CA1045672A - Fusing apparatus - Google Patents

Abstract

IMPROVED FUSING APPARATUS

ABSTRACT OF THE DISCLOSURE

A fusing apparatus is provided for heat fusing a toner image to a sheet of final support material. The apparatus includes curl reducing means comprising at least one seal adjacent the fusing zone for limiting air flow at the zone to an amount at which curl of the sheet is substantially reduced. At least one of the seals comprises an elongated brush-like member.

Description

BACKGROUND OF THE INVE~TION
This invention relates to a fusing apparatus for heat fusing a toner image to a sheet of final support material including means for reducing curl of the sheet during fusing.
When a sheet of final support material having a toner image on a side thereof is subjected to fusing by means of a radiant heat fuser some of the moisture in the sheet is driven out. Depending on the quantity of moisture driven out changes in the length and width of the sheet occur as well as a severe curl. Curl in the resulting sheet after fusing is a severe problem for a reproducing machine, particularly those of the xerographic type. The tendency of the sheet to curl during fusing is one of the causes of jams in the region of the fuser.
Curl is also a significant problem in reproducing machines adapted to provide images on both sides of the sheet, a process referred to in the art as duplexing. A duplexing apparatus requires that the sheet be refed through the machine. Sheets with a severe curl are extremely difficult and sometimes impossible to feed without persistent jamming problems along the paper path.
The problem of sheet curl due to radiant heat fusing has been recognized in the art as exemplified by U. S. Patent Nos. 2,807,703 and 2,807,704. In these patents the fusing apparatus is designed to selectively heat the toner image on the sheet to its fusing point while leaving the sheet per se at a temperature sufficiently below the fusing point of the toner to avoid curl. In fact, the temperature of the sheet is maintained below the boiling point of water so that a substantial portion of the original moisture content of the

- 2 -sheet is not removed. The apparatuses described in these patents are particularly applicable to record cards. In the first of these patents, three embodiments of the fusing apparatus for carrying out the invention are described. In each apparatus the transfer of heat energy to the record card by conduction and convection is kept negligible by a suitable means, and thereby, since the record card per se is made from paper stock and does not readily absorb radiant energy, the temperature of the record card is kept at a lower value than the boiling point of water. Transfer of heat energy by con-duction and convection is reduced either by heat extraction or so called fixing station cooling, or by the use of a heat transfer barrier for preventing heat transfer by conduction and convection such as a water filled glass jacket, or in accordance with the third embodiment, by focusing and concen-trating the radiant energy on the toner image.
; While the approaches of these patents may operate satisfactorily for fusing toner images on record cards, this would not necessarily follow for fusing toner images on support sheet of other types. Toner images on record cards are generally not very dense and, therefore, comprise very little toner so that not as much heat energy is required to fuse them. conventional copying machines can provide denser toner images containing considerably greater proportions of toner over the sheet surface, which would require a greater quantity of heat energy to fuse them to the sheet. Therefore, it is possible that the apparatuses of the aforenoted patents would not operate satisfactorily in the environment of a copying machine since by maintaining the temperature of the

- 3 -sheet below the boiling point of water insufficient heat energy would be impressed on the toner image to consistently fuse the toner image to the sheet.
One successful solution to this problem is set forth in ~. S. Patent No. 3,849,905 to D. P. Bierworth et al issued November 26, 1974. In that case a curl reducing means is provided in a fusing apparatus which comprises at least one seal adjacent to the fusing zone which limits the air flow at the zone to an amount at which curl of the sheet is reduced or eliminated. The seals preferably comprise strip-like members - of a polymeric material.
The seals referred to in the aforemen*ioned patent should be resilient and heat resistant. Teflon and Mylar are disclosed as usable materials. While these materials perform their function adequately, their useful life in the machine environment lS not as great as desired because of the effects of their elevated temperature environment, though they have been used commercially. It has been found that Mylar is not as heat resistant as desired. Teflon, while being heat resistant, is unable to maintain its resiliency in this environ-- ment. The elevated temperatures eventually cause the Teflon to take a permanent set in a deflected condition thereby reducing i*s biasing ability.
One solution which was proposed to overcome the above-noted problems was to employ a polymeric foam, specifical-ly polyurethane foam as the seal. This approach was not successful since the seal which was interposed between a transport roll and the fuser caused sufficient drag to inter-fere with the uniform rotation of the roll.

