U.S. patent number 3,682,078 [Application Number 05/196,657] was granted by the patent office on 1972-08-08 for apparatus for post-exposure treatment of lithographic plates.
This patent grant is currently assigned to Western Litho Plate & Supply Co.. Invention is credited to John H. Alley, William F. Gould, Edward H. Parker.
United States Patent |
3,682,078 |
Parker , et al. |
August 8, 1972 |
APPARATUS FOR POST-EXPOSURE TREATMENT OF LITHOGRAPHIC PLATES
Abstract
Apparatus for post-exposure treatment of lithographic plates
comprising a horizontal endless belt for transporting a
lithographic plate successively to, through and past a series of
operating stations. The apparatus includes a carriage at one of the
stations mounted above the belt for reciprocating movement
transverse to the belt, rubbing members rotatably carried by the
carriage for rubbing developing composition onto the lithographic
plate as it is transported on the belt, and a mechanism movable
with the carriage for rotating the rubbing members as the carriage
is reciprocated.
Inventors: |
Parker; Edward H. (St. Louis,
MO), Gould; William F. (Blackwood, NJ), Alley; John
H. (Greensboro, NC) |
Assignee: |
Western Litho Plate & Supply
Co. (St. Louis, MO)
|
Family
ID: |
26892101 |
Appl.
No.: |
05/196,657 |
Filed: |
November 8, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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745736 |
Jul 18, 1968 |
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Current U.S.
Class: |
396/611; 118/111;
118/109; 118/120; 396/604; 101/463.1 |
Current CPC
Class: |
G03F
7/3042 (20130101) |
Current International
Class: |
G03F
7/30 (20060101); G03d 003/12 () |
Field of
Search: |
;95/89R,89A,94R,99
;118/109,111,120 ;101/451,452 ;15/102 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Matthews; Samuel S.
Assistant Examiner: Braun; Fred L.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation of our copending application
Ser. No. 745,736, filed July 18, 1968, now abandoned.
Claims
Having thus described the invention, what is claimed and desired to
be secured by Letters Patent is:
1. Apparatus for developing lithographic plates comprising a moving
endless belt having a substantially horizontal upper reach, said
upper reach supporting and transporting an exposed lithographic
plate to, through and beyond a succession of operating stations
located along said reach, a carriage mounted for reciprocation
above said upper reach transversely with respect to said upper
reach from adjacent one side thereof to the other, at least one
rubbing member mounted on said carriage for reciprocation therewith
back and forth across said upper reach, said rubbing member having
an active surface disposed for engagement with a subjacent
lithographic plate traveling on said upper reach, means mounting
said rubbing member for rotation relative to the carriage about an
axis substantially perpendicular to said upper reach, means for
driving said carriage in reciprocation back and forth transversely
across said upper reach, and means for rotating said rubbing member
on its said axis as the carriage reciprocates back and forth.
2. The combination of claim 1 in which there is a cluster of
rubbing members rotatably mounted on said carriage, and said
last-mentioned means rotates different members of said cluster in
opposite senses.
3. The combination of claim 1 in which said means for driving said
carriage is an endless chain, a pair of spaced sprockets engaging
said endless chain to confine the path thereof to spaced chords
between the sprockets and end loops at the sprockets, and
force-transmitting means interconnecting said chain with said
carriage to reciprocate the latter while the chain moves
continuously in the same sense about its path.
4. The combination of claim 1 having metering means on the carriage
for dropping measured charges of developer composition on a
lithographic plate being transported by said upper reach before the
plate reaches said rubbing member.
5. The combination of claim 4 having a stationary developer supply
tank, means connecting said supply tank with said metering means
including a flexible tube for conducting developer fluid to said
metering means, and means relatively flexible in the horizontal
direction but relatively stiff in the vertical direction for
supporting said flexible tube adjacent the carriage and following
movement of the carriage during reciprocation.
6. Apparatus for developing lithographic plates comprising a moving
endless belt having a substantially horizontal upper reach, said
upper reach supporting and transporting an exposed lithographic
plate to, through and beyond a succession of operating stations
located along said reach, a carriage mounted for reciprocation
above said upper reach, a rubbing member rotatably mounted on said
carriage, said rubbing member having an active surface disposed for
engagement with a subjacent lithographic plate traveling on said
upper reach, means for driving said carriage in reciprocation in
directions transverse to the movement of said upper reach, and
means for imparting arcuate motion to said rubbing member, said
means for driving the carriage comprising an endless chain, a pair
of spaced sprockets engaging said endless chain to confine the path
thereof to spaced chords between the sprockets and end loops at the
sprockets, and force-transmitting means interconnecting said chain
with said carriage to reciprocate the latter while the chain moves
continuously in the same sense about its path, wherein said
force-transmitting means includes: a follower mounted on and
projecting from one of said carriage and said chain; and raceway
means on the other of said carriage and said chain, said raceway
means accommodating said follower and transmitting force
therebetween throughout the path of said chain.
7. The combination of claim 6 wherein: the follower is affixed to
the chain and has a rotatable bearing member disposed outwardly of
the chain on at least one side thereof; and said raceway is affixed
to the carriage, extends in the direction parallel with the
interspace between said chain chords, and is contoured to be
substantially contrageneric, but have a free-running fit, with said
bearing member as the latter moves about the loops of said
path.
8. Apparatus for developing lithographic plates comprising a moving
endless belt having a substantially horizontal upper reach, said
upper reach supporting and transporting an exposed lithographic
plate to, through and beyond a succession of operating stations
located along said reach, a carriage mounted for reciprocation
above said upper reach, a rubbing member rotatably mounted on said
carriage, said rubbing member having an active surface disposed for
engagement with a subjacent lithographic plate traveling on said
upper reach, means for driving said carriage in reciprocation in
directions transverse to the movement of said upper reach, and
means for imparting arcuate motion to said rubbing member, metering
means on the carriage for dropping measured charges of developer
composition on a lithographic plate being transported by said upper
reach before the plate reaches said rubbing member, a stationary
developer supply tank, means connecting said supply tank with said
metering means including a flexible tube for conducting developer
fluid to said metering means, and means relatively flexible in the
horizontal direction but relatively stiff in the vertical direction
for supporting said flexible tube adjacent the carriage and
following movement of the carriage during reciprocation, wherein
said last-named means is a strip of material having:
a. resiliency sufficient to withstand repeated bowing about an arc
whose radii are substantially parallel with the thickness of said
strip; and
b. stiffness sufficient to resist bowing about an arc whose radii
are substantially parallel with the width of said strip;
said strip being substantially wider than it is thick, and
substantially longer than it is wide, means connecting one end of
said strip to a stationary member, hinge means connecting the other
end of said strip to said carriage, and the length of said strip
being at least about half the reciprocating stroke of said hinge
means.
