US 3677059 A
A semiautomatic machine for simultaneously bending the leading and trailing edges of a lithographic printing plate. The plate bender has a ruggedly constructed frame which supports and guides a vertically movable plate supporting bed. The bed has a fixed anvil with a pair of spaced locating pins and an anvil which is movable relative to the fixed anvil to adapt the bender to bend different size printing plates. A fixed and movable pressure block are supported a short distance above the fixed and movable anvils, respectively. Each of the pressure blocks has a spring biased vertically movable gripping face and a cam operated horizontally movable forming block. An adapter is also provided to enable the bender to shape lithographic plates smaller than the adjustable range of the bender.
Description (OCR text may contain errors)
United States Patent Miller et al.
 LITHOPLATE BENDER  Inventors: Leo H. Miller, Penfield; James A.
Colegrove, Rochester, both of NY.
 Assignee: Burroughs Corporation, Detroit, Mich.
 Filed: Feb. 19, 1971  Appl. No.: 116,975
 US. Cl ..72/403  Int. Cl ..B2ld 5/01  Field of Search... ...72/403, 452, 380, 381, 382,
 7 References Cited UNITED STATES PATENTS 133,975. 12/1872 Foglesong ..72/403 1,701,250 2/1929 Young ....72/382 1,706,273 3/1929 Woodin gs... ....72/403 2,591,483 4/1952 West..... ..72/403 Primary Examiner-Charles W. Lanham Assistant Examiner-Gene P. Crosby Attorney-Kenneth L. Miller and Kevin R. Petersonv 57 ABSTRACT A semiautomatic machine for simultaneously bending the [151 3,677,059 [451 July 18, 1972 leading and trailing edges of a lithographic printing plate. The plate bender has a ruggedly constructed frame which supports and guides a vertically movable plate supporting bed. The bed has a fixed anvil with a pair of spaced locating pins and an anvil which is movable relative to the fixed anvil to adapt the bender to bend different size printing plates. A fixed and movable pressure block are supported a short distance above the fixed and movable anvils, respectively. Each of the pressure blocks has a spring biased vertically movable gripping face and a cam operated. horizontally movable forming block. I
An adapter is also provided to enable the bender to' shape lithographic plates smaller than the adjustable range of the bender.
In operation, a prepunched lithographic printing plate is positioned on the locating pins. The plate supportingbed is then driven vertically. by a pneumatic cylinder to bring the plate and anvils into engagement with the pressure blocks. The bed continues to rise causing the pressure blocks to firmly grip the printing plate and to rise against the downward biasing force.
As the pressure blocks move a camming slot at each end of the blocks acts upon a cam follower within the slot causing it to move in a horizontal direction relative to the pressure block. The cam followers draw the forming blocks inward toward the printing plate causing the leading and trailing edges of the plate to simultaneously bend inward against forming faces on the anvils. After the plate is bent the bed is lowered allowing the operator to slide the formed plate 0E of the anvils.
18 Claims, 9 Drawing figures PATENTED JUL 1 81972 SHEET 1 [1F 4 III INVENTORS.
JAMES A. COLEGROVE BY & LEO H. MILLER 41 fi/ ATTORNEY PATENTEU JUL I 8 I972 SHEET 2 0F 4 INVENTOR.
JAMES A. COLEGROVE & LEO H. MILLER/'1 fLL/X/ 1+ WF/ 5 .t v QM ATTORNEY PATENTEU JUL! 8 I972 SHEET 3 BF 4 m A L P INVENTORS. JAMES A. COLEGROVE BY & LEO H. MILLER PATENIEnmwm 3.677.059
SHEET u 0F 4 FIG. 6
I N VEN TOR.
JAMES A. COLEGROVE & LEO H. MILLER ATTORNEYv LITI-IOPLATE BENDER BACKGROUND OF THE INVENTION In lithographic printing, a photosensitive plate of aluminum is exposed to a photographic image which causes portions of the photosensitive material to become solvent insoluble. Following exposure the plate is washed with a solvent to remove the soluble portion and to prepare the printing image. The plate is then ready for mounting on the plate roll of a lithographic printing press.
