Magnetic recording and reproducing head unit

Abstract: There is disclosed a magnetic recording and reproducing head unit (A) made up of a tape guide (13) and magnetic heads (14, 15), where­ in a top plate (16) and a bottom plate (17) are connected with a predetermined distance therebetween, a center member (20) is disposed between the top and bottom plates to provide the tape guide, a reference plane is set on either of the opposing faces of the top and bottom plates, a convex (25, 26) is formed on the side of the center member, magnetic heads are inserted along the center member between the top and bottom plates, the end faces of the magnetic heads are made to push against the reference plane to thereby limit the height of the track pattern, and the magnetic heads are pivotable with the convex as fulcrum to thereby enable azimuth adjustment.

Description: FIELD OF THE INVENTION The present invention relates to a magnetic recording and reproducing unit for a magnetic recording and reproducing device and particularly to a magnetic recording and reproducing unit so contrived as to facilitate adjustment in height of the track pattern and azimuth adjustment as the magnetic head is attached to the tape guide. BACKGROUND OF THE INVENTION Recently, with digital magnetic recording devices such as tape recorder, too, it has become necessary to arrange a plurality of heads at a fixed distance to cope with variation of requirements, this accompanied by the newly increased significance of setting a relative positional relationship between the magnetic head and tape guide with a high degree of precision. By the way, among the known conditions for concrete positional relationship between a magnetic head and a tape guide are, as shown in Fig. 6 (a), the height h, h′ of track patterns 2a, 3a from and the inclination ϑ a1 , ϑ a2 of the track patterns 2a, 3a against the reference planes 1a of tape guide members 1, the extents of protrusion α₁, α₂ of magnetic heads 2, 3 from tape guide poles 1b and the distance L between magnetic heads 2, 3 shown in Fig. 6 (b) and, further, such factors as tilt and mechanical adjustment, although these are not shown in the figure. Thus, there are quite a number of conditions to be satisfied and since a high precision is required with regard to each condition, it was hitherto accepted to be difficult to preassemble the tape guide and then fix the magnetic head 2 and 3 to the tape guide. It has, therefore, been a usual practice in assembling a magnetic recording and reproducing head unit to data, as shown in Fig.7, to adjust the mutual positional relationship between individual tape guide members 5-7 and individual magnetic heads 8 and 9 on a bottom plate 4 of the tape guide by the use of mechanical stages 10, 11 for positioning thereof along the X and Y axes and another mechanical stage 12 for azimuth adjustment and, after fixing thereof using an adhesive, set a top plate (not shown) in place. With regard to the magnetic recording and reproducing head unit shown in Fig. 7, however, there was a problem of an extremely long time required for assembling the tape guide and the magnetic head after adjustment of the positional relation therebetween, this resulting in a lower productivity. As seen from Fig. 8, therefore, the present inventor contrived an arrangement in which a housing case 51 having a magnetic head 50 housed and fixed therein is positioned and fixed in a hole 53 provided in a position adjusting portion 52 of the tape guide, see JP-A-63-225911. In this arrangement a curved leaf spring 54 for urging the housing case 51 is positioned between the housing case 51 and the bottom of the hole 53, and the position adjusting portion 52 has a tapped hole near the top thereof for a height-adjusting screw 55 for adjusting the height of a magnetic head 50 in contact with the top of the housing case 51. On one side of the housing case 51 there is formed a convex 56 to be in contact with the bore of the hole 53, and the position adjusting portion 52 has set therethrough an adjusting screw 57 for pushing the other side of the housing case 51 near the top thereof and another adjusting screw 60 for pushing the aforesaid side near the bottom thereof through a springy piece 58, and through adjustment by these screws 57 and 60 the housing case 51 can be pivoted with the convex 56 as fulcrum for proper adjustment of the inclination angle of the magnetic head 50. Opposite to the adjusting screw 57 with respect to the housing case 51 there is provided also through the position adjusting portion 52 a fixing screw 61 for tentatively fixing the housing case 51 to the position adjusting portion 52. In the construction illustrated in Fig. 8, however, it is so arranged that the height of the magnetic head 50 is determined as the housing case 51 is pressed against the height adjusting screw 55 by the urging force of the leaf spring 54, hence the inclination angle of the magnetic head 50 is changed as the adjustment of the height of the magnetic head 50. Therefore, sufficient precision is difficult to attain with regard to the adjustment of both height and inclination of the magnetic head 50. Another problem was the inevitable complication of the construction as the position adjusting portion 52 had to be provided with such adjusting and fixing means as the adjusting screws 57 and 60 and the fixing screw 61 et cetera. Another prior art magnetic head mounting arrangement is known from EP-A-0,120,518. SUMMARY OF THE INVENTION It is a primary object of the present invention to provide a magnetic recording and reproducing head unit which allows easy attachment of a magnetic head to a tape guide accurately positioned thereto without the use of such instruments as a mechanical stage. Another