U.S. patent number 3,670,861 [Application Number 05/071,051] was granted by the patent office on 1972-06-20 for carriage drive for high speed printer.
This patent grant is currently assigned to Extel Corporation. Invention is credited to Raymond E. Kranz, Walter J. Zenner.
United States Patent |
3,670,861 |
Zenner , et al. |
June 20, 1972 |
CARRIAGE DRIVE FOR HIGH SPEED PRINTER
Abstract
A carriage drive for a high speed dot matrix printer, including
a reversible stepping motor connected through a clutch to a rotary
driven member that is in turn connected by a belt to the printer
carriage. The clutch remains engaged as long as the motor operates
in a character-spacing direction, but reversal of the motor
disengages the clutch and permits a torsion spring to drive the
carriage back to a line start position. Near the end of the return
movement, a flywheel decelerator absorbs the kinetic energy of the
carriage and then utilizes that kinetic energy to prevent bouncing
of the carriage.
Inventors: |
Zenner; Walter J. (Des Plaines,
IL), Kranz; Raymond E. (Mt. Prospect, IL) |
Assignee: |
Extel Corporation (Chicago,
IL)
|
Family
ID: |
22098938 |
Appl.
No.: |
05/071,051 |
Filed: |
September 10, 1970 |
Current U.S.
Class: |
400/338.2;
192/41S; 400/903; 74/405; 400/320; 474/1 |
Current CPC
Class: |
B41J
19/02 (20130101); B41J 19/72 (20130101); Y10S
400/903 (20130101); Y10T 74/19614 (20150115) |
Current International
Class: |
B41J
19/68 (20060101); B41J 19/72 (20060101); B41J
19/02 (20060101); B41J 19/00 (20060101); B41j
019/02 () |
Field of
Search: |
;197/60,62,64,65,66,68,70,89,91,183,93,82 ;192/41S,.096
;74/220,405 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pulfrey; Robert E.
Assistant Examiner: Eickholt; Eugene H.
Claims
We claim
1. In a high speed printer of the kind comprising a carriage
movable in predetermined incremental steps along a given path in a
character spacing direction from an initial position toward a limit
position and movable along said path in a return direction back to
said initial position from any position on said path, a carriage
drive comprising:
a rotatable drive member;
reversible stepping drive means for rotating said drive member, in
incremental steps, in a normal direction and in a reverse
direction;
a rotatable driven member, operatively connected to said carriage,
for driving said carriage in said character spacing direction in
response to rotation of said driven member in a first
direction;
clutch means actuatable between an engaged condition and a
disengaged condition, coupling said drive member in operative
driving relation to said driven member to rotate said driven member
in said first direction in response to rotation of said drive
member in said normal direction when said clutch is engaged, said
clutch means being actuatable to its disengaged condition in
response to reverse rotation of said drive member;
and spring return means, connected to said carriage, for moving
said carriage in its return direction independently of said drive
means upon disengagement of said clutch means from said driven
member.
2. A carriage drive for a high speed printer, according to claim 1,
in which said clutch means comprises a rotatable idler member
mounted on a pivotally movable idler support, said idler support
being movable to an engaged position with the idler member coupling
the drive member in driving relation to the driven member in
response to normal rotation of the drive member, and said idler
support being movable to a disengaged position, in which said idler
member is free of at least one of said drive and driven members, in
response to reverse rotation of the drive member.
3. A carriage drive for a high speed printer according to claim 2,
in which the drive member, the idler member, and the driven member
are all gears, and in which said idler support comprises a support
lever having one end pivotally mounted in coaxial relation to said
drive member and connected thereto by a slip coupling that tightens
only when said drive member is rotated in its reverse direction,
said idler member being rotatably mounted upon the other end of
said support lever.
4. A carriage drive for a high speed printer according to claim 3,
and further comprising resilient biasing means connected to said
idler support for biasing said idler support toward a position in
which said idler gear is in meshing engagement with both said drive
gear and said driven gear.
5. A carriage drive for a high speed printer, according to claim 3,
in which said slip coupling comprises a spiral spring interposed
between nested concentric walls of said drive member and said idler
support lever and wound in a direction such that the spring
tightens upon reverse rotation of said motor to afford a firm
coupling between said concentric walls and assure movement of said
idler support lever to its disengaged position, and further
comprising biasing means normally urging said idler support lever
toward its engaged position.
6. A carriage drive for a high speed printer, according to claim 2,
and further comprising detent means for limiting reverse rotation
of said idler member to a given number of incremental steps
whenever said drive means is driven in its reverse direction, and
in which return of said idler support to its engaged position
requires a corresponding number of incremental steps of rotation of
said drive means in its normal direction.
7. A carriage drive for a high speed printer, according to claim 1,
in which said drive means comprises a subfractional horsepower
electrical stepping motor energized by an electrical stepping
signal including one cycle for each incremental step of advance
required of said carriage.
8. A carriage drive for a high speed printer, according to claim 1,
in which the operational connection between said driven member and
said carriage comprises a flexible, belt-like drive connector
member, and in which said spring return means comprises a torsion
spring operatively connected to said drive connector member.
9. A carriage drive for a high speed printer, according to claim 8,
in which said drive connector member is a toothed drive belt and in
which said torsion spring has one end connected to a pulley engaged
by said belt.
10. A carriage drive for a high speed printer, according to claim
2, and further comprising decelerator means, including an operating
member projecting into said carriage path, for engaging and braking
said carriage, as said carriage approaches its initial position,
and for using the kinetic energy of the returning carriage to hold
said carriage in its initial position, without substantial
bouncing, once that position is reached.
