Abstract:
Apparatus and methods of controlling the temperature of printing ink or paint in a pad printing apparatus are described. The apparatus comprise temperature control elements that are connected to a chiller unit. Temperature sensors on a support plate or ink cup, or both monitor the temperature of the ink cup and/or ink. As the temperature of the ink in an ink cup rises due to ambient air temperature in the working environment, a chill medium is applied to the support plate, ink cup, ink or any combination thereof to cool the temperature of the ink thereby reducing evaporation of solvents in the ink to maintain a relatively constant ink viscosity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     A claim of benefit is made to U.S. provisional application Ser. No. 60/492,503, filed Aug. 5, 2003, the contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to printing, and more particularly, to an improved control of ink or paint temperature in a pad transfer printing device.  
       BACKGROUND OF THE INVENTION  
       [0003]     In the golf ball industry, the surface of a golf ball usually bears a mark, such as a number, a manufacturer name, and the like. Conventionally, the marked portion is formed on the golf ball surface primarily by a transfer printing method or a pad printing method. In the transfer printing method, a transfer foil which has been formed on transfer paper through printing is transferred onto a marking-portion forming surface of the golf ball through application of heat and pressure. Pad printing is used for printing images on curved or other non-flat surfaces such as spherical, conical, cylindrical and other curved objects.  
         [0004]     Typically, with pad transfer printing, an inked image is lifted from the engraved area of an engraved printing plate, sometimes referred to as a cliche plate, and is transferred to a surface to be printed by a resilient ink transfer pad, normally made of silicone rubber. The surface characteristics of the silicone rubber are such that the ink easily releases from the pad and adheres to the print receiving surface. The transfer pad typically can elastically deform during printing so that virtually any type of raised or irregular shaped surface can be printed, in addition to flat surfaces.  
         [0005]     Both open and closed reservoir ink assemblies are known which may be employed in a pad transfer printing apparatus. With an open-reservoir ink assembly, typically, the ink is held in an open trough or reservoir. The engraved area of the printing plate is filled by taking the ink from the trough or reservoir by means of a brush, spreader blade, wire applicator or the like, and applying the ink to the engraved area of the printing plate. A doctor blade or other type of wiping or scraping device is then used to remove excess ink from the plate so that the ink remains only in the grooves or depressions which define the legend to be printed.  
         [0006]     With a closed-reservoir ink assembly, the ink reservoir may be inverted and the printing plate positioned beneath the assembly so that the plate holds the ink within the reservoir. As the engraved image of the printing plate moves beneath the reservoir, the ink fills the engraving. Typically, the closed-reservoir ink assembly is provided with a doctoring edge that scrapes excess ink from the plate as the plate moves underneath the ink assembly. In some closed-reservoir ink assemblies the doctoring edge is provided on the inverted reservoir.  
         [0007]     Many of the inks and/or paints used in a pad transfer printing process contain among other materials, pigments and solvents. Solvents, usually volatile in nature, maintain the ink or paint at a relatively low viscosity, thereby allowing for easy application and removal from the cliche plate. In a warm operating environment, such as a golf ball manufacturing facility, the ambient air temperature can reach a level that causes the solvent within the ink mixture to evaporate. As solvent evaporates, ink viscosity increases. As ink viscosity increases, when the doctor blade or other type of wiping or scraping device removes excess ink from the plate, the ink tends to smear on the plate resulting in poor ink/print transfer onto the ball. This results in machine downtime for cleaning, etc. which can be a time consuming process. In addition, evaporation of the solvents produces undesirable volatile vapor in the work environment.  
       SUMMARY OF THE INVENTION  
       [0008]     In accordance with the present invention, a pad printing machine is provided that comprises a pad transfer mechanism, an ink cup or reservoir, a cliche plate, a support plate, an excess ink removal device and an ink temperature control apparatus. The ink temperature control apparatus maintains the temperature of the ink at a predetermined level. The ink temperature control apparatus includes a temperature control element adapted to lower the temperature of the ink in the ink cup. A temperature sensor senses the temperature of either the ink in the ink cup or the ink cup surface. A signal is sent to the temperature control apparatus, which, based on the received signal, adjusts the temperature of the temperature control element to lower the temperature of the ink and maintaining the temperature of the ink at a level that reduces evaporation of solvents in the ink.  
         [0009]     According to one aspect of the invention, the temperature control element comprises a unshaped channel formed in the support plate. The channel has an inlet end and an outlet end, and is adapted to circulate a chill fluid throughout the support plate. The chill fluid is circulated via a temperature control unit, such as a refrigerator, etc. The support plate can be a single plate or a plurality plates positioned side-to-side. In this case, each plate may have its own channel arrangement connect to the temperature control unit, and the temperature of each plate can be maintained at a different temperature if desired. An insulating material can be placed between adjacent plates to reduce heat transfer between the plates. A cliche plate is clamped to the top surface of the support plate and the temperature of the support plate controls the temperature of the cliche plate, thus controlling the temperature of the ink applied to the cliche plate.  
