Note: Descriptions are shown in the official language in which they were submitted.
7~
1 -
PRINTHEAD SUITABLE FOR USE IN APPARATUS FOR PRINTING AND
APPLYING PRE5SURE SENSITIVE LABELS
BACKGROUND OF THE INVENTION
This invention relates to print heads such as are
used in labellers for printing and applying pressure sen-
sitive labels carried on a release liner of supporting
material.
Such labellers are used, ~or example, in grocery
stores or the like where labels printed with pricing
information and the like are applied to various objects.
It is an object of this invention to provide a
print head of the type having a plurality of print bands
movable by setting wheels supported on a tubular shaft
wherein a selector is axially shiftable within the tubular
shaft to select a particular print band for movement there-
of and which includes improvements in the tubular shaft
and its coaction with the other components of the print
head.
i Accordingly, the invention provides a print head
including a plurality of print bands, a drive gear in driv-
ing engagement with each respective print band, each drive
gear having a hole, the holes being generally aligned to
provide an opening having a predetermined axis, a selec-
tively shiftable and rotatable selector movable into the
opening, said selector including at least one rack extend-
ing in the axial direction of the selector, detenting means
disposed within said opening for detenting said rack so
that the selector is releasably held in a shifted position
corresponding to a selected one of said drive gears, driv-
ing means connected to said selector for driviny saidselected one drive gear to thereby set the print band cor-
responding to said selected drive gear to a predetermined
position, and a tubular shaft extending through said hole
and having a longitudinally extending slot therein, said
selector shaft extending into said tubular shaft, said
driving means comprising a lug disposed on the selector
-- 2 --
shaft and extending through said slot, and ~aid detenting
means comprising resilient finger means supported at one
end by the shaft and extending in the axial direction of
the shaft into detenting engagement with the rack.
According to another feature of the invention, the
shaft includes a first portion of a predetermined diameter
where a slot extends through said first portion and a sec-
ond portion disposed adjacent said first portion; and the
internal diameter of said second portion of the tubular
shaft is sufficiently greater than that of the first por-
tion thereof that, during assembly of the print head, the
driving member of the selector shaft can be readily in-
serted through the second portion and then into the slot
of the first portion to thereby facilitate said assembly.
Other objects and advantages of this invention will
be apparent from a reading of the following specification
and claims taken with the accompany drawings, in which:
Figure 1 is an exploded perspective view of an
illustrative labeller in accordance with the invention
without the print head.
-- 3 --
Figure 2 is a side elevation view of the lhbeller of
Fiqure 1 including the print head with the left side plate
removed.
Figure 3 i6 a side elevation view of the brake mechan-
ism of Figure 1 which illustrates the manual release fea-
ture thereof.
Figure 4 is a side elevation view of the ink roller
mechanism of Figure 1 which illustrates the i~k roll remov-
al and replacement feature thereof.
Figure 5 is an exploded perspective view of an illus-
trative embodiment of a print head in accordance with th
invention.
Figure 6 is a side elevation view of the print head of
Figure 5.
Figure 7 is a front elevation view of the print head
of Figure 6 illustrating the attachment thereof to the
labeller.
Figure 8 is a cross-sectional view along the line 8-8
of Figure 6 illustrating the hexagonal lower drive gears
for the head print bands.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Reference should be made to the drawing where like
reference numerals refer to like parts.
Referring to Figures 1 and 2, the hand labeller of this
invention comprises a casing including a right side plate 10
thereof and a left side plate 12 between which are mounted
the component parts of the labeller. Both side plates in-
clude rearwardly extending handle portions 14 and 16 and
tubular projections 18, 20, 22 and 24 where the projections
18-24 of side plate 10 are internally threaded to receive
screws 26-32 to thereby effect engagement of the side plates.
