U.S. patent number 3,705,774 [Application Number 05/176,032] was granted by the patent office on 1972-12-12 for writing instrument.
Invention is credited to Werner Kranich.
United States Patent |
3,705,774 |
Kranich |
December 12, 1972 |
WRITING INSTRUMENT
Abstract
This invention relates to a writing instrument, particularly a
ball point pen having a plurality of writing members. A writing
member is selected by depressing a pressure member, inclining the
instrument in a certain direction and then releasing the pressure
member.
Inventors: |
Kranich; Werner (D-8501 Rosstal
near Nuremberg, DT) |
Family
ID: |
25759664 |
Appl.
No.: |
05/176,032 |
Filed: |
August 30, 1971 |
Foreign Application Priority Data
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Sep 2, 1970 [DT] |
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P 20 43 495.1 |
Dec 3, 1970 [DT] |
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P 20 59 456.3 |
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Current U.S.
Class: |
401/33 |
Current CPC
Class: |
B43K
24/16 (20130101) |
Current International
Class: |
B43K
24/00 (20060101); B43K 24/16 (20060101); B43k
027/08 () |
Field of
Search: |
;401/30,32,33 |
Foreign Patent Documents
Primary Examiner: Charles; Lawrence
Claims
I claim:
1. A writing instrument comprising a plurality of writing members,
a holder, for each of the writing members, an axially displaceable
tip projection sleeve, said sleeve having means thereon defining an
opening of a size sufficient to allow only one said writing member
to pass therethrough, a return spring, said return spring acting on
the tip projection sleeve, a pressure member, said pressure member
being adapted to exert pressure on all the writing members and
holders to thereby axially displace all the writing members and the
tip projection sleeve toward a writing position against the action
of the return spring, a weight member, said weight member being
adapted to be displaced radially under the action of gravity to
move a selected one of the writing members into the said writing
position when the writing instrument is inclined in a selected
direction, said tip projection sleeve and said writing members
being arranged such that on release of said pressure member the
non-selected writing members and the said sleeve are urged back
into their retracted positions by said return spring while the
selected writing member passes through the means defining the
opening to assume a final writing position.
2. A writing instrument according to claim 1, in which said tip
projection sleeve has an upper collar, said upper collar providing
a countersupport for one end of said return spring, the writing
instrument further comprising a fixed annular projection for the
other end of the return spring.
3. A writing instrument according to claim 1, in which said weight
member is in the form of a pendulum pin, said pendulum pin being
fixed against axial movement.
4. A writing instrument according to claim 3, which includes a
retainer member, said retainer member carrying the pendulum pin,
the retainer member being provided with an arrangement of guide
ribs and guide edges, said guide ribs and guide edges respectively
constituting guide members and rest position abutments for said
tube holders.
5. A writing instrument according to claim 3, in which each said
tube holder is provided with an engagement edge, and said pendulum
pin is provided with a freely swingable end of the pendulum pin,
said freely swingable end being adapted to engage the said
engagement edge of each tube holder when displaced radially.
6. A writing instrument according to claim 3, in which each tube
holder is provided with a segment-like recess, the said recesses
forming a cylindrical chamber when said tube holders are disposed
at the same axial height.
7. A writing instrument according to claim 1, in which said weight
member is in the form of a ball, and each tube holder being
provided with a segment-like recess, said ball being arranged such
that as said tube holders are moved forward together, the said ball
is disposed in a chamber formed by said segment-like recesses in
the tube holders.
8. A writing instrument according to claim 7, which includes spaced
ribs, said spaced ribs being arranged at the end of the writing
instrument remote from the writing end thereof, said ribs serving
to guide the tube holders and, by means of steps are adapted to
engage said ball in the free space between two ribs when the tube
holders position have been displaced by said pressure member.
9. A writing instrument according to claim 7, in which said tube
holders are provided at their segment-like cross-sections with
abutment shoulders, said abutment shoulders serving as abutments
against the edge portion of said ribs.
10. A writing instrument according to claim 1, in which said tip
projection sleeve is provided with an interior conical ledge, said
ledge surrounding the said opening and extending downwardly toward
the opening.
11. A writing instrument according to claim 1, in which the tip
projection sleeve and the pressure member are formed as a one-piece
projection member, a closure button, said closure button closing
said projection member, engagement ribs, said engagement ribs
extending through longitudinal slots in the one-piece projection
member and the return spring being disposed within the said
projection member between the closure button and the upper edges of
the ribs.