         [0010]     According to another aspect of the invention, the temperature control element comprises a temperature conducting rod adapted to be inserted into the ink cup. The conducting is connected to a temperature control device. As the temperature of the ink in the ink cup rises, the temperature controller chills the conducting rod which is inserted into the ink cup to chill the ink.  
         [0011]     According to a further aspect of the invention, the temperature control element comprises a heat pipe. The heat pipe includes a clamping element attached to the ink cup and a chilling unit located at a distance from the ink cup. The clamping element and the chilling unit are connected via a heat pipe.  
         [0012]     According to another aspect of the invention, the temperature control element comprises a conducting coil formed around the ink cup. The conducting coil has an inlet for receiving chill fluid from a refrigerating unit and an outlet for delivering the chilling fluid back to the refrigerating unit.  
         [0013]     According to another aspect of the invention, the temperature control element comprises a chilled air blower. The air blower is positioned next to the ink cup and chilled air is blown around the ink cup to control the temperature of the ink.  
         [0014]     Each of the above-described aspects of the invention can be used independently or in combination.  
         [0015]     The present invention also provides a method of controlling the temperature of ink in pad transfer. The method includes sensing the temperature of ink in an ink cup, either directly or indirectly. A signal representing the measured temperature is then sent to a temperature control unit. Based on the signal, the temperature control unit supplies a chilling medium to cool and maintain the temperature of the ink. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The above and additional objects and advantages of this invention will be more clearly understood from the following detailed description thereof when read in conjunction with the accompanying drawings in which:  
         [0017]      FIG. 1  is a graph illustrating the relationship between printing ink viscosity and temperature.  
         [0018]      FIG. 2  is a top view schematic diagram of one aspect of the present invention.  
         [0019]      FIG. 3  is a plan view schematic diagram of the aspect of the invention of  FIG. 1 .  
         [0020]      FIG. 4  is a top view schematic diagram of one alternative of the chiller plate of the present invention.  
         [0021]      FIG. 5A -F illustrate in plan view the series of steps taken according to one aspect of the present invention.  
         [0022]      FIG. 6  is another alternative of the chilling element of the present invention.  
         [0023]      FIG. 7  is another alternative for the chilling element of the present invention.  
         [0024]      FIG. 8  is another alternative for the chilling element of the present invention.  
         [0025]      FIG. 9  is another alternative for the chilling element of the present invention.  
         [0026]      FIG. 10  is another alternative for the chilling element of the present invention. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0027]     Referring to  FIG. 1 , the temperature of a solvent-based ink directly affects the viscosity of the ink. As the temperature of the ink increase, the solvents used in the ink to maintain a specific viscosity begin to evaporate out. As this evaporation takes place, the viscosity of the ink gradually increases, thereby increasing the likelihood of smearing, degrading the print transfer and making it more difficult to clean.  
         [0028]      FIGS. 2-4  illustrate one aspect of the present invention. A pad printing machine  10  has a base  11 . A support plate  12  is positioned on top of base plate  11 . A cliché plate  13  is positioned on top of and is clamped to support plate  12 . Cliché plate  13  carries one or more engraved areas  14  that represent the art work or other indicia that is to be printed on an object  27 . As shown in  FIG. 4 , support plate  12  has a series of channels  15  formed therein, through which a unshaped piping assembly  15 A is held. A temperature sensor  15 B ( FIG. 4 ) is mounted to support plate  12  to monitor the temperature of the surface of the plate. temperature sensor  15 B generates signals representing the temperature of plate  12  and sends those signals to a refrigerator or similar cooling device  200 . A cooling medium is circulated through piping assembly  15 A. Refrigerator or similar cooling device  200  provides the cooling medium, preferably a fluid comprising a glycol composition, to an inlet end  16  of piping assembly  15 A. The after looping back and forth through piping assembly  15 A, it returns to refrigerator control unit  200  via outlet  17 . The preferred temperature range for the ink is between about 30° F. to about 90° F.  
