EP0100282B1

EP0100282B1 - A bridge type punch press

Info

Publication number: EP0100282B1
Application number: EP83401523A
Authority: EP
Inventors: James R. Hunter; James S. Lazzarotti
Original assignee: Warner and Swasey Co
Current assignee: Warner and Swasey Co
Priority date: 1982-07-26
Filing date: 1983-07-25
Publication date: 1987-05-06
Also published as: EP0100282A1; EP0100283B1; EP0100283A3; EP0100283A2

Description

Background of the Invention

Technical Field

This invention relates to metal working and more particularly to an improved bridge type sheet metal punching press.

Background Art

Sheet metal punch presses with a bridge type frame supporting a punching head-have been known for some time. US-A-4220062 teaches a punch press which utilizes elongated tool supporting members which can be moved back and forth to select the proper tool. However, the tool supporting members are mounted permanently in the press and cannot be removed to facilitate ready interchangeability. US-A-4168644 teaches a stamping machine including a tool changing mechanism. This machine has the disadvantage that the tools are held singly on a cumbersome and complicated chain arrangement.

Disclosure of the Invention

The invention sets out to avoid disadvantages of the prior art and provides a punch press comprising a frame which spans a punching area, a punch head supported on said frame above the punching area, a two axis worksheet positioning mechanism for positioning a sheet metal workpiece at desired locations in the punching area, an elongated punch support formed from removable punch cartridges each of which supports a plurality of punches, the punch cartridges being joined together and positionable as a unit to bring a selected punch beneath the punch head, and an elongated die support formed from removable die cartridges, each of which supports a plurality of dies, the die cartridges corresponding to said punch cartridges and being joined and positionable as a unit to position an appropriate die to receive the selected punch.
Additional optional features are set out in the dependent claims.

Brief Description of the Drawings

For a better understanding of the invention, reference may be had to the preferred embodiment exemplary of the invention shown in the accompanying drawings in which:

Figure 1 is an isometric view of a punch press constructed according to the teaching of the present invention;
Figure 2 is a top view of the punch press shown in Figure 1;
Figure 3 is a left side view of the punch press shown in Figure 1;
Figure 4 is a front view of the punch press shown in Figure 1;
Figure 5 is a section view through the punching assembly showing the disappearing table and elongated tool cartridges;
- Figure 6 is a view similar-to Figure 5 but with the cartridges moved to the right;
Figure 7 is a section view taken of Figure 6 along the line VII-VII through a punch cartridge and a die cartridge;
Figure 8 is a top view of the upper punch cartridge showing a portion of the driver section and one tool cartridge;
Figure 9 is a section view taken of Figure 8 along the line IX-IX showing the connection between the driver section and the tool cartridge;
Figure 10 is an isometric view of an upper and lower cartridge;
Figure 11 is a top view of the lower die cartridge and driver;
Figure 12 is a view of Figure 11 along the line XII-XII;
Figure 13 is a section view along the line XIII-XIII of Figure 11;
Figure 14 is a view similar to Figure 13 but with an additional cartridge in place;
Figure 15 is a view showing the X-axis cross slide;
Figure 16 is a view showing the Y-axis carriage drive;
Figure 17 is a detailed view of the indexing pin;
Figure 18 is an isometric view from the back of the press showing a tilting unload table;
Figure 19 is a view of the punch head assembly with portions deleted or broken away for clarity;
Figure 20 is a view taken in Figure 19 along the line XX-XX;
Figure 21 is a diagrammatic view of the cartridge drive system showing the die cartridge;
Figure 22 is a diagrammatic view of the cartridge drive system showing the punch cartridge;
Figure 23 is a diagrammatic view of the disappearing table showing the automatic connection system;
Figure 24 is a cross section through a punch holder and die holder;
Figure 25 is an isometric view of the tool changing station; and,
Figure 26 through 30 illustrate cartridge changing operation in a three cartridge press;

