Patent Publication Number: US-2004055481-A1

Title: Sheet punching or stamping and embossing machine

Description:
BACKGROUND OF THE INVENTION  
       [0001] Field of the Invention  
       [0002] The invention relates to a sheet punching or stamping and embossing machine having a stationary table provided with a counter plate and a table provided with a punching knife and being reciprocatingly movable perpendicularly to the counter plate by a stroke drive. The stroke drive has at least one eccentric shaft mounted in the machine frame and pressure rollers eccentrically mounted on the eccentric shaft.  
       [0003] A drive of the foregoing general type for a sheet punching and embossing machine is disclosed in German Patent DE 30 44 083 C3, corresponding to U.S. Pat. Nos. 4,903,560 and 4,470,593. The machine described therein has a fixed lower table, and a reciprocable upper table for punching sheets of paper, paperboard and the like. The reciprocatory movement of the upper table is realized via rollers which are disposed on two eccentric shafts disposed above the upper table. The upper table is spring-biased against the rollers on the eccentric shaft. The upper table is moved perpendicularly towards the lower table by a rotary movement of the eccentric shafts. An at least approximately sinusoidal stroke movement of the upper table is produced by the eccentric drive over the course of time.  
       [0004] In the sheet punching and embossing machine, the sheets are gripped at the leading edge thereof by gripper bar configurations fastened to revolving chains and then intermittently pulled through the punching and embossing device and further stations. During the reciprocating movement of the upper table, the punched sheet must be moved out of the punching table and a new sheet must be inserted. In this regard, the sinusoidal curve of the stroke movement over the course of time opens a constantly remaining large time window which depends, of course, upon the rotational speed of the eccentric shaft. That time window is limited by the minimum stroke of the upper table required by the gripper bars for the passage underneath the upper table. The movement and resting times of the gripper bars are thus determined. However, the cycle times of the machine can be varied via the rotational speed of the eccentric shafts. In this regard, however, physical limits, such as the acceleration of the sheets, fix the maximum number of machine cycles and, therefore, the operating speed of the sheet punching and embossing machine. The time for accelerating and retarding the gripper bars can therefore no longer be shortened in order to increase the operating speed.  
       [0005] A further drive of the foregoing general type is described in U.S. Pat. No. 4,767,393. The punching and embossing machine described therein has a driven upper and lower table. In that regard, the drive is formed by disks disposed eccentrically on a shaft, which act directly on the upper and lower tables. A uniform movement of the upper and lower tables relative to one another is achieved via the eccentric disks by a rotary movement of the shafts.  
       SUMMARY OF THE INVENTION  
       [0006] It is accordingly an object of the invention to provide a sheet punching and embossing machine, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which has a punching and embossing station with a drive that permits an increase in an operating speed of the machine in a simple structural manner.  
       [0007] With the foregoing and other objects in view, there is provided, in accordance with the invention, a sheet punching and embossing machine comprising a stationary table provided with a counter plate, a movable table provided with a punching knife, and a stroke drive for reciprocatingly moving the movable table vertically relative to the counter plate. The reciprocating stroke drive has at least one eccentric shaft mounted in a machine frame and pressure rollers eccentrically mounted on the eccentric shaft. The reciprocating stroke drive further includes a non-uniformly acting mechanism for imparting a non-uniform movement to the movable table.  
       [0008] In accordance with another feature of the invention, the movable table bears with spring force against the pressure rollers of the reciprocating stroke drive.  
       [0009] In accordance with a further feature of the invention, the movable table is disposed above the stationary table.  
       [0010] In accordance with an added feature of the invention, the sheet punching and embossing machine further includes non-circular gears via which the drive for the eccentric shafts is provided.  
       [0011] In accordance with a concomitant feature of the invention, the sheet punching and embossing machine further includes a cam mechanism via which the drive for the eccentric shafts is provided.  
       [0012] Thus, in accordance with the invention, the drive for the eccentric shafts is provided by a mechanism acting non-uniformly, for imparting a non-uniform movement to the moving table. The non-uniform drive for the eccentric shafts provides the possibility for influencing the course over time of the acceleration and deceleration of the reciprocating movement of the movable table as desired and, thereby, increasing the operating speed of the machine.  
       [0013] For this purpose, a non-uniformly acting mechanism is provided as a drive for the eccentric shafts, at minimal expenditure with respect to costs, and with an extremely low construction outlay.  
       [0014] Other features which are considered as characteristic for the invention are set forth in the appended claims.  
