JPH0121548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a magnetic head unit having a magnetic head having one edge of a head surface where a head gap terminates, a magnetic tape is passed along the head surface, and at least one of the magnetic heads is The present invention relates to a magnetic tape cassette device comprising a height limiting member for limiting the movement of a magnetic tape in a direction, and the height limiting members are disposed on both sides of a head gap when viewed in the running direction of the magnetic tape.

In this type of magnetic tape cassette device, the running path of the magnetic tape is defined partly by elements on the magnetic tape cassette device and partly by a tape guide disposed within the magnetic tape cassette. These tape guides are generally mass produced from plastic materials and have fairly large tolerances. In fact, it is mainly caused by so-called azimuth errors in magnetic tape cassette devices.
error), a tolerance that causes errors due to deviations of the headgap position from a position purely perpendicular to the longitudinal edge of the magnetic tape. For example, if there is a 20' shift during stereo playback, the frequency will be 10kHz.
10dB loss occurs. This is particularly undesirable when playing recorded cassettes, so-called music cassettes.

In order to solve this problem, it has been proposed to use a control system that constantly influences the lace up of the magnetic tape by means of piezoelectric elements, for example, to cancel out the misorientation. However, such a control system would make a magnetic tape cassette apparatus of this type very expensive, and in fact does not provide a satisfactory general solution.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic tape cassette device in which the magnetic head unit passively but effectively eliminates misorientation that often occurs.

According to the present invention, the magnetic head has tape guides on both sides of the head gap with respect to the running direction of the magnetic tape, and these tape guides have a radius smaller than the head surface and the position of the tape guide with respect to the head surface. The magnetic tape is arranged to be locally in contact with the tape guide, and further adjoins one height limiting member at one end, and these two height limiting members are arranged so that the magnetic tape has a space between the height limiting members with respect to the magnetic head. The connecting line is arranged so that it extends purely perpendicular to the plane passing through the headgap, and further controls are provided to keep the side edges of the magnetic tape in constant contact with the height limiting member during tape travel. have the means.

In such a magnetic tape cassette device according to the present invention, the output due to misorientation can be reduced to a level so low that it is not a nuisance. It has been found that the error rate can be reduced to 4 minutes or less.
If care is taken during manufacture of the magnetic head unit that the connecting line of the height limiting member extends purely perpendicular to the head gap, a magnetic head unit with essentially correct azimuthal position is obtained. The advantage of this is that no further adjustments to the head unit are required during device manufacture. This also has the advantage that no azimuthal adjustment is required when the magnetic head unit is subsequently replaced, making such repairs substantially cheaper. Additionally, the presence of the height limiting member in accordance with the present invention allows for stable movement of the magnetic tape along the magnetic head within the apparatus, thus providing satisfactory tape-to-head contact.

The magnetic tape cassette device according to the present invention has a height limiting member that accurately maintains the height position of the track, and is capable of recording and reproducing a cassette in which digital information is recorded on a large number of narrow parallel tracks. Especially suitable for.

It should be noted that generally only thin sheet steel lugs on the magnetic head of the cassette device are used to optimize the track height position on the magnetic tape. However, in principle such lugs are not suitable for correcting incorrect azimuthal positions of a magnetic tape moving along a magnetic head. This is because the edges of the magnetic tape can curl or become damaged as a result of these very thin lugs exerting high pressure on the edges, which are at least locally quite loose.

According to a preferred embodiment of the magnetic tape cassette device according to the present invention, the tape guide is a circular tape guide disposed near the head surface, with the axes of these cylindrical bodies extending parallel to the cylindrical axis of the head surface. The cylindrical bodies are configured to protrude from adjacent portions of the head surface to make satisfactory contact with the magnetic tape. These tape guides tension the magnetic tape at the height limiting member, thereby preventing the side edges of the magnetic tape from curling due to contact with the height limiting member. Furthermore, the position of the tape guide is essential for accurate tape movement along the magnetic head.

In another embodiment of the magnetic tape cassette device according to the present invention, it is preferable that the cylindrical body is formed integrally with a portion including the head surface of the magnetic head and is accurately positioned with respect to the reference surface of the magnetic head by polishing. . In this way, a precisely formed magnetic head unit suitable for use in a magnetic tape cassette device according to the invention can be obtained, for example in one continuous polishing process. This also provides the possibility of forming the tape guide by computer control, for which purpose the magnetic head is provided with a reference surface.