Best Mode for Carrying Out the Invention

Referring now to the drawings, and Figures 1 to 4 in particular, there is shown a punch press 20. Punch press 20 is constructed with a bridge frame press assembly 30 having a two axes, X-Y, sheet positioning system 50 integrally connected thereto. Preferably bridge frame 30 supports a pair of punching heads 32 and 34. Punch head 32 is the standard punch head and punch head 34 is optional for twin punching. Twin punching heads 32 and 34 are substantially identical and operate separately or in parallel to double machine productivity.
A cartridge tooling arrangement 90, as shown in Figure 10, consisting of a punch cartridge 92 and a die cartridge 94, is positionable within bridge frame 30. The punch holding cartridge 92 is provided for holding punches, and the die holding cartridge 94 is provided for supporting appropriate dies used with the punches. The punch cartridge 92 and die cartridge 94 are synchronously positionable within frame 30 to bring a selected punch into position for being activated, through an appropriate mechanism, by one of the punching heads 32, 34. During operation a suitable die for use with the selected punch is positioned to receive the activated punch. As shown in Figures 21 and 22 and as will be described in more detail hereinafter the punch cartridge drive and die cartridge drive are synchronized together and driven from a common motor through drive chains whereby each punch is always directly located above its associated die. The punch and die cartridges 92, 94 are moved back and forth in lock step so that when the desired punch is moved to a position under the punch head 32, 34 the desired die is also always properly positioned beneath the punch at exactly the same time. During operation a workpiece 21 to be punched is moved into the proper position beneath one of the punching heads 32, 34 by sheet positioning system 50.
The bridge press frame 30 supports the linear tool holding cartridge 92, 94 and punch heads 32, 34. The two axis sheet positioning system 50 supports and positions a sheet metal workpiece 21. The press frame 30 and integral sheetmetal support table frame 53 define a three point support area and alignment of worksheet 21 relative to a selected punching tool is insured at all times, independent of the support floor. Punch press 20 therefore does not require a special foundation and this reduces installation time and cost, and simplifies relocation. The table carriage 52, which ' supports a cross slide 51 having sheet metal grippers 54, 56 mounted thereon, is of a bridge type construction permitting sheet loading from the side or front end of punch press 20.
A cartridge support cart 70, utilized with punch press 20, receives the punch and die linear cartridges 92, 94 from punch press 20 and permits offline tool changing. While the online cartridges are actively used in punching a worksheet, the offline cartridges can have their tools checked and replaced as required to be ready for the next lot of sheet metal panels to be punched. Setup time for the next set of sheet metal panels will then be short and consist of sliding out one set of cartridges 92, 94 and sliding in the already loaded second set of cartridges 92, 94. This concept increases machine uptime and productivity.
Referring now to Figures 5 through 14 there is shown a linear cartridge tool system 90 utilized in punch press 20. Linear tool cartridge system 90 consists of punch cartridge sections 92 and die cartridge sections 94. Tool cartridges 92 and 94 are simultaneously moved into proper position so that when punching head 32, 34 engages a selected punching tool in cartridge 92 it is reciprocated through the worksheet 21 into an associated die supported by cartridge 94 beneath worksheet 21. As shown in Figures 5 and 6, driver sections 192 and 194, which can engage and position cartridges 92 and 94 respectively, are movable within the frame portion 30 of punch press 20. A plurality of cartridges 92 and 94 can be linked together to form a cartridge with the desired tool selection. A disappearing table 95 is engaged by the last die cartridge 94 and is positioned following the last die cartridge 94 in frame 30.
As best shown in Figures 21, 22 and 23 a common drive motor 202 through an appropriate chain drive arrangement synchronously drives punch drive sprocket 210 and die drive sprocket 230. Sprockets 210 and 230 are attached to drive shafts 212 and 232 respectively. Attached to shafts 212 are sprockets 214 and 216 which drive chains 218 and 220. A driver block 192 is connected to driven chains 218 and 220 to be positioned as these chains are moved by drive motor 202. Driver block 192 attached to the dual drive chains 218 and 220 moves the upper punch cartridge 92 to position a desired tool under punch head 32, 34.
Drive motor 202 drives chain 203 which is connected to sprockets 210 and 230 for synchronous positioning of cartridges 92, 94. As drive motor 202 positions sprocket 230 the connected shaft 232 supports and positions sprockets 234, 236. Sprockets 234 and 236 drive a pair of mating chains 238 and 240 respectively. Driver block 194 is connected to and positioned by the pair of mating chains 238, 240. Connected to driver block 194 are die cartridges 94 which are positioned synchronously with their mating punch cartridges 92.