The typical plate roll has a slot running across the roll into which the ends of the lithoplate are placed. One edge of the slot, the leading edge, is formed at an angle and provides an alignment edge for the printing plate. The tail end of the slot has a radius to allow the plate to be smoothly drawn into the slot. An eccentric rod is mounted within the slot. The rod has a cutout the width and length of a printing plate through which the tail edge of the plate is passed. The eccentric rod can then be rotated to draw the lithoplate tightly about the press roll and to compress the leading edge of the plate against the inside of the slot.
It is essential to the operation of a lithographic press that the plates be bent accurately in order to properly register the printing image on the press roll. The sharp bend of the leading edge of the plate serves to align the plate on the press roll. If this bend is not accurately made the plate will not wrap evenly about the press roll and will produce a crooked or blurred print. Blurring of the print will result if the plate cannot be wrapped tightly against the press roll and has a bulge which is subject to deformation under printing pressure.
The tail portion of the printing plate must also be carefully bent to avoid a sharp crease which could project above the level of the plate. Even after tightening, the ridge fonned by the sharp edge would produce an undesired line of print. The tail portion must be bent in a relatively smooth arc to allow the edge to fit into the slot on the press roll and into the cutout in the eccentric rod to allow for tightening of the plate on the press roll.
In the past, it has been the usual practice to provide a tool for bending the edges of the printing plates adjacent to the press so the press operator could bend the prepared plates for mounting on the press roll. This is an undesirable procedure since it requires the press operator, who is highly paid, to leave the press to do the bending. Also, if the operator does not bend the plate accurately to maintain precise registration of the image or if he does not bend the plate properly it becomes useless for printing and all of the prior time and expense in plate preparation is wasted.
The lithoplate bender of the present invention overcomes the aforementioned problems by making the bending of the plate a semiautomatic operation which can be carried out by an unskilled operator in the plate preparation area. The operator merely has to place a prepunched plate on a pair of registration pins within the bender and then actuate the machine. The bender precisely bends the lead and tail edges of the plate to the proper angle and through the use of the same registration holes used to place the image on the plate insures proper registration of the image with the alignment or leading edge of the plate.
BRIEF SUMMARY OF THE INVENTION The present invention relates to a semiautomatic bender for lithographic printing plates. The bender has a supporting frame which holds a vertically movable table which is driven by a pneumatic ram. A pair of plate forming anvils are mounted on the movable table. One of the anvils has a relatively sharp plate forming surface and a pair of spaced locating pins. The other anvil is adjustable relative to the fixed anvil for bending different size plates. The adjustable anvil has a radius on the bending edge for producing a smooth curve.
Above the anvils and movably supported by the frame are a pair of spring biased pressure blocks. One of the pressure blocks is fixed relative to the fixed anvil while the other pressure block is movable relative to the adjustable anvil. The pressure blocks are provided with spaced camming slots at the ends of the blocks. A movable forming block is mounted between the camming slots on each of the pressure blocks and has a cam follower for moving the forming blocks in a horizontal direction when the pressure block is moved vertically. The table is adapted to move, bringing the anvils into engagement with the pressure blocks. Further movement of the table causes the pressure blocks to move, camming the forming blocks into engagement with the forming surfaces on the anvils.
In operation, a lithographic printing plate is placed on the anvils and hooked over the locating pins. The bender is then actuated causing the table to rise bringing the plate into contact with the pressure blocks. As the table continues to rise the anvils and pressure blocks tightly grip the plate and the camming track begins to draw the forming blocks into engagement with the plate. The table, anvils, plate, and pressure blocks continue to rise and the forming blocks continue to be drawn inwardly until the plate is fully bent. The operator then disengages the machine and the table lowers carrying the finished bent lithographic plate. The machine can also be adapted to automatically lower the table after the bend is completed by means of a limit switch. The plate can he slipped off the anvils by the operator and is ready for mounting on the press roll of a lithographic press.
An adapter is also provided for mounting on the fixed anvil for bending plates smaller than those for which the machine is adjustable. The adapter has plate forming surfaces and locating pins to insure the proper bending of the plate.
