METHOD FOR DECORATIVELY SILK SCREEN PRINTING CANDLES
United States Patent 3771445
Methods and apparatus for silk screen printing of candles and candle compositions for improving the ink adhesion of the candles. The silk screen apparatus includes a candle carriage having a plurality of rollers for supporting a candle and a gear driven by a toothed rack attached to the silk screen frame for rotatably driving the candle by means of radially displaced pins which engage one end of the candle. By this arrangement, the portion of the surface of the candle engaging the screen print moves at the same rate and in the same direction as the screen print while it is engaged thereby. The candle compositions for improving the ink adhesion of candles comprise the addition of certain additives or combinations thereof with paraffin. These additives include stearic acid; low molecular weight polyethylene; and copolymers of low molecular weight polyethylene; and copolymers of low molecular weight polyethylene with polyvinyl alcohol, polyvinyl acetate and polystyrene, especially in block polymer form. Furthermore, high molecular weight polymers of limited solubility in wax such as butadiene, isoprene, polypropylene and polystyrene may also be added to the candle composition.
US Patent References:
Silk screen printing apparatus
Derrickson - July 1964 - 3139824
Tumbler registering mark applicator
Nowak - November 1966 - 3282245
Silk screen printing apparatus
Derrickson - July 1964 - 3139824
Tumbler registering mark applicator
Nowak - November 1966 - 3282245
Inventors:
Campbell, John Scott (Sandy Hook, CT)
Deming, Philip H. (Wilton, CT)
Epstein, Aaron M. (Fairfield, CT)
Deming, Philip H. (Wilton, CT)
Epstein, Aaron M. (Fairfield, CT)
Application Number:
05/218289
Publication Date:
11/13/1973
Filing Date:
01/17/1972
View Patent Images:
Export Citation:
Assignee:
Universal Laboratories, Incorporated (Bridgeport, CT)
Primary Class:
Other Classes:
101/126, 264/132, 431/126, 101/38.100, 44/275
International Classes:
B41F15/08; C11C5/02; C11C5/00; B41F17/22
Field of Search:
264/132 101/129,124,38-40,35 117/94 431/126 44/7.5
Primary Examiner:
Pulfrey, Robert E.
Assistant Examiner:
Crowder, Clifford D.
Claims:
What is claimed is
1. A method for decoratively silk screen printing a candle comprising the steps of:
2. The method of claim 1 wherein the candle is prepared from candle compositions including paraffin and one or more of a group of additives consisting of 0 to 25 percent by weight stearic acid, 0 to 5 percent by weight low molecular polythylene, and 0 to 5 percent by weight copolymers of low molecular weight polyethylene with polyvinyl alcohol, polyvinyl acetate or polystyrene.
1. A method for decoratively silk screen printing a candle comprising the steps of:
2. The method of claim 1 wherein the candle is prepared from candle compositions including paraffin and one or more of a group of additives consisting of 0 to 25 percent by weight stearic acid, 0 to 5 percent by weight low molecular polythylene, and 0 to 5 percent by weight copolymers of low molecular weight polyethylene with polyvinyl alcohol, polyvinyl acetate or polystyrene.
Description:
BACKGROUND OF THE INVENTION
This invention relates to decorative printing of candles and, more particularly, to silk screen printing of candles including candle compositions for enhancing the adhesion of the ink to the candle and methods and apparatus for performing the silk screen printing.
The use of candles for home as well as other interior decorating purposes has become increasingly popular in the past few years. To satisfy this demand, candle manufacturers are producing numerous types of decorative candles including variously colored and shaped candles, sculptured or carved candles and printed candles. Because of the nature of the paraffin from which candles are primarily made, decorative printing on candles has presented a formidable problem to candle manufacturers. The paraffin has a low adhesion for printing inks and therefore the quality of many printed candles is quite low inasmuch as the ink is easily defaced by ordinary handling. Furthermore, this low adhesion of the ink to the wax candle prevents the printing of detailed multicolored designs on candles.
To overcome this problem, some candle manufacturers have used the technique of first coating the candle with a plastic polymer, printing on the coated candle and then putting an overcoat of polymer on the candle to insure the permanence of the printed design. Needless to say, this process is cumbersome and expensive and substantially lengthens the time of candle production as each of the coatings, as well as the printing itself, must be allowed to dry before the next step is taken.
