US3791729A

US3791729A - Apparatus for monitoring a sheet transport mechanism

Info

Publication number: US3791729A
Application number: US00270648A
Authority: US
Inventors: E Steiner
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1972-07-11
Filing date: 1972-07-11
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12
Also published as: GB1413069A; CA991244A; NL7309691A

Abstract

Apparatus for monitoring a sheet transport mechanism included in an electrostatic reproduction machine is disclosed in accordance with the teachings of the present invention. The electrostatic reproduction machine includes a support surface adapted to support a developed image of a character pattern, which developed image is transferred to an image receiving medium that is placed in contact with the support surface at a transfer station. Subsequent to the transfer of the developed image to the image receiving medium, the image receiving medium is removed from the support surface and transported to further operating stations. Detecting means in operable communication with the support surface is adapted to detect the presence of an image receiving medium in contact with said support surface, thereby indicating a failure of said image receiving medium to be removed. Means responsive to the detected presence of the image receiving medium serves to regulate the further operation of the electrostatic reproduction machine accordingly.

Description

United States Patent Steiner Feb. 12, 1974 1 APPARATUS FOR MONITORING A SHEET {57] ABSTRACT TRANSPORT MECHANISM Apparatus for monitoring asheet transport mecha- 5 Inventor; Edward Steiner, Macedon, nism included in an electrostatic reproduction machine is disclosed in accordance with the teachings of [73] Asslgnee: Xerox Corporatlon, stamfolid the present invention. The electrostatic reproduction Connmachine includes a support surface adapted to support [22] Filed: July 11, 1972 a developed image of a character pattern, which de- Appl. No.: 270,648

U.S. Cl 355/3 R, 271/57, 271 IDIG. 2 Int. Cl G03g- 15/22 Field of Search 355/3; 271/57, 64, DIG. 2

Primary Examiner-Joseph F. Peters, Jr. I Assistant ExaminerKenneth C. Hutchison veloped image is transferred to an image receiving medium that is placed in contact with the support surface at a transfer station. Subsequent to the transfer of the developed image to the image receiving medium, the image receiving medium is removed from the support surface and transported to further operating stations. Detecting means in operable communication with the support surface is adapted to detect the presence of an image receiving medium in contact with said support surface, thereby indicating a failure of said image receiving medium to be removed. Means responsive to the detected presence of the image receiving medium static reproduction machine accordingly.

6 Claims, 2 Drawing Figures Terminating PAIENIEDFEB 1 2 m4 SHEET 2 OF 2 APPARATUS FOR MONITORING A SHEET TRANSPORT MECHANISM This invention relates to apparatus for monitoring the operation of a sheet transport mechanism and, more particularly, to apparatus for detecting the failure of a sheet transport mechanism to remove an image receiving medium from a support surface of an electrostatic reproduction machine subsequent to the transfer of a developed image from said support surface to said image receiving medium.

In the practice of xerography as described in US. Pat. No. 2,297,691 to Chester F. Carlson, a xerographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. In the usual method of carrying out the process, the erographic plate is electrostatically charged uniformly over its surface and then exposed to a light pattern of the image beingreproduced to selectively dissipatea charge in the areas where light strikes the layer. The. undischarged areas of the layer thus form an electrostatic charge pattern in conformity with a configuration of the original light pattern.

The electrostatic latent image may then be developed by contacting it with a'finely divided electrostatically attractable materiaLsuch' as a resinous powder. The powder is held in the image areas by the electrostatic field on the layer. Where the field is greatest, the greatest amount of material is deposited; and where the field is least, little or no material is deposited. Thus, a viewable powder image is produced in conformity with the light image of the copy being reproduced. The powder is subsequently transferred to a sheet of paper or other image receiving medium and suitably fused to thereby form a permanent print.

It is contemplated that the developed viewable image which is supported on the support surface is to be dynamically transferred to the image receiving medium. Thus, the support surface is capable of being continuously transported in synchronism with the image receiving medium that is transported to a transfer station. At the transfer station, the image receiving medium contacts the support surface in a manner to facilitate thetransfer of the developed image to the image receiving medium. Subsequent to the transfer of the developed image, the image receiving medium is removed from the support surface and transported to subsequent operating stations, such as a fusing station. Concurrently therewith, the support surface is transported to further operating stations whereat the support surface is cleaned and prepared for subsequent reuse thereof.

Although the foregoing is a general description of the normal operation of a portion of a typical electrostaticreproduction machine, it is not unreasonable to expect that, at times, the image receiving medium to which the developed image has been transferred might not be removed from the support surface subsequent to the transfer operation. In this instance, a final copy of the reproduced image will not be received and, moreover, the support surface cannot be properly reused for sub sequent reproducing operations. Furthermore, the presence of the image receiving medium on the support surface at stations other than the transfer station disrupts the proper operation of the electrostatic reproduction machine resulting in the possibility of serious damage to the machine. Various prior art electrostatic reproduction machines have attempted to provide ported through the various operating stations of the machine. Accordingly, if an image receiving medium is detected at alocation along the transport path prior to the transfer station but not at a location along the transport path following the transfer station, it is presumed that the image receiving medium has not been removed from its contacting relationship with the support surface andfurther operation of the electrostatic reproduction machine is terminated.

