US 4,426,669 AGrant
Transducer Positioner in Disk Files
Issue Date:1984-01-17
•17 Claims
•3 Drawing Sheets
Abstract
The transducer or transducers are mounted to the bottom of a U-frame carrying a coil between the legs; the coil is slipped onto and runs over a bar, facing two permanent magnets. One leg of the U-frame is suspended on leaf springs, being connected also to a base, so that the frame moves strictly linearly without lateral displacement. A similar spring mount may be connected to the other leg of the U-frame. The springs may have a U-configuration or an E-configuration.
Metadata
Inventor
- Philip Bryer
Application Information
Application Number:US 2274167
Filing Date:1981-01-22
Priority Date:1981-01-22
Art Unit:235
Classifications
IPC:
G11B 555
Field of Search:
360310106;103;97;98;104;10516
Patent Drawings (3 sheets)
Description
Background of the Invention
The present invention relates to actuators and positioners for transducers in disk files.
Disk files are well established fast-access-memory units in the computer art. These disk files include large or small disks of a hard or flexible configuration. Magnetic transducers are to be positioned in relation to the disk's surface for interaction therewith. This positioning requires generally a radial displacement, movement, and positioning in relation to the spinning disk. Transducer actuators and positioners are constructed in several varieties. An earlier version includes a stepping motor. A later development has concentrated upon voice coil motors; a new development includes a split band in conjunction with a stepping motor. All of these types of positioners have performed well in the art and are well established accordingly. They are, however, more or less expensive and/or heavy, requiring significant power, and have limitations with respect to speed versus accuracy of positioning.
Description of the Invention
It is an object of the present invention to provide a new and improved actuator and positioner for transducers in magnetic disk file systems.
It is a feature of the present invention to provide a magnetic structure which includes a core and a coil, riding on parts of the core and being coupled to a U-framed member which is linearly guided in direction of the coil displacement under prevention of lateral displacement, the coil extending between the legs of the U-frame; the transducers are mounted to extensions from the cross-member of that frame.
In accordance with the preferred embodiment of the invention, a core structure is to be comprised of a flat, magnetizable bar whose flat sides face two magnets, preferably permanent magnets across two gaps; the magnetic circuit is closed in a manner which shields the transducers from stray flux from the gaps, the transducers being mounted upon the U-framed member whose legs carry the coil. A pair of flat springs, each having two legs, is used to mount the U-frame to the base in that one leg of each spring is anchored to one leg of the U-frame respectively at spaced apart points, while the other leg of each spring is connected to the base. The junctural ends of the spring legs are interconnected by a hollow frame. The anchor points are aligned in the direction of movement of the U-frame, and they are respectively aligned in perpendicular directions with the base-connect points of the respective other spring leg.
The actuator in accordance with the invention is quite economical, and its construction ensures precise, linear, electrically actuated movement of the transducers with no lateral displacement. The U-frame leg to which the springs are connected is made stiff, but the other leg may be flexible if thermal compensation of the coil is needed. If not, a second, similar spring arrangement may be connected to this other U-frame leg. Torsional stiffness may be enhanced by using E-shaped springs, each one with a wider center leg being connected, e.g., to the base, while the respective outer legs are connected to the one U-frame leg, or vice versa.
Description of the Drawings
FIG. 1 is a perspective view of an actuator in accordance with the preferred embodiment of the invention;
FIG. 2 is a top view of the actuator shown in FIG. 1
FIGS. 3, 4, and 5 are, respectively, section views taken along lines 3--3, 4--4, and 5--5 of FIG. 2;
FIG. 6 is a view similar to FIG. 1, but showing a supplemental feature;
FIG. 7 is a view similar to FIG. 1, but showing a modification; and
FIG. 8 is a section view of a feature applicable to all figures for a four-transducer positioner.
Proceeding now to the detailed description of the drawings, FIGS. 1 through 5 illustrate a positioner for a transducer 1, cooperating with a spinning disk 2. The mounting structure for such a transducer head is shown here in a simplified fashion. In reality, more than one transducer has to be mounted to such an actuator, which is shown in FIG. 8.