9. Apparatus for developing lithographic plates comprising a moving
endless belt having a substantially horizontal upper reach, said
upper reach supporting and transporting an exposed lithographic
plate to, through and beyond a succession of operating stations
located along said reach, a carriage mounted for reciprocation
above said upper reach, a rubbing member rotatably mounted on said
carriage, said rubbing member having an active surface disposed for
engagement with a subjacent lithographic plate traveling on said
upper reach, means for driving said carriage in reciprocation in
directions transverse to the movement of said upper reach, and
means for imparting arcuate motion to said rubbing member, said
carriage being entrapped on and movable along parallel spaced guide
rails, means connecting said guide rails together at each of their
ends, means permanently mounting and holding captive both ends of
one of said guide rails, means releasably mounting both ends of the
other guide rail, and said first-mentioned guide rail providing an
axis about which said other guide rail and said carriage may be
hinged to make said rubbing member accessible for replacement.
10. Apparatus for developing lithographic plates comprising means
for continuously conveying an exposed lithographic plate along a
predetermined path with the exposed face of the plate facing up,
means for applying a developer to said face, a carriage mounted for
reciprocation above said path and transversely with respect to said
path, at least one rubbing member for said developer mounted on
said carriage for reciprocation therewith back and forth across
said path, said rubbing member having an active surface disposed
for engagement with a subjacent lithographic plate traveling in
said path, means mounting said rubbing member for rotation relative
to the carriage about an axis substantially perpendicular to said
path, means for driving said carriage in reciprocation back and
forth transversely across said path, and means for rotating said
rubbing member on its said axis as the carriage reciprocates back
and forth.
11. Apparatus as set forth in claim 10 having a plurality of
rubbing members each mounted on the carriage for rotation relative
to the carriage on an axis substantially perpendicular to said
path, said rubbing member rotating means being carried by the
carriage and including means for rotating different rubbing members
in opposite directions.
12. Apparatus as set forth in claim 10 wherein said means for
driving the carriage comprises an endless chain drive including an
endless chain having a reach traveling in one direction
transversely across said path and another reach traveling in the
opposite direction transversely across said path, and means for
interconnecting the carriage and said one reach at one end of said
chain drive for moving the carriage in said one direction across
said path and for interconnecting the carriage and said other reach
at the other end of said chain drive for moving the carriage in the
opposite direction across said path.
13. Apparatus as set forth in claim 10 having support means
extending in downstream direction from said carriage reciprocable
with the carriage, metering means for dropping measured charges of
preservative composition on a lithographic plate moving in said
path downstream from said carriage, and rubbing means carried by
said support means for distributing said preservative over said
lithographic plate.
14. Apparatus as set forth in claim 13 wherein said preservative
rubbing means comprises at least one preservative rubbing member
rotatably mounted on said support means, and means for rotatably
driving said preservative rubbing member.
15. Apparatus as set forth in claim 14 wherein said preservative
rubbing member driving means comprises a stationary rack extending
transversely relative to said path and a pinion carried by said
preservative rubbing member in mesh with said rack for rotatably
driving said preservative rubbing member as it is reciprocated
transversely of said path by the carriage.
16. Apparatus as set forth in claim 10 wherein said carriage
driving means drives the carriage back and forth across said path
at a speed substantially greater than the speed of travel of each
plate along said path so that said rubbing member contacts
substantially the entire area of said face of each plate as it
travels below said rubbing member along said path.
17. Apparatus for developing lithographic plates comprising means
for continuously conveying an exposed lithographic plate along a
predetermined path with the exposed face of the plate facing up,
means at a first location along said path for applying a developer
for the plate on to the said exposed upper face of the plate, and
means at a second location along said path for rubbing the
developer over the upper face of the plate, said rubbing means
comprising a head extending transversely with respect to said path
across said apparatus above said path, sponge means carried by said
head for rubbing movement relative to the head and engageable with
the upper face of the plate to rub in the developer, means carried
by said head for driving said sponge means to effect said rubbing
movement of the sponge means relative to said head, means for
detachably connecting said sponge means to said driving means for
removal and replacement of said sponge means, and means mounting
said head for swinging movement between an operative position with
the sponge means facing downward for engagement with a plate being
conveyed along said path and a raised position for facilitating
removal and replacement of the sponge means.
18. Apparatus as set forth in claim 17 wherein the said mounting
means for the head supports the head for swinging movement about an
axis extending across said apparatus above said path.
Description
The invention relates to process and apparatus for post-exposure
treatment of lithographic plates to press-ready condition by the
"additive process," and the apparatus aspect thereof represents a
compact, simplified, and within limits, more economically
operatable improvement upon the apparatus disclosed in the
copending application of Harrell, Essmueller and Bax, Ser. No.
729,040, filed May 14, 1968, now U.S. Pat. No. 3,608,464.
One object of the invention is to expedite the post-exposure
treatment of lithographic plates, and to minimize the consumption
of chemicals utilized in such treatment.
Another object of the invention is to provide an apparatus for
performing automatically the post-exposure treatments of such
plates, and to reduce the consumption of materials employed in such
treatments.
A further object is to provide an apparatus which is more
economical to manufacture and to operate than that disclosed in the
aforesaid application of Harrell et al.
These and other objects of the invention, which will become
apparent to the skilled in the art as the description proceeds, are
accomplished by providing a process and machine wherein the exposed
lithographic plate is moved continuously to, through and beyond,
stations at each of which one of the steps of the process is
performed. Such steps include: (1) depositing metered quantities of
developer composition upon the active surface of the plate; (2)
spreading the developer composition over the active surface of the
plate and rubbing it with a compound motion which involves both
circular and rectilinear components, each in plural directions,
while the volatile components of the developer composition are
being evaporated; (3) washing away with water all of the developer
which has not adhered to the light-struck areas on the active
surface of the plate; (4) at least partially drying the active
surface of the plate; (5) depositing measured quantities of a
preservative composition upon the plate and (6) spreading the
preservative composition over, and rubbing it on, the plate.