12. A writing instrument according to claim 11, in which said
engagement ribs extending through the longitudinal slots in the
said projection member serve as catches for a ball of the weight
member and are also formed as guide ribs for the tube holders.
13. A writing instrument according to claim 11, in which the tube
holders have segment-like recesses which, when the tube holders are
moved together to the same axial height, define a chamber for
receiving the weight member.
14. A writing instrument according to claim 11, in which the
engagement ribs are formed with different radial heights and
thereby form engagement edges behind which weight member can engage
in the free space between two adjacent ribs when the tube holders
are forwardly displaced, the ball being supported at its other side
on the engagement edge of the corresponding tube holder.
15. A writing instrument according to claim 11, in which the upper
end of the said projection member carries a ring engaged in an
annular recess and retained by a threaded closure button.
16. A writing instrument according to claim 11, in which a ring
clip is secured between the closure button and the end of the
projection part.
Description
The present invention relates to a writing instrument, and more
especially to a multiple color retractable ball point pen, having a
plurality of ink tubes which are arranged in holders and are
axially displaceable by pressure on a pressure member, and can be
retained in a forwardly displaced writing position, the selection
of the ink tube to be moved into the writing position being
effected by holding the pen at an angle and by the consequential
radial displacement of a weight member under the effect of
gravity.
It is the purpose of the invention to provide a writing instrument
with automatic return of the tube in the writing position when a
newly selected tube is moved forwardly which, with a comparatively
simple construction, can be readily manufactured and assembled but
which also provides reliable operation and can be quickly prepared
for use.
Writing instruments are known in which selection of the required
color is effected by holding the instrument at an inclination and
by the consequential radial displacement of a weight member under
the effect of gravity, the selected ink tube then being moved
forwardly by a pressure member, and the ink tube already disposed
in the forwardly displaced position being automatically moved back.
With these writing instruments having automatic return of the ink
tubes, rotary ratchet sleeves with indexing slots or cross-shaped
ratchet members or ratchet discs are employed for the engagement
and disengagement of the forwardly displaced tube or its carrier.
Due to the use of such special engaging elements, which are
arranged around the tubes, the instrument is somewhat unhandy and
moreover of comparatively complicated construction.
According to the present invention there is provided a writing
instrument comprising a plurality of writing members, each of which
is arranged in a holder, an axially displaceable tip projection
sleeve having an opening therein of a size sufficient to allow only
one writing member to pass therethrough, a return spring acting on
the tip projection sleeve, a pressure member adapted to exert
pressure on all the writing members to thereby axially displace all
the writing members and the tip projection sleeve toward a writing
position against the action of the return spring, a weight member
adapted to be displaced radially under the action of gravity to
move a selected one of the writing members into the writing
position when the writing instrument is inclined in a selected
direction, the tip projection sleeve and writing members being
arranged such that on release of the pressure member the
non-selected writing members and the said sleeve are urged back
into their retracted positions by the return spring while the
selected writing member passes through the opening in the sleeve to
assume a final writing position.
The weight member displaced by inclination of the pen can be
constructed as a pendulum rod. In this case, in contrast to known
constructions, the pendulum rod is connected by means of retainer
member to the casing in such a manner that it is not axially
slidable. With this arrangement, a retainer member carrying the
pendulum rod and connected to the casing is advantageously also
formed, by an arrangement of guide ribs and guide edges, as a guide
member and rest position abutment for the tube holders. The holders
have corresponding engagement edges which the pendulum rod can
engage with its freely swingable end on displacement in a radial
direction. To allow return of all four holders, the holders have
segmental recesses which, when the holders are at the same axial
height, define a cylindrical recess.
If the radially displaceable weight member is formed in known
manner as a ball, then preferably the ball is disposed in a chamber
formed by segment-like recesses in the holders. In contrast to
previously known arrangements, the ball is axially moved when the
holders are axially displaced together. The upper part of the
instrument has stepped ribs for guiding the holders, the rib steps
being formed so that the ball deflected from the central position
when the pen is held at an inclination engages behind these steps
and holds the required tube in the forwardly displaced position.
Advantageously, the holders have at the upper part of their
segment-like cross-section abutment shoulders which act as
abutments against the upper edge of the ribs of the upper part of
the pen.
