CA2705646C

CA2705646C - Device and method for preventing a tool from breaking during fine blanking and/or forming a work piece

Info

Publication number: CA2705646C
Application number: CA2705646A
Authority: CA
Inventors: Markus Schaltegger; Alfio Cristofaro; Juerg Ochsenbein
Original assignee: Feintool International Holding AG
Current assignee: Feintool International Holding AG
Priority date: 2009-06-03
Filing date: 2010-05-27
Publication date: 2017-02-14
Anticipated expiration: 2030-05-27
Also published as: JP2010280001A; ATE542617T1; JP5634134B2; KR101691230B1; EP2258496B1; US8113111B2; CA2705646A1; CN101954433A; EP2258496A1; US20100319553A1; KR20100130566A

Abstract

A device and method are provided for preventing a tool from breaking during fine blanking and/or forming in a press.
The device includes a fine blanking head positioned above a ram that carries out a stroke movement. The fine blanking head includes, among other things, a main cylinder retaining a V-shaped projection piston, a touch piston, several V-shaped projection pins, a main plate covering the main cylinder and a touch table to which the tool can be connected. Pressure provided by a hydraulic system is introduced to the device in distinct regions. Gaps between certain device components are maintained and monitored for purposes of determining the undesirable presence of foreign objects in the press operating path. If a sensor determines that the gaps are not maintained then the computer which operates valves that supply the pressure from the hydraulic system will shut the press down.

Description

CA 02705646 201(05-27 Device and method for preventing a tool from breaking during fine blanking and/or forming a work piece Description [0001] The invention relates to a device for preventing a tool consisting of an upper and an lower part from breaking during fine blanking and/or forming in a press with a positioned above a ram carrying out a stroke movement fine blanking head, which comprises a main cylinder accommodating a V-shaped projection piston lying on the stroke axis and several with regard to the stroke axis coaxially arranged V-shaped projection pins, which are axially guided in a main plate covering the main cylinder and supported on a V-shaped projection pressure plate, wherein the main cylinder is hold in the head piece of the press and closed by a V-shaped projection cover and wherein the fine blanking head is connected with a hydraulic system for producing pressure acting on the tool parts via valves, which are triggered by a computer.

, .

2 [0002] The invention further relates to a method for preventing a tool consisting of an upper and an lower part from breaking during fine blanking and/or forming in a press, wherein the guided in the main cylinder of the fine blanking head V-shaped projection and touch pistons for producing a V-shaped projection force and a stripping force are admitted to an adjustable pressure from a hydraulic system, wherein the single pressure values for the pistons are adjusted by valves triggered by a computer.
State of the art

[0003] From the DE 24 19 390 C2 is known a device for the protection of a tool set of a hydraulic fine blanking press, the ram of which can be lifted by quick-elevating piston units and a working stroke pressure unit, wherein between the ram-driving element and a driven ram part exists a detectable gap, that can be maintained in case of the approach of a pressure means with low force and closes in case of higher pressure loads on the parts developing it, the state of which can be monitored by a sensor and a way switch until the ram has neared the tools to start the regular working stroke. The detectable gap is developed between the ram and the frontal surfaces of the piston rods of the quick-elevating pistons and pressure is admitted to the detectable gap by touch cylinders in the ram, when the touch pistons of them respectively rest against a part of the mentioned before frontal surfaces.
In this known protection device the detectable gap before the quick-elevating piston unit is allocated to the ram and positioned upstream to it. This protection device is always then actuated, when the detectable gap closes due to an elevated pressure load.
It has the disadvantage that punchings, parts or foreign bodies in the tool are not detected and thus damages at the tool can not be prevented.

CA 02705646 201(05-27 [00024] Another known solution (DE 69 17 177 U) for a tool protection in presses for processing a blank discloses between a first tool moved by the working piston and a fixed to the frame tool two switches, which have to be actuated in a predetermined sequence, for interrupting the working stroke in case of an inverse actuating sequence. For attaching the first tool is provided an axially movable with regard to the working piston element, which during the working stroke is hold at a small distance before the working piston by elastic flexible means. A first adjustable to the nominal height of the blank to be processed limit stop switch is actuated by a limit stop, when the piston has moved a part of its working stroke predetermined by the adjustment of the first limit stop switch. A further limit stop switch is actuated by a further limit stop, when the element by the blank or a foreign body hitting the second tool is pushed back by the small distance onto the piston.
The element is realized as a lower tool mounting surface supporting on a cylinder together with the working piston enclosing a ring-shaped pressure chamber, which is connected to a pressure fluid pipe having a shutting element, that makes it possible to let as much compressed air into the ring chamber to hold the mounting surface during the working stroke practically floating before the piston.
This known solution has the disadvantage, that besides the hydraulic system a second separate system is necessary, that works with compressed air and thus causes a considerable effort regarding circuitry and construction. Besides that, after the detection of a foreign body there is no possibility to compensate the kinetic energy of the drive.
[0005] Other known solutions for detecting punchings or other foreign bodies in the tool use optical sensors or ultrasonic sensors.

4 Task [0006] At this state of the art the invention has the task to provide a solution for preventing a tool from breaking during fine blanking and/or forming, which is able to simplify the construction and to reduce the quantity of parts simultaneously reducing the costs, to absorb high tilting moments and to compensate the kinetic energy of the drive during a return stroke even before the press is switched off.
[0007] This task is solved by a device and method as described herein.
[0008] Advantageous aspects of the device and the method according to the invention can be learned from the preferred embodiments.
[0009] The solution according to the invention proceeds from the finding to integrate the function of detecting punchings, parts or other foreign bodies into the active elements of the fine blanking head, that is to provide a touch piston between V-shaped projection piston and V-shaped projection pins, that with the V-shaped projection piston on the one hand and with the V-shaped projection pins and the V-shaped projection pressure plate on the other hand develops an axially to each other movable arrangement, wherein the V-shaped projection piston is allocated a pressure room to which a preloading pressure of the hydraulic system can be admitted, between V-shaped projection piston and touch piston is allocated a pressure room to which a touch piston pressure can be admitted and the touch piston is allocated a further pressure room to which can be admitted a differential pressure, wherein the pressure rooms each via one connection in the V-shaped projection cover and the pressure rooms respectively via separate positioned in the main cylinder conduits are . .
connected with the hydraulic system for admitting pressure to the V-shaped projection piston and the touch piston opposite to the effective direction of the preloading pressure, and to provide a touch table suspendedly hold against an applied to

