Thermal printing system

Abstract: To facilitate the removal of crumpled paper sheets from a thermal printing machine the pinch roller or rollers (2) that hold the sheet against the platen (1) have associated with them a means for depressing or releasing the roller or rollers away from the platen when the machine is opened. For this purpose there is provided an operating lever (12 or 14) for effecting the depressing or releasing motion. In one example the lever rotating a cam positioned between a pair of pinch roller levers to move the rollers apart and so allow the crumpled sheet to be removed. In another example the lever itself acts as a cam or a wedge to move the rollers apart.

Description: The present invention relates to a thermal printing system, and more particularly, to a thermal printing system which prints alphanumerical and or graphic information, on a paper sheet cut into unified sheet size of A4, B5 or the like fed from a casette case, by melting a film of printing ink applied on a plastics membrane by the heat imparted by a thermal head, which further comprises at least a means for selectively depressing or releasing a pair of pinch rollers against a platen, thereby allowing the user who operates the system to readily remove any paper crumpled between the platen and the pinch rollers. Various types of thermal printing systems have been developed and are being widely used, which print a number of dots of printing ink corresponding to alphanumerical and or graphic information printed by a thermal head of the printing system on a paper sheet, cut into unified size, by thermally melting a film of printing ink applied on the surface of a plastic membrane in a dried state at an ambient temperature. In these types of thermal printing systems, paper sheets for printing are supplied as a set of cut paper sheets each cut into such a unified size of A4,B5 or the like and are contained in a casette case each capable of receiving a number of paper sheets, ,say, 50 or 100, and these paper sheets are automatically fed or propelled as printing proceeds. That is, a subsequent sheet is advanced as soon as the preceding paper sheet has finished being printed, and the thus newly fed paper sheet is caught, in other words, squeezed between a front pinch roller and a rear pinch roller both of which are disposed as a pair, and the thus caught paper is pressed against the surface of a platen and is subjected to printing. Though such types of printing systems are designed and manufactured such that the way of feeding successive paper sheets one after another from a paper casette case to the pair of pinch roller is done automatically, sometimes trouble may arise in that the automatic feeding of the paper sheets is disturbed and results in malfunction of the system such as crumpling of fed paper sheet between the pinch roller or rollers and a platen, due to slight misalignment and or a minor diferrence in size between the paper sheets, and to a minor deviation in the dimensions of parts or components of the system. By taking these drawbacks in the prior art printing system into account, there has been conceived and developed such a device capable of removing a paper sheet which has actually been crumpled between the pair of pinch rollers as disclosed by Japanese Utility Model Application No.Sho 61(1986)-73966 (Unexamined U.M.Publication No. Sho 62(1987)-187750). This publication discloses a thermal printing system which comprises as shown in Fig. 8; a platen 21, a pair of pinch rollers 23 each pinch roller of which is disposed to be freely rotatable to each of a pair of pinch levers 22 and capable of being pressed against or released from said platen 21, and the aforesaid pressing and releasing action of this printing system is effected by such manner that the pressing of the pinch rollers 23 against the platen 21 is done by a pinch roller lever tensioning spring 24 connected between both the swingable ends of the pinch roller lever 22 and the releasing of the pressed pinch rollers is effected by a manual releasing lever 25 rotatable about a pin as an axis of rotation. This manual releasing lever 25 is provided, at said one end, with a rotary disc 26 which normally does not impart any force to the pinch roller levers 22, but it acts to make the pinch rollers 23 to move away from the platen 21, only when the manual releasing lever 25 is turned at a specified angle in a direction opposite to that for pressing the pinch rollers against the platen, namely, the pinch roller lever at the left side is turned clockwise and the pinch roller lever at the right side is turned oppositely, that is, anticlockwise. The above-mentioned publication also discloses, as another embodiment shown in Fig. 9, a thermal printing system provided with a pressure/ release lever 25' fixedly attached to a return lever 29 for returning the aforesaid lever 25', in which the return lever 29 acts to return the pressure/release lever 25' when the return lever 29 contacts the lower frame 28 when the upper frame 27 is lowered onto the lower frame 28 for closing. However, according to the thermal printing system disclosed by