US2798387A - Apparatus for knurling printing rolls - Google Patents

Description

y 9, 1957 c. L. WOODWORTH 2,798,387

APPARATUS FOR KNURLING PRINTING ROLLS Filed June 25, 1953 2 Sheets-Sheet 1 1N VEN TOR.

BYM Q a ATTORNEY 0/5573? L. WOODWQRTH y 1957 c. wooDwoRTH 2,798,387

APPARATUS FOR KNURLING PRINTING ROLLS Filed June 25, 1955 2 Sheets-Sheet 2 2 Y W h? I 34 4 INVENTOR. w My L WWW/w (59 BY am/imezfl ATTORNEY APPARATUS FOR KNURLING PRINTING ROLLS Chester L. Woodworth, Longmeadow, Mass, assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware Application June 25., 1953,:Seriai No. 364,133

Claims. (Cl. 7813.1)

This invention relates to apparatus for knurling printing rolls. More particularly, this invention relates to apparatus for knurling printing rolls to be used in the printing of plastic interlayers for safety glass laminates.

Safety glass is ,formed from a plastic interlayer sandwiched between glass plates. ,It is widely used in the automobile industry to form Windshields that will not shatter under impact. In order to eliminate the glare encountered in driving, it has become the practice to color the upper portion of such Windshields by dying the plastic interl-ayer. The dye is applied in amanner such that there is a substantially uniform gradation of color of gradually diminishing intensity from the more heavily dyed upper portion of the interlayer to the midportion thereof where the dye is no longer applied. it is conventional practice .to modify the gradation .adjacent to the line of demarcation between "the dyed and undyed portions of the interlayer in order to eliminate the optical aberrationsthatoccur when a completely uniform gradation abruptly ceases. From this, it is seen that the dyeing of interlayers of this character presents a special problem and that the dye must be applied with care .and precision if satisfactory results are to be obtained.

In accordance withconventional practice, an interlayer is colored by being progressively immersed in and withdrawn from-a solvent solution of dye. It has been proposed to apply the dye to the interlayer -by means :of a printing process wherein a knurled printing roll-is'used to apply the dye. .In accordance with this procedure, distinctseparate hollows, ,or knurls, are formed in the surface of a printing :iOll for the reception of the :dye. The dye .pick-up of .each individual knurl is dependent on the depth thereof. By providing ,a printing roll wherein the depth of the individualknurls is progressively diminished in a;predeterrnined manner, it is possibleto prepare plastic interlayers :havinga uniform gradation of color by a printing process.

Reasonably satisfactory printing rolls can be prepared by mechanically 'knurling a printing roll uniformly throughout its length :.so:that the depth of knurl is constant and then manually grinding the roll with an abrasive in order to obtain :aroll that will print a desired gradation as shown in U. S. Patent 2,638,050 to W. H. King. However, this process is .costly and time consuming. Past attempts to knurl such printing rolls by exclusively mechanical means have not been entirely successful in one respect or another.

Accordingly, an object of the present invention is the provision of apparatus for accurately knurling aprinting roll which maybe used in the printing of safety glass interlayers.

Another object is the provision of apparatus for accurately controlling the depth of .knurl imparted to a printing roll.

The manner in whichothese and other objectsarenats taine'd will be apparent from the following detailed-description of a specific embodiment .of the .presentinvem tion, when read in conjunction with the accompanying drawingsin which:

Figure 1 is a side elevation view partly in section illustrating schematically a preferred form of the invention, the electrical circuit for the knurling assemblybeing diagrammatically illustrated;

Figure 2 is a fragmentary top plan View of the apparatus shown in Figure l;

Figure 3 is a top plan view to an enlarged scale of the Lknurling assembly shown in Figures 1 and 2;

Figure 4 is a fragmentary side elevation view to an enlarged scale of a knurling assembly shownin Figure 2, taken along the lines 4-4 of Figure '2;

Figure 5 is a front view of one form of a variable resistance element comprising a part of the current regulator shown in Figure '1; and

Figure 6 is a front view of another form of a Variable resistance element comprising apart of the current regulator shown in Figure =1.

