US2954598A - Plate positioning arrangement for plate finishing machine - Google Patents

Description

0st. 4, 1960 c. SLCRAFTS ETAL 2,954,598

PLATE POSITIONING ARRANGEMENT FOR PLATE FINISHING MACHINE 6 Sheets-Sheet 1 Filed Feb. 20, 1957 INVENTORS CURTIS S. CRAFTS Awvs.

CORSON WALTER CHASE GLENSQ. Knueaan Oct, 4, 1960 c. s. CRAFTS ETAL PLATE POSITIONING ARRANGEMENT FOR PLATE FINISHING MACHINE Filed Feb. 20, 1957 6 Sheets-Sheet 2 s y m R R T 0 SH E T T H m% A Nmmu r cu K V .A v SW TAKQNN o Sm um. c

Oct. 4, 1960 c. s. CRAFTS ETAL PLATE POSITIONING ARRANGEMENT FOR PLATE FINISHING MACHINE 6 Sheets-Sheet 3 Filed Feb. 20. 1957 s 5 W 1 R M e m m Mm RE A s wwfl v N WN W 11 M R S M mm C .W

.1 n m N. u n: 9 g m.

Oct. 4, 1960 c. s. CRAFTS ET-AL PLATE POSITIONING ARRANGEMENT FOR PLATE FINISHING MACHINE Filed Feb. 20, 1957 6 Sheets-Sheet 4 INV ENTOR CURTIS 5. CRAFTS CORSON WALTER CHASE GL/ENN N. KRUEGER Oct. 4, 1960 c. s. CRAFTS ETAL PLATE POSITIONING ARRANGEMENT FOR PLATE FINISHING MACHINE Filed Feb. 20, 1957 6 Sheets-Sheet 5 IFIIIIIIII! INVENTOR CURTIS S. CRAFTS Corason WALTER CHASE Es KZZEIGEW Ill 2,954,598 PLATE POSITIONING ARRANGEMENT FOR PLATE FINISHING MACHINE Filed Feb. 20. 1957 Oct. 4, 1960 c. s. CRAFTS ETI'AL 6 Sheets-Sheet 6 R. Nb

ll N HH INN "will! 11111111 1 I I. \\\\\WN M M$ Mb INVENTORS Cunns 5.CRAFTS Coasow WALTER CHASE GLENN N. KRUEGER 1332 Q ,I

II==F PLATE POSITIONING ARRANGEMENT FOR PLATE FINISHING MACHINE Curtis S. Crafts and Corson Walter Chase, Oak Park, and Glenn N. Krueger, North Riverside, Ill., assignors to Miehle-Goss-Dexter, Incorporated, Wilmington, Del., a corporation of Delaware Filed Feb. 20, 1957, Ser. No. 641,319

8 Claims. (CI. 29-21) This invention relates to machines for milling the tension lockup pockets in stereotype printing plates and more particularly to plate registering methods and apparatus for use with such machines to properly position plates for the milling operation.

Different arrangements are known to hold stereotype printing plates on the cylinders of a printing press. One such arrangement utilizes tension lockup holding mechanism which include hooks or fingers which engage the plates and apply circumferential tension to draw them securingly against the press cylinders. For receiving the hooks or fingers of the plate holding mechanisms, recesses, called tension lockup pockets, are milled in the underside of the curved printing plates adjacent their straight edges. It is customary to mill such recesses or pockets after the printing plates have otherwise been completely prepared for printing, including the step of shaving the undersides of such plates to a finished dimension conforming to the outer surface of a printing cylinder, in order to obtain accuracy in locating the tension lockup pockets.

In the case of plates intended for ordinary black and white reproduction precise adjustment of position may be accomplished with the usual side-lay and circumferential adjustments provided on the cylinders. However, in the case of three color printing, precise register of the colors requires that the plates be slightly distorted longitudinally and circumferentially in addition to being precisely positioned both circumferentially and axially.

Milling machines particularly adapted to prepare stereotype printing plates by cutting pockets' on the underside of the plate have become well known. An example of an improved plate milling machine of this type may be seen by reference to applicants co-pending application, Serial No. 641,176, filed February 19, 1957. Since the tension lockup pocketsformed by machines of this type must be accurately located with respect to the printing image on the plates, particularly when the plates are intended for color printing, the method and apparatus used to register a stereotype plateon the pocket milling machine is of substantial importance.

