GB2131351A - Apparatus for feeding a paper sheet or the like to be printed in a printer - Google Patents

Abstract

Apparatus for inserting a sheet stepwise into a printer and for ejecting said sheet in a continuous manner comprises two stepping couplings 26, 46 are arranged operationally in series behind a continuously rotating drive motor 16, the first, 26, transmitting the drive from the drive motor 16 stepwise to the second stepping coupling 46, the drive shaft 44 of which constantly rotating therewith drives a first gear train 54 which is in driving connection with the feed cylinder. The driven shaft 80 rotating upon engagement of the second stepping coupling actuates a second gear train connected with the sheet- feed cylinder, but in reverse direction of rotation. <IMAGE>

Description

SPECIFICATION Apparatus for feeding paper sheet or the like to be printed in a printer The invention relates to apparatus of the type defined in the preamble of Claim 1.

Printers, in which feed devices of the type in question are used, serve, for example, to print blank receipt forms, which after insertion into a form holder are automatically inserted into the printer, are printed line by line and are ejected again counter to the insertion direction. In this case, it is desirable for the feeding of the forms to be effected rapidly and with line accuracy.

Printers are already known in which the sheet to be printed on is gripped and forwarded in conventional manner between a feed cylinder and pressure rollers cooperating therewith. Generally, a drive motor is used as drive means for the feed cylinder which rotates continuously in one direction of rotation throughout the printing operation and to which the printing cylinder can be coupled in each case controlled with time.The couplings used are generally magnetic couplings In order to enable the feed cylinder to be driven in both directions of rotation, which is required both forthe insertion movement and the ejection movement of the blank form, it is necessary to provide either two magnetic couplings or one double-acting magnetic coupling, by way of which the feed cylinder is connected with different gear trains respectively effecting opposite directions of rotation; another solution lies in providing a reversing gear in the drive train between the drive motor and feed cylinder. In each case the control of the feed path, in particular also the line pitch, is effected by way of the length of engagement time of the couplings.The accuracy of such systems leaves a lot to be desired because of the trailing effect which cannot be accurately determined and which is dependent upon paper thickness and other random influencing variables. Moreover, magnetic couplings and reversing gears constitute very complicated and expensive components.

Another apparatus of the type in question has already been proposed, wherein a stepper coupling is arranged downstream of the drive motor rotating continuously in one direction, which stepper coupling basically makes possible very accurate path control of the blank form in the printer.

The transmission arranged downstream of the stepper coupling comprises a cam disc driven by this latter and with a closed control cam engaged by a control pin connected to a rocker arm. The pivotal movement of the rocker arm is transmitted to a carriage movable in the insertion and ejection direction and carrying the blank sheet. The relatively high degree of accuracy obtainable therewith is counteracted by the disadvantage of relatively high masses to be moved and, above all, the fact that with this apparatus it is possible to print only a quite specific number of lines dependent upon the design of the respective control cam. Furthermore, this known solution is also structurally complex and thus expensive.

It is the object of the present invention to devise an apparatus of the type in question, which ensures a rapid and highly accurate feed movement of the sheet to be printed, which also allows in simple manner the printing of varying numbers of lines and which, at the same time, is of simple construction and is thus inexpensive.

This object is achieved according to the invention by the features of the characterising part of Claim 1.

In perse known manner, the first stepper coupling serves to convert the continuous motion of the drive motor into the desired positioning steps. The mechanical stepper mechanism ensures a very high degree of accuracy of the positioning steps.

The second stepper coupling which is arranged downstream of the first, serves in effect as a transmission junction in that either the rotational movement of the drive shaft of this stepper coupling or the rotational movement of the driven shaft couplabale thereto is used with the help of a transmission disposed downstream, to drive the sheet-feed cylinder in one or other direction of rotation, as will be described in more detail hereinafter.

Stepper couplings of the type described are readily available commercially and exist in very simple, inexpensive designs, for example as freewheelingspring clutches. They are distinguished above all by a very high degree of positioning accuracy and also be substantially lag-free engagement and disengagement. They can be controlled electrically in a simple manner. Therefore, the feed paths, the number of indexing steps and so on are only dependent on the respective control program to which the stepping couplings are subjected.