Such continuous movement of the plate undergoing treatment is
conveniently accomplished by transporting the plate on an endless
belt. The endless belt is preferably smooth enough and held flat
enough that when a thin flexible sheet of metal, such as a common
lithographic plate, is laid upon it, air is excluded from the
interface, and the two "stick" together so long as substantially
flat coincidence is maintained, an action which is facilitated if
either contacting face is damp with a liquid which, at least to
some extent, wets both. Accordingly, the belt is preferably made of
a material which is, at least to some extend, phillic to liquids
which are phillic to the reverse (non-active) surface of the plate,
and the belt is preferably of a material, for example neoprene,
which may be vulcanized into endless condition in situ, i.e., while
trained around one or more drive-, or guide-, rollers. While such a
belt should be kept damp, care should be exercised to have it
substantially devoid of unsorbed or flowable liquid at the time it
receives a plate.
A salient feature of the invention is the provision of mechanism
which both spreads the developer on a plate and rubs it. This is
accomplished, in accordance with the present invention, by
providing a continuously circulating pressurized system for
supplying the developer liquid in metered quantities to a plate,
and immediately thereafter to subject the plate to the action of a
plurality of rotating rubbing heads which are translated,
transversely of the direction of plate movement, while whirling
about their own axes, at a speed sufficient to induce air
circulation of a character to accelerate the evaporation of at
least part of the liquid components of the developer from adjacent
increments of the plate's active surface. Each head is equipped
with a rubbing member which is essentially porous, non-abrasive and
possessed of at least enough resiliency to compress, albeit
slightly without permanent deformation. The rubbing members may
have some, but preferably little, absorptivity toward the viscous
developer. Any natural or synthetic sponge may be used as a rubbing
member, but it is preferable that it be one whose average pore size
is large, such as the so-called "coarse grain" cellulose sponge of
commerce. The "coarse grain" sponge is characterized by the fact
that many of its pores are a quarter inch or more in diameter, the
average pore size being greater than three-thirty-seconds of an
inch with relatively few as small as one-thirty-second inch, as
distinguished from "fine grain" sponges whose pores are
predominantly on the order of one-thirty-second inch in diameter,
and, according to commercial practice, must be no greater than
three-thirty-seconds of an inch.
The several rubbing members are preferably mounted in a cluster so
that their respective axes of rotation are parallel and spaced
apart a distance approximating the diameter (or diagonal) of the
individual rubbing members. Preferably, the rubbing members are
arranged in pairs with the individual members of a pair rotating in
opposite senses so that, at the bight where their respective
peripheries closely approach each other, both are moving in the
same general direction which may be either parallel with, or
transversely of, the direction of movement of the endless belt. A
cluster of two pairs of rubbing members is desirable, so that one
pair (herein termed the "leading pair") has its bight motion
addressed in the direction of plate and belt movement, while
another pair (herein termed the "trailing pair") addressed counter
to the direction of plate and belt movement. The invention
contemplates that the developer be deposited upon a plate on the
moving belt at a position ahead, and preferably immediately ahead,
of the leading pair of rubbing members. Preferably, the developer
is deposited by dropping it in metered quantities from an outlet
substantially aligned, in the direction of plate movement, with the
bight between the leading pair of rubbing members, and as close as
practical thereto.
In accordance with the present invention, the respective rubbing
members are maintained, during operation, under slight, but
substantially uniform, compression, e.g., enough to compress a
coarse grain cellulose sponge normally one inch thick to a
thickness of about seven-eighths inch. While under such
compression, and with an exposed lithographic plate moving
thereunder, the respective rubbing members are moved with a
compound motion, in rotation about their own axes, and in
translation crosswise of the endless belt, and at right angles to
the direction of belt movement. Hence, the relative movement
between a pair of rubbing members and a plate undergoing movement
involves not only relative rotation in opposite senses, but also
relative translation in two rectilinear directions.
The rectilinear translation crosswise of the belt is achieved by
mounting the cluster of rubbing members upon a carriage which is
reciprocated in the crosswise direction with a stroke whose
amplitude preferably exceeds the width of the belt, so that at
least part of each rubbing member will overhang the edge of the
endless belt at one end or the other of the reciprocatory stroke.
Thus, the edge of the belt acts as a scraper blade to remove excess
developer from that or those rubbing members which will be
trailing, in the reciprocatory respect, on the impending stroke. In
spite of the fact that such imposes a practical limit upon the
widthwise (of the belt) dimension of a plate being treated, it is
preferred that the frequency of reciprocation of the rubbing
carriage be so coordinated with the speed of the endless belt, that
the plate move longitudinally no more than about a diameter (or
diagonal) of a rubbing member while the rubbing carriage is making
a complete cycle of reciprocation transversely of the direction of
plate movement in the belt. Hence, the lineal speed of the rubbing
carriage must be substantially greater than the lineal speed of the
belt.
In order to minimize the time consumed in reversing the carriage
stroke (twice during each complete cycle of reciprocation) and to
minimize the mechanical shock involved in such reversals, the
invention contemplates a carriage drive mechanism which, during
operation, moves continuously in the same direction and remains
constantly in engagement with the carriage. The latter is
accomplished by an endless chain and sprocket drive in which one
chain-link or -pin is so connected in force-transmitting
relationship to the carriage that, at each end of a reciprocatory
stroke, the carriage's rate of deceleration to zero velocity, and
its rate of acceleration from zero to the chordal velocity of the
chain, is the same as that undergone by any chosen point on the
chain as it reverses direction in moving about a sprocket at an end
loop, to wit, but for mechanical looseness, like the trigonometric
function "versine" decreases from a maximum to zero, and then
increases to the maximum as a radius moves from one end of a
diameter to the other end of that diameter.
To transmit motive force from the chain to the carriage, the chosen
chain-link or -pin is connected to the carriage by means which
accommodates relative motion (between the chosen link or pin and
the carriage) in the direction perpendicular to a plane which
includes the fixed axes of both sprockets. Thus, when the axes of
the sprockets are horizontal, the aforesaid relative motion is
vertical; and, when the axes of the sprockets are vertical, the
relative motion is horizontal. One of the chain and carriage may
have an affixed raceway, while the other has an affixed follower
caged in the raceway; and the raceway preferably has a length
sufficient to accommodate movement of the follower between opposite
extremities of the sprockets' pitch circle diameter. The latter,
while not imperative, reduces mechanical strain on the
follower.
