Patent Publication Number: US-7213987-B2

Title: Synchronization method and apparatus in a value metering system having a digital print head

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to a value metering system and, more particularly, to a postage meter having a digital print head to print a pattern of substrates one line at a time. 
   BACKGROUND OF THE INVENTION 
   Manually-activated postage meters are well-known in the art. Typically, an envelope or a tape is manually fed under a print head for printing an indicium thereon. The print head is fixedly mounted in the postage meter, and a sensing device is used to sense the presence of the envelope under the print head. In order to print the indicium with minimum distortion, the speed of the envelope must be controlled to match the print speed of the print head. Thus, some mechanism must be used to synchronize the movement of the envelope to the print head. U.S. Pat. No. 4,168,533 (Schwartz) discloses a micro-computerized miniature postage meter, wherein a microcomputer is used to actuate an inkjet printing device to project ink droplets onto a substrate moving relative to the printing device. In particular, the movement of the printing device relative to the substrate is detected by an encoded rotating wheel mounted on the lower contact surface of the printing device. The rotating wheel is coupled to an interrupter disc, which is adapted to provide signal pulses for coordinating the proper time for actuating of the printing device. With such a design, the postage meter becomes costly to produce and to sell. 
   Thus, it is advantageous and desirable to provide a simple synchronization method and apparatus for use in a value metering system, such as a postage meter. 
   SUMMARY OF THE INVENTION 
   The first aspect of the present invention is an apparatus for achieving synchronization in a value metering system. In particular, the value metering system uses a digital print head capable of printing a plurality of printed lines on a substrate, which is displaced relative to the print head in a moving direction, wherein the lines are substantially perpendicular to the moving direction, and a first signal is provided after a line is printed. The apparatus comprises: 
   a first mechanism operable at a first position to restrict the displacement of the substrate and a second position to effectively disengage from the substrate, wherein the first mechanism is operated at the first position while the print head is printing a line; and 
   a second mechanism, responsive to the first signal, for causing the first mechanism to operate at the second position, thereby allowing the displacement of the substrate by a predetermined distance relative to the print head for printing a next line. 
   Preferably, the apparatus further comprises a third mechanism, responsive to the displacement of the substrate, for providing a second signal, indicative of the displacement of the substrate by the predetermined distance for causing the print head to print the next line. The third mechanism can be an optical sensor, a mechanical sensor, or the like. 
   Preferably, a third signal, indicative of a last printed line, is provided for preventing the first mechanism from further operating at the first position after the last line is printed. 
   Preferably, the substrate is manually displaced, but it is possible that the substrate is displaced by a movement device. 
   The second aspect of the present invention is a method of achieving synchronization in a value metering system using a digital print head capable of printing a plurality of lines, one line at a time, on a substrate which is displaced in a moving direction relative to the print head, wherein the lines are substantially perpendicular to the moving direction. The method comprises the steps of: 
   engaging the substrate with a first mechanism capable of restricting the displacement of the substrate while the print head is printing a line; 
   providing a first signal indicating said line is printed; 
   disengaging the first mechanism from the substrate in response to the first signal; and 
   displacing the substrate by a predetermined distance for printing a next line. 
   Preferably, the method further comprises the step of providing a second signal indicative of the displacement of the substrate by the predetermined distance for causing the print head to print the next line, wherein the predetermined distance is substantially equal to the width of the lines or proportional to the width of the lines. 
   Preferably, the method further comprises the step of preventing the first mechanism from further restricting the displacement of the substrate after a last line is printed. 
   The third aspect of the present invention is a value metering system for printing a substrate. The value metering system comprises: 
   a digital print head capable of printing a plurality of lines, one line at a time, on the substrate, wherein the substrate is displaced relative to the print head in a moving direction; 
   a first mechanism capable of operating at a first position to restrict the displacement of the substrate and a second position to disengage from the substrate, wherein the first mechanism is operating at the first position when the print head prints a line; 
   a second mechanism, responsive to said printing, for providing a first signal indicating said line is printed; and 
   a third mechanism, responsive to the first signal, for causing the first mechanism to operate at a second position, thereby allowing the displacement of the substrate by a predetermined distance for printing a next line. 
