Recording substrate wave restrictor

An improved fusing apparatus including a baffle assembly having at least one member for imparting an arcuate-shaped profile in a sheet of recording substrate subsequent to the transport thereof through a fuser nip. The arcuate-shaped profile is imparted along a generally central axis of the recording substrate, substantially perpendicular to the path of movement thereof, providing lateral strength to the substrate for eliminating the formation of longitudinal waves therein.

The present invention relates generally to an electrostatographic printing 
machine, and more particularly concerns a fuser apparatus including a 
baffle assembly for preventing the formation of waves in a sheet of 
recording substrate transported through the fuser assembly. 
Generally, the process of electrostatographic copying is executed by 
exposing an optical image of an original document to a substantially 
uniformly charged photoreceptive member. Exposing an optical image to the 
charged photoreceptive member discharges the photoconductive surface 
thereof in areas corresponding to non-image segments in the original 
document, while maintaining charge on the photoreceptive member in image 
segments, thereby creating an electrostatic latent image of the original 
document on the photoreceptive member. This electrostatic latent image is 
subsequently developed into a visible image by a process in which a 
charged developing material is deposited onto the photoconductive surface 
of the photoreceptor such that the developing material is attracted to the 
charged image areas thereon. The developing material is then transferred 
from the photoreceptive member to a copy sheet on which the image may be 
permanently affixed to provide a reproduction of the original document. 
The final step in this process involves cleaning the photoconductive 
surface of the photoreceptive member to remove any residual developing 
materials therefrom in preparation for successive imaging cycles. 
The process used to produce multi-color electrophotographic copies is 
substantially similar to the process described above for black and white 
copies. However, multi-color electrophotographic printing further 
incorporates the creation of multiple latent images corresponding to 
different primary colors which are each recorded on the photoreceptive 
member and each developed with a developing material of a primary 
complimentary color. One known process for producing multi-color 
electrophotographic copies involves the superimposed transfer of each 
single color toner image to a sheet of recording substrate in perfect 
registration with one another to produce a multi-layered, multi-color 
toner image on the recording substrate. Thereafter, the multi-layered 
toner image is permanently affixed to the recording substrate to generate 
a multi-color copy of the original document. Finally, the recording 
substrate, having the fused toner image thereon, is transported to an 
output tray to provide a finished output document. 
The process of permanently affixing a toner image to a sheet of recording 
substrate is known as fusing. The fusing process permanently bonds, or 
fixes, the toner image to the recording substrate. Several methods are 
known in the art for accomplishing this goal, including: hot roll fusing; 
cold roll fusing; radiant fusing; and solvent fusing. Amongst hot roll 
fusing methods, it is well known to use various combinations of a heated 
fuser roll and a backup pressure roll configured to provide a fuser nip 
through which the recording substrate is passed. In order to permanently 
affix or fuse electroscopic toner material onto a sheet of recording 
substrate using heat, it is necessary to elevate the temperature of the 
toner material to a point at which the constituents of the toner material 
intermingle and become tacky. Thermal action also causes the toner 
material to be absorbed to some extent into the fibers or pores of the 
recording substrate. Thereafter, the toner material cools and solidifies 
to become bonded to the recording substrate. In a typical two-roll fusing 
apparatus, the fuser roll is coated with an adhesive material such as 
silicone rubber or other low surface energy elastomer, as for example, 
room temperature vocanizable silicones, high temperature vocanizable 
silicones, or liquid injection moldable silicone rubbers. The use of 
thermal energy for fixing toner images onto a recording substrate is old 
and well known in both the xerographic as well other electrostatographic 
recording arts. 
Despite the use of low surface energy materials in the fuser roll surface 
of thermal fusing devices, there is a tendency for the recording substrate 
to remain adhered to or tacked to the fuser roll after traveling through 
the fuser nip formed by the fuser roll and the backup pressure roll. As a 
result, the recording substrate does not follow the normal path through 
the nip but rather continues in an arcuate path with the fuser roll. It is 
common practice, therefore, to use one or more techniques to ensure that 
the recording substrate is appropriately separated from the fuser roll in 
accordance with proper product specifications. A common approach for 
inducing separation of the recording substrate is the use of a stripper 
finger or a plurality of stripper fingers which contact the fuser roll or 
the backup pressure roll to form a wedge therebetween. The approach of 
using stripper fingers has the effect of implanting a relatively smooth 
sloping surface between the leading edge of the recording substrate and 
the fuser nip so that the substrate becomes separated from the roll as it 
travels through the nip. Such stripper finger systems have been used 
successfully to ensure that the recording substrate proceeds along a 
predetermined path subsequent to the fuser nip, onto a conveyor or the 
like in order to exit the machine. 
