Patent Publication Number: US-6658714-B2

Title: Compliant clamping mechanism for accurate alignment of a group of miniature parts

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application Ser. No. 60/238,921, filed Oct. 10, 2000 under 35 U.S.C. 119(e). 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of mass storage devices. More particularly, this invention relates to a compliant clamping mechanism for accurate alignment of a group of miniature parts, such as processing of bars of a strip of heads for a disc drive. 
     BACKGROUND OF THE INVENTION 
     One key component of any computer system is a device to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are a disc for storing data. The disc includes a magnetic layer. A transducer is passed over the surface of the disc and is used to either magnetize the magnetic layer of the disc or to detect magnetized portions of the disc. The transducer is typically housed within a small ceramic block known as a slider. The transducer is attached to an actuator. The actuator moves the slider and the transducer within the slider to various locations over the disc where information representing data is written to or retrieved from the disc surface. 
     The process of forming individual sliders starts with forming multiple transducers on a surface of a ceramic wafer using semiconductor fabrication techniques. After forming the transducers on the wafer, the wafer is then sliced or cut to form an elongated bar having a row of transducers (a rowbar). The rowbars are elongated pieces of ceramic that are fragile. The rowbars undergo many manufacturing processes and must be held firmly. The holder for the rowbars must be able to accommodate slight variations in dimension and hold the rowbar firmly throughout these various processing steps. The processing steps include various steps for removing material including lapping to provide a first “rough approximation” removal of material and milling for removing material at a slower, more controlled rate than the lapping process. An air-bearing surface is also formed on the rowbars before being diced into individual sliders. 
     In the past, mechanical clamping fixtures for holding small, fragile parts have been designed to hold single parts. Some clamping fixtures hold multiple small parts but generally these clamps have several problems. One rather large problem associated with clamps for holding multiple parts is that not all the parts are adequately secured due to variations in individual part dimensions. A clamping mechanism for holding small parts has limited space. Due to the limited space, there is little room for fitting a complicated apparatus to securely hold multiple small parts. Furthermore, even if a complicated apparatus can securely hold multiple parts, the more complicated an apparatus is the more difficult the apparatus is to use. Complicated apparatus are also generally more time consuming and costly to produce. 
     As a result, there is a need for a simple clamp that produces an appropriate amount of force to hold multiple small parts. Clamping multiple parts simultaneously is particularly difficult due to variations in individual part dimensions. Thus, there is also a need for a compliant clamping structure that is capable of accommodating size differences in several small or miniature parts and that is self-adjusting so that these parts may be continued to be held as they undergo multiple processing steps. There is also a need for a spring structure that can hold small parts reliably without yielding or plastically deforming. The clamping mechanism must also be capable of enduring the environments associated with the processes that the small or miniature parts undergo during manufacture. Due to their small and varying size, very small or miniature parts are difficult to hold in place for further processing, particularly, when multiple miniature parts need to be held in a limited space. In summary, there is a need for a clamping mechanism that simultaneously secures multiple miniature parts in a limited space that has a reduced cost. 
     SUMMARY OF THE INVENTION 
     A clamping apparatus for holding elements includes a first spring member and a second spring member. The first spring member has a rigid portion that applies the majority of force to the elements. The second spring member is attached to the first spring member. The second spring member is more flexible than the first spring member. The second spring member has a structure that accommodates dimensional variations in elements held by the clamping member. 
     A clamping apparatus for holding elements includes a first spring member. The first spring member includes a rigid portion that applies the majority of force to the elements. The clamping apparatus includes a second spring member. The second spring member is attached to the first spring member. The second spring member is more flexible than the first spring member. The second spring member accommodates dimensional variations in the elements held by the clamping member. The second spring member includes a plurality of flexible structures for holding elements. The first spring element surrounds the second spring member. The first spring element has a notch therein. The first spring element has an opening for handling the spring. The first spring element has at least one slit therein. The dimension of the at least one slit determines the spring force produced by the first spring element. The first spring element may also have a plurality of slits therein. In this case, the plurality of slits determine the spring force produced by the first spring element. 
     The first spring element is rectangular. The second spring element is attached to one side of the rectangle of the first spring element. The second spring element includes a plurality of elongated openings for holding a plurality of elongated elements. The second spring element includes a plurality of elongated bars for contacting a plurality of elements. The second spring element may include a plurality of elongated bars for contacting a plurality of elements. At least one of the elongated bars includes a rounded feature or at least two rounded features for contacting an element. 
