EP0008704B1 - Printing device, particularly for a price marking apparatus - Google Patents

Abstract

Printing apparatus comprising a housing having at least two oppositely disposed side walls; a plurality of sets of juxtaposed printing elements; a plurality of internally toothed, annular setting wheels supported with respect to the housing for respectively positioning the printing elements; a hollow, axially shiftable, setting shaft extending at least into the annular setting wheels, the setting shaft including (a) a drive member for engaging the internal teeth of a selected one of the setting wheels and (b) a detenting member; a pin mounted with respect to one of the side walls, the pin extending into the hollow setting shaft and including a plurality of detent recesses longitudinally extending along the surface of the pin, the distance between at least two of the recesses corresponding to the width of at least one of the setting wheels, the detenting member of the setting shaft engaging a selected one of the recesses for axially positioning the setting shaft at the setting wheel to be driven.

Description

The invention relates to a printing unit, in particular for price labeling devices, in which the printing types can be set by means of adjusting wheels rotatably mounted next to one another about an axis, which have internal teeth into which a driver can be brought into engagement, which is axially adjustable at the free end and around its longitudinal axis is rotatably mounted in a plain bearing-guided adjusting shaft and in which the adjusting shaft additionally has a tongue-shaped resilient catch, which is arranged along the adjusting shaft along the adjusting shaft by axially displacing the adjusting shaft in accordance with the number of adjusting wheels next to one another at intervals which correspond to the widths of the adjusting wheels can be snapped in and in which the adjusting shaft is provided on the inside with a central longitudinal recess into which a guide pin engages, which is held on the housing wall opposite the slide bearing.

Such printing units, in particular intended for price marking devices, are known from DE-PS 1 929 307 (US Pat. No. 3,744,411) and 2433523 and from DE-OS 2 247 732 (US Pat. No. 3,968,745) and 2,715,462.

With the help of the setting wheels and the setting shaft, the print types can be set in the print line.

In the printing units according to DE-PS 1929307 and DE-OS 2715432, the locking recesses are arranged on the adjusting shaft. The setting shaft is provided with the number of setting wheels corresponding to tangential circumferential grooves, which have spacings corresponding to the widths of the setting wheels and into which a resilient catch engages, which is arranged in the housing of the printing unit and is formed by a ball which is formed in a Bore of the housing is guided and which is under the action of a small coil spring.

The known locking device has the disadvantage that its production is complex and that its assembly is complicated and time-consuming.

Furthermore, this printing unit has the disadvantage that adjustment shafts which are adapted to the arrangement of the wider or narrower bands or wheels are required in the case of printing units of the same width but with a different arrangement of wider or narrower printing type bands or printing type wheels.

These disadvantages are at least partially avoided in the printing units according to DE-PS 2 439 523 and DE-OS 2 247 732.

In the printing unit known from DE-PS 2439523, the printing type wheels provided with printing types have recesses on their outer circumference into which projections or teeth of the adjusting wheels engage. In order to bring about the axial locking of the setting shaft, a pointer that extends over the circumference of the setting wheels is axially immovably fastened on the setting shaft and has a detent protruding at right angles to the setting shaft at its free end, which detent extends axially into the locking recesses of a setting wheel next to the setting wheels easily interchangeable catch rail engages. By changing the catch rail, this printing unit can be adapted to the respective arrangement of printing type wheels or printing type bands of different widths.

A disadvantage of this printing unit is that the catch and the locking recesses cooperating therewith are at a distance from the setting shaft, so that bending moments have to be transmitted from the pointer. For this reason, the pointer must be designed and guided to withstand heavy loads. In addition, this construction requires a relatively large amount of space.

In the printing unit according to DE-OS 2 247 732, the locking recesses are formed by bevels which are attached to the inner hubs of the part wheels. The bevels on the edges of two adjuster wheels arranged side by side form a circumferential groove into which resilient catches arranged on the adjuster shaft engage. However, the grooves can also be provided at a point between the edges of each setting wheel in the form of ring-shaped inner recesses machined into the wheel circumference. This printing unit has the advantage that the setting wheels themselves form tangentially circumferential grooves, the axial spacings of which correspond to the respective widths of the setting wheels and the printing type bands guided above them. However, this printing unit has the disadvantage that the grooves formed by bevels or the inner recesses can be only relatively small in cross section and these grooves are interrupted by the internal toothing of the adjusting wheels which cooperates with the driver of the adjusting shaft. The consequence of this is that resilient detents are required to scan the grooves, the width of which is narrower than the tooth pitch of the internal toothing. In order to achieve a sufficient detent effect, at least two resilient detents must be arranged on the adjusting shaft in the known printing unit. Because of the small size of the grooves and the resilient catches and because of the necessary play between the individual setting wheels on the one hand and between the setting shaft and its sliding guide in a housing wall and between the setting shaft and the setting wheels on the other hand, only tight manufacturing tolerances are permitted in the known printing unit, provided that the locking device should be reliable. For these reasons, the production of the known printing unit is expensive.