For certain color applications, it has been found that prior art stripper 
finger systems are unsatisfactory to effect adequate post-fuser nip 
separation of the recording substrate. That is, during the 
electrostatographic printing process, the recording substrate is exposed 
to many stress forces such as high temperature and pressure, as well as 
intensified energy levels required to achieve multi-toner layer transfer. 
Moreover multi-color process involve higher toner transfer mass and 
increased dwell time in the fuser nip relative to comparable black and 
white copying systems. 
The strength of the recording substrate is at its weakest immediately 
following the fuser nip. It has been found that distortions are created in 
the recording substrate if the recording substrate is not permitted to 
exit and cool after passing through the fuser nip in some manner 
consistent with the strains induced thereon. Thus, handling and processing 
of the recording substrate immediately following the fuser nip is 
critical. 
One type of distortion that has been observed in multi-color 
electrostatographic applications is the appearance of waves along a 
longitudinal path parallel to the leading edge of the recording substrate. 
Such waves appear as a ripple undulating across the entire length of the 
paper path. This problem is more prevalent in high relative humidity 
conditions and becomes more prominent when relatively lighter weight paper 
is used as the recording substrate. It has been found that applying 
pressure to the recording substrate as it exits the fuser nip such that 
the central axis of the recording substrate is forced upward relative to 
inboard and outboard edges thereof, imparting an arcuate profile therein, 
eliminates the formation of waves. Accordingly, the primary object of this 
invention is to provide a post fuser nip apparatus for imparting an 
arcuate profile into the recording substrate and to further sustain this 
arcuate profile for a short cooling period after the substrate passes 
through the nip to eliminate the formation of waves therein during the 
fusing process. 
The following disclosures may be relevant to various aspects of the present 
invention: 
U.S. Pat. No. 4,028,050 
Patentee: Bar-on 
Issued: Jun. 7,1977 
U.S. Pat. No. 4,771,310 
Patentee: Leo et al. 
Issued: Sep. 13, 1988 
U.S. Pat. No. 4,929,983 
Patentee: Barton et al. 
Issued: May 29, 1990 
The relevant portions of the foregoing disclosures may be briefly 
summarized as follows: 
U.S. Pat. No. 4,028,050 discloses an apparatus for stripping copy sheets 
from a heated fuser member in a xerographic copier. The apparatus 
comprises a plurality of stripper fingers and a combination support and 
bias means therefor, wherein the support and bias means includes a unitary 
member coupled to each stripper finger constituting an integral assembly. 
Each integral assembly is fixedly supported adjacent the fuser member so 
that the leading edge of each stripper finger engages with the fuser 
member to strip the copy sheet therefrom. 
U.S. Pat. No. 4,771,310 discloses a stripper finger mechanism for 
separating recording sheets from the surface of a roll member. A plurality 
of flexible stripper fingers are arranged such that the finger ends are 
angled against a fuser roller surface to effect initial separation of a 
fused copy sheet therefrom. Each stripper finger includes a generally 
centrally located raised edge for providing a gradually sloping support to 
lift the fused copy sheet following initial separation from the fuser roll 
surface. 
U.S. Pat. No. 4,929,983 discloses a stripper for separating a print 
substrate from a fuser member in an electrostatographic printing machine. 
The stripper includes a substantially flat, resiliently flexible, 
finger-like member having a raised dimple-like bump adjacent one end 
thereof for contacting the print substrate once stripped from the fuser 
member. That patent does not contemplate nor address the problem of waves 
formed in a recording substrate during multi-color electrostatographic 
printing. 
