US2931298A - Electrotype plate, method of making same and the method and apparatus for mounting the electrotype plate upon a printing cylinder - Google Patents

Description

Apnl 5, 1960 H. L. BISHOP 2,931,

ELECTROTYPE PLATE, METHOD OF MAKING SAME AND THE METHOD AND APPARATUS FOR MOUNTING THE ELECTROTYPE PLATE UPON A PRINTING CYLINDER Filed March 14, 1957 3 Sheets-Sheet 1 INVENTOR HOMER L. BISHOP ATTORN Y5 April 5, 1960 H. L. BISHOP 2,931,298

ELECTROTYFE PLATE. METHOD OF MAKING SAME AND THE METHOD AND APPARATUS FOR MOUNTING THE ELECTROTYPE PLATE UPON A PRINTING CYLINDER Filed March 14, 1957 3 Sheets-Sheet 2 Apnl 5, 1960 H. BISHOP 2,931,293

ELECTROTYPE PLATE, METHOD OF MAKING SAME AND THE METHOD AND APPARATUS FOR MOUNTING THE ELECTROTYPE PLATE UPON A PRINTING CYLINDER Filed March 14, 1957 3 Sheets-Sheet 3 III-III INVENTOR HOMER L. BISHOP 7E FIG-6 84 68 ATTORNEYS ELECTROTYPE PLATE, METHOD OF MAKING SAME AND THE METHOD AND APPARATUS FOR MOUNTING THE ELECTROTYPE PLATE UPON A PRINTING CYLINDER Homer L. Bishop, Dayton, Ohio Application March 14, 1957, Serial No. 646,000 15 Claims. (Cl. 101--395) This invention relates to an electrotype plate, the method of making the same, and the method and apparatus for mounting the electrotype plate upon a printing cylinder.

In the past, considerable difliculty has been encountered nited States Patent F in mounting and aligning electrotype plates on print cylinders, and in retaining the mounted plates in proper alignment during the printing operation. The difficulties are especially acute with multicolor electrotypes in that the slightest misalignment of the various color plates on the printing cylinders results in a readily noticeable lack of color registry in the printed product.

While various methods and devices have been developed for mounting and aligning electrotype plates on the printing cylinders or rollers, these methods are costly and time consuming. In some printing plants, the lay-down time for mounting of the electrotype plates may run 16 hours or more. Bearing in mind the huge investment of money and labor involved, any saving of time, such as provided by the methods disclosed hereinbelow, represents an important contribution to the printing industry.

An object of this invention is to provide, in a printing cylinder assembly including a printing cylinder carrying clamps for engaging an electrotype plate, an electrotype plate curved to fit the printing cylinder and having slots or grooves in the backside thereof, whereby the clamps carried by the printing cylinder may engage the underside of the electrotype plate to apply a tensive force to secure the electrotype plate to the cylinder. Current practice in the printing industry is to employ the clamps carried by the printing cylinder to engage the margins of the electrotype plate to apply a compressive force to the electrotype plate. This practice is only partially effective, for the reason that centrifugal forces exerted on the electrotype plates during the printing operation tend to force the center of the electrotype plate radially away from the printing cylinder, thus lessening the effectiveness of the compressive forces exerted by the clamps in holding the electrotype plate in place. When a tensive force is applied to the electrotype plate as described hereinbelow, the centrifugal forces acting on the electrotype plate during the printing operation augment the tensive force exerted by the clamps, such that the electrotype plate is more se curely held by the clamps when the printing cylinder is rotating than when the printing cylinder is stationary.

Another object of this invention is to provide, in an electrotype plate having slots or grooves located in the backside adjacent the margins thereof, which grooves are engageable by electrotype plate clamps carried by printing rollers, a reinforcing grid disposed in the lead backing layer of the electrotype plate for reinforcing the margins g 2,931,298 Patented Apr. 5, 1960 surface of the backing layer for receiving electrotype plate clamps.

A further object of this invention is to provide apparatus for casting a lead backing layer upon an embossed copper printing shell, the apparatus including a machine for conveying a plurality of trays through a molten lead bath to cast the lead to the backside of the copper shell, and weight means for pressing the copper shell in each tray to the bottom of the tray and for supporting a re-- inforcing grid in the backing layer while the lead solidi-- fies, said weight means also carrying core elements for forming slots or grooves in the back surface of the back-- ing layer.

