United States Patent: 3552314

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( 14550 of 14550 )

United States Patent	3,552,314
Skinner , et al.	January 5, 1971

PRINTING PLATE LOCK UP DEVICES

Abstract

A printing plate lock up device, especially for side by side mounting of a plurality of thin printing plates for web offset printing, wherein a spring loaded tensioning member adapted to engage one end of each printing plate is displaceable to relax tension of the plate by means of a cam shaft rotatable from one end of the printing cylinder.

Inventors:	Skinner; Charles Henry (Chiswick, London, EN), Hart; Michael Leonard (Beckenham Kent, EN)
Assignee:	Baker Perkins Limited (Peterborough, EN)
Appl. No.:	04/739,380
Filed:	June 24, 1968

Foreign Application Priority Data


May 30, 1967 [EN]			24820

Current U.S. Class: 101/378 ; 101/415.1

Current International Class: B41F 27/12 (20060101); B41f 027/06 (); B41f 027/12 ()

Field of Search: 101/415.1,378,384,382,375,383,268

References Cited [Referenced By]

U.S. Patent Documents


2049454	August 1936	Lamatsch
2708875	May 1955	Harless
2709406	May 1955	Knowles
3230879	January 1966	Worthington

Primary Examiner: Penn; William B.
Assistant Examiner: Coven; E. M.

Claims

We claim:

1. A printing plate lock up device comprising a carrier in a recess in the periphery of a rotary printing cylinder, tensioning means mounted on said carrier and adapted to be connected to the leading and trailing edge portions of at least two printing plates positioned in side by side printing relationship around at least a segment of said periphery, said tensioning means including abutment means for engaging the leading edge portions of the printing plates and including at least two trailing members for pressure engagement with respective trailing edge portions of said printing plates, and pressure means mounted on said carrier for displacing said trailing means individually with respect to said carrier in a direction causing tensioning of said plates around said periphery while the leading edge portions are in engagement with said abutment means; characterized by a rotatable cam shaft mounted on said carrier for rotation about an axis generally parallel to the axis of the cylinder, a plurality of cam formations on said shaft each constructed to displace, at a respective preselected angular position of the shaft, a respective trailing member against the action of the pressure means so as to relax tension only in the plate engaged by that trailing member, whereby one of the plates may be released without disturbing the other plate.

2. A printing plate lock up device according to claim 1 wherein at least one of said cam formations is adjustable to dispose said cam formations at substantially the same angular positions relative to said cam shaft.

3. A printing plate lock up device according to claim 1 characterized in that said trailing members each comprise several independently movable fingers.

4. A printing plate lock up device according to claim 3 characterized in that said fingers are all pivotally mounted on a common finger shaft extending parallel with said cam shaft and are shiftable axially along said finger shaft for varying the overall width of each trailing member constituted by the fingers.

5. A printing plate lock up device according to claim 4 characterized in that said fingers are resiliently urged apart from each other axially of the finger shaft.

6. A printing plate lock up device according to claim 5 characterized in that said finger shaft is rotatable and has screw engagement with a nut intermediate two of the trailing tensioning members so that rotation of the finger shaft displaces the nut axially to effect expansion in overall width of one of said two trailing members while simultaneously effecting contraction in overall width of the other of said two members.

7. A printing plate lock up device according to claim 1 characterized by an adjustable selector device connected to locate said cam shaft in preselected angular positions.

8. A printing plate lock up device according to claim 1 said abutment means characterized by at least one leading tensioning member pivotally mounted on said cam shaft for engagement with the leading edge portions of at least one printing plate positioned on the cylinder.

9. A printing plate lock up device according to claim 8 characterized by two leading tensioning members mounted on said cam shaft, said cam shaft being displaceable axially to effect a corresponding displacement of said leading tensioning members.

10. A printing plate lock up device according to claim 9 characterized in that said cam formations are located in apertures in the cam shaft mounted leading tensioning members to cause displacement of the latter with axial displacement of the cam shaft.

11. A printing plate lock up device according to claim 9 characterized by a shaft bearing assembly including a screwed sleeve which is rotatable in an end plate of the cylinder to effect the axial displacement of said cam shaft.