In view of the above, a further embodiment of the magnetic tape cassette device according to the invention is characterized in that the at least one height limiting member is formed by a guide element that is axially adjustable relative to the associated cylindrical body. There is. In this way, by adjusting the guide elements, the connecting line between the two height-limiting elements can be made to run purely perpendicular to the headgap.

Another preferred embodiment of the magnetic tape cassette device according to the invention is such that the height limiting member comprises a plate-like projecting lug disposed on the main surface of the magnetic head, the main surface being substantially parallel to the tape running direction. It is characterized by extending parallel to. As a result, the height limiting member can be easily connected to the magnetic head.

In consideration of this point, another embodiment of the magnetic tape cassette device according to the present invention is characterized in that the plate-like body further includes a mounting plate, on which the magnetic head is disposed. In this way, the plate-like body will have a dual function. On the one hand, the plate forms a height limiting member, and on the other hand serves to attach the magnetic head to a magnetic tape cassette device.

Another preferred embodiment of the magnetic tape cassette device according to the present invention, taking the above points into consideration, is as follows:
It is characterized in that the guide element is at the end of a cut-out lug of the mounting plate, which lug can be pivoted relative to the rest of the mounting plate to provide axial adjustment. This simplifies the axial adjustment of the height limiting member and allows the headgap to be adjusted in a simple but accurate manner to a position perfectly perpendicular to the connecting line.

The magnetic head unit of another preferred embodiment of the magnetic tape cassette device according to the invention is provided with a plurality of pins on the side facing the magnetic tape cassette device, which pins allow the magnetic head unit to be inserted into the magnetic tape cassette device and to be inserted into the magnetic tape cassette device. It has the further advantage that it is also configured to be electrically connected. In this way, the magnetic head unit can be installed very easily, both during assembly and during repair.

A magnetic head unit suitable for use in a magnetic tape cassette device according to the invention has a control means for maintaining the side edges of the magnetic tape in constant contact with the height limiting member, the control means comprising two flat springs;
Each of these flat leaf springs is located above the associated tape guide and acts elastically on the axial end of the tape guide, with the axial direction of each tape guide measured from the height limiting member to the flat spring. It is characterized in that its dimensions do not exceed the minimum width dimension of the magnetic tape. The advantage of this construction is that all the equipment to ensure a stable and accurate magnetic tape along the magnetic head is built into the magnetic head unit itself. In this way, devices not equipped with the magnetic head according to the invention can be retrofitted with the magnetic head according to the invention.

Taking this point into consideration, the magnetic head unit according to the present invention includes side members disposed on both sides of the head surface in the running direction of the magnetic tape, and the ends of the side members form a cylindrical body. ,
a flat spring extending along the top surface of the side member and a height limiting member disposed on the underside of the side member; The height of the magnetic head is at most equal to the height of the front surface of the magnetic head. The advantage of doing so is that the height of the magnetic head unit can be such that it can be easily used in standard size cassettes, such as compact cassettes. This makes the magnetic head unit according to the invention suitable for use with magnetic tape cassette devices intended for use with compact cassettes.

Advantageously, the height limiting member comprises a block of wear-resistant material, such as a hardened metal block, arranged against the underside of the side member.
This allows the side members, and therefore the tape guide itself, to be made of an easily manufactured material such as plastic. Additionally, the height limiting member can be made of any suitable material that can withstand the abrasive effects of the edges of the magnetic tape.

Another preferred embodiment of the magnetic head unit according to the invention comprises a knife-edge bearing on the mounting plate between the side members;
It is characterized in that the magnetic head can rotate around an axis perpendicular to the running direction of the magnetic tape. The advantage of doing so is that the magnetic head unit according to the invention can be replaced with a standard commercially available magnetic head without the need for a special magnetic head with a casing adapted to the magnetic head unit. This is particularly suitable when producing magnetic heads according to the invention in relatively small quantities.

Embodiments of the present invention will be described in detail with reference to the drawings.

A first embodiment of a magnetic tape cassette apparatus according to the invention, shown in FIGS. It includes side members 28 and 29 located on either side of surface 27.

