Abstract:
A head drum assembly for a compact-size camcorder such as a digital video camera comprised of a drum cover, stationary and rotating drum, a subcircuit board, a stationary and rotating transformer and a motor stator and rotor. By forming the drum cover, which is attached to the shaft of the rotary drum above the rotary drum, with a conductive material such as an aluminum alloy, the need for a conductive bushing member and earthing plate for the insulating drum cover of the head drum assembly can be omitted, resulting in an overall simpler. As the number of components and manufacturing steps decreases, the manufacturing costs decrease and productivity increases.

Description:
FOREIGN PRIORITY INFORMATION 
   This application is a divisional of U.S. patent application Ser. No. 10/686,539, filed Oct. 16, 2003 now U.S. Pat. No. 7,126,793. This application claims priority under 35 U.S.C. §119 to a Korean Patent Application, Serial No. 2002-63070, filed in the Korean Intellectual Property Office on Oct. 16, 2002, to Korean Patent Application Serial No. 2002-84575, filed in the Korean Intellectual Property Office on Dec. 26, 2002, and to Korean Patent Application, Serial No. 2002-88235 filed in the Korean Intellectual Property Office on Dec. 31, 2002, the contents of all three said applications being incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an improved head drum assembly for use in a tape recorder such as a compact size camcorder of a digital video camera (DVC). 
   2. Description of the Related Art 
   Generally, in a tape recorder such as a compact size camcorder of a digital video camera or a video cassette recorder (VCR), in order to scan magnetic tape and thus record video data thereon and/or reproduce video data therefrom, a tape recorder deck includes a head drum assembly having a magnetic head rotatable at high speed. 
   Referring to  FIGS. 1A and 1B , a conventional head drum assembly  100  for a tape recorder includes a rotary drum  110 , a stationary drum  120  and a drum cover  130 . The rotary drum  110  supports a magnetic head (h), which scans a moving magnetic tape (not shown) to record/reproduce video data thereon/therefrom, and is rotatably mounted on the shaft  140 . The stationary drum  120  and the drum cover  130  are press-fitted to be placed on the lower and the upper parts of the shaft  140 , respectively, with the rotary drum  110  being interposed therebetween. 
   The drum cover  130  includes a conductive bushing member  131  in a form of a flange which is press-fitted in the shaft  140  so as to be positioned on the rotary drum  110 , a cover member  132  formed by a resin molding and joined with the bushing member  131  by a pair of screws (s), and a conductive earth plate  133  supported by one of the screws (s) to be exposed through the upper surface of the cover member  132  and electrically connected to the sub circuit board  153 . 
   Between the drum cover  130  and the rotary drum  110 , a rotary transformer  152  and a stationary transformer  151  facing the rotary transformer  152  are disposed to transmit the signals recorded/reproduced on/from tape by the magnetic head (h). In order to connect the magnetic head (h) and the coil (c) of the rotary transformer  152  through soldering, a terminal  155  is preferably interconnected therebetween as a medium because direct soldering is not easy. Accordingly, in order to enable easy soldering of the coil (c) first, terminal  155  is attached to the lower part of the rotary transformer  152 . Next, a hole  115  is defined in the rotary drum  110 , and the upper part of the terminal pin  111  is attached to the terminal  115 . Next, one end of the coil (c) is soldered to the connecting area between the terminal  155  and the terminal pin  111 . As shown in  FIG. 2A , the lower end of the terminal pin  111  is soldered to a fine patter coil (FPC)  117  which is disposed at the lower part of the rotary drum  110 . Of course, the FPC  117  is connected to the magnetic head (h) by soldering. 
   To the lower part of the rotary drum  110  is provided a motor rotor  160  which has a donut-shaped magnet  162  disposed within a ring-type rotor casing  161  thereof, and to the upper part of the stationary drum  120 , a motor stator  170  is mounted. The motor stator  170  is formed in a type in which the so-called FP coil (fine pattern coil) is formed into a disc pattern and disposed to face the donut-type magnet  162  to obtain a result of a more compact-sized head drum assembly  100 . Such motor stator  170  usually has the three-layered structure consisting of first substrate  171 , a second substrate  172  and a third substrate  17  which are stacked on one another in turn. 
   With regard to the motor stator  170 , there is a torque generation coil pattern (A) formed on the first and second substrates  171 ,  172 , while a frequency generation coil pattern (B) for speed control and a phase generation coil pattern (C) for phase control is formed on the third substrate  173 . 
