[1]2 1 7 3 l t 9 l 2 Uni'ted States Patent Office patented Jan. 24, 1956 2,731,912 I%IETHOD AND APPARATUS FOR APPLYING RESINOUS OR TI]ERMOPLASTIC COLORS 5 TO OBJECTS Reg-'@S Welsh, Pittsburgh, Pa.@ assignor to The 0. Hounnel Company, Pittsburgh, Pa., a corporation of Pennsyl,vania 10 Application March 23, 1950, Serial No. 151,366 7 Claims. (Cl. 101-129) This invention relates to the application of color to 15 obje cts such as ceramic ware, i. e., china, glass or porcelainenamel ware, or other materials including wood, meta l, etc., by what is commonly referred to as "screeni.ng, " and, iri particular, a method and apparatus for scre ening thermoplastic or resinous coloring compounds 20 onto the objects and keeping it in a proper fluid condition during application. in the process of decorating objects such as ceramic ware by screening, a fine mesh screen is used, and areas of this screen are masked or coated over, and the un- 25 coat ed or unmasked areas provide a pattern of the desired outline or contour throtigh Nvhich coloring material is forced by movement of a squeegee over the screen. 'Ibis process is widely used at the present titne, but mostly for the application of a single color to the object to be 30 deco rated. Where more than a single color is used, the colo r or paiit first applied must be allowed to thoroughly dry or harden before any succeeding color can be put onto the ware. This is expensive and requires considerable handlir@g and labor. It has heretofore been pro- 35 pose d to use colors of a thermoplastic character which are rnaintained in a liquid condition until forced through the screen into contact with the ware. Upon contact with the ware which is relatively cold, the theri-noplastic mate rial quiclcly haidens so that the object can be applied 40 dire ctly over a preceding one, and several colors can be appli ed ;n immediate succession. Diffictilty has been enco untered, however, in keeping the thermoplastic color or paint at a proper consistency to pass through the screen und er the action of the squeegee. Attempts have been 45 mad e to use heaters above the screen to keep the thermoplasti c rr@aterial at a proper temperature, but this has not prov ed satisfactory because the heaters have to be so locat ed that they viill not interfere with the movement of the squeegee over the screen, and the t emperature 50 of the r@iaterial at the surface of the screen cannot be unif ormly controlled. Also, infra-red lamps have been tried with indifferent success. Moreover, if the thermoplasti c material hardens in the screen, as it may for exa mple between the end of one day's work and the 55 begi nning of another, considerable time is lost in getting the screen clear of the hardened therrnoplastic material. I have invented a novel method and apparatus for heati ng a body of thermoplastic or resinous color compou nd resting on a screen, wh;ch overcome the - afore- 60 ment ioned objections and, in addition, afford a uniforrn, easil y controlled heating so that the color may be constantl y maintained at just the right fluidity for ready flow thro ugh the interstices of the screen. In a preferred emb odimeiit and practice, I provide means for heating 65 the screen by electrical resistance, the heat generated in the screen bei-.qg thus immediately available for heat:lng the color layer thereon. I preferably tise a screen formed of fine mesh nietal wire s, and connect opposite ends or opposite edges of the screeli wilh a source of electric current whereby the 70 wires are heated by their resistance to the passage of 2 current therethrough, and the body of color material which lies over the wires is thus heated and kept at a proper viscosity or condition of fluidity, and the heat is applied so that the color composition is in just the right condition to pass through the screen. However I may use in place of a wire screen a silk screen with an overlying series of wires or wire screen immediately adjacent thereto and the electric current may be passed through such wires or wire screen, keepin.- the temperature of the thermoplastic part at just the proper point to flow through the silk screen. Altematively to this, the silk or other fa.bric screen may have conducting wires or resistor wires woven directly into it at suitably spaced intervals. These thermoplastic colors are normally hard solids which may be liquified by heat. The melting points of the different thermoplastic colors vary and therefote the temperature that must be used in maintaining the necessary viscosity of the fluid thermoplastic will depend upon the viscosity characteristics of the different thermoplastics. A complete understanding of the invention may be obtained from the following detailed description and explanation thereof which refer to the accompanying drawings illustrating the preferred embodiment and practice. In the drawings: Fig. I is a perspective view of an apparatus for applying color to ware, having the invention incorporated therein; Fig. 2 is a partial section through the scree-ii and the body of color thereon, parts being shown in elevation; Fig. 3 is a bottom view of the screen showing the pattern to be applied to the ware in one color; Fig. 4 is a partial view similar to Fig. 3 showing the pattern to be applied in another color; Fig. 5 is a per pective view showing a piece of ware having the complete pattern applied thereto; Fig. 6 is a diagrarnmatic view showing the rear of the power pack for supplying low-voltage heating current from a house-current supply, and the wiring connections between the several elements thereof; Fig. 7 is a more or less schematic view showing a longitudinal section through a screen wherein the stencil screen itself is of silk or other fabric and the electrical conducting and heating screen is immediately above it; and Fig. 8 is a transverse section through a screen formed of fabric with longitudinally-extending conducting wires replacing the threads at spaced intei-vals in the screen, Referrin.