Note: Descriptions are shown in the official language in which they were submitted.
CA 02218984 1997-10-22
WO 96/3558 PCTIUS96104943
CLEANING FLUID APPARATUS AND METHOD FOR
CONTINUOUS PRINTING INK-JET NOZZLE
FIELD OF THE INVENTION
The invention relates to the fields of print nozzles
and, in particular, drop-on-demand printer nozzles,
such as ink jet and bubble jet printer nozzles. The
invention f-~as particuler application to the problems
associated with dust, other particles and ink that
disrupt and clog tf-~ese printing nozzles during
continuous operation.
BACKGROUND AND SUMMARY OF THE 1NVENTtON
Drop-on-demand ink-jet and bubble-jet printers
[collectively referred to as ink jet printers] propel fine
ink droplets from nozzles onto a paper substrate
adjacent the nozzle. Examples of these types of
printers are the Cannon nozzles known as BCO'1 and
BC02. By precisely controlling the trajectory and tf-~e=_
time of ejection of the ink droplets, the ink jet nozzles
print clear dots on paper. To achieve precise
positioning of droplets of ink, ink jet nozzles must
' provide clear and clean orifices for the droplets to
pass through as they fly from tf~e nozzle to the surface
of the paper. In a conventional drop-on-demand ink jest
nozzle, there is an array of several orinces on the face
CA 02218984 1997-10-22
WO 96/3558.1 PCT/US96/04943
2
d
of the nozzle from which the ink droplets are propelled.
During printing, ink is ejected out of selected orifices in
the array to form the desired images on the paper.
The flight of the ink droplets and especially their impact
on the paper surface creates a fine mist of ink that
coats the surface of the nozzle. Also. durinr, rr,o
ejection of the droplets, extraneous ink is sprayed and
deposited on the nozzle face adjacent the orinces.
This moist ink coating attracts paper fiber, dust, grit
and other types of particles that can obstruct the
nozzle orifices and block the ink droplets being sprayed
from the nozzle. Also, the extraneous ink can build up
such that it blocks the orifices. Accordingly, there is a
need to regularly clean the nozzle plate of ink jet
printers so that the array of orifices remains clear of
ink and particles that would otherwise interfere with
the printing of ink on the paper.
In the past, ink jet printers I-gave been cleaned by
wiper mechanisms that clean the nozzle plates and
orifices. Between print jobs, the printer head moves
away from the paper web to a cleaning station where is
slides against a cleaning wiper. These wipers
squeegee across the face of the nozzle plate and the
2~ openings of the orifices to remove particles that may
be obstructing ink in the nozzles. Because the wipers
themselves temporarily obstruct the nozzles, the
wipers are used only when the ink jet printer is not
CA 02218984 1997-10-22
printing. For example, a wiper may be positioned at
the far edges of a carriage path, beyond the edges of
the paper held adjacent the carriage path. Examples
of wiping systems are disclosed in U.S. Patent No.
5 S,'1 2!=,765, entitled "Ink Jet Recording Apparatus
Having Cleaning Means For Cleaning A Recording
Head" and in German Patent Document No. DE
~, 8'I 7,~S4A.
10 Wipers have proven generally acceptable for
desk top printing applications where each individual
print job is relatively short and the times between
when the print nozzles are wiped clean are relatively
brief. In a typical desk-top ink-jet printer the carriage
15 with the ink jet printing head can be shifted to a
cleaning station after each print operation. Thus, in
the usual desktop application, the printing nozzles
are cleaned frequently by conventional wipers and
tend not to clog with particles.
20
With continuous web-feed printing, the print
nozzle is required to constantly print for many hours.
This is unlike typical desk-top printing applications in
which each printing operation is conducted in a
25 relatively short period of time. shifting the print head
to a cleaning station away from the paper to be
printed necessarily interrupts the printing operation
of a continuous printer. While these interruptions do
not substantially interfere with typical desktop print
30 jobs,
AMIENDED SHEE?
CA 02218984 1997-10-22
WO 96/3558=t PCT/US96104943
4
they do interfere with commercial printing of
continuous webs. In this regard, conventional ink jet
print heads have been found to require cleaning for
every ~D to ~D minutes of continuous printing.
Remote cleaning stations for ink jet printers are
undesirable for commercial continuous printers
because the print operation must be interrupted every
one-foaff hour to one hour to clean the nozzles.
