Note: Descriptions are shown in the official language in which they were submitted.
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MECHANISM FOR ST BILIZING PLATEN
Background of the Invention
In the field of printing, the most common
type of printer has been the printer which impacts
against record media that is caused to be moved past a
line of printing. As is well-known, the impact
printing operation depends upon the movement of impact
members, such as print hammers or wires or the like,
which are typically moved by means of an
electromechanical-type system and which system enables
precise control of the impact members.
In the field of dot matrix printers, it has
been quite common to provide a print head which has
included therein a plurality of print wire actuators
or solenoids arranged or grouped in a manner to drive
the respective print wires a very short, precise
distance from a rest or non-printing position to an
impact or printing position. The print wires are
generally either secured to or engaged by the solenoid
plunger or armature which is caused to be moved such
precise distance when the solenoid coil is energized
and wherein the plunger or armature normally operates
against the action of a return spring.
It has also been quite common to provide an
arrangement or grouping of such solenoids in a
circular configuration to take advantage of reduced
space available in the manner of locating the print
wires in that specific area between the solenoids and
the front tip of the print head adjacent the record
media. In this respect, the actuating ends of the
print wires are positioned in accordance with the
circular arrangement and the operating or working ends
of the print wires are closely spaced in vertically-
aligned manner adjacent the record media. The
availability of narrow or compact actuators permits a
narrower or smaller print head to be used and thereby
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red~ces the width of the printer because of the
reduced clearance at the ends of the print line. The
print head can also be made shorter because the narrow
actuators can be placed in side-by-side manner closer
to the record media for a given amount of wire
curvature.
In the wire matrix printer which is utilized
for receipt and journal printing operation, the print
head structure may be a multiple element type and
horizontally disposed with the wire elements aligned
in a vertical line and supported on a print head
carriage which is caused to be moved or driven in a
horizontal direction for printing in line manner
across the receipt or journal paper and wherein the
drive elements or transducers may be positioned in a
circular configuration with the respective wires
leading to the front tip of the print head. In the
wire matrix printer which is utilized for business
forms or like record media printing operation, the
print head may be oriented in a manner wherein the
nose is pointed downward for printing on the form or
record media while the carriage and print head are
moved above and across the form or media in the
horizontal direction.
Further, the printer structure may be an
arrangement which includes a plurality of equally-
spaced, horizontally-aligned, single element print
heads which are caused to be moved in back and forth
manner to print successive lines of dots in making up
the lines of characters. In this latter arrangement,
the drive elements or transducers are individually
supported along a line of printing. These single wire
actuators or solenoids are generally tubular or
cylindrically shaped and include a shell which
encloses a coil, an armature and a resilient member
arranged in manner and form wherein the actuator is
operable to cause the print wire to be axially moved a
small precise distance in dot matrix printing.
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In the case of a wire matrix printer which is
utilized for form or multi-copy printing, the
difference in thickness of the forms or copies may
require some means or mechanism for adjusting the gap
or the distance between the print head and the printer
platen. In view of the impact nature of such wire
matrix printer relative to form or multi-copy
printing, the platen should preferably be adjustably
stabilized under certain printing conditions. It is
with the field of printing receipt, journal, and
business forms or like record media of different
thicknesses that the subject matter of the present
invention is most closely associated, and provides for
improved and advantageous positioning of such record
media during the printing operation. In prior designs
the platen generally has been contained or stabilized
by means of a compression spring backing up each end
of the platen, which spring can allow the platen gap
to change durincl the printing operation.
Representative documentation in the field of
wire matrix print heads used for printing forms or
like record media includes United States Patent No.
3,776,341, issued to R. G. Dobner et al. on December
4, 1973, which discloses a document support system
that includes front and rear paper guides which
cooperate to maintain the document in a fixed
location. The rear guide is spring biased towards the
front guide.
