Abstract:
An ink jet droplet generator body for an ink jet droplet generator comprising an orifice plate with a plurality of nozzles forming a jet array entails a throughbore with an entrance and exit port, the throughbore provides a path through that flows fluid from a fluid supply to the first slot. The first slot connects the throughbore to the orifice plate. One or more holes or a slot are located in the top of the generator body to direct fluid or a secondary source of fluid to the first slot and then the orifice plate.

Description:
FIELD OF THE INVENTION 
   The present embodiments relate generally to an improved droplet generator for ink jet printer. 
   BACKGROUND OF THE INVENTION 
   The overall thickness and height of continuous inkjet droplet generators must decrease to enable the frequency of droplet formation to increase. To further increase the droplet generation rates, the diameter of the bore through the droplet generator must decrease as well. This decrease conflicts with the need for increased amounts of ink flow required at higher frequencies. Turbulence occurs in the smaller through bores and affects the stimulation performance of the drop let generator. The turbulence problem also exists when attempting to fabricate a longer droplet generator with increased ink flow rates in order to supply the increased number of inkjets with a small through bore. 
   A need exists for an increased amount of ink flowing to the droplet generator and while using a small bore. 
   SUMMARY OF THE INVENTION 
   An ink jet droplet generator body for an ink jet droplet generator comprising an orifice plate with a plurality of nozzles forming a jet array entails a throughbore with an entrance and exit port, the throughbore provides a path through which fluid flows from a fluid supply to the first slot. The first slot connects the throughbore to the orifice plate. One or more holes or a slot are located in the top of the generator body to direct fluid or a secondary source of fluid to the first slot and then the orifice plate. 
   The present embodiments are advantageous over the prior art because the ink jet printer can be run at higher frequencies and with longer arrays for more throughput than known devices. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings, in which: 
       FIG. 1  depicts an isometric view of an embodiment of a droplet generator with discrete holes in the top. 
       FIG. 2  depicts a perspective view  FIG. 1  exampling the fluid flowing from the fluid supply to the droplet generator. 
       FIG. 3  depicts a cross section detail of the fluid supply to the droplet generator of  FIG. 1  and  FIG. 2 . 
       FIG. 4  depicts an isometric view of an alternate embodiment of the ink jet droplet generator using two slots with a throughbore. 
       FIG. 5  depicts a cross section detail of the fluid supply to the droplet generator of  FIG. 4 . 
       FIG. 6  depicts an isometric view of another embodiment of the ink jet droplet generator using two slots without a throughbore. 
       FIG. 7  depicts a cross section detail of the fluid supply to the droplet generator of  FIG. 6 . 
   