the above mentioned unexamined U.M. Publication No. Sho 62-187750, it is required for one who uses the system to manually operate the release lever 25, it becomes necessary for him to release the pinch rollers 23 when they are pressed against the platen 21, so a person who is not skilled in the operation of the apparatus cannot know the way of handling the pressure/release lever unless he reads the operating manual of the device, or he may apt to involuntarily try to pull out the paper sheet P in crumpled state without manipulating the release lever. The present invention has been conceived and developed to solve the above-mentioned problems, and it aims to provide a thermal printing system which can prevent such a misuse and also to make it possible that a paper sheet in a crumpled state can be readily removed by such a mere simple action of opening the upper frame upwards, by providing a mechanism which enables the application of the pinch rollers against the platen or the release of the pinch rollers from the platen to be automatically set in connection with the opening or closing of the upper frame with respect to the lower frame of the system. In DE 3319490 a pinch roller mechanism is disclosed in which a pair of rollers are mounted on a carrier which is itself displaceably mounted on the lower part of a pair of upper and lower frame parts to move the rollers towards and away from a cylindrical platen. A lever projects from the carrier to be engageable by a linkage that is connected to the upper frame so that raising the upper frame moves the carrier away from the platen. This is a relatively complicated and bulky mechanism. Also, because the rollers are in fixed positions on the carrier they cannot embrace the platen at diametrically opposite sides. According to the invention, there is provided a thermal printing machine comprising upper and lower frame parts, said frame parts having a closed, operative position and the upper frame part being movable relative to the lower frame part to an open, non-operative position, one of said parts carrying a platen and a pair of pinch rollers resiliently biased towards the platen to hold against the platen a sheet to be printed, a lever mounted on said one frame part being displaceable by the opening and closing of the frame parts to move the pinch rollers away from the platen when the frame parts are opened and to allow the resilient bias to urge them towards the platen when the frame is closed, and wherein the pinch rollers are displaceable away from each other by the operation of said lever moving them away from the platen, the lever is resiliently biased towards a position in which the pinch rollers are displaced away from each other and the lever is displaced against its bias by contact with the other frame part when the frame parts are closed, thereby to allow the pinch rollers to be urged towards the platen. In one form of the invention, a pressure/release lever is provided which acts in response to the user's opening or closing action. In more detail, a front end of the pressure/release lever will engage a part of the lower frame when the upper frame is lowered down onto the lower frame to a "closed" state, so that the lever is allowed to rotate with accompanying rotation of a coaxially fixed cam means to move away from the pinch roller levers, whereupon the pinch rollers are pressed by a resilient force against the surface of the platen ready for normal printing. On the other hand, if crumpling of the fed paper sheet occurs, if merely the upper frame is raised upwards away from the lower frame to set the system in the "opened" state, the pinch roller lever will move away from contact with the frame, and the pressure /release lever also rotates being urged by a tension spring, resulting in rotation of the cam coaxially fixed the pressure/release lever, whereby the space between the pair of pinch roller levers is widened allowing the pinch rollers to be released from the platen. Thereby it becomes possible to take out the paper sheet crumpled between these parts constituting the platen-pinch roller assembly. In another form of the invention, components such as pinch rollers, a platen and means for pressing and releasing the pinch rollers are disposed on the lower frame and include a pivotable pressure/release lever as said pressing and releasing means. One end of the lever is engageable with the lower face of the upper frame, while the other, free end is provided with protrusions which act as a wedge or cam means and act to engage the inside face of each support pin of the pinch roller levers. When these protrusions engage the support pins, they act to release the pinch rollers from the contact with the platen against the tension force imparted by a pinch roller lever tension spring. By virtue of this construction, in the event of a paper sheet crumpling, it is possible to remove the crumpled paper by forming a clearance between the platen and the pinch rollers merely by raising the upper frame from the lower frame. A description will now be given of the preferred embodiments of the present invention with reference to the