FIELD AND BACKGROUND OF THE INVENTION
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The present invention relates generally to the field of
writing instruments and in particular to a new and useful
mechanism for expanding the length of a writing instrument
barrel while extending a writing tip from a retracted
position in the barrel to a writing position.
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Compact devices of all types are sometimes preferred
over full-size versions because they occupy less space.
However, some compact devices are not as useful as full-sized
versions of the same product for a variety of reasons.
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In the case of writing instruments, a small or reduced
size pen can be difficult to hold and use for many people,
including the elderly, children, the infirm, and people with
large fingers. At the same time, a pen or pencil which
occupies less space is more easily carried in a pocket or
purse.
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Sometimes, pens and pencils are sized to fit with other
products they are used with, such as a miniature pen
provided with a date planner or a golf pencil stored on the
steering wheel of a golf cart. These smaller pens and
pencils are non-refillable and must be discarded when the
ink or lead is used up. While these writing instruments are
a compact, convenient size for storing, they are not as,
comfortably for writing with and suffer the problem that
they can be difficult for some persons to use.
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Telescoping writing instruments having spiral grooves
and followers in overlapping body sections have been
produced by the A. T. Cross Company as early as 1875. These
writing instruments have at least three movable body
sections which move both rotatably and longitudinally
relative to each other to either increase or decrease the
length of the writing instrument. Follower pins in one
section correspond to a spiral groove in another section, so
that pulling the ends of the writing instrument cause the
middle section to rotate while the instrument lengthens and
the writing tip is exposed.
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In a copending U.S. patent application, serial no.
09/688,659 filed October 16, 2000, having some common
inventorship, an expandable pen having a cam mechanism for
extending the writing tip when front and cap pen sections
are pulled apart is disclosed. The cam is activated by the
sliding longitudinal movement of the cap section away from
the front section on the pen body.
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Other attempts to provide pens having extendable
bodies, include a miniaturized ball point pen which is
expandable to a more comfortable length for use as disclosed
in U.S. Patent 3,174,461. The pen point is always exposed
and does not retract within the body of the pen. The body
expands by simply sliding two concentric overlapping
sections apart. The overlapping sections are frictionally
fit to each other. A lower section secures the ball point
and ink supply inside the body. The upper section slides
inside the lower section and has a tapered end which catches
the top of the ink supply to prevent the upper section from
being completely separated from the lower section. A cap
fits over the upper section and its lower edge stops against
the upper edge of the lower section.
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U.S. Patent 3,709,620 teaches a ball point pen having
a body which is expandable for use as a pointer. The pen
body is formed by a series of telescoping tubes which
support and contain the ball point and ink supply. The ball
point may be extended or retracted from the pen body by a
spring-loaded operation button at the top end of the body.
The button has a horizontal channel with a spring-loaded
slider having a tab which is forced into an opening in the
side of the upper tube when the button is depressed to hold
the button and keep the pen tip extended. Pressing the top
end of a clip mounted outside the upper tube over the tab
pushes the tab and slider back within the button, releasing
the button from the depressed position. The button spring
may then force the button back upward, retracting the pen
tip.
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While the pen tip may be retracted in this pen, it
requires a relatively complex arrangement of springs and
sliders and it requires the presence of a clip. The
extension/retraction mechanism for the pen tip is not
integrated with the expansion for the device either. The
pen tip cannot be extended outside the pen point when the
tubes are expanded for use as a pointer.
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A folding ball point pen is disclosed by U.S. Patent
5,061,104. The pen is hinged near the center of the pen and
a recess is provided in the upper section, so that the lower
section containing the pen point and ink reservoir may be
folded flush into the side of the upper section. The pen
point is not retractable.
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These prior pens suffer from the problem that either
the pen tip is always exposed, which either requires the use
of a pen cap, or there is the risk of accidental marks. The
pen is not replaceable; once the ink is used up, the device
must simply be thrown away and replaced in its entirety.
SUMMARY OF THE INVENTION
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It is an object of the present invention to provide a
writing instrument which can be easily expanded from a
compact storage size to a longer writing size.
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It is a further object of the invention to provide a
writing instrument which includes an internal mechanism for
extending and retracting a writing tip when the writing
instrument is expanded from a compact storage size to a
full-size position for use.
