Device for pivoting a printing unit

A printing unit is guided along a straight line in parallel relation with the printing plane of a printing support. A device is arranged to pivot the printing unit between at least two printing supports spaced angularly apart. The device includes a coupling assembly interconnecting the printing unit with a drive member. A part of the coupling assembly includes a slotted crosshead or plate in which rollers move through branch slots disposed angularly to one another. Due to the guidance afforded the printing unit as it is pivoted between different angularly spaced printing supports, it moves along a curve significantly flatter than the arc of a circle on which the printing planes of the printing supports are located.

SUMMARY OF THE INVENTION 
The present invention is directed to a device for pivoting a printing unit, 
movable along a straight line parallel to the printing plane of a printing 
support, between two printing positions each located at a different 
printing support. The printing unit includes a carrier and a printing head 
mounted on the carrier with the unit supported on a guide shaft for 
movement between a pair of side members spaced apart by a distance 
corresponding to the largest possible printing support. 
In the Federal Republic of Germany Offenlegungsschrift No. 28 23 153, a 
pivoting device is disclosed where a printing head on a printer moves with 
its printing point--the printing point is defined as the point where the 
central printing needle of the needle printer touches the printing 
support--along a circle from one printing position to another relative to 
two different supports. This movement of the printing head from one 
position to another has the consequence that the overall arrangement is 
relatively high with the disadvantage that when the printer is placed on a 
table for use, because of its height, the operator is unable to view the 
upper printing position. 
Furthermore, during pivoting movement, the printing head moves along a very 
flat path or curve into the printing position and because of various paper 
guide parts adjacent the printing position at the printing support, the 
printing head can be moved along a path so that it does not interfere with 
the paper guide parts. 
Another disadvantage of this known device is that the crank mechanism used 
for pivoting the printer permits stopping the print head in only two end 
positions determined by the two dead center positions of the crank 
mechanism. As a result, it is not possible to pivot the printer only 
partially between the two end positions. 
Therefore, it is the primary object of the present invention to overcome 
the disadvantages experienced with the known pivoting devices and to 
provide a device for pivoting a printing unit so that the device has a 
relatively low height permitting printing on several printing supports 
whereby an on-the-table printer can be produced in which the operator is 
able to follow the printing process on the upper printing support. 
Another object of the present invention is to drive the pivoting device so 
that partial pivoting between the end positions can be effected with the 
pivoting device stopped between the end positions. Further, in these 
intermediate positions the printing head can be pivoted. 
In accordance with the present invention, a coupling assembly is provided 
between the side members of the printing unit and a driving member. The 
coupling assembly includes a slotted crosshead or Scotch yoke containing 
two slots or recesses intersecting one another with rollers movable 
through the slots for effecting the pivoting of the printing unit between 
two different printing supports. In the end positions where the printing 
unit is located for movement in a straight line parallel to a printing 
support, the printing point of the printing unit extends perpendicularly 
to the printing plane on the printing support. 
In another embodiment of the coupling assembly, a toothed or gear wheel is 
connected with the side members and during pivotal movement it rolls in 
meshed engagement with a stationary internally toothed surface of a 
support or guide part. The diameter of the gear wheel and of the 
internally toothed surface on the support is in a ratio of 1:2 so that the 
gear wheel effects the pivoting movement of the printing unit between the 
two printing positions. 
In accordance with the present invention, the printing device has the 
advantage that the printing unit can be moved from one printing position 
to the other along a very steep curve as compared to the arcs of the 
circles on which the printing supports are located whereby the device 
requires much less space. When the printing unit is moved between two 
printing positions each opposite a different printing support, the 
intersecting recesses or slots in the slotted crosshead from two branch 
slots, one extending perpendicularly to the other with each branch slot 
extending parallel to the printing plane of one of the printing supports. 
Such an arrangement has the advantage that during the movement of the 
pivoting device, as the printing head moves into the printing position, 
its movement is almost parallel with the printing plane. Therefore, the 
printing unit does not pass through any paper guide parts or the like so 
that the pivoting movement can be effected in any lateral position of the 
printing head. 
When a stepping motor is used as the driving element for the pivoting 
device, a partial pivoting movement is possible so that the printing head 
is not always moved into one of the end positions, rather it can be 
pivoted only to the extent that the printing surface or plane can be 
viewed. When partial positioning of the printing head is carried out, 
special retraction of the printing head for the purpose of line spacing of 
the record carrier is no longer required so that the printing unit is 
simplified. 
Another advantage involved in partial pivoting is that the printing head 
may be moved by a distance less than the width of one needle. In such 
movement, it is possible by the multiple movement of the printing head 
over one line to print the same data with better quality, since the second 
printing operation fills gaps left in the first operation, that is, due to 
the roundings of the printing needles. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its use, reference 
should be had to the accompanying drawings and descriptive matter in which 
there are illustrated and described preferred embodiments of the 
invention.