       [0015] Although the invention is illustrated and described herein as embodied in a sheet punching or stamping and embossing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.  
       [0016] The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0017]FIG. 1 is a diagrammatic, side-elevational view of a basic structure of a sheet punching and embossing machine;  
     [0018]FIG. 2 is an enlarged, fragmentary view of FIG. 1 showing a sheet punching and embossing station of the sheet punching and embossing machine in greater detail, with eccentric shafts being driven by non-circular gears;  
     [0019]FIG. 2A is a view similar to that of FIG. 2, but with the eccentric shafts being alternatively driven by a cam drive; and  
     [0020]FIG. 3 is a plot diagram graphically illustrating a reciprocating movement of the upper table as a function of the rotary movement of the eccentric shafts, which is shown plotted in degrees of arc. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0021] Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a basic structure of a sheet punching and embossing machine  1  for punching, waste stripping and depositing sheets of paper, paperboard and the like. The punching and embossing machine  1  includes various stations, namely a punching device  2 , a stripping device  3  and a depositing device  4 , which are carried and enclosed by a common machine housing  5 .  
     [0022] Sheets  6  are gripped at a leading edge thereof by gripper bars  8  fastened to revolving chains  7  and are pulled intermittently through the various stations  2 ,  3  and  4  of the punching and embossing machine  1 .  
     [0023] The station or punching device  2  is a punching and embossing station which has a lower table  9  and an upper table  10 . The lower table  9  is fixedly mounted in the machine frame and provided, as shown in FIG. 2, with a counter plate  15  opposing a punching knife  16  carried by the upper table  10 . The upper table  10  is reciprocatingly mounted and drivable by a drive apparatus described in greater detail below.  
     [0024] The gripper bar  8  transports the sheet  6  from the punching and embossing station  2  into the next following station  3  which is a stripping station to be equipped with stripping tools. In the stripping station  3 , non-required pieces of waste  11  from the punched-out sheet  6  are downwardly expelled with the aid of the stripping tools. As a result, these pieces of waste  11  fall into a container-like trolley  12  pushed-in under the stripping station  3 .  
     [0025] The sheet  6  passes from the stripping station  3  into the station  4  which is a deposit station wherein the sheet  6  is either only simply deposited or, more advantageously, separation of the individual blanks or copies takes place simultaneously. The deposit station  4  can also contain a pallet  13  whereon the individual sheets are stacked in the form of a pile  14 , so that after a specific pile height has been reached, the pallets  13  with the stacked or piled sheets  14  can be moved away out of the region of the punching and embossing machine  1 .  
     [0026] As may be apparent, the chains  7  carry a plurality of gripper bars  8 , for example eight bars in the illustrated embodiment of FIG. 1. Therefore, several sheets  6  can be processed simultaneously in the various stations  2 ,  3  and  4 . A preferred embodiment of the punching device  2  of the punching and embossing machine  1  of the invention is illustrated in greater detail in FIG. 2. The punching device  2  includes the stationary lower table  9  provided with the counter plate  15  and the upwardly and downwardly reciprocating upper table  10  provided with the punching knife  16 . In the punching station  2 , the sheet  6  is held between the counter plate  15  and the punching knife  16  by a gripper bar  8 . In order to position the sheet  6  in the punching station  2  by a carriage of the gripper bar  8 , the upper table  10  is moved vertically in the direction of an arrow  17  towards the lower table  9 . The upper table  10  is kept under tension in the direction of eccentric shafts  18  and  19  by spring force.  
     [0027] The eccentric shafts  18  and  19  have eccentric holders whereon rotatably mounted pressure rollers  20  and  21  are fixed. A drive for the eccentric shafts is provided via gears  22  and  23  connected firmly to the respective eccentric shafts  18  and  19 . In order to produce a non-uniform drive of the eccentric shafts  18  and  19 , a non-circular gear  24  is firmly connected to the eccentric shaft  19 . The non-uniformly acting mechanism of the drive for the eccentric shafts  18  and  19  in the illustrated exemplary embodiment of FIG. 2 includes the two non-circular gears  24  and  25 . A drive, for example an electric motor, can then be connected directly to the noncircular gear  25 .  