Turning now to the drawings and especially to Figures 1 and 2, there is schematically shown a conventional lathe including a suitable base ,12, a headstock 14 carrying a chuck jaw 16 and a tail stock 18 carrying a dead center .20. A printing roll 22 is mounted between the chuck jaw 16 and thedead center 20 forrotational movement about its longitudinal axis. A power-driven lead screw 24 and a ,guide vrail 26 support ,a carriage 28 heneath the live center .16 and the dead Center .20 for travel therebetween in response ,to rotation ,of the lead screw 24. The lathe is connected with a suitable poWersour-ce (not shown) by any conventional means, a drive pulley 30 interconnected with the power source by means of a belt 32 being one satisfactory means "by which this ;is accomplished. The chuck jaw 16 and lead screw 24 may be driven by the same power source-or the lead screw-24 may be driven independently of the chuck jaw 16 by any suitable .means :(not shown). .Lathes of this character have long been in .use and their-construction and manner of operation is well-known to those skilled ,in the art. Accordingly, in .the interest of s mplicity, .the lathe has been schematically illustrated, the construction of the lathe, ,per-se, .not constituting a part of the present invention.

A vibrator assembly 34 mounted on the carriage 28 .is used .toiknurl the printing roll 22, -the vibrator assembly 34 being energized by a suitable electric current-that is preferably derived from a power source independent of the power source for the lathe. Any suitable vibrator assembly 34 may be utilized to knurl the roll 22, it only being necessary to adopt a construction that .will not set ripen-undesirable resonance.

A preferred form of vibrator assembly '34 is shown in thedrawings, the construction being more apparent from an inspection of Figures 3 and 4. In accordance with the preferred construction, a generallyU-shaped channel member formed of a non-magnetized material such as brass is fixed to the carriage 28 by any suitable means such as an upstanding column '38 formedintegral-ly therewith. The channel memberis defined by a web 40 interconnecting a pair of spaced parallel flanges 42 and 44 that face the roll 22. A suitable apparatus for energizing a stylus is fixed to the web 40 intermediate the flanges 42 and 44. Such apparatus may be, for example, a conventional electromagnet comprising an iron core 48 surrounded by a coil 50.

A yibrator plate 52 is fixed to the ends of the flanges 42 and .44 in proximity to the electromagnet by-any suitable meanssuch as bolts 54, rubber blocks 56 being interposed between t-hevibrator plate 52, the heads of the-bolts 54 .andtheends of the flanges 42 and.44 in ordertoprevent the transmission of undesirable vibrations to the fixed to the side of the vibrator plate 52 facing the electromagnet in spaced alignment with the iron core 48. A stylus 60 having a base 62 is fixed to the other side of the vibrator plate 52, the base 62 being attached to the vibrator plate 52 opposite the button 58.' The stylus 60 should be of length such that the tip thereof is normally spaced from but is engageable with the surface of the roll 22. The tip of the stylus 60 is preferably'of a pyramid shape in order to produce pyramid-shaped knurls in the surface of the roll 22.

The coil 50 is energized by a pulsating electric current generates a pulsating magnetic field, e. g., an alternating current or a pulsating direct current. The electric current should be derived from a power source capable of delivering a current of substantially uniform intensity and, in addition, the frequency of the pulsating current f should be substantially uniform throughout knurling operations.

- When the coil 50 is energized by means of an alternating current, the iron core 48 is magnetized during each alternate half cycle in a degree proportional to the current flowing through the coil 50; the magnetic force being released on each passage of the alternate current through zero voltage. As a result, the button 58 will be drawn towards the iron core 48 while it is magnetized and, when the magnetic force is released, the button 58 ing through the coil 50. During oscillation, the pyramidshaped tip of the stylus 60 will repeatedly strike the roll 22 and produce knurls or depressions in the surface thereof, the depth of the knurl likewise being proportional to the intensity of the electric current flowing through the coil 50. When a pulsating direct current is used, the 1 stylus 60 is vibrated in the same manner. The iron core 48 is magnetized by each pulse of current passing through the coil 50 and the magnetic force is released between pulses. As a result, the amplitude of vibration of the stylus 60 and the depth of knurl produced in the surface of the roll 22 will be proportional to the intensity of the pulsating direct current.

