US3532423A - Photoelectrostatic copying machine - Google Patents

Description

v Oct. 6, 1970 I J. v. BRUNING ET AL 3,532,423

' PHOTOELECTROSTAT-IC cor me MACHINE OriginaljFiled May 21, 1965 7 Sheets-Sheet 1 M 4 12 K pnu'ry Kfizz 73% wail/Z, L.

OZO/ZIL Q1 O zegyfqy Oct. 6, 1970 J. v. BRUNING ETA!- 3,532,423

PHOTOELECTROSTATIC COPYING MACHINE Original Filed May'2l, 1965 7 Sheets-Sheet 2 5g 1 xyiif 0 212 2 J/ dist-73 21 2 /o/uz QZeg/q y M1. Adm

Oct. 6, 1970 J. v. BRUNING ET AL 3,532,423

PHOTQELECTROSTATIC COPYING MACHINE '7 Sheets-Sheet 5 7 Original Filed May 21, 1965 Oct. 6, 1970 J. v. BRUNING ETAL 3,532,423

PHOTOEL ECTROSTATIC COPYING MACHINE Original Filed May 21, 1965 7 Sheets-Sheet 1 Oct. 6, 1970 I J. v. BRUNING ET AL 3,532,423

PHOTOELECTROSTATIC COPYING MACHINE Original Filed May 21, 1965 7 Sheets-Sheet 5 Oct, 6, 1970' J. v. BRUNING ET AL 3,

PHOTOELECTROSTATIC COPYING MACHINE Original Filed May 21, 1965 7 Sheets-Sheet 6 Oct. 6, 1970 J. v. BRUNING ET AL 3,532,423 PHOTOELECTROSTATIC COPYING MACHINE Original Filed May 21, 1965 7 Sheet-Sheet 7 6 w N C %w m a a 2 v 6 :2 w M 4 b 2 8 i--- 8 0 6 6 2 W/v 2 i b m 2 1 w w z United States Patent Office US. Cl. 355-27 6 Claims ABSTRACT OF THE DISCLOSURE A sheet feeding assembly for feeding a sheet from a stack including a support for the stack and a sheet engaging friction wheel spaced from the stack. A solenoid having a movable armature is flexibly connected to the support for the wheel such that operation of the solenoid applies a positive force to resiliently bias the wheel against the stack.

This application is a division of copending application Ser. No. 457,649, filed May 21, 1965, now US. Pat. No. 3,397,627, issued Aug. 20, 1968.

This invention relates to a copying apparatus and, more particularly to a new and improved photoelectrostatic reproducing apparatus.

The technology of making copies of a graphic original electrostatically involves the application of a uniform electrostatic charge in the dark to a photoconductive surface selectively discharging the surface by exposure to a pattern of light and shadow in accordance with the original being copied to provide a latent electrostatic image, and rendering the latent image visible by applying finely divided electroscopic particles. The latent image can be devolped directly on a photoconductive copy sheet or on another surface from which the visible image is subsequently transferred to a plain sheet. A wide range of apparatus is available to carry out the foregoing operations. They provide for the synchronous relative movement of a graphic original to the moving charged photoconductive surface during the exposure step in which the latent charge image is formed. In other prior machines, the original is held in a fixed position and a corresponding light pattern produced by light scanning the fixed original in synchronism with the moving charged surface. These copying machines, operating on the principle of transporting the original and/or the sheet on which the copy is produced, enjoy the advantage of high rate copy output since the operational steps are carried out while the elements are in motion. The mechanisms required for these synchronous movements and transporting assemblies are complex and of precision construction increasing not only the initial cost but the cost of maintenance. The optical systems employed must be carefully controlled so that the machines are capable of only a fixed size relative to the original.

Accordingly, one subject of the present invention is to provide a new and improved photoelectrostatic copying machine.

Another object is to provide a photoelectrostatic copying machine of a compact and economically fabricated construction.

Another object is to provide a copying machine in which an image of a stationary object is projected onto a stationary copy sheet.

A further object is to provide a photoelectrostatic copying machine including new and improved sheet conveying means.

3,532,423 Patented Oct. 6, 1970 A further object is to provide a photoelectrostatic copying machine including an intermittently operating copy sheet conveying means for moving a copy sheet to an exposing station in which it is held in a stationary position during exposure, the conveying means then being placed in operation to feed the exposed copy sheet to a developing station.

A further object is to provide a photoelectrostatic copying machine in which the area for receiving the subject to be copied, the copy delivery station and the copy sheet feed station are all accessible at or near the top of the machine.

A further object is to provide a copying machine in which the air intake to and the air discharged from an air impelling means are used to mount flexible material on a conveying means at spaced points in the path of movement of the flexible material.

Another object is to provide a copying machine including new and improved means for easily changing the size of copies produced by the machine by simple manual adjustments that can be made externally of the machine by its operator.

Another object is to provide a copying machine including novel means for changing the copy size by varying the relative positions of components of the optical system provided in the machine.

A further object is to provide a copying machine including new and improved means for feeding copy sheets.

Another object is to provide a new and improved assembly for feeding sheets of flexible material.

In accordance with these and many other objects, an embodiment of the invention comprises a photoelectrostatic copying machine adapted to be mounted on a desk or table and having a somewhat rectangular housing with a generally uniplanar upper surface. An illuminating station is provided at one end of the housing and includes a light transmitting or transparent glass plate forming a part of the top wall structure and having an edge coextensive with an edge of the housing. This permits not only sheets of original material but also pages from bound volumes to be copied by placing the page to be copied on the glass plate with the remainder of the book disposed along the side of the housing. Suitable illuminating means for directing light on the transparent member provide a reflected light image whichis supplied through an optical system including a reflecting assembly and a lens assembly to an exposure station disposed in a fixed plane. By manually adjusting the relative positions of the lens assembly and the reflecting assembly relative to each other and to the fixed exposure plane from a control located external of the machine, the original can be copied in different selected sizes.

To supply a copy sheet of the photoelectrostatic type to the exposure station, the copying machine includes a copy sheet feeding assembly mounted immediately adjacent but just below the top wall surface of the housing, the housing being provided with a removable cover to permit the insertion of copy sheets on a stack supporting table or tray forming a part of the sheet feeding assembly. This assembly includes driven sheet engaging rollers carried on pivotally mounted lever means which are normally biased by resilient means to a position in which the drive rollers are spaced from the stack. When a copy is to be produced, a solenoid is energized to retract an armature which is connected by flexible connecting means including a resilient means to the lever. The retraction of the armature pivots the lever against its resilient bias to move the rollers against the top sheet in the stack to feed this sheet out of the feeding assembly and into a guideway including a pair of driven rollers. The solenoid is then released, and the separated sheet is fed in the generally horizontal direction into a curved guideway into which a switch operator arm projects. When the leading edge of the sheet engages the switch operator to actuate the switch, a corona charging unit including a generally vertically extending sheet passageway is energized so that as the sheet is advanced by the driven rollers, uniform electrostatic charges of opposite polarities are applied to both sides of the copy sheet.

