US3230882A

US3230882A - Sheet securing device having teeth to penetrate said sheet

Info

Publication number: US3230882A
Application number: US263446A
Authority: US
Inventors: Donald L Snyder
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1963-03-07
Filing date: 1963-03-07
Publication date: 1966-01-25
Anticipated expiration: 1983-01-25

Description

Jan. 25, 1966 D. SNYDER 3,230,382

SHEET SECURING DEVICE HAVING TEETH TO PENETRATE SAID SHEET Filed March '7, 1963 IN VENTOR.

QO/V/Mfl L. 5/10 05? BY United States Fatent Ofiice Patented Jan. 25, 1966 SHEET SECURiNG DEVECE HAVING TEETH T PENETRATE AKD SHEET Donald L. Snyder, St. Paul, Minn., assignor t0 Minnesota Mining and Manufacturing Company, St. Paui, Minm, a corporation of Delaware Filed Mar. 7, 1963, Ser. No. 263,446 6 Claims. (Cl. 101-415.]l)

This invention relates to means for securing printing plates to the printing cylinder of a press. More particularly this invention relates to a novel bar adapted to be attached to printing cylinders for securing planographic printing plates thereto and may be used to hold both the leading and the trailing edge thereof.

Previously known devices for attaching printing plates to printing cylinders have been formed such that they are usable with only one particular type of printing plate, e.g., plates formed with a sinuous edge and preformed slots, straight edged plates with either slots or small holes of the type known as pin bar, and straight out plates without any preformed openings of any type. The press clamps for these various types of plates used either upstanding hooks or pins fitted on a press bar or a system for gripping the (plate across the whole length of the edge portions thereof. These prior art devices have proved inconvenient to the operator as it is necessary for the printer to be careful to purchase the correct type and size of plate. Alternatively, it may require that the operator remove one clamping arrangement and add a different clamping arrangement to use a different type or size of .plate on a single press.

In the field of printing different types of plates are available to satisfy different printing requirements.

Where very short runs are to be made an inexpensive paper plate can be used and for more substantial runs more expensive metal plates are used. Modern techniques have led to the development of printing plates formed of a laminate material which provides a comparatively inexpensive plate but yet a plate having essentially the same quality afforded previously only by the more expensive metal plates. These laminate plates are generally formed of polyethylene, paper, and aluminum foil which is coated with a light-sensitive coating providing a plate having an overall thickness of 0.005 inch. Plates of this nature are good for use on jobs which do not require too long a run, but yet, the press life of this plate should not be determined by how many copies can be made before it creeps out of register or completely tears away from the press because of poor clamping systems.

The press bar of the present invention has as one of its many advantages a universal character permitting its use with any common type or size of printing plate.

The press bar of the present invention provides a novel fastening using the combination of a fold in the plate plus the holding force of a tooth that engages appropriate holes in the plate or which will cleanly perforate the Plate to make their own holes and this fastening bar will increase the press life of existing printing plates many times that presently known.

This novel invention has as a further advantage the fact that the plates do not have to be .preshaped before they can be fitted on this novel press bar.

Additionally, the novel press bar of the present invention does not use up appreciably more plate area than previously known devices, to preform the superior job of holding the plate on the cylinder.

These and other advantages will become more apparent as the following description proceeds, especially when read in connection with the accompanying drawings in which:

FIGURE 1 is a plan view, partly broken away, illustrating a press bar embodying the present invention;

FIGURE 2 is a sectional view taken generally along the line 22 of FIGURE 1, showing the bar mounted on a printing cylinder, only a portion of which is shown;

FIGURE 3 is an enlarged sectional view of the b ar showing the particular construction of one of the teeth;

FIGURE 4 is a sectional View taken along the line 4-4 of FIGURE 3; and

FIGURE 5 is an enlarged perspective view to show the detail of one of the teeth.

