GB2186406A - Motor speed control system for a hand-held labeling machine - Google Patents

Abstract

A hand-held labeler, e.g. with a thermo-graphic print head, senses the position of the web to control the position of the imprints on the web. A circular indexing member having a plurality of position defining indices provides indications representative of the position of the web. The speed of the web-advancing motor (48) is controlled by providing it with an energising pulse, then sampling (176) the thresholded (174) amplitude of the back EMF after a predetermined delay following the end of the pulse and, if for a given sample, the amplitude is below the threshold, providing another energising pulse. <IMAGE>

Description

GB 2 186 406 A SPECIFICATION adjacent to the label boundary defining index

that in forms the system that the label boundary is app Motor speed control system for a hand-held labeling roaching. The indices are sensed by the sensor and machine used to provide position indicative sig na Is to the 70 system for controlling the operation of the printing Th is invention relates generally to printing devices, head.

and more particularlyto hand-held labelers utilizing Because of the precise positioning information circuitry accuratelyto determine the position of the provided by the timing disc, manufacturing tol printing web, and to control the operation of the erances become significant. Consequently, there is printing head, preferably the thermographic printing 75 preferably provided an adjusting mechanism for head, in responseto position signalsto thereby ac- adjusting the angular position of thetiming disc re curately position the imprints on the web. lativeto the feed mechanism. This is accomplished Hand-held labelers utilizing thermographic print- by permitting the discto be positioned on the shaft ing devices are known. Examples of such hand-held driving the disc at a plurality of discrete angular posi labelers are illustrated in our United States Patents 80 tions, each associated with one of the home position Nos. 4,264,396 and 4,407,692, and United States indices. Such positioning can be accomplished by patent application Serial No. 485,012 filed April 14, providing a plurality of unequally spaced key slots or 1983 (see British Patent Application No. 2,138,190 the like in the disc, by providing a single key orspline published October 17,1984). on the shaftfor engaging one of the key slots. By Whilethe devices disclosed in the above- 85 making the angular position of each key slotslightly described references do provide a wayto make im- different relative to its associated home position prints on a thermosensitive web,they are capable of index and positioning indices, an adjustment can be improvement in certain respects. For example, when readily achieved by positioning the appropriate key printing with a thermal printing device, particularly slot overthe key or spline to provide the desired with a high density printing device such as one of the 90 offset between the shaft and the disc.

devices illustrated in the aforementioned U.S. Patent The invention will now be described in more de No. 4,407,692 and British Patent Application No. tail, byway of example, with reference to the 2,138,190, it is necessary accuratelyto control the drawings, in which:

timing of the energization of the various printing el- Figure 1 is a perspective view of a hand-held lab ements as a function of the position of the web. For 95 eler constructed in accordance with the principles of example, in such a system, the web is continuously the present invention; fed, and the appropriate printing elements must be Figure2 is a system block diagram of the logiccir energized atthe precisetime thatthe portion of the cuitry controlling thethermographic printing appar web on which the imprinting is desired is positioned atus according tothe invention; adjaceritthe printing head. The difficulty of the pro- 100 Figure3 is a plan view of a thermographic print blem isfurther compounded bythefaetthat each of head usablewith the printing apparatus according to the printing elements has a length and a width of the present invention; only a few mils. As a result, the position of the web or Figure 4 is a block diagram illustrating one emb the timing of the energization of the printing elodiment of the print head driving circuitry; ements, must be precisely controlled to avoid print- 105 Figure5is a block diagram of an alternative emb ing gaps and changes in print density, aswell as odiment of the print head driving circuitry; changes in charactershape, particularly when the Figure 6is a block diagram illustrating the position speed of theweb varies as it passes the printing sensing and printercontrol circuitry according tothe head, as for example, in the case of a labeler having a invention; hand advanced web. 110 Figure 7is a detailed illustration of the timing disc The invention in its various aspects is defined in illustrated in Figure 6; the appended claims to which reference should now Figure 8 is a block diagram of the motorspeed con be made. trol portion of the control circuitry of the invention; In a preferred embodiment of the invention, there Figure 9 is a timing diagram illustrating the oper- is provided a hand-held labeler utilizing a micro- 115 ation of the motor speed control circuit according to processor-based control system that sensesthe pos- the invention; ition of the web and controlsthe operation of the Figure 10 is a logical flow diagram illustrating the printing head in accordancewith the position of the operation of the control circuit according to the in web in orderto assure that any imprints are acvention; and curately positioned on theweb, and on anylabelscut 120 Figures lland 12 illustrate circuitry for protecting from the web. Ths system employs a precise timing the data stored in the labeler in the event of a dischar discthat is coupled to the label advancing mech- ged battery and when the battery is removed.