An intermittently operated first sheet conveying or transporting assembly, which forms a part of the ex posure station, receives the charged sheet discharged from the corona unit. This conveying means includes a plurality of spaced flexible belts or closed loops which form one side of a duct structure or plenum chamber connected to the intake of an air impelling means. Thus, when the leading edge of the charged sheet is discharged from the charging station into proximity to the first sheet conveying means, the sheet is held against the flexible belts by the negative pressure induced across the belts by the air impelling means. The conveying belts extract the charged copy sheet from the charging station and advance it in a generally downwardly extending direction to an exposure position in which it is disposed in the fixed exposure plans. At this time, the leading edge of the switch engages a switch operator projecting into the path of movement of the first sheet conveying means. When this switch is actuated by engagement of the switch operator, the first conveying means is rendered inoperative, and the charged copy sheet is held in a stationary predetermined position. The actuation of this switching means also causes the momentary energization of the illuminating means so that a light image representing the original material to be copied is forwarded through the optical assembly to selectively discharge the illuminated surface of the copy sheet to provide a latent charge image representing the original to be copied.

After a predetermined time delay, the first sheet conveying means is again placed in operation to advance the exposed copy sheet to a developing station including a tank filled with a liquid developer comprising electroscopic powder and a liquid carrier. This developer station includes a guide structure with an inlet disposed immediately beneath the discharge of the first conveying means and an outlet or exit disposed immediately beneath the inlet of a generally vertically extending discharge conveying and drying means. Thus, when the first conveying means is placed in operation, the exposed copy sheet is fed through the liquid in the developer tank to permit the selective disposition of electroscopic powder on the exposed surface of the sheet in accordance with the electrostatic image. This selective adherence or deposition of electroscopic material converts the latent electrostatic image into a visible image.

The discharge conveying and drying means comprises a plurality of flexible belts disposed in spaced apart relation and extending in a generally vertical direction parallel to and spaced to one. side of the first conveying means. A louvered duct or chamber connected to the discharge side of the air impelling means is spaced from the flexible belts so that the air discharged from the impelling means is directed agains the outer surface of the belts. Thus, when the leading edge of the developed copy sheet leaves the exit opening in the developer tank, this leading edge passes between a pair of driven rollers to be advanced to a position engaging the flexible belts in the discharge conveying means with the image bearing surface of the sheet facing the louvered discharge of the duct structure connected to the'air impelling means. The air discharged from this duct structure holds the sheet in engagement with the upwardly moving flexible belts and thus detachably mounts the copy sheet on these belts for movement therewith. The air discharged from the duct structure not only mounts the developed copy sheet on the conveying belts but also provides a flow of air for removing any liquid remaining on the copy sheet. The upper end of the discharge conveying and drying means discharges the copy sheet with the image side up on the top wall structure of the housing.

Many other objects and advantages of the present invention will become apparent from considering the following detailed description in conjunction with the drawings in which:

FIG. 1 is a perspective view of a photoeleetrostatic copying apparatus embodying the present invention;

FIG. 2 is a sectional view taken generally along line 22 in FIG. 1;

FIG. 3 is an enlarged sectional view illustrating an optical system and adjusting means therefor which are included in the copying apparatus;

FIG. 4 is an enlarged fragmentary end elevational view in partial section illustrating the adjusting linkage for the optical system;

FIG. 5 is an enlarged fragmentary sectional view of a copy sheet feeding assembly included in the copying machine;

FIG. 6 is a fragmentary top elevational view of the copying apparatus illustrating an assembly for producing a controlled flow of air for controlling the transportation and drying of copy sheets in the apparatus; and

FIG. 7 is a schematic diagram of a circuit for controlling the operation of the copying machine.

Referring now more specifically to FIGS. 1 and 2 of the drawings, therein is illustrated a copying machine which is indicated generally as 10 and which embodies the present invention. The machine 10 includes a housing 12 having four threaded or adjustable feet 14 (FIG. 2) for mounting the machine 10 in a level position on a supporting bench, table, or desk 16. An illuminating station indicated generally as 18 is provided adjacent one end of the generally rectangular housing 12 and includes a plate 20 of glass or other light transmitting material which forms a part of a top wall structure 22 for the housing 12. The glass pane 20 is so positioned in the top wall 22 that its edge is coextensive with the left-hand (FIG. 2) vertical wall of the housing 12. This permits the original material to be copied by the machine 10 to comprise not only sheet material but also material from bound volumes, such as a page of a book 24, shown in FIG. 1. The book 24 can be placed with its back along the edge formed by the glass pane 20 and the vertical wall of the housing 12 with the page to be copied overlying the glass pane 20 and with the remainder of the book extending vertically along the adjacent wall of the housing 12.

A light source included in the illuminating station 18 provides light which is reflected from the original at the station 18 and is transmitted through an optical system indicated generally as 24 (FIG. 2) to impinge on an electrophotostatic copy sheet 26 which is held in a stationary position at an exposing station indicated generally as 28 during the exposure operation. The optical system 24 can be adjusted-to a plurality of different settings by a control assembly or linkage indicated generally as 30 (FIG. 3) to permit the machine 10 to provide copies on the copy sheet 26 of different sizes, e.g., full or reduced size. The assembly 30 is manually actuated by the operator at a position outside of the housing 12 and does not require factory adjustment in order to provide copies of different sizes. To provide means for supplying a copy sheet 26 at the exposing station 28, the machine 10 includes a magazine assembly indicated generally as 32 (FIG. 2) containing a stack 34 of individual copy sheets 26.

When the machine 10 is placed in operation, a novel control means in the sheet feeding assembly 32 is actuated to feed a single sheet from the stack 34 over a paper guideway to a charging station indicated generally as 36. As the forward edge of the sheet 26 provided by the assembly 32 approaches the charging station 36, a switch 38 is operated to place the charging station 36 in operation so that the opposite sides of the copy sheet 26 are provided with uniform electrostatic charges. A first sheet conveying assembly, which is indicated generally as 40 and which is intermittently operated, advances a charged sheet received from the charging station 36 to a position disposed in a fixed and predetermined exposure plane at the station 28. The copy sheet 26 is held in engagement With the conveying means 40 by an air flow assembly indicated generally as 42 (FIG. 6) including an air impelling means whose intake is placed in communication with the conveying means 40 to hold the copy sheet 26 on the conveying means by suction or negative pressure.