BRIEF DESCRIPTION OF THE DRAWINGS The invention, both as to its organization and method of operation, together with further advantages thereof, will best be understood by reference to the following detailed description taken in connection with the accompanying drawings, in which:
FIG. I is a front elevation view of the lithoplate bender of the present invention.
FIG. 2 is a side elevation view of the lithoplate bender.
FIG. 3 is a top plan view.
FIG. 4 is a sectional view taken in the direction of the line 44 of FIG. 1.
FIGS. 5a, 5b, and 5c are schematic views illustrating the operation of the lithoplate bender.
FIG. 6 is a front elevation view of the bender showing the small plate adapter in place on the anvil of the bender.
FIG. 7 is a sectional view taken in the direction of the line 7-7 of FIG. 6.
DETAILED DESCRIPTION Referring to FIGS. 1 and 2, the lithoplate bender is shown to have a box-like supporting frame made up of four substantially identical legs 11 which are preferably made of heavy angle iron. A heavy plate 13 is joined to the legs and forms a fixed table top. Four substantially identical posts 15 are fixed at each of the corners of the table top 13. The posts 15 support a heavy metal top plate 17, completing the framework for the lithoplate bender. Each of the members forming the frame for the lithoplate bender are of heavy metal construction in order to preclude distortion of the bender while shaping a printing plate. If the bender tended to distort while forming the edges of a printing plate, it could result in poor registration of the ultimate print.
The lithoplate bender is designed to be adjustable so that it can handle many different size printing plates. The usual lithographic plates range from 14 inches X 20 inches up to 27 inches X 26 inches. The range of printing plates for which the bender was originally designed was 17 inches X 20 inches to 22 inches X 32 inches. For this reason, the fixed table top 13 was designed to have dimensions approximately 36 inches X 4l inches X l inches. Obviously, the lithoplate bender can be scaled up or down in size to correspond to the range of lithoplates to be bent. While the usual lithographic printing plates come in many different sizes, they are all approximately 0.009 inches thick. Since this is a little more than the thickness of a sheet of paper, the substantial construction of the bender appears to be out of place. However, as pointed out above, the heavy construction insures the proper bending of each plate and in turn the proper registration of each print relative to the leading edge of the plate and the locating pins.
The lithoplate bender has a movable bed 19 which is supported and guided by the fixed table top 13. As shown in FIG. 1, the bed 19 is driven vertically by a pneumatic ram 21 which has a drive shaft 23 journaled through the top 13. The pneumatic ram 21 is attached to and is supported by the top 13. Near each end of the movable bed 19 is a depending guide post 25 which is journaled through a ball bushing 27 in the table top 13. The guide posts 25 are approximately six inches long by one inch in diameter and preclude any tilting or cocking of the movable bed 19 as it is driven by the pneumatic ram 21.
On the upper surface of the bed 19 are mounted a fixed anvil 29 and a movable anvil 31. The fixed anvil 29 has locating pins 32 and 34 which are used to align the lithographic plate on the surface of the anvil. The pins 32 and 34 are substantially identical to the pins used in aligning the plate during the exposure and image-forming steps. By using the same locating hole in the plate and substantially identical locating pins, proper registration of the image relative to the printing plate is assured in the bent plate. The anvil 29 is fixed on the movable bed 19 and has a working face 33 which is used to form the sharp angle at the leading edge of the printing plate. The anvil 31 is adjustable relative to the fixed anvil 29 and has a working face 35 which forms the tail edge of the printing plate. The face 35 should be formed with a radius to provide for smooth tightening ofthe plate on the press roll.
The position of the tail anvil 31 relative to the lead or fixed anvil 29 is controlled by a handwheel 37 and lead screw 39. The lead screw 39 is journaled near each end in bushings 41 and has a tail anvil adjustment carriage 47 which can travel along the lead screw. A rod 45 is attached to the tail anvil and passes through the tail anvil adjustment carriage. The rod 45 can be driven horizontally by the lead screw 39 and is free to move vertically through the carriage 47 when the movable bed 19 is driven upwardly by the ram 21.