11. In a high speed printer of the kind comprising a carriage
movable along a given path in a character spacing direction from an
initial position toward a limit position and movable along said
path in a return direction back to said initial position from any
position on said path, a carriage drive comprising:
precision drive means, coupled to said carriage, for advancing said
carriage along said path in said character spacing direction;
spring return means, coupled to said carriage, for rapidly moving
said carriage in its return direction, independently of said drive
means, back to said initial position;
a fixed stop for said carriage, at said initial position;
and declerator means for engaging and braking said carriage, as
said carriage approaches its initial position, and for using the
kinetic energy of the returning carriage to hold said carriage in
its initial position, without substantial bouncing, once that
position is reached, said decelerator means comprising:
an operating lever extending into the path of said carriage at a
given position;
a flywheel;
and a two-way frictional coupling between said operating lever and
said flywheel, such that during its rapid return movement said
carriage engages said operating lever at said given position and
starts rotation of the flywheel to absorb part of the kinetic
energy of the carriage, and continuing rotation of the flywheel
causes said lever to press said carriage against said stop.
12. A carriage drive for a high speed printer, according to claim
11 in which said coupling between said operating lever and said
flywheel includes a drive gear element mounted on said lever, a
driven gear element mounted coaxially with said flywheel,
justaposed engaged friction members on said flywheel and said
driven gear element, and resilient biasing means maintaining said
friction members in engagement.
13. In a high speed printer of the kind comprising a carriage
movable along a given path in a character spacing direction from an
initial position toward a limit position and movable along said
path in a return direction back to said initial position from any
position on said path, a carriage drive comprising:
drive means, coupled to said carriage, for advancing said carriage
along said path in said character spacing direction;
spring return means, coupled to said carriage, for rapidly moving
said carriage in its return direction, independently of said drive
means, back to said initial position;
a low-inertia carriage-engaging means comprising an operating
member projecting into position to be engaged by said carriage on
its return movement;
a high-inertia acceleration-resisting means comprising a
flywheel;
a two-way friction coupling between said carriage-engaging means
and said acceleration resisting means;
and a fixed stop for interrupting return movement of said carriage
at said initial position,
said carriage-engaging means, said acceleration-resisting means and
said friction coupling conjointly comprising a free-moving
high-inertia decelerator system which intercepts and decelerates
said carriage as it approaches its initial position during return
movement, limiting the decelerating force applied to the carriage
to a predetermined maximum and converting a major portion of the
kinetic energy of the moving carriage into heat,
said friction coupling maintaining said operating lever in
engagement with said stop, in response to continuing rotation of
said flywheel, to prevent bouncing of the carriage.
14. A carriage drive for a high speed printer, according to claim
13, in which said drive means comprises a stepper motor, a drive
linkage connecting said stepper motor to said carriage, and a
clutch, interposed in said drive linkage, for releasing said
carriage for return movement in response to said spring means.
Description
BACKGROUND OF THE INVENTION
In a wide variety of different kinds of high speed printers, a
carriage is moved in incremental steps along a given path in the
course of the printing operation. In some typewriters, in
conventional telegraphic printers, and in many other printing
machines the increments of advance are usually equal to one
character width. In other machines, and particularly in some forms
of dot matrix printers, the incremental carriage movements are much
smaller. For example, in a dot matrix printer the carriage may
advance eight distinct steps in the formation of each character,
five steps for the formation of five individual columns of dots
that form a character and three additional steps to afford a blank
space between that character and the next character in the
line.
In any of these printing machines, the overall speed and efficiency
of the printer is dependent to a considerable extent on a rapid
return of the carriage from the end of one line to the starting
point for beginning the next line. During the carriage return
operation, it is usually necessary to advance a sheet of paper or a
paper web by one line space in the printing machine. Except for the
time required for a line space operation, however, the entire
carriage return interval is completely wasted.
In some high speed printers, spring return mechanisms have been
used to return the carriage rapidly from the end of one line to the
beginning of the next line. These spring devices can be constructed
to afford a high speed carriage return movement, materially
reducing the wasted time. But a spring return for the carriage
frequently creates other problems. In particular, when the carriage
reaches the end of its return movement, travelling at a high speed,
it tends to bounce; if bouncing occurs, it is necessary to wait an
additional period of time until it is suppressed or to accept
printing irregularities at the beginning of each line. Another
difficulty results from the need to release the carriage from its
normal driving connection to the motor or other drive apparatus
that advances the carriage incrementally from the beginning of the
line, in order to allow operation of the return spring. In general,
it is rather difficult to adapt conventional clutches or like
mechanisms to afford adequately rapid release of the carriage while
retaining the capability of restoring the normal incremental drive
connection to the carriage as soon as it reaches the beginning line
position.
SUMMARY OF THE INVENTION
It is a principal object of the present invention, therefore, to
provide a new and improved carriage drive for a high speed printer,
and particularly a carriage drive of the kind that utilizes a
spring mechanism to achieve rapid return movement of the printer
carriage from any intermediate position on a line back to an
initial position to start a new line.
A particular object of the invention is to provide a new and
improved carriage drive for a high speed printer, especially
adapted for use in a dot matrix printer, that affords accurate,
consistent, and rapid movement of the carriage in extremely short
increments, with several increments to each character width.
Another specific object of the invention is to provide a new and
improved decelerator for the carriage of a high speed printer that
effectively minimizes any bounce of the carriage as the carriage
reaches its initial position, upon return from an advanced
position.