In both of the above embodiments of the writing instrument there is
provided a tip projection sleeve which is subject to the action of
a return spring and has an upper collar as a counter-support for
the return spring. The other end of the return spring is supported
on an annular ledge on the front of the pen. Advantageously, the
tip projection sleeve is so formed that it has a conical portion
extending around an opening, which conical portion serves as a
counter-support for the tips of the tubes. The diameter of the
opening is so dimensioned that it allows only one tube to pass
therethrough.
The tip projection sleeve and the pressure member may be
constructed as a one-piece projection part which is closed by a
closure knob, engagement ribs on the casing of the pen extending
through longitudinal slots in the projection part, and the return
spring being disposed within the projection part, and in particular
between the closure knob and the upper edges of the ribs. In this
case the engagement ribs extending through the longitudinal slots
in the projection part advantageously serve as catches for the ball
and also as guide ribs for the holders. The holders have segmental
sections which, when the holders are moved together to the same
axial height, form a chamber serving to receive the ball. The
engagement ribs are formed with different heights in the radial
direction and thereby form engagement edges behind which the ball
can engage in the free space between two adjacent ribs when the
holders are forwardly displaced, the ball being supported at its
other side on the engagement edge of the corresponding holder.
Since the axial slots of the projection member extend to the upper
end, where a ring is provided in an annular groove and retained by
a threaded closure knob, the securing of the ring clip is
advantageously effected between the closure knob and the end of the
projection part or the ring.
Illustrative embodiments of the invention will now be described
with reference to the accompanying drawings, in which:
FIG. 1 shows a longitudinal section through a four-color
retractable ball point pen having a pendulum arrangement for color
selection;
FIG. 2 shows a cross-section through the pen of FIG. 1 taken along
the section line II--II;
FIG. 3 shows a cross-section through the pen of FIG. 1 along the
section line III--III;
FIG. 4 shows a longitudinal section through the pen of FIG. 1, in
which all four tubes are forwardly displaced;
FIG. 5 shows a cross-section taken along the section line V--V of
FIG. 4;
FIG. 6 shows a cross-section taken along the section line VI--VI of
FIG. 4;
FIG. 7 shows a longitudinal section through the pen of FIG. 1 but
with a pre-engaged ink tube;
FIG. 8 shows a cross-section taken along the section line
VIII--VIII of FIG. 7;
FIG. 9 shows a cross-section taken along the section line IX--IX of
FIG. 7;
FIG. 10 shows a view from underneath of the retainer member
carrying the pendulum of the pen shown in FIG. 1;
FIG. 11 shows a longitudinal section of retainer member shown in
FIG. 10 with the pendulum broken away;
FIG. 12 shows a view from above of the retainer member shown in
FIG. 10;
FIG. 13 shows a tube holder in cross-section along the section line
XIII--XIII of FIG. 14;
FIG. 14 shows a longitudinal section through the tube holder shown
in FIG. 13;
FIG. 15 shows a view from above of the tube holder of FIG. 13;
FIG. 16 shows a cross-section through the tip projection
sleeve;
FIG. 17 shows the tip projection sleeve of FIG. 16 viewed from
above;
FIG. 18 shows a longitudinal section through a four color ball
point pen with ball engagement;
FIG. 19 shows a cross-section through the pen of FIG. 18 along the
section line XIX--XIX;
FIG. 20 shows a cross-section through the pen of FIG. 18 along the
section line XX--XX;
FIG. 21 shows the pen of FIG. 18 with all four tubes in their
forwardly displaced positions;
FIG. 22 shows a cross-section taken along the section line
XXII--XXII of FIG. 21;
FIG. 23 shows a transverse section taken along the section line
XXIII--XXIII of FIG. 21;
FIG. 24 shows the pen of FIG. 18 but with a pre-engaged ink
tube;
FIG. 25 shows a transverse section taken along the section line
XXV--XXV of FIG. 24;
FIG. 26 shows a cross-section taken along the section line
XXVI--XXVI of FIG. 24;
FIG. 27 shows the upper part of the writing instrument of FIG. 18
in longitudinal section;
FIG. 28 shows the upper part shown in FIG. 27 viewed from
above;
