GB2025329A

GB2025329A - Magnetic Marking Pencil

Info

Publication number: GB2025329A
Application number: GB7923846A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1978-07-14
Filing date: 1979-07-09
Publication date: 1980-01-23
Also published as: AT356942B; IT7924304A0; NL7905406A; GB2025329B; ES251206Y; AU4887479A; IT1122157B; FR2431160A1; ES251206U; DE2927490A1; BE877668A; SE7906028L; ATA510278A

Abstract

A marking pencil with a rod- shaped axially magnetised permanent writing magnet (10) for writing marks on a strip-shaped carrier (23) with magnetically orientable particles which record said marks in an optically readable manner comprises a rod-shaped holder (1), which at one end carries the said writing magnet (10). Furthermore, there is provided a permanent erase magnet (15) at the other end of the holder, which magnet serves for erasing the carrier (23), the holder (1) comprising guide means (19, 20) near the erase magnet for keeping the carrier (23) on a magnetic tape cassette (21) with its carrier plane in a substantially perpendicular position relative to a pole end face (16, 17) of the erase magnet (15) during a relative movement between the carrier and the erase magnet. <IMAGE>

Description

SPECIFICATION Magnetic Marking Pencil The invention relates to a marking pencil having a rod-shaped axially magnetised permanent writing magnet with two pole endfaces, for writing marks, signs or the like on a leafshaped carrier with magnetically orientable particles which record said marks in an optically readable manner.

Such a marking pencil comprising a single rodshaped permanent writing magnet is known from US-PS 3,221 31 5. The magnetic field which emanates from a pole end face of such a writing magnet serves for writing marks on the carrier, the magnet being moved over the carrier in a similar way as when writing with a normal pencil. The marks are produced by re-orientation of those particles in the carrier which are influenced by the magnetic field of the magnet relative to the other particles in the vicinity, which are pre-oriented in a substantially perpendicular direction relative to the re-oriented particles. In incident light the reoriented particles are then distinct from those in the vicinity, so that the marks become visible.

Erasing the marks is effected with a magnetic field which again pre-orients all the particles.

It is an object of the invention to provide a particular advantageous form of a marking pencil of the type mentioned in the opening paragraph and to extend its range of application. To this end the invention is characterised in that the marking pencil includes a rod-shaped holder, that the writing magnet is at one end the holder coaxial with said holder and that at the other end of the holder there is provided permanent erase magnet for erasing said marks on a strip-shaped said carrier, the holder comprising guide means situated near the erase magnet, for keeping the strip carrier with its carrier plane in substantially perpendicular position relative to a pole-end face of the erase magnet during a relative movement between the strip carrier and the erase magnet.

By giving the writing magnet for writing these marks the form of a short rod-shaped permanent magnet, which is secured to the holder, a magnet which is comparatively thin relative to the thickness of the holder can be used, so that clearly visible marks in the form of thin, sharply bounded lines or signs can be obtained, because the magnetic field, which emanates from the small pole end-face of the writing magnet in a perpendicular direction and which produces the marks, is strongly concentrated. Furthermore, such a marking pencil not only enables marks to be written on the carrier, but is also enables them to be erased again, for which purpose the erase magnet is provided on the holder.The erase magnet may have comparatively large pole endfaces relative to those of the writing magnet, from which end faces the emanating magnetic field extends essentially perpendicularly to said pole end-faces at a comparatively large distance from these faces, so that a uniform erase field is produced.

The guide means may be advantageously formed by at least one groove, which is formed in the holder near an adjacent pole end-face of the erase magnet. In this way a specific path through the magnetic field is defined for the carrier so that said carrier is erased in a uniform and reliable manner. In this respect it is furthermore found to be advantageous if for erasing a carrier which is arranged on a magnetic tape cassette the groove has a cross-section in accordance with an orthogonal triangle. In this way the groove may always be used as a guide, regardless of the surface of the magnetic tape cassette on which carrier is arranged, because the required relative position between the carrier and the pole endface can always be obtained.It is also found to be advantageous if, for erasing a carrier which is arranged on a major surface of the magnetic tape cassette, the groove has a rectangular crosssection, the width of the groove corresponding to the thickness of the magnetic tape cassette. A groove of this form provides a particularly exact guidance for the magnetic tape cassette and the carrier.

Furthermore it is found to be advantageous if the end of the holder, where the writing magnet is disposed has a rounded tip whose bounding surface smoothly adjoins the pole end-face of the writing magnet. As a result of this the marks on the carrier can be very distinct, because they are formed directly by the magnetic field emanating from the pole end-face, and damaging or scratching of the carrier is avoided when the rounded tip is passed over the carrier.