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Accordingly, an expandable pen is provided with a pen
barrel having a cap section which slides longitudinally from
a closed position covering a middle section to an elongated
use position in which the middle section is exposed. The
pen barrel holds a retractable pen refill cartridge. When
the pen is expanded, the writing tip of the refill is
extended from a retracted position inside the pen barrel to
a writing position, while the barrel becomes full length for
comfort when writing.
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The pen has a front section secured to a pen body with
a cap liner which slidably fits over the pen body and mates
with the front section when the pen is in the compacted
state. A decorative cap may be placed over the cap liner to
enclose the end of the pen and form a cap section. The
refill cartridge fits within a chamber defined by the front
section, pen body and cap liner and is held at a pen point
end by a coil spring. A gear is mounted on the pen body and
has two sets of teeth which engage a track in the cap liner
and a second track on a plunger positioned over the end of
the refill cartridge. When the cap section is slid
backwards away from the front section, the gear rotates
between the track and the scaled track. The different size
teeth on the gear scale the sliding movement of the cap
section and translate it to a smaller movement for the
plunger to force the cartridge downward and the coil spring
to compress so the writing tip is exposed. The writing tip
on the cartridge is thus extended for use, while the length
of the pen is expanded for more comfortable writing.
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The various features of novelty which characterize the
invention are pointed out with particularity in the claims
annexed to and forming a part of this disclosure. For a
better understanding of the invention, its operating
advantages and specific objects attained by its uses,
reference is made to the accompanying drawings and
descriptive matter in which a preferred embodiment of the
invention is illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
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In the drawings:
- Fig. 1
- is a sectional left side elevational view of a
writing instrument according to the invention in
a use or open position;
- Fig. 2
- is a sectional right side elevational view of the
writing instrument of Fig. 1 in a closed or
storage position;
- Fig. 3
- is a sectional top plan view of the writing
instrument of Fig. 1;
- Fig. 4
- is a front, side, end perspective view of a
refill plunger used in the writing instrument of
Fig. 1; and
- Fig. 5
- is a side elevational view of a gear used in the
writing instrument of Fig. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
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Referring now to the drawings, in which like reference
numerals are used to refer to the same or similar elements,
Fig. 1 shows a writing instrument according to the invention
in the form of an expandable ball point pen 50. As seen in
Fig. 1, the pen 50 is in an expanded, use position with
writing tip 10 of pen refill 65 extended through pen point
60. Pen refill 65 compresses spring 15 against the inside
of the front section 20 when the writing tip 60 is extended.
Pen body 40 is secured to front section 20 via a threaded
connection 45 at one end. A cap liner 30 is slidably
mounted over pen body 40 at the other end. The cap liner 30
is preferably covered by a decorative cap (not shown) or
formed as an integrated piece. The cap liner 30 only is
shown for convenience, but it should be understood that any
reference to the cap liner 30 herein may refer to a unitary
cap having the same features or to a combined cap and cap
liner.
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The front section 20, pen body 40, pen point 60, and
cap liner 30 define a chamber for holding the refill
cartridge 65. The coil spring 15 supports the bottom end of
the refill cartridge 65 against the upper edge of the pen
point 60 inside the front section 20. The spring 15 tends
to force the refill cartridge 65 away from the pen point 60
and keep it in a retracted position when the pen 50 is
collapsed.
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The cap liner 30 is slidably mounted on the pen body 40
so that the cap liner 30 can move between the closed and
expanded positions without completely separating from the
pen body 40. A gear 70 having two sets of teeth 75, 77 with
different diameters is rotatably mounted to the end of the
pen body 40 between a cap track 35 and a track 95 of a
plunger 90.
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In the storage position, shown in Figs. 2 and 3, the
front section 20 mates with cap liner 30 to form a compact,
generally cylindrical pen 50.
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Figs. 1-3 show the internal connections of the pen 50
components and gear mechanism used to extend and retract
refill cartridge 65 when the pen 50 is expanded and
collapsed.
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A slide stop tab 32 on the cap liner 30 mates with
corresponding stop slots 47, 48 formed in the pen body 40 to
hold the cap liner 30 and cap on the pen body 40 when it is
expanded and to help keep the pen 50 in a closed position
when stored. The slide stop tab 32 can be disengaged with
either slot 47, 48 by pulling or pushing the cap section as
needed.
