Tape printing device

Abstract: A label tape printer has a more-or-less conventional label tape cassette gear train mechanism (23 - 28) except that the main motor (3) has a clutching means (22,23, 51, 53) that can disengage the motor when the motor is not on and turning. This allows the motor loads to turn the gear trains without any tendency of the motor to hold the gear train frozen by its advantage through the gear reduction. Therefore a pull on the label tape end will result in the entire gear train turning and thereby preventing the ink ribbon from forming a loose loop that can get sucked into an adhesive tape sandwich (with catastrophic results). The label tape cassette is provided with a guide roller having deep grooves, giving the appearance of a piece of machine screw threaded stock, tat is positioned to keep the adhesive tape from sticking to the inside walls if the tape reels loosen. The adhesive tape has a reduced surface area on the guide roller to become stuck on it also.

Description: This invention relates generally to label tape printers and more particularly to tape cassettes and their drive mechanisms. A series of label tape printers and matching print cassettes for them have very recently become popular, especially in Japan. These printers have as a very remote ancestor, the DYMO plastic tape label maker that was popular in the United States in the 1960's and 1970's. A more recent and closer relative is the KROY lettering machine. The new label tape printers are able to print a line of characters on an adhesive tape strip that is cut off at the end of the print line and which can be stuck on things, very much like SCOTCH tape can. The label tape used in these printers is special, and comes ready-to-use in a tape cassette that includes an ink ribbon for the print head. The finished tape output by the printer really has three parts, a transparent tape on which ink is printed, a double-sticky adhesive tape, and a backing that is peeled-off later to apply the label. The backing and adhesive tape are on a first reel inside a fresh cassette, the transparent tape is on a second reel, and the ink ribbon, usually a thermal ink type, is supplied on a third reel and taken up by a fourth reel. To print a label, the ink ribbon and print head are brought into contact with the transparent tape. An inside-out image is printed by the head on the transparent tape so that the image will read right when viewed through the tape. The transparent tape is then pressed together with one sticky side of the adhesive tape such that the printed ink is inside the sandwich. That way, the ink will not rub off. On the other side of the adhesive tape is the peel-off backing. After the tape sandwich has been pressed together, it exits one end of the tape casette, and a cutting unit usually cuts the tape after the line of print has been finished. The user then pulls the piece out and uses it. The prior art, as could be expected, had a complex series of gears, pulleys, and rollers to manage the printing, feeding, and assembly of the tape during use. During printing, it is important that the ink ribbon and transparent tape move together at the same rate. This prevents rubbing that can cause ink smudging. The least amount of tape will be wasted in leaders and trailers if the label tape is pressed together and cut near the point of ink printing. But to assemble the tape, the ink ribbon must be gotten out of the way quickly after serving its purpose under the print head. Since the ink is winding up on the inside of the tape sandwich, and since the tapes must be sandwiched very close to the point of printing, the ink ribbon, by necessity, must be positioned very close to the "jaws" of tape coming together. And extremely important job of the printer gearing mechanism is to keep the ink ribbon taught and out of harm's way. Most of the time everything works as was intended. But in prior art label tape drive mechanisms, if a user pulls on a tape that has not yet been cut, the gears on the tape rollers and reels will be dragged against the resistance of the transport motor and its high reduction gears. The usual, catastrophic result is the ink ribbon sucks up into the jaws of the pressure rollers pressing the transparent tape to the adhesive tape. The entire cassette is ruined at that point and the damage cannot be undone or the tapes unstuck. Cutting the tape off with the cutter also cuts the ink ribbon (because a loop of it is stuck inside). The ink ribbon then will not feed because its take-up reel is effectively out of the system. Given human nature, the above scenario is all too common an occurrence. A tape printer according to the precharacterizing portion of claim 1 is disclosed in the document EP-A-0 322 918 which also describes a tape casette for use with the printer. In this prior art the ribbon winding means (take-up drive member) and the tape feed means (tape