The positioner includes a mounting base 10, serving as a stationary reference. A magnetic structure is mounted on that base, and it includes a flat, magnetizable bar 11 sandwiched in between mounting pieces 12, 12b, 12c, and 12d. The pieces 12a and 12b are mounted to base 10, while pieces 12c and 12d carry a top 13. Parts 12 and 13 as well as base 10 are made of magnetically conductive material; so is bar 11.
A pair of permanent magnets 14 and 15 is provided; they are respectively mounted on base 10 and cover 13 and are in intimate, magnetically conductive contact therewith. It is convenient and practical to employ permanent magnets in order to obtain stator energization; however, one could also use electromagnetic energization. The magnetic axes of these magnets run transverse to their flat sides so that their faces, facing bar 11 across gaps 16 and 17, are magnetic pole faces. The poles are of opposite orientation so that the bar 11 is traversed by a uniform magnetic field.
The device of carriage being positioned is basically a U-shaped frame 20, having legs 21 and 22 and a transverse bottom structure or element 23. The transducer 1 is shown to be mounted to that bottom structure, particularly to a lateral extension 24 thereof. The bottom traverse 23 and the extension 24 together exhibit a T-shaped cross section so that the bottom of this U-shaped frame is quite stiff.
Leg 21 is provided with a stiffening ridge 26, but leg 22 has some flexibility. A coil 25 is mounted between the ends of legs 21 and 22. This coil traverses the gaps 16 and 17 respectively between magnets 14 and 15 and bar 11. The U-shaped frame with the coil is, thus, a carriage provided for movement in directions of double arrows 29. This movement is obtained by electrically energizing the coil.
The bar is covered with a thin, axially limited copper coating, serving as a short-circuited, single winding transformer secondary for reducing the effective inductance of the coil 25. The signal-arise time is reduced by this feature. Additional, rather elastic mounting pieces 18a, 18b, 18c, and 18d serve as spacers between the magnets and elements 12. These spacers limit the travel of the coil should it be driven hard, such as in a failure condition. The elastic spacer stops prevent the coil from coming to an abrupt stop since that may cause the transducer to crash onto the spinning disk, thereby damaging either or both.
Unlike voice coil motor constructions, this core-and-stator construction exhibits a particularly important feature. The two elements 12b and 12c, together with one end of flat bar 11, shield the transducers and the magnetic disk 2 from any magnetic field emanating from the coil 25 and from the permanent magnets. Stray flux toward the transducers and the disks is not permitted because these elements 12b, 12c, and 11 short-circuit such flux as well-defined return path for any magnetic field. Any stray flux laterally escaping from the magnets does not affect the transducers and the disk.
The U-shaped frame with coil as a whole is mounted as follows. A mounting structure 30 includes a pair of leaf-springs 31 and 32, having legs 31a, 31b, and 32a, 32b, and, respectively, juncture portions 31c and 32c. The respective free ends of legs 31b and 32b are fastened to lugs 27a, 27b of U-frame leg 21. The respective free ends of spring legs 31a and 32a are secured to the base. The anchoring points for spring legs 31a and 31b are aligned in a direction perpendicular to the extensions of the legs and running in parallel to the direction of deflection of the coil and of the U-shaped frame, which is parallel to arrow 29. The anchoring points for spring legs 32a and 32b are analogously aligned, as specifically shown in FIG. 5. Moreover, the anchoring points for the spring legs 31a and 32a on U-shaped frame leg 21 are precisely aligned in a direction parallel to arrow 29; so are the anchoring points of spring legs 31a and 32b on base 10.
The juncture portions 31c and 32c of the two springs are secured to a hollow rectangular frame 33. As a consequence, the anchoring points of spring arms 31a and 32a on leg 21 move in a single direction, precisely parallel to arrow 29, whithout lateral displacement. In other words, the U-shaped frame 20 is guided for movement in a perfectly linear direction. The particular mounting prevents any lateral displacement, though frame 33 will undergo a slight displacement as per double-arrow 34. There is no such lateral displacement of frame 20 relative to base 10 and to the core structure of this drive. Also, the springs are stiff in the vertical direction being transverse to arrows 34 and 29 so that the device is stable in that direction.
