GB2344404A

GB2344404A - Guide roller for magnetic tape recording/reproducing apparatus

Info

Publication number: GB2344404A
Application number: GB9928708A
Authority: GB
Inventors: Ikuichiro Nawa
Original assignee: Mitsumi Electric Co Ltd
Current assignee: Mitsumi Electric Co Ltd
Priority date: 1998-12-04
Filing date: 1999-12-03
Publication date: 2000-06-07
Anticipated expiration: 2019-12-03
Also published as: JP2000173136A; GB2344404B; GB9928708D0

Abstract

The guide roller assembly has a supporting shaft, 23, a top flange 28 restricting the position of a top edge of a running magnetic tape and a roller 27 for guiding the magnetic tape. The roller comprises a roller part 27a, bottom flange 27b for preventing the tape from slipping off the roller and a downward extension part 27c. The roller is subject to an uneven force F4 exerted by the magnetic tape. The downward extension part 27c bears against the shaft so that its bottom inner rim (53 Fig. 8b) acts as a fulcrum to apply a moment (M) ensuring that tilting of the roller on the shaft due to the uneven force does not occur and the roller can rotate in a stable way.

Description

"GUIDE ROLLER AND MAGNETIC TAPE RECORDING/REPRODUCING APPARATS" The present invention relates generally to a guide roller and magnetic tape recording/reproducing apparatus, and more particularly, to a guide roller and magnetic tape recording/reproducing apparatus for guiding the run of a magnetic tape.

As a magnetic tape recording/reproducing apparatus, for example, a so-called Digital Audio Tape Recorder, or DAT, is known. The DAT works by moving a guide roller-mounted loading base along a guide groove, extracting a magnetic tape from a compact tape cassette and winding the magnetic tape about a rotary cylinder carrying a helical-scan magnetic head across a predetermined range to perform digital recording and reproduction.

FIG. 1 and FIG. 2 show a conventional guide roller 30. The guide roller 30 has a top flange 32 that determines the position of the top edge of the magnetic tape (not shown in the drawing), a roller 34 that guides the run of the magnetic tape, a bottom flange 38 that prevents the magnetic tape from slipping off the roller 34, a positioning screw portion 36 that adjusts the position of the run of the magnetic tape, and a shaft 35 that bears all these constituent parts of the conventional guide roller 30.

The top flange 32, the bottom flange 38 and the positioning screw portion 36 are fixed in place by the pressed insertion of the shaft 35, with the shaft 35 penetrating a hole 39 formed all the way through the longitudinal center of the roller 34, the shaft 35 being free to rotate. Additionally, a bottom surface of the roller 34 contacts the bottom flange 38 so as to prevent the roller 34 from slipping off the shaft 35.

The conventional guide roller 30 having the structure described above is mounted on a loading base 40 and installe in a magnetic tape recording/reproducing apparatus. The loading base 40 is provided with a post base bush 33, the shaft 35 of the guide roller 30 being inserted in an insertion hole 41 formed inside the center of the post base bush 33.

Additionally, a positioning thread portion 37 for engaging the positioning screw portion 36 is formed on an upper part of the insertion hole 41. The height of the top flange 32 can be determined by the positioning screw portion 37 and the positioning thread portion 36, and, accordingly, the position of the run of the magnetic tape can be adjusted.

FIG. 3 shows a state in which a magnetic tape 43 is in a tape loading state. In this tape loading state, the magnetic tape 43 is guided by guide rollers 30 and tilted posts 42 and wound helically about a rotary cylinder 44 at a predetermined angle.

However, when the magnetic tape 43 is extracted from the tape cassette (not shown in the drawing), the height of the tape on the supply side and the take-up side is identical. By contrast, it is necessary to wind the magnetic tape 43 helically about the rotary cylinder 44 as shown in FIG. 3, which means that the position of the magnetic tape 43 upon entry to the rotary cylinder 44 is higher than the position of the magnetic tape 43 upon exit from the rotary cylinder 44. As a result, the guide rollers 30 and the tilted posts 42 are slanted so as to form the tapered pass described above.