In order to support the sheet during punching, as the cartridges move back and forth, a disappearing table 95 is provided. Disappearing table 95 consists of sections 97, which are positioned by the last cartridge 94, and sections 242, which are positioned with the driver block 194. As shown in Figures 13 and 14, when cartridges 94 are being connected together pin 110 is in a raised position and locking pin 112 moves into position to maintain pin 110 in a raised position. For the last cartridge 94 used however, pin 110 is not locked in an upward position. Pin 110 is spring biased to a down position and when not locked in an up position will, as the last cartridge 94 enters punch press frame 30, engage and move disappearing table sections 97. Disappearing table 95 will then fill in the area beneath the punching heads within frame 30 which is not occupied by cartridges 94. The disappearing table 95 is provided to provide support for the sheet metal workpiece next to the die cartridge 94. Two arrangements of disappearing tables are utilized. In one arrangement portions 242 of disappearing table 95 are attached to and positioned by the pair of mating chains 238, 240. The disappearing table 95 consists of a series of U-shaped support surfaces that are capable of disappearing from the horizontal plane and moving downward vertically as the cartridge 94 moves to the right. Each table link 242 is articulated from its connection to chains 238 and 240 to negotiate the 90 degree corner. As die cartridge 94 is moved back and forth disappearing tables sections 242 move into and out of the horizontal plane to provide support for the sheetmetal workpiece on one side of die cartridge sections 94. The pair of mating chains 238 and 240 extend around sprockets which are attached to shafts 244 and 246 and complete the loop at driver 194.
A different arrangement is provided for disappearing table sections 97 which are positioned and provide support at the rear of die cartridge 94. Disappearing tables sections 97 which are provided at the rear of cartridge 94 are attached to a second pair of mating chains 250 and 252. The second set of mating chains extend around idler sprocket 254, 256, 258, 260 which are supported by idler shafts 244, 246. Disappearing tables sections 97 follow automatically the last die cartridge sections 94 to be pulled into punch press 20. Idler sprockets 254, 256 and idler sprockets 258, 260 which support chains 250, 252 have bearing supports from shafts 244 and 246 respectively. Thus idler sprockets 254, 256, 258, 260 can turn independently of their supporting shafts 244, 246. These sprockets 254, 256, 258 and 260 which support chains 250 and 252 have ball bearing centers in order to turn freely on the respective support shafts 244, 246 and therefor do not necessarily turn and rotate when mating chains 238, 240 are positioned. Chains 250, 252 are attached to the vertical support pins 110 located in cartridge 94 by means of an anchor shaped hook 262 having two U-shaped portions. The hook 262 allows the engaged cartridge 94 to pull chains 250 and 252 and position the associated disappearing table sections 97. An air cylinder 270 positions an idler shaft 272 to maintain a constant pull on chains 250, 252 so that the hooks 262 firmly attach to pins 110 even when cartridge 94 moves in opposite direction. That is, cylinder 270 biases chains 250, 252 towards retracted position into engagement with pins 110.
An automatic connection system is provided for automatically engaging and positioning the drive chain 250, 252 for disappearing table sections 97. Since punch press 20 can be operated with one or more die cartridges it is important that the disappearing table sections 97 follow the last cartridge 94 section to be introduced into press frame 20 to support the worksheet 21 to be punched. The disclosed system requires no operator intervention or any special tool or fixtures to accommodate automatic connections of chains 250, 252 to the last die cartridge 94.
During operation as the die cartridge driver block 194 moves to project die cartridges 94 outside of the press frame 30 and onto the change station cart 70 the disappearing tables sections 97 move around the corner and descend vertically towards the lower chain level. When the disappearing table elements have totally left the horizontal upper position and have cleared a path for the cartridge to pass above them the hook 262 on each of the two chains 250 and 252 contact the stationary chain pins 271. The bias force to pull the chains 250, 252 downward to a retracted position provided by the air cylinder 270, acts as a constant spring force pulling hooks 262 into contact with pins 271.
Each hook 262 has two U-shaped portions. One of the U-shaped portions engage pin 110 when the disappearing table sections 97 are moved by cartridge 94. The other U-shaped portion engages pin 271 when cartridges 94 are moved out of punch press 20. The cartridge 94 when moved onto tool cart can be slid horizontally to disconnect locking elements 120 and 122. It should be noted that the tool cartridge 94 can be interchanged and replaced without the need for the operator to use any tools. Sliding cartridge 94 horizontally on cart 70 disconnects the joints. When a new cartridge has been slid into position and the control system for the press energized a punch driver block tows cartridge 94 back into the press frame. During this initial motion sections 97 of the disappearing table remains stationary since hook 262 remains in engagement with pin 271. If a following die cartridge 94 is in position, pin 110 is held in the up position as shown in Figure 14. In this fashion as cartridge 94 is towed past hook 262 no connection will be made and the disappearing table sections 97 will remain in a stationary downward position. As the last cartridge 94 is pulled in, from the tool change stations on cart 70, pin 110 moves vertically downward as it is pulled off of cam surface 274. Pin 110 is then in position as shown in Figure 13. As the end of the last cartridge 94, to go into the press frame, enters it engages hook 262 and moves the associated chains 250, 252. After this point motion of the cartridge entering the frame is followed by the disappearing table sections 97 as they are elevated up to the horizontal position. Disappearing table sections 97 are towed evenly by the two pins 110 which contact the hooks 262 that attaches the ends of chains 250, 252.
