US3159735A

US3159735A - Fixing unit for photocopy machines

Info

Publication number: US3159735A
Application number: US209122A
Authority: US
Inventors: Burton D Eisner; George C Kent; Edwin A Larson; Jr Meyer L Sugarman
Original assignee: American Photocopy Equipment Co
Current assignee: American Photocopy Equipment Co
Priority date: 1962-07-11
Filing date: 1962-07-11
Publication date: 1964-12-01
Anticipated expiration: 1981-12-01
Also published as: GB1023602A

Description

Dec. 1, 1964 B. D. EISNER ETAL FIXING UNIT FOR PHOTOCOPY MACHINES 4 Sheets-Sheet 1 Filed July 11, 1962 MVEIIQTOYLJ Borfh 6 L6 3e c. k

L e? $17? 4 V \TORIOELY/ 6mm QQ mm mm Dec. 1, 1964 D. EISNER ETAL FIXING UNIT FOR PHOTOCOPY MACHINES 4 Sheets-Sheet 5 Filed July 11, 1962 B n D EMTORJ gum e a sn n fifii$fw Laa rson.

yer L. u

no RMEYf 1964 B. D. EISNER ETAL 3,159,735

FIXING UNIT FOR PHOTOCOPY MACHINES Filed July 11, 1962 4 Sheets-Sheet 4 Q I I 9 ISO I 22 so A w 1% m United States Patent 3,159,735 FIXING UNIT FOR PHGTOCUPY MACHINES Burton D. Eisner and George C. Kent, Highland Park, Edwin A. Larson, Chicago, and Meyer L. Sugarmau, Jr., Glencoe, IlL, assignors to American Photocopy Equipment Company, Evanston, Hit, a corporation of Illinois Filed July 11, 1962, Ser. No. 269,122. Claims. (Cl. 219-347) The present invention relates to electrophotographic printing and, more particularly, to an improved means for fixing a developed image to the copy sheet.

The electrophotographic printing process employed in olfice photocopy machines and the like commonly involves the steps of uniformly charging an electrographic sheet, exposing the sheet to produce a latent image thereon with dissipation of the charge from the light-struck areas, development of the image by applying a pigmented powder or toner which tends to adhere selectively to the charged areas, and then fixing the powder in place by heat. The powder conventionally includes a minor proportion of heat settable resin which, upon being heated, causes the powder to adhere to the surface of the sheet. A machine of this type is disclosed in Sugarman US. Patent 3,088,366 which issued on May 7, 1963. However, one of the problems encountered in known types of photocopy machines is either that fixing is incomplete or uneven resulting in smeared or imperfect copies or that the temperature tends to build up when the machine is operated for long periods, thereby running the risk of scorching. Moreover, prior devices have been subject to malfunction by reason of buckling of the sheet, particularly the leading edge thereof as the sheet passes into the fixing station and before the sheet is nipped by the final expeller rollers so that a copy sheet may become hung up within the machine to produce a jam and a possible fire hazard. The prior Sugarman application embodied one solution to this problem; an improved arrangement is described and claimed herein.

Accordingly it is an object to provide an improved fixing unit for an electrophotographic machine which is more reliable than prior fixing arrangements and which is capable of fixing the powder image uniformly and to the correct degree, tree of blemish or imperfection, regardless of how long the machine has been operating and Without risk of scorching and overheating. It is a related object to provide a fixing unit of the above type in which each sheet is passed through the unit and positively discharged and in which there is no danger of a sheet buckling or becoming hung up within the fixing unit, thereby obviating the nuisance and hazard which results when a sheet catches fire. In this connection it is also an object to provide a fixing unit capable of reliably handling copy sheets which are thinner than those which may be handled by conventional machines, even light weight tissue stock. At the opposite extreme, sheets of double weight or card stock may be efiiciently handled.

It is an other object to provide a heat fixing unit for a photocopy machine which is highly efiicient and which effectively utilizes the radiant heat from the heat lamp with the radiant heat being concentrated in a novel fashion upon the sheet being acted upon. It is a related object to provide a fixing unit having convenient means for adjusting the radiant heat source relative to the sheet so that the radiant energy is focused upon the sheet along a narrow transverse strip and which does not require that a large area of the sheet be acted upon simultaneously by the heat source. It is an object to provide novel adjusting means for controlling the peak temperature of the sheet. Nevertheless it is a feature of the machine that the focusing adjustment is non-critical and that the sheet may depart from the fixing plane, as may happen at the leading edge of the sheet and prior to nipping by the expeller 3,159,735 Patented Dec. 1, 1964 rollers, without sacrifice of reliability. It is one of the objects to provide a fixing unit which is capable of acting uniformly over the entire length of the sheet from the leading edge to the trailing edge.

It is a detailed object to provide apparatus of the above type in which the source of radiant energy is at the back of the sheet for avoidance of hot spots in the pigmented areas.

It is still another object of the present invention to provide a fixing unit having novel and etficient means for carrying away the excess or unwanted heat, and particularly the non-radiant heat components, without reducing the radiant component of heat energy which is primarily effective to accomplish the fixing so that the environment of the sheet is maintained at a safe low temperature and so that the casing of the machine becomes no more than slightly Warm to the touch even during extended periods of operation.