When the sheet 26 is advanced to a proper position in the fixed and predetermined exposure plane at the station 28 by the conveying means 40, the leading edge of the sheet engages an operator 44a on a switch 44 and operates this switch. When the switch 44 is operated, further movement of the sheet conveying means 40 is arrested, and the light source at the illuminating station 18 is momentarily energized to forward a light image through the optical system 24 to selectively discharge the exposed surface of the copy sheet 26 at the exposure station 28.

After a suitable time delay, the conveying means 40 is placed in operation so that the exposed copy sheet containing a latent electrostatic image is advanced to a developing station 46 of a liquid type in which electroscopic powder in a liquid carrier is placed in contact with the electrically charged surface of the copy sheet 26 to provide a visible image by th selective deposition or attraction of the electroscopic powder. The leading edge of the developed copy sheet is received on a discharge and drying conveying means indicated generally as 48 and is held in engagement therewith by the air discharged from the air impelling assembly 42. This flow of air not only holds the developed copy sheet 26 on the conveying means 48 but also dries any residual liquid retained on this copy sheet. The dried and developed copy sheet 26 is discharged into a sheet receiving receptacle 50 carried on and forming a part of the top wall structure 22 of the housing 12.

Referring now more specifically to the illuminating station, this station is disposed at the left end of the housing 12 (FIGS. 1 and 2) immediately adjacent the top wall structure 22 and includes the light transmitting member or glass pane 20. A flexible opaque cover 52 is pivotally mounted on the housing adjacent the rear wall to provide means for securing the original material to be copied in a uniplanar position adjacent the glass pane 20. To provide a light source at the illuminating station 18, a pair of lamps 54 (FIGS. 24) and cooperating reflectors 56 are provided adjacent the front and rear walls of the housing 12. The lamps 54 and the corresponding reflectors 56 are so disposed as to direct light against the lower surface of the glass pane to provide a reflected light image which is directed by the optical system 24 onto the exposed surface of the copy sheet 26 at the exposure station 28.

The optical system or'assembly 24 (FIGS. 2 and 3) includes a reflecting or mirror means 58 which is mounted in an inclined position below the glass pane 20 in a position to direct light reflected from the original to a lens assembly 60 included in the optical system 24. The mirror means 58 is mounted on a supporting structure 62 which is secured at its base to a plate 64. Opposite ends of the plate 64 are secured to a pair of bushing or sleeve members 66 which are slidably mounted on a pair of rods 68 supported on the base of the housing 12 at spaced positions by a pair of standards 70. The sleeves 66 to which the supporting structure for the reflecting means 58 is connected are slidably mounted on the rods 68 to permit the mirror or reflecting means 58 to be moved toward and away from the lens assembly 60.

The lens assembly 60 includes a plurality of lens elements 72 carried in a lens barrel 74 that is secured to a front wall 76 of an extensible bellows 70. The other end of the bellows 78 is secured to an apertured end member 80 which is secured to a dividing wall or partition 82 in the housing 12 in alignment with an opening therein which places the lens assembly 60 in communication with the exposure station 28.

The lens assembly 60 is also slidably supported on the housing 12 by means of a pair of spaced shafts or rods 84 which are rigidly secured at one end to the member 80. The front wall 76 of the bellows assembly is secured at its opposite edges to a pair of sleeves 86 which are slidably mounted on the rods 84. An apertured plate 88 secured to the front end of the rods 84 by a pair of nuts 89 provides a front stop for limiting movement to the left (FIG. 3) of the sleeves 86. By moving the sleeves 86 on the rods 84, the bellows 78 is expanded and contracted and the position of the lens barrel 74 relative to the exposure plane and the reflecting means or mirror '58 can be varied.

The linkage or control assembly 30 (FIGS. 3 and 4) provides means for changing the size of the light image impinging on the copy sheet 26 at the exposure station 28 by adjusting the relative positions of the mirror 58 and the lens assembly 60. The control assembly 30 includes a manual operating arm or knob 90 slidably mounted in and extending through a slot 92 (FIGS. 1, 3, and 4) in a shelf 12a disposed at the front of the housing 12. The lower end of the knob structure 90 is connected to a pair of connected links 94 and 96, and the other end of the link 96 is pivotally connected to the upper end of an arm 98 whose lower end is rigidly secured to one end of a shaft 100. The shaft 100. is pivotally mounted in a U-shaped bracket 102 carried on an intermediate wall of the housing 12. The other end of the shaft 102 is rigidly secured to the upper end of an arm 104, and the lower end of the arm 104 is provided with an elongated slot 106 in which is received a pin 108 secured to the adjacent sleeve 86. In this manner, the knob 90 is coupled to the sleeves 86 connected to the lens barrel 74.

The pin or shaft 108 is also received within an elongated slot 110 in the upper end of a lever 112. An intermediate portion of the lever 112 is pivotally mounted on a shaft 114 carried on a U-shaped bracket 116 secured to the intermediate wall of the housing 12. The lower end of the lever 112 is pivotally connected to one end of a link 118, the other end of which is pivotally connected to an upstanding arm or plate which is secured to the base plate 64. Thus, the knob 90 is also coupled to the support for the reflecting means or mirror 58.

When the control assembly is in the position shown in FIG. 1, the optical system 24 provides a 1:1 ratio between the size of the original to be copied and the image projected onto the copy sheet 26 in the exposure plane at the exposing station 28. In this setting, the control linkage 30 occupies the position shown in solid line in FIG. 3. When it is desired to produce a reduced size copy in which the ratio of the area of the copy sheet to the image area of the original is, for instance, 11:14, the knob 90 is moved to the left (FIG. 3) to pivot the arm 98 in a counterclockwise direction to the position shown in dashed line. This rotates the shaft 100 in a counterclockwise direction and swings the arm 104 to the right. As the arm 104 moves to the right, the sleeves 86 are moved to the right on the rods 84 to the position shown in dashed outline, and the lens elements 72 in the lens barrel 74 are moved to the right or closer to the exposure plane.

When the sleeves 86 and the pin 108 are moved to the right by the arm 104, the lever 112 is pivoted in a clockwise direction (FIG. 3) about the shaft 114 so that the link 118 is moved to the left to move the supporting structure 62 for the mirror to the left. This increases the distance from the mirror to the lens elements 72 in the lens barrel 74. With the lens elements 72 now positioned more closely adjacent the plane of exposure at the station 28 and with the reflecting means 58 shifted in a direction parallel to the light transmitting pane 20 away from the lens assembly 60, the image applied to the copy sheet 26 at the exposure station 28 is reduced in size relative to the original graphic material at the illuminating station 18. Accordingly, by manually adjusting the knob 90 at a position outside of the housing 12, the copying machine can be easily adjusted to provide copies of various sizes relative to the original.