5 the main plate fixing means in a determined detection distance weight compensated by the main plate, to which is allocated a sensor that in case of a change of the detection distance transmits a signal to the computer to immediately stop the press to protect the upper part of the tool.
[0010] Of special importance is that the touch table, the main plate, the central support, the main cylinder and the adjusting nut non-positively and/or positively divert the pressing force into the head piece of the press depending on the motion of V-shaped projection piston, V-shaped projection pins and touch piston between upper and lower dead points.
[0011] According to an especially advantageous aspect of the device according to the invention the second pressure room allocated to the V-shaped projection piston is developed below a projecting in the direction of the stroke axis supporting shoulder at the wall of the main cylinder in the direction of the lower piston surface of the V-shaped projection piston.
At the same time the touch piston is allocated a pressure room developed below a provided at the touch piston shoulder and above a projecting in the direction of the stroke axis supporting shoulder at the wall of the main cylinder.
This design in a simple manner guarantees that in the opposite direction to the preloading pressure P1 applied to the V-shaped projection piston a touch piston pressure P2 can act on the V-shaped projection piston and a differential pressure P3 on the touch piston, what causes an axial shift of V-shaped projection piston, touch piston and V-shaped projection pins.

CA 02705646 201(05-27

6 [0012] Further it is of advantage that the pressure room of the V-shaped projection piston via a connection in the V-shaped projection cover is connected to a pressure pipe of the hydraulic system, that via a proportional valve applies to the pressure room a preloading pressure for producing the V-shaped projection force or a stripping pressure for producing a stripping force or makes it motionless.
[0013] Moreover, it is preferred that the second pressure room of the V-shaped projection piston and at the same time the pressure room for the touch piston via a connection at the V-shaped projection cover and a directional control valve to connect the pressure in the second pressure room by a feeding pipe are connected with the pressure pipe of the hydraulic system.
[0014] According to a further aspect of the device according to the invention the conduits leading into the pressure rooms are axially arranged in the direction to the stroke axis in the wall of the main cylinder and open respectively bending into the respective pressure rooms.
[0015] Furthermore, for feeding different quantities of hydraulic fluid into the single pressure rooms it is provided, that the conduit for the V-shaped projection piston with regard to the conduit for the touch piston has a bigger diameter.
[0016] In an especially advantageous aspect of the device according to the invention the fixing means comprises a pressure spring and a straining screw, which are positioned in a recess of the main plate, wherein the straining screw penetrates the main plate and the pressure spring serves for compensating the weight of the touch table and the upper part of the tool.

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7 [0017] A further advantageous aspect of the device according to the invention provides, that the sensor is adjustably positioned in a seat of the main plate, the measuring point of which is determined by an arranged in the touch table switch flag, what guarantees an exact adjustment of the detection distance to the gap distance.
The gap distance in case of an immediate stop of the press serves to advantageously compensate the kinetic energy even before the press has stopped.
[0018] Furthermore, it is preferred to provide, that the main plate is attached at a frontal side of the main cylinder facing the ram with screwing means.
[0019] In a further preferred aspect of the device according to the invention the touch table is torsion-proof and axially movable arranged to the main plate by axially parallel to the stroke axis guided in holes guiding pins.
[0020] An especially advantageous aspect of the device according to the invention consists in, that the V-shaped projection pins and the V-shaped projection pressure plate are positioned coaxially with regard to the stroke axis, wherein the pressure plate is fixed at the touch table by a retaining ring and a central support is integrated in the main plate.
[00211 Furthermore, the task of the invention is solved by the method that way, that the pressure force is diverted by means of a non-positive and/or positive connection by hydraulic locking and unlocking of a touch table, a main plate, a central support, a main cylinder and an adjusting nut into the head piece of the press and by axially shifting of V-shaped projection piston and touch piston in alignment with the stroke axis (HU) prior to feeding in the pressure force until the non-positive and/or positive connection between V-=

8 shaped projection pressure plate, V-shaped projection pins, touch piston and V-shaped projection piston is reached, wherein between touch piston and V-shaped projection pins with hydraulic means is adjusted a gap distance and between main plate and touch table with mechanical means is adjusted an adjusted to the gap distance weight compensated detection distance, the change of which is scanned by the V-shaped pressure plate and/or the touch table in case of an inverse sequence of the stroke and detected by a sensor transmitting a signal to the computer, what causes the immediate stop of the press.
The kinetic energy is compensated in the gap distance between touch table and V-shaped projection pins because the touch table can move in the direction of the V-shaped projection pins.
[0022] The method according to the invention is realized especially in the following preferred steps:
a Preloading of V-shaped projection piston and touch piston to a preloading pressure P1 to realize the non-positive connection between them Permanently applying a different from the preloading pressure P1 differential pressure P3 to the touch piston for axially shifting the touch piston, Maintaining a detection distance TA adjusted to a gap distance between touch piston and V-shaped projection pins by the applied to the touch piston differential pressure P3 and the acting against it preloading pressure P1 for realizing a non-positive connection between touch piston and V-shaped projection piston, wherein the preloading pressure P1, the touch piston pressure P2 and

9 the differential pressure P3 are adjusted to the condition P1 P3 and P2 . 0, d Superseding the hydraulic fluid being under differential pressure P3 in the allocated to the touch piston pressure room by the applied to the upper pressure room preloading pressure P1, e Relieving the V-shaped projection piston by switching off the preloading pressure P1 in the upper dead point for reaching a motionless state of V-shaped projection piston and touch piston, f Stripping of V-shaped projection piston and touch piston by applying a stripping pressure P4 and a touch piston pressure P2 with a constant value to the pressure rooms of V-shaped projection piston and touch piston, g Shifting the V-shaped projection piston and the touch piston until a sensor triggers a signal, h Switching off the stripping pressure P4 for the V-shaped projection piston and the touch piston and applying the preloading pressure P1 to the upper pressure room of the V-shaped projection piston, i Repeating the step sequence a) to h) in case the sensor has not detected a depending on the ram stroke premature change of the detection distance TA.
[0023] A further preferred aspect of the method according to this invention provides, that the preloading pressure for the V-shaped projection piston is adjusted to a high pressure of more than 110 bar.

