Abstract:
A print carriage and ink supply system for a printer includes: (a) a print carriage adapted for lateral reciprocation along a print medium within a printer, where the print carriage includes at least one print head; (b) an ink pump including an ink inlet in fluid communication with an ink source, an ink outlet in fluid communication with the print head, and a pump actuator for at least initiating displacement of ink through the ink pump upon actuation; and (c) an inertial mass coupled to the print carriage for reciprocating movement with respect to the print carriage in opposing reaction to acceleration of the print carriage laterally along the print medium; where the inertial mass is indirectly linked to the pump actuator by a mechanical linkage such that the combination of the inertial mass and mechanical linkage actuates the pump at least upon certain accelerations of the print carriage laterally along the print medium.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to ink jet printers and, more particularly, to pumping systems used to deliver ink from the ink source to the print head.  
         [0002]     Inkjet printers are one of the most widely used print technologies, providing low cost, high speed, and high resolution printing. In order to print at high resolutions while maintaining high speed of operation, it is desired that a steady flow of ink is rapidly delivered to the print head. Various means have been employed in the art to deliver ink to the print head. Some ink jet systems, particularly the low-end models, have used disposable ink supply cartridges mounted on the print carriage, directly coupled to the print head. Other ink jet systems have used an electrically-powered pump to deliver the ink from a fixed supply tank to the print heads located on the print carriage.  
         [0003]     U.S. Pat. Nos. 6,145,971 and 6,431,694 describe ink jet systems employing an ink pump driven by the motion of the print carriage; and, more specifically, driven by a passive inertial mass that moves in reaction to the acceleration of the print carriage. Such passively-driven ink pumps represent an important step in ink jet technology because they provide a mechanically simple pump that can be mounted directly on the print carriage. One of the shortcomings of this passively-driven ink pump seen in the prior art is the mass and, hence, the volume required to produce a pump that can achieve the pressures and flow rates required for commercial ink jet printers is too large. In order to supply enough force to generate the required pump capacity, the inertial mass as implemented in the prior art must be sufficiently large that it presents significant design limitations to the installation of the pump on the print carriage. If multiple ink pumps are required, as is necessary in a color printer, it becomes substantially difficult and impractical to fit the ink pumps on the print carriage due to their size.  
         [0004]     In light of these shortcomings, there is a desire for a passive ink jet pump driven by an inertial mass that is smaller and lighter than those previously developed.  
       SUMMARY  
       [0005]     Exemplary embodiments of the present invention employ the inertial motion of a mass coupled to an ink jet printer&#39;s print carriage to drive a displacement-type ink pump located on the carrier. The pump delivers the ink, which is stored off the carrier, to the print heads. In accordance with the present invention, a mechanical linkage, such as a lever mechanism, is employed to couple the inertial mass to the pump&#39;s actuator, which in the exemplary embodiments includes a diaphragm and/or “displacement volume.” The mechanical advantage provided by this mechanical linkage allows a sufficiently smaller inertial mass to achieve the required pump capacity, thus enabling multiple ink supply pumps to be fitted to the print head carrier if desired.  
         [0006]     It is a first aspect of the invention to provide a print carriage and ink supply system for a printer that includes: a print carriage adapted for lateral reciprocation along a print medium within a printer; an ink pump including an ink inlet in fluid communication with an ink source, an ink outlet in fluid communication with the print head on the print carriage, and a pump actuator for at least initiating displacement of ink through the ink pump upon actuation; and a pendulum pivotally coupled to the print carriage for pivotal movement with respect to the print carriage in reaction to acceleration of the print carriage laterally along the print medium, where the pendulum is mechanically linked to the pump actuator. In such a system the pendulum actuates the pump at least upon certain accelerations of the print carriage laterally along the print medium. In more detailed embodiment the pendulum is pivotally coupled to the print carriage at a pivot point and includes an internal mass arm extending below the pivot point and an actuator arm extending above the pivot point, where the actuator arm is mechanically linked to the pump actuator. In a further detailed embodiment the actuator arm is coupled to a piston carried on the ink pump and the piston is in contact with the pump actuator along at least a portion of the piston&#39;s reciprocation path. In yet a further detailed embodiment, the pump is a displacement type pump. In yet a further detailed embodiment, the pump is a diaphragm pump and the pump actuator includes a pump diaphragm enclosing at least a portion of a displacement volume of the diaphragm pump. In yet a further detailed embodiment, the diaphragm pump includes a pump housing containing: the displacement volume, the pump diaphragm, the pump inlet in fluid communication with the displacement volume, and the pump outlet in fluid communication with the displacement volume. In yet a further detailed embodiment, the pump housing is coupled to the print carriage, the pump housing contains the piston, and the pendulum is pivotally coupled to the pump housing. In yet a further detailed embodiment, the pump housing contains a first check valve in fluid communication with the valve inlet and a second check valve in fluid communication with the valve outlet. In yet a further detailed embodiment, the first and second check valves comprise reed valves.  