An attendant disadvantage of such prior art electrostatic reproduction machines is the failure of such detecting mechanism to safe guard the operation of the machine if superposed or multiple sheets of an image receiving medium are transported to the transfer station. More particularly, if superposed sheets are transported into a contacting relationship with the support surface, the developed image will be transferred to the lower sheet and the upper sheet will be successfully conveyed to the further operating stations, such as the fuser station, by the sheet transport mechanism. However, the lower sheet willremain in contact with the supportsurface presenting. a potential hazard to the proper operation of the electrostatic reproduction machine. Nevertheless, the presence of an image receiving medium will be detected at a location alongthe transport path followingthe transfer station. Consequently,

the electrostatic reproduction machine will continue to operate notwithstanding the occurrence of conditions that require a termination of the operation thereof.

Accordingly, it has been found necessary to monitor the support surface itself to detect the presence of an image receiving medium thereon that has not been previously removed therefrom. A proposed solution to this task has suggested the use of a deflecting device, such as stripper fingers, disposed at a fixed location and in contact with the moving support surface. It is expected that if an image receiving medium remains on the support surface, the deflecting device will remove said image receiving medium, direct the removed image receiving medium along an established removal path and actuate a suitable switching mechanism in response to the deflectedimage receiving medium to terminate the further operation of the electrostatic reproduction machine. However, it hasbeen found that the contact between the moving support surface and the fixed deflecting device results in a sufficient deterioration of the support surface to cause substantial damage thereto. In an effort to overcome this problem systems have been proposed that have resulted in the tendency of the deflecting device to bounce upon the support surface and occasionally fail to remove, or strip, an image receiving medium therefrom.

Therefore, it is an object of the present invention to provide apparatus for detecting when an image receiving medium has not been properly removed from a support surface in an electrostatic reproduction machine.

A further object of this invention is to provide apparatus for monitoring the operation of a transport mechanism included in an electrostatic reproduction machine and to regulate the operation of said machine accordingly.

Another object of this invention is to provide apparatus for removing an image receiving medium from a support surface after a developed image has been transferred to the medium if said medium has not been previously removed from said support surface.

Yet another object of this invention is to provide apparatus for sensing the presence of an image receiving medium on a support surface of an electrostatic reproduction machine and to promptly terminate the further operation of said machine if the detected image receiving medium has not been removed from said support surface.

It is an additional object of the present invention to provide apparatus for detecting the presence of an image receiving medium on a support surface of an electrostatic reproduction machine and to terminate the further operation of said machine after a determined delay subsequent to the removal of said image receiving medium from said support surface.

Still another object of this invention is to provide an optical sensing device for detecting the presence of an image receiving medium on a support surface.

A further object of this invention is to provide actuatable deflection means for deflecting an image receiving medium to a removal path established by the detection means when said image receiving medium is detected in a contacting relationship with a support surface.

An additional object of the present invention is to provide sensing means disposed in a removal path to detect the deflection of animage receiving medium to said removal path in the event that said image receiving medium had not been previously removed from a contacting relationship with a support surface.

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

In accordance with this invention, there is disclosed an electrostatic reproduction machine having a support surface upon which a developed image of a character pattern is supported, said developed image being transferred to an image receiving medium in contact with said support surface at a transfer station, said image receiving medium being removed from said support surface subsequent to the transfer of said developed image; apparatus is provided for detecting when said image receiving medium has not been properly removed from said support surface subsequent to said transfer of the developed image, said apparatus comprising detecting means in operable communication with the support surface to detect the presence of an image receiving medium in contacting relationship with said support surface subsequent to the transfer of said developed image; and means coupled to said detecting means and responsive to the detected presence of said image receiving medium to selectively regulate the further operation of the electrostatic reproduction machine.

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

FIG. 1 is a schematic sectional view of an electrostatic reproduction machine embodying the principles of the instant invention; and

FIG. 2 is a schematic illustration of the mechanical apparatus in accordance with the present invention and including a block diagram of responsive electrical components.

For a general understanding of the illustrated copier/reproduction machine in which the invention may be incorporated, reference is had to FIG. 1 in which the various system components for the machine are schematically illustrated. As in all electrostatic systems, such as a xerographic machine of the type illustrated, a light image of a document to be reproduced is projected onto the sensitized surface of a photoreceptor to form an electrostatic latent image thereon. Thereafter, the latent image may be transferred to a support surface, the transferred latent image then being developed with an oppositely charged developing material to form a xerographic image. Alternatively, the latent image formed on the photoreceptor may be developed and the developed image transferred to a reusable support surface. In either embodiment, the powder image on the support surface is then electrostatically transferred to an image receiving medium and fixed by a fusing device to cause the powder image to adhere permanently to the image receiving medium.

In the illustrated machine, a document D to be copied is placed upon a transparent support platen P fixedly arranged in an illumination assembly, generally indicated by the reference numeral 10, positioned at the left end of the machine. In the embodiment illustrated herein, it is contemplated that the illumination assembly includes suitable lamps 101 capable of being rapidly discharged to create a bright flash of light. Light rays from the lamps are flashed upon the document to produce image rays corresponding to the informational areas thereon. The image rays are projected by means of an optical system 11 onto the photosensitive surface of a photoreceptor which is in the form of flexible photoconductive belt 12 arranged on a belt assembly, generally indicated by the reference numeral 14.

