BACKGROUND 
     Materials such as paints, aerosols, varnishes, polishes, coatings, and oils may emit volatile organic compounds (VOCs) and other air pollutants, some of which may contribute to the formation of ground level ozone or smog. These emissions may be regulated by local and national regulatory agencies to protect the environment and/or health of the populace. In a printer or press, printing ink may be mixed with oil or other solvents that may emit such compounds. It would be desirable to reduce the emission of such compounds from these printers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a printer according to embodiments of the invention; 
         FIG. 2  is a conceptual block diagram of part of a printer according to embodiments of the invention; 
         FIGS. 3A and 3B  are conceptual illustrations of the air flows through parts of a printer when inlet doors are open and closed, respectively, according to embodiments of the invention; 
         FIGS. 4A and 4B  are flowcharts illustrating processes to reduce VOC emissions according to embodiments of the invention; and 
         FIGS. 5A and 5B  are conceptual illustrations of the interlock control in parts of a printer when inlet doors are open and closed, respectively, according to embodiments of the invention. 
     
    
    
     Where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements. Moreover, some of the blocks depicted in the drawings may be combined into a single function. 
     DETAILED DESCRIPTION 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the invention. However, it will be understood by those of ordinary skill in the art that the embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to obscure the present invention. 
     Embodiments of the present invention may be used in a variety of applications. Although the present invention is not limited in this respect, the techniques disclosed herein may be used in paper handling machines such as printers, presses, copiers, multi-function printers, and the like. 
     In some printers or presses, the oil that carries the printer ink may evaporate into the atmosphere, emitting hydrocarbons including VOCs in the process. Embodiments of the present invention operate to reduce vapor emissions, including VOCs, from such a printer by treating in a chamber, while the machine is operating, vapor-laden air and sealing inlets to the chamber, while the machine is idle, from which the vapors may otherwise escape to the atmosphere. 
     Reference is now made to  FIG. 1 , which is a schematic illustration of a printer  1  according to embodiments of the invention. Printer  1  may include a printing area  100  (or printing engine) that includes writing head  10 , photo imaging plate (PIP) drum  20 , intermediate transfer medium (ITM) drum  30 , impression drum  40 , ink containers  50 , ink rollers  60 , and scorotrons  70 . Printer  1  may also include paper handling areas, such as paper feed unit  5  (including paper trays) and output paper stacker  95 . Printer  1  may also include cooling cabinet  200 , discussed in more detail below. 
     The parts and blocks shown in  FIG. 1  are examples of parts that may comprise printer  1 , and do not limit the parts or modules that may be part of or connected to or associated with printer  1 . 
     Embodiments of the present invention may use a liquid electrophotography (LEP) process to print on a substrate  75 , such as coated or uncoated paper or card stock or other media. In LEP, scorotrons  70  charge PIP drum  20 . Writing head  10  then uses scanning laser beam  15  to electrostatically charge a latent image onto PIP drum  20 . A colorant, such as liquid ink or toner, stored in ink containers  50 , may be applied to charged PIP drum  20 , using ink rollers  60  (also called “binary ink developers” (BID)). This colorant may be transferred to ITM drum  30 , or, more precisely, to a blanket wrapped around ITM drum  30 , and then transferred from the blanket to substrate  75  using impression drum  40  to form the image on the substrate. 
     Liquid ink or toner (an example of which is Hewlett-Packard&#39;s ElectroInk®) used in LEP may be a combination of a solid pigment in a liquid solvent or carrier. The solid part may be paste-like and may include micron-sized electrically charged particles. The liquid solvent may be an oil, or an oil mixture (such as HP Imaging Oil), which may include an isoparaffinic fluid such as Isopar® or Isopar-L (made by ExxonMobil Chemical Co.). 
     During printing, the ink paste may be mixed with the imaging oil and then delivered to the printing area. After printing, the substrate may be dried by evaporating the liquid (oil) part of the ink from the printed image, and then cooling the vapor in a cooling cabinet to recover the oil. This process is shown generally in a conceptual block diagram in  FIG. 2 , which includes printing area  100  and cooling cabinet  200 . Warm oil vapor  207  is shown exiting printing area  100  and entering cooling cabinet  200  via inlet  205 . Cooling cabinet  200  cools the vapor to condense the oil, and then cool air  293  exits cooling cabinet  200  and enters printing area  100  via outlet  295 . 
       FIG. 3A  shows in more detail the cooling operation between printing area  100  and cooling cabinet  200 . Blowers (or evaporators)  160  suck warm vapor-laden air (oil vapor) from a freshly-printed image (e.g., from impression drum  40  or I™ drum  30 ) and blow it through inlet  205  to cooling cabinet  200 . The oil vapor enters heat exchanger  250 , which may use cold water to cool the vapor down to 40-50° F. (4-10° C.) and condense the oil from the vapor. The condensed oil is mixed with the ink paste again to be used for further printing. Blower  260  blows the treated air through outlet  295  to printing area  100 . 