Accordingly, the invention is directed to a carriage drive for a
high speed printer of the kind comprising a carriage movable in
predetermined incremental steps along a given path in a
character-spacing direction from an initial position toward a limit
position and movable back along that path to its initial position
from any position on the path. The carriage drive comprises a
rotatable drive member and reversible drive means, preferably a
reversible electrical stepping motor, for rotating the drive member
in incremental steps in either a normal direction or a reverse
direction. A rotatable driven member is operatively connected to
the carriage of the printer and is employed to drive the carriage
in its character-spacing direction when the driven member is
rotated in a first direction. The carriage drive includes clutch
means for coupling the drive member to the driven member to rotate
the driven member in the aforementioned first direction in response
to rotation of the drive member in its normal direction; the clutch
means, however, is actuatable to a disengaged position whenever the
drive member is rotated in its reverse direction. Spring return
means are provided for moving the carriage in its return direction,
independently of the drive means, whenever the clutch is
disengaged. A carriage decelerator is provided for engaging and
braking the carriage, as the carriage approaches its initial
position. The decelerator also uses the kinetic energy of the
returning carriage to hold the carriage in its initial position,
without bouncing, once that position is reached.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a high speed printer in which the
carriage drive of the invention may be employed;
FIG. 2 is a front perspective view of a high speed printer
incorporating the carriage drive of the present invention, with the
cover and some other parts of the printer stripped away;
FIG. 3 is a rear perspective view of the printer of FIG. 2;
FIG. 4 is a cut away plan view of the printer, with most of the
platen and carriage omitted;
FIG. 5 is a sectional side elevation view taken approximately as
indicated by line 5--5 in FIG. 2;
FIG. 6 is a detail sectional view of a declerator incorporated in
the carriage drive;
FIG. 7 is a detail sectional view of a clutch and certain sensing
switches included in the carriage drive;
FIG. 8 is a sectional side elevation, partially cut away, taken
approximately along line 8--8 in FIG. 3;
FIG. 9 is a detail, from FIG. 8, showing an alternate operating
condition;
FIG. 10 is a detail plan view, partly in cross section;
FIG. 11 is a detail sectional view taken approximately along line
11--11 in FIG. 10;
FIG. 12 is a detail view of a part of the apparatus that has been
cut away in FIG. 8;
FIG. 13 is a front perspective view of a high speed printer
incorporating another embodiment of the carriage drive of the
present invention; and
FIG. 14 is a side elevation view of the printer of FIG. 13.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 through 12 illustrate a high speed printer 20, comprising a
dot matrix printer, that incorporates a carriage drive constructed
in accordance with a preferred embodiment of the present invention.
Printer 20 comprises a base 21; two vertical side plates 23 and 24
are mounted upon base 21 at the left- and right-hand sides,
respectively, of the printer. The spacing between the upper parts
of side plates 23 and 24 is effectively maintained by a series of
tie rods that span the distance between the side plates. These
include a rear tie rod 25, an upper tie rod 26, and a lower tie rod
27, joining plates 23 and 24 and base 21 in a rigid frame.
A platen shaft 28 extends across the upper central portion of
printer 20; shaft 28 is journalled in bearings mounted in the two
side plates 23 and 24. Shaft 28 carries a hollow platen 29,
described more fully hereinafter. Platen 29 is accessible through
an opening 30 that extends across the top of the metal cover 31 for
printer 20 (FIG. 1). A sheet of paper 32, which may be a part of a
continuous web drawn from a roll 33, extends into the housing 31,
around the platen 29, and back out as shown in FIGS. 1 and 5. A
separate sheet of paper can be used if desired.
Since printer 20 is a dot matrix printer, it is essential that the
paper 32 be held tightly against platen 29 at the point of printing
impact within the machine, in order to avoid perforation of the
paper. This is accomplished in part by a wire bail 34 that extends
across the entire width of platen 29. The opposite ends of bail 34
are pivotally mounted to the frame of the printer. The right hand
end of bail 34, as seen in FIGS. 2 and 10, is pivotally mounted in
side plate 24, whereas the opposite end of the bail is pivotally
mounted in a bracket 35 that is affixed to side plate 23. At the
end of the bail adjacent plate 24, a lug 36 is mounted on the bail;
lug 36 is connected to a spring 37, the other end of the spring
being connected to a post 38 mounted upon side plate 24. At the
other end of bail 34, a lug 39 is mounted on the bail and is
connected to a spring 41 having its opposite end connected to a
projecting post 42 on bracket 35. Springs 37 and 41 normally
maintain bail 34 in firm contact with platen 29, as shown
particularly in FIGS. 2, 10 and 12. However, the bail can be
pivoted away from the platen to a second stable position, shown by
dash outline 34A in FIGS. 5 and 12, to facilitate renewal of the
paper supply for the printer.
Printer 20 also includes a pressure roll assembly 44 that is best
illustrated in FIGS. 4 and 5. The pressure roll assembly comprises
a pressure roll support lever 45 that is pivotally mounted at a
central point upon the rear tie rod 25. One end of lever 45
projects down beneath platen 29. It terminates in a U-shaped
bracket 46 in which a pressure roll 47 is mounted. At the opposite
end of lever 45, a spring 48 is connected to the lever, the other
end of spring 48 being connected to base 21. It is thus seen that
spring 48 continuously maintains roller 47 in firm contact with
paper 32, pressing the paper against platen 29 (FIG. 5).
A paper guide 51 is also mounted upon tie rod 25 (FIGS. 4 and 5).
Guide 51 affords a sloped guide surface 52 that guides the paper
web 32 into contact with platen 29 (FIG. 5). The paper guide 51
terminates at a lip 53 (FIGS. 4 and 5) that extends across the
entire width of the platen. A spring 54 connects guide 51 to the
pressure roll support lever 45 so that both members can be
displaced from platen 29 simultaneously if this is necessary or
desirable to facilitate clearance of a paper jam or for maintenance
activities.
At the front of the high speed printer 20, as shown in FIGS. 2, 4
and 5, two carriage guide rails 56 and 57 extend across the printer
from side plate 23 to side plate 24; the two guide rails are
located on opposite sides of the lower tie rod 27. A print carriage
60 is mounted upon guide rails 56 and 57 and moves longitudinally
of the guide rails, from left to right as seen in FIG. 2, in
printing each line.