feeder) can be reversibly driven by a stepping motor and a power transmission mechanism. The power transmission mechanism for the ribbon winding means includes a slip mechanism which provides a function such that the rate of take-up of the ink ribbon on the take-up drive member is varied according to the load on the drive member. The present invention solves the problem explained above by allowing the user to go ahead and yank on the tape, but then arranging the gears so that they can spin free of the motor. The various reels, gears, and rollers then all maintain their respective positions and the ink ribbon simply is taken up by its take-up reel, instead of loosening up to become sucked into the final tape assembly. A second, related problem is also solved by the present invention. The adhesive tape has an exposed sticky surface between the reel and the pressure rollers that combine it with the transparent tape. A guide roller is needed between the reel and the rollers to keep the adhesive tape from flopping around and getting stuck to the inside walls of the cassette, or worse, to the ink ribbon. But ordinary cylindrical guide rollers give the adhesive tape too much surface area to attach to, and so can become stuck, especially after long idle periods. A guide roller having deep grooves and giving the appearance of a piece of machine screw threaded stock is used to solve this problem. According to this invention, a label tape printer has a conventional label tape cassette gear train mechanism except that the motor has a clutching means that disengages the motor when the motor is not on and turning. This allows the motor loads to turn the gear trains without any tendency of the motor to hold the gear train frozen by its advantage through the gear reduction. Therefore a pull on the label tape end will result in the entire gear train turning and thereby prevent the ink ribbon from forming a loose loop that can get sucked into an adhesive tape sandwich (with catastrophic result). The label tape cassette is provided with a guide roller having deep grooves, giving the appearance of a piece of machine screw threaded stock, that is positioned to keep the adhesive tape from sticking to the inside walls if the tape reel loosens. The adhesive tape has less of a surface area on the guide roller to become stuck on. An advantage of the present invention is that the rather innocent act of a user in yanking on a label tape end will not ruin a label tape cassette. Another advantage of the present invention is that adhesive tape inside the tape cassette will not become attached to the inside walls of the cassette or lock to the guide roller that keeps the tape away from the inside walls. Another advantage of the present invention is that even if a user pulls out exiting label tape, any slack in the thermal ink ribbon will be taken up. The thermal ink will not sag between the print head and the ribbon take-up core. Therefore, it is possible to maintain an ideal peel off angle. Excellent print quality is a direct benefit. Another advantage of the present invention is that overfeed of the thermal ink ribbon in the tape cassette is prevented, eliminating the hazard of rendering the tape cassette unusable. Another advantage of the present invention is that the present invention allows a reduction in the amount of force needed to pull out the adhesive tape because the adhesion between the adhesive tape and the tape roller has been reduced, the amount of electric power consumed by the motor also can be reduced. This extends the life of batteries. Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings. Fig. 1(a) is an end view of a label tape cassette drive mechanism for a printer according to the present invention. Fig. 1(b) is a top view of the mechanism of Fig. 1(a) and has some of the gears shown in phantom view that are located behind the base plate; Fig. 2(a) is a top view of a label tape cassette that can be loaded on the mechanism of Figs. 1(a)-1(b). Elements located inside the cassette and not visible with the top outside cover removed are shown in phantom view; Fig. 2(b) is a top view of the cassette of Fig. 2(a) with the top removed; Fig. 3 is a view of the adhesive tape guide roller and cross-section of the adhesive tape taken along the line 3-3 in Fig. 2(b). The shape of the guide roller is such that only the peaks formed by grooving contact a sticky side of the adhesive tape. The guide roller is round and generally cylindrical in shape (except, of course for the deep grooves on its surface); Fig. 4(a) is an end view of the label tape cassette drive mechanism of Figs. 1(a)-1(b) when a cassette loading cover on the printer is open; Fig. 4(b) is the top view. Note how the thermal print head 5 has been retracted from roller 35 and pinch roller 11 and 36 are opened; Fig. 5(a) is an end view of the label tape cassette drive mechanism when a cassette loading cover on