US3318289A

US3318289A - Bi-stable mechanism

Info

Publication number: US3318289A
Application number: US454778A
Authority: US
Inventors: Marynissen William
Original assignee: NORTHERN IND PRODUCTS
Current assignee: NORTHERN IND PRODUCTS
Priority date: 1965-05-11
Filing date: 1965-05-11
Publication date: 1967-05-09
Anticipated expiration: 1984-05-09

Description

y 9, 1967 w. MARYNISSEN 3,318,289

BI-STABLE MECHANISM I Filed May 11, 1965 4 Sheets-Sheet 1 mm mm 3 mm g w mm QW INVENTOR WILL/AM MARYlV/SSEA/ I i T IA! If 4. 1 3 mm w W AV mm 3 WM W WW mm mm ww g am it 6%,;

ATTORNEYS y 1967 w. MARYNISSEN 3,318,289

BI-STABLE MECHANISM Filed May 11, 1965 4 Sheets-Sheet 5 66 74 72 FIG. 5

92 88 '05 INVENTOR 92 WILL/AM MARY/V/SSE/V ATTORNEYS y 1967 w. MARYNISSEN 3,318,289

BI-STABLE MECHANISM Filed May 11, 1965 4 Sheets-Sheet 4 INVENTOR WILL/44M MARY/WJ'SE/V ATTORNEYS United States Patent corporation of New Jersey Filed May 11, 1965, Ser. No. 454,778 9 Claims. (Cl. 120-42.03)

This invention relates to bi-stable mechanisms and more particularly to writing instruments which employ bi-stable mechanisms to constitute protract-retract devices.

It is generally an object of this invention to provide improved writing instruments although, as will become apparent hereinafter, the advantages and features of the invention are applicable in various other types of mechanisms in which bi-stable devices are employed.

Generally the invention contemplates the conversion of an axially applied force into a rotary motion which is employed to direct a controlling element into one of two operative positions, a writing element being moved to extended or retracted positions in accordance with which of the operative positions the controlling element assumes.

The general provisions which have been outlined above have previously been employed in writing instruments. However, among various disadvantages which are inherent in known instruments of this type is the disadvantage that a spring member is employed which bears against a rotating element and consequently causes a comparatively rapid deterioration of the same. Accordingly, it is an object of the invention to provide an improved writing instrument of the above noted type wherein a spring or resilient element is employed, but in which such spring is not brought to bear against a rotatable element. Moreover, as will be shown, the invention achieves this particular advantageous relationship without the use of special hearings or other costly or complicated devices.

A further disadvantage of the writing instruments of the above noted type, as well as of other types, is that they are so constructed that the bi-stable device incorporated therein includes operative portions supported in separable casing sections such that the elements can become detached and possibly lost when the casing sections are detached to permit, for example, replacement of the ink cartridge therein. In this respect, it is another object of the invention to provide an improved writing instrument of the above noted type constructed With separable casing sections but wherein the bi-stable mechanism is supported in entirety in one of the casing sections so that detachment of the casing sections for any reason whatsoever cannot possible result in the loss of any of the components of the bi-stable mechanisms.

Advantageously, as will be seen hereinafter, the arrangement of the bi-stable mechanism as aforesaid permits the same to be assembled in entirety and tested without the need for entirely assembling the writing instrument at the same time. Thus, for example, in the manufacturing of ball point pens with protract-retract mechanisms it is possible, in accordance with the invention, to assemble completely the bi-stable mechanism in one of the casing sections without assembling therewith the ink cartridge and a possibly accompanying spring. It will be appreciated that this represents a material savings and improvement in assembly time and efficiency.

According to a further feature of the invention, it is possible to avoid the use of springs which encircle ink cartridges adjacent the writing ends thereof, for it is an object of the invention to incorporate such resilient loading means as may be necessary within the bi-stable device itself for purposes of simplification. This has the very important advantage of increasing the space available to the ink cartridge inasmuch as such space was formerly restricted by the housing of spring elements therein. Accordingly, in line with the teachings of the invention, it is possible to employ ink cartridges of increased capacity.

