Abstract:
A head drum assembly and method of a magnetic recording/reproducing apparatus are disclosed. In the assembly, for application of a pre-load on the upper and the lower bearings, the upper and the lower bearings are installed in a loosely fitting manner on the shaft. An elastic member for applying a load on an inner ring of either of the upper and the lower bearings is provided so that simplification of the manufacturing process of the head drum assembly, cost reduction, and productivity improvement are achieved.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit under 35 U.S.C. § 119(a) from Korean Patent Application No. 2004-48818, filed on Jun. 28, 2004, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a magnetic recording/reproducing apparatus. More particularly, the present invention relates to a head drum assembly rotatably mounted on a main deck, for recording and reproducing information on and from a tape and a magnetic recording/reproducing apparatus having the same, and a method for assembling the head drum assembly.  
         [0004]     2. Description of the Related Art  
         [0005]     Generally, a bearing is installed between a rotary body and a shaft to support the rotary body so that the rotary body may rotate around the shaft. However, due to the tolerance of the bearing, the accuracy of the rotation of the rotary body deteriorates. Thus, a head drum assembly of the magnetic recording/reproducing apparatus requiring high speed and accuracy in rotation compensates for inaccuracies in rotation due to the tolerance of a bearing by applying a predetermined pre-load on the bearing.  
         [0006]      FIG. 1  is a cross-sectional view schematically showing a conventional head drum assembly.  
         [0007]     Referring to  FIG. 1 , the head drum assembly of the magnetic recording/reproducing apparatus includes a rotational drum  40  for supporting a magnetic head  44  for recording and reproducing information by scanning a moving magnetic tape; a fixing drum  48  forcedly fit, in parallel with the rotational drum  40 , into the lower side of a shaft  10  joined to a middle axial cavity  42  formed in the rotational drum  40 ; an upper bearing  20  and a lower bearing  30  structured and arranged such that they are located one above the other between the rotational drum  40  and the shaft  10 ; and a coil spring  50  interposed between the upper bearing  20  and the lower bearing  30  applying a pre-load on the upper bearing  20  and the lower bearing  30  and installed on an outer periphery of the shaft  10 , for applying a load on a respective inner ring  22  and  32  in opposite direction.  
         [0008]     Here, an outer ring  24  of the upper bearing  20  is forcedly fit in the middle axial cavity  42 , and the inner ring  22  of the upper bearing  20  is forcedly fit in the shaft  10 . An outer ring  34  of the lower bearing  30  is forcedly fit in the middle axial cavity  42 , and the inner ring  32  of the lower bearing  30  is inserted into the shaft  10  in a loosely fitting manner. The coil spring  50  applies a load, in opposing directions, on the inner ring  22  of the upper bearing  20  and the inner ring  32  of the lower bearing  30 . Since the inner ring  22  of the upper bearing  20  is forcedly fit in the shaft  10 , force applied on the inner ring  22  of the upper bearing  20  by the coil spring  50  is transferred to the shaft and expended. However, since the inner ring  32  of the lower bearing  30  is loosely fit in the shaft  10 , force transferred to the inner ring  32  of the lower bearing  30  by the coil spring  50  causes displacement of the inner ring  32  of the lower bearing  30  to the lower part of the rotational drum  40 . Accordingly, the force transferred to the inner ring  32  of the lower bearing  30 , as shown in  FIG. 1 , acts on a lower bearing ball  36  to apply a pre-load thereon. Also, the force transferred to the lower bearing ball  36  acts on a lower part of the rotational drum  40  by way of the inner ring  32  of the lower bearing  30  and such force is transferred to the outer ring  24  of the upper bearing  20  forcedly fit in the middle axial cavity  42  of the rotational drum  40  to cause displacement of the outer ring  24  of the upper bearing  20  to a lower position. By such displacement, the force transferred to the outer ring  24  of the upper bearing  20  acts on an upper bearing ball  26  in a direction shown in  FIG. 1  to apply a pre-load thereon.  
         [0009]     If the upper and the lower bearings  20  and  30  are all forcedly fit in the shaft  10 , force of the coil spring  50  is transferred to the shaft  10  and expended. Therefore, a pre-load is not applied on the upper and the lower bearing balls  26  and  36 . Also, if both the upper and the lower bearings  20  and  30  are fit in the shaft  10  in a loosely fitting manner, the inner ring  22  and  32  of the upper and the lower bearings  20  and  30  make a relative motion with respect to each other and a problem that the rotational drum  40  moves up and down, is generated. For such a reason, the inner ring  22  of the upper bearing  20  is forcedly fit in the shaft  10  and the inner ring  32  of the lower bearing  30  should be loosely fit in the shaft  10 .  