object of the present invention is provision of a magnetic recording and reproducing head simplified in construction by dispensing with incorporating in the tape guide of the adjusting members hitherto required for adjustment of the height of the track pattern and the inclination angle of the magnetic head. The invention provides a magnetic recording and/or reproducing head unit comprising a top plate and a bottom plate vertically spaced apart by a predetermined spacing to define a guide for magnetic tape therebetween, a head positioning member disposed between said top and bottom plates, said positioning member providing an upright side surface having a projection at a position partway between said plates, and a magnetic head element inserted between said top and bottom plates, said head element having a first surface positioned alongside said upright side surface of the positioning member and in contact with said projection, which acts as a fulcrum for the azimuthal adjustment of said head element, and a second surface in contact with a reference plane provided by one of the opposing faces of said top and bottom plates, which determines the height of a track pattern of the head element within said predetermined spacing of the tape guide. In a more concrete embodiment there are provided left and right spacers between the top and bottom plates to keep a given distance therebetween, and there are provided a plurality of guide poles for guiding a magnetic tape. Also, in order to control the height of the track pattern of the magnetic head, it may concretely be feasible, for instance, to provide on the topside of the aforesaid bottom plate upper guide faces which come into contact with the left and right spacers and a guide head face as a reference plane having a given difference in level against the aforesaid upper guide faces. Where the topside of the bottom plate is taken as the reference plane, the aforesaid magnetic head may have the bed plate fixed behind the head portion and have the underside of the bed plate above the underside of the head portion so that the underside of the head portion alone is in agreement with the reference plane. Where the topside of the bottom plate is taken as the reference plane, it may as well be so arranged that there is set a predetermined distance between the underside of the aforesaid head portion and the track pattern so that the height of the track pattern is adjusted accordingly. Another alternative may be to set the height of the aforesaid positioning member to be a bit smaller than the distance between the top and bottom plates and have the positioning member attached to the top plate with its topside in contact with the underside of the top plate. In a still more concrete embodiment it is possible to have each one convex on both sides of the aforesaid positioning member and have it so dimensioned that the distance between the opposite tips of the convexes agrees with the predetermined one, and to have a pair of magnetic heads inserted along both sides of the aforesaid center member between the top and bottom plates. In such a case, the aforesaid positioning member may have its width increased toward the forward ends of the pair of magnetic heads inserted along both sides thereof to be approximately trapezoidal in plan view. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of the magnetic recording and reproducing head unit of the present invention. Fig. 2 is a front elevation of the magnetic recording and reproducing head unit of the present invention. Fig. 3 is a plan view of the magnetic recording and reproducing head unit of the present invention. Fig. 4 (a) and (b) are the plan view and the front elevation of the center spacer used in the magnetic recording and reproducing head unit. Fig. 5 is a perspective view of the magnetic head of the magnetic recording and reproducing head unit. Fig. 6 (a) and (b) are a schematic front elevation and a schematic plan view showing the positional relationship between the magnetic head and the tape guide. Fig. 7 is a perspective view showing a way a conventional magnetic recording and reproducing head unit is assembled. Fig. 8 is a front elevation showing the essential parts of another conventional magnetic recording and reproducing head unit. DESCRIPTION OF THE EMBODIMENTS Referring to the accompanying drawings 1 through 5 showing a preferred embodiment, the present invention is now described in greater detail. As shown in Fig. 1, a magnetic recording and reproducing head A comprises a tape guide 13 and two magnetic heads 14 and 15. The tape guide 13 is made up of a top plate 16, a bottom plate 17, a left spacer 18, a right spacer 19 and a center spacer 20 serving as an center member. The magnetic heads 14 and 15 are arranged along both, left and right, sides of the center spacer 20. As seen from Fig. 2 and Fig. 3, the height "t" of the left spacer 18 and the right spacer 19 is set to be somewhat greater than the width of the magnetic tape (not shown), and the top plate 16 and the bottom plate 17 are connected by screws 21, 21 outside the left and right spacers. The top plate 16 and the bottom plate 17 are, therefore, disposed parallel to each other at a predetermined distance "t". Holes 22, 23 provided at a plurality of positions near the front edges of the top plate 16 and the bottom plate 17 have set therein the upper and lower ends of guide poles 24 for guiding the aforesaid magnetic tape respectively. As seen from Figs. 4 (a) and (b), the center spacer 20 is finished to a height t′ which is somewhat less than that of the left spacer 18 and right spacer 19. On both, left and right, sides of the center spacer there are formed convexes 25 and 26 being protrusions or crownings roughly