In previously designed protract-retract mechanisms of the specific type with which the invention is concerned,

there have sometimes been provisions in accordance with which positive control over the various elements is not exerted at all times therefore creating a hiatus in the control during which uncontrolled movements of certain of the elements are possible. It is, however, a further object of the invention to provide an improved mechanism wherein a positive control is exerted over the entire working cycle, as will appear in greater detail hereinafter.

Yet another object of the invention is to provide improvements pertaining to ink cartridges and the like and in accordance with which such ink cartridges are frictionally imparted a rotating motion each time they are moved between extended and retracted positions and/or vice-versa. This is an important aspect of the invention, for it exposes different portions of the writing point to wear rather than concentrating such wear at a single zone of the writing point which would, as a result, rapidly deteriorate.

According to still a further feature of the invention there is contemplated a threaded member adapted for connecting the casing sections of a writing instrument while at the same time serving as a base for the protractretract mechanism and more particularly for any spring component utilized therein.

Y Still another feature of the invention relates to improved provisions for the accommodation and operation of a plunger mechanism conventionally employed in pens of the above noted type by means of which the plunger assumes certain fixed positions which will indicate whether the writing point of the pen is retracted or extended. This is particularly of interest where the writing point is concealed (e.g., such as when the writing point is within the interior of a pocket of the user). This provision, as will be seen hereinafter, has the additional advantage of providing for the constitution of an anti-rattle plunger.

Yet another object and feature of the invention relates to the provision of a click-type operation which assures the user that the mechanism is functioning properly and has not been damaged nor excessively worn.

In accordance with the above objects and advantages there is contemplated, in accordance with one embodiment of the invention, a bi-stable apparatus comprising a tubular section provided with a plurality of equally spaced axially extending slots which open radially inwards while at the same time being open axially towards one end of the tubular section. Said section includes teeth arranged between these slots which define receptacles between and of lesser axial extent than such slots. Further contema plated is a non-rotatable actuator slidable axially in the tubular section, there being employed resilient means such as a spring operating against the actuator towards said one end of the tubular section. In addition, there is employed a ratchet within the section and including axially extending radial projections sandwiched between the actuator and said teeth, these radial projections being alternately accommodated in the slots and receptacles respectively to constitute first and second working positions. Moreover, the actuator and ratchet have cooperating cam faces, there being means to act on the ratchet to bring the cam faces into engagement whereby the ratchet is rotated and the radial projections thereon are displaced for selective seating in the receptacles and slots to cause the assuming of one of said working positions.

Other. objects and features of the invention, as well as advantages thereof, will become apparent from the following detailed description of a preferred embodiment as illustrated in the accompanying drawings in which:

FIGURE 1 is a full length view of a ball point pen, partially broken away and partially in hidden view, the writing point thereof being in retracted position;

FIGURE 2 is an enlarged view of the upper end of the pen ofFIG. 1 showing certain of the constructional details of the protract retract mechanism;

FIGURE 3 is an overall viewcorresponding to FIG. 1, but showing the writing point in extended position;

FIGURE 4 is a view coresponding to FIG. 2 with the various components adjusted to provide for extension of the writing point as in FIG. 3;

FIGURE 5 is a side view, partially broken away, of a sleeve employed in the protract-retract mechanism of the invention, said sleeve providing guide slots and cams controlling certain of the operations of the protract-retract mechanism;

FIGURE 6 is an end view of the sleeve of FIG. 5;

FIGURE 7 illustrates the cams and slots of the sleeve of FIGS. 5 and 6 shown in a fiat plane;

FIGURE 8 is a side view of a rotatable component employed in the protract-retract mechanism and the posi tion of which controls the position of the associated writing point;

FIGURE 9 is an end view taken from the left end of FIG. 8;

FIGURE 10 is an end view taken from the right end of FIG. 8;

FIGURE 11 is an end view of an actuator mechanism employed in the protract-retract mechanism of the invention;

FIGURE 12 is a sectional view taken along line XII- XII of FIG. 11;

FIGURE 13 is a side view of a plunger employed in accordance with the invention, the interior thereof being shown in hidden line; and

FIGURE 14 is a diagram corresponding to the illustra- :tion of FIG. 7 demonstrating how the various components of the bi-stable device ofthe invention co-act to produce the desired result.