United States Patent No. 3,987,886, issued to
F. A. Mahoney et al. on October 26, 1976, discloses
mechanism for varying the print gap, including
eccentric means formed and disposed to move housing
means toward and away from the type font of a printer.
United States Patent No. 4,063,630, issued to
W. R. Crowe et al. on December 20, 1977, discloses
platen carrier means for maintaining the platen in a
constant vertical position at least during relative
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vertical adjustment of the print element with respect
to the platen.
United States Patent No. 4,189,244, issued to
G. ~. Harrison on February 19, 1980, discloses a
platen gap adjuster including an eccentric shaft
mounted by means of offset spindles.
Summary of the Invention
The present invention relates generally to
impact type printers which have the capability of
printing on record media of receipt or journal type,
or forms of different thicknesses. More particularly,
the present invention relates to means for positioning
and stabilizing the printer platen in a manner to
compensate for the difference in thicknesses of the
several types of record media being used in the
printer. The record media may be a single layer sheet
or a variety of multilayer forms, any of which may be
of different or greater thickness than other media.
In accordance with the present invention,
there is provided a stabilizing mechanism for a platen
in a printer having a frame and an impact type print
element, said mechanism comprising guide means
comprising a palr of generally rectangular members
secured to the frame of the printer and having
elongated apertures in a plate portion of each of said
generally rectangular members, platen carrying means
supported by the guide means and including members
projecting through said apertures and adjustably
coupled to said guide means, said platen carrying
means including a wall member positioned at an angle
relative to and having a surface opposed to a surface
of the platen, said surfaces defining a space
narrowing in one direction, a substantially spherical
member positioned between and engaging the surface of
the wall member and the surface of the platen, and
resilient means urging the spherical member in the
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direction oE the narrowing space between the surfaces
for holding the platen in position upon impact by said
print element.
A platen stabilizing mechanism or assembly is
provided in the printer and such stabilizing mechanism
includes a guide bracket which is secured to the
printer at the sides thereof. An adjustable platen
carrier is operably associated with the guide bracket
and such platen carrier defines a slanting surface
portion against which a locking ball is urged by a
spring to secure and stabilize the platen in position.
An adjusting screw is utilized to set the precise
position of the platen.
In view of the above discussion, the
principal object of the present invention is to
provide mechanism in a printer for setting the print
gap to accommodate different thicknesses of record
media.
Another object of the present invention is to
provide camming means in a manner to set the platen
gap at a predetermined space.
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An additional object of the present invention
is to provide mechanism for adjustin~ and for setting
or stabili~ing the platen gap for record media
inserted between the platen and the print head.
A further object of the present invention is
to provide camming means including a locking ball
operable against a slanting surface to accommodate
record media of different thicknesses at a printing
station and means for holding the platen in precise
position during printing operation.
Additional advantages and features of the
present invention will become apparent and fully
understood from a reading of the following description
taken together with the annexed drawing.
Brief Description of the Drawing
Fig. 1 is a side elevational view, partly in
sectionr incorporating the subject matter of the
present invention;
Fig. 2 is a top view of certain of the
structure shown in Fig. l; and
Fig. 3 is a view taken on the line 3-3 of
Fig. 1.
Description of the Preferred Embodiment
Referring now to the drawing, Fig. 1
illustrates a side elevational view of the apparatus
of the present invention wherein 20 represents a
platen for use in a journal, a receipt, or a slip type
printer. A print head 22 is supported from the
printer in well-known manner for impact printing
against paper or like record media 24 which media is
caused to be driven in a path between the print head
and the platen 20. For purposes of illustrating the
subject matter of the present invention, Fig. 2 is a
top or plan view of certain of the apparatus of Fig. 1
and Fig. 3 is a view taken along the line 3-3 or
Fig. 1.
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It should be noted that Figs. 2 and 3 `
illustrate the apparatus at one side of the printer
and that similar but oppositely oriented apparatus is
provided at the other side, the platen 20 extending
across the printer and the print head 22 traversing
along the platen in forth and back motion in printing
operation.