Additionally, in order to perform magnetic recording and reproduction with a high degree of accuracy it is necessary to position the run of the magnetic tape 43 accurately so that the bottom edge of the magnetic tape 43 runs along a lead 47 formed on the rotary cylinder 44, that is, a step formed on the rotary cylinder 44 so as to guide the run of the magnetic tape 43. The positioning of the run of the magnetic tape 43 is performed mainly by the top flange 32 of the guide roller 30 restricting the top edge of the magnetic tape 43.

Accordingly, in order to make it easier to limit the position of the run of the magnetic tape 43 by the top flange 32, the angle at which the guide rollers 30 and tilted posts 42 are slanted is set so that the tape tension at the top edge of the magnetic tape 43 is less than the tape tension at the bottom edge of the magnetic tape 43.

However, in order for the roller 34 to rotate smoothly in a mounted state about the shaft 35, it is desirable that a force F1 exerted on a top edge 45 of the roller 34 by the magnetic tape 43 and a force F2 exerted on a bottom edge 46 of the roller 34 by the magnetic tape 43 be equal. If force F1 and force F2 are equal, then the roller 34 can rotate about the shaft 35 without deviation or tilting as shown in FIG. 4A. It will be appreciated that the forces F1 and F2 exerted by the magnetic tape 43 are proportional to the tape tension of the magnetic tape 43.

At the same time, however, when the tape tension at the top edge of the magnetic tape 43 is set to be less than the tape tension at the bottom edge of the magnetic tape 43 as described above, an accompanying force F3 exerted on the roller 34 by the magnetic tape 43 is concentrated largely at the bottom edge 46 of the roller 34 as shown in FIG. 4B. As a result, a bottom edge 49 located at the bottom of the hole 39 contacts the shaft 35 but a top edge 48 located at the top of the hole 39 alternately contacts and does not contact the shaft 35, that is, rotates in an unstable state. Additionally, if the bottom edge 49 of the hole 39 is higher than the position at which the force F3 is exerted, then the roller 34 rotates in a state in which it is tilted at an angle with respect to the shaft 35.

Accordingly, the roller 34 cannot form a stable axis of rotation and rotates in an unstable state, that is, slanted at an angle with respect to the shaft 35, causing tape fluctuation and tape damage as a result.

Further, when the rotation of the roller 34 is unstable, fluctuations in the tape and tape damage such as curling occur, hindering efforts to increase the recording density or capacity of the magnetic tape 43 by making the recording tracks narrower and the magnetic tape 43 thinner Additionally, the roller 34 locally contacts the shaft 35 and suffers wear as a result, reducing the useful life of the guide roller 30.

It should be noted that in FIGS. 4A and 4B the clearance between the shaft 35 and the hole 39 of the roller 34 is exaggerated in order to facilitate an understanding of the conventional art and its disadvantages.

Accordingly, it is a general object of the present invention to provide an improved and useful guide roller and magnetic tape recording/reproducing apparatus, in which the disadvantages described above are eliminated.

Another and more specific object of the present invention to provide a guide roller capable of delivering stable rotation of the roller.

According to a first aspect of the present invention, there is provided a guide roller, characterized by having: a top flange that restricts a position of a top edge of a running magnetic tape; a roller for guiding a run of said magnetic tape, said roller be subjected unevenly to a force exerted by said magnetic tape ; a bottom flange for preventing said magnetic tape from slipping off said roller ; and a shaft for rotatably supporting said top flange, said roller and said bottom flange, said roller having a bearing portion borne by said shaft, said bearing portion configured so that a strongest of a plurality of forces exerted by said magnetic tape on said roller arises at a position between a top edge of said roller and a bottom edge of said roller.

