Drive mechanism including floating pressure ring for ink ribbon cassette

An improved drive mechanism for an ink ribbon cassette for advancing an ink ribbon particularly well suited for use in a typewriter is provided. The drive mechanism includes a drive roller rotatably supported in the casing with a free floating pressure ring supported by a roller. The pressure ring is supported against the roller and against the drive roller so that there is an increase in pressure with an increase in the tension of the ribbon.

BACKGROUND OF THE INVENTION 
This invention relates in general to ribbon drive mechanisms, and in 
particular, to ribbon drive mechanisms for ink ribbons employed in a 
ribbon cartridge in printing applications. 
Ribbon drive mechanisms are known in the art as disclosed in U.S. Pat. No. 
4,011,933. This prior art cassette has a drive roller with a driver 
supported in fixed position in the cassette casing and a free floating 
pressure ring on a bearing stud with play between the pressure ring and 
the driver. The drive roller is positioned on the receiving or rolling-up 
side of the bearing stud and pulls the ink ribbon from a storage roll 
within the cassette through a printing location. Tension of the ribbon 
wedges the pressure ring between the bearing stud and the driver to create 
pressure of the pressure ring on the drive roller with the frictional 
connection between ribbon and drive roller increasing with increasing 
ribbon tension. 
This prior art mechanism has been satisfactory; however, it suffers from 
the disadvantage that threading of the ink ribbon between the pressure 
ring and drive roller is very difficult when the drive roller has flanges 
to guide the ink ribbon which necessarily overlap the pressure ring. 
Another disadvantage is the sliding friction of the pressure ring on the 
bearing stud, which also increases with increasing ribbon tension. Because 
of this undesirable sliding friction, the pressure ring must have a low 
coefficient of friction, which greatly limits the material selection. It 
is also desirable that for interchangeable uses of the ink ribbon to 
provide a cassette which can be used at different ribbon advance speeds. 
This necessitates using drive rollers having different diameters. This is 
possible in the known cassette only by shifting the position of the 
bearing stud in relation to the axis of the drive roller. Therefore, such 
a solution requires another casing for each reduction or speed change. 
Accordingly, it is desireable to provide a drive mechanism for an ink 
ribbon cassette which overcomes the shortcomings of the prior art device 
described above. 
SUMMARY OF THE INVENTION 
Generally speaking, in accordance with the invention, an ink ribbon 
cassette having an improved drive mechanism for advancing an ink ribbon is 
provided. The cassette includes a drive roller mounted on the cassette 
casing with a bearing stud mounted adjacent thereto. A roller is mounted 
for rotation about the bearing stud with a pressure ring supported on its 
inner surface by the roller and on its outer surface by the drive roller. 
The pressure increases with an increase in tension on the ribbon. 
It is an object of this invention to provide an improved drive mechanism 
for an ink ribbon cassette. 
Another object of this invention is to provide a drive mechanism for an ink 
ribbon cassette which has conical surfaces to facilitate threading the ink 
ribbon between the prssure ring and drive roller. 
A further object of this invention is to provide a drive mechanism for an 
ink ribbon cassette which reduces the sliding friction on the pressure 
ring as ribbon tension increases. 
Still another object of this invention is to provide a drive mechanism for 
an ink ribbon cassette which will allow the cassette casing to be used 
with rollers of different sizes and operate at various ribbon winding 
speeds. 
Still other objects and advantages of the invention will in part be obvious 
and will in part be apparent from the specification and drawings. 
The invention accordingly comprises features of construction, combination 
of elements, and arrangement of parts which will be exemplified in the 
construction hereinafter set forth and the scope of the invention will be 
indicated in the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Reference is made to FIG. 1, wherein a plan view of an ink ribbon cassette 
constructed in accordance with the invention is shown. The cassette 
includes a casing base 1 and a casing cover 2 supported by a side wall 59, 
a portion of which is shown. A supply roll 14 of an ink ribbon 4 is wound 
on core 3 supported within casing cover 2 and base 1. Roll 14 is braked 
against casing cover 2 and base 1 to provide a definite ribbon tension. 
Ink ribbon 4 wound on supply roll 14 unwinds through an outlet 5 and 
advances in the direction of the arrows to a location 6 and drawn into an 
inlet opening 7 by means of a drive mechanism to a winding core 12 also 
supported within casing base 1 and cover 2. 
The drive mechanism includes a drive roller 11 mounted for rotation within 
casing cover 2 and casing base 1 with ink ribbon 4. Ink ribbon 4 is 
pressed against drive roller 11 by a pressure ring 8 with ink ribbon 4 
also wrapped thereabout. Pressure ring 8 is free floating about the roller 
9 which is supported in rotary arrangement on a bearing stud 10 attached 
to the casing base 1 and cover 2. Pressure ring 8 is supported by the 
force exerted upon it at its outer surface by drive roller 11 and the 
force exerted on its inner surface by roller 9. The internal diameter of 
pressure ring 8 is substantially larger than the external diameter of 
roller 9 so that pressure ring 8 surrounds roller 9 with considerable 
play. The pressing force of pressure ring 8 against drive roller 11 is 
dependent on the tension of ink ribbon 4 between inlet opening 7 and 
pressure ring 8. As ink ribbon 4 advances, pressure ring 8 rolls on roller 
9, which produces a light friction. 
As is seen from FIG. 2, drive roller 11 is rotatably supported by a lower 
cylindrical stud 28, in a staged borehole 26 formed in casing base 1 and 
by an upper cylindrical stud 29 in a staged borehole 27 formed in cover 2. 
