Writing instrument

A writing instrument with an advance-retract mechanism is operable by rotation of a knob opposite the writing tip. The knob rotates a shaft disposed in, and extending rearwardly from, the instrument body to advance and retract the writing tip when rotated. A retainer member has a first cylindrical portion with a plurality of inwardly extending tangs into which the shaft is received and a larger cylindrical portion having a surface directed toward the instrument body.

BACKGROUND OF THE INVENTION 
The present invention relates to writing instruments in general, and more 
particularly to a writing instrument having a mechanism for advancing and 
retracting the writing tip of the instrument wherein the mechanism is 
actuated by rotation of a knob disposed at the non-writing end of the pen 
barrel. 
Various writing instruments such as pencils or ball point pens are known in 
the art wherein the writing tip is advanced or retracted relative to the 
barrel by means of rotating or pushing the external element on the barrel 
of the instrument. Typical of such advance-retract devices are to be found 
in U.S. Pat. No. 3,679,318, issued Jul. 25, 1972, to Thomas A. Liguori; 
U.S. Pat. No. 4,290,706, issued Sep. 22, 1981, to Tatsuo Ariga; U.S. Pat. 
No. 4,786,197, issued Nov. 22, 1988, to Harold E. Koeln et al.; French 
patent 1004813, published Apr. 3, 1952, in the name of Poursier; and 
British patent specification 934160, published Aug. 14, 1963, in the name 
of Ronald Hare. These, as well as other devices have been disclosed, and 
many mechanisms of this type have been produced, and have met with 
commercial success. 
One such device is disclosed in co-pending U.S. patent application Ser. No. 
08/107,519, filed Aug. 17, 1993, in the name of William B. Tucker, and 
assigned to The Gillette Company now U.S. Pat. No. 5,342,135. In that 
application, a writing instrument is provided that includes an 
advance-retract mechanism serving to project the writing tip from within 
the barrel for employment of the writing instrument, and to retract the 
tip to a point within the barrel when the writing instrument is not in 
use. A plunger assembly includes a rotatable knob which is disposed at the 
rear of the barrel and is interconnected to a finger which contacts a cam 
surface of a slidable actuator. Rotation of the knob in one direction 
advances the writing tip from within the barrel, and opposite rotation of 
the knob is effective to retract the writing tip into the barrel. 
While the structure disclosed in the above-referenced application has 
proved successful in accomplishing its various objectives, it is 
considered that improvement of the knob attachment to the shaft of the 
plunger assembly may be accomplished by more firmly fixing the connection 
between the rotating knob assembly to the rotating shaft of the plunger 
assembly, while increasing the ease of rotation of the knob during the 
actuating process. 
It is therefore an object of the present invention to provide a writing 
instrument of the type described wherein the rotatable shaft portion of 
the actuating mechanism which extends into the rotatable knob is more 
firmly affixed to the knob while further providing a more easily rotatable 
knob for actuating the mechanism. 
A further object of the invention is to provide a retainer and bearing 
assembly which is mounted at the rear of the writing instrument barrel and 
is effective to firmly affix the shaft of the advance-retract mechanism 
onto the barrel while providing for ease of rotation of the actuating 
knob. 
A further object of the invention is to provide, in an alternative 
embodiment, a retainer which is mounted at the rear of the writing 
instrument barrel and is effective to firmly affix the shaft of the 
advance retract mechanism onto the barrel while providing for ease of 
rotation of the actuating knob, without the use of a bearing assembly. 
SUMMARY OF THE INVENTION 
The above objects and other objectives which will become apparent as the 
description proceeds are accomplished by providing a writing instrument 
having a barrel and an advance-retract mechanism actuated by rotation of a 
knob disposed at the rear of the instrument barrel opposite the writing 
tip. The shaft extends rearwardly from within the barrel to receive the 
knob for rotation of said shaft, the shaft being effective to advance and 
retract the writing tip when so rotated. A retainer member having a first 
cylindrical portion enveloping the shaft and a plurality of rearwardly 
inwardly extending tangs contacts the surface of the shaft. The retainer 
member has a second cylindrical portion disposed forwardly of the retainer 
first cylindrical portion which has a forward facing surface in spaced 
relation with a rearwardly facing end surface of the barrel. Biasing means 
is provided to force the retainer member rearwardly, and is disposed 
between the second cylindrical portion forward facing surface and the rear 
surface of the barrel. The biasing means is effective to force the tangs 
into the shaft and also provides a bearing surface between the retainer 
member and the barrel. 
