Abstract:
An image forming apparatus having a pair of fuser rollers for fusing toner onto the surface of recording sheets. The apparatus further includes an oil applicator mounted for dispensing oil onto at least one of the fuser rollers. The oil applicator includes a tank for holding oil, a pad disposed adjacent to one of the rollers for applying oil thereto, and an oil reservoir mounted adjacent the pad and connected to the tank for receiving oil therefrom. The oil reservoir includes an ejection port that permits oil within the reservoir to be dispensed to the pad. A flexible diaphragm extends over at least a portion of the oil reservoir, and a seal is secured to the diaphragm. At least one piezo element is secured to the diaphragm for moving the diaphragm and seal between two positions in response to the piezo element being selectively operable between engaged and non-engaged states. In one of the positions the seal effectively closes the oil reservoir ejection port, while in the other position the seal is spaced from the ejection port such that oil may flow from the oil reservoir through the ejection port and to the pad.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to an electronically controlled oil dispenser for an image forming apparatus and, more particularly, to an oil dispenser having a piezo element for distributing oil to a roller within the image forming apparatus. 
     BACKGROUND OF THE INVENTION 
     The printing process of an image forming device, such as a laser printer, includes distributing toner to a recording sheet. The toner is usually a fine powder made of plastic granules that is transferred from a photoconductive drum, or intermediate transfer device, to the recording sheet. The toner is then fixed to the recording sheet by applying heat and/or pressure. In one popular embodiment, the heat and/or pressure is applied through a pair of fuser rollers that are spaced a distance apart between which the recording sheet and toner pass. 
     Problems may occur when the recording sheet with toner passes through the fuser rollers. One problem occurs when the toner on the recording sheet adheres to one of the fuser rollers resulting in image contamination as the toner does not adhere to the correct location on the recording sheet, or remains on the roller and is not transferred to the recording sheet. Another problem occurs when the recording sheet is inadvertently wound around one of the fuser rollers causing a jam. 
     To overcome these problems, oil is applied to one or both of the fuser rollers. The oil reduces the amount of toner that adheres to the rollers, and also lessens the likelihood of the recording sheet becoming entangled. An oil applicator is positioned adjacent to the rollers for distributing the oil. However, the application of oil to the fuser rollers may result in additional problems. 
     One problem is inconsistent oil transfer to the rollers during the life of the oil applicator. Many designs result in an over-abundance of oil being transferred to the fuser roller early in the life of the applicator. Too much oil distributed onto the rollers may be transferred to the recording sheet resulting in oil spots that are visible to the user thereby ruining the sheet. Conversely, the same applicators often do not apply an adequate amount of oil during the end of their life. Inadequate oil results in toner adhering to the fuser rollers and/or the recording sheet sticking to the fuser rollers, both of which are unacceptable results. Inconsistent oil application also makes it difficult to predict the expected life of the oil applicator. 
     Many currently existing oil applicators are messy to install and remove from the image forming device. One common design features a pad through which oil is applied and then wicked to the fuser rollers. Installation of this type of applicator may require that the pad be doused with oil during the installation which may result in oil contacting the user and also portions of the image forming device which may then be transferred to the recording sheet. Removal of a used oil applicator may again be messy as the oil applicator may be coated with oil that was dispelled during use. The oily applicator may inadvertently contact other parts of the image forming device or get on the user&#39;s hands or clothes. 
     Therefore, there is a need for an oil applicator that coats the fuser roller with a consistent amount of oil during its life, and is not messy to install and remove from the image forming apparatus. 
     SUMMARY OF THE INVENTION 
     The oil applicator of the present invention distributes oil to one of the fuser rollers to reduce and eliminate toner adherence and sheet jams within the rollers. The device includes an oil reservoir for housing the oil with at least one ejection port positioned within the reservoir. A seal is disposed adjacent to the ejection port and is movable between a closed position where the seal effectively closes the ejection port and an open position where the seal is spaced from the outlet such that oil may flow through the ejection port. At least one piezo element is positioned for moving the seal between the open and closed positions in response to the piezo element being switched between energized and non-energized states. 