- 4 -* trade marks .~.

SUMMARY OF THE I~VENTION
In accordance with this invention a fusing apparatus has been developed wherein curl of the sheet during fusing is substantially reduced or eliminated. The fuser includes a source of heat radiation. A fusing zone is defined wherein the heat source is effective to fuse a toner image to a sheet of final support material. A flow of air is present at the zone due to influences which are internal and/or external of the fuser. Curl reducing means are provided which comprise at least one seal adjacent to the fusing zone which limits the air flow at the zone to an amount at which curl of the sheet is reduced or eliminated. In accordance with this invention the seal comprises an elongated brush-like member.
Contrary to the aforenoted prior art teachings in accordance with this invention, the air flow has to be limited severely in order to reduce moisture gradients and to prevent the moisture driven off from the sheet from being completely withdrawn from the fusing zone.
In accordance with preferred embodiments, transport means are provided at the exit and/or entrance regions of the fuser to transport the sheet. One or more of these transports may include suction means for holding the sheet to the transport.
The seals preferably extend between the transports and the fuser. Preferably the seal comprises an elongated backing strip and a plurality of elongated fibers extending out from the strip in a brush-like configuration.
Therefore, it is an object of~this invention to provide an improved fusing apparatus for heat fusing a toner image to a sheet of final support material.

It is an object of an aspect of this invention to provide an apparatus as above including improved means for reducing the curl of the sheet during fusing.
It is an object of an aspect of this invention to provide an apparatus as above wherein the curl reducing means includes a brush-like seal.
These and other objects will become more apparent from the following description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
-Figure 1 shows schematically an exemplary reproducing machine including the fusing apparatus of this invention.
Figure 2 is a perspective view of a sheet of final support material after fusing by a prior art radiant fuser.
Figure 3 is a cross-sectional side view of the fusing apparatus of this invention including the curl reducing means.
Figure 4 (first sheet of drawings) is a perspective view of a brush-like seal in accordance with this invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to Figure 1 in accordance with this invention, a fusing apparatus 1 is provided for heat fusing a toner image to a sheet 2 of final support material. The fusing apparatus l includes a fuser 3 having a source of heat radiation 4 for application to the sheet. The fuser 3 defines a fusing zone 5 wherein the heat source 4 is effective to fuse the image to the sheet 2. A f low of air is present at the zone 5 due to influences which may be internal and/or external of the fuser 3. An essential part of this invention comprises means which cooperate with the fuser 3 for reducing curl of the ~f~

