GB2300850A

GB2300850A - Reel for magnetic tape cassette

Info

Publication number: GB2300850A
Application number: GB9608556A
Authority: GB
Inventors: Kiyoo Morita
Original assignee: Fuji Photo Film Co Ltd
Current assignee: Fujifilm Holdings Corp
Priority date: 1995-05-16
Filing date: 1996-04-25
Publication date: 1996-11-20
Anticipated expiration: 2016-04-25
Also published as: GB9608556D0; DE19619716A1; GB2300850B; JPH08315539A; JP3464312B2

Description

2300850 REEL FOR MAGNETIC TAPE CASSETTE The present invention relates to a

reel to be used for a magnetic tape cassette, and more particularly to such a reel to be suitably used for a highly densified magnetic recording tape having upper and lower f langes disposed above and below upper and lower edges of a circumferential surface of the reel around which a magnetic tape is to be wound, and a commercially used magnetic tape having a large diameter of wound tape.

There have been conventionally used various types of magnetic tape cassettes to be used for VTR (video tape recorder). Such magnetic tape cassettes usually have contains therein a pair of reels for rotation around which a magnetic tape is wound, and are described in, for example, U.S. Patent Nos. 4,791,504 and 4,896,238 which are incorporated herein by reference.

As is known, a reel 40 to be used for a magnetic tape cassette has upper and lower flanges 44 and 100 just above and below a cylindrical body 41 around which a magnetic tape 102 is to be wound, as illustrated in Fig. 3. In most of reels, the lower flange 100 is integrally formed with the cylindrical body 41, whereas the upper flange 44 is separately fabricated from the cylindrical body 41 and the upper flange is secured to the 1 cylindrical body 41 at its upper end by welding or fitting. This is because the upper and lower flanges 44 and 100 are made of different materials, as mentioned below.

That is, the lower flange 100 is necessary to have high mechanical strength due to reasons such as that the lower flange is to be engaged at an outer circumferential edge thereof to a reel braking device, a driving shaft of VTR for rotating a reel is to be f it into a hole f ormed at a center of the lower f lange, and a leaf spring disposed in a magnetic tape cassette for biasing a reel downwardly of a cassette is to be engaged to the lower flange. Thus, the lower flange is integrally formed of resin such as polyoxymethylene (POM) and high impact polystyrene (HIPS).

On the other hand, the upper flange 44 is not necessary to have so high mechanical strength as the lower flange. In addition, since the upper flange is required to be transparent so that a magnetic tape wound around a cylindrical body can be viewed outside the cassette, the upper flange is made of different material from the lower flange, which material is relatively low in fabrication cost, such as acrylnitrile styrene copolymer (AS) and general purpose polystyrene (GPPS).

As illustrated in Fig. 4, the lower flange 100 of a conventional reel 40 to be used for a magnetic tape cassette is formed at an outer circumference thereof with teeth 101 to which a reel braking device is to be engaged. An upper surface 103 of the lower flange 100 which is to contact with a magnetic tape -102 has a stepped structure by which the surface 103 is raised towards the upper flange relative to an upper surface of the teeth 101 (the surface 103 is higher than an upper surface of the teeth, in Fig. 4).

The upper surface 103 of the lower flange is formed with an outer circumferential edge having a curvature radius R of about 0.2 mm, which curvature radius R is defined as viewed in a cross-section obtained when the lower flange is cut by a plane passing through a rotation axis of the reel 40 (hereinafter, such curvature radius is referred to simply as curvature radius R).

On the other hand, since the magnetic tape 102 is held taken out of a cassette when a video tape cassette is loading in VTR, there would arise a problem by the magnetic tape 102 being waved in the tape widthwise direction (vertically, in Fig. 4) if tape running speed is relatively high, for instance, when the magnetic tape 102 is to be unwound or wound up. That is, when the magnetic tape 102 is waved downward (towards the lower flange), a lower edge 105 of the magnetic tape 102 comes to contact with the edge 104 of the lower flange 100. The conventional edge 104 has a quite smaller curvature radius, namely about 0.2 mm, as mentioned earlier, and thus the lower edge 105 of the magnetic tape 102 is worn by the edge 104, resulting in that magnetic substance having been applied to the magnetic tape 102 is peeled off or that the magnetic tape 102 together with a base thereof is damaged.