FIG. 29 shows a view from below of a tube holder;
FIG. 30 shows the tube holder of FIG. 29 in longitudinal
section;
FIG. 31 shows a cross-section taken along the section line
XXXI--XXXI of FIG. 31;
FIG. 32 shows a longitudinal section through a tip projection
sleeve;
FIG. 33 shows the tip projection sleeve of FIG. 32 viewed from
above;
FIG. 34 shows a longitudinal section through a modified embodiment
of the four color ball point pen employing a ball for color
selection;
FIG. 35 shows a transverse section through the pen of FIG. 34 along
the section line XXXV--XXXV;
FIG. 36 shows a transverse section through the pen of FIG. 34 along
the section line XXXVI--XXXVI;
FIG. 37 shows a longitudinal section along the section line
XXXVII--XXXVII of FIG. 35 with the projection sleeve in its
forwardly displaced position;
FIG. 38 shows a cross-section taken along the section line
XXXVIII--XXXVIII of FIG. 37;
FIG. 39 shows a cross-section taken along the section line
XXXIX--XXXIX of FIG. 37;
FIG. 40 shows a longitudinal section through the four color ball
point pen with a pre-engaged ink tube;
FIG. 41 shows a cross-section taken along the section line XLI--XLI
of FIG. 40;
FIG. 42 shows a cross-section through the pen of FIG. 40 taken
along the section line XLII--XLII;
FIG. 43 shows a longitudinal section through the casing of the
writing instrument;
FIG. 44 shows a view from below of the casing of FIG. 43;
FIG. 45 shows a tube holder viewed from below;
FIG. 46 shows the tube holder of FIG. 45 in front elevation;
FIG. 47 shows the tube holder of FIG. 46 viewed from above;
FIG. 48 shows the tube holder of FIG. 46 in side view;
FIG. 49 shows the closure button in side elevation;
FIG. 50 shows the slip-on ring in longitudinal section;
FIG. 51 shows the projection part formed in one piece with the
pressure member in longitudinal section; and
FIG. 52 shows a view from above of the projection part of FIG.
51.
Referring now to FIGS. 1 to 17 there is shown a writing instrument
which includes:
a. A two-part ball point pen casing 1, 2 having a retainer member 8
which is slidable relative thereto and which carries a pendulum pin
9;
b. Four tube holders 7, which are guided axially relative to and in
the retainer member 8;
c. A pressure member 4 formed as a press button which is
displaceable relative to the casing 1, 2;
d. A tip projection sleeve 3 subject to the action of a return
spring 12 and displaceable relative to the casing 1, 2; and
e. Four writing members in the form of ball point pen ink tubes 11
which are comparatively long and of four different colors.
The pressure member 4 is in the form of a hollow knob and, when
depressed, presses with its under edge against all four tube
carriers. The hollow pressure member 4 is prevented from falling
out by a threaded bush 5 which also retains a ring clip 6 in the
normal manner. The tip projection sleeve 3 is axially displaceably
inserted into the front part 2 of the ball point pen casing. A
return spring 12 seated at one end on the front edge of the front
part 2 and at its other end on a collar 3a on the tip projection
sleeve 3 ensures that the tip projection sleeve 3 is resiliently
returned. The retainer member 8 is prevented from being axially
displaced by ribs 8" in the casing. The lower ends of the ribs 8"
are disposed at the height of an abutment edge 1' on the retainer
member 8. The under-edge 5' of the threaded bush 5 serves as an
upper limit for the ribs 8". By means of curved lateral guide
surfaces 8' on the retainer member 8, it is ensured that the tube
holders 7 are properly guided during their axial movement. In the
lower part of the retainer member 8, by means of an insert ring 10,
the pendulum pin 9 is movably held so that it can pivot to any side
laterally or in the radial direction.
Each tube holder 7 is so constructed that it is readily axially
displaceable relative to the retainer member 8. It has a
segment-like recess 7c. The segment-like recesses of the holders 7
define, when the holders 7 are all in the same axial position, a
cylindrical recess 7c' (FIG. 4). An ink tube is inserted in the
usual manner into a cylindrical recess 7b in each holder 7 and
there retained. An engagement edge 7a serves for retaining the
holder 7 in the forwardly displaced position by means of the
pendulum pin 9 swung in the radial direction and engaged in this
position behind this edge. An edge 7d serves as an upper abutment
on the holder against an abutment edge 1" on the retainer member
8.