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The gear mechanism relies upon the interaction of gear
70 with plunger 90 and cap liner 30.
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As seen in Fig. 4, the plunger has track 95 extending
from the opposite side of a pushing surface 97. The pushing
surface 97 is arranged inside the pen body to press against
the end of refill cartridge 65. A pair of guides 92 are
provided on the sides of the plunger 90 which correspond to
a pair of tracks 43 in the sides of the pen body. The
guides 92 prevent the plunger from rotating and changing the
position of the plunger track 95 within the pen.
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Fig. 5 illustrates the gear 70 with a set of large
diameter teeth 77 which engage the cap track 35 and a set of
small diameter teeth 75 which engage the plunger track 95.
The two sets of teeth 75, 77 are concentric around gear axle
72.
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Referring again to Figs. 1-3, the gear 70 is seen
mounted to the end of pen body 40 by the gear axle 72 held
inside axle support channel 42 of the pen body 40. The
interaction of the two sets of gear teeth 75, 77 with the
two tracks 32, 95 cause the plunger 90 to be forced forward
toward the pen tip 60 when the cap section (cap liner 30 and
a decorative cap) are pulled back to extend the pen 50 for
use from the collapsed position. The plunger 90 in turn
presses on refill cartridge 65, forcing it against spring 15
and the writing tip 10 to extend out from the pen tip 60.
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The particular ratio of the diameters of the two sets
of gear teeth 75, 77 is determined based on the ratio of the
distance the cap section will move to reach the extended
position where slide stop 32 mates in slot 48 to the
distance the refill cartridge 65 must move to extend the
writing tip 10 to a use position. Preferred ranges for the
ratio of the larger diameter to the smaller diameter are
between 5:1 and 1:1, although the ratio could be greater
than 5:1. In a case where a ratio of 1:1 is acceptable for
use, the gear may have a single set of gear teeth engaging
both tracks.
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To collapse the pen 50 from the writing position, the
cap liner 30 is pushed toward the pen tip 60 until stop tab
32 disengages from slot 48 and begins to slide closed. As
the cap liner 30 slides back to the closed position, the
gear 70 rotates in the reverse direction, causing the
plunger 90 to move away from the pen tip 60 and removing
pressure from the end of the refill cartridge 65. The
spring 15 then forces the refill cartridge 65 back into the
pen body 40 until the cap liner 30 abuts the front section
20 and stop tab 32 is mated in slot 47 to hold the pen 50
closed. The writing tip 10 is then completely retracted
into pen tip 60 for storage.
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As an alternative to using spring 15 to force the
refill cartridge 65 back into the pen body 40 when the pen
50 is collapsed, the plunger pushing surface 97 could be
secured to the end of the refill plunger. The plunger 90
would then pull the refill cartridge 65 into the pen body
40. The plunger 90 could be secured to the refill cartridge
65 by having opening 99 frictionally fit over a tapered end
of a refill cartridge 65. Alternatively, the plunger
pushing surface could be secured to the end of the refill
cartridge 65 using an adhesive.
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To maintain the pen 50, the refill cartridge 65 can be
replaced by unscrewing threaded connection 45 between the
front section 20 and pen body 40, removing the spent
cartridge 65 and replacing it with a new one. The front
section 20 and pen body 40 can be rejoined and the pen 50
used as described above.
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Using the pen 50, a compact writing instrument can be
quickly expanded to a larger writing position while
simultaneously extending the pen tip 10 for use.
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In the event that a disposable version of the pen 50 is
desired, the front section 20 and pen body 40 could be fused
together as a single piece, rather than connected by a
threaded connection. Similarly, the pen point 10 could be
formed integral with the front section 20 as a single piece
instead of as separate components.
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The use of the term refill cartridge herein is intended
to mean any self-contained disposable unit which has both a
writing material supply and a marking tip for making a
visible mark on paper or other material with the writing
material. The refill cartridge may be disposable with the
pen, or removable from the pen and replaceable.
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While a specific embodiment of the invention has been
shown and described in detail to illustrate the application
of the principles of the invention, it will be understood
that the invention may be embodied otherwise without
departing from such principles.