It is preferable to use an alternating current such as an alternating current derived from an independent power source 64 (schematically shown) that is capable of delivering a current of uniform intensity and frequency. The coil is electrically connected with the power source 64 by means of a circuit comprising a lead wire 66, a return wire 68, a voltage regulator 70 and, preferably, a suitable switch 72, the various elements being connected in series. If a pulsating direct current is to be used, the

coil 50 should be connected in the indicated manner with intensity over a comparatively wide range if the desired gradation of depth of knurl is to be obtained.

When the coil 50 is energized by an alternating current, the currentregulator to be used in accordance with the present invention should be one of two general constructions. Preferably, the construction should be such that the phase relationship of current to voltage 18 not changed during knurling operations. However, if desired, a current regulator that will continuously and umforrnly modify the phase relationship of current to voltage as the intensity of current is continuously modified may be used. Current regulators of these two general constructions are inherently operable to continuously and uniformly modify current intensity. A current regulator that modifies the phase relationship of current to voltage at a variable rate will generally be incapable of accurately controlling current intensity over the entire range that must be used if satisfactory printing'rolls are to be prepared. a

In accordance with the illustrated form of the invention, current intensity is modified through the use of a voltage regulator 70 that is controlled by lateral movement of the carriage 28 relative to a roll 22 being knurled, the illustrated regulator being operable to control current intensity when either a direct or alternating current is used. It is to be understood that the invention is not limited in its application to the details of construction and arrangement of elements comprising the illustrated voltage regulator 70 since the invention is capable of other embodiments and of being carried out in difierent ways.

As is more clearly shown in Figure l of the drawings, a preferred embodiment of the voltage regulator 70 comprises a container 74 partially filled with a liquid electrolyte 76 and a pair of spaced electrically conductive plates 78 and 80 immersed in the electrolyte 76. The plate 78 is fixedly mounted on the container 74 so that the immersed area thereof will remain constant throughout knurling operations and the plate 80 is movably suspended in the electrolyte 76 so that the immersed area may be varied.

Voltage regulators of this general construction will accurately register 1 ohm changes in resistance over a 200 ohm range and will not modify the phase relationship of current to voltage when an alternating current is used. The electrical conductivity of the voltage regulator is determined by plate size, plate spacing, the chemical composition and concentration of the electrolyte and the temperature at which the electrolyte is maintained during knurling operations. As a result, electrical conductivity can be controlled with precision in order to provide any desired degree of conductivity. The plates 78 and 80 may be formed from any suitable electrically conductive metal such as aluminum. Any suitable liquid that is capable of conducting an electric current may be used as the electrolyte 76. A suitable electrolyte may comprise, for example, an aqueous solution of 0.6 gram K of disodium phosphate per liter of distilled water. During knurling operations, the portion of the electrolyte intermediate the plates 78 and 80 will be heated due to the transmission of current between the plates. Since the temperature of the electrolyte affects conductivity, it is preferable to mount a suitable agitator 82 intermediate the plates 78 and 80 to prevent localized overheating. The overall temperature of the electrolyte 76 is preferably maintained constant throughout knurling operations by any suitable means such as a cooling coil 84 connected to a suitable thermostatically controlled cooler (not shown). It is preferable to provide a cover 86 having suitable openings for the admission of the plates 78 and 80, the agitator 82 and the coil 84 in order to prevent contamination of the electrolyte 76.

The voltage regulator 70 is placed adjacent the base 12 of the lathe and interconnected with the stylus assembly 34 in a maner such that movement of the stylus 60 longitudinally of the roll 22 will cause the plate 80 to be progressively withdrawn from the electrolyte. A suitable interconnection comprises a cord 88 passing about a suitable pulley 90, one end of the cord 88 being fixed to the stylus carriage 28 and the other end being fixed to the plate 80. While this is a very simple and diceztive arrangement, it will the apparent to, those skilled-in the art that the interconnectionbetween the stylus 60 and the ,plate --80'may be accomplished in many different ways through theuse 'of a iwide tvarietyof apparams.