A ~uide bracket 26 of rectangular shape is
secured by screws 28 (Fig. 2) to the printer frame 30.
The bracket 26 includes spaced sides 32 and 34 and
ends 36 and 38 (Fig. 1) formed to provide a box-like
structure. A pair of top plate portions 40 and 42
define elongated openings 44 and 46 therein for
receiving projections 48 and 50 of a platen carrier
52. An upstanding portion 54 extending above end
portion 36 has a tapped opening 56 therein for
receiving an adjusting screw 58. A pair of gusset
plates 60 and 62 (Fig. 2) provide support for the
upstanding portion 54.
The platen carrier 52 includes a base plate
64 (Figs. 1 and 3~ with the projections 48 and 50
integral therewith. The base plate 64 seats on the
top plate portions 40 and 42 of the guide bracket 26.
The carrier 52 has upstanding walls or end portions 66
and 68, the portion 66 being spaced from and facing
the upstanding portion 54 of the guide bracket, and
the portion 68 facing and engaging with the platen 20
in a seating arrangement thereof. The platen carrier
52 also includes an upstanding portion in the form of
a slanted wall 69 (Fig. 1) positioned between the end
portions 66 and 68. When the platen carrier 52 is
placed on the guide bracket 26, the projections 48 and
50 are positioned for slidable movement in the
elongated openings 44 and 46 in response to ad]usting
action of the screw 58 in the threaded opening 56.
The screw 58 has a reduced diameter end portion 65
extending through the upstanding end portion 66 of the
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platen carrier 52. The end portion 65 provides an
abutment 67 bearing against one side of the end
portion 66 for moving the platen carrier 52 in a
direction toward and away from the print head 22.
The platen carrier 52 also includes a well 70
positioned between the projections 48 and 50 and
extending downwardly from the base plate 64. The well
70 is formed with a side wall 72 and a bottom portion
74 having an aperture 76 therein.
A locking ball member 80 is positioned
between a surface 82 of the slanted wall 69 (Fig. 1)
of the platen carrier 52, which slanted wall extends
upwardly and adjacent the well 7Q, and a surface 81 of
the platen 20. The locking ball 80 has a rod or tenon
portion 84 as an integral part thereof extending into
the well 70 and through the aperture 76. The well 70
is of sufficient diameter to receive a coil spring 86
encircling the rod portion 84 and engaging the well
bottom portion 74 on the top side thereof and the ball
80 on the bottom side thereof for exerting continuing
pressure on the ball and urging the ball in an upward
direction.
In the operation of the apparatus of the
present inventian, the front surface of the platen 20
is seated against the upstanding portion 68 of the
platen carrier 52 and the ball 80 is wedged between
the rear surface of the platen and the front surface
of the slanted portion 82. The print gap between the
platen 20 and the print head 22 is adjusted by turning
the screw 58 in the threaded opening 56, the abutment
67 of such screw bearing against the side surface of
the upstanding end portion 66 for moving the platen 20
and the platen carrier 52, with such gap being
provided in predetermined manner and position by the
several parts of the invention. The spring 86
continually urges the ball 80 upwardly into the
narrowing or reducing space between surface 81 of the
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platen 20 and the surface 82 of the inclined wall 69.
When it is desired to remove or change the position of
the platen 20, the ball 80 is manually depressed
against the action of the coil spring 86 and may seat
into a curved portion 88 formed in the side wall 72 of
the well 70.
It is thus seen that herein shown and
described is apparatus for setting and for stabilizing
the platen in an impact type printer. The mechanism
and arrangement enables the accomplishment of the
objects and advantages mentioned above, and while a
preferred embodiment of the invention has been
disclosed herein, variations thereof may occur to
those skilled in the art. It is contemplated that all
such variations not departing from the spirit and
scope of the invention hereof are to be construed in
accordance with the following claims.
