GB2302837A - Manufacture of ink transfer cores for writing instruments - Google Patents

Abstract

Ink transfer cores (6, Figures 4A and 4B not shown) for ball point writing instruments having at least one chisel shaped end portion (11, Figures 4A and 4B not shown) are manufactured by a method comprising an extrusion step wherein a rod 21 of extruded, resin bonded fibrous material is formed using an extruder 20 and a cutting step wherein said cores are cut from said rod 21 of extruded material in their finished shape using cutting means 22 having an appropriately shaped blade 24 (Fig 6B, not shown). The cores may be chisel shaped at both end portions and the cutting step may be such that at each cut of the extruded material one of the cores is formed in its finished shape.

Description

Ink Transfer Cores This invention relates to ink transfer cores of resin bonded fibrous material for ball point writing instruments and to a method of manufacturing such cores.

Such cores act to transfer ink within a writing instrument during writing from an ink source to a ball point writing tip. The writing tip may have a grooved feed passage into which a core end portion is inserted as disclosed, for example, in GB2025857A. Alternatively, the cores may act to transfer ink directly to a ball of the ball point writing tip.

An essential step in known methods of manufacturing ink transfer cores is a grinding operation to form the core into its finished shape.

Ink transfer cores manufactured by such methods may have pointed conical end portions or frusto-conical end portions.

In particular, it is known to form ink transfer cores having pointed end portions by extruding fibrous material into a rod, cutting the extruded rod into lengthwise pieces and plunge form grinding the pieces.

One disadvantage of such known methods is that with any form of grinding operation it is difficult in practice to manufacture each core to the exact length required. This causes problems during assembly of cores manufactured using such methods in writing tips, because a core which is too short, for example by as little as 0.005-0.010 inches (0.13 - 0.25mm), results in poor core/feed passage contact and prevents good ink transfer capillary action, and a core which is too long results in a compressed end portion and consequent poor ink flow. A further disadvantage of such methods is that any form of grinding can block or reduce the effectiveness of capillaries in the cores.

It is an object of the present invention to provide a method of manufacturing ink transfer cores for ball point writing instruments wherein a grinding operation is omitted.

In accordance with the present invention there is provided a method of manufacturing ink transfer cores for ball point writing instruments, at least one end portion of each core having a chisel shape, said method comprising an extrusion step wherein a rod of extruded, resin bonded fibrous material is formed and a cutting step wherein said rod is cut into lengthwise pieces to form said cores in their finished shape.

It has been found that cores having chisel shaped end portions provided by the above method perform satisfactorily in ball point writing instruments whilst use of the above method facilitates speedy and economic production of such cores.

Preferably, said cutting step consists of one cutting operation for each core formed. This is advantageous in that it enables each core to be manufactured to the exact length required, avoiding the disadvantages mentioned in the last but three paragraphs.

Preferably, said cutting step cuts said rod of extruded material such that the or each chisel shaped end portion of each core has an edge at its tip which intersects a centre axis of the core and lies substantially perpendicular to said axis.

Preferably, said cutting step is such that each end portion of each core has a chisel shape.

Preferably, said cutting step is carried out on said rod of extruded material as it is being extruded.

The invention also includes an ink transfer core manufactured using a method as defined in the last but five preceding paragraph.

The invention also includes a ball point writing instrument having such an ink transfer core.

The invention also includes an ink transfer core of resin bonded fibrous material, wherein each end portion has a chisel shape.

In order that the invention may be well understood, an embodiment thereof, which is given by way of example only, will now be described with reference to the accompanying drawings, in which: Figure 1 is a side axial section of an ink transfer core end portion inserted in a ball point writing tip having a grooved feed passage; Figure 2 is a front axial section of the ink transfer core end portion inserted in the writing tip; Figure 3 is a schematic representation of an extruder and a cutting means for use in a method of manufacturing the core; Figures 4A and 4B are side and front views respectively of the core; Figures SA and 5B are end views of the core; Figure 6A is a side view of a cutting blade of the cutting means, enlarged; Figure 6B is a view of the cutting blade on line VI-VI in Figure 6A;; Figure 7 is a side view of the cutting means shown in section taken on line VII-VII in Figure 9; Figure 8 is a sectional view of the cutting means taken on line VIII-VIII in Figure 7; and Figure 9 is an end view of the cutting means.

The writing tip 1 of Figures 1 and 2 is for use with aqueous ink and comprises an elongate housing 2 and a writing ball 3 retained in a socket 4 at one end 5 of the housing. An ink transfer core, or feed core, 6 extends into a bore 7 in the housing from the other end 8 thereof for transferring ink from a source thereof (not shown) to the ball 3 via a grooved feed passage 9 between the bore 7 and the socket 4. The housing is also provided with an annular abutment 10 by which it is located in a writing instrument (not shown).