It is thus an object of the present invention to provide improved plate registering apparatus and procedure for a pocket milling machine which enables a set of color printing plates to be milled so that when mounted in the press they automatically occupy positions of precise register with respect to one another. It is an object to provide a novel procedure for accomplishing the above which is simpler and more rapid, hence more economical, than conventional procedures. It is a related object to provide a plate positioning procedure and apparatus for a pocket milling machine which dispenses with the reference marks, such as pointers, cross hairs, etc., which characterize conventional devices and which instead provides for positioning each of a succession of color plates using any selected critical area of such plates as the registering criterion. More specifically it is an object to provide an apparatus which permits visual access to all portions of the copy so that any portion is available for registering purposes when using the improved procedure.

It is another object of the invention, in one of its aspects to provide an improved image transferring arrangement to permit precise registration of a reference image with the copy on successive color plates comprising a set which may be readily swung out of the way with a hinging action for substitution of plates but which upon being replaced occupies exactly tthe same position without dependence on hinge mechanism.

It is a further object to provide a milling machine which is ideally suited for registered milling of a set of colored plates but which may be used with equal facility in the preparation of plates for black and white printing.

With more particularity, it is an object to provide a novel support for printing plates in a pocket milling machine of the above type which permits the plates to be smoothly slid onto, and eventually slid through, the machine without lifting or other manual effort and which includes novel positioning stops which retract so as not to hinder the free sliding movement of the plate. It is a related object of the invention to provide a novel distorting stop construction which enables the relatively high distorting pressures to be developed but which is nevertheless easily adjusted with light manual pressure and inherently strong, requiring little or no maintenance even in the face of constant hard usage.

It is a further object to provide a registering apparatus of the type referred to above that is rugged and sturdy so as to be suitable for long, heavy duty operation without losing its accuracy.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

Figure l is a perspective view of a tension lockup pocket milling machine embodying the present invention.

Fig. 2 is a transverse section of the milling machine shown in Fig. 1 showing the milling cutters in operation.

Fig. 3 is a fragmentary end view, partially in section, of the machine shown in Fig. 1.

Fig. 4 is a fragmentary end view, partially in section, of the opposite end of the machine shown in Fig. 1.

Fig. 5 is a fragmentary, longitudinal sectional view of a portion of the machine shown in Fig. 1.

Fig. 6 is a perspective view showing a registering device in use, constructed in accordance with the present invention.

Fig. 7 is a plan view showing the registering device in position on the milling machine of Fig. l and with parts of the machine omitted.

Figs. 8 and 9 are fragmentary transverse sectional views taken along lines 8-8 and 9-9, respectively, of Fig. 7.

Fig. 10 is a fragmentary plan view of the machine shown in Fig. 1 with the clamps omitted.

Fig. 11 is a fragmentary elevational view of the machine shown in Fig. 1.

Fig. 12 is a plan view of a stop device as utilized in the machine of Fig. 1, constructedaccording to the present invention.

. Fig. 13 is an elevation view of the stop structure shown in Fig. 12. V

Fig. 14 is an end view of the stop structure shown in Fig. 12.

Fig. 15 is a fragmentary view similar to Fig. 13 showing the stop in a retracted position.

While the invention will be described in connection with a preferred embodiment and procedure, it will be understood that I do not intend to limit the invention to that embodiment and procedure, but on the contrary, intend to cover all alterations, modifications and equiva- Patented Oct. 4, H260.

lents as may be included within the spirit and scope of the invention as defined by the appended claims.

General description of the milling machine Turning first to Fig. 1, there is shown a tension lockup pocket milling machine which is designed to accept semi-cylindrical curved stereo-type printing plates P and cut rows of tension lockup pockets TP into the inner cylindrical surface of the printing plate (see Fig. 2). The machine 10 is of a type more fully and completely described in applicants related application Serial No. 641,176, filed February 19, 1957, to which reference may be had for additional details of the machine construction and operation.

