Printing media roll mounting and positioning mechanism

A printing media roll mounting mechanism including a frame defining a roll compartment for accommodating a printing media roll. First and second roll holders are mounted in the compartment in axial alignment substantially perpendicular to the web path for concurrent oppositely directed linear movement. The first and second roll holders are spring urged toward one another but can be moved apart to receive different width media rolls therebetween. When the first roll holder is moved outwardly, e.g., to the right, against the spring urging, the second roll holder will also move outwardly to the left. The two roll holders are spring urged toward each other to respectively engage opposite ends of a media roll core placed therebetween.

This application claims the benefit of U.S. Provisional application No. 
60/005,813 filed Oct. 23, 1995. 
FIELD OF THE INVENTION 
This invention relates generally to mechanisms useful in computer driven 
printers for mounting a printing media roll in a position to supply web 
material to be printed upon along a path to a printing station. 
Computer driven thermal printers are widely used in diverse applications 
for printing receipts, labels, etc. Such printers typically use a printing 
media roll comprised of a web of printing media wound on an internal 
tubular core. The printing media can, for example, comprise plain thermal 
paper or linerless adhesive backed label paper. It is generally desirable 
that the printer accommodate a variety of rolls of different widths and 
that a user be able to readily replace a roll. 
SUMMARY OF THE INVENTION 
The present invention is directed to a mounting mechanism useful in a 
computer driven printer for accommodating media rolls of different widths 
and for automatically positioning each such roll relative to the center 
line of a defined web path. 
Apparatus in accordance with the invention includes a frame defining a roll 
compartment for accommodating a printing media roll. First and second roll 
holders are mounted in the compartment in axial alignment substantially 
perpendicular to the web path for concurrent oppositely directed linear 
movement. The first and second roll holders are spring urged toward one 
another but can be moved apart to receive different width media rolls 
therebetween. In accordance with the invention, when the first roll holder 
is moved outwardly, e.g., to the right, against the spring urging, the 
second roll holder will also move outwardly to the left. The two roll 
holders are spring urged toward each other to respectively engage opposite 
ends of a media roll core placed therebetween. 
In accordance with a preferred embodiment of the invention, the first and 
second roll holders are respectively mounted on first and second elongate 
racks, each mounted for reciprocal linear movement parallel to the axis of 
a media roll accommodated in the roll compartment. The racks are 
respectively engaged with a common pinion mounted for rotation around a 
fixed spindle. Rotation of the pinion in a first direction, e.g., 
clockwise, moves both racks inwardly. Rotation of the pinion in the 
opposite direction, e.g., counterclockwise, moves the racks outwardly. A 
spring coupled between at least one of the racks and the frame biases the 
racks inwardly against the ends of the roll core. 
In accordance with the preferred embodiment, each roll holder defines a 
contact face for engaging one end of the roll core. Each contact face is 
preferably conically shaped so that it can extend into and support 
different diameter roll cores. 
The novel features of the invention are set forth with particularity in the 
appended claims. The invention will be best understood from the following 
description when read in conjunction with the accompanying drawings.

