Patent Publication Number: US-6982737-B2

Title: Printing method and apparatus

Description:
BACKGROUND OF INVENTION 
   Portable printing or writing devices, and more specifically, portable printing devices used in the medical field are known. Typically, portable printing devices are integrated in, or otherwise attached to portable medical devices used to monitor patient data, such as heart rate, blood pressure, blood oxygenation, respiration, brain activity, and the like. The printing devices enable the physician, nurse, medical technician or other healthcare worker (collectively “clinician”) to print a hard copy of the patient data, which can be useful in studying and documenting changes in the patient&#39;s condition. 
   SUMMARY OF INVENTION 
   While it is desirable to reduce the size of portable medical components (e.g., electrocardiograph (ECG) units, defibrillators, monitors, and the like) there is a concern that reductions in printer size will hinder, and perhaps even impair the clinician&#39;s ability to quickly and accurately assess the printed patient data. A better understanding of this dilemma can be illustrated with the following example. 
   ECG units often include integral printers capable of printing data on standard 8.5×11 inch paper. The ECG output or report is typically printed in landscape format and includes textual patient data on the top one-third to one-fourth of the page and one or more waveforms (corresponding to measured patient data) on the bottom two-thirds to three-fourths of the page. The paper is often continuously supplied from a continuous fan-folded supply or a roll. Individual cut sheets can also be used. 
   In an effort to make portable ECG units smaller, and therefore more portable, the standard integral printers are sometimes replaced with smaller printers capable of printing on narrower strips of paper. These narrower strips are usually approximately four-and-one-quarter inches wide. Because it is not practical to simply reduce the size of the standard ECG report to fit on this narrower paper (from a practical standpoint, the smaller printout would be difficult and awkward to read, and from a technical standpoint, the standard waveform orientation produced by a 12-lead ECG unit would become severely distorted), it has been known to print the ECG report in halves. The first half printed includes the textual patient data and at least one waveform, both of which are normally found on the top half of a standard 8.5 inch wide report. The second half printed includes the remaining waveforms, which are normally found on the bottom half of a standard 8.5 inch wide report. Because the report must be printed in halves, the print time is double that of the print time for a standard 8.5×11 report. 
   After both halves have been printed, the health care provider must cut or tear the strip of paper between the first and second printed halves and realign the halves vertically (i.e., relative to a vertical reference line) to observe the time correlation of the data. This tearing and realigning process is burdensome and inaccurate and often involves taping or otherwise fastening the halves together. In yet another step, the two-piece report might be mounted on a separate backing. 
   The present invention overcomes this and other problems by providing an improved printing method and apparatus that promotes the use of smaller, more portable printing devices without sacrificing the speed, readability, or accuracy of the printout. More specifically, the invention provides a method of printing including passing a medium through a printing device and printing on oppositely facing portions of the medium during a single pass of the medium through the printing device. Preferably, printing on oppositely facing portions includes printing on one portion with a first print head and printing on the other portion with a second print head. 
   In one aspect of the invention, the medium is folded so that after the printing is completed and the folded medium is unfolded, the printed information on one portion of the medium correlates with the printed information on the other portion of the medium. In one embodiment, the printed information is data that has been measured with respect to time, and the printed data on the oppositely facing portions correlate with respect to time. Preferably, the data is medical patient data in the form of textual data, physiological waveforms, or a combination of both. 
   The invention also provides a printing device for printing on oppositely facing portions of a medium in a single pass. The printing device includes a feed path for receiving the medium, a first print head adjacent a first side of the feed path, and a second print head adjacent a second side of the feed path. In one embodiment, the print heads are thermal print heads. 
   In one aspect of the invention, the medium is folded and the feed path is sized to receive the folded medium. When folded, the medium is preferably approximately four to six inches wide. The feed path can include a separation member positioned between the oppositely facing portions of the folded medium. The first print head is configured to print data in a first orientation and the second print head is configured to print data in a second orientation. After printing, the medium can be unfolded and the data printed by the first print head correlates with the data printed by the second print head. 
   In another aspect of the invention, the printing device is coupled to a piece of medical equipment, such as an ECG unit, a defibrillator, a monitor, or the like. Data collected by the medical device, including physiological waveforms, can be printed by the printing device. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is perspective view of a device embodying the invention. 
       FIG. 2  is a perspective view of a print head arrangement with parts removed for ease of illustration. 
       FIG. 3  is a section view taken along line  3 — 3  of FIG.  2 . 
       FIG. 4  is a section view similar to  FIG. 3  of an alternative embodiment of the invention having a separation member between the print heads. 
       FIG. 5  is a perspective view similar to  FIG. 2  showing an alternative print head configuration and paper supply. 