         [0007]     In an alternate detailed embodiment of the first aspect of the present invention, the pendulum is pivotally coupled to the print carriage at a pivot point and includes an internal mass arm extending below the pivot point and an actuator arm extending above the pivot point, where the actuator arm is mechanically linked to the pump actuator, and the inertial mass arm of the pendulum is substantially longer and heavier than the actuator arm of the pendulum. In a further detailed embodiment, the inertial mass arm has a mass of approximately 2 grams to approximately 200 grams. In yet a further detailed embodiment, the ratio of pivot distance of travel between the inertial mass arm and the actuator arm is between approximately 0.5 and approximately 10 to one.  
         [0008]     It is a second aspect of the present invention to provide a print carriage and ink supply system for a printer that includes: a print carriage adapted for lateral reciprocation along a print medium within a printer, where the print carriage includes at least one print head; an ink pump including an ink inlet in fluid communication with an ink source, an ink outlet in fluid communication with the print head, and a pump actuator for at least initiating displacement of ink through the ink pump upon actuation; and an inertial mass coupled to the print carriage for reciprocating movement with respect to the print carriage in opposing reaction to acceleration of the print carriage laterally along the print medium; where the inertial mass is indirectly linked to the pump actuator by a mechanical linkage such that the combination of the inertial mass and mechanical linkage actuates the pump at least upon certain accelerations of the print carriage laterally along the print medium. In a more detailed embodiment, the inertial mass is provided on a first arm of a pendulum pivotally coupled to the print carriage, and the pendulum is a component of the mechanical linkage. In a further detailed embodiment, the mechanical linkage includes a piston pivotally coupled to an opposing arm of the pendulum, the piston is mounted for reciprocation along a piston path on the print carriage, and the piston path includes the pump actuator. In yet a further detailed embodiment, the pump is a displacement type pump. In yet a further detailed embodiment, the pump is a diaphragm pump and the pump actuator includes a pump diaphragm enclosing at least a portion of a displacement volume of the diaphragm pump. In yet a further detailed embodiment, the diaphragm pump includes a pump housing containing: the displacement volume, the pump diaphragm, the pump inlet in fluid communication with the displacement volume, and the pump outlet in fluid communication with the displacement volume. In yet a further detailed embodiment, the pump housing is coupled to the print carriage, the pump housing contains the piston, and the pendulum is pivotally coupled to the pump housing. In yet a further detailed embodiment, the pump housing contains a first check valve in fluid communication with the valve inlet and a second check valve in fluid communication with the valve outlet. In yet a further detailed embodiment, the first and second check valves comprise reed valves.  
         [0009]     In an alternate detailed embodiment of the second aspect of the present invention, the pendulum is pivotally coupled to the print carriage at a pivot point and includes an internal mass arm extending below the pivot point and an actuator arm extending above the pivot point, where the actuator arm is mechanically linked to the pump actuator, and the inertial mass arm of the pendulum is substantially longer and heavier than the actuator arm of the pendulum. In a further detailed embodiment, the inertial mass arm has a mass of approximately 2 grams to approximately 200 grams. In yet a further detailed embodiment, the ratio of pivot distance of travel between the inertial mass arm and the actuator arm is between approximately 0.5 and approximately 10 to one.  
         [0010]     In another alternate detailed embodiment of the second aspect of the present invention, the inertial mass extends downwardly with respect to the print carriage and reciprocates a swinging motion. In a further detailed embodiment, the inertial mass extends below the print carriage.  
         [0011]     In another alternate detailed embodiment of the second aspect of the present invention, the system further includes a plurality of the ink pumps for a corresponding plurality of printer inks. In a more detailed embodiment, the system further includes a corresponding plurality of the inertial mass and mechanical linkage combinations for the respective plurality of the ink pumps. Alternatively, the inertial mass is indirectly linked to each of the pump actuators by the mechanical linkage.  
