US3745304A

US3745304A - Selective fusing

Info

Publication number: US3745304A
Application number: US00235571A
Authority: US
Inventors: M Hutner
Original assignee: Xerox Corp
Current assignee: Videojet Technologies Inc
Priority date: 1972-03-17
Filing date: 1972-03-17
Publication date: 1973-07-10
Anticipated expiration: 1990-07-10
Also published as: CA981741A

Abstract

Fuser regulating methods and the apparatus therefor are provided in accordance with the teachings of the present invention wherein a fuser assembly is selectively energized to obtain variable heating levels in accordance with the intermittent movement of successive portions of a support base through the fuser assembly such that said fuser assembly rapidly attains an operating temperature sufficient to fuse to said support base the electroscopic particles supported thereon. The fuser assembly is energized to a first heating level when successive portions of the support base are moved therethrough within a first time duration. The fuser assembly is energized to a second heating level greater than the first level when a first interval of time has expired since the immediately preceding energization thereof. If a second interval of time has expired since the immediately preceding energization of the fuser assembly, the assembly is energized to a third heating level when the next successive portion of the support base is advanced thereto. The second interval of time is greater than the first interval of time and the third heating level is greater than the second heating level. Further levels of energization may be established in accordance with the amount of time that has expired since an immediately preceding energization.

Description

United States Patent 1 1 Hutner l l 3,745,304 [4 1 July 10, 1973 52 us. 01 219/216, 219/388, 250/65 ZE 51 Int. Cl. H05b 3/00 [58] Field 61 Search 219/216, 388; 355/9;

263/6 E; 250/65 ZE; 118/637 [56] References Cited UNITED STATES PATENTS I 5/1969 Michaels 219/388 X 8/1968 Tregay et al 219/388 X Primary Exa miner-C. L. Albritton Attorney-James J. Ralabate, James C. .langarathis et al.

[57] ABSTRACT Fuser regulating methods and the apparatus therefor are provided in accordance with the teachings of the cordance with the intermittent movement of successive portions of a support base through the fuser assembly such that said fuser assembly rapidly attains an operating temperature sufficient to fuse to said support base the electroscopic particles supported thereon. The fuser assembly is energized to a first heating level when successive portions of the support base are moved therethrough within a first time duration. The fuser assembly is energized to a second heating level greater than the first level when a first interval of time has expired since the immediately preceding energization thereof. If a second interval of time has expired since the immediately preceding energization of the fuser assembly, the assembly is energized to a third heating level when the 'next successive portion of the support base is advanced thereto. The second interval of time is greater than the first interval of time and the third heating level is greater than the secondheating level. Further levels of energization may be established in accordance with the amount of time that has expired since an immediately preceding energization.

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Electrophotographic reproducing techniques of the type described in detail in US. Pat. No. 2,297,691 which issued to Chester F. Carlson, form electrostatic latent images of original documents by selectively dissipating a uniform layer of electrostatic charges deposited on the surface of a photoreceptor in accordance with modulated radiation imaged thereon. The electrostatic latent image thus formed is developed and transferred to a support surface to form a final copy of an original document. The' development process is effected by applying electroscopic particles, conventionally known as toners, to the electrostatic latent image whereat such particles are electrostatically attracted to the latent image in proportion to the amount of charge comprising such image. Hence, the areas of small charge concentration are developed to form areas of low particle density, while areas of greater charge concentration are developed to form areas wherein the particle density is greater. Once transferred to the support surface, the developed image may be permanently fixed thereto by heat fusing techniques wherein the individual particles soften and coalesce when heated so as to readily adhere to the support surface.

Various modifications in fusing techniques have heretofore been developed which achieve divers results, such techniques including selective fusing. In selective fusing, toner areas admitting of a higher density are preferentially fused leaving low density or background areas unfused. Unfused toner particles comprising background can then be removed to yield a cleaner, more readable copy. Selective fusing also contemplates the irregular, non-continuous, non-periodic operation of a fuser assembly in response to particular predetermined conditions. In this regard, selective fusing techniques are readily adapted to cooperate with selective xerographic printing techniques. Thus, if copies of only selected ones of successively scanned original documents are to be printed, the fuser assembly must be energized each time a developed image of a selected original is transferred to the support surface. It is appreciated that if the support surface comprises a web of suitable material, such as paper, the web will be transported through the fuser assembly in an irregular manner corresponding to the scanning of those unique originals to be reproduced. Consequently, scorching or burning of the web that is stationarily disposed within the fuser assembly must be avoided, while, at the same time, sufficient heat must be accummulated in the assembly to assure an adequate fusing of the toner areas to the web.

In the implementation of either of the aforementioned selective fusing techniques, i.e., the fusing of toner areas of a high density to the exclusion of relatively low density areas on a continuously moving support surface or the fixing of successive toner areas disposed in image configuration upon an irregularly moving support surface, it has been found, that in addition to the problem of scorching the support surface, it is necessary to provide for an intrinsic delay in raising the temperature of the fuser assembly to a proper value in response to the energization thereof, the accumulation of heat within the assembly during the duration of energization thereof and the temperature to which the assembly has cooled in the time that has expired since the immediately preceding energization thereof. An attendant disadvantage of prior art selective fusing techniques is the failure of such techniques to vary the amount of heat emitted by the fuser assembly in accordance with the length of time such assembly has been permitted to cool. An attempt to overcome this difficulty has resulted in maintaining the fuser assembly at a quiescent temperature level that, in some instances, has caused the scorching of the support surface disposed therein. An advantageous solution to this problem is described in detail in copending application Ser. No. 221193, filed on Jan. 27, 1972, in the name of the instant inventor and assigned to Xerox Corporation, the assignee of the present invention. An alternative solution employing a distinct technique to achieve desirable results is set forth hereinbelow.

Therefore, it is an object of the present invention to provide a method of and apparatus for selectively fusing electroscopic particles to a support surface.

It is another object of the invention to provide a method of and apparatus for regulating the operation of a fuser assembly in accordance with selected conditions requiring the energization of said assembly wherein the heat accumulated by the assembly is a function of the expiration of time from an immediately preceding energization thereof.

'A further object of the present invention is to provide a method of fusing electroscopic particles to successive portions of a support base intermittently moving through a fuser assembly, and the apparatus therefor.

An additional object of the present invention is to provide apparatus for selectively energizing a heating element that is maintained at a temperature level no lower than a quiescent level such that said heating element is energized to variable heating levels for attaining a substantially equal average radiant energy level during each energization irrespective of the length of time that has expired since an immediately preceding energization thereof.

Still another object of this invention is to provide a method of rapidly energizing a fuser assembly to permit the fixing of toner particles thereby, while precluding the possibility of scorching a support surface disposed therein, and the apparatus therefor.

Yet a further object of the present invention is to provide a method of selectively energizing a fuser assembly, and the apparatus therefor, in accordance with the amount of cooling to which said assembly has been sub jected.

Another object of this invention is to provide a method of and apparatus for fusing electroscopic particles disposed in image configuration on" a support surface in accordance with the intermittent movement of said surface through a fuser assembly.

Various other objects and advantages of the invention will become clear from the following detailed description of an exemplary embodiment thereof, and the novel features will be particularly pointed out in connection with the appended claims.

In accordance with this invention, there are disclosed fuser regulating methods and the apparatus therefor, wherein the fuser assembly is selectively energized in accordance with the occurrence of preselected conditions such that the fuser assembly rapidly attains an operating energy level sufficient to fuse to a support surface the electroscopic particles supported thereon; said fuser assembly being energized to a preestablished heating level when the immediately preceding energization thereof occurred within a first time duration; and said fuser assembly being energized to variable heating levels in accordance with the interval that has expired since the immediately preceding energization thereof.

The invention will be more clearly understood by reference to the following detailed description of an exemplary embodiment thereof in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a typical selective printing apparatus with which the instant invention may be utilized;

FIG. 2 is a schematic diagram of a conventional heating element that may be utilized in the fuser assembly of FIG. 1 and variable supply of energy therefor;

FIG. 3 is a schematic illustration of the logic circuitry that may be utilized to selectively regulate thevariable supply of energy depicted in FIG. 2; and

FIG. 4 depicts a timing diagram representing the voltage signals produced by the logic circuit of FIG. 3.