12. A printing plate lock up device according to claim 8 characterized by at least one adjusting bolt having screw engagement through the leading tensioning member and bearing against said carrier for varying the angular position of a printing plate engaging formation of the leading tensioning member relative to the carrier.

13. A printing plate lock up device according to claim 1 characterized in that at least one cam formation has two alternative angular positions of connection to the cam shaft, enabling said one formation to be set in phase with another of said formations to provide for simultaneous displacement of two of the trailing tensioning members.

14. A printing plate lock up device according to claim 4 characterized in that each trailing tensioning member is capable of overall variation in width between 151/2 inches and 163/4 inches approximately.

15. A printing plate lock up device according to claim 9 wherein one leading tensioning member is approximately 153/4 inches wide and the neighboring tensioning member is approximately 17 inches wide with a separation of approximately five-eighth inches between their adjacent ends.

16. A printing plate lock up device according to claim 4 characterized in that at least one of said shafts has connection at one end of the carrier with a respective stub shaft rotatably mounted in an end plate of the cylinder with an exposed shaft end to facilitate rotation of said shaft from one end of the carrier.

17. A lock up device according to claim 1 wherein the carrier is integral with the printing cylinder.

18. A printing cylinder characterized by its incorporation of two printing plate lock up devices, each according to claim 1, wherein their respective cam shafts are coaxial and are angularly adjustable from respective opposite ends of the printing cylinder.

19. A printing cylinder characterized by its incorporation of two lock up devices, each according to claim 1, located at respective angular positions on the cylinder periphery for tensioning two pairs of side-by-side printing plates about respective segments of the said periphery.

Description

This invention concerns printing plate lock up devices, more especially for web offset printing machines wherein exchangeable printing plates, usually of the order of .012" thick require by virtue of their thinness, particularly accurate and reliable positioning, securing and tensioning about the printing cylinder.

Usual known lock up devices are constructed separately from the printing cylinder and are adapted for installation in a channel in the periphery of the cylinder to extend across the cylinder parallel to the cylinder axis so that a spring loaded member of the lock up device can engage one hook preformed end of the printing plate with the other hook preformed end of the plate usually located in a fixed groove in the printing cylinder whereby the plate is positioned, secured and tensioned.

With the object of increasing productivity, present developments seek to utilize multiple printing plates mounted side by side across the axial length of the printing cylinder. This leads to various difficulties including for example difficulty in exchanging one plate without unnecessarily disturbing another mounted plate, difficulty in lateral positioning of the plates where each of these can vary in width over an appreciable range, and difficulty in obtaining any adjustment of the position of a plate in the circumferential direction of the cylinder which is a particular need for obtaining registration in multicolor printing. The object of this invention is the provision of an improved plate lock up device which overcomes one or more of these difficulties and which is particularly simple and convenient in use.

According to the invention a printing plate lock up device comprises a carrier adapted for attachment to or integral with a printing cylinder, a tensioning member mounted on the carrier for engagement with an end of a printing plate, and pressure means acting to displace the tensioning member with respect to the carrier in a direction for tensioning the plate, characterized by a cam shaft which is rotatable from one end of the carrier to displace the tensioning member against the action of the pressure means so as to relax tension of the plate.

Preferably the tensioning member comprises several separate fingers which are acted upon by respective cams on the cam shafts, and conveniently the axial separation of the fingers is adjustable to vary the overall length of the tensioning member.

Preferably in all types of tensioning members the longitudinal position of the tensioning member is adjustable through the agency of a shaft providing a pivotal mounting of the member and accessible at one end of the length of the device for adjustment of the shaft position.

A lock up device having the above defined features has particular advantage when designed for mounting a plurality of side by side printing plates on a printing cylinder, when provision is made for control of separate tensioning members for respective plates to permit individual mounting and removal of a plate without need to disturb an adjacent plate, and to permit mounting of a wide range of plate widths.