The belt 12 comprises a photoconductive layer of selenium, which is the light receiving surface and imaging medium for the apparatus, on a conductive backing. The surface of the photoconductive belt is made photosensitive by a previous step of uniformly charging the same by means of a corona generating device, or corotron 13. V

The belt is journaled for continuous movement upon three

rollers

20, 21, and 22 positioned with their axes in parallel. The photoconductive belt assembly 14 is slidably mounted upon two support shafts 23 and 24 with the roller 22 rotatably supported on shaft 23 which is secured to the frame of the apparatus and is rotatably driven by a suitable motor and drive assembly (not shown) in the direction of the arrow at a constant rate. During exposure of the belt 12, the portion exposed is that portion of the belt running between

rollers

20 and 21. As the-belt is transported in the indicated direction, the projected light image of the original document positioned on the platen is flashed on the surface of the belt to produce an electrostatic latent image thereon at exposure station A.

The belt surface continues its movement whereby the electrostatic latent image passes through a developing station B in which there is positioned a developer assembly generally indicated by the reference numeral 15, which provides development of the electrostatic latent image by means of multiple brushes 16 as the image moves through the development zone. In the illustrated embodiment, it may be appreciated that belt 12 now serves as a suitable support surface to support the developed image ofthe character pattern presented by the original document. Alternatively, the electrostatic latent image on the belt may be transferred to a further insulating means, which insulating means is then transported through a suitable developing station. In this alternative embodiment, it may be appreciated that the insulating means thus provides a suitable support surface for the developed image of the character pattern. A still further embodiment contemplates the transfer of the developed image from belt 12 to suitable reusable means, which reusable means now provides a support surface for the developed image.

In any of the foregoing embodiments, the developed image carried by the support surface is transported to a transfer station C whereat an image receiving medium, such as a sheet of copy paper, is moved between a transfer roller and the support surface at a speed in synchronism with the moving support surface in order to accomplish a final transfer of the developed image by an electrical bias on the transfer roller. As illustrated in the exemplary embodiment depicted in FIG. 1, the support surface here comprises belt 12 ane the image receiving medium is transported between a transfer roller and the belt to thereby exhibit a contacting relationship with said support surface. A sheet transport mechanism, generally indicated at 17, is adapted to transport individual sheets of the image receiving medium from a movable platform included in a suitable sheet handling mechanism, generally indicated by the reference numeral 18, to the developed image on the support surface at the station C.

After the developed image is transferred from the support surface to the sheet of image receiving medium, the sheet is removed from its contacting relationship and directed onto a further sheet transport mechanism, the further sheet transport mechanism including endless belt 32. The thus removed image receiving medium is transported by the sheet transport mechanism into a fuser assembly, generally indicated by the reference numeral 19, wherein the developed and transferred powder image, is permanently affixed to the sheet of image receiving medium. The further sheet transport mechanism may include suitable vacuum means, such as a conventional vacuum shoe, capable of reducing the air pressure above endless belt 32, resulting in a'force which urges the sheet of image receiving medium against the belt. After fusing, the finished copy is discharged from the apparatus at a suitable point for collection externally therefrom.

The support surface, after passing the transfer station C is conveyed to a cleaning station comprised of precleaning corotron 25 and'brush means 26. The precleaning corotron serves to discharge the remaining charged areas present on the support surface. Brush means 26 is capable of removing the residual electroscopic particles that have not been transferred from the support surface to the image receiving medium. Accordingly, the brush means 26 includes a suitable brush housing in which is disposed a rotatable brush such as a fur brush. Electroscopic particles thus removed from the support surface are conveyed to a reclaiming system by air circulating through an air duct that extends from the brush housing to the reclaiming system. The support surface is now adapted to be reused for a subsequent reproduction operation.

In accordance with the present invention, detecting means 30 is fixedly disposed in operable communication with the support surface such that a given point of the support surface will traverse the detecting means following the passage thereof through transfer station C. The detecting means 30 is adapted to detect the presence of a sheet of image receiving medium that remains in contact with the support surface and has not been removed to belt 32. Upon detecting the presence of the image receiving medium upon the support surface, detecting means 30 actuates deflection means, to be described hereinbelow, to thereby deflect the detected image receiving medium from the support surface to an established removal path. Sensing means 31 is disposed in the removal path and is capable of sensing the proper deflection of theimage receiving medium from the support surface. Detecting means 30 and sensing means 31 cooperate with further apparatus to regulate the operation of the electrostatic reproduction machine of FIG. 1.

A more detailed description of the detecting means of the present invention and the manner in which the operation of the electrostatic reproduction machine is regulated thereby now follows. Referring to FIG. 2, wherein like reference numerals are utilized to identify the like component parts that are identical to corresponding component parts of FIG. 1, there is illustrated detecting means 30, deflecting means 306 and sensing means 31. In addition, the operable location of the detecting means, deflecting means and sensing means with respect to the precleaning corotron 25 and brush means 26 is also indicated. As illustrated herein, precleaning corotron 25 is suitably supported in juxta position to the support surface 12, which in this instance, may comprise the photoconductivebelt, by a frame member 265. The frame member 265 supports the precleaning corotron at a suitable distance from the brush means 26. In addition, the frame member 265 is rigidly fastened to the brush housing 261 of brush means 26 by a support member 264. As may be observed, the precleaning corotron 25 and brush means 26 together with frame member. 265 and support member 264 are disposed in the space subtended by the angle defined by the support surface 12 and the. endless belt 32 included in the further sheet transport mechanism.