[0024] The method according to the invention further provides in a preferred aspect, that - the touch piston pressure P2 and the stripping pressure P4 are adjusted to a low pressure below 110 bar, - the differential pressure P3 is adjusted to a low pressure below 110 bar or to zero.
[0024a] Accordingly, in one aspect, the present invention

10 provides device for preventing a tool from breaking during fine blanking and/or forming operations in a press, the tool comprising an upper and lower part, the device being positioned above a ram provided in the press, the ram carrying out a stroke movement along a stroke axis, the device positioned above the ram, the upper part of the tool connected to the device at a touch table provided on a ram side of the device, the device comprising: a fine blanking head, the fine blanking head including a head piece frame holding a main cylinder, the main cylinder retaining a V-shaped projection piston aligned on the stroke axis, V-shaped projection pins that are coaxially arranged, with respect to the stroke axis, the V-shaped projection pins being axially guided by a main plate covering the main cylinder on a ram side thereof, the V-shaped projection pins being supported on a V-shaped projection pressure plate, wherein the main cylinder is provided with a pressure-tight seal at a top side of the main cylinder by a V-shaped projection cover; a hydraulic system for generating pressure in the main cylinder, the hydraulic system being in connection with the fine blanking head and a source of pressurized fluid, the hydraulic system provided with valves under the control and operation of a computer, whereby the computer, through valve operation, controls and regulates the flow of pressurized fluid; the main cylinder further retaining a touch piston positioned between the V-, 10a shaped projection piston and V-shaped projection pins, the V-shaped projection piston, the V-shaped projection pins, and the V-shaped projection pressure plate being in an axially movable arrangement with respect to each other in alignment along the stroke axis; first, second, and third pressure rooms provided in the main cylinder, each respectively having a connection to the hydraulic system through, respectively, first, second, and third connections provided in the V-shaped projection cover; the first pressure room allocated to a space in the main cylinder on an upper side of the V-shaped projection piston, whereby, upon admission of a pressure from the hydraulic system to the first pressure room, the first pressure room is pressurized with a preloading pressure; the second pressure room allocated to a space in the main cylinder between the V-shaped projection piston and the touch piston, whereby, upon admission of a pressure from the hydraulic system to the second pressure room, the second pressure room is pressurized with a touch piston pressure; and the third pressure room allocated to a space in the main cylinder associated with the touch piston, whereby, upon admission of a pressure from the hydraulic system to the third pressure room, the third pressure room is pressurized with a differential pressure; the second and third pressure rooms each being in connection with the hydraulic system though second and third pressure room conduits, respectively, whereby, when the first pressure room and at least one of the second and third pressure rooms are pressurized to effective pressure levels, the V-shaped projection piston and the touch piston are influenced by pressure in a direction opposite to the direction of the influence of the preloading pressure applied in the first pressure room to the V-shaped projection piston;
a touch table fixedly attached in suspension to the main plate by fixing means, the fixing means providing a gap having a 10b predetermined gap dimension between the main plate and touch table, the predetermined gap dimension being detected by a sensor, the touch table being provided with means for attaching the upper part of the tool; and whereby, during operation of the press, in the event of a change in the predetermined gap dimension, the sensor transmits a signal to the computer, and in processing the signal, the computer stops the operation of the press to protect the upper part of the tool against damage.
[0024b]
In another aspect, the present invention provides a method for preventing a tool with an upper and lower part from breaking during fine blanking and/or forming operations in a press employing a device positioned above a ram provided in the press, the ram carrying out a stroke movement along a stroke axis, the upper part of the tool connected to the device at a touch table provided an a ram side of the device, the device comprising: a fine blanking head, the fine blanking head including a head piece frame holding a main cylinder, the main cylinder retaining a V-shaped projection piston aligned on the stroke axis, V-shaped projection pins that are coaxially arranged, with respect to the stroke axis, the V-shaped projection pins being axially guided by a main plate covering the main cylinder on a ram side thereof, the V-shaped projection pins being supported on a V-shaped projection pressure plate, wherein the main cylinder is provided with a pressure-tight seal at a top side of the main cylinder by a V-shaped projection cover; a hydraulic system for generating pressure in the main cylinder, the hydraulic system being in connection with the fine blanking head and a source of pressurized fluid, the hydraulic system provided with valves under the control and operation of a computer, whereby the computer, through valve operation, controls and regulates the 10c flow of pressurized fluid; the main cylinder further retaining a touch piston positioned between the V-shaped projection piston and V-shaped projection pins, the V-shaped projection piston, the V-shaped projection pins, and the V-shaped projection pressure plate being in an axially movable arrangement with respect to each other in alignment along the stroke axis; first, second, and third pressure rooms provided in the main cylinder, each respectively having a connection to the hydraulic system through, respectively, first, second, and third connections provided in the V-shaped projection cover;
the first pressure room allocated to a space in the main cylinder on an upper side of the V-shaped projection piston, whereby, upon admission of a pressure from the hydraulic system to the first pressure room, the first pressure room is pressurized with a preloading pressure; the second pressure room allocated to a space in the main cylinder between the V-shaped projection piston and the touch piston, whereby, upon admission of a pressure from the hydraulic system to the second pressure room, the second pressure room is pressurized with a touch piston pressure; and the third pressure room allocated to a space in the main cylinder associated with the touch piston, whereby, upon admission of a pressure from the hydraulic system to the third pressure room, the third pressure room is pressurized with a differential pressure; the second and third pressure rooms each being in connection with the hydraulic system though second and third pressure room conduits, respectively, whereby, when the first pressure room and at least one of the second and third pressure rooms are pressurized to effective pressure levels, the V-shaped projection piston and the touch piston are influenced by pressure in a direction opposite to the direction of the influence of the preloading pressure applied in the first pressure room to the V-shaped projection piston; a touch table 10d fixedly attached in suspension to the main plate by fixing means, the fixing means providing a gap having a predetermined gap dimension between the main plate and touch table, the predetermined gap dimension being detected by a sensor, the touch table being provided with means for attaching the upper part of the tool; and whereby, during operation of the press, in the event of a change in the predetermined gap dimension, the sensor transmits a signal to the computer, and in processing the signal, the computer stops the operation of the press to protect the upper part of the tool against damage, the method comprising the steps of: diverting a pressure force through a non-positive connection and/or positive connection through hydraulic locking and unlocking of the touch table, the main plate, a central support, the main cylinder and an adjusting nut that are provided in the head piece; axially shifting the V-shaped projection piston and the touch piston in alignment with the stroke axis prior to delivering the pressure force, until a time when the non-positive and/or positive connection between the V-shaped projection pressure plate, the V-shaped projection pins, the touch piston and V-shaped projection piston is attained; adjusting a gap distance between the touch piston and V-shaped projection pins to a predetermined gap distance value through hydraulic means;
adjusting a gap dimension between the main plate and the touch table by mechanical means to a predetermined value, whereby the predetermined value of the gap dimension between the main plate and the touch table is substantially the same as the gap distance between the touch piston and V-shaped projection pins; transmitting a signal to the computer, in the event a change in the predetermined value of the gap dimension between the main plate and the touch table during press operation is detected by a sensor; and shutting off the press, in response to the transmitting of the signal to the computer.