By pressure on the pressure member 4, all four holders 7 with the
ink tubes 11 are moved forwardly together, the tips of the ink
tubes 11 pressing against inclined edges 3' on the tip projection
sleeve 3 which extend inclined in the direction towards a central
opening which is provided at the lower end of the tip projection
sleeve 3 and which allows only one ink tube to pass therethrough.
In this way, the tip projection sleeve 3 is simultaneously shifted
against the action of the return spring 12 from the casing front
part 2, as shown in FIG. 4. If the writing instrument is now held
at an angle, then the pendulum pin 9 is pivoted sideways in a
radial direction so that the free end of the pendulum pin 9 engages
behind the engagement edge 7a of the holder 7 of the required ink
tube 11'. When the pressure on the pressure member 4 is released,
the remaining three tubes 11 are moved back from the tip projection
sleeve 3, retaining their axial orientation, by the action of the
return spring 12, while the selected tube retained in the forwardly
displaced position by the free end of the pendulum pin is prevented
from moving backwardly and, during the rearward movement of the tip
projection sleeve 3, presses its tip over the inclined surface 3'
downwardly and through the opening in the tip projection sleeve 3.
The pen now has the required last-mentioned ink tube in its
position of use.
By rotating the pen into a different inclined position a different
color can be selected. By pressure on the pressure member 4 the
holders 7 in the reserve position and the tip projection sleeve 3
are again moved into the forwardly displaced position, where they
are at the same height as the tube previously located in the
writing position, the tip of which is now drawn back through the
opening and disposed above the inclined edge 3'. The pendulum pin
is released and can swing, in accordance with the newly selected
inclined position of the pen, behind the engagement edge 7a of the
holder 7 of the newly selected ink tube 11 and there engage. The
return operation is then effected in the above-described
manner.
If it is desired to bring all four tubes 11 into the rearward rest
position shown in FIG. 1, then with the pen held upright and with
pressure on the pressure member 4, all four holders 7 and the tubes
11 are moved into the forwardly displaced position and in this way
the pendulum pin previously engaged behind one of the tubes is
released. The pendulum pin 9 swings in the space above the
cylindrical recess 7c' formed by the segment-like recesses 7c. When
the pressure on the pressure member 4 is released, all four tubes
are returned by the returning tip projection sleeve 3 into their
initial positions (FIG. 1).
The writing instrument shown in FIGS. 18 to 33 includes:
a. A two-part casing 13, 14;
b. A pressure member 16, which acts on four holders 19, which have
ink tubes 21;
c. A selector ball 20; and
d. A tip projection sleeve 15, which is axially displaceably
disposed in the front part of the casing and which, analogous to
the tip projection sleeve 3, is subject to the action of a return
spring 22. The pressure member 16, which is formed as a press
button, is prevented from falling out by a threaded sleeve 17,
which also retains the clip 18.
In the casing upper part 13, corresponding to the four holders 19,
there are provided four stepped ribs 13', 13", which serve both to
guide the holders 19 and also as engagement edges for the selector
ball 20.
The holders 19 have segment-like recesses 19k which, when the
holders are disposed in the same axial height, define a cylindrical
space 19k'. The lowermost edges 19a of these recesses 19k are
preferably formed inclined as engagement edges for the ball 20. The
tubes 21 are fixed in known manner to the holders 19 by pins 19"
and longitudinal grooves can be provided in the pins 19" for better
ventilation of the tubes. At the upper ends, abutment edges 19' are
advantageously provided, which limit the forward movement by
abutment against the ribs 13'.
The tip projection sleeve 15 is constructed similarly to that in
the preceding embodiment, but in this case has a somewhat greater
length. Also, in this case, an upper collar 15a is provided for
abutment of the return spring 22. Moreover, the conical support
surface for the tips 21" of the ball point ink tubes 21 is provided
in the front part of this tip projection sleeve 15.
By pressure on the pressure member 16, all four holders 19 with
their tubes 21 are brought into the forwardly displaced position,
the selector ball 20 lying within the cylindrical space 19k' formed
by the segment-like recesses 19k in the holders 19. At the same
time, the tip projection sleeve 15 is displaced forwardly against
the action of the return spring 22. In this forwardly displaced
position, by inclination of the pen, the selector ball 20 is
deflected sideways so that it comes to lie within the holder of the
selected color between the engagement edge 19a and the step formed
between the ribs 13' and 13". When the pressure on the pressure
member 16 is released, by means of the tip projection sleeve 15
under the action of the return spring 22, the remaining three tubes
are moved backwardly, while the selected tube 21' remains in the
forwardly displaced position and projects from the opening of the
tip projection sleeve 15. In this way, the pen is brought into
readiness for use as shown in FIG. 24. If the pen is rotated into a
new inclined position and the pressure member 16 is pressed, then
the selector ball 20 can move into the corresponding chamber 19k of
the newly selected tube, whereby after return of the remaining
tubes the new tube remains in the writing position.