A further object of this invention is to provide a method and apparatus for processing a cast electrotype plate for attachment to a printing cylinder.

Still another object of this invention is to provide a. method and apparatus for securing electrotype plates to a printing cylinder, whereby a tensive force is employed in retaining the electrotype plate to the cylinder.

Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacture and the mode of operation, as will become more apparent from the following description.

in the drawings, Figure 1 is a schematic illustration of an electrotype casting machine.

Figure 2 is a perspective view of a grid or reinforcing member that is to be embedded in the backing metal of the electrotype plate.

Figure 3 is a perspective view of a mechanism for holding the grid or reinforcing member in fixed spaced relation relative to the rear side of the embossed electrotype shell.

Figure 4 is a cross-sectional view of a casting tray disclosing the embossed shell located in the bottom of the tray, the grid or reinforcing member, the molten metal and the mechanism for holding the grid or reinforcing member infixed spaced relation with respect to the electrotype shell.

Figure 5 is a rear view of a finished electrotype plateprovided with grooves or slots for receiving electrotype; plate clamps.

Figure 6 discloses an electrotype plate positioned in the device used for hydraulically or pneumatically compressing the backing metal so as to eliminate voids, blowholes and imperfections therein and to provide, when desired, a relief image in the electrotype plate.

Figure 7 is an enlarged view of a portion of Figure 6, disclosing the use of a face treating mat used in providing a relief image in the electrotype plate.

Figure 8 discloses an electrotype plate mounted in a curving frame used in curving the electrotype plate.

Figure 9 discloses the electrotype plate and the curving frame being fed through curving rollers.

Figure 1-0 discloses a portion of a printing cylinder having an electrotype plate mounted thereon.

Figure 11 discloses an electrotype plate clamp that is positioned in a spiral groove of a printing cylinder, the electrotype plate being shown in phantom.

Figure 12 is a cross-sectional view, taken substantially on the line 1212 of Figure 11, disclosing an end view of the clamp mounted in the groove.

Figure 13 is a sectional view of a portion of the cylinder, taken along the spiral groove in the cylinder, with the clamp mounted in position, the bottom of the groove in the cylinder being provided with threaded sectors for use in adjusting the clamp.

Figure 14 is a perspective enlarged view of the electrotypeplate clamp.

Referring to the drawings in detail, Figure 1 illustrates a casting machine for casting a lead backing upon an embossed copper printing shell so as to form an electrotype plate.

sprocket assembly 16.

cast and solidified elec-trctype plate.

The casting machine daily" as described 111' my United States Letters Patent NO.

, 2,782,474 entitled Apparatus for Casting Electrotypes.

In thelcperation oifthe casting .machine, molds or trays 16 are conveyed aion'g a bed 12 which is a eontinuous web driven 'upon rollers 14 by a suitable chain and sprocket assembly 15 operated by a motor 18. The trays are supported by arms 20 secured to conveyer chains 22, these conveyer chains 22 moving in synchro= nism with the bed 12. Chains 22 for supporting the trays it! are provided on either side of the machine.

functions substan- Each tray it? moving upon the bed 12 advances to a vat 24 containing a molten metal such as lead; The

trays, as they approach the vat 24, follow a guide 26 into the molten metal and are filled with a molten metal. As the tray is carried across the vat 24 by the chains 22, the tray engages a slide '28, which guides the tray out of the molten metal and onto a bed 30 which comprises a suitable web' driven uponrollers 32 by the chain and The slope of the" slide 28 is preset to permit a predetermined amount of the molten metal to run out of the tray as the tray is conveyed up the slide so that the tray, upon leveling out on the hori zontal bed 3%, will have a predetermined amount of the molten metal deposited therein. The molten metal is permitted to cool and solidify in the trays was these trays are con-ducted along the bed 30. The walls of the trays'lii are tapered so as'to facilitate removal of the In utilizing this casting ma'chinl to put a backinglayer on the embossed image bearing she'll ofian' electro'type i ment with the flange portions 62 of the grid 6% The on either side of the grid. The flanges 62 are notched at 64" iii the" starter the grid to provide an' open spree along the length of the flanges. A parallel array of rectangular perforations 57 has been illustrated in the base portion of the grid of Figure 2, however, it is to be understood that the base portion of the grid may be perforated in any other suitable, manner.