It is a further object of the present invention to provide a fixing unit which is easy to service and in which it is possible either to inspect the fixing region or to inspect or replace the fixing lamp at the front of the machine simply by swinging the lamp and reflector assembly downwardly about a horizontal axis. It is a more detailed object to provide a lamp and reflector assembly which includes an integral heat duct but which does not require that such duct be disconnected when an assembly is swung to its exposed, or servicing, position. It is an other detailed object to provide for immediate and complete access to the lamp and fixing region by swinging the lamp assembly out of the way but without, however, disturbing the focusing adjustment of the lamp assembly.

Finally, it is an object of the present invention to provide a fixing unit which consists of a minimum number of simply formed pants, primarily extrusions, and which may be constructed, assembled and maintained at minimum expense.

Other objects and advantages of the invention will become apparent upon reading the attached description and upon reference to the drawings in which:

FIGURE 1 is a simplified vertical section of a photocopy machine employing the present invention and with the stationary air duct broken away to reveal the fixing station.

FIG. 2 is a horizontal fragmentary section showing the fixing unit and taken along line 22 in FIG. 1.

FIG. 3 is a fragmentary View showing the disengagement of the adjusting pins required to swing the lamp and reflector assembly into its exposed, servicing position.

FIG. 4 is a fragmentary view showing one of the lamp mounting brackets.

FIG. 5 is a fragment showing the left hand focusing mechanism.

FIG. 6 is a transverse section taken through the fixing unit along the line 6-6 in FIG. 2.

FIG. 7 is a face view at reduced scale of one of the wire guarding members.

FIG. 8 is a transverse section similar to FIG. 6 but showing an alternative form of sheet guiding means.

FIG. 9 is a horizontal section, foreshortened and with portions broken away taken along the line 99 in FIG. 8.

FIG. 10 is a transverse vertical section taken along the line 10-10 in FIG. 8.

While the invention has been described in connection with certain preferred embodiments, it will be understood that we do not intend to be limited to the particular embodiments shown but intend to cover the various alte native and equivalent constructions falling within the spirit and scope of the appended claims.

Turning now to FIG. 1 of the drawings, an electrophotographic copying machine intended for oifice use has a frame 11, a base 12 and a housing 13. At the front of the housing two inlet slots are provided, a first slot 14 for the original and a second slot 15 for the copy sheet, with the two sheets, indicated at 16, 17, being fed in together, face to face. The sheets are separated and the copy sheet passes through a charging unit 18 where the face of the sheet acquires an overall static electric charge. The sheet is coated with zinc oxide or similar material having the ability to dissipate charge in areas which are selectively struck by light.

The original 16 is fed into an illuminating station 21 at the same time that the copy sheet 17 is fed into an exposing station 22. Light from a source 23 illuminates the original, with the image thereof being reflected by a mirror and lens assembly 24 onto the moving copy sheet and with the speed of the original corresponding exactly to the speed of the copy sheet. Subsequently the original is discharged into a return chute 25 while the copy sheet is conveyed upwardly by transport rollers 26, 2'7 into a developing unit 28 and fixing unit 39 for discharge upon a tray 31 at the top of the machine.

For details of the developing unit 28 reference is made to copending application Ser. No. 211,779, filed July 23, 1962. It will sufiice to say that the non-exposed areas on the copy sheet retain their electrostatic charge and hence attract toner particles. It is the function of the fixing unit 36 to heat the sheet with the toner particles thereon so that the particles, which include a heat-set binding agent adhere to the surface of the sheet, thereby to produce a permanent copy. In the paragraphs of description which follow, attention will be focused upon the novel fixing unit which forms the subject of the present in vention.

For the purpose of guiding the copy sheet 17 upwardly through the fixing unit 30 for positive discharge, the copy sheet is passed from the developing unit 28 straight up along a fixing plane and into the nip of

expeller rollers

36, 37 which are topped by a deflector 38. While the means for driving the

rollers

26, 27 and 36, 37 is not shown, it will be understood that the rollers are powered from the main driving motor via any desired belt or gearing arrangement producing a constant and predetermined surface speed.

Spaced from the sheet 17 and extending transversely with respect to the movement of the sheet is a lamp and reflector assembly 40. The reflector 41 is of C shape having an internal reflecting surface 42 terminating in

lips

43, 44. The reflector is made of metal having good heat conducting properties such as aluminum and is of relatively massive construction, as shown, terminating in an enlarged base 45 to provide a good heat conduction path. The reflecting surface may be gold plated if desired.

Enclosed within the reflecting surface 42 is a heat lamp 54) in the form of a thin tube having sockets 51, 52 at its ends. The sockets extend the ends of the reflector 41 as shown in FIG. 2. The lamp is preferably made of quartz having a tungsten filament extending longitudinally therein and may be either evacuated or gas filled. The filament is preferably operated at a high temperature, on the order of l800-2400 K. with a power dissipation of 650 watts. This not only produces radiation within an optimum range for absorption by the image on the copy sheet but also tend to minimize warm-up time. In the present design of machine the warm-up time is on the order of nine second or less so that there is no delay in putting the machine in operation.