As set forth above, the sheet feeding assembly 32 (FIGS. 2 and 5) is operable to feed a single photoelectrostatic copying sheet 26 from the stack 34 thereof each time that a copy is to be produced by the machine 10. The sheet feeding assembly 32 can be of any suitable construction but preferably comprises one of the type shown and described in detail in the copending application of John L. Tregay, Ser. No. 441,063, filed Mar. 19, 1965, which application is assigned to the same assignee as the present application. As shown therein, the assembly 32 include a sheet or stack supporting table 130 on which a pair of adjustably mounted side rails or edge guides 132 are mounted for movement to spaced positions determined by the width of the copy sheets 26 to be supplied to the machine 10. A pair of separator arms 134 connected at their rear end to the bight portion of two U-shaped brackets 136 are pivotally mounted thereby on a transversely extending rod or shaft 138. The forward ends of the two separator arms 134 include a vertically extending portion 134a which provides a front stop for the stack 34 and a rearwardly projecting lip or separator portion 1341) which is adapted to rest on the top sheet 26 in the stack 34 adjacent a corner thereof.

When the top sheet 26 is engaged and fed forwardly by suitable drive means, the forward corners of the top sheet 26 buckle slightly to permit the sheet to pass beyond the two separator elements 134 which are disposed immediately adjacent the side rails or edge guides 132. The leading edge of the sheet 26 fed from the stack 34 is guided between a pair of feed rollers 140 and 142 which are driven by suitable means (not shown) so as to be rotated during the interval in which the first sheet conveying assembly 40 is in operation. The leading edge of the sheet 26 is guided to the nip between the rollers 140 and 142 by an upwardly inclined and somewhat centrally disposed guide portion 130a formed integral with the stack supporting table 130.

The sheet feeding assembly 32 includes new and improved means for controlling the movement of sheet engaging and driving means into intermittent engagement of the top sheet 26 in the stack 34 so that sheets can be fed from the assembly 32 at times determined by the operating cycle of the machine 10. To provide means for feeding a sheet from the assembly 32, a pair of friction wheels 144 are mounted in spaced apart positions on a shaft 146 which is rotatably mounted between two levers 148 spaced outwardly from the two sides of the sheet feeding assembly 32. The two levers 148 are pivotally mounted on a shaft 150 intermediate its ends, the shaft 150 being provided with a driven pulley 152 which is coupled by a flexible belt 154 to a pulley (not shown) rigidly secured to the shaft 146. The pulley 142 rotates the shaft 146 and the friction wheels 144 secured thereto in a clockwise direction (FIG. 5) about the axis of the shaft 146 to feed the sheets 26 to the left (FIG. 5) or to the right (FIG. 2).

The two levers 148 are normally pivoted in a counterclockwise direction (FIG. 5) about the shaft 150 to a normal position determined by a stop (not shown) to hold the friction wheels 144 out of engagement with the sheet 26 in the stack 34. To bias the levers or supporting arms 148 to this position, a rod 156 connected between ends of these two levers is connected to one end of a flexible connector 158. The flexible connector 158 passes around one of the two pulleys 160 rotatably mounted on a shaft 162 and is connected at its other end to a tension spring 164. The other end of the tension spring 164 is connected to a lead screw 166 threadedly mounted in a downwardly extending flange or wall 168a on a supporting bracket 168 carried in a fixed position on the housing 12 of the machine 10. By rotating the lead screw 166 to move to the right, greater tension is applied to the levers 148 through the flexible connector 158 and the tension spring 164. By rotating the lead screw 166 to move to the left (FIG. 5), the bias applied by the spring 164 is reduced.

To provide means for selectively moving the friction wheels 144 into engagement with the top sheet 26 in the stack 34, the two levers or supporting arms 148 are connected by a rod 170 at a point disposed on the other side or to the right (FIG. 5) of the pivotal axis defined by the shaft 150. A flexible connector 172 is connected at one end to the rod 170 and passes around the second one of the pulleys 160 rotatably mounted on the shaft 162 to be secured at its other end to one end of a tension spring 174. The other end of the tension spring 174 is connected to the outer end of a magnetic armature 176 which is mounted for reciprocating motion within an axial opening in a winding in an electrical solenoid indicated generally as 178. A stop nut is threadedly mounted on the magnetic armature 176.

When the solenoid 178 is energized, the armature 176 moves to the right and applies a resilient bias to the spring 174 and the flexible connector 172 tending to pivot the levers or arms 148 in a clockwise direction about the shaft 150. The force provided by the operation of the solenoid 178 is sufficient to overcome the resilient bias provided by the spring 164 so that the arms 148 pivot in a clockwise direction to move wheels 144 into engagement with the top sheet 26 in the stack 34. Since this deflecting force is applied to the arms 148 through the tension spring 174, the wheels 144 are resiliently biased into engagement with the top sheet 26, and the same stroke of the armature 176 can cause movement of the arms 148 through different distances in a clockwise direction about the shaft 150 to compensate for stacks 34 of varying heights. The stroke of the armature 176 can be adjusted by threading the stop nut 180 to various positions. When the solenoid 178 is released, the tension spring 164 pivots the arms 148 in a counterclockwise direction about the axis of the shaft 150 to move the friction wheels 144 out of engagement with the stack 34. It is only necessary for the friction wheels 144 to engage and drive the top sheet 26 of the stack 34 until the leading edge of the separated sheet 26 is received in the nip between the driven rollers 140 and 142.

As illustrated in FIG. 2 of the drawings, the sheet feeding and separating assembly 32 extends in a generally horizontal direction interposed between the illuminating station 18, on the left, and the charging station 36 and the exposure station 28, on the right, in a position closely underlying the top well structure 22. To permit the insertion of a stack 34 of copy sheets 26 between the side rails 132 in the assembly 32, the top wall structure includes a removable or hinged cover 182. Suitable means are provided which are accessible when the cover 182 is removed or displaced for lifting the separator arms 134 to permit the insertion of a new stack 34 under the rearwardly projecting portions 134!) on these separator arms. A switch 184 which is operated when the cover 182 is removed disables certain components of the machine 10' to prevent its operation when the cover is not in place. A switch 186 in the assembly 32 is operated when the supply of copy sheets 26 has been depleted and is used to arrest operation of the machine 10 when this occurs.

The separated sheet 26 from the feeding assembly 22 enters the nip between the rollers 140 and 142 and moves in a generally horizontal direction (FIG. 2) to enter a guideway formed by a pair of arcuate or generally semicircular members 190 defining a passageway for directing the leading edge of the copy sheet downwardly toward the charging station 36. During movement through the pas- 9 sageway formed by the guideways 190, the leading edge of the sheet 26 engages and displaces an actuator arm 38a for the switch means 38 so that this switch is operated to energize the charging station 26.