DETAILED DESCRIPTION OF THE INVENTION 
In FIG. 1 a printing unit 2 is positioned in front of a first printing 
support 1. The printing unit 2 includes a carrier 3 with a printing head 4 
mounted on it and including an orifice 5 positioned immediately in front 
of the printing support 1. A ribbon 6 is positioned between the printing 
head 4 and the printing support 1 and the printing action is effected by 
printing needles, not shown, on paper positioned on the printing support 
1. The printing needles print on a first printing plane D.sub.1 on the 
printing support 1, note FIG. 4. Ribbon 6 is located in a cassette 7 
having two parts 7a, 7b arranged on a guide member 8 located at the 
opposite ends of the printing support 1, that is, on the opposite sides of 
the printing position 9. The ribbon 6 is stored in part 7a of the cassette 
7 and is moved by driving means located in part 7b and is guided in front 
of the printing position 9. 
The printing unit 2 is mounted on and moves along a shaft 10 which acts as 
a guide for the unit between two side parts 11, 12. As viewed in FIG. 1, a 
motor 13 is positioned on the right side member 11. By means of a belt 
wheel 14, a belt 15 and another belt wheel, not shown, the motor moves the 
printing unit 2 along the guide shaft 10 so that it travels rectilinearly 
for printing against the first printing support 1. 
A second printing support 16, note FIG. 3, is positioned angularly apart 
from the first printing support 1 by approximately 90.degree.. In the 
second printing position at the second printing support 16, the printing 
head 4 prints downwardly on the printing plane of the support. The 
printing head 4 moves over a second printing plane D.sub.2 formed on the 
second printing support 16. Perpendicularly of the first printing plane 
D.sub.1 there is a plane P.sub.1 containing the printing point A.sub.1. 
Similarly, extending perpendicularly of the second printing plane D.sub.2, 
there is a plane P.sub.2 containing the printing point A.sub.2. Printing 
points A.sub.1 and A.sub.2 refer to the points at which the central 
printing needle, not shown, touches the printing planes D.sub.1, D.sub.2. 
The combination of the guide shaft 10, the side members 11, 12 and the 
printing unit 2 can be pivoted by the pivoting device in a manner 
described in the following so that the printing head 4 can print on either 
the first printing support 1 or the second printing support 16. 
With particular reference to FIGS. 2 and 3, the pivoting device for the 
printing unit 2 will now be described. As shown in FIG. 1, a coupling 
assembly 17 is connected between the guide shaft 10 and the side members 
11, 12 and the means for pivoting these components. As viewed in FIG. 1, 
the coupling assembly 17 on the left-hand side consists of two members 18, 
19 connected to one another. On the right-hand side in FIG. 1, the 
coupling assembly includes only member 19. As can be seen in FIGS. 2 and 
3, at the opposite ends of the printing supports 1,16, rollers 20, 21 are 
associated with the member 19. The two rollers 20, 21 are rotatably 
mounted at two diagonally opposite corners of the four-sided member 19 and 
the rollers are positioned in the two branch slots 22, 23 of a slotted 
crosshead or Scotch yoke 24. Rollers 20, 21 define the end points of the 
pivoting movement afforded by the coupling assembly 17 when located at the 
ends of the branch slots 22, 23 spaced from their intersection. The 
slotted crosshead 24 made up of the branch slots 22, 23 is formed in a 
guide plate 25 fixed to a support or lateral plate 26. The end positions 
of the rollers 20, 21 within the branch slots 22, 23 spaced from the 
intersection, are defined by stop levers 27, 28 each of which is under the 
influence of a spring 29, 30. The levers 27, 28 are at the opposite ends 
of the branch slots 22, 23 from the intersection of the slots. With roller 
21 in the end position illustrated in FIG. 2, the spring 30 is slightly 
tensioned. As a result of the tensioning of the spring 30, at the 
commencement of the movement of the coupling assembly 17 from this end 
position to the other an additional acceleration is afforded so that the 
pivoting movement can be quickly speeded up. When there is movement in the 
opposite direction, the spring cushions the pivoting movement as it is 
contacted by the roller 21. Stop lever 27 acts in a similar manner. When 
the coupling assembly 17 is in the other end position, note FIG. 3, roller 
20 presses against the stop lever 27 so that the spring 29 is slightly 
tensioned. When movement is effected from the position shown in FIG. 3, 
the spring serves to accelerate the pivotal movement at the beginning and 
also cushions the movement as the roller 20 moves against the stop lever 
27. Each of the stop levers 27, 28 acts to support the weight of the 
device. 