When cartridges 90 are moved to the offline position the tooling cartridges are moved outside of the main bridge press frame structure 30 onto a support tray structure 70. An upper support tray supports the punch holder offline cartridge 92 while a lower tray supports the die holder offline cartridge 94. Once the cartridges 92, 94 are outside of the bridge frame 30 they may be separated by moving the offline cartridge sections 92, 94 towards the operator. As can best be seen in Figure 9, separation of the offline cartridges 92. 94 from the online cartridges 92, 94 is accomplished by sliding the upward projecting member 120 from the downward projecting latch 122. Similar latching members are provided on both punch cartridges 92 and die cartridge 94.
As shown in Figures 24 and 10, the upper tool cartridge 92 contains standard punch holders 149. The punch holder 149 contains the punch 301 and serves as the moving bearing surface against the punch cartridge 92 during punching periods. Index pin holes 91 are provided in line with each punch holder 149, which is supported in punch cartridge 92. Index pin holes 93 are provided in die cartridge 94 in line with each die holder 151. Cartridges 92 and 94 have a bearing surface for use in sliding the desired punch holder 149 and die holder 151 under the punch head 32, 34. To increase the tool density in the cartridges 92, 94 two parallel rows of tools have been used. The rows of tools are staggered along their longitudinal axes so that only one tool at a time is engaged by a punch head 32, 34. Normally several tool cartridges 92, 94 will be used. The tools in the first cartridge 92, 94 are the ones to be used on a wide variety of parts. These tools will be maintained online for most parts. In this fashion it is not necessary to have a duplicate set of these common tools in place. The offline cartridges 92, 94 contain various punches and dies that change from part to part. The number of tools in the cartridge 92, 94 which is maintained online most of the time versus the number of tools in the cartridges 92, 94 which are frequently offline can be varied to suit specific requirements. Cartridges 92, 94 can be configured to hold as many tools as desired by the user.
When twin punching heads 32 and 34 are utilized, any number, size and position of the tools in the second cartridge can be a repeat of the tools in the first cartridge. The two punching heads 32 and 34 are offset by the length of one cartridge. In this manner when the first cartridge positions a specific tool under the first punch head 32 an identical tool can also be positioned under the second punch head 34. Punch heads 32 and 34 operate in parallel thereby producing two identical parts or holes at the same time. The two punch heads 32, 34 can also be operated separately to produce similar parts at the same time. This can be accomplished when one panel needs one additional hole or one less hole by simply programming one punch head to run when the other does not. This operation creates similar panels while still enjoying the twin punch productivity benefits for the majority of common holes in both panels.
Figures 25 to 30 illustrate cart 70 which is used for changing cartridges. Cart 70 provide support for three sets of tool cartridges. Cart 70 also includes a storage area beneath the support area for holding additional tools. In the top work area the cartridges can easily be manipulated for changing punches and dies. As a punch and die cartridge set 90 exit from the press onto the tool station each cartridge 92, 94 enters its own respective support tray. The punch and die support trays are equipped with a series of roller wheels which engage and support the cartridge 92, 94 as it leaves the press frame 30 and enters onto its associated tray. This provides for low friction and allows the cartridges to easily be inserted into the hat shaped section trays. When a punch and die cartridge set 90 have been fully pushed into position on the tool changing cart 70 the upper and lower trays may then be manually moved forward and backward in a direction perpendicular to their longitudinal axes. The upper and lower trays are equipped. with roller wheels that mate with the top of the tool change station to allow the cartridges 92, 94 to be easily separated from one another. The separated cartridges can be replaced with other cartridges. These cartridges can be connected with other cartridges which remain in the press or with the driver blocks. The sliding disconnection of one set of cartridges from another is accomplished by the horizontal separation of the upward projecting member 120 from downward projecting latch 122. No tools are required by the operator to interchange cartridges at the tool change station.
Figures 26 to 30 illustrate a three cartridge system and a changing sequence. Cartridge set 901 contains standard tools that are used on all jobs. Cartridge set 902 is attached to cartridge set 901 and contains the special tools associated with a first job. Cartridge sets 901 and 902 then operate inside of press frame 30 to produce holes in the sheetmetal workpiece 21. Cartridge set 903 in the meantime is sitting offline at the tool change station 70 and is populated with tools to be used in the next job. The interchange of cartridge set 902 and 903 is shown in sequence in Figures 27 to 30. During changing cartridge set 902, as shown in Figure 28, is moved onto the tool cartridge cart 70. Cartridge sets 902 and 903 are then manually slid in a direction horizontally perpendicular to the tool cartridge motion in the press, leaving cartridge set 903 connected to cartridge set 901. The servo system then pulls cartridge set 903 and 901 back into operation in the press. Before press 20 resumes operation tool change station 70 is moved backward to a position as shown in Figure 26. Tool change station 70 rides on fixed rails and is moved back and forth between the positions shown in Figures 26 and 27 by a pneumatic cylinder.