In accordance with one of the aspects of the present invention, the reflecting surface 42 is elliptical and the lamp is so positioned that the filament coincides with one of the elliptical foci 53 while the other elliptical focus 54 substantially coincides with the fixing plane. For mounting the lamp in place, mounts 55, 56 are provided for engaging the sockets 51, 52. Taking the mount by way of example (FIG. 4) it will be seen that it is in the form of a C-shaped plate of metal having a central recess 57 bridged by a releasable spring clip 58 and til anchored to the ends of the reflector member upon pedestals 59.

It will be appreciated by one skilled in the art that with the reflecting surface 42 in elliptical

form having foci

53, 5 positioned as shown, the radiant energy will be focused along the focus 54, i.e., along a line or relatively narrow fixing ban extending transversely on the sheet 17. As a result of this concentration of radiant energy, the region of high temperature is localized so that the temperature at the fixing band is much higher than the temperature elsewhere in the fixing unit. Stated in other terms, the present arrangement enables a high temperature to be achieved along a narrow band on the paper to raise the particles of toner to fusing temperature while the temperature of the fixing unit as a whole is kept at a low level. This is to be contrasted with prior arrangements which rely primarily upon oven effect, i.e., upon keeping a relatively large region within the fixing unit at the fusing temperature.

In accordance with one of the aspects of the invention there is provided, aligned with and directly opposite the reflecting surface 42, a heat reflecting member 62 for confining the heat and for reflecting back at least a portion thereof. The nature of the surface is not critical although polished metal is preferred. The member 62 serves to reflect back the longer, penetrating rays of radiant energy in the direction of the sheet but also serves, in the absence of the sheet to reflect back cumulatively the energy directly radiated by the lamp so that the device comes up to operating temperature promptly after the current is turned on. In a practical design of machine such initial Warm-up period may be on the order of ten seconds. Moreover, because of the multiple reflection which takes place the fixing region is largely free of high temperature gradients which might tend to cause curling of the advancing sheet. In order to prevent unwanted scatter of the radiant energy outside of the fixing region, additional heat absorbing walls are provided above and below the reflector 42 and mirror 62. The heat absorb-ing walls associated with the reflector and indicated at 63, 64 are preferably formed integral with the reflector body, for example, as part of the same extrusion, so as to provide a good heat conducting path. The

heat absorbing walls

65, 66 lying above and below the mirror 62 are also made of good conducting metal with means being provided for efliciently carrying. away the absorbed heat.

It is one of the features of the present construction that means are provided for preventing contact between the sheet and any flat surface which may serve as a drag upon the sheet and which, therefore, might tend to buckle the leading edge thereof before such edge is nipped by the expeller rollers. Thus there is provided in front of the reflector member 41 a guard 70 which consists of spaced generally vertical wires lying in a plane and secured top and bottom to headers 71, 72, preferably by welding. To maintain the wire guard 76 in position, the bottom header is fitted into notches 73 in the frame plates While the upper header is secured by a spring clip 74. As will become apparent, this enables the guard to be quickly removed for access to the fixing region. For the purpose of preventing contact between the sheet and the

flat surfaces

62, and 66 on the other side, a guard 8i) is provided which consists of spaced generally vertical wires secured top and bottom to

headers

81, 82. The lower header is received in notches 83 in the frame and the ends of the upper header are received in holes 84 formed in the frame members 114, 114a which will be described in detail at a later point. The wires are preferably profiled as shown in FIG. 6 projecting forwardly at the upper end to guide the leading edge of the copy sheet into the nip of rollers 3-6, 37. It will be noted that the wires are bentbackwardly to provide clearance opposite the lamp 5t) which is the region of highest temperature. By the time that the sheet reaches the point 85, it is sufficiently cool.

so that contact with the guard wires will not deface the pigmented side of the sheet.

While it has been stated above that the wires forming the

guards

70, 80 are generally vertical, it is preferred to arrange the wires in herringbone pattern as set forth in FIG. 7, with the wires diverging somewhat outwardly and upwardly with respect to the center line. It is found that this tends to keep the copy sheet flat, particularly where one of the corners of the advancing edge of the copy sheet has been turned over or is dog-cared and might, therefore, become caught on one of the wires or headers. The action of the diverging guard wires is to tend to straighten out the corner, keeping it flat in the plane of the sheet ready for engagement with the nipping rollers. Equally important, keeping in mind that the wires are in the path of radiation, the heat transferred from the Wires to the sheet tends to be distributed over the surface of the sheet rather than being concentrated along narrow paths.

If desired and without departing from the invention, the guard 89 may be dispensed with and the paper may be held forwardly by an air blast from a series of horizontally arranged holes directly opposite the heat source; however, this requires a corresponding increase in capacity of the blower which is used for cooling purposes. If desired, also, a vacuum may be drawn in the C-shaped reflector by a vacuum line.