The core 6 is formed as a stick of longitudinally extending man-made fibres which are bonded together with a resin to provide aqueous ink feeding capillaries for feeding ink to the grooved passage 9 from the ink source, for example a transorbe or reservoir in the writing instrument.

Cores 6 are manufactured by a method having an extrusion step and a cutting step as shown schematically in Figure 3. In the extrusion step material containing man-made fibres and a resin is formed into a rod 21 of extruded, resin bonded fibrous material using an extruder 20. In the cutting step, the rod 21 of material is cut as it is being extruded using cutting means 22.

The cutting means 22 is shown in Figures 7, 8 and 9 and comprises a cutting blade 24 and a guide means having first and second guide members 26 and 28.

Respective guide passages 32, 34 in the first and second guide members 26, 28 together form a guideway for guiding the cutting blade 24.

In the illustrated method, an end of the rod 21 passes through a passage 30 which is disposed through the second guide member 28 perpendicular to the guide passage 34 such that the rod 21 moves transversely across the cutting path of the blade 24.

The cutting blade 24 is configured as illustrated in Figures 6A and 6B and is reciprocated in timed relationship to the rate of extrusion to cut the rod 21 transversely into pieces of predetermined length to form the cores in their finished shape. Each core 6 is formed in its finished shape in one cut of the cutting blade 24, whereby chisel, or wedge, shaped ends of the blade cut the rod 21. The sides of the blade merely interconnect the ends thereof and do not cut the rod 21. Timing of the blade movement is adjusted such that the size of the offcut from the end of the rod 21 is small and waste is minimized. The core exits the base through the passage 32 after cutting.

In its finished shape the core 6, as shown in Figures 4A, 4B, 5A and SB, is circular in crosssection and has two chisel shaped end portions 11 with respective edges 19 which intersect the core's centre axis 18 and lie substantially perpendicular thereto, the edges 19 being defined by the tips of the respective chisel shapes. The shape of the core 6 facilitates moulding, or reshaping, of one of the end portions 11 on insertion thereof into the passage 9 because there is less material to be displaced. This moulding results in the inserted end portion 11 having a cross-section which is generally round at least at one axial location therealong. The illustrated core 6 is also advantageous in that it can be orientated with either end inserted into the passage 9, thus preventing misorientation during assembly.

The grooved passage 9 illustrated has axially extending, circumferentially spaced grooves 12 which are capable of providing a capillary feed.

To provide good transfer of ink between the core 6 and passage 9, the core 6 is inserted into the end 13 of the passage 9 remote from the ball 3. Good contact between the core and the grooves 12 of the passage 9 is achieved without significant compression of the core material which would hinder the working of the capillaries of the core.

In the illustrated tip, this is achieved by arranging the core and housing such that on insertion of the core 6 into the passage 9 material of the core is displaced without significant compression into the grooves 12 of the feed passage 9.

Although in the illustrated tip the core 6 transfers ink to the spaced grooves 12 to provide a capillary feed to the ball 3, the illustrated core 6 can be used in other writing tips, for example tips in which a core transfers ink direct to a ball.

Claims (10)

1. A method of manufacturing ink transfer cores for ball point writing instruments, at least one end portion of each core having a chisel shape, said method comprising an extrusion step wherein a rod of extruded, resin bonded fibrous material is formed and a cutting step wherein said rod is cut into lengthwise pieces to form said cores in their finished shape.

2. A method as claimed in claim 1, wherein said cutting step consists of one cutting operation for each core formed.

3. A method as claimed in claim 1 or 2, wherein said cutting step cuts said rod of extruded material such that the or each chisel shaped end portion of each core has an edge at its tip which intersects a centre axis of the core and lies substantially perpendicular to said axis.

4. A method as claimed in claim 1, 2 or 3, wherein said cutting step is such that each end portion of each core has a chisel shape.

5. A method as claimed in any one of claims 1 to 4, wherein said cutting step is carried out on said rod of extruded material as it is being extruded.

6. A method of manufacturing ink transfer cores substantially as herein described with reference to the accompanying drawings.

7. An ink transfer core manufactured using a method as claimed in any one of the preceding claims.

8. A ball point writing instrument having an ink transfer core as claimed in claim 7.

9. An ink transfer core of resin bonded fibrous material, wherein each end portion has a chisel shape.

10. An ink transfer core substantially as hereinbefore described with reference to Figures 4A and B and 5A and B of the accompanying drawings.