Similarly, the gear transmission can be designed very simply in the form of a rotating gear, by having the gear carrier locked to the central gearwheel which is driven and transmits its rotational movement to the counter-rotating output shaft; in another case, the central gearwheel and also the whole gear carrier are rotated in the same direction, so that the gear does not carry out any rolling motion and so that the output shaft rotates in the direction of input rotation, as will be explained in more detail later.

According to another feature of the invention, pressure rollers are associated with the sheet-feed cylinder, which rollers can be moved between a feed position abutting thereagainst and a raised rest position. This movement is effected by way of a simple cam disc which acts on the pressure-roller support and which, in turn, is in driving connection with a third stepper coupling. All three stepper couplings may be similar, in the sense that as many as possible like components are used, in which case, optionally according to the design of the apparatus, it is only necessary to distinguish between couplings rotating in clockwise or anticlockwise direction.

Furthermore, according to another feature of the invention, stop means pivotable into the path of the sheet are provided in front of the sheet-feed cylinder in the insertion direction of the sheet. These stop means prevent the sheet introduced into the printer from being able to slide between the disengaged feed cylinder and the pressure rollers respectively, but is initially held against the stop means and is thereby accurately aligned, this also being of importance for the accuracy of the subsequent feed motion.

Moreover, it is also proposed with the invention that, upon pivoting in, the stop means are applied against the pressure-roller support and move this latter into its rest position, in which case the stop means themselves are movable by the cam disc in driving connection with the third stepper coupling. In this way there is effected accurate coupling between the pivoting in and out of the stop means and also the movement of the pressure rollers between their feed position and their rest position.

Although the positioning accuracy of the stepping coupling is very high, it is possible for inaccuracies to occur in the drive train between the first stepping coupling and the output shaft of the toothed-wheel gear as a result of elasticity, tooth backlash and the like. Therefore, according to another feature of the invention, it is proposed to provide on the gear carrier an indexing gearwheel which is in driving connection with a gearwheel of the gearwheel transmission close to the output shaft and which has an indexing pitch corresponding to the feed steps of the sheet-feed means. This indexing gearwheel cooperates with a spring-loaded pawl which allows rotation only in the direction of rotation of the gearwheel transmission provided during stepwise feeding of the sheet.The indexing gearwheel and the pawl have the purpose of compensating for the above-mentioned inaccuracies in the drive train and of ensuring an accurate angular position of the output shaft in the respective positions. Moreover, they also prevent any reversing of the output shaft during operation in which the gear carriage is rotating and the output shaft is loaded in reversing direction. In the case of stepping couplings, in particular conventional freewheeling-spring clutches, generally the drive shaft passes right through the coupling body so that it also projects on the actual output side. The rotational motion of the drive shaft and also of the driven shaft arranged coaxially thereto can thus be taken up on the same side of the coupling body.With such a development, in particular of the second stepping coupling, according to the invention there is obtained a very simple and advantageous development of the gearwheel transmission in accordance with the characterising features of Claim 6. The gear carrier, which is in the form of a gear casing, is mounted on the input side on the driven pinion and on the drive shaft arranged concentrically thereto, while on the output side it is mounted on the output shaft. A more extensive mounting of the gear casing is unnecessary.

Further advantages and features of the invention are evident from the claims, drawings and the specific description. One example of an embodiment of the invention is illustrated in the drawings, which will be described in more detail below, wherein: Figure 1 shows a plan view of a feed apparatus, a number of details having been omitted in the interests of greater clarity; Figure 2 shows a view of the gear casing in the direction of the arrow II; Figure 3 shows a section through the apparatus shown in Figure 1 along the line Ill-Ill.