the printer is closed; Fig. 5(b) is the top view. Note how the thermal print head 5 has been loaded against roller 35 to pinch ink ribbon 34 and transparent tape 33, note also pinch rollers 11 and 36 are closed; Fig. 6 is a block diagram of the printer and its computer control unit; Fig. 7 is a timing chart showing the sequencing of various gears and motors during several operations; and Fig. 8 is a three-dimensional perspective view of a complete label making printer that incorporates the print mechanism and label tape cassette disclosed here and shows in phantom how the cover opens to expose the cassette for service. The finished label tape is shown coming out the left side and the printed letters "PRIN" are visible and the word "PRINT" is being displayed on an LCD panel. Referring to Fig. 1, a print mechanism (60, Fig. 6) comprises a frame 1 and a base plate 2. A print head assembly mounted on base plate 2 comprises a thermal print head 5, a head support 6, a head arm 7, a head support shaft 8, a head arm shaft 9, and a head hold-down spring 10. Label tape is gripped and released by a retractable roller assembly mounted on base plate 2, the assembly comprises a tape feed roller 11, a swing arm 12, a spring 13, a release lever 14, and a release lever support sleeve or shaft 15, all of which rotate on a shaft 16 when a pushrod 17 engages a cover cam 18. (Tape feed roller 11 and its opposing roller in a tape cassette supply the only force to unwind and join the two tapes from their respective reels within cassette.) The head arm 7 has a section 7-1 that makes direct contact with release lever shaft 16. Arm 7 rotates a short distance on head arm shaft 9. Head support shaft 8 allows head support plate 6 and print head 5 to wobble slightly in and out at the label tape edges on head arm 7. Head hold-down spring 10 is wound around shaft 9 and forces head arm 7 to swing on shaft 9 in direction "E". The use of spring pressure allows some amount of "give" between print head 5 and a platen roller (35) carried in the tape cassette that slips over shaft 31. Notwithstanding the small amount of give, enough pressure will be maintained over the range of movement to give good printing results. Tape feed roller 11 rotates on shaft 28-1 and is driven by tape feed gear 28. The tape feed roller swing arm 12 has a contact area 12-1 and can pivot around slightly on a shaft 29. The swinging action of arm 12 allows tape feed gear 28 to be engaged/disengaged with a gear 27. When engaged, roller 11 presses against the opposing roller (36 that is carried in the tape cassette and that slips over shaft 30). A printer case 19 houses the above mechanisms and has a cover 20 that can open to receive a label tape cassette. See the discussion below for Figs. 4 and 5 regarding the operation of release lever 14 the occurs as a consequence of opening cover 20. Spring 13 is wound around shaft 28-1 such that it pushes roller 11 in direction "F". This allows some give between tape feed roller 11 and opposing roller (36) carried in the tape cassette that slips over shaft 30. Nevertheless adequate pinching pressure is maintained between the rollers. Release lever 14 carries shaft 15 so that it makes contact with the frame and is able to rotate back and forth in the directions indicated by "G". The release lever shaft 16 attaches to release lever 14. Pushrod 17 is held in position by base plate 2 and is able to move in and out, as indicated by "H". One end of pushrod 17 is in contact with one end of release lever 14. The above embodiment of the present invention differs from the prior art especially in the fact that its motor can automatically disengage from the gear train. A stepper motor 3 drives gear 22. A planetary (epicyclic) gear assembly frame 51 is supported by motor shaft 3-1 and carries a shaft 52 and a gear 53 than is driven by motor gear 22. Although motor 3 is a stepper motor in this example, a DC motor with appropriate position sensors could serve just as well. When motor 3 turns in direction "P1" gear 22 will also turn in direction "P1" and frame 51 rotates in direction "Q1" such that gear 53 engages a reduction gear 23. As motor 3 turns more, frame 51 slips on shaft 3-1 and planetary gear 53 is kept under slight pressure against gear 23. A transfer gear 24 is driven by gear 23 and turns ink ribbon take-up reel shaft 4 and gear 26 in direction "U". Ribbon take-up reel shaft 4 has a friction clutch and pulls the ink ribbon in the tape cassette by turning the take-up reel. In a second drive power path, a transfer gear 25 turns tape feed transfer gear 27. Gear 28 engages transfer gear 27 and turns roller 11 when cover 20 is closed and release lever 14 has moved in direction "L". In Figs. 2(a)-2(b), a tape label cassette compatible with the above printer mechanism comprises a ribbon take-up core 32, a transparent tape 33 and supply reel, the platen roller 35, the tape hold-down