     The applicator may also include a diaphragm that extends over at least a portion of the oil reservoir. In this embodiment, both the seal and piezo element are secured to the diaphragm. A pad may be disposed adjacent to the ejection port of the oil reservoir to receive oil and transfer it to the roller. 
     A processor may control the activation of the piezo element such that a substantially equal volume of oil is dispensed through the ejection port for each cycle between the energized and non-energized states. The processor may be connected to a voltage source for supplying voltage to and activating the piezo element. The processor may also monitor the number of recording sheets passing through the fuser rollers and cycle the piezo elements based on the number. For example, the processor may cycle the piezo element to distribute oil after every five recording sheets have passed through the rollers. Likewise, a sensor may be positioned within the image forming apparatus for sensing the installation of a new oil applicator. The sensor signals the processor of the new applicator, resulting in the processor cycling the piezo elements a predetermined number of times to ensure an adequate oil supply is distributed to the rollers. 
     The applicator may also include a supply tank for holding an additional amount of oil. The supply tank is connected to the oil reservoir and supplies the oil, preferably via gravity. 
     The oil reservoir may further include a number of individual cells each having at least one ejection port. A separate piezo element may be positioned over each of the cells for controlling the distribution of oil. Each piezo element may be individually energized to control the location of where the oil is distributed to the roller. 
     The invention also includes a method of dispensing oil from the oil reservoir by energizing a piezo element thereby opening an ejection port within the oil reservoir. The oil flow is stopped by de-energizing the piezo element thereby closing the ejection port within the oil reservoir. Within the method, energizing the piezo element moves a seal from a closed position over the ejection port, and de-energizing the piezo element returns the seal to the closed position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side cross sectional view of an image forming apparatus constructed in accordance with the present invention; 
     FIG. 2A is a perspective view of the fuser rollers and adjacent oil applicator; 
     FIG. 2B is a side view taken along line  2 B— 2 B of FIG. 2A; 
     FIG. 3 is a partial perspective view of the oil applicator pump constructed in accordance with the present invention; 
     FIG. 4A is a side view of a cell reservoir in a relaxed, non-energized orientation; 
     FIG. 4B is a side view of the cell of FIG. 4A in an energized orientation; and 
     FIG. 5 is a schematic diagram illustrating a processor for controlling the oil applicator. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention, generally designated  10  in FIG. 2, is directed to a oil applicator and method of supplying oil to at least one of the fuser rollers  20  of an image forming apparatus  100 . The invention includes an oil applicator  10  having a supply tank  29  for housing oil that is supplied to a pump  31 . The pump  31  includes at least one piezo element  39  that is selectively movable between energized and non-energized states for dispensing oil to the fuser rollers  20 . 
     FIG. 1 illustrates the basic elements of an image forming device and is incorporated for an understanding of the overall electrophotographic image forming process. A color laser printer is illustrated as  100 , however, one skilled in the art will understand that the present invention is applicable to other types of image forming devices using toner for printing through a photoconductive drum. The image forming apparatus  100  includes a plurality of similar toner cartridges  110 ,  210 ,  310 , and  410 . Each toner cartridge has a similar construction but is distinguished by the toner color contained therein. In one embodiment, the image forming apparatus includes a black cartridge  110 , a magenta cartridge  210 , a cyan cartridge  310 , and a yellow cartridge  410 . The different color toners form individual images of a single color that are combined in layered fashion to create the final multi-colored image. Alternatively, the apparatus  100  may include a single cartridge for monochromatic images. As the individual cartridges are identical except for the toner color, the cartridge for forming black images will be described with an understanding that the other cartridges employed within a multi-color image forming apparatus would be substantially similar in both construction and function. 