The respective ends 30 and 3 of these side members
1 forms a tape guide and is adjacent to the head surface 27, but here again, as in the previous embodiment, it forms a cylindrical body and protrudes from the adjacent portion of the head surface 27, and has a slight length. It is designed to cross over and come into contact with the magnetic tape (Figure 2). lateral member 28 in a direction perpendicular to the direction of travel of the magnetic loop.
and 29 are lower in height than the height of the front surface of the magnetic head comprising the head surface 27. This provides space above and below the side members 28 and 29 for accommodating elements relevant to the invention. For example, a steel plate spring 32 is fixed to the upper surface of the magnetic head 26 by adhesive or welding. This sheet steel spring 32 is at least substantially U-shaped in the plan view shown in FIG. This steel plate spring 32
the two legs 33 and 34 form a flat spring;
It extends from the side of magnetic head 26 remote from head surface 27 to the tape guide formed by ends 30 and 31. The upper sides of the ends 30 and 31 serve as abutments for the springs 33 and 34 in order to provide the springs with a suitable elastic force. When lifted in this manner, springs 33 and 34 provide a suitable force of 2 to 5 g. In the plan view shown in FIG. 2, the flat springs 33 and 34 are provided with ends 35 and 36 bent above the cylinder in order to obtain the correct pressure. These ends contact the tape where the magnetic tape contacts ends 30 and 31. The ends of springs 33 and 34 form the control means described above, and the side edges of the magnetic tape moving along the magnetic head unit are kept in constant contact with associated height limiting members 37 and 38, respectively. What is important in this respect is that the ends 30 and 31
(100 in FIG. 1) such that springs 33 and 34 constantly exert pressure on the tape edges. Height limiting member 3
7 and 38 and the tape guides 30 and 31 form part of support plates 39 and 40, which are fixed to the sides of the side members 28 and 29.
As in the previous embodiment, the first height limiting member 37
First, the support plate 39 with a support plate 39 is fixed to the magnetic head.
This height limiting member 37 determines the track position on the magnetic tape. The second height limiting member 38 is fixed to the magnetic head 26 having a support plate 40.
In this case, it is provided that the connecting line between the two height limiting elements 37 and 38 once again runs perpendicular to the plane passing through the head gap 41. It has been found that in this way an accuracy of 90° ± 10" can be obtained. For this purpose a manipulator is used and the support plate 40 is, for example, spot welded to the magnetic head after the correct position has been obtained. Alternatively, the reference plane may be formed on the magnetic head by computer control, and the height limiting members 37 and 3 may be fixed using screws.
8 can also be placed automatically with such precision that no further adjustment is required.

In this embodiment, tape guides 30 and 31 formed by cylindrical bodies are integrated with a portion of a magnetic head 26 having a head surface. The axial heights of these cylindrical bodies are smaller than the height of the front surface of the magnetic head 26, as described above. Height limiting member 37, 38 and end 3 of spring 33 or 34
This axial dimension, measured between 5 and 36, is at most equal to the minimum width dimension of the magnetic tape. To ensure proper contact with the magnetic tape, tape guides 30 and 31 formed by cylinders are polished so that the head surface 27 and the cylinder's generatrics are exactly parallel to each other. It has been extended. Due to the shape of the side members 28 and 29 with the springs 33 and 34 above and the height limiting members 37 and 38 below, the overall height at the location of these side members is at most that of the front surface of the magnetic head. A structure of the magnetic head unit of equal height is obtained. As a result of the shape of the side members 28 and 29 there are springs 33 and 34 above them and height limiting members 3 below them.
7 and 38, one magnetic head unit structure is obtained in a position where the side members have a total height at most equal to the height of the front surface of the magnetic head. As a result, the magnetic head unit according to the invention is suitable for use with standard compact cassettes. In this embodiment, the height limiting member is disposed on the lower side. Since the tracks on the compact-cassette tape are located close to the lower edge of the tape, this arrangement has the advantage of providing accurate track location. It should be noted that the magnetic head unit according to the present invention is arranged on a mounting plate 42, and this mounting plate 42 is fixed to the head mounting plate 1 using screws 43, if necessary, via a spacer, and further adjustment is necessary. There are things you can do to avoid it. This rather rough fixation method is sufficient. This is because the azimuthal position is completely defined by the magnetic head unit 25. Another advantage of this construction according to the invention is that in this example all the equipment for obtaining the correct azimuthal position is integrated within the magnetic head unit itself. This makes it possible to replace existing magnetic head units with the magnetic head unit according to the present invention.

