Apparatus for counterbalancing the movement of a platen cover or document handler between a first closed position and a second open position. The counterbalancing apparatus comprises a gas spring and a tension spring. The tension spring is arranged to increasingly counter the force exerted by the gas spring as the platen cover is moved from the first to the second position. This compensates for the reduced force exerted by the platen cover as it is opened. The platen cover in the second position preferably has moved past vertical and the tension spring is effective to counter the force exerted by the cover between vertical and the second position.

CROSS REFERENCE TO RELATED APPLICATIONS 
U.S. application Ser. No. 811,736, filed June 30, 1977, to Taylor et al, 
for a Belt Tensioning System; U.S. application Ser. No. 811,735, filed 
June 30, 1977, to Taylor et al, for an Improved Document Handling 
Apparatus and Reproducing Machine; and U.S. application Ser. No. 818,781, 
filed July 25, 1977, to Hacknauer, for a Document Decelerator and Stacker. 
BACKGROUND OF THE INVENTION 
This invention relates to a counterbalance mechanism. It is particularly 
adapted for use in conjunction with a document handling apparatus for 
advancing documents on and off a viewing station of a reproducing machine. 
A reproducing machine employing the document handler and counterbalance 
mechanism also forms part of this invention. 
PRIOR ART STATEMENT 
A variety of devices have been utilized in the prior art for the purpose of 
counterbalancing the movement of a cover or other type member which is 
arranged to be opened and closed. These mechanisms have conventionally 
utilized springs of various types. 
Gas springs, as in U.S. Pat. No. 3,207,498 to Wiistenhagen, et al., have 
found considerable application as counterbalances in the automotive 
industry for window hatch covers or doors. Their use is, of course, not 
limited to automotive applications, and they have been used in a wide 
variety of applications as, for example, that described in U.S. Pat. No. 
3,444,830 to Doetsch, wherein a gas spring is used to counterbalance a 
drawing table. The gas spring in the Doetsch patent includes within the 
cylinder of the spring a compression spring which comes into action as the 
piston is withdrawn. 
The use of counterbalances for balancing the movement of a platen cover or 
a document handling system of a reproducing machine are also known. An 
example of such a device is found in U.S. Pat. No. 3,615,134 to Newcomb. 
Newcomb discloses a counterbalance mechanism for controlling the position 
of a platen cover of a reproducing machine. The cover is operatively 
connected to the mechanism which includes a slide which moves in a 
horizontal direction as the platen cover is raised or lowered. A pair of 
mechanically biased members act on the slide and coact with each other to 
support the cover in a stationary position when the cover is raised above 
a pre-determined position and automatically moves the cover into closure 
when it is placed below the predetermined position. Plural springs are 
employed for biasing the members. 
Several reproducing machines currently commercially available employ 
document handling systems for advancing documents on and off the viewing 
station of the machine. The document handling systems presently in use may 
be classified as semi-automatic when the documents are individually 
manually inserted into the document handler which then feeds them on and 
off the viewing platen. In some machines fully automatic document handling 
systems are employed wherein the documents are automatically separated 
from a stack thereof and serially fed to the platen. In some cases 
provision has been made to recirculate the documents so that they may be 
serially fed on and off the platen a desired number of times to form a 
desired number of sets. 
The present invention is particularly adapted for use with document 
handling systems which employ a single stretch-type document handling belt 
as the platen transport. Such document handling systems are exemplified by 
the following U.S. Pat. Nos. 3,565,420 to Howard, 3,889,943 to Krayer, and 
3,941,376 to Liechty. In each of these patents a single wide document 
transport belt is utilized to advance a document on and off the viewing 
platen of the reproducing machine in a fully automatic or recirculating 
fashion. The document transport belt is supported about first and second 
pulleys. This approach is used commercially in the Xerox 9200 duplicator. 
U.S. Pat. Nos. 3,844,552 to Bleau, 3,908,986 to Bleau, 3,910,570 to Bleau, 
are illustrative of semi-automatic type document handling systems. Such 
systems include a pre-registration station into which the operator 
manually places a document which is either manually registered against a 
stop or automatically registered against the stop as in the Bleau '986 
patent. U.S. Pat. No. 3,936,041 to Shiina, et al. is illustrative of a 
fully automatic document handling system wherein documents are separated 
from a stack and then advanced on and off the platen all automatically 
without operator intervention. These patents are also of interest for 
their disclosures with respect to belt transport type document handling 
systems. 
In addition to the aforenoted patents, the following disclosures are 
believed to be of interest with respect to document handling systems of 
the type contemplated in accordance with this invention. IBM Technical 
Disclosure Bulletin, Vol. 19, No. 5, October 1976, pages 1589 to 1591, 
discloses a semi-automatic document handling system control arrangement 
employing multiple sensors. IBM Technical Disclosure Bulletin, Vol. 17, 
No. 4, September 1974, page 1131, discloses a platen registration gate 
mechanism. IBM Technical Disclosure Bulletin, Vol. 17, No. 4, September 
1974, page 1135, discloses an output tray stacking system. The output tray 
stacker includes a wire guide for decelerating documents entering the 
tray. 
SUMMARY OF THE INVENTION 
This invention relates to a counterbalancing mechanism for balancing the 
movement of a member between first and second positions. The 
counterbalancing apparatus of this invention is particularly adapted for 
use in balancing a platen cover member of a reproducing machine or a 
document handling system and platen cover member combination used with a 
reproducing machine. A reproducing machine employing the counterbalancing 
apparatus of this invention is also provided. 
The apparatus for counterbalancing the movement of the member comprises the 
member and means for supporting the member for movement between a first 
position and a second position. A counterbalancing means is provided for 
balancing the movement of the member between its respective positions. The 
counterbalancing means comprises a gas spring and a tension spring each 
connected to the member. The tension spring is arranged to increasingly 
counter the force exerted on the gas spring as the member is moved from 
the first position to the second position. 