The writing instrument illustrated in, FIGS. 1-4 comprises generally an elongated tubular casing 20 consisting of at least two

sections

22 and 24. and provided with a central bore 26 extending between the ends of said casing.

Section 22 constitutes one end portion of the writing instrument and is provided with an opening 28. Section 24 includes the opposite end portion of the writing instrument and is provided with an opening in which can, for exmple, be provided an insert 32.

Casing section 22 may consist of an appropriately formed metal wall 34, the extremity of which is turned in to constitute a retaining section36. Mounted on the section 22 in conventional manner may be a clip 38.

The

sections

22 and 24 are detachably connected sec tions which may, for example, be connected through the intermediary of a threaded element 40, some further purposes of which will be discussed hereinunder.

An ink cartridge 42 is housed within the casing 20 and almost in entirety lies within the casing section 22. Cartridge 42 constitutes a writing device or element andis exemplary of a number of utility dtvices which may usefully assume extended and retracted positions relative to an associated housing.

Cartridge 42 includes a Writing end or point 44 shown in extended or protracted position in FIG. 3 and in retracted position in FIG. 1. This cartridge also includes an interior end 46 which is engaged with the protractretra ct mechanism of the invention to be hereinafter described in greaterdetail.

It will be noted that there is no spring or the like within casing section 22, thereby freeing the entire interior of this section for occupation by the bulk of the ink cartridge 42. Therefore, ink cartridge 42 may be provided in as large a proportion as is consistent with the construction of casing section 22 without making provision for any additional element within this casing section. Therefore it is at once possible to provide larger and more eflicient ink cartridges in accordance with the invention than has generally been heretofore possible, while at the same time retaining the other benefits of the invention as will hereinafter appear.

The invention, as has been indicated above, contemplates the provision of a bi-stable mechanism, generally indicated at 48. In FIG. 1 said bi-stable mechanism is shown in condition for retracting the point 44, whereas in FIG. 3, the mechanism 48 provides for extending the point 44.

The protract-retract mechanism 48 generally comprises 'a ratchet 50, an actuator 52, a spring 54 and a plunger 56, the latter being provided with an end cup 58 preferably fabricated of metal and constituting a friction-fit element covering that part of the protract-retract mechanism which protrudes outwardly through the opening 28.

Generally speaking, an axial force exerted on the plunger 56 in the direction indicated by an arrow 60 in FIGS. 1 and 2 will be translated into a rotary movement of ratchet 50 which will operate to cause the ratchet 50 to assume one of two working positions under the influence of the spring 54 which working position will control whether the point 44 is extended or retracted.

The aforesaid action is controlled generally by the actuator 52 working in conjunction with another very important component of the protract-retract mechanism, namely a sleeve 62 which may be operatively disposed in fixed position within sleeve 34 or which may instead constitute itself the outer wall of the section 22 should it be desired to dispense with a metal cover.

Before a detailed explanation of the operation of the protract-retract mechanism will be possible, however, it will be essential to understand the various details of the construction of the components of the protract-retract mechanism as listed above.

One of the most important of these components is the sleeve 62 (which is fixed within the section 22 of FIGS. 2 and 4). Said sleeve is illustrated in detail in FIGS. 57. It consists preferably of a plastic tubular wall 64 having a central bore 66 extending completely therethrough. On the interior of said wall at a first diametral range D is a wall section 68 which defines a plurality of equally spaced slots 70 of equal length and corresponding disposition which open radially inwards and when considered relative to FIGS. 1 and 2 also open axially in the direction of the opening through which the point 44 is extended.

Said slots are provided equally spaced around the inner periphery of the wall and are formed by the axially extending spokes 72 having pointed ends 74 which facilitate the assembling of the apparatus but which do not otherwise perform an active part in the operation of the device.

At a second diametral range D is a second wall thickness or wall section 76 which provides a plurality of equally spaced slots 78 and between adjacent slots provides a pair of equally spaced

teeth

80 and 82 which constitute triangular or sawtooth shaped cam elements between the slots 78 and assist in performing a very important function as will hereinafter become apparent.