7 The grid 60 is attached to the weight mechanism 34 by manually drawing the parallel frame'members 42 and 42a one toward the otherfcompressing the springs 46 then positioning the grid 69- in abutment with the wedge elements 54, with the flanges 62 of the grid 60 being in spaced parallel relation to the wedge elements 54 of the weight, mechanism 34. When the grid 60 has been posititonedin' abiltrheii-t witlithe wedge elements 54, the frarnemember 42a is released, whereupon the springs 46 drive the wedge elements 54 into compressive engage grid 60, being thus supported by the Weight mechanism 3'4; is automatically positioned in spaced parallel rela- =tioii to the'elech'otype shell 52 when the weight mechanism 34 is lowered into the tray'10;

As best seen in Figure 4, the outer vertically extending surfaces 'ofth e'wedge elements 54' are inclined fr'o'mthe vertical so'as" to supportthe' flange elements 62 of the grid 60 at an acute angle with respect to the back surface of the electrotype plate. Upon immersion of the tray 10 in the molten lead vat, followed by subsequent drainage'of some of the lead from the tray 10' and solidification of the remainder of the lead in the tray 10, the

, grid .66 becomes firmly embedded in the lead backing plate, a Weight mechanism 34 illustrated in detail in Fig ure 3 is employed. The weight mechanism includes parallel rails 36 provided with bolts as at are end thereof,

adapted to rest on the sides of the tray 10. The rails 36 support cross bars 49 which, in turn, support spaced frame members 42 and 42a extending parallel to the rails 3-6. One of the frame members 42a; is} slidably mounted upon the cross bars '40 within'b'r'ack'ets 44, these brackets 44 being fitedly attached to the cross bars 40-. Springs 46 within the brackets act upon the'fra'm'e member 42a to drive that frame member an extreme distance away from .the parallel frame member 42;

' 'Blo'cks' 43 secured to the frame members :42 and 42a support elongate spikes 59;

, As illustrated in Figure 4, whenan embossed copper eiectrotyp'e shell 52, tinned on the'ba'ckside; has been positioned face down in a tray 10, the'spikes 50- carried layer of the electrotype plate. Upon removal of the weight mechanism 34, the electrotype plate is provided with four slots or grooves arranged in spaced parallel pairs, as'illustratedin Figure 5.- The spikes 50 of the weightmechanism'M are made very thin and are caused to taperto'a point so as'to displace a'minimum of backin'g metal during the casting operation.

,Iriorder' to insure that the gridt) will be firmly embedded in the backing layer and to further insure that a the grid Gil will not be the source of a separation or fault in the backing layer; it is'fo und preferable to treat the grid 6%); such that the grid will form a bond witlithe metal. in the backing layers Since lead is the preferred backing material and copper the preferred grid material, the co'pperof the grid is tinned, such that a bond with the lead'of the backing layer will be formed. As illustrated in Figure 2, the bas'e portion of the grid 60 is tinned.

by the weight mechanism 34 are lowered upon the elec} Y trotype plate, such that the weightImechanism 34 will function to hold the electrotype plate securely 'against the" bottom of the tray 10. Once the weight mechanism 34 has een so positioned, the bolts 33 carried by the rails 36 may be adjusted to engage the ;sidesof the tray 10 to relieve the weight of the Weight mechanism 34 to prevent puncture of the'electrotype' shell by the spikes 5t e The Weight mechanism 34-also includes wedge-shaped elements 54 which are supported by rods 56in spaced parallel relation to the frame members 42 and 42a.' The distance of these'wedge elements 54 from the frame members 42 and 42a is slightly less than the projective length of the spikes 59, such that when the weight rhecha nism 341's positioned in the tray 10 to holdthe electrotype sheli'in place,'the wedge elements 54 are s'paced' a very short distance above the electrotypeshell.- As 'il-lus tratedin Figure 3, four coplanar wedge el'ements'f54 are carried by the weight mechanism '34, there being two linearly aligned wedge elements oneither side-ofthe weight mechanism 34; More or less wedgemembersmay be used. e

These'wed ge elements 54 are adapted toi' support a grid. 61 illustrated in detail in Figure 2. The grid 60 comprises aperfor'atd metal sheet, preferably copper, haivingbpposite margins turned u'pto form flafiges 62 The layer of: tin is excluded from the inner surface of the flanges 62 toinsure that upon'remo'val of the wedge elements 54 from the backing layer, all lead which may 7 have V crept into the interfaces between the wedge elemerits 54 and the flanges 62 may be peeled away.