Figures 5 and 6 illustrate the cartridge system installed in a bridge frame punch press structure 30. The bridge frame 30 provides excellent rigidity and support for the punching heads 32 and 34 and the tool cartridges 92 and 94. A cartridge tool changing window 98 is provided at one side of the press frame 30. This window 98 provides an opening to allow tool cartridges 92, 94 to be moved out of the press frame 30 onto tool cart 70.
Figure 24 shows a vertical section elevation of a punch holder 149 in an upper cartridge 92 above a die holder 151 in a lower cartridge 94. Punch holder 149 is held in an upright or raised position in upper cartridge 92 by means of a cam 302 resting against a plunger pin 304. Plunger pin 304 is pressed tightly against cam surface 302 by spring 306. This mechanism will adequately retain the punch holder 149 in its raised position. When the punch holder 149 is inserted under the puch head ram the force of the ram pushes punch holder 149 downward and cam 302 pushes the plunger pin 304 back into its cavity thereby allowing the punch holder to proceed downward out of the upper cartridge 92. The punch 301 held by punch holder 149 can then mate with an appropriate die 321 through the intervening sheetmetal workpiece to produce the desired hole. The crank shaft and ram then move to a part position at top dead center. At the top dead center position plunger pin 304 has remated with the cam surface 302 and will hold the punch holders 149 in their upward position as they leave the mating T-shaped head area in the ram.
The punch cartridge 94 and die cartridge 92 feature a guideway bearing system consisting of a plastic type bearing material on the cartridge mating with the metallic way strips. Both punch cartridge 94 and die cartridge 92 are equipped with seal strips that mate with the way track to keep foreign debris out of the area of the bearing surface and distribute lubrication to the surfaces.
Cartridge 92 is supported by an angled way 126 and a flat way 128. During punching an index pin 87 engages an opening 91 in cartridge 92 and urges cartridge 92 against a vertical face 132 of slanted way 126. This index pin arrangement provides for accurate alignment of cartridge 92. The lower die cartridge 94 also is guided on an angled way 136 and a flat way surface 138. During the punching operation an index pin 87 engages an opening 93 in cartridge 94 and urges it into high accuracy contact with a vertical face 142 of guideway 136. The lower cartridge 94 is supported by a bolster plate 124 during punching, thus preventing punching loads from being applied to the bearing guideway system.
Referring now to Figure 17 there is shown a more detailed view of the indexing pin mechanism. When cartridge 92 is positioned with the desired punching tool beneath punching head 32, 34 index pin 87 is driven by an appropriate drive mechanism 89 into indexing hole 91. Driving indexing pin 87 into hole 91 accurately aligns punch cartridge 92 longitudinally and moves it back against vertical surface 132 of the slanted guideway 126. This provides for high accuracy alignment of the selected tool in cartridge 92. A similar mechanism is provided for aligning the mating die in die cartridge 94. Thus, accurate alignment of the punch and die during operation is assured. When twin punching heads 32, 34 are provided two sets of index pins are utilized. At each punch head location there is an index pin for the upper cartridge and one for the lower cartridge for a total of four index pins.
In order for one of the punch heads 32, 34 to select and operate one of the two rows of tooling in punch cartridges 92 an interposer mechanism is required. As can be seen in Figures 19 and 20, the T-shaped punch head 159 fits within a T-shaped slot 161 in an interposer 160. Two interposers are provided to line up with the front and rear rows of punch tools in the cartridge 92. As described above, the tools in the cartridge 92 are located in a staggered pitch configuration such that when the specific punching tool is brought in line with the two interposers only one of the T-shaped slots 161 engages a punching tool. In this fashion the cartridge can be brought onto an interposer centerline and the punching head 32, 34 operated to stroke the interposer 160 and the aligned punching tool in a vertical plane. The other-interposer 160 and T-slot 161 is located between punching tool positions of the alternate row of tools and therefore does not actuate a punch in that row. The two-row tooling cartridge greatly enhances the packing density of tools within the cartridge 92, 94. More than two rows is possible.