semicircular in section. The sideway projections of the convexes 25 and 26 are set at δ₁ and δ₂, the lengths of the convexes 25 and 26 along the sides of the center spacer are set at ℓ₁ and ℓ₂, the inclination angle of the convexes 25 against the horizontal, longitudinal line of the tape guide 13 is set at the predetermined ϑ₁ and ϑ₂ , and the distance between the tips of the two convexes 25 and 26 is set at L′ respectively. The center spacer 20 has provided therein pin holes 27 and tapped holes 28, and the center spacer 20 is fixedly secured to the top plate 16 with the topside thereof fitting closely to the underside of the top plate 16 by the use of positioning pins 29 and screws 30. The center spacer 20 is increased in width toward the tips of the magnetic heads 14 and 15 inserted along both sides thereof so as to be trapezoidal in plan view. As seen from Fig. 2, the bottom plate 17 is precisionfinished with a predetermined difference in level of h₁ between the topside 31 which comes into contact with the lower end faces of the left spacer 18 and the right spacer 19 and the guide head face 32 which is taken as the reference plane. As seen from Fig. 5, the magnetic head 14 comprises a head portion 35 consisting of a head board 33 and a protective plate 34. Although no detailed illustration is shown, this head portion 35 comprises integrated circuits, capacitors et cetera housed in a case and is bonded to a base board 36 located behind it. The underside 37 as the end face of the head portion 35 is precision-finished so that a predetermined distance of h p is provided between it and the lower end of a track pattern 38. The underside 37 is directly pressed onto a guide head face 32, not covered by the aforesaid case. The base board 36 is attached to the head portion 35 so that its underside 39 is at a level higher than the underside 37 of the head portion 35 by hd , hence, even if the underside 37 of the head portion 35 should be pressed against guide head face 32, the underside 39 of the base board 36 does not come into contact with the guide head face 32. A gap is provided also between the base board 36 and the center spacer 20. The magnetic head 15, too, is composed similar to the magnetic head 14, its positional relationship with the guide head face 32 etc., being the same as described above. Hereinafter, the assembling procedure for the aforesaid magnetic recording and reproducing head unit A is to be described. First, the top plate 16 and the bottom plate 17 are connected using the screws 21 with the left spacer 18 and the right spacer 19 in between and the upper and lower ends of the guide poles 24 are set in the holes 22 and 23 Then, the center spacer 20 is secured to the top plate 16 by the use of the pins 29 and the screws 30 and the assembly of the tape guide 13 is now over. Then, as shown in Figs. 2 and 3 by two-dot chain line, a front reference plate 40 for the assembling apparatus is positioned at a predetermined inclination angle against a tape guide 13, the corners of pole contact faces 41 and 42 are applied to the guide pole 24 (set through a hole) on the left-hand side of the tape guide 13, and the guide pole 24 is fixed to the aforesaid reference plate 40 by means of e.g. vacuum sucking. Now, the magnetic head 14 is inserted into the space between the top plate 16 and the bottom plate 17 along the sides of the center spacer 20 and the front end of the magnetic head 14 is pressed against the front reference plate 40, and kept pressed with a force Fa applied longitudinally of the magnetic head 14 by means of a spring or the like (not shown). Thereafter, the topside of the head portion 35 of the magnetic head 14 is pressed down with a pin or the like (not shown) with a force Fb to have the lower end face 37 of the magnetic head 14 pressed against the guide head face 32, and, further, horizontal forces Fc and Fd are applied at two, upper and lower, positions on the protective plate 34 of the head portion 35 to have the head board 33 of the head portion 35 pressed against the convex 25 formed on the side of the center spacer 20. Now, an optical observation system for observing two points 38a and 38b on the track pattern 38, for instance, the upper and lower ends of the track pattern 38 of the magnetic head 14, are arranged opposite to the magnetic head 14. If the magnetic head 14 is to be attached to the tape guide 13 to be perpendicular to the bottom plate 17, electronic lines perpendicular to the guide head face 32 of the bottom plate 17 are to be set on the monitor of the optical observation system, the forces Fc and Fd are so adjusted that the two points 38a and 38b displayed on the monitor are both overlapped on the aforesaid electronic lines, and the magnetic head 14 is caused to pivot in the direction B or C with the convex 25 as fulcrum. The moment the two spotty images 38a and 38b have overlapped with the aforesaid electronic lines, an instantaneous adhesive or the like may be poured into the gap between the magnetic head 14 and the center spacer 20 to tentatively fix the magnetic head 14 to the tape guide 13. It is thereby possible to accomplish azimuth adjustment of the track pattern 38 of the magnetic head 14 and, further, the height of the track pattern 38 can be fixed at a predetermined level above the guide head face 32 taken as the reference plane on the bottom plate 17. The upper guide face 31 and the guide head face 32 of the bottom plate 17 are precision-finished for the difference in level to be h₁, and the finishing precision is also high so that the distance between the underside of the head portion 35 and the lower end of the track pattern 38 is exactly h p . Moreover, the head portion 35 is not encased and is directly pressed against the guide