Print ribbon guide

A type writing ribbon guide device in a type writing appliance which comprises a pair of inner ribbon guides disposed adjacent to the type writing zone in the appliance and a pair of outer ribbon guides positioned outwardly from the inner ribbon guides and in which a type writing ribbon presents concave and convex curved shapes having different radius of curvature as the ribbon is guided along the outer and inner ribbon guides.

BACKGROUND OF THE INVENTION 
This invention relates to a type writing ribbon guide device to be disposed 
at an area in the vicinity of the type writing head in a type writing 
appliance. 
PRIOR ART 
In the prior art type writing appliance as shown in FIG. 10, the type 
writing head 1 positioned in the type writing zone strikes against the 
type write ribbon 2 being fed below the head to type-write letters and the 
like on a sheet of paper (not shown) through the ribbon mask 3. 
The type writing ribbon 2 is guided along a pair of inner ribbon guides 4 
positioned in opposing and spaced relationship adjacent to the type 
writing head 1, a pair of outer ribbon guides 5 positioned outwardly from, 
respectively, of the respective inner ribbon guides 4 while running 
through the appliance. 
When the type writing ribbon 2 now being employed is to be replaced by a 
ribbon having a color different from the color of the ribbon being 
employed, the ribbon being employed is shifted in the transverse direction 
of the ribbon. Thus, in order that the ribbon can be easily shifted in the 
transverse direction thereof, the under-surface of the inner ribbon guide 
4 which contacts the ribbon is formed concave having the radius of 
curvature R as seen from the head 1 side in the transverse direction of 
the ribbon 2 as shown in FIG. 11. 
Since the undersurface of the inner ribbon guide 4 is formed concave in the 
transverse direction of the ribbon as described hereinabove, when a 
portion of the running type writing ribbon 2 is positioned between the 
inner ribbon guides 4, 4, that is, at the type writing zone, the ribbon 2 
presents the concave shape in the transverse direction thereof as seen 
from the head 1 side as shown by reference numeral 2a in FIG. 12. 
However, since the type writing ribbon 2 is directed from either one outer 
ribbon guide 5 to the adjacent inner ribbon guide 4, the ribbon 2 is bent 
over the outer ribbon guide 5. Thus, in the prior art ribbon guide device, 
the ribbon bending portion of the outer ribbon guides 5 are formed linear. 
As a result, the ribbon 2 also presents a linear shape when the ribbon 2 
is guided along the bending portions on the outer ribbon guides 5 as shown 
by reference numeral 2b in FIG. 12. 
Therefore, as the type writing ribbon 2 passes between either one inner 
ribbon guide 4 and the adjacent outer ribbon guide 5, the ribbon forms the 
portion as shown by reference numeral 2c in FIG. 12 in which the area 
adjacent to the longitudinal center line of the ribbon is pulled with a 
force higher than that pulling the opposite side edges of the portion to 
thereby form the slack ripples or creases at the opposite side edges as 
shown by reference numeral 2d in FIG. 12. 
Therefore, the prior art presents the problem that the feed and/or 
transverse shift of the type writing ribbon encounter difficulties 
resulting in low quality of type writing. 
SUMMARY OF THE INVENTION 
In order to overcome the above-mentioned problem, the present invention 
provides a novel and improved type writing ribbon guide device positioned 
at an area in the vicinity of the type writing head in a type writing 
appliance. The improved ribbon guide device comprises a pair of opposing 
and spaced inner ribbon guides positioned adjacent to the type writing 
head and a pair of outer ribbon guides each positioned outwardly from the 
respective inner ribbon guide. Each inner ribbon guide has a ribbon 
bending area on the ribbon guide face thereof for directing the type 
writing ribbon towards the type writing zone below the type writing head 
and each outer ribbon guide has a ribbon bending area on the ribbon guide 
face thereof for directing the ribbon towards the adjacent inner ribbon 
guide. In operation of the type writing appliance, the running type 
writing ribbon presents in a position inwardly from the ribbon bending 
areas of the guides or at the type writing zone the concave shape having 
the radius of curvature R1 as seen from the type writing head side, in a 
position outwardly from the bending area of each outer ribbon guide the 
concave shape having the radius of curvature R2 slightly smaller than R1 
as seen from the type writing head and the convex shape having the radius 
of curvature R3 varying continuously from R1 and R2 as seen from the 
printing head side between the bending area on each inner ribbon guide and 
the bending area of the adjacent outer ribbon guide. 
According to the ribbon guide device of the present invention described 
hereinabove, in the position between the respective adjacent inner and 
outer ribbon guides the ribbon is pulled at the oppposite side edges with 
a force higher than that with which the area between the opposite side 
edges is pulled whereby there is no possibility of occurence of a crease 
on the ribbon. 
The above and other objects and attendant advantages of the present 
invention will be more readily apparent to those skilled in the art from a 
reading of the following detailed description in conjunction with the 
accompanying drawings which show one preferred embodiment of the present 
invention for illustration purpose only, but not for limiting the scope of 
the same in any way.