     Also shown in  FIG. 3A  are inlet door  210  and outlet door  290 , the opening and closing of which are controlled using hydraulic cylinders  215  and  285 , respectively. Inlet door  210  and outlet door  290  are used to control the emission of VOCs and other compounds from the printer to the atmosphere. More specifically, when the printer is operating, inlet door  210  and outlet door  290  are open to allow for the flow of oil vapor and oil between cooling cabinet  200  and printing area  100 . Because blowers  160  and  260  are operating when the printer is operating, VOCs and other compounds do not escape from the printer into the atmosphere. When the printer is idle, however, inlet door  210  and outlet door  290  are closed, as shown in  FIG. 3B , to prevent the oil from evaporating from cooling cabinet  200 . Blowers  160  and  260  are also shut off to eliminate convection in cooling cabinet  200 , which would tend to spread the vapors. 
     Besides the benefit of controlling VOC and other vapor emissions (at least 40% reduction in some instances for the printer as a whole), having the ability to open and close the inlet and outlet doors retains and saves the oil (as much as 98% of the printer oil, which may constitute three to four liters or more per day), which can be used when the press begins operating again (e.g., the next day), so much less oil is used and wasted. 
     Reference is now made to  FIGS. 4A and 4B , which are flowcharts showing the operation of embodiments of the present invention. In  FIG. 4A , a general process of the present invention may include several operations. In operation  410 , the cooling cabinet may be sealed while the printer is idle to keep the VOCs and other vapors from escaping. Blowers  160 ,  260  may also be shut off to prevent convection of the vapor-laden air. In operation  420 , the cooling cabinet may be unsealed and the blowers started while the printer is operating. These two operations may operate in a cycle. 
     In  FIG. 4B , while the cooling chamber is unsealed, in operation  430 , oil vapor may be sucked from printing area  100  into cooling cabinet  200 , possibly using blowers  160 . In operation  440 , oil may be condensed from the oil vapor using heat exchanger  250 . In operation  450 , treated air may be blown back to printing area  100 , possibly using blower  260 . In operation  460 , oil may be reused in the printing process. 
     Besides the flowcharts in  FIGS. 4A and 4B , other operations or series of operations may be used. Moreover, the actual order of the operations in the flowcharts may not be critical. 
     Reference is now made to  FIGS. 5A and 5B , which are conceptual illustrations of the mechanism that controls the opening and closing of the inlet and outlet doors. The system may be controlled using a valve  245 , controlled by, for example, an electrical signal, e.g., a 24V signal. When printer  1  is operating, valve  245  controls air from air supply  240  to cause hydraulic cylinders  215  and  285  to open doors  210  and  290 . When the inlet and outlet doors  210 ,  290  are opened, they each engage an interlock  220 ,  280 , respectively, which confirms to printer  1  that the doors are open. When the machine is idle, valve  245  is closed, causing inlet and outlet doors  210 ,  290  to be closed.  FIG. 5B  shows no air flow into inlet  205  from printing area  100 . Upon startup of printer  1 , inlet and outlet doors  210 ,  290  are closed. Heat exchanger  250  is started up in order to begin condensing the oil vapor already within cooling cabinet  200 . Then, the inlet and outlet doors  210 ,  290  are opened and blowers  160 ,  260  are started to ensure that the vapors can be captured immediately. Interlocks  220 ,  280  ensure that blowers  160 ,  260  are not activated before inlet and outlet doors  210 ,  290  are opened. 
     Prior attempts to reduce VOC or other emissions included capturing these compounds and destroying them or diverting them to other locations or adding small permanent enclosures around the whole press or large permanent enclosures around the press room or warehouse. These methods still emit the compounds, however. In flexographic printing, which uses an embossed relief plate as in offset printing, enclosed doctor blade chambers have been used to enclose the area right next to the main ink drum (within the printing area), scrape off excess ink from the drum with one or two blades, and return the ink to a reservoir to be used again. But these chambers do not control VOCs emitted from the other printing drums, the printed substrate, or the printing area as a whole. They also do not open and close depending on the operational status of the printer. 
     In sum, a novel arrangement is described that may be used to reduce VOC or other emissions from a printer, press, or copier by using doors to seal, typically while the machine is idle, inlets to the chamber from which the compounds may escape to the atmosphere. This limits environmental emissions of these compounds. Other benefits of the arrangement are reduced oil consumption, because the oil stays in the printer rather than evaporating to the atmosphere, reduced maintenance, because there is no need to refill oil each day, reduced operation cost, because of the saving of the cost of oil, and reduced environmental impact, because there is less of a need to produce oil. 
     The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications. It is also intended that the word “printer” in the claims include apparatuses such as presses and copiers, in addition to printers.
An apparatus for reducing vapor emissions from a printer may include a treatment chamber having an inlet and an outlet. While the printer is operating, vapor-laden air may enter the treatment chamber via the inlet and treated air may exit the treatment chamber via the outlet. While the printer is idle, the inlet and outlet can be sealed to prevent vapors located in the treatment chamber from being emitted to the atmosphere.