         [0029]     A print transfer pad assembly  18  includes one or more print pads  19  adapted to pickup and transfer the ink image from engraved areas  14  and print the image on object  27 . Object  27  can include a plurality of objects carried in nests  25  on a conveyor  26 . Ink is supplied to engraved areas  14  through an ink transfer apparatus  20 . Ink transfer apparatus  20  includes one or more ink cups or reservoirs  21  held in a clamping element  22 . Clamp element  22  is held by an arm  24  to a frame  28 , and is adapted to move in the direction of arrows A/B along a track  31 . An optional ink wiper or doctor  23  is positioned adjacent to ink cups  21  to wipe excess ink from engraved areas  14 . Ink cups  21  can be either open or closed cups as is generally known in the art and may carry a temperature sensor  21 A that monitors the temperature of each ink cup  21 . Print transfer pad assembly  18  includes a reciprocating arm  30  to which print pad  19  is attached. Reciprocating arm  30  is connected to a cylinder  29  adapted to reciprocate arm  30  via air, hydraulic fluid etc. Print transfer pad assembly  18  is attached to frame  28  and is adapted to move in unison with arm  24  and wiper  23  in the direction of arrows A/B.  
         [0030]     FIGS.  5 A-F illustrate schematically a printing operation using the temperature control system according to the invention.  
         [0031]      FIG. 6  illustrates schematically another embodiment of the invention. Since this aspect of the invention only relates to the support plate  12 , the other elements of the printing device as illustrated in  FIGS. 2 through 5  are the same herein. According to this embodiment of the invention, support plate  60  comprises three separate plates  61 ,  62 ,  63 , each plate carrying a separate temperature sensor  61 A,  62 A,  63 A respectively. Insulating material  64 ,  65  is positioned between adjacent plates to reduce or eliminate heat transfer between the plates. Each of plates  61 ,  62 ,  63  may have it&#39;s own channel arrangement,  66 ,  67 ,  68  respectively, each having it&#39;s own inlet and outlet ports  66 A and B,  67 A and B, and  68 A and B, connected to the temperature control unit, and the temperature of each plate can be maintained at a different temperature if desired. A cliche plate is clamped to the top surface of each support plate and the temperature of each support plate controls the temperature of the adjacent cliche plate, thus controlling the temperature of the ink applied to the cliche plate.  
         [0032]     According to another aspect of the invention as illustrated in  FIG. 7 , the temperature control element comprises a temperature conducting rod  71  adapted to be inserted into the ink cup  21 . The conducting rod  71  is connected to a runner  72 , which is slideably mounted to track  73 . A temperature sensor  71 A is mounted to the ink cup and monitors the temperature of the cup. A signal generated by the temperature sensor  71 A is sent to cooling device  200 . As the temperature of the ink cup rises, the temperature controller chills the conducting rod  71  which is inserted into the ink cup to chill the ink therein.  
         [0033]     According to a further aspect of the invention as illustrated in  FIG. 8 , the temperature control element comprises a heat pipe device  80  connected to each ink cup  21 . The heat pipe device  80  includes a clamping element  81  attached to the ink cup and a chilling unit  83  located at a distance from the ink cup. The clamping element  81  and the chilling unit  83  are connected via a heat pipe  81 . A temperature sensor  81 A monitors the temperature of the ink cup and generates a signal representing the temperature and sends the signal to cooler  200 . Cooler  200  generates a control signal to chilling unit  83  through which chill medium is used to draw heat from ink cup  21  through heat pipe  82 , thus chilling the ink cup.  
         [0034]     According to yet another aspect of the invention as illustrated in  FIG. 9 , the temperature control element comprises a conducting coil  91  formed around the ink cup. The conducting coil  91  has an inlet  91 A for receiving chill fluid from refrigerating unit  200  and an outlet  91 B for delivering the chilling fluid back to refrigerating unit  200 . A temperature sensor  92  monitors the temperature of ink cup  21  and sends a signal to refrigerating unit  200  to control the temperature of the ink cup.  
         [0035]     According to another aspect of the invention as shown in  FIG. 10 , the temperature control element comprises a chilled air blower  101 . The air blower  101  is positioned next to the ink cup and chilled air  102  is blown around the ink cup to control the temperature of the ink. Temperature of the ink cup is monitored by temperature sensor  102 A.  
         [0036]     While described above as separate temperature control elements, each of the described embodiments can be used individually or in any combination to control the temperature of the ink cups and ink contained therein.  
         [0037]     The present invention also provides a method of controlling the temperature of ink in pad transfer. The method includes sensing the temperature of ink in an ink cup, either directly or indirectly. A signal representing the measured temperature is then sent to a temperature control unit. Based on the signal, the temperature control unit supplies a chilling medium to cool and maintain the temperature of the ink.  
         [0038]     It is to be recognized and understood that the invention is not to be limited to the exact configuration as illustrated and described herein. For example, it should be apparent that a variety of suitable materials would be suitable for use in the composition or method of making the golf balls according to the Detailed Description of the Invention. Accordingly, all expedient modifications readily attainable by one of ordinary skill in the art from the disclosure set forth herein are deemed to be within the spirit and scope of the present claims.