Between

teeth

80 and 82 is defined a recess, or as will hereinafter be referred to, a receptacle 84 having a particular relationship to the slots 78. Slots 78, which are all of equal axial extent and are equally spaced around the inner periphery of the wall 64 will be considered as having an axial extent L Relative thereto receptacles 84 have an axial extent L which is significantly smaller than the axial extent of said slots 78. The diiference between these two axial extents, as will hereinafter be shown in greater detail, constitutes the distance through which .5 the point 44 is displaced in moving between protract and retract positions.

Slots 70 also bear a particular relationship with slots 78 and receptacles 84, there being a number of slots 70 equal in magnitude to the total number of slots 78 and receptacles 84, one slot 70 being aligned with either a slot 78 or a receptacle 84. The purpose of this arrangement will be later explained although variation is permissible.

A second important component of the protract-retract mechanism is the ratchet 50, the details of which appear in FIGS. 8l0, said ratchet comprising a main body 86 having a first and hollow axial extension 88 and a second axial extension 90. As will be seen, extension 88 extends at least partly through the actuator 52 in the general direction of the-writing point 44 whereas extension 90 extends in opposite axial direction.

The main body 86 supports on the outer periphery thereof a plurality of radial projections 92 which extend axially along the ratchet and are equal in number to the number of slots 78 as appears in FIGS. and 7. Each radial projection 92 is a generally rectilinear element having

inclined end portions

94 and 96, whereof inclined end portion 94 constitutes an inclined segment of .a cam face cooperating with a cam face hereinafter described with reference to the actuator 52. End portion 94 may be inclined, for example, at an angle A of, for example, about 25. Inclined end portion 96 may be inclined, for example, at an angle B at about 45. Radial projections 92, in view of the aforesaid shape, may be considered as having a profile of generally trapezoidal shape.

Extending through the interior of axial extension 88 and perhaps the main body 86 of the ratchet is an interior bore 98 of generally cylindrical shape. This bore serves to accommodate the interior end 46 (FIGS. 14) of the related ink cartridge.

To provide for firmly engaging said interior end 46, there is provided on the interior of extension 88 an important feature of the invention constituted by three axially aligned ribs or ridges 100 which are equidistantly spaced around said interior in a common plane and which are of a particular profile and cross section.

As appears in FIG. 8, each rib has an elliptical cross section terminated in

points

102 and 104 located on the larger axis of the ellipse and each ridge is further provided with an .arcuate profile 106 which also appears in FIG. 8. This enables the cartridge to be grasped with essentially a point contact and in such a manner as enables the cartridge to be firmly and frictionally grasped so as to rotate with the ratchet 50 when the latter is rotated.

Extension 90 of the ratchet 50 is provided with an annular collar 108 adjacent an annular groove 110. The purpose of these provisions is to enable locking the plunger 56 thereto as will be shown in such a manner that the plunger and ratchet are locked together for common axial displacement whereas the ratchet is free to rotate relative to said plunger. In other words, when the ratchet 50 assumes one of the working positions indicated above, and to be discussed in greater detail hereinunder, the plunger 56 is locked to the ratchet and hence gives an external indication of the position of this ratchet and thus of the writing point 44. Moreover, the plunger 56 is not free to move about and thus provides an anti-rattle construction.

The actuator member 52 appears in detail in FIGS. 11 and 12 wherein this component is seen to be constituted by an annular ring 112 through which extends a central bore 114. It is through the bore 114 that the axial extension 88 of the ratchet 50 extends and to avoid interference with rotation of the ratchet the bore 114 is provided pref-t erably with a perfectly smooth cylindrical wall.

One end of actuator '52 is provided with a cup-shaped recess 116, the general purpose of which is to accommodate the corresponding end of the spring 54 (FIGS. 1-4). The other end of the actuator is a very important part of this element as it defines a cam face 118 6 which cooperates with the cam faces or end portions 94 of radial projections 92 on the ratchet 50.

