US3020842A

US3020842A - Offset printing plate clamp

Info

Publication number: US3020842A
Application number: US28573A
Authority: US
Inventors: Neal Frank
Original assignee: R Hoe and Co Inc
Current assignee: R Hoe and Co Inc
Priority date: 1960-05-12
Filing date: 1960-05-12
Publication date: 1962-02-13
Anticipated expiration: 1979-02-13

Description

Feb. 13, 1962 F. NEAL OFFSET PRINTING PLATE CLAMP I INVENTCR 7 0% M BY k Filed May 12, 1960 Ill. ll ll ATTORNEY l'l l I I i l I l l I l I I I lllullll Ir l l l I l l I I I l T I l l l III 3,020,842 OFFSET PRINTING PLATE CLAMP Frank Neal, New City, N.Y., assignor to R. Hoe & Co., Inc., New York, N.Y., a corporation of New York Filed May 12, 1960, Ser. No. 28,573 2 Claims. (Cl. 101-4151) This invention relates to improvements in plate clamps, and more particularly to clamps of this type such as are used for offset printing plates.

In offset printing machines, the printing plate is of relatively thin, strong metal, such as aluminum alloy or steel, and is tensioned around the plate cylinder by suitable clamping means gripping its ends and operating within longitudinal channels or bores formed in the cylinder and communicating with the cylinder periphery through a gap.

It is an object of the invention to provide a plate clamping mechanism of this character which allows simple insertion of the plate ends into a relatively small gap in the cylinder periphery and a positive gripping thereof by the clamping means regardless of the precise position of the plate edge with relation to such means, together with a rapid release.

A further object is to provide a mechanism of the character indicated, in which the plate ends require no special preparation such as preparation for the incorporation of clamp engaging elements.

With these and other objects which will appear in the following full description in mind, a mechanism embodying the invention in a preferred form will now first be described with reference to the accompanying drawing, and the features forming the invention will then be pointed out in the appended claims.

In the drawing:

FIG. 1 is a fragmentary section, partly broken away, of the plate cylinder clamping mechanism, and is taken on the line '1-1 of FIG. 2;

FIG. 2 is a section on the general line 22 of FIG. 1; and

FIG. 3 is a detail looking in the direction of the arrow 3-3 of FIG. 2, showing a worm and worm wheel operating mechanism.

The plate cylinder body 1 has a generally cylindrical surface 2 interrupted by a gap 3 which extends chordwise of the cylinder and at an angle about 45 to a radial or axial plane. A wall 5 of this gap making an acute angle with the cylinder surface is joined to the cylinder surface 2 by a somewhat rounded nose 6 and takes the end 7 of the plate 8, which is bent to the shape indicated prior to attachment to the cylinder, and serves to position the plate circumferentially. The other end 9 of the plate lies against the other wall 10 of the gap which makes an obtuse angle of about 135 with the cylinder surface and is blended therewith in a gentle curve 11 as indicated.

While only the ends of the plate 8 are shown, it will be understood that the plate exends around the entire circumference of the cylinder 1.