A label stock holder 34 is provided for mounting a roll
of label stock 35 which typically comprises a plurality of
sequentially disposed, pressure sensitive labels adhesively
adhered to a release liner as is known in ~his art. The
label stock is directed from the holder through an upper
47;2~
chute 59 to an anvil 52 where the labels are ~equentially
printed with each actuation o a hand lever 54 which iB
pivotally mounted with xespect to the casing. Attached to
the forward end of the hand lever i~ a print head 62 (see
Figures 2 and 6) which reciprocates within front and rear
print head frames 67 and 69. The print head include~ a
plurality of movable print elements ~3 which are inked ~y
an ink roller mechanism 65. When hand lever 54 is sgueezed
counterclockwise, the print head is brought into contact
with a label positioned on anvil 52 to effect printing thereof.
Forward edge 68 of anvil 52 cons~itutes a peel edge at
which p~int the labels are ~uccessively peeled from the re-
lease liner. The peeled labels may then be dispensed by an
applicator roller 70 to an object to indicate, for ex~mple,
the price ther~of~ The release liner reverses its direction
a~ peel edge 68 and passes under anvil 52 to a feed wheel 72
via ~n idle roller 74. The release liner passes over the
feed wheel and is then fed from the casing out of a rearward
opening 76 in a lower chute 78 having a release liner tear
edge 80.
As stated ~bove, printing of the labels occurs each time
hand lever 54 is sgueezed. Incremental advancement of the
label stock through the tool occurs each time the hand lever
is released~ A compression spring 82 disposed on mounts 84
and 86 extending between the hand lever 54 ~nd handle por-
tions 14 and 16 returns the lever to its rest position shown
in solid lines in Figure 2 where an abutment surface 88 of
the lever engage~ a rear surface 90 of the casing. During
the return movement of the lever, a pawl 92 pivotally con-
nected to the hand lever engages a circular ratchet g4 onfeed wheel 72 to clockwise advance the feed wheel a predeter-
mined distance corresponding to the length of one label.
Thus, after each label is printed, it is advanced to applica-
tor roller 70 where the rear edge of the label re~; n~ ad-
hered to the release liner until it is applied to the ob ject .The next label to be printed is positi~ned over anvil 52 and
726
aligned with the print head 62. To maintain this aliynment
during dispensing of the printed label by applicator 70, a
brake 96 is provided which includes a pointed edge 98 (see
Figure 2) which engages the label stock during dispensing
thereof.
Having generally described the component parts of the
labeller and the relationship thereof with respect to the
incrementally advanced label stock, the component parts will
now be described in more detail.
Label Stock Advancement Mechanism
Label stock holder 34 includes an opening 36 in the
forward end thereof for pivotally mounting the holder around
tubular projections 20 and a spool 38 for mounting the roll
in an opening 39 extending through the holder. Recessed
portions 40 are provided at the rearward end of the holder
which engage lugs 42 formed in side plates 10 and 12 when
holder 34 is lowered into its operative position. The re-
cesses 40 expand slightly in engaging ~he lugs 42 to effect
a releasably secure engagement of the holder with respect to
the casing. Holder 34 also includes knobs 44 which hold
holder 34 in its raised, loading position, the knobs 44 rest-
ing against the upper surfaces of side plates 10 and 12. As
can be seen in Figure 1, the side plates have cut-out por-
tions 46 and 48 which constitute an opening through which
holder 34 can be raised and lowered. ~en lowering the hol-
der into the casing, the sides thereof are inwardly depressed
to permit knob 44 to pass through the opening.
As stated above, the label stock is incrementally ad--
vanced a distance corresponding to the length of one label
each time the hand lever 54 is returned to its rest position
by spring 82~ ~and lever 54 includes a grip portion 100
and a forwardly extending portion 102 which includes side
plates 58 and 60. Openings 56 in these side plates permit
pivotal mounting of the hand lever on tubular projections 22.