- now in detail to the drawiligs, and, for the present, to Figs. 1 and 2, an apparatus for applyiiig color to ceramic ware or other objects to be decorated through a screen is indicated generally at 10. It comprises a cross beam 11 suitablysupported, spaced parall,-l rails 12 ex-. tending forwardly therefrom, and clatnl)@-rig blocks 13 slidable along the rails. A screen frame 14 has tongues 15 extending outwardly from both ends thereof adapted to be clainped to the rails 12 by thumbscrews 16. These screws are threaded througli tapped holes in lugs 17 projecting forwardly from blocks 13. A screen 18 is stretched across and overlies the frame 14, being secured in any suitable maiiner to the lower surface thereof as clearly shown in Fig. 2. The screen is appropriately masked to leave unobstructed the pattern which :@t is desired to apply to the ware in color. Such a pattern is shown at 19 in Fig. 3 and another at 20 in Fig. 4, the pattern 20 being formed on a second screen 21 carried by a frame 22. The patterns 19 and 20 are complem-,ntary parts of an entire multi-color design. The two screens are mounted in different color-applying mechanisms so that a two-color design, for example, may be laid on in successive steps. While I specifically mention two colors, there may be a succession of several colors. A layer 23 of thermoplastic color, e. g., green, is placed
[2]3 on screen 18, while a layer of contrasting color, such as red or yellow, is carried by screen 21. The ware or other object to which the design is to be applied is held in color-receiving position by a rec,.procating arm 24. In the illustrated embodiment, tbe ware is a tumbler 25. it is carried by a pair of i)osts 26 adjustably mounted on the arm and fitted wit@ spaced studs 27 of resilient material such as rubber or the l-@ke. Color is forced throu,-h the unobstructed interstices of the screen by a squeeg-,e 28 which is a blade of rubber or the like mounted on an arm 29 extendiiig -,tbove the scree,i and oscillated lengthwise thereof by known means (r,ot shown). The sq-,-,eegee 23 wipes across the screen and deposits a thin film of thermoplastic on the viare which hardens almost iiistantly. The squeegee merely modifies the surface tension of tl-ic fluid tli.-rmoplast;c to permit a thin fil-m to pass throtigh the scro-en. In order to maintain the layer ol color on the screeii at the proper temperature, 1 provide means to cause a flow of electric current through the screen. i'l of wire. If the screen proper be of tiber such as Sill-, T ether weave fine conducting wires therein along with the silk threads, or provide a stipplementat wire screen adjacent the silk, preferably above it. Instead of a wire screen, a series of coiiductor Nvires separate from the patterned screen, but positioned thereadjacent, could be employed. In any event, the screen frame 14 must be of insulating materiai to prevent short-circuiting the screen or other conductor wires whicti are heated by their resistance on the passage of elee'ric current therethrough. Conducting strips 30 are brazed or soldered +o the screen 18, for exar,ip'te, -,d:l@qcent the ends thereof, and constitiite terminals or electrodes to which condiictors )r lead wires extending from a current source may b-- connected. This arrangement prevents If-,calized heatilig or sparking. With this arrangeinent, i@L w;ll be apparent that ctirre@,it will flow throii.ah the longitudinal qcreen wires and thereby generate heat there-@n. By stiitably co-@itrolling the current flow, the aiiiount of heat generated may be varied as desired. A power pick 31 is shown acljacent the positio-@i of the operator of the c@llorapplying anparatus, for the purpose of convertiiig and c-ontrolling ciectrical energy from a source of supply si-ich as the usu@,.l comi-tei-cial power circu-'t. As shown iii F;S. 1, the power pack is mounted on a supporting frarr.,e 32 stand-Ing bpck of the beam 11 where it is in ftill view of and convetiiently accessible to the operator. The elements co-.riposing the pack are shown best in Fi,-. 6. They ilieltide a step-dov-in transfoni-ier 33 and a @,ar@able reactor 34 j3-t,)tiiited -'@ii an enclosiiig case 35. The operating shaft of the reactor extends thre.-@lg@, llic@ fron', pa-,ict ZG o@r 'Lhe cas-, - ,tncl is provided with a knob 37 hi)7'@,@ig a pointer c(,,operatirig with a grpduated sc!lle 3?,. A i-eceptacte 39 ,it one e@id of the case is adapled to accommoclate a pltig 40 on a twocondlictor cable cojiiiected to any conveiiient house-current slijply. A 1".-ise 4t -Is co,-inecteet in o-tic side of the eirciii't i'roiii hc to the reactor. The reactor is conrecte@! !(,, pri!iii@,ry vii,-idinL, oF the tran,,,@@Ormer in the knowii manner so os to vary the proportion of the line vo,ta.-e iiiipressed on thi@ I-,tter, in order correspoiidi,.igly to the second,-.i-y voita-,C. A,,i outptit rer-eptaci-- 4. al the other end o'l the case is coiinected -.cross the seco.