anism. The timing disc co-operates with a sensor, such as, for example, an optical sensorthat senses Detailed description of thepreferred embodiment the position of indices on the timing disc, and prov- 125 Referring now to the drawing, with particular ides a signal representative of web position. Thetim- attention to Figure 1, there is shown a thermographic ing disc includes at least one and preferably more microprocessor-control led hand-held labelerac home position indices that defines the boundary becordingtothe invention, generally designated bythe tween two successive labels, one or more position reference numeral 10. The labeler 10 includes a determining indices and a warning index disposed 130housing 12 that supports a roll 14 of adhesive backed 2 GB 2 186 406 A 2 labels 16 that are supported on a backing web 18. A via a display driver 54. The display 24 is used to dis keyboard 20 is disposed on the housing 12 and con- play data being inputted intothe microprocessor as tains a plurality of individually operable key switches well as other messages such, for example, prompt 22 for entering data into the labeler. A display 24, ing and diagnostic messages generated bythe mic which may be a liquid crystal or light emitting diode 70 roprocessor.A read-only memory (ROM) 56 is prov display, is also disposed on the housing to permitthe ided for storing permanent data, such asthe entered data and microprocessor-generated promprogram defining operation of the device. The read- pting instructionsto beviewed bythe operator. A only memory 56 may either be permanently installed battery pack,which may be contained in a removable in the labeler 10, or may be removably installed in a battery pack-handle unit 25 containing a battery 26 75 socket orthe like to permitthe font and/orformatto having an internal resistance 27, provides electrical be changed by changing the memory 56. In addition, powerforthe labeler 10. Atrigger 28 is provided to a random access memory (RAM) 58, usable forstor initiate the label printing operation, and a label app- ing shortterm data, such as data entered via the key lying roller 30 is used to apply pressure to the adhes- board 20, is provided, as is a non-volatile randomive backed label 16 when the label 16 is being applied 80 access memory (NVRAM) 60, suitablefor storing to an article of merchandise. A label stripper (not data such asformat data. The input/output connector shown) is contained within the housing 12 to sep- 32 provides communications between the device arate the labels 16 from the backing strip 18. A pluraand an external computer. Printing is accomplished lity of guide rollers are provided to guidethesepar- by a print head assembly 64 that containsaprint ated labels 16 to the forward portion of the housing 85 head 66 and print head driver 68 coupled to the per beneath the label applying roller 30, and to guide the ipheral interface adapter40. An analog-to-digital backing strip tothe rear of the housing beneaththe converter70 coupled to the peripheral interface roll 14. adapter40 sensesthe batteryvoltage orthevoltage As previously stated, the labeler according tothe applied to the print head assembly 64, and provides a invention is quite versatile and is capable of printing 90 digital indication of thatvoltageto the peripheral in alphanumerics, as well as bar codes including the terface adapter 40 so that the microprocessor may Universal Product Code (UPC) and the European Art- adjustthe timethatthe print head is energized to icle Number (EAN). The type of format,whether compensate forvariations in battery or print head alphanumeric or bar code, is readily selected by en- voltage.

tering the appropriate format and fonts defining data 95 One example of the print head assembly 64 is illus via the keyboard 20. The data to be printedjorex- trated in simplified form in Figure 3. In the illustrated ample, price, product defining data and other in- embodiment, the print head assembly 64 contains formation aboutthe product such as the size, color, the print head driver 68 and the print head 66 dis etc. is also entered via the keyboard 20. In addition, posed on a thin film substrate. The print head has a the number of labels to be printed may be entered. 100 single line of print elements disposed transverse to Also, a data inputloutput connector 32, may be prov- the direction of travel of the web 18, and is part ided on the housing to permit data to be entered into icuiarly suitable for use in a hand-held labeler be the labeler by an external source, such as, a re- cause of the high density of the print elementsthat motely-located computer, and to permitthe battery make up the print head 66, particularly if both alpha- 26 to be charged. 105 numerics and bar codes are to be printed. One print Referring to Figure 2, the keyboard 20 is coupled to head assembly particularly usable asthe print head a peripheral interface adapter (PIA) 40 which prov- assembly 66 employs 224 printing elementsthat are ides an interface between various input and output each 10 mils long and 4.4 mils wide, and spaced on devices and a microprocessor 42. Also coupled to 5.2 mil centers. Such a configuration permits a virtu- the peripheral interface adapter 40 are a trigger 110 ally continuous line to be printed.

switch 44that is controlled bythe trigger 28, and a Each of the printing elements constitutes a resist control circuit 46 that operates a motor 48 that drives ive heating element 80 (Figure 4) that is individually a web advancing wheel 49. A detector 50 senses a energizable bythe print head driver circuitry 68 mark or index on the web advancing wheel 49, or which contains a heater driver transistor 82 for each preferably on a separate timing disc 51. The control 115 of the printing elements 80. A gate 84 controls each circuit 46 responds to data received from the micro- of the heater driver transistors 82, and an input regi processor 42 and controls the operation of theweb ster 86 and a data register 88 control the operation of advancing motor 48, which may preferably be a D.C. the gates 84. Thus, if a 224-element head is used as motor. An audible alarm 52 is also connected to the the print head 66, 224 drivertransistors 82 and 224 peripheral interface adapter 40, and is usef u 1 for indi- 120 gates 84 must be provided, and the i nput register 86 cating to the operatorthat a problem or potential and the data reg ister 88 must each have at least 224 problem exits. For example,Ihe audible alarm 52 stages.

may be used to indicate a discharged or fau Ity bat- The input register 86 receives data serial ly f rom a tery, a faulty pri nt head, thatthe labeler is out of data input line 90 under the control of clock signals labels, a jam, or may simply be used to indicate that 125 applied to a clock line 92. When the input register 86 data entered into the device has been received. 1 n the is full, the data is transferred in parallel to the data latter case, the audible alarm 52, can be used to pro- register 88 u nderthe control of a latch sig nal applied vide an audible indication each time one of the key to the data register 88 by a line 94. The input register switches 22 on the keyboard 20 is depressed. 86 is then reset by a reset pulse applied to the reset The display 24 is coupled to the microprocessor 42 130line 96, and new data is supplied to the input register.