Pawl 92 is provided with a lug 104 which is rotatably mounted
26
in an opening 106 in side plate 58. As can be seen in
Figure 2, the pawl includes a resilient finger 108 which
engages the underside of a lug 110 provided on the in~ide
surface of ~ide plate 58. A lug 112 provided on the pawl
and a ~econd lug 114 provided on the inside surface of plate
58 a~sist in maintaining the pawl in place with re6pect to
side plate 58. The pawl al~o includes a downwardly extend-
ing finger 116 which normally engages, due to the bias of
resilient finger 108, one of the teeth of circular ratchet
94 which is preferably integrally connected to feed wheel 72
Thus, when hand lever 54 is squeezed to its raised pvsition,
finger 116 is lowered to its dotted line position 116' shown
in Figure 2. When the hand le~er i5 released to its solid
line position, the finger engages the next tooth of the rat-
chet to incrementally advance the feed wheel as the fingerreturns to its solid line position. The feed wheel is pro-
vided with a plurality of circumferentially dispose~ lugs 118
which pierce prefabricated cuts in the release liner to ef-
fect advancement thereof, the feed wheel being rotatably
mou~ted on a tubular projection 11~ on side plate 10 which
engages a corresponding tubular projection, not shown, on
side plate 12.
As the label ~tock is drawn from roll 35, it is first
directed through upper chute 50 which includes an upper plate
120 and a lower plate 122. The width of the upper plate 120
approximately corresponds to the inside distance between
plates 58 and 60 of hand lever 54. The lower plate 122 in-
cludes a recessed portion 124 which is mounted upon tubular
projection 22 to thus assist in the mounting of the chute
within the labeller. ~n opening 126 at the bottom of the
chute, where plates 120 and 122 are relatively close to one
another is provided through which label stock is advanced and
directed toward anvil 52.
After leaving opening 126 the label stock is directed on-
to an upper surface 128 of lower chute 78. Lower chute 78 in-
cludes a pair of fingers 130 which engage recesses 132 pxovid-
ed at the forward edge of anvil 52 whereby a substantially
726
- 7 --
continuous c~nnection is provided between surface 128 and
the upper surface of the anvil to thereby provide a smooth
path for the label stock to the anvil. After the release
liner reverses its direction at peel edge 68, it passes
beneath idle roller 74 which is rotatably mounted inside
bearings 134 provided on side plates 10 and 12. The pre-
fabricated cuts in the release liner are then engaged by
lugs 118 of feed wheel 72, the liner passin~ be~ween the
lower surface of chute 78 and the outer circumference of
the feed wheel. Chute 78 is provided with a relief portion
136 so that lugs 118 may pass therethrough, inasmuch as the
clearance between the outer circumference of the feed wheel
and the upper inside surface of chute 78 is preferably quite
small such as 0.020 inches~ for example. At the rearward
end thereof, chute 78 includes a peel finger 138 which peels
the release liner from the feed wheel and directs it out
opening 76 of the chute. Excessive release liner extending
out of the casi~g may be removed at teax edge ~0, also formed
at the rearward portion of the chute. ~ower chute 78, in
addition to being mounted with respect to anvil 52 by fingers
130, is also mounted between side plates 10 and 12 via pro-
jections 140 and 142 which non-rotatably engage lug~ 144 and
146 respectively in the side plates. Surface 128 of chute 78
is also provided with an opening 148 through which extends a
projection 150 of upper chute 50 to thereby further facili-
tate the mounting of the upper chute within the labeller.
Applicator 70 includes an applicator roll 188 which is
rotatably mounted on a pin 190 which extends between the for-
ward portions 192 of front print head frame 67 as shown in
Figure 2. The applicator is thus so positioned with respect
to the peel edge 68 of anvil 52 that the peeled labels pro-
ject under roll 188 preparatory to dispensing thereo0 As
is known in this art, dispensing of the labels occurs when
the operator rolls roll 188 across an object whereby the
peeled label is separated at its rear edge from the release
liner and applied to the object.
7,.>6
BRAKE MEC~NISM
As stated above, brake 96 holds the label ~tock in
place during application of a label by applicator 70 to
thereby facilitate alignment of the labels with respect to
print head 62. The brake comprises first and second side
plates 152 and 154, the side plates having openings 156 ex-
tending therethrough so that the brake is rotatably mounted
on the outer surface of bearings 134 independently of idle
roller 74 which is mounted on the interior surface of th~se
bearings as stated above. The distance between side plates
152 and 154 approximately correspo~ds to the distance between
side plates 58 and 60 of hand lever 54. Extending forwardly
and downwardly from the side plates is the brake portion 158.