This charging station applies a uniform electrostatic charge of opposite polarity to opposite surfaces of the sheet 26. The charging station 36 includes a housing 192 having a centrally disposed passageway extending in a generally vertical direction. Supporting structures 194 on opposite sides of the passageway support corona discharge wires or other suitable means for imparting uniform electrostatic charge blankets to the opposite sides of the copy sheet 26 as it passes through the charging station 36. As the leading edge of the copy sheet 26 leaves the housing 192, it is placed in engagement with the first sheet conveying means 40 in the exposure station 28 to be moved to a position for exposure in which the uniform electrostatic charge on one surface of the sheet is selectively dissipated in accordance with the light image provided by the optical system 24.

The first sheet conveying means includes a plurality of flexible belts 196 disposed in side-by-side spaced positions and carried on three lines of guide rollers or pulleys 198, 200, and 202. A drive motor 204 is coupled by flexible drive means 206 to one line of the rollers, such as the rollers 202. The direction of rotation of the driven line of rollers 202 is such that the flexible belts 196 move downwardly in the exposure plane and move upwardly in a position disposed to the rear or the right of the exposure plane.

To provide means for retaining the copy sheet 26 in engagement with the flexible belts 196 without requiring the provision of opposing structures which would interfere with the transmission of the light image to the copy sheet 26, a duct structure or plenum chamber 208 (FIGS. 2 and 6) is provided which is disposed between the different flights of the flexible belts 196. A forward or lefthand wall 208a of the duct structure or plenum chamber is provided with apertures placing the interior of this chamber in communication with the interior of the housing 12 immediately adjacent the belts 196. If desired, the belts 196 can be provided with perforations which are aligned with the openings in the walls 208. The opposite ends of the duct or plenum chamber 208 are placed in communication with the air intakes to a pair of blowers or air impelling means 210 and 212 disposed generally adjacent the front and 'back walls of the housing 12. The air impelling means 210 and 212 can comprise squirrel cage type exhaust blowers.

The air drawn from the interior of the housing 12 into the duct structure 208 provides a pressure differential across the belts 196 and the superimposed copy sheet 26 to detachably retain this sheet in engagement with the belts 196 for movement therewith. Accordingly, as the leading edge of the sheet 26 passes out of the exit of the charging station 36, it is fed between the belts 196 and a roller 214 (FIG. 2) and is then held in engagement with the belts 196 during their downward movement. When the trailing edge of the copy sheet 26 passes beyond the operator 38a, the switch 38 is released. The drive motor 204 continues in operation until the leading edge of the sheet 26 on the conveying belts 196 engages and actuates the operator arm 44a for the switch means 44. The operation of the switch means 44 interrupts the operation of the motor 204 so that the charged copy sheet 26 is retained in the exposure plane at the station 28 in a position to receive the light image supplied from the illuminating station 18 through the optical system 24. After a suitable delay, operation of the motor 204 is initiated, and the leading edge of the exposed sheet v26 passes between a roller 216 and the belts 196 to be discharged to the developing station 46.

The developing station 46 can be of any suitable type well known in the industry, such as a magnetic brush or cascade developer using electroscopic or toner powder.

In the illustrated copying machine 10, the developing station 46 utilizes a liquid developing technique and comprises a tank or reservoir 218 having mounted therein a pair of spaced and somewhat arcuately formed plates 220 defining a passageway having an inlet disposed immediately below the discharge end of the conveying means 40 and an exit or outlet disposed immediately below the inlet to the drying and discharge conveying means 48. The interior of the reservoir or vessel 218 is filled with a suitable liquid developer such as a mixture of electroscopic powder and a liquid vehicle. This liquid developer can, for instance, be of the type described in detail in US. Pat. No. 2,907,674. The lower giude structure 220 is provided with a plurality of spaced apertures 220a to permit the liquid developer solution to enter the passageway defined by the guide elements 220.

When the uniformly charged outer surface of the copy sheet 26- at the exposure station 28 is exposed in accordance with the light image provided by the optical system 24, this surface is selectively discharged to provide a latent electrostatic image which is developed at the developing station 416 by the selective deposition, attraction, or adherence of particles of electroscopic or toner powder from the liquid developer to the selectively charged surface of the sheet. This means that after a period of use, the concentration of the electroscopic powder or particles in the liquid developer becomes depleted and necessitates the replacement of this material. To accomplish this, the copying machine 10 includes a unit 219 for metering the liquid concentrate or slurry of electroscopic powder from a bulk supply thereof to the liquid developer unit. The unit 219 includes a vessel or reservoir tank filled with a liquid developer of the same concentration as in the developer tank 220. The unit 219 also includes a replaceable bottle or other container of the liquid concentrate which has a much higher percentage of the developer powder together with electrically operated or controlled dispensing means for feeding metered amounts of the concentrate to the reservoir tank portion of the unit 219. The electrically controlled dispensing means in the unit 219 can be of any suitable known construction. The unit 219 meters a quantity of the toner concentrate or slurry in response to the length of copy sheet material passed through the machine 10. Manually controlled means for operating the dispensing means can also be provided.

As illustrated in FIG. 2 of the drawings, the unit 219 is connected to the interior of the vessel 218 through a pair of lines 219a and 2191). A pumping means 221 is disposed in the line 219a to circulate the liquid developer replenished with concentrate between the unit 219' and the vessel 218. This circulation aids in equally distributing the electroscopic powder in the liquid developer serving to agitate the mixture and prevent the electroscopic powder from settling. The lines 219a and 2191) preferably are provided in positions communicating with the interior of the vessel 218 at spaced apart locations to insure the adequate distribution of a liquid developer of uniform concentration throughout the interior of the vessel.

The machine 10 also includes means for detecting when the level of the liquid developer within the tank 218 falls below a level at which proper developing takes place. More specifically, a float controlled valve 223 of any of the well known constructions is provided which is actuated whenever the level of liquid developer within the vessel 218 falls below the minimum level required for proper development of the exposed copy sheets 26.

When the leading edge of the exposed copy sheet 26 is fed past the idler or guide roller 216 into the entrance of the passageway defined by the guide members 220, this sheet is fed beneath the surface of the liquid developer and passed through the passageway propelled by the first transport means 40. A leading edge of the sheet leaves the developing passageway in the reservoir 218 through 1 1 the exit or outlet opening and is fed into the nip between a pair of continuously driven rollers 222 and 224. Further movement of the developed sheet 26 is controlled by the discharge and drying conveying means 48.

The discharge and drying conveying means 48 includes a plurality of flexible belts 226 passing around a plurality of spaced lines of pulleys or rollers 228, 230, 232, and 234. A selected one of the lines of the pulleys, such as the line of pulleys 234, is coupled to a continuously operating drive motor 236 by flexible coupling or connecting means 238. The drive motor 236 can also be coupled to drive one of the rollers 222 and 224. The direction of rotation of the drive motor 236 is such that the righthand portions of the flexible belts 226 are driven vertically upward.