As shown in FIG. 5, carriage 60 includes a vertically extending
print magnet support member 61 from which two cantilever upper
carriage support rollers 62 project. Each of the carriage support
rollers 62 includes a pair of spaced flanges 63 that engage the
upper surface of carriage guide rail 56 to maintain carriage 60 in
accurate alignment on the guide rails, preventing shifting of the
carriage in a direction along the axes of carriage support rollers
62. The free end of each of the support rollers 62 is of circular
cross sectional configuration and merely rests upon the other
carriage guide rail 57. Each of the two upper support rollers 62 is
preferably formed of molded plastic and is rotatably supported upon
a metal cantilever shaft 64 that is mounted upon support member
61.
At the lower end of support member 61, two shafts 65 are mounted
upon the carriage, projecting from support member 61 beneath guide
rail 56. On each of the shafts 65 there is a roller 66 that engages
the lower surface of guide rail 56 (FIG. 5). In addition, each
shaft 65 is provided with an extension 67 that carries a second
roller 68 which engages the bottom surface of guide rail 57. The
rollers 66 and 68 are each vertically aligned with one of the upper
support rollers 62, maintaining carriage 60 in fixed accurate
alignment with respect to the guide rails 56 and 57 throughout the
movement of the carriage along the path defined by the guide
rails.
The particular dot matrix utilizes in printer 20, in the
reproduction of alphabetic and numeric characters, is a 5 .times. 7
matrix, seven dots high and five dots wide. A full column of seven
dots is reproduced in one operation, requiring seven individual dot
printing devices in vertical alignment. Two of these dot printing
devices are illustrated in FIG. 5. The upper dot printing device
shown therein comprises a print magnet 71 mounted upon the curved
outer surface 72 of support member 61; magnet 71 projects through
an opening 70 in support member 61, the opening 72 being shown in
FIG. 2. An elongated, stiff needle-like print wire 73 projects from
print magnet 72 through a print wire guide 74, terminating at a
point immediately adjacent the surface of platen 29. Guide 74 is
mounted upon a bracket 75 that is supported upon a pair of
cantilever print guides 76 mounted upon carriage support member 61.
The lower-most printing device, also illustrated in FIG. 5,
comprises a similar print magnet 77 mounted upon the arcuate outer
surface 72 of support member 61. Print magnet 77 actuates an
elongated needle-like print wire 78 which, like needle 73, projects
from the print magnet through the needle guide 74 and terminates at
a point immediately adjacent the surface of platen 29. The
remaining five printing devices have been omitted from the drawing;
the apertures for mounting the remaining printing devices on
support member 61 are shown in FIG. 2.
There is a projection 81 extending inwardly from the lower end of
support member 61 (FIG. 5). An actuator member 82 is mounted upon
projection 81 and extends downwardly from carriage 60. Actuator 82
is utilized to actuate a series of control switches, as described
hereinafter, and is also employed as a connecting member in the
carriage decelerator that is a part of the present invention, as
described hereinafter.
At the left-hand side of printer 20, as seen in FIGS. 2 and 4, an
adjustable stop 83 is mounted upon side plate 23. Stop 83 is a
cantilever device that projects from side member 23 toward the
carriage, terminating in a replaceable cushion member 84 formed of
rubber or other like resilient material.
The carriage drive of the present invention, in printing machine
20, comprises a reversible electric stepping motor 86 mounted upon
a pair of vertical posts 87 as shown particularly in FIGS. 3, 4 and
5. The shaft 88 of motor 86 extends in a vertical direction, and
the lower end of the shaft is journalled in a bearing 89 mounted
upon base 21 (FIG. 5). The lower end of shaft 88 carries a pulley
91 that engages a toothed drive belt 92 of the kind commonly
referred to as a timing belt. Belt 92, at its other end, engages a
rotatable drive pulley 93 that is mounted upon a short vertical
shaft 94 as shown in FIGS. 4, 5 and 7. An idler support lever 95 is
also pivotally mounted upon shaft 94. Lever 95 and pulley 93 are
formed with complementary spaced parallel walls and a helical
spring 96 is mounted in the space between members 93 and 95, as
best shown in the sectional views of FIGS. 5 and 7. One arm 98 of
the idler support lever 95 includes a downwardly extending shaft
portion 99 upon which an idler gear 101 is mounted by means of a
retainer 102 (FIG. 7). The idler support lever 95 is also connected
to a spring 104 that is anchored to side plate 24. A detent spring
103, mounted on base 21, projects into alignment with idler gear
101, but does not normally engage the idler.
Spring 104 normally biases the idler support member 95 in a
clockwise direction, maintaining idler 101 in meshing engagement
with a driven gear 105 mounted upon a vertically extending shaft
106. Idler 101 is always in mesh with a pinion gear 107 that is
formed as an integral part of the rotatable drive pulley 93. Thus,
idler 101 normally affords a positive driving connection between
the rotatable drive member 93 and the rotatable driven member 105;
however, this drive connection can be interrupted quite easily and
quickly by rotation of the idler support lever 95 as described more
fully hereinafter.
The driven gear 105 is affixed to an elongated sleeve 108 that is
mounted upon shaft 106 by appropriate bearings, preferably ball
bearings as illustrated in FIG. 5. The upper end of sleeve 108
includes a pulley section 109 that engages a carriage driven belt
110. The carriage drive belt 110 is preferably a toothed flexible
drive belt of the kind generally referred to as a timing belt. One
end of the carriage drive belt 110 is fastened to the right-hand
side of the print carriage 60. The other end of the carriage drive
belt extends around a pulley 111 and is secured to the left-hand
side of carriage 60, as shown particularly in FIGS. 2 and 4.
Pulley 111 is mounted upon a vertical shaft 112 and is part of an
elongated sleeve 113 substantially similar in construction to the
sleeve 108. A torsion spring 114 is affixed to one end of sleeve
113, and the other end of torsion spring 114 is secured to base 21.
The orientation of torsion spring 114 is such that, as carriage 60
moves from left to right in the printing of a line, the torsion
spring is wound tighter and tighter. Torsion spring 114 comprises a
spring return means for moving carriage 60 back to its initial
position, in engagement with stop 83, to begin each new line of
printing.