Briefly, the milling machine 10 comprises a base frame 11 on which is supported a semi-cylindrical saddle 12 that is proportioned to uniformly engage and support the finished, inner, cylindrical surface of a stereotype printing plate P. The saddle 12 is hollow and a pair of milling cutters 13 and 14 (see Fig. 2) are mounted for longitudinal reciprocation within the saddle.

Supporting and carrying the milling cutters 13 and 14 is a traveling carriage 15, which reciprocates within the base frame 11 and below the saddle 12 along the longitudinally extending ways 16 and 17. As the carriage carries the milling cutters 13, 14 beneath the plate P, the cutters are urged outwardly through openings 18 and 19 formed in the saddle 12 so as to selectively engage the inner surface of a printing plate P and cut the desired tension lockup pockets TP.

In order to hold the stereotype printing plate P in position during the milling operation, the machine 10 is provided with a clamping structure which is effective to press downwardly and hold the plate P on the saddle 12. The clamping structure comprises two arcuate clamp units 21, 22 which slide in spaced relation to the saddle 12 along parallel longitudinal rods 23 and 24. The clamp units 21, 22 are of a type more fully described in applicants related application Serial No. 641,056, filed Pebruary 19, 1957, and reference may be had to this application for details of construction and operation. It will be sufiicient for present purposes to recognize that the clamp units 21, 22 may be slid along their supporting rods 23, 24 to a position overlying a printing plate P on the saddle 12 where the clamp units 21, 22 can be activated so as to press the plate P uniformly and firmly against the saddle 12, thus fixing the printing plate with respect to the cutting paths followed by the milling cutters 13, 14.

To assure that printing plates being cast and finished to a particular set of dimensions are firmly supported on the saddle 12 without looseness, the saddle 12 is pro- 'vided with edge supporting means which may be properly positioned to exactly support a particular set of stereotype printing plates. In the illustrated embodiment the supporting means takes the form of a pair of eccentric cams 26, 27 (see Fig. 11) mounted on each side of the saddle 12. The cams 26, 27 of each pair may be properly adjusted and fixed in position, by loosening and then tightening a central cam mounting screw, so that the peripheries of the cams engage and support the straight longitudinal edges of a printing plate P when the inner curved surface of the plate rests in smooth engagement with the saddle 12.

Plate supporting apparatus Since the cutting path followed by the milling cutters '13, 14 is automatically controlled and thus remains the same for each successive milling operation, it is apparent that the position of the printing plate P itself must be altered to properly orient the cutting path and the plate. Therefore, in order .to precisely position the tension lock up pockets TP with respect to the printing image on the outer surface of the printing plate means are provided to both rotate and axially shift the saddle 12 so that the plate P may be carried into proper alinement.

Turning to the illustrative rotatable and shiftable mounting for the saddle 12, shown in Figs. 3, 4 and 5, it can be seen that the saddle. 12 is provided with axially alined trunnions 31, 32 supported for both rotating and sliding movements within bearings 33, 34, respectively, which are suitably fixed within the machine frame 11. In order to rotate the saddle 12, a shaft extension 35, extending axially from the trunnion 31, is slidably keyed to a rocking arm 36. Rocking of the arm 36 is accomplished by rotating an adjusting screw 37 that is fixed against axial movement in the frame 11 and threaded into a nut 38 carried between the bifurcated lower end 39 of the rocking arm 36. For convenience in rotating the adjusting screw 37, a handle 40 is provided at its outer end. It will be apparent that by rotating the handle 40, the screw 37 is revolved within the nut 38 thereby forcing the nut laterally and rotating the lever 36 which in turn rotates the saddle 12.

In order to shift the saddle 12 axially, the trunnion 32 is provided with an axially alined shaft extension 43 to which is pinned a sleeve 44 having an external helical thread. Threaded onto the sleeve 44 is a nut 45 held axially captive within a gear housing 46 formed integrally with the machine frame 11. Since the nut 45 is restrained against axial movement, it is apparent that rotation of the nut will cause axial movement of the sleeve 44 to which it is threaded, and thus will axially shift the entire saddle 12. To rotate the nut 45, it is provided with a worm gear on its periphery which engages an adjusting worm 4-7 on a shaft 43. \For convenience in rotating the adjusting shaft 48, a handle 50 is fixed to the outer end of the shaft. It will be apparent that rotating the adjusting shaft 48 causes the worm 47 to rotate the nut 45 and thus shift the saddle 12 axially.