   Preferably, the value metering system also includes a fourth mechanism, responsive to the displacement of the substrate by the predetermined distance, for causing the print head to print the next line. 
   Preferably, the value metering system also includes a fifth mechanism, operatively connected to the print head for preventing the first mechanism from further operating at the first position after a last line is printed. 
   The value metering system can be a countertop system or a hand-held system. 
   It is possible that the substrate is manually displaced, but it is also possible that the substrate is displaced by a movement device. 
   The present invention will become apparent upon reading the description taken in conjunction with  FIGS. 1 to 7 . 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatic representation illustrating the principle of synchronizing the printing speed of a print head and the displacement of a substrate to be printed, according to the present invention. 
       FIG. 2  is a diagrammatic representation illustrating a postage indicium and a print line on substrate. 
       FIG. 3  is a diagrammatic representation illustrating a hand-held postage meter. 
       FIG. 4  is a diagrammatic representation illustrating a manually activated postage meter, wherein the substrate is manually displaced relative to the print head. 
       FIG. 5   a  is an isometric representation of an exemplary apparatus for synchronizing the print speed and the manual displacement of the substrate. 
       FIG. 5   b  is a side view of the same apparatus. 
       FIG. 5   c  is a side view of the same apparatus showing a substrate being fed into the print zone. 
       FIG. 5   d  is a side view showing the substrate being moved forward relative to the print head. 
       FIGS. 6   a – 6   g  are timing diagrams illustrating the time relationship between the print head, the movement restraining mechanism, and the displacement of the substrate. 
       FIG. 7  is a flow chart illustrating the method of synchronizing the print speed and the movement of the substrate, according to the present invention. 
   

   DETAILED DESCRIPTION 
   The general principle of synchronizing the print speed and the movement of the substrate, according to the present invention, is shown in  FIG. 1 . As shown, synchronization system  1  includes mainly four components: print head  2 , print-head control  4 , movement restraining means  6  and sensor  8 . System  1  can be used on a variety of value metering systems for synchronization. In particular,  FIG. 1  shows a postage meter for printing text or images on a mailpiece, which is herein referred to as a substrate. However, the value metering system can be a ticket printer to produce tickets for a concert, for a sporting event, or other gathering. The value metering system can also be used to print coupons or other value-redeemable items. Basically, movement restraining means  6  is used to restrict the movement of substrate  100 , such as an envelope or a tape, to be printed by print head  2  at print zone  12  in postage meter. The movement of substrate  100  is relative to print head  2  and is denoted by arrow  110 . Thus, print head  2  can be located at a fixed location in the postage meter, and substrate  100  is advanced along direction  110 , as in a desk-top postage meter. It is also possible to move print head  2  against a stationary substrate  100  in a direction opposite to the arrow  110  (see  FIG. 3 ), as in a hand-held postage meter. It is understood that print head  2 , under the control of print head control  4 , is capable of printing a plurality of lines, one or more lines at a time. The printed lines are substantially perpendicular to moving direction  100 , as shown in  FIG. 2 . The movement of substrate  100  is restricted during the printing of line  82  in indicium  80  or in other image or text by print head  2 . After a line is printed, print head control  4  sends signal  102  to release movement restraining means  6 , allowing substrate  100  to advance to the next print line position. After substrate  100  is moved to the next print line position, sensor  8  sends a signal  104  to movement restraining means  6  and print head control  4 . Responsive to signal  104 , movement restraining means  4  again restricts movement of substrate  100 , and print head control  4  signals print head  2  to print a new line, until last line  84  is printed. It should be understood that print head  2  can also be used to print return address  90 , mailing address  92  and message  94 , as shown in  FIG. 2 . 