In addition to the problems mentioned above, the actual printing techniques themselves are time consuming and cumbersome. For example, in order to get detailed multicolored prints, conventional silk screen printing techniques have been utilized. Typically, these have involved printing the desired matter on a flat sheet of material utilizing conventional silk screening techniques and apparatus. The printed flat sheet is then bonded to a core candle pillar. Although slik screen printing of cylindrical objects has been known, the apparatus utilized for such objects is not practical to use for candles because of the inherent property of paraffin as a lubricant and because the apparatus tends to damage the easily deformable candle.
SUMMARY OF THE INVENTION
The present invention overcomes these problems by providing a new candle composition which improves ink adhesion; and silk screen printing apparatus specifically designed for silk screen printing on candles which improves the quality and design definition of single as well as multicolored designs and prevents damage to the candles. More specifically, the candle composition of the present invention includes adding to the paraffin certain additives which increase ink adhesion. These additives may include stearic acid in the range of 0 to 25 percent by weight; low molecular weight polyethylene and copolymers thereof with polyvinyl alcohol, polyvinyl acetate and polystyrene up to about 5 percent by weight; and limited amounts of high molecular weight polymers, such as butadiene, isoprene, polypropylene and polystyrene up to about 0.5 percent by weight.
The apparatus includes a candle carriage having a plurality of rollers on which the candle rests freely and a centering driver which engages the candle at one end. The centering driver is driven by a gear which in turn is driven by a toothed rack mounted on the silk screen print holding frame.
It is, therefore, a general object of the present invention to obviate and minimize the problems of the prior art.
It is a more specific object of the present invention to provide an improved candle composition for improving the ink adhesion of candles.
It is another object of the present invention to provide silk screen printing apparatus for the decorative printing of candles.
It is still another object of the present invention to provide silk screen printing apparatus for candles which permit high production rates of printed candles.
It is a further object of the present invention to provide silk screen printing apparatus which provides good multicolored design definition in printed candles.
It is a still further object of the present invention to provide silk screen printing apparatus for candles which will not damage the candles.
It is another object of the present invention to provide a method of silk screen printing on candles which yields high quality prints.
BRIEF DESCRIPTION OF THE DRAWINGS
These as well as other objects, and advantages of the present invention will become apparent to those skilled in the art from a perusal of the appended claims and the following description when read in conjunction with the attached drawings in which:
FIG. 1 is a simplified perspective view of the silk screen printing apparatus of the present invention;
FIG. 2 is a top view thereof partially broken away to show the details of the candle carriage;
FIG. 3 is a side view thereof, and
FIG. 4 is an end view thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, the silk screen printing apparatus of the present invention includes a candle carriage 10 and a silk screen carrying frame 12. The candle carriage 10 is greatly simplified in this figure to avoid unnecessary confusion in the illustration as this figure is designed merely to give an overall idea of the configuration of the apparatus.
The candle carriage 10 includes a base 14 on which are mounted upstanding brackets 16 and 17, a candle 18 is carried between the brackets 16 and 17 and is engaged by a gear 20 rotatably mounted between the brackets 16 and 17. The gear 20 is adapted to engage a toothed rack 22 provided on the underside of one edge of the silk screen frame 12. Other than the provision of a toothed rack 22, the silk screen frame 12 may be entirely conventional including a rectangular frame support 24 in which the silk screen 26 is securely mounted. In order to bring the candle 18 into engagement with the underside of the silk screen 26, suitable means such as an air cylinder 28 is mounted to the underside of the base 14. The air cylinder 28 is operable to lift the entire candle carriage 10 upward so that the candle 18 engages the silk screen and the gear 20 engages the toothed rack 22.
Briefly, in operation the candle 18 is positioned on the candle carriage 10 in engagement with the gear 20. The candle carriage 10 is then moved upwardly by way of the air cylinder 28 so that the candle 18 engages the silk screen 26 and the gear 20 engages the toothed rack 22. The silk screen frame 12 is fixed in its vertical position but is movable laterally in a direction transverse to the axis of the candle carriage 10. Ink placed on the silk screen 26 may then be printed on the candle by moving the silk screen frame 12 across the surface of the candle 18. This is accomplished by appropriate apparatus (not shown), such as air cylinders or motor operated pulleys. As the frame is moved laterally, (to the left in FIG. 1) engagement of the gear 20 with the toothed rack 22 causes the gear to rotate. The candle 18 also rotates by virtue of the engagement between it and the gear 20 with the portion of the candle surface engaging the screen moving in the same direction and at the same rate as the screen, while it is engaged therewith to allow the ink to be deposited through the silk screen 26 on to the cylindrical surface of the candle 18 as desired. This independent, rotational, positive drive of the candle is an important feature of the present invention inasmuch as the lubricating quality of the paraffin would cause slippage between the screen and the candle if only that engagement were relied on to rotate the candle.