It is also found to be advantageous if the writing magnet is accommodated in a shank-type insert inserted in the holder so as to be capable of deflecting resiliently in the axial direction. This provides a construction which is simple in respect of manufacturing technology, and when an excessive pressure is exerted on the carrier with the tip of the pencil damaging or scratching of the carrier is avoided.

Writing is found to be particularly effective if the writing ma#gnet is constituted by a length of magnetised wire. This permits the use of a very thin magnet, so that particularly fine marks can be made on the carrier.

The invention is described in more detail with reference to the accompanying drawings, which show some embodiments of the invention, by way of example only.

Figure 1 is an axial cross-section of a marking pencil with a writing magnet and an erase magnet, Figure 2 is an axial cross-section on an enlarged scale through the tip of the pencil of Figure 1 which contains the writing magnet, Figure 3 is a sectional view taken on the line Ill-Ill in Figure 1, Figure 4 shows the same view as Figure 3 of an alternative arrangement with an erase magnet of circular cross-section, Figure 5 schematically shows how marks are made with the pencil of Figure 1 on a carrier which is arranged on the major surface of a magnetic tape cassette, Figure 6 schematically represents how marks on a carrier arranged on a major surface of a magnetic tape cassette are erased with the pencil of Figure 1, Figure 7 shows how marks on a carrier arranged on a narrow side of a magnetic tape cassette are erased with a different pencil, Figure 8 shows how marks on a separate carrier are erased with yet a different pencil.

Leaf-shaped carriers with magnetically orientable particles for recording optically readable marks, signs or the like are known from United States Patent Specification 3,221,315.

Depending on whether the particles are oriented in one of two directions which are substantially perpendicualr to each other, they appear bright or dark in incident light. Such orientation can be achieved selectively with a free end of a rodshaped axially magnetised permanent magnet, so that the relevant particles, as a result of the magnetic field which extends essentially perpendicularly to the carrier surface, are alsb oriented perpendicularly to the carrier surface and are thus optically distinct from the surrounding particles which are pre-oriented in the plane of the carrier surface, so that a mark becomes visible. Such a mark can be erased by re-orienting all particles in the plane of the carrier surface by a magnetic field which extends in the plane of the carrier surface, which is a pre-orientation similar to that applied before a mark is made on a carrier.

Hereinafter, a marking pencil is described with which marks can both be made and erased on a strip-shaped such carrier with magnetically orientable particles.

The marking pencil shown in Figure 1 comprises a rod-shaped holder 1, which consists of a cylindrical shank 2 coaxially connected to a sleeve 3, for example in that it is fitted on a shaft end by a screw-thread. In the sleeve 3, which is for example manufactured from a plastics known as acrylonitrile butadiene styrene (ABS), a shankshaped insert 4 and a helical spring 5 are fitted.

The insert 4 bears on a stop surface 8 at the location of the sleeve opening 7 with a rim 6. The spring 5 in its turn bears on the rim 6 of the insert 4 and on the shank 2. In this way it is ensured that the insert 4 is mounted in the sleeve 3 so as to be capable of deflecting resiliently in the axial direction. Furthermore, the insert 4 comprises a conical tip 9, which projects from the opening 7 of the sleeve 3.

At the location of the tip 9 a rod-shaped axially magnetised permanent magnet 10 is coaxially embedded in the insert 4, which is for example made of a plastics, known as Delrin, a polymethylene oxide from Du Point de Nemours. As can be seen in Figure 1, the permanent magnet 10 is short relative to the length of the holder and, in order to obtain small pole end-faces 1 1 and 12 it is made thin relative to the thickness of the holder. In the embodiment shown the diameter of the magnet 10 is approximately 0.3 mm and the length approximately 5~15 mm, whilst the tt# {J{g tpptoXííHåfeAy ir4mm and its length approximately 11 5 mm.In this way the permanent magnet 10 produces concentrated magnetic fields at the location of its pole endfaces 1 1 and 12, which extend perpendicularly to the pole end-faces and thus in the axial direction of the marking pencil. Such a concentrated magnetic field is specifically suitable for writing marks, signs or the like on a carrier with magnetically orientable particles, because it acts only in the immediate vicinity of the pole end-face 11 which is situated in the tip 9 of the marking pencil. The magnetic field at the pole end-face is narrower if the permanent magnet hereinafter breifly referred to as writing magnet, is thinner, so that finer marks can be made with such a writing magnet. It is therefore advantageous if such a writing magnet is constituted by a length of magnetised wire.

As is in particular apparent from Figure 2, the pole end-face 1 1 of the writing magnet 10 in the present embodiment is situated directly in the bounding surface 13 of the tip 9 of the insert 4.