Accordingly, there is a long-felt need for an apparatus
and method for cleaning an ink jet nozzle without
interrupting a print job.
Other prior art techniques for cleaning the nozzle
face of an ink printer are to blow air at or around the
l~ ink nozzles to blow particles ofF the nozzle face or
prevent particles from adhering to the nozzle face.
Some of these techniques have included using ionized
air to neutralize the static charges on dust particles
that attract the dust to the nozzles. These techniques
have achieved only partial success as is reported in
U.S. Patent No. 4,4'I '1 ,7Oo, entitled "Method And
Apparatus For ~(iminating Dust From Ink Jet Printers."
While blowing air at the nozzles can_be accomplished
as the nozzles are spraying ink, the turbulent air flow
caused by the prior art blowers disrupts the trajectory
of the ink droplets to the paper. Given that the prior
systems for cleaning ink jet nozzles have been lass
than satisfactory, there f-gas been a Long felt-need for a
CA 02218984 1997-10-22
WO 96/35584 PCTIUS96I04943
S
technique for effectively cleaning the nozzles. That
' need was not fully satisfied until the current invention.
Tf-~e current invention relates to a tecf-inique for
~ cleaning an ink jet nozzle with a fluid, such as water or
air, that flows across the face of the printing nozzle
and entrains the dust and paper particles that adhere=_
to the face of the nozzle. Once caught in the fluid, them
particles are removed from the nozzles by the flow of
the fluid.
fn one embodiment of the invention, a fluid stream
flows across the face of the nozzle of an ink jet printer,
to clean the printer. This stream is located proximate=
l~ to the nozzle array from which the ink droplets are
propelled. Dust and paper particles that would
otherwise clog the nozzle array are entrained in the
fluid stream before they obstruct the orifices of the
nozzle. A fluid source, drain supply fluid and network of
fluid channels on the nozzle create a fluid stream patf
adapted to remove the particles and dust in the vicinity
of the nozzle array. By continuously flowing fluid across
the nozzle face, ink, grit and paper particles are
continuously captured and removed from the nozzle
array. In some embodiments, the fluid stream does
not disrupt the projection of ink droplets from the
nozzle array and, thus, does not interfere with printing.
CA 02218984 1997-10-22
WO 96/35584 PCT/US96104943
f~
In a first embodiment of the invention, the
cleaning fluid is confined to channels adjacent the
nozzle orifices. The orifices are not flushed with fluid.
Accordingly, the ink jet nozzle can print while the
cleaning fluid is flowing because the fluid flow does not
obstruct or interfere with the ink droplets ejected
from the nozzles to the paper. Accordingly, the first
embodiment of the current invention provides a
. technique and apparatus for continually removing
particles from an ink jet printer face while printing
continues.
In a second embodiment of the invention, cleaning
fluid flows directly over the print nozzle orifices to wash
1~ the orifices and nozzle in general. Printing is
interrupted while the orifices are washed using the
second embodiment. This orince wash embodiment of
the invention flushes out any ink residue, dust or paper
fibers clogging the orinces. Ti-ius, the second
embodiment provides a more thorough cleaning of the
print nozzle than does the first embodiment. The
second embodiment of the invention may be used in
conjunction with the first embodiment.
In a third embodiment of the invention, the array
of nozzle orifices is shielded from ink spray and splatter
by a nozzle plate. The nozzle plate is positioned in front
of the orifices and includes a narrow slit through which
CA 02218984 2005-07-13
51269-137
7
ink droplets fly. The nozzle plate is separated by a small
gap from the array of nozzle orifices and excess ink drains
through this gap away from the nozzle orifices. This third
embodiment may be used in conjunction with the first and
second embodiments of the invention.
Thus, in a broad aspect, the invention provides an
ink jet printer head comprising: a. an array of nozzle
orifices through which ink droplets are projected in a path
towards a substrate for printing and a front surface of said
array of nozzle orifices having channels passing between the
orifices; b. a nozzle plate disposed between said array of
nozzle orifices and the substrate and separated by a gap
from the array, said nozzle plate having a slit aligned with
respect to the path to allow the ink droplets to fly through
the slit; and c. a liquid cleaning fluid stream flowing in
the channels of the front surface, and through the gap
between the nozzle plate and array of nozzle orifices,
wherein said liquid fluid stream flows while ink droplets
are being projected from the nozzle orifices during
printing.
