Magnetic head

Abstract: A magnetic head for writing and/or reading out data into and/or from a magnetic tape (5), at portions of travel surfaces (12a, 22a, 32a, 42a, 52a, 62a, 72a, 82a, 92a; 12b, 22b, 32b, 42b, 52b, 62b, 72b, 82b, 92b; 12b′, 22b′, 32b′, 42b′, 52b′, 62b′, 72b′, 82b′, 92b′) over which the magnetic tape travels, has a reference plane defined by a projection (16a, 26a, 36a, 46a; 16a′, 26a′, 36a′, 46a′) for determining a position of a traveling magnetic tape in the widthwise direction thereof and a inclined plane defined by a projection (16b, 26b, 36b, 46b; 16b′, 26b′, 36b′, 46b′) for urging the magnetic tape to the correspondent reference plane, a tape travel surface (16c, 26c, 16c′, 26c′) defined at a correspondent portion to the reference and inclined planes being aligned with an other tape travel surface (12b, 22b, 32b, 12b′, 22b′, 32b′) in a thickness wise direction. A recess (510, 510′, 611a, 611b, 611c, 611d, 712a, 712b, 712c, 712d, 810, 810′, 811a, 811b, 811c, 811d, 910, 910′, 912a, 912b, 912c, 912d) is formed at a portion of the tape travel surface and especially a corresponding to the side edges of the magnetic tape.

Description: The present invention relates to a magnetic head and more particularly a magnetic head for writing and reading out data into and/or from a magnetic tape in the magnetic recording apparatuses such as video tape recorders, audio tape recorders and the like. Prior art of the magnetic head similar to the magnetic head disclosed in US-A- 4,485,420, DE-C-3518126 or EP-A- 0120518B1 is shown in Figs. 1, 2 and 3. Fig. 1 illustrates a cross sectional view, a part of which is omitted, taken along the longitudinal direction of the magnetic tape of the magnetic head; Fig. 2 is a top view thereof; and Fig. 3 is a side view thereof. Reference numeral 1 is a case which is one of the component parts of the magnetic head and is made of a magnetic shield material. A gap 3 is formed in a portion of a core 4 which contacts with the magnetic tape. The core 4 is embed in the case 1 through a resin 7. Tape guides 6 and 6' are provided with both sides of the case 1, respectively, in the longitudinal direction of the magnetic tape. The magnetic tape 5 is traveling over the upper surface of the magnetic head in which data are written into and/or read out from the magnetic tape 5. Concave portions 8 and 8' are formed at a portion of the upper surface of the magnetic head to which the resin 7 is exposed to avoid the magnetic tape 5 contacting with the resin 7, so that a deboning of magnetic particles from the magnetic tape 5 can be prevented. As a result, the tape travel surfaces defined on the upper surface of the magnetic head are represented by 2a, 2b and 2b'. It is now assumed that the magnetic tape 2 is traveling in the direction indicated by the arrow A in Fig. 2. Then the magnetic tape 5 is made into contact with the inclined plane formed on a projection 6b of the tape guide 6 and is biased to the reference plane formed on a projection 6a. As best shown in Fig. 3, the width of the magnetic tape traveling passage defined between the inclined plane and the reference plane is narrower than that of the magnetic tape 5 and the tension is exerted to the magnetic tape 5. Therefore, in order to ensure the smooth traveling over the surface of the magnetic head, the positions of the magnetic tape 5 in the direction of its thickness must be limited so that a bottom plane 6c is provided with between the projection 6a and 6b. The reference plane is substantially perpendicular to the bottom plane (to be referred to as "the position control plane) 6c so that one side edge of the magnetic tape 5 is traveling along the reference plane. The reference planes defined on the projections 6a and 6a' are substantially perpendicular to the direction in which the gap 3 is extended so that the position of the traveling and the longitudinal direction of the magnetic tape 5 can be stabilized. As a result, the so-called gap angle between the tape 5 and the gap 3 can be maintained constant so that the azimuth loss due to the difference in the gap angle between a writing mode and a reading mode can be reduced. In general, the tape guides are formed by the injection molding of a plastic material which is nonexpensive, thereby reducing the production cost, but almost all the tape guides thus fabricated have the rough surfaces. As a result, due to the contact of the magnetic tape 5 with the bottom planes 6c and 6c' of the tape guides 6 and 6', there occurs frequently that the magnetic material and the