In order to insure proper registration and design definition where a multicolor print is being made, a pair of registration marks 30 and 32 are provided on the silk screen frame 12 and the gear 20, respectively, to allow the candle carriage 10 to be properly aligned with the silk screen frame 12 so that the printing begins at the same starting point for each of the separate color printing steps. Other conventional silk screen printing apparatus (not shown), such as a flexible brush which engages the top surface of the silk screen 26 to uniformly spread the ink and to increase the pressure of the engagement between the printed object and the silk screen, may also be utilized.
The details of the candle carriage 10 will now be described with reference to FIGS. 2, 3 and 4. The candle carriage 10 includes a pair of shafts 34 and 36 freely, rotatably mounted on conical pins 38 which are threadable secured in the brackets 16 and 17. The conical pins 38 are received in complementarily shaped recesses in the ends of the shafts 34 and 36 to support the shafts 34 and 36 and allow free rotation thereof. The shafts 34 and 36 are mounted parallel to each other at the same height above the base 14. Mounted on each of the shafts 34 and 36 are a pair of rollers 40 and 42. Each of the rollers 40 and 42 are cylindrical in shape having an enlarged cylindrical back portion 44 and a smaller cylindrical front portion 46. The pair of rollers 40 and 42 are mounted on each of the shafts 34 and 36 so that the front portions 46 face each other.
The rollers 40 are freely rotatable on the shafts 34 and 36 and are limited in movement towards the bracket 17 by coil springs 48. The coil springs 48 are mounted on the end of the shafts 34 and 36 adjacent the enlarged back portion 44 of the rollers 40 and are adapted to be compressed between the rollers 40 and the bracket 17. The rollers 42 are fixed to the shafts 34 and 36 by appropriate set screws 50. The candle 18 rests on the front portions 46 of the rollers 40 and 42 with the ends thereof abutting the back portions 44 thereof. The coil springs 48 are dimensioned so that they are compressed between the bracket 17 and the back portions 44 of the rollers 40 when the candle 18 is positioned on the rollers 40 and 42. This allows the distance between the rollers 40 and 42 to be automatically adjusted to securely hold the candle 18 and prevent axially movement thereof. This automatic adjustment is particularly desirable inasmuch as candles will vary in size with respect to changes in the ambient temperature. Compression of the springs, however, is very light so that the candle is freely rotatable on the rollers 40 and 42 and no damage is caused to the ends of the candles by virtue of compression between the rollers 40 and 42.
At the end of the candle carriage 10 opposite the spring bias rollers 40, a candle centering shaft 52 is rotatably supported between a pair of shaft supports 54 and 56. The shaft support 54 may be mounted on a bracket 58 secured to the base 14 of the candle carriage 10. The other shaft support 56 may be suitably mounted to the bracket 16. These shaft supports 54 and 56 may include suitable bearings 60 to permit the center shaft 52 to rotate freely therein. Centering shaft 52 includes a conical end 62 which is adapted to engage the center hole of the candle 18 which is typically provided in the bottom of the candle so that it may be securely mounted on a candle holder.
Adjacent the conical end 62 a pair of L-shaped candle engaging pins 64 are securely fixed to the centering shaft 52. These pins 64 also include conical tips 66 which are adapted to engage radially displaced recesses formed in the bottom of the candle. These pins 64 allow the candle to be rotatably driven by rotation of the centering shaft 52 whereas a single center driving arrangement would be inadequate due to the low surface friction of the paraffin. Alternative means for driving the candle, such as a cross-shaped end on the centering shaft 52 for engaging complementary shaped slots on the end of the candle 18 may also be used. However, the illustrated arrangement is preferred inasmuch as the pins engage the candle at widely spaced points thereby providing better driving engagement between the centering shaft 52 and the candle 18 and preventing the possibility of slightly deforming the recesses in the candle which would prevent proper registration of the candle with the silk screen where multicolored process is used.