As shown in Figure 2, pointed edge 98 extends downwardly from
brake portion 158 and normally holds the labels against the
rear portion of anvil 52 due to the bias exerted by a spring
160. The spring i5 connected between a pawl 16~ which ex
tends from side plate 154 of the brake and a lug 164 dis-
posed on the upper, rear surface of lower chut~ 78.
In accordance with one aspect of the invention, pawl
162 is provided with a latching portion 166 which engages
ratchet 168 pr~ferably integrally connected to the rear side
of feed wheel 72. The brake pawl with its latching portion
performs two functions, the first of which is to prevent back
up of feed wheel 72 as feed pawl 92 is lowered from its solid
line to its dotted line position shown in Figure 2. That is,
since the pawl 92 is biased against the feed wheel by resili-
ent finger 108, there might be a tendency for the pawl to
back up the feed wheel as it is lowered. However, since pawl
162 and its associated latching portion 166 act as an anti-
back up device, this is prevented. A further function of pawl
162 is that of removing the brake from the label stock to
thereby permit advancement thereof. Thus, as the feed wheel
is advanced by pawl 92, one of the teeth of ratchet 168 will
depress pawl 162 to its dotted line position 162' shown in
~igure 2 whereby the brake will be clockwise rotated away
Z6
g
from label stock.
In accordance with another aspect of the ir~vention, in
order to ensurP removal of the brake prior to incremental
advancement thereof by the feed wheel, the brake i~ provided
with an upwardly extending projection 170 which include~
forwardly extending portion 171. When hand lever 54 is in
its solid line position as shown in Figure 2, pro jection 170
engages at its upper extremity a bar 172 which extends be-
tween the side plates 58 and 60. When the hand lever is
squee~ed, the bar 172 rides along portion 171 and assumes
the position 172 I shown in Figure 2 to thereby rot~te the
brake clockwise away from the label stock. Thus, the brake
is removed as the hand lever is squeezed. Since incremental
advancemen~ of the label stock occurs during the return of
the hand lever to its rest position, the brake is removed
well before advancement occurs. As the lever is returned to
its rest position, the brake removal effected by the inter-
action of projec~ion 170 and bar 172 begins to terminate.
However, by this time the brake removal effected by the in-
teraction of ratchet 168 with the latching portion 166 of
pawl 162 bPcomes effective to maintain removal of the brake
from the label stoc~. After the label stDck has been incre-
mentally advanced, pawl 162 i~ returned to i~s solid line
position shown in Figure 2. The brake is now effective to
maintain the label stock in place as a label is applied with
applicator 70O
When label stock is initially loaded into the lab~ller
by threading the label stock through its intended path of
travel, brake 96 must be raised from anvil 52 in order to
facilitate khreading of the label stock over ~he anvil. Thus,
in accordance with a further aspect of the invention, brake
96 is provided with a projection 174 which horizontally ex-
tends from side plate 154 through an opening 176 in casing
side plate 10 as indicated in Figures 2 and 3. The brake is
also provided with a curved resilient arm 17B which extends
upwardly from ~ide plate 154 and which is spring loaded against
726
-- 10 --
a notch 180 formed in a rib 182 of side plate 10. Re~ilient
arm 178 includes a latch portion 184. Al~o provided ~n side
plate 60 of hand lever 54 is a downwardly extending projec-
tion 186 which is aligned with resilient arm 178 to facili-
tate engagement therewith.
In normal operation, the brake is in the solid lineposition shown in Figure 3 except when temporarily raised
from anvil 52 to permit incremental advancement of the label
~tock as described above. In order to latch the brake above
the anvil to provide clearance for loading label stock, the
the operator manually pushes extension 174 to the dotted
line position 174'. Due to the resilience of arm 178, latch
portion 184 will spring into the dotted line po~ition shown
in Figure 3 behind body rib 182 whereby the brake edge 9 8 is
raised to and latched in its dotted line position with rPs-
pect to anvil 52. The brake will remain in this latched
position until the first squeeze of hand lever 54. At this
time, the protrusion 186 on hand lever side plate bO will be
moved downwardly until it engages arm 178 to thereby release
the arm from the latch. Spring 160 will ~hen counterclockwise
rotate brake 96 to its solid line position so that the brake
now engages the loaded label stock.