The object of the invention is a printing unit to create the type specified in the preamble of claim 1, the latching device for the axially displaceable adjusting shaft while adapting to the respective widths of the printing type wheels or printing type bands allows larger manufacturing tolerances in comparison to the known devices of this type and at the same time is robust, compact and highly reliable is.

This object is achieved in that the guide pin is held rotatably about its longitudinal axis on the housing wall, and the latching recesses are provided in the form of at least two different, circumferentially offset rows of latching recesses on the pin circumference that the cross section of the longitudinal recess of the adjusting shaft and Cross section of the guide pin are out of round, and that the catch is designed as an inwardly resilient tongue on the adjusting shaft.

By simply rotating the pin, which is preferably made of plastic and is held in a recess in the housing wall in the manner of a push button in particular via an outwardly resilient push-in catch, the locking device can be adapted to the respective arrangement of printing tape bands or printing wheel types of different widths. No additional parts are required for the locking device.

An easy and simple positioning of the driver in the axial direction is achieved if the latching recesses have a wave-like or sinusoidal profile in the axial direction.

Although the printing unit can be equipped differently with printing strips or wheels of different widths simply by moving the pin in two, three or four ways, the possible printing unit variants can still be doubled if the row of locking recesses is seen in the axial direction - Are arranged asymmetrically with respect to the portion of the pin which is limited by the end faces of the pin at both ends and the pin can be fixed with one or the other end on the housing wall.

• Fig. 1 eine Schnittansicht des Druckwerks,
• Fig. eine Seitenansicht des Druckwerks bei abgenommener Gehäuseseitenwand,
• Fig. eine Draufsicht (teilweise geschnitten) der Einstellwelle,
• Fig. 4 eine Schnittansicht derselben,
• Fig. 5 eine Frontansicht der Einstellwelle,
• Fig. 6 eine Draufsicht des Zapfens,
• Fig. 7 eine Seitenansicht desselben,
• Fig. 8 eine Frontansicht des Zapfens und
• Fig. 9 eine Ansicht nach der Schnittlinie IX-IX in Fig. 7.

In the following description an embodiment of a printing unit according to the invention is explained in more detail with reference to the drawings. The drawings show in

• 1 is a sectional view of the printing unit,
• 1 shows a side view of the printing unit with the housing side wall removed,
• FIG. 1 shows a top view (partly in section) of the adjusting shaft,
• 4 is a sectional view of the same;
• 5 is a front view of the adjusting shaft,
• 6 is a top view of the pin,
• 7 is a side view of the same,
• Fig. 8 is a front view of the pin and
• 9 is a view along the section line IX-IX in FIG. 7.

The printing unit according to FIGS. 1 and 2 has five type bands 1, which have printing types 2 on their outer sides and which have driver knobs 3 on their inner sides. The driver knobs 3 engage in tooth gaps 4, which are attached to the circumference of setting wheels 5. The setting wheels 5 are rotatably mounted in a trough 8 between the housing walls 6 and 7. The printing types 2 can be set with the aid of an adjusting shaft 9, which has an adjusting knob 10 at its outer end and which has a driver 11 designed as a pinion at its inner free end, which can be brought into engagement with an internal toothing 12 of the adjusting wheels 5 The setting shaft 9 is rotatable and axially displaceable in a slide bearing 13 arranged on the housing wall 6. The setting shaft 9 has a central longitudinal recess 14 into which a pin 15 engages, which is held on the housing wall 7 by an insertion catch 16. The pin 15 is provided with locking recesses 17, 17 '(details of which will follow later), which are provided on the pin 15 at intervals which correspond to the distances between the setting wheels 5 from one another.