While a copy sheet will normally remain in flat condition and will move upwardly along the fixing plane 35, it does sometimes happen that the paper has, or acquires curvature. This may happen for example where the sheets have been stored in a damp environment and where sudden subjection to heat will produce differential effects on the opposite sides of the sheet causing the leading edge to curl in one direction or the other. It is one of the features of the present invention that movement of the sheet through the fixing region is entirely unobstructed so that there is no tendency for the sheet to buckle with localized guiding edges being provided so that even in the case where the paper acquires a serious curl contact is so limited that the curl is kept under control, with minimum drag, until such time as the leading edge is engaged by the expeller rollers. Since the drag upon the advancing sheet, regardless of whether it is straight or curled, is minimum, the present fixing unit is able to handle sheets which are much thinner than can be accommodated in conventional fixing units, even sheets of tissue weight.

In accordance with the present invention, parallel air ducts are provided on the opposite sides of the fixing unit and having close thermal coupling to the reflector member, mirror and associated heat absorbing surfaces so that unwanted heat is efilciently conducted away from the fixing unit. In the present instance the ducts indicated at 86, 86a are of rectangular cross section having alined inlets 87, 87a. For supplying air to the inlets a blower 83 is provided, coupled to the ducts by a conduit 88a. The conduit terminates in

outlets

89, 89a which are, as shown in FIG. 2, alined with the duct inlets.

In order to provide close thermal coupling between the reflector member 41 and the air flowing through the adjacent duct, a heat sink member 90 is provided (FIG. 6) which is in flat face-to-face contact with the base 45 of the reflector and which has integral heat conducting fins 91 spaced the entire width of the duct. For the purpose of securing the reflector member 41 to the member 90 screws 92 are used.

At the other side of the fixing unit there is a second heat sink member 100 having fins 101. Because of the close thermal coupling provided by the construction described above, it will be apparent that the heat which is conducted by the reflector member including the scatter radiation employed by the absorbing walls 63-66, is not allowed to build up but is immediately withdrawn into the air stream.

In order to maintain the temperature of the

expeller rollers

36, 37, especially the roller 37 which contacts the face of the sheet, at a safe level, and considering that the rollers are in the direct path of upward heat convection from the fixing region, an auxiliary air vent 185 is provided along the upper edge of the duct 82. The upper portion of the duct 82 is preferably blocked at its end by a plug 106 of sponge plastic or the like in order to develop sufllcient back pressure to produce a forceful jet of air. It will be apparent to one skilled in the art that a partial barrier may be provided along the length of the upper air chamber as may be necessary to cause the air to be emitted from the vent at approximately the same velocity along its entire length. The air from the vent serves the additional purpose of blowing the leading edge of the sheet into a position where it is more readily engaged by the nip of the expeller rollers.

In accordance with an aspect of the present invention, means are provided for bodily moving the reflector 41, and the lamp mounted within it, toward and away from the fixing plane 35 thereby to achieve a variation in the peak temperature to which the passing sheet is subjected. This is accomplished in the present instance by providing adjustable mounts having a pin and cam at each end between the reflector and lamp assembly and the frame of the machine. Referring to the mount 110 at the left hand end of the reflector assembly (FIGS. 2, 3 and 5), it will be noted that it is in the form of a bracket 111 which is secured to the member 90 by screws 112. Means are provided for pivoting the lower end of the bracket to the frame of the machine so that the reflector assembly may be rocked through a limited range of adjustment. This is accomplished by a pivot pin 113 which is secured to the frame bracket 114 of the machine and which engages an opening 115.

Adjustment is provided by a pin and cam connection which, in the present instance, includes a pin mounted on the frame bracket 114 previously referred to and which engages a cam slot 121 (FIGS. 5, 6). For the purpose of adjusting the earn, the cam slot 121 is formed in a slide member 125 which is mounted on the supporting bracket 111 by pin and slot connections indicated at 126, 127. A finger tab 128 is provided at the upper end of the slide. It will be apparent that pressing down upon the finger tab 128 causes the pin 120 to slide to the top end of the cam surface 121 thereby roclc'ng the reflector assembly outwardly and away from the sheet. A corresponding bracket and adjusting arrangement Him is provided at the other end of the member 90, with corresponding parts indicated by reference numerals with the subscript a. Normally the adjustment of the slides 125, 125a will be kept in step with one another so that the reflector and lamp are kept parallel to the sheet. Adjustment of the slides may be either done as a factory operation or may be done at the time that the machine is installed in place with the setting depending in part on line voltage conditions at the place of use. By positional adjustment of the reflector the radiant energy may be focused onto a narrow transverse band on the paper or may be deliberately thrown out of focus so that the radiant energy is distributed over an area with corresponding reduction in temperature. It has been found that the mechanical adjustment provides precise temperature con trol more conveniently and at less cost than when using variable resistors or the like.

While it is true that the leading edge of the sheet may not fall precisely on the fixing plane 35, nevertheless it is found in practice that the sheet is kept sufiiciently close to the plane by the

guard wires

70 and 80 so that adequate and reliable fixing is achieved at the leading edges and trailing edges of the sheet as Well as over the central portion.

