US2064850A - Plate straightener - Google Patents

Description

Dec. 22, 1936.- F. T. POWERS PLATE STRAIGHTENER Original Filed Jari. 28, 1932 Patented Dec. 22, 1936 UNITED STATES PATENT ()FFICE Application January 28, 1932, Serial No. 589,399 Renewed June 1, 1936 '3 Claims.

My invention relates to the art of making printing plates by photo-mechanical processes, and particularly to a novel and useful mechanism for straightening plates which have become bent,

twisted or warped during the process of powdering and etching.

Objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practise with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.

In the process of etching half tones or line cuts it is customary to heat the plates to set the powdered dragons blood, which is commonly used as a resist to protect the shoulders of each successive bite, to prevent undercutting and to permit carrying the etching process to a sufficient depth 20 to insure satisfactory printing quality. This heating process is immediately followed by a quenching or cooling process which usually con sists of bringing cold water into contact with the back of the plate. During these heating and cooling processes the plate is subjected to such a wide range of temperatures that the plate becomes warped and twisted or curled. The result is that the plate does not lie flat on a cooling surface nor will it present a plane, flat surface to the action of powdering brushes in an automatic powdering machine. Another factor which also contributes to the bending of the plate is the fact that when the powdering process is carried out by hand the operator commonly uses a pair of pincers or pliers to handle the hot plate from the heater to the cooler. By means of these pliers gripping the edge of the plate it is lifted and moved from the heating device to the cooling device. This operation has a marked tendency to bend the plate along the edge gripped by the pliers. When the plate is powdered in an automatic powdering machine, such as is described in my co-pending application Serial Number 513,364, filed February 4, 1931, it is important that the plate be kept straight and flat, so that it will receive a uniform action of the powder brushes over its entire surface.

Heretofore, the method commonly employed by skilled workmen to flatten a warped or bent plate has been to slam the bent or warped plate violently against a flat surface, such as a table top or a slab of lithographic stone, or the workman may bend the plate with his hands, or by utilizing the edge of a table or other convenient object he may bend the plate in an effort to flatten it.

Such methods are at best crude and inaccurate and not always productive of satisfactory results even in the hands of a skilled and experienced workman.

By my invention I provide a mechanical means whereby warped or bent plates may be automatically straightened or flattened more accurately and in less time than is required to perform the operation by hand.

In the accompanying drawing, I have shown a preferred embodiment of my invention, which, taken together with the description, will serve to explain the principles and method of operation of my invention.

Fig. 1 is a vertical sectional elevation of the apparatus on its longitudinal median line. Fig. 2 is a section on the line 22 of Fig. 1.

In the drawing like characters are used to designate the same or similar parts and arrows indicate the direction of movement or rotation.

In the drawing, two pairs of sprocket wheels, I and 2, only one of each pair being shown, are mounted on shafts 3 and 4 respectively, operating in suitable bearings 5 and 6. A pair of detachable link chains I, one on either side of the mechanism, cooperate with the pairs of sprockets I and 2. Attached to these chains at suitable intervals are a plurality of cross bars, 8, the ends of which are attached to suitable attachment links in the chains I. Between the chains I and under the cross bars 8 and supporting them, is a plurality of grid bars, 9, extending lengthwise of the apparatus parallel to the chains. These grid bars terminate at the sprocket wheels I and 2, thus permitting the cross bars, 8, to be carried around the sprockets without interference. Mounted about midway of the apparatus and below the grid bars, 9, is a shaft, II], which is movable vertically by means of the adjustable bearing, II, which may be raised or lowered by means of the screws, I2, in the guides, I3. Upon the shaft, II], are mounted a plurality of rollers, I4, which are located between the grid bars, 9, and which at their uppermost portion project above the tops of the grid bars. The amount of such projection is susceptible of regulation by means of the screws, I2. Above the grid bars, 9, are rigidly mounted on shafts I5 and I6 operating in bearings, I1 and I8, respectively, two rollers, I9 and 20, each provided with sprocket wheels 2I and 22, respectively, which are also rigidly mounted on shafts I5 and I6 and engage the chains 1. To the shaft Ill are also rigidly attached sprockets 23, which also engage the chains I from their under side.