Many parts processed on punch presses are of the type where multiple identical parts are grouped onto a common larger sheet. With the disclosed punch press 20 significant productivity increases can be obtained by incorporating two identical punch head mechanisms 32, 34 that interact with identical tooling in the tooling cartridge system 90. Each cartridge system 90 consists of a punch cartridge 92 and a die cartridge 94. In the preferred embodiment each system 90 contains twelve punches and dies. The punches and dies used in the cartridge system are identical to those used in some prior art punching machines. In the present preferred embodiment in the cartridges 92, 94 are 24" (about 60 cm) long. It is to be understood however, that different length cartridges could also be used. The spacing between twin punch head mechanisms 32, 34 is also designed to be 24" (about 60 cm). The second tool cartridge set 90 can be loaded to contain identical tool size and spacing patterns as the first tool cartridge set 90. For twin punching the two sets of cartridge sets 90 containing common tools are loaded into the cartridge system. A common sheet metal panel can then be loaded onto the table 51 and processed by means of actuating both punch heads at the same time while the sheet is stationary at each of its desired X-Y coordinates. The result is simultaneous punching of two identical parts and the throughput of the machine is virtually doubled.
Carriage 52 spans and extends around the sides of workpiece support table 53. Table 53 includes a plurality of spherical roller support members which permit low friction movement of work sheet 21. As shown on Figure 16 carriage 52 is constructed to extend around work table 53 and engages a ball screw positioning mechanism. As servo motor 55 is driven, through an appropriate ball screw arrangement, carriage 52 moves a workpiece to the desired Y-axis location. Servo drive motor 55 rotates a supported ball screw which is engaged by a ball screw nut attached to an underportion of carriage 52. Carriage 52 rides on linear ways and supports.
Referring now to Figure 15 there is shown a partial section view of the cross slide 51 which provides for X-axis" positioning of the workpiece. Servo drive motor 57 drives a ball screw arrangement which positions cross slide 51 along the X-axes. Sheet grippers 54 and 56 are retained in T-slot formed in cross slide member 51. Sheet grippers 54 and 56. are relatively positionable on cross slide 51 and they can grip the end or sides of a work sheet 21. Grippers 54 and 56 are supported by member 51 which is movable across carriage 52 to provide for X-axis positioning of the gripped worksheet 21.
When utilizing a worksheet gripping system which can be loaded from the end or the side it is necessary to have workholders 54, 56 that are capable of gripping the end of the sheet, as is standard fashion, or the sides of the sheet. One configuration of an acceptable workholder is illustrated in Figure 2.
Figure 18 illustrates an automatic unloading feature. By utilizing a linear tool cartridge concept, finished small size sheet metal parts can be separated from the parent material by means of a blade tool with the resulting part extending through the punch press 20 and not being trapped between turrets. The finished parts can be supported on a tiltable unload table 170. During operation the finished parts can be cut free from . the parent material and the unload table 170 tilted to allow the part to slide off onto a stack on a receiving cart 172. This concept can also work with individual parts where upon completion of punching the workholders 54, 56 would be released and the table 170 tilted to allow the part to slide off onto an unload stack. This construction increases the system throughput by elimination of the manual unload cycle and also reduces loading time by allowing the carriage 52 and workholders 54, 56 to return to the load position in parallel with the unload function and come to rest with the workholders 54, 56 open ready to receive the next part.
The size of part that can be cut free by a blade tool is limited to one where the part itself due to its size and mass may become unstable and move as its retaining piece of metal to the main panel becomes smaller and smaller as it is cut off. The twin punch construction eliminates this problem by doing the cutoff action on approximately 24" (about 60 cm) centers thereby always leaving a widely spaced two tab connections to the panel until the finished cutoff stroke when the two punches in parallel sever the finished part from the parent panel. The bridge frame 30 is an I-beam structure that offers structural strength and rigidity in the vertical and horizontal planes. This rigidity provides more support for the tooling and will result in better punch and die alignment during all phases of punching, forming, and nibbling. This increased rigidity will in turn improve tool life. The locking indexing pins 87 are mounted in close proximity to the punch and die stations and this aids in alignment. Supporting the integral bridge frame and table assembly on three mounting pad areas reduces stresses in the machine due to uneven and settling floors. Shock absorbing pads are inserted underneath the mounting pads, without disturbing the sheet to punch alignment, to further reduce dynamic floor loading. This three support area construction and shock pads eliminates the need for special foundations and press 20 can rest on a standard concrete shop floor.
Punch press 20 also includes an improved clutch-brake slider crank punch head 32 or 34. Punch head 32, 34 includes a crankshaft 179 which is driven by an electric motor through a clutch 181. A brake 182 is utilized for stopping crankshaft 179 at the top dead center position. Each time a punch head 32, 34 completes a punch cycle the brake 182 dissipates a fixed amount of energy as heat in stopping crankshaft 179 rotation. When the punch head 32, 34 is operated at its maximum punching rate the heat load on the brake 182 and the brake lining temperatures are at a peak. High brake lining temperatures affect braking friction and cause variations to occur in the crankshaft 179 stopping position. In the disclosed punch press 20 the crankshaft r.p.m. speed is reduced to lighten the heat load on the brake 182. This is very effective since the energy absorbed by brake 182 is a function of