In the cast electrotype'plate, the outer'wall of the slots'orgrdoves' 661's tapered to an acute angle with respect to the backingsurface of the electrotype plate and is formed-by a material of relatively high tensile strength as compared to the tensile strength of lead. The notches 64 between the flanges 62, which'are filled with lead during the casting operation, strengthen the. backing metal. As is apparent in Figure 4, the dimensions of the flanges 62 aresuch thatth'ese flanges terminate substantially at thes irface'of the backing layer. V

Afteri'the castjelectrotype plate, identified by the referenc'e'r'iuiner'al 68, has been removed from the tray 10; the" ele'ctrot'ype'plate is shaved on the'backside to a predetermined thickness' and cut to predetermined dimensions. The shaved electrotype' plate is'illu'stratedin Figure 5. a V 1 w Following the shaving'operation, the slots 66 in'the backing layer of the electrotype plate are filled with inserts 70 as illustrated in Figure 6. These inserts are prefei'ably of the "samemat'erial asthebackinglayer or of a I n' iater'ial havingjsimiiar structural characteristics; With the insertsflin plaicetheiele'ctr'otype plate 68' is inserted into a compression device, as illustrated in Figure 6. This compression device has been described in detail in my copending application Serial No. 589,762, filed June 6, 1956, and entitled Apparatus and Method of Molding Plates.

The compression device includes a base plate 72 and a cover 74 supported in spaced parallel relation by side members 76 so as to enclose a rectangular cavity. An airtight elastomeric bag 78 is positioned in the upper part of this cavity, this bag 78 being provided with laterally extending flanges 80 which are anchored between the cover 74 and the side members 76. The cover 74, side members 76, and base portion 72 are united by bolts 82 which are sutficiently strong to withstand a considerable pressure within the compression cavity.

In loading the compression device, a make-ready mat 84, comprising three laminated layers of a fibrous material, such as paper, is placed in the bottom of the mold cavity and the electrotype plate 68 is positioned between the make-ready mat and the elastomeric bag 78. Where it is desired to supplement the embossed electrotype plate with a relief image, as described in my United States Letters Patent No. 2,088,398, entitled Printing Process,

one or more of the layers of the make-ready mat 84 may be stripped away in the mirror image of the electrotype plate image. The number of layers stripped from the make-ready mat is varied in accordance with the image density sought in the printed image.

With the make-ready mat and the electrotype plate assembled in the compression device, air, or another suitable gas, or a hydraulic liquid is introduced under pressure into the elastomeric bag 78 through a conduit 88. The pressure thus uniformly applied to the electrotype plate performs two essential functions. First, blow holes, voids, and other faults or imperfections in the backing layer are squeezed out, and second, where a relief image is provided in the make-ready mat 34, this relief image is impressed upon the electrotype plate. In Figure 7, the effect on the electrotype plate of removing a portion of the mat 84 is illustrated schematically.

After the electrotype plate 68 has been compressed in the mold of Figure 6, the electrotype plate is removed from the compression chamber and inserted in a curving frame, as illustrated in Figure 8, the inserts 70 filling the slots 66 being left in place. The curving frame of Figure 8 is substantially as described in my United States Letters Patent No. 2,722,261, entitled Device for Use in Manufacturing Electrotypes, and includes an elastomeric sheet 90 having thickened end portions 92 into which are recessed the ends of a thin sheet of steel 93 lining one surface of the elastomeric sheet 90. Threaded bolts 94 secure metallic clamps 96 to the opposite ends of the sheet 93. These clamps 96 have beveled edges adapted to engage complementary beveled edges of the electrotype plate 68. The plate 68 is inserted in the curving frame by flexing the curving frame to increase the distance between the clamps 96.

With the electrotype plate 68 secured in the curving frame, the electrotype plate is curved between rollers 98, as shown schematically in Figure 9. This curving operation has been described in detail in the aforementioned United States Letters Patent No. 2,722,261.

When the electrotype plate has been curved to the desired contour, the electrotype plate is separated from the curving frame by flexing one end of the curving frame to release one of the clamps 96 from engagement with the electrotype plate.

After the curving operation, the inserts 70 in the slots 66, which have served to prevent localized distortion of the metal in the backing layer during the compression and curving operations, are removed and the electrotype plate is ready for attachment to a printing cylinder. A portion of a typical printing cylinder is illustrated in Figure 10.