In another aspect, the invention provides an ink
jet printer comprising: a. an ink jet printer head having a
front surface and an array of nozzle orifices arranged on
the front surface, wherein ink droplets are projected
through the orifices along a path towards a substrate; b. a
bracket having a recess adapted to receive the ink jet
printer head; c. a mounting plate removably attached to said
bracket and securing said ink jet printer head in the
recess, said mounting plate having an opening into which
projects the front surface of the ink jet printer heads;
d. a nozzle plate attached to said mounting plate and
covering the opening in the mounting plate and separated by
a gap from the front surface the ink jet printer head,
, CA 02218984 2005-07-13
51269-137
7a
wherein said nozzle plate having a slit aligned with the
array of nozzle orifices and through which pass ink jet
droplets on their path, and e. liquid cleaning fluid stream
flowing in the gap between the nozzle plate and front
surface of the printer head, wherein said liquid fluid
stream flows adjacent to the nozzle orifices while ink
droplets are projected from the nozzle orifices to the
substrate.
In another aspect, the invention provides a method
for cleaning an ink jet printing head having a front surface
with a nozzle array of orifices, and a nozzle plate
separated by a gap from the front surface of the printing
head, the method comprising the following steps:
a. propelling ink from the nozzle array through a slit in
the nozzle plate and towards a web for printing on the web;
b. shielding the orifices from ink splatter and airborne
fibers and particles with the nozzle plate; c. washing the
front surface of the printing head with a liquid fluid
stream while propelling ink during step (a), and d. draining
the liquid fluid stream and excess ink on the nozzle array
down through the gap between the front surface of the
printing head and nozzle plate.
CA 02218984 2005-07-13
51269-137
7b
An object of the current invention is to clean the
nozzle array of an ink jet printer and prevent ink, dirt
and paper particles from obstructing the orinces of
the nozzle array. It is a further object of the invention
to continually capture and remove ink and particles
from the nozzle array while the nozzles are printing and
to wash the nozzles completely at other times. A
further object of the invention is to extend the period
of maintenance Free printing for ink jet printers and to
reduce the frequency of ofr print cleaning occurrences
required for ink jet printers. Moreover, another
objective of the invention is to enhance the print quality
of ink jet printers by overcoming many of the problems
caused by extraneous, girt and paper particles that
I ~ have clogged prior ink jet printers. These and other
objectives are achieved by the invention that is shown
and described in detail below.
CA 02218984 1997-10-22
WO 96/35584 PCT/US96/04943
8
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be explained in greater detail
with reference to the drawings identified as follows:
FIGURE 'I is a cross-sectional view of an ink jet
printer head with an associated fluid cleaning
mechanisms, forming a nrst embodiment of the
invention;
FIGURE 2 is a front view of the face of the ink jet
printer head shown in Figure 'I , and
F=LURES ~ and 4 show cross-sectional and front
1~ views, respectfully, of another embodiment of the
invention;
F=ICURI= ~ shows a front view of a further
embodiment of the invention, and
FIGURES ~ and 7 show a front view of yet
another embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure '1 shows an ink jet printer head '1 O
mounted as a carriage on a shaft 'I 2 in a printing
mechanism. In particular, the printing mechanism may
CA 02218984 1997-10-22
WU 96!35584 PCTIUS96I04943
'
be an otherwise conventional continuous web-feed
printer, for high volume computer printing. It is
common for the web speed in such printers to be OOO
feet per minute and have an operating speed range of
~ 200 to SOO web-feet per minute. In addition, these
printers operate continuously and will typically print for'
periods as long as twelve hours without interruption,
provided that the ink jet printer does not require
cleaning in that period.