3 GB 2 186 406 A 3 Because the resistive heating elements 80 draw a the seven registers 86' contain the bits 1-32,33-64, substantial amount of current, for example, app- 65-96,97-128,129-160,161- 192 and 193-224. Since roximately 50 milliamps per element, and because of this data completely defines a line, the data f rom the the extreme density of the elements, for example, registers 86'can be transferred to a data register, approximately 200 elements per inch, the current 70 such as the data register 88 (Figure 4), orto a plurality drain on the battery 26 would be excessive if all of the of individual data registers 88' (Figure 5). The output elements 80 were turned on simultaneously. Forthis of the data register 88'can be applied to a plurality of reason, the heater driver transistors 82 are strobed three-inputAND gates 84, orto any suitable device bythe gates 84 so that no more than one-fourth of for limiting the number of individual elements that the heater drivers 82 may be energized at any one 75 can be simultaneously energized.

time. In Figure 5, the strobe function that limits the In the embodiment illustrated in Figure 4, the number of elements that can be simultaneously en strobing is accomplished by utilizing three input ergized is provided by a plurality of circuits 83. Each AND gates asthe gates 84, and by enabling the gates of the circuits 83 contains 32two-inputAND gates 84 in blocks. This is accomplished by providing two 80 and appropriate driving circuitryfor driving the print block enable signals BE1 and BE2on lines 100and head 66. Such a system is somewhat simpler than 102, respectively, and strobes ST1 and ST2 on lines the system illustrated in Figure 4 because onlytwo 104 and 106, respectively. Each of the block enable inputAND gates, ratherthan thethree-inputAND signals is connected to one-half of the gates 84so gates, are required. By providing three strobe signals thatone-half of the gates 84 are enabled when the 85 S1, S2 and S3, the number of printing elementsthat BE1 signal is high, and the other half are enabled can be simultaneously energized is restricted to app when the BE2 signal is high. The ST1 signal is app- roximately one-third of thetotal number of print el lied to one-half of the gates 84 receiving the BE1 ements.

signal and to one-half of the gates 84 receiving the In the embodiment illustrated in Figure 5,the BE2 signal. Similarly,the ST2 signal is applied tothe 90 strobe signal S1 is applied to the firsttwo and the last gates 84 not receiving the ST1 signal. Thus, since it is one of the circuits 83. The strobe signal S2 is applied necessaryfor each gate to receive one of the block to the third and fourth ones of the circuits 83, and the enable signals and one of the strobe signals in order strobe signal S3 is applied to thefifth and sixth ones to befully enabled, only one-fourth of the gates 84 of the circuits 83. Consequently, no morethan two are enabled at any given time. Thus, the data from 95 out of seven printing elements may be simu the data register88 is applied to the heater driver ltaneously energized when eitherthe strobe signal transistor 82 in four steps, so that no morethan one- S2 orthe strobe signal S3 is present. Theoretically, fourth of thetransistors 82 may be energized at a as many asthree out of seven elements may be en given time. ergized when the strobe signal S1 is present, but in An alternative embodiment of the print head driv- 100 practice, the line of print is seldom as wide asthe ing mechanism is illustrated in Figure 5. The embodi- width of the print head 66, and consequently, it is ment illustrated in Figure 5 is similarto the one illust- unlikelythat more than one-half of the total elements rated in Figure4, exceptthatthe input register 86 is in thefirst and last ones of the circuits 83 would be broken up into a plurality of smaller registers, for ex- energized.

ample, seven 32-stage registers Win the illustrated 105 The control circuit46 (Figure 6) includes a control embodiment. Such an arrangement hasthe advan- processor 130that includes a read-only memory tagethat it permits data to be entered more rapidly (ROM) 132that may be located either on the same into the system,thereby permitting a faster printing integrated circuitasthe control processor 130 or in a speed. This occurs because each of the seven shift separate package. The various components required registers 86'can be fed in parallel from said seven 110 to carry outthe print control function are notshown separate data lines 90'. Consequently, the data need in Figure 6for purposes of clarity; however, itshould be shifted only32 timesto load the registers 86', as be understood thatthe microprocessor 42 of Figure 6 opposed to the 224shifts required to load the input must be coupled to componentsthat arethe same or register86. However,when loading the shift regis- analogoustothe components shown in Figure 2to ters 86'the 224 bits defining each line cannot befed 115 providethe printing function. The control processor serially intothe shift registers 86', butthe bits must 130 controls a motor drive/brake circuit 134that be grouped so thatthey may be applied to the app- selectively applies energizing or dynamic braking ropriate registers. This is accomplished bytaking currentsto the motor48. An analog-to-digital con every 32nd bitfrom the data defining a line, and app- verter 136 measuresthe back EMF of the motor48 lying itto the appropriate one of the shift registers 120 when it is coasting, and applies a digital representa 86'. For example, if 224 bits are used to define a line, tion of the back EIVIFto the control processor 130 in the 32nd, 64th, 96th, 128th, 160th, 192nd and 224th orderto provide an indication of the speed of the bits are selected and applied to seven stages of a buf- motor 48to the control processor 130. The detector fer 108 (Figure 5). These bits are then applied in par- 50 includes a light source, such asJor example, a allel to the shift registers 86'. Next, the 31 st, 63rd, 125 light emitting diode 138 and a light sensitive device 95th, 127th, 159th, 191 st and 223rd bits are applied to such as a photodetector 140 disposed on opposite the buffer 108 and shifted to the registers 86'. The sides of the timing disc 51. The detector 50 serves to process is repeated until the first, 33rd, 65th, 97th, detect indices formed as a series of light contrasting 129th, 161 st and 193rd bits are loaded into the buffer marks such as opaque and transparent portions on 108 and supplied to the registers 86'. At this point, 130the disc 51. Preferably, the indices are fabricated as a 4 GB 2 186 406 A 4 series of apertures about the periphery of the disc 51 ment that is equal to an integral multiple of the which are used to indicate to the system the position length of the print elements 80. For example, when a of the disc 51, and consequently, the position of the printing head such as the previously described print web 18 as it is advanced by the advancing wheel 49. ing head 66 is used, the distance between the detec Although, an optical system is used to detectthe 70 tion of adjacent edges of the slots 148,150 and 152 position of the disc 51, other systems may also be corresponds to a web travel that is equal to an in used. tegral multiple of 10 mils (the length of the print el Thetiming disc 51 is illustrated in greater detail in ements 80). In thetiming disc 51 illustrated in Figure Figure 7. The disc illustrated in Figure 7 isfabricated 7, the integral multiple has been selected to be equal from an opaque material. Because of the relatively 75 to two, thus providing a web travel of 20 mils be small size of the disc 51, for example, on the order of tween the detection of successive edges of the slots approximately 1.25 inches in diameter, and because 148,150 and 152. As a result,the position of theweb of the precise tolerances required, the use of electro- 14 is defined in 20 mil increments.