         [0010]     However, to form such a pre-load structure in view of the dimensional problem of the inner ring where the inner ring  22  of the upper bearing  20  should be forcedly fit in the shaft  10  and the inner ring  32  of the lower bearing  30  should be loosely fit in the shaft  10 , an inner diameter of the inner ring  22  of the upper bearing  20  is not the same as an inner diameter of the inner ring  32  of the lower bearing  30  and two types of bearings should be used. Since two types of bearings should be used, the assembly process becomes complicated, and the manufacturing costs of the bearings also increases.  
         [0011]     An assembly order of the head drum assembly will be briefly described. The upper bearing  20  is forcedly fit in the shaft  10 . Next, the upper bearing  20  forcedly fit in the shaft  10  is forcedly fit in the rotational drum  40 . Subsequently, the coil spring  50  fits over the shaft  10  from its lower part to its upper part so that the coil spring  50  is positioned on the inner ring  22  of the upper bearing  20 . Next, the lower bearing  30  is fit in the shaft  10  and forcedly fit in the rotational drum  40 . Lastly, the shaft  10  inserted into the rotational drum  40  is forcedly fit in a drum cover  46  and the fixing drum  48 . Since the foregoing process includes lots of forcedly fitting steps, manufacturing efficiency of the head drum assembly is reduced.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention has been developed in order to solve the above drawbacks and other problems associated with the conventional art. Therefore, an aspect of the present invention is to provide a head drum assembly capable of improving a pre-load structure, and a magnetic recording/reproducing apparatus having the same.  
         [0013]     Another aspect of the present invention is to provide an improved method for assembling a head drum assembly, capable of simplifying an assembly process.  
         [0014]     To achieve the above aspects, there is provided a head drum assembly of a magnetic recording/reproducing apparatus, which includes a rotational drum rotatably disposed on a shaft; an upper bearing and a lower bearing installed between the rotational drum and the shaft; and a fixing drum and a drum cover, respectively fixed in the shaft, the head drum assembly of the magnetic recording/reproducing apparatus is configured in such a way, in which to apply a pre-load on the upper and the lower bearings, the upper and the lower bearings are installed, in a loosely fitting manner, in the shaft, and an elastic member for applying a load on an inner ring of either of the upper and the lower bearings is provided.  
         [0015]     The upper bearing may have the same inner diameter as the lower bearing.  
         [0016]     A projection may be formed on the fixing drum, for supporting the inner ring of the lower bearing, and the elastic member applies a load on the inner ring of the upper bearing.  
         [0017]     The elastic member may be a coil spring.  
         [0018]     In another aspect of the present invention, there is provided a magnetic recording/reproducing apparatus, which includes a deck on which a variety of parts for recording and reproducing data on and from the magnetic tape is installed; and a head drum assembly having: a rotational drum mounted on the deck and rotatably disposed on a shaft, for recording and reproducing information on and from the magnetic tape; an upper bearing and a lower bearing installed between the rotational drum and the shaft; and a fixing drum and a drum cover fixed in the shaft; wherein for application of a pre-load on the upper and the lower bearings, the upper and the lower bearings are installed, in a loosely fitting manner, on the shaft, and an elastic member for applying a load on an inner ring of either of the upper and the lower bearings is provided.  
         [0019]     The upper bearing may have the same inner diameter as the lower bearing.  
         [0020]     On the fixing drum, a projection may be formed for supporting the inner ring of the lower bearing, and the elastic member applies a load on the inner ring of the upper bearing.  
         [0021]     To achieve the above aspects of the present invention, there is provided a method for assembling a head drum assembly of a magnetic recording/reproducing apparatus rotatably installed on a deck, for recording and reproducing data on and from a magnetic tape. The method includes the steps of making a first assembly by forcedly fitting a shaft in a fixing drum; making a second assembly by forcedly fitting a plurality of bearings in a rotational drum; and combining the first assembly and the second assembly by loosely fitting a plurality of bearings in the shaft; and installing an elastic member on the shaft so that a load is applied on an inner ring of either of a plurality of bearings.  
