Ball point tip and writing instrument fitted with such a ball point tip

Abstract

A ball point tip comprising a ball holder having an ink conduit and a ball house, a ball accommodated into the ball house and a leaf spring axially disposed between the ball and an axial end of the ink conduit, the leaf spring having a main body and a plurality of tongues extending radially from the main body, ink passages being formed between the tongues in order to fluidly connect the ink conduit and the ball house, wherein the ball holder and the leaf spring are made of plastic and unitary formed.

Claims

1. A ball point tip comprising: a ball holder having an ink conduit and a ball house, the ink conduit extending axially and comprising a first axial end, a second axial end, and opening into the ball house, the ball house including a stop, and a ball accommodated into the ball house, a leaf spring axially disposed between the ball and the second axial end of the ink conduit, the leaf spring having a main body and a plurality of tongues extending radially from the main body, ink passages being formed between the plurality of tongues in order to fluidly connect the ink conduit and the ball house; a shoulder axially disposed between the first axial end of the ink conduit and the leaf spring; and an annular reinforcement filet is axially disposed between the first axial end of the ink conduit and the shoulder, wherein the stop has a frustoconical shape and is disposed radially between a wall of the ball house and the leaf spring, wherein the ball holder and the leaf spring are made of plastic and form together a single piece.

2. The ball point tip according to claim 1, wherein the main body is the center of the leaf spring and the plurality of tongues extending radially and outwardly from the main body and wherein a reinforcement extending from the wall of the ink conduit, along the plurality of tongues, to the main body of the leaf spring, wherein the reinforcement tapers radially-inwardly toward a central longitudinal axis that is co-axial with the main body of the leaf spring, in a direction from the first axial end toward the second axial end.

3. The ball point tip according to claim 2, wherein a distal end of each tongue is larger at a radial end than at an interface with the main body.

4. The ball point tip according to claim 2, wherein the ball house includes a cylindrical wall and the stop tapers radially-inwardly in a direction from the second axial end toward the first axial end, and wherein the stop is configured to limit movements of the ball within the ball house with regard to the leaf spring.

5. The ball point tip according to claim 4, wherein the stop is annular and comprises a stop face.

6. The ball point tip according to claim 1, wherein the main body is solid, and a total flow cross section of the ink passages is greater or equal to 0.01 mm.sup.2 and lower or equal to 0.09 mm.sup.2.

7. The ball point tip according to claim 1, comprising an annular lip configured to retain the ball within the ball holder, wherein the leaf spring is configured to be elastically deformed during writing so that a gap between the ball and the annular lip is greater or equal to 0.002 mm and lower or equal to 0.2 mm.

8. The ball point tip according to claim 1, wherein the leaf spring is pre-stressed.

9. The ball point tip according to claim 8, having an axis, wherein the ball exerts the pre-stress to the leaf spring, the leaf spring having an axial deformation which is greater or equal to 0.01 mm and lower or equal to 0.2 mm due to the pre-stress exerted by the ball.

10. A writing instrument comprising a ball point tip according to claim 1 and a reservoir configured to feed the ball point tip with ink, the reservoir comprising gel ink.

11. The ball point tip according to claim 1, wherein the main body is solid, a total flow cross section of the ink passages is greater or equal to 0.01 mm.sup.2 and lower or equal to 0.08 mm.sup.2.

12. The ball point tip according to claim 1, further comprising a reinforcement extending into the ink conduit from the leaf spring, the reinforcement being disposed between an individual tongue and a wall of the ink conduit.

13. The ball point tip according to claim 12, wherein the reinforcement is radially tapered from the wall of the ink conduit toward an x-axis.

14. The ball point tip according to claim 12, wherein the reinforcement is formed into the wall of the ink conduit.

15. The ball point tip according to claim 12, wherein the reinforcement is distant from the wall of the ink conduit.

16. A ball point tip comprising: a ball holder having an ink conduit and a ball house, the ink conduit defined by a wall and extending axially, comprising a first axial end and a second axial end, and opening into the ball house; a ball accommodated into the ball house; a leaf spring axially disposed between the ball and the second axial end of the ink conduit, the leaf spring having a main body and a plurality of tongues extending radially from the main body, ink passages being formed between the plurality of tongues in order to fluidly connect the ink conduit and the ball house; a reinforcement extending from the wall of the ink conduit, along the plurality of tongues, to the main body of the leaf spring, wherein the reinforcement tapers radially-inwardly toward a central longitudinal axis that is co-axial with the main body of the leaf spring, in a direction from the first axial end toward the second axial end; a shoulder axially disposed between the first axial end of the ink conduit and the leaf spring; an annular reinforcement filet is axially disposed between the first axial end of the ink conduit and the shoulder, wherein the ball holder and the leaf spring are made of plastic and form together a single piece.