deposited nickel provides a convenient way to fabri- Thewidth of each of the warning tracks defined by cate the disc. The thickness of the disc 51 isnomi- 80 the widened areas 154,156 and 158 must be made nally3 mils, but mayvaryfrom 2 mils to 4 mils. wide enough to permitthe warning tracksto be dis As is illustrated in Figure 6, the disc 51 is mounted tinguished from the areas between the position def on the same shaft (shaft 141) as is the web advancing ining slots. In the embodiment illustrated in Figure 7, wheel 49 and rotates therewith to form a shaft enco- the width of the areas 154,156 and 158 is selected to der. In the illustrated embodiment, the wheel 49 85 be approximately twice as wide as the widths of the rotates one-third of a revolution each time a com- areas separating the slots 148,150 and 152. This pro plete label is fed. Three home position indices in the vides a warning track having a width that cor form of three apertures 142,144 and 146 are prov- responds to approximately four times the length of ided in the disc 51. In the illustrated embodiment, the printing elements 80, or approximately 40 mils.

three home position indices are provided because 90 Thewidth of the areas 154,156 and 158 isselected the disc 51 rotates one third of a revolution each time such thatthe areas 154,156 and 158 can be readily a label is fed; however, it should be understood that distinguished from the narrower areas separating if the advancing mechanism were modified such that the slots 148,150 and 152, and although in the emb the disc 51 rotated at a different rate, the number of odiment illustrated in Figure 7, the widened areas home position indices would have to be changed ac- 95 154,156 and 158 have been selected to be app cordingly. For example, if the disc 51 rotated one roximately twice aswide as the areas separating the fourth of a revolution each time a label was fed, a slots 148,150 and 152, other widths may be used.

discwith four home position indices would be used. In operation. when the labeler is not printing a Following each of the apertures 142,144 and 146 is label, one of the home position defining indicesJor a plurality of position defining indices in theform of a 100 example,the aperture 142 is aligned with the detec piuralityof apertures orslots 148,150 and 152, retor 50.When the trigger switch 44 (or othermanually spectively (Figure 7), which accurately define the operable switch) is depressed,the microprocessor position of the label with respectto the printing 42 (Figure 6) issues a start motor command to the head. Although the position defining indices 148,150 control processor 130 which in turn rendersthe and 152 can be referred to as either apertures or 105 motor drive/brake circuit 134 operativeto energize slots, or by other terminology they will be referred to the motor48. The light-emitting diode 138 is also en as slots in the following description for purposes of abled. When the motor 48 is energized, thetiming clarity in orderto better distinguish them from the disc 51 is rotated in the direction shown bythe home position apertures 142,144 and 146. Awarning arrows in Figures 6 and 7. As the motor rotates,any track is provided ahead of each of the home position 110 slack present in the web 18 and any backlash in any indices in the form of three widened areas 154,156 of the web advancing mechanism istaken up while a and 158. portion of the aperture 142 is still aligned withthe When no labels are being printed, one of the home detector 50. The motor 48 continuesto rotate until position defining apertures 142,144 or 146 is aligned the trailing edge of the aperture 142 is detected by with the sensor 50. Each of the apertures 142,144, 115 the detector 50. Atthis point, all slack in the system and 146 is sufficiently wide to permit some backlash has been taken up and the motor 48 is up to operat in the web and drive train to occurwithout causing ing speed.

an opaque area of the disc 51 to be detected bythe When thetrailing edge of the aperture 142 is detec sensor 50. This prevents the motor48 from hunting ted bythe detector 50, the amplitude of the signal in an attempt to keep one of the home position aper- 120 applied bythe photodetector 140 to the control pro tures aligned with the sensor 50. The size of the apercessor 130 changes. The control processor 130 re tures 142,144 and 146 is also selected to permitany sponds to this change by issuing a start print com slack in the web 18 to be taken up before one of the mand to the microprocessor 42. The start printsignal position defining indices is moved into alignment indicatesto the microprocessor 42 that the motor is with the detector 50. 125 up to speed and the web is positioned to accept print The width of the position defining slots 148,150 ing atthe printing positions defined by the selected and 152 and the width of the areas between the posi- printformat.