accompanying drawings, in which: Fig. 1 is a schematic side view illustrating the cam and its related parts in a first embodiment of the present invention, in their positions when the upper frame is lowered; Fig. 2 is a schematic side view illustrating the pressure/release lever and its related parts in this first embodiment when the upper frame is lowered; Fig. 3 is a schematic side view illustrating the pressure/release lever and its related parts the first embodiment when the upper frame is raised to open the system; Fig. 4 is a side view illustrating the thermal printing system of the first embodiment where the upper frame is raised to open the system; Fig. 5 is a schematic side view illustrating the pressure/release lever and its related parts in a second embodiment of the present invention when the upper frame is lowered; Fig. 6 is a schematic side view illustrating the pressure/release lever and its related parts of the second embodiment when the upper frame is raised to open the system; Fig 7 is a side view illustrating the thermal printing system of the second embodiment where the upper frame is raised to open the system; Fig. 8 is a schematic side view illustrating the manual release lever and its related parts of a prior art thermal printing system when the upper frame is lowered; Fig. 9 is a schematic side view illustrating the manual release lever and its related parts of another example of the prior art thermal printing system when the upper frame is lowered; Explanation will be made now of the first embodiment of the present invention by referring to Figs. 1 to 4 of the accompanying drawings. Figs. 1 and 2 are schematic side views illustrating the cam and the pressure/release lever and their related parts of a thermal printing system of the present invention when the upper frame is closed with respect to the lower frame, and showing the pinch rollers being urged towards the platen, while Fig. 3 depicts the cam and the pressure/release lever and their related parts, where the upper frame is opened with respect to the lower frame. In the drawings, numeral 10 is an upper frame and 11 is a lower frame, and the former is attached to the latter being able to be selectively opened or closed with each other, so that the upper frame can be secured tightly to the lower frame by a locking means (not shown). Numeral 1 is a platen and 2 is a pair of pinch rollers opposedly facing with each other and 3 denotes a pair of pinch roller levers, and these members, together with their related parts,are attached to the platen 1. Each of the pinch roller levers 3 is swingably mounted at its one end on a pinch roller lever supporting pin 7, while the other end supports a freely rotatable pinch roller 2, which together with the other one constitute a pair of rollers to be resiliently biased by a tension spring 5 extending between the two pinch roller levers 3, so that the pinch rollers as a pair can be pressed against the surface of the platen 1 from opposite sides, as if the rollers 2 embrace or hold the platen 1 from opposite sides. In the drawings, numeral 4 is a cam and 12 denotes a crank-arm type pressure/release lever for acting on the pinch roller levers 3. The cam 4 is disposed between the oppositely facing pinch roller levers 3 of a pair, so that it normally does not exert any force on the pinch roller levers 3, but it acts to urge the pinch roller levers 3 to move away from each other against the force imparted by the tension spring 5 when the cam is turned through a specified angle, while the lever 12 is disposed such that its front end engages with or moves away from the lower frame 11 depending on the user's closing or opening of the upper frame. Further, the cam 4 and the lever 12 are fixedly attached to a rotatable connecting pin 8, so the cam 4 and lever 12 can rotate integrally as a single member. In addition, the lever 12 is biased by a tension force applied by a tension spring 9 to be normally wound in the anticlockwise direction. Consequently, when the upper frame 10 is closed down on the lower frame 11, the front end of the pressure/release lever 12 engages with a certain part of the lower frame 11, so the lever 12 cannot rotate beyond the position given by that engagement, despite the force applied by the tension spring 9, and therefore, the cam 4 does not act on the oppositely facing pinch roller levers 3, allowing both pinch rollers to approach with each other. Thus, the opposing pinch rollers 2 are pressed resiliently against the surface of the platen roll. In order to prevent interference between the mating parts, sufficient clearance is secured between the cam 4 and the pinch roller levers 3. When the upper frame 10 is raised upward to an"Open" position, the front end of the pressure/ release lever 12 also moves away from the lower frame 11. As a result, the lever 12 is rotated anticlockwise by the tension spring 9, whereby the cam 4 is turned through a specified angle or more, to widen the space between the oppositely facing pinch roller levers 3, thereby causing the two opposing pinch rollers to move away from their pressure contact with the platen 1. Since