[0001] The present invention relates to an active cambering device of bending presses.
[0002] Currently, in bending presses, comprising an upper beam and a lower beam, it is known
to use a cambering circuit, which comprises a high-capacity pump, in which the deformation
of the jacks is controlled by a proportional pressure valve that performs this control
by operating on the pressure of the circuit.
[0003] In order to do this, large quantities of oil must be drained and therefore large
amounts of energy are wasted uselessly because of the construction of this type of
valve.
[0004] Therefore, there are high management costs, also because the time necessary in order
to perform the manufacturing cycle increases and therefore productivity decreases.
[0005] The aim of the present invention is therefore to solve the above technical problems,
eliminating the drawbacks of the cited background art, by providing a device that
makes it possible to achieve higher energy savings.
[0006] Within this aim, an object of the invention is to provide a device that allows activating
the press in very short times by supplying, in a set pressure range, large instantaneous
oil flows.
[0007] Another object of the invention is to allow the use of only the amount of oil that
is necessary, avoiding discharging the pressurized excess uselessly.
[0008] Another object of the invention is to allow having a lower installed power.
[0009] Another object of the invention is to allow achieving a higher reaction speed of
the cambering, reducing the cycle time and increasing productivity.
[0010] Another object is to obtain a device that is structurally simple, has low manufacturing
costs and can be provided with usual known plants.
[0011] This aim and these and other objects that will become more apparent hereinafter are
achieved by an active cambering device of bending presses comprising an upper beam
and a lower beam,
characterized in that it comprises a pump adapted to load at least one accumulator, said accumulator being
adapted to actuate said lower beam by means of a proportional direction valve.
[0012] Further characteristics and advantages of the present invention will become more
apparent from the detailed description of a particular but not exclusive embodiment,
illustrated by way of non-limiting example in the accompanying drawings, wherein:
Figure 1 is a hydraulic diagram of a bending press that comprises an accumulator with
a capacity of less than one liter, according to the present invention;
Figure 2 is a hydraulic diagram of a bending press that comprises an accumulator with
a capacity of more than one liter, according to the present invention;
Figure 3 is a flowchart.
[0013] In the exemplary embodiments that follow, individual characteristics, given in relation
to specific examples, may actually be interchanged with other different characteristics
that exist in other exemplary embodiments.
[0014] Moreover, it is noted that anything found to be already known during the patenting
process is understood not to be claimed and to be the subject of a disclaimer.
[0015] With reference to the previously cited figures, the reference numeral 1 designates
an active cambering device of bending presses comprising an upper beam 2 and a lower
beam 3.
[0016] In the accompanying drawings, some components have been designated by reference signs
that are explained hereinafter:
M1 = asynchronous motor
P1 = pump
V1 = pump discharge electric valve
V2 = electric valve for accumulator discharge on safety block
V3 = accumulator insertion electric valve
V4 = safety valve on control unit
V5 = one-way valve for pump protection
V6 = circuit separation one-way valve
V7 = accumulator oil side safety valve
V8 = proportional direction valve
V9 = safety valve
BL1 = accumulator block
BL2 = cambering block
T I = pressure transducer
ACC = accumulator(s)
UT = position transducer on upper beam
LT = position transducer on lower beam
CNC = numeric control
Y1 = left cylinder
YY1 = left cylinder target level (level to which the left cylinder of the press must
be brought in order to perform the set bending)
Y2 = right cylinder
YY2 = right cylinder target level (level to which the right cylinder of the press
must be brought in order to perform the set bending)
QUT = level detected by the transducer UT on upper beam
QLT = level detected by the transducer LT on lower beam
[0017] The device comprises a pump 4, P1 adapted to load at least one accumulator 5, ACC,
said accumulator being adapted to actuate said lower beam 3 by means of a proportional
direction valve 6, V8.
[0018] The position of the slider of the proportional direction valve 6, V8 is continuous
and proportional to the current that flows through the coils/solenoids installed therein;
in the specific case, the proportional direction valve 6, V8 has three possible positions
between which the slider can move, affecting them both partially and completely.
