DIES CHANGING METHOD FOR PRESSES

Abstract: A method of changing dies for a press machine of the type including two or more slides (3a, 4a) arranged in a side-by-side relationship of which lower dead point in terms of a crank angle is different from one another, wherein resilient means (10) is interposed between upper die halves (7a, 8a) and lower die halves (7b, 8b) for the respective slides (3a, 4a) and movement of the respective slides (3a, 4a) is simultaneously interrupted at a crank angle in the proximity of an intermediate angle between the plural lower dead points so that clamping of upper die halves (7a, 8a) to and unclamping of the upper die halves (7a, 8a) from the respective slides are achieved during the interruption of movement of the respective slides, whereby mounting of dies on or dismounting of the same from presses is simultaneously achieved for the respective slides (3a, 4a). Abstract This invention relates to a dies changing method for a press in which not less than two slides (3a, 4a) having differ­ ent crank angles at respective lower dead centers are provided in parallel with each other. Elastic members (15) are inter­ posed between the upper dies (7a, 8a), on the slides (3a, 4a) and lower dies (7b, 8b), and the slides (3a, 4a) are stopped si­ multaneously when a crank angle is in the vicinity of a level which is halfway between a plurality of crank angles at the lower dead centers mentioned above. At this time, the attaching or detaching of the upper dies (7a, 8a) to or from the slides (3a, 4a) is done, whereby the attaching or detaching of the dies is done simultaneously for each slide (3a, 4a).

Description: The present invention relates to changing dies for a press machine such as a transfer press or the like having two or more slides arranged in a side-by-side relationship whose lower dead points in terms of a crank angle are different from each other. As shown in Fig. 10, a hitherto known transfer press employable mainly for deep drawing operations is provided with a link driven type slide b adapted to be driven by a link mechanism on the upstream side as seen in the direction of transference of workpieces (as represented by arrow a ) and an eccentric gear driven type slide (hereinafter referred to as an eccentric driven type slide) d adapted to be driven by an eccentric portion on the main shaft via a connecting rod on the downstream side. With such conventional transfer press, a crank angle representative of the lower dead point of the link driven type slide b for deep drawing operation on the upstream side differs from a crank angle representative of the lower dead point of the eccentric driven type slide d by an angle in the range from 10° to 20°. When one slide has reached its lower dead point, the other slide has still a certain amount of gap between the upper die half and the lower die half. In view of this fact, conventional die changing is achieved for two slides in such a manner that one of the dies is separately unclamped from the corresponding slide at a different time from when it is lowered to its lower dead point. This leads to drawbacks that a long time is required for die changing and die changing operations are performed at a reduced efficiency. DE-A-2816928 describes a press machine including a single slide having upper die halves, lower die halves and means for clamping each of the upper die halves to the slide and unclamping each of the upper die halves from the slide when the movement of the slide has been interrupted. The transfer bars of the press, which are used to feed workpieces through the press, are moved with the dies of the press when the dies are changed. The present invention has been made with the foregoing background in mind and its object resides in providing a method of changing dies for a press machine of the type including two or more slides whose lower dead point in terms of a crank angle are different from each other which assures that the dies on the slides can simultaneously be exchanged with other ones and a time required for die changing can be reduced substantially. According to one aspect of the present invention there is provided a press machine including first and second slides, each of said slides having an upper die half and a lower die half and one of the slides having its lower dead point at a different crank angle from that of the other slide, and a die changing device for changing the upper and lower die halves of each of said slides when each slide is near its lower dead point, said device comprising: elastic means interposed between the upper die halves of each of said slides and their respective lower die half; interrupt control means for interrupting movement of said slides at a crank angle between the crank angles corresponding to the respective lower dead points of said slides; and die changing means for clamping each of said upper die halves to its respective slide and unclamping each of said upper die halves from its respective slide when the movement of the slides has been interrupted. According to another aspect of the present invention