According to another aspect of the present invention, there is provided a magnetic tape recording/reproducing apparatus having a guide roller, said guide roller characterized by having: a top flange that restricts a position of a top edge of a running magnetic tape; a roller for guiding a run of said magnetic tape, said roller be subjected unevenly to a force exerted by said magnetic tape; a bottom flange for preventing said magnetic tape from slipping off said roller; and a shaft for rotatably supporting said top flange, said roller and said bottom flange, and further, said roller having a bearing portion borne by said shaft, said bearing portion configured so that a strongest of a plurality of forces exerted by said magnetic tape on said roller arises at a position between a top edge of said roller and a bottom edge of said roller.

According to the invention described above, the point of contact between the bottom edge of the bearing portion and the shaft becomes a fulcrum by means of which a force is applied in a direction so as to contact the top edge as well with the roller. As a result, the frictional state of the roller against the shaft can be stabilized and the rotation of the roller can be made smooth.

According to another aspect of the present invention, there is provided the guide roller as described above, wherein the bottom flange and the roller are separate parts, the bottom flange being fixedly mounted on the shaft.

According to the invention described above, the roller can be formed more easily. Additionally, the useful life of the roller can be extended because the roller and the shaft do not touch.

Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which: FIG. 1 is an exploded view of an example of a conventional guide roller shown together with a loading base; FIG. 2 is a cross-sectional view of an example of the conventional guide roller; FIG. 3 is a diagram showing a state in which a magnetic tape is in a tape loading state; FIGS. 4A and 4B are diagrams illustrating the problems that arise with the conventional guide roller ; FIG. 5 is a plan view of a magnetic tape recording/reproducing apparatus capable of applying an embodiment of a guide roller according to the present invention; FIG. 6 is an enlarged cross-sectional view of the embodiment of a guide roller according to the present invention; FIG. 7 is an exploded view of the embodiment of a guide roller according to the present invention shown together with a loading base; FIGS. 8A and 8B are diagrams illustrating the operation of the embodiment of the guide roller according to the present invention; and FIG. 9 is a diagram illustrating a variation of the present invention.

A description will now be given of an embodiment of the present invention, with reference to the accompanying drawings.

FIG. 6, FIG. 7 and FIGS. 8A and 8B show guide rollers 16,17 which are an embodiment of the present invention. FIG. 5 shows an example of a magnetic tape recording/reproducing apparatus 1, hereinafter referred to simply as the apparatus 1, capable of adapting the guide rollers 16,17 shown in FIGS. 6,7,8A and 8B.

The apparatus 1 shown in FIG. 5 is a rotary type DAT, and comprises a chassis 2, a cassette load/unload mechanism 3, a reel drive mechanism 4, a rotary cylinder 5 and a tape loading mechanism 6, all mounted on the chassis 2. All these mechanisms and devices are configured so as to be mountable on the chassis 2 from above the chassis 2, thus simplifying the assembly process.

The cassette load/unload mechanism 3 loads a tape cassette (not shown in the diagram) to a predetermined recording/reproducing position inside the apparatus 1. In the present embodiment, a so-called kangaroo pocket-type cassette load/unload mechanism is used.

The reel drive mechanism 4 rotatably drives a supply reel 9 and a take-up reel 10, the drive power for which is supplied in the present embodiment by a capstan motor 11. The speed of rotation and the direction of rotation of the reels 9,10 are controlled by the apparatus 1 modes, that is, recording/reproducing mode, fast forward/rewind mode, search mode, and so on.

As a result, a variety of gears, pulleys, idlers and so forth are compactly arranged inside the reel drive mechanism 4. The individual parts which together make up the reel drive mechanism 4 are made of high-strength plastic or some similar material, so it is possible to make the reel drive mechanism 4 compact despite the existence of so many constituent parts.

The rotary cylinder 5 is mounted on a drum base 7 formed from hard plastic. A magnetic tape 43 is wound helically about this rotary cylinder 5 at a predetermined angle.

The tape loading mechanism 6 winds the magnetic tape 43 extracted from the tape cassette about the rotary cylinder 5 at a predetermined angle. So-called M loading is used for this tape loading mechanism 6, which moves a pair of loading bases 12,13 along guide grooves 14,15 formed in the drum base 7 by means of a link mechanism not shown in the drawing, loading or unloading the magnetic tape 43 in the process.