     A method for clamping elements includes the steps of holding at least one element with at least one flexible bar, and attaching the flexible bar to a rigid frame. The one flexible bar and a portion of the rigid frame hold the element. The rigid frame produces a majority of the force for holding the at least one element. The flexible bar is dimensioned to accommodate variations in dimensions associated with the one element. One or more slits may be placed in the rigid frame to adjust the amount of force applied to clamp the element. A second flexible bar may be added to hold a second element. The second flexible bar is spaced away from the first flexible bar so as to accommodate the dimension of a second element. The first flexible bar contacts a first element on one side and a second element on the other side. 
    
    
     These and various other features as well as advantages that characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a disc drive with a multiple disc stack and a ramp assembly for loading and unloading transducers to and from the surfaces of the discs. 
     FIG. 2 is a perspective view of an embodiment of a compliant clamping assembly of the present invention. 
     FIG. 3 is a perspective view of the two-stage spring structure of the compliant clamping assembly of FIG.  2 . 
     FIG. 4 is a top view of the two-stage spring structure of the compliant clamping assembly of FIG.  2 . 
     FIG. 5 is a top view of the two-stage spring structure of the compliant clamping assembly holding a plurality of rowbars. 
     FIG. 6 is a top view of an embodiment of a two-state spring structure of the present invention wherein the flexible portion has one flexible arm that holds a single rowbar. 
     FIG. 7 is a top view of another embodiment of a two-state spring structure of the present invention wherein the flexible portion has one flexible arm that holds a single rowbar. 
     FIG. 8 is a top view of another embodiment of a two-state spring structure of the present invention wherein the flexible portion has a plurality of flexible arms that hold a plurality of rowbars. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
     The invention described in this application is useful with all mechanical configurations of disc drives having either rotary or linear actuation. In addition, the invention is also useful in all types of disc drives including hard disc drives, zip drives, floppy disc drives and any other type of drives where unloading the transducer from a surface and parking the transducer may be desirable. 
     FIG. 1 is an exploded view of one type of a disc drive  100  having a rotary actuator. The disc drive  100  includes a housing or base  112 , and a cover  114 . The base  112  and cover  114  form a disc enclosure. Rotatably attached to the base  112  on an actuator shaft  118  is an actuator assembly  120 . The actuator assembly  120  includes a comb-like structure  122  having a plurality of arms  123 . Attached to the separate arms  123  on the comb  122 , are load beams or load springs  124 . Load beams or load springs are also referred to as suspensions. Attached at the end of each load spring  124  is a slider  126  that carries a magnetic transducer  150 . The slider  126  with the transducer  150  form what is many times called the head. It should be noted that many sliders have one transducer  150  and that is what is shown in the figures. It should also be noted that this invention is equally applicable to sliders having more than one transducer, such as what is referred to as an MR or magneto resistive head in which one transducer  150  is generally used for reading and another is generally used for writing. On the end of the actuator arm assembly  120  opposite the load springs  124  and the sliders  126  is a voice coil  128 . 
     Attached within the base  112  is a first magnet  130  and a second magnet  131 . As shown in FIG. 1, the second magnet  131  is associated with the cover  114 . The first and second magnets  130 ,  131  and the voice coil  128  are the key components of a voice coil motor that applies a force to the actuator assembly  120  to rotate it about the actuator shaft  118 . Also mounted to the base  112  is a spindle motor. The spindle motor includes a rotating portion called the spindle hub  133 . In this particular disc drive, the spindle motor is within the hub. In FIG. 1, a number of discs  134  are attached to the spindle hub  133 . In other disc drives a single disc or a different number of discs may be attached to the hub. The invention described herein is equally applicable to disc drives that have a plurality of discs as well as disc drives that have a single disc. The invention described herein is also equally applicable to disc drives with spindle motors that are within the hub  133  or under the hub. 
     As shown in FIG. 2, an embodiment of the present invention includes a compliant clamping mechanism assembly  200 . The clamping assembly  200  has a base  210  and a two-stage spring  300 . The base  210  includes openings  220 ,  222 ,  224 ,  226 . Each opening  220 ,  222 ,  224 ,  226  includes a standoff  230 ,  232 ,  234  and  236  that holds one side of element  680  (see FIG.  6 ). The standoff and element are collectively called the part. The standoffs are alignment features. One standoff  230  engages a notch  315  of the two-stage spring  300  in order to provide the counterforce to the spring as it is pulled out. The other standoffs  232 - 236  are attached to the base, just like the first standoff  230 , and provide a surface to engage an element  680 , such as a rowbar. The base  210  also includes an oblong or circular protrusion  240  that is a peg over which the corresponding opening  340  in the two-stage spring  300  can be placed when stretched. The two-stage spring  300  includes a first stage  310  and a second stage  320 . Throughout the specification the term “first stage” is interchangeable with the terms “first-stage spring”, “first-stage spring element” and “rigid portion.” Also, the term “second stage” is interchangeable with the terms “second-stage spring”, “second-stage spring element” and “flexible portion.”The first stage  310  of the two-stage spring  300  includes a first leg  311 , a second leg  312 , a third leg  313 , and a fourth leg  314 . The first stage  310  is a rectangular frame that is attached along leg  312  to the base  210 . The base  210  includes a protrusion attached to the base  210 . 