-,ci,,iry winding, of the transformer. A voltmeter 43 is coi-,nected across the seconda.ry atici aii aiinieller 44 in se-ies tiiere%vith. These i-neters are mounted on the front 3C@ their faces exposed tbrotigh opeiiiigs the@,-;-,i. A two-conductor cable 45 li@,s -.t plug at one end adal)ted to cooperate with recep'L,,@cle 42, and lias the ot'-ter ends ol its conductors cotiiiected to terminal strips 30 as clearly showr@ in Figs. I aiid 6. l,,y ',his arra@,.gen-ient aiid coniiection of the elements of the power pack, I am enabled to apply reduced voltage to the terminals 30, tliereby catising sufficient current to flow throi:@gh the screen wires to heat 2,731,912 4 them to a temperature that will just sutice to maintain the color layer 23 in proper fl@uid conditior@. The applied voltage may be easily varied by adjusting ti@e reactor 34. This voltage is indicated on voltmeter 43 and the current flowing through the screen on ammeter 44. It is thus possible for the operator to keep a close check on the heating current at all times and make adjustment therein, as may be necessary. The current used in the screen is preferably a low volt10 z,,ge current of sufficiently high amperage so that the operation can be carried on without danger to -,vorkers or to the operators who may from time to t@.me run a metal spatula or paint knife over the scree@is while they are in operation, or who may be holding pieces of metal 15 vvare while the decoration is b-.ing applied, ar@d of course by using spatulas with - insulating handles, danger may be avoided even with iiigher voltages. 'Lt will also be understood that where feasible the same resistaiice heating of the wires may be effected by the use of ,) hir,,h frequency 20 field -,irronged to induce currents in the wires. In the case of a silk screen, conductcr wires woven therein as mentioned above may be sccured to the terminal strips 30 or a separate wire screen placed above it and the strips brazed or soldered thereto. The only 25 i.-,ssent:@al requirement is that tl-ic electric-resistance heating eleme-@its be in heat-exchange relation to the color layer, and adjacent the patterned screen so that they will not interfere with the wiping of color therethrough by the soueegee. In any case, the conducting wires serve iTi the 30 manner of immersion heaters to generate heat in the color layer itself immediately adjacent the plane in which the color is forced through the screen iiito the w,,lre. In Fig. 7 1 have shown one modification in -,vhich the silk or fabric screen is designated 50, and 51 is the frame 35 N@,hich stipports the screen, and which is formed ofinsulating n-iaterial. Immediately overlying the fabric screen 50 are resistance wires preferably in the form of a wire mesh screen 52, and current is supplied to c)pposite edges or opposite ends of the wires or screen 52 by current supply 40 v!:,es 53 and 54. In the modification illustrated in Fig. 8, t@e textile fabric forining the stencil is designated 55, but certain of the longitudinally-.extending threads are replaced by fine wire threads designated 56, the wires being at suitably spaced intervals. The supporting frame is designated 45 57. In this -instance current is applied to opposite ends of the wires 56. In Fig. 7 the overlying screen is in intimate contact with the silk screen, and so closely associated therewith as to form in effect a part thereof, and in Fig. 8 the conducting wires associated with the screen 50 do actually constitute a part of the screen. A silk screen is well adapted for placing sliarp patterns on wares such as glassware: The glassware, for example, Nvhen plpced in the screening frame is cold and will act to coiigeal the thermoplastic resinous color compound 5,5 plrticularly in the interstices of the silk screen. By the present invention wherein the heating element is the screen itself or is in direct contact with or within the screen, the heating may be accurately controlled to keep the screen and color compotind in ptoper condition for transfer to 60 ilie ceramic ware. Further, with lar.-e patterns, using a plurality of screens, the best results may be obtained by controlling the heat to havediffereiit viscosities of the color compounds for different portions of the pattern. It will be apparent from the foregoing that the inven65 '.@,in provides a sirnple, efficient method of heating color during application to ceramic ware, which may be easily practiced, and an apparatus therefor which is readily adaptable to existing color-applying meebanisms, requiring but little skill in the operation thereof, beyond reading 70 the two meter dials and adjusting the applied voltage to render the color more or less fluid, to suit various operating conditions, If the thp-rmoplastic or resinous material cools in the screen during an interruption to the operation of the 7;i screen, the material in the screen that hardens upon cool-
[3]5 ing will be the fint material melted when the current is again turned on, so that a minimum loss of time is suffered in putting the machine into operation and clearing the stencil when it is again put into use. While I have referred especially to thermoplastic colors, various compounds not strictly considered thermoplastics, as monomeric or partially polymerized resinous or plastic materials, may also be used with heat, and such materials are comprehended herein as thermoplastic materials. I