On the loading bases 12,13 are provided the guide rollers 16,17 that constitute the distinctive feature of the present invention.

A description of guide rollers 16,17 will now be given with reference to FIGS. 6 and 7. FIG. 6 is an enlarged cross-sectional view of the embodiment of a guide roller according to the present invention. FIG. 7 is an exploded view of the embodiment of a guide roller according to the present invention shown together with the loading base. It should be noted that although the drawings show only guide roller 16 and loading base 12, guide roller 17 and loading base 13 have a structure identical to that of guide roller 16 and loading base 12.

As shown in FIG. 7, loading bases 12,13 mount guide rollers 16,17 and also mount tilted posts 18,19 as well. Additionally, loading bases 12,13 also mount a post base bush 20 that adjusts the height and then mounts the guide rollers 16,17. It should be noted that reference numeral 21 is a connecting pin for connecting the link mechanism mentioned previously.

Broadly, guide rollers 16,17 comprise a top flange 28, a roller 27, a shaft 23 and a positioning screw portion 24. The top flange 28 has the shape of a sword guard and is fixed in place by a top edge portion of the shaft 23 pressing down on the top flange 28. This top flange 28 functions to restrict the run position of the magnetic tape 43 when the top edge of the magnetic tape 43 contacts the top flange 28.

By passing the shaft 23 through a hole 29 formed in the center of the roller 27, the shaft 23 is rotatably disposed. The roller 27 functions to guide the run of the magnetic tape 43. For ease of explanation a detailed description of the roller 27 will be deferred until later.

The positioning screw portion 24 is fixed in place by the shaft 23 pressing down on the positioning screw portion 24. Additionally, the positioning screw portion 24 is positioned at a predetermined position below the roller 27. Additionally, the shaft 23 extends well below the position of the positioning screw portion 24.

An insertion hole 25 for the insertion of the shaft 23 of the guide rollers 16,17 is formed inside the post base bush 20 mounted on the loading bases 12,13.

Additionally, a positioning thread portion 26 is formed at a top portion of the insertion hole 25. This positioning thread portion 26 engages the positioning screw portion 24.

In order to mount the guide rollers 16,17 on the loading bases 12,13, the shaft 23 is first inserted into the insertion hole 25 formed in the post base bush 20.

Next, the positioning screw portion 24 is made to engage the positioning thread portion 26. The extent to which the positioning screw portion 24 is threaded into the positioning thread portion 26 determines the height of the top flange 28 with respect to the loading base 12,13.

Accordingly, the height of the top flange 28 is adjusted to a predetermined height, thereby enabling the mounting of the guide rollers 16,17 on the loading bases 12,13 in a state in which it is possible for the run of the magnetic tape 43 to be positioned correctly.

Next, a description will be given of the composition of the roller 27 that comprises the essential element of the present invention, with reference to FIGS.

6,7,8A and 8B.

The roller 27 comprises a roller part 27a, a bottom flange 27b and a downward extension part 27c. The roller part 27a, which has a cylindrical shape, is the part that contacts the magnetic tape 43. Additionally, the bottom flange 27b is formed on an outer periphery of a bottom edge of the roller part 27a, and has a diameter greater than the diameter of the roller part 27a.

Accordingly, the bottom flange 27b has the shape of a sword guard with respect to the roller part 27a, and as a result, the magnetic tape 43 is prevented from slipping off the roller part 27a.

Additionally, the downward extension part 27c is formed on a bottom part of the bottom flange 27b. In the present invention, this downward extension part 27c has a diameter less than the diameter of the roller part 27a.

However, this downward extension part 27c may be of any diameter, provided that it does not interfere with the run of the magnetic tape 43 or with the fully assembled unit.

Additionally, the roller part 27a, bottom flange 27b and downward extension part 27c of the above-described roller 27 form a single integrated unit. The roller 27 may be formed from hard plastic or metal, so even a roller like the roller 27 described above can be machined or formed easily and inexpensively.