The paper or other web substrate moves as a
web '1 4 in the direction of arrow 'I S. The web moves
across the surface of a platen 'I B adjacent the printer
head. The platen positions the web for printing directly
l~ in front of and generally parallel to tf-~e ink jet printer
head. The printing mechanism may include
conventional web handling devices [not shown], e.g.,
tractor feeders, to move the web at a predetermined
speed, in a precisely controlled fashion and along a
predetermined path. The ink jet printer head is
attached to the shaft by a bracket 'I 7 such that the
printer head may be fixed in position on the shaft and
arranged in an array with other printer heads uniformly
spaced across the width of the web. Alternatively, the
printer head may be slidably mounted on the shaft, and
moved back and forth across the shaft in a controlled
fashion during printing, to position the printer head
with respect to the moving web. The bracket may also
CA 02218984 1997-10-22
WO 96!35584 PCT/US96/04943
'I O
includes fins 'I 8 that dissipate heat away from the ink
jet printer head. A thermocouple may be attached to
the root of a heat fin to sense the temperature of the
printer head. The bracket may be formed of aluminum
or any other material that is suitable for securely
holding the ink jet nozzle assembly.
The ink jet nozzle assembly includes a mounting
plate 'I J on the front face of the print head bracket
'1 7. The mounting plate holds the print head in a
recess 2O of the bracket. The plate overlaps the
bracket recess and is removably attached to the
bracket by screws or other fastening devices. The
mounting plate includes a rectangular slot 2'I through
1~ which protrudes the front nose 2~ of the printer head.
The array of nozzle orinces 2~ are located on the front
surface of the nose of the print head. The mounting
plate may be made of machined copper and coated
with a hydrophilic coating, e.g. Teflon, at and near the
area of the orifices 2~ to reduce the tendency of
excess ink to clog the orifices.
A nozzle plate 24 overlaps the.mounting plate and
the nose of the print head. The nozzle plate is
attached to the mounting plate or bracket by screws
or other fastening device. A seal 2S may be located
between the nozzle plate and mounting plate prevents
cleaning fluid from leaking out from the gap between
CA 02218984 1997-10-22
WO 96/35584 PCTIUS96104943
the two plates. In addition, the nozzle plate includes a
narrow slit 28 aligned with the array of orifice nozzles
23 in the print head to allow ink droplets to fly from the
orifices, through the slit 28 and towards the paper
web 'I 4. The slit is in alignment with the array of orifice
nozzles. In addition, the slit has an opening area that is
just slightly larger than the area of the nozzle array.
The nozzle plate partially shields the nozzle array from
the splash of ink hitting the paper web. The nozzle
plate may be formed of a pores material so that ink
splattered onto the nozzle plate can be drawn through
the plate and into the gap between the back of tf-re
nozzle plate and the mounting plate.
The nozzle plate shields the printer head from the=_
splatter of ink droplets as they impact on the paper
web. lnk spray collects on the outer face of the nozzle
plate instead of splashing back onto the nozzle array.
In addition, ink that does seep into the gap 40 between
?0 the mounting and nozzle plate is shielded from paper
and web fibers and other particles that tend to be
attracted to surfaces wetted with ink. The ink that
does collect on the nozzle surface 48 of the printer
head does not collect web fibers and other particles
?5 because of tine nozzle plate. It is believed that the
presence of the nozzle plate alone can extend to
several hours [opposed to O.S to 'I .S hours] the period
CA 02218984 1997-10-22
WO 96/35584 PCT/US96/04943
of time during which a print head nozzle can reliably and
continuously print between cleanings. ,
Ink droplets 27 are propelled from the nozzle
orifices ~~ in a direction towards the paper web 'I 4 for
printing. As the ink droplets impact on the web, most
of the ink remains on the web as dots ~O, or other
indicia. Some of the ink will splatter as it hits the paper
and form a mist of ink particles ~2. In addition, there
will be some residue of ink mist resulting from the
ejection of the ink droplets from the nozzle orifices.
This ink mist floats in the vicinity of the nozzle plate,
print head nose 22 and paper web, and tends to settle
on these surfaces, as an ink coating 34 that builds in
I~ thickness a' ink printing continues. Since the paper
web is moving, there is no noticeable build-up on any
one section of the web. The print head does not move.
Accordingly, the ink build up on the print head surfaces
can pose problems, that are solved by the current
invention.