For a general understanding of selective printing apparatus in which the instant invention may be incorporated, reference is made to FIG. 1 in which some of the various system components for the apparatus are schematically illustrated. Like component parts are identified by like reference numerals throughout and primed reference numerals identify the waveforms produced by corresponding component parts identified by unprimed reference numerals. The printing apparatus illustrated herein employs electrophotographic concepts originally disclosed in US. Pat. No. 2,297,691, which issued to Chester F. Carlson. Accordingly, the selective printing apparatus comprises an electrostatic system wherein a light image of an original to be reproduced is projected onto the sensitized surface of a photosensitive plate to form an electrostatic latent image thereon. Thereafter, the latent image is developed with an oppositely charged developing material comprising electroscopic particles, known as toner particles, to form a powder image corresponding to the latent image on the photosensitive surface. The powder image is then electrostatically transferred to a support base to which it may be fixed by a fusing assembly whereby the powder is caused to adhere permanently to the support surface.

In the illustrated apparatus, visible document information is provided on each of the data cards 1 that are successively transported from a feeder tray 2 to a restack tray 49. The data cards are transported in timed sequence with respect to the operation of the remaining apparatus illustrated herein, and are caused to traverse detecting and scanning station B and slit exposure device 34 in successive order. Each data card is additionally provided with precoded information thereon, which precoded information is determinative of the selective printing of the visible document information carried by the card. More particularly, if the precoded information scanned from the card by scanning station B admits of a particular precondition, additional logic circuitry, not shown, responds to such scanned information to derive a print signal. The thus derived print signal is operated upon in a timed sequence to provide a direct correspondence between the sequential manipulation of such print signal and the particular operation performed by the apparatus illustrated in FIG. 1.

The sequential passage of data cards from the scanning station B through the projection system 33 to the restack tray 49 will cause optical images of the visible document information on each of the data cards passing through the slit exposure device 34 to be sequentially projected upon the surface of photosensitive drum 20. If desired, the projected images may admit of magnification. The photosensitive drum 20 is continuously driven at a constant angular velocity such that the surface thereof is moving at a velocity equal to that of the data cards moving past the exposure device 34. In moving in the direction indicated by the arrow, prior to reaching the exposure station C, that portion of the photosensitive drum being exposed is uniformly charged by a corona discharge station G.

The exposure of the photosensitive drum surface to the light image selectively dissipates the electrostatic charge on the surface thereof in the areas struck by light, thereby forming an electrostatic latent image in image configuration corresponding to the light image projected from the-visible document information on the data card transported throughthe slit exposure device 34. As the photosensitive drum surface continues its movement, the electrostatic image passes through a developing station D in which there is positioned a developing apparatus generally indicated by the reference numeral 13.

If the electrostatic latent image passing through development station'D is derived from a data card having a print signal associated therewith, such print signal is utilized to activate the developer motor 24 such that the developing apparatus may be operated to develop such electrostatic latent image. In contradistinction thereto, should the electrostatic latent image passing through the developing station D be derived from a data card not having a print signal associated therewith, the developer motor 24 is not activated and such elec-. trostatic latent image is not developed. It is therefore appreciated that the developing apparatus 13 is operated in an intermittent manner wherein only those electrostatic latent images derived from data cards having print signals associated therewith are developed at station D. Hence, as the photosensitive drum 20 continues to rotate in the direction indicated by the arrow, successive areas thereof will be provided with image information distributed thereon in the form of a distributed electrostatic charge pattern. However, only selected ones of successive areas will be developed. As illustrated herein, the developing apparatus 13may typically be provided with electroscopic particles that are cascaded across the surface of photosensitive drum 20, which particles are attracted electrostatically to the distributed charge pattern to form powder images.

The developed electrostatic image is transported by the photosensitive drum 20 to a transfer station E located at a point of tangency on the photosensitive drum whereat a support base 9 is intermittently moved at a speed in synchronism with the moving drum in order to accomplish transfer of the developed image. The support base 9 is here depicted as a web comprised of suitable material such as paper, plastic or the like, that is driven from a supply 13 through selective transfer mechanism 25, through fuser assembly 40, about strip driving means 16 and into a strip receiving tray 14. At the time a developed image having a print signal associated therewith arrives at the transfer station E, the associated print signal is operated upon to cause the web driving means 16 to be activated, thereby transporting the support base 9 at a velocity equal to the surface velocity of the photosensitive drum 20. Moreover, the print signal is used to operate the selective transfer mechanism 25 whereby the support base 9 engages the photosensitive drum 20 in an arc of contact. In addition, charging means 30 may be energized to provide a charge on the support base 9 prior to its engagement with the photosensitive drum so that the developed image may be electrostatically transferred from the surface of drum 20 to the adjacent side of the support base as such support base is brought into contact therewith. Thus, it is seen, that each developed electrostatic image is transferred to the support base 9; and the support base is, therefore, advanced in an intermittent manner in accordance with each print signal that is derived from the scanning information carried by the transported data cards.

After transfer, the support base 9 is transported tothe fuser assembly, generally indicated by the reference numeral 40, wherein the developed and transferred powder image on the support base is permanently fixed thereto. The fuser assembly 40 may comprise conventional apparatus capable of carrying out various fusing techniques such as oven fusing, hot air fusing, radiant fusing, hot and cold pressure roll fixing and fusing and flash fusing. Merely for the purpose of explanation, it will be assumed that the fuser assembly 40 is comprised of one or more quartz lamps connected in parallel relationship and adapted to emit an amount of heat when energized that is directly related to the magnitude of the enerigzing voltage. The dimensions of the assembly may be such as to admit of a plurality of transferred images to be disposed therein. Additionally, the fuser assembly is maintained at a quiescent operating temperature when not energized, said quiescent operating temperature being slightly less than the temperature normally required to fix the powder image, to prevent scorching of the support base. It is, therefore, readily apparent that the print signal derived from a data card is operated upon in a preselected sequential manner in correspondence with the transporting of a transferred image to the fuser assembly 40. Since, however, immediately succeeding areas of the support base 9 are provided with transferred images, but succeeding ones of v the data cards are not necessarily provided with the unique precoded scanning information, it is recognized that the support base is moved intermittently through the fuser assembly in an irregular manner. Consequently, the fuser assembly 40 must not be continuously energized in order to avoid the scorching of the support base that is maintained in a temporary stationary relationship with respect thereto. Nevertheless, as an immediately succeeding portion of the support base is advanced to the fuser assembly, the latter must be rapidly energized to an operating level capable of fixing the electroscopic powder image upon the support base. The manner in which the fuser assembly 40 is regulated to provide the just-mentioned selective fusing is described in detail hereinbelow.

The excess electroscopic particles remaining as residue on the developed images, as well as those particles not otherwise transferred therefrom, are carried by the photosensitive drum 20 to a cleaning station F on the periphery of the drum adjacent the charging station G.

The cleaning station may comprise a rotating brush and a corona discharge device for neutralizing charges remaining on the nontransferred electroscopic particles. Various other configurations and components may comprise the cleaning station F as is well known to those of ordinary skill in the art.

A more complete description of the selective printing apparatus illustrated in FIG. 1, and the manner in which such apparatus operates, is set forth in detail in copending application, Ser. No. 221,229, filed on Jan. 27, 1972, by Mark A. Hutner, et al., and assigned to Xerox Corporation, the assignee of the instant invention. It should, however, be clearly understood that the selective fusing techniques to be described in detail hereinbelow are readily adapted for broad application and should not be unnecessarily limited to the specific system described above. It will, therefore, become readily apparent that the instant invention may be readily utilized whenever selected ones of original documents are to be reproduced. Stated otherwise, the selective fusing techniques described hereinbelow are readily adapted to fix powder images to a support base therefor on an irregular basis in accordance with the occurrence of preselected conditions. Thus, in addition to the selected use as described with respect to FIG. 1, the selective fusing techniques of the present invention may be employed for the preferential fusing of dense image areas while leaving low density or background areas unfused.

Turning now to the subject matter of the present invention, and in particular, to FIG. 2, there is schematically illustrated a conventional heating element 105 that may be typically included in the fuser assembly 40 of FIG. 1. The heating element 105, which may comprise a plurality of quartz lamps connected in parallel relationship, is coupled'to a variable supply of voltage, generally designated by the reference numeral 100, the latter being adapted to supply the heating element 105 with energy. The variable supply may be a conventional voltage regulator such as model 9T68Y700l manufactured by General Electric, and therefore need not be described in detail herein. It should however, be noted that the variable supply 100 includes bidirectional current conducting means 101 which may be a silicon bi-directional triode device, such as a triac, capable of conducting relatively high AC current in both directions and whose time of initial conduction during a half cycle is dependent upon the magnitude of a control voltage applied to the trigger input 101a thereof. Hence, the bi-directional current conducting means 101 may function as a triggerable switch that is rendered conductive during a half-cycle of an AC voltage applied thereto when the voltage exceeds a threshold or firing level. Those of ordinary skill in the art will recognize that the bi-directional current conducting means may be a conventional thyristor. 0nce rendered conductive, the bi-directional current conducting means 101 is adapted to remain conductive until the voltage applied thereto commences a successive halfcycle.