Detecting means 30 is suitably fastened to the frame member 265 by any suitable fastening means such as screws, by welding or by using any suitablecement. In the preferred embodiment of the present invention, detecting means 30 is comprised of a suitable housing within which are disposed a light emissive element 301, such as a light emitting diode, and a photosensitive device 302, such as phototransistor, a photodiode, a photoelectric cell, a photoresistor device, or the like, in operable communication with said light emissive element. The photosensitive device 302 is adapted to generate an output signal having a magnitude determined by the intensity of light impinging thereon. Light emissive element 301 is capable of transmitting radiant energy and may alternatively be comprised of a conventional lamp. The relative positions of light emissive element 301 and photosensitive device 302 are established such that a reflective optical path is defined therebetween by the support surface 12. More particularly, the optical path extends from the light emissive element 301 to the support surface 12 and from the point of incidence on the support surface to the photosensitive device 302. It is recognized by those of ordinary skill in the xerography art that if support surface 12 is comprised of the photoconductive belt described hereinabove with respect to F l6. 1, the photoconductive material of which the belt is comprised exhibits a spectral sensitivity to a portion of the light spectrum. More particularly, the photoconductive material exhibits a relatively high light transmission coefficient to impinging radiant energy that admits of a selected portion of the light spectrum. Thus, the photoconductive material is substantially transparent to such impinging radiant energy. In one embodiment of the present invention, the photoconductive material is comprised of selenium which is substantially transparent to radiant energy whose wavelength is greater than the wavelength of red light. Accordingly, if the spectrum of light emitted by the light emissive element 301 is constrained such that wavelengths that exceed the wavelength of red light are emitted thereby, the support surface 12 will not reflect the emitted light to the photosensitive device 302. It is, of course, recognized that the spectral sensitivity of photosensitive device 302 should be complimentary to the spectrum emitted by the light emissive element 301. If the light emissive element is selected to emit only red and infrared light, the photosensitive device 302 may comprise a conventional infrared sensor. It should be clearly understood that the spectral distribution of the radiant energy emitted by light emissive element 301 need not include that portion of the spectrum reserved for visible light. Moreover, in the presently described embodiment, it is merely preferred to select a light emissive element capable of emitting radiant energy exhibiting a spectral distribution to which the support surface is substantially transparent, and should not be interpreted as a distinctlimitation thereto. Thus, although the considerations governing the selection of a suitable light emissive element are now manifest, it is apparent that the light emissive element, may comprise any suitable source of radiant energy. If desired, conventional optical filters may be utilized with the light emissive element 301 such that a selected spectral distribution of radiant energy may be transmitted thereby to the support surface. Alternatively, photosensitive device 302 may be particularly selected as to be responsive only to a predetermined spectral portion of the light spectrum. Accordingly, if light emissive element 301 is adapted to transmit radiant energy, admitting of a wide spectrum, the photosensitive device 302 may be responsive only to a limited portion of the transmitted spectrum. Hence, if the photosensitive device 302 is capable of detecting radiant energy admitting of a wavelength greater than that exhibited by red light, it should be apparentthat if support surface 12 is substantially transparent to red light the photosensitive device will not detect the light reflected thereto by the support surface. This obtains because the radiant energy to which the light response is sensitive is transmitted through the support surface and not reflected thereby.

Deflecting means 306 comprises a deflecting guide operably pivoted about pivotal point 307 and including a portion thereof capable of contacting the support surface 12. The deflection means maycomprise one or more suitable stripper fingers capable of establishing a removal path and for intercepting an image receiving medium that is in contact with the support surface 12 and to direct the intercepted image receiving medium to the established removal path. As illustrated herein, deflection means 306 may admit of a quiescent position, depicted by the full lines thereof, and an activated position, depicted by the broken lines. Thus, in its quiescent position, the deflection means is disposed remotely from the support surface; Whereas in its activated position, the deflection means is disposed in contact with said support surface and is capable of intercepting an image receiving medium carried thereon. The deflection means 306 is fixedly secured to an arm 305, the latter being rotatably fastened to lever 304 of solenoid means 303. Solenoid means 303 is rigidly supported on support member 264 and may comprise a conventional rotary solenoid comprised of an energization coil and rotatable armature. The rotary solenoid is adapted to activate the armature thereof in response to an energizing current that flows through said energization coil. The rotatable armature of solenoid means 303 may thus comprise the illustrated lever 304 that is fastened to arm 305. It may be appreciated that when an energizing current flows through the energization coil of solenoidmeans 303, armature 304 may be activated to rotate in a counter clockwise direction. Consequently, arm 305 is rotated by armature 304 in a clockwise direction about pivoted point 307. Hence, deflection means 306, securely fastened to arm 305, likewise rotates about pivotal point 307 in-a clockwise direction to assume its activated position. The energization coil of solenoid means 303 is coupled to suitable circuitry included in block 40 and, as will soon be described, is responsive to an output signal produced by the photosensitive device 302. Hence, detecting means 30 is also coupled to block 40.

