Abstract:
A screen printing safety system is provided. The system includes a screen printing machine, and a plurality of zones in the vicinity of the screen printing machine. Each of the zones includes at least one sensor for sensing encroachment past a predetermined point. The sensors are adapted to stop operation of the screen printing machine when encroachment is sensed in at least one of the plurality of zones.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/715,072, filed Oct. 17, 2012. 
    
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     TECHNICAL FIELD 
     The present invention generally relates to screen printing machines, and in particular to a safety system for use with such machines. 
     BACKGROUND OF THE INVENTION 
     Indicia applied permanently to articles of clothing and other textiles have become very popular. Fanciful indicia, such as logos, slogans, college names, sports team names and sayings, are now commonplace. As a result, screen printing has become very popular. Large, commercial operations screen printing textiles are common today. 
     Indicia can be one or more colors. Typically, a screen printing machine has at least one station for each color employed. For example, a design incorporating two colors will have at least two printing stations, one for each color. A design employing eight colors will have at least eight stations. Each station generally includes a printing head, which supports a single screen, the ink to be used at that particular station and a mechanism for applying the ink to the textile. Each color is carried by a single screen. The textile to be screened travels from printing station to printing station by one of a number of methods, such as a chain or a rigid arm. The textile is usually carried by a metal pallet, pallet support, flat bed, or platen. Common printing machines include turret, oval and linear type machines. In addition to printing stations, there may also be curing stations to heat and set the inks placed on the textile or substrate. 
     In the screen printing process, a stencil screen is typically blocked (called “masked” in the industry) to embody the desired indicia and is then placed over the item to be printed. Ink of one color is then added to the screen surface and flooded onto the indicia by a flood bar of conventional design. The ink may be of any type well-known in the industry for screen printing. After the ink is flooded onto the screen, the ink is squeegeed through the screen interstices onto the item, leaving ink of the desired color where the interstices in the screen are unblocked. The squeegee can be of any type known in the art. 
     After the item is printed on, it is moved to a station where one or more operators transfer the article to a drying rack, conveyor surface leading to a dryer, or the like. This requires quick and deft handling by the operator because the cycling of the printing machine may print a shirt every four to six seconds. Further, as the articles are typically adhered to the platen with an adhesive, the article must be lifted at an angle to break the adhesive seal without smudging the print on the article. 
     Unfortunately, operators, bystanders, and others are sometimes injured while working with or near the machine when it is in operation. This is sometimes caused by inattentiveness and/or failure to appreciate the possible dangers associated with printing machines when they are being operated. The present invention provides a system that stops all printing activities when a person is in an unauthorized zone, and in danger of potential harm. 
     SUMMARY OF THE INVENTION 
     A screen printing safety system is provided that is to be used for oval and turret style printing machines. The system includes a plurality of zones in the vicinity of the screen printing machine. Each of the zones includes at least one sensor for sensing encroachment past a predetermined point. The sensors are adapted to stop operation of the screen printing machine when encroachment is sensed in at least one of the plurality of zones. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which: 
         FIG. 1  is a perspective view of a screen printing safety system made in accordance with the teachings of the present invention; 
         FIG. 2  is a perspective view of a first zone of the screen printing safety system of  FIG. 1 ; 
         FIG. 3  is a perspective view of a second zone of the screen printing safety system of  FIG. 1 ; 
         FIG. 4  is a further perspective view of the second zone of the screen printing safety system of  FIG. 1 ; 
         FIG. 5  is a still further perspective view of the second zone of the screen printing safety system of  FIG. 1  in operation; 
         FIG. 6  is a perspective view of a third zone of the screen printing safety system of  FIG. 1 ; 
         FIG. 7  is a further perspective view of the third zone of the screen printing safety system of  FIG. 1 ; 
         FIG. 8  is a still further perspective view of the third zone of the screen printing safety system of  FIG. 1 ; 
         FIG. 9  is a perspective view of a screen printing safety system made in accordance with the teachings of the present invention; 
         FIG. 10  is a perspective view of a screen printing safety system made in accordance with the teachings of the present invention; 
         FIG. 11  is a perspective view of a scanner and display in accordance with the teachings of the present invention; 
         FIG. 12  is a perspective view of a scanner in accordance with the teachings of the present invention; 
         FIG. 13  is a perspective view of a scanner in accordance with the teachings of the present invention; 
         FIG. 14  is a perspective view of a display in accordance with the teachings of the present invention; 
         FIG. 15  is a perspective view of an air curtain in accordance with the teachings of the present invention; and 
         FIG. 16  is a perspective view of a screen printing safety system made in accordance with the teachings of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. 
     Referring to the FIGS., a screen printing safety system  10  is shown. The system  10  includes a printing machine  12 . The printing machine  12  can be any type of printing machine, including a turret, oval or linear type machine having multiple stations. The system  10  also includes three zones: a first zone  14 , a second zone  16 , and a third zone  18 . 
     The first zone  14  is located in an area where one or more machine operators load and/or unload textiles or other printed materials onto or off of the textile supporting pallets. The first zone  14  includes a barrier  20  ( FIG. 2 ). The barrier  20  is located at a distance and in a position in the vicinity of the machine  12  to ensure the safety of the operators as they load and/or unload the textiles. The barrier  20  preferably includes a gate  22 . The gate  22  spans the operators&#39; area and acts as a physical barrier to prevent an operator from approaching the machine  12  past a certain point or the line formed by the gate. The distance of the gate from the rotating pallets is such that it permits an operator to reach over the gate and comfortably put the textile on a stopped pallet or remove the textile from a stopped pallet. The gate  22  is preferably about waist-high to prohibit an operator from physically crossing the gate  22 , but to also allow the operator to reach over the gate  22  to load and/or unload textiles from the machine  12 . 