This bounding surface 13 is now constituted by a spherical surface, so that a rounded tip is obtained, which cannot damage the carrier when the carrier is touched. Such a tip is for example obtained in that after the writing magnet 10 has been embedded in the insert 4 the tip 9 is ground until the pole end face 11 is situated completely in the bounding surface 13 of the tip 9, so that the end face 1 1 of the writing magnet 10 smoothly adjoins the bounding surface 13 of the rounded tip 9. In this way the axial magnetic field emanating in concentrated form from the pole end-face 11, of which Figure 2 schematically shows a line of force 14, is used directly for making the marks, so that these marks become very distinct. Obviously, it is also possible for the pole end-face 1 1 of the writing magnet 10 to be situated within the tip 9.Damage to the carrier is furthermore avoided because the insert 4 is arranged in the holder 1 so as to be resiliently deflectable in the axial direction, in that the insert 4 springs back when the tip 9 is pressed onto the carrier with excessive force.

As is shown in Figure 1 there is provided an erase magnet 15 near the end of the shank 2 which is remote from the sleeve 3, which in the present embodiment is embedded in a shank 2 made of a plastics, for example Versalow (a polyamide from Scherring AG, W-Germany); however, it may also be mounted in a corresponding opening of the shank 2. As can be seen in Figure 3, the permanent magnet 15 has a parallelepiped from. It is magnetised perpendicularly to its longitudinal direction, so that pole end-faces 16 and 17 are formed. The dimensions of the permanent magnet 15 are selected so that its pole end-faces 16, 17 are large relative to the pole end-faces 1 1 and 12 of the writing magnet 10. In the embodiment shown the faces measure approximately 1 6x0 mm.In this way a magnetic field is formed in a larger area around the pole end-faces 16 and 17, which essentially extends perpendicularly to said pole end faces. Figure 1 schematically shows a line of force 18 of this magnetic field. Such a magnetic field is particularly suitable for erasing marks made on a strip-shaped carrier during relative movement between such a carrier and the permanent magnet 15~briefly referred to as erase magnet hereinafter-with the carrier surface essentially perpendicular to a pole endface 1 6 of 1 7 of said magnet. In this way the magnetically orientable particles of the carrier are correctly aligned in the carrier surface.

Obviously, the erase magnet 15 may alternatively have a circular cross-section as is shown in Figure 4. In that case the pole end faces 16 and 17 are constituted by portions of the cylindrical surface of the magnet, which are magnetised transversely to the axial direction.

In order to ensure that during said relative movement between the carrier and the erase magnet 15, the required perpendicular position of the carrier surface relative to a pole end face is maintained in the simplest and most reliable manner, guide means are provided, formed by a groove 19 or 20 at the location or each pole 16 and 1 7, respectively, of the erase magnet 1 5 in the shank 2. In the present embodiment the grooves 19. 20 extend transversely to the axis of the holder. However, it is also possible for the grooves to extend in the axial direction. It would also suffice to provide only one groove at the location of one pole end face, because for erasing preactically always only one groove is used.

However, in the present embodiment there are two grooves, so as to improve the appearance of the complete marking pencil.

The marking pencil described in the foregoing is intended to make and erase marks on a carrier which is arranged on a major surface of a magnetic tape casette. Figures 5 and 6 schematically show such a magnetic tape cassette 21, on whose major surface 22 a stripshaped carrier 23 is arranged. Adjacent the carrier 23 a scale 24 extends in the longitudinaldirection of said carrier, so that a specific point on the carrier 23 corresponds to the length of tape would from a tape reel in the cassette, whereby during the transport of the magnetic tape for example a pointer or a marking device which is part of the cassette machine moved along the scale 24 and the carrier 23 respectively.

The marking pencil now enables marks to be made on the carrier by hand which marks for example denote the beginning or end of a recording on the magnetic tape. To this end, as is schematically shown in Figure 5, the point 9 of the marking pencil, which is held approximately at right angles to the carrier surface, is placed at the desired point of the carrier and moved accordingly, so that at the points covered by the writing magnet 10 the magnetically oriented particles are oriented in a direction perpendicular to the carrier surface. Thus in incident light these particles differ from the surrounding particles, which as a result of a preceding erase process or a pre-orientation are oriented in the plane of the carrier surface. In this way a mark will be visible at the relevant point.