         [0012]     It is a third aspect of the present invention to provide a printer that includes: a printer housing; a drive assembly provided in the printer housing for driving a print medium through the printer housing; a print carriage adapted for lateral reciprocation along a print medium carried by the drive assembly within the printer housing, where the print carriage includes at least one print head; a controller for coordinating the operations of the drive assembly and print carriage with respect to each other; an ink pump provided in the printer housing, including an ink inlet in fluid communication with an ink source, an ink outlet in fluid communication with the print head, and a pump actuator for at least initiating displacement of ink through the ink pump upon actuation; and an inertial mass coupled to the print carriage for reciprocating movement with respect to the print carriage in opposing reaction to acceleration of the print carriage laterally along the print medium; where the inertial mass is indirectly linked to the pump actuator by a mechanical linkage such that the combination of the inertial mass and mechanical linkage actuates the pump at least upon certain accelerations of the print carriage laterally along the print medium. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a schematic diagram of illustrating conventional ink jet printer components;  
         [0014]      FIG. 2  is a perspective exploded view of an exemplary embodiment of the ink pump according to the present invention;  
         [0015]      FIG. 3  is an elevational, cross-sectional view of the ink pump of  FIG. 2 ;  
         [0016]      FIG. 4  is a cross-sectional view of ink pump of  FIGS. 2 and 3 , taken along lines  4 - 4  of  FIG. 3 ; and  
         [0017]      FIG. 5  is partial perspective view of an ink jet printer incorporating exemplary embodiments of the ink pump according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0018]     Exemplary embodiments of the present invention employ the inertial motion of a mass coupled to an ink jet printer&#39;s print carriage to drive a displacement-type ink pump located on the carrier. The pump delivers the ink, which is stored off the carrier, to the print heads. In accordance with the present invention, a mechanical linkage, such as a lever mechanism, is employed to couple the inertial mass to the pump&#39;s actuator, which in the exemplary embodiments includes a diaphragm and/or “displacement volume.” The mechanical advantage provided by this mechanical linkage allows a sufficiently smaller inertial mass achieve the required pump capacity, thus enabling multiple ink supply pumps to be fitted to the print head carrier if desired.  
         [0019]     As shown in  FIG. 1 , a conventional inkjet printer  10  contains a print carriage  12  that carries the print heads and related apparatus for applying ink to the print medium or page  14 , which is driven through the printer past the print carriage  12  by associated drive mechanisms  15 . The coordinated operations of the print carriage  12  and drive mechanism  15  are controlled by one or more controllers  13  as will be appreciated by those of ordinary skill in the art. During print operations, the print carriage  12  typically continuously travels in a lateral direction  16 , first accelerating to the left, then momentarily coming to rest upon reaching the left-most position  18 , then accelerating to the right, then momentarily coming to rest upon reaching the right-most position  20 . This motion is repeated during the print operations. Thus, the print carriage  12  is constantly experiencing acceleration as it accelerates across the page along directional axis  16  and reverses direction at the axis endpoints  18  and  20 .  
         [0020]     As shown by  FIGS. 2-4 , exemplary embodiments of the present invention employ a displacement-type ink pump  30  that is located on the print carriage  12 . The ink pump  30  is driven by the motion of an inertial mass or pendulum  32  in reaction to the acceleration of the print carriage  12  to which the pendulum  32  and its ink pump  30  are coupled. In a first exemplary embodiment, the ink pump  30  is a diaphragm-type pump, wherein a displacement volume  34  is partially enclosed by a flexible diaphragm  36 . The diaphragm  36  is actuated by a piston or slider  38 , which is mechanically coupled to the pendulum  32  by means of a lever mechanism that generates a mechanical advantage, thus increasing the force applied to the diaphragm as will be described in further detail below.  
         [0021]     The pump  30  includes a displacement volume housing  40  having a chamber  42  formed therein that is capped by the domed diaphragm  36 , carried on a diaphragm plate  37 , to provide the displacement volume  34 . The chamber  42  includes an ink inlet  44  and an ink outlet  46  extending out through an outer end  48  of the displacement volume housing  40 , where the outer end  48  receives a valve plate  50 , which includes an inlet reed valve  52  in fluid communication with the ink inlet  44  of the chamber  42  and an outlet reed valve  54  in fluid communication with the ink outlet  46  of the chamber. An end cap  56  is attached to the valve plate  50  and includes a pump inlet  58  in fluid communication with the inlet reed valve  52  and a pump outlet  60  in fluid communication with the outlet reed valve  54 .  
