Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 ¦ , DESCRIPTION
2 ¦ DUST SHIELD FOR A PRINTER
¦ BACKGROUND 03? THE INVENTION
41 l. Field of the Invention
51 The present invention generally relates to printers such
61 as those which are commonly used in conjunction with a
81 computer terminal. More particularly, the presant invention
l relates to a shielding device for keeping printing media
91 particles away from the printhead and other moving parts of
lll the printer that such particles or accumulations of particles
121 can disrupt.
l 2. Description of the Related Art
13¦ one of the problems with the use of computer-type
14¦ printers is paper dust and accumulations o~ paper dust ox the
15¦ interference such can cause to the printhead and other moving
16¦ parts within the printer. For example, in an impact-hammer
17 type printhead, dust can accumulate on the hammerheads and
18 degrade the print ~uality. The problem is increased when the
printer uses continuous, ~an-fold paper which has
2 perforations between each sheet. If the paper is of the type
22l which uses sprocket wheel paper advance drive, sprocket holes
23 and perforations also exist along tear-off strips on each
side of each sheet, adding further sources of unwanted paper
24 dust.
In fact, experiments by the inventors indicate that the
26 primary source of paper dust is the æprocketiholes
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themselves. In other words, as the sprocket is inserted
and withdrawn during paper advance, the contact between
the sprocket and the perimeter of each sprocket hole
creates paper dust.
Paper dust is particularly a nuisance to a thermal
ink jet printhead which has a set of tiny orifices
designed to eject boiled ink vapor droplets. A single
particle of paper dust may be sufficient to clog such an
orifice. A general description of such ink jet
technology can be found, for example, in the Hewlett
Packard Journal, Volume 36, Number 5, May 1985.
WALLACE ET AL., U.S. Patent 4,411,706, present a
method and apparatus for keeping dust away from ink jet
printhead orifices by using an air counterflow
technique. This concept requires complicated, costly
mechanism design.
Hence, there is a need for a simple means for
preventing paper dust from interfering with the
operational parts of a printer.
SUMMARY OF THE INVENTION
Various aspects of the invention are as follows:
A printing media particle shielding device mounted
on a printer sprocket wheel drive assembly for advancing
printing media, said printer having a means for printing
on said media, comprising:
means for initially catching particles emitted by
said media at said assembly, having an enclosed channel
region for catching and directing said particles away
from said means for printing; and
means for channeling said particles, attached to
said means for initially catching particles, for
channeling said particles away from said means for
initially catching particles, said assembly, and said
means for printing.
A paper dust shield for a printer having a sprocket
wheel paper drive assembly for advancing paper, having
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edges perforated with peripherally located holes for
catching by sprockets of said assembly, past a
printhead, comprising:
a component which fully covers the sprockets of
said assembly over that portion of said sprocket wheel
wherein said sprockets catch said holes and which
downwardly channels paper dust particles emitted by the
contact of said sprockets with said paper away from said
assembly and said printhead.
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1 ¦ An advantage of the present invention is that it
2 ¦ decreases the susceptibility of the printhead to paper dust
3 ¦ interference or clogging.
4 ¦ Another advantage of the preferred embodiment of the
51 present invention is that it provides protection for the
61 printhead by holding down the sides of the print media as it
71 passes by the printhead.
81 Other objects, features and advantages of the present
9¦ invention will become apparent upon consideration of the
10¦ following detailed description and the accompanying drawings,
11 in which like reference designations represent like features
12 throughout th~ FIGURES.
13 BRIEF DESCRIPTION OF THE DR~WINGS
14 FIGURE 1 is a schematic perspective view of the
preferred embodiment of the present invention;
16 FIGURE 2 is a schematic plan view (front) of the present
17 invention as shown in FIGURE 1;
18 FIGURES 3-3B are schematic plan views o~ the present
19 invention as shown in FIGURE 1 in which FIGURES 3 and 3A are
side views an~ 3B is taken in plane 4-4 as shown in FIGURE 3,
22 and
FIGURE 4 is a perspective view of the embodiment as
24 shown in FIGURE 1 in combination with a sprocket wheel
assembly.
26¦~ he drawings re~erred to in this description should ~e
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1 ¦ understood as not being drawn to scale except if specifically
32 ¦ noted.