The biasing means disclosed herein comprises a unitary bearing member, the 
bearing member having a cylindrical body through which the shaft extends 
and having a surface contacting the end surface of the barrel. A radially 
outwardly extending flange is disposed on the bearing member for 
contacting the forward facing surface of the retainer member. 
The unitary bearing member is generally formed of a resilient plastic 
material and the radially outwardly extending flange is compressible 
between the end surfaces of the barrel and the forward facing surface of 
the retainer member, causing the biasing action to force the tangs into 
the shaft. The shaft is generally formed of plastic and the retainer 
member is formed of a metallic material to provide the locking action 
between the retainer and the shaft when the metallic tangs are forced into 
the plastic shaft. 
In an alternative embodiment the biasing means maybe deleted from the 
apparatus, thereby eliminating one piece from and simplifying the assembly 
process.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawing, and particularly to FIG. 1 there is shown a 
writing instrument 10 in the form of a ball point pen having an elongated 
writing assembly 12 disposed in a barrel 14. The various elements and the 
function of the writing assembly 12 are disclosed in the aforementioned 
U.S. Pat. No. 5,342,135, and therefore will not be explained in detail in 
the present disclosure. It should however be understood, that the present 
invention is not limited to those elements of the writing assembly as 
shown, but may be employed with any of a number of writing assemblies 
which are actuated by rotation of a shaft carrying external knob, or other 
device. 
As shown and described in the aforementioned Tucker Patent, the actuating 
member comprises a shaft 16 as shown in FIG. 2, having a portion extending 
into the barrel 14, and a portion extending through an opening in the 
barrel for access by the user to rotate the shaft and thereby cause a 
finger 18 to manipulate those elements of the writing assembly 12, and 
move the writing tip into and out of the barrel 14. 
Referring still to FIG. 1, taken with FIGS. 2 through 4, the barrel 14 has 
an opening 20 through which the shaft 16 extends, and a rivet 22 extends 
into the opening 20 having a planar surface 23 and a portion 24 which is 
peened over to encapsulate a clip 25. As best shown in FIG. 1, the shaft 
16 extends outwardly through the opening 20 to a point at which a shoulder 
26 of the shaft contacts the surface 22 of the rivet. 
While the interface of the shoulder 26 of the shaft 16 with the peened 
portion 24 of the rivet is effective to retain the shaft from rearward 
movement, it is necessary to provide means for clamping the shaft in place 
such that it is held from movement either forwardly, or rearwardly, and 
yet is allowed to rotate freely for actuation of the writing assembly 12. 
Referring now to FIGS. 5 through 10 there is shown a novel retainer 28 and 
bearing 30 which combine to achieve both the clamping action, and produce 
the ease of rotation desired in the assembly. 
Referring particularly to FIGS. 5, 6 and 7 taken in conjunction with FIG. 1 
the retainer 28 is shown to comprise a first cylindrical portion 32 which 
is of a size to substantially envelope the shaft 16 when inserted therein, 
and three inwardly extending tangs 33 which project inwardly to contact 
the shaft in interfitting engagement with the outer surface of the shaft. 
A second cylindrical portion 34, of larger diameter than the cylindrical 
portion 32, is disposed forwardly of the portion 32 and comprises a 
forward facing surface 36 with the retainer mounted as shown in FIG. 1, 
the surface 36 being disposed in spaced relation with the barrel 14 which 
has the rivet 22 set in place. It is well to note that the cylindrical 
portion 34 substantially forms a cup for retaining the bearing 30, however 
the forward edge of the retainer cylindrical portion 34 lies outside of 
the peened portion 24 of the rivet, thereby allowing only the bearing 30 
to provide rotatable surfaces between the barrel 14 and the surface 36 of 
the retainer 28. 
With reference to FIGS. 8 through 10 the bearing 30 is of unitary 
construction and comprises a cylindrical body 38 through which the shaft 
16 extends and a planar surface 40 which contacts the barrel 14 at the 
portion 24 of the rivet 22. A radially outwardly extending flange 42 is 
provided with a planar bearing surface 44 for contacting the forward 
facing surface 36 of the retainer 28. It will further be noted that the 
flange 42, in addition to extending radially outwardly, is canted 
rearwardly to in effect form a spring-like or biasing effect when 
compressed between the surface 36 of the retainer 28 and the barrel 14. 
In the construction of FIG. 1, both the shaft 16 and the bearing 30 are 
manufactured of a resilient plastic material such as acetal. The retainer 
28 is manufactured of a metallic material such as brass or the like, to 
provide tangs 33 which will pierce and enter the surface of the shaft 16 
when forced rearwardly by the biasing action of the flange 42 of the 
bearing 30. 