10e [0025] Further advantages and details of the invention accrue from the following description with reference to the attached drawings.
Embodiment [0026] In the following the invention will be explained in more detail on the example of one embodiment.
It is shown in:
[0027] Fig. 1 a perspective view of the press with the device according to the invention assembled in the head piece, [0028] Fig.2 a cross-section of the device according to the invention in the extended state, [0029] Fig.3. a cross-section of the device according to the invention in the retracted state, [0030] Fig. 4 a cross-section of the main plate and the touch table with illustration of the mechanical weight compensation and [0031] Fig. 5 a cut out cross-section of the main plate and the touch table illustrating the arrangement of the sensor and the position of gap distance and detection distance.

=

11 [0032] Fig. 1 shows a perspective view of a mechanically driven toggle-type fine blanking press. The supporting a table top ram 1 of this press carries out a lifting movement in the direction of the stroke axis HU and in the direction of the head piece 2 of the press. In the head piece 2 of the press is positioned the device according to the invention in alignment with the stroke axis HU.
[0033] Fig. 2 shows a cross-section of the device according to the invention. The device according to the invention as compact construction unit is assembled into the head piece 2 of the press and form-fit fixed there. The device according to the invention comprises a fine blanking head FSK, which essentially consists of a main cylinder 3, an adjusting nut 4, a fixed to the head piece 2 flange 5, a main plate 6 and a touch table 7. Main cylinder 3, adjusting nut 4, flange 5, main plate 6 and touch table 7 together develop a non-positive arrangement diverting the whole pressure force into the head piece 2 of the press. The non-positive connection is achieved by locking the motion threads BW1 and BW2 at the head of the main cylinder 3 and at the adjusting nut 4 by pressing the motion thread BW1 of the main cylinder 3 against the motion thread BW2 of the adjusting nut 4 into the direction of the upper dead point OT by means of a hydraulic pressure PV. The unlocking of the two motion threads BW1 and 3W2 is carried out by switching off the hydraulic pressure PV.
The non-positive connection is illustrated by the gray colored area in Fig. 2.
The head piece 2 is connected to the frame 8 of the press by straining screws SB (see Fig. 1).
[0034] In the main cylinder 3 are accommodated a V-shaped projection piston 9 and a touch piston 10 in axial alignment to each other. The V-shaped projection pins 11 penetrate the main plate 6 and support on a V-shaped projection pressure . .

12 plate 12, which is secured by a V-shaped projection retaining ring 13 fixed to the touch table 7.
The main cylinder 3 is pressure-tight closed at its head side by a V-shaped projection cover 15 and above the V-shaped projection piston 9 develops a pressure room 16, which via a connection 17 and an adjustable valve 18 by a feeding pipe 19 is connected to the pressure pipe 56 of the hydraulic system for producing a hydraulic preloading pressure P1 acting on the V-shaped projection piston 9 in the direction of the lower dead point UT.
[0035] The main cylinder 3 - as Fig. 3 shows - at is internal wall 20 has a first step-like projecting in the direction of the stroke axis HU shoulder 21 for supporting and limiting the stroke into the direction of the lower dead point UT of the V-shaped projection piston 9. Below this first shoulder 21 is positioned a second projecting in the direction of the stroke axis HU shoulder 22 bordering the pressure room 31 of the touch piston 10.
In the wall 20 of the main cylinder 3 is accommodated an axially extending conduit 23, which bending around about 45 in the direction of the stroke axis HU below the first shoulder 21 opens through the internal wall 20. Below the V-shaped projection piston 9 develops a pressure room 24 into which is fed the hydraulic fluid under a touch piston pressure P2.
The conduit 23 to this is connected with a connection 25 at the V-shaped projection cover 15, which is connected via a controllable valve 26 and a respective feeding pipe 27, which on its part is connected to the low-pressure pipe 56a of the hydraulic system.
Furthermore, in the wall 20 of the main cylinder 3 is provided an axially extending conduit 29, which bending around about 45 in the direction of the stroke axis HU opens from the internal wall 20 below the second developed at the internal wall 20 shoulder 22 and develops a pressure room 31 below a shoulder

13 30 of the touch piston 10. The conduit 29 at the V-shaped projection cover 15 is connected with a connection 32, which is connected via a controllable valve 33, via a feeding pipe 34 and reservoir 28 to the hydraulic system. To the pressure room 31 in the direction of the upper dead point OT is admitted hydraulic fluid under a differential pressure P3, so that the touch piston 9 tries to move in the direction of the upper dead point OT.
The pressures P2 and P3 act against the preloading pressure Pl, wherein the pressure P3 causes the touch piston 10 to non-positively connect to the lower side 35 of the V-shaped projection piston 9.
[0036] Between the lower side 36 of the touch piston 10 and the frontal surface 37 of the V-shaped projection pins 11 is provided a determined gap distance SP, that can amount to for example 4 to 10 mm, preferably is 6 mm.
The gap distance SP forms a sufficiently long stopping distance needed in case of a immediate stop of the press to brake the kinetic energy or to retard it.
The V-shaped projection pins 11 non-positively and/or positively support on the V-shaped projection pressure plate 12, so that a hydraulic displacement can be realized in dependence on the touch stroke and the pressure P3 against the pressure Pl. The total V-shaped projection force produced by the preloading pressure than is reduced by the force produced by the differential pressure P3.
[0037] The head piece 2 at its facing the stroke axis HU
internal wall 42 has a projecting in the direction of the stroke axis HU step-like upper shoulder 43, on which supports the adjusting nut 4 and is axially secured in the direction to the upper dead point OT. The adjusting nut 4 is axially hold in the direction to the lower dead point UT by the tube-like part 39 of the flange 5.