Referring now to the drawings, there is illustrated therein one form of a press bar, generally designated by the reference numeral 6, incorporating the novel features of the present invention. This bar is formed from sheet metal, preferably 20 gauge (0.035 inch) sheet steel, by punching a blank formed with mounting holes and with projections along one edge from which teeth 7 are formed. The projections on the blank are then bent tothe desired position and are shaped to form the teeth 7. Thereafter, the blank is plated with cadmium or other corrosionresistant coating and the blank is bent back upon itself along one bend line to form a pair of uniformly spaced and

parallel strip portions

8 and 9. The blank is also bent along a second bend line to form an upwardly inclined plate guiding lip 10 on the lower strip 9 of the pair of strip portions.

The

strip portions

8 and 9 define therebetween an elongate uniform plate-receiving slot or groove 11 which extends the length of the bar 6. The spacing between the strips 3 and 9 gives the slot 11 a dimension within the range of 0.01-0.l0 inch, and in a preferred embodiment this dimension between the strips is 0.02 inch. The illustrated embodiment is especially adapted for use with a slotted plate 112, i.e., a plate formed with a straight edge 13 and spaced precut perforations 14 therealong (as shown in dotted lines in FIGURE 1), and the slot 11 has a depth, measured from edge 15 of the upper strip portion 8 to the base of the slot, which is equal to the dimension from the edge 13 of the printing plate to the adjacent edge of the perforations 14 as illustrated on the left hand side of FIGURE 1. This depth for the slot 11 is critical only as concerns the use of the bar 6 with the straight out and prepunched plate 14 of the type illustrated. A bar adapted especially for use with pin bar plates would have a depth for the slot commeasurable with the spacing between the edge of the plate and the edge of the holes in such a plate.

When using a slotted plate the leading edge 13 of the plate is guided into the slot 11 until the edge 13 thereof strikes the base of the slot as shown on the left hand side of FIGURE 1. The base of the slot 11 thus serves to align the plate 12 with the surface of a printing cylinder 16 (only a portion of which is shown) and aligns the ends of perforations 14 with the teeth 7 on the bar 6. The .plate is then drawn around the edge 15 of the upper strip 8 to fold the plate around said edge 15 as shown in dotted lines at the right hand side of FIGURE 1 and in solid lines in FIGURE 2. This folding fits the plate onto the cylinder and provides a fastening for the plate utilizing a bend in the plate to resist the pulling force on said plate during use and also the teeth 7 engage the perforations 14 in the plate 12 to give an added holding power. It is important to note at this time that neither the folding in itself nor the use of such hooks without a fold can adequately perform the task of keeping thin plates from pulling out due to the forces exerted thereon as exemplified by use of previously known clamps. The construction or configuration of the teeth '7, which will be described in greater detail hereinafter, is such that the 3 plate perforations engage a substantial area on the teeth which curtails a tearing of the plate at said perforations.

The lower strip 9 is formed with counter-sunk holes 17 which are pressed therein during the blanking operation and when the blank is bent said holes 3.7 are aligned with holes 18 formed in the upper strip 3, providing therethrou-gh access to the said counter-sunk holes 17, permitting a screw 19 to be fitted through the countersunk holes 17 and into threaded bores of a movable bar 16a on the cylinder 16 for mounting the bar 6 thereon. Due to the necessity for counter-sinking the head of the screws 19 in the lower strip portion 9, a plate or shim 20 is positioned beneath the bar 6 and is provided with suitable holes 21 which align themselves with the holes 17 and said shim provides a stable mounting for the bar 6. On some types of existing presses it may be advantageous to use several shims of this nature to provide the proper height [for the bar 6 with respect to the platereceiving surface of the cylinder.

In the illustrated embodiment the shim 2% is formed with an upwardly projecting flange 22 which fits along one end of the lower strip portion and projects thereabove to serve as an edge guide for the plates as they are inserted into the slot 11 of the press bar 6.