Preferably the first position is generally horizontal, and the second 
position is more vertical then the first. In a most preferred embodiment, 
the second position is arranged past vertical so that a cover member 
travels from a generally horizontal orientation through vertical to a 
position past vertical. 
Preferably the tension spring is operable over a range of motion of the 
cover member which is less than its total range of motion. Initial 
operation of the tension spring is from a position intermediate the first 
and second positions up to the second position. 
Accordingly, it is an object of this invention to provide an improved 
counterbalancing apparatus. 
It is a further object of this invention to provide an apparatus as above 
utilizing a gas spring and a countering tension spring for 
counterbalancing the movement of a member. 
It is a further object of this invention to provide an apparatus as above 
used to counterbalance a document handling system of a reproducing 
machine. 
It is a still further object of this invention to provide a reproducing 
machine employing the document handling system and counterbalancing 
apparatus as above. 
These and other objects will become more apparent from the following 
description and drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1 there is shown by way of example an automatic 
xerographic reproducing machine 10 which includes a document handling 
apparatus 11 of the present invention. The reproducing machine 10 depicted 
in FIG. 1 illustrates the various components utilized therein for 
producing copies from an original. Although the apparatus 11 of the 
present invention is particularly well adapted for use in an automatic 
xerographic reproducing machine 10, it should become evident from the 
following description that it is equally well suited for use in a wide 
variety of processing systems including other electrostatographic systems 
and it is not necessarily limited in its application to the particular 
embodiment or embodiments shown herein. 
The reproducing machine 10 illustrated in FIG. 1 employs an image recording 
drum-like member 12, the outer periphery of which is coated with a 
suitable photoconductive material 13. One type of suitable photoconductive 
material is disclosed in U.S. Pat. No. 2,970,906, issued to Bixby in 1961. 
The drum 12 is suitably journaled for rotation within a machine frame (not 
shown) by means of shaft 14 and rotates in the direction indicated by 
arrow 15 to bring the image-bearing surface 13 thereon past a plurality of 
xerographic processing stations. Suitable drive means (not shown) are 
provided to power and coordinate the motion of the various cooperating 
machine components whereby a faithful reproduction of the original input 
scene information is recorded upon a sheet of final support material 16 
such as paper or the like. 
The practice of xerography is well known in the art and is the subject of 
numerous patents and texts including Electrophotography by Schaffert, and 
Xerography and Related Processes by Dessauer and Clark, both published in 
1965 by the Focal Press. 
Initially, the drum 12 moves the photoconductive surface 13 through a 
charging station 17. In the charging station 17, an electrostatic charge 
is placed uniformly over the photoconductive surface 13 preparatory to 
imaging. The charging may be provided by a corona generating device of the 
type described in U.S. Pat. No. 2,836,726, issued to Vyverberg in 1958. 
Thereafter, the drum 12 is rotated to exposure station 18 wherein the 
charged photoconductive surface 13 is exposed to a light image of the 
original input scene information whereby the charge is selectively 
dissipated in the light exposed regions to record the original input scene 
in the form of a latent electrostatic image. A suitable exposure system 
may be of a type described in U.S. Pat. No. 3,832,057, issued to Shogren 
in 1974. After exposure drum 12 rotates the electrostatic latent image 
recorded on the photoconductive surface 13 to development station 19 
wherein a conventional developer mix is applied to the photoconductive 
surface 13 of the drum 12 rendering the latent image visible. A suitable 
development station is disclosed in U.S. Pat. No. 3,707,947, issued to 
Reichart in 1973. That patent describes a magnetic brush development 
system utilizing a magnetizable developer mix having coarse ferromagnetic 
carrier granules and toner colorant particles. The developer mix is 
brought through a directional flux field to form a brush thereof. The 
electrostatic latent image recorded on the photoconductive surface 13 is 
developed by bringing the brush of developer mix into contact therewith. 
Sheets 16 of final support material are supported in a stack arrangement on 
an elevating stack support tray 20 or in an auxiliary tray 21. Sheet 
separators 22 and 23 selectively feed individual sheets from their 
respective stacks to a registration system which includes rolls 24 and 25. 
The sheet is then forwarded to the transfer station 26 in proper 
registration with the image on the drum. The developed image on the 
photoconductive surface 13 is brought into contact with the sheet 16 of 
final support material within the transfer station 26 and the toner image 
is transferred from the photoconductive surface 13 to the contacting side 
of the final support sheet 16. The final support material may be paper, 
plastic, etc., as desired. 
After the toner image has been transferred to the sheet of final support 
material 26 the sheet with the image thereon is advanced to a suitable 
fuser 27 which coalesces the transferred powder image thereto. One type of 
suitable fuser is described in U.S. Pat. No. 2,701,765, issued to 
Codichini, et al. in 1955. After the fusing process the sheet 16 is 
advanced selectively to a suitable output device such as tray 28 or sorter 
29. 
Although a preponderance of the toner powder is transferred to the final 
support material 16, invariably some residual toner remains on the 
photoconductive surface 13 after the transfer of the toner powder image to 
the final support material. The residual toner particles remaining on the 
photoconductive surface 13 after the transfer operation are removed from 
the drum 12 as it moves through a cleaning station C. The toner particles 
may be mechanically cleaned from the photoconductive surface 13 by any 
conventional means as, for example, the use of a blade as set forth in 
U.S. Pat. No. 3,740,789, issued to Ticknor in 1973. 
A document handling system 11 of this invention is used to advance 
documents on and off a viewing platen P where they are scanned by the 
optical system 18. 
It is believed that the foregoing description is sufficient for purposes of 
the present application to illustrate the general operation of an 
automatic xerographic copier 10 which can embody the apparatus 11 in 
accordance with the present invention. 
Referring now to FIGS. 1 through 5, the basic elements of the document 
handling system 11, in accordance with the present invention, will be 
described along with their operation. The document handler 11 includes an 
input transport 30 comprised of input pinch rolls 31 and 32, which are 
selectively disengageable so that a document may be readily placed between 
them. The input transport 30 also includes a wait station 33 for 
pre-registering the document. The wait station 33 is comprised of a 
pivotally supported registration gate 34 and a pivotally supported upper 
chute 35. The gate 34, chute 35, and pinch rolls 31 and 32 are 
inter-connected so that when the gate is up in a sheet 16 blocking 
position, the pinch rolls are separated. As the gate 34 drops out of sheet 
blocking position the pinch rolls come together to advance the document 
into the next station which comprises the belt-type platen transport 40. 