A preferred embodiment of the invention intended for processing double width paper webs of between 63" and 68" width for multicolor printing is now described by way of example only of the invention with reference to the accompanying drawings wherein:

FIG. 1 is a fragmentary elevation of one end of a printing cylinder embodying a printing plate lock up device according to the invention.

FIG. 2 is an end view of the lock up device of FIG. 1 on an enlarged scale with certain operating parts omitted for clarity.

FIG. 3 is a cross section of the lock up device taken generally along line 3-3 of FIG. 4.

FIG. 4 is a longitudinal section on the line 4-4 of FIG. 2.

FIG. 5 is a similar view to FIG. 4 but taken on the line 5-5 of FIG. 3.

FIG. 6 is a fragmentary cross section on the line 6-6 of FIG. 4, and FIG. 7 is a similar view to that of FIG. 2 but illustrating an alternative embodiment of the invention.

Referring now to FIGS. 1 to 6 the improved printing plate lock up device comprises leadings and trailings pairs of tensioning members 10,11 for respectively engaging the two conventionally preformed hook ends adjoining the leading and trailing edges of a side by side pair of printing plates, the pairs of members being respectively mounted on a parallel pair of shafts 12,13 mounted in a common carrier block 14 of generally channel section adapted for installation in a rectangular recess in the periphery of the printing cylinder 15.

The leading pair of tensioning members 10 intended for engaging the leading edges of the two printing plates comprises blades 10A, 10B (hereinafter called the leading blades) which are independently fulcrummed in lever fashion on the common shaft 12 (hereinafter called the cam shaft) which is rotatably mounted in bearing blocks 16 mounted on the carrier block 14. The outer edge of each leading blade 10A, 10B, terminates at the arcuate outermost surface 17 of the carrier which is to be contiguous with that of the printing cylinder 15 and this edge incorporates an inclined slot 18 to receive the hook leading end of the printing plate. An arm 19 of the leading blade on the opposite side of the shaft 12 to an arm 20 having the slot 18 presents a face towards the adjacent sidewall of the carrier 14 which face bears against a series of compression spring loaded plungers 21 (FIG. 3) incorporated along the length of carrier wall. These plungers 21 serve to urge the slotted ends of the leading blades towards the adjacent carrier wall in a direction tending to relax tension in the printing plate. The slotted arm 20 of each blade incorporates along its length a plurality of screw tapped holes which receive bolts 22 having heads accessible adjacent the median plane of the carrier with the opposite ends of the bolts bearing against the adjacent carrier sidewall under the pressure provided by the spring loaded plungers 21. Adjustment of these bolts 22 serves to adjust the angular position of the leading blades 10A, 10B and hence provide for adjustment of the circumferential register position of the leading edge of a printing plate with respect to the printing cylinder.

The pair of above described leading blades are freely rotatably mounted in approximate alignment on the cam shaft 12 with a fixed separation between their adjacent ends which separation is preserved by the fitting of cams 23 on the shaft 12 in apertures 24 in the leading blades so that the blades move longitudinally with any axial movement imparted to the shaft 12. One end 25 of the shaft is coupled with a stub shaft 26 rotatably mounted in a bearing assembly 27 mounted in an end plate 28 of the printing cylinder 15, and an indented plate 29 rotatable with the stub shaft 26 coacts with a spring plunger 30 of the bearing assembly 27 to locate the shafts 12 and 26 in any selected one of a plurality of angular positions.

The bearing assembly 27 further comprises a bearing bush 32 wherein the stub shaft 26 is anchored by circlips 33. The bush 32 has a screw threaded mounting in a sleeve 34 anchored in the plate 28 by circlips 35 and C-spanner holes 36 facilitate relative rotation between the bearing bush 32 and sleeve 34 whereby the former together with the shafts 26 and 12 are caused to shift axially. This latter movement and the fitting of the cams 23 in their apertures in the blades 10A and 10B imparts axial movement to these blades 10A and 10B, the bearing blocks 16 being guided in this movement by engagement of the latter with fixed guides 37 fastened to the carrier 14. A squared end 38 of the stub shaft 26 projecting externally of the plate 28 facilitates the angular adjustment of the shafts as hereinafter more fully described.