binder of the magnetic tape 5 are separated. In the case of the magnetic head of the type described above, the radius of curvature of the tape travel surface defined by the travel surfaces 2a, 2b and 2b' is relatively small and furthermore the bottom planes 6c and 6c' of the tape guides are more extended than the tape travel surfaces 2b and 2b'. Therefore the passage of the tape traveling is located on the line interconnecting the bottom planes 6c and 6c' of the tape guides 6 and 6' and the top of the travel surface 2a containing the gap 3. It follows therefore that the magnetic tape 5 is almost not in contact with the tape travel surfaces 2b and 2b'. However, when the magnetic head is used for a long time under the above-described condition, the dust such as magnetic particles and binder particles of the magnetic tape 5 separated at the bottom plane 6c and 6c' of the tape guides 6 and 6' are forced to reattach the magnetic tape 5 and then transported to the portion in the vicinity of the gap 3 and adhere to such the portion. As a result, such dust adversely affects a predetermined distance between the gap 3 and the magnetic tape 5 so that it becomes one of the causes which degrades the writing and reading characteristics of the magnetic head. In general, the adhesion or accumulation of such dust tends to occur at high temperatures so that the magnetic head of the type described above cannot be used in the stereophonic audio equipment mounted on a car whose temperature becomes relatively high. Fig. 4, 5 and 6 illustrate another prior art of the magnetic head. Fig. 4 is a top plane view thereof; Fig. 5 is a front view thereof and Fig. 6 is a perspective view thereof. Same reference numerals are used to designate similar parts in both the magnetic heads illustrated in Figs. 4-6 and the description of the component parts already made with reference to Figs. 1-3 shall not be repeated. It should be noted here that in the second prior art of the magnetic head, the tape guides are not illustrated. In the second prior art of the magnetic head, the length of the magnetic core 4 perpendicular to the longitudinal direction of the magnetic tape 5 is designed to be shorter than the width of the magnetic tape 5. For instance, while the length of the magnetic core 4 is 3.72 ± 0.05 mm, the width of the magnetic tape 5 is 3.81 - 0.05 mm to 3.81 + 0 mm so that over the surface 2a the magnetic tape 5 and the resin 7 are made into contact with each other by the designation width of 0.09 mm. As described above, because of the contact between the magnetic head and the magnetic tape, dust such as magnetic particles and binder particles tend to be separated from the resin 7 so that the dust particles are transported by the magnetic tape 5 and are accumulated at the tape travel surfaces 2b and 2b'. In the case of the second-mentioned prior art of the magnetic head, the accumulation or adhesion of such dust particles is concentrated at the portions of the tape travel surface 2b or 2b' corresponding to the both side edges of the magnetic tape 5 so that a thin dust film is formed between the magnetic tape 5 and the travel surface 2b or 2b'. As a result, a degree of wear at the portion, at which such dust film are formed, of the tape travel surface 2b or 2b' is different from that of wear at the portion corresponding to the center portion of the magnetic tape 5 at which no dust adhesion or accumulation occurs. In general, a portion of the tape travel surfaces 2b and 2b' corresponding to the whole width of the magnetic tape 5 should be worn out uniformally, but in practice because of the nonuniform wear described above, there arises the problem that the position of the travel of the magnetic tape 5 cannot be uniformly maintained. The resin 7 becomes the source from which the dust particles are produced and such dust particles thus produced tend to adhere to the resin 7 compared with the tape travel surfaces. As a result, however the area of the contact between the magnetic film 5 and the resin 7 is small, for instance, when the dust particles adhere to the resin 7 in the tape travel surface, the dust particles grow from the first adhered dust particle as a nucleus. Sometimes, such growing of the dust particles prevents the smooth traveling of the magnetic tape. In view of the above, an object of the present invention is to provide a magnetic head which can reduce the separation of dust particles from the magnetic tape so that the smooth traveling of the magnetic tape can be always ensured and therefore the degradation of the