The same reciprocatory drive may also motivate a reciprocating
rubbing member at the preservative station of the apparatus, and,
if desired, may, through a rack and pinion, impart rotary motion to
one or more such rubbing members.
After an increment of a plate moving with the endless belt has
departed from the region of operation by the developer rubbing
members, the active surface of the plate is subjected to a spray of
water which erodes and washes from the plate passing therebeneath
all of the loose material, solid and liquid, of the developer which
has not, during the preceding treatments, become adhered to the
light-reacted areas of the plate. Beyond the water spray station, a
wiping member of the squeegee type makes water-sealing engagement
against the active surface of the plate. Such a squeegee may be
either a roller or a blade, in either event having a contacting
part of rubber, or other relatively soft material, which makes a
substantially water-tight seal with the plate traveling
therebeneath. Thus unsorbed and flowable water on the active
surface of the plate is wiped off as the belt moves the plate under
the squeegee, and such water is drained sidewise off the belt, as
by tilting the belt at that region; and any tendency for such water
to flow, counter to the belt movement, back into the developer
station may be overcome by tilting the apparatus, or at least that
region of the belt, so that gravity prevents such counterflow.
Beyond the last-mentioned squeegee, the plate passes to a
preservative station under another rubbing member, which may be of
like character to those previously mentioned, but not necessarily
so because the preservative composition usually requires less
rubbing then does the developer composition. Prior to passing under
the preservative rubbing member, there is dropped upon the
dewatered moving plate metered quantities of the preservative
composition. As at the developer station, one, or a series of
spaced metering devices is arranged so as to drop the requisite
quantity (usually less than that of the developer) of the
preservative composition upon the subjacent plate. The preservative
composition then undergoes rubbing of like character to, but lesser
degree than, that which the developer previously underwent. Upon
emerging from the preservative rubbing member, the plate is
squeegeed to remove excess "preservative" (including entrained
water and organic solvent). This completes the post-exposure
treatment in situations where the treated plates are transported
individually from the apparatus to the press, as the time consumed
in such transportation and in mounting the plates on the press is
sufficient to permit natural evaporation of such water and organic
solvent as may remain entrained in the residual preservative after
the last-mentioned squeegeeing. On the other hand, where it is
desired to accumulate plates emerging from the apparatus by
stacking them one upon the other, it is advisable to expedite the
evaporation of water and organic solvent as by passing the plates
individually through any suitable dryer before they are
stacked.
The series of post-exposure treatment operations requires an
elapsed time which is but a small fraction of that required when
the operations are carried out by hand, and the drying aspect of
the development operation, as well as that of the preservative
application, is expedited by the air circulation induced by the
motion of the several rubbing members.
One form of apparatus embodying the inventions is disclosed in the
accompanying drawings, in which:
FIG. 1 is a perspective view taken from above the plate input end
of the apparatus, and looking toward the discharge end thereof;
FIG. 2 is a sectional view taken along line 2--2 of FIG. 1;
FIG. 3 is a sectional view corresponding to FIG. 2, but taken along
line 3--3 of FIG. 1, and showing a relationship of parts not shown
in FIG. 2, as well as omitting certain other parts;
FIG. 4 is a sectional view taken along line 4--4 of FIG. 1, showing
the rubbing carriage for the developer station on enlarged scale,
and with portions broken away to reveal the relationship of driving
parts;
FIG. 5 is a sectional view taken along line 5--5 of FIG. 4, and
showing the gear system for driving the cluster of rubbing members
in rotation;
FIG. 6 is a perspective view showing the bottom or plate-engaging
surface of one of the rubbing members shown in FIG. 4;
FIG. 7 is a perspective view showing the same rubbing member
illustrated in FIG. 6 from the upper or mechanically connecting
surface thereof;
FIG. 8 is a detail view in side elevation, showing the link of the
drive chain for the rubbing carriage which is equipped with the
means for transmitting reciprocatory force to the rubbing
carriage;
FIG. 9 is a perspective view showing the storage and distribution
systems for the developer composition and the preservative
composition;
FIG. 10 is a top plan view of the apparatus shown in FIG. 1, with
the rubbing carriage in a different position; and
FIG. 11 is a sectional view taken along line 11--11 of FIG. 10.
FIG. 12 is a sectional view of the preservative station of FIG. 2
with a rotatable rubbing member.
The embodiment illustrated in the drawings includes an endless belt
1, the front loop of which is trained about a roller 2, and the
rear loop of which is trained about a roller 3. An adjustable
tension roller (not shown) can be provided on the lower reach of
the belt.
An exposed lithographic plate to be treated is fed into the
apparatus adjacent roller 2, and transported on the upper reach of
belt 1 toward roller 3. The roller 3 is, in the embodiment shown, a
drive roll, while the roller 2 is an idler roll, so that the upper
reach of the belt moves from the roller 2 toward the roller 3, and
is constantly tensioned in the direction of its movement to,
through, and beyond, a superimposed idler roll 4, a developing
station 5, a washing station 6, a preservative station 7, and a
squeegee roll 8, all as indicated in FIG. 1.
At the developing station 5, there is provided a carriage 9, which
is driven in reciprocation to translate transversely of the
direction of the movement of the upper reach of belt 1. The
carriage is mounted upon spaced trunnions 10 and 11, which guide it
during the aforesaid reciprocatory translation; and the carriage is
driven in such reciprocatory translation by an endless chain 12
threaded about an idler sprocket 13 and a driven sprocket 14. The
sprockets 13 and 14 are mounted for rotation about shafts supported
by cross-bar 15, from which there projects radially a bracket 16
for mounting a motor 17. The motor 17 drives shaft 18 (and sprocket
14 fixedly mounted on that shaft) in rotation which may be either
clockwise or counterclockwise, but is always in the same
direction.
THe trunnion 10 has its opposite ends mounted respectively in links
19 and 20, while the opposite ends of said links are hinged on
trunnion 11, which is permanently mounted to opposite pedestals 21
and 22, which are in turn securely mounted upon the side frames of
a table 23 which subtends the developing station portion of the
upper reach of belt 1. A comparable pair of pedestals 24 and 25
support the front ends of links 19 and 20, and may be provided with
any suitable means 124 and 125 for releasably latching or detenting
such front ends, and the intervening trunnion 10, in the operating
position shown in FIG. 1. The hinging of the parts for limited
rotation about trunnion 11 serves no function in the operation of
the apparatus, but does facilitate the removal and replacement of
expendable parts of a rubbing assembly mounted upon and movable
with carriage 9, later to be described. Since motor 17 is a part of
the thus hingedly mounted assembly, the motor is preferably
equipped with a mercury switch, or other tilt-sensitive device, to
automatically disconnect the source when the hingedly mounted
assembly is moved out of the position shown in FIG. 1 and toward
the position shown in dotted lines in FIG. 3.