sheet 2 during fusing. The curl reducing means 6 preferably comprise at least one seal comprising a brush-like member adjacent to the fusing zone 5 which is adapted to limit air flow through the zone to a volume at which curl of the sheet is substantially reduced.
It is believed in accordance with this invention that paper curl in the final support sheet after fusing by means of a radiant fuser is the result of plastic deformation of the paper sheet. The deformation is made up of two com-ponents which may be summed algebraically. One component is related to the type of paper and to the bulk paper changes that occur during fusing. It is possible to think of these as resulting from one or both of the following: 1. a locked in asymmetric residual stress distribution which relaxes or yields under a bulk temperature or moisture level excursion.
2. variations in paper properties across the thickness of the sheet, as for example, the coefficient or expansion with moisture. This can result in non-uniform elongation of the sheet and curl in the absence of any assymetry or gradients.
The other component is believed to relate to the asymmetrical conditions or gradients imposed on the paper by the fuser and adjacent machine components or other external influences. The curl from this component is always in the direction of the source of radiant energy.
The curl is believed to result from stresses imposed on the sheet associated with the gradient moisture through the thickness of the sheet. This invention is not directed at preventing curl induced by mechanical deformation which may occur in the copier and which can, in iO45672 fact, result in curl in either direction depending on the direction of deformation. For example, curl induced by a roll fusing apparatus.
The primary source of the stresses is the moisture gradient which causes the top surface of the sheet to shrink more than the bottom surface. The moisture gradient is determined by the temperature gradient, the initial moisture content and the moisture mass transfer effects. In many cases the moisture mass transfer is significant. In configurations where the fuser is near an air moving device such as a suction box of a vacuum transport the air moving device may aggrevate curl by increasing the rate of moisture mass transfer due to increased air flow in the fusing zone. The rate of moisture mass transfer is substantially increased in the top surface of the sheet thus causing a larger moisture gradient which results in higher stresses and greater deformation of the sheet. Other aspects of the mechanism causing curl in the sheets are described in U. S. Patent No. 2,807,703.
The aforenoted description of the mechanism for causing curl is not meant to be limitative of the invention and is presented here by way of example. The aforenoted mechanism is believed to be the mechanism involved in accordance with this invention, however, other factors not yet appreciated could be taking part in the mechanism.
Referring now to Figure 2, a sheet 2 of final support material is shown after fusing by an apparatus not including the curl preventing means 6 in accordance with this invention.
The sheet 2 shown therein has a substantial curl 7 of about 1.5 inches at the trailing edge portion 8 thereof. This type of curl 7 in a sheet 2 is formed by an apparatus 10 as will be described in more detail with reference to Figure 1 when the curl preventing means 6 are not employed. In other apparatuses the curl 7 may be more or less pronounced. There may be curl 7 at the trailing 8 and/or the leading 9 edges of the sheet 2. Irrespectively, by following the teachings of the present invention, it should be possible to substantially reduce or eliminate curl 7 from the sheet 2 due to fusing when the curl is produced by means other than mechanical deformation.
Referring now to Figure 1, there is shown by way of example an automatic xerographic reproducing machine 10 which incorporates the improved fusing apparatus 1 of the present invention. The reproducing machine 10 depicted in Figure 1 illustrates the various components utilized therein for producing copies from an original. Although the fusing apparatus 1 of the present invention is particularly well adapted for use in an automatic xerographic reproducing machine 10, it should become evident from the following description that it is equally well suited for use in a wide variety of machines where an image is fused to a sheet of final support material and it is not necessarily limited in its application to the particular embodiment shown herein.
The reproducing machine 10 illustrated in Figure 1 employs an image recording drum-like member 11 the outer periphery of which is coated with a suitable photoconductive material 12. One type of suitable photoconductive material is disclosed in U. S. Patent ~o. 2,970,906 issued to Bixby in 1961. The drum 11 is suitably journaled for rotation within a _ g _ machine frame (not shown) b~ means of a shaft 13 and rotates in the direction indicated by arrow 13, to brinq the imaqe retaining surface thereon past a plurality of xerographic processing stations. Suitable drive means (not shown) are provided to power and coordinate the motion of the various cooperating machine components whereby a faithful reproduction of the original input scene information is recorded upon a sheet 2 of final support material.
The practice of xerography is well know in the are and is the subject of numerous patents and texts including Electrophotography by Schaffert, published in 1965, and .