The ridge 26 avoids skewing of the spring anchoring points, one about the other, in direction of arrow 34 and , in particular, prevents any flexing of leg 21 of the U-shaped frame 20. The ridge and transducer-carrying platform 24 stabilizes the bottom traverse 23, thereby preventing its flexing in a direction parallel to arrow 29 and about any corner point of the "U." Thus, the transducers (and that is ultimately the decisive goal) move on a linear path and in increments that are the precise duplicates of the path of movement and of increments of movement of coil 25, there being practically no lateral parasitic movement as between the coil and the transducers.
For reasons of weight, U-shaped frame 20 is made of plastic; so is rectangular frame 33. This means that the two springs 31 and 32 are electrically isolated from each other provided that at least a portion of the base 10 is also made of insulating material. This fact can be used conveniently for facilitating the current feed to the movable coil. One end of the coil 25 is electrically connected to the free end of leg 32a, the other end to leg 31a. Accordingly, feed wires 36a and 36b of different electrical potential are connected to legs 31b and 32b to, thereby, feed current from a stationary source to the movable coil.
An actuator of the type and construction shown in FIG. 1 was tested in conjunction with a noise generator. The noise signals were applied to the coil 25 as well as to an input of a spectrum analyzer. An accelerometer was placed onto the carriage and U-shaped frame. It appeared that the amplitude transfer function, specifically as between the amplitude of the signal applied to coil 25 and the resulting measured acceleration is practically independent from frequency in the range of from 0 Hz to a few kilohertz. Also, the phase between the signal applied and the acceleration measured was constant.
The device as described will, of course, exhibit certain very high-order deviations from the ideal conditions of strict linearity of movements, simply on account of the flexibility of the springs. However, these deviations can be expected to be minute. For example, the assembly 31-32-33 is subject to some flexing (torsion), commensurate with a rotation about an axis running vertical through frame 33, parallel to the direction of extension of the spring Also, the flexibility of arm 22 introduces a higher-order, parasitic displacement, corresponding to a rotation of the "U" of frame 20 about an axis transverse to the plane of the U. These two high-order effects are eliminated by structures shown in FIGS. 6 and 7.
The device of FIG. 6 is a supplemented structure of FIGS. 1 to 5, in that the U-frame arm 22' is not stiff but rigid (ridge 26'), and a second spring mount 31'-32'-33' is attached to that arm. The resulting symmetry, thus, ensures the desired parallel motion. This particular device is disadvantaged by the fact that any thermal coil expansion or contraction is not compensated for. This, however, may not be a disadvantage if, in fact, the temperature variations are minute.
FIG. 7 illustrates an assembly in which the two-leg springs of the suspension are replaced by two three-leg springs 41 and 42. The center legs 41a and 42a each are twice as wide as the respective two outer legs 41b, 41d, and 42b, 42d. This relation between the width dimensions is necessary in order to obtain equal conditions for flexing; the frame 43 must be displaced by exactly half the distance of the displacement of the U-shaped frame 20 relative to a disposition in which all of the springs are perfectly flat and coplanar.
The assembly as per FIG. 7 shows the free ends of all outer legs to be attached to the stationary structure. This structure includes base 10 as well as an L-shaped mounting structure 45 extending upward from base 10 and across the space above the attachment of spring legs 41a, 42b to the U-frame leg 21. This way, no rotational displacement of the assembly 41-42-43 is possible. A torque is provided as a result of opposite deflections by legs 41a and 41b as well as by legs 42a and 42 b. This torque is particularly set up about an axis running parallel to the spring arms; that torque is offset by a torque resulting from the symmetrical arrangement of oppositely deflected legs 41a and 41d as well as legs 42a and 42d.
It should be noted that anchoring the middle one of each spring leg to the U-shaped frame leg is convenient from a construction point of view; but that is not essential. The middle one could be connected to the base, and the outer ones are connected to the U-shaped frame.
It will be appreciated that, commensurate with the symmetrical duplication feature as shown in FIG. 6, the spring assembly as per FIG. 7 can likewise be duplicated to be effective on both of the U-shaped frame arms. In other words, the two constructions as per FIGS. 6 and 7 can be combined by duplicating the structure 41, 42, and 43 at the other arm of the U-shaped frame.