writing and reading characteristics can be prevented. This object is achieved by a magnetic head as claimed in claim 1. The objects effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings. Fig. 1 is a cross sectional view taken along the longitudinal direction of the magnetic tape illustrating a first prior art of the magnetic head; Fig. 2 is a top plan view thereof; Fig. 3 is a side view thereof; Fig. 4 is a top plan view of a second prior art of the magnetic head; Fig. 5 is a front view thereof; Fig. 6 is a perspective view thereof; Fig. 7 is a cross sectional view taken along the passage of a traveling magnetic tape illustrating a first embodiment of a magnetic head in accordance with the present invention; Fig. 8 is a top plan view thereof; Fig. 9 is a side view thereof; Fig. 10 is a cross sectional view taken along the passage of the traveling magnetic tape illustrating a modification of the magnetic head of the first embodiment shown in Figs. 7-9; Fig. 11 is a top plan view thereof; Fig. 12 is a side view thereof; Fig. 13 is a cross sectional view taken along the passage of the traveling magnetic tape illustrating a second embodiment of a magnetic head in accordance with the present invention; Fig. 14 is a top plan view thereof; Fig. 15 is a side view thereof; Fig. 16 is a cross sectional view, taken along the passage of the traveling magnetic tape illustrating a modification of the magnetic head of the second embodiment shown in Figs. 13-15; Fig. 17 is a top plan view thereof; Fig. 18 is a side view thereof; Fig. 19 is a top plan view of a third embodiment of a magnetic head in accordance with the present invention; Fig. 20 is a front view thereof; Fig. 21 is a perspective view thereof; Fig. 22 is a side view illustrating the magnetic head shown in Fig. 19 having tape guides; Fig. 23 is a top plan view of the magnetic head shown in Fig. 22; Fig. 24 is a top plan view of a fourth embodiment of a magnetic head in accordance with the present invention; Fig. 25 is a front view thereof; Fig. 26 is a perspective view thereof; Fig. 27 is a top plan view illustrating a modification of the magnetic head of the fourth embodiment shown in Figs. 24-26; Fig. 28 is a front view thereof; Fig. 29 is a perspective view thereof; Fig. 30 is a side view illustrating the magnetic head shown in Fig. 27 having tape guides; Fig. 31 is a top plan view thereof; Fig. 32 is a top plan view illustrating a fifth embodiment of a magnetic head in accordance with the present invention; Fig. 33 is a front view thereof; Fig. 34 is a perspective view thereof; Fig. 35 is a top plan view illustrating a modification of the magnetic head of the fifth embodiment shown in Figs. 32-34; Fig. 36 is a front view thereof; Fig. 37 is a perspective view thereof; Fig. 38 is a side view illustrating the magnetic head shown in Fig. 25 having tape guides; and Fig. 39 is a top plan view thereof. In the following embodiments and their modifications, like reference numerals prefixed with the various number represent corresponding parts in the several views. For instance, the case designated by the reference numeral 1 in Figs. 1-6 is changed to 11. These component parts have been already described in detail so that the component part corresponding to those in Figs. 1-6 shall not be described hereinafter except when their explanation is especially needed. Preliminary Embodiment In the preliminary embodiment, which does not cover the present invention, shown in Figs. 7-9, the radius of curvature of the type travel surfaces 12a 12b and 12b' is made greater than those of the tape travel surfaces of the prior art of the magnetic heads described above. More particularly, when the radius of curvature of the tape travel surfaces in the prior art of the magnetic heads is between 10 and 15 mm, in the first embodiment, the corresponding radius of curvature is of the order of 20 mm. In this case, the radius of curvature of the curved surface interconnecting the tape travel surfaces 12a, 12b and 12b' is so determined that the bottom plane 16c and 16c' of the tape guides 16 and 16' are slightly extended beyond the curved surface interconnecting the tape travel surfaces. When it is assumed that the magnetic tape 5 is traveling in the direction indicated by the arrow A in Fig. 8, because of the increase in radius of curvature of the curved surface interconnecting the tape travel surface 12a, 12b and 12b', in other words, the bottom plane 16c and the tape travel surface 12b, the bottom plane 16c' and the tape travel surface 12b' being substantially aligned