Patent Publication Number: US-2005116078-A1

Title: Reel clutch device and method for tape recorders

Description:
This application claims benefit under 35 U.S.C.§ 119(a) from Korean Patent Application No. 2003-86264, filed on Dec. 1, 2003, the entire contents of which is incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a reel disk assembly for tape recorders that plays a tape cassette. More particularly, the present invention relates to a reel clutch device and method for tape recorders which transfers the rotary torque of a reel gear to a reel disk.  
      2. Description of the Related Art  
      Tape recorders are devices for recording information on a recording medium such as magnetic tapes and reproducing the recorded information. Examples of tape recorders are video cassette tape recorders(VCRs), camcorders, and so on.  
      Referring to  FIG. 1 , a tape recorder has a main deck  2  on which a head drum  1  is rotatably mounted, a sub-deck  3  mounted on the main deck  2  and able to be loaded and unloaded on the main deck  2 , a pair of reel disk assemblies  20  rotatably mounted on the sub-deck  3  for driving the tape reel of a tape cassette (not shown), and a power transmission unit  10  for selectively transmitting the power of a capstan motor (not shown) mounted on the main deck  2  to one of the pair of reel disk assemblies  20 .  
      The pair of reel disk assemblies  20  is provided with a supply reel disk assembly  22  for supplying magnetic tape from a tape cassette and a take-up reel disk assembly  21  for winding up the supplied magnetic tape.  
      The power transmission unit  10  has a capstan gear  15  meshed with a shaft gear  5  of the capstan motor, a timing belt  11  for transmitting the power of the capstan gear  15  to a pulley gear  12 , and an idle gear  14  meshed with the pulley gear  12  and selectively coupled by a rotation lever  13  with one of the pair of reel disk assemblies  21  and  22  to transmit power, with the rotation lever  13  rotating about the shaft of the pulley gear depending upon the rotation direction of the pulley gear  12 .  
      According to the described structure, the power of the capstan motor rotating at a high speed is transmitted to one of the pair of reel disk assemblies  21  and  22  via the power transmission unit  10  depending upon an operation mode, to thereby play the magnetic tape in a forward or a reverse direction. The pair of reel disk assemblies  20  has a reel clutch device for producing a proper torque to adjust the traveling speed of the magnetic tape based on the tension of the magnetic tape.  
       FIG. 2  is a cross-sectioned view showing a conventional magnet reel clutch device for tape recorders, for example, the described reel clutch device. Referring to  FIG. 2 , the magnet reel clutch device includes a reel gear  32  and a reel disk  31  assembled stacked on the deck (not shown) of the tape recorder, an iron-plate base  35  and an iron plate  33  which are mounted in the reel gear  32  and the reel disk  31  are opposite each other, and a magnet  34  mounted between the iron base  35  and the iron plate  33 .  
      In the reel clutch device having the described structure, when the power is transmitted from the capstan motor via the reel gear  32 , an adequate torque is transmitted to the reel disk  31  by a magnetic force which is generated between the iron plate  33  and the magnet  34 .  
      However, in the described reel clutch device, the iron-plate base  35  supporting the magnet  34  is press-fitted to the reel gear  32  in an inserting manner, and the iron plate  33  is press-fitted to the reel disk  31  in an outserting manner, which results in problems with assembling the device. Further, the magnet is expensive.  