The impact of the ink droplets, movement of the
paper web and other factors cause paper fibers and
other nne particles ~~ to dislodge from the web and
2~ other surfaces and float in the ink mist. In addition to
the build-up of ink around the nozzle caused by the
misting of the ink, some of these particles contribute
to tl-~e build-up ~4 of ink and particles in tF-~e vicinity of
CA 02218984 1997-10-22
WO 96/35554 PCTlUS96104943
~8
the ink-jet nozzles. If this build-up is permitted to
continue without being removed by cleaning, the build-
up will clog the nozzle orifices 28 and disrupt printing of
the ink. While the nozzle plate shields the print head
from much of the ink spray and stray particles, the
nozzle plate does not entirety avoid the need to wipe
clean the array of nozzle orifices. The current
invention also includes a technique for removing ink and
particle build-up surrounding the nozzle orifices while
printing continues.
It has been found that by filushing a fluid, such as
water or air, across the face of the nose 2~ of the
print head, that the ink and particles coating the nozzles
1~ array can be washed away. In one embodiment, water
is supplied to the gap 40 between the mounting plate
'I J and nozzle plate 24 from a water source via conduirt;
42 that passes through the bracket '1 7 and mounting
plate and discharges from an relatively wide opening[s]
44 on the front surface of the mounting plate. Fluid
discharged from these openings enters the gap 40
between the mounting and nozzle plates and flows
downwardly, as indicated by arrow 48, between those
plates and towards the nose 22 of the print head. As
" ?5 the fluid reaches the print head nose 22, it wets and
flows over the front surface 48 of that nose. In doing
so, ink, web fibers and particles coating the front
surface of the nose are washed away with the fluid.
CA 02218984 1997-10-22
WO 96/3558=1 PCT/US96/04943
'I 4
The fluid with the ink, fibers and other particles
flows downward through the gap between the
mounting and nozzle plates until reaching a suction
opening SO in the mounting plate. Due to a slight
suction applied at that opening, the fluid is drawn into
the opening and away through conduits S2 to a
discharge [not shown). The fluid, if water or other
liquid, may be disposed of or filtered and recycled
through the printer. Alternatively, the fluid drawn by
suction into the suction opening SO may be just the
excess ink in the gap 40 between the mounting and
nozzle plates. The suction of fluid will create capillary
farces in the gap that draw the ink downward through
the gap to the suction opening and away from the
1~ nozzle array. In this alternative embodiment, a
separate source of fluid, supply conduits 42 and fluid
discharge openings 44 above the printer head are
unnecessary, because the excess ink is itself used as
the cleaning fluid.
If a washing fluid, such as distilled water, is
supplied, then printing may have to be interrupted or
may continue while the fluid washes the front surface
48 of the nozzle, depending on the flow path of fluid
across the face of the nozzle array. If the flow of fluid is
heavy across the entire nozzle array, then the fluid will
wash across the orifices 28. While such a heavy flow is
particularly effective at cleaning clogged print orifices,
CA 02218984 1997-10-22
WO 96/35584 PCTIUS96lOd9d3
S
the fluid would interfere with the projection of ink
'' droplets and, thus, printing may be interrupted or
even stopped for heavy flows of cleaning fluid.
Alternatively, a fighter flow of fluid confined to channels
S4 on the mounting plate and/or front surface 4i~ of
the nozzle may be used while printing continues
because the channels do not cut across any of the
print orifices thereby interfering with the ink flow.
>=xcess ink, fibers and other particles can be attracted
to these channels by coating the channels and
surfaces near the channels with hydrophilic coatings.
Ti-~e fluid in tf-~e channels carries the ink, fibers and
other particles away from the front surface of the
nozzle array and to the suction opening SO.
1~
In another alternative embodiment, such as
shown in FIGURES ~ and 4, [the same numerals from
figures 'I and 2 have been used in these figures to
refer to features that era common to all figures], the
single filuid path of the first embodiment has been
changed to a dual-path fluid system for cleaning away
excess ink, paper fibers and other particles. This dual-
path fluid wash is intended for use while the print head
is not printing, as the wash might interfere with the
2~ printing operation. A pair of fluid conduits 60, E2
extend through a top portion of the .print head bracke=t
'I 7 from a pair of outlets E=4 to a fluid source [not
shown] to first and second fluid discharge ports, ~~,
CA 02218984 2005-07-13
51269-137
1B
6B, respectively. In this embodiment, the nozzle plate
is attached directly to the mounting plate by means of
screws 74 or other attachment means.