with each other, first the magnetic tape 5 is made into contact with the bottom 16c of the tape guide 16 so that the direction and position of the traveling magnetic tape can be correctly controlled. Thereafter the magnetic tape 5 is made into contact with almost all the tape travel surface 12b. Then the dust particles produced at the bottom plane 16c are reattached to the magnetic tape 5 and almost all of them attach or adhere to the tape travel surface 12b. Therefore, there exists almost no chance that the dust particles reach the tape travel surface 12a through which the magnetic gap 13 is defined. As a result, even when the magnetic head is used for a long time under the high temperature condition, the writing and reading characteristics can be prevented from being degraded due to the adhesion or accumulation of the dust in the vicinity of the magnetic gap. The travel surfaces 12b and 12b' are integrally formed with the case 11 made of a magnetic shielding material. This material, metal, is ground by a grinder or the like until the surfaces become so smooth that the roughness of surface becomes in excess of 0.1 S. It follows therefore that at the travel surfaces 12b and 12b', the rate of production of dust such as magnetic particles and binder particles separated from the magnetic tape 5 is very low, and the rate of the adhesion or accumulation of dust is higher than that at the bottom surfaces 16 and 16c' of the tap guides 16 and 16', respectively. Same is true when the magnetic tape 5 is traveling in the direction indicated by the arrow B in Fig. 8. That is, the dust particles produced at the bottom surface 16c' of the tap guide 16' almost attach or adhere to the tape travel surface 12b' so that the degradation of the magnetic characteristics due to the adhesion or accumulation of the dust particles in the vicinity of the magnetic gap can be prevented. In order to slightly extend upwardly the bottom surfaces 16c and 16c' of the tape guide 16 beyond the tape travel surfaces, the precise position adjustment is required. Otherwise the above-described merit cannot be satisfactorily attained. On the other hand, in accordance with the preliminary embodiment, as best shown in Figs. 7 and 8, the projections 16a and 16b of the tape guide 16 are made into contact with the tape travel surface 12b on the side of the tape guide in assembly so that the position of the position control plane 16c relative to the tape travel surface 12b can be correctly determined. In the same manner, the projections 16a' and 16b' of the tape guide 16' can be made into contact with the tape travel surface 12b' on the side of the tape guide in assembly, the position of the position control plane 16c' relative to the tape travel surface 12b' can be correctly determined. Modification of the preliminary Embodiment In the case of a modification of the preliminary embodiment illustrated in Figs. 10, 11 and 12, the radius of curvature of the tape travel surfaces and the positions of the bottom plane 26c and 26c' of the tape guide 26 are determined in a manner substantially similar to that described above in the preliminary embodiment. In addition, as best shown in Figs. 10 and 11, the upper portion of the case 11 is formed with cutout portions 21a and 21a' extended on the tape travel surfaces 22b and 22b' in the widthwise direction of the magnetic tape 5 and the position control planes 26c and 26c' of the tape guides 26 and 26' are extended to the cutout portions or notches 21a and 21a', respectively. When the length of the position control plane 26c and 26c' along the longitudinal direction of the magnetic tape is increased, the pressure of contact between the position control planes 26c and 26c' on the one hand and the magnetic tape 5 on the other hand can be lowered so that the resistance to wear of the position control planes 26c and 26c' can be improved. In the preliminary embodiment and its modification, the positions of the bottom planes relative to the tape travel surfaces and the radius of curvature of the tape travel surfaces are suitably determined as described above so that the magnetic tape is forced to make into contact with the inclined planes and the bottom planes of the tape guides and is forcibly biased satisfactorily toward the reference planes of the other projection, whereby the position and direction of the traveling tape can be stabilized. Furthermore, in the case of the preliminary embodiment and its modification, the dust particles produced at the bottom planes of the tape guides are forced to adhere to the