tion defining slots is selected such thatthe distance As the motor48 continues to rotate, the transitions between the detection of successive edges of the between the slots 148 and the opaque areas dis slots 148,150 and 152 corresponds to a web move- 130 posed therebetween are detected by the photodector GB 2 186 406 A 5 140, and signals representative of the transitions are andthedisc51 provided with a single keyslot or slot applied to the control processor 130. The control pro- engaging member. Othervariations could be used.

cessor 130 responds to the transitions and generates In the illustrated embodiment, this is accomplished a position pulse signal and applies itto the micro- by mounting the timing disc 51 on a keyed shaft and processor 42 each time a transition occurs. The posi- 70 providing a plurality of offset keyslots on the disc 51.

tion signals are counted by the microprocessor 42 in Each of the offset keyslots is associated with one of orderto determine the position of the label with re- the home position indices 142,144 and 146 and is spectto the print head 66. When the print head 66 is offset therefrom bythe amount of adjustment requi positioned over a print area on the label, as defined, red. Thus, any required adjustment may be obtained for example, by the printformat, the entered data is 75 by positioning the appropriate slot on the key of the printed on the labels 16. The process continues with shaft.

the microprocessor 42 receiving position pulse For example, in the timing disc illustrated in Figure signals from the control processor 130 until the ente- 7, three keyways captioned 1, 2 and 3 are shown. In red data is printed on one or more print areas of the the angular displacement between the keyways 1 labels 16. 80 and 3 is nominally 122% whMethe angular displace Asthe printing process continues, thetiming disc ment between the keyways 1 and 2, and 2 and 3 is 51 continues to rotate until the warning track defined nominally 1190. This compares with a 120'angular bythe widened area 154 is detected. The widened displacement between the leading edges of the aper area 154 is detected by the control processor 130 tures 142,144 and 146, and permits a 1 0 adjustment when the length of time that an opaque area is being 85 ofthedisc51 relative to the web advancing wheel 49 detected by the photodector 140 exceeds the length and the detector 50.

of time between the transition pulses generated by If for example, the keyway designated bythe the slots 148 by a predetermined amount. Once it has numeral 1 were keyed to the shaft 141 byakey160, been determined that a warning track such as the the trailing edge of the aperture 142 will lead the area 154 has been detected, the microprocessor is 90 center line of the key 160 by approximately 2'. The 2' conditioned to respond to the nexttransition by ren- offset shall be called the minus 1'position. If thedering the motor drive/brake circuit 134 operativeto keywaycaptioned bythe numeral 3 is keyed tothe brake the motor48. Thus,when the leading edge of key 160, because the keyways 1 and 3 are spaced by the aperture 144 is detected, a brake sig nal is applied 122% the trailing edge of the aperture 144 will lead to the motor d rive/brake cireu it 134 to cause the 95 the center of the key 160 by 4% thus resu lting in a motor drive/brake circu it 134 to shunt the armatu re positive 2'shift in the position of the positioning winding of the motor48to thereby dynamically slots with respeetto the minus 1'position. Adding 2' brakethe motor48. The motor48 continues to coast to minus 1 o results in positive 1% so this position can for a short distance until the aperture 144 is aligned be considered the plus 1'position. If the keyway with the detector 50, and the printing process ister- 100 captioned bythe numeral 2 is keyed to the key 160, minated. If it is desired to print another labeLthe the disc 51 will have been rotated a total of 122'plus trigger switch 44 is again depressed and another 11 9'or 241 o relative to its position when keyed to label is printed as the disc 51 is advanced until the keyway number 1, thus resulting in a positive 1 0 shift aperture 146 is aligned with the detector 50. in the position of the positioning slots relative to the Also, although the timing disc 51 is shown in con- 105 minus 1 " position. Thus, this position becomes the junction with a motor driven advancing mechanism, zero degree position, and positive and negative 1 it may also be used in conjunction with a hand or degree adjustments of the disc 51 relative to the zero manually operated advancing mechanism. In such degree position may be readily attained. Other an event, even though the signals provided bythe adjustments may be achieved by altering offsets timing disc 51 would not be used to control a motor, 110 between the keyways 1, 2 and 3. For example, a 2' the position signals would still be used to indicateto adjustment by spacing the keyway captioned 3 by the microprocessor when a printable area is beneath 124'from the keyway captioned 1, and by spacing the print head, and cause printing to be initiated the keyway captioned 2 by 1180 from the keyways when such an area is present. captioned 1 and 3. In general, any offset may be As previously stated, the timing disc 51 provides 115 achieved by appropriately spacing the keyways 1 very accurate information defining the position of and 3 bythe total desired positive and negative offset the web. However, in orderto make use of the ac- added to 120'. If equal positive and negative offsets curate position signals provided bythetiming disc are desired, such equal positive and negative offsets 51, it is necessary to compensate for manufacturing may be achieved by dividing the remainder of the tolerances present in the web advancing mechanism 120 360'are between the keyways captioned 2 and the and in the positioning of the print head 66. Consequ- keyways captioned 1 and 3.