The apparatus illustrated in Figure 1 is intended for installation in a printer in which the sheet or form to be printed on is inserted in perse known manner by means of a sheet-feed cylinder and is ejected again in the opposite direction. The individual components are arranged substantially between a plurality of cross-pieces 4 to 12 mounted on a base plate 2. The base plate 2 can be arranged in the printer housing so that it can be swung out or pushed out in such a way that the device mounted thereon is readily accessible for maintenance purposes.

A drive motor 16 is mounted on the cross-piece 6 and is in driving connection via a gearwheel arrangement 18 with a shaft 20 likewise rotatably mounted in the cross-piece 6. The shaft 20 drives an intermediate shaft 22 connected thereto via a driving pin; this intermediate shaft is itself connected via a further driving pin to a drive shaft 24 of a freewheeling-spring clutch 26 orto a flange 28 connected with the drive shaft. The end 30 of the drive shaft 24 projecting on the driven side of the freewheelingspring clutch 26 is rotatably mounted in the crosspiece 10. A pawl 32 serves to operate the freewheeling-spring clutch 26, which pawl can engage with its bent-over end in detents provided on the outer face of the freewheeling-spring clutch 26. In this position the coupling is disengaged.To engage the freewheeling-spring clutch 26, the pawl 32 can be raised by a magnetically actuated switch 36 against the force of a tension spring 38, whereupon the drive shaft 24 is coupled with a driven shaft provided in the housing of the freewheeling-spring clutch 26; a driven pinion 40 is a part of this driven shaft or is securely connected thereto. When the current supply to the magnetically actuated switch 36 is interrupted, the pawl 32 is engaged once more in the detents of the freewheeling-spring clutch 26 by the tension spring 38 and thus the coupling between the drive shaft 24 and the driven shaft or driven pinion 40 is again disengaged. The operation of the stepping mechanism will be explained more precisely hereinafter with reference to the third freewheelingspring clutch.

The driven shaft or the driven pinion 40 are connected via an intermediate shaft 42 mounted in the cross-piece 10 to the drive shaft 44 of a second freewheeling-spring clutch 46 or to a flange 48 connected therewith. The end 50 protruding on the output side from the housing of this freewheelingspring clutch 46 drives a gearwheel transmission identified generally by 54 and disposed in a gear casing 52. This gearwheel transmission comprises a gearwheel 56 mounted overhung on the drive shaft 44, an intermediate gearwheel 58, a toothed roller 60 and also the output gearwheel 62 which is securely connected to the output shaft 64 of the gearwheel transmission. The free end of the output shaft 64 is rotatably mounted in a cross-piece 14. An output pinion 66 formed on the output shaft 64 is in driving connection, via gearwheels (not shown), with the sheet-feed cylinder (likewise not shown).

The output gearwheel 62 further drives a control pinion 68 which is mounted on the gear casing 52 and which is connected to an indexing gearwheel 70 coaxial thereto. A spring-loaded pawl 72 pivotably mounted on the gear casing 52 cooperates with the indexing gearwheel, as will be explained in more detail with reference to Figure 2.

The freewheeling-spring clutch 46 can likewise be operated by way of a pawl 74 which by a tension spring 76 is kept in engagement with the detents on the outer side of the freewheeling-spring clutch. A magnetically actuated switch 78 can serve to raise the pawl 74. When the freewheeling-spring clutch is disengaged, the drive shaft 44 driven via the freewheeling-spring clutch 26 rotates and drives the gearwheels 56 to 62 in the direction of the arrows shown. It is evident that the output shaft 64 rotates with the output pinion 66 in the opposite direction of rotation to that of the gearwheel 56. When the freewheeling-spring clutch 46 is engaged as a result of the pawl 74 being raised, the driven shaft or the driven pinion 80 connected thereto rotates with the drive shaft 44 in the same direction.The gear casing 52 is fitted on the driven pinion 80 with an internal ring gear 82 formed on the casing wall facing the loop-spring coupling 46. With the freewheelingspring clutch 46 engaged, the drive shaft 44 and the driven pinion 80 rotate in the same direction, as indicated by the arrow drawn in broken line.