A suitable static eliminating device 36 is arranged between the input 
transport 30 and the platen belt transport 40. In the embodiment shown in 
FIG. 3, the static eliminator 36 is comprised of a pin-type corona 
generating device wherein a plurality of pins are spaced transversely to 
the direction in which the document is moving. The corona generator is 
arranged to spray the document with an appropriate AC corona to neutralize 
or discharge any static build-up on the document before it enters the 
platen transport 40. While it is unusual to place the static eliminating 
device 36 before the platen belt transport 40, it has been found effective 
at such a location for reducing the static build-up on the belt and for 
providing adequate stacking of documents in the output tray 41. For the 
sake of simplicity the static eliminator 36 is shown solely in FIG. 3, and 
has been removed from the other views of the apparatus 11 in order to 
reveal other components. 
Referring to FIGS. 1 through 5, the platen belt transport 40 is comprised 
of a single wide belt 42 having one run 43 over the platen P. This is 
desirable to avoid the print-out of the belt on the resulting copy sheet. 
The belt 42 is normally formed of a stretch-type material which is white 
in color so as to reduce the occurrence of a black border print-out on the 
copies. The belt 42 is wrapped about two pulleys 44 and 45, which are 
arranged so that the belt surface at the bottom of a pulley is slightly 
above the surface of the platen, perhaps by about 0.030 inches. The sag of 
the belt 42 is sufficient so that the belt engages the platen. The drive 
force which the belt 42 imparts to the document is controlled by means of 
back-up rolls 46 and 47, supported internally of the belt. 
The input back-up roll 46 is arranged close to the input drive pulley 44, 
and controls the normal force applied by the belt 42 to the document as it 
is driven onto the platen P. A platen registration gate 50 is provided at 
the far end of the platen P. The document is driven by the belt 42 against 
the gate 50 in order to properly position the document on the platen P for 
imaging. During the imaging cycle the registration gate 50 is retracted. 
After imaging the document is advanced off the platen P by means of the 
belt transport 40 and a set of output pinch rolls 55. The output pinch 
rolls corrugate the document to increase its beam strength so that it will 
properly stack in the output tray 41 of the document handling system 11. 
Document decelerators 56 associated with the output tray 41 act upon the 
document as it enters the output tray to properly stack it therein. 
The document handling system is actuated by a number of sensors as in FIG. 
2. A lever actuated switch 60 is positioned just ahead of the nip of the 
input transport rolls 31 and 32 and serves to condition the machine for 
operation in a document handling mode. A second sensor 61, which 
preferably comprises a photocell, is arranged to sense proper corner 
registration of the document at the wait station 33. A third sensor 62 
also preferably comprising a photocell is used to detect that the document 
has been advanced off the platen P. The third sensor is arranged just 
prior to the output pinch rolls 55. 
In operation the document handling system 11 is activated by inserting a 
document into the wait station 33. This actuates the mode switch 60 which 
in turn activates the input sensor 61 and signals the logic (not shown) of 
the machine that a "DHS" copy is desired. When the corner of the document 
interrupts the input registration sensor 61, a ready-to-feed light is lit, 
and the system is assured that the original has been inserted within a 
predetermined skew and side shift tolerance. The logic then provides a 0.4 
second delay after the start-print button is pressed, or after a second 
document is inserted when in a chain feed mode. This allows the operator 
time to let go of the document before it is advanced onto the platen P. 
As the wait station 33 fingers 34 retract, the pivoting upper chute 35 is 
raised which increases the clearance for bulky originals. At the same time 
the input rolls 31 and 32 pinch is made. A short time later a clutch 65, 
as in FIG. 13, is actuated and the drives 66 are started. The document is 
driven onto the platen P by the input rolls 31 and 32 and by the input 
back-up roll 46 of the belt transport 40. 
In the event that a document does not uncover the input sensor 61, a jam is 
signaled. At an appropriate time the register edge 51 is raised from its 
normally retracted position. This also raises the registration back-up 
roll 47 as well. The document is driven against the register edge 51 by 
the document belt alone, removing any skew by coast over-drive. The 
register edge 51 is lowered during scan of the exposure system 18. 
When scan is complete the drives 66 start again. If a second document has 
been properly inserted into the wait station 33 during scan, this document 
will be transported onto the platen P at the same time the first document 
is fed off. If the second original has not been inserted soon enough to 
allow the wait station 33 to be actuated, it will be held up at the wait 
station until the first document is driven off the platen P. 
The registration back-up roll 47 provides the necessary normal force to 
drive the first document off the platen P. If this document does not reach 
the exit sensor 62 within an alloted time, the logic signals a jam. The 
exiting document is fed into the exit tray 41 by the output rolls 55 which 
corrugate it to provide the beam strength needed to stack easily. Failure 
to leave the exit sensor 62 at the end of a cycle signals a jam. 
Having thus described the general features of the document handling system 
11 of this invention and its general mode of operation, further detail 
will now be given for the various sub-assemblies and sub-systems which 
make up the document handler. 
WAIT STATION AND INPUT TRANSPORT 
Referring now to FIGS. 2, 3, 6, and 7, the wait station and input transport 
will be described in greater detail. The wait station 33 and input 
transport 31 and 32 are supported by a structurally rigid casting or frame 
member 70 which is connected to the optical frame (not shown) in such a 
manner as to align the wait station 33 with the optical system 18 to 
ensure that the input transport 31 and 32 advances the document properly 
onto the platen P without skew or misregistration. The input transport is 
comprised of a set of pinch rolls 31 and 32. The four spaced apart upper 
rolls 31 are mounted to the input roll drive shaft 71 and are used to 
drivingly engage the document for advancement onto the platen P. The lower 
input pinch rolls 32 are supported in cantilever fashion by spring members 
72 secured to the input frame member 70. Two of the lower input pinch 
rollers 32 are rotatably supported to idle upon a first shaft 73, and the 
other two are rotatably supported to idle upon a separate second shaft 74. 