The gear 20 is mounted on the centering shaft 52 between the shaft supports 54 and 56 and connected thereto by a set screw 68, so that rotation of the gear causes rotation of the centering shaft 52, which in turn through the connection of the pins 64 will cause rotation of the candle 18.
In use, the candle 18 is placed on the candle carriage by engaging the bottom end thereof with the conical tip 62 of the centering shaft 52 and the L-shaped pin 64 in the recesses provided therefor. The rollers 40 are then moved toward the bracket 17 compressing the coil springs 48 until the candle can freely rest on the front portions 46 of the rollers 40 and 42 between the back portions 44 thereof. The particular gear 20 which is utilized has a pitch diameter equal to the diameter of the candle 18. When different diameter candles are being printed, the gear 20 may be replaced with a suitably sized gear by loosening the set screw 68 and removing the centering shaft 52 from the supports 54 and 56. An appropriate sized gear may then be placed between the supports 54 and 56 on the centering shaft 52 reinserted therethrough.
When the air cylinder 28 is actuated, the candle carriage 10 is moved upwardly so that the candle 18 engages the silk screen 26 and the gear 20 engages the toothed rack 22, as shown in phantom lines in FIG. 4. Lateral movement of the silk screen frame 12 will rotate the gear 20, which in turn rotates the centering shaft 52 thereby rotating the candle 18 through the engagement of the pins 64. The conical tip 62 of the centering shaft 52 serves as a pivot around which the candle 18 rotates. The candle 18 freely rotates on the rollers 40 and 42 with the rollers 40 rotating freely on the shafts 34 and 36 and the rollers 42 causing the shafts 34 and 36 to rotate.
In order to print directly on the candles as formed rather than on a polymer coating as has been done in the past, and still provide high quality printing, the ink adhesion of the candle must be greatly enhanced. It has been found that the mixing of certain additives or combinations thereof with the paraffin prior to molding the candles greatly increase the ink adhesion of the resultant candles and provide high quality printed candles and good design definition for multicolored prints. These additives include stearic acid in the range of 0 to 25 percent by weight; low molecular weight polythylene in the range of 0 to 5 percent by weight; and copolymers of low molecular weight polyethylene with polyvinyl acetate, polyvinyl alcohol or polystyrene in the range of 0 to 5 percent by weight. In addition, high molecular weight polymers of limited solubility in wax such as polystyrene, butadiene, isoprene and polypropylene in the range of 0 to 0.5 percent yield improved printing quality.
Candles made from compositions including various combinations of these additives in the ranges specified have been printed on with good results. The ink adhesion of such candles has been sufficient to withstand inadvertent smearing or destruction of the printing thereon, and have allowed detailed scenes to be printed with good design definition, even with multicolored designs.
The particular combination of additives which is to be mixed with the paraffin may be widely varied and still yield candle compositions of improved ink adhesion. It has been found that the addition of copolymers of low molecular weight polyethylene with polyvinyl acetate, polyvinyl alcohol or polystyrene in block polymer form improves their effect on the ink adhesion of the resultant candle.
Furthermore, it is noted that increasing the percentage of one additive within the specified ranges allows the reduction or elimination of other of the additives without sacrificing the ink adhesion quality of the resultant candle composition. This allows the particular combination of additives to be varied to account for the availability and cost of the particular additives.
Thus, the present invention provides improved silk screen printing apparatus for economically printing candles. The improved apparatus allows quicker printing of candles with good design definition while preventing damage thereto. The present invention also provides novel candle compositions which greatly enhance the ink adhesion of the paraffin so that good quality printing may be accomplished without the need for coating the candles before and after printing.
It will be readily apparent to those skilled in the art that a number of variations and modifications may be made in this invention without departing from its spirit and scope. Accordingly, the foregoing description is to be considered illustrative rather than limiting.
This invention relates to decorative printing of candles and, more particularly, to silk screen printing of candles including candle compositions for enhancing the adhesion of the ink to the candle and methods and apparatus for performing the silk screen printing.
The use of candles for home as well as other interior decorating purposes has become increasingly popular in the past few years. To satisfy this demand, candle manufacturers are producing numerous types of decorative candles including variously colored and shaped candles, sculptured or carved candles and printed candles. Because of the nature of the paraffin from which candles are primarily made, decorative printing on candles has presented a formidable problem to candle manufacturers. The paraffin has a low adhesion for printing inks and therefore the quality of many printed candles is quite low inasmuch as the ink is easily defaced by ordinary handling. Furthermore, this low adhesion of the ink to the wax candle prevents the printing of detailed multicolored designs on candles.