Since the gear housing 52 is driven by the drive shaft 44 via the driven pinion 80 in the same direction of rotation as the gearwheel 56, the gearwheel transmission does not undergo any rolling motion so that the output shaft 64 also rotates with the output pinion 66 in the same direction of rotation, i.e. in the opposite direction to the indicated arrow.

Figure 2 shows the gear casing 52 with the gearwheel transmission 54 in a view corresponding to the arrow II. In this there are shown the gearwheel 56 arranged coaxially to the drive shaft 44 of the freewheeling-spring clutch 46, the intermediate gearwheel 58 driven thereby, the toothed roller 60 connected therewith and the output gearwheel 62 driven by the toothed roller. Here too there are shown the arrows indicating the direction of rotation corresponding to Figure 1. Figure 2 also shows that the output pinion 66 drives the sheet-feed cylinder 86 via an intermediate gearwheel 84.

The indexing gearwheel 70 is likewise driven by the output gearwheel 62 via the control pinion 68 connected thereto. The transmission ratio from the stepping clutch 26 to the sheet-feed cylinder 86 is so chosen that one switching step corresponds to one line step. Simultaneously, the indexing gearwheel 70 rotates further by one tooth. As evident in Figure 2, the spring-loaded pawl 72 allows rotation in the direction of the rotation arrow 88 but blocks rotation in the opposite direction. The force of the spring 90 is sufficiently high for the indexing gearwheel to be urged by the pawl 72 always into an exact angular position determined by the interacting profile of the pawl and of the indexing gearwheel, so that exact line control is possible, as has already been described.

As evident in Figure 1, a further stepping coupling or free-wheeling-spring clutch 92 is provided, which is used to control pressure rollers cooperating with the sheet-feed cylinder and to control stop means for the sheet to be printed on. This clutch is driven by the intermediate shaft 22 via gearwheels 94, 96, 98 and another intermediate shaft 100. The freewheeling-spring clutch 92 is of the same design as the freewheeling-spring clutch 26. A pawl 102 is held by a tension spring 104 in engagement with the detents formed on the freewheeling-spring clutch 92 and can be raised by a magnetically actuated switch 106, whereby the drive shaft 108 is coupled with the driven shaft or with the driven pinion 110. A cam disc 112 is secured connected with the driven pinion 110.

The drive shaft 108 passes rotatably through a cam disc 112 and is mounted rotatably in the cross-piece 10.

As shown in Figure 1 and also in particular in Figure 3, four detents 114 displaced by 90" are formed on the outer circumference of the coupling body 1 16 of the freewheeling-spring clutch 92. The pawl 102 is held by the tension spring 104 in engagement with a detent 114. In this position the clutch is disengaged, the cam disc 112 does not rotate even though the drive shaft 108 is rotating. To engage the clutch, the magnetically actuated switch 106 is briefly energized so that the pawl 102 is raised from the coupling body 116. The clutch body 116, which is connected with the drive shaft 108 via a slipping or friction clutch, rotates further by a certain amount in the direction of the arrow.Meanwhile, the current supply to the magnetically actuated switch is interrupted again so that the pawl 102 is again applied on the outer circumference of the coupling body 116. When the next detent 114 offset through 90" comes into engagement with the pawl 102, the clutch body 116 is again arrested and the clutch is disengaged once more.

In this way, it is possible for the cam disc 112 to be rotated respectively in exact 900steps. The trip cams 118, formed on the cam disc 112 and offset through 1800, cause a rocker arm 120 to pivot between the position indicated in solid line and the position shown in chain line. Stop means 122 are fastened to the rocker 120, which stop means move between the position (solid line) projecting into the path of the form or sheet 124 and a position (chain line) retracted therefrom. When the stop means pivot into their operative position, they come into contact with the pressure-roller support 128 carrying the pressure rollers 126 and so move this support so that the pressure rollers 126 are disengaged from the sheetfeed cylinder 86.

Since the freewheeling-spring clutch 92 operates in 90" steps, two trip cams 118 offset by 1800 are provided. The trip cam respectively remote from the rocker arm 120 is used to operate a microswitch 130.