In accordance with a further aspect of the present invention means are provided for disengaging the reflector and lamp assembly 40 so that the same may be swung forwardly and downwardly to expose the lamp for servicing wit-hout upsetting the adjustment of the focus and without requiring any disconnection of the air ducts. This is accomplished in the present instance by providing a slip joint at the pivot pins 113, 113a permitting the reflector and lamp assembly to be moved endwise for simultaneously disengaging the pins 120, 120a which cooperate with the

cam adjusting slots

121, 121a. Thus, as it will be noted in FIG. 2, the pivot pin 113 is extended to the left and the pin 113a is somewhat elongated. In order to bias the reflector and lamp assembly to its normal pin engaging position, a coil spling 130 surrounds the pin 113 and is held captive by a knob 131 on the end of the pin. To unseat the cam surfaces from the adjusting pins, leftward axial pressure is applied to the duct 8% (see FIG. 3) compressing the spring 131? and causing the

slots

121, 121a to move endwise out of engagement with the pins 120, 1219a which are shorter than the pivot pins 113, 113a, permitting the reflector and lamp assembly to be rocked forwardly about its pivot axis, using the knob 81a, through the position indicated by the dotdash lines in FIG. 6. This exposes the lamp 513 for inspection and replacement. To replace the lamp, the spring clips 58 which engage the lamp sockets are simply unhooked so that a new lamp may be readily inserted. Replacing the lamp does not require refocusing since the lamp filament is automatically positioned. at the elliptical focus. Access may be had to the fixing region simply by unhooking the spring clip 74 from the wire guard 70. These operations are simply reversed to reassemble the unit. Moving the reflector unit back in place reestablishes an air connection between the blower and the duct 86 (F1612).

It is one of the features of the above construction that the radiant heat from the lamp and elliptical reflector is applied to the back of the sheet. It is found that this produces more even heating over the region of focus since the rate of absorption of the heat is substantially the same over each unit of the exposed area. This is to be contrasted with fixing units which illuminate the face of the sheet and where the temperature may vary widely between the heat-absorbing powdered areas and non-powdered areas. As a result of the back illumination combined with the other features described above, hot spots are completely avoided.

In a typical automatic operating cycle the lamp is turned on approximately ten seconds before the arrival of the copy sheet. During this period the radiation is unobstructed and, because of the mirror 62 and the resulting multiple reflection, there is a build up in the radiation intensity bringing the temperature within the fixing unit immediately up to the operating level. Any scatter radiation is controlled by the walls 63-66 so that radiation is confined to the fixing region. When the leading edge of the sheet moves into the fixing unit under the urging of

rollers

26, 27, it will tend to follow the fixing plane 35, but in the event that the paper tends to curl or buckle, the guide members 7t), 89 on each side insure that the paper is kept in close proximity to the fixing plane. Since any contact between the sheet and the machine takes place along localized edges, drag upon the paper is minimized so that there is no danger of a sheet buckling within a fixing region. Any contact between the guard St) and the face of the sheet will, in a practical case, occur at the upper end of the guard after the image has already been fixed in place so that there is minimum risk of marring the copy. The

rollers

36, 37 are preferably operated at a surface speed which is just slightly greater than that of the

rollers

26, 27, on the order of one percent, to take up any curl or slack. Preferably the biasing force between the

upper rollers

36, 37 is less than that at the lower rollers so that relative slippage may take place. As soon as the leading edge is nipped between the

rollers

36, 37, the remainder of the sheet is positively maintained in the fixing plane.

Since the heat is concentrated along a narrow band in the region of focus 5% it is not necessary to maintain the entire fixing unit at high temperature. Because of this and because of the efiicient withdrawal of unwanted heat through the heat sinks for transfer to the cooling air, the temperature of the fixing unit is maintained at a low level. In short, the machine may be operated substantially below the temperature level at which scorching or charring will take place and there is no danger of a sheet catching on fire. This is true even in the unlikely event that the expeller roller drive is interrupted. The latter has been found to produce simple, localized charring along the narrow band at the focal point and without actual ignition of the sheet.

While the sheet guiding means shown in FIGS. 5, 6 and 7 constitutes a workable arrangement having a number of important advantages over the prior art, an alternative arrangement having certain additional advantages is set forth in FIGS. 8, 9 and 10. In these figures corresponding reference numerals have been employed, where applicable, with subscript a. For the purpose of preventing the leading edge of a sheet, or the body portion thereof, from approaching too closely to the source of heat, particularly where the sheet has any tendency to curl or buckle, a guard 76a is employed consisting of a plurality of spaced, generally vertical wires lying in a plane and secured at top and bottom to headers 71a, 72a respectively. The bottom header 72a may be secured in position by any desired means, for example, in notches formed in the frame plates, as in the case of the previous embodiment. The upper header is supported in place by a spring clip 74a consisting of two portions, one at each end of the assembly to permit easy movement.

In accordance with one of the aspects of the present invention a plurality of loosely mounted discs or rollers are provided at the lower end of the guard 70a for the purpose of engaging the leading edge of the sheet for guiding the same into the fixing region and for maintaining the body of the sheet in position, with the sheet in the region of the fixing plane, as the sheet is propelled upwardly. We prefer to use discs 14% mounted on a shaft 141 which shaft is mounted in extensions formed on a supporting member 55a or by any other desired means. The discs are spaced at intervals along the shaft and in a typical chain a total of six or more discs may be used.