It may be observed that the control voltage applied to the trigger input 101a of bi-directional current conducting means 101 is derived from a voltage dividing means that comprises series connected resistance means 102, 103 and 104. Trigger input 101a is coupled to the junction formed by the series connection of resistance means 102 and 103. The value of the resistance the bi-directional current conducting means 101 is rendered conductive, is decreased by selectively reducing the voltage derived by the illustrated voltage dividing means. A plurality of resistance means 106-108 are capable of being selectively connected in series relationship with resistance means 102 by energizable shunting switch means 106a-108a. Resistance means 106 is greater than resistance means 107 which, in turn, is greater than resistance means 108. In addition, switch means l06a-108a are capable of being individually opened as will soon be seen. It should be appreciated that the effective resistance of the first stage of the illustrated voltage dividing means is increased when one or more of resistance means 106-108 is connected in series with resistance means 102. Consequently, the threshold or firing level voltage applied tothe trigger input 101a of bidirectional current conducting means 101 is correspondingly reduced in accordance with the total value of series resistance. Thus, the time of initial conduction during a half cycle is advancedand the duration of conductivity of the bi-directional current conducting means'l01 is increased. With one or more of resistance means .106-108 connected in series with resistance means 102, the root mean square (RMS) voltage applied to heating element 105 is increased proportionally. resulting in a corresponding increase in the amount of heat radiated therefrom. Typically, when shunting switch means 106a is opened to connect resistance means 106, in series withresistance means 102, a maximum fusing voltage is applied to heating element 105 whereby a maximum heating level is obtained thereby. Similarly, when shunting switch means 107a is opened to connect resistance means 107 in series with resistance means 102, an intermediate fusing voltage is applied to heating element 105 whereby an intermediate heating level is obtained thereby. And when shunting switch means 108:; is opened to connect resistance means 108 in series with resistance means 102, a minimum fusing voltage is applied to heating element 105 whereby a minimum heating level is obtained thereby. Obviously, additional series connected resistance means may be provided to obtain various other heating levels, a'sdesired.

When 'an energizable'shunting switch means is energized so as to assume an open state, a corresponding resistance means 106-108 is thereby connected in seties with resistance means 102. It may be recognized that the shunting switch means may comprise the movable contacts of conventional relays, electronic switches or the like. The connecting of resistance means 106-108 to resistance means 102 alters the ratio of division of the voltage dividing means to thereby alter'the threshold level applied to trigger input 101a. Accordingly, the point at which the bi-directional current conducting means 101 is rendered conductive during the positive half cycle of the AC voltage applied thereto is advanced in accordance with the value of the connected resistance means. The conductivity of the bi-directional current conducting means is maintained until the conclusion of the positive half-cycle. During the negative half-cyle of the AC voltage, bi-directional current conducting means 101 is rendered conductive at a symmetrical point. The relatively large duration of conductivity during each cycle is effective to apply a correspondingly increased RMS voltage to heating element 105 whereby the level of heat radiated by the heating element is sufficient to fuse the electroscopic material. It should be readily. apparent that various other switching circuits and associated switch means may be provided to increase the resistance of the first stage of the voltage dividing means, thereby altering the ratio of division thereof in a suitable manner.

An exemplary embodiment of apparatus that may be utilized to energize energizable shunting switch means 10611-10811 is schematically illustrated by the logic circuit of FIG. 3 and comprises storage means 200, gating means 203, 204 and 205 and driver means 208, 209, 210. Storage means 200 is adapted to store a history of the'preceding energizations of the heating element includedin the fuser assembly 40 illustrated in FIG. 1 and, therefore, may comprise a plural stage shift register meansincluding an input terminal for receiving an irregularly occurring selective enerigzing signal and a shift terminal for receiving a periodic shift signal. It is recalled that the selective printing apparatus with which the present invention may be utilized is adapted to develop and transfer an image of a given data card when said card is provided with scanning information from which is derived a print signal. As described in copending application Ser. No. 221,229, filed Jan. 27, 1972, a derived print signal is shifted through shift register means in timed relation with the rotation of image information obtained from a corresponding data card. The image information is distributed on the surface of a rotating photosensitive drum in the form of a distributed electrostatic charge pattern. Accordingly, the relative positionof the image information at any given time may be determinedby the particular position oc cupied by the print signal as said print signal is shifted through the shift register means. Moreover, once the image information is developed and transferred to a portion of the support base, the movement of that portion may be represented by a corresponding shifting of the printsignal through the shift register means. It should, therefore, be readily apparent that a print signal will be shifted to a predetermined position within the shift register means when a portion of the support base is advanced to the fuser assembly. I-Ience, electroscopic particles thatare disposed in image configuration on the support base are to be fused to the support base when a print signal occupies said predetermined position. As will soon become apparent, the print signal occupying the predetermined position need not be associated with that particular portion of the support base that is advanced to the fuser assembly, However, except for initial portionsof the support base, each succeeding portion that is transported to the fuser has a powder image disposed thereon. Storage means 200 may, therefore, comprise a portion of the aforementioned shift register means having a first stage corresponding to the predetermined position and including a plurality of succeeding stages. Alternatively, the storage means 200 maycomprise an individual plural stage shiftregister means having a first stage corresponding to the aforementioned predetermined position and including a plurality of succeeding stages. In either case, the storage means is illustrated in FIG. 3 as comprising a plural stage shift register means wherein only stages l-8 have been designated as only these stages are of interest here. As is understood by those of ordinary skill in the art, a conventional shift register is adapted to shift an input signal applied thereto consecutively through the stages thereof in accordance with a transition in the shift signal applied. The shift register may, therefore, comprise a counter capable of representing timing information relating to the times of occurrence of successive input signals in accordance with the particular stages occupied thereby.

The input terminal of storagemeans 200 is coupled to terminal 201 to which is applied a preselected information signal such as the aforementioned print signal. The shift terminal of storage means 200 is coupled to terminal 202 to which is applied a periodic shift signal. The periodic shift signal may be derived from the systern clock which is explained in detail in copending application Ser. No. 221,229, filed Jan. 27, 1972. Accordingly, the periodic shift signal may take the form of clock pulses having a period corresponding to the rate at which the data cards are scanned and imaged.

The clock pulse period is thus equal to the interval of time required to transfer successive developed images from the photosensitive drum to support base 9. Consequently, the clock pulse period is also equal to the interval of time required to translate successive portions of the support base 9 to the fuser assembly 40.

The outputs of stages l-7 of storage means 200 are coupled to the illustrated decoding means, which decoding means is adapted to analyze the sequence of the print signals that have been supplied to storage means 200. The decoding means includes first gating means 203, second gating means 204 and third gating means 205. First gating means 203 is comprised of a coincidence means including a first input terminal coupled to the first stage of storage means 200, a second input terminal coupled to the output terminal of second gating means 204 and a third input terminal coupled to the output terminal of third gating meand 205. The coincidence means is adapted to sense successive occurrences of a print signal and the expiration of no more than a preestablished interval of time therebetween. Coincidence means 203 is adapted to produce an output signal in response to the application of a predetermined signal at each input terminal thereof. Accordingly, coincidence means 203 may comprise a conven tional NAND gate whereby a binary 0 is produced at the output terminal thereof when a binary l is supplied to each input terminal thereof. For the purpose of the present discussion, it will be assumed that a binary l is represented by a positive DC potential and a binary 0 is represented by ground potential. It is, of course, understood that the foregoing binary signals may be represented by any suitable voltage potentials. Similarly, coincidence means 203 may comprise a conventional AND gate whereby a binary l is produced at an output terminal thereof when a binary l is supplied to each input terminal thereof.