This latter emits, for example in the position illustrated, a signal to a control device which signifies that the rocker arm 120 and thus the stop means 122 occupy their operative position and that the pressure rollers 126 are disengaged.

When the stop means 122 are swung back or retract into their position shown in chain line, the pressure rollers 126 are applied against the formfeed cylinder 86. At the same time the sheet 124 can drop down until it is gripped by the sheet-feed cylinder 86 and the pressure rollers 126 and is forwarded on. The sheet 124 is then guided past the writing head 132 and a sheet abutment 134, where it is printed on line by line in known manner. The sheet 124 is preferably introduced stepwise into the printer, whereupon it is printed on line by line; subsequently, it is ejected in the opposite direction in a continuous ejection movement.

The sheet-feed cylinder 86 and the stop means 122 are arranged as above, with respect of the viewing direction of Figure 1. It is evident that in the present case the sheet-feed cylinder 86 is divided into two cylinder portions 86a, 86b; the stop means 122 are likewise divided into individual portions 122a, 122b, 1 22c and are arranged respectively on either side of the cylinder portions 86a, 86b and therebetween.

It is further apparent from Figure 1 that a signal transmitter 136 is provided, which registers the passing of a sheet edge entering the apparatus and reports this via a line 138 to an electronic control unit 140. Another signal transmitter 142 registers the passing of the trailing sheet edge and reports this via a line 144 likewise to the control unit 140. The signal from the microswitch 130 is also fed to the control unit 140 via a line 146. The control unit 140, which is shown twice in Figure 1 for greater clarity, controls in turn the drive motor 16 as well as the magnetically actuated switches 36,78 and 106, respectively via leads 148 to 154.

For the insertion of a sheet, the drive motor 16 is activated by the signal transmitter 136 via the control unit 140. This motor drives the drive shafts 24 and 108 of the two loop-spring couplings 126 and 92. The magnetically actuated switch 106 is then energized so that, via the freewheeling-spring clutch 92 and the cam disc 112 connected therewith, the stop means 122 are retracted and the pressure rollers 126 are applied against the feed cylinder 86. By stepwise energizing of the magnetically actuated switch 36 the driven pinion 40 is likewise rotated stepwise; this stepping movement is transmitted via the drive shaft 44 of the freewheeling-spring clutch 46 and via the gearwheel transmission 54 to the output pinion 66 and thus to the sheet-feed cylinder 86 which introduces the sheet stepwise, so that it can be printed on line by line. When the trailing sheet edge passes the signal transmitter 142, the magnetically actuated switch 78 is energized so that, in the manner described above, the direction of rotation of the output pinion 66 and thus of the sheet-feed cylinder 86 is reversed. The magnetically actuated switch 36 is no longer energized stepwise but continuously. In this way the sheet-feed cylinder is driven continuously in the opposite direction, so that the sheet is ejected continuously. When the sheet has been completely fed back, the drive motor 16 and the magnetically actuated switches 36,78 and 106 are de-energized via the control unit 140, so that the stop means 122 drop back into their operative position and thus raise the pressure rollers 126, while at the same time the drive to the sheet-feed cylinder is cut off.

Claims (12)

1. Apparatus for feeding a paper sheet or the like to be printed in a printer, in particularforthe stepwise feeding of the sheet in a first direction of movement and for the continuous feeding of the sheet in an opposite direction, with a drive motor capable of rotating continuously in one direction of rotation, with a stepping coupling which is arranged downstream of this drive motor and which has a drive shaft and a driven shaft coupleable with this drive shaft by means of a mechanical stepping mechanism respectively for set angles of rotation, with transmission means arranged downstream of the stepping coupling for driving sheetfeed means in the first direction of movement and also in opposite direction, and also with a control unit for controlling the drive motor and the stepping coupling, characterised in - that the driven shaft of the first stepping coupling is in driving connection with the drive shaft of a second stepping coupling which can be controlled via the control unit; - that downstream of the second stepping cou pling there is arranged a gearwheel transmission which is mounted on a gear carrier and which has an output shaft rotating counter to the input direction of rotation and in driving connection with a sheet-feed cylinder or the like; - that the drive shaft of the second stepping coupling is in driving connection with the gearwheel transmission input; and - that the gear carrier is rotatably mounted in the printer about an axis coaxial to the output shaft of the gearwheel transmission and is in driving connection with the driven shaft of the second stepping coupling.