     The second zone  16  includes a sensor incorporating a light curtain  24 . The light curtain  24  spans the operators&#39; position of the first zone  14 , and begins at a height at about the top of the gate  22 , approximately waist-high, and extends upward to a height of approximately six feet from ground level. The light curtain  24  preferably includes a light producing component or components  26  and a light reflecting component  27  or components ( FIGS. 3 and 4 ). The light curtain  24  permits an operator to reach over the gate  22  when the arms or pallets of the printing machine  12  are stopped during a print cycle to load and/or unload textiles. However, should the operator cross, encroach, or break the area over or plane formed by the gate  22  while the machine  12  is in operation and the arms or pallets are moving, the light curtain  24  will sense the crossing, encroachment, or break and stop the machine  12  from rotating for the time when the light curtain  24  senses that the plane above the gate  22  has been crossed. When the light curtain  24  senses that the encroachment has stopped, it restarts the machine  12 . 
     Adjacent each side of the gate  22  is a fence  25  that supports the light curtain  24 . One fence  25  supports adjacent the gate  22  the light producing component or components  26  and the other fence  25  supports adjacent the gate  22  the light reflecting component  27 , components or sensors. The fences  25  prevent one from physically reaching around or bypassing the gate  22  to unload or load a textile from the machine. Scanners  50  can also be used to define the boundaries of light curtain  24  ( FIGS. 11 and 12 ). 
     The third zone  18  includes a perimeter guard  28  ( FIG. 6 ). The perimeter guard  28  establishes a safe perimeter  31  around the machine  12 . The perimeter guard  28  includes an encircling sensor or sensors having a light curtain  29  formed by a series of spaced apart light emitting components  30 , light receiving components  33  and light reflecting components  32  located along the perimeter of the machine  12 . The perimeter guard  28  is located at a distance from the machine  12  sufficient to ensure the safety of persons near the machine  12 . 
     The embodiment shown uses four reflectors  32  to set up the third zone  18 . In another embodiment, for smaller printing machines  12 , the third zone  18  can be constructed using three points. The light emitting component  30  and light receiving component  33  can be located at one point, for example on or near the gate  22 , and two reflectors  32  can be used with them to create the perimeter  28 . 
     In another embodiment, a deflection mirror  60  can be used in conjunction with the light curtain  24  in the second zone  16 . The deflection mirror  60  can be placed in the center of the gate  22  to deflect light emitted by the light producing component  26  to the light receiving component  27 . The light curtain  24 , therefore, follows the contour of the gate  22 . 
     In operation, the system  10  functions as follows. If an operator moves or opens the gate  22  of the first zone  14 , or if the operator crosses the light curtain  24  of the second zone  16 , the light curtain  24  senses the movement or opening or crossing, and stops the machine  12 . Additionally, if the perimeter guard  28  of the third zone  18  senses through the light curtain  29  that the perimeter guard  28  has been crossed, the machine  12  is stopped. The machine  12  restarts once the encroachment has ceased. The stopping of the machine  12  is accomplished by a signal from the light curtains  24  or  29  to a controller (not shown) that acts like an emergency OFF switch. Once the signal from the light curtain  24  or  29  is no longer blocked, the controller signals the machine  12  to restart from the point where it stopped. 
     In an embodiment of the present invention shown in  FIGS. 10 through 15 , an electronic laser scanner  36  is mounted to the printing machine  12 . The scanner  36  is preferably of the type manufactured by Leuze Electronic GmbH+Co., Model Rotoscan RS4-2E. The scanner  36  scans a designated protective area. The scanner  36  can be programmed to create a protective area of any desired size or shape. Preferably, the scanner  36  is mounted such that it detects the presence of an object such as a hand or other body part in the operator area or first zone  14  of the printing machine. Additional scanners  36  can be situated to create the second and third zones  16  and  18 . 
     The scanner  36  can be programmed to have both a warning field  41  and a protective field  43 . For the warning field  41 , the scanner  36  alerts a visual and/or audible warning when an object enters the area designated as the warning field  41 . For the protective field  43 , the printing machine  12  is instantly stopped should an object be detected entering or encroaching into the protective field  43 . The controller of the printing machine  12  can be programmed to have a delay of a desired time to allow an operator to enter the warning field  41  and/or the protective field  43  for a desired amount of time before stopping the machine  12 . This will, for instance, allow the operator to spray adhesive on platens  38 , or place or remove a substrate from the platens  38 . The controller of the printing machine  12  is programmed such that it starts up again after the object has been removed from the protective field  43 . 
     The scanner  36  can be associated with a display  39 . As shown in  FIG. 14 , the display  39  can show the outlines of the warning field  41  and the protective field  43 . The outline  45  also shows objects within the range of the scanner  36  and their proximity to the fields  41  and  43 . 
     It was found that when an operator sprayed glue onto the platens  38  of the printing machine  12  to adhere a substrate thereto, errant adhesive spray would interfere with operation of the scanner  36 . An air curtain bar  40  mounted in front of the scanner  36  directs a curtain of air downward from the scanner  36 . The air curtain bar  40  is hollow and includes a plurality of air openings  42  in the bottom thereof. The air curtain bar  40  deflects errant spray and other airborne particles away from the scanner  36 . 
     While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention, and the scope of protection is only limited by the scope of the accompanying Claims.