FIG. 2 shows the location of tape guide 44, which forms part of the compact cassette housing. In this operating position, these tape guides are located on either side of the magnetic head unit. The structure of the head unit according to the present invention eliminates or alleviates the adverse effects of these tape guides on the running of the magnetic tape.

A second embodiment of the magnetic head unit 45 shown in FIG. 3 includes a magnetic head 46 housed within an extruded casing. As in the previous embodiment, magnetic head 46 has side members 47 and 48 having a height less than the height of the front surface of magnetic head 46, including the head surface. Control means formed by flat springs 49 or 50 are arranged on the upper side of each side member 47 or 48;
These springs are connected to the side members on the side of the magnetic head remote from the head surface. Essentially the shape of the free end of each spring 49 or 50 corresponds to that of the previous embodiment. The same thing applies to side member 4.
Cylindrical bodies 51 and 52 giving ends of 7 and 48
This also applies to the shape of . The main difference with the previous embodiment is the structure of the height limiting member on the underside of the cylinders 51 and 52. These height limiting members form part of the mounting plate 53 of the magnetic head 46. The lug 54 of the mounting plate 53 is located on the underside of the cylindrical body 51, but the lug 54 is extended slightly upward from the main part of the mounting plate 53, and the lug 54 is
Advantageously, the ends of the lateral members 47 are positioned relative to the underside of the side members 47. This protruding lug 54 constitutes a guiding element or height limiting member that defines the position of the track on the magnetic tape. A mounting plate 53 or a cut-out lug 55 is provided, and the cut-out lug 55 extends from the main part of the mounting plate 53 to the cylindrical body 5.
The lug 55 is cut out from the mounting plate 53 so as to be pivotable relative to the main part of the mounting plate. A set screw 56 extends through the lug 55, one end of which bears against the underside of the side member 48. The free end of the protruding lug 55, which thus constitutes a height limiter or guide element, can be adjusted in the height direction by means of a screw. This adjustment is performed with the manipulator measuring device as previously described, but the screw 56 is turned until the connecting line between the two height limiting members is completely perpendicular to the plane passing through the headgap 58. Side member 48
The gap created between the underside of the lug 55 and the lug 55 can be filled with adhesive for fixing purposes to ensure that the correct setting is maintained. Alternatively, the screw 56 itself can be fixed.

Instead of using screws to adjust the height limiting members 55 as shown in FIG. 3, keys or wedges may be used as shown in FIG.
It can also be inserted into the gap between the lower side of the lug 59 and the upper side of the lug 59 serving as the height limiting member, as shown by the arrow 60. By means of a manipulator, e.g. wedge 6
1 is pushed in the direction of arrow 60 until the connecting line between the two height limiting members 54 and 55 is again perpendicular to the plane passing through the headgap 58. The head gap between the lug and side member is then filled with adhesive and secured. Preferably, the lugs 59 slope upwardly from the mounting plate 53 for proper adjustment. In this way, the cut-out lugs 55,
59 forms a height limiting member or an adjustable guide element.

The magnetic head unit 62 shown in FIGS. 5, 6 and 7 employs a conventional magnetic head 63 which is commercially available. Moreover, the magnetic head unit 62
is provided with a mounting plate 64, and this mounting plate 6
4 is integrally formed with side members 65 and 66. Again, the height of these side members 65 and 66 is lower than the height of the front side of the magnetic head 63 with its head surface. The ends of the side members 65 and 66 form cylindrical bodies 67 and 68, respectively. Side members 65 and 66, as well as mounting plate 64, may be made of any suitable material such as plastic.
It is important when selecting the material that it has satisfactory dimensional stability so that the columns 67 and 68 retain their correct shape during use. Control means, in this embodiment formed by flat springs 70 and 71, are arranged on the upper sides of side members 65 and 66, so that only a relatively small pressure is applied to the upper edge of the magnetic tape, and these The control means ensure that the lower edge of the magnetic tape is constantly in contact with the height control members forming the projecting lugs 72 and 73 during running. The height limiting members 72 and 73 may be part of the side members 65 and 66.