tape travel surfaces on the side of the tape guides due to the suitable selection of the above-mentioned radius of curvature. Thus the dust particles almost uniformly adhere so that the position and the direction of the traveling tape will not be adversely affected. Embodiment of the present invention Next referring to Figs. 13, 14 and 15, the embodiment of a magnetic head in accordance with the present invention will be described. Recesses 39a, 39a', 39b and 39b' are formed at the area in vicinity of the edges of the tape travel surfaces 32b and 32b', respectively, and the reference planes and inclined planes of the projections 36a, 36a' and 36b, 36b' of the tape guides 36 and 36' are defined within the recesses 39a, 39a', and 39b, 39b' respectively. In other words, the projections 36a, 36a', 36b and 36b' are extended by three to six millimeters from the magnetic gap 33 in the longitudinal direction of the tape, respectively. In the embodiment, the reference planes and inclined planes of the projections intersect the tape travel surfaces 36b and 32b' through the recesses 39a, 39a' and 39b, 39b', respectively. When the length of the magnetic head along the longitudinal direction of the tape is determined 11.4 mm and the quantity of the projection of the magnetic head is 1.8 mm in the embodiment, the overall tape travel surface interconnecting the tape travel surfaces 32a, 32b and 32b' is so defined as to have a radius of curvature in excess of 20 mm. Thus, the magnetic tape 5, which is, traveling, initially makes into contact with the tape travel surface 32b or 32b' at the edge thereof on the side of the tape guide, that is, at the tape travel surface 32b or 32b' between the projection 36a and 36b or between the projections 36a' and 36b'. Next when the magnetic tape 5 is traveling in the direction indicated by the arrow A in Fig. 14, the magnetic tape initially makes contact with the tape travel surface 32b on the side of the tape guide. Under this condition, a portion of the tape travel surface 32b which is made into contact with the magnetic tape 5 is located between the inclined plane of the projection 36b and the reference plane of the projection 36a. As a result, the travel direction and the travel position can be correctly controlled by the inclined plane of the projection 36b and the reference plane of the projection 36a. As best shown in Fig. 13, the bottom plane 36c and 36c' of the tape guides 36 and 36', respectively are not located so as to interfere the traveling of the magnetic tape 5 so that the dust particles due to the contact between the magnetic tape 5 and the bottom planes 36c and 36c' can be prevented from being produced. Furthermore, the tape travel surface 32b are defined over the top surface of the case 31 as in the case of the preliminary embodiment and its modification described above and the case 31 is made of a metal. In addition, the surfaces of the case 31 are finished very smoothly. As a result, the production of the dust particles such as magnetic particles and binder particles at the tape travel surface 32b can be substantially eliminated so that unlike the conventional magnetic heads, no dust is accumulated or adhered to the surface in the vicinity of the magnetic gap 33. Same is true for the case in which the magnetic tape 5 is traveling in the direction indicated by the arrow B in Fig. 14 so that there is no fear that the production of the dust particles such as magnetic particles and binder particles resulting from the traveling of the magnetic tape occurs. Modification of the Embodiment of the Invention Next referring to Figs. 16, 17 and 18, a modification of the embodiment of a magnetic head in accordance with the present invention will be described in detail hereinafter. Unlike the embodiment described above, the modification of the embodiment is not especially formed with the recesses at both the side edges of the tape travel surface, but the radius of curvature of the overall tape travel surface is determined in a manner similar to the described above with reference to Figs. 13-15 (the embodiment). The positions of the bottom plane 46c and 46c' of the tape guides 46 and 46', respectively, are located so as not to interfere the traveling of the magnetic tape 5 while the magnetic tape 5 initially makes in contact with the tape travel surface 42b or 42b'. Furthermore, the end surfaces including the ridgelines or profile lines of the side edges of the tape travel surfaces 42b and 42b' are made into intimate contact with the side surfaces of the case 41. As a