To provide means for concurrently mounting the developed sheet 26 on the flexible belts 226 and to provide means for drying any liquid retained on the copy sheet, a duct structure or chamber 240 (FIGS. 2 and 6) is provided having a plurality of louver-type openings 242 therein. The louvered openings 242 are spaced from and directed toward the adjacent portion of the flexible belts 226. The duct or chamber 240 is coupled to the air discharge or outlet from the impelling means 210 and 212 so that the air discharged by these impelling means is directed against the flexible belts 226. Thus, as the leading edge of the developed copy sheet is discharged from between the rollers 222 and 224, the air blast forces this sheet against the flexible belts 226 to move therewith with the image bearing surface facing toward the duct structure 240. The flow of air directed out of the louvered openings 242 also dries the sheet 26. Thus, the air impelling means 210 and 212 serve to hold the copy sheet 26 in the exposure station 28 in position on the first conveying means 40 by suction and serve to dry and hold the developed copy sheet 26 on the flexible belts 226 in the conveying means 49 by a positive pressure.

As the leading edge of the developed copy sheet 26 passes beyond the upper end of the duct or chamber 240, the image is in a fixed or permanent state in which it is not distorted. The leading edge then passes between the flexible belts 226 and an additional set of flexible belts 244 which pass around a plurality of line of rollers or pulleys 246, 248, and 250 and which are driven in synchronism with the belts 226. When the leading edge of the copy sheet 26 reaches the upper end of the housing 12, it is discharged from between the belts 226 and 244 into the print or copy receiving tray 50 with the developed and fixed image facing upwardly to permit immediate visual inspection without requiring the sheet to be inverted. The upper portion of the conveying means 48 including the lines of rollers 228, 246, and 248 and the upper portions of the flexible belts 226 and 244 is enclosed in an upwardly projecting housing 251 having an opening in its left-hand wall through which the developed copy sheets 26 are discharged to the copy receiving tray or receptacle 50.

A control circuit 260 (FIG. 7) coordinates and controls the operation of the various components of the copying machine 10. The machine is placed in condition for operation by removing the cover 182 and placing a stack 34 of copy sheets 26 in the sheet feeding assembly 32. With the cover 182 replaced and a stack 34 of sheets 26 on the table 130, both the sheet detecting switch 186 and the cover control switch 184 are operated to their normal conditions. In the normal condition of the switch 186, a pair of contacts 186a (FIG. 7) are closed, and a pair of contacts 18617 areopened. The switch 184 (FIG. 7) is operated from the position shown to a closed position when the cover 182 is closed. The machine 10 is then prepared for operation by closing a main switch 262 to supply conventional alternating current potential to the control circuit 260. This potential is applied through the closed switch 184 to the winding of the developer pump 221 so that the liquid developer is circulated within the vessel 218. The input potential is also applied through the closed switch 184 to the winding of the motor 236 so that the discharge and drying conveying means 48 is placed in operation. This input potential is directly for- Warded to the two air impelling means or blowers 210 and 212 so that a flow of air is produced through the ducts 208 and 240 to condition the conveying means 40 and 48 for operation. The input potential is also forwarded through a pair of normally closed contacts 264b on a relay 264 to energize the drive motor 204 so that the flexible belts 196 in the sheet conveying means 40 are advanced and the rollers 140 and 142 are placed in rotation.

If the supply of liquid developer in the tank 218 is at a high enough level to permit proper development of an exposed copy sheet 26, the level or float controlled switch 223 is in the operated condition shown as a closed pair of contacts in FIG. 7 of the drawings. The input potential is supplied through the contacts 223 across an operating winding 266 to operate this relay to close a pair of contacts 266a and to open a pair of contacts 266b. The closed contacts 266a connect the input potential through the closed contacts 186a to the input of a full wave rectifier bridge 267, thereby providing a direct current operating potential for a number of components of the control circuit 260. The control circuit 260 remains in this condition until the copying machine 10 is started.

When a copy is to be made of an original, such as a page from the book 24, the page to be copied is placed on the light transmitting pane 20, and the knob is adjusted to its left-hand or right-hand position (FIG. 1) in accordance with the size of the copy to be reproduced. The adjustment of the knob 90 controls the assembly 30 to place the reflecting means or mirror 58 and the lens assembly 60 in a correct position for producing the desired copy. The operator then adjusts an automatic counting control assembly or unit 268 to a setting representing the desired number of copies. The control unit 268 includes a manual operating knob 270 (FIGS. 1 and 6) mounted on the shelf 12a on the housing 12. The unit 268 is of a conventional construction and includes a pair of normally open contacts 268a (FIG. 7) which are closed when the knob 270 is turned to a setting representing a desired number of copies. The setting of the knob 270 also advances a counting mechanism whose setting represents the desired number of copies. This counting mechanism is operated a single step in a direction toward a normal setting by a pawl and ratchet mechanism or other suitable means each time that a solenoid 26812 is energized. Accordingly, when the knob 270 is turned to a setting representing the desired number of copies to be made from the original, the contacts 268a are closed to initiate the cyclic operation of the machine 10 under the control of the control circuit 260.

When the contacts 268a are closed, the operating winding of the solenoid 178 is connected across the output of the bridge 267 and normally closed contacts 28% of relay 280, in a time delay circuit 272. When the solenoid 178 is operated, the armature 176 is retracted to pivot the levers 148 in a clockwise (FIG. 5) or counterclockwise (FIG. 2) direction about shaft 150. The continuously driven rollers 144 move into engagement with the top copy sheet 26 disposed in the sheet feeding assembly 32. This moves the top sheet 26 to the right (FIG. 2) into the nip between the rollers and 142, which are rotated by the energized motor 204. The rollers 140 and 142 advance the leading edge of the copy sheet 26 through the guideway provided by the structures 190 until the leading edge of the sheet 26 engages and deflects the operator 38a for the switch 38. When the switch 38 is operated, a pair of contacts 38b (FIG. 7) are closed.

The closure of the contacts 281) completes an energizing circuit for a timing motor 282 in the toner dispensing assembly 219 so that a cam mechanism shown schematically at 282a is driven. After a period of time 13 determined by the period that the contacts 38b are maintained in a closed condition, the cam means 282a closes a pair of normally open contacts 28212 to connect a solenoid 284 across the output of the bridge 267. When the solenoid 284 is energized, a predetermined quantity of the toner concentrate is dispensed into the liquid developer in the unit 219. This energization of the solenoid 284 can also be controlled by a manually actuated switch 286. The contacts 28211 are closed in a random time sequence relative to the feeding of the copy sheets 26 in dependence on the linear length of copy sheet exposed by the machine 10. In other words, the contacts 28212 may not be closed during any given copy feeding operation and at random times during the copying cycle. The contacts 282k are opened by the cam means 282a in response to continuing operation of the timer motor 282.