Alternatively, as shown in FIGS. 8 and 9, the height limiting member is a block 7 of wear-resistant material.
4, each with a pin 75 clamped to an opening in the lower side of the side member. The block is made of a wear-resistant material, such as chrome steel or ceramic material. The block can also be slightly conical on the upper side, with the axis of the pin 75 in the center of the cone. In the embodiment shown in FIG. 8, the portion of the height limiting member constituting the tape guiding element is turned off by approximately 5°.
There is. Each block has flat sides 76 to facilitate insertion of the magnetic head unit into the compact cassette. The mounting plate 64 includes a knife engine bearing 77, which is located directly below the head gap 78 of the magnetic head. After the magnetic head 63 is attached to the mounting plate 64 between the side members 65 and 66, the magnetic head 63 is mounted around an axis determined by rotating the upper edge of the knife edge bearing 77 perpendicular to the running direction of the magnetic tape. There is a small gap to allow rotation. In this way, the connecting line between the height limiting members 72 and 73 can be adjusted so that it is exactly perpendicular to the plane passing through the head gap 78. After the magnetic head is rotated to a precise position by the manipulator, the magnetic head is also fixed in that position with adhesive in this embodiment. In this embodiment as well, the connecting line between the height limiting members can be adjusted to an accuracy of within 10" so that it extends perpendicular to the plane passing through the head gap 78. As shown in FIG. The structure of the magnetic head unit according to the present invention includes a tape guide 79 in the cassette housing.
and 80 have particular advantages in that they eliminate the influence that they have on the running of the magnetic tape. The structure of the magnetic head unit according to the present invention eliminates or alleviates these undesirable effects by correcting the magnetic head unit for movement of the magnetic tape after the tape guide so that the correct azimuthal position is obtained at the location of the head gap 78. .

FIG. 10 shows a magnetic head unit 81 in which two separate side members 83 and 84 of strip material are fixed to the side walls of a conventional commercially available magnetic head.
It shows. A cylindrical body is formed with a rounded front end of the strip material. By techniques described below, the side members are again connected to magnetic head 85 such that the connection between height limiting members 86 and 87 extends completely perpendicular to the plane passing through head gap 88. Again, the side members 83 and 84 have a height that leaves a gap of about 2 mm between the upper and lower sides compared to the overall height of the front surface of the magnetic head 85 including the head surface. FIG. 10 shows how height limiting members 86 and 87 of flat spring material can be formed below the side members in an alternative embodiment. By fixing these springs at their rear and front ends to the associated side members, the height limiting member is controlled by the control means formed by the leaf springs 89 and 90 arranged on the upper side of the side members 83 and 84. has also become substantially stiffer. In this way, the height limiting member acts as a substantially rigid component relative to the magnetic tape. During adjustment, the side members are lightly pressed against the side walls of the magnetic head, the lower edges of the side members are kept at the same level, and during adjustment they move parallel to each other. For adjustment purposes, the magnetic head is mounted on an alignment jig which is provided with knife-edge bearings to accurately tilt the magnetic head and which is provided with supports to keep the side members 83 and 84 at the correct level during adjustment of the magnetic head. 85 are arranged. Once the adjustment is correct, the side pieces are fixed to the magnetic head, for example by welding. After adjustment and fixing, magnetic head 85
is fixed to the mounting plate 91. Another advantage of this embodiment is the use of relatively inexpensive components.

It should be noted that the magnetic head units of the embodiments described above are broad improvements over magnetic tape cassette devices. This can be continued in current cassette devices, such as so-called compact cassettes and microcassettes, so that the structure according to the invention eliminates the need to develop new cassette devices. Furthermore, the proposed magnetic head unit has a tape running direction opposite to the normal running direction.
In other words, it has also been improved in recording signals using the so-called auto-reverse method, in which the running direction of the magnetic tape is automatically reversed when it reaches the end. The azimuthal position of the magnetic head relative to the magnetic tape in both running directions is exactly perpendicular. The construction of the magnetic head unit according to the invention also has the advantage of providing precise height stability of tape travel in cassettes with tape guides, such as compact cassettes.
The structure according to the invention thus allows the well-known compact cassette to be adapted for digital recording purposes when very narrow track widths are used.

It should be noted that the present invention is suitable not only for the structure of the magnetic tape cassette device itself, but also for the structure of the magnetic head unit, and because the azimuth position is essentially accurate, it is suitable for service purposes. It is something that can be used.