result, the profile lines on the sides of the guides of the tape travel surfaces 42b and 42b' are located very close to the reference planes defined by the projections 46a and 46a' and the inclined planes defined by the projections 46b and 46b'. More particularly, in the direction of the traveling of the magnetic tape 5, the tape travel surfaces 42b and 42b' on the side of the tape guide becomes continuous with the reference planes defined by the projection 46a and 46a' and the inclined planes defined by the projections 46b and 46b', respectively. Thus, like the embodiment described above with reference to Figs. 13-15, the direction and position of the traveling of the magnetic tape 5 can be correctly controlled. When the tape travel surfaces 42b and 42b' on the sides of the tape guides are continuous with or merge with the reference planes defined by the projections 46a and 46a' and the inclined plans defined by the projections 46b and 46b', like the embodiment described above with reference to Figs. 13-15, the position and direction of the traveling of the magnetic tape 5 can be correctly controlled. When the tape travel surfaces 42b and 42b' on the sides of the tape guides, respectively, merge with the reference planes defined by the projections 46a and 46a' and the inclined planes defined by the projections 46b and 46b', they cannot be defined as strictly continuous when the spaces required for the thickness of the adhesive between the tape guides 46 and 46' on the one hand and the case 41 on the other hand are taken into consideration, but the discontinuity among them may be tolerated as long as the effects described above is not reduced. Referring next to the Figs. 19, 20 and 21, another embodiment of a magnetic head which does not cover the present invention will be described. First the other embodiment is formed with grooves 510 and 510' at the tape travel surface 52a defined by the resin 57 so that the contact of the magnetic tape 5 and the resin 57 is avoided. These grooves 510 and 510' will be described in detail below. The distance between the inner side surfaces of the grooves 510 and 510' is made smaller than the width of the magnetic core 54 (which is 3.72 ± 0.05 mm) and furthermore no resin 57 remains at the end faces of the core 54 along the boundary between the core 54 and the resin 57. The width of the grooves 510 and 510' is of the order of 0.2 mm and the size of the grooves 510 and 510' is so determined that both of the side edges of the magnetic tape 5 may be located within the recesses 510 and 510' and is preferably reduced as small as possible so that the contact of the sides edges of the magnetic tape 5 will not make contact with the resin 57 located outwardly of the recesses or grooves 510 and 510'. When the width of the recesses 510 and 510' is determined in excess of 1 mm, a portion of a pad (not shown) which presses against the tape travel surface 52a from the upper side of the core 54 falls into the recesses 510 and 510' so that the magnetic tape 5 is bent within the recesses 510 and 510'. As a result, there occur various problems that the writing and reading characteristics are degraded due to the failure of the correct determination of the azimuth and that the side edges of the magnetic tape 5 are twisted, causing the damage to the magnetic tape 5. The depth of the recesses 510 and 510' is so determined that a shorter length of the side edges of the magnetic tape 5 remain within the recesses 510 and 510', for instance, even when the magnetic tape 55 is pressed by the pad (of the type described above), it will not be made in contact with the bottoms of the recesses 510 and 510'. With the magnetic head with the above-described construction, the contact of the magnetic tape 5 with some portions of the resin 57 located on both sides of the magnetic core 54 can be prevented so that the separation and adhesion of the dust particles at these portions can be avoided. When the other embodiment is provided with the tape guides 56 and 56' as shown in Figs. 22 and 23, more advantageous effects can be attained. Figs. 22 and 23 illustrate the other embodiment provided with tape guides 56 and 56'. First, the function of the tape guides 56 and 56' will be described. The magnetic tape 5 is pressed against the bottom plane 56c of the tape guide 56 under the tension of the magnetic tape 5, and is made into contact with the inclined plane defined by the projection 56b of the tape guide 56 and is biased toward the reference plane defined by the projection 56a of the tape guide 56. The