INK ROLLER MæCHANISM
As shown in Figures 1, 2 and 4, ink roller 65 includes
an ink roll 194 which is rotatably mounted on a shaft 196,
~he shaft being journaled in openings in a pair of end caps
198. A carrier 202 for ~he ink roller 194 includes side
plates 204 and 206 which are recessed at the lower ends
thereof at 208 and 210. End caps 198 are provided with
tubular projections 212 which are inserted into the recesses
208 and 210 to therehy mount ink roller 194 in carrier 202.
In order to releasably latch the ink roller into the carrier,
a latch 214 is provided which is mounted with respect to bars
216 and 218 extending between si~e plates 204 and 206.
4~2~i
At the upper end of side plates 204 and 206 are open-
ings 200 which are respectively rotatably mounted on bear-
ings 220 and 222 on front and rear print head frames 67
and 69. A semicircular ~upport 224 extends between the
upper ends of side plates 204 and 206 and downwardly depend
ing therefrom is a resilient finger 226 which is loaded
against the side plate 10 as shown in Figure 4 sc that the
ink roller follows ~he movement of print head 62. When ~he
print head is in its raised position, ~he ink roller con-
tacts the type elements 63 as shown in Figure 2. As the
print head is lowered toward anvil 52, the ink roller car-
rier 202 swings out of the print head path of movement to-
ward side plate 10. As it does, ink roll 194 ink5 ~he type
elements. It is then returned to its Figure 2 position by
resilient finger 226 when the print head is once again
raised.
In accordance with another aspect of the invention,
ink roll 194 may be readily replaced without tools. Accord-
ingly, an opening 228 is provided in casing side plate 10
through which the ink roll may be removed from recesses 20 8
and 210 and replaced. In particular, latch 214 includes
side plates 230 and 232 and an upper plate 234 which con-
nects the side plates. A projection 236 extends downwardly
from the rear edge of upper plate 234 so that rec~sses 238
are formed in the side plates. Thus, as shown in Figure 4,
latch 214 is slideably mounted on bar 218, the bar being
disposed within the recessed portions 238.
In order to slideably position latch 214 in either its
ink roller latching position shown in solid lines in Figure
4 or in its ink roller removal position shown in do~ted
lines, a detenting ~urface 240 is provided on the lower,
inner surface of downwardly extending projection 236. This
detenting surface may comprise a plurality of rounded protru-
sions. Also provided on ~he lower inner ~urface of bar 218
is a rece~ed portion 242 (also see Figure 1) in which ~he
- 12 -
detenting ~urace 240 rest6 when the latch i~ i~ it~ ~olid
line, ink roller latching position. In order to remove
the latch from the ink roller, the operator places his
finger underneath upper plate 234 and pushes the latch up-
wardly to its dotted line position. Provided on the outer,lower edge of downwardly extending projection 236 i6 a stop
244 which may comprise a series of pointed projections as
shown in Figure 1. These projections engage the l~wer edge
of bar 216 while the detenting members 240 rest on the up-
per edge of bar 218 when the latch is in its dotted line,ink roller ~emoval position. As can be saen, the lower
edge of the latch is above recesses 208 and 210 ~o that the
ink roller may be shaken out through opening 228 and re-
placed. Due to the soft, resilient, plastic material com-
prising latch 214, the latch may then be sn~pped down tolock the ink roller in position. As can be appreciated, no
tool~ are required.
PRINT HEAD AND SUPPORT THEREFOR
Referring to Figures 1, 2 and 6, the support for print
head 62 comprises front and rear print head frames 67 and
69. Front frame 67 includes anvil 52 with its peel edge 68.
Mount~d on the lower forward portion of frame b7 is applica-
tor roller 70, there being an opening 24B between peel edge
68 and roller 70 whereby the peeled labels pass from the
upper surface of anvil 52 beneath roll 188.