[0019] There is a first inactive position with closed centers, in which there is no connection
between the various branches P (pressurized branch), T (discharge), A (use) and B
(use) which arrive at/exit from the proportional direction valve 6, V8, which behaves
like a plug, preventing the passage of the oil in any direction.
[0020] There is a second position, designated by V8A, with crossed centers, in which the
branch P is connected to the branch B; in this condition the oil flows toward the
cambering jacks 7 of the lower beam 3; the branch T is also connected to the branch
A; in this condition, since A is plugged, nothing happens.
[0021] There is a third position, designated by V8B, with straight centers: the branch P
is thus connected to the branch A (and since A is plugged, nothing happens) and the
branch T is connected to the branch B: in this case the oil that arrives from the
cambering jacks 7 is discharged.
[0022] The pump 4, P1 is activated at power-on of the machine or press: in this step a motor
8, M is switched on which, by rotating the pump 4, P1, starts to make the oil circulate
in the circuit.
[0023] The oil flows through a first valve 9, V5, which is a one-way valve for protecting
the pump 4, P1; it is a one-way valve that prevents the flow of the oil toward the
pump 4, P1 whereas it allows its flow toward the user device.
[0024] In this condition, the circuit is not pressurized, because the fluid is discharged
through a first electric valve 10, V1 that is in the inactive position.
[0025] The first electric valve 10, V1 in the inactive position discharges the circuit onto
the tank 11, whereas in the position V1A it prevents the passage of the oil toward
the tank 11, i.e., it acts as a plug.
[0026] In order to pressurize the circuit, all the drains to the tank 11 must be closed,
and therefore the first electric valve 10, V1 is energized and reaches the position
V1A and, if there is a safety block 12 for accumulators 5, ACC, as shown in Figure
2, a second electric valve 13, V2 also is energized which in turn reaches the position
V2A.
[0027] The proportional direction valve 6, V8 is in the inactive position with the centers
closed, i.e., with P, T, A and B plugged; the oil cannot pass through it and therefore
the part of the circuit that is upstream thereof is pressurized.
[0028] In the configuration of the preceding case, one achieves also the loading of the
accumulator 5, ACC, since the first valve 9, V5 and a second valve 14, V5 and a third
electric valve 15, V3, the first two being simple one-way valves and the last one
being a one-way valve in the inactive position, prevent the flow of the oil only downward;
therefore, once the circuit is pressurized the accumulator 5, ACC begins to load.
[0029] When a pressure transducer 16, T1 sends the signal that the reference pressure (target)
has been reached, the first electric valve 10, V1 is deactivated and the oil resumes
flowing through it from the pump 4, P to the tank 11.
[0030] Due to the configuration of the third electric valve 15, V3, which is inactive, the
accumulator 5, ACC remains pressurized.
[0031] Once the preparatory step for the power-on of the machine or press has ended, the
bending cycle can begin; initially there is a quick descent of the upper beam 2 and
then the step of approach to the metal plate to be bent (not shown) at the working
speed begins.
[0032] Shortly before the metal plate to be bent interacts with the lower beam 3, the pump
4, P1 is inserted in the circuit again by activation of the first electric valve 10,
V1, moving it to the position V1A.
[0033] One reaches a situation of equilibrium as regards the pressures, between the branches
upstream and downstream of the third electric valve 15, V3, which therefore can be
in the position V3A so that the oil of the accumulator 5, ACC can flow in the circuit;
as long as this situation of pressure balance persists, nothing happens.
[0034] Upstream of the proportional direction valve 6, V8, which continues to remain inactive,
the circuit is pressurized and the accumulator 5, ACC is inserted.
[0035] The bending step begins and therefore following, deformation and cambering in position
occur.
[0036] The main cylinders 17a, 17b of the press push downward in order to reach the levels
YY1 and YY2 that will allow reaching the target angle of the plate being bent.