To enable mounting of the discs so that the periphery thereof lies in a desired sheet guiding path and to position the discs as closely adjacent the lower end of the guard 7th; as possible, the shaft 141 which carries the discs is mounted, as shown, behind the lower heat-absorbing wall or apron 64a, with the discs projecting through clearance slots 142 formed therein. The slots 142 also serve the purpose of guiding and maintaining proper spacing between the adjacent discs. Since the discs are loosely mounted on the shaft 141 and since the discs have appreciable radius, the slightest grazing contact between the back of the advancing sheet and the discs sufices to rotate the discs. Since the sheet does not have to overcome sliding friction at the region of entry, the sheet, even where made of extremely light paper stock, is free to pass upwardly into the fixing region. it is to be particularly noted that if the leading edge of the sheet tends to be curled or buckled, such leading edge simply rides up on the discs without any risk of doubling back upon itself. T he rollers project slightly beyond the wires forming the guide 7th; so that the leading edge of the sheet is certain to clear the lower end of the guard.

Moreover, any small amount of toner which may be pushed up by the leading edge of the sheet upon passing through the developing unit, and which tends to collect upon the discs, cannot increase friction as where stationary guide wires are employed.

Further in accordance with the invention outlet guides are provided at the upper end of the fixing region in the form of thin plates of metal secured to the heat sink memher 160a and presenting guiding edges which are angled inwardly and upwardly thereby to guide the sheet into the nip of the expeller rollers 36a, 37a. As shown in FIG. 9, these outlet guides, indicated at 150, are in the form of angles having an anchoring portion 151 and a projecting portion 152 which is cut at an angle to define the angled guide edge 153. Similarly to the earlier embodiment, the face of the sheet is clear of any guiding means in the region of high temperature. Stated in other words, by limiting the effective guiding edge at the face of the sheet to the region of the exit there is no possibility of contact with the face of the sheet until after the toner thereon has been fixed in place by heat and cooled below the point where it is capable of being smeared. Moreover, because of the intimate thermal coupling between the guide members 150 and the heat sink and since the guide members are in the path of the cooling air blow from the upper vent 105, the members are maintained at a safely low temperature, i.e., at a tempertaure that is below that which might cause remelting of the toner. It is found that the present arrangement, by delaying any contact with the face of the sheet until the last possible moment, and by insuring that the guiding means which does contact the base of the sheet is at a low temperature, any possibility of vertical streaks on the face of the sheet, is avoided. While the number of outlet guides 150 may be varied without departing from the present invention, we prefer, in a practical oifice machine to employ a total of six.

In accordance with one of the other features of the present invention a series of guide' wires are provided at the expeller rollers for guiding the sheet into the nip, and completely through the expeller rollers, with the upper ends of the wires terminating in a curved deflector so that the sheets are directed horizontally onto a receiving tray or other suitable receptacle. More specifically, a final guide member is provided in the form of a grid consisting of spaced wires, with the wires being received and recessed in registering grooves formed in one of the expeller rollers. Thus, referring to FIGS. 8 and 10 of the drawings, the guide consists of a set of wires 161) secured, by welding or the like, to an upper header 161 and a lower header 162. The headers are secured in any desired fashion, for example, to the side plates of the machine. For accommodating the wires, the expeller roller 36a is formed with a plurality of grooves 165. Preferably the wires are angled as shown, in a shallow herringbone pattern, the width of the individual grooves being suflicient to insure lateral clearance for the angled wires. The plane of the final guide wires 16% is preferably angled with respect to the plane of tangency between the expeller rollers, intersecting such plane of tangency along a line which is spaced above the roller axis. Thus, referring to FIG. 8 the outlet guide member bears an angle to the plane of tangency as indi cated at b and which may be on the order of 10 to 30 with intersection at the line or locus 167 on the downstream side. Such arrangement, it is found, absolutely insures the guiding of the leading edge of the sheet into the nip regardless of the curl or condition of the leading edge. After the sheet passes through the nip, engagement occurs along the line 167, with the leading edge of the sheet being guided rearwardiy along the curved portion of the guide indicated at 163 and with the sheet being deposited in the tray 31 (see FIG.' 1) at the top of the machine for removal by the operator.

It will be apparent from the above that the present fixing unit is reliable, foolproof and safe in operation under all conditions which may be encountered in a business office. The unit may be constructed of a minimum of simply formed parts, with the larger parts being in the form of low cost aluminum extrusions minimizing the cost of fabrication and assembly. The unit is capable of operating over long periods of time with no maintenance except occasional renewing of the lamp.