the square of the crankshaft 179 rotational speed. Axial brake air flow is also utilized and this provides superior cooling. To offset the lower r.p.m. and to further improve the punching rate, the crankshaft 179 eccentricity is increased significantly. By doing this, a smuch smaller portion of the crankshaft 179 revolution is utilized when punching. In the disclosed punch press 20 the punch is exposed from cartridge 92 for less than 183 degrees of crankshaft rotation. thus, only a portion of the crankshaft revolution cycle is in series with the table move time; the remainder of the crankshaft revolution is in parallel with table move time allowing a higher punch rate. The overall result of the reduced crankshaft r.p.m. and the increased crankshaft eccentricity is that while the system operates at a lower crank r.p.m. a higher punching rate can be achieved. This construction permits continuous stroke nibbling and thus eliminates a major source of heat generation.
Continuous stroke nibbling can be achieved by engaging the clutch 181 for the first punching stroke and then leaving it engaged until the last punch stroke has been performed. The clutch 181 is then disengaged and brake 182 applied in the same fashion as during intermittent punching. Each 360 degree revolution of punch head crankshaft 179 movement is divided into two segments, punching cycle and work sheet advance cycle. In order to insure that the worksheet 21 is not in motion during the punching cycle, the carriage 52 is not allowed to advance until the punch is safely retracted up inside the upper cartridge 92. This assures that the punch has been stripped from the sheet even if the stripper has not performed its task. The carriage 52 is then advanced to the next position before the punch reaches the top surface of the workpiece to be punched. To have sufficient time to advance the sheet 21 between punch cycles, it is desirable to have a larger percentage of each crankshaft revolution associated with table movement. The disclosed press 20 with its increased eccentricity crankshaft 179 allows more than 177 degrees of rotation for table movement. This coupled with the lower r.p.m. provides for adequate sheet movement during continuous stroke nibbling. Even higher hits per minute can be achieved by allowing the carriage 52 to advance as soon as the punch stripper has lifted to the top surface of worksheet 21.
Referring to Figure 10 there is shown a pair of cartridges 92 and 94 and a pair of aligning pins 21 and 23 which can be used for offline tool cartridge alignment. In order to allow the operator to check the alignment between a new punch and die added to the cartridge system 90 the two precision pins 21 and 23 can be inserted to couple the upper cartridge 92 to the lower cartridge 94 in precise alignment. When this is done the operator can manually push the punch holder 149 assembly down compressing the punch holder support spring 306 and moving pin 304 to allow the punch to enter into the die to verify proper alignment and the proper tool is in place. In most prior applications tool alignment is normally done at the punching station where the tools are brought into position. They are then locked in position and the crankshaft is manually rotated with a hand tool to verify that the proper punch enters the die. This time consuming operation reduces productivity. Prechecking of the alignment of the punch and dies in the offline tool cart 70 will enhance throughput of the system.
An additional feature of the twin punch system is that it will allow sheets wider than the normal capacity of the press to be punched. For example, referring to the 24" (about 60 cm) (distance between the two punch head, it is possible to punch a sheet 24" (about 60 cm) wider than normal capacity by first punching normal width capability across the sheet and then removing the sheet and turning it around 180 degrees or turning the sheet over to expose the unpunched side to the second punch head. The sheet would then have the remaining unpunched areas punched by the second punch head. Using this technique allows one less cartridge worth of tools to be utilized on the sheet since all three cartridges cannot be brought under both punch heads for use on the machine. However, if the operator can put a suitable number of tools in the two cartridges to perform the desired punching operation, this feature is very powerful since it adds the equivalent of 24" (about 60 cm) additional width capacity to the machine.
A controller 18, as shown in Figure 4, is provided for controlling operation of punch press 20. Controller 18 is a three axes Computer Numerical Control (CNC). The X-Y table positioning axes and the positioning of the tool cartridge are of a closed loop servo design. This ensures that machine drives are at the prescribed positions prior to punching. The controller maintains on all three axes the proper acceleration and velocity profiles and limits as well as controls the axes positioning.
Controller 18 also controls all other major machine functions such as the punching heads 32, 24, the workholders 54, 56 the worksheet positioning system, the lubrication system, the worksheet load-unload system, the slug removal system and various other automatic functions which might be used on punch press 20. The controller 18 continuously monitors all important machine functions and parameters. It automatically diagnoses operating errors and/or out of limit conditions. Controller 18 then disables affected functions and displays the appropriate error message on the visual readout. Controller 18 is designed to operate on piece part data supplied from paper-tape, the operator's panel keyboard or a remot source such as another computer via a built in communication part.