there is provided a method for changing the dies of a press machine, the press machine comprising a plurality of slides, each of said slides having an upper die half and a lower die half and one of said slides having its lower dead point at a different crank angle from that of the other slide, the method comprising interposing elastic means between each of the upper die halves and its respective lower die half, interrupting movement of both of said slides at a crank angle between the crank angles corresponding to the respective lower dead points of said slides, and unclamping each of the upper die halves from its respective slide so that each upper die half is borne by said elastic means. Consequently, according to the present invention, die changing (die unclamping/die clamping) can simultaneously be achieved with the respective slides. This assures that a time required for die changing can substantially be reduced and a transfer press can be operated at an improved efficiency in comparison with the conventional method, in which die changing has been executed separately for respective slides. Further, since there is no need to provide a separate control circuit for die changing for respective presses, electric circuits can be simplified and they can be produced at an inexpensive cost. Fig. 1 is a front view illustrating a transfer press for which a method in accordance with an embodiment of the present invention is employed, Fig. 2 is a plan view of the transfer press in Fig. 2, Fig. 3 is a timing diagram for a link driven type slide, Fig. 4 is a timing diagram for an eccentric driven type slide, Fig. 5 is a timing diagram for both the link driven type slide and the eccentric driven type slide, Fig. 6 is an enlarged front view of an elastic stopper usable for the transfer press in accordance with the embodiment of the present invention shown in Figs. 1 and 2, Fig. 7 is a partial view illustrating both presses at the time of clamping/unclamping of dies, Fig. 8 is a block diagram illustrating by way of example the structure of a control system, Fig. 9 is a step diagram illustrating a series of steps to be performed at the time of die changing, and Fig. 10 is a front view illustrating a transfer press for which a conventional method is employed. Fig. 1 is a front view illustrating a transfer press for which the method in accordance with an embodiment of the present invention is employed and Fig. 2 is a plan view of the transfer press in Fig. 1. In Figs. 1 and 2, reference numeral 1 designates a housing for a three column type transfer press including three sets of uprights 1a, 1b and 1c. The transfer press comprises a link press 3, disposed on the upstream side as seen in the direction a of transference of workpieces 2, including a link driven type slide 3a; and an eccentric press 4 disposed on the downstream side and including an eccentric gear driven type slide 4a (hereinafter referred to as an eccentric driven type slide). Both the link driven type slide 3a and the eccentric driven type slide 4a are driven by a single main motor (not shown). The link press 3 is such that the slide 3a is driven in the vertical direction via a link mechanism so that workpieces 2 are subjected to press forming between three upper die halves 7a clamped to the slide 3a and three lower die halves 7b clamped to a moving bolster 3b. With this link driven type slide 3a, a relationship as represented by a curve A in Fig. 3 is established between a crank angle and a feed stroke. In the illustrated case, the slide 3a has a lower dead point represented by a crank angle of 192°. Usually, the link driven type slide 3a has a crank angle representative of the lower dead point in the range from 190° to 200°. Incidentally, in Fig. 3 curves B, C and D show operations of transfer bars 6. As is well known, the eccentric press 4 is such that the slide 4a is driven in the vertical direction via a slide driving mechanism (not shown) comprising an eccentric portion arranged round the main shaft and a connecting rod so that workpieces 2 are subjected to press forming between three upper die halves 8a clamped to the slide 4a and three lower die halves 8b clamped to a moving bolster 4b. With this eccentric driven type slide 4a, a relationship as represented by a curve A′ in Fig. 4 is established between a crank angle and a feed stroke. This eccentric driven type slide 4a has a lower dead point represented by a crank angle of 180°. Incidentally, in Fig. 4 curves B, C and D likewise show operations of transfer bars 6. As is apparent from Fig. 5, the transfer press in accordance with this embodiment has a difference of about 12° between the lower dead point crank angle for the slide 3a of the link press 3 and the lower dead point crank angle for the slide 4a of the eccentric press 4. Referring to Figs. 1 and 2 again, workpieces 2 which have been introduced into the housing 1 of the transfer press by a destacker 5 are successively transferred to respective work stations in the eccentric press 4 by the transfer bars 6 adapted to be displaced three-dimensionally. In the illustrated