CA 02705646 201(05-27

14 [0038] In the flange 5 are provide two positioned diametrically opposite holes 38, which are positioned in the tube-like part 39 parallel to the stroke axis RU.
These holes 38 serve for accommodating pin-like guiding pins 40 axially guiding the main plate 6 and serving as antitwist protection for the main plate 6 and the main cylinder 3.
[0039] As Fig. 4 shows in the main plate 6 is located a recess 45 for accommodating a fixing means 46 consisting of a pressure spring 47 and an adjusting screw 48. The fixing means 46 makes it possible to hold the touch table 7 and the upper part of the tool 50 compensated according to weight. In other words, the weights of the touch table 7 and the upper part of the tool 50 are compensated. At the lower side 49 of the touch table 7 are located standard fixing means for fixing the upper tool part 50, so that it is not necessary to describe them in detail.
[0040] Fig. 5 shows a cut out cross-section of the main plate 6 and the touch table 7. In the main plate 6 vertically to the stroke axis HU is provided a recess 51 in which is positioned a sensor 52 for detecting the detection distance TA. The measuring point MP of the sensor 52 ends in an arranged parallel to the stroke axis RU accessible from the lower side 53 of the main plate 6 recess 54 for the measuring point MP of the sensor 52.
Via the sensor 52 the distance to be detected TA is exactly adjusted.
[0041] Fig. 5 also illustrates the position of the gap distance SP between the lower side of the touch piston 10 and the frontal surface of the V-shaped projection pins 11 on the one hand and of the detection distance between the lower side 53 of the main plate 6 and the upper side of the touch table 7 on the other hand.

15 .
[0042] The hydraulic system - as shown in Fig 3 - consists of a pressure pipe 56, which by a not shown pressure source is loaded to a pressure of 250 bar. To this pressure pipe 56 is connected the feeding pipe 19 extending via the controllable proportional valve 18 to the positioned above the V-shaped projection piston 9 pressure room 16. Via the proportional valve 18 is fed the hydraulic preloading pressure P1 acting in the direction to the lower dead point UT on the V-shaped projection piston 9 for producing the V-shaped projection force. The preloading pressure P1 can be adjusted to a pressure between 20 and 250 bar.
From a low-pressure pipe 56a a feeding pipe 27 via the controllable directional control valve 26 extends into the pressure room 24 producing the stripping pressure P4 for the touch piston 10. The touch piston pressure P2 is directly provided from the hydraulic system.
A further feeding pipe 34 extends from the low-pressure pipe 56a via a reservoir 28 into the pressure room 31 below the touch piston 10. The differential pressure P3 acts against the preloading pressure P1 and makes it possible to not-positively connect touch piston 10 and V-shaped projection piston 9, to hold them connected but also to disconnect the non-positive connection again by switching on the valve 33. In addition this way the pressure potential of the reservoir 28 can be emptied.
[0043] In the following the method according to the invention is described in more detail.
The preloading pressure P1 developing the V-shaped projection force is diverted by the non-positive and/or positive connection of touch piston 10, V-shaped protection piston 9 and V-shaped projection pins 11. Before the preloading pressure P1 is admitted until the non-positive connection of V-shaped projection piston 9 and touch piston 10 is reached the latter are moving in alignment with the stroke axis HU

16 because of the applied differential pressure P3. This results in a non-positive connection between the lower side of the touch piston 10 and the frontal surface of the V-shaped projection piston 9. Between the touch piston 10 and the V-shaped projection pins 11 is realized a fix gap distance SP, which for instance is 6 mm.
The touch table 7 is weight compensated suspendedly positioned at the main plate 6, wherein for its axial movement are provided four guiding pins 40 and for the weight compensation four mechanical fixing means 46.
A sensor 52 allocated to the detection distance TA detects a dependent on the ram stroke too early change of the detection distance TA and produces a signal fed into a computer 57 for processing the signals.
It is differentiated between two signal conditions. The proper form-fit connection between V-shaped projection pressure plate 12, V-shaped projection pin 11, touch piston 10 and V-shaped projection piston 9 causes a displacement against the preloading pressure P1, that is it is carried out a standard cancellation of the detection stroke, that is the touch table 7 and the V-shaped projection pressure plate 12 touch the main plate 6 without a change of the detection distance TA could be detected. The single process steps of the method according to the invention are carried out continuously.
In case the detection distance TA is changed for example by punchings or other foreign bodies the sensor 52 detects this change and transmits this information to the computer 57, where it is further processed. The change of the detection distance leads to a too early cancellation of the detection stroke, so that the computer 57 causes an immediate stop of the press. The kinetic energy during an immediate stop due to the sufficient high detection distance is braked or retarded by the drive.

17 [0044] In the process step a) the V-shaped projection piston 9 and the touch piston10 are preloaded to a high pressure P1.
[0045] The detection distance TA adjusted to the gap distance SP of touch piston 10 and V-shaped projection pins 11 in step b) is kept by the resulting differential pressure P3, whereby a non-positive connection between touch piston 10 and V-shaped projection piston 9 is realized.
The differential pressure P3 for example was adjusted to 65 bar.
[0046] The process step c) provides, that the being under differential pressure P3 touch piston 10, V-shaped projection pins 11, V-shaped projection pressure plate 12 and the being under preloading pressure P1 V-shaped projection piston 9 are displaced by the ram 1.
[0047] The V-shaped projection piston 9 then by switching off the preloading pressure P1 in the upper dead point OT is relieved in step d).
[0048] According to process step e) to the touch piston 10 is applied a differential pressure P3 of for example 65 bar, which makes it possible to realize or cancel the non-positive connection between touch piston 10 and V-shaped projection piston 9 due to an axial movement of the touch piston 10.
[0049] In step f) the V-shaped projection piston 9 and the touch piston 10 are stripped and a desired stripping pressure P4 of for example 70 bar is adjusted with the valve 18 in the belonging to the V-shaped projection piston 9 pressure room 16 with the differential pressure P3 being applied.
Simultaneously with the stripping pressure P4 is applied the touch piston pressure P2 of for example 65 bar.