     FIG. 3 is a perspective view of the two-stage spring structure  300  of the compliant clamping assembly  200  of FIG.  2 . FIG. 4 is a top view of the two-stage spring structure of the compliant clamping assembly of FIG.  2 . As shown in FIGS. 3 and 4, leg  312  of the first stage includes a notch  315 . The notch accommodates irregularities in the dimensions of the elements to be held by the two-stage spring structure  300 . In addition, before loading the bars the notch  315  is aligned with the base  210 . There is an interface between the standoff surface  236  and the arm  312  that provides an interface between the first stage  310  of the two-stage spring  300  and the base  210  (see FIG.  2 ). The fourth leg  314  of the first stage  310  includes the handling opening  340 . Also included in the fourth leg  314  are a number of slits  331 ,  332 ,  333 ,  334 . The slits are elongated and are dimensioned to produce an exact force on the second-stage spring  320 . The first stage  310  is connected to the second stage  320  by a bar  350  between the fourth leg  314  of the first stage  310  and the second-stage spring element  320 . The second-stage spring element  320  is also substantially rectangular in shape and fits within the inner boundaries of the first spring element  310 . In other words, the second-stage spring element  320  fits inside the legs  311 ,  312 ,  313 ,  314  of the first stage  310  of the two-stage spring element  300 . 
     Still referring to FIGS. 3 and 4, the second stage  320  is also rectangular in shape. The outer dimensions of the rectangle of the second-stage spring  320  produce a narrow gap between the first-stage spring  310  and the second-stage spring  320  on the three of the four sides of the second-stage spring  320 . The rectangular shape of the second-stage spring  320  falls significantly short of the second arm  312  of the first-stage spring  310 . The spacing between the second arm  312  of the first-stage spring  310  and the edge of the second-stage spring element  320  provides for a gap capable of holding an element between the arm  312  of the first stage and the second-stage spring element  320 . The second-stage spring element includes four flexible beams  361 ,  362 ,  363 ,  364 . The flexible beam  361  is along the edge of the second-stage spring  320  that is closest to the second arm  312  of the first-stage spring  310 . Each of the flexible beams  361 ,  362 ,  363 ,  364  are designed so that they are flexible enough to avoid plastic deformation yet rigid enough to deliver sufficient clamping force to each of the elements that are clamped by the two-stage spring assembly  300 . The flexible beams  361 ,  362 ,  363 ,  364  are also flexible enough to accommodate variations in the dimensions of the elements to be held by the two-stage spring assembly  300 . Each flexible beam, such as  361 , includes a first rounded shoulder  366  and a second rounded shoulder  368 . The rounded shoulders  366 ,  368  contact the element to be clamped along its links. The rounded feature provides for accommodating slight differences in dimension since the rounded feature can essentially contact the element to be held along a line or point. The rounded element also floats or moves slightly with respect to the element to be held. The spacing between flexible beams  361  and  362 , and the spacing between flexible beams  362  and  363 , and the spacing between flexible beams  363  and  364  are all approximately equal or substantially equal. Spacing between the flexible arms  361 ,  362 ,  363 , and  364  is very close to one of the dimensions of an element to be held between these flexible beams  361 ,  362 ,  363 ,  364 . In addition, the spacing between flexible beam  361  and the second arm  312  of the first-stage spring  310  is also close to a dimension of the element or elements to be held by the two-stage spring structure  300 . In addition, the second-stage spring  320  includes a slit  370 . The slit  370  provides for flexible arm  364 . 