       FIG. 3  is an exploded perspective view showing a conventional felt reel clutch device  20  for tape recorders. Specifically,  FIG. 3  is a view for showing another conventional reel disk assembly  20  including a felt reel clutch device. Referring to  FIG. 3 , the reel disk assembly  20  has an upper disk  41  having the tape reel of a tape cassette fitted thereto and seated thereon, a lower disk  45  fitted from the bottom of and coupled with the upper disk  41 , and a reel gear  42 , a spring  43 , and a contact piece  44  which are installed between the respective disks  41  and  45  to provide a friction force. Felt piece  46  provided on the lower disk  45  contacts with the bottom surface of the reel gear  42  so that torque is transmitted by friction. Further, the transmitted torque is properly adjusted by the force of the spring  43 . In the described structure, the idle gear  14  of FIG. I is coupled with and transmits the power of the capstan motor to the reel gear  42 , and the power is transmitted to the upper disk  41  through the lower disk  45  by the friction between the felt  46  and the reel gear  42 . Therefore, an adequate torque is transmitted to the upper disk  41  through the lower disk  45  depending upon the tension of the magnetic tape. Further, the tape reel of a tape cassette seated on the upper disk  41  turns based on the torque transmitted to the upper disk  41  so that the magnetic tape is wound.  
      The reel clutch device using felt as described has an advantage of having a low manufacturing cost due to a simple assembly and low supply cost compared to the magnet reel clutch device. However, the reel clutch device using the felt has less functional reliability due to variations of transmission torque resulting from the characteristics of the felt which are affected by temperature and humidity. In particular, the felt reel clutch device has a problem in transmitting a constant torque since the torque rapidly increases in high humidity and goes through severe variations in its magnitude at low temperatures.  
     SUMMARY OF THE INVENTION  
      The present invention has been developed in order to solve the above drawbacks associated with the conventional arrangement. An aspect of the present invention is to provide a reel clutch device and method for tape recorders which can be manufactured at low cost and transmit a constant torque regardless of variations of ambient environment.  
      The foregoing and other objects and advantages are substantially realized by providing a reel clutch device and method for tape recorders mounted in a reel disk assembly to transmit rotary torque of a reel gear to a reel disk, the reel disk assembly being mounted on a deck of each of the tape recorders and having the reel gear and the reel disk, comprising an elastic member mounted in the lower side of the reel disk; a reel washer mounted between the elastic member and the reel gear to be in frictional contact with the top surface of the reel gear; a reel plate mounted to be in frictional contact with the bottom surface of the reel gear; and a reel stopper mounted on the lower side of the reel plate, and for adjusting a gap between the reel disk and the reel gear in order for adequate friction torque to occur between the reel washer and the top surface of the reel gear and the reel plate and the bottom surface of the reel gear.  
      The friction torque is transmitted to the reel disk by the reel stopper. Further, the reel washer has an opening in a hexagonal shape, and a corresponding part of the reel stopper to which the reel washer is fitted is formed in a hexagon-shaped shaft. Furthermore, the reel plate has an opening in a hexagonal shape, and a corresponding part of the reel stopper to which the reel plate is fitted is formed in a hexagon-shaped protrusion.  
      In the reel clutch device and method for tape recorders according to one aspect of the present invention, the reel gear has a serration formed on at least one side thereof with which the reel washer and the reel plate are in contact. The serration is formed with plural concentric circles having a certain interval between each other. The reel washer and the reel plate are preferably each formed of any one of iron, somaraito, and Teflon. Lubricant is applied between the reel washer, reel plate, and reel gear.  
      The elastic member is a cone-shaped coil spring.  
      As described above, the reel clutch device and method for tape recorders according to the present invention can be manufactured at low manufacturing cost due to low supplies cost and less assembly work.  
      Furthermore, the reel clutch device and method according to the present invention can transmit a constant torque regardless of variations of ambient environment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      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 drawings, in which:  
       FIG. 1  is a plan view for schematically showing a conventional tape recorder;  
       FIG. 2  is a cross-sectioned view showing a conventional magnet reel clutch device for tape recorders;  
       FIG. 3  is an exploded perspective view showing a conventional felt reel clutch device for tape recorders;  
       FIG. 4  is a cross-sectioned view showing a reel clutch device for tape recorders according to an embodiment of the present invention;  
       FIG. 5  is an enlarged cross-sectioned view for showing a portion A of  FIG. 4 ; and  
       FIG. 6  is an exploded perspective view showing the reel clutch device for tape recorders shown in  FIG. 4 .  