The second gating means 204 is adapted to sense the expiration of a first interval of time intermediate successive occurrences of a print signal and to produce a signal in response thereto. More particularly, gating means 204 is adapted to detect when more than two clock pulse periods, but less than a predetermined number of clock pulse periods, have expired since the occurrence of the immediately preceding print signal. Such expiration corresponds to an elapsed time since the previous enerigzation of the heating element included in fuser assembly 40 that the fuser assembly has cooled to a temperature requiring a higher level energization thereof to attain a suitable accumulation of radiant energy in the assembly. Second gating means 204 includes a first input terminal coupled to a given stage, such as the first stage, of storage means 200 via inverting means 206, a second input terminal coupled to a second stage of storage means 200, a third input terminal coupled to a third stage of storage means 200 and a fourth input terminal coupled to the output termini of third gating means 205 via inverting means 207. An output signal is produced by second gating means 204 when the first stage of storage means 200 is occupied by a print signal but the second and third stages, respectively, of storage means 200 are not occupied by a print signal. Accordingly, second gating means 204 may comprise a conventional OR circuit wherein a binary 0 is produced at the output terminal thereof when a binary 0 is applied to each input terminal thereof. Alternatively, the second gating means 204 may comprise a conventional NOR gate, a NAND gate or an AND gate, wherein a first input terminal thereof is coupled directly to the first stage of storage means 200 and the second and third input terminals thereof are coupled to the second and third stages, respectively, of storage means 200 via inverting means. The inverting means 206 and 207 illustrated herein may each comprise a conventional logic negation circuit adapted to produce a binary 0 in response to a binary l supplied thereto, and, conversely, to produce a binary l in response to a binary 0 supplied thereto.

The third gating means 205 is adapted to sense the expiration of a second interval of time intermediate successive occurrences of the print signal, the second interval being greater than the aforementioned first interval. More particularly, gating means 205 is adapted to detect when more than the aforementioned predetermined number of clock pulse periods have expired since the occurrence of the immediately preceding print signal. For the purpose of explanation, it will here be assumed that the predetermined number is six; however, any other arbitrary number of clock pulse periods may be selected. Should this condition obtain, it is appreciated that the time that has elapsed since the previous energization of the heating element included in the fuser assembly 40 is sufficient to permit cooling of the fuser assembly to a point whereat a maximum level of energization thereof ispreferred to achieve a suitable accumulation of radiant energy therein. Gating means 205 may include a first input terminal coupled to the first stage of storage means 200 via inverting means 206 and second through seventh input terminals coupled to stages 2-7, respectively, of storage means 200. The gating means may comprise a conventional OR circuit similar to OR circuit 204 or, alternatively, an AND gate, NAND gate, NOR circuit or other suitable gating means. It is recognized that if gating means 205 is constructed of commercially available logic components, a seven-input OR circuit might not be feasible. Accordingly, the OR circuit may be comprised of a pair of readily available four-input OR circuits having output terminals coupled to a further OR circuit.

Although not specifically illustrated herein, additional gating means, similar to those just described, may be provided to sense the expiration of other intervals of time intermediate the successive occurrences of a print signal. Similarly, the interconnections between gating means 205 and storage means 200 may adopt any suitable configuration to permit the sensing of the expiration of any corresponding interval of time.

The configuration of NAND gate 203, OR circuit 204 and OR circuit 205 is adapted for mutually exclusive operation. Hence, an output signal may be produced by one and only one of the illustrated gating means at any instant of time. This is achieved by utilizing the output signals of some of the gating means as inhibit signals to inhibit the operation of other gating means. More particularly, the output terminal of OR circuit 205 is coupled to the input terminals of OR circuit 204 and NAND gate 203, respectively, and the output terminal of OR circuit 204 is coupled to another input terminal of NAND gate 203. Consequently, an output signal produced by OR circuit 205 serves to inhibit OR circuit 204 and NAND gate 203 from producing output signals; and an output signal produced by OR circuit 204 serves to inhibit NAND gate 203 from producing an output signal.

As illustrated in FIG. 3, the output terminals of NAND gate 203, OR circuit 204 and OR circuit 205 are coupled to corresponding driving means 208, 209 and 210, respectively. The driving means are conventional in that each responds .to a binary applied thereto to provide a reference potential, such as ground, at its output terminal. The output terminals of driving means 208, 209 and 210 are coupled to the energizing coils 108b, l07b and 106b, respectively, of conventional relays. It should be recognized that each energizing coil is associated with the contact of a switch means 108a, 107a and 106a of FIG. 2. Hence, the energization of a coil effects the opening of a corresponding switch means.

Each of driving means 208, 209 and 210 is adapted to respond to a binary 0 switch energizing signal applied thereto to supply an associated energizing coil with ground potential. Accordingly, driving means 208 may comprise a conventional intergrated circuit such as model SN 75451A manufactured by Texas Instruments, lnc., and having an input coupled to NAND gate 203, and an output to energizing coil 108b. Driving means 209 and 210 may be similarly constructed and further description thereof is not deemed necessary for a sufficient understanding of the present invention.

The operation of the apparatus illustrated in FIG. 3 will now be described. It is recalled that the successive portions of the support base 9 upon which the electroscopic particles are disposed in image configuration are intermittently moved through the fuser assembly 40 even though the .data cards and photosensitive drum are continually advanced and rotated, respectively. Consequently, it is expected that if one out of five cards, for example, are to be printed, only1one print receiving portion of the support base 9 will be moved through the fuser assembly 40 during the interval required to process the five data cards. Stated otherwise, only one print signal in the form of a pulse will be applied to terminal 201 notwithstanding the application of five clock pulses to terminal 202. To facilitate the ready understanding of the instant invention, the example represented by the timing diagram of FIG. 4, as read in a left to right configuration, will be assumed. This example is assumed merely for purposes of illustration and should not be considered to unnecessarily limit the instant teachings of the invention thereto. It will also be assumed that the fuser assembly and printing apparatus operatively associated therewith has been in operation for some time. At the first timing period under consideration, i.e., at timimg pulse 1 of waveform 202', the first print signal, represented by the first pulse at the left-hand portion of waveform 201 is applied to terminal 201. It is seen that this first pulse 201 represents that a portion of the support base 9 has been advanced to the fuser assembly 40, the heating element included in the fuser assembly must now be energized to attain a temperature sufficient to achieve the fixing of the electroscopic particles to the support base and the heating element has not been energized since the last occurrence of the immediately preceding pulse 201, not shown. Thus, at clock pulse 1, the print signal is shifted into the first stage of storage means 200 and stages 2-7 thereof are not provided with print signals. The storage means 200 may be responsive to the positive transition of the clock pulses 202 applied thereto. Of course, the negative transitions of the clock pulses may be utilized to shift applied signals through the storage means, if so desired. Accordingly, the binary l stored in the first stage of storage means 200 is inverted by inverting means 206 and applied as a binary 0 to OR circuit 205. Since each of stages 2-7 now stores a binary O the remaining input terminals of OR circuit 205 are each supplied with a binary 0 Consequently, OR circuit 205 produces a binary 0 switch energizing signal as illustrated by waveform 205, representing that more than six clock'pulse periods have expired since the occurrence of the immediately preceding print signal. This switch energizing signal is applied to NAND gate 203 and OR circuit 204 as inhibit signals. Thus, NAND gate 203 produces a binary l in response to the binary 0 supplied thereto by OR circuit 205. Similarly, inverter means 207 supplies OR circuit 204 with a binary 1 whereby a binary l is produced by the latter OR circuit. Waveforms 203' and 204' illustrate the inhibiting of NAND gate 203 and OR circuit 204.

It is thus appreciated that only driving means 210 is supplied with a binary 0 .Consequently, only energizing coil 106b is energized as illustrated by waveform 106b. At clock pulse 1, therefore, current flows from the source of energizing potential +V through energizing coil 106b to ground potential applied to the energizing coilby driving means 210. Switch means 106a is activated, and thereby opened, to connect resistance means 106 in series with resistance means 102. The resistance means 106 exhibits the maximum resistance, thereby triggering bi-directional current conducting means 101' to supply the heating element 105 with energizing voltage admitting of a maximum amplitude. Heating element 105 is thus energized to a maximum heating level as indicated by waveform 105. This maximum heating level is preferred because it is recognized that the fuser assembly 40 had not been previously energized for a prolonged period of time and the heating element therein had cooled to a lower quiescent temperature. Energization of the heating element with a maximum voltage level will permit the fuser assembly to accumulate additional radiant energy whereby a higher temperature is attained.