     FIG. 5 is a top view of the two-stage spring structure  300  of the compliant clamping assembly  200  holding a plurality of row bars  510 ,  511 ,  512 , and  513 . In operation, the first-stage spring  310  provides the total force to be applied to individual elements held by the flexible beams  361 ,  362 ,  363 ,  364 . In other words, the first-stage spring  310  is attached to the base. The base  210  provides a reaction force or reactive force. The first stage spring  310  is elongated slightly via the handling hole  340  and elements are placed between arm  312  of the first-stage  310  spring and flexible arm  361  of the second-stage spring  320  as well as in the openings between the flexible beams  361 ,  362 ,  363 ,  364 . By releasing or moving the first-stage spring  310  to a contracted position, each of the flexible beams  361 ,  362 ,  363 ,  364  engages one side of the element and the second arm  312  of the first-stage spring  310  as well as a flat side of each of the flexible beams  361 ,  362 ,  363  engage the other side of each of the elements. The first stage  310  of the two-stage spring  300  provide the majority of the spring force for holding the various element while the flexible beams  361 ,  362 ,  363 ,  364  are stiff enough to deliver the force to the elements held by the two-stage spring and yet flexible enough to accommodate dimensional variation in each of the elements. 
     The elements  510 ,  511 ,  512 ,  513  held by the two-stage spring need not necessarily be rowbars. The two-stage spring and the openings between the flexible beams  361 ,  362 ,  363 ,  364  and the opening between the first stage and flexible beam  361  can be dimensioned to hold any type of element. It should be noted that in order to work, the elements need to be inserted within the second stage so that the total force produced by the first stage is placed on all four elements  510 ,  511 ,  512 ,  513 . It is also worthy of note that the elements  510 ,  511 ,  512 ,  513  held in the two-stage spring structure  300  are very fragile pieces of ceramic in this particular application. Thus, the two-stage spring structure  300  is capable of holding a fragile element  510 ,  511 ,  512 ,  513  with an adequate amount of force so that various operations may be conducted upon the elements  510 ,  511 ,  512 ,  513 . 
     FIG. 6 is a top view of an embodiment of a two-stage spring structure  600 . The two-stage spring structure includes a first stage  610  and a second stage  620 . The first stage  610  includes a first arm  611 , a second arm  612 , a third arm  613 , and a fourth arm  614 . The second arm  612  includes a notch  615 . The first stage  610  is substantially rectangular in shape and has a rectangular opening  630  therein. The rectangular opening is between the arms or legs  611 ,  612 ,  613 ,  614  of the first stage  610  of the two-stage spring structure  600 . The second-stage spring structure includes a single flexible beam  661 . The second-stage spring structure is essentially a thin metal piece that includes a slit  670  near the flexible beam  661 . The second-stage spring  620  is attached to the first-stage spring structure  610  via arm  650 . 
     The flexible beam  661  includes rounded shoulder portions  666  and  668 . In operation, the spring is elongated after the spring is attached to the base by moving the spring using the handling opening  640 . And element  680  is placed into the opening between the flexible arm  661  and the second leg  612  of the first stage  610 . Moving the pin in the handling opening or releasing the pin produces a spring force by the first-stage spring element  610 . The second leg  612  of the first-stage spring structure holds the element  680  on one edge while the flexible arm  661  and, more specifically, the rounded shoulders  666  and  668  contact the element  680  on the other side. The flexible arm  661  and the rounded shoulders on  666 ,  668  on the flexible beam  661  accommodate slight dimensional variations between different elements  680  when they are held by the two-stage spring structure  600 . Now that 
     FIG. 7 is a top view of an embodiment of a two-stage spring structure  700 . The two-stage spring structure includes a first stage  710  and a second stage  720 . The first stage  710  includes a first arm  711 , a second arm  712 , a third arm  713 , and a fourth arm  714 . The second arm  712  includes a notch  715 . The first stage  710  is substantially rectangular in shape and has a rectangular opening  730  therein. The rectangular opening is between the arms or legs  711 ,  712 ,  713 ,  714  of the first stage  710  of the two-stage spring structure  700 . The second-stage spring structure includes a single flexible beam  761 . The second-stage spring structure is essentially a thin metal piece that includes a slit  770  near the flexible beam  761 . The second-stage spring  720  is attached to the first-stage spring structure  710  via arm  750 . The flexible beam  761  includes rounded shoulder portions  766  and  768 . The two-stage spring structure shown in FIG. 7 differs from the two-stage spring element shown in FIG. 6 in that the second-stage spring structure  720  has a smaller dimension than the second-stage spring structure  620 . 
     Again referring to FIG. 7, in operation, the spring is elongated after the spring is attached to the base by moving the spring using the handling opening  740 . And element  780  is placed into the opening between the flexible arm  761  and the second leg  712  of the first stage  710 . Moving the pin in the handling opening or releasing the pin produces a spring force by the first-stage spring element  710 . The second leg  712  of the first-stage spring structure holds the an element (not shown) on one edge while the flexible arm  761  and, more specifically, the rounded shoulders  766 ,  768 , contact the element  780  on the other side. The flexible arm  761  and the rounded shoulders on  766 ,  768  on the flexible beam  761  accommodate slight dimensional variations between the different elements (not shown) when they are held by the two-stage spring structure  700 . 