ently, in accordancewith anotheraspectof the pre- Although varioustypes of motors, including sent invention,there is provided a wayto alterthe stepping motors, are usable asthe web advancing angular position of thetiming disc 51 with respectto motor48, it has been found that a D.C. motor is the angular position of theweb advancing wheel 49. 125 particularly useful asthe web advancing motor48, Various other keying means could be used to affix partly because of its good low speed torque the disc 51 to the shaft. For example, a slot could be characteristics. However, when a D.C. motor is used, provided on the shaft, and slot engaging members it is necessaryto provide circuitryfor controlling the could be provided on the disc. Alternatively, the shaft speed of the motor shaft. In the present could be provided with a plurality of keys or keyslots, 130 embodiment, the motor speed control is provided by 6 GB 2 186 406 A 6 the control processor 130. As previously discussed, the motor 48. Consequently, the voltage across the the control processor 130 receives signals motor 48 is not immediately sampled because it is representative of the back EMF generated bythe not representative of the back EIVIF being generated motor 48 when it is coasting, and adjusts the drive bythe motor. Instead, the sampling is delayed until a signal applied to the motor 48 to thereby maintain 70 sampling period 182 thatfollows the time 2T by a the speed of the motor 48 substantially constant. time interval sufficieritto allowthe transieritto die Referring to Figure 8, the motor 48 is driven bythe down. It has been determined that delaying the motor drivelbrake circuit 134which includes a sampling period 182 for approximately 300 transistor drive circuit 170 that applies an energizing microseconds following the termination of a run potential to the motor 48 when a run signal is 75 pulse allows enough of the transieritto die down to received from the control processor 130. An interlock permit an accurate reading of the back EIVIF of the circuit prevents both the run and brake signaisfrom motor 48 to be made; however, the delaytime is being applied to the drive/brake circuit 134 dependent on the size and inductance of the motor, simultaneously in the event of a microprocessor or as well as otherfactors, and othervalues may be other malfunction. The motor drive/brake circuit 134 80 used depending on the particular components used.

also includes a dynamic braking circuit 172 that The sampling is done underthe control of the shunts the armature of the motor48 to provide sampling gate 176 which is enabled during the dynamic braking when a brake signal is received sampling period 182 and other sampling periods by from the control processor 130. A comparator 174 is the microprocessor 130.

connected to the motor48 and servesto comparethe 85 If the back EIVIF measured during the sampling back EIMF9enerated bythe motor48when it is period 182 istoo low, another run pulse 184is coasting and with a reference voltage. Asampling generated during thetime interval between 3Tand gate 176 couplesthe output of the comparator 174to 4T, andthe back EMF is again sampled during a the control processor 130. sampling period 186 occurring priorto the time 5T. If The run signal applied to the drive circuit 170 90 the back EMF during the sampling period 186 is includes a series of pulses which cause the drive again too low, another run pulse will be generated at circuit 170 to energize the motor48 at periodic time 5T; however, if the back EMF is higherthan the intervals. The back EMF generated bythe motor48 reference voltage, no run pulse will be generated at between drive pulses is sampled bythe comparator time 5T, as is illustrated in Figure 9. Rather,the back 174and the sampling gate 176, which operate as an 95 ENIFwill be sampled during a subsequent sampling analog-to-digital converter,to indicate to the control interval 188 priorto the time 6T, and if the back EMF processor 130whetherthe back EIVIF generated by has dropped belowthe reference voltage, another the motor48 is greaterthan or less than the reference run pulse 190 will be generated atthetime 6T.The voltage applied tothe comparator 174. If the back process will be repeated at periodic intervals with the EMF is lesthan the reference voltage, the next run 100 run pulses being eliminated as required to maintain pulse is generated bythe control processor 130 the speed of the motor48 substantially constant.

again to energizethe motor48. If the back EMF Referring nowto Figure 10, when the labeler is generated bythe motor48 is greaterthan the intially energized,the parameters in the reference voltage, indicating thatthe speed of the microprocessor 42 and the control processor46 are motor is excessive,the next run pulse is eliminated, 105 initialized, and the control processor46 is and the motor is allowed to coast. During the conditioned to initiatethe feeding of theweb upon coasting period the back EMF is measured at receipt of a start pulsefrom the microprocessor 42.

periodic intervals until it drops belowthe reference Upon receipt of a start pulse, a clock in the control voltage, atwhich point another run pulse is processor46 is resetto zero. Subsequently, a generated. The speed of the motor may be adjusted 110 separatetimer is updated to indicate how many by adjusting the reference voltage. times the control processor clock has been reset.