      In the drawings, it should be noted that the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Embodiments of the present invention will be described in greater detail with reference to the accompanying drawings.  
      In the following description, the same drawing reference numerals are used for the same elements in different drawings. Examples are used to describe embodiments of the present invention. Thus, it should be apparent that the present invention can be performed without the examples shown without departing from the scope of the invention. Also, well-known functions or constructions are not described in detail for conciseness.  
       FIG. 4  is a cross-sectioned view showing a reel disk assembly including a reel clutch device for tape recorders according to an embodiment of the present embodiment,  FIG. 5  is an enlarged cross-sectioned view showing a portion A of  FIG. 4 , and  FIG. 6  is an exploded perspective view showing the reel clutch device for tape recorders shown in  FIG. 4 .  
      Referring to  FIG. 4  to  FIG. 6 , a reel clutch device  110  for tape recorders according to an embodiment of the present invention has an elastic member  111 , a reel washer  112 , a reel plate  114 , first and second serrations  104  and  105  formed on the upper and lower sides of the reel gear  102 , and a reel stopper  120 .  
      The elastic member  111  is mounted in the lower side of the reel disk  101 , and applies a constant pressure to the reel washer  112  against the upper surface of the reel gear  102 . A cone-shaped coil spring is used for the elastic member  111  in an embodiment of the present invention.  
      The reel washer  112  is interposed between the reel gear  102  and the elastic member  111 , and assembled on the reel stopper  120 , in frictional contact with the upper surface of the reel gear  102 . The opening  112   a  of the reel washer  112  is formed in a polygonal shape such as a rectangular shape, a hexagonal shape, and a portion  127  of the reel stopper  120  on which the reel washer  112  is assembled is shaped in relation to the opening  112   a  of the reel washer  112 . Therefore, if the opening  112   a  of the reel washer  112  is shaped in hexagon as shown in the present embodiment, the portion  127  of the reel stopper to be assembled is shaped as a hexagonal shaft.  
      The reel plate  114  is located between the bottom of the reel gear  102  and the reel stopper  120 , and assembled to be in frictional contact with the bottom of the reel gear  102 . The opening  114   a  of the reel plate  114  is formed in a polygonal shape such as a rectangular shape, a hexagonal shape, and a portion  122  of the reel stopper  120  on which the reel plate  114  is assembled is shaped in relation to the opening  114   a  of the reel plate  114 . Therefore, if the opening  114   a  of the reel plate  114  is formed in the hexagonal shape, a hexagonal projection portion  122  is formed on the base portion  121  of the reel stopper  120  to be assembled.  
      The reel washer  112  and the reel plate  114  can be formed of, for example, iron plate, somaraito or teflon. Since somaraito and teflon have a lubrication property, extra lubricant may not be required. If substances such as an iron plate are used, lubricant such as oil is applied on the surface of the iron plate which is in contact with the reel gear  102 , to thereby reduce abrasion and friction torque variations that can occur upon friction.  
      Serrations are provided on the reel gear  102  to reduce variations of the torque transmitted by friction. The first serration  104  is formed on the top surface of the reel gear  102  in frictional contact with the reel washer  112 , and the second serration is formed on the bottom surface of the reel gear  102  in frictional contact with the reel plate  114 . As shown in  FIG. 5  and  FIG. 6 , the first and second serrations  104  and  105  have plural protrusions formed in the concentric circles about the rotation shaft of the reel gear  102 .  
      The reel stopper  120  is assembled on the bottom of the reel plate  114 , and force-fitted to the reel disk  101  to rotate about the reel shaft  103  fixed to the sub-deck  3  integrally with the reel disk  101 . The reel stopper  120  includes the base part  121  and a shaft part  125 , and the base portion  121  has the protrusion portion  122  to which the reel plate  114  is fitted. Further, the shaft part  125  has a reel gear fitting portion  126  to which the reel gear  102  is rotatably assembled, a reel washer fitting portion  127  to which the reel washer  112  is fixed, and a reel disk fitting portion  128  to which the reel disk  101  is fitted. Further, the assembling gap between the reel stopper  120  and the reel disk  101  and the elastic force of the elastic member  111  determine the friction torque occurring between the reel washer  112  and the top surface of the reel gear  102  and between the reel plate  114  and the bottom surface of the reel gear  102 . Thus, the feature of the elastic member  111  and the assembling gap between the reel stopper  120  and the reel disk  101  are determined in order for the power of the capstan motor transmitted to the reel gear  102  be properly transmitted to the reel disk  101 .  