case, each of the transfer bars 6 has five sections 6 1 , 6 2 , 6 3 , 6 4 and 6 5 divided by bar connectors 6a, 6b, 6c and 6d on one side. To assure that the workpieces 2 are clamped between both the upper and lower die halves, the respective transfer bars 6 have a plurality of fingers 9 attached thereto. The moving bolsters 3b and 4b are intended to move on rails 11 in the transverse direction relative to the direction of transference of the workpieces 2 in order to assure that die changing is achieved easily and quickly. In the illustrated case, the transfer press has two moving bolsters for the link press and two bolsters for the eccentric press (i.e., four moving bolsters in total). This is intended to provide such a convenience that with respect to both the link press and the eccentric press one of the moving bolsters remains in a waiting state with a die and transfer bars to be used for the next workpiece placed thereon while the other one is put in practical use. Each of the four moving bolsters 3b, 3b′, 4b and 4b′ is provided with a plurality of bar holders 12 on which the transfer bars 6 are placed when they are expanded to their maximum width. In addition, each of the moving bolsters 3b, 3b′ , 4b and 4b′ is provided with workpiece holders 13 on one side wall thereof so as to provide between the link press 3 and the eccentric press 4 an idle station on which a workpiece is temporarily held. This means that in this transfer press, the transfer bars 6 have a feed stroke which is set to 1/4 of a center distance L between the link press 3 and the eccentric press 4, i.e., L/4. To prevent the workpiece holders 13 constituting an idle station from colliding with the upright 1b during movement of the moving bolster, they are turnable by 90 degrees. To provide a safety for press operations, a plurality of safety fences 14 are arranged outside of the transfer press in such a manner that they are automatically lifted up when the moving bolsters move. With such construction of the transfer press, each of the lower die halves 7b and 8b is equipped with four elastic stoppers 15 made of, e.g., polyurethane resin. The elastic stoppers 15 serve not only as shock absorbers between upper and lower die halves during press operation but also as interpositions between upper and lower die halves during die changing. Specifically, each elastic stopper 15 assumes a state as represented by solid lines in Fig. 6 under no load but assumes a state as represented by dotted lines in the drawing because of its elasticity when it receives a certain intensity of press force. The transfer press in accordance with the present invention is intended to perform a step of die changing by utilizing the aforementioned nature of the elastic stoppers 15. In detail, while the step of die exchanging is performed, the slides 3a and 4a of the link press 3 and the eccentric press 4 are simultaneously stopped when an intermediate angle between the lower dead point crank angle of the link driven type slide 3a (192° in the illustrated case) and the lower dead point crank angle of the eccentric driven type slide 4a (180° in the illustrated case), i.e. the intermediate angle of 186° in the illustrated case, is reached. At this moment, the upper die halves 7a and 8a for both the presses 7a and 8a can simultaneously be unclamped from the slides 3a and 4a. As shown in Fig. 7, when the intermediate angle of 186° is reached, the slide 3a of the link press 3 is moving downwardly toward the lower dead point while the slide 4a of the eccentric press 4 is moving upwardly away from the lower dead point. At this moment, an appreciable amount of gap corresponding to a crank angle of 6° is existent between both the upper and lower die halves of the presses 3 and 4. In practice, each elastic stopper 15 is so designed that the gap is less than the height h of the elastic stopper 15 under no load (see Fig. 6). Thus, there is no fear that the upper die halves 7a and 8a fall down on the floor when they are unclamped from their slides 3a and 4a, as long as the aforementioned state is maintained. Namely, they are immovably held on the lower die halves 7b and 8b via the elastic stoppers 15 interposed therebetween. Then, die changing can simultaneously be achieved for the link press 3 and the eccentric press 4 by raising up the slides 3a and 4a and then exchanging the working bolsters with the waiting bolsters. Fig. 8 shows by way of example the structure of a control system for the transfer press. The control system comprises a bolster driving unit 20 for controlling the movement of moving bolsters 3b, 3b′, 4b and 4b′ and the driving of respective components associated therewith, a transfer bar driving unit 30 for controlling the three-dimensional movement of transfer bars 6 and the driving of respective components associated therewith, a press driving unit 40 for controlling the raising/lowering of slides of the link press 3 and the eccentric press 4 and the driving of respective components associated therewith, a safety fence raising/lowering unit 50 for raising and lowering the safety fences 