As in the case of the supporting frame for the bender, the movable bed 19 and the anvils 29 and 31 are of heavy steel construction to preclude distortion in bending the printing plate. The bed 19 is approximately 1 inch thick while the anvils are approximately 1 1% inches thick. Since the anvils are -quite large and heavy, refer to FIG. 4, the fixed anvil 29 is broken into several smaller segments 30 of the same configuration. Breaking up the large anvil 29 in this manner substantially reduces the weight which must be lifted by the ram.
The working faces of the anvils 29 and 31 are preferably formed at different angles. The working face 33 of the anvil 29 forms the leading edge of the printing plate and is preferably cut at an angle of 45. The working face 35 of the adjustable or tail anvil 31 is preferably cut at an angle of 60. As previously discussed, the tail angle is not as sharp as the leading edge angle since this portion of the plate is drawn into the cutout in the press roll in tightening the plate and it is undesirable to form a sharp edge since this may produce a print line during use of the plate.
Spaced approximately 3 inches above each of the anvils are pressure block assemblies 49 and 51. The pressure block assembly 49 is fixed in position relative to the fixed anvil 29 and cooperates with the anvil in shaping the leading edge of the printing plate. The pressure block assembly 51 is adjustable relative to the anvil 31 and cooperates with the anvil 31 in forming the tail edge of the printing plate. The pressure block assemblies like their cooperating anvils extend completely across the movable bed l9.
The fixed pressure block assembly 49 is supported from the top plate 17 by a pair of supporting brackets 53 and 55. The assembly is made up of four major elements, a pressure block or gripping foot 57, a pair of identical camming plates 59, and a fonning block 61. The camming plates 59 are mounted outside of the forming block and have camming slots 63 in which cam followers 65, which are mounted on each end of the forming block, travel. The pressure block 57 and camming plates 59 can be driven upwardly when the anvil 29 is raised by the pneumatic ram 21. As these elements move upwardly, the camming slots 63 draw the cam followers 65 inwardly, causing forming block 61 to come into contact with the working face 33 on the anvil 29. The pressure block 57 is guided vertically by a pair of similar guide posts 67 which are journaled in bushings 69 in the top plate 17. Coil springs 71 surround each of the guide posts 67 and apply the gripping force against a lithographic plate supported on the anvil 29. The forming block 61 is prevented from rising by the shafts 73 which are journaled through bushings 75 in the supports 53 and 55.
The camming block assembly 51 is adjustable to cooperate with the anvil 31 in forming the bend for the tail edge of the plate. The assembly has a pressure block or gripping foot 77, a pair of identical camming plates 79, and a forming block 81. The camming plates 79 are mounted outside of the forming blocks and have camming slots 83 in which cam followers 85 on the forming block 81 travel. The foot 77 is guided vertically by a pair of similar guide posts 87 which pass through similar bushings 89 in the top plate 17. Coil springs 91 about each post 87 provide a gripping force for the foot 77 against a printing plate supported by the tail anvil 31. It also provides a force for returning the pressure block assembly to its downward position after the movable bed 19 is lowered.
As previously indicated, the pressure block assembly 51 is adjustable to cooperate with the tail anvil 31. To provide for adjustment, the assembly 51 is supported by a plate 93 which can be moved across the surface of the top plate 17. In order to provide for rapid adjustment of the assembly 51 into predetermined positions T pins 95 can be passed through apertures 97 in the plate 93 and into recesses 99 in the plate 17. The bushings 89 are supported by the plate 93 and pass through elongated slots in the top plate 17. An additional plate 100 is supported below the top plate 17 and can be drawn upward by hendwheels 102 to tighten the assembly to the top plate 17 after it has been adjusted into position.
The gripping foot 77 and camming plates 79 are pushed upwardly by the tail anvil 31 when the movable bed 19 rises. The forming block 81 is prevented from rising by the guide posts 101 which project through bushings 103 in supports 105 which depend from the plate 93. As the foot 77 tends to rise the camming plates 79 and camming slots 83 draw cam followers 85 and forming block 81 inwardly against the working face 35 on the anvil 31. When the movable bed 19 is lowered, the springs 91 force the foot 77 downwardly and the camming slots again act on the cam followers 85 to push the forming block 81 back to its starting position. The pressure blocks 57 and 77 and associated anvils 29 and 31 apply only enough pressure to the lithographic plate to hold it from moving during the bending operation. The pressure should not be so high that the plate is crushed or distorted.