PREFERRED EMBODIMENT OF THE INVENTION 
The present invention will be now described referring to FIGS. 1 to 9 
inclusive in which the preferred embodiment of the invention is shown for 
illustration purpose only. 
FIGS. 1 to 5 inclusive show the inner ribbon guide 11 and outer ribbon 
guide 12 of the type writing ribbon guide device according to the present 
invention. 
Although only one of the inner ribbon guides 11 and only one of the outer 
ribbon guides 12, are shown respectively, as in the case of the prior art 
ribbon guide device in which two inner ribbon guides 4, 4 and two outer 
ribbon guides 5, 5 are provided in symmetrical relationship, respectively, 
two inner ribbon guides 11 and two outer ribbon guides 12 can be provided 
in symmetrical relationship with respect to the type writing head in the 
ribbon guide device of the present invention. 
The inner ribbon guide 11 has a convex ribbon guide face 11a having the 
radius of curvature R1 and a concave ribbon guide face 11b having the 
radius of curvature R2 of which description will be made hereinafter. 
Provided between the convex and concave guide faces 11a, 11b is a ribbon 
bending area 11c where a ribbon 20 is bent. 
Similarily, the outer ribbon guide 12 has a concave ribbon guide face 12a 
having the radius of curvature R2 slightly smaller than the radius of 
curvature R1 and a convex ribbon guide face 12b having the radius of 
curvature R3. Provided between the guide faces 12a, 12b is a ribbon 
bending area 12c where the ribbon 20 is bent. 
Needless to say, the ribbon guide faces 11a, 11b, 12a, 12b lie in the same 
one plane containing the type writing head 1 and the concave face of the 
ribbon guide face 11b and convex guide face 12b are positioned so as to 
complement each other. 
The radius of curvature R3 of the guide faces 11b, 12b varies continuously 
from the radius of curvature R1 at the bending area 11c to the radius of 
curvature R2 at the bending area 12c. 
With the above-mentioned construction and arrangement of the components of 
the ribbon guide device of the present invention, as shown in FIGS. 6 to 9 
inclusive in the operation of the type writing appliance, the type writing 
ribbon 20 to be guided along the inner ribbon guides 11 and outer ribbon 
guides 12 presents the concave shape having the radius of curvature R1 
seen from the type writing head side as shown by reference numeral 20' 
(see the cross-sectional view of FIG. 7) between the inner guide 11, 11, 
the concave shape having the radius of curvature R2 slightly smaller than 
the radius of curvature R1 seen from the head side as shown by reference 
numeral 20" (see the cross-sectional view of FIG. 8) at an area positioned 
outwardly from the ribbon bending area 12c of the outer ribbon guide 12 
and the convex shape having the radius of curvature R3 varying 
continuously from the radius of curvature R1 to R2 as seen from the type 
writing head side as shown by reference numeral 20"' (see the 
cross-sectional view of FIG. 9) between the bending area 11c of the inner 
guide 11 and the bending area 12c of the outer guide 12. 
In the convex curve 20"' shown in FIG. 9, the ribbon 20 is pulled on the 
opposite sides of the center of the curve with a force higher than that 
with which the center of the curve of the ribbon is pulled and thus, there 
is no possibility for occurrence of "crease" in the ribbon. 
While one preferred embodiment of the invention has been shown and 
described in detail, it will be understood that the same is for 
illustration purpose only and not to be taken as a definition of the scope 
of the invention, which scope is defined by the appended claims.