Furthermore, it should be noted that separate details of the various embodiments can also be combined. For example, the steel plate spring 32 shown in FIG. 1 could be replaced by the flat springs 49 and 50 of FIG.

FIGS. 11-16 show the results of a number of measurements to illustrate the advantages of accurate tape travel provided by the magnetic head unit of the present invention. Figures other than Figure 16 are graphs showing orientation error (A) as a function of time (T).

Figure 11 shows the orientation error tolerance, while Figure 11A shows a standard ferromagnetic tape with a ferromagnetic tape in a correctly constructed housing (metal frame and tape guide).
This is for a 10KHz azimuth test cassette. Although this magnetic tape is recorded by an external standard high-quality magnetic tape device, this test tape will hereinafter be referred to as the "standard test tape." FIG. 11A shows that even if the tape is accurately guided during recording, the orientation error tolerance increases to ±0.5' when the cassette is played back with a hi-fi magnetic tape cassette device not equipped with a magnetic head unit according to the present invention. This orientation error tolerance is too large for precise measurements (as is clear from the measurements below).

Therefore, a special azimuth test cassette was made for placing magnetic tape on a magnetic tape device that does not use the magnetic head unit of the present invention, although it has high sound quality. to be called. FIG. 11B shows that when this particular azimuth test cassette is played back in a high-fidelity cassette device equipped with a magnetic head unit according to the invention, the azimuth error is at most ±0.1'. This shows that a magnetic tape device incorporating a magnetic head unit according to the invention can reproduce orientation test cassettes five times more accurately than conventional tests.

FIG. 12 shows a typical commercial high-fidelity magnetic tape cassette device (FIG. 12A) and the same cassette device including a magnetic head unit according to the invention (FIG. 12B) when the special orientation test cassette described above is applied. A comparison of measurement results is shown. 1st
The maximum tolerance for Figure 2A is approximately ±0.5' and for Figure 12B it is ±0.1'. Here too, the orientation error has been reduced to 1/5.

Figure 13 shows the measurement results when a 10kHz signal was recorded on a conventional ferro C60 type cassette using a commercially available high-fidelity magnetic tape cassette device (Figure 13A) and a similar device using the magnetic head unit of the present invention (Figure 13B). shows a comparison. It can also be seen here that the orientation error is improved by about 5 times. This comparison shows that when recorded on a conventional high-fidelity magnetic tape cassette device equipped with a magnetic head unit according to the invention, the orientation tolerance is reduced by about a factor of 5.

FIG. 14 shows a comparison of measurements of the special magnetic tape described above housed in the housings of three relatively inexpensive commercially available plastic cassettes having tape guides exhibiting normal tolerances. Millions of such housings are manufactured each year using injection molding technology. 14th D,
Figures E and F, using housings corresponding to Figures 14A, B and C, respectively, show that when applied to a high-speed cassette device comprising a magnetic head unit according to the invention, the orientation error is limited to ±0.3'. ing. Figures 14A, B, and C show that for a high-speed cassette device that does not use this special magnetic head unit, the orientation error varies from ±4' (Figure 14D) to ±1.5' (Figure 14F). It can be concluded from this that with the magnetic head unit according to the present invention, errors in tape guidance within the cassette housing can be almost eliminated. This is what is done in so-called music cassettes, when a modulated magnetic tape is played outside the cassette housing.
This shows that the reproduction quality can be substantially improved by the magnetic head unit according to the invention.

FIG. 15 shows the change in orientation error tolerance between the beginning and end of a magnetic tape when using a conventional test tape. While the magnetic tape runs from the beginning to the end, the tension applied to the tape changes, and this change in tension is mainly due to changes in the roll diameter of the magnetic tape. Tape tension can vary by about 2 1/2 times between beginning and end. For this measurement, a standard test cassette housing is used, but one of the winding hubs has an eccentric shape with a radius of minimum 10 mm and maximum 25 mm relative to the axis of rotation. Thus, during one rotation of this eccentric take-up hub, the same change in tape tension occurs between the beginning and end of a magnetic tape as occurs in a conventional cassette. Figures 15A, B and C show that when three such cassettes are run through a conventional high-speed cassette machine, a tolerance of ±2' will result starting from the initial zero position. Figures 15D, E and F show that when the cassette of Figures 15A, B and C is loaded into a high-speed cassette device having a magnetic head unit according to the present invention, the orientation error tolerance is ±.
It shows that it becomes 0.5′. This result is the 11th
It can be compared with the measurement results in Figure B. Therefore, with the structure according to the invention, changes in tape tension have little or no effect and the orientation error tolerance does not change from beginning to end.

