Ribbon guide system for a line printer

A printer apparatus has a frame member supporting an endless revolving type band in alignment with a row of print hammers with a gap therebetween. Ribbon spools with ribbon wound thereon are rotatably supported in spool housings at either end and on opposite sides of the frame member. The spool housings each have a receptacle portion and a cover portion which enclose the spool. A gap in the spool houses enables the ribbon to extend between the housing and through the gap. The ink ribbon is guided through the gap in parallel with the row of hammers and at an angle to the print line by a set of guide pins on the cover of one spool housing and a set set of guide pins mounted on the frame member in proximity with the other spool housing. Both sets of guide pins engage the same side of the ink ribbon in a manner whereby touching the ribbon is not required to install or remove the ribbon from the printer apparatus. Individual drive motors for rotating the ribbon spools are mounted on the receptacles of the spool housings.

This invention relates to printer apparatus and particularly to a ribbon 
guide system for a line printer. The invention has utility in high speed 
line printers but in not necessarily limited thereto. 
BACKGROUND OF THE INVENTION 
High speed impact line printers comprise an endless type carrier band with 
a single row of characters moving parallel with a row of print hammers. 
The band is trained on spaced drive and idler or tension pulleys which are 
motor driven to revolve the band at constant speed. The band drive, as it 
is commonly called, is generally mounted on a support or frame member that 
holds the band in proximity to the row of print hammers mounted on another 
frame member. The hammers and the band are separated by a gap or throat 
which defines a passageway for a print medium such as paper forms and an 
ink ribbon. 
The printing ribbon is sometimes a narrow strip wound on two widely 
separated spools with a section extending across the paper and lengthwise 
through the gap. Commonly the ribbon path is slanted relative to the line 
of the hammers and type band so that the entire width of the ribbon is 
presented for printing. Ribbon drive motors rotate the spools to feed the 
ribbon through the gap. Guide means between the spools is provided for 
maintaining the ribbon in proper alignment as it travels through the gap. 
The guide means necessarily are also widely separated to avoid 
interference with the hammer and paper feed operations and hence 
maintaining the ribbon on track presents a problem. The structures and 
arrangement of the guide means and the spool mountings have made it 
necessary to manually touch the ribbon when the ribbon is replaced and/or 
installed. The publication in the IBM Technical Disclosure Bulletin Vol. 
31, No. 10, March 1989 pp. 32-33, shows a printer unit in which the type 
band drive is mounted on a frame above the horizontal paper path. A 
stretch of the ribbon between ribbon spools passes horizontally between 
the type band and paper. No guidance structure is shown. The ribbon spools 
are inserted into enclosures on either side of the paper path frame. Such 
an arrangement is not convenient because of space limitations if the print 
unit is located within a cabinet and the direction of paper feeding is 
from side to side instead of front to back. 
SUMMARY OF THE INVENTION 
The invention provides a printer apparatus having a printing ribbon drive 
and guidance system that does not require finger contact with the ribbon 
itself when installing the ribbon. Basically this is accomplished in 
accordance with the invention by providing an assembly in which the band 
drive and the ribbon drive are mounted on a common support member which 
supports the band drive above a horizontal row of print hammers. The 
support for the band drive and the ribbon drive comprises a frame member 
with gap therebetween. The ribbon drive comprises spaced apart ribbon 
spool housings mounted on either side of the frame member at opposite ends 
of the type band. A ribbon guidance system comprises movable ribbon guide 
means mounted on one spool housing and a fixed guide means mounted on the 
frame member. Each ribbon guide means comprises a series of guide elements 
with guide surfaces arranged to maintain the ribbon aligned with the 
spools and parallel within the gap with the type band and row of print 
hammers. The guide means includes a transition guide element between the 
other guide elements so that the ribbon can move therebetween in such a 
way that the configuration of the ribbon is distortion free and compatible 
with stable ribbon tracking. 
It will be seen that the invention provides a ribbon drive assembly 
arrangement which is simple in construction and easy to use to assemble 
and remove ink ribbon from a printer apparatus. Other advantages will 
become apparent from the detailed description which follows.

DETAILED DESCRIPTION OF THE INVENTION 
As seen in FIG. 1, a printer apparatus comprises cabinet 10 within which is 
installed a print unit 11. The cabinet 10 has side walls 12 on which top 
door 13 and a pair of front doors 14 are hingedly attached. A pedestal 15 
on bottom wall 16 supports print unit 11 within the cabinet 10. When 
installed in cabinet 10, print unit 11 prints on paper fed from side to 
side so that stacks of folded paper (not shown) would rest on bottom wall 
16 on the right and left sides of pedestal 15. 