To overcome this problem, some candle manufacturers have used the technique of first coating the candle with a plastic polymer, printing on the coated candle and then putting an overcoat of polymer on the candle to insure the permanence of the printed design. Needless to say, this process is cumbersome and expensive and substantially lengthens the time of candle production as each of the coatings, as well as the printing itself, must be allowed to dry before the next step is taken.
In addition to the problems mentioned above, the actual printing techniques themselves are time consuming and cumbersome. For example, in order to get detailed multicolored prints, conventional silk screen printing techniques have been utilized. Typically, these have involved printing the desired matter on a flat sheet of material utilizing conventional silk screening techniques and apparatus. The printed flat sheet is then bonded to a core candle pillar. Although slik screen printing of cylindrical objects has been known, the apparatus utilized for such objects is not practical to use for candles because of the inherent property of paraffin as a lubricant and because the apparatus tends to damage the easily deformable candle.
SUMMARY OF THE INVENTION
The present invention overcomes these problems by providing a new candle composition which improves ink adhesion; and silk screen printing apparatus specifically designed for silk screen printing on candles which improves the quality and design definition of single as well as multicolored designs and prevents damage to the candles. More specifically, the candle composition of the present invention includes adding to the paraffin certain additives which increase ink adhesion. These additives may include stearic acid in the range of 0 to 25 percent by weight; low molecular weight polyethylene and copolymers thereof with polyvinyl alcohol, polyvinyl acetate and polystyrene up to about 5 percent by weight; and limited amounts of high molecular weight polymers, such as butadiene, isoprene, polypropylene and polystyrene up to about 0.5 percent by weight.
The apparatus includes a candle carriage having a plurality of rollers on which the candle rests freely and a centering driver which engages the candle at one end. The centering driver is driven by a gear which in turn is driven by a toothed rack mounted on the silk screen print holding frame.
It is, therefore, a general object of the present invention to obviate and minimize the problems of the prior art.
It is a more specific object of the present invention to provide an improved candle composition for improving the ink adhesion of candles.
It is another object of the present invention to provide silk screen printing apparatus for the decorative printing of candles.
It is still another object of the present invention to provide silk screen printing apparatus for candles which permit high production rates of printed candles.
It is a further object of the present invention to provide silk screen printing apparatus which provides good multicolored design definition in printed candles.
It is a still further object of the present invention to provide silk screen printing apparatus for candles which will not damage the candles.
It is another object of the present invention to provide a method of silk screen printing on candles which yields high quality prints.
BRIEF DESCRIPTION OF THE DRAWINGS
These as well as other objects, and advantages of the present invention will become apparent to those skilled in the art from a perusal of the appended claims and the following description when read in conjunction with the attached drawings in which:
FIG. 1 is a simplified perspective view of the silk screen printing apparatus of the present invention;
FIG. 2 is a top view thereof partially broken away to show the details of the candle carriage;
FIG. 3 is a side view thereof, and
FIG. 4 is an end view thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, the silk screen printing apparatus of the present invention includes a candle carriage 10 and a silk screen carrying frame 12. The candle carriage 10 is greatly simplified in this figure to avoid unnecessary confusion in the illustration as this figure is designed merely to give an overall idea of the configuration of the apparatus.
The candle carriage 10 includes a base 14 on which are mounted upstanding brackets 16 and 17, a candle 18 is carried between the brackets 16 and 17 and is engaged by a gear 20 rotatably mounted between the brackets 16 and 17. The gear 20 is adapted to engage a toothed rack 22 provided on the underside of one edge of the silk screen frame 12. Other than the provision of a toothed rack 22, the silk screen frame 12 may be entirely conventional including a rectangular frame support 24 in which the silk screen 26 is securely mounted. In order to bring the candle 18 into engagement with the underside of the silk screen 26, suitable means such as an air cylinder 28 is mounted to the underside of the base 14. The air cylinder 28 is operable to lift the entire candle carriage 10 upward so that the candle 18 engages the silk screen and the gear 20 engages the toothed rack 22.