We claim as our invention:

1. In a fixing unit for a copy sheet in a photocopy machine having a powder image thereon including a binding agent capable of fixing the powder in place by heat, the combination comprising means for advancing the sheet along a fixing plane, a longitudinal radiant lamp spaced from the fixing plane and at right angles to the direction of the movement of the sheet, a generally C-shaped reflector surrounding the lamp and extending to within a short distance of the fixing plane, said reflector being of good conducting metal and of substantial thickness, an air duct adjacent the reflector, fins thermally coupled to the reflector and extending into the air duct, the reflector surface lying in the locus of an ellipse with the lamp at one focus and with the fixing plane ear the other so that the radiant energy is concentrated at the fixing plane, a mirror arranged directly in front of the reflector and on the opposite side of the fixing plane, an air duct adjacent the mirror, fins thermally coupled to the mirror and extending into the adjacent air duct, and a blower for supplying both of said ducts.

2. In a fixing unit for a copy sheet in a photocopy machine having a powder image thereon including a binding agent capable of fixing the powder in place by heat, the combination comprising means for advancing the sheet along a fixing plane, a longitudinal radiant lamp spaced from the fixing plane and at right angles to the direction of the movement of the sheet, a longitudinal reflector surrounding the lamp and extending to within a short distance of the fixing plane, said reflector being of good conducting metal and of substantial thickness, an air duct adjacent the reflector, and fins thermally coupled to the reflector and extending into the air duct for constantly maintaining the reflector at a relatively cool temperature, the reflector surface lying in the locus of an ellipse with the lamp at one focus and with the fixing plane near the other so that the radiant energy is concentrated at the fixing plane.

3. In a fixing unit for a copy sheet in a photocopy machine having a powder image thereon including a binding agent capable of fixing the powder in place by heat, the combination comprising means for advancing the sheet along a fixing plane, a longitudinal radiant lamp spaced from the fixing plane and at right angles to the direction of the movement of the sheet, a longitudinal reflector surrounding the lamp and extending to Within a short distance of the fixing plane, said reflector being of good conducting metal and of substantial thickness, an air duct adjacent the reflector and thermally coupled thereto for con-tsantly maintaining the reflector at a relatively cool temperature, the reflector surface lying in the locus of an ellipse with the lamp at one focus and with the fixing plane at the other so that the radiant energy is concentrated at the fixing plane, and means for positionally adjusting the reflector and the lamp contained therein relatively toward and away from the fixing plane thereby to altlljust the width of the band of radiation applied to the s eet.

4. In a fixing unit for a copy sheet in a photocopy machine having a powder image thereon including a binding agent capable of fixing the powder in place by heat, the combination comprising means for advancing the sheet along a fixing plane, a longitudinal radiant lamp spaced from the fixing plane and at right angles to the direction of the movement of the sheet, a longitudinal reflector surrounding the lamp and extending to within a short distance of the fixing plane, cooling means for constantly maintaining the reflector at a safe temperature, the reflector surface lying in the locus of an ellipse with the lamp at one focus and with the fixing plane near the other so that the radiant energy is concentrated at a band extending along the fixing plane, a heat reflecting surface on the opposite side of the fixing plane for the said lamp, and sheet guiding means in the form of narrow guiding edges spaced side by side on the opposite sides of the fixing plane, the guiding edges at the face of the sheet being spaced away from said band so that the face of the sheet is engaged by the guiding edges only at regions of reduced temperature.

5. In a fixing unit for a copy sheet in a photocopy machine having a powder image thereon including a binding agent capable of fixing the powder in place by heat, the combination comprising means for advancing the sheet along a fixing plane, a radiant heat lamp spaced from the fixing plane and extending longitudinally at right angles to the direction of movement of the sheet, a longitudinal reflector surrounding the lamp for focusing the radiant energy on the fixing plane, the reflector being formed of good conducting metal and of massive cross section, and a heat sink thermally coupled to the reflector for keeping its temperature at a safe level during the time that the heat lamp is energized and regardless of whether a sheet is passing through the fixing plane, heat absorbing walls integrally formed along the edges of the reflector for thermal coupling to the heat sink and lying in a plane parallel to the fixing plane, and a series of guide wires oriented in the direction of movement of the sheet and interposed between the fixing plane and the reflector.

6. In a fixing unit for a copy sheet in a photocopy machine having a powder image thereon including a binding agent capable of fixing the powder in .place by heat, the combination comprising means for guiding the sheet along a fixing plane, a lamp and reflector assembly adjacent the fixing plane, said assembly including a longitudinally extending air duct and a reflector secured to the wall of the air duct and in good thermal coupling there with, said reflector having a C-shaped recess including a heat lamp extending longitudinally therein so that heat is focused in a narrow band upon the fixing plane, means defining an air duct on the frame having a mouth in register with said longitudinal duct, means for moving air through the duct, and means for hingedly mounting the lamp and reflector assembly for swinging movement about a horizontal axis so that the assembly may be swung outwardly away from the fixing planeto move said longitudinal duct out of a condition of register and to expose said reflector for servicing of the heat lamp.