The closure of the contacts 38b also connects the time delay circuit 272 across the input potential so that the winding of the relay 280 is energized and a capacitor 278 is charged by pusating half cycle signals supplied through a resistor 274 and a diode 276. The energization of the winding of the relay 280 operates this relay to open the contacts 28% and to close a pair or normally open contacts 280a. The closure of the contacts 280a connects the alternating current input potential to a power supply 288 forming a part of the charging station 36 so that a pair of corona discharge wires 290 and 292 for applying oppositely poled charges to the opposite sides of the copy sheet 26 are supplied with direct current potentials. Thus, the charging station 36 is now placed in operation to apply uniform electrostatic charges of opposite polarity to the opposite sides of the copy sheet 26 as it passes through the charging station 36. The opening of the contacts 28% interrupts the above-described circuit for energizing the winding in the solenoid 178, and the tension spring 164 pivots the levers 148 in a clockwise direction (FIG. 2) to move the friction wheels 144 out of engagement with the stack 34. The copy sheet 26 previously separated from the stack 34 is propelled through the charging station 36 toward the exposure station 28 by the rollers 140 and 142.

As the leading edge of the charged copy sheet 26 emerges from the housing 192 of the charging station 36, it passes between the pressure roller 214 and the flexible belts 196 of the sheet conveying means 40 to be advanced to a position at which it is under the influence of the air intake to the blowers of air impelling means 210 and 212. Thus, the sheet 26 is held in engagement and for movement with the belts 196 by the negative pressure or suction resulting from the air intake to the blowers 210 and 212. The sheet 26 moves downwardly in a generally vertical direction with the belts 196 in the sheet conveying means.

As the trailing edge of the copy sheet 26 passes the operator arm 38a for the switch 38, this switch is released to open the contact 38b. This terminates the energization of the timer motor 282. The opening of the contacts 38b also interrupts the energizing circuit for the winding of the relay 280. However, this relay does not release at this time because of the time delay aiforded by the charged capacitor 278 which now discharges through the winding of the relay 280 to maintain this relay in an operated condition. The time delay provided by the circuit 272 is such that the contacts 280a remain energized to maintain the energization of the power supply 288 until the trailing edge of the copy sheet 26 has been discharged from the charging station 36. This insures that the corona discharge wires 290 and 292 remain energized long enough to completely charge both surfaces of the copy sheet 26. This delay in the release of the relay 280 also maintains the contacts 28% in an open condition so that the copy feed solenoid 17 8 cannot be operated.

When the charged sheet 26 is disposed in the exposure plane, its leading edge engages the operator 44a (FIG. 2) for the switch 44 and operates this switch to close a pair of normally open contacts 44b. When the contacts 44b (FIG. 7) are closed, a timing unit 294 is rendered operative to control the illumination of the original at the illuminating station 18 and to momentarily arrest operation of the sheet conveying means 40. More specifically, when the contacts 4412 are closed, a timing motor 296 is placed in operation, and the relay 264 is connected across the input alternating current potential over a circuit including a pair of normally closed contacts 296a controlled by the timer motor 296. The time of exposure of the copy sheet to the projected light image is selected by turning a control knob 297 (FIG. 1) which positions the timing motor operated cam 296 with respect to the switch 296a. The completion of the circuit including the closed contacts 296a operates the relay 264 to close a plurality of contacts 264a and 2640 and to open the contacts 264b.

The opening of the contacts 264b interrupts the energizing circuit for the drive motor 204 so that the rollers and 142 are no longer driven and so that the flexible belts 146 remain in a fixed position. In this position, the air passing through the duct structure 208 holds the charged copy sheet 26 in a fixed exposure plane at the exposing station 28. The closure of the contacts 2640 connects the lamps 54 across the input potential so that the original disposed on the light transmitting pane 20 at the illuminating station 18 is illuminated, and the light selectively reflected therefrom is transmitted over the optical system 24 to selectively discharge the uniformly charged surface of the copy sheet 26 at the exposing station to provide a latent electrostatic image corresponding to the original to be copied. The closure of the contacts 264c also energizes an operating winding in a counter 298 so that this counter is operated to add an increment of value indicating the production of a copy by the machine 10.

When the contacts 264a are closed by the operation of the relay 264, the solenoid 268b in the counting control unit 268 is connected to the open contacts 28% On the relay 280 in the time delay unit 272. Thus, when the contacts 28% are closed at the end of the delay period of the unit 272, the solenoid 268b is energized to return the counting mechanism a single step in the direction of the normal setting of this unit. If only a single copy was requested, the unit 268 is returned to its normal position by the single operating pulse, and the contacts 268a are opened. This interrupts the operating circuit for the solenoid 268b and also interrupts the operating circuit for the copy feed solenoid 178 which was also completed by the closure of the contacts 28012. This momentary energization of the solenoid 178 may result in partial feeding of a sheet 26 from the stack 34, but this does not affect the operation of the copying machine 10 inasmuch as it has not been fed a suflicient distance to be received between the rollers 140 and 142.

At the end of the exposure step controlled by the exposure timer 294 as selected by turning knob 297, the contacts 296a are opened to interrupt the operating circuit for the relay 264 so that the contacts 264a and 2640 are opened and so that the contacts 264b are closed. The opening of the contacts 264:: interrupts one point in the operating circuit for the solenoid 268b, and the opening of the contacts 264a terminates the energization of the lamps 54 and releases the counter 298. The closure of the contacts 264!) completes the energizing circuit for the drive motor 204 so that this motor places the sheet conveying means 40 in operation and also initiates the rotation of the rollers 140 and 142. The rollers 140 and 142 will feed a copy sheet 26 from the assembly 32 if more than a single copy has been requested. When the conveying means 40 is placed in operation, the exposed copy sheet 26 at the station 28 is fed past the roller 216 into the guideway formed by the structures 220 within the tank 218 at the developing station 46. The selectively discharged surface containing the latent electrostatic image is disposed face down within the liquid developer so that the electroscopic powder from the developer is selectively deposited on the surface to convert the latent electrostatic image into a visible image. When the leading edge of the developed copy sheet leaves the guideway provided by the structure 220, it is received within the nip between the rollers 222 and 224 to be fed to a position in which the back surface of the copy sheet 26 engages the flexible belts 226 with the developed surface facing the louvered openings 242 in the duct structure 240.

When the trailing edge of the copy sheet 26 moves beyond the operator 44a for the switch 44, this switch is released to open the contacts 44b. This terminates the energization of the timing motor 296 in the unit 294 and permits the contacts 296a to return to a closed condition to partially prepare the control circuit 260 for an additional cycle of operation.