     A photoconductive drum  114  is generally cylindrically-shaped having a smooth surface for receiving an electrostatic charge over the surface as the drum rotates past charging roller  116 . The drum rotates through a laser imaging device  120  that directs a laser onto a selected portion of the drum surface forming an electrostatically latent image across the width of the drum representative of the outputted image. This process continues as the entire image pattern is formed on the drum surface. 
     After receiving the latent image, the drum rotates through a developer housing  122  having a toner bin for housing the toner and a developer roller  124  for uniformly transferring toner to the drum  114 . The toner is a fine powder usually constructed of plastic granules that are attracted and cling to the electrostatic latent image formed by the laser imaging device  120 . 
     Drum  114  next rotates past an adjacently positioned intermediate transfer medium belt  500  (hereinafter, ITM belt) where the toner is transferred from the drum  114 . As illustrated in FIG. 1, the ITM belt  500  is endless and extends around a series of rollers adjacent to the drums. The ITM belt  500  and the image on each drum  114 ,  214 ,  314 ,  414  are synchronized providing for the toner from each drum to precisely align on the ITM belt during a single pass. By way of example as viewed in FIG. 1, the yellow (Y) toner will be placed on the ITM belt, followed by cyan (C), magenta (M), and black (B). 
     As the drums are being charged and gathering toner, a recording sheet  60 , such as a sheet of paper, is being routed to intercept the ITM belt  500 . The recording sheet  60  may be placed in one of the lower trays  510 , or introduced into the image forming device through a side track tray  520 . A series of rollers and belts (not illustrated) transports the recording sheet  60  to point Z where the sheet contacts the ITM belt  500  and the toner is transferred. The sheet  60  and attached toner next travel through a pair of fuser rollers  20  that includes a heating element that heats and fuses the toner to the sheet. The sheet  60  with fused image is then transported out of the image forming apparatus  100 . 
     FIG. 2A illustrates the oil applicator  10  placed adjacent to one of the fuser rollers  20 . Each of the fuser rollers  20  may have a variety of diameters, and the two may not have the same diameter roller. The length of each fuser roller  20  is preferably about equal to the width of the recording sheet  60  to fuse the toner along the entire sheet width. Preferably, the rollers  20  have a substantially smooth surface to lessen the likelihood of toner adherence and of the recording sheet  60  becoming jammed. In a preferred embodiment, one of the rollers  20  contains a heating element for improving the bond between the toner and the recording sheet  60 . Usually, the heating element is contained within the top roller that contacts the toner on the surface of the recording sheet  60 . 
     The oil applicator  10  is positioned against one of the fuser rollers  20  as illustrated in FIGS. 2A and 2B and functions to supply oil across the length of the fuser roller  20 . The oil applicator  10  includes a supply tank  29  for housing oil that is to be distributed to a pump  31  through a supply line  12  illustrated in FIG.  3 . When the oil applicator  10  is mounted within the image forming apparatus  100 , the supply tank  29  is preferably positioned vertically above the pump  31  such that oil can feed into the pump  31  through the supply line  12  via gravity. The oil supply line  12  is preferably positioned within walls of the oil applicator for containing the oil and preventing any possible leakage. A vent  14  may be positioned on the oil applicator  10  for venting air into the applicator for consistent oil flow. The vent  14  preferably includes a one-way check valve constructed such that oil cannot leak out if the oil applicator  10  is inverted such as during shipping, installation, or removal. 
     FIG. 3 illustrates the interior sections of the pump  31  within the oil applicator  10 . The pump  31  includes a distribution channel  30  extending along the length of the pump for distributing oil throughout the applicator. A plurality of cell reservoirs  32  are positioned in proximity to the distribution channel  30 . The cell reservoirs  32  and distribution channel  30  are separated by inlets  34  through which the inflow of oil into the reservoirs is controlled. As illustrated in FIGS. 4A and 4B, an ejection port or outlet  36  is positioned within each cell reservoir  32  for distributing oil to the fuser roller  20 . Although only one ejection port  36  is illustrated within each cell reservoir  32 , there may be any number of ports positioned within each reservoir. 