   As shown in  FIG. 2C , the first substrate  171  is formed of a structure in which a copper membrane  171   b  in fine pattern is formed on an epoxy substrate  171   a , i.e., on a base plate, and a protective layer  171   c  is formed thereon. The second and the third substrates  172  and  173  are formed in the same structure. 
   In the head drum assembly  100  constructed as above, the rotary drum  110  is rotated by the electro-magnetic interaction between the motor rotor  160  and the motor stator  170 . As the rotary drum  110  is rotated, the magnetic head (h) mounted in the rotary drum  110  is also subsequently rotated, thereby scanning the tape and recording/reproducing data on/from the magnetic tape. The data obtained from the scanning of the magnetic head (h) is transmitted to the rotary transformer  152  and the stationary transformer  151  via the terminal pin  111  and the coil (c), and then to the camcorder system via the sub circuit board  153 , which is connected to the stationary transformer  151 . The data is then processed at the camcorder system. Reference numerals  140   a  and  140   b  denote bearings, and  141  an elastic member, respectively. 
   However, the conventional head drum assembly  100  constructed as above for use in the tape recorder is accompanied with the following drawbacks: 
   First, because the cover member  132  is formed of an insulating resin through a molding process, the conductive bushing member  131  and the screws (s) are required to ensure stable electric connection between the sub circuit board  153  and the earth plate  133  for a stable earthing of the head drum assembly  100 . 
   Additionally, because the drum cover  130  requires various components such as the bushing member  131 , the cover member  132 , the earth plate  133 , and a pair of screws (s) to connect the related parts, the number of manufacturing steps such as soldering of the earth plate  133  with respect to the sub circuit board  153 , or bonding of the cover member  132  to the bushing member  131 , are also increased. As a result, due to increased number of necessary parts and manufacturing steps, productivity deteriorates while the manufacturing costs increase. 
   Second, a significant amount of components and manufacturing steps are also required in order to connect the magnetic head (h) and the coil (c) of the rotary transformer  152 . The terminal  155  has to be attached to, and the hole  115  has to be formed in, the rotary drum  110 , so that the upper part of the terminal pin  111 , the terminal  155  and the coils (c), can be connected through the hole  115 . Then, the lower part of the terminal pin  111  is attached to the FPC  117  which is disposed at the lower part of the rotary drum  110 , and the FPC  117  is connected to the magnetic head (h) by soldering. 
   Furthermore, because signal connection between the rotary transformer  152  and the magnetic head (h) can be achieved only after a plurality of processes, signal transmission rate is degraded, and thus performance of the product deteriorates. 
   Third, because the motor stator  170  is formed in the three-layered structure having the first substrate  171 , the second substrate  172  and the third substrate  173 , each of which are bonded to one another in turn, the number of parts and manufacturing steps increase and manufacturing costs increase. Furthermore, the copper patterning on the respective substrates also causes decreased productivity. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an aspect of an embodiment of the present invention to provide a head drum assembly for a tape recorder, which provides an improved productivity at a reduced manufacturing cost through an improvement to the structure of a drum cover thereof. 
   It is another aspect of an embodiment of the present invention to provide a head drum assembly for a tape recorder, which is improved in a connecting structure for a rotary transformer and a magnetic head. 
   It is yet another aspect of an embodiment of the present invention to provide a head drum assembly for a tape recorder, which provides improved manufacturing processes at a reduced manufacturing cost through an improvement to the structure of a motor stator. 
   In order to achieve the above aspects, an embodiment of present invention provides a head drum assembly for a tape recorder, including a rotary drum supporting a magnetic head thereon and being rotatably disposed on a shaft, a stationary drum and a drum cover secured to the shaft to be positioned respectively on lower and upper parts of the rotary drum with the rotary drum being interposed therebetween, a sub circuit board. The embodiment of the invention further includes a stationary transformer and a rotary transformer, each being disposed between the stationary drum and the rotary drum for signal transmission with the magnetic head, a motor stator mounted on the stationary drum, and a motor rotor disposed in the rotary drum to oppose the motor stator and rotate. 
   The drum cover is formed of a conductive material and is press-fitted to contact with the shaft, and a connecting member is disposed on the conductive body of the drum cover for supporting and electrically connecting the sub circuit board with the conductive body. 
   The drum cover is formed of the same or similar material as that of the rotary drum and the stationary drum. 
   The connecting member is a screw fastened to coupling holes which are respectively formed in the drum cover and in the sub circuit board to correspond to each other. 