The cam faces 118 are constituted by a plurality of isosceles triangles 120 having

equal sides

122 and 124. The relationship of these isosceles triangles with radial projections 92 of ratchet 50 (FIG. 8) will be made apparent hereinafter, and it will be pointed out that the isosceles triangles have their apices 126 located centrally relative to said radial projections 92 of the ratchet, there also being one isosceles triangle for each slot 78 and receptacle 84 (FIGS. 5 and 7) of the sleeve 62.

Actuator 52 includes a plurality of axially extending projections 128, these projections being accommodated in the slots 70 of sleeve 62 (FIGS. 5 and 7) and providing that the actuator 52 be axially displaceable within the sleeve 62 while being restricted against rotation therein, as well as in the casing section 22.

The details of the plunger 56 appear in FIG. 13. This plunger includes an interior bore 130 having an enlarged section 132 within which is accommodated the collar 108 (FIG. 8) of ratchet 50. The accommodation of said collar in said enlargement can be etfected simply by pushing these two elements together and this locks the ratchet and plunger together for common axial displacement or positioning while nevertheless permitting a relative rotative displacement therebetween. Said plunger includes a tapered end portion 134 facilitating the mounting therein of the cap 58 (FIGS. 1 and 3). The extension of bore 130 completely through the plunger emphasizes the flexibility thereof and assures cooperation with the cap 58 for frictional engagement of the same.

The various elements described above may be fabricated of a variety of materials. For example, the ratchet 50, the actuator 52 and the plunger 56 may be fabricated of a polyacetal copolymer or various other plastics may similarly be employed. The sleeve 62 may be, for example, a polycarbonate or cellulose propionate.

As has been generally indicated above, the ratchet comprises an extension 88 which is encircled by the actuator 5-2, these two components being movable relative to each other in both a rotational and axial sense. The plunger 56 is engaged with the ratchet 50 and while being rotatively displaceable relative thereto is locked to the ratchet in an axial sense. The radial projections 92 on the ratchet 50 are accommodated in slots 78 but can move therefrom to a position between

teeth

80 and 82 into receptacles 84. The projections 128 on the actuator 52 are accommodated in slots 78.

All of the aforesaid relationship appears in the planar view of the aforesaid elements diagrammatically appearing in FIG. 14 wherein the location of projections 128 in slots 70 is shown to vary in an axial sense, this taking place under the urging of the spring 54 and being limited by the corresponding permissible displacement of the ratchet 50 as more particularly is governed by the positions of projections 92. One such position 92A is shown for a given projection when accommodated in slot 78 and a second position 92B is indicated when the same projection has been rotatively displaced with the ratchet to displace the projection to the receptacle 84.

Stated otherwise, a projection 92 may assume position 92A in slot 78 in which event the point 44 will be retracted as indicated above, whereas the projection 92 may assume position 92B in which event the writing point 44 will be extended.

The technique by which the ratchet 50 is rotated will now be described with reference to FIG. 14 wherein appears the cam face 118 in position 118A and in position 118B, the actuator 52 being displaceable axially and continuously from one position to the other under the influence of plunger 56 and through the intermediary of the ratchet.

Since the apices 126 are positioned centrally of projections 92, the inclinations of these cam segments, when the ratchet 50 is urged against the actuator 52, will imactuator 52 which is urged thereagainst by the spring 54 sothat a positive control is maintained on the projections 92 at all times whereby an arbitrary movement of these projections and of the ratchet is avoided. This constitutes another of the features of the invention.

-At the same time it will be understood that the angles of inclinations of the

teeth

80 and 82 are greater than the angles of inclinations of the sides of the isosceles triangles 118 such that it will be assured that the projections will always come to rest fully seated in the receptacles 84 when located in these receptacles.

Since the cartridge 42 is fixed in the ratchet 52 the axial position of the ink cartridge will correspond to the axial positions of the projections 92. Accordingly, the two different positions indicated in FIG. 4 indicate the protract-retract positions of the writing point 44.

In addition, since the cartridge is fixed for rotation with the ratchet, as aforesaid the different rotative positions indicated for the projections 92 in FIG. 14 indicate different rotative positions for the cartridge and thus for the writing point 44. Accordingly, since the users of writing instruments normally align the same similarly for successive writing operations (such as by reference to the clip provided on the writing instrument) different exposures of the point to wear are virtually assured and wear of the point will be evenly distributed over the same.

