 is installed on the bottom of the upper apron 7 and a lower die 17 is installed on the top of the lower apron 9.
According to the above-described construction, hydraulic oil is supplied to the left and right hydraulic cylinders 11L, 11R. As a result, the lower apron 9 is raised so as to engage the upper tool and lower die 15, 17 appropriately, such that the work W is bent and processed by the upper tool and lower die 15, 17.
When the work W is bent as described above, the upper apron 7 is inclined to curve so as to protrude upward and the lower apron 9 is inclined to curve so as to protrude downward. As a result, the bending shape of the work W becomes so-called "ship-shaped" so that the center portion thereof tends to be loose.
Thus, to correct the curve of the lower apron 9, a pressurized oil is supplied to the crowning cylinders 13 and the curve is corrected in a trial and error manner to make the upper and lower aprons parallel to each other, which consumes a significant amount of time.
Moreover, the bending angle of the work W can be arbitrarily set by controlling the engagement positional relation between the upper tool and lower die 15, 17. To control the engagement positional relation between the upper tool and lower die 15, 17, the ascent stop position of the lower apron 9 can be arbitrarily set.
That is, as schematically shown in FIG. 7, hydraulic pumps P are connected to the left and right hydraulic cylinders 11L, 11R. With respect to the connection of the hydraulic pump P to the left and right hydraulic cylinders 11L, 11R, separate hydraulic pumps may be connected thereto separately or a single hydraulic pump may be connected thereto through branching.
A connecting oil path 19, connecting to the hydraulic pump P and the left and right hydraulic cylinders 11L, 11R, is connected to a branch line 23, which is connected to an upper limit valve 21.
In the above upper limit valve 21, a valve 21V is pressed by a spool 21S against the pressure of a spring SP to control the degree of opening between the valve 21V and the seat SE, so that hydraulic oil flowing from the branch line 23 to a tank T is controlled.
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Amada Company Ltd.
Jones David
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