It can thus be seen that by the manipulation of handles 40 and 50, the saddle 12 may be axially and peripherally shifted so as to carry a printingplate P into a desired position with relation to the cutting paths of the milling cutters 13, 14. It has been found in practice that only small amounts of axial and rotational movements are required to accomplish the desired results, a total of A usually being sufficient. However, it will be understood that this structure cannot be effective unless utilized in conjunction with some means for indicating to an operator the proper position of the saddle that will precisely position the plate with respect to the milling cutters. Furthermore, those skilled in the art will appreciate that stereotype printing plates ofen carry copy, i.e., a printing image, that is slightly distorted due to unavoidable factors in the plate casting process. This means that the printing image can not be completely positioned by merely shifting the printing plate axially and peripherally by positioning the saddle 12.

Positioning and skewing stop structure clamping the plate adjacent each of its straight edges, with.

provision for moving the stops independently to distort the plate longitudinally and circumferentially so that it may be clamped in distorted position during the milling of the pockets. The stops are resiliently mounted and shaped-to permit a plate to slide easily over them in one direction by carnming the stops to a retracted position. In addition, the saddle 12 is provided with adjustable distorting stops constructed to permit their easy retraction beneath the saddle surface so that a plate P may pass thereover, and which together with the positioning stops, are effective for distorting the plate P longitudinally and circumferentially for precise registration. In the present embodiment two positioning stops 61 and 62 and two distorting stops 63 and 64 are provided (see Fig. 10). The stops 62, 6.4

are mounted in extensions in the opening 18 formed i through the saddle 12, while the stops 61, 63 are mounted in the similar but opposite opening 19. The construction of each of the stops 6164 is substantially identical, with the two distorting stops having an adidtional feature incident to their function, and therefore it will be convenient to describe in detail only the distorting stop 63 for illustrative purposes. It will be understood that the distorting stop 64 is identical to the stop 63, and that the positioning stops 61, 62 are also identical except for the omission of certain parts, as will be made clear below.

Referring to Figs. 12-15, the distorting stop 63 comprises a finger 65 having an inversely inclined abutment face 66 and a sloping upper surface 67. The finger 65 is journaled by means of a pin 68 within the bifurcated end of a mounting block 69. To urge the finger 65 into its upraised, operative poistion, a resilient fiat spring 70 is fastened to the bottom of the mounting block 69 and extends forwardly to bear against a lower lip 71 on the finger '65. When the finger 65 is swung downwardly so that its surface 67 is below and approximately parallel to the surface of the saddle 12, the lower lip 71 flexes the spring 70 (see Fig. 15) so that there is imposed a resilient force urging the finger 65 into its upraised, operational position.

To positively limit the upward swinging movement of the finger 65, it is provided with a positioning pin 72 that extends laterally from each side of the finger and engages forwardly extending lugs 73, 74 formed at the bifurcated ends of the mounting block 69. It will be apparent that the engagement of the pin 72 with the lugs 73, 74 provides a positive limit to the upward swinging movement of the finger 65.

In order to permit movement of the stop 63 axially of the saddle 12, the mounting block 69 is slidably supported in an opening formed in the saddle and a positioning screw is provided to move the mounting block along the opening. In the illustrated embodiment, the block 69 is provided with integrally formed, laterally extending ledges or tongues 80, 81 which slidingly fit within grooves 82, 83, respectively, formed in the saddle 12. A rotatable adjusting screw 84 is held captive at the rear end of the mounting block 69 by means of a set screw 85 threaded into the block which engages the side walls of a groove 86 formed at the end of the adjusting screw 84. It will be apparent that this construction permits the adjusting screw 84 to be rotated relative to the block 69, but that the block will be moved axially with the adjusting screw. To cause the adjusting screw 84 to move axially and thereby position the mounting block 69, the screw is threaded into a nut portion 87 formed integrally with the under surface of the saddle 12 and extends outwardly through the end of the saddle to support a handle 88. It will be understood that by manually rotating the handle 88, the adjusting screw 84 is threadably advanced or retracted through the nut portion 87 and will be effective to slide the mounting block 69 along the grooves 82, 83 to any desired position. i

