GB2134691A

GB2134691A - Tape guide assembly

Info

Publication number: GB2134691A
Application number: GB08332627A
Authority: GB
Inventors: Hiroyuki Uchida; Keisuke Fujiwara; Hideko Imamura
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1982-12-08
Filing date: 1983-12-07
Publication date: 1984-08-15
Also published as: NL8304156A; GB8332627D0; DE3344307A1; FR2537758A1

Abstract

A tape guide assembly includes first and second tape guide means 30, 31 disposed respectively on both sides of a recording head and/or a playback head in proximity thereto and third and fourth tape guide means 32, 33 disposed respectively on both sides of the first and second tape guide means. The first to fourth tape guide means are each provided with a flange portion so as to restrict one and the other side edge portions of a tape alternately so that in the region of the recording and/or playback head(s) the centre line of the tape remains in the same position despite variations in the width of the tape. Guide constructions are detailed (Figs. 5-8). An erase head may have flanges to replace guide means 32, 33. Relative width settings are detailed. <IMAGE>

Description

SPECIFICATION Tape guide assembly The present invention relates to a tape guide assembly for restricting transverse movements of a tape.

In a tape recorder using a multitrack fixed head, it is important to restrict transverse movements of the travelling tape. Particularly, in a tape recorder for recording and reproducing digital audio signals which has recently been under development, the guard band between tracks becomes extremely narrow because several tens of tracks are formed on a tape. As a result, if the tape moves up and down in its transverse direction during recording, the tracks which are formed may meander. In addition, if the tape makes such vertical movements in its transverse direction also during playback, it is no longer possible for the playback head to accurately trace the recording tracks.Thus, in the case of such digital tape recorder, vertical movements of the tape must be restricted more strictly than in the conventional analog tape recorders. in this case, since there are variations in the tape width, the restriction of the movements in question should take such variations into account.

According to the present invention, there is provided a tape guide assembly for a tape recorder having a recording head and/or a playback head, said tape guide assembly including: first and second tape guide means disposed respectively on each side of said recording head and/or said playback head in proximity thereto; and third and fourth tape guide means disposed respectively on both sides of said first and second tape guide means, said first, second, third and fourth tape guide means being each provided with a flange portion so as to restrict one and the other side edge portions of the tape in an alternate manner.

The invention will be further described by way of example with reference to the accompanying drawings, in which~ Fig. 1 is a plan view of a lower half of a tape cassette to which the present invention is applicable; Fig. 2 is a front view thereof; Fig. 3 is a plan view of a principal portion showing an embodiment of the present invention; Fig. 4 is a front view thereof; Figs. 5 and 6 are perspective views showing examples of tape guides; Fig. 7 is a view illustrative of the arrangement of tape guides; Fig. 8 is a perspective view showing another example of a tape guide; Fig. 9 is a view showing the relation between tape guides and the width of a tape; and Fig. 10 is a view showing a tape format to which the present invention is applicable.

Figs. 1 and 2 illustrate a conventional compact cassette 1 to which the present invention is applicable, Fig. 1 showing a lower half 2 and Fig.

2 showing the front of the cassette 1.

The cassette 1 is composed of a lower half 2 and an upper half 3 as shown in Fig. 2. On the lower half 2 are mounted a pair of reel hubs 5 an 6 onto which is wound a tape 4 as shown in Fig.

1. The tape 4 delivered from the reel hub 5 is wound onto the reel hub 6 via guide pin 7, guide roller 8, guide pin 9, tape pad 10, guide pin 11, guide roller 12, and guide pin 13. The tape pad 1C is bonded to a leaf spring 14 which is fitted on a sheild plate 1 5. In the front face of the cassette 1 are formed recording and playback head insertion window 16, erase head insertion windows 17 and 18 and pinch roller insertion window 19 and 20.

The lower half 2 is further provided with capstan insertion holes 21 and 22 and pins 23 and 24, and a sheet 25 is disposed thereon.

Referring now to Figs. 3 and 4, there is shown a tape guide assembly 26 according to an embodiment of the present invention. The guide assembly 26 is disposed on a head base 27 as shown in Fig. 3. Figs. 3 and 4 show a recording or reproducing state, in which the head base 27 has been moved in the direction of arrow "a" from its stepped state. ~g.4 is a schematic view, seen from the direction of arrow "c" in Fig. 3, of only a principal portion of the travelling path of the tape 4 at the front face of the cassette 1.