For erasing a mark or pre-orienting the particles, relative movement is effected betweeen the carrier and the erase magnet 15 with the carrier surface perpendicular to the pole end-face 1 6 or 1 7 of said erase magnet. In order to enable this to be realized in a simple and exact manner, the grooves 19 and 20 have a square crosssection, the width of the grooves corresponding to the thickness of the magnetic tape cassette. In this way a guide is obtained which defines the relative movement between the marking pencil and the magnetic tape cassette (and hence the carrier) in an unambiguous manner.As is shown schematically in Figure 6, the marking pencil is placed with a groove, for example the groove 20, onto the side surface 25 of the magnetic tape cassette, which surface adjoins the carrier 23 and extends along said carrier, and is moved along the magnetic tape cassette in the direction of the arrow 26. The magnetic field which emanates from the relevant pole end-face 1 7 of the erase magnet 1 5, whose lines of force consequently extend essentially in the plane of the carrier surface, then orients all particles of the carrier in the plane of the carrier surface, so that any mark, at whose location the particles are oriented in a direction perpendicular to the carrier surface, is erased.As the pole end-faces of the erase magnet are comparatively large, it is ensured that also at a slightly larger distance from the pole end-faces a magnetic field is obtained which extends perpendicularly to the pole end-faces, so that although the carrier 23 is arranged on the cassette in a direction perpendicular to the side surface 25 at a distance from the said surface, it is nevertheless perfectly erased by a magnetic field which extends in the plane of the carrier surface.

In the embodiment of Figure 7 the marking pencil is shown for simplicity as consisting of a rod-shaped holder 1 of a plastics, in which the writing magnet 10 and the erase magnet 16 are mounted similar means as in the embodiment of Figure 1. If desired, the write magnet 10 may alternatively project from the holder 1 in the form of a pin. The erase magnet 15 is arranged obliquely relative to the longitudinal axis of the marking pencil and at the location of its pole endface 16 a groove 27 is formed having a crosssection which corresponds to an orthogonal triangle. Guide means formed by such a groove enables carriers to be erased which are arranged on an arbitrary surface of a magnetic tape cassette, i.e. either on a major surface or on a side face, so that in whichever of these positions the carrier is arranged on the cassette it can always be guided in the groove in such a way that the carrier surface extends perpendicularly to the pole end-face 16. Figure 7 shows an example for a cassette 21, with the carrier 23 being arranged on a side face 25. If the carrier 23 is arranged on a major surface of the cassette, it should be moved along the groove 27, rotated through 900 relative to the position shown in Figure 7.

The marking pencil shown in Figure 8 is of a construction similar to that of the marking pencil of Figure 7. The erase magnet 15 is now arranged in the pencil in such a way that its pole end-face 16 faces the end 28 of the marking pencil, in which a groove 29 is formed which extends perpendicularly to the pole end-face 16. The guide means formed by this groove 29 is comparatively narrow and only accepts a separate carrier 23.

Claims

1. A marking pencil having a rod-shaped axially magnetised permanent writing magnet with the two pole end-faces for writing marks, signs or the like on a leaf shaped carrier with magnetically orientable particles which record said marks in in optically readable manner, characterised in that the marking pencil includes a rod-shaped holder, that the writing magnet is at one end of the holder coaxial with said holder, and that at the other end of the holder there is provided a permanent erase magnet for erasing said marks on a strip-shaped said carrrier, the holder comprising guide means situated near the erase magnet, for keeping the strip carrier with its carrier plane in a substantially perpendicular position relative to a pole end-face of the erase magnet during a relative movement between the strip carrier and the erase magnet.

2. A marking pencil as claimed in Claim 1, characterised in that the guide means are formed by at least one groove which is formed in the holder near an adjacent pole end face of the erase magnet.

3. A marking pencil as claimed in Claim 2, characterised in that for erasing said marks on a carried which is arranged on a magnetic tape cassette the groove has a cross-section in accordance with an orthogonal triangle.

4. A marking pencil as claimed in Claim 2, characterised in that for erasing said marks on a carrier which is arranged on a major surface of a magnetic tape cassette the groove has a rectangular cross-section, the width of the grooves corresponding to the thickness of the magnetic tape cassette.

5. A marking pencil as claimed in any of the preceding Claims, characterised in that the end of the holder, when the writing magnet is disposed has a rounded tip, whose bounding surface smoothly adjoins the pole end-face of the writing magnet.

6. A marking pencil as claimed in any of the preceding Claims, characterised in that the writing magnet is accommodated in a shankshaped insert, inserted in the holder so as to be capable of deflecting resiliently in the axial direction.

7. A marking pencil as claimed in any of the preceding Claims, characterised in that the writing magnet is constituted by a length of magnetised wire.

8. A magnetic marking pencil substantially as herein described with reference to Figures 1, 2, 3, 5 and 6 of the accompanying drawings.

9. A magnetic marking pencil substantially as herein described with reference to Figures 1, 2, 3, 5 and 6 as modified by Figure 4 of the accompanying drawings.

10. A magnetic marking pencil substantially as herein described with reference to Figures 1, 2, 3, 5 and 6 as modified by Figure 7 of the accompanying drawings.

11. A magnetic marking pencil substantially as herein described with reference to Figures 1, 2, 3, 5 and 6 as modified by Figure 8 of the accompanying drawings.