As carriage 60 moves from left to right across printer 20, along
the path defined by guide rails 56 and 57, actuator 82 serves to
indicate arrival of the carriage at certain critical positions. At
the right-hand end of printer 20, a sensing switch element 116
projects upwardly through base 21 in position to engage actuator 82
(see FIGS. 4 and 7). Sensing switch element 116 defines the
right-hand limit of travel for carriage 60. To the left of sensing
switch element 116, there is another sensing switch element 117
that also projects upwardly through base 21 in position to engage
actuator 82 on carriage 60. Sensing switch element 117 is located
at an arbitrarily defined position from which the carriage should
be returned to the initial position at stop 83 once the printing of
a word is completed. In one form of printer 20, using a 48
character line, sensing switch element 117 has been located to
identify the completion of the printing of a total of 40
characters. Another sensing switch element 118 projects upwardly
through base 21 at the left-hand end of the path of movement of
carriage 60. Sensing switch element 118, shown in FIGS. 4 and 6, is
engaged by actuator 82 to signal the completion of a carriage
return movement, being engaged by actuator 82 when the carriage has
been returned to its initial position in engagement with stop
83.
The line space mechanism for printer 20 is best illustrated in
FIGS. 8-11, although parts of this mechanism also appear in other
views. The line space mechanism comprises a solenoid 121 having an
armature 122 upon which a U-shaped plunger 123 is mounted. A shaft
124 extends beyond plunger 123 and is engaged in a guide 125 in a
fixed guide bracket 126. The U-shaped bracket 123 engages the lower
end 128 of an operating lever 129 that is pivotally mounted on a
short shaft 131 supported upon side plate 23. The lower end 128 of
operating lever 129 carries a pin 132 to which a spring 133 is
connected; the other end of spring 133 is connected to a post 134
mounted upon side plate 23 (FIGS. 8 and 9).
The upper end of operating lever 129 is bifurcated and engages a
pin 135 on a rocker arm 136. Rocker arm 136 includes an extension
137 that carries a pin 138. A pawl 139 is pivotally mounted upon
pin 138. A helical biasing spring 141 is mounted upon an extension
of pin 138; one end of the spring is affixed to the pin and the
other end is engaged in an extension 142 of pawl 139. A fixed upper
stop 152 and a fixed lower stop 153 are mounted on side plate 23,
extending outwardly from the side plate above and below the
pawl.
Rocker arm 136 is rotatably mounted upon the end of platen shaft 28
adjacent side plate 23. It is positioned immediately adjacent a
detent wheel 143 that is affixed to the platen shaft 28. A press
fit, supplemented with adhesive, may be employed. The detent wheel
143 is provided with a series of teeth 144 positioned in alignment
with and engaged by pawl 139. The teeth 144 on detent wheel 143 are
also engaged by a detent roller 146 mounted upon a lever 147 that
is pivotally mounted upon a shaft 148 affixed to side plate 23.
Detent roller 146 is maintained in engagement with detent wheel 143
by a spring 149 having one end connected to the bottom of lever 147
and the opposite end connected to a post 151 mounted upon side
plate 24 (FIGS. 3 and 8).
The carriage drive of the present invention includes a decelerator
system 160, best illustrated in FIGS. 3-6. Decelerator 160
comprises a low-inertia carriage-engaging means including an
operating lever 161 that is pivotally mounted on a post 162 affixed
to base 21. The end of lever 161 that projects toward the front of
the printing machine 20 is bifurcated to afford a sensing element
162A and a restraining element 163; the sensing element 162A is
normally disposed in the path of the actuator 82 of the printing
machine carriage as shown in FIG. 4. Operating lever 161 is
normally maintained in the position illustrated in FIG. 4 by a
biasing spring 164.
The operating lever 161 of decelerator 160 includes an arm 165 that
terminates in a gear segment 166. Gear segment 166 is disposed in
meshing engagement with a driven gear 167, FIG. 4, that is a part
of a high-inertia acceleration-resisting means for controlling
carriage deceleration. As shown in FIG. 6, gear 167 is mounted upon
a post 169 that is affixed to and projects vertically upwardly from
base 21. A relatively large and heavy flywheel 171 is rotatably
mounted upon the central portion of gear 167. A pair of felt
washers 172 and 173 are disposed upon the top and bottom surfaces,
respectively, of flywheel 171 and are keyed to gear 167. The felt
washers 172 and 173 are engaged by two mounting washers 174 and
175, respectively. The entire assembly is maintained in good
frictional contact by a spring washer 176, interposed between
washer 174 and an additional washer 177; a pair of retainer rings
178 complete the high-inertia acceleration-resisting assembly.
In considering the operation of printing machine 20, and
particularly the carriage drive of the printing machine which
constitutes the subject matter of the present invention, the best
starting point is at the beginning of a line, with the carriage 60
displaced to the extreme left-hand end of its path in contact with
the rubber bumper 84 on the adjustable stop 83 (FIG. 4). With the
carriage in this position, actuator 82 is in engagement with the
left-hand limit switch 118. This is the initial position for the
imprinting of each line of characters by the printer.
To start printing, motor 86 is energized to rotate shaft 88 in a
clockwise direction, as viewed in FIG. 4, driving belt 92 in the
direction indicated by the arrows. This is the normal direction of
rotation for motor 86 and the normal direction of movement for belt
92 for printing operations. Motor 86 is a stepper motor and moves
in predetermined incremental steps, so that the movement of its
shaft 88, belt 92, and the remainder of the carriage drive always
occurs in closely controlled incremental steps as the carriage
performs its character spacing movements along guides 56 and
57.