- Sensing means 31 is disposed in the removal path established by deflection means 306 and is adapted to sense an image receiving medium stripped from the support surface 12 by deflection means 306 and deflected onto the removal path. Accordingly, sensing means 31 may comprise a conventional switching device, such as a microswitch or the like, having a protruding member 310 extending into an intersecting relationship with respect to the removal path. The protruding member, is adapted to be contacted by the image receiving medium'stripped from the support surface 12 by deflection means 306, thereby activating switch means 31. The switch means is electrically coupled to a timing circuit 41 and to terminating means 42 through block 40. As will soonbe described, the timing circuit 41 may comprise a conventional time measuring network, such as a digital counter, a time delay network, and monostable multivibrator such as'one-shot means, a time delay relay circuit or the like, adapted to respond to an electrical signal applied thereto to generate at the output thereof an electrical signal at a predetermined time interval subsequent to the activation thereof. The activation of switch means 31 serves to interrupt the operation of timing circuit 41 such that said timing circuit is inhibited from generating a signal as its output terminal if said timing circuit has not yet completed the timing of said predetermined time interval. Accordingly, switch means 31 may, in one exemplary embodiment, comprise normally closed contacts such that a series circuitv including said normally closed contacts is included in timing circuit 41 for the normal operation of said timing circuit in response to a signal applied thereto. The activation of switch means 31 opens the normally closed contacts thereof to thereby interrupt the series circuit essential for the normal operation of timing circuit 41 thereby inhibiting said timing circuit from continuing the normal operation thereof. Hence, activation of switch means 31 results in the interruption of the operation of timing circuit 41 prior to the completion of the timing of the predetermined time interval. An alternative embodiment contemplates switch means 31 including-normally opened contacts connected in series to timing circuit 41. The activation of switch means 31 results in the closing of said normally opened contacts to thereby inhibit the continued operation of timing circuit 41. Accordingly, the contacts of switch means 31 may for example, be coupled through block 40 to a conventional clamping circuit or the like connected to the timing circuit.

Block 40 may include conventional circuitry adapted to receive the output signal generated by the photosensitive device 302 and to activate the timing circuit 41 and solenoid means 303 in response thereto. Since, the output signal generated by photosensitive device 302 is proportional to the intensity of light impinging thereon, block 40 may include conventional threshold detecting means, such as a Schmitt trigger circuit, which responds to the output signal generated by the photosensitive device if said output signal exceeds a preestablished threshold level. Hence, block 40 may prevent the unwanted activation of timing circuit 41 and solenoid means 303 in response to spurious signals that might be generated by photosensitive device 302. Moreover, as has been generally described hereinabove, block 40 responds to the activation of switch means 31 to interrupt the operation of timing circuit 41. As illustrated herein, block 40 and timing circuit 41 are each coupled to block 42, hereinafter referred to as terminating means. A signal supplied to terminating means 42 by block 40 is adapted to activate the terminating means whereby the further operation of the electrostaticreproduction machine with which the present invention may be utilized is terminated after a determined delay. More particularly, the activation of switch means 31 is sufficient to energize a circuit included in block 40, such as a latching relay circuit, to thus supply a signal to the terminating means 42 from block 40. The terminating means may include suitable circuitry which prevents the electrostatic reproduction machine from commencing subsequent reproducing cycles of operation but nevertheless enables the fuser assembly 19 and transport mechanism associated therewith to continue their respective operations, thereby enabling a sheet of image receiving medium disposed within the fuser assembly to exit therefrom and to be conveyed to a suitable receptacle located externally of the machine. Hence, terminating means 42 may include suitable control circuits, such as switch means, relay circuits, or the like, responsive to a signal supplied by block 40 to selectively regulate the operation of particular ones of the machine components which are illustrated in the schematic illustration of FIG. 1. The terminating means further includes additional circuitry responsive to the signal applied thereto by timing circuit 41, which additional circuitry is adapted to immediately terminate the operation of the electrostatic reproduction machine of FIG. 1. The further circuitry included in the terminating means may thus include control circuits such as switching means, relay circuits or the like, adapted to respond to the signal supplied by timing circuit 41 to thereby deactivate some or all of the machine components illustrated in FIG. 1. It will soon become apparent that, if desired, block 40 may respond to the output signal generated by the photosensitive device 302 to produce a signal which may be applied in common relationship to timing circuit41, terminating means 42 and solenoid means 303. Moreover, switch means 31 may be coupled directly to timing circuit 41 to interrupt the operation of said timing circuit in response to the activation of the switch means.

FIG. 2' additionally illustrates brush means 26 comprised of brush housing 261, rotatable brush 262 and flicker bar 263. In addition, air duct 267 extends from the brush housing 261 to an electroscopic particle claiming system, (not shown). Rotatable brush 262, which may be, for example, a fur brush, is adapted to rotate into a contacting relationship with support surface 12. The rotatable brush 262 is thus adapted to remove the residual electroscopic material from the support surface to permit said support surface to be reused. transported thereby to flicker bar 263. As may be observed, the flicker bar comprises an obstacle interposed into the rotational path of rotatable brush 262. Consequently. the interception of the particle laden brush with the flicker bar serves to dislodge the electroscopic particles from the brush. A flow of air is maintained in the air duct 267 such that a pressure is maintained within brush housing 261 whereby the dislodged electroscopicparticles are conveyed by the air current through duct 267. Suitable air baffles, here designated by referencenumeral 266, may be provided at the ex,- tremities of the brush housing 261 opposite support surface 12 to maintain the proper air pressure within said housing. Although not illustrated herein, it is contemplated that a pressure sensing switch be included within brush housing 261 such that a change of pressure within the housing caused by the transporting of a sheet of image receiving medium thereinto may be sensed. It may be appreciated that such pressure sensing switch may serve as an auxiliary sensing device should the remaining illustrated apparatus fail to operate properly. More particularly, if detecting means 30 fails to detect a sheet of image receiving medium on support surface 12, or if deflection means 306 fails to strip a sheet of image receiving medium from the support surface or if timing circuit 41 does not operate to time a predetermined interval, the image receiving medium will be carried by the support surface into the brush housing 261. The presence of the image receiving medium within brush housing 261 causes-a change in the air pressure therein to thus activate the pressure sensing switch disposed'within the brush housing. Accordingly, this pressure sensing switch may be coupled to terminating means 42 to achieve the same results as that achieved by the signal produced by timing circuit 41.