At the free end of the setting shaft 9, a resilient catch 18 is attached, which is formed by a tongue 19. The tongue 19 is connected in one piece to the adjusting shaft 9 made of plastic and is formed by axially extending incisions 20 (cf. FIG. 3). On the part of the setting shaft 9 protruding from the printing unit housing, first a pointer 21 and then the adjusting button 10 are pushed on. The setting shaft 9 can be rotated relative to the pointer 21, while the adjusting knob 10 is connected to the setting shaft in a rotationally fixed manner via the non-circular end region 22.

3 and 4 show, the driver 11 and the resilient catch 18 are arranged at the free end of the adjusting shaft 9. Carriers 11 and detent 18 can be arranged in the same plane perpendicular to the axis of rotation of the setting shaft 9 or can also be offset somewhat axially.

5 shows, the cross section of the longitudinal recess 14 has two flattened sides 23. The resilient catch 18 in the form of the tongue 19 is arranged on one of these flattened sides.

8 and 9 show that the cross section of the pin 15 corresponds to the cross section of the longitudinal recess 14. The pin 15 can therefore not rotate in the longitudinal recess 14. Different rows of locking recesses 17 and 17 'are arranged on the flat sides of the pin 15. If the catch 18 of the setting shaft 9 works together with the catch recesses 17 shown in FIGS. 6 and 7, then the printing unit is equipped with six printing type bands 1 and setting wheels 5 which are of essentially the same width. However, the catch 18 of the adjusting shaft 9 works with the one from FIG. 7 visible locking recesses 17 'together, then the printing unit is equipped with eight printing strips 1 of essentially the same width and adjusting wheels 5.

Because the printing type bands 1 are narrower for certain printing types than for other printing types, the latching recesses 17, 17 'can also be arranged at different intervals.

The latching recesses 17, 17 'are arranged asymmetrically or axially offset from the end faces 24, 24' of the pin 15. As the figure shows, resilient plug-in catches 16, 16 'can be arranged on both end faces of the pin, so that the sequence of the different printing type widths - viewed in the axial direction - can be shifted in terms of position when the pin 15 is rotated by 180 ° its other end is inserted into the housing wall 6.

Claims (5)

1. A printing mechanism, in particular for price labelling devices, wherein the printing types can be set by means of setting wheels which are mounted rotatably about an axis one beside the other and which have an internal toothing into which a drive member can be engaged, which drive member is fixed to the free end of a setting shaft which is mounted in a plain bearing in such a way as to be axially settable and rotatable about its longitudinal axis, and wherein the setting shaft additionally has a resilient tongue- like latch member which, by axial displacement of the setting shaft, can be engaged into latching recesses which are arranged along the setting shaft in accordance with the number of setting wheels one beside the other at spacings which correspond to the width of the setting wheels, and wherein the setting shaft is internally provided with a central longitudinal recess into which engages a guide pin which is mounted to the wall of the housing which is disposed opposite to the plain bearing, characterised in that the guide pin (15) is mounted to the housing wall (7) rotatably about its longitudinal axis, and the latching recesses are provided at the periphery of the pin, in the form of at least two different rows of latching recesses (17, 17'), which rows are respectively displaced in the peripheral direction, that the cross-section of the longitudinal recess (14) in the setting shaft (9) and the cross-section of the guide pin (15) are non-round, and that the latch member (18) is in the form of an inwardly resilient tongue (19) on the setting shaft (9).

2. A printing mechanism according to claim 1 characterised in that the latching recesses (17) are of an undulatory configuration as viewed in longitudinal section of the guide pin (15).

3. A printing mechanism according to claim 1 or claim 2 characterised in that the pin (15) is of substantially oval cross-section with flattened sides and the latching recesses (17, 17') are arranged on the flattened sides.

4. A printing mechanism according to one of claims 1 to 3 characterised in that the pin (15) is of such a nature that it can be easily replaceably secured to the housing wall (7), both with one end of the pin and with the other end, and that, as viewed in the axial direction, the latching recesses (17, 17') are arranged asymmetrically with respect to the portion of the pin (15) which is delimited by the end contact surfaces (24, 24') of the pin (15) at the two ends thereof.

5. A printing mechanism according to one of claims 1 to 4 characterised in that the pin (15) is provided at at least one end with a radially resilient insertion latch member (16) which can be pressed in the manner of a push button into a recess in the housing wall (7).

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