OPERATIGN .A printing roll to be .knurled, .for example, a roll 22 formed from mild steel, 'is mounted-on the-lathe between the chuck jaw 16 and the dead center 20, care being taken to besure that theicenters are true. The stylus assembly 34 is positioned adjacent the dead center 20 at one end of the roll 22 with the tip of the stylus spaced from the surface -of-the roll "22. The current regulator 70 is then set to --provide an initial maximum depth of knurl. This is accomplished by immersing the plate 80 in the electrolyte 76-to*a predetermined maximum extent, the spacing betweenthe plates '78 and 80, the immersed area of -the-plate 78 and the 'composition'and temperature of the electrolyte'76beingtaken into account.

When the 'proper'adjustments have been made, ,power. is delivered to the lathe '10 "byrneans of a drive pulley in order to rotate-the roll '22 about its:longitudinal .axis and also to rotate the lead screw24. As the lead screw 24 rotates, the carriage1'28 :andthe/vibrator assembly 34 mounted thereon are movedlengthwise of the troll-22 towards the chuck jaw 16. Simultaneously, the switch 72 is closed in order to energize the coil by an alternating current delivered from the power source 64. Alternate magnetization and demagnetization of the iron core 48 will cause the vibrator plate 52 and the stylus to oscillate whereby the stylus 60 will repeatedly strike the rotating roll 22 and produce knurls on the surface thereof. Since the carriage 28 is continuously moving relative to the length of the continuously rotating printing roll 22, oscillation of the stylus 60 will produce a spiral pattern of separate knurls in the surface of the roll 22. The spacing between the individual knurls in the spiral will be determined by the rate at which the roll 22 rotates and the rate of oscillation of the stylus 60. The spacing between laps of the spiral will be determined by the rate at which the carriage 28 moves relative to the length of the roll 22. Any desired knurl spacing can be obtained by suitably regulating the rate at which the roll 22 is rotated, the rate at which the carriage 28 is moved relative to the roll 22, and the rate at which the stylus 60 oscillates.

As the carriage 28 moves progressively towards the chuck jaw 16 due to the rotation of the lead screw 24, the cord 88 will progressively raise the plate 80 of the voltage regulator 70. This Will cause the resistance of the voltage regulator 70 to progressively increase at a uniform rate and thereby cause a correspondingly diminution of depth of knurl in the surface of the roll 22.

When the plate 80 has straight parallel sides as shown in Figure 5, a substantially uniform gradation of depth of knurl will be obtained. If the plate 80 is tapered adjacent the bottom edge as shown in Figure 6, the gradation will be initially uniform but will be modified adjacent the lightly knurled end of the roll 22 in order to prevent an abrupt termination of gradation. Other patterns may be formed in the surface of the roll 22 by using a plate 80 having any desired shape.

The following specific example illustrates the manner in which a printing roll having a uniform depth of knurl is prepared When using the illustrated device which constitutes a preferred embodiment of the invention.

Example I A printing roll 22 having a diameter of 2.90 inch is mounted between the chuck jaw 16 and the dead center 20 of a suitable lathe, the centers having a trueness of plus or minus 0.0005 inch. The chuck jaw is set to rotate the roll 22 at a rate of 6.7 R. P. M. in order to provide a cell spacing of 120 knurls per inch about the circumference of the roll 22 when using an alternating current having afrequency of 60 cycles ,per second. The-carriage .28 is positioned adjacent the dead center :20 and set to moveilengthwise ofthe roll 22 ataspeed to give 128 laps of knurls ,per inch .of roll 22. A-pyramid-tipped carbide .steel stylus Ma inchin diameter and inch long mounted .on the ,plate .52 is .used for the actual lending. The plate .52 .is :spaced about A inch from the iron core 48 .of theelectromagnet. The stylus 60.is mounted with the tip ithereof spaced .0.0 1-2.inch from the surface of the troll '22,..the stylus 60 beinghorizontaland-Ms inch below the horizontal axis of the roll 22. By mounting .the stylus .60.slightly .below the center-of the roll 22 'in this fashion, the burrs orsmall-projections .of metal formed-on the surface of..the ?roll.22 by the gouging action .of the stylus .60are equalized on :opposite .sides of .the individual .knurls for v.easy removal with an emery cloth or other siutable abrasive.