roller 36, and an adhesive tape 37 and supply reel, all of which are housed between a cassette case bottom 38 and top 39. Platen roller 35 rotates on a hollow axle shaft which has a hole 35-1 that is meant to receive platen roller shaft 31 for support (but not for roller drive). The tape hold-down roller 36 also rotates on a hollow shaft which has a hole 36-1. Tape feed transfer gear shaft 30 is intended to slip into hole 36-1, and shaft 30 does not drive roller 36. The only tape drive force comes from roller 11, and it must press the label tape hard against roller 36 so that there is enough pinching pressure and friction to pull the label tape through its circuit. A thermal ink ribbon 34 winds on the ribbon take-up core 32, which has a splinted hole 32-1. The splinted hole 32-1 is intended to engage ribbon take-up reel shaft 4, when the cassette is installed on the drive mechanism, and, as such, they provide the drive force needed to advance the ink ribbon 34 during printing. Transparent tape 33 is joined to two-sided sticky adhesive tape 37 between rollers 11 and 36. A separation material keeps tape 37 from sticking to itself too much and doubles as a peel-off backing. A tape guide roller 40 is on the exposed adhesive side of adhesive tape 37 and is positioned to keep adhesive tape 37 from wandering around and perhaps sticking to the inside walls or other structures of the cassette. Guide roller 40 is free spinning and therefore better able to break free of any attachment the develops between it and adhesive tape 37. To further reduce the ability of adhesive tape 37 to get itself stuck on the wrong things, guide roller 40 has a special shape, described below in reference to Fig. 3. Although Fig. 2(b) shows only one guide roller 40, as many more as are needed can be used, especially if the exposed path of adhesive tape 37 is long. Notwithstanding the number and positioning of guide roller(s) 40, a small, sharp bulge can form in adhesive tape 37 around roller 36. This bulge can contact the inside walls of the cassette or worse, can contact ink ribbon 34. A wall area 41 has a plurality of peaks that present a reduced surface area for adhesive tape 37. Wall area can be positioned near roller 36. Guide roller 40 and wall area 41 form an adhesive tape guide means. The cassette case bottom 38 has a pair of alignment holes 38-1 and 38-2 that engage a matching pair of tape cassette alignment shafts 2-1 and 2-2 (Fig. 4(b)). The cassette case top 39 fits over the case bottom 38 and is shown only in Fig. 2(a) for clarity in presenting the other structures. Fig. 3 illustrates how ridges and grooves are formed around the circumference of tape roller 40 in a system of parallel rings. Just the tips of these peaks will contact adhesive tape 37. A cylinder tangent to a plane will have an intersection that is a line. Here, the intersection is reduced to a series of dots. Therefore, the area of contact is substantially reduced, and it follows that very little adhesive will have an opportunity to contact and grip guide roller 40. The system of peaks on guide roller 40 does not need to be regular, and it does not need to consist of ridges. However, ridges are preferred, as shown. The peaks could be randomly distributed like the quills or spines on a porcupine or sea urchin. The same is true of the wall area 41. Such spines need to be dull so that tape does not impale on the spines. The wall, of course, does not have the advantage of guide roller 40, in that it cannot rotate away to twist and break free of any tape attachment. But the wall area 41 does present a reduced surface area for attachment, and can help to control and manage the movement of adhesive tape 37. Other positions are possible for wall area 41 within the label tape cassette. Figs. 4(a)-4(b) illustrate a tape cassette sitting in position in the printer with cover 20 open. Holes 38-1 and 382, at the underside of cassette case bottom 38, engage tape cassette alignment shafts 2-1 and 2-2 to align the cassette in the right spot. Print head 5 and tape feed roller 11 are shown in their retracted positions and do not interfere with the installing or removing of the cassette. Figs. 5(a)-5(b) are similar to Figs. 4(a)-4(b), but with cover 20 closed. Print head 5 and tape feed roller 11 are shown in their operational positions and would prevent any attempt to insert or remove a cassette. By rotating cover 20 in direction "K", head arm 7 swings in direction "E" and swing arm 12 moves in direction "F". As a result, print head 5 loads under force of head hold-down spring 10 and makes contact with platen roller 35 (if a cassette is installed, which it should be). In addition, tape feed roller 11 is forced by type feed roller spring 13, so contact is made with tape hold-down roller 36 (again, if a cassette is installed). Tape feed transfer gear 27 and tape feed gear 28 then mesh together. This is the "printing