14 and a press controller 60 for executing total control for the aforementioned units. Next, operations during the die exchanging as mentioned above will be described in detail below with reference to Fig. 9 which is a step diagram. First, a die change button (not shown) is turned on by an operator (step 1). When completion of the step 1 is confirmed, the press controller 60 gives a command to the transfer bar driving unit 30 to lock feed levers (not shown) so as not to allow the transfer bars 6 to be displaced in the direction a of transference of workpieces as the crank shaft is rotated (step 2). At this moment, the press controller 60 executes a forcible bar unclamping operation for expanding the width between the transfer bars 6 on both the sides to the maximum one (step 3). In addition, at the same time, lowering of the die cushions (not shown) is initiated, whereby the moving bolsters 3b and 4b are ready to move (step 9). Next, the press controller 60 gives a command to the bolster driving units 20 and the transfer bar driving unit 30 at the same time as the step 3 is terminated so that the transfer bars 6 are lowered so as to allow them to be placed on the bar holders 12 attached to the moving bolsters 3b and 4b while their width is expanded to the maximum one (step 4). At this moment, the workpiece holders 13 attached to the bolsters 3b and 4b as idle stations are turned by an angle of 90° until the workpiece holders are received in the bolsters (step 5). Then, the idle fingers 9 (representative of fingers fitted to the transfer bars 6 3 ) adapted to clamp a work on the idle station are displaced to predetermined positions on the bolster 3b or 4b (step 6). Displacing means (not shown) is provided for the purpose of displacing the idle fingers 9 so that retraction of the idle fingers 9 permits them to be replaced with new ones in correspondence to a die to be next used. Thereafter, the press controller 60 gives a command to the transfer bar driving unit 30 at the same time as the steps 4, 5 and 6 are terminated so that the joint connectors 6a, 6b, 6c and 6d for the transfer bars 6 are released so as to allow the transfer bars 6 to be divided into five sections 6 1 to 6 5 (steps 7 and 8). In addition, the press controller 60 gives a command to the press driving unit 40 at the same time as the steps 7 and 8 are initiated so that the link press 3 and the eccentric press 4 start to lower their slides 3a and 4a (step 10). At this moment, the slide 3a of the link press 3 and the slide 4a of the eccentric press 4 perform their lowering movement along curves A and A′ in Fig. 5. As both the slides 3a and 4a are lowered, first the slide 4a of the eccentric press 4 reaches its lower dead point (represented by a crank angle of 180°) and then it starts to be raised up. Thereafter, when the crank angle reaches 186°, the slides 3a and 4a of both the presses 3 and 4 have the same height, as shown in Fig. 7. Namely, when the crank angle has reached 186°, the slide 3a is moving downwardly and the slide 4a is moving upwardly. When the press controller 60 detects that the crank angle has reached 186°, it gives a command to the press driving unit 40 so that upward/downward movement of both the slides 3a and 4a is interrupted and upper die halves 7a and 8a are simultaneously unclamped from the slides 3a and 4a (step 11). At this moment, an appreciable amount of gap corresponding to a crank angle of 6° exist between the upper and lower die halves on the presses 3 and 4, as mentioned above. To adapt to the gap, the elastic stoppers 15 are so designed that the gap is less than the height h of the elastic stopper 15 under no load (see Fig. 6). As long as the foregoing state is maintained, there does not arise a malfunction that the upper die halves 7a and 8a fall down on the floor when they are unclamped from the slides 3a and 4a but they are immovably held on the lower die halves 7b and 8b with the elastic stoppers 15 interposed therebetween. On completion of the unclamping operations for the upper die halves 7a and 8a, the press controller 60 restarts to drive the slides 3a and 4a. Namely, the slide 3a of the link press 3 is lowered further and it is then raised up after it reaches the lower dead point (representative of a crank angle of 192°). In the meantime, the slide 4a of the eccentric press 4 is raised up. Thereafter, on completion of the dividing operations for the transfer bars 6 at the step 8, the press controller 60 outputs a command to the bolster driving unit 20 so as to allow MB clampers (not shown) with which the moving bolsters 3b and 4b are fixed to their beds to be unclamped (step 13). Then, the MB clampers are raised up (step 14), whereby the moving bolsters 3b and 4b are ready to move on the rails 11. At the same time, the press controller 60 gives a command the safety fence raising/lowering unit 50 so that all the safety fences 14 are raised up (step 17). Next, the press controller 60 outputs a command to the bolster driving unit 20 so as to allow the moving bolsters 3b and 4b to move in the direction of arrow marks e in Fig. 