An electric motor 26, having a drive shaft 27 projecting axially
downward, is mounted upon carriage 9, and its shaft 27 is equipped
with a pinion 28 which engages a gear 29 and drives the same in
rotation. Gear 29 is one of a cluster of four identical gears 29,
30, 31 and 32, which intermesh with each other, as shown in fig. 5,
so that alternate ones of the cluster rotate in opposite directions
about their respective shafts.
The lower end of each gear shaft projects beneath carriage 9, and
has removably mounted thereon a rubbing member 33 of which there
are four in the embodiment shown. As clearly shown in FIGS. 6 and
7, each rubbing member is preferably composed of a slab 34 of
coarse grain cellulose sponge, or other comparable material,
secured to a metal plate 35. The obverse and reverse faces of the
rubbing members are shown in FIGS. 6 and 7, respectively; the
obverse face being the one which makes rubbing engagement with a
plate undergoing treatment; and the metal plate being the reverse
face. In the form shown, the rubbing members are of circular
periphery, but other curvilinear or polygonal shapes may be
employed. The obverse face of each such rubbing member has a
central aperture 36 which is preferably acircular, and shown as
rectangular. Such a central aperture accomplishes a dual function:
first, it accommodates parts which project downwardly from discs 37
(one of which is fixedly mounted on each of the shafts for gears
29-32) through keyways 38 in mounting plate 35 for snap-on
connection with the respective rubbing members 33, and provides
access to retaining screws therefor; and second, if acircular, it
tends to keep in motion any developer composition which may
accumulate therein and thereby minimize caking thereof with
resultant short-radius streaking of a lithographic plate undergoing
treatment.
The reciprocatory traversing movement of carriage 9 and its adjunct
parts transversely of the motion of belt 1 (and transversely of a
lithographic plate moving with the belt) is accomplished without
reversing the direction of rotation of drive sprocket 14, or the
direction of movement of chain 12 about its orbit by means now to
be described. The drive chain 12 is a common link and roller, or
link and block, endless chain. In such a chain, opposite links 39
are connected by a common pin 40 either to preceding and succeeding
links, or to adjacent blocks. The invention contemplates that one
such pin in the chain be equipped with a round-ended cylindrical
projection or follower 41 at one side of the chain, and with a ball
bearing projection or follower 42 at the other side of the chain.
The follower members 41 and 42 project sidewardly from the chain in
opposite directions, as shown in FIG. 8. The parts 41 and 42 are
thus free to rotate about the axis of pin 40, and may, if desired,
be separated from links 39 by nylon washers 43 and 44. The driving
force for carriage 9 is transmitted from chain 12 through the
single pin 40 of the chain which has bearing members 41 and 42
associated with it. The transverse components of the motion of pin
40 are transmitted to the carriage through a C-shaped yoke 45,
shown in FIG. 4. The yoke 45 is permanently affixed to carriage 9,
and moves with it in translatory reciprocation horizontally at
right angles to the direction of movement of the belt 1. For
confining, yet accommodating vertical movement of, bearing member
41 at the end loops of chain 12, the yoke 45 is provided with a
raceway 46 in the continuous side of the C-shaped yoke, and
likewise the bearing member 42 is movably confined in opposite
discontinuous, but vertically aligned, raceways 47 and 48 in the
discontinuous side of the yoke. These raceways are
cross-sectionally contoured to be substantially contrageneric with
the cross-sections of bearing members 41 and 42, respectively, and
to accommodate said bearing members for free running vertical
movement while held captive therein, as pin 40 of the chain changes
direction at either sprocket, 13 or 14, from the upper chord of
chain 12 to the lower chord thereof, or vice versa. To facilitate
the installation and caging of the ball extensions 41 and 42 in the
raceways, the yoke 45 may have a separable part 145 which
constitutes both the top bar of the C shape and the upper dependent
in which raceway 47 is located.
Upon the carriage 9, there is also mounted a metering device 49 for
delivering measured quantities of developer composition, and
depositing it, either as a continuous stream or drop by drop at
spaced intervals, on a subjacent lithographic plate 50 at a
position immediately ahead of the rubbing members. While economy of
developer composition may be effected by the drop-by-drop
technique, the continuous stream technique is preferred for
assurance of quality. In any event, the developer composition is
preferably deposited on a subjacent plate at a position which will
cause each increment to be caught in the bight between the leading
pair of rubbing members 33 and 33', as seen in FIG. 10. At this
position, each member of the leading pair of rubbing members 33 and
33' (when rotating as shown in FIG. 10) has its increments adjacent
the bight moving toward each other and generally rearward, i.e., in
the direction of movement of the belt 1. Accordingly, such
increments of so-deposited developer, as are not smeared on the
plate by the leading pair of rubbing members, are cast toward the
trailing pair of rubbing members and are either smeared on the
plate by them, or cast back toward the leading pair.
The metering device 49 is supplied with developer from a tank 51
which can be arranged at any convenient place about the apparatus,
but, for clarity of illustration, is shown mounted upon a
stationary part of the apparatus over the washing station, but it
will be understood that the tank can be mounted upon, and movable
with, carriage 9, if desired. The tank 51 has a discharge line 52
extending to a pump 53 which discharges through a line 54 to a T
55, one side of which leads to a T 56, one branch 57 of which
returns to tank 51 and terminates with a fixed restrictive orifice
located within the tank; and the other branch 58 of which extends
to a flexible tube 59 leading to the developer metering device 49,
as shown in FIG. 1. In order to prevent the flexible tube 59 from
becoming entangled with adjacent parts during the translatory
reciprocation of carriage 9, the flexible tube 59, which conducts
developer composition to metering device 49, and the electrical
conductors 60, which control operation of the metering device 49,
are each mounted upon a spring strip 61 pivotally secured at one
end 62 to channel 15, and pivotally secured at the other end 63 to
carriage 9. The spring strip 61 may be formed of stainless steel
having a thickness (e.g., 0.020 inch) such that it is readily bowed
in the thickness direction without exceeding its elastic limit, a
width sufficient (such as 1 inch or more) to make it relatively
stiff and resistant to bending in the widthwise direction under the
load which it is required to sustain, and of a length sufficient to
reach from the pivotal connection 62 to pivotal connection 63 when
the carriage 9 is at either extreme of its stroke, but when the
carriage is intermediate the ends of its stroke, the strip 61 bows
as shown in FIG. 1. The tube 59, as well as electrical conductors
60, are anchored to the spring strip 61 not only at the ends of the
latter, but at at least one intermediate position, and the security
of such anchorage is preferably such as to prevent creepage of
either tube 59 or conductors 60 relative to the spring strip during
repeated bowing and straightening of the strip.