¦ D~TAILED DESCRIPTION OF THE INVENTION
4 ~ Reference is made now in detail to a specific embodiment
5 ¦ of the present invention, which illustrates the best mode
6 ¦ presently conte~nplated by the inventor(s) for practicing the
71 invention. Alternative embodiments are also briefly
81 described as applicable. Referring now to FIGURE 1, a
9¦ preferred embodiment of the dust shield 1 of the present
10¦ invention is shown. Each sprocket wheel paper drive assembly
21 of the printer is to be equipped with such a shield 1. The
31 dust shield 1 has two particular features: a sprocket hole
1 1 dust catcher 3 and a channeling plate 5.
The catcher 3, as shown in more detail in FIGURES 2 and
3, is formed to have a curved channel region 7 which will
16 allow free passage o~ paper catching sprockets. A shield
17 strip 9, ~' borders each side of the channel region 7 in
18 order to prevent paper dust particles generated by the
sprocket/paper hole contact from being discharged over the
rim 11 of the channel region 7 where it still could cause a
2221 problem, such as by transferring to and blocking a printhead
23 orifice (not shown). There i5 al~o provided a keyed pin 13
fox connecting the catcher 3 to a sprocket wheel assqmbly 101
24 as shown in FIGURE 4. The combination o~ keyed pin 13 with
fixed pin 14 aligns and~connects the shield 1 to the sproket
26 wheel assembly 101.
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¦ As will be apparent to a person skilled in the art, the
l channel region can be made large enough also to guide larger
31 pieces of paper which may be torn loose by the sprocket
41 assembly out of the top of the catcher where they can be
51 easily removed by the operator.
6 The channeling plate 5 in this embodiment is formed of a
thin, flexible metal sheet. Its upper edge 15 is connected
8 to the lower edge 17 of the catcher 3, ~uch as by well-known
insert molding techniques, e.g. tabs 16 are inserted into the
mold prior to plastic injection. The lower portion 19 of the
12 plate 5 has a bend 21. The flat 23 which forms the lower end
25 of the channeling plate 5 has a catch-hole 27 for
13 attaching the channeling plate 5 to the sprocket wheel
14 assembly 101, as shownin FIGURE 4, by allowing a catch
projection 103 on the assembly 101 to be inserted into the
16 catch-hole 27.
As will be recognized by a person ~killed in the art,
18 the channeling plate 5 and the shield strips ~, 9' can also
19 act as a paper guide to prevent the sprockets 107 from
221 prematurely releasing the paper. By having the dust shield 1
22 ~ixed to the drive sprocket assembly 101, the need for the
23 operator to open and close typical, known sprocket paper
24 hold-down mechanisms is eliminated. ~
In operation, as can be seen in FIGURE 4, the sprocket
wheel 105 rotates (counter-clockwise) and the sprockets 107
26 grab and pull the paper around the wheel assembly 101. As
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1 ¦ the wheel 105 turns, the sprockets 107 are partially encased
~¦ firstly by the channelling plate 5 and, secondly, by the
31 catchex 3, the prockets passing unimpaired along the channel
41 7. Paper dust emitted from each hole in the paper tear-off
51 strips falls (generally due to the force of gravity) down the
6 catcher channel region 7 to the channel plate 5. The shield
strips 9, 9' prevent dust particles from being emitted over
8 the rim of the channel region 7. The channel plate 5 further
9 directs the paper dust particles away from the operational
mechanisms of the printer toward the bottom of the sprocket
11 wheel assembly 101 where it can be sa~ely released to fall to
12 the bottom of the printer housing (not shown). If the
sprockets 107 enter the paper holes before reaching the
154 position where the sprocket is in the channel region 7 of the
catcher 3, dus~ emitted will ~all directly onto the
16 channeling plate 5 and thus be channelled toward the bottom
17 o~ the printer housing.
18 It will also be recognized by a person skilled in the
19 art that the paper dust shield could be constructèd from many
21 materials. Moreover, the invention could be made as an
2 integral unit and even as an integral member of a sprocket
23 whesl assembly. Furthermore, the dust shield 1 can be made
Z4 to be retrofitted to sprocket wheel assemblies by modi~ying
the pin 13 and catch-hole 27 to adapt the dust shield to the
particular sprocket wheel assembly in ~uestion.
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1¦ The foregoing description of the preferred embodiment of
21 the present invention has been presented for purposes of
31 illustration and description. It is not intended to be
41 exhaustive or to limit the invention to the precise form
61 disclosed. Obviously, many modifications and variations will
71 be apparent to practitioners skilled in this art. The
l embodiment was chosen and described in order to best explain
81 the principles of the invention and its practical application
l to thereby anable others sXilled in the art to understand the
invention for various embodiments and with various
11 modifications as are suited to the particular use
12 contemplated. It is intended that the scope of the invention
13 be defined by the claims appended hereto and their
e valents.
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