In accordance with one aspect of the present invention, an apparatus for 
preventing the formation of waves in a sheet substrate is provided, 
wherein an assembly including a pair of roll members forming a nip for 
transporting the sheet substrate along a path of movement therethrough is 
further provided with an element for imparting an arcuate-shaped profile 
in the sheet substrate along a generally central axis substantially 
perpendicular to the path of movement of the sheet substrate subsequent to 
the transport thereof through the nip. 
In accordance with another aspect of the invention, a fusing apparatus for 
affixing a toner image onto a recording substrate is provided, wherein a 
pair of roll members, including at least one heated roll member, forms a 
nip therebetween for transporting the substrate along a path of movement 
therethrough. The fusing apparatus further includes an element for 
preventing the formation of waves in a sheet substrate comprising a member 
for imparting an arcuate-shaped profile in the substrate along a generally 
central axis substantially perpendicular to the path of movement of the 
substrate subsequent to the transport thereof through the nip. 
In yet another aspect of the invention, an electrostatographic printing 
apparatus including a fuser apparatus having a heated fuser roll and a 
backup pressure roll forming a fuser nip therebetween is provided with a 
baffle assembly supported transversely adjacent the fuser nip for 
receiving the sheet substrate subsequent to the transport thereof through 
the fuser nip. The fuser apparatus further includes means, mounted to the 
baffle assembly, for imparting an arcuate-shaped profile in the sheet 
substrate along a generally central axis substantially perpendicular to 
the path of movement thereof.

For a general understanding of the features of the present invention, 
reference is made to the drawings wherein like reference numerals have 
been used throughout to designate identical elements. While the present 
invention will be described in connection with a preferred embodiment 
thereof, it will understood that it is not intended that the invention be 
limited to this preferred embodiment. On the contrary, the present 
invention is intended to cover all alternatives, modifications, and 
equivalents as may be included within the spirit and scope of the 
invention as defined by the appended claims. 
Referring initially to FIG. 4 before describing the specific features of 
the present invention, a schematic depiction of the various components of 
an exemplary multi-color electrophotographic reproducing apparatus 
incorporating the fuser apparatus of the present invention is provided. 
Although the apparatus of the present invention is particularly well 
adapted for use in an automatic multi-color electrophotographic 
reproducing machine, it will become apparent from the following discussion 
that the present fuser apparatus is equally well-suited for use in a wide 
variety of electrostatographic processing machines as well as various 
other systems requiring transport of a sheet substrate through a nip. 
Thus, it will be appreciated that the invention described in detail herein 
is not necessarily limited in its application to the particular embodiment 
or embodiments shown. 
Inasmuch as the art of electrophotographic printing is well known, the 
various processing stations employed in FIG. 4 will be shown schematically 
and their operation described briefly with reference thereto. The 
exemplary electrophotographic reproducing apparatus illustrated in FIG. 4 
shows a multi-color electroreprographic printing machine wherein a 
multi-color original document 38 is positioned on a raster input scanner 
(RIS), indicated generally be reference numeral 10. The RIS 10 contains 
document illumination lamps, optics, a mechanical scanning drive, and at 
least one charge coupled device or CCD array coupled together in a system 
for capturing the entire multi-color image of the original document 38 and 
for converting the image to a series of raster scan lines having a set of 
primary color density information, i.e. red, green and blue densities, for 
each point in the original document. 
The information developed by RIS 10 is transmitted to an image processing 
system (IPS), indicated generally by the reference numeral 12. IPS 12 
converts the set of density information to a set of colorimetric 
coordinate signals and manages the image data flow to a raster output 
scanner (ROS), indicated generally by the reference numeral 16. A user 
interface (UI), indicated generally by the reference numeral 14, is 
coupled to IPS 12 for communication therewith, enabling an operator to 
control various operator adjustable functions. UI 14 may be a touch 
screen, or any other suitable control panel which provides a machine 
operator with the capability to adjust selective parameters of the copy or 
print. 
ROS 16 includes a laser with rotating polygon mirror blocks. Preferably, a 
nine facet polygon is used to produce a flowing light image of the 
original document in a non-distorted manner. The ROS 16 illuminates, via 
mirror 37, the charged portion of a photoconductive belt 20 of a printer 
or marking engine, indicated generally by the reference numeral 18, at a 
rate of about 400 pixels per inch. 