The rollers l4, l9 and 20 are each provided with pockets or depressions, 24, in their periphery extending lengthwise the full length of the rollers. The circumference of the rollers, l4, l9 and 20, are equal to the spacing of the cross bars, 8, and the number of teeth in the sprocket is equal to the number of links in the chains 1 between successive cross bars, 8, so that a movement of the chains, I,v a distance equal to the spacing of the cross bars and the consequent rotation of the rollers, I4, [9 and 20 by the sprockets 2|, 22 and 23, produces exactly one revolution of the rollers. The timing of each of the rollers and the position of the pockets, 24, is such that these pockets always coordinate with and receive the cross bars, 8, thus permitting the cross bars to pass the rollers without interference. At the delivery end of the chain conveyor, 1, is a receiving table, 25, spaced apart from the ends of the grid bars, 9, to permit the passage of the cross bars around the sprockets 2. 'Motive power may be derived from any convenient suitable source, such as a motor, 26, cooperating with belt, 21, and pulley, 28, attached to shaft, 4. The entire mechanism is suitably mounted on a supporting framework.

The operation of the mechanism is carried out i as follows: The bent or curled plate to be straightened is placed in position 13 on top of the grid bars, 9', between two of the-cross bars, 8, either before or after the apparatus has been started in motion. The next succeeding cross bar, 8,

' comes into contact with the trailing edge of the plate andslides it along on top of the grid bars under the roller, l9, Whose peripheral surface is moving at exactly the same speed as that of the plate and consequently contacts with the upper surface of the plate without any relative motion occurring between the two surfaces and, therefore, there is no rubbing or scratching of the surface of the plate by the roller. As the plate is pushing forward by the cross bar, 8, its advancing edge meets and is flexed or bent slightly upward by the rotating under-roller, M. The amount of the upward bending or flexing action caused by roller I4 is under the control of the operator by adjusting the height of this roller by means of the adjusting screws, l2. As the plate advances further, its advancing edge meets and is fie'xed downwardly or in a direction the reverse of its previous bending by the rotating roller, 20. As the plate is still further advanced by the cross bar, it again contacts with the top of the grid bars, 9, and is again slightly flexed in the reverse direction. As the plate is further advanced it is pushed onto the receiving table, 25, into position C, as the cross bar travels around the sprocket, 2, on its circuit. It is obvious that any number of plates may be passed consecutively through the apparatus when placed one at a time in position B between consecutive advancing cross bars. In

its travel under and over the three rollers, each plate is given three slight reversals of bending with the result that with the roller, 14, properly adjusted as to its height, the plate comes out of the operation in a substantially flat plane condition, and is ready for any subsequent operation.

My new apparatus is equally adaptable for use.

as a separate machine for performing the single operation of straightening plates, or for incorporation in a mechanical powdering machine, as an integral part thereof, such, for example, as my automatic mechanical powdering machine described in my co-pending application, serial number 513,364, filed February 4, 1931, in which I find my new device particularly effective in keeping the'plates fiat and in a proper condition forreceivingthe various operations applied to them.

It will be obvious that my invention may be reduced to practice in a variety of forms other than that shown and described herein, without departing from its spirit and I do not wish to be understood as limiting myself except as set forth in the claims.

I claim: I

1. A device for straightening photo-mechanical printing plates, comprising in combination three or more parallel rotatable cylindrical rollers, successive rollers being positioned on opposite sides of the path of travel of the plates, aportion of them being entirely on one side of a plane and the remainder predominantly but not entirely on the other side of the same plane, means for varying the position of a portion of said rollers,

travelling means for conveying the plates bev tween successive rollers, and means for rotating said rollers at a peripheral speed equal to the speed of the plate.

2. A device for straightening photo-mechanical printing plates, comprising three or more cylindrical rollers of similar diameter, having longitudinal depressions in their periphery, positioned to flex the plates as they pass between adjacent rollers, conveying means for passing the plates between said rollers including a plurality of cross bars spaced apart a distance equal to the periphery of said rollers, and timed to coordinate with said depressions, means for driving said conveying means and said rollers at identical lineal and peripheral velocities respectively.

3. A device for straightening photo-mechanical printing plates, comprising three or more cylindrical rollers of similar diameter, having longitudinal depressions in their peripheries, positioned to flex the plates as they pass between adjacent rollers, and conveyng means for passing the plates between said rollers, including a cross bar timed to coordinate with said depressions.

FRANK T. POWERS.

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