Print unit 11 includes a casing having a base 17 and cover 18 on which is 
mounted a hammer unit 19. Mounted on hammer unit 19 is band and ribbon 
drive assembly 20 which in accordance with this invention comprises frame 
member 20a on which is supported both the type band drive and ink ribbon 
drive system. As described in copending application Ser. No. 07/664,255 
filed Mar. 4, 1991, now U.S. Pat. No. 5,108,205 issued on Apr. 28, 1992, 
frame member 20a has pivot arms 20b and 20c pivotably mounted on hammer 
unit 19 so that an adjustable gap exists for the passage of the ink ribbon 
and paper to be printed on. The gap adjustment mechanism includes levers 
21 and 22 for rotating cam 23 as more fully described in said copending 
application. The paper feed mechanism comprises pin belt tractors 24 and 
25 which engage edge perforations in the paper and which are adjustably 
spaced along drive shaft 26 by dual coaxial rotatable lead screws 27 and 
28 operated by knob 29 as more fully described in copending application 
Ser. No. 7/662,863 filed on Mar. 1, 1991. The tractors 24 and 25 feed 
paper across the top of cover 18 and over the hammer unit so that the 
paper movement is from side to side through the print unit as previously 
mentioned. 
As best seen in FIG. 3, frame member 20a is a plate-like casting on which 
are mounted both the band drive and the ribbon drive. The band drive 
comprises endless type band 30 wrapped around a pair of drive pulleys 31 
and 32 mounted on one side 20d of frame member 20a and could include an 
electric motor (not shown) mounted on the other side of frame member 20a 
and connected to one of the drive pulleys for rotating type band 30 at 
constant speed. A shelf-like platen 33 between the pulleys 31 and 32 at 
the bottom edge of the casting 20a provides backup to the type band 30. 
Platen 33 has a surface which, when frame member 20a is mounted on cover 
18 of print unit 11, extends over a distance which is at least 
co-extensive with the row of print hammers 19. 
As seen in the various figures, the ribbon drive comprises ribbon spool 
housings 34 and 35 mounted on opposite sides of frame member 20a at 
opposite ends of the type band 30. This enables ribbon 14 to be fed 
lengthwise through the gap at an angle to the print line formed by the row 
of hammers and the single row of characters on band 30 so that 
substantially the entire width of the ribbon 14 is presented for printing. 
Ribbon spool housings 34 and 35 are also tilted at an angle away from the 
vertical plane of frame member 20a. The degree of tilt can vary depending 
on the amount of space available between the top of the print unit 11 and 
the cover of cabinet 10. Tilting also enhances positioning and directing 
of ribbon 14 toward the path of travel as will be more fully understood 
hereinafter. When print unit 11 is contained in cabinet 10 as previously 
described, spool housings 34 and 35 are the back and front ribbon housings 
respectively. Mounting spool housings 34 and 35 on frame member 20a makes 
them more accessible for installing and replacing ribbon 14 within the 
print unit 11. Located within the spool housings 34 and 35 are spools 36 
and 37 on which ink ribbon 14 is wound with a stretch of ribbon extending 
therebetween (see FIG. 7). Spools 36 and 37 are any well known type having 
flanges 36a and 37a with external gears 36b and 37b and stub shafts. 
Mounted on spool housing 35 is drive motor 38 having a pinion gear (not 
shown) which engages gear 37b on spool 37. Similarly, a drive motor (not 
shown) is mounted on ribbon spool housing 34 with the same gearing for 
engaging gear 36b on spool 36. 
As seen in FIGS. 8 and 10, back spool housing 34 comprises housing or 
receptacle member 34a and cover member 34b hingedly connected thereto so 
that ribbon housing 34 can be opened and closed. Housing member 34a has 
parallel sidewalls 34c and 34d with saddle bearings 34e and 34f in which 
stub shafts on spool 36 rest when spool 36 is installed between sidewalls 
34c and 34d. Pins 34g on sidewall 34c around opening 34h serve as the 
mount for a drive motor so that gearing on the motor shaft extending 
through opening 34h makes a drive connection with the gearing 36b on spool 
36 when spool 36 is placed in housing member 34a. Between sidewalls 34c 
and 34d is cross member 34i with bearing edge 34j which engages the bottom 
side of ribbon 14 where it exits from inside the spool housing 34. Bearing 
edge 34j is concave to center the ribbon relative to the spool 36. 
Cover member 34b comprises parallel side walls 34k and 341 and curved end 
wall 34m. The hinge connection for movement of cover member 34b between 
closed and open positions comprises hinge pins 34n on sidewalls 34k and 
341 of cover member 34b and hinge elements 34o and 34p on sidewalls 34k 
and 341. Cover member 34b is locked in closed position or unlocked by 
operating latch element 34q pivoted on the sidewalls of cover member 34b 
and which has hooks 34r which engage housing member 34a in closed 
position. When closed, bearing edges 34s and 34t on the sidewalls 34k and 
341 of cover member 34bx close the saddle bearings 34e and 34f so that 
spool gear 36b is brought into engagement with gearing on the drive motor 
shaft and the stub shafts on spool 36 are captured in place. 