It is to be pointed out that the

positions

92A and 92B in FIG. 14 illustrate the direction of movement of a single projection and all of the projections in fact move from left to right in FIG. 14.

As regards the spring 54, it will be noted in respect of FIGS. 2 and 4, that this spring is sandwiched between the threaded member 40 on the one hand and the actuator 52 on the other and is accommodated in the cupped recess 116 as indicated hereinabove.

From the above, it will be appreciated that the invention provides an improved bi-stable mechanism and, moreover, provides an improved writing instrument in which is employed a writing element housed in a casing wherein said bi-stable mechanism provides arotata-ble protractretract means engaged with the writing element and displaceable axially between first and second working positions whereat the writing element is extended or retracted, there being provided in addition resilient means for urging the protract-retract means toward one of the working positions. It will also appear that the actuator constitutes a non-rotative means sandwiched between the resilient means or spring 54'and the protract-retract means constituted by the ratchet 52 which is engaged and rotated by the actuator.

It will also appear from the above description that the ratchet constitutes a means exerting and constituting the sole source of axial force to act on the writing element to extend and retract the same.

From the above it will appear that the casing section 24 can be removed in entirety from the casing section 22 which houses the protract-retract mechanism so that the protract-retract mechanism can be assembled in entirety in section 22 and tested for operation independently of the remainder of the writing instrument assembly. At the same time it will appear that cartridge 42 can be coupled to the protract-retract mechanism independently of the casing section 24 and without the need for a spring element in the section 24 as was heretofore conventional in certain constructions. Accordingly, cartridge 42 may be replaced without fear of losing the accompanying spring since the only spring in the mechanism of the invention is fixed in place within casing section 22.

There will now be obvious to those skilled in the art many modifications and variations of the structure set forth above. These modifications and variations will not depart from the scope of the invention if defined by the following claims.

What is claimed is:

1. A writing instrument comprising a tubular casing, a non-rotatable, axially displaceable actuator in said casing, a rotatable and axially displaceable ratchet in said casing, spring means in said casing, said actuator directly engaging the spring means and being sandwiched between said spring means and said ratchet, means to force said ratchet against said actuator and to displace the ratchet and actuator together against the force of the spring means, said ratchet and actuator including cooperating means whereby the ratchet tends to rotate when forced against the actuator, position establishing means to hold the ratchet selectively in one of two axially spaced positions depending on the angle of rotation of the ratchet, and a writing element coupled to said ratchet and selectively extending from the casing depending on the axial position of the ratchet.

2. An instrument as claimed in claim 1, wherein said position establishing means includes means preventing rotation of said ratchet until the ratchet has been axially displaced against the force of the spring means by a predetermined amount.

3. Apparatus comprising a tubular section provided with at least two axially extending slots opening radially inwards and axially towards one end of said section, said section including teeth between said slots which define a receptacle between and of lesser axial extent than said slot, an actuator nOn-rotata'bly slidable in said section, resilient means in said section acting against said actuator from said one end, a ratchet within said section and lncluding an axially extending radial projection adapted for being sandwiched between said actuator and said teeth, said radial projection being alternate-1y accommodated in said slot in a first working position and in said receptacle in a second working position, said actuator and the ratchet having cooperating cam faces, and means to act on the ratchet and force said cam faces into cooperating relation; the radial projection on the ratchet being displaceable to a position free of the teeth and free of said slot with said cam faces engaged, engagement of the cam face rotating said ratchet to move the radial projection selectively between alignments with said receptacle and slot for selective seating therein under the urging of said resilient means.