The run pulse generation and back EMF sampling This provides an indication of how long the motor48 is illustrated in greater detail in Figure 9. Referring to has been running. If thetime exceeds a Figure 9,the back EMF is sampled during a first predetermined limit,the run timertimes out,the sampling period 179 occurring during a portion of 115 motor is stopped and braked, and the control the time interval ranging from zero to T. If the back processor 46 is conditioned to awaitthe next start ENIF is less than the reference a run pulse, as pulse. A signal may also be seritto the audio alarm illustrated bythe pulse 180 is generated during the 52 to indicate a jam. If no timeout occurs,the time interval between T and 2T. The duration of the detector 50 is sampled to determined whether a start pulse 180 is controlled bythe clock (notshown) in the 120 print edge (first opaque edge after home position control processor 130, and is preferably on the order aperture, Figure 7) has been encountered. If the edge of 500 microseconds to 1 millisecond. No sample is has been detected, a start print pulse is seritto the taken during the time interval between T and 2T microprocessor 42, and the condition of the motor is because such a sample would be meaningless checked, as is described later. If the edge passed because all that would be measured would be the 125 previously, the timing disc is checked for a position amplitude of the pulse 180. index. If a position index is detected, a position pulse Afterthe run pulse 180 has been terminated atthe is seritto the microprocessor 42. If no index is time 2TAhe drive to the motor48 is also terminated; detected, the timing disc is checked forthe presence however, thetermination of the drive to the motor48 of the warning track (widened opaque area, Figure results in a transient across the armature winding of 130 7). The widened area can be readily determined by 7 GB 2 186 406 A 7 the length of time it is aligned with thesensor50. 1 1)that monitors the voltage produced bythe main When the end of the warning track is detected,the battery, such as,the battery26, and protectsthe motor is stopped,the brake isturned onfora various memories andthe print head in the eventof a predetermined time interval, and the control low battery condition, and in the everitthatthe processor is conditioned to awaitthe next start 70 battery is removed. This is accomplished by a motorcommand. comparator 200 that compares the voltage atthe The purpose of the above-described steps is to battery 26 with a low battery voltage reference. In the determine the position of the timing disc, and hence event thatthe voltage provided bythe battery 26 the position of the label during the printing cycle. In drops belowthe low battery reference potential,the addition to determining the position of the label,the 75 comparator 200 applies a signal to the speed of the motor must be determined. In the logic microprocessor 42 and to the control processor46 in diagram illustrated in Figure 1 0,the motorspeed orderto putthe processors in a reset condition to check is made subsequeritto each position check. prevent erratic operation thereof. In addition, the Thus, if the run timer has nottimed out, and the end comparator200 applies a disabling signal tothe of the warning track has notyet been detected, a 80 RAM 58 andthe NVRAM 60to prevent datafrom motor speed check is made. This is accomplished by being written onto or erased from the RAMs. A first checking the motor to see if it is on or off. If the disabling signal is also applied to the print head 64to motor is off, the system waits until a sampling period clamp the print head driver 68 to thereby prevent is reached. When the sampling period is reached, the energization of the print head 66. Thus, the RAMs back EMF is checked to determined motor speed. 85 and the print head are effectively protected from The result of the check, indicating whetherthe motor erratic operation of the microprocessors.

speed is too fast ortoo slow, is stored. If the motor is In orderto preveritthe loss of data from a on, no speed check can be made, and the motor is non-volatile read-only memory such asthe NVRAM turned off. 60, a back-up battery, such as, for example, a lithium Afterthe back EMF has been checked, or afterthe 90 battery 210 (Figure 12), is provided. The use of a motor has been turned off, the system waits forthe lithium batteryfor such a purpose is particularly processor clockto reach time T, that is, the nexttime advantageous because such batteries have a at which a run pulse can be generated. When the relatively long shelf life, on the order of time T is reached, the stored result is checked to approximately ten years. However, if the lithium determine whetherthe motor speed was too slow. If 95 battery were used to powerthe NVRAM for extended the motor speed had been too slow, the motor is periods of time, it would become discharged turned on, the control processor clock is resetto relatively rapidly. Therefore, some means must be zero, the run time is updated to include the time provided to preveritthe back-up battery 21 Ofrom accumulated bythe processor clock during the last discharging prematurely. Thus, when the labeler is cycle, and the cycle is repeated. If the speed of the 100 turned on, the NVRAM 60 is powered from the main motorwas nottoo slow, the motor is notturned on battery, such as the battery 26; however, some before the processor clock is resetto zero and the run provision must be provided to powerthe NVRAM 60 timer updated. In the everitthatthe motorwas when the labeler is stored in an off condition for an previously on, and no back EMF checkwas made and extended period of time.

stored, it is assumed thatthe motorspeed was not 105 In the hand-held labeler according to the too slow, and the processorclock is resetto zero invention,the labeler circuits are powered bythe withoutturning on the motor. Because the motor is battery 26which is connected to a voltage regulator now off, a speed checkcan be readily made during 212 via an on-off switch 214 (both notshown in the next cycle. Figure 2). The regulator 212 provides a regulated As previously discussed, the labeler according to 110 voltage, for example, 5.6 volts, to the labeler circuits the invention is a hand-held labeler that is powered wheneverthe on-off switch 214 is closed. Under by a battery. As in the case of all battery-powered these conditions, the outputvoltage of the regulator devices, thevoltage applied to the various circuits 212 is applied to the NVRAM 60 by means of a drops as the battery discharges, and may even reach blocking diode 216, and the NVRAM 60 is powered zero when the battery is completely discharged or is 115 by the battery 26 via the switch 214, the regulator 212 removed. Such voltage variations can cause serious and the diode 216 wheneverthe labeler is operating.

problems. For example, when the voltage applied to Adiode211 isolates the battery 210 from the rest of a microprocessor drops below a predetermined the circuitry under these conditions because the level. the operataion of the microprocessor becomes voltage applied to the NVRAM 60 is higher than the erratic. When this occurs, the errative signaisfrom 120 voltage of the battery 210, and the diode 211 is the microprocessor can alter or erase the data stored reverse biased.