Claims

1. A punch press (20) comprising a frame (30) which spans a punching area, a punch head (32) supported on said frame above the punching area, a two axis worksheet positioning mechanism (50) for positioning a sheet metal workpiece (21) at desired locations in the punching area, an elongated punch support formed from removable punch cartridges (92) each of which supports a plurality of punches (301), the punch cartridges being joined together and positionable as a unit to bring a selected punch beneath the punch head, and an elongated die support formed from removable die cartridges (94), each of which supports a plurality of dies (321), the die cartridges corresponding to said punch cartridges (92) and being joined together and positionable as a unit to position an appropriate die to receive the selected punch.

2. A punch press (20) as claimed in Claim 1 further comprising a second punch head (34) supported on said frame (30) above the punching area and separated from the first-mentioned punch head (32) by the length of a cartridge (92, 94).

3. A punch press (20) as claimed in either preceding claim further comprising a punch driver section (192) for engaging and positioning a punch cartridge (92), and a die driver section (194) for engaging and positioning a die cartridge (94).

4. A punch press (20) as claimed in any preceding claim further comprising a disappearing. table which is engaged and positioned by the last removable die cartridge (94) forming said elongated die support.

5. A punch press (20) as claimed in any preceding claim wherein there are at least two rows of longitudinally aligned punches supported in each punch cartridge (92).

6. A punch press as claimed in Claim 5 wherein the punches in each row are staggered with respect to the punches in the other row.

7. A punch press (20) as claimed in any preceding claim wherein there is a plurality of openings (91) formed on one side of each punch cartridge (92), each opening being associated with one of the punches in the cartridge, a punch index pin (87) movable into engagement with the opening which corresponds to the punch to be activated for accurate alignment during punching, a plurality of openings (93) formed on one side of each die section, each such opening being associated with a die to be aligned with its associated punch, and a die index pin (87) movable into engagement with the proper opening for accurate alignment of the die during punching.

8. A punch press (20) as claimed in any preceding claim wherein the frame (30) is supported from two areas, the punch press further comprising a table frame (53) securely attached to the first-mentioned frame (30) and having a single area support spaced apart from the connection to the first frame (30) to define in conjunction with the first frame a three-area support system.

9. A punch press (20) as claimed in any preceding claim wherein the worksheet positioning mechanism comprises a carriage (52) extending above and across said table frame (53) on which the workpiece (21) is supported, the carriage being movable in a Y-axis direction with respect to said table frame, a cross slide (51) supported from and movable along said carriage in an X-axis direction, and a pair of worksheet grippers (54, 56) supported from said carriage and movable with said cross slide in an X-axis direction.

10. A punch press (20) as claimed in Claim 9 wherein said sheet metal grippers (54, 56) can grip an end or side of the workpiece (21).

11. A punch press as claimed in Claim 9 or Claim 10 wherein the worksheet positioning mechanism further comprises a second pair of worksheet grippers (54, 56), spaced apart from said first pair of worksheet grippers (54, 56), supported from and movable along said carriage (52).

12. A punch press (20) as claimed in any preceding claim further comprising an unloading table (170) disposed on said frame (30) and means fortilting said unloading table with respect to said frame for automatically unloading pieces which are formed from the workpiece (21).

13. A punch press (20) as claimed in any preceding claim further comprising an interposer (160) acted on by the punch head (32) for engaging and reciprocating a punch (301) to act on the workpiece (21).

14. A punch press as claimed in Claim 13 wherein a slotted T-shaped opening (161) is formed in the interposer (160) through which T-shaped members (159) attached to the tops of the punches (301) pass as the punch cartridges (92) are moved.

15. A punch press as claimed in any preceding claim wherein said punch head comprises a large eccentric crankshaft (179) which during a punching operation causes the operated punch (301) to project through the associated punch cartridge (92) for less than 183 degrees of rotation of said crankshaft.

16. A punch press (20) as claimed in Claim 15 wherein during operation the punch (301) is withdrawn above the punching area for sufficient time to permit the workpiece (21) to be moved to another position providing for continuous nibbling.

17. A punch press (20) as claimed in any preceding claim having an opening formed in at least one side thereof to permit said punch cartridges (92) and said die cartridges (94) to pass therethrough.

18. A punch press (20) as claimed in any preceding claim wherein an angled way guide (126, 136) is provided on one side only of a support for the cartridges (92, 94).