The stop structure thus far described is common to all of the four stops, including the positioning stops 61, 62. In the case of the positioning stops 61, 62, it will be apparent that printing plates sliding along the saddle 12 from right to left in Fig. 1, will engage the upper sloping surfaces of the pivoted fingers forming parts of the stops 61, 62 and cam them downwardly into retracted position beneath the surface of saddle 12. Thus, the plates need not be lifted onto the milling machine but may he slid onto the saddle 12 from an adjoining plate finishing machine. As soon as a plate has passed beyond the pivoted fingers of stops 61, 62, the fingers will snap to their upraised positions with their inversely inclined forward faces providing a convenient abutment against which the plate may be properly positioned on the saddle 12.

The stops 61, 62 are also provided with adjusting handles 90, 91 respectively,which are equivalent in construction and function to the handle 88 described in connection with distorting stop 63. It will thus be appreciated that by rotating the handles 90, 91, the positioning stops 61,62 may be moved axially of the saddle 12. The distorting stop 64 is identical to the stop 63 and is similarly provided with an adjusting handle 89 permitting axial movement of the stop 64. The stops 6164 may therefore be easily adjusted to accommodate plates ranging widely in size, as from the smaller plate shown in dot-dash outline in Figs. 10, 11 to the longer plate outlined in dashed lines in those figures.

It can thus be seen that by moving companion distorting and position stops together in either direction, i.e., stops 64 and 62 or 63 and 61, non-alined forces are exerted causing a twisting force to be imposed on a plate positioned between the stops which will be effective to slightly distort the printing plate bot-h longitudinally and circumferentially. The inversely inclined abutment faces of the positioning and distorting stops, such as face 66 of the stop 63, will exert a downward component of force when the stop is tightened against a printing plate P so that the plate is firmly retained on the saddle 12.

Returning to the construction of the distorting stops 63, 64, it is a feature of the invention that the stops may be quickly retracted beneath the surface of the saddle 12 so as to permit a printing plate P to he slid over them and off of the saddle. In the illustrated embodiment the stop 63, which is identical to the stop 64, is provided with an adjustably positionable tilting rod which is threadably fixed to a clamp block 96. The rod 95 extends through a bore 97 formed in the mounting block 69 to bear against the rear surface of the finger 65, sufiicient clearance being provided in the bore so that the rod and clamp block can -move freely. The block 96 includes laterally extending ledges 98 and 99 (see Fig. 12) which are adapted to ride within the grooves 82, 83. In order to clamp the block 96 into position, two screws 101, 102 are passed through the block 96 and threaded into a strap block 103 positioned beneath the clamp block 96 and in engagement with the underside of the saddle 12. It can be seen that by tightening the screws 101,102, the strap block is drawn tightly against the underside of the saddle 132, thus clamping the block 96 in place and fixing the tilting rod 95 with respect to the mounting block 69.

In operation, the tilting rod 95 contacts the finger 65 above the axis of the finger pivot pin 68 when the mounting block 69 is drawn rearwardly along the grooves 82, 83 so that further rearward motion of the block 69 with respect to the tilting rod 95 causes the finger 65 to pivot forwardly, i.e., clockwise in Figs. 13 and 15, to its flush position below the surface of the saddle 12 (see Fig. 15). It will be appreciated then, that the handles 88, 89 not only permit the distorting stops 63, 64 to be advanced in order to distort a printing plate P, but also cause the stops 63, 64 to be retracted into their out-of-the-way position. The tilting rods for the stops such as rod 95 for the stop 63, may be adjustably positioned so that only a slight withdrawal of the mounting block causes the stop finger to retract, and thus it requires only a quick spin of the handles 88, 89 to clear the surface of the saddle 12 and allow a printing plate P to be slid along the saddle, over the distorting stops 63, 64, and off the milling machine 10.