Xe~ography ana ~elated ~ro~esses by Dessauer and Clark, published in 1965. The various processing stations for - producing a copy of an original are herein represented in Figure 1 as blocks A to E. Initially, the drum 11 moves photocon-; ductive surface 12 through carging station A. At charging station A an electrostatic charge is placed uniformly over the photoconductive surface 12 of the drum 11 preparatory to imaging. The charging may be provided by a corona generating device of a type described in U. S. Patent ~o. 2,836,725 issued to Vyverberg in 1958.
Thereafter, the drum 11 is rotated to exposure station B where the charged photoconductive surface 12 is exposed to a light image of the original imput scene infor-mation, whereby the charge is selectively dissipated in the light exposed regions to record the original input scene in the form of a latent electrostatic image. A suitable exposure ~ystem may be of the type described in U. S. Patent No.
3,832,057 to D. K. Shogren issued August 27, 1974.
After exposure, drum 11 rotates the electrostatic latent image recorded on the photoconductive surface 12 to development station C wherein a conventional developer mix is applied to the photoconductive surface 12 rendering the latent image visible. A suitable development station is disclosed in Canadian Patent No. 991,394 to R. Ashton et al issued June 22, 1976. The Canadian patent describes a magnetic brush development system utilizing a magnetizable developer mix having carrier granules and a toner colorant.
The developer mix is continuously brought through a direc-tional flux field to form a brush thereof. The electrostatic latent image recorded on photoconductive surface 12 is deve-loped by bringing the brush of developer mix into contact therewith.
The developed image on the photoconductive surface 12 is then brought into contact with a sheet 2 of inal support material within a transfer station D and the toner image is transferred from the photoconductive surface 12 to - the contacting side of the final support sheet 2. The final support material may be paper, plastic, etc., as desired.
After the toner image has been transferred to the sheet of final support material 2, the sheet with the image thereon is advanced to a suitable fuser 3, which coalesces the - transferred powdered image thereto. One type of suitable - fuser is described in U. S. Patent No. 2,701,765, issued to Codichini et al in 1955. After the fusing process, the sheet 2 is advanced by snuffing rolls 14 and then by rolls 15 to a catch tray 16 for subsequent removal therefrom by the machine operator.
Although a preponderance of the toner powder is transferred to the final support material 2, invariably some residual toner remains on the photoconductive surface 12 after the transfer of the toner powder image to the final support material 2. The residual toner particles remaining on the photoconductive surface 12 after the transfer operation are removed therefrom as it moves throu~h cleaning station E.
Here the residual toner particles are first brought under the influence of a cleaning corona generating device (not shown) adapted to neutralize the electrostatic charge remaining on the toner particles. The neutralized toner particles are then mechanically cleaned from the photocon-ductive surface 12 by conventional means as, for example, the use of a resiliently biased knife blade as set forth in U. S. Patent no. 3,660,863 issued to Gerbasi in 1972 If desired, in accordance with this invention, the sheets 2 of final support material processed in the automatic xerographic reproducing machine 10 can be stored in the machine within a removable paper cassette 17. A suit-able paper cassette is set forth in U. S. Patent No.
3,767,187 to C. Mahler et al issued October 23, 1973.
The reproducing apparatus in accordance with this invention can also have the capability of accepting and processing copy sheets 2 of varying lengths. The length of thè copy sheet 2, of course, being dictated by the size of the original input scene or information recorded on the photoconductive surface 12. To this end the paper cassette 17 is preferably provided with an adjustable feature whereby sheets ~04S672 of varying length and width can be conveniently accommodated.
In operation the cassette 17 is filled with a stack of final support material 2 of pre-selected size and the cassette is inserted into the machine by sliding along a base plate (not shown) which guides the cassette into operable relationship with a pair of feed rollers 18. When properly positioned in communication with the feed rollers 18, the top sheet of the stack is separated and forwarded from the stack into the transfer station D by means of registration rolls 19.
It is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of the automatic xerographic reproducing machine l which can embody the teachings of the present invention.
Referring now to Figure 3, that portion of the reproducing machine lO of Figure 1 embodying the fusing apparatus l of this invention is shown in greater detail.
The view shown is a side view and it should be readily evident that the fusing apparatus extends across the entire sheet in a direction normal to the plane of the Figure. The-image bearing sheet 2, after passing through the transfer station D
of Figure l upon separation from the photoconductive surface 12, is allowed to fall into contact with a vacuum belt transport system 20 which conveys the sheet directly to the fusing apparatus l.
The fusing apparatus l shown includes a ~rcd~ant type fuser 3. The fuser 3 includes a heated platen 30 mounted to engage the non-image bearing side of the copy sheet ~ which moves in sliding contact therewith as it is transported through ~045672 the fusing zone. The heated platen 30 is designed so that an efficient heat flow is established between the platen and the copy sheet 2 to raise the temperature of the sheet rapidly to a level somewhat below the sheet's scorch temperature. By controlling the temperature of the sheet 2 in this manner the ability of the sheet to act as a heat sink during image fixing is minimized. The radiant energy source for fusing is provided by an infrared quartz lamp 31 which is mounted in a reflector assembly 32 in opposing relationship to the heated platen 30 and in a position to thermally communicate with the newly imaged side of the copy sheet 2. Preferably the spectral output of the lamp 31 is within a range at which the imaging material which may be toner for a xerographic machine 10 is highly absorptive and at which the support material ~F-which may be paper is relatively non-absorptive. As a result, the toner images are rapidly raised to the desired fusing temperature while the support sheet 2 remains at a relatively lower temperature.