In the embodiment shown, the metering device 49 is controlled
electrically to open and close a valve therein at predetermined
intervals, as, for example, the time interval required for the
carriage to move 4 to 6 inches. While the tank 51 may be covered,
in the arrangement shown, it is open to the atmosphere, and in
order to assure the existence of necessary pressure on the
developer composition in flexible tube 59 as and when the valve in
metering device 49 opens, means is provided for causing the liquid
developer in pipe 56 to preferentially flow through branch 58 and
tube 59. Such means may comprise a constriction in branch 57, or
making the entire branch 57 of smaller bore than branch 58 and tube
59, or providing a valve in branch 57 which automatically closes
when the valve in metering device 49 opens. Alternatively,
especially when the developer is thixotropic, the branch 57 may be
replaced by a return line from metering device 49 to tank 51, so
that there is a continuous flow of developer past the inlet orifice
for metering device 49. In either event, the continuous movement of
developer from tank 51 through pump 53 and back to tank 51
maintains the developer liquid in well-agitated condition, but when
thixotropic developer is employed, the aforesaid alternative
prevents such increase in its viscosity that supply to metering
device 49 is impeded.
For the purpose of ready removal of residual developer composition
from tank 51, as at shut-down of the apparatus at the end of a day,
T 55 is also connected to a line 64 controlled by a valve 65, which
leads to a flexible tube 66 whose open end is situated at a
convenient place for capturing the developer discharged
therethrough. Under operating conditions, however, valve 65 is
closed.
For convenience in removing and replacing the rubbing members 33
which are expendable, the entire carriage 9 and its associated
parts, including trunnion 10, chain 12, sprockets 13 and 14, motor
17, and the spring strip 61, is mounted for hinging about trunnion
11 (as shown in broken lines in FIG. 3) to an extent sufficient to
enable the rubbing members 33 to be readily accessible.
At the washing station 6, there is provided an inverted trough 67
within which there is housed a water header having a series of
transversely spaced nozzles 68 for spraying water downwardly and
away from the developing station, upon subjacent increments of
plate 50 as they pass beneath the trough 67. Such rinses away the
hydrophilic components of the developer which have not become
adhered to the now-hardened lacquer-forming components of the
developer. While normally the volume of water so sprayed is
insufficient, particularly when the belt is moving to tend to flow
backward toward the developing station, the entire apparatus may be
tilted slightly to eliminate any such tendency. As shown, however,
the table 23 terminates short of the washing station so that there
is no supporting member in contact with the lower side of the upper
reach of belt within the washing station. This has the two-fold
effect of reducing the mechanical drag on the belt, and of
facilitating the elimination of washing water without back-flow
into the developing station.
At the rear end of the washing station, there is provided a
squeegee which, in the form shown, is a rubber lip 69 biased into
contiguity with the upper reach of belt 1, and consequently when a
plate, such as 50, moves therebeneath on the belt, the rubber lip
69 flexes slightly to wipe all flowable water from a plate as it
passes. The thus removed water flows over the edges of belt 1 and
is caught by sink 85, shown in FIG. 2. Preferably, the squeegee 69
engages the upper surface of belt 1 at a position where the belt is
supported as by table 230 which also sustains the load of rubbing
under pressure at the preservative station 7.
The preservative station 7 is immediately behind the squeegee
device just mentioned. At station 7, there is provided one or more
metering devices 70 for depositing metered increments of a
preservative composition upon a subjacent plate. While, in the
embodiment shown, the metering device 70 is stationary, it will be
understood that, if desired, it can be reciprocated in a manner
comparable to the reciprocation of metering device 49, but
otherwise, it suffices to provide metering devices 70 permanently
located in spaced relation 8 to 10 inches apart transversely
(widthwise) of the belt 1.
Metering device 70 is supplied with preservative composition from a
tank 71 which, as shown in FIG. 9, is equipped with a pump 72,
which discharges into a tee 73, one leg of which extends to tube 74
leading to metering devices 70. As in the case with metering device
49, metering devices 70 are electrically controlled to regulate the
time interval between successive discharges, and they may, if
desired, have a master control which deactivates all of them save
when a plate is present therebeneath. The other leg of T 73 is
connected to a pipe 75 having a valve 76, which is closed during
normal operation of the apparatus, but, as in the case of the
developer, may be opened to drain tank 71 at shut-down. While the
nature of the preservative composition is usually not such as to
require continuous agitation during operation, where the
preservative composition does require it, line 74 may be provided
with a branch leading back to tank 71, as in the case of the
developer system.
