Replaceable ribbon cartridge for printers

In a replaceable ribbon cartridge (12) for printers in which the ribbon (14) can be guided out of the cartridge through an exit opening (16) and at the end of a tension segment extending outside the cartridge can be reintroduced into the cartridge through an entrance opening (18), there is arranged on the cartridge (12) in the zone of the tension segment at least one deflection slide (24, 26) displaceable in a direction approximately perpendicular to the ribbon plane between a position of retraction into the cartridge (12) and an extended position deflecting the ribbon (14). Through the deflection slide or slides (24, 26), the ribbon (14) is generally spread away from the cartridge sufficiently so that upon insertion of the cartridge into the printer, it places itself around the printer head. During the last phase of insertion, the deflection slides (24, 26) are retracted, as by means of rams (56) arranged on the printer, so that during the subsequent ribbon advance, the ribbon (14) can become tensioned in its guide.

TECHNICAL FIELD 
The present invention generally relates to a replaceable ribbon cartridge, 
especially of the type in which a portion of the ribbon is held in tension 
which is impacted by a printing head. 
BACKGROUND ART 
In general, ink ribbons for printers and other comparable appliances are 
presently housed in cartridges which permit rapid and simple changing of 
ink ribbons. In order to keep the ribbon under tension in the printing 
zone, the ribbon loop extending outside the ribbon cartridge must be 
trained, in general, around guide webs or along the front surface of the 
printing head itself. Therefore, it is generally necessary, upon insertion 
of the ribbon cartridge, to thread the ribbon manually into the guide 
path, which renders the insertion process more difficult and causes the 
hands of the operator to be soiled by the highly staining ribbon. 
A replaceable ribbon cartridge is disclosed in West German Patent 
Publication DE-OS No. 3214633, in which the ink ribbon is installed 
automatically around the guide webs upon insertion of the ribbon cartridge 
and subsequent feeding of the ribbon. The construction of the guide webs 
is comparatively costly in that either a plurality of guide webs must be 
mounted on each printing head carrier precisely opposite one another or 
must be molded integrally with the head, such that the molds and the 
molding process become more complicated. 
SUMMARY OF THE INVENTION 
The purpose of the present invention is to provide an ink ribbon cartridge 
which facilitates automatic threading of the ribbon without any manual 
intervention, is simple in construction and also permits simple 
construction of the printing head and cartridge carriers. 
By means of an extendable deflection slide, the ribbon loop portion 
extending outside the cartridge is spread off the cartridge sufficiently 
so that it places itself about the front surface of either the printing 
head or guide webs. Thereafter, the deflection slides are moved into their 
retracted position(s) so that the ribbon is tensioned during subsequent 
feeding along the guide path. When the cartridge is removed, the ribbon is 
lifted off again from the front surface of the printing head and the guide 
webs by extension or moving-out of the deflection slides. 
In a preferred embodiment of the invention, deflection slides are 
respectively arranged in the direction of moving of the ribbon behind the 
exit opening and ahead of the entrance opening. In this manner, the ribbon 
is lifted off essentially over its entire tensioned path outside the 
cartridge whereby the so-called threading-in process is further assisted. 
In a further refinement of the invention, each deflection slide is rendered 
as a three-part web whose sections are connected by joints with one 
another. A first section of the web is firmly anchored in the cartridge. 
The second section is fixed in a swivelling fashion on the first one and 
cooperates with a swivel-actuating ram. A third section is linearly 
displaced by the second section. The third section constitutes the element 
which deflects the ribbon. The three-part web is preferably formed by a 
flexible material, in one piece, whereby the joints connecting the 
sections are rendered as so-called film hinges. Such deflection slides can 
be produced simply and at low cost as plastic elements. 
In a still further refinement of the invention, the actuation of the 
deflection slides is achieved by means of swivel-actuating rams which, 
through openings formed in the cartridge, can be introduced into the 
cartridge interior and thereby swivel the second section of the deflection 
slide. Preferably, the deflection slides are formed of an elastic 
material, so that they assume their extended position in an elastically 
relaxed state and so that they can be shifted to an elastically tensioned 
retracted position by means of the actuating rams. The swivel-actuating 
rams are designed in the form of pins which are fixedly arranged in the 
cartridge seat of the printer and which, when the ink ribbon cartridge is 
inserted, penetrate the openings formed on the cartridge. Accordingly, the 
ribbon in its normal condition is spread out off the cartridge and is 
ready for insertion. When the cartridge is set in, the pins penetrate the 
cartridge and, during the last phase of the insertion process, the 
deflection slides are retracted so that the ink ribbon applies itself 
against the guide webs and, respectively, the front surface of the 
printing head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The embodiment chosen to illustrate the invention and described below is 
particularly suited for a dot matrix printer. FIG. 1 shows a matrix 
printer head 2 with a driving element 4 and a pin guide element 6 directed 
towards the printing plane. The matrix printer head 2 is fixed in a 
conventional manner on the printer head support of a printer, not shown. 
The printing plane extends a small distance from the front surface 8 of 
the pin guide element 6 perpendicular to the plane of the drawing. 
A conventional ribbon cartridge 12, which receives the matrix printer head 
2 within a clearance 10, is likewise supported on the printer head 
support. It contains an ink ribbon 14 which emerges from the ribbon 
cartridge through an exit opening 16 and is introduced again into the 
cartridge through an entrance opening 18. In the example illustrated, the 
ribbon cartridge is of the type in which the ribbon 14 is arranged in a 
plurality of loops, which need not be shown in detail, in a retaining 
space 20. 