      Descriptions will now be made on the exemplary assembling order of the reel disk assembly including the reel clutch device for tape recorders which has the previously described structure.  
      First, the reel plate  114  is fitted to the base part  121  of the reel stopper  120 . At this time, the reel plate  114  is precisely fitted to the opening  114   a  to the protrusion portion  122  of the reel stopper base part  121 . Next, the reel gear  102  is fitted to the shaft part  125  of the reel stopper  120 . Thus, the reel gear  102  is fitted to the reel gear fitting portion  126  of the reel stopper  120  through the opening  102   a.  Next, the reel washer  112  is inserted into the shaft part  125  of the reel stopper  120  through the opening  112   a  so as to be in contact with the first serration  104  of the reel gear  102 . At this time, the reel washer  112  is precisely fitted to the reel washer fitting portion  127  of the reel stopper  120  through the opening  112   a.  Next, the elastic member  111  is inserted into the shaft part  125  of the reel stopper  120 , and the reel disk  101  is press-fitted to the reel disk fitting portion  128  of the reel stopper  120 . For the complete assembly, the fully assembled reel disk assembly  100  is inserted into the reel shaft  103  fixed to the sub-deck  3 .  
      Descriptions will now be made on operations of the reel clutch device for tape recorders according to one exemplary embodiment of the present invention with reference to  FIG. 1 , and  FIG. 4  to  FIG. 6 .  
      The power of the capstan motor is transmitted through the power transmission unit  10  (refer to  FIG. 10 ) so that the reel gear  102  rotates. Since the reel gear  102  is assembled to the reel gear fitting portion  126  of the reel stopper  120  by loose-fitting, the power of the reel gear  102  is not transmitted to the reel stopper  120  directly even though the reel gear  102  rotates. That is, the reel gear  102  rotates in friction contact of the first and second serrations  104  and  105  thereof with the reel washer  112  and the reel plate  114  respectively. Since the reel washer  112  and the reel plate  114  press the reel gear  102  by the elastic member  111 , the reel washer  112  and the reel plate  114  rotate with the reel gear  102  by a friction force between the first serration  104  and the reel washer  112  and a friction force between the second serration  105  and the reel plate  114 . However, since the reel washer  112  and the reel plate  114  are fixed to the reel stopper  120  by the hexagonal reel washer fitting portion  127  and the protrusion part  122 , the reel stopper  120  rotates as the reel washer  112  and the reel plate  114  rotate. That is, the power of the reel gear  102  changes to a friction torque on the reel washer  112  and the reel plate  114  to rotate the reel stopper  120 . Thus, the reel disk  101  coupled in one body with the reel stopper  120  rotates, which causes the magnet tape to be wound on the tape reel seated on the reel disk  101 . At this time, the friction torque transmitted by the friction force between the first and second serrations  104  and  105  of the reel gear  102 , the reel washer  112 , and the reel plate  114  is adequately adjusted depending upon the tension of the magnet tape.  
      As described above, the reel clutch device for tape recorders has an advantage of having a low supply cost since the magnets are not used, and of easy assembly since it can be assembled with the reel plate, reel gear, reel washer, elastic member, and reel disk inserted in order of the reel stopper. Further, the reel clutch device can minimize variations of the friction torque transmitted due to the changes of ambient environment such as temperature, humidity, and so on, since the members for friction are formed of iron, somaraito, Teflon, and the like, which are robust against ambient environment changes.  
      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.