At the preservative station 7, and immediately behind the metering
device 70, there is also provided means for rubbing the
preservative composition and spreading it throughout the length and
breadth of a subjacent plate. Such a device may, if desired, be in
the form of a reciprocating carriage comparable to carriage 9, and
in such case, the metering device 70 may be mounted upon, and
movable with, such a carriage, but need not embody a gang of
rubbing members, as one will suffice. However, in the embodiment
shown in the drawings, the rubbing means is mounted upon an arm 78
having a boss 79 encircling trunnion 11 (for both sliding movement
axially of, and rotational movement about, trunnion 11), and
restrained against movement relative to the carriage 9 in the
direction of the latter's reciprocation. Thus, the bar 78
reciprocates with the carriage 9, but may be hinged relative to the
carriage 9 about trunnion 11 as an axis when the carriage and
adjunct structure are tilted to the position shown in dotted lines
in FIG. 3, or the arm 78 may be independently tilted in the
counterclockwise direction from the position shown in FIG. 2. As
clearly shown in FIGS. 2 and 10, the arm 78 projects rearwardly
from trunnion 11 over the washing station 6 and into the
preservative station 7, so that its free end can support a rubbing
member for operation upon a lithographic plate at the preservative
station. Two forms of rubbing member are illustrated in the
drawings. In the form illustrated in FIGS. 2 and 10, a single
rubbing member 77, of the same material as rubbing members 33, but
of length (widthwise of the belt) approximately equal to twice the
diameter of a rubbing member 33, is fixedly mounted upon the
rearward extremity of arm 78. Hence, the rubbing member 77 is
reciprocated in translation concurrently with carriage 9, and the
rubbing member is so disposed that its stroke (widthwise of the
belt) in such reciprocation is equal to that of the leading pair of
rubbing members 33 and 33' on carriage 9. Thus, the rubbing member
77 operates upon a subjacent plate with compound relative motion
consisting of the component which is moving the plate lengthwise of
the belt 1, and the component which is moving the rubbing member 77
in reciprocation widthwise of the belt. Under circumstances
depending upon the materials employed, where it is desirable to
impart a rotational motion to the rubbing member at the
preservative station, the rubbing member 77 may be replaced by a
rotatable one 770 as shown in FIG. 12. The rotatable rubbing member
770 is preferably formed of the same material as rubbing members 77
and 33, and is preferably circular in external periphery, but due
to space limitations at the preservative station, is somewhat
smaller in diameter than the rubbing members 33. The rotatably
rubbing member 770 is mounted on the lower end of a shaft 771,
retained in a bearing block 772, which is secured to the free end
of arm 78. Shaft 771 has affixed to it a pinion 773 which engages a
fixed rack 774 extending transversely of the apparatus, and mounted
upon a stationary bar 90, as shown in FIG. 3.
Immediately after emerging from the ambit of rubbing member 77, the
leading edge of a plate, such as 50, enters the nip between idler
roll 8 and belt 1, and as the belt 1 makes the turn about drive
roll 3, the plate which has been operated upon is peeled from the
belt and delivered to a discharge apron 80. While the roll 8 may be
spring biased toward the belt, such is likely to permanently deform
the surface of roll 8 when the apparatus is idle, as over a long
weekend, unless some means is provided to automatically release the
bias when the apparatus is idle. A simpler safeguard against such
deformation is to mount one end of roll 8 with a fixed nip as shown
in FIG. 1, while the other end is provided with a suitable
quick-release mechanism 108 as shown in FIGS. 2 and 3.
A receiving apron 81 is arranged at the front end of the apparatus
to guide a plate to be treated into the nip between idler roll 4
and belt 1, and apron 81 is equipped with a plate sensor 82 which
is the operator of an electric switch, and so disposed that the
switch is normally open, but when a plate passes thereunder, the
switch is closed to initiate, in predetermined sequence, the
energization of a plurality of electrical circuits which
respectively control motors 17, 26, and pumps 53 and 72, as well as
metering devices 49 and 70; movement of the belt 1 being similarly
controlled and so interlocked with the plate sensor 82 that the
latter will not initiate the energization of any circuit unless the
belt is running.
Since relative movement, between the belt 1 and a lithographic
plate being transported by it, is restrained only by surface
tension which requires substantial exclusion of air from the
belt-plate interface, it is important that the belt 1 be
sufficiently wet with liquid to assure such exclusion of air from
the interface that the plate adheres to the belt with sufficient
tenacity to prevent its movement relative to the belt while being
operated upon by the rubbing members. Hence, means for wetting the
belt prior to reaching its loop about idler roll 2 is provided. In
the embodiment shown, such a means comprises a water spray head 83
situated below the lower reach of belt 1, and disposed to direct a
spray of water upwardly onto the lower surface of the lower reach
of belt 1 for the full width thereof. In order to assure that there
is no flowable liquid on the belt as it passes under idler roll 4,
a squeegee device 84, shown in the form of a wiping blade in FIGS.
2 and 3, is provided for surface engagement with the belt as it
makes the turn about idler roll 2. Thus, when an increment of belt
1 comes into contact with the inactive surface of a lithographic
plate being fed through the nip between idler roll 4 and belt 1,
the belt is damp at least to the extent that whatever pores may be
in the belt are filled with liquid, and there is at least a
monomolecular film of liquid on the surface of the belt, but there
is substantially no flowable or unsorbed water on the surface of
the belt. This precaution has a two-fold effect: first, it
minimizes the transfer of water from belt 1 to idler roll 4 when
idler roll 4 is running in contact with the belt, i.e., with no
plate intervening; and second, it minimizes the likelihood that
liquid will be squirted out of the interface between a plate and
the belt at the developing station when the plate is being squeezed
between rubbing members 33 and the belt. While, in the embodiment
shown, the belt is pre-wet with water, it will be understood that
other liquids can be used for this purpose. With the arrangement
shown, water is discharged above the belt at station 6 and drains
into collector sink 85, which also receives the drippings from the
lower reach of belt 1, as well as the excess discharged by spray
head 83 and the drippings from squeegee member 84.
In situations where it is desired to stack the processed
lithographic plates one upon the other immediately as they emerge
on to discharge apron 80, it is desirable to completely dry them
before they are stacked one upon the other, and accordingly the
discharge apron 80 may be equipped with any suitable drying
apparatus, such as one which directs a stream of warm, dry air
against the emerging plate, and before it is stacked. Since, in
accordance with the present invention, a plate, such as 50, being
processed in the apparatus is held fast on the belt 1 by virtue of
moisture at the interface, it is of particular importance to dry
the lower surface of any such plate which is to be stacked upon
another because the moisture on the inactive surface of a plate is
more detrimental to the active surface of the plate next below it
in the stack than is residual moisture in the active surface of the
lower plate. Accordingly, the invention contemplates the provision
of a warm air duct 86 for conducting a stream of warm, dry air from
a suitable source, and directing it through a series of louvers 87
in discharge apron 80, so as to impinge the warm air against the
inactive surface (which has been in contact with belt 1) of a
processed lithographic plate as it passes over the louvers 87.
For features of the apparatus which are not specifically described
herein such as the character and speed of the belt 1, the mode of
securing the lithographic plate against movement relative to the
belt, automatic control of discharges, and the material of which
the rubbing members may be formed, reference may be had to the
aforesaid application of Harrel et al.