         [0022]     The step of installing the elastic member may include the steps of mounting the elastic member on the shaft so that one side of the inner ring of either of a plurality of bearings is touched by one side of the elastic member; and forcedly fitting the drum cover in the shaft so that a load is applied on the other side of the elastic member.  
         [0023]     Also, a plurality of bearings includes an upper bearing and a lower bearing, the fixing drum has a projection in its upper part, and, preferably, the step of combining the first assembly and the second assembly includes the steps of loosely fitting the shaft in the lower bearing; loosely fitting the shaft in the upper bearing; and closely fitting the second assembly in the shaft so that the inner ring of the lower bearing is supported by the projection. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0024]     The above aspects and features of the present invention will be more apparent by describing certain embodiments of the present invention with reference to the accompanying drawing figures, in which:  
         [0025]      FIG. 1  is a cross-sectional view of a conventional head drum assembly;  
         [0026]      FIG. 2  is a perspective view schematically showing a magnetic recording/reproducing apparatus according to an embodiment of the present invention;  
         [0027]      FIG. 3  is a cross-sectional view taken along line III-III of  FIG. 2 ;  
         [0028]      FIG. 4  is a conceptual view illustrating a pre-load principle of upper and lower bearings shown in  FIG. 3 ; and  
         [0029]      FIGS. 5A through 5E  are cross-sectional views illustrating a process for assembling a head drum assembly according to an embodiment of the present invention. 
     
    
       [0030]     In the drawing figures, it should be understood that like reference numerals refer to like structure and features.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]     Construction and operation of embodiments of the present invention will be described in greater detail with reference to the accompanying drawings.  
         [0032]     In the following description, the same reference numerals are used for the same elements throughout the drawings. The matters defined in the description such as a detailed construction and elements are exemplary. Thus, it should be apparent that the present invention can be performed without the examples. Also, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.  
         [0033]      FIG. 2  is a perspective view schematically illustrating a magnetic recording/reproducing apparatus according to an embodiment of the present invention.  
         [0034]     Referring to  FIG. 2 , the magnetic recording/reproducing apparatus according to an embodiment of the present invention includes a deck  100  on which a magnetic tape is mounted and where a variety of parts for recording and reproducing data on and from the magnetic tape is installed, and having a sub-deck  120  and a main deck  110 ; and a head drum assembly  200  installed on the deck  100 , for recoding and reproducing information on and from the magnetic tape. The head drum assembly  200  is installed at a predetermined inclination on the main deck  110  and has a rotational drum  210  rotating at a high speed, for recording and reproducing information on and from the magnetic tape. Such a rotational drum  210  applies a predetermined pre-load, due to its high rotational speed, on a bearing where the rotational drum  210  is rotatably supported by a shaft  240 . Such a pre-load structure and the head drum assembly  200  will be described in detail in the following.  
         [0035]      FIG. 3  is a cross-sectional view showing the head drum assembly  200  according to the embodiment of the present invention.  
         [0036]     Referring to  FIG. 3 , the head drum assembly  200  according to the embodiment of the present invention includes a rotational drum  210  whose central axis is arranged in parallel with a shaft  240 ; upper and lower bearings  220  and  230  arranged up and down between the rotational drum  210  and the shaft  240 ; a drum cover  250  and a fixing drum  260  arranged up and down of the rotational drum  210  and fixed to both ends of the shaft  240 , respectively; and an elastic member  270  installed in such a way that its one end is touched, in a pressing manner, by an inner ring  222  of the upper bearing  220  and its other end is supported by the drum cover  250 .  
         [0037]     The rotational drum  210  is joined to the shaft  240  with the rotational drum  210  being interposed between the upper and the lower bearings  220  and  230 , so that it can rotate around the shaft  240 . Such rotation is performed by interaction between a motor stator  214  installed on the fixing drum  260  and the rotor  266  installed in the lower part of the rotational drum  210 . If the rotational drum  210  rotates, a head  216  fixed on the rotational drum  210  obtains and records information or, records information onto the magnetic tape.  