It is apparent from waveform 201', that at clock pulse 2 a print signal is not applied to terminal 201. Hence, the next successive portion of the support base 9 is not moved through the fuser assembly 40. This, of course, means that the image information derived from the data card corresponding to clock pulse 2 is not to be printed. Hence, a binary 0 is stored in the first stage of storage means 200 and the print signal is shifted into the second stage thereof. NAND gate 203 is thus supplied with a binary O to produce a binary l at the output terminal thereof. OR

circuits

204 and 205 are each supplied with a binary l stored in the second stage of storage means 200 to produce a binary l Consequently, none of the driving means 208-210 are supplied with switch energizing signals and each of the switch means 106a-108a remains closed. Fuser assembly 40 is not energized and the heating element is maintained at a quiescent level. At clock pulse 3, terminal 201 is not provided with a print signal and, therefore, the fuser assembly 40 need not be energized. In addition, at this time, the first print signal that had been applied to terminal 201 is shifted into the third stage of storage means 200. Similarly, at clock pulse 4, that print signal is shifted into the fourth stage of storage means 200.

Waveform 201' indicates that the next successive print signal pulse is applied to terminal 201 during clock pulse period 5. At this time, the immediately preceding print signal is shifted into the fifth stage of storage means 200. Hence, if each clock pulse period is assumed to be 332 milliseconds, approximately 1,328 milliseconds (i.e., four clock pulse periods) have elapsed since a given portion of the support base 9 was moved into the fuser assembly 40. Moreover, approximately 996 milliseconds have elapsed since the energization of the heating element of the fuser assembly 40 was terminated. The fuser assembly has, therefore, cooled such that the accumulated energy therein has dissipated below the fusing level. At clock pulse 5, the immediately preceding print signal is shifted into the fifth stage of storage means 200 to supply OR circuit 205 with a binary l It is apparent that the condition precedent to the production of a switch energizing signal by OR circuit 205 has not been fulfilled. The OR circuit responds to the binary 1 supplied thereto to apply a binary 0., via inverter means 207, to OR circuit 204 and to apply a binary I to NAND gate 203. It is noted that the elapsed time between successive print signals has exceeded two clock pulse periods. The second and third stages of storage means 200 are not provided with print signals and, therefore, each of the input terminals of OR circuit 204 coupled to the second and third stages is supplied with a binary Now, the print signal stored in the first stage of storage means 200 is subject to a logic negation by inverter means 206 and is supplied to OR circuit 204 as a binary 0 Consequently, each input terminal of OR circuit 204' is provided with a binary 0 resulting in the production of a binary 0 at the output terminal thereof as may be observed from waveform 204'. NAND gate 203 is supplied with the binary 0 produced by OR circuit 204, whereby the operation of the NAND gate is inhibited as indicated by waveform 203'. Consequently, driving means 209 is provided with a binary 0 whereas driving means 208 and 210 are each provided with a binary l At clock pulse 5, OR circuit 204 produces a switch energizing signal whereby coil l07b is energized as denoted by waveform 107b. Switch means 1070 is thus activated to connect resistance means 107 in series with resistance means 102. Heating element 105 is supplied with an intermediate voltage amplitude, as represented by waveform 105, and is energized to an intermediate heating level. The electroscopic particles disposed on the support base 9 in image configuration are thus fused to the support base. Furthermore, the intermediate energizing level of the heating element is sufficient to enable the fuser assembly to attain a desirably high temperature, thus accumulating an adequate amount of radiant energy.

A print signal is not applied to terminal 201 at the next clock pulse period 6 and, therefore, further movement of the support base 9 is interrupted. Thus, that portion of the support base that was previously advanced into the fuser assembly 40 remains therein and the accumulated radiant energy serves to properly complete the fusing operation. In addition, at clock pulse 6, a binary 0 is shifted into the first stage of storage means 200 and the previous print signal is shifted into the second stage of storage means 200. Accordingly, NAND gate 203, OR circuit 204 and OR circuit 205 are each disabled and thus do not produce output signals.

The next succeeding print signal is applied to terminal 201 at clock pulse 8 and is shifted into the first stage of storage means 200 as indicated by the waveform 201'. Hence, three clock pulse periods have elapsed since the immediately preceding print signal was applied to terminal 201 and approximately 664 milliseconds have elapsed since the energization of the heating element included in the fuser assembly was terminated. At clock pulse 8, the immediately preceding print signal is shifted into the fourth stage of storage means 200 and the first print signal is shifted into the eighth stage of storage means 200. Accordingly, OR circuit 205 is inhibited from producing a binary 0 switch energizing signal because of the binary l supplied-thereto by the fourth stage of storage means 200. Moreover, the binary 1 produced by the OR circuit is inverted by inverter means 207 and applied as a binary 0 to OR circuit 204. In addition, since the elapsed time between successive print signals exceeds two clock pulse periods, OR circuit 204 is supplied with a binary O by each of the second and third stages of storage means 200. Finally, the print signal stored in the first stage of storage means 200 is inverted by inverter means 206 and applied to OR circuit 204 as a binary O Consequently, the OR circuit produces a binary 0 switch energizing signal as depicted by waveform 204', which switch energizing signal is coupled to and serves to inhibit NAND gate 203. Driving means 209 responds to the switch energizing signal applied thereto to energize coil 107b, as indicated by'waveform 107b. Energization of coil l07b serves to activate switchmeans 107a to connect resistance means 107 in series with resistance means 102. Heating element is thus supplied with an intermediate voltage amplitude and is energized to an intermediate heating level. The fuser assembly is thus enabled to attain a desirable temperature whereby an adequate amount of radiant energy may be accumulated. Consequently, the electroscopic particles disposed in configuration upon the third successive portion of the support base 9 are fused thereto.

At clock pulse 9 an immediately succeeding print signal is applied to terminal 201, thereby representing that the support base 9 is advanced through fuser assembly 40 to expose the next successive portion of the support base to a fusing operation. It is, therefore, appreciated that the image information derived from consecutive data cards are to be printed. Hence, at clock pulse 9 the first and second stages of storage means 200 are each occupied by a print signal, the fifth stage of storage means 200 is occupied by a print signal and the remaining stages of storage means 200 are not provided with print signals. At this time, the binary l stored in the second stage of storage means 200 is effective to inhibit OR

circuits

204 and 205 from producing respective binary 0 switch energizing signals. It is, therefore, appreciated that each OR circuit supplies NAND gate 203 with a binary 1 enabling the NAND gate to respond to the signal applied to the remaining input terminal thereof. The print signal applied to terminal 201 and stored in the first stage of storage means 200 is applied as a binary 1 to NAND gate 203. Consequently, the NAND gate is activated to produce a binary 0 switch energizing signal in response to the binary 1 applied to each input terminal thereof, as illustrated by waveform 203'. Driving means 208 responds to the switch energizing signal applied thereto by NAND gate 203 to energize coil 108b, as represented by waveform 108b'. The energized coil activates switch means 108a to open, thereby connecting resistance means 108 in series with resistance means 102. It is recalled that a minimum energizing voltage is applied to heating element 105 when resistance means 108 is connected to resistance means 102. This is depicted by waveform 105'. Hence, a minimum heating level is obtained by the fuser assembly. The successive energizations of the heating element is sufficient to apply an adequate amount of heat to the electroscopic particles disposed in image configuration on support base 9 to fuse said particles to the support base. Hence, it is not necessary to energize the heating element to a level greater than said minimum heating level. The printed images derived from the successive data cards are suitably fixed to the support base to form permanent copies thereof.

At clock pulse 10, the immediately preceding print signal is shifted into the second stage of storage means 200, the next preceding print signal is shifted into the third stage of storage means 200 and the next preceding print signal is shifted into the sixth stage of storage ceding print signal, the fourth stage of storage means 200 is occupied by the next preceding print signal and the seventh stage of storage means 200 is occupied by the third preceding print signal. Since the elapsed time between successively occurringprint signals does not exceed two clock pulse periods, only NAND gate 203 producesan output signal, represented by waveform 203'. The signal produced by NAND gate 203 is applied as a switch energizing signal to driving means 208. Consequently, coil. 108b is energized and switch means 108a is activated to thereby connect switch means 108 in series with switch means 102. Thus, the heating element 105 included in the fuser assembly 40 is energized to a minimum heating level as represented by waveform 105'. Electroscopic particles are thus fused to the intermittently moving support base.