To pivot the coupling assembly and with it the printing unit 2 and its 
guide shaft 10 and side members 11, 12, the coupling assembly is connected 
to a stirrup-shaped part 31 which is pivotally mounted on a nut 32. A 
driving spindle 33 extends through the nut 32 and the spindle is rotated 
by a gear wheel 34 driven from the shaft 35 of a stepping motor 36. As the 
spindle 33 rotates, it moves the nut 32 along the spindle. 
As shown in FIGS. 2 and 3, a mounting part 37 located on the plate 26 
supports two microswitches 38, 39 with which switching levers 40, 41 
cooperate. Bolts 42 on the members 18, 19 control the movement of the 
switching levers 40, 41 so that one of the microswitches is closed in one 
end position of the coupling assembly 17 and the other microswitch is 
closed in the other end position. This arrangement serves to transmit 
corresponding signals on the position of the coupling assembly to 
electronic parts. 
The various components shown in FIGS. 2 and 3 which effect the driving 
action, that is, the stepping motor 36, the spindle 33 and the nut 32 on 
part 31 are arranged on the left-hand side of the printing device as shown 
in FIG. 1. On the opposite end or right-hand side there is a member 19 of 
the coupling assembly 17 along with the rollers 20, 21 and the plate 25 
forming the slotted crosshead 24. Further, stop levers 27, 28 are located 
on both sides of the printing device. 
To carry out the pivoting movement, the stepping motor 36 is switched on. 
The motor 36 via its gear wheel 34 drives the spindle 33 so that the nut 
32 moves along the spindle and via the stirrup-shaped part pivots the 
coupling assembly 17 in the direction as shown in FIG. 3. Accordingly, 
rollers 20, 21 move in the branch slots 22, 23 of the slotted crosshead 24 
from the position illustrated in FIG. 3 to the position displayed in FIG. 
2. As can be seen in FIG. 3, where the first and second printing supports 
1, 16 are shown, the printing head 4 cooperates with the first printing 
support 1 while in the position of FIG. 2 the printing head cooperates 
with the second printing support 16. 
As mentioned above, it is possible to run the motor so that only individual 
steps or small movements between the end positions are effected. The 
printing head can be moved so that a view of the printing position 9 is 
afforded and the printed matter can be viewed. Further, it is possible to 
move the printing head by only part of the width of one needle point so 
that by moving twice over one of the printing supports marks will be 
produced in which the points normally formed by needle printers are 
doubled thereby filling in any gaps between individual points. 
To clarify the basic design principle, FIG. 4 shows in a diagrammatic 
representation the two printing planes D.sub.1, D.sub.2, the two end 
positions of the coupling assembly 17 within the branch slots of the 
slotted crosshead 24, and the planes P.sub.1, P.sub.2 in which the 
printing points A.sub.1, A.sub.2 extend perpendicularly to the printing 
planes. In FIG. 4 the coupling assembly 17 are shown schematically in 
solid lines arranged for printing in the printing plane D.sub.1 of 
printing support 1, and in dashed lines for printing in the printing plane 
D.sub.2 of the printing support 16. In the positions illustrated, the 
planes P.sub.1, P.sub.2 intersect at right angles in this schematic 
showing of the coupling assembly, however, this is not really necessary 
such as when the branch slots of the slotted crosshead take up another 
angular position relative to the printing planes. Further, in FIG. 4 a 
relatively flat or steep curve B.sub.1 is shown in dotted line along which 
the printing head 4 moves between the printing positions represented by 
points A.sub.1 and A.sub.2. 
FIG. 5 shows, in a diagrammatic representation, another coupling assembly 
usable in place of the embodiment shown in FIGS. 1-4. In this second 
embodiment the coupling assembly 17 includes a toothed or gear wheel 40 in 
meshed engagement with a fixed guide member 42 having an internal toothed 
surface 41. The diameter of the internal toothed surface 41 is twice the 
diameter of the gear wheel 40. By means of a suitable connection the gear 
wheel 40 is driven by the spindle 33 and the stepping motor 36 to produce 
the pivotal movement of the printing device. When the gear wheel is 
rotated in the clockwise direction it rolls along the internal toothed 
surface 41 until it reaches, after half a revolution, the position shown 
in dot-dash lines. In other words, one end position is represented in full 
lines and the other end position is represented in dot-dash lines. The 
positions of the printing planes D.sub.1, D.sub.2 and of the printing head 
4 are shown. The end points of the coupling assembly in this embodiment 
are the points of engagement of the gear wheel 40 with the internal 
toothed surface 41 in the two end positions with the movement of the 
center of the gear wheel 40 between the two positions being illustrated by 
the curved line K.sub.1. 
In FIG. 5, it can be seen that the printing head pivoted between the two 
printing points A.sub.1, A.sub.2 moves along a flat or steep curve 
B.sub.2. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the inventive principles, it 
will be understood that the invention may be embodied otherwise without 
departing from such principles.