. .

18 (0050) The stripping pressure P4 then in step g) is switched off and the pressure P1 is applied to the upper pressure room 16 of the V-shaped projection piston 9, when via touch piston 10, V-shaped projection pins 11 and V-shaped projection pressure plate 12 was transmitted the signal for reaching the gap distance SP from the sensor 52.
[0051] The sequence of the steps a) to g) then is repeated.
[0052] When this closing movement is actuated by a too early change of the detection distance TA, is carried out a quick stop, that is an immediate stop of the press. A too early closing movement is always then actuated, when punchings, parts or other foreign parts are in the upper tool, because this leads to a too early change of the detection distance TA.
[0053] List of reference signs ram 1 head of the press 2 main cylinder 3 adjusting nut 4 flange 5 main plate 6 touch table 7 frame of the press 8 V-shaped projection piston 9 touch piston 10 V-shaped projection pins 11 V-shaped projection pressure plate 12 V-shaped projection retaining ring 13 central support 14 V-shaped projection cover 15 upper pressure room for 9 16 connection in 15 17 CA 02705646 201(05-27

19 proportional valve 18 feeding pipe for 16 19 internal wall of 3 20 first projecting shoulder 21 second projecting shoulder 22 conduit for 24 23 lower pressure room of 9 24 connection for 24 in 15 25 controllable valve in 27 26 feeding pipe for 24 27 reservoir for 24 28 conduit 29 shoulder in touch piston 10 30 pressure room for touch piston 10 31 connection for 31 32 controllable valve for 34 33 feeding pipe for 31 34 lower side of the V-shaped projection piston 9 35 lower side of touch piston 10 36 frontal surface of V-shaped projection piston 9 37 holes 38 tube-like part of 5 39 guiding pins 40 frontal surface of 40 41 internal wall of 2 42 shoulder at 2 43 screwed connection 44 recess in main plate 6 45 fixing means 46 pressure spring 47 adjusting screw 48 lower side of touch table 49 upper part of tool 50 recess 51 sensor 52 . .
lower side of the main plate 53 axial recess in 6 54 limit stops 55 high-pressure pipe of the hydraulic system 56 5 low-pressure pipe of the hydraulic system 56a computer 57 motion thread at main cylinder 3 BW1 motion thread at adjusting nut 4 BW2 fine blanking head FSK
10 stroke axis of 1 HU
measuring point of 52 MP
upper dead point OT
preloading pressure P1 touch piston pressure P2 15 differential pressure P3 stripping pressure P4 locking and unlocking pressure PV
gap distance SP
detection distance TA

20 lower dead point UT
To this belong 5 sheets with drawings

Claims

We Claim:

1. A
device for preventing a tool from breaking during fine blanking and/or forming operations in a press, the tool comprising an upper and lower part, the device being positioned above a ram provided in the press, the ram carrying out a stroke movement along a stroke axis, the device positioned above the ram, the upper part of the tool connected to the device at a touch table provided on a ram side of the device, the device comprising:
a fine blanking head, the fine blanking head including a head piece frame holding a main cylinder, the main cylinder retaining a V-shaped projection piston aligned on the stroke axis, V-shaped projection pins that are coaxially arranged, with respect to the stroke axis, the V-shaped projection pins being axially guided by a main plate covering the main cylinder on a ram side thereof, the V-shaped projection pins being supported on a V-shaped projection pressure plate, wherein the main cylinder is provided with a pressure-tight seal at a top side of the main cylinder by a V-shaped projection cover;
a hydraulic system for generating pressure in the main cylinder, the hydraulic system being in connection with the fine blanking head and a source of pressurized fluid, the hydraulic system provided with valves under the control and operation of a computer, whereby the computer, through valve operation, controls and regulates the flow of pressurized fluid;
the main cylinder further retaining a touch piston positioned between the V-shaped projection piston and V-shaped projection pins, the V-shaped projection piston, the V-shaped projection pins, and the V-shaped projection pressure plate being in an axially movable arrangement with respect to each other in alignment along the stroke axis;

first, second, and third pressure rooms provided in the main cylinder, each respectively having a connection to the hydraulic system through, respectively, first, second, and third connections provided in the V-shaped projection cover;
the first pressure room allocated to a space in the main cylinder on an upper side of the V-shaped projection piston, whereby, upon admission of a pressure from the hydraulic system to the first pressure room, the first pressure room is pressurized with a preloading pressure;
the second pressure room allocated to a space in the main cylinder between the V-shaped projection piston and the touch piston, whereby, upon admission of a pressure from the hydraulic system to the second pressure room, the second pressure room is pressurized with a touch piston pressure; and the third pressure room allocated to a space in the main cylinder associated with the touch piston, whereby, upon admission of a pressure from the hydraulic system to the third pressure room, the third pressure room is pressurized with a differential pressure;
the second and third pressure rooms each being in connection with the hydraulic system though second and third pressure room conduits, respectively, whereby, when the first pressure room and at least one of the second and third pressure rooms are pressurized to effective pressure levels, the V-shaped projection piston and the touch piston are influenced by pressure in a direction opposite to the direction of the influence of the preloading pressure applied in the first pressure room to the V-shaped projection piston;
a touch table fixedly attached in suspension to the main plate by fixing means, the fixing means providing a gap having a predetermined gap dimension between the main plate and touch table, the predetermined gap dimension being detected by a sensor, the touch table being provided with means for attaching the upper part of the tool; and whereby, during operation of the press, in the event of a change in the predetermined gap dimension, the sensor transmits a signal to the computer, and in processing the signal, the computer stops the operation of the press to protect the upper part of the tool against damage.