2 until they are simultaneously displaced to their waiting positions as represented by dotted lines in Fig. 2. It should be noted that in addition to the upper and lower die halves, the transfer bars 6 2 and 6 4 and the idle fingers are mounted on the moving bolsters 3b and 4b. On the other hand, another moving bolsters 3b′ and 4b′ are previously provided for the presses 3 and 4, and in addition to die halves 7a′, 7b′, 8a′ and 8b′ to be next used, transfer bars 6 2 ′ and 6 4 ′ having fingers 9 attached thereto in correspondence to these die halves and idle fingers are previously mounted on the bolsters 3b′ and 4b′. As the moving bolsters 3b and 4b are displaced away from their working positions, the moving bolsters 3b′ and 4b′ are caused to move in the press housing 1 (step 16). Thereafter, reverse operations to those in the steps 1 to 15 are performed at steps 17 to 31 so that lowering of the safety fences 14, clamping of the upper die halves 7a′ and 8a′ to the slides 3a and 4a and returning of the transfer bars to their operative state are achieved, whereby the intended die changing is terminated completely. Incidentally, at the steps 20 to 22 movement of both the slides 3a and 4a is interrupted when the crank angle reaches an intermediate angle of 186° between the lower dead point crank angles of both the slides 3a and 4a in the same manner as at the aforementioned steps 10 to 12. At this time, upper die halves 7a′ and 8a′ can simultaneously be clamped to both the slides 3a and 4a. In this manner, according to the foregoing embodiment, when die changing is executed in a transfer press of the type including a link press 3 and an eccentric press 4, of which each slide has a different lower dead point represented by a crank angle from the other, movement of the slides 3a and 4a of both the presses 3 and 4 is simultaneously interrupted so as to allow upper die halves to be unclamped from the slides and the unclamped upper die halves are elastically supported on elastic stoppers on lower die halves. With the above construction, there does not arise a malfunction that the upper die halves fall down on the floor. Instead, they are immovably held on the lower die halves. Thereafter, by displacing moving bolsters away from their working positions, the working dies for both the presses can be removed simultaneously. Next, die mounting is achieved in the following manner. New dies each including an upper die half to be next used and a lower die half to be next used, the former being placed on the latter with elastic stoppers interposed therebetween, are clamped to the moving bolsters. Then, movement of the slides 3a and 4a of both the presses 3 and 4 is simultaneously interrupted at an intermediate angle between the lower dead point crank angles of both the slides in the same manner as mentioned above. While the foregoing state is maintained, upper die halves are clamped to both the slides. In this manner, the new dies for both the presses can simultaneously be mounted on the latter. Thus, the method of the present invention makes it possible to remarkably reduce a time required for die changing in comparison with the conventional method of die changing. This permits the transfer press to be operated at an improved operational efficiency. Further, since there is no need of arranging a control circuit required for die changing separately for the respective presses, the electrical circuits can be simplified and thereby they can be produced at a reduced cost. In the foregoing embodiment, the crank angle employed at the time of unclamping/clamping of the dies is set to an intermediate angle between the lower dead point crank angles of both the slides. Strictly speaking, the intermediate angle should not necessarily be selected in that way. Alternatively, an angle in the vicinity of the intermediate angle can be employed with the same advantageous effects as in the foregoing embodiment. Namely, the crank angle at the time of unclamping/clamping may be determined in dependence on the height h of the elastic stoppers under no load, their elastic properties and so forth. The foregoing embodiment has been described above with respect to a transfer press of the type including two slides. Alternatively, the present invention may be applied to a transfer press including three or more slides of which lower dead point in terms of a crank angle is different from each other. Further, in the foregoing embodiment, the elastic stoppers 15 are fitted to the lower die half. Alternatively, they may be fitted to the upper die half. Moreover, in the foregoing embodiment, a transfer die feeder is employed as work transferring means. Alternatively, the present invention may be applied to a press machine including a progressive die or the like for which a work is transferred by transferring means other than a transfer feeder. INDUSTRIAL APPLICABILITY The present invention is useful for changing dies for a press machine such as a transfer press or the like including two or more slides of which lower dead point in terms of a crank angle is different from each other.