[0037] As this step proceeds, the upper beam 2 is deformed; the numeric control or computer
18, CNC begins comparing the values of the deformation of the upper beam 2 with those
of the lower beam 3, measured respectively by adapted position transducers 19, UT
and 20, LT, and operates accordingly; its purpose is to render the deflection of the
lower beam 3 equal to the deflection of the upper beam 2.
[0038] To achieve this, the cambering jacks 17a, 17b must be opened more or less according
to need; the 'more or less' is obtained by operating on the proportional direction
valve 6, V8, moving its slider continuously and proportionally to the supply current
of the coils between the positions V8A and V8B.
[0039] By moving toward the position V8A, the oil flows toward the cambering jacks 17a,
17b, pressurizing them and opening them.
[0040] By moving toward the position V8B, the cambering is depressurized and consequently
the deformation of the lower central beam 3 is reduced.
[0041] The numeric control or computer 18, CNC operates therefore in the following manner:
if the level QUT detected by the transducer 19, UT on the upper beam 2 is higher than
the level QLT detected by the transducer 20, LT on the lower beam 3, the slider of
the proportional direction valve 6, V8 is induced to move toward the position V8A
and the deformation of the lower beam 3 is increased.
[0042] If instead QUT<QLT, the slider of the proportional direction valve 6, V8 is caused
to move toward the position V8B and the deformation of the lower beam 3 is decreased.
[0043] If QUT = QLT, the slider of the proportional direction valve 6, V8 is caused to move
toward the inactive position and the deformation of the lower beam 3 is kept constant.
[0044] All this occurs in a continuous and dynamic manner; as the two deflections mutually
approach, the proportional direction valve 6, V8 approaches the central closure position;
as the demand for oil decreases, the excess oil reloads the accumulator 5, ACC.
[0045] Once the main cylinders 17a, 17b of the machine or press have reached the target
levels YY1 and YY2 and the values of the deflections of the two beams, the lower one
3 and the upper one 2, are identical, this means that the part has been bent, and
therefore the relaxation step begins, in which the pressure in the main cylinders
17a, 17b is decreased and the structure relaxes.
[0046] The upper beam 2 returns to the horizontal and therefore, since cambering is still
active, the lower beam 3, which continues to follow its deflection, also returns to
the horizontal, discharging the excess oil from the cambering jacks 7.
[0047] Once the relaxation step has finished, with the upper beam 2 and the lower beam 3
by now perfectly horizontal, the proportional direction valve 6, V8 is returned to
the inactive position and one is ready to restart with a new bending cycle by reloading
the accumulators 5, ACC if necessary.
[0048] It is noted that in circuits with accumulators 5, ACC of a capacity greater than
one liter, and therefore with a safety block 12 certified according to the mandatory
standards of the country of destination, once the machine or press has been powered
on, the second electric valve 13, V2 remains always active (discharge closed) so that
the oil cannot be discharged into the tank 11; it can be deactivated at the end of
the day.
[0049] The maximum pressure in the circuit is determined first by the third safety valve
21, V4 and then by the fourth safety valve 22, V7 and the fifth safety valve 23, V9.
[0050] The pressure of the accumulator 5, ACC never drops below the minimum value necessary
for cambering.
[0051] The proportional direction valve 6, V8 does not determine the pressure of the circuit,
but merely passes either toward the cambering or toward the discharge quantities of
oil that are proportional to the current that flows through the coils that move its
slider.
[0052] The first electric valve 10, V1 and the third electric valve 15, V3 are fundamentally
on/off - open/closed valves; the third electric valve 15, V3 actually always lets
the oil flow 'upward from below', whereas it behaves as on-off only downward from
above.
[0053] It is possible to provide for the use of multiple accumulators 5, ACC with a capacity
of less than one liter which are mutually connected.
[0054] In practice it has been found that the invention fully achieves the intended aim
and objects cited above, more energy being saved than in the illustrated background
art; the device allows moving small volumes of oil, but when it intervenes these volumes
are supplied in very short times; there are, therefore, high flow-rates of oil and
therefore many liters/minute.