enabled" condition. Fig. 6 illustrates a complete system for printing comprising print mechanism 60, having as its principal parts print head 5 and motor 3 (described above); a CPU 72, a print head control circuit 75, a motor control circuit 76, an interface 71, and memory comprising a ROM 73 and a RAM 74. The electronics can consist mainly of a microcomputer or personal computer system with appropriate software. Preferably, a small microcomputer is used so that the entire electronics control package can be housed in the printer case 19 (Fig. 8). CPU 72 passes print head control signals 77 to print head control circuit 75, which, in turn, outputs print head drive signal 81 to print head 5. A pair of motor direction signals 78 (forward) and 79 (reverse) and stepper motor signal 80 from CPU 72 combine in motor control circuit 76 to form motor drive signal 82 that eventually drives motor 3. When print data is received at interface 71, it is temporarily stored in RAM 74. The CPU 72 takes in this data and uses character font data in ROM 73 and coordinates signals 81 and 82 to effect tape printing. Fig. 7 illustrates, in a highly simplified way, the basic signal coordination timing necessary between signals 81 and 82. Starting at time "Z1", signals 78 and 80 cause motor 3 to rotate in (forward) direction "P1". (Refer also to Figs. 1(a)-1(b)). This causes gear assembly frame 51 to rotate in direction "Q1 such that planetary gear 53 meshes with reduction gear 23, indicated at time "Z2". If motor 3 keeps moving, planetary gear 53 will turn in direction "R". Reduction gear 23 turns in direction "S", and tape feed transfer gear 27 turns in direction "T". The ribbon take-up gear 26 turns in direction "U", corresponding to time "Z3". Tape feed transfer gear 27 turns in direction "T" to rotate tape feed gear 28 in direction "W". Referring also to Fig. 5, tape feed roller 11 rotates in direction "W", since it is directly coupled to tape feed gear 28. Transparent tape 33 and adhesive tape 37, which are stuck together, therefore feed (exit) in direction "V". Transparent tape 33 feeds past print head 5, in direction "X". To prevent ink smudging, thermal ink ribbon 34 feeds on past roller 35 at about the same speed as transparent tape 33. Thermal ink ribbon 34 may sag between print head 5 and ribbon take-up core 32, but ribbon take up core 32 will rotate in direction "U" to keep it taught. As a result, no slack will normally appear in thermal ink ribbon 34 between print head 5 and core 32. While transparent tape 33 moves in direction "X", a signal 77 is sent to circuit 75 ("Z4" to "Z5"). Sending signal print head drive signal 81 to print head 5 causes transparent tape 33 to be printed. Transparent tape 33 locks onto adhesive tape 37 and exits in direction "V", between rollers 36 and 11. When printing is done, motor forward rotation signal 78 is turned off and motor 3 stops (time "Z6"). To disengage gear 53 from the rest of the drive train, motor 3 is reversed by turning signal 79 on (time "Z7"), motor 3 turns in direction "P2" and gear assembly frame 51 swings out in direction "Q2". Planetary gear 53 leaves reduction gear 23 (time "Z8") Signal 79 is turned off, and motor 3 stops (time "Z9"). The gear train from tape feed gear 28 to ribbon take-up gear 26 is free to turn without having to drag motor 3. A yank by the user of the tape in direction "V" will tend to turn rollers 11 and 36 rather than slip passed them, since the gear train is not locked up. Ink ribbon take-up 26 can then be turned by the gear train to keep ink ribbon 34 out of harm's way. Thermal ink ribbon 34 will wind around the ribbon take-up core 32 without sagging. Fig. 8 shows a portable printer of the present invention that contains each of the elements described above. Other configurations are possible. An LCD display 90 shows a user the keystrokes that have been entered at keyboard 91. The "Print Date" of Fig. 6 could be sourced by keyboard 91 if interface 71 comprised the appropriate circuits. The construction of a microcomputer to read a keyboard and drive an LCD display are conventional and need not be explained further here. While the invention has been described in conjunction with several specific embodiments, it is evident to those skilled in the art that many further alternatives, modifications and variations is apparent in light of the foregoing description. For example, a one-way clutch placed on motor 3, instead of the planetary gear system described above, could give acceptable results too. (A one-way clutch transmits power from a shaft S1 to a shaft S2 in one direction, but not the other; in the other direction shafts S1 and S2 will free-wheel; such mechanisms are conventional in automobile automatic transmissions.) Thus, the invention described herein is intended to embrace all such alternatives, modifications, applications and variations as may fall within the scope of the appended claims.