   The present embodiments are detailed below with reference to the listed FIGS. 
   DETAILED DESCRIPTION OF THE INVENTION 
   The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well-known to those skilled in the art. 
   Turbulence in the cavity section of ink jets occurs as attempts are made to increase flow rates for ink jets. Traditionally, turbulence has been reduced by making the droplet generators throughbore larger. The larger sizes of the bore diameter of the droplet generator array results in a lower operating frequency for the droplet generator, which in turn means lower speed of operation. 
   The present embodiments provide the benefit of smaller bore diameters with the benefit of increased speed without the turbulence usually encountered. The embodied ink jet droplet generator bodies permits higher frequency of operation for the droplet generator and longer droplet generators. 
   The embodied top feed droplet generator supplies ink to the droplet generator fluid cavity through a number of small fluid ports down the length of the array. The small ports are on the side opposite the jet array. The ports are small enough to not change the vibration pattern of the droplet generator. The small ports are connected to an external fluid supply plenum by flexible tubing. The tubing is acoustically dead and does not affect vibration of the droplet generator. 
   The fluid usable in this droplet generator includes ink, flush fluids, and replenishment fluid. 
   With reference to the figures,  FIG. 1  depicts an isometric view of an embodiment of a droplet generator  5  with discrete holes in the top. The ink jet droplet generator body  8  is for use with an ink jet droplet generator. A typical ink jet droplet generator includes an orifice plate  6  with a plurality of nozzles  9   a ,  9   b ,  9   c , and  9   d  forming a jet array  10 .  FIG. 1  examples four nozzles  9   a ,  9   b ,  9   c , and  9   d , but a typical jet array  10  can include up to 600 holes per inch. The generator includes an actuator  12  adapted to stimulate the jet array  10 . 
   The embodied generator body  8  includes a throughbore  13 , a first slot  18 , one or more discrete holes  20   a ,  20   b ,  20   c , and  20   d , and a seal. The throughbore  13  includes a first (fluid receiving) port  14  and a second (fluid returning) port  15 . The generator body  8  can be composed of a metal, such as stainless steel or beryllium. The preferred metal for the generator body  8  is 17-4PH stainless steel. 
     FIG. 2  depicts a perspective view of the generator body  5  exampled in  FIG. 1 .  FIG. 2  more clearly shows the fluid  16  flowing from the fluid supply  17  into the first port  14  of the throughbore  13 . The throughbore  13  allows the fluid  16  to reach the to the orifice plate  6  through the first slot  18 . 
   Returning to  FIG. 1 , an embodiment of the generator body  8  includes one or more discrete holes  20   a ,  20   b ,  20   c , and  20   d  disposed in the top of the generator body  8 .  FIG. 1  and  FIG. 2  example four discrete holes. The discrete holes  20   a ,  20   b ,  20   c , and  20   d  receive additional fluid from the fluid supply  17  and communicate the additional fluid to the throughbore  13  and then to the orifice plate  6 . Each discrete hole  20   a ,  20   b ,  20   c , and  20   d  typically has a diameter ranging from about 30 mils to about 120 mils. Each hole can vary in diameter. The holes are capable of supporting operating pressures up to 80 psi. 
     FIG. 3  depicts a cross section detail of the fluid supply to the droplet generator  5  of  FIG. 1  and  FIG. 2 . As shown in  FIG. 3 , the first slot  18  is vertically above the orifice plate  6 . The fluid  16  can enter through the throughbore  13  to the first slot  18  and thence vertically below to the orifice plate  6 . Fluid  16  or addition fluid can enter though the discrete hole  20   a  on top of the generator body  8  and can reach the orifice plate though the throughbore  13 . 
   In an alternative embodiment depicted in  FIG. 4 , a second slot  24  disposed in the generator body  8  vertically above the first slot  18  can be used to receive additional fluid from the fluid supply  17  and communicate the additional fluid to the throughbore  13 . The second slot  24  is used in conjunction with the throughbore&#39;s inlet port  14 , wherein both the inlet port  14  and the second slot  24  can provide fluid. A seal  25  can be disposed in the second slot  24 . The seal  25  is adapted to provide an acoustic impedance mismatch to the generator body  8 .  FIG. 5  depicts a cross section detail of the fluid supply to the drop generator of  FIG. 4 . 
   In another alternative embodiment depicted in  FIG. 6 , a second slot  24  disposed in the generator body  8  vertically above the first slot  18  can be used to receive fluid from the fluid supply  17  and communicate the fluid to the first slot  18  and thence vertically below to the orifice plate  6 . In this embodiment, the second slot  24  is the sole source of fluid into the droplet generator body  8 . A seal  25  can be disposed in the second slot  24 . The seal  25  is adapted to provide an acoustic impedance mismatch to the generator body  8 .  FIG. 7  depicts a cross section detail of the fluid supply to the drop generator of  FIG. 6 . 
   The length of the second slot  24  can be approximately the same length as the first slot  18  or longer than the first slot  18 . The width of the second slot  24  is typically larger than the width of the first slot  18 . The width of the second slot  24  can be from about 30 mils to about 120 mils. The second slot  24  can support operating pressures up to 80 psi. 
   The second slot  24  can include a first end wall  28  and a second end wall  30  located opposite one another. The end walls are sloped to converge toward the orifice plate  6 , or instead may be parallel. 
   In an example of the method, small holes are drilled in the top of the droplet generator. Small 15-gage polypropylene tubes, typically EFD part number 5115PP-B, are bonded with epoxy into the holes. The polypropylene tubes connect the droplet generator to an external manifold for supplying ink. The normal droplet generator inlet and outlet are retained in order to facilitate cross-flushing the droplet generator for particle and air bubble removal. 
   The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
   PARTS LIST 
   
       
         5 . droplet generator 
         6 . orifice plate 
         8 . droplet generator body 
         9   a . nozzles 
         9   b . nozzles 
         9   c . nozzles 
         9   d . nozzles 
         10 . jet array 
         12 . actuator 
         13 . throughbore 
         16 . fluid 
         17 . fluid supply 
         18 . first slot 
         20   a . discrete hole 
         20   b . discrete hole 
         20   c . discrete hole 
         20   d . discrete hole 
         24 . second slot 
         25 . seal 
         28 . first end wall 
         30 . second end wall