In order to prevent the accidental distorting of a printing plate P beyond the elastic limit of the plate material, each of the adjusting handles 88, 89, 98, 91 is provided with a travel limiting shim, of which only the shim 92 for the handle 88 is identified in the drawings (see Figs. 12, 13). The shim 92 is selected to be of such a thickness that the handle 88 can be advanced only approximately 1 of an inch before the shim 92 comes in abutting contact with the end of the saddle 12. This, of course, limits the forward distorting movement of the stop 63 to that same distance,-and therefore prevents accidental permanent distortion or damage to a plate P being distorted or twisted into proper registry on the saddle 12.

7 Transparent sheet structure The present invention is also concerned with the provision of a readily detachable and simply used transparent sheet structure for accurately establishing a reference image that is precisely alined with the cutting path of the milling cutters 13, 14 and thus permits precise orientation of the entire printing image on a series of color printing plates. The registering apparatus comprises a flexible transparent sheet 110 (see Figs. 6, 7, 8 and 9) which is releasably pivoted at one side of the saddle 12 and is provided with a weighted bar 111 at its opposite edge that is effective to smoothly tension the transparent sheet 110 over the outer surface of a printing plate P supported on the saddle 12.

In order to releasably pivot the sheet 110, the latter is provided with a strap 112 along one edge from which hook members 113 depend at each end. The hook members 113 may be snapped about pivot pins 114, each of which cooperate with a retaining spring 115 (see Fig. 8) to cause the member 113 to be received with a detent action. The pivot pins 114- extend inwardly from two alining blocks 116, 117, which in turn are fastened to an upstanding, angle bracket 118 that is mounted on the base frame 11. When the hook members 113 are snapped over the pivot pins 114-, they are held on the pins by the resilience of the springs 115, and each of the hook members 113 is then disposed in close fitting, sliding engagement between the alining blocks 116, 117.

To ensure that the opposite edge of the transparent sheet 110 is likewise exactly positioned, the weighted bar 111 is closely and slidably fitted between two alining blocks 121, 122, which are secured to an upstanding angle bracket 123 fastened to the machine frame 11. To permit the convenient handling of the transparent sheet 116,

the strap 112 is provided with a handle 12 1, and the weighted bar 111 is provided with a similar handle 125.

In operation, the hook members 113 are snapped over the pivot pins 114 and the transparent sheet 110 laid over a printing plate P carried on the saddle 12. The weighted bar 111 will then rest between the alining blocks 121, 122. It can be readily seen that the alining blocks 121, 122, cooperating with the weighted bar 111, and the alining blocks 116, 117, which cooperate with the hook members 113, serve to keep the transparent sheet 110 precisely positioned with respect to the frame of the milling machine 10, although the printing plate P may be shifted or rocked beneath the transparent sheet. When the transparent sheet is no longer in use, it may be quickly lifted from the saddie 12, utilizing the handles 124, 125, and unsnapped from the pivot pins 114 so that it may be placed in an out of the way position where there is no likelihood of accidental damage.

Operating procedure Following the preferred procedure, the key or black plate of a given color series is first slid onto the saddle 12 and against the positioning stops 61, 62. At this time it is desirable to have turned the hand wheels 40, t and to have adjusted the positioning screw handles 90, 91 so that the saddle 12 and the positioning stops 61, 62 are in intermediate positions, free to be adjusted in either of their directions of possible movement. To conven iently indicate the intermediate positions of the saddle 12 and the positioning stops 61, 62, suitable indicia marks, e.g., 61a, 62a, can be etched or otherwise placed on adjacent relatively movable parts in the conventional manner well known to those skilled in the art.

With the parts in their intermediate positions, and the black or key plate supported on the saddle 12, the transparent sheet 1111 is pivoted to the side of the saddle in the manner described above and an image is transferred from the key or black plate to the underside of the transparent sheet 1111 by utilizing proofing ink on the plate and rolling the sheet over the plate. The plate is then clamped firmly on the saddle 12 by clamp units 21, 22.

and the tension lockup pockets are milled in the underside of the plate.