reference plane is substantially perpendicular to the bottom plane 56c so that one side edges of the magnetic tape 5 is traveling along the reference surface. In this case, the reference plane is defined to the substantially perpendicular to the magnetic gap 53 so that the position and direction of the traveling tape can be maintained always in the stabilized conditions. The angle defined by the magnetic tape 5 and the magnetic gap 53 is also maintained in the stabilized condition so that the azimuth loss resulting from the difference in gap angle between the data writing mode and the data readout mode can be reduced to a minimum. As described above, the tape guides 56 and 56' are in general formed by the injection molding of a resin which is inexpensive, but their surfaces are almost rough. Therefore when the magnetic tape 5 is pressed against the reference planes defined by the projections 56a and 56a' of the tape guides 56 and 56', the separation of the dust particles along one side edge of the magnetic tape 5 tends to occur frequently. As a result, in the case of the conventional magnetic head of the type described above, the dust particles produced from the side edges of the magnetic tape 5 adhere to the resin over the tape travel surface 52a in many cases, but the other embodiment is remarkably effective to prevent satisfactorily the dust particles from adhering the resin. More particularly, since the recesses are formed in some resin located on both sides of the core, the position and direction of the traveling tape in the modification of the other embodiment described above can be maintained in the stabilized state. Next referring to Figs. 24, 25 and 26, a further embodiment of a magnetic head which does not cover the present invention will be described. In the further embodiment, grooves or elongated recesses 611a, 611b, 611c and 611d are formed at the top surface of the head case 61 at which are defined the tape travel surfaces 62b and 62b' so that the contact of both side edges of the magnetic tape 5 with the tape travel surfaces 62b and 62b' is prevented. The function of the recesses 611a, 611b, 611c and 611d will be described in detail below. First the distance between the inside surfaces of the recesses 611a and 611c and between the recesses 611b and 611d is made smaller than the width of the magnetic core 64 (3.72 ± 0.05 mm). Then the dust particles produced especially due to the contact of the side edges of the magnetic tape 5 with the resin 67 and adhered to the sides edges of the tape 5 are carried to the tape travel surface 62a or 62b', but the dust particles will not adhere to the tape travel surfaces 62b and 62b'. As described in the other embodiment, the depth of the recesses 611a, 611b, 611c and 611d is so determined that the side edges of the magnetic tape 5 will not be made into contact with the bottom of these recesses. With the magnetic head of the type described above, the dust particles adhered to the side edges of the tape 5 can be prevented to adhere to the tape travel surface 62b or 62b' so that nonuniform wear of the head case 61 can be prevented. Referring now to Figs. 27, 28 and 29, a modification of the further embodiment of a magnetic head which does not cover the present invention will be described. According to the further embodiment, recesses 712a, 712b, 172c and 712d in such a manner that the inner distance between the opposing recesses 712a and 712c and between the opposing recesses 712b and 712d is slightly smaller than the width of the magnetic tape 5 are formed over a portion of the tape travel surface of the head case 71 at which the tape travel surfaces 72b and 72b' are defined . Thus the contact of the side edges of the magnetic tape 5 with the tape travel surfaces 72b and 72b' can be prevented. Therefore, like the further embodiment shown in Figs. 24, 25 and 26 the magnetic head modified in the manner described above can be used for a long time at high temperature without causing any adverse effects to the traveling of the magnetic tape 5. Moreover when the magnetic head of the further embodiment and its modification is provided with tape guides as will be described below with reference to Figs. 30 and 31, it can attain more remarkable effects. Figs. 30 and 31 illustrates the magnetic head which is substantially similar in construction to the modification of the further embodiment described above with reference to Figs. 27, 28 and 29 and which is further provided with tape guides. As described above with reference to Figs. 22 and 23, because of the