Referring now to FIG. 1 taken in conjunction with FIGS. 11 through 14 a 
knob 46 is provided at the rearwardmost end of the shaft 16 for rotation 
of the shaft to actuate the writing assembly 12. The elements of the knob 
46 comprise a sleeve 48 and cap 50 the sleeve 48 being manufactured of a 
resilient plastic material and the cap 50 being formed of a metallic 
material. The sleeve 48 is provided with 4 inwardly directed projections 
52 having arcuate surfaces which are spaced to provide an engagement with 
the rearwardmost end of the shaft 16. The sleeve 48 further has four 
outwardly projecting blocks 54 which extend outwardly from the body of the 
sleeve 48. As best shown in FIG. 14 the cap 50 is a tubular member and has 
four slots 56 formed therein and positioned to receive the blocks 54 
therein, the cap aiding to retain the resilient sleeve 48 into 
interfitting engagement with the shaft 16 when the cap is in place. 
In an alternative embodiment of the invention the biasing member i.e. 
bearing 30 is eliminated. Referring now to FIGS. 15-19, elimination of the 
bearing 30 (FIG. 1 ) eases the assembly operation of the cap 50A, knob 46A 
and retainer 28A onto the shaft 16A. Since the bearing 30 has been 
eliminated, such that there is no longer an imposed force acting from the 
tang 33A to the shaft 16A, the tangs 33A are redesigned to engage the 
shaft in a more aggressive manner. Comparing the original tang design 
(FIG. 5, FIG. 7) with the revised tang design (FIG. 18 and FIG. 19) it can 
be seen that the new tang 33A includes a chevron side A 82 and a chevron 
side B 84 which merge at a chevron side A, B junction 86. The chevron's 
82, 84 are forced sufficiently downward from the surface of the first 
cylindrical portion 32A of the retainer 28A, such that a definite tang 
opening 88 is formed between the exterior and interior surfaces of the 
retainer 28A. 
The retainer 28A, as before includes the forward facing surface 36A, the 
retainer second cylindrical portion outer surface 78, and the second 
cylindrical portion 34A. 
The shaft 16A as before includes a shoulder 26A and a main shaft shoulder 
72, but also includes tang shoulder 70, and centralizer shoulder 74. The 
centralizer shoulder 74 is of smaller outer diameter than the tang 
shoulder 70, the tang shoulder 70 being of smaller outer diameter than the 
main shaft shoulder 72. The outer diameters of the shoulder 74, and 70 are 
selected such that the retainer 28A may first be centralized relative to 
the shaft 16A during assembly over the shaft 16A. As the assembly 
progresses, the tangs 33A drag over and securely engage with the tang 
shoulder 70, preventing the cap from being withdrawn from the shaft. The 
tang shoulder 70 in one embodiment has an outer diameter slightly less 
than the adjacent main shaft shoulder 72. It should be well understood 
that the tang shoulder, depending on the design of the tangs, may have an 
outer diameter equal to, or even greater than the main shoulder 72. 
Additionally, though the tangs are shown in FIG. 18 located centrally from 
either end of the first cylindrical portion, they may be located toward 
either end of the first cylindrical portion, so as to cooperate with the 
tang shoulder 70. 
As can be seen from the new FIGS. 15-19, the second cylindrical portion 
outer surface 78 engages in an interference fit with the cap inner surface 
76. The engagement force of the cap inner surface with the second 
cylindrical portion outer surface is designed to exceed the engagement 
force of the tangs with the centralizer shoulder and the tang shoulder, 
such that the cap remains fixed relative to the retainer when the tangs 
are engaged with the tang shoulder. In other words, during assembly, the 
knob 46A is first inserted into openings in cap 50A, and the retainer 28A 
is thereafter inserted into the cap 50A. The retainer 28A remains fixed 
relative to the cap 50A, by strong interference fit, even while the tangs 
are dragged upwardly over the centralizer shoulder and the tang shoulder. 
The selection of tang geometry, tang shoulder and centralizer shoulder 
dimensions, and the strength of the interference fit between the retainer 
28A and cap 50A are such to create a strongly secured cap, retainer and 
knob system on the end of the shaft 16A. 
As can be seen from the drawings, inward motion of the shaft is prevented 
by the cap striking the end of the pen barrel 14A. 
While it is apparent that changes and modifications can be made within the 
spirit and scope of the present invention, it is our intention, however, 
only to be limited by the appended claims.