2. Apparatus according to Claim 1, characterised in - that pressure rollers orthe like are associated with the sheet-feed cylinder, which pressure rollers are mounted on a pressure-roller support and can be moved between a feed position, in which they are applied underthe influence of pressing spring means against the sheet-feed cylinder, and a rest position away therefrom, and - that for moving the pressure-roller support, there is provided a rotatable cam disc which is in driving connection with the driven shaft of a third stepping coupling, controllable via the control unit, the drive shaft of the third stepping coupling being in driving connection with the drive motor.

3. Apparatus according to Claim 2, characterised in - that stop means, pivotable into the path of the sheet, are provided in front of the sheet-feed cylinder in the insertion direction of the sheet, which stop means, upon pivoting in, are applied against the pressure-roller support and move this latter into its rest position, and - that the stop means are moved by the cam disc in driving connection with the third stepping coupling.

4. Apparatus according to one of Claims 1 to 3, characterised in that the stepping couplings are respectively designed as freewheeling-spring clutch es each with a pawl respectively actuatable by a magnetically actuated switch.

5. Apparatus according to one of Claims 1 to 4, characterised in that on the gear carrier there is provided an indexing gearwheel which is in driving connection with the gearwheel of the gearwheel transmission closed to the output shaft and which has an indexing pitch corresponding to the feed steps of the sheet-feed cylinder, this indexing gearwheel cooperating with a spring-loaded pawl allowing rotation of said indexing gearwheel only in the direction of rotation of the gearwheel transmission provided during stepwise feeding of the sheet.

6. Apparatus according to one of Claims 1 to 5, having the second stepping coupling, in which the drive shaft projects from the coupling body both on the driving side and on the driven side and in which the driven shaft comprises a driven pinion mounted on the driven side of the coupling body and concentric to the drive shaft, characterised in - that the gear carrier is in the form of a gear casing with an internal ring gear which is formed on the casing outside and which can be fitted on to the driven pinion of the second stepping coupling; - that in the casing wall there is provided a bore disposed concentrically to the internal ring gear and serving for the passage of the drive shaft is rotatably connected with an input gearwheel arranged in the gear casing; and - that in the casing wall opposite the casing wall carrying the internal ring gear there is mounted the output shaft rotatably connected with the output gearwheel of the gearwheel transmission; moreover, said last mentioned output shaft is mounted with its free end in the printer.

7. Apparatus according to Claim 6, characterised in that the output gearwheel of the gearwheel transmission meshes with a control pinion which is rotatably mounted on the gear casing and which carries the indexing gearwheel, and in that the pawl is likewise pivotably mounted on the gear casing.

8. Apparatus according to one of Claims 2 to 7, wherein the second stepping coupling is designed for 900steps, characterised in that the cam disc has two cams offset by 1800, and in that the cam respectively remote from the pressure-roller support cooperates with a microswitch or the like serving to report the position of the cam disc to the control unit.

9. Apparatus according to one of Claims 1 to 8, characterised in that a signal transmitter actuated by the initially entering front edge of the sheet and a signal transmitter actuated by the end edge of the sheet in its fully inserted position are arranged in the path of the sheet in front of the sheet-feed cylinder, said signal transmitters emitting signals to the control unit.

10. Apparatus according to one of Claims 1 to 9, characterised in that the gear casing and the gearwheels of the gearwheel transmission consists of plastics material.

11. Apparatus according to one of Claims 1 to 10, characterised in that the control unit is designed as an electronic control system.

12. Apparatusforfeeding a paper sheet or the like to be printed in a printer substantially as herein described with reference to the accompanying drawings.