FIG. 16 shows the measurement results of the height stability of the magnetic tape. Generally, the magnetic tape runs along the magnetic head through the tape guide, which is offset by 1' from the horizontal, for example, because the first tape guide is positioned 3 1/2 μm higher than the second tape guide. In this case, the edge of the magnetic tape assumes a precise height position within 2 μm near the head gap.
The measurements shown in FIG. 16 were made with a measuring instrument equipped with a photodiode and a phototransistor to detect the lower edge of the magnetic tape. 2
A C60 type cassette tape with chromium oxide was used. This test was carried out using a high-fidelity cassette record whose magnetic head was replaced with the above-mentioned measuring device, and the measuring device was used to measure the magnetic head unit without and with the tape guide structure of the present invention, respectively. This means that the tape guide, the height limiting member and the control means for keeping the edge of the magnetic tape in contact with the height limiting member are arranged on the meter.
The graph of FIG. 16 plots the height deviation (H) as a function of time (T). FIG. 16A shows that a conventional high-speed cassette device that does not utilize the tape guide structure of the present invention will experience a height deviation of as much as 20 .mu.m. This is because an interruption in the running of the magnetic tape, such as in the case of a temporary stop operation, results in a fairly large change in height. This effect can be explained by the fact that each time the magnetic tape is started, it takes some time to reach the correct height.
FIG. 16B shows that in a high-fiber cassette device equipped with the tape guide structure of the present invention, the height deviation is at most 1 .mu.m, an improvement of ten times. FIG. 16B shows the same tape run interruption situation as FIG. 16A. This indicates that the magnetic tape race-up is restored to its correct position at a substantially faster rate after an interruption in running.

It can be concluded from FIG. 16 that the magnetic head unit according to the invention is particularly suitable for digital recording where it is necessary to maintain very accurate track position in the height direction. As a result, very narrow tracks can be chosen and the number of tracks on the magnetic tape can be increased, thereby reducing the speed of the magnetic tape.

[Brief explanation of drawings]

1 is a perspective view of a part of a first embodiment of the present invention, FIG. 2 is a plan view of the apparatus shown in FIG. 1, FIG. 3 is a perspective view of an embodiment of the present invention, and FIG. 5 is a side view of a portion of the third embodiment of the present invention, which is a modification of the device shown in FIG. 3; FIG. 5 is a perspective view of a portion of the fourth embodiment of the invention; and FIG. The figure is number 5
7 is a plan view of a part of the device shown in FIG. 5, and FIG. 8 is a modification of the device shown in FIG. 5 according to the present invention. FIG. 9 is a plan view of a height limiting member used in the apparatus shown in FIG. 8; FIG.
The figures are perspective views of the sixth embodiment of the present invention, and the eleventh embodiment.
Figures 1 to 16 are diagrams showing measurement results during tape running with and without the magnetic head unit according to the present invention. DESCRIPTION OF SYMBOLS 1... Head mounting plate, 25... Magnetic head unit, 26... Magnetic head, 27... Head surface, 28, 29... Side member, 30, 31... End or tape guide, 32... Steel plate spring ,3
3, 34... legs or springs, 35, 36... ends or control means or control elements, 37, 3
8... Height limiting member, 39, 40... Support plate, 4
1...Head gap, 42...Mounting plate, 4
3...screw, 44...tape guide, 45...magnetic head unit, 46...magnetic head, 47,
48... side members, 49, 50... flat springs or control means or control elements, 51, 52...
... Cylindrical body or tape guide, 53 ... Mounting plate, 54 ... Cut-out lug or height-limiting member or projecting lug, 55 ... Cut-out lug or height-limiting member or projecting lug or adjustable guide element, 56 ... ...Set screw, 58...
Head gap, 59... cut-out lug or adjustable guide element, 60... arrow, 61... wedge, 62... magnetic head unit, 63... magnetic head, 64... mounting plate, 65, 66...
Side members, 67, 68... Cylindrical bodies or tape guides, 70, 71... Flat springs or control means or control elements, 72, 73... Height limiting members or protruding lugs, 74... Wear resistance. Material block or height limiting member, 75...pin,
76...Flat side surface, 77...Knife edge bearing, 78...Head gap, 79, 80...Tape guide, 81...Magnetic head unit, 8
3, 84...Side member, 85...Magnetic head, 8
6, 87... Height limiting member, 88... Head gap, 89, 90... Leaf spring or control means or control element, 91... Mounting plate, 100...
...Axial dimension of ends 30 and 31.