3 - Thus, it seems that the above mentioned problem can be solved merely by making the curvature radius of the edge 104 greater, for instance, to the range from 6 mm to 10 mm. However, if the curvature radius is actually made greater, or if the upper surface 103 is formed in an inclined surface to be continuous with the edge 104 so that there is formed a step, it was found that the problem is not solved, but the magnetic tape 102 is further damaged.

In particular, tape feeding speed at which a magnetic tape of a magnetic tape cassette is to be fast forwarded or rewound becomes greater and greater recently, and hence the above mentioned problem becomes serious. In addition, more highly densified recording is required recently. Thus, since only slight peel off of the above mentioned magnetic substance induces drop out, the above mentioned problem becomes a big one with respect to cassette performance.

In view of conventional problems, it is an object of the present invention to provide a reel to be used f or a magnetic tape cassette which reel can prevent magnetic substance applied to a magnetic tape from being peeled off, and can prevent a magnetic tape itself from being damaged.

The inventor has studied the conventional problems, and have found the solution. That is, the above mentioned object is accomplished by a reel to be used for a magnetic tape 4 cassette with upper and lower edges, which provides a cylindrical surface around which the magnetic tape is wound, and upper and lower flanges disposed above and below the upper and lower edges of the magnetic tape, respectively, the lower flange including teeth at an outer circumference of the lower flange and an upper surface except for the teeth to be raised towards the upper flange relative to an upper edge of the teeth, the upper surface having an outer circumferential edge of which a curvature radius is 1 mm to 4 mm both inclusive in a cross-section obtained when the lower flange is cut by a plane passing through a rotation axis of the reel.

In a preferred aspect of the present invention, the curvature radius of the outer circumferential edge is in the range of 1.5 mm to 3 mm.

In the reel to be used for a magnetic tape cassette, the outer circumferential edge of the upper surface of the lower flange other than the teeth is designed to have the curvature radius R in the range of 1 mm to 4 mm, preferably in the range of 1. 5 mm to 3 mm. In the lower limit of the curvature radius range, even if a magnetic tape is downwardly waved to thereby make contact with the outer circumferential edge of the upper surface of the lower flange, the magnetic tape is just rubbed in wider range than in a conventional reel, and thus is prevented from being locally rubbed. In addition, in the upper limit of the curvature radius range, it is considered that it is possible to avoid contact between the . 5 - edge of the magnetic tape and the edge of the teeth by forming inclination structure so that the outer circumferential edge has almost no step with the edge of the teeth.

In the accompanying drawings:

Fig. 1 is an enlarged view showing an outer circumferential portion of a lower flange of a magnetic tape cassette reel made in accordance with the present invention.

Fig. 2 is a cross-sectional view illustrating a structure of a magnetic tape cassette reel made in accordance with the present invention.

Fig. 3 is a cross-sectional view of a conventional magnetic tape cassette reel.

Fig. 4 is an enlarged view showing an outer circumferential portion of a lower flange of a conventional magnetic tape cassette reel.

Hereinbelow an embodiment of a reel to be used for a magnetic tape cassette, made in accordance with the present invention is explained with reference to Figs. 1 and 2. For the sake of better understanding of the present invention, a whole structure of a magnetic tape cassette and a magnetic tape cassette reel is first explained with reference to Fig. 2, and then a lower flange is explained with reference to Fig. 1.

As illustrated in Fig. 2, a magnetic tape cassette 200 having a pair of magnetic tape cassette reels 1 made in accordance with the present invention is formed at a bottom surface thereof with an opening 203 through which a driving shaft of a data regenerating apparatus for rotating the magnetic tape cassette reel is to be inserted and which corresponds to the magnetic tape cassette reel 1. The magnetic tape cassette is also formed at a front thereof with a guard panel 201 for opening and closing front opening 204 through which a magnetic tape 2 can be drawn out by a non-illustrated drawing pin (illustrated guide pins 210 are guide pins forming a tape bus).

The reel 1 to be used for a magnetic tape cassette includes a cylindrical body 11 (core) around which the magnetic tape 2 is to be wound. The cylindrical body is centrally formed with an engagement hole 12 through which a driving shaft of VTR (not illustrated) for rotating the magnetic tape cassette is to be inserted. The cylindrical body 11 around which the magnetic tape is to be wound is integrally formed at a lower end thereof with a lower flange 13.