The two trailing tensioning members 11 intended for engagement with the trailing edges of the pair of printing plates, are each constituted by several lever fingers 40 mounted in side by side relationship on the common shaft 13 (hereinafter called the finger shaft) which shaft 13 is mounted in bearing blocks 41 fastened to the carrier 14 so that the shaft can rotate without axial movement.

As seen in FIG. 5, axially extending pairs of recesses 42 surrounding the shaft apertures in the opposite sides of adjoining pairs of fingers 40 accommodate helical thrust springs (not shown to preserve clarity) which serve to urge the fingers apart. Approximately midway along its length the finger shaft 13 is screw threaded at 43 and engages in a split nut 44 capable of longitudinal displacement relative to the shaft 13 and carrier 14 upon rotation of the shaft effected by turning a squared end 45 of a stub shaft 46 rotatably mounted in the plate 28 and connected to the finger shaft 13 by a coupling sleeve 47. Rotation of the shafts 13 and 46 to effect movement of the nut 44 in one direction serves to reduce the separation between the fingers 40 constituting a trailing blade on one side of the nut (as shown in their fully closed position on the right-hand side of FIG. 5) and simultaneously permits the thrust springs to increase the separation of the fingers constituting a second trailing blade on the other side of the nut (as shown in their fully extended position on the left-hand side of FIG. 5). Hence rotation of the finger shaft 13 serves simultaneously to adjust the overall effective lengths of the two trailing tensioning members 11 in opposite senses.

The fingers all extend from the finger shaft to reach the arcuate outermost surface 17 of the carrier where they incorporate a slot 48 aligned with the slots of the other fingers so that all fingers can simultaneously engage the trailing edges of two printing plates. Mounted in a recess in the sidewall of the carrier adjacent the fingers 40 is a series of spring loaded pressure pads 49 which bear upon the fingers to urge the latter towards the leading blade in a direction to tension the plates, the uniform tensioning of the plates being greatly facilitated by the independent mounting of the many fingers.

Formed as an integral part of each finger is a shoulder 50 projecting towards the cams 23 on the first shaft 12. The two sets of cams 23 associated with the two leading blades 10A, 10B are 45.degree. out of phase and are free to move through a generally semicylindrical recess 51 in the wall of the carrier adjacent the cam shaft. The function of the cams 23 is as follows. In a first angular position of the cam shaft 12, all of the cams are inoperative, the slots 18 in the leading tensioning members 10 are positioned in accordance with the setting of their adjusting bolts 22, and the trailing tensioning members 11 constituted by the fingers 40 all assume a position determined by the balance between the thrust of the pressure pads 49 and length of their respective two printing plates. With the cam shaft 12 turned through 135.degree. to a second position the cams 23 are repositioned so that one set of cams bears against the shoulders 50 of the fingers 40 constituting one trailing blade sufficiently to force these fingers towards the adjacent wall of the carrier block to overcome the thrust of the pressure pads 49 and so relax the tension in their respective printing plate sufficiently to permit its removal. At the same second position the other set of cams fails to touch the shoulders of the fingers constituting the other trailing blade so that the latter maintains its tension upon its respective printing plate. In a third position where the cam shaft 23 is turned through 135.degree. from the first position in the opposite direction to the second position, the second set of cams serves to relax the tension in the second plate whilst permitting the first trailing blade fingers to maintain tension in the first plate. Thus either of the two plates can be removed without disturbing the other plate. In a fourth position of the cam shaft at 180.degree. to the first position both sets of cams 23 act on the finger shoulders of both trailing tensioning members sufficiently to permit disengagement of both plates. Conveniently a marking of the exposed end 38 of the stub shaft registers with reference markings on an adjoining part of the plate 28 to facilitate the setting of the shaft in a desired position as located by the selector plate 29 and plunger 30.

In certain applications, the above lock up device is required to mount a double width plate instead of two separate plates in which case the two settings of the cam shaft which provide operation of one or other set of cams only is disadvantageous. This disadvantage can be overcome by provision for resetting the cams 23 relative to the shaft 12 in a second position wherein all cams are "in phase" and this feature is illustrated in FIG. 6 wherein the cam set screws 60 each have alternative engagement with the two recesses 61 and 62 in the cam shaft 12.