DETAILED DESCRIPTION 
Attention is now directed to FIGS. 1 and 2 which depict a computer driven 
printer 10 in accordance with the invention incorporating a mechanism 12 
for mounting and positioning a printing media roll (not shown). More 
particularly, the printer 10 is comprised of a frame 16 defining an 
internal roll compartment 18 for accommodating a variety of differently 
dimensioned standard printing media rolls. Such rolls are typically 
comprised of a web of printing media, e.g., plain thermal paper or 
linerless adhesive back thermal paper. These are commercially available in 
different widths and lengths and typically have internal tubular cores 
which may have different inner diameters. Apparatus in accordance with the 
present invention is intended for accommodating a variety of differently 
dimensioned rolls. 
The printer 10 is depicted as including a print head 20 mounted opposite to 
a drive roller/platen 22. Printing media is fed from a roll (not shown) in 
the compartment 18 along a path extending between print head 20 and platen 
22 which together define a printing station. The drive roller/platen 22 is 
driven by a motor 24 via gearing 26. 
Attention is now directed to FIG. 3 which better illustrates the roll 
mounting and positioning mechanism in accordance with the present 
invention. FIG. 3 shows frame 16 which includes roll compartment 18 
defined essentially between front wall 30, rear wall 32, first and second 
end walls 34, 36 and floor 38. First and second roll holders 40, 42 are 
mounted in the compartment 18 for reciprocal linear movement along paths 
respectively defined by elongate slots 44, 48 defined in floor 38. 
As can best be seen in FIG. 5, each roll holder is essentially comprised of 
a post portion 50 and a cylindrical head portion 52. The cylindrical 
portion 52 defines an essentially conically shaped roll contact face 56 
formed by stepped axially spaced concentric portions 58, 60, etc. (FIG. 6) 
configured to accommodate the inner diameters of differently dimensioned 
tubular cores. The cylindrical head 52 further defines an axially oriented 
rectangular bore 62 dimensioned to accommodate spaced spring legs 64 of an 
insert 66 (FIG. 6). The insert 66 includes a flange 68 and a forwardly 
projecting tapered button 70. When the legs 64 of insert 66 are 
accommodated in the rectangular bore 62, the flange 68 and button 70 
cooperate with the aforementioned concentric step portions 58, 60 to 
extend the truncated conical form defined by steps 58 and 60 by an 
additional step portion 71. 
Each of the roll holders preferably also includes a finger tab 72 extending 
radially from the cylindrical head 52 in a direction opposite to post 50. 
Roll holders 40 and 42 are respectively mounted on the ends of elongate 
racks 76, 78 extending through floor slots 44, 48. Note in FIG. 5 that 
each rack includes a mounting stud 80 which extends into a pocket 82 
formed in the roll holder post 50 for orienting and retaining the roll 
holder. 
The elongate rack 76 defines a series of teeth 86 which engage with teeth 
88 circumferentially formed on pinion 90 mounted for rotation on spindle 
91 (FIG. 4). Similarly, rack 78 defines a series of teeth 92 which engage 
the pinion teeth 88 at a location essentially diametrically displaced from 
rack 76. Racks 76 and 78 are mounted for parallel reciprocal linear 
movement in opposite directions. That is, when rack 76 of FIG. 5 moves to 
the left, i.e., roll holder 40 moves inwardly, it will turn pinion 90 in a 
clockwise direction which in turn moves rack 78 to the right, thus also 
moving roll holder 42 inwardly, that is toward roll holder 40. 
On the other hand, when an axial force is exerted on one of the roll 
holders to move it outwardly, the other roll holder will correspondingly 
move outwardly. Thus, when rack 76 of FIG. 5 moves to the right, pinion 90 
will turn counter clockwise to move rack 78 to the left, thus moving roll 
holders 40 and 42 apart. 
In accordance with the present invention, a spring 96 is provided to bias 
the roll holders 40 and 42 toward one another to the position depicted in 
FIG. 5. More particularly, note that one end 97 of coil spring 96 is 
looped through hole 98 in tab 100 extending outwardly from rack 86. The 
other end 102 of spring 96 is looped through hole 104 in frame 16 (FIG. 
4). Thus, spring 96 is biased to pull rack 76 to close the gap between 
roll holders 40 and 42. When a user desires to place a printing media roll 
between the contact faces 56 of the roll holders, he need merely push one 
of the roll holders axially. Because of their coupling through common 
pinion 90, the roll holders will concurrently linearly move away from the 
center of pinion 90. Thus, the media roll will always be positioned 
centrally with respect to the axis of pinion 90 regardless of the width of 
the media roll being used. 
From the foregoing, it should be recognized that a mechanism has been 
disclosed herein for easily mounting media rolls of different sizes within 
a roll compartment of a computer driven printer. A wide range of roll 
sizes can be accommodated and each roll will be centered with respect to 
the axis of pinion 90 in the disclosed embodiment. The spring bias acting 
on racks 76 and 78 urges the contact faces 56 of roll holders 40 and 42 
toward each other to accommodate the narrowest rolls when inserts 66 are 
used. However, by pushing one of the roll holders outwardly, the roll 
holders will move away from each other to enable them to accommodate 
increasingly larger width rolls therebetween. The conical faces of the 
roll holders are configured to extend into the ends of the roll core with 
the core being able to rotate on the steps 58, 60. Inserts 66 can be 
removed to maximize the spacing between contact faces 66. 
Although one specific embodiment of the invention has been described, it is 
recognized that variations and modifications within the spirit and scope 
of the invention will readily occur to those skilled in the art. For 
example only, the spring can be configured in various ways to bias the 
roll holders toward one another.