         [0038]     The outer rings  224  and  234  of the upper and the lower bearings  220  and  230  are forcedly fit on a middle axial cavity  211  formed in the rotational drum  210 , so that those bearings  220  and  230  are joined to the rotational drum  210 . Also, the upper and the lower bearings  220  and  230  are inserted into the shaft  240  in a loosely fitting manner. The upper end of the inner ring  222  of the upper bearing  220  is touched, in a pressing manner, by the elastic member  270  and the lower end of the outer ring  224  of the upper bearing  220  is settled on a bearing settling part  212  formed on the middle axial cavity  211  of the rotational drum  210 . The lower end of the inner ring  232  of the lower bearing is supported by a projection  264  formed on the upper end of a lower axial cavity  262  of the fixing drum  260 . Also, the upper end of the outer ring  234  of the lower bearing  230  is settled on a bearing settling part  212  formed on the middle axial cavity  211  of the rotational drum  210 .  
         [0039]     An upper axial cavity  252  is formed on the drum cover  250  so that the upper part of the shaft  240  is fixed in a forcedly fitting manner. The elastic member  270  is supported by the periphery of the lower part of the upper axial cavity  252 . Also, a fixing transformer  254  is installed on the drum cover  250  so that it corresponds to a rotational transformer  218  installed on the rotational drum  210 . With such a construction, a signal exchange is possible between the rotational drum  210  and the controlling part. Since a detailed description thereof is obvious to those skilled in the art, a detailed description will be omitted.  
         [0040]     A lower axial cavity  262  is formed on the fixing drum  260  so that the fixing drum  260  is fixed to the lower part of the shaft  240  in a forcedly fitting manner. A projection  264  is formed upward on the periphery of the upper end of the lower axial cavity  262 , and a lower end of the inner ring  232  of the lower bearing  230  is supported by such a projection  264 . Also, a motor stator  214  is installed on the fixing drum  260  so that it corresponds to a rotor  266  fixed on the rotational drum  210 .  
         [0041]     The elastic member  270  is supported on its one end by the upper end of the inner ring  222  of the upper bearing  220  so that it applies a load on the inner ring  222  of the upper bearing  220 . The other end of the elastic member  270  is supported by the periphery of the lower part of the upper axial cavity  252  of the drum cover  250 .  
         [0042]     Though the fixing transformer  254  is formed on the drum cover  250  and the motor stator  214  is installed on the fixing drum  260  according to the embodiment of the present invention, the present invention is not limited to this construction. Namely, the head drum assembly  200  may change in its construction in such a way that the motor stator  214  is installed in the drum cover  250  and the fixing transformer  254  is installed on the fixing drum  260 . Also, a coil spring is shown in the drawing as an example for the elastic member  270 , the elastic member is not limited to this and the embodiment of the present invention is applicable to any member as far as it has elasticity.  
         [0043]     A pre-load is applied, in the direction of an arrow, on the upper and the lower bearings  220  and  230  as shown in  FIG. 3 . The principle by which such a pre-load is applied, will be described in detail with reference to  FIG. 4 .  
         [0044]      FIG. 4  is a conceptual view explaining the principle by which a pre-load is applied according to the embodiment of the present invention.  
         [0045]     Referring to  FIG. 4 , the elastic member  270  applies a load on the inner ring  222  of the upper bearing  220 . By such a load, the inner ring  222  of the upper bearing  220  joined to the shaft  240  in a loosely fitting manner, is moved downward in its displacement. Though the movement in the displacement of the inner ring  222  of the upper bearing  220  is shown in an exaggerated manner for an understanding of this embodiment of the present invention, in reality a fine movement in the displacement that may not be identified by the human eye, is made. As the inner ring  222  of the upper bearing  220  is moved downward in its displacement in this manner, an upper bearing ball is moved downward. However, the outer ring  224  of the upper bearing  220  is forcedly fit in the rotational drum  210 , the displacement of the outer ring  224  is not generated. Resultantly, the structure of the upper bearing  220  enters a state as shown in  FIG. 4 . With such a structure, force applied on the inner ring  222  of the upper bearing  220  by the elastic member  270 , is transferred to the upper bearing ball  226  in an arrow direction as shown in  FIG. 4  so that a pre-load is applied.  