the mechanism is constructed as explained above, the pinch rollers 2 can be selectively depressed upon or released from the surface of the platen 1 in an interrelated manner. In carrying out thermal printing operation,upper frame 10 is lowered down onto the lower frame 11, a paper sheet is fed from the casette case, and a desired image of information can be printed at the contact point with the platen 1 by means of thermal printing effected by the thermal head 6. A second embodiment of the present invention will be explained by referring to Figs. 5, 6 and 7. In the first embodiment explained above, the platen, pinch rollers and related parts or components are mounted on the upper frame 10 as shown in Figs. 2 and 3,however, these members in the second embodiment are attached to the lower frame 11 as shown in Figs. 5, 6 and 7. Fig. 5 is a side view showing a pressure/release lever 14 and its related parts or components, when the upper frame 10 is closed onto the lower frame. Fig. 7 shows that the upper frame 10 can be opened or closed with respect to the lower frame 11. The upper frame 10 shown by solid line is in its raised open state, while it is shown by dash and dot line in its closed state. As in the first example, numeral 1 is a platen, 2 and 3 are pair of pinch rollers and pinch roller levers, respectively. These pinch rollers and pinch roller levers in each pair are oppositely facing with each other and these members including the platen are disposed on the lower frame 11. Each of the pinch roller levers 3 is rotatably disposed at its one end on a pinch roller lever supporting pin 7 and supports a pinch roller 2 at its the other end. Both pinch rollers oppositely facing with each other are resiliently biased by a pinch roller lever tensioning spring 5 so that both pinch rollers can be pressed against the surface of the platen 1 from opposite sides. Numeral 14 is a pressure/release lever swingably received at an intermediate portion by a supporting pin 8 disposed on the lower frame 11, while one end of the lever 14 is engageable with the lower face of the upper frame 10 and its the other end is formed with two protrusions 4a and 4b in the manner of two cams or wedges, each of which is engageable with the inside face of a pair of pins 2a for supporting the pair of pinch rollers 2, respectively. When the upper frame 10 is swung upwards to its "Open" position its lower face moves away from said one end of the pressure/release lever as shown in Fig. 6, and the other end of the lever 14 is lowered by the tension spring 9. The cam shaped protrusions at the other end of the lever 14 are lowered by this action of the tension spring 9 and the protrusions 4a and 4b will engage the inside faces of the supporting pins 2a, each with a respective protrusion. As a consequence, the oppositely facing pinch roller levers 3 are urged to move away from each other, resulting in that the pinch rollers 2 are also moved away from the biased contact with the platen 1 against the resilient tension force imparted by the pinch roller tension spring 5. When the upper frame 10 is swung down to the closed position and its lower face engages the lever 14, as shown in Fig. 5, the other end of the lever 14 is raised counter to the resilient force of the tension spring 9 on the lever, this result in disengagement of the cam shaped protrusions 4a and 4b with the respective inside faces of the supporting pins 2a. Thus the two opposing pinch roller levers 3 are allowed to approach each other under the action of the resilient force applied by the pinch roller lever tension spring 5, so that the oppositely facing two pinch rollers 2 are able to hold and press against the platen 1 from opposite sides. Since the thermal printing system according to the second embodiment is constructed as explained above, pressing and releasing of the pinch rollers 2 to the platen 1 can be automatically effected by closing or by opening the upper frame 10 to the lower frame 11. When it is necessary to perform printing relying on the thermal printing system of this invention, it is only needed to close the upper frame 10 onto the lower frame 11 and to feed a paper sheet which is then printed at the point of contact with the platen 1 by the heat transsmitted from the thermal head 6. Although in the prior art thermal printing system already described a slightly crumpled paper sheet could be removed by pulling out the paper sheet remaining outside the frame, a seriously crumpled paper sheet had to be taken out by opening the upper frame and maually separating the pinch rollers from their resilient engagement with a platen. Using the mechanisms described above, the pinch rollers are automatically released from their engagement with the platen in conjunction with user's opening motion, and the rollers can be returned to their engagement with the platen also by the user's closing motion of the upper frame. The user can thus be relieved of troublesome work encountered in the prior art system. In addition, even an unskilled user can handle such a thermal printing system without the risk of involuntarily missing the use of the release lever.