Claims (1)

Claims: 1. A magnetic head unit 25; 45; 62; 81 suitable for use with a magnetic tape device, comprising - a convexly curved head surface, wherein a head gap 41; 58; 78; 46; a magnetic head 26 having a front surface terminating in 88 and across which a magnetic tape runs during operation of the apparatus;
63; 85 and - with a convexly curved surface, the head gap 4
1; 58; 78; 88; two tape guides 3 disposed adjacent to the front surface of the head surface 27 and protruding forward from the adjacent portion of the front surface;
0, 31; 51, 52; 67, 68; - each tape guide 30, 31; 51, 52;
The head gap 41; 58; 78;
88, each having a height limiting surface arranged to limit the movement of said magnetic tape in at least one direction parallel to the plane tangent to the head surface 27; two height-limiting members 3 configured such that a plane perpendicular to the plane of
7,38;54,55;72,73;74;8
6, 87; - control means 35, 36; 49, 50; 70, 71; 89, for constantly bringing the side edges of the magnetic tape into contact with said height limiting surface while the magnetic tape is running;
90, wherein: - said control means are connected to each height limiting member 3;
7,38;54,55;72,73;86,8
- two tape guides 30, 31; 51, 52;
67, 68, two height limiting members 37, 38;
54, 55; 72, 73; 74; 86, 87 and control elements 35, 36; 49, 50; 70, 7
1; 89, 90 are the above magnetic head units 2;
5; 45; 62;
8; 54, 55; 72, 73; 86, 87 and respective control elements 35, 36; 49, 50; 7
A magnetic head unit having an axial dimension not larger than the minimum width dimension of a magnetic tape as measured between 0.71; 89.90. 2 Above tape guides 30, 31; 51, 5
2; 67, 68 guide surfaces and corresponding height limiting members 37, 38; 54, 55; 72, 73; 8
6, 87 and control elements 35, 36; 49, 50;
70, 71; 89, 90 combined is not larger than the height of the front surface of the magnetic head 26; 46; 63; 85, so that the head surface can be inserted into the opening of the cassette. A magnetic head unit according to claim 1. 3. Before connecting the magnetic head 63 to the magnetic head unit 62, in order to position the above-mentioned plane perpendicular to the above-mentioned connection line and passing through the head gap 78, the magnetic head is moved around an axis perpendicular to the above-mentioned plane tangent to the head surface. 63, said pivoting means comprising a knife edge bearing 77 disposed on the head mounting plate 64 and located directly below the head gap 78 of the magnetic head. A magnetic head unit according to item 1 or 2 of the range. 4 Projecting lugs 54, 55; 72, 73 in which the height limiting member is integrally formed with the mounting plate.
4. A magnetic head unit according to claim 3, characterized in that the magnetic head unit comprises: 5. Claim 1, characterized in that at least one height limiting element is formed by an adjustable guide element 55; 59 which is adjustable in the axial direction of the corresponding cylindrical body 52. The magnetic head unit described in Section 1. 6 The above adjustable guide element is attached to the mounting plate 53.
4 or 5, characterized in that it is formed as an end of a cut-out lug 55; 59, said lug being pivotable relative to the rest of the mounting plate for axial adjustment. The magnetic head unit described in . 7. Two side members 65, 66; 83, 84 arranged on both sides of the head surface in the running direction of the magnetic tape.
In the magnetic head unit according to claim 1, wherein the ends 67, 68 of the above members form tape guide surfaces, the two side members 65, 66; 83, 84 are used for attaching the head. board 64
A magnetic head unit characterized in that it is formed integrally with a magnetic head unit. 8. A magnetic head unit according to claim 7, characterized in that said height limiting member (74) comprises a block of wear-resistant material located at one end of the side member (65).