When the leading edge of the developed copy sheet is fed by the rollers 222 and 224 onto the flexible belts 226 in the discharge and drying conveying means 40, the air discharged from the duct 240 through the openings 242 not only forces the sheet against the belts 226 to move therewith but also dries the copy sheet. The developed copy sheet 26 is advanced by the belts 226 past the duct structure 240 so that the leading edge passes between the belts 226 and the belts 244. These two arrays of belts continue the generally vertical elevation of the developed copy sheet so that it is discharged from the housing 260 into the print receiving tray or receptacle 50. Since the conveying means 48 operates continuously and since the energizing circuit for the solenoid 178 is completed as soon as the time delay unit 272 releases the relay 280, a subsequent copy sheet in multiple copy runs can be charged and exposed during the time interval in which the developed copy sheet is being discharged by the conveying means 48.

In the event that the supply of copy sheets 26 in the assembly 34 becomes depleted during the operation of the machine 10, the switch 186- is operated to open the contacts 1 86a and to close the contacts 1186b. The closure of the contacts 1-86b illuminates a lamp 300 (FIGS. 1, 6, and 7) to provide a visible indication that the supply of copy sheets 26 has been depleted. The opening of the contacts 186a interrupts the circuit for energizing the input of the rectifier bridge 2167 so that the components energized by this bridge cannot be operated. Thus, further operation of the machine 10 is disabled whenever the supply of copy sheets 26 in the assembly 32 becomes depleted. Whenever the supply of copy sheets is replaced, the switch 186 is operated to open the contacts 186]) and to close the contacts 186a to return the machine 10 to its normal condition.

Similarly, when the supply of liquid developer in the vessel or receptacle 218 falls below the predetermined level necessary for properly developing exposed copy sheets, the float controlled switch 223 is operated to interrupt the operating circuit for the relay 266. The release of the relay 266 opens the contacts 2166a and closes a pair of contacts 266b. The closure of the contacts 266 h causes the illumination of a lamp 302 (FIGS. 1, 6, and 7) to provide a visible indication that it is necessary to provide additional liquid developer to the machine 10. The opening of the contacts 266a interrupts the input circuit to the rectifier bridge 267 and disables the components energized thereby to prevent operation of the control circuit 260 and the machine 10. When the supply of liquid developer is replenish so that the switch 223 is closed, the relay 266 is again operated to restore the control circuit 260 to its normal condition.

Whenever the cover 182i is opened to replenish the supply of copy sheets 32, the switch 184 is opened. The opening of the switch 184 disables all of the components in the control circuit 260 with the exception of the blowers 210 and 212 which are maintained in an energized condition over a circuit independent of the switch 184-.

16 Replacing the cover 1 82 closes the switch 184- so that the control circuit 260 is restored to its normal condition.

Although the present invention has been described with reference to a single illustrative embodiment thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall Within the spirit and scope of the principles of this invention.

What is claimed and desired to be secured by Letters Patent of the United States is:

1. In an apparatus for making a copy of an orginal on a copy sheet, copysheet exposing means, copy sheet feeding means for feeding a copy sheet from a stack of copy sheets to the exposing means, said copy sheet feeding means including driven sheet engaging means disposed above the stack, lever means mounted for pivotal movement about an axis and carrying the sheet engaging means, first resilient means connected to the lever means and effective to positively bias the lever in one direction to place the sheet engaging means in a position spaced from the stack, a solenoid including a movable armature, means connecting the armature to the lever means and including a second resilient means, and means for operating the solenoid to apply a force to move the armature so that the lever means is moved against the force of the first resilient means to place and maintain the sheet engaging means in engagement with the stack, the second resilient means being stressed by the operation of the solenoid to positively, resiliently bias the sheet engaging means into engagement with the stack.

2. A sheet feeding assembly for use with sheet material comprising a sheet receiving tray for supporting a stack of sheets, driven sheet engaging means for feeding the top sheet from the stack, shiftable supporting structure for the sheet engaging means, first resilient means for positively biasing the supporting structure to a position in which the 'sheet engaging means are spaced from the stack of sheets, a solenoid having a movable armature, and means including a second resilient means connecting the armature to the supporting structure so that the operation of the solenoid moves the armature and is effective through the second resilient means to move the supporting structure to overcome the force of the first resilient means and provide a second force to positively move and maintain the sheet engaging means in engagement with the stack of sheets.

3. A sheet feeding assembly for feeding sheets from a stack comprising means for supporting a stack of sheets, sheet engaging means for feeding a sheet from a stack, a movably mounted supporting structure normally mounting the sheet engaging means spaced from the stack, a solenoid having a movable armature, flexible connecting means connecting the armature to the supporting structure, and resilient means included in the flexible connecting means, the operation of the solenoid moving the armature to apply a positive force through the flexible connecting means and the resilient means to positively resiliently bias and maintain the sheet engaging means against the stack.

4. A sheet feeding assembly for feeding sheets from a stack comprising a table for supporting a stack of sheets, driven sheet engaging means for feeding sheets from the stack, a sheet receiving structure disposed at the forward edge of the table, lever means normally supporting the sheet engaging means spaced from the stack, means for pivotally mounting the lever means adjacent the forward edge of the table, solenoid means mounted in a fixed position below the table and having movable armature means, pulley means rotatably mounted adacent the forward edge of the table, and flexible connecting means connected between the armature means and the lever means and passing around the pulley means, the operation of the solenoid means actuating the armature means and flexible connecting means to positively pivot the lever means 17 to place and maintain the sheet engaging means in engagement with the stack.

'5. A sheet feeding assembly for feeding sheets from a stack comprising a generally horizontally extending stack supporting table, a sheet receiving structure adjacent a front edge of the table, lever means mounted adjacent the front edge of the table for pivotal movement about an axis, sheet feeding means carried on the lever means, pulley means mounted adjacent the front edge of the table, a solenoid mounted below the table, first flexible connecting means connected to the lever means at one side of the axis, the first flexible means passing around the pulley means and including first resilient means for positively biasing the lever means to hold the sheet feeding means out of engagement with the stack, second flexible connecting means connected between the solenoid and the lever means at the other side of the axis, said second flexible connecting means passing around the pulley means and including a second resilient means so that the operation of the solenoid is effective through the second 18 flexible connecting means to apply a positive force to pivot the lever means and positively resiliently bias and maintain the sheet feeding means in engagement with the stack.

6. A sheet feeding assembly as claimed in claim 2 wherein the armature of said solenoid is adjustable to increase or decrease said second force applied through said second resilient means to move and maintain said sheet engaging means in engagement with the stack of sheets.

References Cited UNITED STATES PATENTS 3,137,495 6/1964 Eichorn 27l-36 X JOHN M. HORAN, Primary Examiner R. A. W'INTERCORN, Assistant Examiner US. Cl. X.R. 271-36, 39, 40; 355-66

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