Claims: A label tape printing device, comprising: means (5, 34) for ink ribbon printing on a label tape (33, 37); tape feed means for (11) for feeding the label tape (33, 37) past said ink ribbon printing means (5, 34), ribbon winding means (4) for winding an ink ribbon (34); driving force transfer means (23 - 28) drivingly connecting the tape feed means and the ribbon winding means to each other; a reversible motor (3); and coupling means (22, 23, 51, 53) for connecting the motor (3) to the driving force transfer means (23 - 28) such, that when the motor rotates in a first direction, the ink ribbon and the label tape are moved via said driving force transfer means, characterized in that said coupling means (22, 23, 51, 53) is arranged such that when the motor (3) is rotated in a second direction, the motor is de-coupled from said driving force transfer means (23 - 28) while said tape feed means and said ribbon winding means remain drivingly connected via the driving force transfer means. The device of claim 1, wherein the coupling means comprises a planetary mechanism having planetary levers (51) and planetary gears (52, 53) in an epicyclic arrangement. The device of claim 1 or 2, wherein: the ink ribbon (34) and label tape (33, 37) are disposed within a tape cassette (38, 39); the label tape comprises at least two parts, a first part being a transparent tape (33), a second part being an adhesive tape (37), the first and second parts being kept separate in the cassette until after printing with the ink ribbon; and at least one guide roller (40) having a plurality of grooves around the circumference of the guide roller that form a system of ridges that ring the guide roller, the guide roller positioned to keep the second part of the label tape from coming into contact with anything other than the first part of the label tape. The device of claim 1, further comprising means (72, 76) to turn said motor in said second direction a predetermined amount after completing a printing operation. The device according to any of the preceding claims for an adhesive tape, comprising: at least one guide roller (40) generally cylindrical in shape having a plurality of peaks in porcupine fashion disposed within the circumferential surface of the guide roller such that an adhesive tape (37) in contact with and being guided by the guide roller can only adhere to the tips of the peaks, wherein the contact area of the guide roller exposed to actual risk of being adhered to by adhesive tape is substantially reduced. The device of claim 5, wherein said peaks are aligned into ridges having parallel grooves between the ridges and said ridges ring the circumference of the guide roller. The device of claim 5, further comprising a plurality of peaks formed on areas of the inside walls (41) of a housing to contain the guide roller(s) and an adhesive tape (37), said peaks such that surface areas of the inside walls of said housing that can be adhered to by said adhesive tape are substantially reduced. The device of claim 7, wherein said peaks are aligned in parallel ridges and resemble grooving. The device according to any of the preceding claims further comprising means to de-couple the motor (3) from the driving force transfer means (23 - 28) when the driving force transfer means (23 - 28) attempts to run faster than the motor is turning it. The device of claim 9 in combination with any of the preceding claims except for claim 2, wherein the means to de-couple comprises a one-way clutch. The device of claim 9 in combination with any of the preceding claims except for claim 2, wherein means to couple and the means to de-couple the motor (3) to or from the driving force transfer means (23 - 28) are both comprised of a one-way clutch.

Inventors: HIROKI GODO, TSUTOMU YAMAZAKI, HIROKI, GODO, TSUTOMU, YAMAZAKI
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1991
Main classification: B41J3
IPC codes: B41J3, B41J33, B41J32