For processing double width webs, two of the above described lock up devices with either separate carriers or a common carrier are mounted in alignment in a common recess in the printing cylinder 15 with their respective adjustable shaft ends 38 and 45 exposed at respective ends of the cylinder. However, in order to mount the two lock up devices end to end in a double width cylinder, they must be constructed for left-hand and right-hand actuation by shafts which extend from the opposite ends of the cylinder. In the case where more than one printing plate is accommodated in the circumferential direction of the cylinder a like number of sets of lock up devices must be incorporated in respective channels in the cylinder.

In practice a double width web processing cylinder is required to mount four printing plates in side by side relationship along the axial length of the cylinder and these plates conventionally each have any width in a range of 151/2 inches to 163/4 inches. It has been ascertained by experiment that a printing plate must not overlap the length of its blades by more than one-half inch on each side for satisfactorily high speed printing. Any width plate within this range can be accommodated by use of the above described lock up device where their blades are dimensioned and adjusted as now described.

Considering one half of the printing cylinder only (as illustrated in FIGS. 1 and 2), on the basis that precisely the same considerations apply to the other cylinder half, the leading blade 10a disposed nearer the centerline of the cylinder has a fixed length of 153/4 inches, the outer leading blade 10B has a fixed length of 17 inches and the adjacent ends of the two leading blades have a constant separation of five-eighth inch. The trailing tensioning members 11 are both continuously adjustable throughout at least the range of 151/2 inches to 163/4 inches.

Considering the need for mounting two side by side 151/2 inches plates, the cam shaft bearing bush 32 and finger shaft 13 are both rotated to position both leading blades 10A, 10B at their extreme position nearest the center line of the half cylinder and to contract the inner trailing tensioning member and permit spring urged expansion of the outer trailing tensioning member so that both trailing tensioning members are at least 151/2 inches long. The inner plate in now hook engaged with the inner leading blade so that the two ends of the latter both project one-eighth inch beyond the edges of the inner plate, whereas the outer plate is mounted with one-eighth inch extension of the inner end of the outer leading blade beyond the inner edge of the outer plate, and 13/8 inch projection of the outer end of this blade beyond the outer edge of this plate. The opposite ends of the two plates are hook engaged with the two trailing tensioning members over the entire width of the plates.

To mount two plates of maximum 163/4 inch width, the cam shaft bearing bush 32 and finger shaft 13 are both adjusted to displace both leading blades five-eighth inch further from the cylinder half center line and to adjust the overall lengths of each of the trailing tensioning members to at least 163/4 inch. The inner plate is now mounted on the cylinder with one-half inch overlap of its inner and outer edges beyond the inner and outer ends of the inner leading blade, and the outer plate is mounted with its two edges each three-eighth inch inside the two ends of the outer leading blade. Again the opposite ends of the two plates are hook engaged with the two trailing tensioning members over the entire widths of the plates.

Thus it will be appreciated that all printing plate widths between these limits can be accommodated. Also, as already mentioned, by appropriate turning of the cam shaft 12 any plate can be released without disturbance of the other plates. In all cases these adjustments are very conveniently effected from one or both exposed ends of the printing cylinder. Also, by adjustment of the bolts 22 associated with the relevant leading blade, the circumferential position of any plate can be adjusted, without disturbing the circumferential position of the other plate to adjust registration in multicolor printing.

For monochrome printing where adjustment for registration purposes is not normally required various simplifications or modifications can be adopted. For example, the lock up device can be provided with finger type blades for engagement with one end of the plates whereas the other ends of the plates are engaged in a fixed slot 70 in the carrier as illustrated in FIG. 7, or in a slot in the printing cylinder.

* * * * *

Current U.S. Class:	101/378 ; 101/415.1
Current International Class:	B41F 27/12 (20060101); B41f 027/06 (); B41f 027/12 ()
Field of Search:	101/415.1,378,384,382,375,383,268