     FIG. 8 is a top view of an embodiment of a two-stage spring structure  800 . The two-stage spring structure includes a first stage  810  and a second stage  820 . The first stage  810  includes a first arm  811 , a second arm  812 , a third arm  813 , and a fourth arm  814 . The second arm  812  includes a notch  815 . The first stage  810  is substantially rectangular in shape and has a rectangular opening  830  therein. The rectangular opening is between the arms or legs  811 ,  812 ,  813 ,  814  of the first stage  810  of the two-stage spring structure  800 . The second-stage spring structure includes a first flexible beam  861  and a second flexible beam  862 . The second-stage spring structure  820  is essentially a thin metal piece that includes a slit  870  near the flexible beam  862 . The second-stage spring  820  is attached to the first-stage spring structure  810  via arm  850 . Flexible beams  861 ,  862  includes rounded shoulder portions  866  and  868 . The rounded shoulders on beam  862  have not been numbered for the sake of clarity. In operation, the spring is elongated after the spring is attached to the base by moving the spring using the handling opening  840 . An element (not shown) is placed into the opening between the flexible beam  861  and the second leg  812  of the first stage  810 . Another element (not shown) is placed between the flexible beam  861  and the flexible beam  862 . Moving the pin in the handling opening releases the pin to produce a spring force by the first-stage spring element  810 . The second leg  812  of the first-stage spring structure holds one element on one edge while the flexible arm  861  and, more specifically, the rounded shoulders  866 ,  868 , contact the element on the other side. The flexible arm  861  and the rounded shoulders on  866 ,  868  on the flexible beam  861  accommodate slight dimensional variations between different elements  880  when they are held by the two-stage spring structure  800 . The spring force produced by the first stage portion  810  also holds another element between the flexible beam  861  and the flexible beam  862 . The two-stage spring structure shown in FIG. 8 differs from other spring structures because it holds a different number of elements. It should be noted that the number of elements held is not determinative of the invention. A two-stage spring capable of holding any number of elements is within the scope of this invention. 
     Conclusion 
     A clamping apparatus for holding elements includes a first spring member. The first spring member includes a rigid portion that applies the majority of force to the elements. The clamping apparatus includes a second spring member. The second spring member is attached to the first spring member. The second spring member is more flexible than the first spring member. The second spring member accommodates dimensional variations in the elements held by the clamping member. The second spring member includes a plurality of flexible structures for holding elements. The first spring element surrounds the second spring member. The first spring element has a notch therein. The first spring element has an opening for handling the spring. The first spring element has at least one slit therein. The dimension of the at least one slit determines the spring force produced by the first spring element. The first spring element may also have a plurality of slits therein. In this case, the plurality of slits determine the spring force produced by the first spring element. The first spring element is rectangular. The second spring element is attached to one side of the rectangle of the first spring element. The second spring element includes a plurality of elongated openings for holding a plurality of elongated elements. The second spring element includes a plurality of elongated bars for contacting a plurality of elements. The second spring element may include a plurality of elongated bars for contacting a plurality of elements. At least one of the elongated bars includes a rounded feature or at least two rounded features for contacting an element. 
     A method for clamping elements includes the steps of holding at least one element with at least one flexible bar, and attaching the flexible bar to a rigid frame. The one flexible bar and a portion of the rigid frame hold the element. The rigid frame produces a majority of the force for holding the at least one element. The flexible bar is dimensioned to accommodate variations in dimensions associated with the one element. One or more slits may be placed in the rigid frame to adjust the amount of force applied to clamp the element. A second flexible bar may be added to hold a second element. The second flexible bar is spaced away from the first flexible bar so as to accommodate the dimension of a second element. The first flexible bar contacts a first element on one side and a second element on the other side. 
     A clamping apparatus includes a flexible portion for holding an element and accommodating differences in dimension of the element, and a rigid device attached to the flexible portion. The rigid device produces a force to hold the element. The flexible element is an elongated bar spaced from the rigid device. The rigid device is a rectangular frame having a first opening therein. The first opening is dimensioned to surround the flexible member. The rigid device also includes a connecting portion for connecting the flexible member to the rigid frame, and a second opening formed by spacing the flexible member from the rigid frame. The flexible member includes a third opening on the other side of the flexible member. The rigid device includes at least one slit therein, the dimensions of the slit being varied to vary the amount of force applied by the rigid means. In the alternative, the rigid member may have multiple slits therein. 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.