[0055] The use of the accumulator allows using a pump having a small capacity, despite supplying,
in the set pressure range, high immediate flow-rates of oil.
[0056] It is noted, moreover, that the device allows having the quantity of oil necessary
only when it is needed, without draining it uselessly.
[0057] Therefore, higher energy savings are achieved thanks to the use of the proportional
direction valve 6, V8: in the background art the deformation of the jacks was controlled
by a proportional pressure valve that operated this control, acting on the pressure
of the circuit, but in order to do this large quantities of oil were drained and therefore
large amounts of energy were 'wasted' uselessly.
[0058] The device allows instead a position control by means of a proportional direction
valve and therefore one drains and then produces the laminar flow of a quantity of
oil that is positively lower than before, thus saving more energy.
[0059] There is, moreover, a lower installed power: the main purpose of the pump 4, P1 is
to charge the accumulator 5, ACC during idle times, whereas the supply of the cambering
jacks 7 is provided almost exclusively by the latter.
[0060] It is possible therefore to install a pump 4, P1 with a lower capacity than that
of a circuit of the known type without accumulator.
[0061] Finally, there is a higher speed of reaction of the cambering, due to the greater
instantaneous flow supplied by the accumulator 5, ACC and the use of the proportional
direction valve 6, V8 with respect to the traditional circuit of the known type, where
the function of supplying power to the cambering was performed by a larger pump and
a proportional pressure valve was used.
[0062] With the device, the cycle time is reduced and productivity increases.
[0063] The materials used, as well as the dimensions that constitute the individual components
of the invention, may of course be more pertinent to the specific requirements.
[0064] The various means for performing certain different functions need not certainly coexist
only in the illustrated embodiment but can be present per se in many embodiments,
including embodiments that are not illustrated.
[0065] The characteristics indicated as advantageous, convenient or the like may also be
omitted or be replaced with equivalents.
[0067] Where technical features mentioned in any claim are followed by reference signs,
those reference signs have been included for the sole purpose of increasing the intelligibility
of the claims and accordingly such reference signs do not have any limiting effect
on the interpretation of each element identified by way of example by such reference
signs.
1. An active cambering device (1) of bending presses comprising an upper beam (2) and
a lower beam (3), characterized in that it comprises a pump (4, P1) adapted to load at least one accumulator (5, ACC), said
accumulator (5, ACC) being adapted to actuate said lower beam (3) by means of a proportional
direction valve (6, V8).
2. The device according to claim 1, characterized in that said proportional direction valve (6, V8) has a positioning of the slider that is
continuous and proportional to the current that flows through the coils/solenoids
installed therein, said proportional direction valve (6, V8) having three possible
positions, between which said slider can move, affecting them both partially and completely:
a first inactive position with closed centers, in which there is no connection between
the various branches P (pressurized branch), T (discharge), A (use) and B (use) which
arrive at/exit from said proportional direction valve (6, V8), which behaves like
a plug, preventing the passage of the oil in any direction; a second position V8A
with crossed centers, in which said branch P is connected to said branch B so that
in this condition the oil flows toward the cambering jacks (7) of said lower beam
(3) and said branch T is also connected to said branch A, which is plugged; a third
position V8B with said centers straight, so as to connect said branch P to said plugged
branch A, and said branch T to said branch B so as to discharge the oil that arrives
form said cambering jacks (7).
3. A method for active cambering of bending presses comprising an upper beam (2) and
a lower beam (3), characterized in that once all the drains to a tank (11) are closed, in order to pressurize the circuit
a first electric valve (10, V1) is energized and reaches the position V1A and, if
a safety block (12) for at least one accumulator (5, ACC) is provided, a second electric
valve (13, V2) also is energized and in turn reaches the position V2A, a proportional
direction valve (6, V8) being provided in the inactive position with the branches
(P, T, A, B) closed, allowing pressurization of the part of the circuit that is upstream
thereof, achieving also the loading of said at least one accumulator (5, ACC) since
a first valve (9, V5) and a second valve (14, V5) and a third electric valve (15,
V3), the first two being simple one-way valves and the last one being a check valve
in the inactive position, prevent the flow of the oil only downward, so that once
the circuit is pressurized said at least one accumulator (5, ACC) begins to load.