         [0022]     The opposite end of the pump  30  includes a driver housing  62  containing the pump driver assembly  64 , which drives the operation of the pump by activating the actuator/diaphragm  36  in reaction to lateral movement (illustrated by arrow  16 ) of the print carriage to which the pump  30  is attached. The driver housing  62  includes an elongated passage  66  extending perpendicular to the diaphragm  36  within which a piston or slider  38  reciprocates to continuously compress and release (i.e., activate) the diaphragm, which in turn causes ink to flow through the pump  30  as will be described in greater detail below. The pendulum  32  is pivotally coupled to the driver housing  62  below the slider  38  by a pivot pin  70 , which extends through a bearing hole  71  in the pendulum  32 , such that the pendulum  32  swings in the opposite direction that the print carriage  12  moves. In other words, the pendulum  32  swings on an axis extending substantially perpendicular to the direction  16  of carriage travel. The pendulum  32  includes an inertial mass arm  72  extending below the pivot pin  70  (and below the driver housing  62 ) and includes a follower arm  74  extending above the pivot pin and into a slot provided in the bottom of the slider  38 , where it is pivotally coupled to the slider  38  by a cylindrical boss  76  on the inertial mass arm that is received within a bearing seat in the slider  38 . The inertial mass arm  72  of the pendulum includes a relatively large cylindrical mass  78  provided thereon to provide most of the inertial mass for the inertial mass arm  72 .  
         [0023]     Specific dimensions and associated design data of this exemplary embodiment are provided (for illustration purposes only, and without intending to be limited thereto) as follows:  
                                       Carrier Acceleration   1 g (386 in/sec 2 )       Min Travel   (accel or decal) 10.8 mm           (0 to 18.1 to 0 in/sec; 0.0938 sec accel/decel)       Pendulum Mass   11.99 gm       Pendulum/Slide Ratio   3.93/1 (8.84/2.5)       Slide Force   47.12 gmf       Slide Stroke   3.0 mm       Diaphragm Area   19.63 mm 2         Displacement Volume   0.0318 cm 3         Design Pressure   2.5 psi       Ideal Max Flow Rate   0.339 cm 3 /sec                  
 
         [0024]     In alternate embodiments the Pendulum Mass has a mass of approximately 2 grams to approximately 200 grams; and the Pendulum/Slide Ratio is between approximately 0.5 and approximately 10 to one.  
         [0025]     An equation that may be used to determine certain dimensions and values for the pump is provided as follows:  
               P   ⁢     Q   Sq       =     k   ×   Mi   ×   A             Eq   .           ⁢   1             
 
 where, 
        S M  Stroke of the Inertial Mass     k Mechanical Advantage or (S M /S Q )     M i  Inertial Mass     a Acceleration     Q Pump Volume Displacement     P Pressure     A Displacement Area     S Q  Stoke of the Displacement Area     d Displacement Diameter        
 
         [0035]     Usually values of P, a, M i , and S M  are chosen first, and the equation is solved for the needed mechanical advantage k.  
         [0036]     Additionally the following equations are utilized:  
         [0037]     The diameter equation:  
             d   =         4   ×   4     π               Eq   .           ⁢   2             
 
         [0038]     The mechanical advantage definition:  
             k   =       S   M       S   Q               Eq   .           ⁢   3             
 
         [0039]     In the exemplary embodiment, when the pump  30  is coupled to an associated print head on the print carriage  12 , an ink supply is coupled to the pump inlet  58  with a supply line tube and the pump outlet  60  is connected to an accumulator &amp; vent tank by an output supply tube. The accumulator serves as a small reservoir of ink feeding a pressure regulator in the print head. The regulator serves to reduce the positive ink supply pressure to the negative (back pressure) pressure just above the print head&#39;s ejection nozzles.  
         [0040]     Referring to  FIGS. 3 and 4 , to explain the operations of the pump, the ink pump  30  would be attached to the print carriage  12  in a manner so that the pendulum  32  would be free to swing on the pivot pin  70  as the print carrier  12  moves in the direction of the carrier travel  16 . When the print carriage  12  accelerates to the right, inertia will cause the inertial mass arm  72  to swing to the left (in the opposite direction), swinging from position A to position B. This motion of the pendulum  32  causes the slider  38  to slide to the right proportionally with respect to the relative arm lengths of the pendulum  32 . For the exemplary embodiment shown, the pendulum  32  would be displaced 10.8 mm to the left, causing the slider  38  to displace 3 mm to the right. The slider  38  contacts and compresses the dome of the diaphragm  36 , and the described displacement reduces the displacement volume  34 , thus expelling ink from that volume out through the ink outlet  46 , reed valve  54  and pump outlet  60 . On reversal of carrier acceleration (movement to the left), inertial will cause the inertial mass arm  72  to swing to the right, swinging from position B to position A. This motion of the pendulum  32  causes the slider  38  to slide to the left proportionally away from the diaphragm  36 , allowing the displacement volume  34  to be returned to the original state. In this return motion, the resulting suction will pull ink through the pump inlet  58 , reed valve  52  and ink inlet  44  to refill the displacement volume  34  with ink.  