Also disposed at the forward end of frame 67 is an up-
wardly extending plate 250 to which is integrally connected
rearward facing raceways 252 and 254. Disposed within these
raceways are ball retainers 256 and 258 respectively. Each of
the retainers incorporates a plurality of rotatably mounted
balls 260 in a known manner. The retainers 256 and 258 are
held in the raceways by fingers 262. Stop surfaces 264 are
provided at the upper and lower ends of the raceways to res-
trict vertical movemen of the retainers within the raceways.
A similar ball retain~r 266 is mounted in a centrally disposed,
forward facing raceway 268 in rear frame 69.
'726
~ 13 -
Plate 250 of front frame 67 i~ al~o provided with a
pair of upper and lower recesses 270 at each ~ide thereof,
these recessed portions being mounted on lUg6 272 extend-
ing from the side plates 10 and 12. Rear print head frame
69 is similarly mounted in that a pair of upper and lower
recesses 274 are provided at each side thereof, the
recessed portions being moun~ed on lugs 27S on side plates
10 and 12. In order to facilitate connection of hand lever
54 to print head 62, a pair of rectangular openings 278
extend through rear frame 69. Through these openings, the
respective forward portions of side plates 58 and 60
ex~end as indicated in Figure 2. Mounted at these forward
portions are lugs 64 and 66 which are adapted to engage
the print head.
Referring to Figures 5 and 6, print head 62 includes
front and rear head cove~ 280 and 282. As can be seen in
Figure 5, the rear head cover includes a centrally dis-
posed, rearward facing raceway 284, there being two simi-
lar, forward facing raceways ~not shown) disposed at the
outer edges 4f front head cover 280. The balls 260 of
retainers 256, 258 and 266 engage these raceways to permit
reciprocal vertical movement of the print head between the
front and re~r frames 67 and 69. Rear head cover 282 in-
cludes a pair of side plates2B6 having notches 290. As
can best be seen in Figures 5 and 7, ~he lower portions of
side plates 286 are inwardly tapered at 292 to thereby
facilitate engagement of print head 62 wi~h ~he forward
portion of hand lever 54. In particular, in accordance
with a further aspect of the invention, an opening 291 is
formed in the upper surface of the casing by cut~out
portions 294 and 296 in side plates
- 14 -
10 and 12. In fabricating a labeller, a selected one of a
plurality of different kinds of print heads may be inserted
through opening 291 and then connected to hand lever 54.
As a print head is lowered through opening 291, the tapered
surfaces 292 of rear head cover 282 engage and spread apart
lugs 64 and 66 of the hand lever as indicated in Figure 7.
As the print head is pushed further into the casing, the
spread apart lugs 62 and 64 shown in dotted lines will slide
along the outer surfaces of side plates 286 until they en-
counter notches 290 at which time, they will snap into the
notches to thereby establish a secure, essentially perma-
nent connection between the hand lever and print head. The
side plates 58 and 60 of the hand lever are preferably made
of a relatively soft, resilient, plas~ic material to facili-
tate the spreading thereof as the print head is insertedin~o the labeller.
The foregoing feature of the invention is advantage-
ous in that a print head need not be incorporated into the
labeller until, for example, an order is placed for a label-
ler having a particular kind of print head. Thus, theremay be kept in inventory print heads capable of printing
either 5, 6 or 8 digits of information per line where one
or more lines may be printed. If a customer orders 6 digit,
one line labellers, the appropriate print heads may then be
incorporated in the labeller in the manner described above
to fill the order. In this manner, it can be seen the num-
ber of labeller bodies required for dif~erent customers'
needs can be m;n;m; zed while at the same time a capability
is provided of immediately satisfying a wide range of cus-
tomer requirements.
Front head cover 280 includes an expandable fastener
298 which engages forked pro~ections 300 on rear cover 282
to connect the covers with one another. Disposed between
the covers is a body 302 having an opening 304 through which
35 fastener 298 extends. Disposed on each side of body 302 are
lugs 306 which are inserted in openings 308 on the interior
7~
15 -
surfaces of covers 280 and 282. A plurality of print bands
310 are mounted on annular upper drive gear wheels 312 and
hexagonal lower drive gear wheels 314. The hexagonal shape
of year wheels 314 can be seen in Figure 8. In accordance
with a further aspect of the invention, gear wheels 314 are
hexagonal in shape in order that more pre-load can be
placed on the print bands. The distance from the center of
the gear to a corner is less in a hexagonal shape than in a
square one. Thus, the band doesn't have to stretch as much
when a particular character is being selected for printing.