The operation of the apparatus illustrated in FIG. 2 will now be described. Let it be assumed that a sheet of image receiving medium adheres to the support surface 12 subsequent to the transfer of a developed image thereto. Consequently, the adhering sheet of image receiving medium will not be directed onto belt 32 and will not be transported to the fuser assembly 19 by the associated sheet transport mechanism. Prior to the entry of the image receiving medium into the vicinity of detecting means 30, it may be appreciated that light emissive element 301. directs radiant energy to the support surface 12. If the radiant energy transmitted by the light emissive elements admits of a spectral distribution to which the support surface 12 is substantially transparent, it may be appreciated that the radiant energy received by the support surface is transmitted therethrough and is not reflected to the photosensitive device 302. It may be expected that if support surface 12 comprised of a photoconductive belt having a layer of photoconductive material overlying a conductive backing, the radiant energy transmitted through the photoconductive layer might be reflected by the conductive backing to the photosensitive device 302. However, the light reflecting properties of such conductive backing would result in the reflection of low intensity radiant energy to the photosensitive device 302. Accordingly, the output signal generated by the photosensitive device is proportional to the intensity of reflected radiant energy and, therefore, is not sufficient to activate solenoid means 303 or to initiate the operation of timing circuit 41.

When the adhering sheet of image receiving medium traverses the reflected optical path defined between the light emissive element 301 and the photosensitive device 302, the intensity of radiant energy now reflected to the photosensitive device increases. This may be appreciated if it is assumed that the image receiving medium comprises a sheet of copy paper, such as white paper having a relatively high reflection coefficient. The increase in intensity of the radiant energy reflected to the photosensitive device 302 results in an output signal generated thereby, which output signal is applied to block 40. if block 40 includes amplifying circuits and threshold detecting circuits, the applied output signal now sufficiently exceeds the predetermined threshold level to result in the activation of solenoid means 303 and the initiation of timing circuit 41. It is recognized that solenoid means 303 may be activated by supplying energizing current through the energization coil thereof. Hence, the output signal applied to block 40 by photosensitive device 302 may, serve to close a switch to thereby couple the energization coil of solenoid means 303 to a suitable source of energizing potential. Once the energizing coil of solenoid means 303 is energized, the rotatable armature 304 thereof is urged into a counterclockwise rotation. Accordingly, arm 305, which is fastened to armature 304, is rotated in a clockwise direction about pivotal point 307, thus rotating deflection means 306 into its activated position. Deflection means 306 is thus located in the position represented by the broken lines of FIG. 2.

Concurrent with the activation of solenoid means 303, timing circuit 41 initiates a timing operation whereby a signal is produced at the output thereof at a predetermined interval subsequent to the commencing of said timing operation. As the image receiving medium is advanced to deflection means 306 by the movement of support surfacel2, the deflection means strips the image receiving medium from the support surface and guides the removed image receiving medium along the removal path established thereby. The deflectedimage receiving medium is urged into contact with the protruding member 310 of switch means 31. Consequently, switch means 31 is activated. Block 40 detects'the activation of switch means 31 to interrupt the operation of timing circuit 41. It may be recognized that timing circuit 41 has not completed the timing of the predetermined interval at the time the image receiving medium is deflected into contact with protruding member 310. Consequently, the interruption of the operation of timing circuit 41 inhibits the timing circuit from producing a signal at the output thereof. The activation of switch means 31 provides terminating means 12 42 with a signal derived from block 40 to thus effect the termination of the further operation of the electrostatic reproduction machine after a determined delay. Consequently, an image receiving medium that has been transported to the fuser assembly is now allowed to exit therefrom. However, the electrostatic reproduction machine is inhibited from providing further exposures of document D, from providing further sheets of image receiving medium to transfer station C and from providing further sheets of image receiving medium to fuser assembly 19. It may be appreciated that since the electrostatic reproduction machine continues to operate during this determined interval (i.e., until the further operation thereof is terminated by terminating means 42 after the determined delay) the deflected sheet of image receiving medium may be guided by deflection means 306 and by the curvature of brush housing 261 into contact with belt 32. The deflected sheet may be urged against belt 32 by a force exerted thereon as a result of the reduced air pressure above the belt. Accordingly, the deflected sheet may be effectively removed from the vicinity of brush means 26 to enable an operator to gain access to the deflected sheet and remove same from the electrostatic reproduction machine.

If deflection means 306 fails to strip the sheet of image receiving medium from support surface 12, it is appreciated that protruding member 310 is not contacted and switch means 31 is not activated. Accordingly, the operation of timing circuit 41 is not interrupted. The timing circuit may thus complete the timing of the predetennined interval to supply terminating means 42 with a corresponding signal. The terminating means effects the immediate termination of the further operation of the electrostatic reproduction machine when timing circuit 41 completes the timing of said predetermined interval.

It is appreciated that if detecting means 30 fails or if timing circuit 41 fails to supply terminating means 42 with a corresponding signal, the aforedescribed pressure sensing switch disposed within brush assembly housing 261 provides a desirable auxiliary safety mechanism to guard against potential damage to the electrostatic reproduction machine. Thus, a sheet of image receiving medium that has escaped the operation of deflection means 306 will, nevertheless, be prevented from damaging the electrostatic reproduction machine by the operation of timing circuit 41 or the pressure sensing switch (not shown).