A forced air cooling chamber 33 is provided about the backside of the reflector assembly 32 to cool the fuser 3 in operation.
A heating element 34 is provided in the platen 30 to maintain it at the desired temperature during standby periods. When the quartz lamp 31 is operated the pre-heat element is disconnected and the platen 30 receives its heat input directly from the quartz lamp.
The leading edge of the sheet 2 bearing the image is pushed through the entrance port 35 to the fusing zone 5 and moves in sliding contact over the platen 30 through the fuser exit port 36 into a pair of cooperating transport rolls 40 and 41 which comprise a flame snuffing apparatus. The lower snuffing roll 41 is positioned such that its outer periphery lies below the plane of a fuser platen 30 whereby in operation the snuffing rolls 40 and 41 are operative to hold the sheet 2 in sliding contact with the fuser platen 30. The sheet is also held in contact with the platen 30 by means of suction communicated via suction chamber 37 and platen suction ports 38.
The snuffing rolls 40 and 41 forward the sheet along a guide plate 42 into the nip of a pair of advancing rolls 43 which deposit the sheet within a collecting tray 16.
The collecting tray 16 includes a base plate 44 inclined up-wards and an upwardly turned margin stop 45.
The advancing rolls 43 serve to drive the sheet 2 into the collecting tray 16. The advancing rolls 43 further include a compact propelling mechanism 46 which moves the sheet 2 rapidly and efficiently into alignment against the stop 45. The propelling mechanism is described in greater detail in U. S. Patent No. 3,847,388 to T. Lynch issued November 12, 1974.
Having thus described the operation of the fusing apparatus 1, further reference will now be given to the curl control means 6 in accordance with this invention.
In the embodiment of Figure 3 the transport 20 ; comprises a vacuum transport having a suction means 21 which draws air in through or between the belts 22. The suction ; means is connected to any conventional cource of suction ~not shown). The suction means 21 cooperates with the belts 22 to firmly hold a sheet 2 of final support material in contact with the transport. The suction means 21 comprises, however, only one of many possible external influences in the machi~e 104567~
lO which can cause an air flow through the fusing zone 5. The suction means 21 draws air in from an external port (not shown).
Air flows through various passageways defined by the machine components and sub-stations. The paper path provides one of the key flow channels for the air which flows to the suction means 21. In the absence of the curl preventing means 6 in accordance with this invention air is drawn through the fuser 3 in order to satisfy the requirements of the suction means 21 as shown by the arrows 50. While this flow of air has a beneficial effect with respect to cooling the sheet 2 prior to its being received by the snuffing rolls 40 and 41, it has a deleterious effect in that it results in a substantial curl being formed in the sheet during fusing.
There is also in the fuser 3 shown an internal means which causes a flow of air through the fusing zone 5. The internal means comprises a series of orifices 38 in the platen 30 which communicate with a suction means comprising the chamber 37. The purpose of these orifices 38 is to provide a~
vacuum holddown for holding the sheet 2 in contact with the platen 30 as it passes through the fuser 3. When the sheet does not cover these orifices a substantial air flow is produced. The direction of this air flow will vary depending on whether the sheet is entering or leaving the fuser. Another internal cause of air flow comprises the conductive air currents associated with the fuser.
Therefore, as shown, an air flow through the fusing zone is created both by external influences and by internal influences. It is believed, however, that either of these influences alone would be sufficient to provide an air flow In accordance with this invention it is desired to reduce the flow of air through the fuser so as to reduce the curl producing effects of the moisture gradients induced in the sheet 2 during fusing. The mechanism by which this is accomplished is not fully understood, but it is believed to be the result of a localized condition in the fusing zone which reduces the rate that the moisture is driven out of the sheet during the period the thermal and moisture gradients are caused in the sheet by fusing. This may, for example, be due to a localized increased vapor pressure condition which can orm due to the restricted air flow and which temporarily prevents or reduces the rate at which moisture can exit from the sheet 2 until the thermal and moisture gradients in the sheet have been reduced or eliminated.
The temperature and moisture gradients in the portion of the sheet 2 being heated occur for an extremely short period of time, a matter of fractions of a second. Therefore, if the sheet can be sufficiently restrained during this period or if the rate of moisture evaporated from the sheet during the period can be reduced, curl 7 can be reduced.
In the apparatus 1 shown, without the curl preventing means 6 the sheets are subject to substantial trail edge curl 7 as shown in Figure 2. Lead edge 9 curl is not pronounced because of the inner-action of the vacuum transport 20 with the sheet 2. It is believed that the vacuum transport 20 prevents the sheet 2 from being deformed by the influence of the moisture gradients by restraining deformation of the sheet.
However, after the sheet 2 leaves the vacuum transport 20 the trail edge ~ of the sheet is not sufficiently restrained and, therefore, is subject to substantial curl as, for example, that shown in Figure 2.
When the lead edge 9 of the sheet 2 enters the fusing zone 5 the remainder of the sheet closes off some of the suction ports (not shown) in the top of the vacuum transport 20 thus reducing the flow of air flow through the fusing zone

