AIR BEARING SLIDER RAIL DESIGN AND MECHANICAL METHOD FOR PRODUCING IT

Abstract: An air bearing slider (10) for supporting a transducer (24) is provided with a pair of rails having an air bearing surface (12,14) with a trumpet-like part (12A,14A) with its greatest width (LW) at the leading end (20) of the slider. In the rear area of the slider the air bearing surfaces are of equal width (TW). The invention furthermore provides a mechanical grinding process using a grinding wheel (40) having two grinding disks (41,42) separated by a spacer disk (43) and provided with bevelled grinding surfaces (47) on its inner sides. Either by advancing the turning grinding wheel (40) parallel to the surface of the slider from the trailing towards the leading end up to a certain point or in accordance with another embodiment by skipping the slider slightly towards the advance motion and continuously advancing the grinding wheel, the trumpet-like air bearing surface portions (12A,14A) are provided in a simple and efficient manner.

Description: The present invention relates to an air bearing slider for supporting a transducer relative to a moving record medium, said slider being provided on its side opposite said recording medium with a pair of side rails separated by a recessed portion, said rails extending from the leading end of said slider to its trailing end which supports said transducer, each rail comprising an air bearing surface of increasing width and having its widest dimension at the leading end of said rail or slider respectively, and said rails having a tapered portion at the leading end of said slider. The present invention furthermore relates to a mechanical method for producing said slider rail design by a grinding process. US-A-4475135 describes a self-loading magnetic head air bearing slider having a taper across the full width at its leading edge. The slider has two rails along its sides and a recess between the rails. The structure of the rails is flared, so that the rail is wider at the trailing portion of the slider than in the portions closer to the leading edge. Structure and working principle is completely different from the design of the present invention. EP-A-0015383 shows in an example (Fig. 2) a similar rail structure as the one described above. Behind a rail taper at the leading portion and at a cross front portion connecting the two rails, the surface of the rails on their inner opposite edges are tapered so that the rail is widest at the trailing edge where the transducer is provided. This design again is structurally completely different from the one of the present invention. Published European Patent Application EP-A-0129336 shows a three rail slider design in which the two outer rails form the air bearing surfaces of the slider and are of continuous width in that both rails edges are parallel to each other. The surfaces are contoured to be rounded toward the outer edges as well as toward the trailing and leading edges. No departure of constant rail width is shown in this patent. The not prior published EP-A- 0 237 752 shows a rail design that is chamfered at its leading end and that has a leading portion which is wider than an intermediate portion between the leading and trailing portions of the rails. The rail may have a leading portion of constant width, an intermediate portion where the rail becomes progressively narrower along straigh lines to a breakpoint and is then of constant width. Also a flaring toward the trailing edge is shown to make the rail again wider at the transducer position. This design shows no curved, e.g. trumpet-like form by which the rail is changing its width and changing it on its both edges. Also no grinding process and tool is shown for a simple fabrication process. Document JP-A-61 258 327 shows a slider with two rails having sloping surfaces on each side of each rail. By these sloping surfaces the width of the rail decreases linearly from the leading side to the trailing edge where the head is provided. Also here no curved design, e. g. in trumpet-like form is shown, nor a hint is given as to the method of producing the same. Also in US-A-4 333 229 a slider with two rails on it outside is shown. These rails have sloped sides and each rail has three different plains which have different angles to each other. There is a tapered area, a slightly sloped area and in the vicinity of the magnetic head an area which is again differently angled to the two other areas. Also here no curved changing rails or rails with increasing widths are shown nor a hint how to produce it. In document FR-A-2 167 698 there is described the production of the width of gaps, writing gap and reading gap of a magnetic head. No slider design is shown here. For producing the desired gap widths a grinding wheel having two beveled cutting surfaces on its inside, is advanced vertically to the area where the gap is. In rotating the wheel the parts on the side of the gap are removed by rotating the grinding wheel. If the gap or the