This helps to provide a uniform normal force between the pinch rollers 
when they are engaged. The near side lower input pinch roller 32 includes 
a reduced diameter shoulder 75 so that it will not engage the very end of 
an 8 1/2 .times. 11 inch sheet. This reduces the propensity for skewing 
such sheets. 
The pre-registration gate member 34 includes spaced apart registration stop 
fingers 80. It is pivotally supported below the input station frame member 
70 upon shaft 81 so that the fingers 80 project through openings 82 in the 
frame member. Initially the registration fingers 80 are supported as in 
FIG. 3 in raised position so as to block a document from entering the nip 
between the transport belt 42 and the platen P. 
The upper registration chute 35 is also arranged to be pivoted about a 
shaft 83. When the registration fingers 80 are in their operative, or 
raised position, the upper registration chute 35 is in its lowered 
position as in FIG. 3. The upper registration chute 35 serves to limit the 
thickness of a document which can be inserted into the wait station 33 as 
well as serving to prevent documents from jumping the pre-registration 
gate 34. The upper chute 35 is biased in a counterclockwise direction 
about its pivot axis by gravity. Should a document remain lodged over the 
pre-registration gate fingers 80 when the gate is raised, the document 
will not be punctured since the upper chute 35 merely pivots upwardly. 
The upper chute 35 includes an arm 85 as in FIGS. 2, 3, and 6 having an 
adjustable set screw 86 therein. A plate-type actuating member 87 as in 
FIG. 7 is supported by the pre-registration gate 34 pivot shaft 81 and 
includes a tab 88 for engaging the set screw 86 connected to the upper 
registration chute 35. At the opposing end of this actuating member 87, a 
solenoid 90 is connected. In the operative position, as in FIG. 3, a set 
screw 91 in the input station frame 70 is used to limit the height to 
which the registration gate fingers 80 extend above the upper surface of 
the frame. 
The positional arrangement shown in FIG. 3 comprises the operative position 
for pre-registering a document at the wait station 33. In this position 
the solenoid 90 is not actuated and a spring 92 biases the registration 
gate pivot shaft 81 so that the gate is normally in its raised position. 
The rear portion of the registration gate member 34 includes a plurality 
of tabs 93 as shown in FIG. 7 which engage the tops of the lower input 
roll shafts 73 and 74 at their ends so that when the fingers 80 are raised 
the tabs 93 deflect the lower pivot rolls 32 to separate them from the 
upper pinch rolls 31. This allows a sheet to be easily placed between the 
pinch rolls 31 and 32 and registered against the fingers 81. 
To initiate the document handling mode of operation, a document is placed 
into the wait station 30 and up against the pre-registration fingers 80. 
The document is also registered against the input top cover registration 
strip 100 as in FIG. 2, to provide corner registration which is sensed by 
the input sensor 61. 
After a suitable time delay the solenoid 90 is actuated to lower the input 
registration fingers 80 out of sheet blocking relationship as in FIG. 6. 
Since the registration member 34 has pivoted about its axis its tabs 93 no 
longer deflect the shafts 73 and 74 of the lower input rolls 30 so that 
the pinch of the input rolls 31 and 32 is closed to advance the document 
sandwiched therebetween into the belt transport station 40. The actuating 
member 87 connected to the registration member pivot shaft 81 operates 
upon the set screw 86 of the upper chute 35 to pivot it clockwise in order 
to widen the throat between it and the surface of the input frame casting 
70. This serves to reduce the drag on the sheet as it is fed onto the 
platen. The upper chute 35 may be manually pivoted open even wider as 
shown in phantom to facilitate jam clearance. Therefore, upon actuation of 
the input station 30 solenoid 90, the fingers 80 are lowered, the upper 
chute 35 is raised, and the pinch of the input rolls 31 and 32 is closed 
to advance the document into the next station of the document handling 
system 11 which comprises the platen belt transport 40. 
PLATEN BELT TRANSPORT SYSTEM 
Referring now to FIGS. 2, 4, 5, 8, 9, 10, 11, and 12, the platen belt 
transport 40 will be described in greater detail. The platen belt 
transport 40 is supported within a frame assembly 105 comprised of front 
106 and rear 107 adjustable side frame members, and input 108 and exit 109 
end frame members. The frame assembly 105 is pivotally supported at the 
input station 30 about the input pinch roller drive shaft 71 by being 
suitably journaled thereabout. 
The platen belt transport 40 is comprised of a single wide stretch-type 
belt which is arranged about the input drive pulley 44 and an exit idler 
pulley 45. Both the input and exit pulleys 44 and 45 are journaled for 
rotation in the front and rear adjustable side frames 106 and 107. 
Internally of the belt 42, an input back-up roll 46 is pivotally supported 
by means of a pan-like frame member 110. The input back-up roll 46 is 
rotatably arranged at one end of the frame 110 member and the other end 
thereof is pivotally supported about a shaft 111 secured between the front 
and rear adjustable side frames 106 and 107 of the platen belt transport 
40. A second pivotally supported pan-like frame member 115 is pivotally 
arranged at one end about the shaft 111 and rotatably supports the 
registration back-up roll 47 at its free end. 
The frame member 110 supporting the input back-up roll 46 is shorter than 
the frame member 115 supporting the output back-up roll. The back-up rolls 
46 and 47 are urged against the back of the belt 42 by their weight and 
the weight of their associated frame member 110 or 115. The normal force 
exerted by these rolls 46 and 47 against the belt 42 is important for 
obtaining the desired driving force between the belt and the document 
during advancement of the document. In order to provide the desired level 
of drive force, weights 116 and 117 are supported by the respective input 
and registration back-up roll frame members 110 and 115. Therefore, the 
normal force exerted by the back-up rolls 46 and 47 can be regulated by 
the size of the weights 116 and 117 and their positions on their 
respective pans 110 and 115. 