         [0041]     Thus, for a design pressure of 2.5 psi with a displacement of 0.032 cc&#39;s, the exemplary embodiment inertial mass pump  30  weighs only approximately 18 gms. In comparison to the inertial mass pumps of the prior art, which would have weighed approximately 40 to 50 gms for the same performance, the advantage of the present invention is clear. An additional advantage of the exemplary embodiment of the inertial mass pump  30  the pump  30  is relatively small such that multiple pumps can easily be incorporated into a printer&#39;s carriage as described and illustrated below. Additionally, the exemplary embodiment of the pump  30  requires virtually no control system. When the print carriage is in motion the pump is supplying ink, and when not in motion the pump is not supplying ink. The exemplary embodiment is also self pressure limiting in that the maximum pressure is limited to that of the acceleration of the carrier.  
         [0042]     As shown in  FIG. 5 , the compact size that may be achieved using the exemplary embodiment of this invention enables multiple ink pumps  30  to be fitted to a single print carriage  80 , thus allowing the use of multiple ink systems for color printing. The printer  81  shown in  FIG. 5  contains four ink supply tanks  82 , one for each ink color (K, C, M, Y), stored in a fixed location within the printer housing  84 . The ink supply tanks  82  are respectively connected to pump inlets  58  (not shown in  FIG. 5 ) of each of the four pumps  30  mounted on the print carriage  80  by means of a flexible tubing  86 . The print carriage  80  seats a pair of print heads, a tri-color print head  88  coupled to the C, M &amp; Y pumps  30  and a mono print head  90  coupled to the K pump  30 , for printing upon the print medium  92  as the print carriage is driven laterally along the print medium  92 .  
         [0043]     Following from the above description and invention summaries, it should be apparent to those of ordinary skill in the art that, while the apparatuses and methods herein described constitute exemplary embodiments of the present invention, the inventions contained herein are not limited to these precise embodiments and that changes may be made to them without departing from the scope of the inventions as defined by the claims. For example, as will be appreciated by those of ordinary skill in the art, it is within the scope of the invention that the pump be a different type of displacement pump such as a bellows pump or a piston type pump. With such alternate pumps, the inertial mass would be coupled to the pump actuator by a mechanical linkage, such as a lever mechanism as described above, that provides a mechanical advantage. It is also within the scope of the invention that, as will be appreciated by those of ordinary skill in the art, alternate mechanical linkages providing a mechanical advantage may be utilized such as a gear system, a cam system or any other known mechanical advantage linkage. Further, with the multiple pump embodiments (such as shown and described in  FIG. 5 ) it is within the scope of the invention that a single pendulum (or any other mechanical advantage linkage) is coupled to, and drives more than one pump.  
         [0044]     It will also be appreciated by those of ordinary skill that while the exemplary embodiments described and illustrated herein have the inertial mass arm  72  extending below the pump and printer carriage, it is within the scope of the invention that the inertial mass arm extends or resides in other orientations or positions. The pendulum will operate in any orientation so long as the pivot axis is sufficiently perpendicular to the direction of carriage acceleration so as to experience the responsive movements to acceleration described herein. The exemplary embodiments have the inertial mass arm hanging below the pivot axis, but embodiments of the invention works sufficiently well with the inertial mass arm hung at angles, sideways, and even upside-down.  
         [0045]     It will be further appreciated by those of ordinary skill that the slider  38  can also be coupled to the inertial mass arm  72  rather than to the follow arm (i.e., the slider  38  place on the same side of the pivot), by pivotally coupling the slider  38  to the inertial mass arm at a point closer to the pivot  70  than the inertial mass  78 .  
         [0046]     Additionally, it is to be understood that the invention is defined by the claims and it not intended that any limitations or elements describing the exemplary embodiments set forth herein are to be incorporated into the meanings of the claims unless such limitations or elements are explicitly listed in the claims. Likewise, it is to be understood that it is not necessary to meet any or all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of any claims, since the invention is defined by the claims and since inherent and/or unforeseen advantages of the present invention may exist even though they may not have been explicitly discussed herein.