5. As the sheet 2 progresses through the zone 5 more of the suction ports, particularly those adjacent to the fuser 3, are uncovered by the sheet 2 thereby increasing the air flow through the zone. This is also believed to be a major factor in causing the pronounced trail edge 8 curl and insignificant lead edge 9 curl using the specific apparatus 1 shown.
Therefore, in accordance with this invention curl preventing means 6 are provided which comprise in the embodiment shown one or more seals 61, 62, 63 and 64 adjacent to the fusing zone 5 which are adapted to limit the air flow at the zone to an amount at which curl of the sheet is substantially reduced or eliminated. In the apparatus 1 shown which includes the external influence of the vacuum transport 20, the provision of the seal 61 between the top portion 65 of the fuser 3 and the upper transport roll 40 at the exit side of the fuser provides a substantial reduction in curl as compared to the same apparatus without the seal 61.
Experimentally, the reduction in curl due to this seal 61 has been shown to be as much as about 60% or more. Further reductions in curl can be achieved by providing additional seals 62, 63 and 64 as, for example, the lower seal 62 between the bottom portion 66 of the fuser 3 and the lower transport roll 41 has been determined to provide a further 5% to 10%
or more improvement in curl reduction. At the upstream .

side of the fuser 3, because of the external influence of the vacuum transport 20, it has been found desirable to provide slots or holes 67 in the seal 63 between the fuser and the cleaning station E. This allows air flow from the channel 68 as shown by arrow 69 to flow to the transport and thereby reduces the amount of flow drawn through the fuser. The provision of holes 67 in this particular seal 63 which also serves to guide the sheet provides a further 15% or more improvement in curl 7 reduction. Finally, a seal 64 between the vacuum transport 20 and the lower portion 66 of the fuser 3 provides some improvement, but not that significant, namely, less than 5%.
It is quite apparent that the fusing apparatus illustrated in Figure 3 requires seals between the downstream sheet transport 40 and 41 and the fusing apparatus 3 in order to substantially reduce or eliminate curl 7. It should also be apparent that had the vacuum transport 20 or other external source of substantial air flow through the fuser 3 been downstream of the fuser rather than upstream thereof then the effective seals for reducing air flow through the fuser would have been the upstream seals 63 and 64, rather than the downstream seals 61 and 62. In this case the seal 63 between the upper portion 65 of the fuser 3 and the adjacent housing E would have had to be impervious, whereas the seals 61 and 62 on the downstream side of the fuser could have been pervious as desired.
In the embodiment shown the internal suction means 37 and 38 does not exert a controlling influence on the amount of curl which is formed. Regulation of the suction force here, in cooperation with the seals 61 - 64 could help reduce air flow through the fusing zone 5. Conversely increasing the suction force would restrain deformation caused by the moisture gradient, however, it would also increase the retardation forces on the sheet 2 which could cause the sheet to stall in the fuser 3 which is undesirable.
The location of the seals 61 - 64 has to be determined based on the air flow conditions in the apparatus in which the fuser 3 is employed and seals 61 - 64 may be employed at one or all of the locations shown in order to provide the reduced air flow through the fuser. The most significant seals will be those adjacent the image containing side of the sheet 2, for an apparatus 10 where the sheet is passed over a platen 30, since it is on this side of the sheet that the greatest air flow occurs.
It is an essential aspect of this invention that at least one of the seals 61 - 64 comprises an alongated member having a brush-like configuration. The seals 61-64 are at least coextensive with the fusing zone in the transverse direction, (e.g., the direction normal to the plane of Figure 3).
Referring to Figure 4, a seal 100 in accordance with this invention is shown. The seal 100 comprises a backing strip 101 having a plurality of elongated fibers 102 extending out therefrom in a brush-like configuration. The fibers 102 may comprise individual fibers or tufts of fibers formed, for example, from a pile of yarn. The density of the fibers should be such as to provide a substantial baffle or seal to the flow of air through the seal. Preferably it should prevent air flow through the channel being sealed.