As a means for attaching electrotype plates to the 6 printing cylinder, the printing cylinder is provided with a plurality of equispaced helical grooves 100, illustrated in Figures 12 and 13. These grooves are threaded along the bottoms thereof, to provide gear engaging tracks 102 therein. As best seen in Figure 12, channels 104 are provided in the opposite walls of each groove. The grooves are thus adapted to receive a conventional electrotype plate clamp 106.

As best seen in Figure 14, the clamp 106 includes mating body members 108 and 110 adapted to form a bullet-like body encasing a worm gear 112 which is freely rotatable therein. Integral with the worm gear 112 and projecting out of one end of the body of the clamp is a shaft 114 which is used in rotating the work gear 112. Situated in cavities within the body of the clamp are oblong lugs 116 and 118, each being mounted for rotation between two positions, one position being as illustrated in Figure 14, with the ends of the oblong lug projecting outwardly from the sides of the clamp, and the other position pivoted 90 away from the first position with the sides of the oblong lug being flush with the sides of the clamp.

The oblo'ng lug 116 is pivoted by means of a slotted head 120 projecting to the top of the clamp, and the lug 118 is pivoted by means of a clamping bar 122 integral with the lug 118 and freely rotatable on the top surface of the clamp. Clamps 106 are secured within the grooves 100 by first positioning the lugs 116 and 118 flush with the sides of the clamps, then seating the clamps within the grooves so that the gears 112 mesh with the threaded tracks 102. Next, the lugs 116 and 118 are rotated, so that the ends of these lugs seat within the channels 104 in the opposite walls of the grooves. The construction and arrangement is such that the clamping bars 122 extend axially along the surface of the printing cylinder when the lugs 118 are properly seated within the channels 104.

In securing an electrotype plate 68 to the printing cylinder, four clamps are positioned in grooves in the printing cylinder, as illustrated in Figure 10, and the shafts 114 are rotated by a suitable tool to position the clamps 106 on the periphery of the cylinder in a proper position to engage the electrotype plate. Upon the electrotype plate being placed upon the cylinder, the clamping bars 122 carried by the clamps 106 project into the slots 66 in the backside of the electrotype plate. Subsequently, the clamps 106 engaging the opposite ends of the electrotype plate are adjusted in opposite directions, so as to bring the clamping bars 122 carried by these clamps into engagement with the copper flanges 62 lining the slots 66 in the electrotype plate, thereby applying a tensive force to the electrotype plate. To facilitate retaining the electrotype plate in place upon the printing cylinder, the clamping bars 122 may be serrated, as illustrated in Figure 14, so as to bite into the copper flanges 62.

As the printing cylinder rotates in a printing operation, the electrotype plate experiences a centrifugal force, tending to increase the curvature of the electrotype plate and to draw the opposite ends of the electrotype plate closer together. In the present construction, this centrifugal force merely serves to increase the effectiveness of the clamping bars 122 in securing the electrotype plate to the cylinder.

Whereas the lead material conventionally used in backing up electrotype plates may tend to yield along the margins engaged by the clamping bars 122 as the printing cylinder rotates, the copper flanges 62 lining the slots 66 provide sufiicient tensile strength in the margins of the electrotype plate to prevent distortion of these margins as the printing cylinder rotates. Due to the fact that the outer margins of the slots 66 are inclined in an acute angle to the back surface of the electrotype plate, there is no tendency for the electrotype plate to slip off the clamping bars 122 even after the copper flanges 62 have yielded slightly; An angleof to is found sufl'icientf The for. the purposeeof illustration. Theperforated' base portionofthe grid 60further serves the general purposeof strengthening the lead backing'layer to prevent failure thereof during the printing operation.

' The electrotype plate, the method and apparatusof making and forming the'electrotyp e plate and the method and apparatus for attaching the electrotype plate to a printing cylinder described herein accomplishes the desired result that an electrotype plate may be quickly and economically secured to a printing cylinder with little tendency of the electrotype plate attached to the printing cylinder to move out of alignment as the printing cylinder rotates.

By standardizing the position of the notches 66 with respect to the margins ofthe electrotype plates, one set of clamps near one end of the electrotype plate may remain in a fixed, position, upon the cylinder so that when changing plates this one setof clamps is then usedto position the electrotype plate-inthe proper relation with respect to the printing cylinder, the corresponding pairs of. clamps being left intact on the-several cylinders-in a multicolor press, thereby insuring registry of the several electrotype plates. By this arrangement, it ismerely necessary to adjust the clamps on the end of the electrotype plate opposite those that remain fixed, whenever changing electrotype plates.