As best illustrated in FIGURES 3, 4 and 5, the teeth 7 are formed integrally with the upper strip portion 8 and project outwardly normal to the edge 15 and preferably extend upwardly to form an obtuse angle with respect to the upper surface of said upper strip portion 8. The angle thus formed between the teeth and the upper surface of the strip portion 8 is about 150 and preferably within the range of 135 l80. The teeth 7 are each formed with a base portion 23 and a crown portion 24. The base 23 of each of the teeth is semiround having a cross section as best illustrated in FIGURE 4, providing a rounded lower surface for the teeth adjacent the edge 15. This rounded configuration for the teeth 7 affonds greater contact between the edge of the plate around the perforation 14 andt-he teeth to curtail tearing of the plate at the perforation as results when using teeth which are rectangular in cross section. The crown 24 of each of the teeth '7 has a symmetrical arc-uate configuration in plan and the under surface of the crown is beveled as at 25 to form a cutting edge on said teeth. This arcurate cutting edge is very advantageous when it is desired to use plates which differ from that shown, i.e., plates which are not formed with perforations or when the preformed perforations do not match the spacing of the teeth. When using a different type of plate it is inserted in the slot 11 and is then drawn around the teeth 7. Then when pressure is exerted on the plate, the teeth 7 will readily cut their own perforations in the plate as it is folded about the edge 15 of strip portion 8. The combination of the bevel 25 and the arcuate cutting edge provides point contact between the teeth and the partially folded plate (as shown in dotted lines in FIG- URE 2) to initiate the cutting action and then as the plate is pulled over the teeth the remaining arcuate surface of the crown 24 cuts through the plate. An attempt to cut perforations with the hooks of previously known clamps causes the plates to be torn instead of cut such that the perforations formed thereby were jagged and uneven. This novel construction provides very smooth cuts through the plate and when the holding power of the teeth in such perforations is combined with the resistance added by the folding of the plate around the edge 15, the press life of the plate is greatly enhanced.

Tests have been conducted using the conventional clamsp on offset presses and the press bah of the present invention, and from such tests it has been found that the press life of the plate is enhanced as much as ten times when mounted by a bar embodying the features of the present invention. Additionally, the tests have shown that the illustrated mounting structure greatly lessens creeping of the plate on the cylinder, which results in d misalignment, causing the plate to get out of register with the copy sheets. As a result of these tests it was found that plate cree'page of inch was measured with conventional clamps after solid black copies were made while the same amount of creepage using the clamp of the present invention was measurable only after making 1000 or more sol-id black copies. These tests were conducted using a plate with a laminatestructure as above described, and the entire printing area of the plate was inked to produce the solid black copies.

In a preferred embodiment the teeth 7 of the press bar 6 have a width of Vs inch and this width is considered to be ideal as there is nothing gained by using a wider tooth since teeth having this width prevent the plate from pulling out. Also, the teeth are about A; inch in length and this is a length which is sufiicent to facilitate easy plate insertion. The spacing between the teeth 7 may vary depending upon the specific plate type and size for any specific bar, but is preferably not less than three times the width of the teeth.

The novel tooth construction provides the advantage of affording a good cutting edge which will cut and not tear the plate and yet does not result in a construction which is dangerous to the operator of a press using a bar formed in the manner described.

Having thus shown and described one embodiment of a press bar incorporating the present invention, what is claimed as new is:

1. A device attachable to a printing cylinder for securing thin flexible printing plates thereto comprising a pair of flat elongate strip portions positioned in fixed parallel vertically spaced relation defining an elongated platereceiving slot therebetween extending the length of said strip portions, the lower of which strip portions affords a plate-guiding surface to aid in positioning a plate in said slot when said strip portions are mounted on a printing cylinder and the upper of which strip portions is formed with a straight edge extending the length of the strip around which the printing plates may be folded, said upper strip being formed with a plurality of integral teeth projecting from said edge at an obtuse angle with respect to the upper surface of said upper strip portion, each of said teeth having a symmertrical arcuate crown, the under surface of which crown is beveled to provide a cutting edge of said tooth.

2. A device attachable to a printing cylinder for securing thin flexible printing plates thereto comprising a strip of sheet metal bent back upon itself along a line'to form a pair of fixed and uniformly spaced strip portions defining an elongated plate-receiving siot therebetween extending the length of the strip, the lower of which strip portions is adapted .to be mounted to a printing cylinder and the upper of which strip portions is formed with an edge extending the length of the strip parallel to the line of bending, said strip being formed with a plurality of spaced teeth integral with and projecting from said edge at an obtuse angle to the upper surface of said upper strip portion, each of said teeth having a symmetrical arcuate crown, the under surface of which crown is beveled to provide a cutting edge.