     The oil applicator  10  includes a membrane or diaphragm  38  positioned over the pump  31  as illustrated in FIGS. 3,  4 A and  4 B. The diaphragm  38  extends across the oil applicator  10  and is sealed to pump side walls. The diaphragm is constructed of a flexible material such that it may move between energized and non-energized states as illustrated in FIGS. 4A and 4B. The flexing of the diaphragm  38  also assists in pumping oil through the distribution channel  30 , into the cell reservoirs  32 , and out through the ejection ports  36 . 
     A seal  35  is positioned within the cell reservoir  32  for controlling the flow of oil through the ejection port  36 . The seal  35  is attached to the diaphragm  38  and reciprocates over the ejection port  36  during the cycles of the energized and non-energized states. The seal  35  is sized to cover the ejection port  36  and prohibit the flow of oil from the cell reservoir  32  in the non-energized state as illustrated in FIG.  4 A. In the energized state, the diaphragm  38  and attached seal  35  move away from the cell reservoir  32  and the seal moves from the ejection port  36  allowing for oil to exit as illustrated in FIG.  4 B. 
     At least one piezo element  39  is attached to the diaphragm  38  and is selectively movable between energized and non-energized states. The piezo-elements are connected to a voltage source  50  to apply a sinusoidal or pulsed voltage. In the energized state, voltage is applied causing the piezo-element  39  to expand resulting in the element deflecting as illustrated in FIG.  4 B. The attached diaphragm  38  and seal  35  are also moved thereby opening the ejection port  36 . When the voltage is removed from the piezo element  39 , it contracts to the original position thereby returning the diaphragm  38  and seal  35  and closing the ejection port  36 . Preferably, the voltage across the piezo-element is between about one and fifty volts, dependent upon the thickness of the element, the rigidity of the diaphragm  38 , the dimensions of the cell reservoir  32 , and the physical characteristics of the oil. The diaphragm  38  is preferably constructed of a conductive material and is a common electrical contact to the piezo elements  39 , and is connected to a grounding element such as the negative terminal of the voltage source  50 . The use of piezo-elements is well known in the art for ejecting ink within an inkjet printer, such as that disclosed in U.S. Pat. Nos. 5,270,740 and 5,854,645 both of which are herein incorporated by reference in their entirety. 
     Preferably, a separate piezo-element  39  is positioned over each cell reservoir  32  for separately controlling the output of oil from each reservoir. Each piezo-element  39  is connected to the voltage source  50  for individual actuation thereby allowing for oil to be ejected from the cell reservoirs  32 . Alternatively, a single piezo element  32  may be positioned over the diaphragm  38  such that when a voltage is applied, oil is output from each ejection port  36  along the oil applicator  10 . 
     A pad  16  is positioned adjacent to the ejection ports  36  for receiving oil from the applicator  10  and transferring it to the fuser roller  20 . The pad  16  is constructed of a material causing a wicking action when oil is applied for distributing the oil through the pad. Because the pad  16  contacts the fuser roller  20 , it may also remove debris such as paper dust and toner. Additionally, the pad  16  may have more than one layer, and each layer may have a different construction depending upon the specific requirements of the oil application. Pads for wicking oil along the length of the fuser roller are well known in the art. See, for example, U.S. Pat. Nos. 4,182,263; 4,309,957; and 4,359,963, each of which is expressly incorporated herein by reference in their entirety. 
     FIG. 5 illustrates a schematic representation of a processor  90  that monitors the workings of the oil applicator  10 . Processor  90  may include a conventional memory unit such as a ROM, PROM or flash memory accessible for storing a program controlling the functioning of the oil applicator  10 . Additionally, the processor  90  includes logic for determining the number of recording sheets  60  passing through the fuser rollers  20 . Various processors for controlling the functioning of components of the image forming apparatus are well known in the art, including U.S. Pat. Nos. 4,054,380 and 5,749,036, both incorporated herein by reference in their entireties. 