   

   DETAILED DESCRIPTION 
   Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
     FIG. 1  illustrates a device  10  embodying the invention. In the illustrated embodiment, the device  10  is a portable 12-lead ECG unit, however, the device  10  could be any type of device (medical or non-medical, portable or stationary) used to print data. The device  10  includes a processor  14  (shown schematically in  FIG. 1 ) that processes physiological data collected from a patient (not shown) via leads  18 , as is commonly known in the art. The device  10  also includes an input device in the form of a keyboard  22 . The keyboard  22  is used to input textual patient information such as the patient&#39;s name, age, sex, height, weight, and the like. A visual display  26  is located adjacent the keyboard  22  and, among other things, facilitates the input of patient information. 
   The device  10  also includes an integral printing device  30  coupled to the processor  14  through a standard electronic communication link (not shown). The printing device  30  prints the physiological patient data and the textual patient information onto a printable medium, such as paper  34 . Of course, the printing device  30  need not be integral with the device  10 , but could be a separate unit coupled to the device  10  and the processor  14  via suitable connectors. The printing device  30  includes paper feed rollers  38  (shown in phantom in  FIG. 1 ) or other suitable members that advance the paper  34  through the printing device  30 . In the embodiment illustrated in  FIGS. 1-4 , the paper  34  is supplied from a roll  42 , however, as will be described in more detail below, the paper  34  could also be supplied from a fan-folded stack or individual sheets as shown in  FIG. 5. A  hinged panel  46  on the device  10  provides access to the printing device  30  and the roll  42 . 
   As seen in  FIGS. 1-5 , the printing device  30  includes first and second print heads  50  and  54 , respectively. The print heads  50 ,  54  oppose one another and are spaced apart to define a feed path  58  through which the paper  34  advances during printing. Paper is advanced from the roll  42  by the feed rollers  38 , passes through the feed path  58 , and exits the device  10  through an aperture  62 . While the print heads  50 ,  54  are shown to extend substantially horizontally inside the device  10 , it is understood that the print heads  50 ,  54  could alternatively extend substantially vertically inside the device  10 . Of course, if the orientation of the print heads  50 ,  54  is changed, the orientation of the feed rollers  38 , the roll  42 , and the aperture  62  may also be changed. In the preferred embodiment, the print heads  50 ,  54  are thermal print heads that print on thermally-sensitive paper, as is commonly known in the art, and the paper  34  is thermally-sensitive paper. Of course, other types of print heads, such as ink jet, ink pen, or laser print heads could also be used, in which case, the paper  34  need not be thermally-sensitive paper. 
   As best seen in  FIGS. 1-3 , the paper  34  is folded in half on the roll  42  and defines oppositely facing portions  66  and  70 . In the illustrated embodiment, each oppositely facing portion  66  and  70  is between four and six inches wide and is preferably approximately four-and-one-quarter inches wide, so that when the paper  34  is unfolded (see FIG.  1 ), the printed report is in a standard eight-and-one-half inch wide format. The print heads  50 ,  54  and the feed path  58 , are appropriately sized (approximately four to six inches wide) to accommodate the folded paper  34 . As the paper  34  is fed through the feed path  58 , the print head  50  prints an image in a first orientation on the first oppositely facing portion  66  and the print head  54  prints an image in a second orientation on the second oppositely facing portion  70 . The first and second image orientations are such that when the paper  34  is unfolded, the first and second images have the same orientation, as will be described in more detail below. 
   While it is not necessary that the printing device  30  print on folded paper  34  as shown, the folded paper  34  provides the advantages discussed above when the printing device  30  is used in conjunction with the ECG device  10  or other medical devices. As described above, the ECG device  10  monitors patient physiological data that is gathered as a function of time. The physiological data is printed on the report in the form of a plurality of printed waveforms  74  (see FIGS.  1  and  2 ). In addition to the waveforms  74 , the patient textual information is also printed on the report in text blocks  78  (see FIGS.  1  and  2 ). It is to be understood that the number and configuration of waveforms  74  and text blocks  78  shown in the figures are for purposes of illustration only, and can vary according to the specific application and device. As best seen in  FIG. 2 , the print head  50  prints the text blocks  78  and a plurality of waveforms  74  on the oppositely facing portion  66 . At the same time, the print head  54  prints additional waveforms  74  on the oppositely facing portion  70 . Of course, the particular information printed by each of the print heads  50 ,  54  could be reversed so that the print head  54  prints the text blocks  78 . This simultaneous double-sided printing allows a complete, standard ECG report to be printed on the oppositely facing portions  66  and  70  in a single pass through the printing device  30 . After printing, the paper  34  is unfolded to yield the full ECG report. No extra cutting, tearing, taping, or mounting is required. 