In the operation of the device, it is preferred that movement of
the belt and release of water from spray head 83 be initiated first
to pre-condition the belt for the reception of a plate. After the
belt has moved for a distance sufficient to bring the leading
increment, wet by spray head 83, to the nip between idler roll 4
and the belt, an exposed lithographic plate is moved across apron
81 into contact with sensor 82, whereupon the motors 17 and 26 and
developer pump 53 begin to operate. Thereafter, within an increment
of time no greater than that sufficient to bring the leading edge
of the plate into position between the belt and the leading pair of
rubbing members 33 and 33', metering device 49 is energized to
release a charge of developer composition near the leading edge of
the incoming plate; within an increment of time no greater than
that sufficient to enable the leading edge of the plate to reach
washing station 6, the supply of water to header 68 is opened; and
within no greater than the increment of time required for the
leading edge of the plate to reach preservative station 7, pump 72
and metering device 70 are energized. In the embodiment shown, all
these devices remain energized, at least periodically, until
movement of belt 1 is stopped, but it will be understood that
appropriate devices sensing the presence or absence of a plate on
the belt, subjacent the devices operating thereon at the successive
stations 5, 6 and 7, may be provided for discontinuing the
operation of such devices sequentially when there is no plate to be
operated upon by them respectively. Absent such plate-present
sensors in the respective stations, means which is adjustable in
accordance with the dimension (in the direction of movement of the
belt) of the plate may be provided for automatically discontinuing
the operation of the devices at the respective stations.
At developer station 5, increments of developer are dropped on a
subjacent plate throughout the reciprocatory stroke of carriage 9
in both directions, and concurrently rubbed over and into the
active surface of the plate. Preferably, the speed of reciprocation
of the carriage 9 is so coordinated with the speed of belt 1 that
any given increment of plate is operated upon by at least two of
the rubbing members 33 during each half-cycle of reciprocation, but
where speed of the operation is more important than quality of the
development, it is sufficient that each increment of the plate be
operated upon by at least one of the rubbing members during a whole
cycle of reciprocation. In either event, during a full cycle of
reciprocation of the carriage 9, the path of a given rubbing member
on a lithographic plate undergoing treatment on the moving belt is
"V" shaped, or half "W" shaped, depending upon the position chosen
for the beginning of the cycle; and to achieve optimum results with
the form of apparatus shown, the speed of belt 1 is so coordinated
with the speed of the carriage's reciprocation that the belt moves
no more than a radius of a rubbing member 33 during a complete
cycle of reciprocation; but to decrease the time required for the
entire operation, more rubbing members may be added to the cluster
thereof on the carriage 9, and the speed of the belt increased
accordingly. Where, as shown in FIG. 10, the width (i.e., parallel
with trunnions 10 and 11) of the belt 1 is sufficiently less than
the length (i.e., parallel with trunnions 10 and 11) of the stroke
of carriage 9 is such that at least half the surface of the
lefthand pair of rubbing members (33' and the one behind it)
overreach the lefthand edge of the belt at the lefthand extremity
of the reciprocatory stroke, and conversely at least half the area
of the righthand pair of rubbing members (33 and the one behind it)
overreach the right edge of belt 1 at the right extremity of the
reciprocatory stroke. Since the rubbing members are resilient and,
when in contact with a plate or the belt, are under some
compression, the increments thereof which overhang the edge of the
belt at the respective ends of the reciprocatory stroke momentarily
expend as they leave the belt, but are recompressed when, no more
than 180.degree. of rotation later, the re-encounter the edge of
the belt. Hence, the edge of the belt serves as a squeegee member
to remove any excess of developer as the momentarily expended
increments of the rubbing member are re-compressed upon emerging
from a zone at which their compression was released into a zone
wherein their compression is resumed. This, together with the
feature of discharging the developer composition from the
reciprocatory carriage, at spaced intervals during its strokes,
effects improved utilization of the developer composition, and
spreads it uniformly thin so that evaporation of its volatile
components is accelerated -- which latter is further induced by the
air turbulence induced by the rotating, counter-rotating, rubbing
members.
Because of the compound rubbing motion involved, the construction
and mode of operation of the cluster of rubbing members on carriage
9 is ideal for the post-exposure treatment of lithographic plates,
not only with developer composition, but also with preservative.
The compound relative motion between a lithographic plate
undergoing treatment and the cluster of rubbing members involves a
number of components; longitudinal rectilinear motion in the
direction of the single-headed straight arrow in FIG. 10;
transverse rectilinear motion back and forth in the directions
indicated by the double-headed straight arrow in FIG. 10;
curvilinear motion in the clockwise direction by half the rubbing
members in the cluster; and curvilinear motion in the
counterclockwise direction by the other half of the rubbing members
in the cluster. A given increment of a lithographic plate
undergoing treatment is subjected to at least three of those
motions concurrently; and within a given half-cycle (indeed, within
a fractional part of each stroke, which amounts to a maximum of
slightly more than the diameter of a rubbing member 33) of the
carriage's reciprocation, such increment of the plate is subjected
to all four of those motions. Not only is the character of the
relative motion variegated, but the speed thereof is variegated
insofar as concerns the rotation of the rubbing members because the
relative speed between a point on a lithographic plate momentarily
situated near the periphery of a rubbing member 33 is greater than
the relative speed at that same point on the plate when it assumes
a location nearer the center of rotation of a given rubbing
member.
In contrast with the variegated rubbing action which takes place at
the developing station, that which takes place at the preservative
station is not necessarily variegated to the same degree. While, in
the form shown in FIG. 2, the rubbing action at the preservative
station involves only a compounding of longitudinal and transverse
rectilinear motions, there are certain preservative compositions
which perform better if rubbed in a manner comparable with, but not
necessarily in the degree of, the rubbing action which takes place
at the developing station; and accordingly it is contemplated that
where such is necessary, the rectilinearly reciprocating rubbing
member 77 at the preservative station be replaced with one, of the
character shown in FIG. 12, which rotates while reciprocating,
clockwise in one-half cycle of reciprocation and counterclockwise
in the other half-cycle of reciprocation. Whether the rubbing
member at the preservative station is or is not rotating, the
mounting of it with freedom for vertical movement enables its own
weight to impose pressure on the plate being rubbed, and such
pressure can be varied by adding to or subtracting from the dead
weight of the rubbing assembly.
While one complete embodiment of the invention has been illustrated
in the accompanying drawings, and has been described hereinbefore,
save with respect to some details which are common to the
disclosure of the aforesaid application of Harrell et al; and while
certain modifications and variations in the apparatus shown in the
drawings have been hereinbefore indicated, it is not to be
understood that the invention is limited to the specifics of the
foregoing disclosure. From the foregoing description, those skilled
in the art will readily understand the structure, function and mode
of operation of the invention, and realize that it accomplishes its
objectives efficiently, expeditiously, and economically.
* * * * *