During the next succeeding clock pulse periods, the

image information rotating on the photosensitive drum is not printed and, therefore, a print signal pulse is not applied to terminal 201, the support base 9 is not advanced through the fuser assembly 40 and the heating element included in the fuser assembly is not energized. However, at clock pulse 18 image information derived from a data card and transferred to the support base 9 is to be fixed to the support base. Accordingly, a portion of the support base upon which electroscopic particles are disposed in image configuration is advanced to the fuser assembly 40 and a print signal is applied to terminal 201 and shifted into storage means 200 as represented by waveform 201. None of the second to seventh stages of storage means 200 is occupied by a print signal. It is recognized that more than two clock pulse periods have expired since the occurrence of the immediately preceding print signal. In fact, more than six clock pulse periods have'expired. Thus, heating element 105, which has cooled to a lower quiescent temperature, must be energized with a maximum voltage to enable sufficient radiant energy to accumulate in the fuser assembly 40. Consequently, OR circuit 205 receives a binary 0 from each of the second through seventh stages of the storage means 200, as well as a binary 0 from inverter means 206. A binary 0 switch energizing signal is thus applied to driving means 210 by the OR circuit as illustrated by waveform 205'. Moreover, the switch energizing signal serves to inhibit OR circuit 204 and NAND gate 203 from producing their respective switch energizing signals in the now understood manner. Therefore, coil 106b is energized to activate switch means 106a, resulting in the supply of a maximum amplitude energizing voltage to heating element 105, as indicated by waveform 105. It is appreciated that the fuser assembly isthus energized to a maximum heating level.

It should now be fully appreciated from the foregoing description thereof that storage means 200 stores the time related history of the movement of successive portions of support base 9 through the fuser assembly 40.

Clearly, a variable time interval may elapse between consecutive movements. This, of course, is represented by the selected stages of storage means 200 which are occupied by print signals. Moreover, since the energization of the heating element of the fuser assembly is dependent upon the application of a print signal to terminal 201, the selected stages of storage means 200 that are occupied by print signals provide an indication of the-length of time that has expired between successive energizations of the heating element.

In the description of FIG. 3, it has been assumed that conventional, commercially available TTL logic is utilized throughout for each of the NAN D gates, OR circuits, inverting means, storage means and driving means. However, any of the specific logic components or arrangments may be replaced by other components or groups thereof which produce similar output signals in response to corresponding input conditions. Also, the precise mode of logic operation employed thereby may differ from that described hereinabove in a manner that is obvious to those of ordinary skill in the art. Furthermore, the logic circuit illustrated in FIG. 3 may, alternatively, be implemented by MSI logic, individual circuit components or MOS circuit chips. In addition, the variable supply illustrated in FIG. 2 may be replaced by other conventional sources of energy sufficient to supply the heating element with variable voltages in response to the switch energizing signals produced by the NAND gate 203, OR circuit 204 and OR circuit 205 of FIG. Accordingly, suitable high voltage sources may be selectively and/or permutatively coupled to heating element 105 through conventional switching means, the latter being adapted to be activated in response to the switch energizing signals produced by the aforementioned gating means. Although discrete energy levels are illustrated as being applied to the fuser assembly, it is appreciated that energy admitting of a continuous function may be applied. Moreover, the heating element 105 need not be limited merely to a conventional quartz lamp, but, alternatively, may comprise any suitable heat radiating device or other heating device conventionally utilized in fuser assemblies or other electroscopic particle fixing devices.

In the embodiment illustrated in FIGS. 2 and 3, the activation of switch means 1060-10811 and, therefore, the operation of gating means 205, 204 and 203, respectively, need not be mutually exclusive. Accordingly, resistance means 106-108 may all be equal and the operation of the gating means to produce corresponding switch energizing signals will add additional resistance to the voltage dividing means. Thus, the operation of NAND gate 203 need not be inhibited by

OR circuits

204 and 205 and, similarly, the operation of OR circuit 204 need not be inhibited by OR circuit 205. Hence, if NAND gate 203 produces a switch energizing signal upon detecting successive occurrences of a print signal, resistance means 108 is connected to resistance means 102 and the fuser assembly is energized to its minimum heating level. If more than two clock pulse periods have expired between successive print signals, both OR circuit 204 and NAND gate 203 may produce switch energizing signals to connect resistance means 107 and resistance means 108 to resistance means 102. The fuser assembly is then energized to its intermediate heating level. And if more than six clock pulse periods have expired between successive print signals, then OR circuit 205, OR circuit 204 and NAND gate 203 may produce switch energizing signals to connect all of resistance means 106-108 to resistance means 102. The fuser assembly is then energized to its maximum heating level.

While the invention has been particularly shown and described with reference to an exemplary embodiment thereof, it will be obvious to those skilled in the art that various changes and modifications in form and details may be made without departing from the spirit and scope of the invention. Thus, the specific numerical examples described hereinabove are intended to be merely illustrative of the operation of the apparatus disclosed herein and are not intended to limit the teachings of the instant invention. Accordingly, any suitable clock pulse period may be employed herewith. Moreover, storage means 200 may comprise any conventional storage device capable of storing a suitable history of the previous operation of the fuser assembly and, therefore, of the intermittently moving support base. OR circuit 204 may be adapted to produce a switch energizing signal if three or more clock pulse periods have expired since the occurrence of the immediately preceding print signal. Similarly, OR circuit 205 may be adapted to produce a switch energizing signal when any other convenient number of clock pulse periods have expired since the occurrence of an immediately preceding print signal. And additional gating means may be provided to produce further switch energizing signals upon detecting the expiration of other clock pulse periods. It is, of course, recognized that these OR circuits and gating means may, therefore, produce switch energizing signals to energize the heating element of the fuser assembly to a suitable heating level in accordance with the particular interval of time that has expired since the immediately preceding energization of the heating element. In addition, resistance means 106-108 may be replaced with an active element having a variable resistance dependent upon the magnitude of an applied voltage, such as a voltagecontrolled resistor FET transistor, a silicon offset-gate depletion-type MOS transistor, or the like. The control voltage applied to the variable resistance may be derived by summing the switch energizing signals produced by the gating means of FIG. 3. It is, of course, recognized that in this modification, the operation of the gating means is not mutually exclusive. Accordingly, the total number of gating means that are activated and, therefore, the magnitude of the control signal derived, is a function of the expiration of time intermediate successive print signals. Moreover, the voltage that is thus applied to the heating element need not admit of discrete levels, as illustrated in FIG. 4, but may, if desired, be a continuously varying amplitude. It is intended that the appended claims-be interpreted as including the foregoing as well as other obvious changes and modifications.

What is claimed is 1. A method of regulating the operation of a fuser assembly in accordance with selected information requiring the energization of said fuser assembly wherein the radiant energy accumulated by said fuser assembly is a function of the expiration of time from an immediately preceding energization thereof, comprising the steps of:

sensing the occurrence of a preselected information signal to energize said fuser assembly to a preestablished minimum energy level; and

energizing said fuser assembly to a variable energy level that is dependent upon the interval of time that has expired intermediate successive occurrences of said preselected information signal.

2. The method of claim 1 wherein said fuser assembly is energized upon sensing the respective occurrences of the succeeding ones of the succeeding ones of the successive preselected information signals.

3. The method of claim 2 wherein said step of sensing the occurrence of a preselected information signal comprises the steps of:

serially storing each preselected information signal and the number of predetermined time durations separating successive ones of said preselected information signals in consecutive order; and

generating a fuser energizing signal when a preselected information signal is stored in a first position of said consecutive order.

4. The method of claim 3 wherein said step of energizing said fuser assembly comprises the step of generating a variable amplitude fuser energizing signal when a preselected information signal is stored in a first position of said consecutive order and a number of predetermined time durations are stored in the next successive positions of said consecutive order, said fuser energizing signal admitting of an amplitude that is a func- I tion of said number of successively stored predetermined time durations.

5. A method of regulating the operation of a fuser assembly in accordance with selected information requiring the energization of said fuser assembly wherein the heat accumulated by said fuser assembly is a function of the expiration of time from an immediately preceding energization thereof, comprising the steps of:

serially storing each preselected information signal and the number of predetermined time durations separating successive ones of said preselected information signals in consecutive order; generating a first switch energizing signal when a preselected information signal is stored in a first position of said consecutive order;

generating a second switch energizing signal when a preselected information signal is stored in a first position of said consecutive order and a'first selected number of predetermined time durations are stored in the next successive positions of said consecutive order;

generating a third switch energizing signal when a preselected information signal is stored in a second position of said consecutive order and a second selected number of predetermined time durations are stored in the next successive positions of said consecutive order; and

selectively energizing said fuser assembly to first, second and third energy levels in response to said first, second and third switch energizing signals, respectively.

6. The method of claim wherein said fuser assembly is energized to a minimum energy level when said first switch energizing signal is generated, said fuser assembly is energized to a second energy level greater than said minimum energy level when said second switch energizing signal is generated and said fuser assembly is energized to a third energy level greater than said second energy level when said third switch energizing signal is generated.