T he first discharge part E6 opens from the
brack=_t'1 7 out to a gap 70 between the nozzle plate
24 and a front surface section 72 of the bracket and
print head, which section includes the front surface of
the nozzle 46. Fluid flows downwardly through this
gap until it passes over the orinces '3 of the nozzle
array. Below the nozzle array, the front surface of the
print head drops back along an inclined section 74 until
it meets with another vertical section 76 that ends at
the suction opening Sp for the bracket. The inclined
1~ surface widens the gap 70 into a relatively-large
reservoir 78 which collects the fluid, excess ink, web
fibers and other accumulated particles. Fluid flows
downwardly into the reservoir and is drawn by capillary
forces into the suction opening EO of the bracket.
Similarly, the second fluid conduit 60 carries fluid
to ti-~e second discharge port 66, that may constitute
a row of openings as shown in Figure 4, through which
the quid exits to the surface 80 of the nozzle plate 1 J.
The fluid wets and washes the front surface of the
nozzl=_ plate as the fluid flows down.and across the
surface of the plate. At the slit 2fl in nozzle plate 24,
portions of the fluid may flow around, over and into the
CA 02218984 1997-10-22
WO 96/35584 PCTIUS96104943
slit. The fluid that flows around and over the slit,
washes away ink and particles that have collected on
the plate. This outer path fluid, ink and particle mixture
continues its downward flow over the nozzle plate
~ [surface tension holds the fluid stream onto the plate
surface] until the fluid is drawn into an opening 82 in
the nozzle plate in communication with the suction
opening SO of the bracket. Fluid that is drawn into the
slit 28, washes the slit and is drawn into the cavity ~8
between the nozzle plate and printer head, from where
the fluid, ink and particle mixture is drawn in by the
suction opening 80 of the bracket.
FI~U(~E S shows another embodiment of the
invention in which a pair of fluid streams 88, 88 flow
across the nozzle front surface 48 on either side of
the nozzle array 23 to clean ink from the surface 48
while printing is ongoing. This embodiment may be
employed with or without [as shown] a nozzle plate. A
pair of horizontal fluid conduits JO, 82 mounted on or
within the mounting plate '1 3 are connected to a fluid
source [represented by arrows J4] and discharge
from openings H8 adjacent the front surface 48 of the'
print head nozzle. Fluid from the discharge openings
2~ enter a pair of horizontal channels JB, 'I OD that are
parallel and on opposite sides of tf-Ze, nozzle array 28.
The channels and surfaces proximate the channels
and nozzle orifices may be coated with a hydrophobic
CA 02218984 1997-10-22
WO 96135584 PCT/US96/04943
'I 8
material so that ink will not be allowed to accumulate in
these areas and is drawn into the channels and
washed away by the channel flow. As the fluid in the
channel reaches the opposite end of the channel, the
fluid is drawn by suction into openings '1 02, '1 O4 on the
mounting plate. These openings are connected to
conduits '1 08, 'f 08 that are also connected to a drain
'I '1 O that imparts suction to the conduits and openings
'1 02, 'I 04 to draw the fluid through the channels.
FIGURES 8 and 7 show another embodiment of
the invention especially adapted to using air [or other
gas] as a cleaning fluid. An air bellows manifold 'I 'I 2,
such as a oval shaped funnel, provides a low-pressure
l~ air flow directed horizontally [Fig. 8) or vertically [Fig. 7)
across the front surface 48 of the nozzle array 28.
The bellows manifold is connected to a source of
compressed air [not shown]. The air flow pressure
blows on the ink wetted to the front surface of the
nozzle array and causes the ink [including entrained
fibers and other particles] to flow away from the
bellows 'I 'f 2 and towards a vacuum manifold 'I 'I 4, that
may have a shape similar to that of the bellows. The
vacuum manifold collects the ink flow and directs [sea
''S arrow 'I 1 8] towards a drain [not shown]. In addition,
the vacuum manifold may be connected to a vacuum
pump to draw air across the nozzle array and into the
manifold. Depending on whether the pressure of the
CA 02218984 1997-10-22
WO 96/35584 PCTlUS96104943
air flow across the nozzle array disrupts tf~e trajectory
of tf,e ink jet nozzles, the bellows and vacuum manifolds
may or may not be operated wf,ile printing is ongoing.
The invention has been described in what is
considered to be the most practical and preferred
embodiments. The invention is not limited to the
disclosed embodiments, but covers various
modifications and equivalent arrangements included
within tt~e spirit and scope of the appended claims.