The photoconductive belt 20 is preferably fabricated from a photoconductive 
material coated on a grounding layer, which, in turn, is coated on an 
anti-curl backing layer. The photoconductive material is made from a 
transport layer coated on a generator layer. The transport layer 
transports positive charges from the generator layer which is coated on a 
very thin grounding layer which allows light to pass therethrough. The 
transport layer contains molecules of di-m-tolydiphenylbiphenyldiamine 
dispersed in a polycarbonate while the generation layer is made from 
trigonal selenium and the grounding layer is made from a titanium coated 
Mylar. The grounding layer is very thin and allows light to pass 
therethrough. It will be appreciated by one of skill in the art that 
various other suitable photoconductive materials, grounding layers, and 
anti-curl backing layers may also be employed. 
With continued reference to FIG. 4, the printer or marking engine 18 of the 
present multi-color electronic reprographic printing system is an 
electrophotographic printing machine. In the exemplary marking engine, 
photoconductive belt 20, moves in the direction of arrow 22 to advance the 
photoconductive surface thereof through various successive processing 
stations disposed about the path of movement thereof. Photoconductive belt 
20 is entrained about rotatably mounted transfer rollers 24 and 26, 
tension roller 28, and drive roller 30. Drive roller 30 is rotated by a 
motor 32 coupled thereto by any suitable means such as a belt drive, so as 
to advance belt 20. 
Initially, a portion of photoconductive belt 20 passes through a charging 
station, indicated generally by the reference letter A. At charging 
station A, a corona generating device 34 charges photoconductive belt 20 
to a relatively high, substantially uniform potential. A plurality of 
corona generating devices may also be used for this operation. 
Once charged, the photoconductive belt 20 is advanced to an exposure 
station, indicated generally by reference letter B, where a modulated 
light beam corresponding to information derived by RIS 10 is transmitted 
onto the photoconductive surface. The modulated light beam illuminates 
selective portions of the photoconductive surface to form an electrostatic 
latent image of the original multi-color document on the photoconductive 
surface of belt 20. The photoconductive belt 20 is exposed at least three 
times to record at least three latent images thereon corresponding to the 
complementary primary colors in the original multi-color document. 
After the electrostatic latent images have been recorded on photoconductive 
belt 20, the belt 20 advances to a development station, indicated 
generally by C. Development station C comprises a magnetic brush 
development system including four individual developer units indicated by 
reference numerals 40, 42, 44 and 46. The developer units are of a type 
generally referred to in the art as "magnetic brush development units" 
used for depositing developing material onto the electrostatic latent 
image. 
A typical magnetic brush development system employs a magnetizable 
developer material including magnetic carrier granules having toner 
particles adhering triboelectrically thereto. The developer material is 
continually brought through a directional flux field to form a brush of 
developer material. In each developer unit, developer material is 
constantly mixed so as to continually provide a magnetic roll brush with 
fresh developer material such that the magnetic roll brush having 
developer material thereon is brought into contact with the 
photoconductive surface of photoconductive belt 20. In order to achieve 
multi-color development, developer units 40, 42, and 44, respectively, 
apply toner particles of a specific color corresponding to the compliment 
of the specific color separated electrostatic latent image recorded on the 
photoconductive surface. The color of the toner particles in each 
developer unit is adapted to absorb light within a predetermined spectral 
region of the electromagnetic wave spectrum. For example, an electrostatic 
latent image formed by discharging the portions of charge on the 
photoconductive belt 20 corresponding to the green regions of the original 
document 38 will record the red and blue portions as areas of relatively 
high charge density on photoconductive belt 20, while the green areas will 
be reduced to a voltage level ineffective for development. A visible image 
is then developed on the charged areas by having developer unit 40 apply 
green absorbing (magenta) toner particles onto the electrostatic latent 
image recorded on photoconductive belt 20. Similarly, a blue separation is 
developed by developer unit 42 with blue absorbing (yellow) toner 
particles, and the red separation is developed by developer unit 44 with 
red absorbing (cyan) toner particles. Developer unit 46 contains black 
toner particles and may be used to develop the black electrostatic latent 
image areas formed from a color or black and white original document. 