4. A writing instrument comprising an elongated tubular casing including opposite ends provided with openings and being further provided with a central bore extending between said ends, an ink cartridge in said bore and adapted for being protracted and retracted through the opening in one of said ends, and a resiliently loaded protract-retract means in the casing and having connection with said cartridge to protract and retract the same;

said means including a sleeve fixed within said casingand defining in a first diametral range a plurality of equally spaced axially disposed slots opening radially inwards and axially towards said one end through which said cartridge is protracted and retracted, said sleeve defining in a second and smaller diametral range a plurality of equally spaced axially disposed slots opening radially inwards and axially towards said one end, the first said slots being located between the second said slots and said one end, said sleeve including pairs of saw-tooth shaped cam elements between the second said slots which elements define between the second said slots receptacles of lesser axial extent than the second said slots, an annular actuator slidable in said sleeve and including axially extending projections slidable in the first said slots which prevent rotation of said actuator, a spring in said casing and resiliently acting against said actuator to urge the projections on said actuator into the first said slots, and a ratchet within said sleeve and including axially extending radial projections adapted for being sandwiched between said actuator and said cam elements, said radial projections being selectively and alternately accommodated in the second said slots in a first working position and in said receptacles in a second working position, a plunger engaged with said ratchet to permit relative rotational movement of the latter while being locked to said ratchet for common axial displacement, said plunger extending through the opening in the other end of the casing to be exposed for engagement and axial displacement, said actuator and the radial projections on the ratchet having cooperating cam faces which are inclusive of inclined segments and which are jointly displaced upon displacement of said plunger towards said one end, the radial projections on the ratchet being displaceable to a position free of the cam elements on said sleeve and free of said second slots with said cam faces engaged, engagement of the cam faces rotating said ratchet to interchange the alignment of the radial projections between said receptacles and second slots for seating therein under the urging of said spring, the cartridge being detachably coupled to said ratchet for protraction and retraction thereby.

5. An instrument as claimed in claim 4 comprising a threaded member engaged in said other section for engaging said one section, said spring being sandwiched between said threaded member and actuator.

6. An instrument as claimed in claim 4 wherein the angle of inclination of the inclined segments of the cam face of the actuator is smaller than the angle of inclination of the saw-tooth shaped cam elements relative to the axis of the casing whereby the radial projections of the ratchet will always move to the bottoms of the receptacles.

7. An instrument as claimed in claim 4 wherein the ratchet includes an axial extension engaged by said plunger, said axial extension including an annular collar, said plunger being provided with a bore having an enlarged section to accommodate said collar.

8. An instrument as claimed in claim 4 wherein the cam face on the actuator consists of a plurality of isosceles triangles.

9. An instrument as claimed in claim 8 wherein, with the radial projections of the ratchet accommodated with the second said slots, said isosceles triangles have their apices centrally located relative to the projections.

References Cited by the Examiner UNITED STATES PATENTS 2,971,283 2/1961 Parker -334 3,120,837 2/1964 Johnson l2042.03 3,137,276 6/1964 Weisser 42.03

FOREIGN PATENTS 1,129,399 5/1962 Germany.

957,109 5/1964 Great Britain.

562,533 3/1957 Italy.

LAWRENCE CHARLES, Primary Examiner.

Claims

1. A WRITING INSTRUMENT COMPRISING A TUBULAR CASING, A NON-ROTATABLE, AXIALLY DISPLACEABLE ACTUATOR IN SAID CASING, A ROTATABLE AND AXIALLY DISPLACEABLE RATCHET IN SAID CASING, SPRING MEANS IN SAID CASING, SAID ACTUATOR DIRECTLY ENGAGING THE SPRING MEANS AND BEING SANDWICHED BETWEEN SAID SPRING MEANS AND SAID RATCHET, MEANS TO FORCE SAID RATCHET AGAINST SAID ACTUATOR AND TO DISPLACE THE RATCHET AND ACTUATOR TOGETHER AGAINST THE FORCE OF THE SPRING MEANS, SAID RATCHET AND ACTUATOR INCLUDING COOPERATING MEANS WHEREBY THE RATCHET TENDS TO ROTATE WHEN FOCED AGAINST THE ACTUATOR, POSITION ESTABLISHING MEANS TO HOLD THE RATCHET SELECTIVELY IN ONE OF TWO AXIALLY SPACED POSITIONS DEPENDING ON THE ANGLE OF ROTATION OF THE RATCHET, AND A WRITING ELEMENT COUPLED TO SAID RATCHET AND SELECTIVELY EXTENDING FROM THE CASING DEPENDING ON THE AXIAL POSITION OF THE RATCHET.