By holding the pen erect and releasing the pressure on the pressure
member 16, the selector ball can return in the axial direction. It
then comes to lie between the four ribs 13", whereby the initial
position shown in FIG. 18 is reached.
The advantages obtained by the present pen in particular are that
the construction of the pen is comparatively simple, and the same
elements are used for the devices for color selection and for
engaging the selected color, whereby a comparatively short
construction is obtained which enables correspondingly long ink
tubes to be employed. Moreover, both the production and the
assembly of the pen are substantially simplified so that the pens
can be manufactured comparatively inexpensively.
The multiple color ball point pen shown in FIGS. 34 to 52
includes:
a. A writing instrument casing 25 with ribs 26 and 27;
b. A projection part 28 which is formed in one piece with the
pressure member and which is closed by means of a closure button 29
with a slip-on ring 30 therebetween;
c. Four ink tube holders 31 with segment-like recesses 32 which,
when all of the holders 31 with segment-like recesses 32 which,
when all of the holders are moved together to the same axial
height, define a chamber 33;
d. A selector ball 34 in the chamber 33;
e. Four ink tubes 35 having ball points 36; and
f. A return spring 37 which is arranged within the projection part
28 and which is supported between the closure button 29 and the rib
upper edge 38.
FIG. 34 shows the multiple color ball point pen in its initial
position with the ink tubes 35 retracted. In this initial position
the tip projection sleeve 28 is retracted and the four tube holders
31 are located in an upper rest position, this position being
defined by abutment of the lower edges of slots 39 in the tip
projection sleeve 28 against the lower edge of engagement ribs 26
extending through longitudinal slots 39 in the projection part 28
under the action of the return spring 37. The selector ball 34 is
disposed in the chamber 33 formed by segment-like recesses 32 in
the holders 31.
If, as shown in FIG. 37, the projection part 38 is now moved
forwardly against the action of the return spring 37 by pressure on
the closure button 29, then both the holders 31 with their tubes 35
and also the selector ball 34 are moved axially.
In the furthest forward position, due to inclination of the writing
instrument, gravity affects the selector ball 34. The ball 34 rolls
sideways under rib edges 40 within the segment-like recesses 32 in
the selected holder 31. On release of the pressure on the closure
button, and as a result of the action of the return spring, the
projection part 28 with the three remaining tubes and their
associated holders are pressed backwardly in the manner described
in the other embodiment, while the selected ink tube remains in the
forwardly displaced position, i.e., in the writing position, and
therefore projects through the opening which is provided in the
projection part 28 and which can receive only one ink tube.
By pressure on the closure button 29, the position shown in FIG. 37
is again obtained. By corresponding inclination of the pen, the
newly required ink tube can be selected.
The return of the ink tubes into the initial position as shown in
FIG. 37 is brought about by holding the multiple color ball point
pen vertically as shown in FIG. 37, whereby the selector ball 34
remains in its central position, and on return of the projection
part 38, all four ink tubes are retracted until the position shown
in FIG. 34 is again obtained.
41 indicates inclined internal conical surfaces, already known from
the above-described embodiments, which converge downwardly to the
opening 42. As in the above-described embodiment the diameter of
the opening 42 is so dimensioned that only one ink tube 35 can pass
therethrough.
43 indicates a clip retained by the closure button 29.
44 indicates ink tube holder pins projecting into the open ends of
the ink tubes and fixed or formed on the tube holders. The inclined
surfaces 45 on the holders 41 correspond to the inclined surfaces
19a, and the pins 44 to the pins 19" of FIG. 31.
Each pin 44 is provided with a groove 46 for ventilating the tubes
35.
The advantages obtained by the present pen are, in particular that
the construction of the pen is comparatively simple, and the
incorporation of the return spring 37 in the upper part of the
projection part makes possible a particularly slim shape for the
writing instrument. Moreover, the production and assembly of the
pen are very simple, so that the pens can be manufactured
comparatively inexpensively.
* * * * *