gaps have the desired widths, the grinding wheel is retracted in opposite direction. This known prior art concerns a magnetic head and not a slider, the form of the grinding wheel is differently and only a back and forth movement or only into and out of the magnetic core is performed. There is no lengthwise advanced motion and instead of forming rails on a slider here the widths of magnetic gaps on a magnetic head itself is performed. The object of the present invention is to have a rail design for an air bearing slider that increases the pitch angle and at the same time lowers the transducer element towards the recording medium to have a lower flight height. At the same time providing a high pitch angle the leading part and thus also the main part of the slider should be kept away from the recording medium such as a disk, for avoiding serious head disk interferences. A further object of the present invention is to provide a mechanical grinding method for providing the special rail design in accordance with this invention by a simple and economically working grinding process. The foregoing object were solved and the drawbacks of the known rail designs and producing methods are overcome by the solution given in the characterizing parts of the main independent claims. Further advantageous embodiments of the present invention are laid down in the corresponding subclaims dependent on the main claims. The invention provides in advantageous manner an air bearing slider for supporting one or more transducer at its trailing end, the underside of which is provided with two especially designed rails. This especial design provides a parallel rail from the trailing part of the slider towards a point somewhere around of the middle of the lengths of the slider and towards the leading end of the slider a rail of continuously increasing width, having its greatest width at the leading edge of the slider. The form might be trumpet-like or circle like. This form provides a greater air bearing surface in the leading area of the sliders thus having a greater lifting air pressure there which provides a greater pitch angle thus lowering the trailing edge with the transducer. The wider rail surface also provides a slider which is stiffer, more stable, in view of its tendency to roll around the lengths axis of the slider. For providing this advantageous rail form an advantageous mechanical grinding process is provided by the invention using a grinding wheel consisting of two grinding disks preferably diamond disks, which have bevelled cutting surfaces at its outer circumference. Both grinding disks are clamped together with a spacer disk of smaller diameter in between such that the bevelled cutting surfaces are opposite to each other. The grinding wheel with its turning plane is arranged vertically to the air bearing surfaces of the slider and advanced from the trailing end towards the leading end of the slider parallel to the lengths of the slider so far that in the trailing part of the slider a rail form having parallel bordering edges is provided and from a certain point on a rail is provided having an increasing width that means that their bordering edges are no more parallel. This is performed in such a way that the grinding wheel is not completely advanced through the slider but only up to a certain point within its lengths and then retracted towards the trailing edge. By another embodiment of this grinding process it is possible to have an improved manufacturability. In this instant the slider is slightly tilted or inclined respectively so that the plane of the rail is not parallel to the direction of advance movement of the grinding wheel. That means that it is tilted such that the grinding wheel can be advanced in one direction only through the entire slider without having the necessity of retracting it. In this instant also as shown in a further embodiment a plurality of sliders may be tilted in this way and clamped together so that a plurality of sliders can be processed in a continuous way. The invention will be shown in more detail in the following description in accordance with the drawing in which embodiments are shown and in which: Fig. 1 is a perspective view of a slider provided with rails in accordance of the present invention, seen from the bottom side; Fig. 2A shows a bottom view of the slider designed with rails in accordance with the present invention; Fig. 2B shows a side view of the slider shown in Fig. 2A, seen from the leading edge; Fig. 2C shows a side view, seen from the trailing end of the slider shown in Fig. 2A; Fig. 3 shows in a side view schematically the constellation between a recording medium such as a disk and a slider with respect to the pitch angle α; Fig. 4 shows enlarged a detail of the grinding wheel in accordance with the present invention; Fig. 5A shows in a side view schematically the relation between the slider and the grinding wheel; Fig. 5B shows the bottom sight of a slider shown in the side view of Fig. 5A; Fig. 5C shows