With respect .to the voltage regulator 70, a solution of 2.5 ,grams of disodium phosphate :in -4 liters of 'water (the electrolyte 76) -.is placed in a suitable container 74 and .two rectangular chromium vplated steel sheets '4 inches wide and .6 inches long are fully immersed therein. The .plate :18 is-fixed .to the container 74 and the plate '80 is suspended in the electrolyte 76 by a suitable .cord 88 that fiXGdttQthfi carriage 28 and passes about a pulley 90 positioned above :the platez80. "The spacing between the plates is adjusted to give an initial current of 1.4 amperes at an electrolyte temperature of about 40 C.; the electrolyte 76 being maintained at about this tem perature during knurling operations.

When these adjustments have been made, the lathe is set in operation and a 60-cycle alternating current is delivered to the coil 50 of the electromagnet. The ini tial (maximum) depth of knurl will be about 0.003 inch. As the carriage 28 moves lengthwise of the roll 22, the plate will be progressively withdrawn from the electrolyte 76 thus progressively increasing the resistance of the current regulator 70. Since resistance is increased at a constant rate, each individual knurl formed on the surface of the roll 22 will have a depth slightly less than the depth of the next preceeding knurl. As a result, a knurled printing roll having a uniform gradation of depth of knurl is obtained. It is preferable to rub the surface of the roll 22 with an emery cloth or other suitable abrasive after knurling operations are complete in order to remove any burrs that may be present on the surface thereof. A printing roll prepared in the above manner can be used to satisfactorily print a plastic interlayer for use in the preparation of glare-resistant safety glass.

Having thus described my invention, what I claim is:

1. In a device for knurling a printing roll being rotated about its longitudinal axis at a constant rate by means of a vibratable stylus periodically engageable with the roll to produce indentations in the surface thereof, the improvement which comprises support means for moving the stylus lengthwise of the rotating roll from adjacent one end thereof at a constant rate, an electromagnet responsive to an alternating electric current carried by said support means for w'brating said stylus at an amplitude of vibration proportional to the intensity of the electric current, an electric circuit connected to said electromagnet for delivering an alternating current thereto, said circuit including a control member, said control member comprising a container, a liquid electrolyte in said container, means for maintaining the electrolyte at a substantially constant temperature, a first electro-conductive plate fixed to said container and immersed in said electrolyte, a second electro-conductive plate and means carried by said support means for suspending said second electro-conductive plate in said electrolyte and for unidirectionally varying the immersed area thereof at a rate determined by the rate of movement of the stylus relative to the length of the roll.

2. Apparatus as in claim 1 wherein the second electroconductive plate is rectangular in shape.

3. Apparatus as in claim lwherein the second electroconductive plate comprises a first portion of uniform 'width and a second portion of non-uniform width.

4. In a device in which a printing roll beingrotated about its longitudinal axis at a constant rate is knurled by means of a vibratable stylus periodically engageable with electrical means for vibrating the stylus at an amplitude of vibration proportional to the intensity of an electrical current fiowing therethrough, said electrical means including a control element cooperating with the support means to decrease the intensity of the electrical current continuously in direct response to the movement of the support means.

improvement which comprises support means for moving the sylus lengthwise of the rotating roll from adjacent one end thereof at a constant rate, vibratory means carried by the support means for vibrating the stylus in response to a pulsating magnetic field generated by an electric cu'rrent at an amplitude of vibration proportional to the intensity of the current and electrical means for delivering an'eleetric current having a pulsating magnetic field to said vibratory means, said electrical means including a control element cooperating with the support means to decrease the intensity of the electrical current continuously in direct response to the movement of the support means.

References Cited in the file of this patent UNITED STATES PATENTS 515,241 Lyon Feb. 20, 1894 767,833 Phillips Aug. 16, 1904 960,626 Crossland June 7, 1910 1,008,701 'Crump Nov. 14, 1911 1,626,014 Smith et al. Apr. 26, 1927 1,695,617 Teissere et a1. Dec. 18, 1928 1,772,650 Weyandt Aug. 12, 1930 1,918,456 Dodge July 18, 1933 2,588,006 Hufnagel Mar. 4, 1952 2,598,253 Greenberg May 27, 1952 2,638,500 Ernst May 12, 1953 FOREIGN PATENTS 406,163 Great Britain Feb. 14, 1933

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