7. Apparatus for regulating the fusing of electroscopic particles to successive portions of a support base intermittently moving through a fuser assembly wherein said fuser assembly includes a source of thermal radiation coupled to a variable supply of voltage, comprising:

switch means included in said variable supply and adapted when energized to apply a variably increased voltage to said source of thermal radiation from said variable supply to increase the heat radiated by said source whereby said electroscopic particles are fused to said support base; and

means for selectively energizing said switch means for applying a voltage admitting of a selectively variable amplitude to said source of thermal radiation when a portion of said support base is moved through said fuser assembly, said selectively variable amplitude being a function of the interval of time that has expired since an immediately preceding portion of said support base was moved through said fuser assembly.

8. The apparatus of claim 7 including storage means for storing the time related history of the movement of successive portions of said support base through said fuser assembly, said storage means being coupled to said means for selectively energizing said switch means.

9. The apparatus of claim 8 wherein said storage means comprises:

shift register means including an input terminal to which is applied a signal representing the movement of a portion of said support base through said fuser assembly; and

means for continually shifting on a periodic basis each signal applied to said input terminal through said shift register means whereby the relative positions occupied by signals within said shift register means is a function of the history of the movement of said support base through said fuser assembly.

10. The apparatus of claim 9 wherein said means for selectively energizing comprises:

first means for energizing said switch means to apply a voltage admitting of a minimum amplitude to said source of thermal radiation when successive portions of said support base are moved through said fuser assembly within a first duration;

second means for energizing said switch means to apply a voltage admitting of a second amplitude, greater than said minimum amplitude, to said source of thermal radiation when a portion of said support base is moved through said fuser assembly at a time later than the expiration of a first interval of time after an immediately preceding portion is moved therethrough; and

third means for energizing said switch means to apply a voltage admitting of a third amplitude, greater than said second amplitude, to said source of thermal radiation when a portion of said support base is moved through said fuser assembly at a time later than the expiration of a second interval of time after an immediately preceding portion is moved therethrough, said second interval of time being greater than said first interval of time.

11. The apparatusof claim 10 wherein said first means comprises first gating means coupled to the'first position of said shift register means for producing a first switch energizing signal when said first position is occupied by a signal.

12. The apparatus of claim 11 wherein said second means comprises second gating means coupled to the first position of said shift register means and to a first preselected number of successive positions of said shift register means for producing a second switch energizing signal when said first position is occupied by a signal and none of said first preselected number of successive positions is occupied by a signal.

13. The apparatus of claim 12 wherein said third means comprises third gating means coupled to the first position of said shift register means and to a second preselected number of successive positions of said shift register means for producing a third switch energizing signal when said first position is occupied by a signal and none of said second preselected number of successive positions is occupied by a signal.

14. The apparatus of claim 13 wherein said first, second and third gating means are coupled to first, second and third switches, respectively, included in said variable supply, said first switch being responsive to said first switch energizing signal to apply said minimum amplitude voltage to said source of thermal radiation, said second switch being responsive to said second switch energizing signal to apply said second amplitude voltage to said source of thermal radiation and said third switch being responsive to said third switch ener gizing signal to apply said third amplitude voltage to said source of thermal radiation.

15. The apparatus of claim 14 wherein said variable supply includes bidirectional current conducting means supplied with an AC voltage, said bidirectional current conducting means being initially conductive at a point in the half-cycle of said AC voltage that is a function of a control voltage applied thereto such that an increase in said control voltage tends to advance the initial conductive point and a decrease in said control voltage tends to retard the initial conductive point, said control voltage being selectively increased in response to the energization of said first, second and third switches, respectively.

16. Apparatus for regulating the fusing of electroscopic particles to successive portions of a support base intermittently moving through a fuser assembly wherein said fuser assembly includes a source of thermal radiation coupled to a variable supply of voltage, comprising:

variable resistance means included in said variable supply and adapted when energized to apply a variably increased voltage to said source of thermal radiation from said variable supply to increase the heat radiated by said source whereby said electroscopic particles are fused to said support base; and

means for selectively varying said variable resistance means for applying a voltage admitting of a selectively variable amplitude to said source of thermal radiation when a portion of said support base is moved through said fuser assembly, said selectively variable amplitude being a function of the interval of time that has expired since an immediately preceding portion of said support base was moved through said fuser assembly.

17. The apparatus of claim 16 including storage means for storing the time related history of the movement of successive portions of said support base through said fuser assembly, said storage means comprising:

shift register means including an input terrnainl to which is applied a signal representing the movement of a portion of said support base through said fuser assembly; and means for continually shifting on a periodic basis each signal applied to said input terminal through said shift register means whereby the relative positions occupied by signals within said shift register means is a function of the history of the movement of said support base through said fuser assembly. 18. The apparatus of claim 17 wherein said means for selectively varying comprises:

first means for varying said variable resistance means to apply a voltage admitting of a minimum amplitude to said source of thermal radiation when successive portions of said support base are moved through said fuser assembly within a first duration;

second means for varying said variable resistance means to apply a voltage admitting of a second amplitude, greater than said minimum amplitude, to said source of thermal radiation when a portion of said support base is moved through said fuser assembly at a time later than the expiration of a first interval of time after an immediately preceding portion is moved therethrough; and

third means for varying said variable resistance means to apply a voltage admitting ofa third amplitude, greater than said second amplitude, to said source of thermal radiation when a portion of said support base is moved through said fuser assembly at a time later than the expiration of a second interval of time after an immediately preceding portion is moved therethrough, said second interval of time being greater than said first interval of time.

19. In combination with a heating element that is maintained at a temperature level no lower than a quiescent level of temperature, said heating element radiating an amount of heat that is dependent upon the length of time expired between successive energizations thereof, apparatus for selectively energizing said heating element to variable heating levels such that a substantially equal radiant energy level is attained thereby during each energization irrespective of the length of time that has expired since an immediately preceding energization thereof, comprising:

energizing means coupled to said heating element for supplying said heating element with variable magnitudes of energy;

storage means for storing signals representative of the history of the selective energization of said heating element; first means coupled to said storage means and responsive to a selective energizing signal for energizing said heating element to a minimum heating level when the immediately preceding energization of said heating element occurred within a first time duration; second means coupled to said storage means and responsive to a selective energizing signal for energizing said heating element to a second heating level, greater than said minimum heating level, when a first interval of time has expired since the immediately preceding energization of said heating element; and

third means coupled to said storage means and responsive to a selective energizing signal for energizing said heating element to a third heating level, greater than said second heating level, when a second interval of time has expired since the immediately preceding energization of said heating ele ment.

20. The combination of claim 19 wherein said storage means comprises plural stage shift register means including an input terminal for receiving an irregularly occurring selective energizing signal and a shift terminal for receiving a periodic shift signal, whereby the signals applied to said'input terminal are shifted through said plural stages in timed relation such that the relative positions occupied by selective energizing signals is a function of the previous energizations of said heating element.

21. The combination of claim 20 wherein said first, second and third means comprise first, second and third gating means coupled to first, second and third switch means, respectively; said first gating means including an input coupled to a first stage of said shift register means for producing a first switch energizing signal when a selective energizing signal is shifted into said first stage, said second gating means including an input coupled to said first stage of said shift register means and inputs coupled to a first preselected number of successive stages of said shift register means for producing a second switch energizing signal when a selective energizing signal is shifted into said first stage and none of said first preselected number of successive stages receives a selective energizing signal, said third gating means including an input coupled to said first stage of said shift register means and inputs coupled to switch means being responsive to said second switch energizing signal for activating said energizing means to supply said heating element with a second magnitude of energy and said third switch means being responsive to said third switch energizing signal for activating said energizing means to supply said heating element with a third magnitude of energy.

Claims

1. A method of regulating the operation of a fuser assembly in accordance with selected information requiring the energization of said fuser assembly wherein the radiant energy accumulated by said fuser assembly is a function of the expiration of time from an immediately preceding energization thereof, comprising the steps of: sensing the occurrence of a preselected information signal to energize said fuser assembly to a pre-established minimum energy level; and energizing said fuser assembly to a variable energy level that is dependent upon the interval of time that has expired intermediate successive occurrences of said preselected information signal.

2. The method of claim 1 wherein said fuser assembly is energized upon sensing the respective occurrences of the succeeding ones of the successive preselected information signals.