part of the side view of Fig. 5A; and Fig. 6 shows schematically in a side view a tilted arrangement of a plurality of sliders provided on carriers and clamped together, in relation to the grinding wheel which is continuously advanced in only one direction. The rail design in accordance with this invention is shown in detail and described now in connection with Fig. 1 and Fig. 2. A magnetic head slider 10 is provided on its side opposite to a recording medium such as a disk (s. Fig. 3), with two air bearing surfaces 12 and 14. Those air bearing surfaces 12 and 14 are arranged on the side of the slider 10 and are separated by a recessed portion 16 in between. The air bearing surfaces 12 and 14 are provided with a taper 18 close to the leading end 20 of the slider 10. At the trailing end 21 of the slider 10 at least one magnetic transducer 24, preferably of the thin film type, is provided. Those magnetic transducers 24 are provided immediately adjacent to the end of the air bearing surfaces 12 and 14 at the trailing edge 21. The design in accordance of the present invention for the air bearing surfaces 12 and 14 will be described now in connection with Fig. 2A and Fig. 1 in more detail. Between points A and B the air bearing surfaces 12 and 14 are in the trailing part of slider 10 of constant width TW. The rails are confined by parallel border lines 26 at the outside and 28 on the inside. That means that between border lines 26 and 28 the air bearing surface 12 or 14 respectively has a constant trailing width TW. In between point B and C which is situated at the leading end 20 of the slider 10, the air bearing surfaces 12 and 14 are confined by border lines 30 at the outside and 32 on the inside. These border lines 30 and 32 have circle-like form in such a way that seen from point B towards point C the parts 12A and 14A of the air bearing surfaces 12 and 14 have an increasing width. The increase follows the circle line of border line 30 or 32 from point B towards point C. At the leading edge 20 of slider 10 the greatest width is reached forming the leading width LW. The air bearing surfaces 12 and 14 thus have parts between border lines 26 and 28 of constant trailing width TW between points A and B and have with its parts 12A or 14A respectively between border lines 30 and 32 an increasing width, increasing along a circle line in a progressive way, up to the leading width LW. These leading parts 12A and 14A of air bearing surfaces 12 and 14 show a kind of trumpet-like form. These areas 12A and 14A have a larger air bearing surface as the trailing part with the constant width TW, thus increasing the pitch angle α as will be shown later. Furthermore, those areas 12A and 14A of increasing width stabilize the rolling movement of the slider 10 with respect to its length axis LA. The length axis LA is the one parallel to the air bearing surfaces 12 and 14 from point A to point C through the middle of slider 10. The "trumpet-like" form, generally the form in accordance with the present invention, of air bearing surfaces 12 and 14 have the effect to increase the pitch angle α of the slider as shown schematically in Fig. 3. A slider 10′ of conventional rail or surface design respectively is shown in dotted lines. This slider 10′ flighs over a magnetic recording medium such as a disk 31 which rotates in direction of arrow 33. Between the lower trailing edge, indicated by line 37 and the surface 35 of magnetic disk 31 the flight height FH′ is constituted. That means that the transducer element 24′ at the trailing end of slider 10′ has a distance of FH′ between itself and the upper surface 35 of disk 31. Shown in Fig. 3 schematically in contrast to a conventional slider 10′ is in solid lines the slider 10 with the rails respectively air bearing surfaces 12 and 14 and the taper 18 as designed in accordance with the present invention. Between the arrows 34 pitch angle α is shown. This angle is formed between a line 36 parallel to surface line 35 of disk 31 and the plane formed by the air bearing surfaces 12, 14. In contrast to the conventional slider 10′ the slider 10 designed in accordance with the present invention generates a steeper pitch angle α . Thus the flight height FH between transducer element 24 and surface 35 of disk 31 is less than the flight height FH′ of the conventional slider 10′. A further advantage of the rail design of the present invention can also be taken from the schematical view of Fig. 3. With the exception of lower trailing part of slider 10 with transducer 24, the essentially greater part of slider 10 is further distanced from upper surface 35 of disk 31 than the body of conventional slider 10′. That means that in case of a head disk interference only a smaller part of slider 10 would touch disk 31 than it would be the case with conventional slider 10′. The rail design in accordance with the present invention and the surface form of air bearing surfaces 12 and 14 as shown in the Figs. 1,2 and 3 can be performed by different