It has been found that the platen P surface is not absolutely flat and that 
a variation occurs in the force with which the input back-up roll 46 urges 
the belt against the platen from the front to the back side of the platen. 
This can result in a significant loss in latitude for the setting of the 
input back-up roll normal force. Therefore, in accordance with one feature 
of the document handling system 11 herein, the input back-up roll is 
formed so that it includes two doughnut-shaped portions 120 or sections of 
enlarged diameter as in FIG. 4. These back-up roll sections 120 of 
enlarged diameter insure that the input back-up roll 46 applies a uniform 
pressure at the two points where it engages the platen belt 42 even if the 
platen P is not absolutely flat. This reduces the tendency for skewed 
feeding of the document onto the platen P. The aforenoted backup roll 46 
construction results in a substantial improvement in the latitude of the 
platen belt transport reducing its sensitivity to the belt 42 tension and 
the height of the input drive pulley 44. 
Cone-shaped members 121 rotatably supported about stub shafts mounted to 
the front and rear side frames 106 and 107 of the belt transport 40 are 
employed to insure that the belt properly tracks about the input and 
output pulleys 44 and 45. The long pan 115 is sufficiently flexible to 
insure adequate conformity of the registration back-up roll 47 across the 
platen. The front pan 110 is too short to assure such conformity, and, 
therefore, a slot 122 is provided in that pan. This slot 122 allows the 
pan to move about the pivot shaft 111 to insure conformity between the 
raised portions 120 of the roll 46 and the platen P, even if the platen is 
warped. The raised portions 120 of the input back-up roll 46 are arranged 
toward the rear of the document handler 11 so that it can properly handle 
shorter documents. 
In order to balance the input back-up roll 46 loading the normal force 
assisting weight 116 is arranged toward the front side of the pan 110, 
thereby uniformly loading the roll against the belt 42 in the vicinity of 
the raised portions 120 of the roll. 
VERNIER BELT TENSIONING SYSTEM 
The vernier belt tensioning system 130 represents an inexpensive, high 
resolution system for obtaining a highly accurate setting of the 
parallelness of the pulleys 44 and 45. The system is capable of 
maintaining parallelness of the respective pulleys within about .+-. 0.005 
to about .+-. 0.01 inches. 
The cone-shaped members 121, which engage the upper run of the belt 42 at 
the front and rear sides thereof, are effective for overcoming minor 
excursions of the belt to maintain proper belt tracking. It is still 
required, however, that the input drive pulley 44 and the idler pulley 45 
about which the belt 42 is supported, must be sufficiently parallel to 
avoid major excursions of the belt which would result in catastrophic loss 
of belt tracking. To insure this high degree of parallelness between the 
respective belt pulleys 44 and 45, a vernier belt tensioning system 130 is 
employed as shown in FIGS. 8-10. 
The driving engagement between the belt 42 and the document is provided by 
the slack in the belt and the normal force applied through the belt by the 
input and registration back-up rolls 46 and 47. The normal force exerted 
by the belt against the document in the vicinity of the input and 
registration back-up rolls 46 and 47 plays a substantial roll in providing 
consistent skew-free feeding of the document. This normal force is 
controlled as aforenoted by the weight of the rolls and mounting 
assemblies 110 and 115. The belt 42 tension provides an off-setting force 
to the normal force of the rolls 46 and 47 by acting to lift the rolls 
away from the platen. The higher the belt tension the greater is the 
reduction in the effective normal force of the back-up rolls 46 and 47 at 
the platen. Therefore, it is important to be able to set the belt tension 
with a high degree of accuracy. 
The belt tension is set for the document handling system 11 by means of the 
adjustable side frames 106 and 107 which include a vernier system 130 
which allows the belt tension to be incremented in small amounts while 
maintaining the parallelness of the respective belt pulleys 44 and 45. 
The drive belt pulley 44 is journaled for rotation in the front and rear 
side frames 106 and 107 by means of bearings 131. The idler pulley 45 is 
journaled for rotation by means of bearings 132 which are slidably 
sandwiched between the inner 133 and outer 134 vernier plates which 
comprise the adjustable side frames 106 and 107. The bearing 132 is 
positioned in a close fitting hole 135 in the outer plate 134 and slides 
within a slot 136 in the inner plate 133. The outer plate 134 is locked to 
the inner plate 133 by screws 137 and nuts 138 which are welded to the 
inner plate 133. Slots 139 in the outer plates 134 allow them to slide 
relative to the inner plates 133 for setting belt tension. 
The vernier system 130 is comprised of a row of holes 140 spaced an equal 
distance apart arranged in the respective front and rear outer vernier 
plates 134. A second row of holes 141 spaced an equal distance, which is 
less that the spacing of the holes in row 140, are arranged in each of the 
respective inner vernier plates 133. 
The difference in the hole spacings for the holes 140 in the outer vernier 
plates 134 as compared to the holes 141 in the inner vernier plates 133 
provides the desired vernier type read-out when the rows of holes 140 and 
141 are overlapped by application of the outer vernier side plates 134 to 
the inner vernier side plates 135. This difference in the hole 140 and 141 
spacings in the vernier plates 133 and 134 results in only a single pair 
of holes in the respective plates 133 and 134 being completely aligned and 
concentric for any relative position of the vernier plates. 
For example, if the difference in spacing for the holes 141 as compared to 
the holes 140 is about 0.03 inches then it is possible to adjust the 
vernier side plates 133 and 134 relative to one another accurately in 
intervals of 0.03 inches. Similarly, if the difference in the hole 
spacings were 0.01 inches, it would be possible to adjust the vernier side 
plates 133 and 134 in increments of 0.01 inches. Therefore, relative 
movement of the vernier side plates 133 and 134 in either direction of the 
arrow 142 in FIGS. 9 and 10 so that a new set of overlapped boles 140 and 
141 lines up next adjacent to a previously aligned set of holes will 
result in a 0.03 incremental adjustment for a 0.03 inch difference in hole 
spacing. 