The mechanism for gripping the plate end 9 comprises a block 12 slidable in a channel 1'3- having a wall 14 parallel to the gap walls 5 and 10 and which supports the block 12. This block has a beveled nose portion 15 having opposed parallel surfaces 16 and 17 spaced from the gap walls 5 and 10 by somewhat more than twice the thickness of the plate. The gap wall 10 extends part way under the nose 15 as indicated and the plate end 9 is inserted in the space between the two into a recess 18 formed in the member 12. This recess contains a number of rollers 19 substantially coaxial with each other and spaced along the cylinder, as indicated in FIG. 2, at convenient intervals, each roller having associated with States Patent 0 it two springs 20 which seat in bores 21 in the member 12 and urge the roller outwardly of the cylinder. Opposite surface 16, the nose 15 has a beveled surface 22 forming the opposite wall of the recess 18 and against which the rollers 19 are pressed by the spring 20, so as to grip the plate end 9 between the rollers 19 and the surface 16, as indicated in FIG. 1. The gap wall 10 terminates in an abutment 23 in position for engagement by the rollers 19 when the block 12 is moved toward the cylinder surface. As is apparent, such movement of the block 12 beyond the point Where rollers 19 engage abutment 23 will compress springs 20 and bring a lower point of the bevel 22 opposite the roller, thereby releasing pressure of the rollers against the plate end 9, for releasing this plate end. Thus, movement from the plate clamping position of FIG. 1 of the block 12 to substantially the limit permitted will release a plate gripped thereby and position the element 12 for receiving any other plate end which may subsequently be inserted. Movement of the block 12 is accomplished and its position is determined by means of a series of racks 25 carried by this block and spaced along its length, adjacent the rollers 19, which racks are engaged by gear wheels 26 fixed to the operating shaft 27 journaled in the cylinder. Shaft 27 carries at its end and outside the cylinder a worm whee128 which cooperates with a worm 29 mounted in a bracket 30 secured to the cylinder. The worm shaft has an end 31 formed for engagement by a wrench. It will be apparent that by turning the worm 29, the block 12 may be moved (to the left in FIG. 1) to a position releasing a plate and readying the clamp for taking another plate and it may also be moved (to the right in FIG. 1) in the opposite direction so as first to grip the plate inserted under the nose 15 and then tension the same to any required extent.

The mechanism for gripping the opposite end 7 of the plate is essentially similar and comprises a block 32 having a similar recess 18 with walls 16 and 22 respectively parallel to the gap walls and slanted and having similar rollers 19 and springs 20 accommodated in bores 21, all as described in connection with the member 9. The plate end 7 is inserted past the nose 15 of block 12 and between the recess wall 16 of block 32 and the facing Wall 5 of the slot, in the manner shown in FIG. 1, and this plate end is gripped and released by movement of the block 32 in the same manner as described in connection with the block 12. Blocks 12 and 32 slide against each other and against the wall '14 of the channel 13 previously mentioned and opposite wall 33 thereof, thus being maintained in position with relation to the cylinder gap at all times. Elements 32 similarly are provided with rack segments cooperating with gear wheels 26 fixed to a second operating shaft 27 also provided with a worm wheel 28 beyond the end of the cylinder body. As is evident, the rack, gear and operating shaft parts of the two ends of the plate may be, as shown, identical. Worm 29 which operates the block 32 is similar to the worm 29 previously described but has a somewhat shorter shaft due to the positioning of the parts in the cylinder.

While the clamping mechanism of the invention is primarily intended for attaching offset printing plates to their plate cylinders, it may also be used for attaching relief printing plates, where these plates have supports or backing elements in the form of thin, flexible sheet metal members, and for fastening blanket or resilient elements, similarly supported, to impression or other printing cylinders.

What is claimed is:

1. A plate clamping mechanism for printing machine cylinders comprising a cylinder body portion having a slot at substantially 45 to the cylinder axial plane, a pair of clamping elements, means for mounting the said elements in the said slot for movement independently of each other, and comprising opposed parallel guiding surfaces supporting the elements slidably against each other, each element having a recess for receiving a plate end, the said recess having opposed walls, one positioned substantially parallel to the said guiding surfaces for supporting the plate end and the other being beveled, a roller positioned between the two said walls for clamping the plate, a spring within the recess for urging the said roller to wedge the same and a plate engaged thereby between the two said opposed walls, thus clamping it in the element, means for moving the said element between a plate clamping and plate releasing position and means engaging the roller in the latter said position and holdingit back against the action of the spring to release the plate end, one of the said pair of clamping elements having a portion positioned beyond the other said clamping ele- References Cited in the file of this patent UNITED STATES PATENTS 1,159,941 Hohner Nov. 9, 1915 1,937,119 Krantz Nov. 28, 1933 FOREIGN PATENTS 387,695 Germany Ian. 2, 1924