Additionally, by making the roller part 27a and the bottom flange 27b a single integrated unit compared as described above, it is possible to reduce the number of constituent parts of the roller as compare to the conventional guide roller 30 shown in FIGS. 1 and 2. As a result, it is possible to reduce the cost of the guide rollers 16,17.

The above-described roller 27 is rotatably supported by the shaft 23. That is, when the roller 27 rotates, the bottom flange 27b turns together with the roller part 27a. By constructing the roller 27 so that the bottom flange 27b turns with the roller 27, damage to the magnetic tape 43 can be prevented even if the bottom edge of the magnetic tape 43 contacts the bottom flange 27b.

In so doing, it is possible to prevent magnetized particles from falling off the magnetic tape 43 when the magnetic tape 43 is running, and, further, it is possible to prevent the magnetic tape 43 from curling.

Accordingly, it is possible to improve the stability of the run of the magnetic tape 43.

A description will now be given of the function of the downward extension part 27c formed on the roller 27, with reference to FIGS. 6 and 7 and, additionally, FIGS.

8A and 8B.

FIGS. 8A and 8B are diagrams illustrating the operation of the embodiment of the guide roller according to the present invention, and is a schematic view of essential parts of a state in which the roller 27 is seated upon the shaft 23. It should be noted that, for convenience of explanation, in FIGS. 8A and 8B the bottom flange 27b is not shown and, further, the clearance between the shaft 23 and the hole 29 of the roller 27 is exaggerated.

As with the conventional guide roller 30 described above, the guide rollers 16,17 of the present embodiment and the tilted post 18,19 are set at an angle such that the tape tension at the top edge of the magnetic tape 43 is less than the tape tension at the bottom edge of the magnetic tape 43 so that the top flange 28 may more easily restrict the position of the run of the magnetic tape 43.

However, by making the tape tension of the top edge of the magnetic tape 43 less than the tape tension of the bottom edge of the magnetic tape 43, as shown in FIG.

4B a force F3 exerted by the magnetic tape 43 is concentrated mainly at the bottom edge 46 of the roller 34, such that the roller 34 tilts with respect to the shaft 35 and in that tilted state rotates unstably, causing fluctuation of the magnetic tape and damage to the magnetic tape as noted previously.

In order to obtain a more stable rotation of the roller 27, the present embodiment forms a downward extension part 27c on the roller 27.

An explanation of how the provision of a downward extension part 27c on the roller 27 stabilizes the rotation of the roller 27 will now be given with reference to FIGS. 8A and 8B.

FIG. 8A shows a state of the shaft 23 and the roller 27 in which no tape tension is generated because the magnetic tape 43 is not running. If the magnetic tape 43 starts to run from the state shown in FIG. 8A, then tape tension is generated on the magnetic tape 43 and the roller 27 is subjected to a force F4 exerted by the magnetic tape 43 corresponding to the tape tension on the magnetic tape 43.

As noted previously, the tape tension at the top edge of the magnetic tape 43 is smaller than the tape tension at the bottom edge of the magnetic tape 43.

Accordingly, the strongest force F4 exerted on the roller 27 is exerted at the point at which the roller 27 contacts the bottom edge of the magnetic tape 43 as shown in FIG.

8B, that is, the roller bottom edge 52 that is the bottom edge of the roller part 27a.

The conventional guide roller 30 is constructed so that the force F3 is exerted on the bottom edge of the roller 34 as shown in FIG. 4B. By contrast, because a downward extension part 27c is formed on the lower part of the roller part 27a with the guide rollers 16,17 of the present embodiment, the force F4 is exerted at a point, that is, at the roller bottom edge 52, that lies between the guide roller top edge 50 and the guide roller bottom edge 51.

Since the force F4 is exerted on the roller bottom edge 52, that is, at a point between the guide roller top edge 50 and the guide roller bottom edge 51, the point of contact between the bottom edge 53 of the hole 29 in the roller 27 on the one hand and the shaft 23 on the other acts as a fulcrum, generating a moment shown as arrow M in FIG. 8B. This moment M tends to press the roller 27 against the shaft 23 and, as shown in FIG. 8B, the shaft 23 bears the roller 27 along the length of the roller 27.