The holes 140 in each vernier plate 134 are provided with indicia, as 
shown, such as numbers or letters. When a desired belt tension is achieved 
a pin is placed in the aligned vernier holes 140 and 141 of one side frame 
106, for example, hole 0 in FIG. 9. The same holes 140 and 141 are aligned 
at hole 0 in the other side frame 107 and held by a pin. After the side 
frames 107 and 106 have thus been aligned and the proper belt tension set, 
the vernier plates 133 and 134 and locked in position by means of screws 
137. 
In order to set the belt tension, use is made of the relative movement 
between the document handler cover 150 and the document belt frame 
assembly 105. The frame assembly 105 is pivoted about the input roll drive 
shaft 71, whereas the cover is pivoted about a different hinge axis 151. 
This results in relative movement between the transport belt frame 
assembly 105 and the cover 150 when the cover is raised as in FIG. 13. The 
frame assembly 105 is slidingly secured to the cover by removable straps 
152 mounted to bosses 153 on the cover. Tabs 154 on the side frames 106 
and 107 slide on the straps 152 as the frames 105 slides down the cover 
150 as the cover is raised. 
To set the belt tension a fish scale or other suitable tension measuring 
device is secured between one end 155 of the cover 150 and a catch 156 
which is secured on outer vernier plate 134. The screws 137 are loosened 
and the cover 150 is raised until the desired tension is reached, at which 
time note is taken of the vernier hole pair 140 and 141 which are aligned. 
A pin is then placed in that vernier hole pair. The cover 150 is then 
lowered and the tension measuring device removed. When the cover is raised 
again, a pin is similarly placed in the same hole pair 140 and 141 on the 
other side of the DHS frame assembly 105. The vernier plates 133 and 134 
are then locked as aforenoted to maintain the desired belt tension and the 
desired parallinity between the respective belt pulleys 44 and 45. 
PLATEN REGISTRATION SYSTEM 
The purpose of the platen belt transport 40 is to advance the document onto 
the platen, and against the platen registration gate 51 so that the 
document can then be scanned by the optical system 18 to provide one or 
more copies. Referring to FIGS. 5, 11, and 12, the platen registration 
system 50 is shown in greater detail. The registration gate 51 comprises a 
plate-like member which is comparatively thin and sufficiently flexible to 
conform to the beveled edge 160 of the platen P. The registration gate 51 
is arranged for movement in a plane which is inclined with respect to the 
plane of the platen P. 
In the system which will be described the registration edge 51 is normally 
maintained in its retracted position as in FIG. 5. This is desirable in 
order to reduce the possibility of operator injury by engagement with the 
edge of the registration gate 51 when the platen cover 150 and document 
handler is raised off the platen. The registration gate 51 is raised into 
its operative position for registering a document on the platen as in FIG. 
12 only when the document is fed onto the platen P. As soon as the 
document has been registered the gate 51 is retracted so that the document 
can then be fed off the platen at the end of the copy cycle. 
To insure confirmity between the gate member 51 and the beveled edge 160 of 
the platen P, a plurality of springs 161, as in FIGS. 5 and 11, are 
arranged spaced apart across the plate member to bias the gate against the 
platen edge. Four springs 161 are shown. Each is secured to the 
registration gate frame 162 and urged against the gate member 51 in 
cantilever fashion. Because of the variability of the springs 161 the 
force exerted by each spring is adjustable so that proper conformity can 
be maintained between the registration gate 51 and the beveled edge 160 of 
the platen glass P. This adjustment is provided by the mounting screws 165 
which hold the springs to the frame 162. One end 166 of the spring 161 is 
secured in a slot 167 in the registration gate frame 162 and the other end 
is urged against the gate surface. Tightening the screw 165 increases the 
spring pressure and loosening the screw 165 reduces the spring pressure. 
The spring 161 includes a step 168 which is cantilevered to allow the 
spring force adjustment. These springs 161 are operative to correct for 
edge bowing of the gate member 51 and for spring and casting 162 
tolerances. 
The registration gate 57 is arranged for sliding movement on the 
registration gate frame 162. It is urged to its retracted position by 
means of tension springs 170. Screw 171 adjustable stop members 172 are 
provided which include projections which pass through slots 173 in the 
registration gate 51 to limit its range of travel. Actuation of the gate 
51 is provided by means of a solenoid 174 which is connected to the gate 
by means of a pivotally supported link 175. The operative stroke of the 
solenoid 174 is adjusted by means of an adjustment screw and wheel 176 
embedded in the frame 162 which moves the solenoid support frame 177 with 
respect to the register edge frame 162 about pivot screw 178. Screws 179 
lock the position of the solenoid frame 177 on the gate frame 162. 
Referring to FIGS. 5 and 12, the operation of the platen registration gate 
is shown in greater detail. In its operative position, as in FIG. 5, the 
register edge 51 engages the belt 42 so as to raise the register back-up 
roll 42 off the platen to create a registration "pocket" as shown. This 
results in a decrease in the normal force of the belt against the document 
as it is advanced into registration against the gate 51. This is desirable 
since it reduces the occurrence of document damage. The document is 
advanced into engagment with the gate 51 by a coast overdrive of the belt 
transport 40. This removes any document skew and properly positions the 
document on the platen P for imaging. 
After the document has been properly registered on the platen P, the gate 
51 is withdrawn to its retracted position as in FIG. 5. This also results 
in dropping the register roll 47 back into engagement with the document 
through the belt 42 at a desired normal force which is effective to 
advance the document off the platen by actuation of the belt transport 40. 
If another document has been preregistered in the wait station 33, it is 
fed onto the platen P simultaneously as the previous document is fed off 
the platen. If another document is not pre-registered, the first document 
is fed off the platen P before another document is fed on. 
The document which is advanced off the platen P is fed into the nip of the 
output rolls 55. The output rolls 55, as in FIGS. 2, 5, and 7, comprise an 
upper set of rolls 180 supported about the output roll drive shaft 181. 