2. The device according to claim 1, wherein the second pressure room is located below a shoulder provided on an interior wall of the main cylinder, the shoulder projecting in the direction of the stroke axis, the second pressure room being defined, in part, by a lower surface of the V-shaped projection piston.

3. The device according to claim 1, wherein the third pressure room is located below a shoulder of the touch piston that is positioned above a second shoulder provided on an interior wall of the main cylinder, the second shoulder projecting in the direction of the stroke axis.

4. The device according to claim 1, wherein the first pressure room is connected to a high pressure source in connection with the hydraulic system through a high pressure feed line provided with a proportional valve, the high pressure feed line being in connection with the first connection provided in the V-shaped projection cover, whereby the preloading pressure generated in the first pressure room produces a V-shaped projection force.

5. The device according to claim 1, wherein the second pressure room is connected to a low pressure source in connection with the hydraulic system through a second pressure room low pressure feed line provided with a directional control valve, the second pressure room low pressure feed line being in connection with the second connection provided in the V-shaped projection cover, whereby, upon admission of pressure from the low pressure source, the second pressure room is pressurized with a touch piston pressure.

6. The device according to claim 1, wherein the third pressure room is connected to a low pressure source in connection with the hydraulic system through a third pressure room low pressure feed line provided with a directional control valve, the third pressure room low pressure feed line being in connection with the third connection provided in the V-shaped projection cover, whereby, upon admission of pressure from the low pressure source, the third pressure room is pressurized with a differential pressure.

7. The device according to claim 1, wherein the second and third conduits each extend within a wall of the main cylinder, coaxial to the stroke axis for a length portion, and each further being provided with a bend at the ends of their respective length portions, each bend opening into the respective second and third pressure rooms, whereby the second and third conduits deliver, respectively, a touch pressure and a differential pressure to the V-shaped projection piston and the touch piston in a direction of force that opposes a direction of force of the preloading pressure applied to the V-shaped projection piston in the first pressure room.

8. The device according to claim 1, wherein the second conduit has a greater diameter than the third conduit.

9. The device according to claim 1, wherein the fixing means includes a pressure spring positioned around an adjustment screw, the fixing means being housed in an open ended recess that is provided in the main plate, the pressure spring bearing against a surface of the recess and a surface of the adjustment screw to provide a spring bias, the adjustment screw having an attachment portion extending through the open end of the recess, the attachment portion being attached to the touch table; whereby the spring bias provided to the fixing means provides an adjustable weight compensation to the touch table and the upper part of the tool attached thereto.

10. The device according to claim 1, wherein the sensor is positioned in a seat provided in the main plate, whereby the sensor provides an adjustable measuring point of the gap dimension.

11. The device according to claim 1, wherein the main plate is attached to the ram side of the main cylinder by screws.

12. The device according to claim 1, wherein the main plate and a flange fixed to the head piece are provided with axially aligned holes that are coaxial to the stroke axis, the axially aligned holes in the main plate and flange receiving guide pins, whereby the main plate is rendered torsion-proof.

13. The device according to claim 1, wherein the main plate is provided with a central support in alignment with the stroke axis, and the V-shaped projection pressure plate is retained by a retaining ring housed in the touch table.

14. A method for preventing a tool with an upper and lower part from breaking during fine blanking and/or forming operations in a press employing a device positioned above a ram provided in the press, the ram carrying out a stroke movement along a stroke axis, the upper part of the tool connected to the device at a touch table provided an a ram side of the device, the device comprising:
a fine blanking head, the fine blanking head including a head piece frame holding a main cylinder, the main cylinder retaining a V-shaped projection piston aligned on the stroke axis, V-shaped projection pins that are coaxially arranged, with respect to the stroke axis, the V-shaped projection pins being axially guided by a main plate covering the main cylinder on a ram side thereof, the V-shaped projection pins being supported on a V-shaped projection pressure plate, wherein the main cylinder is provided with a pressure-tight seal at a top side of the main cylinder by a V-shaped projection cover;
a hydraulic system for generating pressure in the main cylinder, the hydraulic system being in connection with the fine blanking head and a source of pressurized fluid, the hydraulic system provided with valves under the control and operation of a computer, whereby the computer, through valve operation, controls and regulates the flow of pressurized fluid;
the main cylinder further retaining a touch piston positioned between the V-shaped projection piston and V-shaped projection pins, the V-shaped projection piston, the V-shaped projection pins, and the V-shaped projection pressure plate being in an axially movable arrangement with respect to each other in alignment along the stroke axis;
first, second, and third pressure rooms provided in the main cylinder, each respectively having a connection to the hydraulic system through, respectively, first, second, and third connections provided in the V-shaped projection cover;
the first pressure room allocated to a space in the main cylinder on an upper side of the V-shaped projection piston, whereby, upon admission of a pressure from the hydraulic system to the first pressure room, the first pressure room is pressurized with a preloading pressure;
the second pressure room allocated to a space in the main cylinder between the V-shaped projection piston and the touch piston, whereby, upon admission of a pressure from the hydraulic system to the second pressure room, the second pressure room is pressurized with a touch piston pressure; and the third pressure room allocated to a space in the main cylinder associated with the touch piston, whereby, upon admission of a pressure from the hydraulic system to the third pressure room, the third pressure room is pressurized with a differential pressure;
the second and third pressure rooms each being in connection with the hydraulic system though second and third pressure room conduits, respectively, whereby, when the first pressure room and at least one of the second and third pressure rooms are pressurized to effective pressure levels, the V-shaped projection piston and the touch piston are influenced by pressure in a direction opposite to the direction of the influence of the preloading pressure applied in the first pressure room to the V-shaped projection piston;
a touch table fixedly attached in suspension to the main plate by fixing means, the fixing means providing a gap having a predetermined gap dimension between the main plate and touch table, the predetermined gap dimension being detected by a sensor, the touch table being provided with means for attaching the upper part of the tool; and whereby, during operation of the press, in the event of a change in the predetermined gap dimension, the sensor transmits a signal to the computer, and in processing the signal, the computer stops the operation of the press to protect the upper part of the tool against damage, the method comprising the steps of:
diverting a pressure force through a non-positive connection and/or positive connection through hydraulic locking and unlocking of the touch table, the main plate, a central support, the main cylinder and an adjusting nut that are provided in the head piece;
axially shifting the V-shaped projection piston and the touch piston in alignment with the stroke axis prior to delivering the pressure force, until a time when the non-positive and/or positive connection between the V-shaped projection pressure plate, the V-shaped projection pins, the touch piston and V-shaped projection piston is attained;
adjusting a gap distance between the touch piston and V-shaped projection pins to a predetermined gap distance value through hydraulic means;
adjusting a gap dimension between the main plate and the touch table by mechanical means to a predetermined value, whereby the predetermined value of the gap dimension between the main plate and the touch table is substantially the same as the gap distance between the touch piston and V-shaped projection pins;
transmitting a signal to the computer, in the event a change in the predetermined value of the gap dimension between the main plate and the touch table during press operation is detected by a sensor; and shutting off the press, in response to the transmitting of the signal to the computer.