The normal movement of belt 92, as indicated by the arrows, causes
the rotatable drive member comprising pulley 93 and gear 107 to
rotate in a clockwise direction. Accordingly, idler 101 is driven
in a counterclockwise direction, and the idler drives gear 105 in a
clockwise direction. Thus, belt 110 is driven in a character
spacing direction, as indicated by the arrows in FIGS. 2 and 4, in
response to the clockwise rotation of the driven member 105 in the
drive system that connects motor 86 to carriage drive belt 110.
As long as appropriate energizing signals are received by motor 86,
and until it is necessary to return the carriage to its initial
position to begin a new line, the drive system steps carriage 60
along platen 29, from left to right, as described above. In a
typical 5 .times. 7 dot matrix printer, five character-space steps
are used for the actual imprinting of each alphabetic, numeric, or
other character. Usually, energizing signals are supplied to motor
86 in groups of eight, with the additional three increments being
utilized for spacing between adjacent characters. When a space
between words is required, motor 86 is stepped for the same number
of increments, or any desired number of increments, without the
application of energizing signals to any of the printing devices on
carriage 60.
Printer 20 may be required to reproduce continuous copy that does
not include appropriately timed carriage return signals. This mode
of operation is facilitated by the provision of sensing switch 117,
which is located a selected number of character spaces from the
absolute end of line sensing switch 116 (FIG. 4). When switch 117
is contacted by the actuator 82 on carriage 60, the sensing switch
operates a control circuit (not shown) for printer 20 that
initiates a carriage return operation upon the next occurrence of a
space signal in the telegraphic signal input to the printer. As
noted above, switch 117 may be located about eight characters to
the left of the sensing switch 116. Switch 116, on the other hand,
is utilized to initiate a carriage return operation instantly upon
contact by actuator 82 to prevent loss of copy that could result if
carriage 60 were retained at the far right.
In the formation of each character, the individual print wires
(e.g., print wires 73, 78, FIG. 5) print a number of dots upon the
paper 32 that extends around platen 29. The printing operation goes
forward at a high rate of speed; in a typical commercial printer,
the printing rate is approximately 600 characters per minute.
When a carriage return is triggered, whether by a received
telegraphic signal or by the operation of either of the switches
116 and 117, the direction of rotation of motor 86 is reversed. As
a consequence, drive belt 92 is driven in a direction opposite to
the arrows (FIG. 4) and pulley 93 starts to rotate in a
counterclockwise direction. Counterclockwise rotation of pulley 93
causes spring 96 to tighten and grip the walls of both of the
members 93 and 95 (FIGS. 5 and 6). As a consequence, the idler
support lever 95 begins to pivot in a counterclockwise direction to
move idler 101 out of engagement with the driven gear 105 (FIG. 4).
In a predetermined number of incremental steps of motor 86, in its
reverse direction, idler 101 is moved to its alternate position
101A, completely free of gear 105 and in engagement with detent
spring 103. It is thus seen that the idler support member 95, idler
gear 101, and spring 96 constitute a clutch means that couples
drive member 107 to driven member 105 to rotate the driven member
105 in a first clockwise direction in response to rotation of the
drive member 93, 107 in its normal direction; however, this same
clutch means is automatically and promptly actuated to a disengaged
condition in response to reverse rotation of the drive member 107.
In one commercial machine, disengagement of the clutch is effected
in four cycles of operation of stepper motor 86.
As soon as the clutch mechanism comprising idler 101 is disengaged,
carriage 60 is free to move in response to the biasing force
supplied by the torsion spring 114. Spring 114 has been tightened
with each increment of movement of carriage 60 during the printing
of a line; if the carriage has been moved to near the right-hand
end of its path, as shown in FIG. 2, torsion spring 114 is tightly
wound and exerts a considerable force upon belt 110. As a
consequence of disengagement of the clutch idler gear 101, carriage
60 is rapidly accelerated in a return direction, back toward its
initial position in engagement with stop 83.
As carriage 60 moves in its reverse direction toward stop 83, the
actuator 82 on the carriage contacts the sensing extension 162A of
the operating lever 161 for decelerator 160. The continuing
movement of the carriage rotates operating lever 161 in a clockwise
direction and imparts a similar rotation to the gear segment 166.
This rotates gear 167 in a counterclockwise direction, as viewed in
FIG. 4.
If the carriage return operation has been initiated with the
carriage only a short distance along the line, as occurs when only
a short line is printed, torsion spring 114 is wound up to only a
limited extent and exerts a relatively small force on belt 110.
Under these circumstances, carriage 60 moves relatively slowly in
the return direction and actuator 82 is moving quite slowly when it
engages the sensing extension 162A of operating lever 161. The slow
movement of lever 161 and its gear segment 166 results in a
relatively slow movement of gear 167. The slow movement of gear 167
offers little resistance to the movement of actuator 82 because the
acceleration is minimal. Carriage 60 contacts the resilient pad 84
on stop 83 at a slow speed, with little tendency toward
bouncing.
On the other hand, when a long line of characters has been
imprinted and carriage 60 starts its return movement from at or
near the right-hand end of its travel, the torsion spring 114 has
been wound much more tightly and applies a much greater force to
the carriage. Moreover, under these circumstances there is a
greater distance for carriage 60 to gain speed. Consequently,
actuator 82 strikes sensing extension 162A on operating lever 161
at a high speed, so that gear 167 is accelerated rapidly. When this
occurs, the force required to impart a corresponding acceleration
to flywheel 171 is greater than the frictional coupling between
gear 167 and flywheel 171. Slipping occurs at the faces of felt
washers 172 and 173; this frictional brake absorbs nearly all of
the kinetic energy of the carriage. When the carriage has been
slowed down to a speed matching that of the high-inertia flywheel
171, slipping stops and the braking action terminates. Carriage 60
moves freely but slowly back to its initial position.