         [0046]     The force applied on the upper bearing ball  226  is transferred to the outer ring  224  of the upper bearing  220 . At this point, since the outer ring  224  of the upper bearing  220  is forcedly fit in the rotational drum  210 , downward force is applied on the rotational drum  210 . The force transferred to the rotational drum  210  is transferred to the outer ring  234  of the lower bearing  230  forcedly fit in the middle axial cavity  211  of the rotational drum  210 . By the force transferred in this manner, the outer ring  234  of the lower bearing  230  is moved downward in its displacement. Due to such a displacement, the lower bearing ball  236  is moved slightly downward in its displacement. Due to such a displacement, the lower bearing  230  has an arrangement as shown in  FIG. 4 . Due to such an arrangement, the force transferred to the outer ring  234  of the lower bearing  230  applies a pre-load, in the direction of the arrow as shown in  FIG. 4 , on the lower bearing ball  236 . According to the above pre-load structure, an inner diameter of the inner ring  222  of the upper bearing  220  and an inner diameter of the inner ring  232  of the lower bearing  230  can be manufactured in the same size, and accordingly, the upper bearing  220  and the lower bearing  230  can be constructed with the same bearing. Therefore, the upper and the lower bearings  220  and  230  need not be assembled separately, so that not only the assembly process is simplified but also costs consumed for production of the bearing can be reduced, because the same bearing is used.  
         [0047]      FIGS. 5A through 5E  are cross-sectional views illustrating a method for assembling the head drum assembly  200  according to the embodiment of the present invention.  
         [0048]     Referring to  FIG. 5A , the shaft  240  is forcedly fit in the lower axial cavity  262  formed on the fixing drum  260 . By such forcedly fitting, the shaft  240  is fixed in the fixing drum  260  and the first assembly  300  is completed.  
         [0049]     Referring to  FIG. 5B , the upper bearing  220  is forcedly fit, from the upper part to the lower part, in the middle axial cavity  211  formed on the rotational drum  210 , and the lower bearing  230  is forcedly fit, from the lower part to the upper part of the rotational drum  210 . The upper and the lower bearings  220  and  230  are forcedly fit up to the bearing settling part  212 , so that the second assembly  310  is completed.  
         [0050]     Referring to  FIG. 5C , the shaft  240  forcedly fit in the lower axial cavity  262  of the fixing drum  260  in the first assembly  300 , is inserted, in a sliding manner, into the inner rings  222  and  232  of the upper and the lower bearings  220  and  230  of the second assembly  310 , so that the third assembly  320  is completed. The inner diameters of the inner rings  222  and  232  of the upper and the lower bearings  220  and  230 , are larger than the diameter of the shaft  240 , so that the shaft  240  is inserted, in a loosely fitting manner, into the inner rings  222  and  232  of the upper and the lower bearings  220  and  230 . If the insertion is completed, the projection  264  projected upward on the outer periphery of the lower axial cavity  262  of the fixing drum  260  is touched by the inner diameter of the lower bearing  230 .  
         [0051]     Referring to  FIG. 5D , the elastic member  270  is inserted into the third assembly  320 . The coil spring, elastic member  270  exemplified in the embodiment of the present invention, is inserted along the outer periphery of the shaft  240 , so that the fourth assembly  330  is completed. It is preferable that since having a slightly larger diameter than the diameter of the shaft  240 , the coil spring  270  is inserted by a little force from the upper part. With such a diameter, the coil spring  270  moves little on the outer periphery of the shaft  240  after being inserted onto the shaft  240 .  
         [0052]     Referring to  FIG. 5E , an upper part of the shaft  240  of the fourth assembly  330  is forcedly fit in the upper axial cavity  252  formed on the drum cover  250 . At this point, the elastic member  270  is compressed by being touched by one end of the drum cover  250 . The elastic member  270  compressed in this manner, applies a load on the inner ring  222  of the upper bearing  220 , and the projection  264  of the fixing drum  260  applies a load on the inner ring  232  of the lower bearing  230 . With such a configuration, a pre-load is applied to the upper and the lower bearings  220  and  230  so that the rotational drum  210  is rotated in a stable manner.  
         [0053]     As described above, according to the improved head drum assembly of the present invention and the magnetic recording/reproducing apparatus having the same, and the method for assembling the head drum assembly, the inner diameters of the upper and the lower bearings are made the same, so that the assembling process is simplified. Also, since the same bearing is used for the upper and the lower bearings, bearing manufacturing costs can be reduced.  
         [0054]     Also, since the forcedly fitting process is reduced in the conventional assembling process for the head drum assembly, the productivity of the head drum assembly can be improved.  
         [0055]     The foregoing embodiment and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. Also, the description of the embodiments of the present invention is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.