17. The ball point tip according to claim 16, wherein the reinforcement is radially tapered from the wall of the ink conduit toward an x-axis.

18. The ball point tip according to claim 16, wherein the reinforcement is formed into the wall of the ink conduit.

19. The ball point tip according to claim 16, wherein the reinforcement is distant from the wall of the ink conduit, and wherein the ball house includes a cylindrical wall and a stop that radially extends from the cylindrical wall to the leaf spring.

20. A writing instrument comprising: a ball point tip comprising a ball holder having an ink conduit and a ball house, the ink conduit extending axially and comprising a first axial end and a second axial end, wherein the ink conduit opens into the ball house, the ball house including a cylindrical wall and a stop that is formed of a frustoconical shape that tapers radially-inwardly in a direction from the second axial end toward the first axial end, and a ball accommodated inside the ball house; a leaf spring having a main body and a plurality of tongues in order to fluidly connect the ink conduit and the ball house; and a reservoir configured to feed the ball point tip with ink, the reservoir comprising gel ink; a shoulder axially disposed between the first axial end of the ink conduit and the leaf spring; and an annular reinforcement filet axially disposed between the first axial end of the ink conduit and the shoulder, wherein the ball holder and the leaf spring are made of plastic and form together a single piece.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure and its advantages can be better understood by reading the detailed description of various embodiments of the disclosure given as non-limiting examples. The description refers to the accompanying sheets of figures, in which:

(2) FIG. 1 shows a writing instrument having a ball point tip,

(3) FIG. 2 shows an exploded view of the ball point tip of the writing instrument of FIG. 1 according to a first embodiment,

(4) FIG. 3A shows the leaf spring in the section III of FIG. 2,

(5) FIG. 3B shows a variant of the leaf spring of FIG. 3A,

(6) FIG. 4A shows a first variant of the ball point tip of FIG. 2,

(7) FIG. 4B shows a second variant of the ball point tip of FIG. 2,

(8) FIG. 5A shows an exploded view of a second embodiment of the ball point tip,

(9) FIG. 5B shows the ink passages of the second embodiment seen from arrow V of FIG. 5B,

(10) FIG. 6A shows the leaf spring of the ball point tip of FIG. 5,

(11) FIG. 6B shows a variant of the leaf spring of FIG. 6A,

(12) FIGS. 7A to 7D show different steps of a method for manufacturing the ball point tip of the first embodiment,

(13) FIG. 7E show a variant of FIG. 7D,

(14) FIG. 7F show the ball point of FIG. 7D during writing, and

(15) FIGS. 8A to 8D show different steps of a method for manufacturing the ball point tip of the second embodiment.

DETAILED DESCRIPTION

(16) FIG. 1 shows a writing instrument 100 fitted with a ball point tip 10. An exploded view of the ball point tip 10 is shown FIG. 2. The ball point tip 10 has a ball holder 12, a ball 14 and a leaf spring 16. The writing instrument 100 may comprises an ink reservoir 18 configured to feed the ball point tip 10 with ink. The reservoir 18 may comprise gel ink.

(17) The ball holder 12 comprises an ink conduit 12A and a ball house 12B. The ink conduit 12A extends along the axial direction X and may comprise a first axial end 12A1 configured to receive ink from the ink reservoir 18 and a second axial end 12A2, opposite along the axial direction X to the first axial end 12A1, opening into the ball house 12B. The ball house 12B may comprise a first axial end 12B1 configured to receive ink from the ink conduit 12A and a second axial end 1262, opposite along the axial direction X to the first axial end 1261, from which the ball 14 protrudes in order to write.

(18) The leaf spring 16 is placed axially between the ball 14 and the second axial end 12A2 of the ink conduit 12A. FIG. 3A shows the leaf spring 16 along the cross section III of FIG. 2. The leaf spring 16 may have a main body 16A which is the centre and three tongues 16B which each extends radially and outwardly from the main body 16A. Ink passages 20 are formed between the tongues 16B in order to fluidly connect the ink conduit 12A and the ball house 12B and to feed the ball house 12B with ink flowing from the reservoir 18 throughout the ink conduit 12A. As shown in FIG. 3A, the distal end 16B1 of each tongue 16B may be enlarged when viewed from the axial direction X. In this first embodiment, the leaf spring 16 may be made of plastic as well as the ball holder 12 and unitary/monolithically formed.

(19) FIG. 3B shows a leaf spring 16 according to a variant of the leaf spring 16 of first embodiment. In this example, the leaf spring 16 may have a beam shape. This leaf spring 16 may have a central portion 16A as a main body which is the centre, and two end portions 16B forming tongues extending radially and outwardly from the main body 16A. Passages 20 are formed between the tongues 16B.