   The rotary drum has a linking hole vertically penetrating therein, and a coil of the rotary transformer is passed through the linking hole and directly connected to the magnetic head by soldering. 
   An entry part and an exit part at the upper and the lower parts of the linking hole are rounded, or may be tapered. 
   The linking hole is formed symmetrically with respect to the magnetic head. 
   The motor stator is formed in a two-layered structure having a lower substrate and an upper substrate stacked on the lower substrate. Combinations of a torque generation coil pattern, a frequency generation coil pattern for speed control and a phase generation coil pattern for phase control are formed on the upper and the lower substrates, respectively. 
   The torque generation coil pattern is formed dispersely on the upper and the lower substrates, and the phase generation coil pattern for phase control is formed on one of the upper and the lower substrates, and the frequency generation coil pattern for speed control is formed on the other. 
   The torque generation coil pattern and the phase generation coil pattern are formed dispersely on the upper and the lower substrates, and the frequency generation coil pattern is formed on the lower substrate. 
   Each of the upper and the lower substrates has a copper layer in a predetermined pattern which is formed on a base plate, and a protective layer formed on the copper layer, and the copper layers of the upper and the lower substrates are connected with each other through a passing hole formed in the upper substrate. 
   The copper layer is formed in width from about 10 μm to about 20 μm, and a pitch between the respective copper layers ranges from about 90 μm to about 100 μm. 
   With the head drum assembly for a tape recorder constructed as described above in accordance with an embodiment of the present invention, the conductive bushing members and earth plate, which were respectively provided to the insulating drum cover, can be replaced by a single conductive drum cover. Accordingly, the number of necessary parts and manufacturing steps is reduced, and the manufacturing cost decreases while the productivity increases. 
   Further, because the coil is directly connected to the magnetic head, many parts become unnecessary, and as a result, the number of manufacturing steps decreases. Also, as the signal transmission rate increases due to direct connection between the coil and the magnetic head, the performance of the product is improved. 
   Furthermore, because the motor stator adopts a two-layered structure of an upper and lower substrates, i.e., omitting one layer from the conventional structure, the number of necessary parts is reduced, and subsequently, the manufacturing costs are also decreased. Additionally, because the process of forming copper pattern on the respective substrate layers can be shortened, productivity is increased. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and other features of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings, in which: 
       FIG. 1A  is a schematic sectional view of a conventional head drum assembly; 
       FIG. 1B  is an exploded perspective view of the head drum assembly of  FIG. 1A ; 
       FIG. 2A  is a bottom view illustrating the rotary drum of  FIG. 1A ; 
       FIG. 2B  is a schematic perspective view illustrating the motor stator of  FIG. 1A  being disassembled; 
       FIG. 2C  is a schematic sectional view taken on line II-II of  FIG. 2B ; 
       FIG. 3A  is a schematic sectional view illustrating a head drum assembly according to a preferred embodiment of the present invention; 
       FIG. 3B  is an exploded perspective view of the head drum assembly of  FIG. 3A ; 
       FIG. 4A  is a bottom view of the rotary drum of  FIG. 3A ; 
       FIG. 4B  is a schematic perspective view illustrating the motor stator of  FIG. 3A  being disassembled; and 
       FIG. 4C  is a schematic sectional view taken on line IV-IV of  FIG. 4B . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
   Referring to  FIGS. 3A and 3B , a head drum assembly  200  for a tape recorder according to the present invention includes a rotary drum  210  which rotatably supports a magnetic head (h) thereon to scan and thus record/reproduce data on/from a magnetic tape (not shown), a stationary drum  220  and a drum cover  230  press-fitted to be positioned on the lower and the upper parts of a shaft  240 , respectively, with the rotary drum  210  being interposed therebetween. Here, the shaft  240  is disposed in a center axis hole of the rotary drum  210 . 
   The drum cover  230  receives the shaft  240  which is press-fitted in a shaft hole defined therein, to be disposed on the rotary drum  210 . The drum cover  230  can be formed by shaping a conductive material such as an aluminum alloy. More preferably, the drum cover  230  is made of the same material as that of the rotary drum  210  and the stationary drum  230 . 
   According to an embodiment of the present invention, the drum cover  230  and the sub circuit board  253  are each provided with connecting holes  230   a ,  230   b , respectively, that corresponds to each other. Accordingly, as the screws (s) are fastened into the connecting holes  230   a ,  230   b , the drum cover  230  and the sub circuit board  253  are supported in an electric connection. 