Although the preferred embodiment of the device has :been described, it will be understood that withinv the purview of this invention various changes may be made in. the form, details, proportion and arrangement of parts, the combination thereof and mode of operation, which generally stated consist in a device capable of, carrying out. the objects set forth, as disclosed and defined in the appended claims.

Having thus described my invention I claim:

1. An electrotype plate for use with linearly aligned pairs of plate clamps for clamping the electrotype plate to a. printing cylinder, said plate including a reinforcing backing layer provided with spacedslots in the back surface thereof adapted to receive the clamping bars of electrotype plate clamps carried. by printing cylinders, said slots being disposed in linearly aligned pairs in spaced parallel relation to opposite margins. of the backing layer, and reinforcing means embedded in the backing layer between said linearly aligned slots and the margins of said backing plate, said reinforcing means including a strip of sheet metal extending parallel to each 1inearly aligned pair of slots and forming one wall of each slot.

2. An electrotype plate for use with linearly aligned pairs of plate clamps for clamping the electrotype plate to a printing cylinder, said plate including a reinforcing backing layer provided with spaced slots in the, back surface thereof adapted to receive the clamping bars of electrotype plate clamps carried by printing cylinders, said slots being disposed in linearly aligned, pairs in spaced parallel relation to opposite margins, of the backing layer, and reinforcing means embedded in the backing layer between said linearly aligned slots and the margins of said backing plate, said reinforcing means including a strip of sheet metal extending parallel to each linearly aligned pair of slots and forming one wall of each slot, said sheet metal strips being inclined at an acute angle to the back surface of the electrotype plate.

3. An electrotype plate for use withlinearly. aligned pairs of plate clamps for clamping theelectrotype plate to a printing cylinder, said plateincluding a reinforcing 'backing la yer providedwith spaced slots in the back surface thereof adapted to receive the clamping bars of electrotype plate clamps carried by printing cylinders, said slots being disposed in linearly aligned pairs in spaced parallel relation to opposite margins of the backing layer,

.andreinforcing means embeddedv in the backing layer beangle-shown in the drawings is considerably exaggerated t een; a li ea v l ed: ts n hema s ns i a d h king. p a d. n or means including a i fer-med of sheet metal and embedded in the backinglayer ingspaced parallel relation to the backsurface of the electrotype plate, said grid including marginal flange portions projectingsubstantially to the backsurface of said backing layer toform the walls of saidlinearly'aligned slots nearest the margins of said backing layer, said grid being embedded in said backing layer to a depth from the back surface equal substantially to the depth of said slots.

4. An electrotype plate for use with clamps carried by a printing cylinder, said plate including anembossed metallic shell for printing, a backing layer secured to the rear of said metallic printing shell, and a sheet metal grid embedded in said backing layer inspaced parallel relation to said metallic printing shell, said sheet metal .gr id including marginal flange portions projecting substantially to the back surface of said backing layer in spaced parallel relation to the margins of the electrotype plate, said backing layer having slots in the back surface thereof extending to the depth of said grid and opening tovsaid marginal flanges such that said flanges form one wall of said slots, saidflanges being located betweensaid said slots are arranged in linearly aligned spaced pairs in spaced parallel relation to the opposite ends of said electrotype plate. V

6. The electrotype plate according to claim .4, wherein said flanges are inclined at an acute angle to the back surface of said backing layer. 7 7. The method of casting alead backing layer to the embossed copper printing shell of an electrotype plate so as to provide slots in the surface of said backing layer adapted to receive the clamping bars of electrotype plate clamps carried by printing cylinders, said method including the steps of placing a suitably tinned printing shell in a tray adapted to receive molten lead, placing a weight on said printing shell, said weight carrying spaced spikes adapted to rest on the tinned surface of the printing shell, said weight including parallel wedge elements supported above the ends of said spikes, and spring means biasing ,said Wedge elements in spaced relationsupporting a grid including a perforated base portion having upright'marginal flange portions, said wedge elements being positioned between said marginal flange portions in parallel relation thereto, said spring means biasing said wedge elements oppositely into compressive engagement with the marginal flange portions of said grid whereby said grid is supported in spaced parallel relation to said copper printing shell, introducing molten lead into said tray to fully immerse said grid and partially immerse said wedge elements such that said wedge elements provide cores for forming slots in the back surface of said backing layer, one Wall of said slots being provided by the marginal flange portions of said grid, and removing said weight uponsolidification of the lead.