(20) Both the leaf springs 16 and 16 have a solid main body (or central portion) 16A, 16A, respectively, i.e. without through hole. In the present example, the total flow cross section TS of the ink passages corresponds to the sum of the flow cross sections S, S perpendicular to the axis X, of each of the passages 20, 20, respectively. In other words, for the leaf spring 16, the total flow cross section TS=3S while for the leaf spring 16, the total flow cross section TS'=2S. In this example, TS=0.02 mm.sup.2 and TS=0.08 mm.sup.2.

(21) FIG. 4A shows a first variant of the ball point tip 10 wherein each tongue 16B of the leaf spring 16 may be provided with a reinforcement 17 extending on the ink conduit side and disposed in the corner between the tongue and the ink conduit wall. The reinforcement 17 may be radially tapered from the ink conduit wall toward the axis X. In this example the reinforcement 17 may be joined to/formed with the ink conduit wall. In a second variant show in FIG. 4B, the reinforcement 17 may be distant from the ink conduit wall, i.e. a gap 19 is provided between the reinforcement 17 and the ink conduit wall. Such reinforcements strengthen the tongues 16B, which reduces the risk of ink leakage and improves writing smoothness.

(22) FIGS. 5A and 5B shows a ball point tip 110 according to a second embodiment, which may be mounted on the writing instrument 100. The ball point tip 110 has a ball holder 112, a leaf spring 116 and a ball 14. The ball holder 112 is similar to the ball holder 12 except in that it is not unitary/monolithically formed with the leaf spring 116 and in that it is provided with a shoulder 112C extending radially, the shoulder being disposed between the ink conduit 112A and the ball house 112B. In this example, the shoulder 112 may have an annular shape. An annular reinforcement filet 113 may be former axially opposite to the shoulder 112 (i.e. on the ink conduit side). Except for the above mentioned differences, the description of the ball holder 12 is the same or substantially similar to the description of the ball holder 112.

(23) The leaf spring 116 is disposed between the shoulder 112C and the ball 14. In this example, the ball point tip 110 may comprise only the ball holder 112, the ball 14 and the leaf spring 116 which are distinct and assembled together. In this example, the ball holder 112 and the leaf spring 112 may be each made of metal.

(24) The leaf spring 116 is shown in detail in FIG. 6A and may present a main body 116A as a centre and three tongues 116B extending radially and outwardly. The distal end 116B1 of each tongue 116B is enlarged when viewed from the axial direction X. In this example, the wall portion between two adjacent tongues 116B may have any suitable arcuate shape, for example an arc of circle shape.

(25) FIG. 5B shows ink passages 120 between the tongues 116B when the leaf spring 116 is mounted into the ball holder 112, seen from the arrow V of FIG. 5A.

(26) FIG. 6B shows a leaf spring 116 according to a variant of the leaf spring 116 of the second embodiment. In this example, the leaf spring 116 may have a disc shape with a central cut having a crux shape. This leaf spring 116 may have an outer ring portion 116A as a main body and four tongues 116B extending radially and inwardly from the main body 116A. Passages 120 may be formed between the tongues 116B.

(27) A method for manufacturing a ball point tip having a ball holder made of plastic is now described with reference to FIGS. 7A to 7D. In this example, the ball holder is unitary/monolithically formed with a leaf spring.

(28) A ball holder 212 and a leaf spring 216 are made by moulding during a single step, as shown in FIG. 7A. In this example, two dedicated broaches 50A and 50B and a not shown external mould are used to carry out such a molding step. Such a step is simpler and cost effective with regard to the manufacturing of a ball holder having a dedicated ball seat. For example, a conventional method comprises one step of broaching and one step of coining which are not necessary here.

(29) A partial and magnified cross section of the ball holder 212 and of the leaf spring 216 thus obtained is shown in FIG. 7B. The ball holder 212 has an ink conduit 212A, a ball house 212B and the leaf spring 216 having a main body 216A and a plurality of tongues 216B extending radially from the main body 216A, the ink conduit extending along the axial direction X and opening into the ball house 212B. The leaf spring 216 is arranged between the ball house 212B and the second axial end 212A2 of the ink conduit 212A such that ink passages 220 are formed between tongues 216B of the leaf spring 216 in order to provide fluid connection between the ink conduit 212A and the ball house 212B. The distal end 216B1 of each tongue 216B may be enlarged when viewed from the axial direction. The second axial end 212B2 of the ball house 212B may be provided with an annular lip 212D configured to block a ball inside the ball house 212. In this example, the ball holder 212 may comprise a stop 213 arranged in the ball house 212B, in order to limit the movements, for example the axial movements, of the ball 14 within the ball house 212B. Such a stop 213 may prevent the leaf spring 216 from being damaged by the ball 14. The stop 213 may be disposed in the corner between the leaf spring 216 and the ball house wall. The stop 213 may be radially tapered from the ball house wall toward the axis X. The stop 213 may extend annularly around the axis X. The stop 213 may extend continuously around the axis X, and show only through holes corresponding to the passages 220. The stop 213 has a stop face 213A having a frustoconical shape. In a variant shown in FIG. 7E, the stop face 213A of the stop 213 has a spherical shape. The radius of spherical stop face 213A may be greater or equal to the radius of the ball 14.