Briefly, in operation the candle 18 is positioned on the candle carriage 10 in engagement with the gear 20. The candle carriage 10 is then moved upwardly by way of the air cylinder 28 so that the candle 18 engages the silk screen 26 and the gear 20 engages the toothed rack 22. The silk screen frame 12 is fixed in its vertical position but is movable laterally in a direction transverse to the axis of the candle carriage 10. Ink placed on the silk screen 26 may then be printed on the candle by moving the silk screen frame 12 across the surface of the candle 18. This is accomplished by appropriate apparatus (not shown), such as air cylinders or motor operated pulleys. As the frame is moved laterally, (to the left in FIG. 1) engagement of the gear 20 with the toothed rack 22 causes the gear to rotate. The candle 18 also rotates by virtue of the engagement between it and the gear 20 with the portion of the candle surface engaging the screen moving in the same direction and at the same rate as the screen, while it is engaged therewith to allow the ink to be deposited through the silk screen 26 on to the cylindrical surface of the candle 18 as desired. This independent, rotational, positive drive of the candle is an important feature of the present invention inasmuch as the lubricating quality of the paraffin would cause slippage between the screen and the candle if only that engagement were relied on to rotate the candle.
In order to insure proper registration and design definition where a multicolor print is being made, a pair of registration marks 30 and 32 are provided on the silk screen frame 12 and the gear 20, respectively, to allow the candle carriage 10 to be properly aligned with the silk screen frame 12 so that the printing begins at the same starting point for each of the separate color printing steps. Other conventional silk screen printing apparatus (not shown), such as a flexible brush which engages the top surface of the silk screen 26 to uniformly spread the ink and to increase the pressure of the engagement between the printed object and the silk screen, may also be utilized.
The details of the candle carriage 10 will now be described with reference to FIGS. 2, 3 and 4. The candle carriage 10 includes a pair of shafts 34 and 36 freely, rotatably mounted on conical pins 38 which are threadable secured in the brackets 16 and 17. The conical pins 38 are received in complementarily shaped recesses in the ends of the shafts 34 and 36 to support the shafts 34 and 36 and allow free rotation thereof. The shafts 34 and 36 are mounted parallel to each other at the same height above the base 14. Mounted on each of the shafts 34 and 36 are a pair of rollers 40 and 42. Each of the rollers 40 and 42 are cylindrical in shape having an enlarged cylindrical back portion 44 and a smaller cylindrical front portion 46. The pair of rollers 40 and 42 are mounted on each of the shafts 34 and 36 so that the front portions 46 face each other.
The rollers 40 are freely rotatable on the shafts 34 and 36 and are limited in movement towards the bracket 17 by coil springs 48. The coil springs 48 are mounted on the end of the shafts 34 and 36 adjacent the enlarged back portion 44 of the rollers 40 and are adapted to be compressed between the rollers 40 and the bracket 17. The rollers 42 are fixed to the shafts 34 and 36 by appropriate set screws 50. The candle 18 rests on the front portions 46 of the rollers 40 and 42 with the ends thereof abutting the back portions 44 thereof. The coil springs 48 are dimensioned so that they are compressed between the bracket 17 and the back portions 44 of the rollers 40 when the candle 18 is positioned on the rollers 40 and 42. This allows the distance between the rollers 40 and 42 to be automatically adjusted to securely hold the candle 18 and prevent axially movement thereof. This automatic adjustment is particularly desirable inasmuch as candles will vary in size with respect to changes in the ambient temperature. Compression of the springs, however, is very light so that the candle is freely rotatable on the rollers 40 and 42 and no damage is caused to the ends of the candles by virtue of compression between the rollers 40 and 42.
At the end of the candle carriage 10 opposite the spring bias rollers 40, a candle centering shaft 52 is rotatably supported between a pair of shaft supports 54 and 56. The shaft support 54 may be mounted on a bracket 58 secured to the base 14 of the candle carriage 10. The other shaft support 56 may be suitably mounted to the bracket 16. These shaft supports 54 and 56 may include suitable bearings 60 to permit the center shaft 52 to rotate freely therein. Centering shaft 52 includes a conical end 62 which is adapted to engage the center hole of the candle 18 which is typically provided in the bottom of the candle so that it may be securely mounted on a candle holder.