   The paper  34  preferably includes a background grid  82  (only partially shown in  FIGS. 1 and 2 ) that quantifies the waveforms with respect to time in a “x” or horizontal direction, and magnitude in a “y” or vertical direction. The print heads  50 ,  54  print on the oppositely facing portions  66 ,  70  such that the waveforms  74  printed on the portion  66  correlate with the waveforms  74  printed on the portion  70 . This correlation is best illustrated in FIG.  1 . In  FIG. 1 , an axis x′ is shown with respect to the unfolded paper  34 . The axis x′ represents one instant in time “t” during which physiological data was gathered by the ECG device  10 . Each of the vertically-spaced waveforms  74  is aligned horizontally relative to the axis x′ at time “t” such that all data collected during the time “t” is printed on the axis x′. In other words, the waveforms  74  are printed on both the oppositely facing portions  66  and  70  such that all of the waveforms  74  correlate with respect to time. 
   The waveforms  74  are also correlated with respect to magnitude such that when the paper  34  is unfolded, each of the waveforms  74  depicts a positive change in magnitude in an upward direction (as seen in  FIG. 1 ) and a negative change in magnitude in a downward direction. To achieve this magnitude correlation, it is understood that during printing, the print head  50  prints waveforms  74  in a first orientation (positive magnitude to the right as viewed in  FIG. 3 ) and the print head  54  prints waveforms  74  in an opposite, second orientation (positive magnitude to the left as viewed in FIG.  3 ). 
   Because of the heat produced by the opposing print heads  50 ,  54 , it may be helpful to include a separation member  86  (see  FIG. 4 ) positioned in the feed path  58  between the oppositely facing portions  66  and  70 . The separation member  86  provides a thermal barrier between the oppositely facing portions  66  and  70  so that heat generated by the print head  50  does not obscure the printed information on the oppositely facing portion  70 . Likewise, the separation member  86  prevents heat generated by the print head  54  from obscuring the printed information on the oppositely facing portion  66 . The separation member  86  can be made of any suitable material capable of absorbing or dissipating heat. Of course, the separation member  86  need not be used if the printed information on the oppositely facing portions  66  and  70  is not obscured by the opposed print heads  50 ,  54 . 
     FIG. 5  illustrates an alternative print head configuration wherein the print heads  50 ′ and  54 ′ are laterally offset instead of being directly opposite one another as seen in  FIGS. 1-4 . The lateral offset may occur due to space constraints within the device  10  or due to the particular configuration of the printing device  30 . While not shown, additional backing plates may be needed opposite each print head  50 ′,  54 ′ to maintain contact between the paper  34  and the print heads  50 ′,  54 ′ as the paper passes through the feed path  58 ′. 
   In order to obtain the desired time correlation between all of the waveforms  74  when printing with the offset print heads  50 ′,  54 ′, a print delay is used. The print head  50 ′ prints data collected for a given time “t” on the oppositely facing portion  66  before the print head  54 ′ prints the correlating data for the given time “t” on the oppositely facing portion  70 . The delay can be controlled by the processor  14  to achieve the properly correlated waveforms  74 . Even with the above-described print delay, the full ECG report is still printed in a single pass of the paper  34  through the printing device  30 . 
     FIG. 5  also illustrates an alternative paper feed configuration. As seen in  FIG. 5 , the paper  34 ′ is fed from a fan-folded stack  90 . The stack  90  can be stored inside or outside the device  10 . Once again, it is preferred that the paper  34 ′ in the fan-folded stack  90  is folded in half as described above. While not shown, it is understood that the paper  34  can also be supplied in individual folded sheets. It is also worth noting that the printing device  30  could include a folding fixture or guide (not shown) that folds the paper  34  before the paper  34  enters the feed path  58 . Such a folding fixture would eliminate the need to supply pre-folded paper from a roll, a fan-folded stack, or an individual sheet. Of course, a folding fixture would likely require additional space, resulting in a less-compact printing device  30 . 
   Regardless of the type of paper supply used, the method of printing the medical data collected by the processor  14  includes passing the folded paper  34  through the feed path  58  such that the first thermal print head  50  prints information (including at least one waveform  74 ) on the oppositely facing portion  66  and the second thermal print head  54  prints information (including at least one waveform  74 ) on the oppositely facing portion  70 . Both print heads  50 ,  54  print substantially simultaneously such that a full ECG report is printed in a single pass of the paper  34  through the printing device  30 . Even when the offset print heads  50 ′,  54 ′ are used (see FIG.  5 ), the ECG report is printed during a single pass of the paper  34  through the printing device  30 . The printing delay operates to correlate the data with respect to time. 
   When the paper  34  is unfolded, the waveforms  74  printed on the oppositely facing portions  66 ,  70  are correlated with each other and with respect to time. The text blocks  78  are also oriented properly with respect to the waveforms  74 . The compact printing device  30  thereby generates a ECG report that can be quickly and accurately interpreted by the clinician. The disadvantages of prior art compact printers are overcome by the printing device  30 , without sacrificing size or portability. 
   Other features and advantages of the invention are set forth in the following claims.