15. A method for preventing a tool with an upper and a lower part from breaking during fine blanking and/or forming operations in a press employing a device positioned above a ram provided in the press, the ram carrying out a stroke movement along a stroke axis, the upper part of the tool connected to the device at a touch table provided an a ram side of the device, the device comprising:
a fine blanking head, the fine blanking head including a head piece frame holding a main cylinder, the main cylinder retaining a V-shaped projection piston aligned on the stroke axis, V-shaped projection pins that are coaxially arranged, with respect to the stroke axis, the V-shaped projection pins being axially guided by a main plate covering the main cylinder on a ram side thereof, the V-shaped projection pins being supported on a V-shaped projection pressure plate, wherein the main cylinder is provided with a pressure-tight seal at a top side of the main cylinder by a V-shaped projection cover;
a hydraulic system for generating pressure in the main cylinder, the hydraulic system being in connection with the fine blanking head and a source of pressurized fluid, the hydraulic system provided with valves under the control and operation of a computer, whereby the computer, through valve operation, controls and regulates the flow of pressurized fluid;
the main cylinder further retaining a touch piston positioned between the V-shaped projection piston and V-shaped projection pins, the V-shaped projection piston, the V-shaped projection pins, and the V-shaped projection pressure plate being in an axially movable arrangement with respect to each other in alignment along the stroke axis;
first, second, and third pressure rooms provided in the main cylinder, each respectively having a connection to the hydraulic system through, respectively, first, second, and third connections provided in the V-shaped projection cover;
the first pressure room allocated to a space in the main cylinder on an upper side of the V-shaped projection piston, whereby, upon admission of a pressure from the hydraulic system to the first pressure room, the first pressure room is pressurized with a preloading pressure;
the second pressure room allocated to a space in the main cylinder between the V-shaped projection piston and the touch piston, whereby, upon admission of a pressure from the hydraulic system to the second pressure room, the second pressure room is pressurized with a touch piston pressure; and the third pressure room allocated to a space in the main cylinder associated with the touch piston, whereby, upon admission of a pressure from the hydraulic system to the third pressure room, the third pressure room is pressurized with a differential pressure;
the second and third pressure rooms each being in connection with the hydraulic system though second and third pressure room conduits, respectively, whereby, when the first pressure room and at least one of the second and third pressure rooms are pressurized to effective pressure levels, the V-shaped projection piston and the touch piston are influenced by pressure in a direction opposite to the direction of the influence of the preloading pressure applied in the first pressure room to the V-shaped projection piston;
a touch table fixedly attached in suspension to the main plate by fixing means, the fixing means providing a gap having a predetermined gap a dimension between the main plate and touch table, the predetermined gap dimension being detected by a sensor the touch table being provided with means for attaching the upper part of the tool; and whereby, during operation of the press, in the event of a change in the predetermined gap dimension, the sensor transmits a signal to the computer, and in processing the signal, the computer stops the operation of the press to protect the upper part of the tool against damage, the method comprising the steps of:
(a) preloading the V-shaped projection piston and the touch piston to a preloading pressure (P1) to cause a non-positive connection between the V-shaped projection piston and the touch piston;

(b) applying a differential pressure (P3) to the touch piston to cause axial shifting of the touch piston, wherein the differential pressure (P3) differs from the preloading pressure (P1);
(c) maintaining a predetermined gap dimension between the main plate and the touch table that is adjusted to a gap distance between the touch piston and the V-shaped projection pins through the combination of the differential pressure (P3) applied to the touch piston and the preloading pressure (P1), which the preloading pressure (P1) and the differential pressure (P3) are applied in directions opposite each other, to cause a non-positive connection between the touch piston and the V-shaped projection piston, and wherein P1>P3;
(d) superseding the differential pressure (P3) in the third pressure room with application of the preloading pressure (P1) that is applied in the first pressure room positioned above the third pressure room, relative to the location of the ram;
(e) relieving the preloading pressure (P1) on the V-shaped projection piston by switching off the preloading pressure (P1) at a moment when the V-shaped projection piston and touch piston have reached an upper dead point, whereby, the V-shaped projection piston and the touch piston attain a motionless state;
(f) stripping the V-shaped projection piston and the touch piston by applying a stripping pressure (P4) and a touch piston pressure (P2) to the first and second pressure rooms, respectively, each of the stripping pressure (P4) and the touch piston pressure (P2) having a constant value;
(g) shifting the V-shaped projection piston and the touch piston until a sensor triggers a signal;
(h) turning off the stripping pressure (P4) and applying the preloading pressure (P1) to the first pressure room; and (i) repeating steps (a) to (h) in the event the sensor has not detected a premature change of the predetermined gap dimension, in dependence on the ram stroke along the stroke axis.

16. The method according to claim 15, wherein the preloading pressure (21) is greater than 110 bar.

17. The method according to claim 15, wherein the touch piston pressure (22) and the stripping pressure (P4) are each maintained at pressures below 110 bar and the differential pressure (P3) is maintained at a pressure in the range of 0 to 110 bar.

18. The method according to claim 15, wherein the touch piston pressure (P2) and the differential pressure (P3) can each selectively be turned on and turned off.

19. The device according to claim 1, wherein a stripping pressure is generated in the first pressure room at a predetermined time to strip the V-shaped projection piston and the touch piston.

20. The device according to claim 7, wherein the second conduit has a greater diameter than the third conduit.