~04567Z
The backing strip 101 preferably comprises a com-posite comprising a metal backing component 103 and a poly-meric support component 104, preferably nylon, adjacent to the brush fibers 102. The brush fibers 102 are woven into the nylon support 104 and the metal component 103 is crimped over the support to provide added mechanical strength. While nylon appears to be the preferred material for use as the fibers 102 in the brush-type seals of this invention, other heat resistant materials could also be employed if desired, particularly other polymeric materials. The brush-type seals may be secured to the fuser by any conventional means as, for example, the use of screws (not shown).
In the apparatus of Fig. 3, the upper roll 40 is an idler roll and when the seal 100 is interposed between an idler roll 40 and the fuser 3, it is necessary to avoid too dense a brush or else a drag is placed on the idler roll which prevents its uniform rotation.
By using a brush configuration instead of a strip-type member the life of the seals 61 - 64 can be substantially extended. The brush-type seal 100 does not require the same degree of resiliency for the flbers 102 as is required for the material of the strip-type seals. Further, the resiliency of the individual fibers 102 is maintained by the added support they receive from adjacent fibers.
In the apparatus shown a plurality of spaced apart circumferential ridges 47 are provided on the upper roll 40 to provide an efficient flame snuffing action while reducing off-set problems associated with the upper roll. A strip-type seal leaves a gap of less than about .030" between the 1~45672 seal 61 and the hub of the roll 40 which allows a slight air flow through the sealed air channel. The amount of air flow has been found to be very slight and not enough to cause a substantial curl. However, it is desirable to completely seal the channel between the roll 40 and the fuser 3. A brush-type seal 100 as in accordance with the present invention performs the function of completely sealing off the passageway since the brush fibers 102 follow the contour of the roll surface and, therefore, fill in the valleys between the ridges 47 to substantially close off the air channel.
In the apparatus 1 shown, brush-type seals 100 are employed between the upper and lower transport rolls 40 and 41 on the downstream side of the fuser 3 whereas a strip type seal 64 is employed on the upstream side of the fuser between the fuser base 66 and the transport 20. It is apparent therefore that it is possible in accordance with this invention to employ seals of both the brush type 100 of this invention and the strip type 63 where desired.
The strip type seals 63 comprise an elongated strip type member formed of a resilient material which is biased against the transports 40, 41 or 20 and extends over the respective gap between the transport and the fuser. As with the brush type seal 100 they may be secured to the fuser by any desired means. Preferably they are formed of a polymeric material such as polytetrafluoroethylene sold under the trademark Teflon and polyethyleneterethalate sold under the trademark Mylar.
An exemplary brush 100 usable in accordance with the present invention which has been employed was formed 1~45672 of flame proof Nomex nylon with a pile yarn size of 2/10;
with a plain weave for the backing; with a thread count for the pile ticks of 6.25+ .25/inch and for the pile ends of 24~ l/inch; with the number of tufts per square inch at 150 + 8% and with a tiger texture for the brush. A brush of this type has been found to be effective as seen from the following example.
By way of example for a fuser 3 having a gap between the platen 30 and the reflector 32 o about 1/8 inch and a length normal to the plane of Figure 3 of about 15"
an air flow of less than about .2 cfm will substantially reduce or elimiPate curl. If the seals 61 - 63 are removed the air flow through the fuser 3 shown would be about 5 cfm.
It is believed that for most radiant fusers the air flow should be maintained below about 1 cfm and pre-ferably below about .2 cfm in order to reduce or eliminate curl.
The toner images of this invention may be formed from toner of the type described in U. S Patent Nos.
2,807,703 and 2,807,704.
It is apparent that there has been provided in accordance with this invention a fusing apparatus which fully satisfies the objects , means and advantages set forth hereinbefore. While the invention has been described in conjuction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, 1045~7Z
modifications and variations as fall within the spirit and broad scope of the appended claims.