   As described above, because the drum cover  230  is formed of a conductive material, the drum cover  230  and the sub circuit board  253  can be electrically connected simply by the screws (s), and the drum cover  230  itself can function as the earth plate. 
   By the above-described structure, the need for a conductive bushing member and an earth plate which were usually required in the drum cover  230  can be omitted, and the number of screws (s) for connecting these parts is also reduced. As a result, the conductive drum cover  230  can be provided as one simple element. 
   Stationary transformer  251  and rotary transformer  252  (which faces the stationary transformer  251 ), are provided to the upper part of the rotary drum  210  and to the lower part of the drum cover  230 , respectively. The transformers  251 ,  252  provide signal transmission between the magnetic head (h) and the sub circuit board  253 . 
   The rotary transformer  252  is attached to the upper part of the rotary drum  210 . On the rotary drum  210 , there is the drum cover  230  fixed to the shaft  240 . The stationary transformer  251  is attached to the lower part of the drum cover  230  to face the rotary transformer  252 . The rotary transformer  252  sends and receives signals with the stationary transformer  251  in a non-contact manner. Accordingly, data reproduced or to be recorded by the magnetic head (h) can be transmitted through the respective transformers  251 ,  252 . 
   To this end, the coil (c) of the rotary transformer  252  has to be connected to the magnetic head (h), and accordingly, there is a linking hole  215  vertically penetrating the rotary drum  210 . As shown in  FIG. 3A , a pair of linking holes  215  are symmetrically formed at the right and the left sides with respect to the magnetic head (h). The coil (c) is passed through the linking holes  215  and is directly connected to the magnetic head (h) by soldering. As a result, in the case where there is a pair of magnetic heads (h) employed, a total of four soldering steps are performed: two soldering steps for each coil (c) of each magnetic head (h). Generally, the surface of the coil (c) is coated with enamel for the purpose of insulation. In order to prevent the coating from peeling off by contact with the rotary drum  210 , the upper/lower entry/exit parts  215   a ,  215   b  of the linking holes  215  are preferably rounded. By having the entry and exit parts  215   a ,  215   b  rounded, instead of angular, the peel-off of the coating layer of the coil (c) by the contact can be prevented. 
   In addition, a motor stator  270  is disposed in the upper part of the stationary drum  220 , and a motor rotor  260  is disposed in the lower surface of the rotary drum  210  to oppose the motor stator  270  and rotate. The motor rotor  260  has a donut-shaped magnet  262  disposed inside a ring-type rotor casing  261 . 
   The motor stator  270 , which is one of the main features of an embodiment of the present invention, is formed of the type in which the so-called “FP coil (fine pattern coil)” is formed into a disc pattern and disposed to face the donut-type magnet  162 , to obtain a more compact-sized head drum assembly. As shown in  FIG. 4B , the motor stator  270  has the two-layered structure which consists of a lower substrate  261  and an upper substrate  262  stacked on the lower substrate  261 . In the upper and the lower substrates  262 ,  261 , there are a torque generation coil pattern (A), a frequency generation coil pattern (B) for speed control and a phase generation coil pattern (C) for phase control formed in various shapes and in combination with one another. 
   According to a preferred embodiment of the present invention, as shown in  FIG. 4B , the torque generation coil pattern (A) and the phase generation (PG) coil pattern (C) for phase control are formed dispersely on the upper and the lower substrates  262 ,  261 , while the frequency generation (FG) coil pattern (B) for speed control is formed on the upper substrate  262 . 
   According to another aspect of an embodiment of the present invention, albeit not shown, a predetermined torque generation coil pattern may be formed dispersely on the upper and the lower substrates  262 ,  261 , while there is the PG coil pattern (C) on one of the upper substrate and lower substrate  262 ,  261  and the FG coil pattern (B) on the other substrate  262 ,  261 . Additionally, various other combinations of the patterns are also possible. 
   According to yet another aspect of an embodiment of the present invention, as shown in  FIG. 4C , preferably, each of the upper and the lower substrates  262 ,  261  is formed by coating a copper membrane  261   b  of a predetermined fine pattern on an epoxy substrate  261   a , i.e., on a base plate, and forming a protective layer  261   c  thereon. The copper layer  261   b  may be formed in width (W) from at or about 10 μm to at or about 20 μm, and the pitch (P) between the respective copper layers  261   b  ranges from at or about 90 μm to at or about 100 μm. 
   Although a few preferred embodiments of the present invention have been described, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiments, but various changes and modifications can be made within the spirit and scope of the present invention as defined by the appended claims.