in operating the lithoplate bender, the operator should place the lithographic plate onto the anvils 29 and 31, being careful to place the locating pins 32 and 34 through the locating holes in the printing plate. A pair of operating valves 107 and 109 are then actuated by the operator using palm buttons 111 and 113. Since the operator has to actuate two valves simultaneously, the operators hands will be occupied and protected from inadvertent injury when the anvils and pressure blocks are compressed together. The operator must continue to press the palm button until the movable bed 19 has caused the pressure block assemblies to bring the forming blocks into engagement with the printing plate and the working faces 33 and 35 on the fixed and adjustable anvils. The movable bed 19 rises approximately 3 inches to reach the pressure blocks and then approximately 1% inch to 1 inch further to complete the bend. After the plate is completely bent, the operator may release one or both palm buttons which will vent the pneumatic ram and cause the movable bed 19 to lower onto the support table 13. The operator can then slide the finished bent printing plate off the anvils 29 and 31.
Referring to FIG. 5, a portion of a printing plate is shown resting on the surface of the anvil 29 with the gripping foot 57 and forming block 61 in their initial positions. After the operator initiates the machine action, the anvil 29 rises, bringing the printing plate into contact with the gripping foot 57 and the forming block 61. As the anvil continues to rise, the camming action draws the forming block inwardly, causing the plate to bend and to be shaped around the working face on the anvil 29. When the bend is completed, the anvil lowers and spring pressure on the gripping foot 57 causes the cam to push the forming block 61 back to the initial position. When the anvil is at rest in its lower position, the operator can slide the bent lithographic plate off of the anvils.
While the operation has been described as completely under the control of an operator, it is possible to improve the operation of the bender by placing a limit switch 115, refer to FIG. 1, so that the switch is contacted during the upward movement of the movable bed 19. The switch can be adjusted so that it will trip when the plate is properly bent. In this type of operation the movable bed will rise, bringing the plate into contact with the pressure block assemblies and will continue to rise until the proper degree of bending is achieved. At this point, the limit switch 115 will trip, stopping the upward movement of the movable bed and anvils and allowing them to return to their initial position.
If a limited number of sizes of lithographic plates are to be bent on the machine, it is recommended that the corresponding positions on the frame be marked for the adjustable pressure block assembly and movable anvil and that means such as pins be used to hold the two adjustable members in position during operation. When it is necessary or desired to change the size of the plate being bent, it is merely necessary to pull the pins, move the adjustable members to the appropriate stop, and replace the pins, fixing all of the parts in their proper orientation.
Referring to FIGS. 6 and 7, an adapter plate 117 is shown mounted on the fixed anvil 29. The adapter plate is used when it is necessary to bend a printing plate smaller in size than the adjustment capabilities of the bender. The adapter plate can be attached to the anvil 29 by bolts or other suitable means. The adapter plate is approximately the same thickness as the anvil 29 and has substantially similar leading and tail edge plate working faces. In view of the thickness of the adapter plate, a collar 119 must be placed about the shaft 23 of the pneumatic ram 21 to prevent the ram from rising too far and possibly damaging the pressure block assemblies 49 and 51.
In working with the adapter plate, the fixed pressure block assembly can bend the plate about one working face of the adapter while the movable pressure block assembly can be brought across the supporting plate 17 a sufficient distance to cooperate with the other working face of the adapter plate. As previously mentioned, if a limited number of adapter plates are to be used, it is recommended that pins or other blocking means be provided for the movable pressure block assembly 51 in order to provide for rapid and accurate adjustment of the assembly.
While the pneumatic ram has been shown with the bender of the present invention, it is obvious that other types of driving means can be employed which will provide a similar action. For example, an electric motor and a screw drive could be used to raise and lower the movable bed 19, or even a hydraulic system. A pneumatic drive is recommended as medium pressure air sources, approximately 80 pounds per square inch, are usually available in the plate preparation areas of a lithographic printing shop. Also, in view of the solvents used to prepare the printing plates and the resultant explosive vapors which are present, it is far safer to use a pneumatic drive than a similar electric motor drive. The driving means selected must have sufficient capacity to lift the movable bed and to push it against the pressure blocks to provide the bending force. Obviously, larger than necessary driving means can be used to have ample reserve capacity.