head face 32, hence the error for the height from the upper guide face 31 to the lower end of the track pattern 38 is as small as 10-odd µ m. The other magnetic head 15, too, is to be positioned in the same way as described above, and is to be tentatively fixed to the tape guide 13. Since the distance between the convexes 25 and 26 on the center spacer 20 is set constantly at L′, the distance between the magnetic heads 14 and 15 is constant, too, being L. The tape guide 13 and the magnetic heads 14 and 15 thus assembled are taken out of the assembling apparatus and are finally bonded together using an adhesive, and the magnetic recording and reproducing head unit A is thus completed. In the above embodiment the magnetic head 14 and 15 are attached to the tape guide 13 to be perpendicular to the bottom plate 17, but these may equally be attached to the bottom plate 17 at some other predetermined angle of inclination. It is also possible to first determine the height of the track pattern 38 of the magnetic heads 14 and 15 with the underside of the top plate 16 as the reference plane, and then attach the magnetic heads 14 and 15 to the tape guide 13 at the predetermined angle of inclination. Also, in the above embodiment the top plate 16 and the bottom plate 17 are disposed parallel to each other at a distance "t" by the left spacer 18 and the right spacer 19, but these may equally be disposed parallel to each other at a distance "t" by the center spacer 20 which is finished to a height "t" instead of the left spacer 18 and the right spacer 19. Thus, with the magnetic recording and reproducing head unit of the present invention, it is possible to preassemble the tape guide and then attach the magnetic heads to the tape guide with ease after precise positioning with respect thereto. Further, since the adjustment of the inclination angle of the magnetic heads to the tape guide is to be done on an assembling apparatus separate from that for assembling the magnetic recording and reproducing head unit, the construction of the magnetic recording and reproducing head unit can be simplified with ease.

Claims: A magnetic recording and/or reproducing head unit comprising a top plate (16) and a bottom plate (17) vertically spaced apart by a predetermined spacing (t), a head positioning member (20) disposed between said top and bottom plates, and a magnetic head element (14 or 15) inserted between said top and bottom plates, said head element having a first surface positioned alongside said upright side surface of the positioning member, characterized in that said top and bottom plates define a guide for magnetic tape therebetween, in that said positioning member provides an upright side surface having a projection (25 or 26) at a position partway between said plates, and in that said head element has said first surface in contact with said projection, which acts as a fulcrum for the azimuthal adjustment of said head element, and a second surface (37) in contact with a reference plane provided by one (32) of the opposing faces of said top and bottom plates, which determines the height of a track pattern (38) of the head element within said predetermined spacing of the tape guide. A magnetic head unit according to claim 1, wherein said top and bottom plates are connected by two spacers (18, 19), one on either side of said positioning member, which spacers define said predetermined spacing, and a plurality of guide poles (24) are disposed between said top and bottom plates for guiding said tape. A magnetic head unit according to claim 2, wherein the height (t') of said positioning member (20) is somewhat smaller than the spacing (t) between said top and bottom plates, and said positioning member is attached to said top plate with its upper end face in close contact with the underside of said top plate. A magnetic head unit according to claim 1, wherein said top and bottom plates are connected by said positioning member (20), which defines said predetermined spacing. A magnetic head unit according to claim 2 or claim 3, wherein the topside of said bottom plate provides upper guide faces (31) which contact lower end faces of said left and right spacers (18, 19) and a guide head face (32) representing said reference plane, there being a predetermined level difference (h₁) between said guide head face and said upper guide faces. A magnetic head unit according to any one of the preceding claims, wherein said magnetic head element (14, 15) has a bed plate (36) disposed behind a head portion (35) and the underside (39) of said bed plate is at a level higher than the underside (37) of said head portion, the underside (37) of the head portion constituting said second surface of the head element. A magnetic head unit according to claim 6, wherein a predetermined gap (h p ) is provided between the underside (37) of said head portion (35) and said track pattern (38) of the head element. A magnetic head unit according to any one of the preceding claims, wherein said projection is formed as a respective convex (25, 26) on each of two said upright side surfaces of the positioning member, the distance (L') between the tips of the two convexes being dimensioned to a predetermined value, and two said magnetic head elements (14, 15) are inserted between said top and bottom plates, one alongside each said upright side surface of the positioning member. A magnetic head unit according to claim 8, wherein said positioning member (20) is increased in width toward the forward ends of said magnetic head elements so as to be substantially trapezoidal in plan view.

Inventors: NAKATSUKA MAMORU, NAKATSUKA, MAMORU
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1988
Main classification: G11B15
IPC codes: G11B5, G11B15