It is possible that photosensitive device 302 may generate spurious signals which might erroneously be interpreted as a detected sheet of image receiving medium. Similarly, impurities or particles of dirt residing on support surface 12 might reflect radiant energy from the light emissive element 301 to the photosensitive device 302 such that the photosensitive device generates an output signal. To guard against these possibilities, it might be desirable to require that the output signal generated by the photosensitive device 302 admit of a minimum duration. Such minimum duration output signal would be generated only in response to the actual de-' tection of a sheet of image receiving medium. Accordingly, a conventional integrating circuit may be coupled to the photosensitive device 302, which integrating circuit is characterized by a time constant equal to said minimum duration. The requisite output signal capable of activating solenoid means 303 and initiating timing circuit 41 would be produced by the integrating circuit only when an actual sheet of image receiving medium is detected.

It is recognized that the environment within which the light emissive element 301 is disposed is subjected to contamination by the electroscopic particles adhering to support surface 12. A build-up of such particles may result in reducing the intensity of radiant energy emitted by the light emissive element. Accordingly, a compensating control circuit maybe provided to increase the intensity of emitted radiant energy as the contamination caused by electroscopic particles increases. The control circuit may be adapted to monitor the output signal generated by photosensitive device 302 whereby a predetermined minimum output signal is required to be maintained. It should be noted that the predetermined output signal should not be sufficient to activate solenoid means 303 or initiate timing circuit 41. The control circuit may be coupled in feedback relationship to the light emissive element 301 such that the intensity of radiation emitted by the light emissive element is increased when the monitored output signal generated by the photosensitive device falls below the predetermined minimum value.

.In the design of the electrostatic reproduction machine with which the present invention may be utilized,

it is expected that the operation of terminating means 42 in response to the signal supplied thereto by timing circuit 41 will result in the prompt termination of further operation of the machine. However, it is not beyond the scope of the present invention to provide suitable braking apparatus responsive to the operation of terminating means 42 to rapidly brake the electrostatic reproduction machine to an immediate halt. Once the operation of the electrostatic reproduction machine is terminated in response to the operation of terminating means 42, the machine can be restored to subsequent timing operation in proper operating condition by manually removing the sheet of image receiving medium from the aforedescribed removal path or from the brush housing 261. The removal of such sheet of image receiving medium necessitates the operation by an operator of various components that are mechanically coupled to electrical switches which serve to reset the apparatus illustrated in FIG. 2 to a quiescent state. Thus, solenoid means 303 is deactivated and deflection means 306 returns to its quiescent position illustrated by the full lines. Similarly, timing circuit 41 is reset to an initial condition and is now prepared to commence a subsequent timgin operation in response to the detection of a subsequent sheet by detecting means 30. Furthermore, switch means 31 is deactivated whereby the normally closed contacts therein are returned to their normally closed state. Alternatively, if the contacts of switch means 31 normally assume an opened state, said contacts are returned to their normally opened position.

While the invention hasbeen particularly shown and described with reference to exemplary embodiments thereof, it will be obvious to those skilled in the art that the foregoing and various other changes and modifications in form and details may be made without departing from the spirit and scope of the invention. For example, terminating means 42 has heretofore been described as responding to the activation of switch means 31 to terminate the further operation of the electrostatic reproduction machine after a determined delay interval. However, the terminating means 42 may be coupled to block 40 and responsive to output signal generated by photosensitive device 302 to terminate the further operation of the machine after said determined delay interval. Moreover, block 40 may be omitted and the output signal generated by photosensitive device 302 may be supplied directly to timing circuit 41 and to solenoid means 303. Furthermore, the radiant energy transmitted by light emissive element 301 need not necessarily be limited to a spectral distribution exhibiting a wavelength greater than a predetermined amount. It is merely suggested that a cooperative relationship exists between the light emissive element 301, the photosensitive device 302 and the support surface 12 such that the radiant energy reflected to the photosensitive device by a sheet of image receiving medium results in a generated output signal having a sufficient magnitude whereas radiant energy impinging upon the photosensitive device in the absence of such sheet of image receiving medium result in an output signal having a magnitude that is not sufficient to activate solenoid means 303, and initiate timing circuit 41. It is appreciated that the appended claims should be interpreted as including the foregoing changes and modifications as well as the particular exemplary embodiments described hereinabove. I

What is claimed is:

1. In an electrostatic reproduction machine having a support surface adapted to support a developed image of a character pattern and to transfer said developed image to an image receiving medium in contact therewith at a transfer station, said electrostatic reproduction machine additionally having primary means to remove said image receiving medium from said support surface and to transport said image receiving medium from said transfer station subsequent to said transfer of said developed image thereto, apparatus for detecting when said image receiving medium has not been removed from said support surface subsequent to. said transfer of said developed image, comprising:

detecting means in operable communication with said support surface to detect the presence of said image receiving medium in contact with said support surface subsequent to said transfer of said developed image;

secondary means, responsive to said detecting means to remove said image receiving medium from said support surface; and

means responsive to said detected presence of said image receiving medium to regulate the further operation of said electrostatic reproduction machine.

2. The apparatus of claim 1 wherein said secondary means to remove said image receiving medium c'omprises:

deflection means electrically coupled to said detecting means and responsive to a generated output signal for establishing a removal path and for deflecting said image receiving medium from said support surface to said removal path; and

sensing means disposed in said removal path and responsive to said generated output signal for terminating the further operation of said electrostatic reproduction machine in accordane with the sensing of said image receiving medium in said removal path.