The transducers and their mount have been shown in a somewhat simplified fashion in order to concentrate on the mounting structure of the transducer carriage and positioner proper. FIG. 8 illustrates the preferred structure in which, in fact, four transducers 1a, 1b, 1c, and 1d are positioned with respect to two disks 4 and 5. The bottom 23' of the U-shaped frame has, in transverse view, itself a U-shaped configuration on account of two mounting platforms 28 (replacing the single platform 24) for transducers 1a and 1c. Posts 52 and 53 carry additional holding platforms 54 and 55 for the transducers 1b and 1d.
The invention is not limited to the embodiments described above; but all changes and modifications thereof, not constituting departures from the spirit and scope of the invention, are intended to be included.
Claims
I claim:
1. A linear actuator for positioning at least one transducer in one of a plurality of positions and for moving the transducer from one of the positions to another one thereof, comprising: mounting base means; a flat, bar-shaped, magnetizable core; magnet means for inducing a homogeneous, magnetic field across the bar, there being gaps between the magnet means and opposite, flat sides of the bar, the magnet further including magnetic return path means coupled to the flat bar at opposite ends; a coil looping around the flat bar and extending through the gaps for being movably disposed; frame means of U-shaped configuration, having legs and a transverse base, the coil being fixedly mounted on and between the legs, the transducer being mounted on the base of the frame means; a pair of flat spring means, each of the flat spring means of the pair having a first leg and a second leg, and an integral juncture at one end of each one of the respective first and second leg, each leg of the spring means having a free end, the free ends of the first legs of the spring means of the pair being secured to one of the legs of the U-shaped frame means, one first leg of one of the spring means being secured in a first point of the frame means near said base of the frame means, the first leg of the other spring means being secured to a second point on the one leg of the U-shaped frame and means spaced from the first point; a rectangular frame for interconnecting the junctures of the two spring means; and the second legs of the pair of flat spring means having their respective free ends secured to the mounting base means at points in respective alignment with said points in said one leg of the U-shaped frame means.
2. An actuator as in claim 1, the one leg of the U-shaped frame means to which said first leg of of the other spring means is secured, being provided with a stiffening ridge.
3. An actuator as in claim 1, said rectangular frame being hollow.
4. An actuator as in claim 1, said junctures being spaced by the rectangular frame by a spacing equal to the spacing between said points on the one of the U-shaped frame means.
5. An actuator as in claim 2, said other leg of the U-shaped frame means being relatively flexible.
6. An actuator as in claim 1, including a further pair of flat spring means configured as said first-mentioned spring means, there being also a further rectangular frame connected to said further pair as said first-mentioned rectangular frame is to said first-mentioned spring means, one free end of each of the further pair being connected to the other leg of the U-shaped frame, other free ends of the further pair being connected to the base.
7. An actuator as in claim 1, each of said spring means having a third leg, the respective free end of the third leg being connected to one of the mounting base means and of the U-shaped frame means, those of the legs of each of the spring means flexing similarly upon displacement of the coil, being half as wide as the remaining one.
8. An actuator as in claim 1, the magnet means including two permanent magnets, facing said flat bar across said gaps.
9. An actuator as in claim 1 or 8, including nonmagnetic stop means in said gaps for limiting the coil displacement.
10. An actuator as in claim 1, said spring means as mounted being electrically insulated from each other, the coil being electrically connected to the first legs, the second legs provided for current feed in.
11. A linear actuator, comprising: a core structure on a base; a coil magnetically cooperating with the core structure to be linearly displaced; frame means of U-shaped configuration, having legs and a transverse base, the coil being mounted on and between the legs, the transducer being mounted on the base; a pair of flat spring means, each of the flat spring means having a first leg and a second leg and an integral juncture at one end of each one of the respective first and second legs, each leg of the spring means having a free end, the free ends of the first legs of the spring means of the pair being secured to one of the legs of the U-shaped frame means, one first leg of one of the spring means being secured in a point near said base, the first leg of the other spring means being secured to a point on the one leg of the U-shaped frame means spaced therefrom; a rectangular frame for interconnecting the junctures of the two spring means; and the second legs having their free ends secured to the base means at points in respective alignment with said points in said one U-shaped frame means leg.