The lower set of idler rolls 182 are mounted on individual shafts S and 
cantilevered spring 183 biased for engagement with the upper output 180 
rolls. The lower idler output rolls 182 include an enlarged diameter 
central ring 184 which is located between the engaging upper output drive 
rolls 180. This arrangement serves to corrugate the document as it is 
advanced by the output rolls 55 into the output tray 41. This aids in 
obtaining adequate travel of the document before it engages the other 
documents in the output tray so that it will properly stack in the output 
tray. 
A guide chute 190 is associated with the output rolls 55. The lower guide 
chute 191 is extended by means of a Mylar strip 192 so it flexibly engages 
the registration gate cover 193 thereby preventing a sheet from being 
driven downwardly into the registration gate area rather than out through 
the output roll chute 190. The upper chute 194 also includes slidable 
extension 195 which it adjustably supports. The chute extension 195 
comprises a plate member which includes a plurality of tabs 196 which 
extend through cooperating slots 197 in the upper chute as in FIG. 2. 
Leaf-type springs 198 are inserted through holes in the tabs 196 and serve 
to mount the adjustable chute extension 195 to the upper chute 194 so that 
it can be adjusted to provide a desired gap 199 with respect to the belt 
42. This gap 199 preferably is on the order of about 0.03 inches so as to 
reduce the propensity for a document sheet to jam into the interface 
between the output rolls 55 and the belt transport 40. 
COUNTERBALANCE MECHANISM 
While most copying operations will be performed with the document handler 
11 in its operative position over the platen P, it is also desirable for 
copying books, etc., to be able to manually locate documents on the 
platen. This is accomplished by raising the document handler cover 150 to 
lift the document handler off the platen. A counterbalance mechanism 200, 
as in FIGS. 2 and 13, is provided for off-setting the weight of the 
document handler 11 and cover 150 to make it easy to raise or lower them. 
The counterbalance mechanism 200 is comprised of a gas spring 201 of the 
general type which may be obtained from the Gas Spring Corporation, 17 
Commerce Drive, Montgomeryville, Pennsylvania, and sold under Part Number 
01111-B. 
The gas spring cylinder 201 is pivotally secured at one end to a boss 204 
on the input station frame casting 70. The gas spring piston rod 202 is 
pivotally secured at its free end to a boss 203 on the document feeder 
cover 150. Oil has been added to the gas spring cylinder 201 in order to 
provide a damping effect as the cover is raised or lowered. The oil in the 
gas spring causes it to act like a dash pot and prevents the cover 150 
from falling too fast as it is closed. When the cover is at about 
15.degree. to the horizontal plane of the platen it falls closed since 
there is insufficient force in the gas spring to oppose its closing. 
The force necessary to raise the cover 150 and its associated document 
handler 11 is not uniform throughout the range of motion of the cover. For 
example, as the cover 150 get more vertical the force of the cover and 
document handler against the gas spring is markedly reduced. To compensate 
for this reduction in the opposing force of the document cover 150 and 
handler 11, a compensating spring 205 is provided which is pivotally 
secured to the boss 206 on the input casting 70. The compensating spring 
includes a U-shaped hook 207 at its other end which rides on a pin 208 
secured to the boss 203 of the document handler cover 150. 
As the cover is raised to about 20.degree. to the horizontal the 
compensating spring 205 begins to stretch and thereby apply a counter 
force to the gas spring 201. The amount of this compensating force 
increases as the document feeder cover is raised and the compensating 
spring 205 expands. This combination of the gas spring 201 and 
compensating spring 205 provides a more correlated force distribution on 
the cover 150 and document handler 11 to prevent a rapid -- uncontrolled 
swing during the opening or closing thereof. 
The cover 150 and document handler 11 of this invention are movable from 
the horizontal over a range of motion of from about 0.degree. to about 
105.degree.. This means that the cover and document handler moves past 
vertical. The counterbalance mechanism 200 provides a unique compound type 
of action over that range of motion. A force is applied by the gas spring 
201 to initially lift the platen cover 150. The compensating force of 
spring 205 is then applied at about 20.degree. to counter the force of the 
gas spring as the force exerted by the cover 150 decreases. The amount of 
this compensating force increases as the cover is raised. As the cover 
passes the vertical plane the compensating spring 205 acts to balance and 
counter the force of the cover which is then increasing. 
The counterbalance mechanism 200 is particularly adapted to be employed 
within a confined space. Normally, the document feeder 11 and cover 150, 
as well as the gas spring 201, and tension spring 205 lie generally 
horizontally. The gas spring 201 is inclined about 5.degree. to 10.degree. 
to the horizontal in order to provide the necessary leverage for opening 
the cover 150. Since the gas spring 201 is inclined generally 
horizontally, a large force is necessary to lift the cover initially, 
falling off drastically as the cover moves between 45.degree. to 
105.degree. from the horizontal. 
The compound counterbalance mechanism 200 provides a self-closing platen 
cover 150 since the force of the gas spring is inadequate to support the 
platen cover at an inclination of less than about 15.degree. to 20.degree. 
to the horizontal. The mechanism 200 enables the platen cover 150 and 
document handler 11 to be lifted and held in any desired position over a 
wide range of orientations. 
If desired, the tension spring 205 can be made adjustable to off-set 
tolerance build-ups and optimize the inter-relationship between it and the 
gas spring 201. A tension spring adjustment system is not shown in the 
drawings, however, it could comprise a turn-buckle interposed between the 
U-shaped hook 207 and the coiled portion of the spring 205. The leg of the 
U-shaped hook 207 connected to the coiled portion is severed and the 
resulting ends threaded and connected together by the turn-buckle. In this 
manner the force exerted by the compensating spring 205 could be increased 
or decreased by adjusting the turn-buckle to increase or decrease the 
extension spring. 