3. The apparatus of claim 2 wherein said sensing means comprises:

switch means adapted to be activated by the contact therewith of said image receiving medium; timing means electrically coupled to said detecting means and to said switch means and responsive to said generated output signal for commencing the timing of a predetermined interval and to the activation of said switch means for interrupting said timing prior to the completion of said predetermined interval; and terminating means coupled to said switch means and to said timing means for the further operation of said electrostatic reproduction machine after a determined delay when said switch means is activated and for immediately terminating the further operation of said electrostatic reproduction machine when said timing means completes the timing of said predetermined interval. 4.The apparatus of claim 3 wherein said deflection means comprises rotatable solenoid means including guide means to be rotated into contact with said support surface for removing said image receiving medium and for guiding said removed image receiving medium to said removal path.

5. in an electrostatic reproduction machine having a support surface adapted'to support a developed image of a character pattern and to transfer said developed image to an image receiving medium in contact therewith at a transfer station, said electrostatic reproduction machine having primary means to remove said image receiving medium from said support surface and to transport said image receiving medium from said transfer station subsequent to said transfer of said developed image thereto; apparatus for detecting when said image receiving medium has not been removed from said support surface subsequent to said transfer of said developed image; comprising: a

detecting means in operable communication with said support surface to detect the presence of said image receiving medium in contact with said support surface subsequent to said transfer of said developed image; secondary means responsive to said detecting means to remove said image receiving medium from said support surface and deflect said image receiving medium from said support surface through a removal path; and I sensing means disposed in said removal path to sense the presence of said image receiving medium therein to regulate the further operation of said electrostatic reproduction machine. 6. The apparatus of claim 5 wherein said sensing means comprises:

switch means adapted to be activated by the contact therewith of said image receiving medium; timing means electrically coupled to said detecting means and to said switch means and responsive to said detecting means for commencing the timing of a predetermined interval and to the activation of said switch means for interrupting said timing prior to the completion of said predetermined interval; and terminating means coupled to said switch means and to said timing means for the further operation of said electrostatic reproduction machine after a determined delay when said switch means is'activated and for immediately terminating the further operation of said electrostatic reproduction machine when said timing means completes the timing of said predetermined interval.

Claims

1. In an electrostatic reproduction machine having a support surface adapted to support a developed image of a character pattern and to transfer said developed image to an image receiving medium in contact therewith at a transfer station, said electrostatic reproduction machine additionally having primary means to remove said image receiving medium from said support surface and to transport said image receiving medium from said transfer station subsequent to said transfer of said developed image thereto, apparatus for detecting when said image receiving medium has not been removed from said support surface subsequent to said transfer of said developed image, comprising: detecting means in operable communication with said support surface to detect the presence of said image receiving medium in contact with said support surface subsequent to said transfer of said developed image; secondary means, responsive to said detecting means to remove said image receiving medium from said support surface; and means responsive to said detected presence of said image receiving medium to regulate the further operation of said electrostatic reproduction machine.

2. The apparatus of claim 1 wherein said secondary means to remove said image receiving medium comprises: deflection means electrically coupled to said detecting means and responsive to a generated output signal for establishing a removal path and for deflecting said image receiving medium from said support surface to said removal path; and sensing means disposed in said removal path and responsive to said generated output signal for terminating the further operation of said electrostatic reproduction machine in accordane with the sensing of said image receiving medium in said removal path.

3. The apparatus of claim 2 wherein said sensing means comprises: switch means adapted to be activated by the contact therewith of said image receiving medium; timing means electrically coupled to said detecting means and to said switch means and responsive to said generated output signal for commencing the timing of a predetermined interval and to the activation of said switch means for interrupting said timing prior to the completion of said predetermined interval; and terminating means coupled to said switch means and to said timing means for the further operation of said electrostatic reproduction machine after a determined delay when said switch means is activated and for immediately terminating the further operation of said electrostatic reproduction machine when said timing means completes the timing of said predetermined interval.

4. The apparatus of claim 3 wherein said deflection means comprises rotatable solenoid means including guide means to be rotated into contact with said support surface for removing said image receiving medium and for guiding said removed image receiving medium to said removal path.

5. In an electrostatic reproduction machine having a support surface adapted to support a developed image of a character pattern and to transfer said developed image to an image receiving medium in contact therewith at a transfer station, said electrostatic reproduction machine having primary means to remove said image receiving medium from said support surface and to transport said image receiving medium from said transfer station subsequent to said transfer of said developed image thereto; apparatus for detEcting when said image receiving medium has not been removed from said support surface subsequent to said transfer of said developed image; comprising: detecting means in operable communication with said support surface to detect the presence of said image receiving medium in contact with said support surface subsequent to said transfer of said developed image; secondary means responsive to said detecting means to remove said image receiving medium from said support surface and deflect said image receiving medium from said support surface through a removal path; and sensing means disposed in said removal path to sense the presence of said image receiving medium therein to regulate the further operation of said electrostatic reproduction machine.

6. The apparatus of claim 5 wherein said sensing means comprises: switch means adapted to be activated by the contact therewith of said image receiving medium; timing means electrically coupled to said detecting means and to said switch means and responsive to said detecting means for commencing the timing of a predetermined interval and to the activation of said switch means for interrupting said timing prior to the completion of said predetermined interval; and terminating means coupled to said switch means and to said timing means for the further operation of said electrostatic reproduction machine after a determined delay when said switch means is activated and for immediately terminating the further operation of said electrostatic reproduction machine when said timing means completes the timing of said predetermined interval.