"8. The method of casting a lead backing layer to the embossed copper printing shell of an, electrotype plate so as to provide slots in the surface of said backing layer adapted. to receive the clamping bars of electrotype plate clamps carried by printing cylinders, said method including the steps of placinga suitably tinned electrotype shell in a tray adapted to receive molten lead, placing a weight on said shell, supporting a grid in spaced parallel relation to said shell with said weight, said grid'having up- 9. The method according to claim 8 including the step of providing untinned surfaces on the portions of said grid contacted by said wedge shaped core elements.

10. The method of casting a lead backing layer to the embossed copper printing shell of an electrotype plate so as to provide slots in the surface of said backing layer adapted to receive the clamping bars of electrotype plate clamps carried by printing cylinders, said method including the steps of placing a suitably tinned electrotype shell in a tray adapted to receive molten lead, placing a weight on said shell, supporting a grid in spaced parallel relation to said shell with said weight, positioning wedgeshaped core elements on said grid, introducing molten lead into said tray to fully immerse said grid and to partially immerse said wedge-shaped core elements, and removing said weight and said core elements upon solidification of the lead.

11. In an apparatus for casting the lead backing for electrotype plates including a tray adapted to receive a copper electrotype shell having the backside thereof tinned, said tray having tapered walls such that molten lead may be introduced into said tray and subsequently removed upon solidification, weight means adapted to rest upon the copper shell in said tray so as to press the shell against the bottom of the tray, said weight means including a frame, spikes projecting from said frame to engage said copper shell and press said shell against the bottom of the tray, said frame thereby being elevated above said electrotype shell, and parallel wedge elements supported by said frame in spaced relation to said electrotype plate, said wedge elements providing cores for forming slots in the back surface of the backing layer upon solidification of the backing layer.

12. In an apparatus for casting a lead backing for electrotype plates including a tray adapted to receive a copper electrotype shell having the backside thereof tinned, said tray having tapered walls such that molten lead may be introduced into the tray and subsequently removed upon solidification, weight means adapted to rest upon the copper shell in said tray so as to press the shell against the bottom of the tray, said weight means being adapted to support a grid in spaced parallel relation to the copper shells for immersion in the lead backing, said weight means including a rectangular frame, parallel Wedge elements carried by said frame on either side thereof, said wedge elements being adapted to project between marginal fiange portions of the grid to be supported by said weight means, spring means for biasing said wedge elements oppositely into compressive engagement with the marginal flange portions of the grid so as to engage and support the grid, and elongate spikes carried by said frame adapted to engage the tinned surface of said copper shell and to press said shell against the bottom of said tray, whereby said frame is supported in spaced parallel relation to said shell, said wedge elements upon immersion of said grid in molten lead providing cores for forming slots in the back surface of said lead backing.

13. In an apparatus for casting a lead backing for electrotype plates, weight means according to claim 12 wherein said wedge elements are tapered so as to support the marginal flange portions of the grid at an acute angle with respect to the plane of the back surface of the lead backing.

14. In an electrotype plate including a copper image bearing shell and a lead backing layer bonded to one side of said copper shell, the improvement includinga sheet metal grid embedded in said lead backing layer in spaced parallel relation to the copper shell, said grid comprising a perforated rectangular base portion having the margins on opposite sides thereof bent to a position substantially normal to the plane of the base portion and projecting substantially to the back surface of said backing layer to provide flanges adapted to reinforce the opposite ends of said backing layer.

15. The sheet metal grid according to claim 14, wherein said grid is an integral sheet of copper having tinned surfaces on said perforated base portion, the margins of said base portion and the inner surfaces of said flanges being untinned, and wherein said backing layer has notches formed therein adjacent the untinned surfaces of the base portion and flanges of said grid.

References Cited in the file of this patent UNITED STATES PATENTS 851,049 Wood Apr. 23, 1907 1,076,046 Letz Oct. 21, 1913 1,467,787 Gemmill Sept. 11, 1923 1,703,977 Wood Mar. 5, 1929 2,086,145 Wood July 6, 1937 2,180,732 Durham Nov. 21, 1939 2,222,013 Atwood Nov. 19, 1940 2,305,852 Durham Dec. 22, 1942 2,474,889 Crafts July 5, 1949 2,668,497 McWhorter Feb. 9, 1954 2,746,106 Myers May 22, 1956

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