Claims: A press machine (3, 4) including first and second slides (3a, 4a), each of said slides having an upper die half (7a or 8a) and a lower die half (7b or 8b) and one of the slides having its lower dead point at a different crank angle from that of the other slide, and a die changing device for changing the upper and lower die halves of each of said slides when each slide is near its lower dead point, said device comprising: elastic means (15) interposed between the upper die halves of each of said slides and their respective lower die halves; interrupt control means for interrupting movement of said slides at a crank angle between the crank angles corresponding to the respective lower dead points of said slides; and die changing means for clamping each of said upper die halves to its respective slide and unclamping each of said upper die halves from its respective slide when the movement of the slides has been interrupted. A press machine (3, 4) as claimed in claim 1, wherein said elastic means (15) is fitted to the upper surface of each of said lower die halves (7b, 8b). A press machine (3, 4) as claimed in claim 1, wherein said elastic means (15) is fitted to the lower surface of each of said upper die halves (7a, 8a). A press machine (3, 4) as claimed in any preceding claim, wherein said elastic means (15) is provided in the form of a plurality of elastic members each corresponding to one of said slides (3a, 4a). A press machine (3, 4) as claimed in any preceding claim, wherein said press machine (3, 4) comprises a transfer device for transferring a workpiece (2) from one of said slides (3a, 4a) to another by means of a transfer bar (6). A method for changing the dies of a press machine (3, 4), the press machine comprising a plurality of slides (3a, 4a), each of said slides having an upper die half (7a or 8a) and a lower die half (7b or 8b) and one of said slides having its lower dead point at a different crank angle from that of the other slide, the method comprising interposing elastic means (15) between each of the upper die halves and its respective lower die half, interrupting movement of both of said slides at a crank angle between the crank angles corresponding to the respective lower dead points of said slides, and unclamping each of the upper die halves from its respective slide so that each upper die half is borne by said elastic means. A method for changing dies for a press machine (3, 4) including first and second slides (3a, 4a), each of said slides having a first upper die half (7a or 8a) and a first lower die half (7b or 8b), and at least one of the slides having its lower dead point at a different crank angle from that of the other slide, said method comprising the steps of: interposing an elastic member (15) between the upper die half and the lower die half of each of said slides; interrupting movement of said slides at a crank angle between the crank angles corresponding to the respective lower dead points of said slides; unclamping said first upper die halves (7a, 8a) from their respective slides while said slides are held stationary; restarting movement of said slides; retracting said first upper and first lower die halves from said press machine; introducing into the interior of said press machine a second upper (7a′, 8a′) and a second lower (7b′, 8b′) die half for each of said slides; interrupting movement of said slides at a crank angle between the crank angles corresponding to the respective lower dead points of said slides; clamping said second upper die halves to their respective slides while said slides are held stationary; and restarting movement of said slides. A method as claimed in claim 6 or 7, wherein said elastic member (15) is fitted to the upper surface of each of said lower die halves (7b, 8b). A method as claimed in claim 6 or 7, wherein said elastic member (15) is fitted to the lower surface of each of said upper die halves (7a, 8a). A method as claimed in any of claims 6 to 9, wherein said elastic member (15) is provided in the form of a plurality of elastic members each corresponding to one of the said slides (3, 4).

Inventors: NODA, SHIGEKAZU
Applicants: KABUSHIKI KAISHA KOMATSU SEISAKUSHO
Application year: 1988
Main classification: B21D37
IPC codes: B21D37, B30B15