The continued return movement of carriage 60 brings it into
engagement with the resilient pad 84 on stop member 83. Because the
carriage is still moving at a low speed when it reaches stop 83,
the carriage may bounce unless restrained. However, the restraining
extension 163 on operating lever 161 has now been pulled in behind
actuator 82, due to the clockwise movement of lever 161 caused by
the return movement of the carriage (FIG. 4). When carriage 60
starts to bounce, therefore, it immediately encounters lever
extension 163 and starts to pivot lever 161 in counterclockwise
direction. This bouncing movement is prevented by the continuing
rotational movement of flywheel 171, which continuously urges lever
163 toward further clockwise rotation. As a consequence, the
remaining kinetic energy of carriage 60 is absorbed as a friction
loss at the surfaces bounded by the felt washers 172 and 173 (FIG.
6) and the carriage is arrested at its initial position without
appreciable bouncing.
When the clutch mechanism comprising idler 101 has been disengaged,
and rotation of the idler has been arrested by detent 103, as
described above, the clutch remains disengaged until motor 86 is
again reversed and resumes rotation in its normal direction. This
is accomplished by an electrical signal initiated when actuator 82
contacts the left-hand limit switch 118, indicating that the
carriage has again reaches its initial position at the left-hand
end of a line. The total minimum time interval required for
carriage return and re-engagement of the clutch comprising idler
101 is the time needed for twice the number of incremental steps
utilized for disengaging the clutch. Thus, if the clutch is
disengaged in response to four steps of reverse movement of motor
86, it is re-engaged by four steps of movement in the normal
direction, restoring the printer to condition for further operation
in the time required for imprinting a single character. The actual
elapsed time may be somewhat longer, depending upon the speed of
carriage return and the time required to complete the second
reversal of motor 86.
During the carriage return operation, a line space operation is
necessary to advance a fresh segment of the paper web 32 into
position to receive the next line of printing. In other instances,
a separate line space signal may be utilized to initiate a line
space operation, as when a blank portion of the paper is to be
advanced through the printer to begin a new message.
At the start of a line space operation, the line space mechanism is
in the position illustrated in FIG. 8. The line space operation is
initiated by energizing solenoid 121, pulling its armature 122
inwardly of the solenoid from the position shown in FIG. 8 to that
illustrated in FIG. 9. This movement of armature 122 causes the
U-shaped portion 123 of the solenoid plunger to pull the lower
portion 128 and the line space lever 129 to the left, pivoting
lever 129 in a clockwise direction about its shaft 131. This drives
pin 135 to the right, from the position of FIG. 8 to that of FIG. 9
and rotates rocker arm 136 through a limited arc in a
counterclockwise direction.
As rocker arm 136 rotates counterclockwise, the engagement of pawl
139 with one of the detent teeth 144 drives detent wheel 143
counterclockwise. The counterclockwise motion of detent wheel 143
is arrested when pawl 139 engages the upper stop 152. During the
rotation of detent wheel 143, the detent roller 146 is driven
outwardly against the bias of spring 149 and then moves back
inwardly into engagement with the space between the next pair of
teeth 144. Thus, the paper advancing movement is completed, with
the mechanism in the position shown in FIG. 9.
When the line space operation is complete, solenoid 121 is
de-energized. Spring 133 then pulls the lower portion 128 of
operating lever 129 back to the right, as seen in FIGS. 8 and 9.
This results in a counterclockwise rotation of lever 129 back
through a limited arc from the position shown in FIG. 9 to that
illustrated in FIG. 8. The rotation of lever 129 drives pin 135
back to its original position and rotates rocker arm 136 clockwise
from the position of FIG. 9 to that of FIG. 8. In the course of
this movement, pawl 139 rides over one of the detent teeth 144 and,
as it clears that tooth, the pawl is snapped back into engagement
with the next tooth in response to the bias afforded by spring 141.
During this restoration movement, detent roller 146 prevents
rotation of detent wheel 143, since the sliding movement of pawl
139 on the detent wheel does not exert enough force to overcome the
bias applied to roller 146 by spring 149. Accordingly, the detent
wheel 143 and platen 29 remain in the advanced position with a line
space movement completed.
The carriage drive incorporated in printer 20 affords a number of
advantages in operation of the printer. The clutch mechanism
comprising idler gear 101 and its pivotal support 95 disengages
rapidly in response to a reversal of rotation of stepper motor 86,
initiating the carriage return operation promptly upon the
occurrence of conditions requiring a carriage return without
requiring a separate motor, solenoid, or other actuator.
Disengagement of the clutch does not result in a loss of control or
timing for the carriage drive, since the clutch is disengaged in a
fixed number of steps of motor 86 and re-engagement of the clutch
is effected in a corresponding discrete number of motor steps.
Thus, the carriage return operation is completed with the high
speed printer fully conditioned for immediate operation in printing
the next character.
Torsion spring 114 affords a rapid carriage return operation with a
minimum space requirement for the torsion spring. In cooperation
with the clutch mechanism of idler gear 101, the torsion spring
facilitates a rapid carriage return operation with minimum loss of
time.
Declerator 160 also contributes materially to the advantages of the
carriage drive in high speed printer 20. On a rapid carriage
return, originating at the far end of the path of carriage travel,
the kinetic energy of the carriage is principally dissipated as
frictional heat and a small part is converted into rotational
energy of flywheel 171; that rotational energy is utilized directly
to maintain carriage 60 in contact with stop 83 once the carriage
reaches the stop. In this manner, the carriage energy is
effectively dissipated or usefully employed to prevent carriage
bounce. The decelerator 160, by minimizing bouncing and vibration,
inherently reduces the wear and tear on printer 20 from the
carriage return operation and quickly stabilizes the carriage at
its initial position at the start of each line, maintaining an even
left-hand margin in the reproduced copy. Thus, the decelerator
contributes materially to a rapid, controlled, well-timed
turnaround at the end of the carriage return movement.