methods. In accordance with an extremely advantageous, economical, simple and efficient method, the mechanical grinding process for producing this inventive rail design is described in the following part of the description and the respective Figs. of the drawing. The method in accordance with the invention for producing a slider as designed in accordance with the invention uses a mechanical grinding process. In this grinding process a grinding wheel 40 is used. This grinding wheel 40 is shown schematically in a partial cross section view in Fig. 4. Grinding wheel 40 consists of two diamond grinding disks 41 and 42. These two grinding wheels 41 and 42 are distanced from each other by a spacer disk 43 which has a smaller diameter than the grinding disks 41 and 42. All outer surfaces of the grinding disks 41 and 42, that means outer surface 44, inner surface 45, front surface 46, and bevelled surface 47, are cutting surfaces. For forming the air bearing surfaces 12 and 14 with parts 12A and 14A as shown in Fig. 2 the surfaces 45 and 47 are decisive. Surfaces 45 of disk 41 and disk 42 define the trailing width TW between parallel border lines 26 and 28. The bevelled cutting surface 47 of both disks 41 and 42 define the border lines 30 and 32 in a manner that will be described. The angle β between front cutting surface 46 and bevelled surface 47 is in the shown example 45 degrees. It might be a different angle dependent on the desired steepness of the side portion of the rails. An angle β between 35 and 55 degrees has proven to provide the optimum width increase of the rail portions 12A and 14A. Fig. 5 shows schematically the relationship between the grinding wheel 40 and the slider 10 in providing the rail surfaces in accordance with the present invention. Fig. 5A shows in a side view slider 10, Fig. 5B shows a bottom view of slider 10 with the rails and air bearing surfaces 12 and 14 and Fig. 5C shows in a cross section part of grinding wheel 40 and its relationship to grinded portions of slider 10. Grinding wheel 40 is arranged with its turning plane 48 vertically to the air bearing surfaces 12 and 14. During grinding it turns for example in accordance with arrow 52 and is advanced in direction of arrow 51 parallel to the length axis LA of slider 10. The grinding process thus starts at the trailing edge 22 with point A thus creating between border lines 26 and 28 the parallel area of air bearing surfaces 12 and 14. Grinding wheel 40 for example in relation to providing air surface 12 is advanced in direction of arrow 51 with its not shown center point or its deepest point 49 on the front cutting surface 46 at its circumference from point A towards point B. During this movement the sloped surfaces 57 are created by the two bevelled cutting surfaces 47. Surface 56 is provided by front cutting surface 46. By advancing grinding wheel 40 with its lowest point 49 from point A to point B the area between point B and point C toward the leading end 20 of slider 10, the cut away portions of the sides 57 are getting smaller thus forming the trumpet-like form 12A with its bended border lines 30 and 32. Point B is chosen such that at point C the desired widths LW as shown in Fig. 2A is provided. Thus the grinding wheel 40 is not at all completely advanced through the entire body of slider 10. In contrary, it has to be retracted or lifted respectively. As mentioned before the advance motion of grinding wheel 40 along direction of arrow 51 is parallel to the length axis LA of slider 10. To avoid the somewhat cumbersome retracting or lifting motion of grinding wheel when it has reached point B, another embodiment is provided. As shown schematically in Fig. 6 slider 10 is fixed to a carrier 60 and arranged such that its lengths axis LA is slightly titled out of parallelism to advance direction 61 of grinding wheel 40. As shown in Fig. 6 not only one slider 10 is provided on a carrier 60 but a plurality of sliders 10 might be provided on carriers 60 and staggered such that grinding wheel 40 can be continuously advanced in direction of arrow 61 and still providing the trumpet-like air bearing surface form. The tilting angle γ might have a value of about 1 - 2 degrees. The carriers 60 carrying slider 10 are arranged in a tilted manner and clamped together by an appropriately formed clamping and holding device 62 that can be loosened and clamped together in direction of double arrow 64. This holding and clamping device 62 is not shown in detail. It is obvious for a person skilled in the art that the arrangement in Fig. 6 is especially suited for batch fabrication of sliders which have an air bearing surface contour in accordance with the present invention. It is furthermore obvious to a person skilled in the art and therefore not described in more detail that grinding wheel 40 is stepwise advanced sidewise to provide one rail after another. Thus for example in relation with Fig. 2 and Fig. 5 rails 12 and 14 are provided in different grinding wheel advance process steps.