Each of the developer units is moved into and out of an operative position 
to develop the latent image on belt 20. In the operative position, the 
magnetic brush is positioned substantially adjacent the photoconductive 
belt, while in the non-operative position, the magnetic brush is spaced 
therefrom. In FIG. 4, developer unit 40 is shown in the operative position 
with developer units 42, 44 and 46 being in the non-operative position. 
During development of each electrostatic latent image, only one developer 
unit is in the operative position, while the remaining developer units are 
maintained in the non-operative position. This insures that each 
electrostatic latent image is developed with toner particles of the 
appropriate color without the commingling of developer materials of 
different colors. 
After development, the toner image on photoconductive belt 20 is moved to a 
transfer station, indicated generally by the reference letter D. The 
transfer station D includes a transfer zone, generally indicated by 
reference numeral 64, where the toner image is transferred from the 
photoconductive belt 20 to a recording substrate, such as plain paper or 
other various sheet support materials. The transfer station D further 
includes a transport apparatus, indicated generally by the reference 
numeral 48, for transporting the recording substrate into contact with 
photoconductive belt 20. 
Transport apparatus 48 includes a pair of spaced belts 54 entrained about a 
pair of substantially cylindrical rollers 50 and 52. A gripping apparatus 
(not shown) extends between belts 54 and moves in unison therewith to 
advance a sheet of recording substrate 56 delivered to the gripping 
apparatus from a stack of sheets disposed on a tray 57. A friction feed 
roll 58 advances the uppermost sheet from the stack in tray 57 onto a 
pre-transfer transport 60, which, in turn, advances the sheet of recording 
substrate 56 to sheet transport 48 in synchronism with the movement of the 
gripping apparatus. In this way, the recording substrate 56 arrives at a 
preselected position, namely a loading zone, to be received by the open 
gripping apparatus which secures the sheet of recording substrate thereto 
for transport through a recirculating path. The sheet 56 is thereby placed 
into contact with the photoconductive belt 20, as belts 54 move in the 
direction of arrow 62 in synchronism with the developed toner image on the 
photoconductive belt 20. Thus, the gripping apparatus described 
hereinabove enables each of the appropriately developed electrostatic 
latent images recorded on the photoconductive surface to be transferred to 
the recording substrate in superimposed registration with one another, 
forming a multi-color copy of the colored original document. 
At transfer zone 64, a corona generating device 66 sprays ions onto the 
backside of the recording substrate to induce a charge thereon at a proper 
magnitude and polarity for attracting the toner image from photoconductive 
belt 20. The recording substrate remains secured to the gripping apparatus 
moving in a recirculating path for three cycles such that each different 
color toner image is transferred to the recording substrate in 
superimposed registration with one another. One skilled in the art will 
appreciate that the sheet may move in a recirculating path for four or 
more cycles if desirable such as when under color black removal is used. 
After the last transfer operation, the sheet transport system 48 directs 
the recording substrate to a vacuum conveyor 68 for transporting the 
recording substrate in the direction of arrow 70 to a fusing station, 
indicated generally by the reference letter E. The fusing station includes 
a heated fuser roll 74 and a backup pressure roll 72 forming a fuser nip 
71 therebetween. The sheet of recording substrate 56 passes through the 
fuser nip 71 so that the toner image on the recording substrate 56 
contacts fuser roll 74 to be affixed to the recording substrate 56. 
Thereafter, the recording substrate 56 is advanced through a baffle 
assembly 73 to a pair of rolls 76 for transporting the final output 
document to a catch tray 78 to be removed by a machine operator. 
The last processing station in the direction of movement of belt 20 is a 
cleaning station, indicated generally by the reference letter F. A 
rotatably mounted fibrous brush 80 is positioned in the cleaning station A 
and maintained in contact with photoconductive belt 20 to remove residual 
toner particles remaining after the transfer operation. Thereafter, lamp 
82 illuminates photoconductive belt 20 to remove any residual charge 
remaining thereon prior to the start of the next successive print or copy 
cycle. 