(30) The ball holder 212 differs from the ball holder 12 only in that it shows a stop 213 which is not present on the ball holder 12. In a variant not shown, the ball holder 12 may be provided with the stop 213 or 213. In the same way, the ball holder 212 may be provided with the optional reinforcement 17, with or without the gap 19. The leaf spring 216 may have a shape of a beam, as the leaf spring 16, instead of a similar shape as the leaf spring 16.

(31) As shown in FIG. 7C, a ball 14 may be press fitted into the ball house 212B. As shown in FIG. 7D, a ball point tip 210 is thus obtained, the lip 212D retaining the ball 14 within the ball house 212B. In this example, the leaf spring 216 may be pre-stressed and axially deformed of about 0.02 mm (two hundredths of a millimetre). The ball 14 may be configured to pre-stress the leaf spring 216 when mounted and blocked by the lip 212D. The leaf spring 216 may be pre-stressed by the ball 14 which may axially bear against the leaf spring 216. Such a pre-stress may provide a valve effect between the ball 14 and the lip 212D.

(32) As shown in FIG. 7F, the leaf spring may be configured to be elastically deformed during writing so that a gap G between the ball 14 and the annular lip 212D is about 0.1 mm (one tenth of millimetre). During such deformation, the ball 14 may abut against the stop 213 or 213. In a variant, the leaf spring 216 may be further elastically deformed before the ball 14 abuts against the stop 213, 213. In such a case, the gap G may be increased of about 10% when the ball 14 bears against the stop 213 or 213. The total elastic deformation of the leaf spring 216 may remain within a range of 0.002 m to 0.2 mm. The deformation of the leaf spring 213 show in FIG. 7F is magnified and schematic.

(33) Such a manufacturing method may apply, for example, for manufacturing ball point tips of the first embodiment and its variants of FIGS. 1 to 4B. In other words, any features disclosed with regard to the embodiments disclosed with reference to FIGS. 1 to 4B may apply, alone or in any combination, to the embodiment of FIGS. 7A to 7E, and vice versa, any features disclosed with regard to the embodiments disclosed with reference to FIGS. 7A to 7E may apply, alone or in any combination, to the embodiment of FIGS. 1 to 4B.

(34) A method for manufacturing a ball point tip having a ball holder made of metal is now described with reference to FIGS. 8A to 8D.

(35) A metallic ball holder 112 is provided, this ball holder 112 having, as shown the partial and magnified cross section of FIG. 8A, an ink conduit 112A and a ball house 112B. The ink conduit 112A extending along the axial direction X and opening into the ball house 112B, and a shoulder 112C being formed between the ink conduit 112A and the ball house 112B. In this example the axial walls of the ball house 112B may be straight and may not show any lip or the like. Such a metallic ball holder may be made by forming the cavity of both the ball house and the ink conduit during a single step.

(36) In a second step, as shown in FIG. 8B, a leaf spring 116 is provided and placed within the ball house 112B, onto the shoulder 112C. In a third step, as shown in FIG. 8C, a ball 14 is provided within the ball house 112B, onto the leaf spring 116. The leaf spring 116 is thus disposed between the ball 14 and the shoulder 112C such that ink passages 120 are formed (see FIG. 5B) between the tongues 116B of the leaf spring 116 in order to provide fluid connection between the ink conduit 112A and the ball house 112B. Then, the ball 14 is crimped on the ball holder 112. In this example, the second axial end 11262 of the ball house 112B is machined in order to form a lip 112B which retains the ball 14 into the ball house 112B. The ball point tip 110 is thus obtained is shown in FIG. 8D.

(37) Although the present disclosure is described with reference to specific examples, it is clear that modifications and changes may be made to these examples without going beyond the general scope of the disclosure as defined by the claims. In particular, individual characteristics of the various embodiments shown and/or mentioned may be combined in additional embodiments. Consequently, the description and the drawings should be considered in a sense that is illustrative rather than restrictive.

(38) For example, the leaf springs shown have two, three or four tongues, but may have more than four tongues.

(39) Additionally, all of the disclosed features of an apparatus may be transposed, alone or in combination, to a method and vice versa.