Other plates which are intended to print the additional desired colors to make up the final color image, are then positioned one by one on the saddle 12 adjacent the positioning stops 61, 62. The transparent sheet is laid over each subsequent plate and is precisely re-positioned by the operation of the alinement blocks 116, 117, 121, 122, all as previously described. Since the key of reference image is printed on the underside of the transparent sheet 110, the saddle 12 can be manipulated by the hand wheels 411, 50 to bring a critical portion of the printing image on the plate precisely beneath the corresponding portion of the reference image. As is readily apparent in Fig. 6, the printing and reference images are clearly visible in their entirety, and thus exact orientation of the most critical portion of the color image can be easily sought and obtained.

Following the peripheral and axial shifting of the saddle 12 to bring the critical portion of the printing image in coincidence with the overlying reference image on the transparent sheet 110, the adjusting screws 81} to 91 can be manipulated, if required, to apply non-alined forces and slightly distort the printing plate and bring the entire remaining image in coincidence with the reference image. Again, due to the fact that the entire printing surface of the plate is readily visible, this registry operation becomes relatively simple.

As each subsequent printing plate is brought into registry with the reference image on the transparent sheet 111), it is clamped and the tension lockup pockets are milled into its under surface. Thus, it will be appreciated that when the series of plates are locked into the printing press, each plate of the color series going to make up a complete color picture is in precise relative registry and thus capable of producing a true, effective color reproduction.

We claim as our invention:

1. The method of forming tension lockup pockets precisely located with respect to the printing image in a curved stereotype printing plate having a printing image, comprising the steps of supporting the plate entirely by its inner curved surface and thus exposing its entire printing image, superimposing a transparent reference image which is pre-alined with respect to the pocket forming machine over said plate image, shifting the plate both axially and peripherally to bring a desired portion of the plate image into precise alinement with the corresponding portion of the reference image, distorting the plate longitudinally and circumferentially by applying nonalined forces to bring all other portions of the plate image into alinement with the remaining corresponding portions of said reference image, and forming a set of tension lockup pockets in the inner curved surface of the plate.

2. The method of alining on a forming machine each of a series of curved stereotype color printing plates and forming tension lockup pockets therein, comprising the steps of supporting a black key plate to expose its entire printing image, laying a transparent flexible sheet over the black key plate in fixed relation to the frame of the machine and taking a reference image on the underside of the sheet, clamping the plate firmly to the support, forming a set of tension lockup pockets in the inner surface of the black plate, removing the black plate and supporting the first color plate of the series, and successively the remaining plates of the series, on the machine with the entire plate image exposed, superimposing the transparent flexible sheet and reference image over said plate image, shifting the plate both axially and peripherally to bring a desired portion of the plate image in to precise alinement with the corresponding portion of the reference image, distorting the plate longitudinally and circumferentially by applying non-alined forces to bring all of the portions of the plate image into alinement with the remaining corresponding portions of said reference image, clamping the plate firmly to the support, forming a set of tension lockup pockets in the inner surface of the plate, and removing the plate to replace it with the next plate of the series.

3. In a milling machine for preparing curved stereotype printing plates by automatically machining selected portions of the plates, a saddle assembly for supporting a plate during the machining operation comprising, in combination, a semi-cylindrical saddle member having a plate receiving head end and a plate discharging rear end, an alinement stop positioned in a recess in the saddle member near said head end, said stop being retractable beneath the surface of said saddle member and having a cam surface permitting plates sliding along said saddle member from said head end to engage and cam said stop into said recess, resilient means to urge the alinement stop into its upraised position so that it will snap into alining position when a plate has passed thereover, a distorting stop positioned in a recess near said rear end of the saddle, said distorting stop being retractable beneath the surface of said saddle member, and means remote from said distorting stop operable to cause the stop to retract into its recess and allow a plate sliding on said saddle to pass thereover.