3. The method of claim 2 wherein said step of sensing the occurrence of a preselected information signal comprises the steps of: serially storing each preselected information signal and the number of predetermined time durations separating successive ones of said preselected information signals in consecutive order; and generating a fuser energizing signal when a preselected information signal is stored in a first position of said consecutive order.

4. The method of claim 3 wherein said step of energizing said fuser assembly comprises the step of generating a variable amplitude fuser energizing signal when a preselected information signal is stored in a first position of said consecutive order and a number of predetermined time durations are stored in the next successive positions of said consecutive order, said fuser energizing signal admitting of an amplitude that is a function of said number of successively stored predetermined time durations.

5. A method of regulating the operation of a fuser assembly in accordance with selected information requiring the energization of said fuser assembly wherein the heat accumulated by said fuser assembly is a function of the expiration of time from an immediately preceding energization thereof, comprising the steps of: serially storing each preselected information signal and the number of predetermined time durations separating successive ones of said preselected information signals in consecutive order; generating a first switch energizing signal when a preselected information signal is stored in a first position of said consecutive order; generating a second switch energizing signal when a preselected information signal is stored in a first position of said consecutive order and a first selected number of predetermined time durations are stored in the next successive positions of said consecutive order; generating a third switch energizing signal when a preselected information signal is stored in a second position of said consecutive order and a second selected number of predetermined time durations are stored in the next successive positions of said consecutive order; and selectively energizing said fuser assembly to first, second and third energy levels in response to said first, second and third switch energizing signals, respectively.

6. The method of claim 5 wherein said fuser assembly is energized to a minimum energy level when said first switch energizing signal is generated, said fuser assembly is energized to a second energy level greater than said minimum energy level when said second switch energizing signal is generated and said fuser assembly is energized to a third energy level greater than said second energy leveL when said third switch energizing signal is generated.

7. Apparatus for regulating the fusing of electroscopic particles to successive portions of a support base intermittently moving through a fuser assembly wherein said fuser assembly includes a source of thermal radiation coupled to a variable supply of voltage, comprising: switch means included in said variable supply and adapted when energized to apply a variably increased voltage to said source of thermal radiation from said variable supply to increase the heat radiated by said source whereby said electroscopic particles are fused to said support base; and means for selectively energizing said switch means for applying a voltage admitting of a selectively variable amplitude to said source of thermal radiation when a portion of said support base is moved through said fuser assembly, said selectively variable amplitude being a function of the interval of time that has expired since an immediately preceding portion of said support base was moved through said fuser assembly.

9. The apparatus of claim 8 wherein said storage means comprises: shift register means including an input terminal to which is applied a signal representing the movement of a portion of said support base through said fuser assembly; and means for continually shifting on a periodic basis each signal applied to said input terminal through said shift register means whereby the relative positions occupied by signals within said shift register means is a function of the history of the movement of said support base through said fuser assembly.

10. The apparatus of claim 9 wherein said means for selectively energizing comprises: first means for energizing said switch means to apply a voltage admitting of a minimum amplitude to said source of thermal radiation when successive portions of said support base are moved through said fuser assembly within a first duration; second means for energizing said switch means to apply a voltage admitting of a second amplitude, greater than said minimum amplitude, to said source of thermal radiation when a portion of said support base is moved through said fuser assembly at a time later than the expiration of a first interval of time after an immediately preceding portion is moved therethrough; and third means for energizing said switch means to apply a voltage admitting of a third amplitude, greater than said second amplitude, to said source of thermal radiation when a portion of said support base is moved through said fuser assembly at a time later than the expiration of a second interval of time after an immediately preceding portion is moved therethrough, said second interval of time being greater than said first interval of time.

11. The apparatus of claim 10 wherein said first means comprises first gating means coupled to the first position of said shift register means for producing a first switch energizing signal when said first position is occupied by a signal.

14. The apparatus of claim 13 wherein said first, second and third gating means are coupled to first, second and third switches, respectively, included in said variable supply, said first switch being responsive to said first switch energizing signal to apply said minimum amplitude voltage to said source of thermal radiation, said second switch being responsive to said second switch energizing signal to apply said second amplitude voltage to said source of thermal radiation and said third switch being responsive to said third switch energizing signal to apply said third amplitude voltage to said source of thermal radiation.

16. Apparatus for regulating the fusing of electroscopic particles to successive portions of a support base intermittently moving through a fuser assembly wherein said fuser assembly includes a source of thermal radiation coupled to a variable supply of voltage, comprising: variable resistance means included in said variable supply and adapted when energized to apply a variably increased voltage to said source of thermal radiation from said variable supply to increase the heat radiated by said source whereby said electroscopic particles are fused to said support base; and means for selectively varying said variable resistance means for applying a voltage admitting of a selectively variable amplitude to said source of thermal radiation when a portion of said support base is moved through said fuser assembly, said selectively variable amplitude being a function of the interval of time that has expired since an immediately preceding portion of said support base was moved through said fuser assembly.

17. The apparatus of claim 16 including storage means for storing the time related history of the movement of successive portions of said support base through said fuser assembly, said storage means comprising: shift register means including an input terminal to which is applied a signal representing the movement of a portion of said support base through said fuser assembly; and means for continually shifting on a periodic basis each signal applied to said input terminal through said shift register means whereby the relative positions occupied by signals within said shift register means is a function of the history of the movement of said support base through said fuser assembly.

18. The apparatus of claim 17 wherein said means for selectively varying comprises: first means for varying said variable resistance means to apply a voltage admitting of a minimum amplitude to said source of thermal radiation when successive portions of said support base are moved through said fuser assembly within a first duration; second means for varying said variable resistance means to apply a voltage admitting of a second amplitude, greater than said minimum amplitude, to said source of thermal radiation when a portion of said support base is moved through said fuser assembly at a time later than the expiration of a first interval of time after an immediately preceding portion is moved therethrough; and third means for varying said variable resistance means to apply a voltage admitting of a third amplitude, greater than said second amplitude, to said source of thermal radiation when a portion of said support base is moved through said fuSer assembly at a time later than the expiration of a second interval of time after an immediately preceding portion is moved therethrough, said second interval of time being greater than said first interval of time.

19. In combination with a heating element that is maintained at a temperature level no lower than a quiescent level of temperature, said heating element radiating an amount of heat that is dependent upon the length of time expired between successive energizations thereof, apparatus for selectively energizing said heating element to variable heating levels such that a substantially equal radiant energy level is attained thereby during each energization irrespective of the length of time that has expired since an immediately preceding energization thereof, comprising: energizing means coupled to said heating element for supplying said heating element with variable magnitudes of energy; storage means for storing signals representative of the history of the selective energization of said heating element; first means coupled to said storage means and responsive to a selective energizing signal for energizing said heating element to a minimum heating level when the immediately preceding energization of said heating element occurred within a first time duration; second means coupled to said storage means and responsive to a selective energizing signal for energizing said heating element to a second heating level, greater than said minimum heating level, when a first interval of time has expired since the immediately preceding energization of said heating element; and third means coupled to said storage means and responsive to a selective energizing signal for energizing said heating element to a third heating level, greater than said second heating level, when a second interval of time has expired since the immediately preceding energization of said heating element.

20. The combination of claim 19 wherein said storage means comprises plural stage shift register means including an input terminal for receiving an irregularly occurring selective energizing signal and a shift terminal for receiving a periodic shift signal, whereby the signals applied to said input terminal are shifted through said plural stages in timed relation such that the relative positions occupied by selective energizing signals is a function of the previous energizations of said heating element.

21. The combination of claim 20 wherein said first, second and third means comprise first, second and third gating means coupled to first, second and third switch means, respectively; said first gating means including an input coupled to a first stage of said shift register means for producing a first switch energizing signal when a selective energizing signal is shifted into said first stage, said second gating means including an input coupled to said first stage of said shift register means and inputs coupled to a first preselected number of successive stages of said shift register means for producing a second switch energizing signal when a selective energizing signal is shifted into said first stage and none of said first preselected number of successive stages receives a selective energizing signal, said third gating means including an input coupled to said first stage of said shift register means and inputs coupled to a second preselected number of successive stages of said shift register means for producing a third switch energizing signal when a selective energizing signal is shifted into said first stage and none of said second preselected number of successive stages receives a selective energizing signal; and said first switch means being responsive to said first switch energizing signal for activating said energizing means to supply said heating element with a first magnitude of energy, said second switch means being responsive to said second switch energizing signal for activating said energizing means to supply said heating element with a second magnitude of energy and said third switch means being responsive to said third switch energizing signal for activating said energizing means to supply said heating element with a third magnitude of energy.