     FIG. 3  is a diagrammatic representation illustrating hand-held postage meter  20 . As shown, hand-held postage meter  20  has housing  22  to include the components for printing indicium  80  or other text or image on substrate  100 , and the components for assisting or restricting the movement of postage meter  20  against substrate  100 . As shown, housing  22  includes user interface section  24  for allowing a user to specify the data to be printed and to start the printing process. User interface section  24  is operatively connected to print head control  4  for conveying data thereto. Movement restraining means  6  is operatively engaged with latch  26 , which is capable of stopping gear  28  from turning. A plurality of rollers  34 ,  36  is used to assist the movement of postage meter  20  long direction  111 . Roller  34  is mechanically coupled to gear  30  via pulley system  32  and gear  30  is mechanically engaged with gear  28 . It is understood that when a user presses down postage meter  20  against substrate  100  while the user moves postage meter  20  along direction  111 , roller  34  rotates. Accordingly, gears  28 ,  30  also rotate if latch  26  is not restricting the rotation of gear  28 . Sensor  8 , which can be an optical interrupter, a mechanical switch, or the like, is used to sense the relative displacement of postage meter  20  to substrate  100 . For example, sensor  8  can be arranged to sense the movement of the teeth of gear  30  such that when the rotation of roller  34  is equal to the width of one printed line by print head  2 , sensor  8  sends signal  104  to movement restraining means  6 . Movement restraining means  6  can include, for example, a push-pull solenoid, which pushes down latch  26  to restrict the movement of gear  28  upon receiving signal  104 . The engagement of latch to gear  28  is released after a new line is printed by print head  2 , as indicated in signal  102  sent by print head control  4 . 
     FIG. 4  is a diagrammatic representation of manually activated postage meter  40 , wherein substrate  100  is manually displaced relative to print head  2  along direction  110 . As shown, postage meter  40  includes frame  41  to support upper body  42  and lower body  44 . Similar to housing  22  of hand-held postage meter  20 , as shown in  FIG. 4 , upper body  42  includes user interface section  24 , print head  2 , print head control  4 , movement restraining means  6  and sensor  8 . The function of the components in upper body  42  is also similar to the function of the components in housing  22 , except that movement restraining means  6  in upper body  42  is used to restrict the movement of lower body  44  relative to upper body  42 . Preferably, upper body  42  is fixedly mounted to frame  41  and lower body  44  is movably mounted to frame  41 . Lower body  44  has registration wall  46 , which defines the point where print head  2  starts printing on substrate  100 . Lower body  44  further comprises supporting surface  48  to support substrate  100  as substrate  100  is moved into lower body  44 . Preferably, substrate  100  is secured or trapped in lower body  44  after it reaches registration wall  46 . Subsequently, a user can move lower body  44  along with substrate  100  along direction  110 . Sensor  8 , in cooperation with movement restraining means  6 , restricts the movement of lower body  44  such that lower body  44  is allowed to move by a distance substantially equal to the width of one print line  82  ( FIG. 2 ) after each line is printed. The restriction is removed after last line  84  ( FIG. 2 ) is printed. 
   An exemplary design of the manually activated postage meter is shown in  FIGS. 5   a  to  5   d . As shown in  FIGS. 5   a  and  5   b , postage meter  130  has frame  134  for fixedly mounting upper body  140 , and movably mounting lower body  160  so as to allow lower body  160  to move relative to upper body  140  along direction  110 . Upper body  140  includes control box  142  for housing a plurality of components, which are not shown, including print head  2 , print head control  4 , movement restraining means  6 , and sensor  8 . Movement restraining means  6  is operatively engaged with latching device  144 , which is capable of stopping gear  146  from moving when latching device  144  is lodged between two of the teeth  148 . Upper body  140  has plate  150 , which is connected to a locking mechanism  154 , for fixedly mounting to frame  134 . Plate  150  also has restricting end piece  152 . The lower body  160  has inner wall  162  movably mounted to frame  134  for linear motion along direction  110 . Lower body  160  further includes lower frame  170 , which is fixedly mounted to inner wall  162 , and upper plate  164  extended from inner wall  162 . Lower frame  170  includes a number of shafts  172  for rotatably mounting plurality of roller supports  174 . Number of rollers  176  are rotatably mounted on roller supports  174 . Rollers  176  allow substrate  100  to be fed into lower body  160  between upper plate  164  and rollers  176 , as shown in  FIG. 5   c . Upper plate  164  also has end structure  168  fixedly mounted thereon. End block  165  has vertical wall  166  to serve as a registration wall, which stops substrate  100  when substrate  110  is fed into lower body  160  for printing. As shown in  FIG. 5   a , upper plate  164  has opening  180 , allowing print head  2  (not shown) inside control box  142  to print indicium  80  or other image or text on substrate  100 . Once substrate  100  is properly fed into lower body  160 , the user can move lower body  160  along with substrate  100  along direction  110  for printing. Preferably, roller supports  174  are spring-loaded to provide an upward urging force against substrate  100  for securing substrate  100  between upper plate  164  and rollers  174 . The user can push lower body  160  using end structure  168  for moving lower body  160 . After the printing is completed, lower body  160  is moved over a certain distance along direction  110 , as shown in  FIG. 5   d . Preferably, end block  165  is movably mounted on end structure  168 . When the printing is completed, the end block can be moved upward so that substrate  100  can be retrieved from the front end of lower body  160 . However, before the printing is completed, restricting end piece  152  prevents end block  165  from being completely displaced upward, as shown in  FIGS. 5   a – 5   c.    