Claims: An air bearing slider (10) for supporting a transducer (24) relative to a moving record medium (31), said slider being provided on its side directly opposite said recording medium with a pair of side rails (12,14) separated by a recessed portion (16), said rails extending from the leading end (20) of said slider to its trailing end (22) which supports said transducer (24), each rail (12, 14) comprising an air bearing surface of increasing width and having its widest dimension (LW) at the leading end (20) of said rail or slider respectively, and said rails having a tapered portion (18) at the leading end of said slider, the slider being characterized in that, said air bearing surfaces are provided with an air bearing surface portion (12A, 14A) of increasing width, increasing in a curved form, e.g. in a circle-like or trumpet-like form, seen from an appropriate point (B) within the length of said rail towards the leading end of said slider or rail respectively, and in that said rails are provided with an air bearing surface portion of equal width (TW) seen from said appropriate point (B) within the length of said rail towards the trailing end (22,A) of said slider or rail respectively. Air bearing slider in accordance with claim 1, characterized in that the air bearing surfaces (12,12A;14,14A) are confined by oblique surfaces (57). Air bearing slider in accordance with claim 2, characterized in that the angle for the oblique surfaces (57) is between 35 and 55 degrees. Method for producing a slider (10) as designed in accordance with claim 1, or claim 2, or claim 3, characterized by a grinding process using a grinding wheel (40) consisting of two grinding disks (41,42) having bevelled cutting surfaces (47) at its outer circumference, said two grinding disks being clamped together with a spacer disk (43) of smaller diameter inbetween such that said bevelled cutting surfaces (47) are opposite to each other, said grinding wheel with its turning plane (48) being arranged vertically to the plane of the air bearing surface (12,14) of said slider, and said grinding wheel being turningly advanced in the direction (51,61) of the length axis (LA) of said slider, removing with said bevelled cutting surfaces (47) side portions of said rails during this turningly advance motion to form oblique surfaces (57), performing this removing such that the leading edge (C) of the rail is left in a desired, e.g. original width (LW), finally separating said grinding wheel from said slider. Method as in claim 4, characterized in that said grinding wheel is advanced in the direction from the trailing (22,A) towards the leading end (20,C) up to said point (B) with its lowest circumferential point (49), upon which that grinding wheel is removed opposite to the advance direction (51) or lifted away from the body of slider (10). Method as in claim 4, characterized in that said slider with its lengths axis (LA) is slightly tilted by a small angle (γ) away from the advance direction (61) of said grinding wheel such that a continuous advance motion of said grinding wheel is provided. Method for producing a slider in accordance with claim 6, characterized in that a plurality of sliders (10) is provided on carriers (60) and clamped together by a clamping and holding device (62) such that each of said carriers and sliders is staggered in relation to the other in such a way, that said grinding wheel is advanced in a continuously advance movement (61) through a plurality of sliders.

Inventors: ASTHEIMER, H., FRIEDMANN, H., SCHUY, H.
Applicants: IBM DEUTSCHLAND GMBH, INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1987
Main classification: G11B5
IPC codes: G11B21, B24B19, G11B5