To the head base 27 are attached a recording head 28 and a playback head 29, and a pair of tape guides 30 and 31 are disposed on both sides of the heads 28 and 29. Further, on both sides of the tape guides 30 and 31 are disposed tape guides 32 and 33. The tip end portions of the guides 30 and 31 are inserted into the cassette 1 together with the heads 28 and 29 from the insertion window 16, while the guides 32 and 33 are inserted into the cassette 1 from the insertion windows 17 and 18, respectively.

Referring now to Figs. 5 and 6, there are shown examples of the guides 30 and 31, respectively. In Fig. 5, an L-shaped plate member 35 is fixed to the upper surface of a block member 34, and a tapped hole 36 is formed in the block member 34. To the tip end portion of the plate member 35 is perpendicularly attached a guide pin 38a which is provided only at its upper portion with a guide flange 37a. An adjusting screw 39 is threadedly fitted into the tapped hole 36 at one end portion thereof and also at the other end portion thereof into a tapped hole 40 formed in the head base 27. Further, a spring 41 is interposed between the block member 34 and the head base 27 to urge the block member 34 upward.

According to the above-described construction, the height of the block member 34, namely, the height of the flange 37a, can be adjusted by turning the adjusting screw 39. In this case, even if the adjusting screw 39 is turned, the block member 34 is not turned, but moves only in the vertical direction.

In the case of the guide 31 shown in Fig. 6, the plate member 35 is fixed to the upper surface of the block member 34 and is bent downward, and a flange 37b is formed only at the lower portion of a pin 38b.

In the present invention, the width WO restricted by the flange 37a of the guide 30 and the flange 37b of the guide 31 is set as W0=W1-AW as shown in Fig. 7. More specifically, the width W, of the tape 4 generally has a tolerance jAW, but in the present invention the restricted width WO is set at the minimum value of the tape width, i.e., W1-AW.

Referring now to Fig. 8, there is shown an example of the tape guides 32 and 33, in which the guides 32 and 33 are fixed to the head base 27, and guide flanges 43 and 44 are formed at the top and bottom on one side of a block member 42 integrally at an interval almost equal to the width of the tape. This spacing between the flanges 43 and 44 is formed with a fairly high accuracy. In the case where an erase head is mounted on the head base 27, the erase head is used as a substitute for the guides 32 and 33, and in this case, the flanges 43 and 44 are formed on the front face of the erase head.

The following description is now provided about the adjusting method for restricting vertical movements of the tape 4 using the tape guide assembly 26 constructed as above.

In Fig. 4, the tape 4 is guided by the guides 32, 30,31 and 33. First, the adjusting screw 39 of the guide 30 is turned so that the flange 37a lightly contacts an upper edge portion 4a of the tape 4 and at the same time a lower edge portion 4b of the tape 4 lightly contacts the lower flange 44 of the guide 32. Then, the adjusting screw 39 of the guide 31 is turned so that the flange 37b lightly contacts the lower edge portion 4b of the tape 4 and at the same time the upper flange 43 of the guide 33 lightly contacts the upper edge portion 4a.

In this state, as the tape 4 travels in the direction of arrow "b", the upper and lower edge portions 4a and 4b are alternately restricted by the four guides 32, 30, 31 and 33. In this case, since the distance between the guides 32 and 33 is short and the four guides, 32, 30, 31 and 33 are concentrated, the tape 4 can travel lengthways while being almost stationary in the vertical direction.

In this case, moreover, since the upper and lower edge portions 4a and 4b of the tape 4 are restricted in different positions, variations in the width of the tape 4, if any, would not affect the stable travelling of the tape. In the case where the upper and lower edge portions 4a and 4b are restricted in the same position by using only =E shaped guides such as, for example, the guides 32 and 33, the spacing between the upper and lower flanges of each guide must be set in consideration of variations in the width of the tape 4, and therefore vertical movements are unavoidable during travelling of the tape 4.