While a particular embodiment of the invention has been shown, it will be understood, of course, that it is not desired that the invention be limited thereto since modifications may be made, and it is, therefore, contemplated by the appended claims to cover any such modifications as fall within the true spirit and scope of the invention.
1. A lithoplate bender comprising:
a supporting frame,
a pair of spaced biased pressure blocks mounted within said frame,
a movable table within said frame which is adapted to move toward said pressure blocks,
a pair of spaced anvil means on said table, said anvil means being adapted to move said pressure blocks when the table moves bringing said anvils into engagement with said pressure blocks,
a forming block associated with each of said pressure blocks,
a driving means on each of said pressure blocks,
a driven means on each of said forming blocks which is adapted to move said forming block into engagement with the anvils on said table when said anvils move said pressure blocks, and
a driving means for said table.
2. A lithoplate bender as set forth in claim 1 wherein said pressure blocks are spring biased and are disposed near the top of said supporting frame.
3. A lithoplate bender as set forth in claim 1 wherein one of said pair of spaced biased pressure blocks is adjustable relative to the other pressure block.
4. A lithoplate bender as set forth in claim 1 wherein one of said pair of spaced anvil means is adjustable relative to the other anvil means.
5. A lithoplate bender as set forth in claim 1 wherein said spaced anvil means have plate bend forming surfaces.
6. A lithoplate bender as set forth in claim 1 wherein one of said anvil means has a pair of spaced pins for locating a lithographic printing plate on said spaced anvils.
7. A lithoplate bender as set forth in claim 5 wherein one of said spaced anvil means has approximately a 60 plate forming surface and the other anvil means has approximately a 45 plate forming surface.
8. A lithoplate bender as set forth in claim 1 wherein each of said forming blocks is shaped to mate with the plate forming surface on the cooperating anvil means.
9. A lithoplate bender as set forth in claim 1 wherein said driving means on each of said pressure blocks is a camming slot.
10. A lithoplate bender as set forth in claim 1 wherein said driven means on each of said forming blocks is a cam follower located within the camming slot on each of said pressure blocks.
11. A lithoplate bender as set forth in claim 1 wherein movement of said pressure blocks in a first direction results in movement of the associated forming block in a second direction substantially normal to said first direction.
12. A lithoplate bender as set forth in claim 1 wherein one of said anvil means produces a sharp bend in the printing plate to form an aligning edge while the other of said anvil means produces a smooth bend to provide for tightening of the printing plate on the press roll.
13. A lithoplate bender as set forth in claim 1 wherein an adapter is provided for mounting on one of said anvil means for bending small lithoplates.
14. A lithoplate bender as set forth in claim 13 wherein said adapter has a leading and a tail edge forming surface.
15. A lithoplate bender as set forth in claim 13 wherein said adapter has an approximately 60 leading edge and an approximately 45 tail edge forming surface.
16. A lithoplate bender as set forth in claim-13 wherein said adapter has a pair of spaced pins for locating a small lithographic printing plate on said adapter.
17. A lithoplate bender as set forth in claim 1 wherein the lithoplate bender has a limit switch to release said driving means for lowering said table.
18. A lithoplate bender comprising:
a supporting frame,
a movable table mounted within said frame,
a pneumatic ram on said frame for moving said table,
a fixed anvil having a plate forming surface disposed on said movable table,
an adjustable anvil having a plate forming surface disposed on said table and movable relative to the fixed anvil,
a spring biased pressure block movably supported by said frame for cooperating with said fixed anvil,
an adjustable spring biased pressure block movably sup ported by said frame for cooperating with said adjustable anvil,
a pair of spaced camming slots on each of said pressure blocks,
a movable forming block associated with each of said pressure blocks, and
a pair of cam followers on each of said movable forming blocks which are guided within the camming slots on each pressure block,
said table being adapted to move bringing the anvils into engagement with said pressure blocks, further movement of said table causing said pressure blocks to move camming the forming blocks into engagement with the forming surfaces on said anvils.