In accordance with this invention, a movable ribbon guide is provided at 
one end of the type band 30 which, in the preferred embodiment, comprises 
a series of guide pins 39, 40 and 41 fixedly attached between external 
flanges 34u and 34v at the swing end of cover member 34b. Flanges 34u and 
34v form a ribbon channel in which the stretch of ribbon 14 proximate 
spool housing 34 is caught for engagement with and positioning by the 
guide pins 39-41 when cover member 34b is swung from open to closed 
position. Conversely, when cover member 34b is unlocked and swung open, 
the ribbon 14 in proximity with spool housing 34 is disengaged from guide 
pins 39-41 and removed from the ribbon channel formed by flanges 34u and 
34v on cover member 34b and is thereby removable without hindrance when 
spool 36 is removed from housing member 34a. Likewise, when cover member 
34b is opened, flanges 34u and 34v present no hindrance to the ribbon 14 
when spool 36 is to be installed into housing member 34a. 
As seen in the various figures, guide pins 39-41 have different angular 
orientations. Pin 39 is attached to flanges 34u and 34v so as to present a 
guide surface parallel with the axis of spool 36. This parallelism assures 
ribbon is properly aligned with the spool 36 in housing 34. Pin 39 is also 
located when cover 34b is closed so that it coacts with bearing edge 34j 
to engage opposite surfaces of ribbon 14 so that ribbon 14 moves through a 
bend which applies some amount of tautness to ribbon 14 as it leaves spool 
housing 34. Guide pin 40, mounted on the brackets 34u and 34v so that when 
cover member 34b is closed, pin 40 presents a guide surface that is normal 
to ribbon 14 and that is parallel with the surface of the row of hammers 
19 and the face of type band 30 and since ribbon 14 is slanted at an angle 
relative to the print line as previously described, guide pin 40 in being 
normal to ribbon 14 is also slanted a corresponding amount relative to the 
print line. Guide pin 41 serves as a transition pin for guiding the ribbon 
14 from the plane of pin 39 to the plane of pin 40 and is slanted in such 
a way that the ribbon 14 moves through the guide without wrinkling, 
folding or tearing at the edges. The proper orientation is determined by 
requiring that when the ribbon 14 is stretched over 39-41 with opposite 
forces perpendicular to pins 39 and 40 respectively, the resulting tension 
will not urge the ribbon to move up or down along the pins 39 or 40. 
The front spool housing 35 comprises housing or receptacle member 35a and 
cover member 35b hingedly connected thereto. Spool housing 35 is the same 
as back spool housing 34 in all respects except that cover member 35b has 
a bearing edge near the swing end which when closed coacts with a concave 
bearing edge of the housing member 35a to provide for reverse bending of 
the ribbon 14 as it leaves spool housing 35 and no ribbon guide is 
attached to cover member 35b. Instead a fixed ribbon guide is provided at 
the end of type band 30 for engaging ribbon 14 proximate spool housing 35. 
As best seen in FIG. 9, the fixed ribbon guide comprises pin like guide 
elements 42, 43 and 44 on a bracket 45 attached to the frame member 20a 
between the end of type band 30 and front spool housing 35. As in the case 
of the guide pin 39 of the movable ribbon guide means, guide element 42 is 
parallel with the axis of spool 37 to maintain ribbon 14 in proper 
alignment with spool 37. Guide element 43, like guide pin 40 has a surface 
normal to ribbon 14 and parallel with the surface of type band 30. Guide 
element 43 is also parallel with guide pin 40 when cover member 34b is 
closed. Guide element 44 like guide pin 41 is a transition pin and is 
slanted in the same manner as previously described for guide pin 41. 
Referring to FIG. 5, ribbon is installed in print unit 11 by opening cover 
member 34b on back spool housing 34 and cover member 35b on front cover 
member 35, and holding both spools 36 and 37 by their flanges, spool 36 is 
dropped into housing member 34a so that spool gear 36b engages the gearing 
on the drive motor and then cover member 34b is swung closed and locked. 
When closing, the ribbon guide, formed by flanges 34u and 34v, catches and 
and the guide pins 39-41 engage the top of the ribbon 14 as previously 
described and positions ribbon 14 at the proper level so as to be aligned 
with the gap at the back of frame member 20a. Holding the spool 37 by the 
flanges 37a, a stretch of ribbon 14 is drawn from spool 36 along the side 
of frame member 20a and, while holding the ribbon somewhat taut, ribbon 14 
is brought under, aligned with and wrapped around the guide elements 42-44 
of the fixed guide and spool 37 is dropped into the housing member 35a of 
front spool housing 35 on the other side of frame member 20a. Cover member 
35b is swung closed and locked to complete the installation process. For 
replacement, the process is reversed by removing spool 37 from housing 35 
and, after opening cover member 34b of back spool housing 34, removing 
spool 36 from housing member 34a. 
Thus it can be appreciated that the invention provides a ribbon drive 
system in which the ribbon is accurately guided along the print line and 
in which the ribbon and spools therefor can be easily and cleanly 
installed and removed from the ribbon drive system. While the invention 
has been described with reference to a single embodiment, it will readily 
occur to a person skilled in the art that various changes can be made for 
uses in the same or other embodiments and printer devices without 
departing from the scope of the invention as defined in the following 
claims.