12. A positioner and actuator for at least one transducer, comprising: a mounting base; a U-shaped frame having a bottom traverse and two legs, the transducer being mounted to said bottom; a coil mounted on the two legs; core means magnetically cooperating with the coil for displacing the coil along a particular path; and spring means including two U-shaped leaf springs, having their bottoms interconnected by a laterally displaced element, one leg of each U-shaped leaf spring being connected to one leg of the frame, the respective other leg of each leaf spring being connected respectively to the mounting base of the frame so that, upon displacement of the U-shaped frame, the element is displaced by half of that displacement.
13. A positioner and actuator for at least one transducer, comprising: a mounting base; a U-shaped frame having a bottom traverse and two legs, the transducer being mounted to said bottom; a coil mounted on the two legs; core means magnetically cooperating with the coil for displacing the coil along a particular path; and spring means including two E-shaped leaf springs, each one having two outer legs connected to the mounting base and one leg of the U-shaped frames, a third, middle one of the legs of each spring being connected to the other one of the mounting base and the said one leg of the U-shaped frame, each middle leg of the two "E's" being twice as wide as the respective outer legs, common elements of each spring being interconnected by said laterally displaced element.
14. A positioner as in claim 12 or 13, the element being a hollow rectangular frame.
15. A linear actuator for positioning at least one transducer in one of a plurality of positions and for moving the transducer from one of the positions to another one thereof, comprising: mounting base means; a flat, bar-shaped, magnetizable core; magnet means for inducing a homogeneous, magnetic field across the bar, there being gaps between the magnet means and opposite, flat sides of the bar, the magnet means further including magnetic return path means coupled to the flat bar at opposite ends; a coil looping around the flat bar and extending through the gaps for being movably disposed; U-shaped frame means having legs, said coil being mounted to said legs, and having a bottom traverse, said transducers being mounted to said traverse, said magnetic return path means configured to magnetically shield said transducers from said gaps; a pair of flat spring means, each of the flat spring means having a first leg and a second leg, and an integral juncture at one end of each of the respective first and second leg, each leg of the spring means having a free end, the free ends of the first legs of the spring means of the pair being secured to one of the legs if the U-shaped frame means, one first leg of one of the spring means being secured to the frame means in a first point near said base of the frame means, the first leg of the other spring means being secured to a second point on the one leg of the U-shaped frame means and from the spaced second point; a rectangular frame for interconnecting the junctures of the two spring means; and the second legs of the pair of flat spring means having their free ends secured to the mounting base means at points in respective alignment with said first and second points in said one leg of the U-shaped frame means.
16. A linear actuator for positioning at least one transducer in relation to a spring magnetic disk, comprising: a core structure on a mounting base means; a coil magnetically cooperating with the core structure to be linearly displaced; frame means of U-shaped configuration, having legs and a traverse base, the coil being fixedly mounted on and between the legs, the transducer being mounted on the transverse base of the frame means; a pair of flat spring means, each of the flat spring means having a first leg and a second leg, and an integral juncture at one end of each of the respective first and second leg, each leg of the spring means having a free end, the free ends of the first legs of the spring means of the pair being secured to one of the legs of the U-shaped frame means, one first leg of one of the spring means being secured in a first point of the frame means near said base of the frame means, the first leg of the other spring means being secured to a second point on the one leg of the U-shaped frame means spaced therefrom; a rectangular frame for interconnecting the junctures of the two spring means; and the second legs having their free ends secured to the mounting base means at points in respective alignment with said points in said one leg of the U-shaped frame means.
17. A linear actuator as in claim 11 or 16, said core structure comprising: a flat, bar-shaped, magnetizable core; and magnet means for inducing a homogenic, magnetic field across the bar, there being gaps between the magnet means and opposite, flat sides of the bar, the magnet means further including magnetic return path means coupled to the flat bar at opposite ends.
Patent Citations (2)
| Patent | Date | Inventor | Cited By |
|---|---|---|---|
| US3056962 | 1962-10-01 | Johnson et al. | |
| US4305105 | 1981-12-01 | Ho et al. |
Non-Patent Literature (1)
- N. K. Frater, "Balanced Force Voice Coil Actuator", IBM Technical Disclosure Bulletin, vol. 15, No. 3, Aug. 1972.