     FIGS. 6   a – 6   f are timing diagrams illustrating the time relationship between the print head, the print-head control, the movement restraining means and the sensor in a postage meter, with reference to time axis T, as shown in  FIG. 6   g . As shown in  FIG. 6   a , timing sequence  302  represents the print signal of the postage meter. The printing signal enables the print head at t=t 0  after a substrate is properly fed into the postage meter (see  FIG. 5   c , for example). From t 0  to t 2 , the print head prints a line on the substrate, as represented by the first pulse on time sequence  304 , as shown in  FIG. 6   b . At the end of the line, the print head control conveys a signal to the movement restraining means, as indicated by the first pulse in time sequence  306  between t 1  and t 2 , as shown in  FIG. 6   c . When print head  2  is printing, the movement restraining means is activated, as indicated by the first pulse on time sequence  310  starting at t=t 0 , as shown in  FIG. 6   e . The movement restraining means is deactivated at t 2 . Once the movement restraining means is deactivated, the substrate is allowed to move relative to the print head by a distance substantially equal to the width of a printed line. By then, the sensor activates the movement restraining means, as indicated by the first pulse on time sequence  312  between t 3  and t 4 , as shown in  FIG. 6   f . Subsequently, the print head prints a new line starting at t 4 , as shown in time sequence  304 . The print cycle repeats until the last line is printed. The last line is printed by the print head from t n  to t n+2 , as shown on time sequence  304 . A last line signal, as shown in time sequence  308  of  FIG. 6   d , is provided to override the end of line signal (time sequence  306 ) between t n+1  and t n+2 . The movement restraining means is not activated again after the last line is printed. The system is reset after a new substrate is fed into the postage meter for printing. The last line signal puts an end to the printing process, as indicated by the negative-going edge at t n+2  on time sequence  302 . 
   The method of synchronizing the print speed of a digital print head and the relative movement of a substrate is illustrated in flow chart  200  of  FIG. 7 . As shown, the power switch of the postage meter is turned on at step  202 . The user is prompted to feed a substrate and to select or type in data for printing at step  204 . The print head is activated or enabled at step  206  and the movement restraining means is activated at step  208  to restrict the relative movement between the substrate and the print head. The print head starts printing a line at step  210 . When the printed line is completed, i.e., it is the end of the line, as shown at step  212 , the movement restraining means is deactivated at step  214 . The method will remain at step  212  if it is not the end of the line. If the printed line is not the last line in step  216 , the sensor activates the movement restraining means and determines at step  218  if it is at the next position. If it is not at the next position, it will remain in step  218 . If it is at the next position, it will go to step  208  to activate the movement restraint. If the printed line is the last line in step  216 , the user is prompted to feed a new substrate and to specify the data for printing the new substrate in step  204 . 
   It should be noted that lower body  160  of postage meter  130 , as shown in  FIGS. 5   a – 5   d , is designed to be manually advanced. However, lower body  160  can also be moved along direction  110  by a motor, or the like. Thus, the method and apparatus for synchronization, according to the present invention, are also applicable in a postage meter where a movement device is used to move the substrate or the print head. 
     FIGS. 1–6   g  have been described in regard to a postage meter. However, the synchronization method and apparatus of the present invention can be generally used in a value metering system. The value metering system can be a hand-held system, a counter-top system or other system. The value metering system can be used to print indicia on mailpieces, and can also be used to produce tickets, coupons and the like. 
   Thus, although the invention has been described with respect to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the spirit and scope of this invention.