7. In a fixing unit for a copy sheet in a photocopy machine having a powder image thereon including a binding agent capable of fixing the powder in place by heat, the combination comprising a frame, a means in the frame for conducting a sheet along a fixing plane, a lamp and reflector assembly adjacent said fixing plane and extending transversely with respect to the direction of movement of the sheet, said lamp and reflector assembly having a reflector recess and a heat lamp mounted therein, said lamp and reflector assembly being movably mounted on the frame of the machine and having cam adjusting means coupled to the frame for adjusting the assembly toward and away from the fixing plane so that radiant energy is focused on the fixing plane, said adjusting means including engaging elements disengageable upon slight bodily movement of the lamp and reflector assembly at right angles to the direction of adjustment sothat the elements may be disengaged and the assembly moved outwardly for servicing of the lamp while maintaining the setting of the adjustment.

8. In a fixing unit for a copy sheet in a photocopy machine having a powder image thereon including a binding agent capable of fixing the powder in place by heat, the combination comprising a frame means including a pair of expeller rollers on the frame for conducting the sheet along a fixing plane, a lamp and reflector assembly adjacent said fixing plane and extending transversely with respect to the direction of movement of thesheet, said lamp and reflector assembly having a reflector recess and a heat lamp mounted therein, a heat confining member opposite the reflector, longitudinally extending air ducts having means providing thermal coupling to the air therein, a blower for supplying air to the air ducts, at least one of said ducts having a longitudinally extending vent along its upper edge for discharging air toward said expeller rollers.

9. In a fixing unit for a copy sheet in a photocopy machine having a powder image thereon including a binding agent capable of fixing the powder in place by heat, the combination comprising means defining a fixing region having an inlet and an outlet, a source of radiant heat extending transversely along one side of the fixing region, and extensive heat confining and reflecting member on the other side of said fixing region and extending parallel to said source of radiant heat, means for transportintg a developed but unfixed sheet through said inlet and into the fixing region with the back of the sheet facing the source of radiant heat and with the front of the sheet facing the reflecting member, a pair of driven expeller rollers at the outlet, a first guiding means consisting of a plurality of laterally spaced guiding elements interposed between the back of the sheet and the source of radiant heat for defining a certain minimum spacing between the source and the back of the sheet, and a second guiding means consisting of a plurality of guiding elements interposed between the refiecting surface and the front of the sheet, said second guiding means being so constructed and arranged as to be in proximity to the sheet only during the terminal portion of the path of travel through the firing region and just ahead of the nip of the expeller rollers and out of proximity to the sheet in the fixing region thereby to insure freedom from contact with the face of the sheet during the high temperature portion of its path of travel through the fixing region.

10. In a fixing unit for a copy sheet in a photocopy machine having a powder image thereon including a binding agent capable of fixing the powder in place by heat, the combination comprising means defining a fixing region having an inlet and an outlet, a source of radiant heat extending transversely along one side of the fixing region, means for transporting a developed but unfixed sheet through said inlet and into the fixing region with the back of the sheet facing the source of radiant heat, a pair of expeller rollers at the outlet, guiding means for guiding the back of the sheet and insuring that the sheet is maintained at a predetermined minimum spacing from the source of radiant heat during its path of travel from inlet to outlet, face guiding means positioned opposite the face of the sheet immediately ahead of the expeller rollers for guiding the sheet into the nip of the expeller rollers while leaving the face of the sheet in the remainder of the fixing region free of guiding contact, and means for directing a blast of cooling air upon the sheet and face guiding means just ahead of the nip of the expeller rollers.

References Cited by the Examiner UNITED STATES PATENTS 2,639,364 5/53 Doyle 219-201 2,807,703 9/57 Roshon 25065 2,807,704 9/57 Allen et a1. 250-65 3,005,081 10/61 Kordes et a1. 2l9-473 3,053,962 9/62 Cerasani et al 2l9388 3,076,083 1/63 Codichini et a1 2l9--2l6 FOREIGN PATENTS 264,814 12/27 Great Britain. 278,012 1/52 Switzerland.

RICHARD M. WOOD, Primary Examiner.

Claims

8. IN A FIXING UNIT FOR A COPY SHEET IN A PHOTOCOPY MACHINE HAVING A POWDER IMAGE THEREON INCLUDING A BINDING AGENT CAPABLE OF FIXING THE POWEDER IN PLACE BY HEAT, THE COMBINATION COMPRISING A FRAME MEANS INCLUDING A PAIR OF EXPELLER ROLLERS ON THE FRAME FOR CONDUCTING THE SHEET ALONG A FIXING PLANE, A LAMP AND REFLECTOR ASSEMBLY ADJACENT SAID FIXING PLANE AND EXTENDING TRANSVERSELY WITH RESPECT TO THE DIRECTION OF MOVEMENT OF THE SHEET, SAID LAMP AND REFLECTOR, ASSEMBLY HAVING A REFLECTOR RECESS AND A HEAT LAMP MOUNTED THEREIN, A HEAT CONFINING MEMBER OPPOSITE THE REFLECTOR, LONGITUDINALLY EXTENDING AIR DUCTS HAVING MEANS PROVIDING THERMAL COUPLING TO THE AIR THEREIN, A BLOWER FOR SUPPLYING AIR TO THE AIR DUCTS, AT LEAST ONE OF SAID DUCTS HAVING A LONGITUDINALLY EXTENDING VENT ALONG ITS UPPER EDGE FOR DISCHARGING AIR TOWARD SAID EX PELLER ROLLERS.