In order to guide ink ribbon 4, drive roller 11 includes lower and upper 
flanges 21,22 with conical shoulders 23,24 on both sides of a meshed 
central drive cylinder 25. Drive roller 11 also has a catch coupling 30 
for driving drive roller 11 in a typewriter, for example. The portion of 
drive roller 11 projecting above cover 2 includes a handwheel 32 as well 
as a groove 31, into which a rubber belt 13 is inserted for driving 
winding core 12. Pressure ring 8 is formed with gearing 35 which meshes 
with gearing 60 formed on drive cylinder 25. 
As further shown by FIG. 2, roller 9 is designed symmetrically to its 
radial median plane with a central cylindrical region tapering on both 
sides of the cylindrical pressure surface 40, extending to upper and lower 
cylindrical surfaces 42 and 42'. The difference between the radii of 
surface 40 and upper and lower cylindrical surfaces 42 and 42' is greater 
than the radial width of flanges 21,22. The result achieved is that ink 
ribbon 4 can be inserted effortlessly from above between pressure ring 8 
and drive cylinder 25 with roller 9 removed and pressure ring 8 pressed 
against bearing stud 10. It is also possible to isnert drive roller 11 in 
axial direction into base 1 with ink ribbon 4 in place. In both cases, 
roller 9 is subsequently placed on bearing stud 10, whereby pressure ring 
8 is automatically displaced between flanges 21,22 by cone 41. The 
assembly of the drive mechanism is substantially facilitated in both cases 
in comparison with the the prior art. 
Reference is next made to FIG. 3, which shows a bearing stud 10 with a 
roller 9" and a pressure ring 8" which essentially corresponds to that of 
FIG. 2. In this embodiment, pressure ring 8" is formed with conical 
surfaces instead of roller 9". Pressure ring 8" has a central cylindrical 
inside surface 46 which extends both upwardly and downwardly to cones 45 
and 45' and finally into an expanded cylindrical element 44. Roller 9" 
includes a cylindrical pressure surface 47 which extends in both 
directions into conically tapered surfaces 48 and 48'. Here, too, the 
radial displacement of pressure ring 8" attainable by conical surfaces 45 
and 48 is greater than the radial width of flanges 21 and 22. 
Reference is next made to FIGS. 4 and 5, wherein two ink ribbon winding 
mechanisms for winding at different speeds are shown while maintaining an 
interval A between bearing stud 10 and a drive roller center D. Drive 
roller 11 of FIG. 4 with a diameter B is replaced by another drive roller 
11' with a smaller diameter B' of drive cylinder 25' and, at the same 
time, replacing roler 9 having a diameter C with roller 9' having a 
diameter C'. This arrangement of components permits use of the same casing 
base 1 and cover 2 to provide drive mechanisms which operate at different 
speeds while utilizing the same pressure ring 8. 
Referring now to FIG. 6, another embodiment of the invention is shown for a 
cassette with an endless textile inked ribbon 4', which is drawn in the 
direction of the arrow by roller 56 from an inlet (not shown). Roller 56 
is supported on casing base 1 by a pin 57 attached to casing base 1. The 
drive mechanism again includes pressure ring 8, free-floating on roller 9 
and drive roller 11. Roller 9 is supported on bearing stud 10. Ink ribbon 
4' is wrapped around pressure ring 8 and drive roller 11 along a portion 
of its circumference and is pressed against drive roller 11 at the outlet 
end by spring 51. Spring 51 is biased towards drive roller 11 by a 
pressure lug 54 and a support 55 attached to the cassette and is secured 
against longitudinal displacement by retention leg 53. Ink ribbon 4' is 
fed loosely to a storage region 50 in loose sliding by the drive 
mechanism. Spring 51 is formed with a leg 52 to prevent penetration of 
free ribbon 4' into the drive side of the drive mechanism. 
Roller 9 is supported on bearing stud 10 which is inserted into a borehole 
43 in casing cover 2 in the manner shown in FIG. 2. However, it is also 
possible to connect bearing stud 10 rigidly with roller 9 thereabout and 
have it supported in rotary arrangement in base 1 and in borehole 43 or 
fixed to cover 2 and in a corresponding borehole in base 1. 
Accordingly, by providing a drive mechanism including a bearing stud with a 
roller mounted thereon and a free-floating pressure ring for compressing a 
winding ribbon against a drive roller both assembly and operation are 
enhanced. Additionally, by providing conical surfaces on the exterior 
surface of the roller mounted on the heavy stud or on the interior surface 
of the pressure ring, the roller may be readily inserted into place even 
when the ribbon is biased against the pressure ring. Finally, the drive 
mechanism in accordance with the invention is particularly well suited to 
provide for using the same casing to provide for different winding speeds 
as the distance between the bearing stud and drive roller remains constant 
while varying the diameters of the roller and the drive cylinder of the 
drive roller. 
It will thus be seen that the objects set forth above, among those made 
apparent from the preceding description, are efficiently attained and 
since certain changes may be made in the above construction without 
departing from the spirit and scope of the invention, it is intended that 
all matter contained in the above description or shown in the accompanying 
drawings shall be interpreted as illustrative and not in a limiting sense. 
It is also to be understood that the following claims are intended to cover 
all of the generic and specific features of the invention herein described 
and all statements of the scope of the invention which, as a matter of 
language, might be said to fall therebetween.