In summary, the ROS 16 exposes the photoconductive belt 20 to record a set 
of subtractive primary latent images thereon, corresponding to the signals 
transmitted from IPS 12. One latent image is developed with cyan developer 
material, another is developed with magenta developer material, and the 
third latent image is developed with yellow developer material. These 
developed images are transferred to a recording substrate such as paper or 
vellum in superimposed registration with one another to form a 
multi-colored image thereon. This multi-colored image is then fused to the 
recording substrate to form a color output document. The foregoing 
description should be sufficient for the purposes of the present 
application for patent to illustrate the general application of a 
multi-color electrophotographic printing apparatus incorporating the 
features of the present invention. As described, an electrophotographic 
printing apparatus may take the form of any of several well known devices 
or systems. Variations of specific electrostatographic processing 
subsystems or processes may be expected without effecting the operation of 
the present invention. 
Moving now to FIGS. 1-3, the particular features of the fuser apparatus 
including the improved baffle assembly of the present invention will be 
described in greater detail. As shown in FIG. 1, the fuser assembly 
comprises a heated fuser roll 74 and a backup pressure roll 72 which 
cooperate to form a fuser nip 71 therebetween through which a sheet of 
recording substrate 56 having toner images thereon passes. 
The fuser roll 74 comprises a core 82 having a thin layer 81 of an 
elastomer coated thereon. The core 82 may be made of various metals such 
as iron, aluminum, nickel, stainless steel, etc., as well as various 
synthetic resins. The core 82 is a hollow cylinder having a heating 
element 84 disposed therein, generally along the axis thereof to supply 
thermal energy for the fusing operation. Heating elements suitable for 
this purpose are known in the art and may comprise a quartz heater having 
a quartz envelope and a Tungsten resistance heating element disposed 
internal thereto. Heating means sufficient for providing heat in the 
fusing operation of the present invention are well known in the art and 
will not be described in detail herein. 
The backup pressure roll 72 comprises a metal core 86 having a layer 85 of 
heat resistant material thereon. The backup pressure roll 72 may comprise 
any suitable construction, for example, a steel cylinder, but preferably 
comprises a rigid steel core or shaft having a Viton elastomer surface or 
layer disposed thereover and affixed thereto. The backup pressure roll 72 
further includes a shaft end 89 located at either end thereof, for being 
received by a mounting bearing 88 to rotatably support the backup pressure 
roll 72. A suitable backup pressure roll 72 has an overall diameter of 
approximately 1.55 inches including a 0.1 inch cover layer of Viton 
elastomer or other suitable high temperature elastomeric material, for 
example, fluorosilicone or silicone rubber. The specific dimensions of the 
backup pressure roll 72 will be dictated by the requirements of the 
particular system in which the fuser apparatus is employed. Since it is 
contemplated that the electrostatographic printing machine in which the 
present fuser apparatus is utilized will have the capability of accepting 
and processing recording substrates of varying lengths, the length of 
either roll 72, 74 is approximately 15.5 inches, for accommodating various 
sizes of recording substrates. The dimensions of the recording substrate, 
of course, will be dictated by the size of the original input information 
recorded on the photoconductive surface. 
A pair of mounting brackets 90 located at either end of the backup pressure 
roll 72 are provided for supporting the backup pressure roll 72 and baffle 
member 73 in the electrostatographic printing machine. Each mounting 
bracket 90 further provides a support surface for baffle member 73 
comprising an arcuate plate positioned substantially adjacent to the fuser 
nip 71. Baffle member 73 supports the recording substrate 56 as it passes 
through the nip 71 and directs the recording substrate 56 on a path toward 
the conveyor assembly 76 which transports the recording substrate 56 out 
of the machine. To this end, the baffle member 73 includes a plurality of 
protruding rib elements 75 protruding from the surface thereof and 
interspaced along the length thereof. 
The baffle assembly of the present invention further includes a wedge-like 
member 102 positioned generally along the center of the fuser nip 71 
having a sloped contact surface 104 for contacting the lead edge of the 
recording substrate after it travels out of the fuser nip 71 and a raised 
support surface 103 for exerting upward pressure against the sheet of 
recording substrate 56. In a preferred embodiment, the baffle member 73 
includes at least one slot 98 for receiving the wedge-like member 102. The 
wedge-like member 102 includes a semi-circular segment for mounting onto a 
support bar 96 secured between mounting brackets 90 behind baffle member 
73. This configuration provides a cantilevered mounting assembly for 
supporting the wedge-like member 102 and engaging the wedge-like member 
102 into contact with the surface of the backup pressure roll 72. 