in the various memories. The processor can also When the labeler is turned off,the outputvoltage cause damageto the print headjor example, by of the regulator212 is zero, and consequently. ifthe continuously energizing one or more of the printing labeler is stored for an appreciable length of time, elements. In addition, when a non-volatile RAM, 125 the back-up battery 210 will eventually discharge if such asthe NVRAM 60, is used, a drop or loss of the regulator212 were relied on to powerthe batteryvoltage can causethe data stored in the NVRAM 60. Therefore, in accordancewith another NVRAM to be lost. important aspect of the present invention, there is Thus, in accordance with another aspect of the provided an auxiliary circuitthat powers the NVRAM present invention, there is provided a circuit (Figure 130 60 even when the labeler is off. The auxiliary circuit GB 2 186 406 A 8 includes a Zener diode 218 that is coupled to the following the termination of the energizing pulse; battery side of the switch 214 by a resistor 220. The means for comparing the amplitude of the junction of the resistor 220 and the Zener diode 218 is sam pled back EM F with a predetermined amplitude; coupled to the NVRAM 60 by another blocking diode and 222. Thus, when the switch 214 is open, the NVRAM 70 means responsive to said corn pari ng means for is powered by the auxiliary circuit. As in the case generating another energizing pulse within a second when the switch 214 is on, the diode 211 isolates the predetermined time interval if the amplitude of this battery 210 from the rest of the circuitry as long as back EMF is belowthe predetermined amplitude.

the battery 26 is present and active. By making the 2. A system as recited in claim 1, further voltage of the Zener diode 218 lower than the output 75 including means responsive to said comparing voltage of the regulator 212, for example, 4.2 volts, means for preventing the generation of another interaction between the two circuits is eliminated. energizing pulse within the second predetermined For example, when the switch 214 is closed, the time interval if the amplitude of the back EMF is voltage appearing atthe cathode of the blocking above the predetermined amplitude.

diode 222 is greater than the voltage appearing at its 80 3. A system as recited in claim 2, wherein said anode. This reverse biases the diode 222 and comparing means includes an analog comparator.

prevents currentsfrom flowing from the regulator 4. A system as recited in claim 3, wherein said 212 into the Zener diode 218 and discharging the comparing means responsive means includes a battery 26. When the switch 214 is open, the blocking digital sampling means responsive to said delay diode 216 is reverse biased, thus preventing the 85 means.

labeler circuitry from discharging the batteries 26 5. A hand-held labeling machine comprising; a and 210. If the battery 26 is removed, or becomes housing having a manually engageable handle,the discharged, the diode 211 becomesforward biased housing having meansfor holding a label supply roll and the NVRAM 60 is powered bythe battery 211. of a compositeweb having labels releaseably Underthese conditions,the diodes 216 and 222 90 adhered to a backing strip, meansfor printing on a isolatethe battery 211 from all of the labeler circuitry label at a printing position, meansfor peeling the otherthan the NVRAM 60. printed label from the backing strip,-label applying Thus it is seen thatthe hand-held labeler described means disposed adjacentthe peeling means, means includes a system for precisely sensing the position for advancing the web to peel a printed label from of the web, for adjusting the position of theweb 95 the backing strip atthe peeling means and advance relativeto the printing devicewith greataccuracy, the printed label into label applying relationship with and for controlling the energisation of the printing the label applying means and to advance another elements in accordance with the web position in label into the printing position, means for entering orderto position the imprints on the web with this selected data to be printed, the printing means accuracy. The web position sensing system is 100 including a thermographic pring head having a particularly usable with a thermographic printing plurality of individually selectable print head having device, and minimisesthe possibility of damageto a plurality of individually selectable print elements the printing device. The web positioning device for printing on a thermographic label at a printing positions the webto an accuracy of a few mils and position, means coupled to said data entering means provides a ready positioning adjustmentthat is also 105 for electrically processing the selected data and accurate to within a few mils, The web can be readily energizing the individual print elements in a repositioned with an accuracy of a few mils to predetermined sequence determined bythe selected compensate for manufacturing tolerances. The data to print data on the label, said advancing means system controls the printing device to compensate including an electric motor and meansfor forvariations in the speed of the web, and is usable 110 controlling the speed of the electric motor, said with hand advanced and motorised web advancing speed control means including:

mechanisms. meansfor providing an energizing puiseto said Obviously, many modifications and variations of electric motor; the present invention are possible in light of the meansfor providing a predetermined time delay aboveteachings. Thus, it is to be understood that, 115 following the termination of the energizing pulse; within the scope of the appended claims, the means responsiveto the delay meansfor invention may be practiced otherwise than as sampling the amplitude of the back EIVIFgenerated specifically described above. bythe electric motor after a predetermined delay following the termination of the energizing pulse;

Claims (1)

1. CLAIMS 120 means for comparing the amplitude of the sampled back EMFwith a

   predetermined amplitude; 1. A system for controlling the speed of an and electric motor, comprising: means responsive to said comparing means for means for providing an energizing pulse to said generating another energizing pulse within a second electricmotor; 125 predetermined time interval if the amplitude of this meansfor providing a predetermined time delay back EMF is below the predetermined amplitude.

   following the termination of the energizing pulse; 6. A hand-held labeling machine as recited in means responsive to the delay means for claim 5, further including means responsive to said sampling the amplitude of the back EMF generated comparing means for preventing the generation of by the electric motor after a predetermined delay 130 another energizing pulse within the second 9 GB 2 186 406 A 9 predetermined time interval if the amplitude of the back EM F is above the predetermined amplitude.

   7. A hand-held labeling machine as recited in claim 6, wherein said comparing means includes an 5 analog comparator.

   8. A hand-held label ing machine as recited in claim 7,wherein said comparing means responsive means includes a digital sampling means responsive to said delay means.

   Printed for Her Majesty's Stationery Office by Croy clon Printing Company (L1 K) Ltd,6187, D8991685. Publ Shed by The Patent Office, 25Southampton Buildings, London, WC2A 'I AY, Yorn which copies maybe obtained.

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