According to experiments, in the case of using a conventional D-shaped guide member alone, a gap of 20 to 30 ym is formed between the tape 4 and the guide member, and the tape 4 moves up and down within this gap, while in the case of using the tape guide assembly 26 of the present invention, it has been confirmed that vertical movements of the tape 4 can be maintained within the range of as small as 2 to 3 ym. Such slight degree of vertical movements cause no practical problem even in the case of a multitrack digital tape recorder.

The reason why the width W0 restricted by the guides 30 and 31 is set as WO=W,~åW as shown in Fig. 7 will be explained below with reference to Fig. 9.

In Fig. 9, in the case where the tape 4 has the minimum width W1-AW as shown in solid lines, the tape 4 travels straight ahead in the horizontal direction while being restricted by the flanges 37a and 37b of the guides 30 and 31. On the other hand, in the case where the tape 4 has the maximum width W,+AW as shown in dotted lines, the tape 4 travels while being bent by the flange 37a. If attention is here given to a center line LX of the tape 4 shown in solid line and a center line L2 of the tape 4 shown in dotted line, it is seen that both lines L, and L2 intersect a center line L3 at one point "0" between the guides 30 and 31 , the center line L3 is perpendicular to the travelling direction of the tape 4.Therefore, if the head is disposed in the position of the center line L3 or in the vicinity thereof, influence caused by variations in the width of the tape 4 can be kept to a minimum.

Such arrangement is advantageously used in the case of forming such a tape format as shown in Fig. 10.

Fig. 10 shows a format in the case of making recording and playback with respect to side A and side B while advancing the tape 4. On the side A are formed plural tracks 45t,452, . . 45n in pre- determined positions relative to the center line L, of the tape 4, while on the side B are formed plural tracks 46,, 462,... 46n symmetrically with the tracks 45, to 45n on the side A relative to the center line L. Between the tracks 45n and 46n is formed a guard band 47 of width W3 so that the center line L, passes the center of the of the guard band 47. Thus, even when the tracks on the side A and the tracks on the side B are formed symmetrically with respect to the center line L1, the central guard band 47 is not influenced by variations in the tape width for the reason set forth in connection with Fig. 9, thus permitting the tape 4 to be advanced in an extremely stable manner.

In the illustrated embodiment, first on the upstream side of the tape 4, the lower edge portion 4b is restricted, then toward the downstream side, the upper edge portion 4a, lower edge portion 4b and upper edge portion 4a are restricted successively in this order. But this order may be reversed by replacing the guides 30 and 31 with each other. In the illustrated embodiment, moreover, the upper flange 43 of the guide 32 and the lower flange 44 of the guide 33 are not specially necessary, but these flanges 43 and 44 can function as stoppers against large vertical movements of the tape 4. Further, the structures of the guides 30, 31 and 32, 33 may be modified without being restricted to those exemplified above. Although in the above embodiment the present invention is applied to the conventional compact cassette, the present invention is applicable to various other types of tape cassettes and reels.

According to the illustrated embodiment, as set forth hereinabove, since one and the opposite side edge portions of a tape are restricted in different positions along the length of the tape path and this restricted width is set at the minimum width of the tape, there can be obtained a tape guide assembly of an extremely high accurc~cy not influenced by variations in the tape width. The illustrated tape guide assembly is particularly advantageous in the case of forming tracks symmetrically with respect to the center line of the tape.

Claims

1. A tape guide assembly for a tape recorder having a recording head and/or a playback head, said tape guide assembly including: first and second tape guide means disposed respectively on each side of said recording head and/or said playback head in proximity thereto; and third and fourth tape guide means disposed respectively on both sides of said first and second tape guide means, said first, second, third and fourth tape guide means being each provided with a flange portion so as to restrict one and the other side edge portions of the tape in an alternate manner.

2. A tape guide assembly according to claim 1, wherein the width defined by said flange portions of said first and second tape guide means is at or close to the minimum value of the tape width.

3. A tape guide assembly according to claim 1 or 2, wherein said first tape guide means has a first flange portion which restricts only one side edge portion of the tape, and said second tape guide means has a second flange portion which restricts only the other side edge portion of the tape.

4. A tape guide assembly according to claim 3, wherein means for adjusting the height of said first and second flange portions are further included.

5. A tape guide assembly according to any one of the preceding claims, wherein said third and fourth tape guide means are each provided with upper and lower flanges which are spaced from each other more widely than the maximum value of the tape width.

6. A tape guide assembly constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.