The lo~er gear wheels are mounted on a shaft 316
journalled in openings 318 in the lower portions of head
covers 280 and 282. Also disposed on shaft 316 are spacers
320. The gear wheels are spring loaded by springs 322
mounted in upper recesses 324 in body 302. The other ends
of these springs are mounted on detents 326 which are slide-
ably mounted in lower recesses 328 in body 302 where upper
recesses 324 communicate with lower recesses 326 as can best
be seen in Figure 8.
Disposed between drive gears 312 are annular spacers
332. A sleeve 334 extends through the gears 312 and is ro-
tatably mounted in an opening 336 in front cover 280 and a
recess 338 in cover 282, the sleeve not being capable of
axial movement.
In order to move a desired character on one of the
print bands 310 into the print field, a selector shaft 340
is provided which extends through sleeve 334 and which has
a knob 342 connected to the forward end 343 thereof. A
driving lug 344 extends through a ~lot 346 in sleeve 334 as
can best be seen in Figure 6 and engages one of the inner
teeth 348 of one of the annular drive gears 312. Thus, by
rotating knob 342 a selected print band 310 can be moved to
position a desired character into the print field. As is
known, the print bands may be provided with interior teeth
which engage the exterior teeth of drive wheels 312 and
314. Further, they are provided with prin~ elements 63 at
the lower portions thereof and with corresponding display
726
- 16 -
elements at the upper portions thereof so that the selected
character may be viewed from above.
In accordance with a further aspect of this invention,
an improved means for detenting selector shaft 340 at a par-
ticular print band 310 is employedO The selector shaft 340
is axially ~lideable within sleeve 334 to permit positioning
of lug 344 with respect to a desired one of the print bands.
Once the lug 344 has engaged one of the interior teeth 348
of the drive gear 312 corresponding to the desired print
band, the selector shaft 340 rotates with sleeve 334 as the
desired character i5 being positioned in the print field.
In order to detent the selector shaft at the desired print
band, a pair of racks 350 are provided on opposite sides of
the lower surface of an interior plate 352 formed substan-
tially along the axis of the selector shaft 340. The racks
are detented by two arms 354 of a shaft detent spring 356
which extends into the selector shaft. The spring 356 is
keyed to sleeve 346 via slots 358 formed on opposite sides
of the interior surface of the rearward end of the sleeve.
Thus, shaft detent spring 356 rotates with sleeve 334.
Further, it is prevented from axial movement in one direc-
tion by stop surface 360 in the sleeve which engages sur-
faces 361 of the detent and in the other direction by a
protrusion 363 which may be provided on the inner surface
of recess 338 of rear head cover 282. The spacing between
the teeth of racks 350 corresponds to the spacing between
the print bands 310. Hence, the selector shaft 340 will be
detented at whatever print band the operator axially shifts
the shaft to. As can be appreciated, the detenting of the
shaft is very close to the shaft axis (which preferably
approximately coincides with the axis of sleeve 334) and
thus the operator is provided with a good feel as he shifts
shaft 340 to a particular print band. Further, the detent-
ing action occurs on both sides of the shaft axis in a sub-
stantially symmetrical manner to further enhance the detent-
ing action. It is also in accordance with the invention to
connect the racks 350 so that they form a single rack which
726
is detented at the sides thereof by arms 354 of spring 356.
Further, the single rack may be detented by a single detent
arm which substantially extends along the shaft axis.
In order to provide the operator with an indication
as to which print band has been selected, a print band in-
dicator 362 is mounted on the selector shaft. Accordinyly,
a pointer 364 points to the selected print band in a known
manner.
It is to be understood that the above detailed
description of the various embodiments of the invention is
provided by way of example only. Various details of de~ign
and construction may be modified without departing from the
true spirit and scope of the invention as set forth in the
appended claims.