4. The method according to claim 3, characterized in that when a pressure transducer (16, T1) sends the signal that the reference pressure
(target) has been reached, said first electric valve (10, V1) is deactivated and the
oil resumes flowing through it from a pump (4, P) to said tank (11), the configuration
of said third electric valve (15, V3) when inactive allowing said at least one accumulator
(5, ACC) to remain pressurized.
5. The method according to claim 3, wherein, once the preparatory step for the power-on
of said bending press has ended, the bending cycle begins with an initial quick descent
of said upper beam (2) and then a step of approach to the metal plate to be bent at
the working speed, characterized in that shortly before said metal plate to be bent interacts with said lower beam (3), said
pump (4, P1) is inserted in the circuit again by activating said first electric valve
(10, V1), moving it to the position V1A so that a situation of equilibrium is reached
as regards pressures between the branches upstream and downstream of said third electric
valve (15, V3), which therefore can be in the position V3A so that the oil that is
present in said at least one accumulator (5, ACC) can flow in the circuit.
6. The method according to one or more of claims 3 to 5, characterized in that at the beginning of the bending step main cylinders (17a, 17b) of said upper beam
(2) press downward in order to reach preset heights YY1 and YY2 which are adapted
to allow reaching the target angle of the plate being bent as this step progresses,
said upper beam (2) being deformed while a numeric control or computer (18, CNC) begins
to compare the values of the deformation of said upper beam (2) with those of said
lower beam (3), measured respectively by adapted position transducers (19, UT; 20,
LT) in this step opening partially or fully said cambering jacks (17a, 17b) by acting
on said proportional direction valve (6, V8), moving its slider continuously and proportionally
to the supply current of the coils, between the positions V8A and V8B so that the
deflection of said lower beam (3) matches the deflection of said upper beam (2).
7. The method according to one or more of claims 3 to 6, characterized in that by moving toward said position V8A the oil flows toward said cambering jacks (17a,
17b), pressurizing them and opening them, whereas by moving toward said position V8B
the cambering is depressurized and consequently the deformation of said lower beam
(3) is reduced, said numeric control or computer (18, CNC) operating so that if the
level (QOT) detected by said transducer (19, UT) on said upper beam (2) is higher
than the level (QLT) detected by said transducer (20, LT) on said lower beam (3),
the slider of said proportional direction valve (6, V() is caused to move toward said
position V8A and the deformation of said lower beam (3) is increased; if instead QUT
< QLT the slider of said proportional direction valve (6, V8) is caused to move toward
said position V8B and the deformation of said lower beam (3) is decreased; if QUT
= QLT the slider of said proportional direction valve (6, V8) is caused to move toward
the inactive position and the deformation of said lower beam (3) is kept constant.
8. The method according to one or more of claims 3 to 7, characterized in that as the two deflections mutually approach, said proportional direction valve (6, V8)
approaches the central closure position, whereas as the demand for oil decreases,
the excess oil reloads said at least one accumulator (5, ACC).
9. The method according to one or more of claims 3 to 8, characterized in that once said main cylinders (17a, 17b) of said bending press have reached said levels
YY1 and YY2 and the values of the deflections of said two beams, the lower one (3)
and the upper one (2), are identical, the part has been bent and the relaxation step
begins, in said step the pressure in said main cylinders (17a, 17b) being decreased
and said upper beam (2) and said lower beam (3) returning to the horizontal, discharging
the excess oil from said cambering jacks (7).
10. The method according to one or more of claims 3 to 9, characterized in that the maximum pressure in the circuit is determined by a fourth safety valve (21, V4),
by a fifth valve (22, V7) and by a sixth safety valve (23, V9), said proportional
direction valve (6, V8) merely passing either toward the cambering or toward the discharge
quantities of oil that are proportional to the current that flows through the coils
that move the slider thereof.