Claims: A thermal printing machine comprising upper and lower frame parts (10,11), said frame parts having a closed, operative position and the upper frame part (10) being movable relative to the lower frame part (11) to an open, non-operative position, one of said parts carrying a platen (1) and a pair of pinch rollers (2) resiliently biased towards the platen to hold against the platen a sheet to be printed, a lever (12;14) mounted on said one frame part being displaceable by the opening and closing of the frame parts to move the pinch rollers away from the platen when the frame parts are opened and to allow the resilient bias to urge them towards the platen when the frame is closed, characterised in that the pinch rollers (2) are displaceable away from each other by the operation of said lever (12;14) moving them away from the platen (1), that the lever is resiliently biased towards a position in which the pinch rollers are displaced away from each other and that, the lever is displaced against its bias by contact with the other frame part (10 or 11) when the frame parts are closed, thereby to allow the pinch rollers to be urged towards the platen. A thermal printing machine comprising upper and lower frame parts (10,11), said frame parts having a closed, operative position and the upper frame part (10) being movable relative to the lower frame part (11) to an open, inoperative position, the machine having a platen (1) and a pair of pinch rollers (2) resiliently biased towards the platen to hold against the platen a sheet to be printed, a lever (12) being displaceable by the opening and closing of the frame parts to move the pinch rollers away from the platen when the frame parts are open and to urge them towards the platen when the frame parts are closed, characterised in that the platen (1), pinch rollers (2) and lever (12) are mounted on the upper, movable frame part (10), the pinch rollers are resiliently urged towards each other but are displaceable away from each other by the operation of the lever moving them away from the platen, that the lever is resiliently biased towards a position in which the pinch rollers are displaced away from each other, and that the lever is displaced against its bias by contact with the lower frame part (10) when the frame parts are closed, thereby to allow the pinch rollers to be urged towards the platen. A thermal printing machine according to claim 2 wherein the lever (12) is pivotally displaceable with a cam (4) which is disposed between levers (3) carrying the respective pinch rollers of said pair of rollers (2), engagement of said cam with said roller levers being able to move the pinch rollers apart. A thermal printing machine comprising upper and lower frame parts (10,11), said frame parts having a closed, operative position and the upper frame part (10) being movable relative to the lower frame part (11) to an open, non-operative position, the lower frame part carrying a platen (1) and a pair of pinch rollers (2) resiliently biased towards the platen to hold against the platen a sheet to be printed, a lever (12) mounted on said lower frame part and being displaceable by the opening and closing of the frame parts to move the pinch rollers away from the platen when the frame parts are opened and to allow the resilient bias to urge them towards the platen when the frame is closed, characterised in that the pinch rollers (2) are displaceable away from each other by the operation of the lever (12) moving them away from the platen, that the lever is resiliently biased towards a position in which the pinch rollers are displaced away from each other, and that the release lever is displaced against its bias by contact with the upper frame part (10) when the frame parts are closed together to allow the pinch rollers to be urged towards the platen. A thermal printing machine according to claim 4 wherein the lever has cam or wedge-like protrusions (4a,4b) with which to urge the pinch rollers apart. A thermal printing machine according to claim 5 wherein the lever (14) is pivotally mounted on the lower frame (11) and has said cam or wedge-like protrusions (4a,4b) at one end engageable with support pins (2a) on which the respective pinch rollers (2) are rotatably carried, to urge the pinch rollers apart. A thermal printing machine according to any one of the preceding claims wherein the platen (1) is a rotary cylinder and said pair of pinch rollers (2) are disposed in substantially diametrically opposite positions relative thereto. A thermal printing machine according to claim 7 wherein said pinch rollers (2) are displaceable towards and away from the platen (1) substantially diametrically thereto.

Inventors: ISHIYAMA KIYOSHIGE, MITSUSHIMA SUSUMU, OGITA HIROMITSU, OKUNO TAKESHI, ISHIYAMA, KIYOSHIGE, MITSUSHIMA, SUSUMU, OGITA, HIROMITSU, OKUNO, TAKESHI
Applicants: SHINKO ELECTRIC CO LTD, SHINKO DENKI KABUSHIKI KAISHA
Application year: 1989
Main classification: B41J13
IPC codes: B41J25