On the other hand, a transparent upper flange 14 fabricated separately from the cylindrical body is fixedly secured to an upper end of the cylindrical body 11 around which the magnetic tape is to be wound. The magnetic tape 2 is usually wound so that the magnetic tape makes contact at its lower edge with an upper surface 16 of the lower flange 13, and forms a slight gap between the magnetic tape 2 and the lower 7 flange 14, as illustrated.

As illustrated in Fig. 1, the lower flange 13 is formed at a whole outer circumferential edge thereof with teeth 15 which is to be engaged to reel braking mechanism (not illustrated) of VTR. The structure having been explained so far is the same as a conventional one, but the reel to be used for a magnetic tape cassette of the present invention is characterized by that the upper surface 16 of the lower flange 13 with which the magnetic tape 2 makes contact is raised with a step relative to an upper surface 17 of the teeth 15, and that an outer circumferential edge 18 of the upper surface 16 of the lower flange 13 is designed to have a curvature radius in a specific range. In the embodiment, the curvature radius ranges from 1 mm to 4 mm, and preferably from 1.5 mm to 3 mm.

By designing the edge 18 of the upper surface 16 of the lower flange 13 to have the curvature radius R in a specific range, it is possible, as mentioned below, to prevent magnetic subst,ance applied to the magnetic tape 2 from being peeled off, and prevent the magnetic tape 2 itself from being damaged, even if the magnetic tape 2 is unwound or wound up while vertically waving.

There was conducted the experiment about how much the upper surface of the magnetic tape cassette reel 1 becomes dirty and how much the magnetic tape 2 is damaged when a pair of nine reels having a curvature radius R of the edge 18 varying in the range'of 0 to 0.5 mm are used in the magnetic tape-cassette 200. The specification of the tape reels and others is as follows. A height of upper and flange has surface around which a tape is to be wound has a 13.3 mm and a diameter of 36 mm, a diameter of the lower flanges is 122. 5 mm, the,teeth of the lower a length of 0. 5 mm in a direction of a radius of the reel, and a difference in height between an upper surface of the teeth and the upper surface of the lower flange is 0.2 mm.

In the experiments, after fast forwarding (FF) and rewinding (REW) were carried out each 1000 times, the dirtiness of the lower flange 13 of the reel and physical damage of the lower edge of the magnetic tape were observed with eyes and evaluated in accordance with the following standard. The practically allowable levels are A and B. The results are shown in Table 1.

The standard for evaluation in Table 1 indicates as follows: A indicates that there is no dirtiness of the lower flange, and the lower edge of the magnetic tape is not damaged at all, B indicates that the outer circumferential edge of the lower flange is partially dirty, but the lower edge of the magnetic tape is not damaged at all, C indicates that the outer circumferential edge of the lower flange is wholly dirty, but the lower edge of the magnetic tape is not damaged at all, and D indicates that the outer circumferential edge of the lower flange is wholly dirty, and the lower edge of the magnetic tape is found to have been damaged.

. 9 - Table 1

Number R of edge [mm] Evaluation 1 5.0 c 2 4.0 B 3 3.0 A 4 1.5 A 1.0 B 6 0.5 c 7 0.3 c 8 0.2 D 9 0.0 D As is understood in view of Table 1, when the curvature radius R of the edge 18 is 5. 0 mm, though the tape was not damaged, the outer circumferential edge of the lower flange was wholly dirty. If the curvature radius R is too great like this case, it is considered that the edge 18 is located in the vicinity of a tapered surface, and hence, the magnetic tape 2 makes contact with an edge of the upper surface 17 of the teeth 15 of the lower flange 13. As a result, it is considered that the magnetic tape 2 is locally rubbed and magnetic substance is peeled off, and the thus peeled off magnetic substance is attached to the reel to thereby make the reel dirty.

When the curvature radius R is 4.0 mm, the outer circumferential edge of the lower flange was partially dirty, and the tape was not found to be damaged. When the curvature radius R is 3.0 mm and 1.5 mm, the outer circumferential edge of the lower flange was not dirty at all, and the tape was not - found-to be damaged. When the curvature radius R is 1.0 mm, the outer circumferential edge of the lower flange was only partially dirty, and the tape was not found to be damaged.