Stepper motor 86, as a basic drive element for the carriage drive,
contributes to the accurate and consistent advance of carriage 60
along its operating path. The stepper motor, energized with
discrete pulses that correspond to the required carriage movements,
in combination with timing belt drives and a gear train, so that
there are no friction drive components, makes it possible to
maintain complete control over the carriage movement at all
times.
FIGS. 13 and 14 illustrate a high speed printer 220 that is
generally similar in construction, in many respects, to printer 20,
and that incorporates a carriage drive constructed in accordance
with another embodiment of the present invention. Printer 220
comprises a base 221, with two vertical side plates 223 and 224
mounted on the base. A platen shaft 228 spans the two side plates
and supports a platen 229 therebetween. A bail 234 is normally
maintained in engagement with platen 229 and holds a sheet of paper
(not shown) in printing position on the platen. The printer may
include a paper guide, as described in relation to printer 20.
A pair of carriage guide rails 256 and 257 extend across the frame
of printer 220, between side plates 223 and 224, parallel to platen
229. A printing carriage 260 is mounted upon rails 256 and 257.
Carriage 260 is constructed like carriage 60 of the previous
embodiment and is utilized to support a total of seven dot printing
devices, as generally indicated by the magnetic wire printer
devices 271 and 277. In printing a single line of characters,
carriage 260 starts at the left-hand end of guide rails 256 and
257, in contact with a stop member 283, and moves to the right in a
series of incremental steps. When a given line is completed, the
carriage is returned to its initial position against the stop 283
to begin the next line.
The carriage drive for high speed printer 220 comprises a motor 286
that is mounted upon side plate 224. Motor 286 is an electrical
stepper motor. The motor is mounted horizontally, with its shaft
288 projecting outwardly of side plate 224 as shown in FIG. 14.
Motor shaft 288 carries a pinion 291 that is disposed in meshing
engagement with a drive gear 292. Drive gear 292 is mounted upon a
shaft 293 that is in turn mounted to side plate 224. Drive gear 292
is also in mesh with an idler gear 301. Idler gear 301 is rotatably
mounted upon a shaft 299 that is mounted upon an idler support
member comprising a lever 295. The idler support lever 295 is
pivotally mounted upon a shaft 296 affixed to side plate 224. A
bias spring 304 is connected to the idler support member 295 and
biases member 295 toward rotation in a clockwise direction, and
toward engagement with an adjustable eccentric stop 298. Idler gear
301 is disposed in meshing engagement with a line feed gear 331
that is mounted upon the right-hand end of platen shaft 228. Gear
331 is engaged by a detent spring 303, mounted upon side plate 224,
that prevents counterclockwise rotation of gear 331 while
permitting clockwise rotation.
Idler gear 301 is also disposed in alignment with a driven member
comprising a carriage space gear 305. Gear 305 is mounted upon a
shaft 332 supported upon side plate 224; a pulley 333 is affixed to
gear 305. Pulley 333 is engaged by a drive string 310. From pulley
333, one end of the drive string 310 extends around a pulley 334
mounted on side plate 224; from pulley 334, drive string 310
extends to a pulley 311 that is mounted concentrically with and is
connected to a torsion spring 314. From pulley 311, drive string
310 is extended to and is connected to the left-hand side of the
printer carriage 2160 (FIG. 13).
As shown in FIG. 14, the other end of drive string 310 extends from
pulley 333 around two additional pulleys 335 and 336 that are
mounted upon side plate 224. Drive string 310 continues from pulley
336 to the right-hand end of carriage 260 (FIG. 13).
At the other end of platen shaft 228 from gear 331, a detent wheel
343 is affixed to the shaft (FIG. 13). A detent lever 347 is
pivotally mounted upon side plate 223, adjacent detent wheel 343. A
detent roller (not shown) is mounted upon lever 347 and is
maintained in engagement with detent wheel 343 by an appropriate
spring 349, as in the previous embodiment.
When the high speed printer 220 of FIGS. 13 and 14 is placed in
operation, character space movement of carriage 260, from left to
right along the path defined by the guide rails 256 and 257, is
effected by clockwise rotation of the stepper motor shaft 288.
Rotation of shaft 288 in a clockwise direction causes pinion 291 to
turn drive gear 292 in a counterclockwise direction. The
counterclockwise rotation of drive gear 292 in turn rotates idler
301 in a clockwise direction.
The idler 301 attempts to turn the line space gear 331 in a
counterclockwise direction. However, counterclockwise rotation of
gear 331 is blocked by the spring detent 303. Consequently, idler
gear 301 is driven, by reaction against gear 331 and against the
bias of spring 304, into engagement with the carriage space gear
305. Gear 305 is rotated in a counterclockwise direction and drives
the drive string 310 in the direction indicated by the arrows in
both FIGS. 13 and 14. In this manner, the carriage 260 is stepped
rapidly and repeatedly along the guide rails 256 and 257, printing
a line in the manner described above in connection with printer
20.
As in the previous embodiment, a carriage return operation is
initiated in printer 220 by reversing the direction of rotation of
the drive motor. Thus, to initiate a carriage return, motor 286 is
reversed and its shaft 288 is rotated in a counterclockwise
direction. This turns drive gear 292 clockwise and rotates idler
301 counterclockwise. Line feed gear 331 can rotate in a clockwise
direction and hence is no longer blocked by detent 303.
Accordingly, idler 301 is pulled clear of carriage space gear 305
by spring 304 and rotates the line feed gear 331 in a clockwise
direction to afford a line feed operation for the paper in the
printing machine.
From the foregoing description, it will be seen that the embodiment
of FIGS. 13 and 14 functions in a manner essentially similar to the
embodiment of FIGS. 1-12 except that in the high speed printer 220
of FIGS. 13 and 14 the line feed operation for the paper, as well
as the carriage return operation, is carried out directly in
response to reverse rotation of the carriage drive motor. Thus, the
solenoid 121 is not necessary in the embodiment of FIGS. 13 and
14.
* * * * *