As a result, the state of contact of the roller 27 with the shaft 23 is stabilized and it is possible to make the rotation of the roller 27 smooth. Additionally, the useful life of the guide rollers 16,17 can be extended because the shaft 23 and the roller 27 no longer contact each other locally.

FIG. 9 is a diagram illustrating a variation of the guide rollers 16,17 of the above-described embodiment.

It should be noted that parts shown in FIG. 9 that are identical to parts shown in FIGS. 6,7,8A and 8B are given identical reference numerals and descriptions thereof omitted.

With the guide rollers 16,17 shown in FIGS. 6, 7,8A and 8B, the bottom flange 27b is integrally formed with the roller 27 as a single unit. By contrast, in the guide roller 60 of the variation shown in FIG. 9 the bottom flange 61 and the guide roller 60 are separate parts, with the bottom flange 61 pressed by the shaft 23.

Additionally, in order to achieve the same effects as with the guide rollers 16,17, the present variation forms a downward extension part 27C on a bottom part of the roller 27. As a result, a trapezoidal concavity 62 is formed in the bottom flange 61 at a position opposite the downward extension part 27C.

Accordingly, in an assembled state the downward extension part 27C is positioned within the trapezoidal concavity 62, and a bottom surface of the roller 27 is contactably supported by a sword guard portion 63 continuously formed with the trapezoidal concavity 62.

Accordingly, by forming the bottom flange 61 and the roller 27 as separate parts the roller 27 can be formed more easily than is the case with the embodiment described above, in which the bottom flange 27b and the roller 27 form a single integrated unit.

It should be noted that, although the embodiment described above uses a DAT to illustrate the structure, function and advantages of the present invention, the present invention is not limited to a DAT but can be adapted for use with any magnetic tape recording/reproducing apparatus that uses helical scanning to record and reproduce data to and from a magnetic tape.

The above description is provided in order to enable any person skilled in the art to make and use the invention and sets forth the best mode contemplated by the inventor of carrying out the invention.

The present invention is not limited to the specifically disclosed embodiment and variation, and modifications may be made without departing from the scope of the present invention.

The present application is based on Japanese priority application no. 10-345966 filed on December 4, 1998, the entire contents of which are hereby incorporated by reference.

Claims

CLAIMS:

1. A guide roller, characterized by having: a top flange that restricts a position of a top edge of a running magnetic tape; a roller for guiding a run of said magnetic tape, said roller be subjected unevenly to a force exerted by said magnetic tape; a bottom flange for preventing said magnetic tape from slipping off said roller; and a shaft for rotatably supporting said top flange, said roller and said bottom flange, said roller having a bearing portion borne by said shaft, said bearing portion configured so that a strongest of a plurality of forces exerted by said magnetic tape on said roller arises at a position between a top edge of said roller and a bottom edge of said roller.

2. The guide roller as claimed in claim 1, characterized in that said bottom flange and said roller are separate parts, said bottom flange being fixedly mounted on said shaft.

3. The guide roller as claimed in claim 1, characterized in that a downward extension part having a diameter less than a diameter of said roller is provided on a bottom edge of said roller.

4. A magnetic tape recording/reproducing apparatus having a guide roller, said guide roller characterized by having: a top flange that restricts a position of a top edge of a running magnetic tape ; a roller for guiding a run of said magnetic tape, said roller be subjected unevenly to a force exerted by said magnetic tape; a bottom flange for preventing said magnetic tape from slipping off said roller ; and a shaft for rotatably supporting said top flange, said roller and said bottom flange, and further, said roller having a bearing portion borne by said shaft, said bearing portion configured so that a strongest of a plurality of forces exerted by said magnetic tape on said roller arises at a position between a top edge of said roller and a bottom edge of said roller.

5. The guide roller substantially as hereinbefore described with reference to the drawings.

6. The magnetic tape recording/reproducing apparatus substantially as hereinbefore described with reference to the drawings.