     The processor  90  is operatively connected with a voltage source  50  for controlling the cycling of the piezo element  39  and distribution of oil through the ejection port  36 . An oil sensor  70  is positioned in proximity to the oil applicator  10  for detecting the amount of oil being applied to the fuser roller  20 . In one embodiment, the oil sensor  70  determines the amount of oil on the fuser roller  20  by directing a light source onto the fuser roller and determining the amount of reflected light. This determination is sent to the processor  90  which then distributes oil as needed. The oil applicator  10  may include a single oil sensor  70  for determining the amount of oil distributed to the roller  20 , or may include more than one sensor positioned along the fuser roller  20 . 
     An applicator sensor  80  may also be positioned within the image forming apparatus  100  to determine the installation of a new oil applicator  10 . A new oil applicator  10  preferably includes a dry pad  16  that contains no oil  10 . Therefore, when initially installed, the applicator sensor  80  signals the processor  90  which in turn signals the voltage source  50  to saturate the pad  16 . 
     Each cycle of the piezo element  39  between the energized and non-energized states produces substantially the same amount of oil being dispensed from the ejection ports  36 . This provides for the processor  90  to be preprogrammed such that an appropriate amount of oil is distributed to the fuser roller  20 . By way of example, it may be determined that four cycles of oil should be distributed through each ejection port  36  for every ten recording sheets passing through the fuser rollers  20 . Likewise, the amount of oil that should be dispensed for a new oil applicator  10 , or the amount of oil based upon readings from the oil sensor  70  may also be stored in the processor  90 . Knowing the amount of oil dispensed during each cycle allows for monitoring the expected life of the oil applicator  10 . The processor may further be equipped with a signal light (not illustrated) visible to a user indicating when the oil applicator  10  currently in use should be replaced. 
     In use, the oil applicator  10  is mounted within the image forming device  100  such that oil from the supply tank  29  enters the pump  31  through the oil supply line  12 . As illustrated in FIG. 4A, the seal  35  in the non-energized state is positioned to block oil flow through the ejection port  36 . In FIG. 4B, the processor  90  signals the voltage source  50  to activate the piezo-element  39  to the energized state in which the seal is moved from the ejection port  36 . Oil within the cell reservoir  32  moves into the ejection port  36 , and additional oil is drawn from the distribution channel  30  into the cell reservoir. When the current is interrupted, the piezo-element  39 , diaphragm  38 , and seal  35  return to the relaxed orientation. This movement ejects oil from the ejection port  36  until the seal  35  closes. The contact of the seal  35  over the ejection port  36  stops the oil flow, and breaks the capillary action of the oil into the pad  16 . Once distributed to the pad  16 , the oil migrates through the pad and onto the fuser roller  20 . 
     It is advantageous for containing the entire oil applicator  10  within a single device. When the oil is depleted, the user simply replaces the entire oil applicator  10 . There is less of a likelihood that oil will inadvertently contact the user&#39;s hands or clothes. Additionally, there is less of a likelihood that oil will contact components of the image forming apparatus  100  which may eventually be transferred to an outputted recording sheet resulting in a printing defect. Replacing the entire oil applicator  10  also provides a more straight-forward program for the processor  90  to prime the pad  16  with oil when a new applicator is installed. 
     In the foregoing description, like-reference characters designate like or corresponding parts throughout the several views. Also, it is to be understood that such terms as “forward”, “rearward”, “left”, “right”, “upwardly”, “downwardly”, and the like are words of convenience that are not to be construed as limiting terms. Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. In an alternative embodiment, the oil applicator  10  does not include a supply tank  29 , but rather oil is pumped through the oil supply line  12  from a remote oil reservoir (not illustrated). In another alternative embodiment, the oil applicator  10  distributes the oil directly to the fuser roller  20  through the ejection ports  36  spaced along the roller length. This alternative embodiment does not include a pad  16 . It should be understood that other modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims.