GB2233282A

GB2233282A - Apparatus for printing postal address code markings

Info

Publication number: GB2233282A
Application number: GB8914838A
Authority: GB
Inventors: Edward Gordon Kenneth Agnew; Udo Horst Mohaupt; Oscar Gabriel Nespoli
Original assignee: Z Mark International Inc
Current assignee: Z Mark International Inc
Priority date: 1989-06-28
Filing date: 1989-06-28
Publication date: 1991-01-09
Also published as: GB2234712A; GB8914838D0; GB9014322D0; DE4020578A1; CA2019956A1; CA2019956C; GB2234712B; FR2649022A1

Abstract

The apparatus includes a conveyor track for passing window envelopes through a read station and a print station. At the read station, an optical sensor (40) reads printed marks signifying the postal code through the window, the information being passed to a computer. At the print station (75) fluorescent or other marks are placed on the envelope, as instructed by the computer. The passage of a mail piece is detected by photocells (24, 26) which switch on the reading function. As disclosed, the print station is composed of two dot matrix print heads (75) which are mutually staggered transversely and longitudinally of the document feed path, whereby full height bars of a bar code may be printed as respectively upper and lower portions by the print loads. <IMAGE>

Description

APPARATUS FOR PRINTING POSTAL CODE MARKINGS This Invention relates to the

printing of fluorescent and the like markings on envelopes..for use In automatic postal sorting and similar machinery.-

BACKGROUND TO THE INVENTION

It Is the practice of postal authorities to print roachine -readable markings on envelopes which pass through the postal system.. to signify a particular sorting or delivery code.

one common practice Is that at the sorting office the envelope passes through a station at which the envelope Is visually presented to a clerk; the clerk reads the postal code written by the sender on the outside of the envelope. and then presses the appropriate keys to print the fluorescent bare on the envelope. in the case of window envelopes,, the clerk reads (b ye) the postal code as written on the Item of correspondence that lies Inside the envelope,, and again presses the keys to print the fluorescent bars.

Thereafter. the fluorescent bare can be detected automatically; consequently., once the fluorescent bare have been printed on the envelope., the envelope need not be read. nor even looked at,, by post office personnel again until It Is actually delivered.

Fluorescent Ink, as opposed to ordinary ink., Is specified by most national Post offices for the markings that are to be detected automatically. to make sure that only the markings themselves are read by the automatic detectors. In practice, there Is generally no way in which spurious fluorescent markings could appear by accident, and be detected, on the envelopes. However.. some national Post Offices specify eg black Ink: In that case, In the invention, such Ink as Is specified would be used in place of the fluorescent ink.

The task of manually reading the postal codes. and manually keying-in the appropriate fluorescent markingsr Is tedious,, and requires a high degree of concentration on the part of the coding clerk. Equipment for the machine-reading of postal codes Is In common use.. at least where the codes are printed or typewritten. The equipment can respond to ordinary alpha-numeric characters,, or preferably to special machine -readable characters. degree of accuracy of such equipment however Is only fair,, and it Is stlU necessary to employ clerks to process the many "rejects" that the equipment cannot read.

With window envelopes. the problem of correctly detecting and reading the characters through the window Is worse.. and consequently the accuracy to be expected from the traditional equipment falls still further.

3 - it Is the high-volume user with which the Invention Is mainly concerned,, In which the user sends out e.g. a million items per month,, all of a similar nature. A typical example would be a bank which Issues credit card statements. A saving can be made In postal rates It the envelopes In which these statements are sent can be printed. Inhouse. with the external fluorescent bars.

The high-volume user,, for example a credit card company,. desires not to print up the envelope at the time the statement Is printed. The highvolume user prefers rather that the envelope be not unique to the particular statement.. since trying to keep the envelopes matched to the letters. especially when other enclosures are required to be Inserted into the envelopes In addition to the statements. would be a large administrative control problem. it Is preferred to make only the statement unique -- which leads to the use of window envelopes.

In most cases, It would not 11 icceptable for the fluorescent markings to be put on the statemento and then read through the window. To be acceptable to the sorting and handling machinery at the Post office,, the fluorescent markings must be on the outside of the envelope Itself.

Another reason against putting the fluorescent markings on the statements Is that the markings on the statements preferably should be In the same kind of Ink as that used for printing out the statements., which is.. usually,. ordinary black Ink. Even If fluorescent markings on the statements were acceptable,, It would hardly be more economical to print the statement itself with fluorescent markings,, In additon to ordinary black Ink printing.. than It Is to put the fluorescent markings on the envelopes. It should be understood. however. that the Invention Is not limited only to those cases where the markings to be read through the window are In black Ink,. although the Invention Is herein described as It relates to such cases.

GENERAL FEATURES OF THE INVENTION A first aspect of the Invention provides an apparatus for printing coded markings on an envelope. The apparatus includes a read station and a print station. and a conveyor for transporting the envelope therebetween.

The read station Includes an optical sensor.. which f preferably Is arranged to pick j reflections from the markings on the correspondence,, and Is effective to produce a series of electrical signals In accordance therewith. The apparatus Includes a computer. a means for transmitting the said electrical signals from the optical sensor to the computer,. a means for transmitting resultant signals to the print station.. and a means for arranging the said signals Into a sequence of spaced pulses.

The print station Includes at least one sIgnal-controlled printer,, which. . during normal operation of the apparatus.. remains at a fixed print point at the print station; in the first aspect of the Invention,, the computing means accepts signals of displacement of the passing envelope from the print station and the read station.. and coordinates these displacements with the signals from the read head. whereby the printer Is effective to print a mark on the envelope as the envelope passes the said print point. and to print a series of such marks on the passing envelope In spaced-apart sequence In accordance with the said pulses.

Preferably. each station Is provided with a revolution counter.. or angular-displacement Indicator,, which Is set to engage with the passing envelope., whereby the linear displacement of the passing envelope corresponds to the angular displacement of the counter.

t One of the difficulties with z,--dlng printed markings through a window Is that the read sensor tends to read the edge of the window as one of the markings. The first aspect of the Invention Is described as It relates to Its application to window envelopes., but It should be noted that the said difficulty can arise also In the case where the markings to be read are printed on a stick-on label. wherein the read sensor has a tendency to detect the edge of the 1 label as It it were one of the markings. The scope of the Invention should be construed accordingly. As will be described presently. the first aspect of the invention allows the read sensor to read the markings clearly and accurately, with a good deal of tolerance. and yet enables the read sensor to Ignore the edge of the window. or the edge of the label.

In a preferred constructionj, for use with window envelopeso, at the read station a read head Is provided with a photodetector. The photo-detector scans the window of a passing envelope. and detects the presence of a bar printed on the Item of correpondence inside the envelope. and visible through the window.

The window of a window-envelope Is, as a general rule. provided with a pane of transparent material, such as cellophane.. and the read head must detect the presence of the bars through the transparent material. A springy slipper Is preferably provided.. for the purpose of smoothing the pane down flat onto the Itein of correspondence.

The thickness of the envelopes may vary, In the range from less than 1 mm to about 5 mm. The read head preferably Is mounted on a parallelogram linkage. by the operation of which the passing envelope may deflect the read head upwards, and the read head still remains In the correct position relative to the window. The task of sensing markings through a transparent pane Is a demanding one. and It Is recognised that the orientation of the read head to the window Is critical. A preferred manner In which the read head may be arranged to accommodate these aspects will be described below.

A second aspect of the Invention provides a print station. where the fluorescent bare (or other machine readable markings) are printed on the outside of the envelope,, the pattern of the bars being In accordance with the postal code as read by the read sensor.

In the manual system referred to earlier the fluorescent bars have been applied to the envelope by means of solenoids: the operator presses keys In accordance with the code he reads In. and the keys activate the solenoids. Generally,. Post Offices call for the fluorescent bare to be about 6 mm high and about 1 mm wide, and the designer of the apparatus specifies an appropriate solenoid.

One characteristic of conventional solenoids Is that they are comparatively slow-acting, due to the Inertia of the (large) armature. The present Invention Is for use with apparatus with a throughput of two or three envelopes per second, at which speed there Is a time interval between fluorescent bars of about 5 milliseconds. For speeds like that, printing by conventional solenoids Is unsuitable.

1 The second aspect of the Invention provides a means for printing fluorescent bars on an envelope to signify a postal code. wherein the means for printing the fluorescent bars comprises a pair of dot-matrIx print heads,, which are arranged for printing onto the envelope through a ribbon containing fluorescent Ink. In the Invention,, the print heads are stationary within the apparatus. and are arranged side by side.. In line along the direction of travel of the envelope through the apparatus. The two print heads are offset laterally with respect to the direction of travel of the envelope. whereby one print head prints the bottom half of the bar. and the other prints the top half -of the bar.

A dot-matrix print head., of the styles which are commonly available., will only print a bar with a height of about 3 mm. This Is the reason two print heads are needed to print a bar 6 mm high. Dot-matrix print heads are not made wider than 3 mm, because dot-matrix print heads are invariably controlled by a computer, and, even where taller printing Is needed, it is usually of no great consequence to program the computer to cause the print hh j to make more than one pass over the paper.

The arrangement of the Invention allows conventional dot-matrix print heads to be used.. and the Invention permits advantage to be taken of their characteristic responsiveness., ease of programming.. and well developed reliability.

- 9 In conventional dot-matrix printers -- the usual application in which dot- matrix print heads are found -only one head is provided., and this one head Is driven In motion by a transporter mechanism. which moves the print head at right angles to the motion of the paper.

In the circumstances of the present Invention,. It would not be practicable to move the envelope laterally (le. to move the envelope at right angles to the line of Its passage throught the apparatus) as It passed through the print station. In the Invention.. neither the envelopes nor the print heads are required to move laterally. It would Indeed be almost Impossible to move either a single 3 mm head,, or the envelope., laterally fact enough to print a 6 mm high bar. Also.. It Is recognised that It would be difficult to arrange for the envelope to pass through the print station twice,, which Is a possibUty that might be considered by a designer: It might be considered that,, In order to print a 6 mm high bar.. It would be possible to pass the envelope twice through a single 3 mm print un., However., this would drastically reduce throughput.. and Is not contemplated within the second aspect of the Invention.

Dot-matrIx print heads are computer controlledp and It Is recognised in the Invention that there Is no difficulty In programming the computer to operate the two print heads In correct sequence.

- 10 DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

By way of further explanation of the Invention. an exemplary embodiment of the Invention will now be described with reference to the accompanying drawings. In which:

Fig 1 Is a side elevation of an apparatus which Is assembled and arranged for operation according to the Invention.

Fig 2 Is a block diagram showing the operative connections between the various components of the apparatus of Fig 1; Fig 3 Is a close-up side view of a read station of the apparatus of Fig 1; Fig 4 Is a close-up side view of a print station of the apparatus of Fig 1; M Fig 5 Is a cross-section on lute 5-5 of Fig 3; Fig 6 Is a cross-section on line 6-6 of Fig 3; Fig 7 Is a cross-section on line 7-7 of Fig 4; Fig 8 Is a plan view of an envelope of the kind operated on by the apparatus of Fig 1.

- U - The apparatus shown In the accompanying drawings and described below Is an example which embodies the Invention. It should be noted that the scope of the Invention Is defined by the accompanying claims,, and not necessarily by features of specific embodiments.

The drawings are diagrammatic. and some details of construction have been omitted from the drawings. to enhance the clarity of Illustration.

Fig 1 depicts the overall apparatus. The apparatus Includes a fixed base frame 2.. which comprises a base plate, pillars.. and a lower track frame 3. An upper track frame 4 Is, during operation of the apparatus., unitary with the base frame 2, but Is openable relative thereto for service purposes.

A lower conveyor belt 5 Is driven by a motor (not shown). An upper conveyor belt 7 Is spring loaded at several points 8 against the lower conveyor belt 5, the arrangement being, such that the two belts are driven in unison. The conveyor assembly may Include belt tensioners 9. The arrangement of the conveyor assembly Is such that an envelope Is caught between the upper and lower belts. and Is thereby transported through the apparatus.

The forward ends of the conveyor belts 5f7 (the right-hand 1 end in Fig 1) do not extend right to the end of the f rame. Thus.. the envelope is only picked up between the conveyor belts 5,.7 after the envelope has already traversed some distance Into the apparatus. The first portion of the transport of the envelope. upon entering the apparatus. Is handled by a pair of pinch rollers 10,12 of which the lower roller 10 Is driven by an electric motor (not shown).

The drive arrangement Is that the conveyor belts 5,7 act as if to transport the envelope at a faster rate than do the pinch rollers 10..12. No actual sUppage occurs,, however.. and the effect Is limited to the creation of an Induced tension In the envelope. as It passes from the pinch rollers to the conveyor belts. The read station 16 of the apparatus Is so positioned in the apparatus that the portion of the envelope that Is being read at the read station Is subject to this induced tension.

The read station 16 Is described In more detail below. The apparatus also Includes a print station 17.. which Is also 0 described In more detail below.

Positioned in the lower track frame 3, at the read station 16, is a readstation position-sensor 18,, which comprises a wheel 19.. an associated spring-loaded follower 20,, and a revolution counter 23. The arrangement Is such that as soon as an envelope passes between the wheel 19 and the follower 20.. the wheel 19 starts rotating.. the rotary displacement of the wheel 19 being a measure of the linear displacement of the envelope as the envelope Is conveyed through the read station. The angular output reading from the counter 23 Is therefore a measure of the linear displacement of the envelope with respect to a particular point within the read station.

A photocell 24 Is Incorporated Into the track frame 4, for the purpose of detecting the presence of an envelope. During normal operation of the apparatus, when envelopes are passing continuously through the apparatus, the wheel 19 does not stop rotating between envelopes,, and- In fact,, due to its Inertia, the wheel barely slows down between envelopes. Therefore,, the mere fact that the wheel 19 is revolving cannot be relied upon as the signal that an envelope is present In the station. Instead., the photocell 24 signifies the presence or absence of an envelope passing through the read station 16. A computer 25 Is provided In the apparatus.. the computer being programmed to start receiving the output from the counter 23 only after the photocell 24 has been activatax It will he appreciated that the photocell preferably should be so positioned,, within the station.. that the envelope engages the wheel 19 before the envelope trips the photocell 24. to ensure that the wheel Is up to speed and running,. before readings from the wheel are fed Into the computer.

- 14 A similar arrangement is provided In respect of the print station 17. A photocell 26 senses whether an envelope is present at the print station. Again.. the computer 25 accepts output from a print-statIon revolutioncounter 27 only when the photocell 26 signifies that an envelope has entered the print station.

The photocells are mounted on a fence 34 (Fig 5). The fence Is adJustable lateranyi to accommodate different widths of envelope. The fence, and the photocells. are not shown In Pigs 3 and 4,, for clarity,, but their positions are signified by the numerals 24 and 26 thereon, - An envelope 28.. of the kind with which the Invention Is concerned, Is provided with a window 29, formed by cutting through the material of the envelope. A pane 30 of cellophane or other suitable transparent material Is glued Into the cut-out area.

The conventional arrangement with window envelopes Is that a name and address written o i item of correspondence (in this example a credit card statement) 35 placed within the envelope 28 Is visible through the window 29. In the Invention,, a series 36 of bars 37 Is printed on the statement 35.. such that the series 36 also Is visible through the window 29. The spacing and layout of the bare 37 Is such that the series 36 signifies the appropriate postal code and error-checking verification. The bars 37 - is - are printed In ordinary black ink, and are printed on the statement simultaneously with the other personal details.

It will be described below how the Invention enables a read sensor to read the bare 37. through the pane 30. with the required degree of accuracy and sensitivity. one difficulty that should be considered In the reading process Is that of making the sensor Insensitive to the edges 38, 39 of the window 29 -- the problem is that the read sensor might detect the edges 38,39 of the window as If the edges were bars 37. Similarly.. the read sensor might detect the edges of the envelope 28 as If they were bars.

The read sensor Is signified generally by numeral 40. The difficulty, on the part of the read sensor'40.. of having to detect the difference between a bar 37 and an edge 38,39 may be avoided in the invention. The computer 25 may be so programmed as to Ignore the readings from the read sensor 40 until after the envelope has been displaced a predetermined distance Into the read station Thus, the photocell 24 Is used to signify the Instant when the envelope 28 enters the read station 16. The output from the -read sensor 40 may then be Ignored until after the counter 25 has signified that the leading edge 38 of the window 28 has passed a readline 41. The read-Une 41 Is the line In the read station 16 at which the sensor 40 actually scans the series 36 of bars.

It cannot be avoided that the Item of correspondence 35 must be given a considerable. freedom of movement within the envelope 28. In order to allow the use of conventional envelope -stuffing machines. Also., sometimes the envelopes will be stuffed with ancillary Items of correspondence. but sometimes the envelopes will contain only the bare statement on Its own. and the dimensions of the statement and the envelope must be acceptable for both cases. Therefore,, It cannot be avoided that the first of the bars 37 In the series 36 might sometimes be as close as.. say,, 3mm to the leading edge 38. and on other occasions the first of the bars might be 20 mm behind the leading edge. Similarly, In the lateral sense, the position of the bars 37 on one occasion mdy be laterally displaced by as much as 10 mm from the position of the bars on another occasion. By the same token.. the series 36 may lie at an angle relative to the direction of motion of the envelope.

On the other hand.. there Is little difficulty In manufacturing the envelope to reasonably tight tolerances. whereby the distance 45 from tne leading edge 46 of the envelope to the leading edge 38 of the window may be expected not to vary by more than about 1 mm. The result Is that the photocen 24,. which Is activated very reliably by the edge 46 of the envelope. can be used to signify with adequate accuracy the moment at which the leading edge of the envelope passes the photocen,, and therefore to signify. by simple addition of pre-set accurately-known distances.

k the moment at which the leading edge 38 of the window clears the readline 41. Once that moment Is past,, the computer 25 can be allowed to start to process the readings from the sensor 40.

As mentioned ear.Uer,, the Invention may be applied to the case where the series 36 of bars Is printed on a stick-on mailing label, rather than on an Item of correspondence to be read through a window: the same problem arises. with a label, that the edges of the label might be mistaken for coded markings. However, the Invention is rather less attractive for use in the label situation, forthe following reason. The cut-out area that constitutes the window of a window-envelope is die-cut by machine: therefore, at least over a given batch of envelopes., the variation between the position of the windows., envelope to envelope,. Is very small. The corresponding tolerance of the position of a stuck-on label. however.. Is very much greater. The Invention uses the position of the window or label as the means for Indicating to the cop-uter whether the signal from the read head should be. or should not be. Ignoredo and.the' extra positional tolerance requirement detracts directly from the margin over which the read head can operate accurately.

The series 36 of bars 37 may be set so as always to contain a set number of bars. In which cazej the computer can be programmed to look for exactly that number. and then to 0.

40% 1 ignore any further signals. However, It is preferred in the invention that the computer be programmed so that the processing of signals from the counter continues only for a given displacement of the envelope after the start of processing, ie that the signal upon which the computer stops processing the output of the read sensor Is simply that the envelope has travelled a given pre-set distance since the computer started processing the output of the read sensor. Under this procedure, It Is not possible that the trailing edge 39 of the window could be detected as If It were a bar 37, and also under this procedure there Is no requirement that all the unique series 36 of bars In all the passing envelopes should have the same number of bars.

As regards printing the fluorescent markings on the envelopes, the general rule is that the Post Office specifies the distance 47 It requires between the leading edge 46 of the envelope and the start point 48 of the series 49 of fluorescent markings 50. The instant at which the envelope enters the print station 17 is signalled to the computer by the print-station photocell 26; the computer can be programmed to start the printing process as soon as the envelope has travelled a predetermined distance after that.

It may be noted that the distance specified by the Post office between the leading edge 46 of the envelope (le the edge that activates the photocell 26), and the point at which the series 49 is to start,, will in most Jurisdictions be always the same,, Irrespective of the size of the envelope. Therefore., the print station photocell 26 may remain at a fixed site relative to the print-line 56 at the print station. In contrast,, It will be recalled that the photocell 24 In the read station 16 Is adjustably movable relative to the read-line 41, to cater for the possibility that the windows 28 of one batch of envelopes might lie at a different distance from the leading edge 46 of the envelope than the windows of another batch. Of course.. if the need arises, the position of the photocell 26 at the print station may similarly be made adjustable.

It should be noted that It would be Inadvisable to allow Just one photocell to be the used to control the operational starting points of both stations,. since the distance 45 between the leading edge of the window and the leading edge of the envelope changes more often than. and Independently of.. the distance 47 between the start of the series 49 and the leading edge of the envelope.

It Is possible to provide adjustability f or the various operating points at the stations either by the preferred method of moving the read-station photocell or alternatively by re-programming the computer,, when adjustment Is required.. to respond to a new value for a measured displacement. It Is recognised In the Invention that the former Is much easier than the latter -- an the technician In charge of setting the apparatus needs to do is to make sure that he - 20 follows this rule: that he sets the distance 57 of the photocell 24 from the read-line 41 to be equal to the distance 45 from the leading edge of the envelope to the leading edge of the window (plus C, where C Is an apparatus -dependent constant dimension). As mentioned.. the technician does not need to re-position the corresponding photocell 26 at the print station 17 for each size of envelope. 'because the distance 47 between the leading edge of the envelope and the start-point 48 of the fluorescent markings produced at the print station will generally always be required to be constant.

The construction and operation of the read sensor 40 win now be described.

The read sensor 40 includes a housing 58f attached to a parallelogram linkage 59, by which the housing Is guided for up/down movement. The parallelogram linkage is mounted from a block 60 secured to the upper track frame 4.

Attached to the housing 58 is a springy slipper 64, which Is of such dimensions as to engage resiliently against the top surface of an envelope 28 passing beneath the read sensor 40. The housing 58 also Includes a pair of legs 65,, each having a ball-bearing 67 mounted at its foot. The bearings 67 also engage the top surface of the envelope. but there Is substantially no resilience between the bearings 67 and the housing 58.

A suspension unit 68 Is provided In connection wIth the parallelogram linkage 591 the purpose of the suspension unit 68 being to act in conjunction with the weight of the housing 58 to produce the desired downwards force on the envelope.

The housing 58 contains a lens 69 and an optical-sensor or photo-detector 70. The housing also contains floodUghts 73. The lens 69 and detector 70 are mounted in a focusing tube 74, which can be moved vertically within the housing 58.. and can be locked to the height at which the detector Is focused on the envelope.

To assist In focusing, the detector 70 may be removed from the tube 74 and replaced temporarily with a standardised light source. A spot of light from the source would then appear on a test sheet placed under the sensor. and the height of the tube 74 can be adjusted until. that spot is focused.

When an envelope 28 enters the read station 16. the leading edge 46 of the envelope strikes the baU bearing 67j thereby urging the housing 58 upwards and onto the envelope. The springy slipper 64 presses Ughtly down onto the envelope. The main purpose of the springy slipper Is to smooth out the pane 30.. In order firstly to smooth out any wrinkles that might tend to be present In the pane. and secondly to ensure that the pane Is in direct contact with the paper of the statement 35. The function of the slipper 64 Is In fact critical to the accurate

operation of the apparatus. A wrinkle In the pane 30 might not appear to be significant to a person. because the eye Ignores It, but the photodetector 70 will all too easily detect a wrinkle as If the wrinkle were one of the bars 37. Therefore, the pane preferably should be perfectly smooth and flat. No less Important Is the requirement to ensure that the pane 30 Is pressed Into firm contact with the paper beneath as readsensIng Is taking place: If the pane 30 were to be even slightly clear of the paper below. the resulting scattering of light could produce false readings.

The suspension unit 68 therefore should be such that the combined effect of the weight of the housing and the action of the spring within the unit 68 provides a firm engagement action.' The force of engagement should not be too strong. however, or the envelope might tend to be distorted. Such. distortion would, if It happened, Interfere with the smooth passage of the envelope through the read station. and one of the alms of the Invention Is to create as little resistance as possible to the motion of the envelope. since such Interference would limit the rate of throughput.

The focus of the lens onto the paper 35 is critical in - 23 achieving error-free output from the detector 70: therefore the height of the housing 58 above the paper, when a reading Is being taken, should not be allowed to vary. Consequently, the height of the housing above the envelope Is determined by the rigid leg 65, rather than by the springy slipper 64. The function of the slipper 64 Is to press the pane 30 lightly, smoothly, and delicately, down onto the paper below. but the slipper should not push downwards. so heavily that the housing would thereby be lifted.

Glare and reflections from the transparent material of the pane 30 can be troublesome If not properly dealt with, either producing a false Indication that a bar Is present, or preventing a bar from being detected. The springy slipper 64 consequently Is provided with only a small hole 62.. so that only a small portion of the potentially glareproducing pane Is exposed during reading. The Inside of the focusing tube 74 Is blackened, as Is the upper surface of the slipper 64, to minimize glare. The floodlights 73 are set at an angle.. to minimise spurious reflections from the window and the surface of the paper.

The parallelogram linkage 59 Is Important In achieving the, desired degree of accuracy In the performance of the sensor. It might be considered that the housing 58 could he mounted on a single pivoting arm, as distinct from the two parallel arms as shown, and such an arrangement Is contemplated. However, the position of the pivot-point of such a notional single arm upon the f rame 4 would be critical: If the pivot point were too high, the arcuate operational movement of the - 24 arm would mean that as the housing 58 swung upwards the housing would also be slightly displaced horizontally forwards relative to the hole 62 in the slipper. If the pivot-point were a substantial distance above the envelope, such an error might not be negligible. Such an effect might be alleviated If the pivot-point were low down, at or near the level of the envelope, or It the arm were long, but there is little room In the apparatus for these measures to be taken, especially since there Is generally a requirement also that the read sensor 40 be adjustable as to its lateral position, to cater for the windows being not always in the same lateral position on the envelope.

In the preferred parallelogram arrangement, the pivot-points between the block 60 and the linkage 59 are, as shown, quite high above the envelope, and the linkage is quite short, yet substantially no fore/aft motion accompanies the up/down motion of the housing.

The envelope thickness can vary In the range of about 1-5 mm. The suspension unit 68 is adjustable, and It is usually desirable for the technician to adjust the setting of the suspension unit 68 In accordance with the nominal thickness of a particular run of envelopes: the distance through which the housing 58 Is called upon to rise, as the envelope passes beneath, Is thereby kept to a minimum. The block 60 tends to bounce upwards only very slightly, as the envelope passes beneath, when the suspension unit 68 Is set correctly.

It will be appreciated that the above-described conflicting requirements produce a need for the various forces to be properly balanced against each other.. and the arrangement as described allows this balance to be readily achieved. The arrangement of solid legs with a springy slipper.. together with such a suspension system,, provides a degree of up/down sensitivity.. responsiveness. and balance that allows the sensor 40 to detect the bars 37 in a substantially error-free manner.

Preferably, the two legs 65 and their ball-bearings 67 should be spaced sufficiently widely apart, laterally, that the bearings are well clear of the pane.

The block 60 Is slidable In the lateral sense In a groove in the upper track frame 4,, for adjusting the sensor in accordance with the location of the window 29 upon the envelope 28. Such a lateral adjustment facility Is enhanced by virtue of the fact that the sensor 40 Is located ahead of the belts 5..7.

The construction and operation of the print station 17 will now be described.

At the print station 17, two print heads 75 are provided. These are mounted In a carriage 76, which is mounted on a parallelogram linkage 78 for up/down movement relative to a block 79. The block 79 Is fixed to the upper track frame 4.

Each print head 75 Includes a dot-matrix print unit 80. This print unit Is a conventional proprietary Item.. and will not be described in detail. Such units are readily obtainable either with nine or twenty-four pins. Positioned alongside the print unit 80,, and on the same print-line 56, a roller-follower 81 Is provided, the axle of which Is fixed firmly to the carriage 76. Both the print unit 80 and the roller-follower 81 are arranged to bear onto a strike-roller 82, the axle of which Is fixed firmly to the lower track frame 3.

A ribbon 94 is threaded underneath the print unit 75. The ribbon 94 contains fluorescent Ink.. and Is mounted in a conventional ribboncarrying cartridge 95. The ribbon is continuously circulated by means of a motor 96. (The ribbon has been omitted in Pigs 4 and 7.) The weight of the carriage 76, with the print heads 75 attached. Is partially supported on an adjustable spring unit 83. A leg 84 and attached bearing 85 assembly Is provided, which Is similar to that desribed In respect of the read-sensor 40.. and which also takes a portion of the weight of the carriage. Thus the total weight of the carriage Is divided between four points of support: the two roller followers 81.. the bearing 85.. and the spring unit 83. In addition,. when the print heads 75 are being actuated, the actuation forces on the pins In the two print heads are reacted against the weight of the carriage.

Of these. of course the actuation forces of the pins are the most Important; and In fact the other weight controlling supports are arranged so that the actuation forces of the pins can be controlled with the correct degree of sensitivity and responsiveness.

When an envelope 28, travelling along the tray 97.. enters the print station 17 (from the right, Fig 4) the leading edge 46 of the envelope engages the bearing 85. driving the leg 84 upwards. and raising the carriage 76. The parallelogram linkage 78 ensures that the carriage remains horizontal during the upwards motion.. and remains so while the envelope passes beneath the carriage. It Is desirable that the two print heads 75 be both positioned at exactly the same height above the passing envelope, and this requirement applies even though the thickness of the envelopes may vary. An angle setting means 86 Is Included as part of the carriage. and operates In combination with the parallelogram linkage 18. whereby the angle of the carriage can be adjusted relative to the linkage. The purpose of the leg and Its bearing Is to raise the carriage well before the printing operation actually starts: after Its sudden rise,, which may be accompanied by momentary bouncing, the carriage then has time to settle down gently to Its correct level.. well before printing commences.

- 28 The print pins In the print heads 75 are, as mentioned, arranged so as to strike the envelope,. reacting against the strike-roller 82. The envelopes pass the print head at speeds In the region of 50 cm/sec. Print heads were developed for use in dot matrix printers.. wherein the print head moves much more slowly relative to the paper during printing; and one of the features of the Invention Is the recognition that a dot-matrix print head can be used in a manner which Is so different from that for which it was developed. To accommodate the high relative speed.. steps are taken to allow the print head to move slightly with the passing envelope during the moment the pins are striking the envelope, as will now be described.

As shown In Fig 7,, the print unit 80 is bolted solidly to a rail 87. The rail 87 In turn Is bolted between a pair of thin spring arms 89,, which depend downwardly from a block 90 which Is bolted to the carriage 76. The effect of this arrangement Is that the print head 75 has some "give".. and can move (slightly) In the direction of travel of the envelope. The fact also that the reaction-roller 82 Is moving with the envelope,, but Is providing a solid base against which the pins can strike.. gives a very advantageous manner of printing. It may be noted that exceptional clarity of printing Is not required.. and Indeed the Individual dots preferably are allowed to merge Into each other, but the amount of smudging does need to be controlled to ensure that each fluorescent bar 50 Is cleanly - 29 delineated.

The bars 50 typically have a width or thickness as produced by five pinstrikes. Thus, to produce a bar 50.. the pins are actuated five times -when nine pins are provided. the pins would alternate In a 5-4-5-4-5 sequence.

As mentioned.. the reason two print heads 75 are provided Is that proprietary dot-matrix print heads are normally only 3 mm high.. whereas the fluorescent bar 50 Is required to be 6 mm high. The two print heads are off set the 3 mm difference. Thus, the first print head prints 'the bottom halves of the bars 50, and the second print head prints the top halves of the bars. Naturally, it is Important that the two halves of the bars match up exactly,, and suitable Inter-adJustment means (not shown) Is provided.

As stated above.. the read sensor 40 Is designed to be adjustable laterally, because the position of the window can vary. The print heads 75, on the other hand. do not need to be adjustable laterally. because the fluorescent bars are, required always to be the same distance from the edge of the envelope.

The requirements of different Post Offices may cause the fluorescent bars to be at different places., but again, once the apparatus has been designed for a given positioning of the fluorescent bars., the print heads would remain In that - 30 position. It is unlikely that an apparatus would need to be built to cater for the requirements of more than one Post office,, but such adjustment could be provided If desired.

The apparatus shown In the drawings can be easily servicedr because of Its construction. The upper track frame 4 Is able to pivot about the conveyor belt drive pulley 99. Upon release of a suitable catch (not shown) the upper track frame 4 may be swung upwards, together with all the components attached to it. Including the upper conveyor belt 5, and the read and print stations 16.17. As a f urther aid to servicing,, the print station 17 Is mounted bn a mounting plate 98.. which during operation is bolted down to the upper track frame 4.. but which can swing upwards, for servicing, about an axis parallel to the direction of travel of the envelope, with respect to the upper track frame.

The modular construction of the apparatus Is apparent. Most of the components are designed to be held In place by a single bolt.

As regards the spacing of the fluorescent bare 50. this can be the same as the spacing of the ink bars 37; alternatively the coded pattern of the bars 50 may be different from that of the bars 37.

An alternative construction contemplated In the Invention is that the read and print heads are positioned beneath the tray,, In the lower track frame,, and act upwards. This arrangement would have the benefit that the read and print heads could remain stationary as the envelope passed: roller followers mounted in the upper track frame could move to accommodate the thickness of the passing envelope. Although the construction of the read and print stations would therefore be simplified, such an arrangement Is not preferred because In that arrangement the envelopes would travel face down: other postal machinery requires the envelopes to be face up, so that Inverters would be needed.

Another alternative.. In which the passing envelopes are face up,, Is to arrange that the envelopes pass underneath the tray. and are pressed upwards into contact with the tray. Again., this measure would avoid the need for the read and print heads to float.. but the difficulty now is that the ideal agency -- le gravity -- for holding the envelopes in position on the tray, would not be available.

The conventional dot-matrix print heads as mentioned win only print a height of about 3 mm, which Is why two print heads are provided In the preferred embodiment. However,, an alternative arrangement Is contemplated In the Invention wherein the pins In the print head are operatively engaged with a relatively wide strike-bar. In this arrangement,. when the pins are actuated.. the motion of the pins Is transmitted mechanically to the strike bar, which then strikes through the ribbon onto the envelope. In that case - 32 only one print head would be required, but a disadvantage lies in the fact that the extra Inertia of the strike-bar would slow the speed and responsiveness of the print action.

Claims

CLAIMS.

CLAIM 1. Apparatus for printing coded markings on an envelope. in accordance with pre-printed marks relating to the envelope. wherein:

the apparatus Includes a read station and a print station. and a conveyor for transporting the envelope therebetween, along a conveyor line; the read station Includes an optical sensor, which is effective to produce a series of electrical signals In accordance with the pre-printed marks; a computing means, which accepts signals of displacement of the envelope through the stations, and coordinates the read and print stations; the apparatus Includes a means for transmitting the said electrical signals from the optical sensor to the computer, and a means for arranging the said signals Into a sequence of spaced pulses; the print station includes at least one sIgnal-controlled printer,, which, . during normal operation of the apparatus., remains at a fixed print- point at the print station; and the printer Is effective to print a marking on the - 34 envelope as the envelope passes the said print point, and to print a series of such markings on the passing envelope In spaced-apart sequence In accordance with the pulses received from the transmitting means.
CLAIM 2. Apparatus of claim 1,, wherein:

the print station is provided with a print station displacement counter, and the read station Is provided with a read station displacement counter; and each counter is effective to measure the linear displacement of a passing envelope relative to the stations.
CLAIM 3. Apparatus of claim 2, wherein:

the apparatus Includes means for transducing the measurement of both counters Into electrical signals corresponding to the displacement of a passing envelope; the apparatus Includes a means for co-ordinating these electrical signals with the electrical signals from the optical sensor; the co-ordination Is such as to ensure that the spacing and positioning of the coded markings printed on the envelope by the printer are equivalent to the pre-printed marks as read by the optical sensor.
CLAIM 4. Apparatus of claim 3. wherein:

the print counter comprises a print station wheel,. and the read counter comprises a read station wheel, each wheel being mounted for rotation upon a respective fixed axis; each wheel Is arranged for operational engagement with a passing envelope; and the arrangement Is such that the angular displacement of each wheel about Its axis comprises a measure of the linear displacement of the envelope passing through the respective stations.
CLAIM 5. Apparatus of claim 3, wherein:

the envelope has a window. and the pre-printed marks are upon an Item of correspondence readable through the window, and the window has a leading edge:

and the apparatus Includes a means for disabling electrical signals from the optical sensor,, In respect of a particular passing envelope,, until after the leading edge of the window of that envelope has passed the optical sensor.
CLAIM 6. Apparatus of claim 1,, wherein:

the envelope has a window and the window Includes a pane of transparent material, through which the pre-printed markings are readable; during normal operation of the apparatusj, the optical sensor remains at a read point at the read stationt the read point being fixed In the longitudinal sense reldtive to the conveyor line; the read station Includes a means for compressing a zone of the pane of transparent material against the Item of correspondence; the said compressed zone comprises at least that portion of the pane that lies momentarily at the read point as the envelope passes the read point.
CLAIM 7. Apparatus of claim 6,, wherein:

the means for compressing the read zone comprises a resilient slipper., which Is mounted for engagement directly with the pane; the resilient slipper comprises a length of springy sheet material; and the material Is curved.. the convex side of the curve being In engagement directly with the pane.
CLAIM 8. Apparatus of claim 7.. wherein:

the slipper Is provided with a hole, through which the markings on the correspondence are visible to-the optical sensor; and the hole Is., In substance,, small. whereby glare and reflections from the pane are minimized.
CLAIM 9. Apparatus of claim 1, wherein:

the apparatus Includes a fixed conveyor traye the arrangement being such that the envelope runs on the tray. the pre-printed marks facing upwards; the optical sensor Is positioned above the tray; the apparatus includes a means for mounting the optical sensor for up/down movement; - 38 and the apparatus Includes a means for raising the optical sensor.. the said means being operatively responsive to the presence of an envelope passing along the tray.
CLAIM 10. Apparatus of claim 9., wherein:

the means for raising the optical sensor Includes a bearing means which Is engageable with the passing envelope; the bearing means Is,, In substance,, rigid with respect to the optical sensor; the bearing means Is so positioned In the apparatus that the optical sensor Is raised by the passing envelope well before the said markings pass under the optical sensor.
CLAIM 11. Apparatus of claim 9.. wherein the means for mounting the optical sensor for up/down movement Includes-a means for constraining the optical sensor accurately to a constant vertical orientation as the optical sensor undergoes up/down movement.
CLAIM 12. Apparatus of claim U. wherein the said means for constraining the optical sensor comprises a parallelogram linkage.
CLAIM 13. Apparatus of claim 1,, wherein the apparatus Includes a means for applying tension to the passing envelope, as the envelope passes through the read station.
CLAIM 14. Apparatus of claim 13.. wherein the said means for applying tension comprises two separate drive means for conveying the envelope through the apparatus. positioned one leading and one trailing with respect to the read station. the leading drive means being operated at a slower speed than the trailing drive means.
CLAIM 15. Apparatus for printing fluorescent bars on an envelope.. wherein:

the apparatus Includes a conveyor means for conveying the envelopes through the apparatus. along a conveyor line; the bars are each more than H mm high, measured at right angles to the conveyor line; the bars are arranged In a series. spaced apart along the conveyor line; 1 - 40 the apparatus includes two print heads. each having an effective printing height of no more than H mm.. each print head having a means for printing fluorescent Ink onto the envlope; the apparatus Includes a computer, f or co-ordinating the printing of the two print heads; the two print heads are so mounted In the apparatus as to be not movable laterally sideways with respect to the envelope during printing; the conveyor means is so arranged that the envelope Is not movable laterally sideways with respect to the print heads during printing; the two print heads are arranged side by side along the conveyor line, and are relatively offset laterally sideways slightly; whereby each bar Is printed In two portions,. one by each print head.
CLAIM 16. Apparatus of claim 15, wherein the print heads are dot-matrix print heads. and H is 3 am.

- 41 1 CLAIM
17. Apparatus of claim 15, wherein:

the conveyor means Includes a tray,, which Is so arranged that the envelopes pass along the tray In a horizontal face up orientation; the apparatus Includes a carriage. to which the print heads are attached; the apparatus Includes a means for mounting the carriage for up/down movement; and the apparatus Includes a means for raising the carriage. the said means being operatively responsive to the presence of an envelope passing along the tray.
CLAIM 18. Apparatus of claim 17.. wherein:

the apparatus Includes two strike -rollers.. which are so positioned as to react printing forces on the envelope due to the action of the respective print heads; and the strIke-roners are so mounted In the apparatus that the said forces are reacted substantially without resilience; CLAIM
19. Apparatus of claim 17, wherein the means for raising the carriage Is so positioned in the.apparatus that the carriage is raised by the passing envelope well before the two print heads start to print the bars.
CLAIM 20. Apparatus of claim 17,, wherein the means for mounting the carriage for up/down movement Includes a means for constraining the carriage to a constant orientation with respect to the vertical during the said up/down movement.
CLAIM 21. Apparatus of claim 20.. wherein the said means for constraining the carriage comprises a parallelogram linkage.
CLAIM 22. Apparatus of claim 1, In combination with the apparatus of claim 15.
CLAIM 23. Apparatus of claim 12.. In combination with the apparatus of claim 21.

Published 1991 at 11e Patent office. State House, 66171 High Holborn. LondonWCIR4TP. Further copies may be obtained froni7be Patent Office. Sales Branch. St Mary Cray. Orpington. Kent BR5 3RD. Printed by Multiplex techniques lid. 51 Ma'ry Cray. Kent. Con. 1/87