3. A device attachable to a printing cylinder for securing thin flexible printing plates thereto comprising a strip of sheet metal bent back upon itself along a line to form a pair of relatively fixed parallel strip portions having a uniform spacing therebetween within the range of .01- .10 inch defining an elongated plate-receiving slot which extends the length of the strip, the lower of which strip portions is formed with means for mounting said strip to a printing cylinder and the upper of which strip portions is formed with an edge extending the length of the strip parallel to the line of bending, said strip being formed with a plurality of integral teeth projecting from said edge at an obtuse angle with respect to the upper surface of said upper strip portion, each of said teeth .5 having a symmetrical arcuate crown, the under surface of which crown is beveled to provide a cutting edge.

4. In a printing press having a printing cylinder, a separable device mounted on said cylinder for securing thin flexible printing plates to said cylinder, said device comprising a strip of sheet metal bent back upon itself along a line to form a pair of fixed and uniformly spaced strip portions defining an elongated plate-receiving slot therebetween extending the length of the strip, the upper of which strip portions is formed with a straight edge and the lower of which strip portions is provided with means to facilitate mounting said strip to the printing cylinder with said straight edge parallel to the axis of the cylinder, said strip being formed with a plurality of integral teeth projecting from said edge at an obtuse angle with respect to the upper surface of said upper strip portion and spaced from each other several times the width of a tooth, each of said teeth having a symmetrical arcuate crown, the under surface of which crown is beveled to provide a cutting edge, and the base of each of said teeth being rounded on the undersurface.

5. A device attachable to a printing cylinder for securing thin flexible printing plates thereto comprising a strip of sheet metal bent back upon itself along a line to form a pair of relatively fixed flat parallel strip portions having a uniform spacing therebetween within the range of 0.1- .10 inch defining an elongated plate-receiving slot which extends the length of the strip, the lower of which strip portions is formed with means by which it may be mounted to a printing cylinder and the upper of which strip portions is formed with an edge extending the length 6. of the strip parallel to the line of bending, said strip being formed with a plurality of integral teeth spaced along said edge and projecting therefrom at an obtuse angle with respect to the upper surface of said upper strip portion, the spacing between adjacent teeth being greater than the width of one of said teeth, each of said teeth having a symmetrical arcuate crown, the under surface of which crown is beveled to provide a cutting edge, and the base of each of said teeth being rounded on the undersurface. 6. A device as described in claim 5 wherein the teeth have a width of about /s inch measured in the direction along said edge and have an overall length of about inch.

References Cited by the Examiner UNITED STATES PATENTS 777,813 12/1904 Shaffer 168 783,824 2/1905 Dick 101415.1 1,479,454 1/1924 Carr 24274 2,051,191 8/1936 Watson 16--16 2,197,097 4/1940 Dalton 101415.1 2,554,674 5/1951 Karas 1616 2,702,919 3/1955 Judge 165 2,733,475 2/1956 McMeans 1616 FOREIGN PATENTS 9,896 4/ 1897 Great Britain.

ROBERT E. PULFREY, Primary Examiner.

EUGENE R. CAPOZIO, Examiner.

Claims

1. A DEVICE ATTACHABLE TO A PRINTING CYLINDER FOR SECURING THIN FLEXIBLE PRINTING PLATES THERETO COMPRISING A PAIR OF FLAT ELONGATE STRIP PORTIONS POSITIONED IN FIXED PARALLEL VERTICALLY SPACED RELATION DEFINING AN ELONGATED PLATERECEIVING SLOT THEREBETWEEN EXTENDING THE LENGTH OF SAID STRIP PORTIONS, THE LOWER OF WHICH STRIP PORTIONS AFFORDS A PLATE-GUIDING SURFACE TO AID IN POSITIONING A PLATE IN SAID SLOT WHEN SAID STRIP PORTIONS ARE MOUNTED ON A PRINTING CYLINDER AND THE UPPER OF WHICH STRIP PORTIONS IS FORMED WITH A STRAIGHT EDGE EXTENDING THE LENGTH OF THE STRIP AROUND WHICH THE PRINTING PLATES MAY BE FOLDED, SAID UPPER STRIP BEING FORMED WITH A PLURALITY OF INTEGRAL