Sheet feed construction for compact printers

An improved sheet separator and guide construction for a printer having a supply station and a feeder/platen for feeding a top sheet from a supported sheet stack and transporting it through the printing region. The construction includes a force plate for urging a supported sheet stack so that its top sheet contacts the feeder-platen and is moved toward a supply station egress region. A pair of sheet corner deflectors located respectively at opposite edges of the supply station egress region are constructed to direct sheet corners fed there-against inwardly toward the sheet center, and a central deflector located along a central portion of the egress region in spaced relation between the corner deflectors is constructed to direct the center lead-edge of a sheet fed there-against upwardly toward the printer top.

FIELD OF THE INVENTION 
The present invention relates to compact printers and, more specifically, 
to improved printer constructions for feeding individual sheets in 
succession from a supply station through the printing zone. 
BACKGROUND ART 
U.S. Pat. No. 4,763,138 discloses a compact printer having an integral cut 
sheet feeder which is quite advantageous as a module for cooperation with 
personal computers in an office environment, e.g., because of its 
versatility and compactness. This printer features sheet feed from a 
supply station by the same platen member that transports the sheet through 
the printing region, where, for example, an ink jet printing carriage scan 
prints successive lines. 
U.S. Pat. No. 4,783,669 discloses a highly useful sheet supply station for 
use in printers of the kind described in the '138 patent and also 
discloses one approach for separating top sheets from the supply stack and 
guiding them through the printer. The sheet separator of the '669 patent 
performs well, but has several disadvantages. Thus, the '669 patent 
approach requires considerable free paper length beyond, and space above, 
its top sheet buckler posts. Also, it has been found necessary in some 
applications to adjust the buckler posts for certain paper widths. In 
addition, it would be desirable to avoid contact between all feed/guide 
elements and any printed portions of fed sheets. 
SUMMARY OF INVENTION 
An important aspect of the present invention is to provide improved 
constructions for printers having integral sheet feeders to avoid the 
disadvantages noted above. Thus one advantage of the present invention is 
that its sheet separation construction is compact and can help reduce 
overall printer size. Another advantage of the present invention is that 
its operative sheet-separation components perform reliably without 
adJustments to accommodate different paper width tolerances. A further 
advantage of the present invention is its paper guide elements serve to 
smooth any partially bent sheet corners and direct the fed sheets through 
the printing operation without contacting printed regions on the sheet. 
In one preferred embodiment the present invention constitutes an improved 
sheet separator and guide construction for a printer having a supply 
station supporting a sheet stack and a feeder/platen for feeding a top 
sheet from a supported sheet stack and transporting it through the 
printing region of the printer. The improved construction comprises means 
for urging a supported sheet stack so that the top sheet contacts the 
feeder platen and is moved toward a supply station egress region; a pair 
of sheet corner deflectors located respectively at opposite edges of the 
supply station egress region, the deflectors being constructed to direct 
sheet corners fed there against inwardly toward the sheet center; and a 
central deflector located along a central portion of the egress region in 
spaced relation between the corner deflectors, the central deflector being 
constructed to direct the center lead edge of a sheet fed there against 
upwardly toward the printer top.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
FIGS. 1 and 2 shows the prior art apparatus described in above-noted U.S. 
Pat. No. 4,783,669, which provides a good example of one kind of 
feeder-printer in which the present invention is useful. The FIG. 1 
feeder-printer 1 comprises a housing 2 rotatably mounting a feeder-platen 
2 and having a cut sheet supply station, designated generally 3, in its 
bottom region, below the feeder-platen. The supply station includes a 
force plate member 4 hinged at the printer rear and biased upwardly by 
spring 5 toward the bottom of feeder platen 2. A drawer member 6 is 
slidingly mounted in the printer bottom to receive and index a stack of 
sheets S against abutment members 7. Sheet guide means of this printer 
include fixed bottom guide members 8 and top guide members 9 which are 
movable with the carriage 10 that supports the print head 11. A tab 12 is 
provided on force plate 4 to be engaged by a control cam, e.g. a surface 
of member 13, and disengage the feed engagement between a supported stack 
and the feeder-platen 2. U.S. Pat. No. 4,763,138 describes other 
constructions for effecting controlled engagement between feeder-platen 8 
and sheet stack S and is incorporated herein by reference for those 
teachings. 
Referring now to FIGS. 3 and 4, it can be seen that the printer 30 
constructed in accord with the present invention is generally the same as 
the FIG. 1 apparatus, differing primarily in its constructions for 
separating top sheets from stack S' and for directing the leading ends of 
fed sheets to and through the printing zone P.Z. Similar structures of 
FIG. 3 are denoted with the same, but primed, numerals as used in FIG. 1. 
Referring particularly to the sheet separating and guiding structure of the 
FIGS. 3 and 4 embodiment of the present invention, it can be seen that the 
sheet separating assembly comprises a pair of sheet corner deflectors 31 
and a central deflector 32 located in a spaced relation along the line of 
top sheet egress from the sheet supply station 3'. Deflector 31 each have 
a top plate 33 overlying the corners of the top sheet of a supported stack 
and have an upstanding deflector surface 34 at an angle of about 
45.degree. to the line of the lead edge of the sheet. The central 
deflector 32 has edges 35 that are spaced from the deflectors 31 and 
extends between those edges along a major portion of the sheet stack 
front. The central deflector provides an upstanding abutment surface 36 to 
index the sheet stack and an upper portion 37 that slants upwardly away 
from sheet stack front in spaced relation to the feeder-platen periphery 
(as best seen in FIG. 3). A pair of sheet smoothing arms 38 extend 
upwardly and outwardly toward their respective edges of the sheet path 
from the edges 36 of the central deflector 32. The arms 38 also conform to 
the periphery of the platen and thus define a feed path that guides fed 
sheets into the nip of bail rollers 39 and feeder platen 2'. 
The advantageous functioning of the separator and guide construction Just 
described will become clear from a description of a sheet feeding sequence 
with reference also to FIGS. 5-8. Thus, as a set feed sequence commences 
feeder platen 2' rotates counter clockwise (as viewed in FIG. 3) and its 
frictional surface moves the top sheet of stack 5' toward the sheet egress 
region. As shown in FIGS. 5 and 6, the tips of the top sheet corners abut 
the angled deflector surface 34 and dives-downwardly under the front of 
top plate 33. At the same time, the center of the lead edge of the top 
sheet abuts central deflector 32 and is deflected upwardly. These 
cooperative deflections cause the sheet to bow as shown in FIG. 7 and 
enable the sheet corners to be released from under top plates 33 without 
severe creasing. To the extent that some residual bend exists in the sheet 
corners, the smoothing arms 38 fold back the bend gradually as the sheet 
corner moves toward the nip between bail rollers 39 and the feeder-platen 
2'. 
Referring to FIG. 4, it will be noted that the construction of the present 
invention effects guide of the sheet edges under the edge bail rollers 39 
without blocking the print zone P.Z. from its address by print head 11'. 
Also, it can be seen that the edge bail rollers 39 do not contact printed 
regions of a fed sheet, nor does the central guide 37. 
The invention has been described in detail with particular reference to 
certain preferred embodiments thereof, but it will be understood that 
variations and modifications can be effected within the spirit and scope 
of the invention.