In the exemplary embodiment shown in FIG. 1, the wedge-like member 102 is 
further urged against the backup pressure roller 72 via a spring member 92 
coupled between a right angle bracket 94 fastened against the backside of 
baffle member 73 and a hook member disposed along the back portion of the 
semi-circular segment of the wedge-like member 102. The wedge-like member 
102 is maintained laterally relative to backup pressure roller 72 by slot 
98 formed in baffle member 73. Slot 98 is oversized relative to the 
dimension of the wedge-like member 102 to allow some play or movement 
thereof as the wedge-like member rides on the rotating pressure backup 
roll 72. 
The wedge-like member 102 provides a raised surface along the central 
portion of the baffle member 73, so as to exert an upward force on the 
recording substrate 56 after it travels through the fuser nip 71. This 
upward force imparts an arcuate profile in the recording substrate 56, 
along a generally central axis substantially perpendicular to the path of 
movement thereof. It has been found that imparting such an arcuate-shaped 
profile in the recording substrate 56 provides sufficient lateral support 
thereto for preventing the formation of waves in the recording substrate 
56, as created by the other stresses acting on the recording substrate 56, 
as discussed previously herein. It has further been found that optimum 
wave elimination results when the wedge-like member has a height dimension 
between approximately 3.9 mm to 4.4 mm to raise the recording substrate by 
that amount with respect to the path of movement of the sheet substrate 
through the fuser nip 71. It will be recognized by those of skill in the 
art that the wedge-like member 102 serves as a wave restrictor and can 
take on any configuration or form for imparting an arcuate profile in the 
recording substrate as it passes from the fuser nip 71 to the baffle 
assembly 73. 
The baffle assembly 73 of the present invention further includes a 
plurality of stripper fingers 100 interspaced along the length of baffle 
member 73 adjacent fuser nip 71. Like the wedge-like member 102, each 
stripper finger 100 rides in contact with the backup pressure roll 72, 
contacting the lead edge of the recording substrate 56 as it travels out 
of fuser nip 71. Likewise, in similar manner to wedge-like member 102, 
each stripper finger 100 is mounted through a slot 98 in baffle member 73 
so that the leading edge of each stripper finger 100 is in engagement with 
the backup pressure roll 72 and biased thereagainst by means of a spring 
element 92 coupled between support bar 96 and each stripper finger 100, 
providing a cantilevered mounting configuration therefor. The 
above-described stripper fingers provide an effective mechanism for 
stripping substrates ranging from light weight paper to heavy weight 
specialty substrates including film substrates such as polyethylene 
transparencies and vellums. Any alternate form of stripper finger and/or 
mounting configuration for separating the recording substrate from either 
roll making up the fuser nip 71 can be used, as is well known in the art. 
In recapitulation, it should now be clear from the foregoing discussion 
that the apparatus of the present invention provides a novel baffle 
assembly for eliminating the formation of waves in a recording substrate 
produced by multi-color electrophotographic printing systems. The present 
invention provides a wedge-like member for imparting an arcuate-shaped 
profile on the recording substrate along an axis perpendicular to the path 
of movement thereof as the recording substrate passes beyond the fuser 
nip. It is believed that the position, dimension, and configuration of the 
wedge-like member provides sufficient pressure for imparting a 
substantially arcuate-shaped profile into the recording substrate for 
eliminating wave formation in the recording substrate inherent to prior 
art multi-color xerographic processes. 
It is, therefore, apparent that there has been provided, in accordance with 
the present invention, a novel fuser assembly that fully satisfies the 
aims and advantages set forth hereinabove. While the present invention has 
been described in conjunction with a specific embodiment thereof, it will 
be evident to those skilled in the art that may alternatives modifications 
and variations are possible to achieve the desired results. Accordingly, 
the present invention is intended to embrace all such alternatives, 
modifications, and variations which may fall within the spirit and scope 
of the following claims.