formation of the recesses 712a and 712c or 712b and 712d the dust particles produced from the tape guides in opposing relationship with the side edges of the magnetic tape can be prevented from adhering to the tape travel surface 72b or 72b'. In the case of the further embodiment and its modification described above, when the longitudinal direction of the tape is always maintained in a predetermined direction, it is apparent to those skilled in the art that they may be formed at the downstream side of the direction of the traveling tape. A still further embodiment of a magnetic head which does not cover the present invention is illustrated in Figs. 32, 33 and 34 and is substantially similar in construction to the combination of the other and further embodiments. That is, recesses 810 and 810' are formed at the top surface of the resin 87 at which is defined the tape travel surface 82a so that the contact of the magnetic tape 5 with the resin 87 can be prevented. Moreover when the recesses 811a, 811b, 811c and 811d are formed at the top surface of the case 81 at which are defined the tape travel surfaces 82b and 82b', the side edges of the magnetic tape 5 can be prevented from making into contact with the tape travel surfaces 82b and 82b' during the traveling of the tape. A modification of the still further embodiment illustrated in Figs. 35, 36 and 37 is substantially similar in construction to a combination of the modification of the other and further embodiments. That is, recesses 910 and 910' are formed at the tape travel surface 92a defined over the top surface of the resin 97 and a recesses 912a, 912b, 912c and 912d are formed at the tape travel surfaces 92b and 92b' in such a way that the distance between the inner sides of the opposing recesses 912a and 912c and between the inner sides of the opposing recesses 912b and 912d is slightly narrower than the width of the magnetic tape 5. Figs. 38 and 39 illustrates that the magnetic tape is transported over the modified magnetic head described above with reference to Figs. 35-37. In the cases of the still further embodiment and its modification with or without the tape guides, the production of the dust particles can be reduced to a minimum and oven when they are produced, they are almost completely prevented from adhering to the tape travel surfaces. Because of the synergetic effect obtained by the combination of the reduction in amount of the dust particles and the prevention of the dust particles to adhere to the tape travel surfaces, as compared with the other and further embodiments and their modifications, the stabilized traveling of the magnetic tape for a long period of time and the reading and writing characteristics at the magnetic gap can be satisfactorily maintained.

Claims: A magnetic head for writing and/or reading data into and/or from a magnetic tape (5) , comprising: a) a magnetic core (34; 44) ; b) a case member (31; 41) for holding said magnetic core; and c) a tape guide (36, 36'; 46, 46') having a reference surface which determines a position of an edge of said magnetic tape and an inclined surface which is disposed opposite to said reference surface for urging said magnetic tape to said reference surface, said reference surface and said inclined surface being provided on respective projections (36a,b, 36a',b'; 46a,b, 46a',b') of said tape guide, said tape guide further having a bottom surface (36c,c'; 46c,c') which is located between said respective projections; and d) a tape slide surface (32) on which said magnetic tape slides in contact therewith, said magnetic head being characterized in that e) said bottom surface of said tape guide is lowered with respect to said tape slide surface such that it does not interfere the traveling of said magnetic tape. A magnetic head according to claim 1, characterized by recesses (39a, 39a', 39b, 39b') formed into a section of saic tape slide surface (32) arranged between said reference surface and said inclined surface at the edges of said case member (31) in order to enable an intersection of said reference and said inclined surface with the tape travel surface plane within said recesses (39a, 39a', 39b, 39b') . A magnetic head according to claim 2, characterized in that said section is arranged between a top of said inclined surface and a bottom thereof in a direction of thickness of said magnetic tape (5) .

Inventors: KIMURA TAKESHI, KIMURA, TAKESHI
Applicants: CANON DENSHI KK, CANON DENSHI KABUSHIKI KAISHA
Application year: 1990
Main classification: G11B15
IPC codes: G11B15, G11B5