Thus, it is considered that the curvature radius R in the range of 1. 0 to 4. 0 mm is not so great as the curvature radius R of 5.0 mm, and thus the magnetic tape 2 does not make contact with the edge of the teeth 15, and that the curvature radius R in the range of 1.0 to 4. 0 mm is not so small, and hence the magnetic tape 2 is not locally rubbed, resulting in that the outer circumferential edge of the lower flange does not become dirty at all or slightly dirty, and the magnetic tape is not damaged at all. In particular, when the curvature radius R is in the range of 1. 5 to 3. 0 mm, the remarkably advantageous result was obtained that the outer circumferential is edge of the lower flange does not become dirty at all, and the magnetic tape is not damaged at all.

When the curvature radius R was 0.5 mm. or 0.3 mm, the outer circumferential edge of the lower flange became wholly dirty. Thus, if the curvature radius R is relatively small, it is considered that the magnetic tape 2 is locally rubbed to thereby cause magnetic substance to be peeled off and also cause the magnetic tape 2 to be damaged.

When the curvature radius R was 0 - 2 mm and 0 mm, the outer circumferential edge of the lower flange became significantly dirty, and the tape was remarkably damaged. Accordingly, the curvature radius R below 0.5 mm is not pract-ical.

In view of the results of the experiment, it is considered that the curvature radius R in the range of 1.0 to 4. 0 mm is practical, and the curvature radius R in the range of 1.5 to 3.0 mm is more preferable.

As having been described, the magnetic tape cassette reel 1 made in accordance with the present invention can prevent a reel f rom becoming dirty and a tape f rom being damaged, and hence is suitable in particular to a highly densified magnetic tape to which much of magnetic substance is applied, and a business purpose magnetic tape cassette having a greater diameter of a roll of the magnetic roll 2.

As having been described, in the magnetic tape cassette reel made in accordance with the present invention, an outer circumferential edge of an upper surface of a lower flange is formed to have a curvature radius in a specific range, specifically, in the range of 1 to 4 mm, preferably in the range of 1. 5 to 3 mm, and hence, it can be avoided that a lower edge of a magnetic tape is locally rubbed with an outer circumferential edge or teeth, which rubbing would occur due vertical waving of a magnetic tape. As a result, it is possible to avoid that magnetic substance applied to a magnetic tape is dropped of f or peeled of f, a reel becomes dirty, and an edge of a magnetic tape is damaged.

12

Claims

1 3 4 5 6 7 8 9 11 12 13 1 2 1 2 3 4 5 6 7 8 1. A reel to be used for a magnetic tape cassette with upper and lower edges, comprising:

a cylindrical surface around which the magnetic tape is wound; and upper and lower flanges disposed above and below the upper and lower edges of the magnetic tape, respectively, the lower flange including teeth at an outer circumference of the lower flange and an upper surface except for the teeth to be raised towards the upper flange relative to an upper edge of the teeth, the upper surface having an outer circumferential edge of which a curvature radius is 1 mm to 4 mm both inclusive in a cross-section obtained when the lower flange is cut by a plane passing through a rotation axis of the reel.

2. The reel of claim 1, wherein the curvature radius is preferably 1.5 mm to 3 mm.

3. In a magnetic tape cassette comprising a casing in which a pair of tape reels having a magnetic tape wound thereon are rotatably arranged in a longitudinal direction of said casing and a front of which has a guard panel for opening and closing a front opening through which said magnetic tape can be drawn out by drawing pins of a magnetic recording and/or reproducing apparatus, the improvement characterized in that each of said tape reels comprises:

1 -, J 9 10 11 a cylindrical surface around which the magnetic tape is wound; and upper and lower f langes disposed above and below the upper and lower edges of the magnetic tape, respectively, the lower flange including teeth at an outer circumference of the lower flange and an upper surface except for the teeth to be raised towards the upper flange relative to an upper edge of the teeth, the upper surface having an outer circumferential edge of which a curvature radius is 1 mm to 4 mm both inclusive in a cross-section obtained when the lower flange is cut by a plane passing through a rotation axis of the reel.

12 13 14 is 16 17 18 19 1 2

4. The magnetic tape cassette of claim 3, wherein the curvature radius is preferably 1.5 mm to 3 mm.

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