4. In a milling machine for preparing curved stereotype printing plates by automatically machining selected portions of the plates, a saddle assembly for supporting a plate during the machining operation comprising, in combination, a semi-cylindrical saddle member having a plate receiving head end and a plate dscharging rear end, two alinement stops positioned in elongated recesses in the saddle member near said head end, said stops being retractable beneath the surface of said saddle member and each having a cam surface permitting plates sliding along said saddle member from said head end to engage and cam said stops into their respective recesses, resilient means to urge the alinement stops into upraised positions so that they will snap into alining position when a plate has passed thereover, two distorting stops positioned in elongated recesses near said rear end of the saddle, said distorting stops being retractable to a non-operable position beneath the surface of said saddle member, means remote from said distorting stops operable to selectively cause the stops both to retract into their recesses to said non-operable position and allow a plate sliding on said saddle to pass thereover, and to move said stops while in raised, plate engaging position along their respective recesses, and means remote from said positioning stops operable to selectively move the stops along their respective recesses.

5. In a saddle assembly including a semi-cylindrical saddle for adjustably supporting a curved printing plate, a positionable stop for positioning a plate on the saddle comprising, in combination, a pivoted finger extending above the surface of said saddle and being resiliently urged to its raised position, means for moving said finger forward and backward along said surface so as to provide an adjustable abutment for positioning a plate on the saddle surface, and a finger stop effective as an incident to the fingers backward travel, for pivoting the finger against its resilient urging and thus for retracting it beneath said surface so that plates may freely slide thereover.

6. In a saddle assembly including a semi-cylindrical saddle for adjustably supporting a curved printing plate, a positionable stop for positioning a plate on the saddle comprislng, in combination, a pivoted finger extending above the surface of said saddle and being resiliently urged to its raised position, screw means to move said finger forward and backward along said surface and thus provide an adjustable abutment for positioning a plate on the saddle surface, and a finger retracting stop mounted near the end of the fingers backward movement to pivot the finger against its resilient urging and thus retract it beneath said surface so that plates may freely slide thereover, said finger retracting stop mounting being adjustable along the path of finger travel so as to enable the point at which the finger rises above the saddle surface to be varied in accordance with the size of plate being handled.

7. In a saddle assembly including a semi-cylindrical saddle for adjustably supporting a curved printing plate, a positionable stop for positioning a plate on the saddle comprising, in combination, a pivoted finger having a for ward face extending above the surface of said saddle and in stopping position being resiliently urged to its raised position, the forward face of said finger being reversely angled with respect to the saddle surface, screw means to move said finger forward and backward along said surface and thus provide an adjustable abutment for positioning a plate on the saddle surface, said angled forward finger face being efiective to wedgingly hold down a plate against which it is urged, and a finger retracting stop effective near the end of the fingers backward travel to pivot the finger against its resilient urging and thus retract it beneath said surface so that plates may freely slide thereover.

8. In a plate milling machine for milling tension lock up pockets in a set of color printing plates, the combination comprising a frame, a saddle mounted thereon, means including a pair of milling cutters journaled on said frame and extending through apertures provided in said saddle for milling pockets adjacent the respective straight edges of a plate, image transfer means in the form of a transparent sheet hingedly anchored to said frame in a position to overlie plates successively introduced onto said saddle, means for adjustably positioning the said saddle peripherally and axially relative to the frame, means including stops mounted in the surface of said saddle for distorting a printing plate to provide precise register between an area of said plate and a corresponding image on said transparent sheet, and arcuate clamps on said frame for pressing a plate downwardly onto said saddle, said clamps being mounted for sliding movement endwise to an out of the way position to enable access of said transparent sheet to all portions of successive plates.

References Cited in the file of this patent UNITED STATES PATENTS 1,389,844 Roesen Sept. 6, 1921 1,443,810 Betts Jan. 30, 1923 1,562,752 Fraser Nov. 24, 1925 1,906,876 Christopherson May 2, 1933 2,189,682 Schmutz Feb. 6, 1940 2,293,091 Wood et al. Aug. 18, 1942 2,417,496 Huebner Mar. 18, 1947 2,446,704 Lacure Aug. 10, 1948 2,543,255 Parrish Feb. 27, 1951 2,559,533 Daniels July 3, 1951 2,580,576 Myers Jan. 1, 1952 2,581,220 Tollison Jan. 1, 1952 2,667,832 Ziebell Feb. 2, 1954 2,668,346 Tollison et a1 Feb. 9, 1954 2,736,947 Faeber Mar. 6, 1956 2,756,675 Monaco July 31, 1956

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