     [0028] The drive for the eccentric shafts illustrated in FIG. 2 constitutes the preferred embodiment of the invention. However, it is likewise conceivable to connect a further mechanism or a direct drive, such as a belt mechanism or a linkage, to the non-uniform mechanism having the gears  24 ,  25 . A non-uniform movement is transmitted from the uniform movement of the driven non-circular gear  25  to the eccentric shaft  19  with the aid of the non-circular gear  24 . The non-uniform movement is transmitted via the gear  23  to the gear  22  and, therefore, to the eccentric shaft  18 , so that the two eccentric shafts  18  and  19  move synchronously, and move the upper table  10  in parallel in the direction of the lower table  9 . The rotary movement of the eccentric shafts  18  and  19  is synchronous but in opposite directions.  
     [0029] In another alternative embodiment of the invention illustrated in FIG. 2A, the non-uniformly acting mechanism is a cam mechanism having gears  24 ′,  25 ′ which drives the eccentric shafts  18  and  19  non-uniformly. The cam mechanism having the gears  24 ′,  25 ′ is mounted in the machine housing or frame  5  and can be driven directly via an electric motor M or indirectly, for example via a belt mechanism, a linkage or comparable drives.  
     [0030] The eccentric shafts  18  and  19  move the upper table  10  in the direction of the arrow  17  and counter to the spring force acting on the sheet  6  to be punched. After the punching has occurred, the upper table moves in the direction of the eccentric shafts  18  and  19  again, and a new sheet  6  can be moved between the upper table  10  and the lower table  9 .  
     [0031] The course of the reciprocating movement of the upper table  10  over time is reproduced in FIG. 3, which shows a graph or plot diagram wherein the reciprocating movement of the upper table  10  is plotted in a broken line formed of dashes as a function of the angle of the eccentric shafts. The position 0° represents the lower dead point UT of the movement of the upper table  10 , the position OT the upper dead point of the movement of the upper table  10 , and the position 360° represents the next lower dead point UT of the upper table  10  as the next punching and/or embossing step.  
     [0032] The movements of the gripper bar  8  with the sheet  6  located thereon are represented above the line of movement of the reciprocating table, which is formed of dashes. The line formed of dashes illustrates a virtually sinusoidal course of a conventional eccentric shaft drive for the upper table  10 . Starting at 0°, the gripper bar is at a standstill. It is located in the resting time period R. The gripper bar  8  is then accelerated as far as the time OT. The acceleration time of the gripper bar  8  is represented by BG. Approximately at the upper dead point, i.e., the turning point of the upper table  10 , the gripper bar  8  is also decelerated over the time period VG, until it comes to a standstill. A further resting time period R follows.  
     [0033] In order to move the gripper bar  8 , the upper table  10  must have a prescribed minimum stroke Hmin. From this minimum stroke Hmin, a time window ZF results, during which the gripper bar  8  has had to move the sheet  6  out between the upper table  10  and the lower table  9  and inserted it in again.  
     [0034] Beyond or outside of this time period ZF there may be only small acceleration and deceleration phases of the gripper bar  8 . The acceleration phase of the upper table  10  from the lower dead point UT is virtually identical with the deceleration phase before the upper dead point OT. However, because the gripper bar  8  can be moved only after the height Hmin has been reached, and the acceleration and deceleration phases of the gripper carriage BG, VG cannot be shortened further for physical reasons, the time window ZF can be displaced, for example, by a steeper rise of the movement curve of the upper table  10 . A displacement of the time window ZF to a start earlier in time can be carried out as a result of a steeper rise in the movement curve of the upper table  10 . This results in shorter resting time periods R of the gripper bar  8 , and thus shorter cycle times for punching the sheets  6 . The dash-dot line is supposed to represent the steeper course of the acceleration of the upper table  10 .  
     [0035] The cycle times for the acceleration BG and the deceleration VG of the gripper bar are physically bound at limits. Above a prescribed acceleration, the gripper bar  8  can no longer guide the sheet  6  reliably, so that the time window can be varied only slightly. The use of a non-uniform mechanism for driving the eccentric shafts  18  and  19 , however, has the effect of greater acceleration of the upper table  10 , so that the time window ZF can be enlarged or the resting time R can be shortened. In the preferred embodiment of the invention, the resting time R is reduced, so that the cycle time in the punching station  2  of the punching and embossing machine is shortened. In absolute values, a reduction in the resting time R from 90° to 70° can be indicated here, which corresponds to a reduction in the cycle time of about 5 to 6%.  
     [0036] The dash-dot line shows clearly that, as a result of the steeper rise in the acceleration curve of the upper table  10 , the time window required for the movement of the gripper bar  8  can be displaced. The time window for moving the gripper bar  8  is prescribed by the physical limits. The time gain arising from the steeper rise of the movement curve of the upper table  10  can thus be used for reducing the cycle time of the punching or stamping station  2 .