In the region between the exit opening 16 and the entrance opening 18, the 
ribbon 14 extends outside the cartridge. This region will be referred to 
as the tension segment hereinafter. Over the tension segment, the ink 
ribbon is maintained in a state of tension so that it moves free from 
folds along and in front of the printing plane. The direction of the 
ribbon advance is indicated by the arrow 22. 
In the direction of ribbon advance behind the exit opening 16 and ahead of 
the entrance opening 18 are respectively arranged deflection slides 24, 
26, each of which are displaceable approximately perpendicular to the 
plane of the ribbon between a position retracted into the ribbon cartridge 
12 and an extended or actuated position in which the ribbon 14 is 
deflected from its normal position. The two deflection slides 24, 26 are 
actuated simultaneously and in the same direction so that both deflection 
slides are always either retracted or extended. It is only in order to 
simplify the drawings that in FIG. 1 the deflection slide 24 is shown in 
the retracted position, whereas the deflection slide 26 is shown in the 
extended position. 
When the ribbon cartridge 12 is installed on the printer head support, both 
deflection slides 24, 26 are in the extended position so that the ribbon 
14 is spread sufficiently forward in order to position itself in front of 
the front surface 8 of the pin guide element 6 without being caught 
thereon. In this manner, the ribbon follows the line which in FIG. 1 is 
shown as a full line on the left side and as a broken line on the right 
side. 
It is only during the last phase of the seating movement that the 
deflection slides 24, 26 are moved into their retracted position so that 
the ribbon 14 can stretch itself around the front surface 8 of the pin 
guide element 6. It then follows, on both sides, the path shown in full 
line on the right side. 
The deflection slides 24, 26 each consist of a three-sectioned web having 
the shape shown in perspective in FIG. 2. The web has three sections which 
are connected with one another by joints. The first, anchoring section 28 
is firmly clamped into the cartridge. The second, actuation section 30 is 
connected with the anchoring section 28 in a swivelling fashion by way of 
a hinge-like joint 32 and cooperates with a swivel-actuation ram, as will 
be explained in greater detail below. The third deflection section 34 is 
connected in a swivelling fashion with the actuation section 30 by way of 
a hinge-like joint 36 and is driven thereby so as to achieve linear 
displacement movement. 
On the actuation section there are formed two swivel bearing journals 37 as 
well as two ramp-like actuation surfaces 38. On the deflection section 34, 
there is provided a stop in pin 40. 
The functioning of the deflection slide 24, 26 will now be explained in 
greater detail. The deflection slide 24, 26 is molded in one piece, 
preferably of an elastic plastic material. The joints 32, 36 are formed by 
thinned material regions to form so-called film hinges. FIG. 3 shows a 
deflection slide 24, 26 in side view. 
FIG. 4 represents a cross-section through the zone of the actuation section 
30 corresponding to the line IV--IV in FIG. 3 and more clearly shows the 
ramp-like actuations surfaces 38 and the swivel bearing journals 37. 
FIG. 5 is a plan view of a deflection slide 24, 26 taken along the line of 
view V in FIG. 3. It is particularly clear in this view that the axis 42 
of the swivel bearing journal 37 coincides with the theoretical axis of 
the joint 32. The axis 42 is the pivoting axis for the actuation section 
30. 
FIG. 6 shows a longitudinal section corresponding to the line VI--VI in 
FIG. 3. From this figure, it becomes clear that the joints 32, 36 are each 
formed as film hinges with a smaller thickness of the material, whereby 
the hinge webs are each formed on different sides of the deflection slide, 
corresponding to the bending direction indicated by FIGS. 1 and 7. 
From FIGS. 1 and 7, it is apparent that the swivel bearing journals 37 are 
supported in journal rests 44 in the bottom 46 of the cartridge and, not 
shown in detail, in the cover of the cartridge, where they pivot in the 
direction of the arrow 48. 
The anchoring section 28 is loaded elastically against a material web 50 so 
that the actuation section 30 is pretensioned in the direction of 
extension or actuation of the deflection section 34. The deflection 
section 34 is displaceable in the direction of the arrow 52, between two 
guide webs 54. The outward path of movement is limited by the abutment of 
the stop pin 40 against one of the guide webs 54. 
With each deflection slide 26, there is associated a swivel actuation ram 
56 which is fixed on the printer head support. Upon seating of the ink 
ribbon cartridge, the swivel actuation rams 56 each pass through openings 
58 in the bottom 46 of the cartridge and apply themselves against one of 
the ramp-like actuation surfaces 38 so that the actuation section is 
swivelled so as to result in a retraction of the deflection section 34. 
The design of the swivel actuation ram 56 and of the actuation surfaces 38 
is chosen in a manner such that the retraction of the actuation section 34 
occurs only in the last phase of the seating movement of the ink ribbon 
cartridge on the printer head support. The swivel movement of the 
actuation section 30 related to retraction is limited by a stop pin 60. 
It is clear from FIG. 5 in particular that each deflection slide is 
designed to be symmetrical with respect to a plane which is perpendicular 
to the drawing plane and contains the dividing line VI--VI, so that each 
deflection slide is suitable for arrangement on either side of the pin 
guide element 6.