Claims (11)

WHAT IS CLAIMED IS:

1. In a fusing apparatus for heat fusing a toner image to a sheet of final support material including:
a fuser having a source of heat radiation for application to said sheet, said fuser defining a fusing zone wherein said heat source is effective to fuse said image to said sheet, and a flow of air at said zone; the improvement wherein said apparatus further includes:
means cooperating with said fuser for reducing curl of said sheet during fusing, said curl reducing means comprising at least one seal adjacent said zone for limiting air flow at said zone to an amount at which curl of said sheet is substantially reduced, said seal comprising an elongated member having a brush-like configuration.

2. An apparatus as in Claim 1 wherein said brush-like member comprises a backing strip and a plurality of elongated fibers extending out from said strip in said brush-like configuration.

3. An apparatus as in Claim 2 wherein said fibers are formed of a polymeric material.

4. An apparatus as in Claim 3 wherein said fibers are formed of nylon.

5. An apparatus as in Claim 1 further including first transport means for transporting said sheet, said transport means being located adjacent said fuser, and air channel being defined between said transport means and said fuser, and wherein said seal extends over a gap between said fuser and said transport means.

6. An apparatus as in Claim 5 wherein said first transport means is located at a first side of said fuser and wherein a second transport means is provided at the oppos-ing side of said fuser and wherein at least one of said first and second transport means includes suction means cooperating therewith to hold said sheet to said one of said transport means.

7. An apparatus as in Claim 6 including a plurality of said seals.

8. An apparatus as in Claim 7 wherein a plurality of air channels are formed between the respective transport means and the fuser and wherein said seals are interposed in the channels extending over respective gaps between the fuser and the respective transport means.

9. An apparatus as in Claim 8 wherein said first transport means comprises a pair of pinch rolls and wherein said second transport means comprises a vacuum transport having said suction means and wherein said first transport is located downstream of said fuser and wherein said second transport is located upstream of said fuser.

10. An apparatus as in Claim 1 wherein said air flow is reduced to below 1 cubic foot per minute.

11. An apparatus as in Claim 10 wherein said air flow is reduced to below 0.2 cubic foot per minute.