MANUAL REGISTRATION EDGE 
When the document handler 11 is raised to do copying by manual placement of 
documents on the platen P, the normal document registration edge 51 is in 
its retracted position as described above. Therefore, it is necessary to 
provide some means for providing manual registration of a document on the 
platen P. This is achieved in accordance with this document handling 
system 11 by means of a retractable manual registration edge mechanism 210 
as in FIGS. 13 and 14. The manual registration edge 211 is located at the 
rear or top edge of the platen P. It comprises a plate-like member 212 
which is arranged to slide on and off the platen P. A parallelogram-type 
linkage is used to provide the sliding movement. A first member 213 is 
secured to the optical frame 214 by screws 215. Two parallel, but spaced 
apart pivoting links 216 and 217 are pivotally secured at one end to the 
first member 215 and at their other end to the movable registration member 
212. A tension spring 218 biases each of the links 216 and 217 toward the 
extended position or operative position for the registration member shown 
in solid lines. A cable 219 is secured to one of the pivoting links 216 at 
one end and to an actuating member 220 mounted on the document handler 
cover 150 as in FIG. 13 at its other end. 
When the cover 150 is raised as in FIG. 13, the cable 219 is slack so that 
the manual registration edge 211 is operatively positioned over the platen 
P as in FIG. 14. When the cover is closed as shown in phantom in FIG. 13, 
the movement of the actuating arm 220 pulls the cable taught and retracts 
the manual registration edge 211 to the position shown in phantom in FIG. 
14. Therefore, the manual registration edge 211 is present over the platen 
P only when the document feeder cover 150 and document feeder 11 are 
raised off the platen surface. When the document feeder cover 150 is in 
its normal operative position over the platen surface the manual 
registration edge is retracted. This avoids interference between the 
manual registration edge 211 and the documents being advanced onto the 
platen by belt transport 40. 
DOCUMENT HANDLER DRIVES 
The drive motor 230 is connected to the document handler 11 via clutch and 
pulley 65, timing belts 231 and 232 and intermediate pulleys 233 and 234 
as shown in FIG. 13. The timing belt 232 is wrapped about the outboard 
drive pulley 235 on shaft 71 as in FIG. 2. Timing belts 236 and 237 are 
used to tap the drives input to shaft 71 for connection to the belt drive 
pulley 44 and the output drive rollers 180. 
OUTPUT TRAY AND DOCUMENT DECELERATOR 
Referring now to FIGS. 1, 2, and 15, the document output tray 41 and 
document decelerators 56 features are shown in greater detail. The output 
tray 41 includes a step or depression 240 at its downstream end which 
serves to collect and appropriately stack small sized documents. If a 
larger document is copied, it would extend over the lip 241 of the 
depression 240 in the tray 41. 
A document decelerator support bar 242 is pivotally supported for movement 
between the positions shown in solid lines and in phantom. The bar is 
biased upwardly by spring 247. In the solid line position the bar 242 
supports two Mylar strips 243 which act to decelerate documents exiting 
from the document handler. The documents pass under the upper run 244 of 
the bar 242 and engage the Mylar strips 243 which act to decelerate and 
stack the documents in the tray. Improved document stacking and 
deceleration is accomplished by means of brush-type pads 245 secured to 
the free ends of the cantilever mounted Mylar strips 243. The brush pads 
245 include fibers that are angled with respect to the direction of 
document advancement, namely, they are inclined forwardly and downwardly 
of the direction of document advancement. As a document engages the fiber 
pads 245 it passes easily in the direction in which it is moving because 
of the inclination of the fibers. However, when the document reaches the 
end face 246 of the output tray 41 and attempts to reverse its direction 
of movement, the frictional resistance between the fibers of the pads 245 
and the document is increased because of their inclination. The increased 
frictional resistance causes the documents to stop and stack in a neat 
pile generally against the end face 246 of the output tray 41. 
Preferably in accordance with this invention the coefficient of friction 
between the documents and the fibers of the pads 245 is approximately 
about .2 or less in the direction in which the sheets are advanced into 
the output tray 41. In the reverse direction, however, the frictional 
forces exerted by the fibers of pads 245 should provide a coefficient of 
friction greater than about 1. 
While any desired material can be employed for the fibrous pads 245, a 
material produced by Collin and Aikman, called "Climber" IF-3961 provides 
excellent results. Alternatively, a Fibertran type material as in the 
Sanchez, et al. patent could be employed. 
The material may be installed as a flat type pad as shown in FIG. 15 or 
alternatively it could be applied to a roller at the end of a sheet 
deflector. Both approaches have been shown to provide successful results. 
An example of a roller at the end of a sheet deflector is found in U.S. 
Pat. No. 3,709,492 to Baker, et al. noted in the background of this 
application. The pad shown in the Figures could be easily applied to that 
roller surface to give the same result. 
The strips 243 preferably are resilient so that their cantilever mounting 
serves to bias the pads 245 downwardly toward the bottom of the tray. The 
resiliency of spring-like nature of the strips also provides improved 
damping and deceleration of the document as compared to a rigid member. 
If it is desired to do book copying, the decelerator support bar 242 is in 
the way. However, it can be deflected downwardly, as shown in phantom, so 
that a book can be easily laid over it and the platen P. The registration 
gate assembly 50 has been inclined with respect to the plane of the platen 
P as described above. This orientation provides an ideal book registration 
edge, so that it is not necessary to break the binding of a book as it is 
placed on the platen for copying. Deflection of the bar 24 allows the book 
to be easily placed over the platen without interference with the bar. 
The control system for operating the document handling system described 
above does not form a part of the present invention and any desired system 
could be employed as are known in the prior art. 
The patents, applications, and texts referred to specifically in this 
application are intended to be incorporated by reference into the 
application. 
It is apparent that there has been provided in accordance with this 
invention a counterbalancing apparatus which fully satisfies the objects, 
means and advantages set forth hereinbefore. While the invention has been 
described in conjunction with specific embodiments thereof, it is evident 
that many alternatives, modifications and variations will be apparent to 
those skilled in the art in light of the foregoing description. 
Accordingly, it is intended to embrace all such alternatives, 
modifications and variations as fall within the spirit and broad scope of 
the appended claims.