Adjacent the conical end 62 a pair of L-shaped candle engaging pins 64 are securely fixed to the centering shaft 52. These pins 64 also include conical tips 66 which are adapted to engage radially displaced recesses formed in the bottom of the candle. These pins 64 allow the candle to be rotatably driven by rotation of the centering shaft 52 whereas a single center driving arrangement would be inadequate due to the low surface friction of the paraffin. Alternative means for driving the candle, such as a cross-shaped end on the centering shaft 52 for engaging complementary shaped slots on the end of the candle 18 may also be used. However, the illustrated arrangement is preferred inasmuch as the pins engage the candle at widely spaced points thereby providing better driving engagement between the centering shaft 52 and the candle 18 and preventing the possibility of slightly deforming the recesses in the candle which would prevent proper registration of the candle with the silk screen where multicolored process is used.
The gear 20 is mounted on the centering shaft 52 between the shaft supports 54 and 56 and connected thereto by a set screw 68, so that rotation of the gear causes rotation of the centering shaft 52, which in turn through the connection of the pins 64 will cause rotation of the candle 18.
In use, the candle 18 is placed on the candle carriage by engaging the bottom end thereof with the conical tip 62 of the centering shaft 52 and the L-shaped pin 64 in the recesses provided therefor. The rollers 40 are then moved toward the bracket 17 compressing the coil springs 48 until the candle can freely rest on the front portions 46 of the rollers 40 and 42 between the back portions 44 thereof. The particular gear 20 which is utilized has a pitch diameter equal to the diameter of the candle 18. When different diameter candles are being printed, the gear 20 may be replaced with a suitably sized gear by loosening the set screw 68 and removing the centering shaft 52 from the supports 54 and 56. An appropriate sized gear may then be placed between the supports 54 and 56 on the centering shaft 52 reinserted therethrough.
When the air cylinder 28 is actuated, the candle carriage 10 is moved upwardly so that the candle 18 engages the silk screen 26 and the gear 20 engages the toothed rack 22, as shown in phantom lines in FIG. 4. Lateral movement of the silk screen frame 12 will rotate the gear 20, which in turn rotates the centering shaft 52 thereby rotating the candle 18 through the engagement of the pins 64. The conical tip 62 of the centering shaft 52 serves as a pivot around which the candle 18 rotates. The candle 18 freely rotates on the rollers 40 and 42 with the rollers 40 rotating freely on the shafts 34 and 36 and the rollers 42 causing the shafts 34 and 36 to rotate.
In order to print directly on the candles as formed rather than on a polymer coating as has been done in the past, and still provide high quality printing, the ink adhesion of the candle must be greatly enhanced. It has been found that the mixing of certain additives or combinations thereof with the paraffin prior to molding the candles greatly increase the ink adhesion of the resultant candles and provide high quality printed candles and good design definition for multicolored prints. These additives include stearic acid in the range of 0 to 25 percent by weight; low molecular weight polythylene in the range of 0 to 5 percent by weight; and copolymers of low molecular weight polyethylene with polyvinyl acetate, polyvinyl alcohol or polystyrene in the range of 0 to 5 percent by weight. In addition, high molecular weight polymers of limited solubility in wax such as polystyrene, butadiene, isoprene and polypropylene in the range of 0 to 0.5 percent yield improved printing quality.
Candles made from compositions including various combinations of these additives in the ranges specified have been printed on with good results. The ink adhesion of such candles has been sufficient to withstand inadvertent smearing or destruction of the printing thereon, and have allowed detailed scenes to be printed with good design definition, even with multicolored designs.
The particular combination of additives which is to be mixed with the paraffin may be widely varied and still yield candle compositions of improved ink adhesion. It has been found that the addition of copolymers of low molecular weight polyethylene with polyvinyl acetate, polyvinyl alcohol or polystyrene in block polymer form improves their effect on the ink adhesion of the resultant candle.
Furthermore, it is noted that increasing the percentage of one additive within the specified ranges allows the reduction or elimination of other of the additives without sacrificing the ink adhesion quality of the resultant candle composition. This allows the particular combination of additives to be varied to account for the availability and cost of the particular additives.
Thus, the present invention provides improved silk screen printing apparatus for economically printing candles. The improved apparatus allows quicker printing of candles with good design definition while preventing damage thereto. The present invention also provides novel candle compositions which greatly enhance the ink adhesion of the paraffin so that good quality printing may be accomplished without the need for coating the candles before and after printing.
It will be readily apparent to those skilled in the art that a number of variations and modifications may be made in this invention without departing from its spirit and scope. Accordingly, the foregoing description is to be considered illustrative rather than limiting.